Investigation on Sensing Performance of Highly Doped Sb/SnO2.

Zhifu Feng,Soufiane Krik,Vincenzo Guidi,Stefano Caramori,Barbara Fabbri,Lia Vanzetti,Simona Fioravanti,Matteo Valt,Michele Della Ciana,Andrea Gaiardo,Davide Casotti,Alberto Rota

doi:10.3390/s22031233

Abstract

Tin dioxide (SnO2) is the most-used semiconductor for gas sensing applications. However, lack of selectivity and humidity influence limit its potential usage. Antimony (Sb) doped SnO2 showed unique electrical and chemical properties, since the introduction of Sb ions leads to the creation of a new shallow band level and of oxygen vacancies acting as donors in SnO2. Although low-doped SnO2:Sb demonstrated an improvement of the sensing performance compared to pure SnO2, there is a lack of investigation on this material. To fill this gap, we focused this work on the study of gas sensing properties of highly doped SnO2:Sb. Morphology, crystal structure and elemental composition were characterized, highlighting that Sb doping hinders SnO2 grain growth and decreases crystallinity slightly, while lattice parameters expand after the introduction of Sb ions into the SnO2 crystal. XRF and EDS confirmed the high purity of the SnO2:Sb powders, and XPS highlighted a higher Sb concentration compared to XRF and EDS results, due to a partial Sb segregation on superficial layers of Sb/SnO2. Then, the samples were exposed to different gases, highlighting a high selectivity to NO2 with a good sensitivity and a limited influence of humidity. Lastly, an interpretation of the sensing mechanism vs. NO2 was proposed.

Highlights

Air pollution is becoming increasingly severe as a result of industrial expansion and population growth
For X-ray Photoelectron Spectroscopy (XPS) and X-ray Fluorescence Spectrometer (XRF) measurements, the powders were placed freely on double-sided carbon tape that was adhered to the aluminum sample holder; all samples were analyzed at room temperature
The surface morphology of the samples was investigated by using Scanning Electron Microscope (SEM), and the results are shown in Figure 2, where all the sample powders show a spherical-like shape

Summary

Introduction

Air pollution is becoming increasingly severe as a result of industrial expansion and population growth. Doping with noble elements can change the position of energy levels in the conduction band of SnO2, such as by doping Pd [24], Ru [25], Al [26], Pt [27], Sb [28], Ce [29], Ag [30], and Ti [31], which is a more reliable and economical way to increase the selectivity and sensitivity compared to nanostructure modification and heterojunction structure building towards the gas sensing performance optimization [6] Among these above-mentioned doping elements, Sb-doped SnO2 (ATO) acts as a transparent n-type semiconductor, which is widely employed as a transparent conducting thin film for solar cell, optoelectronic, and gas sensor material due to its quasi-metallic conductivity feature [11,32,33,34,35,36]. The sensitivity and selectivity of fabricated devices towards NO2 at different temperatures in dry and wet air were investigated

Samples Preparation

Measurement Techniques

Morphological and Elemental Studies

Gas Sensing Characterization

Gas Sensing Mechanism Discussion