• Korean Journal of Materials Research
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• v.17 no.12
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• pp.629-633
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• 2007

This study examined the effect of growth temperature on the electrical and optical properties of hydrogenated Al-doped zinc oxide (AZO:H) thin films deposited by rf magnetron sputtering using a ceramic target (98 wt.% ZnO, 2 wt.% $Al_2O_3$). Various AZO films on glass were prepared by changing the substrate temperature from room temperature to $200^{\circ}C$. It was shown that intentionally incorporated hydrogen plays an important role on the electrical properties of AZO : H films by increasing free carrier concentration. As a result, in the 2% $H_2$ addition at the growth temperature of $150^{\circ}C$, resistivity of $3.21{\times}10^{-4}{\Omega}{\cdot}cm$, mobility of $21.9cm^2/V-s$, electric charge carrier concentration of $9.35{\times}10^{20}cm^{-3}$ was obtained. The AZO : H films show a hexagonal wurtzite structure preferentially oriented in the (002) crystallographic direction.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.329.1-329.1
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• 2014

In this paper, we report electrical, optical and structural properties of Al-doped zinc oxide (AZO) thin films deposited at different substrate temperatures and pressures. The films were prepared by radio frequency (RF) magnetron sputtering on glass substrates in argon (Ar) ambient. The X-ray diffraction analysis showed that the AZO films deposited at room temperature (RT) and 20 Pa were mostly oriented along a-axis with preferred orientation along (100) direction. There was an improvement in resistivity ($3.7{\times}10^{-3}{\Omega}-cm$) transmittance (95%) at constant substrate temperature (RT) and working pressure (20 Pa) using the Hall-effect measurement system and UV-vis spectroscopy, respectively. Our results have promising applications in low-cost transparent electronics, such as the thin-film solar cells and thin-film transistors due to favourable deposition conditions. Furthermore our film deposition method offers a procedure for preparing highly oriented (100) AZO films.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.7
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• pp.8-16
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• 2010

In this paper, we investigated the effects of $O_2$ fraction on the properties of Al-doped ZnO (AZO) thin films prepared by radio frequency (RF) magnetron sputtering. Hall, photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS) measurements revealed that the p-type conductivity was exhibited for AZO films with an $O_2$ fraction of 0.9 while the n-type conductivity was observed for films with $O_2$ fractions in range of 0 - 0.6. PL and XPS also showed that the acceptor-like defects, such as zinc vacancies and oxygen interstitials, increased in films prepared by an $O_2$ fraction of 0.9, resulting in the p-type conductivity in the films. Hall results indicated that AZO films prepared by $O_2$ fractions in range of 0 - 0.6 can be used for electrode layers in the applications of transparent thin film transistor. We concluded from the X-ray diffraction analysis that worse crystallinity with a smaller grain size as well as higher tensile stress was observed in the films prepared by a higher $O_2$ fraction, which is related to incorporation of more oxygen atoms into the films during deposition. The study of atomic force microscope suggested that the smoother surface morphology was observed in films prepared by using $O_2$ fraction, which causes the higher resistivity in those films, as evidenced by Hall measurements.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.123-123
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• 2015

Al doped ZnO(AZO) films as a transparent conductive oxide (TCO) electrode were deposited on glass, polyethylene naphthalate (PEN) and polyethylene terephthalate (PET) at room temperature by a conventional rf-magneton sputtering (CMS) and a facing target sputtering (FTS) using Al2O3 and ZnO targets. In order to investigation of AZO properties, the structural, surface morphology, electrical, and optical characteristics of AZO films were respectively analyzed. The resistivities of AZO films using FTS system were $6.50{\times}10-4{\Omega}{\cdot}cm$ on glass, $7.0{\times}10-4{\Omega}{\cdot}cm$ on PEN, and $7.4{\times}10-4{\Omega}{\cdot}cm$ on PET substrates, while the values of AZO films using CMS system were $7.6{\times}10-4{\Omega}{\cdot}cm$ on glass, $1.20{\times}10-3{\Omega}{\cdot}cm$ on PEN, and $1.58{\times}10-3{\Omega}{\cdot}cm$ on PET substrates. The AZO-films deposited by FTS system showed uniform surface compared to those of the films by CMS system. We thought that the films deposited by FTS system had low stress due to bombardment of high energetic particles during CMS process, resulted in enhanced electrical conductivity and crystalline quality by highly c-axis preferred orientation and closely packed nano-crystalline of AZO films using FTS system.

• 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.22 no.2
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• pp.137-141
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• 2009

AZO transparent conductive thin films were grown on $SiO_2$/Si and glass substrates using diethylzinc (DEZ) and trimethylaluminium (TMA) as the precursor and $H_2O$ as oxidant by atomic layer deposition. The structural, electrical, and optical properties of the AZO films were characterized as a function of film thickness at a deposition temperature of $150^{\circ}C$. The AZO films with various thicknesses show well-crystallized phases and smooth surface morphologies. The 190-nm-thick AZO films grown on Coming 1737 glass substrates exhibit rms(root mean square) roughness of 8.8 nm, electrical resistivity of $1.5{\times}10^{-3}\;{\Omega}-cm$, and an optical transmittance of 84% at 600nm wavelength. Atomic layer deposition technique for the transparent conductive oxide films is possible to apply for the deposition on flexible polymer substrates.

• Korean Journal of Metals and Materials
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• v.46 no.4
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• pp.249-256
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• 2008

0.5 wt% Al doped ZnO thin films (AZO) were prepared on glass substrates using RF magnetron sputtering method. Thin films were grown at substrate temperature of $250^{\circ}C$, RF power of 75W, working pressure of 10 mTorr, by changing the $O_2/Ar$ pressure ratio from 0% to 16.7%. The effects of oxygen partial pressure during the deposition process on structural and optical properties of the films were investigated using XRD, SEM, AFM, EPMA and UV-visible spectroscopy. All the AZO thin films were grown as hexagonal wurtzite phase with the c-axis preferred out-of-plane orientation. The surface roughness and grain size of AZO films decreased with increasing oxygen ratio from 10.6 nm to 3.2 nm and 94.9 nm to 30.9 nm, respectively. On the other hand, the transmittance and band gap energy of the AZO films increased from 84.7% to 92.6% and 3.24 eV to 3.28 eV, respectively with increasing the $O_2/Ar$ pressure ratio.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.3
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• pp.691-698
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• 2010

In this study Al-doped ZnO (AZO) thin films have been fabricated on Eagle 2000 glass substrates at various substrate temperature ($100{\sim}500^{\circ}C$) and working pressure (10 ~ 40 mTorr) by RF magnetron sputtering in order to investigate the structural, electrical, and optical properties of the AZO thin films. The obtained films were polycrystalline with a hexagonal wurtzite structure and preferentially oriented in the (002) crystallographic direction. The AZO thin films, which were deposited at $T=300^{\circ}C$ for 10 mTorr, shows the highest (002) orientation, and the full width at half maximum (FWHM) of the (002) diffraction peak is $0.42^{\circ}$. The lowest resistivity ($2.64{\times}10^{-3}\;{\Omega}cm$) with the highest cartier concentration ($5.29{\times}10^{20}\;cm^{-3}$) and a Hall mobility of ($6.23\;cm^2/Vs$) are obtained in the AZO thin films deposited at $T=300^{\circ}C$ for 10 mTorr. The optical transmittance in the visible region is approximately 80%, regardless of process conditions. The optical band-gap depends on the Al doping level as the substrate temperature increases and the working pressure decrease. The optical band-gap widening is proportional to cartier concentration due to the Burstein-Moss effect.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.67-68
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• 2006

We prepared the AZO thin film with different $O_2$ gas flow rate. the AZO thin films were deposited on glass substrate at room temperature, working gas pressure of 1mTorr. the electrical, structural and optical properties of AZO thin films were investigated by using Hall Effect measurement system, X-ray Diffractometer (XRD) and UV-VIS spectrometer. From the results, we could obtain that AZO thin film with low resistivity of $8.5{\times}10^{-4}{\Omega}cm$ was exhibited in specific $O_2$ gas flow rate. Also, the transmittance of over 80% in visible range was observed in specific $O_2$ gas flow rate. In all of the AZO thin film with the transmittance of over 80%, diffraction peak of (002) direction was observed, while amorphous peak was observed in the AZO thin film with the low transmittance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.403-404
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• 2007

We prepared the Al doped ZnO (AZO) thin film on polyethersulfon (PES) without any substrate heating by Facing Targets Sputtering (FTS) system. ZnO doped the content of Al 2 wt% was used and the sputtering conditions were gas pressure 1mTorr and input power 100W. The electrical, structural and optical properties of AZO thin films were investigated. To investigate the as-deposited thin film properties, we employed four-point probe, UV/VIS spectrometer, X-ray diffractometer (XRD), scanning electron microscopy (SEM), Hall Effect measurement system and Atomic Force Microscope (AFM).