Academic literature on the topic 'Silicon(Si)'

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (p. 253-263).<br>Ge-on-Si devices are explored for photonic integration. Importance of Ge in photonics has grown and through techniques developed in our group we demonstrated low density of dislocations (<1x109cm-2) and point defects Ge growth for photonic devices. The focus of this document will be exclusively on Ge light emitters. Ge is an indirect band gap material that has shown the ability to act like a pseudo direct band gap material. Through the use of tensile strain and heavy doping, Ge exhibits properties thought exclusive of direct band gap materials. Dependence on temperature suggests strong interaction between indirect bands, [Delta] and L, and the direct band gap at [Gamma]. The behavior is justified through increase in photoluminescence on Ge. The range of efficient emission is to 120° with the first band interaction, and above 400° on the second band interaction. Low defect concentration in Ge is achieved through chemical vapor deposition at high vacuum (~1x10-8 mbar) in a two-step process. The high temperature growth and low concentration of particles permits epitaxial growth with low defect concentration. Chemical selectivity forbids Ge growth on oxide. Oxide trenches permit the growth on Si for a variety of shapes, without detrimentally affecting the strain of the Ge devices. Dopant concentration above intrinsic growth concentration, ~1x1019cm-3 phosphorus, have been achieved through a series of methods non-CMOS, spin-on dopant; and CMOS, implantation and delta doping. All the techniques explored use enhanced dopant diffusion observed in Ge under heavy n-type doping. A dopant source, or well, is used to distribute the dopants in the Ge without increasing the defect concentration. The approach lead to the development of electrically injected devices, LEDs and LDs. Ge pnn double heterostructure diodes were made under low, ~1x1018cm-3, and heavy n-type doping, >1x1019cm-3. Both devices showed improved performance compared to pin Ge LED. Furthermore, heavy doped Ge diodes exhibit evidence of bleaching or transparency. The techniques described permitted the development of Ge-on-Si laser with a concentration ~1-2x1019cm-3. It is the first demonstration of a Ge laser optically pumped working under the direct band gap assumption like other semiconductors. It represents the evidence of carrier inversion on an indirect band gap semiconductor. With 50cm-1 gain, the material shows Fabry-Perot cavity behavior. Finally, we demonstrated a fully functioning laser diode monolithically integrated on Si. Ge pnn lasers were made exhibiting a gain >1000cm-1 and exhibiting a spectrum range of over 200nm, making Ge the ideal candidate for Si photonics.<br>by Rodolfo E. Camacho-Aguilera.<br>Ph.D.

Primary silicon crystals grown from an Al-Si melt has been investigated by solidifying directionally and under electromagnetic field. The goal of this thesis was to increase the size of the primary Si crystals and to agglomerate the crystals to one part of the melt. If achieved, this could simplify the following acid leaching process that is necessary to collect the crystals from the melt. Seven experiments were conducted in a resistance furnace with directional solidification to investigate the agglomeration and size of the Si crystals. A mono-crystalline Si seed was added to the Al-Si melt in three of these experiments as an attempt to increase the crystal growth. The impact of stirring in the melt before solidification was investigated. Al-Si melt was directionally solidified without the aid of seed in three experiments. The silicon content in the alloy and pulling rate during solidification was varied in these experiments to find the appropriate Si crystal growth conditions. The growth of silicon crystals from a mono-crystalline Si seed without aluminium was performed to investigate the impact aluminium had on the seeded growth. One experiment was conducted in an induction furnace to investigate the influence electromagnetic force has on the agglomeration of primary Si crystals. Agglomeration of Si primary crystals was found not to be successful for either directional solidification or electromagnetic force method, as the crystals were not gathered to one part of the melt. The size of the primary Si crystals was not as large as expected and addition of mono-crystalline Si seed did not improve the crystal size. A single Si crystal was successfully grown from a mono-crystalline Si seed when there was no aluminium in the melt.

High-energy Si implantation into silicon creates a net defect distribution that is characterized by an excess of interstitials near the projected range and a simultaneous excess of vacancies closer to the surface. This defect distribution is due to the spatial separation between the distributions of interstitials and vacancies created by the forward momentum transferred from the implanted ion to the lattice atom. This dissertation investigates the evolution of the near-surface vacancy excess in MeV Si-implanted silicon both during implantation and post-implant annealing. Although previous investigations have identified a vacancy excess in MeV-implanted silicon, the investigations presented in this dissertation are unique in that they are designed to correlate the free-vacancy supersaturation with the vacancies in clusters. Free-vacancy (and interstitial) supersaturations were measured with Sb (B) dopant diffusion markers. Vacancies in clusters were profiled by Au labeling; a new technique based on the observation that Au atoms trap in the presence of open-volume defects. The experiments described in this dissertation are also unique in that they were designed to isolate the deep interstitial excess from interacting with the much shallower vacancy excess during post-implant thermal processing.

Stable disilenides, silicon analogues of vinyl anions, offer a valuable entry point to unsymmetrically substituted disilenes of the A2 Si=SiAB (substituents A ≠ B) form otherwise impossible to obtain. Disilenes, although kinetically stabilised by bulky substituents, readily react with a broad range of substrates consuming the silicon double bond in a multitude of addition reactions. This makes manipulations in the periphery of the disilene scaffold a challenging task. This thesis concentrates mainly on the synthetic approach to novel functionalised unsymmetrically substituted disilenes by reaction of a disilenide with suitable precursors and transformation of functionality in the presence of Si-Si double bonds. The second major topic is the preparation of extended (conjugated) systems with multiple Si=Si units using a disilenide as transfer reagent. Stable compounds featuring between one and six Si=Si units were obtained and fully characterised including para-(halosilanyl)phenyl disilenes, thiophenyl disilenes, aminophenyl disilenes as well as disilenyl functionalised amine- and silane-centred dendritic molecules. Spectroscopic data for each class of compounds is presented showing the influence of functional groups on the molecular properties, especially the HOMO-LUMO gap.

Cette dissertation présente les résultats des mesures des sections efficaces inclusives de production des particules chargées légères (protons, deutons, tritons, 3He, alpha, 6Li, 7Li et 7Be) ainsi que les multiplicités neutroniques associées, relevés lors des réactions nucléaires induites par protons et alpha sur une cible de natSi. Ces mesures ont été réalisées auprès du cyclotron CYCLONE de Louvain-la-Neuve aux énergies de 26.5, 48.5 et 62.9 MeV pour les réactions (p, (nat)Si) et de 25.4, 45.5 et 57.8 MeV pour les réactions (alpha, (nat)Si). Le système de détection, original dans sa conception, a été assuré par 15 télescopes constitués d'un assemblage de jonctions silicium et de scintillateurs inorganiques CsI assurant une couverture angulaire de 0 à 360°. Toutes les particules chargées étudiées dans ce travail ont été identifiées sur base de l'information de leurs pertes d'énergie dans les différentes jonctions et par la technique de l'analyse en forme des signaux lumineux issus des CsI. La détection des neutrons a été assurée par le multi-détecteur à neutrons DEMON constitué de 81 scintillateurs organiques liquides. Ces neutrons ont été identifiés par la technique de l'analyse en forme du signal lumineux. L'énergie des neutrons a été déduite par mesure de leur temps de vol. Les distributions angulaires des pics élastiques et inélastiques de la diffusion des protons et des alpha sur le 28Si ont été confrontées aux prédictions des modèles Optique, DWBA et Canaux Couplés, utilisant différents potentiels optiques. Une comparaison des résultats expérimentaux avec ceux déjà publiés sur des réactions similaires ou comparables a également fait l'objet de ce travail. De plus, les résultats ont été confrontés à ceux des prédictions des codes de simulation GNASH et TALYS. Une attention particulière a été portée aux prédictions du code TALYS. Enfin, ce travail fournit une très large et très complète base de nouvelles données expérimentales qui constitue un atout majeur et bénéfique aussi bien dans l'amélioration des codes théoriques de simulation de ce type de réactions que dans les prédictions des dégâts radiatifs induits par les différents rayonnements ionisants dans les semi-conducteurs, en général, et les composants électroniques, en particulier.

<p> The rapidly evolving global information infrastructure requires ever faster data transfer within computer networks and stations. Integrated chip scale photonics can pave the way to accelerated signal manipulation and boost bandwidth capacity of optical interconnects in a compact and ergonomic arrangement. A key building block for integrated photonic circuits is an on-chip laser. In this dissertation we explore ways to reduce the physical footprint of semiconductor lasers and make them suitable for high density integration on silicon, a standard material platform for today's integrated circuits. We demonstrated the first room temperature metalo-dielectric nanolaser, sub-wavelength in all three dimensions. Next, we demonstrated a nanolaser on silicon, showing the feasibility of its integration with this platform. We also designed and realized an ultracompact feedback laser with edge-emitting structure, amenable for in-plane coupling with a standard silicon waveguide. Finally, we discuss the challenges and propose solutions for improvement of the device performance and practicality.</p>