A new method of amorphous hydrogenated silicon (a-Si:H) chemical vapor deposition is presented in which SiH4 is homogeneously decomposed at high temperature and pressure to produce films on low-temperature substrates having up to 30-at. % H and properties very similar to plasma-deposited material. Kinetic studies provide a film growth activation energy of 54 kcal/mole, confirming that SiH2 is the primary gas phase intermediate. A mechanism based on SiH2 chemistry is presented to account for the rapid surface reactions leading to a-Si:H growth and its possible relevance to the plasma deposition process is emphasized.

Amorphous hydrogenated silicon has been deposited by plasma decomposition of Si2H6 and Si3H8. A major feature of the process is a deposition rate enhancement of over a factor of 20 compared to monosilane. The resulting films are compositionally similar to monosilane-produced intrinsic a-Si(H), but films deposited at 300 °C substrate temperature show greater photoconductivity. On the basis of our deposition experiments and the known thermolysis chemistry of the silanes, a conjectural model for the deposition process is presented.

Articles you may be interested inVibrational spectroscopy of a transient species through time-resolved Fourier transform infrared emission spectroscopy: The vinyl radical Measurement of the rate of bimolecular electron spin relaxation between pairs of reactive radicals using time resolved electron spinecho spectroscopyThe gas phase IR spectrum of t -butyl radicals near -31l m has been observed by the time-resolved infrared technique known as TRISP. The transient spectrum is observed to decay with second-order kinetics, and a total rate of decay k, + k" = 10,0.2. liter mole-' sec-' is measured. From a gas chromatograph/mass spectrometer analysis of the reaction products, it is found that k,,/k, = 2.9. Thus kc = 10'·1 and k" = 10,013 liter mole" sec-I. The I-butyl radicals were created by ruby laser photolysis of monomeric (CH))]CNO vapor.

The structural, morphological, and magnetic properties of small nickel particles prepared by the metal atom technique from toluene, SF6, and xenon matrices at 77 K are reported. X-ray scattering and electron microscopy measurements indicate that the smallest particles are obtained from toluene matrices. Particle size depends upon the initial nickel concentration in the toluene matrix, reaching ~16-Á average diameter for the highest concentrations studied. The microcrystals prepared from toluene are surrounded by a thin amorphous organic layer, comprising up to 10 wt % of the total sample, due to solvent decomposition on melt-down and subsequent heating to room temperature. The particles are dispersed within larger agglomerates >100 Á in diameter. Microcrystallites obtained from SF6 and xenon are larger. The xenon-prepared nickel is relatively pure, typically -100 Á in size, and exhibits faceting. Toluene-prepared powders display ferromagnetic behavior with magnetic moments ~40% that of bulk Ni for the largest microcrystallites and paramagnetism for the smallest (metal clusters). The role of matrix solvent in the nucleation and growth of clusters and microcrystallites is also examined and discussed in view of current interest in their catalytic properties.Registry No. Ni, 7440-02-0.

Compositional, structural and transport data are presented for amorphous hydrogenated silicon (a-Si:H) prepared by homogeneous chemical vapor deposition (HOMOCVD). We find a remarkable similarity in properties between HOMOCVD and plasma a-Si:H, including a nearly identical range (250–300 °C) for the preparation of highly photoconductive films. However, unlike plasma material, HOMOCVD a-Si:H exhibits negligible photo-induced instabilities (Staebler–Wronski effect) and low spin concentrations over a wide span of deposition conditions. These results indicate that a significant defect-creating reaction, most likely surface Si-H bond scission, is occurring in the plasma environment, but absent in HOMOCVD.