| Abstract |
The scope of this master thesis is the fabrication of an apparatus which produces
ZnO films by Aerosol Spray Pyrolysis and the investigation of ozone sensitivity of
them.
Initially, there is a brief reference to the basic sensor types for oxidation gases
(Ο3, ΝΟ2, CO2) and the operating principles of each category with emphasis to
the resistive-mode semiconducting metal oxide films.
Secondly, the gas sensing mechanisms on the surface of deposited ZnO films
was reported in details. Apart from the presentation of all possible gas sensing
mechanisms, it is also presented the common instability and degrading factors
associated with ZnO semiconducting oxides films as moisture and the catalysts’
effects.
Then follows the experimental part where are hereby described and compared
with the main methods of manufacture of gas sensors based of metal oxides and
specifically the technical CVD (Chemical Vapor Deposition) which variant of
constitute the technical ASP (Aerosol Spray Pyrolysis) and with which we
prepared zinc oxide films for this work. It is followed by analytical description of
methods of growth of provision ASP that was manufactured in the frames of this
work and determination of most optimal deposition conditions of zinc oxide films
as ozone sensors.
In addition there is an extensive description of attributes of zinc oxide, with
regard to electronic and crystal structure and how these characteristics affect the
ozone sensitivity of films. Also we investigate the defect of different
constructional parameters of films: as the thickness, geometrical shape of
deposition area, the form of their electric contacts, crystalline size, and ratio of
volume to surface (porosity), to ozone response.
Then are described the methods that were used for films surface characterization
(Scan Electron Microscopy - SEM), and crystallographic characterization (XRD
and Transmittion Electron Microscopy of Passage - TEM). Determination of zinc
oxide films response in ozone via the quotient of intensity of films at the different
stages of oxidation in flow of synthetic air with different concentrations of ozone
at the room temperature and reduction under UV irradiation. Special apparatus
and system of benefit and recording of different concentrations of ozone were
manufactured for these electric measurements.
Finally in this work we concluded that the manufacture of provision of deposition
of zinc oxide films (ASP) sensitive in ozone is successful. Zinc oxide films
prepared with this technique presents to have minimal limit of ozone detection in
the exceptionally small concentration of 16 ppb (parts per billion) in flow of
synthetic air at room temperature the lowest ever reported in the open literature
|
Εναπόθεση λεπτών υμενίων ZnO με την τεχνική spray pyrolysis και η ευαισθησία αυτών σε Οζον
