Effect of Annealing on Microstructure in (Doped and Undoped) Hydrogenated Amorphous Silicon Films

2014 ◽  
Vol 1666 ◽  
Author(s):  
W. Beyer ◽  
W. Hilgers ◽  
D. Lennartz ◽  
F.C. Maier ◽  
N.H. Nickel ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Hydrogen Content ◽  
Hydrogenated Amorphous Silicon ◽  
Silicon Films ◽  
Boron Doped ◽  
Scan Time ◽  
Laser Treatments ◽  
Laser Impact ◽  
Definition Of ◽  
Hydrogenated Amorphous

ABSTRACTLaser heating and annealing of hydrogenated amorphous silicon (a-Si:H) films is of interest for improved material properties. Due to the variety of possible laser treatments with regard to wavelength, pulse duration, scan time etc., the definition of laser impact on the material is a challenge which we try to approach by comparing properties of laser and oven treated materials. Here we report on the effect of oven heat treatment (up to TA= 575°C) on microstructure and hydrogen content of hydrogenated amorphous silicon films, as detected by measurements of infrared absorption and of effusion of hydrogen as well as of implanted helium. The latter technique has been found to measure isolated voids (cavities) of the size of silicon divacancies and larger. Undoped as well as phosphorus and boron doped plasma-deposited a-Si:H films of various hydrogen content (< 15 at.%) were investigated, including undoped device grade a-Si:H. The results show little indication for void-related microstructure in the as-deposited and annealed state for material with a concentration of silicon bonded hydrogen below 5 at. %. At higher hydrogen concentration, evidence is found that hydrogen out-diffusion due to annealing causes isolated voids in concentrations up to about 1020 cm-3. A possible mechanism for the annealing induced (micro-)void generation is discussed.

Hydrogen Diffusion in Boron-Doped Hydrogenated Amorphous Silicon Films: Crystallization and Induced Structural Changes

2005 ◽  
Vol 864 ◽  
Author(s):  
F. Kail ◽  
A. Hadjadj ◽  
P. Roca i Cabarrocas
Keyword(s):  
Amorphous Silicon ◽  
Structural Changes ◽  
Hydrogen Diffusion ◽  
Hydrogen Plasma ◽  
Hydrogenated Amorphous Silicon ◽  
Silicon Films ◽  
Hydrogen Atoms ◽  
Boron Doped ◽  
Hydrogenated Amorphous ◽  
Positively Charged

AbstractWe have studied the evolution of the structure of boron-doped hydrogenated amorphous silicon films exposed to a hydrogen plasma. From the early stages of exposure, hydrogen diffuses and forms a thick H-rich subsurface. At longer times, hydrogen plasma leads to the formation of a microcrystalline layer via chemical transport without crystallization of the initial layer. We observe that the hydrogen content increases in the films during a plasma exposure and once the microcrystalline layer is formed hydrogen diffuses out of the sample accompanied with a decrease in the boron content. This effect can be attributed to the electric field developed within the heterojunction a-Si:H/μc-Si:H that drives the positively charged hydrogen atoms in the boron-doped layer towards the μc-Si:H layer.

How much hydrogen and voids are energetically stable in silicon thin films?

2004 ◽  
Vol 813 ◽  
Author(s):  
Anna Fontcuberta i Morral ◽  
Holger Vach ◽  
Pere Roca i Cabarrocas
Keyword(s):  
Thin Films ◽  
Amorphous Silicon ◽  
Void Fraction ◽  
Hydrogen Content ◽  
Formation Energy ◽  
Hydrogenated Amorphous Silicon ◽  
Silicon Films ◽  
Homogeneous Distribution ◽  
Silicon Thin Films ◽  
Hydrogenated Amorphous

ABSTRACTWe have developed a model to account for the effects of hydrogen and voids on the structural stability of silicon thin films. The model is based on both experiments and theory. First, hydrogenated amorphous silicon films (a-Si:H) with various hydrogen contents were obtained by Plasma Enhanced Chemical Vapor Deposition. A linear correlation between hydrogen content and void fraction was observed. By tuning the deposition conditions, polymorphous silicon films with hydrogen contents up to 15%, very small void fractions (0.5%) and excellent electronic properties were also obtained. Density Functional Theory (DFT) calculations were performed to determine the formation energy for four types of silicon tetrahedra of the form Si-SinH4−n (n=1, 2, 3, 4). In our model, these tetrahedral units are considered as the building blocks of the silicon thin films. Considering a homogeneous distribution of hydrogen in the solid, the proportion of the different SiSinH4−n tetrahedra as a function of the hydrogen concentration was calculated. Then, the formation energy of hydrogenated amorphous silicon (a-Si:H) was calculated as a function of the hydrogen content and for various porosities. The model predicts that hydrogen incorporation does render the a-Si:H structure unstable for different hydrogen contents depending on the void fraction. Our results show that polymorphous silicon films with hydrogen concentrations up to 15% can be as stable as standard amorphous silicon with 2% hydrogen content, provided that the presence of hydrogen is not associated with the incorporation of porosity in the film.

Microstructure Characterization of Hydrogenated Amorphous Silicon Films by Rare Gas Effusion Studies

2001 ◽  
Vol 664 ◽  
Author(s):  
Wolfhard Beyer
Keyword(s):  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Silicon Films ◽  
Rare Gas ◽  
Rare Gases ◽  
Boron Doped ◽  
Rare Gas Atoms ◽  
Hydrogenated Amorphous ◽  
Substrate Temperatures

ABSTRACTThe effusion of the rare gases neon and helium, as well as of hydrogen, was studied for plasma deposited (boron-doped and undoped) hydrogenated amorphous silicon films, grown at various substrate temperatures. Rare gas atoms were incorporated into the material during the growth process or by ion implantation. The results suggest that helium and neon effusion spectra give information on the material microstructure.

Reduction of Si-H2 Bond Content in Hydrogenated Amorphous Silicon Prepared by Mercury-Sensitized Photochemical Vapor Deposition

1990 ◽  
Vol 192 ◽  
Author(s):  
N. Sakuma ◽  
H. Nozaki ◽  
T. Niiyama ◽  
H. Ito
Keyword(s):  
Light Intensity ◽  
Amorphous Silicon ◽  
Hydrogen Content ◽  
Vapor Deposition ◽  
Hydrogenated Amorphous Silicon ◽  
Silicon Films ◽  
The Other ◽  
Photochemical Vapor Deposition ◽  
Hydrogenated Amorphous ◽  
Deposition Conditions

ABSTRACTThe ratio of Si-H2 bonds to hydrogen content in hydrogenated amorphous silicon films, prepared by mercury-sensitized photochemical vapor deposition, depends on the deposition conditions, in particular on the distance between the substrate and the light-transparent window.The ratio is reduced from 20 % to 8 % by decreasing the distance from 30 mm to 8 mm. On the other hand, the hydrogen content remains constant at 15 at.%. Decreasing the distance has been found to be almost equivalent to increasing the light intensity, especially 254 nm-light intensity.

scholarly journals Infrared analysis on hydrogen content and Si-H bonding configurations of hydrogenated amorphous silicon films

2003 ◽  
Vol 52 (1) ◽  
pp. 169
Author(s):  
Luo Zhi ◽  
Lin Xuan-Ying ◽  
Lin Shun-Hui ◽  
Yu Chu-Ying ◽  
Lin Kui-Xun ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Hydrogen Content ◽  
Hydrogenated Amorphous Silicon ◽  
Silicon Films ◽  
Infrared Analysis ◽  
Hydrogenated Amorphous
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