Ung Lee

Role of ZrO2 incorporation in the suppression of negative bias illumination- induced instability in Zn-Sn-O thin film transistors

Thin film transistors (TFTs) with In and Ga-free multicomponent Zn–Sn–Zr–O (ZTZO) channel layers were fabricated using the cosputtering approach. The incorporation of ZrO2 into the Zn–Sn–O (ZTO) films increased the contact resistance, which led to the degradation of the transport properties. In contrast, the threshold voltage shift under negative bias illumination stress (NBIS) was largely improved from −12.5 V (ZTO device) to −4.2 V (ZTZO device). This improvement was attributed to the reduction in the oxygen vacancy defects in the ZTZO film, suggesting that the photoinduced transition from VO to VO2+ was responsible for the NBIS-induced instability.

Improvement of electrical and optical properties of molybdenum oxide thin films by ultralow pressure sputtering method

In this work, we investigated the structural, electrical and optical properties of molybdenum oxide thin films deposited by the reactive dc magnetron sputtering method. The molybdenum oxide films were prepared at sputtering pressures ranging from 6.7 × 10−1 to 6.7 × 10−2 Pa. In order to promote their electrical conductivity, all the deposited MoOx films were annealed in Ar ambient at 450 °C for 8 h. The resistivity of the MoOx films varied from 10−4 to 10−2 Ω cm depending on the O2 content in the sputtering ambient. The lowering of the resistivity of the MoO2 films was mainly attributed to the formation of a monoclinic MoO2 polycrystalline phase. As the sputtering pressure decreased, the content of monoclinic polycrystalline MoO2 phase increased, resulting in low resistivity films. The formation of the dominant MoO2 phase at lower sputtering pressures was attributed to the stress induced crystallization. The post-deposition annealed (PDA) MoOx film, deposited at an ultralow sputtering pressure (6.7 × 10−2 Pa) and O2 content of 40%, had an atomic ratio of O to Mo ≈ 2.85 and was highly transparent and conductive: the transmittance in the visible wavelength range of 400–500 nm was about 73% and the resistivity was 1.05 × 10−3 Ω cm. This result is superior to those of MoOx films epitaxially grown by the pulse laser deposition method.In this work, we investigated the structural, electrical and optical properties of molybdenum oxide thin films deposited by the reactive dc magnetron sputtering method. The molybdenum oxide films were prepared at sputtering pressures ranging from 6.7 × 10−1 to 6.7 × 10−2 Pa. In order to promote their electrical conductivity, all the deposited MoOx films were annealed in Ar ambient at 450 °C for 8 h. The resistivity of the MoOx films varied from 10−4 to 10−2 Ω cm depending on the O2 content in the sputtering ambient. The lowering of the resistivity of the MoO2 films was mainly attributed to the formation of a monoclinic MoO2 polycrystalline phase. As the sputtering pressure decreased, the content of monoclinic polycrystalline MoO2 phase increased, resulting in low resistivity films. The formation of the dominant MoO2 phase at lower sputtering pressures was attributed to the stress induced crystallization. The post-deposition annealed (PDA) MoOx film, deposited at an ultralow sputtering pressure (6.7 × 10−2...

Effect of Liquefaction Plant Performance and Location on the Cost of CO2 Transport

Abstract Carbon capture and storage (CCS), a key technology for addressing global warming is in between demonstration to commercialization phase. Transportation of CO 2 is required since storage sites are not necessarily present under the source sites. Ships can be used for long distance transport of CO 2 ; liquefaction being a vital component in ship transportation. In this study, a state of art CO 2 liquefaction process has been designed by taking account of source facilities (i.e. post-combustion and pre-combustion). The proposed liquefaction process offers lower liquefaction energy requirement compared with other available literature. Three different scenarios for post-combustion and pre-combustion each have been studied on the basis of liquefaction plant location. The considered scenarios are categorized as: a) capture site, liquefaction plant and shipping terminal are located close to each other; b) capture site and liquefaction plant are far from shipping terminal; c) capture site is far from liquefaction plant and shipping terminal. Finally, an economic analysis is performed in order to evaluate the feasibility of CO 2 transport from source sites to ship loading terminal including liquefaction plant.