A series of soluble pentacene precursors are designed, from which pure pentacene can be generated either thermally or
photochemically. Small volatile fragments like CO and CO2 are extruded during the dissociation reactions. Thin films
of pentacene made from these precursors exhibited typical OTFT characteristics.
Scaling behaviors of ZnO transparent thin-film transistors (TTFTs) have been studied by fabricating series of
miniaturized ZnO TTFTs having various channel widths and lengths. Mobility of >8 cm2/V.s and on/off ratio of up to
107 are achieved with these TTFTs. Results show that these ZnO TTFTs retain rather well-behaved transistor
characteristics down to the channel length of ~5 &mgr;m, rendering possible high-resolution applications. More apparent
short-channel effects (e.g., lowering of threshold voltages, degradation of the subthreshold slope with the decrease of the
channel length and the increase of the drain voltage, and loss of hard saturation, etc.) are observed when the channel
length is reduced below 5 &mgr;m. Influences of parasitic effects on TFT characteristics are also studied by extracting
parasitic resistance and channel resistance using devices of various dimensions. The ratio of parasitic resistance to
channel resistance at VG = 10 V was increased from 0.04 to 0.36, when the channel length decreased from 20 &mgr;m to 2 &mgr;m.
This indicates that parasitic resistance has substantial influences on device performances (e.g., output drain current,
apparent field effect mobility, etc.) when the channel length is reduced, and better contact techniques may be required.
To extend the usage of silicon as light emitter in optoelectronics, two ways are exploited to overcome its indirect bangap obstacle. Metal-oxide-semiconductor structures with silicon dioxide (SiO2) nanoparticles as oxide layer exhibits electroluminescence with 1.5 x 10-4 external efficiency at Si bandgap energy. The enhancement in light emission is attributed to carrier concentration due to non-uniformity of oxide thickness. Another approach is to take advantage of direct bandgap materials. Chemically synthesized cadmium sulfide (CdS) nanoparticles are deposited on Si substrate and exhibits electroluminescence corresponding to different process treatment.