Mi Ran Moon

Solution-processed InGaZnO-based thin film transistors for printed electronics applications

This letter reports the utility of using the sol-gel process for exploring the library of multicomponent ZnO-based oxides as an active layer of thin film transistors. We chose InGaZnO as a starting material and modulated the Ga content to examine the potential of this material. Increasing the Ga ratio from 0.1 to 1 brought about a dynamic shift in the electrical behavior from conductor to semiconductor. This exploratory work critically helped us fabricate a device with robust device performance (a mobility of 1∼2 cm2 V−1 s−1 for the 400 °C-sintered samples and 0.2 cm2 V−1 s−1 for the 300 °C-sintered samples).

Effects of Substrate Heating on the Amorphous Structure of InGaZnO Films and the Electrical Properties of Their Thin Film Transistors

This study examines the effects of substrate heating on the amorphous structure of InGaZnO4 (IGZO) films and the device performance of transistors produced from these films. By combining high-resolution transmission electron microscopy (HRTEM) and energy-filtered selected area electron diffraction (EF-SAED), we found that the atomic order improved significantly for the IGZO films deposited on a heated substrate, compared to the samples deposited on an unheated substrate and postannealed. Measurement of the electrical characteristics of the transistors discloses that the amorphous structure changes induced by substrate heating profoundly influenced the overall device performance, leading to a substantial increase in electron mobility.

Effects of Post Annealing on the Electrical Properties of ZnO Thin Films Transistors

This paper reports the effects of post-annealing of ZnO thin films on their microstructure and the device performance of the transistors fabricated from the films. From X-ray diffraction and transmission electron microscopy characterization, we uncovered that the grain size increased with the annealing temperature escalating and that the film stress shifted from compressive to tensile due to the grain size increment. Electrical characterization revealed that the grain size increase damaged the device performance by drastically lifting the off-current level. By annealing the devices in an ambient (instead of air), we were able to suppress the off-current while improving the electron mobility.

Performance Improvement of the Organic Light-Emitting Diodes by Using a LiF/Pyromellitic Dianhydride Stacked Cathode Interfacial Layer

A bilayered cathode interfacial structure consisting of lithium fluoride (LiF) and pyromellitic dianhydride (PMDA) was used between Al and tris-(8-hydroxyquinoline) aluminum (Alq 3 ) in the organic light-emitting diode (OLED), and a better performance enhancement compared to the OLED with a single LiF interfacial layer was achieved by using an optimal thickness combination of the bilayered interfacial structure (0.3 nm LiF/0.7 nm PMDA). The bilayered interfacial stucture with an optimum thickness combination decreased the parallel bulk resistance and lowered the electron injection barrier height between Al and Alq 3 according to the impedance and in situ ultraviolet photoelectron spectroscopy measurements, respectively.