Anomalous Diffusion of Hydrogen and the Dependence of the Diffusion Constants on Hydrogen Content in Hydrogenated Amorphous Silicon

ABSTRACTThe diffusion constant of hydrogen DH(t) in hydrogenated amorphous silicon (a-Si:H) is strongly dependent on the Si-bonded H content CH of the films. It increases by over four orders of magnitude for CH ranging from 1 to 19 at. %. In an rf sputter-deposited film of CH ∼5 at. % it increases with time at 300 ≤ T ≤ 362°C. The dispersion parameter α in DH(t) = D∞ (ωt)-αis thus negative. This observation and the increase of α with T above a sample-dependent temperature Tτ are discussed in relation to low temperature structural relaxation processes in the amorphous network.

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Improved Light Soaking Stability of R.F. Sputter Deposited Amorphous Silicon

MRS Proceedings ◽

10.1557/proc-219-105 ◽

1991 ◽

Vol 219 ◽

Author(s):

A. Wynveen ◽

J. Fan ◽

J. Kakalios ◽

J. Shinar

Keyword(s):

Amorphous Silicon ◽

Hydrogen Content ◽

Defect Density ◽

Hydrogenated Amorphous Silicon ◽

Dark Conductivity ◽

Initial Defect ◽

Optical Gap ◽

Sputter Deposited ◽

Staebler Wronski Effect ◽

Hydrogenated Amorphous

ABSTRACTStudies of r.f. sputter deposited hydrogenated amorphous silicon (a-Si:H) find that the light induced decrease in the dark conductivity and photoconductivity (the Staebler-Wronski effect) is reduced when the r.f. power used during deposition is increased. The slower Staebler-Wronski effect is not due to an increase in the initial defect density in the high r.f. power samples, but may result from either the lower hydrogen content or the smaller optical gap found in these films.

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Kinetics of Growth and Recovery of Light-Induced Defects Under High-Intensity Illumination

MRS Proceedings ◽

10.1557/proc-258-473 ◽

1992 ◽

Vol 258 ◽

Cited By ~ 4

Author(s):

Masao Isomura ◽

Sigurd Wagner

Keyword(s):

Light Intensity ◽

Amorphous Silicon ◽

High Intensity ◽

Hydrogenated Amorphous Silicon ◽

Increased Sensitivity ◽

Induced Defects ◽

Hydrogenated Amorphous ◽

Kinetics Of ◽

Diffusion Of Hydrogen

ABSTRACTWe report a study of the rates of generation and of annealing of the light-induced defects in hydrogenated amorphous silicon (a-Si:H). The rates of generation are found to be sensitive to temperature when the light intensity is high. This increased sensitivity to temperature at high rates suggests that a temperature-activated process such as hydrogen motion controls the rates of generation more when they are high. The rate of annealing at 130°C is strongly accelerated by illumination, and depends strongly on the light intensity. This may be explained by the diffusion of hydrogen, accelerated by excess carriers.

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Hydrogen motion in thermally annealed sputter‐deposited hydrogenated amorphous silicon

Journal of Applied Physics ◽

10.1063/1.339675 ◽

1987 ◽

Vol 62 (4) ◽

pp. 1240-1244 ◽

Cited By ~ 2

Author(s):

A. J. Bevolo ◽

M. L. Albers ◽

H. R. Shanks ◽

J. Shinar

Keyword(s):

Amorphous Silicon ◽

Hydrogenated Amorphous Silicon ◽

Sputter Deposited ◽

Hydrogenated Amorphous

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Impurity-Defect Complexes in Hydrogenated Amorphous Silicon

MRS Proceedings ◽

10.1557/proc-209-397 ◽

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.

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Structural Equilibration in Pure and Hydrogenated Amorphous Silicon

MRS Proceedings ◽

10.1557/proc-297-237 ◽

1993 ◽

Vol 297 ◽

Cited By ~ 6

Author(s):

Gerhard Müller ◽

Gerhard KrÖtz

Keyword(s):

Amorphous Silicon ◽

Degrees Of Freedom ◽

Crystalline Silicon ◽

Hydrogenated Amorphous Silicon ◽

Electronic System ◽

Relaxation Processes ◽

Electrochemical Processes ◽

Local Bonding ◽

Defect Sites ◽

Hydrogenated Amorphous

Chemically pure (a-Si) and hydrogenated amorphous silicon (a-Si:H) are metasta- ble materials which are thermodynamically unstable with respect to crystalline silicon (c-Si). In both materials, however, partial thermal equilibria can be established between certain structural, configurational and electronic degrees of freedom. The present paper discusses experiments on both amorphous (a-) materials showing that two kinds of structural change can take place within random Si networks: structural relaxation and configurational equilibration. The first process can be observed in both materials indicating that it is supported by intrinsic degrees of freedom of the random Si networks. During these changes partial thermal equilibria between distorted and broken bonds are established via irreversible and relatively long-range relaxation processes. The second kind of change can only be observed in a-Si:H, indicating that it is H-related. The H-related degrees of freedom support reversible valence alternation reactions in which the local bonding configuration of the dopant and defect sites is changed and in which their charge states are altered. These latter interactions establish a strong coupling between the electronic system and the configurational degrees of freedom of the random Si networks. Formally, these latter changes bear strong similarity to the electrochemical processes that take place in liquid electrolytes.

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Hydrogenated amorphous silicon: Hydrogen content, bonding configurations and morphology in sputter-deposited, in-chamber annealed thin films

Thin Solid Films ◽

10.1016/0040-6090(94)90836-2 ◽

1994 ◽

Vol 251 (1) ◽

pp. 30-35 ◽

Cited By ~ 15

Author(s):

R. Rüther ◽

J. Livingstone

Keyword(s):

Thin Films ◽

Amorphous Silicon ◽

Hydrogen Content ◽

Hydrogenated Amorphous Silicon ◽

Sputter Deposited ◽

Hydrogenated Amorphous

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Spin Relaxation Spectroscopy of the D-Center in Hydrogenated Amorphous Silicon

MRS Proceedings ◽

10.1557/proc-149-113 ◽

1989 ◽

Vol 149 ◽

Author(s):

Sufi Zafar ◽

E. A. Schiff

Keyword(s):

Amorphous Silicon ◽

Spin Relaxation ◽

Hydrogenated Amorphous Silicon ◽

Relaxation Processes ◽

Substantial Variation ◽

Paramagnetic Resonance ◽

Electron Spin Relaxation ◽

Order Of Magnitude ◽

Hydrogenated Amorphous ◽

Electron Paramagnetic

ABSTRACTMeasurements of the dependence of the D-center electron paramagnetic resonance absorption signal upon the incident microwave power are reported in undoped hydrogenated amorphous silicon (a-Si:H) for specimens prepared at differing deposition temperatures and also as the state of a given specimen was varied by illumination and subsequent annealing. These measurements are sensitive to electron spin relaxation processes of the D-center. Substantial variation in spin-relaxation behavior was found, corresponding to approximately one order of magnitude in the spin relaxation rate; no significant variations in absorption lineshape were observed. A model for these spin relaxation observations invoking two differing local microstructures near the D-center is proposed. The model indicates that illumination increases the density of defects in one microstructure but can irreversibly diminish the density in a second.

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Large-grain poly-crystalline silicon thin films prepared by aluminum-induced crystallization of sputter-deposited hydrogenated amorphous silicon

Journal of Materials Research ◽

10.1557/jmr.2006.0091 ◽

2006 ◽

Vol 21 (3) ◽

pp. 761-766 ◽

Cited By ~ 9

Author(s):

Maruf Hossain ◽

Harry M. Meyer ◽

Husam H. Abu-Safe ◽

Hameed Naseem ◽

W.D. Brown

Keyword(s):

Amorphous Silicon ◽

Crystallization Process ◽

Crystalline Silicon ◽

Hydrogenated Amorphous Silicon ◽

Glass Substrates ◽

Silicon Thin Films ◽

Diffraction Patterns ◽

Sputter Deposited ◽

Hydrogenated Amorphous ◽

Induced Crystallization

A metal-induced crystallization (MIC) technique was used to produce large-grain poly-crystalline silicon. Two sets of samples were prepared by first sputtering Al onto glass substrates. For one set of samples, hydrogenated amorphous silicon (a-Si:H) was sputtered on top of the Al without breaking the vacuum. For the second set, the samples were taken out of the vacuum chamber and exposed to the atmosphere to grow a very thin layer of native aluminum oxide before sputter depositing the a-Si:H. Both sets of samples were then annealed at temperatures between 400 and 525 °C for 40 min. X-ray diffraction patterns confirmed the crystallization of the samples. Scanning Auger microanalysis was used to confirm that the a-Si:H and Al layers exchanged positions in this structure during the crystallization process. Auger mapping revealed the formation of large grain poly-silicon (10–20 μm). A model is proposed to explain how the crystallization process progresses with anneal temperature.

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