Temperature‐ and Atmosphere‐Dependent Defect Chemistry Model of SnO₂ Nanocrystalline Film

Abstract

By combining the concept of defect chemistry and the smallpolaron hopping conduction model, the present work takes an intensively considering of the electron conduction mechanism in the nonstoichiometric SnO 2 nanocrystalline film. The temperature-dependent and atmosphere-dependent relationship between the electrical conductivity and the defect reaction is outlined. To investigate the influence of temperature and atmosphere on the electrical properties of the SnO 2 nanocrystalline film, a temperature-programmed system integrated with the high-throughput screening platform of gas-sensing materials (HTSP-GM) is developed as the test tool in this work. With this platform, the temperature-dependent conductivity of SnO 2 nanocrystalline film in different atmosphere (dry air, nitrogen, and formaldehyde) was conducted. A good fit between the theoretical deductions and experimental results is achieved.

Effect of Nickel Vacancies on the Room-Temperature NO2 Sensing Properties of Mesoporous NiO Nanosheets

“…It is generally assumed that a thermally acitivated small-polaron hopping mechanism can be well used to depict the hole transport property in such defect-rich metal oxides. 49 On the basis of our previous studies, 50 the motion of free carries in metal oxides can be divided into three steps, including the ionization of defects, the hopping of carriers from defect wells, and the motion of ionized free carriers. Accordingly, the motion of holes in p-type NiO can also be divided into similar steps as shown in Figure 10, including the ionization of nickel vacancies, the hopping of the holes from well, and the motion of ionized holes.…”

A new method in the gas identification by using MOS gas sensor based on the temperature-programmed technique

“…[5] In this work, a 36-matrices flat-type material chip was used to load the sensor films, the specific fabrication process can refer to our previous work. [3] …”

“…The R-T curves of the sensor films in different atmospheres were obtained at a heating rate (β) of 10 K/min under a flow rate of 1000 mL/min of the test gas over a temperature range of 300-700 K. The whole tests were taken in the high throughput screening platform of the gas sensing materials (HTSP-GM) integrated with the temperature-programmed system. [3] …”

“…Since WO 3 with a band gap of about 2.6 eV, intrinsic excitation (valence band to conductance band) at the test temperature range (300 to 700 K) can be ignored and the defect ionization is believed to be responsible for the electrical variations. Furthermore, the most common defects in the nonstoichiometric WO 3 ). [4] Therefore, the main defect reactions with temperature increase from 300 to 700K in the nitrogen and dry air atmospheres are concluded in Table1.…”

“…Fortunately, our research group recently proposed a method that enabled to examine the temperature-dependent conductivity of the MOS films real-time in different atmospheres by utilizing the high throughput screening platform of the gas sensing materials (HTSP-GM) integrated with the temperature-programmed system. [3] By using this platform, we report a breakthrough solution based on the temperature-dependent electrical conductivity (TEC) spectra obtained through programmed changing the heating temperature of the MOS sensor film in different atmospheres. Furthermore, WO 3 is chosen as a model sensor material in this work due to the existence of valence transition (…”