Effects of substrate temperature on the magnetic and electrical properties of cobalt ferrite/metal composite thin films

The magnetic and electrical properties of the cobalt ferrite/metal composite thin films, prepared by reactive sputtering, were studied as a function of substrate temperature. With increasing substrate temperature, the saturation magnetization of the thin films increased owing to precipitation of the Co_0.67Fe_0.33 phase. Also, the electrical resistivity of the thin films decreased. From Hall experiments, the decrease of electrical resistivity of the composite thin films was mainly attributed to the increase of electron concentration. The Seebeck coefficient measurement shows that the electrical conduction mechanism of the thin films containing 37.8 and 33.7 at % Co changes from p-type to n-type and that of the thin films containing 28.5 at % Co remains n-type with increasing substrate temperature. This might be attributed to the change in composition of the cobalt ferrite matrix to Fe-excess with precipitation of Co-rich Fe alloy. ©1999 Kluwer Academic Publishers     

High coercivity of CoCrTa on a very thin Cr underlayer

RF sputtered CoCrTa films (Co-15 wt.% Cr-4.7 wt.% Ta) deposited on various thicknesses of Cr underlayer (200 Å to 800 Å) for longitudinal magnetic recording were investigated. A coercivity of 1500 Oe can be easily obtained on a 200-Å Cr underlayer with low argon pressure (4 mtorr) and high substrate bias (-100 V). Emphasis has been placed on the influence of (101¯0) texture formation on the in-plane coercivity. Microstructure observation revealed by TEM shows that the grain size and grain structure were changed with the thickness of the Cr underlayer. Several mechanisms are proposed to explain the experimentally observed phenomena of argon pressure and substrate bias effects on the coercivity change of this CoCrTa/Cr film     

Sputter deposited ZnO nanowires/thin film structures on glass substrate

Integrated ZnO nanowires/thin film structures were grown using radio-frequency magnetron sputter deposition on amorphous glass substrates having an electroless plated copper surface layer. The growth took place under different deposition times and O₂/Ar ratios. The substrate was not heated or biased during the deposition. Regardless of the O₂/Ar ratio, both nanowires and the film grew simultaneously. However, the growth of the nanowires and the film was diffusion-controlled and reaction-controlled, respectively. On the other hand, the O₂/Ar ratio substantially affected the crystal structure and morphology of the resulting ZnO deposits.     

Magnetic and recording properties of sputtered CoCrTa/Cr thin-film media

The magnetic and recording properties of CoCrTa/Cr, longitudinal, magnetic, recording media, with various Cr contents, were investigated by changing the deposition temperature, the Cr thickness and the CoCrTa thickness. The Cr content of the CoCrTa magnetic layer was varied from 10 to 14 at % Cr and the films were deposited on textured NiP/AIMg substrates by direct-current (d.c.) magnetron sputtering. Both the circumferential magnetic coercivity (H _c) and the coercivity orientation ratio (Or) of the media increased as the deposition temperature increased. The optimum Cr thickness was 50 70 nm; below this optimum value both H _c and the Or were small, and above this value the Or decreased. As the CoCrTa thickness increased, the Or continuously decreased, while H _c had a maximum of about 1600 Oe near the 40 nm thickness. The signal-to-noise ratio of the CoCrTa/Cr films increased as the deposition temperature, the Cr thickness and the CoCrTa thickness increased. However, the bit shift was lowest when the thicknesses of the CoCrTa and Cr layers were 50 60 nm and 50 70 nm, respectively. The CoCrTa magnetic films with 10 at % Cr had the highest signal to noise ratio of 33 dB and the lowest bit shift of 9 ns. Our results showed that the Or factor is an important parameter for high-performance recording characteristics as is a high H _c.     

衬底温度对低温制备纳米晶硅薄膜的影响

采用传统的射频等离子体增强化学气相沉积技术,在较高的工作气压130Pa和较高的射频功率70W下,在＞100℃的低温下,以0.14nm/s速率制备出优质的纳米晶硅薄膜.研究结果表明,薄膜晶化率和沉积速率与衬底温度有密切关系.当衬底温度＞100℃,薄膜由非晶相向晶相转化,随着衬底温度的进一步升高,薄膜晶化率增大,当温度为300℃时,薄膜的晶化率达82%,暗电导率为10-4·cm-1数量级,激活能为0.31eV.当薄膜晶化后,沉积速率随衬底温度升高而略有增加.     

Effects of elastic anisotropy on the surface stability of thin film/substrate system

The surface stability of thin film/substrate system is an important problem both in the film synthesis and reliability of micro electrical and mechanical system (MEMS). In this work, the elastic anisotropy effect on surface stability of thin film/substrate system was considered. The theoretical analysis indicates that elastic anisotropic influence could play an important role in the surface stability of thin film/substrate system. And the anisotropy effect should be considered both in the thin film synthesis process and its service reliability. In addition, there exists an nondimensional parameter k for cubic crystalline thin film materials in evaluating the anisotropic effect. When k is larger than one unit, the surface stability will be weakened by anisotropic effect; vice versa. The method used in present work could be easy extended to multi-layered thin film/substrate system and help us to consider the elastic anisotropy effect.     

Titanium oxide thin film deposited on metallic Cr substrate by RF-magnetron sputtering

In order to develop a colored mirror with hydrophilicity, TiO₂ films are deposited on the Cr and amorphous-TiO₂ substrate. In TiO₂/Cr, a mixed phase comprising of anatase and rutile is formed. In TiO₂/amorphous-TiO₂/Cr, pure anatase phase is obtained. The amorphous-TiO₂ film as interlayer tends to induce micro-columnar-shaped anatase phase. The formation of anatase phase leads to an abrupt decrease of the contact angle by UV-irradiation. Hydrophilic to hydrophobic reconversion by electron-hole recombination is retarded, which seems to be due to pure anatase phase without rutile phase.     

Effects of composition and substrate temperature on the a.c. properties of co-evaporated Mn/SiOx thin films

Capacitance, a.c. conductance and loss factor have been measured in Cu-Mn/SiOx-Cu sandwich structures with compositions 1, 3, 5 and 10 at% Mn in the frequency range 10–106 Hz between temperatures of 110 and 500 K. The capacitance has a weak minimum at 1.0 MHz for all temperatures, whilst the a.c. conductance increases between four and eight orders of magnitude for temperatures of 150 and 473 K, respectively. Various a.c. conduction models have been considered, and it has been concluded that correlated barrier hopping best describes the results. The Goswami-Goswami model was used to describe the variation of loss factor with temperature and composition. This revised version was published online in November 2006 with corrections to the Cover Date.     

Interface and temperature dependent magnetic properties in permalloy thin films and tunnel junction structures

Magnetization dynamics and field dependent magnetization of different devices based on 25-30 nm thick Permalloy (Py) films: such as single Py layers (Py/MgO; Py/CoFeB/Al2O3) and Py inserted as a magnetic layer in magnetic tunnel junctions (Py/CoFe/Al2O3/CoFe; Py/CoFeB/Al2O3/CoFe; Py/MgO/Fe) have been extensively studied within a temperature range between 300 K down to 5 K. The dynamic response was investigated in the linear regime measuring the ferromagnetic resonance response of the Py layers using broadband vector network analyzer technique. Both the static and the dynamic properties suggest the possible presence of a thermally induced spin reorientation transition in the Py interface at temperatures around 60 K in all the samples investigated. It seems, however, that the details of the interface between Py and the hardening ferromagnet/insulator structure, the atomic structure of Py layers (amorphous vs. textured) as well as the presence of dipolar coupling through the insulating barrier in the magnetic tunnel junction structures could strongly influence this low temperature reorientation transition. Our conclusions are indirectly supported by structural characterization of the samples by means of X-Ray diffraction and high resolution transmission electron microscopy techniques. Micromagnetic simulations indicate the possibility of strongly enhanced surface anisotropy in thin Py films over CoFe or CoFeB underlayers. Comparison of the simulations with experimental results also shows that the thermally-induced spin reorientation transition could be influenced by the presence of strong disorder at the surface.     

Effect of substrate temperature on the structural and magnetic properties of Fe/Ag superlattices

In the present work, Fe/Ag superlattices were grown by molecular beam epitaxy (MBE) on MgO(001) single crystal substrates maintained at room temperature or at 423 K during the deposition. The structural properties were carried out using small and high angle X-ray diffraction techniques. The magnetic hysteresis loops with the magnetic field applied parallel or perpendicular to the plane of the films were measured by a superconducting quantum interference device (SQUID) magnetometer in the temperature range 5–300 K. A comparison of the obtained results showed that the heating of MgO substrates leads to a strong interdiffusion and causes a significant modification of structural and magnetic properties of Fe/Ag superlattices.     

Non-uniform stress distribution and deformation bifurcation of thin film/substrate system subjected to gradient temperature

Stresses in thin films or coatings control the reliability of the thin film/substrate structure. By considering a circular thin film/substrate system subjected to gradient temperature, we derive relations between the non-uniform stresses in film and temperature, and between the non-uniform system curvatures and temperature. These relations featured a “local” part that involves a direct dependence of the stress or curvature components on the temperature at the same point, and a “non-local” part which reflects the effect of temperature of other points on the location of scrutiny. Furthermore, the deformation bifurcation behavior of the thin film/substrate system is analyzed. As the thermo-mismatch strain in the thin film increases, the system may transit to a biaxial curvature state (non-spherical deformation), in other words, the bifurcation of curvature will occur.     

Influence of the substrate temperature on the properties of MoSi2 thin films

Investigations of the microcrystalline structure of sputtered MoSi₂ thin films deposited at temperatures in the range 60–500 °C are described. At low temperatures the films are amorphous, and in the higher range of temperature hexagonal MoSi₂ is detected. Annealing the films at 960 °C to form the low resistivity tetragonal MoSi₂ phase results in different grain sizes depending on the substrate temperature during deposition.     

The influence of the substrate temperature on the preparation of thin film In2Te3

An optimum substrate temperature T_o of 453 K was found for the preparation of thin film In₂Te₃ by electron beam evaporation. Films prepared at this temperature are stoichiometric and exhibit a maximum hole mobility of 48 cm² V^-1s^-1 and a maximum hole concentration of 4.2 × 10¹⁸ cm^-3. These observations can be explained on the basis of the Vincett-Barlow-Roberts theory which predicts a value for T_o/T_b, where T_b is the boiling point, of 0.3. The electrical activation energies of the films were also determined and are discussed in terms of the possible defects present.     

Effects of substrate temperature on dielectric and structural properties of Ti and Er co-doped HfO2 thin films

We report dielectric and structural properties of Ti and Er co-doped HfO₂ (HfTiErO_x) thin films at different substrate temperatures. The film at 400 °C substrate temperatures has the highest k value of 33, improved flat band voltage of −0.3 V, small hysteresis voltage and the significant interface-state density, which shows better dielectric properties for new high-k microstructure. XPS and XRD results reveal that Hf-Ti-Er-O bond may exist in addition with Hf-O, Hf-Er-O and Hf-Ti-O bonds, while the change in chemical structure and degradation of crystallization quality of HfO₂ thin films are directly related to Ti and Er co-doping.     

镍锌铁氧体薄膜的显微结构和低温磁性质

通过溶胶凝胶甩膜工艺,在抛光的硅晶片(100)基底上制备出Ni0.5Zn0.5Fe2O4(NZF)薄膜并对其结构和磁性的测量结果进行了分析。薄膜表面平整,具有较好的单相结构,其颗粒平均粒径约30nm。制备的NZF薄膜厚度分别约90、120和180nm。实验结果表明,薄膜在低温下表现出自旋玻璃态行为。当外加磁场为7.96×103A/m时,NZF薄膜自旋冻结温度大约在Tf=140K,自旋冻结程度随薄膜厚度增加而降低。在40~300K之间,薄膜饱和磁化强度和矫顽力都随着温度增加而降低。NZF薄膜在T=40K处存在最大磁化强度。较薄薄膜在40K以下饱和磁化强度的降低是因为磁性颗粒表面自旋被部分冻结而导致的磁性离子相互间自旋耦合作用减弱的结果。