CeO2掺杂对ZnO薄膜气敏特性的影响

ZnO薄膜进行CeO2掺杂,研究掺杂含量和热氧化对薄膜结构、表面、晶粒尺寸及气敏特性的影响.结果显示,用热蒸发制备的高纯Zn膜经500℃热氧化,获得c轴取向ZnO多晶薄膜.掺CeO2可抑制晶粒生长使颗粒细化平均粒径减小,同时改善了ZnO薄膜的体相化学计量比,Zn与O的比例从未掺杂时1∶1.28降到1∶1.191.XPS...     

稀土Nd掺杂纳米ZnO薄膜气敏特性

研究了用真空气相沉积法在玻璃衬底上制备掺稀土Nd的ZnO薄膜的气敏特性,实验给出,经温度为500℃,时间为45min的氧化、热处理的掺Nd的ZnO薄膜的晶粒尺寸、结构特性均发生变化。随掺Nd质量分数的增大,薄膜的晶粒尺寸从53nm减小至20nm。经掺Nd(质量分数为4.96×10-2)后纳米ZnO薄膜对乙醇气体的选择性和灵敏性均得到明显的改善。在1.5×10-3体积分数的乙醇气体中最高灵敏度为34,相应的薄膜工作温度为200℃。     

Fabrication and characteristics of ZnO thin films deposited by RF sputtering on plastic substrates for flexible display

ZnO thin films were successfully grown on flexible plastic substrates using radio-frequency mag-netron sputtering method at room temperature.The effects of the sputtering power on the quality of the ZnO films have been investigated.The results show that thin films were polycrystalline,with wurtzite structure and a strong preferred c-axis orientation (002).The root-mean-square (rms) surface roughness of the ZnO thin films is 22.1 nm.The ZnO thin films fabricated by sputtering with 70 W sputtering power have a high mobility of 34.33 cm 2 /V·s.The ZnO films are shown to be compatible with flexible display on plastic substrates.     

Hydrothermal synthesis of hierarchical nanoparticle-decorated ZnO microdisks and the structure-enhanced acetylene sensing properties at high temperatures

Nanoparticle-decorated ZnO microdisks showing a hierarchical structure were successfully synthesized through a citric acid-assisted hydrothermal process. The ZnO microdisks had a hexagonal wurtzite structure with high crystallinity. Sensors based on these microdisks exhibited high response values, fast response-recovery, good selectivity and long-term stability to 1-4000 ppm acetylene at 420 °C. In addition, even 1 ppm acetylene can be detected with high response (S = 7.9). The hierarchical structure can facilitate to fix the ZnO nanoparticles leading to a less aggregated configuration, which is expected to contribute much to the excellent acetylene sensing properties at high temperatures.     

The influence of the surface morphologies of Langmuir Blodgett (LB) thin films of porphyrins on their gas sensing properties

In this work, 2,3,7,8,12,13,17,18-Octaethyl-21H,23H-porphine (OEP) in its free base form and metalated with iron (III) chloride (FeOEP), magnesium(II) (MgOEP) and cobalt(II) (CoOEP) have been used to fabricate Langmuir-Blodgett (LB) thin films. Using the surface pressure-surface area (Π-A) isotherm graphs optimum conditions for thin film deposition have been determined and by changing the deposition parameters various thin films have been deposited. Quartz Crystal Microbalance (QCM) system was used to investigate their gas sensing performances during exposure to Volatile Organic Compounds (VOCs) including chloroform, benzene and toluene. The surface properties have been investigated using Atomic Force Microscopy (AFM) and analyzed together with the QCM results to understand the effect of the surface properties on gas sensing mechanism. It is observed that larger surface area leads to higher response in gas sensing applications in terms of resonance frequency change.     

Temperature dependent H2S and Cl2 sensing selectivity of Cr2O3 thin films

The conductometric gas sensing characteristics of Cr₂O₃ thin films - prepared by electron-beam deposition of Cr films on quartz substrate followed by oxygen annealing - have been investigated for a host of gases (CH₄, CO, NO₂, Cl₂, NH₃ and H₂S) as a function of operating temperature (between 30 and 300 °C) and gas concentration (1-30 ppm). We demonstrate that these films are highly selective to H₂S at an operating temperature of 100 °C, while at 220 °C the films become selective to Cl₂. This result has been explained on the basis of depletion of chemisorbed oxygen from the surface of films due to temperature and/or interaction with Cl₂/H₂S, which is supported experimentally by carrying out the work function measurements using Kelvin probe method. The temperature dependent selectivity of Cr₂O₃ thin films provides a flexibility to use same film for the sensing of Cl₂ as well as H₂S.     

Pyroelectric and dielectric properties of sol–gel derived barium–strontium–titanate (Ba0.64Sr0.36TiO3) thin films

The barium–strontium–titanate (BST, Ba_0.64Sr_0.36TiO₃) thin films have been prepared by the sol–gel method on a platinum-coated silicon substrate. The resulting thin films show very good dielectric and pyroelectric properties. The dielectric constant and dissipation factor for Ba_0.64Sr_0.36TiO₃ thin film at a frequency of 200 Hz were 592 and 0.028, respectively. The dependence of the capacitance as a function of the voltage shows a strongly non-linear character, and two peaks characterizing spontaneous polarization switching can be clearly seen in this curve, indicating that the films have a ferroelectric nature. The capacitance changed from 495 to 1108 pF with the applied voltage in the −5 to +5 V range at a frequency of 100 kHz. The peak pyroelectric coefficient at 30 °C is 1080 μC/m² K. The pyroelectric coefficient at room temperature (25 °C) is 1860 μC/m² K, and the figure-of-merit of this film is 37.4 μC/m³ K. The high pyroelectric coefficients and the greater figures-of-merit of Ba_0.64Sr_0.36TiO₃ thin films make it possible to be used for thermal infrared detection and imaging.     

A comparative study of the physical properties of CdS, Bi2S3 and composite CdS–Bi2S3 thin films for photosensor application

Thin films of CdS, Bi₂S₃ and composite CdS–Bi₂S₃ have been deposited using modified chemical bath deposition (M-CBD) technique. The various preparative parameters were optimized to obtain good quality thin films. The as-deposited films of CdS, Bi₂S₃ and composite were annealed in Ar gas at 573 K for 1 h. A comparative study was made for as-deposited and annealed CdS, Bi₂S₃ and composite thin films. Annealing showed no change in crystal structure of these as-deposited films. However, an enhancement in grain size was observed by AFM studies. In addition change in band gap with annealing was seen. A study of spectral response, photosensitivity showed that the films can be used as a photosensor.