Modulation of Growing Surface with Atomic Hydrogen and Excited Argon to Fabricate Narrow Gap a-Si:H

1996 ◽  
Vol 420 ◽  
Author(s):  
W. Futako ◽  
I. Shimizu ◽  
C. M. Fortmann
Keyword(s):  
Thin Layer ◽  
Substrate Temperature ◽  
Amorphous Silicon ◽  
Atomic Hydrogen ◽  
Hydrogenated Amorphous Silicon ◽  
High Substrate Temperature ◽  
Narrow Gap ◽  
High Quality ◽  
Chemical Annealing ◽  
Hydrogenated Amorphous

AbstractHydrogenated amorphous silicon (a-Si:H) with a gaps narrower than 1.7 eV were made by repeating the deposition of a thin layer (1–3 nm thick) and the treatment of growing surface with a mixture of H and Ar*. Crystallization induced by permeation of hydrogen into the subsurface at high substrate temperature (>200C) was efficiently prevented by treating with a mixture of H and Ar*. The activation of growing surface may arise from releasing a part of hydrogen on surface by treating with Ar*. High quality a-Si:H films containing hydrogen of 3 atom % with a gap of 1.6 eV were made by chemical annealing with a mixture of H and Ar*.

High Substrate Temperature (420 °C) Excimer Laser Crystallization of Hydrogenated Amorphous Silicon

1992 ◽  
Vol 283 ◽  
Author(s):  
R. Carluccio ◽  
A. Pecora ◽  
G. Fortunato ◽  
J. Stoemenos ◽  
N. Economou
Keyword(s):  
Substrate Temperature ◽  
Amorphous Silicon ◽  
Excimer Laser ◽  
Hydrogenated Amorphous Silicon ◽  
High Substrate Temperature ◽  
Solidification Velocity ◽  
Laser Crystallization ◽  
Excimer Laser Crystallization ◽  
Hydrogenated Amorphous ◽  
Substrate Temperatures

ABSTRACTExcimer laser crystallization of hydrogenated amorphous silicon has been investigated as a function of substrate temperature. At low substrate temperatures hydrogen out-diffusion strongly influences the film morphology, while at 420 °C homogeneous recrystallized films are obtained, as a result of the reduced solidification velocity. This process has been successfully tested by fabricating with the recrystalllized material thin-film transistors according to the bottom-gate configuration.

Extremely Narrow Band Gap,∼1·50Ev, Amorphous Silicon

1998 ◽  
Vol 507 ◽  
Author(s):  
K. Fukutani ◽  
T. Sugawara ◽  
W Futako ◽  
T. Kamiya ◽  
C.M. Fortmann ◽  
...  
Keyword(s):  
Substrate Temperature ◽  
Amorphous Silicon ◽  
Band Gap ◽  
Deposition Time ◽  
Narrow Band ◽  
Hydrogenated Amorphous Silicon ◽  
Treatment Technique ◽  
Layer By Layer ◽  
Narrow Gap ◽  
Hydrogenated Amorphous

ABSTRACTHydrogenated amorphous silicon (a-Si:H) films were prepared by a layer-by-layer (LBL) argon treatment technique. Thin amorphous silicon layers are first deposited and then treated by Ar. Thick films are built up by repeatedly the process many times. By reducing the deposition rate during deposition time (T, sec), a-Si:H with the gaps narrower than 1·55eV were prepared at substrate temperature lower than 300°C. These narrow-gap films contained less than 2 at.% hydrogen and had rigid Si network. Also, these narrow gap films exhibited good light soaking stability.

Low Hydrogen Content, High Quality Hydrogenated Amorphous Silicon Grown by Hot-Wire CVD

1999 ◽  
Vol 557 ◽  
Author(s):  
Brent P. Nelson ◽  
Richard S. Crandall ◽  
Eugene Iwaniczko ◽  
A. H. Mahan ◽  
Qi Wang ◽  
...  
Keyword(s):  
Substrate Temperature ◽  
Amorphous Silicon ◽  
Hydrogen Content ◽  
Defect Density ◽  
Flow Direction ◽  
Scale Up ◽  
Hydrogenated Amorphous Silicon ◽  
Hot Wire ◽  
High Quality ◽  
Hydrogenated Amorphous

AbstractWe grow hydrogenated amorphous silicon (a-Si:H) by Hot-Wire Chemical Vapor Deposition (HWCVD). Our early work with this technique has shown that we can grow a-Si:H that is different from typical a-Si:H materials. Specifically, we demonstrated the ability to grow a-Si:H of exceptional quality with very low hydrogen (H) contents (0.01 to 4 at. %). The deposition chambers in which this early work was done have two limitations: they hold only small-area substrates and they are incompatible with a load-lock. In our efforts to scale up to larger area chambers—that have load-lock compatibility—we encountered difficulty in growing high-quality films that also have a low H content. Substrate temperature has a direct effect on the H content of HWCVD grown a-Si:H. We found that making dramatic changes to the other deposition process parameters—at fixed substrate temperature and filament-to-substrate spacing—did not have much effect on the H content of the resulting films in our new chambers. However, these changes did have profound effects on film quality. We can grow high-quality a-Si:H in the new larger area chambers at 4 at. % H. For example, the lowest known stabilized defect density of a-Si:H is approximately 2 × 1016 cm-3, which we have grown in our new chamber at 18 Å/s. Making changes to our original chamber—making it more like our new reactor—did not increase the hydrogen content at a fixed substrate temperature and filament-to-substrate spacing. We continued to grow high quality films with low H content in spite of these changes. An interesting, and very useful, result of these experiments is that the orientation of the filament with respect to silane flow direction had no influence on film quality or the H content of the films. The condition of the filament is much more important to growing quality films than the geometry of the chamber due to tungsten-silicide formation on the filament.

Wide-Gap a-Si:H Fabricated by Controlling Voids

1996 ◽  
Vol 420 ◽  
Author(s):  
K. Yoshino ◽  
W. Futako ◽  
Y. Wasai ◽  
I. Shimizu
Keyword(s):  
Amorphous Silicon ◽  
Band Gap ◽  
Hydrogenated Amorphous Silicon ◽  
Band Gaps ◽  
High Quality ◽  
Chemical Annealing ◽  
Improved Stability ◽  
Wide Gap ◽  
Hydrogenated Amorphous ◽  
Defect Densities

AbstractHigh quality wide gap hydrogenated amorphous silicon has been prepared using the chemical annealing technique. It was possible to prepare materials with band gaps ranging 1.8 to 2.1 eV by varying the preparation parameters. Low defect densities less than (3–8) x 1015 cm-3 could be maintained over the entire band gap range. Improved stability for light soaking was also observed in the wide gap materials.

Hydrogenated amorphous silicon films prepared at high substrate temperature: Properties and light induced degradation

1993 ◽  
Vol 73 (11) ◽  
pp. 7435-7440 ◽  
Author(s):  
Ratnabali Banerjee ◽  
Sukriti Ghosh ◽  
S. Chattopadhyay ◽  
A. K. Bandyopadhyay ◽  
P. Chaudhuri ◽  
...  
Keyword(s):  
Substrate Temperature ◽  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
High Substrate Temperature ◽  
Silicon Films ◽  
High Substrate ◽  
Hydrogenated Amorphous

High Rate Deposition of Stable Hydrogenated Amorphous Silicon in Transition from Amorphous to Microcrystalline Silicon

2003 ◽  
Vol 762 ◽  
Author(s):  
Guofu Hou ◽  
Xinhua Geng ◽  
Xiaodan Zhang ◽  
Ying Zhao ◽  
Junming Xue ◽  
...  
Keyword(s):  
Phase Transition ◽  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Chemical Vapor ◽  
High Rate ◽  
Very High Frequency ◽  
High Quality ◽  
Working Pressure ◽  
Hydrogen Dilution ◽  
Hydrogenated Amorphous

AbstractHigh rate deposition of high quality and stable hydrogenated amorphous silicon (a-Si:H) films were performed near the threshold of amorphous to microcrystalline phase transition using a very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) method. The effect of hydrogen dilution on optic-electronic and structural properties of these films was investigated by Fourier-transform infrared (FTIR) spectroscopy, Raman scattering and constant photocurrent method (CPM). Experiment showed that although the phase transition was much influenced by hydrogen dilution, it also strongly depended on substrate temperature, working pressure and plasma power. With optimized condition high quality and high stable a-Si:H films, which exhibit σph/σd of 4.4×106 and deposition rate of 28.8Å/s, have been obtained.

Fabrication of narrow-band-gap hydrogenated amorphous silicon by chemical annealing

1998 ◽  
Vol 84 (3) ◽  
pp. 1333-1339 ◽  
Author(s):  
Wataru Futako ◽  
Shinya Takeoka ◽  
Charles M. Fortmann ◽  
Isamu Shimizu
Keyword(s):  
Amorphous Silicon ◽  
Band Gap ◽  
Narrow Band ◽  
Hydrogenated Amorphous Silicon ◽  
Chemical Annealing ◽  
Hydrogenated Amorphous
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