先驱硼薄膜的质量对MgB2超导薄膜的影响

以高纯乙硼烷(B2H6)为B源,采用化学气相沉积(CVD)方法在多晶Al2O3衬底上沉积B薄膜,然后在Mg蒸气中异位退火来制备MgB2超导薄膜.通过X射线衍射和MgB2超导薄膜的电阻-温度曲线,研究了先驱硼薄膜的质量对MgB2超导薄膜的影响.     

MoOx thin films deposited by magnetron sputtering as an anode for aqueous micro-supercapacitors

Abstract

In order to examine the potential application of non-stoichiometric molybdenum oxide as anode materials for aqueous micro-supercapacitors, conductive MoO_x films (2  x  2.3) deposited via RF magnetron sputtering at different temperatures were systematically studied for composition, structure and electrochemical properties in an aqueous solution of Li₂SO₄. The MoO_x (x ≈ 2.3) film deposited at 150 °C exhibited a higher areal capacitance (31 mF cm^?2 measured at 5 mV s^?1), best rate capability and excellent stability at potentials below ?0.1 V versus saturated calomel electrode, compared to the films deposited at room temperature and at higher temperatures. These superior properties were attributed to the multi-valence composition and mixed-phase microstructure, i.e., the coexistence of MoO₂ nanocrystals and amorphous MoO_x (2.3 < x  3). A mechanism combining Mo(IV) oxidation/reduction on the hydrated MoO₂ grain surfaces and cation intercalation/extrusion is proposed to illustrate the pseudo-capacitive process.     

New MOCVD precursor for iridium thin films deposition

Thin films of metallic iridium were grown by metal organic chemical vapor deposition in a vertical hot-wall reactor. The new solid compound Ir(thd)₃ (thd = 2,2,6,6-tetramethyl-3,5-heptadione) was used as the iridium source. The iridium precursor was analyzed by elemental analysis, infrared spectroscopy, ¹H NMR spectroscopy and thermogravimetry (TG). The results of TG showed that the iridium β-diketonate was found to vary with the nature of the β-diketonate group and the use of the thd led to a precursor with higher volatilities than the Ir(acac)₃ (acac = acetylacetonate) source. Deposited iridium films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM) in order to determine crystallinity and surface morphology.     

Solution precursor plasma deposition of nanostructured CdS thin films

Cadmium sulfide (CdS) films are used in solar cells, sensors and microelectronics. A variety of techniques, such as vapor based techniques, wet chemical methods and spray pyrolysis are frequently employed to develop adherent CdS films. In the present study, rapid deposition of CdS thin films via plasma spray route using a solution precursor was investigated, for the first time. Solution precursor comprising cadmium chloride, thiourea and distilled water was fed into a DC plasma jet via an axial atomizer to create ultrafine droplets for instantaneous and accelerated thermal decomposition in the plasma plume. The resulting molten/semi-molten ultrafine/nanoparticles of CdS eventually propel toward the substrate to form continuous CdS films. The chemistry of the solution precursor was found to be critical in plasma pyrolysis to control the stoichiometry and composition of the films. X-ray diffraction studies confirmed hexagonal α-CdS structure. Surface morphology and microstructures were investigated to compare with other synthesis techniques in terms of process mechanism and structural features. Transmission electron microscopy studies revealed nanostructures in the atomized particulates. Optical measurements indicated a decreasing transmittance in the visible light with increasing the film thickness and band gap was calculated to be ～2.5 eV. The electrical resistivity of the films (0.243 ± 0.188 × 10⁵ Ω cm) was comparable with the literature values. These nanostructured polycrystalline CdS films could be useful in sensing and solar applications.     

Substrate considerations for graphene synthesis on thin copper films

Chemical vapor deposition on copper substrates is a primary technique for synthesis of high quality graphene films over large areas. While well-developed processes are in place for catalytic growth of graphene on bulk copper substrates, chemical vapor deposition of graphene on thin films could provide a means for simplified device processing through the elimination of the layer transfer process. Recently, it was demonstrated that transfer-free growth and processing is possible on SiO(2). However, the Cu/SiO(2)/Si material system must be stable at high temperatures for high quality transfer-free graphene. This study identifies the presence of interdiffusion at the Cu/SiO(2) interface and investigates the influence of metal (Ni, Cr, W) and insulating (Si(3)N(4), Al(2)O(3), HfO(2)) diffusion barrier layers on Cu-SiO(2) interdiffusion, as well as graphene structural quality. Regardless of barrier choice, we find the presence of Cu diffusion into the silicon substrate as well as the presence of Cu-Si-O domains on the surface of the copper film. As a result, we investigate the choice of a sapphire substrate and present evidence that it is a robust substrate for synthesis and processing of high quality, transfer-free graphene.     

Conduction mechanism in codeposited AgSe thin films

Thin films of AgSe of varying compositions and thicknesses have been formed on glass substrates employing the three-temperature method.I–V characteristics and thermoelectric power, α, of annealed samples have been measured as functions of composition, thickness and temperature of the films. Films exhibitn-type conductivity. Nonohmic conduction in films of Ag _x Se_1−x (0<x<0·5) and Ag _x Se_1−x (0>x>0·5) have been accounted for on the basis of the theory of Rose of defect insulator containing shallow traps and on Schottky emission respectively.     

Substrate effects on the crystallization kinetics of amorphous selenium thin films

A thermoanalytical technique has been used to study crystallization in thin amorphous selenium (a-Se) films deposited on polyimide and on aluminum-coated polyimide substrates. Through analysis of thermograms obtained by differential scanning calorimetry, the activation enthalpy of crystallization for a-Se on these substrates has been measured. It has been found that the film deposited on Al-coated polyimide crystallizes with an activation enthalpy similar to that obtained for bulk-quenched a-Se, while the film deposited on bare polyimide crystallizes with a lower activation enthalpy than that for the bulk sample. This suggests that the structure of a-Se films can be influenced by the choice of substrate.     

以CuCl纳米棒薄膜为前驱体制备CuS纳米/微米管和CuO纳米/微米晶薄膜

在本文中,以由氯化亚铜纳米棒组成的薄膜为前驱体,分别通过气-固相的硫化和氧化反应获得了由直径150到200纳米,长度达数微米的硫化铜管组成的薄膜和粒径为150到200纳米的氧化铜纳米/微米晶所组成的薄膜.利用XRD,SEM,TEM测试方法对薄膜的晶化度,纯度,形貌及结构特点进行了分析.制备的薄膜具有大尺寸,高比表面积,构筑单元为单晶的特点.研究表明,硫化铜纳米/微米管是通过克肯达尔效应形成的,而氧化铜纳米/微米晶是氯化亚铜与空气反应通过类似于化学气相沉积过程形成的.     

Substrate temperature influence on ZnS thin films prepared by ultrasonic spray

ZnS thin films were deposited by ultrasonic spray technique. The starting solution is a mixture of 0.1 M zinc chloride as source of Zn and 0.05 M thiourea as source of S. The glass substrate temperature was varied in the range of 250 °C-400 °C to investigate the influence of substrate temperature on the structure, chemical composition and optical properties of ZnS films. The DRX analyses indicated that ZnS films have nanocrystalline hexagonal structure with (002) preferential orientation and grain size varied from 20 to 50 nm, increasing with substrate temperature. The optical films characterization was carried out by the UV-visible transmission. The optical gap and films disorder were deduced from the absorption spectra and the refractive indices of the films were determined by ellipsometric measurements. It is shown that the obtained films are generally composed of ZnO and ZnS phases with varied proportion, while at deposition temperature of 400 °C, they are near stoichiometric ZnS.     

锗纳米镶嵌薄膜的电致发光及其机制

采和射频磁控溅射技术,在Ge纳米镍嵌薄膜的基础上制备出电致发光器件。器件的结构为半透明Au膜／Ge纳米镍嵌薄膜／p-Si基片。当正向邻居坟大于6V时,用肉眼可以观察到可见的电致发光,但在反向偏压下探测不到光发射。所测电致发光谱中只有一个发光峰,峰位在510nm（2．4eV,绿光）,并且随着正向偏坟的升高,峰位不发生移动;对于不同温度退火的样品,峰位也保持不变。根据分析结果讨论了可能的电致发光机制。     

Homoepitaxial 6H-SiC thin films by vapor-liquid-solid mechanism

Silicon carbide (SiC) is a IV-IV compound semiconductor with a wide energy band gap. Because of its outstanding properties, SiC can be used in high-power, high-temperature devices with high radiation resistance. In this study, a two-step vapor-liquid-solid (VLS) method was proposed for homoepitaxial growth of high quality 6H-SiC thin films, combining VLS growth and conventional chemical vapor deposition (CVD) processes. VLS growth was used to eliminate the micro-pipes (MPs) in the first step, and the subsequent step based on the CVD process was employed to improve the surface roughness. The morphology and structure of the as-grown thin films were investigated by scanning electron microscopy, X-ray energy dispersive spectroscopy, atomic force microscopy and high-resolution X-ray diffraction, showing that thin films grown by two-step method have good crystalline quality and small surface roughness.     

Characterization of lanthanum-doped bismuth titanate thin films prepared by polymeric precursor method

Lanthanum-modified bismuth titanate, Bi_4−xLa_xTi₃O₁₂ (BLT), with x ranging from 0 to 0.75 was grown on Pt/Ti/SiO₂/Si substrates using a polymeric precursor solution and spin-coating method. The dielectric constant of highly doped bismuth titanate was equal to 148 while dielectric losses remained low (tan δ=0.0018), and the films showed well-saturated polarization-electric field curves (2P_r=40.6 μC/cm² and V_c=0.99 V). The leakage current densities improve for the lanthanum-doped system. For five-layered BLT films with x=0.75, a charge storage density of 35 fC/μm² and a thickness of 320 nm were found.     

氧化钨薄膜电致变色机理的探讨

研究磁控溅射生成的氧化钨薄膜处于电解液系列中的循环伏安特性，充电电流厦光学特性．采用配体场理论来解释氧化钨薄膜在电场作用下，锂离子注入引起薄膜变色的现象，认为注入的锂离子破坏了薄膜界面层内氧化钨分子的八面体结构的对称性，在内部静电场和外部电场的共同作用下，鸽离子d轨道的五重简并能级分裂。从而使得薄膜对可见光产生d-d吸收，导致氧化钨薄膜变色．     

Alloying reaction in thin nickel films deposited on GaAs

The alloying reaction in a thin nickel film deposited on a GaAs substrate was investigated using microprobe Auger spectroscopy, reflection high energy electron diffraction and transmission electron diffraction. A nickel film reacts with the substrate above 200°C to form a metastable hexagonal reaction product with the composition Ni:Ga:As = 2:1:1, which is monocrystalline with the orientation relation 〈0001〉 hexagonal // 〈111〉 GaAs and 〈11$\text{2}$0〉 hexagonal // 〈110〉 GaAs. Above 400°C the metastable reaction product decomposes into NiAs and β-NiGa, both of which are also monocrystalline with the same orientation relation as the metastable reaction product. The role of nickel in GaAs contact systems is explained by the high reactivity of nickel with GaAs in the solid-solid phase.     

Interfacial reaction in bimetallic Sn/Cu thin films

Interfacial reaction in electroplated bimetallic Sn/Cu (the layer grown last is given first) thin films was studied by Auger depth profiling and X-ray diffraction measurements. Direct experimental evidence was found for the formation of intermetallic compounds in the SnCu interface, i.e. η'-Cu₆Sn₅ at room temperature and both η'-Cu₆Sn₅ and ε-Cu₃Sn at 150°C. The results of a quantitative analysis of the film composition and sputtering-induced effects are also discussed.     

Fabricating two-dimensional nanostructured tellurium thin films via pyrolyzing a single-source molecular precursor

A simple route to fabricate tellurium (Te) thin film with a well-defined two-dimensional nanostructure is presented in this study. The method involves dip-coating and subsequently pyrolyzing a single-source molecular precursor diethyldithiocarbamato tellurium (TDEC) onto a glass substrate. The pyrolysis temperature and the initial thickness (?) of TDEC film exhibited strong influence on the morphology of Te film, where films composed of uniform Te nanoflakes have been obtained at 440 °C and ? ≈ 490 nm. Investigations on the thermodynamic properties of TDEC through thermogravimetry, differential thermogravimetry, and differential scanning calorimetry techniques suggest that the production of Te from TDEC features random and continuous nucleation, shedding light on the possible growth mechanism of the two-dimensional Te film.     

Substrate effects on surface morphologies and magnetic properties of nanostructured FePt thin films

The substrate effects on surface morphologies, crystal structures, and magnetic properties of the sputter-deposited FePt thin films on Corning 1737, normal glass, and Si wafer substrates, respectively, were investigated. High in-plane coercivities of 10 kOe were obtained for the air-annealed films on Corning 1737 and Si wafer, where both films similarly have granular-like morphologies. Besides, increasing grain size and surface roughness of all the FePt films with the post-anneal temperature were observed. Moreover, partially separated grains were seen in the film on Si wafer, where the formation of Fe silicides during post-anneal is suspected, in which has enhanced the magnetic ordering.