Journal articles: 'Sub band'

1

Yu, Guiqiang, Lu Wen, Guoyu Luo, and Yan Wang. "Band structures and topological properties of twisted bilayer MoTe₂ and WSe₂." Physica Scripta 96, no. 12 (December 1, 2021): 125874. http://dx.doi.org/10.1088/1402-4896/ac4192.

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Abstract We calculate the electronic band structures and topological properties of twisted homobilayer transition metal dichalcogenides(t-TMDs), in particular, bilayer MoTe2 and WSe2 based on a low-energy effective continuum model. We systematically show how the twist angle, vertical electric field and pressure modify the band structures of t-TMDs, often accompanied by topological transitions.We find the variation of topological transitions mainly take place in a limited range of parameters. The electric field can efficiently tune the energy of the topmost second valence band to motify the Chern numbers of the topmost three valance bands. The topological property of the topmost first valance band can be modified by electric field and pressure, but doesn’t depend on twist angle. We show the band gap between the topmost second and third valance bands that both change from non-trivial to trivial closes at κ − -point of the moiré Brillouin zone.

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Wang, Zhi Long, Shi Qin Wang, Nin Yao, and Xing Min Wei. "VUV-Photoluminescence Properties of (Gd, La)₂O₂CO₃: Eu³⁺." Advanced Materials Research 1052 (October 2014): 203–6. http://dx.doi.org/10.4028/www.scientific.net/amr.1052.203.

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(Gd,La)2-x O2CO3:Eux3+(0.01 ≤x≤0.04) were synthesized via a flux method at 400°C, and their photoluminescence properties under vacuum ultraviolet (VUV) excitation were examined. The excitation spectra showed two bands in the region from 125 nm to 300 nm, the first band centered at 190 nm was ascribed to absorption of related CO32- complex, and the second broad band centered at 246nm and 278nm in Gd2O2CO3:Eu3+ was ascribed to the charge transfer band of O2-→ Eu3+. Series samples exhibited red emission at around 611 nm under vacuum ultraviolet excitation corresponding to the 5D0→ 7F2.transition of Eu3+.

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Kaewjaeng, Siriprapa, Smit Insiripong, Hong Joo Kim, Utumma Maghanemi, Suchart Kothan, S. Ruengsri, and Jakrapong Kaewkhao. "Optical and Luminescence Properties of Pr³⁺ in Gd₂O₃-CaO-SiO₂-B₂O₃ Glasses." Key Engineering Materials 675-676 (January 2016): 359–63. http://dx.doi.org/10.4028/www.scientific.net/kem.675-676.359.

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This paper reports on the results concerning optical absorption and luminescence properties of 25Gd2O3-10CaO-10SiO2-(55-x) B2O3-xPr2O3 (where x is 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol %) have been synthesized by melting and quenching process. The locations of the absorption peak observed are investigated for the first time. It is shown that the f-f transitions in the studied glasses are allowed by distortions of Pr3+ ions. Seven absorption bands corresponding to the 3H4 → 3P2, 1I6+3P1, 1D2, 1G4, 3F4, 3F3 and 3F2, respectively absorption bands peaked at 459,483,575,1011,1418,1513 and 1931 nm. The luminescence intensity of Pr3+ doped glass under excited at 459 and 483 nm, the emission band under excited at 459 nm wavelengths emission centered at 542 nm (3P0→3H5), 602 nm (1D2→3H4), 646 nm (3P0→3F2) and 689 nm (1D2→3H5) .The emission bands with 483 nm excitation wavelength, the emission band centered at 532 nm (3P1→3H5), 602 nm (1D2→3H4), 646 nm (3P0→3F2) and 725 nm (3P0→3F4), respectively. The present paper brings out the results pertaining to the studies carried out on different structural and optical absorption in UV-VIS-NIR region are also measured and discussed in term of energy levels, energy band gap and emission spectra of Pr3+ ions doped in Gd2O3-CaO-SiO2-B2O3 glasses.

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He, Ling, Wei Min Sun, Yu Tian Ding, and Yu Hua Wang. "Synthesis and Photoluminescence Properties of the Novel Red Phosphor Gd₂MoB₂O₉: Eu." Advanced Materials Research 311-313 (August 2011): 1327–31. http://dx.doi.org/10.4028/www.scientific.net/amr.311-313.1327.

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A novel phosphor, Gd2MoB2O9:Eu3+ has been synthesized by solid-state reaction and its photoluminescence in UV-VUV range are investigated. A sharp excitation band is observed in the region of 120–135 nm, which is related to the charge-transfer (CT) band of Gd3+. The broad band around 135–160 nm can be assigned to the BO3 host absorption. The broad bands around 248 nm are assigned to the CT band of Eu3+-O2-. The phosphors emit strong red luminescence centered at about 591 nm, 614 nm and 626 nm due to the5D0–7F1 and 5D0–7F2 transitions of Eu3+. The main emission peak under 254 and 147 nm excitations also shows different shifts with increasing Eu3+ concentration. This could be due to the different luminescence sites selected at high doping concentrations of Eu3+. Gd2MoB2O9:Eu3+ shows the pure red emission under both 254 and 147 nm excitations.

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Xia, Xinyi, Nahid Sultan Al-Mamun, Chaker Fares, Aman Haque, Fan Ren, Anna Hassa, Holger von Wenckstern, Marius Grundmann, and S. J. Pearton. "Band Alignment of Al₂O₃ on α-(Al_xGa_1-x)₂O₃." ECS Journal of Solid State Science and Technology 11, no. 2 (February 1, 2022): 025006. http://dx.doi.org/10.1149/2162-8777/ac546f.

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X Ray Photoelectron Spectroscopy was used to measure valence band offsets for Al2O3 deposited by Atomic Layer Deposition on α-(AlxGa1-x)2O3 alloys over a wide range of Al contents, x, from 0.26–0.74, corresponding to a bandgap range from 5.8–7 eV. These alloys were grown by Pulsed Laser Deposition. The band alignments were type I (nested) at x <0.5, with valence band offsets 0.13 eV for x = 0.26 and x = 0.46. At higher Al contents, the band alignment was a staggered alignment, with valence band offsets of − 0.07 eV for x = 0.58 and −0.17 for x = 0.74, ie. negative valence band offsets in both cases. The conduction band offsets are also small at these high Al contents, being only 0.07 eV at x = 0.74. The wide bandgap of the α-(AlxGa1-x)2O3 alloys makes it difficult to find dielectrics with nested band alignments over the entire composition range.

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He, Da Wei, Fang Shen, Xin Li, Peng Zhi Lu, and Yong Sheng Wang. "Luminescence Properties of LnZr(BO₃)₂:Re (Ln=Ba, Sr; Re=Eu, Ce,Tb)." Key Engineering Materials 368-372 (February 2008): 369–71. http://dx.doi.org/10.4028/www.scientific.net/kem.368-372.369.

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The excitation spectrum of BaZr(BO3)2:Eu3+ is composed of two broad bands. One band in the range from 120 nm to 170 nm is attributed to the borate groups, and the other band at 230 nm is due to the charge-transfer state (CTS) of the Eu3+ ion. The excitation spectrum of BaZr(BO3)2:Tb3+consists of one broad band in the range from 120 nm to 170 nm and the bands peaking at 226 nm, 245 nm and 272 nm respectively. The former is also attributed to the absorption of the BO3 groups. The latter correspond to the 4f8-4f75d transition of Tb3+.Main peak of the host absorption moves about 30 nm to high energy region as Sr2+ replaces Ba2+ partially.

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7

Смагин, В. П., А. А. Исаева, and Н. С. Еремина. "Фотолюминесценция квантовых точек Zn-=SUB=-1-x-y-=/SUB=-Cu-=SUB=-x-=/SUB=-Eu-=SUB=-y-=/SUB=-S/EuL-=SUB=-3-=/SUB=- в полиакрилатной матрице." Журнал технической физики 128, no. 5 (2020): 651. http://dx.doi.org/10.21883/os.2020.05.49326.326-19.

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Zinc sulfide is one of the most popular luminescent semiconductors of group A(II)B(VI). Doping ZnS quantum dots with Ln3+ ions makes it possible to form nanoscale structures in a semiconductor matrix containing isolated centers of narrow-band luminescence. The introduction of quantum dots into the acrylate matrix further stabilizes the particles and allows them to form their morphology. Nanoscale structures of Zn1-x-yCuxEuyS/EuL3, where L − trifluoroacetate are anions, were synthesized by the method of emerging reagents in situ in the medium of methyl methacrylate (MMA). ZnS doping was performed by simultaneous introduction of soluble precursors of zinc sulfide, as well as copper and europium trifluoroacetates into the acrylate reaction mixture. Polymer optically transparent compositions of PMMA/Zn1-x-yCuxEuyS/EuL3 were obtained by radical polymerization of MMA in the block. The excitation of luminescence of compositions is associated with Interzone electron transitions in ZnS, with a system of levels that form alloying ions in the forbidden zone of ZnS, as well as with their own energy absorption by Eu3+ ions. Broadband luminescence of compositions is caused by intracrystalline defects formed in ZnS during doping. Narrow-band luminescence occurs as a result OF 5D0→7Fj electronic transitions in Eu3+ ions associated with quantum dots, as well as being in the polymer matrix independently of them. The transfer of energy from the donor levels of the semiconductor matrix to the levels of Eu3+ ions, followed by its release in the form of luminescence, was confirmed by the imposition of absorption bands doped with ZnS and excitation bands of luminescence compositions, as well as an increase in the intensity of narrow-band luminescence of Eu3+ ions while reducing the intensity of a wide band of recombination luminescence of doped ZnS. A decrease in the intensity of the ZnS recombination luminescence band with an increase in the concentration of Eu3+ >1.0∙10-3 mol/L ions is also associated with the formation of a layer of complex europium compounds on the particle surface that prevent the passage of exciting radiation to the particle core.

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8

Omehe, Nnamdi, and Divine Ojuh. "The Electronic Band Structure and Vibrational Properties of Cubic B_xIn_1-xN Alloy." Applied Mechanics and Materials 446-447 (November 2013): 98–103. http://dx.doi.org/10.4028/www.scientific.net/amm.446-447.98.

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We have performed the electronic and phonon band structures of BxIn1-xN for various concentration of Boron using the pseudopotential method. The electronic band structure calculation was done using the GW approximation while the phonon band structure was done using the density functional perturbation theory. All calculations were done within the frame work of the density functional theory (DFT). From our calculations, the direct band gap for B0.25In0.75N, B0.5In0.5N and B0.75In0.25N were found to be 0.024eV, 2.2 eV and 6.01 eV respectively while the indirect band gap obtained were 0.59 eV, 3.24 eV and 6.9 eV. For the phonon calculations, it was also observed that an increase in the Boron content results in corresponding increase in the frequency of the topmost LO at the zone centre. For B0.25In0.75N, B0.5In0.5N and B0.75In0.25N, the topmost LO obtained were 735 cm-1, 885 cm-1 and 1105 cm-1 respectively. We also saw that as the Boron concentration decreases, the number of optical bands across which the acoustic bands overlap increases.

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9

Nieken, Rachel, Anna Roche, Fateme Mahdikhanysarvejahany, Takashi Taniguchi, Kenji Watanabe, Michael R. Koehler, David G. Mandrus, John Schaibley, and Brian J. LeRoy. "Direct STM measurements of R-type and H-type twisted MoSe₂/WSe₂." APL Materials 10, no. 3 (March 1, 2022): 031107. http://dx.doi.org/10.1063/5.0084358.

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When semiconducting transition metal dichalcogenide heterostructures are stacked, the twist angle and lattice mismatch lead to a periodic moiré potential. As the angle between the layers changes, so do the electronic properties. As the angle approaches 0° or 60°, interesting characteristics and properties, such as modulations in the band edges, flat bands, and confinement, are predicted to occur. Here, we report scanning tunneling microscopy and spectroscopy measurements on the bandgaps and band modulations in MoSe2/WSe2 heterostructures with near 0° rotation (R-type) and near 60° rotation (H-type). We find a modulation of the bandgap for both stacking configurations with a larger modulation for R-type than for H-type as predicted by theory. Furthermore, local density of states images show that electrons are localized differently at the valence band and conduction band edges.

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10

Zeng, Wei, Qi Jun Liu, and Zheng Tang Liu. "Structural, Electronic and Optical Properties of S-Doped Anatase TiO₂." Applied Mechanics and Materials 727-728 (January 2015): 79–82. http://dx.doi.org/10.4028/www.scientific.net/amm.727-728.79.

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Structural, electronic and optical properties of S-doped anatase TiO2 have been investigated using the first-principles density-functional theory. The band structure and density of states show that the band gap of anatase TiO2 narrows due to the presence of the S-3p energy level in the top of the valence bands. Compared with the optical absorption edge of the undoped anatase TiO2, the optical absorption edge of S-doped anatase TiO2 shifts to a lower energy, which indicates that S-doped anatase TiO2 can be used for visible-light absorption applications.

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11

Xia, Xinyi, Chaker Fares, Fan Ren, Anna Hassa, Holger von Wenckstern, Marius Grundmann, and S. J. Pearton. "Al Composition Dependence of Band Offsets for SiO₂ on α-(Al_xGa_1−x)₂O₃." ECS Journal of Solid State Science and Technology 10, no. 11 (November 1, 2021): 113007. http://dx.doi.org/10.1149/2162-8777/ac39a8.

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Valence band offsets for SiO2 deposited by Atomic Layer Deposition on α-(AlxGa1-x)2O3 alloys with x = 0.26–0.74 were measured by X-ray Photoelectron Spectroscopy. The samples were grown with a continuous composition spread to enable investigations of the band alignment as a function of the alloy composition. From measurement of the core levels in the alloys, the bandgaps were determined to range from 5.8 eV (x = 0.26) to 7 eV (x = 0.74). These are consistent with previous measurements by transmission spectroscopy. The valence band offsets of SiO2 with these alloys of different composition were, respectively, were −1.2 eV for x = 0.26, −0.2 eV for x = 0.42, 0.2 eV for x = 0.58 and 0.4 eV for x = 0.74. All of these band offsets are too low for most device applications. Given the bandgap of the SiO2 was 8.7 eV, this led to conduction band offsets of 4.1 eV (x = 0.26) to 1.3 eV (x = 0.74). The band alignments were of the desired nested configuration for x > 0.5, but at lower Al contents the conduction band offsets were negative, with a staggered band alignment. This shows the challenge of finding appropriate dielectrics for this ultra-wide bandgap semiconductor system.

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12

Dai, Y. D., M. J. Hu, L. L. Guo, M. H. Cao, and H. X. Liu. "The Band Structure Analysis of the Hybrid Compound (C₄H₉NH₃)₂Gel₄." Solid State Phenomena 111 (April 2006): 51–54. http://dx.doi.org/10.4028/www.scientific.net/ssp.111.51.

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The organic-inorganic hybrid compounds have attracted much attention for their interesting structures and various properties. In present work, we concentrated on the band structures of the hybrid compound (C4H9NH3)2GeI4 and tried to find out the relations between the geometry structure and the properties. The hybrid’s primitive cell was large and including too many atoms, so it was difficult to have a direct and clear analysis on the band structure. The hybrids’ DOS and PDOS were analyzed instead, as it was another effective way to analyze the band structure of the hybrid especially when the band structure was complicated. The model of (C4H9NH3)2GeI4 was set up, and the program based on the first principle had been employed to calculate its band structure. The difference of iodine’s PDOS caused by structure was also discussed.

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13

Khirunenko, Lyudmila I., Yu V. Pomozov, Mikhail G. Sosnin, A. V. Duvanskii, Vitor J. B. Torres, J. Coutinho, R. Jones, Patrick R. Briddon, Nikolay V. Abrosimov, and H. Riemann. "Interstitial Carbon-Related Defects in Si_1-xGe_x Alloys." Solid State Phenomena 131-133 (October 2007): 59–64. http://dx.doi.org/10.4028/www.scientific.net/ssp.131-133.59.

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The interstitial carbon impurity (CI) vibrational modes in monocrystalline Si-rich SiGe were investigated by Fourier Transform Infra Red spectroscopy and density functional modelling. The two absorption bands of CI are found to be close to those in silicon, but show shifts in opposite directions with increasing Ge content. The transversal mode band at 932 cm-1 shifts slightly to the high frequency side, while the longitudinal mode at 922 cm-1 suffers a pronounced red-shift. Each Ci-related band is found to consist of two components. An annealing of CI in Si1-xGex occures in two stage. During the first stage (210-250 K) the main components of bands anneals and revealed components grow in intensity. At T>250 K all components disappear. Two component structure of bands is suppose most likely correspond to different combinations of Si and Ge atoms in the neighbourhood of the carbon atom. The interstitial carbon defect was modelled by a supercell density-functional pseudopotential method (AIMPRO) for alloys with 4.69% Ge concentration. From energetics, it has been found that each Ge-C bond costs at least 0.4 eV in excess of a Si-C bond. However, structures where Ge atoms are second neighbors to the C atom are marginally bound, and may explain the two-component band structure in the absorption measurements. The vibrational mode frequencies taken from several randomly generated SiGe cells produce the observed opposite shifts for the transverse and longitudinal modes.

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Sekikawa, Takuya, Hiroyuki Kawai, and Yoshiaki Ōno. "Surface electronic structure of possible high-T_c surface superconductor WO₃ based on the first-principles calculation." Journal of Physics: Conference Series 2323, no. 1 (August 1, 2022): 012006. http://dx.doi.org/10.1088/1742-6596/2323/1/012006.

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Abstract The first-principles calculation is performed to investigate the surface electronic structure of WO3 in which high-Tc surface superconductivity up to Tc =120 K is observed when alkali metals are alightly doped. To take into account of the surface effect, we employ the tetragonal 14-layers slab model and find that a remarkable in-gap band with a narrow band width of 0.13 eV appears at about 0.6 eV below the conduction bands. Detailed analysis of the wave functions reveal that the in-gap band mainly consists of orbitals in the first and second layers on the surface. Therefore, the in-gap band is considered to play crucial role for the surface superconductivity in the slightly electron-doped WO3.

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15

Лабзовская, М. Э., Б. В. Новиков, А. Ю. Серов, С. В. Микушев, В. Ю. Давыдов, А. Н. Смирнов, and В. Г. Талалаев. "Оптические свойства нановискеров Cu-=SUB=-2-=/SUB=-O." Физика и техника полупроводников 56, no. 11 (2022): 1075. http://dx.doi.org/10.21883/ftp.2022.11.54258.4272.

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The optical properties of Cu2O nanowhiskers grown by the liquid method with material deposition in an electric field have been studied. The spectral lines forbidden by the selection rules for perfect Cu2O crystals were found in the Raman spectra. The nature of related phonon states is analyzed. In the photoluminescence spectra in the red and near-IR regions, broad bands of defective origin are observed. It was found that the presence of a band at 650 nm (1.9 eV) is a specific feature of the photoluminescence of nanowhiskers. Its properties are studied and possible radiation mechanisms are discussed. In the intrinsic absorption region of nanowhiskers, the photoluminescence band at 572 nm (2.17 eV) associated with band−band transitions is detected. At a low excitation level, the emission of a free exciton n = 1 of the yellow exciton series is observed with simultaneous emission of an optical phonon.

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Zhong, Rui Xia, Zi Ran Liu, Xiao Peng Meng, Ming Ya Li, and Xiao Yan Zhang. "Energy Transfer and Green/Red Phosphorescence in γ-Zn₃(PO₄)₂:Mn²⁺, Ga³⁺." Advanced Materials Research 538-541 (June 2012): 2396–400. http://dx.doi.org/10.4028/www.scientific.net/amr.538-541.2396.

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In this letter, γ-Zn3(PO4)2: Mn2+ phosphors have only one emission band centered at 620 nm while two emission bands are observed in γ-Zn3(PO4)2: Mn2+, Ga3+, which are respectively centered at 507 nm and 620 nm. The spectral overlap between the green emission band and the excitation band monitored at 620 nm, which supports the occurrence of the energy transfer from Mn2+ (CN=4) to Mn2+ (CN=6), has been studied. The influence of Ga3+ ions on luminescence and long lasting phosphorescence properties of Mn2+ in phosphor γ-Zn3(PO4)2: Mn2+, Ga3+ are also investigated. It is found that the green/red phosphorescence performance of Mn2+ ion such as brightness and duration is largely improved when Ga3+ ion is co-doped into the matrix in which Mn2+ ion acts as luminescent center and Ga3+ ion plays an important role of electron trap.

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Pan, Hong Liang, Teng Li, Shi Liang Yang, and Yi Ming Liu. "Ab Initio Study of Structural and Optical Properties of SrTi_0.5Nb_0.5O₃." Advanced Materials Research 846-847 (November 2013): 1935–38. http://dx.doi.org/10.4028/www.scientific.net/amr.846-847.1935.

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The electronic structure, including band structure, density of states ( DOS) and optical properties of SrTi0.5Nb0.5O3are calculated from the first principles of plane wave ultra soft pseudo potential technology. The calculated results reveal that due to the electron doping, the Fermi level moves into the conduction bands and the system shows metallic behavior. The optical properties are also discussed in detail.

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Yan, Xiao Song, Wan Wan Li, and Kang Sun. "White-Light-Emitting Phosphate Phosphors of SrZn₂(PO₄)₂: Eu²⁺, Mn²⁺ Synthesized through Combustion Process." Materials Science Forum 688 (June 2011): 344–48. http://dx.doi.org/10.4028/www.scientific.net/msf.688.344.

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The SrZn2(PO4)2: Eu2+, Mn2+ phosphors were synthesized through combustion process with varying mixture ratio of Eu2+, Mn2+. The SrZn2(PO4)2: Eu2+, Mn2+ phosphor presents three emission bands under 365nm radiation: the blue emission band of 416 nm from Eu2+ occupying the Sr2+ site, the green emission band of 538 nm and the red emission band of 630 nm from Mn2+ occupying two different Zn2+ sites. Compared with the SrZn2(PO4)2: Eu2+, Mn2+ phosphor prepared through solid state reaction, the luminous intensity of the phosphor is greatly improved through the combustion reaction. White emission light with a high color rending index of 84.7 can be obtained from the phosphor of SrZn2(PO4)2: Eu2+, Mn2+, and the emission color tone of the phosphor varies from blue, white, and finally yellow by increasing the ratio of the concentrations of Eu2+ and Mn2+.

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Lim, Joon Hoong. "Band Structure and Thermoelectric Properties of Ni_(x)Zn_(1-x)Fe₂O₄." Solid State Phenomena 317 (May 2021): 28–34. http://dx.doi.org/10.4028/www.scientific.net/ssp.317.28.

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Thermoelectric materials has made a great potential in sustainable energy industries, which enable the energy conversion from heat to electricity. The band structure and thermoelectric properties of Ni(x)Zn(1-x)Fe2O4 have been investigated. The bulk pellets were prepared from analytical grade ZnO, NiO and Fe2O3 powder using solid-state method. It was possible to obtain high thermoelectric properties of Ni(x)Zn(1-x)Fe2O4 by controlling the ratios of dopants and the sintering temperature. XRD analysis showed that the fabricated samples have a single phase formation of cubic spinel structure. The thermoelectric properties of Ni(x)Zn(1-x)Fe2O4 pellets improved with increasing Ni. The electrical conductivity of Ni(x)Zn(1-x)Fe2O4 pellets decreased with increasing Ni content. The electrical conductivity of Ni(x)Zn(1-x)Fe2O4 (x = 0.0) is (0.515 x10-3 Scm-1). The band structure shows that ZnxCu1-xFe2O4 is an indirect band gap material with the valence band maximum (VBM) at M and conduction band minimum (CBM) at A. The band gap of Ni(x)Zn(1-x)Fe2O4 increased with increasing Ni content. The increasing band gap correlated with the lower electrical conductivity. The thermal conductivity of Ni(x)Zn(1-x)Fe2O4 pellets decreased with increasing Ni content. The presence of Ni served to decrease thermal conductivity by 8 Wm-1K-1 over pure samples. The magnitude of the Seebeck coefficient for Ni(x)Zn(1-x)Fe2O4 pellets increased with increasing amounts of Ni. The figure of merit for Ni(x)Zn(1-x)Fe2O4 pellets and thin films was improved by increasing Ni due to its high Seebeck coefficient and low thermal conductivity.

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Zhao, Dong-Hui, Zi-Liang Tian, Hang Xu, Jin-Xin Chen, Hao Zhu, Lin Chen, Qing-Qing Sun, and David Wei Zhang. "Band alignment of atomic layer deposited MoS₂/(HfO₂)_x(Al₂O₃)_1−x heterojunctions for device applications." Journal of Physics D: Applied Physics 55, no. 22 (March 3, 2022): 225102. http://dx.doi.org/10.1088/1361-6463/ac570f.

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Abstract In this work, wafer-scale continuous and uniform MoS2/(HfO2) x (Al2O3)1−x (HfAlO) heterojunctions were prepared by atomic layer deposition. The energy band alignment of MoS2/HfAlO heterojunctions was systematically investigated using x-ray photoelectron spectroscopy. The valence band offsets were deduced to be 3.19 ± 0.1, 3.01 ± 0.1, 2.94 ± 0.1, and 2.91 ± 0.1 eV for the heterojunctions of MoS2/Al2O3, MoS2/(HfO2)0.45(Al2O3)0.55, MoS2/(HfO2)0.60(Al2O3)0.40 and MoS2/(HfO2)0.78(Al2O3)0.22, while the conduction band offsets were measured as 2.51 ± 0.1, 2.17 ± 0.1, 2.00 ± 0.1, and 1.85 ± 0.1 eV, respectively. All MoS2/HfAlO interfaces exhibited type-I band alignment. Furthermore, a MoS2 field-effect transistor with HfAlO as the gate dielectric layer was fabricated, and the gate leakage of the device was only a few picoamperes, which ensured high reliability and low power consumption. These encouraging results suggest that HfAlO is a promising dielectric material for applications in MoS2-based electronics and optoelectronics.

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Hwang, Seong-Mee, Sang-il Kim, Min-Su Heo, Kiyoung Lee, Heesun Yang, Won-Seon Seo, and Hyun-Sik Kim. "Characterization of Electronic Transport Properties of Narrow-Band Gap Fe(Se1-xTex)2 Alloys via the Two-Band Model." Korean Journal of Metals and Materials 61, no. 2 (February 5, 2023): 98–106. http://dx.doi.org/10.3365/kjmm.2023.61.2.98.

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Environmentally sustainable thermoelectric technologies can be more broadly applied in industries once the performance of thermoelectric materials is improved. Several approaches have been proposed to improve the electronic transport properties of thermoelectric materials. The effects of each approach on the electronic properties can be evaluated by changes in the band parameters. The Single Parabolic Band (SPB) model has been widely used to determine the effect of different materials engineering strategies on band parameters, such as the density-of-states effective mass and deformation potential. However, when the material has a narrow band gap, the Two-Band (TB) model better describes the changes in band parameters, as it includes the bipolar conduction from the minority carrier band. Here, the band parameters of previously reported Fe(Se1-xTex)2 (x = 0, 0.2, 0.6, 0.8, 1) alloys, whose band gap significantly decreases with x, have been estimated using the SPB and TB models. While the x-dependent band parameters obtained via the SPB model varied abruptly with x, all the band parameters estimated by the TB model changed linearly with x. The abruptness observed in the band parameters of the SPB model can be attributed to artifacts reflected in the single band, which occurs when the minority carrier band and band gap change are not included. The bipolar thermal conductivity of Fe(Se1-xTex)2 alloys was also calculated using the TB model, and is understood in terms of changes in the weighted mobility ratio, Hall carrier concentration, and band gap in terms of alloy composition, x.

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Донаев, С. Б. "Получение наноразмерных пленок CoSiO на поверхности СoSi-=SUB=-2-=/SUB=- методом ионной имплантации." Письма в журнал технической физики 46, no. 16 (2020): 16. http://dx.doi.org/10.21883/pjtf.2020.16.49847.18293.

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The morphology, composition, and electronic properties of the CoSiO film obtained on the CoSi2/Si(111) surface by implantation of O2+ ions in combination with annealing were studied. The parameters of energy bands are determined and information on the density of state of electrons of the valence band and conduction band is obtained. In particular, it was shown that the band gap of this film is ~ 2.4 eV.

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23

Лунин, Л. С., М. Л. Лунина, Д. Л. Алфимова, А. С. Пащенко, Н. А. Яковенко, and О. С. Пащенко. "Варизонные гетероструктуры Al-=SUB=-x-=/SUB=-In-=SUB=-y-=/SUB=-Ga-=SUB=-1-x-y-=/SUB=-P-=SUB=-z-=/SUB=-As-=SUB=-1-z-=/SUB=-/GaAs для фотоэлектрических преобразователей." Письма в журнал технической физики 47, no. 20 (2021): 27. http://dx.doi.org/10.21883/pjtf.2021.20.51610.18907.

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The AlxInyGa1-x-yPzAs1-z/GaAs graded-gap heterostructures were grown by the temperature gradient zone recrystallization with a liquid zone reciprocating, where energy band gap varied from 1.43 to 2.2 eV. The influence of technological parameters on the varying in the energy band gap of the grown AlxInyGa1-x-yPzAs1-z/GaAs solid solutions is investigated. In the p-AlxInyGa1-x-yPzAs1-z/n-GaAs heterostructure, the maximum energy band gap gradient of 10490 eV/cm is reached, and an increase in the external quantum efficiency is shown in the wavelength range of 500-900 nm.

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24

Milutinović, A., Z. Dohčević-Mitrović, Diana Nesheva, M. Šćepanović, M. Grujić-Brojčin, and Zoran V. Popović. "Infrared and Photoluminescence Study of Rapidly Thermally Annealed SiO_x Thin Films." Materials Science Forum 555 (September 2007): 309–14. http://dx.doi.org/10.4028/www.scientific.net/msf.555.309.

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Silicon suboxide, SiOx thin films with different oxygen contents (1.15≤x≤1.70) were prepared by thermal evaporation of silicon monoxide at a residual oxygen pressure of 1·10-3 Pa and deposition rates of 0.2, 1.0, 3.0 and 6.0 nm/s. Rapid thermal annealing (RTA) of films was carried out at 1100°C in vacuum for 15 and 30 s and the films were analyzed by infrared (FTIR) and photoluminescence (PL) spectroscopy. In the FTIR spectra of SiOx annealed samples, a blue-shift of the stretching band with initial oxygen content, x, is observed. This band is shifted to a much lower frequency with prolonged RTA time. This behavior can be interpreted in terms of the partial decrease of oxygen content and film density upon annealing in vacuum. With annealing time increase a new band at 1106 cm-1 appears. Therefore, infrared spectra of SiOx films are significantly affected by the oxygen content. PL spectra of these films also change drastically with increasing annealing time. In the PL spectra of films annealed for 15 s two bands are easily visible: broad redorange band at 2.2 eV and a green band at 2.4 eV, while for 30 s annealing only low-energy band exists. Green band is connected with the defects in the SiOx matrix while red-orange band can be deconvoluted into several bands at 2.0, 2.3 and 2.5 eV. Two types of defects can be responsible for the PL band at about 2 eV: defects in a-Si (amorphous silicon) nanoparticles separated during RTA, and nonbridging oxygen hole recombination centers (NBOHC) formed by loosing of oxygen during RTA. The PL band at 2.3 eV is associated with the defects formed at a-Si/SiOx interfaces while a hardly visible band at 2.5 eV is related to the defects connected with the oxygen deficiency formed in the SiOx matrix during RTA.

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25

Daghero, Dario, R. S. Gonelli, A. Calzolari, G. A. Ummarino, M. Tortello, V. A. Stepanov, N. D. Zhigadlo, K. Rogacki, J. Karpinski, and M. Putti. "Point-Contact Spectroscopy in Doped and Irradiated MgB₂." Advances in Science and Technology 47 (October 2006): 75–81. http://dx.doi.org/10.4028/www.scientific.net/ast.47.75.

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We review recent results of point-contact spectroscopy (PCS) in doped (with Al, C or Mn) and neutron-irradiated samples of the two-band superconductor MgB2. The aim of these measurements was to clarify the role of inter- and intra-band scattering, and to test the theoretical expectations about the effects of substitutions and disorder on two-band superconductivity. The gap amplitudes, Δπ and Δσ, were obtained as a function of the critical temperature of the junctions (or of the doping content) by fitting the conductance curves with the two-band BTK model. The analysis of the resulting curves within the Eliashberg theory allowed us to extract information on the partial DOSs, as well as on the scattering rates within and between the two bands. The results are discussed and compared to theoretical expectations.

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26

Bhuiyan, A. F. M. Anhar Uddin, Lingyu Meng, Hsien-Lien Huang, Jinwoo Hwang, and Hongping Zhao. "In situ MOCVD growth and band offsets of Al₂O₃ dielectric on β-Ga₂O₃ and β-(Al_xGa_1−x)₂O₃ thin films." Journal of Applied Physics 132, no. 16 (October 28, 2022): 165301. http://dx.doi.org/10.1063/5.0104433.

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The in situ metalorganic chemical vapor deposition (MOCVD) growth of Al2O3 dielectrics on β-Ga2O3 and β-(AlxGa1−x)2O3 films is investigated as a function of crystal orientations and Al compositions of β-(AlxGa1−x)2O3 films. The interface and film qualities of Al2O3 dielectrics are evaluated by high-resolution x-ray diffraction and scanning transmission electron microscopy imaging, which indicate the growth of high-quality amorphous Al2O3 dielectrics with abrupt interfaces on (010), (100), and [Formula: see text] oriented β-(AlxGa1−x)2O3 films. The surface stoichiometries of Al2O3 deposited on all orientations of β-(AlxGa1−x)2O3 are found to be well maintained with a bandgap energy of 6.91 eV as evaluated by high-resolution x-ray photoelectron spectroscopy, which is consistent with the atomic layer deposited (ALD) Al2O3 dielectrics. The evolution of band offsets at both in situ MOCVD and ex situ ALD deposited Al2O3/β-(AlxGa1−x)2O3 is determined as a function of Al composition, indicating the influence of the deposition method, orientation, and Al composition of β-(AlxGa1−x)2O3 films on resulting band alignments. Type II band alignments are determined at the MOCVD grown Al2O3/β-(AlxGa1−x)2O3 interfaces for the (010) and (100) orientations, whereas type I band alignments with relatively low conduction band offsets are observed along the [Formula: see text] orientation. The results from this study on MOCVD growth and band offsets of amorphous Al2O3 deposited on differently oriented β-Ga2O3 and β-(AlxGa1−x)2O3 films will potentially contribute to the design and fabrication of future high-performance β-Ga2O3 and β-(AlxGa1−x)2O3 based transistors using MOCVD in situ deposited Al2O3 as a gate dielectric.

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27

Yun, Jiang Ni, Tieen Yin, and Zhi Yong Zhang. "First-Principles Calculation of the Electronic Structure of SrTiO₃." Advanced Materials Research 750-752 (August 2013): 1199–202. http://dx.doi.org/10.4028/www.scientific.net/amr.750-752.1199.

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The electronic structure, band structure, density of states (DOS) and electronic density difference of paraelectric SrTiO3 in the cubic phase were performed by the first-principles calculation based on the density functional theory (DFT). The energy levels of high symmetry points in the Brillouin zone were listed and Mulliken population analysis was performed for valence bond structures. The top valence band of SrTiO3 is at the R point, and the minimum of the conduction bands is at the Γ point. The calculated value for indirect band gap is 1.84eV in the Brillouin zone. As in other perovskite ABO3 ferroelectrics, the population analysis, DOS and electron density difference show that there is a very strong hybridization between the Ti3d and O2p states in the valence bands, which is responsible for the ferroelectricity tendency.

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28

Jurczyk, Mieczyslaw, Marek Nowak, Izabela Okonska, Lewlaw Smardz, and A. Szajek. "Nanocomposite Hydride LaNi₅/A- and Mg₂Ni/A-Type Materials (A=C, Cu, Pd)." Materials Science Forum 610-613 (January 2009): 472–79. http://dx.doi.org/10.4028/www.scientific.net/msf.610-613.472.

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In this work, we have synthesized LaNi5/A and Mg2Ni/A (A = graphite, copper or palladium) nanocomposites. The A elements were distributed on the surface of ball milled alloy particles homogenously and role of these particles is to catalyze the dissociation of molecular hydrogen on the surface of studied alloy. Mechanical coating with graphite or palladium effectively reduced the degradation rate of the studied electrode materials. Results showed a significant broadening of the valence bands of studied nanocomposites compared to those obtained by theoretical band calculations. The reasons responsible for the band broadening of the nanocrystalline LaNi5- and Mg2Ni-type alloys are probably associated with a strong deformation of the nanocrystals in the mechanically alloyed (MA) samples. Normally the interior of the nanocrystal is constrained and the distances between atoms located at the grain boundaries expanded. The valence band spectra of the MA samples could be also broadened due to an additional disorder introduced during formation of the nanocrystalline structure.

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29

Xia, Xinyi, Jian-Sian Li, Md Irfan Khan, Kamruzzaman Khan, Elaheh Ahmadi, David C. Hays, Fan Ren, and S. J. Pearton. "Band alignment of sputtered and atomic layer deposited SiO₂ and Al₂O₃ on ScAlN." Journal of Applied Physics 132, no. 23 (December 21, 2022): 235701. http://dx.doi.org/10.1063/5.0131766.

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The band alignments of two candidate dielectrics for ScAlN, namely, SiO2 and Al2O2, were obtained by x-ray photoelectron spectroscopy. We compared the effect of deposition method on the valence band offsets of both sputtered and atomic layer deposition films of SiO2 and Al2O3 on Sc0.27Al0.73 N (bandgap 5.1 eV) films. The band alignments are type I (straddled gap) for SiO2 and type II (staggered gap) for Al2O3. The deposition methods make a large difference in relative valence band offsets, in the range 0.4–0.5 eV for both SiO2 and Al2O3. The absolute valence band offsets were 2.1 or 2.6 eV for SiO2 and 1.5 or 1.9 eV for Al2O3 on ScAlN. Conduction band offsets derived from these valence band offsets, and the measured bandgaps were then in the range 1.0–1.1 eV for SiO2 and 0.30–0.70 eV for Al2O3. These latter differences can be partially ascribed to changes in bandgap for the case of SiO2 deposited by the two different methods, but not for Al2O3, where the bandgap as independent of deposition method. Since both dielectrics can be selectively removed from ScAlN, they are promising as gate dielectrics for transistor structures.

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30

Yan, Xin Pei, Lan Fang Yao, and Xiong Tang. "First-Principle Calculation of the Co Doped Anatase TiO₂." Key Engineering Materials 562-565 (July 2013): 1161–65. http://dx.doi.org/10.4028/www.scientific.net/kem.562-565.1161.

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Using first-principle calculations based on density function theory (DFT), the geometry , band structure and electronic density of states of Co-doped anatase titanium dioxide (Co/TiO2) have been studied at plane wave ultra-soft pseudo-potential (PWPP). The states of the valence bands and conduction bands of pure and Co doped TiO2 with anatase structure were calculated. The density of states of pure anataseTiO2 and Co-doped TiO2 is analyzed in detail based on the calculations using the first-principles. From the calculated results, the band gaps of anataseTiO2 and Co doped TiO2 are about 2.15 and 0.78eV, respectively. It shows that Co doped anatase titanium dioxide may lead to the narrowing of the band gap in Co/TiO2. The Co doped anataseTiO2 could be a potential candidate for photocatalyst because it can enhance the photocatalytic activity of anatase TiO2.

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31

Dahal, Shiva, Gyanu Kafle, Gopi Chandra Kaphle, and Narayan Prasad Adhikari. "Study of Electronic and Magnetic Properties of CuPd, CuPt, Cu₃Pd and Cu₃Pt: Tight Binding Linear Muffin-Tin Orbitals Approach." Journal of Institute of Science and Technology 19, no. 1 (November 8, 2015): 137–44. http://dx.doi.org/10.3126/jist.v19i1.13839.

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Electronic structure of ordered alloys CuPd, CuPt, Cu3Pd and Cu3Pt have been studied using Tight Binding Linear Muffin-Tin Orbitals Atomic Sphere Approximation (TB-LMTO-ASA). For the electronic properties, we have performed band structure calculations. Our findings show that all the systems considered are metallic in nature. To know the contribution of the orbitals in the bands, the system is analyzed via fat bands which reveal most of the contributions on valence band for CuPd, CuPt, Cu3Pd and Cu3Pt is from d-orbital and on conduction band is from s and p-orbitals. We have also checked the magnetic properties of the alloys. The density of states for spin up and spin down electrons have found to be same in each and every steps, showing non-magnetic nature of CuPd, CuPt, Cu3Pd and Cu3Pt.Journal of Institute of Science and Technology, 2014, 19(1): 137-144

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32

Dumcenco, Dumitru O., Yu Chen Su, Yi Ping Wang, Kuei Yu Chen, Ying Sheng Huang, Ching Hwa Ho, and Kwong Kau Tiong. "Piezoreflectance and Raman Characterization of Mo_1−xW_xS₂ Layered Mixed Crystals." Solid State Phenomena 170 (April 2011): 55–59. http://dx.doi.org/10.4028/www.scientific.net/ssp.170.55.

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A systematic optical characterization of a series of Mo1-xWxS2 (0 ≤ x ≤ 1) layered mixed crystals grown by chemical vapour transport method were carried out by using piezoreflectance (PzR) and Raman scattering measurements. From a detailed lineshape fit of the PzR spectra over an energy range from 1.6 to 5.0 eV, the energies of the band-edge excitonic and higher lying interband transitions were determined accurately. The transition energies and their splittings vary smoothly with the tungsten composition x indicating that the nature of the band structure is similar for the Mo1-xWxS2 series compounds. The peaks of the two dominant first-order Raman-active modes, and , and several second-order bands are observed in the range of 250-450 cm-1. The peaks corresponding to mode show a one-mode type behavior, while the peaks of mode demonstrate two-mode type behavior for the entire series of Mo1-xWxS2 crystals. These behaviors were discussed on the basis of the lattice vibrational properties of 2H-MoS2 and 2H-WS2 compounds.

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33

Sherman, Alexei. "Magnetic Response of Pr_1-xLaCe_xCuO₄ in Comparison with Hole-Doped Cuprates." Solid State Phenomena 215 (April 2014): 11–16. http://dx.doi.org/10.4028/www.scientific.net/ssp.215.11.

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The magnetic susceptibility of the optimally doped Pr1-xLaCexCuO4in the superconducting state is calculated using thet-Jmodel of Cu-O planes, the Mori projection operator technique, and the dispersion of electron bands derived from photoemission experiments. The electron band folding across the antiferromagnetic Brillouin zone border, which is inherent in the crystal, leads to a commensurate low-frequency response. The same band folding causes the appearance of a supplementary spin-excitation branch, which coexists with usual spin excitations. This coexistence can explain two maxima observed in the frequency dependence of the susceptibility. The two nested spin-excitation branches lead to a comb of closely spaced peaks in momentum cuts, which presumably are not resolved in experiment, being seen as a broad commensurate peak up to 100 meV. Reasons for differences in magnetic responses of electron- and hole-doped cuprates are discussed.

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34

Jeong, Kwanghun, Jonghoon Jeon, and Junhong Park. "Sub-band attention CNN with feature evaluation for chatter detection." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 265, no. 3 (February 1, 2023): 4284–85. http://dx.doi.org/10.3397/in_2022_0612.

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In chatter detection, feature evaluation is an important task to identify mechanical systems and achieve higher classification accuracy. The importance of frequency bands is useful under various operating conditions. In this study, we propose a new methodology to identify the importance of frequency bands based on sub-band attention CNN. The sub-band attention CNN is a structure that combines the sub-band CNN and the attention layer. Unlike conventional CNNs that treat all frequency components with the same filter, the sub-band CNN processes different filters for each band. The attention layer is used to evaluate the importance of each band. The time-varying variance in frequency domain is used to extract chatter characteristics that vary greatly with time and it is used as an input for chatter detection. The useful frequency bands for chatter detection are obtained from the sub-band attention CNN. The importance of the frequency band is analyzed with the frequency response of the mechanical system.

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35

Chukova, Oksana, Sergiy G. Nedilko, Sergiy A. Nedilko, Tetiana Voitenko, Olga Gomenyuk, and Vadym Sheludko. "Study of Temperature Behavior of Luminescence Emission of LaVO₄ and La_1-xEu_xVO₄ Powders." Solid State Phenomena 230 (June 2015): 153–59. http://dx.doi.org/10.4028/www.scientific.net/ssp.230.153.

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The La1‑xEuxVO4 powders were synthesized by co-precipitation method. Emission spectra of the LaEuVO4 and La1‑xEuxVO4 powders consist of wide non-structural bands of the matrix emission and narrow spectral lines caused by inner f-f electron transitions in the Eu3+ ions, respectively. The both types of emission were studied within 8 – 300 K temperature range. Decomposition of spectra of the wide matrix emission on three bands has been carried out and temperature dependencies for each band were studied. Temperature behavior of the Eu3+ emission was investigated for lines assigned to different Eu3+ centres. Obtained dependencies are analyzed and discussed using proposed schemes of transitions in the VO43- groups and structure of the nearest surrounding of the Eu3+ emission centres.

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36

Liu, Hongxia, Xinyue Zhang, Wen Li, and Yanzhong Pei. "Advances in thermoelectric (GeTe)_x(AgSbTe₂)_{100 – x}." Chinese Physics B 31, no. 4 (March 1, 2022): 047401. http://dx.doi.org/10.1088/1674-1056/ac3cae.

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The (GeTe) x (AgSbTe2)100 – x alloys, also called TAGS-x in short, have long been demonstrated as a promising candidate for thermoelectric applications with successful services as the p-type leg in radioisotope thermoelectric generators for space missions. This largely stems from the complex band structure for a superior electronic performance and strong anharmonicity for a low lattice thermal conductivity. Utilization of the proven strategies including carrier concentration optimization, band and defects engineering, an extraordinary thermoelectric figure of merit, zT, has been achieved in TAGS-based alloys. Here, crystal structure, band structure, microstructure, synthesis techniques and thermoelectric transport properties of TAGS-based alloys, as well as successful strategies for manipulating the thermoelectric performance, are surveyed with opportunities for further advancements. These strategies involved are believed to be in principle applicable for advancing many other thermoelectrics.

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37

Zhang, Jun, Zhen Qiang Chen, Chun Hao Wang, An Ming Li, Hao Yin, and Zhen LI. "Optical Characterization of Novel Crystal Na₅Bi (WO₄)₂(MoO₄)₂ :Yb³⁺." Advanced Materials Research 787 (September 2013): 281–85. http://dx.doi.org/10.4028/www.scientific.net/amr.787.281.

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The compound-anion polycrystalline material Yb3+:Na5Bi (WO4)2(MoO4)2 was synthesized by flux method. Many characterization of XRD, DSC-TG, absorption spectrum and emission spectrum were studied. The result is shown that the new crystal belongs to Tetragonal, and space group is I41/a (88). Its melting point is 619 °C and the absorption band, emission band, center emission wavelength are about 83 nm, 50 nm, 1006 nm respectively.

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38

Sulimov, Mikhail A., Mikhail V. Yakushev, Ian Forbes, Jose M. Prieto, Alexander V. Mudryi, Juri Krustok, Paul R. Edwards, and Robert W. Martin. "A PL and PLE study of high Cu content Cu-=SUB=-2-=/SUB=-ZnSnSe-=SUB=-4-=/SUB=- films on Mo/glass and solar cells -=SUP=-*-=/SUP=-." Физика твердого тела 61, no. 5 (2019): 1001. http://dx.doi.org/10.21883/ftt.2019.05.47608.38f.

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AbstractCu_2ZnSnSe_4 (CZTSe) is amongst leading candidates for the absorber layer in sustainable solar cells. We examine CZTSe thin films with [Cu]/[Zn + Sn] of 0.99 and [Zn]/[Sn] of 1.07, deposited on Mo/glass substrates, and solar cells fabricated from these films. The bandgap ( E _ g ) of the as deposited films and solar cells was examined by photoluminescence excitation (PLE) whereas the temperature and excitation intensity dependence of photoluminescence (PL) spectra was used to examine the nature of radiative recombination. The 6 K PL spectra of CZTSe/Mo exhibit an intense broad and asymmetrical band P1 at 0.822 eV and a lower intensity band P2 at 0.93 eV. The shape of this band, high rates of blue shift with excitation intensity rise ( j -shift) j (P1) = 14 meV and j (P2) = 8 meV per decade, and red shifts of both bands with increasing temperature suggest that both bands are associated with valence band tails due to potential fluctuations caused by high populations of charged defects. The mean depth of such fluctuation γ of 24 meV was estimated from the low energy side of P1. Device processing increased E _ g , blue shifted P1, decreased its width, j -shift and the mean depth of potential fluctuations. These can be due to the annealing and/or can partly be related to KCN etching and the chemical effect of Cd, from CdS replacing copper at the CdS–CZTSe interface layer. Processing induced a new broad band P3 at 1.3 eV (quenching with E _ a = 200 meV). We attributed P3 to defects in the CdS layer.

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39

Pournia, Seyyedesadaf, Giriraj Jnawali, Ryan F. Need, Howard E. Jackson, Stephen D. Wilson, and Leigh M. Smith. "Band structure and polarization effects in photothermoelectric spectroscopy of a Bi₂Se₃ device." Applied Physics Letters 120, no. 12 (March 21, 2022): 122110. http://dx.doi.org/10.1063/5.0075924.

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Bi2Se3 is a prototypical topological insulator, which has a small bandgap (∼0.3 eV) and topologically protected conducting surface states. This material exhibits quite strong thermoelectric effects. Here, we show in a mechanically exfoliated thick (∼100 nm) nanoflake device that we can measure the energy dependent optical absorption through the photothermoelectric effect. Spectral signatures are seen for a number of optical transitions between the valence and conduction bands, including a broad peak at 1.5 eV, which is likely dominated by bulk band-to-band optical transitions but is at the same energy as the well-known optical transition between the two topologically protected conducting surface states. We also observe a surprising linear polarization dependence in the response of the device that reflects the influence of the metal contacts.

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40

Millers, Donats, Larisa Grigorjeva, Witold Łojkowski, and A. Opalińska. "Luminescence of ZrO₂ Nanocrystals." Solid State Phenomena 106 (September 2005): 103–8. http://dx.doi.org/10.4028/www.scientific.net/ssp.106.103.

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The luminescence of nanocrystalline tetragonal and cubic ZrO2 has been investigated. The tetragonal undoped ZrO2 revealed two luminescence bands, at ~2.0 eV and 2.7 eV , but only one band at ~2.7 eV was observed from cubic ZrO2. This luminescence was shown to be intrinsic. The regular zirconium-oxygen complex excited state is suggested as being responsible for intrinsic luminescence.

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41

Yang, Fazhi, Giao Ngoc Phan, Renjie Zhang, Jin Zhao, Jiajun Li, Zouyouwei Lu, John Schneeloch, et al. "Fe_1+yTe_xSe1-_x: A Delicate and Tunable Majorana Material." Chinese Physics Letters 40, no. 1 (January 1, 2023): 017401. http://dx.doi.org/10.1088/0256-307x/40/1/017401.

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We report the observation for the pz electron band and the band inversion in Fe1 + y Te x Se1–x with angle-resolved photoemission spectroscopy. Furthermore, we found that excess Fe (y > 0) inhibits the topological band inversion in Fe1 + y Te x Se1 – x , which explains the absence of Majorana zero modes in previous reports for Fe1+y Te x Se1 – x with excess Fe. Based on our analysis of different amounts of Te doping and excess Fe, we propose a delicate topological phase in this material. Thanks to this delicate phase, one may be able to tune the topological transition via applying lattice strain or carrier doping.

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42

Pan, Hong Liang, Teng Li, Shi Liang Yang, and Yi Ming Liu. "Electronic Structure and Optical Properties of SrTi_0.5Zr_0.5O₃." Advanced Materials Research 846-847 (November 2013): 1919–22. http://dx.doi.org/10.4028/www.scientific.net/amr.846-847.1919.

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The electronic-energy band structure and optical properties of SrTi0.5Zr0.5O3are calculated by the pseudo-potential plane wave (PP-PW) mehod with the generalized gradient approximation (GGA). The energy band structure, density of states (DOS) are obtained. The optical properties including the dielectric function, reflectivity, absorption spectrum, extinction coefficient, energy-loss spectrum and refractive index are also discussed.

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43

Yang, Shi Liang, Hong Liang Pan, Teng Li, and Yi Ming Liu. "Electronic Structure and Optical Properties of BaTi_0.75Nd_0.25O₃." Advanced Materials Research 846-847 (November 2013): 1923–26. http://dx.doi.org/10.4028/www.scientific.net/amr.846-847.1923.

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The electronic-energy band structure and optical properties of BaTi0.75Nd0.25O3are calculated by the pseudo-potential plane wave (PP-PW) mehod with the generalized gradient approximation (GGA). The energy band structure, density of states (DOS) are obtained. The optical properties including the dielectric function, reflectivity, absorption spectrum, extinction coefficient, energy-loss spectrum and refractive index are also discussed.

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44

Chukova, Oksana, Sergiy G. Nedilko, Sergiy A. Nedilko, Vasyl Sherbatsky, and Tetiana Voitenko. "Comparable Structural and Luminescent Characterization of the La_1-xEu_xVO₄ Solid Solutions Synthesized by Solid State and Co-Precipitation Methods." Solid State Phenomena 200 (April 2013): 186–92. http://dx.doi.org/10.4028/www.scientific.net/ssp.200.186.

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Luminescence properties of the two series of the La1-xEuxVO4 (x ranges from to 0.3) solid solutions synthesized by the solid state and co-precipitation methods were investigated.. Luminescence spectra of the investigated samples consist of narrow spectral lines caused by inner f - f electron transitions in the impurity Eu3+ ions. Excitation spectra consist of three main bands those correspond to different types of transitions in the investigated matrices. There are O - Eu3+ charge transfer transitions, band-to-band transitions in the matrix of the vanadate compounds and electron transitions in the VO43- vanadate anion. Dependences of the structure and luminescence properties on rate compositions and method of synthesis were studied. Origins of the observed differences between luminescence characteristics of the samples obtained by two different methods are discussed.

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45

Mi, Ling Ling, and Guo Zhong Zhao. "First Principles Study of the Electronic Structure of In_1-xGa_xN." Advanced Materials Research 502 (April 2012): 144–48. http://dx.doi.org/10.4028/www.scientific.net/amr.502.144.

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The In1-xGaxN electronic structure is calculated by First principle based on density functional theory. The energy band structures and density of state is calculated. It can be found that the hybridization of the Ga4s4p and N2p，In5s5p is stronger than that of N2p，In5s5p in the undoped system. And it leads to the valence band moving towards to low energy level and the conduction band moving to the high energy level. Correspondingly, we can find a larger band gap than that of undoped InN. In conclusion, the wide band gap lead to the blue shift and Moss-Burstein effect occurs near the top valence band.

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46

Garigapati, Navya Sri, Lasse Södergren, Patrik Olausson, and Erik Lind. "Strained In_xGa₍₁₋_x₎As/InP near surface quantum wells and MOSFETs." Applied Physics Letters 120, no. 9 (February 28, 2022): 092105. http://dx.doi.org/10.1063/5.0073918.

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We present electronic band structure properties of strained In xGa(1− x)As/InP heterostructure near surface quantum wells oriented in the (100) crystallographic direction using eight-band [Formula: see text] theory, which are further parameterized by an energy level, effective mass, and nonparabolicity factor. The electronic band structure parameters are studied for the well composition of 0.2 ≤ x ≤ 1 and thickness from 5 to 13 nm. The bandgap and effective mass of the strained wells are increased for x >0.53 due to compression strain and decreased for x < 0.53 due to tensile strain as compared to that of unstrained wells. The calculated band structure parameters are utilized in modeling long channel In0.71Ga0.29As/InP quantum well MOSFETs, and the model is validated against measured I–V and low frequency C–V characteristics at room temperature and cryogenic temperature. Exponential band tails and first- and second-order variation of the charge centroid capacitance and interface trap density are included in the electrostatic model. The Urbach parameter obtained in the model is E0 = 9 meV, which gives subthreshold swing (SS) of 18 mV/dec at T = 13 K and agrees with the measured SS of 19 mV/dec. Interface trap density is approximately three orders higher at T = 300 K compared to T = 13 K due to multi-phonon activated traps. This model emphasizes the importance of considering disorders in the system in developing device simulators for cryogenic applications.

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47

Susilo, Resta A., Yu Liu, Hongwei Sheng, Hongliang Dong, Raimundas Sereika, Bongjae Kim, Zhixiang Hu, et al. "A tunable band gap of the layered semiconductor Zn₃In₂S₆ under pressure." Journal of Materials Chemistry C 10, no. 5 (2022): 1825–32. http://dx.doi.org/10.1039/d1tc05098b.

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A highly tunable band gap of the layered semiconductor Zn3In2S6 under pressure is reported. The change in the band gap is strongly coupled to the variation and transformation of the crystal structure.

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48

Krolik, Jeffrey, and Granger Hickman. "Joint range-velocity estimation with continuous active sonar." Journal of the Acoustical Society of America 152, no. 4 (October 2022): A243. http://dx.doi.org/10.1121/10.0016147.

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Active sonars using linear frequency-modulated (LFM) continuous waveforms are typically processed in sub-bands to facilitate high target range update rates. Target range-rate is then estimated using incoherently processed matched-filter outputs from each sub-band as input to a tracker. Target returns can easily be confused with clutter because sub-band width is typically chosen to avoid decoherence caused by target and/or platform motion. In this paper, we present methods for joint range-velocity estimation which allows for coherent combination of sub-band outputs and accounts for target/platform motion. The approach involves pre-filtering beamformed sub-band outputs using the transmitted LFM waveform, match-filtering each frequency-domain pre-filtered sub-band under a range-velocity hypothesis, and coherently combining the results. A maximum likelihood estimate (MLE) of range-velocity is formed which involves adaptively suppressing clutter and noise using an estimate of sub-band clutter covariance matrices. Simulation results are presented which indicate that joint range-velocity estimation using coherent processing across sub-bands offers a significant improvement over conventional methods and allows for more flexible selection of sub-band processing bandwidth. Moreover, the approach lends itself to handling the case of partial coherence across sub-bands and offers the potential for improved discrimination of slowly moving targets versus clutter discretes. Work supported by ONR.

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49

Gong, Jiarui, Zheyang Zheng, Daniel Vincent, Jie Zhou, Jisoo Kim, Donghyeok Kim, Tien Khee Ng, Boon S. Ooi, Kevin J. Chen, and Zhenqiang Ma. "Interfacial band parameters of ultrathin ALD–Al₂O₃, ALD–HfO₂, and PEALD–AlN/ALD–Al₂O₃ on c-plane, Ga-face GaN through XPS measurements." Journal of Applied Physics 132, no. 13 (October 7, 2022): 135302. http://dx.doi.org/10.1063/5.0106485.

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Ultrathin oxides (UOs) and ultrathin nitrides (UNs) play a crucial role in forming lattice-mismatched semiconductor heterostructures that are fabricated by using semiconducting grafting approach. The grafting approach has shown its great potential to realize GaN-based heterojunction bipolar transistors by fulfilling the missing high-performance p-type nitrides with other p-type semiconductors. A handful of UO and UN dielectrics readily available by atomic layer deposition (ALD) satisfy the requirements of double-sided surface passivation and quantum tunneling for semiconductor grafting. Due to the states existing between the UO or UN conduction band and that of the GaN, the ALD deposited UO or UN layer can generate significant effects on the surface band-bending of GaN. Understanding the band parameters of the interface between UO or UN and c-plane Ga-face GaN can guide the selection of interfacial dielectrics for grafted GaN-based devices. In this study, we performed x-ray photoelectron spectroscopy measurements to obtain the band-bending properties on c-plane, Ga-face GaN samples coated by different ALD cycles of ultrathin-HfO2 or ultrathin AlN. The valence band spectra of GaN coated with ultrathin-ALD–Al2O3, ALD–HfO2, or PEALD–AlN/ALD–Al2O3 were further analyzed to calculate the valence and conduction band offsets between the ALD dielectrics and the Ga-face GaN under different thicknesses and post-deposition annealing conditions of the dielectrics.

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Jiao, Jun Rong, Jia Heng Wang, Chang Wei Gong, Yue Sheng Chai, and Wei Shao. "Structural, Optical and Magnetic Properties of W-Doped TiO₂." Applied Mechanics and Materials 556-562 (May 2014): 330–34. http://dx.doi.org/10.4028/www.scientific.net/amm.556-562.330.

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Based on the density functional theory method, the ab initio calculation with GGA+U was performed to investigate the electronic structure and properties of W-doped TiO2. The results indicated that W-doping induced ferromagnetism and shifted the absorption spectra to visible light region. The ferromagnetism derived from the spin-split of O 2p and W 5d caused by p–d orbit hybridization. Several impurity bands under the conduction band decreased the band gap.

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Journal articles on the topic 'Sub band'

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