C.-Y. Park

Low-temperature synthesis of graphene on nickel foil by microwave plasma chemical vapor deposition

Microwave plasma chemical vapor deposition (MPCVD) was employed to synthesize high quality centimeter scale graphene film at low temperatures. Monolayer graphene was obtained by varying the gas mixing ratio of hydrogen and methane to 80:1. Using advantages of MPCVD, the synthesis temperature was decreased from 750 °C down to 450 °C. Optical microscopy and Raman mapping images exhibited that a large area monolayer graphene was synthesized regardless of the temperatures. Since the overall transparency of 89% and low sheet resistances ranging from 590 to 1855 Ω∕sq of graphene films were achieved at considerably low synthesis temperatures, MPCVD can be adopted in manufacturing future large-area electronic devices based on graphene film.

Randomized controlled trial to investigate the effects of a newly developed formulation of phentermine diffuse-controlled release for obesity

Aim: To evaluate the efficacy and safety of a newly developed formulation of phentermine diffuse‐controlled release (DCR) in patients with obesity.

Optical quenching of NiO∕Ni coated ZnO nanowires

Low temperature photoluminescence (PL) measurements were carried out to investigate optical transition characteristics of ZnO nanowires, Ni nanodot, and NiO coated ZnO nanowires (NWs). PL emission spectra show emission peaks of distinctive bound exciton to neutral donor (DX0) and to acceptor (AX0) transition. The authors found that the optical quenching was drastic with increasing temperature and the activation energies are unusually small. The major PL emission peak for ZnO NW was switched from DX0 to AX0 for Ni–ZnO nanodot NWs. This is due to the reason that diffused hydrogen atoms into ZnO NWs during thermal annealing played as acceptors.

Lobeglitazone and pioglitazone as add‐ons to metformin for patients with type 2 diabetes: a 24‐week, multicentre, randomized, double‐blind, parallel‐group, active‐controlled, phase III clinical trial with a 28‐week extension

We aimed to compare the efficacy and safety of lobeglitazone and pioglitazone as add‐ons to metformin in patients with type 2 diabetes. Patients who were inadequately controlled by metformin were randomized and treated once daily with either lobeglitazone (0.5 mg, n = 128) or pioglitazone (15 mg, n = 125) for 24 weeks, with a 28‐week extension trial of lobeglitazone treatment in patients who consented. The primary endpoint was the change in glycated haemoglobin (HbA1c) concentration from baseline to week 24. At week 24, the mean change from baseline in HbA1c was −0.74% for the lobeglitazone group and −0.74% for the pioglitazone group, with a mean difference of 0.01% [95% confidence interval (CI) of difference, −0.16 to 0.18]. The effects of lobeglitazone on lipid variables and the adverse events associated with lobeglitazone were similar to those observed with pioglitazone. Lobeglitazone was not inferior to pioglitazone as an add‐on to metformin in terms of their efficacy and safety.

Bulk and Interface effects on voltage linearity of ZrO2–SiO2 multilayered metal-insulator-metal capacitors for analog mixed-signal applications

Quadratic voltage coefficient of capacitance (VCC) for ZrO2–SiO2 multilayered dielectric metal-insulator-metal capacitors depends strongly on the stacking sequence of the layered dielectrics. The quadratic VCC of an optimized SiO2/ZrO2/SiO2 stack and ZrO2/SiO2/ZrO2 stack were +42 and −1094 ppm/V2, respectively, despite the same total SiO2 and ZrO2 dielectric thickness in the stack. The observed difference in quadratic VCC depending on dielectric stacking sequence is explained by taking into account both the interface and bulk dielectric responses to the applied voltage.

Simple, green, and clean removal of a poly(methyl methacrylate) film on chemical vapor deposited graphene

The clean removal of a poly(methyl methacrylate) (PMMA) film on graphene has been an essential part of the process of transferring chemical vapor deposited graphene to a specific substrate, influencing the quality of the transferred graphene. Here we demonstrate that the clean removal of PMMA can be achieved by a single heat-treatment process without the chemical treatment that was adopted in other methods of PMMA removal. The cleanness of the transferred graphene was confirmed by four-point probe measurements, synchrotron radiation x-ray photoemission spectroscopy, optical images, and Raman spectroscopy.

Indium-induced triple-period atomic wires on a vicinal Si(111) surface: In/Si(557)

An indium-induced one-dimensional (1D) surface reconstruction on a Si(557) surface was studied by the combined approach of scanning tunneling microscopy (STM) and first principles calculations. Low-energy electron diffraction revealed a (1◊3) phase with a triple-period along the step edge direction, which was also confirmed by STM. The STM images showed that the 1D structure consists of two atomic chains. One is located on the terrace and consists of triple-period bright protrusions. The other shows a weak ◊3 modulation at the step edge. Five atomic structure models based on the In adatom of a In/Si(111)- p 3◊ p 3 surface were considered to figure out the underlying structure of the STM images of the In/Si(557)-1◊3 surface. Interestingly, a heterogeneous In-Si adatom chain model reproduced most of the features of STM images and was the most stable energetically at a wide range of In chemical potential.

Influence of graphene-substrate interactions on configurations of organic molecules on graphene: Pentacene/epitaxial graphene/SiC

Pentacene has been used widely in organic devices, and the interface structure between pentacene and a substrate is known to significantly influence device performances. Here we demonstrate that molecular ordering of pentacene on graphene depends on the interaction between graphene and its underlying SiC substrate. The adsorption of pentacene molecules on zero-layer and single-layer graphene, which were grown on a Sifaced 6H-SiC(0001) wafer, was studied using scanning tunneling microscopy (STM). Pentacene molecules form a quasi-amorphous layer on zero-layer graphene which interacts strongly with the underlying SiC substrate. In contrast, they form a uniformly ordered layer on the single-layer graphene having a weak graphene-SiC interaction. Furthermore, we could change the configuration of pentacene molecules on the singlelayer graphene by using STM tips. The results suggest that the molecular ordering of pentacene on graphene and the pentacene/graphene interface structure can be controlled by a graphene-substrate interaction.

Chemical phase transitions of the HfO2∕SiON∕Si nanolaminate by high-temperature thermal treatments in NO and O2 ambient

Temperature-dependent chemical phase transitions of the HfO2∕SiON∕Si(100) nanolaminate in O2 and NO ambient have been investigated using high-resolution photoemission spectroscopy. Hf4f, Si2p, O1s, and N1s photoemission spectra were measured after annealing the nanolaminate at a temperature between 750 and 1150°C. These spectra show that the chemical phase transitions of the nanolaminate strongly dependend on the ambient gases. The nanolaminate in an O2 ambient is stable below 750°C but the HfO2 and SiON layers dissociate by producing Hf silicides above 950°C. In contrast, the nanolaminate in NO ambient does not transit into Hf silicides up to 1050°C. Interestingly, the HfO2 and SiON layers transforms into HfOxNy and SiNx layers, respectively, with a high thermal stability, where the HfOxNy layers are a high-k dielectric material and the SiNx layers work as a barrier against both Si and O diffusion

Chemical phase transitions of a Si oxide film on SiC by MeV electron beam irradiation

An ultrathin Si oxide film grown on a 6H-SiC(0001) wafer was irradiated with 1MeV electron beam to examine its effect on the chemical species of a Si oxide/SiC wafer, where the Si oxide film was composed of SiO2, Si suboxides (Si3+, Si2+, and Si1+), and Si oxycarbides (Si–C–O). Scanning photoelectron microscopy and Si 2p core-level spectroscopy show that e-beam irradiation induces chemical phase transitions from the Si suboxides and Si oxycarbides to SiO2. This suggests that e-beam irradiation is an efficient and simple method of producing a chemically uniform SiO2 film on SiC without thermal and chemical treatments.