Document Type
Thesis
Date of Award
Fall 10-31-1996
Degree Name
Master of Science in Applied Physics - (M.S.)
Department
Physics
First Advisor
Ken K. Chin
Second Advisor
Kenneth Rudolph Farmer
Third Advisor
William N. Carr
Abstract
Polycrystalline tin-dioxide is widely used in the detection of reducing gases (such as H2, CO, CH4, C2H5OH,...) in air by measuring its conductivity changes. The advantage of gas sensors based on such sensing devices is low cost and high sensitivity. In contrast to their widespread applications and to their successful empirical research and development work, the present understanding of the chemical sensing mechanisms is still immature.
In this thesis, for gas sensors based on thick and porous tin-dioxide layers, a study of the response function upon variation of the partial pressure of ethanol vapors in 100% humidified air has been carried out. The influence of the working temperature and of the water vapors on the conductivity of the sensor was particularly emphasized.
Based on our experimental data, a theoretical model of the sensing mechanism in thick and porous tin-dioxide layers is presented. The model accepts the conduction mechanism as being governed by the Schottky potential barriers at the junction between grains. For describing the adsorption of gas molecules on the solid surface a method of "conditioned adsorption" was developed. The central idea was to assume that the reducing gas molecules are "adsorbed" (i.e. react) only on pre-adsorbed oxygen. The predictions made in the frame of our theoretical model are in good agreement with the experimental data.
Recommended Citation
Fluerasu, Andrei A., "Surface phenomena on the Tin-dioxide polycrystalline layers" (1996). Theses. 1089.
https://digitalcommons.njit.edu/theses/1089
