scholarly journals Hydrogen dynamics and light-induced structural changes in hydrogenated amorphous silicon

2006 ◽  
Vol 74 (8) ◽  
Author(s):  
T. A. Abtew ◽  
D. A. Drabold
Keyword(s):  
Amorphous Silicon ◽  
Structural Changes ◽  
Hydrogenated Amorphous Silicon ◽  
Hydrogenated Amorphous

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.

Annealing of Ion-Implanted Hydrogenated Amorphous Silicon: Stable and Removable Damage

1993 ◽  
Vol 297 ◽  
Author(s):  
A.J.M. Berntsen ◽  
P.A. Stolk ◽  
W.F. VAN DER WEG ◽  
F.W. Saris
Keyword(s):  
Amorphous Silicon ◽  
Structural Changes ◽  
Hydrogenated Amorphous Silicon ◽  
Structural Disorder ◽  
High Dose ◽  
Angle Variation ◽  
Reflection And Transmission ◽  
Hydrogenated Amorphous ◽  
Average Bond ◽  
High Dose Implantation

Hydrogenated amorphous silicon (a-Si:H) films were irradiated with 1-MeV Si+ ions. The accumulation and annealing of ion damage was investigated by Raman scattering, optical reflection and transmission, and conductivity measurements. For damage levels up to 0.003 displacements per atom, electrical defects are created with no measurable effect on the structural properties. These defects can be completely annealed out at 180°C. Further irradiation results in an increase in the average bond-angle variation in the films. This structural disorder causes a decrease of the optical band gap with 0.46 eV. The structural changes caused by high-dose implantation can not be reversed by annealing at 180° C, which results in the formation of anneal-stable electrical defects.

Mechanisms for Metastability in Hydrogenated Amorphous Silicon

2000 ◽  
Vol 609 ◽  
Author(s):  
R. Biswas ◽  
Y.-P. Li ◽  
B.C. Pan
Keyword(s):  
Amorphous Silicon ◽  
Structural Changes ◽  
Defect Formation ◽  
Hydrogenated Amorphous Silicon ◽  
Dangling Bond ◽  
Dangling Bonds ◽  
New Model ◽  
Gap States ◽  
Hydrogenated Amorphous ◽  
Metastable Defect

ABSTRACTWe propose metastabilities in amorphous silicon fall into two classes. One class is the local changes of structure affecting a macroscopic fraction of sites. The other class is the metastable generation of dangling bonds with mid-gap states. The local metastability is explained by a new metastable state formed when H is flipped to the backside of the Si-H bond at monohydride sites. The dipole moment of this H-flip defect is larger and increases the infrared absorption. This H-flip defect accounts for large structural changes observed on light soaking including larger absorption and volume dilation. We propose a new model for the generation of metastable dangling bonds. The new ‘silicon network rebonding model’ involves breaking of weak silicon bonds and formation of isolated dangling bonds, through rebonding of the silicon network. Hydrogen motion is not involved in metastable defect formation. Defect formation proceeds by breaking weak silicon bonds and formation of dangling bond-floating bond pairs. The floating bonds migrate through the network and annihilate, producing isolated dangling bonds. This new model provides a new platform for understanding the atomistic origins of lightinduced degradation.

scholarly journals Sputtered Non-Hydrogenated Amorphous Silicon as Alternative Absorber for Silicon Photovoltaic Technology

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6550
Author(s):  
Susana Fernández ◽  
J. Javier Gandía ◽  
Elías Saugar ◽  
Mª Belén Gómez-Mancebo ◽  
David Canteli ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Room Temperature ◽  
Structural Changes ◽  
Continuous Wave ◽  
Low Cost ◽  
Hydrogenated Amorphous Silicon ◽  
Amorphous Structure ◽  
Gas Pressure ◽  
Hydrogenated Amorphous ◽  
Deposition Conditions

Non-hydrogenated amorphous-silicon films were deposited on glass substrates by Radio Frequency magnetron sputtering with the aim of being used as precursor of a low-cost absorber to replace the conventional silicon absorber in solar cells. Two Serie of samples were deposited varying the substrate temperature and the working gas pressure, ranged from 0.7 to 4.5 Pa. The first Serie was deposited at room temperature, and the second one, at 325 °C. Relatively high deposition rates above 10 Å/s were reached by varying both deposition temperature and working Argon gas pressure to ensure high manufacturing rates. After deposition, the precursor films were treated with a continuous-wave diode laser to achieve a crystallized material considered as the alternative light absorber. Firstly, the structural and optical properties of non-hydrogenated amorphous silicon precursor films were investigated by Raman spectroscopy, atomic force microscopy, X-ray diffraction, reflectance, and transmittance, respectively. Structural changes were observed in the as-deposited films at room temperature, suggesting an orderly structure within an amorphous silicon matrix; meanwhile, the films deposited at higher temperature pointed out an amorphous structure. Lastly, the effect of the precursor material’s deposition conditions, and the laser parameters used in the crystallization process on the quality and properties of the subsequent crystallized material was evaluated. The results showed a strong influence of deposition conditions used in the amorphous silicon precursor.

Photoinduced Structural Changes in Hydrogenated Amorphous Silicon

1998 ◽  
Vol 507 ◽  
Author(s):  
K. Shimizu ◽  
T. Tabuchi ◽  
K. Hattori ◽  
H. Kida ◽  
H. Okamoto
Keyword(s):  
Amorphous Silicon ◽  
Network Structure ◽  
Structural Changes ◽  
Light Exposure ◽  
Hydrogenated Amorphous Silicon ◽  
Structural Disorder ◽  
Separation Procedure ◽  
Absorption Signal ◽  
Amorphous Network ◽  
Hydrogenated Amorphous

ABSTRACTPolarized electroabsorption method has been used to study photo-induced structural changes in hydrogenated amorphous silicon. The field-modulated absorption signal consists of two components, one of which is the true polarization-dependent electroabsorption serving as an indicator of the structural disorder, and the other is the thermoabsorption resulted from the temperature modulation due to Joule heating. The thermoabsorption component has removed from the observed field-modulated absorption signal to make an accurate and reliable evaluation of structural disorder by phase-separation procedure. As a result, about 15-25 % of the observed signal arises from the thermoabsorption effect for the Tauc gap region. Nevertheless, any essential alteration is not needed for our previous PEA results. The internal stress as well as density have been measured to provide another evidences for the photo-induced structural change. It is found that amorphous silicon film expands and the density tends to decrease upon light-exposure, the temporal behaviors of which coincide with that of the PEA ratio factor indicating disorderness of the amorphous network structure. The results permit us to conclude that a large scaled change in the amorphous network structure occurs under light-exposure, which might proceed the light-induced creation of metastable dangling bond defects.

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