• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.423-423
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• 2007

In this study, the effects of annealing conditions on the structural and optical properties of ZnO films were investigated. ZnO oxide (ZnO) films were deposited onto $SiO_2$/Si substrates by RF magnetron sputtering from a ZnO target. The substrate was not heated during deposition. ZnO films were annealed in temperature ranges of $500{\sim}650^{\circ}C$ in the $O_2$ flow for 5 ~ 20 min. The film average thicknesses were in the range of 291 nm. The surface morphologies and structures of the samples were characterized by SEM and XRD, respectively. The optical properties were evaluated by PL measurement at room temperature using a He-Cd 325 nm laser. According to the results, the optimal annealing conditions for the best photoluminescence (PL) characteristics were found to be oxygen fraction, ($O_2/O_2+Ar$) of 20%, RF power of 240W, substrate temperature of RT (room temperature), annealing condition of $600^{\circ}C$ for 20 min, and sputtering pressure of 20 mTorr. The obtained wavelength of light emission was found at 379 nm (ultraviolet-UV region). However, the optimal parameters for the best PL characteristics of ZnO thin films were not consistent with those obtained from the (002) intensities of XRD analyses. As a result, XRD pattern was not considered as the key issue concerning the intensity of PL of ZnO thin film. The intensity of the emitted UV light will correspond to the grain size of ZnO film.

• Transactions on Electrical and Electronic Materials
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• v.9 no.1
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• pp.24-27
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• 2008

ZnO has intensively attracted interest for the next generation of short wavelength LEDs and semiconductor lasers. However, for the development and application of the devices based on this material, the fabrication of p-type ZnO thin films is pivotal. Generally, the process of preparation of ZnO is unavoidably accompanied by the natural donor ions such as interstitial Zn ions and oxygen vacancy ions that show n-type electrical property and make fabrication of p-type ZnO to be a hard problem. On this study, to realize stable high-quality p-type ZnO thin films, the undoped ZnO thin films were diffused with P in vapor state. The ZnO:P thin films showed high-quality p-type properties electrically and optically.

• Korean Journal of Materials Research
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• v.18 no.2
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• pp.84-91
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• 2008

The effects of the deposition and annealing temperature on the structural, electrical and optical properties of Ag doped ZnO (ZnO : Ag) thin films were investigated. All of the films were deposited with a 2wt% $Ag_2O-doped$ ZnO target using an e-beam evaporator. The substrate temperature varied from room temperature (RT) to $250^{\circ}C$. An undoped ZnO thin film was also fabricated at $150^{\circ}C$ as a reference. The as-grown films were annealed in temperatures ranging from 350 to $650^{\circ}C$ for 5 h in air. The Ag content in the film decreased as the deposition and the post-annealing temperature increased due to the evaporation of the Ag in the film. During the annealing process, grain growth occurred, as confirmed from XRD and SEM results. The as-grown film deposited at RT showed n-type conduction; however, the films deposited at higher temperatures showed p-type conduction. The films fabricated at $150^{\circ}C$ revealed the highest hole concentration of $3.98{\times}1019\;cm^{-3}$ and a resistivity of $0.347\;{\Omega}{\cdot}cm$. The RT PL spectra of the as-grown ZnO : Ag films exhibited very weak emission intensity compared to undoped ZnO; moreover, the emission intensities became stronger as the annealing temperature increased with two main emission bands of near band-edge UV and defect-related green luminescence exhibited. The film deposited at $150^{\circ}C$ and annealed at $350^{\circ}C$ exhibited the lowest value of $I_{vis}/I_{uv}$ of 0.05.

• Journal of the Korean Ceramic Society
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• v.26 no.2
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• pp.258-266
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• 1989

The effects of grain size and dopant ZnO on the photoelectrochemical conversion in TiO2 ceramic electrodes have been investigated. The photocurrent increases with increasing grain size in the undoped TiO2 ceramic electrode. In ZnO-doped TiO2 electrodes, the photocurrent decreases with increasing ZnO up to 0.4 wt% due to decrease of donor concentration, and then with further addition of ZnO, photocurrent increases according to the formation of second phase. However, the photoresponse appears at wavelength of 420nm, which is very close to the energy band gap of TiO2, regardless of grain size and amount of ZnO.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.147-147
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• 2010

PTC Thermistors specimens were fabricated by added $MnO_2$ as donors, and $Nb_2O_5$ as acceptors and sintered $1250^{\circ}C$/2hrs. Average grain size decreased with increased in added $MnO_2$, and increased with added in $Nb_2O_5$. But, appeared liquid phase as $Bi_2O_3$ and $TiO_2$, affect to grain growth. XRD result, peak strength waslowed then crystallization not well, but, secondary phase were not showed all specimens. All specimens resistance were so high, about $40M{\Omega}$ over, couldn't measured to those resistance and doesn't appear PTCR effect.

• Journal of the Korean Vacuum Society
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• v.19 no.5
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• pp.385-390
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• 2010

We studied the optical characteristics of ZnO:Al and $Al_2O_3$ coated ZnO nanorods. When ZnO:Al is deposited around the undoped ZnO nanorods, thermal diffusion of Al into ZnO gives rise to decrease the binding energy of neutral donor bound exciton whereas an insulating Al2O3 is coated around ZnO, we found that semiconducor-insulator interface states play an important role in optical quenching.

• Journal of the Korean Ceramic Society
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• v.35 no.1
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• pp.17-22
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• 1998

B-doped ZnO thin films on glass substrates were prepared by sputtering the ceramic targets which had been prepared by sintering disks consisting of ZnO and various amounts of B2O3 While pure ZnO films show-ed a c-axis oriented growth the B-doping retarded the prefered orientation and grain growth of the film. Electron concentrations for undoped and B-doped ZnO films were on the order of 7.8${\times}$1018 cm-3 and 5${\times}${{{{ {10 }^{20 } }} c{{{{ {m }^{-3 } }} respectively. The electron mobility however decreased with the B-doping concentration. Optical meas-urements on the films showed that the average transmittance in the visible range was higher than 85% The measurements also indicated a blueshift of the absorption edge with doping.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.420-420
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• 2012

ZnO seed layer were deposited on quartz substrate by sol-gel method and prism-like Al-doped ZnO nanorods (AZO nanorods) were grown on ZnO seed layer by hydrothermal method with various Al concentration ranging from 0 to 2.0 at.%. Structural and optical properties of the AZO nanorods were investigated by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), photoluminescence (PL). The diameter of the AZO nanorods was smaller than undoped ZnO nanorods and its diameter of the AZO nanorods decreased with increasing Al concentration. In XRD spectrum, it was observed that stress and full width at half maximum (FWHM) of the AZO nanorods decreased and the 'c' lattice constant increased as the Al concentration increased. From undoped ZnO nanorods, it was observed that the green-red emission peak of deep-level emission (DLE) in PL spectra. However, after Al doping, not only a broad green emission peak but also a blue emission peak of DLE were observed.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.452-452
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• 2013

ZnO is one of the most attractive transparent conductive oxide (TCO) films because of low toxicity, a wide band gap material and relatively low cost. However, the electrical conductivity of un-doped ZnO is too high to use it as TCO films in practical application. To improve electrical properties of undoped ZnO, transition metal (TM) doped ZnO films such as Al doped ZnO or Ti doped ZnO have been extensively studied. Here, we prepared Ti doped ZnO thin films by atomic layer deposition (ALD) for the application of TCO films. ALD was used to prepare Ti-doped ZnO thin films due to its inherent merits such as large area uniformity, precise composition control in multicomponent thin films, and digital thickness controllability. Also, we demonstrated that ALD method can be utilized for fabricating highly ordered freestanding nanostructures of Ti-doped ZnO thin films by combining with BCP templates, which can potentially used in the photovoltaic applications.

• Korean Journal of Materials Research
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• v.30 no.8
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• pp.399-405
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• 2020

In the present investigation we show the effect of Al doping on the length, size, shape, morphology, and sensing property of ZnO nanorods. Effect of Al doping ultimately leads to tuning of electrical and optical properties of ZnO nanorods. Undoped and Al-doped well aligned ZnO nanorods are grown on sputtered ZnO/SiO₂/Si (100) pre-grown seed layer substrates by hydrothermal method. The molar ratio of dopant (aluminium nitrate) in the solution, [Al/Zn], is varied from 0.1 % to 3 %. To extract structural and microstructural information we employ field emission scanning electron microscopy and X-ray diffraction techniques. The prepared ZnO nanorods show preferred orientation of ZnO <0001> and are well aligned vertically. The effects of Al doping on the electrical and optical properties are observed by Hall measurement and photoluminescence spectroscopy, respectively, at room temperature. We observe that the diameter and resistivity of the nanorods reach their lowest levels, the carrier concentration becomes high, and emission peak tends to approach the band edge emission of ZnO around 0.5% of Al doping. Sensing behavior of the grown ZnO nanorod samples is tested for H₂ gas. The 0.5 mol% Al-doped sample shows highest sensitivity values of ~ 60 % at 250 ℃ and ~ 50 % at 220 ℃.