Date of Award

2007

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Physics

Advisor

Rosemary L. Smith

Second Committee Member

Scott D. Collins

Third Committee Member

Robert J. Lad

Abstract

In this thesis, a new multi-parameter Field Effect Gas sensor (GasFE) using Semiconducting-Metal-Oxide (SMO) films was developed and studied. The sensor integrates a field effect gas sensor based on Metal-Oxide-Semiconductor (MOS) capacitor and a chemiresistor. In this work, firstly, the work functions of tungsten oxide thin films were studied by in situ electron spectroscopy. The thin films were deposited by reactive Radio Frequency (RF) magnetron sputtering technique at elevated temperatures. Ultraviolet Photoelectron Spectroscopy (UPS) and X-ray Photoelectron Spectroscopy (XPS) were employed to measure the work function values and study the electronic structures of tungsten oxides. The results show that tungsten oxide thin films are excellent candidates for GasFET sensors that operate using a work function change mechanism. Secondly, a new transducing platform using micro InterDigitated Electrodes (IDE) to form the MOS gate electrode was fabricated using microtechnology. The platform has the capability of monitoring changes of work function, conductivity, and/or effective capacitance of the sensing film using a single device. Tungsten oxide thin film was deposited as the sensing element on the micro IDE and the resulting sensor was tested and studied using Resistance-Voltage (RV) and Capacitance-Voltage (CV) methods. Our results show that the novel GasFE sensor inherits all the advantages of the traditional GasFET sensors, such as IC compatibility, low power consumption, and high sensibility. Moreover, it even over weighs the prevalent GasFET sensors based on its advantages such as versatility and simplicity.

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