Porous Silicon from Hydrogenated Amorphous Silicon: Comparison with Crystalline Porous Silicon

1996 ◽  
Vol 452 ◽  
Author(s):  
J.-N. Chazalviel ◽  
R. B. Wehrspohn ◽  
I. Solomon ◽  
F. Ozanam
Keyword(s):  
Porous Silicon ◽  
Room Temperature ◽  
Quantum Confinement Effect ◽  
Confinement Effect ◽  
High Resistivity ◽  
Hydrogenated Silicon ◽  
Boron Doped ◽  
Amorphous Hydrogenated Silicon ◽  
Recombination Centers ◽  
Hydrogenated Amorphous

AbstractDevice-grade, boron-doped amorphous hydrogenated silicon can be made microporous by anodization in ethanoic HF. The thickness of the porous layer is limited by an instability due to the high resistivity of the material. Amorphous porous silicon exhibits strong room-temperature photoluminescence around 1.5 eV even in samples containing a high density of non-radiative recombination centers. This demonstrates the presence of a spatial confinement effect, as opposed to quantum confinement effect for crystalline porous silicon. The temperature dependence of the luminescence intensity is also accounted for on the same grounds.

Efficient Visible Room Temperature Photoluminescence in Wide Gap Hydrogenated Amorphous Silicon-Carbon Alloys

1994 ◽  
Vol 336 ◽  
Author(s):  
Leandro R. Tessler ◽  
Ionel Solomon
Keyword(s):  
Room Temperature ◽  
Urbach Energy ◽  
Photoluminescence Intensity ◽  
Tetrahedral Coordination ◽  
Hydrogenated Silicon ◽  
Amorphous Hydrogenated Silicon ◽  
Silicon Carbon ◽  
Hydrogenated Amorphous ◽  
Carbon Concentrations ◽  
Phonon Model

ABSTRACTWe report a photoluminescence study on amorphous hydrogenated silicon carbon (a-Si1-xCx:H) alloys with carbon concentration in the range O < x < 0.5, prepared by PECVD in the “low-power” regime, that preserves the tetrahedral coordination of the carbon atoms. These samples have optical gaps higher than conventional “high power” alloys with the same carbon content. For carbon concentrations below x = 0.2 the photoluminescence behaves essentially as in pure a-Si:H with increased gap, Urbach energy and DOS. For higher carbon concentrations there is a change in the recombination process, that we attribute to a change in the dominating diffusion process of the photogenerated carriers. The integrated photoluminescence intensity for carbon-rich samples is very weakly dependent on the temperature, and at room temperature it approaches that of pure a-Si:H at 77K. For all samples, the photoluminescence bandwidth can be well described by a zero-phonon model.

Room Temperature Light Induced Electron Spin Resonauce In Undoped Hydrogenated Amorphous Silicon (a-Si:H)

1986 ◽  
Vol 70 ◽  
Author(s):  
R. Pandya ◽  
S. Zafar ◽  
E. A. Schiff
Keyword(s):  
Electron Spin ◽  
Room Temperature ◽  
Small Shift ◽  
Hydrogenated Silicon ◽  
Transient Photocurrent ◽  
Amorphous Hydrogenated Silicon ◽  
Spin Resonance ◽  
Absorption Studies ◽  
G Value ◽  
Hydrogenated Amorphous

ABSTRACTThe effects of illumination upon the absorption electron spin resonance spectrum of the dangling bond defect system have been studied in undoped amorphous hydrogenated silicon (a-Si:H). A small shift of the inhomogeneous envelope of the system towards higher g-value is observed at roomtemperature. The shift is not accompanied by a significant change in the signal. Results are reported which indicate that this shift is not due to illumination induced heating of the specimen or calibration changes of the spectrometer. The results may be related to previously reported optical bias effects upon transient photocurrent and photoinduced absorption studies.

Room-temperature electroluminescence from erbium-doped amorphous hydrogenated silicon

1998 ◽  
Vol 80 (1-4) ◽  
pp. 335-338 ◽  
Author(s):  
O.B Gusev ◽  
M.S Bresler ◽  
E.I Terukov ◽  
K.D Tsendin ◽  
I.N Yassievich
Keyword(s):  
Room Temperature ◽  
Hydrogenated Silicon ◽  
Amorphous Hydrogenated Silicon ◽  
Erbium Doped

Enhanced Surface Diffusion in Low-temperature a-Si:H Processing

2004 ◽  
Vol 808 ◽  
Author(s):  
George T. Dalakos ◽  
Joel L. Plawsky ◽  
Peter D. Persans
Keyword(s):  
Surface Roughness ◽  
Surface Diffusion ◽  
Room Temperature ◽  
Cathodic Deposition ◽  
Hydrogenated Silicon ◽  
Surface Diffusivity ◽  
Amorphous Hydrogenated Silicon ◽  
Anodic Deposition ◽  
Enhanced Surface ◽  
Global Parameters

ABSTRACTGlow discharge amorphous hydrogenated silicon (a-Si:H) prepared at near room temperature typically results in an inhomogeneous morphology that is undesirable for a number of thin film applications. The most commonly observed features of this include columnar morphology and surface roughness. This usually results from anodic deposition, where substrates are placed on the grounded electrode. We have discovered that placing substrates on the RF-powered electrode (referred to as cathodic deposition) offers a much wider processing range for homogenous growth than anodic growth. We have also found that the magnitude of the surface roughness and the bulk void fraction of both anodic and cathodic a-Si:H thin films processed at low-temperatures is proportional to ∼D/F, where D is the surface diffusivity and F, the adatom flux, though anodic and cathodic deposition affect these global parameters differently. Surface processes unique to cathodic deposition can enhance adatom surface diffusion, while diffusion during anodic deposition is fixed and cannot attain homogeneous growth at high adatom fluxes. Processing a-Si:H on the cathode, associated with enhanced adatom surface diffusion, allows for homogeneous growth even at high deposition rates that has benefits for a number of applications.

Room-temperature electroluminescence of erbium-doped amorphous hydrogenated silicon

1997 ◽  
Vol 70 (2) ◽  
pp. 240-242 ◽  
Author(s):  
O. B. Gusev ◽  
A. N. Kuznetsov ◽  
E. I. Terukov ◽  
M. S. Bresler, ◽  
V. Kh. Kudoyarova ◽  
...  
Keyword(s):  
Room Temperature ◽  
Hydrogenated Silicon ◽  
Amorphous Hydrogenated Silicon ◽  
Erbium Doped

Phosphorus and Boron Doping of a-Si:H Effects of Deposition Temperature

1987 ◽  
Vol 95 ◽  
Author(s):  
M. J. M. Pruppers ◽  
K. H. M. Maessen ◽  
J. Bezemer ◽  
F. H. P. M. Habraken ◽  
W. F. van der Weg
Keyword(s):  
Deposition Temperature ◽  
Room Temperature ◽  
Hydrogenated Amorphous Silicon ◽  
Boron Doping ◽  
Dark Conductivity ◽  
Temperature Conductivity ◽  
Room Temperature Conductivity ◽  
Boron Doped ◽  
Hydrogenated Amorphous ◽  
Deposited Films

AbstractHeavily phosphorus and boron doped hydrogenated amorphous silicon films were deposited in the temperature range 50 to 300 °C. Concentrations of P, B and H, IR spectra and room temperature conductivity have been measured. When the deposition temperature is raised from 50 to 300 °C the concentration of P increases, while the concentration of B decreases. The dark conductivity of both P and B doped films decreases dramatically when the deposition temperature is lowered. We interpret these results on the basis of assumptions concerning the microstructure of the deposited films, and especially the variation of this structure with deposition temperature.

PREPARATION AND CHARACTERIZATION OF GRADED BANDGAP AMORPHOUS HYDROGENATED SILICON-SULFUR THIN FILMS

1992 ◽  
Vol 06 (08) ◽  
pp. 469-475
Author(s):  
M. HAMMAM
Keyword(s):  
Amorphous Silicon ◽  
Hydrogenated Silicon ◽  
Amorphous Hydrogenated Silicon ◽  
Graded Layers ◽  
Rf Glow Discharge ◽  
Optical Bandgaps ◽  
Silicon Based ◽  
Hydrogenated Amorphous ◽  
Graded Bandgap

Compositionally graded hydrogenated amorphous silicon-sulfur alloys ( a-Si 1−x S x: H ) were grown by RF glow discharge decomposition of silane and hydrogen sulfide gases. Infrared spectra show clear evidence for the incorporation of sulfur in the form of Si-S bonds in the material. The graded bandgap films possess optical bandgaps ranging from 1.91 to 2.05 eV depending on the RF power. The compositionally graded layers display high photosensitivities indicating that they may be ideal candidates for use in amorphous silicon based tandem cells.

Microstructure and Dangling Bond Defects in Amorphous Hydrogenated Silicon Deposited Near Room Temperature

1992 ◽  
Vol 258 ◽  
Author(s):  
Man Ken Cheung ◽  
Mark A. Petrich
Keyword(s):  
Room Temperature ◽  
Dangling Bond ◽  
Optimum Conditions ◽  
Band Tail ◽  
Hydrogenated Silicon ◽  
Photothermal Deflection Spectroscopy ◽  
Amorphous Hydrogenated Silicon ◽  
Photothermal Deflection ◽  
Substrate Temperatures ◽  
Absorption Measurements

ABSTRACTThe microstructure of high-density amorphous hydrogenated silicon (a-S.i:H) films deposited at 50°C substrate temperature was revealed by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopies to be similar to that of “device-quality” a-Si:H films deposited at standard “optimum” conditions. However, optical absorption measurements of these low microstructure 50°C films with photothermal deflection spectroscopy indicate that they have higher densities of gap state defects and localized band tail states than “device-quality” films deposited at standard substrate temperatures. The correlation between the amount of microstructure and electronic properties is not unique. A low amount of microstructure is a necessary, but not sufficient, requirement for high electronic quality a-Si:H films.

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