• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.7 no.2
• /
• pp.250-254
• /
• 2003

A film bulk acoustic resonator (FBAR) device for 2 GHz radio frequency (RF) bandpass filter application is presented. This FBAR device consists of an aluminum nitride (AlN) film sandwiched between top(Al) and bottom(Au) electrodes and an acoustic multilayer reflector of a silicon dioxide/tungsten (SiO2/W). The A/N film deposited using a RF sputtering was observed to have small columnar grains with a strongly preferred orientation towards c axis. In addition to a high quality factor (4300), a large return loss of 37.19 dB was obtained.

• Journal of the Korean Applied Science and Technology
• /
• v.20 no.2
• /
• pp.148-153
• /
• 2003

Electron transfer through an Langmuir-Blodgett(LB) monolayer film sandwiched between metal electrodes. We used an eicosanoic acid material and the material was very famous as a thin film insulating material. Eicosanoic acid monolayer was deposited by Langmuir-Blodgett(LB) technique and a subphase was a $CdCl_2$ solution as a 2${\times}10^{-4}$ mol/L. Also we used a bottom electrode as an Al/$Al_2O_3$ and a top electrode as a Al and Ti/Al. Here, the $Al_2O_3$ on the bottom electrode was deposited by thermal evaporation method. The $Al_2O_3$ layer was acted on a tunneling barrier and insulating layer in tunnel diode. It was found that the proper transfer surface pressure for film deposition was 25 mN/m and the limiting area per molecule was about 24 ${\AA}^2$/molecule. When the positive and negative bias applied to the molecular device, the behavior shows that a tunnel switching characteristics. This result were analyzed regarding various mechanisms.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1997.11a
• /
• pp.364-368
• /
• 1997

We have investigated Pt and RuO$_2$as a bottom electrode for a device application of PZT thin film. The bottom electrodes were prepared by using an RF magnetron sputtering method. We studied some of the property influencing factors such as substrate temperature, gas flow rate, and RF power. An oxygen partial pressure from 0 to 50% was investigated. The results show that only Ru metal was grown without supp1ying any O$_2$gas. Both Ru and RuO$_2$phases were formed for O$_2$partial pressure between 10∼40%. A Pure RuO$_2$ phase was obtained with O$_2$partial pressure of 50%. A substrate temperature from room temperature to 400$^{\circ}C$ was investigated with XRD for the film crystallinity examination. The substrate temperature influenced the surface morphology and the resistivity of Pt and RuO$_2$as well as the film crystal structure. From the various considerations, we recommend the substrate temperature of 300$^{\circ}C$ for the bottom electrode growth. Because PZT film growth on top of bottom electrode requires a temperature process higher than 500$^{\circ}C$, bottom electrode properties were investigated as a function of post anneal temperature. As post anneal temperature was increased, the resistivity of Pt and RuO$_2$was decreased. However, almost no change was observed in resistivity for an anneal temperature higher than 700$^{\circ}C$. From the studies on resistivity and surface morphology, we recommend a post anneal temperature less than 600$^{\circ}C$.

• Progress in Superconductivity
• /
• v.11 no.1
• /
• pp.36-41
• /
• 2009

Superconducting quantum phenomena are getting attention from the field of metrology area. Following its first successful application of Josephson effect to voltage standard, piconewton force standard was suggested as a candidate for the next application of superconducting quantum effects in metrology. It is predicted that a micron-sized superconducting Nb ring in a strong magnetic field gradient generates a quantized force of the order of sub-piconewtons. In this work, we studied the design and fabrication of Nb superconducting quantum interference device (SQUID) on an ultra-thin silicon cantilever. The Nb SQUID and electrodes were structured on a silicon-on-insulator (SOI) wafer by dc magnetron sputtering and lift-off lithography. Using the resulting SOI wafer, we fabricated V-shaped and parallel-beam cantilevers, each with a $30-{\mu}m$-wide paddle; the length, width, and thickness of each cantilever arm were typically $440{\mu}m,\;4.5{\mu}m$, and $0.34{\mu}m$, respectively. However, the cantilevers underwent bending, a technical difficulty commonly encountered during the fabrication of electrical circuits on ultra-soft mechanical substrates. In order to circumvent this difficulty, we controlled the Ar pressure during Nb sputtering to minimize the intrinsic stress in the Nb film and studied the effect of residual stress on the resultant device.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.05a
• /
• pp.130.2-130.2
• /
• 2011

본 연구에서는 RF magnetron sputtering을 이용하여 실리콘 박막 태양전지용 ZnO:Al 전면전극을 제작하고 다양한 식각조건에 따른 ZnO:Al 박막의 표면형상 변화와 함께 전기적 및 광학적 특성 변화를 조사하였다. pin 구조를 갖는 실리콘 박막 태양전지의 효율 향상을 위해서는 입사광의 산란효과에 따른 광포획 증가가 필수적이며 이를 위하여 ZnO:Al 전면전극의 표면텍스처링 형성이 필요하다. 식각용액으로는 HCl과 HF 등을 사용하였으며 식각용액 농도 및 식각시간을 변화시켰다. 식각 후의 ZnO:Al 박막의 표면형상은 SEM(Scanning Electron Microscope)과 AFM(Atomic Force Microscope)을 이용하여 분석을 하였고, UV-visible-nIR spectrometer를 이용하여 총 투과도 및 산란 투과도를 측정하였다. 이 외에도 four-point probe 및 Hall measurement를 이용하여 전기적 특성 변화를 조사하였다. 다양한 식각조건에 따라 제조된 ZnO:Al 박막 위에 실리콘 박막 태양전지를 제작하여 전면전극의 표면형상에 따른 태양전지 성능변화를 비교 분석하였다.

• Journal of Sensor Science and Technology
• /
• v.17 no.3
• /
• pp.183-187
• /
• 2008

A sub-ppm level MEMS gas sensor that can be used for the detection of formaldehyde (HCHO) is presented. It is realized by using a zinc oxide (ZnO) thin-film material with a Ni-seed layer as a sensing material and by bulk micromachining technology. To enhance sensitivity of the MEMS gas sensor with Ni-seed layer was embedded with ZnO sensing material and sensing electrodes. As experimental results, the changed sensor resistance ratio for HCHO gas was 9.65 % for 10 ppb, 18.06 % for 100 ppb, and 35.7 % for 1 ppm, respectively. In addition, the minimum detection level of the fabricated MEMS gas sensor was 10 ppb for the HCHO gas. And the measured output voltage was about 0.94 V for 10 ppb HCHO gas concentration. The noise level of the fabricated MEMS gas sensor was about 50 mV. The response and recovery times were 3 and 5 min, respectively. The consumption power of the Pt micro-heater under sensor testing was 184 mW and its operating temperature was $400^{\circ}C$.

• Journal of the Korean Applied Science and Technology
• /
• v.27 no.1
• /
• pp.50-55
• /
• 2010

본 논문은 메탈 이중층 전극을 이용한 유기 박막 트랜지스터를 제작하여 Au나 Ag 금속만으로 제작한 일반적인 유기 박막 트랜지스터와의 전기적 특성을 비교하였다. 전기적 특성에서 게이트 절연층은 높은 K 값을 갖는 $Al_2O_3$를 사용하였고, 유기 반도체층은 펜타센을 사용하였다. 본 실험에서 제작한 유기 박막 트랜지스터는 $1.6 \;{\times}\;10^{-1}\;cm^2$의 포화영역 이동도를 얻을 수 있었으며, 또한 드레인 전압을 -5V로 하고, 게이트 전압을 3 V에서 -10 V 까지 인가하였을 때 $3{\times}10^5$의 전멸 비를 얻을 수 있었다.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2007.08b
• /
• pp.1292-1294
• /
• 2007

In this report, the effects of chemical surface treatments of ITO gate electrodes of OTFTs have been studied by using acid and base solutions. As a result, it is observed that the threshold voltage of OTFTs could be influenced and modified by the surface treatments. The device with an ITO gate electrode surface-treated by a base solution shows the lowest threshold voltage of -7.66 V, while the threshold voltages are about -13.51 V and -15.3 V for the devices without a surface treatment and with the acid solution treatment, respectively. It is thought that the work function of ITO electrode surface might be affected by the surface treatments, thereby influencing the threshold voltage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.04b
• /
• pp.45-48
• /
• 2002

Poly(3-hexylthiophene) or P3HT based organic thin film transistor (OTFT) array was fabricated on flexible poly carbonate substrates and the electrical characteristics were investigated. As the gate dielectric, a dual layer structure of polyimide-$SiO_2$ was used to improve the roughness of $SiO_2$ surface and further enhancing the device performance and also source-drain electrodes were $O_2$ plasma treated for improvement of the electrical properties, such as drain current and field effect mobility. For the active layer, polymer semiconductor, P3HT layer was printed by contact-printing and spin-coating method. The electrical properties of OTFT devices printed by both methods were evaluated for the comparison. Based on the experiments, P3HT-based OTFT array with field effect mobility of 0.02~0.025 $cm^{2}/V{\cdot}s$ and current modulation (or $I_{on}/I_{off}$ ratio) of $10^{3}\sim10^{4}$ was fabricated.

• Transactions on Electrical and Electronic Materials
• /
• v.6 no.1
• /
• pp.18-21
• /
• 2005

Monolayers of lipids on a water surface have attracted much interest as models of biological membranes, but also as precursors of multilayer systems promising many technical applications. Until now, many methodologies have been developed in order to gain a better understanding of the relationship between the structure and function of the monolayers. Maxwell displacement current (MDC) measurement has been employed to study the dielectric property of Langmuirfilms. MDC flowing across monolayers is analyzed using a rod-like molecular model. A linear relationship between the monolayer compression speed a and the molecular area Am. Compression speed a was about 30, 40, and 50 mm/min. Langmuir-Blodgett(LB) layers of Arachidic acid deposited by LB method were deposited onto slide glass as Y-type film. The structure of manufactured device is Aul Arachidic acid! AI, the number of accumulated layers are $9{\sim}21$. Also, we then examined of the Metal-Insulator-Metal(MIM) device by means of I-V. The I-V characteristics of the device are measured from -3 to+3 V. The insulation property of a thin film is better as the distance between electrodes is larger.