Modeling of polycrystalline ZnO thin-film transistors with a consideration of the deep and tail states

We report a model of the carrier transport and the subgap density of states in a polycrystalline ZnO film for simulating a polycrystalline ZnO thin film transistor. This simple model considering the deep and the band tail states reproduces well the characteristics of polycrystalline ZnO thin film transistors. Furthermore, using the developed model, we study the effects of defect parameters on the electrical performances of the polycrystalline ZnO thin film transistors.

Optimizing a Single-Absorption-Layer Thin-Film Solar Cell1 Model to Achieve 31% Efficiency

This research builds upon the authors’ previous work that introduced and modeled a novel Gallium-Arsenide, Emitterless, Back-surface Alternating Contact (GaAs-EBAC) thin-film solar cell to achieve >30% power conversion efficiency. Key design parameters are optimized under an Air-Mass (AM) 1.5 spectrum to improve performance and approach the 33.5% theoretical efficiency limit. A second optimization is performed under an AM0 spectrum to examine the cell’s potential for space applications. This research demonstrates the feasibility and potential of a new thin-film solar cell design for terrestrial and space applications. Results suggest that the straight-forward design may be an inexpensive alternative to multi-junction solar cells.

Influence of lateral size on dielectric properties of ferroelectric thin films with structure transition zones

By taking into account structural transition zones near the lateral and thickness direction edges,this paper uses a modified transverse Ising model to study dielectric properties of a finite size ferroelectric thin film in the framework of the mean-field approximation.The results indicate that the influence of the lateral size on the dielectric susceptibility cannot be neglected and lateral structural transition zones could be a crucial factor that improves the mean susceptibility of the fixed size film.

Electric dipolar interaction assisted growth of single crystalline organic thin films

We report on a forest-like-to-desert-like pattern evolution in the growth of an organic thin film observed by using an atomic force microscope. We use a modified diffusion limited aggregation model to simulate the growth process and are able to reproduce the experimental patterns. The energy of electric dipole interaction is calculated and determined to be the driving force for the pattern formation and evolution. Based on these results, single crystalline films are obtained by enhancing the electric dipole interaction while limiting effects of other growth parameters.

Temperature-dependent bias-stress-induced electrical instability of amorphous indium-gallium-zinc-oxide thin-film transistors

The time and temperature dependence of threshold voltage shift under positive-bias stress（PBS） and the following recovery process are investigated in amorphous indium-gallium-zinc-oxide（a-IGZO） thin-film transistors. It is found that the time dependence of threshold voltage shift can be well described by a stretched exponential equation in which the time constant τ is found to be temperature dependent. Based on Arrhenius plots, an average effective energy barrier Eτ stress= 0.72 eV for the PBS process and an average effective energy barrier Eτ recovery= 0.58 eV for the recovery process are extracted respectively. A charge trapping/detrapping model is used to explain the threshold voltage shift in both the PBS and the recovery process. The influence of gate bias stress on transistor performance is one of the most critical issues for practical device development.

Positronium diffusion in porous methylsilsesquioxane thin films

Depth profiled positronium （Ps） annihilation lifetime spectroscopy （PALS） is an extremely useful probe of the pore characteristics in nanoporous low-dielectric （low-k） constant thin films. PALS has also been considered as a potential probe to investigate diffusion barrier integrity and the structural changes of porous low-k films during their integration with Cu. Hence, it is essential to understand the diffusion behaviour of positronium/Cu atoms in the films. In this work, based on the fact that porous materials possess characteristics of statistical self-similarity, a fractal model, the Menger sponge model, has been applied to simulate the structure of a promising dielectric, porous methylsilsesquioxane （MSQ） films. The diffusion behaviour of Ps out of the fractal model and into the surrounding vacuum is studied by means of the diffusion equation and traditional adveetive diffusive theory. Predictive results from our model show good agreement with measurement data.

Strain tunability of dielectric and ferroelectric properties in epitaxial lead titanate thin films

Many distinguished properties of epitaxial ferroelectric thin films can be tunable through the misfit strain.The strain tunability of ferroelectric and dielectric properties in epitaxial lead titanate ultrathin films is numerically investigated by using a phase field model,in which the surface effect of polarization is taken into account.The response of polarization to the applied electric field in the thickness direction is examined with different misfit strains at room temperature.It is found that a compressive misfit strain increases the coercive field and the remanent polarization while a tensile misfit strain decreases both of them.The nonlinear dielectric constants of the thin films with tensile misfit strains are much larger than those of the thin films without misfit strains,which are attributed to the existence of the a/c/a/c multiple domains in the thin films under tensile misfit strains.

On study of horizontal thin film flow of Sisko fluid due to surface tension gradient

The present paper is concerned with the steady thin film flow of the Sisko fluid on a horizontal moving plate, where the surface tension gradient is a driving mechanism. The analytic solution for the resulting nonlinear ordinary differential equation is obtained by the Adomian decomposition method （ADM）. The physical quantities are derived including the pressure profile, the velocity profile, the maximum residue time, the stationary points, the volume flow rate, the average film velocity, the uniform film thickness, the shear stress, the surface tension profile~ and the vorticity vector. It is found that the velocity of the Sisko fluid film decreases when the fluid behavior index and the Sisko fluid parameter increase, whereas it increases with an increase in the inverse capillary number. An increase in the inverse capillary number results in an increase in the surface tension which in turn results in an increase in the surface tension gradient on the Sisko fluid film. The locations of the stationary points are shifted towards the moving plate with the increase in the inverse capillary number, and vice versa locations for the stationary points are found with the increasing Sisko fluid parameter. Furthermore, shear thinning and shear thickening characteristics of the Sisko fluid are discussed. A comparison is made between the Sisko fluid film and the Newtonian fluid film.

Molecular Dynamics of Ultra-thin Lubricating Films under Confined Shear

The molecular dynamics simulation of ultra-thin films under confined shear was performed to investigate the relation between dynamic properties of ultra-thin films and their microstructure. The solid walls were modelled using an Au crystal and the fluid molecules were modeled using decane. The simulation results indicate that the microstructure of ultra-thin films is a kind of solid-like layering structure. The density and velocity profiles of the fluid molecules are symmetric. The slip and shear thinning behavior was founded and interpreted.A mathematic model was set up according to the results of the simulation and experiments.

The microwave response of MgB2 /Al2O3 superconducting thin films

Microwave characteristics of MgB2/Al2O3 superconducting thin films were investigated by coplanar resonator technique. The thin films studied have different grain sizes resulting from different growth techniques. The experimental results can be described very well by a grain-size model which combines coplanar resonator theory and Josephson junction network model. It was found that the penetration depth and surface resistance of thin films with smaller grain sizes are larger than those of thin films with larger grain sizes.

Critical properties of XY model dimensional layered magnetic on two- films

Using Monte Carlo simulations, we have investigated the classical XY model on triangular lattices of ultra-thin film structures with middle ferromagnetic layers sandwiched between two antiferromagnetic layers. The internal energy, the specifc heat, the chirality and the chiral susceptibility are calculated in order to clarify phase transitions and critical phenomena. Prom the finite-size scaling analyses, the values of critical exponents are determined. In a range of interaction parameters, we find that the chirality steeply goes up as temperature increases in a temperature range; correspondingly the value of a critical exponent for this change is estimated.

Numerical Study of Thin Film Condensation in Forced Convection of Saturated Vapor on a Vertical Wall Covered with a Porous Material

The study of forced convection in a porous medium has aroused and still arouses today the interest of many scientists and industrialists. A considerable amount of work has been undertaken following the discovery of the phenomenon. Solving a standard problem of forced convection in porous media comes down to predicting the temperature and velocity fields as well as the intensity of the flow as a function of the various parameters of the problem. A numerical study of the condensation in forced convection of a pure and saturated vapor on a vertical wall covered with a porous material is presented. The transfers in the porous medium and the liquid film are described respectively by the Darcy-Brinkman model and the classical boundary layer equations. The dimensionless equations are solved by an implicit finite difference method and the iterative Gauss-Seidel method. Our study makes it possible to examine and highlight the role of parameters such as: the Froude number and the thickness of the porous layer on the speed and the temperature in the porous medium. Given the objective of our study, the presentation of velocity and temperature profiles is limited in the porous medium. The results show that the Froude number does not influence the thermal field. The temperature increases with an increase in the thickness of the dimensionless porous layer. The decrease in the Froude number leads to an increase in the hydrodynamic field.

Design and Simulation of the Thin Film Pulse Transformer

A new thin film pulse transformer for using in ISND and ADSL systems has been designed based on a domain wall pinning model, the parameters of nano-magnetic thin film such as permeability and coercivity can be calculated. The main properties of the thin film transformer including the size, parallel inductance, Q value and turn ratio have been simulated and optimized. Simulation results show that the thin film transformer can be fairly operated in a frequency range of 0.001~20 MHz.

Influence of Prandtl Number on Thin Film Condensation in Forced Convection in an Inclined Wall Covered with a Porous Material

The numerical study of thin film type condensation in forced convection of a saturated pure vapor in an inclined wall covered with a porous material is presented. The generalized Darcy-Brinkman-Forchheimer (DBF) model is used to describe the flow in the porous medium while the classical boundary layer equations have been exploited in the case of a pure liquid. The dimensionless equations are solved by an implicit finite difference method and the iterative Gauss-Seidel method. The objective of this study is to examine the influence of the Prandtl number on the hydrodynamic and thermal fields but also on the local Nusselt number and on the boundary layer thickness. For Pr ≤ 0.7 (low) the velocity and the longitudinal temperature increase with the Prandtl number. On the other hand, when Pr ≥ 2 (high) the Prandtl number no longer influences the velocity and the longitudinal temperature. The local Nusselt number increases as the Prandtl number increases and the thickness of the hydrodynamic boundary layer increases as the Prandtl number decreases.

薄膜压力传感器在液压振动沉桩试验中的应用

薄膜压力传感器因厚度薄、测试单元面积小和灵敏度高等优点在土木工程领域逐渐得到应用。为探究薄膜压力传感器在液压振动沉桩中监测桩侧法向应力的适用性,在砂土中开展液压振动沉桩大比尺模型试验。试验结果表明:液压振动沉桩的桩侧残余法向应力显著小于振动时的法向应力;在合适的保护措施下,薄膜压力传感器能有效监测沉桩过程中的桩侧法向应力。

Numerical Modeling and Simulation of CIGS-Based Solar Cells with ZnS Buffer Layer

Usually a buffer layer of cadmium sulphide is used in high efficiency solar cells based on Cu(In,Ga)Se2(CIGS). Because of cadmium toxicity, many in-vestigations have been conducted to use Cd-free buffer layers. Our work focuses on this type of CIGS-based solar cells where CdS is replaced by a ZnS buffer layer. In this contribution, AFORS-HET software is used to simulate n-ZnO: Al/i-ZnO/n-ZnS/p-CIGS/Mo polycrystalline thin-film solar cell where the key parts are p-CIGS absorber layer and n-ZnS buffer layer. The characteristics of these key parts: thickness and Ga-content of the absorber layer, thickness of the buffer layer and doping concentrations of absorber and buffer layers have been investigated to optimize the conversion efficiency. We find a maximum conversion efficiency of 26% with a short-circuit current of 36.9 mA/cm2, an open circuit voltage of 824 mV, and a fill factor of 85.5%.

A Dugdale model based geometrical amplifier enables the measurement of separation-to-failure for a cohesive interface

Regardless of all kinds of different formulae used for the traction-separation relationship in cohesive zone modeling,the peak tractionσ_m and the separation-to-failureδ_0(or equivalently the work-to-separationΓ) are the primary parameters which control the interfacial fracture behaviors. Experimentally,it is hard to determine those quantities,especially forδ_0,which occurs in a very localized region with possibly complicated geometries by material failure.Based on the Dugdale model,we show that the separation-to-failure of an interface could be amplified by a factor of L/r_p in a typical peeling test,where L is the beam length and r_p is the cohesive zone size.Such an amplifier makesδ_0 feasible to be probed quantitatively from a simple peeling test. The method proposed here may be of importance to understanding interfacial fractures of layered structures,or in some nanoscale mechanical phenomena such as delamination of thin films and coatings.

基于ARCS模型的产教研融合模式的课程改革与实践——以“薄膜光学与技术”课程为例

针对当前薄膜光学与技术课程教学中存在的学生学习积极性不高、实践能力培养不充分、人才培养与社会需求关联不紧密等问题,结合专业特色和人才培养目标,基于新时代发展对创新人才的需求,提出基于ARCS动机模型的产教研融合模式对课程进行改革与实践,充分调动学生学习主动性,提高学生的实践能力和创新能力。探索基于ARCS模型的产教研融合的教学模式在薄膜光学与技术课程中的应用,优化知识体系,重构教学设计,将教学内容和课程思政深度融合,致力于培养具有创新意识和解决复杂问题能力的高质量人才。

Al/CuO含能薄膜换能芯片薄膜反应的模拟分析

为了探究含能薄膜在换能元火工品点火过程中的点燃机制,建立Al/CuO含能薄膜换能芯片结构的傅里叶传热模型,利用COMSOL仿真软件对不同电压或电容条件下含能薄膜换能芯片的点火过程进行数值模拟,对比分析电容或电压对含能薄膜温升曲线的影响。仿真结果表明:提高电压或电容使得含能薄膜温升曲线峰值增高或延长,两者都能扩大薄膜反应区域;电容与电压增大或减小均影响半导体桥对含能薄膜的传热效率,导致含能薄膜的温升曲线相对于半导体桥具有滞后性与相似性。