• ETRI Journal
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• v.27 no.6
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• pp.677-684
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• 2005

A phased array antenna was fabricated using four-element ferroelectric phase shifters with a coplanar waveguide (CPW) transmission line structure based on a $Ba_{0.6}Sr_{0.4}TiO_3(BST)/MgO$ structure. Epitaxial BST films were deposited on MgO (001) substrates by pulsed laser deposition. To attain the large differential phase shift and small losses for a ferroelectric CPW phase shifter, an impedance-matching-part adding technique between the effective transmission line and connecting cable was used. The return loss and insertion loss for this techniqueadapted BST CPW device were improved with respect to those for a normal BST CPW device. For an X-band phased array antenna system consisting of ferroelectric BST CPW phase shifters, power divider, dc block, patch antenna, and programmed dc power, the steering beam could be tilted by $15^{\circ}$ in either direction.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.981-982
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• 2006

In this study, the synthesis and semiconducting properties of cation and defect-doped KTaO3 film is reported. KTaO3is an important material for optoelectronic and tunable microwave applications. It is an incipient ferroelectric with a cubic structure that becomes ferroelectric when doped with Nb. the films were grown on (001) MgO single crystal substrates using pulsed-laser deposition. Semiconducting behavior is achieved by inducing oxygen vacancies in the KTaO3 lattice via growth in a hydrogen atmosphere. The resistivity of semiconducting KTaO3:Ca films was as low as 10cm, and n-type semiconducting behavior was indicated. Hall mobility and carrier concentration were 0.27 cm2/Vs and 3.21018cm-3.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.138-143
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• 2004

Recently there has been a great world-wide interest in developing and characterizing new nano-structured materials. These newly developed materials are often prepared in limited quantities and shapes unsuitable for the extensive mechanical testing. The development of depth sensing indentation methods have introduced the advantage of load and depth measurement during the indentation cycle. In the present work, ZnO thin films are prepared on Si(111), Si(100) substrates at different temperatures by pulsed laser deposition(PLD) method. Because the potential energy in c-axis is low, the films always show c-axis orientation at the optimized conditions in spite of the different substrates. Thin films are investigated by X-ray diffractometer and Nano indentation equipment. From these measurements it is possible to get elastic modulus and hardness of ZnO thin films on Si substrates.

• Korean Journal of Materials Research
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• v.7 no.5
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• pp.431-433
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• 1997

We investigated a double ring resonator(DRR)device to improve the resonating Q value of a superconductor resonator. To make a DRR device, we made a large area YBCO film on a MgO substrate by pulsed laser deposition(PLD). Thetransition temperature was 88 K and the film was uniformly deposited. We also deposited 500$\AA$SrTiO$_{3}$on the YBCO thin film to protect the superconducting properties from degradation. The loaded Q value was measured as 50000 from simulation and as 2000 from experiment near 10GHz at 77K.

• Journal of the Korean Ceramic Society
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• v.43 no.11 s.294
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• pp.738-742
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• 2006

We report on the effects of co-doping with fluorine on properties of ZnO thin films grown by pulsed-laser deposition. The transport characteristics of Ag-F and Li-F codoped ZnO films were determined by Hall-effect measurements at room temperature. Ag-F codoped ZnO films showed n-type semiconducting behaviors. An ambiguous carrier type was observed in Li-F codoped ZnO films grown at a temperature of 500$^{\circ}C$ with the oxygen pressures of 20 and 200 mTorr. The qualities of the codoped ZnO films were studied by X-ray diffraction, atomic force microscopy, X-ray photoemission spectroscopy, and photoluminescence.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.108-111
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• 2001

ZnO thin films on (001) sapphire substrates knave been deposited by pulsed laser deposition(PLD) technique for light emitting device applications. We have controlled the emission intensity of UV and visible light, depending on film thickness and various post-annealing time. UV emission became strong as the thickness of ZnO thin films increased. The intensity of visible light was strong as post-annealing temperature increased. The optical properties of the ZnO thin films were characterized by PL(photoluminescence) and the structural properties of the ZnO were characterized by XRD for the application of ZnO light emission device.

• Journal of Sensor Science and Technology
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• v.20 no.4
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• pp.230-233
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• 2011

In this paper, highly-efficient optical gating in a junction device based on vanadium dioxide($VO_2$) thin film grown by a sol-gel method was investigated as a gate terminal of a three-terminal device using infrared light with a wavelength of ~1554.6 nm. Due to the photoinduced phase transition, the threshold voltage of the $VO_2$ junction device, at which the device current abruptly jumps, could be tuned with a sensitivity of ~96.5 V/W by adjusting the optical power of the infrared light directly illuminating the device. Compared with the tuning efficiency of the previous device fabricated using $VO_2$ thin film deposited by a pulsed laser deposition method, the threshold voltage of this device could be tuned by ~76.8 % at an illumination power of ~39.8 mW resulting in a tuning efficiency of ~1.930 %/mW, which is ~4.9 times larger than the previous device.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.242-243
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• 2007

Highly transparent conducting aluminum-doped zinc oxide (AZO) thin films were deposited on Corning glass substrate using an Nd:YAG pulsed laser deposition technology. AZO thin films deposited with 650nm thickness showed the best electrical properties of the electrical resistivity of $4.6{\times}10^{-4}[{\Omega}{\cdot}cm]$, a carrier concentration of $9.3{\times}10^{20}[cm^{-3}]$, and a carrier mobility of $31[cm^2/V{\cdot}s]$. Besides, the optical transmittance spectra in visible region (200-800nm) of AZO thin films show an high average transmittance over 90%.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1349-1350
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• 2007

Epitaxial thin films of aluminum-doped zinc oxide (AZO) have been deposited on commercial corning glass using an Nd:YAG pulsed laser deposition technology. The structural, electrical and optical properties of these films were investigated as a function of oxygen pressure. The experimental results show that the electrical resistivity of films deposited at 5 mTorr with substrate temperature of $300^{\circ}C$ were $4.633{\times}10^{-4}$. The average transmission of AZO thin films in the visible range were over 90%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.794-797
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• 2000

The fabrication of high quality superconducting thin films using pulsed laser deposition (PLD) has been reported to find optimized processing conditions and to make the millimeter-wave devices. High temperature superconducting (HTS) YBCO films were prepared on MgO (10${\times}$10${\times}$0.5mm) substrates by the PLD. The 3 pole bandpass filter with the center frequency of 22 GHz for satellite communication was designed consisting of hairpin coupled-lines to reduce the configuration in size. YBCO films are c-axis oriented and show superconductive transition temperatures of 88∼89 K with the transition widths < 0.5 K. The insertion loss of passband at 70 K was about 5 dB. The measured frequency response of superconducting filter will be compared with the simulation result.