The photoconductive effect in Pb2CrO5 thin films prepared by an electron-beam evaporation technique

Photoconductivity in Pb₂CrO₅ thin film prepared by an electron-beam evaporation technique is described. Crystallographically, three kinds of thin films are fabricated which depend on substrate temperature. A sample showing a similar x-ray diffraction profile to the evaporation source material gives the highest photoconductive response. Light illumination from the glass substrate onto the sample improves photoconductivity. A pair of interdigital electrodes is more effective than a pair of planar electrodes on the photoconductive measurement. A band gap energy level of Pb₂CrO₅ thin film is around 2.2–2.4 eV as a result of the spectral photoconductive response.     

Electrochemical and structural properties of MoO3–V2O5 nanocomposite thin film electrodes for lithium rechargeable batteries

We have investigated the electrochemical properties of V₂O₅-based thin film electrodes as a function of the amount of MoO₃ by means of X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), and transmission electron microscopy (TEM). XRD results show that the V₂O₅-based thin film electrodes give an amorphous characteristic. XPS results reveal the formation of V₂O₅ and MoO₃ phases. TEM results show that MoO₃ dots (5–30 nm in size) are embedded in the amorphous V₂O₅ matrix. It is further shown that cells fabricated with the MoO₃–V₂O₅ nanocomposite thin film electrodes give better cycling performance than those made with the single V₂O₅ thin film electrodes. A possible explanation for the MoO₃ nano-dot dependence on the cycling performance of the V₂O₅-based thin film electrodes is described.     

Ultrasonic attenuation of surface acoustic waves in a thin film of superconducting Nb3Sn

The attenuation of 660 MHz surface acoustic waves propagating in a thin film of Nb₃Sn 5000 Å thick has been measured as a function of temperature from 4.2 K to 16 K. The A 15 Nb₃Sn, electron-beam codeposited on YZ lithium niobate and annealed at 700°C, was studied using 5.1 μm wavelength interdigital electrodes. The film revealed a transition temperature of 14.2 ± 0.1 K and using the BCS theory, an energy gap 2Δ(0) = 3.5 k_BT_c.     

Preparation of Pb2CrO5 thin films by an electron-beam evaporation technique

Pb₂CrO₅ thin films have been prepared by an electron-beam evaporation deposition technique on glass substrates using ceramic disks. The thin film fabrication conditions are studied by x-ray diffraction, replica electron micrography and scanning electron microscopy as parameters of substrate temperature, annealing temperature and annealing time. As-deposited Pb₂CrO₅ thin films in the amorphous state are crystallized by heat treatment. Annealed thin films are structurally classified into three types according to the preferred orientations which depend on substrate temperatures (T _s:

1. (i)

   (020) atT _s=room temperature

2. (ii)

   mainly (310) atT _s=100 ‡C, and

3. (iii)

   (200) atT _s=350 ‡C.

The substrate temperature contributes to film orientations; annealing temperature and time-enhance film crystallinity. The annealing temperature is fixed between 400 and 500 ‡C in making appropriate Pb₂CrO₅ thin films. These thin films, ranging between 0.3 and 2.0 Μm in thickness, are prepared at a deposition rate of 1500 å/m.

     

Effect of process parameters on surface morphology and characterization of PE-ALD SnO2 thin films for gas sensing

Tin dioxide (SnO₂) thin films were deposited by plasma enhanced-atomic layer deposition (PE-ALD) on Si(1 0 0) substrate using dibutyl tin diacetate (DBTA) ((CH₃CO₂)₂Sn[(CH₂)₃-CH₃]₂) as precursor. The process parameters were optimized as a function of substrate temperature, source temperature and purging time. It is observed that the surface phenomenon of the thin films was changed with film thickness. Atomic force microscopy (AFM) images and X-ray diffraction (XRD) pattern were used to observe the texture and crystallanity of the films. The films deposited for 100, 200 and 400 cycles were characterized by XPS to determine the chemical bonding properties. XPS results reveal that the surface dominant oxygen species for 100, 200 and 400 cycles deposited films are O₂⁻, O⁻ and O²⁻, respectively. The 200 cycles film has exhibited highest concentration of oxygen (O⁻) species before and after annealing. Conductivity studies revel that this film has best adsorption strength to the oxygen ions forming on the surface. The sensor with 200 cycles SnO₂ thin film has shown highest sensitivity to CO gas than other films. A correlation between the characteristics of Sn3d_5/2 and O1s XPS spectra before and after annealing and the electrical behavior of the SnO₂ thin films is established.     

Growth of orientation-controlled Pb(Mg,Nb)O3-PbTiO3 thin films on Si(100) by using oriented MgO films as buffers

Thin films of relaxor ferroelectric Pb(Mg,Nb)O₃-PbTiO₃ with different orientations were grown by pulsed-laser deposition on Si(100). By using (111)-, (110)- and (100)-oriented MgO thin film as buffer and the LaNiO₃ thin film as a bottom electrode, (110)- and (100)- oriented or preferred and polycrystalline PMN-PT thin films were obtained. The (110)-oriented PMN-PT thin film showed dielectric permittivity of about 1350 and loss factor cosδ of <0.07. PACS 68.55.Jk; 81.15.Fg; 77.84.Dy     

X-ray pole-figure study of the epitaxial growth of C60 thin films on mica (001)

The growth of epitaxial C₆₀ thin films on mica(001) by thermal evaporation has been studied in detail by X-ray pole-figure measurements. The influence of the deposition rate, the substrate temperature and the film thickness on the in-plane epitaxial arrangements and the formation of twins has been investigated. It has been demonstrated that the C₆₀ growth is determined by two independent and equivalent C₆₀-crystal grain alignments (type-A and type-B). The nearly six-fold symmetry of the mica(001)-substrate surface offers the three-fold fcc-(111)-oriented C₆₀-crystal grains two equivalent crystal alignments. A high deposition rate of 0.5 Å/s is responsible for the formation of twins at a substrate temperature of 150°C, which diminishes by a higher substrate temperature of 200°C. By a decrease of the deposition rate down to 0.08 Å/s the twins vanish at a film thickness of 200 nm and at the substrate temperature of 150°C. Under the same sublimation conditions, in addition to the type-A and type-B crystal orientations, the growth of the thin C₆₀ films starts with a slight fibre texture which does not appear at a larger film thickness.     

Fabrication of piezoelectric AlN thin film for FBARs

This paper focuses on the fabrication of film bulk acoustic-wave resonator (FBAR) comprising an aluminum nitride (AlN) piezoelectric thin film sandwiched between two metal electrodes and located on a silicon substrate with a low-stress silicon nitride (Si₃N₄) support membrane for high frequency wireless applications, and analyzes the optimization of the thin AlN film deposition parameters on Mo electrodes using the reactive RF magnetron sputter system. Several critical parameters of the sputtering process such as RF power and Ar/N₂ flow rate ratio were studied to clarify their effects on different electrodes characteristics of the AlN films. The experiment indicated that the process for Mo electrode was easier compared with that of the Pt/Ti or Au/Cr bi-layer electrode as it entailed only one photo resist and metal deposition step. Besides, Pt/Ti or Au/Cr electrodes reduced the resonance frequency due to their high mass density and low bulk acoustic velocity. Compared with the case of the Al bottom electrode, there is no evident amorphous layer between the Mo bottom electrode and the deposited AlN film. The characteristics of the FBAR devices depend not only upon the thickness and quality of the AlN film, but also upon the thickness of the top electrode and the materials used. The results indicate that decreasing the thickness of either the AlN film or the top electrode increases the resonance frequency. This suggests the potential of tuning the performance of the FBAR device by carefully controlling AlN film thickness. Besides, increasing either the thickness of the AlN film or higher RF power has improved a stronger c-axis orientation and tended to promote a narrower rocking curve full-width at half-maximum (FWHM), but increased both the grain size and the surface roughness. An FBAR device fabricated under optimal AlN deposition parameters has demonstrated the effective electromechanical coupling coefficient (k _eff²) and the quality factor (Q _{f x} ) are about 1.5% and 332, respectively.     

Effects of photocrosslinking on photorefractive properties in polymer-liquid crystal composites

This article presents effects of photocrosslinking on photorefractive properties in polymer-liquid crystal composites doped with fullerene (C₆₀) as a photoconductive agent. The efficiency of the photorefraction was improved by crosslinking the polymer network and reached near to the theoretical limit for the thin phase grating. The carrier conduction in the composite films was investigated and the high-performance photorefractivity of the photocrosslinked mesogenic composite was explained by low dark current and high photocurrent. The firm crosslinked polymer network in the polymer-liquid crystal composite has also employed for the stable photorefractive diffraction at elevated temperature and under a static dc field applied the mesogenic composite film.     

Epitaxial growth of PbTiO3 thin film on (110) NdGaO3 substrate by metalorganic chemical vapor deposition

(001) preferentially oriented PbTiO₃ thin films have been grown on (110) NdGaO₃ substrates by metalorganic chemical vapor deposition (MOCVD) under reduced pressure at 650°C. Atomic force microscopy (AFM) surface morphology of the as-deposited film showed the evidence of layer-by-layer growth in the MOCVD process. By using a grazing-angle scattering technique, a highly resolved Raman spectrum of the epitaxial PbTiO₃thin film on perovskite substrate was first time recorded. Other microstructure of the film, such as the element composition, the c-domain percentage and the epitaxial nature, were investigated by Rutherford backscattering spectrometry (RBS), x-ray θ ? 2θ diffraction patterns and x-ray φ scans, respectively. All measurements indicate that NdGaO₃single crystal, which used to be a substrate for the growth of high-T_c superconducting thin films, is also suitable for the growth of high quality PbTiO₃ thin film. This indicates the promising use of the NdGaO₃ for the integration of ferroelectric thin films and superconducting electrodes.     

Non-polarized memory effect in amorphous point-contact diodes driven by currents smaller than 0.5 mA

A reliable memory effect in point-contact diodes, which is independent of the polarity of driving voltage and strongly dependent on the material of the electrodes, has been observed. Antimony and As₂S₃ were the most appropriate for the point-contact electrode and the amorphous thin film respectively. The diodes could be driven by current smaller than 0.5 mA.     

Effects of texture on the dielectric properties of Ba(Zr0.2Ti0.8)O3 thin films prepared by pulsed laser deposition

Ba(Zr_0.2Ti_0.8)O₃ (BZT) thin films were deposited on Pt(111)/Ti/SiO₂/Si(100) substrates by a pulsed laser deposition process. The BZT thin films directly grown on annealed and un-annealed Pt/Ti/SiO₂/Si substrates exhibited random and high (100) orientations, respectively. The dielectric constant of a 400-nm-thick BZT film with (100) orientation was 331, which was higher than that of a BZT film with random orientation (∼236). This result is attributed to the fact that the polar axis of the (100)-oriented films was more tilted away from the normal to the film surface than that of the randomly oriented films. Also, the tunabilities of BZT thin films with random and (100) orientations were ∼50% and ∼59% at an applied field of 400 kV/cm, respectively. Improved tunability has been attributed to the (100) texture of the film leading to an enhancement of the in-plane-oriented polar axis. PACS 77.22.-d; 77.55.+f; 77.80.-e; 77.84.-s     

Single-electron tunneling in granular Ag–SiO2films

Current transport properties of thin Ag–SiO₂granular films were studied. In spite of very simple device structures (i.e., just sandwiching the granular film with Al electrodes), clear Coulomb blockade and Coulomb staircase structures were observed in the current–voltage (I–V) characteristics. The observedI–Vcharacteristics were qualitatively explained by a double-barrier and a triple-barrier tunnel-junction model.     

择优取向MgO缓冲层上制备的硅基Ba0.7Sr0.3TiO3薄膜的结构和性能研究

分别采用sol-gel法和磁控溅射法在Si（001）单晶衬底上制备出（111）和（001）取向的MgO缓冲层薄膜,随后在其上生长Ba_0.7Sr_0.3TiO₃（BST30）铁电薄膜.通过X射线衍射,扫描电子显微镜,原子力显微镜等方法研究了薄膜的微结构.实验结果发现,在较厚的MgO（001）缓冲层上可长出（101）取向的BST30薄膜,而在较薄的MgO（111） 缓冲层上则表现出（101）和（111）取向相互竞争的现象,随着MgO（111）缓冲 关键词： 0.7Sr_0.3TiO₃')" href="#">Ba_0.7Sr_0.3TiO₃ 铁电薄膜 择优取向 sol-gel     

Photoconductivity in a Pb2CrO5 ceramic disk with surface electrodes

The photoconductive behavior of a Pb₂CrO₅ ceramic disk with one pair of electrodes on one surface has been studied at room temperature. When illuminated with light in the visible region, the device exhibits photocurrent which is much larger than the dark current. The current-voltage characteristics and the variation of photocurrent with (i) applied field, (ii) light intensity, and (iii) wavelength are presented with transient behavior.     

Pseudo-epitaxial C60 films prepared by a hot-wall method

We have used both reflection-geometry and grazing-incidence-geometry X-ray scattering to study thin films of C₆₀ evaporated onto mica substrates via a hot-wall technique. The growth mode yields close-packed C₆₀ planes, which are parallel to the substrate surface and which exhibit out-of-plane correlation lengths of 850 Å. In the film plane the C₆₀ is at best pseudo-epitaxial, with a 0.9° distribution of crystallite orientations, a 450 Å in-plane correlation length, and a 3.7% lattice mismatch, better than obtained by other thin film techniques but far from the accepted definition of single crystal thin film epitaxy.     

Effect of deposition temperature on orientation and electrical properties of (K0.5Na0.5)NbO3 thin films by pulsed laser deposition

Lead-free ferroelectric K_0.5Na_0.5NbO₃ (KNN) thin films have been prepared on Pt/TiO₂/SiO₂/Si substrates by pulsed laser deposition process. The structures, crystal orientations and electrical properties of thin films have been investigated as a function of deposition temperature from 680 °C to 760 °C. It is found that the deposition temperature plays an important role in the structures, crystal orientations and electrical properties of thin films. The crystallization of thin films improves with increasing deposition temperature. The thin film deposited at 760 °C exhibits strong (0 0 1) preferential orientation, large dielectric constant of 930 and the remnant polarization of 8.54 μC/cm².     

Structure and catalytic properties of MoSe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> thin films containing Mo nanoparticles in electrochemical production of hydrogen in solution

The introduction of molybdenum nanoparticles in MoSe _x thin films formed by pulsed laser deposition led to changes in the film structure. The base planes of the layered atomic packing of the MoSe _х matrix around Mo nanoparticles rotated; as a consequence, the edge sites that formed during the “breaking” of the Se–Mo–Se layered atomic packing came out to the film surface. At high nanoparticle concentrations, this effect led to high density of edge sites possessing increased catalytic activity (compared with that of the base planes) for initiating the electrochemical evolution of hydrogen in a 0.5 M H₂SO₄ solution. Voltammetric measurements at room temperature showed that when the carbon cathode was coated with MoSe _x thin films under optimum conditions, the hydrogen overvoltage considerably decreased, and the cathodic current increased. The results indicate that developments in the field of preparation of nanostructured electrodes based on layered transition metal dichalcogenides show promise as an alternative to expensive electrodes based on platinum group metals for electrocatalysts of hydrogen evolution.     

金属有机化学气相沉积法制备钛酸铅铁电薄膜

利用低压ＭＯＣＶＤ工艺分别在（００１）取向的ＬａＡｌＯ_３，ＳｒＴｉＯ_３和重掺杂硅单晶衬底上制备ＰｂＴｉＯ_３铁电薄膜，并通过Ｘ射线衍射谱对薄膜的微结构进行分析．Ｘ射线θ－２θ扫描显示硅衬底上得到了ＰｂＴｉＯ_３多晶薄膜，另两种衬底上得到了择优取向的ＰｂＴｉＯ_３薄膜．ＬａＡｌＯ_３衬底上的ＰｂＴｉＯ_３薄膜有ａ和ｃ两个取向，也就是薄膜中存在着９０°畴结构，而生长在ＳｒＴｉＯ_３衬底上的ＰｂＴｉＯ_３薄膜中只存在ｃ方向的择优取向．由于薄膜的尺度效应，发现ｃ轴晶格常数与块材相比均缩短．Ｘ射线的φ扫描验证了后两类薄膜的外延特性，利用同步辐射的高强度和高能量分辨率用摇摆曲线方法研究了这两种外延薄膜的品质，进一步证明了ＳｒＴｉＯ_３衬底上的ＰｂＴｉＯ_３薄膜的单畴特性．利用重掺杂的硅衬底作底电极，测量显示直接生长于硅衬底上的ＰｂＴｉＯ_３多晶薄膜具有良好的铁电性能 关键词：     

Roles of Al-doped ZnO (AZO) modification layer on improving electrochemical performance of LiNi<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript> thin film cathode

Al-doped ZnO (AZO) was sputtered on the surface of LiNi_1/3Co_1/3Mn_1/3O₂ (NCM) thin film electrode via radio frequency magnetron sputtering, which was demonstrated to be a useful approach to enhance electrochemical performance of thin film electrode. The structure and morphology of the prepared electrodes were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectrometer, and transmission electron microscopy techniques. The results clearly demonstrated that NCM thin film showed a strong (104) preferred orientation and AZO was uniformly covered on the surface of NCM electrode. After 200 cycles at 50 μA μm^?1 cm^?2, the NCM/AZO-60s electrode delivered highest discharge capacity (78.1 μAh μm^?1 cm^?2) compared with that of the NCM/AZO-120s electrode (62.4 μAh μm^?1 cm^?2) and the bare NCM electrode (22.3 μAh μm^?1 cm^?2). In addition, the rate capability of the NCM/AZO-60s electrode was superior to the NCM/AZO-120s and bare NCM electrodes. The improved electrochemical performance can be ascribed to the appropriate thickness of the AZO coating layer, which not only acted as HF scavenger to keep a stable electrode/electrolyte interface but also reduced the charge transfer resistance during cycling.