Publication Date
2019
Document Type
Dissertation/Thesis
First Advisor
Xu, Tao
Degree Name
Ph.D. (Doctor of Philosophy)
Legacy Department
Department of Chemistry and Biochemistry
Abstract
A program of research was undertaken to develop the next generation of metal oxide gas sensors, which, for the purpose of this research, were made from materials using a unique approach of glancing angle deposition (GLAD) that is scalable to large scale production. This research seeks to demonstrate that high-sensitivity sensors can be produced. The sensors were examined in a test system of novel design in which the units underwent performance measurements using analyte gases, such as carbon dioxide, nitrogen, and water.
Gas sensors can be improved by increasing the surface area of the active sensing media, and in this research the active surface is increased by forming the active material that is made of NiO into 1D nanopillars. A unique technique, which integrates magnetron sputtering with a variant of GLAD to deposit an array of NiO nanopillars, is described. The deposition angle is increased to 90° (i.e., the magnetron gun axis is parallel to the target surface), and reactive sputtering is used to make NiO nanostructures. The nanopillars made by fully orthogonal glancing angle deposition (“ortho-GLAD”) are produced by NiO adatom scattering above the surface sample. In the study, different materials (i.e., Al, Nichrome A, Sn, and NiO) were tested to see if nanopillars could be made. Other investigators believe that there is a relationship between the length of the pillar and its width, so by using a plasma on the sample, the researcher investigated whether the width can be modified independently of the length by changing the adatom surface mobility. The coatings were analyzed using SEM, EDS, and XRD and show the composition and morphology of the materials.
The research also describes the performance of an NiO gas sensor that was composed of an array of nanopillars. These nanopillars were made using a combination of GLAD and reactive sputtering. The material was analyzed using a number of characterization techniques, which identified it to be nearly stoichiometric NiO. Measurements of the nanopillars show them to be 50 nm across with lengths of 400 nm. Sensors were made using this process and were tested using carbon dioxide, ethanol, nitrogen, and water vapor. The threshold of sensing for CO2 is 1.6 × 10˗3 torr at 305 °C, 6 × 10˗4 torr at 310 °C for ethanol, and 6 × 10˗4 torr at 330 °C for water vapor.
Recommended Citation
Walters, Dean R., "Studies on Semiconductor Gas Sensors Using Nanostructure Growth Employing Ortho-Glancing Angle Deposition" (2019). Graduate Research Theses & Dissertations. 7763.
https://huskiecommons.lib.niu.edu/allgraduate-thesesdissertations/7763
Extent
135 pages
Language
eng
Publisher
Northern Illinois University
Rights Statement
In Copyright
Rights Statement 2
NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.
Media Type
Text
