Hyek-Hwan Choi

Zinc oxide thin film doped with Al2O3, TiO2 and V2O5 as sensitive sensor for trimethylamine gas

Abstract To obtain a sensitive sensor for TMA gas, ZnO-based films were fabricated by a rf magnetron sputtering method using targets added with Al2O3, TiO2, or V2O5. The films were heat-treated at a temperature between 400°C and 800°C for 60 min in oxygen. It was found that the sensitivity and selectivity of the films for TMA gas at 300°C increased by doping with 4.0 wt% Al2O3, 1.0 wt% TiO2 and 0.2 wt% V2O5. The sensor with the doped film 120 nm thick and annealed at 700°C for 60 min in oxygen exhibited fairly excellent sensitivity and selectivity to TMA, and electrical stability. Upon exposure to odors from a mackerel, the sensor using this film could trace well its deterioration during storage.

A low jitter phase-lock loop based on a new adaptive bandwidth controller

This paper presents the analog adaptive phase-locked loop (PLL) architecture with a new adaptive bandwidth controller to reduce locking time and minimize jitter in PLL output for wireless communication. It adaptively controls the loop bandwidth according to the locking status. The adaptive bandwidth control is implemented by controlling charge pump current depending on the locking status. It is simulated by HSPICE and achieves the primary reference sidebands at the output of the VCO at approximately -80dBc

Pyroelectric Infrared Sensors using (Pb,La)TiO 3 /LiTaO 3 /(Pb,La)TiO 3 Multilayer Ferroelectric Thin Films

For fabrication of the pyroelectric IR sensor //(LTO)/PLT ferroelectric thin films was deposited by rf magnetron sputtering followed by rapid thermal annealing and the crystallinity as a function of annealing temperature and time was investigated. Permittivity and dielectric loss factor of ferroelectric thin films as a function of c-axis preffered orientation was measured. Also pyroelectric coefficient of ferroelectric thin films with largest c-axis preffered orientation was measured and obtain figure of merit of voltage response() and detectivity(). In this case , was , , respectively.Ā᐀會Ā᐀遆?⨀碋쾴Ā᐀會Ā᐀?⨀쾴瀀ꀏ會Ā䁇?⨀끰쾴Ā᐀會Ā᐀顇?⨀䡱쾴Ā㰀會Ā㰀?⨀쾴Ā㈀會Ā㈀䡈?⨀硲쾴Ā᐀會Ā᐀ꁈ?⨀쾴Ā᐀會Ā᐀?⨀ꡳ쾴Ā저會Ā저偉?⨀偮쾴Ā저會Ā저ꡉ?⨀쾴㌀Ā저會Ā저J?⨀聯쾴Ā저會Ā저塊?⨀ႌ쾴؀Ā؀會Ā؀끊?⨀衬쾴刀Ā切會Ā切ࡋ?⨀롭쾴Ā搀會Ā搀恋?⨀�쾴Ā저會Ā저롋?⨀灸쾴Ā저會Ā저၌?⨀ၶ쾴ࠀĀࠀ會Āࠀ桌?⨀꡶쾴Ā저會Ā

Ferroelectric Properties of Pb[(Zr,Sn)Ti]NbO 3 Thin Films with Various Composition Ratio

Ferroelectric (PNZST) thin films were deposited by a RF magnetron sputtering on (LSCO)/Pt/Ti//Si substrate using a PNZST target with excess PbO of 10 mole%. The crystallinity and electrical properties of the thin films with various composition ratio were investigated. The thin films deposited at the substrate temperature of and the power of 80 W were crystallized to a perovskite phase after rapid thermal annealing(RTA) at for 10 seconds in air. A PNZST thin films with Ti of 10 mole% showed the good crystallinity and ferroelectric properties. The remanent polarization and coercive field of the PNZST capacitor were about and 50 kV/cm, respectively. The reduction of the polarization after switching cycles was less than 10%.