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Sample records for 3n161 mos transistors

  1. MOS-transistor power switches

    NASA Astrophysics Data System (ADS)

    Konev, Iu. I.; Mashukov, E. V.

    The output characteristics of vertical-channel MOS power transistors are analyzed. It is shown that it is possible to remove the basic energy and weight-volume constraints associated with the nonlinearity of the characeristics of devices with carrier injection (i.e., diodes, transistors, and thyristors). This makes it possible to increase the specific power of all types of power switches. The discussion covers switches for ac and dc power circuits, low-voltage rectifiers, and switches with pulse width modulation.

  2. Effects on focused ion beam irradiation on MOS transistors

    SciTech Connect

    Campbell, A.N.; Peterson, K.A.; Fleetwood, D.M.; Soden, J.M.

    1997-04-01

    The effects of irradiation from a focused ion beam (FIB) system on MOS transistors are reported systematically for the first time. Three MOS transistor technologies, with 0.5, 1, and 3 {mu}m minimum feature sizes and with gate oxide thicknesses ranging from 11 to 50 nm, were analyzed. Significant shifts in transistor parameters (such as threshold voltage, transconductance, and mobility) were observed following irradiation with a 30 keV Ga{sup +} focused ion beam with ion doses varying by over 5 orders of magnitude. The apparent damage mechanism (which involved the creation of interface traps, oxide trapped charge, or both) and extent of damage were different for each of the three technologies investigated.

  3. Metal Oxide Silicon /MOS/ transistors protected from destructive damage by wire

    NASA Technical Reports Server (NTRS)

    Deboo, G. J.; Devine, E. J.

    1966-01-01

    Loop of flexible, small diameter, nickel wire protects metal oxide silicon /MOS/ transistors from a damaging electrostatic potential. The wire is attached to a music-wire spring, slipped over the MOS transistor case, and released so the spring tensions the wire loop around all the transistor leads, shorting them together. This allows handling without danger of damage.

  4. Ambipolar MoS2 thin flake transistors.

    PubMed

    Zhang, Yijin; Ye, Jianting; Matsuhashi, Yusuke; Iwasa, Yoshihiro

    2012-03-14

    Field effect transistors (FETs) made of thin flake single crystals isolated from layered materials have attracted growing interest since the success of graphene. Here, we report the fabrication of an electric double layer transistor (EDLT, a FET gated by ionic liquids) using a thin flake of MoS(2), a member of the transition metal dichalcogenides, an archetypal layered material. The EDLT of the thin flake MoS(2) unambiguously displayed ambipolar operation, in contrast to its commonly known bulk property as an n-type semiconductor. High-performance transistor operation characterized by a large "ON" state conductivity in the order of ~mS and a high on/off ratio >10(2) was realized for both hole and electron transport. Hall effect measurements revealed mobility of 44 and 86 cm(2) V(-1) s(-1) for electron and hole, respectively. The hole mobility is twice the value of the electron mobility, and the density of accumulated carrier reached 1 × 10(14) cm(-2), which is 1 order of magnitude larger than conventional FETs with solid dielectrics. The high-density carriers of both holes and electrons can create metallic transport in the MoS(2) channel. The present result is not only important for device applications with new functionalities, but the method itself would also act as a protocol to study this class of material for a broader scope of possibilities in accessing their unexplored properties.

  5. Physics-based stability analysis of MOS transistors

    NASA Astrophysics Data System (ADS)

    Ferrara, A.; Steeneken, P. G.; Boksteen, B. K.; Heringa, A.; Scholten, A. J.; Schmitz, J.; Hueting, R. J. E.

    2015-11-01

    In this work, a physics-based model is derived based on a linearization procedure for investigating the electrical, thermal and electro-thermal instability of power metal-oxide-semiconductor (MOS) transistors. The proposed model can be easily interfaced with a circuit or device simulator to perform a failure analysis, making it particularly useful for power transistors. Furthermore, it allows mapping the failure points on a three-dimensional (3D) space defined by the gate-width normalized drain current, drain voltage and junction temperature. This leads to the definition of the Safe Operating Volume (SOV), a powerful frame work for making failure predictions and determining the main root of instability (electrical, thermal or electro-thermal) in different bias and operating conditions. A comparison between the modeled and the measured SOV of silicon-on-insulator (SOI) LDMOS transistors is reported to support the validity of the proposed stability analysis.

  6. MoS2 transistors operating at gigahertz frequencies.

    PubMed

    Krasnozhon, Daria; Lembke, Dominik; Nyffeler, Clemens; Leblebici, Yusuf; Kis, Andras

    2014-10-01

    The presence of a direct band gap and an ultrathin form factor has caused a considerable interest in two-dimensional (2D) semiconductors from the transition metal dichalcogenides (TMD) family with molybdenum disulfide (MoS2) being the most studied representative of this family of materials. While diverse electronic elements, logic circuits, and optoelectronic devices have been demonstrated using ultrathin MoS2, very little is known about their performance at high frequencies where commercial devices are expected to function. Here, we report on top-gated MoS2 transistors operating in the gigahertz range of frequencies. Our devices show cutoff frequencies reaching 6 GHz. The presence of a band gap also gives rise to current saturation, allowing power and voltage gain, all in the gigahertz range. This shows that MoS2 could be an interesting material for realizing high-speed amplifiers and logic circuits with device scaling expected to result in further improvement of performance. Our work represents the first step in the realization of high-frequency analog and digital circuits based on 2D semiconductors. PMID:25243885

  7. MoS2 transistors with 1-nanometer gate lengths

    NASA Astrophysics Data System (ADS)

    Desai, Sujay B.; Madhvapathy, Surabhi R.; Sachid, Angada B.; Llinas, Juan Pablo; Wang, Qingxiao; Ahn, Geun Ho; Pitner, Gregory; Kim, Moon J.; Bokor, Jeffrey; Hu, Chenming; Wong, H.-S. Philip; Javey, Ali

    2016-10-01

    Scaling of silicon (Si) transistors is predicted to fail below 5-nanometer (nm) gate lengths because of severe short channel effects. As an alternative to Si, certain layered semiconductors are attractive for their atomically uniform thickness down to a monolayer, lower dielectric constants, larger band gaps, and heavier carrier effective mass. Here, we demonstrate molybdenum disulfide (MoS2) transistors with a 1-nm physical gate length using a single-walled carbon nanotube as the gate electrode. These ultrashort devices exhibit excellent switching characteristics with near ideal subthreshold swing of ~65 millivolts per decade and an On/Off current ratio of ~106. Simulations show an effective channel length of ~3.9 nm in the Off state and ~1 nm in the On state.

  8. Hysteresis in single-layer MoS2 field effect transistors.

    PubMed

    Late, Dattatray J; Liu, Bin; Matte, H S S Ramakrishna; Dravid, Vinayak P; Rao, C N R

    2012-06-26

    Field effect transistors using ultrathin molybdenum disulfide (MoS(2)) have recently been experimentally demonstrated, which show promising potential for advanced electronics. However, large variations like hysteresis, presumably due to extrinsic/environmental effects, are often observed in MoS(2) devices measured under ambient environment. Here, we report the origin of their hysteretic and transient behaviors and suggest that hysteresis of MoS(2) field effect transistors is largely due to absorption of moisture on the surface and intensified by high photosensitivity of MoS(2). Uniform encapsulation of MoS(2) transistor structures with silicon nitride grown by plasma-enhanced chemical vapor deposition is effective in minimizing the hysteresis, while the device mobility is improved by over 1 order of magnitude.

  9. Variability of electrical contact properties in multilayer MoS2 thin-film transistors

    NASA Astrophysics Data System (ADS)

    Kim, Seong Yeoul; Park, Seonyoung; Choi, Woong

    2014-09-01

    We report the variability of electrical properties of Ti contacts in back-gated multilayer MoS2 thin-film transistors based on mechanically exfoliated flakes. By measuring current-voltage characteristics from room temperature to 240 °C, we demonstrate the formation of both ohmic and Schottky contacts at the Ti-MoS2 junctions of MoS2 transistors fabricated using identical electrode materials under the same conditions. While MoS2 transistors with ohmic contacts exhibit a typical signature of band transport, those with Schottky contacts indicate thermally activated transport behavior for the given temperature range. These results provide the experimental evidence of the variability of Ti metal contacts on MoS2, highlighting the importance of understanding the variability of electronic properties of naturally occurring MoS2 for further investigation.

  10. Tuning the threshold voltage of MoS2 field-effect transistors via surface treatment

    NASA Astrophysics Data System (ADS)

    Leong, Wei Sun; Li, Yida; Luo, Xin; Nai, Chang Tai; Quek, Su Ying; Thong, John T. L.

    2015-06-01

    Controlling the threshold voltage (Vth) of a field-effect transistor is important for realizing robust logic circuits. Here, we report a facile approach to achieve bidirectional Vth tuning of molybdenum disulfide (MoS2) field-effect transistors. By increasing and decreasing the amount of sulfur vacancies in the MoS2 surface, the Vth of MoS2 transistors can be left- and right-shifted, respectively. Transistors fabricated on perfect MoS2 flakes are found to exhibit a two-fold enhancement in mobility and a very positive Vth (18.5 +/- 7.5 V). More importantly, our elegant hydrogen treatment is able to tune the large Vth to a small value (~0 V) without any performance degradation simply by reducing the atomic ratio of S : Mo slightly; in other words, it creates a certain amount of sulfur vacancies in the MoS2 surface, which generate defect states in the band gap of MoS2 that mediates conduction of a MoS2 transistor in the subthreshold regime. First-principles calculations further indicate that the defect band's edge and width can be tuned according to the vacancy density. This work not only demonstrates for the first time the ease of tuning the Vth of MoS2 transistors, but also offers a process technology solution that is critical for further development of MoS2 as a mainstream electronic material.Controlling the threshold voltage (Vth) of a field-effect transistor is important for realizing robust logic circuits. Here, we report a facile approach to achieve bidirectional Vth tuning of molybdenum disulfide (MoS2) field-effect transistors. By increasing and decreasing the amount of sulfur vacancies in the MoS2 surface, the Vth of MoS2 transistors can be left- and right-shifted, respectively. Transistors fabricated on perfect MoS2 flakes are found to exhibit a two-fold enhancement in mobility and a very positive Vth (18.5 +/- 7.5 V). More importantly, our elegant hydrogen treatment is able to tune the large Vth to a small value (~0 V) without any performance degradation

  11. Dynamic Memory Cells Using MoS2 Field-Effect Transistors Demonstrating Femtoampere Leakage Currents.

    PubMed

    Kshirsagar, Chaitanya U; Xu, Weichao; Su, Yang; Robbins, Matthew C; Kim, Chris H; Koester, Steven J

    2016-09-27

    Two-dimensional semiconductors such as transition-metal dichalcogenides (TMDs) are of tremendous interest for scaled logic and memory applications. One of the most promising TMDs for scaled transistors is molybdenum disulfide (MoS2), and several recent reports have shown excellent performance and scalability for MoS2 MOSFETs. An often overlooked feature of MoS2 is that its wide band gap (1.8 eV in monolayer) and high effective masses should lead to extremely low off-state leakage currents. These features could be extremely important for dynamic memory applications where the refresh rate is the primary factor affecting the power consumption. Theoretical predictions suggest that leakage currents in the 10(-18) to 10(-15) A/μm range could be possible, even in scaled transistor geometries. Here, we demonstrate the operation of one- and two-transistor dynamic memory circuits using MoS2 MOSFETs. We characterize the retention times in these circuits and show that the two-transistor memory cell reveals MoS2 MOSFETs leakage currents as low as 1.7 × 10(-15) A/μm, a value that is below the noise floor of conventional DC measurements. These results have important implications for the future use of MoS2 MOSFETs in low-power circuit applications.

  12. Dynamic Memory Cells Using MoS2 Field-Effect Transistors Demonstrating Femtoampere Leakage Currents.

    PubMed

    Kshirsagar, Chaitanya U; Xu, Weichao; Su, Yang; Robbins, Matthew C; Kim, Chris H; Koester, Steven J

    2016-09-27

    Two-dimensional semiconductors such as transition-metal dichalcogenides (TMDs) are of tremendous interest for scaled logic and memory applications. One of the most promising TMDs for scaled transistors is molybdenum disulfide (MoS2), and several recent reports have shown excellent performance and scalability for MoS2 MOSFETs. An often overlooked feature of MoS2 is that its wide band gap (1.8 eV in monolayer) and high effective masses should lead to extremely low off-state leakage currents. These features could be extremely important for dynamic memory applications where the refresh rate is the primary factor affecting the power consumption. Theoretical predictions suggest that leakage currents in the 10(-18) to 10(-15) A/μm range could be possible, even in scaled transistor geometries. Here, we demonstrate the operation of one- and two-transistor dynamic memory circuits using MoS2 MOSFETs. We characterize the retention times in these circuits and show that the two-transistor memory cell reveals MoS2 MOSFETs leakage currents as low as 1.7 × 10(-15) A/μm, a value that is below the noise floor of conventional DC measurements. These results have important implications for the future use of MoS2 MOSFETs in low-power circuit applications. PMID:27559610

  13. High performance MoS2-based field-effect transistor enabled by hydrazine doping.

    PubMed

    Lim, Dongsuk; Kannan, E S; Lee, Inyeal; Rathi, Servin; Li, Lijun; Lee, Yoontae; Khan, Muhammad Atif; Kang, Moonshik; Park, Jinwoo; Kim, Gil-Ho

    2016-06-01

    We investigated the n-type doping effect of hydrazine on the electrical characteristics of a molybdenum disulphide (MoS2)-based field-effect transistor (FET). The threshold voltage of the MoS2 FET shifted towards more negative values (from -20 to -70 V) on treating with 100% hydrazine solution with the channel current increasing from 0.5 to 25 μA at zero gate bias. The inverse subthreshold slope decreased sharply on doping, while the ON/OFF ratio increased by a factor of 100. Gate-channel coupling improved with doping, which facilitates the reduction of channel length between the source and drain electrodes without compromising on the transistor performance, making the MoS2-based FET easily scalable.

  14. High performance MoS2-based field-effect transistor enabled by hydrazine doping

    NASA Astrophysics Data System (ADS)

    Lim, Dongsuk; Kannan, E. S.; Lee, Inyeal; Rathi, Servin; Li, Lijun; Lee, Yoontae; Atif Khan, Muhammad; Kang, Moonshik; Park, Jinwoo; Kim, Gil-Ho

    2016-06-01

    We investigated the n-type doping effect of hydrazine on the electrical characteristics of a molybdenum disulphide (MoS2)-based field-effect transistor (FET). The threshold voltage of the MoS2 FET shifted towards more negative values (from ‑20 to ‑70 V) on treating with 100% hydrazine solution with the channel current increasing from 0.5 to 25 μA at zero gate bias. The inverse subthreshold slope decreased sharply on doping, while the ON/OFF ratio increased by a factor of 100. Gate–channel coupling improved with doping, which facilitates the reduction of channel length between the source and drain electrodes without compromising on the transistor performance, making the MoS2-based FET easily scalable.

  15. High performance MoS2-based field-effect transistor enabled by hydrazine doping.

    PubMed

    Lim, Dongsuk; Kannan, E S; Lee, Inyeal; Rathi, Servin; Li, Lijun; Lee, Yoontae; Khan, Muhammad Atif; Kang, Moonshik; Park, Jinwoo; Kim, Gil-Ho

    2016-06-01

    We investigated the n-type doping effect of hydrazine on the electrical characteristics of a molybdenum disulphide (MoS2)-based field-effect transistor (FET). The threshold voltage of the MoS2 FET shifted towards more negative values (from -20 to -70 V) on treating with 100% hydrazine solution with the channel current increasing from 0.5 to 25 μA at zero gate bias. The inverse subthreshold slope decreased sharply on doping, while the ON/OFF ratio increased by a factor of 100. Gate-channel coupling improved with doping, which facilitates the reduction of channel length between the source and drain electrodes without compromising on the transistor performance, making the MoS2-based FET easily scalable. PMID:27098430

  16. Density functional studies on edge-contacted single-layer MoS2 piezotronic transistors

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Zhang, Aihua; Zhang, Yan; Wang, Zhong Lin

    2015-08-01

    The piezotronic effect uses strain-induced piezoelectric charges at interfaces and junctions to tune and/or control carrier transport in piezoelectric semiconductor devices. This effect has recently been observed in single-layer 2D MoS2 materials. However, previous work had found that metallic states are generated at the edge of a free-standing MoS2 flat sheet, and these states may screen the piezoelectric charges. Using density functional theory simulations, we found that the metal-MoS2 interface structure plays an important role in enhancing both the piezoelectric and piezotronic effects in MoS2 transistors by breaking the metallic state screening effect at the MoS2 edge. This study not only provides an understanding of the piezoelectric and piezotronic effects based on first principles calculations but also offers guidance for the design of two-dimensional piezotronic devices.

  17. The intrinsic origin of hysteresis in MoS2 field effect transistors.

    PubMed

    Shu, Jiapei; Wu, Gongtao; Guo, Yao; Liu, Bo; Wei, Xianlong; Chen, Qing

    2016-02-01

    We investigate the hysteresis and gate voltage stress effect in MoS2 field effect transistors (FETs). We observe that both the suspended and the SiO2-supported FETs have large hysteresis in their transfer curves under vacuum which cannot be attributed to the traps at the interface between the MoS2 and the SiO2 or in the SiO2 substrate or the gas adsorption/desorption effect. Our findings indicate that the hysteresis we observe comes from the MoS2 itself, revealing an intrinsic origin of the hysteresis besides some extrinsic factors. The fact that the FETs based on thinner MoS2 have larger hysteresis than that with thicker MoS2 suggests that the surface of MoS2 plays a key role in the hysteresis. The gate voltage sweep range, sweep direction, sweep time and loading history all affect the hysteresis observed in the transfer curves.

  18. High performance and transparent multilayer MoS2 transistors: Tuning Schottky barrier characteristics

    NASA Astrophysics Data System (ADS)

    Hong, Young Ki; Yoo, Geonwook; Kwon, Junyeon; Hong, Seongin; Song, Won Geun; Liu, Na; Omkaram, Inturu; Yoo, Byungwook; Ju, Sanghyun; Kim, Sunkook; Oh, Min Suk

    2016-05-01

    Various strategies and mechanisms have been suggested for investigating a Schottky contact behavior in molybdenum disulfide (MoS2) thin-film transistor (TFT), which are still in much debate and controversy. As one of promising breakthrough for transparent electronics with a high device performance, we have realized MoS2 TFTs with source/drain electrodes consisting of transparent bi-layers of a conducting oxide over a thin film of low work function metal. Intercalation of a low work function metal layer, such as aluminum, between MoS2 and transparent source/drain electrodes makes it possible to optimize the Schottky contact characteristics, resulting in about 24-fold and 3 orders of magnitude enhancement of the field-effect mobility and on-off current ratio, respectively, as well as transmittance of 87.4 % in the visible wavelength range.

  19. Polarity control in MoS2 and MoSe2 field effect transistors

    NASA Astrophysics Data System (ADS)

    Fragapane, A.; Bobek, S.; Barroso, D.; Nguyen, A.; Bonilla, E.; Naghibi, S.; von Son Palacio, G.; Klee, V.; Preciado, E.; Martinez, J.; Pleskot, D.; Mann, J.; Shidpoor, R.; Bartels, L.; Sorger, V.; Liu, A.; Paranjape, M.; Barbara, P.

    2014-03-01

    Ambipolar operation is essential for a variety of optoelectronic applications, where both electron and hole transport are required simultaneously. However, hole transport and p-type Schottky barriers have been difficult to achieve in all-solid state field effect transistors based on MoS2 charge channels. In prior work we demonstrated that Schottky barriers of either polarity (p-type or n-type) can be obtained with multilayer MoS2 flakes exfoliated from geological crystals. Here we study Schottky barrier polarity in thinner flakes of MoS2 and MoSe2 (down to single-layer thicknesses) that are grown by CVD, towards understanding how both variations in the bandgap and material work functions affect band alignment at the interface between the flakes and the metal contacts. Supported by the NSF, DMR-1008242, 1106210 and C-SPIN.

  20. Atomistic full-band simulations of monolayer MoS2 transistors

    NASA Astrophysics Data System (ADS)

    Chang, Jiwon; Register, Leonard F.; Banerjee, Sanjay K.

    2013-11-01

    We study the transport properties of deeply scaled monolayer MoS2 n-channel metal-oxide-semiconductor field effect transistors (MOSFETs), using full-band ballistic quantum transport simulations, with an atomistic tight-binding Hamiltonian obtained from density functional theory. Our simulations suggest that monolayer MoS2 MOSFETs can provide near-ideal subthreshold slope, suppression of drain-induced barrier lowering, and gate-induced drain leakage. However, these full-band simulations exhibit limited transconductance. These ballistic simulations also exhibit negative differential resistance (NDR) in the output characteristics associated with the narrow width in energy of the lowest conduction band, but this NDR may be substantially reduced or eliminated by scattering in MoS2.

  1. MoS2 Field-effect Transistors with Graphene/Metal Hetero-contacts

    NASA Astrophysics Data System (ADS)

    Du, Yuchen; Yang, Lingming; Zhang, Jingyun; Conrad, Nathan; Liu, Han; Ye, Peide

    2014-03-01

    MoS2, as one of the mostly studied transition-metal dichalcogenides, has already revealed a series of new physics and potential device applications. However, the performance of the MoS2 field-effect transistors is limited by the large contact resistance at metal/MoS2 interface due to the non-negligible Schottky barrier. In this study, n-type few-layer MoS2 field-effect transistors with graphene/Ti as the metal contacts have been fabricated showing more than 160 mA/mm drain current at 1 μm gate length and on-off current ratio of 107. Different metal contacts (Ti, Ni, Au, and Pd) from low work function to high work function metals on MoS2/graphene hetero contacts have been performed and studied. Moreover, for the first time, 2D Fermi-level pinning concept is introduced to understand the band alignment of hetero-structured metal/graphene/MoS2 or other 2D semiconductor interfaces. Temperature dependent, noise, and stress measurement results will also be presented.

  2. Method of making self-aligned lightly-doped-drain structure for MOS transistors

    DOEpatents

    Weiner, Kurt H.; Carey, Paul G.

    2001-01-01

    A process for fabricating lightly-doped-drains (LDD) for short-channel metal oxide semiconductor (MOS) transistors. The process utilizes a pulsed laser process to incorporate the dopants, thus eliminating the prior oxide deposition and etching steps. During the process, the silicon in the source/drain region is melted by the laser energy. Impurities from the gas phase diffuse into the molten silicon to appropriately dope the source/drain regions. By controlling the energy of the laser, a lightly-doped-drain can be formed in one processing step. This is accomplished by first using a single high energy laser pulse to melt the silicon to a significant depth and thus the amount of dopants incorporated into the silicon is small. Furthermore, the dopants incorporated during this step diffuse to the edge of the MOS transistor gate structure. Next, many low energy laser pulses are used to heavily dope the source/drain silicon only in a very shallow region. Because of two-dimensional heat transfer at the MOS transistor gate edge, the low energy pulses are inset from the region initially doped by the high energy pulse. By computer control of the laser energy, the single high energy laser pulse and the subsequent low energy laser pulses are carried out in a single operational step to produce a self-aligned lightly-doped-drain-structure.

  3. Estimation of temperature impact on gamma-induced degradation parameters of N-channel MOS transistor

    NASA Astrophysics Data System (ADS)

    Jafari, H.; Feghhi, S. A. H.

    2015-03-01

    The physical parameters of MOS transistors can be impressed by ionizing radiation and that leads to circuit degradation and failure. These effects require analyzing the basic mechanism that results in the buildup of induced defect in radiation environments. The reliable estimation also needs to consider external factors, particularly temperature fluctuations. I-V characteristic of the device was obtained using a temperature-dependent adapted form of charge-sheet model under heating cycle during irradiation with several ionizing dose levels at different gate biases. In this work, the analytical calculation for estimating the irradiation temperature impact on gamma-induced degradation parameters of N-channel MOS transistors at different gate biases was investigated. The experimental measurement was done in order to verify and parameterize the analytical model calculations. The results indicated that inserting irradiation temperature in the calculations caused a significant variation in radiation-induced MOS transistor parameters such as threshold voltage shift and off-state leakage current. According to the results, these variations were about 10.1% and 23.4% for voltage shifts and leakage currents respectively during investigated heating cycle for total dose of 20 krad at 9 V gate bias.

  4. Using a Floating-Gate MOS Transistor as a Transducer in a MEMS Gas Sensing System

    PubMed Central

    Barranca, Mario Alfredo Reyes; Mendoza-Acevedo, Salvador; Flores-Nava, Luis M.; Avila-García, Alejandro; Vazquez-Acosta, E. N.; Moreno-Cadenas, José Antonio; Casados-Cruz, Gaspar

    2010-01-01

    Floating-gate MOS transistors have been widely used in diverse analog and digital applications. One of these is as a charge sensitive device in sensors for pH measurement in solutions or using gates with metals like Pd or Pt for hydrogen sensing. Efforts are being made to monolithically integrate sensors together with controlling and signal processing electronics using standard technologies. This can be achieved with the demonstrated compatibility between available CMOS technology and MEMS technology. In this paper an in-depth analysis is done regarding the reliability of floating-gate MOS transistors when charge produced by a chemical reaction between metallic oxide thin films with either reducing or oxidizing gases is present. These chemical reactions need temperatures around 200 °C or higher to take place, so thermal insulation of the sensing area must be assured for appropriate operation of the electronics at room temperature. The operation principle of the proposal here presented is confirmed by connecting the gate of a conventional MOS transistor in series with a Fe2O3 layer. It is shown that an electrochemical potential is present on the ferrite layer when reacting with propane. PMID:22163478

  5. Using a floating-gate MOS transistor as a transducer in a MEMS gas sensing system.

    PubMed

    Barranca, Mario Alfredo Reyes; Mendoza-Acevedo, Salvador; Flores-Nava, Luis M; Avila-García, Alejandro; Vazquez-Acosta, E N; Moreno-Cadenas, José Antonio; Casados-Cruz, Gaspar

    2010-01-01

    Floating-gate MOS transistors have been widely used in diverse analog and digital applications. One of these is as a charge sensitive device in sensors for pH measurement in solutions or using gates with metals like Pd or Pt for hydrogen sensing. Efforts are being made to monolithically integrate sensors together with controlling and signal processing electronics using standard technologies. This can be achieved with the demonstrated compatibility between available CMOS technology and MEMS technology. In this paper an in-depth analysis is done regarding the reliability of floating-gate MOS transistors when charge produced by a chemical reaction between metallic oxide thin films with either reducing or oxidizing gases is present. These chemical reactions need temperatures around 200 °C or higher to take place, so thermal insulation of the sensing area must be assured for appropriate operation of the electronics at room temperature. The operation principle of the proposal here presented is confirmed by connecting the gate of a conventional MOS transistor in series with a Fe(2)O(3) layer. It is shown that an electrochemical potential is present on the ferrite layer when reacting with propane.

  6. Radio Frequency Transistors and Circuits Based on CVD MoS2.

    PubMed

    Sanne, Atresh; Ghosh, Rudresh; Rai, Amritesh; Yogeesh, Maruthi Nagavalli; Shin, Seung Heon; Sharma, Ankit; Jarvis, Karalee; Mathew, Leo; Rao, Rajesh; Akinwande, Deji; Banerjee, Sanjay

    2015-08-12

    We report on the gigahertz radio frequency (RF) performance of chemical vapor deposited (CVD) monolayer MoS2 field-effect transistors (FETs). Initial DC characterizations of fabricated MoS2 FETs yielded current densities exceeding 200 μA/μm and maximum transconductance of 38 μS/μm. A contact resistance corrected low-field mobility of 55 cm(2)/(V s) was achieved. Radio frequency FETs were fabricated in the ground-signal-ground (GSG) layout, and standard de-embedding techniques were applied. Operating at the peak transconductance, we obtain short-circuit current-gain intrinsic cutoff frequency, fT, of 6.7 GHz and maximum intrinsic oscillation frequency, fmax, of 5.3 GHz for a device with a gate length of 250 nm. The MoS2 device afforded an extrinsic voltage gain Av of 6 dB at 100 MHz with voltage amplification until 3 GHz. With the as-measured frequency performance of CVD MoS2, we provide the first demonstration of a common-source (CS) amplifier with voltage gain of 14 dB and an active frequency mixer with conversion gain of -15 dB. Our results of gigahertz frequency performance as well as analog circuit operation show that large area CVD MoS2 may be suitable for industrial-scale electronic applications. PMID:26134588

  7. Negative Differential Transconductance in a MoS2 /WSe2 Heterojunction Field Effect Transistor

    NASA Astrophysics Data System (ADS)

    Zubair, Ahmad; Nourbakhsh, Amirhasan; Dresselhaus, Mildred; de Gendt, Stefan; Palacios, Tomas

    2015-03-01

    In this work, we demonstrate the negative transconductance in heterojunction transistors made of two-dimensional materials for the first time. Negative transconductance plays a key role in multi-valued logic/memory and frequency multiplication circuits. The simpler fabrication method of stacked van der Waals heterostructures compared to the conventional bulk semiconductors and large area CVD growth of the layered 2D materials systems makes it a prime candidate for scalable novel applications of their heterostructures. Vertically stacked MoS2/WSe2 heterostructures are fabricated by mechanical exfoliation and an in-house dry transfer process. A two-step process of e-beam lithography and metal deposition (Au on MoS2, and Pd on WSe2) were performed to fabricate n-type MoS2 and ambipolar WSe2 FET. The transfer characteristics on the non-overlapping regions shows the expected characteristics of the n-type, MoS2 FET and ambipolar WSe2 FET. At the same time, the transfer characteristics of the overlapping region between MoS2 and WSe2 show negative differential transconductance. With proper scaling and careful optimization this negative differential transconductance will lead to novel applications.

  8. Electric stress-induced threshold voltage instability of multilayer MoS2 field effect transistors.

    PubMed

    Cho, Kyungjune; Park, Woanseo; Park, Juhun; Jeong, Hyunhak; Jang, Jingon; Kim, Tae-Young; Hong, Woong-Ki; Hong, Seunghun; Lee, Takhee

    2013-09-24

    We investigated the gate bias stress effects of multilayered MoS2 field effect transistors (FETs) with a back-gated configuration. The electrical stability of the MoS2 FETs can be significantly influenced by the electrical stress type, relative sweep rate, and stress time in an ambient environment. Specifically, when a positive gate bias stress was applied to the MoS2 FET, the current of the device decreased and its threshold shifted in the positive gate bias direction. In contrast, with a negative gate bias stress, the current of the device increased and the threshold shifted in the negative gate bias direction. The gate bias stress effects were enhanced when a gate bias was applied for a longer time or when a slower sweep rate was used. These phenomena can be explained by the charge trapping due to the adsorption or desorption of oxygen and/or water on the MoS2 surface with a positive or negative gate bias, respectively, under an ambient environment. This study will be helpful in understanding the electrical-stress-induced instability of the MoS2-based electronic devices and will also give insight into the design of desirable devices for electronics applications.

  9. Drain-extended MOS transistors capable for operation at 10 V and at radio frequencies

    NASA Astrophysics Data System (ADS)

    Mai, Andreas; Rücker, Holger

    2011-11-01

    This work reports on the integration of n-type lateral-drain-extended MOS transistors (LDMOS) in a 0.13 μm SiGe BiCMOS technology. The transistors are realized with no additional process steps using the core dual-gate-oxide CMOS flow only. LDMOS drift regions are formed by compensating lightly-doped drain (LDD) implantations of NMOS and PMOS transistors of the baseline process. Stable operation with less than 10% parameter variations in 10 years is achieved up to operating voltages VDD,max of 10 V for devices with breakdown voltages BVDSS = 30 V and on-resistances RON = 7.3 Ω mm. Devices for different operating voltages VDD,max are realized by layout variations. Devices with VDD,max = 6 V demonstrate breakdown voltages BVDSS = 25 V, on-resistances RON = 4.9 Ω mm, and peak transit frequencies fT = 32 GHz.

  10. Evaluation of pulsed laser annealing for flexible multilayer MoS2 transistors

    NASA Astrophysics Data System (ADS)

    Kwon, Hyuk-Jun; Kim, Sunkook; Jang, Jaewon; Grigoropoulos, Costas P.

    2015-03-01

    To realize the proper electrical characteristics of field-effect transistors, the quality of the contact and interface must be improved because they can substantially distort the extracted mobility, especially for materials with low densities of states like molybdenum disulfide (MoS2). We show that mechanically flexible MoS2 thin-film transistors (TFTs) with selectively laser annealed source/drain electrodes achieve enhanced device performance without plastic deformation including higher field-effect mobility (from 19.59 to 45.91 cm2 V-1 s-1) in the linear regime, decreased subthreshold swing, and enhanced current saturation. Furthermore, numerical thermal simulations, measured current-voltage characteristics, and contact-free mobility extracted from the Y-function method suggest that the enhanced performance originated from a decrease in the Schottky barrier effect at the contact and an improvement of the channel interface. These results demonstrate that picosecond laser annealing can be a promising technology for building high performance flexible MoS2 TFTs in flexible/stretchable circuitry, which should be processed at low temperatures.

  11. Low-frequency noise in bilayer MoS(2) transistor.

    PubMed

    Xie, Xuejun; Sarkar, Deblina; Liu, Wei; Kang, Jiahao; Marinov, Ognian; Deen, M Jamal; Banerjee, Kaustav

    2014-06-24

    Low-frequency noise is a significant limitation on the performance of nanoscale electronic devices. This limitation is especially important for devices based on two-dimensional (2D) materials such as graphene and transition metal dichalcogenides (TMDs), which have atomically thin bodies and, hence, are severely affected by surface contaminants. Here, we investigate the low-frequency noise of transistors based on molybdenum disulfide (MoS2), which is a typical example of TMD. The noise measurements performed on bilayer MoS2 channel transistors show a noise peak in the gate-voltage dependence data, which has also been reported for graphene. To understand the peak, a trap decay-time based model is developed by revisiting the carrier number fluctuation model. Our analysis reveals that the peak originates from the fact that the decay time of the traps for a 2D device channel is governed by the van der Waals bonds between the 2D material and the surroundings. Our model is generic to all 2D materials and can be applied to explain the V, M and Λ shaped dependence of noise on the gate voltage in graphene transistors, as well as the noise shape dependency on the number of atomic layers of other 2D materials. Since the van der Waals bonding between the surface traps and 2D materials is weak, in accordance with the developed physical model, an annealing process is shown to significantly reduce the trap density, thereby reducing the low-frequency noise.

  12. Ionic Liquid Gating of Suspended MoS2 Field Effect Transistor Devices.

    PubMed

    Wang, Fenglin; Stepanov, Petr; Gray, Mason; Lau, Chun Ning; Itkis, Mikhail E; Haddon, Robert C

    2015-08-12

    We demonstrate ionic liquid (IL) gating of suspended few-layer MoS2 transistors, where ions can accumulate on both exposed surfaces. Upon application of IL, all free-standing samples consistently display more significant improvement in conductance than substrate-supported devices. The measured IL gate coupling efficiency is up to 4.6 × 10(13) cm(-2) V(-1). Electrical transport data reveal contact-dominated electrical transport properties and the Schottky emission as the underlying mechanism. By modulating IL gate voltage, the suspended MoS2 devices display metal-insulator transition. Our results demonstrate that more efficient charge induction can be achieved in suspended two-dimensional (2D) materials, which with further optimization, may enable extremely high charge density and novel phase transition.

  13. Fabrication of flexible MoS2 thin-film transistor arrays for practical gas-sensing applications.

    PubMed

    He, Qiyuan; Zeng, Zhiyuan; Yin, Zongyou; Li, Hai; Wu, Shixin; Huang, Xiao; Zhang, Hua

    2012-10-01

    By combining two kinds of solution-processable two-dimensional materials, a flexible transistor array is fabricated in which MoS(2) thin film is used as the active channel and reduced graphene oxide (rGO) film is used as the drain and source electrodes. The simple device configuration and the 1.5 mm-long MoS(2) channel ensure highly reproducible device fabrication and operation. This flexible transistor array can be used as a highly sensitive gas sensor with excellent reproducibility. Compared to using rGO thin film as the active channel, this new gas sensor exhibits much higher sensitivity. Moreover, functionalization of the MoS(2) thin film with Pt nanoparticles further increases the sensitivity by up to ∼3 times. The successful incorporation of a MoS(2) thin-film into the electronic sensor promises its potential application in various electronic devices. PMID:22778003

  14. Fabrication and Characterization of Surface P - MOS Transistors with Channel Lengths to 200 Nanometers

    NASA Astrophysics Data System (ADS)

    Kugelmass, Sheldon Michael

    The scaling of MOS devices requires the development of new fabrication processes, device structures and characterization techniques. A process architecture for the fabrication of nanometer scale, surface p-channel MOS transistors was developed and used to study the impact of gate oxide thickness and gate length scaling as well as to investigate a novel source/drain structure. A new capacitance-based technique for the characterization of hot carrier induced degradation in p-channel MOS transistors was developed and applied to the fabricated devices. Several process modules were developed and integrated into the device fabrication sequence. Rapid Thermal Processing was used for growth of the gate oxide, reoxidation of the gate polysilicon and formation of shallow p^+ /n junctions. The deposition of in situ doped polysilicon films was characterized. P-channel MOS transistors were fabricated with gate oxides as thin as 5 nm as were devices with channel lengths below 200 nm. Polysilicon depletion, due to insufficient doping of the gate polysilicon, increased as the gate oxide decreased. The transconductance increased with decreasing effective length, reaching a value of 82.3 muS/mum for L_{rm eff} = 180 nm. Formation of shallow source/drain junctions using gallium was investigated. A high temperature anneal (1050 ^circC) was required to eliminate implant damage. SIMS analysis showed that after 15 seconds at 1050^circC, over 50% of the dopant was lost to the ambient. A Ga source/drain extension was integrated into the existing MOS device structure and had 15-25% less lateral encroachment of dopant into the channel than an equivalent boron doped structure. The difference in the gate to source/drain capacitance before and after hot carrier stress reflects the influence of a localized trapped charge distribution in the gate oxide. A simple model indicated that both the length and the threshold voltage shift of the degraded region increase with increasing stress time. The

  15. DETECTORS AND EXPERIMENTAL METHODS: Radiation response of pseudo-MOS transistors fabricated in hardened fully-depleted SIMOX SOI wafers

    NASA Astrophysics Data System (ADS)

    Bi, Da-Wei; Zhang, Zheng-Xuan; Zhang, Shuai; Chen, Ming; Yu, Wen-Jie; Wang, Ru; Tian, Hao; Liu, Zhang-Li

    2009-10-01

    The total dose radiation response of pseudo-MOS transistors fabricated in hardened and unhardened FD (fully-depleted) SIMOX (Separation by Implanted Oxygen) SOI (Silicon-on-insulator) wafers is presented. At 1 Mrad(Si) radiation dose, the threshold voltage shift of the pseudo-MOS transistor is reduced from -115.5 to -1.9 V by the hardening procedure. The centroid location of the net positive charge trapped in BOX, the hole-trap density and the hole capture fraction of BOX are also shown. The results suggest that hardened FD SIMOX SOI wafers can perform well in a radiation environment.

  16. Conduction Mechanisms in CVD-Grown Monolayer MoS2 Transistors: From Variable-Range Hopping to Velocity Saturation.

    PubMed

    He, G; Ghosh, K; Singisetti, U; Ramamoorthy, H; Somphonsane, R; Bohra, G; Matsunaga, M; Higuchi, A; Aoki, N; Najmaei, S; Gong, Y; Zhang, X; Vajtai, R; Ajayan, P M; Bird, J P

    2015-08-12

    We fabricate transistors from chemical vapor deposition-grown monolayer MoS2 crystals and demonstrate excellent current saturation at large drain voltages (Vd). The low-field characteristics of these devices indicate that the electron mobility is likely limited by scattering from charged impurities. The current-voltage characteristics exhibit variable range hopping at low Vd and evidence of velocity saturation at higher Vd. This work confirms the excellent potential of MoS2 as a possible channel-replacement material and highlights the role of multiple transport phenomena in governing its transistor action.

  17. Multiple MoS2 Transistors for Sensing Molecule Interaction Kinetics

    PubMed Central

    Nam, Hongsuk; Oh, Bo-Ram; Chen, Pengyu; Chen, Mikai; Wi, Sungjin; Wan, Wenjie; Kurabayashi, Katsuo; Liang, Xiaogan

    2015-01-01

    Atomically layered transition metal dichalcogenides (TMDCs) exhibit a significant potential to enable next-generation low-cost transistor biosensors that permit single-molecule-level quantification of biomolecules. To realize such potential biosensing capability, device-oriented research is needed for calibrating the sensor responses to enable the quantification of the affinities/kinetics of biomolecule interactions. In this work, we demonstrated MoS2-based transistor biosensors capable of detecting tumor necrosis factor – alpha (TNF-α) with a detection limit as low as 60 fM. Such a detection limit was achieved in both linear and subthreshold regimes of MoS2 transistors. In both regimes, all sets of transistors exhibited consistent calibrated responses with respect to TNF-α concentration, and they resulted in a standard curve, from which the equilibrium constant of the antibody-(TNF-α) pair was extracted to be KD = 369 ± 48 fM. Based on this calibrated sensor model, the time-dependent binding kinetics was also measured and the association/dissociation rates of the antibody-(TNF-α) pair were extracted to be (5.03 ± 0.16) × 108 M−1s−1 and (1.97 ± 0.08) × 10−4 s−1, respectively. This work advanced the critical device physics for leveraging the excellent electronic/structural properties of TMDCs in biosensing applications as well as the research capability in analyzing the biomolecule interactions with fM-level sensitivities. PMID:26014289

  18. Extended characterization of the damage by hot charge carriers in gate oxide by short channel MOS field effect transistors

    NASA Astrophysics Data System (ADS)

    Mahnkopf, Reinhard

    Transistors from several technologies are tested by measurements of the capacities and the characteristic curves. A model allows obtaining of the gate and substrate currents. The damages at the phase limit and in the oxide are characterized by macroscopic current and voltage variations and by generated charge densities. For p-MOS (Metal Oxide Semiconductor) transistors, the production of oxide charges is the most important fact, in relation to the injected hot electrons; for n-MOS transistors, the generation of phase limit states is the main phenomenon. It is proved that the damages are located at the chain contact in the lateral direction but appear in the transistor channel with increasing functioning time or voltage.

  19. Tailoring the electrical properties of MoS2 field effect transistors by depositing Au nanoparticles and alkanethiol molecules.

    PubMed

    Cho, Kyungjune; Jeong, Hyunhak; Kim, Tae-Young; Pak, Jinsu; Kim, Jae-Keun; Choi, Barbara Yuri; Lee, Takhee

    2016-05-11

    We fabricated and characterized MoS2 field effect transistors. First, we measured the electrical properties of MoS2 field effect transistors (FETs) that were made with mechanically exfoliated MoS2 flakes. Then, we deposited Au nanoparticles on the MoS2 channel and measured the electrical properties. We observed whether the source-drain current increased or decreased after the Au particles were deposited. The deposited Au particles either formed an extra current path and increased the current or behaved as charge-withdrawing sites and decreased the current. Next, we deposited alkanethiol molecules on the Au particles to reduce the work function of the Au. Alkanethiol molecules are known to form a self-assembled monolayer on the Au surface, and the electric dipole moment of the molecules causes the work function of the Au to decrease. Au particles can capture electrons from the MoS2 channel due to their high work function. However, the decreased work function of the Au particles subjected to alkanethiol treatment could cause captured electrons to be released from the Au particles to MoS2. Therefore, the current increased after alkanethiol treatment. This study may provide useful methods to utilize surface treatments with particles and molecules to tailor the electrical properties of MoS2-based FETs.

  20. Uncovering edge states and electrical inhomogeneity in MoS2 field-effect transistors.

    PubMed

    Wu, Di; Li, Xiao; Luan, Lan; Wu, Xiaoyu; Li, Wei; Yogeesh, Maruthi N; Ghosh, Rudresh; Chu, Zhaodong; Akinwande, Deji; Niu, Qian; Lai, Keji

    2016-08-01

    The understanding of various types of disorders in atomically thin transition metal dichalcogenides (TMDs), including dangling bonds at the edges, chalcogen deficiencies in the bulk, and charges in the substrate, is of fundamental importance for TMD applications in electronics and photonics. Because of the imperfections, electrons moving on these 2D crystals experience a spatially nonuniform Coulomb environment, whose effect on the charge transport has not been microscopically studied. Here, we report the mesoscopic conductance mapping in monolayer and few-layer MoS2 field-effect transistors by microwave impedance microscopy (MIM). The spatial evolution of the insulator-to-metal transition is clearly resolved. Interestingly, as the transistors are gradually turned on, electrical conduction emerges initially at the edges before appearing in the bulk of MoS2 flakes, which can be explained by our first-principles calculations. The results unambiguously confirm that the contribution of edge states to the channel conductance is significant under the threshold voltage but negligible once the bulk of the TMD device becomes conductive. Strong conductance inhomogeneity, which is associated with the fluctuations of disorder potential in the 2D sheets, is also observed in the MIM images, providing a guideline for future improvement of the device performance.

  1. Uncovering edge states and electrical inhomogeneity in MoS2 field-effect transistors.

    PubMed

    Wu, Di; Li, Xiao; Luan, Lan; Wu, Xiaoyu; Li, Wei; Yogeesh, Maruthi N; Ghosh, Rudresh; Chu, Zhaodong; Akinwande, Deji; Niu, Qian; Lai, Keji

    2016-08-01

    The understanding of various types of disorders in atomically thin transition metal dichalcogenides (TMDs), including dangling bonds at the edges, chalcogen deficiencies in the bulk, and charges in the substrate, is of fundamental importance for TMD applications in electronics and photonics. Because of the imperfections, electrons moving on these 2D crystals experience a spatially nonuniform Coulomb environment, whose effect on the charge transport has not been microscopically studied. Here, we report the mesoscopic conductance mapping in monolayer and few-layer MoS2 field-effect transistors by microwave impedance microscopy (MIM). The spatial evolution of the insulator-to-metal transition is clearly resolved. Interestingly, as the transistors are gradually turned on, electrical conduction emerges initially at the edges before appearing in the bulk of MoS2 flakes, which can be explained by our first-principles calculations. The results unambiguously confirm that the contribution of edge states to the channel conductance is significant under the threshold voltage but negligible once the bulk of the TMD device becomes conductive. Strong conductance inhomogeneity, which is associated with the fluctuations of disorder potential in the 2D sheets, is also observed in the MIM images, providing a guideline for future improvement of the device performance. PMID:27444021

  2. Phase-engineered low-resistance contacts for ultrathin MoS2 transistors

    NASA Astrophysics Data System (ADS)

    Kappera, Rajesh; Voiry, Damien; Yalcin, Sibel Ebru; Branch, Brittany; Gupta, Gautam; Mohite, Aditya D.; Chhowalla, Manish

    2014-12-01

    Ultrathin molybdenum disulphide (MoS2) has emerged as an interesting layered semiconductor because of its finite energy bandgap and the absence of dangling bonds. However, metals deposited on the semiconducting 2H phase usually form high-resistance (0.7 kΩ μm-10 kΩ μm) contacts, leading to Schottky-limited transport. In this study, we demonstrate that the metallic 1T phase of MoS2 can be locally induced on semiconducting 2H phase nanosheets, thus decreasing contact resistances to 200-300 Ω μm at zero gate bias. Field-effect transistors (FETs) with 1T phase electrodes fabricated and tested in air exhibit mobility values of ~50 cm2 V-1 s-1, subthreshold swing values below 100 mV per decade, on/off ratios of >107, drive currents approaching ~100 μA μm-1, and excellent current saturation. The deposition of different metals has limited influence on the FET performance, suggesting that the 1T/2H interface controls carrier injection into the channel. An increased reproducibility of the electrical characteristics is also obtained with our strategy based on phase engineering of MoS2.

  3. Ionic-Liquid Gated Few-layer MoS2 Field-Effect Transistors

    NASA Astrophysics Data System (ADS)

    Perera, Meeghage; Lin, Ming-Wei; Chuang, Hsun-Jen; Chamlagain, Bhim; Wang, Chongyu; Tan, Xuebin; Cheng, Mark Ming-Cheng; Zhou, Zhixian

    2013-03-01

    We report the electrical characterization of ionic-liquid-gated bilayer and few-layer MoS2 field-effect transistors. The extrinsic mobility of our ionic-liquid-gated devices exceeds 70 cm2V-1S-1 at 250 K, which is 1-2 orders of magnitude higher than that measured in the Si back-gate configuration (without ionic liquid). These devices also show ambipolar behavior with a high ON-OFF current ratio of > 107 for electrons and > 106 for holes, and a near ideal subthreshold swing (SS) of ~ 50 mV/decade at 250 K for the electron channel. More significantly, we show that the mobility increases from ~ 100 cm2V-1S-1 at 180 K to ~ 220 cm2V-1S-1 at 77K as the temperature decreases following a μ ~ T-γ dependence with γ ~ 1, indicating that the intrinsic phonon-limited mobility can be achieved in few-layer MoS2 FETs. We attribute the enhanced device performance to the drastic reduction of the Schottky barrier width (thus higher tunneling efficiency) via highly efficient band bending at the MoS2/metal interface afforded by the extremely large electrical double layer capacitance of the ionic liquid. This work was supported by NSF (No. ECCS-1128297).

  4. Programmable Schottky Junctions Based on Ferroelectric Gated MoS2 Transistors

    NASA Astrophysics Data System (ADS)

    Xiao, Zhiyong; Song, Jingfeng; Drcharme, Stephen; Hong, Xia

    We report a programmable Schottky junction based on MoS2 field effect transistors with a SiO2 back gate and a ferroelectric copolymer poly(vinylidene-fluoride-trifluorethylene) (PVDF) top gate. We fabricated mechanically exfoliated single layer MoS2 flakes into two point devices via e-beam lithography, and deposited on the top of the devices ~20 nm PVDF thin films. The polarization of the PVDF layer is controlled locally by conducting atomic force microscopy. The devices exhibit linear ID-VD characteristics when the ferroelectric gate is uniformly polarized in one direction. We then polarized the gate into two domains with opposite polarization directions, and observed that the ID-VD characteristics of the MoS2 channel can be modulated between linear and rectified behaviors depending on the back gate voltage. The nonlinear ID-VD relation emerges when half of the channel is in the semiconductor phase while the other half is in the metallic phase, and it can be well described by the thermionic emission model with a Schottky barrier of ~0.5 eV. The Schottky junction can be erased by re-write the entire channel in the uniform polarization state. Our study facilitates the development of programmable, multifunctional nanoelectronics based on layered 2D TMDs..

  5. Enhancement of photodetection characteristics of MoS2 field effect transistors using surface treatment with copper phthalocyanine.

    PubMed

    Pak, Jinsu; Jang, Jingon; Cho, Kyungjune; Kim, Tae-Young; Kim, Jae-Keun; Song, Younggul; Hong, Woong-Ki; Min, Misook; Lee, Hyoyoung; Lee, Takhee

    2015-11-28

    Recently, two-dimensional materials such as molybdenum disulfide (MoS2) have been extensively studied as channel materials for field effect transistors (FETs) because MoS2 has outstanding electrical properties such as a low subthreshold swing value, a high on/off ratio, and good carrier mobility. In this study, we characterized the electrical and photo-responsive properties of MoS2 FET when stacking a p-type organic copper phthalocyanine (CuPc) layer on the MoS2 surface. We observed that the threshold voltage of MoS2 FET could be controlled by stacking the CuPc layers due to a charge transfer phenomenon at the interface. Particularly, we demonstrated that CuPc/MoS2 hybrid devices exhibited high performance as a photodetector compared with the pristine MoS2 FETs, caused by more electron-hole pairs separation at the p-n interface. Furthermore, we found the optimized CuPc thickness (∼2 nm) on the MoS2 surface for the best performance as a photodetector with a photoresponsivity of ∼1.98 A W(-1), a detectivity of ∼6.11 × 10(10) Jones, and an external quantum efficiency of ∼12.57%. Our study suggests that the MoS2 vertical hybrid structure with organic material can be promising as efficient photodetecting devices and optoelectronic circuits.

  6. Enhancement of photodetection characteristics of MoS2 field effect transistors using surface treatment with copper phthalocyanine.

    PubMed

    Pak, Jinsu; Jang, Jingon; Cho, Kyungjune; Kim, Tae-Young; Kim, Jae-Keun; Song, Younggul; Hong, Woong-Ki; Min, Misook; Lee, Hyoyoung; Lee, Takhee

    2015-11-28

    Recently, two-dimensional materials such as molybdenum disulfide (MoS2) have been extensively studied as channel materials for field effect transistors (FETs) because MoS2 has outstanding electrical properties such as a low subthreshold swing value, a high on/off ratio, and good carrier mobility. In this study, we characterized the electrical and photo-responsive properties of MoS2 FET when stacking a p-type organic copper phthalocyanine (CuPc) layer on the MoS2 surface. We observed that the threshold voltage of MoS2 FET could be controlled by stacking the CuPc layers due to a charge transfer phenomenon at the interface. Particularly, we demonstrated that CuPc/MoS2 hybrid devices exhibited high performance as a photodetector compared with the pristine MoS2 FETs, caused by more electron-hole pairs separation at the p-n interface. Furthermore, we found the optimized CuPc thickness (∼2 nm) on the MoS2 surface for the best performance as a photodetector with a photoresponsivity of ∼1.98 A W(-1), a detectivity of ∼6.11 × 10(10) Jones, and an external quantum efficiency of ∼12.57%. Our study suggests that the MoS2 vertical hybrid structure with organic material can be promising as efficient photodetecting devices and optoelectronic circuits. PMID:26505460

  7. Enhancement of carrier mobility in MoS2 field effect transistors by a SiO2 protective layer

    NASA Astrophysics Data System (ADS)

    Shao, Peng-Zhi; Zhao, Hai-Ming; Cao, Hui-Wen; Wang, Xue-Feng; Pang, Yu; Li, Yu-Xing; Deng, Ning-Qin; Zhang, Jing; Zhang, Guang-Yu; Yang, Yi; Zhang, Sheng; Ren, Tian-Ling

    2016-05-01

    Molybdenum disulfide is a promising channel material for field effect transistors (FETs). In this paper, monolayer MoS2 grown by chemical vapor deposition (CVD) was used to fabricate top-gate FETs through standard optical lithography. During the fabrication process, charged impurities and interface states are introduced, and the photoresist is not removed cleanly, which both limit the carrier mobility and the source-drain current. We apply a SiO2 protective layer, which is deposited on the surface of MoS2, in order to avoid the MoS2 directly contacting with the photoresist and the ambient environment. Therefore, the contact property between the MoS2 and the electrodes is improved, and the Coulomb scattering caused by the charged impurities and the interface states is reduced. Comparing MoS2 FETs with and without a SiO2 protective layer, the SiO2 protective layer is found to enhance the characteristics of the MoS2 FETs, including transfer and output characteristics. A high mobility of ˜42.3 cm2/V s is achieved, which is very large among the top-gate CVD-grown monolayer MoS2 FETs.

  8. New highly linear tunable transconductor circuits with low number of MOS transistors

    NASA Astrophysics Data System (ADS)

    Yucel, Firat; Yuce, Erkan

    2016-08-01

    In this article, two new highly linear tunable transconductor circuits are proposed. The transconductors employ only six MOS transistors operated in saturation region. The second transconductor is derived from the first one with a slight modification. Transconductance of both transconductors can be tuned by a control voltage. Both of the transconductors do not need any additional bias voltages and currents. Another important feature of the transconductors is their high input and output impedances for cascadability with other circuits. Besides, total harmonic distortions are less than 1.5% for both transconductors. A positive lossless grounded inductor simulator with a grounded capacitor is given as an application example of the transconductors. Simulation and experimental test results are included to show effectiveness of the proposed circuits.

  9. Low-frequency electronic noise in single-layer MoS2 transistors.

    PubMed

    Sangwan, Vinod K; Arnold, Heather N; Jariwala, Deep; Marks, Tobin J; Lauhon, Lincoln J; Hersam, Mark C

    2013-09-11

    Ubiquitous low-frequency 1/f noise can be a limiting factor in the performance and application of nanoscale devices. Here, we quantitatively investigate low-frequency electronic noise in single-layer transition metal dichalcogenide MoS2 field-effect transistors. The measured 1/f noise can be explained by an empirical formulation of mobility fluctuations with the Hooge parameter ranging between 0.005 and 2.0 in vacuum (<10(-5) Torr). The field-effect mobility decreased, and the noise amplitude increased by an order of magnitude in ambient conditions, revealing the significant influence of atmospheric adsorbates on charge transport. In addition, single Lorentzian generation-recombination noise was observed to increase by an order of magnitude as the devices were cooled from 300 to 6.5 K.

  10. Monolayer MoS2 Bandgap Modulation by Dielectric Environments and Tunable Bandgap Transistors

    PubMed Central

    Ryou, Junga; Kim, Yong-Sung; KC, Santosh; Cho, Kyeongjae

    2016-01-01

    Semiconductors with a moderate bandgap have enabled modern electronic device technology, and the current scaling trends down to nanometer scale have introduced two-dimensional (2D) semiconductors. The bandgap of a semiconductor has been an intrinsic property independent of the environments and determined fundamental semiconductor device characteristics. In contrast to bulk semiconductors, we demonstrate that an atomically thin two-dimensional semiconductor has a bandgap with strong dependence on dielectric environments. Specifically, monolayer MoS2 bandgap is shown to change from 2.8 eV to 1.9 eV by dielectric environment. Utilizing the bandgap modulation property, a tunable bandgap transistor, which can be in general made of a two-dimensional semiconductor, is proposed. PMID:27378032

  11. Random telegraph signals in small gate-area p-MOS transistors

    SciTech Connect

    Scofield, J.H.; Borland, N. ); Fleetwood, D.M. )

    1993-08-10

    We report the observation of random telegraph signals (RTS) in the channel resistances of nominally 1.25 [mu]m[times]1.25 [mu]m, enhancement-mode pMOS transistors fabricated using the AT T 1-[mu]m radiation hardened technology. Devices were operated in strong inversion in the linear regime. Measurements, performed for temperatures ranging from 77 to 300 K and various gate voltages, show that capture and emission times are both thermally activated and that the capture time depends strongly on the gate voltage. Results suggest that the unfilled trap is charged and that, after capturing a hole, the trap relaxes to a lower energy. Basic features of a model are discussed.

  12. Pure valley- and spin-entangled states in a MoS2-based bipolar transistor

    NASA Astrophysics Data System (ADS)

    Bai, Chunxu; Zou, Yonglian; Lou, Wen-Kai; Chang, Kai

    2014-11-01

    In this study, we show that the local Andreev reflection not only can be tuned largely by the type of the normal metal electrode, it also is related to the electrostatic potential in the superconductor region in a MoS2-based n (p ) -type metal/superconductor junction. In a MoS2-based n -type metal/n (p ) -type superconductor/p -type metal (n Sp ) transistor, nonlocal pure valley- and spin-entangled current can be tuned by the length and local gate voltage of a superconductor region. In particular, switching the quasiparticle type in both structures results in a series of intriguing features. Such an effect is not attainable in a graphene-based junction where the electron-hole symmetry enables the symmetry results to be observed. Besides, we have shown that the crossed Andreev reflection exhibits a maximum around ξ /2 instead of the exponential decay behavior in conventional superconductors and a maximum around ξ in the graphene material. The proposed straightforward experimental design and pure valley- and spin-entangled state can pave the way for a wider use in the entanglement based on material group-VI dichalcogenides.

  13. Back-gated Nb-doped MoS2 junctionless field-effect-transistors

    NASA Astrophysics Data System (ADS)

    Mirabelli, Gioele; Schmidt, Michael; Sheehan, Brendan; Cherkaoui, Karim; Monaghan, Scott; Povey, Ian; McCarthy, Melissa; Bell, Alan P.; Nagle, Roger; Crupi, Felice; Hurley, Paul K.; Duffy, Ray

    2016-02-01

    Electrical measurements were carried out to measure the performance and evaluate the characteristics of MoS2 flakes doped with Niobium (Nb). The flakes were obtained by mechanical exfoliation and transferred onto 85 nm thick SiO2 oxide and a highly doped Si handle wafer. Ti/Au (5/45 nm) deposited on top of the flake allowed the realization of a back-gate structure, which was analyzed structurally through Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). To best of our knowledge this is the first cross-sectional TEM study of exfoliated Nb-doped MoS2 flakes. In fact to date TEM of transition-metal-dichalcogenide flakes is extremely rare in the literature, considering the recent body of work. The devices were then electrically characterized by temperature dependent Ids versus Vds and Ids versus Vbg curves. The temperature dependency of the device shows a semiconductor behavior and, the doping effect by Nb atoms introduces acceptors in the structure, with a p-type concentration 4.3 × 1019 cm-3 measured by Hall effect. The p-type doping is confirmed by all the electrical measurements, making the structure a junctionless transistor. In addition, other parameters regarding the contact resistance between the top metal and MoS2 are extracted thanks to a simple Transfer Length Method (TLM) structure, showing a promising contact resistivity of 1.05 × 10-7 Ω/cm2 and a sheet resistance of 2.36 × 102 Ω/sq.

  14. Theoretical study on the top- and enclosed-contacted single-layer MoS2 piezotronic transistors

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Zhou, Yongli; Zhang, Aihua; Zhang, Yan; Wang, Zhong Lin

    2016-05-01

    Recently, the piezotronic effect has been observed in two-dimensional single-layer MoS2 materials, which have potential applications in force and pressure triggered or controlled electronic devices, sensors, and human-machine interfaces. However, classical theory faces the difficulty in explaining the mechanism of the piezotronic effect for the top- and enclosed-contacted MoS2 transistors, since the piezoelectric charges are assumed to exist only at the edge of the MoS2 flake that is far from the electronic transport pathway. In the present study, we identify the piezoelectric charges at the MoS2/metal-MoS2 interface by employing both the density functional theory and finite element method simulations. This interface is on the transport pathway of both top- and enclosed-contacted MoS2 transistors, thus it is capable of controlling their transport properties. This study deepens the understanding of piezotronic effect and provides guidance for the design of two-dimensional piezotronic devices.

  15. Enhancement of photodetection characteristics of MoS2 field effect transistors using surface treatment with copper phthalocyanine

    NASA Astrophysics Data System (ADS)

    Pak, Jinsu; Jang, Jingon; Cho, Kyungjune; Kim, Tae-Young; Kim, Jae-Keun; Song, Younggul; Hong, Woong-Ki; Min, Misook; Lee, Hyoyoung; Lee, Takhee

    2015-11-01

    Recently, two-dimensional materials such as molybdenum disulfide (MoS2) have been extensively studied as channel materials for field effect transistors (FETs) because MoS2 has outstanding electrical properties such as a low subthreshold swing value, a high on/off ratio, and good carrier mobility. In this study, we characterized the electrical and photo-responsive properties of MoS2 FET when stacking a p-type organic copper phthalocyanine (CuPc) layer on the MoS2 surface. We observed that the threshold voltage of MoS2 FET could be controlled by stacking the CuPc layers due to a charge transfer phenomenon at the interface. Particularly, we demonstrated that CuPc/MoS2 hybrid devices exhibited high performance as a photodetector compared with the pristine MoS2 FETs, caused by more electron-hole pairs separation at the p-n interface. Furthermore, we found the optimized CuPc thickness (~2 nm) on the MoS2 surface for the best performance as a photodetector with a photoresponsivity of ~1.98 A W-1, a detectivity of ~6.11 × 1010 Jones, and an external quantum efficiency of ~12.57%. Our study suggests that the MoS2 vertical hybrid structure with organic material can be promising as efficient photodetecting devices and optoelectronic circuits.Recently, two-dimensional materials such as molybdenum disulfide (MoS2) have been extensively studied as channel materials for field effect transistors (FETs) because MoS2 has outstanding electrical properties such as a low subthreshold swing value, a high on/off ratio, and good carrier mobility. In this study, we characterized the electrical and photo-responsive properties of MoS2 FET when stacking a p-type organic copper phthalocyanine (CuPc) layer on the MoS2 surface. We observed that the threshold voltage of MoS2 FET could be controlled by stacking the CuPc layers due to a charge transfer phenomenon at the interface. Particularly, we demonstrated that CuPc/MoS2 hybrid devices exhibited high performance as a photodetector compared

  16. Transport Properties of a MoS2/WSe2 Heterojunction Transistor and Its Potential for Application.

    PubMed

    Nourbakhsh, Amirhasan; Zubair, Ahmad; Dresselhaus, Mildred S; Palacios, Tomás

    2016-02-10

    This paper studies band-to-band tunneling in the transverse and lateral directions of van der Waals MoS2/WSe2 heterojunctions. We observe room-temperature negative differential resistance (NDR) in a heterojunction diode comprised of few-layer WSe2 stacked on multilayer MoS2. The presence of NDR is attributed to the lateral band-to-band tunneling at the edge of the MoS2/WSe2 heterojunction. The backward tunneling diode shows an average conductance slope of 75 mV/dec with a high curvature coefficient of 62 V(-1). Associated with the tunnel-diode characteristics, a positive-to-negative transconductance in the MoS2/WSe2 heterojunction transistors is observed. The transition is induced by strong interlayer coupling between the films, which results in charge density and energy-band modulation. The sign change in transconductance is particularly useful for multivalued logic (MVL) circuits, and we therefore propose and demonstrate for the first time an MVL-inverter that shows three levels of logic using one pair of p-type transistors.

  17. High-performance chemical sensing using Schottky-contacted chemical vapor deposition grown monolayer MoS2 transistors.

    PubMed

    Liu, Bilu; Chen, Liang; Liu, Gang; Abbas, Ahmad N; Fathi, Mohammad; Zhou, Chongwu

    2014-05-27

    Trace chemical detection is important for a wide range of practical applications. Recently emerged two-dimensional (2D) crystals offer unique advantages as potential sensing materials with high sensitivity, owing to their very high surface-to-bulk atom ratios and semiconducting properties. Here, we report the first use of Schottky-contacted chemical vapor deposition grown monolayer MoS2 as high-performance room temperature chemical sensors. The Schottky-contacted MoS2 transistors show current changes by 2-3 orders of magnitude upon exposure to very low concentrations of NO2 and NH3. Specifically, the MoS2 sensors show clear detection of NO2 and NH3 down to 20 ppb and 1 ppm, respectively. We attribute the observed high sensitivity to both well-known charger transfer mechanism and, more importantly, the Schottky barrier modulation upon analyte molecule adsorption, the latter of which is made possible by the Schottky contacts in the transistors and is not reported previously for MoS2 sensors. This study shows the potential of 2D semiconductors as high-performance sensors and also benefits the fundamental studies of interfacial phenomena and interactions between chemical species and monolayer 2D semiconductors.

  18. Ab initio simulation of single- and few-layer MoS2 transistors: Effect of electron-phonon scattering

    NASA Astrophysics Data System (ADS)

    Szabó, Áron; Rhyner, Reto; Luisier, Mathieu

    2015-07-01

    In this paper, we present full-band atomistic quantum transport simulations of single- and few-layer MoS2 field-effect transistors (FETs) including electron-phonon scattering. The Hamiltonian and the electron-phonon coupling constants are determined from ab initio density-functional-theory calculations. It is observed that the phonon-limited electron mobility is enhanced with increasing layer thicknesses and decreases at high charge concentrations. The electrostatic control is found to be crucial even for a single-layer MoS2 device. With a single-gate configuration, the double-layer MoS2 FET shows the best intrinsic performance with an ON current, ION=685 μ A /μ m , but with a double-gate contact the transistor with a triple-layer channel delivers the highest current with ION=1850 μ A /μ m . The charge in the channel is almost independent of the number of MoS2 layers, but the injection velocity increases significantly with the channel thickness in the double-gate devices due to the reduced electron-phonon scattering rates in multilayer structures. We demonstrate further that the ballistic limit of transport is not suitable for the simulation of MX 2 FETs because of the artificial negative differential resistance it predicts.

  19. Enhanced carrier mobility of multilayer MoS2 thin-film transistors by Al2O3 encapsulation

    NASA Astrophysics Data System (ADS)

    Kim, Seong Yeoul; Park, Seonyoung; Choi, Woong

    2016-10-01

    We report the effect of Al2O3 encapsulation on the carrier mobility and contact resistance of multilayer MoS2 thin-film transistors by statistically investigating 70 devices with SiO2 bottom-gate dielectric. After Al2O3 encapsulation by atomic layer deposition, calculation based on Y-function method indicates that the enhancement of carrier mobility from 24.3 cm2 V-1 s-1 to 41.2 cm2 V-1 s-1 occurs independently from the reduction of contact resistance from 276 kΩ.μm to 118 kΩ.μm. Furthermore, contrary to the previous literature, we observe a negligible effect of thermal annealing on contact resistance and carrier mobility during the atomic layer deposition of Al2O3. These results demonstrate that Al2O3 encapsulation is a useful method of improving the carrier mobility of multilayer MoS2 transistors, providing important implications on the application of MoS2 and other two-dimensional materials into high-performance transistors.

  20. Non-Faradaic Electrochemical Detection of Exocytosis from Mast and Chromaffin Cells Using Floating-Gate MOS Transistors.

    PubMed

    Jayant, Krishna; Singhai, Amit; Cao, Yingqiu; Phelps, Joshua B; Lindau, Manfred; Holowka, David A; Baird, Barbara A; Kan, Edwin C

    2015-01-01

    We present non-faradaic electrochemical recordings of exocytosis from populations of mast and chromaffin cells using chemoreceptive neuron MOS (CνMOS) transistors. In comparison to previous cell-FET-biosensors, the CνMOS features control (CG), sensing (SG) and floating gates (FG), allows the quiescent point to be independently controlled, is CMOS compatible and physically isolates the transistor channel from the electrolyte for stable long-term recordings. We measured exocytosis from RBL-2H3 mast cells sensitized by IgE (bound to high-affinity surface receptors FcεRI) and stimulated using the antigen DNP-BSA. Quasi-static I-V measurements reflected a slow shift in surface potential () which was dependent on extracellular calcium ([Ca]o) and buffer strength, which suggests sensitivity to protons released during exocytosis. Fluorescent imaging of dextran-labeled vesicle release showed evidence of a similar time course, while un-sensitized cells showed no response to stimulation. Transient recordings revealed fluctuations with a rapid rise and slow decay. Chromaffin cells stimulated with high KCl showed both slow shifts and extracellular action potentials exhibiting biphasic and inverted capacitive waveforms, indicative of varying ion-channel distributions across the cell-transistor junction. Our approach presents a facile method to simultaneously monitor exocytosis and ion channel activity with high temporal sensitivity without the need for redox chemistry. PMID:26686301

  1. Non-Faradaic Electrochemical Detection of Exocytosis from Mast and Chromaffin Cells Using Floating-Gate MOS Transistors

    PubMed Central

    Jayant, Krishna; Singhai, Amit; Cao, Yingqiu; Phelps, Joshua B.; Lindau, Manfred; Holowka, David A.; Baird, Barbara A.; Kan, Edwin C.

    2015-01-01

    We present non-faradaic electrochemical recordings of exocytosis from populations of mast and chromaffin cells using chemoreceptive neuron MOS (CνMOS) transistors. In comparison to previous cell-FET-biosensors, the CνMOS features control (CG), sensing (SG) and floating gates (FG), allows the quiescent point to be independently controlled, is CMOS compatible and physically isolates the transistor channel from the electrolyte for stable long-term recordings. We measured exocytosis from RBL-2H3 mast cells sensitized by IgE (bound to high-affinity surface receptors FcεRI) and stimulated using the antigen DNP-BSA. Quasi-static I-V measurements reflected a slow shift in surface potential () which was dependent on extracellular calcium ([Ca]o) and buffer strength, which suggests sensitivity to protons released during exocytosis. Fluorescent imaging of dextran-labeled vesicle release showed evidence of a similar time course, while un-sensitized cells showed no response to stimulation. Transient recordings revealed fluctuations with a rapid rise and slow decay. Chromaffin cells stimulated with high KCl showed both slow shifts and extracellular action potentials exhibiting biphasic and inverted capacitive waveforms, indicative of varying ion-channel distributions across the cell-transistor junction. Our approach presents a facile method to simultaneously monitor exocytosis and ion channel activity with high temporal sensitivity without the need for redox chemistry. PMID:26686301

  2. Self-screened high performance multi-layer MoS2 transistor formed by using a bottom graphene electrode

    NASA Astrophysics Data System (ADS)

    Qu, Deshun; Liu, Xiaochi; Ahmed, Faisal; Lee, Daeyeong; Yoo, Won Jong

    2015-11-01

    We investigated the carrier transport in multi-layer MoS2 with consideration of the contact resistance (Rc) and interlayer resistance (Rint). A bottom graphene contact was suggested to overcome the degradation of Id modulation in a back gated multi-layer MoS2 field effect transistor (FET) due to the accumulated Rint and increased Rc with increasing thickness. As a result, non-degraded drain current (Id) modulation with increasing flake thickness was achieved due to the non-cumulative Rint. Benefiting from the low Rc induced by the negligible Schottky barrier at the graphene/MoS2 interface, the intrinsic carrier transport properties immune to Rc were investigated in the multi-layer MoS2 FET. ~2 times the enhanced carrier mobility was attained from the self-screened channel in the bottom graphene contacted device, compared to those with top metal contacts.We investigated the carrier transport in multi-layer MoS2 with consideration of the contact resistance (Rc) and interlayer resistance (Rint). A bottom graphene contact was suggested to overcome the degradation of Id modulation in a back gated multi-layer MoS2 field effect transistor (FET) due to the accumulated Rint and increased Rc with increasing thickness. As a result, non-degraded drain current (Id) modulation with increasing flake thickness was achieved due to the non-cumulative Rint. Benefiting from the low Rc induced by the negligible Schottky barrier at the graphene/MoS2 interface, the intrinsic carrier transport properties immune to Rc were investigated in the multi-layer MoS2 FET. ~2 times the enhanced carrier mobility was attained from the self-screened channel in the bottom graphene contacted device, compared to those with top metal contacts. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06076a

  3. Optically transparent thin-film transistors based on 2D multilayer MoS2 and indium zinc oxide electrodes

    NASA Astrophysics Data System (ADS)

    Kwon, Junyeon; Hong, Young Ki; Kwon, Hyuk-Jun; Park, Yu Jin; Yoo, Byungwook; Kim, Jiwan; Grigoropoulos, Costas P.; Oh, Min Suk; Kim, Sunkook

    2015-01-01

    We report on optically transparent thin film transistors (TFTs) fabricated using multilayered molybdenum disulfide (MoS2) as the active channel, indium tin oxide (ITO) for the back-gated electrode and indium zinc oxide (IZO) for the source/drain electrodes, respectively, which showed more than 81% transmittance in the visible wavelength. In spite of a relatively large Schottky barrier between MoS2 and IZO, the n-type behavior with a field-effect mobility (μeff) of 1.4 cm2 V-1 s-1 was observed in as-fabricated transparent MoS2 TFT. In order to enhance the performances of transparent MoS2 TFTs, a picosecond pulsed laser was selectively irradiated onto the contact region of the IZO electrodes. Following laser annealing, μeff increased to 4.5 cm2 V-1 s-1, and the on-off current ratio (Ion/Ioff) increased to 104, which were attributed to the reduction of the contact resistance between MoS2 and IZO.

  4. Thermally activated trap charges responsible for hysteresis in multilayer MoS2 field-effect transistors

    NASA Astrophysics Data System (ADS)

    Park, Youngseo; Baac, Hyoung Won; Heo, Junseok; Yoo, Geonwook

    2016-02-01

    Hysteresis, which is induced by both extrinsic and intrinsic causes, is often observed in molybdenum disulphide (MoS2) field-effect transistors (FETs), and several extrinsic hysteresis effects have been reported in unpassivated bottom-gate MoS2 device structures. In this study, interface-trap-induced hysteresis and other electrical properties are examined. We experimentally investigate thermally activated trap charges near a silicon-dioxide (SiO2)-MoS2 interface that gives rise to hysteresis in a multilayer MoS2 FET in a temperature region of 10-300 K. The threshold voltage (VTH) and field-effect mobility (μFE) decrease with the increase in temperature, regardless of the gate-bias sweep direction. The hysteresis that coincides with the trend of subthreshold swing increases sharply above T = 150 K as the released charges from interface traps become dominant over the fixed charges. Based on a temperature-dependent hysteresis analysis, we discussed the activation energy of interface traps and maximum interface trap density of the fabricated multilayer MoS2 FET.

  5. TCAD simulation of the co-implantation species C, F, and N in MOS transistors

    NASA Astrophysics Data System (ADS)

    Bazizi, E. M.; Mok, K. R. C.; Benistant, F.; Yeong, S. H.; Teo, R. S.; Zechner, C.

    2012-11-01

    The optimization of advanced CMOS nodes below 65nm requires stringent control of both the lateral and vertical diffusion of the source/drain. One way to control this diffusion is to use co-implant species such as Carbon, Fluorine, and Nitrogen with the standard dopants (Boron, Phosphorus, and Arsenic). The role played by the co-implant species is to reduce dopant transient enhanced diffusion (TED), which is caused by the large number of interstitials generated during ion implantation. Although the mechanisms responsible for controlling TED are well understood, the modeling of such mechanisms in a continuum TCAD simulator remains a challenge. We shall first review the current physical understanding behind TED reduction by the co-implant species. Subsequently, we shall show how this can be implemented in a continuum simulator. Afterward, we will present a set of models capable not only of reproducing experimental data based on SIMS measurements, but can also be used in the simulation of 2D and 3D MOS transistors. The models are based on the trapping of interstitials by the co-implant species and their complexes. The evolution of these complexes will affect the diffusion and activation of the doping species and the shape of the final source/drain junction profiles.

  6. Assessment of performance potential of MoS2-based topological insulator field-effect transistors

    NASA Astrophysics Data System (ADS)

    Liu, Leitao; Guo, Jing

    2015-09-01

    It was suggested that single-layer MoS2 at the 1T' phase is a topological insulator whose electronic structure can be modulated by a vertical electric field for field-effect transistor (FET) applications [X. Qian, J. Liu, L. Fu, and J. Li, Science 346, 1344 (2014)]. In this work, performance potential of FETs based on vertical field modulation of the topological edge states is assessed by using quantum transport device simulations. To perform efficient device simulations, a phenomenological Hamiltonian is first proposed and validated to capture the effects of electric fields. Because the ON-state conductance is determined by transport through gapless edge states with a long scattering mean free path and the OFF-state conductance by transport through the gapped bulk states, the ON/OFF ratio is sensitive to the channel length, which is different from conventional FETs. Although a high vertical electric field is required to modulate the topological edge state, a reasonably small subthreshold swing of 131 mV/dec can still be achieved for a practical value of the gate insulator thickness.

  7. Characterization of interface traps on MOS transistor submicronic by the three level charge pumping

    NASA Astrophysics Data System (ADS)

    Sellami, M.; Bouchemat, M.; Kahouadji, M.; Djahli, F.

    2005-05-01

    Because of its efficiency, its high precision and its easy use regarding to classical techniques of Si-Sio2 (C-V, DLTS, Conductanceldots), interface characterization, the charge pumping technique has seen a large evolution these years. Many improvements have been made other, derivation techniques have been developed (at three-level charge pumping, spectroscopic charge pumping ldots) This technique is particularly used for very slight geometry MOS transistors damaging, where other techniques have no utility. This damaging often leads to the creation of a fixed trapped charge in the oxide coat and active electronically defaults in the oxide Semi-conductor interface after the application of ageing constraint (ionizing radiation, injection carrier). This ageing is so pronounced when the dimensions are slight this represents the main obstacle that the microelectronics must face. In this article we simulate the three-level charge pumping technique with SPICE3F4 simulator. This simulation will permit the obtaining of spatial and energetic spread of defaults at the interface.

  8. Separation of interlayer resistance in multilayer MoS2 field-effect transistors

    NASA Astrophysics Data System (ADS)

    Na, Junhong; Shin, Minju; Joo, Min-Kyu; Huh, Junghwan; Jeong Kim, Yun; Jong Choi, Hyung; Hyung Shim, Joon; Kim, Gyu-Tae

    2014-06-01

    We extracted the interlayer resistance between two layers in multilayer molybdenum disulfide (MoS2) field-effect transistors by confirming that contact resistances (Rcontact) measured using the four-probe measurements were similar, within ˜30%, to source/drain series resistances (Rsd) measured using the two-probe measurements. Rcontact values obtained from gated four-probe measurements exhibited gate voltage dependency. In the two-probe measurements, the Y-function method was applied to obtain the Rsd values. By comparing those two Rcontact (˜9.5 kΩ) and Rsd (˜12.3 kΩ) values in strong accumulation regime, we found the rationality that those two values had nearly the same properties, i.e., the Schottky barrier resistances and interlayer resistances. The Rsd values of devices with two-probe source/drain electrodes exhibited thickness dependency due to interlayer resistance changes. The interlayer resistance between two layers was also obtained as ˜2.0 Ω mm.

  9. Caractérisation des dégradations de transistors MOS de puissance sous irradiations

    NASA Astrophysics Data System (ADS)

    Bendada, E.; Raïs, K.; Mialhe, P.

    1997-11-01

    The aim of this work is the characterization of D-MOS (HEXFET) structure before and after irradiations. An innovative method for device characterisation is experimented to quantify radiation effects. This study is based on the determination of importants parameters: series resitance, ideality factor, reverse recombination and reverse diffusion currents of the substrate-drain junction by the analysis of its current voltage characteristics. The form of I V characteristics of the substrate-drain junction with operating conditions is found dependent of defects induced by irradiations. It is shown that values of the series resistance, the ideality factor and the reverse recombination current increases with the gate voltage and with the dose absorbed. The reverse diffusion current is shown to be not albered by radiation exposures. Une nouvelle méthode de caractérisation de la dégradation sous irradiations des transistors à structure D-MOS de type HEXFET est proposée. Elle est basée sur l'analyse des propriétés de la diode substrat-drain en utilisant les méthodes bien établies de modélisation des jonctions p-n. La description des caractéristiques courant-tension à l'aide des modèles permettant de séparer les processus de diffusion et de recombinaison des porteurs, conduit à déterminer d'une manière simple des paramètres importants: résistance série, facteur de qualité, courant inverse de recombinaison et courant inverse de diffusion. La forme des caractéristiques courant-tension de la jonction avec les conditions de fonctionnement est trouvée dépendante des défauts induits par les irradiations. Il est montré que les valeurs de la résistance série, du facteur de qualité et du courant inverse de recombinaison augmentent avec la tension de grille et avec la dose absorbée. Le courant inverse de diffusion est non altéré par l'exposition aux radiations.

  10. Low voltage and high ON/OFF ratio field-effect transistors based on CVD MoS2 and ultra high-k gate dielectric PZT

    NASA Astrophysics Data System (ADS)

    Zhou, Changjian; Wang, Xinsheng; Raju, Salahuddin; Lin, Ziyuan; Villaroman, Daniel; Huang, Baoling; Chan, Helen Lai-Wa; Chan, Mansun; Chai, Yang

    2015-05-01

    MoS2 and other atomic-level thick layered materials have been shown to have a high potential for outperforming Si transistors at the scaling limit. In this work, we demonstrate a MoS2 transistor with a low voltage and high ON/OFF ratio. A record small equivalent oxide thickness of ~1.1 nm has been obtained by using ultra high-k gate dielectric Pb(Zr0.52Ti0.48)O3. The low threshold voltage (<0.5 V) is comparable to that of the liquid/gel gated MoS2 transistor. The small sub-threshold swing of 85.9 mV dec-1, the high ON/OFF ratio of ~108 and the negligible hysteresis ensure a high performance of the MoS2 transistor operating at 1 V. The extracted field-effect mobility of 1-10 cm2 V-1 s-1 suggests a high crystalline quality of the CVD-grown MoS2 flakes. The combination of the two-dimensional layered semiconductor and the ultra high-k dielectric may enable the development of low-power electronic applications.MoS2 and other atomic-level thick layered materials have been shown to have a high potential for outperforming Si transistors at the scaling limit. In this work, we demonstrate a MoS2 transistor with a low voltage and high ON/OFF ratio. A record small equivalent oxide thickness of ~1.1 nm has been obtained by using ultra high-k gate dielectric Pb(Zr0.52Ti0.48)O3. The low threshold voltage (<0.5 V) is comparable to that of the liquid/gel gated MoS2 transistor. The small sub-threshold swing of 85.9 mV dec-1, the high ON/OFF ratio of ~108 and the negligible hysteresis ensure a high performance of the MoS2 transistor operating at 1 V. The extracted field-effect mobility of 1-10 cm2 V-1 s-1 suggests a high crystalline quality of the CVD-grown MoS2 flakes. The combination of the two-dimensional layered semiconductor and the ultra high-k dielectric may enable the development of low-power electronic applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01072a

  11. Improving Breakdown Behavior by Substrate Bias in a Novel Double Epi-layer Lateral Double Diffused MOS Transistor

    NASA Astrophysics Data System (ADS)

    Li, Qi; Wang, Wei-Dong; Liu, Yun; Wei, Xue-Ming

    2012-02-01

    A new lateral double diffused MOS (LDMOS) transistor with a double epitaxial layer formed by an n-type substrate and a p-type epitaxial layer is reported (DEL LDMOS). The mechanism of the improved breakdown characteristic is that the high electric field around the drain is reduced by substrate reverse bias, which causes the redistribution of the bulk electric field in the drift region, and the vertical blocking voltage is shared by the drain side and the source side. The numerical results indicate that the trade-off between breakdown voltage and on-resistance of the proposed device is improved greatly in comparison to that of the conventional LDMOS.

  12. Transport properties of unrestricted carriers in bridge-channel MoS2 field-effect transistors

    NASA Astrophysics Data System (ADS)

    Qiu, Dongri; Lee, Dong Uk; Park, Chang Soo; Lee, Kyoung Su; Kim, Eun Kyu

    2015-10-01

    Unsuppressed carrier scattering from the underlying substrate in a layered two-dimensional material system is extensively observed, which degrades significantly the performance of devices. Beyond the material itself, understanding the intrinsic interfacial and surficial properties is an important issue for the analysis of a high-κ/MoS2 heterostructure. Here, we report on the electronic transport properties of bridge-channel MoS2 field-effect transistors fabricated by a contamination-free transfer method. After neglecting all the surrounding perturbations, it is possible to reveal the significant improvement of room-temperature mobility and subthreshold slope. A systematic study on variable-temperature transport measurements has quantified the trap density of states both in free-standing and SiO2-supported MoS2 systems. Compared to the bridge-channel MoS2 devices with an ideal interface, the unsuspended devices have a large amount of band tail states, and then the impact of their electronic states on the device performance is also discussed.Unsuppressed carrier scattering from the underlying substrate in a layered two-dimensional material system is extensively observed, which degrades significantly the performance of devices. Beyond the material itself, understanding the intrinsic interfacial and surficial properties is an important issue for the analysis of a high-κ/MoS2 heterostructure. Here, we report on the electronic transport properties of bridge-channel MoS2 field-effect transistors fabricated by a contamination-free transfer method. After neglecting all the surrounding perturbations, it is possible to reveal the significant improvement of room-temperature mobility and subthreshold slope. A systematic study on variable-temperature transport measurements has quantified the trap density of states both in free-standing and SiO2-supported MoS2 systems. Compared to the bridge-channel MoS2 devices with an ideal interface, the unsuspended devices have a large

  13. The role of charge trapping in MoS2/SiO2 and MoS2/hBN field-effect transistors

    NASA Astrophysics Data System (ADS)

    Illarionov, Yury Yu; Rzepa, Gerhard; Waltl, Michael; Knobloch, Theresia; Grill, Alexander; Furchi, Marco M.; Mueller, Thomas; Grasser, Tibor

    2016-09-01

    The commonly observed hysteresis in the transfer characteristics of MoS2 transistors is typically associated with charge traps in the gate insulator. Since in Si technologies such traps can lead to severe reliability issues, we perform a combined study of both the hysteresis as well as the arguably most important reliability issue, the bias-temperature instability. We use single-layer MoS2 FETs with SiO2 and hBN insulators and demonstrate that both phenomena are indeed due to traps in the gate insulator with time constants distributed over wide timescales, where the faster ones lead to hysteresis and the slower ones to bias-temperature instabilities. Our data show that the use of hBN as a gate insulator considerably reduces the number of accessible slow traps and thus improves the reliability. However, the reliability of hBN insulators deteriorates with increasing temperature due to the thermally activated nature of charge trapping.

  14. Enhancing Photoresponsivity of Self-Aligned MoS2 Field-Effect Transistors by Piezo-Phototronic Effect from GaN Nanowires.

    PubMed

    Liu, Xingqiang; Yang, Xiaonian; Gao, Guoyun; Yang, Zhenyu; Liu, Haitao; Li, Qiang; Lou, Zheng; Shen, Guozhen; Liao, Lei; Pan, Caofeng; Lin Wang, Zhong

    2016-08-23

    We report high-performance self-aligned MoS2 field-effect transistors (FETs) with enhanced photoresponsivity by the piezo-phototronic effect. The FETs are fabricated based on monolayer MoS2 with a piezoelectric GaN nanowire (NW) as the local gate, and a self-aligned process is employed to define the source/drain electrodes. The fabrication method allows the preservation of the intrinsic property of MoS2 and suppresses the scattering center density in the MoS2/GaN interface, which results in high electrical and photoelectric performances. MoS2 FETs with channel lengths of ∼200 nm have been fabricated with a small subthreshold slope of 64 mV/dec. The photoresponsivity is 443.3 A·W(-1), with a fast response and recovery time of ∼5 ms under 550 nm light illumination. When strain is introduced into the GaN NW, the photoresponsivity is further enhanced to 734.5 A·W(-1) and maintains consistent response and recovery time, which is comparable with that of the mechanical exfoliation of MoS2 transistors. The approach presented here opens an avenue to high-performance top-gated piezo-enhanced MoS2 photodetectors.

  15. Enhancing Photoresponsivity of Self-Aligned MoS2 Field-Effect Transistors by Piezo-Phototronic Effect from GaN Nanowires.

    PubMed

    Liu, Xingqiang; Yang, Xiaonian; Gao, Guoyun; Yang, Zhenyu; Liu, Haitao; Li, Qiang; Lou, Zheng; Shen, Guozhen; Liao, Lei; Pan, Caofeng; Lin Wang, Zhong

    2016-08-23

    We report high-performance self-aligned MoS2 field-effect transistors (FETs) with enhanced photoresponsivity by the piezo-phototronic effect. The FETs are fabricated based on monolayer MoS2 with a piezoelectric GaN nanowire (NW) as the local gate, and a self-aligned process is employed to define the source/drain electrodes. The fabrication method allows the preservation of the intrinsic property of MoS2 and suppresses the scattering center density in the MoS2/GaN interface, which results in high electrical and photoelectric performances. MoS2 FETs with channel lengths of ∼200 nm have been fabricated with a small subthreshold slope of 64 mV/dec. The photoresponsivity is 443.3 A·W(-1), with a fast response and recovery time of ∼5 ms under 550 nm light illumination. When strain is introduced into the GaN NW, the photoresponsivity is further enhanced to 734.5 A·W(-1) and maintains consistent response and recovery time, which is comparable with that of the mechanical exfoliation of MoS2 transistors. The approach presented here opens an avenue to high-performance top-gated piezo-enhanced MoS2 photodetectors. PMID:27447946

  16. Extrinsic Origin of Persistent Photoconductivity in Monolayer MoS2 Field Effect Transistors

    PubMed Central

    Wu, Yueh-Chun; Liu, Cheng-Hua; Chen, Shao-Yu; Shih, Fu-Yu; Ho, Po-Hsun; Chen, Chun-Wei; Liang, Chi-Te; Wang, Wei-Hua

    2015-01-01

    Recent discoveries of the photoresponse of molybdenum disulfide (MoS2) have shown the considerable potential of these two-dimensional transition metal dichalcogenides for optoelectronic applications. Among the various types of photoresponses of MoS2, persistent photoconductivity (PPC) at different levels has been reported. However, a detailed study of the PPC effect and its mechanism in MoS2 is still not available, despite the importance of this effect on the photoresponse of the material. Here, we present a systematic study of the PPC effect in monolayer MoS2 and conclude that the effect can be attributed to random localized potential fluctuations in the devices. Notably, the potential fluctuations originate from extrinsic sources based on the substrate effect of the PPC. Moreover, we point out a correlation between the PPC effect in MoS2 and the percolation transport behavior of MoS2. We demonstrate a unique and efficient means of controlling the PPC effect in monolayer MoS2, which may offer novel functionalities for MoS2-based optoelectronic applications in the future. PMID:26112341

  17. Extrinsic Origin of Persistent Photoconductivity in Monolayer MoS2 Field Effect Transistors.

    PubMed

    Wu, Yueh-Chun; Liu, Cheng-Hua; Chen, Shao-Yu; Shih, Fu-Yu; Ho, Po-Hsun; Chen, Chun-Wei; Liang, Chi-Te; Wang, Wei-Hua

    2015-06-26

    Recent discoveries of the photoresponse of molybdenum disulfide (MoS2) have shown the considerable potential of these two-dimensional transition metal dichalcogenides for optoelectronic applications. Among the various types of photoresponses of MoS2, persistent photoconductivity (PPC) at different levels has been reported. However, a detailed study of the PPC effect and its mechanism in MoS2 is still not available, despite the importance of this effect on the photoresponse of the material. Here, we present a systematic study of the PPC effect in monolayer MoS2 and conclude that the effect can be attributed to random localized potential fluctuations in the devices. Notably, the potential fluctuations originate from extrinsic sources based on the substrate effect of the PPC. Moreover, we point out a correlation between the PPC effect in MoS2 and the percolation transport behavior of MoS2. We demonstrate a unique and efficient means of controlling the PPC effect in monolayer MoS2, which may offer novel functionalities for MoS2-based optoelectronic applications in the future.

  18. Charge trapping at the MoS2-SiO2 interface and its effects on the characteristics of MoS2 metal-oxide-semiconductor field effect transistors

    NASA Astrophysics Data System (ADS)

    Guo, Yao; Wei, Xianlong; Shu, Jiapei; Liu, Bo; Yin, Jianbo; Guan, Changrong; Han, Yuxiang; Gao, Song; Chen, Qing

    2015-03-01

    The field effect transistors (FETs) based on thin layer MoS2 often have large hysteresis and unstable threshold voltage in their transfer curves, mainly due to the charge trapping at the oxide-semiconductor interface. In this paper, the charge trapping and de-trapping processes at the SiO2-MoS2 interface are studied. The trapping charge density and time constant at different temperatures are extracted. Making use of the trapped charges, the threshold voltage of the MoS2 based metal-oxide-semiconductor FETs is adjusted from 4 V to -45 V. Furthermore, the impact of the trapped charges on the carrier transport is evaluated. The trapped charges are suggested to give rise to the unscreened Coulomb scattering and/or the variable range hopping in the carrier transport of the MoS2 sheet.

  19. High-performance, highly bendable MoS2 transistors with high-k dielectrics for flexible low-power systems.

    PubMed

    Chang, Hsiao-Yu; Yang, Shixuan; Lee, Jongho; Tao, Li; Hwang, Wan-Sik; Jena, Debdeep; Lu, Nanshu; Akinwande, Deji

    2013-06-25

    While there has been increasing studies of MoS2 and other two-dimensional (2D) semiconducting dichalcogenides on hard conventional substrates, experimental or analytical studies on flexible substrates has been very limited so far, even though these 2D crystals are understood to have greater prospects for flexible smart systems. In this article, we report detailed studies of MoS2 transistors on industrial plastic sheets. Transistor characteristics afford more than 100x improvement in the ON/OFF current ratio and 4x enhancement in mobility compared to previous flexible MoS2 devices. Mechanical studies reveal robust electronic properties down to a bending radius of 1 mm which is comparable to previous reports for flexible graphene transistors. Experimental investigation identifies that crack formation in the dielectric is the responsible failure mechanism demonstrating that the mechanical properties of the dielectric layer is critical for realizing flexible electronics that can accommodate high strain. Our uniaxial tensile tests have revealed that atomic-layer-deposited HfO2 and Al2O3 films have very similar crack onset strain. However, crack propagation is slower in HfO2 dielectric compared to Al2O3 dielectric, suggesting a subcritical fracture mechanism in the thin oxide films. Rigorous mechanics modeling provides guidance for achieving flexible MoS2 transistors that are reliable at sub-mm bending radius.

  20. Nanoimprint-Assisted Shear Exfoliation (NASE) for Producing Multilayer MoS2 Structures as Field-Effect Transistor Channel Arrays.

    PubMed

    Chen, Mikai; Nam, Hongsuk; Rokni, Hossein; Wi, Sungjin; Yoon, Jeong Seop; Chen, Pengyu; Kurabayashi, Katsuo; Lu, Wei; Liang, Xiaogan

    2015-09-22

    MoS2 and other semiconducting transition metal dichalcogenides (TMDCs) are of great interest due to their excellent physical properties and versatile chemistry. Although many recent research efforts have been directed to explore attractive properties associated with MoS2 monolayers, multilayer/few-layer MoS2 structures are indeed demanded by many practical scale-up device applications, because multilayer structures can provide sizable electronic/photonic state densities for driving upscalable electrical/optical signals. Currently there is a lack of processes capable of producing ordered, pristine multilayer structures of MoS2 (or other relevant TMDCs) with manufacturing-grade uniformity of thicknesses and electronic/photonic properties. In this article, we present a nanoimprint-based approach toward addressing this challenge. In this approach, termed as nanoimprint-assisted shear exfoliation (NASE), a prepatterned bulk MoS2 stamp is pressed into a polymeric fixing layer, and the imprinted MoS2 features are exfoliated along a shear direction. This shear exfoliation can significantly enhance the exfoliation efficiency and thickness uniformity of exfoliated flakes in comparison with previously reported exfoliation processes. Furthermore, we have preliminarily demonstrated the fabrication of multiple transistors and biosensors exhibiting excellent device-to-device performance consistency. Finally, we present a molecular dynamics modeling analysis of the scaling behavior of NASE. This work holds significant potential to leverage the superior properties of MoS2 and other emerging TMDCs for practical scale-up device applications.

  1. Electrical characteristics and optimization of extended-drain MOS transistor with dual-workfunction-gate for mixed-signal applications

    NASA Astrophysics Data System (ADS)

    Baek, Ki-Ju; Na, Kee-Yeol; Kim, Yeong-Seuk

    2014-10-01

    This paper presents the electrical characteristics of high-voltage (HV) extended-drain MOS (EDMOS) field-effect transistor with dual-workfunction-gate (DWFG) to enhance the device performance and device optimization for mixed-signal applications. For n-channel DWFG EDMOS device fabrication, the polycrystalline-silicon (poly-Si) gate on the source and drain side were doped by p+ and n+ ion implantation, respectively. The DWFG device with shorter p+ poly-Si gate length showed lower on-resistance (RON) characteristics compared to the conventional device. Therefore, the DWFG device with shorter p+ poly-Si gate length is suitable for switching applications. On the other hand, the best improvements in the drain conductance (gds) and intrinsic voltage gain (AV), which is important parameters of analog circuits, were shown in the DWFG device with identical n+ and p+ poly-Si gate length.

  2. Electromechanical coupling and design considerations in single-layer MoS2 suspended-channel transistors and resonators

    NASA Astrophysics Data System (ADS)

    Yang, Rui; Islam, Arnob; Feng, Philip X.-L.

    2015-11-01

    We report on the analysis of electromechanical coupling effects in suspended doubly-clamped single-layer MoS2 structures, and the designs of suspended-channel field-effect transistors (FETs) and vibrating-channel nanoelectromechanical resonators. In DC gating scenario, signal transduction processes including electrostatic actuation, deflection, straining on bandgap, mobility, carrier density and their intricate cross-interactions, have been analyzed considering strain-enhanced mobility (by up to 4 times), to determine the transfer characteristics. In AC gating scenario and resonant operations (using 100 MHz and 1 GHz devices as relevant targets), we demonstrate that the vibrating-channel MoS2 devices can offer enhanced signals (than the zero-bandgap graphene counterparts), thanks to the resonant straining effects on electron transport of the semiconducting channel. We also show dependence of signal intensity and signal-to-background ratio (SBR) on device geometries and scaling effects, with SBR enhancement by a factor of ~8 for resonance signal, which provide guidelines toward designing future devices with desirable parameters.

  3. A Commercial off-the-shelf pMOS Transistor as X-ray and Heavy Ion Detector

    NASA Astrophysics Data System (ADS)

    Silveira, M. A. G.; Melo, M. A. A.; Aguiar, V. A. P.; Rallo, A.; Santos, R. B. B.; Medina, N. H.; Added, N.; Seixas, L. E., Jr.; Leite, F. G.; Cunha, F. G.; Cirne, K. H.; Giacomini, R.; de Oliveira, J. A.

    2015-07-01

    Recently, p-channel metal-oxide-semiconductor (pMOS) transistors were suggested as fit for the task of detecting and quantifying ionizing radiation dose. Linearity, small detection volume, fast readout, portability, low power consumption and low radiation attenuation are some of the pMOS advantages over PIN diode and thermoluminiscent dosimeters. A hand-held measurement system using a low power commercial off-the-shelf pMOSas the sensor would have a clear advantage due to the lower cost incurred by a standard technological process. In this research work, we tested the commercial device 3N163 regarding its behaviouras an X-ray sensor, as well as its possible application as a heavy-ion detector. To study the radiation effects of X-rays, a XRD-7000 (Shimadzu) X-ray diffraction setup was used to produce 10-keV effective energy photons. Heavy ions tests involved 12C, 16O, 19F, 28Si, 35Cl, 63Cu and 107Ag beams scattered at 15° by a 275 μg/cm2 gold target, which provide LETs (Linear Energy Transfer) from 4 to 40 MeV/mg/cm2. The signal readout was done using a 1 GHz oscilloscope with a 10-Gsamples/s conversion rate, high enough to permit the recording of transient pulses in the drain current. In this case, an ion can cause a current signal proportional to the ion beam used. Through this study it was found that a simple commercial pMOS device can be reliably used as a detector of X-rays as well as heavy ion detector.

  4. Effects of annealing on electrical performance of multilayer MoS2 transistors with atomic layer deposited HfO2 gate dielectric

    NASA Astrophysics Data System (ADS)

    Wen, Ming; Xu, Jingping; Liu, Lu; Lai, Pui-To; Tang, Wing-Man

    2016-09-01

    Atomic layer deposited HfO2 annealed in different ambients (N2, O2, and NH3) is used to replace SiO2 as a gate dielectric for fabricating back-gated multilayer MoS2 transistors. Excellent electrical properties such as a mobility of 15.1 cm2/(V·s), an on/off ratio exceeding 107, and a hysteresis of 0.133 V are achieved for samples annealed in NH3 at 400 °C for 10 min. This is caused by the NH3 annealing passivation effects that reduce defective states in the HfO2 dielectric and the interface. The capacitance equivalent thickness is only 7.85 nm, which is quite small for a back-gated MoS2 transistor and is conducive to the scaling down of the device.

  5. Laser direct writing and inkjet printing for a sub-2 μm channel length MoS2 transistor with high-resolution electrodes

    NASA Astrophysics Data System (ADS)

    Kwon, Hyuk-Jun; Chung, Seungjun; Jang, Jaewon; Grigoropoulos, Costas P.

    2016-10-01

    Patterns formed by the laser direct writing (LDW) lithography process are used either as channels or barriers for MoS2 transistors fabricated via inkjet printing. Silver (Ag) nanoparticle ink is printed over patterns formed on top of the MoS2 flakes in order to construct high-resolution source/drain (S/D) electrodes. When positive photoresist is used, the produced grooves are filled with inkjetted Ag ink by capillary forces. On the other hand, in the case of negative photoresist, convex barrier-like patterns are written on the MoS2 flakes and patterns, dividing the printed Ag ink into the S/D electrodes by self-alignment. LDW lithography combined with inkjet printing is applied to MoS2 thin-film transistors that exhibit moderate electrical performance such as mobility and subthreshold swing. However, especially in the linear operation regime, their features are limited by the contact effect. The Y-function method can exclude the contact effect and allow proper evaluation of the maximum available mobility and contact resistance. The presented fabrication methods may facilitate the development of cost-effective fabrication processes.

  6. Strain-Gated Field Effect Transistor of a MoS2-ZnO 2D-1D Hybrid Structure.

    PubMed

    Chen, Libo; Xue, Fei; Li, Xiaohui; Huang, Xin; Wang, Longfei; Kou, Jinzong; Wang, Zhong Lin

    2016-01-26

    Two-dimensional (2D) molybdenum disulfide (MoS2) is an exciting material due to its unique electrical, optical, and piezoelectric properties. Owing to an intrinsic band gap of 1.2-1.9 eV, monolayer or a-few-layer MoS2 is used for fabricating field effect transistors (FETs) with high electron mobility and on/off ratio. However, the traditional FETs are controlled by an externally supplied gate voltage, which may not be sensitive enough to directly interface with a mechanical stimulus for applications in electronic skin. Here we report a type of top-pressure/force-gated field effect transistors (PGFETs) based on a hybrid structure of a 2D MoS2 flake and 1D ZnO nanowire (NW) array. Once an external pressure is applied, the piezoelectric polarization charges created at the tips of ZnO NWs grown on MoS2 act as a gate voltage to tune/control the source-drain transport property in MoS2. At a 6.25 MPa applied stimulus on a packaged device, the source-drain current can be tuned for ∼25%, equivalent to the results of applying an extra -5 V back gate voltage. Another type of PGFET with a dielectric layer (Al2O3) sandwiched between MoS2 and ZnO also shows consistent results. A theoretical model is proposed to interpret the received data. This study sets the foundation for applying the 2D material-based FETs in the field of artificial intelligence.

  7. Strain-Gated Field Effect Transistor of a MoS2-ZnO 2D-1D Hybrid Structure.

    PubMed

    Chen, Libo; Xue, Fei; Li, Xiaohui; Huang, Xin; Wang, Longfei; Kou, Jinzong; Wang, Zhong Lin

    2016-01-26

    Two-dimensional (2D) molybdenum disulfide (MoS2) is an exciting material due to its unique electrical, optical, and piezoelectric properties. Owing to an intrinsic band gap of 1.2-1.9 eV, monolayer or a-few-layer MoS2 is used for fabricating field effect transistors (FETs) with high electron mobility and on/off ratio. However, the traditional FETs are controlled by an externally supplied gate voltage, which may not be sensitive enough to directly interface with a mechanical stimulus for applications in electronic skin. Here we report a type of top-pressure/force-gated field effect transistors (PGFETs) based on a hybrid structure of a 2D MoS2 flake and 1D ZnO nanowire (NW) array. Once an external pressure is applied, the piezoelectric polarization charges created at the tips of ZnO NWs grown on MoS2 act as a gate voltage to tune/control the source-drain transport property in MoS2. At a 6.25 MPa applied stimulus on a packaged device, the source-drain current can be tuned for ∼25%, equivalent to the results of applying an extra -5 V back gate voltage. Another type of PGFET with a dielectric layer (Al2O3) sandwiched between MoS2 and ZnO also shows consistent results. A theoretical model is proposed to interpret the received data. This study sets the foundation for applying the 2D material-based FETs in the field of artificial intelligence. PMID:26695840

  8. High performance multilayer MoS2 transistors with scandium contacts.

    PubMed

    Das, Saptarshi; Chen, Hong-Yan; Penumatcha, Ashish Verma; Appenzeller, Joerg

    2013-01-01

    While there has been growing interest in two-dimensional (2-D) crystals other than graphene, evaluating their potential usefulness for electronic applications is still in its infancy due to the lack of a complete picture of their performance potential. The focus of this article is on contacts. We demonstrate that through a proper understanding and design of source/drain contacts and the right choice of number of MoS(2) layers the excellent intrinsic properties of this 2-D material can be harvested. Using scandium contacts on 10-nm-thick exfoliated MoS(2) flakes that are covered by a 15 nm Al(2)O(3) film, high effective mobilities of 700 cm(2)/(V s) are achieved at room temperature. This breakthrough is largely attributed to the fact that we succeeded in eliminating contact resistance effects that limited the device performance in the past unrecognized. In fact, the apparent linear dependence of current on drain voltage had mislead researchers to believe that a truly Ohmic contact had already been achieved, a misconception that we also elucidate in the present article.

  9. Lifetime studies of 130nm nMOS transistors intended for long-duration, cryogenic high-energy physics experiments.

    SciTech Connect

    Hoff, J.R.; Arora, R.; Cressler, J.D.; Deptuch, G.W.; Gui, P.; Lourenco, N.E.; Wu, G.; Yarema, R.J.; /Fermilab

    2011-12-01

    Future neutrino physics experiments intend to use unprecedented volumes of liquid argon to fill a time projection chamber in an underground facility. To increase performance, integrated readout electronics should work inside the cryostat. Due to the scale and cost associated with evacuating and filling the cryostat, the electronics will be unserviceable for the duration of the experiment. Therefore, the lifetimes of these circuits must be well in excess of 20 years. The principle mechanism for lifetime degradation of MOSFET devices and circuits operating at cryogenic temperatures is via hot carrier degradation. Choosing a process technology that is, as much as possible, immune to such degradation and developing design techniques to avoid exposure to such damage are the goals. This requires careful investigation and a basic understanding of the mechanisms that underlie hot carrier degradation and the secondary effects they cause in circuits. In this work, commercially available 130nm nMOS transistors operating at cryogenic temperatures are investigated. The results show that the difference in lifetime for room temperature operation and cryogenic operation for this process are not great and the lifetimes at both 300K and at 77K can be projected to more than 20 years at the nominal voltage (1.5V) for this technology.

  10. Novel reverse conducting insulated gate bipolar transistor with anti-parallel MOS controlled thyristor

    NASA Astrophysics Data System (ADS)

    Liheng, Zhu; Xingbi, Chen

    2014-07-01

    Novel reverse-conducting IGBT (RC-IGBT) with anti-parallel MOS controlled thyristor (MCT) is proposed. Its major feature is the introduction of an automatically controlled MCT at the anode, by which the anode-short effect is eliminated and the voltage snapback problem is solved. Furthermore, the snapback-free characteristics can be realized in novel RC-IGBT by a single cell with a width of 10 μm with more uniform current distribution. As numerical simulations show, compared with the conventional RC-IGBT, the forward conduction voltage is reduced by 35% while the reverse conduction voltage is reduced by 50% at J = 150 A/cm2.

  11. Symmetric complementary logic inverter using integrated black phosphorus and MoS2 transistors

    NASA Astrophysics Data System (ADS)

    Su, Yang; Kshirsagar, Chaitanya U.; Robbins, Matthew C.; Haratipour, Nazila; Koester, Steven J.

    2016-03-01

    The operation of an integrated two-dimensional complementary metal-oxide-semiconductor inverter with well-matched input/output voltages is reported. The circuit combines a few-layer MoS2 n-MOSFET and a black phosphorus (BP) p-MOSFET fabricated using a common local backgate electrode with thin (20 nm) HfO2 gate dielectric. The constituent devices have linear threshold voltages of -0.8 V and +0.8 V and produce peak transconductances of 16 μS μm-1 and 41 μS μm-1 for the MoS2 n-MOSFET and BP p-MOSFET, respectively. The inverter shows a voltage gain of 3.5 at a supply voltage, V DD = 2.5 V, and has peak switching current of 108 μA and off-state current of 8.4 μA (2.4 μA) at V IN = 0 (V IN = 2.5 V). In addition, the inverter has voltage gain greater than unity for V DD ≥ 0.5 V, has open butterfly curves for V DD ≥ 1 V, and achieves static noise margin over 500 mV at V DD = 2.5 V. The voltage gain was found to be insensitive to temperature between 270 and 340 K, and AC large and small-signal operation was demonstrated at frequencies up to 100 kHz. The demonstration of a complementary 2D inverter which operates in a symmetric voltage window suitable for driving a subsequent logic stage is a significant step forward in developing practical applications for devices based upon 2D materials.

  12. Laser direct writing and inkjet printing for a sub-2 μm channel length MoS2 transistor with high-resolution electrodes.

    PubMed

    Kwon, Hyuk-Jun; Chung, Seungjun; Jang, Jaewon; Grigoropoulos, Costas P

    2016-10-01

    Patterns formed by the laser direct writing (LDW) lithography process are used either as channels or barriers for MoS2 transistors fabricated via inkjet printing. Silver (Ag) nanoparticle ink is printed over patterns formed on top of the MoS2 flakes in order to construct high-resolution source/drain (S/D) electrodes. When positive photoresist is used, the produced grooves are filled with inkjetted Ag ink by capillary forces. On the other hand, in the case of negative photoresist, convex barrier-like patterns are written on the MoS2 flakes and patterns, dividing the printed Ag ink into the S/D electrodes by self-alignment. LDW lithography combined with inkjet printing is applied to MoS2 thin-film transistors that exhibit moderate electrical performance such as mobility and subthreshold swing. However, especially in the linear operation regime, their features are limited by the contact effect. The Y-function method can exclude the contact effect and allow proper evaluation of the maximum available mobility and contact resistance. The presented fabrication methods may facilitate the development of cost-effective fabrication processes.

  13. Laser direct writing and inkjet printing for a sub-2 μm channel length MoS2 transistor with high-resolution electrodes.

    PubMed

    Kwon, Hyuk-Jun; Chung, Seungjun; Jang, Jaewon; Grigoropoulos, Costas P

    2016-10-01

    Patterns formed by the laser direct writing (LDW) lithography process are used either as channels or barriers for MoS2 transistors fabricated via inkjet printing. Silver (Ag) nanoparticle ink is printed over patterns formed on top of the MoS2 flakes in order to construct high-resolution source/drain (S/D) electrodes. When positive photoresist is used, the produced grooves are filled with inkjetted Ag ink by capillary forces. On the other hand, in the case of negative photoresist, convex barrier-like patterns are written on the MoS2 flakes and patterns, dividing the printed Ag ink into the S/D electrodes by self-alignment. LDW lithography combined with inkjet printing is applied to MoS2 thin-film transistors that exhibit moderate electrical performance such as mobility and subthreshold swing. However, especially in the linear operation regime, their features are limited by the contact effect. The Y-function method can exclude the contact effect and allow proper evaluation of the maximum available mobility and contact resistance. The presented fabrication methods may facilitate the development of cost-effective fabrication processes. PMID:27576743

  14. Enhancement mode AlGaN/GaN MOS high-electron-mobility transistors with ZrO2 gate dielectric deposited by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Anderson, Travis J.; Wheeler, Virginia D.; Shahin, David I.; Tadjer, Marko J.; Koehler, Andrew D.; Hobart, Karl D.; Christou, Aris; Kub, Francis J.; Eddy, Charles R., Jr.

    2016-07-01

    Advanced applications of AlGaN/GaN high-electron-mobility transistors (HEMTs) in high-power RF and power switching are driving the need for insulated gate technology. We present a metal-oxide-semiconductor (MOS) gate structure using atomic-layer-deposited ZrO2 as a high-k, high-breakdown gate dielectric for reduced gate leakage and a recessed barrier structure for enhancement mode operation. Compared to a Schottky metal-gate HEMT, the recessed MOS-HEMT structure demonstrated a reduction in the gate leakage current by 4 orders of magnitude and a threshold voltage shift of +6 V to a record +3.99 V, enabled by a combination of a recessed barrier structure and negative oxide charge.

  15. Enhancement mode AlGaN/GaN MOS high-electron-mobility transistors with ZrO2 gate dielectric deposited by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Anderson, Travis J.; Wheeler, Virginia D.; Shahin, David I.; Tadjer, Marko J.; Koehler, Andrew D.; Hobart, Karl D.; Christou, Aris; Kub, Francis J.; Eddy, Charles R., Jr.

    2016-07-01

    Advanced applications of AlGaN/GaN high-electron-mobility transistors (HEMTs) in high-power RF and power switching are driving the need for insulated gate technology. We present a metal–oxide–semiconductor (MOS) gate structure using atomic-layer-deposited ZrO2 as a high-k, high-breakdown gate dielectric for reduced gate leakage and a recessed barrier structure for enhancement mode operation. Compared to a Schottky metal-gate HEMT, the recessed MOS-HEMT structure demonstrated a reduction in the gate leakage current by 4 orders of magnitude and a threshold voltage shift of +6 V to a record +3.99 V, enabled by a combination of a recessed barrier structure and negative oxide charge.

  16. On the turn-around phenomenon in n-MOS transistors under NBTI conditions

    NASA Astrophysics Data System (ADS)

    Benabdelmoumene, A.; Djezzar, B.; Chenouf, A.; Tahi, H.; Zatout, B.; Kechouane, M.

    2016-07-01

    We have experimentally analyzed negative bias temperature instability (NBTI) stress/recovery cycle on n-channel metal oxide semiconductor field effect transistors (n-MOSFET's). Data obtained by current-voltage (I-V) and charge pumping (CP) techniques have revealed a turn-around phenomenon in both threshold voltage shift (ΔVth) and maximum CP current shift (ΔICP-Max). This allows us to separate the evolution of interface traps (permanent) and near interfacial oxide traps "border traps" (recoverable) as a function of the stress time. The ability of separation comes from the fact that interface and oxide traps induce opposite shifts in ΔVth. Contrarily to NBTI/n-MOSFET, NBTI/p-MOSFET is unable to achieve trap separation because both trap types induce shifts in the same direction. Exploiting the turn-around effect, we have been able to follow the evolution of the degradation over the stress time. NBTI stress/relaxation cycle CP measurements on n-MOSFET have shown a progressive creation of traps; starting from the interface traps to near interfacial traps. This new and simple procedure will give a deeper insight into the dynamics of traps build up under NBTI conditions.

  17. Laser Direct Writing Process for Making Electrodes and High-k Sol-Gel ZrO2 for Boosting Performances of MoS2 Transistors.

    PubMed

    Kwon, Hyuk-Jun; Jang, Jaewon; Grigoropoulos, Costas P

    2016-04-13

    A series of two-dimensional (2D) transition metal dichalcogenides (TMDCs), including molybdenum disulfide (MoS2), can be attractive materials for photonic and electronic applications due to their exceptional properties. Among these unique properties, high mobility of 2D TMDCs enables realization of high-performance nanoelectronics based on a thin film transistor (TFT) platform. In this contribution, we report highly enhanced field effect mobility (μ(eff) = 50.1 cm(2)/(V s), ∼2.5 times) of MoS2 TFTs through the sol-gel processed high-k ZrO2 (∼22.0) insulator, compared to those of typical MoS2/SiO2/Si structures (μ(eff) = 19.4 cm(2)/(V s)) because a high-k dielectric layer can suppress Coulomb electron scattering and reduce interface trap concentration. Additionally, in order to avoid costly conventional mask based photolithography and define the patterns, we employ a simple laser direct writing (LDW) process. This process allows precise and flexible control with reasonable resolution (up to ∼10 nm), depending on the system, and enables fabrication of arbitrarily patterned devices. Taking advantage of continuing developments in laser technology offers a substantial cost decrease, and LDW may emerge as a promising technology.

  18. Electrical characterization of electron beam induced damage on sub-10 nm n-channel MOS transistors using nano-probing technique

    NASA Astrophysics Data System (ADS)

    Kang, Jonghyuk; Lee, Sungho; Choi, Byoungdeog

    2016-11-01

    Electron beam induced damage on sub-10 nm n-channel MOS transistors was evaluated using an atomic force microscopy-based nano-probing technique. After electron beam irradiation, all the device parameters shifted including threshold voltage (V th), saturation current, sub-threshold slope and transistor leakage current. A negative shift in V th occurred at low electron beam acceleration voltage (V acc) because of the increase in oxide trapped holes generated by excited plasmons. At high V acc, however, a positive V th shift was observed because of an increased contribution of interface trap generation caused by the deeper electron penetration depth. In addition, interface trap generation not only degraded the sub-threshold slope due to the additional capacitance from the generated interface traps, but also increased transistor leakage current due to changes in junction characteristics. Our studies show that it is critical to avoid electron beam exposure before electrical characterization on sub-10 nm devices even in the range of less than 1.0 kV of V acc using nano-probe systems.

  19. Electronic properties of MoS2/MoOx interfaces: Implications in Tunnel Field Effect Transistors and Hole Contacts

    PubMed Central

    K. C., Santosh; Longo, Roberto C.; Addou, Rafik; Wallace, Robert M.; Cho, Kyeongjae

    2016-01-01

    In an electronic device based on two dimensional (2D) transitional metal dichalcogenides (TMDs), finding a low resistance metal contact is critical in order to achieve the desired performance. However, due to the unusual Fermi level pinning in metal/2D TMD interface, the performance is limited. Here, we investigate the electronic properties of TMDs and transition metal oxide (TMO) interfaces (MoS2/MoO3) using density functional theory (DFT). Our results demonstrate that, due to the large work function of MoO3 and the relative band alignment with MoS2, together with small energy gap, the MoS2/MoO3 interface is a good candidate for a tunnel field effect (TFET)-type device. Moreover, if the interface is not stoichiometric because of the presence of oxygen vacancies in MoO3, the heterostructure is more suitable for p-type (hole) contacts, exhibiting an Ohmic electrical behavior as experimentally demonstrated for different TMO/TMD interfaces. Our results reveal that the defect state induced by an oxygen vacancy in the MoO3 aligns with the valance band of MoS2, showing an insignificant impact on the band gap of the TMD. This result highlights the role of oxygen vacancies in oxides on facilitating appropriate contacts at the MoS2 and MoOx (x < 3) interface, which consistently explains the available experimental observations. PMID:27666523

  20. Static and Dynamic Performance of Complementary Inverters Based on Nanosheet α-MoTe2 p-Channel and MoS2 n-Channel Transistors.

    PubMed

    Pezeshki, Atiye; Hosseini Shokouh, Seyed Hossein; Jeon, Pyo Jin; Shackery, Iman; Kim, Jin Sung; Oh, Il-Kwon; Jun, Seong Chan; Kim, Hyungjun; Im, Seongil

    2016-01-26

    Molybdenum ditelluride (α-MoTe2) is an emerging transition-metal dichalcogenide (TMD) semiconductor that has been attracting attention due to its favorable optical and electronic properties. Field-effect transistors (FETs) based on few-layer α-MoTe2 nanosheets have previously shown ambipolar behavior with strong p-type and weak n-type conduction. We have employed a direct imprinting technique following mechanical nanosheet exfoliation to fabricate high-performance complementary inverters using α-MoTe2 as the semiconductor for the p-channel FETs and MoS2 as the semiconductor for the n-channel FETs. To avoid ambipolar behavior and produce α-MoTe2 FETs with clean p-channel characteristics, we have employed the high-workfunction metal platinum for the source and drain contacts. As a result, our α-MoTe2 nanosheet p-channel FETs show hole mobilities up to 20 cm(2)/(V s), on/off ratios up to 10(5), and a subthreshold slope of 255 mV/decade. For our complementary inverters composed of few-layer α-MoTe2 p-channel FETs and MoS2 n-channel FETs we have obtained voltage gains as high as 33, noise margins as high as 0.38 VDD, a switching delay of 25 μs, and a static power consumption of a few nanowatts. PMID:26631357

  1. Floating gate memory-based monolayer MoS2 transistor with metal nanocrystals embedded in the gate dielectrics.

    PubMed

    Wang, Jingli; Zou, Xuming; Xiao, Xiangheng; Xu, Lei; Wang, Chunlan; Jiang, Changzhong; Ho, Johnny C; Wang, Ti; Li, Jinchai; Liao, Lei

    2015-01-14

    Charge trapping layers are formed from different metallic nanocrystals in MoS2 -based nanocrystal floating gate memory cells in a process compatible with existing fabrication technologies. The memory cells with Au nanocrystals exhibit impressive performance with a large memory window of 10 V, a high program/erase ratio of approximately 10(5) and a long retention time of 10 years.

  2. Theory and experiments of electron-hole recombination at silicon/silicon dioxide interface traps and tunneling in thin oxide MOS transistors

    NASA Astrophysics Data System (ADS)

    Cai, Jin

    2000-10-01

    Surface recombination and channel have dominated the electrical characteristics, performance and reliability of p/n junction diodes and transistors. This dissertation uses a sensitive direct-current current voltage (DCIV) method to measure base terminal currents (IB) modulated by the gate bias (VGB) and forward p/n junction bias (VPN) in a MOS transistor (MOST). Base terminal currents originate from electron-hole recombination at Si/SiO2 interface traps. Fundamental theories which relate DCIV characteristics to device and material parameters are presented. Three theory-based applications are demonstrated on both the unstressed as well as hot-carrier-stressed MOSTs: (1) determination of interface trap density and energy levels, (2) spatial profile of interface traps in the drain/base junction-space-charge region and in the channel region, and (3) determination of gate oxide thickness and impurity doping concentrations. The results show that interface trap energy levels are discrete, which is consistent with those from silicon dangling bonds; in unstressed MOS transistors interface trap density in the channel region rises sharply toward source and drain, and after channel-hot-carrier stress, interface trap density increases mostly in the junction space-charge region. As the gate oxide thins below 3 nm, the gate oxide leakage current via quantum mechanical tunneling becomes significant. A gate oxide tunneling theory which refined the traditional WKB tunneling probability is developed for modeling tunneling currents at low electric fields through a trapezoidal SiO2 barrier. Correlation with experimental data on thin oxide MOSTs reveals two new results: (1) hole tunneling dominates over electron tunneling in p+gate p-channel MOSTs, and (2) the small gate/drain overlap region passes higher tunneling currents than the channel region under depletion to flatband gate voltages. The good theory-experimental correlation enables the extraction of impurity doping concentrations

  3. Charge transport in ion-gated mono-, bi-, and trilayer MoS2 field effect transistors

    PubMed Central

    Chu, Leiqiang; Schmidt, Hennrik; Pu, Jiang; Wang, Shunfeng; Özyilmaz, Barbaros; Takenobu, Taishi; Eda, Goki

    2014-01-01

    Charge transport in MoS2 in the low carrier density regime is dominated by trap states and band edge disorder. The intrinsic transport properties of MoS2 emerge in the high density regime where conduction occurs via extended states. Here, we investigate the transport properties of mechanically exfoliated mono-, bi-, and trilayer MoS2 sheets over a wide range of carrier densities realized by a combination of ion gel top gate and SiO2 back gate, which allows us to achieve high charge carrier (>1013 cm−2) densities. We discuss the gating properties of the devices as a function of layer thickness and demonstrate resistivities as low as 1 kΩ for monolayer and 420 Ω for bilayer devices at 10 K. We show that from the capacitive coupling of the two gates, quantum capacitance can be roughly estimated to be on the order of 1 μF/cm2 for all devices studied. The temperature dependence of the carrier mobility in the high density regime indicates that short-range scatterers limit charge transport at low temperatures. PMID:25465059

  4. Low-Resistance 2D/2D Ohmic Contacts: A Universal Approach to High-Performance WSe2, MoS2, and MoSe2 Transistors.

    PubMed

    Chuang, Hsun-Jen; Chamlagain, Bhim; Koehler, Michael; Perera, Meeghage Madusanka; Yan, Jiaqiang; Mandrus, David; Tománek, David; Zhou, Zhixian

    2016-03-01

    We report a new strategy for fabricating 2D/2D low-resistance ohmic contacts for a variety of transition metal dichalcogenides (TMDs) using van der Waals assembly of substitutionally doped TMDs as drain/source contacts and TMDs with no intentional doping as channel materials. We demonstrate that few-layer WSe2 field-effect transistors (FETs) with 2D/2D contacts exhibit low contact resistances of ∼0.3 kΩ μm, high on/off ratios up to >10(9), and high drive currents exceeding 320 μA μm(-1). These favorable characteristics are combined with a two-terminal field-effect hole mobility μFE ≈ 2 × 10(2) cm(2) V(-1) s(-1) at room temperature, which increases to >2 × 10(3) cm(2) V(-1) s(-1) at cryogenic temperatures. We observe a similar performance also in MoS2 and MoSe2 FETs with 2D/2D drain and source contacts. The 2D/2D low-resistance ohmic contacts presented here represent a new device paradigm that overcomes a significant bottleneck in the performance of TMDs and a wide variety of other 2D materials as the channel materials in postsilicon electronics.

  5. Comparison of short-channel effects in monolayer MoS2 based junctionless and inversion-mode field-effect transistors

    NASA Astrophysics Data System (ADS)

    Agarwal, Tarun; Sorée, Bart; Radu, Iuliana; Raghavan, Praveen; Fiori, Gianluca; Iannaccone, Giuseppe; Thean, Aaron; Heyns, Marc; Dehaene, Wim

    2016-01-01

    Conventional junctionless (JL) multi-gate (MuG) field-effect transistors (FETs) require extremely scaled channels to deliver high on-state current with low short-channel effect related leakage. In this letter, using ultra-thin 2D materials (e.g., monolayer MoS2), we present comparison of short-channel effects in JL, and inversion-mode (IM) FETs. We show that JL FETs exhibit better sub-threshold slope (S.S.) and drain-induced-barrier-lowering (DIBL) in comparison to IM FETs due to reduced peak electric field at the junctions. But, threshold voltage (VT) roll-off with channel length downscaling is found to be significantly higher in JL FETs than IM FETs, due to higher source/drain controlled charges (dE/dx) in the channel. Further, we show that although VT roll-off in JL FETs improves by increasing the gate control, i.e., by scaling the oxide, or channel thickness, the sensitivity of threshold voltage on structural parameters is found out to be high.

  6. Substrate dependence of Hall and Field-effect mobilities in few-layer MoS2 field-effect transistors

    NASA Astrophysics Data System (ADS)

    Chamlagain, Bhim; Perera, Meeghage; Chuang, Hsuen-Jen; Bowman, Arthur; Rijal, Upendra; Andrews, Kraig; Klesko, Joseph; Winter, Charles; Zhou, Zhixian

    In this work, we systematically study the Hall and field-effect mobilities of few-layer MoS2 FETs fabricated on different substrates. Hall bar devices were fabricated on SiO2 and hBN to directly measure carrier density. Standard four-probe transport measurement and Hall effect measurement were carried out for a wide temperature range to determine the carrier mobility and understand the scattering mechanisms. By comparing field-effect and Hall mobilities, we demonstrate that the intrinsic drift mobility of multiplayer MoS2 in the high carrier density metallic region is independent of substrate and sample thickness. While the optical-phonon scattering remains the dominant scattering mechanism in MoS2 devices on h-BN down to ~100 K, extrinsic scattering mechanisms start to degrade the carrier mobility of MoS2 on all other substrates below ~200 K. NSF Grant Number DMR-1308436.

  7. Research Update: Nanoscale surface potential analysis of MoS2 field-effect transistors for biomolecular detection using Kelvin probe force microscopy

    NASA Astrophysics Data System (ADS)

    Kim, Min Hyung; Park, Heekyeong; Lee, Hyungbeen; Nam, Kihwan; Jeong, Seokhwan; Omkaram, Inturu; Yoon, Dae Sung; Lee, Sei Young; Kim, Sunkook; Lee, Sang Woo

    2016-10-01

    We used high-resolution Kelvin probe force microscopy (KPFM) to investigate the immobilization of a prostate specific antigen (PSA) antibody by measuring the surface potential (SP) on a MoS2 surface over an extensive concentration range (1 pg/ml-100 μg/ml). After PSA antibody immobilization, we demonstrated that the SP on the MoS2 surface characterized by KPFM strongly correlated to the electrical signal of a MoS2 bioFET. This demonstration can not only be used to optimize the immobilization conditions for captured molecules, but can also be applied as a diagnostic tool to complement the electrical detection of a MoS2 FET biosensor.

  8. MOS integrated circuit fault modeling

    NASA Technical Reports Server (NTRS)

    Sievers, M.

    1985-01-01

    Three digital simulation techniques for MOS integrated circuit faults were examined. These techniques embody a hierarchy of complexity bracketing the range of simulation levels. The digital approaches are: transistor-level, connector-switch-attenuator level, and gate level. The advantages and disadvantages are discussed. Failure characteristics are also described.

  9. Tuning the threshold voltage from depletion to enhancement mode in a multilayer MoS2 transistor via oxygen adsorption and desorption.

    PubMed

    Jiang, Jie; Dhar, Sarit

    2016-01-14

    Selective chemical doping in two-dimensional (2D) molybdenum disulfide (MoS2) is attractive for tailoring electrical properties according to device requirements. However, the ultra-thin 2D nature of MoS2 makes it difficult to realize effective doping by conventional ion implantation. Here, a simple method based on low-temperature (150 °C) annealing in air is developed for effective chemical doping in MoS2. We have demonstrated that the threshold voltage (V(th)) of multilayer MoS2 FET can be effectively tuned from depletion mode (V(th) = -1.8 V) to enhancement mode (V(th) = 1.1 V) by annealing in air at 150 °C. An energy band model based on electron trapping/detrapping due to oxygen adsorption on the MoS2 surface is proposed to explain the underlying mechanism. The model is consistent with an oxygen adsorption-desorption process evidenced by vacuum annealing that recovers the V(th) to its original value. These results can provide a simple approach for V(th) engineering and make a significant step toward 2D nanoelectronic device applications. PMID:26658374

  10. High quality PECVD SiO2 process for recessed MOS-gate of AlGaN/GaN-on-Si metal–oxide–semiconductor heterostructure field-effect transistors

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Gil; Kim, Hyun-Seop; Seo, Kwang-Seok; Cho, Chun-Hyung; Cha, Ho-Young

    2016-08-01

    A high quality SiO2 deposition process using a plasma enhanced chemical vapor deposition system has been developed for the gate insulator process of normally-off recessed-gate AlGaN/GaN metal-oxide-semiconductor-heterostructure field-effect transistors (MOS-HFETs). SiO2 films were deposited by using SiH4 and N2O mixtures as reactant gases. The breakdown field increased with increasing the N2O flow rate. The optimum SiH4/N2O ratio was 0.05, which resulted in a maximum breakdown field of 11 MV/cm for the SiO2 film deposited on recessed GaN surface. The deposition conditions were optimized as follows; a gas flow rate of SiH4/N2O (=27/540 sccm), a source RF power of 100 W, a pressure of 2 Torr, and a deposition temperature of 350 °C. A fabricated normally-off MOS-HFET exhibited a threshold voltage of 3.2 V, a specific on-resistance of 4.46 mΩ cm2, and a breakdown voltage of 810 V.

  11. High quality PECVD SiO2 process for recessed MOS-gate of AlGaN/GaN-on-Si metal-oxide-semiconductor heterostructure field-effect transistors

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Gil; Kim, Hyun-Seop; Seo, Kwang-Seok; Cho, Chun-Hyung; Cha, Ho-Young

    2016-08-01

    A high quality SiO2 deposition process using a plasma enhanced chemical vapor deposition system has been developed for the gate insulator process of normally-off recessed-gate AlGaN/GaN metal-oxide-semiconductor-heterostructure field-effect transistors (MOS-HFETs). SiO2 films were deposited by using SiH4 and N2O mixtures as reactant gases. The breakdown field increased with increasing the N2O flow rate. The optimum SiH4/N2O ratio was 0.05, which resulted in a maximum breakdown field of 11 MV/cm for the SiO2 film deposited on recessed GaN surface. The deposition conditions were optimized as follows; a gas flow rate of SiH4/N2O (=27/540 sccm), a source RF power of 100 W, a pressure of 2 Torr, and a deposition temperature of 350 °C. A fabricated normally-off MOS-HFET exhibited a threshold voltage of 3.2 V, a specific on-resistance of 4.46 mΩ cm2, and a breakdown voltage of 810 V.

  12. Negative differential resistance and effect of defects and deformations in MoS2 armchair nanoribbon metal-oxide-semiconductor field effect transistor

    NASA Astrophysics Data System (ADS)

    Sengupta, Amretashis; Mahapatra, Santanu

    2013-11-01

    In this work, we present a study on the negative differential resistance (NDR) behavior and the impact of various deformations (like ripple, twist, wrap) and defects like vacancies and edge roughness on the electronic properties of short-channel MoS2 armchair nanoribbon MOSFETs. The effect of deformation (3°-7° twist or wrap and 0.3-0.7 Å ripple amplitude) and defects on a 10 nm MoS2 ANR FET is evaluated by the density functional tight binding theory and the non-equilibrium Green`s function approach. We study the channel density of states, transmission spectra, and the ID-VD characteristics of such devices under the varying conditions, with focus on the NDR behavior. Our results show significant change in the NDR peak to valley ratio and the NDR window with such minor intrinsic deformations, especially with the ripple.

  13. Highly Stable, Dual-Gated MoS2 Transistors Encapsulated by Hexagonal Boron Nitride with Gate-Controllable Contact, Resistance, and Threshold Voltage.

    PubMed

    Lee, Gwan-Hyoung; Cui, Xu; Kim, Young Duck; Arefe, Ghidewon; Zhang, Xian; Lee, Chul-Ho; Ye, Fan; Watanabe, Kenji; Taniguchi, Takashi; Kim, Philip; Hone, James

    2015-07-28

    Emerging two-dimensional (2D) semiconductors such as molybdenum disulfide (MoS2) have been intensively studied because of their novel properties for advanced electronics and optoelectronics. However, 2D materials are by nature sensitive to environmental influences, such as temperature, humidity, adsorbates, and trapped charges in neighboring dielectrics. Therefore, it is crucial to develop device architectures that provide both high performance and long-term stability. Here we report high performance of dual-gated van der Waals (vdW) heterostructure devices in which MoS2 layers are fully encapsulated by hexagonal boron nitride (hBN) and contacts are formed using graphene. The hBN-encapsulation provides excellent protection from environmental factors, resulting in highly stable device performance, even at elevated temperatures. Our measurements also reveal high-quality electrical contacts and reduced hysteresis, leading to high two-terminal carrier mobility (33-151 cm(2) V(-1) s(-1)) and low subthreshold swing (80 mV/dec) at room temperature. Furthermore, adjustment of graphene Fermi level and use of dual gates enable us to separately control contact resistance and threshold voltage. This novel vdW heterostructure device opens up a new way toward fabrication of stable, high-performance devices based on 2D materials.

  14. Gyrator employing field effect transistors

    NASA Technical Reports Server (NTRS)

    Hochmair, E. S. (Inventor)

    1973-01-01

    A gyrator circuit of the conventional configuration of two amplifiers in a circular loop, one producing zero phase shift and the other producing 180 deg phase reversal is examined. All active elements are MOS field effect transistors. Each amplifier comprises a differential amplifier configuration with current limiting transistor, followed by an output transistor in cascode configuration, and two load transistors of opposite conductivity type from the other transistors. A voltage divider control circuit comprises a series string of transistors with a central voltage input to provide control, with locations on the amplifiers receiving reference voltages by connection to appropriate points on the divider. The circuit produces excellent response and is well suited for fabrication by integrated circuits.

  15. John Bardeen and transistor physics

    NASA Astrophysics Data System (ADS)

    Huff, Howard R.

    2001-01-01

    John Bardeen and Walter Brattain invented the point-contact semiconductor amplifier (transistor action) in polycrystalline germanium (also observed in polycrystalline silicon) on Dec. 15, 1947, for which they received a patent on Oct. 3, 1950. Bill Shockley was not a co-patent holder on Bardeen and Brattain's point-contact semiconductor amplifier patent since Julius Lilienfeld had already received a patent in 1930 for what would have been Shockley's contribution; namely, the field-effect methodology. Shockley received patents for both his minority-carrier injection concept and junction transistor theory, however, and deservedly shared the Nobel prize with Bardeen and Brattain for his seminal contributions of injection, p-n junction theory and junction transistor theory. We will review the events leading up to the invention of Bardeen and Brattain's point-contact semiconductor amplifier during the magic month of November 17-December 16, 1947 and the invention of Shockley's junction semiconductor amplifier during his magic month of December 24, 1947-January 23, 1948. It was during the course of Bardeen and Brattain's research in November, 1947 that Bardeen also patented the essence of the MOS transistor, wherein the induced minority carriers were confined to the inversion layer enroute to the collector. C. T. Sah has described this device as a sourceless MOS transistor. Indeed, John Bardeen, co-inventor of the point-contact semiconductor amplifier and inventor of the MOS transistor, may rightly be called the father of modern electronics.

  16. Quantitative evaluation of slow traps near Ge MOS interfaces by using time response of MOS capacitance

    NASA Astrophysics Data System (ADS)

    Tanaka, Katsuhisa; Zhang, Rui; Takenaka, Mitsuru; Takagi, Shinichi

    2015-04-01

    Time-dependent changes in current and threshold voltage due to slow traps near Ge metal-oxide-semiconductor (MOS) interfaces is one of the most serious problems in Ge metal-oxide-semiconductor field-effect transistors (MOSFETs). In this study, we propose a new evaluation method of slow traps near MOS interfaces utilizing the time response of capacitance in MOS capacitors at a constant gate voltage, allowing us to evaluate the density and time constant of slow traps. We apply this method to Au/Al2O3/GeOx/Ge MOS capacitors and evaluate the density and average time constant of slow traps. The slow trap density of n-Ge MOS capacitors is found to be much larger than that of p-Ge MOS capacitors, indicating that a higher density of slow traps exists near the conduction band edge. We also examine the effects of post deposition annealing in a variety of ambient gases, including several hydrogen-based species, on the properties of slow traps.

  17. MoS2 Surface Structure Tailoring via Carbonaceous Promoter

    NASA Astrophysics Data System (ADS)

    Shi, Yumeng; Li, Henan; Wong, Jen It; Zhang, Xiaoting; Wang, Ye; Song, Huaihe; Yang, Hui Ying

    2015-05-01

    Atomically thin semiconducting transition-metal dichalcogenides have been attracting lots of attentions, particularly, molybdenum disulfide (MoS2) monolayers show promising applications in field effect transistors, optoelectronics and valleytronics. However, the controlled synthesis of highly crystalline MoS2 remain a challenge especially the systematic approach to manipulate its structure and morphology. Herein, we report a method for controlled synthesis of highly crystalline MoS2 by using chemical vapor deposition method with carbonaceous materials as growth promoter. A uniform and highly crystalline MoS2 monolayer with the grain size close to 40 μm was achieved. Furthermore, we extend the method to the manipulation of MoS2 morphology, flower-shape vertical grown MoS2 layers were obtained on growth promoting substrates. This simple approach allows an easy access of highly crystalline MoS2 layers with morphology tuned in a controllable manner. Moreover, the flower-shape MoS2 grown on graphene oxide film used as an anode material for lithium-ion batteries showed excellent electrochemical performance.

  18. MoS2 Surface Structure Tailoring via Carbonaceous Promoter

    PubMed Central

    Shi, Yumeng; Li, Henan; Wong, Jen It; Zhang, Xiaoting; Wang, Ye; Song, Huaihe; Yang, Hui Ying

    2015-01-01

    Atomically thin semiconducting transition-metal dichalcogenides have been attracting lots of attentions, particularly, molybdenum disulfide (MoS2) monolayers show promising applications in field effect transistors, optoelectronics and valleytronics. However, the controlled synthesis of highly crystalline MoS2 remain a challenge especially the systematic approach to manipulate its structure and morphology. Herein, we report a method for controlled synthesis of highly crystalline MoS2 by using chemical vapor deposition method with carbonaceous materials as growth promoter. A uniform and highly crystalline MoS2 monolayer with the grain size close to 40 μm was achieved. Furthermore, we extend the method to the manipulation of MoS2 morphology, flower-shape vertical grown MoS2 layers were obtained on growth promoting substrates. This simple approach allows an easy access of highly crystalline MoS2 layers with morphology tuned in a controllable manner. Moreover, the flower-shape MoS2 grown on graphene oxide film used as an anode material for lithium-ion batteries showed excellent electrochemical performance. PMID:25994238

  19. Chemical sensing with ultra-thin MoS2

    NASA Astrophysics Data System (ADS)

    Friedman, Adam; Perkins, Keith; Cobas, Enrique; Campbell, Paul; Jernigan, Glenn; Jonker, Berend

    2013-03-01

    Although the majority of focus and excitement in recent years has been on studying the remarkable properties of single atomic-layer graphene, there exists a whole class of materials called dichalcogenides that are relatively easily fabricated in single-crystal mono- or few-layer format. Graphene, being chemically inert, does not lend itself to chemical sensing applications. However, MoS2, a dichalcogenide of recent interest because of its potential for transistor applications, possesses many advantageous properties for chemical sensing. Two primary examples include a sizable bandgap, which is necessary for fabricating transistors with large on/off current ratios, and a chemically reactive surface, which is necessary for easy surface functionalization. In this talk, we discuss our current research effort on MoS2 chemical sensors. We discuss aspects of transistor device fabrication and chemical sensing experiments. We expose MoS2 chemical sensors to a variety of analytes, finding the best response to triethylamine, a nerve gas by product, and explain our results based on a donor-acceptor model. MoS2 sensors are compared to other similar low-dimensional sensors and found to be of comparable quality.

  20. Channel length scaling of MoS2 MOSFETs.

    PubMed

    Liu, Han; Neal, Adam T; Ye, Peide D

    2012-10-23

    In this article, we investigate electrical transport properties in ultrathin body (UTB) MoS(2) two-dimensional (2D) crystals with channel lengths ranging from 2 μm down to 50 nm. We compare the short channel behavior of sets of MOSFETs with various channel thickness, and reveal the superior immunity to short channel effects of MoS(2) transistors. We observe no obvious short channel effects on the device with 100 nm channel length (L(ch)) fabricated on a 5 nm thick MoS(2) 2D crystal even when using 300 nm thick SiO(2) as gate dielectric, and has a current on/off ratio up to ~10(9). We also observe the on-current saturation at short channel devices with continuous scaling due to the carrier velocity saturation. Also, we reveal the performance limit of short channel MoS(2) transistors is dominated by the large contact resistance from the Schottky barrier between Ni and MoS(2) interface, where a fully transparent contact is needed to achieve a high-performance short channel device.

  1. Reducing Sodium Contamination in MOS Devices

    NASA Technical Reports Server (NTRS)

    Dehaye, R. F.; Feltner, W. R.

    1986-01-01

    Method of removing positive ions from oxides in metal-oxide-semiconductor (MOS) transistors and intergrated circuits ensure freedom from contamination by sodium and other mobile positive ions. Electric field applied during oxide growth to push mobile Na + ions to surface. After cooling from growth temperature, field turned off and Na + contaminated surface layer etched away. New method intended to suplement established methods of minimizing ion contamination, such as scrupulous cleanliness in processing, purging with hydrogen chloride to react with and remove contaminants, and growing extra-thick gate oxide, then etching it to remove large portion of contaminants concentrated near surface.

  2. Atomic layer deposition of MoS2 thin films

    NASA Astrophysics Data System (ADS)

    Browning, Robert; Padigi, Prasanna; Solanki, Raj; Tweet, Douglas J.; Schuele, Paul; Evans, David

    2015-03-01

    Atomic layer deposition (ALD) was used to grow thin films of MoS2 over 5 × 5 cm areas of silicon oxide coated silicon wafers. Smooth, uniform, and continuous films were produced over a temperature range of 350 °C-450 °C. The as-grown films were analyzed using x-ray photoelectron spectroscopy, Raman spectroscopy, photoluminescence, and x-ray diffraction. Electrical characteristics of the films were evaluated by fabricating a back gated field effect transistor. These analyses indicate that ALD technique can produce large area, high quality MoS2 films.

  3. Large-area atomically thin MoS2 nanosheets prepared using electrochemical exfoliation.

    PubMed

    Liu, Na; Kim, Paul; Kim, Ji Heon; Ye, Jun Ho; Kim, Sunkook; Lee, Cheol Jin

    2014-07-22

    Molybdenum disulfide (MoS2) is an extremely intriguing material because of its unique electrical and optical properties. The preparation of large-area and high-quality MoS2 nanosheets is an important step in a wide range of applications. This study demonstrates that monolayer and few-layer MoS2 nanosheets can be obtained from electrochemical exfoliation of bulk MoS2 crystals. The lateral size of the exfoliated MoS2 nanosheets is in the 5-50 μm range, which is much larger than that of chemically or liquid-phase exfoliated MoS2 nanosheets. The MoS2 nanosheets undergo low levels of oxidation during electrochemical exfoliation. In addition, microscopic and spectroscopic characterizations indicate that the exfoliated MoS2 nanosheets are of high quality and have an intrinsic structure. A back-gate field-effect transistor was fabricated using an exfoliated monolayer MoS2 nanosheet. The on/off current ratio is over 10(6), and the field-effect mobility is approximately 1.2 cm(2) V(-1) s(-1); these values are comparable to the results for micromechanically exfoliated MoS2 nanosheets. The electrochemical exfoliation method is simple and scalable, and it can be applied to exfoliate other transition metal dichalcogenides.

  4. Tuning the hysteresis voltage in 2D multilayer MoS2 FETs

    NASA Astrophysics Data System (ADS)

    Jiang, Jie; Zheng, Zhouming; Guo, Junjie

    2016-10-01

    The hysteresis tuning is of great significance before the two-dimensional (2D) molybdenum disulfide (MoS2) field-effect transistors (FETs) can be practically used in the next-generation nanoelectronic devices. In this paper, a simple and effective annealing method was developed to tune the hysteresis voltage in 2D MoS2 transistors. It was found that high temperature (175 °C) annealing in air could increase the hysteresis voltage from 8.0 V (original device) to 28.4 V, while a next vacuum annealing would reduce the hysteresis voltage to be only 2.0 V. An energyband diagram model based on electron trapping/detrapping due to oxygen adsorption is proposed to understand the hysteresis mechanism in multilayer MoS2 FET. This simple method for tuning the hysteresis voltage of MoS2 FET can make a significant step toward 2D nanoelectronic device applications.

  5. FETSIM user's manual and example. [D.C. and transient analysis of MOS circuits

    NASA Technical Reports Server (NTRS)

    1978-01-01

    A batch program written in FORTRAN IV which does D.C. and transient analysis of MOS circuits is presented. Circuits employing N-MOS transistors and/or P-MOS transistors in either a bulk technology or an SOS technology, or almost any combination of R-C elements may be analyzed. The program requires as input data the complete circuit topology, device parameters, process parameters, and control parameters. The user can specify initial node conditions and the input pulse format. For example, pulse rise time, fall time, width and time between succeeding pulses are all independently controllable. The program contains a sophisticated mathematical model that can accurately handle either NMOS, P-MOS, Bulk or SOS devices. Sensitivity to process changes is maintained by requiring such process parameters as threshold voltage and doping level as program inputs.

  6. Improved Gate Dielectric Deposition and Enhanced Electrical Stability for Single-Layer MoS2 MOSFET with an AlN Interfacial Layer

    NASA Astrophysics Data System (ADS)

    Qian, Qingkai; Li, Baikui; Hua, Mengyuan; Zhang, Zhaofu; Lan, Feifei; Xu, Yongkuan; Yan, Ruyue; Chen, Kevin J.

    2016-06-01

    Transistors based on MoS2 and other TMDs have been widely studied. The dangling-bond free surface of MoS2 has made the deposition of high-quality high-k dielectrics on MoS2 a challenge. The resulted transistors often suffer from the threshold voltage instability induced by the high density traps near MoS2/dielectric interface or inside the gate dielectric, which is detrimental for the practical applications of MoS2 metal-oxide-semiconductor field-effect transistor (MOSFET). In this work, by using AlN deposited by plasma enhanced atomic layer deposition (PEALD) as an interfacial layer, top-gate dielectrics as thin as 6 nm for single-layer MoS2 transistors are demonstrated. The AlN interfacial layer not only promotes the conformal deposition of high-quality Al2O3 on the dangling-bond free MoS2, but also greatly enhances the electrical stability of the MoS2 transistors. Very small hysteresis (ΔVth) is observed even at large gate biases and high temperatures. The transistor also exhibits a low level of flicker noise, which clearly originates from the Hooge mobility fluctuation instead of the carrier number fluctuation. The observed superior electrical stability of MoS2 transistor is attributed to the low border trap density of the AlN interfacial layer, as well as the small gate leakage and high dielectric strength of AlN/Al2O3 dielectric stack.

  7. Improved Gate Dielectric Deposition and Enhanced Electrical Stability for Single-Layer MoS2 MOSFET with an AlN Interfacial Layer

    PubMed Central

    Qian, Qingkai; Li, Baikui; Hua, Mengyuan; Zhang, Zhaofu; Lan, Feifei; Xu, Yongkuan; Yan, Ruyue; Chen, Kevin J.

    2016-01-01

    Transistors based on MoS2 and other TMDs have been widely studied. The dangling-bond free surface of MoS2 has made the deposition of high-quality high-k dielectrics on MoS2 a challenge. The resulted transistors often suffer from the threshold voltage instability induced by the high density traps near MoS2/dielectric interface or inside the gate dielectric, which is detrimental for the practical applications of MoS2 metal-oxide-semiconductor field-effect transistor (MOSFET). In this work, by using AlN deposited by plasma enhanced atomic layer deposition (PEALD) as an interfacial layer, top-gate dielectrics as thin as 6 nm for single-layer MoS2 transistors are demonstrated. The AlN interfacial layer not only promotes the conformal deposition of high-quality Al2O3 on the dangling-bond free MoS2, but also greatly enhances the electrical stability of the MoS2 transistors. Very small hysteresis (ΔVth) is observed even at large gate biases and high temperatures. The transistor also exhibits a low level of flicker noise, which clearly originates from the Hooge mobility fluctuation instead of the carrier number fluctuation. The observed superior electrical stability of MoS2 transistor is attributed to the low border trap density of the AlN interfacial layer, as well as the small gate leakage and high dielectric strength of AlN/Al2O3 dielectric stack. PMID:27279454

  8. Improved Gate Dielectric Deposition and Enhanced Electrical Stability for Single-Layer MoS2 MOSFET with an AlN Interfacial Layer.

    PubMed

    Qian, Qingkai; Li, Baikui; Hua, Mengyuan; Zhang, Zhaofu; Lan, Feifei; Xu, Yongkuan; Yan, Ruyue; Chen, Kevin J

    2016-01-01

    Transistors based on MoS2 and other TMDs have been widely studied. The dangling-bond free surface of MoS2 has made the deposition of high-quality high-k dielectrics on MoS2 a challenge. The resulted transistors often suffer from the threshold voltage instability induced by the high density traps near MoS2/dielectric interface or inside the gate dielectric, which is detrimental for the practical applications of MoS2 metal-oxide-semiconductor field-effect transistor (MOSFET). In this work, by using AlN deposited by plasma enhanced atomic layer deposition (PEALD) as an interfacial layer, top-gate dielectrics as thin as 6 nm for single-layer MoS2 transistors are demonstrated. The AlN interfacial layer not only promotes the conformal deposition of high-quality Al2O3 on the dangling-bond free MoS2, but also greatly enhances the electrical stability of the MoS2 transistors. Very small hysteresis (ΔVth) is observed even at large gate biases and high temperatures. The transistor also exhibits a low level of flicker noise, which clearly originates from the Hooge mobility fluctuation instead of the carrier number fluctuation. The observed superior electrical stability of MoS2 transistor is attributed to the low border trap density of the AlN interfacial layer, as well as the small gate leakage and high dielectric strength of AlN/Al2O3 dielectric stack.

  9. Improved Gate Dielectric Deposition and Enhanced Electrical Stability for Single-Layer MoS2 MOSFET with an AlN Interfacial Layer.

    PubMed

    Qian, Qingkai; Li, Baikui; Hua, Mengyuan; Zhang, Zhaofu; Lan, Feifei; Xu, Yongkuan; Yan, Ruyue; Chen, Kevin J

    2016-01-01

    Transistors based on MoS2 and other TMDs have been widely studied. The dangling-bond free surface of MoS2 has made the deposition of high-quality high-k dielectrics on MoS2 a challenge. The resulted transistors often suffer from the threshold voltage instability induced by the high density traps near MoS2/dielectric interface or inside the gate dielectric, which is detrimental for the practical applications of MoS2 metal-oxide-semiconductor field-effect transistor (MOSFET). In this work, by using AlN deposited by plasma enhanced atomic layer deposition (PEALD) as an interfacial layer, top-gate dielectrics as thin as 6 nm for single-layer MoS2 transistors are demonstrated. The AlN interfacial layer not only promotes the conformal deposition of high-quality Al2O3 on the dangling-bond free MoS2, but also greatly enhances the electrical stability of the MoS2 transistors. Very small hysteresis (ΔVth) is observed even at large gate biases and high temperatures. The transistor also exhibits a low level of flicker noise, which clearly originates from the Hooge mobility fluctuation instead of the carrier number fluctuation. The observed superior electrical stability of MoS2 transistor is attributed to the low border trap density of the AlN interfacial layer, as well as the small gate leakage and high dielectric strength of AlN/Al2O3 dielectric stack. PMID:27279454

  10. I-V characteristics of MOS FET devices with a variable channel width

    NASA Astrophysics Data System (ADS)

    Vateva, D. D.

    Three variations of the geometry of three channels of an EPROM with a two-transistor memory cell are investigated. The address and memory transistors are connected with a floating gate in series. An analytical model is developed for the MOS transistor, including a function describing variations in the channel width from source to drain, i.e., a theoretical I-V relationship representing an MOS transistor with a rectangularly shaped trapezoidally shaped channel. Expressions are defined for the channel current and width, the electric field, and the drain current, and the measured ratio of currents in a triode region is quantified. The model, applied to laboratory structures with measured characteristics, was accurate to within 13 pct.

  11. Photothermoelectric and photovoltaic effects both present in MoS2

    NASA Astrophysics Data System (ADS)

    Zhang, Youwei; Li, Hui; Wang, Lu; Wang, Haomin; Xie, Xiaomin; Zhang, Shi-Li; Liu, Ran; Qiu, Zhi-Jun

    2015-01-01

    As a finite-energy-bandgap alternative to graphene, semiconducting molybdenum disulfide (MoS2) has recently attracted extensive interest for energy and sensor applications. In particular for broad-spectral photodetectors, multilayer MoS2 is more appealing than its monolayer counterpart. However, little is understood regarding the physics underlying the photoresponse of multilayer MoS2. Here, we employ scanning photocurrent microscopy to identify the nature of photocurrent generated in multilayer MoS2 transistors. The generation and transport of photocurrent in multilayer MoS2 are found to differ from those in other low-dimensional materials that only contribute with either photovoltaic effect (PVE) or photothermoelectric effect (PTE). In multilayer MoS2, the PVE at the MoS2-metal interface dominates in the accumulation regime whereas the hot-carrier-assisted PTE prevails in the depletion regime. Besides, the anomalously large Seebeck coefficient observed in multilayer MoS2, which has also been reported by others, is caused by hot photo-excited carriers that are not in thermal equilibrium with the MoS2 lattice.

  12. Effects of plasma treatment on surface properties of ultrathin layered MoS2

    NASA Astrophysics Data System (ADS)

    Kim, Suhhyun; Choi, Min Sup; Qu, Deshun; Ra, Chang Ho; Liu, Xiaochi; Kim, Minwoo; Song, Young Jae; Jong Yoo, Won

    2016-09-01

    This work investigates the use of oxygen plasma (O2) treatment, applied as an inductively coupled plasma, to control the thickness and work function of a MoS2 layer. Plasma-etched MoS2 exhibited a surface roughness similar to that of the pristine MoS2. The MoS2 field effect transistors fabricated using the plasma-etched MoS2 displayed a higher n-type doping concentration than that of pristine MoS2. The x-ray photoelectron spectroscopy was performed to analyze chemical composition to demonstrate the minimum level of chemical reactions occurred upon plasma treatment. Moreover, Kelvin probe force microscopy measurements were conducted to probe the changes in the work function that could be attributed to the changes in the surface potential. The measured work functions suggest the modification of a band structure and n-doping effect after plasma treatments that depended on the number of MoS2 layers. This study suggests that the O2 plasma can control the layer number of the MoS2 as well as the electronic properties of a MoS2 film.

  13. Selective decoration of Au nanoparticles on monolayer MoS2 single crystals.

    PubMed

    Shi, Yumeng; Huang, Jing-Kai; Jin, Limin; Hsu, Yu-Te; Yu, Siu Fung; Li, Lain-Jong; Yang, Hui Ying

    2013-01-01

    We report a controllable wet method for effective decoration of 2-dimensional (2D) molybdenum disulfide (MoS2) layers with Au nanoparticles (NPs). Au NPs can be selectively formed on the edge sites or defective sites of MoS2 layers. The Au-MoS2 nano-composites are formed by non-covalent bond. The size distribution, morphology and density of the metal nanoparticles can be tuned by changing the defect density in MoS2 layers. Field effect transistors were directly fabricated by placing ion gel gate dielectrics on Au-decorated MoS2 layers without the need to transfer these MoS2 layers to SiO2/Si substrates for bottom gate devices. The ion gel method allows probing the intrinsic electrical properties of the as-grown and Au-decorated MoS2 layers. This study shows that Au NPs impose remarkable p-doping effects to the MoS2 transistors without degrading their electrical characteristics.

  14. Electrical and Optical Characterization of MoS2 with Sulfur Vacancy Passivation by Treatment with Alkanethiol Molecules.

    PubMed

    Cho, Kyungjune; Min, Misook; Kim, Tae-Young; Jeong, Hyunhak; Pak, Jinsu; Kim, Jae-Keun; Jang, Jingon; Yun, Seok Joon; Lee, Young Hee; Hong, Woong-Ki; Lee, Takhee

    2015-08-25

    We investigated the physical properties of molybdenum disulfide (MoS2) atomic crystals with a sulfur vacancy passivation after treatment with alkanethiol molecules including their electrical, Raman, and photoluminescence (PL) characteristics. MoS2, one of the transition metal dichalcogenide materials, is a promising two-dimensional semiconductor material with good physical properties. It is known that sulfur vacancies exist in MoS2, resulting in the n-type behavior of MoS2. The sulfur vacancies on the MoS2 surface tend to form covalent bonds with sulfur-containing groups. In this study, we deposited alkanethiol molecules on MoS2 field effect transistors (FETs) and then characterized the electrical properties of the devices before and after the alkanethiol treatment. We observed that the electrical characteristics of MoS2 FETs dramatically changed after the alkanethiol treatment. We also observed that the Raman and PL spectra of MoS2 films changed after the alkanethiol treatment. These effects are attributed to the thiol (-SH) end groups in alkanethiols bonding at sulfur vacancy sites, thus altering the physical properties of the MoS2. This study will help us better understand the electrical and optical properties of MoS2 and suggest a way of tailoring the properties of MoS2 by passivating a sulfur vacancy with thiol molecules.

  15. Ultrasensitive photodetectors based on monolayer MoS2.

    PubMed

    Lopez-Sanchez, Oriol; Lembke, Dominik; Kayci, Metin; Radenovic, Aleksandra; Kis, Andras

    2013-07-01

    Two-dimensional materials are an emerging class of new materials with a wide range of electrical properties and potential practical applications. Although graphene is the most well-studied two-dimensional material, single layers of other materials, such as insulating BN (ref. 2) and semiconducting MoS2 (refs 3, 4) or WSe2 (refs 5, 6), are gaining increasing attention as promising gate insulators and channel materials for field-effect transistors. Because monolayer MoS2 is a direct-bandgap semiconductor due to quantum-mechanical confinement, it could be suitable for applications in optoelectronic devices where the direct bandgap would allow a high absorption coefficient and efficient electron-hole pair generation under photoexcitation. Here, we demonstrate ultrasensitive monolayer MoS2 phototransistors with improved device mobility and ON current. Our devices show a maximum external photoresponsivity of 880 A W(-1) at a wavelength of 561 nm and a photoresponse in the 400-680 nm range. With recent developments in large-scale production techniques such as liquid-scale exfoliation and chemical vapour deposition-like growth, MoS2 shows important potential for applications in MoS2-based integrated optoelectronic circuits, light sensing, biomedical imaging, video recording and spectroscopy.

  16. Improving crystalline quality of sputtering-deposited MoS2 thin film by postdeposition sulfurization annealing using (t-C4H9)2S2

    NASA Astrophysics Data System (ADS)

    Ishihara, Seiya; Hibino, Yusuke; Sawamoto, Naomi; Suda, Kohei; Ohashi, Takumi; Matsuura, Kentarou; Machida, Hideaki; Ishikawa, Masato; Sudoh, Hiroshi; Wakabayashi, Hitoshi; Ogura, Atsushi

    2016-04-01

    A sputtered MoS2 thin film is a candidate for realizing enhancement-mode MoS2 metal-oxide-semiconductor field-effect transistors (MOSFETs). However, there are some sulfur vacancies in the film, which degrade the device performance. In this study, we performed postdeposition sulfurization annealing (PSA) on a sputtered MoS2 thin film in order to complement sulfur vacancies, and we investigated the fundamental properties of the MoS2 film. As a result, a high-quality crystalline 10-layer MoS2 film with an ideal stoichiometric composition was obtained at a relatively low process temperature (500 °C). The MoS2 film had an indirect bandgap of 1.36 eV and a high Hall mobility compared with the as-deposited sputtered MoS2 film.

  17. Transistor Effect in Improperly Connected Transistors.

    ERIC Educational Resources Information Center

    Luzader, Stephen; Sanchez-Velasco, Eduardo

    1996-01-01

    Discusses the differences between the standard representation and a realistic representation of a transistor. Presents an experiment that helps clarify the explanation of the transistor effect and shows why transistors should be connected properly. (JRH)

  18. Radiation effects on junction field-effect transistors (JFETS), MOSFETs, and bipolar transistors, as related to SSC circuit design

    SciTech Connect

    Kennedy, E.J. Oak Ridge National Lab., TN ); Alley, G.T.; Britton, C.L. Jr. ); Skubic, P.L. ); Gray, B.; Wu, A. )

    1990-01-01

    Some results of radiation effects on selected junction field-effect transistors, MOS field-effect transistors, and bipolar junction transistors are presented. The evaluations include dc parameters, as well as capacitive variations and noise evaluations. The tests are made at the low current and voltage levels (in particular, at currents {le}1 mA) that are essential for the low-power regimes required by SSC circuitry. Detailed noise data are presented both before and after 5-Mrad (gamma) total-dose exposure. SPICE radiation models for three high-frequency bipolar processes are compared for a typical charge-sensitive preamplifier.

  19. Observing the semiconducting band-gap alignment of MoS2 layers of different atomic thicknesses using a MoS2/SiO2/Si heterojunction tunnel diode

    NASA Astrophysics Data System (ADS)

    Nishiguchi, Katsuhiko; Castellanos-Gomez, Andres; Yamaguchi, Hiroshi; Fujiwara, Akira; van der Zant, Herre S. J.; Steele, Gary A.

    2015-08-01

    We demonstrate a tunnel diode composed of a vertical MoS2/SiO2/Si heterostructure. A MoS2 flake consisting four areas of different thicknesses functions as a gate terminal of a silicon field-effect transistor. A thin gate oxide allows tunneling current to flow between the n-type MoS2 layers and p-type Si channel. The tunneling-current characteristics show multiple negative differential resistance features, which we interpret as an indication of different conduction-band alignments of the MoS2 layers of different thicknesses. The presented tunnel device can be also used as a hybrid-heterostructure device combining the advantages of two-dimensional materials with those of silicon transistors.

  20. Strain and structure heterogeneity in MoS2 atomic layers grown by chemical vapour deposition.

    PubMed

    Liu, Zheng; Amani, Matin; Najmaei, Sina; Xu, Quan; Zou, Xiaolong; Zhou, Wu; Yu, Ting; Qiu, Caiyu; Birdwell, A Glen; Crowne, Frank J; Vajtai, Robert; Yakobson, Boris I; Xia, Zhenhai; Dubey, Madan; Ajayan, Pulickel M; Lou, Jun

    2014-11-18

    Monolayer molybdenum disulfide (MoS2) has attracted tremendous attention due to its promising applications in high-performance field-effect transistors, phototransistors, spintronic devices and nonlinear optics. The enhanced photoluminescence effect in monolayer MoS2 was discovered and, as a strong tool, was employed for strain and defect analysis in MoS2. Recently, large-size monolayer MoS2 has been produced by chemical vapour deposition, but has not yet been fully explored. Here we systematically characterize chemical vapour deposition-grown MoS2 by photoluminescence spectroscopy and mapping and demonstrate non-uniform strain in single-crystalline monolayer MoS2 and strain-induced bandgap engineering. We also evaluate the effective strain transferred from polymer substrates to MoS2 by three-dimensional finite element analysis. Furthermore, our work demonstrates that photoluminescence mapping can be used as a non-contact approach for quick identification of grain boundaries in MoS2.

  1. Strain and structure heterogeneity in MoS2 atomic layers grown by chemical vapour deposition

    DOE PAGES

    Liu, Zheng; Amani, Matin; Najmaei, Sina; Xu, Quan; Zou, Xiaolong; Zhou, Wu; Yu, Ting; Qiu, Caiyu; Birdwell, A. Glen; Crowne, Frank J.; et al

    2014-11-18

    Monolayer molybdenum disulfide (MoS2) has attracted tremendous attention due to its promising applications in high-performance field-effect transistors, phototransistors, spintronic devices, and nonlinear optics. The enhanced photoluminescence effect in monolayer MoS2 was discovered and, as a strong tool, was employed for strain and defect analysis in MoS2. Recently, large-size monolayer MoS2 has been produced by chemical vapor deposition but has not yet been fully explored. Here we systematically characterize chemical vapor deposition grown MoS2 by PL spectroscopy and mapping, and demonstrate non-uniform strain in single-crystalline monolayer MoS2 and strain-induced band gap engineering. We also evaluate the effective strain transferred from polymermore » substrates to MoS2 by three-dimensional finite element analysis. In addition, our work demonstrates that PL mapping can be used as a non-contact approach for quick identification of grain boundaries in MoS2.« less

  2. Nonvolatile memory cells based on MoS2/graphene heterostructures.

    PubMed

    Bertolazzi, Simone; Krasnozhon, Daria; Kis, Andras

    2013-04-23

    Memory cells are an important building block of digital electronics. We combine here the unique electronic properties of semiconducting monolayer MoS2 with the high conductivity of graphene to build a 2D heterostructure capable of information storage. MoS2 acts as a channel in an intimate contact with graphene electrodes in a field-effect transistor geometry. Our prototypical all-2D transistor is further integrated with a multilayer graphene charge trapping layer into a device that can be operated as a nonvolatile memory cell. Because of its band gap and 2D nature, monolayer MoS2 is highly sensitive to the presence of charges in the charge trapping layer, resulting in a factor of 10(4) difference between memory program and erase states. The two-dimensional nature of both the contact and the channel can be harnessed for the fabrication of flexible nanoelectronic devices with large-scale integration.

  3. Polarization-dependent photocurrent in MoS2 phototransistor

    NASA Astrophysics Data System (ADS)

    Li, Jiu; Yu, Wentao; Chu, Saisai; Yang, Hong; Shi, Kebin; Gong, Qihuang

    2015-03-01

    Monolayer or few-layer molybdenum disulfide (MoS2) has attracted increasing interests in studying light-induced electronic effect due to its prominent photo-responsivity at visible spectral range, fast photo-switching rate and high channel mobility. However, the atomically thin layers make the interaction between light and matter much weaker than that in bulk state, hampering its application in two-dimensional material optoelectronics. One of recent efforts was to utilize resonantly enhanced localized surface plasmon for boosting light-matter interaction in MoS2 thin layer phototransistor. Randomly deposited metallic nano-particles were previously reported to modify surface of a back-gated MoS2 transistor for increasing light absorption cross-section of the phototransistor. Wavelength-dependent photocurrent enhancement was observed. In this paper, we report on a back-gated multilayer MoS2 field-effect-transistor (FET), whose surface is decorated with oriented gold nanobar array, of which the size of a single nanobar is 60nm:60nm:120nm. With these oriented nanostructures, photocurrent of the MoS2 FET could be successfully manipulated by a linear polarized incident 633nm laser, which fell into the resonance band of nanobar structure. We find that the drain-source current follows cos2θ relationship with respect to the incident polarization angle. We attribute the polarization modulation effect to the localized enhancement nature of gold nanobar layer, where the plasmon enhancement occurs only when the polarization of incident laser parallels to the longitudinal axis of nanobars and when the incident wavelength matches the resonance absorption of nanobars simultaneously. Our results indicate a promising application of polarization-dependent plasmonic manipulation in two-dimension semiconductor materials and devices.

  4. Single-layer MoS2 electronics.

    PubMed

    Lembke, Dominik; Bertolazzi, Simone; Kis, Andras

    2015-01-20

    CONSPECTUS: Atomic crystals of two-dimensional materials consisting of single sheets extracted from layered materials are gaining increasing attention. The most well-known material from this group is graphene, a single layer of graphite that can be extracted from the bulk material or grown on a suitable substrate. Its discovery has given rise to intense research effort culminating in the 2010 Nobel Prize in physics awarded to Andre Geim and Konstantin Novoselov. Graphene however represents only the proverbial tip of the iceberg, and increasing attention of researchers is now turning towards the veritable zoo of so-called "other 2D materials". They have properties complementary to graphene, which in its pristine form lacks a bandgap: MoS2, for example, is a semiconductor, while NbSe2 is a superconductor. They could hold the key to important practical applications and new scientific discoveries in the two-dimensional limit. This family of materials has been studied since the 1960s, but most of the research focused on their tribological applications: MoS2 is best known today as a high-performance dry lubricant for ultrahigh-vacuum applications and in car engines. The realization that single layers of MoS2 and related materials could also be used in functional electronic devices where they could offer advantages compared with silicon or graphene created a renewed interest in these materials. MoS2 is currently gaining the most attention because the material is easily available in the form of a mineral, molybdenite, but other 2D transition metal dichalcogenide (TMD) semiconductors are expected to have qualitatively similar properties. In this Account, we describe recent progress in the area of single-layer MoS2-based devices for electronic circuits. We will start with MoS2 transistors, which showed for the first time that devices based on MoS2 and related TMDs could have electrical properties on the same level as other, more established semiconducting materials. This

  5. Large-area MoS2 grown using H2S as the sulphur source

    NASA Astrophysics Data System (ADS)

    Dumcenco, Dumitru; Ovchinnikov, Dmitry; Lopez Sanchez, Oriol; Gillet, Philippe; Alexander, Duncan T. L.; Lazar, Sorin; Radenovic, Aleksandra; Kis, Andras

    2015-12-01

    We report on the growth of molybdenum disulphide (MoS2) using H2S as a gas-phase sulfur precursor that allows controlling the domain growth direction of domains in both vertical (perpendicular to the substrate plane) and horizontal (within the substrate plane), depending on the H2S:H2 ratio in the reaction gas mixture and temperature at which they are introduced during growth. Optical and atomic force microscopy measurements on horizontal MoS2 demonstrate the formation of monolayer triangular-shape domains that merge into a continuous film. Scanning transmission electron microscopy of monolayer MoS2 shows a regular atomic structure with a hexagonal symmetry. Raman and photoluminescence spectra confirm the monolayer thickness of the material. Field-effect transistors fabricated on MoS2 domains that are transferred onto Si/SiO2 substrates show a mobility similar to previously reported exfoliated and chemical vapor deposition-grown materials.

  6. Chemical doping of MoS2 multilayer by p-toluene sulfonic acid

    NASA Astrophysics Data System (ADS)

    Andleeb, Shaista; Singh, Arun Kumar; Eom, Jonghwa

    2015-06-01

    We report the tailoring of the electrical properties of mechanically exfoliated multilayer (ML) molybdenum disulfide (MoS2) by chemical doping. Electrical charge transport and Raman spectroscopy measurements revealed that the p-toluene sulfonic acid (PTSA) imposes n-doping in ML MoS2. The shift of threshold voltage for ML MoS2 transistor was analyzed as a function of reaction time. The threshold voltage shifted toward more negative gate voltages with increasing reaction time, which indicates an n-type doping effect. The shift of the Raman peak positions was also analyzed as a function of reaction time. PTSA treatment improved the field-effect mobility by a factor of ~4 without degrading the electrical characteristics of MoS2 devices.

  7. Switching Transistor

    NASA Astrophysics Data System (ADS)

    1981-01-01

    Westinghouse Electric Corporation's D60T transistors are used primarily as switching devices for controlling high power in electrical circuits. It enables reduction in the number and size of circuit components and promotes more efficient use of energy. Wide range of application from a popcorn popper to a radio frequency generator for solar cell production.

  8. Experimental investigation of a double-diffused MOS structure

    NASA Technical Reports Server (NTRS)

    Lin, H. C.; Halsor, J. L.

    1976-01-01

    Self-aligned polysilicon gate technology was applied to double-diffused MOS (DMOS) construction in a manner that retains processing simplicity and effectively eliminates parasitic overlap capacitance because of the self-aligning feature. Depletion mode load devices with the same dimensions as the DMOS transistors were integrated. The ratioless feature results in smaller dimension load devices, allowing for higher density integration with no increase in the processing complexity of standard MOS technology. A number of inverters connected as ring oscillators were used as a vehicle to test the performance and to verify the anticipated benefits. The propagation time-power dissipation product and process related parameters were measured and evaluated. This report includes (1) details of the process; (2) test data and design details for the DMOS transistor, the load device, the inverter, the ring oscillator, and a shift register with a novel tapered geometry for the output stages; and (3) an analytical treatment of the effect of the distributed silicon gate resistance and capacitance on the speed of DMOS transistors.

  9. Ferroelectric Field-Effect Transistor Differential Amplifier Circuit Analysis

    NASA Technical Reports Server (NTRS)

    Phillips, Thomas A.; MacLeod, Todd C.; Ho, Fat D.

    2008-01-01

    There has been considerable research investigating the Ferroelectric Field-Effect Transistor (FeFET) in memory circuits. However, very little research has been performed in applying the FeFET to analog circuits. This paper investigates the use of FeFETs in a common analog circuit, the differential amplifier. The two input Metal-Oxide-Semiconductor (MOS) transistors in a general MOS differential amplifier circuit are replaced with FeFETs. Resistors are used in place of the other three MOS transistors. The FeFET model used in the analysis has been previously reported and was based on experimental device data. Because of the FeFET hysteresis, the FeFET differential amplifier has four different operating modes depending on whether the FeFETs are positively or negatively polarized. The FeFET differential amplifier operation in the different modes was analyzed by calculating the amplifier voltage transfer and gain characteristics shown in figures 2 through 5. Comparisons were made between the FeFET differential amplifier and the standard MOS differential amplifier. Possible applications and benefits of the FeFET differential amplifier are discussed.

  10. Few-layer molybdenum disulfide transistors and circuits for high-speed flexible electronics

    PubMed Central

    Cheng, Rui; Jiang, Shan; Chen, Yu; Liu, Yuan; Weiss, Nathan; Cheng, Hung-Chieh; Wu, Hao; Huang, Yu; Duan, Xiangfeng

    2014-01-01

    Two-dimensional layered materials, such as molybdenum disulfide, are emerging as an exciting material system for future electronics due to their unique electronic properties and atomically thin geometry. Here we report a systematic investigation of MoS2 transistors with optimized contact and device geometry, to achieve self-aligned devices with performance including an intrinsic gain over 30, an intrinsic cut-off frequency fT up to 42 GHz and a maximum oscillation frequency fMAX up to 50 GHz, exceeding the reported values for MoS2 transistors to date (fT ~ 0.9 GHz, fMAX ~ 1 GHz). Our results show that logic inverters or radio frequency amplifiers can be formed by integrating multiple MoS2 transistors on quartz or flexible substrates with voltage gain in the gigahertz regime. This study demonstrates the potential of two-dimensional layered semiconductors for high-speed flexible electronics. PMID:25295573

  11. Fast and slow border traps in MOS devices

    SciTech Connect

    Fleetwood, D.M.

    1995-09-01

    Convergent lines of evidence are reviewed which show that near-interfacial oxide traps (border traps) that exchange charge with the Si can strongly affect the performance, radiation response, and long-term reliability of MOS devices. Observable effects of border traps include capacitance-voltage (C-V) hysteresis, enhanced 1/f noise, compensation of trapped holes, and increased thermally stimulated current in MOS capacitors. Effects of fast (switching times between {approximately} 10{sup {minus}6} and 1 s) and slow (switching times greater than {approximately} 1 s) border traps have been resolved via a dual-transistor technique. In conjunction with studies of MOS electrical response, electron paramagnetic resonance and spin dependent recombination studies suggest that different types of E{prime} defects (trivalent Si centers in SiO{sub 2} associated with O vacancies) can function as border traps in MOS devices exposed to ionizing radiation or high-field stress. Hydrogen-related centers may also be border traps.

  12. Extraordinary attributes of 2-dimensional MoS2 nanosheets

    NASA Astrophysics Data System (ADS)

    Rao, C. N. R.; Maitra, Urmimala; Waghmare, Umesh V.

    2014-08-01

    The discovery of the amazing properties of graphene has stimulated exploration of single- and few-layer structures of layered inorganic materials. Of all the inorganic 2D nanosheet structures, those of MoS2 have attracted great attention because of their novel properties such as the presence of a direct bandgap, good field-effect transistor characteristics, large spin-orbit splitting, intense photoluminescence, catalytic properties, magnetism, superconductivity, ferroelectricity and several other properties with potential applications in electronics, optoelectronics, energy devices and spintronics. MoS2 nanosheets have been used in lithium batteries, supercapacitors and to generate hydrogen. Highlights of the impressive properties of MoS2 nanosheets, along with their structural and spectroscopic features are presented in this Letter. MoS2 typifies the family of metal dichalcogenides such as MoSe2 and WS2 and there is much to be done on nanosheets of these materials. Linus Pauling would have been pleased to see how molybdenite whose structure he studied in 1923 has become so important today.

  13. Shielded silicon gate complementary MOS integrated circuit.

    NASA Technical Reports Server (NTRS)

    Lin, H. C.; Halsor, J. L.; Hayes, P. J.

    1972-01-01

    An electrostatic shield for complementary MOS integrated circuits was developed to minimize the adverse effects of stray electric fields created by the potentials in the metal interconnections. The process is compatible with silicon gate technology. N-doped polycrystalline silicon was used for all the gates and the shield. The effectiveness of the shield was demonstrated by constructing a special field plate over certain transistors. The threshold voltages obtained on an oriented silicon substrate ranged from 1.5 to 3 V for either channel. Integrated inverters performed satisfactorily from 3 to 15 V, limited at the low end by the threshold voltages and at the high end by the drain breakdown voltage of the n-channel transistors. The stability of the new structure with an n-doped silicon gate as measured by the shift in C-V curve under 200 C plus or minus 20 V temperature-bias conditions was better than conventional aluminum gate or p-doped silicon gate devices, presumably due to the doping of gate oxide with phosphorous.

  14. Abnormal electrical characteristics of multi-layered MoS2 FETs attributed to bulk traps

    NASA Astrophysics Data System (ADS)

    Kim, Choong-Ki; Yu, Chan Hak; Hur, Jae; Bae, Hagyoul; Jeon, Seung-Bae; Park, Hamin; Kim, Yong Min; Choi, Kyung Cheol; Choi, Yang-Kyu; Choi, Sung-Yool

    2016-03-01

    Multiple layers of MoS2 are used as channel materials in a type of field-effect transistor (FET). It was found that the hysteresis in transfer curves and low-frequency noise (LFN) characteristics are varied by the number of layers in MoS2 due to the different influences of bulk traps. The LFN characteristics of a FET composed of a ‘bi-layer’ MoS2 channel, which was passivated with an atomic-layer-deposited (ALD) Al2O3 layer, follow the conventional carrier number fluctuation (CNF) model. However, FETs consisting of multi-layered MoS2 channels (4, 7, 9, and 18 layers) show abnormal LFN characteristics, which substantially deviate from well-established 1/f noise models such as the CNF and Hooge’s mobility fluctuation models. The bulk traps inside the MoS2 layers are the origin of the abnormal LFN characteristics and the large hysteresis of FETs with multi-layered MoS2 is due to its randomly embedded bulk traps. Secondary ion mass spectrometry (SIMS) confirms the existence of oxygen species that induce the electrical bulk trap in the MoS2 layers.

  15. Electron-hole transport and photovoltaic effect in gated MoS2 Schottky junctions.

    PubMed

    Fontana, Marcio; Deppe, Tristan; Boyd, Anthony K; Rinzan, Mohamed; Liu, Amy Y; Paranjape, Makarand; Barbara, Paola

    2013-01-01

    Semiconducting molybdenum disulfphide has emerged as an attractive material for novel nanoscale optoelectronic devices due to its reduced dimensionality and large direct bandgap. Since optoelectronic devices require electron-hole generation/recombination, it is important to be able to fabricate ambipolar transistors to investigate charge transport both in the conduction band and in the valence band. Although n-type transistor operation for single-layer and few-layer MoS2 with gold source and drain contacts was recently demonstrated, transport in the valence band has been elusive for solid-state devices. Here we show that a multi-layer MoS2 channel can be hole-doped by palladium contacts, yielding MoS2 p-type transistors. When two different materials are used for the source and drain contacts, for example hole-doping Pd and electron-doping Au, the Schottky junctions formed at the MoS2 contacts produce a clear photovoltaic effect.

  16. Superconducting transistor

    DOEpatents

    Gray, Kenneth E.

    1979-01-01

    A superconducting transistor is formed by disposing three thin films of superconducting material in a planar parallel arrangement and insulating the films from each other by layers of insulating oxides to form two tunnel junctions. One junction is biased above twice the superconducting energy gap and the other is biased at less than twice the superconducting energy gap. Injection of quasiparticles into the center film by one junction provides a current gain in the second junction.

  17. Characterization of degradation processes in MOS VLSI structures

    NASA Astrophysics Data System (ADS)

    Brozek, Tomasz; Jakubowski, Andrzej; Majkusiak, Bogdan

    1992-08-01

    The detailed investigations of degradation processes, their characterization and understanding of mechanisms responsible for degradation is of great technological interest, both from the fabrication point of view, and as a long-term reliability concern. Some of the effects usually need investigation in the completed MOS transistor structure (hot carrier degradation, threshold voltage, and channel mobility deterioration), but others should be studied with the special test structures so that effects can be investigated independently (electromigration, radiation effects, oxide wear-out). The paper presents a review of problems related to reliability of VLSI ICs, degradation processes, and their characterization.

  18. High frequency integrated MOS filters

    NASA Technical Reports Server (NTRS)

    Peterson, C.

    1990-01-01

    Several techniques exist for implementing integrated MOS filters. These techniques fit into the general categories of sampled and tuned continuous-time filters. Advantages and limitations of each approach are discussed. This paper focuses primarily on the high frequency capabilities of MOS integrated filters.

  19. Switching mechanism in single-layer molybdenum disulfide transistors: an insight into current flow across Schottky barriers.

    PubMed

    Liu, Han; Si, Mengwei; Deng, Yexin; Neal, Adam T; Du, Yuchen; Najmaei, Sina; Ajayan, Pulickel M; Lou, Jun; Ye, Peide D

    2014-01-28

    In this article, we study the properties of metal contacts to single-layer molybdenum disulfide (MoS2) crystals, revealing the nature of switching mechanism in MoS2 transistors. On investigating transistor behavior as contact length changes, we find that the contact resistivity for metal/MoS2 junctions is defined by contact area instead of contact width. The minimum gate dependent transfer length is ∼0.63 μm in the on-state for metal (Ti) contacted single-layer MoS2. These results reveal that MoS2 transistors are Schottky barrier transistors, where the on/off states are switched by the tuning of the Schottky barriers at contacts. The effective barrier heights for source and drain barriers are primarily controlled by gate and drain biases, respectively. We discuss the drain induced barrier narrowing effect for short channel devices, which may reduce the influence of large contact resistance for MoS2 Schottky barrier transistors at the channel length scaling limit.

  20. Direct growth of single- and few-layer MoS2 on h-BN by CVD method

    NASA Astrophysics Data System (ADS)

    Yan, Aiming; Velasco, Jairo, Jr.; Kahn, Salman; Watanabe, Kenji; Taniguchi, Takashi; Wang, Feng; Crommie, Michael; Zettl, Alex

    As a promising candidate for the next-generation electronics, large-scale single- and few-layer molybdenum disulfide (MoS2) grown by CVD method is an important advancement towards technological implementation of this material. However, the choice of substrate can significantly affect the performance of MoS2 based devices. An attractive insulating substrate or mate for MoS2 (and related materials such as graphene) is hexagonal boron nitride (h-BN). Stacked heterostructures of MoS2 and h-BN have been produced by manual transfer methods, but a more efficient and scalable assembly method is needed. Here we demonstrate the direct growth of single- and few-layer MoS2 on h-BN by chemical vapor deposition (CVD) method. The growth mechanisms for single- and few-layer samples are found to be distinct, and for single-layer samples low relative rotation angles (<5°) between the MoS2 and h-BN lattices prevail. In addition, MoS2 directly grown on h-BN maintains its intrinsic 1.89 eV bandgap. Our CVD synthesis method presents a viable path towards high-quality MoS2 based field effect transistors in a controllable and scalable fashion. Acknowledgement: the U.S. Department of Energy under Contract DE-AC02-05CH11231; NSF Grant DMR-1206512.

  1. Theoretical and experimental investigation of vacancy-based doping of monolayer MoS2 on oxide

    NASA Astrophysics Data System (ADS)

    Valsaraj, Amithraj; Chang, Jiwon; Rai, Amritesh; Register, Leonard F.; Banerjee, Sanjay K.

    2015-12-01

    Monolayer (ML) transition metal dichalcogenides are novel, gapped two-dimensional materials with unique electrical and optical properties. Toward device applications, we consider MoS2 layers on dielectrics, in particular in this work, the effect of vacancies on the electronic structure. In density-functional based simulations, we consider the effects of near-interface O vacancies in the oxide slab, and Mo or S vacancies in the MoS2 layer. Band structures and atom-projected densities of states for each system and with differing oxide terminations were calculated, as well as those for the defect-free MoS2-dielectrics system and for isolated dielectric layers for reference. Among our results, we find that with O vacancies, both the Hf-terminated HfO2-MoS2 system, and the O-terminated and H-passivated Al2O3-MoS2 systems appear metallic due to doping of the oxide slab followed by electron transfer into the MoS2, in manner analogous to modulation doping. The n-type doping of ML MoS2 by high-k oxides with oxygen vacancies then is experimentally demonstrated by electrically and spectroscopically characterizing back-gated ML MoS2 field effect transistors encapsulated by oxygen deficient alumina and hafnia.

  2. High efficiency DC-DC converter using GaN transistors

    NASA Astrophysics Data System (ADS)

    Tómaş, Cosmin-Andrei; Grecu, Cristian; Pantazicǎ, Mihaela; Marghescu, Ion

    2015-02-01

    The paper presents a new high-efficiency power switching supply using the Gallium Nitride (GaN) technology. There are compared two solutions, the first using standard MOS transistors and the second using the new GaN transistor. The actual green technologies for obtaining the maximum energy and minimum losses have pushed the semiconductor industry into a continuous research regarding high power and high frequency devices, having uses in both digital communications and switching power supplies.

  3. Electrical transport properties of metal and graphene contacts to MoS2

    NASA Astrophysics Data System (ADS)

    Luo, Yunqiu (Kelly); Wen, Hua; Zhu, Tiancong

    2014-03-01

    Two-dimensional crystals are an exciting class of materials for novel physics and nanoelectronics. MoS2 and related transition metal dichalcogenides have received tremendous interest due to its native band gap and strong spin orbit coupling. Unlike graphene, the presence of the band gap leads to transistors with high on-off ratios. One important issue is the electrical properties of the contacts to the MoS2. Recent studies have shown the presence of a Schottky barrier and its dependence on the metal workfunction, back gate voltage, and interfacial oxide barriers. In this work, we investigate the interfacial properties of metal to MoS2 contact and graphene to MoS2 contact by studying the junction's Schottky barrier formation and bias dependence. We utilize a polymer based transfer method to precisely position exfoliated graphene flakes onto exfoliated MoS2 flakes. We intensively study various junction combination between monolayer/few-layer graphene and monolayer/few-layer MoS2. Dependence on temperature and back gate will be discussed.

  4. Growth of wafer-scale MoS2 monolayer by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Tao, Junguang; Chai, Jianwei; Lu, Xin; Wong, Lai Mun; Wong, Ten It; Pan, Jisheng; Xiong, Qihua; Chi, Dongzhi; Wang, Shijie

    2015-01-01

    The two-dimensional layer of molybdenum disulfide (MoS2) exhibits promising prospects in the applications of optoelectronics and valleytronics. Herein, we report a successful new process for synthesizing wafer-scale MoS2 atomic layers on diverse substrates via magnetron sputtering. Spectroscopic and microscopic results reveal that these synthesized MoS2 layers are highly homogeneous and crystallized; moreover, uniform monolayers at wafer scale can be achieved. Raman and photoluminescence spectroscopy indicate comparable optical qualities of these as-grown MoS2 with other methods. The transistors composed of the MoS2 film exhibit p-type performance with an on/off current ratio of ~103 and hole mobility of up to ~12.2 cm2 V-1 s-1. The strategy reported herein paves new ways towards the large scale growth of various two-dimensional semiconductors with the feasibility of controllable doping to realize desired p- or n-type devices.The two-dimensional layer of molybdenum disulfide (MoS2) exhibits promising prospects in the applications of optoelectronics and valleytronics. Herein, we report a successful new process for synthesizing wafer-scale MoS2 atomic layers on diverse substrates via magnetron sputtering. Spectroscopic and microscopic results reveal that these synthesized MoS2 layers are highly homogeneous and crystallized; moreover, uniform monolayers at wafer scale can be achieved. Raman and photoluminescence spectroscopy indicate comparable optical qualities of these as-grown MoS2 with other methods. The transistors composed of the MoS2 film exhibit p-type performance with an on/off current ratio of ~103 and hole mobility of up to ~12.2 cm2 V-1 s-1. The strategy reported herein paves new ways towards the large scale growth of various two-dimensional semiconductors with the feasibility of controllable doping to realize desired p- or n-type devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06411a

  5. Band Structure and Effective Mass in Monolayer MoS2.

    PubMed

    Wu, Ming-Ting; Fan, Jun-Wei; Chen, Kuan-Ting; Chang, Shu-Tong; Lin, Chung-Yi

    2015-11-01

    Monolayer transition-metal dichalcogenide is a very promising two-dimensional material for future transistor technology. Monolayer molybdenum disulfide (MoS2), owing to the unique electronic properties of its atomically thin two-dimensional layered structure, can be made into a high-performance metal-oxide-semiconductor field-effect transistor, or MOSFET. In this work, we focus on band structure and carrier mobility calculations for MoS2. We use the tight-binding method to calculate the band structure, including a consideration of the linear combination of different atomic orbitals, the interaction of neighboring atoms, and spin-orbit coupling for different tight-binding matrices. With information about the band structure, we can obtain the density of states, the effective mass, and other physical quantities. Carrier mobility using the Kubo-Greenwood formula is calculated based on the tight-binding band structure. PMID:26726660

  6. Enhancement of field-effect mobility in molybdenum-disulfide transistor through the treatment of low-power oxygen plasma

    NASA Astrophysics Data System (ADS)

    Chen, Kuan-Chao; Wu, Chong-Rong; Chang, Xiang-Rui; Chang, Shu-Wei; Lee, Si-Chen; Lin, Shih-Yen

    2016-09-01

    We experimentally demonstrate that the treatment with low-power oxygen plasma can raise the field-effect mobility in molybdenum-sulfide (MoS2) transistors from 0.01 to 9.6 cm2 V-1 s-1, which is an increment of about three orders of magnitude. The decrease in threshold voltage and the increase in the drain current of the devices indicate that the electron density increases significantly after the mild plasma treatment. The emergence of Mo-O characteristics but the suppression of Mo-S features on the X-ray photoelectron spectrum of the plasma-treated sample suggests that a portion of the MoS2 film becomes conductive molybdenum oxide. This transformation may considerably upgrade the performance of MoS2 transistors.

  7. Electrical Transport Properties of Polymorphic MoS2.

    PubMed

    Kim, Jun Suk; Kim, Jaesu; Zhao, Jiong; Kim, Sungho; Lee, Jin Hee; Jin, Youngjo; Choi, Homin; Moon, Byoung Hee; Bae, Jung Jun; Lee, Young Hee; Lim, Seong Chu

    2016-08-23

    The engineering of polymorphs in two-dimensional layered materials has recently attracted significant interest. Although the semiconducting (2H) and metallic (1T) phases are known to be stable in thin-film MoTe2, semiconducting 2H-MoS2 is locally converted into metallic 1T-MoS2 through chemical lithiation. In this paper, we describe the observation of the 2H, 1T, and 1T' phases coexisting in Li-treated MoS2, which result in unusual transport phenomena. Although multiphase MoS2 shows no transistor-gating response, the channel resistance decreases in proportion to the temperature, similar to the behavior of a typical semiconductor. Transmission electron microscopy images clearly show that the 1T and 1T' phases are randomly distributed and intervened with 2H-MoS2, which is referred to as the 1T and 1T' puddling phenomenon. The resistance curve fits well with 2D-variable range-hopping transport behavior, where electrons hop over 1T domains that are bounded by semiconducting 2H phases. However, near 30 K, electrons hop over charge puddles. The large temperature coefficient of resistance (TCR) of multiphase MoS2, -2.0 × 10(-2) K(-1) at 300 K, allows for efficient IR detection at room temperature by means of the photothermal effect. PMID:27399325

  8. Electrical Transport Properties of Polymorphic MoS2.

    PubMed

    Kim, Jun Suk; Kim, Jaesu; Zhao, Jiong; Kim, Sungho; Lee, Jin Hee; Jin, Youngjo; Choi, Homin; Moon, Byoung Hee; Bae, Jung Jun; Lee, Young Hee; Lim, Seong Chu

    2016-08-23

    The engineering of polymorphs in two-dimensional layered materials has recently attracted significant interest. Although the semiconducting (2H) and metallic (1T) phases are known to be stable in thin-film MoTe2, semiconducting 2H-MoS2 is locally converted into metallic 1T-MoS2 through chemical lithiation. In this paper, we describe the observation of the 2H, 1T, and 1T' phases coexisting in Li-treated MoS2, which result in unusual transport phenomena. Although multiphase MoS2 shows no transistor-gating response, the channel resistance decreases in proportion to the temperature, similar to the behavior of a typical semiconductor. Transmission electron microscopy images clearly show that the 1T and 1T' phases are randomly distributed and intervened with 2H-MoS2, which is referred to as the 1T and 1T' puddling phenomenon. The resistance curve fits well with 2D-variable range-hopping transport behavior, where electrons hop over 1T domains that are bounded by semiconducting 2H phases. However, near 30 K, electrons hop over charge puddles. The large temperature coefficient of resistance (TCR) of multiphase MoS2, -2.0 × 10(-2) K(-1) at 300 K, allows for efficient IR detection at room temperature by means of the photothermal effect.

  9. Memristive Phenomena in Polycrystalline Single Layer MoS2

    NASA Astrophysics Data System (ADS)

    Sangwan, Vinod; Jariwala, Deep; Kim, In-Soo; Chen, Kan-Sheng; Marks, Tobin; Lauhon, Lincoln; Hersam, Mark; Hersam Laboratory Team

    Recently, a new class of layered two-dimensional semiconductors has shown promise for various electronic applications. In particular, single layer transition metal dichalcogenides (e.g. MoS2) present a host of attractive features such as high electrical conductivity, tunable band-gap, and strong light-matter interaction. However, available growth methods produce large-area polycrystalline films with grain-boundaries and point defects that can be detrimental in conventional electronic devices. In contrast, we have developed unconventional device structures that exploit these defects for useful electronic functions. In particular, we observe grain-boundary mediated memristive phenomena in single layer MoS2 transistors. Memristor current-voltage characteristics depend strongly on the topology of grain-boundaries in MoS2. A grain boundary directly connecting metal electrodes produces thermally assisted switching with dynamic negative differential resistance, whereas a grain boundary bisecting the channel shows non-filamentary soft-switching. In addition, devices with intersecting grain boundaries in the channel show bipolar resistive switching with high on/off ratios up to ~103. Furthermore, the gate electrode in the field-effect geometry can be used to control the absolute resistance of the on and off states. Complementary electrostatic force microscopy, photoluminescence, and Raman microscopy reveal the role of sulfur vacancies in the switching mechanism.

  10. Memristive Phenomena in Polycrystalline Single Layer MoS2

    NASA Astrophysics Data System (ADS)

    Sangwan, Vinod; Jariwala, Deep; Kim, In-Soo; Chen, Kan-Sheng; Marks, Tobin; Lauhon, Lincoln; Hersam, Mark; Hersam Laboratory Team

    Recently, a new class of layered two-dimensional semiconductors has shown promise for various electronic applications. In particular, ultrathin transition metal dichalcogenides (e.g. MoS2) present a host of attractive features such as high carrier mobility and tunable band-gap. However, available growth methods produce polycrystalline films with grain-boundaries and point defects that can be detrimental in conventional electronic devices. In contrast, we have developed unconventional device structures that exploit these defects for useful electronic functions. In particular, we observe grain-boundary mediated memristive phenomena in single layer MoS2 transistors. Memristor current-voltage characteristics depend strongly on the topology of grain-boundaries in MoS2. A grain boundary directly connecting metal electrodes produces thermally assisted switching with dynamic negative differential resistance, whereas a grain boundary bisecting the channel shows non-filamentary soft-switching. In addition, devices with intersecting grain boundaries in the channel show bipolar resistive switching with high on/off ratios up to ~103. Furthermore, the gate electrode in the field-effect geometry can be used to control the absolute resistance of the on and off states. Correlated electrostatic force microscopy, photoluminescence, and Raman microscopy reveal the role of sulfur vacancies in the switching mechanism. This abstract is replacing MAR16-2015-004166 that had exceeded the character limit.

  11. Total Ionizing Dose Effects in MOS Oxides and Devices

    NASA Technical Reports Server (NTRS)

    Oldham, Timothy R.; McLean, F. B.

    2003-01-01

    The development of military and space electronics technology has traditionally been heavily influenced by the commercial semiconductor industry. The development of MOS technology, and particularly CMOS technology, as dominant commercial technologies has occurred entirely within the lifetime of the NSREC. For this reason, it is not surprising that the study of radiation interactions with MOS materials, devices and circuits has been a major theme of this conference for most of its history. The basic radiation problem in a MOS transistor is illustrated. The application of an appropriate gate voltage causes a conducting channel to form between the source and drain, so that current flows when the device is turned on. In Fig. lb, the effect of ionizing radiation is illustrated. Radiation-induced trapped charge has built up in the gate oxide, which causes a shift in the threshold voltage (that is, a change in the voltage which must be applied to turn the device on). If this shift is large enough, the device cannot be turned off, even at zero volts applied, and the device is said to have failed by going depletion mode.

  12. Analysis of the influence of MOS device geometry on predicted SEU cross sections

    SciTech Connect

    Warren, K.; Massengill, L.; Schrimpf, R.; Barnaby, H.

    1999-12-01

    An investigation into the single-event sensitive area geometry of a body-tied-to-source (BTS) SOI nMOS transistor has been performed through a novel simulation technique. Results are presented which demonstrate the influence of spatial variations in charge collection efficiency on the shape of the predicted upset cross section curve. Observations are made on a technique for inferring sensitive area or intra-cell collection efficiencies from cross section data.

  13. Experimental investigation of a shielded complementary Metal-Oxide Semiconductor (MOS) structure

    NASA Technical Reports Server (NTRS)

    Lin, H. C.; Halsor, J. L.

    1974-01-01

    A shielded integrated complimentary MOS transistor structure is described which is used to prevent field inversion in the region not occupied by the gates and which permits the use of a thinner field oxide, reduces the chip area, and has provision for simplified multilayer connections. The structure is used in the design of a static shift register and results in a 20% reduction in area.

  14. Large-area few-layer MoS2 deposited by sputtering

    NASA Astrophysics Data System (ADS)

    Huang, Jyun-Hong; Chen, Hsing-Hung; Liu, Pang-Shiuan; Lu, Li-Syuan; Wu, Chien-Ting; Chou, Cheng-Tung; Lee, Yao-Jen; Li, Lain-Jong; Chang, Wen-Hao; Hou, Tuo-Hung

    2016-06-01

    Direct magnetron sputtering of transition metal dichalcogenide targets is proposed as a new approach for depositing large-area two-dimensional layered materials. Bilayer to few-layer MoS2 deposited by magnetron sputtering followed by post-deposition annealing shows superior area scalability over 20 cm2 and layer-by-layer controllability. High crystallinity of layered MoS2 was confirmed by Raman, photo-luminescence, and transmission electron microscopy analysis. The sputtering temperature and annealing ambience were found to play an important role in the film quality. The top-gate field-effect transistor by using the layered MoS2 channel shows typical n-type characteristics with a current on/off ratio of approximately 104. The relatively low mobility is attributed to the small grain size of 0.1-1 μm with a trap charge density in grain boundaries of the order of 1013 cm-2.

  15. Study of interface state trap density on characteristics of MOS-HEMT

    NASA Astrophysics Data System (ADS)

    Tseng, Ming-Chun; Hung, Ming-Hsien; Wuu, Dong-Sing; Horng, Ray-Hua

    2015-03-01

    In this study, the effects of chemical treatment on the properties of MOS capacitors and metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) were studied. The structure consist of Al2O3/u-GaN/AlN buffer/ Si substrate and Al2O3 (10 nm)/u-AlGaN (25 nm)/u-GaN (2μm)/AlN buffer/Si substrate for MOS capacitor and MOS-HEMT device, respectively. There are four chemical treatment recipes, which consist of organic solvents, oxygen plasma, BCl3 plasma, dilute acidic solvent, hydrofluoric acid and RCA-like clean process to remove the metal ions, organic contamination and native oxide. Four different chemical treatment recipes treated the surface of u-GaN before Al2O3 was grown on the treated surface to reduce the interface state trap densities (Dit). The Dit value was calculated from measurement of C-V curve with 1M Hz frequency. The formation of interface state trap of u-GaN surface is modified by different chemical solution of varied chemical treatment recipe, which further influence the breakdown voltage (Vbk), on-resistance (Ron), threshold voltage (Vth) and drain current (Id) of MOS-HEMT. The Vth of MOS-HEMT with organic solvents clean treatment is -11.00V. The MOS-HEMT after BCl3 plasma and organic solvents clean treatment shows the lowest Vth of -9.55V. The electronic characteristics of MOS HEMT device with four different chemical treatment recipes were investigated in this article.

  16. Inversion layer MOS solar cells

    NASA Technical Reports Server (NTRS)

    Ho, Fat Duen

    1986-01-01

    Inversion layer (IL) Metal Oxide Semiconductor (MOS) solar cells were fabricated. The fabrication technique and problems are discussed. A plan for modeling IL cells is presented. Future work in this area is addressed.

  17. Interface Properties of Atomic-Layer-Deposited Al2O3 Thin Films on Ultraviolet/Ozone-Treated Multilayer MoS2 Crystals.

    PubMed

    Park, Seonyoung; Kim, Seong Yeoul; Choi, Yura; Kim, Myungjun; Shin, Hyunjung; Kim, Jiyoung; Choi, Woong

    2016-05-11

    We report the interface properties of atomic-layer-deposited Al2O3 thin films on ultraviolet/ozone (UV/O3)-treated multilayer MoS2 crystals. The formation of S-O bonds on MoS2 after low-power UV/O3 treatment increased the surface energy, allowing the subsequent deposition of uniform Al2O3 thin films. The capacitance-voltage measurement of Au-Al2O3-MoS2 metal oxide semiconductor capacitors indicated n-type MoS2 with an electron density of ∼10(17) cm(-3) and a minimum interface trap density of ∼10(11) cm(-2) eV(-1). These results demonstrate the possibility of forming a high-quality Al2O3-MoS2 interface by proper UV/O3 treatment, providing important implications for their integration into field-effect transistors.

  18. Computational design of p-type contacts for MoS2-based electronic devices

    NASA Astrophysics Data System (ADS)

    Kumar, Priyank; Musso, Tiziana; Foster, Adam; Grossman, Jeffrey

    2015-03-01

    The excellent physical and semiconducting properties of transition metal dichalcogenide (TMDC) monolayers make them promising materials for many applications. A well-known example is MoS2, which has gained significant attention as a channel material for next-generation transistors. While n-type MoS2 field-effect transistors (n-FETs) can be fabricated with relative ease, fabrication of p-FETs remains a challenge as the Fermi-level of elemental metals used as contacts are pinned close to the conduction band, leading to large p-type Schottky barrier heights (SBHs). Using ab initio computations, we design and propose efficient hole contacts utilizing high work function oxide-based hole injection materials, with the aim of advancing p-type MoS2 device technology. Our calculations will highlight the possibility to tune and lower the p-type SBH at the metal/semiconductor interface by controlling the structural properties of oxide materials. Taken together, our results provide an interesting platform for experimental design of next-generation MoS2-based electronic and optoelectronic devices.

  19. Flexible low-power RF nanoelectronics in the GHz regime using CVD MoS2

    NASA Astrophysics Data System (ADS)

    Yogeesh, Maruthi

    Two-dimensional (2D) materials have attracted substantial interest for flexible nanoelectronics due to the overall device mechanical flexibility and thickness scalability for high mechanical performance and low operating power. In this work, we demonstrate the first MoS2 RF transistors on flexible substrates based on CVD-grown monolayers, featuring record GHz cutoff frequency (5.6 GHz) and saturation velocity (~1.8×106 cm/s), which is significantly superior to contemporary organic and metal oxide thin-film transistors. Furthermore, multicycle three-point bending results demonstrated the electrical robustness of our flexible MoS2 transistors after 10,000 cycles of mechanical bending. Additionally, basic RF communication circuit blocks such as amplifier, mixer and wireless AM receiver have been demonstrated. These collective results indicate that MoS2 is an ideal advanced semiconducting material for low-power, RF devices for large-area flexible nanoelectronics and smart nanosystems owing to its unique combination of large bandgap, high saturation velocity and high mechanical strength.

  20. Al2O3 as a suitable substrate and a dielectric layer for n-layer MoS2

    NASA Astrophysics Data System (ADS)

    Singh, Arunima K.; Hennig, Richard G.; Davydov, Albert V.; Tavazza, Francesca

    2015-08-01

    Sapphire (α-Al2O3) is a common substrate for the growth of single- to few-layer MoS2 films, and amorphous aluminium oxide serves as a high-κ dielectric gate oxide for MoS2 based transistors. Using density-functional theory calculations with a van der Waals functional, we investigate the structural, energetic, and electronic properties of n-layer MoS2 (n = 1and 3) on the α-Al2O3 (0001) surface. Our results show that the sapphire stabilizes single-layer and tri-layer MoS2, while having a negligible effect on the structure, band gap, and electron effective masses of MoS2. This combination of a strong energetic stabilization and weak perturbation of the electronic properties shows that α-Al2O3 can serve as an ideal substrate for depositing ultra-thin MoS2 layers and can also serve as a passivation or gate-oxide layer for MoS2 based devices.

  1. Growth of large-area and highly crystalline MoS2 thin layers on insulating substrates.

    PubMed

    Liu, Keng-Ku; Zhang, Wenjing; Lee, Yi-Hsien; Lin, Yu-Chuan; Chang, Mu-Tung; Su, Ching-Yuan; Chang, Chia-Seng; Li, Hai; Shi, Yumeng; Zhang, Hua; Lai, Chao-Sung; Li, Lain-Jong

    2012-03-14

    The two-dimensional layer of molybdenum disulfide (MoS(2)) has recently attracted much interest due to its direct-gap property and potential applications in optoelectronics and energy harvesting. However, the synthetic approach to obtain high-quality and large-area MoS(2) atomic thin layers is still rare. Here we report that the high-temperature annealing of a thermally decomposed ammonium thiomolybdate layer in the presence of sulfur can produce large-area MoS(2) thin layers with superior electrical performance on insulating substrates. Spectroscopic and microscopic results reveal that the synthesized MoS(2) sheets are highly crystalline. The electron mobility of the bottom-gate transistor devices made of the synthesized MoS(2) layer is comparable with those of the micromechanically exfoliated thin sheets from MoS(2) crystals. This synthetic approach is simple, scalable, and applicable to other transition metal dichalcogenides. Meanwhile, the obtained MoS(2) films are transferable to arbitrary substrates, providing great opportunities to make layered composites by stacking various atomically thin layers.

  2. Layer-controlled CVD growth of large-area two-dimensional MoS2 films

    NASA Astrophysics Data System (ADS)

    Jeon, Jaeho; Jang, Sung Kyu; Jeon, Su Min; Yoo, Gwangwe; Jang, Yun Hee; Park, Jin-Hong; Lee, Sungjoo

    2015-01-01

    In spite of the recent heightened interest in molybdenum disulfide (MoS2) as a two-dimensional material with substantial bandgaps and reasonably high carrier mobility, a method for the layer-controlled and large-scale synthesis of high quality MoS2 films has not previously been established. Here, we demonstrate that layer-controlled and large-area CVD MoS2 films can be achieved by treating the surfaces of their bottom SiO2 substrates with the oxygen plasma process. Raman mapping, UV-Vis, and PL mapping are performed to show that mono, bi, and trilayer MoS2 films grown on the plasma treated substrates fully cover the centimeter scale substrates with a uniform thickness. Our TEM images also present the single crystalline nature of the monolayer MoS2 film and the formation of the layer-controlled bi- and tri-layer MoS2 films. Back-gated transistors fabricated on these MoS2 films are found to exhibit the high current on/off ratio of ~106 and high mobility values of 3.6 cm2 V-1 s-1 (monolayer), 8.2 cm2 V-1 s-1 (bilayer), and 15.6 cm2 V-1 s-1 (trilayer). Our results are expected to have a significant impact on further studies of the MoS2 growth mechanism as well as on the scaled layer-controlled production of high quality MoS2 films for a wide range of applications.In spite of the recent heightened interest in molybdenum disulfide (MoS2) as a two-dimensional material with substantial bandgaps and reasonably high carrier mobility, a method for the layer-controlled and large-scale synthesis of high quality MoS2 films has not previously been established. Here, we demonstrate that layer-controlled and large-area CVD MoS2 films can be achieved by treating the surfaces of their bottom SiO2 substrates with the oxygen plasma process. Raman mapping, UV-Vis, and PL mapping are performed to show that mono, bi, and trilayer MoS2 films grown on the plasma treated substrates fully cover the centimeter scale substrates with a uniform thickness. Our TEM images also present the single

  3. Multibit data storage states formed in plasma-treated MoS₂ transistors.

    PubMed

    Chen, Mikai; Nam, Hongsuk; Wi, Sungjin; Priessnitz, Greg; Gunawan, Ivan Manuel; Liang, Xiaogan

    2014-04-22

    New multibit memory devices are desirable for improving data storage density and computing speed. Here, we report that multilayer MoS2 transistors, when treated with plasmas, can dramatically serve as low-cost, nonvolatile, highly durable memories with binary and multibit data storage capability. We have demonstrated binary and 2-bit/transistor (or 4-level) data states suitable for year-scale data storage applications as well as 3-bit/transistor (or 8-level) data states for day-scale data storage. This multibit memory capability is hypothesized to be attributed to plasma-induced doping and ripple of the top MoS2 layers in a transistor, which could form an ambipolar charge-trapping layer interfacing the underlying MoS2 channel. This structure could enable the nonvolatile retention of charged carriers as well as the reversible modulation of polarity and amount of the trapped charge, ultimately resulting in multilevel data states in memory transistors. Our Kelvin force microscopy results strongly support this hypothesis. In addition, our research suggests that the programming speed of such memories can be improved by using nanoscale-area plasma treatment. We anticipate that this work would provide important scientific insights for leveraging the unique structural property of atomically layered two-dimensional materials in nanoelectronic applications. PMID:24680193

  4. STABILIZED TRANSISTOR AMPLIFIER

    DOEpatents

    Noe, J.B.

    1963-05-01

    A temperature stabilized transistor amplifier having a pair of transistors coupled in cascade relation that are capable of providing amplification through a temperature range of - 100 un. Concent 85% F to 400 un. Concent 85% F described. The stabilization of the amplifier is attained by coupling a feedback signal taken from the emitter of second transistor at a junction between two serially arranged biasing resistances in the circuit of the emitter of the second transistor to the base of the first transistor. Thus, a change in the emitter current of the second transistor is automatically corrected by the feedback adjustment of the base-emitter potential of the first transistor and by a corresponding change in the base-emitter potential of the second transistor. (AEC)

  5. Phase-driven magneto-electrical characteristics of single-layer MoS2

    NASA Astrophysics Data System (ADS)

    Yang, Chao-Yao; Chiu, Kuan-Chang; Chang, Shu-Jui; Zhang, Xin-Quan; Liang, Jaw-Yeu; Chung, Chi-Sheng; Pan, Hui; Wu, Jenn-Ming; Tseng, Yuan-Chieh; Lee, Yi-Hsien

    2016-03-01

    Magnetism of the MoS2 semiconducting atomic layer was highlighted for its great potential in the applications of spintronics and valleytronics. In this study, we demonstrate an evolution of magneto-electrical properties of single layer MoS2 with the modulation of defect configurations and formation of a partial 1T phase. With Ar treatment, sulfur was depleted within the MoS2 flake leading to a 2H (low-spin) --> partial 1T (high-spin) phase transition. The phase transition was accompanied by the development of a ferromagnetic phase. Alternatively, the phase transition could be driven by the desorption of S atoms at the edge of MoS2via O2 treatment while with a different ordering magnitude in magnetism. The edge-sensitive magnetism of the single-layer MoS2 was monitored by magnetic force microscopy and validated by a first-principle calculation with graded-Vs (sulfur vacancy) terminals set at the edge, where band-splitting appeared more prominent with increasing Vs. Treatment with Ar and O2 enabled a dual electrical characteristic of the field effect transistor (FET) that featured linear and saturated responses of different magnitudes in the Ids-Vds curves, whereas the pristine MoS2 FET displayed only a linear electrical dependency. The correlation and tuning of the Vs-1T phase transition would provide a playground for tailoring the phase-driven properties of MoS2 semiconducting atomic layers in spintronic applications.Magnetism of the MoS2 semiconducting atomic layer was highlighted for its great potential in the applications of spintronics and valleytronics. In this study, we demonstrate an evolution of magneto-electrical properties of single layer MoS2 with the modulation of defect configurations and formation of a partial 1T phase. With Ar treatment, sulfur was depleted within the MoS2 flake leading to a 2H (low-spin) --> partial 1T (high-spin) phase transition. The phase transition was accompanied by the development of a ferromagnetic phase. Alternatively, the

  6. Single-layer MoS2 nanopores as nanopower generators.

    PubMed

    Feng, Jiandong; Graf, Michael; Liu, Ke; Ovchinnikov, Dmitry; Dumcenco, Dumitru; Heiranian, Mohammad; Nandigana, Vishal; Aluru, Narayana R; Kis, Andras; Radenovic, Aleksandra

    2016-08-11

    Making use of the osmotic pressure difference between fresh water and seawater is an attractive, renewable and clean way to generate power and is known as 'blue energy'. Another electrokinetic phenomenon, called the streaming potential, occurs when an electrolyte is driven through narrow pores either by a pressure gradient or by an osmotic potential resulting from a salt concentration gradient. For this task, membranes made of two-dimensional materials are expected to be the most efficient, because water transport through a membrane scales inversely with membrane thickness. Here we demonstrate the use of single-layer molybdenum disulfide (MoS2) nanopores as osmotic nanopower generators. We observe a large, osmotically induced current produced from a salt gradient with an estimated power density of up to 10(6) watts per square metre--a current that can be attributed mainly to the atomically thin membrane of MoS2. Low power requirements for nanoelectronic and optoelectric devices can be provided by a neighbouring nanogenerator that harvests energy from the local environment--for example, a piezoelectric zinc oxide nanowire array or single-layer MoS2 (ref. 12). We use our MoS2 nanopore generator to power a MoS2 transistor, thus demonstrating a self-powered nanosystem.

  7. MoS2-InGaZnO Heterojunction Phototransistors with Broad Spectral Responsivity.

    PubMed

    Yang, Jaehyun; Kwak, Hyena; Lee, Youngbin; Kang, Yu-Seon; Cho, Mann-Ho; Cho, Jeong Ho; Kim, Yong-Hoon; Jeong, Seong-Jun; Park, Seongjun; Lee, Hoo-Jeong; Kim, Hyoungsub

    2016-04-01

    We introduce an amorphous indium-gallium-zinc-oxide (a-IGZO) heterostructure phototransistor consisting of solution-based synthetic molybdenum disulfide (few-layered MoS2, with a band gap of ∼1.7 eV) and sputter-deposited a-IGZO (with a band gap of ∼3.0 eV) films as a novel sensing element with a broad spectral responsivity. The MoS2 and a-IGZO films serve as a visible light-absorbing layer and a high mobility channel layer, respectively. Spectroscopic measurements reveal that appropriate band alignment at the heterojunction provides effective transfer of the visible light-induced electrons generated in the few-layered MoS2 film to the underlying a-IGZO channel layer with a high carrier mobility. The photoresponse characteristics of the a-IGZO transistor are extended to cover most of the visible range by forming a heterojunction phototransistor that harnesses a visible light responding MoS2 film with a small band gap prepared through a large-area synthetic route. The MoS2-IGZO heterojunction phototransistors exhibit a photoresponsivity of approximately 1.7 A/W at a wavelength of 520 nm (an optical power of 1 μW) with excellent time-dependent photoresponse dynamics. PMID:26989951

  8. Single-layer MoS2 nanopores as nanopower generators.

    PubMed

    Feng, Jiandong; Graf, Michael; Liu, Ke; Ovchinnikov, Dmitry; Dumcenco, Dumitru; Heiranian, Mohammad; Nandigana, Vishal; Aluru, Narayana R; Kis, Andras; Radenovic, Aleksandra

    2016-08-11

    Making use of the osmotic pressure difference between fresh water and seawater is an attractive, renewable and clean way to generate power and is known as 'blue energy'. Another electrokinetic phenomenon, called the streaming potential, occurs when an electrolyte is driven through narrow pores either by a pressure gradient or by an osmotic potential resulting from a salt concentration gradient. For this task, membranes made of two-dimensional materials are expected to be the most efficient, because water transport through a membrane scales inversely with membrane thickness. Here we demonstrate the use of single-layer molybdenum disulfide (MoS2) nanopores as osmotic nanopower generators. We observe a large, osmotically induced current produced from a salt gradient with an estimated power density of up to 10(6) watts per square metre--a current that can be attributed mainly to the atomically thin membrane of MoS2. Low power requirements for nanoelectronic and optoelectric devices can be provided by a neighbouring nanogenerator that harvests energy from the local environment--for example, a piezoelectric zinc oxide nanowire array or single-layer MoS2 (ref. 12). We use our MoS2 nanopore generator to power a MoS2 transistor, thus demonstrating a self-powered nanosystem. PMID:27409806

  9. Single-layer MoS2 nanopores as nanopower generators

    NASA Astrophysics Data System (ADS)

    Feng, Jiandong; Graf, Michael; Liu, Ke; Ovchinnikov, Dmitry; Dumcenco, Dumitru; Heiranian, Mohammad; Nandigana, Vishal; Aluru, Narayana R.; Kis, Andras; Radenovic, Aleksandra

    2016-08-01

    Making use of the osmotic pressure difference between fresh water and seawater is an attractive, renewable and clean way to generate power and is known as ‘blue energy’. Another electrokinetic phenomenon, called the streaming potential, occurs when an electrolyte is driven through narrow pores either by a pressure gradient or by an osmotic potential resulting from a salt concentration gradient. For this task, membranes made of two-dimensional materials are expected to be the most efficient, because water transport through a membrane scales inversely with membrane thickness. Here we demonstrate the use of single-layer molybdenum disulfide (MoS2) nanopores as osmotic nanopower generators. We observe a large, osmotically induced current produced from a salt gradient with an estimated power density of up to 106 watts per square metre—a current that can be attributed mainly to the atomically thin membrane of MoS2. Low power requirements for nanoelectronic and optoelectric devices can be provided by a neighbouring nanogenerator that harvests energy from the local environment—for example, a piezoelectric zinc oxide nanowire array or single-layer MoS2 (ref. 12). We use our MoS2 nanopore generator to power a MoS2 transistor, thus demonstrating a self-powered nanosystem.

  10. Effect of interfaces on electron transport properties of MoS2-Au Contacts

    NASA Astrophysics Data System (ADS)

    Aminpour, Maral; Hapala, Prokop; Le, Duy; Jelinek, Pavel; Rahman, Talat S.; Rahman's Group Collaboration; Nanosurf Lab Collaboration

    2014-03-01

    Single layer MoS2 is a promising material for future electronic devices such as transistors since it has good transport characteristics with mobility greater than 200 cm-1V-1s-1 and on-off current ratios up to 108. However, before MoS2 can become a mainstream electronic material for the semiconductor industry, the design of low resistive metal-semiconductor junctions as contacts of the electronic devices needs to be addressed and studied systematically. We have examined the effect of Au contacts on the electronic transport properties of single layer MoS2 using density functional theory in combination with the non-equilibrium Green's function method. The Schottky barrier between Au contact and MoS2, transmission spectra, and I-V curves will be reported and discussed as a function of MoS2 and Au interfaces of varying geometry. This work is supported in part by the US Department of Energy under grant DE-FG02-07ER15842.

  11. A subthreshold MOS circuit for the Lotka-Volterra neural network producing the winners-share-all solution.

    PubMed

    Asai, T; Fukai, T; Tanaka, S

    1999-03-01

    An analog MOS circuit is proposed for implementing a Lotka-Volterra (LV) competitive neural network which produces winners-share-all solutions. The solutions give multiple winners receiving large inputs and are particularly useful for selecting a set of inputs through "decision by majority". We show that the LV network can easily be implemented using subthreshold MOS transistors. Results of extensive circuit simulations prove that the proposed circuit does exhibit a reliable selection compared with winner-take-all circuits, in the possible presence of device mismatches. These results pave a way to future implementation on a real device.

  12. Phase-driven magneto-electrical characteristics of single-layer MoS2.

    PubMed

    Yang, Chao-Yao; Chiu, Kuan-Chang; Chang, Shu-Jui; Zhang, Xin-Quan; Liang, Jaw-Yeu; Chung, Chi-Sheng; Pan, Hui; Wu, Jenn-Ming; Tseng, Yuan-Chieh; Lee, Yi-Hsien

    2016-03-14

    Magnetism of the MoS2 semiconducting atomic layer was highlighted for its great potential in the applications of spintronics and valleytronics. In this study, we demonstrate an evolution of magneto-electrical properties of single layer MoS2 with the modulation of defect configurations and formation of a partial 1T phase. With Ar treatment, sulfur was depleted within the MoS2 flake leading to a 2H (low-spin) → partial 1T (high-spin) phase transition. The phase transition was accompanied by the development of a ferromagnetic phase. Alternatively, the phase transition could be driven by the desorption of S atoms at the edge of MoS2via O2 treatment while with a different ordering magnitude in magnetism. The edge-sensitive magnetism of the single-layer MoS2 was monitored by magnetic force microscopy and validated by a first-principle calculation with graded-Vs (sulfur vacancy) terminals set at the edge, where band-splitting appeared more prominent with increasing Vs. Treatment with Ar and O2 enabled a dual electrical characteristic of the field effect transistor (FET) that featured linear and saturated responses of different magnitudes in the Ids-Vds curves, whereas the pristine MoS2 FET displayed only a linear electrical dependency. The correlation and tuning of the Vs-1T phase transition would provide a playground for tailoring the phase-driven properties of MoS2 semiconducting atomic layers in spintronic applications. PMID:26892905

  13. Scalable Patterning of MoS2 Nanoribbons by Micromolding in Capillaries.

    PubMed

    Hung, Yu-Han; Lu, Ang-Yu; Chang, Yung-Huang; Huang, Jing-Kai; Chang, Jeng-Kuei; Li, Lain-Jong; Su, Ching-Yuan

    2016-08-17

    In this study, we report a facile approach to prepare dense arrays of MoS2 nanoribbons by combining procedures of micromolding in capillaries (MIMIC) and thermolysis of thiosalts ((NH4)2MoS4) as the printing ink. The obtained MoS2 nanoribbons had a thickness reaching as low as 3.9 nm, a width ranging from 157 to 465 nm, and a length up to 2 cm. MoS2 nanoribbons with an extremely high aspect ratio (length/width) of ∼7.4 × 10(8) were achieved. The MoS2 pattern can be printed on versatile substrates, such as SiO2/Si, sapphire, Au film, FTO/glass, and graphene-coated glass. The degree of crystallinity of the as-prepared MoS2 was discovered to be adjustable by varying the temperature through postannealing. The high-temperature thermolysis (1000 °C) results in high-quality conductive samples, and field-effect transistors based on the patterned MoS2 nanoribbons were demonstrated and characterized, where the carrier mobility was comparable to that of thin-film MoS2. In contrast, the low-temperature-treated samples (170 °C) result in a unique nanocrystalline MoSx structure (x ≈ 2.5), where the abundant and exposed edge sites were obtained from highly dense arrays of nanoribbon structures by this MIMIC patterning method. The patterned MoSx was revealed to have superior electrocatalytic efficiency (an overpotential of ∼211 mV at 10 mA/cm(2) and a Tafel slope of 43 mV/dec) in the hydrogen evolution reaction (HER) when compared to the thin-film MoS2. The report introduces a new concept for rapidly fabricating cost-effective and high-density MoS2/MoSx nanostructures on versatile substrates, which may pave the way for potential applications in nanoelectronics/optoelectronics and frontier energy materials. PMID:27462874

  14. Scalable Patterning of MoS2 Nanoribbons by Micromolding in Capillaries.

    PubMed

    Hung, Yu-Han; Lu, Ang-Yu; Chang, Yung-Huang; Huang, Jing-Kai; Chang, Jeng-Kuei; Li, Lain-Jong; Su, Ching-Yuan

    2016-08-17

    In this study, we report a facile approach to prepare dense arrays of MoS2 nanoribbons by combining procedures of micromolding in capillaries (MIMIC) and thermolysis of thiosalts ((NH4)2MoS4) as the printing ink. The obtained MoS2 nanoribbons had a thickness reaching as low as 3.9 nm, a width ranging from 157 to 465 nm, and a length up to 2 cm. MoS2 nanoribbons with an extremely high aspect ratio (length/width) of ∼7.4 × 10(8) were achieved. The MoS2 pattern can be printed on versatile substrates, such as SiO2/Si, sapphire, Au film, FTO/glass, and graphene-coated glass. The degree of crystallinity of the as-prepared MoS2 was discovered to be adjustable by varying the temperature through postannealing. The high-temperature thermolysis (1000 °C) results in high-quality conductive samples, and field-effect transistors based on the patterned MoS2 nanoribbons were demonstrated and characterized, where the carrier mobility was comparable to that of thin-film MoS2. In contrast, the low-temperature-treated samples (170 °C) result in a unique nanocrystalline MoSx structure (x ≈ 2.5), where the abundant and exposed edge sites were obtained from highly dense arrays of nanoribbon structures by this MIMIC patterning method. The patterned MoSx was revealed to have superior electrocatalytic efficiency (an overpotential of ∼211 mV at 10 mA/cm(2) and a Tafel slope of 43 mV/dec) in the hydrogen evolution reaction (HER) when compared to the thin-film MoS2. The report introduces a new concept for rapidly fabricating cost-effective and high-density MoS2/MoSx nanostructures on versatile substrates, which may pave the way for potential applications in nanoelectronics/optoelectronics and frontier energy materials.

  15. Dual-mode operation of 2D material-base hot electron transistors

    PubMed Central

    Lan, Yann-Wen; Torres, Jr., Carlos M.; Zhu, Xiaodan; Qasem, Hussam; Adleman, James R.; Lerner, Mitchell B.; Tsai, Shin-Hung; Shi, Yumeng; Li, Lain-Jong; Yeh, Wen-Kuan; Wang, Kang L.

    2016-01-01

    Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (VCB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (VCB < 0). That is, our 2D material-base hot electron transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications. PMID:27581550

  16. Dual-mode operation of 2D material-base hot electron transistors

    NASA Astrophysics Data System (ADS)

    Lan, Yann-Wen; Torres, Carlos M., Jr.; Zhu, Xiaodan; Qasem, Hussam; Adleman, James R.; Lerner, Mitchell B.; Tsai, Shin-Hung; Shi, Yumeng; Li, Lain-Jong; Yeh, Wen-Kuan; Wang, Kang L.

    2016-09-01

    Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (VCB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (VCB < 0). That is, our 2D material-base hot electron transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications.

  17. Dual-mode operation of 2D material-base hot electron transistors.

    PubMed

    Lan, Yann-Wen; Torres, Carlos M; Zhu, Xiaodan; Qasem, Hussam; Adleman, James R; Lerner, Mitchell B; Tsai, Shin-Hung; Shi, Yumeng; Li, Lain-Jong; Yeh, Wen-Kuan; Wang, Kang L

    2016-01-01

    Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (VCB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (VCB < 0). That is, our 2D material-base hot electron transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications. PMID:27581550

  18. Dual-mode operation of 2D material-base hot electron transistors.

    PubMed

    Lan, Yann-Wen; Torres, Carlos M; Zhu, Xiaodan; Qasem, Hussam; Adleman, James R; Lerner, Mitchell B; Tsai, Shin-Hung; Shi, Yumeng; Li, Lain-Jong; Yeh, Wen-Kuan; Wang, Kang L

    2016-09-01

    Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (VCB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (VCB < 0). That is, our 2D material-base hot electron transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications.

  19. BATMAN: MOS Spectroscopy on Demand

    NASA Astrophysics Data System (ADS)

    Molinari, E.; Zamkotsian, F.; Moschetti, M.; Spano, P.; Boschin, W.; Cosentino, R.; Ghedina, A.; González, M.; Pérez, H.; Lanzoni, P.; Ramarijaona, H.; Riva, M.; Zerbi, F.; Nicastro, L.; Valenziano, L.; Di Marcantonio, P.; Coretti, I.; Cirami, R.

    2016-10-01

    Multi-Object Spectrographs (MOS) are the major instruments for studying primary galaxies and remote and faint objects. Current object selection systems are limited and/or difficult to implement in next generation MOS for space and ground-based telescopes. A promising solution is the use of MOEMS devices such as micromirror arrays, which allow the remote control of the multi-slit configuration in real time. TNG is hosting a novelty project for real-time, on-demand MOS masks based on MOEMS programmable slits. We are developing a 2048×1080 Digital-Micromirror-Device-based (DMD) MOS instrument to be mounted on the Galileo telescope, called BATMAN. It is a two-arm instrument designed for providing in parallel imaging and spectroscopic capabilities. With a field of view of 6.8×3.6 arcmin and a plate scale of 0.2 arcsec per micromirror, this astronomical setup can be used to investigate the formation and evolution of galaxies. The wavelength range is in the visible and the spectral resolution is R=560 for a 1 arcsec object, and the two arms will have 2k × 4k CCD detectors. ROBIN, a BATMAN demonstrator, has been designed, realized and integrated. We plan to have BATMAN first light by mid-2016.

  20. The OverMOS project

    NASA Astrophysics Data System (ADS)

    Das, D.; Dopke, J.; McMahon, S. J.; Turchetta, R.; Villani, G.; Wilson, F.; Worm, S.

    2016-07-01

    The OverMOS project aims to create a fast radiation hard tracking detector sensor, based on High Resistivity CMOS technology. In a first prototype submission, different pixel and charge collection node geometries have been produced, which have lately been returned from fabrication and are currently under test.

  1. Metal-insulator crossover in multilayered MoS2.

    PubMed

    Park, Min Ji; Yi, Sum-Gyun; Kim, Joo Hyung; Yoo, Kyung-Hwa

    2015-10-01

    The temperature dependence of electrical transport properties was investigated for multilayered MoS2 field effect transistor devices with thicknesses of 3-22 nm. Some devices showed typical n-type semiconducting behavior, while others exhibited metal-insulator crossover (MIC) from metallic to insulating conduction at finite temperatures. The latter effect occurred near zero gate voltage or at high positive gate voltages. Analysis of Raman spectroscopy revealed the key difference that devices with MIC have a metallic 1T phase as well as a semiconducting 2H phase, whereas devices without the MIC did not have a metallic 1T phase. These results suggest that the metallic 1T phase may contribute to inducing the MIC.

  2. Correspondence between MOS and modulation-doped structures

    NASA Astrophysics Data System (ADS)

    Pierret, R. F.; Lundstrom, M. S.

    1984-03-01

    There is currently considerable interest in the development of modulation-doped field-effect transistors suitable for high-speed applications. A promising version of the modulation-doped FET consists of a Schottky-barrier contact atop a thin Al(x)Ga(1-x)As layer on a lightly doped GaAs underlayer. It is pointed out that for a n-AlGaAs/p-GaAs structure, the conduction band discontinuity at the AlGaAs-GaAs interface gives rise to an inversion layer at the GaAs surface. The present paper is concerned with the physical correspondence between n-AlGaAs/p-GaAs modulation-doped structures and MOS structures. It is shown that certain key modulation-doped relationships can be obtained directly from MOSFET relationships.

  3. Utilizing self-assembled-monolayer-based gate dielectrics to fabricate molybdenum disulfide field-effect transistors

    NASA Astrophysics Data System (ADS)

    Kawanago, Takamasa; Oda, Shunri

    2016-01-01

    In this study, we apply self-assembled-monolayer (SAM)-based gate dielectrics to the fabrication of molybdenum disulfide (MoS2) field-effect transistors. A simple fabrication process involving the selective formation of a SAM on metal oxides in conjunction with the dry transfer of MoS2 flakes was established. A subthreshold slope (SS) of 69 mV/dec and no hysteresis were demonstrated with the ultrathin SAM-based gate dielectrics accompanied by a low gate leakage current. The small SS and no hysteresis indicate the superior interfacial properties of the MoS2/SAM structure. Cross-sectional transmission electron microscopy revealed a sharp and abrupt interface of the MoS2/SAM structure. The SAM-based gate dielectrics are found to be applicable to the fabrication of low-voltage MoS2 field-effect transistors and can also be extended to various layered semiconductor materials. This study opens up intriguing possibilities of SAM-based gate dielectrics in functional electronic devices.

  4. Toward epitaxially grown two-dimensional crystal hetero-structures: Single and double MoS2/graphene hetero-structures by chemical vapor depositions

    NASA Astrophysics Data System (ADS)

    Lin, Meng-Yu; Chang, Chung-En; Wang, Cheng-Hung; Su, Chen-Fung; Chen, Chi; Lee, Si-Chen; Lin, Shih-Yen

    2014-08-01

    Uniform large-size MoS2/graphene hetero-structures fabricated directly on sapphire substrates are demonstrated with layer-number controllability by chemical vapor deposition (CVD). The cross-sectional high-resolution transmission electron microscopy (HRTEM) images provide the direct evidences of layer numbers of MoS2/graphene hetero-structures. Photo-excited electron induced Fermi level shift of the graphene channel are observed on the single MoS2/graphene hetero-structure transistors. Furthermore, double hetero-structures of graphene/MoS2/graphene are achieved by CVD fabrication of graphene layers on top of the MoS2, as confirmed by the cross-sectional HRTEM. These results have paved the possibility of epitaxially grown multi-hetero-structures for practical applications.

  5. Enhancement of field-effect mobility in molybdenum-disulfide transistor through the treatment of low-power oxygen plasma

    NASA Astrophysics Data System (ADS)

    Chen, Kuan-Chao; Wu, Chong-Rong; Chang, Xiang-Rui; Chang, Shu-Wei; Lee, Si-Chen; Lin, Shih-Yen

    2016-09-01

    We experimentally demonstrate that the treatment with low-power oxygen plasma can raise the field-effect mobility in molybdenum-sulfide (MoS2) transistors from 0.01 to 9.6 cm2 V‑1 s‑1, which is an increment of about three orders of magnitude. The decrease in threshold voltage and the increase in the drain current of the devices indicate that the electron density increases significantly after the mild plasma treatment. The emergence of Mo–O characteristics but the suppression of Mo–S features on the X-ray photoelectron spectrum of the plasma-treated sample suggests that a portion of the MoS2 film becomes conductive molybdenum oxide. This transformation may considerably upgrade the performance of MoS2 transistors.

  6. Electrical characteristics of multilayer MoS2 FET's with MoS2/graphene heterojunction contacts.

    PubMed

    Kwak, Joon Young; Hwang, Jeonghyun; Calderon, Brian; Alsalman, Hussain; Munoz, Nini; Schutter, Brian; Spencer, Michael G

    2014-08-13

    The electrical properties of multilayer MoS2/graphene heterojunction transistors are investigated. Temperature-dependent I-V measurements indicate the concentration of unintentional donors in exfoliated MoS2 to be 3.57 × 10(11) cm(-2), while the ionized donor concentration is determined as 3.61 × 10(10) cm(-2). The temperature-dependent measurements also reveal two dominant donor levels, one at 0.27 eV below the conduction band and another located at 0.05 eV below the conduction band. The I-V characteristics are asymmetric with drain bias voltage and dependent on the junction used for the source or drain contact. I-V characteristics of the device are consistent with a long channel one-dimensional field-effect transistor model with Schottky contact. Utilizing devices, which have both graphene/MoS2 and Ti/MoS2 contacts, the Schottky barrier heights of both interfaces are measured. The charge transport mechanism in both junctions was determined to be either thermionic-field emission or field emission depending on bias voltage and temperature. On the basis of a thermionic field emission model, the barrier height at the graphene/MoS2 interface was determined to be 0.23 eV, while the barrier height at the Ti/MoS2 interface was 0.40 eV. The value of Ti/MoS2 barrier is higher than previously reported values, which did not include the effects of thermionic field emission.

  7. Surface defect passivation of MoS2 by sulfur, selenium, and tellurium

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Qi, Long; Shen, Lei; Wu, Yihong

    2016-04-01

    Few-layer MoS2 field-effect transistors often show an n-type conduction behavior due to the presence of high-density sulfur vacancies. Here, we investigated the possibility of surface defect passivation of MoS2 by sulfur treatment in (NH4)2S solution or coating with an ultrathin layer of selenium or tellurium. It was found that all three elements investigated are able to induce a p-doping effect through suppressing the residual electron concentration by an amount exceeding 0.5 × 1012 cm-2 in few-layer MoS2. Among them, the sulfur-treatment exhibits the most superior thermal stability that survives thermal annealing at temperatures ≥120 °C for at least 10 h. Tellurium exhibits the strongest p-doping effect due to electron trapping by physisorption-induced gap states near the valence band edge. On the other hand, selenium is highly volatile on MoS2; it evaporates and desorbs easily due to Joule heating during electrical measurements in vacuum. The results of first-principles calculations support the experimental observations.

  8. MOS-FET as a Current Sensor in Power Electronics Converters.

    PubMed

    Pajer, Rok; Milanoviĉ, Miro; Premzel, Branko; Rodiĉ, Miran

    2015-07-24

    This paper presents a current sensing principle appropriate for use in power electronics' converters. This current measurement principle has been developed for metal oxide semiconductor field effect transistor (MOS-FET) and is based on U(DS) voltage measurement. In practice, shunt resistors and Hall effect sensors are usually used for these purposes, but the presented principle has many advantages. There is no need for additional circuit elements within high current paths, causing parasitic inductances and increased production complexity. The temperature dependence of MOS-FETs conductive resistance R(DS-ON) is considered in order to achieve the appropriate measurement accuracy. The "MOS-FET sensor" is also accompanied by a signal acquisition electronics circuit with an appropriate frequency bandwidth. The obtained analogue signal is therefore interposed to an A-D converter for further data acquisition. In order to achieve sufficient accuracy, a temperature compensation and appropriate approximation is used (R(DS-ON) = R(DS-ON)(θj)). The MOS-FET sensor is calibrated according to a reference sensor based on the Hall-effect principle. The program algorithm is executed on 32-bit ARM M4 MCU, STM32F407.

  9. Photoinduced valley-polarized current of layered MoS2 by electric tuning.

    PubMed

    Yu, Yunjin; Zhou, Yanfeng; Wan, Langhui; Wang, Bin; Xu, Fuming; Wei, Yadong; Wang, Jian

    2016-05-01

    A photoinduced current of a layered MoS2-based transistor is studied from first-principles. Under the illumination of circular polarized light, a valley-polarized current is generated, which can be tuned by the gate voltage. For monolayer MoS2, the valley-polarized spin-up (down) electron current at K (K') points is induced by the right (left) circular polarized light. The valley polarization is found to reach +1.0 (-1.0) for the valley current that carried such a K (K') index. For bilayer MoS2, the spin-up (down) current can be induced at both K and K' valleys by the right (left) circular light. In contrast to monolayer MoS2, the photoinduced valley polarization shows asymmetric behavior upon reversal of the gate voltage. Our results show that the valley polarization of the photoinduced current can be modulated by the circular polarized light and the gate voltage. All the results can be well understood using a simple kp model.

  10. Admittance spectroscopy of interface traps in MoS2 nanosheet capacitors

    NASA Astrophysics Data System (ADS)

    Molle, Alessandro; Rotta, Davide; Paleari, Stefano; Cinquanta, Eugenio; Fanciulli, Marco

    2015-03-01

    Two dimensional MoS2 nanosheets are complementary to graphene as post-silicon material for low power electronic, optoelectronic, and photovoltaic applications. However, when integrated as active channels in a transistor, the transport properties of a MoS2 nanosheet can be dramatically influenced by the intrinsic interface traps which may degrade the carrier mobility or interfere with the radiative recombination. Electrically active interface traps are here quantified in different configurations incorporating MoS2 nanosheet capacitors by means of temperature resolved admittance spectroscopy. The density of states of the interface traps is probed from midgap to the majority carrier band-edge therein making evidence of localized midgap traps and conduction band tail states. The resulting scenario is corroborated by the inspection of the local electronic properties explored by scanning tunneling spectroscopy. The former traps are related to native defects such S vacancy whereas the latter feature is discussed in terms of intrinsic disorder which is responsible for the previously reported metal-insulator transition in MoS2 flakes.

  11. MOS-FET as a Current Sensor in Power Electronics Converters

    PubMed Central

    Pajer, Rok; Milanovič, Miro; Premzel, Branko; Rodič, Miran

    2015-01-01

    This paper presents a current sensing principle appropriate for use in power electronics’ converters. This current measurement principle has been developed for metal oxide semiconductor field effect transistor (MOS-FET) and is based on UDS voltage measurement. In practice, shunt resistors and Hall effect sensors are usually used for these purposes, but the presented principle has many advantages. There is no need for additional circuit elements within high current paths, causing parasitic inductances and increased production complexity. The temperature dependence of MOS-FETs conductive resistance RDS−ON is considered in order to achieve the appropriate measurement accuracy. The “MOS-FET sensor” is also accompanied by a signal acquisition electronics circuit with an appropriate frequency bandwidth. The obtained analogue signal is therefore interposed to an A-D converter for further data acquisition. In order to achieve sufficient accuracy, a temperature compensation and appropriate approximation is used (RDS−ON=RDS−ON(ϑj)). The MOS-FET sensor is calibrated according to a reference sensor based on the Hall-effect principle. The program algorithm is executed on 32-bit ARM M4 MCU, STM32F407. PMID:26213938

  12. Memristive Behavior and Ideal Memristor of 1T Phase MoS2 Nanosheets.

    PubMed

    Cheng, Peifu; Sun, Kai; Hu, Yun Hang

    2016-01-13

    Memristor, which had been predicted a long time ago (Chua, L. O. IEEE Trans. Circuit Theory 1971, 18, 507), was recently invented (Strukov, D. B.; et al. Nature 2008, 453, 80). The introduction of a memristor is expected to open a new era for nonvolatile memory storage, neuromorphic computing, digital logic, and analog circuit. Furthermore, several breakthroughs were made for memristive phenomena and transistors with single-layer MoS2 (Sangwan, V. K.; et al. Nat. Nanotechnol. 2015, 10, 403. van der Zande, A. M.; et al. Nat. Mater. 2013, 12, 554. Liu, H.; et al. ACS Nano 2014, 8, 1031. Bessonov, A. A.; et al. Nat. Mater. 2015, 14, 199. Yuan, J.; et al. Nat. Nanotechnol. 2015, 10, 389). Herein, we demonstrate that 2H phase of bulk MoS2 possessed an ohmic feature, whereas 1T phase of exfoliated MoS2 nanosheets exhibited a unique memristive behavior due to voltage-dependent resistance change. Furthermore, an ideal odd-symmetric memristor with odd-symmetric I-V characteristics was successfully fabricated by the 1T phase MoS2 nanosheets via combining two asymmetric switches antiserially.

  13. MOS-FET as a Current Sensor in Power Electronics Converters.

    PubMed

    Pajer, Rok; Milanoviĉ, Miro; Premzel, Branko; Rodiĉ, Miran

    2015-01-01

    This paper presents a current sensing principle appropriate for use in power electronics' converters. This current measurement principle has been developed for metal oxide semiconductor field effect transistor (MOS-FET) and is based on U(DS) voltage measurement. In practice, shunt resistors and Hall effect sensors are usually used for these purposes, but the presented principle has many advantages. There is no need for additional circuit elements within high current paths, causing parasitic inductances and increased production complexity. The temperature dependence of MOS-FETs conductive resistance R(DS-ON) is considered in order to achieve the appropriate measurement accuracy. The "MOS-FET sensor" is also accompanied by a signal acquisition electronics circuit with an appropriate frequency bandwidth. The obtained analogue signal is therefore interposed to an A-D converter for further data acquisition. In order to achieve sufficient accuracy, a temperature compensation and appropriate approximation is used (R(DS-ON) = R(DS-ON)(θj)). The MOS-FET sensor is calibrated according to a reference sensor based on the Hall-effect principle. The program algorithm is executed on 32-bit ARM M4 MCU, STM32F407. PMID:26213938

  14. A MOS for all seasons

    NASA Technical Reports Server (NTRS)

    Bryant, Larry

    1993-01-01

    From a systems perspective, this paper examines the challenges of a single system to support multiple JPL space exploration missions and the need for unitary responsibility for the system. The focus is a Mission Operations System (MOS), which is effectively a mission management organization with direct authority over data system operations, command sequencing, flight operations control, data management, trajectory determination, telemetry and data acquisition, and spacecraft analysis. Stratagems for training and the approach to processes, procedures, and interfaces to facilitate the transition from the present situation to a truly multimission operational environment are developed. The outcome is a paradigm for a MOS that is achievable, that can effectively support multiple projects, and that can take advantage of technological changes without perturbing the entire system.

  15. A MOS for all seasons

    NASA Astrophysics Data System (ADS)

    Bryant, Larry

    1995-01-01

    From a systems perspective, this paper examines the challenges of a single system to support multiple Jet Propulsion Laboratory (JPL) space exploration missions and the need for unitary responsibility for the system. The focus is a Mission Operations System (MOS), which is effectively a mission management organization with direct authority over data system operations, command sequencing, flight operations control, data management, trajectory determination, telemetry and data acquisition, and spacecraft analysis. Stratagems for training and the approach to processes, procedures, and interfaces to facilitate the transition from the present situation to a truly multimission operational environment are developed. The outcome is a paradigm for a MOS that is achievable, that can effectively support multiple projects, and that can take advantage of technological changes without perturbing the entire system.

  16. Theoretical study of the NO, NO2, CO, SO2, and NH3 adsorptions on multi-diameter single-wall MoS2 nanotube

    NASA Astrophysics Data System (ADS)

    Cao, Rongfang; Zhou, Bo; Jia, Cuifang; Zhang, Xiaodong; Jiang, Zhenyi

    2016-02-01

    On the basis of first-principles calculations, the ability of a single-wall MoS2 nanotube to detect NO, NO2, CO, SO2, and NH3 gas molecules is studied. The most stable adsorption configurations, adsorption energies, and charge transfers are calculated. Among these gas molecules, the NO molecule has the biggest interaction with the MoS2 nanotube. The adsorption energy of NO on the nanotube is 129.3 meV, which is almost double compared to that for the monolayer (74.4 meV). The charge density difference calculation shows that all the molecules on the MoS2 nanotube act as electron acceptors except NH3. The charge transfer between NO and the nanotube is still one order of magnitude higher than that for the monolayer. Compared with the results for these molecules adsorbed on the MoS2 monolayer, the nanotube is more sensitive, especially for the NO molecule. Moreover, a comparative study of MoS2 nanotubes with different diameters (curvatures) indicates that the NO adsorption capability of the outer surface decreases on the increasing radius. It is predicted that the MoS2 nanotube with a smaller diameter should increase the stability and sensitivity of MoS2-based field-effect-transistor (FET) sensors.

  17. MoS2 spaser

    NASA Astrophysics Data System (ADS)

    Jayasekara, Charith; Premaratne, Malin; Gunapala, Sarath D.; Stockman, Mark I.

    2016-04-01

    We present a comprehensive analysis of a spaser made of a circular shaped highly doped molybdenum disulfide (MoS2) resonator. "Spaser" is an acronym for "surface plasmon amplification by stimulated emission of radiation"-a nanoscale source of surface plasmons generated by stimulated emission in a plasmonic resonator which receives energy nonradiatively. By considering localized surface plasmon modes, operation characteristics of the model are analysed, and tunability of the design is demonstrated. We find the optimum geometric and material parameters of the spaser that provides efficient outputs and carryout a comparative analysis with a similar circular spaser made of graphene. Owing to physical and chemical properties of MoS2 and the active medium, the proposed design delivers efficient outputs in terms of spaser mode energy, operating thresholds, Q-factor, and electric field amplitude. Lower operating thresholds and higher mode energies are notable advantages of the design. Owing to having many superior features to existing similar designs, this MoS2 spaser may be much suited for applications in nanoplasmonic devices.

  18. Resonant tunneling through discrete quantum states in stacked atomic-layered MoS2.

    PubMed

    Nguyen, Linh-Nam; Lan, Yann-Wen; Chen, Jyun-Hong; Chang, Tay-Rong; Zhong, Yuan-Liang; Jeng, Horng-Tay; Li, Lain-Jong; Chen, Chii-Dong

    2014-05-14

    Two-dimensional crystals can be assembled into three-dimensional stacks with atomic layer precision, which have already shown plenty of fascinating physical phenomena and been used for prototype vertical-field-effect-transistors.1,2 In this work, interlayer electron tunneling in stacked high-quality crystalline MoS2 films were investigated. A trilayered MoS2 film was sandwiched between top and bottom electrodes with an adjacent bottom gate, and the discrete energy levels in each layer could be tuned by bias and gate voltages. When the discrete energy levels aligned, a resonant tunneling peak appeared in the current-voltage characteristics. The peak position shifts linearly with perpendicular magnetic field, indicating formation of Landau levels. From this linear dependence, the effective mass and Fermi velocity are determined and are confirmed by electronic structure calculations. These fundamental parameters are useful for exploitation of its unique properties.

  19. Oxidation of gallium arsenide in a plasma multipole device. Study of the MOS structures obtained

    NASA Technical Reports Server (NTRS)

    Gourrier, S.; Mircea, A.; Simondet, F.

    1980-01-01

    The oxygen plasma oxidation of GaAs was studied in order to obtain extremely high frequency responses with MOS devices. In the multipole system a homogeneous oxygen plasma of high density can easily be obtained in a large volume. This system is thus convenient for the study of plasma oxidation of GaAs. The electrical properties of the MOS diodes obtained in this way are controlled by interface states, located mostly in the upper half of the band gap where densities in the 10 to the 13th power/(sq cm) (eV) range can be estimated. Despite these interface states the possibility of fabricating MOSFET transistors working mostly in the depletion mode for a higher frequency cut-off still exists.

  20. The casein kinase II beta subunit binds to Mos and inhibits Mos activity.

    PubMed Central

    Chen, M; Li, D; Krebs, E G; Cooper, J A

    1997-01-01

    Mos is a germ cell-specific serine/threonine kinase and is required for Xenopus oocyte maturation. Active Mos stimulates a mitogen-activated protein kinase (MAPK) by directly phosphorylating and activating MAPK kinase (MKK). We report here that the Xenopus homolog of the beta subunit of casein kinase II (CKII beta) binds to and regulates Mos. The Mos-interacting region of CKII beta was mapped to the C terminus. Mos bound to CKII beta in somatic cells ectopically expressing Mos and CKII beta as well as in unfertilized Xenopus eggs. CKII beta inhibited Mos-mediated MAPK activation in rabbit reticulocyte lysates and repressed MKK activation by v-Mos in a coupled kinase assay. In addition, microinjection of CKII beta mRNA into Xenopus oocytes inhibited progesterone-induced meiotic maturation and MAPK activation, presumably by binding of CKII beta to Mos and thereby inhibiting MAPK activation. Moreover, this inhibitory phenotype could be rescued by another protein that binds to CKII beta, CKII alpha. The ability of ectopic CKII beta to inhibit meiotic maturation and the detection of a complex between endogenous Mos and CKII beta suggest that CKII beta may act as an inhibitor of Mos during oocyte maturation, perhaps setting a threshold beyond which Mos protein must accumulate before it can activate the MAPK pathway. PMID:9121438

  1. Polarity control in WSe2 double-gate transistors

    PubMed Central

    Resta, Giovanni V.; Sutar, Surajit; Balaji, Yashwanth; Lin, Dennis; Raghavan, Praveen; Radu, Iuliana; Catthoor, Francky; Thean, Aaron; Gaillardon, Pierre-Emmanuel; de Micheli, Giovanni

    2016-01-01

    As scaling of conventional silicon-based electronics is reaching its ultimate limit, considerable effort has been devoted to find new materials and new device concepts that could ultimately outperform standard silicon transistors. In this perspective two-dimensional transition metal dichalcogenides, such as MoS2 and WSe2, have recently attracted considerable interest thanks to their electrical properties. Here, we report the first experimental demonstration of a doping-free, polarity-controllable device fabricated on few-layer WSe2. We show how modulation of the Schottky barriers at drain and source by a separate gate, named program gate, can enable the selection of the carriers injected in the channel, and achieved controllable polarity behaviour with ON/OFF current ratios >106 for both electrons and holes conduction. Polarity-controlled WSe2 transistors enable the design of compact logic gates, leading to higher computational densities in 2D-flatronics. PMID:27390014

  2. Polarity control in WSe2 double-gate transistors

    NASA Astrophysics Data System (ADS)

    Resta, Giovanni V.; Sutar, Surajit; Balaji, Yashwanth; Lin, Dennis; Raghavan, Praveen; Radu, Iuliana; Catthoor, Francky; Thean, Aaron; Gaillardon, Pierre-Emmanuel; de Micheli, Giovanni

    2016-07-01

    As scaling of conventional silicon-based electronics is reaching its ultimate limit, considerable effort has been devoted to find new materials and new device concepts that could ultimately outperform standard silicon transistors. In this perspective two-dimensional transition metal dichalcogenides, such as MoS2 and WSe2, have recently attracted considerable interest thanks to their electrical properties. Here, we report the first experimental demonstration of a doping-free, polarity-controllable device fabricated on few-layer WSe2. We show how modulation of the Schottky barriers at drain and source by a separate gate, named program gate, can enable the selection of the carriers injected in the channel, and achieved controllable polarity behaviour with ON/OFF current ratios >106 for both electrons and holes conduction. Polarity-controlled WSe2 transistors enable the design of compact logic gates, leading to higher computational densities in 2D-flatronics.

  3. Experimental study of time-dependent dielectric breakdown in tri-gate nanowire transistor

    NASA Astrophysics Data System (ADS)

    Ota, Kensuke; Tanaka, Chika; Numata, Toshinori; Matsushita, Daisuke; Saitoh, Masumi

    2016-08-01

    We systematically investigate the size dependence of the time-dependent dielectric breakdown (TDDB) in a tri-gate nanowire transistor (NW Tr.). It is newly found that TDDB reliability is degraded in NW Tr. as compared with that in a planar transistor owing to the locally enhanced electric field at the NW corner. Moreover, in the region with a width (W) less than 40 nm, nanowire width reduction leads to a shorter time to gate dielectric breakdown indicating additional degradation of TDDB reliability in NW Tr. with smaller W. Although TDDB in three-dimensional (3D) MOS structures such as a trench MOS capacitor has already been reported, the size dependence of TDDB in scaled NW Tr. is firstly discussed in this paper since a trench capacitor is different from recent NW Tr. in structure, device size, gate dielectric thickness, and scaling effect on TDDB.

  4. Vibrational and optical properties of MoS2: From monolayer to bulk

    NASA Astrophysics Data System (ADS)

    Molina-Sánchez, Alejandro; Hummer, Kerstin; Wirtz, Ludger

    2015-12-01

    Molybdenum disulfide, MoS2, has recently gained considerable attention as a layered material where neighboring layers are only weakly interacting and can easily slide against each other. Therefore, mechanical exfoliation allows the fabrication of single and multi-layers and opens the possibility to generate atomically thin crystals with outstanding properties. In contrast to graphene, it has an optical gap of ~1.9 eV. This makes it a prominent candidate for transistor and opto-electronic applications. Single-layer MoS2 exhibits remarkably different physical properties compared to bulk MoS2 due to the absence of interlayer hybridization. For instance, while the band gap of bulk and multi-layer MoS2 is indirect, it becomes direct with decreasing number of layers. In this review, we analyze from a theoretical point of view the electronic, optical, and vibrational properties of single-layer, few-layer and bulk MoS2. In particular, we focus on the effects of spin-orbit interaction, number of layers, and applied tensile strain on the vibrational and optical properties. We examine the results obtained by different methodologies, mainly ab initio approaches. We also discuss which approximations are suitable for MoS2 and layered materials. The effect of external strain on the band gap of single-layer MoS2 and the crossover from indirect to direct band gap is investigated. We analyze the excitonic effects on the absorption spectra. The main features, such as the double peak at the absorption threshold and the high-energy exciton are presented. Furthermore, we report on the the phonon dispersion relations of single-layer, few-layer and bulk MoS2. Based on the latter, we explain the behavior of the Raman-active A1g and E2g1 modes as a function of the number of layers. Finally, we compare theoretical and experimental results of Raman, photoluminescence, and optical-absorption spectroscopy.

  5. Synthesis and characterization of large-area and continuous MoS2 atomic layers by RF magnetron sputtering.

    PubMed

    Hussain, Sajjad; Shehzad, Muhammad Arslan; Vikraman, Dhanasekaran; Khan, Muhammad Farooq; Singh, Jai; Choi, Dong-Chul; Seo, Yongho; Eom, Jonghwa; Lee, Wan-Gyu; Jung, Jongwan

    2016-02-21

    In this article, we report layer-controlled, continuous and large-area molydenum sulfide (MoS2) growth onto a SiO2/Si substrate by RF sputtering combined with sulfurization. A two-step process was employed to synthesize MoS2 films. In the first step, an atomically thin MoO3 film was deposited by RF magnetron sputtering at 300 °C. Subsequently, the as-sputtered MoO3 film was further subjected to post-annealing and sulfurization processes at 650 °C for 1 hour. It was observed that the number of layers of MoS2 can be controlled by adjusting the sputtering time. The fabricated MoS2 transistors exhibited high mobility values of ∼21 cm(2) V(-1) s(-1) (bilayer) and ∼25 cm(2) V(-1) s(-1) (trilayer), on/off ratios in the range of ∼10(7) (bilayer) and 10(4)-10(5) (trilayer), respectively. We believe that our proposed paradigm can start a new method for the growth of MoS2 in future electronics and optoelectronics applications.

  6. Plasmonic Gold Nanorods Coverage Influence on Enhancement of the Photoluminescence of Two-Dimensional MoS2 Monolayer

    PubMed Central

    Lee, Kevin C. J.; Chen, Yi-Huan; Lin, Hsiang-Yu; Cheng, Chia-Chin; Chen, Pei-Ying; Wu, Ting-Yi; Shih, Min-Hsiung; Wei, Kung-Hwa; Li, Lain-Jong; Chang, Chien-Wen

    2015-01-01

    The 2-D transition metal dichalcogenide (TMD) semiconductors, has received great attention due to its excellent optical and electronic properties and potential applications in field-effect transistors, light emitting and sensing devices. Recently surface plasmon enhanced photoluminescence (PL) of the weak 2-D TMD atomic layers was developed to realize the potential optoelectronic devices. However, we noticed that the enhancement would not increase monotonically with increasing of metal plasmonic objects and the emission drop after the certain coverage. This study presents the optimized PL enhancement of a monolayer MoS2 in the presence of gold (Au) nanorods. A localized surface plasmon wave of Au nanorods that generated around the monolayer MoS2 can provide resonance wavelength overlapping with that of the MoS2 gain spectrum. These spatial and spectral overlapping between the localized surface plasmon polariton waves and that from MoS2 emission drastically enhanced the light emission from the MoS2 monolayer. We gave a simple model and physical interpretations to explain the phenomena. The plasmonic Au nanostructures approach provides a valuable avenue to enhancing the emitting efficiency of the 2-D nano-materials and their devices for the future optoelectronic devices and systems. PMID:26576041

  7. Tunable Electrical and Optical Characteristics in Monolayer Graphene and Few-Layer MoS2 Heterostructure Devices.

    PubMed

    Rathi, Servin; Lee, Inyeal; Lim, Dongsuk; Wang, Jianwei; Ochiai, Yuichi; Aoki, Nobuyuki; Watanabe, Kenji; Taniguchi, Takashi; Lee, Gwan-Hyoung; Yu, Young-Jun; Kim, Philip; Kim, Gil-Ho

    2015-08-12

    Lateral and vertical two-dimensional heterostructure devices, in particular graphene-MoS2, have attracted profound interest as they offer additional functionalities over normal two-dimensional devices. Here, we have carried out electrical and optical characterization of graphene-MoS2 heterostructure. The few-layer MoS2 devices with metal electrode at one end and monolayer graphene electrode at the other end show nonlinearity in drain current with drain voltage sweep due to asymmetrical Schottky barrier height at the contacts and can be modulated with an external gate field. The doping effect of MoS2 on graphene was observed as double Dirac points in the transfer characteristics of the graphene field-effect transistor (FET) with a few-layer MoS2 overlapping the middle part of the channel, whereas the underlapping of graphene have negligible effect on MoS2 FET characteristics, which showed typical n-type behavior. The heterostructure also exhibits a strongest optical response for 520 nm wavelength, which decreases with higher wavelengths. Another distinct feature observed in the heterostructure is the peak in the photocurrent around zero gate voltage. This peak is distinguished from conventional MoS2 FETs, which show a continuous increase in photocurrent with back-gate voltage. These results offer significant insight and further enhance the understanding of the graphene-MoS2 heterostructure.

  8. Field-effect transistors based on few-layered α-MoTe(2).

    PubMed

    Pradhan, Nihar R; Rhodes, Daniel; Feng, Simin; Xin, Yan; Memaran, Shahriar; Moon, Byoung-Hee; Terrones, Humberto; Terrones, Mauricio; Balicas, Luis

    2014-06-24

    Here we report the properties of field-effect transistors based on a few layers of chemical vapor transport grown α-MoTe2 crystals mechanically exfoliated onto SiO2. We performed field-effect and Hall mobility measurements, as well as Raman scattering and transmission electron microscopy. In contrast to both MoS2 and MoSe2, our MoTe2 field-effect transistors are observed to be hole-doped, displaying on/off ratios surpassing 10(6) and typical subthreshold swings of ∼140 mV per decade. Both field-effect and Hall mobilities indicate maximum values approaching or surpassing 10 cm(2)/(V s), which are comparable to figures previously reported for single or bilayered MoS2 and/or for MoSe2 exfoliated onto SiO2 at room temperature and without the use of dielectric engineering. Raman scattering reveals sharp modes in agreement with previous reports, whose frequencies are found to display little or no dependence on the number of layers. Given that MoS2 is electron-doped, the stacking of MoTe2 onto MoS2 could produce ambipolar field-effect transistors and a gap modulation. Although the overall electronic performance of MoTe2 is comparable to those of MoS2 and MoSe2, the heavier element Te leads to a stronger spin-orbit coupling and possibly to concomitantly longer decoherence times for exciton valley and spin indexes.

  9. Field-effect transistors based on few-layered α-MoTe(2).

    PubMed

    Pradhan, Nihar R; Rhodes, Daniel; Feng, Simin; Xin, Yan; Memaran, Shahriar; Moon, Byoung-Hee; Terrones, Humberto; Terrones, Mauricio; Balicas, Luis

    2014-06-24

    Here we report the properties of field-effect transistors based on a few layers of chemical vapor transport grown α-MoTe2 crystals mechanically exfoliated onto SiO2. We performed field-effect and Hall mobility measurements, as well as Raman scattering and transmission electron microscopy. In contrast to both MoS2 and MoSe2, our MoTe2 field-effect transistors are observed to be hole-doped, displaying on/off ratios surpassing 10(6) and typical subthreshold swings of ∼140 mV per decade. Both field-effect and Hall mobilities indicate maximum values approaching or surpassing 10 cm(2)/(V s), which are comparable to figures previously reported for single or bilayered MoS2 and/or for MoSe2 exfoliated onto SiO2 at room temperature and without the use of dielectric engineering. Raman scattering reveals sharp modes in agreement with previous reports, whose frequencies are found to display little or no dependence on the number of layers. Given that MoS2 is electron-doped, the stacking of MoTe2 onto MoS2 could produce ambipolar field-effect transistors and a gap modulation. Although the overall electronic performance of MoTe2 is comparable to those of MoS2 and MoSe2, the heavier element Te leads to a stronger spin-orbit coupling and possibly to concomitantly longer decoherence times for exciton valley and spin indexes. PMID:24878323

  10. A highly sensitive, highly transparent, gel-gated MoS2 phototransistor on biodegradable nanopaper

    NASA Astrophysics Data System (ADS)

    Zhang, Qing; Bao, Wenzhong; Gong, Amy; Gong, Tao; Ma, Dakang; Wan, Jiayu; Dai, Jiaqi; Munday, Jeremy N.; He-Hau, Jr.; Hu, Liangbing; Zhang, Daihua

    2016-07-01

    Transition metal dichalcogenides hold great promise for a variety of novel electrical, optical and mechanical devices and applications. Among them, molybdenum disulphide (MoS2) is gaining increasing attention as gate dielectrics and semiconductive channels for high-performance field effect transistors. Here we report on the first MoS2 phototransistor built on a flexible, transparent and biodegradable substrate with an electrolyte gate dielectric. We have carried out systematic studies on its electrical and optoelectronic properties. The MoS2 phototransistor exhibited an excellent photoresponsivity of ~1.5 kA W-1, about two times higher compared to typical back-gated devices reported in previous studies. The device is highly transparent at the same time with an average optical transmittance of 82%. Successful fabrication of phototransistors on flexible cellulose nanopaper with excellent performance and transparency suggests that it is feasible to achieve an ecofriendly and biodegradable phototransistor with great photoresponsivity, broad spectral range and durable flexibility.Transition metal dichalcogenides hold great promise for a variety of novel electrical, optical and mechanical devices and applications. Among them, molybdenum disulphide (MoS2) is gaining increasing attention as gate dielectrics and semiconductive channels for high-performance field effect transistors. Here we report on the first MoS2 phototransistor built on a flexible, transparent and biodegradable substrate with an electrolyte gate dielectric. We have carried out systematic studies on its electrical and optoelectronic properties. The MoS2 phototransistor exhibited an excellent photoresponsivity of ~1.5 kA W-1, about two times higher compared to typical back-gated devices reported in previous studies. The device is highly transparent at the same time with an average optical transmittance of 82%. Successful fabrication of phototransistors on flexible cellulose nanopaper with excellent

  11. Novel Field-Effect Schottky Barrier Transistors Based on Graphene-MoS2 Heterojunctions

    NASA Astrophysics Data System (ADS)

    Tian, He; Tan, Zhen; Wu, Can; Wang, Xiaomu; Mohammad, Mohammad Ali; Xie, Dan; Yang, Yi; Wang, Jing; Li, Lain-Jong; Xu, Jun; Ren, Tian-Ling

    2014-08-01

    Recently, two-dimensional materials such as molybdenum disulphide (MoS2) have been demonstrated to realize field effect transistors (FET) with a large current on-off ratio. However, the carrier mobility in backgate MoS2 FET is rather low (typically 0.5-20 cm2/V.s). Here, we report a novel field-effect Schottky barrier transistors (FESBT) based on graphene-MoS2 heterojunction (GMH), where the characteristics of high mobility from graphene and high on-off ratio from MoS2 are properly balanced in the novel transistors. Large modulation on the device current (on/off ratio of 105) is achieved by adjusting the backgate (through 300 nm SiO2) voltage to modulate the graphene-MoS2 Schottky barrier. Moreover, the field effective mobility of the FESBT is up to 58.7 cm2/V.s. Our theoretical analysis shows that if the thickness of oxide is further reduced, a subthreshold swing (SS) of 40 mV/decade can be maintained within three orders of drain current at room temperature. This provides an opportunity to overcome the limitation of 60 mV/decade for conventional CMOS devices. The FESBT implemented with a high on-off ratio, a relatively high mobility and a low subthreshold promises low-voltage and low-power applications for future electronics.

  12. Few-layer molybdenum disulfide transistors and circuits for high-speed flexible electronics.

    PubMed

    Cheng, Rui; Jiang, Shan; Chen, Yu; Liu, Yuan; Weiss, Nathan; Cheng, Hung-Chieh; Wu, Hao; Huang, Yu; Duan, Xiangfeng

    2014-10-08

    Two-dimensional layered materials, such as molybdenum disulfide, are emerging as an exciting material system for future electronics due to their unique electronic properties and atomically thin geometry. Here we report a systematic investigation of MoS2 transistors with optimized contact and device geometry, to achieve self-aligned devices with performance including an intrinsic gain over 30, an intrinsic cut-off frequency fT up to 42 GHz and a maximum oscillation frequency fMAX up to 50 GHz, exceeding the reported values for MoS2 transistors to date (fT~0.9 GHz, fMAX~1 GHz). Our results show that logic inverters or radio frequency amplifiers can be formed by integrating multiple MoS2 transistors on quartz or flexible substrates with voltage gain in the gigahertz regime. This study demonstrates the potential of two-dimensional layered semiconductors for high-speed flexible electronics.

  13. High Power Switching Transistor

    NASA Technical Reports Server (NTRS)

    Hower, P. L.; Kao, Y. C.; Carnahan, D. C.

    1983-01-01

    Improved switching transistors handle 400-A peak currents and up to 1,200 V. Using large diameter silicon wafers with twice effective area as D60T, form basis for D7 family of power switching transistors. Package includes npn wafer, emitter preform, and base-contact insert. Applications are: 25to 50-kilowatt high-frequency dc/dc inverters, VSCF converters, and motor controllers for electrical vehicles.

  14. Black Phosphorus RF Transistor

    NASA Astrophysics Data System (ADS)

    Wang, Han; Wang, Xiaomu; Xia, Fengnian; Wang, Luhao; Jiang, Hao; Xia, Qiangfei; Chin, Mattew L.; Dubey, Madan; Han, Shu-Jen

    2015-03-01

    Few-layer and thin film form of layered black phosphorus (BP) has recently emerged as a promising material for applications in high performance thin film electronics and infrared optoelectronics. Layered BP offers a ~ 0.3eV bandgap and high mobility, leading to transistor devices with decent on/off ratio and high on-state current density. Here, we demonstrate the GHz frequency operation of black phosphorus field-effect transistor for the first time. BP transistors demonstrated here show excellent current saturation with an on-off ratio exceeding 2 × 103. The S-parameter characterization is performed for the first time on black phosphorus transistors, giving a 12 GHz short-circuit current-gain cut-off frequency and 20 GHz maximum oscillation frequency in 300 nm channel length devices. A current density in excess of 270 mA/mm and DC transconductance above 180 mS/mm are achieved for hole conductions. The results reveal the promising potential of black phosphorus transistors for enabling the next generation thin film transistor technology that can operate in the multi-GHz frequency range and beyond.

  15. Transistor-based interface circuitry

    DOEpatents

    Taubman, Matthew S.

    2004-02-24

    Among the embodiments of the present invention is an apparatus that includes a transistor, a servo device, and a current source. The servo device is operable to provide a common base mode of operation of the transistor by maintaining an approximately constant voltage level at the transistor base. The current source is operable to provide a bias current to the transistor. A first device provides an input signal to an electrical node positioned between the emitter of the transistor and the current source. A second device receives an output signal from the collector of the transistor.

  16. Transistor-based interface circuitry

    DOEpatents

    Taubman, Matthew S.

    2007-02-13

    Among the embodiments of the present invention is an apparatus that includes a transistor, a servo device, and a current source. The servo device is operable to provide a common base mode of operation of the transistor by maintaining an approximately constant voltage level at the transistor base. The current source is operable to provide a bias current to the transistor. A first device provides an input signal to an electrical node positioned between the emitter of the transistor and the current source. A second device receives an output signal from the collector of the transistor.

  17. A New Electrolytic Synthesis Method for Few-Layered MoS2 Nanosheets and Their Robust Biointerfacing with Reduced Antibodies.

    PubMed

    Kukkar, Manil; Tuteja, Satish K; Sharma, Amit L; Kumar, Vinod; Paul, Ashok K; Kim, Ki-Hyun; Sabherwal, Priyanka; Deep, Akash

    2016-07-01

    We report an efficient method for the synthesis of few-layered MoS2 nanosheets and demonstrate their application in the label-free detection of the prostate-specific antigen (PSA) cancer marker. As a novel strategy, the electro-dissolution of molybdenum metal sheets in the presence of Na(+) and S(2-) ions led to the formation of Na(+) intercalated MoS2. Further exfoliation by ultrasonication yielded the desired formation of few-layered MoS2 nanosheets. After comprehensive characterization, the synthesized MoS2 nanosheets were channeled in a field-effect transistor (FET) microdevice. Chemically reduced anti-PSA antibodies were immobilized on the MoS2 channel above the FET microdevice to construct a specific PSA immunosensor. The antibodies were deliberately reduced to expose the hinge-region disulfide bonds. This approach offered a robust and site-directed immunosensing device through biointerfacing of the sulfhydryl groups (-SH) in the reduced antibody with the surface S atoms of MoS2. This device was validated as an effective immunosensor with a low detection limit (10(-5) ng/mL) over a wide linear detection range (10(-5) to 75 ng/mL). PMID:27296984

  18. A New Electrolytic Synthesis Method for Few-Layered MoS2 Nanosheets and Their Robust Biointerfacing with Reduced Antibodies.

    PubMed

    Kukkar, Manil; Tuteja, Satish K; Sharma, Amit L; Kumar, Vinod; Paul, Ashok K; Kim, Ki-Hyun; Sabherwal, Priyanka; Deep, Akash

    2016-07-01

    We report an efficient method for the synthesis of few-layered MoS2 nanosheets and demonstrate their application in the label-free detection of the prostate-specific antigen (PSA) cancer marker. As a novel strategy, the electro-dissolution of molybdenum metal sheets in the presence of Na(+) and S(2-) ions led to the formation of Na(+) intercalated MoS2. Further exfoliation by ultrasonication yielded the desired formation of few-layered MoS2 nanosheets. After comprehensive characterization, the synthesized MoS2 nanosheets were channeled in a field-effect transistor (FET) microdevice. Chemically reduced anti-PSA antibodies were immobilized on the MoS2 channel above the FET microdevice to construct a specific PSA immunosensor. The antibodies were deliberately reduced to expose the hinge-region disulfide bonds. This approach offered a robust and site-directed immunosensing device through biointerfacing of the sulfhydryl groups (-SH) in the reduced antibody with the surface S atoms of MoS2. This device was validated as an effective immunosensor with a low detection limit (10(-5) ng/mL) over a wide linear detection range (10(-5) to 75 ng/mL).

  19. Preventing Simultaneous Conduction In Switching Transistors

    NASA Technical Reports Server (NTRS)

    Mclyman, William T.

    1990-01-01

    High voltage spikes and electromagnetic interference suppressed. Power-supply circuit including two switching transistors easily modified to prevent simultaneous conduction by both transistors during switching intervals. Diode connected between collector of each transistor and driving circuit for opposite transistor suppresses driving signal to transistor being turned on until transistor being turned off ceases to carry current.

  20. Tunneling in thin MOS structures

    NASA Technical Reports Server (NTRS)

    Maserjian, J.

    1974-01-01

    Recent results on tunneling in thin MOS structures are described. Thermally grown SiO2 films in the thickness range of 22-40 A have been shown to be effectively uniform on an atomic scale and exhibit an extremely abrupt oxide-silicon interface. Resonant reflections are observed at this interface for Fowler-Nordheim tunneling and are shown to agree with the exact theory for a trapezoidal barrier. Tunneling at lower fields is consistent with elastic tunneling into the silicon direct conduction band and, at still lower fields, inelastic tunneling into the indirect conduction band. Approximate dispersion relations are obtained over portions of the silicon-dioxide energy gap and conduction band.

  1. Facile fabrication of a ultraviolet tunable MoS2/p-Si junction diode

    NASA Astrophysics Data System (ADS)

    Serrano, William; Pinto, Nicholas J.; Naylor, Carl H.; Kybert, Nicholas J.; Johnson, A. T. Charlie

    2015-05-01

    Chemical vapor deposition grown MoS2 single crystals were transferred onto the edge of a p-Si/SiO2 wafer, forming an abrupt heterogeneous junction diode at the MoS2/p-Si interface. When electrically characterized as a field effect transistor, MoS2 exhibits an n-type response and can be doped in the presence of ultraviolet (UV) light. As a diode, it operates satisfactorily in air, but has higher currents in vacuum with a turn on voltage of ˜1.3 V and an on/off ratio of 20 at ±2 V. UV irradiation increases the diode on state current, decreases the turn-on voltage, and reduces the ideality parameter below 2. These changes are reversible after annealing in air as desorption of electron trapping species like O2- and H2O- are believed responsible for this effect. A circuit integrating this diode was used to rectify a 1 kHz signal with an efficiency of 12%. Its simple design, coupled with the ability to clip AC signals, sense UV light, and reversibly tune these diodes, makes them inexpensive, multifunctional, and usable as active or passive circuit components in complex electronics.

  2. Gate-Tunable Atomically Thin Lateral MoS2 Schottky Junction Patterned by Electron Beam.

    PubMed

    Katagiri, Y; Nakamura, T; Ishii, A; Ohata, C; Hasegawa, M; Katsumoto, S; Cusati, T; Fortunelli, A; Iannaccone, G; Fiori, G; Roche, S; Haruyama, J

    2016-06-01

    Among atomically thin two-dimensional (2D) materials, molybdenum disulfide (MoS2) is attracting considerable attention because of its direct bandgap in the 2H-semiconducting phase. On the other hand, a 1T-metallic phase has been revealed, bringing complementary application. Recently, thanks to top-down fabrication using electron beam (EB) irradiation techniques, in-plane 1T-metal/2H-semiconductor lateral (Schottky) MoS2 junctions were demonstrated, opening a path toward the co-integration of active and passive two-dimensional devices. Here, we report the first transport measurements evidencing the formation of a MoS2 Schottky barrier (SB) junction with barrier height of 0.13-0.18 eV created at the interface between EB-irradiated (1T)/nonirradiated (2H) regions. Our experimental findings, supported by state-of-the-art simulation, reveal unique device fingerprint of SB-based field-effect transistors made from atom-thin 1T layers. PMID:27152475

  3. Gate-Tunable Atomically Thin Lateral MoS2 Schottky Junction Patterned by Electron Beam.

    PubMed

    Katagiri, Y; Nakamura, T; Ishii, A; Ohata, C; Hasegawa, M; Katsumoto, S; Cusati, T; Fortunelli, A; Iannaccone, G; Fiori, G; Roche, S; Haruyama, J

    2016-06-01

    Among atomically thin two-dimensional (2D) materials, molybdenum disulfide (MoS2) is attracting considerable attention because of its direct bandgap in the 2H-semiconducting phase. On the other hand, a 1T-metallic phase has been revealed, bringing complementary application. Recently, thanks to top-down fabrication using electron beam (EB) irradiation techniques, in-plane 1T-metal/2H-semiconductor lateral (Schottky) MoS2 junctions were demonstrated, opening a path toward the co-integration of active and passive two-dimensional devices. Here, we report the first transport measurements evidencing the formation of a MoS2 Schottky barrier (SB) junction with barrier height of 0.13-0.18 eV created at the interface between EB-irradiated (1T)/nonirradiated (2H) regions. Our experimental findings, supported by state-of-the-art simulation, reveal unique device fingerprint of SB-based field-effect transistors made from atom-thin 1T layers.

  4. Deuterium-incorporated gate oxide of MOS devices fabricated by using deuterium ion implantation

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Sung; Lear, Kevin L.

    2012-04-01

    In the aspect of metal-oxide-semiconductor (MOS) device reliability, deuterium-incorporated gate oxide could be utilized to suppress the wear-out that is combined with oxide trap generation. An alternative deuterium process for the passivation of oxide traps or defects in the gate oxide of MOS devices has been suggested in this study. The deuterium ion is delivered to the location where the gate oxide resides by using an implantation process and subsequent N2 annealing process at the back-end of metallization process. A conventional MOS field-effect transistor (MOSFET) with a 3-nm-thick gate oxide and poly-to-ploy capacitor sandwiched with 20-nm-thick SiO2 were fabricated in order to demonstrate the deuterium effect in our process. An optimum condition of ion implantation was necessary to account for the topography of the overlaying layers in the device structure and to minimize the physical damage due to the energy of the implanted ion. Device parameter variations, the gate leakage current, and the dielectric breakdown phenomenon were investigated in the deuterium-ion-implanted devices. We found the isotope effect between hydrogen- and deuterium-implanted devices and an improved electrical reliability in the deuterated gate oxide. This implies that deuterium bonds are generated effectively at the Si/SiO2 interface and in the SiO2 bulk.

  5. A new bipolar transistor - GAT

    NASA Astrophysics Data System (ADS)

    Kondo, H.; Yukimoto, Y.

    1980-02-01

    A new bipolar transistor named Gate Associated Transistor (GAT) was proposed and the operating mechanisms were verified. The structure of the GAT has a unique base region consisting of an FET merged into the base of a standard bipolar transistor. The operating mechanisms and characteristics of the GAT were investigated and compared with those of standard power transistors. The most outstanding feature of the GAT was a large area for safe operation.

  6. Epitaxial growth of a monolayer WSe2-MoS2 lateral p-n junction with an atomically sharp interface

    NASA Astrophysics Data System (ADS)

    Li, Ming-Yang; Shi, Yumeng; Cheng, Chia-Chin; Lu, Li-Syuan; Lin, Yung-Chang; Tang, Hao-Lin; Tsai, Meng-Lin; Chu, Chih-Wei; Wei, Kung-Hwa; He-Hau, Jr.; Chang, Wen-Hao; Suenaga, Kazu; Li, Lain-Jong

    2015-07-01

    Two-dimensional transition metal dichalcogenides (TMDCs) such as molybdenum sulfide MoS2 and tungsten sulfide WSe2 have potential applications in electronics because they exhibit high on-off current ratios and distinctive electro-optical properties. Spatially connected TMDC lateral heterojunctions are key components for constructing monolayer p-n rectifying diodes, light-emitting diodes, photovoltaic devices, and bipolar junction transistors. However, such structures are not readily prepared via the layer-stacking techniques, and direct growth favors the thermodynamically preferred TMDC alloys. We report the two-step epitaxial growth of lateral WSe2-MoS2 heterojunction, where the edge of WSe2 induces the epitaxial MoS2 growth despite a large lattice mismatch. The epitaxial growth process offers a controllable method to obtain lateral heterojunction with an atomically sharp interface.

  7. Quantum Thermal Transistor.

    PubMed

    Joulain, Karl; Drevillon, Jérémie; Ezzahri, Younès; Ordonez-Miranda, Jose

    2016-05-20

    We demonstrate that a thermal transistor can be made up with a quantum system of three interacting subsystems, coupled to a thermal reservoir each. This thermal transistor is analogous to an electronic bipolar one with the ability to control the thermal currents at the collector and at the emitter with the imposed thermal current at the base. This is achieved by determining the heat fluxes by means of the strong-coupling formalism. For the case of three interacting spins, in which one of them is coupled to the other two, that are not directly coupled, it is shown that high amplification can be obtained in a wide range of energy parameters and temperatures. The proposed quantum transistor could, in principle, be used to develop devices such as a thermal modulator and a thermal amplifier in nanosystems.

  8. Quantum Thermal Transistor.

    PubMed

    Joulain, Karl; Drevillon, Jérémie; Ezzahri, Younès; Ordonez-Miranda, Jose

    2016-05-20

    We demonstrate that a thermal transistor can be made up with a quantum system of three interacting subsystems, coupled to a thermal reservoir each. This thermal transistor is analogous to an electronic bipolar one with the ability to control the thermal currents at the collector and at the emitter with the imposed thermal current at the base. This is achieved by determining the heat fluxes by means of the strong-coupling formalism. For the case of three interacting spins, in which one of them is coupled to the other two, that are not directly coupled, it is shown that high amplification can be obtained in a wide range of energy parameters and temperatures. The proposed quantum transistor could, in principle, be used to develop devices such as a thermal modulator and a thermal amplifier in nanosystems. PMID:27258859

  9. Interpreting Transistor Noise

    NASA Astrophysics Data System (ADS)

    Pospieszalski, M. W.

    2010-10-01

    The simple noise models of field effect and bipolar transistors reviewed in this article are quite useful in engineering practice, as illustrated by measured and modeled results. The exact and approximate expressions for the noise parameters of FETs and bipolar transistors reveal certain common noise properties and some general noise properties of both devices. The usefulness of these expressions in interpreting the dependence of measured noise parameters on frequency, bias, and temperature and, consequently, in checking of consistency of measured data has been demonstrated.

  10. Influence of Stoichiometry on the Optical and Electrical Properties of Chemical Vapor Deposition Derived MoS2

    PubMed Central

    2015-01-01

    Ultrathin transition metal dichalcogenides (TMDCs) of Mo and W show great potential for digital electronics and optoelectronic applications. Whereas early studies were limited to mechanically exfoliated flakes, the large-area synthesis of 2D TMDCs has now been realized by chemical vapor deposition (CVD) based on a sulfurization reaction. The optoelectronic properties of CVD grown monolayer MoS2 have been intensively investigated, but the influence of stoichiometry on the electrical and optical properties has been largely overlooked. Here we systematically vary the stoichiometry of monolayer MoS2 during CVD via controlled sulfurization and investigate the associated changes in photoluminescence and electrical properties. X-ray photoelectron spectroscopy is employed to measure relative variations in stoichiometry and the persistence of MoOx species. As MoS2−δ is reduced (increasing δ), the field-effect mobility of monolayer transistors increases while the photoluminescence yield becomes nonuniform. Devices fabricated from monolayers with the lowest sulfur content have negligible hysteresis and a threshold voltage of ∼0 V. We conclude that the electrical and optical properties of monolayer MoS2 crystals can be tuned via stoichiometry engineering to meet the requirements of various applications. PMID:25223821

  11. Lithography-free plasma-induced patterned growth of MoS2 and its heterojunction with graphene.

    PubMed

    Chen, Xiang; Park, Yong Ju; Das, Tanmoy; Jang, Houk; Lee, Jae-Bok; Ahn, Jong-Hyun

    2016-08-18

    Application-oriented patterned growth of transition metal dichalcogenides (TMDCs) and their heterojunctions is of critical importance for sophisticated, customized two-dimensional (2D) electronic and optoelectronic devices; however, it is still difficult to fabricate these patterns in a simple, clean, and high controllability manner without using optical lithography. Here, we report the direct synthesis of patterned MoS2 and graphene-MoS2 heterojunctions via selective plasma treatment of a SiO2/Si substrate and chemical vapor deposition of MoS2. This method has multiple merits, such as simple steps, a short operating time, easily isolated MoS2 layers with clean surfaces and controllable locations, shapes, sizes and thicknesses, which enable their integration into the device structure without using a photoresist. In addition, we demonstrate the direct growth of patterned graphene-MoS2 heterojunctions for the fabrication of transistor. This study reveals a novel method to fabricate and use patterned MoS2 and graphene-MoS2 heterojunctions, which could be generalized to the rational design of other 2D materials, heterojunctions and devices in the future. PMID:27432242

  12. Influence of stoichiometry on the optical and electrical properties of chemical vapor deposition derived MoS2.

    PubMed

    Kim, In Soo; Sangwan, Vinod K; Jariwala, Deep; Wood, Joshua D; Park, Spencer; Chen, Kan-Sheng; Shi, Fengyuan; Ruiz-Zepeda, Francisco; Ponce, Arturo; Jose-Yacaman, Miguel; Dravid, Vinayak P; Marks, Tobin J; Hersam, Mark C; Lauhon, Lincoln J

    2014-10-28

    Ultrathin transition metal dichalcogenides (TMDCs) of Mo and W show great potential for digital electronics and optoelectronic applications. Whereas early studies were limited to mechanically exfoliated flakes, the large-area synthesis of 2D TMDCs has now been realized by chemical vapor deposition (CVD) based on a sulfurization reaction. The optoelectronic properties of CVD grown monolayer MoS2 have been intensively investigated, but the influence of stoichiometry on the electrical and optical properties has been largely overlooked. Here we systematically vary the stoichiometry of monolayer MoS2 during CVD via controlled sulfurization and investigate the associated changes in photoluminescence and electrical properties. X-ray photoelectron spectroscopy is employed to measure relative variations in stoichiometry and the persistence of MoOx species. As MoS2-δ is reduced (increasing δ), the field-effect mobility of monolayer transistors increases while the photoluminescence yield becomes nonuniform. Devices fabricated from monolayers with the lowest sulfur content have negligible hysteresis and a threshold voltage of ∼ 0 V. We conclude that the electrical and optical properties of monolayer MoS2 crystals can be tuned via stoichiometry engineering to meet the requirements of various applications.

  13. Lithography-free plasma-induced patterned growth of MoS2 and its heterojunction with graphene.

    PubMed

    Chen, Xiang; Park, Yong Ju; Das, Tanmoy; Jang, Houk; Lee, Jae-Bok; Ahn, Jong-Hyun

    2016-08-18

    Application-oriented patterned growth of transition metal dichalcogenides (TMDCs) and their heterojunctions is of critical importance for sophisticated, customized two-dimensional (2D) electronic and optoelectronic devices; however, it is still difficult to fabricate these patterns in a simple, clean, and high controllability manner without using optical lithography. Here, we report the direct synthesis of patterned MoS2 and graphene-MoS2 heterojunctions via selective plasma treatment of a SiO2/Si substrate and chemical vapor deposition of MoS2. This method has multiple merits, such as simple steps, a short operating time, easily isolated MoS2 layers with clean surfaces and controllable locations, shapes, sizes and thicknesses, which enable their integration into the device structure without using a photoresist. In addition, we demonstrate the direct growth of patterned graphene-MoS2 heterojunctions for the fabrication of transistor. This study reveals a novel method to fabricate and use patterned MoS2 and graphene-MoS2 heterojunctions, which could be generalized to the rational design of other 2D materials, heterojunctions and devices in the future.

  14. VOLTAGE-CONTROLLED TRANSISTOR OSCILLATOR

    DOEpatents

    Scheele, P.F.

    1958-09-16

    This patent relates to transistor oscillators and in particular to those transistor oscillators whose frequencies vary according to controlling voltages. A principal feature of the disclosed transistor oscillator circuit resides in the temperature compensation of the frequency modulating stage by the use of a resistorthermistor network. The resistor-thermistor network components are selected to have the network resistance, which is in series with the modulator transistor emitter circuit, vary with temperature to compensate for variation in the parameters of the transistor due to temperature change.

  15. An RF energy harvester system using UHF micropower CMOS rectifier based on a diode connected CMOS transistor.

    PubMed

    Shokrani, Mohammad Reza; Khoddam, Mojtaba; Hamidon, Mohd Nizar B; Kamsani, Noor Ain; Rokhani, Fakhrul Zaman; Shafie, Suhaidi Bin

    2014-01-01

    This paper presents a new type diode connected MOS transistor to improve CMOS conventional rectifier's performance in RF energy harvester systems for wireless sensor networks in which the circuits are designed in 0.18  μm TSMC CMOS technology. The proposed diode connected MOS transistor uses a new bulk connection which leads to reduction in the threshold voltage and leakage current; therefore, it contributes to increment of the rectifier's output voltage, output current, and efficiency when it is well important in the conventional CMOS rectifiers. The design technique for the rectifiers is explained and a matching network has been proposed to increase the sensitivity of the proposed rectifier. Five-stage rectifier with a matching network is proposed based on the optimization. The simulation results shows 18.2% improvement in the efficiency of the rectifier circuit and increase in sensitivity of RF energy harvester circuit. All circuits are designed in 0.18 μm TSMC CMOS technology.

  16. A new method of VLSI conform design for MOS cells

    NASA Astrophysics Data System (ADS)

    Schmidt, K. H.; Wach, W.; Mueller-Glaser, K. D.

    An automated method for the design of specialized SSI/LSI-level MOS cells suitable for incorporation in VLSI chips is described. The method uses the symbolic-layout features of the CABBAGE computer program (Hsueh, 1979; De Man et al., 1982), but restricted by a fixed grid system to facilitate compaction procedures. The techniques used are shown to significantly speed the processes of electrical design, layout, design verification, and description for subsequent CAD/CAM application. In the example presented, a 211-transistor, parallel-load, synchronous 4-bit up/down binary counter cell was designed in 9 days, as compared to 30 days for a manually-optimized-layout version and 3 days for a larger, less efficient cell designed by a programmable logic array; the cell areas were 0.36, 0.21, and 0.79 sq mm, respectively. The primary advantage of the method is seen in the extreme ease with which the cell design can be adapted to new parameters or design rules imposed by improvements in technology.

  17. Two Dimensional Ising Superconductivity in Gated MoS2

    NASA Astrophysics Data System (ADS)

    Yuan, Noah; Lu, Jianming; Law, Kam Tuen; Zheliuk, Oleksandr; Leermakers, Inge; Zeitler, Ulrich; Ye, Jianting

    The Zeeman effect, which is usually considered to be detrimental to superconductivity, can surprisingly protect the superconducting states created by gating a layered transition metal dichalcogenide. This effective Zeeman field, which is originated from intrinsic spin orbit coupling induced by breaking in-plane inversion symmetry, can reach nearly a hundred Tesla in magnitude. It strongly pins the spin orientation of the electrons to the out-of-plane directions and protects the superconductivity from being destroyed by an in-plane external magnetic field. In magnetotransport experiments of ionic-gate MoS2 transistors, where gating prepares individual superconducting state with different carrier doping, we indeed observe a spin-protected superconductivity by measuring an in-plane critical field Bc 2 far beyond the Pauli paramagnetic limit. The gating-enhanced Bc 2 is more than an order of magnitude larger compared to the bulk superconducting phases where the effective Zeeman field is weakened by interlayer coupling. Our study gives the first experimental evidence of an Ising superconductor, in which spins of the pairing electrons are strongly pinned by an effective Zeeman field.

  18. Accelerating the life of transistors

    NASA Astrophysics Data System (ADS)

    Haochun, Qi; Changzhi, Lü; Xiaoling, Zhang; Xuesong, Xie

    2013-06-01

    Choosing small and medium power switching transistors of the NPN type in a 3DK set as the study object, the test of accelerating life is conducted in constant temperature and humidity, and then the data are statistically analyzed with software developed by ourselves. According to degradations of such sensitive parameters as the reverse leakage current of transistors, the lifetime order of transistors is about more than 104 at 100 °C and 100% relative humidity (RH) conditions. By corrosion fracture of transistor outer leads and other failure modes, with the failure truncated testing, the average lifetime rank of transistors in different distributions is extrapolated about 103. Failure mechanism analyses of degradation of electrical parameters, outer lead fracture and other reasons that affect transistor lifetime are conducted. The findings show that the impact of external stress of outer leads on transistor reliability is more serious than that of parameter degradation.

  19. Multimode Silicon Nanowire Transistors

    PubMed Central

    2014-01-01

    The combined capabilities of both a nonplanar design and nonconventional carrier injection mechanisms are subject to recent scientific investigations to overcome the limitations of silicon metal oxide semiconductor field effect transistors. In this Letter, we present a multimode field effect transistors device using silicon nanowires that feature an axial n-type/intrinsic doping junction. A heterostructural device design is achieved by employing a self-aligned nickel-silicide source contact. The polymorph operation of the dual-gate device enabling the configuration of one p- and two n-type transistor modes is demonstrated. Not only the type but also the carrier injection mode can be altered by appropriate biasing of the two gate terminals or by inverting the drain bias. With a combined band-to-band and Schottky tunneling mechanism, in p-type mode a subthreshold swing as low as 143 mV/dec and an ON/OFF ratio of up to 104 is found. As the device operates in forward bias, a nonconventional tunneling transistor is realized, enabling an effective suppression of ambipolarity. Depending on the drain bias, two different n-type modes are distinguishable. The carrier injection is dominated by thermionic emission in forward bias with a maximum ON/OFF ratio of up to 107 whereas in reverse bias a Schottky tunneling mechanism dominates the carrier transport. PMID:25303290

  20. Towards the ultimate transistor

    NASA Astrophysics Data System (ADS)

    Natelson, Douglas

    2009-06-01

    The first transistor, made more than 60 years ago at Bell Labs, was a couple of inches across. Today, a typical laptop computer uses a processor chip that contains well over a billion transistors, each one with electrodes separated by less than 50 nm of silicon, which is less than a thousandth of the diameter of a human hair. This continual drive for miniaturization, with the density of transistors doubling roughly every two years, was first noted by Intel co-founder Gordon Moore in 1965, and has been such a mainstay of electronics development that it is now enshrined as "Moore's law". These billions of transistors are made by "top down" methods that involve depositing thin layers of materials, patterning nano-scale stencils and effectively carving away the unwanted bits. The incredible success of this approach is almost impossible to overstate. The end result is billions of individual components on a single chip, essentially all working perfectly and continuously for years on end. No other manufactured technology comes remotely close in reliability or cost-per-widget.

  1. Multimode silicon nanowire transistors.

    PubMed

    Glassner, Sebastian; Zeiner, Clemens; Periwal, Priyanka; Baron, Thierry; Bertagnolli, Emmerich; Lugstein, Alois

    2014-11-12

    The combined capabilities of both a nonplanar design and nonconventional carrier injection mechanisms are subject to recent scientific investigations to overcome the limitations of silicon metal oxide semiconductor field effect transistors. In this Letter, we present a multimode field effect transistors device using silicon nanowires that feature an axial n-type/intrinsic doping junction. A heterostructural device design is achieved by employing a self-aligned nickel-silicide source contact. The polymorph operation of the dual-gate device enabling the configuration of one p- and two n-type transistor modes is demonstrated. Not only the type but also the carrier injection mode can be altered by appropriate biasing of the two gate terminals or by inverting the drain bias. With a combined band-to-band and Schottky tunneling mechanism, in p-type mode a subthreshold swing as low as 143 mV/dec and an ON/OFF ratio of up to 10(4) is found. As the device operates in forward bias, a nonconventional tunneling transistor is realized, enabling an effective suppression of ambipolarity. Depending on the drain bias, two different n-type modes are distinguishable. The carrier injection is dominated by thermionic emission in forward bias with a maximum ON/OFF ratio of up to 10(7) whereas in reverse bias a Schottky tunneling mechanism dominates the carrier transport. PMID:25303290

  2. Radiation-hardened transistor and integrated circuit

    DOEpatents

    Ma, Kwok K.

    2007-11-20

    A composite transistor is disclosed for use in radiation hardening a CMOS IC formed on an SOI or bulk semiconductor substrate. The composite transistor has a circuit transistor and a blocking transistor connected in series with a common gate connection. A body terminal of the blocking transistor is connected only to a source terminal thereof, and to no other connection point. The blocking transistor acts to prevent a single-event transient (SET) occurring in the circuit transistor from being coupled outside the composite transistor. Similarly, when a SET occurs in the blocking transistor, the circuit transistor prevents the SET from being coupled outside the composite transistor. N-type and P-type composite transistors can be used for each and every transistor in the CMOS IC to radiation harden the IC, and can be used to form inverters and transmission gates which are the building blocks of CMOS ICs.

  3. Environmental Effects on Hysteresis of Transfer Characteristics in Molybdenum Disulfide Field-Effect Transistors

    PubMed Central

    Shimazu, Yoshihiro; Tashiro, Mitsuki; Sonobe, Satoshi; Takahashi, Masaki

    2016-01-01

    Molybdenum disulfide (MoS2) has recently received much attention for nanoscale electronic and photonic applications. To explore the intrinsic properties and enhance the performance of MoS2-based field-effect transistors, thorough understanding of extrinsic effects such as environmental gas and contact resistance of the electrodes is required. Here, we report the effects of environmental gases on the transport properties of back-gated multilayered MoS2 field-effect transistors. Comparisons between different gases (oxygen, nitrogen, and air and nitrogen with varying relative humidities) revealed that water molecules acting as charge-trapping centers are the main cause of hysteresis in the transfer characteristics. While the hysteresis persisted even after pumping out the environmental gas for longer than 10 h at room temperature, it disappeared when the device was cooled to 240 K, suggesting a considerable increase in the time constant of the charge trapping/detrapping at these modestly low temperatures. The suppression of the hysteresis or instability in the easily attainable temperature range without surface passivation is highly advantageous for the device application of this system. The humidity dependence of the threshold voltages in the transfer curves indicates that the water molecules dominantly act as hole-trapping centers. A strong dependence of the on-state current on oxygen pressure was also observed. PMID:27435309

  4. Environmental Effects on Hysteresis of Transfer Characteristics in Molybdenum Disulfide Field-Effect Transistors.

    PubMed

    Shimazu, Yoshihiro; Tashiro, Mitsuki; Sonobe, Satoshi; Takahashi, Masaki

    2016-07-20

    Molybdenum disulfide (MoS2) has recently received much attention for nanoscale electronic and photonic applications. To explore the intrinsic properties and enhance the performance of MoS2-based field-effect transistors, thorough understanding of extrinsic effects such as environmental gas and contact resistance of the electrodes is required. Here, we report the effects of environmental gases on the transport properties of back-gated multilayered MoS2 field-effect transistors. Comparisons between different gases (oxygen, nitrogen, and air and nitrogen with varying relative humidities) revealed that water molecules acting as charge-trapping centers are the main cause of hysteresis in the transfer characteristics. While the hysteresis persisted even after pumping out the environmental gas for longer than 10 h at room temperature, it disappeared when the device was cooled to 240 K, suggesting a considerable increase in the time constant of the charge trapping/detrapping at these modestly low temperatures. The suppression of the hysteresis or instability in the easily attainable temperature range without surface passivation is highly advantageous for the device application of this system. The humidity dependence of the threshold voltages in the transfer curves indicates that the water molecules dominantly act as hole-trapping centers. A strong dependence of the on-state current on oxygen pressure was also observed.

  5. Environmental Effects on Hysteresis of Transfer Characteristics in Molybdenum Disulfide Field-Effect Transistors

    NASA Astrophysics Data System (ADS)

    Shimazu, Yoshihiro; Tashiro, Mitsuki; Sonobe, Satoshi; Takahashi, Masaki

    2016-07-01

    Molybdenum disulfide (MoS2) has recently received much attention for nanoscale electronic and photonic applications. To explore the intrinsic properties and enhance the performance of MoS2-based field-effect transistors, thorough understanding of extrinsic effects such as environmental gas and contact resistance of the electrodes is required. Here, we report the effects of environmental gases on the transport properties of back-gated multilayered MoS2 field-effect transistors. Comparisons between different gases (oxygen, nitrogen, and air and nitrogen with varying relative humidities) revealed that water molecules acting as charge-trapping centers are the main cause of hysteresis in the transfer characteristics. While the hysteresis persisted even after pumping out the environmental gas for longer than 10 h at room temperature, it disappeared when the device was cooled to 240 K, suggesting a considerable increase in the time constant of the charge trapping/detrapping at these modestly low temperatures. The suppression of the hysteresis or instability in the easily attainable temperature range without surface passivation is highly advantageous for the device application of this system. The humidity dependence of the threshold voltages in the transfer curves indicates that the water molecules dominantly act as hole-trapping centers. A strong dependence of the on-state current on oxygen pressure was also observed.

  6. Environmental Effects on Hysteresis of Transfer Characteristics in Molybdenum Disulfide Field-Effect Transistors.

    PubMed

    Shimazu, Yoshihiro; Tashiro, Mitsuki; Sonobe, Satoshi; Takahashi, Masaki

    2016-01-01

    Molybdenum disulfide (MoS2) has recently received much attention for nanoscale electronic and photonic applications. To explore the intrinsic properties and enhance the performance of MoS2-based field-effect transistors, thorough understanding of extrinsic effects such as environmental gas and contact resistance of the electrodes is required. Here, we report the effects of environmental gases on the transport properties of back-gated multilayered MoS2 field-effect transistors. Comparisons between different gases (oxygen, nitrogen, and air and nitrogen with varying relative humidities) revealed that water molecules acting as charge-trapping centers are the main cause of hysteresis in the transfer characteristics. While the hysteresis persisted even after pumping out the environmental gas for longer than 10 h at room temperature, it disappeared when the device was cooled to 240 K, suggesting a considerable increase in the time constant of the charge trapping/detrapping at these modestly low temperatures. The suppression of the hysteresis or instability in the easily attainable temperature range without surface passivation is highly advantageous for the device application of this system. The humidity dependence of the threshold voltages in the transfer curves indicates that the water molecules dominantly act as hole-trapping centers. A strong dependence of the on-state current on oxygen pressure was also observed. PMID:27435309

  7. Wafer-scale monolayer MoS2 grown by chemical vapor deposition using a reaction of MoO3 and H2S

    NASA Astrophysics Data System (ADS)

    Kim, Youngchan; Bark, Hunyoung; Ryu, Gyeong Hee; Lee, Zonghoon; Lee, Changgu

    2016-05-01

    Monolayer MoS2 nanosheets are potentially useful in optoelectronics, photoelectronics, and nanoelectronics due to their flexibility, mechanical strength, and direct band gap of 1.89 eV. Experimentalists have studied the synthesis of MoS2 using chemical vapor deposition (CVD) methods in an effort to fabricate wafer-scale nanofilms with a high uniformity and continuity for practical electronic applications. In this work, we applied the CVD method to a reaction of MoO3 powder and H2S gas to grow high-quality polycrystalline monolayer MoS2 sheets with unprecedented uniformity over an area of several centimeters. The monolayer MoS2 was characterized using Raman spectroscopy, photoluminescence (PL) spectroscopy, atomic force microscopy (AFM), x-ray photoemission spectroscopy (XPS), and transmission electron microscopy (TEM). The top-gate field-effect transistor prepared with a 30 nm HfO2 capping layer displayed an electrical mobility of 1 cm2 v-1 s-1 and an I on/off of ~105. This method paves the way for the development of practical devices with MoS2 monolayers and advances fundamental research.

  8. Interface Properties of Atomic-Layer-Deposited Al2O3 Thin Films on Ultraviolet/Ozone-Treated Multilayer MoS2 Crystals.

    PubMed

    Park, Seonyoung; Kim, Seong Yeoul; Choi, Yura; Kim, Myungjun; Shin, Hyunjung; Kim, Jiyoung; Choi, Woong

    2016-05-11

    We report the interface properties of atomic-layer-deposited Al2O3 thin films on ultraviolet/ozone (UV/O3)-treated multilayer MoS2 crystals. The formation of S-O bonds on MoS2 after low-power UV/O3 treatment increased the surface energy, allowing the subsequent deposition of uniform Al2O3 thin films. The capacitance-voltage measurement of Au-Al2O3-MoS2 metal oxide semiconductor capacitors indicated n-type MoS2 with an electron density of ∼10(17) cm(-3) and a minimum interface trap density of ∼10(11) cm(-2) eV(-1). These results demonstrate the possibility of forming a high-quality Al2O3-MoS2 interface by proper UV/O3 treatment, providing important implications for their integration into field-effect transistors. PMID:27117229

  9. Wafer-scale monolayer MoS2 grown by chemical vapor deposition using a reaction of MoO3 and H2S

    NASA Astrophysics Data System (ADS)

    Kim, Youngchan; Bark, Hunyoung; Ryu, Gyeong Hee; Lee, Zonghoon; Lee, Changgu

    2016-05-01

    Monolayer MoS2 nanosheets are potentially useful in optoelectronics, photoelectronics, and nanoelectronics due to their flexibility, mechanical strength, and direct band gap of 1.89 eV. Experimentalists have studied the synthesis of MoS2 using chemical vapor deposition (CVD) methods in an effort to fabricate wafer-scale nanofilms with a high uniformity and continuity for practical electronic applications. In this work, we applied the CVD method to a reaction of MoO3 powder and H2S gas to grow high-quality polycrystalline monolayer MoS2 sheets with unprecedented uniformity over an area of several centimeters. The monolayer MoS2 was characterized using Raman spectroscopy, photoluminescence (PL) spectroscopy, atomic force microscopy (AFM), x-ray photoemission spectroscopy (XPS), and transmission electron microscopy (TEM). The top-gate field-effect transistor prepared with a 30 nm HfO2 capping layer displayed an electrical mobility of 1 cm2 v‑1 s‑1 and an I on/off of ~105. This method paves the way for the development of practical devices with MoS2 monolayers and advances fundamental research.

  10. Wafer-scale monolayer MoS2 grown by chemical vapor deposition using a reaction of MoO3 and H2S.

    PubMed

    Kim, Youngchan; Bark, Hunyoung; Ryu, Gyeong Hee; Lee, Zonghoon; Lee, Changgu

    2016-05-11

    Monolayer MoS2 nanosheets are potentially useful in optoelectronics, photoelectronics, and nanoelectronics due to their flexibility, mechanical strength, and direct band gap of 1.89 eV. Experimentalists have studied the synthesis of MoS2 using chemical vapor deposition (CVD) methods in an effort to fabricate wafer-scale nanofilms with a high uniformity and continuity for practical electronic applications. In this work, we applied the CVD method to a reaction of MoO3 powder and H2S gas to grow high-quality polycrystalline monolayer MoS2 sheets with unprecedented uniformity over an area of several centimeters. The monolayer MoS2 was characterized using Raman spectroscopy, photoluminescence (PL) spectroscopy, atomic force microscopy (AFM), x-ray photoemission spectroscopy (XPS), and transmission electron microscopy (TEM). The top-gate field-effect transistor prepared with a 30 nm HfO2 capping layer displayed an electrical mobility of 1 cm(2) v(-1) s(-1) and an I on/off of ~10(5). This method paves the way for the development of practical devices with MoS2 monolayers and advances fundamental research.

  11. Ultralow Density, Monolithic WS2, MoS2, and MoS2/Graphene Aerogels.

    PubMed

    Worsley, Marcus A; Shin, Swanee J; Merrill, Matthew D; Lenhardt, Jeremy; Nelson, Art J; Woo, Leta Y; Gash, Alex E; Baumann, Theodore F; Orme, Christine A

    2015-05-26

    We describe the synthesis and characterization of monolithic, ultralow density WS2 and MoS2 aerogels, as well as a high surface area MoS2/graphene hybrid aerogel. The monolithic WS2 and MoS2 aerogels are prepared via thermal decomposition of freeze-dried ammonium thio-molybdate (ATM) and ammonium thio-tungstate (ATT) solutions, respectively. The densities of the pure dichalcogenide aerogels represent 0.4% and 0.5% of full density MoS2 and WS2, respectively, and can be tailored by simply changing the initial ATM or ATT concentrations. Similar processing in the presence of the graphene aerogel results in a hybrid structure with MoS2 sheets conformally coating the graphene scaffold. This layered motif produces a ∼50 wt % MoS2 aerogel with BET surface area of ∼700 m(2)/g and an electrical conductivity of 112 S/m. The MoS2/graphene aerogel shows promising results as a hydrogen evolution reaction catalyst with low onset potential (∼100 mV) and high current density (100 mA/cm(2) at 260 mV).

  12. Measurement and Analysis of a Ferroelectric Field-Effect Transistor NAND Gate

    NASA Technical Reports Server (NTRS)

    Phillips, Thomas A.; MacLeond, Todd C.; Sayyah, Rana; Ho, Fat Duen

    2009-01-01

    Previous research investigated expanding the use of Ferroelectric Field-Effect Transistors (FFET) to other electronic devices beyond memory circuits. Ferroelectric based transistors possess unique characteris tics that give them interesting and useful properties in digital logic circuits. The NAND gate was chosen for investigation as it is one of the fundamental building blocks of digital electronic circuits. In t his paper, NAND gate circuits were constructed utilizing individual F FETs. N-channel FFETs with positive polarization were used for the standard CMOS NAND gate n-channel transistors and n-channel FFETs with n egative polarization were used for the standard CMOS NAND gate p-chan nel transistors. The voltage transfer curves were obtained for the NA ND gate. Comparisons were made between the actual device data and the previous modeled data. These results are compared to standard MOS logic circuits. The circuits analyzed are not intended to be fully opera tional circuits that would interface with existing logic circuits, bu t as a research tool to look into the possibility of using ferroelectric transistors in future logic circuits. Possible applications for th ese devices are presented, and their potential benefits and drawbacks are discussed.

  13. Device perspective for black phosphorus field-effect transistors: contact resistance, ambipolar behavior, and scaling.

    PubMed

    Du, Yuchen; Liu, Han; Deng, Yexin; Ye, Peide D

    2014-10-28

    Although monolayer black phosphorus (BP), or phosphorene, has been successfully exfoliated and its optical properties have been explored, most of the electrical performance of the devices is demonstrated on few-layer phosphorene and ultrathin BP films. In this paper, we study the channel length scaling of ultrathin BP field-effect transistors (FETs) and discuss a scheme for using various contact metals to change the transistor characteristics. Through studying transistor behaviors with various channel lengths, the contact resistance can be extracted with the transfer length method (TLM). With different contact metals, we find out that the metal/BP interface has different Schottky barrier heights, leading to a significant difference in contact resistance, which is quite different from previous studies of transition metal dichalcogenides (TMDs), such as MoS2, where the Fermi level is strongly pinned near the conduction band edge at the metal/MoS2 interface. The nature of BP transistors is Schottky barrier FETs, where the on and off states are controlled by tuning the Schottky barriers at the two contacts. We also observe the ambipolar characteristics of BP transistors with enhanced n-type drain current and demonstrate that the p-type carriers can be easily shifted to n-type or vice versa by controlling the gate bias and drain bias, showing the potential to realize BP CMOS logic circuits.

  14. High-Current Gain Two-Dimensional MoS₂-Base Hot-Electron Transistors.

    PubMed

    Torres, Carlos M; Lan, Yann-Wen; Zeng, Caifu; Chen, Jyun-Hong; Kou, Xufeng; Navabi, Aryan; Tang, Jianshi; Montazeri, Mohammad; Adleman, James R; Lerner, Mitchell B; Zhong, Yuan-Liang; Li, Lain-Jong; Chen, Chii-Dong; Wang, Kang L

    2015-12-01

    The vertical transport of nonequilibrium charge carriers through semiconductor heterostructures has led to milestones in electronics with the development of the hot-electron transistor. Recently, significant advances have been made with atomically sharp heterostructures implementing various two-dimensional materials. Although graphene-base hot-electron transistors show great promise for electronic switching at high frequencies, they are limited by their low current gain. Here we show that, by choosing MoS2 and HfO2 for the filter barrier interface and using a noncrystalline semiconductor such as ITO for the collector, we can achieve an unprecedentedly high-current gain (α ∼ 0.95) in our hot-electron transistors operating at room temperature. Furthermore, the current gain can be tuned over 2 orders of magnitude with the collector-base voltage albeit this feature currently presents a drawback in the transistor performance metrics such as poor output resistance and poor intrinsic voltage gain. We anticipate our transistors will pave the way toward the realization of novel flexible 2D material-based high-density, low-energy, and high-frequency hot-carrier electronic applications. PMID:26524388

  15. Improved chopper circuit uses parallel transistors

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Parallel transistor chopper circuit operates with one transistor in the forward mode and the other in the inverse mode. By using this method, it acts as a single, symmetrical, bidirectional transistor, and reduces and stabilizes the offset voltage.

  16. Transistor voltage comparator performs own sensing

    NASA Technical Reports Server (NTRS)

    Cliff, R. A.

    1965-01-01

    Detection of the highest voltage input among a group of varying voltage inputs is accomplished by a transistorized voltage comparison circuit. The collector circuits of the transistors perform the sensing function. Input voltage levels are governed by the transistors.

  17. Thin film transistor circuits for active matrix liquid crystal displays

    NASA Astrophysics Data System (ADS)

    Edwards, Martin John

    The demand for a high quality flat panel video display device for use in consumer and professional products has led to the rapid development of Active Matrix Liquid Crystal Displays (AMLCD). The majority of these displays use Thin Film Transistors (TFTs) as the active devices and improvements in the performance of these transistors is creating the opportunity to integrate increasingly sophisticated circuits onto the glass substrates of the displays. This thesis describes a number of aspects of the use of thin film transistor circuits for active matrix liquid crystal displays. The electrical characteristics of TFTs differ in a number of respects from those of conventional MOS devices. This is illustrated with measurements of transistors and simple circuits fabricated using two different low temperature poly-Si TFT technologies. At present the key application for TFT circuits is integration of the row and column drive circuits for active matrix liquid crystal displays. The issues which arise in the design of TFT drive circuits are discussed and the design and operation of a prototype display with integrated drive circuits is described. The availability of high mobility TFTs makes it possible to integrate signal processing functions within the pixels of a display. A novel technique employing digital to analogue conversion of the video data within the pixels of a display is presented. This technique allows the display to be addressed with digital column drive waveforms simplifying the column drive circuit. Operation of the pixel data converters has been demonstrated by the design and measurement of small arrays of test pixels.

  18. Hybrid Flexible Resistive Random Access Memory-Gated Transistor for Novel Nonvolatile Data Storage.

    PubMed

    Han, Su-Ting; Zhou, Ye; Chen, Bo; Wang, Chundong; Zhou, Li; Yan, Yan; Zhuang, Jiaqing; Sun, Qijun; Zhang, Hua; Roy, V A L

    2016-01-20

    Here, a single-device demonstration of novel hybrid architecture is reported to achieve programmable transistor nodes which have analogies to flash memory by incorporating a resistive switching random access memory (RRAM) device as a resistive switch gate for field effect transistor (FET) on a flexible substrate. A high performance flexible RRAM with a three-layered structure is fabricated by utilizing solution-processed MoS2 nanosheets sandwiched between poly(methyl methacrylate) polymer layers. Gate coupling with the pentacene-based transistor can be controlled by the RRAM memory state to produce a nonprogrammed state (inactive) and a programmed state (active) with a well-defined memory window. Compared to the reference flash memory device based on the MoS2 floating gate, the hybrid device presents robust access speed and retention ability. Furthermore, the hybrid RRAM-gated FET is used to build an integrated logic circuit and a wide logic window in inverter logic is achieved. The controllable, well-defined memory window, long retention time, and fast access speed of this novel hybrid device may open up new possibilities of realizing fully functional nonvolatile memory for high-performance flexible electronics.

  19. Hybrid Flexible Resistive Random Access Memory-Gated Transistor for Novel Nonvolatile Data Storage.

    PubMed

    Han, Su-Ting; Zhou, Ye; Chen, Bo; Wang, Chundong; Zhou, Li; Yan, Yan; Zhuang, Jiaqing; Sun, Qijun; Zhang, Hua; Roy, V A L

    2016-01-20

    Here, a single-device demonstration of novel hybrid architecture is reported to achieve programmable transistor nodes which have analogies to flash memory by incorporating a resistive switching random access memory (RRAM) device as a resistive switch gate for field effect transistor (FET) on a flexible substrate. A high performance flexible RRAM with a three-layered structure is fabricated by utilizing solution-processed MoS2 nanosheets sandwiched between poly(methyl methacrylate) polymer layers. Gate coupling with the pentacene-based transistor can be controlled by the RRAM memory state to produce a nonprogrammed state (inactive) and a programmed state (active) with a well-defined memory window. Compared to the reference flash memory device based on the MoS2 floating gate, the hybrid device presents robust access speed and retention ability. Furthermore, the hybrid RRAM-gated FET is used to build an integrated logic circuit and a wide logic window in inverter logic is achieved. The controllable, well-defined memory window, long retention time, and fast access speed of this novel hybrid device may open up new possibilities of realizing fully functional nonvolatile memory for high-performance flexible electronics. PMID:26578160

  20. TRANSISTOR HIGH VOLTAGE POWER SUPPLY

    DOEpatents

    Driver, G.E.

    1958-07-15

    High voltage, direct current power supplies are described for use with battery powered nuclear detection equipment. The particular advantages of the power supply described, are increased efficiency and reduced size and welght brought about by the use of transistors in the circuit. An important feature resides tn the employment of a pair of transistors in an alternatefiring oscillator circuit having a coupling transformer and other circuit components which are used for interconnecting the various electrodes of the transistors.

  1. High voltage power transistor development

    NASA Technical Reports Server (NTRS)

    Hower, P. L.

    1981-01-01

    Design considerations, fabrication procedures, and methods of evaluation for high-voltage power-transistor development are discussed. Technique improvements such as controlling the electric field at the surface and perserving lifetimes in the collector region which have advanced the state of the art in high-voltage transistors are discussed. These improvements can be applied directly to the development of 1200 volt, 200 ampere transistors.

  2. Ion bipolar junction transistors

    PubMed Central

    Tybrandt, Klas; Larsson, Karin C.; Richter-Dahlfors, Agneta; Berggren, Magnus

    2010-01-01

    Dynamic control of chemical microenvironments is essential for continued development in numerous fields of life sciences. Such control could be achieved with active chemical circuits for delivery of ions and biomolecules. As the basis for such circuitry, we report a solid-state ion bipolar junction transistor (IBJT) based on conducting polymers and thin films of anion- and cation-selective membranes. The IBJT is the ionic analogue to the conventional semiconductor BJT and is manufactured using standard microfabrication techniques. Transistor characteristics along with a model describing the principle of operation, in which an anionic base current amplifies a cationic collector current, are presented. By employing the IBJT as a bioelectronic circuit element for delivery of the neurotransmitter acetylcholine, its efficacy in modulating neuronal cell signaling is demonstrated. PMID:20479274

  3. Polarization induced doped transistor

    DOEpatents

    Xing, Huili; Jena, Debdeep; Nomoto, Kazuki; Song, Bo; Zhu, Mingda; Hu, Zongyang

    2016-06-07

    A nitride-based field effect transistor (FET) comprises a compositionally graded and polarization induced doped p-layer underlying at least one gate contact and a compositionally graded and doped n-channel underlying a source contact. The n-channel is converted from the p-layer to the n-channel by ion implantation, a buffer underlies the doped p-layer and the n-channel, and a drain underlies the buffer.

  4. Wafer-scale synthesis of thickness-controllable MoS2 films via solution-processing using a dimethylformamide/n-butylamine/2-aminoethanol solvent system

    NASA Astrophysics Data System (ADS)

    Yang, Jaehyun; Gu, Yeahyun; Lee, Eunha; Lee, Hyangsook; Park, Sang Han; Cho, Mann-Ho; Kim, Yong Ho; Kim, Yong-Hoon; Kim, Hyoungsub

    2015-05-01

    The wafer-scale synthesis of two-dimensional molybdenum disulfide (MoS2) films, with high layer-controllability and uniformity, remains a significant challenge in the fields of nano and optoelectronics. Here, we report the highly thickness controllable growth of uniform MoS2 thin films on the wafer-scale via a spin-coating route. Formulation of a dimethylformamide-based MoS2 precursor solution mixed with additional amine- and amino alcohol-based solvents (n-butylamine and 2-aminoethanol) allowed for the formation of a uniform coating of MoS2 thin films over a 2 inch wafer-scale SiO2/Si substrate. In addition, facile control of the average number of stacking layers is demonstrated by simply manipulating the concentration of the precursor solution. Various characterization results reveal that the synthesized MoS2 film has wafer-scale homogeneity with excellent crystalline quality and a stoichiometric chemical composition. To further demonstrate possible device applications, a mostly penta-layered MoS2 thin film was integrated into a top-gated field-effect transistor as the channel layer and we also successfully transferred our films onto transparent/flexible substrates.The wafer-scale synthesis of two-dimensional molybdenum disulfide (MoS2) films, with high layer-controllability and uniformity, remains a significant challenge in the fields of nano and optoelectronics. Here, we report the highly thickness controllable growth of uniform MoS2 thin films on the wafer-scale via a spin-coating route. Formulation of a dimethylformamide-based MoS2 precursor solution mixed with additional amine- and amino alcohol-based solvents (n-butylamine and 2-aminoethanol) allowed for the formation of a uniform coating of MoS2 thin films over a 2 inch wafer-scale SiO2/Si substrate. In addition, facile control of the average number of stacking layers is demonstrated by simply manipulating the concentration of the precursor solution. Various characterization results reveal that the

  5. SEMICONDUCTOR INTEGRATED CIRCUITS: An enhanced close-in phase noise LC-VCO using parasitic V-NPN transistors in a CMOS process

    NASA Astrophysics Data System (ADS)

    Peijun, Gao; J, Oh N.; Hao, Min

    2009-08-01

    A differential LC voltage controlled oscillator (VCO) employing parasitic vertical-NPN (V-NPN) transistors as a negative gm-cell is presented to improve the close-in phase noise. The V-NPN transistors have lower flicker noise compared to MOS transistors. DC and AC characteristics of the V-NPN transistors are measured to facilitate the VCO design. The proposed VCO is implemented in a 0.18 μm CMOS RF/mixed signal process, and the measurement results show the close-in phase noise is improved by 3.5-9.1 dB from 100 Hz to 10 kHz offset compared to that of a similar CMOS VCO. The proposed VCO consumes only 0.41 mA from a 1.5 V power supply.

  6. Hydrogen intercalation in MoS2

    NASA Astrophysics Data System (ADS)

    Zhu, Zhen; Peelaers, Hartwin; Van de Walle, Chris G.

    2016-08-01

    We investigate the structure and energetics of interstitial hydrogen and hydrogen molecules in layered 2 H -MoS2, an issue of interest both for hydrogen storage applications and for the use of MoS2 as an (opto)electronic material. Using first-principles density functional theory we find that hydrogen interstitials are deep donors. H2 molecules are electrically inactive and energetically more stable than hydrogen interstitials. Their equilibrium position is the hollow site of the MoS2 layers. The migration barrier of a hydrogen molecule is calculated to be smaller than 0.6 eV. We have also explored the insertion energies of hydrogen molecules as a function of hydrogen concentration in MoS2. For low concentrations, additional inserted H2 molecules prefer to be located in hollow sites (on top of the center of a hexagon) in the vicinity of an occupied site. Once two molecules have been inserted, the energy cost for inserting additional H2 molecules becomes much lower. Once all hollow sites are filled, the energy cost increases, but only by a modest amount. We find that up to 13 H2 molecules can be accommodated within the same interlayer spacing of an areal 3 ×3 supercell.

  7. Integrated p-channel MOS gyrator

    NASA Technical Reports Server (NTRS)

    Hochmair, E. S.

    1973-01-01

    Several circuits can be integrated into one chip for applications which require more than one gyrator. They can also be integrated with other p-channel MOS circuits to eliminate need for external connections. Devices can operate at economical low-power levels, because they use FET amplifiers that do not degrade with decreases in supply.

  8. REGENERATIVE TRANSISTOR AMPLIFIER

    DOEpatents

    Kabell, L.J.

    1958-11-25

    Electrical circults for use in computers and the like are described. particularly a regenerative bistable transistor amplifler which is iurned on by a clock signal when an information signal permits and is turned off by the clock signal. The amplifier porforms the above function with reduced power requirements for the clock signal and circuit operation. The power requirements are reduced in one way by employing transformer coupling which increases the collector circuit efficiency by eliminating the loss of power in the collector load resistor.

  9. Power transistor switching characterization

    NASA Technical Reports Server (NTRS)

    Blackburn, D. L.

    1981-01-01

    The switching properties of power transistors are investigated. The devices studied were housed in IO-3 cases and were of an n(+)-p-n(-)-n(+) vertical dopant structure. The effects of the magnitude of the reverse-base current and temperature on the reverse-bias second breakdown characteristics are discussed. Brief discussions of device degradation due to second breakdown and of a constant voltage turn-off circuit are included. A description of a vacuum tube voltage clamp circuit which reduces clamped collector voltage overshoot is given.

  10. Ambipolar conduction in MoS2/WSe2 hetero-bilayers

    NASA Astrophysics Data System (ADS)

    Movva, Hema Chandra Prakash; Kang, Sangwoo; Rai, Amritesh; Banerjee, Sanjay

    2015-03-01

    Recent interest in layered semiconductors, and the ability to assemble them into artificial heterostructures with atomically sharp interfaces has opened up new avenues for the design of future electronic devices. In this work, we fabricated vertical heterostructures of exfoliated monolayer MoS2 and monolayer WSe2 using a facile flake pick-up-and-place technique, and studied their optical and electrical properties. Photoluminescence measurements showed evidence of indirect excitons at ~ 1.55 eV, indicating a clean interface between the two layers. We observed back-gate tunable, layer-selective ambipolar conduction in field effect transistors (FETs) made using these hetero-bilayers, with e-transport occurring through the MoS2, and h-transport through WSe2. The addition of a top-gate using a thin hBN dielectric further enabled selective operation of the hetero-bilayer FET as an n-FET/p-FET depending on the back-gate bias.

  11. Graphene - ferroelectric and MoS2 - ferroelectric heterostructures for memory applications

    NASA Astrophysics Data System (ADS)

    Lipatov, Alexey; Sharma, Pankaj; Gruverman, Alexei; Sinitskii, Alexander

    In recent years there has been an unprecedented interest in two-dimensional (2D) materials with unique physical and chemical properties that cannot be found in their three-dimensional (3D) counterparts. One of the important advantages of 2D materials is that they can be easily integrated with other 2D materials and functional films, resulting in multilayered structures with new properties. We fabricated and tested electronic and memory properties of field-effect transistors (FETs) based on a single-layer graphene combined with lead zirconium titanate (PZT) substrate. Previously studied graphene-PZT devices exhibited an unusual electronic behavior such as clockwise hysteresis of electronic transport, in contradiction with counterclockwise polarization dependence of PZT. We investigated how the interplay of polarization and interfacial phenomena affects the electronic behavior and memory characteristics of graphene-PZT FETs, explain the origin of unusual clockwise hysteresis and experimentally demonstrate a reversed polarization-dependent hysteresis of electronic transport. In addition we fabricated and tested properties of MoS2-PZT FETs which exhibit a large hysteresis of electronic transport with high ON/OFF ratios. We demonstrate that MoS2-PZT memories have a number of advantages over commercial FeRAMs, such as nondestructive data readout, low operation voltage, wide memory window and the possibility to write and erase them both electrically and optically.

  12. Chloride molecular doping technique on 2D materials: WS2 and MoS2.

    PubMed

    Yang, Lingming; Majumdar, Kausik; Liu, Han; Du, Yuchen; Wu, Heng; Hatzistergos, Michael; Hung, P Y; Tieckelmann, Robert; Tsai, Wilman; Hobbs, Chris; Ye, Peide D

    2014-11-12

    Low-resistivity metal-semiconductor (M-S) contact is one of the urgent challenges in the research of 2D transition metal dichalcogenides (TMDs). Here, we report a chloride molecular doping technique which greatly reduces the contact resistance (Rc) in the few-layer WS2 and MoS2. After doping, the Rc of WS2 and MoS2 have been decreased to 0.7 kΩ·μm and 0.5 kΩ·μm, respectively. The significant reduction of the Rc is attributed to the achieved high electron-doping density, thus a significant reduction of Schottky barrier width. As a proof-of-concept, high-performance few-layer WS2 field-effect transistors (FETs) are demonstrated, exhibiting a high drain current of 380 μA/μm, an on/off ratio of 4 × 10(6), and a peak field-effect mobility of 60 cm(2)/(V·s). This doping technique provides a highly viable route to diminish the Rc in TMDs, paving the way for high-performance 2D nanoelectronic devices.

  13. Enhanced mobility electrons at the monolayer / multilayer MoS2 homo-interface

    NASA Astrophysics Data System (ADS)

    Jia, Y.; Lenferink, E. J.; Stanev, T.; Stern, N. P.

    2015-03-01

    Energy band alignment at interface of heterostructures can give rise to non-trivial local electronic structure and charge states with low dimensionality. In transition metal dichalcogenides (TMDCs), the optical band gap depends on the number of 2D crystal layers, transitioning from 1.29 eV in bulk to 1.88 eV for a monolayer of MoS2, for example, and providing the possibility to create unusual charge state at the monolayer/multilayer homo-interface. Here, we examine the boundaries between MoS2 monolayers and multilayers using scanning photocurrent microscopy and gate-dependent transport. Enhanced photocurrent and conductance were observed at the 1D homo-interface, which can be explained as accumulated carriers in the bent-band region of the junction. Our heterojunction modeling suggests a high local carrier density and enhanced mobility at the homo-interface. Our work presents an opportunity to achieve a 1D electron state in a homojunction and a pathway to break the mobility limit of TMDC monolayer transistors. This work was supported by the Institute for Sustainability and Energy at Northwestern and the U.S. Department of Energy (DE-SC0012130). N.P.S. acknowledges support as an Alfred P. Sloan Research Fellow.

  14. Characterizing the Switching Thresholds of Magnetophoretic Transistors.

    PubMed

    Abedini-Nassab, Roozbeh; Joh, Daniel Y; Van Heest, Melissa A; Yi, John S; Baker, Cody; Taherifard, Zohreh; Margolis, David M; Garcia, J Victor; Chilkoti, Ashutosh; Murdoch, David M; Yellen, Benjamin B

    2015-10-28

    The switching thresholds of magnetophoretic transistors for sorting cells in microfluidic environments are characterized. The transistor operating conditions require short 20-30 mA pulses of electrical current. By demonstrating both attractive and repulsive transistor modes, a single transistor architecture is used to implement the full write cycle for importing and exporting single cells in specified array sites. PMID:26349853

  15. Temperature-dependent characteristics of AlGaN/GaN FinFETs with sidewall MOS channel

    NASA Astrophysics Data System (ADS)

    Im, Ki-Sik; Kang, Hee-Sung; Kim, Do-Kywn; Vodapally, Sindhuri; Park, YoHan; Lee, Jae-Hoon; Kim, Yong-Tae; Cristoloveanu, Sorin; Lee, Jung-Hee

    2016-06-01

    AlGaN/GaN fin-shaped field-effect transistors (FinFETs) with variable fin width have been fabricated and characterized. Low-temperature measurements reveal distinct operation modes for wide FinFET, narrow FinFET and planar FET. The wide fin device exhibits broad transconductance (gm) that decreases sublinearly with increasing temperature due to the existence of the sidewall metal-oxide-semiconductor (MOS) channel. By comparison, the conventional planar AlGaN/GaN metal-insulator-semiconductor heterostructure FET (MISHFET) features relatively narrow gm curve and near-exponentially decay of gm with temperature. The effect of the sidewall channel becomes more prominent for the narrow fin device and leads to two distinct gm peaks. The first peak at negative gate voltage corresponds to the two-dimensional electron gas (2-DEG) channel, while the second peak at positive gate voltage is related to the sidewall MOS channel. Measurements also show that the electrons in 2-DEG channel experience polar-optical-phonon scattering unlike the electrons in the sidewall MOS channel which are mainly subject to Coulomb scattering.

  16. GaN MOS-HEMT Using Ultra-Thin Al2O3 Dielectric Grown by Atomic Layer Deposition

    NASA Astrophysics Data System (ADS)

    Yue, Yuan-Zheng; Hao, Yue; Feng, Qian; Zhang, Jin-Cheng; Ma, Xiao-Hua; Ni, Jin-Yu

    2007-08-01

    We report a GaN metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) with atomic layer deposited (ALD) Al2O3 gate dielectric. Based on the previous work [Appl. Phys. Lett. 86 (2005) 063501] of Ye et al. by decreasing the thickness of the gate oxide to 3.5 nm and optimizing the device fabrication process, the device with maximum transconductance of 150 mS/mm is produced and discussed in comparison with the result of 100 mS/mm of Ye et al. The corresponding drain current density in the 0.8-μm-gate-length MOS-HEMT is 800 mA/mm at the gate bias of 3.0 V. The gate leakage is two orders of magnitude lower than that of the conventional AlGaN/GaN HEMT. The excellent characteristics of this novel MOS-HEMT device structure with ALD Al2O3 gate dielectric are presented.

  17. A hybrid nanomemristor/transistor logic circuit capable of self-programming.

    PubMed

    Borghetti, Julien; Li, Zhiyong; Straznicky, Joseph; Li, Xuema; Ohlberg, Douglas A A; Wu, Wei; Stewart, Duncan R; Williams, R Stanley

    2009-02-10

    Memristor crossbars were fabricated at 40 nm half-pitch, using nanoimprint lithography on the same substrate with Si metal-oxide-semiconductor field effect transistor (MOS FET) arrays to form fully integrated hybrid memory resistor (memristor)/transistor circuits. The digitally configured memristor crossbars were used to perform logic functions, to serve as a routing fabric for interconnecting the FETs and as the target for storing information. As an illustrative demonstration, the compound Boolean logic operation (A AND B) OR (C AND D) was performed with kilohertz frequency inputs, using resistor-based logic in a memristor crossbar with FET inverter/amplifier outputs. By routing the output signal of a logic operation back onto a target memristor inside the array, the crossbar was conditionally configured by setting the state of a nonvolatile switch. Such conditional programming illuminates the way for a variety of self-programmed logic arrays, and for electronic synaptic computing.

  18. Interfacial n-Doping Using an Ultrathin TiO2 Layer for Contact Resistance Reduction in MoS2.

    PubMed

    Kaushik, Naveen; Karmakar, Debjani; Nipane, Ankur; Karande, Shruti; Lodha, Saurabh

    2016-01-13

    We demonstrate a low and constant effective Schottky barrier height (ΦB ∼ 40 meV) irrespective of the metal work function by introducing an ultrathin TiO2 ALD interfacial layer between various metals (Ti, Ni, Au, and Pd) and MoS2. Transmission line method devices with and without the contact TiO2 interfacial layer on the same MoS2 flake demonstrate reduced (24×) contact resistance (RC) in the presence of TiO2. The insertion of TiO2 at the source-drain contact interface results in significant improvement in the on-current and field effect mobility (up to 10×). The reduction in RC and ΦB has been explained through interfacial doping of MoS2 and validated by first-principles calculations, which indicate metallic behavior of the TiO2-MoS2 interface. Consistent with DFT results of interfacial doping, X-ray photoelectron spectroscopy (XPS) data also exhibit a 0.5 eV shift toward higher binding energies for Mo 3d and S 2p peaks in the presence of TiO2, indicating Fermi level movement toward the conduction band (n-type doping). Ultraviolet photoelectron spectroscopy (UPS) further corroborates the interfacial doping model, as MoS2 flakes capped with ultrathin TiO2 exhibit a reduction of 0.3 eV in the effective work function. Finally, a systematic comparison of the impact of selective doping with the TiO2 layer under the source-drain metal relative to that on top of the MoS2 channel shows a larger benefit for transistor performance from the reduction in source-drain contact resistance.

  19. Monolithic metal oxide transistors.

    PubMed

    Choi, Yongsuk; Park, Won-Yeong; Kang, Moon Sung; Yi, Gi-Ra; Lee, Jun-Young; Kim, Yong-Hoon; Cho, Jeong Ho

    2015-04-28

    We devised a simple transparent metal oxide thin film transistor architecture composed of only two component materials, an amorphous metal oxide and ion gel gate dielectric, which could be entirely assembled using room-temperature processes on a plastic substrate. The geometry cleverly takes advantage of the unique characteristics of the two components. An oxide layer is metallized upon exposure to plasma, leading to the formation of a monolithic source-channel-drain oxide layer, and the ion gel gate dielectric is used to gate the transistor channel effectively at low voltages through a coplanar gate. We confirmed that the method is generally applicable to a variety of sol-gel-processed amorphous metal oxides, including indium oxide, indium zinc oxide, and indium gallium zinc oxide. An inverter NOT logic device was assembled using the resulting devices as a proof of concept demonstration of the applicability of the devices to logic circuits. The favorable characteristics of these devices, including (i) the simplicity of the device structure with only two components, (ii) the benign fabrication processes at room temperature, (iii) the low-voltage operation under 2 V, and (iv) the excellent and stable electrical performances, together support the application of these devices to low-cost portable gadgets, i.e., cheap electronics. PMID:25777338

  20. Microwave field effect transistor

    NASA Technical Reports Server (NTRS)

    Huang, Ho-Chung (Inventor)

    1989-01-01

    Electrodes of a high power, microwave field effect transistor are substantially matched to external input and output networks. The field effect transistor includes a metal ground plane layer, a dielectric layer on the ground plane layer, a gallium arsenide active region on the dielectric layer, and substantially coplanar spaced source, gate, and drain electrodes having active segments covering the active region. The active segment of the gate electrode is located between edges of the active segments of the source and drain electrodes. The gate and drain electrodes include inactive pads remote from the active segments. The pads are connected directly to the input and output networks. The source electrode is connected to the ground plane layer. The space between the electrodes and the geometry of the electrodes extablish parasitic shunt capacitances and series inductances that provide substantial matches between the input network and the gate electrode and between the output network and the drain electrode. Many of the devices are connected in parallel and share a common active region, so that each pair of adjacent devices shares the same source electrodes and each pair of adjacent devices shares the same drain electrodes. The gate electrodes for the parallel devices are formed by a continuous stripe that extends between adjacent devices and is connected at different points to the common gate pad.

  1. Graphene as tunable contact for high performance thin film transistor

    NASA Astrophysics Data System (ADS)

    Liu, Yuan

    performance and mechanical robustness. By using the graphene as a work-function tunable contact for amorphous indium gallium zinc oxide (IGZO) thin film, the vertical current flow across the graphene-IGZO junction can be effectively modulated by an external gate potential to enable VTFTs with a highest on-off ratio exceeding 105. The unique vertical transistor architecture can readily enable ultrashort channel devices with very high delivering current and exceptional mechanical flexibility. Furthermore, I will, demonstrate a new design strategy for vertical OTFT with ultra-short channel length without using conventional high-resolution lithography process. They can deliver a high current density over 1.8 A/ cm2 and thus enable a high cutoff frequency devices (~ 0.4 MHz) comparable with the ultra-short channel organic transistors. Importantly, with unique vertical architecture, the entire organic channel material is sandwiched between the source and drain electrodes and is thus naturally protected to ensure excellent air-stability. Finally I will present a new strategy by using graphene as the back electrodes to achieve Ohmic contact to MoS2. With a finite density of states, the Fermi level of graphene can be readily tuned by a gate potential to enable a nearly perfect band alignment with MoS2. For the first time, a transparent contact to MoS2 is demonstrated with zero contact barrier and linear output behaviour at cryogenic temperatures (down to 1.9 K) for both monolayer and multilayer MoS2. Benefiting from the barrier-free transparent contacts, we show that a metal-insulator-transition (MIT) can be observed in a two-terminal MoS2 device, a phenomenon that could be easily masked by Schottky barriers found in conventional metal-contacted MoS2 devices. With further passivation by boron nitride (BN) encapsulation, we demonstrate a record-high extrinsic (two-terminal) field effect mobility up to 1300 cm2/V s in MoS2 at low temperature. These findings can open up exciting new

  2. Graphene as tunable contact for high performance thin film transistor

    NASA Astrophysics Data System (ADS)

    Liu, Yuan

    performance and mechanical robustness. By using the graphene as a work-function tunable contact for amorphous indium gallium zinc oxide (IGZO) thin film, the vertical current flow across the graphene-IGZO junction can be effectively modulated by an external gate potential to enable VTFTs with a highest on-off ratio exceeding 105. The unique vertical transistor architecture can readily enable ultrashort channel devices with very high delivering current and exceptional mechanical flexibility. Furthermore, I will, demonstrate a new design strategy for vertical OTFT with ultra-short channel length without using conventional high-resolution lithography process. They can deliver a high current density over 1.8 A/ cm2 and thus enable a high cutoff frequency devices (~ 0.4 MHz) comparable with the ultra-short channel organic transistors. Importantly, with unique vertical architecture, the entire organic channel material is sandwiched between the source and drain electrodes and is thus naturally protected to ensure excellent air-stability. Finally I will present a new strategy by using graphene as the back electrodes to achieve Ohmic contact to MoS2. With a finite density of states, the Fermi level of graphene can be readily tuned by a gate potential to enable a nearly perfect band alignment with MoS2. For the first time, a transparent contact to MoS2 is demonstrated with zero contact barrier and linear output behaviour at cryogenic temperatures (down to 1.9 K) for both monolayer and multilayer MoS2. Benefiting from the barrier-free transparent contacts, we show that a metal-insulator-transition (MIT) can be observed in a two-terminal MoS2 device, a phenomenon that could be easily masked by Schottky barriers found in conventional metal-contacted MoS2 devices. With further passivation by boron nitride (BN) encapsulation, we demonstrate a record-high extrinsic (two-terminal) field effect mobility up to 1300 cm2/V s in MoS2 at low temperature. These findings can open up exciting new

  3. Evaluation of a gate-first process for AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors with low ohmic annealing temperature

    NASA Astrophysics Data System (ADS)

    Liuan, Li; Jiaqi, Zhang; Yang, Liu; Jin-Ping, Ao

    2016-03-01

    In this paper, TiN/AlOx gated AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) were fabricated for gate-first process evaluation. By employing a low temperature ohmic process, ohmic contact can be obtained by annealing at 600 °C with the contact resistance approximately 1.6 Ω·mm. The ohmic annealing process also acts as a post-deposition annealing on the oxide film, resulting in good device performance. Those results demonstrated that the TiN/AlOx gated MOS-HFETs with low temperature ohmic process can be applied for self-aligned gate AlGaN/GaN MOS-HFETs. Project supported by the International Science and Technology Collaboration Program of China (Grant No. 2012DFG52260).

  4. Integrated P-channel MOS gyrator

    NASA Technical Reports Server (NTRS)

    Hochmair, E. S. (Inventor)

    1974-01-01

    A gyrator circuit is described which is of the conventional configuration of two amplifiers in a circular loop, one producing zero phase shift and the other producing 180 phase reversal, in a circuit having medium Q composed of all field effect transistors of the same conductivity type. The current source to each gyrator amplifier comprises an amplifier which responds to changes in current, with the amplified signals feed back so as to limit current. The feedback amplifier has a large capacitor connected to bypass high frequency components, thereby stabilizing the output. The design makes possible fabrication of circuits with transistors of only one conductivity type, providing economies in manufacture and use.

  5. Theoretical analysis of the combined effects of sulfur vacancies and analyte adsorption on the electronic properties of single-layer MoS2

    NASA Astrophysics Data System (ADS)

    Akdim, Brahim; Pachter, Ruth; Mou, Shin

    2016-05-01

    We report a first-principles theoretical investigation on the electronic structure and electron transport of defective single-layer (SL) MoS2, as well as of corresponding structures adsorbed with benzyl viologen (BV), which was shown to provide improved performance of a field effect transistor. O2 adsorption was included to gain an understanding of the response upon air-exposure. Following analysis of the structure and stability of sulfur single vacancy and line defects in SL MoS2, we investigated the local transport at the adsorbed sites via a transport model that mimics a scanning tunneling spectroscopy experiment. Distinct current-voltage characteristics were indicated for adsorbed oxygen species at a sulfur vacancy. The electronic structures of defective MoS2 indicated the emergence of impurity states in the bandgap due to sulfur defects and oxygen adsorption. Electron transport calculations for the MoS2 surface with an extended defect in a device setting demonstrated that physisorption of BV enhances the output current, while facile chemisorption by O2 upon air-exposure causes degradation of electron transport.

  6. Theoretical analysis of the combined effects of sulfur vacancies and analyte adsorption on the electronic properties of single-layer MoS2.

    PubMed

    Akdim, Brahim; Pachter, Ruth; Mou, Shin

    2016-05-01

    We report a first-principles theoretical investigation on the electronic structure and electron transport of defective single-layer (SL) MoS2, as well as of corresponding structures adsorbed with benzyl viologen (BV), which was shown to provide improved performance of a field effect transistor. O2 adsorption was included to gain an understanding of the response upon air-exposure. Following analysis of the structure and stability of sulfur single vacancy and line defects in SL MoS2, we investigated the local transport at the adsorbed sites via a transport model that mimics a scanning tunneling spectroscopy experiment. Distinct current-voltage characteristics were indicated for adsorbed oxygen species at a sulfur vacancy. The electronic structures of defective MoS2 indicated the emergence of impurity states in the bandgap due to sulfur defects and oxygen adsorption. Electron transport calculations for the MoS2 surface with an extended defect in a device setting demonstrated that physisorption of BV enhances the output current, while facile chemisorption by O2 upon air-exposure causes degradation of electron transport. PMID:26999310

  7. Interference-based molecular transistors

    PubMed Central

    Li, Ying; Mol, Jan A.; Benjamin, Simon C.; Briggs, G. Andrew D.

    2016-01-01

    Molecular transistors have the potential for switching with lower gate voltages than conventional field-effect transistors. We have calculated the performance of a single-molecule device in which there is interference between electron transport through the highest occupied molecular orbital and the lowest unoccupied molecular orbital of a single molecule. Quantum interference results in a subthreshold slope that is independent of temperature. For realistic parameters the change in gate potential required for a change in source-drain current of two decades is 20 mV, which is a factor of six smaller than the theoretical limit for a metal-oxide-semiconductor field-effect transistor. PMID:27646692

  8. Interference-based molecular transistors.

    PubMed

    Li, Ying; Mol, Jan A; Benjamin, Simon C; Briggs, G Andrew D

    2016-01-01

    Molecular transistors have the potential for switching with lower gate voltages than conventional field-effect transistors. We have calculated the performance of a single-molecule device in which there is interference between electron transport through the highest occupied molecular orbital and the lowest unoccupied molecular orbital of a single molecule. Quantum interference results in a subthreshold slope that is independent of temperature. For realistic parameters the change in gate potential required for a change in source-drain current of two decades is 20 mV, which is a factor of six smaller than the theoretical limit for a metal-oxide-semiconductor field-effect transistor. PMID:27646692

  9. Compensating For Changes in MOS Sensors

    SciTech Connect

    Matzke, Brett D.

    2006-09-29

    AirAdvice provided the following introduction: “AirAdvice uses metal oxide semiconductor (MOS) sensors for measuring total volatile organic compounds (TVOC) in air. These sensors are incorporated into AirAdvice’s indoor air quality (IAQ) monitors. The IAQ monitors are designed so that they require annual calibration to maintain acceptable accuracy. Since the MOS TVOC sensors used in the monitors change in sensitivity with time and exposure to gases, AirAdvice has developed an algorithm-based process that automatically compensates for changes in the sensors. The proposed project is to have PNNL analyze data provided by AirAdvice with these objectives: (1) assess how effective AirAdvice’s automatic drift correction process is, (2) identify any problems in the process, and (3) propose improvements to the process.”

  10. Rolling Up a Monolayer MoS2 Sheet.

    PubMed

    Meng, Jianling; Wang, Guole; Li, Xiaomin; Lu, Xiaobo; Zhang, Jing; Yu, Hua; Chen, Wei; Du, Luojun; Liao, Mengzhou; Zhao, Jing; Chen, Peng; Zhu, Jianqi; Bai, Xuedong; Shi, Dongxia; Zhang, Guangyu

    2016-07-01

    MoS2 nanoscrolls are formed by argon plasma treatment on monolayer MoS2 sheet. The nanoscale scroll formation is attributed to the partial removal of top sulfur layer in MoS2 during the argon plasma treatment process. This convenient, solvent-free, and high-yielding nanoscroll formation technique is also feasible for other 2D transition metal dichalcogenides.

  11. High transconductance organic electrochemical transistors

    PubMed Central

    Khodagholy, Dion; Rivnay, Jonathan; Sessolo, Michele; Gurfinkel, Moshe; Leleux, Pierre; Jimison, Leslie H.; Stavrinidou, Eleni; Herve, Thierry; Sanaur, Sébastien; Owens, Róisín M.; Malliaras, George G.

    2013-01-01

    The development of transistors with high gain is essential for applications ranging from switching elements and drivers to transducers for chemical and biological sensing. Organic transistors have become well-established based on their distinct advantages, including ease of fabrication, synthetic freedom for chemical functionalization, and the ability to take on unique form factors. These devices, however, are largely viewed as belonging to the low-end of the performance spectrum. Here we present organic electrochemical transistors with a transconductance in the mS range, outperforming transistors from both traditional and emerging semiconductors. The transconductance of these devices remains fairly constant from DC up to a frequency of the order of 1 kHz, a value determined by the process of ion transport between the electrolyte and the channel. These devices, which continue to work even after being crumpled, are predicted to be highly relevant as transducers in biosensing applications. PMID:23851620

  12. Transistorized converter provides nondissipative regulation

    NASA Technical Reports Server (NTRS)

    1964-01-01

    A transistorized regulator converter efficiently converts fluctuating input voltages to a constant output voltage, avoiding the use of saturable reactors. It is nondissipative in operation and functions in an open loop through variable duty cycles.

  13. Solder Bonding for Power Transistors

    NASA Technical Reports Server (NTRS)

    Snytsheuvel, H. A.; Mandel, H.

    1985-01-01

    Indium solder boosts power rating and facilitates circuit changes. Efficient heat conduction from power transistor to heat sink provided by layer of indium solder. Low melting point of indium solder (141 degrees C) allows power transistor to be removed, if circuit must be reworked, without disturbing other components mounted with ordinary solder that melts at 181 degrees C. Solder allows devices operated at higher power levels than does conventional attachment by screws.

  14. Magnetoresistance in Co/2D MoS2/Co and Ni/2D MoS2/Ni junctions.

    PubMed

    Zhang, Han; Ye, Meng; Wang, Yangyang; Quhe, Ruge; Pan, Yuanyuan; Guo, Ying; Song, Zhigang; Yang, Jinbo; Guo, Wanlin; Lu, Jing

    2016-06-28

    Semiconducting single-layer (SL) and few-layer MoS2 have a flat surface, free of dangling bonds. Using density functional theory coupled with non-equilibrium Green's function method, we investigate the spin-polarized transport properties of Co/2D MoS2/Co and Ni/2D MoS2/Ni junctions with MoS2 layer numbers of N = 1, 3, and 5. Well-defined interfaces are formed between MoS2 and metal electrodes. The junctions with a SL MoS2 spacer are almost metallic owing to the strong coupling between MoS2 and the ferromagnets, while those are tunneling with a few layer MoS2 spacer. Both large magnetoresistance and tunneling magnetoresistance are found when fcc or hcp Co is used as an electrode. Therefore, flat single- and few-layer MoS2 can serve as an effective nonmagnetic spacer in a magnetoresistance or tunneling magnetoresistance device with a well-defined interface.

  15. Magnetoresistance in Co/2D MoS2/Co and Ni/2D MoS2/Ni junctions.

    PubMed

    Zhang, Han; Ye, Meng; Wang, Yangyang; Quhe, Ruge; Pan, Yuanyuan; Guo, Ying; Song, Zhigang; Yang, Jinbo; Guo, Wanlin; Lu, Jing

    2016-06-28

    Semiconducting single-layer (SL) and few-layer MoS2 have a flat surface, free of dangling bonds. Using density functional theory coupled with non-equilibrium Green's function method, we investigate the spin-polarized transport properties of Co/2D MoS2/Co and Ni/2D MoS2/Ni junctions with MoS2 layer numbers of N = 1, 3, and 5. Well-defined interfaces are formed between MoS2 and metal electrodes. The junctions with a SL MoS2 spacer are almost metallic owing to the strong coupling between MoS2 and the ferromagnets, while those are tunneling with a few layer MoS2 spacer. Both large magnetoresistance and tunneling magnetoresistance are found when fcc or hcp Co is used as an electrode. Therefore, flat single- and few-layer MoS2 can serve as an effective nonmagnetic spacer in a magnetoresistance or tunneling magnetoresistance device with a well-defined interface. PMID:27257639

  16. A high-performance complementary inverter based on transition metal dichalcogenide field-effect transistors

    NASA Astrophysics Data System (ADS)

    Cho, Ah-Jin; Park, Kee Chan; Kwon, Jang-Yeon

    2015-03-01

    For several years, graphene has been the focus of much attention due to its peculiar characteristics, and it is now considered to be a representative 2-dimensional (2D) material. Even though many research groups have studied on the graphene, its intrinsic nature of a zero band-gap, limits its use in practical applications, particularly in logic circuits. Recently, transition metal dichalcogenides (TMDs), which are another type of 2D material, have drawn attention due to the advantage of having a sizable band-gap and a high mobility. Here, we report on the design of a complementary inverter, one of the most basic logic elements, which is based on a MoS2 n-type transistor and a WSe2 p-type transistor. The advantages provided by the complementary metal-oxide-semiconductor (CMOS) configuration and the high-performance TMD channels allow us to fabricate a TMD complementary inverter that has a high-gain of 13.7. This work demonstrates the operation of the MoS2 n-FET and WSe2 p-FET on the same substrate, and the electrical performance of the CMOS inverter, which is based on a different driving current, is also measured.

  17. A high-performance complementary inverter based on transition metal dichalcogenide field-effect transistors.

    PubMed

    Cho, Ah-Jin; Park, Kee Chan; Kwon, Jang-Yeon

    2015-01-01

    For several years, graphene has been the focus of much attention due to its peculiar characteristics, and it is now considered to be a representative 2-dimensional (2D) material. Even though many research groups have studied on the graphene, its intrinsic nature of a zero band-gap, limits its use in practical applications, particularly in logic circuits. Recently, transition metal dichalcogenides (TMDs), which are another type of 2D material, have drawn attention due to the advantage of having a sizable band-gap and a high mobility. Here, we report on the design of a complementary inverter, one of the most basic logic elements, which is based on a MoS2 n-type transistor and a WSe2 p-type transistor. The advantages provided by the complementary metal-oxide-semiconductor (CMOS) configuration and the high-performance TMD channels allow us to fabricate a TMD complementary inverter that has a high-gain of 13.7. This work demonstrates the operation of the MoS2 n-FET and WSe2 p-FET on the same substrate, and the electrical performance of the CMOS inverter, which is based on a different driving current, is also measured. PMID:25852410

  18. Vertically stacked multi-heterostructures of layered materials for logic transistors and complementary inverters

    PubMed Central

    Yu, Woo Jong; Li, Zheng; Zhou, Hailong; Chen, Yu; Wang, Yang; Huang, Yu; Duan, Xiangfeng

    2014-01-01

    The layered materials such as graphene have attracted considerable interest for future electronics. Here we report the vertical integration of multi-heterostructures of layered materials to enable high current density vertical field-effect transistors (VFETs). An n-channel VFET is created by sandwiching few-layer molybdenum disulfide (MoS2) as the semiconducting channel between a monolayer graphene and a metal thin film. The VFETs exhibit a room temperature on-off ratio >103, while at same time deliver a high current density up to 5,000 A/cm2, sufficient for high performance logic applications. This study offers a general strategy for the vertical integration of various layered materials to obtain both p- and n-channel transistors for complementary logic functions. A complementary inverter with larger than unit voltage gain is demonstrated by vertically stacking the layered materials of graphene, Bi2Sr2Co2O8 (p-channel), graphene, MoS2 (n-channel), and metal thin film in sequence. The ability to simultaneously achieve high on-off ratio, high current density, and logic integration in the vertically stacked multi-heterostructures can open up a new dimension for future electronics to enable three-dimensional integration. PMID:23241535

  19. Evolvable circuit with transistor-level reconfigurability

    NASA Technical Reports Server (NTRS)

    Stoica, Adrian (Inventor); Salazar-Lazaro, Carlos Harold (Inventor)

    2004-01-01

    An evolvable circuit includes a plurality of reconfigurable switches, a plurality of transistors within a region of the circuit, the plurality of transistors having terminals, the plurality of transistors being coupled between a power source terminal and a power sink terminal so as to be capable of admitting power between the power source terminal and the power sink terminal, the plurality of transistors being coupled so that every transistor terminal to transistor terminal coupling within the region of the circuit comprises a reconfigurable switch.

  20. Facile Routes To Improve Performance of Solution-Processed Amorphous Metal Oxide Thin Film Transistors by Water Vapor Annealing.

    PubMed

    Park, Won-Tae; Son, Inyoung; Park, Hyun-Woo; Chung, Kwun-Bum; Xu, Yong; Lee, Taegweon; Noh, Yong-Young

    2015-06-24

    Here, we report on a simple and high-rate oxidization method for producing solution-based compound mixtures of indium zinc oxide (IZO) and indium gallium zinc oxide (IGZO) metal-oxide semiconductors (MOS) for thin-film transistor (TFT) applications. One of the issues for solution-based MOS fabrication is how to sufficiently oxidize the precursor in order to achieve high performance. As the oxidation rate of solution processing is lower than vacuum-based deposition such as sputtering, devices using solution-processed MOS exhibit relatively poorer performance. Therefore, we propose a method to prepare the metal-oxide precursor upon exposure to saturated water vapor in a closed volume for increasing the oxidization efficiency without requiring additional oxidizing agent. We found that the hydroxide rate of the MOS film exposed to water vapor is lower than when unexposed (≤18%). Hence, we successfully fabricated oxide TFTs with high electron mobility (27.9 cm(2)/V·s) and established a rapid process (annealing at 400 °C for 5 min) that is much shorter than the conventional as-deposited long-duration annealing (at 400 °C for 1 h) whose corresponding mobility is even lower (19.2 cm(2)/V·s). PMID:26043206

  1. Impact of field-induced quantum confinement on the onset of tunneling field-effect transistors: Experimental verification

    SciTech Connect

    Smets, Quentin Verreck, Devin; Heyns, Marc M.; Verhulst, Anne S.; Martens, Koen; Lin, Han Chung; Kazzi, Salim El; Simoen, Eddy; Collaert, Nadine; Thean, Aaron; Raskin, Jean-Pierre

    2014-11-17

    The Tunneling Field-Effect Transistor (TFET) is a promising device for future low-power logic. Its performance is often predicted using semiclassical simulations, but there is usually a large discrepancy with experimental results. An important reason is that Field-Induced Quantum Confinement (FIQC) is neglected. Quantum mechanical simulations show FIQC delays the onset of Band-To-Band Tunneling (BTBT) with hundreds of millivolts in the promising line-TFET configuration. In this letter, we provide experimental verification of this delayed onset. We accomplish this by developing a method where line-TFET are modeled using highly doped MOS capacitors (MOS-CAP). Using capacitance-voltage measurements, we demonstrate AC inversion by BTBT, which was so far unobserved in MOS-CAP. Good agreement is shown between the experimentally obtained BTBT onset and quantum mechanical predictions, proving the need to include FIQC in all TFET simulations. Finally, we show that highly doped MOS-CAP is promising for characterization of traps deep into the conduction band.

  2. Chemical assembly of atomically thin transistors and circuits in a large scale

    NASA Astrophysics Data System (ADS)

    Zhao, Mervin; Ye, Yu; Han, Yimo; Xia, Yang; Zhu, Hanyu; Wang, Yuan; Muller, David; Zhang, Xiang

    Next-generation electronics calls for new materials beyond silicon for increased functionality, performance, and scaling in integrated circuits. 2D gapless graphene and semiconducting TMDCs have emerged as promising electronic materials due to their atomic thickness, chemical stability and scalability. However, difficulties in the assembly of 2D electronic structures arise in the precise spatial control over the conducting and semiconducting crystals, typically relying on physically transferring them. Ultimately, this renders them unsuitable for an industrial scale and impedes the maturity of integrating atomic elements in modern electronics. Here, we report the large-scale spatially controlled synthesis of the single-layer MoS2 laterally in electrical contact with graphene using a seeded growth method. TEM studies reveal that the single-layer MoS2 nucleates at the edge of the graphene, creating a lateral van der Waals heterostructure. The graphene allows for electrical injection into MoS2, creating 2D atomic transistors with high transconductance, on-off ratios, and mobility. In addition, we assemble 2D logic circuits, such as a heterostructure NMOS inverter with a high voltage gain, up to 70.

  3. Vertically Conductive MoS2 Spiral Pyramid.

    PubMed

    Ly, Thuc Hue; Zhao, Jiong; Kim, Hyun; Han, Gang Hee; Nam, Honggi; Lee, Young Hee

    2016-09-01

    MoS2 spirals grown by the chemical vapor deposition method, driven by a threading dislocation, has a peculiar rhombohedral-like structure. This threading dislocation can carry helical current in the vertical direction and greatly enhances the vertical conductance in the MoS2 multilayer samples.

  4. Torsional Deformations in Subnanometer MoS Interconnecting Wires.

    PubMed

    Koh, Ai Leen; Wang, Shanshan; Ataca, Can; Grossman, Jeffrey C; Sinclair, Robert; Warner, Jamie H

    2016-02-10

    We use aberration-corrected transmission electron microscopy to track the real time atomic level torsional dynamics of subnanometer wires of MoS interconnecting monolayer regions of MoS2. An in situ heating holder is used inside the transmission electron microscope to raise the temperature of the sample to 400 °C to increase crystallization rates of the wires and reduce contamination effects. Frequent rotational twisting of the MoS wire is captured, demonstrating elastic torsional deformation of the MoS wires. We show that torsional rotations of the crystal structure of the MoS wires depend upon the specific atomic structure of the anchored sections of the suspended wire and the number of unit cells that make up the wire length. Elastic torsional flexibility of the MoS wires is revealed to help their self-adapting connectivity during the structural changes. Plastic torsional deformation is also seen for MoS wires that contain defects in their crystal structure, which produce small scale rotational disorder within the wires. Upon removal of the defects, the wire returns back to pristine form. These results provide detailed insights into how the atomic structure of the anchoring site significantly influences the nanowire configurations relative to the monolayered MoS2. PMID:26785319

  5. Seeing diabetes: visual detection of glucose based on the intrinsic peroxidase-like activity of MoS2 nanosheets

    NASA Astrophysics Data System (ADS)

    Lin, Tianran; Zhong, Liangshuang; Guo, Liangqia; Fu, Fengfu; Chen, Guonan

    2014-09-01

    Molybdenum disulfide (MoS2) has attracted increasing research interest recently due to its unique physical, optical and electrical properties, correlated with its 2D ultrathin atomic-layered structure. Until now, however, great efforts have focused on its applications such as lithium ion batteries, transistors, and hydrogen evolution reactions. Herein, for the first time, MoS2 nanosheets are discovered to possess an intrinsic peroxidase-like activity and can catalytically oxidize 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to produce a color reaction. The catalytic activity follows the typical Michaelis-Menten kinetics and is dependent on temperature, pH, H2O2 concentration, and reaction time. Based on this finding, a highly sensitive and selective colorimetric method for H2O2 and glucose detection is developed and applied to detect glucose in serum samples. Moreover, a simple, inexpensive, instrument-free and portable test kit for the visual detection of glucose in normal and diabetic serum samples is constructed by utilizing agarose hydrogel as a visual detection platform.Molybdenum disulfide (MoS2) has attracted increasing research interest recently due to its unique physical, optical and electrical properties, correlated with its 2D ultrathin atomic-layered structure. Until now, however, great efforts have focused on its applications such as lithium ion batteries, transistors, and hydrogen evolution reactions. Herein, for the first time, MoS2 nanosheets are discovered to possess an intrinsic peroxidase-like activity and can catalytically oxidize 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to produce a color reaction. The catalytic activity follows the typical Michaelis-Menten kinetics and is dependent on temperature, pH, H2O2 concentration, and reaction time. Based on this finding, a highly sensitive and selective colorimetric method for H2O2 and glucose detection is developed and applied to detect glucose in serum samples. Moreover, a simple, inexpensive

  6. Gate-defined Single Electron Transistor in a Graphene-MoS2 van der Waals Heterostructure

    NASA Astrophysics Data System (ADS)

    Wang, Ke; Taniguchi, Takashi; Watanabe, Kenji; Kim, Philip

    We report experimental demonstration of fabrication of laterally confined single electron transistor (SET) on MoS2 transition metal dichalcogenide (TMDC) semiconductor. A few atomic layers of MoS2 single crystals are encapsulated in hBN layers in order to improve mobility of 2-dimensional (2D) electron channel. Graphene layers are employed to provide Ohmic contact to the TMDC channels. The laterally confined quantum dots are formed by electrostatically depleting the near-by 2D channel employing local gate fabricated by electron lithography. Typical SET transport signatures such as gate-tunable Coulomb blockade have been observed. We have demonstrated the quantum confinement can be sensitively tuned to adjust the dot-reservoir coupling. The work paves way for more complicated device structure such as valley-spin filter and vertically coupled quantum dots in Coulomb drag devices.

  7. Atomic Layer Deposition of Gallium Oxide Films as Gate Dielectrics in AlGaN/GaN Metal-Oxide-Semiconductor High-Electron-Mobility Transistors.

    PubMed

    Shih, Huan-Yu; Chu, Fu-Chuan; Das, Atanu; Lee, Chia-Yu; Chen, Ming-Jang; Lin, Ray-Ming

    2016-12-01

    In this study, films of gallium oxide (Ga2O3) were prepared through remote plasma atomic layer deposition (RP-ALD) using triethylgallium and oxygen plasma. The chemical composition and optical properties of the Ga2O3 thin films were investigated; the saturation growth displayed a linear dependence with respect to the number of ALD cycles. These uniform ALD films exhibited excellent uniformity and smooth Ga2O3-GaN interfaces. An ALD Ga2O3 film was then used as the gate dielectric and surface passivation layer in a metal-oxide-semiconductor high-electron-mobility transistor (MOS-HEMT), which exhibited device performance superior to that of a corresponding conventional Schottky gate HEMT. Under similar bias conditions, the gate leakage currents of the MOS-HEMT were two orders of magnitude lower than those of the conventional HEMT, with the power-added efficiency enhanced by up to 9 %. The subthreshold swing and effective interfacial state density of the MOS-HEMT were 78 mV decade(-1) and 3.62 × 10(11) eV(-1) cm(-2), respectively. The direct-current and radio-frequency performances of the MOS-HEMT device were greater than those of the conventional HEMT. In addition, the flicker noise of the MOS-HEMT was lower than that of the conventional HEMT. PMID:27129687

  8. Atomic Layer Deposition of Gallium Oxide Films as Gate Dielectrics in AlGaN/GaN Metal-Oxide-Semiconductor High-Electron-Mobility Transistors.

    PubMed

    Shih, Huan-Yu; Chu, Fu-Chuan; Das, Atanu; Lee, Chia-Yu; Chen, Ming-Jang; Lin, Ray-Ming

    2016-12-01

    In this study, films of gallium oxide (Ga2O3) were prepared through remote plasma atomic layer deposition (RP-ALD) using triethylgallium and oxygen plasma. The chemical composition and optical properties of the Ga2O3 thin films were investigated; the saturation growth displayed a linear dependence with respect to the number of ALD cycles. These uniform ALD films exhibited excellent uniformity and smooth Ga2O3-GaN interfaces. An ALD Ga2O3 film was then used as the gate dielectric and surface passivation layer in a metal-oxide-semiconductor high-electron-mobility transistor (MOS-HEMT), which exhibited device performance superior to that of a corresponding conventional Schottky gate HEMT. Under similar bias conditions, the gate leakage currents of the MOS-HEMT were two orders of magnitude lower than those of the conventional HEMT, with the power-added efficiency enhanced by up to 9 %. The subthreshold swing and effective interfacial state density of the MOS-HEMT were 78 mV decade(-1) and 3.62 × 10(11) eV(-1) cm(-2), respectively. The direct-current and radio-frequency performances of the MOS-HEMT device were greater than those of the conventional HEMT. In addition, the flicker noise of the MOS-HEMT was lower than that of the conventional HEMT.

  9. Atomic Layer Deposition of Gallium Oxide Films as Gate Dielectrics in AlGaN/GaN Metal-Oxide-Semiconductor High-Electron-Mobility Transistors

    NASA Astrophysics Data System (ADS)

    Shih, Huan-Yu; Chu, Fu-Chuan; Das, Atanu; Lee, Chia-Yu; Chen, Ming-Jang; Lin, Ray-Ming

    2016-04-01

    In this study, films of gallium oxide (Ga2O3) were prepared through remote plasma atomic layer deposition (RP-ALD) using triethylgallium and oxygen plasma. The chemical composition and optical properties of the Ga2O3 thin films were investigated; the saturation growth displayed a linear dependence with respect to the number of ALD cycles. These uniform ALD films exhibited excellent uniformity and smooth Ga2O3-GaN interfaces. An ALD Ga2O3 film was then used as the gate dielectric and surface passivation layer in a metal-oxide-semiconductor high-electron-mobility transistor (MOS-HEMT), which exhibited device performance superior to that of a corresponding conventional Schottky gate HEMT. Under similar bias conditions, the gate leakage currents of the MOS-HEMT were two orders of magnitude lower than those of the conventional HEMT, with the power-added efficiency enhanced by up to 9 %. The subthreshold swing and effective interfacial state density of the MOS-HEMT were 78 mV decade-1 and 3.62 × 1011 eV-1 cm-2, respectively. The direct-current and radio-frequency performances of the MOS-HEMT device were greater than those of the conventional HEMT. In addition, the flicker noise of the MOS-HEMT was lower than that of the conventional HEMT.

  10. Toward Ferroelectric Control of Monolayer MoS2.

    PubMed

    Nguyen, Ariana; Sharma, Pankaj; Scott, Thomas; Preciado, Edwin; Klee, Velveth; Sun, Dezheng; Lu, I-Hsi Daniel; Barroso, David; Kim, SukHyun; Shur, Vladimir Ya; Akhmatkhanov, Andrey R; Gruverman, Alexei; Bartels, Ludwig; Dowben, Peter A

    2015-05-13

    The chemical vapor deposition (CVD) of molybdenum disulfide (MoS2) single-layer films onto periodically poled lithium niobate is possible while maintaining the substrate polarization pattern. The MoS2 growth exhibits a preference for the ferroelectric domains polarized "up" with respect to the surface so that the MoS2 film may be templated by the substrate ferroelectric polarization pattern without the need for further lithography. MoS2 monolayers preserve the surface polarization of the "up" domains, while slightly quenching the surface polarization on the "down" domains as revealed by piezoresponse force microscopy. Electrical transport measurements suggest changes in the dominant carrier for CVD MoS2 under application of an external voltage, depending on the domain orientation of the ferroelectric substrate. Such sensitivity to ferroelectric substrate polarization opens the possibility for ferroelectric nonvolatile gating of transition metal dichalcogenides in scalable devices fabricated free of exfoliation and transfer.

  11. Photoluminescence from chemically exfoliated MoS2.

    PubMed

    Eda, Goki; Yamaguchi, Hisato; Voiry, Damien; Fujita, Takeshi; Chen, Mingwei; Chhowalla, Manish

    2011-12-14

    A two-dimensional crystal of molybdenum disulfide (MoS2) monolayer is a photoluminescent direct gap semiconductor in striking contrast to its bulk counterpart. Exfoliation of bulk MoS2 via Li intercalation is an attractive route to large-scale synthesis of monolayer crystals. However, this method results in loss of pristine semiconducting properties of MoS2 due to structural changes that occur during Li intercalation. Here, we report structural and electronic properties of chemically exfoliated MoS2. The metastable metallic phase that emerges from Li intercalation was found to dominate the properties of as-exfoliated material, but mild annealing leads to gradual restoration of the semiconducting phase. Above an annealing temperature of 300 °C, chemically exfoliated MoS2 exhibit prominent band gap photoluminescence, similar to mechanically exfoliated monolayers, indicating that their semiconducting properties are largely restored.

  12. Passivated ambipolar black phosphorus transistors

    NASA Astrophysics Data System (ADS)

    Yue, Dewu; Lee, Daeyeong; Jang, Young Dae; Choi, Min Sup; Nam, Hye Jin; Jung, Duk-Young; Yoo, Won Jong

    2016-06-01

    We report the first air-passivated ambipolar BP transistor formed by applying benzyl viologen, which serves as a surface charge transfer donor for BP flakes. The passivated BP devices exhibit excellent stability under both an ambient atmosphere and vacuum; their transistor performance is maintained semi-permanently. Unlike their intrinsic p-type properties, passivated BP devices present advantageous ambipolar properties with much higher electron mobility up to ~83 cm2 V-1 s-1 from 2-terminal measurement at 300 K, compared to other reported studies on n-type BP transistors. On the basis of the n-type doping effect that originated from benzyl viologen, we also systematically investigated the BP thickness dependence of our devices on electrical properties, in which we found the best electron transport performance to be attained when an ~10 nm thick BP flake was used.We report the first air-passivated ambipolar BP transistor formed by applying benzyl viologen, which serves as a surface charge transfer donor for BP flakes. The passivated BP devices exhibit excellent stability under both an ambient atmosphere and vacuum; their transistor performance is maintained semi-permanently. Unlike their intrinsic p-type properties, passivated BP devices present advantageous ambipolar properties with much higher electron mobility up to ~83 cm2 V-1 s-1 from 2-terminal measurement at 300 K, compared to other reported studies on n-type BP transistors. On the basis of the n-type doping effect that originated from benzyl viologen, we also systematically investigated the BP thickness dependence of our devices on electrical properties, in which we found the best electron transport performance to be attained when an ~10 nm thick BP flake was used. Electronic supplementary information (ESI) available: Transfer characteristics of BP field effect transistors (BV1-BV4) (Fig. S1 and S2 and Table S1); output characteristics of BP field effect transistors in different directions (Fig. S3

  13. Chemistry of MOS-LSI radiation hardening

    NASA Technical Reports Server (NTRS)

    Grunthaner, P.

    1985-01-01

    The objective of this task was to obtain chemical information on MOS test samples. Toward this end, high resolution X-ray photoemission spectroscopy (XPS) has been the primary techniques used to characterize the chemistry and structure of the SiO2/Si interface for a variety of MOS structures with differing degrees of susceptibility to damage by ionizing radiation. The major accomplishments of this program are: (1) the identification of a structurally distinct region of SiO2 in the near-interfacial region of thermal SiO2 on Si; (2) the identification in the near-interfacial region of SiO2 structural differences between radiation hard and soft gate oxides; (3) the direct observation of radiation-induced damage sites in thermal SiO2 with XPS using in situ electron stress; (4) the correlation of suboxide state distributions at the SiO2/Si interface with processing parameters and radiation susceptibility; (5) the development of a chemical mechanism for radiation-induced interface state generation in SiO2/Si structures; and (6) the development benign chemical profiling techniques which permit the investigation of oxide/semiconductor structures using surface sensitive electron spectroscopic techniques.

  14. Factors acting on Mos1 transposition efficiency

    PubMed Central

    Sinzelle, Ludivine; Jégot, Gwenhael; Brillet, Benjamin; Rouleux-Bonnin, Florence; Bigot, Yves; Augé-Gouillou, Corinne

    2008-01-01

    Background Mariner-like elements (MLEs) are widespread DNA transposons in animal genomes. Although in vitro transposition reactions require only the transposase, various factors depending on the host, the physico-chemical environment and the transposon sequence can interfere with the MLEs transposition in vivo. Results The transposition of Mos1, first isolated from drosophila mauritiana, depends of both the nucleic acid sequence of the DNA stuffer (in terms of GC content), and its length. We provide the first in vitro experimental demonstration that MITEs of MLE origin, as small as 80 to 120-bp, are able to transpose. Excessive temperature down-regulates Mos1 transposition, yielding excision products unable to re-integrate. Finally, the super-helicity of the DNA transposon donor has a dramatic impact on the transposition efficiency. Conclusion The study highlights how experimental conditions can bias interpretation of mariner excision frequency and quality. In vitro, the auto-integration pathway markedly limits transposition efficiency to new target sites, and this phenomenon may also limit events in the natural host. We propose a model for small transposons transposition that bypasses DNA bending constraints. PMID:19036139

  15. Passivated ambipolar black phosphorus transistors.

    PubMed

    Yue, Dewu; Lee, Daeyeong; Jang, Young Dae; Choi, Min Sup; Nam, Hye Jin; Jung, Duk-Young; Yoo, Won Jong

    2016-07-01

    We report the first air-passivated ambipolar BP transistor formed by applying benzyl viologen, which serves as a surface charge transfer donor for BP flakes. The passivated BP devices exhibit excellent stability under both an ambient atmosphere and vacuum; their transistor performance is maintained semi-permanently. Unlike their intrinsic p-type properties, passivated BP devices present advantageous ambipolar properties with much higher electron mobility up to ∼83 cm(2) V(-1) s(-1) from 2-terminal measurement at 300 K, compared to other reported studies on n-type BP transistors. On the basis of the n-type doping effect that originated from benzyl viologen, we also systematically investigated the BP thickness dependence of our devices on electrical properties, in which we found the best electron transport performance to be attained when an ∼10 nm thick BP flake was used. PMID:27283027

  16. High current gain transistor laser.

    PubMed

    Liang, Song; Qiao, Lijun; Zhu, Hongliang; Wang, Wei

    2016-06-10

    A transistor laser (TL), having the structure of a transistor with multi-quantum wells near its base region, bridges the functionality gap between lasers and transistors. However, light emission is produced at the expense of current gain for all the TLs reported up to now, leading to a very low current gain. We propose a novel design of TLs, which have an n-doped InP layer inserted in the emitter ridge. Numerical studies show that a current flow aperture for only holes can be formed in the center of the emitter ridge. As a result, the common emitter current gain can be as large as 143.3, which is over 15 times larger than that of a TL without the aperture. Besides, the effects of nonradiative recombination defects can be reduced greatly because the flow of holes is confined in the center region of the emitter ridge.

  17. Magnetic Vortex Based Transistor Operations

    PubMed Central

    Kumar, D.; Barman, S.; Barman, A.

    2014-01-01

    Transistors constitute the backbone of modern day electronics. Since their advent, researchers have been seeking ways to make smaller and more efficient transistors. Here, we demonstrate a sustained amplification of magnetic vortex core gyration in coupled two and three vortices by controlling their relative core polarities. This amplification is mediated by a cascade of antivortex solitons travelling through the dynamic stray field. We further demonstrated that the amplification can be controlled by switching the polarity of the middle vortex in a three vortex sequence and the gain can be controlled by the input signal amplitude. An attempt to show fan–out operation yielded gain for one of the symmetrically placed branches which can be reversed by switching the core polarity of all the vortices in the network. The above observations promote the magnetic vortices as suitable candidates to work as stable bipolar junction transistors (BJT). PMID:24531235

  18. High current gain transistor laser

    NASA Astrophysics Data System (ADS)

    Liang, Song; Qiao, Lijun; Zhu, Hongliang; Wang, Wei

    2016-06-01

    A transistor laser (TL), having the structure of a transistor with multi-quantum wells near its base region, bridges the functionality gap between lasers and transistors. However, light emission is produced at the expense of current gain for all the TLs reported up to now, leading to a very low current gain. We propose a novel design of TLs, which have an n-doped InP layer inserted in the emitter ridge. Numerical studies show that a current flow aperture for only holes can be formed in the center of the emitter ridge. As a result, the common emitter current gain can be as large as 143.3, which is over 15 times larger than that of a TL without the aperture. Besides, the effects of nonradiative recombination defects can be reduced greatly because the flow of holes is confined in the center region of the emitter ridge.

  19. High current gain transistor laser

    PubMed Central

    Liang, Song; Qiao, Lijun; Zhu, Hongliang; Wang, Wei

    2016-01-01

    A transistor laser (TL), having the structure of a transistor with multi-quantum wells near its base region, bridges the functionality gap between lasers and transistors. However, light emission is produced at the expense of current gain for all the TLs reported up to now, leading to a very low current gain. We propose a novel design of TLs, which have an n-doped InP layer inserted in the emitter ridge. Numerical studies show that a current flow aperture for only holes can be formed in the center of the emitter ridge. As a result, the common emitter current gain can be as large as 143.3, which is over 15 times larger than that of a TL without the aperture. Besides, the effects of nonradiative recombination defects can be reduced greatly because the flow of holes is confined in the center region of the emitter ridge. PMID:27282466

  20. Phonon thermoelectric transistors and rectifiers

    NASA Astrophysics Data System (ADS)

    Jiang, Jian-Hua; Kulkarni, Manas; Segal, Dvira; Imry, Yoseph

    2015-07-01

    We describe nonlinear phonon-thermoelectric devices where charge current and electronic and phononic heat currents are coupled, driven by voltage and temperature biases, when phonon-assisted inelastic processes dominate the transport. Our thermoelectric transistors and rectifiers can be realized in a gate-tunable double quantum-dot system embedded in a nanowire which is realizable within current technology. The inelastic electron-phonon scattering processes are found to induce pronounced charge, heat, and cross rectification effects, as well as a thermal transistor effect that, remarkably, can appear in the present model even in the linear-response regime without relying on the onset of negative differential thermal conductance.

  1. TILBW Bipolar Power Switching Transistor

    NASA Astrophysics Data System (ADS)

    Silard, Andrei P.; Nani, Gabriel

    1989-03-01

    The work reports the development of TILBW (Two Interdigitation Levels with heavily-doped Base Wells) bipolar power switching transistors, which combine the main advantages of both TIL and GAT devices. The TILBW transistors exhibit the following many-fold advantages in comparison with identical, yet conventional devices of the same class (identical area and case) processed simultaneously: a reduction of the turn-on time by a factor of ˜ 20; a two-fold reduction of the fall time tf; an ˜ 18-percent increase of VCEO(SUS); an ˜ 23-percent increase of VCBO; an enhanced RBSOA.

  2. Programmable, automated transistor test system

    NASA Technical Reports Server (NTRS)

    Truong, L. V.; Sundburg, G. R.

    1986-01-01

    A programmable, automated transistor test system was built to supply experimental data on new and advanced power semiconductors. The data will be used for analytical models and by engineers in designing space and aircraft electric power systems. A pulsed power technique was used at low duty cycles in a nondestructive test to examine the dynamic switching characteristic curves of power transistors in the 500 to 1000 V, 10 to 100 A range. Data collection, manipulation, storage, and output are operator interactive but are guided and controlled by the system software.

  3. Experimental study on vertical scaling of InAs-on-insulator metal-oxide-semiconductor field-effect transistors

    SciTech Connect

    Kim, SangHyeon E-mail: sh-kim@kist.re.kr; Yokoyama, Masafumi; Nakane, Ryosho; Takenaka, Mitsuru; Takagi, Shinichi; Ichikawa, Osamu; Osada, Takenori; Hata, Masahiko

    2014-06-30

    We have investigated effects of the vertical scaling on electrical properties in extremely thin-body InAs-on-insulator (-OI) metal-oxide-semiconductor field-effect transistors (MOSFETs). It is found that the body thickness (T{sub body}) scaling provides better short channel effect (SCE) control, whereas the T{sub body} scaling also causes the reduction of the mobility limited by channel thickness fluctuation (δT{sub body}) scattering (μ{sub fluctuation}). Also, in order to achieve better SCEs control, the thickness of InAs channel layer (T{sub channel}) scaling is more favorable than the thickness of MOS interface buffer layer (T{sub buffer}) scaling from a viewpoint of a balance between SCEs control and μ{sub fluctuation} reduction. These results indicate necessity of quantum well channel structure in InAs-OI MOSFETs and these should be considered in future transistor design.

  4. Silicon on insulator self-aligned transistors

    DOEpatents

    McCarthy, Anthony M.

    2003-11-18

    A method for fabricating thin-film single-crystal silicon-on-insulator (SOI) self-aligned transistors. Standard processing of silicon substrates is used to fabricate the transistors. Physical spaces, between the source and gate, and the drain and gate, introduced by etching the polysilicon gate material, are used to provide connecting implants (bridges) which allow the transistor to perform normally. After completion of the silicon substrate processing, the silicon wafer is bonded to an insulator (glass) substrate, and the silicon substrate is removed leaving the transistors on the insulator (glass) substrate. Transistors fabricated by this method may be utilized, for example, in flat panel displays, etc.

  5. Imaging spectroscopic ellipsometry of MoS2

    NASA Astrophysics Data System (ADS)

    Funke, S.; Miller, B.; Parzinger, E.; Thiesen, P.; Holleitner, A. W.; Wurstbauer, U.

    2016-09-01

    Micromechanically exfoliated mono- and multilayers of molybdenum disulfide (MoS2) are investigated by spectroscopic imaging ellipsometry. In combination with knife edge illumination, MoS2 flakes can be detected and classified on arbitrary flat and also transparent substrates with a lateral resolution down to 1-2 µm. The complex dielectric functions from mono- and trilayer MoS2 are presented. They are extracted from a multilayer model to fit the measured ellipsometric angles employing an anisotropic and an isotropic fit approach. We find that the energies of the critical points of the optical constants can be treated to be independent of the utilized model, whereas the magnitude of the optical constants varies with the used model. The anisotropic model suggests a maximum absorbance for a MoS2 sheet supported by sapphire of about 14% for monolayer and of 10% for trilayer MoS2. Furthermore, the lateral homogeneity of the complex dielectric function for monolayer MoS2 is investigated with a spatial resolution of 2 µm. Only minor fluctuations are observed. No evidence for strain, for a significant amount of disorder or lattice defects can be found in the wrinkle-free regions of the MoS2 monolayer from complementary µ-Raman spectroscopy measurements. We assume that the minor lateral variation in the optical constants are caused by lateral modification in the van der Waals interaction presumably caused by the preparation using micromechanical exfoliation and viscoelastic stamping.

  6. Imaging spectroscopic ellipsometry of MoS2

    NASA Astrophysics Data System (ADS)

    Funke, S.; Miller, B.; Parzinger, E.; Thiesen, P.; Holleitner, A. W.; Wurstbauer, U.

    2016-09-01

    Micromechanically exfoliated mono- and multilayers of molybdenum disulfide (MoS2) are investigated by spectroscopic imaging ellipsometry. In combination with knife edge illumination, MoS2 flakes can be detected and classified on arbitrary flat and also transparent substrates with a lateral resolution down to 1–2 µm. The complex dielectric functions from mono- and trilayer MoS2 are presented. They are extracted from a multilayer model to fit the measured ellipsometric angles employing an anisotropic and an isotropic fit approach. We find that the energies of the critical points of the optical constants can be treated to be independent of the utilized model, whereas the magnitude of the optical constants varies with the used model. The anisotropic model suggests a maximum absorbance for a MoS2 sheet supported by sapphire of about 14% for monolayer and of 10% for trilayer MoS2. Furthermore, the lateral homogeneity of the complex dielectric function for monolayer MoS2 is investigated with a spatial resolution of 2 µm. Only minor fluctuations are observed. No evidence for strain, for a significant amount of disorder or lattice defects can be found in the wrinkle-free regions of the MoS2 monolayer from complementary µ-Raman spectroscopy measurements. We assume that the minor lateral variation in the optical constants are caused by lateral modification in the van der Waals interaction presumably caused by the preparation using micromechanical exfoliation and viscoelastic stamping.

  7. Synthesis and characterization of MoS2 nanosheets.

    PubMed

    Deokar, G; Vignaud, D; Arenal, R; Louette, P; Colomer, J-F

    2016-02-19

    Here, we report on the synthesis of MoS2 nanosheets using a simple two-step additive-free growth technique. The as-synthesized nanosheets were characterized to determine their structure and composition, as well as their optical properties. The MoS2 nanosheets were analyzed by scanning electron microscopy, transmission electron microscopy (TEM), including high-resolution scanning TEM imaging and energy-dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy (XPS), Raman spectroscopy and photoluminescence (PL). The as-produced MoS2 nanosheets are vertically aligned with curved edges and are densely populated. The TEM measurements confirmed that the nanosheets have the 2H-MoS2 crystal structure in agreement with the Raman results. The XPS results revealed the presence of high purity MoS2. Moreover, a prominent PL similar to mechanically exfoliated few and mono-layer MoS2 was observed for the as-grown nanosheets. For the thin (≤50 nm) nanosheets, the PL feature was observed at the same energy as that for a direct band-gap monolayer MoS2 (1.83 eV). Thus, the as-produced high-quality, large-area, MoS2 nanosheets could be potentially useful for various optoelectronic and catalysis applications.

  8. Imaging spectroscopic ellipsometry of MoS2.

    PubMed

    Funke, S; Miller, B; Parzinger, E; Thiesen, P; Holleitner, A W; Wurstbauer, U

    2016-09-28

    Micromechanically exfoliated mono- and multilayers of molybdenum disulfide (MoS2) are investigated by spectroscopic imaging ellipsometry. In combination with knife edge illumination, MoS2 flakes can be detected and classified on arbitrary flat and also transparent substrates with a lateral resolution down to 1-2 µm. The complex dielectric functions from mono- and trilayer MoS2 are presented. They are extracted from a multilayer model to fit the measured ellipsometric angles employing an anisotropic and an isotropic fit approach. We find that the energies of the critical points of the optical constants can be treated to be independent of the utilized model, whereas the magnitude of the optical constants varies with the used model. The anisotropic model suggests a maximum absorbance for a MoS2 sheet supported by sapphire of about 14% for monolayer and of 10% for trilayer MoS2. Furthermore, the lateral homogeneity of the complex dielectric function for monolayer MoS2 is investigated with a spatial resolution of 2 µm. Only minor fluctuations are observed. No evidence for strain, for a significant amount of disorder or lattice defects can be found in the wrinkle-free regions of the MoS2 monolayer from complementary µ-Raman spectroscopy measurements. We assume that the minor lateral variation in the optical constants are caused by lateral modification in the van der Waals interaction presumably caused by the preparation using micromechanical exfoliation and viscoelastic stamping.

  9. Recovery of damage in rad-hard MOS devices during and after irradiation by electrons, protons, alphas, and gamma rays

    NASA Technical Reports Server (NTRS)

    Brucker, G. J.; Van Gunten, O.; Stassinopoulos, E. G.; Shapiro, P.; August, L. S.; Jordan, T. M.

    1983-01-01

    This paper reports on the recovery properties of rad-hard MOS devices during and after irradiation by electrons, protons, alphas, and gamma rays. The results indicated that complex recovery properties controlled the damage sensitivities of the tested parts. The results also indicated that damage sensitivities depended on dose rate, total dose, supply bias, gate bias, transistor type, radiation source, and particle energy. The complex nature of these dependencies make interpretation of LSI device performance in space (exposure to entire electron and proton spectra) difficult, if not impossible, without respective ground tests and analyses. Complete recovery of n-channel shifts was observed, in some cases within hours after irradiation, with equilibrium values of threshold voltages greater than their pre-irradiation values. This effect depended on total dose, radiation source, and gate bias during exposure. In contrast, the p-channel shifts recovered only 20 percent within 30 days after irradiation.

  10. Electronic system for data acquisition to study radiation effects on operating MOSFET transistors

    NASA Astrophysics Data System (ADS)

    de Oliveira, Juliano Alves; de Melo, Marco Antônio Assis; da Silveira, Marcilei A. Guazzelli; Medina, Nilberto H.

    2014-11-01

    In this work we present the development of an acquisition system for characterizing transistors under X-ray radiation. The system is able to carry out the acquisition and to storage characteristic transistor curves. To test the acquisition system we have submitted polarized P channel MOS transistors under continuous 10-keV X-ray doses up to 1500 krad. The characterization system can operate in the saturation region or in the linear region in order to observe the behavior of the currents or voltages involved during the irradiation process. Initial tests consisted of placing the device under test (DUT) in front of the X-ray beam direction, while its drain current was constantly monitored through the prototype generated in this work, the data are stored continuously and system behavior was monitored during the test. In order to observe the behavior of the DUT during the radiation tests, we used an acquisition system that consists of an ultra-low consumption16-bit Texas Instruments MSP430 microprocessor. Preliminary results indicate linear behavior of the voltage as a function of the exposure time and fast recovery. These features may be favorable to use this device as a radiation dosimeter to monitor low rate X-ray.

  11. Electronic system for data acquisition to study radiation effects on operating MOSFET transistors

    SciTech Connect

    Alves de Oliveira, Juliano; Assis de Melo, Marco Antônio; Guazzelli da Silveira, Marcilei A.; Medina, Nilberto H.

    2014-11-11

    In this work we present the development of an acquisition system for characterizing transistors under X-ray radiation. The system is able to carry out the acquisition and to storage characteristic transistor curves. To test the acquisition system we have submitted polarized P channel MOS transistors under continuous 10-keV X-ray doses up to 1500 krad. The characterization system can operate in the saturation region or in the linear region in order to observe the behavior of the currents or voltages involved during the irradiation process. Initial tests consisted of placing the device under test (DUT) in front of the X-ray beam direction, while its drain current was constantly monitored through the prototype generated in this work, the data are stored continuously and system behavior was monitored during the test. In order to observe the behavior of the DUT during the radiation tests, we used an acquisition system that consists of an ultra-low consumption16-bit Texas Instruments MSP430 microprocessor. Preliminary results indicate linear behavior of the voltage as a function of the exposure time and fast recovery. These features may be favorable to use this device as a radiation dosimeter to monitor low rate X-ray.

  12. Analysing organic transistors based on interface approximation

    SciTech Connect

    Akiyama, Yuto; Mori, Takehiko

    2014-01-15

    Temperature-dependent characteristics of organic transistors are analysed thoroughly using interface approximation. In contrast to amorphous silicon transistors, it is characteristic of organic transistors that the accumulation layer is concentrated on the first monolayer, and it is appropriate to consider interface charge rather than band bending. On the basis of this model, observed characteristics of hexamethylenetetrathiafulvalene (HMTTF) and dibenzotetrathiafulvalene (DBTTF) transistors with various surface treatments are analysed, and the trap distribution is extracted. In turn, starting from a simple exponential distribution, we can reproduce the temperature-dependent transistor characteristics as well as the gate voltage dependence of the activation energy, so we can investigate various aspects of organic transistors self-consistently under the interface approximation. Small deviation from such an ideal transistor operation is discussed assuming the presence of an energetically discrete trap level, which leads to a hump in the transfer characteristics. The contact resistance is estimated by measuring the transfer characteristics up to the linear region.

  13. Photoconductivities in MoS2 Nanoflake Photoconductors

    NASA Astrophysics Data System (ADS)

    Shen, Wei-Chu; Chen, Ruei-San; Huang, Ying-Sheng

    2016-03-01

    Photoconductivities in molybdenum disulfide (MoS2) layered nanostructures with two-hexagonal crystalline structure prepared by mechanical exfoliation were investigated. The photoconductor-type MoS2 nanoflakes exhibit remarkable photoresponse under the above bandgap excitation wavelength of 532 nm at different optical intensity. The photocurrent responsivity and photoconductive gain of nanoflakes can reach, respectively, 30 AW-1 and 103 at the intensity of 50 Wm-2, which are several orders of magnitude higher than those of their bulk counterparts. The vacuum-enhanced photocurrent and power-independent responsivity/gain indicate a surface-controlled photoconduction mechanism in the MoS2 nanomaterial.

  14. C- V characterization of MOS capacitors in SOI structures

    NASA Astrophysics Data System (ADS)

    Rustagi, S. C.; Mohsen, Z. O.; Chandra, S.; Chand, A.

    1996-06-01

    The capacitance-voltage characterization of a MOS structure in the SOI film has been carried out and the results have been interpreted with the help of a numerical solution to the one-dimensional Laplace-Poisson's equation. Various parameters characterizing the SOI MOS structures have been extracted. It has been shown that the C- V data on a simple three-terminal SOI MOS capacitor structure can yield all the information such as the thickness of the gate oxide, buried-oxide as well as the SOI film, along with the doping density in the film and the substrate.

  15. Black phosphorus nonvolatile transistor memory.

    PubMed

    Lee, Dain; Choi, Yongsuk; Hwang, Euyheon; Kang, Moon Sung; Lee, Seungwoo; Cho, Jeong Ho

    2016-04-28

    We demonstrated nanofloating gate transistor memory devices (NFGTMs) using mechanically-exfoliated few-layered black phosphorus (BP) channels and gold nanoparticle (AuNPs) charge trapping layers. The resulting BP-NFGTMs exhibited excellent memory performances, including the five-level data storage, large memory window (58.2 V), stable retention (10(4) s), and cyclic endurance (1000 cycles). PMID:27074903

  16. The four-gate transistor

    NASA Technical Reports Server (NTRS)

    Mojarradi, M. M.; Cristoveanu, S.; Allibert, F.; France, G.; Blalock, B.; Durfrene, B.

    2002-01-01

    The four-gate transistor or G4-FET combines MOSFET and JFET principles in a single SOI device. Experimental results reveal that each gate can modulate the drain current. Numerical simulations are presented to clarify the mechanisms of operation. The new device shows enhanced functionality, due to the combinatorial action of the four gates, and opens rather revolutionary applications.

  17. Improved linearity and reliability in GaN metal-oxide-semiconductor high-electron-mobility transistors using nanolaminate La2O3/SiO2 gate dielectric

    NASA Astrophysics Data System (ADS)

    Hsu, Ching-Hsiang; Shih, Wang-Cheng; Lin, Yueh-Chin; Hsu, Heng-Tung; Hsu, Hisang-Hua; Huang, Yu-Xiang; Lin, Tai-Wei; Wu, Chia-Hsun; Wu, Wen-Hao; Maa, Jer-Shen; Iwai, Hiroshi; Kakushima, Kuniyuki; Chang, Edward Yi

    2016-04-01

    Improved device performance to enable high-linearity power applications has been discussed in this study. We have compared the La2O3/SiO2 AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) with other La2O3-based (La2O3/HfO2, La2O3/CeO2 and single La2O3) MOS-HEMTs. It was found that forming lanthanum silicate films can not only improve the dielectric quality but also can improve the device characteristics. The improved gate insulation, reliability, and linearity of the 8 nm La2O3/SiO2 MOS-HEMT were demonstrated.

  18. Electrical transport and low-frequency noise in chemical vapor deposited single-layer MoS2 devices

    NASA Astrophysics Data System (ADS)

    Sharma, Deepak; Amani, Matin; Motayed, Abhishek; Shah, Pankaj B.; Birdwell, A. Glen; Najmaei, Sina; Ajayan, Pulickel M.; Lou, Jun; Dubey, Madan; Li, Qiliang; Davydov, Albert V.

    2014-04-01

    We have studied temperature-dependent (77-300 K) electrical characteristics and low-frequency noise (LFN) in chemical vapor deposited (CVD) single-layer molybdenum disulfide (MoS2) based back-gated field-effect transistors (FETs). Electrical characterization and LFN measurements were conducted on MoS2 FETs with Al2O3 top-surface passivation. We also studied the effect of top-surface passivation etching on the electrical characteristics of the device. Significant decrease in channel current and transconductance was observed in these devices after the Al2O3 passivation etching. For passivated devices, the two-terminal resistance variation with temperature showed a good fit to the activation energy model, whereas for the etched devices the trend indicated a hopping transport mechanism. A significant increase in the normalized drain current noise power spectral density (PSD) was observed after the etching of the top passivation layer. The observed channel current noise was explained using a standard unified model incorporating carrier number fluctuation and correlated surface mobility fluctuation mechanisms. Detailed analysis of the gate-referred noise voltage PSD indicated the presence of different trapping states in passivated devices when compared to the etched devices. Etched devices showed weak temperature dependence of the channel current noise, whereas passivated devices exhibited near-linear temperature dependence.

  19. Electrical transport and low-frequency noise in chemical vapor deposited single-layer MoS2 devices.

    PubMed

    Sharma, Deepak; Amani, Matin; Motayed, Abhishek; Shah, Pankaj B; Birdwell, A Glen; Najmaei, Sina; Ajayan, Pulickel M; Lou, Jun; Dubey, Madan; Li, Qiliang; Davydov, Albert V

    2014-04-18

    We have studied temperature-dependent (77-300 K) electrical characteristics and low-frequency noise (LFN) in chemical vapor deposited (CVD) single-layer molybdenum disulfide (MoS2) based back-gated field-effect transistors (FETs). Electrical characterization and LFN measurements were conducted on MoS2 FETs with Al2O3 top-surface passivation. We also studied the effect of top-surface passivation etching on the electrical characteristics of the device. Significant decrease in channel current and transconductance was observed in these devices after the Al2O3 passivation etching. For passivated devices, the two-terminal resistance variation with temperature showed a good fit to the activation energy model, whereas for the etched devices the trend indicated a hopping transport mechanism. A significant increase in the normalized drain current noise power spectral density (PSD) was observed after the etching of the top passivation layer. The observed channel current noise was explained using a standard unified model incorporating carrier number fluctuation and correlated surface mobility fluctuation mechanisms. Detailed analysis of the gate-referred noise voltage PSD indicated the presence of different trapping states in passivated devices when compared to the etched devices. Etched devices showed weak temperature dependence of the channel current noise, whereas passivated devices exhibited near-linear temperature dependence. PMID:24642948

  20. Breakdown properties of irradiated MOS capacitors

    SciTech Connect

    Paccagnella, A.; Candelori, A. |; Milani, A.; Formigoni, E.; Ghidini, G.; Drera, D.; Pellizzer, F. |; Fuochi, P.G.; Lavale, M.

    1996-12-01

    The authors have studied the effects of ionizing and non-ionizing radiation on the breakdown properties of different types of MOS capacitors, with thick (200 nm) and thin (down to 8 nm) oxides. In general, no large variations of the average breakdown field, time-to-breakdown at constant voltage, or charge-to-breakdown at constant voltage, or charge-to-breakdown values have been observed after high dose irradiation (20 Mrad(Si) 9 MeV electrons on thin and thick oxides, 17(Si) Mrad Co{sup 60} gamma and 10{sup 14} neutrons/cm{sup 2} only on thick oxides). However, some modifications of the cumulative failure distributions have been observed in few of the oxides tested.

  1. Scalable fabrication of a hybrid field-effect and acousto-electric device by direct growth of monolayer MoS2/LiNbO3

    PubMed Central

    Preciado, Edwin; Schülein, Florian J.R.; Nguyen, Ariana E.; Barroso, David; Isarraraz, Miguel; von Son, Gretel; Lu, I-Hsi; Michailow, Wladislaw; Möller, Benjamin; Klee, Velveth; Mann, John; Wixforth, Achim; Bartels, Ludwig; Krenner, Hubert J.

    2015-01-01

    Lithium niobate is the archetypical ferroelectric material and the substrate of choice for numerous applications including surface acoustic wave radio frequencies devices and integrated optics. It offers a unique combination of substantial piezoelectric and birefringent properties, yet its lack of optical activity and semiconducting transport hamper application in optoelectronics. Here we fabricate and characterize a hybrid MoS2/LiNbO3 acousto-electric device via a scalable route that uses millimetre-scale direct chemical vapour deposition of MoS2 followed by lithographic definition of a field-effect transistor structure on top. The prototypical device exhibits electrical characteristics competitive with MoS2 devices on silicon. Surface acoustic waves excited on the substrate can manipulate and probe the electrical transport in the monolayer device in a contact-free manner. We realize both a sound-driven battery and an acoustic photodetector. Our findings open directions to non-invasive investigation of electrical properties of monolayer films. PMID:26493867

  2. Scalable fabrication of a hybrid field-effect and acousto-electric device by direct growth of monolayer MoS2/LiNbO3.

    PubMed

    Preciado, Edwin; Schülein, Florian J R; Nguyen, Ariana E; Barroso, David; Isarraraz, Miguel; von Son, Gretel; Lu, I-Hsi; Michailow, Wladislaw; Möller, Benjamin; Klee, Velveth; Mann, John; Wixforth, Achim; Bartels, Ludwig; Krenner, Hubert J

    2015-01-01

    Lithium niobate is the archetypical ferroelectric material and the substrate of choice for numerous applications including surface acoustic wave radio frequencies devices and integrated optics. It offers a unique combination of substantial piezoelectric and birefringent properties, yet its lack of optical activity and semiconducting transport hamper application in optoelectronics. Here we fabricate and characterize a hybrid MoS2/LiNbO3 acousto-electric device via a scalable route that uses millimetre-scale direct chemical vapour deposition of MoS2 followed by lithographic definition of a field-effect transistor structure on top. The prototypical device exhibits electrical characteristics competitive with MoS2 devices on silicon. Surface acoustic waves excited on the substrate can manipulate and probe the electrical transport in the monolayer device in a contact-free manner. We realize both a sound-driven battery and an acoustic photodetector. Our findings open directions to non-invasive investigation of electrical properties of monolayer films. PMID:26493867

  3. Scalable fabrication of a hybrid field-effect and acousto-electric device by direct growth of monolayer MoS2/LiNbO3

    NASA Astrophysics Data System (ADS)

    Preciado, Edwin; Schülein, Florian J. R.; Nguyen, Ariana E.; Barroso, David; Isarraraz, Miguel; von Son, Gretel; Lu, I.-Hsi; Michailow, Wladislaw; Möller, Benjamin; Klee, Velveth; Mann, John; Wixforth, Achim; Bartels, Ludwig; Krenner, Hubert J.

    2015-10-01

    Lithium niobate is the archetypical ferroelectric material and the substrate of choice for numerous applications including surface acoustic wave radio frequencies devices and integrated optics. It offers a unique combination of substantial piezoelectric and birefringent properties, yet its lack of optical activity and semiconducting transport hamper application in optoelectronics. Here we fabricate and characterize a hybrid MoS2/LiNbO3 acousto-electric device via a scalable route that uses millimetre-scale direct chemical vapour deposition of MoS2 followed by lithographic definition of a field-effect transistor structure on top. The prototypical device exhibits electrical characteristics competitive with MoS2 devices on silicon. Surface acoustic waves excited on the substrate can manipulate and probe the electrical transport in the monolayer device in a contact-free manner. We realize both a sound-driven battery and an acoustic photodetector. Our findings open directions to non-invasive investigation of electrical properties of monolayer films.

  4. Scalable fabrication of a hybrid field-effect and acousto-electric device by direct growth of monolayer MoS2/LiNbO3.

    PubMed

    Preciado, Edwin; Schülein, Florian J R; Nguyen, Ariana E; Barroso, David; Isarraraz, Miguel; von Son, Gretel; Lu, I-Hsi; Michailow, Wladislaw; Möller, Benjamin; Klee, Velveth; Mann, John; Wixforth, Achim; Bartels, Ludwig; Krenner, Hubert J

    2015-10-23

    Lithium niobate is the archetypical ferroelectric material and the substrate of choice for numerous applications including surface acoustic wave radio frequencies devices and integrated optics. It offers a unique combination of substantial piezoelectric and birefringent properties, yet its lack of optical activity and semiconducting transport hamper application in optoelectronics. Here we fabricate and characterize a hybrid MoS2/LiNbO3 acousto-electric device via a scalable route that uses millimetre-scale direct chemical vapour deposition of MoS2 followed by lithographic definition of a field-effect transistor structure on top. The prototypical device exhibits electrical characteristics competitive with MoS2 devices on silicon. Surface acoustic waves excited on the substrate can manipulate and probe the electrical transport in the monolayer device in a contact-free manner. We realize both a sound-driven battery and an acoustic photodetector. Our findings open directions to non-invasive investigation of electrical properties of monolayer films.

  5. Extended life testing evaluation of complementary MOS integrated circuits

    NASA Technical Reports Server (NTRS)

    Brosnan, T. E.

    1972-01-01

    The purpose of the extended life testing evaluation of complementary MOS integrated circuits was twofold: (1) To ascertain the long life capability of complementary MOS devices. (2) To assess the objectivity and reliability of various accelerated life test methods as an indication or prediction tool. In addition, the determination of a suitable life test sequence for these devices was of importance. Conclusions reached based on the parts tested and the test results obtained was that the devices were not acceptable.

  6. Ab initio studies of phosphorene island single electron transistor

    NASA Astrophysics Data System (ADS)

    Ray, S. J.; Venkata Kamalakar, M.; Chowdhury, R.

    2016-05-01

    Phosphorene is a newly unveiled two-dimensional crystal with immense potential for nanoelectronic and optoelectronic applications. Its unique electronic structure and two dimensionality also present opportunities for single electron devices. Here we report the behaviour of a single electron transistor (SET) made of a phosphorene island, explored for the first time using ab initio calculations. We find that the band gap and the charging energy decrease monotonically with increasing layer numbers due to weak quantum confinement. When compared to two other novel 2D crystals such as graphene and MoS2, our investigation reveals larger adsorption energies of gas molecules on phosphorene, which indicates better a sensing ability. The calculated charge stability diagrams show distinct changes in the presence of an individual molecule which can be applied to detect the presence of different molecules with sensitivity at a single molecular level. The higher charging energies of the molecules within the SET display operational viability at room temperature, which is promising for possible ultra sensitive detection applications.

  7. Device performance simulations of multilayer black phosphorus tunneling transistors

    NASA Astrophysics Data System (ADS)

    Liu, Fei; Shi, Qing; Wang, Jian; Guo, Hong

    2015-11-01

    We report a theoretical investigation of ballistic transport in multilayer black phosphorus (BP) tunneling transistors (TFETs) with HfO2 as the gate oxide. First-principles calculations show that monolayer BP can be preserved well on HfO2 (111) surface. For a better device performance, the optimum layer and transport direction at different channel lengths are investigated. It is shown that BP TFETs have larger drain current in the armchair direction (AD) than in the zigzag direction, and the current difference can be several orders of magnitude. On-state current can be enhanced in the BP TFETs using thicker BP film, while the minimal leakage current is increased at the same time. To reduce the leakage current and subthreshold swing in the multilayer BP TFETs, lower source/drain doping concentration and smaller drain voltage should be applied. Compared to monolayer MoS2, MoSe2, and MoTe2 TFETs monolayer BP TFETs in AD can reach larger on-state current at the same Ion/Ioff ratio.

  8. Translational regulation of MOS messenger RNA in pig oocytes.

    PubMed

    Dai, Yanfeng; Newman, Barbara; Moor, Robert

    2005-11-01

    The temporal and spatial translation control of stored mRNA in oocytes is regulated by elements in their 3'-untranslated region (3'-UTR). The MOS 3'-UTR in pig oocytes is both heterogeneous (180, 480, or 530 nucleotides), and it contains multiple U-rich elements and extensive A-rich sequences (CA13CA5CA5CA6). We have examined the role of these potential regulatory elements by fusing wild-type or mutant MOS 3'-UTRs to luciferase mRNA and then injecting these chimeric transcripts into oocytes. We draw six main conclusions. First, the length of the MOS 3'-UTR tightly controls the level of translation of luciferase during oocyte maturation. Second, two U-rich (U5A) elements and the hexanucleotide signal (AAUAAA) are required for translation. Third, mutations, duplications, or relocations of the A-rich sequence reduce or block translation. Fourth, the relative importance of the A-rich and U-rich elements in controlling the level of translation differs. Fifth, none of our MOS 3'-UTR manipulations relieved translational repression before germinal vesicle breakdown. Sixth, all the MOS mRNA variants underwent polyadenylation during maturation. Whereas mutations to the hexanucleotide signal block both polyadenylation and translation, mutations to either the A-rich sequence or the U-rich elements block translation without fully blocking polyadenylation. We conclude that MOS mRNA translation in pig oocytes is subject to a more extensive series of controls than that in lower vertebrates.

  9. Spin polarized transport in MoS2

    NASA Astrophysics Data System (ADS)

    Dankert, André; Pashaei, Parham; Mutta, Venkata Kamalakar; Dash, Saroj Prasad; Spintronic SPD Team

    The two-dimensional (2D) semiconductor MoS2 possesses a high potential for spintronic devices due to a rich spin-valley physics and large spin-orbit coupling. While there have been significant advances in studying the spin and valley dynamics in MoS2 using optical spectroscopy techniques, electronic spin transport in semiconducting MoS2 or its heterostructures have not yet been demonstrated. Here we report the electronic and spin transport properties in MoS2 employing ferromagnetic electrodes in a vertical device geometry. Such vertical devices with MoS2 channel length defined by the thickness of the 2D layer allow to investigate the spin injection, transport and detection. We observe a magnetoresistance effect over a large temperature range up to 300 K and investigate the temperature and bias dependence behavior. Using magnetotransport data and calculations we extract spin parameters in the MoS2 spin valve devices. These findings can open new avenues for exploring spin functionalities in 2D semiconductor heterostructures for spin logic applications.

  10. Interaction between genes Mos and mwh expressed in somatic cells of Drosophila melanogaster

    SciTech Connect

    Vaisman, N.Ya.; Zakharov, I.K.

    1995-07-01

    Gene Mosaic (Mos) of chromosome 3 of Drosophila melanogaster was located by means of dominant markers Ly, Sb, and Dr. This gene was shown to be located between Ly and Sb in the centromeric region (45-50 map units). An analysis of interaction between Mos and mwh genes in cis- and trans-heterozygotes showed a significant effect of the Mos gene on mutability (recombinogenesis) of chromosome mwh in somatic cells. In the cis heterozygote mwh Mos/++, the frequency of small mutant clones on wings of flies increased. In mwh/Mos heterozygotes, the Mos gene caused a significant reduction of dorsocentral and scutellar bristles (78% in mwh/Mos, 85% in mwh +/+ Mos, and 98% in mwh Mos/mwh +). 20 refs., 3 tabs.

  11. v-mos proteins encoded by myeloproliferative sarcoma virus and its ts159 mutant.

    PubMed Central

    Singh, B; Stocking, C; Walker, R; Yang, Y D; Ostertag, W; Arlinghaus, R B

    1992-01-01

    The myeloproliferative sarcoma virus (MPSV) v-mos protein was predicted to be identical in size to p39c-mos because of an observed one-base deletion in the seventh codon of the env-mos open reading frame, which would allow translation to initiate at the methionine equivalent to codon 32 of the env-mos gene. On the basis of published results, p39c-mos is known to have greatly reduced in vitro protein kinase activity compared with p37env-mos encoded by Moloney murine sarcoma virus. Unexpectedly, the relative activity of the MPSV v-mos protein kinase was comparable to that of p37env-mos. Consistent with this finding, the size of MPSV v-mos protein was found to be similar to the size of p37env-mos. Moreover, the pattern and sizes of phosphorylated bands produced by autophosphorylation of the MPSV v-mos protein were similar to those of p37env-mos. These results were confirmed by in vitro transcription-translation of the MPSV v-mos gene. Resequencing portions of the MPSV mos gene failed to show the deletion within codon 7. Except for the codon 262 deletion, other mutations characteristic of MPSV and temperature-sensitive MPSV v-mos genes were confirmed. A glycine-to-arginine mutation at residue 338 of the MPSV env-mos sequence, previously shown to cause thermosensitivity of the mutant virus (termed ts159) transforming function, yielded a v-mos protein that had significantly reduced protein kinase activity in vitro. These findings indicate that MPSV, like other Moloney murine sarcoma virus strains, also encodes a functional env-mos protein. Images PMID:1309903

  12. Trap densities and transport properties of pentacene metal-oxide-semiconductor transistors. I. Analytical modeling of time-dependent characteristics

    NASA Astrophysics Data System (ADS)

    Basile, A. F.; Cramer, T.; Kyndiah, A.; Biscarini, F.; Fraboni, B.

    2014-06-01

    Metal-oxide-semiconductor (MOS) transistors fabricated with pentacene thin films were characterized by temperature-dependent current-voltage (I-V) characteristics, time-dependent current measurements, and admittance spectroscopy. The channel mobility shows almost linear variation with temperature, suggesting that only shallow traps are present in the semiconductor and at the oxide/semiconductor interface. The admittance spectra feature a broad peak, which can be modeled as the sum of a continuous distribution of relaxation times. The activation energy of this peak is comparable to the polaron binding energy in pentacene. The absence of trap signals in the admittance spectra confirmed that both the semiconductor and the oxide/semiconductor interface have negligible density of deep traps, likely owing to the passivation of SiO2 before pentacene growth. Nevertheless, current instabilities were observed in time-dependent current measurements following the application of gate-voltage pulses. The corresponding activation energy matches the energy of a hole trap in SiO2. We show that hole trapping in the oxide can explain both the temperature and the time dependences of the current instabilities observed in pentacene MOS transistors. The combination of these experimental techniques allows us to derive a comprehensive model for charge transport in hybrid architectures where trapping processes occur at various time and length scales.

  13. An RF energy harvester system using UHF micropower CMOS rectifier based on a diode connected CMOS transistor.

    PubMed

    Shokrani, Mohammad Reza; Khoddam, Mojtaba; Hamidon, Mohd Nizar B; Kamsani, Noor Ain; Rokhani, Fakhrul Zaman; Shafie, Suhaidi Bin

    2014-01-01

    This paper presents a new type diode connected MOS transistor to improve CMOS conventional rectifier's performance in RF energy harvester systems for wireless sensor networks in which the circuits are designed in 0.18  μm TSMC CMOS technology. The proposed diode connected MOS transistor uses a new bulk connection which leads to reduction in the threshold voltage and leakage current; therefore, it contributes to increment of the rectifier's output voltage, output current, and efficiency when it is well important in the conventional CMOS rectifiers. The design technique for the rectifiers is explained and a matching network has been proposed to increase the sensitivity of the proposed rectifier. Five-stage rectifier with a matching network is proposed based on the optimization. The simulation results shows 18.2% improvement in the efficiency of the rectifier circuit and increase in sensitivity of RF energy harvester circuit. All circuits are designed in 0.18 μm TSMC CMOS technology. PMID:24782680

  14. Single-transistor-clocked flip-flop

    DOEpatents

    Zhao, Peiyi; Darwish, Tarek; Bayoumi, Magdy

    2005-08-30

    The invention provides a low power, high performance flip-flop. The flip-flop uses only one clocked transistor. The single clocked transistor is shared by the first and second branches of the device. A pulse generator produces a clock pulse to trigger the flip-flop. In one preferred embodiment the device can be made as a static explicit pulsed flip-flop which employs only two clocked transistors.

  15. Coaxial inverted geometry transistor having buried emitter

    NASA Technical Reports Server (NTRS)

    Hruby, R. J.; Cress, S. B.; Dunn, W. R. (Inventor)

    1973-01-01

    The invention relates to an inverted geometry transistor wherein the emitter is buried within the substrate. The transistor can be fabricated as a part of a monolithic integrated circuit and is particularly suited for use in applications where it is desired to employ low actuating voltages. The transistor may employ the same doping levels in the collector and emitter, so these connections can be reversed.

  16. A comparison between HfO2/Al2O3 nano-laminates and ternary HfxAlyO compound as the dielectric material in InGaAs based metal-oxide-semiconductor (MOS) capacitors

    NASA Astrophysics Data System (ADS)

    Krylov, Igor; Pokroy, Boaz; Eizenberg, Moshe; Ritter, Dan

    2016-09-01

    We compare the electrical properties of HfO2/Al2O3 nano-laminates with those of the ternary HfxAlyO compound in metal oxide semiconductor (MOS) capacitors. The dielectrics were deposited by atomic layer deposition on InGaAs. Water, ozone, and oxygen plasma were tested as oxygen precursors, and best results were obtained using water. The total dielectric thickness was kept constant in our experiments. It was found that the effective dielectric constant increased and the leakage current decreased with the number of periods. Best results were obtained for the ternary compound. The effect of the sublayer thicknesses on the electrical properties of the interface was carefully investigated, as well as the role of post-metallization annealing. Possible explanations for the observed trends are provided. We conclude that the ternary HfxAlyO compound is more favorable than the nano-laminates approach for InGaAs based MOS transistor applications.

  17. Principles of an atomtronic transistor

    NASA Astrophysics Data System (ADS)

    Caliga, Seth C.; Straatsma, Cameron J. E.; Zozulya, Alex A.; Anderson, Dana Z.

    2016-01-01

    A semiclassical formalism is used to investigate the transistor-like behavior of ultracold atoms in a triple-well potential. Atom current flows from the source well, held at fixed chemical potential and temperature, into an empty drain well. In steady-state, the gate well located between the source and drain is shown to acquire a well-defined chemical potential and temperature, which are controlled by the relative height of the barriers separating the three wells. It is shown that the gate chemical potential can exceed that of the source and have a lower temperature. In electronics terminology, the source-gate junction can be reverse-biased. As a result, the device exhibits regimes of negative resistance and transresistance, indicating the presence of gain. Given an external current input to the gate, transistor-like behavior is characterized both in terms of the current gain, which can be greater than unity, and the power output of the device.

  18. Black phosphorus nonvolatile transistor memory

    NASA Astrophysics Data System (ADS)

    Lee, Dain; Choi, Yongsuk; Hwang, Euyheon; Kang, Moon Sung; Lee, Seungwoo; Cho, Jeong Ho

    2016-04-01

    We demonstrated nanofloating gate transistor memory devices (NFGTMs) using mechanically-exfoliated few-layered black phosphorus (BP) channels and gold nanoparticle (AuNPs) charge trapping layers. The resulting BP-NFGTMs exhibited excellent memory performances, including the five-level data storage, large memory window (58.2 V), stable retention (104 s), and cyclic endurance (1000 cycles).We demonstrated nanofloating gate transistor memory devices (NFGTMs) using mechanically-exfoliated few-layered black phosphorus (BP) channels and gold nanoparticle (AuNPs) charge trapping layers. The resulting BP-NFGTMs exhibited excellent memory performances, including the five-level data storage, large memory window (58.2 V), stable retention (104 s), and cyclic endurance (1000 cycles). Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr02078j

  19. A SPICE Model and Electrostatic Field Analysis of the MOS Turn-Off Thyristor

    SciTech Connect

    Kelly, D Q; Mayhall, D J; Wilson, M J; Lahowe, D A

    2002-08-05

    This paper presents a circuit model and an electrostatic field analysis with an approximate model of the SDM170HK MOS turn-off thyristor (MTO) fabricated by Silicon Power Corporation. The circuit model consists of five cells, each containing two bipolar junction transistors and three resistors. The turn-off feature of the MTO was simulated by inserting an array of 21 Fairchild FDS6670A MOSFET importable sub-circuit components between the cathode and the turn-on gate. The model was then used to create a four-terminal sub-circuit component representing the MTO that can be readily imported into computer-aided circuit design programs such as PSPICE and Micro-Cap. The generated static I-V characteristics and simulated switching waveforms are shown. The electrostatic field analysis was done for the maximum operating voltage of 4.5 kV using the Ansoft Maxwell 3D field simulator. Electrostatic field magnitudes that exceed the nominal air breakdown threshold of 30 kV/cm were observed surrounding the simulated turn-off gate wire, the turn-off gate ring contact, and the cathode ring contact. The resulting areas of high fields are a concern, as arc track marks have been found on the inner surface of the ceramic insulator near the internal gate connections of a failed device.

  20. Large Work Function Modulation of Monolayer MoS2 by Ambient Gases.

    PubMed

    Lee, Si Young; Kim, Un Jeong; Chung, JaeGwan; Nam, Honggi; Jeong, Hye Yun; Han, Gang Hee; Kim, Hyun; Oh, Hye Min; Lee, Hyangsook; Kim, Hyochul; Roh, Young-Geun; Kim, Jineun; Hwang, Sung Woo; Park, Yeonsang; Lee, Young Hee

    2016-06-28

    Although two-dimensional monolayer transition-metal dichalcogenides reveal numerous unique features that are inaccessible in bulk materials, their intrinsic properties are often obscured by environmental effects. Among them, work function, which is the energy required to extract an electron from a material to vacuum, is one critical parameter in electronic/optoelectronic devices. Here, we report a large work function modulation in MoS2 via ambient gases. The work function was measured by an in situ Kelvin probe technique and further confirmed by ultraviolet photoemission spectroscopy and theoretical calculations. A measured work function of 4.04 eV in vacuum was converted to 4.47 eV with O2 exposure, which is comparable with a large variation in graphene. The homojunction diode by partially passivating a transistor reveals an ideal junction with an ideality factor of almost one and perfect electrical reversibility. The estimated depletion width obtained from photocurrent mapping was ∼200 nm, which is much narrower than bulk semiconductors.

  1. Black phosphorus-monolayer MoS2 van der Waals heterojunction p-n diode.

    PubMed

    Deng, Yexin; Luo, Zhe; Conrad, Nathan J; Liu, Han; Gong, Yongji; Najmaei, Sina; Ajayan, Pulickel M; Lou, Jun; Xu, Xianfan; Ye, Peide D

    2014-08-26

    Phosphorene, a elemental 2D material, which is the monolayer of black phosphorus, has been mechanically exfoliated recently. In its bulk form, black phosphorus shows high carrier mobility (∼10,000 cm(2)/V·s) and a ∼0.3 eV direct band gap. Well-behaved p-type field-effect transistors with mobilities of up to 1000 cm(2)/V·s, as well as phototransistors, have been demonstrated on few-layer black phosphorus, showing its promise for electronics and optoelectronics applications due to its high hole mobility and thickness-dependent direct band gap. However, p–n junctions, the basic building blocks of modern electronic and optoelectronic devices, have not yet been realized based on black phosphorus. In this paper, we demonstrate a gate-tunable p–n diode based on a p-type black phosphorus/n-type monolayer MoS2 van der Waals p–n heterojunction. Upon illumination, these ultrathin p–n diodes show a maximum photodetection responsivity of 418 mA/W at the wavelength of 633 nm and photovoltaic energy conversion with an external quantum efficiency of 0.3%. These p–n diodes show promise for broad-band photodetection and solar energy harvesting.

  2. Investigations of AlGaN/GaN MOS-HEMT with Al2O3 deposition by ultrasonic spray pyrolysis method

    NASA Astrophysics Data System (ADS)

    Chou, Bo-Yi; Hsu, Wei-Chou; Liu, Han-Yin; Lee, Ching-Sung; Wu, Yu-Sheng; Sun, Wen-Ching; Wei, Sung-Yen; Yu, Sheng-Min; Chiang, Meng-Hsueh

    2015-01-01

    This work investigates Al2O3/AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) grown on SiC substrate by using the non-vacuum ultrasonic spray pyrolysis deposition (USPD) method. The Al2O3 was deposited as gate dielectric and surface passivation simultaneously to effectively suppress gate leakage current, enhance output current density, reduce RF drain current collapse, and improve temperature-dependent stabilities performance. The present MOS-HEMT design has shown improved device performances with respect to a Schottky-gate HEMT, including drain-source saturation current density at zero gate bias (IDSS: 337.6 mA mm-1 → 462.9 mA mm-1), gate-voltage swing (GVS: 1.55 V → 2.92 V), two-terminal gate-drain breakdown voltage (BVGD: -103.8 V → -183.5 V), unity-gain cut-off frequency (fT: 11.3 GHz → 17.7 GHz), maximum oscillation frequency (fmax: 14.2 GHz → 19.1 GHz), and power added effective (P.A.E.: 25.1% → 43.6%). The bias conditions for measuring fT and fmax of the studied MOS-HEMT (Schottky-gate HEMT) are VGS = -2.5 (-2) V and VDS = 7 V. The corresponding VGS and VDS biases are -2.5 (-2) V and 15 V for measuring the P.A.E. characteristic. Moreover, small capacitance-voltage (C-V) hysteresis is obtained in the Al2O3-MOS structure by using USPD. Temperature-dependent characteristics of the present designs at 300-480 K are also studied.

  3. Investigations on MgO-dielectric GaN/AlGaN/GaN MOS-HEMTs by using an ultrasonic spray pyrolysis deposition technique

    NASA Astrophysics Data System (ADS)

    Lee, Ching-Sung; Hsu, Wei-Chou; Liu, Han-Yin; Wu, Ting-Ting; Sun, Wen-Ching; Wei, Sung-Yen; Yu, Sheng-Min

    2016-05-01

    This work investigates GaN/Al0.24Ga0.76N/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) grown on a Si substrate with MgO gate dielectric by using the non-vacuum ultrasonic spray pyrolysis deposition (USPD) technique. The oxide layer thickness is tuned to be 30 nm with the dielectric constant of 8.8. Electron spectroscopy for chemical analysis (ESCA), secondary ion mass spectrometry (SIMS), atomic force microscopy (AFM), transmission electron microscopy (TEM), C-V, low-frequency noise spectra, and pulsed I-V measurements are performed to characterize the interface and oxide quality for the MOS-gate structure. Improved device performances have been successfully achieved for the present MOS-HEMT (Schottky-gate HEMT) design, consisting of a maximum drain-source current density (I DS, max) of 681 (500) mA/mm at V GS = 4 (2) V, I DS at V GS = 0 V (I DSS0) of 329 (289) mA/mm, gate-voltage swing (GVS) of 2.2 (1.6) V, two-terminal gate-drain breakdown voltage (BV GD) of -123 (-104) V, turn-on voltage (V on) of 1.7 (0.8) V, three-terminal off-state drain-source breakdown voltage (BV DS) of 119 (96) V, and on/off current ratio (I on/I off) of 2.5 × 108 (1.2 × 103) at 300 K. Improved high-frequency and power performances are also achieved in the present MOS-HEMT design.

  4. Complementary junction heterostructure field-effect transistor

    DOEpatents

    Baca, A.G.; Drummond, T.J.; Robertson, P.J.; Zipperian, T.E.

    1995-12-26

    A complimentary pair of compound semiconductor junction heterostructure field-effect transistors and a method for their manufacture are disclosed. The p-channel junction heterostructure field-effect transistor uses a strained layer to split the degeneracy of the valence band for a greatly improved hole mobility and speed. The n-channel device is formed by a compatible process after removing the strained layer. In this manner, both types of transistors may be independently optimized. Ion implantation is used to form the transistor active and isolation regions for both types of complimentary devices. The invention has uses for the development of low power, high-speed digital integrated circuits. 10 figs.

  5. Complementary junction heterostructure field-effect transistor

    DOEpatents

    Baca, Albert G.; Drummond, Timothy J.; Robertson, Perry J.; Zipperian, Thomas E.

    1995-01-01

    A complimentary pair of compound semiconductor junction heterostructure field-effect transistors and a method for their manufacture are disclosed. The p-channel junction heterostructure field-effect transistor uses a strained layer to split the degeneracy of the valence band for a greatly improved hole mobility and speed. The n-channel device is formed by a compatible process after removing the strained layer. In this manner, both types of transistors may be independently optimized. Ion implantation is used to form the transistor active and isolation regions for both types of complimentary devices. The invention has uses for the development of low power, high-speed digital integrated circuits.

  6. Electrical Properties of Synthesized Large-Area MoS₂ Field-Effect Transistors Fabricated with Inkjet-Printed Contacts.

    PubMed

    Kim, Tae-Young; Amani, Matin; Ahn, Geun Ho; Song, Younggul; Javey, Ali; Chung, Seungjun; Lee, Takhee

    2016-02-23

    We report the electrical properties of synthesized large-area monolayer molybdenum disulfide (MoS2) field-effect transistors (FETs) with low-cost inkjet-printed Ag electrodes. The monolayer MoS2 film was grown by a chemical vapor deposition (CVD) method, and the top-contact Ag source/drain electrodes (S/D) were deposited onto the films using a low-cost drop-on-demand inkjet-printing process without any masks and surface treatments. The electrical characteristics of FETs were comparable to those fabricated by conventional deposition methods such as photo- or electron beam lithography. The contact properties between the S/D and the semiconductor layer were also evaluated using the Y-function method and an analysis of the output characteristic at the low drain voltage regimes. Furthermore, the electrical instability under positive gate-bias stress was studied to investigate the charge-trapping mechanism of the FETs. CVD-grown large-area monolayer MoS2 FETs with inkjet-printed contacts may represent an attractive approach for realizing large-area and low-cost thin-film electronics.

  7. Electrical Properties of Synthesized Large-Area MoS₂ Field-Effect Transistors Fabricated with Inkjet-Printed Contacts.

    PubMed

    Kim, Tae-Young; Amani, Matin; Ahn, Geun Ho; Song, Younggul; Javey, Ali; Chung, Seungjun; Lee, Takhee

    2016-02-23

    We report the electrical properties of synthesized large-area monolayer molybdenum disulfide (MoS2) field-effect transistors (FETs) with low-cost inkjet-printed Ag electrodes. The monolayer MoS2 film was grown by a chemical vapor deposition (CVD) method, and the top-contact Ag source/drain electrodes (S/D) were deposited onto the films using a low-cost drop-on-demand inkjet-printing process without any masks and surface treatments. The electrical characteristics of FETs were comparable to those fabricated by conventional deposition methods such as photo- or electron beam lithography. The contact properties between the S/D and the semiconductor layer were also evaluated using the Y-function method and an analysis of the output characteristic at the low drain voltage regimes. Furthermore, the electrical instability under positive gate-bias stress was studied to investigate the charge-trapping mechanism of the FETs. CVD-grown large-area monolayer MoS2 FETs with inkjet-printed contacts may represent an attractive approach for realizing large-area and low-cost thin-film electronics. PMID:26820160

  8. Self-screened high performance multi-layer MoS₂ transistor formed by using a bottom graphene electrode.

    PubMed

    Qu, Deshun; Liu, Xiaochi; Ahmed, Faisal; Lee, Daeyeong; Yoo, Won Jong

    2015-12-01

    We investigated the carrier transport in multi-layer MoS2 with consideration of the contact resistance (R(c)) and interlayer resistance (R(int)). A bottom graphene contact was suggested to overcome the degradation of I(d) modulation in a back gated multi-layer MoS2 field effect transistor (FET) due to the accumulated R(int) and increased R(c) with increasing thickness. As a result, non-degraded drain current (I(d)) modulation with increasing flake thickness was achieved due to the non-cumulative R(int). Benefiting from the low R(c) induced by the negligible Schottky barrier at the graphene/MoS2 interface, the intrinsic carrier transport properties immune to R(c) were investigated in the multi-layer MoS2 FET. ∼2 times the enhanced carrier mobility was attained from the self-screened channel in the bottom graphene contacted device, compared to those with top metal contacts. PMID:26531884

  9. Monolayer-by-monolayer stacked pyramid-like MoS2 nanodots on monolayered MoS2 flakes with enhanced photoluminescence.

    PubMed

    Yuan, Cailei; Cao, Yingjie; Luo, Xingfang; Yu, Ting; Huang, Zhenping; Xu, Bo; Yang, Yong; Li, Qinliang; Gu, Gang; Lei, Wen

    2015-11-01

    The precise control of the morphology and crystal shape of MoS2 nanostructures is of particular importance for their application in nanoelectronic and optoelectronic devices. Here, we describe a single step route for the synthesis of monolayer-by-monolayer stacked pyramid-like MoS2 nanodots on monolayered MoS2 flakes using a chemical vapor deposition method. First-principles calculations demonstrated that the bandgap of the pyramid-like MoS2 nanodot is a direct bandgap. Enhanced local photoluminescence emission was observed in the pyramid-like MoS2 nanodot, in comparison with monolayered MoS2 flakes. The findings presented here provide new opportunities to tailor the physical properties of MoS2via morphology-controlled synthesis.

  10. Remarkably high mobility ultra-thin-film metal-oxide transistor with strongly overlapped orbitals

    NASA Astrophysics Data System (ADS)

    Wei Shih, Chen; Chin, Albert; Fu Lu, Chun; Fang Su, Wei

    2016-01-01

    High mobility channel thin-film-transistor (TFT) is crucial for both display and future generation integrated circuit. We report a new metal-oxide TFT that has an ultra-thin 4.5 nm SnO2 thickness for both active channel and source-drain regions, very high 147 cm2/Vs field-effect mobility, high ION/IOFF of 2.3 × 107, small 110 mV/dec sub-threshold slope, and a low VD of 2.5 V for low power operation. This mobility is already better than chemical-vapor-deposition grown multi-layers MoS2 TFT. From first principle quantum-mechanical calculation, the high mobility TFT is due to strongly overlapped orbitals.

  11. Remarkably high mobility ultra-thin-film metal-oxide transistor with strongly overlapped orbitals.

    PubMed

    Shih, Chen Wei; Chin, Albert; Lu, Chun Fu; Su, Wei Fang

    2016-01-08

    High mobility channel thin-film-transistor (TFT) is crucial for both display and future generation integrated circuit. We report a new metal-oxide TFT that has an ultra-thin 4.5 nm SnO2 thickness for both active channel and source-drain regions, very high 147 cm(2)/Vs field-effect mobility, high ION/IOFF of 2.3 × 10(7), small 110 mV/dec sub-threshold slope, and a low VD of 2.5 V for low power operation. This mobility is already better than chemical-vapor-deposition grown multi-layers MoS2 TFT. From first principle quantum-mechanical calculation, the high mobility TFT is due to strongly overlapped orbitals.

  12. Remarkably high mobility ultra-thin-film metal-oxide transistor with strongly overlapped orbitals

    PubMed Central

    Wei Shih, Chen; Chin, Albert; Fu Lu, Chun; Fang Su, Wei

    2016-01-01

    High mobility channel thin-film-transistor (TFT) is crucial for both display and future generation integrated circuit. We report a new metal-oxide TFT that has an ultra-thin 4.5 nm SnO2 thickness for both active channel and source-drain regions, very high 147 cm2/Vs field-effect mobility, high ION/IOFF of 2.3 × 107, small 110 mV/dec sub-threshold slope, and a low VD of 2.5 V for low power operation. This mobility is already better than chemical-vapor-deposition grown multi-layers MoS2 TFT. From first principle quantum-mechanical calculation, the high mobility TFT is due to strongly overlapped orbitals. PMID:26744240

  13. Spike-timing dependent plasticity in a transistor-selected resistive switching memory.

    PubMed

    Ambrogio, S; Balatti, S; Nardi, F; Facchinetti, S; Ielmini, D

    2013-09-27

    In a neural network, neuron computation is achieved through the summation of input signals fed by synaptic connections. The synaptic activity (weight) is dictated by the synchronous firing of neurons, inducing potentiation/depression of the synaptic connection. This learning function can be supported by the resistive switching memory (RRAM), which changes its resistance depending on the amplitude, the pulse width and the bias polarity of the applied signal. This work shows a new synapse circuit comprising a MOS transistor as a selector and a RRAM as a variable resistance, displaying spike-timing dependent plasticity (STDP) similar to the one originally experienced in biological neural networks. We demonstrate long-term potentiation and long-term depression by simulations with an analytical model of resistive switching. Finally, the experimental demonstration of the new STDP scheme is presented. PMID:23999495

  14. BIMOS transistor solutions for ESD protection in FD-SOI UTBB CMOS technology

    NASA Astrophysics Data System (ADS)

    Galy, Philippe; Athanasiou, S.; Cristoloveanu, S.

    2016-01-01

    We evaluate the Electro-Static Discharge (ESD) protection capability of BIpolar MOS (BIMOS) transistors integrated in ultrathin silicon film for 28 nm Fully Depleted SOI (FD-SOI) Ultra Thin Body and BOX (UTBB) high-k metal gate technology. Using as a reference our measurements in hybrid bulk-SOI structures, we extend the BIMOS design towards the ultrathin silicon film. Detailed study and pragmatic evaluations are done based on 3D TCAD simulation with standard physical models using Average Current Slope (ACS) method and quasi-static DC stress (Average Voltage Slope AVS method). These preliminary 3D TACD results are very encouraging in terms of ESD protection efficiency in advanced FD-SOI CMOS.

  15. Highly Enhanced Gas Adsorption Properties in Vertically Aligned MoS2 Layers.

    PubMed

    Cho, Soo-Yeon; Kim, Seon Joon; Lee, Youhan; Kim, Jong-Seon; Jung, Woo-Bin; Yoo, Hae-Wook; Kim, Jihan; Jung, Hee-Tae

    2015-09-22

    In this work, we demonstrate that gas adsorption is significantly higher in edge sites of vertically aligned MoS2 compared to that of the conventional basal plane exposed MoS2 films. To compare the effect of the alignment of MoS2 on the gas adsorption properties, we synthesized three distinct MoS2 films with different alignment directions ((1) horizontally aligned MoS2 (basal plane exposed), (2) mixture of horizontally aligned MoS2 and vertically aligned layers (basal and edge exposed), and (3) vertically aligned MoS2 (edge exposed)) by using rapid sulfurization method of CVD process. Vertically aligned MoS2 film shows about 5-fold enhanced sensitivity to NO2 gas molecules compared to horizontally aligned MoS2 film. Vertically aligned MoS2 has superior resistance variation compared to horizontally aligned MoS2 even with same surface area exposed to identical concentration of gas molecules. We found that electrical response to target gas molecules correlates directly with the density of the exposed edge sites of MoS2 due to high adsorption of gas molecules onto edge sites of vertically aligned MoS2. Density functional theory (DFT) calculations corroborate the experimental results as stronger NO2 binding energies are computed for multiple configurations near the edge sites of MoS2, which verifies that electrical response to target gas molecules (NO2) correlates directly with the density of the exposed edge sites of MoS2 due to high adsorption of gas molecules onto edge sites of vertically aligned MoS2. We believe that this observation extends to other 2D TMD materials as well as MoS2 and can be applied to significantly enhance the gas sensor performance in these materials.

  16. Protection of MOS capacitors during anodic bonding

    NASA Astrophysics Data System (ADS)

    Schjølberg-Henriksen, K.; Plaza, J. A.; Rafí, J. M.; Esteve, J.; Campabadal, F.; Santander, J.; Jensen, G. U.; Hanneborg, A.

    2002-07-01

    We have investigated the electrical damage by anodic bonding on CMOS-quality gate oxide and methods to prevent this damage. n-type and p-type MOS capacitors were characterized by quasi-static and high-frequency CV-curves before and after anodic bonding. Capacitors that were bonded to a Pyrex wafer with 10 μm deep cavities enclosing the capacitors exhibited increased leakage current and interface trap density after bonding. Two different methods were successful in protecting the capacitors from such damage. Our first approach was to increase the cavity depth from 10 μm to 50 μm, thus reducing the electric field across the gate oxide during bonding from approximately 2 × 105 V cm-1 to 4 × 104 V cm-1. The second protection method was to coat the inside of a 10 μm deep Pyrex glass cavity with aluminium, forming a Faraday cage that removed the electric field across the cavity during anodic bonding. Both methods resulted in capacitors with decreased interface trap density and unchanged leakage current after bonding. No change in effective oxide charge or mobile ion contamination was observed on any of the capacitors in the study.

  17. Near interface oxide trap capture kinetics in metal-oxide-semiconductor transistors: Modeling and measurements

    NASA Astrophysics Data System (ADS)

    Bauza, D.

    1998-12-01

    The traps situated in the oxide in the vicinity of the Si-SiO2 interface in metal-oxide-semiconductor (MOS) transistors, are studied. This is achieved using a new technique, based on the measurement of drain current transients and called T-CDLTS (tunnel-current deep level transient spectroscopy). For this, the traps are repeatedly filled with majority carriers using gate pulses which bias the device in accumulation. Each time the device returns in inversion, the drain current transient induced by the filling of the traps with minority carriers is monitored. A model for extracting the interface trap depth concentration profiles from the current transients is derived. It is based on Shockley-Read-Hall's statistics [R. N. Hall, Phys. Rev. 87, 387 (1952), W. Shockley and W. T. Read, Phys. Rev. 87, 835 (1952)] and on the Heiman and Warfield tunneling model [F. P. Heiman and G. Warfield, IEEE Trans. Electron Devices ED-12, 167 (1965)]. The slow trap densities measured in a virgin device agree with those obtained in state-of-the-art MOS transistors using noise measurements. In virgin and stressed devices they also compare favorably with the trap densities obtained using a recently proposed charge pumping technique. The evolution, with the experimental conditions, of the trap concentrations measured is discussed with respect to that expected from the model. In some experimental conditions, a very good agreement is obtained while in some others, discrepancies are observed. These discrepancies are discussed as regard to the hypothesis introduced in the model.

  18. Excitation intensity dependence of photoluminescence from monolayers of MoS2 and WS2/MoS2 heterostructures

    NASA Astrophysics Data System (ADS)

    Kaplan, D.; Gong, Y.; Mills, K.; Swaminathan, V.; Ajayan, P. M.; Shirodkar, S.; Kaxiras, E.

    2016-03-01

    A detailed study of the excitation dependence of the photoluminescence (PL) from monolayers of MoS2 and WS2/MoS2 heterostructures grown by chemical vapor deposition on Si substrates has revealed that the luminescence from band edge excitons from MoS2 monolayers shows a linear dependence on excitation intensity for both above band gap and resonant excitation conditions. In particular, a band separated by ∼55 meV from the A exciton, referred to as the C band, shows the same linear dependence on excitation intensity as the band edge excitons. A band similar to the C band has been previously ascribed to a trion, a charged, three-particle exciton. However, in our study the C band does not show the 3/2 power dependence on excitation intensity as would be expected for a three-particle exciton. Further, the PL from the MoS2 monolayer in a bilayer WS2/MoS2 heterostructure, under resonant excitation conditions where only the MoS2 absorbs the laser energy, also revealed a linear dependence on excitation intensity for the C band, confirming that its origin is not due to a trion but instead a bound exciton, presumably of an unintentional impurity or a native point defect such as a sulfur vacancy. The PL from the WS2/MoS2 heterostructure, under resonant excitation conditions also showed additional features which are suggested to arise from the interface states at the heteroboundary. Further studies are required to clearly identify the origin of these features.

  19. MoS2 actuators: reversible mechanical responses of MoS2-polymer nanocomposites to photons

    NASA Astrophysics Data System (ADS)

    Fan, Xiaoming; Khosravi, Farhad; Rahneshin, Vahid; Shanmugam, Mariyappan; Loeian, Masoud; Jasinski, Jacek; Cohn, Robert W.; Terentjev, Eugene; Panchapakesan, Balaji

    2015-07-01

    New molybdenum disulfide (MoS2)-based polymer composites and their reversible mechanical responses to light are presented, suggesting MoS2 as an excellent candidate for energy conversion. Homogeneous mixtures of MoS2/polydimethylsiloxane (PDMS) nanocomposites (0.1-5 wt.%) were prepared and their near infrared (NIR) mechanical responses studied with increasing pre-strains. NIR triggering resulted in an extraordinary change in stress levels of the actuators by ~490 times. Actuation responses of MoS2 polymer composites depended on applied pre-strains. At lower levels of pre-strains (3-9%) the actuators showed reversible expansion while at high levels (15-50%), the actuators exhibited reversible contraction. An opto-mechanical conversion (η)˜0.5-3 MPa W-1 was calculated. The ratio of maximum stress due to photo-actuation (σmax) at 50% strain to the minimum stress due to photo-actuation (σmin) at 3% strain was found to be ˜315-322% for MoS2 actuators (for 0.1 to 5 wt.% additive), greater than single layer graphene (˜188%) and multi-wall nanotube (˜172%) photo-mechanical actuators. Unlike other photomechanical actuators, the MoS2 actuators exhibited strong light-matter interactions and an unambiguous increase in amplitude of photomechanical response with increasing strains. A power law dependence of σmax/σmin on strains with a scaling exponent of β = 0.87-1.32 was observed, suggesting that the origin of photomechanical response is intertwined dynamically with the molecular mechanisms at play in MoS2 actuators.

  20. High frequency MoS2 nanomechanical resonators.

    PubMed

    Lee, Jaesung; Wang, Zenghui; He, Keliang; Shan, Jie; Feng, Philip X-L

    2013-07-23

    Molybdenum disulfide (MoS2), a layered semiconducting material in transition metal dichalcogenides (TMDCs), as thin as a monolayer (consisting of a hexagonal plane of Mo atoms covalently bonded and sandwiched between two planes of S atoms, in a trigonal prismatic structure), has demonstrated unique properties and strong promises for emerging two-dimensional (2D) nanodevices. Here we report on the demonstration of movable and vibrating MoS2 nanodevices, where MoS2 diaphragms as thin as 6 nm (a stack of 9 monolayers) exhibit fundamental-mode nanomechanical resonances up to f0 ~ 60 MHz in the very high frequency (VHF) band, and frequency-quality (Q) factor products up to f0 × Q ~ 2 × 10(10)Hz, all at room temperature. The experimental results from many devices with a wide range of thicknesses and lateral sizes, in combination with theoretical analysis, quantitatively elucidate the elastic transition regimes in these ultrathin MoS2 nanomechanical resonators. We further delineate a roadmap for scaling MoS2 2D resonators and transducers toward microwave frequencies. This study also opens up possibilities for new classes of vibratory devices to exploit strain- and dynamics-engineered ultrathin semiconducting 2D crystals.

  1. Mos limits the number of meiotic divisions in urochordate eggs.

    PubMed

    Dumollard, Rémi; Levasseur, Mark; Hebras, Céline; Huitorel, Philippe; Carroll, Michael; Chambon, Jean-Philippe; McDougall, Alex

    2011-03-01

    Mos kinase is a universal mediator of oocyte meiotic maturation and is produced during oogenesis and destroyed after fertilization. The hallmark of maternal meiosis is that two successive M phases (meiosis I and II) drive two rounds of asymmetric cell division (ACD). However, how the egg limits the number of meioses to just two, thereby preventing gross aneuploidy, is poorly characterized. Here, in urochordate eggs, we show that loss of Mos/MAPK activity is necessary to prevent entry into meiosis III. Remarkably, maintaining the Mos/MAPK pathway active after fertilization at near physiological levels induces additional rounds of meiotic M phase (meiosis III, IV and V). During these additional rounds of meiosis, the spindle is positioned asymmetrically resulting in further rounds of ACD. In addition, inhibiting meiotic exit with Mos prevents pronuclear formation, cyclin A accumulation and maintains sperm-triggered Ca(2+) oscillations, all of which are hallmarks of the meiotic cell cycle in ascidians. It will be interesting to determine whether Mos availability in mammals can also control the number of meioses as it does in the urochordates. Our results demonstrate the power of urochordate eggs as a model to dissect the egg-to-embryo transition.

  2. Capturing Ion-Solid Interactions with MOS structures

    NASA Astrophysics Data System (ADS)

    Shyam, R.; Field, D. A.; Chambers, S.; Harrell, W. R.; Sosolik, C. E.

    2011-10-01

    We have fabricated metal-oxide-semiconductor (MOS) devices for a study of implantation rates and damage resulting from low energy ion-solid impacts. Specifically, we seek to capture ion irradiation effects on the oxides. Fabrication of the MOS devices follows a standard procedure where Ohmic contacts are first created on the wafer backside followed by the thermal growth of various thicknesses of SiO2 (from 50 nm to 200 nm) on the wafer frontside. As-grown SiO2 layers are then exposed to various singly-charged alkalis ions with energies in the range of 100 eV to 10 keV in our beamline setup. Following this exposure, the MOS devices are completed in situ with the deposition of a top Al contact. Characterization of the ion-modified devices involves the standard device technique of biased capacitance-voltage (C-V) measurements where a field is applied across the MOS structure at an elevated temperature to move implanted ions resulting in changes in surface charge density that are reflected as shifts in the flatband voltage (VFB). Similarly, a triangular voltage sweep (TVS) test can be utilized to measure the ionic displacement current as it is driven by a slow linear voltage ramp and it should reveal the total ionic space charge in an MOS.

  3. Controlling Transistor Temperature During Burn-In

    NASA Technical Reports Server (NTRS)

    Scott, B. C.

    1986-01-01

    Boiling refrigerant provides simple temperature control for newly manufactured power transistors. Heat-transfer liquid is Fluorinert FC-77 (or equivalent). Liquid boils at 100 degrees C, which is specified temperature at which transistor cases should be maintained during burn-in with this technique.

  4. Field effect transistors improve buffer amplifier

    NASA Technical Reports Server (NTRS)

    1967-01-01

    Unity gain buffer amplifier with a Field Effect Transistor /FET/ differential input stage responds much faster than bipolar transistors when operated at low current levels. The circuit uses a dual FET in a unity gain buffer amplifier having extremely high input impedance, low bias current requirements, and wide bandwidth.

  5. MoS2 -Based Tactile Sensor for Electronic Skin Applications.

    PubMed

    Park, Minhoon; Park, Yong Ju; Chen, Xiang; Park, Yon-Kyu; Kim, Min-Seok; Ahn, Jong-Hyun

    2016-04-01

    A conformal tactile sensor based on MoS2 and graphene is demonstrated. The MoS2 tactile sensor exhibits excellent sensitivity, high uniformity, and good repeatability in terms of various strains. In addition, the outstanding flexibility enables the MoS2 strain tactile sensor to be realized conformally on a finger tip. The MoS2 -based tactile sensor can be utilized for wearable electronics, such as electronic skin. PMID:26833813

  6. Magnetoamplification in a bipolar magnetic junction transistor.

    PubMed

    Rangaraju, N; Peters, J A; Wessels, B W

    2010-09-10

    We have demonstrated the first bipolar magnetic junction transistor using a dilute magnetic semiconductor. For an InMnAs p-n-p transistor magnetoamplification is observed at room temperature. The observed magnetoamplification is attributed to the magnetoresistance of the magnetic semiconductor InMnAs heterojunction. The magnetic field dependence of the transistor characteristics confirm that the magnetoamplification results from the junction magnetoresistance. To describe the experimentally observed transistor characteristics, we propose a modified Ebers-Moll model that includes a series magnetoresistance attributed to spin-selective conduction. The capability of magnetic field control of the amplification in an all-semiconductor transistor at room temperature potentially enables the creation of new computer logic architecture where the spin of the carriers is utilized.

  7. Universal power transistor base drive control unit

    DOEpatents

    Gale, Allan R.; Gritter, David J.

    1988-01-01

    A saturation condition regulator system for a power transistor which achieves the regulation objectives of a Baker clamp but without dumping excess base drive current into the transistor output circuit. The base drive current of the transistor is sensed and used through an active feedback circuit to produce an error signal which modulates the base drive current through a linearly operating FET. The collector base voltage of the power transistor is independently monitored to develop a second error signal which is also used to regulate base drive current. The current-sensitive circuit operates as a limiter. In addition, a fail-safe timing circuit is disclosed which automatically resets to a turn OFF condition in the event the transistor does not turn ON within a predetermined time after the input signal transition.

  8. Universal power transistor base drive control unit

    DOEpatents

    Gale, A.R.; Gritter, D.J.

    1988-06-07

    A saturation condition regulator system for a power transistor is disclosed which achieves the regulation objectives of a Baker clamp but without dumping excess base drive current into the transistor output circuit. The base drive current of the transistor is sensed and used through an active feedback circuit to produce an error signal which modulates the base drive current through a linearly operating FET. The collector base voltage of the power transistor is independently monitored to develop a second error signal which is also used to regulate base drive current. The current-sensitive circuit operates as a limiter. In addition, a fail-safe timing circuit is disclosed which automatically resets to a turn OFF condition in the event the transistor does not turn ON within a predetermined time after the input signal transition. 2 figs.

  9. In Situ Synthesis of Carbon Nanotube Hybrids with Alternate MoC and MoS2 to Enhance the Electrochemical Activities of MoS2.

    PubMed

    Li, Xin; Zhang, Jinying; Wang, Rui; Huang, Hongyang; Xie, Chong; Li, Zhihui; Li, Jun; Niu, Chunming

    2015-08-12

    Molybdenum disulfides and carbides are effective catalysts for hydrogenation and hydridesulfurization, where MoS2 nanostructures are also highly promising materials for lithium ion batteries. High surface-to-volume ratio and strong interactions with conducting networks are crucial factors for their activities. A new hybrid structure of multiwalled carbon nanotube (MWCNT) with alternate MoC nanoparticles and MoS2 nanosheets (MoS2 + MoC-MWCNT) has been synthesized by controlled carburization of core-shell MoS2-MWCNT hybrid nanotubes and demonstrated by HRTEM, FFT, XRD, and Raman scattering. The MoS2 nanosheets (∼10 nm) remain tightly connected to MWCNT surfaces with {001} planes in parallel to MWCNT walls and the highly crystallized α-MoC particles (∼10 nm) are adhered to MWCNTs at angles of 60-80° between {111} planes and MWCNT walls. The electrochemical performances of the hybrid structures have been demonstrated as anodes for lithium ion batteries to be significantly increased by breaking MoS2 nanotubes into nanosheets (patches) on MWCNT surfaces, especially at high current rates. The specific capacities of MoS2 + MoC-MWCNT sample with ∼23% MoS2 have been demonstrated to be higher than those of MoS2-MWCNTs containing ∼70% MoS2.

  10. Ferromagnetism in Single Crystal MoS2

    NASA Astrophysics Data System (ADS)

    Saeidi Varnoosfaderani, Sima; Tongay, Sefaattin; Appleton, Bill; Wu, Junqiao; Hebard, Arthur

    2013-03-01

    We report on the magnetic properties of MoS2 flakes measured from room temperature down to 10 K and magnetic fields up to 5 Tesla. Molybdenum disulfide (MoS2) is one of the most stable layered transition metal dichalcogenides, which has a finite band gap and is regarded as a complementary (quasi-) 2D material to graphene. We find that single crystals of MoS2 display ferromagnetism superimposed onto a large temperature-dependent diamagnetism and observe that ferromagnetism persists from 10 K up to room temperature. We attribute the existence of ferromagnetism partly to the presence of zigzag edges in the magnetic ground state at the grain boundaries. Since the magnetic measurements are relatively insensitive to the interlayer coupling, these results are expected to be also valid in the single layer limit. This work is supported by the Office of Naval Research and National Science Foundation

  11. Towards an optimised sputtered MoS2 lubricant film

    NASA Technical Reports Server (NTRS)

    Roberts, E. W.

    1986-01-01

    It is shown that the tribological quality of MoS2 lubricant films formed by magnetron sputtering is determined by the choice of sputtering conditions. By selecting the appropriate conditions, films of extremely high lubricity and endurance (in vacuum), which are well suited to many space applications, are obtained. Such MoS2 films, when applied to precision ball hearings, give rise to the lowest torques (for the given test conditions) yet seen in our laboratory. While a remarkably good performance is obtained in vacuum, tests in air show a marked deterioration in lubricating qualities. It is demonstrated that this is attributable to the adsorption of water vapor on MoS2 surfaces and that the degree of deterioration is related to the partial pressure of water vapor present. Analysis of results indicates that the factors relevant to obtaining optimum films are deposition rate and film composition.

  12. MoS2 sputtering coating for ultrahigh vacuum manipulation

    NASA Astrophysics Data System (ADS)

    Maruyama, Toshiyuki; Nakagawa, Jun; Endo, Katsumi; Kasahara, Akira; Goto, Masahiro; Tosa, Masahiro

    2013-03-01

    Lubrication applied to sliding part is one of the key components for the development of high performance driving mechanism and manipulator in ultrahigh vacuum. Some solid lubrication has been widely used for this purpose, especially molybdenum disulfide (MoS2). Low friction, low wear and low outgassing during the sliding motion on lubrication are required for a high performance manipulation in ultrahigh vacuum. Although the tribology of MoS2 has been reported to be suitable in a vacuum, the outgassing characteristics while sliding are not clean, in this work, we investigate the characteristics of MoS2 sputtering coating in order to develop high performance ultrahigh vacuum driving mechanism. Their friction and outgassing characteristics were evaluated and we have found out suitable parameters for manipulation.

  13. Defects Engineered Monolayer MoS2 for Improved Hydrogen Evolution Reaction

    DOE PAGES

    Ye, Gonglan; Gong, Yongji; Lin, Junhao; Li, Bo; He, Yongmin; Pantelides, Sokrates T.; Zhou, Wu; Vajtai, Robert; Ajayan, Pulickel M.

    2016-01-13

    MoS2 is a promising, low-cost material for electrochemical hydrogen production due to its high activity and stability during the reaction. Our work represents an easy method to increase the hydrogen production in electrochemical reaction of MoS2 via defect engineering, and helps to understand the catalytic properties of MoS2.

  14. Effects of Bio-Mos on growth and survival of channel catfish challenged with Edwardsiella ictaluri

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Research examined the effects of Bio-Mos on growth and disease resistance in channel catfish. Catfish were fed either a Con-Sink (36% crude protein (CP) diet) or Bio-Mos-Sink (36% CP diet with Bio-Mos supplemented at 2 g/kg) sinking pellet for 6 wks. followed by an E. ictaluri challenge. Growth pe...

  15. Validity and reliability of Arabic MOS social support survey.

    PubMed

    Dafaalla, Mohamed; Farah, Abdulraheem; Bashir, Sheima; Khalil, Ammar; Abdulhamid, Rabab; Mokhtar, Mousab; Mahadi, Mohamed; Omer, Zulfa; Suliman, Asgad; Elkhalifa, Mohammed; Abdelgadir, Hanin; Kheir, Abdelmoneim E M; Abdalrahman, Ihab

    2016-01-01

    We aimed to generate a valid reliable Arabic version of MOS social support survey (MOS-SSS). We did a cross sectional study in medical students of Faculty of Medicine in Khartoum, Sudan. We did a clustered random sampling in 500 students of which 487 were suitable for analysis. We followed the standard translation process for translating the MOS-SSS. We accomplished factor analysis to assess construct validity, and generated item-scales correlations to evaluate the convergent and discriminant validity. We extracted the Cronbach's α and Spearman Brown coefficient of spit half method to determine internal consistency. We measured stability by correlation between the scores of the MOS survey taken at two different occasions with ten days apart in 252 participants. All items correlated highly (0.788 or greater) with their hypothesized scales. All items in subscales correlated higher by two standard errors with their own scale than with any other scale. Principle component analysis with varimax rotation was conducted on the 19 items and examination of scree plot graphically suggested 4 predominant factors that account for 72 % of variance. It showed high loadings, ranging from 0.720 to 0.84 for items of emotional support, 0.699-0.845 for tangible support, 0.518-0.823 for affectionate support, and 0.740-0.816 for positive social interaction. Cronbach's alpha for overall MOS scale and subscales indicated high internal consistency. The test-retest correlation showed weak correlation between the test and retest (ranges from 0.04 to 0.104). The Arabic MOS-SSS had high validity and internal consistency. PMID:27547680

  16. Magnetic properties of MoS2: Existence of ferromagnetism

    NASA Astrophysics Data System (ADS)

    Tongay, Sefaattin; Varnoosfaderani, Sima S.; Appleton, Bill R.; Wu, Junqiao; Hebard, Arthur F.

    2012-09-01

    We report on the magnetic properties of MoS2 measured from room temperature down to 10 K and magnetic fields up to 5 T. We find that single crystals of MoS2 display ferromagnetism superimposed onto large temperature-dependent diamagnetism and have observed that ferromagnetism persists from 10 K up to room temperature. We attribute the existence of ferromagnetism partly to the presence of zigzag edges in the magnetic ground state at the grain boundaries. Since the magnetic measurements are relatively insensitive to the interlayer coupling, these results are expected to be valid in the single layer limit.

  17. Conduction quantization in monolayer MoS2

    NASA Astrophysics Data System (ADS)

    Li, T. S.

    2016-10-01

    We study the ballistic conduction of a monolayer MoS2 subject to a spatially modulated magnetic field by using the Landauer-Buttiker formalism. The band structure depends sensitively on the field strength, and its change has profound influence on the electron conduction. The conductance is found to demonstrate multi-step behavior due to the discrete number of conduction channels. The sharp peak and rectangular structures of the conductance are stretched out as temperature increases, due to the thermal broadening of the derivative of the Fermi-Dirac distribution function. Finally, quantum behavior in the conductance of MoS2 can be observed at temperatures below 10 K.

  18. Formation of nanosized monolayer MoS2 by oxygen-assisted thinning of multilayer MoS2

    NASA Astrophysics Data System (ADS)

    Neupane, Guru P.; Dhakal, Krishna P.; Kim, Hyun; Lee, Jubok; Kim, Min Su; Han, Ganghee; Lee, Young Hee; Kim, Jeongyong

    2016-08-01

    We report the controllable nanosized local thinning of multi-layer (2 L and 3 L)-thickness MoS2 films down to the monolayer (1 L) thickness using the simple method of annealing in a dry oxygen atmosphere. The annealing temperature was optimized in the range of 240 °C to 270 °C for 1.5 h, and 1 L thick nanosized pits were developed on the uniform film of the 2 L and 3 L MoS2 grown using the chemical vapor deposition method. We characterized the formation of the 1 L nanosized pits using nanoscale confocal photoluminescence (PL) and Raman spectroscopy. We observed that the PL intensity increased and the Raman frequency shifted, representative of the characteristics of 1 L MoS2 films. A subsequent hydrogen treatment process was useful for removing the oxygen-induced doping effect resulting from the annealing.

  19. Inversion channel diamond metal-oxide-semiconductor field-effect transistor with normally off characteristics.

    PubMed

    Matsumoto, Tsubasa; Kato, Hiromitsu; Oyama, Kazuhiro; Makino, Toshiharu; Ogura, Masahiko; Takeuchi, Daisuke; Inokuma, Takao; Tokuda, Norio; Yamasaki, Satoshi

    2016-01-01

    We fabricated inversion channel diamond metal-oxide-semiconductor field-effect transistors (MOSFETs) with normally off characteristics. At present, Si MOSFETs and insulated gate bipolar transistors (IGBTs) with inversion channels are widely used because of their high controllability of electric power and high tolerance. Although a diamond semiconductor is considered to be a material with a strong potential for application in next-generation power devices, diamond MOSFETs with an inversion channel have not yet been reported. We precisely controlled the MOS interface for diamond by wet annealing and fabricated p-channel and planar-type MOSFETs with phosphorus-doped n-type body on diamond (111) substrate. The gate oxide of Al2O3 was deposited onto the n-type diamond body by atomic layer deposition at 300 °C. The drain current was controlled by the negative gate voltage, indicating that an inversion channel with a p-type character was formed at a high-quality n-type diamond body/Al2O3 interface. The maximum drain current density and the field-effect mobility of a diamond MOSFET with a gate electrode length of 5 μm were 1.6 mA/mm and 8.0 cm(2)/Vs, respectively, at room temperature. PMID:27545201

  20. Inversion channel diamond metal-oxide-semiconductor field-effect transistor with normally off characteristics

    NASA Astrophysics Data System (ADS)

    Matsumoto, Tsubasa; Kato, Hiromitsu; Oyama, Kazuhiro; Makino, Toshiharu; Ogura, Masahiko; Takeuchi, Daisuke; Inokuma, Takao; Tokuda, Norio; Yamasaki, Satoshi

    2016-08-01

    We fabricated inversion channel diamond metal-oxide-semiconductor field-effect transistors (MOSFETs) with normally off characteristics. At present, Si MOSFETs and insulated gate bipolar transistors (IGBTs) with inversion channels are widely used because of their high controllability of electric power and high tolerance. Although a diamond semiconductor is considered to be a material with a strong potential for application in next-generation power devices, diamond MOSFETs with an inversion channel have not yet been reported. We precisely controlled the MOS interface for diamond by wet annealing and fabricated p-channel and planar-type MOSFETs with phosphorus-doped n-type body on diamond (111) substrate. The gate oxide of Al2O3 was deposited onto the n-type diamond body by atomic layer deposition at 300 °C. The drain current was controlled by the negative gate voltage, indicating that an inversion channel with a p-type character was formed at a high-quality n-type diamond body/Al2O3 interface. The maximum drain current density and the field-effect mobility of a diamond MOSFET with a gate electrode length of 5 μm were 1.6 mA/mm and 8.0 cm2/Vs, respectively, at room temperature.

  1. Inversion channel diamond metal-oxide-semiconductor field-effect transistor with normally off characteristics

    PubMed Central

    Matsumoto, Tsubasa; Kato, Hiromitsu; Oyama, Kazuhiro; Makino, Toshiharu; Ogura, Masahiko; Takeuchi, Daisuke; Inokuma, Takao; Tokuda, Norio; Yamasaki, Satoshi

    2016-01-01

    We fabricated inversion channel diamond metal-oxide-semiconductor field-effect transistors (MOSFETs) with normally off characteristics. At present, Si MOSFETs and insulated gate bipolar transistors (IGBTs) with inversion channels are widely used because of their high controllability of electric power and high tolerance. Although a diamond semiconductor is considered to be a material with a strong potential for application in next-generation power devices, diamond MOSFETs with an inversion channel have not yet been reported. We precisely controlled the MOS interface for diamond by wet annealing and fabricated p-channel and planar-type MOSFETs with phosphorus-doped n-type body on diamond (111) substrate. The gate oxide of Al2O3 was deposited onto the n-type diamond body by atomic layer deposition at 300 °C. The drain current was controlled by the negative gate voltage, indicating that an inversion channel with a p-type character was formed at a high-quality n-type diamond body/Al2O3 interface. The maximum drain current density and the field-effect mobility of a diamond MOSFET with a gate electrode length of 5 μm were 1.6 mA/mm and 8.0 cm2/Vs, respectively, at room temperature. PMID:27545201

  2. Low-frequency noise in MoSe2 field effect transistors

    NASA Astrophysics Data System (ADS)

    Das, Suprem R.; Kwon, Jiseok; Prakash, Abhijith; Delker, Collin J.; Das, Saptarshi; Janes, David B.

    2015-02-01

    One of the important performance metrics of emerging nanoelectronic devices, including low dimensional Field Effect Transistors (FETs), is the magnitude of the low-frequency noise. Atomically thin 2D semiconductor channel materials such as MoX2 (X ≡ S, Se) have shown promising transistor characteristics such as ION/IOFF ratio exceeding 106 and low IOFF, making them attractive as channel materials for next generation nanoelectronic devices. However, MoS2 FETs demonstrated to date exhibit high noise levels under ambient conditions. In this letter, we report at least two orders of magnitude smaller values of Hooge parameter in a back-gated MoSe2 FET (10 atomic layers) with nickel S/D contacts and measured at atmospheric pressure and temperature. The channel dominated regime of noise was extracted from the total noise spectrum and is shown to follow a mobility fluctuation model with 1/f dependence. The low noise in MoSe2 FETs is comparable to other 1D nanoelectronic devices such as carbon nanotube FETs (CNT-FETs) and paves the way for use in future applications in precision sensing and communications.

  3. Vertical Silicon Nanowire Field Effect Transistors with Nanoscale Gate-All-Around.

    PubMed

    Guerfi, Youssouf; Larrieu, Guilhem

    2016-12-01

    Nanowires are considered building blocks for the ultimate scaling of MOS transistors, capable of pushing devices until the most extreme boundaries of miniaturization thanks to their physical and geometrical properties. In particular, nanowires' suitability for forming a gate-all-around (GAA) configuration confers to the device an optimum electrostatic control of the gate over the conduction channel and then a better immunity against the short channel effects (SCE). In this letter, a large-scale process of GAA vertical silicon nanowire (VNW) MOSFETs is presented. A top-down approach is adopted for the realization of VNWs with an optimum reproducibility followed by thin layer engineering at nanoscale. Good overall electrical performances were obtained, with excellent electrostatic behavior (a subthreshold slope (SS) of 95 mV/dec and a drain induced barrier lowering (DIBL) of 25 mV/V) for a 15-nm gate length. Finally, a first demonstration of dual integration of n-type and p-type VNW transistors for the realization of CMOS inverter is proposed. PMID:27094824

  4. Voltage regulator for battery power source. [using a bipolar transistor

    NASA Technical Reports Server (NTRS)

    Black, J. M. (Inventor)

    1979-01-01

    A bipolar transistor in series with the battery as the control element also in series with a zener diode and a resistor is used to maintain a predetermined voltage until the battery voltage decays to very nearly the predetermined voltage. A field effect transistor between the base of the bipolar transistor and a junction between the zener diode and resistor regulates base current of the bipolar transistor, thereby regulating the conductivity of the bipolar transistor for control of the output voltage.

  5. Electrical coupling between cells and graphene transistors.

    PubMed

    Hess, Lucas H; Becker-Freyseng, Christoph; Wismer, Michael S; Blaschke, Benno M; Lottner, Martin; Rolf, Felix; Seifert, Max; Garrido, Jose A

    2015-04-01

    In this work, both experimental data and a model are presented on the coupling between living cells and graphene solution-gated field-effect transistors. Modified HEK 293 cells are successfully cultured on graphene transistor arrays and electrically accessed by the patch clamp method. Transistor recordings are presented, showing the opening and closing of voltage-gated potassium ion channels in the cell membrane. The experimental data is compared with the broadly used standard point-contact model. The ion dynamics in the cell-transistor cleft are analyzed to account for the differences between the model and the experimental data revealing a significant increase in the total ionic strength in the cleft. In order to describe the influence of the ion concentration resulting from the cell activity, the ion-sensitivity of graphene solution-gated field-effect transistors is investigated experimentally and modelled by considering the screening effect of the ions on the surface potential at the graphene/electrolyte interface. Finally, the model of the cell-transistor coupling is extended to include the effect of ion accumulation and ion sensitivity. The experimental data shows a very good agreement with this extended model, emphasizing the importance of considering the ion concentration in the cleft to properly understand the cell-transistor coupling.

  6. High-performance vertical organic transistors.

    PubMed

    Kleemann, Hans; Günther, Alrun A; Leo, Karl; Lüssem, Björn

    2013-11-11

    Vertical organic thin-film transistors (VOTFTs) are promising devices to overcome the transconductance and cut-off frequency restrictions of horizontal organic thin-film transistors. The basic physical mechanisms of VOTFT operation, however, are not well understood and VOTFTs often require complex patterning techniques using self-assembly processes which impedes a future large-area production. In this contribution, high-performance vertical organic transistors comprising pentacene for p-type operation and C60 for n-type operation are presented. The static current-voltage behavior as well as the fundamental scaling laws of such transistors are studied, disclosing a remarkable transistor operation with a behavior limited by injection of charge carriers. The transistors are manufactured by photolithography, in contrast to other VOTFT concepts using self-assembled source electrodes. Fluorinated photoresist and solvent compounds allow for photolithographical patterning directly and strongly onto the organic materials, simplifying the fabrication protocol and making VOTFTs a prospective candidate for future high-performance applications of organic transistors. PMID:23637074

  7. Morphology engineering of monolayer MoS2 by adjusting chemical environment during growth

    NASA Astrophysics Data System (ADS)

    Cao, Yingjie; Luo, Xingfang; Yuan, Cailei; Han, Shuming; Yu, Ting; Yang, Yong; Li, Qinliang

    2015-11-01

    The precise control of the morphology of monolayer MoS2 is of particular importance for their potential applications and device performance. In this work, we present an experimental method to study the shape evolution of the chemical vapor deposition (CVD) grown MoS2 flakes. We observed that the morphology of monolayer MoS2 flakes transformed from truncated triangular shape to triangular shape by increasing the stoichiometric ratio of S:Mo, and consequently tailor the optical properties of MoS2 flakes. The results suggest the possibility to engineer the morphology of monolayer MoS2 by adjusting the chemical environment during growth.

  8. Nonvolatile Ferroelectric Memory Circuit Using Black Phosphorus Nanosheet-Based Field-Effect Transistors with P(VDF-TrFE) Polymer.

    PubMed

    Lee, Young Tack; Kwon, Hyeokjae; Kim, Jin Sung; Kim, Hong-Hee; Lee, Yun Jae; Lim, Jung Ah; Song, Yong-Won; Yi, Yeonjin; Choi, Won-Kook; Hwang, Do Kyung; Im, Seongil

    2015-10-27

    Two-dimensional van der Waals (2D vdWs) materials are a class of new materials that can provide important resources for future electronics and materials sciences due to their unique physical properties. Among 2D vdWs materials, black phosphorus (BP) has exhibited significant potential for use in electronic and optoelectronic applications because of its allotropic properties, high mobility, and direct and narrow band gap. Here, we demonstrate a few-layered BP-based nonvolatile memory transistor with a poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)) ferroelectric top gate insulator. Experiments showed that our BP-based ferroelectric transistors operate satisfactorily at room temperature in ambient air and exhibit a clear memory window. Unlike conventional ambipolar BP transistors, our ferroelectric transistors showed only p-type characteristics due to the carbon-fluorine (C-F) dipole effect of the P(VDF-TrFE) layer, as well as the highest linear mobility value of 1159 cm(2) V(-1) s(-1) with a 10(3) on/off current ratio. For more advanced memory applications beyond unit memory devices, we implemented two memory inverter circuits, a resistive-load inverter circuit and a complementary inverter circuit, combined with an n-type molybdenum disulfide (MoS2) nanosheet. Our memory inverter circuits displayed a clear memory window of 15 V and memory output voltage efficiency of 95%.

  9. Pass-transistor very large scale integration

    NASA Technical Reports Server (NTRS)

    Maki, Gary K. (Inventor); Bhatia, Prakash R. (Inventor)

    2004-01-01

    Logic elements are provided that permit reductions in layout size and avoidance of hazards. Such logic elements may be included in libraries of logic cells. A logical function to be implemented by the logic element is decomposed about logical variables to identify factors corresponding to combinations of the logical variables and their complements. A pass transistor network is provided for implementing the pass network function in accordance with this decomposition. The pass transistor network includes ordered arrangements of pass transistors that correspond to the combinations of variables and complements resulting from the logical decomposition. The logic elements may act as selection circuits and be integrated with memory and buffer elements.

  10. Transistors using crystalline silicon devices on glass

    DOEpatents

    McCarthy, Anthony M.

    1995-01-01

    A method for fabricating transistors using single-crystal silicon devices on glass. This method overcomes the potential damage that may be caused to the device during high voltage bonding and employs a metal layer which may be incorporated as part of the transistor. This is accomplished such that when the bonding of the silicon wafer or substrate to the glass substrate is performed, the voltage and current pass through areas where transistors will not be fabricated. After removal of the silicon substrate, further metal may be deposited to form electrical contact or add functionality to the devices. By this method both single and gate-all-around devices may be formed.

  11. MOS11: A New Component in the mRNA Export Pathway

    PubMed Central

    Cheng, Yu Ti; Lee, EunKyoung; Huang, Yan; Dong, Oliver Xiaoou; Gannon, Patrick; Huang, Shuai; Ding, Pingtao; Li, Yingzhong; Sack, Fred; Zhang, Yuelin; Li, Xin

    2010-01-01

    Nucleocytoplasmic trafficking is emerging as an important aspect of plant immunity. The three related pathways affecting plant immunity include Nuclear Localization Signal (NLS)–mediated nuclear protein import, Nuclear Export Signal (NES)–dependent nuclear protein export, and mRNA export relying on MOS3, a nucleoporin belonging to the Nup107–160 complex. Here we report the characterization, identification, and detailed analysis of Arabidopsis modifier of snc1, 11 (mos11). Mutations in MOS11 can partially suppress the dwarfism and enhanced disease resistance phenotypes of snc1, which carries a gain-of-function mutation in a TIR-NB-LRR type Resistance gene. MOS11 encodes a conserved eukaryotic protein with homology to the human RNA binding protein CIP29. Further functional analysis shows that MOS11 localizes to the nucleus and that the mos11 mutants accumulate more poly(A) mRNAs in the nucleus, likely resulting from reduced mRNA export activity. Epistasis analysis between mos3-1 and mos11-1 revealed that MOS11 probably functions in the same mRNA export pathway as MOS3, in a partially overlapping fashion, before the mRNA molecules pass through the nuclear pores. Taken together, MOS11 is identified as a new protein contributing to the transfer of mature mRNA from the nucleus to the cytosol. PMID:21203492

  12. First-principles study of the structural and electronic properties of MoS2-WS2 and MoS2-MoTe2 monolayer heterostructures

    NASA Astrophysics Data System (ADS)

    Wang, Qianwen; Wu, Ping; Cao, Gengyu; Huang, Min

    2013-12-01

    Using first-principles calculations, we have systematically investigated the geometric and electronic structure of MoS2-WS2 and MoS2-MoTe2 monolayer (ML) heterostructures. Analysis of the variation of the total density of states and partial density of states of the specific atoms in the interfaces demonstrates that the two heterostructures show rather different properties and different changes from the initial MoS2 ML. The MoS2-WS2 ML heterostructure is still a semiconductor with a band gap of 1.58 eV, which is smaller than that of MoS2 and WS2 MLs. However, the strong interactions between MoS2and MoTe2 at the interfacial sites induce the MoS2-MoTe2 ML heterostructure to display metallic characteristics. Our results indicate that the ML heterostructures of MoS2-WS2 and MoS2-MoTe2 are expected to be a possible way to extend the application of the transition-metal dichalcogenides.

  13. Single step, bulk synthesis of engineered MoS2 quantum dots for multifunctional electrocatalysis

    NASA Astrophysics Data System (ADS)

    Tadi, Kiran Kumar; Palve, Anil M.; Pal, Shubhadeep; Sudeep, P. M.; Narayanan, Tharangattu N.

    2016-07-01

    Bi- or tri- functional catalysts based on atomic layers are receiving tremendous scientific attention due to their importance in various energy technologies. Recent studies on molybdenum disulphide (MoS2) nanosheets revealed that controlling the edge states and doping/modifying with suitable elements are highly important in tuning the catalytic activities of MoS2. Here we report a bulk, single step method to synthesize metal modified MoS2 quantum dots (QDs). Three elements, namely Fe, Mg and Li, are chosen to study the effects of dopants in the catalytic activities of MoS2. Fe and Mg are found to act like dopants in the MoS2 lattice forming respective doped MoS2 QDs, while Li formed an intercalated MoS2 QD. The efficacy and tunability of these luminescent doped QDs towards various electrocatalytic activities (hydrogen evolution reaction, oxygen evolution reaction and oxygen reduction action) are reported here.

  14. Layer-by-layer self-assembly of polyelectrolyte functionalized MoS2 nanosheets.

    PubMed

    Shen, Jianfeng; Pei, Yu; Dong, Pei; Ji, Jin; Cui, Zheng; Yuan, Junhua; Baines, Robert; Ajayan, Pulickel M; Ye, Mingxin

    2016-05-01

    Few-layered polyelectrolyte functionalized MoS2 nanosheets were obtained for the first time through in situ polymerization of MoS2 nanosheets with poly(acrylic acid) and poly(acrylamide), both of which demonstrated excellent dispersibility and stability in water. After designing and optimizing the components of this series of polyelectrolyte functionalized MoS2 nanosheets, by exploiting the electrostatic interactions present in the modified MoS2 nanosheets, we further created a series of layer-by-layer (LBL) self-assembling MoS2-based films. To this end, uniform MoS2 nanosheet-based LBL films were precisely deposited on substrates such as quartz, silicon, and ITO. The polyelectrolyte functionalized MoS2 nanosheet assembled LBL film-modified electrodes demonstrated enhanced electrocatalytic activity for H2O2. As such, they are conducive to efficient sensors and advanced biosensing systems.

  15. Single step, bulk synthesis of engineered MoS2 quantum dots for multifunctional electrocatalysis.

    PubMed

    Tadi, Kiran Kumar; Palve, Anil M; Pal, Shubhadeep; Sudeep, P M; Narayanan, Tharangattu N

    2016-07-01

    Bi- or tri- functional catalysts based on atomic layers are receiving tremendous scientific attention due to their importance in various energy technologies. Recent studies on molybdenum disulphide (MoS2) nanosheets revealed that controlling the edge states and doping/modifying with suitable elements are highly important in tuning the catalytic activities of MoS2. Here we report a bulk, single step method to synthesize metal modified MoS2 quantum dots (QDs). Three elements, namely Fe, Mg and Li, are chosen to study the effects of dopants in the catalytic activities of MoS2. Fe and Mg are found to act like dopants in the MoS2 lattice forming respective doped MoS2 QDs, while Li formed an intercalated MoS2 QD. The efficacy and tunability of these luminescent doped QDs towards various electrocatalytic activities (hydrogen evolution reaction, oxygen evolution reaction and oxygen reduction action) are reported here.

  16. Single step, bulk synthesis of engineered MoS2 quantum dots for multifunctional electrocatalysis.

    PubMed

    Tadi, Kiran Kumar; Palve, Anil M; Pal, Shubhadeep; Sudeep, P M; Narayanan, Tharangattu N

    2016-07-01

    Bi- or tri- functional catalysts based on atomic layers are receiving tremendous scientific attention due to their importance in various energy technologies. Recent studies on molybdenum disulphide (MoS2) nanosheets revealed that controlling the edge states and doping/modifying with suitable elements are highly important in tuning the catalytic activities of MoS2. Here we report a bulk, single step method to synthesize metal modified MoS2 quantum dots (QDs). Three elements, namely Fe, Mg and Li, are chosen to study the effects of dopants in the catalytic activities of MoS2. Fe and Mg are found to act like dopants in the MoS2 lattice forming respective doped MoS2 QDs, while Li formed an intercalated MoS2 QD. The efficacy and tunability of these luminescent doped QDs towards various electrocatalytic activities (hydrogen evolution reaction, oxygen evolution reaction and oxygen reduction action) are reported here. PMID:27231837

  17. Distinct development patterns of c-mos protooncogene expression in female and male mouse germ cells

    SciTech Connect

    Mutter, G.L.; Wolgemuth, D.J.

    1987-08-01

    The protooncogene c-mos is expressed in murine reproductive tissues, producing transcripts of 1.7 and 1.4 kilobases in testis and ovary, respectively. In situ hybridization analysis of c-mos expression in histological sections of mouse ovaries revealed that oocytes are the predominant if not exclusive source of c-mos transcripts. /sup 35/S- or /sup 32/P-labelled RNA probes were transcribed. c-mos transcripts accumulate in growing oocytes, increasing 40- to 90-fold during oocyte and follicular development. c-mos transcripts were also detected in male germ cells and are most abundant after the cells have entered the haploid stage of spermatogenesis. This developmentally regulated pattern of c-mos expression in oocytes and spermatogenic cells suggest that the c-mos gene product may have a function in normal germ-cell differentiation or early embryogenesis.

  18. Plasma nanocoating of thiophene onto MoS2 nanotubes

    NASA Astrophysics Data System (ADS)

    Türkaslan, Banu Esencan; Dikmen, Sibel; Öksüz, Lütfi; Öksüz, Aysegul Uygun

    2015-12-01

    MoS2 nanotubes were coated with conductive polymer thiophene by atmospheric pressure radio-frequency (RF) glow discharge. MoS2 nanotubes were prepared by thermal decomposition of hexadecylamine (HDA) intercalated laminar MoS2 precursor on anodized aluminum oxide template and the thiophene was polymerized directly on surface of these nanotubes as in situ by plasma method. The effect of plasma power on PTh/MoS2 nanocomposite properties has been investigated by means of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM and EDX), and X-ray diffraction spectroscopy (XRD). The presence of PTh bands in the FTIR spectra of PTh/MoS2 nanotube nanocomposites corresponding XRD results indicates that the polythiophene coating onto MoS2 nanotube. The chemical structure of PTh is not changed when the plasma power of discharge differ from 117 to 360 W. SEM images of nanocomposites show that when the discharge power is increased between 117 and 360 W the average diameter of PTh/MoS2 nanotube nanocomposites are changed and the structure become more uniformly.

  19. Thermal conductivity of MoS2 polycrystalline nanomembranes

    NASA Astrophysics Data System (ADS)

    Sledzinska, M.; Graczykowski, B.; Placidi, M.; Saleta Reig, D.; El Sachat, A.; Reparaz, J. S.; Alzina, F.; Mortazavi, B.; Quey, R.; Colombo, L.; Roche, S.; Sotomayor Torres, C. M.

    2016-09-01

    Heat conduction in 2D materials can be effectively engineered by means of controlling nanoscale grain structure. A favorable thermal performance makes these structures excellent candidates for integrated heat management units. Here we show combined experimental and theoretical studies for MoS2 nanosheets in a nanoscale grain-size limit. We report thermal conductivity measurements on 5 nm thick polycrystalline MoS2 by means of 2-laser Raman thermometry. The free-standing, drum-like MoS2 nanomembranes were fabricated using a novel polymer- and residue-free, wet transfer, in which we took advantage of the difference in the surface energies between MoS2 and the growth substrate to transfer the CVD-grown nanosheets. The measurements revealed a strong reduction in the in-plane thermal conductivity down to about 0.73 ± 0.25 {{{W}}{{m}}}-1 {{{K}}}-1. The results are discussed theoretically using finite elements method simulations for a polycrystalline film, and a scaling trend of the thermally conductivity with grain size is proposed.

  20. Tribotronic Enhanced Photoresponsivity of a MoS2 Phototransistor

    PubMed Central

    Pang, Yaokun; Xue, Fei; Wang, Longfei; Chen, Jian; Luo, Jianjun; Jiang, Tao

    2016-01-01

    Molybdenum disulfide (MoS2) has attracted a great attention as an excellent 2D material for future optoelectronic devices. Here, a novel MoS2 tribotronic phototransistor is developed by a conjunction of a MoS2 phototransistor and a triboelectric nanogenerator (TENG) in sliding mode. When an external friction layer produces a relative sliding on the device, the induced positive charges on the back gate of the MoS2 phototransistor act as a “gate” to increase the channel conductivity as the traditional back gate voltage does. With the sliding distance increases, the photoresponsivity of the device is drastically enhanced from 221.0 to 727.8 A W−1 at the 100 mW cm−2 UV excitation intensity and 1 V bias voltage. This work has extended the emerging tribotronics to the field of photodetection based on 2D material, and demonstrated a new way to realize the adjustable photoelectric devices with high photoresponsivity via human interfacing. PMID:27812472

  1. Structural Properties of Finite MoS2 Nanowires

    NASA Astrophysics Data System (ADS)

    Clark, Shaylyn; Salgado, Andres; Fernandez-Seivane, Lucas; Lopez-Lozano, Xochitl

    2015-03-01

    Molybdenum disulfide (MoS2) has been one of the most important catalysts used in refineries worldwide for hydrodesulfurization over the past century. In the last decade, and with the advent of nanotechnology, there has been a special interest in MoS2 nanostructures due to their high potential as novel nanocatalysts. The study of the properties of these systems is of fundamental interest for the experimental design of their catalytic activity and efficiency. In this work, we have performed ab initio density-functional calculations (DFT) to investigate the structural properties of finite MoS2 nanostrutures. All the models here presented were based on newly experimentally observed morphologies in MoS2 industrial catalysts using high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images. We simulated STEM images of the theoretical models to compare it with the experimental ones. In contrast with infinite models, the finite models prefer a rippled/twisted structure morphology over the planar or helical ones. The rippled/twisted models appear to be structurally more stable.

  2. Nucleoporin MOS7/Nup88 is required for mitosis in gametogenesis and seed development in Arabidopsis.

    PubMed

    Park, Guen Tae; Frost, Jennifer M; Park, Jin-Sup; Kim, Tae Ho; Lee, Jong Seob; Oh, Sung Aeong; Twell, David; Brooks, Janie Sue; Fischer, Robert L; Choi, Yeonhee

    2014-12-23

    Angiosperm reproduction is characterized by alternate diploid sporophytic and haploid gametophytic generations. Gametogenesis shares similarities with that of animals except for the formation of the gametophyte, whereby haploid cells undergo several rounds of postmeiotic mitosis to form gametes and the accessory cells required for successful reproduction. The mechanisms regulating gametophyte development in angiosperms are incompletely understood. Here, we show that the nucleoporin Nup88-homolog MOS7 (Modifier of Snc1,7) plays a crucial role in mitosis during both male and female gametophyte formation in Arabidopsis thaliana. Using a mutagenesis screen, we identify the mos7-5 mutant allele, which causes ovule and pollen abortion in MOS7/mos7-5 heterozygous plants, and preglobular stage embryonic lethality in homozygous mos7-5 seeds. During interphase, we show that MOS7 is localized to the nuclear membrane but, like many nucleoporins, is associated with the spindle apparatus during mitosis. We detect interactions between MOS7 and several nucleoporins known to control spindle dynamics, and find that in pollen from MOS7/mos7-5 heterozygotes, abortion is accompanied by a failure of spindle formation, cell fate specification, and phragmoplast activity. Most intriguingly, we show that following gamete formation by MOS7/mos7-5 heterozygous spores, inheritance of either the MOS7 or the mos7-5 allele by a given gamete does not correlate with its respective survival or abortion. Instead, we suggest a model whereby MOS7, which is highly expressed in the Pollen- and Megaspore Mother Cells, enacts a dosage-limiting effect on the gametes to enable their progression through subsequent mitoses.

  3. Pressure confinement effect in MoS2 monolayers.

    PubMed

    Li, Fangfei; Yan, Yalan; Han, Bo; Li, Liang; Huang, Xiaoli; Yao, Mingguang; Gong, Yuanbo; Jin, Xilian; Liu, Baoli; Zhu, Chuanrui; Zhou, Qiang; Cui, Tian

    2015-05-21

    With ever increasing interest in layered materials, molybdenum disulfide has been widely investigated due to its unique optoelectronic properties. Pressure is an effective technique to tune the lattice and electronic structure of materials such that high pressure studies can disclose new structural and optical phenomena. In this study, taking MoS2 as an example, we investigate the pressure confinement effect on monolayer MoS2 by in situ high pressure Raman and photoluminescence (PL) measurements. Our results reveal a structural deformation of monolayer MoS2 starting from 0.84 GPa, which is evidenced by the splitting of E(1)2g and A1g modes. A further compression leads to a transition from the 1H-MoS2 phase to a novel structure evidenced by the appearance of two new peaks located at 200 and 240 cm(-1). This is a distinct feature of monolayer MoS2 compared with bulk MoS2. The new structure is supposed to have a distorted unit with the S atoms slided within a single layer like that of metastable 1T'-MoS2. However, unlike the non-photoluminescent 1T'-MoS2 structure, our monolayer shows a remarkable PL peak and a pressure-induced blue shift up to 13.1 GPa. This pressure-dependent behavior might enable the development of novel devices with multiple phenomena involving the strong coupling of the mechanical, electrical and optical properties of layered nanomaterials.

  4. Noise spectroscopy of polymer transistors

    NASA Astrophysics Data System (ADS)

    Harsh, Rishav; Narayan, K. S.

    2015-11-01

    Noise studies constitute an important approach to study polymer based field effect transistors (FETs) from the perspective of disorder physics as well as device application. The current fluctuations in an all organic solution-processable FET in different regimes of operation (I-V) are measured and analyzed. The intrinsic transport noise is sizable and readily observed in the current time series measurements. The ensuing current spectrum (SI(f)) exhibits a typical 1/f characteristics. It is observed that this noise amplitude scales with respect to current bias and indicative of mobility as well as number fluctuations at dielectric-semiconductor interface. FETs with leakage (lossy) dielectric layer indicate characteristic noise spectrum features which can serve as a diagnostic tool to monitor device stability.

  5. Near-Field Thermal Transistor

    NASA Astrophysics Data System (ADS)

    Ben-Abdallah, Philippe; Biehs, Svend-Age

    2014-01-01

    Using a block of three separated solid elements, a thermal source and drain together with a gate made of an insulator-metal transition material exchanging near-field thermal radiation, we introduce a nanoscale analog of a field-effect transistor that is able to control the flow of heat exchanged by evanescent thermal photons between two bodies. By changing the gate temperature around its critical value, the heat flux exchanged between the hot body (source) and the cold body (drain) can be reversibly switched, amplified, and modulated by a tiny action on the gate. Such a device could find important applications in the domain of nanoscale thermal management and it opens up new perspectives concerning the development of contactless thermal circuits intended for information processing using the photon current rather than the electric current.

  6. Field-effect transistor improves electrometer amplifier

    NASA Technical Reports Server (NTRS)

    Munoz, R.

    1964-01-01

    An electrometer amplifier uses a field effect transistor to measure currents of low amperage. The circuit, developed as an ac amplifier, is used with an external filter which limits bandwidth to achieve optimum noise performance.

  7. Logic gates based on ion transistors.

    PubMed

    Tybrandt, Klas; Forchheimer, Robert; Berggren, Magnus

    2012-01-01

    Precise control over processing, transport and delivery of ionic and molecular signals is of great importance in numerous fields of life sciences. Integrated circuits based on ion transistors would be one approach to route and dispense complex chemical signal patterns to achieve such control. To date several types of ion transistors have been reported; however, only individual devices have so far been presented and most of them are not functional at physiological salt concentrations. Here we report integrated chemical logic gates based on ion bipolar junction transistors. Inverters and NAND gates of both npn type and complementary type are demonstrated. We find that complementary ion gates have higher gain and lower power consumption, as compared with the single transistor-type gates, which imitates the advantages of complementary logics found in conventional electronics. Ion inverters and NAND gates lay the groundwork for further development of solid-state chemical delivery circuits. PMID:22643898

  8. Ultra-stable oscillator with complementary transistors

    NASA Technical Reports Server (NTRS)

    Kleinberg, L. L. (Inventor)

    1974-01-01

    A high frequency oscillator, having both good short and long term stability, is formed by including a piezoelectric crystal in the base circuit of a first bi-polar transistor circuit, the bi-polar transistor itself operated below its transitional frequency and having its emitter load chosen so that the input impedance, looking into the base thereof, exhibits a negative resistance in parallel with a capacitive reactance. Combined with this basic circuit is an auxiliary, complementary, second bi-polar transistor circuit of the same form with the piezoelectric crystal being common to both circuits. By this configuration small changes in quiescent current are substantially cancelled by opposite variations in the second bi-polar transistor circuit, thereby achieving from the oscillator a signal having its frequency of oscillation stable over long time periods as well as short time periods.

  9. Logic gates based on ion transistors

    NASA Astrophysics Data System (ADS)

    Tybrandt, Klas; Forchheimer, Robert; Berggren, Magnus

    2012-05-01

    Precise control over processing, transport and delivery of ionic and molecular signals is of great importance in numerous fields of life sciences. Integrated circuits based on ion transistors would be one approach to route and dispense complex chemical signal patterns to achieve such control. To date several types of ion transistors have been reported; however, only individual devices have so far been presented and most of them are not functional at physiological salt concentrations. Here we report integrated chemical logic gates based on ion bipolar junction transistors. Inverters and NAND gates of both npn type and complementary type are demonstrated. We find that complementary ion gates have higher gain and lower power consumption, as compared with the single transistor-type gates, which imitates the advantages of complementary logics found in conventional electronics. Ion inverters and NAND gates lay the groundwork for further development of solid-state chemical delivery circuits.

  10. Dual role of monolayer MoS2 in enhanced photocatalytic performance of hybrid MoS2/SnO2 nanocomposite

    NASA Astrophysics Data System (ADS)

    Ding, Shuang-Shuang; Huang, Wei-Qing; Yang, Yin-Cai; Zhou, Bing-Xin; Hu, Wang-Yu; Long, Meng-Qiu; Peng, P.; Huang, Gui-Fang

    2016-05-01

    The enhanced photocatalytic performance of various MoS2-based nanomaterials has recently been observed, but the role of monolayer MoS2 is still not well elucidated at the electronic level. Herein, focusing on a model system, hybrid MoS2/SnO2 nanocomposite, we first present a theoretical elucidation of the dual role of monolayer MoS2 as a sensitizer and a co-catalyst by performing density functional theory calculations. It is demonstrated that a type-II, staggered, band alignment of ˜0.49 eV exists between monolayer MoS2 and SnO2 with the latter possessing the higher electron affinity, or work function, leading to the robust separation of photoexcited charge carriers between the two constituents. Under irradiation, the electrons are excited from Mo 4d orbitals to SnO2, thus enhancing the reduction activity of latter, indicating that the monolayer MoS2 is an effective sensitizer. Moreover, the Mo atoms, which are catalytically inert in isolated monolayer MoS2, turn into catalytic active sites, making the monolayer MoS2 to be a highly active co-catalyst in the composite. The dual role of monolayer MoS2 is expected to arise in other MoS2-semiconductor nanocomposites. The calculated absorption spectra can be rationalized by available experimental results. These findings provide theoretical evidence supporting the experimental reports and pave the way for developing highly efficient MoS2-based photocatalysts.

  11. Transistor package for high pressure applications

    NASA Technical Reports Server (NTRS)

    Zantos, P. J.

    1981-01-01

    TO63 transistor package can operate in hydraulic oil ar pressures of 200 psi or greater without leakage failure if it is reinforced by alumina disk brazed to cap and terminals. This inexpensive modification has been used successfully on power transistors in hydraulic circulating-pump assemblies for Space Shuttle orbiter and should be effective in other pressurized environments, such as in oil exploration equipment.

  12. Shaping Transistor Leads for Better Solder Joints

    NASA Technical Reports Server (NTRS)

    Mandel, H.; Dillon, J. D.

    1982-01-01

    Special lead-forming tool puts step in leads of microwave power transistors without damaging braze joints that fasten leads to package. Stepped leads are soldered to circuit boards more reliably than straight leads, and stress on brazes is relieved. Lead-forming hand-tool has two parts: a forming die and an actuator. Spring-loaded saddle is adjusted so that when transistor package is placed on it, leads rest on forming rails.

  13. Physical understanding of trends in current collapse with atomic layer deposited dielectrics in AlGaN/GaN MOS heterojunction FETs

    NASA Astrophysics Data System (ADS)

    Ramanan, Narayanan; Lee, Bongmook; Misra, Veena

    2016-03-01

    Many passivation dielectrics are pursued for suppressing current collapse due to trapping/detrapping of access-region surface traps in AlGaN/GaN based metal oxide semiconductor heterojuction field effect transistors (MOS-HFETs). The suppression of current collapse can potentially be achieved either by reducing the interaction of surface traps with the gate via surface leakage current reduction, or by eliminating surface traps that can interact with the gate. But, the latter is undesirable since a high density of surface donor traps is required to sustain a high 2D electron gas density at the AlGaN/GaN heterointerface and provide a low ON-resistance. This presents a practical trade-off wherein a passivation dielectric with the optimal surface trap characteristics and minimal surface leakage is to be chosen. In this work, we compare MOS-HFETs fabricated with popular ALD gate/passivation dielectrics like SiO2, Al2O3, HfO2 and HfAlO along with an additional thick plasma-enhanced chemical vapor deposition SiO2 passivation. It is found that after annealing in N2 at 700 °C, the stack containing ALD HfAlO provides a combination of low surface leakage and a high density of shallow donor traps. Physics-based TCAD simulations confirm that this combination of properties helps quick de-trapping and minimal current collapse along with a low ON resistance.

  14. Comparing the Ocean Color Measurements Between MOS and SeaWiFS: A Vicarious Intercalibration Approach for MOS

    NASA Technical Reports Server (NTRS)

    Wang, Menghua; Franz, Bryan A.

    1998-01-01

    One of the primary goals of the NASA Sensor Intercomparison and Merger for Biological and Interdisciplinary Oceanic Studies (SIMBIOS) project is to develop methods for meaningful comparison and possible merging of data products from multiple ocean color missions. The Modular Optoelectronic Scanner (MOS) is a German instrument that was launched in the spring of 1996 on the Indian IRS-P3 satellite. With the successful launch of NASA's Sea-viewing Wide Field-of-view Sensor (SeaWiFS) in the summer of 1997, there are now two ocean color missions in concurrent operation and there is interest within the scientific community to compare data from these two sensors. In this paper, we describe our efforts to retrieve ocean optical properties from both SeaWiFS and MOS using consistent methods. We first briefly review the atmospheric correction, which removes more than 90% of the observed radiances in the visible, and then describe how the atmospheric correction algorithm used for the SeaWiFS data can be modified for application to other ocean color sensors. Next, since the retrieved water-leaving radiances in the visible between MOS and SeaWiFS are significantly different, we developed a vicarious intercalibration method to recalibrate the MOS spectral bands based on the optical properties of the ocean and atmosphere derived from the coincident SeaWiFS measurements. We present and discuss the MOS retrieved ocean optical properties before and after the vicarious calibration, and demonstrate the efficacy of this approach. We show that it is possible and efficient to vicariously intercalibrate sensors between one and another.

  15. Sub-10 nm carbon nanotube transistor.

    PubMed

    Franklin, Aaron D; Luisier, Mathieu; Han, Shu-Jen; Tulevski, George; Breslin, Chris M; Gignac, Lynne; Lundstrom, Mark S; Haensch, Wilfried

    2012-02-01

    Although carbon nanotube (CNT) transistors have been promoted for years as a replacement for silicon technology, there is limited theoretical work and no experimental reports on how nanotubes will perform at sub-10 nm channel lengths. In this manuscript, we demonstrate the first sub-10 nm CNT transistor, which is shown to outperform the best competing silicon devices with more than four times the diameter-normalized current density (2.41 mA/μm) at a low operating voltage of 0.5 V. The nanotube transistor exhibits an impressively small inverse subthreshold slope of 94 mV/decade-nearly half of the value expected from a previous theoretical study. Numerical simulations show the critical role of the metal-CNT contacts in determining the performance of sub-10 nm channel length transistors, signifying the need for more accurate theoretical modeling of transport between the metal and nanotube. The superior low-voltage performance of the sub-10 nm CNT transistor proves the viability of nanotubes for consideration in future aggressively scaled transistor technologies.

  16. Enhanced two dimensional electron gas transport characteristics in Al{sub 2}O{sub 3}/AlInN/GaN metal-oxide-semiconductor high-electron-mobility transistors on Si substrate

    SciTech Connect

    Freedsman, J. J. Watanabe, A.; Urayama, Y.; Egawa, T.

    2015-09-07

    The authors report on Al{sub 2}O{sub 3}/Al{sub 0.85}In{sub 0.15}N/GaN Metal-Oxide-Semiconductor High-Electron-Mobility Transistor (MOS-HEMT) on Si fabricated by using atomic layer deposited Al{sub 2}O{sub 3} as gate insulator and passivation layer. The MOS-HEMT with the gate length of 2 μm exhibits excellent direct-current (dc) characteristics with a drain current maximum of 1270 mA/mm at a gate bias of 3 V and an off-state breakdown voltage of 180 V for a gate-drain spacing of 4 μm. Also, the 1 μm-gate MOS-HEMT shows good radio-frequency (rf) response such as current gain and maximum oscillation cut-off frequencies of 10 and 34 GHz, respectively. The capacitance-voltage characteristics at 1 MHz revealed significant increase in two-dimensional electron gas (2DEG) density for the MOS-HEMT compared to conventional Schottky barrier HEMTs. Analyses using drain-source conductivity measurements showed improvements in 2DEG transport characteristics for the MOS-HEMT. The enhancements in dc and rf performances of the Al{sub 2}O{sub 3}/Al{sub 0.85}In{sub 0.15}N/GaN MOS-HEMT are attributed to the improvements in 2DEG characteristics.

  17. Stability and Electronic Properties of Hydrogenated MoS2 Monolayer: A First-Principles Study.

    PubMed

    Zhang, Weibin; Zhang, Zhijun; Yang, Woochul

    2015-10-01

    First-principles total energy studies are used to investigate the stability of hydrogenated MoS2 monolayer (MoS2-Hx) (x = 1-8), which is a compound with different numbers of H atoms adsorbed on the MoS2 surface. Energetically, the S-top side of the MoS2 is found to be the most favorable for H-adsorption. H2S and graphene are well-known to be stable, and MoS2-Hx is predicted to be even more stable because its binding energy is lower than that of H2S and its formation energy and adsorption energy are lower than those of graphene. The analysis of the electronic density distribution and the orbital hybrid also shows that MoS2-Hx forms stable structures. In addition, the influence of the number of the adsorbed H-atoms in the MoS2-Hx on the electronic structure of the compound is also investigated. The MoS2-Hx band structure exhibits a dispersion and the MoS2-Hx band gap gradually decreases from 1.72 eV to 0 eV as the number of adsorbed H atoms increases. The corresponding work function increases as a result of the strengthening of the dipole moment formed between the H atoms that are adsorbed and the hydrogenated MoS2.

  18. Oxidation of atomically thin MoS2 on SiO2

    NASA Astrophysics Data System (ADS)

    Yamamoto, Mahito; Cullen, William; Einstein, Theodore; Fuhrer, Michael

    2013-03-01

    Surface oxidation of MoS2 markedly affects its electronic, optical, and tribological properties. However, oxidative reactivity of atomically thin MoS2 has yet to be addressed. Here, we investigate oxidation of atomic layers of MoS2 using atomic force microscopy and Raman spectroscopy. MoS2 is mechanically exfoliated onto SiO2 and oxidized in Ar/O2 or Ar/O3 (ozone) at 100-450 °C. MoS2 is much more reactive to O2 than an analogous atomic membrane of graphene and monolayer MoS2 is completely etched very rapidly upon O2 treatment above 300 °C. Thicker MoS2 (> 15 nm) transforms into MoO3 after oxidation at 400 °C, which is confirmed by a Raman peak at 820 cm-1. However, few-layer MoS2 oxidized below 400 °C exhibits no MoO3 Raman mode but etch pits are formed, similar to graphene. We find atomic layers of MoS2 shows larger reactivity to O3 than to O2 and monolayer MoS2 transforms chemically upon O3 treatment even below 100 °C. Work supported by the U. of Maryland NSF-MRSEC under Grant No. DMR 05-20741.

  19. Enhanced second harmonic generation of MoS2 layers on a thin gold film.

    PubMed

    Zeng, Jianhua; Yuan, Maohui; Yuan, Weiguang; Dai, Qiaofeng; Fan, Haihua; Lan, Sheng; Tie, Shaolong

    2015-08-28

    The linear and nonlinear optical properties of thin MoS2 layers exfoliated on an Au/SiO2 substrate were investigated both numerically and experimentally. It was found that the MoS2 layers with different thicknesses exhibited different colors on the gold film. The reflection spectra of the MoS2 layers with different thicknesses were calculated by using the finite-difference time-domain technique and the corresponding chromaticity coordinates were derived. The electric field enhancement factors at both the fundamental light and the second harmonic were calculated and the enhancement factors for second harmonic generation (SHG) were estimated for the MoS2 layers with different thicknesses. Different from the MoS2 layers on a SiO2/Si substrate where the maximum SHG was observed in the single-layer MoS2, the maximum SHG was achieved in the 17 nm-thick MoS2 layer on the Au/SiO2 substrate. As compared with the MoS2 layers on the SiO2/Si substrate, a significant enhancement in SHG was found for the MoS2 layers on the Au/SiO2 substrate due to the strong localization of the electric field. More interestingly, it was demonstrated experimentally that optical data storage can be realized by modifying the SHG intensity of a MoS2 layer through thinning its thickness.

  20. Hierarchical MoS2-rGO nanosheets with high MoS2 loading with enhanced electro-catalytic performance

    NASA Astrophysics Data System (ADS)

    Zhou, Jing; Xiao, Han; Zhou, Bowen; Huang, Feifan; Zhou, Shoubin; Xiao, Wei; Wang, Dihua

    2015-12-01

    Incorporation of high-loading redox-active materials with small amounts of graphene is a general protocol to achieve high-performance catalysts. Herein, hierarchical MoS2-reduced graphene oxide nanosheet (denoted as MoS2-rGO nanosheets) hybrids with a loading of MoS2 as high as 94 wt% are synthesized. The obtained hierarchical MoS2-rGO nanosheets simultaneously integrate the structural and compositional design rationales for high-efficiency and durable electrocatalysts based on high weight ratio of MoS2 in hybrid composite, highly stable/conducting rGO, well-dispersed two-dimensional ultrathin MoS2 nanosheets, more exposed edge sites and micro/nano hierarchical structure. When evaluated as electrocatalysts for hydrogen evolution and oxygen reduction reactions, the hierarchical MoS2-rGO nanosheets demonstrates enhanced activity and excellent stability, promising their applications in MoS2 based electrochemical, photo-catalytic and photo-elecrocatalytic cells.

  1. Interface modification of MoS2/SiO2 leading to conversion of conduction type of MoS2

    NASA Astrophysics Data System (ADS)

    Lin, Yow-Jon; Su, Ting-Hong

    2016-11-01

    Few-layer MoS2 prepared by the chemical vapor deposition method is deposited on SiO2 samples with/without sulfide treatment in order to experimentally study the mechanism of conduction-type conversion in MoS2. The MoS2 thin film deposited on a SiO2 substrate with sulfide treatment shows n-type behavior, whereas the MoS2 thin film deposited on a SiO2 substrate without sulfide treatment exhibits p-type behavior. Experimental identification confirms that n-type conversion is due to a combined effect of the broken Sisbnd O bonds and the formation of Sisbnd S bonds at the SiO2 surface that results in the removal of oxygen dangling bonds and a change in the MoS2sbnd SiO2 interaction.

  2. Fabrication and independent control of patterned polymer gate for a few-layer WSe2 field-effect transistor

    NASA Astrophysics Data System (ADS)

    Hong, Sung Ju; Park, Min; Kang, Hojin; Lee, Minwoo; Jeong, Dae Hong; Park, Yung Woo

    2016-08-01

    We report the fabrication of a patterned polymer electrolyte for a two-dimensional (2D) semiconductor, few-layer tungsten diselenide (WSe2) field-effect transistor (FET). We expose an electron-beam in a desirable region to form the patterned structure. The WSe2 FET acts as a p-type semiconductor in both bare and polymer-covered devices. We observe a highly efficient gating effect in the polymer-patterned device with independent gate control. The patterned polymer gate operates successfully in a molybdenum disulfide (MoS2) FET, indicating the potential for general applications to 2D semiconductors. The results of this study can contribute to large-scale integration and better flexibility in transition metal dichalcogenide (TMD)-based electronics.

  3. Covalent Modification of MoS2 with Poly(N-vinylcarbazole) for Solid-State Broadband Optical Limiters.

    PubMed

    Cheng, Hongxia; Dong, Ningning; Bai, Ting; Song, Yi; Wang, Jun; Qin, Yuanhao; Zhang, Bin; Chen, Yu

    2016-03-18

    New soluble MoS2 nanosheets covalently functionalized with poly(N-vinylcarbazole) (MoS2-PVK) were in situ synthesized for the first time. In contrast to MoS2 and MoS2 /PVK blends, both the solution of MoS2 -PVK in DMF and MoS2-PVK/poly(methyl methacrylate) (PMMA) film show superior nonlinear optical and optical limiting responses. The MoS2-PVK/PMMA film shows the largest nonlinear coefficients (βeff) of about 917 cm GW(-1) at λ=532 nm (cf. 100.69 cm GW(-1) for MoS2/PMMA and 125.12 cm GW(-1) for MoS2/PVK/PMMA) and about 461 cm GW(-1) at λ=1064 nm (cf. -48.92 cm GW(-1) for MoS2/PMMA and 147.56 cm GW(-1) for MoS2/PVK/PMMA). A larger optical limiting effect, with thresholds of about 0.3 GW cm(-2) at λ=532 nm and about 0.5 GW cm(-2) at λ=1064 nm, was also achieved from the MoS2-PVK/PMMA film. These values are among the highest reported for MoS2-based nonlinear optical materials. These results show that covalent functionalization of MoS2 with polymers is an effective way to improve nonlinear optical responses for efficient optical limiting devices.

  4. Analyses of Transistor Punchthrough Failures

    NASA Technical Reports Server (NTRS)

    Nicolas, David P.

    1999-01-01

    The failure of two transistors in the Altitude Switch Assembly for the Solid Rocket Booster followed by two additional failures a year later presented a challenge to failure analysts. These devices had successfully worked for many years on numerous missions. There was no history of failures with this type of device. Extensive checks of the test procedures gave no indication for a source of the cause. The devices were manufactured more than twenty years ago and failure information on this lot date code was not readily available. External visual exam, radiography, PEID, and leak testing were performed with nominal results Electrical testing indicated nearly identical base-emitter and base-collector characteristics (both forward and reverse) with a low resistance short emitter to collector. These characteristics are indicative of a classic failure mechanism called punchthrough. In failure analysis punchthrough refers to an condition where a relatively low voltage pulse causes the device to conduct very hard producing localized areas of thermal runaway or "hot spots". At one or more of these hot spots, the excessive currents melt the silicon. Heavily doped emitter material diffuses through the base region to the collector forming a diffusion pipe shorting the emitter to base to collector. Upon cooling, an alloy junction forms between the pipe and the base region. Generally, the hot spot (punch-through site) is under the bond and no surface artifact is visible. The devices were delidded and the internal structures were examined microscopically. The gold emitter lead was melted on one device, but others had anomalies in the metallization around the in-tact emitter bonds. The SEM examination confirmed some anomalies to be cosmetic defects while other anomalies were artifacts of the punchthrough site. Subsequent to these analyses, the contractor determined that some irregular testing procedures occurred at the time of the failures heretofore unreported. These testing

  5. MoS2 Heterojunctions by Thickness Modulation

    DOE PAGES

    Tosun, Mahmut; Fu, Deyi; Desai, Sujay B.; Ko, Changhyun; Seuk Kang, Jeong; Lien, Der-Hsien; Najmzadeh, Mohammad; Tongay, Sefaattin; Wu, Junqiao; Javey, Ali

    2015-06-30

    In this work, we report lateral heterojunction formation in as-exfoliated MoS2 flakes by thickness modulation. Kelvin probe force microscopy is used to map the surface potential at the monolayer-multilayer heterojunction, and consequently the conduction band offset is extracted. Scanning photocurrent microscopy is performed to investigate the spatial photocurrent response along the length of the device including the source and the drain contacts as well as the monolayer-multilayer junction. The peak photocurrent is measured at the monolayer-multilayer interface, which is attributed to the formation of a type-I heterojunction. Finally, the work presents experimental and theoretical understanding of the band alignment andmore » photoresponse of thickness modulated MoS2 junctions with important implications for exploring novel optoelectronic devices.« less

  6. Analysis of displacement damage effects on MOS capacitors

    NASA Astrophysics Data System (ADS)

    Fernández-Martínez, P.; Palomo, F. R.; Hidalgo, S.; Fleta, C.; Campabadal, F.; Flores, D.

    2013-12-01

    Displacement damage effect on MOS capacitors is analyzed in this work with the aid of TCAD simulations. A noticeable capacitance reduction in the accumulation mode is observed in the High Frequency C-V characteristic curve after a 24 GeV proton irradiation. This effect is clearly distinguishable from ionizing damage effects, otherwise negligible under the specific conditions of the experiment. The capacitance reduction is identified with the increase of the substrate resistivity, due to the modification of its effective doping concentration. Supported on a well-established traps model, the expected displacement damage defects are simulated as a function of the fluence, allowing the identification of donor trap levels as the responsible of the phenomenon for p-type substrate MOS capacitors.

  7. Further study of inversion layer MOS solar cells

    NASA Technical Reports Server (NTRS)

    Ho, Fat Duen

    1987-01-01

    A group of inversion layer MOS solar cells has been fabricated. The highest value of open-circuit voltage obtained for the cells is 0.568V. One of the cells has produced a short-circuit current of 79.6 mA and an open-circuit voltage of 0.54V. It is estimated that the actual area AMO efficiency of this cell is 6.6 percent with an assumed value of 0.75 for its fill factor. Efforts made for fabricating an IL/MOS cell with reasonable efficiencies are reported. Future work for 4 sq cm IL cells and 25 sq cm IL cells is discussed.

  8. Anomalous Random Telegraph Signal Extractions from a Very Large Number of n-Metal Oxide Semiconductor Field-Effect Transistors Using Test Element Groups with 0.47 Hz-3.0 MHz Sampling Frequency

    NASA Astrophysics Data System (ADS)

    Abe, Kenichi; Fujisawa, Takafumi; Teramoto, Akinobu; Watabe, Shunichi; Sugawa, Shigetoshi; Ohmi, Tadahiro

    2009-04-01

    Random telegraph signal (RTS) noise in small gate area metal oxide semiconductor (MOS) transistors occurs frequently and causes serious problems in the field of flash memories and complementary MOS (CMOS) image sensors. The trap in the gate insulator, which is considered the origin of RTS, varies widely in terms of spatial location and energy level, so that RTS characteristics including the amplitude and time constants have large variability by nature and statistical analysis of RTS should become indispensable. In this paper, we propose a high-speed RTS measurement system with a newly developed test circuit and discuss the drain current and temperature dependences of RTS amplitude distributions. Moreover, we expand the sampling frequency between 0.47 Hz-3.0 MHz and the observation length up to about 4 h and can thereby observe some anomalous RTSs such as ones with long time constants, ones generated abruptly, and ones disappearing.

  9. Microwave irradiation induced band gap tuning of MoS2-TiO2 nanocomposites

    NASA Astrophysics Data System (ADS)

    Shakya, Jyoti; Mohanty, T.

    2016-05-01

    The MoS2-TiO2 nanocomposites have been synthesized by sol-gel method and characterized by different microscopic and spectroscopic techniques. The crystallinity of these nanocomposites has been confirmed by X-ray diffraction (XRD) analysis. The Raman spectrum of MoS2-TiO2 nanocomposites consists of three distinct peaks (E1 g, E1 2g and A1g) which are associated with TiO2 and MoS2. The morphological study is carried out by scanning electron microscope. The effect of microwave irradiation on the band gap of MoS2-TiO2 nanocomposites has been investigated; it is observed that the microwave irradiation causes decrease in the band gap of MoS2-TiO2 nanocomposites. The microwave treated MoS2-TiO2 thin films offers a novel process route in treating thin films for commercial applications.

  10. Synthesis and characterization of vertically standing MoS2 nanosheets.

    PubMed

    Li, Han; Wu, Huaqiang; Yuan, Shuoguo; Qian, He

    2016-01-01

    Molybdenum disulfide (MoS2) has been attracting much attentions due to its excellent electrical and optical properties. We report here the synthesis of large-scale and uniform MoS2 nanosheets with vertically standing morphology using chemical vapor deposition method. TEM observations clearly reveal the growth mechanism of these vertical structures. It is suggested that the vertical structures are caused by the compression and extrusion between MoS2 islands. More importantly, the vertical morphology of two dimensional (2D) materials hold many promising potential applications. We demonstrate here the as-synthesized vertically standing MoS2 nanosheets could be used for hydrogen evolution reaction, where the exchange current density is about 70 times of bulk MoS2. The field emission performance of vertically standing MoS2 were also improved due to the abundantly exposed edges. PMID:26888690

  11. Synthesis and characterization of vertically standing MoS2 nanosheets

    NASA Astrophysics Data System (ADS)

    Li, Han; Wu, Huaqiang; Yuan, Shuoguo; Qian, He

    2016-02-01

    Molybdenum disulfide (MoS2) has been attracting much attentions due to its excellent electrical and optical properties. We report here the synthesis of large-scale and uniform MoS2 nanosheets with vertically standing morphology using chemical vapor deposition method. TEM observations clearly reveal the growth mechanism of these vertical structures. It is suggested that the vertical structures are caused by the compression and extrusion between MoS2 islands. More importantly, the vertical morphology of two dimensional (2D) materials hold many promising potential applications. We demonstrate here the as-synthesized vertically standing MoS2 nanosheets could be used for hydrogen evolution reaction, where the exchange current density is about 70 times of bulk MoS2. The field emission performance of vertically standing MoS2 were also improved due to the abundantly exposed edges.

  12. Growth of MoS2 Layers by Two-Step Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Sheu, An-Di

    Monolayer molybdenum disulfide (MoS2), a two-dimensional (2D) crystal with a direct bandgap, is a promising candidate for nano electronic devices, energy storage, and photocatalysts. People are researching for large-area single-layer MoS2 growth. In my work, I investigated the growth of monolayer MoS2 on SiO2/Si substrate by chemical vapor deposition (CVD). Using sulfur and molybdenum trioxide (MoO3) as precursors to grow 2D MoS2 in the tube furnace CVD system. As part of my thesis, I carried out several growth experiments while varying the deposition parameters. The as-grown samples are characterized using optical, scanning electron, and atomic force microscopes and Raman spectroscopy. I have also developed a two-step approach to grow MoS2 layers. This new approach has great potential to grow large-area single-layer MoS2.

  13. Synthesis and characterization of vertically standing MoS2 nanosheets

    PubMed Central

    Li, Han; Wu, Huaqiang; Yuan, Shuoguo; Qian, He

    2016-01-01

    Molybdenum disulfide (MoS2) has been attracting much attentions due to its excellent electrical and optical properties. We report here the synthesis of large-scale and uniform MoS2 nanosheets with vertically standing morphology using chemical vapor deposition method. TEM observations clearly reveal the growth mechanism of these vertical structures. It is suggested that the vertical structures are caused by the compression and extrusion between MoS2 islands. More importantly, the vertical morphology of two dimensional (2D) materials hold many promising potential applications. We demonstrate here the as-synthesized vertically standing MoS2 nanosheets could be used for hydrogen evolution reaction, where the exchange current density is about 70 times of bulk MoS2. The field emission performance of vertically standing MoS2 were also improved due to the abundantly exposed edges. PMID:26888690

  14. MOS1 epigenetically regulates the expression of plant Resistance gene SNC1

    PubMed Central

    Li, Yingzhong; Dong, Oliver X; Johnson, Kaeli; Li, Xin

    2011-01-01

    MOS1 (MODIFIER OF snc1) was identified through a genetic screen for suppressors of snc1, an autoimmune mutant caused by a gain-of-function mutation in a TIR-NB-LRR-type Resistance gene. Loss of MOS1 function completely suppresses snc1-mediated autoimmunity. The MOS1 protein contains a BAT2 domain and regulates the expression of SNC1 in a locus-specific manner, but the mechanism on how MOS1 epigenetically regulates SNC1 gene expression is unclear. Here, we report the gene expression pattern and subcellular localization of MOS1. In addition, we analyze and discuss the roles of DNA and histone methylation in mos1-mediated suppression of SNC1 expression. PMID:21350329

  15. Subthreshold transport in mono- and multilayered MoS2 FETs

    NASA Astrophysics Data System (ADS)

    Nan, Fang; Nagashio, Kosuke; Toriumi, Akira

    2015-06-01

    The subthreshold transport properties in exfoliated MoS2 FETs are reported. The temperature dependence of subthreshold characteristics in multilayered MoS2 FETs behaves in the same way as that of conventional semiconductors, while conductance fluctuations and random telegraphic signals in the subthreshold region of Ids-Vgs characteristics were observed much more frequently in monolayered FETs than in multilayered ones. This fact is understandable from the viewpoint of a three-dimensional to two-dimensional percolation transport process in MoS2 with defects, which should be located in the MoS2 layer or at the MoS2/SiO2 interface. Thus, it is suggested that few-layered MoS2 FETs are more viable for practical applications from the viewpoint of suppressing defect-induced current fluctuations.

  16. Bending response of single layer MoS2.

    PubMed

    Xiong, Si; Cao, Guoxin

    2016-03-11

    Using molecular mechanics (or dynamics) simulations, three different approaches, including the targeted molecular mechanics, four-point bending and nanotube methods, are employed to investigate the bending response of single layer MoS2 (SLMoS2), among which four-point bending is the most accurate approach to determine the bending stiffness according to the continuum theory. It is found that when the bending curvature radius is large enough (e.g. >4 nm), three approaches will give the same bending stiffness of SLMoS2 and the bending behavior is isotropic for SLMoS2, whereas the nanotube method with small tubes (e.g. <4 nm) cannot give the correct bending stiffness. Compared with the reported result from the MoS2 nanotube calculated by density functional theory, the revised Stillinger-Weber (SW) and reactive empirical bond-order (REBO) potentials can give the reasonable bending stiffness of SLMoS2 (8.7-13.4 eV) as well as the effective deformed conformation. In addition, since the Mo-S bond deformation of SLMoS2 under bending is similar to that under in-plane tension/compression, the continuum bending theory can quite accurately predict the bending stiffness of SLMoS2 if a reasonable thickness of SLMoS2 is given. For SLMoS2, the reasonable thickness should be larger than the distance between its two S atomic planes and lower than the distance between two Mo atomic planes of bulk MoS2 crystal, e.g. 0.375-0.445 nm. PMID:26861930

  17. Unusual reactivity of MoS2 nanosheets

    NASA Astrophysics Data System (ADS)

    Mondal, Biswajit; Som, Anirban; Chakraborty, Indranath; Baksi, Ananya; Sarkar, Depanjan; Pradeep, Thalappil

    2016-05-01

    The reactivity of the 2D nanosheets of MoS2 with silver ions in solution, leading to their spontaneous morphological and chemical transformations, is reported. This unique reactivity of the nanoscale form of MoS2 was in stark contrast to its bulk counterpart. While the gradual morphological transformation involving several steps has been captured with an electron microscope, precise chemical identification of the species involved was achieved by electron spectroscopy and mass spectrometry. The energetics of the system investigated supports the observed chemical transformation. The reaction with mercury and gold ions shows similar and dissimilar reaction products, respectively and points to the stability of the metal-sulphur bond in determining the chemical compositions of the final products.The reactivity of the 2D nanosheets of MoS2 with silver ions in solution, leading to their spontaneous morphological and chemical transformations, is reported. This unique reactivity of the nanoscale form of MoS2 was in stark contrast to its bulk counterpart. While the gradual morphological transformation involving several steps has been captured with an electron microscope, precise chemical identification of the species involved was achieved by electron spectroscopy and mass spectrometry. The energetics of the system investigated supports the observed chemical transformation. The reaction with mercury and gold ions shows similar and dissimilar reaction products, respectively and points to the stability of the metal-sulphur bond in determining the chemical compositions of the final products. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00878j

  18. Physics and chemistry of MoS2 intercalation compounds

    NASA Technical Reports Server (NTRS)

    Woollam, J. A.; Somoano, R. B.

    1977-01-01

    An investigation is made of the physics and chemistry of MoS2 intercalation compounds. These compounds may be separated into two groups according to their stoichiometry, structure and superconducting properties. The first group consists of Na, Ca, and Sr intercalates, and the second group consists of K, Rb, and Cs intercalates. Particular attention is given to the structure of the electronic energy band and to the normal state and superconducting properties of these compounds.

  19. Time-dependent MOS breakdown. [of Na contaminated capacitors

    NASA Technical Reports Server (NTRS)

    Li, S. P.; Bates, E. T.; Maserjian, J.

    1976-01-01

    A general model for time-dependent breakdown in metal-oxide-silicon (MOS) structures is developed and related to experimental measurements on samples deliberately contaminated with Na. A statistical method is used for measuring the breakdown probability as a function of log time and applied field. It is shown that three time regions of breakdown can be explained respectively in terms of silicon surface defects, ion emission from the metal interface, and lateral ion diffusion at the silicon interface.

  20. Indium foil with beryllia washer improves transistor heat dissipation

    NASA Technical Reports Server (NTRS)

    Hilliard, J.; John, J. E. A.

    1964-01-01

    Indium foil, used as an interface material in transistor mountings, greatly reduces the thermal resistance of beryllia washers. This method improves the heat dissipation of power transistors in a vacuum environment.

  1. Field effect transistors used as voltage controlled resistors

    NASA Technical Reports Server (NTRS)

    1964-01-01

    Two new methods of incorporating field effect transistors into circuit designs have resulted in linear response of this type transistor over a wide range of controlled voltage levels. This increases its usefulness as a voltage-controlled resistor.

  2. Ambipolar phosphorene field effect transistor.

    PubMed

    Das, Saptarshi; Demarteau, Marcel; Roelofs, Andreas

    2014-11-25

    In this article, we demonstrate enhanced electron and hole transport in few-layer phosphorene field effect transistors (FETs) using titanium as the source/drain contact electrode and 20 nm SiO2 as the back gate dielectric. The field effect mobility values were extracted to be ∼38 cm(2)/Vs for electrons and ∼172 cm(2)/Vs for the holes. On the basis of our experimental data, we also comprehensively discuss how the contact resistances arising due to the Schottky barriers at the source and the drain end effect the different regime of the device characteristics and ultimately limit the ON state performance. We also propose and implement a novel technique for extracting the transport gap as well as the Schottky barrier height at the metal-phosphorene contact interface from the ambipolar transfer characteristics of the phosphorene FETs. This robust technique is applicable to any ultrathin body semiconductor which demonstrates symmetric ambipolar conduction. Finally, we demonstrate a high gain, high noise margin, chemical doping free, and fully complementary logic inverter based on ambipolar phosphorene FETs.

  3. Graphene nanopore field effect transistors

    SciTech Connect

    Qiu, Wanzhi; Skafidas, Efstratios

    2014-07-14

    Graphene holds great promise for replacing conventional Si material in field effect transistors (FETs) due to its high carrier mobility. Previously proposed graphene FETs either suffer from low ON-state current resulting from constrained channel width or require complex fabrication processes for edge-defecting or doping. Here, we propose an alternative graphene FET structure created on intrinsic metallic armchair-edged graphene nanoribbons with uniform width, where the channel region is made semiconducting by drilling a pore in the interior, and the two ends of the nanoribbon act naturally as connecting electrodes. The proposed GNP-FETs have high ON-state currents due to seamless atomic interface between the channel and electrodes and are able to be created with arbitrarily wide ribbons. In addition, the performance of GNP-FETs can be tuned by varying pore size and ribbon width. As a result, their performance and fabrication process are more predictable and controllable in comparison to schemes based on edge-defects and doping. Using first-principle transport calculations, we show that GNP-FETs can achieve competitive leakage current of ∼70 pA, subthreshold swing of ∼60 mV/decade, and significantly improved On/Off current ratios on the order of 10{sup 5} as compared with other forms of graphene FETs.

  4. A correlated nickelate synaptic transistor.

    PubMed

    Shi, Jian; Ha, Sieu D; Zhou, You; Schoofs, Frank; Ramanathan, Shriram

    2013-01-01

    Inspired by biological neural systems, neuromorphic devices may open up new computing paradigms to explore cognition, learning and limits of parallel computation. Here we report the demonstration of a synaptic transistor with SmNiO₃, a correlated electron system with insulator-metal transition temperature at 130°C in bulk form. Non-volatile resistance and synaptic multilevel analogue states are demonstrated by control over composition in ionic liquid-gated devices on silicon platforms. The extent of the resistance modulation can be dramatically controlled by the film microstructure. By simulating the time difference between postneuron and preneuron spikes as the input parameter of a gate bias voltage pulse, synaptic spike-timing-dependent plasticity learning behaviour is realized. The extreme sensitivity of electrical properties to defects in correlated oxides may make them a particularly suitable class of materials to realize artificial biological circuits that can be operated at and above room temperature and seamlessly integrated into conventional electronic circuits. PMID:24177330

  5. Radiation damage in MOS integrated circuits, Part 1

    NASA Technical Reports Server (NTRS)

    Danchenko, V.

    1971-01-01

    Complementary and p-channel MOS integrated circuits made by four commercial manufacturers were investigated for sensitivity to radiation environment. The circuits were irradiated with 1.5 MeV electrons. The results are given for electrons and for the Co-60 gamma radiation equivalent. The data are presented in terms of shifts in the threshold potentials and changes in transconductances and leakages. Gate biases of -10V, +10V and zero volts were applied to individual MOS units during irradiation. It was found that, in most of circuits of complementary MOS technologies, noticable changes due to radiation appear first as increased leakage in n-channel MOSFETs somewhat before a total integrated dose 10 to the 12th power electrons/sg cm is reached. The inability of p-channel MOSFETs to turn on sets in at about 10 to the 13th power electrons/sq cm. Of the circuits tested, an RCA A-series circuit was the most radiation resistant sample.

  6. Capturing Ion-Solid Interactions with MOS structures

    NASA Astrophysics Data System (ADS)

    Shyam, R.; Harrell, W. R.; Harriss, J. E.; Sosolik, C. E.

    2012-02-01

    We have fabricated metal-oxide-semiconductor (MOS) devices for a study of implantation rates and damage resulting from low energy ion-solid impacts. Specifically, we seek to capture ion irradiation effects on oxides by exposing as-grown SiO2 layers (50 nm to 200 nm) to incident beams of alkali ions with energies in the range of 100 eV to 10 keV. The oxide is analyzed post exposure by encapsulating the irradiated region under a top metallic contact or within a finished MOS device. Characterization of the resulting ion-modified MOS device involves the standard techniques of room temperature and bias-dependent capacitance-voltage (C-V) measurements. The C-V results reveal alkali ion-induced changes in the flatband voltage of irradiated devices which can be used to extract both the range and implantation probabilities of the ions. Biased C-V measurements are utilized to confirm the concentration or dosage of ions in the oxide. A triangular voltage sweep (TVS) measurement at elevated temperatures also reveals the total ionic space charge in the oxide and can be used to extract a mobility for the ions as they pass through the damaged oxide. Comparisons of these measurements to standard device models as well as to ion range calculations in the oxide are presented.

  7. Monolayer MoS2 self-switching diodes

    NASA Astrophysics Data System (ADS)

    Al-Dirini, Feras; Hossain, Faruque M.; Mohammed, Mahmood A.; Hossain, Md Sharafat; Nirmalathas, Ampalavanapillai; Skafidas, Efstratios

    2016-01-01

    This paper presents a new molybdenum disulphide (MoS2) nanodevice that acts as a two-terminal field-effect rectifier. The device is an atomically-thin two-dimensional self-switching diode (SSD) that can be realized within a single MoS2 monolayer with very minimal process steps. Quantum simulation results are presented confirming the device's operation as a diode and showing strong non-linear I-V characteristics. Interestingly, the device shows p-type behavior, in which conduction is dominated by holes as majority charge carriers and the flow of reverse current is enhanced, while the flow of forward current is suppressed, in contrast to monolayer graphene SSDs, which behave as n-type devices. The presence of a large bandgap in monolayer MoS2 results in strong control over the channel, showing complete channel pinch-off in forward conduction, which was confirmed with transmission pathways plots. The device exhibited large leakage tunnelling current through the insulating trenches, which may have been due to the lack of passivation; nevertheless, reverse current remained to be 6 times higher than forward current, showing strong rectification. The effect of p-type substitutional channel doping of sulphur with phosphorus was investigated and showed that it greatly enhances the performance of the device, increasing the reverse-to-forward current rectification ratio more than an order of magnitude, up to a value of 70.

  8. Magnetic field effects on superconductivity in alkali metal intercalates of MoS2

    NASA Technical Reports Server (NTRS)

    Woollam, J. A.; Flood, D. J.; Wagoner, D. E.; Somoano, R. B.; Rembaum, A.

    1972-01-01

    The effects of a magnetic field on the superconducting transition in MoS2 intercalated with potassium and sodium were studied. It was found that the potassium intercalated MoS2 has better properties in a magnetic field. In zero magnetic field the transition to superconductivity begins near 6.4 K. Diagrams of the basic circuitry for superconducting transition studies, and charts showing critical magnetic field versus critical temperature for the intercalated MoS2 are included.

  9. MoS2 nanolayers grown on carbon nanotubes: an advanced reinforcement for epoxy composites.

    PubMed

    Zhou, Keqing; Liu, Jiajia; Shi, Yongqian; Jiang, Saihua; Wang, Dong; Hu, Yuan; Gui, Zhou

    2015-03-25

    In the present study, carbon nanotubes (CNTs) wrapped with MoS2 nanolayers (MoS2-CNTs) were facilely synthesized to obtain advanced hybrids. The structure of the MoS2-CNT hybrids was characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy measurements. Subsequently, the MoS2-CNT hybrids were incorporated into EP for reducing fire hazards. Compared with pristine CNTs, MoS2-CNT hybrids showed good dispersion in EP matrix and no obvious aggregation of CNTs was observed. The obtained nanocomposites exhibited significant improvements in thermal properties, flame retardancy and mechanical properties, compared with those of neat EP and composites with a single CNT or MoS2. With the incorporation of 2.0 wt % of MoS2-CNT hybrids, the char residues and glass transition temperature (Tg) of the EP composite was significantly increased. Also, the addition of MoS2-CNT hybrids awarded excellent fire resistance to the EP matrix, which was evidenced by the significantly reduced peak heat release rate and total heat release. Moreover, the amount of organic volatiles from EP decomposition was obviously decreased, and the formation of toxic CO was effectively suppressed, implying the toxicity of the volatiles was reduced and smoke production was obviously suppressed. The dramatically reduced fire hazards were generally ascribed to the synergistic effect of MoS2 and CNTs, containing good dispersion of MoS2-CNT hybrids, catalytic char function of MoS2 nanolayers, and physical barrier effects of MoS2 nanolayers and CNT network structure. PMID:25742464

  10. Nucleoside triphosphate-dependent DNA-binding properties of mos protein.

    PubMed Central

    Seth, A; Priel, E; Vande Woude, G F

    1987-01-01

    We have previously shown that the mos gene product, p40mos, produced in Escherichia coli binds ATP and has ATPase activity. In the present study, we investigated the DNA-binding properties of p40mos and two mos deletion mutant proteins. Nitrocellulose blot protein-DNA binding assays showed that p40mos binds DNA in the presence of Mg2+-ATP and certain other nucleoside triphosphates. Ninety percent of the p40mos-bound DNA is dissociated if the complex is washed in the presence of 1 M NaCl or in the absence of ATP. p40mos-DNA binding is not observed in the presence of AMP or the nonhydrolyzable ATP analog adenosine 5'-[beta, gamma-methylene]-triphosphate; however, in the presence of ADP, p40mos binds DNA at 20% of the level that is observed with ATP. An N-terminal-deletion mutant protein, p19mos, has no DNA-binding activity, whereas a C-terminal-deletion mutant protein, p25mos, does. p25mos contains the ATP-binding domain, binds DNA in the presence of either ADP or ATP, and shows 5% and 45% binding (relative to that in the presence of ATP) in the presence of AMP and adenosine 5'-[beta, gamma-methylene]triphosphate, respectively. These results suggest that the N-terminal domain of p40mos is responsible for nucleoside triphosphate-mediated DNA binding. We also observed differential histone-DNA binding in the presence and absence of ATP. Images PMID:3035537

  11. Electron trapping in 4H-SiC MOS capacitors fabricated by pre-oxidation nitrogen implantation

    NASA Astrophysics Data System (ADS)

    Basile, A. F.; Dhar, S.; Mooney, P. M.

    2011-06-01

    Incorporation of nitrogen (N) atoms by ion implantation prior to oxidation of SiO2/4H-SiC interfaces has been investigated by capacitance-voltage (C-V) characteristics and constant capacitance deep-level-transient spectroscopy (CCDLTS) measurements. The shift of the C-V curves to negative voltages can be explained by the partial activation of implanted N atoms during oxidation. The maximum amplitude of the CCDLTS spectra, proportional to the density of near-interface oxide traps, decreases with increasing N dose, but remains significantly larger than that of SiO2/SiC interfaces fabricated by post oxidation annealing in nitric oxide (NO). Intrinsic defects in the SiC epi-layer associated with implantation damage are also observed in N-implanted samples. In contrast, electron traps energetically close to the SiC conduction band, detected in NO annealed samples and presumably introduced during oxidation, are not observed in N-implanted samples. The improved transport characteristics of MOS transistors fabricated on N-implanted epi-layers compared to those fabricated by NO annealing is suggested to result from the effects of the greater N donor concentration and also possibly to the suppression of shallow electron traps in the SiC epilayer.

  12. Modeling, Fabrication and Test Results of a MOS Controlled Thyristor — MCT - with high controllable current density

    NASA Astrophysics Data System (ADS)

    Chernyavskiy, Evgeny; Popov, Vladimir; Vermeire, Bert

    2005-06-01

    A simple 2D static model for the evaluation of the maximum controllable current density in a MOS Controlled Thyristor (MCT) will be presented. It is shown that a 2D model of a P-I-N diode with a cathode PMOS transistor is appropriate for simulating the carrier distribution in an MCT. The maximum controllable current density can be modeled accurately using a static model of the free electron and acceptor concentrations. The simple physics rationale for this is discussed. MCT test results validate this simplified modeling approach. Punchthrough technology (PT) for high voltage application was used to manufacture an MCT with breakdown voltage of 2500 V and a maximum controllable current of 33 A with active area 0.33 cm2. The total number of N-type cathode emitter cells is 144,042. For optimization, transient power dissipation electron irradiation with 2 MeV energy was used. This increased the maximum controllable current to 50 A. To our knowledge, our current density values of 100 A/cm2 for non irradiated and 150 A/cm2 for irradiated MCTs are the highest that have been reported for large area devices.

  13. Hafnium transistor design for neural interfacing.

    PubMed

    Parent, David W; Basham, Eric J

    2008-01-01

    A design methodology is presented that uses the EKV model and the g(m)/I(D) biasing technique to design hafnium oxide field effect transistors that are suitable for neural recording circuitry. The DC gain of a common source amplifier is correlated to the structural properties of a Field Effect Transistor (FET) and a Metal Insulator Semiconductor (MIS) capacitor. This approach allows a transistor designer to use a design flow that starts with simple and intuitive 1-D equations for gain that can be verified in 1-D MIS capacitor TCAD simulations, before final TCAD process verification of transistor properties. The DC gain of a common source amplifier is optimized by using fast 1-D simulations and using slower, complex 2-D simulations only for verification. The 1-D equations are used to show that the increased dielectric constant of hafnium oxide allows a higher DC gain for a given oxide thickness. An additional benefit is that the MIS capacitor can be employed to test additional performance parameters important to an open gate transistor such as dielectric stability and ionic penetration.

  14. High Accuracy Transistor Compact Model Calibrations

    SciTech Connect

    Hembree, Charles E.; Mar, Alan; Robertson, Perry J.

    2015-09-01

    Typically, transistors are modeled by the application of calibrated nominal and range models. These models consists of differing parameter values that describe the location and the upper and lower limits of a distribution of some transistor characteristic such as current capacity. Correspond- ingly, when using this approach, high degrees of accuracy of the transistor models are not expected since the set of models is a surrogate for a statistical description of the devices. The use of these types of models describes expected performances considering the extremes of process or transistor deviations. In contrast, circuits that have very stringent accuracy requirements require modeling techniques with higher accuracy. Since these accurate models have low error in transistor descriptions, these models can be used to describe part to part variations as well as an accurate description of a single circuit instance. Thus, models that meet these stipulations also enable the calculation of quantifi- cation of margins with respect to a functional threshold and uncertainties in these margins. Given this need, new model high accuracy calibration techniques for bipolar junction transis- tors have been developed and are described in this report.

  15. Polyphosphonium-based ion bipolar junction transistors

    PubMed Central

    Gabrielsson, Erik O.; Berggren, Magnus

    2014-01-01

    Advancements in the field of electronics during the past few decades have inspired the use of transistors in a diversity of research fields, including biology and medicine. However, signals in living organisms are not only carried by electrons but also through fluxes of ions and biomolecules. Thus, in order to implement the transistor functionality to control biological signals, devices that can modulate currents of ions and biomolecules, i.e., ionic transistors and diodes, are needed. One successful approach for modulation of ionic currents is to use oppositely charged ion-selective membranes to form so called ion bipolar junction transistors (IBJTs). Unfortunately, overall IBJT device performance has been hindered due to the typical low mobility of ions, large geometries of the ion bipolar junction materials, and the possibility of electric field enhanced (EFE) water dissociation in the junction. Here, we introduce a novel polyphosphonium-based anion-selective material into npn-type IBJTs. The new material does not show EFE water dissociation and therefore allows for a reduction of junction length down to 2 μm, which significantly improves the switching performance of the ion transistor to 2 s. The presented improvement in speed as well the simplified design will be useful for future development of advanced iontronic circuits employing IBJTs, for example, addressable drug-delivery devices. PMID:25553192

  16. Polyphosphonium-based ion bipolar junction transistors.

    PubMed

    Gabrielsson, Erik O; Tybrandt, Klas; Berggren, Magnus

    2014-11-01

    Advancements in the field of electronics during the past few decades have inspired the use of transistors in a diversity of research fields, including biology and medicine. However, signals in living organisms are not only carried by electrons but also through fluxes of ions and biomolecules. Thus, in order to implement the transistor functionality to control biological signals, devices that can modulate currents of ions and biomolecules, i.e., ionic transistors and diodes, are needed. One successful approach for modulation of ionic currents is to use oppositely charged ion-selective membranes to form so called ion bipolar junction transistors (IBJTs). Unfortunately, overall IBJT device performance has been hindered due to the typical low mobility of ions, large geometries of the ion bipolar junction materials, and the possibility of electric field enhanced (EFE) water dissociation in the junction. Here, we introduce a novel polyphosphonium-based anion-selective material into npn-type IBJTs. The new material does not show EFE water dissociation and therefore allows for a reduction of junction length down to 2 μm, which significantly improves the switching performance of the ion transistor to 2 s. The presented improvement in speed as well the simplified design will be useful for future development of advanced iontronic circuits employing IBJTs, for example, addressable drug-delivery devices. PMID:25553192

  17. Correlation between latent interface trap buildup and 1/{ital f} noise in metal{endash}oxide{endash}semiconductor transistors

    SciTech Connect

    Johnson, M.J.; Fleetwood, D.M.

    1997-03-01

    A long-term delayed increase in the 1/{ital f} noise of {ital p}-channel metal{endash}oxide{endash}semiconductor (MOS) transistors is observed in devices that show significant latent interface-trap buildup after exposure to ionizing radiation. During positive-bias postirradiation anneal, the noise increases by more than an order of magnitude above the level observed after irradiation. The increase in noise precedes the latent buildup of interface traps by at least 4.5 days during room-temperature annealing, and by {approximately}1 h during 100{degree}C annealing. The time and temperature dependencies of the increases in noise and interface trap buildup are consistent with the thermally activated motion of protons into the near-interfacial region of the oxide, followed by increases in border trap and interface trap densities. These results suggest hydrogen-related species can significantly affect the 1/{ital f} noise of MOS devices.{copyright} {ital 1997 American Institute of Physics.}

  18. MOS1 Osmosensor of Metarhizium anisopliae Is Required for Adaptation to Insect Host Hemolymph▿

    PubMed Central

    Wang, Chengshu; Duan, Zhibing; St. Leger, Raymond J.

    2008-01-01

    Entomopathogenic fungi such as Metarhizium anisopliae infect insects by direct penetration of the cuticle, after which the fungus adapts to the high osmotic pressure of the hemolymph and multiplies. Here we characterize the M. anisopliae Mos1 gene and demonstrate that it encodes the osmosensor required for this process. MOS1 contains transmembrane regions and a C-terminal Src homology 3 domain similar to those of yeast osmotic adaptor proteins, and homologs of MOS1 are widely distributed in the fungal kingdom. Reverse transcription-PCR demonstrated that Mos1 is up-regulated in insect hemolymph as well as artificial media with high osmotic pressure. Transformants containing an antisense vector directed to the Mos1 mRNA depleted transcript levels by 80%. This produced selective alterations in regulation of genes involved in hyphal body formation, cell membrane stiffness, and generation of intracellular turgor pressure, suggesting that these processes are mediated by MOS1. Consistent with a role in stress responses, transcript depletion of Mos1 increased sensitivity to osmotic and oxidative stresses and to compounds that interfere with cell wall biosynthesis. It also disrupted developmental processes, including formation of appressoria and hyphal bodies. Insect bioassays confirmed that Mos1 knockdown significantly reduces virulence. Overall, our data show that M. anisopliae MOS1 mediates cellular responses to high osmotic pressure and subsequent adaptations to colonize host hemolymph. PMID:18055914

  19. Interfacial chemical reactions between MoS2 lubricants and bearing materials

    NASA Technical Reports Server (NTRS)

    Zabinski, J. S.; Tatarchuk, B. J.

    1989-01-01

    XPS and conversion-electron Moessbauer spectroscopy (CEMS) were used to examine iron that was deposited on the basal plane of MoS2 single crystals and subjected to vacuum annealing, oxidizing, and reducing environments. Iron either intercalated into the MoS2 structure or formed oriented iron sulfides, depending on the level of excess S in the MoS2 structure. CEMS data demonstrated that iron sulfide crystal structures preferentially aligned with respect to the MoS2 basal plane, and that alignment (and potentially adhesion) could be varied by appropriate high-temperature annealing procedures.

  20. Cylindrical nanostructured MoS2 directly grown on CNT composites for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Yoo, Heejoun; Tiwari, Anand P.; Lee, Jeongtaik; Kim, Doyoung; Park, Jong Hyeok; Lee, Hyoyoung

    2015-02-01

    Direct attachment of MoS2 to materials with carbonaceous architecture remains a major challenge because of non-intimate contact between the carbonaceous materials and active MoS2 material. In this study, we report a new unique synthetic method to produce a new type of hybrid nanostructure of MoS2-CNTs composites. We developed a novel strategy for the synthesis of cylindrical MoS2 directly grown on CNT composites without the use of any other additives, exhibiting superior electrochemical performance as the anode material of lithium-ion batteries via a microwave irradiation technique. We adopted a simple step-by-step method: coating sulfur on CNTs and then reaction with a Mo source to synthesize hybrid cylindrical nanostructures of the MoS2-CNT composite. X-ray diffraction, field emission scanning electron microscopy, and high-resolution transmission electron microscopy analyses demonstrated that the as-synthesized MoS2-CNTs possessed a hybrid nanostructure, in which MoS2 sheets were well attached to the CNTs. The directly attached MoS2 sheets on the CNTs showed superior electrochemical performance as anode materials in a lithium-ion battery.Direct attachment of MoS2 to materials with carbonaceous architecture remains a major challenge because of non-intimate contact between the carbonaceous materials and active MoS2 material. In this study, we report a new unique synthetic method to produce a new type of hybrid nanostructure of MoS2-CNTs composites. We developed a novel strategy for the synthesis of cylindrical MoS2 directly grown on CNT composites without the use of any other additives, exhibiting superior electrochemical performance as the anode material of lithium-ion batteries via a microwave irradiation technique. We adopted a simple step-by-step method: coating sulfur on CNTs and then reaction with a Mo source to synthesize hybrid cylindrical nanostructures of the MoS2-CNT composite. X-ray diffraction, field emission scanning electron microscopy, and high