Polarized memory switching effects in Ag2Se/Se/M thin film sandwiches

The current-voltage characteristics of Ag₂Se/Se/M thin film sandwiches were studied as functions of the shapes of the electrodes, which were either symmetrical or asymmetrical, as well as their composition (M is a metal (gold, chromium or silver) or Ag₂Se). A polarized memory switching effect independent of air exposure was observed.The first commutation occurs at a formation voltage V_F which is dependent on the selenium thickness. After some cycles this voltage stabilizes to a value V_S (where V_S<V_F). V_S is a function of temperature, frequency and the maximum reverse voltage but is independent of the selenium thickness.All these results are explained in terms of Ag⁺ ionic diffusion: the formation is related to the growth of Ag₂Se dendrites through selenium as shown by temperature-dependent experiments. Furthermore the variations in V_S are accounted for by ionic motion localized at the M-Se interface.     

Effect of Ag addition on crystallization in As2Se3 glasses

Differential scanning calorimetry (DSC) behaviours of glassy As₂Se₃ containing Ag up to 5 at % were measured at various heating rates. The effect of addition of Ag on crystallization of glassy As₂Se₃ was investigated. The glass transition temperature decreased with increasing Ag content. Crystallization kinetics were analysed on the basis of the two-step process model, where crystal growth takes place after nucleation. For non-doped As₂Se₃ two-dimensional growth of crystal was predominant, while for Ag-doped ones three-dimensional growth was very likely. It was supposed for all glassy Ag-doped samples that crystal nuclei exist, though micro-crystallites were not observed on X-ray diffraction traces. The activation energy for crystallization and the glass-forming tendency decreased by the addition of Ag.     

Phase formation in a nanosize silicon oxide film on the surface of aluminum oxide

Phase formation has been studied in a nanosize composition of aluminum oxide and silicon dioxide. The temperature ranges for an intensive solid-phase reaction have been determined. A mechanism is proposed for phase formation in nanosize film compositions. Pis’ma Zh. Tekh. Fiz. 24, 3–8 (January 12, 1998)     

Solid-phase crystallization of β-FeSi2 thin film in Fe/Si structure

Dependence of solid-phase growth of β-FeSi₂ thin films on the crystal orientation of Si substrates has been investigated by using a-Fe (thickness: 20 nm)/c-Si(100), (110) and (111) stacked structures. X-ray diffraction (XRD) measurements suggested that the substrate orientation dependence of the formation rate of β-FeSi₂ was as follows: (100)>(111)>(110). This dependence can be explained on the basis of the lattice mismatch between β-FeSi₂ and Si substrates, i.e., the lattice mismatch between β-FeSi₂(100) and Si(100), β-FeSi₂(110) or (101) and Si(111), and β-FeSi₂(010) or (001) and Si(110) of 1.4-2.0%, 5.3-5.5% and 9.2%, respectively. The substrate orientation dependence of solid-phase growth becomes relatively remarkable for very thin films.     

Glass formation in the Se–Ge–Zn and GeSe3–ZnSe–Ag2Se systems

The glass-forming region in the Se–Ge–Zn (I) and GeSe₃–ZnSe–Ag₂Se (II) systems are determined, as well as some physical and chemical properties (temperatures of softening, crystallization and melting, density and microhardness). The glass-forming region in system I on the Se–Ge side (concentration limits 0–43% Ge). The maximum solubility of Zn is around 6% (at Se:Ge = 9:1). The glass-forming region in system II lies on the side Ag₂Se–GeSe₃ (from 54 to 100% GeSe) and ZnSe–GeSe₃ (from 78 to 100% GeSe₃) of the Gibbs’ concentration triangle for GeSe₃–ZnSe–Ag₂Se. This revised version was published online in November 2006 with corrections to the Cover Date.     

Variation of the structure of amorphous lead titanate in the course of crystallization

The laws of formation of an equilibrium crystalline structure of lead titanate during crystallization from an amorphous state were studied. The initial thermal treatment leads to structural relaxation of the amorphous state. Subsequently, an intermediate state is formed whereby cubic phases with perovskite and pyrochlore structures coexist in the amorphous matrix. Finally, an equilibrium tetragonal phase is established at room temperature.     

涤纶基材表面沉积Ag/ZnO复合膜形貌结构及性能研究

以组织结构不同的纯涤纶非织造布、机织布、针织布作为基材,采用直流射频共溅法,在织物表面沉积Ag/ZnO复合膜,通过扫描电子显微镜、X射线衍射仪、X射线光电子能谱仪对镀膜织物的表面形貌以及结构成分进行分析,测试了镀膜织物的抗静电、抗紫外线性能。结果表明:沉积Ag/ZnO复合膜后,机织布表面最不平整,针织布表面最平整;纯涤纶非织造布的结晶度较低。X射线光电子能谱表征证明Ag以单质形式存在于纯涤纶非织造布表面;纯涤纶非织造布的抗静电性最差,针织布最好;机织布抗紫外线性能最好,纯涤纶非织造布最差。     

Classification of the amorphous film crystallization types with respect to structure and morphology features

Based on the results of electron-microscopic investigations and analysis of the published data, a classification of the types of crystallization of amorphous films with respect to their structure and morphology features is proposed. According to this, the layer, island, and dendrite polymorphous crystallization types, as well as the fluid-phase crystallization that proceeds with the phase separation of a medium, are distinguished.     

n-CdS/p-ZnIn2Se4 thin film solar cell

The photovoltaic behaviour of a CdS/ZnIn₂Se₄ vacuum-evaporated thin film solar cell is reported for the first time. Because of the band gap of ZnIn₂Se₄ (1.93 eV) this combination of semiconductor materials seems to be suitable for use as one of the junctions in tandem solar cell configurations. Uncoated cells exhibited efficiencies of the order of 1.5% under an illumination of 100 mW cm^-2.     

铝诱导对磁控溅射制备CdZnTe薄膜结晶的影响

选用Cd0.9Zn0.1Te晶体和纯度为99.999%的铝为靶材,结合Al诱导晶化技术,采用磁控溅射法在普通玻璃衬底上制备了CdZnTe薄膜。研究了铝诱导CdZnTe薄膜的结构和形核机理。研究表明,铝诱导的CZT薄膜为闪锌矿结构,且为(111)晶面的取向生长;在薄膜生长过程中,覆盖在CdZnTe表面的铝首先与ZnTe结合,形成了ZnAl2Te4相,并以此为核心,诱导CdZnTe异质形核结晶,重新形成了小晶粒团簇的较致密颗粒状薄膜,提高了薄膜(111)面的优势取向结晶,提高了CdZnTe薄膜的结晶质量。讨论了薄膜的光学性能。     

Effect of the thickness of Si film on Si/Se film doped silicon prepared by femtosecond laser

The high infrared absorption of silicon could be achieved by doping silicon with chalcogens via femtosecond laser. In the paper, the samples of Se-doped silicon with different thickness of Si film were prepared with the aid of femtosecond laser. The effect of the thickness of silicon film on optical and the electrical properties of se-doped silicon is investigated. All the samples were thermally annealed at 500 °C for 1 h, and the absorptance of all the samples was found with a certain degree of reduction. With the increase of thickness of silicon film, the results of visible-near infrared spectrum showed that the infrared absorptance increased first and then decreased. In particular, the optical absorption, sheet carrier density and responsivity for samples prepared with the silicon film that was 300 nm thick were greater than that of the samples prepared with the Si films of other thickness. The experiment demonstrated that it is significant to select the silicon film of appropriate thickness in the fabrication of Se doped silicon.     

Non-isothermal crystallization of As2Se3 glass

The results of non-isothermal crystallization studies performed at different heating rates on batches of As₂Se₃ glasses prepared from melts at 400°C, 600°C and 800°C are reported. The peak temperature of crystallizationT _p, the enthalpy of crystallization ΔH _c and the activation energy for crystallizationE _c are independent of the melt temperature used in the preparation. Bulk nucleation with three-dimensional growth of crystals is indicated for As₂Se₃. The values of ΔH _c andE _c are found to be respectively 23·3 ± 0·9 cal/g and 36·5 ± 0·9 kcal/mol for As₂Se₃.     

Compound formation and energy levels at the interface betweeb amorphous Se and Cu,Ag and Al electrodes

The formation of selenide layers at the interface between Se and Cu, Ag and Al electrodes has been studied by vacuum photoemission. Cu and Ag react rapidly to form thick selenide layers while Al rectts to produce a layer protective against further reaction. The valence band maximum in the thick Se layer lies 1.26 eV below E_F with the copper electrode, 1.2 eV below E_F with an Ag electrode and 1.0 eV with an aluminum electrode.     

Features in the formation of Ge/Si multilayer nanostructures under ion-beam-assisted crystallization

A method of combined ion-beam crystallization of the Ge/Si multilayer nanostructures is proposed. Using atomic-force microscopy and electron microscopy, we observed the formation of an array of germanium quantum dots with lateral dimensions 〈a〉 = 12–15 nm at the following conditions: silicon-substrate temperature T = 330–350°C, ion-beam energies E _Ge + = 30–40 eV, $E_{Ar^ + }^0 = 230 - 240$ eV (primary pulsed defect formation mode), $E_{Ar^ + } = 130 - 140$ eV (permanent diffusion stimulation mode), and ion-beam fluences $f_{Ge^ + } = 1.5 \times 10^{14} cm^{ - 2} s^{ - 1} $ , $f_{Ar^ + } = 5 \times 10^{12} cm^{ - 2} s^{ - 1} $ . The Raman spectroscopy data indicate the experimental possibility of low-temperature ion-stimulated growth of the spacer layers of silicon (T = 420–450°C, $E_{Ar^ + } = 80 - 90$ eV, $E_{Si^ + } = 30 - 40$ eV, $f_{Si^ + } = 3.5 \times 10^{14} cm^{ - 2} s^{ - 1} $ ) and the formation of multilayer structures with Ge _x Si_{1 ? x} quantum dots (x > 0.85).     

The formation,structure and crystallization of non-crystalline nickel produced by splat-quenching

A non-crystalline phase has been formed in electron-transparent (0.1 to 0.5m thick) areas of splat-quenched foils of nickel. The positions in diffraction co-ordinates of the first two peaks and of a shoulder on the high-angle side of the second peak of the electron diffraction pattern agree closely with those for non-crystalline vapour-deposited Ni. The presence of the shoulder suggests that the structure is similar to that of dense random packed hard spheres, i.e. that it is amorphous rather than microcrystalline. The crystallization behaviour of the glassy phase studiedin situ in 1 MV electron microscope also supports this view. The crystallization temperature of about 150 C is unexpectedly high and suggests that stabilization by impurities (possibly up to 0.7 wt %) was occurring. The critical cooling rate for the formation of the glassy phase has been estimated from theories of homogeneous nucleation, crystal growth and transformation kinetics to be 10¹⁰ K sec^–1 which is in satisfactory agreement with experimentally derived estimates of the maximum cooling rate in electron-transparent areas of foils.     

纳米烧绿石型钛酸铅的水热合成

钙钛矿结构的钛酸铅是重要的电子陶瓷材料,在合成钙钛矿型钛酸铅的过程中,经常出现烧绿石结构的钛酸铅物相,但目前尚未见到合成单一物相烧绿石结构的钛酸铅报道.本文报道了用水热法制备烧绿石型钛酸铅纯相的结果,以及体系的碱度对产物的种类和形貌的影响.     

激光辐射法用于聚酰亚胺/纳米Ag复合膜的制备

在涂覆有PVP/AgNO3胶体的聚酰亚胺(PI)薄膜上,采用激光辐射法将Ag+还原成Ag纳米粒子并嵌入到PI表面,从而制备出聚酰亚胺/纳米Ag复合膜。通过XPS、AFM、SEM等表征手段研究了复合膜表面的化学成分、以及激光通量和PVP/AgNO3配比对纳米银粒子形貌的影响。结果表明,激光通量的提高可使聚酰亚胺/纳米Ag复合膜上的纳米Ag粒子产生一定程度的定向排列;调节PVP/AgNO3的配比,可大致控制Ag粒子尺寸在25～160nm间变化。     

In situ hydroxyapatite crystallization for the formation of hydroxyapatite/polymer composites

In an attempt to synthesize hydroxyapatite (HAP)/polymer composites, HAP crystallization was investigated in solution in the presence of ionic synthetic polymers. The side groups of the polymers used include carboxylate, dihydrogen phosphate, sulfate, and primary amine. Spontaneous HAP precipitation and amorphous-crystalline transformation occurring in both the presence or absence of ionic polymers were studied by measuring the solution turbidity change and titrating the released protons, respectively. The rates of HAP nucleation and growth were determined from an induction period before onset of crystallization and the subsequent propagation of HAP crystallites. The added anionic and cationic polymers, were found to suppress the crystallization in a concentration-dependent manner. An exception was a concentrated poly(acrylic acid), which was precipitated by calcium ion binding to accelerate the nucleation and the growth of HAP crystallites. These results suggest that a molecular interaction is operative between the ionic polymer chains and the growing HAP crystallites. Infrared spectroscopy and X-ray diffraction analysis revealed that the HAP precipitated in the presence of ionic polymers incorporated the polymer chains in the HAP microcrystalline aggregates. Based on these findings, HAP/poly(acrylic acid) composites were prepared through in situ HAP crystallization in the presence of poly(acrylic acid). Tensile testing of the composites and electron microscopic observation of their fractured surfaces revealed that the composite prepared through this wet process was superior to that obtained by simple physical mixing with respect to the wet state mechanical properties and homogeneity in mixing. This revised version was published online in November 2006 with corrections to the Cover Date.     

Acoustic properties of the film/plate layered structure

A new propagation medium-a layered structure composed of a film and a plate-is suggested and studied, using c-oriented ZnO and AlN films on (001), {100}-Si plate, as two opposite examples of slow-on-fast and fast-on-slow material combinations. For both structures, the modes belonging to Lamb, quasi-longitudinal (QL), and Anisimkin Jr.' (AN) families are found. For each family, the velocities v(n), displacement profiles, and electromechanical coupling coefficients K(n)2 for 4 electrode configurations are numerically calculated by the matrix method as a function of the mode order n = 0 to 8, plate thickness H/λ = 0 to 2.0, and film thickness h/λ = 0.02 to 0.04 (H and h are thicknesses; λ is the wavelength). Some high-order modes in the structure have K(n)2 = 0 for any H/λ, h/λ, and electrode configuration. Other modes possess variable K(n) 2 with a maximum value larger than the coupling coefficient for the Rayleigh SAWs in ZnO and AlN single crystals or layered structures using the same films and semi-infinite silicon substrate. There are also QL-modes having high velocity v(n), large K(n)2, and low propagation loss caused by liquid loading. These modes are well suited for liquid sensors.