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Boosting Ge-epi N-well Mobility with Sn Implantation and P-well Mobility with Cluster-C Implantation
(2018-01-01)
Borland, John
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Chaung, Shang-Shiun
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Tseng, Tseung-Yuen
;
Lee, Yao-Jen
;
Joshi, Abhijeet
We investigated the effects of Sn, Si and cluster-C implantation into both P-well and N-well doped regions of 100nm Ge-epilayer on Si wafers after RTA annealing. For the P-well case a 7.3x increase in Hall bulk mobility to 3384cm(2)/Vs with cluster-C implant and for the N-well case a 4.6x increase in Hall bulk mobility to 2062cm(2)/Vs with Sn implant. Measuring layer mobility depth profiles shows mobility in the top 10-20nm of the surface can be up to 6000cm(2)/Vs for N-well with Sn implant and >10,000cm(2)/Vs for P-well with Sn implant.
Suboxide interface induced digital-to-analog switching transformation in all Ti-based memristor devices
(2020-08-17)
Chang, Lung-Yu
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Simanjuntak, Firman Mangasa
;
Hsu, Chun-Ling
;
Chandrasekaran, Sridhar
;
Tseng, Tseung-Yuen
Oxidation of TiN is a diffusion-limited process due to the high stability of the TiN metallic state at the TiN/TiO2 junction. Hence, the TiN/TiO2/TiN device being the inability to form a suitable interfacial layer results in the exhibition of abrupt current (conductance) rise and fall during the set (potentiation) and reset (depression) processes, respectively. Interfacial engineering by depositing Ti film served as the oxygen gettering material on top of the TiO2 layer induces a spontaneous reaction to form a TiOx interfacial layer (due to the low Gibbs free energy of suboxide formation). Such an interface layer acts as an oxygen reservoir that promotes gradual oxidation and reduction during the set and reset processes. Consequently, an excellent analog behavior having a 2-bit per cell and robust epoch training can be achieved. However, a thick interfacial layer may degrade the switching behavior of the device due to the high internal resistance. This work suggests that interfacial engineering could be considered in designing high-performance analog memristor devices.
Transparent planar indium tin oxide for a thermo-photovoltaic selective emitter
(2020-09-01)
Chen, Yu-Bin
;
Parashar, Parag
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Yang, Yi-Hua
;
Rawat, Tejender Singh
;
Chen, Shih-Wei
Designing an efficient emitter design is an important step for achieving a highly efficient TPV conversion process. Wavelength-selective emissivity, spectra match between the emitter and TPV cells, and high thermal stability are three main characteristics that must be considered before implementing the emitter. In this work, an indium tin oxide (ITO)/sapphire emitter structure is investigated for TPV application over the temperature range from 200 degrees C to 1000 degrees C. A 1-mu m-thick ITO layer is deposited on a 650-mu m-thick sapphire substrate. In addition, 50-nm-thick SiO2 is deposited on top of the ITO to enhance the performance of emitter at high temperatures. High-temperature emissivity and absorptivity measurement of the emitter samples are obtained using FTIR and a Hitachi U-4100 spectrophotometer, respectively. The resultant SiO2/ITO/sapphire/stainless-steel planar emitter structure has selective emission with high emissivity of similar to 0.8 in the 1-1.6 mu m wavelength regime at 1000 degrees C. This emission range lies at the bandgap edge of silicon TPV cells and thus can be used to harness the true potential for making a low-cost thermophotovoltaic system. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Boosting Ge-epi P-well Mobility & Crystal Quality with Si or Sn Implantation and Melt Annealing
(2018-01-01)
Borland, John
;
Chaung, Shang-Shuin
;
Tseng, Tseung-Yuen
;
Joshi, Abhij Eet
;
Basol, Bulent
We investigated the effects of Si, Sn and cluster-C implantation into both P-well and N-well doped regions of Ge-epi on Si wafers after laser annealing. XRD analysis shows improved Ge-epi crystallinity after >1.5J/cm(2) laser melt annealing (liquid phase epitaxial regrowth) compared to sub-melt annealing (solid phase epitaxial regrowth). For the P-well case the Ge-epi Rs decreased to 1,600 Omega/square compared to Si at 3,400 Omega/square suggesting a hole mobility increase of 2.1x from 150cm(2)/V-s to 315cm(2)/V-s but actual measured Hall mobility was 650cm(2)/V-s to a depth of 60nm, an increase of 4.3x. The 1.8J/cm(2) laser melt anneal with Si implant improved mobility uniformly to 700cm(2)/V-s to a depth of 100nm while Sn implant improved mobility to 900cm(2)/V-s from the Ge-epi surface to a depth of 70nm then increases to 3000cm(2)/V-s at a depth of 100nm. Measuring mobility depth profiles can be very critical in engineering surface and bulk mobility improvements which can be determined by chemical compositional changes in the Ge-epilayer especially for C where no liquid phase diffusion or movement could be detected.
Electrophoretic Deposition of Nitrogen-Boron Co-Doped Graphene as High Performance Electrode for Next Generation Supercapacitors
(2018-01-01)
Kumar, Amit
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Kumar, Nagesh
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Singh, Pragya
;
Leu, Jihperng
;
Tseng, Tseung-Yuen
In this study, we report the electrophoretic deposition (EPD) of nitrogen-boron co-doped graphene (NBG) synthesized via simple hydrothermal method and subsequent annealing at 750 degrees C in reducing environment. The structural, chemical-compositional and morphological investigations of the as synthesized NBG have been investigated using X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The electrochemical properties of the samples have been studied via cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) cycling and electrochemical impedance spectroscopy (EIS) in a conventional three-electrode system using 6M KOH aqueous electrolyte. The EPD grown binder free NBG electrode exhibits high specific capacitance of 217 Fg(-1) at the scan rate of 5 mVs(-1) which is about 1.2 times higher than the specific capacitance (180 Fg(-1) at 5 mVs(-1)) of pristine reduced graphene oxide synthesized via similar approach. Furthermore, this sample exhibits excellent rate capability, and similar to 103% retention after 8800 successive charge-discharge cycles at 1 Ag-1.
Neutral oxygen irradiation enhanced forming-less ZnO-based transparent analog memristor devices for neuromorphic computing applications
(2020-04-09)
Simanjuntak, Firman Mangasa
;
Ohno, Takeo
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Chandrasekaran, Sridhar
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Tseng, Tseung-Yuen
;
Samukawa, Seiji
Surface oxidation employing neutral oxygen irradiation significantly improves the switching and synaptic performance of ZnO-based transparent memristor devices. The endurance of the as-irradiated device is increased by 100 times, and the operating current can be lowered by 10 times as compared with the as-deposited device. Moreover, the performance-enhanced device has an excellent analog behavior that can exhibit 3 bits per cell nonvolatile multistate characteristics and perform 15 stable epochs of synaptic operations with highly linear weight updates. A simulated artificial neural network comprising 1600 synapses confirms the superiority of the enhanced device in processing a 40 x 40 pixels grayscale image. The irradiation effectively decreases the concentration of oxygen vacancy donor defects and promotes oxygen interstitial acceptor defects on the surface of the ZnO films, which consequently modulate the redox process during rupture and rejuvenation of the filament. This work not only proposes the potential of ZnO-based memristor devices for high-density invisible data storage and in-memory computing application but also offers valuable insight in designing high-performance memristor devices, regardless of the oxide system used, by taking advantage of our neutral oxygen irradiation technique.
Sensing performance of gas sensors fabricated from controllably grown ZnO-based nanorods on seed layers
(2020-07-01)
Singh, Pragya
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Simanjuntak, Firman Mangasa
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Wu, Yi-Chu
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Kumar, Amit
;
Zan, Hsiao-Wen
ZnO nanorods (NRs) grown on different ZnO seed layers deposited at various Ar-O-2 ambient conditions, and the morphologies of the seed layers that affect their response to nitric oxide (NO) gas were investigated. The sensing performance of the devices fabricated with the seed layers deposited under an O-2-rich condition tends to deteriorate. We believe that the surface roughness, grain size, and defect concentration of the seed layer are responsible for this phenomenon. Despite the response to the gas was found to be less dependent on NR length, the gas sensing response is significantly dependent on the oxygen vacancy concentration and the exposure of the NR structure to the NO gas ambient surface. Excellent gas response (57.5% at 1 ppm and 7.1% at 100 ppb of NO gas) was achieved at room temperature-superior to the response presented by other proposed methods. This study not only proposes the potential of ZnO-NRs for high-performance NO gas sensor devices but also offers a simple and low-cost method to optimize the response without using any catalyst and additional treatment.
Facile and One-Step in Situ Synthesis of Pure Phase Mesoporous Li2MnSiO4/CNTs Nanocomposite for Hybrid Supercapacitors
(2020-03-23)
Kumar, Nagesh
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Singh, Meetesh
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Kumar, Amit
;
Tseng, Tseung-Yuen
;
Sharma, Yogesh
In material sciences, synergistic effect and nanostructuring are the two factors which enable researchers to look beyond the conventionally defined categories of the materials. Here, we report the synthesis mechanism of pure phase mesoporous Li2MnSiO4 (LMS) with a high specific surface area by varying the concentration of metal precursors and solvents in one-step hydrothermal technique. Furthermore, the effect of MWCNTs addition on the electrochemical performance of LMS is studied. The quantitative contribution of current generating from EDLC and/or the surface pseudocapacitance reactions, and the current caused by diffusion-controlled redox reactions in the total current is also evaluated. The pure phase LMS/CNTs nanocomposite with 2% MWCNTs (abbreviated as LMS2C) is found to be the best supercapacitor material among studied nanocomposites as it exhibits specific capacitance of similar to 290 F g(-1) @ 1 A g(-1), good rate capability, small relaxation time constant (tau = 87 ms), and higher diffusion coefficient of electrolytic cations (D-k(+) = 9.4 x 10(-9) cm(2) s(-1)) in 2 M KOH aqueous electrolyte. A hybrid supercapacitor cell (HSC) designed using LMS2C as positive and activated carbon as negative electrodes shows the maximum energy density of 31 W h kg(-1), which is much higher than several recently reported hybrid supercapacitor systems. Two series connected HSCs can power a drone motor and light up 8 red LEDs for more than 3 min, indicating practical applicability of our designed hybrid supercapacitor system.
ZrN-Based Flexible Resistive Switching Memory
(2020-05-01)
Kumar, Dayanand
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Chand, Umesh
;
Siang, Lew Wen
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
In this letter, ZrN-based resistive random access memory (RRAM) is investigated for flexible memory applications for the near future. Due to the room-temperature fabrication process, the device is suitable for low-temperature flexible monolithic technologies. The TiN/ZrN/TiN device exhibits excellent AC endurance cycling (10(7)), a rapid speed (45 ns) and stable retention (10(4) s) at 100 degrees C without any degradation. In addition, RRAM devices built with an additional HfN interface layer exhibit small operational voltage variations and stable switching characteristics. The flexibility of the device is excellent, and it maintains excellent electrical characteristics at a bending radius of up to 4 mm.
Cathodic plasma-induced syntheses of graphene nanosheet/MnO2/WO3 architectures and their use in supercapacitors
(2020-05-10)
Huang, Shih-Yu
;
Phuoc-Anh Le
;
Yen, Po-Jen
;
Lu, Yi-Chun
;
Sahoo, Sumanta Kumar
In this study, we synthesized new 0.01-2 mu m graphene nanosheet/MnO2WO3(G/MnO2/WO3) architectures through an electrochemically induced cathodic plasma process in a single batch at a lower temperature (70 degrees C) and for a shorter time (2 h) than those required for the syntheses of similar structures when using a hydrothermal method. We first obtained 0.01-1 mu m leaf-like graphene (G) nanosheets, then 0.1-0.3 mu m long and approximately 10 nm diameter petiole-like MnO2 nanowires on the G nanosheets, and finally 0.20-2.0 mu m petal-like WO3 on MnO2/G - thereby forming the G/MnO2/WO3 architectures - as evidenced using scanning electron microscopy and transmission electron microscopy. We deciphered the step-wise reaction mechanism behind the formation of the G/MnO2/WO3 architectures during the plasma process. The high surface area of 291 m(2) g(-1) in the G/MnO2/WO3 architecture was contributed mainly by the G nanosheets, providing a suitable surface area for diffusion of the charge carriers during the charging and discharging process. As a result, an electrode incorporating the G/MnO2/WO3 architectures exhibited an excellent specific capacitance of 620 F g(-1) - 45 and 200% higher than those of G/MnO2 (421 F g(-1)) and G (189 F g(-1)) electrodes, respectively - at a current density of 0.5 A g(-1). Moreover, the G/MnO2/WO3-incorporated electrode exhibited good electrochemical cycling stability, with 90% capacitance retention over 5000 cycles at 1 A g(-1). Such new G/MnO2/WO3 heterojunction structures, not only provide high-performance electrode applications, but also suggest a potential approach toward fabricating other heterojunction structures having high surface areas for energy storage applications. (C) 2020 Elsevier Ltd. All rights reserved.

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