• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.12
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• pp.794-799
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• 2017

Ga-doped ZnO (GZO) films were deposited by an RF magnetron sputtering method on glass substrates using ZnO as a target containing 5 wt% $Ga_2O_3$ powder (for Ga doping). The structural, electrical, and optical properties of the GZO thin films were investigated as a function of the substrate temperatures. The deposition rate decreased with increasing substrate temperatures from room temperature to $350^{\circ}C$. The films showed typical orientation with the c-axis vertical to the glass substrates and the grain size increased up to a substrate temperature of $300^{\circ}C$ but decreased beyond $350^{\circ}C$. The resistivity of GZO thin films deposited at the substrate temperature of $300^{\circ}C$ was $7{\times}10^{-4}{\Omega}cm$, and it showed a dependence on the carrier concentration and mobility. The optical transmittances of the films with thickness of $3,000{\AA}$ were above 80% in the visible region, regardless of the substrate temperatures.

• Current Photovoltaic Research
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• v.8 no.2
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• pp.60-65
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• 2020

In perovskite solar cells with planar heterojunction configuration, selection of proper charge-transporting layers is very important to achieve stable and efficient device. Here, we developed solution processible Cu doped NiO_x (Cu:NiO_x) thin film as a hole-transporting layer (HTL) in p-i-n structured methylammonium lead trihalide (MAPbI₃) perovskite solar cell. The transmittance and thickness of NiO_x HTL is optimized by control the spin-coating rate and Cu is additionally doped to improve the surface morphology of undoped NiO_x thin film and hole-extraction properties. Consequently, a perovskite solar cell containing Cu:NiO_x HTL with optimal doping ratio of Cu exhibits a power conversion efficiency of 14.6%.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.56-56
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• 2018

Transparent conductive oxides (TCOs) have attracted attention due to their high electrical conductivity and optical transparency in the visible region. Consequently, TCOs have been widely used as electrode materials in various electronic devices such as flat panel displays and solar cells. Previous studies on TCOs focused on their electrical and optical performances; there have been numerous attempts to improve these properties, such as chemical doping and crystallinity enhancement. Recently, due to rapidly increasing demand for flexible electronics, the academic interest in the mechanical stability of materials has come to the fore as a major issue. In particular, long-term stability under bending is a crucial requirement for flexible electrodes; however, research on this feature is still in the nascent stage. Hydrogen-incorporated amorphous In-Sn-O (a-ITO) thin films were fabricated by introducing hydrogen gas during deposition. The hydrogen concentration in the film was determined by secondary ion mass spectrometry and was found to vary from $4.7{\times}10^{20}$ to $8.1{\times}10^{20}cm^{-3}$ with increasing $H_2$ flow rate. The mechanical stability of the a-ITO thin films dramatically improved because of hydrogen incorporation, without any observable degradation in their electrical or optical properties. With increasing hydrogen concentration, the compressive residual stress gradually decreased and the subgap absorption at around 3.1 eV was suppressed. Considering that the residual stress and subgap absorption mainly originated from defects, hydrogen may be a promising candidate for defect passivation in flexible electronics.

• Progress in Superconductivity and Cryogenics
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• v.16 no.3
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• pp.4-6
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• 2014

Among Fe-based superconductors, potassium doped $BaFe_2As_2$ is favorable for applications because of its relatively high transition temperature and low anisotropy. To study the superconducting properties and the applicable aspects, high quality thin films of potassium doped $BaFe_2As_2$ should be fabricate. However, the high volatility of potassium makes it difficult to fabricate thin films of this compound. In this paper, we discuss the details of the experimental conditions used to fabricate $Ba_{1-x}K_xFe_2As_2$ films by ex situ PLD method. In the first set of samples, barium ratio in the target was controlled to make films with various potassium doping rate. However, in the second set of samples, the amount of potassium was controlled to find out optimal conditions for making high quality $Ba_{1-x}K_xFe_2As_2$ films.

• Journal of the Korean Ceramic Society
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• v.46 no.2
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• pp.181-188
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• 2009

The electrical property and microstructure in $BaTiO_3$ ceramics doped rare-earth ions with intermediate ionic size ($Dy^{3+},Ho^{3+},Y^{3+}$) were investigated. Microstructures have been characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Incorporation of rare-earth ions to $BaTiO_3$ ceramics depended on their ionic radius sensitively. Compared to Ho and Y ions, Dy ions provide $BaTiO_3$ ceramics with the high rate of densification and well-developed shell formation, due to their high solubility in the $BaTiO_3$ lattice, but the microstructure of Dy doped $BaTiO_3$ ceramics is unstable at high temperature, because Dy ions could not play a role of grain growth inhibition, leading to diffuse into $BaTiO_3$ lattice continuously after completion of densification during sintering. Comparing electrical property and microstructure, it is shown that the reliability of capacitor improved by high shell ratio.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.28-28
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• 2008

We have demonstrated the combinatorial synthesis of a variety of transparent conducting oxides using a combinatorial sputter system. The effects of a wide range of Nb or Zn doping rate on the optical and electrical properties of Indium-tin oxides (ITO) films were investigated. The Nb or Zn doped ITO films were fabricated on glass substrates, using combinatorial sputtering system which yields a linear composition spread of Nb or Zn concentration in ITO films in a controlled manner by co-sputtering two targets of ITO and $Nb_2O_5$ or ITO and ZnO. We have examined the work-function, resistivity, and optical properties of the Nb or Zn-doped ITO films. Furthermore, the effects of Hz plasma treatment on the physical properties of Ga or Zn doped ITO films synthesized by combinatorial sputter system were investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.159-159
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• 2008

Indium-tin oxides (ITO) films have been widely used as transparent electrodes for optoelectronic devices such as organic light emitting diodes (OLEDs), photovoltaics, touch screen devices, and flat-paneldisplay. In particular, to improve hole injection efficiency in OLEDs, transparent electrodes should have high work-function besides their transparency and low resistivity. Nevertheless, few studies have been made on engineering the work function of ITO for use as an efficient anode. In this study, the effects of a wide range of Nb or Zn doping rate on the changes in work functions of ITO anode were investigated. The Nb or Zn doped ITO films were fabricated on glass substrates using combinatorial sputtering system which yields a linear composition spread of Nb or Zn concentration in ITO films in a controlled manner by co-sputtering two targets of ITO and Nb2O5 or ITO and ZnO. We have also examined the resistivity, transmittance, and other structural properties of the Nb or Zn-doped ITO films. Furthermore, OLEDs employing Nb or Zn-doped ITO anodes were fabricated and the device performances were investigated concerned with the work function changes.

• Journal of Magnetics
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• v.8 no.4
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• pp.129-132
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• 2003

We investigated the crystallographic and magnetic properties of double perovskite $Sr_2Fe_{l-x}Cr_{x}MoO_{6}$ (x=0.0, 0.01, 0.03, 0.05, and 0.10). Mossbauer spectra of the $Sr_2Fe_{l-x}Cr_{x}MoO_{6}$ have been taken at various temperatures ranging from 15 to 415 K. As the temperature increased towards $T_{c}$(415 K), the Mossbauer spectra showed line broadening and 1, 6 and 3, 4 line-width differences because of anisotropic hyperfine field fluctuation. The Mossbauer spectra indicated that an anisotropic field fluctuation of +H ( $P_{+}$=0.85) was greater than that of -H ($P_{-}$=0.15). We also calculated the field fluctuation frequency factors and the temperature dependence of anisotropy energies from its relaxation rate. We interpreted the effect of Cr ($t^3$$_{2g}$) doping as a decrease in the anisotropy energy.

• Journal of Surface Science and Engineering
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• v.28 no.3
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• pp.142-151
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• 1995

In this research, a thin layer of Cr was coated on the pure Ni and Inconel 601 by PECVD (Plasma Enhanced Chemical Vapor Deposition) in order to study the effect of Cr on the oxidation behavior at high temperature. Cr coated Inconel 601, which was oxidized at $1100^{\circ}C$ for 24 hours, formed a protective $Cr_2O_3$ oxide layer and the resistance to isothermai oxidation was improved. On the other hand, oxidation resistance of Cr coated Inconel 601 at 100$0^{\circ}C$ was not significantly improved, probably due to the formation or insufficient $Cr_2O_3$ layer. But, when oxidized at $1000^{\circ}C$ and $1100^{\circ}C$ for 100 hours, Cr coated Inconel 601 improved isothermal oxidation resistance by the formation of continuous $Cr_2O_3$ external scale and by the development of $Al_2O_3$ subscales. Cr coated Ni formed inner layer of $Cr_2O_3$ within almost pure NiO, which provided additional cation vacancies, thus increasing the mobility of Ni ions in this region. It is believed that this doping effect resulted in an increase in the observed oxidation rate compared with pure Ni and did not improve the oxidation resistance.

• Journal of Sensor Science and Technology
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• v.19 no.3
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• pp.197-201
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• 2010

This paper describes the fabrication and characteristics of a NO sensor using ZnO thin film integrated 3C-SiC micro heater based on polycrystalline 3C-SiC thin film of operation in harsh environments. The sensitivity, response time, and operating properties in high temperature and voltages of NO sensors based SiC MEMS are measured and analyzed. The sensitivity of device with pure ZnO thin film at the heater operating power of 13.5 mW ($300^{\circ}C$) is 0.875 in NO gas concentration of 0.046 ppm. In the case of Pt doping, the sensitivity of at power consumption of 5.9 mW ($250^{\circ}C$) was 1.92 at same gas flow rate. The ZnO with doped Pt was showed higher sensitivity, lower working temperature and faster adsorption characteristics to NO gas than pure ZnO thin film. The NO gas sensor integrated SiC micro heater is more strength than others in high voltage and temperature environments.