GdFeCo非晶薄膜磁温度特性

本文以分子场理论为依据,通过实验数据的拟合和分析计算,计算了GdFeCo非晶薄膜饱和磁化强度、交换常数、磁各向异性常数的温度特性,并分析了薄膜成分变化对补偿温度、居里温度等的影响规律,为GdFeCo薄膜在新型磁光存储技术中的应用提供了理论依据.     

张应力对FeCoSiB非晶薄膜磁特性的影响

采用磁控溅射方法,在弯曲的玻璃基片上制备出受张应力作用的FeCoSiB非晶薄膜,研究了张应力大小对FeCoSiB薄膜的磁畴、矫顽力、剩磁、各向异性场等磁特性的影响.结果表明,薄膜的畴结构显著依赖于张应力,其磁畴宽度随张应力增加而增加;张应力导致FeCoSiB薄膜内形成较强的磁各向异性,其各向异性随应力的增大而增大.     

退火及成分对Co-C纳米复合薄膜磁性能的影响

用磁控溅射方法制备了Co含量介于13.0%～24.6%（原子分数）的Co-C纳米复合薄膜,在真空下对薄膜进行退火处理。测试了样品在5、77和300K下的磁化曲线,详细研究了退火及成分对薄膜微结构和磁性能的影响。结果表明未经退火的样品磁性较弱,退火之后样品磁性能增强,低Co含量的薄膜经退火后呈现出低温铁磁性、室温超顺磁性的颗粒薄膜特征。随着Co含量增加,薄膜的磁化强度和矫顽力均明显增大,冻结温度也随之升高。     

Thickness dependence of magnetic properties of Co90Fe10 nanoscale thin films

Ferromagnetic monolayers Co90Fe10 thin films with individual layer thicknesses 2, 6, and 8 nm were grown on thermally oxidized Si substrate and magnetic properties of these were investigated with Ferromagnetic resonance (FMR) technique at room temperature. The magnetoresistance (MR) of the samples were measured as a function of applied DC magnetic field and the thickness dependence of the MR was plotted. The FMR spectra were recorded for both parallel and perpendicular geometry. The X-band (9.5 GHz) FMR spectra and resonance field of samples were analyzed and fitted theoretically by using the Landau-Lifshits dynamic equation of motion for magnetization with the Bloch-Bloembergen type damping term. The computer programs have been written to extract the effective magnetization (M), g-values and spin-spin relaxation time (T2) fitting parameters. The thickness dependence of magnetic parameters has been obtained from experimental data by mean of a theoretical model.     

氟化非晶碳薄膜的低频介电性质分析

研究了电子回旋共振等离子体技术沉积的氟化非晶碳(α-C：F)薄膜的低频(10^2～10^6Hz)介电性质。发现α-C：F薄膜的低频介电色散随源气体CHF3／C6H6的比例、微波入射功率而改变。结合薄膜键结构的红外分析,发现薄膜中C=C相对含量的增大是导致低频介电色散增强的原因,而C—F相对含量的增大则使低频介电色散减弱。     

Wear properties of tetrahedrally bonded amorphous thin films

The abrasion wear rates of amorphous carbon, silicon, germanium and SiN_x films have been measured. The wear rate of all these films is shown to depend systematically on the amount of hydrogen incorporated in the film during the deposition process (either plasma or ion beam sputter deposition). This dependence can be understood from a decrease in the degree of cross-linking of the amorphous network when hydrogen is increasingly incorporated in the film. The resistance of unhydrogenated films to abrasive wear correlates with the atomic bond strengths of these materials, decreasing in the order carbon, SiN_x, silicon, germanium. The wear properties of SiN_x films depend on the incorporated hydrogen as well as on the N---Si composition of the films.     

Temperature dependence of the band gap, refractive index and single-oscillator parameters of amorphous indium selenide thin films

InSe thin films are obtained by evaporating InSe crystal onto ultrasonically cleaned glass substrates under pressure of 10⁻⁵ Torr. The structural and compositional analysis revealed that these films are of amorphous nature and are atomically composed of 51% In and 49% Se. The reflectance and transmittance of the films are measured at various temperatures (300–450 K) in the incident photon energy range of 1.1–2.1 eV. The direct allowed transitions band gap – calculated at various temperatures – show a linear dependence on temperature. The absolute zero value band gap and the rate of change of the band gap with temperature are found to be (1.62 ± 0.01) eV and −(4.27 ± 0.02) × 10⁻⁴ eV/K, respectively. The room temperature refractive index is estimated from the transmittance spectrum. The later analysis allowed the identification of the static refractive index, static dielectric constant, oscillator strength and oscillator energy.     

Optical properties of thin films of amorphous vanadium oxides

The results of an experimental investigation of the optical properties of anodic vanadium oxide films are presented. It is shown that films of different phase composition (VO₂, V₂O₅, or a mixture of two phases) can be obtained, depending on the oxidation regime, and that the absorption and transmission spectra are modified significantly in accordance. The optical properties of the oxides, whose composition is close to stoichiometric vanadium dioxide, demonstrate the occurrence of a metal-semiconductor phase transition in the amorphous films. The results presented are important both from the standpoint of technical applications of thin film systems based on anodic vanadium oxides and for more detailed understanding of the physical mechanism of the metal-semiconductor phase transition and the influence of structural disorder on the transition. Pis’ma Zh. Tekh. Fiz. 25, 81–87 (April 26, 1999)     

Thickness dependence of microstructures and magnetic properties for CoPt/Ag nanocomposite thin films

Ag underlayer (30 nm) has improved the degree of ordering and perpendicular magnetic anisotropy of CoPt films (7.5-10 nm). After annealing at 600 °C and 700 °C, the perpendicular coercivity of CoPt/Ag films has been raised as the thicknesses of CoPt layers are increased. The magnetic easy axis of CoPt/Ag films would change from a random orientation to an out-of-plane orientation. It is found that Ag underlayer with thickness of 30 nm can improve the perpendicular magnetic properties of CoPt layers with thicknesses in the range of 7.5-10 nm. The CoPt/Ag films would be a candidate for perpendicular magnetic recording media.     

Electrical and switching properties of InSe amorphous thin films

In this work electrical and switching properties of InSe thin films have been studied.

The semiconductor compound InSe was obtained by direct synthesis from stoichiometric amounts of spectroscopically pure indium and selenium. By slow cooling of the synthesized InSe a polycrystalline material is obtained. The amorphous films were obtained by thermal evaporation under vacuum of the polycrystalline material on glass or pyrographite substrates.

From electrical measurements, it was found that for all films the dark electrical resistivity decreases with an increase in film thickness and temperature. The InSe compound exhibits non-linear I–V characteristics and switching phenomena. The threshold voltage decreases with increasing annealing temperature and increases with increasing film thickness.     

Temperature dependence of the electromagnetic response function for strong-coupling amorphous Bi films

The temperature dependence of the electromagnetic response functionI(0, 0,T) has been inferred from the temperature dependence of the kinetic inductance of thin, amorphous Bi films. For normalization purposesI(0, 0, 0) has been calculated from tunneling data with the microscopic strong-coupling theory. The results are not consistent with scaled weak-coupling theory, but instead exhibit strong-coupling effects. The calculated value ofI(0, 0, 0) is approximately 40% below the BCS value for a weak-coupling superconductor, qualtiatively in agreement with determinations ofI(0, 0, 0) for Pb by Kerchner and Ginsberg. The temperature dependence ofI(0, 0,T) differs in the opposite direction from the BCS dependence as that observed for Pb.Research supported by the Robert A. Welch Foundation, Houston, Texas.     

Temperature dependence of the experimental penetration depth of superconducting thin films

Experimental magnetic field penetration depths (t, d, H) of the stable and superheated Meissner state were calculated as a function of temperature for various applied magnetic fields and various film thicknesses for two cases: (1) (t)/d and (2) 2(t)/d ( is the Ginzburg-Landau penetration depth,d is the film thickness, is the GL parameter). The results of the first case should be a useful tool for obtaining (0) of amorphous superconducting thin films.¹ This work was supported in part by NSF Grant No. INT 8006927.     

Photo-induced changes in the optical properties of amorphous As-Ge-S thin films

Changes in the transmission, absorption edge and refractive coefficient in the UV-VIS and the transmission in the IR spectrum of thin As-Ge-S films after irradiation with an argon laser with =488 nm were studied. X-ray microanalysis showed that the composition of the films (with small variations) corresponded to that of the initial substances. Films with a defined concentration of the elements could also be deposited by evaporation of As₂S₃ and GeS₂ from two sources. The optical properties of thin films prepared by thermal evaporation, flash evaporation and coevaporation from two crucibles have been compared. It was found that depending on the component content, both photodarkening and photobleaching coatings in a wide region of can be obtained in thin As-Ge-S films. The results have been explained from the viewpoint of the photostructural changes in chalcogenide layers.     

Composition dependence of electrical properties of Al-Sb thin films

Thin films of Al-Sb of varying compositions and thickness have been formed on glass substrates employing three-temperature method. Electrical resistivity (ρ) and activation energy (ΔE) have been studied as a function of composition, thickness (d) and temperature of the film. Films of Al-Sb system with aluminium < 50 at.%, ∼ 50 at.% and > 50 at.% exhibit metallic, semiconducting and metallic to semiconducting behaviours respectively. Activation energy (ΔE) of semiconducting films found to vary inversely with thickness, is attributed to combined effects of change in barrier height due to the size of grains and stoichiometry in the films.     

Temperature effects on the properties of Ge thin films

The effects of substrate temperature (T_s) on the properties of vacuum evaporated p-type Ge thin films have been investigated for 25s<400°C. Increase in the substrate temperature improves the crystallinity and increases the grain size resulting a gradual change from amorphous to polycrystalline structure which was attained above a substrate temperature of 225°C. Low resistive (1×10^–2 ohm-cm) and high mobility (280 cm²/V·s) films were obtained at T_s=400°C. It has been observed that the conduction mechanism in polycrystalline films was dominated successively by hopping, tunneling and thermionic emission as the sample temperature was increased from 40 to 400 K. In amorphous samples, conduction was described in terms of different hopping mechanisms.     

Temperature dependence of ZnO thin films grown on Si substrate

The structural and optical properties of ZnO thin films grown on Si substrates were investigated for different growth temperatures in the range of 520–720 °C. X-ray diffraction investigations revealed the preferred c-axis oriented growth of ZnO thin films, which was further confirmed by the presence of ZnO (0002) diffraction spots with arc shape. The increase in growth temperature transformed surface morphology from pyramidal with columnar grains to relatively flat surface with increased grain size. In addition, the increased growth temperature caused redshift and intensity enhancement of band-edge emission of the ZnO, which were related to the increase in tensile strain and the grain size, respectively.     

Sputtering of FeCo-B amorphous films with soft magnetic properties

Microstructures, optimum sputtering conditions, and annealing methods were investigated for the purpose of obtaining zero magnetostriction amorphous films with good magnetic softness. Sputtering conditions which suppress formation of columnar structure in films were studied, and films with high density were obtained. The mechanism of columnar structure suppression is discussed. Annealing in an ellipitically rotating field is effective to reduce in-plane anisotropy and Barkhausen-type noise, and to obtain very weak anisotropy for high initial permeability. Some of the samples thus obtained exhibit excellent softness with high initial permeability.     

Temperature dependence of concentrations and mobilities in thin bismuth films

The resistivity, Hall coefficient and magnetoresistance of thin bismuth films were measured at various temperatures (80–300 K) and thicknesses (0.1–3 μm). The mobilities and concentrations of the free electrons and holes were calculated from the experimental data using an anisotropic two-carrier model. Four approaches to the calculation were applied and the results were compared with one another. It was found that the electron and hole concentrations are approximately equal.