Effects of Bottom Layer Sputtering Pressures and Annealing Temperatures on the Microstructures, Electrical and Optical Properties of Mo Bilayer Films Deposited by RF/DC Magnetron Sputtering

Most of the molybdenum (Mo) bilayer films are deposited by direct current (DC) magnetron sputtering at the bottom and the top layer (DC/DC). However, the deposition of Mo bilayer film by radio frequency (RF) Mo bottom layer and DC Mo top layer magnetron sputtering has been less studied by researchers. In this paper, the bottom layer of Mo bilayer film was deposited by RF magnetron sputtering to maintain its good adhesion and high reflectance, and the top layer was deposited by DC magnetron sputtering to obtain good conductivity (RF/DC). Generally, the bottom layer sputtering pressure is relatively random, in this paper, the effects of the bottom layer RF sputtering pressures on the microstructures and properties of Mo bilayer films were first studied in detail. Next, in order to further improve their properties, the as-prepared Mo bilayer films at 0.4 Pa bottom layer RF sputtering pressure were annealed at different temperatures and then investigated. Specifically, Mo bilayer films were deposited on soda-lime glass substrates by RF/DC magnetron sputtering at different bottom layer RF sputtering pressures in the range of 0.4–1.2 Pa, the powers of bottom layer RF sputtering and top layer DC sputtering were 120 W and 100 W, respectively. Then, Mo bilayer films, prepared at a bottom layer sputtering pressure of 0.4 Pa and top layer sputtering pressure of 0.3 Pa, were annealed for 30 min at various temperatures in the range of 100–400 °C. The effects of bottom layer sputtering pressures and the annealing temperatures on the microstructures, electrical and optical properties of Mo bilayer films were clarified by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic-force microscopy (AFM), and ultraviolet (UV)-visible spectra, respectively. It is shown that with decreasing bottom layer sputtering pressure from 1.2 to 0.4 Pa and increasing annealing temperature from 100 to 400 °C, the crystallinity, electrical and optical properties of Mo bilayer films were improved correspondingly. The optimized Mo bilayer film was prepared at the top layer sputtering pressure of 0.3 Pa, the bottom layer sputtering pressure of 0.4 Pa and the annealing temperature of 400 °C. The extremely low resistivity of 0.92 × 10−5 Ω.cm was obtained. The photo-conversion efficiency of copper indium gallium selenium (CIGS) solar cell with the optimized Mo bilayer film as electrode was up to as high as 13.5%

High energy solutions of modified quasilinear fourth-order elliptic equation

Abstract This paper focuses on the following modified quasilinear fourth-order elliptic equation: {△2u−(a+b∫R3|∇u|2dx)△u+λV(x)u−12△(u2)u=f(x,u),in R3,u(x)∈H2(R3), \textstyle\begin{cases} \triangle^{2}u-(a+b\int_{\mathbb{R}^{3}} \vert \nabla u \vert ^{2}\,dx)\triangle u+\lambda V(x)u-\frac{1}{2}\triangle(u^{2})u=f(x,u),& \mbox{in }\mathbb{R}^{3}, \\ u(x)\in H^{2}(\mathbb{R}^{3}), \end{cases} where △2=△(△) $\triangle^{2}=\triangle(\triangle)$ is the biharmonic operator, a>0 $a>0$, b≥0 $b\geq 0$, λ≥1 $\lambda\geq 1$ is a parameter, V∈C(R3,R) $V\in C(\mathbb{R}^{3},\mathbb{R})$, f(x,u)∈C(R3×R,R) $f(x,u)\in C(\mathbb{R}^{3}\times\mathbb{R}, \mathbb{R})$. V(x) $V(x)$ and f(x,u)u $f(x,u)u$ are both allowed to be sign-changing. Under the weaker assumption lim|t|→∞∫0tf(x,s)ds|t|3=∞ $\lim_{ \vert t \vert \rightarrow\infty}\frac{\int^{t}_{0}f(x,s)\,ds}{ \vert t \vert ^{3}}=\infty$ uniformly in x∈R3 $x\in\mathbb{R}^{3}$, a sequence of high energy weak solutions for the above problem are obtained

Laplace’s equation with concave and convex boundary nonlinearities on an exterior region

Abstract This paper studies Laplace’s equation −Δu=0 $-\Delta u=0$ in an exterior region U⊊RN $U\varsubsetneq {\mathbb{R}}^{N}$, when N≥3 $N\geq 3$, subject to the nonlinear boundary condition ∂u∂ν=λ|u|q−2u+μ|u|p−2u $\frac{\partial u}{\partial \nu }=\lambda \vert u \vert ^{q-2}u+\mu \vert u \vert ^{p-2}u$ on ∂U with 10 $\lambda >0$ and μ∈R $\mu \in \mathbb{R}$ arbitrary, then there exists a sequence {uk} $\{u_{k} \}$ of solutions with negative energy converging to 0 as k→∞ $k\to \infty$; on the other hand, when λ∈R $\lambda \in \mathbb{R}$ and μ>0 $\mu >0$ arbitrary, then there exists a sequence {u˜k} $\{\tilde{u}_{k} \}$ of solutions with positive and unbounded energy. Also, associated with the p-Laplacian equation −Δpu=0 $-\Delta _{p} u=0$, the exterior p-harmonic Steklov eigenvalue problems are described

Study on Interface Structure of Cu/Al Clad Plates by Roll Casting

Large scale Atomic/Molecular dynamic Parallel Simulator (LAMMPS) molecular dynamics simulation software was used to simulate the copper and aluminum atom diffusion and changes of interface during heating and cooling process of copper and aluminum composite panels. The structures of the interface were characterized through scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron microscope (TEM), and the mechanical properties were also tested. The simulation results show that the diffusion rate of copper atom is higher than that of aluminum atom, and that the CuAl2 radial distribution function of the interface at 300 K is consistent with that of pure CuAl2 at room temperature. At 930 K, t = 50 ps Cu atoms spread at a distance of approximately four Al lattice constants around the Al layer, and Al atoms spread to about half a lattice constant distance to the Cu layer. The experimental results show that the thickness of the interface in copper–aluminum composite plate is about 1 μm, and only one kind of CuAl2 with tetragonal phase structure is generated in the interface, which corresponds with the result of molecular dynamics simulation

Effects of Heating Mode and Temperature on the Microstructures, Electrical and Optical Properties of Molybdenum Thin Films

In this paper, molybdenum (Mo) thin films are deposited on soda-lime glass (SLG) substrates by direct current magnetron sputtering and heated in three different modes at different temperatures, including substrate heating, annealing treatment, and both substrate heating and annealing treatment. The effects of heating temperature and heating mode on the structures, morphology, optical and electrical properties of Mo thin films were systematically investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), atomic force microscope (AFM) and UV-visible spectrophotometer (UV-vis spectra). It is shown that as the substrate and annealing temperature increase, the crystallinity of Mo thin films is improved, and the grain sizes become bigger. Especially in the mode of both substrate heating and annealing treatment at higher temperature, the obtained Mo thin films show higher crystallinity and conductivity. Moreover, with the increase of substrate and annealing temperature in different heating modes, both the surface compactness of Mo films and the optical reflectance increase correspondingly. Furthermore, the Mo film, prepared at the substrate heating temperature of 400 °C and annealed at 400 °C, showed excellent comprehensive performance, and the resistivity is as low as 1.36 × 10−5 Ω·cm. Using this optimized Mo thin film as an electrode, copper indium gallium selenium (CIGS) solar cells have a maximum photo-conversion efficiency of 12.8%

Effects of Thickness Ratios and Sputtering Mode on the Structural, Electrical and Optical Properties of Bilayer Molybdenum Thin Films

In this paper, the bilayer Mo films with a constant thickness were deposited by direct current and direct current (DC/DC), radio frequency and direct current mixed (RF/DC) magnetron sputtering, respectively. Changing thickness ratios of bottom layer to total thickness of bilayer film in the range from 10% to 50%, ten types of bilayer Mo thin films were deposited. The purpose is to improve the photo-conversion efficiency of Cu(In, Ga)Se2(CIGS) solar cells by changing the sputtering modes and thickness ratio. The microstructures, electrical and optical properties of the bilayer Mo thin films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscope (AFM), Hall Effect measurement system, ultraviolet-visible spectrophotometer (UV-vis) and four-point probe resistance system. It was found that with the increase of thickness ratios in two sputtering modes, both the crystallinity and grain size decreased, while the reflectance increased. Especially, when the thickness ratio was 40%, the resistivity of Mo film prepared in RF/DC mode was as low as 3.365 ×10-5 Ω·cm and the highest reflectance was above 60%. Using this optimized Mo thin film as electrode, the highest photo-conversion efficiency for the CIGS thin film solar cells was as high as 11.5%