Microstructure and electrical properties of ultrathin gold films prepared by DC sputtering

Ultrathin gold films with different thicknesses were prepared by direct current magnetron sputtering technique and analyzed by X-ray diffraction, atomic force microscopy, transmission electron microscopy and temperature-varying four-wire technique. For thicknesses d < 24.1 nm, both D_{avg {111}} and D_{avg {220}} increase rapidly with the thickness. For 24.1 ≤ d ≤ 97.8 nm, D_{avg {220}} increases at a slower rate than before but D_{avg {111}} remains the same. Surface morphology analysis shows that, as the thickness increases, the average particle size changes from 22.1 to 54.3 nm; at the same time, rms roughness decreases to a minimum and then increases. The electrical properties of the thin films from 80 to 300 K were measured. The results show that the temperature coefficient of resistance of the thin films is positive, and increases from 2.2 × 10⁻⁴ to 8.5 × 10⁻⁴ K⁻¹ with increasing film thickness.     

等离子熔覆Ni—Cr合金涂层的组织与性能研究

采用等离子熔覆技术在40Cr钢基材表面熔覆Ni-Cr合金涂层,研究了熔覆层的组织特征、成分和显微硬度分布特点.结果表明:等离子熔覆层与基体的结合面是由等轴晶构成的,熔覆层与基体呈现良好的冶金结合状态;熔覆层中部分布着沿逆热流方向生长的排列较规则的枝晶组织;熔覆层表层是细小的枝晶组织.能谱分析表明在结合面处Ni,Cr含量发生显著变化,等离子熔覆可以实现低稀释率.熔覆层的显微硬度呈梯度过渡到基体,熔覆层外层硬度值最高,在结合面附近硬度出现显著的变化.     

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.     

The electrical and compositional structure of thin Ni-Cr films

Owing to its technological importance for thin film resistor elements, vacuum-deposited NiCr has been the subject of much investigation. Unfortunately most measurements of the resistivity and the temperature coefficient of resistivity have been made on films whose composition and structure were largely unknown.We describe work in which both pure and oxygen-contaminated films were deposited, electrically characterized and chemically analysed by Auger depth profiling, all in the same vacuum environment. The in situ Auger measurements were quantified both by the use of bulk alloy standards and by Rutherford backscattering analysis of the evaporated films.     

Ce掺杂ZnO压敏薄膜的微观结构与电学性能研究

通过溶胶-凝胶法制备了一种稀土Ce掺杂的ZnO-Bi2O3压敏薄膜,对薄膜进行了XRD、AFM、介电与压敏性能的表征。结果表明,Ce掺杂不会影响ZnO-Bi2O3压敏薄膜的晶体结构,但是会减小ZnO-Bi2O3压敏薄膜的晶粒尺寸。Ce掺杂会降低ZnO-Bi2O3压敏薄膜的漏电流,减小材料的介电损耗,提升ZnO-Bi2O3压敏薄膜的非线性性能。当Ce掺杂量达到0.3%(摩尔分数)时,ZnO-Bi2O3压敏薄膜的压敏电压达到了175V/mm,漏电流降低至502μA。     

Q235钢表面Ni-Cr电镀层的组织及性能

为提高Q235钢的表面防护性能,对其进行表面电镀Ni-Cr处理,并采用正交试验对电镀Ni-Cr工艺进行优化。采用X射线衍射仪(XRD)、扫描电镜(SEM)和激光共聚焦显微镜(OM)分别对镀层进行物相表征和形貌观察,利用显微硬度计、磨粒磨损机和电化学工作站对镀层硬度和耐蚀性进行研究。结果表明:以镀层沉积速率为指标,正交试验所得电镀Ni-Cr优化工艺为柠檬酸钠含量30 g/L,镀液pH值3.0,电流密度20 A/dm~2,电镀温度35℃,镀层沉积速率可达40.17μm/h;Ni-Cr镀层相结构由γ-Ni和Cr_(1.22)Ni_(2.88)组成;镀层表面平整,表面形貌为密集球形颗粒;与基体相比,正交试验所得Ni-Cr镀层硬度提高了81.62~649.08 HV_(2N),磨损率减少了9.14~29.99mg/cm~2,自腐蚀电位提高了2.05~121.28 mV。     

电火花沉积Ni-Cr合金涂层的组织及性能

利用电火花沉积技术,采用自制电极在P20钢基材表面沉积Ni-Cr合金涂层,研究了沉积层的组织特征、显微硬度分布及耐磨、耐蚀性能.结果表明:通过优化沉积工艺参数可以获得厚度高达430μm的沉积层.电火花沉积层与基体的结合界面属于非均匀混合互熔结晶型界面,沉积层与基体呈现良好的冶金结合;涂层中下部组织为细小的枝晶组织,而上部组织为纳米晶结构.沉积层的硬度呈梯度分布,涂层外层硬度值最高.涂层的耐磨、耐蚀性能比基体有较大提高,涂层上部超细的纳米晶结构是其耐磨性能及耐蚀性能提高的主要因素.     

Microstructure and electrical properties of YBCO thin films

Microstructures of c-axis oriented YBCO thin films made by high-pressure d.c. sputtering on LaAlO₃ and MgO substrates were examined by TEM. The a-axis oriented grains, second phases and micro-twins were frequently observed in the film. The a-axis oriented grains expanded along their c-axis directions during film growth. The a- and b-axis misorientations were observed in the film on MgO due to serious lattice mis-match between YBCO and MgO. The second phases were often accompanied with a-axis oriented grains suggesting they act as nuclei. These observed results were correlated with the measured T _c and J _c of the films.     

Carbon incorporation process in GaAsN films grown by chemical beam epitaxy using MMHy or DMHy as the N source

Crystal quality of GaAsN films can be improved by using CBE for low-temperature growth. However, low-temperature growth increases C incorporation in the films, which degrades their electrical properties. Consequently, C incorporation was investigated in view of the surface reaction of N sources on a substrate surface, and MMHy and DMHy were compared. When MMHy was used as an N source, C concentration in GaAsN drastically increases below 380 °C than that in GaAs due to insufficient CH_x desorption. In the case of DMHy, N(CH₃)₂ is desorbed more readily than CH_x, therefore, the C concentration can then be reduced using DMHy.     

Reactively sputtered GaAsxN1−x thin films

Thin films of GaAs_xN_1−x alloys were deposited by reactive rf magnetron sputtering of GaAs target with a mixture of argon and nitrogen as the sputtering gas. Growth rate was found to decrease from ∼ 7 μm/h to ∼ 2 μm/h as the nitrogen content increased from 0% to 40%. XRD and TEM studies of the films reveal the presence of hexagonal GaN with a significant increase of the lattice parameters in a narrow range of composition of the sputtering gas (5-10% nitrogen), which is attributed to the incorporation of arsenic. The limited availability of nitrogen in the sputtering atmosphere is found to encourage the incorporation of arsenic in the alloy films. Optical absorption coefficient spectra of the films were obtained from reflection and transmission data. The effect of arsenic incorporation is seen in the optical absorption spectra of the films, which show a continuous shift of the absorption edge to lower energies with respect to that of gallium nitride.     

Hydrogen reduction in GaAsN thin films by flow rate modulated chemical beam epitaxy

The amount of residual H in the GaAsN film grown by chemical beam epitaxy (CBE) can be decreased by flow rate modulation growth. Many H atoms in the films grown by CBE exist as N-H or N-H₂ structures. Although a higher growth temperature was required for decreasing the H concentration ([H]), it caused a decrease in the N concentration ([N]). A reduction in [H] while keeping [N] constant was necessary. By providing an intermittent supply of Ga source while continuously supplying As and N sources, [H] effectively decreased in comparison with the [H] value in the film grown at the same temperature by conventional CBE without reducing [N].     

C-Ti nanocomposite thin films: Structure, mechanical and electrical properties

Carbon-titanium nanocomposite thin films were deposited by DC magnetron sputtering on oxidized silicon substrates in argon. The films were prepared at different deposition temperatures between 25 and 800 °C. Transmission electron microscopy was used to determine the structure of the films. All the C-Ti nanocomposites consisted of columnar TiC structure with average column width ∼10 and 20 nm and a thin carbon matrix. The thickness of the carbon matrix between adjacent TiC columns was ∼2-5 nm.Mechanical properties (hardness, reduced modulus) of C-Ti films showed a distinct variation depending on the deposition temperature. Films deposited at 200 °C had the highest hardness ∼18 GPa and the highest reduced modulus ∼205 GPa.Temperature dependence of the film resistance was measured between 80 and 330 K. C-Ti nanocomposites have a non-metallic conduction mechanism characterized by a negative temperature coefficient of resistivity (TCR). The most negative TCR was observed for films showing high hardness and reduced modulus of elasticity.     

Growth and defects of GaAs and InGaAs films on porous GaAs substrates

We investigated the opportunities to increase the electric uniformity of GaAs and InGaAs films grown by molecular-beam epitaxy (MBE) technique on monocrystalline (single crystal) GaAs: both on porous and conventional so-called “monolithic” (without pores) GaAs (100) substrates. The basic attention was given to study the electrically active defects in films by using scanning electron microscope (SEM) with new technique which is called “Rau-detector” [E.I. Rau, A.N. Zhukov and E.B. Yakimov, Solid-State Phenomena, 1998, v. 53-54, 327.]. We compared the main properties of epitaxial GaAs and InGaAs films grown on above mentioned substrates. The films grown on porous substrates had higher structural perfection including the following advantages: (a) smoother surface due to lateral growth mechanism; (b) less density of structural defects (without dislocation walls), the density of pyramidal defects was ∼ 2 × 10⁵ cm^− 2 as compared with the density 2 × 10⁷ cm^− 2 in the films grown on monolithic substrates; (c) less electrical activity of various structural defects and increased electric uniformity of grown films. The electrical activity of defects in films grown on porous substrates was essentially lowered due to gettering properties of porous substrate.     

沉积速率对EB-PVD Ni-Cr薄膜表面形貌的影响

采用动态蒙特卡罗(KMC)方法模拟电子束物理气相沉积(EB-PVD)制备Ni-Cr合金薄膜过程中沉积速率与薄膜微观结构之间的关系,并用分维理论研究薄膜表面形貌.研究结果表明:对于基板温度为500K,入射角度为35°的情况,沉积速率＜5μm/min时,薄膜表面分维均＜2.04,表面光滑,而当沉积速率＞5μm/min时薄膜分维随沉积速率增大而增大,表面变得越来越粗糙,直到沉积速率升高到1000μm/min时,分维达到最大值2.31,表面非常粗糙,具有细致的皱褶和缺陷.分维与沉积速率间的关系说明低沉积速率有利于分维小、表面光滑薄膜的制备,而高沉积速率使薄膜分维增大、表面结构更加复杂.该研究结果与沉积速率对EB-PVD薄膜表面粗糙度影响的研究结果一致,表明分维也是评价薄膜表面形貌的途径.     

Deposition and electrical characteristics of S-doped boron nitride thin films

cBN/Si n-p heterojunctions have been fabricated and characterized. n-type cBN films were grown on p-type Si wafers using RF reactive sputter, and the n-type cBN films were obtained by adding S (sulfur) into working gas. The I-V (current-voltage) characteristics have obvious rectification. The fitting results show that the current transporting model for the cBN/Si n-p heterojunctions is the same as Anderson’s transporting model. The C-V (capacitance-voltage) characteristics are close to that of ideal heterojunctions. The built-in potential in the cBN/Si n-p heterojunctions was determined from C-V measurements at 4.71 V. The dopant concentration in the n-type cBN films was also determined from the C-V measurements at 6.50 × 10¹⁴/cm³.     

Determination of optical and electrical properties of ZnSe thin films

A thin film of zinc selenide (ZnSe) was deposited onto a clean glass substrate using a vacuum evaporation technique. This thin film was characterized through X-ray diffraction, which indicated that the film was polycrystalline in nature. Absorption and transmission spectra of this thin film were recorded using a spectrophotometer. The energy band gap, refractive index and extinction coefficient were determined using these spectra. It was found that the energy band gap of ZnSe film was 2.55 eV. It was also observed that the refractive index and extinction coefficient of the film decreased with the increase of wavelength. The conductivity of this thin film was determined by current–voltage measurement using an electrometer over the temperature range from room temperature to 413 K. It was observed that conductivity increased with increase in temperature. This is explained on the basis of structural changes occurring due to the change in grain size and the increase in carrier density.     

The electrical resistivity and resistance-temperature characteristics of thin titanium films

In this communication are described the results on the electrical resistivity and resistance-temperature characteristics of titanium films, measured in vacuum. They were evaporated onto soda glass microscope slides at room temperature in a sputter-ion pumped glass belljar vacuum system at about 5×10^-8 torr. The films varied in their thickness from 50 to 1100 Å, and the resistivity was very high for the thinnest films but for the thickest ones it approached approximately double the bulk value. The measured resistivities for the continuous freshly prepared films are too high to be explained on the basis of the Fuchs-Sondheimer theory^{1, 2} for diffuse scattering, and are attributed to porosity and the gaseous impurities taken down during and after their formation. The temperature coefficient of resistance (TCR) was negative for films less than 50–60 Å thick but positive for thicker ones. A bulk mean free path of 285 Å in titanium was calculated at room temperature.     

Deposition and electrical characteristics of S-doped boron nitride thin films

cBN/Si n–p heterojunctions have been fabricated and characterized. n-type cBN films were grown on p-type Si wafers using RF reactive sputter, and the n-type cBN films were obtained by adding S (sulfur) into working gas. The I–V (current–voltage) characteristics have obvious rectification. The fitting results show that the current transporting model for the cBN/Si n–p heterojunctions is the same as Anderson’s transporting model. The C–V (capacitance–voltage) characteristics are close to that of ideal heterojunctions. The built-in potential in the cBN/Si n–p heterojunctions was determined from C–V measurements at 4.71 V. The dopant concentration in the n-type cBN films was also determined from the C–V measurements at 6.50 × 10¹⁴/cm³.     

氧化钒薄膜的结构、性能及制备技术的相关性

氧化钒薄膜及其在微电子和光电子领域中的已成为国际上新颖的功能材料研究的热点之一。本文综述了V2O5和VO2薄膜电学性能与薄膜组分的结构的相关性,比较了不同工艺制备的氧化钒薄膜的电学性能差异。     

Microstructure and corrosion characteristics of CrN/NiP sputtering thin films

The CrN top layer and NiP interlayer were sequentially deposited to form a CrN/NiP composite coating through sputtering technique. The CrN/NiP coating systems deposited at 350 °C, 450 °C, and 550 °C, showed amorphous/nanocrystalline, nanocrystallize with precipitations, and fully crystallized microstructure respectively for the NiP interlayers. With the introduction of NiP interlayer, the coating assemblies exhibited superior corrosion characteristics than single CrN coatings. The amorphous NiP interlayer deposited at 350 °C revealed a lower corrosion current as compared to those with crystallized NiP layers owing to their structural defects in the alloy layer. With the combination of CrN and NiP layers the corrosion attach was retarded and a better corrosion resistance was found for the CrN/NiP composite coating.