Relevant bibliographies by topics / Phase Change Random Access Memory

Contents

  1. Journal articles
  2. Dissertations / Theses
  3. Book chapters
  4. Conference papers

Academic literature on the topic 'Phase Change Random Access Memory'

Author: Grafiati
Published: 4 June 2021
Last updated: 6 September 2023

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Journal articles on the topic "Phase Change Random Access Memory"

1

SONG, ZhiTang, LiangCai WU, Feng RAO, SongLin FENG, and XiLin ZHOU. "Study of phase change materials for phase change random access memory." SCIENTIA SINICA Physica, Mechanica & Astronomica 46, no. 10 (September 6, 2016): 107309. http://dx.doi.org/10.1360/sspma2016-00216.

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Raoux, S., G. W. Burr, M. J. Breitwisch, C. T. Rettner, Y. C. Chen, R. M. Shelby, M. Salinga, et al. "Phase-change random access memory: A scalable technology." IBM Journal of Research and Development 52, no. 4.5 (July 2008): 465–79. http://dx.doi.org/10.1147/rd.524.0465.

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Lee, Hock, textscShi Luping, textscZhao Rong, textscYang Hongxin, textscLim Kian Guan, textscLi Jianming, and textscChong Tow Chong. "Elevated-Confined Phase-Change Random Access Memory Cells." Japanese Journal of Applied Physics 49, no. 4 (April 20, 2010): 04DD16. http://dx.doi.org/10.1143/jjap.49.04dd16.

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Kim, Young-Tae, Young-Nam Hwang, Keun-Ho Lee, Se-Ho Lee, Chang-Wook Jeong, Su-Jin Ahn, Fai Yeung, et al. "Programming Characteristics of Phase Change Random Access Memory Using Phase Change Simulations." Japanese Journal of Applied Physics 44, no. 4B (April 21, 2005): 2701–5. http://dx.doi.org/10.1143/jjap.44.2701.

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Wang, Qiang, Gang Niu, Wei Ren, Ruobing Wang, Xiaogang Chen, Xi Li, Zuo‐Guang Ye, Ya‐Hong Xie, Sannian Song, and Zhitang Song. "Phase Change Random Access Memory for Neuro‐Inspired Computing." Advanced Electronic Materials 7, no. 6 (March 17, 2021): 2001241. http://dx.doi.org/10.1002/aelm.202001241.

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Kim, Sung Soon, Jun Hyun Bae, Woo Hyuck Do, Kyun Ho Lee, Young Tae Kim, Young Kwan Park, Jeong Taek Kong, and Hong Lim Lee. "Thermal Stress Model for Phase Change Random Access Memory." Solid State Phenomena 124-126 (June 2007): 37–40. http://dx.doi.org/10.4028/www.scientific.net/ssp.124-126.37.

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Thermal stress model considering the effect of phase transformation is proposed for Phase-Change Random Access Memory (PRAM). The results of simulation show that the high level of stress is generated on the junction where Ge2Sb2Te5(GST), TiN and SiO2 meet together. The high level of stress can also be observed in the interface between TiN and SiO2. From simulation results, it can be predictable that delamination between GST and TiN can occur during operation of PRAM. It is expected that the simulation model, which has been developed in this research, is very useful tool for PRAM device design.
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Kim, Kyung Soo, Jongho Lee, and Il Hwan Cho. "Highly Scalable Vertical Channel Phase Change Random Access Memory." Japanese Journal of Applied Physics 50, no. 5R (May 1, 2011): 050206. http://dx.doi.org/10.7567/jjap.50.050206.

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Miao, X. S., L. P. Shi, H. K. Lee, J. M. Li, R. Zhao, P. K. Tan, K. G. Lim, H. X. Yang, and T. C. Chong. "Temperature Dependence of Phase-Change Random Access Memory Cell." Japanese Journal of Applied Physics 45, no. 5A (May 9, 2006): 3955–58. http://dx.doi.org/10.1143/jjap.45.3955.

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Kim, Kyung Soo, Jongho Lee, and Il Hwan Cho. "Highly Scalable Vertical Channel Phase Change Random Access Memory." Japanese Journal of Applied Physics 50, no. 5 (May 6, 2011): 050206. http://dx.doi.org/10.1143/jjap.50.050206.

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Lee, Jung-Min, Yuta Saito, Yuji Sutou, Junichi Koike, Jin Won Jung, Masashi Sahashi, and Yun-Heub Song. "Multiple phase change structure for the scalable phase change random access memory array." Japanese Journal of Applied Physics 53, no. 4 (March 28, 2014): 041801. http://dx.doi.org/10.7567/jjap.53.041801.

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Dissertations / Theses on the topic "Phase Change Random Access Memory"

1

Seong, Nak Hee. "A reliable, secure phase-change memory as a main memory." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/50123.

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The main objective of this research is to provide an efficient and reliable method for using multi-level cell (MLC) phase-change memory (PCM) as a main memory. As DRAM scaling approaches the physical limit, alternative memory technologies are being explored for future computing systems. Among them, PCM is the most mature with announced commercial products for NOR flash replacement. Its fast access latency and scalability have led researchers to investigate PCM as a feasible candidate for DRAM replacement. Moreover, the multi-level potential of PCM cells can enhance the scalability by increasing the number of bits stored in a cell. However, the two major challenges for adopting MLC PCM are the limited write endurance cycle and the resistance drift issue. To alleviate the negative impact of the limited write endurance cycle, this thesis first introduces a secure wear-leveling scheme called Security Refresh. In the study, this thesis argues that a PCM design not only has to consider normal wear-out under normal application behavior, most importantly, it must take the worst-case scenario into account with the presence of malicious exploits and a compromised OS to address the durability and security issues simultaneously. Security Refresh can avoid information leak by constantly migrating their physical locations inside the PCM, obfuscating the actual data placement from users and system software. In addition to the secure wear-leveling scheme, this thesis also proposes SAFER, a hardware-efficient multi-bit stuck-at-fault error recovery scheme which can function in conjunction with existing wear-leveling techniques. The limited write endurance leads to wear-out related permanent failures, and furthermore, technology scaling increases the variation in cell lifetime resulting in early failures of many cells. SAFER exploits the key attribute that a failed cell with a stuck-at value is still readable, making it possible to continue to use the failed cell to store data; thereby reducing the hardware overhead for error recovery. Another approach that this thesis proposes to address the lower write endurance is a hybrid phase-change memory architecture that can dynamically classify, detect, and isolate frequent writes from accessing the phase-change memory. This proposed architecture employs a small SRAM-based Isolation Cache with a detection mechanism based on a multi-dimensional Bloom filter and a binary classifier. The techniques are orthogonal to and can be combined with other wear-out management schemes to obtain a synergistic result. Lastly, this thesis quantitatively studies the current art for MLC PCM in dealing with the resistance drift problem and shows that the previous techniques such as scrubbing or error correction schemes are incapable of providing sufficient level of reliability. Then, this thesis proposes tri-level-cell (3LC) PCM and demonstrates that 3LC PCM can be a viable solution to achieve the soft error rate of DRAM and the performance of single-level-cell PCM.
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Tsai, Min-Chuan, and 蔡旻錞. "Characteristics of Doped-GeSbTe Thin Films Applied to Phase-change Random Access Memory Devices." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/96424932293214116563.

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碩士
國立交通大學
材料科學與工程系所
98
This study investigates the microstructure and property changes of cerium (Ce)-doped GeSbTe thin films applied to phase-change random access memory (PRAM). X-ray diffraction (XRD) showed that Ce doping may stabilize the amorphous GST and inhibit the emergence of hexagonal GST phase after annealing. Transmission electron microscopy (TEM) revealed Ce doping causes the grain refinement in GST. The element mapping depicted a uniform distribution of Ce in all types of GST films, indicating that Ce atoms reside in GST in solid-solution form. Kissinger’s analysis found that the recrystallization temperature (Tc) and the activation energy (Ea) of doped-GST increase with the increase of Ce content. However, intermetallic compound (IMC) likely formed in crystalline GST with Ce concentration exceeded 10% area coverage ratio and thus led to the decrease of Ea. A significant result observed in this part of study is that the Ce doping does not alter the resistivities of amorphous and crystalline GSTs and hence the resistivity ratio (R-ratio) remains the same at about 105. This greatly benefits the preservation of signal contrast as well as the high-density signal storage and will be a distinguishing finding in recent development of PRAM materials. Isothermal experiment in conjunction with Johnson-Mehl-Avrami (JMA) analysis revealed that Ce doping suppresses the dimensionality of phase-change process in GST. This is attributed to the heterogeneous nucleation effects occurring during the phase-change process. The retention time analysis found that the retention time increases with the increase of Ce doping amount in GST. In the study of PRAM device applications, it was found that the threshold voltage (Vth) of device containing doped-GST increases with the Ce content. It nevertheless illustrates that the Ce-doped GST films are indeed feasibile to PRAM device fabrication.
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Huang, Yu-Jen, and 黃郁仁. "Characteristics of Doped-Chalcogenides and Its Nanocomposite Thin Films Applied to Phase-change Random Access Memory." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/06855262275044889682.

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博士
國立交通大學
材料科學與工程學系
100
Phase-change random access memory (PRAM) has been widely recognized as the next-generation electronic data storage media. In this study, a self-assembly in-situ electrical property measurement system and dynamic/static I–V measurement system were adopted to study the phase-change kinetics and I–V characterization of Ge2Sb2Te5 (GST) thin films doped with molybdenum (Mo), nitrogen (N) and cerium (Ce) as well as the AgInSbTe (AIST) and AIST-SiO2 nanocomposite thin films. The applicability of these chalcogenide thin films to phase-change random access memory (PRAM) was also evaluated. In the fist part of this study, phase-change behaviors of GST thin films doped with Mo and N were investigated by in-situ electrical property measurement, x-ray diffraction (XRD), and transmission electron microscopy (TEM). It was found that the Mo-doping mainly reduces the resistivity level of amorphous GST while the N-doping raises both the resistivity levels of amorphous and crystalline GST. XRD and TEM analyses indicated that the element doping stabilizes the amorphous state of GST and suppresses the grain growth in GST films. This resulted in the increase of recrysatllization temperature (Tc) and activation energy (Ea) of amorphous-to-crystalline phase transition in GST layers as revealed by the Kissinger’s analysis. The results of data fitting into various percolation models and Johnson-Mehl-Avrami (JMA) theory indicated the heterogeneous feature of phase-transition process in GST layers that the nucleation first occurs at the air/sample interface and the recrystallization front advances into the interior of sample in a layer-by-layer manner along the direction of surface normal. As to Ce doping, XRD showed that Ce doping may stabilize the amorphous GST and inhibit the emergence of hexagonal GST phase after high-temperature annealing. TEM revealed Ce doping causes the grain refinement in GST. The element mapping depicted an almost uniform distribution of Ce in all types of GST films, indicating that Ce atoms reside in GST in solid-solution form. Kissinger’s analysis found that the Tc and the Ea of doped-GST increase with the increase of Ce content. In contrast to other metallic dopants that suppress the resistivity of amorphous GST, a significant finding in this part of study is that the Ce doping does not alter the resistivities of amorphous and crystalline GSTs and hence the resistivity ratio (R-ratio) remains the same at about 105. This greatly benefits the preservation of signal contrast as well as the high-density signal storage. Isothermal experiment in conjunction with JMA analysis revealed that Ce doping suppresses the dimensionality of phase-change process in GST. This is attributed to the heterogeneous nucleation effects occurring during the phase-change process. The retention time analysis found that the retention time increases with the increase of Ce doping amount in GST. In the study of PRAM device applications, it was found that though threshold voltage (Vth) of device containing doped-GST increases with the Ce content, it nevertheless illustrates that the Ce-doped GST films are indeed feasible to PRAM device fabrication. Second part of this study investigates the phase-transition kinetics and microstructures of AIST and AIST-SiO2 nanocomposite applied to PRAMs. In-situ electrical property measurement found that the incorporation of SiO2 escalates the Tc of nanocomposite films. Both XRD and TEM showed the grain refinement in the nanocomposite which, in turn, results in an increases of the Ea of phase transition as indicated by subsequent Kissinger’s analysis. Increase of Tc and Ea in the nanocomposite was ascribed to AIST grain refinement and hindrance to grain growth due to dispersed SiO2 particles in the sample matrix. JMA analysis revealed the decrease of Avrami exponent of nanocomposite, implying that the dispersed SiO2 particles promote the heterogeneous phase transition. Static I-V characteristics and reversible binary switching behavior of PRAM devices not only confirmed the results of microstructure characterizations, but also illustrated the feasibility of AIST and its nanocomposite layer to PRAM fabrication.
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Tsai, Hsi-Chun, and 蔡希鈞. "Development of Phase Change Random Access Memory SPICE Model and Physical Mechanism of Resistive Random Access Memory and Analysis of Effect of Extreme Ultra Violet on Heterojunction Bipolar Transistors." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/26595726550050075005.

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碩士
臺灣大學
電子工程學研究所
98
In this thesis, the first chapter is to research the EUV effect on HBTs, the device under test is a test-key made by TSMC, and irradiated with EUV at NSRRC. The DC measurement is conducted at NTU, and the AC S-parameter is measured at NDL. The results show the EUV will introduce traps in emitter-base and base-collector depletion region. The traps will enhance the generation current of base current to degrade the DC performance. The traps will delay the onset of Kirk effect to increase the frequency of unity current gain. The second part is to develop the physical mechanism of resistive random access memory (RRAM). The model interpret the forming mechanism, low resistance state (LRS) conduction, high resistance (HRS) conduction, state switching, cycling fluctuation, and multi-level operation well. However, the model cannot interpret the current density induced high temperature under LRS, and the low resistance value versus temperature measurement. Maybe the introduction of ballistic theory can interpret the phenomenon well. In the third chapter, the SPICE model development by ELDO of phase change memory (PCRAM) is developed based on previous reports. The structure with falling edge problem solved and crystallization time calibrated. The I-V and R-I curve are fit well and the cell temperature and crystallization fraction is well calculated.
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Vinod, E. M. "Investigations of Phase Change Memory Properties of Selenium Doped GeTe and Ge2Sb2Te5." Thesis, 2013. http://etd.iisc.ac.in/handle/2005/3339.

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GeTe and Ge2Sb2Te5 alloys are potential candidates for non-volatile phase change random access memories (PCRAM). For electrical data storage applications the materials should have stable amorphous and crystalline phases, fast crystallization time, low power to switch, and high crystallization activation energy (to be stable at normal operating temperatures). Phase change memories can be tuned through compositional variations to achieve sufficient phase change contrast and thermal stability for data retention. Selenium is one of the attractive choices to use as an additive material owing to its flexible amorphous structure and a variety of possible applications in optoelectronics and solar cells. GeSb2Te3Se alloy, in which 25 at.% of Se substituted for Te, show a higher room temperature resistance with respect to parent GeSb2Te4 alloy, but the transition temperature is lowered which will affect the thermal stability. The RESET current observed for Sb65Se35 alloys were reduced and the crystallization speed increased 25 % faster with respect to Ge2Sb2Te5. Alloys of Ga-Sb-Se possess advantages such as higher crystallization temperatures, better data retention, higher switching speed, lower thermal conductivity and lower melting point than the GST, but the resistance ratio is limited to about two orders of magnitude. This affects the resistance contrast and data readability. It is with this background a study has been carried out in GeTe and GeSbTe system with Se doping. Studies on structural, thermal and optical properties of these materials all through the phase transition temperatures would be helpful to explore the feasibility of phase change memory uses. Thin films along with their bulk counterparts such as (GeTe)1-x Sex ( 0 < x ≤ 0.50) and (GST)1-xSex (0 < x ≤ 0.50), including GeTe and GST alloys, have been prepared. The results are presented in four chapters apart from the Introduction and Experimental techniques chapters. The final chapter summarizes the results. Chapter 1 provides an introduction to chalcogenide glasses, phase change memory materials and their applications. The fundamental properties of amorphous solids, basic phase change properties of Ge2Sb2Te5 and GeTe alloys and their applications are presented in detail. Various doping studies on GeTe and Ge2Sb2Te5 reported in literatures are reviewed. The limitations, challenges, future and scope of the present work are presented. In chapter 2, the experimental techniques used for thin film preparation, electrical characterizations, optical characterization and surface characterizations etc. are explained. Chapter 3 deals entirely on Ge2Sb2Te5 films studied throughout the phase transition, by annealing at different temperatures. Changes in sheet resistance, optical transmission, morphology and surface bonding characteristics are analyzed. The crystallization leads to an increase of roughness and the resistance changes to three orders of magnitude at 125 oC. Optical studies show distinct changes in transmittance during phase transitions and the optical parameters are calculated. Band gap contrast and disorder variation with annealing temperatures are explained. The surface bonding characteristics studied by XPS show Ge-Te, Sb-Te bonds are present in both amorphous and crystalline phases. The temperature dependent modifications of the band structure of amorphous GST films at low temperatures have been little explored. The band gap increment of around 0.2 eV is observed at low temperature (4.2 K) compared to room temperature 300 K. Other optical parameters like Urbach energy and B1/2 are studied at different temperatures and are evaluated. The observed changes in optical band gap (Eopt) are fitted to Fan’s one phonon approximation, from which a phonon energy (ћω) corresponding to a frequency of 3.59 THz resulted. The frequency of 3.66 THz optical phonons has already been reported by coherent phonon spectroscopy experiment in amorphous GST. This opens up an indirect method of calculating the phonon frequency of the amorphous phase change materials. Chapter 4 constitutes comparison of optical, electrical and structural investigation of GST and (GST)1-xSex films. It is well known that GST alloys have vacancy in their structure, which leads to the possibility of switching between the amorphous and crystalline states with minimum damage. Added Se may occupy the vacancy or change the bonding characteristics which intern may manifest in the possibility of change in optical and electrical parameters. The structural studies show a direct amorphous to hexagonal transition in (GST)1-xSex, where x ≥ 0.10 at.%. Raman spectra of the as deposited and annealed (GST)1-xSex films show structural modifications. The infrared transmission spectra indicate a shift in absorption edges from low to high photon energy when Se concentration increases in GST. Band gap values calculated from Tauc plot show the band gap increment with Se doping. It is noted that a small amount of Se doping increases the resistance of the amorphous and crystalline phases and maintains the same orders of resistance contrast. This will be beneficial as it improves the thermal stability and reduces the write current in a device. Switching studies show an increasing threshold voltage as the Se doping concentration increases. Chapter 5 comprises compositional dependent investigations of the bulk GeTe chalcogenides alloys added with different selenium concentrations. The XRD investigations on bulk (GeTe)1-xSex (x = 0.0, 0.02, 0.10, 0.20 and 0.50 at.%) alloys show that the crystalline structure of GeTe alloys does not affect ≤ 0.20 at.% of Se concentration. With increasing amount of Se concentration the alloys gets modified in to a homogeneous amorphous structure. This result has been verified from the XRD, Raman, XPS, SEM and DSC measurements. The possibility that Se occupying the Ge vacancy sites in GeTe structure is explained. Since Se is an easy glass former, the amorphousness increases in the alloys due to new amorphous phases formed by the Se with other elements. It is shown from Raman and XPS analysis that the Ge-Te bonds exists up to Se 0.20 at.% alloys. Ge-Se and GeTe2 bonds are increasing with increasing Se at.%. Melting temperature has found decreases and the reduction in melting point may reduces the RESET current. Further studies on switching behavior may bring out its usefulness. Chapter 6 deals with studies on (GeTe)1-xSex films for phase change memory applications based on the insight received from their bulk study. Even at low at.% addition of Se makes the as prepared (GeTe)1-xSex film amorphous. At 200 oC, GeTe crystalline structure is evolved and the intensity of the peaks reduces in the alloys with increase of Se content. At 300 oC, more evolved GeTe crystalline structure is seen compared to 200 oC annealed films whereas 0.20 at.% Se alloy remain amorphous. Resistance and thermal studies shows increase in crystallization temperature. It is expected that Se sits in the vacancies of the GeTe crystalline structural formation. This may also account for the increased threshold voltages with increasing Se doping. The band gap increase with increase of Se at.% signifying the possibility of band gap tuning in the material. Possible explanation for the increased order in GeTe due to Se doping is presented. The modifications in the alloy with Se addition can be explained with the help of chemical bond energy approach. Those bonds having higher energy leads to increased average bond energy of the system and hence the band gap. The XPS core level spectra and Raman spectra investigation clearly shows the GeTe bonds are replaced by Ge-Se bonds and GeTe2 bonds. The 0.10 at.% Se alloy is found to have a higher thermal stability in the amorphous state and maintains a gigantic resistance contrast compared to other Se concentration alloys. This alloy can be considered as an ideal candidate for multilevel PCM applications. Chapter 7 summarizes the major findings from this work and the scope for future work.
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6

Vinod, E. M. "Investigations of Phase Change Memory Properties of Selenium Doped GeTe and Ge2Sb2Te5." Thesis, 2013. http://etd.iisc.ernet.in/2005/3339.

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Abstract:
GeTe and Ge2Sb2Te5 alloys are potential candidates for non-volatile phase change random access memories (PCRAM). For electrical data storage applications the materials should have stable amorphous and crystalline phases, fast crystallization time, low power to switch, and high crystallization activation energy (to be stable at normal operating temperatures). Phase change memories can be tuned through compositional variations to achieve sufficient phase change contrast and thermal stability for data retention. Selenium is one of the attractive choices to use as an additive material owing to its flexible amorphous structure and a variety of possible applications in optoelectronics and solar cells. GeSb2Te3Se alloy, in which 25 at.% of Se substituted for Te, show a higher room temperature resistance with respect to parent GeSb2Te4 alloy, but the transition temperature is lowered which will affect the thermal stability. The RESET current observed for Sb65Se35 alloys were reduced and the crystallization speed increased 25 % faster with respect to Ge2Sb2Te5. Alloys of Ga-Sb-Se possess advantages such as higher crystallization temperatures, better data retention, higher switching speed, lower thermal conductivity and lower melting point than the GST, but the resistance ratio is limited to about two orders of magnitude. This affects the resistance contrast and data readability. It is with this background a study has been carried out in GeTe and GeSbTe system with Se doping. Studies on structural, thermal and optical properties of these materials all through the phase transition temperatures would be helpful to explore the feasibility of phase change memory uses. Thin films along with their bulk counterparts such as (GeTe)1-x Sex ( 0 < x ≤ 0.50) and (GST)1-xSex (0 < x ≤ 0.50), including GeTe and GST alloys, have been prepared. The results are presented in four chapters apart from the Introduction and Experimental techniques chapters. The final chapter summarizes the results. Chapter 1 provides an introduction to chalcogenide glasses, phase change memory materials and their applications. The fundamental properties of amorphous solids, basic phase change properties of Ge2Sb2Te5 and GeTe alloys and their applications are presented in detail. Various doping studies on GeTe and Ge2Sb2Te5 reported in literatures are reviewed. The limitations, challenges, future and scope of the present work are presented. In chapter 2, the experimental techniques used for thin film preparation, electrical characterizations, optical characterization and surface characterizations etc. are explained. Chapter 3 deals entirely on Ge2Sb2Te5 films studied throughout the phase transition, by annealing at different temperatures. Changes in sheet resistance, optical transmission, morphology and surface bonding characteristics are analyzed. The crystallization leads to an increase of roughness and the resistance changes to three orders of magnitude at 125 oC. Optical studies show distinct changes in transmittance during phase transitions and the optical parameters are calculated. Band gap contrast and disorder variation with annealing temperatures are explained. The surface bonding characteristics studied by XPS show Ge-Te, Sb-Te bonds are present in both amorphous and crystalline phases. The temperature dependent modifications of the band structure of amorphous GST films at low temperatures have been little explored. The band gap increment of around 0.2 eV is observed at low temperature (4.2 K) compared to room temperature 300 K. Other optical parameters like Urbach energy and B1/2 are studied at different temperatures and are evaluated. The observed changes in optical band gap (Eopt) are fitted to Fan’s one phonon approximation, from which a phonon energy (ћω) corresponding to a frequency of 3.59 THz resulted. The frequency of 3.66 THz optical phonons has already been reported by coherent phonon spectroscopy experiment in amorphous GST. This opens up an indirect method of calculating the phonon frequency of the amorphous phase change materials. Chapter 4 constitutes comparison of optical, electrical and structural investigation of GST and (GST)1-xSex films. It is well known that GST alloys have vacancy in their structure, which leads to the possibility of switching between the amorphous and crystalline states with minimum damage. Added Se may occupy the vacancy or change the bonding characteristics which intern may manifest in the possibility of change in optical and electrical parameters. The structural studies show a direct amorphous to hexagonal transition in (GST)1-xSex, where x ≥ 0.10 at.%. Raman spectra of the as deposited and annealed (GST)1-xSex films show structural modifications. The infrared transmission spectra indicate a shift in absorption edges from low to high photon energy when Se concentration increases in GST. Band gap values calculated from Tauc plot show the band gap increment with Se doping. It is noted that a small amount of Se doping increases the resistance of the amorphous and crystalline phases and maintains the same orders of resistance contrast. This will be beneficial as it improves the thermal stability and reduces the write current in a device. Switching studies show an increasing threshold voltage as the Se doping concentration increases. Chapter 5 comprises compositional dependent investigations of the bulk GeTe chalcogenides alloys added with different selenium concentrations. The XRD investigations on bulk (GeTe)1-xSex (x = 0.0, 0.02, 0.10, 0.20 and 0.50 at.%) alloys show that the crystalline structure of GeTe alloys does not affect ≤ 0.20 at.% of Se concentration. With increasing amount of Se concentration the alloys gets modified in to a homogeneous amorphous structure. This result has been verified from the XRD, Raman, XPS, SEM and DSC measurements. The possibility that Se occupying the Ge vacancy sites in GeTe structure is explained. Since Se is an easy glass former, the amorphousness increases in the alloys due to new amorphous phases formed by the Se with other elements. It is shown from Raman and XPS analysis that the Ge-Te bonds exists up to Se 0.20 at.% alloys. Ge-Se and GeTe2 bonds are increasing with increasing Se at.%. Melting temperature has found decreases and the reduction in melting point may reduces the RESET current. Further studies on switching behavior may bring out its usefulness. Chapter 6 deals with studies on (GeTe)1-xSex films for phase change memory applications based on the insight received from their bulk study. Even at low at.% addition of Se makes the as prepared (GeTe)1-xSex film amorphous. At 200 oC, GeTe crystalline structure is evolved and the intensity of the peaks reduces in the alloys with increase of Se content. At 300 oC, more evolved GeTe crystalline structure is seen compared to 200 oC annealed films whereas 0.20 at.% Se alloy remain amorphous. Resistance and thermal studies shows increase in crystallization temperature. It is expected that Se sits in the vacancies of the GeTe crystalline structural formation. This may also account for the increased threshold voltages with increasing Se doping. The band gap increase with increase of Se at.% signifying the possibility of band gap tuning in the material. Possible explanation for the increased order in GeTe due to Se doping is presented. The modifications in the alloy with Se addition can be explained with the help of chemical bond energy approach. Those bonds having higher energy leads to increased average bond energy of the system and hence the band gap. The XPS core level spectra and Raman spectra investigation clearly shows the GeTe bonds are replaced by Ge-Se bonds and GeTe2 bonds. The 0.10 at.% Se alloy is found to have a higher thermal stability in the amorphous state and maintains a gigantic resistance contrast compared to other Se concentration alloys. This alloy can be considered as an ideal candidate for multilevel PCM applications. Chapter 7 summarizes the major findings from this work and the scope for future work.
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7

Chang, Yao-Feng, and 張耀峰. "The Role of Oxygen Vacancies and Phase Change in TiN/SiO2/PtFe Resistance nonvolatile Random Access Memories." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/54011021411886228424.

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Abstract:
碩士
國立交通大學
電子工程系所
97
Recently, since nonvolatile memories acquire a lot of attention and flash memories are facing with the scale limit issue, the next generation nonvolatile memory has been carried out to discover extensively. The resistive random access memories (ReRAMs) that have the strengths of high cell density array, high operation speed, low power consumption, high endurance, lower scale limit and non-destructive readout, are one of the most potential candidate for flash memories. In this thesis, a physical model and mechanism which is about the role of oxygen vacancies and phase change in TiN/SiO2/PtFe resistance nonvolatile random access memories is proposed. This study can be categorized into three parts, different structures, different thermal treatments and small size devices, all of these electrical results can support the model and mechanism. In the first part, replacing metal electrode materials and SiO2 thickness with different structures was found the results which the effective resistance switching region is at interface region, and Fe element plays an important role to cause resistance switching behavior. In the second part, with different thermal treatments to examine the resistance switching characteristics, was discovered that amount of Fe2O3 and oxygen vacancies would affect endurance reliability and electric characteristics. In the third part, using small size cells to examine the resistance switching characteristics was found the results which are similar with the electric faucet theory and the proposed model. Moreover, a possible model about electric faucet is proposed by physical and mathematical methods. Further investigation, including interfacial electric faucet structure and electrode effects, would help to achieve a better understanding.
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Book chapters on the topic "Phase Change Random Access Memory"

1

Breitwisch, Matthew J. "Phase Change Random Access Memory Integration." In Phase Change Materials, 381–408. Boston, MA: Springer US, 2009. http://dx.doi.org/10.1007/978-0-387-84874-7_17.

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Shi, Luping, Rong Zhao, and Tow C. Chong. "Phase Change Random Access Memory." In Developments in Data Storage, 277–96. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2011. http://dx.doi.org/10.1002/9781118096833.ch13.

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Chen, Yi-Chou. "Phase Change Random Access Memory Advanced Prototype Devices and Scaling." In Phase Change Materials, 331–54. Boston, MA: Springer US, 2009. http://dx.doi.org/10.1007/978-0-387-84874-7_15.

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Kim, Sung Soon, Jun Hyun Bae, Woo Hyuck Do, Kyun Ho Lee, Young Tae Kim, Young Kwan Park, Jeong Taek Kong, and Hong Lim Lee. "Thermal Stress Model for Phase Change Random Access Memory." In Solid State Phenomena, 37–40. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/3-908451-31-0.37.

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Kim, Myoung Sub, Jin Hyung Jun, Jin Ho Oh, Hyeong Joon Kim, Jae Sung Roh, Suk Kyoung Hong, and Doo Jin Choi. "Electrical Switching Characteristics of Nitrogen Doped Ge2Sb2Te5 Based Phase Change Random Access Memory Cell." In Solid State Phenomena, 21–24. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/3-908451-31-0.21.

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"Phase-Change Random Access Memory." In Data Storage at the Nanoscale, 485–612. Jenny Stanford Publishing, 2015. http://dx.doi.org/10.1201/b18094-13.

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Cai, Daolin, Zhitang Song, and Yifeng Chen. "Optimization of the Phase Change Random Access Memory Employing Phase Change Materials." In Phase Change Materials and Their Applications. InTech, 2018. http://dx.doi.org/10.5772/intechopen.74786.

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Chand Verma, Kuldeep. "Synthesis and Characterization of Multiferroic BiFeO3 for Data Storage." In Bismuth - Fundamentals and Optoelectronic Applications. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.94049.

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Multiferroic BiFeO3 deals with spintronic devices involved spin-charge processes and applicable in new non-volatile memory devices to store information for computing performance and the magnetic random access memories storage. Since multiferroic leads to the new generation memory devices for which the data can be written electrically and read magnetically. The main advantage of present study of multiferroic BiFeO3 is that to observe magnetoelectric effects at room temperature. The nanostructural growth (for both size and shape) of BiFeO3 may depend on the selection of appropriate synthesis route, reaction conditions and heating processes. In pure BiFeO3, the ferroelectricity is induced by 6s2 lone-pair electrons of Bi3+ ions and the G-type antiferromagnetic ordering resulting from Fe3+ spins order of cycloidal (62-64 nm wavelength) occurred below Neel temperature, TN = 640 K. The multiferroicity of BiFeO3 is disappeared due to factors such as impurity phases, leakage current and low value of magnetization. Therefore, to overcome such factors to get multiferroic enhancement in BiFeO3, there are different possible ways like changes dopant ions and their concentrations, BiFeO3 composites as well as thin films especially multilayers.
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Verma, R. "Applications of Hard Ferrites in Memory Devices." In Materials Research Foundations, 185–206. Materials Research Forum LLC, 2023. http://dx.doi.org/10.21741/9781644902318-7.

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Ferrites are the important material for memory devices. In this we discuss the ferrites in detail with their classification, preparation method to their applications. We also present a brief introduction about hard ferrites and their application in memory devices. Ferrites are the materials that offer distinct electrical and magnetic features that are helpful for various applications. It is noted that spin transmission torques may change magnetization through the current travelling through a magnetic tunnel interface, an effect followed by the spin transfer torque magnet random access memory as the switching mechanism. Also, it is observed that the transistor-type memory devices that employ nanostructured materials as loading sites for the trap are nano-floatting Gate (NFGM). Thus, this chapter presents a way forward for the memory devices.
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Zardari, Munwar Ali, and Low Tang Jung. "Classification of File Data Based on Confidentiality in Cloud Computing Using K-NN Classifier." In Cloud Security, 678–97. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-8176-5.ch034.

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Cloud computing is a new paradigm model that offers different services to its customers. The increasing number of users for cloud services i.e. software, platform or infrastructure is one of the major reasons for security threats for customers' data. Some major security issues are highlighted in data storage service in the literature. Data of thousands of users are stored on a single centralized place where the possibility of data threat is high. There are many techniques discussed in the literature to keep data secure in the cloud, such as data encryption, private cloud and multiple clouds concepts. Data encryption is used to encrypt the data or change the format of the data into the unreadable format that unauthorized users could not understand even if they succeed to get access of the data. Data encryption is very expensive technique, it takes time to encrypt and decrypt the data. Deciding the security approach for data security without understanding the security needs of the data is a technically not a valid approach. It is a basic requirement that one should understand the security level of data before applying data encryption security approach. To discover the data security level of the data, the authors used machine learning approach in the cloud. In this paper, a data classification approach is proposed for the cloud and is implemented in a virtual machine named as Master Virtual Machine (Vmm). Other Vms are the slave virtual machines which will receive from Vmm the classified information for further processing in cloud. In this study the authors used three (3) virtual machines, one master Vmm and two slaves Vms. The master Vmm is responsible for finding the classes of the data based on its confidentiality level. The data is classified into two classes, confidential (sensitive) and non-confidential (non-sensitive/public) data using K-NN algorithm. After classification phase, the security phase (encryption phase) shall encrypt only the confidential (sensitive) data. The confidentiality based data classification is using K-NN in cloud virtual environment as the method to encrypt efficiently the only confidential data. The proposed approach is efficient and memory space friendly and these are the major findings of this work.
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Conference papers on the topic "Phase Change Random Access Memory"

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Shi, L. P., T. C. Chong, X. Q. Wei, R. Zhao, W. J. Wang, H. X. Yang, H. K. Lee, et al. "Investigation of Nano-Phase Change for Phase Change Random Access Memory." In 2006 7th Annual Non-Volatile Memory Technology Symposium. IEEE, 2006. http://dx.doi.org/10.1109/nvmt.2006.378881.

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Zhitang Song, Feng Rao, Yun Ling, Liangcai Wu, and Bo Liu. "Phase change materials and random access memory." In 2010 IEEE International Conference of Electron Devices and Solid- State Circuits (EDSSC). IEEE, 2010. http://dx.doi.org/10.1109/edssc.2010.5713744.

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Raoux, Simone, Huai-Yu Cheng, Jury Sandrini, Jing Li, and Jean Jordan-Sweet. "Materials engineering for Phase Change Random Access Memory." In 2011 11th Annual Non-Volatile Memory Technology Symposium (NVMTS). IEEE, 2011. http://dx.doi.org/10.1109/nvmts.2011.6137090.

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Huan-Lin Chang, Hung-Chih Chang, Shang-Chi Yang, Hsi-Chun Tsai, Hsuan-Chih Li, and C. W. Liu. "Improved SPICE macromodel of phase change random access memory." In 2009 International Symposium on VLSI Design, Automation and Test (VLSI-DAT). IEEE, 2009. http://dx.doi.org/10.1109/vdat.2009.5158113.

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Miao, X. S., L. P. Shi, R. Zhao, P. K. Tan, K. G. Lim, J. M. Li, and T. C. Chong. "Temperature Dependence of Phase Change Random Access Memory Cell." In 2005 International Conference on Solid State Devices and Materials. The Japan Society of Applied Physics, 2005. http://dx.doi.org/10.7567/ssdm.2005.h-10-3.

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Li, Yi-Jin, Zhi-Tang Song, Yun Ling, Chao Zhang, Yue-Feng Gong, Sheng-Qin Luo, and Xiao-Ling Jia. "A design of access-diode-array in phase change Random Access memory." In 2010 10th IEEE International Conference on Solid-State and Integrated Circuit Technology (ICSICT). IEEE, 2010. http://dx.doi.org/10.1109/icsict.2010.5667572.

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Zhao, R., L. P. Shi, W. J. Wang, H. X. Yang, H. K. Lee, K. G. Lim, E. G. Yeo, E. K. Chua, and T. C. Chong. "Study of Phase Change Random Access Memory (PCRAM) at the Nano-Scale." In 2007 Non-Volatile Memory Technology Symposium. IEEE, 2007. http://dx.doi.org/10.1109/nvmt.2007.4389941.

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Yang, H. X., L. P. Shi, H. K. Lee, R. Zhao, and T. C. Chong. "Endurance enhancement of elevated-confined phase change random access memory." In 2011 International Conference on Solid State Devices and Materials. The Japan Society of Applied Physics, 2011. http://dx.doi.org/10.7567/ssdm.2011.p-4-11.

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Zhang, Xingyao, Qi Guo, Dong Zhou, and Yudong Li. "Total Ionizing Dose (TID) of Phase Change Random Access Memory." In 2021 4th International Conference on Radiation Effects of Electronic Devices (ICREED). IEEE, 2021. http://dx.doi.org/10.1109/icreed52909.2021.9588721.

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Li, J. M., L. P. Shi, H. X. Yang, K. G. Lim, X. S. Miao, H. K. Lee, and T. C. Chong. "Integrated Analysis and Design of Phase-Change Random Access Memory (PCRAM) Cells." In 2006 7th Annual Non-Volatile Memory Technology Symposium. IEEE, 2006. http://dx.doi.org/10.1109/nvmt.2006.378880.

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