共查询到20条相似文献,搜索用时 46 毫秒
1.
Thin film electro-optic and non-linear optical materials are of interest for applications in high-speed integrated optical devices. Materials of the system Pb 1−x/100La x/100(Zr y/100 Ti1−y/100) 1−x/400O3 or PLZT x/ y/(100− y) are attractive since they can be integrated into Si and GaAs substrates using suitable deposition techniques. In this investigation we examine the structural properties of r.f. magnetron sputter-deposited PLZT using X-ray absorption near-edge spectroscopy (XANES). For XANES analysis, four samples were selected: (1) a highly oriented PLZT 28/0/100 film of ≈ 4500 Å deposited on SiO 2; (2) a highly oriented PLZT 28/0/100 film of ≈ 4500 Å deposited on a 2 ωm SiO 2 buffer layer over a Si(100) substrate; (3) a highly oriented PLZT 28/0/100 film of ≈4500 Å deposited on Al 2O 3 (1
02); and (4) a commercial ceramic wafer of PLZT 9/65/35. The XANES experiments were performed at the Stanford Synchrotron Radiation Laboratory (SSRL) using electron yield and fluorescence techniques. Data was taken at the Ti K-edge (4966.4eV) and compared to reference spectra. Of the reference spectra, the Ti K-edge spectra of the PLZT most closely resemble perovskite (SrTiO 3). The surface and bulk thin film are similar and all the 28/0/100 spectra resemble the spectra of 9/65/35, indicating similar cubic perovskite structures for these materials. 相似文献
2.
Structural properties of ion-beam-induced epitaxial crystallization (IBIEC) for amorphous layers of GaAs on GaAs(100), BP on BP(100) and Si1−xGex and Si1−x−yGexCy on Si(100) have been investigated. Crystallization was induced by ion bombardment with 400 keV Ne, Ar or Kr at 150 °C for GaAs and at 350 °C for BP. Epitaxial crystallization up to the surface was observed both in GaAs and BP at temperatures much below those required for the solid phase epitaxial growth (SPEG). The growth rate per nuclear energy deposition density has shown a larger dependence on ion dose rate in cases of heavier ion bombardments both for GaAs and BP. Crystallization of a-GaAs with ions whose projected ranges are within the amorphous layer thickness was also observed at 150 °C. Epitaxial crystallization of Si1−xGex and Si1−x−yGexCy layers ( x = 0.13 and y = 0.014 at peak concentration) on Si(100) formed by high-dose implantation of 80 keV Ge and 17 keV C ions has been observed in the IBIEC process with 400 keV Ar ion bombardments at 300–400 °C. Crystalline growth by IBIEC has shown a larger growth rate in Si1−x−yGexCy/ Si} than in Si1−xGex/ Si} with the same Ge concentration for all bombardments under investigation. X-ray rocking-curve measurements have shown a strain-compensated growth in Si1−x−yGexCy/ Si}, whereas Si1−xGex/ Si} samples have shown a growth with strain accommodation. 相似文献
3.
Thin films of different molybdenum carbides ( δ-MoC 1−x, γ′-MoC 1−x and Mo 2C) have been deposited from a gas mixture of MoCl 5/H 2/C 2H 4 at 800°C by CVD. The H 2 content in the vapour has a strong influence on the phase composition and microstructure. Typically, high H 2 contents lead to the formation of nanocrystalline δ-MoC 1−x films while coarse-grained γ′-MoC 1−x is formed with an H 2-free gas mixture. This phase has previously only been synthesized by carburization of Mo in a CO atmosphere and it has therefore been considered as an oxycarbide phase stabilized by the presence of oxygen in the lattice. Our results, however, show that γ′-MoC 1−x films containing only trace amounts of oxygen can be deposited by CVD. Stability calculations using a FP-LMTO method confirmed that the γ′-MoC 1−x phase is stabilized by oxygen but that the difference in energy between e.g. δ-MoC 0.75 and oxygen-free γ′-MoC 0.75 is small enough to allow the synthesis of the latter phase in the absence of kinetic constraints. Annealing experiments of metastable δ-MoC 1−x and γ′-MoC 1−x films showed two different reaction products suggesting that kinetic effects play an important role in the decomposition of these phases. 相似文献
4.
AgInSn xS 2−x ( x = 0–0.2) polycrystalline thin films were prepared by the spray pyrolysis technique. The samples were deposited on glass substrates at temperatures of 375 and 400 °C from alcoholic solutions comprising silver acetate, indium chloride, thiourea and tin chloride. All deposited films crystallized in the chalcopyrite structure of AgInS 2. A p-type conductivity was detected in the Sn-doped samples deposited at 375 °C, otherwise they are n-type. The optical properties of AgInSn xS 2−x ( x < 0.2) resemble those of chalcopyrite AgInS 2. Low-temperature PL measurements revealed that Sn occupying an S-site could be the responsible defect for the p-type conductivity observed in AgInSn xS 2−x ( x < 2) thin films. 相似文献
5.
Variable angle spectroscopic ellipsometry (VASE) has been used to characterize several SixGe1−x/ Ge heterostructures. First, SixGe1−x/ Ge superlattice (SL) structures were characterized in terms of the layer thicknesses, composition, x, of the SixGe1− x layer, and oxide thickness. High-resolution X-ray diffraction results are also presented for the SixGe1−x/ Ge SL structures and are shown to be in close agreement with the VASE results once strain effects are taken into account. VASE has also been used to study thick, Ge-rich SixGe1−x/ Ge heterostructures that have been grown on Si substrates. A stepped buffer has been deposited first in order to minimize the strain in the SixGe1−x/ Ge layers. VASE can be used to give a qualitative determination of the residual strain along with the thickness of all layers within the optical penetration depth from the surface. 相似文献
6.
Highly preferred oriented lead barium titanate (Pb 1−x,Ba x)TiO 3 thin film, with particular emphasis on (Pb 0.5,Ba 0.5)TiO 3, can be obtained by spin-coating on MgO (100) substrate by using the precursor sol, which was synthesized from acetylacetone chelating with titanium isopropoxide and ethylene glycol as a solvent, in the sol-gel process. Film thickness, pyrolysis temperature and heating rate were studied systemically to investigate their influences on the formation of preferred oriented thin films. The highly preferred (001)/(100) oriented thin film could be obtained by the pyrolysis of wet film at 500 °C and annealing at 600 °C at a slow heating rate of 5 °C/min. It is confirmed that the tetragonal perovskite structure of the titanate ceramic decreases with an increase of Ba content in (Pb 1−x,Ba x)TiO 3. The (001)/(100) oriented films were synthesized from all compositions between x = 0.2 and x = 0.8, at a crystallization temperature of 600 °C. In particular, for the Ba content in the range of x = 0.50.6, highly preferred (001)/(100) planes were observed. 相似文献
7.
B-doped a-Si 1−xC x:H films for a window layer of Si thin film solar cells have been prepared by the Cat-CVD method. It is found that C is effectively incorporated into the films by using C 2H 2 as a C source gas, where an only little C incorporation is observed from CH 4 and C 2H 6 under similar deposition conditions. Using a-Si 1−xC x:H films grown from C 2H 2, heterojunction p–i–n solar cells have been prepared by the Cat-CVD method. The cell structure is (SnO 2 Asahi-U)/ZnO/a-Si 1−xC x:H(p)/a-Si:H(i)/μc-Si:H(n)/Al. The obtained conversion efficiency was 5.4%. 相似文献
8.
Tungsten–carbon thin films have been deposited by reactive (Ar+C 6H 6) DC magnetron sputtering onto various substrates. Deposition onto glass, monocrystalline silicon, tantalum and stainless steel at room temperature yielded W–C films, having XRD patterns corresponding to the structure of heavily disordered W 2C or WC 1−x carbides. The samples deposited upon the Au or Cu foils were nanocrystalline cubic WC 1−x with the grain size of 2.9 nm. Disordered tungsten–carbon films were stable up to 1200°C. Microhardness of the films with disordered W 2C phase was about 5–6 GPa while that of the films with disordered WC 1−x phase was about 17 GPa. The characteristics of films can be understood considering the effects of the incorporation of free carbon and/or carbon–hydrogen fragments into the tungsten carbide layer. 相似文献
9.
Transmission electron microscopy (TEM) studies of epitaxial YBa 2Cu 3O 7−x thin films and YBa 2Cu 3O 7/PrBa 2Cu 3O 7 superlattices are summarized. High-resolution imaging of cross-sections and plan views and energy-dispersive X-ray microanalysis and electron energy loss spectroscopy in the transmission electron microscope were the methods applied. In the first section results on YBa 2Cu 3O 7−x thin films With varying oxygen stoichiometry deposited onto SrTiO 3 are discussed. Then, YBa 2Cu 3O 7/PrBa 2Cu 3O 7 superlattices deposited onto SrTiO 3 and MgO are investigated. Finally, an interface analysis of high-quality YBa 2Cu 3O 7−x thin films deposited onto sapphire with yttrium-stabilized zirconia buffer layers is presented. 相似文献
10.
The E1 and E1+Δ 1 energy bands of metal–organic chemical vapor deposition grown Al xGa 1−xAs, with x in the range 0–0.55, have been determined using photoreflectance technique. The aluminum composition for each sample was determined using the energy of the room-temperature photoluminescence compensated peak value and a suitable fundamental band gap formula. The positions of the E1 and E1+Δ 1 peaks were determined from curve-fitting an appropriate theoretical model to our experimental data by a modified downhill simplex method. Using the results, we propose new E1 and E1+Δ 1 cubic expressions as functions of the aluminum composition, x, and compare them with the available reported expressions. 相似文献
11.
Measurements of optical constants (absorption coefficient, refractive index, extinction coefficient, real and imaginary part of the dielectric constant) have been made on a-(Se 70Te 30) 100−x (Se 98Bi 2) x thin films (where x=0, 5, 10, 15 and 20) of thickness 2000 Å in the wavelength range 450–1000 nm. It is found that the optical bandgap decreases with the increase of Se 98Bi 2 concentration in the a-(Se 70Te 30) 100−x(Se 98Bi 2) x system. The value of refractive index ( n) decreases, while the extinction coefficient ( k) increases with increasing photon energy. The results are interpreted in terms of concentration of localized states varying effective Fermi level. 相似文献
12.
In this work, we present the effect of nitrogen incorporation on the dielectric function of GaAsN samples, grown by molecular beam epitaxy (MBE) followed by a rapid thermal annealing (for 90 s at 680 °C). The GaAs 1 − xN x samples with N content up to 1.5% ( x = 0.0%, 0.1%, 0.5%, 1.5%), are investigated using room temperature spectroscopic ellipsometry (SE). The optical transitions in the spectral region around 3 eV are analyzed by fitting analytical critical point line shapes to the second derivative of the dielectric function. It was found that the features associated with E1 and E1 + Δ1 transitions are blue-shifted and become less sharp with increasing nitrogen incorporation, in contrast to the case of E0 transition energy in GaAs 1 − xN x. An increase of the split-off Δ 1 energy with nitrogen content was also obtained, in agreement to results found with MOVPE GaAs 1 − xN x grown samples. 相似文献
13.
The Ba xSr 1−xTiO 3 (BST)/Pb 1−xLa xTiO 3 (PLT) composite thick films (20 μm) with 12 mol% amount of xPbO–(1 − x)B 2O 3 glass additives ( x = 0.2, 0.35, 0.5, 0.65 and 0.8) have been prepared by screen-printing the paste onto the alumina substrates with silver bottom electrode. X-ray diffraction (XRD), scanning electron microscope (SEM) and an impedance analyzer and an electrometer were used to analyze the phase structures, morphologies and dielectric and pyroelectric properties of the composite thick films, respectively. The wetting and infiltration of the liquid phase on the particles results in the densification of the composite thick films sintered at 750 °C. Nice porous structure formed in the composite thick films with xPbO–(1 − x)B 2O 3 glass as the PbO content ( x) is 0.5 ≥ x ≥ 0.35, while dense structure formed in these thick films as the PbO content ( x) is 0.8 ≥ x ≥ 0.65. The volatilization of the PbO in PLT and the interdiffusion between the PLT and the glass lead to the reduction of the c-axis of the PLT phase. The operating temperature range of our composite thick films is 0–200 °C. At room temperature (20 °C), the BST/PLT composite thick films with 0.35PbO–0.65B 2O 3 glass additives provided low heat capacity and good pyroelectric figure-of-merit because of their porous structure. The pyroelectric coefficient and figure-of-merit FD are 364 μC/(m 2 K) and 14.3 μPa −1/2, respectively. These good pyroelectric properties as well as being able to produce low-cost devices make this kind of thick films a promising candidate for high-performance pyroelectric applications. 相似文献
14.
We propose a new approach to fabrication of hydrogenated amorphous silicon carbide (a-Si 1−xC x:H) thin films for solar cells by the catalytic chemical vapor deposition (Cat-CVD) method using a carbon catalyzer, which is more stable than tungsten or tantalum. It was found that by using the carbon catalyzer, undoped and boron-doped a-Si 1−xC x:H films were easily obtained from a SiH 4, CH 4 and B 2H 6 mixture without any change in the catalyzer surface, even after deposition for longer than 30 h. 相似文献
15.
Microcrystalline silicon carbide (μc-Si 1−xC x) films were successfully deposited by the hot wire cell method using a gas mixture of SiH 4, H 2 and C 2H 2. It was confirmed by Fourier transform infrared and X-ray diffraction analyses that the films consisted of μc-Si grains embedded in a-Si 1−xC x tissue. The p-type μc-Si 1−xC x films were deposited using B 2H 6 as a doping gas. A dark conductivity of 0.2 S/cm and an activation energy of 0.067 eV were obtained. The p-type μc-Si 1−xC x was used as a window layer of a-Si solar cells, in which the intrinsic layer was deposited by photo-chemical vapor deposition, and an initial conversion efficiency of 10.2% was obtained. 相似文献
16.
The formation, composition and propagation of laser-produced plasmas used for pulsed laser deposition (PLD) of Y1Ba2Cu3O7−x have been studied under film growth conditions. Four complementary spatially and temporally resolved in situ diagnostic techniques are applied to characterize the expansion of the laser plume into both vacuum and ambient gases: optical emission and absorption spectroscopy, fast ion probe measurements, and fast photography with a gated, image-intensified charge-coupled detector-array (ICCD) camera system. Transient optical absorption spectroscopy reveals large densities of ground state atoms, ions, and molecules in the plume as well as a slower component to the plume transport than is indicated by the plasma fluorescence and ion current. Ablation into background gases results in scattering and attenuation of the laser plume. The exponential attenuation of the positive ion flux transmitted through 50–300 mTorr background oxygen is measured and used to define an overall ion-oxygen reaction cross-section σi−O2 = 2.3 × 10−16 cm2 under the described film growth conditions. The slowing of the laser plasma and formation of shock structures due to collisions with the ambient gas are described using ion probe measurements and ICCD photographic comparisons of expansion into vacuum and background oxygen. At the pressures used for PLD, distance-time R−t plots derived from the photographs and ion probe waveforms indicate that the higher pressure plume initially expands through the ambient gas in accordance with a drag model (where R = xf[1 − exp( − βt)]), experiencing little slowing until a visible shock structure forms. Following a transition period, in which the plume appears to have two components, a single-component shock structure propagates in better agreement with a shock, or blast wave (R = ξ0(E/0)1/5t2/5) model. 相似文献
17.
Doping and electrical characteristics of in-situ heavily B-doped Si 1−x−yGe xC y (0.22< x<0.6, 0< y<0.02) films epitaxially grown on Si(100) were investigated. The epitaxial growth was carried out at 550°C in a SiH 4–GeH 4–CH 3SiH 3–B 2H 6–H 2 gas mixture using an ultraclean hot-wall low-pressure chemical vapor deposition (LPCVD) system. It was found that the deposition rate increased with increasing GeH 4 partial pressure, and only at high GeH 4 partial pressure did it decrease with increasing B 2H 6 as well as CH 3SiH 3 partial pressures. With the B 2H 6 addition, the Ge and C fractions scarcely changed and the B concentration ( CB) increased proportionally. The C fraction increased proportionally with increasing CH 3SiH 3 partial pressures. These results can be explained by the modified Langmuir-type adsorption and reaction scheme. In B-doped Si 1−x−yGe xC y with y=0.0054 or below, the carrier concentration was nearly equal to CB up to approximately 2×10 20 cm −3 and was saturated at approximately 5×10 20 cm −3, regardless of the Ge fraction. The B-doped Si 1−x−yGe xC y with high Ge and C fractions contained some electrically inactive B even at the lower CB region. Resistivity measurements show that the existence of C in the film enhances alloy scattering. The discrepancy between the observed lattice constant and the calculated value at the higher Ge and C fraction suggests that the B and C atoms exist at the interstitial site more preferentially. 相似文献
18.
We report on epitaxial {1 0 0} K 1−xRb xTiOPO 4 waveguide films for the visible spectral range grown on KTiOPO 4 substrates by liquid phase epitaxy. Using the m-line technique a refractive index increase of Δ nx≈0.007 and Δ nz≈0.004 for TM and TE polarisation has been determined for a K 0.78Rb 0.22TiOPO 4 film. Optical transmission and nearfield distribution are comparable to conventional ion-exchanged waveguides. Typical attenuation of about 1 dB/cm for both TM and TE polarisation was obtained at λ=532 and 1064 nm. Energy-dispersive X-ray spectrometry reveals solid-solution films with graded rubidium composition profiles. X-ray rocking curve analyses confirm the epitaxial growth process and indicate perfect and relaxed K 1−xRb xTiOPO 4 films. Atomic force microscopy investigations reveal regular step structures with step heights Δ h<1.3 nm resulting in rms-roughness values of ≈0.4 nm. 相似文献
19.
In 2O 3 thin films have been prepared from commercially available pure In 2O 3 powders by high vacuum thermal evaporation (HVTE) and from indium iso-propoxide solutions by sol-gel techniques (SG). The films have been deposited on sapphire substrates provided with platinum interdigital sputtered electrodes. The as-deposited HVTE and SG films have been annealed at 500°C for 24 and 1 h, respectively. The film morphology, crystalline phase and chemical composition have been characterised by SEM, glancing angle XRD and XPS techniques. After annealing at 500°C the films’ microstructure turns from amorphous to crystalline with the development of highly crystalline cubic In 2O 3−x (JCPDS card 6-0416). XPS characterisation has revealed the formation of stoichiometric In 2O 3 (HVTE) and nearly stoichiometric In 2O 3−x (SG) after annealing. SEM characterisation has highlighted substantial morphological differences between the SG (highly porous microstructure) and HVTE (denser) films. All the films show the highest sensitivity to NO 2 gas (0.7–7 ppm concentration range), at 250°C working temperature. At this temperature and 0.7 ppm NO 2 the calculated sensitivities ( S= Rg/ Ra) yield S=10 and S=7 for SG and HVTE, respectively. No cross sensitivity have been found by exposing the In 2O 3 films to CO and CH 4. Negligible H 2O cross has resulted in the 40–80% relative humidity range, as well as to 1 ppm Cl 2 and 10 ppm NO. Only 1000 ppm C 2H 5OH has resulted to have a significant cross to the NO 2 response. 相似文献
20.
Cat-CVD method has been applied to the growth of Si–C and Si–C–O alloy thin films. Growth mechanism has been studied with emphasis on the effects of filament materials. Growth rates and alloy compositions were measured for W, Ta, Mo and Pt filaments at the filament temperatures ranging from 1300 to 2000 °C. Si 1−xC x films with x ranging from 0.38 to 0.7 could be grown by using single molecule source Si(CH 3) 2H 2 (dimethylsilane). Si–C–O ternary alloy films was successfully prepared by using Si(OC 2H 5) 4 (tetraethoxysilane) and Si(CH 3) 2(OCH 3) 2 (dimethyldimethoxysilane) molecules. 相似文献
|