21941-60-6Relevant academic research and scientific papers
Thermal Stability of Methyl Groups on Si(100) Generated by the Decomposition of Tetramethylgermane
Greenlief, C. Michael,Klug, Debra-Ann
, p. 5424 - 5429 (1992)
The adsorption and thermal decomposition of tetramethylgermane on Si(100) have been studied by ultraviolet photoelectron spectroscopy, static secondary ion mass spectrometry, temperature-programmed desorption, and Auger electron spectroscopy.Tetramethylgermane adsorbs molecularly on Si(100) at 110 K.In temperature-programmed desorption experiments, most of the tetramethylgermane reversibly desorbs at 141 +/- 4 K.The remaining tetramethylgermane decomposes at higher surface temperatures by breaking of a C-Ge bond resulting in formation of a methyl group and Ge(CH3)3, the latter involving into the gas phase.Further heating causes decomposition of the methyl group.The hydrogen atoms released by methyl group decomposition form surface Si monohydrides, which later combine to desorb molecular H2.The methyl groups decompose with a pseudo-first-order preexponential of (1 +/- 5) *108 s-1 and an activation energy of 29 +/- 1 kcal mol-1.
Thermal decomposition of tetramethylsilane and tetramethylgermane by flash pyrolysis vacuum ultraviolet photoionization time-of-flight mass spectrometry
Lemieux, Jessy M.,Zhang, Jingsong
, p. 50 - 55 (2014)
Thermal decomposition of tetramethylsilane (TMS) and tetramethylgermane (TMG) was studied on a short time scale of 20100 ms using flash pyrolysis vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS). Primary decomposition of TMS and TMG occurred via loss of a methyl radical to form ?Si(CH3)3 and ?Ge(CH3)3, respectively. Both the ?Si(CH3)3 and ?Ge(CH3)3 radicals underwent secondary loss of a second methyl radical to form :Si(CH3)2 and :Ge(CH3)2, respectively. A previously unobserved secondary decomposition process in TMS involving loss of H atom from ?Si(CH3)3 followed by elimination of H2 to form SiC3H8, SiC3H6, and SiC3H4 was also identified. Sequential loss of the third and fourth methyl radical with significant formation of Ge and Ge2 was observed in the TMG pyrolysis. Loss of a third methyl radical in the TMS pyrolysis was not significant, while Si and SiC products were possibly produced. Secondary reactions of methyl to form unsaturated CxHy species, particularly in the TMG decomposition, were also observed.
Molecular beam photochemistry of organopolysilanes and organopolygermanes
Borthwick, Ian,Baldwin, Lawrence C.,Sulkes, Mark,Fink, Mark J.
, p. 139 - 146 (2008/10/08)
The molecular beam photochemistry of various polysilanes and polygermanes was investigated. In most cases, the precursor compounds were photolyzed in the nozzle region of a supersonic jet by a 193 nm laser and the photoproducts analyzed downstream by 118 nm photoionization pulses followed by time-of-flight mass spectrometry. The polysilane and polygermane compounds included in this study were PhMeSi(SiMe3)2, PhSi(SiMe3)3, (Me2-Si)6, (Me2Ge)6, and 1,3-diphenyl-1,2,2,3-tetramethyl-1,2,3-trisilacycloheptane. The 193 nm photoproducts of PhSiMe3, Me3SiSiMe3, and vinyltrimethylsilane were also examined for comparison purposes. Dimethylsilylene (Me2Si:) was directly observed as the major one-photon photoproduct from the cyclic precursors (Me2Si)6 and 1,3-diphenyl-1,2,2,3-tetramethyl-1,2,3-trisilacycloheptane. Likewise, dimethylgermylene (Me2Ge:) was directly observed in the photolysis of(Me2Ge)6. One-photon photolysis of the noncyclic polysilanes PhMeSi(SiMe3)2 and PhSi(SiMe3)3, however, gave radical products derived from the homolytic scission of a single Si-Si bond with little or no evidence of silylene being generated directly. A mechanism explaining the difference in photochemical outcome for cyclic vs noncyclic molecules is presented. Finally, molecular Si2C is found to be a ubiquitous product resulting from the multiphoton photochemistry of a number of organosilicon precursors.
The Ge-H bond dissociation energies of organogermanes. A laser-induced photoacoustic study
Clark, K. Brady,Griller, David
, p. 746 - 750 (2008/10/08)
The Ge-H bond dissociation energies (BDE's) of several alkyl- and aryl-substituted germanium hydrides have been measured in hydrocarbon solution at room temperature by a photoacoustic technique. The BDE's of these hydrides are unaffected by alkyl substitution when compared to those for GeH4 and are in the range of 81.6-82.6 kcal/mol. Aryl substitution leads to a slightly weakened Ge-H bond (79.2-80.2 kcal/mol) in the cases of phenyl-, diphenyl-, and triphenylgermane. In an effort to further characterize the formation, spectral and decay properties of the germyl radicals some laser flash photolysis studies were carried out. The rate constants for hydrogen abstraction by tert-butoxy radicals were determined by nanosecond laser flash photolysis and fell in the range (0.7-4.4) × 108 M-1 s-1. The aryl-substituted germyl radicals add to the aromatic rings of the germane precursor. Diphenylgermyl radical adds to diphenylgermane with a rate constant of 2.9 × 105 M-1 s-1, while phenylgermyl radical adds to phenylgermane with a rate constant of 1.2 × 106 M-1 s-1.
