Document Type

Thesis - Open Access

Award Date

2026

Degree Name

Master of Science (MS)

Department / School

Electrical Engineering and Computer Science

First Advisor

David W. Galipeau

Abstract

Homeland security, clinical diagnosis, food analysis, cosmetics and air quality are among the many rapidly growing areas where odor detection is an important concern. The electronic nose ( e-nose) is the most common technology for measuring odor. However, its performance is limited by the poor sensitivity, selectivity, and stability of the sensing elements. A new theory of biological olfaction, which postulates that the sense of smell is based on inelastic electron tunneling spectroscopic (IETS), suggests that it is possible to dramatically improve the performance of gas sensor arrays. However, tunnel junctions for IETS based devices have not been studied as room temperature gas sensors. The objective of this work was to develop an IETS gas sensor that can be used at room temperature in an electronic nose system. Tunnel junction sensors for performing IETS were fabricated with overlapping and crossover designs using grown and sputterdeposited oxide layers, and with field enhanced oxidation. The crossover tunnel junction design appears to be the most promising since IET spectra of SiO2 lattice vibrations, water and methanol were obtained at room temperature. The spectral peak positions were similar to those measured at 4 K; however, the peaks were broader due to temperature and repeatability was limited. A digital (DSP) lock-in amplifier was found to be superior for IETS measurements versus an analog lock-I amplifier and I-V measurement system. Future work should include fabricating devices without breaking the vacuum to reduce impurities in the junction, thereby improving device yield, and stability. It should also include examining other materials and process for forming the oxide layer to improve spectral reproducibility.

Library of Congress Subject Headings

Gas detectors 
Chemical detectors 
Tunneling spectroscopy 
Electron spectroscopy 
Olfactometry

Publisher

South Dakota State University

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Rights Statement

In Copyright