The effects of substrate position on electroless polyol deposited nanostructured FeNi films

The nanostructured FeNi thin films were deposited on a polycrystalline Cu substrate by reducing constituent metal salts in refluxing ethylene glycol. The effect of substrate position was investigated. During deposition, the substrate was subject to one of the following processes: (a) complete immersion in solution, (b) repeated immersion followed by suspension above solution (denoted as quenching), and (c) suspension above the solution. Compared to the conventional polyol synthesis of FeNi where Fe concentration could not exceed 30 at%, the quenching process dramatically increased Fe at% to above 40%. Complete suspension of substrate above the solution resulted in Fe-rich films where Fe at% >90%. The microhardness, adhesion, and magnetic properties of deposited films showed a strong dependence on the long-range and short-range order of the film, which, in turn, depended on the substrate position. Quenched films with ordered local Ni environment and higher crystallinity had the highest Vickers hardness, best adhesion to substrate, and largest saturation magnetization compared to those deposited on substrates placed in other positions. The oxidation of Fe occurring in the vapor deposition significantly affected the film properties.     

Structure and magnetization reversal mechanism in L10 FePt films with perpendicular magnetic anisotropy

A series of L1₀ Fe₆₃Pt₃₇ films with controlled thickness (t_FM) were deposited on MgO(100) substrates for microstructure and magnetization reversal mechanism study. X-ray diffraction measurements show that face-centered tetragonal (200) peak also exists in addition to face-centered tetragonal (002) one, and becomes weak for thick films. High resolution electron microscopy study reveals the existence of periodic misfit dislocations at the FePt/MgO interface and other types of defects such as twins and antiphase boundary inside the film. Out-of-plane initial magnetization shows a slow increase responding to the external magnetic field and then follows a steep increase. The out-of-plane coercivity H_C at room temperature decreases with increasing t_FM and increases when the angle θ_H between the external magnetic field and the film normal direction increases. H_C at θ_H = 0 changes as a linear function of temperature for individual samples and the slope decreases with increasing t_FM. In addition, magnetic viscosity measurements show that the fluctuation field at room temperature decreases with increasing t_FM. These phenomena indicate that the magnetization reversal in the L1₀ FePt films should be realized by the motion of weakly pinned domain wall and thus governed by the thermal activation model. The magnetization reversal thermal activation volume and corresponding energy increase with increasing t_FM, as a result of the interactions between domain walls and structural defects can be attributed to the sample microstructural characteristic evolution with t_FM.     

Magnetization reversal of antiferromagnetically coupled perpendicular anisotropy films driven by current

By inserting an ultrathin Pt layer at Co/Ru interface,we established antiferromagnetic coupling with outof-plane magnetization in Co/Ru/Co film stacks fabricated by sputtering.To achieve configuration suitable for free layer,the magnetic properties of the stacks have been investigated by changing the thickness of Co,Ru and Pt layers using an orthogonal wedges technique.It is found that magnetic properties for upper Co layer thinner than 0.5 nm are sensitive to little change in Ru thickness.Improving continuity of upper Co layer by slightly increasing the thickness can effectively increase the squareness of minor loop.The switching magnetization of synthetic antiferromagnetic(SAF) structure is achieved by DC current under an in-plane static magnetic field of ± 500 Oe.This structure is very promising for free layer in spintronic application.     

有机玻璃基材表面电子束蒸镀铬-铝-二氧化硅薄膜及其性能研究

采用电子束蒸镀的方法,以有机玻璃为基材,在其表面蒸镀铬过渡层,再蒸镀铝,最后蒸镀保护层二氧化硅.实验结果表明:增加铬过渡层的样品,铝膜结合的非常牢固,附着力得到很大的提高.和未蒸镀二氧化硅保护层的样品进行耐腐蚀性测试对比,发现二氧化硅薄膜具有很好的保护性,铝膜在10%的碱性溶液中完好无损;而没镀二氧化硅保护层的样品,铝膜很快溶解.试验结果表明,采用电子束蒸发技术,在使用合适的工艺参数下,可以在有机玻璃表面制备附着力好、耐腐蚀的高反射铝膜.     

Ultrathin barium titanate films by polyol thermal decomposition process

We have successfully fabricated barium titanate (BaTiO₃) films on Si (100) and Pt(111)/Ti/SiO₂/Si substrates using the polyol thermal decomposition (PTD) process by spin-coating technique. In PTD process, we confirmed that the crystalline oxycarbonate Ba₂Ti₂O₅CO₃ films were directly formed as a consequence of evaporation of polyol precursor solution prepared simply by mixing metal chlorides and ethylene glycol, and then converting them into crystalline BaTiO₃ films through thermal decomposition at >500 °C. This feature makes it possible to grow densely packed and crack-free BaTiO₃ films as thin as 70 ? per cycle. Although PTD is described here for a complex metal-oxide film of BaTiO₃, other simple and complex metal-oxide thin films with high-dielectric constant materials are also likely to be suitable for deposition with accurate control of film thickness and composition using the polyol precursor solutions.     

Recording on perpendicular anisotropy media with ring heads

This paper reports experimental studies directed at the application of ring head structures to a perpendicular recording system. The media tested were sputter deposited films of CoCrTa alloys. Ferrite heads were studied, but the thin film head was chosen for evaluating roll-off, overwrite, and superposition. The data presented in the paper demonstrates the potential of high density recording with a single layer medium with perpendicular magnetic anistropy and a thin film head separated by 0.20 micrometers.     

Antireflective coating for ITO films deposited on glass substrate

The refractive index n of radio-frequency (r.f.) magnetron sputtered indium tin oxide (ITO) films varies with sputtering parameters, such as sputtering power and oxygen percentage in the sputtering ambient. In this study, the feasibility to fabricate multilayer antireflective (AR) coating with a single ITO target by controlling the sputtering conditions is explored. Reduction in the reflectance can be achieved by using a one-quarter-wavelength inner layer ITO with a refractive index n = 1.87 and a one-quarter-wavelength outer layer ITO with n = 2.17. Hence, a single ITO target suffices in the preparation of multilayer AR coating. This simplifies the deposition processes and equipment for the fabrication of AR coating. Surface corrugation, another approach to the reduction of reflectance, is also discussed.     

Anomalous optical absorption in dielectric thin films deposited by electron bombardment

The advantages of electron bombardment sources over conventional resistance-heated ones for the deposition of dielectric films can occasionally be outweighed by the occurrence of anomalous optical absorption.Work is described which attempts to identify the cause of this unwanted absorption. A charge analyser was developed which showed that relatively large electron currents can accompany the vapour stream emanating from this type of source. The resulting electron bombardment of the substrate during film deposition apparently gives rise to “colour centre” types of absorption phenomena in the condensed film. Although the mechanism of this process is not fully understood, experimental results are presented which demonstrate the importance of the effect in optical coating technology and show how the absorption can be either eliminated or enhanced by controlling the deposition conditions.     

Fabrication and characterization of thin films with perpendicular magnetic anisotropy for high-density magnetic recording

Perpendicular magnetic anisotropy (PMA) was first observed in thin films of cobalt-chromium alloys in 1974, and perpendicular magnetic recording was proposed in 1977. After less than ten years, a new technology for high-density magnetic recording is firmly established. This breakthrough of the science and technology of magnetic recording has been made possible mainly through the ingenuity and concerted efforts of Iwasaki and other researchers. The preparation, characterization, and application of the Co-Cr films featuring PMA have been extensively studied. This paper reviews the large number of reports on PMA films with emphasis in three areas: (1) processing of PMA films; (2) correlation of magnetic properties and microstructures of PMA films; and (3) state-of-the-art techniques for fabricating PMA films.Nomenclature PMA Perpendicular magnetic anisotropy - PMR Perpendicular magnetic recording - B Magnetic induction - H Magnetic field - H _c Coercivity - H _c, Perpendicular coercivity - H _d Demagnetizing field - H _K Anisotropy field - H Perpendicular anisotropy constant - M _r Remanent magnetization - M _s Saturation magnetization - P _Ar Argon pressure - T _s Substrate temperature - V _b Substrate bias voltage - Incidence angle - ₅₀ Half-width dispersion angle in the rocking curve - _c Curie temperature - _o Internal stress     

Fabrication and characterization of thin films with perpendicular magnetic anisotropy for high-density magnetic recording

Perpendicular magnetic anisotropy (PMA) was first observed in thin films of cobalt-chromium alloys in 1974, and perpendicular magnetic recording was proposed in 1977. After less than ten years, a new technology for high-density magnetic recording is firmly established. This breakthrough of the science and technology of magnetic recording has been made possible mainly through the ingenuity and concerted efforts of researchers. The preparation, characterization, and application of the Co-Cr films featuring PMA have been extensively studied. This paper reviews the large number of reports on PMA films with emphasis on three areas: 1. processing of PMA films; 2. correlation of magnetic properties and microstructures of PMA films; and 3. state-of-art techniques for fabricating PMA films.Nomenclature PMA Perpendicular magnetic anisotropy - PMR Perpendicular magnetic recording - B Magnetic induction - H Magnetic field - H _c Coercivity - H _c, Perpendicular coercivity - H _d Demagnetizing field - H _k Anisotropy field - H Perpendicular anisotropy constant - M _r Remanent magnetization - M_s Saturation magnetization - P _Ar Argon pressure - T _s Substrate temperature - V _b Substrate bias voltage - Incidence angle - ₅₀ Half-width dispersion angle in the rocking curve - _c Curie temperature - ₀ Internal stress     

Characterization of low-k dielectric SiCOH films deposited with decamethylcyclopentasiloxane and cyclohexane

Ultra low-k dielectric SiCOH films were deposited with decamethylcyclopentasiloxane (DMCPSO, C10H30O5Si5) and cyclohexane (C6H12) precursors by plasma-enhanced chemical vapor deposition at the deposition temperature between 25 and 200 degrees C and their chemical composition and deposition kinetics were investigated in this work. Low dielectric constants of 1.9-2.4 were obtained due to intrinsic nanoscale pores originating from the relatively large ring structure of DMCPSO and to the relatively large fraction of carbon contents in cyclohexane. Three different deposition regions were identified in the temperature range. Deposition rates increased with temperature below 40 degrees C and decreased as temperature increased to 75 degrees C with apparent activation energies of 56 kJ/mol x K at < 40 degrees C, -26 kJ/mol x K at 40-100 degrees C, respectively. In the temperature region of 40-100 degrees C hydrocarbon deposition and decomposition process compete each other and decomposition becomes dominant, which results in apparent negative activation energy. Deposition rates remain relatively unaffected with further increases of temperature above 100 degrees C. FTIR analysis and deposition kinetic analysis showed that hydrocarbon deposition is the major factor determining chemical composition and deposition rate. The hydrocarbon deposition dominates especially at lower temperatures below 40 degrees C and Si-O fraction increases above 40 degrees C. We believe that dielectric constants of low-k films can be controlled by manipulating the fraction of deposited hydrocarbon through temperature control.     

离子辅助蒸发TixOy制备氧化钛薄膜及特性

采用离子辅助沉积的方法,分别以TiO2和Ti3O5为初始膜料在K9玻璃上制备了氧化钛薄膜,并研究了离子束流密度对以Ti3O5为膜料制备的薄膜透射性能的影响.实验结果表明,热处理前薄膜都为无定形结构;热处理后有明显的锐钛矿结构(101)择优取向,以Ti3O5为初始膜料制备的薄膜吸收优于以TiO2为膜料制备的薄膜;薄膜透射率极值随束流密度增大有临界值.     

Influence of substrate temperature on N-doped ZnO films deposited by RF magnetron sputtering

Nitrogen-doped ZnO films were deposited by RF magnetron sputtering in 75% of N₂ / (Ar + N₂) gas atmosphere. The influence of substrate temperature ranging from room temperature (RT) to 300 °C was analyzed by X-ray diffractometry (XRD), spectrophotometry, X-ray photoelectron spectroscopy (XPS), secondary-ion mass spectrometry (SIMS) and Hall measurements setup. The XRD studies confirmed the hexagonal ZnO structure and showed that the crystallinity of these films increased with increasing substrate temperature (T_s). The optical studies indicate the average visible transmittance in the wavelength ranging 500-800 nm increases with increasing T_s. A minimum transmittance (9.84%) obtained for the films deposited at RT increased with increasing T_s to a maximum of 88.59% at 300 °C (500-800 nm). Furthermore, it was understood that the band gap widens with increasing T_s from 1.99 eV (RT) to 3.30 eV (250 °C). Compositional analyses (XPS and SIMS) confirmed the nitrogen (N) incorporation into the ZnO films and its decreasing concentration with increasing T_s. The negative sign of Hall coefficients confirmed the n-type conducting.     

纳米氧化锌掺铝薄膜的微观结构研究

采用溶胶-凝胶(sol-gel)法在玻璃衬底上制备了纳米ZnO掺铝薄膜,利用X射线衍射仪(XRD)和透射电镜(TEM)对薄膜的微观结构进行了系统的研究。结果表明,所有在玻璃衬底上生长的ZnO薄膜均具有c轴择优取向。掺杂量为2%(原子分数)时,Al在ZnO薄膜中达到最高水平。过量Al掺杂明显减弱薄膜的c轴择优取向。随着Al掺杂量的增加,ZnO晶粒进一步细化。其原因是未进入ZnO晶格的Al以非晶Al2O3的形式在ZnO晶界上形成了对晶界运动的钉扎,从而阻碍了ZnO晶粒进一步长大。     

Properties of Ce-doped ITO films deposited on polymer substrate by DC magnetron sputtering

Ce-doped indium tin oxide (ITO:Ce) films were deposited on flexible polyimide substrates by DC magnetron sputtering using ITO targets containing various CeO₂ contents (CeO₂ : 0, 0.5, 3.0, 4.0, 6.0 wt.%) at room temperature and post-annealed at 200 °C. The crystallinity of the ITO films decreased with increasing Ce content, and it led to a decrease in surface roughness. In addition, a relatively small change in resistance in dynamic stress mode was obtained for ITO:Ce films even after the annealing at high temperature (200 °C). The minimum resistivity of the amorphous ITO:Ce films was 3.96 × 10^− 4 Ωcm, which was deposited using a 3.0 wt.% CeO₂ doped ITO target. The amorphous ITO:Ce films not only have comparable electrical properties to the polycrystalline films but also have a crystallization temperature > 200 °C. In addition, the amorphous ITO:Ce film showed stable mechanical properties in the bended state.     

Characterization of cathodically deposited carbonaceous films on a silicon substrate

Carbon-based deposits were electrochemically formed on silicon substrates in ethanol at room temperature. This work was based on the work reported by Namba, who described the electrochemical deposition of diamond from organic solutions. The deposits were analysed using a scanning electron microscope, energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and electrochemical impedance spectroscopy. Scanning electron micrographs showed some crystalline deposits on the silicon. EDS was unable to identify carbon in the film, but did reveal impurities such as sodium, potassium, calcium and zinc. It was later established that the impurities most likely came from impurities in the graphite used for a counter electrode. XPS showed the presence of carbon species, and subsequently Raman spectroscopy was used to classify further the carbon deposits. Raman spectroscopy showed the presence of amorphous carbon in some films, but no diamond peak was observed for any of the films. EIS revealed that the impedance of the deposited films was nearly identical to that of the uncoated silicon, and did not resemble the impedance of diamond. Thus, in this work, carbon–based films were formed electrochemically, but these films were not diamond.     

Properties of ZnO:Al films deposited on polycarbonate substrate

Transparent conducting aluminum-doped zinc oxide (ZnO:Al) films have been prepared on polycarbonate (PC) substrates by pulsed laser deposition technique at low substrate temperature (room-100 °C); Nd-YAG laser with wavelength of 1064 nm was used as laser source. The experiments were performed at various oxygen pressures (3 pa, 5 pa, and 7 Pa). In order to study the influence of the process parameters on the deposited (ZnO:Al) films, X-ray diffraction and atomic force microscopy were applied to characterize the structure and surface morphology of the deposited (ZnO:Al) films. Polycrystalline ZnO:Al films having a preferred orientation with the c-axis perpendicular to the substrate were deposited with a strong single violet emission centering about 377–379 nm without any accompanying deep level emission. The average transmittances exceed 85% in the visible spectrum for 300 nm thick films deposited on polycarbonate.     

Grain-boundary scattering in aluminium films deposited on to calcite substrate

Electrical resistivity and temperature coefficient of resistivity of polycrystalline aluminium films deposited onto calcite substrates have been measured in situ. It was observed that films deposited at 130° C substrate temperature show reversible and reproducible behaviour with thermal cycling. The grain-boundary scattering theory of Mayadas and Shatzkes reproduces the experimental observations quite faithfully with the coefficient of specular reflection p=0 and grain-boundary reflection coefficient R=0.38 indicating that the grain-boundary scattering plays a significant role in electron transport in aluminium film deposited on to calcite substrate.