Showing papers by "John Kouvetakis published in 1996"

Synthesis and characterization of heteroepitaxial diamond‐structured Ge1−xCx (x=1.5–5.0%) alloys using chemical vapor deposition

Abstract: We report growth of high quality heteroepitaxial Ge1−xCx alloys on Si(100) with C concentrations ranging from 1.5 to 5 at.%. The materials were obtained by reactions of the novel methylgermanes CH3GeH3 and HC(GeH3)3 with GeH4 at 470 °C using ultrahigh‐vacuum chemical‐vapor deposition techniques. The crystallinity, composition, and microstructure of the films were characterized by Rutherford backscattering, carbon‐resonance spectroscopy, and cross‐sectional transmission electron microscopy. Ge1−xCx (x=0.015–0.030) materials were deposited using CH3GeH3 and displayed excellent crystallinity. Films with higher C content were deposited using HC(GeH3)3. These films were epitaxial and of high crystallinity but they also displayed interfacial defects which sometimes persisted through the entire layer. Electron diffraction data and carbon‐ion channeling experiments indicated that carbon primarily occupied substitutional sites in the Ge diamond‐cubic lattice. Secondary ion mass spectrometry revealed that the films...

Low temperature inorganic chemical vapor deposition of heteroepitaxial GaN

Abstract: We have developed a highly efficient method of growing thin oriented films of GaN on basal plane sapphire and (100) Si substrates using an exclusively inorganic single‐source precursor free of carbon and hydrogen. Cross sectional transmission electron microscopy of the highly conformal films revealed columnar material growth on Si and heteroepitaxial columnar growth of crystalline GaN on sapphire. Rutherford backscattering spectroscopy (RBS) of layers grown at 700 °C confirmed stoichiometric GaN. Auger and RBS oxygen and carbon resonance profiles indicated that the films were pure and highly homogeneous. With respect to current chemical vapor deposition processes for GaN growth, our approach offers a number of potentially important improvements. These include high growth rates of 5–350 nm/min, low deposition temperature of 650–700 °C, nearly ideal Ga–N stoichiometry, elimination of the highly inefficient use of toxic ammonia, and a carbon–hydrogen free growth environment that could prove to be beneficial ...

Chemical Synthesis of Metastable Germanium-Carbon Alloys Grown Heteroepitaxially on (100) Si

Abstract: High-quality diamond-structured Ge1-xCx alloys have been grown on (100) Si using ultrahigh-vacuum chemical vapor deposition techniques and novel chemical precursors. Two-dimensional growth of single-crystal heteroepitaxial layers (30−120 nm thick) of germanium−carbon alloys with carbon concentrations up to 7% has been achieved by reactions of GeH4 with germylmethanes, (GeH3)4-xCHx (x = 1−3), at 470 °C. The composition of the materials was established by extensive Rutherford backscattering (RBS) carbon resonance analysis, and the layer crystallinity was characterized by cross-sectional transmission electron microscopy and RBS channeling experiments. RBS ion channeling revealed that the carbon primarily occupied substitutional sites in the diamond-like Ge lattice. Alloys with low carbon content displayed virtually perfect crystallinity whereas materials with high carbon incorporation had structural defects in the form of {111} stacking faults and microtwins. The thin film microstructure of a given alloy com...

New Silicon-Carbon Materials Incorporating Si4C Building Blocks

Abstract: Novel precursor chemistry and ultrahigh-vacuum chemical vapor deposition have been used to deposit Si1-y C y th in films on (001) Si substrates. Films with carbon compositions ranging up to 20 at. % were deposited at substrate temperatures of 600–750°C using interactions of C(SiH3)4 or C(SiH2Cl)4 (C-H free precursors incorporating Si4C tetrahedra) and SiH4 gas mixtures. The composition of the resulting materials was obtained by Rutherford backscattering spectrometry including carbon resonance analysis. Cross-sectional transmission electron microscopy and infrared spectroscopy were used to provide microstructural and bonding information respectively. The effect of precursor chemistry on the composition and structure of the materials is discussed.

New Pathways to Heteroepitaxial GaN by Inorganic CVD Synthesis and Characterization of Related Ga-C-N Novel Systems

Abstract: The authors describe the development of a new deposition method for thin oriented films of GaN on basal plane sapphire using an exclusively inorganic single-source precursor free of carbon and hydrogen, Cl{sub 2}GaN{sub 3}. The films have been characterized by Rutherford backscattering spectroscopy (RBS) and cross sectional transmission electron microscopy (TEM) for composition morphology and structure. RBS analysis confirmed stoichiometric GaN and TEM observations of the highly conformal films revealed heteroepitaxial columnar growth of crystalline wurtzite material on sapphire. Auger and RBS oxygen and carbon resonance profiles indicated that the films were pure and highly homogeneous. They also report the reactions of Cl{sub 2}GaN{sub 3} with organometallic nitrides to yield a crystalline, novel gallium carbon nitride of composition GaC{sub 3}N{sub 3}. Quantitative X-ray powder diffraction has been used to refine the cubic structure of this material which consists of Ga atoms octahedrally surrounded by on the average three C and three N atoms. The structurally analogous LiGaC{sub 4}N{sub 4} phase has also been prepared and characterized.