TFT-LCD Display Characterization Using Spectroscopic Ellipsometry
LCD devices consist of a nematic liquid crystal sandwiched between two plates of glass. In detail, first a sheet of glass is coated with a transparent conducting metal oxide film which acts as an electrode. Next, a polymer alignment layer is applied. When an electric field is applied between the two electrodes, liquid crystal molecules will react in such a way as to control light passage.
Most displays in current use employ cathode ray tube (CRT) technology similar to that used in most television sets. The CRT technology requires a certain distance from the projection device to the screen to function. Using other technologies, displays can be much thinner and are known as flat-panel displays.
Flat panel technologies include light-emitting diode (LED), liquid crystal display (LCD) and gas plasma. LED and gas plasma work by lighting up display screen positions based on voltages at different grid intersections. LCDs are categorized as non-emissive display devices, in that respect they do not produce any form of light. LCDs either pass or block light that is reflected from an external light source or provided by a back/side lighting system. LCDs require far less energy than LED and gas plasma technologies are currently the primary technology for notebook and other laptop computers.
Full TFT-LCD device characterization:
Non-destructive characterization of the different parts of the TFT-LCD device was successfully carried out by Spectroscopic Ellipsometry (SE). The ellipsometric data were collected at an angle of incidence of 700 using the Jobin Yvon UVISEL NIR (260-1700 nm).
The UVISEL Spectroscopic Phase Modulated Ellipsometer is a unique instrument that provides significant advantages for display applications when compared to conventional ellipsometers. Its technology is the most suitable for accurate thin film measurement on transparent substrates as the software includes advanced capabilities for automatic correction of backside reflections.
