Controlling the Properties of a-ZTO and a-IGZO via Low Temperature Annealing and Novel Layered Structures
Citation:
Kaisha, Aitkazy, Controlling the Properties of a-ZTO and a-IGZO via Low Temperature Annealing and Novel Layered Structures, Trinity College Dublin, School of Physics, Physics, 2022Download Item:
Abstract:
This thesis deals with the broader implications of amorphous ZnSnO
(a-ZTO) growth via two synthesis methods, examining the in-situ
resistivity monitoring approach to optimising a low-annealing temperature
<300 ?C and exploring oxide-oxide lamination system is to
control the properties of TCOs.
Chapter 4 describes the effects of reactive and nonreactive sputtering
methods on the growth of a-ZTO. Two techniques broadly correspond
to an oxygen-poor and rich atmosphere. Both approaches lead to identical
conductivities of a-ZTO films. The best properties are found in
two distinct compositions. The elemental ratio shifts were found to be
due to shifts in local bond arrangements. These local bond arrangements
were confirmed by Raman spectroscopy. This demonstrates the
complex relationship between growth conditions and oxygen structure
in a-ZTO.
I will then discuss in-situ post-deposition annealing to improve the
conductivity of a-ZTO films at lower annealing temperature <300 ?C.
The optimal conditions for annealing were examined via a specialist
system that allowed in-situ monitoring of the resistivity in the annealing
process. The system also allows for control of the annealing
atmosphere. This setup examined the impacts of different annealing
parameters on final film properties. The parameters examined
include the gas composition of the annealing atmosphere, the relationship
between annealing time and temperatures, and the thickness
of the films. A lower annealing point of 220 ?C temperature was identified
that produced similar conductivities to those attained at a higher
temperature of 300 ?C. The successful post-deposition treatment with
a highly conductive film on a Kapton substrate demonstrated the benefits
of a well-controlled annealing approach.
Chapter 5 explored a layered structure to achieve a low carrier density
of TCOs. This method involved inserting an ultra-thin layer
of an alternative oxide between two TCO material layers. Two common
ultra-thin TCOs and insulators were used to examine the layered
structures. SiOx used as one of the layers in the trilayer that showed
a marked decrease in carrier density in the insertion of SiOx in the
laminated films. The free carrier density of a-ZTO/SiOx/a-ZTO declined
by a factor of three compared to a similar thickness a-ZTO,
but just 40% of reduction in carrier mobility was found. The insertion
of TiOx layers into the laminated oxides was also investigated in
a similar tri-layer arrangement. Although the TiOx layer suppressed
the density of current carriers less effectively compared to the layer
of SiOx, in a-ZTO/TiOx/a-ZTO trilayers, a significantly reduced influence
on carrier mobility was observed. The lowest density of free
carriers in the trilayer of a-ZTO/Insulator/a-ZTO structures was established
by a small thickness 2nm thick SiOx and TiOx insulators.
By utilising a broader range of characterisation techniques, the carrier
concentration drop in a-IGZO/SiOx/a-IGZO was assessed (a-IGZO is
amorphous InGaZnO). a-IGZO was selected for this study as the effect
is markedly similar to a-ZTO while significantly enhancing in magnitude.
The film growth was established to be continuous regardless of
thickness by SEM due to discontinuous leads to increase resistivity.
No variation in oxygen structures in trilayer structures was confirmed
via in-situ XPS studies. The effect of oxygen flow on the SiOx layer
in trilayers was studied, and the oxygen flow eliminated a reduction
in charge carrier in trilayers.
Description:
APPROVED
Author: Kaisha, Aitkazy
Advisor:
Chvets, IgorPublisher:
Trinity College Dublin. School of Physics. Discipline of PhysicsType of material:
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