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Fatigue Behaviors of Silicon Nanowire Field-Effect Transistors on Bendable Substrate
Kim, Yoonjoong,Jeon, Youngin,Lim, Doohyeok,Kim, Sangsig American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.12
<P>In this study, we fabricated an island-structured silicon nanowire (SiNW) field-effect transistor (FET) on an Ecoflex substrate and analyzed the device reliability against the bending fatigue. A SiNW-FET was fabricated on a plastic substrate and this FET on the plastic substrate was transferred onto the Ecoflex substrate. Compared to a SiNW-FET on a plastic substrate, the SiNW-FET with the island plastic structure on the Ecoflex substrate showed the stable electrical characteristics under various bending strain. Variations less than 10% of the threshold voltage and transconductance were observed under the bending strain of 15%. Moreover, the electrical characteristics were maintained even after 2000 bending cycles.</P>
Kim, Kyoungwon,Park, Dong-Hoon,Debnath, Pulak Chandra,Lee, Dong-Yun,Kim, Sangsig,Jang, Gun-Eik,Lee, Sang Yeol American Scientific Publishers 2012 Journal of nanoscience and nanotechnology Vol.12 No.4
<P>Using a hot-walled pulsed laser deposition (HW-PLD), nanowires (NWs) comprising 3 weight% Ga-doped ZnO (3GZO) have been successfully grown on a sapphire substrate. The structural and optical properties of 3GZO nanostructures have also been systematically investigated with respect to the target-substrate (T-S) distance and the growth temperature. The morphology transformations of nanostructures such as nano-horns, NWs, and clusters are strongly affected by growth temperatures due to different thermal energy. Also, the morphologies of nanostructures--including length, diameter, and density--are strongly affected by the T-S distance, illustrating a close correlation between the growth kinetics and the position in the plume formed by the particles from the GZO target. Also, the exciton that is bound to the neutral donor (D(0)X) peak of the 3GZO nanostructures is found at the low temperature PL spectra, indicating successful Ga-doping into ZnO NWs.</P>
Steep switching characteristics of single-gated feedback field-effect transistors
Kim, Minsuk,Kim, Yoonjoong,Lim, Doohyeok,Woo, Sola,Cho, Kyoungah,Kim, Sangsig IOP Pub 2017 Nanotechnology Vol.28 No.5
<P>In this study, we propose newly designed feedback field-effect transistors that utilize the?positive feedback of charge carriers in single-gated silicon channels to achieve steep switching behaviors. The band diagram, <I>I–V</I> characteristics, subthreshold swing, and on/off current ratio are analyzed using a commercial device simulator. Our proposed feedback field-effect transistors exhibit subthreshold swings of less than 0.1 mV dec<SUP>−1</SUP>, an on/off current ratio of approximately 10<SUP>11</SUP>, and an on-current of approximately 10<SUP>−4</SUP> A at room temperature, demonstrating that the switching characteristics are superior to those?of other silicon-based devices. In addition, the device parameters that affect the device performance, hysteresis characteristics, and temperature-dependent device characteristics are discussed in detail.</P>
Kim, Sutae,Kim, Minsuk,Woo, Sola,Kang, Hyungu,Kim, Sangsig Elsevier 2018 CURRENT APPLIED PHYSICS Vol.18 No.3
<P>In this paper, we investigate the performance of ring oscillators composed of gate-all-around (GAA) silicon nanowire (NW) field-effect transistors (FETs) with four different numbers of NW channels, for sub-10-nm logic applications. Our simulations reveal that ring oscillators with double, triple, and quadruple NW channels exhibit improvements of up to 50%, 85%, and 97%, respectively, in the oscillation frequencies (f(osc)), compared to a ring oscillator with a single NW channel, due to the large drive current, in spite of the increased intrinsic capacitance of a given device. Moreover, our work shows that the f(osc) improvement ratio of the ring oscillators becomes saturated with triple NW channels with additional load capacitances of 0.1 fF and 0.01 fF, which are similar to, or less than the intrinsic device capacitance (similar to 0.1 fF). Thus, our study provides an insight for determining the capacitive load and optimal number of NW channels, for device development and circuit design of GAA NW FETs. (C) 2017 Elsevier B.V. All rights reserved.</P>
Kim, Yoonjoong,Kim, Sangsig Institute of Physics 2018 Semiconductor science and technology Vol.33 No.10
<P>In this study we investigate the influence of substrate materials on the electrical characteristics of feedback field-effect transistors (FETs) when subjected to bending fatigue. Each of our transistors are composed of a <I>p</I> <SUP>+</SUP>–<I>i</I>–<I>n</I> <SUP>+</SUP> doped silicon nanowire and dual-top metal gates. Feedback FETs on Ecoflex substrates feature outstanding stability compared to those on polyethersulphone and polydimethysiloxane substrates, even at a bending strain of 11.67%. The threshold voltage shift is within the range of 0.3 V, and the on-current only decreases by 15.5% (or less), when compared to the initial flat conditions. Moreover, our devices have outstanding reliability, even after 5000 cycles of repeated bending.</P>
Sensitivity-tuned CO gas sensors with tailored Ga-doping in ZnO nanowires.
Kim, Kyoungwon,Lee, Deuk-Hee,Jeong, Dawoon,Debnath, Pulak Chandra,Lee, Dong-Yun,Kim, Sangsig,Lee, Sang Yeol American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.5
<P>Sensitivity-customization of zinc oxide (ZnO) nanowire (NW) gas sensors has been demonstrated by controlling Ga-doping, thereby tuning the resistance of the NWs. Both un-doped and 5 weight% Ga-doped ZnO (GZO) NWs are synthesized for the highly sensitive sensing within a narrow detection window and a less sensitive one within an expanded window, respectively. We have employed hot-walled pulsed laser deposition (HW-PLD) for the NW synthesis. With CO gas injection, the resistance reduction of NWs is detected and analyzed in a self-designed gas chamber that guarantees the precise control of gas flow and, gas concentration, as well as temperature. NW sensitivity is proportional to the sensing temperature and inversely proportional to the doping concentration resulting in widening the sensing window up to 230 times by the 5 wt.% Ga-doping.</P>
Electrically driven lasing in light-emitting devices composed of n-ZnO and p-Si nanowires
Kim, Kwangeun,Moon, Taeho,Kim, Jeongyong,Kim, Sangsig IOP Pub 2011 Nanotechnology Vol.22 No.24
<P>Electrically driven lasing was demonstrated in light-emitting devices composed of n-ZnO and p-Si nanowires (NWs). The ZnO NWs were synthesized by thermal chemical vapor deposition and the Si NWs were formed by crystallographic wet etching of a Si wafer. The p–n heterojunction devices were constructed using the NWs by the direct transfer and dielectrophoresis methods. At an excitation current of 2 µA, the electroluminescence spectrum showed lasing behavior, and this phenomenon was explained by the ZnO-nanostructure-related cavity property. </P>
Kim, Tae-Geun,Hwang, Jongseung,Kang, Jeongmin,Kim, Sangsig,Hwang, Sungwoo American Scientific Publishers 2011 Journal of nanoscience and nanotechnology Vol.11 No.2
<P>We have successfully fabricated nanometer-scale carbon nanotube field effect transistors (CNT FETs) on a flexible and transparent substrate by electron-beam lithography. The measured current-voltage data show good hole conduction FET characteristics, and the on/off ratio of the current is more than 10(2). The conductance (as well as current) systematically decreases with the increase of the strain, suggesting that the bending of the substrate still affects the deformation condition of the short channel CNT FETs.</P>
Kim, Sangsig,Sung, Man Young,Hong, Jinki,Lee, Moon-Sook The Korean Institute of Electrical and Electronic 2000 Transactions on Electrical and Electronic Material Vol.1 No.1
The ~1540 nm $^4$ $I_{13}$ 2/ longrightarro $w^4$ $I_{15}$ 2/ emissions of E $r^{3+}$ in Er-implanted GaN annealed at temperatures in the 400 to 100$0^{\circ}C$ range were investigated to gain a better understanding of the formation and dissociation processes of the various E $r^{3+}$ sites and the recovery of damage caused by the implantation with increasing annealing temperature ( $T_{A}$).The monotonic increase in the intensity of the broad defect photoluminescence(PL) bands with incresing $T_{A}$ proves that these are stable radiative recombination centers introduced by the implantation and annealing process. Theser centers cannot be attributed to implantation-induced damage that is removed by post-implantation annealing. Selective wavelength pumpling of PL spectra at 6K reveals the existence of at least nine different E $r^{3+}$ sites in this Er-implanted semiconductor. Most pf these E $r^{3+}$ PL centers are attributed to complexed of Er atoms with defects and impurities which are thermally activated at different $T_{A}$. Only one of the nine observed E $r^{3+}$ PL centers can be pumped by direct 4f absorption and this indicates that it is highest concentration E $r^{3+}$ center and it represents most of the optically active E $r^{3+}$ in the implanted sample. The fact that this E $r^{3+}$ center cannot be strongly pumped by above-gap light or broad band below-gap absorption indicates that it is an isolated center, i.e not complexed with defects or impurities, The 4f-pumped P: spectrum appears at annealing temperatures as low as 40$0^{\circ}C$, and although its intensity increase monotonically with increasing $T_{A}$ the wavelengths and linewidths of its characteristic peaks asre unaltered. The observation of this high quality E $r_{3+}$PL spectrum at low annealing temperatures illustrates that the crystalline structure of GaN is not rendered amorphous by the ion implantation. The increase of the PL intensities of the various E $R_{3+}$sites with increasing $T_{A}$is due to the removal of competing nonradiative channels with annealing. with annealing.annealing.