Low Substrate Temperature Deposition of Crystalline SiC using HWCVD

2005 ◽  
Vol 862 ◽  
Author(s):  
S. Klein ◽  
R. Carius ◽  
L. Houben ◽  
F. Finger
Keyword(s):  
Band Gap ◽  
Crystalline Silicon ◽  
Chemical Vapour ◽  
Structural Disorder ◽  
Dark Conductivity ◽  
Band Gap Energy ◽  
Crystalline Material ◽  
High Hydrogen ◽  
Hydrogen Dilution ◽  
Columnar Grains

AbstractMicrocrystalline silicon carbide (μc-SiC) was prepared at substrate temperatures between 300°C and 450°C using Hot Wire Chemical Vapour Deposition (HWCVD). The SiC films were deposited from monomethylsilane (MMS) diluted in hydrogen on glass and crystalline silicon substrates. The influence of the hydrogen dilution on the deposition rate and the structural and the optoelectronic properties was investigated. Infrared and Raman spectroscopy and transmission electron microscopy (TEM) were applied to study the structural properties. Highly crystalline material with large columnar grains was obtained at high hydrogen dilutions. The optical absorption below the band gap is high and the dark conductivities are far above the values expected for intrinsic SiC. At lower hydrogen dilution, less crystalline or amorphous Si1-xCx is growing, showing broader IR- and Raman peaks, lower dark conductivity and higher absorption above the band gap energy. An extended nucleation zone with large structural disorder was observed even for highly crystalline material.

Optical absorption in PECVD deposited thin hydrogenated silicon in light of ordering effects

Open Physics ◽  
2009 ◽  
Vol 7 (2) ◽  
Author(s):  
Jarmila Müllerová ◽  
Veronika Vavruňková ◽  
Pavel Å utta
Keyword(s):  
Chemical Vapour ◽  
Optical Transmittance ◽  
Band Gap Energy ◽  
Absorption Coefficients ◽  
Hydrogenated Silicon ◽  
Transmittance Spectra ◽  
Silicon Thin Films ◽  
Hydrogen Dilution ◽  
Ordering Effects ◽  
Amorphous Hydrogenated Silicon

AbstractWe report results obtained from measurements of optical transmittance spectra carried out on a series of silicon thin films deposited by plasma-enhanced chemical vapour deposition (PECVD) from silane diluted with hydrogen. Hydrogen dilution of silane results in an inhomogeneous growth during which the material evolves from amorphous hydrogenated silicon (a-Si:H) to microcrystalline hydrogenated silicon (µc-Si:H). Spectral refractive indices and absorption coefficients were determined from transmittance spectra. The spectral absorption coefficients were used to determine the Tauc optical band gap energy, the B factor of the Tauc plots, E 04 (energy at which the absorption coefficient is equal to 104 cm−1), and the Urbach energy as a function of the hydrogen dilution. The results were correlated with microstructure, namely volume fractions of the amorphous and crystalline phase with voids, and with the grain size.

Nanostructured silicon films produced by PECVD

2001 ◽  
Vol 664 ◽  
Author(s):  
R. Martins ◽  
H. Águas ◽  
V. Silva ◽  
I. Ferreira ◽  
A. Cabrita ◽  
...  
Keyword(s):  
Surface Passivation ◽  
Chemical Vapour ◽  
General Rule ◽  
Silicon Films ◽  
Process Conditions ◽  
Low Density ◽  
High Hydrogen ◽  
Hydrogen Dilution ◽  
Nanostructured Silicon ◽  
Powder Formation

ABSTRACTThis paper presents the process conditions that lead to the production of nanostructured silicon films grown by plasma enhanced chemical vapour deposition close to the so-called gamma regime (powder formation), highly dense and with low density of bulk states. Thus, the powder management is one important issue to be addressed in this paper. As a general rule we observed that high quality films (low density of states and high μτ products) are obtained when films are grown under low ion bombardment at high hydrogen dilution and deposition pressure conditions, to allow the proper surface passivation and surface activation.

N-Type Silicon Films Produced by Hot Wire Technique

2000 ◽  
Vol 609 ◽  
Author(s):  
Isabel M. M. Ferreira ◽  
Ana M. F. Cabrita ◽  
Elvira M. C. Fortunato ◽  
Rodrigo F. P. Martins
Keyword(s):  
Pressure Range ◽  
Chemical Vapour ◽  
Dark Conductivity ◽  
Hot Wire ◽  
Large Area ◽  
Deposition Pressure ◽  
Hydrogen Dilution ◽  
Exponential Increase ◽  
Sims Analysis

ABSTRACTThe role of the deposition pressure (p) and the type of filaments (tungsten, W or tantalum, Ta) used to produce large area (10cm×10cm) n-type Si:H films by hot wire chemical vapour (HW-CVD) deposition technique was investigated. The data show that the electro-optical properties of the films produced are dependent on the gas pressure used. In the pressure range of 1×10-3 Torr to 1.0 Torr, the room dark conductivity (σd) varies from 1×10-8 to 2 S/cm for films produced at the same hydrogen dilution and filament temperature (Tfil.). On the other hand, the hydrogen concentration (CH) decreases from 10% to 2%, while the growth rate (R) shows an exponential increase, from 1 to 9 Å/s. The SIMS analysis, within the detection limits, does not reveal the existence of any significant W or Ta contamination in the films produced.

Solar-Cell Suitable μc-Si Films Grown by ECR-CVD

2000 ◽  
Vol 609 ◽  
Author(s):  
M. Birkholz ◽  
E. Conrad ◽  
K. Lips ◽  
B. Selle ◽  
I. Sieber ◽  
...  
Keyword(s):  
Electron Cyclotron Resonance ◽  
Film Growth ◽  
Dark Conductivity ◽  
Film Deposition ◽  
Degree Of Crystallinity ◽  
High Hydrogen ◽  
Hydrogen Dilution ◽  
Impurity Contamination ◽  
Si Films ◽  
High Degree

ABSTRACTThe preparation of μc-Si films from SiH4-H2 mixtures by electron-cyclotron resonance (ECR) CVD at deposition temperatures ≤ 400°C on foreign substrates is reported. Deposition conditions were identified for which Si films with a high degree of crystallinity were grown as was confirmed by Raman spectroscopy. A factorial analysis was carried out, for which the influence of deposition temperature, microwave power, hydrogen dilution and total pressure on film growth were investigated. Samples of optimized crystallinity were prepared in a lowpressure and high-hydrogen dilution regime. In-plane grain sizes were measured by TEM and found to be on the order of 10 - 12 nm. Next to the optimization of crystallinity several sources of impurity contamination during film deposition were identified and eliminated. Intrinsic μc-Si layers could be prepared under these conditions that exhibited a dark conductivity σd of 2 × 10-7 S/cm and photosensitivity σph/σd of 150. It is concluded that ECR CVD is capable of producing intrinsic layers with electronic properties as necessary for use in state-of-the-art n-i-p μc-Si solar cells.

High Quality Microcrystalline Silicon-Carbide Films Prepared by Photo-CVD Method Using Ethylene Gas as a Carbon Source

1999 ◽  
Vol 557 ◽  
Author(s):  
Seung Yeop Myong ◽  
Hyung Kew Lee ◽  
Euisik Yoon ◽  
Koeng Su Lim
Keyword(s):  
Silicon Carbide ◽  
Vapor Deposition ◽  
Crystalline Silicon ◽  
Chemical Vapor ◽  
Dark Conductivity ◽  
Microcrystalline Silicon ◽  
Cvd Method ◽  
Hydrogen Dilution ◽  
Boron Doped

AbstractHydrogenated boron-doped microcrystalline silicon-carbide (p-μc-SiC:H) films were grown by a photo chemical vapor deposition (photo-CVD) method from silane (SiH4), hydrogen (H2), diborane (B2H6), and ethylene (C2H4) gases. Since the photo-CVD is a mild process (~10mW/cm2), we can avoid the ion damage of the film, which is inevitable during the deposition of μc-SiC:H employing conventional PECVD technique. A dark conductivity as high as 5 × 10-1 S/cm, together with an optical bandgap of 2 eV, was obtained by the C2H4 addition, which is the first approach in photo-CVD systems. From the Raman and FTIR spectra, it is clear that our p-μc-SiC:H films are made up of crystalline silicon grains embedded in amorphous silicon-carbide tissue. We investigate the role of the hydrogen dilution and ethylene addition on the electrical, optical, and structural properties of p-μc-SiC:H films.

Near-Intrinsic Microcrystalline Silicon for Use in Thin Film Transistors

1997 ◽  
Vol 467 ◽  
Author(s):  
M. W. D. Froggatt ◽  
W. I. Milne ◽  
M. J. Powell
Keyword(s):  
Thin Film ◽  
Activation Energy ◽  
Thin Film Transistors ◽  
Chemical Vapour ◽  
Contact Layer ◽  
Dark Conductivity ◽  
Dilution Method ◽  
Microcrystalline Silicon ◽  
High Hydrogen ◽  
Channel Region

ABSTRACTInverted-staggered thin film transistors (TFTs) incorporating hydrogenated microcrystalline silicon for both contact and channel regions have been fabricated by plasma enhanced chemical vapour deposition (PECVD) using the high hydrogen-dilution method. The deposition parameters for the channel region were chosen to yield near-intrinsic material with a dark conductivity activation energy of 0.7 eV and a Tauc gap of 1.98 eV, while the doped contact layer was optimised to produce a high dark conductivity of 10 S/cm.These devices exhibit a low off-current but the field effect mobility is found to be lower than that of similar devices incorporating an optimised amorphous silicon channel region. The mobility activation energy in these devices is similar to those incorporating an amorphous channel, but the mobility pre-factor is reduced. We propose that this is due to inhomogeneous conduction through a microcrystalline region with a smaller grain size at the dielectric/channel interface.

Investigation of the Amorphous to Nanocrystalline Phase Transition at the Deposition of Silicon Films in an ECWR Plasma of Pure SiH4

1996 ◽  
Vol 420 ◽  
Author(s):  
M. Scheib ◽  
B. Schrcder ◽  
H. Oechsner
Keyword(s):  
Phase Transition ◽  
Chemical Vapour ◽  
Optical Emission ◽  
Nanocrystalline Silicon ◽  
Nanocrystalline Phase ◽  
Plasma Parameters ◽  
Deposition Rates ◽  
High Hydrogen ◽  
Hydrogen Dilution ◽  
Wave Resonance

AbstractA novel plasma based chemical vapour deposition (PECVD) technique employing electron cyclotron wave resonance (ECWR) for plasma excitation was applied to the deposition of hydrogenated nanocrystalline silicon (nc-Si:H) films. nc-Si:H films were produced at deposition rates up to 8Å/sec (TS = 200°C) with a pure SiH4 plasma in contrast to the conventional glow discharge technique where the high hydrogen dilution usually needed leads to considerable lower deposition rates. The amorphous-to-nanocrystalline phase transition was investigated in dependence of substrate temperature, the hf-power and magnetic field mandatory for ECWR, and SiH4-flow into the plasma. With the knowledge of the plasma parameters derived from single probe measurements, and the intensities of excited plasma species detected by means of optical emission spectroscopy we can qualitatively describe the silane-plasma dissociation behaviour. The nanocrystalline phase is found to be always deposited when the dissociation degree of the SiH4 plasma is almost saturated.

EFFECT OF Ca-SUBSTITUTION ON THE OPTICAL BAND GAP AND URBACH ENERGY OF BaTi2O5 BULK GLASS

2009 ◽  
Vol 23 (25) ◽  
pp. 3045-3052 ◽  
Author(s):  
JAVED AHMAD ◽  
JIANDING YU ◽  
YASUTOMO ARAI
Keyword(s):  
Band Gap ◽  
Optical Band Gap ◽  
Urbach Energy ◽  
Wavelength Region ◽  
Fundamental Absorption Edge ◽  
Optical Transmittance ◽  
Structural Disorder ◽  
Band Gap Energy ◽  
Bulk Glass ◽  
Ca Substitution

Optical transmittance of Ba 1-x Ca x Ti 2 O 5 (x=0, 0.01, 0.03) bulk glasses of ferroelectric BaTi 2 O 5 is measured at room temperature in the wavelength range 190–800 nm. The fundamental absorption edge located in the ultraviolet (UV) region tends to shift toward the longer wavelength region on increasing x. The optical band gap of 3.31 eV estimated for x=0 decreases on increasing x. The decrease in the optical band gap energy is related to the creation of non-bridging oxygen ions, which increase on Ca substitution. The observed increase in the Urbach energy with increasing x is associated with the possible increase of structural disorder in the ferroelectric BaTi 2 O 5-based bulk glass occurred by substituting Ca for Ba .

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