This content will become publicly available on September 29, 2023
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- Journal of the American Chemical Society
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- National Science Foundation
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Towards Horizontal Heterojunctions for Tunnel Field Effect Transistors with Template Assisted Selective Epitaxy via MOCVDTunneling field effect transistors (TFETs) have gained much interest in the previous decade for use in low power CMOS electronics due to their sub-thermal switching . To date, all TFETs are fabricated as vertical nanowires or fins with long, difficult processes resulting in long learning cycle and incompatibility with modern CMOS processing. Because most TFETs are heterojunction TFETs (HJ-TFETs), the geometry of the device is inherently vertically because dictated by the orientation of the tunneling HJ, achieved by typical epitaxy. Template assisted selective epitaxy was demonstrated for vertical nanowires  and horizontally arranged nanorods  for III-V on Si integration. In this work, we report results on the area selective and template assisted epitaxial growth of InP, utilizing SiO2 based confined structures on InP substrates, which enables horizontal HJs, that can find application in the next generation of TFET devices. The geometries of the confined structures used are so that only a small area of the InP substrate, dubbed seed, is visible to the growth atmosphere. Growth is initiated selectively only at the seed and then proceeds in the hollow channel towards the source hole. As a result, growth resembles epitaxial lateral overgrowth from a single nucleation point , reapingmore »
A multistep deposition technique is developed to produce highly oriented diamond films by hot filament chemical vapor deposition (HFCVD) on Si (111) substrates. The orientation is produced by use of a thin, 5–20 nm, Ni interlayer. Annealing studies demonstrate diffusion of Ni into Si to form nickel silicides with crystal structure depending on temperature. The HFCVD diamond film with Ni interlayer results in reduced non-diamond carbon, low surface roughness, high diamond crystal quality, and increased texturing relative to growth on bare silicon wafers. X-ray diffraction results show that the diamond film grown with 10 nm Ni interlayer yielded 92.5% of the diamond grains oriented along the (110) crystal planes with ~ 2.5 µm thickness and large average grain size ~ 1.45 µm based on scanning electron microscopy. Texture is also observed to develop for ~ 300 nm thick diamond films with ~ 89.0% of the grains oriented along the (110) crystal plane direction. These results are significantly better than diamond grown on Si (111) without Ni layer with the same HFCVD conditions. The oriented growth of diamond film on Ni interlayers is explained by a proposed model wherein the nano-diamond seeds becoming oriented relative to the β1-Ni3Si that forms during the diamond nucleation period. The model also explains the silicidation and diamond growthmore »
High quality diamond film with minimum surface roughness and ~93% oriented grains along (110) crystallographic direction is grown on Si substrate using a thin 5 to 20 nm nickel layer.
A detailed report on the formation of different phases of nickel silicide, its stability with different temperature, and its role for diamond film texturing at HFCVD growth condition is presented.
A diamond growth model on Si substrate with Ni interlayer to grow high quality-oriented diamond film is established.
Synergistic roles of vapor- and liquid-phase epitaxy in the seed-mediated synthesis of substrate-based noble metal nanostructuresColloidal growth modes reliant on the replication of the crystalline character of a preexisting seed through homoepitaxial or heteroepitaxial depositions have enriched both the architectural diversity and functionality of noble metal nanostructures. Equivalent syntheses, when practiced on seeds formed on a crystalline substrate, must reconcile with the fact that the substrate enters the syntheses as a chemically distinct bulk-scale component that has the potential to impose its own epitaxial influences. Herein, we provide an understanding of the formation of epitaxial interfaces within the context of a hybrid growth mode that sees substrate-based seeds fabricated at high temperatures in the vapor phase on single-crystal oxide substrates and then exposed to a low-temperature liquid-phase synthesis yielding highly faceted nanostructures with a single-crystal character. Using two representative syntheses in which gold nanoplates and silver–platinum core–shell structures are formed, it is shown that the hybrid system behaves unconventionally in terms of epitaxy in that the substrate imposes an epitaxial relationship on the seed but remains relatively inactive as the metal seed imposes an epitaxial relationship on the growing nanostructure. With epitaxy transduced from substrate to seed to nanostructure through what is, in essence, a relay system, all of the nanostructures formed in a givenmore »
Solid-State Electrochemical Synthesis of Silicon Clathrates Using a Sodium-Sulfur Battery Inspired Approach
Clathrates of Tetrel elements (Si, Ge, Sn) have attracted interest for their potential use in batteries and other applications. Sodium-filled silicon clathrates are conventionally synthesized through thermal decomposition of the Zintl precursor Na4Si4, but phase selectivity of the product is often difficult to achieve. Herein, we report the selective formation of the type I clathrate Na8Si46using electrochemical oxidation at 450 °C and 550 °C. A two-electrode cell design inspired by high-temperature sodium-sulfur batteries is employed, using Na4Si4as working electrode, Na
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Influence of the Seed Layer and Electrolyte on the Epitaxial Electrodeposition of Co(0001) for the Fabrication of Single Crystal Interconnects
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