Target voltage behaviour of a vanadium-oxide thin film during reactive magnetron sputtering

This paper simulates reactive magnetron-sputtering in constant current mode in a Vanadium-O 2 /Ar system equipped with a DC power supply by adopting both kinetics model and Berg’s model.The target voltage during the reactive sputtering has been investigated as a function of reactive gas flow.Both experiments and simulations demonstrate a hysteresis curve with respect to the oxygen supply.The time-dependent variation of the target mode is studied by measuring the target voltage for various reactive oxygen gas flows and pre-sputtering times.The presputtering time increases with the increased initial target voltage.Furthermore,a corresponding time-dependent model simulating target voltage changes is also proposed.Based on these simulations,we find some relationships between the discharge voltage behaviour and the properties of the formed oxide.In this way,a better understanding of the target voltage changes during reactive sputtering can be achieved.We conclude that the presented theoretical models for parameter-dependent case and time-dependent case are in qualitative agreement with the experimental results and can be used to comprehend the target voltage behaviour in the deposition of vanadium oxide thin films.     

核壳结构上转换发光纳米粒子的合成及用于细胞色素C的检测

本工作合成了三层核壳结构的上转换发光纳米粒子,其中第一层是惰性核,第二层为发光层,为了增强上转换发光强度,又在表面包覆了第三层惰性壳层。该材料粒径均一、分散性良好,其发光层厚度约为2.4 nm,惰性壳层厚度约为2.9 nm。在其表面修饰了细胞色素C的适配体链及互补链,在适配体的3’端修饰了BHQ3基团,能够猝灭上转换纳米粒子在655 nm波长处的发光。当细胞色素C存在时,适配体与细胞色素C结合从而离开其表面,使655 nm处的发光恢复。在检测过程中,540 nm处的发光强度不会发生变化,可以用作细胞色素C的比率荧光检测。结果表明,当细胞色素C浓度在5～80μmol/L范围时,发光信号恢复程度与细胞色素C浓度呈线性相关,相关系数为0.998,检出限为1μmol/L。所建立方法可为细胞色素C的荧光检测提供一种新的技术思路。     

Modeling for V–O_2 reactive sputtering process using a pulsed power supply

In this article, we present a time-dependent model that enables us to describe the dynamic behavior of pulsed DC reactive sputtering and predict the film compositions of VOx prepared by this process. In this modeling, the average current J is replaced by a new parameter of Jeff. Meanwhile, the four species states of V, V2O3, VO2, and V2O5 in the vanadium oxide films are taken into consideration. Based on this work, the influences of the oxygen gas supply and the pulsed power parameters including the duty cycle and frequency on film compositions are discussed. The model suggests that the time to reach process equilibrium may vary substantially depending on these parameters. It is also indicated that the compositions of VOx films are quite sensitive to both the reactive gas supply and the duty cycle when the power supply works in pulse mode. The ‘steady-state’ balance values obtained by these simulations show excellent agreement with the experimental data, which indicates that the experimentally obtained dynamic behavior of the film composition can be explained by this time-dependent modeling for pulsed DC reactive sputtering process. Moreover, the computer simulation results indicate that the curves will essentially yield oscillations around the average value of the film compositions with lower pulse frequency.