Microcrystallinity in a-Si & a-SiC Films Made by Hg-Sensitized Photo-CVD

1989 ◽  
Vol 149 ◽  
Author(s):  
N. Saxena ◽  
C. M. Fortmann ◽  
T. W. F. Russell
Keyword(s):  
Carbon Content ◽  
Gas Phase ◽  
Growth Rates ◽  
Film Growth ◽  
Selective Etching ◽  
Gas Phase Reactions ◽  
And Diffusion ◽  
Sic Films ◽  
Reactor Pressure

ABSTRACTA model for the role of H atoms as an etchant specie during deposition of microcrystalline (μc) films of Si:H and SiC:H is explored. Growth rates and etch rates of films made by Hg-sensitized photo-CVD have been measured as a function of reactor pressure (between 5 and 0.5 torr) and H2 dilution (up to 30:1). Gas phase reactions and diffusion to the substrate of depositing and etching species, have been modelled. It is found that high H radical flux (not necessarily high H2 dilution) promotes μc film growth. There are two surface etching reactions by H radicals: (i) selective etching of uncoordinated Si surface atoms (amorphous phase) from the film, leaving behind the more etch-resistant μc phase; (ii) in SiC:H alloy systems, a selective etching of C species, causing a decrease in C incorporation into the growing microcrystalline film. Films with increasing carbon content do not contain a μc-SiC phase because hydrogen is not eliminated from the carbon containing film precursors, thus inhibiting the development of crystalline Si-C network.

The Role of Starting Potential in the Kinetics of Chemical Reactions under Electrodeless Discharge

1970 ◽  
Vol 25 (11) ◽  
pp. 1772
Author(s):  
T.S.R Ao ◽  
A. Patil
Keyword(s):  
Gas Phase ◽  
Chemical Reactions ◽  
Electric Discharge ◽  
Specific Rate ◽  
Gas Phase Reactions ◽  
Electrodeless Discharge ◽  
First Order ◽  
Kinetics Of

Abstract It has been shown that in kinetically first order gas phase reactions occuring under electric discharge, such as the decomposition of N2O, the application, at various initial pressures, of the same multiple of the respective starting potential ensures that the reaction occurs at the same specific rate.

Low Temperature Deposited Highly-Conductive N-type SiC Thin Films

1997 ◽  
Vol 472 ◽  
Author(s):  
Kuan-Lun Cheng ◽  
Huang-Chung Cheng ◽  
Wen-Horng Lee ◽  
Chiapyng Lee ◽  
Tri-Rung Yew
Keyword(s):  
Low Temperature ◽  
Film Growth ◽  
Thin Film Transistor ◽  
Impurity Scattering ◽  
Gas Analyzer ◽  
Flow Rates ◽  
Sic Film ◽  
Dopant Source ◽  
Sic Films

ABSTRACTLow-temperature deposited highly-conductive SiC films has long been a goal for many researchers involved in hetero-junction bipolar transistor, thin-film transistor, solar cell.… etc. Here in this paper, we study the influences of the diluted PH3 flow rates on SiC film quality as well as electrical properties. PH+ was determined from residual gas analyzer to be the main dopant source. Phosphorous atoms will play a role of enhancing the SiC grain growth and resulting in a smaller film growth rate. Carrier concentrations increase monotonically with the diluted PH3 flow rates. While Hall mobility first increases than decreases with it due to a combination effect of the impurity scattering and a film quality improvement which dominates when the 1% PH3/H2 flow rate is above or below 40 seem, respectively.

Gas-phase reactions of anions with halogenated methanes at 297 ± 2 K

1976 ◽  
Vol 54 (10) ◽  
pp. 1643-1659 ◽  
Author(s):  
K. Tanaka ◽  
G. I. Mackay ◽  
J. D. Payzant ◽  
D. K. Bohme
Keyword(s):  
Gas Phase ◽  
Rate Constants ◽  
Hydrogen Atom Transfer ◽  
Gas Phase Reactions ◽  
Phase Measurements ◽  
Displacement Reactions ◽  
Nucleophilic Reactivity ◽  
Apparent Activation Energies

The rate constants for a number of exothermic displacement (SN2) reactions of the type X− + CH3Y → Y− + CH3X where X− = H−, O−, C−, F−, S−, Cl−, OH−, C2−, CN−, SH−, S2−, C2H−, NH2−, NO2−, CHF−, CH2Cl−, CH2Br−, CH3O−, CH3S−, and CH3NH− and Y = F, Cl, and Br, have been measured in the gas phase at 297 ± 2 K using the flowing after-glow technique. These gas-phase measurements provided an opportunity to determine the intrinsic nucleophilic reactivity of 'nude' anions and hence to assess the role of solvation in the kinetics of SN2 reactions proceeding in solution. Comparisons of the experimental rate constants with rate constants calculated using classical theories of capture indicate that several displacement reactions may possess large intrinsic energies of activation, [Formula: see text]. Correlations were found between apparent activation energies and the heats of reaction. These correlations provided a convenient classification of the various anion nucleophiles. Displacement was observed to compete with proton transfer in reactions involving nucleophiles of high intrinsic basicity and with hydrogen atom transfer and H2+ transfer in the reactions of the O− radical anion.

Epitaxial Si1−yCy alloys: The role of surface and gas phase reactions

1999 ◽  
Vol 85 (2) ◽  
pp. 1240-1242 ◽  
Author(s):  
A. C. Mocuta ◽  
D. W. Greve
Keyword(s):  
Gas Phase ◽  
Gas Phase Reactions

The interaction of chemical kinetics and diffusion in the dynamics of chemical vapor infiltration

1989 ◽  
Vol 4 (6) ◽  
pp. 1515-1524 ◽  
Author(s):  
Stanley Middleman
Keyword(s):  
Gas Phase ◽  
Film Growth ◽  
Classical Model ◽  
Chemical Vapor ◽  
Chemical Vapor Infiltration ◽  
Reactor Model ◽  
Cylindrical Pore ◽  
Complex Chemistry ◽  
And Diffusion ◽  
Vapor Infiltration

The classical model of Chemical Vapor Infiltration (CVI) treats diffusion and surface reaction in a representative cylindrical pore. Two significant modifications to that approach are presented herein. One accounts for more complex chemistry by allowing for both gas-phase and surface reactions which lead to film growth. The other couples the pore model to a reactor model for the region external to the porous preform. The results demonstrate that it is possible to select chemical schemes that yield densification from the interior to the exterior of the preform, thus avoiding premature trapping of interior voids.

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