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RISS 인기검색어
- 검색키워드
- 저자 : Omkaram, Inturu (검색결과 6 건)
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Yeonsung Lee,Omkaram, Inturu,Park, Jozeph,Hyun-Suk Kim,Ki-Uk Kyung,Wook Park,Sunkook Kim IEEE 2015 IEEE electron device letters Vol.36 No.1
<P>This letter presents a highly sensitive near-infrared (IR) a -Si:H phototransistor for touch sensor applications. The narrow bandgap of a-Si exhibits a wideband spectrum response from IR to ultraviolet region, where the IR bandpass filter layers allow the a -Si:H phototransistor to respond to the selective IR light uninterrupted by visible light. The time-resolved photoresponse and transfer I V characteristics for the near-IR a -Si:H phototransistor as a function of power at 785-nm illumination allow the observation of fast photoresponse (tau similar to 0.1 ps), high external quantum efficiency (7.52), and high photoresponse. A prototype unit pixel structure for touch sensors composed of amorphous Si-based switching/amplification/near-IR phototransistors and a storage capacitor, is proposed and designed. The overall results suggest that the near-IR a -Si:H phototransistor offers unique possibilities for user-friendly, low-cost, and large-area touch sensors, especially aimed at consumer applications and other areas of optoelectronics.</P>
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High-temperature Electrical Behavior of a 2D Multilayered MoS2 Transistor
이연성,박희경,권준연,Omkaram Inturu,김선국 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.7
This paper reports the high-temperature-dependent electrical behavior of a 2D multilayer MoS2transistor. The existence of a big Schottky barrier at the MoS2-Ti junction can reduce carriertransport and lead to a lower transistor conductance. At a high temperature (380 K), the fieldeffectmobility of the multilayer MoS2 transistor increases to 16.9 cm2V−1sec−1, which is 2 timeshigher than the value at room temperature. These results demonstrate that at high temperature,carrier transport in a MoS2 with a high Schottky barrier is mainly affected by thermionic emissionover the energy barrier.
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Baek, J.,Yin, D.,Liu, N.,Omkaram, I.,Jung, C.,Im, H.,Hong, S.,Kim, S. M.,Hong, Y. K.,Hur, J. Springer Science + Business Media 2017 NANO RESEARCH Vol.10 No.6
<P>Layered semiconductors with atomic thicknesses are becoming increasingly important as active elements in high-performance electronic devices owing to their high carrier mobilities, large surface-to-volume ratios, and rapid electrical responses to their surrounding environments. Here, we report the first implementation of a highly sensitive chemical-vapor-deposition-grown multilayer MoSe2 field-effect transistor (FET) in a NO2 gas sensor. This sensor exhibited ultra-high sensitivity (S = ca. 1,907 for NO2 at 300 ppm), real-time response, and rapid on-off switching. The high sensitivity of our MoSe2 gas sensor is attributed to changes in the gap states near the valence band induced by the NO2 gas absorbed in the MoSe2, which leads to a significant increase in hole current in the off-state regime. Device modeling and quantum transport simulations revealed that the variation of gap states with NO2 concentration is the key mechanism in a MoSe2 FET-based NO2 gas sensor. This comprehensive study, which addresses material growth, device fabrication, characterization, and device simulations, not only indicates the utility of MoSe2 FETs for high-performance chemical sensors, but also establishes a fundamental understanding of how surface chemistry influences carrier transport in layered semiconductor devices.</P>
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Im, Healin,Lee, Yunsu,Kim, Do Hyeong,Inturu, Omkaram,Liu, Na,Lee, Sungho,Kwon, Seung-Jun,Lee, Han-Seung,Kim, Sunkook Elsevier BV 2017 Construction and Building Materials Vol.156 No.-
<P><B>Abstract</B></P> <P>In this paper, an embedded ultrathin-film iron (Fe) corrosion sensor passivated with an anion-exchange membrane is developed to reveal the extent of corrosion tendency in reinforced concrete. Rebar in reinforced concrete is mainly corroded due to penetration of chloride ions which are one of the most dominant degradation factor for reinforced concrete. An effective method to monitor the extent of corrosion is to determine the positions where the chloride ions are present beyond the chloride threshold level (CTL). The sensors consist of ultrathin-film iron (Fe) layers deposited on the PET substrate, Au lines as electrode connection lines, and anion exchange membrane encasing the sensor. As the chloride ions exist near Fe layer of sensors, as if rebar has been corroded in reinforced concrete, the macro cells which occur relatively low anode and high cathode with somehow distance between them are made up and pitting corrosion accelerates. The pitting corrosion on the Fe layer of sensor induces the variation of electrical properties, which indicates the corrosion level using variations of resistance (<I>R</I>) and electrical response (<I>R</I>/<I>R<SUB>0</SUB> </I>). To protect the sensor from mechanical and chemical stimuli in a concrete, sensors are encapsulated with an anion exchange membrane that functions not only as a protector, but also as a selector of anions including chloride ions among degradation factors. Therefore, by embedding sensors at every 10 mm depth from the surface of reinforced concrete, we can monitor the corrosion tendency causing penetration of chloride ions with respect to depth. Through the variation of electrical properties in sensors, the velocity of corrosion ( Δ R · R 0 - 1 · <SUP> t - 1 </SUP> ) is suggested as a new parameter, which shows the tendency for corrosion under the surrounding conditions. To confirm the relationship between corrosion velocity as determined by the sensor and the concentration of diffused chloride ions, the chloride concentration in mortar is measured. The developed sensors in this paper are effective to sensitively and accurately monitor the corrosion level of concrete.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Embedding sensors in a fresh mortar. </LI> <LI> Chlorides permeating toward anion exchange membrane of sensors. </LI> <LI> Corroding iron channel by diffused chlorides. </LI> <LI> Occurring rapid variation in electrical changes of sensors by diffused chlorides. </LI> <LI> Indicating corrosion velocities at the spot based on the surrounding condition. </LI> </UL> </P>
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Hong, Seongin,Yoo, Geonwook,Kim, Dong Hak,Song, Won Geun,Le, Ong Kim,Hong, Young Ki,Takahashi, Kaito,Omkaram, Inturu,Son, Do Ngoc,Kim, Sunkook WILEY‐VCH Verlag Berlin GmbH 2017 Physica status solidi. PSS. C, Current topics in s Vol.14 No.3
<P>Seongin Hong et al. (article no. <url href='http://doi.wiley.com/10.1002/pssc.201600262'>1600262</url>) have investigated the polyethylenimine (PEI) doping mechanism and its effect on the electrical and optical properties of multilayer MoS<SUB>2</SUB> field effect transistors (FETs). Density functional theory (DFT) calculation and X‐ray photoelectron spectroscopy (XPS) measurement confirm that the PEI molecules were successfully doped and formed Mo–N bonds on the MoS<SUB>2</SUB> channel, generating new energy states near the valence band. The strong n‐doping changed the threshold voltage as well as the Schottky barrier width attributed to the induced interfacial dipoles. Therefore, the ON‐current of the doped MoS<SUB>2</SUB> FETs was improved in comparison with the pristine FETs. Furthermore, the PEI doping also enhanced the photoresponsivity of the MoS<SUB>2</SUB> FETs from 0.14 A/W to 4.41 A/W. This study suggests that PEI molecular doping could be widely applicable to two‐dimensional materials in order to improve the electrical and optical properties of respective devices.</P>
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