夹心结构FeNi/Cu/FeNi多层膜巨磁阻抗效应研究

采用MEMS技术在玻璃基片上制备了夹心结构FeNi/Cu/FeNi多层膜,并在1～40MHz范围内研究了它的巨磁阻抗效应.纵向巨磁阻抗效应先随着外加磁场的增大而迅速增加,在某一磁场下达到最大值后随磁场的增加而逐渐减小.在频率为5MHz时,Hext为0.8kA/m时巨磁阻抗效应最大值达到32.06%.另外,夹心结构多层膜表现出较大的负巨磁阻抗效应,在频率5MHz,Hext=9.6kA/m时,负最大巨磁阻抗效应可达-24.50%.     

Thermal stability of the phase composition and structure of hafnium diboride films

The thermal stability of the composition and crystal structure of hafnium diboride films grown by rf magnetron sputtering have been studied by X-ray diffraction and secondary ion mass spectrometry. We have assessed the effect of high-temperature annealing in air on the phase composition and structure of the hafnium diboride films. The results demonstrate that annealing produces a HfO₂ oxide layer on the surface of the HfB₂ film. Raising the annealing temperature from 600 to 1000°C leads to an increase in the thickness of the oxide layer from 100 to 600 nm and to the formation of a multilayer HfB₂-HfO₂ coating.     

三明治结构FeNi/Cu/FeNi多层膜巨磁阻抗效应研究

采用MEMS技术在玻璃基片上制备了三明治结构FeNi/Cu/FeNi多层膜,在1～40 MHz范围内研究了FeNi/Cu/FeNi多层膜中的巨磁阻抗效应特性.当磁场Ha施加在薄膜的长方向时,巨磁阻抗效应随磁场的增加而增加,在某一磁场下达到最大值,然后随磁场的增加而下降到负的巨磁阻抗效应.在频率为5MHz时,巨磁阻抗效应在磁场Ha=800 A/m时达到最大值26.6%.巨磁阻抗效应的最大值及负的巨磁阻抗效应与多层膜中磁各向异性轴的取向及发散有关.另外,当磁场施加在薄膜的短方向时,薄膜表现出负的巨磁阻抗效应,在频率5 MHz、磁场Ha=9600 A/m时,巨磁阻抗效应可达-15.6%.     

类金刚石碳膜的热稳定性

总结了各种ＤＬＣ膜的热稳定性及分析手段,概述了加热退火情况下ＤＬＣ膜结构,内应力的变化,评述了国内的最新研究进展,并提出了有等进一步研究的问题。     

Thermal stability of carrier centers in various types of transparent conductive ZnO and Ga-doped ZnO films

We investigated the thermal stability of the transparent conductive properties of undoped ZnO and Ga-doped ZnO (GZO) films when they were annealed in a high vacuum with stepwise increasing temperature. The ZnO samples included V_O-rich and Zn-rich ZnO films; the primary donors were respectively oxygen vacancies (V_O) or Zn atoms highly unsaturated with oxygen atoms. V_O-rich ZnO was the most unstable against annealing; resistivity initially within the 10⁻³ Ω cm range diverged higher than 10 Ω cm when a critical temperature was exceeded. The critical temperature between 350 and 450 °C depended on the film thickness, which indicated that V_O's were diminished through recombination with migrating interstitial oxygen atoms. In contrast, Zn-rich ZnO films remained highly conductive up to 550 °C. They became more and more transparent and their crystallinity improved at higher annealing temperatures, which was the consequence of metallic-like Zn atoms being removed through desorption from the surface or being accommodated into the crystalline lattice. Comparatively, GZO films were more robust against annealing with their resistivities remaining unchanged up to 350 °C.     

Quality enhancement of AZO thin films at various thicknesses by introducing ITO buffer layer

Due to the simultaneously superior optical transmittance and low electrical resistivity, transparent conductive electrodes play a significant role in semiconductor electronics. To enhance the electrical properties of these films, one approach is thickness increment which degrades the optical properties. However, a preferred way to optimize both electrical and optical properties of these layers is to introduce a buffer layer. In this work, the effects of buffer layer and film thickness on the structural, electrical, optical and morphological properties of AZO thin films are investigated. Al-doped zinc oxide (AZO) is prepared at various thicknesses of 100 to 300 nm on the bare and 100 nm-thick indium tin oxide (ITO) coated glass substrates by radio frequency sputtering. Results demonstrate that by introducing ITO as a buffer layer, the average values of sheet resistance and strain within the film are decreased (about 76 and 3.3 times lower than films deposited on bare glasses), respectively. Furthermore, the average transmittance of ITO/AZO bilayer is improved nearly 10% regarding single AZO thin film. This indicates that bilayer thin films show better physical properties rather than conventional monolayer thin films. As the AZO film thickness increases, the interplanar spacing, d₍₀₀₂₎, strain within the film and compressive stress of the film in the hexagonal lattice, decreases indicating the higher yield of AZO crystal. Moreover, with the growth in film thickness, carrier concentration and optical band gap (E_g) of AZO film are increased from 4.62?×?10¹⁹ to 8.21?×?10¹⁹ cm^?3 and from 3.55 to 3.62 eV, respectively due to the Burstein-Moss (BM) effect. The refractive index of AZO thin film is obtained in the range of 2.24–2.26. With the presence of ITO buffer layer, the AZO thin film exhibits a resistivity as low as 6?×?10^?4 Ω cm, a sheet resistance of 15 Ω/sq and a high figure of merit (FOM) of 1.19?×?10⁴ (Ω cm)^?1 at a film thickness of 300 nm. As a result, the quality of AZO thin films deposited on ITO buffer layer is found to be superior regarding those grown on a bare glass substrate. This study has been performed over these two substrates because of their significant usage in the organic light emitting diodes and photovoltaic applications as an enhanced carrier injecting electrodes.     

Thermal stability of gold-PS nanocomposites thin films

Low-temperature transmission electron microscopy (TEM) studies were performed on polystyrene (PS, M _w = 234 K) — Au nanoparticle composite thin films that were annealed up to 350°C under reduced pressure conditions. The composite thin films were prepared by wet chemical approach and the samples were then subsequently spin-coated on a carbon-coated copper grid for TEM measurements. TEM measurements were performed at liquid nitrogen temperatures to reduce the electron-beam-induced radiation damage. The results showed a marginal increase in Au nanoparticle diameter (2.3 nm–3.6 nm) and more importantly, an improved thermal stability of the polystyrene (PS) composite film much above its glass transition temperature.     

Thermal stability of sputtered zirconium oxide films

In this work, the effect of post-growth annealing on the structural and optical properties of sputtered zirconium oxide films has been investigated. The temperature dependence of structure, density, and optical constants has been systematically studied by X-ray diffraction, X-ray reflectometry, atomic force microscopy (AFM) and optical spectroscopy. X-ray diffraction studies show no variation in the crystalline phase upon annealing except grain growth. X-ray reflectivity measurements determine a density increase of approximately 11% and a simultaneous thickness reduction of 10% upon annealing. The surface roughness of the films increases upon annealing as determined by XRR and confirmed by AFM measurements. Optical spectroscopy measurements confirm that the refractive index n of the films decreases with increasing annealing temperature. At the same time the optical band gap E_g of the films increases from 4.58 to 4.97 eV annealing at 900°C. The surprising decrease of refractive index upon annealing is attributed to both the intermixing of Si with ZrO₂ and the increasing surface roughness of the films.     

Thermal stability of magnetron sputtering amorphous carbon nitride films

Magnetron sputtered amorphous carbon nitride films were annealed at different temperatures (450-900°C) and time (30-120 min). Compositional, bonding structural and surface morphological modifications of the films were characterized by Fourier transformation infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy. The as-deposited film was found to have nitrogen content of 30 at%, and the carbon atoms were bonded to nitrogen atoms in the chemical structure state of CN, CN and CN bonds. The FTIR and XPS results showed that the films were thermally stable without an obvious change in the films as annealing temperature was lower than 600°C. The relative intensity ratio of CN over CN bonds reached a maximum at annealing temperature of 750°C, and then decreased gradually at annealing temperature up to 900°C. The CN bonds in the films decreased with the increase of annealing temperature and eliminated completely at annealing temperature of 900°C. These results revealed that annealing caused a substantial decrease in the number of weak bonds between carbon and nitride atoms. The CN bonds have higher thermal stability than CN bonds and CN bonds in the films. Simultaneously annealing also led to the formation of a large fraction graphitic-like carbon in the films while nitrogen escaped from the film. Besides, the surface roughness of the films increased with annealing temperature. However, when annealing time was increased from 30 to 120 min at annealing temperature of 750°C, only a slight effect of the annealing time on composition, bonding structure and the surface roughness of the films was observed.     

磁控溅射非晶CNx薄膜的热稳定性研究

为了研究非晶CNx薄膜的热稳定性,采用射频磁控溅射方法沉积了非晶CNx薄膜样品,并在真空中退火至900℃,利用FTIR,Raman和XPS谱探讨了高温退火对CNx薄膜化学成分及键合结构的影响.研究表明:CNx薄膜样品中N原子分别与sp、sp2和sp3杂化状态的C原子相结合,退火处理极大地影响了CN键合结构的稳定性;当退火温度低于600℃时,膜内N含量的损失较少,CNx薄膜的热稳定性较好,退火温度超过600℃时,将导致CNx膜中大多数C、N间的键合分离,造成N大量损失,膜的热稳定性下降;退火可促使膜内sp3型键向sp2型键转变,在膜中形成大量的sp2型C键,导致CNx膜的石墨化.     

Thermal stability and decomposition kinetics of amorphous hydrogenated films

The kinetics of decomposition of the SiH₂ and SiH centers in amorphous hydrogenated silicon films were studied by thermomanometric analysis. The methods of preparation and analysis are described. Experimental values of the enthalpy and entropy of activation are given in both cases. Tentative reaction mechanisms are proposed on the basis of an interpretation of the results.     

Thermal stability of silver thin films on zirconia substrates

The thermal stability of silver thin films between 100 nm and 820 nm thick deposited onto single crystal yttria-stabilised zirconia (YSZ) substrates by evaporation was investigated by annealing the films between 250 °C and 550 °C for different durations. Films approximately 100 nm thick were thermally unstable at temperatures as low as 250 °C. A dewetting process occurred in which grain boundaries ruptured, to uncover the substrate and reduce the overall energy of the system, by a combination of grain boundary grooving at the outer surface and void growth at the Ag-YSZ interface. The surface self diffusion coefficient of Ag was determined from the kinetics of the process to be 2.6 ± 0.3 × 10^− 5 cm²s^− 1 at 500 °C. The resulting silver morphology ranged from ‘self-organised’ interconnected silver network structures to completely isolated silver islands. A structure predominance map of the rearrangement process is presented.     

Microstructure and dielectric characteristics of high-k tetragonal ZrO2 films with various thicknesses processed by sol-gel method

High-k ZrO2/Si films were fabricated by a sol-gel method and the effects of the thickness of ZrO2 on the phase formation, interface chemical structure, and dielectric performance were studied. The 0.1 M precursor sol was prepared by using Zr acetylacetonate, coated, dried on Si substrates, and finally annealed at 500 degrees C. The thickness of ZrO2 was varied in the range from 7 to 51 nm by repeating the coating and drying sequences. The deposited ZrO2 was amorphous for the sample with a thickness of -7 nm, but tetragonal (t-) phases appeared as the thickness increased. As the thickness increased, the flat-band voltage and hysteresis width in the capacitance-voltage curves increased. The sol-gel deposited ZrO2 dielectrics showed a high k value (-33) due to the formation of the t-phase, while retaining gate leakage current levels of less than -4.0 x 10(-5) A/cm2 at 1 MV/cm.     

Thermal and electrical properties of FeNi/Cu composites

Abstract

Powder metallurgy FeNi/Cu composites with low thermal expansivity and high electrical (thermal) conductivity were fabricated. The effects of Cu content, FeNi particle size, sintering temperature, and rolling reduction on the coefficient of thermal expansion (CTE) and electrical (thermal) resistivity were investigated. The results show that the CTE and electrical resistivity were affected by the volume fraction of the components, the particular properties of the FeNi alloy, diffusion between the FeNi particles and the Cu particles, and the distribution of the Cu particles and the FeNi particles. The experiments indicated that the FeNi/Cu composites could be used as heat sinks in welding type bolt silicon rectifier tubes.     

Thermal stability and strength of Mo/Pt multilayered films

The strength of Mo/Pt multilayers of varying thicknesses has been investigated using nanoindentation. Metallic composites with individual layer thicknesses ranging from 100 to 20 nm were fabricated. Of specific interest in this study was the strength of the nanocomposites after annealing in air at relatively high temperatures (475 °C) since potential applications involve high temperature and oxidizing environments. Annealing causes significant losses in strength, with the highest losses corresponding to the structures with the thinner Pt layers. Annealing caused grain coarsening as well as loss of the continuous interface between the individual layers when the Pt thickness was less than 35 nm. Oxidation of the Mo layers occurred during annealing, causing an increase in the thickness of the Mo containing layers. The oxidation of Mo occurs in a uniform manner which results in an increase of the total film thickness while the layered structure is maintained. Deconvolution of the Mo 3d spectrum from X-ray Photoelectron Spectroscopy revealed several oxide species, and no Pt–Mo intermetallics were detected. The changes in microstructure are related to the changes in mechanical properties. Films with thinner layer thicknesses were stronger prior to annealing; however, they showed larger losses in strength after the thermal treatment. Structures with thicker Pt layers should be used when the multilayers are exposed to elevated temperatures.     

高致密度FeNi纳米颗粒薄膜制备与性能研究

传统磁控溅射装置制备的纳米颗粒薄膜粒径不均一并且实现粒径大小调控比较困难.本研究采用电场辅助沉积技术,在沉积平台施加5～30 kV的电场,以Si(100)为衬底制备了一系列纳米颗粒粒径均一的高致密度FeNi纳米颗粒薄膜材料.通过XRD、SEM以及VSM测量,研究了不同沉积电场下FeNi纳米颗粒薄膜的结构、形貌和磁性能....     

Micro-structures of BF2- and As-implanted polycrystalline silicon thin films of various thicknesses and heat treatments

Characterization of annealed BF₂⁺- and As⁺-doped polycrystalline silicon (polysilicon) films is presented. Effects of heat treatment, doping concentration, and thickness of film on the grain size and mobility of polysilicon films are investigated and discussed. By using transmission electron microscopy (TEM), it is found that the grain size, effective carrier concentration, and carrier mobility of a polysilicon thin film increases with increasing film thickness. Our results show that a high concentration of As dopant could enhance the recrystallization of the polysilicon films. Heavily As⁺-doped samples were seen to have a relatively larger grain size compared to the lightly doped film. The maximum grain size of about 278 nm can be realized in a polysilicon film with 150 nm in thickness. In contrast, the B dopant has a negligible effect on the recrystallization of polysilicon films. With increasing film thickness and thermal annealing temperature, a high performance polysilicon film with high mobility and grain size can be obtained.     

Optical characteristics of thin ZnSe films of different thicknesses

Polycrystalline ZnSe films of thicknesses 54–785 nm deposited on glass substrates by thermal evaporation were investigated. X-ray diffraction analysis was carried out on as-deposited and annealed films to determine their structure. The ZnSe films were polycrystalline of cubic structure with preferred [111] orientation. Transmission and reflection at normal incidence were performed on ZnSe films in the wavelength range 350–2500 nm to determine the optical constants and optical energy gap. The optical gaps of ZnSe films show remarkable dependence on the film thickness. Analysis of the absorption data revealed the existence of two transition processes (with energy gaps at 2.7 and 2.22 eV for the bulk ZnSe).