Synthesis of Mn-Al alloy nanoparticles by plasma arc discharge

Alloy nanoparticles in the Mn-Al system were prepared by the plasma arc discharge method. The influence of process parameters on the vaporization rate, composition, particle size, and magnetic properties of the as-produced nanoparticles was investigated. The Mn content was found to be higher in the nanoparticles than in the corresponding mother alloy, although the difference diminished with the reaction time. With increasing H₂ content in the reaction gas, both vaporization rate and particle size increased. With 30 at.% Mn, the average particle diameter in pure Ar was 35.2 nm, whereas that in an atmosphere with Ar:H₂ = 60:40 was 95.4 nm. With the addition of a small amount of carbon, ε-phase nanoparticles were synthesized. After heat treatment in a vacuum for 30 min at 400-600 °C, the nonmagnetic ε-phase was transformed into the ferromagnetic τ-phase and a very high coercivity of about 446 kA/m was achieved.     

Characterization of activated reactive evaporated MoO3 thin films for gas sensor applications

Thin films of molybdenum trioxide (MoO₃) were prepared by activated reactive evaporation technique on Pyrex glass substrates. The influence of oxygen partial pressure, substrate temperature and glow power on the structure, surface morphology and optical properties of MoO₃ thin films was studied. The MoO₃ films deposited in an oxygen partial pressure of 1×10⁻³ Torr, glow power of 10 W and substrate temperature of 573 K exhibited predominantly a (0 k 0) orientation corresponding to the orthorhombic layered structure of -MoO₃. The evaluated optical band gap was 3.24 eV. The sensing property of these MoO₃ films for gases like NH₃ and CO was also studied to see the applicability for environmental monitoring. We have observed that the MoO₃ thin films of -phase are capable of detecting NH₃ and CO gases at concentrations lower than 10 ppm in dry air.     

Optical and ferromagnetic characteristics of Mn doped ZnO thin films grown by filtered cathodic vacuum arc technique

Mn doped ZnO (ZnO:Mn) thin films with ~ 10 at.% of Mn were grown on quartz substrates by filtered cathodic vacuum arc (FCVA) technique at low substrate temperature (≤ 200 °C). The influence of substrate temperature and oxygen flow rate on the optical, electrical and magnetic properties of the ZnO:Mn thin films was studied. Both room temperature ferromagnetism and ultraviolet photoluminescence were observed in all films. A maximum saturation moment of 2.9 × 10⁻²⁴ A m²/Mn can be achieved for the films grown in an optimum condition. This suggests that the fabrication of high-quality ZnO:Mn films by FCVA technique has the potential to realize efficient magneto-optic devices operating at ultraviolet regime.     

Characterization of indium zinc oxide thin films prepared by pulsed laser deposition using a Zn3In2O6 target

Using a Zn₃In₂O₆ target, indium-zinc oxide films were prepared by pulsed laser deposition. The influence of the substrate deposition temperature and the oxygen pressure on the structure, optical and electrical properties were studied. Crystalline films are obtained for substrate temperatures above 200°C. At the optimum substrate deposition temperature of 500°C and the optimum oxygen pressure of 10⁻³ mbar, both conditions that indeed lead to the highest conductivity, Zn₃In₂O₆ films exhibit a transparency of 85% in the visible region and a conductivity of 1000 S/cm. Depositions carried out in oxygen and reducing gas, 93% Ar/7% H₂, result in large discrepancies between the target stoichiometry and the film composition. The Zn/In (at.%) ratio of 1.5 is only preserved for oxygen pressures of 10⁻²–10⁻³ mbar and a 93% Ar/7% H₂ pressure of 10⁻² mbar. The optical properties are basically not affected by the type of atmosphere used during the film deposition, unlike the conductivity which significantly increases from 80 to 1400 S/cm for a film deposited in 10⁻² mbar of O₂ and in 93% Ar/7% H₂, respectively.     

Aging effect on coercivity of iron oxide thin films

Changes in magnetic properties for Fe_3-x□_x O₄ (x: oxidation degree) thin films made by reactive sputtering and subsequent heat treatments have been examined under room temperature aging and constant temperature annealing. Aging causes variations in coercivity of insufficiently oxidized films which have a specific resistance of less than 1×10¹ Ω·cm, while the coercivity of γ-Fe₂O₃ (x=1/3) did not change. This phenomenon did not depend on additive elements or preparation method. Other magnetic properties such as saturation magnetization, residual magnetization, squareness ratio and coercive squareness, were not affected by aging for any Fe_3-x □_xO₄ composition. The activation energy for a coercivity change is 0.72-0.95 eV near room temperature for films with a specific resistance below 1×10¹ Ω·cm. It was confirmed that only the coercivity varied at 20°C, while both coercivity and the degree of oxidation changed with annealing at 100°C     

Ta additive effect on RF magnetron sputtered CoCr films

Magnetic properties for sputtered CoCrTa films (18 at.% Cr and 2.0-3.0 at.% Ta), which were deposited under various background pressures P_i, and argon sputtering pressures, P _Ar, have been examined. The perpendicular anisotropy field H_k for CoCrTa films maintains high values of 5-6 kOe in a wide range of P_i and P_Ar , as compared with that for CoCr films. In order to optimize Ta composition, magnetic properties and crystalline microstructures for Ta additive content (0-4.0 at.%) have been investigated. H_k and perpendicular coercivity H_c⊥ increase with increasing Ta concentration above 2.0 at.% Ta. C-axis orientation is improved by adding Ta to CoCr films. However, above 3.0 at.% Ta, H_c⊥ steeply decreases and domain wall motion is observed, owing to the increase in crystalline grain size. The appropriate Ta composition is 2.0-3.0 at.%     

Electrical properties of evaporated polycrystalline Ge thin-films

Electrical properties of Ge thin films evaporated on Si₃N₄ CVD-coated Si substrate were improved by introducing a heat treatment after the deposition of Ge films. Evaporation conditions were optimized by changing the substrate temperature and deposition rate, and then, heat treatment was performed. At substrate temperatures during the evaporation lower than 300 °C and higher than 400 °C, deposited films were amorphous and polycrystalline, respectively. At substrate temperatures lower than 400 °C, Ge films were evaporated without degrading the surface roughness. The Hall mobility of films evaporated at room temperature increased with increasing the substrate and heating temperature and showed about 400 cm² V⁻¹ s⁻¹ for the hole concentration of 4 × 10¹⁷ cm⁻³ at the heating temperature of 900 °C. This value was almost comparable to that of p-type Ge single crystal.     

Structural, chemical, and electrical characterisation of reactively sputtered WSx thin films

WS_x films were sputter-deposited on Si, SiO₂/Si, and glass substrates from a WS₂ target in an Ar/H₂S atmosphere. Their structure, morphology, chemical composition, and electrical properties were investigated as a function of deposition parameters such as working pressure and H₂S fraction. Films could be grown in the composition range WS_0.3−WS_3.5. Crystallisation was achieved at substrate temperatures T_s > 70 °C and compositions 0.7 ≤ x ≤ 1.95. While the first 5–50 nm near the interface exhibited a basal orientation (c), further growth resulted in the formation of edge-oriented platelets (c) giving rise to a porous, lamellar microstructure. The crystalline structure was mainly turbostratic, while some degree of ordered stacking was present in samples grown at high substrate temperature (600 °C). Resistivity measurements showed a semiconductor-type temperature dependence characterised by activation energies up to 95 meV. Sheet resistance was found to be nearly independent of film thickness, suggesting that the main carrier transport takes place in an interfacial layer of about 20 nm in thickness.     

Preparation of strontium titanate thin films by mirror-confinement-type electron cyclotron resonance plasma sputtering

Using mirror-confinement-type electron cyclotron resonance (ECR) plasma sputtering method, strontium titanate (SrTiO₃) thin films have been prepared on Si and Pt/Ti/SiO₂/Si substrates at a low substrate temperature (below 450 K) in a low pressure (2.7×10⁻² Pa) environment of pure Ar and Ar/O₂ mixture. Prepared film surfaces were very smooth regardless of high deposition rate (8.5 nm/min). The composition ratio Sr/Ti of Sr to Ti in the films varied with the distance between the target and the substrate. All as-deposited films on Si substrates were found to be amorphous and were crystallized by post-deposition annealing using an electric furnace at 650 K, i.e. approximately 250 K lower than annealing for films obtained by conventional RF magnetron sputtering. Post-deposition annealing of these films using millimeter-wave radiation decreased the crystallization temperature to a value of 550 K. Furthermore, all as-deposited films on Pt/Ti/SiO₂/Si substrates by a plasma of Ar and O₂ gas mixture were found to be crystallized regardless of no substrate heating.     

VACUUM VAPOR DEPOSITION PROCESS FOR CERAMICS DEVELOPMENT OF THE VACUUM VAPOR DEPOSITION PROCESS FOR CERAMICS BY CO2 LASER

The vacuum vapor deposition process using a CO₂lase; has been studied (or producing high adhesion ceramic films on various materials. Deposition of aluminum oxide and silicon oxide films with adhesion strengths above 50 MPa on stainless steel was achieved at high deposition rates with substrate heating, For silicon oxide films, addition of a moderate oxygen supply allowed deposition of highly adherent films at lower substrate temperatures. Adhesion strengths above 50 MPa were estimated at a substrate temperature of 470°K and an oxygen flow rate of 1.9 x 10^-7 m₃/s, in spitof the high deposition rate of 30 nm/s     

电镀法制备CoNiMnP永磁薄膜阵列的研究

采用光刻和电镀技术在5mm×5mm×0.2mm的硅片上设计并制备了2000个大小为50μm×50μm的CoNiMnP垂直各向异性永磁薄膜阵列,并对该薄膜陈列的组成、磁性能等进行了分析与测试.结果表明:薄膜阵列的组成为:Co90.32wt％、Ni7.83wt％、Mn0.74wt％、P1.11wt％,阵列垂直方向磁性能为:H_c=59.7kA/m,B_r=0.53T,(BH)_max=11.3kJ/m³;阵列水平方向磁性能为:H_c=27.8kA/m,B_r=53715T,(BH)_max=1.585kJ/m³.     

Varying mode of disorder of the MnAl6 alloy phase in the recovery process of vacuum codeposited films

Mn-Al films with different compositions ranging from 8 to 21 at.% Mn were prepared by simultaneous vacuum codeposition and their crystallization during a temperature rise was investigated by transmission electron microscopy. The film whose composition is exactly that of the MnAl₆ phase shows discrete nucleation of MnAl₆ crystals and they grow in a beautiful circular form. As the manganese content of the film increases from that of MnAl₆, the crystals grow in circular, in blade-like and in avalanche-like form, respectively. Diffraction patterns of these crystals show that they have a differently disordered MnAl₆ lattice and that the modes of disorder depend on the film composition. Extra spots, diffuse streaks and a deficiency of spots were observed in the respective crystals and almost all of them can be interpreted as being due to disorder in the stacking of atomic planes parallel to the (001) plane of the MnAl₆ lattice. A model of the atomic arrangement is proposed to account for the deficiency of spots.     

Corrosion-resisting Co-Pt thin film medium for high density recording

This paper describes a new material medium for high density longitudinal recording. Sputtered Co-Pt thin films will be shown to have excellent corrosion resistance and magnetic properties. Co-Pt thin films do not need a thick overcoat like plated Co-Ni-P films do, and have higher remanent flux density than ferrite thin films. Co1-xPtx(X=0-0.60) thin films prepared by r.f. diode sputtering have a maximum Hc value near X=20. The Hc, Bs and squareness, for 20 at.% Pt film are 1,100 Oe, 12,000 G and 0.80-0.90, respectively, at 0.1 μm film thickness. These values are not changed over 1-15 Watt/cm²power densities, corresponding to 6-85nm/min deposition rates. Films with more than 28 at.% Pt have no Bs change after immersion in water for over one month, indicating that the films are passive by this test, at least. Ni additions improve magnetic and corrosion properties. There is no Bs change for Co0.070Ni0.010Pt0.020films after immersion in water for over one month. Finally, 51 KFRPI linear recording density was obtained, at D50, using a Co0.70Ni0.10Pt0.20thin film disc with a 0.46 μm gap length head and a 0.12 μm head-medium spacing.     

Crystal orientation in CuSn-alloy coatings obtained by magnetron sputtering

Crystal orientation in copper-tin alloy coatings of different chemical composition as a function of substrate temperature has been studied using the X-ray texture goniometer technique. The coatings were obtained by magnetron sputtering an alloy target in argon at a gas pressure of 6 × 10⁻¹ Pa using two kinds of substrate—one of ferritic stainless steel and the other of a glass ceramic material. It has been established that Cu-Sn 7.8% alloy films, which represent an α-solution of Sn in Cu are textured. At low substrate temperature (710–770 K) the α-phase crystals have a mixed 〈100〉 and 〈110〉 orientation and at temperatures in the range from 870 to 1000 K—〈110〉 orientation. No orientation was detected when the condensation proceeded by the mechanism vapour→liquid→solid. The η-Cu₆Sn₅ and Sn phase crystals in CuSn 74% alloy films were not oriented.     

Magnetic-field-induced phase separation via spinodal decomposition in epitaxial manganese ferrite thin films

In this study, we report about the occurrence of phase separation through spinodal decomposition (SD) in spinel manganese ferrite (Mn ferrite) thin films grown by Dynamic Aurora pulsed laser deposition. The driving force behind this SD in Mn ferrite films is considered to be an ion-impingement-enhanced diffusion that is induced by the application of magnetic field during film growth. The phase separation to Mn-rich and Fe-rich phases in Mn ferrite films is confirmed from the Bragg’s peak splitting and the appearance of the patterned checkerboard-like domain in the surface. In the cross-sectional microstructure analysis, the distribution of Mn and Fe-signals alternately changes along the lateral (x and y) directions, while it is almost homogeneous in the z-direction. The result suggests that columnar-type phase separation occurs by the up-hill diffusion only along the in-plane directions. The propagation of a quasi-sinusoidal compositional wave in the lateral directions is confirmed from spatially resolved chemical composition analysis, which strongly demonstrates the occurrence of phase separation via SD. It is also found that the composition of Mn-rich and Fe-rich phases in phase-separated Mn ferrite thin films deposited at higher growth temperature and in situ magnetic field does not depend on the corresponding average film composition.     

Effect of microstructural evolution on magnetic properties of Ni thin films

The magnetic properties of Ni thin films, in the range 20–500 nm, at the crystalline-nanocrystalline interface are reported. The effect of thickness, substrate and substrate temperature has been studied. For the films deposited at ambient temperatures on borosilicate glass substrates, the crystallite size, coercive field and magnetization energy density first increase and achieve a maximum at a critical value of thickness and decrease thereafter. At a thickness of 50 nm, the films deposited at ambient temperature onto borosilicate glass, MgO and silicon do not exhibit long-range order but are magnetic as is evident from the non-zero coercive field and magnetization energy. Phase contrast microscopy revealed that the grain sizes increase from a value of 30–50 nm at ambient temperature to 120–150 nm at 503 K and remain approximately constant in this range up to 593 K. The existence of grain boundary walls of width 30–50 nm is demonstrated using phase contrast images. The grain boundary area also stagnates at higher substrate temperature. There is pronounced shape anisotropy as evidenced by the increased aspect ratio of the grains as a function of substrate temperature. Nickel thin films of 50 nm show the absence of long-range crystalline order at ambient temperature growth conditions and a preferred [111] orientation at higher substrate temperatures. Thin films are found to be thermally relaxed at elevated deposition temperature and having large compressive strain at ambient temperature. This transition from nanocrystalline to crystalline order causes a peak in the coercive field in the region of transition as a function of thickness and substrate temperature. The saturation magnetization on the other hand increases with increase in substrate temperature.     

Pulsed laser deposition of NiTi shape memory alloy thin films with optimum parameters

A series of experiments was carried out to optimize the pulsed laser deposition parameters for the fabrication of high quality NiTi shape memory alloy thin films. Smooth NiTi shape memory alloy thin films were deposited at high growth rate with optimum deposition parameters based on the analysis of the relationships among the morphology of the target surface and the deposited thin film, the laser energy, the target–substrate distance, the thin film composition and its growth rate. Crystal structures and phase transformation temperatures of the annealed Ni_49.7Ti_50.3 thin film were characterized by using X-ray diffraction and differential scanning calorimetry, respectively. The martensitic transformation temperature of the crystallized Ni_49.7Ti_50.3 thin film is found to be lower than room temperature and 27°C lower than that of the NiTi target material. These results are attributed to the refined grain size of the thin film and its composition, which deviates slightly from Ni₅₀Ti₅₀.     

Characterization of europium doped zinc aluminate luminescent coatings synthesized by ultrasonic spray pyrolysis process

Europium doped zinc aluminate (ZnAl₂O₄) photoluminescent films have been deposited by ultrasonic spray pyrolysis deposition process. Different substrate temperatures and doping concentrations in the start spraying solution were studied. It is observed that the crystalline structure of this material depends on the substrate temperature during deposition of the films. For low substrate temperatures, the deposited films are amorphous. When the substrate temperature is increased at 500 °C some peaks corresponding to hexagonal phase of ZnO (zincite) appears. At substrate temperatures of 550 °C, the crystalline structure of the ZnAl₂O₄:Eu films presents the close-packed face centered cubic phase. The excitation and emission spectra were obtained; for an excitation wavelength of 260 nm, all the photoluminescence (PL) spectra show peaks located at 589, 615, 652 and 700 nm. Concentration quenching of the PL occurs at activator concentrations greater than 0.85 at.% inside the deposited films. The PL intensity increases as the substrate temperature rises. In addition, the surface morphology features of the films, as a function of the deposition temperature, are shown.     

Effect of deposition temperature on the structural and thermoelectric properties of bismuth telluride thin films grown by co-sputtering

Thermoelectric bismuth telluride thin films were prepared on SiO₂/Si substrates by radio-frequency (RF) magnetron sputtering. Co-sputtering method with Bi and Te targets was adopted to control films' composition. Bi_xTe_y thin films were elaborated at various deposition temperatures with fixed RF powers, which yielded the stoichiometric Bi₂Te₃ film deposition without intentional substrate heating. The effects of deposition temperature on surface morphology, crystallinity and electrical transport properties were investigated. Hexagonal crystallites were clearly visible at the surface of films deposited above 290 °C. Change of dominant phase from rhombohedral Bi₂Te₃ to hexagonal BiTe was confirmed with X-ray diffraction analyses. Seebeck coefficients of all samples have negative value, indicating the prepared Bi_xTe_y films are n-type conduction. Optimum of Seebeck coefficient and power factor were obtained at the deposition temperature of 225 °C (about − 55 μV/K and 3 × 10^− 4 W/K²·m, respectively). Deterioration of thermoelectric properties at higher temperature could be explained with Te deficiency and resultant BiTe phase evolution due to the evaporation of Te elements from the film surface.     

氧化物La-Ca-Mn-O巨磁电阻薄膜的制备及其结构特性的研究

采用磁控溅射方法在ＺｒＯ２（００１）、Ｓｉ（００１）和玻璃衬底上成功地制备了ＬａＣａＭｎＯ（以下简称为ＬＣＭＯ）巨磁电阻薄膜。Ｘ－射线分析表明，ＺｒＯ２的晶格常数与ＬＣＭＯ的晶格常数失配虽然较大，仍可得到较好的ＬＣＭＯ薄膜。在Ｓｉ片上难以制备出致密完整的ＬＣＭＯ薄膜，其原因有待查明。玻璃衬底上可以获得纯相的ＬＣＭＯ巨磁电阻薄膜，在ＺｒＯ２衬底上制备的ＬＣＭＯ薄膜，其巨磁电阻效应在１５０Ｋ，３０００Ｇａｕｓ下达１３％左右。