Ultrathin Elementary Te Nanocrystalline Films Prepared by Pure Physical Method for NO 2 Detection

Detection characteristics of elementary tellurium (Te) nanocrystalline thin film for nitrogen dioxide (NO 2 ) gas detection are presented. An electron beam evaporation method (eBE) was used to deposit elementary Te ultrathin nanocrystalline films at room temperature, with the thickness from 10 nm to 40 nm. An intermittent deposition method was employed to regulate the distribution of grains during the whole film deposition process. A type of compact and continuous nanocrystalline film structure was confirmed by x-ray diffraction and transmission electron microscopy analysis. Such a structural feature of thin films is able to provide a continuous grain boundary, which can increase the surface-to-volume ratio and further improve the sensitivity of the sensors. The effects of film thickness and gas concentration with respect to the sensor performance have been evaluated. The sensor presents a ppm (parts per million)-level NO 2 detection limit in an atmospheric environment, and the maximum sensitivity is up to 7.926 × 10 5 ppm −1 . In addition, a complete evaluation demonstration system was developed for a NO 2 concentration real-time monitor, which provides the possibility for the sensor to be applied to actual environmental monitoring.