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Effect of Hydrogen Peroxide on the Stability of Undoped p-Type ZnO Prepared by Magnetron Sputtering
윤의중,Hyoung G. Nam,Hyeong-Sik Park,이규항,Kyung-Hwan Cha,조남인 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.3
In this study, we demonstrate that ZnO deposited onto SiO2 substrates by magnetron sputtering produces p-type ZnO at higher O2 pressure and n-type ZnO at lower O2 pressure. We also report the effect of hydrogen peroxide (H2O2) on the stability of undoped ZnO thin lms. The lms were immersed in 30 % H2O2 for 1 min at 30℃ and annealed in O2 at 450℃. The surface morphologies and structures of the samples were characterized by scanning electron microscopy (SEM) and X- ray diffaction (XRD), respectively. The optical properties were evaluated by PL measurements at room temperature. The carrier concentration, mobility, and conductivity were measured by using a Hall effect measurement system. The Hall measurement results for the ZnO flms untreated with H2O2 but annealed in O2 indicate that oxygen fractions greater than ~0.5 produce undoped p-type ZnO flms whereas oxygen fractions less than 0.5 produce undoped n-type ZnO flms. This is attributed to the fact that the oxygen vacancies (Vo) decrease and the oxygen interstitials (Oi) or zinc vacancies (VZn) increase with increasing oxygen atoms incorporated into ZnO flms during deposition and O2 post-annealing. From the XRD and the resistivity measurements, the changes induced by O2 annealing were observed to be quenched by H2O2. p-type ZnO flms deposited at an oxygen fraction of 0.67 showed a dominant UV peak at 3.194 eV related to a neutral acceptor bound exciton and Oi or VZn whereas n-type ZnO flms deposited at an oxygen fraction of 0.2 showed a dominant UV peak at 3.261 eV related to a neutral donor bound exciton and zinc interstitials (Zni) defects. We concluded from the experimental results that the active oxygen species decomposed from H2O2 can combine with Zni and fll Vo defects; thus, H2O2 improves the stability of undoped p-type ZnO thin lms by reducing Zni and Vo defects and/or passivating grain boundaries.
Development of Transparent Thin Film Transistors on PES Polymer Substrates
윤의중,정진우,고경남,송영욱,Hyoung G. Nam,조남인 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.41
In this study, we demonstrate ZnO-based transparent thin film transistors (TTFT’s) implemented on polyethersulfone (PES) polymer substrates. For the developed TTFT’s, radio-frequencymagnetron sputter techniques were used to deposit Al-doped ZnO (AZO) at zero oxygen partial pressures for the source, the drain, and the gate-contact electrodes, undoped ZnO at low oxygen partial pressures for the active p-type layer, and SiO2 for the gate dielectric. The TTFT’s were processed at room temperature (RT), except for a 100 ℃ sputtering step to deposit the AZO source,drain, and gate-contact electrodes. The devices have bottom-gate structures with top contacts,are optically transparent, and operate in an enhancement mode with a threshold voltage of +13V, a mobility of 0.1 cm2/Vs, an on-off ratio of about 0.5 × 103 and, a sub-threshold slope of 4.1V/decade.
Effect of RF Plasma Treatment of Plastic Substrates on the Properties of ZnO Thin Films
Jin-Woo Jung,Young-Wook Song,Hyoung G. Nam,조남인,윤의중 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.1
We explored in this work the effects of radio frequency (RF) plasma treatment of plastic substrates on the properties of ZnO thin films. Plastic substrates [polycarbonate (PC)] were treated with a RF plasma at atmospheric pressure for 5 min. The flow gases were Ar and O2. The O2/(O2 + Ar) fraction for the plasma treatment was varied from 0 (Ar plasma condition) to 1 (O2plasma condition). Then the ZnO films were deposited at room temperature onto plasma treated plastic substrates by using RF magnetron sputtering techniques. The surface morphologies and the structures of the ZnO films were characterized by using a scanning electron microscope and a X-ray diffractometer, respectively. A Fourier-transform infrared spectrometer equipped with an attenuated total reflexion accessory was used for the surface analysis to obtain the chemical changes induced by the plasma treatment. We conclude from the experimental data that the structural properties of the ZnO films grown on PC substrates treated with an Ar plasma were the best among all samples considered in this work.
Serratia marcescens S3-R1이 생산한 효소에 의한 유청단백질 가수분해물의 특성과 면역조절 활성
유재민(Jae min Yu),렌친핸드(G. Renchinkhand),정석근(Seok Geun Jeong),배형철(Hyoung Churl Bae),남명수(Myoung Soo Nam) 충남대학교 농업과학연구소 2013 농업과학연구 Vol.40 No.3
Degrees of hydrolysis by alkaline protease produced from Serratia marcescens S3-R1 is 3.95-6.30% of whey proteins during 5, 15, 30, 60, 90, 120,180, 240 min incubation at 40℃. Proteolytic pattern of the whey proteins showed that various low molecular weight peptides were generated during the incubation periods. The biological function of in Raw 264.7 cells treated with whey protein hydrolytic peptides, anti-inflammatory effect showed exhibit in the expression of pro-inflammatory cytokines such as TNF-α, IL-6, COX-2 and iNOS by PCR analysis. COX-2 and iNOS gene expression inhibited in Raw 264.7 cells on whey protein hydrolysates below 3,000 dalton. The protease from Serratia marcescens S3-R1 showed a potential in production of low molecular weight whey protein hydrolysates which could be used for industrial application.
Characterization of Undoped ZnO Films Post-Annealed by Using Helium Gas
윤의중,Hyeong-Sik Park,Kyu H. Lee,Hyoung G. Nam 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.2
In this study, we used helium gas for the first time for annealing undoped ZnO films at different temperatures in the range of 500 ~800℃ and we report their structural, optical and electrical properties. All measurements were carried out at room temperature. The undoped ZnO samples exhibited a (002) preferential orientation with the c-axis perpendicular to the substrate, suggesting that samples of high quality were prepared. The PL spectra of the ZnO samples revealed a strong near-band-edge ultraviolet (UV) emission peak at 3.26 eV, a strong red emission peak at 1.91 eV and a weak green emission peak at 2.36 eV, which were attributed to a free electron-acceptor transition, a zinc interstitial and a single ionized oxygen vacancy, respectively. All peak strengths in the PL spectra increased with increasing post-annealing temperature. We also confirmed from PL and Hall measurements that all samples revealed n-type conductivity. With increasing post-annealing temperature, the electron carrier concentration and the strength of UV emission peak increased, suggesting that they are related to each other. In this study, we used helium gas for the first time for annealing undoped ZnO films at different temperatures in the range of 500 ~800℃ and we report their structural, optical and electrical properties. All measurements were carried out at room temperature. The undoped ZnO samples exhibited a (002) preferential orientation with the c-axis perpendicular to the substrate, suggesting that samples of high quality were prepared. The PL spectra of the ZnO samples revealed a strong near-band-edge ultraviolet (UV) emission peak at 3.26 eV, a strong red emission peak at 1.91 eV and a weak green emission peak at 2.36 eV, which were attributed to a free electron-acceptor transition, a zinc interstitial and a single ionized oxygen vacancy, respectively. All peak strengths in the PL spectra increased with increasing post-annealing temperature. We also confirmed from PL and Hall measurements that all samples revealed n-type conductivity. With increasing post-annealing temperature, the electron carrier concentration and the strength of UV emission peak increased, suggesting that they are related to each other.
Serratia marcescens S3-R1이 생산한 효소에 의한 유청단백질 가수분해물의 특성과 면역조절 활성
유재민(Jae min Yu),렌친핸드(G. Renchinkhand),정석근(Seok Geun Jeong),배형철(Hyoung Churl Bae),남명수(Myoung Soo Nam) 충남대학교 농업과학연구소 2013 Korean Journal of Agricultural Science Vol.40 No.3
Degrees of hydrolysis by alkaline protease produced from Serratia marcescens S3-R1 is 3.95-6.30% of whey proteins during 5, 15, 30, 60, 90, 120,180, 240 min incubation at 40℃. Proteolytic pattern of the whey proteins showed that various low molecular weight peptides were generated during the incubation periods. The biological function of in Raw 264.7 cells treated with whey protein hydrolytic peptides, anti-inflammatory effect showed exhibit in the expression of pro-inflammatory cytokines such as TNF-α, IL-6, COX-2 and iNOS by PCR analysis. COX-2 and iNOS gene expression inhibited in Raw 264.7 cells on whey protein hydrolysates below 3,000 dalton. The protease from Serratia marcescens S3-R1 showed a potential in production of low molecular weight whey protein hydrolysates which could be used for industrial application.