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Park, Jun-Hyun,Jeon, Kichan,Lee, Sangwon,Kim, Sangwook,Kim, Sunil,Song, Ihun,Park, Jaechul,Park, Youngsoo,Kim, Chang Jung,Kim, Dong Myong,Kim, Dae Hwan The Electrochemical Society 2010 Journal of the Electrochemical Society Vol.157 No.3
<P>The self-consistent technique for extracting density of states [DOS: [Formula]] in an amorphous indium gallium zinc oxide (a-IGZO) thin film transistor is proposed and demonstrated. The key parameters are the [Formula] of the a-IGZO active layer and the intrinsic channel mobility [Formula]. While the energy level [Formula] is scanned by the photon energy and gate-to-source voltage [Formula] sweep, its density is extracted from an optical response of capacitance–voltage characteristics. Using the [Formula]-dependent [Formula] as another boundary condition, a linearly mapped DOS assuming a linear relation between [Formula] and [Formula] is translated into a final DOS by fully considering a nonlinear relation between [Formula] and [Formula]. The final DOS is finally extracted and verified by finding the self-consistent solution satisfying both the linearly mapped DOS and the measured [Formula] dependence of [Formula] with the numerical iteration of a DOS-based [Formula] model. The extracted final DOS parameters are [Formula], [Formula], [Formula], [Formula], and [Formula] with the formula of exponential tail states and Gaussian deep states.</P>
Jun-Hyun Park,Sangwon Lee,Kichan Jeon,Sunil Kim,Sangwook Kim,Jaechul Park,Ihun Song,Chang Jung Kim,Youngsoo Park,Dong Myong Kim,Dae Hwan Kim IEEE 2009 IEEE electron device letters Vol.30 No.10
<P>The density of states (DOS)-based DC <I>I</I>-<I>V</I> model of an amorphous gallium-indium-zinc oxide (<I>a</I>-GIZO) thin-film transistor (TFT) is proposed and demonstrated with self-consistent methodologies for extracting parameters. By combining the optical charge-pumping technique and the nonlinear relation between the surface potential (phi<I>S</I>) and gate voltage (<I>V</I> <SUB>GS</SUB>), it is verified that the proposed DC model reproduces well both the measured <I>V</I> <SUB>GS</SUB>-dependent mobility and the <I>I</I> <SUB>DS</SUB>-<I>V</I> <SUB>GS</SUB> characteristics. Finally, the extracted DOS parameters are <I>N</I> <SUB>TA</SUB> = 4.4 times 10<SUP>17</SUP> cm<SUP>-3</SUP> middot eV<SUP>-1</SUP>, <I>N</I> <SUB>DA</SUB> = 3 times 10<SUP>15</SUP> cm<SUP>-3</SUP> middot eV<SUP>-1</SUP>, <I>kT</I> <SUB>TA</SUB> = 0.023 eV, <I>kT</I> <SUB>DGA</SUB> = 1.5 eV, and <I>EO</I> = 1.8 eV, with the formulas of exponential tail states and Gaussian deep states.</P>
Sangwon Lee,Sungwook Park,Sungchul Kim,Yongwoo Jeon,Kichan Jeon,Jun-Hyun Park,Jaechul Park,Ihun Song,Chang Jung Kim,Youngsoo Park,Dong Myong Kim,Dae Hwan Kim IEEE 2010 IEEE electron device letters Vol.31 No.3
<P>An extraction technique for subgap density of states (DOS) in an n-channel amorphous InGaZnO thin-film transistor (TFT) by using multifrequency capacitance-voltage (<I>C</I> -<I>V</I>) characteristics is proposed and verified by comparing the measured <I>I</I>- <I>V</I> characteristics with the technology computer-aided design simulation results incorporating the extracted DOS as parameters. It takes on the superposition of exponential tail states and exponential deep states with characteristic parameters for <I>N</I> <SUB>TA</SUB> = 1.1 × 10<SUP>17</SUP> cm<SUP>-3</SUP> · eV<SUP>-1</SUP>, <I>N</I> <SUB>DA</SUB> = 4 × 10<SUP>15</SUP> cm<SUP>-3</SUP> · eV<SUP>-1</SUP>, <I>kT</I> <SUB>TA</SUB> = 0.09 eV, and <I>kT</I> <SUB>DA</SUB> = 0.4 eV. The proposed technique allows obtaining the frequency-independent <I>C</I>-<I>V</I> curve, which is very useful for oxide semiconductor TFT modeling and characterization, and considers the nonlinear relation between the energy level of DOS and the gate voltage <I>V</I> <SUB>GS</SUB>. In addition, it is a simple, fast, and accurate extraction method for DOS in amorphous InGaZnO TFTs without optical illumination, temperature dependence, and numerical iteration.</P>
Subgap Density-of-States-Based Amorphous Oxide Thin Film Transistor Simulator (DeAOTS)
Yong Woo Jeon,Sungchul Kim,Sangwon Lee,Dong Myong Kim,Dae Hwan Kim,Jaechul Park,Chang Jung Kim,Ihun Song,Youngsoo Park,U-In Chung,Je-Hun Lee,Byung Du Ahn,Sei Yong Park,Jun-Hyun Park,Joo Han Kim IEEE 2010 IEEE transactions on electron devices Vol.57 No.11
<P>The amorphous oxide thin-film transistor (TFT)-oriented simulator [subgap Density of states (DOS)-based Amorphous Oxide TFT Simulator (DeAOTS)] is proposed, implemented, and demonstrated for amorphous indium-gallium-zinc-oxide (a-IGZO) TFTs. It only consists of parameters having their physical meanings and is supplied with concrete techniques for parameter extraction. Among the physical parameters, the acceptor-like DOS <I>gA</I>(<I>E</I>) was experimentally extracted using the multifrequency <I>C</I>-<I>V</I> technique, whereas the donor-like DOS <I>gD</I>(<I>E</I>) and the doping concentration <I>ND</I> were extracted using numerical iterations. The simulation result reproduces the DOS and thin-film-thickness-dependence of dc <I>I</I>-<I>V</I> characteristics very well. Compared with the previously reported a-Si TFT models, the proposed DeAOTS model not only reflects the strong <I>V</I><SUB>GS</SUB> dependence of the effective mobility (μ<SUB>eff</SUB>) but also clarifies the relations between process-controlled DOS parameters and dc <I>I</I>- <I>V</I> characteristics based on experimentally extracted DOS parameters. Also, it sufficiently takes into account the peculiar situation of amorphous oxide TFTs where the free-carrier charge can be larger than the localized one out of the total induced charge. Moreover, it reproduces the measured electrical characteristics within the wide range of <I>V</I><SUB>GS</SUB>/<I>V</I><SUB>DS</SUB> with a single equation, not distinguishing the operation regions such as the subthreshold, linear, and saturation regimes.</P>
Park, Younghyun,Cho, Hyunwoo,Yu, Jaechul,Min, Booki,Kim, Hong Suck,Kim, Byung Goon,Lee, Taeho Elsevier 2017 Bioresource technology Vol.233 No.-
<P><B>Abstract</B></P> <P>Microbial community structures and performance of air-cathode microbial fuel cells (MFCs) inoculated with activated sludge from domestic wastewater were investigated to evaluate the effects of three substrate pre-acclimation strategies: 1, serial pre-acclimation with acetate and glucose before supplying domestic wastewater; 2, one step pre-acclimation with acetate before supplying domestic wastewater; and 3, direct supply of domestic wastewater without any pre-acclimation. Strategy 1 showed much higher current generation (1.4mA) and Coulombic efficiency (33.5%) than strategies 2 (0.7mA and 9.4%) and 3 (0.9mA and 10.3%). Pyrosequencing showed that microbial communities were significantly affected by pre-acclimation strategy. Although <I>Proteobacteria</I> was the dominant phylum with all strategies, <I>Actinobacteria</I> was abundant when MFCs were pre-acclimated with glucose after acetate. Not only anode-respiring bacteria (ARB) in the genus <I>Geobacter</I> but also non-ARB belonging to the family <I>Anaerolinaceae</I> seemed to play important roles in air-cathode MFCs to produce electricity from domestic wastewater.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Three strategies were applied for substrate pre-acclimation of air-cathode MFCs. </LI> <LI> Serial pre-acclimation with acetate-glucose produced higher current from wastewater. </LI> <LI> Microbial communities were significantly varied by pre-acclimation strategies. </LI> <LI> <I>Anaerolinaceae</I> seemed to play important roles in MFCs using domestic wastewater. </LI> </UL> </P>