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Simple process for the fabrication of Co/TiO2/Pt resistive random access memory, called ReRAM, has been developed by selective deposition of Co on micro-contact printed (μ-CP) self assembled monolayers (SAMs) patterns. Atomic Layer Deposition (ALD) was used to deposit TiO2 thin films, showing its ability of precise control over the thickness of TiO2, which is crucial to obtain proper resistive switching properties of TiO2 ReRAM. The fabrication process for Co/TiO2/Pt ReRAM involves the ALD of TiO2 on sputter-deposited Pt bottom electrode, followed by μ-CP with SAMs and then selective deposition of Co. This results in the Co/TiO2/Pt structure ReRAM. For comparison, Pt/TiO2/Pt ReRAM was produced and revealing the similar switching characteristics as that of Co/TiO2/Pt, thus indicating the feasibility of Co replacement with Pt top electrode. The ratios between the high-resistance state (Off state) and the low-resistance state (On state) were larger than 102. Consequently, the selective deposition of Co with μ-CP, newly developed in this study, can simplify the process and thus implemented into the fabrication of ReRAM.

We have investigated selective deposition of Co thin films on the OTS-patterned glass surface by using μ-CP(Micro-Contact Printing) coupled with MOCVD(Metal Organic Chemical Vapor Deposition) method with Co2(CO)8 as a Co precursor. Co thin films in the thickness of 5-180 nm has been selectively formed on the glass surface in the presence of the OTS(Octadecyltrichlrosilane) monolayer at the temperatures 60-90[removed info], at the pressure of 0.03-0.6 Torr. The self-assembled OTS monolayer on the surface passivates the surface hydroxyl(-OH), adsorption sites for Co precursors, and thus significantly increases the induction period to nucleate Co metals on the OTS monolayer, compared with on the bare glass. Lowering the temperature and the processing pressure is likely to increase the difference in the induction period for the two substrate surfaces and thus improves the selectivity. About 180 nm-thick Co thin film was selectively formed on the OTS-patterned glass at 70[removed info], however, lowering the temperature to 60[removed info] decreased the thickness, which is attributed to the reduced growth rate of Co at the lower temperature. The Co thin films deposited at 60-90[removed info] and at 0.03-0.6 Torr have the resistivities of 10-20 μ4-cm and are free of contamination. Consequently, the low temperature process for the selective deposition of Co in the presence of the OTS monolayer can be utilized for a variety of applications including flexible electronics and semiconductor devices.

Influence of nitrogen and oxygen annealing atmospheres on the carrier concentration, carrier mobility, electrical resistivity and PL characteristics as well as the crystallinity of ZnO films deposited on sapphire substrates by atomic layer deposition (ALD) were compared. X-ray diffraction (XRD) and photoluminescence (PL) analyses, and Hall measurement were performed to investigate the crystallinity, optical properties and electrical properties of the ZnO thin films, respectively. The UV emission intensity for oxygen annealing is stronger than that for nitrogen annealing in the case of annealing at 600°C, but the difference decreases with the Increase of annealing temperature. The strongest UV emission is obtained by oxygen annealing at 800°C. However, from the viewpoint of electrical resistivity annealing at 1,000°C in either an oxygen or a nitrogen atmosphere is more desirable. Taking both the PL and electrical properties into consideration it may be concluded that optimum annealing condition for ZnO thin films grown on the sapphire substrate by ALD is an annealing temperature of 900°C and an annealing atmosphere of oxygen although the effects of annealing atmosphere on the optical and electrical properties are not so significant.

Ferroelectric properties and reliability characteristics of (111) and (100) preferred tetragonal Pb(Zr0.2Ti0.8)O3(PZT) thin film capacitors have been investigated as a function of top electrode thickness. The (111) preferred films exhibit better squareness of the hysteresis loop with larger remanant polarization and coercive field than the (100) preferred films. Top electrode thickness dependence of switching polarization can be explained by the compressive stress induced by the top electrode annealing. The film with thinner top electrode shows less initial switching polarization, however, better endurance characteristics due to enhancing partial switching region.

ABSTRACTIn Korea, vancomycin-resistant enterococci have become important nosocomial pathogens since the late 1990s, and most vancomycin-resistant enterococcal isolates have been VanA phenotype-vanAgenotype strains. In 2001, we experienced an outbreak of VanB phenotype-vanAgenotype vancomycin-resistant enterococci at a university hospital. This is the first report of VanB-vanAvancomycin-resistant enterococci from humans in Korea.