Fabrication of porous anodic aluminum oxide by hybrid pulse anodization at relatively high potential

Anodic aluminum oxide (AAO) containing high-aspect ratio pore channels has been widely used as a template for fabricating nanowires or other 1D nanostructures. For AAO prepared in oxalic acid, the anodizing potential is set as 40 V in order to balance the oxidation and dissolution rates. In practice, a higher potential is beneficial in increasing the pore size. However, a higher potential increases the local electrolyte temperature and therefore damages the pore structure. In this article, this problem is resolved by means of a high-potential hybrid pulse anodization (HPA) technique, in which a period of small negative potential is applied to suppress the Joule heating effect during the AAO preparation process. The scanning electron microscope results showed that HPA with an anodizing potential of 60 V resulted in an intact pore structure on the AAO surface. By contrast, the AAO formed using conventional direct current anodization with the same anodizing potential contained many small irregular pores around each original pore. The present results suggest that HPA has significant potential for the fabrication of high-quality nanowires with various diameters for such applications as magnetic recording, super capacitors or field emission devices.     

Fabrication of various nano-structured nickel stamps using anodic aluminum oxide

This paper presents a fabrication method of various nickel stamps based on anodic aluminum oxide (AAO) and nickel electroforming (NE) processes. By AAO process, master templates which have closely-packed nano dimple or pore structure array are fabricated. Then nickel stamps having negative surface topology of the master templates are fabricated by NE process. Also positive nickel stamps are fabricated from the negative stamps by NE process with the help of nickel passivation technique. So achieved nickel stamps are employed in injection molding and hot embossing processes for replication of nano-structured surfaces.     

Numeric simulation of the formation of hexagonal nanoscale structure arrays in anodic aluminum oxide

Formation of hexagonal periodic nanoscale structures at the surface of aluminum oxide is considered in the present paper. The mathematical model of chemical reactions at metal-oxide and oxide/electrolyte interfaces is described. A weak nonlinear approximation near the instability threshold results in the two-dimensional Kuramoto-Sivashinsky equation. The solution of this equation provides the same regular hexagonal nanoscale structure arrays that are observed in physical experiments. The two-stage complex Rosenbrock scheme developed by the author is applied for the numerical simulation of this problem in the present paper. The high accuracy O(τ⁴) and L1 stability, along with the relative simplicity of the method, make it possible to use a conventional PC to perform the calculations.     

Light induced enhancing gas sensitivity of copper-doped zinc oxide at room temperature

Copper-doped zinc oxide (ZnO) (1 mol%) nanocrystals were synthesized using a sol–gel method and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), inductive coupled plasma with optical emission spectrometry (ICP-OES). The XRD result indicated that the introduction of copper had no influence on the crystal structure of ZnO, though ICP-OES exhibited the molar ratio of copper and zinc was 0.86:100. The gas response of the copper-doped ZnO was also studied to ethanol and acetone without and with the illumination of 355 nm light. It was found that the ultraviolet light irradiation could enhance the gas response, and the mechanism with irradiation was discussed. Our results demonstrated that light irradiation was a promising approach to achieve large response at room temperature.     

石墨烯/氧化钨复合材料室温响应NO2传感器

采用溶剂热法制备了石墨烯/氧化钨复合材料,通过XRD,SEM,Raman表征方法对复合材料形貌、晶体结构进行表征,结果表明:制备的氧化钨为六方相结构的WO3,呈现一维管状形貌,石墨烯均匀分散在复合材料中.石墨烯/氧化钨复合材料涂覆在叉指电极制作成传感器进行气敏性能测试,结果表明:传感器可室温条件下实现对NO2检测,检测...     

Nickel stamp fabrication and hot embossing for mass-production of micro/nano combined structures using anodic aluminum oxide

Recently, “micro/nano combined structure” has attracted many researchers’ attentions due to its high potential in various research fields and applications such as biomimetics, tissue engineering, micro systems for biochemical analysis and so forth. The present paper proposes a simple and promising method for mass-production of the micro/nano combined structure, in particular, nano dimple array with micro structures with cost-effective procedures. Three major procedures of (a) master template fabrication; (b) nickel electroforming onto the master template; (c) replication by hot embossing process, are employed: the master template is fabricated by utilizing an anodic aluminium oxide (AAO) process and UV lithography technique; nickel stamp is then obtained by means of electroforming onto the master template; finally, micro/nano combined structures are moulded on a polymethyl methacrylate (PMMA) substrate using the nickel stamp via hot embossing. So replicated micro/nano combined structures turns out to be quite successful according to experimental observation via scanning electron microscope (SEM) and atomic force microscope (AFM).     

体积连接性指数预测离子液体的室温粘度

离子液体(ILs)被视为潜在的"绿色溶剂",在溶剂的应用过程中粘度是最重要的热力学数据之一,但目前ILs的粘度数据仍然较为缺乏,除实验测定外,基团贡献、连接性指数等思想也为设计和筛选ILs提供了重要的性质预测方法。在已有的基于分子体积的粘度预测方法基础上,结合分子连接性指数来区分ILs不同基团的连接方式,建立了一个新的体积连接性指数模型用于预测ILs的室温粘度。由于该模型的基本参数来源于确定的基团物理体积值,因此为预测未知的ILs粘度等性质提供了可能性。通过对90种ILs室温粘度的预测,结果表明平均相对偏差为5.95%,方差检验所得的R~2和rmsd分别为0.9905和21cP,证明建立的模型可用于预测ILs的室温粘度。     

Development of high sensitivity tin oxide based sensors for gas/odour detection at room temperature

An effort has been made to develop thick film tin oxide gas sensors which could detect various gases/odours at room temperature. To achieve this, the fabricated sensors were annealed in oxygen plasma for various durations. It was then found that, the room temperature sensitivity of such sensors was increased to about ten times as compared to the sensitivity of the non-annealed sensors. Further, plasma annealed sensors are found to be practically independent of temperature and the room temperature sensitivity of these sensors are found to be about 1.5 times the sensitivity of the conventional sensors at its operating temperature of 300°C. Studies on the variation of d.c. resistance, sensitivity, temporal response, current–temperature characteristics and impedance spectroscopy with the annealing time have also been made. These studies reveal that, with the increase in annealing time, there is a permanent gradual reduction in the d.c. resistance of annealed sensors. Further, it is also observed that with the increase in annealing time, the response time improves, barrier height reduces, barrier capacitance increases and the dependence of the sensitivity with temperature reduces while the sensitivity itself improves many-fold.     

Simultaneous measurement of Pb, Cd and Zn using differential pulse anodic stripping voltammetry at a bismuth/poly(p-aminobenzene sulfonic acid) film electrode

A novel sensor was developed for simultaneous detection of Pb, Cd and Zn, based on the differential pulse anodic stripping response at a bismuth/poly(p-aminobenzene sulfonic acid) (Bi/poly(p-ABSA)) film electrode. This electrode was generated in situ by depositing simultaneously bismuth and the metals by reduction at −1.40 V on the poly(p-ABSA) modified electrode. Compared with the bismuth film electrode, the Bi/poly(p-ABSA) film electrode can yield a larger stripping signal for Pb, Cd and Zn. Under the optimum conditions, a linear response was observed for Cd and Zn in the range from 1.00 to 110.00 μg L⁻¹ and for Pb in the range from 1.00 to 130.00 μg L⁻¹. The detection limits of Pb(II), Cd(II) and Zn(II) were 0.80, 0.63 and 0.62 μg L⁻¹, respectively. Finally this sensor had been applied to the simultaneous determination of Pb(II), Cd(II) and Zn(II) in river water samples and the results were quite corresponding to the value obtained by atomic absorption spectrometry.     

半导体复合氧化物的室温固相合成研究

以无机盐为原料 ,遵守热力学定律 ,室温下研磨 ,使反应物发生固相化学反应而合成CdSnO3 、ZnFe2 O4、CdFe2 O4等半导体复合氧化物的纳米粉体 ,用XRD、TEM测试手段对产物的物相和微观结构进行了表征和分析 ,结果表明 ,固相化学反应完全 ,所得产物为理论产物 ,且平均粒径小于 10 0nm。     

半导体复合氧化物的室温固相合成研究

以无机盐为原料,遵守热力学定律,室温下研磨,使反应物发生固相化学反应而合成CdSnO3、ZnFe2O4、CdFe2O4等半导体复合氧化物的纳米粉体,用XRD、TEM测试手段对产物的物相和微观结构进行了表征和分析,结果表明,固相化学反应完全,所得产物为理论产物,且平均粒径小于100?nm.     

Driving characteristics of the electrowetting-on-dielectric device using atomic-layer-deposited aluminum oxide as the dielectric

Electrowetting on dielectric (EWOD) is useful in manipulating droplets for digital (droplet-based) microfluidics, but its high driving voltage over several tens of volts has been a barrier to overcome. This article presents the characteristics of EWOD device with aluminum oxide (Al₂O₃, ε _r  ≈ 10) deposited by atomic layer deposition (ALD), for the first time as the high-k dielectric for lowering the EWOD driving voltage substantially. The EWOD device of the single-plate configuration was fabricated by several steps for the control electrode array of 1 mm × 1 mm squares with 50 μm space, the dielectric layer of 1,270 Å thick ALD Al₂O₃, the reference electrode of 20 μm wide line electrode, and the hydrophobic surface treatment by Teflon-AF coating, respectively. We observed the movement of a 2 μl water droplet in an air environment, applying a voltage between one of the control electrodes and the reference electrode in contact with the droplet. The droplet velocity exponentially depending on the applied voltage below 15 V was obtained. The measured threshold voltage to move the droplet was as low as 3 V which is the lowest voltage reported so far in the EWOD researches. This result opens a possibility of manipulating droplets, without any surfactant or oil treatment, at only a few volts by EWOD using ALD Al₂O₃ as the dielectric.     

Effect of ‘Pt’ loading in ZnO-CuO hetero-junction material sensing carbon monoxide at room temperature

Sensing of carbon monoxide (CO) was carried out with ZnO-CuO and Pt/ZnO-CuO. Synthesized materials were characterized by temperature-programmed reduction (TPR), high-resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD). The composite materials of ZnO-CuO were found to have an active sensing center, The sensor response obtained for an optimized ratio of ZnO and CuO (1:1 weight ratio) yielded the highest response of 1.28 (R_co/R_air) for 1000 ppm of CO at room temperature; the response and recovery times were found to be 41 and 86 s, respectively. However, loading 1:1 ZnO-CuO with 0.4% Pt boosted the sensor response to 2.64 (R_co/R_air) for the same CO concentration. The sensor (0.4% Pt/ZnO-CuO) response was linear towards CO concentrations between 100 and 1000 ppm. In the Pt loaded case both the response and recovery times were found to be 81 s. A mechanism for CO sensor response was put forward with reference to CO adsorption and desorption.     

Synthesis of ScAlN thin films on Si (100) substrates at room temperature

Microsystem Technologies - Scandium aluminum nitride alloy (ScAlN) thin films have been synthesized using reactive sputtering of a scandium aluminum alloy (Sc0.40Al0.60) target on Si (100)...     

Effects of anodization parameters on the corrosion resistance of 6061 Al alloy using the Taguchi method

Microsystem Technologies - Anodizing 6061 aluminum alloy (AA6061) in a H2SO4 electrolyte solution is a crucial process in the formation of anodic aluminum oxide (AAO) film for enhancing the...     

Sensing of CO2 at room temperature using work function readout of (hetero-)polysiloxanes sensing layers

Organically modified silicates based on primary amino groups are known to be CO₂ sensitive, as they can undergo a reversible acid base reaction. In order to generate detectable CO₂ signals and to limit the cross-sensitivity to humidity, some sources suggest that these materials should be operated at higher temperatures (50-70 °C). In this paper, a new variant of CO₂ sensing is to be presented, namely a combination of work function readout and organically modified silicates, which yields CO₂ detection even at room temperature. Kelvin probe measurements are used for work function readout. The layers are intended to be used in a “Floating Gate Field Effect Transistors” (FGFETs) sensing platform (mySens) by Micronas. The reversible interaction of CO₂ with spin-coated heteropolysiloxane sensitive layers results in changes of the work function with typical signal heights of 15-20 mV (change from 400 to 4000 ppm CO₂) and response times of only a few minutes. Also, results will be presented regarding variations in the chemical nature of the films. The findings summarized in this paper point towards the possibility of a new room temperature CO₂ sensor, which comprises fast response times and sufficient sensitivity for ambient CO₂ variations.     

Absolute potential analysis of the mixed potential occurring at the oxide/YSZ electrode at high temperature in NOx-containing air

Mixed potential phenomena occurring at the oxide/YSZ electrode in the presence of NO_x-containing air is explained in terms of the absolute potential model, which demonstrates how maintaining a non-equilibrium state with gas phase, through catalytic inactiveness of the electrode, is important to obtain a noticeable EMF response to NO₂ and NO. The directions of the EMF response of oxide electrodes to NO and NO₂ gas are coincident with the prediction from the absolute potential analysis. Simulated results of anodic and cathodic currents for Pt electrode clearly show the insensitivity to NO₂ and NO as suggested in the analysis.     

常温下氧化钨基NO2传感器气敏特性的光照强度依赖研究

为了研究WO3的常温气敏性能,以热氧化钨丝的方法制备WQ3纳米材料并制作厚膜气敏元件,通过XRD对材料的晶体结构进行表征,对敏感元件进行了气敏性能测试,测得该元件在常温、0.4W/cm2紫外光(波长:300～450nm)辐照条件下对50ppm的NO2的灵敏度S=15.4,响应时间τres=2.5s,恢复时间τrec=18.1s;在加热功率为0.81W条件下,元件对50ppm NO2的灵敏度为S=22.5,响应时间τres=1.5s,恢复时间τrec=10.7s,研究了灵敏度对光功率密度和加热功率的依赖关系,实验结果表明WO3纳米材料在常温、紫外光照条件下对NO2具有较好的气敏性能.     

Effect of temperature in selective buried oxide TFET in the presence of trap and its RF analysis

This work explores the temperature associated reliability issues of selective buried oxide (SELBOX) TFET. The proposed device is optimized for maximum I_ON/I_OFF ratio considering various gap positions in the buried oxide. The variation of DC parameters such as I_D‐V_GS characteristics, subthreshold swing (SS) and I_ON/I_OFF ratio for a wide range of temperature from 300 K to 500 K has been studied. The proposed SELBOX device is compared with conventional silicon‐on‐insulator device considering various RF parameters. Moreover, the dependency of RF performance of the proposed device on temperature has been examined. The variation of RF parameters such as transconductance (g_m), cut‐off frequency (f_T), gate capacitance (C_GG), intrinsic delay and transconductance frequency product (TFP) with temperature has also been studied. The linearity of the device has been explored by analyzing the influence of temperature variation on 1‐dB compression point. Further, temperature dependency in the presence of quantum correction (QC) model has been analyzed.