Sputtered multilayer films for digital magnetic recording

Layered films of cobalt over chromium deposited by dc sputtering onto heated substrates exhibit magnetic properties suitable for digital saturation recording. A cobalt layer of a few tens of nanometers thickness deposited over a chromium layer of several hundred nanometers has coercivity between 1100 and 300 Oe and remanence-thickness product between 0.014 and 0.07 G.cm with squareness between 0.7 and 0.95. Additional alternate layers of chromium and cobalt can increase remanent flux without reduction of coercivity. Magnetic properties can be tailored to specific needs by varying layer thicknesses.     

Electrical resistivity of thin bismuth films

The thickness dependence of electrical resistivity of thin bismuth films deposited on to glass substrates has been studied in the temperature range 77 to 350 K. The structural studies show that films are polycrystalline with grain size increasing with thickness. The electrical resistivity decreases with increasing temperature. This type of temperature dependence of electrical resistivity arises due to the competition between the temperature dependences of carrier density and carrier mobility, the temperature coefficients of which are opposite in sign. The electrical properties of bismuth films are greatly affected by the presence of surface states. The size effect theory of Pichard and colleagues (PTT) has been modified to investigate the variation of charge carrier concentration with thickness. The experimental results on electrical resistivity are found to be consistent with the predictions of this modified three-dimensional model (PTT). The value of specularity parameter,p, is about 0.43 and it exhibits no temperature dependence. The experimental results on grain-boundary resistivity agree fairly well with the theoretical variations. The values of transmission coefficient,t, are determined from the experimental data.     

Electrical resistivity of thin bismuth films

For quantitative and reproducible observation of the quantum size effect (QSE) 78 samples of thin bismuth films were deposited at one time onto three muscovite substrates in ultrahigh vacuum. The electrical resistivity of these films, either in step-up series or a fixed thickness, was measured between 4.2 and 320 K. The experiments covered a thickness range from 300 to 3350 Å. The measured resistivities had a large scatter among simultaneously deposited samples of a fixed thickness. This scatter became more pronounced with decreasing temperature and it was due to the variation of the TCR above liquid nitrogen temperature. The thickness dependence of the ratio of resistivities at 4.2 K and 77 K (?_4.2/?₇₇), which had a relatively small scatter, did not show the oscillatory behavior predicted by Sandomirskii.     

High frequency magnetic properties and intergranule interaction of nano-granular films with high resistivity and high permeability

In order to get magnetic films with high permeability and high resistivity for applications in high frequency devices, (Fe65Co35)x(SiO2)1-x nano-granular films with low metal volume fraction were fabricated by radio frequency magnetron sputtering, and excellent soft magnetic properties have been acquired by annealing the sample with x = 0.38 at 260 degrees C in a magnetic field. The real part micro' of complex permeability is larger than 100 when frequency f is lower than 0.7 GHz, and the ferromagnetic resonance frequency f(r) is as high as 1.8 GHz. More interestedly, the resistivity of this sample reaches 13.4 momega x cm, 4 orders higher than that of pure FeCo alloy. Ferromagnetic resonance experiment and deltam-H curve study were employed to elucidate the mechanism of soft magnetic properties. The results reveal that the intergranule exchange coupling plays an important role in realizing good soft magnetic properties for metal-insulator granular films.     

Saturation magnetostriction measurements of magnetic thin films under high magnetic fields

Saturation magnetostriction measurements of magnetic thin films have been studied using a system equipped with a motor driven electromagnet and a laser displacement meter. A new method to reduce the errors caused by applied rotating magnetic field is proposed for high-sensitive and accurate measurements of saturation magnetostriction. It is shown that accurate measurements are possible for magnetic fields up to around 1 kOe, by extracting the 2nd harmonic output through Fourier analysis as a function of applied rotating magnetic field and then by taking the extrapolation of 2nd harmonic output to zero magnetic field. This method is applied to measure a saturation magnetostriction of single-crystal fcc-Co(111) film and the value of − 30 × 10^− 6 is obtained.     

Recording properties of thin magnetic films at high densities

A set of recording measurements obtained from a series of cobalt-phosphorus thin film rigid discs is presented. Directly measured roll-off curves are compared with those obtained by linear superposition of both experimental and analytic isolated pulses. Nonlinear behavior at high densities is observed     

Anomalous electrical resistivity of thin gadolinium films

Electrical resistivity measurements at room temperature on thin gadolinium films in the thickness range 200–1000 Å are described. The resistivity-thickness curve in this case is anomalous in the sense that it exhibits a decrease in resistivity at lower thicknesses (less than about 500 Å). This is in marked contrast with other work and seems to represent the first observation of a resistivity decrease with decreasing thickness. It is suggested that this curious resistivity characteristic in Gd films results from the thickness dependences of the structural phase and of the spin-disorder resistivity.     

Nanocrystalline wurtzite Si–nickel silicide composite thin films with large band gap and high resistivity

Stabilization of wurtzite Si nanocrystals embedded in a metal/metal silicide matrix by the metal induced crystallization process is demonstrated. The process involves the growth of 50 nm thick Ni films on borosilicate glass (BSG) substrates followed by 700 nm thick amorphous Si films and annealing of this multilayered stack at 550 °C in furnace atmosphere for 1 h. The presence of wurtzite Si is established based on electron diffraction studies and is also confirmed by the Raman signature of wurtzite Si at 504 cm⁻¹. It is shown that the growth of wurtzite Si is mediated by the formation of Nickel Silicide, as evidenced by the Raman signal at 294 cm⁻¹. The films exhibit a band gap greater than 1.9 eV with dc resistances of the order of 10 GΩ. It is proposed that such high resistivities should make this form of Si ideal for PV and microwave device applications.     

CoNbZr非晶软磁薄膜晶化动力学研究

采用 DSC热分析技术,结合 XRD、TEM和AFM实验,对磁控溅射制备的 Co85.5Nb8.9Zr5.6非晶合金软磁薄膜进行了变温和等温晶化动力学的研究。研究结果表明:升温晶化时,薄膜的晶化的表观激活能为99.82kJ/mol;局域激活能随晶化度增加;在等温晶化过程中,平均激活能为 88. 51kJ/mol, Avrami 指数1.17~1.39, 晶化行为主要是一维表面晶化,晶核长大受扩散控制的过程。     

Sputtered lead scandium tantalate thin films: a microstructural study

Lead scandium tantalate (PST) thin films have been deposited on a platinized silicon substrate with and without a buffer layer of MgO at the temperature of 525°C. It was found that PST films on the substrate without a buffer layer were strongly (1 1 1) oriented perovskite, whilst films on the substrate with a buffer layer showed the presence of second-phase pyrochlore, and the films were (1 1 1) and (1 1 0) oriented. These structural differences were believed to result from the structural differences between the platinum layers immediately below the respective PST layers. The lines which divide PST into network of islands were found to be no more than wider grain boundaries, rather than cracks as believed previously. Micro-beam diffraction and energy dispersive X-ray analysis showed that grain boundaries were tantalum-rich and lead-deficient compared to perovskite grain centres. Electrical properties, such as relative permittivity and dielectric loss, for the films were also measured.     

A continuous electrical resistivity measurement in thin films

The continuous electrical resistivity measurement, while an interesting parameter is being changed, can be a useful tool for in-situ thin film analysis as most changes in films are accompanied by changes in the electrical resistivity. In-situ measurements in a tube furnace at atmospheric pressure during different heat treatments are presented for oxidation tracing in Cr films and the TiN/CrN multilayer and for detection of interactions in Ni/Si}, Ti/Si} and Ni/Al multilayers. Results of electrical resistivity measurements c correlated well with weight gain measurements, X-ray diffraction, Rutherford backscattering spectroscopy and Auger electron spectroscopy depth profiling. It is therefore shown that the measurement of the resistivity with its time and temperature derivatives can represent a useful basis for the application of other analytical methods.