Jaewon Cho

Nanohole arrays with sub-30 nm diameter formed on GaAs using nanoporous alumina mask

Nanohole arrays with a sub-30 nm diameter were formed on GaAs substrates by inductively coupled plasma reactive-ion etching (ICP-RIE) using nanoporous alumina films as transfer masks. Whether the pore configurations of the alumina masks were transferred onto the GaAs substrates depended on the exposure time of ICP-RIE. In spite of the sub-30 nm pore diameter of the alumina masks, the ion bombardment induced in SiCl4/Ar gas by ICP-RIE properly responded on the GaAs substrate through the pores of the alumina masks. ICP-RIE using nanoporous alumina masks can be used as a prospective method to produce nanostructures.

Fabrication of a miniaturized electron lens system and laser micro-machining condition for Silicon membrane

For a miniaturized electron beam system application, miniaturized electrostatic electron lenses and their assembly, called a microcolumn, have been fabricated using an active Q-switched 1.06 µm Nd:YAG pulsed laser beam. The laser micro-machining condition for 20 µm thick Si membrane has been investigated by varying the pulse width and the effect of power density will be discussed. The geometrical structures of laser micro-machined electron lenses such as diameter, the roundness of the aperture wall and the degree of the thermal distortion are thought to be dependent on the characteristics of the individual laser pulse. A successful alignment of electron lenses using a simple laser diffraction pattern will be reported, also.

Improved output characteristics of organic thin film transistors by using an insulator/protein overlayer and their applications

We herein present our study of the effect of an insulator/protein overlayer deposited onto semiconducting active layers in organic thin film transistors (OTFTs) with regard to their electrical performance. The active layers used were composed of 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-PEN) blended with poly(α-methylstyrene) (PaMS), and the overlayer consisted of a bottom insulating (protecting) layer of an amorphous perfluoropolymer (Cytop) and a top protein layer of negatively charged bovine serum albumin (BSA). The functional layers were deposited using a simple solution-coating method which involved a horizontal dip coating process. We show that the Cytop/BSA overlayer on the TIPS-PEN:PaMS active layer improved the electrical performance of the OTFTs; the devices with the Cytop/BSA overlayer exhibited an average effective mobility of 0.25 cm2 V−1 s−1, which was higher than that of bare devices without any overlayer (0.20 cm2 V−1 s−1). This improved performance of OTFTs with the overlayer was successfully simulated and was found to stem from the formation of a second current channel in the TIPS-PEN:PaMS active layer via the electric field effect of the negatively charged BSA overlayer. These results demonstrate that OTFTs employing charged protein overlayers show considerable promise for the production of high-performance OTFT devices.

Photoluminescence Study on O-plasma Treated ZnO Thin Films

A temperature dependent (10K-290K) photoluminescence (PL) study for two differently prepared ZnO thin films (as-grown and O-plasma treated) is presented. Four characteristic peaks were identified for both samples: (i) neutral donor-bound excitons (

The Optical Property of Plasma-treated ZnO Nanorods

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Dielectric cap quantum well disordering for band gap tuning of InGaAs/InGaAsP quantum well structure using various combinations of semiconductor-dielectric capping layers

), (ii) two electron satellites (TES), (iii) phonon replica of

Control of the Intermixing of InGaAs/InGaAsP Quantum Well in Impurity Free Vacancy Disordering by Changing NH 3 Flow Rate During the Growth of SiN x Capping Layer

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Structural and optical properties of InP/GaAs strained heterostructures grown by metal-organic chemical vapor deposition

(

PL Study on the ZnO Thin Film with Temperatures

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PL Study on the Oxygen-Plasma-Treated ZnO Thin Film

-1LO), and (iv) donor-acceptor pair transition (DAP). As the sample temperature increased,