• 한국세라믹학회지
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• 제40권6호
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• pp.547-552
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• 2003

RF 마그네트론 스퍼터링법을 이용하여 유리기판위에 인가전력 100 W, 1.33Pa, Ar/O2=50 : 50, 20$0^{\circ}C$ 그리고 타겟과 기판사이의 거리 4 cm의 조건으로 ZnO 압전 박막을 성장시켰다. 증착된 박막의 결정성, 표면형상, 화학적 결합비와 전기적 특성을 XRD, SEM, AFM, RBS와 electrometer를 이용하여 측정 분석하였다 제조된 박막은 우수한 c축 우선 배향성을 보였고 또한 화학 양론적인 결합비를 나타내었다. 전극 구조가 single 및 double IDT를 갖는 ZnO/1DT/glass SAW 필터를 제작하여 특성을 분석한 결과, 전파속도는 각각 2,589 m/sec, 2,533 m/sec이었고, 삽입손실은 -11 dB과 -21 dB 값을 나타내어 박막형 SAW 필터로 응용이 기대된다.

• 한국전기전자재료학회논문지
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• 제13권10호
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• pp.828-833
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• 2000

Growth characteristics and microstructure of AIN thin films grown by plasma assisted molecular beam epitaxy on Si substrates have been investigated. Growing temperature and substrate orientation were chosen as major variables of the experiment. Reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy/diffraction (TEM/TED) techniques were employed to characterize the micorstructure of the films. On Si(100) substrates, AlN thin films were grown along the hexagonal c-axis preferred orientation at temperature range 850-90$0^{\circ}C$. However on Si(111), the AlN films were epitaxially grown with directional coherency in AlN(0001)/Si(111), AlN(1100)/Si(110), and AlN(1120)/Si(112) at 85$0^{\circ}C$ and the epitaxial coherencry seemed to be slightly distorted with increasing temperature. The microstructure of AlN thin films on Si(111) substrates showed that the films include a lot of crystal defects and there exist micro-gaps among the columns.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.111-114
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• 2000

Growth characteristics and microstructure of AlN thin films grown by plasma assisted molecular beam epitaxy on Si substrates have been investigated. Growing temperature and substrate orientation were chosen as major variables of the experiment. Reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy/diffraction (TEM/TED) techniques were employed to characterize the microstructure of the films. On Si(100) substrates, AlN thin films were grown along the hexagonal c-axis preferred orientation at temperature range 850-90$0^{\circ}C$. However on Si(111), the AlN films were epitaxially grown with directional coherency in AlN(0001)/Si(111), AlN(1100)/Si(110), and AlN(1120)/Si(112) at 85$0^{\circ}C$ and the epitaxial coherencry seemed to be slightly distorted with increasing temperature. The microstructure of AlN thin films on Si(111) substrates showed that the films include a lot of crystal defects and there exist micro-gaps among the columns.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1340-1342
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• 2001

ZnO thin films are Prepared on Si(111) substrate by RF magnetron sputtering. Two-step deposition method is proposed to obtain ZnO thin films with high c-axis (002) TC value and electrical resistivity. This method consists of the following two-step deposition procedures: 1st-deposition for 10$\sim$30 min without oxygen at 100W and 2nd-deposition with oxygen added in the range of $O_2/(Ar+O_2)$ = 10 $\sim$ 50%. SAW filters with IDT/ZnO/Si(111) configuration are also fabricated. From the frequency response characteristics, the insertion loss and the side-lobe rejection are estimated.

• 센서학회지
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• 제4권2호
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• pp.45-50
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• 1995

The excellent c-axis oriented zinc oxide thin films were prepared by the RF magnetron sputtering method on glass substrates. Optimum fabrication conditions of the ZnO films were such that RF power, substrate temperature, and gas pressure of mixture Ar(50%):$O_{2}$(50%) were 150 W, $200^{\circ}C$, and 5 mTorr, respectively. In these conditions, the deposition rate was $310\;{\AA}/min$, and the resistivity of the film was $1{\times}10^6\;{\Omega}{\cdot}cm$. The ZnO film also showed high c-axis orientation and crystalinity according to XRD pattern and SEM photograph. A fabricated interdigital transducer generated 1st mode surface acoustic wave at 46.6 MHz and 2nd mode surface acoustic wave at 52.5 MHz. At the 1st mode, the phase velocity of surface acoustic wave and the electromechanical coupling coefficient were 2795 m/sec and 0.031 %, respectivly. At the 2nd mode, they were 3149 m/sec and 0.019 %. respectivly.

• 한국표면공학회지
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• 제41권4호
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• pp.142-146
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• 2008

Trivalent ions(Ga, Al, In) doped ZnO films were deposited by DC magnetron sputtering on non-alkali glass substrate at substrate temperature of $300^{\circ}C$. We used the different three types of high density($95%{\sim}$) ceramic sintered disks(doped with $Ga_2O_3$; 6.65 wt%, $Al_2O_3$; 3.0 wt%, $In_2O_3$; 9.54 wt%). This study examined the effect of different dopants(Ga, Al, In) on the electrical, structural, and optical properties of the films. The lowest resistivity of $5.14{\times}10^{-4}{\Omega}cm$ and the highest optical band gap of 3.74 eV were obtained by Ga doped ZnO(GZO) film. All the films had a preferred orientation along the(002) direction, indicating that the growth orientation has a c-axis perpendicular to the substrate surface. The average transmittance of the films was more than 85% in the visible range.

• Progress in Superconductivity
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• 제5권1호
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• pp.75-79
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• 2003

YBCO films were deposited with various thicknesses from 100nm to 1.6$\mu\textrm{m}$ on single crystal $SrTiO_3$ substrates by pulsed laser deposition (PLD). The effects of different deposition conditions, especially different deposition rates by means of changing the pulsed laser frequency up to 200Hz, on the J$_{c}$ value were studied. For YBCO film with the thickness of 200nm, the $J_{c}$ value of $2.1MA/\textrm{cm}^2$ has been achieved under the high deposition rate of 3.2nm/s (190nm/min). The $J_{c}$ can be maintained greater than $1M/\textrm{cm}^2$ with the thickness less than 1$\mu\textrm{m}$. The X-ray analysis was used to examine the texture, crystallization and surface quality. The SEM was employed to analyze the surface of YBCO, and it was shown the surface of YBCO film became rougher with increasing the thickness. There were many large singular outgrowths and networks of outgrowths on the surface of YBCO films which lowered the density of thick YBCO film. The outgrowth network was probably the a-axis YBCO corresponding to XRD $\theta$-2$\theta$scan and $\chi$-scan which were used to characterize a-axis orientation of YBCO film. The reason for J$_{c}$ declining with increasing the thickness was studied and discussed.sed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.367-367
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• 2008

Aluminum nitride (AlN) thin films have been deposited on Si substrate by using reactive RF magnetron sputtering method in a gas mixture of Ar and $N_2$ at different $N_2$ concentration. It was found that $N_2$ concentration was varied in the range up to 20-100%, highly c-axis oriented film can be obtained at 50% $N_2$ with full width at half maximum (FWHM) $4.5^{\circ}$. Decrease in surface roughness from 7.5 nm to 4.6 nm found to be associated with decrease in grain size, with $N_2$ concentration; however, the AlN film fabricated at 20% $N_2$ exhibited a granular type of structure with non-uniform grains. The absorption peak was observed around 675 $cm^{-1}$ in fourier transform infrared spectroscopy (FTIR). It is concluded that the AlN film deposited at $N_2$ concentration of 50% exhibited the most desirable properties for the application of high-frequency surface acoustic devices.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.9-9
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• 2009

1 wt % Ga-dope ZnO (ZnO:Ga) thin films with n-type semiconducting behavior were grown on c-sapphire substrates by radio frequency magnetron sputtering at various growth temperatures. The room temperature grown ZnO:Ga film showed the faint preferred orientation behavior along the c-axis with small domain size and high density of stacking faults, despite limited surface diffusion of the deposited atoms. The increase in the growth temperature in the range between $300\sim550^{\circ}C$ led to the granular shape of epitaxial ZnO:Ga films due to not enough thermal energy and large lattice mismatch. The growth temperature above $550^{\circ}C$ induced the quite flat surface and the simultaneous improvement of electrical carrier concentration and carrier mobility, $6.3\;\times\;10^{18}/cm^3$ and $27\;cm^2/Vs$, respectively. In addition, the increase in the grain size and the decrease in the dislocation density were observed in the high temperature grown films. The low-temperature photoluminescence of the ZnO:Ga films grown below $450^{\circ}C$ showed the redshift of deep-level emission, which was due to the transition from $Zn_j$ to $O_i$ level.

• 한국초전도ㆍ저온공학회논문지
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• 제12권3호
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• pp.7-11
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• 2010

For many large-scale applications of high-temperature superconducting materials, large critical current density($J_c$) in high applied magnetic fields are required. A number of methods have been reported to introduce artificial pinning centers(APCs) in $YBa_2Cu_3O_{7-\delta}$(YBCO) films for enhancement of their $J_c$. In this work, we investigated electric characteristic of YBCO films on $SrTiO_3$ (100) substrates whose surfaces were modified by the introduction of Au nanoparticles (AuNPs). Au nanoparticles were uniformly dispersed on STO substrates with one of typical solution techniques, self assembled monolayer. After heating the STO substrates with Au nanoparticles, the size of Au nanoparticles was around 29~32 nm in height and 41~49 nm in diameter. XRD diffraction patterns taken on the YBCO film with Au nanoparticles show the c-axis orientation. The measured $T_c$ of YBCO /AuNPs films was around 89K and the $J_c$ was 0.75 MA/$cm^2$ at 65 K and 1 T.