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1.
Hall effect measurements were performed on epitaxial CoxTi1−xO2–δ thin films grown on (0 0 1) LaAlO3 by reactive RF magnetron co-sputter deposition. Magnetization measurements reveal ferromagnetic behavior in MH loop at room temperature for CoxTi1−xO2–δ thin films for which x?0.02. An anomalous Hall effect was observed for Co0.10Ti0.90O2−δ films grown with the partial pressure of water P(H2O)=4×10−4 Torr or less. These films exhibit a positive ordinary Hall coefficient and a positive magnetoresistance. X-ray diffraction on films grown under these conditions shows evidence for TinO2n−1 phase due to the deficiency of oxygen. In contrast, Hall measurements taken for undoped and Co-doped TiO2 thin films grown under more oxidizing conditions show only the ordinary Hall effect with a negative Hall coefficient consistent with n-type conduction. For these films, the magnetoresistance was positive and increased monotonically with increasing magnetic field. The results suggest that Co-doped TinO2n−1 may be a dilute magnetic semiconducting oxide for which the carriers couple to the spin polarization.  相似文献   

2.
In-N codoped ZnMgO films have been prepared on glass substrates by direct current reactive magnetron sputtering. The p-type conduction could be obtained in ZnMgO films by adjusting the N2O partial pressures. The lowest resistivity was found to be 4.6 Ω cm for the p-type ZnMgO film deposited under an optimized N2O partial pressure of 2.3 mTorr, with a Hall mobility of 1.4 cm2/V s and a hole concentration of 9.6 × 1017 cm−3 at room temperature. The films were of good crystal quality with a high c-axis orientation of wurtzite ZnO structure. The presence of In-N bonds was identified by X-ray photoelectron spectroscopy, which may enhance the nitrogen incorporation and respond for the realization of good p-type behavior in In-N codoped ZnMgO films. Furthermore, the ZnMgO-based p-n homojunction was fabricated by deposition of an In-doped n-type ZnMgO layer on an In-N codoped p-type ZnMgO layer. The p-n homostructural diode exhibits electrical rectification behavior of a typical p-n junction.  相似文献   

3.
We report on the growth of cubic spinel ZnCo2O4 thin films by reactive magnetron sputtering and bipolarity of their conduction type by tuning of oxygen partial pressure ratio in the sputtering gas mixture. Crystal structure of zinc cobalt oxide films sputtered in an oxygen partial pressure ratio of 90% was found to change from wurtzite Zn1−xCoxO to spinel ZnCo2O4 with an increase of the sputtering power ratio between the Co and Zn metal targets, DCo/DZn, from 0.1 to 2.2. For a fixed DCo/DZn of 2.0 yielding single-phase spinel ZnCo2O4 films, the conduction type was found to be dependent on the oxygen partial pressure ratio: n-type and p-type for the oxygen partial pressure ratio below ∼70% and above ∼85%, respectively. The electron and hole concentrations for the ZnCo2O4 films at 300 K were as high as 1.37×1020 and 2.81×1020 cm−3, respectively, with a mobility of more than 0.2 cm2/V s and a conductivity of more than 1.8 S cm−1.  相似文献   

4.
Thin GaAs films were prepared by pulse plating from an aqueous solution containing 0.20 M GaCl3 and 0.15 M As2O3 at a pH of 2 and at room temperature. The current density was kept as 50 mA cm−2 the duty cycle was varied in the range 10-50%. The films were deposited on titanium, nickel and tin oxide coated glass substrates. Films exhibited polycrystalline nature with peaks corresponding to single phase GaAs. Optical absorption measurements indicated a direct band gap of 1.40 eV. Photoelectrochemical cells were made using the films as photoelectrodes and graphite as counter electrode in 1 M polysulphide electrolyte. At 60 mW cm−2 illumination, an open circuit voltage of 0.5 V and a short circuit current density of 5.0 mA cm−2 were observed for the films deposited at a duty cycle of 50%.  相似文献   

5.
The synthesis by pulsed laser deposition technique of zinc oxide thin films suitable for gas sensing applications is herein reported. The ZnO targets were irradiated by an UV KrF* (λ = 248 nm, τFWHM ∼7 ns) excimer laser source, operated at 2.8 J/cm2 incident fluence value, whilst the substrates consisted of SiO2(0 0 1) wafers heated at 150 °C during the thin films growth process. The experiments were performed in an oxygen dynamic pressure of 10 Pa. Structural and optical properties of the thin films were investigated. The obtained results have demonstrated that the films are c-axis oriented. Their average transmission in the visible-infrared spectral region was found to be about 85%. The equivalent refractive indexes and extinction coefficients were very close to those of the tabulated reference values. Doping with 0.5% Au and coating with 100 pulses of Au clusters caused but a very slight decrease (with a few percent) of both transmission and refractive index values. The coatings with the most appropriate optical properties as waveguides have been selected and their behavior was tested for butane sensing.  相似文献   

6.
Raman spectra, atomic force microscope (AFM) images, hardness (H) and Young's modulus (E) measurements were carried out in order to characterize carbon thin films obtained from a C60 ion beam on silicon substrates at different deposition energies (from 100 up to 500 eV). The mechanical properties were studied via the nanoindentation technique. It has been observed by Raman spectroscopy and AFM that the microstructure presents significant changes for films deposited at energies close to 300 eV. However, these remarkable changes have not been noticeable on the mechanical properties: apparently H and E increase with higher deposition energy up to ∼11 and ∼116 GPa, respectively. These values are underestimated if the influence of the film roughness is not taken into account.  相似文献   

7.
Ferromagnetic Resonance (FMR) measurements at room temperature and X-band microwave frequency were performed on polycrystalline FePt thin films with face-centered cubic structure. With the external field perpendicular to the film plane, the absorption fields Hn of the odd and even spin-wave resonance modes n detected for the Fe0.44Pt0.56(45 nm)/Si(1 0 0) and Fe0.51Pt0.49(105 nm)/Pt(55 nm)/MgO(1 0 0) films, were found to obey the well-known Hn×n2 ratio, giving for these films the exchange stiffness constant values of 3.9×10−8 and 4.4×10–7 erg/cm, respectively. The study of the out-of-plane angular dependence of the absorption field of the uniform FMR mode allowed the measurement of the effective magnetic anisotropy constants of 5.3×106 , 6.4×106 , and 6.7×106 erg/cm3, related, respectively, to the [1 1 1], [1 0 0], and [1 1 0] textures present in the films.  相似文献   

8.
Biaxially textured YBa2Cu3O7−x (YBCO) films were grown on inclined-substrate-deposited (ISD) MgO-textured metal substrates by pulsed laser deposition. CeO2 was deposited as a buffer layer prior to YBCO growth. CeO2 layers of different thickness were prepared to evaluate the thickness dependence of the YBCO films. The biaxial alignment features of the films were examined by X-ray diffraction 2θ-scans, pole-figure, ?-scans and rocking curves of Ω angles. The significant influence of the CeO2 thickness on the structure and properties of the YBCO films were demonstrated and the optimal thickness was found to be about 10 nm. High values of Tc = 91 K and Jc = 5.5 × 105 A/cm2 were obtained on YBCO films with optimal CeO2 thickness at 77 K in zero field. The possible mechanisms responsible for the dependence of the structure and the properties of the YBCO films on the thickness of the CeO2 buffer layers are discussed.  相似文献   

9.
Anatase phase TiO2 films have been grown on fused silica substrate by pulsed laser deposition technique at substrate temperature of 750 °C under the oxygen pressure of 5 Pa. From the transmission spectra, the optical band gap and linear refractive index of the TiO2 films were determined. The third-order optical nonlinearities of the films were measured by Z-scan method using a femtosecond laser (50 fs) at the wavelength of 800 nm. The real and imaginary parts of third-order nonlinear susceptibility χ(3) were determined to be −7.1 × 10−11esu and −4.42 × 10−12esu, respectively. The figure of merit, T, defined by T=βλ/n2, was calculated to be 0.8, which meets the requirement of all-optical switching devices. The results show that the anatase TiO2 films have great potential applications for nonlinear optical devices.  相似文献   

10.
Thermoelectric films of n-Bi2Te3−ySey were prepared by potentiostatic electrodeposition technique onto stainless steel and gold substrates at room temperature. These films were used for morphological, compositional and structural analysis by environment scanning electron microscope (ESEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The effect of different substrates on the structure and morphology of Bi2Te3−ySey films and relation between Se content in the electrodepositing solutions and in the films were also investigated. These studies revealed that Bi, Te and Se could be co-deposited to form Bi2Te3−ySey semiconductor compound in the solution containing Bi3+, HTeO2+ and H2SeO3. The morphology and structure of the films are sensitive to the substrate material. The doped content of Se element in the Bi2Te3−ySey compound can be controlled by adjusting the Se4+ concentration in the electrodepositing solution. X-ray diffraction analysis indicates that the films prepared at −40 mV versus saturated calomel electrode (SCE) exhibit strong (1 1 0) orientation with rhombohedral structure.  相似文献   

11.
12.
Well-crystallized 250 nm-thick SrTiO3 thin films on fused-quartz substrate were prepared by pulsed laser deposition. The band-gap of SrTiO3 thin film by transmittance spectra is equal to 3.50 eV, larger than 3.22 eV for the bulk crystal. The nonlinear optical properties of the films were examined with picosecond pulses at 1.064 μm excitation. A large two-photon absorption (TPA) with absorption coefficient of 87.7 cm/GW was obtained, larger than 51.7 cm/GW for BaTiO3 thin films. The nonlinear refractive index n2 is equal to 5.7×10−10 esu with a negative sign, larger than 0.267×10−11 esu for bulk SrTiO3. The large TPA is attributed to intermediate energy levels introduced by the grain boundaries, and the optical limiting behaviors stemming from both TPA and negative nonlinear refraction were also discussed.  相似文献   

13.
We have used X-ray diffraction, volume magnetocrystalline anisotropy constant and resistance measurements to study solid-state synthesis in Ni(0 0 1)/Fe(0 0 1), Ni/Fe(0 0 1) and Ni/Fe thin films with the atomic ratio between Fe and Ni of 1:1 (1Fe:1Ni), and 3:1 (3Fe:1Ni). We have found that the formation of Ni3Fe and NiFe phases in the 1Fe:1Ni films takes place at temperatures ∼620 and ∼720 K, correspondingly. In the case of the 3Fe:1Ni films the solid-state synthesis starts with Ni3Fe and NiFe phase formation at the same temperatures as for the 1Fe:1Ni films. The increasing of annealing temperature above 820 K leads to the nucleation of a paramagnetic γpar phase at the FeNi/Fe interface. The final products of solid-state synthesis in the Ni(0 0 1)/Fe(0 0 1) thin films are crystallites which consist of the epitaxially intergrown NiFe and γpar phases according to the [1 0 0](0 0 1)NiFe||[1 0 0](0 0 1)γpar orientation relationship. The crystalline perfection and epitaxial growth of the (NiFe+γpar) crystallites on the MgO(0 0 1) surface allow to distinguish (0 0 2)γpar and (0 0 2)NiFe X-ray peaks (the cell parameters are: a(γpar)=0.3600±0.0005 nm and a(NiFe)=0.3578±0.0005 nm, correspondingly). At low temperatures the paramagnetic γpar phase undergoes the martensite γpar→αγparα phase transition which can be hindered by thermal and epitaxial strains and epitaxial clamping with a MgO substrate. On the basis of the studies of the thin-film solid-state synthesis we predict the existence of two novel structural phase transformations at the temperatures of about 720 and 820 K for alloys of the invar region of the Fe–Ni system.  相似文献   

14.
Nanocrystalline silicon (nc-Si) films were prepared by a plasma-enhanced chemical vapor deposition method at a deposition temperature below 220 °C with different dynamic pressures (Pg), hydrogen flow rates ([H2]), and RF powers, using SiH4/H2/SiF4 mixtures. We examined the photo-luminescence (PL) spectra and the structural properties. We observed two stronger and weaker PL spectra with a peak energies around EPL = 1.8 and 2.2-2.3 eV, respectively, suggesting that the first band was related to nanostructure in the films, and another band was associated with SiO-related bonds. The nc-Si films with rather large PL intensity was obtained for high [H2] and/or low pressure values, However, effects of [H2] are likely to be different from those of Pg. The average grain size (δ) and the crystalline volume fraction (ρ) at first rapidly increase, and then slowly increase, with increasing Pg. Other parameters exhibited opposite behaviors from those of δ or ρ. These results were discussed in connection with the changes in the PL properties with varying the deposition conditions.  相似文献   

15.
The crystal structure, band gap energy and bowing parameter of In-rich InxAl1−xN (0.7 < x < 1.0) films grown by magnetron sputtering were investigated. Band gap energies of InxAl1−xN films were obtained from absorption spectra. Band gap tailing due to compositional fluctuation in the films was observed. The band gap of the as-grown InN measured by optical absorption method is 1.34 eV, which is larger than the reported 0.7 eV for pure InN prepared by molecular beam epitaxy (MBE) method. This could be explained by the Burstein-Moss effect under carrier concentration of 1020 cm−3 of our sputtered films. The bowing parameter of 3.68 eV is obtained for our InxAl1−xN film which is consistent with the previous experimental reports and theoretical calculations.  相似文献   

16.
NiO thin films have been deposited by chemical spray pyrolysis using a perfume atomizer to grow the aerosol. The influence of the precursor, nickel chloride hexahydrate (NiCl2·6H2O), nickel nitrate hexahydrate (Ni(NO3)2·6H2O), nickel hydroxide hexahydrate (Ni(OH)2·6H2O), nickel sulfate tetrahydrate (NiSO4·4H2O), on the thin films properties has been studied. In the experimental conditions used (substrate temperature 350 °C, precursor concentration 0.2-0.3 M, etc.), pure NiO thin films crystallized in the cubic phase can be achieved only with NiCl2 and Ni(NO3)2 precursors. These films have been post-annealed at 425 °C for 3 h either in room atmosphere or under vacuum. If all the films are p-type, it is shown that the NiO films conductivity and optical transmittance depend on annealing process. The properties of the NiO thin films annealed under room atmosphere are not significantly modified, which is attributed to the fact that the temperature and the environment of this annealing is not very different from the experimental conditions during spray deposition. The annealing under vacuum is more efficient. This annealing being proceeded in a vacuum no better than 10−2 Pa, it is supposed that the modifications of the NiO thin film properties, mainly the conductivity and optical transmission, are related to some interaction between residual oxygen and the films.  相似文献   

17.
This paper focuses the influence of porous morphology on the microstructure and optical properties of TiO2 films prepared by different sol concentration and calcination temperatures. Mesoporous TiO2 thin films were prepared on the glass substrates by sol-gel dip coating technique using titanium (IV) isopropoxide. Porous morphology of the films can be regulated by chemical kinetics and is studied by scanning electron microscopy. The optical dispersion parameters such as refractive index (n), oscillator energy (Ed), and particle co-ordination number (Nc) of the mesoporous TiO2 films were studied using Swanepoel and Wemple-DiDomenico single oscillator models. The higher precursor concentration (0.06 M), films exhibit high porosity and refractive index, which are modified under calcination treatment. Calcinated films of low metal precursor concentration (0.03 M) possess higher particle co-ordination number (Nc = 5.05) than that of 0.06 M films (Nc = 4.90) due to calcination at 400 °C. The lattice dielectric constant (E) of mesoporous TiO2 films was determined by using Spintzer model. Urbach energy of the mesoporous films has been estimated for both concentration and the analysis revealed the strong dependence of Urbach energy on porous morphology. The influence of porous morphology on the optical dispersion properties also has been explained briefly in this paper.  相似文献   

18.
Ablation of Fe3O4 targets has been performed using a pulsed UV laser (KrF, λ = 248 nm, 30 ns pulse duration) onto Si(100) substrates, in reactive atmospheres of O2 and/or Ar, with different oxygen partial pressures. The as-deposited films were characterised by atomic force microscopy (AFM), X-ray diffraction (XRD), conversion electron Mössbauer spectroscopy (CEMS) and extraction magnetometry, in order to optimise the deposition conditions in the low temperature range. The results show that a background mixture of oxygen and argon improves the Fe:O ratio in the films as long as the oxygen partial pressure is maintained in the 10−2 Pa range. Thin films of almost stoichiometric single phase polycrystalline magnetite, Fe2.99O4, have been obtained at 483 K and working pressure of 7.8 × 10−2 Pa, with a high-field magnetization of ∼490 emu/cm3 and Verwey transition temperature of 112 K, close to the values reported in the literature for bulk magnetite.  相似文献   

19.
IrO2 thin films were prepared on Si(1 0 0) substrates by laser ablation. The effect of substrate temperature (Tsub) on the structure (crystal orientation and surface morphology) and property (electrical resistivity) of the laser-ablated IrO2 thin films was investigated. Well crystallized and single-phase IrO2 thin films were obtained at Tsub = 573-773 K in an oxygen partial pressure of 20 Pa. The preferred orientation of the laser-ablated IrO2 thin films changed from (2 0 0) to (1 1 0) and (1 0 1) depending on Tsub. With the increasing of Tsub, both the surface roughness and crystallite size increased. The room-temperature electrical resistivity of IrO2 thin films decreased with increasing Tsub, showing a low value of (42 ± 6) × 10−8 Ω m at Tsub = 773 K.  相似文献   

20.
Diamond-like carbon films (DLC) were deposited on titanium substrates in acetonitrile and N,N-dimethyl formamide (DMF) liquids by the liquid-phase electrodeposition technique at ambient pressure and temperature. The applied voltage between the electrodes was high (1200 V) due to the use of resistive organic liquids. The surface morphology was examined by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Corrosion performance of the coatings was investigated by potentiodynamic polararization tests in phosphate buffer saline solution. Raman spectroscopy analysis of the films revealed two broad bands at approximately 1360 cm−1 and 1580 cm−1, related to D and G-band of DLC, respectively. The coated Ti was tested in a ball-on-plate type wear test machine with Al2O3 balls. The films presented a low friction coefficient (about 0.1), and the films deposited from DMF presented the best wear resistance.  相似文献   

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