| Summary: | 博士 === 國立交通大學 === 光電工程系所 === 98 === Low-temperature thin film transistors (TFTs) with the active-layer material of pentacene were discussed in this dissertation. Besides, the current results in the material of amorphous indium-gallium-zinc-oxide (a-IGZO) were also discussed in this dissertation. Pentacene-based organic thin films grown on a self-assembled monolayer (SAM), octadecyltrimethoxysilane (ODMS), treated dielectric with various functional groups and molecular lengths were discussed. The functional groups and molecular lengths on the dielectric surface were modified using a SAM treatment followed by ultra violet (UV) light exposure. Surface energy was used to observe the surface polarity variation during UV light exposure. The surface morphology and crystalline structures of pentacene films were varied when they were deposited on various surfaces at different UV exposure times. Using this simple and convenient method, the pentacene growth modes and characteristics were controlled and demonstrated. Controlling the pentacene growth modes and characteristics on the ODMS treated SiO2 surface, pentacene patterning on the SiO2 surface was realized by controlling the variation in the surface energy. To pattern the pentacene film, the SiO2 surface energy was modified by SAM treatment and exposure to UV light through a quartz-glass mask. Then, following pentacene deposition, dipping in water was used to remove pentacene from the UV-exposed area.
Pentacene patterning on the hydrophobic aluminum nitride (AlN) surface was also achieved and demonstrated in this thesis. Controlling the carbon attachment on the AlN surface, the surface polarity was changed from hydrophilic to hydrophobic. The AlN surface was patterned using a conventional photo lithography process and then treated with oxygen (O2) plasma on uncovered AlN to modify surface polarity. Following pentacene deposition, the sample was dipped in water to remove pentacene from the O2 plasma treated area. In addition, pentacene based OTFTs on the carbon-attached AlN surface showed excellent performance was demonstrated. To control the amount of the carbon attachment on the AlN surface, the methane (CH4) was introduced to modify the polarity of the AlN surface and improve the performance of OTFTs on the CH4 treated AlN surface.
Finally, a reversible changes on the device characteristics of a-IGZO TFTs upon post-annealing were discovered in this thesis. After the a-IGZO devices were annealed at a temperature of 500oC in a low-pressure furnace, they become quite conductive, independent of the gate voltage, and similar to the behavior of a conductor. When the devices were annealed again at 350oC in air, the electrical characteristic returns to a standard field-effect-transistor behavior. Results imply that the oxygen changes the carrier concentration in the a-IGZO layer, resulting in varied electrical characteristics.
|
|---|
