Unique properties of composite materials based on liquid crystals
Date Issued
2006
Date
2006
Author(s)
Chu, Kung-Ching
DOI
en-US
Abstract
In this thesis we report the studies of optical and electrical properties on the composites based on liquid crystals, which include CdSe semiconductors and gold nanorods. Quite interesting results have been obtained from our studies, which are very useful for the understanding as well as application of these materials. They are presented as follows.
I. Liquid crystals driven by CdSe semiconductor Schottky diode
We report an approach of controlling liquid crystals using a laser beam without external bias. In our design, in addition to liquid crystals, a patterned semiconductor was also included. We discovered that the average pretilt angle of liquid crystals can be controlled by adjusting excitation power, and the relationship was found to follow the possible predicted photovoltaic effect. Besides, the photogenerated field was found to have both perpendicular and horizontal components, which is very useful to control the orientation of liquid crystals to an arbitrary direction. Optical switch devices can be possible to design using our method.
II. Electrically controlled surface plasmon resonance frequency of gold nanorods
We have presented the voltage-controlled tuning of plasmonic response of absorption spectra of gold nanorods in liquid crystals. We observe that gold nanorods can be aligned along the rubbed polyimide substrate before applying external voltage. It is found that the transverse mode of gold nanorods shows a blue shift and red shift when rotating the analyzer parallel or perpendicular to the rubbing direction, respectively, while all longitudinal modes display a red shift behavior. This work offers an easy way to tune the transverse and longitudinal modes of gold nanorods simultaneously, which makes it feasible to establish the color tunable devices.
Subjects
液晶
半導體
硒化鎘
表面電漿子
金奈米柱
liquid crystal
semiconductor
CdSe
surface plasmon
gold nanorod
SDGs
Type
thesis
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