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1.
The article reports on correlations between the process parameters of reactive pulsed dc magnetron sputtering, physical properties and the photocatalytic activity (PCA) of TiO2 films sputtered at substrate surface temperature Tsurf ≤ 180 °C. Films were deposited using a dual magnetron system equipped with Ti (Ø50 mm) targets in Ar + O2 atmosphere in oxide mode of sputtering. The TiO2 films with highly photoactive anatase phase were prepared without a post-deposition thermal annealing. The decomposition rate of the acid orange 7 (AO7) solution during the photoactivation of the TiO2 film with UV light was used for characterization of the film PCA. It was found that (i) the partial pressure of oxygen pO2 and the total sputtering gas pressure pT are the key deposition parameters influencing the TiO2 film phase composition that directly affects its PCA, (ii) the structure of sputtered TiO2 films varies along the growth direction from the film/substrate interface to the film surface, (iii) ∼500 nm thick anatase TiO2 films with high PCA were prepared and (iv) the structure of sputtered TiO2 films is not affected by the substrate surface temperature Tsurf when Tsurf < 180 °C. The interruption of the sputtering process and deposition in long (tens of minutes) pulses alternating with cooling pauses has no effect on the structure and the PCA of TiO2 films and results in a decrease of maximum value of Tsurf necessary for the creation of nanocrystalline nc-TiO2 film. It was demonstrated that crystalline TiO2 films with high PCA can be sputtered at Tsurf ≤ 130 °C. Based on obtained results a phase zone model of TiO2 films was developed.  相似文献   

2.
We evidenced an early-stage ordering (ESO) in Fe51Pt49 film before the appearance of superlattice diffraction (long-range-order, LRO) using 40-nm-thick films prepared by magnetron sputtering onto quartz substrate. The appearance of L10 phase for samples deposited at substrate temperatures (Ts) 400 °C and higher was verified by X-ray diffraction. Surface roughness of Fe51Pt49 films, obtained via X-ray specular reflectivity with computational fitting, increases from 3.8 to 11 Å as Ts is increased from 25 to 275 °C. As further increase of Ts to 375 °C, the roughness drops to 3.2 Å and then increases again to 38 Å with Ts up to 700 °C. Measurement on residual strain demonstrates that it is initially compressive at Ts<400 °C. Thereafter the strain transfers to a tensile one and increases in magnitude as increasing Ts up to 700 °C corresponding to LRO transformation. Local atomic rearrangement is observed for samples deposited at Ts>250 °C by using extended X-ray absorption fine structure. Coercivity of films increases from 10 to 460 Oe as Ts increase from 25 to 375 °C (ESO) and then from 460 to 10,700 Oe with Ts 375-700 °C (normal LRO). The worked out quantitative estimation of ESO engages with that of LRO before Ts 400 °C.  相似文献   

3.
Hafnium oxide (HfO2) thin films have been made by radio-frequency (rf) magnetron-sputtering onto Si(1 0 0) substrates under varying growth temperature (Ts). HfO2 ceramic target has been employed for sputtering while varying the Ts from room temperature to 500 °C during deposition. The effect of Ts on the growth and microstructure of deposited HfO2 films has been studied using grazing incidence X-ray diffraction (GIXRD), and high-resolution scanning electron microscopy (HR-SEM) coupled with energy dispersive X-ray spectrometry (EDS). The results indicate that the effect of Ts is significant on the growth, surface and interface structure, morphology and chemical composition of the HfO2 films. Structural characterization indicates that the HfO2 films grown at Ts < 200 °C are amorphous while films grown at Ts > 200 °C are nanocrystalline. An amorphous-to-crystalline transition occurs at Ts = 200 °C. Nanocrystalline HfO2 films crystallized in a monoclinic structure with a (−1 1 1) orientation. An interface layer (IL) formation occurs due to reaction at the HfO2-Si interface for HfO2 films deposited at Ts > 200 °C. The thickness of IL increases with increasing Ts. EDS at the HfO2-Si cross-section indicate that the IL is a (Hf, Si)-O compound. The electrical characterization using capacitance-voltage measurements indicate that the dielectric constant decreases from 25 to 16 with increasing Ts. The current-voltage characteristics indicate that the leakage current increases significantly with increasing Ts due to increased ILs.  相似文献   

4.
We present the results of a study of structural and superconducting properties of polycrystalline Nb thin films (200 Å, 300 Å, 400 Å, 700 Å and 1000 Å) and Nb/Cu bilayers (300 Å/300 Å and 400 Å/300 Å) prepared on Si substrates by ion beam sputtering at room temperature. The thicknesses, roughnesses at the surfaces and interfaces were determined by X-ray reflectivity whereas the grain sizes were determined from grazing incidence X-ray diffraction and transmission electron microscopic studies. The superconducting transition temperature (TC) of Nb thin films are smaller than TC of bulk Nb. The Nb-200 Å sample does not show TC down to 2.3 K. The average size of the grains varies from 42 Å for Nb-200 Å sample to 69 Å for Nb-1000 Å sample. Our results show that the TC in these polycrystalline films is not only limited by its thickness but also by the size of the grains. The Nb films deposited in situ on the Cu layer (Nb/Cu) show a marginal increase in average sizes of the grains as compare to their respective values in Nb films of same thicknesses. As a result a marginal increase in TC of these films is also observed. The maximum decrease in TC due to oxygen intake during deposition should be about 0.5 K from its bulk value (9.28 K). We have attributed the large decrease in TC in our case on the basis of decrease in the Debye temperature and density of states at the Fermi level for Nb thin films as compared to their respective values for bulk Nb.  相似文献   

5.
Influence of both substrate temperature, Ts, and annealing temperature, Ta, on the structural, electrical and microstructural properties of sputtered deposited Pt thin films have been investigated. X-ray diffraction results show that as deposited Pt films (Ts = 300, 400 °C) are preferentially oriented along (1 1 1) direction. A little growth both along (2 0 0) and (3 1 1) directions are also noticed in the as deposited Pt films. After annealing in air (Ta = 500-700 °C), films become strongly oriented along (1 1 1) plane. With annealing temperature, average crystallite size, D, of the Pt films increases and micro-strain, e, and lattice constant, a0, decreases. Residual strain observed in the as deposited Pt films is found to be compressive in nature while that in the annealed films is tensile. This change in the strain from compressive to tensile upon annealing is explained in the light of mismatch between the thermal expansion coefficients of the film material and substrate. Room temperature resistivity of Pt films is dependant on both the Ts and Ta of the films. Observed decrease in the film resistivity with Ta is discussed in terms of annihilation of film defects and grain-boundary. Scanning electron microscopic study reveals that as the annealing temperature increases film densification improves. But at an annealing temperature of ∼600 °C, pinholes appear on the film surface and the size of pinhole increases with further increase in the annealing temperature. From X-ray photoelectron spectroscopic analysis, existence of a thin layer of chemisorbed atomic oxygen is detected on the surfaces of the as deposited Pt films. Upon annealing, coverage of this surface oxygen increases.  相似文献   

6.
Relationship between magnetic anisotropy field Hk and thermal processes during the preparation has been studied for FeCoB thin films. The FeCoB films deposited on the glass substrates by facing targets sputtering successfully showed strong magnetic anisotropy when the substrate was heated at the substrate temperature Ts above 100 °C. Additionally, the lattice spacing of FeCo(1 1 0) in the perpendicular direction was found to decrease depending on the substrate temperature Ts. Among various temperature histories, the heating processes with a phase of increasing Ts revealed the further improvement of Hk. Meanwhile, high Hk in the films disappears after the post-deposition annealing at the temperature above 400 °C.  相似文献   

7.
Yttrium iron garnet (YIG) thin films were deposited on fused quartz substrate at different substrate temperatures (Ts) varying from room temperature (RT) to 850 °C using pulsed laser deposition (PLD) technique. All the films in the as-deposited state were X-ray amorphous and non-magnetic at RT. The film deposited at RT after annealing at temperatures Ta?700 °C showed both X-ray peaks and the magnetic order. The films deposited at higher Ts (500–850 °C) and then annealed at 700 °C resulted in better-quality films with higher 4πMs value. The highest value of magnetization was for the sample deposited at 850 °C and annealed at 700 °C, which is 68% of the bulk 4πMs value.  相似文献   

8.
Deposited with different oxygen partial pressures and substrate temperatures, MgxZn1−xO thin films were prepared using a Mg0.6Zn0.4O ceramic target by magnetron sputtering. The structural and optical properties of the prepared thin films were investigated. The X-ray diffraction spectra reveal that all the films on quartz substrate are grown along (2 0 0) orientation with cubic structure. The lattice constant decreases and the crystallite size increases with the increase of substrate temperature. Both energy dispersive X-ray spectroscopy and calculated results suggest the ratio of Mg/Zn increases with increasing substrate temperature. The thin film deposited with Ts = 500 °C has a minimal rms roughness of 7.37 nm. The transmittance of all the films is higher than 85% in the visual region. The optical band gap is not sensitive to the oxygen partial pressure, while it increases from 5.63 eV for Ts = 100 °C to 5.95 eV for Ts = 700 °C. In addition, the refractive indices calculated from transmission spectra are sensitive to the substrate temperature. The photoluminescence spectra of MgxZn1−xO thin films excited by 330 nm ultraviolet light indicate that the peak intensity of the spectra is influenced by the oxygen partial pressure and substrate temperature.  相似文献   

9.
In this paper, TaxC1−x coatings were deposited on 316L stainless steel (316L SS) by radio-frequency (RF) magnetron sputtering at various substrate temperatures (Ts) in order to improve its corrosion resistance and hemocompatibility. XRD results indicated that Ts could significantly change the microstructure of TaxC1−x coatings. When Ts was <150 °C, the TaxC1−x coatings were in amorphous condition, whereas when Ts was ≥150 °C, TaC phase was formed, exhibiting in the form of particulates with the crystallite sizes of about 15-25 nm (Ts = 300 °C). Atomic force microscope (AFM) results showed that with the increase of Ts, the root-mean-square (RMS) values of the TaxC1−x coatings decreased. The nano-indentation experiments indicated that the TaxC1−x coating deposited at 300 °C had a higher hardness and modulus. The scratch test results demonstrated that TaxC1−x coatings deposited above 150 °C exhibited good adhesion performance. Tribology tests results demonstrated that TaxC1−x coatings exhibited excellent wear resistance. The results of potentiodynamic polarization showed that the corrosion resistance of the 316L SS was improved significantly because of the deposited TaxC1−x coatings. The platelet adhesion test results indicated that the TaxC1−x coatings deposited at Ts of 150 °C and 300 °C possessed better hemocompatibility than the coating deposited at Ts of 25 °C. Additionally, the hemocompatibility of the TaxC1−x coating on the 316L SS was found to be influenced by its surface roughness, hydrophilicity and the surface energy.  相似文献   

10.
YSZ films for anode-supported SOFCs were prepared by reactive sputtering method. It was found that the surface morphology of anode substrate has a very important effect on the quality of sputtered films. By applying an anode functional layer and making the anode surface smooth, dense and uniform YSZ films of 10 µm in thickness were successfully fabricated. The sintering behaviors of the sputtered YSZ films were also discussed. It is suggested that the optimized densification condition for the deposited YSZ films is sintering at 1250 °C for 4 h. Single cells with sputtered YSZ film as electrolyte and LSM-YSZ as active cathode materials were tested. 1.08 V open circuit voltage and a 700 mW/cm2 maximum power density were achieved at 750 °C by using humidified H2 as fuel and air as oxidant.  相似文献   

11.
The effects of thermal annealing in vacuum on the bonding structures, optical and mechanical properties for germanium carbide (Ge1−xCx) thin films, deposited by radio frequency (RF) reactive sputtering of pure Ge(1 1 1) target in a CH4/Ar mixture discharge, are investigated. We find that there are no significant changes in the bonding structure of the films annealed below 300 °C. The fraction of Ge-H bonds for the film annealed at temperatures (Ta) above 300 °C decreases, whereas that of C-H bonds show a decrease only when Ta exceeds 400 °C. The out-diffusion of hydrogen promotes the formation of Ge-C bonds at Ta above 400 °C and thus leads to a substantial increase in the compressive stress and hardness for the film. The refractive indices and optical gaps for Ge1−xCx films are almost constant against Ta, which can be ascribed to the unchanged ratios of Ge/C and sp2-C/sp3-C concentrations. Furthermore, we also find that the excellent optical transmission for an antireflection Ge1−xCx double-layer film on ZnS substrate is still maintained after annealing at 700 °C.  相似文献   

12.
Polycrystalline thin films of Ge-C were grown on Si (1 1 1) substrates by means of reactive pulsed laser deposition with methane pressure of 100 mTorr. Effect substrate temperature, Ts, on C incorporation to substitutional sites (x) in Ge1−xCx was investigated systematically by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyzes. The substrate temperatures were ranging from 250 to 400 °C. The substitutional C composition x in the films by XRD were estimated using the Vegard's linear law. The maximum value of x calculated by XRD was 0.032 for Ts of 350 °C. The position of the C 1s peak at 283.4 eV in the XPS spectrum confirmed the germanium-carbon alloys. XRD measurements indicated that x increased with Ts from 250 °C to 350 °C. At Ts = 400 °C, the estimation of x was lowered. However, the C content calculated by XPS analyzes increased with Ts being more these values than substitutional C composition x. XPS and XRD analyzes demonstrate that the remaining C atoms are incorporated to interstitial sites. The use of the Ts plays important roles in the incorporation of substitutional C and in restraining C-cluster formation in the reactive pulsed laser deposition growth of Ge-C/Si.  相似文献   

13.
N-doped ZnO films were deposited by RF magnetron sputtering in N2/Ar gas mixture and were post-annealed at different temperatures (Ta) ranging from 400 to 800 °C in O2 gas at atmospheric pressure. The as-deposited and post-annealed films were characterized by their structural (XRD), compositional (SIMS, XPS), optical (UV-vis-NIR spectrometry), electrical (Hall measurements), and optoelectronic properties (PL spectra). The XRD results authenticate the improvement of crystallinity following post-annealing. The weak intensity of the (0 0 2) reflection obtained for the as-deposited N-doped ZnO films was increased with the increasing Ta to become the preferred orientation at higher Ta (800 °C). The amount of N-concentration and the chemical states of N element in ZnO films were changed with the Ta, especially above 400 °C. The average visible transmittance (400-800 nm) of the as-deposited films (26%) was increased with the increasing Ta to reach a maximum of 75% at 600 °C but then decreased. In the PL spectra, A0X emission at 3.321 eV was observed for Ta = 400 °C besides the main D0X emission. The intensity of the A0X emission was decreased with the increasing Ta whereas D0X emission became sharper and more optical emission centers were observed when Ta is increased above 400 °C.  相似文献   

14.
High temperature superconducting GdBa2Cu3O7 (GdBCO) thin films were grown by pulsed laser ablation. Textured MgO on metal substrates was used as a template for second generation wire applications. Growth conditions of GdBCO thin films were investigated for substrate temperature (Ts) and oxygen partial pressure (PO2) during deposition. Superconducting critical currents of the films were obtained in the films grown at 790–810 °C of Ts and at 100–700 mTorr of PO2. Scanning electron micrographs of the films revealed uniform and well-connected grains with some outgrown structures. X-ray θ–2θ scans of the films grown at 810 °C and 300–500 mTorr exhibited c-axis oriented texture. In-plane alignment and c-axis mosaic spread of the films were determined from X-ray Φ scans and rocking curves, respectively. Polarized Raman scattering spectroscopy was used to characterize optical phonon modes, oxygen content, cation disorder, and some possible second phases of the films. The Raman spectra of the films with large critical current density showed modes at 326–329 cm−1, 444–447 cm−1, 500–503 cm−1 related to vibration of oxygen atoms. Origin of small peaks near 600 cm−1 will be discussed as well. The information obtained from Raman scattering measurements will be useful for quality control of the conductors as well as optimization of the process conditions.  相似文献   

15.
(1 0 0) oriented BaNb2O6 films have been successfully grown on LaAlO3 (1 0 0) substrate at 750 °C or 450 °C in vacuum by pulsed laser deposition. The deposited BaNb2O6 PLD films exhibit room-temperature ferromagnetism. Ab initio calculations demonstrate that stoichiometric BaNb2O6 and that with barium vacancy are nonmagnetic, while oxygen and niobium vacancy can induce magnetism due to the spin-polarization of Nb s electrons and O p electrons respectively. Moreover, ferromagnetic coupling is energetically more favorable when two Nb/O vacancies are located third-nearest-neighbored. The observed room temperature ferromagnetism in BaNb2O6 films should be mainly induced by oxygen vacancies introduced during vacuum deposition, with certain contribution by Nb vacancies.  相似文献   

16.
Strontium ferrite (SrM) thin films were deposited on thermally oxidized silicon wafer with Au underlayer. Gold underlayers were prepared at various substrate temperatures by using a magnetron sputtering system. C-axis oriented SrM perpendicular films and preferred (1 1 1) orientation of underlayer have confirmed by X-ray diffraction patterns. The intensity of (1 1 1) diffraction line for Au and that of (0 0 l) diffraction line for strontium ferrite decrease with increase in substrate temperature (Tu) The maximum coercivity and remanent squareness ratio in perpendicular direction, at Tu of 500 °C, are 5.4 kOe and 0.68, respectively. The strength of the intergranular interaction of SrM magnetic particles is described by the parameter Δm. The SrM/Au films prepared at Tu above 100 °C have smaller Δm peak values than that for SrM/Au films prepared at Tu of room temperature. This behavior is related to low magnetostatic coupling between the magnetic particles separated by the non-magnetic amorphous phase.  相似文献   

17.
We report orientation-controllable growth of ZnO thin films and their orientation-dependent electrical characteristics. ZnO thin films were deposited on single-crystalline (1 0 0) LaAlO3 and (1 0 0) SrTiO3 substrates using pulsed laser deposition (PLD) at different substrate temperatures (400-800 °C). It was found that the orientation of ZnO films could be controlled by using different substrates of single-crystalline (1 0 0) LaAlO3 and (1 0 0) SrTiO3. The a-plane () and c-plane (0 0 0 2) oriented ZnO films are formed on LaAlO3 and SrTiO3, respectively. In both cases, the degree orientation increased with increasing deposition temperature Ts. Both the surface free energy and the degree of lattice mismatch are ascribed to play an important role for the orientation-controllable growth. Further characterization show that the grain size of the films with both orientations increases for a substrate temperature increase (i.e. from Ts = 400 °C to Ts = 800 °C), whereas the electrical properties of ZnO thin films depend upon their crystalline orientation, showing lower electrical resistivity values for a-plane oriented ZnO films.  相似文献   

18.
Pulsed laser deposition (PLD) was used to grow nanocrystalline SnO2 thin films onto alumina substrates. The reactive PLD process was carried out at different substrate deposition temperatures (Td) between 20 and 600 °C under an oxygen background pressure of 150 mtorr. The same PLD technique was used to produce SnO2 films in situ-doped with Pt (at the level of ∼2 at. %) through the concomitant ablation of both SnO2 target and Pt strips. Conventional and high-resolution transmission electron microscopy (HRTEM) observations have revealed that the microstructure of the PLD SnO2 films is highly sensitive to their deposition temperature. Indeed, its changes from a porous granular structure with extremely fine equiaxed grains (∼4 nm diameter), at Td=20 °C to a very compact and textured columnar structure characterized by SnO2 columns (∼25 nm diameter) composed of grains of ∼12 nm of diameter, at Td=600 °C. In addition, the PLD SnO2 films were found to exhibit the highest nanoporosity at Td=300 °C which also coincides with the granular-to-columnar microstructural transition. On the other hand, the microstructure of the Pt-doped SnO2 films, deposited at 300 °C, was found to contain a high density of defects, such as twin boundaries and edge dislocations. By combining HRTEM and EDS microanalysis, we were able to show that the Pt-dopant self-organizes into spherical nanoparticles (1-2 nm diameter) randomly distributed at the SnO2 grain boundaries. Finally, doping the films with such platinum nanoclusters is found to affect the SnO2 nanostructure by particularly reducing the SnO2 mean grain size (from ∼10 nm when undoped to ∼6 nm for the doped films).  相似文献   

19.
We report a successful fabrication of c-axis oriented GdBa2Cu3O7−δ (GdBCO) films on the BaSnO3 (BSO) buffer layers on ion-beam assisted deposition (IBAD)-MgO template by pulsed-laser deposition (PLD). The (0 0 l) growth and in-plane textures of BSO buffer layers were found sensitive to the substrate temperature (Ts). With increasing the BSO layer thickness up to ∼165 nm, in-plane texture (Δ? ∼ 6.2°) of BSO layers was almost unaltered while completely c-axis oriented BSO layers were obtainable from samples with the thickness below ∼45 nm. On the BSO buffer layers showing in-plane texture of 6.2° and RMS surface roughness of ∼8.6 nm, GdBCO films were deposited at 780–800 °C. All GdBCO films exhibited Δ? values of 4.6–4.7°, Tc,zero of ∼91 K, and critical current density (Jc) over 1 MA/cm2 at 77 K in a self-field. The highest Jc value of 1.82 MA/cm2 (Ic of 51 A/cm-width) was achieved from the GdBCO film deposited at Ts of 790 °C. These results support that BSO can be a promising buffer layer on the IBAD-MgO template for obtaining high-Jc GdBCO coated conductors.  相似文献   

20.
In this work, silicon suboxide (SiOx) thin films were deposited using a RF magnetron sputtering system. A thin layer of gold (Au) with a thickness of about 10 nm was sputtered onto the surface of the deposited SiOx films prior to the thermal annealing process at 400 °C, 600 °C, 800 °C and 1000 °C. The optical and structural properties of the samples were studied using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR) and optical transmission and reflection spectroscopy. SEM analyses demonstrated that the samples annealed at different temperatures produced different Au particle sizes and shapes. SiOx nanowires were found in the sample annealed at 1000 °C. Au particles induce the crystallinity of SiOx thin films in the post-thermal annealing process at different temperatures. These annealed samples produced silicon nanocrystallites with sizes of less than 4 nm, and the Au nanocrystallite sizes were in the range of 7-23 nm. With increased annealing temperature, the bond angle of the Si-O bond increased and the optical energy gap of the thin films decreased. The appearance of broad surface plasmon resonance absorption peaks in the region of 590-740 nm was observed due to the inclusion of Au particles in the samples. The results show that the position and intensity of the surface plasmon resonance peaks can be greatly influenced by the size, shape and distribution of Au particles.  相似文献   

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