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1.
Silicon carbide (SiC) thin films were prepared by hot-wire chemical vapor deposition from SiH4/CH4/H2 and their structural properties were investigated by X-ray diffraction, Fourier transform infrared absorption and Raman scattering spectroscopies. At 2 Torr, Si-crystallite-embedded amorphous SiC (a-Si1 − xCx:H) grew at filament temperatures (Tf) below 1600 °C and nanocrystalline cubic SiC (nc-3C-SiC:H) grew above Tf = 1700 °C. On the other hand, At 4 Torr, a-Si1 − xCx:H grew at Tf = 1400 °C and nc-3C-SiC grew above Tf = 1600 °C. When the intakes of Si and C atoms into the film per unit time are almost the same and H radicals with a high density are generated, which takes place at high Tf, nc-3C-SiC grows. On the other hand, at low Tf the intake of Si atoms is larger than that of C atoms and, consequently, Si-rich a-Si1 − xCx:H or Si-crystallite-embedded a-Si1 − xCx:H grow.  相似文献   

2.
Thin-film transistors deposited by hot-wire chemical vapor deposition   总被引:6,自引:0,他引:6  
In the past few years hot-wire chemical vapor deposition (HWCVD) has become a popular technique for the deposition of silicon-based thin-film transistors (TFTs). Several groups have been using hot-wire deposited amorphous and microcrystalline silicon as the active layers in TFTs. In such devices either thermal SiO2 or plasma-deposited silicon nitride was the gate insulator. Recently ‘All-Hot-Wire TFTs’ have been realized, with also the silicon nitride deposited by HWCVD. This paper reviews the characteristics of hot-wire TFTs with amorphous and microcrystalline silicon using plasma- or hot-wire deposited silicon nitride as the gate insulator. It has been shown that hot-wire TFTs have a higher stability upon gate-bias stress as compared to their plasma-deposited counterparts. We present an overview of the stability of hot-wire TFTs deposited at a range of substrate temperatures. The higher stability of hot-wire TFTs that have been deposited at temperatures of 400–500 °C is ascribed to an enhanced structural order, i.e. a higher degree of medium-range order of the silicon network.  相似文献   

3.
Crystalline WO3 nanoparticles are employed in the development of flexible electrochromic (EC) devices. The nanoparticles are synthesized at high-density with a hot-wire chemical vapor deposition process where the hot filament provides the source of the tungsten metal. Polyethylene terephthalate coated with indium tin oxide is employed as a transparent flexible substrate. A simple electrophoresis technique is employed to deposit the WO3 nanoparticles on the polymer, resulting in a uniform thin film. The EC performance is optimized for WO3 particles that were baked at ~ 300 °C for 2 h prior to electrode fabrication. The transmittance is modulated between ~ 94% and ~ 28% without degradation for 100 cycles.  相似文献   

4.
For nitride layer formation on a hydrogenated microcrystalline silicon film surface, post-deposition treatments were carried out using a tungsten wire heated to 1700 °C in N2 (12 Torr) or N2/H2 (4 Torr) atmospheres. The nitride layers were investigated with an X-ray photoelectron spectroscopy. The intense peaks due to the Si-N bonds were observed. Those in N2 treatment were larger with increasing the treating time and decreased with depth direction, while those in N2/H2 treatment were virtually unchanged with the treating time and the depth up to about 20 nm. These findings indicate that even at a low wire temperature of 1700 °C, N2 molecules decompose sufficiently and nitride layers can be formed when high gas pressures are used.  相似文献   

5.
We report on the formation and the structural characterization of nanocrystalline Si/SiC (nc-Si/SiC) multilayers on Si(100) by hot filament assisted chemical vapor deposition using CH3SiH3 gas pulse jets. Si rich amorphous SiC (a-Si1  xCx, ~ 0.33) was initially grown at the substrate temperature (Ts) of 600 °C with heating a hot filament at ~ 2000 °C. The following crystalline SiC layers were grown at Ts = 850 °C without utilizing a hot filament. When the a-Si1  xCx layer was ultrathin (< 2 nm) on Si(100), this a-Si1  xCx layer was transformed to a single epitaxial SiC layer during the subsequent SiC growth process. The Si{111} faceted pits were formed at the SiC/Si(100) interface due to Si diffusion processes from the substrate. When the thickness of the initial a-Si1  xCx layer was increased to ~ 5 nm, a double layer structure was formed in which this amorphous layer was changed to nc-Si and nc-SiC was grown on the top resulting in the considerable reduction of the {111} faceted pits. It was found that nc-SiC was formed by consuming the Si atoms uniformly diffused from the a-Si1 − xCx layer below and that Si nanocrystals were generated in the a-Si1  xCx layers due to the annealing effect during further multilayer growths.  相似文献   

6.
Large grain polycrystalline silicon (poly-Si) films on glass substrates have been deposited on an aluminum-induced crystallization (AIC) seed layer using hot-wire chemical vapor deposition (HWCVD). A poly-Si seed layer was first formed by the AIC process and a thicker poly-Si film was subsequently deposited upon the seed layer using HWCVD. The effects of AIC annealing parameters on the structural and electrical properties of the poly-Si seed layers were characterized by Raman scattering spectroscopy, field-emission scanning electron microscopy, and Hall measurements. It was found that the crystallinity of seed layer was enhanced with increasing the annealing duration and temperature. The poly-Si seed layer formed at optimum annealing parameters can reach a grain size of 700 nm, hole concentration of 3.5 × 1018 cm− 3, and Hall mobility of 22 cm2/Vs. After forming the seed layer, poly-Si films with good crystalline quality and high growth rate (> 1 nm/s) can be obtained using HWCVD. These results indicated that the HWCVD-deposited poly-Si film on an AIC seed layer could be a promising candidate for thin-film Si photovoltaic applications.  相似文献   

7.
CeO2 films were prepared on amorphous silica substrates by laser chemical vapor deposition using cerium dipivaloylmethanate precursor and a semiconductor InGaAlAs (808 nm in wavelength) laser system. The laser spot size was about 20 mm, which was sufficient to cover the whole substrate. Highly (100)-oriented CeO2 films were obtained at extraordinary high deposition rates ranging from 60 to 132 μm/h. Films exhibited a columnar feather-like structure with a large number of nano-sized voids, and a surface morphology consisting of either nearly flat or pyramidal top-ending columns depending on the laser power. Nearly flat top-ending columns could be fairly (100)-oriented at the top and (111)-oriented laterally.  相似文献   

8.
B.R. Wu  M.S. Wan  R.H. Horng 《Thin solid films》2009,517(17):4749-4752
The Si heterojunction (HJ) solar cells were fabricated on the textured p-type mono-crystalline Si (c-Si) substrates using hot-wire chemical vapor deposition (HWCVD). In view of the potential for the bottom cell in a hybrid junction structure, the microcrystalline Si (μc-Si) film was used as the emitter with various PH3 dilution ratios. Prior to the n-μc-Si emitter deposition, a 5 nm-thick intrinsic amorphous Si layer (i-a-Si) was grown to passivate the c-Si surface. In order to improve the indium-tin oxide (ITO)/emitter front contact without using the higher PH3 doping concentration, a laser doping technique was employed to improve the ITO/n-μc-Si contact via the formation of the selective emitter structure. For a cell structure of Ag grid/ITO/n-μc-Si emitter/i-a-Si/textured p-c-Si/Al-electrode, the conversion efficiency (AM1.5) can be improved from 13.25% to 14.31% (cell area: 2 cm × 2 cm) via a suitable selective laser doping process.  相似文献   

9.
Clean oriented Al2O3 thin film with a dominant Al2O3 <1 1 3> plane was deposited on Si <1 0 0> substrate at 550 °C, by single-source chemical vapor deposition (CVD) using aluminium(III) diisopropylcarbamate, Al2(O2CNiPr2)6. This process represents a substantial reduction in typical CVD film growth temperatures which are typically > 1000 °C. Through the studies of thermal stability of this precursor, we propose a specific β-elimination decomposition pathway to account for the low temperature of the precursor decomposition at the substrate, and for the lack of carbon impurity byproducts in the resulting alumina films that are characterized using X-ray photoelectron spectroscopy and depth profiling.  相似文献   

10.
Silicon nanoparticles on fused silica have potential as recombination centers in infrared detectors due quantum confinement effects that result in a size dependent band gap. Growth on fused silica was realized by etching in HF, annealing under vacuum at 700-750 °C, and cooling to ambient temperature before ramping to the growth temperature of 600 °C. Silicon particles could not be grown in a thermal chemical vapor deposition (CVD) process with adequate size uniformity and density. Seeding fused silica with Si adatoms in a hot-wire chemical vapor deposition (HWCVD) process at a disilane pressure of 1.1 × 10− 5 Pa followed by thermal CVD at a disilane pressure of 1.3 × 10− 2 Pa, or direct HWCVD at a disilane pressure of 2.1 × 10− 5 Pa led to acceptable size uniformity and density. Dangling bonds at the surface of the as-grown nanoparticle were passivated using atomic H formed by cracking H2 over the HWCVD filament.  相似文献   

11.
Magnéli phases of Ti27O52 and Ti6O11 films were prepared by laser chemical vapor deposition using Ti(dpm)2(O-i-Pr)2 as a precursor. Ti6O11 film was obtained at a laser power (PL) of 200 W and a deposition temperature (Tdep) of 1270 K. Ti27O52 film was obtained at PL = 150 to 200 W and Tdep = 1120 to 1250 K. Ti6O11 and Ti27O52 films had a faceted texture about 2 μm in grain size and a columnar cross section. The deposition rate of Ti27O52 and Ti6O11 films were 90 and 70 μm h− 1, respectively.  相似文献   

12.
We grow silicon films by hot-wire/catalytic chemical vapor deposition using a new filament material: TaC-coated graphite rods. The filaments are 1.6 mm diameter rigid graphite rods with ~30 μm thick TaC coatings. Whereas heated W or Ta wire filaments are reactive and embrittle in silane (SiH4), the TaC/graphite filament is stable. After > 2 h of exposure to SiH4 gas at a range of filament temperatures, the full length of a TaC/graphite filament retains its shiny golden color with no indication of swelling or degradation. In comparison, a W wire exposed to SiH4 under the same conditions becomes swollen and discolored at the cold ends, indicating silicide formation. Scanning electron microscopy images of the filament material are nearly identical before and after SiH4 exposure at 1500-2000 °C. This temperature-independent chemical stability could enable added control of the gas phase chemistry during deposition that does not compromise the filament lifetime. The larger surface area of the 1.6 mm diameter TaC coated graphite filament (compared to the 0.5 mm W filament) allows for a ~ 2× increase in the deposition rate of Si thin films grown for photovoltaic applications.  相似文献   

13.
Hydrogenated silicon nitride films were deposited with NH3, SiH4 and N2 gas mixture at 700 °C by rapid thermal chemical vapor deposition (RTCVD) system. The NH3/N2 flow ratio and deposition pressure are found to influence the film properties. The stress of SiNx:H films deposited by RTCVD is tensile, which can reach ~ 1.5 GPa in our study. The stress of SiNx:H films is dependent on the deposition parameters, which can be associated with chemical configuration of the film. It is suggested that the presence of hydrogen atoms will relax the Si-N network, which results in the decrease of tensile stress of the SiNx:H film.  相似文献   

14.
TiO2 thin films prepared by Hot-Wire CVD method have been studied as a protecting material of transparent conducting oxide (TCO) against atomic hydrogen exposures for the fabrications of Si thin film solar cells. It was found that electrical conductivity of the films at room temperature reached a value of 0.4 S/cm. This value is 2-3 orders of magnitude higher than that of TiO2 films prepared by RF magnetron sputtering and electron-beam evaporation methods in our previous works. The conductivity improvement seems to be partly due to the enlargement of TiO2 crystallites.  相似文献   

15.
Catalytic chemical vapor deposition (Cat-CVD) has been demonstrated as a promising way to prepare device-quality silicon films. However, catalyst ageing due to Si contamination is an urgency to be solved for the practical application of the technique. In this study, the effect of carbonization of tantalum catalyst on its structure and performance was investigated. The carbonized Ta catalyst has a TaC surface layer which is preserved over the temperature range between 1450 and 1750 °C and no Si contamination occurs on the catalyst after long-term use. Si film prepared using the carbonized Ta catalyst has a similar crystal structure to that prepared by uncarbonized Ta catalyst. Formation of the TaC surface layer can alleviate the ageing problem of the catalyst, which shows great potential as a stable catalyst for Cat-CVD of Si films.  相似文献   

16.
The piezoresistive property of n-type and p-type nanocrystalline silicon thin films deposited on plastic (PEN) at a substrate temperature of 150 °C by hot-wire chemical vapor deposition, is studied. The crystalline fraction decreased from 80% to 65% in p-type and from 84% to 62% in n-type films, as the dopant gas-to-silane flow rate ratio was increased from 0.18% to 3-3.5%. N-type films have negative gauge factor (− 11 to − 16) and p-type films have positive gauge factor (9 to 25). In n-type films the higher gauge factors (in absolute value) were obtained by increasing the doping level whereas in p-type films higher gauge factors were obtained by increasing the crystalline fraction.  相似文献   

17.
Sequential flow chemical vapor deposition (SFCVD), utilizing TiCl4/NH3 as reactants and immediate NH3 treatment after film deposition, is applied to produce TiN barrier films in the contact process. Secondary ion mass spectroscopy results indicate that the SFCVD TiN film can effectively block the diffusion of WF6 into the underlying Ti layer during W deposition. NH3 treatment immediately after film deposition causes SFCVD TiN films to be less contaminated with carbon than TiN films that are formed by metallic organic compounds chemical vapor deposition (MOCVD) and to contain less chlorine residue than conventional TiCl4/NH3 CVD TiN layers even at a low reaction temperature. According to the resistance measurement of Kelvin contacts, the SFCVD process yields a lower resistance and a more uniform distribution than the MOCVD or CVD process. Transmission electron microscopic observations demonstrate that WF6 can diffuse through the MOCVD TiN to react with the underlying Ti layer, causing a rupture at the Ti/TiN interface and poor W adhesion. The SFCVD TiN can serve as a sufficient diffusion barrier against WF6 penetration during W CVD deposition.  相似文献   

18.
We have obtained thanks to reduced pressure-chemical vapor deposition germanium nanocrystals in a high quality SiO2 matrix. A perfect control of (i) the tunnel and control oxide layer thicknesses and (ii) the germanium nanocrystals' density and diameter has been achieved. Scanning electron microscopy was used to (i) determine the nucleation and growth rate of the germanium nanocrystals and (ii) evaluate their morphological stability during their embedding. We have also studied the influence of thin selectively grown Si films in order to passivate the surface of the germanium nanocrystals. X-ray photoelectron spectroscopy has shown that the germanium nanocrystals' surface properties are better with a Si capping. The polycrystalline state of the nanocrystals has been evaluated with X-ray diffraction. Transmission electron microscopy image reveals the lack of germanium diffusion and precipitation in the SiO2 matrix.  相似文献   

19.
SiC fiber was fabricated by chemical vapor deposition on tungsten filament heated by direct current in a CH3SiCl3-H2 gas system. Microstructure of W/SiC interfacial reaction zone in the fiber was identified by means of scanning electron microscope and transmission electron microscope. Results showed that the thickness of the interfacial reaction zone is between 350 and 390 nm, and two reaction products of W5Si3 and WC were formed during fabricating SiC fiber. Electron diffraction analysis and composition detection indicated that W5Si3 is adjacent to tungsten core and WC is adjacent to SiC sheath, and the W/SiC interface can be described as W/W5Si3/WC/SiC. Furthermore, the formation mechanism of the interfacial reaction zone is discussed.  相似文献   

20.
Epitaxial chromium dioxide (CrO2) thin films have been deposited by low pressure chemical vapor deposition (LPCVD) on (100) TiO2 substrates using the precursor chromium hexacarbonyl (Cr(CO)6) within a narrow temperature window of 380-400 °C. Normal θ-2θ Bragg x-ray diffraction results show that the predominant phase is CrO2 with only a small amount of Cr2O3 present, mostly at the film surface. The LPCVD films have a reasonably smooth surface morphology with a root mean square roughness of 4 nm on a scale of 5 μm. Raman spectroscopy confirms the existence of rutile CrO2 in the deposited films, while transmission electron microscopy confirms the single-crystalline nature of the films. The LPCVD films showing a dominant CrO2 phase exhibit clear uniaxial magnetic anisotropy with the easy axis oriented along the c direction.  相似文献   

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