The synthesis and characterization of metastable materials generated by UHV-CVD reactions of molecular precursors

The design and synthesis of novel materials which could be of value in microelectronics and ceramics are described. The synthetic routes involve the use of molecular precursors which have been designed to incorporate the stoichiometry and/or structural architecture of the desired materials into the molecular framework of the precursors, as well as facile decomposition pathways which are likely to lead to metastable phases. The materials are primarily synthesized as thin films deposited through ultra high vacuum chemical vapor deposition (UHV-CVD) processing.; The focus of the research involves heteroepitaxial growth of diamond cubic structured {dollar}rm Sisb{lcub}1-x-y{rcub}Gesb{lcub}x{rcub}Csb{lcub}y{rcub}{dollar} and {dollar}rm Gesb{lcub}1-x{rcub}Csb{lcub}x{rcub}{dollar} semiconductor alloy systems and zinc-blende compounds on (100)Si. Carbon incorporation into Si-Ge has been achieved by reactions of tetrasilylmethane, {dollar}rm (Hsb3Si)sb4C{dollar}, with SiH{dollar}sb4{dollar} and GeH{dollar}sb4{dollar} at 470-500{dollar}spcirc{dollar}C to yield single-crystalline diamond-like {dollar}rm Sisb{lcub}1-x-y{rcub}Gesb{lcub}x{rcub}Csb{lcub}y{rcub}{dollar} (y = 0.04-0.06) alloys. Solid solutions of {dollar}rm (Sisb{lcub}1-x{rcub}Gesb{lcub}x{rcub})C{dollar} possessing the zinc-blende structure have been deposited by the thermal decomposition of tetrakis-(trimethylsilyl)germane, {dollar}rm lbrack (Hsb3C)sb3Sirbrack sb4Ge{dollar}, at 600-775{dollar}spcirc{dollar}C.; Rutherford backscattering spectroscopy (RBS), high resolution cross-sectional transmission electron microscopy (HR X-TEM), Fourier transform infrared spectroscopy (FTIR) and secondary ion mass spectrometry (SIMS) were routinely used to characterize the films for composition, thickness, homogeneity, microstructure and bonding properties. Ternary {dollar}rm Sisb{lcub}1-x-y{rcub}Gesb{lcub}x{rcub}Csb{lcub}y{rcub}{dollar} alloys offer the possibility of bandgap engineering and the prospect of strain compensation relative to the {dollar}rm Sisb{lcub}1-x{rcub}Gesb{lcub}x{rcub}{dollar} system. Ordered SiC-GeC phases may be of utility in high temperature microelectronics.; Single crystal heteroepitaxial {dollar}rm Gesb{lcub}1-x{rcub}Csb{lcub}x{rcub}{dollar} alloys (x {dollar}le{dollar} 7 at.%) have been synthesized by reactions of GeH{dollar}sb4{dollar} with germylmethanes, {dollar}rm (Hsb3Ge)sb{lcub}4-x{rcub}CHsb{lcub}x{rcub}{dollar} (x = 1-3) at 500{dollar}spcirc{dollar}C. The thin films were deposited on (100)Si and were characterized through the use of RBS, HR X-TEM and SIMS. Alloys with low carbon contents possed virtually perfect crystallinity whereas materials with higher carbon contents exhibited some structural defects. Further characterization by Auger electron spectroscopy (AES) showed that the materials were pure and homogeneous, and electron energy loss spectroscopy (EELS) indicated sp{dollar}sp3{dollar} hybridized diamond-like carbon. Non-stoichiometric GeC alloys are potentially useful in microelectronics applications involving band-gap engineering on (100)Si substrates.; Stoichiometric carbon nitride ({dollar}rm Csb3Nsb4{dollar}) has been synthesized for the first time. The synthetic method involves the thermal decomposition of novel molecular precursors of the form {dollar}rm Csb3Nsb3Xsb2N(M(CHsb3)sb3)sb2{dollar} (X = Cl, F; M = Si, Sn) which eliminate stable {dollar}rm XM(CHsb3)sb3{dollar} species to yield thin films and bulk materials of composition {dollar}rm Csb3Nsb4{dollar}. The materials were characterized for composition, thickness and homogeneity using RBS and SIMS. They were also examined using FTIR, EELS and solid state NMR techniques which revealed that the materials were primarily sp{dollar}sp2{dollar} hybridized. These materials should serve as excellent precursors for the high pressure synthesis of tetrahedral {dollar}rm Csb3Nsb4{dollar}, the compositional analog of {dollar}rm Si...