• Journal of the Korean Vacuum Society
• /
• v.22 no.3
• /
• pp.119-125
• /
• 2013

In this study, we studied the properties of ZnO(Al) and ZnO(AlGa) thin film according to film thickness deposited on SLG by In-line magnetron sputtering system. XRD, FESEM, 4-point probe, Hall measurement system and UV/Vis-NIR spectrophotometer were employed to analyze the properties of ZnO(Al) and ZnO(AlGa) thin film. The all films exhibited (002) preferential orientation with clear peak shape and high intensity. The carrier concentration and Hall mobility of ZnO(Al) and ZnO(AlGa) thin film were improved with increasing thickness. The resistivity of both films decreased when the film thickness was raised from 500 nm to 1,450 nm. And then relatively the resistivity of ZnO(AlGa) film was lower than that of ZnO(Al) film. The transmittance of the films decreased with increasing film thickness but all films exhibited optical transmittances of over 83.3% in the visible region.

• Korean Journal of Materials Research
• /
• v.13 no.8
• /
• pp.519-523
• /
• 2003

We report the synthesis of cubic spinel $ZnCo_2$$O_4$thin films and the tunability of the conduction type by control of the oxygen partial pressure ratio. Zinc cobalt oxide films were grown on$ SiO_2$(200 nm)/Si substrates by reactive magnetron sputtering method using Zn and Co metal targets in a mixed Ar/$O_2$atmosphere. We found from X-ray diffraction measurements that the crystal structure of the zinc cobalt oxide films grown under an oxygen-rich condition (the $O_2$/Ar partial pressure ratio of 9/1) changes from wurtzite-type $Zn_{1-x}$ $Co_{X}$O to spinel-type $ZnCo_2$$O_4$with the increase of the Co/Zn sputtering ratio,$ D_{co}$ $D_{zn}$ . We noted that the above structural change accompanied by the variation of the majority electrical conduction type from n-type (electrons) to p-type (holes). For a fixed $D_{co}$ $D_{zn}$ / of 2.0 yielding homogeneous spinel-type $_2$O$ZnCo_4$films, the type of the majority carriers also varied, depending on the$ O_2$/Ar partial pressure ratio: p-type for an $O_2$-rich and n-type for an Ar-rich atmosphere. The maximum electron and hole concentrations for the Zn $Co_2$ $O_4$films were found to be 1.37${\times}$10$^{20}$ c $m^{-3}$ and 2.41${\times}$10$^{20}$ c $m^{-3}$ , respectively, with a mobility of about 0.2 $\textrm{cm}^2$/Vs and a high conductivity of about 1.8 Ω/$cm^{-1}$ /.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.454-454
• /
• 2010

In order to achieve a high efficient a-Si solar cell, the TCO (transparent conductive oxide) substrates are required to be a low sheet resistivity, a high transparency, and a textured surface with light trapping effect. Recently, a zinc oxide (ZnO) thin film attracts our attention as new coating material having a good transparent and conductive for TCO of solar cells. In this paper the optical properties of $H_2$ post-treated BZO (boron doped ZnO, ZnO:B) thin film are investigated with $O_2$-plasma treatment. The BZO thin films by MOCVD (Metal Organic Chemical Vapor Deposition) are investigated and the samples of $H_2$ post-treated BZO thin film are tested with $O_2$-plasma treatment by plasma treatment system with 13.56 MHz as RIE (Reactive Ion Etching) type. We measured the optical properties and surface morphology of BZO thin film with and without $O_2$-plasma treatment. The optical properties such as transmittance, reflectance and haze are measured with integrating sphere and ellipsometer. This result of the BZO thin film with and without $O_2$-plasma treatment is application to the TCO for solar cells.

• Journal of the Korean Ceramic Society
• /
• v.43 no.2 s.285
• /
• pp.79-84
• /
• 2006

We studied the microstructure and magnetic property of the pulsed DC magnetron sputtered $Zn_{\0.8}Co_{0.2}O$ film as a function of substrate temperatures. The X-ray patterns of the $Zn_{\0.8}Co_{0.2}O$ film showed a strong (002) preferential orientation at $500^{\circ}C$. The films with a crystallite size of 23-35 nm were grown in the form of nano-sized structure and this tendency was remarkable with increasing substrate temperature. The UV-visible result showed that the $Zn_{\0.8}Co_{0.2}O$ film prepared above $300^{\circ}C$ has a high optical transmittance of over $80\%$ in the visible region. The absorption bands were observed due to sp-d interchange action by $Co^{2+}$ complex ion and dd transition in the region from 500 to 700nm. The resistivity of the film was below $10^{-1}\;\Omega-cm\;above\;300^{\circ}C$. The AGM analysis results for the all films showed the magnetic hysteresis curves of ferromagnetic nature. The low electrical resistivity and room temperature ferromagnetism of ZnCoO thin films 'deposited above $300^{\circ}C$ suggested the possibility for the application to Diluted Magnetic Semiconductors (DMSs).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.30 no.5
• /
• pp.307-311
• /
• 2017

ZnO:Al thin films were deposited on glass substrate by RF magnetron sputtering followed by in situ heat treatment in the same chamber. Effects of in situ heat treatment on properties of ZnO:Al thin films were investigated in this study. As heat treatment temperature was increased, crystal quality was improved first and then it was deteriorated, surface roughness was decreased, and sheet resistance was also decreased. The decrease in sheet resistance was caused by increasing carrier concentration due to decreased surface roughness. The decrease in surface roughness resulted in increase of transmittance. Therefore, in situ heat treatment is an effective method for obtaining films with better electrical characteristics.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.334-334
• /
• 2012

Transparent oxide semiconductors have recently attracted much attention as channel layer materials due to advantageous electrical and optical characteristics such as high mobility, high stability, and good transparency. In addition, transparent oxide semiconductor can be fabricated at low temperature with a low production cost and it permits highly uniform devices such as large area displays. A variety of thin film transistors (TFTs) have been studied including ZnO, InZnO, and InGaZnO as the channel layer. Recently, there are many studies for substitution of Ga in InGaZnO TFTs due to their problem, such as stability of devices. In this work, new quaternary compound materials, tantalum-indium-tin oxide (TaInSnO) thin films were fabricated by using co-sputtering and used for the active channel layer in thin film transistors (TFTs). We deposited TaInSnO films in a mixed gas (O2+Ar) atmosphere by co-sputtering from Ta and ITO targets, respectively. The electric characteristics of TaInSnO TFTs and thin films were investigated according to the RF power applied to the $Ta_2O_5$ target. The addition of Ta elements could suppress the formation of oxygen vacancies because of the stronger oxidation tendency of Ta relative to that of In or Sn. Therefore the free carrier density decreased with increasing RF power of $Ta_2O_5$ in TaInSnO thin film. The optimized characteristics of TaInSnO TFT showed an on/off current ratio of $1.4{\times}108$, a threshold voltage of 2.91 V, a field-effect mobility of 2.37 cm2/Vs, and a subthreshold swing of 0.48 V/dec.

• Korean Journal of Materials Research
• /
• v.23 no.3
• /
• pp.155-160
• /
• 2013

ZnO thin films co-doped with Mg and Ga (MxGyZzO, x + y + z = 1, x = 0.05, y = 0.02 and z = 0.93) were prepared on glass substrates by RF magnetron sputtering with different sputtering powers ranging from 100W to 200W at a substrate temperature of $350^{\circ}C$. The effects of the sputtering power on the structural, morphological, electrical, and optical properties of MGZO thin films were investigated. The X-ray diffraction patterns showed that all the MGZO thin films were grown as a hexagonal wurtzite phase with the preferred orientation on the c-axis without secondary phases such as MgO, $Ga_2O_3$, or $ZnGa_2O_4$. The intensity of the diffraction peak from the (0002) plane of the MGZO thin films was enhanced as the sputtering power increased. The (0002) peak positions of the MGZO thin films was shifted toward, a high diffraction angle as the sputtering power increased. Cross-sectional field emission scanning electron microscopy images of the MGZO thin films showed that all of these films had a columnar structure and their thickness increased with an increase in the sputtering power. MGZO thin film deposited at the sputtering power of 200W showed the best electrical characteristics in terms of the carrier concentration ($4.71{\times}10^{20}cm^{-3}$), charge carrier mobility ($10.2cm^2V^{-1}s^{-1}$) and a minimum resistivity ($1.3{\times}10^{-3}{\Omega}cm$). A UV-visible spectroscopy assessment showed that the MGZO thin films had high transmittance of more than 80 % in the visible region and that the absorption edges of MGZO thin films were very sharp and shifted toward the higher wavelength side, from 270 nm to 340 nm, with an increase in the sputtering power. The band-gap energy of MGZO thin films was widened from 3.74 eV to 3.92 eV with the change in the sputtering power.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.27 no.7
• /
• pp.472-476
• /
• 2014

We report the characteristics of thin-film transistor (TFT) to make the bi-channel structure with stacked $Mg_{0.1}Zn_{0.9}O$ (Mg= 10 at.%) and ZnO. The ZnO and $Mg_{0.1}ZnO_{0.9}O$ thin films were deposited by radio frequency (RF) co-sputter system onto the thermally oxidized silicon substrate. A total thickness of active layer was 50 nm. Firstly, the ZnO thin films were deposited to control the thickness from 5 nm to 30 nm. Sequentially, the $Mg_{0.1}ZnO_{0.9}O$ thin films were deposited to change from 45 nm to 20 nm. The bi-layer TFT shows more improved properties than the single layer TFT. The field effect mobility and subthreshold slope for $Mg_{0.1}ZnO_{0.9}O$/ZnO-TFT are $7.40cm^2V^{-1}s^{-1}$ and 0.24 V/decade at the ZnO thickness of 10 nm, respectively.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.222-222
• /
• 2010

Transparent semiconductor oxide thin films have been attracting considerable attention as potential channel layers in thin film transistors (TFTs) owing to their several advantageous electrical and optical characteristics such as high mobility, high stability, and transparency. TFTs with ZnO or similar metal oxide semiconductor thin films as the active layer have already been developed for use in active matrix organic light emitting diode (AMOLED). Of late, there have been several reports on TFTs fabricated with InZnO, AlZnSnO, InGaZnO, or other metal oxide semiconductor thin films as the active channel layer. These newly developed TFTs were expected to have better electrical characteristics than ZnO TFTs. In fact, results of these investigations have shown that TFTs with the new multi-component material have excellent electrical properties. In this work, we present TFTs with inverted coplanar geometry and with a novel HfInZnO active layer co-sputtered at room temperature. These TFTs are meant for use in low voltage, battery-operated mobile and flexible devices. Overall, the TFTs showed good performance: the low sub-threshold swing was low and the $I_{on/off}$ ratio was high.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2005.12a
• /
• pp.174-175
• /
• 2005