• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.466-468
• /
• 2012

Amorphous InGaZnO (${\alpha}$-IGZO) thin-film transistors (TFTs) are are very promising due to their potential use in thin film electronics and display drivers [1]. However, the stability of AOS-TFTs under the various stresses has been issued for the practical AOSs applications [2]. Up to now, many researchers have studied to understand the sub-gap density of states (DOS) as the root cause of instability [3]. Nomura et al. reported that these deep defects are located in the surface layer of the ${\alpha}$-IGZO channel [4]. Also, Kim et al. reported that the interfacial traps can be affected by different RF-power during RF magnetron sputtering process [5]. It is well known that these trap states can influence on the performances and stabilities of ${\alpha}$-IGZO TFTs. Nevertheless, it has not been reported how these defect states are created during conventional RF magnetron sputtering. In general, during conventional RF magnetron sputtering process, negative oxygen ions (NOI) can be generated by electron attachment in oxygen atom near target surface and accelerated up to few hundreds eV by self-bias of RF magnetron sputter; the high energy bombardment of NOIs generates bulk defects in oxide thin films [6-10] and can change the defect states of ${\alpha}$-IGZO thin film. In this paper, we have confirmed that the NOIs accelerated by the self-bias were one of the dominant causes of instability in ${\alpha}$-IGZO TFTs when the channel layer was deposited by conventional RF magnetron sputtering system. Finally, we will introduce our novel technology named as Magnetic Field Shielded Sputtering (MFSS) process [9-10] to eliminate the NOI bombardment effects and present how much to be improved the instability of ${\alpha}$-IGZO TFTs by this new deposition method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.19 no.9
• /
• pp.818-824
• /
• 2006

The effects of high-temperature process required to fabricate the SiC devices on the surface morphology and the electrical characteristics were investigated for 4H-SiC Schottky diodes. The 4H-SiC diodes without a graphite cap layer as a protection layer showed catastrophic increase in an excess current at a forward bias and a leakage current at a reverse bias after high-temperature annealing process. Moreover it seemed to deviate from the conventional Schottky characteristics and to operate as an ohmic contact at the low bias regime. However, the 4H-SiC diodes with the graphite cap still exhibited their good electrical characteristics in spite of a slight increase in the leakage current. Therefore, we found that the graphite cap layer serves well as the protection layer of silicon carbide surface during high-temperature annealing. Based on a closer analysis on electric characteristics, a conductive surface transfiguration layer was suspected to form on the surface of diodes without the graphite cap layer during high-temperature annealing. After removing the surface transfiguration layer using ICP-RIE, Schottky diode without the graphite cap layer and having poor electrical characteristics showed a dramatic improvement in its characteristics including the ideality factor[${\eta}$] of 1.23, the schottky barrier height[${\Phi}$] of 1.39 eV, and the leakage current of $7.75\{times}10^{-8}\;A/cm^{2}$ at the reverse bias of -10 V.

• Journal of Satellite, Information and Communications
• /
• v.5 no.2
• /
• pp.82-86
• /
• 2010

In this paper, a power amplifier module for WCDMA base-station applications is designed and implemented using GaN field-effect transistors (FETs), which uses an envelope tracking bias system. The designed module consists of an high gain MMIC amplifier, a driver amplifier, a power amplifier, and bias circuits for envelope tracking applications. Especially, a FET bias sequencing circuit and two isolators are integrated for stable RF operations. All circuits are assembled within a single housing, so its dimension is just $17.8{\times}9.8{\times}2.0\;cm3$. Measured results show that the developed power amplifier module has good envelope tracking capability: the power-added efficiency of 35% at the output power range from 30dBm to 40dBm over a wide range of drain bias.

• Journal of IKEEE
• /
• v.20 no.3
• /
• pp.251-259
• /
• 2016

This paper describes that how to enhance the robustness of semiconductor TRM(Transmitter and Receiver Module) through the bias sequencing and tuning the switching time. Previous circuit designs focused on improving the MDS(Minimum Detection Signal) performance. Because TRM has critical problem which transmission output signal leak into receiver by it's compact design. Under this condition, TRM was frequently broken down within the MTBF(Mean Time Between Failure). This study proposes the bias sequencing and tuning the switching time to improve above problem. At first, we collected major failure symptom and infer it's cause. Second, we demonstrated it's effect by derive the improvement method and apply it to our system. And finally we can convinced that the proposed method clear the frequent failure problem with its lack of isolation.

• Journal of the Korean Magnetics Society
• /
• v.8 no.5
• /
• pp.288-294
• /
• 1998

Effect of degree of intermixing at the Ta/NiFe interface induced by varying applied substrate bias voltage during NiFe free layer deposition on change of magnetoresistance in Substrate/Ta/NiFe/Cu/NiFe/FeMn/Ta spin valve multilayers was investigated. It was found that the optimum NiFe free layer thickness showing a maximum MR increase with increasing the bias voltage. The increase of the optimum thickness was due to the increase of the intermixed layer thickness with a bias voltage. The weak ferromagnetic or non ferromagnetic intermixed layer plays as a spin-independent scattering region and does not contribute on spin-dependent scattering. The existence of the intermixed layer was proved by the means of electrical resistivity and magnetization changes. In the present study, the optimum "effective" free layer thickness which gives the highest MR ratio was a constant independent of the magnitude of the bias voltage we have used.have used.

• Journal of Surface Science and Engineering
• /
• v.50 no.6
• /
• pp.473-479
• /
• 2017

CrN coatings have been used as protective coatings for cutting tools, forming tools, and various tribological machining applications because these coatings have high hardness. Cr-Al-N coatings have been investigated to improve the properties of CrN coatings. Cr-Al-N coatings were fabricated by a hybrid physical vapor deposition method consisting of unbalanced magnetron sputtering and arc ion plating with different working pressure and substrate bias voltage. The phase analysis of the composition was performed using XRD (x-ray diffraction). Cr-Al-N coatings were grown with textured CrN phase and (111), (200), and (220) planes. The adhesion strength of the coatings tested by scratch test increased. The friction coefficient and removal rate of the coatings were measured by a ball-on-disk test. The friction coefficient and removal rate of the coatings decreased from 0.46. to 0.22, and from $2.00{\times}10^{-12}m^2/N$ to $1.31{\times}10^{-13}m^2/N$, respectively, with increasing bias voltage. The tribological properties of the coatings increased with increasing substrate bias voltage.

• Journal of the Korean Vacuum Society
• /
• v.22 no.4
• /
• pp.193-197
• /
• 2013

In order to investigate the photo-electric property in $VO_2$ film grown by a sol-gel method, the currents generated by the light irradiation and nonirradiation were measured as functions of the bias voltage and the temperature. From the result, the generated current in the film changed with the light irradiation and nonirradiation, and it gradually increased with the bias voltage. In particular, the maximum current was generated at $50^{\circ}C$ under the light irradiation; the temperature is lower comparing the MIT (metal-insulator transition) temperature in $VO_2$. This result indicates that $VO_2$ shows the photo-voltaic effect, and so that, it is expected that the $VO_2$ film is applied for a photo-voltaic device.

• The Korean Journal of Applied Statistics
• /
• v.32 no.4
• /
• pp.631-642
• /
• 2019

Many methods have been developed to solve problems found in sample surveys involving a large number of item non-responses that cause inaccuracies in estimation. However, the non-response adjustment method used under the assumption of random non-response generates a bias in cases where the response rate is affected by the variable of interest. Chung and Shin (2017) and Min and Shin (2018) proposed a method to improve the accuracy of estimation by appropriately adjusting a bias generated when the response rate is a function of the variables of interest. In this study, we studied a case where the response rate function is linear and the error of the super population model follows normal distribution. We also examined the effect of the number of stratum population on bias adjustment. The performance of the proposed estimator was examined through simulation studies and confirmed through actual data analysis.

• Journal of Physiology & Pathology in Korean Medicine
• /
• v.34 no.6
• /
• pp.299-308
• /
• 2020

This study aimed to evaluate the effects of Chuna therapy for Sciatica. We searched the following 16 online databases without a language restriction (Pubmed, Cochrane, Embase, CINAHL, Ovid, Kmbase, RISS, NDSL, OASIS, KISS, KNAL, KTKP, DBpia, CNKI, Wangfang, J-stage) to find randomized controlled clinical trials that used Chuna therapy for Sciatica. The methodological quality of randomized controlled clinical trials (RCTs) were assessed using the Cochrane risk of bias tool and meta-analysis were performed. Among 496 articles that were searched, 15 RCTs were finally selected for systematic review. 14 studies showed that Chuna therapy has positive effect on sciatica. Two studies noted that there were side effects, and the difference between the intervention group and the control group was statistically insignificant. One study noted no side effects and the rest of the study, there was no mention of side effects. Meta-analysis showed positive results for Chuna single therapy in terms of efficiency rate compared to painkiller, herb medicine excepting acupuncture. When comparing Chuna therapy plus acupuncture and acupuncture, Chuna therapy plus acupuncture had a more positive result than acupuncture in terms of efficiency rate. Cochrane Risk of Bias (RoB)evaluation method, most of the studies's selection, performance, detection and reporting bias were unclear. The studies showed that Chuna therapy can significantly effective on sciatica. However, most of the studies's Risk of Bias included in the analysis were not low enough. In the future, to prove the level of evidence of Chuna therapy, more high-quality studies will be needed.

• Journal of Digital Convergence
• /
• v.20 no.3
• /
• pp.1-8
• /
• 2022

Despite increasing damages caused by violations of COVID-19 precautions, studies on violations of precautions have not yet received much attention. This study identified antecedents that could theoretically influence the intention to violate COVID-19 precautions based on the black swan theory, and collected 215 responses by conducting an online survey from February 11, 2021 to March 10, 2021. As a result of the regression analysis, this study found that dissonance with COVID-19 preventive information, representativeness bias, and availability bias increase the intention to violate COVID-19 precautions. However, optimistic bias did not have a significant effect on the intention to violate precautions. This study not only provides new antecedents but also suggests theoretical evidence for decreasing intention to violate precautions. This study also proposes the necessity to identify differences in violation intention by regions, countries, and theories.