Ya Dong Jiang

Fabrication and Formaldehyde-Sensing Property of Quartz Crystal Microbalance (QCM) Coated with PVP-MWCNTs Composites

In this paper, the quartz crystal microbalance (QCM) sensors coated with polyvinyl pyrrolidone (PVP)-multiwalled carbon nanotubes (MCWNTs) nanocomposite thin films were developed by the spray process, which were used for the detection of low concentration formaldehyde at room temperature. The surface morphology and structure of films was analyzed by scanning electron microscope (SEM), UV-Vis absorption spectrometry, respectively, and the formaldehyde-sensing properties of sensors were investigated. The results showed that the prepared QCM gas sensor exhibited the linear characteristic, fast response, good reproducibility to low concentration formaldehyde within 6 ppm, and the poisoning of films was observed when the formaldehyde concentration exceeded 6ppm. Moreover, the sensitivity of the sensor could achieve up to 1Hz/ppm and had the good stability of response values.

The Investigation of a Novel Large-Strain Sensor Based on a Dual Capacitive Structure

In this paper, a novel large-strain sensor based on a dual planar capacitive structure has been developed. It has the capacity of large-strain measurement up to 200,000 με (0.2 ε). The change in strain causes a measurable transformation in the capacitance of the sensor by relative shift of the overlap area between two capacitive plates, one fixed (i.e. fixed plate) and the other one movable (i.e. movable plate), and is thus converted into a voltage signal by a read-out circuit module. The dual capacitor structure was designed for increasing the initial capacitance and improving the resolution of sensors compared with a single capacitor structure. The experimental results showed that the sensor had a linearity of 2.29% full scale (FS), a hysteresis error of 1.146%FS, repeatability of 0.226%FS and a resolution of 0.5%FS, suggesting excellent performance of the sensor.

Effect of Annealing Oxygen Flow Rate on the Properties of Vanadium Oxide Films Deposited by Reactive Magnetron Sputtering

Vanadium oxide films were prepared on indium-tin oxide glass substrates at low temperature by means of reactive direct current magnetron sputtering and subsequent in-situ annealing process in pure oxygen ambient. In the process of annealing, the oxygen flow rates were varied from 0 to 15 SCCM in order to investigate the effect of annealing oxygen flow rates on the properties of the deposited films. The experimental results indicate that only the vanadium oxide films annealed under relatively high oxygen flow rates (≥ 0.8 SCCM) displayed insulator-metal transition. In addition, it was found that vanadium valence states, surface morphology, optical transmittance and phase transition temperature of the deposited films were sensitive to the annealing oxygen flow rates while the width of thermal hysteresis was relatively insensitive to the annealing oxygen flow rates.

Comparison of Hydrogen Sulfide Sensing Properties between Multiple-Walled Carbon Nanotubes (MWNTs) and MWNTs-HAuCl4 Materials

The rapid and precise detection of hydrogen sulfide (H2S) has great significance due to its high toxicity. In this work, the response properties of multiple-walled carbon nanotubes (MWNTs) and MWNTs-HAuCl4 to H2S at room temperature were compared. Scanning electron microscopy (SEM) technique was used to characterize MWNTs and MWNTs-HAuCl4 films. It was found that sensors with MWNTs-HAuCl4 exhibited much higher response value. On the other hand, sensors with MWNTs were observed to have faster response time and better recovery properties.

Surface Passivation of Crystalline Silicon by a-Si:H Thin Films

Surface passivation of c-Si by a-Si:H thin films has been studied. In this paper, the minority carrier lifetime of 345μs (from 85μs) is obtained at optimal hydrogen flow rate (8.0sccm) by using RF-magnetron sputtering method.

Formaldehyde Detection Based on P3HT/InSnO Composite Thin Film Transistor

Formaldehyde, a colorless and pungent-smelling gas, had been confirmed be a huge threat to people health. The detection of formaldehyde was necessary and important at room temperature. Sprayed P3HT/InSnO composite film based on organic thin film transistors (OTFT) was fabricated to detect formaldehyde at room temperature in this paper. The results showed that P3HT/ InSnO-OTFT showed better response and recovery to HCHO compared with P3HT-OTFT at room temperature.

Preparation of Ethanol-Sensing Gas Sensor Based on PECH/Multi-Wall Carbon Nanotubes Sensitive Films

Abstract: In this paper, Polyepichlorohyron(PECH)/multi-wall carbon nanotubes(MWCNTs) composite films and PECH/multi-wall carbon nanotubes twolayer film were deposited on interdigitated electrodes by airbrush technology to detect ethanol vapor of various concentrations at room temperature. Thickness and structure of the film were taken into account, so films of different thicknesses and with different structures were prepared respectively. The responses of the sensors to ethanol showed that composite film had a higher response thantwolayer film, and the thick composite film performed better than its counterpart when they were exposed to ethanol vapor.

Study on Reactive Ion Etching of Vanadium Oxide Thin Film by Taguchi Method

A high selectivity patterning technology of vanadium oxide (VOx) thin film was suggested in this paper. VOx thin film was etched through a photoresist (PR) mask using Cl/N based gases in a reactive ion etching (RIE) system. Taguchi method was used for process design to identify factors that influence the patterning and find optimum process parameters. Experimental results suggested that RF power was the largest contribution factor for VOx etch rate, PR selectivity and uniformity on 6 inch diameter wafer. Uniformity and PR selectivity were improved by introducing a small amount of N2. High resolution and low roughness patterning transfer was achieved with a non uniformity of 2.4 %, an VOx etch rate of 74 nm/min, a PR selectivity of 0.96, a Si3N4 selectivity of 5 and a SiO2 selectivity of 10.

Development and Property Investigation of a Large-Scale Strain Sensor by Grating Moiré Fringe Method

A large-scale strain sensor for measuring the strain between 0~0.2ε has been developed using grating moiré fringe in this work. The gallium arsenide near-infrared solid-state light-emitting diode was used for light source of the sensor, and photodiode array sensor was chosen for the photodetector. The signal received was converted into digital pulses for the output by the signal processing system and displayed. The results indicated that the fabricated large-scale strain sensor showed the good linearity and repeatability, and low hysteresis. Strain sensitivity of 620ε-1 and a minimum strain of 0.004 ε can be achieved.

Reactive ion etching and OES endpoint detection of AlCu thin film

Patterning of AlCu alloy thin films is a key technology in MEMS fabrication. In this paper, reactive ion etching (RIE) process of Al-1%Cu films was described using BCl3 and Cl2 as etching gases and N2 and CH4 as neutral gases. A four-step process was presented to meet the etching requirements using BCl3, Cl2, N2 and CF4 as process gases. Optical emission spectroscopy (OES) was used to monitor the state of the plasma in real time. The etching endpoint was detected by detecting the spectral intensity change in the wavelength range of 395 ~ 400nm.