THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING

 GEORGIA INSTITUTE OF TECHNOLOGY

 Under the provisions of the regulations for the degree

DOCTOR OF PHILOSOPHY

on Monday, November 21, 2016

1:00-3:00 PM
in MRDC 3515

 will be held the

 DISSERTATION PROPOSAL DEFENSE

for

 Ning Xia

 "Fabrication, Characterization and Application of Indium Tin Oxide Thin Films Made by Solution-based Processing Methods"

 Committee Members: 

Prof. Rosario Gerhardt, Advisor, MSE

Prof. Vladimir Tsukruk, MSE

Prof. Qin Dong, MSE

Prof. Nazanin Bassiri-Gharb, ME/MSE 

Prof. Manos Tentzeris, ECE

Dr. David Gottfried, IEN

Abstract:

Because of its excellent optical transparency and high electrical conductivity, Indium tin oxide (ITO) is the most widely used transparent conducting oxide. ITO films have been used in numerous optoelectronic devices, such as photovoltaic cells, cell phones and monitors. Currently, vacuum-based methods are the main coating methods used by industry for depositing ITO films. These methods usually require strict vacuum conditions and high-cost equipment. In contrast, solution-based processing methods do not require expensive equipment. In addition, these methods can greatly reduce the waste of ITO materials during deposition and patterning steps.

In this doctoral work, three different ITO inks were investigated: colloidal ITO, ITO nanoparticle suspensions and ITO made by sol-gel processing. ITO films were first deposited by spin coating methods. The electrical resistivity, optical transmittance and surface morphology of these ITO films were characterized and compared using several different characterization tools, including confocal microscopy, SEM and AFM. Next, ITO films were printed by ink-jet printing using the sol-gel ITO ink custom-made formulation. Experiments were used to determine the desired pixel resolution and heat treatment to obtain films with the optimum properties. All-printed Liquid crystal display (LCD) devices were successfully fabricated with these ITO films because of the good combination of optical, electrical and surface properties (sheet resistance 500 ohms/square, > 90% transmittance and, < 2nm roughness).

There are two proposed research directions. The first direction is to fabricate solution-processed ITO films on flexible substrates while maintaining good optical and electrical properties. The difficulty is that solution-processed ITO films always require relative high temperature when most flexible substrates cannot withstand high temperature annealing. The second direction is to analyze the electrical properties of the ITO films by finite element analysis combined with experimental electrical characterization. The goal will be to determine the equivalent circuits that govern these interesting materials response and better understand the conducting mechanism of ITO films as a function of composition.