Choon-Bae Park

The Electrical and Optical Properties of Al-Doped ZnO Films Sputtered in an Ar:H 2 Gas Radio Frequency Magnetron Sputtering System

Al-doped ZnO (AZO) films were prepared by an Ar: gas radio frequency (RF) magnetron sputtering system with a AZO () ceramic target at the low temperature of and annealed in hydrogen ambient at the temperature of . To investigate the influence of the flow ratio on the properties of the AZO films, the flow ratio was changed from 0.5% to 2%. As a result, the AZO films, deposited with a 1% addition, showed a resistivity of . When the AZO films were annealed at for 1 hour in a hydrogen atmosphere, the resistivity decreased from to . The lowest resistivity of was obtained by adding 1% hydrogen gas to the deposition and annealing process. The X-ray diffraction patterns of all the films showed a preferable growth orientation in the (002) plane. The spectrophotometer measurements showed that the transmittance of 85% was obtained by the film deposited with the flow ratio of 1% at 940 nm for GaAs/GaAlAs LEDs.

Analysis of Photoluminescence for N-doped and undoped p-type ZnO Thin Films Fabricated by RF Magnetron Sputtering Method

N-doped ZnO thin films were deposited on n-type Si(100) and homo-buffer layer, and undoped ZnO thin film was also deposited on homo-buffer layer by RF magnetron sputtering method. After deposition, all films were in-situ annealed at for 5 minutes in ambient of with pressure of 10Torr. X -ray diffraction shows that the homo-buffer layer is beneficial to the crystalline of N-doped ZnO thin films and all films have preferable c-axis orientation. Atomic force microscopy shows that undoped ZnO thin film grown on homo-buffer layer has an evident improvement of smoothness compared with N-dope ZnO thin films. Hall-effect measurements show that all ZnO films annealed at possess p-type conductivities. The undoped ZnO film has the highest carrier concentration of . The photoluminescence spectra show the emissions related to FE, DAP and many defects such as , , and . The p-type defects (, , and ) are dominant. The undoped ZnO thin film has a better p-type conductivity compared with N-doped ZnO thin film.

Enhancement of Electrical Properties on ZnO: Al Thin Film due to Hydrogen Annealing and SiO 2 Coating in Damp-heat Environment

The electrical stability of ZnO: Al thin films deposited on glass substrate by the RF magnetron sputtering method have been modified by a hydrogen annealing treatment and protection layer. AZO thin films were deposited at room temperature and different RF powers of 50, 100, 150, and 200 W to optimize the AZO film growth condition. The lowest value of resistivity of was obtained at 2 mtorr, room temperature, and a power level of 150 W. Then, the AZO thin films were annealed at for 1 h in hydrogen ambient. The minimum resistivity obtained was as-annealed at . The electrical properties were enhanced by the hydrogen annealing treatment. After a 72 h damp-heat treatment in harsh conditions of a water steam at for four representative samples, a degradation of electrical properties was observed. The sample of hydrogen-annealed AZO thin films with protection layer showed a slight degradation ratio(17%) of electrical properties and a preferable transmittance of 90%. The electrical stability of AZO thin films had been modified by hydrogen annealing treatment and protection layer.

Characterization, stability, and antioxidant activity of Salicornia herbaciea seed oil

We investigated the physicochemical properties, chemical composition, stability and antioxidant activity from seed oil of Salicornia herbaciea grown in Korea. The density, refractive index, acid value, peroxide value, iodine value, saponification value, and unsaponifiable matter of oil were 0.91mg/mL, 1.48 at 20 °C, 1.89mg KOH/g oil, 10.20 mEq/kg oil, 1.08 g I/g oil, 216.21 mg KOH/g oil, and 2.60%, respectively. The major fatty acids were linoleic acid (43.73%), oleic acid (19.81%), arachidic acid (13.52%), and palmitic acid (11.84%), respectively. The oil contained high levels of α-tocopherol (249.2 mg/kg oil), followed by δ-tocopherol (89.3 mg/kg), and γ-tocopherol (75.6 mg/kg oil). The oil was found to have high levels of β-sitosterol (94.5mg/kg oil) and stigmasterol (65.7mg/kg oil), respectively. The total phenol, chlorophyll and β-carotene content of oil was 15.2, 94.5, and 8.2 mg/kg oil, respectively. The oil had good oxidative stability during 60 days of storage in a dark area at 50 °C. The maximum degradation rates of the oil were observed at 242.3 °C (9.5%/min), 382.6 °C (5.2%/min), and 440.7 °C (1.3%/min), respectively, where the rate of the weight decrease increased to a maximum up to this point. The ABTS radical scavenging activity of the oil was increased from 50.2 to 71.8% when the oil concentration extracted by methanol was increased from 100 to 300 μg/mL. This study suggests that S. herbaciea seed oil has potential use in functional foods, cosmetics or pharmaceuticals.

Implementation of High Carrier Mobility in Al-N Codoped p-Type ZnO Thin Films Fabricated by Direct Current Magnetron Sputtering with ZnO:Al 2 O 3 Ceramic Target

In this study, Al-N codoped p-type zinc oxide (ZnO) thin films were deposited on Si and homo-buffer layer templates in a mixture of and gas with ceramic ZnO:(2 wt% ) as a sputtering target using DC- magnetron sputtering. X-ray diffraction spectra of two-theta diffraction showed that all films have a predominant (002) peak of ZnO Wurtzite structure. As the fraction in the mixed and gases increased, field emission secondary electron microscopy revealed that the surface appearance of codoped films on Si varied from smooth to textured structure. The p-type ZnO thin films showed carrier concentration in the range of , resistivity in the range of 131.2-2.864 , and mobility in the range of respectively.

PL Property of Al-N Codoped p-type ZnO Thin Films Fabricated by DC Magnetron Sputtering

High-quality Al-N doped p-type ZnO thin films were deposited on Si and buffer layer/Si by DC magnetron sputtering in a mixture of and gas. The target was ceramic ZnO mixed with (2 wt%). The p-type ZnO thin films showed a carrier concentration in the range of , resistivity in the range of 131.22.864 , mobility in the range of 3.9931.6 , respectively. It was easier to dope p-type ZnO films on Si substrates than on buffer layer/Si. The film grown on Si showed the highest quality of photoluminescence (PL) characteristics. The Al donor energy level depth of Al-N codoped ZnO films was reduced to about 50 meV, and the N acceptor energy level depth was reduced to 63 meV.

Analysis of Electrical Property of Room Temperature-grown ZnO:Al Thin films Annealed in Hydrogen Ambient

In this paper, to establish growth technology of ZnO:Al thin films at low temperature applied to photoelectronic devices, ZnO:Al were prepared by RF magnetron sputtering on glass substrate at room temperature using different RF power with subsequent annealing process at different temperature in ambient. The resistivity of hydrogen-annealed ZnO:Al thin film at temperature of was reduced to from which was optimal value for as-grown films. X-ray photoelectron spectroscopy(XPS) revealed that improved electrical properties are ascribed to desorption of the negatively charged oxygen species from the grain boundary surfaces by the hydrogen annealing process.

Analysis of microstructure and electrical properties of Al-doped p-type ZnO thin films

We present the Al-doped p-type ZnO thin films fabricated by RF magnetron sputtering on n-Si (100) and homo-buffer layers in pure oxygen ambient. Al₂O₃ 2wt%-mixed ZnO ceramic was selected as a sputtering target. XRD spectra show that the Al-doped ZnO thin films have ZnO crystal structure. Hall Effect experiments show that p-type carrier concentrations are arranged from 1.66times10¹⁶ to 4.04times10¹⁸ cm^-3, mobility from 0.194 to 198 cm² V^-1 s^-1 and resistivity from 0.0963 to 18.4 Omegacm. FESEM cross-sectional images show compact structure of a p- type ZnO:Al thin film annealed at 800degC with mass density of 5.40 g/cm³ which is smaller than that of theoretical value of 5.67 g/cm³.I-V curve of p-n junction shows rectifying feature with turn-on voltage of 1.8 V.

Realization and Analysis of p-Type ZnO:Al Thin Film by RF Magnetron Sputtering

Al-doped p-type ZnO thin films were fabricated by RF magnetron sputtering on n-Si (100) and homo-buffer layers in pure oxygen ambient. ZnO ceramic mixed with 2 wt% was selected as a sputtering target. XRD spectra show that the Al-doped ZnO thin films have ZnO crystal structure. Hall Effect experiments with Van der Pauw configuration show that p-type carrier concentrations are arranged from to , mobilities from 0.194 to and resistivities from 0.0963 to . FESEM cross section images of different parts of a p-type ZnO:Al thin film annealed at show a compact structure. Measurement for same sample shows that density is which is smaller than theoretically calculated value of . Photoluminescence (PL) spectra at 10 K show a shoulder peak of p-type ZnO film at about 3.117 eV which is ascribed to electron transition from donor level to acceptor level (DAP).

Defect Analysis via Photoluminescence of p-type ZnO:N Thin Film fabricated by RF Magnetron Sputtering

ZnO is a promising material to make high efficient ultraviolet(UV) or blue light emitting diodes(LEDs) because of its large binding energy and energy bandgap. In this study, we prepared ZnO thin films with p-type conductivity on silicon(100) substrates by RF magnetron sputtering in the mixture of and . The process was accompanied by low pressure in-situ annealing in at and respectively. Hall effect in Van der Pauw configuration showed that the N-doped ZnO film annealed at has p-type conductivity. Photoluminescence(PL) spectrum of the film annealed at showed UV emission related to exciton and bound to donor-acceptor pair(DAP) as well as visible emission related to many intrinsic defects.