Molecular Hydrogen in Hot-Wire Hydrogenated Amorphous Silicon

1998 ◽  
Vol 507 ◽  
Author(s):  
Xiao. Liu ◽  
E. Iwaniczko ◽  
R.O. Pohl ◽  
R.S. Crandall
Keyword(s):  
Internal Friction ◽  
Amorphous Silicon ◽  
Molecular Hydrogen ◽  
Solid Phase ◽  
Hydrogenated Amorphous Silicon ◽  
Chemical Vapor ◽  
Amorphous Solid ◽  
Hot Wire ◽  
Hydrogenated Amorphous ◽  
Triple Point Temperature

ABSTRACTWe have studied the elastic properties of hydrogenated amorphous silicon (a-Si:H) prepared by hot wire chemical-vapor deposition (HWCVD). With 1 at.% H, this material has been found to be the only amorphous solid which has a low-temperature internal friction more than two orders of magnitude smaller than all other amorphous solids studied to date, as reported recently. As the hydrogen concentration increases above 1 at.%, a broad relaxation peak in internal friction around 5 K is observed. Even more striking is an extremely narrow peak in internal friction accompanied by a discontinuous change in the sound velocity at 13.8 K, which coincides with the triple point temperature of molecular hydrogen. Evidences are provided to show that this anomaly is caused by bulk molecular hydrogen which undergoes a liquid-solid phase transition. This is the first observation for the existence of bulk H2 in HWCVD a-Si:H.

Light-Induced Increase in Two-Level Tunneling States in Hydrogenated Amorphous Silicon

1999 ◽  
Vol 557 ◽  
Author(s):  
Xiao Liu ◽  
R.O. Pohl ◽  
R.S. Crandall
Keyword(s):  
Chemical Vapor Deposition ◽  
Low Temperature ◽  
Internal Friction ◽  
Amorphous Silicon ◽  
Vapor Deposition ◽  
Room Temperature ◽  
Hydrogenated Amorphous Silicon ◽  
Chemical Vapor ◽  
Hot Wire ◽  
Hydrogenated Amorphous

AbstractWe observe an increase of the low-temperature internal friction of hydrogenated amorphous silicon prepared by both hot-wire and plasma-enhanced chemical-vapor deposition after extended light-soaking at room temperature. This increase, and the associated change in sound velocity, can be explained by an increase of the density of two-level tunneling states, which serves as a measure of the lattice disorder. The amount of increase in internal friction is remarkably similar in both types of films although the amount and the microstructure of hydrogen are very different. Experiments conducted on a sample prepared by hot-wire chemical-vapor deposition show that this change anneals out gradually at room temperature in about 70 days. Possible relation of the light-induced changes in the low-temperature elastic properties to the Staebler-Wronski effect is discussed.

Rapid solid-phase crystallization of high-rate, hot-wire chemical-vapor-deposited hydrogenated amorphous silicon

2006 ◽  
Vol 89 (16) ◽  
pp. 161910 ◽  
Author(s):  
David L. Young ◽  
Paul Stradins ◽  
Yueqin Xu ◽  
Lynn Gedvilas ◽  
Bob Reedy ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Solid Phase ◽  
Hydrogenated Amorphous Silicon ◽  
Chemical Vapor ◽  
High Rate ◽  
Hot Wire ◽  
Solid Phase Crystallization ◽  
Chemical Vapor Deposited ◽  
Hydrogenated Amorphous

New Results on the Microstructure of Amorphous Silicon as Observed by Internal Friction

1997 ◽  
Vol 467 ◽  
Author(s):  
R. S. Crandall ◽  
A. H. Mahan ◽  
E. Iwaniczko ◽  
K. M. Jones ◽  
X. Liu ◽  
...  
Keyword(s):  
Internal Friction ◽  
Amorphous Silicon ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Amorphous Solid ◽  
Amorphous Solids ◽  
Electron Beam Evaporation ◽  
Hot Wire ◽  
Si Films ◽  
Hydrogenated Amorphous

ABSTRACTWe have measured the low temperature internal friction (Q−1) of amorphous silicon (a-Si) films. Electron-beam evaporation leads to the well-known temperature-independent plateau common to all amorphous solids. For hydrogenated amorphous silicon (a-Si:H) with about 1 at.% H produced by hot wire chemical vapor deposition, however, the value of is over two hundred times smaller than for e-beam a-Si. This is the first observation of an amorphous solid without any significant low energy excitations. This finding offers the opportunity to study amorphous solids containing controlled densities of tunneling defects, and thus to explore their nature.

Saturated defect densities of hydrogenated amorphous silicon grown by hot-wire chemical vapor deposition at rates up to 150 Å/s

2001 ◽  
Vol 78 (24) ◽  
pp. 3788-3790 ◽  
Author(s):  
A. H. Mahan ◽  
Y. Xu ◽  
B. P. Nelson ◽  
R. S. Crandall ◽  
J. D. Cohen ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Amorphous Silicon ◽  
Vapor Deposition ◽  
Hydrogenated Amorphous Silicon ◽  
Chemical Vapor ◽  
Hot Wire ◽  
Hydrogenated Amorphous ◽  
Defect Densities

Solid phase crystallization of hot-wire CVD amorphous silicon films

2005 ◽  
Vol 862 ◽  
Author(s):  
David L. Young ◽  
Paul Stradins ◽  
Eugene Iwaniczko ◽  
Bobby To ◽  
Bob Reedy ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Solid Phase ◽  
Chemical Vapor ◽  
High Deposition Rate ◽  
Halogen Lamp ◽  
Hot Wire ◽  
Solid Phase Crystallization ◽  
Glass Substrates ◽  
Tube Furnaces ◽  
Hydrogenated Amorphous

AbstractWe measure times for complete solid phase crystallization (SPC) of hydrogenated amorphous silicon (a-Si:H) thin films that vary eight orders of magnitude, from a few ms to a few days. The time-to-crystallization activation energy is consistent with literature values of approximately 3.4 eV but the prefactor is markedly different for hot-wire chemical vapor deposition (HWCVD) films than for plasma-enhanced (PE) CVD films. The crystallized films were 0.3 – 2 μm thick, and deposited by high deposition rate (10-100 Å/s) HWCVD or standard PECVD onto glass substrates. We annealed these a-Si:H films over a wide temperature range (500 to 1100 °C) using techniques including simple hot-plates and tube furnaces, rapid thermal annealing by a tungsten-halogen lamp, and microwave electromagnetic heating at 2.45 GHz (magnetron) and 110 GHz (gyrotron).

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