Shin Woo Jeong

Flexible low-voltage pentacene memory thin-film transistors with combustion-processable Al2O3 gate dielectric and Au nanoparticles

A Au nanoparticles (NPs) embedded pentacene thin-film transistor (TFT) with solution-based Al2O3 was fabricated on a polyethersulfone substrate. The TFT for low-voltage operation within −3 V was realized with the Al2O3 dielectric film. By a combustion process for Al2O3, efficient driving of conversion reaction at low annealing temperature of 200 °C can be achieved and the device can be made on a plastic substrate. And, the Au NPs were deposited by the contact printing method using the polydimethylsiloxane stamp. From the electrical characteristics of the devices, a saturation mobility value of 4.25 cm2 V−1 s−1, threshold voltage (Vth) of ~0.5 V, subthreshold swing of 70 mV dec−1 and memory window of 0.21 V at −3 V programming gate bias voltage were obtained.

The vertically stacked organic sensor-transistor on a flexible substrate

The authors report on the photo-response characteristics of flexible sensor-transistor circuits (ST-circuits) made with (poly(3-hexylethiophene)/phenyl-C61-butryic acid methyl ester) (P3HT/PCBM) bulk heterojunction polymer and pentacene-based organic field-effect transistors, which are stacked via poly(dimethylsiloxane) (PDMS) on the plastic substrate. The results indicate that the anode-source current is variable because of both the charge separation of the photogenerated excitons and the accumulated charges at the OFET channel layer. The light dependent photo response (ΔI/I0) is modulated from 0.47 to 1.9 by the gate-source voltage at the fixed anode-source voltage of the ST-circuits.

High-Performance Amorphous Indium Oxide Thin-Film Transistors Fabricated by an Aqueous Solution Process at Low Temperature

This paper presents low temperature solution-processed fabrication techniques for modern thin-film transistors (TFTs). We have investigated the electrical performance of aqueous solution-processed amorphous indium oxide (a-In2O3) TFTs prepared using different annealing temperatures. Even though the a-In2O3 TFTs were annealed at 200 °C, electrical characteristics of aqueous solution-processed a-In2O3 TFTs were obtained. High performance such as a saturation mobility of 8.6 cm2 V-1 s-1 and an on/off current ratio of over 106 was exhibited by a-In2O3 TFTs annealed at 250 °C.

The silicon Schottky diode on flexible substrates by transfer method

A flexible silicon barrier diode was fabricated by the transfer printing method. Micro-line patterned p-type single crystalline silicon membranes were created from a silicon on insulator wafer. The dark current of our device was very low, about 1 pA for reverse bias voltages up to 5 V, and showed rectifying behavior with an ideality factor of 1.05. The photo-response and the responsivity was 32 and 0.3 A/W, respectively, for light intensity of 1.2 mW/cm2. Also, the current of the photodetector changed under compressive stress or tensile stress. Our device is functional as the piezotronic sensor as well as the photodetector.

The electrical and photoconductivity characteristics of donor-acceptor alternating copolymer using solution process

The authors report on the electrical and photoconductivity characteristics of donor-acceptor alternating copolymer, poly(dioctyloxinapthalenediketopyrrolopyrrole) (PONDPP) with Al/PONDPP/p-Si/Al hybrid organic/inorganic Schottky diode for optoelectronic applications. The fabricated device shows ideality factor value of 2.6 and barrier height of 0.68 eV obtained from current-voltage characteristics. The high rectification ratio of 1.86 × 104 and photo-responsivity of 55 mA/W at 650 nm is achieved. From results, we found that the fine photo-response and electrical characteristics are attributed to the modified band-gap structure to have Schottky barrier at highest occupied molecular orbital to valence band of silicon and high hole mobility of PONDPP.

The effect of Au nanoparticle on metal organic semiconductor field effect transistor on plastic substrate by transfer method

We report on organic nonvolatile memory devices, using pentacene as the active semiconductor layer and gold nanoparticles (Au NPs) array as charge storage elements. An effective and facile fabrication by self-assembly of Au NPs at a toluene/water interface with ethanol as the inducer is used for the forming of gold nanoparticles (Au NPs) monolayer. The organic memory devices exhibited good memory effects by hole trapping/detrapping in the gold nanoparticles. And also we design a modification of memory window by transfer times.