Structure, Surface Morphology, Chemical Composition, and Sensing Properties of SnO2 Thin Films in an Oxidizing Atmosphere.

Weronika Izydorczyk,Jacek Izydorczyk

doi:10.3390/s21175741

Abstract

We conducted experiments on SnO2 thin layers to determine the dependencies between the stoichiometry, electrochemical properties, and structure. This study focused on features such as the film structure, working temperature, layer chemistry, and atmosphere composition, which play a crucial role in the oxygen sensor operation. We tested two kinds of resistive SnO2 layers, which had different grain dimensions, thicknesses, and morphologies. Gas-sensing layers fabricated by two methods, a rheotaxial growth and thermal oxidation (RGTO) process and DC reactive magnetron sputtering, were examined in this work. The crystalline structure of SnO2 films synthesized by both methods was characterized using XRD, and the crystallite size was determined from XRD and AFM measurements. Chemical characterization was carried out using X-ray photoelectron (XPS) and Auger electron (AES) spectroscopy for the surface and the near-surface film region (in-depth profiles). We investigated the layer resistance for different oxygen concentrations within a range of 1–4%, in a nitrogen atmosphere. Additionally, resistance measurements within a temperature range of 423–623 K were analyzed. We assumed a flat grain geometry in theoretical modeling for comparing the results of measurements with the calculated results.

Highlights

The surface deposition of semiconductor metal oxides, such as SnO2, TiO2, ZnO, In2 O3, and WO3, is used to create sensitive films for gas sensors [1,2,3,4,5,6]
We present our results on the structure and surface morphology, chemical composition, and sensing properties of both types of synthesized SnO2 thin films
270 °C [33], in2 of the qualitative analysis revealed that theatcrystalline which appropriate potential chemical reactions responsible for the sensor response changes layer was deposited on quartz or on alundum ceramics

Summary

Introduction

The surface deposition of semiconductor metal oxides, such as SnO2 , TiO2 , ZnO, In2 O3 , and WO3 , is used to create sensitive films for gas sensors [1,2,3,4,5,6]. Oxygen on top of such surface layers is an essential part of the system because it is highly reactive [7,8,9,10,11]. Oxygen absorbed on a layer’s surface reduces its conductance, emergence, and rises its work function (in the range of 423–723 K) [12,13]. The SnO2 layer properties are crucial in determining the interaction of gas with the surface and, developing new sensors. Sensors are able to work in the temperature range of 420–720 K at 1 atm pressure in an atmosphere with high concentrations of oxygen. Under such conditions, surface oxygen frequently reacts with atmospheric gas

Methods

Results

Conclusion