Sun-Kyu Hwang

Fabrication of Highly Ordered Pore Array in Anodic Aluminum Oxide

Highly ordered pore array in anodic aluminum oxide was fabricated by anodizing pure aluminum. The order of a pore array was affected by anodizing voltage, electrolyte temperature, and first anodizing time. A regular pore array with mean diameter of 24 nm and interpore distance of 109 nm could be formed by two-step anodization at 40 V., oxalic acid concentration of 0.3 M and electrolyte temperature of 15 ‡C. The measured interpore distance showed linearity with anodizing voltage. The diameter of pores was adjusted by pore widening treatment in a 5 wt% phosphoric acid solution at 30 ‡C after two step anodization. The mechanism of self-arrangement of pores could be explained by the repulsive interaction between the pore walls.

Fabrication of carbon nanotube emitters in an anodic aluminium oxide nanotemplate on a Si wafer by multi-step anodization

AAO template technology was combined with silicon technology to be directly applied to electronic device fabrication. Thin film anodic aluminium oxide (AAO) templates were fabricated on a silicon wafer by multiple anodizations. No electropolishing was used after the deposition of the aluminium layer on Si wafers. The ordering of the pore arrangement was improved by repeated anodizations, and highly ordered AAO templates could be obtained on Si wafers. CNT field emitter arrays were made with the AAO templates on Si wafers. Field emission measurement revealed that the emission current density increased with the synthesis temperature of CNTs. The large field enhancement factor in the range of 2440–4000 indicates the potential of the CNT field emitter array based on the AAO template on a Si wafer.

FE‐based On‐Line Model for the Prediction of Strip Temperature in Hot Strip Rolling

Investigated via a series of finite‐element(FE) process simulation is the effect of diverse process variables on some selected non‐dimensional parameters characterizing the thermomechanical behavior of the roll and strip in hot strip rolling. Then, on the basis of these parameters, on‐line models are derived for the precise prediction of the temperature changes occurring in the bite zones as well as in the inter‐stand zones in a finishing mill. The prediction accuracy of the proposed models is examined through comparison with predictions from a FE process model.

Template‐based carbon nanotubes field emitter

Abstract The growth of carbon nanotubes(CNTs) in anodic aluminum oxide(AAO) template and their application to a field emitter are described. AAO templates were fabricated by anodizing bulk aluminum and sputtered thin Al film on Nb‐coated Si wafers. After Co catalyst had been electrochemically deposited into the bottom of the pores in AAO template, CNTs were grown by pyrolyzing C2H2. Depending on the reaction conditions, CNTs grew up to or over the top of the pores in AAO template with different structures. The morphology and structure of CNTs were observed with a scanning electron microscope and a transmission electron microscope. The diameter of CNTs strongly depended on the size of the pores in AAO template and the growing conditions. The electron field emission measurement of the samples resulted in the turn‐on field of 1.9–2.2 V/μm and the field enhancement factor of 2450–5200. The observation of high field enhancement factors is explained in terms of low field screening effect.