Properties of Nano-crystalline Silicon-Carbide Films Prepared Using Modulated RF- PECVD

2009 ◽  
Vol 1153 ◽  
Author(s):  
Feng Zhu ◽  
Jian Hu ◽  
Ilvydas Matulionis ◽  
Augusto Kunrath ◽  
Arun Madan
Keyword(s):  
Silicon Carbide ◽  
Volume Fraction ◽  
Crystalline Silicon ◽  
Dark Conductivity ◽  
Crystalline Volume Fraction ◽  
Photothermal Deflection Spectroscopy ◽  
Nano Crystalline ◽  
Dc Bias ◽  
Photothermal Deflection ◽  
Sic Films

AbstractWe report on the fabrication of nano-crystalline silicon-carbide (nc-SiC) using pulse modulated RF-PECVD technique, from silane (SiH4) and methane (CH4) gas mixtures which is highly diluted in hydrogen (H2). The microstructure of nc-SiC material is nanometer-size silicon crystallites embedded in amorphous silicon-carbide (a-SiC) matrix. As carbon incorporation in nc-Si film increases, the bandgap is enlarged from 1.1eV to 1.55eV as measured by Photothermal Deflection Spectroscopy (PDS) while the crystalline volume fraction decreases from 70% to about 20%. It is found that the crystalline volume fraction, grain size and dark conductivity of nc-SiC films can be enhanced with applying a negative DC bias to substrate during deposition.

Electronic Properties of Microcrystalline Silicon

1997 ◽  
Vol 467 ◽  
Author(s):  
R. Carius ◽  
F. Finger ◽  
U. Backhausen ◽  
M. Luysberg ◽  
P. Hapke ◽  
...  
Keyword(s):  
Vapour Deposition ◽  
Volume Fraction ◽  
Crystalline Silicon ◽  
Chemical Vapour ◽  
Structural Defects ◽  
Photoluminescence Properties ◽  
Crystalline Volume Fraction ◽  
Microcrystalline Silicon ◽  
Photothermal Deflection Spectroscopy ◽  
Photothermal Deflection

ABSTRACTThe electronic and optical properties of microcrys tall ine silicon films prepared by plasma enhanced chemical vapour deposition are investigated with Hall-effect, electrical conductivity, photothermal deflection spectroscopy and photoluminescence measurements. In particular, the influence of the grain size and the crystalline volume fraction on the conductivity, the carrier density and the Hall mobility is investigated in highly doped films. A percolation model is proposed to describe the observed transport data. Photoluminescence properties were studied in un-doped films. It is proposed that the photoluminescence is due to recombination at structural defects similar to those observed in crystalline silicon.

Nano-Crystalline Si Based Alloy (nc-SiXY) with Band Gap of 1.5 eV as the Solar Cell Absorber Layer Fabricated by VHF-PECVD Technique

2012 ◽  
Vol 1426 ◽  
pp. 87-92
Author(s):  
Feng Zhu ◽  
Jian Hu ◽  
Ilvydas Matulionis ◽  
Josh Gallon ◽  
Arun Madan
Keyword(s):  
Volume Fraction ◽  
Crystalline Silicon ◽  
Chemical Vapor ◽  
Optical Bandgap ◽  
Absorber Layer ◽  
Crystalline Volume Fraction ◽  
Very High Frequency ◽  
Nano Crystalline ◽  
Silicon Based ◽  
Gas Ratio

ABSTRACTWe describe the properties of nano-crystalline silicon based alloy (nc-SiXY) prepared by a very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) technique with silane (SiH4) and XY gas mixtures and diluted in hydrogen (H2) at low deposition temperature. Varying the gas ratio among SiH4, H2 and XY gasses could alter the optical bandgap and structure. The nc-Si films with high crystalline volume fraction were first prepared, and then the XY gasses were added in order to tune the microstructure and opto-electronic properties of this nano-crystalline silicon based alloy. We have characterized the materials using UV-VIS-NIR, Raman, Constant Photocurrent Method (CPM), dark- and photo-conductivity. As XY gas flows were increased, the optical bandgap of nc-SiXY films increased, while its crystalline volume fraction and conductivity decreased. With proper control of the silane concentration, XY/SiH4 gas ratio, and deposition pressure, we have fabricated the nc-SiXY film with optical bangap of about 1.5eV. Applying this material as the absorber layer in p-i-n devices with configuration of textured ZnO/nc-p+/nc-SiXY/a-n+/Ag, the efficiency is 7.25% (Voc=0.616V, Jsc=17.69mA/cm2, FF= 0.666) with thickness of ∼0.8μm.

Transport Path in Hydrogenated Microcrystalline Silicon

2002 ◽  
Vol 715 ◽  
Author(s):  
N. Wyrsch ◽  
C. Droz ◽  
L. Feitknecht ◽  
J. Spitznagel ◽  
A. Shah
Keyword(s):  
Raman Spectroscopy ◽  
Volume Fraction ◽  
Conductivity Measurement ◽  
Dark Conductivity ◽  
Transition Regime ◽  
Conductivity Data ◽  
Crystalline Volume Fraction ◽  
Microcrystalline Silicon ◽  
Crystalline Fraction ◽  
Transport Path

AbstractUndoped microcrystalline silicon samples deposited in the transition regime between amorphous and microcrystalline growth have been investigated by dark conductivity measurement and Raman spectroscopy. From the latter, a semi-quantitative crystalline volume fraction Xc of the sample was deduced and correlated with dark conductivity data in order to reveal possible percolation controlled transport. No threshold was observed around the critical crystalline fraction value Xc of 33%, as reported previously, but a threshold in conductivity data was found at Xc≈50%. This threshold is interpreted here speculatively as being the result of postoxidation, and not constituting an actual percolation threshold.

Intrinsic and Doped m c-Si:H TFT Layers using 13.56 MHz PECVD at 250°C

2004 ◽  
Vol 808 ◽  
Author(s):  
Czang-Ho Lee ◽  
Denis Striakhilev ◽  
Arokia Nathan
Keyword(s):  
Performance Improvement ◽  
Volume Fraction ◽  
Chemical Vapor ◽  
Dark Conductivity ◽  
Rf Power ◽  
Crystalline Volume Fraction ◽  
Microcrystalline Silicon ◽  
Bias Stress ◽  
Hydrogen Dilution ◽  
Low Threshold

ABSTRACTUndoped and n+ hydrogenated microcrystalline silicon (μc-Si:H) films for thin film transistors (TFTs) were deposited at a temperature of 250°C with 99 ∼ 99.6 % hydrogen dilution of silane by standard 13.56 MHz plasma enhanced chemical vapor deposition (PECVD). High crystallinity m c-Si:H films were achieved at 99.6 % hydrogen dilution and at low rf power. An undoped 80 nm thick m c-Si:H film showed a dark conductivity of the order of 10−7 S/cm, the photosensitivity of an order of 102, and a crystalline volume fraction of 80 %. However, a 60 nm thick n+ μc-Si:H film deposited using a seed layer showed a high dark conductivity of 35 S/cm and a crystalline volume fraction of 60 %. Using n+ μc-Si:H films as drain and source contact layers in a-Si:H TFTs provides substantial performance improvement over n+ a-Si:H contacts. Finally, fully μ c-Si:H TFTs incorporating intrinsic m c-Si:H films as channel layers and n+ μc-Si:H films as contact layers have been fabricated and characterized. These TFTs exhibit a low threshold voltage and a field effect mobility of 0.85 cm2/Vs, and are far more stable under gate bias stress than a-Si:H TFTs.

Photoluminescence in B-doped μc-Si:H

1992 ◽  
Vol 283 ◽  
Author(s):  
S. Q. Gu ◽  
J. M. Viner ◽  
P. C. Taylor ◽  
M. J. Williams ◽  
W. A. Turner ◽  
...  
Keyword(s):  
Broad Band ◽  
Chemical Vapor ◽  
Boron Doping ◽  
Dark Conductivity ◽  
Microcrystalline Silicon ◽  
Band Tail ◽  
Pl Spectra ◽  
Photothermal Deflection Spectroscopy ◽  
Photothermal Deflection ◽  
Hydrogenated Amorphous

ABSTRACTPhotoluminescence (PL) has been investigated in hydrogenated microcrystalline silicon (μc-Si:H) samples as a function of boron doping for films prepared by remote plasma enhanced chemical vapor deposition. When the dark conductivity a is below about 10-5 S/cm, the PL spectra exhibit a shape which is close to that of the so-called band tail PL in undoped hydrogenated amorphous silicon (a-Si:H) at 77 K. When a increases, the PL intensity decreases at 77 K. For samples with a on the order of 10-3 S/cm, the PL spectra show only a narrow, low energy PL band which peaks around 0.8–0.9 eV. In these samples, the PL at higher energy is essentially not observable. This trend is similar to that which occurs in doped a-Si:H. However, for higher doping levels (σ ∼ 1 S/cm) the PL in μc-Si:H, although very weak, exhibits a broad band which contains intensity at higher energies. The absorption spectra in these samples, as measured by photothermal deflection spectroscopy (PDS), show the same relationships with the corresponding PL spectra as do the PDS spectra in doped a-Si:H.

Electronic and Optical Properties of a-Si1−xCx:H Films Produced From Admixtures of Silane and Ditertiarybutylsilane

1994 ◽  
Vol 336 ◽  
Author(s):  
K. Gaughan ◽  
J.M. Viner ◽  
P.C. Taylor
Keyword(s):  
Electrical Conductivity ◽  
Silicon Carbide ◽  
Optical Properties ◽  
Chemical Vapor Deposition ◽  
Amorphous Silicon ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Photothermal Deflection Spectroscopy ◽  
Optical And Electronic Properties ◽  
Photothermal Deflection

ABSTRACTWe investigated the optical and electronic properties of amorphous silicon carbide (a-Si1−xCx:H) films produced by plasma enhanced chemical vapor deposition from admixtures of silane and ditertiarybutylsilane [SiH2 (C4H9) 2 or DTBS] using photothermal deflection spectroscopy, electrical conductivity and its temperature dependence as well as photoconductivity. These a-Si1−xCx:H films exhibit low Urbach energies and high photoconductivities similar to films produced with other carbon feedstock sources. We also present our results for hydrogen diluted a-Si1−xCx:H films using DTBS as the carbon feedstock source.

Optimization of Optoelectronic Properties of a-SiC:H Films

1993 ◽  
Vol 297 ◽  
Author(s):  
F. Demichelis ◽  
G. Crovini ◽  
C.F. Pirri ◽  
E. Tresso ◽  
R. Galloni ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Silicon Carbide ◽  
Ftir Spectroscopy ◽  
Amorphous Silicon ◽  
Reflectance Spectroscopy ◽  
High Hydrogen ◽  
Hydrogen Dilution ◽  
Photothermal Deflection Spectroscopy ◽  
Device Structures ◽  
Photothermal Deflection

Amorphous silicon carbide films have been deposited by PECVD in SiH4+CH4+H2 mixtures at different hydrogen dilutions. The optoelecuonic properties of the films have been measured by transmittance-reflectance spectroscopy, photothermal deflection spectroscopy and photo and dark electrical conductivity. Structural properties have been obtained by FTIR spectroscopy. It was found that high hydrogen dilution leads to materials of improved quality, p-i-n device structures have been deposited with intrinsic layers at different hydrogen dilution levels.

Defects in Hydrogenated Amorphous Silicon Carbide Alloys using Electron Spin Resonance and Photothermal Deflection Spectroscopy

2009 ◽  
Vol 1153 ◽  
Author(s):  
Brian J. Simonds ◽  
Feng Zhu ◽  
Josh Gallon ◽  
Jian Hu ◽  
Arun Madan ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Electron Spin Resonance ◽  
Amorphous Silicon ◽  
Electron Spin ◽  
Carbon Concentration ◽  
Hydrogenated Amorphous Silicon ◽  
Photothermal Deflection Spectroscopy ◽  
Spin Resonance ◽  
Photothermal Deflection ◽  
Hydrogenated Amorphous

AbstractHydrogenated amorphous silicon carbide alloys are being investigated as a possible top photoelectrode in photoelectrochemical cells used for hydrogen production through water splitting. In order to be used as such, it is important that the effects of carbon concentration on bonding, and thus on the electronic and optical properties, is well understood. Electron spin resonance experiments were performed under varying experimental conditions to study the defect concentrations. The dominant defects are silicon dangling bonds. At room temperature, the spin densities varied between 1016 and 1018 spins/cm3 depending on the carbon concentration. Photothermal deflection spectroscopy, which is an extremely sensitive measurement of low levels of absorption in thin films, was performed to investigate the slope of the Urbach tail. These slopes are 78 meV for films containing the lowest carbon concentration and 98 meV for those containing the highest carbon concentration.

Optical properties of Microcrystalline Silicon determined by Spectroscopic Ellipsometry and Photothermal Deflection Spectroscopy

2002 ◽  
Vol 715 ◽  
Author(s):  
Kyung Hoon Jun ◽  
Helmut Stiebig ◽  
Reinhard Carius
Keyword(s):  
Optical Properties ◽  
Spectroscopic Ellipsometry ◽  
Volume Fraction ◽  
Large Deviation ◽  
Effective Medium Theory ◽  
Dense Medium ◽  
Medium Theory ◽  
Enhanced Absorption ◽  
Photothermal Deflection Spectroscopy ◽  
Photothermal Deflection

AbstractThe effect of the microstructure and bonded hydrogen on the optical properties of microcrystalline films (μc-Si:H) was investigated by Spectroscopic Ellipsometry (SE) and Photothermal Deflection Spectroscopy (PDS). On samples with a high crystalline volume fraction we studied the reason for a large deviation of absorption coefficient in the energy range between 1.6 eV and 3.2 eV from the value predicted by effective medium theory. This enhancement can be attributed to scattering by the inhomogeneity of μc-Si:H, which is investigated by the introduction of the dense medium radiative transfer formalism to an optical scattering simulation. Further, we suggest strain as a reason for the enhanced absorption in highly crystalline μc-Si:H.

Study of Electrical Properties of Microcrystalline Silicon Films Using AC Measurements

2001 ◽  
Vol 664 ◽  
Author(s):  
Ely A. T. Dirani ◽  
Alexandre M. Nardes ◽  
Adnei M. Andrade ◽  
Fernando J. Fonseca ◽  
Reginaldo Muccillo
Keyword(s):  
Electrical Properties ◽  
Electrical Transport ◽  
Deposition Temperature ◽  
Volume Fraction ◽  
Crystalline Silicon ◽  
Dark Conductivity ◽  
Silicon Films ◽  
Electrical Transport Properties ◽  
Large Area ◽  
Average Grain Size

ABSTRACTHydrogenated amorphous (a-Si:H) and microcrystalline (µc-Si:H) silicon films are indispensable materials for large area electronic devices like solar cells, image sensors and thin film transistors (TFTs). The interest of the µc-Si:H films arise from the fact that they combine the high optical absorption of a-Si:H and the electrical transport properties close to those of crystalline silicon. In this work we show the correlation between substrate deposition temperature, crystallinity and electrical properties of a-Si:H and µc-Si:H films. The films were prepared by a conventional PECVD (13.56 MHz) RF system from PH3/SiH4/H2 gas mixtures in the temperature range of 100 to 250°C. While phosphorus doped (n) a-Si:H are deposited yielding conductivity values no better than 10−2 S/cm, (n) µc-Si:H layers deposited at substrate temperature of 250°C show conductivity values higher than 101 S/cm, crystalline fraction up to 80% and Hall mobility of about 0.9 cm2. V−1.s−1. It was observed that a change in the dark conductivity behavior occurs around 140°C, with a large increase in the conductivity values. A corresponding increase is not seen in the average grain size and in the crystalline volume fraction, which shows an almost linear increase with the deposition temperature. This stronger influence of the temperature in the electrical characteristics of the µc-Si:H films may be related to the phosphorus activation, which occurs in higher degree at higher deposition temperatures. The correlation among Raman spectroscopy, Hall effect and AC conductivity measurements (frequency range 6 Hz to 13 MHz) shows that the crystalline phase dominates the electrical transport mechanism in µc-Si:H films. Preliminary results of AC measurements indicate that the electrical resistivity of each phase of this material can be determined.

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