Calculations of SiH3 Diffusion and Growth Processes on a-Si:H Surfaces

2003 ◽  
Vol 762 ◽  
Author(s):  
P Vigneron ◽  
P W Peacock ◽  
K Xiong ◽  
J Robertson
Keyword(s):  
Total Energy ◽  
Amorphous Silicon ◽  
Surface Diffusion ◽  
Bound States ◽  
Smooth Surface ◽  
Hydrogenated Amorphous Silicon ◽  
Weakly Bound ◽  
Growth Site ◽  
Pseudopotential Calculations ◽  
Hydrogenated Amorphous

AbstractSurface diffusion of a growth species is needed to give the observed smooth surface of hydrogenated amorphous silicon (a-Si:H). But what diffuses, the weakly bound SiH3 radical on the hydrogenated surface, or the bound SiH3 at a growth site. Diffusion is complicated by the change in the surface termination of a-Si:H as temperature rises. We use total energy pseudopotential calculations on a variety of periodic Si:H surface configurations to show that it is the weakly bound SiH3 that diffuses. We provide an overall energy scheme of the bound states and transport levels of SiH3 on a-Si:H surfaces.

Reduction of the Defect Density in a-Si:H Deposited at ≤250°C

1993 ◽  
Vol 297 ◽  
Author(s):  
Hitoshi Nishio ◽  
Gautam Ganguly ◽  
Akihisa Matsuda
Keyword(s):  
Diffusion Coefficient ◽  
Amorphous Silicon ◽  
Surface Diffusion ◽  
Film Growth ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Device Fabrication ◽  
Surface Diffusion Coefficient ◽  
Hydrogenated Amorphous ◽  
Substrate Temperatures

We present a method to reduce the defect density in hydrogenated amorphous silicon (a-Si:H) deposited at low substrate temperatures similar to those used for device fabrication . Film-growth precursors are energized by a heated mesh to enhance their surface diffusion coefficient and this enables them to saturate more surface dangling bonds.

Surface Diffusion of SiH3 Radicals and Growth Mechanism of a-Si:H and μc-Si

2002 ◽  
Vol 715 ◽  
Author(s):  
R Dewarrat ◽  
J Robertson
Keyword(s):  
Amorphous Silicon ◽  
Growth Mechanism ◽  
Crystalline Silicon ◽  
Local Density ◽  
Hydrogenated Amorphous Silicon ◽  
Growth Mechanisms ◽  
Surface Hydrogen ◽  
Pseudopotential Calculations ◽  
Conventional Models ◽  
Hydrogenated Amorphous

AbstractExisting growth mechanisms of hydrogenated amorphous silicon (a-Si:H) and micro-crystalline silicon assume that the growth species SiH3 can diffuse over the hydrogen-saturated Si surface. However, recent calculations suggest that this could not happen. Local density formalism pseudopotential calculations have been carried out of binding of SiH3 to hydrogen terminated (111)Si surfaces. The bound site is not the three-centre Si-H-Si bridging site previously assumed. It has a direct Si-Si bond between the SiH3 and the surface Si, and the surface hydrogen is displaced to a bond centre of a surface Si-Si bond. A bound site confirms conventional models of growth of a-Si:H and microcrystalline Si, in which a mobile growth species creates smooth surfaces.

scholarly journals Impurity-Defect Complexes in Hydrogenated Amorphous Silicon

1990 ◽  
Vol 209 ◽  
Author(s):  
Lin H. Yang ◽  
C. Y. Fong ◽  
Carol S. Nichols
Keyword(s):  
Amorphous Silicon ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Dangling Bond ◽  
Defect Complexes ◽  
Amorphous Network ◽  
Pseudopotential Calculations ◽  
Impurity Defect ◽  
Supercell Model ◽  
Hydrogenated Amorphous

ABSTRACTThe two most outstanding features observed for dopants in hydrogenated amorphous silicon (a-Si:H) - a shift in the Fermi level accompanied by an increase in the defect density and an absence of degenerate doping - have previously been postulated to stem from the formation of substitutional dopant-dangling bond complexes. Using firstprinciples self-consistent pseudopotential calculations in conjunction with a supercell model for the amorphous network and the ability of network relaxation from the first-principles results, we have studied the electronic and structural properties of substitutional fourfoldcoordinated phosphorus and boron at the second neighbor position to a dangling bond defect. We demonstrate that such impurity-defect complexes can account for the general features observed experimentally in doped a-Si:H.

Fluctuating Defect Density Probed with Noise Spectroscopy in Hydrogenated Amorphous Silicon

1997 ◽  
Vol 467 ◽  
Author(s):  
P.A.W.E. Verleg ◽  
O. Uca ◽  
J. I. Dijkhuis
Keyword(s):  
Amorphous Silicon ◽  
Low Temperatures ◽  
Noise Source ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Weakly Bound ◽  
Thermally Activated ◽  
Noise Spectroscopy ◽  
Resistance Fluctuations ◽  
Hydrogenated Amorphous

ABSTRACTResistance fluctuations have been studied in hydrogenated amorphous silicon in the temperature range between 300 K and 450 K. The primary noise source has a power spectrum of approximately 1/f and is ascribed to hydrogen motion. Hopping of weakly bound hydrogen is thermally activated at such low temperatures with an average activation energy of 0.85 eV. The attempt rate amounts to 7 · 1012 s−1.

On the Role of Surface Diffusion and Its Relation to the Hydrogen Incorporation During Hydrogenated Amorphous Silicon Growth

2003 ◽  
Vol 762 ◽  
Author(s):  
A.H.M. Smets ◽  
W.M.M. Kessels ◽  
M.C.M. van de Sanden
Keyword(s):  
Activation Energy ◽  
Amorphous Silicon ◽  
Surface Diffusion ◽  
Diffusion Processes ◽  
Growth Parameters ◽  
Hydrogenated Amorphous Silicon ◽  
Hydrogen Incorporation ◽  
Silicon Growth ◽  
Surface Diffusion Processes ◽  
Hydrogenated Amorphous

AbstractThe incorporation of hydrogen in vacancies and at void surfaces during hydrogenated amorphous silicon growth from a remote expanding thermal plasma (ETP) is systematically studied by variation of the mass growth flux Γa-Si:H and substrate temperatureTsub. An evident relation between the void incorporation and the growth parameters Γa-Si:H andTsubhas been observed. We speculate on a possible relation with the surface diffusion processes during deposition. An activation energy for surface diffusion during a-Si:H growth of 0.8-1.1 eV is obtained using this assertion, similar to the activation energy deduced from surface roughness evolution studies. For compact films hydrogen is predominantly present at vacancies, and a possible relation with the hydrogen removal mechanism during deposition is discussed.

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