• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.5
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• pp.1057-1061
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• 2007

In this study, we investigated the properties of ZnO thin films prepared by layer-by-layer method in RF magnetron sputtering system using AlAs and ZnO targets. Effects of $H_2O_2$ dip prior to thermal treatment were studied as well. Either n-type or p-type films were observed in our study depending on the annealing conditions. It thus indicates the feasibility of arbitrarily modifying the conductivity type. At the same time, it also implies the thermal instabilities of the film properties. Property measurements after stressing the films up to 144 hours showed that thermal variations of properties nay be suppressed by pre-treatment in 30% $H_2O_2$ for 1 min.

• Journal of the Korean Ceramic Society
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• v.44 no.6 s.301
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• pp.303-307
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• 2007

Transparent In-doped zinc oxide (IZO) thin films are deposited with variation of pulsed DC power at Ar atmosphere on coming 7059 glass substrate by pulsed DC magnetron sputtering. A c-axis oriented IZO thin films were grown in perpendicular to the substrate. The optical transmittance spectra showed high transmittance of over 80% in the UV-visible region and exhibited the absorption edge of about 350 nm. Also, the IZO films exhibited the resistivity of ${\sim}10^{-3}{\Omega}\;cm$ and the mobility of ${\sim}6cm/V\;s$. Organic Light-emitting diodes (OLEDs) with IZO/N,N'-diphenyl-N, N'-bis(3-methylphenl)-1, 1'-biphenyl-4,4'-diamine (TPD)/tris (8-hydroxyquinoline) aluminum ($Alq_3$)/LiF/Al configuration were fabricated. LiF layer inserted is used as an interfacial layer to increase the electron injection. Under a current density of $100\;mA/cm^2$, the OLEDs show an excellent efficiency (9.4 V turn-on voltage) and a good brightness ($12000\;cd/m^2$) of the emission light from the devices. These results indicate that IZO films hold promise for anode electrodes in the OLEDs application.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.7
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• pp.567-571
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• 2009

Polycrystalline ZnO and Ga doped ZnO (GZO) films are deposited on glass substrate by RF magnetron sputtering at room temperature. The characteristics of ZnO and GZO films are investigated with X-ray diffraction measurement, UV-VIS-NIR spectrophotometer $(250{\sim}1200nm)$ and hall measurement. The post-growth thermal treatment of these films is carried out in N2 ambient at $500^{\circ}C$ for 30 min and an hour. ZnO and GZO films have different changing behavior of structural and optical properties by annealing. To use transparent conductive films for solar cell, films should have not only high transmittance but also good electrical property. Although as deposited GZO films have electrical properties than ZnO films, GZO films have not good transmittance properties. Consequently, we succeed that the high transmittance of GZO films is improved by annealing process.

• Korean Journal of Materials Research
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• v.11 no.10
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• pp.889-894
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• 2001

2wt% $Al_2O_3-doped$ ZnO (AZO) thin films were deposited on sapphire (0001) single crystal substrate by parellel type rf magnetron sputtering at 55$0^{\circ}C$. The as-grown AZO thin films was polycrystalline and showed only broad deep defect-level photoluminescence (PL). In order to examine the change of PL property, AZO thin films were annealed in $N_2$ (N-AZO) and $H_2$ (H-AZO) at the temperature of $600^{\circ}C$~$1000^{\circ}C$ through rapid thermal annealing. After annealed at $800^{\circ}C$, N-AZO shows near band edge emission (NBE) with very small deep-level emission, and then N-AZO annealed at $900^{\circ}C$ shows only sharp NBE with 219 meV FWHM. In Comparison with N-AZO, H-AZO exhibits very interesting PL features. After $600^{\circ}C$ annealing, deep defect-level emission was quire quenched and NBE around 382 nm (3.2 eV) was observed, which can be explained by the $H_2$passivation effect. At elevated temperature, two interesting peaks corresponding to violet (406 nm, 3.05 eV) and blue (436 nm, 2.84 eV) emission was firstly observed in AZO thin films. Moreover, peculiar PL peak around 694 nm (1.78 eV) is also firstly observed in all the H-AZO thin films and this is believed good evidence of hydrogenation of AZO. Based on defect-level scheme calculated by using the full potential linear muffin-tin orbital (FP-LMTO), the emission 3.2 eV, 3.05 eV, 3.84 eV and 1.78 eV of H-AZO are substantially deginated as exciton emission, transition from conduction band maximum to $V_{ Zn},$ from $Zn_i$, to valence band maximum $(V_{BM})$ and from $V_{o} to V_BM}$, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.2
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• pp.121-124
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• 2012

The characteristics of Ga-doped zinc oxide (GZO) thin films deposited at different deposition temperatures (TS~250 to $550^{\circ}C$) on 4H-SiC have been investigated. Structural and electrical properties of GZO thin film on n-type 4H-SiC(0001) were investigated by using x-ray diffraction(XRD), atomic force microscopy(AFM), Hall effect measurement, barrier height from I-V curve and Auger electron spectroscopy(AES). XRD $2\theta$ scan shows GZO thin film has preferential orientation with c-axis perpendicular to SiC substrate surface. The lowest resistivity ($\sim1.9{\times}10^{-4}{\Omega}cm$) was observed for the GZO thin film deposited at $400^{\circ}C$. As deposition temperature increases, barrier height between GZO and SiC was increased. Whereas, resistivity of GZO thin films as well as barrier height between GZO and SiC were increased after annealing process in air atmosphere. It has been found that the c-axis oriented crystalline quality as well as the relative amount of activated Ga3+ ions and oxygen vacancy may affect the electrical properties of GZO films on SiC.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.34-35
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• 2006

Transparent ZnO thin film transistor (TFT) is fabricated on the glass substrates. The device consists of a high mobility intrinsic ZnO as a semiconductor active channel, Ga doped ZnO (GZO) as an electrode, $HfO_2$ as a gate insulator. GZO and $HfO_2$ layers are prepared by using a pulsed laser deposition and intrinsic ZnO layers are fabricated by using an rf-magnetron sputtering, respectively. The transparent TFT is highly transparent (> 87 %) and exhibits n-channel, enhancement mode behavior with a field-effect mobility as large as $11.7\;cm^2/Vs$ and a drain current on-to-off ratio of about $10^5$.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.1
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• pp.97-101
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• 2016

ZnO has nanostructured material because of unique properties suitable for various applications. Amongst all chemical and physics methods of synthesis of ZnO nanostructure, the hydrothermal method is attractive for its simplicity and environment friendly condition. Nanostructure ZnO thin films have been successfully synthesized on fluorine doped tin oxide (FTO) substrate using hydrothermal method. A possible growth mechanism of the various nanostructures ZnO is discussed in schematics. The prepared materials were characterized by standard analytical techniques, i.e., X-ray diffraction (XRD) and Field-emission scanning electron microscopy (SEM). The XRD study showed that the obtained ZnO nanostructure thin films are in crystalline nature with hexagonal wurtzite phase. The SEM image shows substrate surface covered with nanostructure ZnO nanrod. The UV-vis absorption spectrum of the synthesized nanostructure ZnO shows a strong excitonic absorption band at 365 nm which indicate formation nanostructure ZnO thin film. Photoluminescence spectra illustrated two emission peaks, with the first one at 424 nm due to the band edge emission of ZnO and the second broad peak centered around 500 nm possibly due to oxygen vacancies in nanostructure ZnO. The Raman measurements peaks observed at $325cm^{-1}$, $418cm^{-1}$, $518cm^{-1}$ and $584cm^{-1}$ indicated that nanostrusture ZnO thin film is high crystalline quality. We trust that nanostructure ZnO material can be effectively will be used as a highly active and stable phtocatalysis application.

• Electrical & Electronic Materials
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• v.8 no.1
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• pp.21-26
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• 1995

Highly sensitive and mechanically stable gas sensors have been fabricated using the microfabrication and micromaching techniques. The sensing material used to detect the offensive trimethylarnine ((CH$_{3}$)$_{3}$N) gas is 6 wt% $Al_{2}$O$_{3}$-doped, 1000.angs.-thick ZnO deposited by r. f. magnetron sputtering. The optimum operating temperature of the sensor is 350.deg.C and the corresponding heater power is about 85mW. Excellent thermal insulation is achieved by the use of a double-layer structure of 0.2.mu.m -thick silicon nitride and 1.4.mu.m-thick phosphosilicate glass(PSG) prepared by low pressure chemical vapor deposition(LPCVD) and atmospheric pressure chemical vapor deposition(APCVD), respectively. The sensors are mechanically stable enough to endure at least 43, 200 heat cycles between room temperature and 350.deg. C.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.707-710
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• 2006

Zinc oxide (ZnO) is typically highly doped n-type semiconductor. To be used for thin-film transistor (TFT) devices, carrier concentration must be controlled precisely. We studied characteristics of ZnO grown by MOCVD at temperatures between $200^{\circ}C$ and $400^{\circ}C$. We found that hydrogen incorporated during growth plays important role in determining carrier density.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.2
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• pp.115-118
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• 2017

Highly photosensitive and wide bandgap amorphous silicon oxide (a-$SiO_x$:H) films were developed at low temperature ranges ($100{\sim}150^{\circ}C$) with employing plasma-enhanced chemical vapor deposition by optimizing $H_2/SiH_4$ gas ratio and $CO_2$ flow. Photosensitivity more than $10^5$ and wide bandgap (1.81~1.85 eV) properties were used for making the a-$SiO_x$:H thin film solar cells, which exhibited a high open circuit voltage of 0.987 V at the substrate temperature of $100^{\circ}C$. In addition, a power conversion efficiency of 6.87% for the cell could be improved up to 7.77% by employing a new n-type nc-$SiO_x$:H/ZnO:Al/Ag triple back-reflector that offers better short circuit currents in the thin film photovoltaic devices.