Abstract
Nanocrystalline and amorphous nanostructured tellurium (Te) thin films were grown and their gas-sensing properties were investigated at different operating temperatures with respect to scanning electron microscopy and X-ray diffraction analyses. It was shown that both types of films interacted with nitrogen dioxide, which resulted in a decrease of electrical conductivity. The gas sensitivity, as well as the response and recovery times, differed between these two nanostructured films. It is worth mentioning that these properties also depend on the operating temperature and the applied gas concentration on the films. An increase in the operating temperature decreased not only the response and recovery times but also the gas sensitivity of the nanocrystalline films. This shortcoming could be solved by using the amorphous nanostructured Te films which, even at 22 °C, exhibited higher gas sensitivity and shorter response and recovery times by more than one order of magnitude in comparison to the nanocrystalline Te films. These results were interpreted in terms of an increase in disorder (amorphization), leading to an increase in the surface chemical activity of chalcogenides, as well as an increase in the active surface area due to substrate porosity.
Highlights
Tellurium (Te) is a multifunctional chemical element used for the development of many devices, such as diodes with high (106) rectification ratios, thin-film field-effect transistors, optical recording media, infrared and UV detectors, strainsensitive devices and others
Even though Te has a biological relevance, it is largely used in the development of thin films in chemicalsensing applications, especially for toxic gas sensing
It was expected that the physical properties, including the adsorptive ones, of these films would differ from each other and from those observed in the microcrystalline Te-based films. This assumption, previously mentioned in our review paper [29], was confirmed by our results presented in Figure 3, which shows the normalized response kinetics to the target gas NO2 when in contact with microcrystalline, nanocrystalline or amorphous nanostructured Te-based films
Summary
Tellurium (Te) is a multifunctional chemical element used for the development of many devices, such as diodes with high (106) rectification ratios, thin-film field-effect transistors, optical recording media, infrared and UV detectors, strainsensitive devices and others (see [1,2] for extended reviews on the topic). Te has become an attractive element with great biological applicability since it can be used as quantum dots in imaging and diagnostics and has antibiotic properties [3]. Even though Te has a biological relevance, it is largely used in the development of thin films in chemicalsensing applications, especially for toxic gas sensing. Szaro [4] pioneered the studies regarding the effects of oxygen and nitrogen, diluted in either dry or wet air, on the electrical properties of Te films.
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