Keywords
SnO2, FTIR, nanomaterials, gas sensors
Abstract
Nanocrystalline metal/metal oxide is an important class of transparent and electronic materials due to its potential use in many applications, including gas sensors. At the nanoscale, many of the phenomena observed that give nanocrystalline semiconducting oxide enhanced performance as a gas sensor material over other conventional engineering materials is still poorly understood. This study is aimed at understanding the low temperature electrical and chemical properties of nanocrystalline SnO2 that makes it suitable for room temperature gas detectors. Studies were carried out in order to understand how various synthesis methods affect the surfaces on the nano-oxides, interactions of a target gas (in this study hydrogen) with different surface species, and changes in the electrical properties as a function of dopants and grain size. A correlation between the surface reactions and the electrical response of doped nanocrystalline metal-oxide-semiconductors exposed to a reducing gas is established using Fourier Transform Infrared (FTIR) Spectroscopy attached to a specially built custom designed catalytic cell. First principle calculations of oxygen vacancy concentrations from absorbance spectra are presented. FTIR is used for effectively screening of these nanostructures for gas sensing applications. The effect of processing temperature on the microstructural evolution and on the electronic properties of nanocrystalline trivalent doped-SnO2 is also presented. This study includes the effect of dopants (In and Ce) on the growth of nano-SnO2, as well as their effects on the electronic properties and gas sensor behavior of the nanomaterial at room temperature. Band bending affects are also investigated for this system and are related to enhanced low temperature gas sensing. The role and importance of oxygen vacancies in the electronic and chemical behavior of surface modified nanocrystalline SnO2 are explored in this study. A generalized explanation for the low temperature gas sensor behavior of nanocrystalline oxide is presented that can be generalized to other nano-oxide systems and be useful in specific engineering of other nanomaterials. Deeper understanding of how nano-oxides react chemically and electronically would be extremely beneficial to issues present in current low cost, low temperature sensor technology. Ability to exactly monitor and then engineer the chemistry of nanostructures in the space charge region as well as the surface is also of great significance. Knowledge of the mechanisms responsible for enhanced sensor response in this material system could viably be applied to other material systems for sensor applications.
Notes
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Graduation Date
2007
Semester
Summer
Advisor
Seal, Sudipta
Degree
Doctor of Philosophy (Ph.D.)
College
College of Engineering and Computer Science
Department
Mechanical, Materials, and Aerospace Engineering
Degree Program
Materials Science and Engineering
Format
application/pdf
Identifier
CFE0001668
URL
http://purl.fcla.edu/fcla/etd/CFE0001668
Language
English
Release Date
April 2008
Length of Campus-only Access
None
Access Status
Doctoral Dissertation (Open Access)
STARS Citation
Drake, Christina, "Understanding The Low Temperature Electrical Propertiesof Nanocrystalline Sno2 For Gas Sensor Applications" (2007). Electronic Theses and Dissertations. 3147.
https://stars.library.ucf.edu/etd/3147