Preparation And NH₃ Gas-sensing Characteristics Research Of Microstructure Silicon Sensor

Porous silicon(PS) is a kind of material with porous structure, which is prepared by etching of the silicon substrate. Because of their huge internal surface area, high activity in surface chemical reactions and easy gas molecules adsorption, porous silicon(PS) layers have attracted much attention either as a gas-sensing material or as a gas sensor substrate. In this paper, a novel microstructure silicon array(MSSA) was prepared by different silicon etching techniques on the research basis of PS, and two kinds of novel microstructure silicon ammonia(NH3) sensors with different sensitive films were designed and prepared. The main results are as follows:A novel polyaniline(PANI)/MSSA thin film sensor was developed by modifying MSSA with self-assembled PANI sensing thin film. The MSSA was fabricated by the alkaline etching and Au interdigitated electrodes were evaporated on the surface of PANI thin film. The influence of the MSSA with different height(alkaline etching time of 0min, 2min, 4min and 6min) on NH3-sensing properties was researched and compared at room temperature, and the process parameters were optimized. The results indicated that the PANI/MSSA thin film sensor exhibited superior NH3-sensing properties than PANI/plane silicon sensor. Meanwhile, the sensor with MSSA height of 400.7nm produced by 4min etching possessed the highest response, good reversibility, repeatability and selectivity when exposed to NH3. The morphology analyses revealed that, PANI nanorods mesh was deposited on all substrates surfaces, and the sample with MSSA height of 400.7nm was mainly densely covered by interleaved PANI nanorods network. It was speculated that the hemispheric morphology is more compatible with in-situ self-assembly process. The gas-sensing mechanism of PANI/MSSA thin film sensor was analyzed combined with energy band theory and the gas-sensing model was established.A novel pentacene/MSSA thin film sensor was fabricated combined the reactive ion etching(RIE) of the plane silicon and vacuum evaporation of pentacene. The NH3 sensing properties and gas-sensing mechanism were preliminarily studied. It was found that height of the MSSA had important effects on gas-sensing performances of sensors. The characteristics of sensors with four different height of MSSA(with etching time of 1.5min, 3min, 4.5min, 6min) were compared, and it was found that the sensor with the MSSA height of 684.8nm(etching time 4.5min) showed the optimal gas-response properties, as well as the superior repeatability and selectivity. The SEM images showed the MSSA exhibited a uniform cylinder array, and pentacene nano-particles film was formed evenly on the MSSA surface, which can significantly improve the gas-sensing properties. The gas-sensing mechanism of pentacene/MSSA thin film sensor was analyzed.