Instability of Epitaxially Strained Thin Films Based on Nonlocal Elasticity

We perform a linear analysis of the elastic fields and stability of epitaxially strained thin films based on nonlocal elasticity. We derive expressions of perturbed stresses to the first order of perturbation amplitude, which show that the stresses are directly proportional to the lattice mismatch and the perturbation amplitude, and decrease with an increase in the perturbation wavelength. The critical perturbation wavelength distinguishes whether the flat film for the perturbation is stable, which is inversely proportional to the square of the mismatch and decreases with the thickness of the film.     

Critical Dynamics in Thin Films

Critical dynamics in film geometry is analyzed within the field-theoretical approach. In particular we consider the case of purely relaxational dynamics (Model A) and Dirichlet boundary conditions, corresponding to the so-called ordinary surface universality class on both confining boundaries. The general scaling properties for the linear response and correlation functions and for dynamic Casimir forces are discussed. Within the Gaussian approximation we determine the analytic expressions for the associated universal scaling functions and study quantitatively in detail their qualitative features as well as their various limiting behaviors close to the bulk critical point. In addition we consider the effects of time-dependent fields on the fluctuation-induced dynamic Casimir force and determine analytically the corresponding universal scaling functions and their asymptotic behaviors for two specific instances of instantaneous perturbations. The universal aspects of nonlinear relaxation from an initially ordered state are also discussed emphasizing the different crossovers occurring during this evolution. The model considered is relevant to the critical dynamics of actual uniaxial ferromagnetic films with symmetry-preserving conditions at the confining surfaces and for Monte Carlo simulations of spin system with Glauber dynamics and free boundary conditions.     

Growth Rate of Spherulites in Thin Films: Direct Evidence of Failure of Traditional Growth Theory

Growth rates of PPS and PVDF spherulites in very thin films were measured. The growth rates change by about four orders of magnitude within the crystallization temperature ranges examined in this work. Film thickness at the position of the spherulite for which growth rates were determined was measured; the film thickness was deduced from retardation in the spherulite. In the light of the criterion we proposed, film thicknesses more than several tens of microns are required for the growth rate to change by four orders of magnitude. However, the thickness of the thinnest film examined experimentally was less than 1 μm. This discrepancy between theory and experiment is large and violates the framework of the traditional growth model unrecoverably.     

Melting and Electromigration in Thin Chromium Films

Physics of the Solid State - Chromium films with a thickness of 10–40 nm deposited onto silicon substrates by magnetron sputtering are subjected to the action of electric current induced by...     

Preparation and Characterization of SnS:Bi Thin Films

Thin films based on Sn-S compounds are currently of great interest because of their potential applications in optoelectronic devices including solar cells. In this work, SnS:Bi thin films are prepared using a novel procedure based on sulfurization of their metallic precursors, varying the Bi content. The effect of the synthesis conditions on the optical properties, phase, and chemical composition of the SnS:Bi thin films was studied through spectral transmittance, X-ray diffraction, and X-ray photoelectron spectroscopy. It was established from transmittance measurements that the optical gap of the deposited films varies between 1.27 and 1.37 eV depending on the Bi content. The analysis revealed that the SnS:Bi thin films grow with a mixture of several phases which include SnS, Sn₂S₃ SnS₂, and Bi₂S₃, depending on the Bi concentration. The studies also revealed that the conductivity type of the SnS:Bi films depends on the Bi content in the SnS lattice.     

Progress in Optical Waveguiding Thin Films

Overview of recent activities in the development of active and passive thin film waveguides, waveguide lasers and laser-deposited waveguiding films is given. Published results and parameters are summarized. The focus is on films fabricated by laser deposition.     

Magnetic Pseudoresonance in Manganite Thin Films

A strong narrow peak in the field dependence of the radio-frequency absorption (the magnetic pseudoresonance) has been found and investigated in epitaxial thin films of La_2/3Sr_1/3MnO₃ possessing uniaxial magnetic anisotropy in the film plane. The peak is observed when the in-plane external magnetic field H is directed perpendicular to the easy axis and equals to the anisotropy field H _u. The frequency dependence of the peak magnitude measured in the frequency range of 10–300 MHz approximately follows the Debye law behavior with the characteristic relaxation time of about 2.2 ns. The physical model of the phenomenon is suggested, based on the giant increase in static transversal susceptibility due to a sharp reorientation of the equilibrium magnetization when approaching the pseudoresonance conditions.     

Processing,Structure, Properties,and Applications of PZT Thin Films

There has been a resurgence of complex oxides of late owing to their ferroelectric and ferromagnetic properties. Although these properties had been recognized decades ago, the renewed interest stems from modern deposition techniques that can produce high quality materials and attractive proposed device concepts. In addition to their use on their own, the interest is building on the use of these materials in a stack also. Ferroelectrics are dielectric materials that have spontaneous polarization in certain temperature range and show nonlinear polarization–electric field dependence called a hysteresis loop. The outstanding properties of the ferroelectrics are due to non-centro-symmetric crystal structure resulting from slight distortion of the cubic perovskite structure. The ferroelectric materials are ferroelastic also in that a change in shape results in a change in the electric polarization (thus electric field) developed in the crystal and vice versa. Therefore they can be used to transform acoustic waves to electrical signal in sonar detectors and convert electric field into motion in actuators and mechanical scanners requiring fine control. In a broader sense the ferroelectric materials can be used for pyroelectric and piezoelectric sensors, voltage tunable capacitors, infrared detectors, surface acoustic wave (SAW) devices, microactuators, and nonvolatile random-access memories (NVRAMs), including the potential production of one transistor memory cells, and applications requiring nonlinear optic components. Another set of potential applications seeks to exploit the ferroelastic properties in stacked templates where they are juxtaposed to ferromagnetic materials. Doing so would allow the control of magnetic properties with electric field, which is novel. Such templates taking advantage two or more properties acquired a new name and now goes by multiferroics. After a brief historical development, this article discusses technological issues such as growth and processing, electrical and optical properties, piezo, pyro, and ferroelectric properties, degradation, measurements methods, and application of mainly lead-zirconate-titanate (PZT = PbZr_1?xTi_xO₃). The focus on PZT stems from its large electromechanical constant, large saturation polarization and large dielectric constant.     

Magneto-optical and Microwave Properties of LuBiIG Thin Films Prepared by Liquid Phase Epitaxy Method from Lead-Free Flux

Lu2.1Bi0.9Fe5O12 （LuBiIG） garnet films are prepared by liquid phase epitaxy （LPE） method on gadolinium gallium garnet （GGG） substrates from lead-free flux. Three-inch single crystal garnet films with （444） orientation and good surface are successfully fabricated. The lattice mismatch to the GGG（111） substrate is as small as 0.08%. The ferromagnetic resonance （FMR） linewidth of the film is 2AH = 2.8-5.10e, the Faraday rotation is 1.64 deg/μm at 633nm at room temperature and the optical absorption coefficient of the film is 600cm-1 in visible range and about 100-170 cm-1 when the wavelength is larger than 800 nm. The epitaxy film possesses dominating in-plane magnetization with a saturation magnetization of about 1562G. These superior optical, magnetic-optical （MO） and microwave properties of our garnet films have potential applications in both MO and microwave devices.     

Fe-Vacancy-Induced Ferromagnetism in Tetragonal FeSe Thin Films

Motivated by recent experiments, we investigate structural, electronic, and magnetic properties of tetragonal FeSe with Fe vacancies using the state-of-the-art first-principles method. We show that Fe vacancies tend to stay in the same one of the two sublattices and thus induce ferromagnetism in the ground-state phase. Our calculated net moment is in good agreement with the experimental data available. Therefore, the ferromagnetism observed in tetragonal FeSe thin films is explained. It could be made controllable soon for spintronic applications.     

CdSyTe1-y多晶薄膜的制备及光谱表征

采用真空共蒸发法制备了CdSyTe1-y(0≤y≤1)多晶薄膜,并用X射线衍射谱(XRD)、能量色散谱(EDS)研究了CdSyTe1-y多晶薄膜的结构、组分。实验结果表明:石英振荡法监控的组分与EDS谱结果较为一致;当y<0·3时,CdSyTe1-y多晶薄膜为立方结构,当y≥0·3时,CdSyTe1-y多晶薄膜为六方结构。采用XRD线形分析法可计算出CdSyTe1-y多晶薄膜晶粒大小约20～50nm。最后,用紫外-可见-近红外谱(UV-Vis-NIR),测得300～2500nmCdSyTe1-y多晶薄膜的透过率曲线,并结合一阶Sellmeier模型的折射率色散关系,表征了CdSyTe1-y多晶薄膜的光学性质,获得了CdS0·22Te0·78多晶薄膜的光学厚度d～535nm,光能隙Eg～1·41eV,以及吸收系数α(λ)、折射率n(λ)等光学量。结果也表明,采用真空共蒸发法可以制备需要组分的CdSyTe1-y多晶薄膜,对CdSyTe1-y多晶薄膜光学性质的表征方法可推广到其他的半导体薄膜材料。     

Thin Films Made Fast and Modified Fast

Hyperfine Interactions - Thin films are playing a more and more important role for technological applications and there are many aspects of materials surface processing and thin film production,...     

Nonlinear Absorption Properties of nc-Si:H Thin Films

It is reported in this paper that the phenomenon of the saturated absorption of the exciton in hydrogenated nanocrystalline silicon (nc-Si:H) thin film fabricated by plasma enhanced chemical vapor deposition (PECVD) without any post-processing is observed at room temperature using pump-probe technology. This nonlinear optical absorption property is induced by the surface effect of the silicon nanoparticles in nc-Si:H thin films.     

Spontaneous and Induced Magnetization Reversal in Thin GaMnSb Films

The time, temperature, and magnetic field dependences of the magnetic moment of thin GaMnSb films containing MnSb clusters are measured using a SQUID (superconducting quantum interference device) magnetometer. It is found that magnetic field-induced magnetization reversal and thermally activated spontaneous magnetization reversal in thin GaMnSb films are interrelated as follows: the maximum of the magnetic-field dependence of the magnetic viscosity coincides with the coercive force for the samples.     

High-Temperature Electron-Hole Liquid in Diamond Films

Russian Physics Journal -     

Mechanisms of Stress Generation in Thin Films and Coatings

Technical Physics - Analysis of the literature data on the reasons for the development of mechanical stresses in epitaxial, polycrystalline, and amorphous films during their formation and under...