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Ultra-High Sensitivity to Low Hydrogen Gas Concentration With Pd-Decorated IGZO Film
Kumaresan, Yogeenth,Kim, Hyeonghun,Jeong, Yeonggyo,Pak, Yusin,Cho, Sungjun,Lee, Ryeri,Lim, Namsoo,Jung, Gun Young IEEE 2017 IEEE electron device letters Vol.38 No.12
<P>To enhance the performance of semiconducting metal oxides, as hydrogen (H<SUB>2</SUB>) sensor, we introduced a high carrier concentration ( <TEX>${N}_{d}$</TEX>) metal oxide, indium-gallium–zinc oxide (IGZO), combined with palladium (Pd) catalysis. This allowed the detection of low concentrations of H<SUB>2</SUB> at room temperature. The base current level was linearly increased with the Pd thickness. As a result, a high sensor sensitivity of <TEX>$6.1 \times 10^{6}$</TEX>% at 5% H<SUB>2</SUB> concentration was obtained using a 1-nm-thick Pd-decorated IGZO film. Comparative studies with a zinc oxide (ZnO) counterpart showed that the <TEX>${N}_{d}$</TEX> of IGZO ( <TEX>$8 \times 10^{18}$</TEX> cm <TEX>$^{-3}$</TEX>) is significantly higher than that of ZnO ( <TEX>$2 \times 10^{16}$</TEX> cm <TEX>$^{-3}$</TEX>), indicating a closer location for the Fermi level of IGZO to the conduction band. Therefore, a relatively small amount of electron-donating H<SUB>2</SUB> was required to overcome the energy barrier in IGZO. Consequently, the 1-nm-thick Pd-decorated IGZO sensor responded to a gas level as low as 0.01% (100 ppm) and demonstrated a 70-fold higher sensitivity compared with ZnO sensor at all H<SUB>2</SUB> concentrations.</P>
Kumaresan, Yogeenth,Pak, Yusin,Lim, Namsoo,Lee, Ryeri,Song, Hui,Kim, Tae Heon,Choi, Boran,Jung, Gun Young American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.6
<P>We demonstrated the effect of active layer (channel) thickness and annealing temperature on the electrical performances of Ga2O3-In2O3-ZnO (GIZO) thin film transistor (TFT) having nanoscale channel width (W/L: 500 nm/100 mu m). We found that the electron carrier concentration of the channel was decreased significantly with increasing the annealing temperature (100 degrees C to 300 degrees C). Accordingly, the threshold voltage (V-T) was shifted towards positive voltage (-12.2 V to 10.8 V). In case of channel thickness, the V-T was shifted towards negative voltage with increasing the channel thickness. The device with channel thickness of 90 nm annealed at 200 degrees C revealed the best device performances in terms of mobility (10.86 cm(2)/Vs) and V-T (0.8 V). The effect of channel length was also studied, in which the channel width, thickness and annealing temperature were kept constant such as 500 nm, 90 nm and 200 degrees C, respectively. The channel length influenced the on-current level significantly with small variation of V-T, resulting in lower value of on/off current ratio with increasing the channel length. The device with channel length of 0.5 mu m showed enhanced on/off current ratio of 106 with minimum V-T of 0.26 V.</P>
Kim Taeheon,Kumaresan Yogeenth,Cho Sung Jun,Lee Chang-Lyoul,이헌,Jung Gun Young 나노기술연구협의회 2016 Nano Convergence Vol.3 No.33
As metal nanostructures demonstrated extraordinary plasmon resonance, their optical characteristics have widely been investigated in photo-electronic applications. However, there has been no clear demonstration on the location effect of plasmonic metal layer within the photoanode on both optical characteristics and photovoltaic performances. In this research, the gold (Au) nano-islands (NIs) film was embedded at different positions within the TiO2 nanoparticulate photoanode in dye-sensitized solar cells (DSSC) to check the effect of plasmon resonance location on the device performance; at the top, in the middle, at the bottom of the TiO2 photoanode, and also at all the three positions. The Au NIs were fabricated by annealing a Au thin film at 550 °C. The DSSC having the Au NIs-embedded TiO2 photoanode exhibited an increase in short circuit currents (Jsc) and power conversion efficiency (PCE) owing to the plasmon resonance absorption. Thus, the PCE was increased from 5.92% (reference: only TiO2 photoanode) to 6.52% when the Au NIs film was solely positioned at the bottom, in the middle or at the top of TiO2 film. When the Au NIs films were placed at all the three positions, the Jsc was increased by 16% compared to the reference cell, and consequently the PCE was further increased to 7.01%.
High-performance printed electronics based on inorganic semiconducting nano to chip scale structures
Dahiya Abhishek Singh,Shakthivel Dhayalan,Kumaresan Yogeenth,Zumeit Ayoub,Christou Adamos,Dahiya Ravinder 나노기술연구협의회 2020 Nano Convergence Vol.7 No.33
The Printed Electronics (PE) is expected to revolutionise the way electronics will be manufactured in the future. Building on the achievements of the traditional printing industry, and the recent advances in flexible electronics and digital technologies, PE may even substitute the conventional silicon-based electronics if the performance of printed devices and circuits can be at par with silicon-based devices. In this regard, the inorganic semiconducting materials-based approaches have opened new avenues as printed nano (e.g. nanowires (NWs), nanoribbons (NRs) etc.), micro (e.g. microwires (MWs)) and chip (e.g. ultra-thin chips (UTCs)) scale structures from these materials have been shown to have performances at par with silicon-based electronics. This paper reviews the developments related to inorganic semiconducting materials based high-performance large area PE, particularly using the two routes i.e. Contact Printing (CP) and Transfer Printing (TP). The detailed survey of these technologies for large area PE onto various unconventional substrates (e.g. plastic, paper etc.) is presented along with some examples of electronic devices and circuit developed with printed NWs, NRs and UTCs. Finally, we discuss the opportunities offered by PE, and the technical challenges and viable solutions for the integration of inorganic functional materials into large areas, 3D layouts for high throughput, and industrial-scale manufacturing using printing technologies.
Jeong, Huisu,Song, Hui,Lee, Ryeri,Pak, Yusin,Kumaresan, Yogeenth,Lee, Heon,Jung, Gun Young Springer US 2015 NANOSCALE RESEARCH LETTERS Vol.10 No.1
<P>We present a holey titanium dioxide (TiO<SUB>2</SUB>) film combined with a periodically aligned ZnO nanorod layer (ZNL) for maximum light utilization in dye-sensitized solar cells (DSCs). Both the holey TiO<SUB>2</SUB> film and the ZNL were simultaneously fabricated by imprint technique with a mold having vertically aligned ZnO nanorod (NR) array, which was transferred to the TiO<SUB>2</SUB> film after imprinting. The orientation of the transferred ZNL such as laid, tilted, and standing ZnO NRs was dependent on the pitch and height of the ZnO NRs of the mold. The photoanode composed of the holey TiO<SUB>2</SUB> film with the ZNL synergistically utilized the sunlight due to enhanced light scattering and absorption. The best power conversion efficiency of 8.5 % was achieved from the DSC with the standing ZNL, which represented a 33 % improvement compared to the reference cell with a planar TiO<SUB>2</SUB>.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1186/s11671-015-0961-9) contains supplementary material, which is available to authorized users.</P>
Kim, Hyeonghun,Kim, Woochul,Park, Jiyoon,Lim, Namsoo,Lee, Ryeri,Cho, Sung Jun,Kumaresan, Yogeenth,Oh, Myoung-Kyu,Jung, Gun Young The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.45
<P>ZnO nanomaterials are promising building blocks for an efficient UV photodetector; however, their slow sensing behavior and undesired response to visible light, which are attributed to surface defects, such as oxygen or zinc vacancies, are challenges that remain to be addressed. Here, we transformed the ZnO nanorod surface into a zeolitic imidazolate framework-8 (ZIF-8) to eliminate ZnO surface defects. Vertical-type photodetectors were fabricated incorporating a Schottky junction at the ZIF-8/gold (Au) top electrode and could respond to UV light with a rapid response and recovery (1-2 s) and demonstrated a UV-to-visible rejection ratio in the order of 10<SUP>3</SUP>, qualifying them as efficient visible-blind UV photodetectors. It is noteworthy that the ZIF-8 layer effectively separated the photogenerated electron-hole pairs, and thus reduced their recombination probability. The enhanced photodetector displayed excellent figures-of-merit: a responsivity of 291 A W<SUP>−1</SUP> and a detectivity of 5.9 × 10<SUP>13</SUP> cm Hz<SUP>1/2</SUP> W<SUP>−1</SUP> under illumination at 295 nm.</P>