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Sample records for based metal semiconductor

  1. Metal-semiconductor-metal UV photodetector based on Ga doped ZnO/graphene interface

    NASA Astrophysics Data System (ADS)

    Kumar, Manoj; Noh, Youngwook; Polat, Kinyas; Kemal Okyay, Ali; Lee, Dongjin

    2015-12-01

    Fabrication and characterization of metal-semiconductor-metal (MSM) ultraviolet (UV) photodetector (PD) based on Ga doped ZnO (ZnO:Ga)/graphene is presented in this work. A low dark current of 8.68 nA was demonstrated at a bias of 1 V and a large photo to dark contrast ratio of more than four orders of magnitude was observed. MSM PD exhibited a room temperature responsivity of 48.37 A/W at wavelength of 350 nm and UV-to-visible rejection ratio of about three orders of magnitude. A large photo-to-dark contrast and UV-to-visible rejection ratio suggests the enhancement in the PD performance which is attributed to the existence of a surface plasmon effect at the interface of the ZnO:Ga and underlying graphene layer.

  2. Vacuum Violet Photo-Response of AlGaN-Based Metal-Semiconductor-Metal Photodetectors

    NASA Astrophysics Data System (ADS)

    Zhou, Dong; Lu, Hai; Chen, Dun-Jun; Ren, Fang-Fang; Zhang, Rong; Zheng, You-Dou; Li, Liang

    2013-11-01

    Al0.5Ga0.5 N-based metal-semiconductor-metal photodetectors (PDs) with a large device area of 5 × 5 mm2 are fabricated on a sapphire substrate, which are tested for vacuum ultraviolet light detection by using a synchrotron radiation source. The PD exhibits low dark current of less than 1 pA under 30 V bias and a spectral cutoff around 260 nm, corresponding to the energy bandgap of Al0.5Ga0.5N. A peak photo-responsivity of 14.68 mA/W at 250 nm with a rejection ratio (250/360 nm) of more than four orders of magnitude is obtained under 30 V bias. For wavelength less than 170 nm, the photoresponsivity of the PD is found to increase as wavelength decreases, which is likely caused by the enhanced photoemission effect.

  3. Nanomesh electrode on MgZnO-based metal-semiconductor-metal ultraviolet photodetectors

    NASA Astrophysics Data System (ADS)

    Lee, Ching-Ting; Lin, Heng-Yu; Tseng, Chun-Yen

    2015-09-01

    In this work, the nano-scaled mesh electrodes are fabricated by obliquely depositing metals through the highly ordered polystyrene nanosphere mask. Furthermore, the intrinsic MgZnO film is deposited as the absorption layer for the metal-semiconductor-metal ultraviolet photodetectors (MSM-UV-PDs) using the vapor cooling condensation system. The 100-nm-linewidth nanomesh electrodes with metal occupying a roughly 10% of the device surface region consequently render PDs with a high transmittance in the ultraviolet (UV) wavelength range. The photoresponsivity of MgZnO-based MSM-UV-PDs evaluated at the wavelength of 330 nm with the operating bias voltage of 5 V is elevated from 0.135 to 0.248 A/W when the thin metal electrode is replaced by the nanomesh electrode, and the corresponding quantum efficiency is improved from 50.75 to 93.23%. Finally, adopting the nanomesh electrode also helps to enhance the UV-visible rejection ratio (R330nm/R450nm) and the detectivity from 1663 and 1.78 × 1010 cmHz0.5W-1 to 2480 and 2.43 × 1010 cmHz0.5W-1, respectively.

  4. Nanomesh electrode on MgZnO-based metal-semiconductor-metal ultraviolet photodetectors.

    PubMed

    Lee, Ching-Ting; Lin, Heng-Yu; Tseng, Chun-Yen

    2015-01-01

    In this work, the nano-scaled mesh electrodes are fabricated by obliquely depositing metals through the highly ordered polystyrene nanosphere mask. Furthermore, the intrinsic MgZnO film is deposited as the absorption layer for the metal-semiconductor-metal ultraviolet photodetectors (MSM-UV-PDs) using the vapor cooling condensation system. The 100-nm-linewidth nanomesh electrodes with metal occupying a roughly 10% of the device surface region consequently render PDs with a high transmittance in the ultraviolet (UV) wavelength range. The photoresponsivity of MgZnO-based MSM-UV-PDs evaluated at the wavelength of 330 nm with the operating bias voltage of 5 V is elevated from 0.135 to 0.248 A/W when the thin metal electrode is replaced by the nanomesh electrode, and the corresponding quantum efficiency is improved from 50.75 to 93.23%. Finally, adopting the nanomesh electrode also helps to enhance the UV-visible rejection ratio (R330nm/R450nm) and the detectivity from 1663 and 1.78 × 10(10) cmHz(0.5)W(-1) to 2480 and 2.43 × 10(10) cmHz(0.5)W(-1), respectively. PMID:26324247

  5. Metal-semiconductor-metal ultraviolet photodetectors based on gallium nitride grown by atomic layer deposition at low temperatures

    NASA Astrophysics Data System (ADS)

    Tekcan, Burak; Ozgit-Akgun, Cagla; Bolat, Sami; Biyikli, Necmi; Okyay, Ali Kemal

    2014-10-01

    Proof-of-concept, first metal-semiconductor-metal ultraviolet photodetectors based on nanocrystalline gallium nitride (GaN) layers grown by low-temperature hollow-cathode plasma-assisted atomic layer deposition are demonstrated. Electrical and optical characteristics of the fabricated devices are investigated. Dark current values as low as 14 pA at a 30 V reverse bias are obtained. Fabricated devices exhibit a 15× UV/VIS rejection ratio based on photoresponsivity values at 200 nm (UV) and 390 nm (VIS) wavelengths. These devices can offer a promising alternative for flexible optoelectronics and the complementary metal oxide semiconductor integration of such devices.

  6. Terahertz Modulator based on Metamaterials integrated with Metal-Semiconductor-Metal Varactors

    PubMed Central

    Nouman, Muhammad Tayyab; Kim, Hyun-Woong; Woo, Jeong Min; Hwang, Ji Hyun; Kim, Dongju; Jang, Jae-Hyung

    2016-01-01

    The terahertz (THz) band of the electromagnetic spectrum, with frequencies ranging from 300 GHz to 3 THz, has attracted wide interest in recent years owing to its potential applications in numerous areas. Significant progress has been made toward the development of devices capable of actively controlling terahertz waves; nonetheless, further advances in device functionality are necessary for employment of these devices in practical terahertz systems. Here, we demonstrate a low voltage, sharp switching terahertz modulator device based on metamaterials integrated with metal semiconductor metal (MSM) varactors, fabricated on an AlGaAs/InGaAs based heterostructure. By varying the applied voltage to the MSM-varactor located at the center of split ring resonator (SRR), the resonance frequency of the SRR-based metamaterial is altered. Upon varying the bias voltage from 0 V to 3 V, the resonance frequency exhibits a transition from 0.52 THz to 0.56 THz, resulting in a modulation depth of 45 percent with an insertion loss of 4.3 dB at 0.58 THz. This work demonstrates a new approach for realizing active terahertz devices with improved functionalities. PMID:27194128

  7. Terahertz Modulator based on Metamaterials integrated with Metal-Semiconductor-Metal Varactors.

    PubMed

    Nouman, Muhammad Tayyab; Kim, Hyun-Woong; Woo, Jeong Min; Hwang, Ji Hyun; Kim, Dongju; Jang, Jae-Hyung

    2016-01-01

    The terahertz (THz) band of the electromagnetic spectrum, with frequencies ranging from 300 GHz to 3 THz, has attracted wide interest in recent years owing to its potential applications in numerous areas. Significant progress has been made toward the development of devices capable of actively controlling terahertz waves; nonetheless, further advances in device functionality are necessary for employment of these devices in practical terahertz systems. Here, we demonstrate a low voltage, sharp switching terahertz modulator device based on metamaterials integrated with metal semiconductor metal (MSM) varactors, fabricated on an AlGaAs/InGaAs based heterostructure. By varying the applied voltage to the MSM-varactor located at the center of split ring resonator (SRR), the resonance frequency of the SRR-based metamaterial is altered. Upon varying the bias voltage from 0 V to 3 V, the resonance frequency exhibits a transition from 0.52 THz to 0.56 THz, resulting in a modulation depth of 45 percent with an insertion loss of 4.3 dB at 0.58 THz. This work demonstrates a new approach for realizing active terahertz devices with improved functionalities. PMID:27194128

  8. Terahertz Modulator based on Metamaterials integrated with Metal-Semiconductor-Metal Varactors

    NASA Astrophysics Data System (ADS)

    Nouman, Muhammad Tayyab; Kim, Hyun-Woong; Woo, Jeong Min; Hwang, Ji Hyun; Kim, Dongju; Jang, Jae-Hyung

    2016-05-01

    The terahertz (THz) band of the electromagnetic spectrum, with frequencies ranging from 300 GHz to 3 THz, has attracted wide interest in recent years owing to its potential applications in numerous areas. Significant progress has been made toward the development of devices capable of actively controlling terahertz waves; nonetheless, further advances in device functionality are necessary for employment of these devices in practical terahertz systems. Here, we demonstrate a low voltage, sharp switching terahertz modulator device based on metamaterials integrated with metal semiconductor metal (MSM) varactors, fabricated on an AlGaAs/InGaAs based heterostructure. By varying the applied voltage to the MSM-varactor located at the center of split ring resonator (SRR), the resonance frequency of the SRR-based metamaterial is altered. Upon varying the bias voltage from 0 V to 3 V, the resonance frequency exhibits a transition from 0.52 THz to 0.56 THz, resulting in a modulation depth of 45 percent with an insertion loss of 4.3 dB at 0.58 THz. This work demonstrates a new approach for realizing active terahertz devices with improved functionalities.

  9. Light-induced resistive switching in silicon-based metal-insulator-semiconductor structures

    NASA Astrophysics Data System (ADS)

    Tikhov, S. V.; Gorshkov, O. N.; Koryazhkina, M. N.; Antonov, I. N.; Kasatkin, A. P.

    2016-05-01

    We have studied light-induced resistive switching in metal-insulator-semiconductor structures based on silicon covered with a tunneling-thin SiO2 layer and nanometer-thick layer of antimony. The role of an insulator was played by yttria-stabilized zirconia.

  10. Influence of Deuterium Treatments on the Polysilicon-Based Metal-Semiconductor-Metal Photodetector.

    PubMed

    Lee, Jae-Sung

    2016-06-01

    The electrical behavior of metal-semiconductor-metal (MSM) Schottky barrier photodetector structure, depending on deuterium treatment, is analyzed by means of the dark current and the photocurrent measurements. Al/Ti bilayer was used as Schottky metal. The deuterium incorporation into the absorption layer, undoped polysilicon, was achieved with annealing process and with ion implantation process, respectively. In the photocurrent-to-dark current ratio measurement, deuterium-ion-implanted photodetector shows over hundred higher than the control device. It means that the heightening of the Schottky barrier and the passivation of grain boundary trap were achieved effectively through the deuterium ion implantation process. PMID:27427689

  11. Quasiparticle band structure of the almost-gapless transition-metal-based Heusler semiconductors

    NASA Astrophysics Data System (ADS)

    Tas, M.; Şaşıoǧlu, E.; Galanakis, I.; Friedrich, C.; Blügel, S.

    2016-05-01

    Transition-metal-based Heusler semiconductors are promising materials for a variety of applications ranging from spintronics to thermoelectricity. Employing the G W approximation within the framework of the FLAPW method, we study the quasiparticle band structure of a number of such compounds being almost gapless semiconductors. We find that in contrast to the s p -electron based semiconductors such as Si and GaAs, in these systems, the many-body corrections have a minimal effect on the electronic band structure and the energy band gap increases by less than 0.2 eV, which makes the starting point density functional theory (DFT) a good approximation for the description of electronic and optical properties of these materials. Furthermore, the band gap can be tuned either by the variation of the lattice parameter or by the substitution of the s p -chemical element.

  12. Retinal Stimulation on Rabbit Using Complementary Metal Oxide Semiconductor Based Multichip Flexible Stimulator toward Retinal Prosthesis

    NASA Astrophysics Data System (ADS)

    Tokuda, Takashi; Asano, Ryosuke; Sugitani, Sachie; Taniyama, Mari; Terasawa, Yasuo; Nunoshita, Masahiro; Nakauchi, Kazuaki; Fujikado, Takashi; Tano, Yasuo; Ohta, Jun

    2008-04-01

    The Functionality of a complementary metal oxide semiconductor (CMOS) LSI-based, multichip flexible retinal stimulator was demonstrated in retinal stimulation experiments on rabbits. A 1×4-configured multichip stimulator was fabricated for application to experiments on animals. An experimental procedure including surgical operations was developed, and retinal stimulation was performed with the fabricated multichip stimulator. Neural responses on the visual cortex were successfully evoked by the fabricated stimulator. The stimulator is confirmed to be applicable to acute animal experiments.

  13. Flexible perovskite solar cells based on the metal-insulator-semiconductor structure.

    PubMed

    Wei, Jing; Li, Heng; Zhao, Yicheng; Zhou, Wenke; Fu, Rui; Pan, Huiyue; Zhao, Qing

    2016-09-14

    The metal-insulator-semiconductor (MIS) structure is applied to perovskite solar cells, in which the traditional compact layer TiO2 is replaced by Al2O3 as the hole blocking material to realize an all-low-temperature process. Flexible devices based on this structure are also realized with excellent flexibility, which hold 85% of their initial efficiency after bending 100 times. PMID:27524362

  14. Printable Ultrathin Metal Oxide Semiconductor-Based Conformal Biosensors.

    PubMed

    Rim, You Seung; Bae, Sang-Hoon; Chen, Huajun; Yang, Jonathan L; Kim, Jaemyung; Andrews, Anne M; Weiss, Paul S; Yang, Yang; Tseng, Hsian-Rong

    2015-12-22

    Conformal bioelectronics enable wearable, noninvasive, and health-monitoring platforms. We demonstrate a simple and straightforward method for producing thin, sensitive In2O3-based conformal biosensors based on field-effect transistors using facile solution-based processing. One-step coating via aqueous In2O3 solution resulted in ultrathin (3.5 nm), high-density, uniform films over large areas. Conformal In2O3-based biosensors on ultrathin polyimide films displayed good device performance, low mechanical stress, and highly conformal contact determined using polydimethylsiloxane artificial skin having complex curvilinear surfaces or an artificial eye. Immobilized In2O3 field-effect transistors with self-assembled monolayers of NH2-terminated silanes functioned as pH sensors. Functionalization with glucose oxidase enabled d-glucose detection at physiologically relevant levels. The conformal ultrathin field-effect transistor biosensors developed here offer new opportunities for future wearable human technologies. PMID:26498319

  15. Graphene-based half-metal and spin-semiconductor for spintronic applications

    NASA Astrophysics Data System (ADS)

    Qi, Jingshan; Chen, Xiaofang; Hu, Kaige; Feng, Ji

    2016-03-01

    In this letter we propose a strategy to make graphene become a half-metal or spin-semiconductor by combining the magnetic proximity effects and sublattice symmetry breaking in graphone/graphene and graphone/graphene/BN heterostructures. Exchange interactions lift the spin degeneracy and sublattice symmetry breaking opens a band gap in graphene. More interestingly, the gap opening depends on the spin direction and the competition between the sublattice asymmetry and exchange field determines the system is a half-metal or a spin-semiconductor. By first-principles calculations and a low-energy effective model analysis, we elucidate the underlying physical mechanism of spin-dependent gap opening and spin degeneracy splitting. This offers an alternative practical platform for graphene-based spintronics.

  16. Graphene-based half-metal and spin-semiconductor for spintronic applications.

    PubMed

    Qi, Jingshan; Chen, Xiaofang; Hu, Kaige; Feng, Ji

    2016-03-31

    In this letter we propose a strategy to make graphene become a half-metal or spin-semiconductor by combining the magnetic proximity effects and sublattice symmetry breaking in graphone/graphene and graphone/graphene/BN heterostructures. Exchange interactions lift the spin degeneracy and sublattice symmetry breaking opens a band gap in graphene. More interestingly, the gap opening depends on the spin direction and the competition between the sublattice asymmetry and exchange field determines the system is a half-metal or a spin-semiconductor. By first-principles calculations and a low-energy effective model analysis, we elucidate the underlying physical mechanism of spin-dependent gap opening and spin degeneracy splitting. This offers an alternative practical platform for graphene-based spintronics. PMID:26933773

  17. Transmission enhancement based on strong interference in metal-semiconductor layered film for energy harvesting

    NASA Astrophysics Data System (ADS)

    Li, Qiang; Du, Kaikai; Mao, Kening; Fang, Xu; Zhao, Ding; Ye, Hui; Qiu, Min

    2016-07-01

    A fundamental strategy to enhance optical transmission through a continuous metallic film based on strong interference dominated by interface phase shift is developed. In a metallic film coated with a thin semiconductor film, both transmission and absorption are simultaneously enhanced as a result of dramatically reduced reflection. For a 50-nm-thick Ag film, experimental transmission enhancement factors of 4.5 and 9.5 are realized by exploiting Ag/Si non-symmetric and Si/Ag/Si symmetric geometries, respectively. These planar layered films for transmission enhancement feature ultrathin thickness, broadband and wide-angle operation, and reduced resistance. Considering one of their potential applications as transparent metal electrodes in solar cells, a calculated 182% enhancement in the total transmission efficiency relative to a single metallic film is expected. This strategy relies on no patterned nanostructures and thereby may power up a wide spectrum of energy-harvesting applications such as thin-film photovoltaics and surface photocatalysis.

  18. Silicon metal-semiconductor-metal photodetector

    DOEpatents

    Brueck, Steven R. J.; Myers, David R.; Sharma, Ashwani K.

    1995-01-01

    Silicon MSM photodiodes sensitive to radiation in the visible to near infrared spectral range are produced by altering the absorption characteristics of crystalline Si by ion implantation. The implantation produces a defected region below the surface of the silicon with the highest concentration of defects at its base which acts to reduce the contribution of charge carriers formed below the defected layer. The charge carriers generated by the radiation in the upper regions of the defected layer are very quickly collected between biased Schottky barrier electrodes which form a metal-semiconductor-metal structure for the photodiode.

  19. Silicon metal-semiconductor-metal photodetector

    DOEpatents

    Brueck, Steven R. J.; Myers, David R.; Sharma, Ashwani K.

    1997-01-01

    Silicon MSM photodiodes sensitive to radiation in the visible to near infrared spectral range are produced by altering the absorption characteristics of crystalline Si by ion implantation. The implantation produces a defected region below the surface of the silicon with the highest concentration of defects at its base which acts to reduce the contribution of charge carriers formed below the defected layer. The charge carriers generated by the radiation in the upper regions of the defected layer are very quickly collected between biased Schottky barrier electrodes which form a metal-semiconductor-metal structure for the photodiode.

  20. Hot-electron-based solar energy conversion with metal-semiconductor nanodiodes.

    PubMed

    Lee, Young Keun; Lee, Hyosun; Lee, Changhwan; Hwang, Euyheon; Park, Jeong Young

    2016-06-29

    Energy dissipation at metal surfaces or interfaces between a metal and a dielectric generally results from elementary excitations, including phonons and electronic excitation, once external energy is deposited to the surface/interface during exothermic chemical processes or an electromagnetic wave incident. In this paper, we outline recent research activities to develop energy conversion devices based on hot electrons. We found that photon energy can be directly converted to hot electrons and that hot electrons flow through the interface of metal-semiconductor nanodiodes where a Schottky barrier is formed and the energy barrier is much lower than the work function of the metal. The detection of hot electron flow can be successfully measured using the photocurrent; we measured the photoyield of photoemission with incident photons-to-current conversion efficiency (IPCE). We also show that surface plasmons (i.e. the collective oscillation of conduction band electrons induced by interaction with an electromagnetic field) are excited on a rough metal surface and subsequently decay into secondary electrons, which gives rise to enhancement of the IPCE. Furthermore, the unique optical behavior of surface plasmons can be coupled with dye molecules, suggesting the possibility for producing additional channels for hot electron generation. PMID:27168177

  1. Spatially correlated two-dimensional arrays of semiconductor and metal quantum dots in GaAs-based heterostructures

    SciTech Connect

    Nevedomskiy, V. N. Bert, N. A.; Chaldyshev, V. V.; Preobrazhernskiy, V. V.; Putyato, M. A.; Semyagin, B. R.

    2015-12-15

    A single molecular-beam epitaxy process is used to produce GaAs-based heterostructures containing two-dimensional arrays of InAs semiconductor quantum dots and AsSb metal quantum dots. The twodimensional array of AsSb metal quantum dots is formed by low-temperature epitaxy which provides a large excess of arsenic in the epitaxial GaAs layer. During the growth of subsequent layers at a higher temperature, excess arsenic forms nanoinclusions, i.e., metal quantum dots in the GaAs matrix. The two-dimensional array of such metal quantum dots is created by the δ doping of a low-temperature GaAs layer with antimony which serves as a precursor for the heterogeneous nucleation of metal quantum dots and accumulates in them with the formation of AsSb metal alloy. The two-dimensional array of InAs semiconductor quantum dots is formed via the Stranski–Krastanov mechanism at the GaAs surface. Between the arrays of metal and semiconductor quantum dots, a 3-nm-thick AlAs barrier layer is grown. The total spacing between the arrays of metal and semiconductor quantum dots is 10 nm. Electron microscopy of the structure shows that the arrangement of metal quantum dots and semiconductor quantum dots in the two-dimensional arrays is spatially correlated. The spatial correlation is apparently caused by elastic strain and stress fields produced by both AsSb metal and InAs semiconductor quantum dots in the GaAs matrix.

  2. Highly sensitive sensors for alkali metal ions based on complementary-metal-oxide-semiconductor-compatible silicon nanowires

    NASA Astrophysics Data System (ADS)

    Zhang, Guo-Jun; Agarwal, Ajay; Buddharaju, Kavitha D.; Singh, Navab; Gao, Zhiqiang

    2007-06-01

    Highly sensitive sensors for alkali metal ions based on complementary-metal-oxide- semiconductor-compatible silicon nanowires (SiNWs) with crown ethers covalently immobilized on their surface are presented. A densely packed organic monolayer terminated with amine groups is introduced to the SiNW surface via hydrosilylation. Amine-modified crown ethers, acting as sensing elements, are then immobilized onto the SiNWs through a cross-linking reaction with the monolayer. The crown ether-functionalized SiNWs recognize Na+ and K+ according to their complexation ability to the crown ethers. The SiNW sensors are highly selective and capable of achieving an ultralow detection limit down to 50nM, over three orders of magnitude lower than that of conventional crown ether-based ion-selective electrodes.

  3. A metal-semiconductor-metal detector based on ZnO nanowires grown on a graphene layer

    NASA Astrophysics Data System (ADS)

    Xu, Qiang; Cheng, Qijin; Zhong, Jinxiang; Cai, Weiwei; Zhang, Zifeng; Wu, Zhengyun; Zhang, Fengyan

    2014-02-01

    High quality ZnO nanowires (NWs) were grown on a graphene layer by a hydrothermal method. The ZnO NWs revealed higher uniform surface morphology and better structural properties than ZnO NWs grown on SiO2/Si substrate. A low dark current metal-semiconductor-metal photodetector based on ZnO NWs with Au Schottky contact has also been fabricated. The photodetector displays a low dark current of 1.53 nA at 1 V bias and a large UV-to-visible rejection ratio (up to four orders), which are significantly improved compared to conventional ZnO NW photodetectors. The improvement in UV detection performance is attributed to the existence of a surface plasmon at the interface of the ZnO and the graphene.

  4. A metal-semiconductor-metal detector based on ZnO nanowires grown on a graphene layer.

    PubMed

    Xu, Qiang; Cheng, Qijin; Zhong, Jinxiang; Cai, Weiwei; Zhang, Zifeng; Wu, Zhengyun; Zhang, Fengyan

    2014-02-01

    High quality ZnO nanowires (NWs) were grown on a graphene layer by a hydrothermal method. The ZnO NWs revealed higher uniform surface morphology and better structural properties than ZnO NWs grown on SiO2/Si substrate. A low dark current metal-semiconductor-metal photodetector based on ZnO NWs with Au Schottky contact has also been fabricated. The photodetector displays a low dark current of 1.53 nA at 1 V bias and a large UV-to-visible rejection ratio (up to four orders), which are significantly improved compared to conventional ZnO NW photodetectors. The improvement in UV detection performance is attributed to the existence of a surface plasmon at the interface of the ZnO and the graphene. PMID:24407201

  5. Transmission enhancement based on strong interference in metal-semiconductor layered film for energy harvesting

    PubMed Central

    Li, Qiang; Du, Kaikai; Mao, Kening; Fang, Xu; Zhao, Ding; Ye, Hui; Qiu, Min

    2016-01-01

    A fundamental strategy to enhance optical transmission through a continuous metallic film based on strong interference dominated by interface phase shift is developed. In a metallic film coated with a thin semiconductor film, both transmission and absorption are simultaneously enhanced as a result of dramatically reduced reflection. For a 50-nm-thick Ag film, experimental transmission enhancement factors of 4.5 and 9.5 are realized by exploiting Ag/Si non-symmetric and Si/Ag/Si symmetric geometries, respectively. These planar layered films for transmission enhancement feature ultrathin thickness, broadband and wide-angle operation, and reduced resistance. Considering one of their potential applications as transparent metal electrodes in solar cells, a calculated 182% enhancement in the total transmission efficiency relative to a single metallic film is expected. This strategy relies on no patterned nanostructures and thereby may power up a wide spectrum of energy-harvesting applications such as thin-film photovoltaics and surface photocatalysis. PMID:27404510

  6. Transmission enhancement based on strong interference in metal-semiconductor layered film for energy harvesting.

    PubMed

    Li, Qiang; Du, Kaikai; Mao, Kening; Fang, Xu; Zhao, Ding; Ye, Hui; Qiu, Min

    2016-01-01

    A fundamental strategy to enhance optical transmission through a continuous metallic film based on strong interference dominated by interface phase shift is developed. In a metallic film coated with a thin semiconductor film, both transmission and absorption are simultaneously enhanced as a result of dramatically reduced reflection. For a 50-nm-thick Ag film, experimental transmission enhancement factors of 4.5 and 9.5 are realized by exploiting Ag/Si non-symmetric and Si/Ag/Si symmetric geometries, respectively. These planar layered films for transmission enhancement feature ultrathin thickness, broadband and wide-angle operation, and reduced resistance. Considering one of their potential applications as transparent metal electrodes in solar cells, a calculated 182% enhancement in the total transmission efficiency relative to a single metallic film is expected. This strategy relies on no patterned nanostructures and thereby may power up a wide spectrum of energy-harvesting applications such as thin-film photovoltaics and surface photocatalysis. PMID:27404510

  7. The role of the substrate on the dispersion in accumulation in III-V compound semiconductor based metal-oxide-semiconductor gate stacks

    NASA Astrophysics Data System (ADS)

    Krylov, Igor; Ritter, Dan; Eizenberg, Moshe

    2015-09-01

    Dispersion in accumulation is a widely observed phenomenon in metal-oxide-semiconductor gate stacks based on III-V compound semiconductors. The physical origin of this phenomenon is attributed to border traps located in the dielectric material adjacent to the semiconductor. Here, we study the role of the semiconductor substrate on the electrical quality of the first layers at atomic layer deposited (ALD) dielectrics. For this purpose, either Al2O3 or HfO2 dielectrics with variable thicknesses were deposited simultaneously on two technology important semiconductors—InGaAs and InP. Significantly larger dispersion was observed in InP based gate stacks compared to those based on InGaAs. The observed difference is attributed to a higher border trap density in dielectrics deposited on InP compared to those deposited on InGaAs. We therefore conclude that the substrate plays an important role in the determination of the electrical quality of the first dielectric monolayers deposited by ALD. An additional observation is that larger dispersion was obtained in HfO2 based capacitors compared to Al2O3 based capacitors, deposited on the same semiconductor. This phenomenon is attributed to the lower conduction band offset rather than to a higher border trap density.

  8. The role of the substrate on the dispersion in accumulation in III-V compound semiconductor based metal-oxide-semiconductor gate stacks

    SciTech Connect

    Krylov, Igor; Ritter, Dan; Eizenberg, Moshe

    2015-09-07

    Dispersion in accumulation is a widely observed phenomenon in metal-oxide-semiconductor gate stacks based on III-V compound semiconductors. The physical origin of this phenomenon is attributed to border traps located in the dielectric material adjacent to the semiconductor. Here, we study the role of the semiconductor substrate on the electrical quality of the first layers at atomic layer deposited (ALD) dielectrics. For this purpose, either Al{sub 2}O{sub 3} or HfO{sub 2} dielectrics with variable thicknesses were deposited simultaneously on two technology important semiconductors—InGaAs and InP. Significantly larger dispersion was observed in InP based gate stacks compared to those based on InGaAs. The observed difference is attributed to a higher border trap density in dielectrics deposited on InP compared to those deposited on InGaAs. We therefore conclude that the substrate plays an important role in the determination of the electrical quality of the first dielectric monolayers deposited by ALD. An additional observation is that larger dispersion was obtained in HfO{sub 2} based capacitors compared to Al{sub 2}O{sub 3} based capacitors, deposited on the same semiconductor. This phenomenon is attributed to the lower conduction band offset rather than to a higher border trap density.

  9. Electrical Characteristics and Interface Properties of III Nitride-Based Metal-Insulator-Semiconductor Structure

    SciTech Connect

    Mahyuddin, A.; Hassan, Z.; Yusof, Y.; Cheong, K. Y.

    2010-07-07

    In this work, III-Nitride based metal-insulator-semiconductor (MIS) structure has been studied using AlN/GaN heterostructures on Si (111) with AlN buffer layer grown by plasma-assisted molecular beam epitaxy (MBE). The structural and electrical characteristics of the films were studied through high resolution x-ray diffraction (HRXRD), capacitance-voltage (C-V) and current-voltage (I-V) measurements. The value of flat-band voltage was -0.7 V. A total fixed oxide charge density of 2.73x10{sup 11} cm{sup -2} was estimated. Terman's method was used to obtain the density of interface state in the MIS structure. The analysis showed low interface state density values of 3.66x10{sup 11} cm{sup -2} eV{sup -1}.

  10. Metal-Insulator-Semiconductor Photodetectors

    PubMed Central

    Lin, Chu-Hsuan; Liu, Chee Wee

    2010-01-01

    The major radiation of the Sun can be roughly divided into three regions: ultraviolet, visible, and infrared light. Detection in these three regions is important to human beings. The metal-insulator-semiconductor photodetector, with a simpler process than the pn-junction photodetector and a lower dark current than the MSM photodetector, has been developed for light detection in these three regions. Ideal UV photodetectors with high UV-to-visible rejection ratio could be demonstrated with III–V metal-insulator-semiconductor UV photodetectors. The visible-light detection and near-infrared optical communications have been implemented with Si and Ge metal-insulator-semiconductor photodetectors. For mid- and long-wavelength infrared detection, metal-insulator-semiconductor SiGe/Si quantum dot infrared photodetectors have been developed, and the detection spectrum covers atmospheric transmission windows. PMID:22163382

  11. Hydrogen in semiconductors and metals

    SciTech Connect

    Nickel, N.H.; Jackson, W.B.; Bowman, R.C.; Leisure, R.G.

    1998-12-31

    Major highlights of the conference include further understanding of the structure of extended hydrogen clusters in semiconductors, switchable optical properties of metal-hydride films, reversible changes in the magnetic coupling in metallic superlattices, and increased lifetime of integrated circuits due to deuterium device passivation. Continued progress has also been achieved in understanding hydrogenation of defects in compound semiconductors and on surfaces. Total energy calculations in semiconductors have progressed sufficiently to predict energetics and vibration frequencies as measured by experiment. Similarly, electronic structure calculations of hydrogen-metal systems provide a deeper understanding of stability, bonding, and phase changes. Various nuclear techniques have been refined to yield important information regarding the concentration and transport of hydrogen in condensed matter. Finally, the interaction of hydrogen to create thermal donors has been used to create deep p-n junctions without the need for deep diffusion of dopants. The volume has been organized along the order of presentation within the conference. Similar methods and subjects have been grouped together. The authors have attempted to keep similar metal and semiconductor papers together in order to further promote cross-fertilization between the fields. Major categories include hydrogen on surfaces, theory and thermodynamics, hydrogen transport phenomena, nuclear characterization techniques, compound semiconductors, metal bulk, devices and applications, bulk silicon, and carbon and carbon-like materials. Separate abstracts were prepared for most papers.

  12. Low dielectric constant-based organic field-effect transistors and metal-insulator-semiconductor capacitors

    NASA Astrophysics Data System (ADS)

    Ukah, Ndubuisi Benjamin

    This thesis describes a study of PFB and pentacene-based organic field-effect transistors (OFET) and metal-insulator-semiconductor (MIS) capacitors with low dielectric constant (k) poly(methyl methacrylate) (PMMA), poly(4-vinyl phenol) (PVP) and cross-linked PVP (c-PVP) gate dielectrics. A physical method -- matrix assisted pulsed laser evaporation (MAPLE) -- of fabricating all-polymer field-effect transistors and MIS capacitors that circumvents inherent polymer dissolution and solvent-selectivity problems, is demonstrated. Pentacene-based OFETs incorporating PMMA and PVP gate dielectrics usually have high operating voltages related to the thickness of the dielectric layer. Reduced PMMA layer thickness (≤ 70 nm) was obtained by dissolving the PMMA in propylene carbonate (PC). The resulting pentacene-based transistors exhibited very low operating voltage (below -3 V), minimal hysteresis in their transfer characteristics, and decent electrical performance. Also low voltage (within -2 V) operation using thin (≤ 80 nm) low-k and hydrophilic PVP and c-PVP dielectric layers obtained via dissolution in high dipole moment and high-k solvents -- PC and dimethyl sulfoxide (DMSO), is demonstrated to be a robust means of achieving improved electrical characteristics and high operational stability in OFETs incorporating PVP and c-PVP dielectrics.

  13. High voltage trapping effects in GaN-based metal-insulator-semiconductor transistors

    NASA Astrophysics Data System (ADS)

    Meneghesso, Gaudenzio; Meneghini, Matteo; Silvestri, Riccardo; Vanmeerbeek, Piet; Moens, Peter; Zanoni, Enrico

    2016-01-01

    This paper presents an analysis of the high voltage trapping processes that take place in high-electron mobility transistors based on GaN, with a metal-insulator-semiconductor (MIS) structure. The study is based on combined pulsed and transient measurements, carried out with trapping voltages in the range from 50 to 500 V. The results indicate that: (i) dynamic Ron is maximum for trapping voltages between 200 and 300 V, and decreases for higher voltage levels; (ii) Ron-transient measurements reveal the presence of a dominant trap with activation energy Ea1 = 0.93 eV and of a second trap with activation energy equal to Ea2 = 0.61 eV; (iii) the deep level transient spectroscopy (DLTS) signal associated to trap Ea1 is completely suppressed for high trapping voltages (VDS = 500 V). The results are interpreted by considering that the trap Ea1 is located in the buffer, and originates from CN defects. The exposure to high drain voltages may favor the depletion of such traps, due to a field-assisted de-trapping process or to the presence of vertical leakage paths.

  14. Semiconductor assisted metal deposition for nanolithography applications

    DOEpatents

    Rajh, Tijana; Meshkov, Natalia; Nedelijkovic, Jovan M.; Skubal, Laura R.; Tiede, David M.; Thurnauer, Marion

    2002-01-01

    An article of manufacture and method of forming nanoparticle sized material components. A semiconductor oxide substrate includes nanoparticles of semiconductor oxide. A modifier is deposited onto the nanoparticles, and a source of metal ions are deposited in association with the semiconductor and the modifier, the modifier enabling electronic hole scavenging and chelation of the metal ions. The metal ions and modifier are illuminated to cause reduction of the metal ions to metal onto the semiconductor nanoparticles.

  15. Semiconductor assisted metal deposition for nanolithography applications

    DOEpatents

    Rajh, Tijana; Meshkov, Natalia; Nedelijkovic, Jovan M.; Skubal, Laura R.; Tiede, David M.; Thurnauer, Marion

    2001-01-01

    An article of manufacture and method of forming nanoparticle sized material components. A semiconductor oxide substrate includes nanoparticles of semiconductor oxide. A modifier is deposited onto the nanoparticles, and a source of metal ions are deposited in association with the semiconductor and the modifier, the modifier enabling electronic hole scavenging and chelation of the metal ions. The metal ions and modifier are illuminated to cause reduction of the metal ions to metal onto the semiconductor nanoparticles.

  16. Photocapacitive light sensor based on metal-YMnO3-insulator-semiconductor structures

    NASA Astrophysics Data System (ADS)

    Bogusz, A.; Choudhary, O. S.; Skorupa, I.; Bürger, D.; Lawerenz, A.; Lei, Y.; Zeng, H.; Abendroth, B.; Stöcker, H.; Schmidt, O. G.; Schmidt, H.

    2016-02-01

    Technology of light sensors, due to the wide range of applications, is a dynamically developing branch of both science and industry. This work presents concept of photodetectors based on a metal-ferroelectric-insulator-semiconductor, a structure which has not been thoroughly explored in the field of photodetectors. Functionality of the presented light sensor exploits the effects of photocapacitive phenomena, ferroelectric polarization, and charge trapping. This is accomplished by an interplay between polarization alignment, subsequent charge distribution, and charge trapping processes under given illumination condition and gate voltage. Change of capacitance serves as a read out parameter indicating the wavelength and intensity of the illuminating light. The operational principle of the proposed photocapacitive light sensor is demonstrated in terms of capacitance-voltage and capacitance-time characteristics of an Al/YMnO3/SiNx/p-Si structure exposed to green, red, and near infrared light. Obtained results are discussed in terms of optical properties of YMnO3 and SiNx layers contributing to the performance of photodetectors. Presented concept of light sensing might serve as the basis for the development of more advanced photodetectors.

  17. Experimental characterization of a metal-oxide-semiconductor field-effect transistor-based Coulter counter.

    PubMed

    Sridhar, Manoj; Xu, Dongyan; Kang, Yuejun; Hmelo, Anthony B; Feldman, Leonard C; Li, Dongqing; Li, Deyu

    2008-05-15

    We report the detailed characterization of an ultrasensitive microfluidic device used to detect the translocation of small particles through a sensing microchannel. The device connects a fluidic circuit to the gate of a metal-oxide-semiconductor field-effect transistor (MOSFET) and detects particles by monitoring the MOSFET drain current modulation instead of the modulation in the ionic current through the sensing channel. The minimum volume ratio of the particle to the sensing channel detected is 0.006%, which is about ten times smaller than the lowest detected volume ratio previously reported in the literature. This volume ratio is detected at a noise level of about 0.6% of the baseline MOSFET drain current, clearly showing the amplification effects from the fluidic circuits and the MOSFETs. We characterize the device sensitivity as a function of the MOSFET gate potential and show that its sensitivity is higher when the MOSFET is operating below its threshold gate voltage than when it is operating above the threshold voltage. In addition, we demonstrate that the device sensitivity linearly increases with the applied electrical bias across the fluidic circuit. Finally, we show that polystyrene beads and glass beads with similar sizes can be distinguished from each other based on their different translocation times, and the size distribution of microbeads can be obtained with accuracy comparable to that of direct scanning electron microscopy measurements. PMID:19479001

  18. Using metal complex-labeled peptides for charge transfer-based biosensing with semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Medintz, Igor L.; Pons, Thomas; Trammell, Scott A.; Blanco-Canosa, Juan B.; Dawson, Philip E.; Mattoussi, Hedi

    2009-02-01

    Luminescent colloidal semiconductor quantum dots (QDs) have unique optical and photonic properties and are highly sensitive to charge transfer in their surrounding environment. In this study we used synthetic peptides as physical bridges between CdSe-ZnS core-shell QDs and some of the most common redox-active metal complexes to understand the charge transfer interactions between the metal complexes and QDs. We found that QD emission underwent quenching that was highly dependent on the choice of metal complex used. We also found that quenching traces the valence or number of metal complexes brought into close proximity of the nanocrystal surface. Monitoring of the QD absorption bleaching in the presence of the metal complex provided insight into the charge transfer mechanism. The data suggest that two distinct charge transfer mechanisms can take place. One directly to the QD core states for neutral capping ligands and a second to surface states for negatively charged capping ligands. A basic understanding of the proximity driven charge-transfer and quenching interactions allowed us to construct proteolytic enzyme sensing assemblies with the QD-peptide-metal complex conjugates.

  19. Mechanisms of current flow in metal-semiconductor ohmic contacts

    SciTech Connect

    Blank, T. V. Gol'dberg, Yu. A.

    2007-11-15

    Published data on the properties of metal-semiconductor ohmic contacts and mechanisms of current flow in these contacts (thermionic emission, field emission, thermal-field emission, and also current flow through metal shunts) are reviewed. Theoretical dependences of the resistance of an ohmic contact on temperature and the charge-carrier concentration in a semiconductor were compared with experimental data on ohmic contacts to II-VI semiconductors (ZnSe, ZnO), III-V semiconductors (GaN, AlN, InN, GaAs, GaP, InP), Group IV semiconductors (SiC, diamond), and alloys of these semiconductors. In ohmic contacts based on lightly doped semiconductors, the main mechanism of current flow is thermionic emission with the metal-semiconductor potential barrier height equal to 0.1-0.2 eV. In ohmic contacts based on heavily doped semiconductors, the current flow is effected owing to the field emission, while the metal-semiconductor potential barrier height is equal to 0.3-0.5 eV. In alloyed In contacts to GaP and GaN, a mechanism of current flow that is not characteristic of Schottky diodes (current flow through metal shunts formed by deposition of metal atoms onto dislocations or other imperfections in semiconductors) is observed.

  20. DNA-decorated carbon-nanotube-based chemical sensors on complementary metal oxide semiconductor circuitry

    NASA Astrophysics Data System (ADS)

    Chen, Chia-Ling; Yang, Chih-Feng; Agarwal, Vinay; Kim, Taehoon; Sonkusale, Sameer; Busnaina, Ahmed; Chen, Michelle; Dokmeci, Mehmet R.

    2010-03-01

    We present integration of single-stranded DNA (ss-DNA)-decorated single-walled carbon nanotubes (SWNTs) onto complementary metal oxide semiconductor (CMOS) circuitry as nanoscale chemical sensors. SWNTs were assembled onto CMOS circuitry via a low voltage dielectrophoretic (DEP) process. Besides, bare SWNTs are reported to be sensitive to various chemicals, and functionalization of SWNTs with biomolecular complexes further enhances the sensing specificity and sensitivity. After decorating ss-DNA on SWNTs, we have found that the sensing response of the gas sensor was enhanced (up to ~ 300% and ~ 250% for methanol vapor and isopropanol alcohol vapor, respectively) compared with bare SWNTs. The SWNTs coupled with ss-DNA and their integration on CMOS circuitry demonstrates a step towards realizing ultra-sensitive electronic nose applications.

  1. DNA-decorated carbon-nanotube-based chemical sensors on complementary metal oxide semiconductor circuitry.

    PubMed

    Chen, Chia-Ling; Yang, Chih-Feng; Agarwal, Vinay; Kim, Taehoon; Sonkusale, Sameer; Busnaina, Ahmed; Chen, Michelle; Dokmeci, Mehmet R

    2010-03-01

    We present integration of single-stranded DNA (ss-DNA)-decorated single-walled carbon nanotubes (SWNTs) onto complementary metal oxide semiconductor (CMOS) circuitry as nanoscale chemical sensors. SWNTs were assembled onto CMOS circuitry via a low voltage dielectrophoretic (DEP) process. Besides, bare SWNTs are reported to be sensitive to various chemicals, and functionalization of SWNTs with biomolecular complexes further enhances the sensing specificity and sensitivity. After decorating ss-DNA on SWNTs, we have found that the sensing response of the gas sensor was enhanced (up to approximately 300% and approximately 250% for methanol vapor and isopropanol alcohol vapor, respectively) compared with bare SWNTs. The SWNTs coupled with ss-DNA and their integration on CMOS circuitry demonstrates a step towards realizing ultra-sensitive electronic nose applications. PMID:20139486

  2. First principles study of Fe in diamond: A diamond-based half metallic dilute magnetic semiconductor

    SciTech Connect

    Benecha, E. M.; Lombardi, E. B.

    2013-12-14

    Half-metallic ferromagnetic ordering in semiconductors, essential in the emerging field of spintronics for injection and transport of highly spin polarised currents, has up to now been considered mainly in III–V and II–VI materials. However, low Curie temperatures have limited implementation in room temperature device applications. We report ab initio Density Functional Theory calculations on the properties of Fe in diamond, considering the effects of lattice site, charge state, and Fermi level position. We show that the lattice sites and induced magnetic moments of Fe in diamond depend strongly on the Fermi level position and type of diamond co-doping, with Fe being energetically most favorable at the substitutional site in p-type and intrinsic diamond, while it is most stable at a divacancy site in n-type diamond. Fe induces spin polarized bands in the band gap, with strong hybridization between Fe-3d and C-2s,2p bands. We further consider Fe-Fe spin interactions in diamond and show that substitutional Fe{sup +1} in p-type diamond exhibits a half-metallic character, with a magnetic moment of 1.0 μ{sub B} per Fe atom and a large ferromagnetic stabilization energy of 33 meV, an order of magnitude larger than in other semiconductors, with correspondingly high Curie temperatures. These results, combined with diamond's unique properties, demonstrate that Fe doped p-type diamond is likely to be a highly suitable candidate material for spintronics applications.

  3. The physical origin of dispersion in accumulation in InGaAs based metal oxide semiconductor gate stacks

    NASA Astrophysics Data System (ADS)

    Krylov, Igor; Ritter, Dan; Eizenberg, Moshe

    2015-05-01

    Dispersion in accumulation is a widely observed phenomenon in technologically important InGaAs gate stacks. Two principal different interface defects were proposed as the physical origin of this phenomenon—disorder induced gap states and border traps. While the gap states are located at the semiconductor side of the interface, the border traps are related to the dielectric side. The study of Al2O3, HfO2, and an intermediate composition of HfxAlyO deposited on InGaAs enabled us to find a correlation between the dispersion and the dielectric/InGaAs band offset. At the same time, no change in the dispersion was observed after applying an effective pre-deposition treatment which results in significant reduction of the interface states. Both observations prove that border traps are the physical origin of the dispersion in accumulation in InGaAs based metal-oxide-semiconductor gate stacks.

  4. Monolithic integration of GaN-based light-emitting diodes and metal-oxide-semiconductor field-effect transistors.

    PubMed

    Lee, Ya-Ju; Yang, Zu-Po; Chen, Pin-Guang; Hsieh, Yung-An; Yao, Yung-Chi; Liao, Ming-Han; Lee, Min-Hung; Wang, Mei-Tan; Hwang, Jung-Min

    2014-10-20

    In this study, we report a novel monolithically integrated GaN-based light-emitting diode (LED) with metal-oxide-semiconductor field-effect transistor (MOSFET). Without additionally introducing complicated epitaxial structures for transistors, the MOSFET is directly fabricated on the exposed n-type GaN layer of the LED after dry etching, and serially connected to the LED through standard semiconductor-manufacturing technologies. Such monolithically integrated LED/MOSFET device is able to circumvent undesirable issues that might be faced by other kinds of integration schemes by growing a transistor on an LED or vice versa. For the performances of resulting device, our monolithically integrated LED/MOSFET device exhibits good characteristics in the modulation of gate voltage and good capability of driving injected current, which are essential for the important applications such as smart lighting, interconnection, and optical communication. PMID:25607316

  5. Noble metal-free hydrogen-evolving photocathodes based on small molecule organic semiconductors

    NASA Astrophysics Data System (ADS)

    Morozan, A.; Bourgeteau, T.; Tondelier, D.; Geffroy, B.; Jousselme, B.; Artero, V.

    2016-09-01

    Organic semiconductors have great potential for producing hydrogen in a sustainable and economically-viable manner because they rely on readily available materials with highly tunable properties. We demonstrate here the relevance of heterojunctions to the construction of H2-evolving photocathodes, exclusively based on earth-abundant elements. Boron subnaphthalocyanine chloride proved a very promising acceptor in that perspective. It absorbs a part of the solar spectrum complementary to α-sexithiophene as a donor, thus generating large photocurrents and providing a record onset potential for light-driven H2 evolution under acidic aqueous conditions using a nanoparticulate amorphous molybdenum sulfide catalyst.

  6. Noble metal-free hydrogen-evolving photocathodes based on small molecule organic semiconductors.

    PubMed

    Morozan, A; Bourgeteau, T; Tondelier, D; Geffroy, B; Jousselme, B; Artero, V

    2016-09-01

    Organic semiconductors have great potential for producing hydrogen in a sustainable and economically-viable manner because they rely on readily available materials with highly tunable properties. We demonstrate here the relevance of heterojunctions to the construction of H2-evolving photocathodes, exclusively based on earth-abundant elements. Boron subnaphthalocyanine chloride proved a very promising acceptor in that perspective. It absorbs a part of the solar spectrum complementary to α-sexithiophene as a donor, thus generating large photocurrents and providing a record onset potential for light-driven H2 evolution under acidic aqueous conditions using a nanoparticulate amorphous molybdenum sulfide catalyst. PMID:27455142

  7. Interfaces in semiconductor/metal radial superlattices

    SciTech Connect

    Deneke, Christoph; Sigle, Wilfried; Eigenthaler, Ulrike; Aken, Peter A. van; Schuetz, Gisela; Schmidt, Oliver G.

    2007-06-25

    Semiconductor/metal radial superlattices are produced by the roll-up of inherently strained InGaAs/Ti/Au as well as InAlGaAs/GaAs/Cr films. Cross sections of the obtained structures are prepared and investigated in detail by diverse transmission electron microscopy as well as microanalysis techniques. Special attention is paid to the interfaces of the semiconductor/metal hybrid superlattice. The study reveals amorphous, noncrystalline layers for the semiconductor/metal as well as for the metal/semiconductor interface. The chemical analysis suggests that the observed interlayers are oxides giving rise to a semiconductor/oxide/metal/oxide superlattice rather than a pure semiconductor/metal superlattice.

  8. Nitride-Based UV Metal-Insulator-Semiconductor Photodetector with Liquid-Phase-Deposition Oxide

    NASA Astrophysics Data System (ADS)

    Hwang, J. D.; Yang, Gwo Huei; Yang, Yuan Yi; Yao, Pin Cuan

    2005-11-01

    A low-temperature (30-40°C), low-cost and reliable method of liquid phase deposition (LPD) has been employed to grow SiO2 layers on GaN. The LPD process uses a supersaturated acid aqueous solution of hydrofluosilicic (H2SiF6) as a source liquid and an aqueous solution of boric acid (H3BO3) as a deposition rate controller. In this study, the LPD SiO2 was prepared at 40°C with concentrations of H2SiF6 and H3BO3 at 0.2 and 0.01 M, respectively. The minimum interface-trap density, Dit, of a metal-insulator-semiconductor (MIS) capacitor with a structure of Al/20 nm LPD-SiO2/n-GaN was estimated to be 8.4× 1011 cm-2 V-1. Furthermore, a MIS photodetector with a 10-nm-thick LPD-SiO2 layer has been fabricated successfully. The dark current density was as low as 4.41× 10-6 A/cm2 for an applied field of 4 MV/cm. A maximum responsivity of 0.112 A/W was observed for incident ultraviolet light of 366 nm with an intensity of 4.15 mW/cm2. Defect-assisted tunneling was invoked to explain these results.

  9. Low dark current metal-semiconductor-metal ultraviolet photodetectors based on sol-gel-derived TiO2 films

    NASA Astrophysics Data System (ADS)

    Xie, Yannan; Huang, Huolin; Yang, Weifeng; Wu, Zhengyun

    2011-01-01

    The titanium dioxide (TiO2) films prepared by sol-gel processing were used to fabricate metal-semiconductor-metal ultraviolet photodetectors. A very low dark current of 5.38 pA (current density of 3.84 nA/cm2) at 5 V bias is obtained, which is ascribed to the high effective Schottky barrier between Au and TiO2 films. The x-ray photoelectron spectroscopy analysis demonstrates that the concentration of oxygen vacancies is very low in the surface of the TiO2 films, which is responsible for the high effective Schottky barrier. The devices exhibit a cutoff wavelength at about 380 nm and a large UV-to-visible rejection ratio (340 versus 400 nm) of three orders of magnitude. The peak responsivity of the devices is 17.5 A/W at 5 V bias, indicating the presence of internal photoconductive gain induced by desorption of oxygen on the TiO2 surface.

  10. Dilute magnetic semiconductors based on wide bandgap SiO 2 with and without transition metal elements

    NASA Astrophysics Data System (ADS)

    Dinh, Van An; Sato, Kazunori; Katayama-Yoshida, Hiroshi

    2005-10-01

    Material designs based on the first principle calculations of electronic structures are proposed for α-quartz SiO 2-based dilute magnetic semiconductors. The incorporation of transition metals (TMs) into Si sites and of the non-TM atoms into O sites are treated for various concentrations. At temperatures higher than room temperature, most of the TM-doped SiO 2 have no magnetism, yet Si 1- xMn xO 2 might achieve the ferromagnetism. The substitution of O by non-TM atoms as C or N also induces the magnetism in the host. However, while the N's substitution induces the ferromagnetism, C's substitution causes an anti-ferromagnetic behavior in the host material SiO 2.

  11. GaN-Based Trench Gate Metal Oxide Semiconductor Field-Effect Transistor Fabricated with Novel Wet Etching

    NASA Astrophysics Data System (ADS)

    Kodama, Masahito; Sugimoto, Masahiro; Hayashi, Eiko; Soejima, Narumasa; Ishiguro, Osamu; Kanechika, Masakazu; Itoh, Kenji; Ueda, Hiroyuki; Uesugi, Tsutomu; Kachi, Tetsu

    2008-02-01

    A novel method for fabricating trench structures on GaN was developed. A smooth non-polar (1100) plane was obtained by wet etching using tetramethylammonium hydroxide (TMAH) as the etchant. A U-shape trench with the (1100) plane side walls was formed with dry etching and the TMAH wet etching. A U-shape trench gate metal oxide semiconductor field-effect transistor (MOSFET) was also fabricated using the novel etching technology. This device has the excellent normally-off operation of drain current-gate voltage characteristics with the threshold voltage of 10 V. The drain breakdown voltage of 180 V was obtained. The results indicate that the trench gate structure can be applied to GaN-based transistors.

  12. Capacitance-voltage characteristics of Si and Ge nanomembrane based flexible metal-oxide-semiconductor devices under bending conditions

    NASA Astrophysics Data System (ADS)

    Cho, Minkyu; Seo, Jung-Hun; Park, Dong-Wook; Zhou, Weidong; Ma, Zhenqiang

    2016-06-01

    Metal-oxide-semiconductor (MOS) device is the basic building block for field effect transistors (FET). The majority of thin-film transistors (TFTs) are FETs. When MOSFET are mechanically bent, the MOS structure will be inevitably subject to mechanical strain. In this paper, flexible MOS devices using single crystalline Silicon (Si) and Germanium (Ge) nanomembranes (NM) with SiO2, SiO, and Al2O3 dielectric layers are fabricated on a plastic substrate. The relationships between semiconductor nanomembranes and various oxide materials are carefully investigated under tensile/compressive strain. The flatband voltage, threshold voltage, and effective charge density in various MOS combinations revealed that Si NM-SiO2 configuration shows the best interface charge behavior, while Ge NM-Al2O3 shows the worst. This investigation of flexible MOS devices can help us understand the impact of charges in the active region of the flexible TFTs and capacitance changes under the tensile/compressive strains on the change in electrical characteristics in flexible NM based TFTs.

  13. Performance improvement of GaN-based metal-semiconductor-metal photodiodes grown on Si(111) substrate by thermal cycle annealing process

    NASA Astrophysics Data System (ADS)

    Lin, Jyun-Hao; Huang, Shyh-Jer; Su, Yan-Kuin

    2014-01-01

    A simple thermal cycle annealing (TCA) process was used to improve the quality of GaN grown on a Si substrate. The X-ray diffraction (XRD) and etch pit density (EPD) results revealed that using more process cycles, the defect density cannot be further reduced. However, the performance of GaN-based metal-semiconductor-metal (MSM) photodiodes (PDs) prepared on Si substrates showed significant improvement. With a two-cycle TCA process, it is found that the dark current of the device was only 1.46 × 10-11 A, and the photo-to-dark-current contrast ratio was about 1.33 × 105 at 5 V. Also, the UV/visible rejection ratios can reach as high as 1077.

  14. Metal oxide semiconductors for solar energy harvesting

    NASA Astrophysics Data System (ADS)

    Thimsen, Elijah James

    The correlation between energy consumption and human development illustrates the importance of this societal resource. We will consume more energy in the future. In light of issues with the status quo, such as climate change, long-term supply and security, solar energy is an attractive source. It is plentiful, virtually inexhaustible, and can provide more than enough energy to power society. However, the issue with producing electricity and fuels from solar energy is that it is expensive, primarily from the materials (silicon) used in building the cells. Metal oxide semiconductors are an attractive class of materials that are extremely low cost and can be produced at the scale needed to meet widespread demand. An industrially attractive thin film synthesis process based on aerosol deposition was developed that relies on self-assembly to afford rational control over critical materials parameters such as film morphology and nanostructure. The film morphology and nanostructure were found to have dramatic effects on the performance of TiO2-based photovoltaic dye-sensitized solar cells. Taking a cue from nature, to overcome the spatial and temporal mismatch between the supply of sunlight and demand for energy consumption, it is desirable to produce solar fuels such as hydrogen from photoelectrochemical water splitting. The source of water is important---seawater is attractive. The fundamental reaction mechanism for TiO2-based cells is discussed in the context of seawater splitting. There are two primary issues with producing hydrogen by photoelectrochemical water splitting using metal-oxide semiconductors: visible light activity and spontaneous activity. To address the light absorption issue, a combined theory-experiment approach was taken to understand the fundamental role of chemical composition in determining the visible light absorption properties of mixed metal-oxide semiconductors. To address the spontaneous activity issue, self-biasing all oxide p/n bulk

  15. HfO2-based InP n-channel metal-oxide-semiconductor field-effect transistors and metal-oxide-semiconductor capacitors using a germanium interfacial passivation layer

    NASA Astrophysics Data System (ADS)

    Kim, Hyoung-Sub; Ok, I.; Zhang, M.; Zhu, F.; Park, S.; Yum, J.; Zhao, H.; Lee, Jack C.; Majhi, Prashant

    2008-09-01

    In this letter, we present our experimental results of HfO2-based n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) and metal-oxide-semiconductor capacitors (MOSCAPs) on indium phosphide (InP) substrates using a thin germanium (Ge) interfacial passivation layer (IPL). We found that MOSCAPs on n-InP substrates showed good C-V characteristics such as a small capacitance equivalent thickness (14Å ), a small frequency dispersion (<10% and <200mV), and a low dielectric leakage current (˜5×10-4A/cm2 at Vg=1.5V), whereas MOSCAPs on p-InP exhibited poor characteristics, implying severe Fermi level pinning. It was also found that InP was more vulnerable to a high temperature process such that C-V curves showed a characteristic "bump" and inversion capacitance at relatively high frequencies. From n-channel MOSFETs on a semi-insulating InP substrate using Ge IPL, HfO2, and TaN gate electrodes, excellent electrical characteristics such as a large transconductance (9.3mS /mm) and large drain currents (12.3mA/mm at Vd=2V and Vg=Vth+2V) were achieved, which are comparable to other works.

  16. Optical Properties of Planar Nanostructures Based on Semiconductor Quantum Dots and Plasmonic Metal Nanoparticles

    NASA Astrophysics Data System (ADS)

    Bakanov, A. G.; Toropov, N. A.; Vartanyan, T. A.

    2016-03-01

    The optical properties of a composite material consisting of a thin polymer film, which is activated by semiconductor CdSe/ZnS quantum dots (QDs) and silver nanoparticles, on a transparent dielectric substrate have been investigated. It is revealed that the presence of silver nanoparticles leads to an increase in the QD absorption (by a factor of 4) and in the fluorescence intensity (by a factor of 10), whereas the fluorescence time drops by a factor of about 10. Excitation of the composite medium by a pulsed laser is found to result in narrowing of the fluorescence band and a sublinear dependence of its intensity on the pulse energy. In the absence of silver nanoparticles, the fluorescence spectrum of QDs is independent of the excitation-pulse energy density, and the fluorescence intensity depends linearly on the pulse energy in the entire range of energy densities, up to 75 mJ/cm2.

  17. CdSe Nanowire-Based Flexible Devices: Schottky Diodes, Metal-Semiconductor Field-Effect Transistors, and Inverters.

    PubMed

    Jin, Weifeng; Zhang, Kun; Gao, Zhiwei; Li, Yanping; Yao, Li; Wang, Yilun; Dai, Lun

    2015-06-24

    Novel CdSe nanowire (NW)-based flexible devices, including Schottky diodes, metal-semiconductor field-effect transistors (MESFETs), and inverters, have been fabricated and investigated. The turn-on voltage of a typical Schottky diode is about 0.7 V, and the rectification ratio is larger than 1 × 10(7). The threshold voltage, on/off current ratio, subthreshold swing, and peak transconductance of a typical MESFET are about -0.3 V, 4 × 10(5), 78 mV/dec, and 2.7 μS, respectively. The inverter, constructed with two MESFETs, exhibits clear inverting behavior with the gain to be about 28, 34, and 38, at the supply voltages (V(DD)) of 3, 5, and 7 V, respectively. The inverter also shows good dynamic behavior. The rising and falling times of the output signals are about 0.18 and 0.09 ms, respectively, under 1000 Hz square wave signals input. The performances of the flexible devices are stable and reliable under different bending conditions. Our work demonstrates these flexible NW-based Schottky diodes, MESFETs, and inverters are promising candidate components for future portable transparent nanoelectronic devices. PMID:26061530

  18. A Three-Stage Inverter-Based Stacked Power Amplifier in 65 nm Complementary Metal Oxide Semiconductor Process

    NASA Astrophysics Data System (ADS)

    Kiumarsi, Hamid; Mizuochi, Yutaka; Ito, Hiroyuki; Ishihara, Noboru; Masu, Kazuya

    2012-02-01

    A three-stage inverter-based stacked power amplifier (PA) in complementary metal oxide semiconductor (CMOS) process is proposed to overcome low breakdown voltage problem of scaled CMOS technologies. Unlike previous reported stacked PAs which radio frequency choke (RFC) was inevitable, we proposed stacked nMOS and pMOS transistors which effectively eliminates use of RFC. By properly setting self-biased circuits' and transistors' parameters, output impedance could reach up to 50 Ω which together with not employing the RFC makes this topology very appealing for the scalable PA realization. As a proof of concept, a three-stage PA using 65 nm CMOS technology is implemented. With a 6 V power supply for the third stage, the fabricated PA shows a small-signal gain of 36 dB, a saturated output power of 16 dBm and a maximum power added efficiency of 10% at 1 GHz. Using a 7.5 V of power supply, saturated output power reaches 18 dBm. To the best of our knowledge, this is the first reported inverter-based stacked PA.

  19. Chip-scale fluorescence microscope based on a silo-filter complementary metal-oxide semiconductor image sensor.

    PubMed

    Ah Lee, Seung; Ou, Xiaoze; Lee, J Eugene; Yang, Changhuei

    2013-06-01

    We demonstrate a silo-filter (SF) complementary metal-oxide semiconductor (CMOS) image sensor for a chip-scale fluorescence microscope. The extruded pixel design with metal walls between neighboring pixels guides fluorescence emission through the thick absorptive filter to the photodiode of a pixel. Our prototype device achieves 13 μm resolution over a wide field of view (4.8 mm × 4.4 mm). We demonstrate bright-field and fluorescence longitudinal imaging of living cells in a compact, low-cost configuration. PMID:23722754

  20. C-V measurements of micron diameter metal-oxide-semiconductor capacitors using a scanning-electron-microscope-based nanoprobe.

    PubMed

    Zheng, T; Jia, H; Wallace, R M; Gnade, B E

    2007-10-01

    The C-V electrical characterization of microstructures on a standard probe station is limited by the magnification of the imaging system and the precision of the probe manipulators. To overcome these limitations, we examine the combination of in situ electrical probing and a dual column scanning electron microscope/focused ion beam system. The imaging parameters and probing procedures are carefully chosen to reduce e-beam damage to the metal oxide semiconductor capacitor device under test. Estimation of shunt capacitance is critical when making femtofarad level measurements. C-V measurements of micron size metal-oxide-silicon capacitors are demonstrated. PMID:17979444

  1. Metal insulator semiconductor solar cell devices based on a Cu{sub 2}O substrate utilizing h-BN as an insulating and passivating layer

    SciTech Connect

    Ergen, Onur; Gibb, Ashley; Vazquez-Mena, Oscar; Zettl, Alex; Regan, William Raymond

    2015-03-09

    We demonstrate cuprous oxide (Cu{sub 2}O) based metal insulator semiconductor Schottky (MIS-Schottky) solar cells with efficiency exceeding 3%. A unique direct growth technique is employed in the fabrication, and hexagonal boron nitride (h-BN) serves simultaneously as a passivation and insulation layer on the active Cu{sub 2}O layer. The devices are the most efficient of any Cu{sub 2}O based MIS-Schottky solar cells reported to date.

  2. Contact resistivities of metal-insulator-semiconductor contacts and metal-semiconductor contacts

    NASA Astrophysics Data System (ADS)

    Yu, Hao; Schaekers, Marc; Barla, Kathy; Horiguchi, Naoto; Collaert, Nadine; Thean, Aaron Voon-Yew; De Meyer, Kristin

    2016-04-01

    Applying simulations and experiments, this paper systematically compares contact resistivities (ρc) of metal-insulator-semiconductor (MIS) contacts and metal-semiconductor (MS) contacts with various semiconductor doping concentrations (Nd). Compared with the MS contacts, the MIS contacts with the low Schottky barrier height are more beneficial for ρc on semiconductors with low Nd, but this benefit diminishes gradually when Nd increases. With high Nd, we find that even an "ideal" MIS contact with optimized parameters cannot outperform the MS contact. As a result, the MIS contacts mainly apply to devices that use relatively low doped semiconductors, while we need to focus on the MS contacts to meet the sub-1 × 10-8 Ω cm2 ρc requirement for future Complementary Metal-Oxide-Semiconductor (CMOS) technology.

  3. Quantitative analysis and prediction of experimental observations on quasi-static hysteretic metal-ferroelectric-metal-insulator-semiconductor FET and its dynamic behaviour based on Landau theory

    NASA Astrophysics Data System (ADS)

    Li, Yang; Lian, Yong; Samudra, Ganesh S.

    2015-04-01

    Due to internal voltage amplification induced by the negative capacitance of ferroelectrics, the metal-ferroelectric-metal-insulator-semiconductor (MFMIS) FET has been widely investigated to explore its potential application in low power devices. Based on Landau theory and stability criterion, a simulation program is implemented and MFMIS structure is quantitatively analyzed. The results show that it can be appropriately designed for both integrated circuits and memory devices by tuning capacitances contributed by MOSFET dielectric stack and ferroelectrics. Our simulation results on electrical characteristics of ferroelectric devices agree well with both quasi-static and dynamic experimental observations. The influence of the ferroelectric/dielectric layer thickness and area as well as temperature on hysteretic polarization-electric field characteristic of a ferroelectric are successfully explained. For a C-V loop sweeping over the gate voltage in MFMIS, possible asymmetry in the accessible negative capacitance region is also interpreted. Moreover, experimentally observed reduction in the equivalent capacitance of the ferroelectric-dielectric bilayer at high frequency is confirmed by Landau-Khalatnikov theory based simulation. Our work provides a more complete and explicit analytical treatment to understand the effect of negative capacitance of a ferroelectric on device performance.

  4. Dopant in Near-Surface Semiconductor Layers of Metal-Insulator-Semiconductor Structures Based on Graded-Gap p-Hg0.78Cd0.22Te Grown by Molecular-Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Voitsekhovskii, A. V.; Nesmelov, S. N.; Dzyadukh, S. M.

    2016-02-01

    Peculiarities in determining the dopant concentration and dopant distribution profile in the near-surface layer of a semiconductor are investigated by measuring the admittance of metal-insulator-semiconductor structures (MIS structures) based on p-Hg0.78Cd0.22Te grown by molecular beam epitaxy. The dopant concentrations in the near-surface layer of the semiconductor are determined by measuring the admittance of MIS structures in the frequency range of 50 kHz to 1 MHz. It is shown that in this frequency range, the capacitance-voltage characteristics of MIS structures based on p-Hg0.78Cd0.22Te with a near-surface graded gap layer demonstrate a high-frequency behavior with respect to the recharge time of surface states located near the Fermi level for an intrinsic semiconductor. The formation time of the inversion layer is decreased by less than two times, if a near-surface graded-gap layer is created. The dopant distribution profile in the near-surface layer of the semiconductor is found, and it is shown that for structures based on p-Hg0.78Cd0.22Te with a near-surface graded-gap layer, the dopant concentration has a minimum near the interface with the insulator. For MIS structure based on n-Hg0.78Cd0.22Te, the dopant concentration is more uniformly distributed in the near-surface layer of the semiconductor.

  5. Flexible germanium nanomembrane metal-semiconductor-metal photodiodes

    NASA Astrophysics Data System (ADS)

    Kim, Munho; Seo, Jung-Hun; Yu, Zongfu; Zhou, Weidong; Ma, Zhenqiang

    2016-08-01

    We demonstrate flexible Ge nanomembrane (Ge NM) based metal-semiconductor-metal photodiodes. The effect of uniaxial tensile strain on Ge NM based photodiodes was investigated using bending fixtures. Dark current density is decreased from 21.5 to 4.8 mA/cm2 at 3 V by a tensile strain of 0.42% while photon responsivity is increased from 0.2 to 0.45 A/W at the wavelength of 1.5 μm. Enhanced responsivity is also observed at longer wavelengths up to 1.64 μm. The uniaxial tensile strain effectively reduces the direct bandgap energy of the Ge NM, leading to a shift of the absorption edge toward a longer wavelength.

  6. Circular electrode geometry metal-semiconductor-metal photodetectors

    NASA Technical Reports Server (NTRS)

    Mcaddo, James A. (Inventor); Towe, Elias (Inventor); Bishop, William L. (Inventor); Wang, Liang-Guo (Inventor)

    1994-01-01

    The invention comprises a high speed, metal-semiconductor-metal photodetector which comprises a pair of generally circular, electrically conductive electrodes formed on an optically active semiconductor layer. Various embodiments of the invention include a spiral, intercoiled electrode geometry and an electrode geometry comprised of substantially circular, concentric electrodes which are interposed. These electrode geometries result in photodetectors with lower capacitances, dark currents and lower inductance which reduces the ringing seen in the optical pulse response.

  7. Circular electrode geometry metal-semiconductor-metal photodetectors

    NASA Technical Reports Server (NTRS)

    Mcadoo, James A. (Inventor); Towe, Elias (Inventor); Bishop, William L. (Inventor); Wang, Liang-Guo (Inventor)

    1995-01-01

    The invention comprises a high speed, metal-semiconductor-metal photodetector which comprises a pair of generally circular, electrically conductive electrodes formed on an optically active semiconductor layer. Various embodiments of the invention include a spiral, intercoiled electrode geometry and an electrode geometry comprised of substantially circular, concentric electrodes which are interposed. These electrode geometries result in photodetectors with lower capacitances, dark currents and lower inductance which reduces the ringing seen in the optical pulse response.

  8. Hybrid Semiconductor-Metal Nanorods as Photocatalysts.

    PubMed

    Ben-Shahar, Yuval; Banin, Uri

    2016-08-01

    Semiconductor-metal hybrid nanoparticles manifest combined and often synergistic properties exceeding the functionality of the individual components, thereby opening up interesting opportunities for controlling their properties through the direct manipulation of their unique semiconductor-metal interface. Upon light absorption, these structures exhibit spatial charge separation across the semiconductor-metal junction. A significant and challenging application involves the use of these nanoparticles as photocatalysts. Through this process, the charge carriers transferred to the metal co-catalyst are available as reduction or oxidation reagents to drive the surface chemical reactions. In this review, we discuss synthesis approaches that offer a high degree of control over the hybrid nanoparticle structure and composition, the number of catalytic sites and the interfacial characteristics, including examples of a variety of photocatalyst architectures. We describe the structural and surface effects with regard to the functionality of hybrid nanosystems in photocatalysis, along with the effects of solution and chemical conditions on photocatalytic activity and efficiency. We conclude with a perspective on the rational design of advanced semiconductor-metal hybrid nanoparticles towards their functionality as highly efficient photocatalysts. PMID:27573406

  9. Recent progress on ZnO-based metal-semiconductor field-effect transistors and their application in transparent integrated circuits.

    PubMed

    Frenzel, Heiko; Lajn, Alexander; von Wenckstern, Holger; Lorenz, Michael; Schein, Friedrich; Zhang, Zhipeng; Grundmann, Marius

    2010-12-14

    Metal-semiconductor field-effect transistors (MESFETs) are widely known from opaque high-speed GaAs or high-power SiC and GaN technology. For the emerging field of transparent electronics, only metal-insulator-semiconductor field-effect transistors (MISFETs) were considered so far. This article reviews the progress of high-performance MESFETs in oxide electronics and reflects the recent advances of this technique towards transparent MESFET circuitry. We discuss design prospects as well as limitations regarding device performance, reliability and stability. The presented ZnO-based MESFETs and inverters have superior properties compared to MISFETs, i.e., high channel mobilities and on/off-ratios, high gain, and low uncertainty level at comparatively low operating voltages. This makes them a promising approach for future low-cost transparent electronics. PMID:20878625

  10. Controlling the interface charge density in GaN-based metal-oxide-semiconductor heterostructures by plasma oxidation of metal layers

    SciTech Connect

    Hahn, Herwig Kalisch, Holger; Vescan, Andrei; Pécz, Béla; Kovács, András; Heuken, Michael

    2015-06-07

    In recent years, investigating and engineering the oxide-semiconductor interface in GaN-based devices has come into focus. This has been driven by a large effort to increase the gate robustness and to obtain enhancement mode transistors. Since it has been shown that deep interface states act as fixed interface charge in the typical transistor operating regime, it appears desirable to intentionally incorporate negative interface charge, and thus, to allow for a positive shift in threshold voltage of transistors to realise enhancement mode behaviour. A rather new approach to obtain such negative charge is the plasma-oxidation of thin metal layers. In this study, we present transmission electron microscopy and energy dispersive X-ray spectroscopy analysis as well as electrical data for Al-, Ti-, and Zr-based thin oxide films on a GaN-based heterostructure. It is shown that the plasma-oxidised layers have a polycrystalline morphology. An interfacial amorphous oxide layer is only detectable in the case of Zr. In addition, all films exhibit net negative charge with varying densities. The Zr layer is providing a negative interface charge density of more than 1 × 10{sup 13 }cm{sup –2} allowing to considerably shift the threshold voltage to more positive values.

  11. Highly tunable-emittance radiator based on semiconductor-metal transition of VO2 thin films

    NASA Astrophysics Data System (ADS)

    Hendaoui, Ali; Émond, Nicolas; Chaker, Mohamed; Haddad, Émile

    2013-02-01

    This paper describes a VO2-based smart structure with an emittance that increases with the temperature. A large tunability of the spectral emittance, which can be as high as 0.90, was achieved. The transition of the total emittance with the temperature was fully reversible according to a hysteresis cycle, with a transition temperature of 66.5 °C. The total emittance of the device was found to be 0.22 and 0.71 at 25 °C and 100 °C, respectively. This emittance performance and the structure simplicity are promising for the next generation of energy-efficient cost-effective passive thermal control systems of spacecrafts.

  12. Theoretical study of the noble metals on semiconductor surfaces and Ti-base shape memory alloys

    SciTech Connect

    Ding, Yungui

    1994-07-27

    The electronic and structural properties of the ({radical}3 {times} {radical}3) R30{degrees} Ag/Si(111) and ({radical}3 {times} {radical}3) R30{degrees} Au/Si(111) surfaces are investigated using first principles total energy calculations. We have tested almost all experimentally proposed structural models for both surfaces and found the energetically most favorable model for each of them. The lowest energy model structure of the ({radical}3 {times} {radical}3) R30{degrees} Ag/Si(111) surface consists of a top layer of Ag atoms arranged as ``honeycomb-chained-trimers`` lying above a distorted ``missing top layer`` Si(111) substrate. The coverage of Ag is 1 monolayer (ML). We find that the honeycomb structure observed in STM images arise from the electronic charge densities of an empty surface band near the Fermi level. The electronic density of states of this model gives a ``pseudo-gap`` around the Fermi level, which is consistent with experimental results. The lowest energy model for the ({radical}3 {times} {radical}3) R30{degrees} Au/Si(111) surface is a conjugate honeycomb-chained-trimer (CHCT-1) configuration which consists of a top layer of trimers formed by 1 ML Au atoms lying above a ``missing top layer`` Si(111) substrate with a honeycomb-chained-trimer structure for its first layer. The structures of Au and Ag are in fact quite similar and belong to the same class of structural models. However, small variation in the structural details gives rise to quite different observed STM images, as revealed in the theoretical calculations. The electronic charge density from bands around the Fermi level for the ({radical}3 {times} {radical}3) R30{degrees}, Au/Si(111) surface also gives a good description of the images observed in STM experiments. First principles calculations are performed to study the electronic and structural properties of a series of Ti-base binary alloys TiFe, TiNi, TiPd, TiMo, and TiAu in the B2 structure.

  13. Multilevel metallization method for fabricating a metal oxide semiconductor device

    NASA Technical Reports Server (NTRS)

    Hollis, B. R., Jr.; Feltner, W. R.; Bouldin, D. L.; Routh, D. E. (Inventor)

    1978-01-01

    An improved method is described of constructing a metal oxide semiconductor device having multiple layers of metal deposited by dc magnetron sputtering at low dc voltages and low substrate temperatures. The method provides multilevel interconnections and cross over between individual circuit elements in integrated circuits without significantly reducing the reliability or seriously affecting the yield.

  14. Responsivity drop due to conductance modulation in GaN metal-semiconductor-metal Schottky based UV photodetectors on Si(111)

    NASA Astrophysics Data System (ADS)

    Ravikiran, L.; Radhakrishnan, K.; Dharmarasu, N.; Agrawal, M.; Wang, Zilong; Bruno, Annalisa; Soci, Cesare; Lihuang, Tng; Kian Siong, Ang

    2016-09-01

    GaN Schottky metal-semiconductor-metal (MSM) UV photodetectors were fabricated on a 600 nm thick GaN layer, grown on 100 mm Si (111) substrate using an ammonia-MBE growth technique. In this report, the effect of device dimensions, applied bias and input power on the linearity of the GaN Schottky-based MSM photodetectors on Si substrate were investigated. Devices with larger interdigitated spacing, ‘S’ of 9.0 μm between the fingers resulted in good linearity and flat responsivity characteristics as a function of input power with an external quantum efficiency (EQE) of ∼33% at an applied bias of 15 V and an input power of 0.8 W m‑2. With the decrease of ‘S’ to 3.0 μm, the EQE was found to increase to ∼97%. However, devices showed non linearity and drop in responsivity from flatness at higher input power. Moreover, the position of dropping from flatter responsivity was found to shift to lower powers with increased bias. The drop in the responsivity was attributed to the modulation of conductance in the MSM due to the trapping of electrons at the dislocations, resulting in the formation of depletion regions around them. In devices with lower ‘S’, both the image force reduction and the enhanced collection efficiency increased the photocurrent as well as the charging of the dislocations. This resulted in the increased depletion regions around the dislocations leading to the modulation of conductance and non-linearity.

  15. CMOS array design automation techniques. [metal oxide semiconductors

    NASA Technical Reports Server (NTRS)

    Ramondetta, P.; Feller, A.; Noto, R.; Lombardi, T.

    1975-01-01

    A low cost, quick turnaround technique for generating custom metal oxide semiconductor arrays using the standard cell approach was developed, implemented, tested and validated. Basic cell design topology and guidelines are defined based on an extensive analysis that includes circuit, layout, process, array topology and required performance considerations particularly high circuit speed.

  16. Toward Photochemical Water Splitting Using Band-Gap-Narrowed Semiconductors and Transition-Metal Based Molecular Catalysts

    SciTech Connect

    Muckerman,J.T.; Rodriguez, J.A.; Fujita, E.

    2009-06-07

    We are carrying out coordinated theoretical and experimental studies of toward photochemical water splitting using band-gap-narrowed semiconductors (BGNSCs) with attached multi-electron molecular water oxidation and hydrogen production catalysts. We focus on the coupling between the materials properties and the H{sub 2}O redox chemistry, with an emphasis on attaining a fundamental understanding of the individual elementary steps in the following four processes: (1) Light-harvesting and charge-separation of stable oxide or oxide-derived semiconductors for solar-driven water splitting, including the discovery and characterization of the behavior of such materials at the aqueous interface; (2) The catalysis of the four-electron water oxidation by dinuclear hydroxo transition-metal complexes with quinonoid ligands, and the rational search for improved catalysts; (3) Transfer of the design principles learned from the elucidation of the DuBois-type hydrogenase model catalysts in acetonitrile to the rational design of two-electron hydrogen production catalysts for aqueous solution; (4) Combining these three elements to examine the function of oxidation catalysts on BGNSC photoanode surfaces and hydrogen production catalysts on cathode surfaces at the aqueous interface to understand the challenges to the efficient coupling of the materials functions.

  17. Ultra low-loss, isotropic optical negative-index metamaterial based on hybrid metal-semiconductor nanowires

    PubMed Central

    Paniagua-Domínguez, R.; Abujetas, D. R.; Sánchez-Gil, J. A.

    2013-01-01

    Recently, many fascinating properties predicted for metamaterials (negative refraction, superlensing, electromagnetic cloaking,…) were experimentally demonstrated. Unfortunately, the best achievements have no direct translation to the optical domain, without being burdened by technological and conceptual difficulties. Of particular importance within the realm of optical negative-index metamaterials (NIM), is the issue of simultaneously achieving strong electric and magnetic responses and low associated losses. Here, hybrid metal-semiconductor nanowires are proposed as building blocks of optical NIMs. The metamaterial thus obtained, highly isotropic in the plane normal to the nanowires, presents a negative index of refraction in the near-infrared, with values of the real part well below −1, and extremely low losses (an order of magnitude better than present optical NIMs). Tunability of the system allows to select the operating range in the whole telecom spectrum. The design is proven in configurations such as prisms and slabs, directly observing negative refraction. PMID:23514968

  18. SOI metal-oxide-semiconductor field-effect transistor photon detector based on single-hole counting.

    PubMed

    Du, Wei; Inokawa, Hiroshi; Satoh, Hiroaki; Ono, Atsushi

    2011-08-01

    In this Letter, a scaled-down silicon-on-insulator (SOI) metal-oxide-semiconductor field-effect transistor (MOSFET) is characterized as a photon detector, where photogenerated individual holes are trapped below the negatively biased gate and modulate stepwise the electron current flowing in the bottom channel induced by the positive substrate bias. The output waveforms exhibit clear separation of current levels corresponding to different numbers of trapped holes. Considering this capability of single-hole counting, a small dark count of less than 0.02 s(-1) at room temperature, and low operation voltage of 1 V, SOI MOSFET could be a unique photon-number-resolving detector if the small quantum efficiency were improved. PMID:21808317

  19. Ratiometric, filter-free optical sensor based on a complementary metal oxide semiconductor buried double junction photodiode.

    PubMed

    Yung, Ka Yi; Zhan, Zhiyong; Titus, Albert H; Baker, Gary A; Bright, Frank V

    2015-07-16

    We report a complementary metal oxide semiconductor integrated circuit (CMOS IC) with a buried double junction (BDJ) photodiode that (i) provides a real-time output signal that is related to the intensity ratio at two emission wavelengths and (ii) simultaneously eliminates the need for an optical filter to block Rayleigh scatter. We demonstrate the BDJ platform performance for gaseous NH3 and aqueous pH detection. We also compare the BDJ performance to parallel results obtained by using a slew scanned fluorimeter (SSF). The BDJ results are functionally equivalent to the SSF results without the need for any wavelength filtering or monochromators and the BDJ platform is not prone to errors associated with source intensity fluctuations or sensor signal drift. PMID:26073812

  20. Complementary Metal Oxide Semiconductor Based Multimodal Sensor for In vivo Brain Function Imaging with a Function for Simultaneous Cell Stimulation

    NASA Astrophysics Data System (ADS)

    Tagawa, Ayato; Mitani, Masahiro; Minami, Hiroki; Noda, Toshihiko; Sasagawa, Kiyotaka; Tokuda, Takashi; Ohta, Jun

    2010-04-01

    We have developed a multimodal complementary metal oxide semiconductor (CMOS) sensor device embedded with Au electrodes for fluorescent imaging and cell stimulation in the deep brain of mice. The Au electrodes were placed on the pixel array of the image sensor. Windows over the photodiodes were opened in the electrode area for simultaneous fluorescent imaging and cell stimulation in the same area of the brain tissue. The sensor chip was shaped like a shank and was packaged by two packaging methods for high strength or minimal invasion. The experimental results showed that the 90 ×90 µm2 Au electrodes with windows were capable of injecting theta burst stimulation (TBS)-like current pulses at 0.2-1 mA in a saline solution. We successfully demonstrated that fluorescent imaging and TBS-like current injection can be simultaneously performed in the electrode area of a brain phantom.

  1. Complementary Metal Oxide Semiconductor Based Multimodal Sensor for In vivo Brain Function Imaging with a Function for Simultaneous Cell Stimulation

    NASA Astrophysics Data System (ADS)

    Ayato Tagawa,; Masahiro Mitani,; Hiroki Minami,; Toshihiko Noda,; Kiyotaka Sasagawa,; Takashi Tokuda,; Jun Ohta,

    2010-04-01

    We have developed a multimodal complementary metal oxide semiconductor (CMOS) sensor device embedded with Au electrodes for fluorescent imaging and cell stimulation in the deep brain of mice. The Au electrodes were placed on the pixel array of the image sensor. Windows over the photodiodes were opened in the electrode area for simultaneous fluorescent imaging and cell stimulation in the same area of the brain tissue. The sensor chip was shaped like a shank and was packaged by two packaging methods for high strength or minimal invasion. The experimental results showed that the 90 × 90 μm2 Au electrodes with windows were capable of injecting theta burst stimulation (TBS)-like current pulses at 0.2-1 mA in a saline solution. We successfully demonstrated that fluorescent imaging and TBS-like current injection can be simultaneously performed in the electrode area of a brain phantom.

  2. Fermi level dependent native defect formation: Consequences for metal--semiconductor and semiconductor--semiconductor interfaces

    SciTech Connect

    Walukiewicz, W.

    1988-07-01

    The amphoteric native defect model of the Schottky barrier formation is used to analyze the Fermi level pinning at metal/semiconductor interfaces for submonolayer metal coverages. It is assumed that the energy required for defect generation is released in the process of surface back-relaxation. Model calculations for metal/GaAs interfaces show a weak dependence of the Fermi level pinning on the thickness of metal deposited at room temperature. This weak dependence indicates a strong dependence of the defect formation energy on the Fermi level, a unique feature of amphoteric native defects. This result is in very good agreement with experimental data. It is shown that a very distinct asymmetry in the Fermi level pinning on p- and n-type GaAs observed at liquid nitrogen temperatures can be understood in terms of much different recombination rates for amphoteric native defects in those two types of materials. Also, it is demonstrated that the Fermi level stabilization energy, a central concept of the amphoteric defect system, plays a fundamental role in other phenomena in semiconductors such as semiconductor/semiconductor heterointerface intermixing and saturation of free carrier concentration.

  3. Fermi level dependent native defect formation: Consequences for metal-semiconductor and semiconductor-semiconductor interfaces

    SciTech Connect

    Walukiewicz, W.

    1988-02-01

    The amphoteric native defect model of the Schottky barrier formation is used to analyze the Fermi level pinning at metal/semiconductor interfaces for submonolayer metal coverages. It is assumed that the energy required for defect generation is released in the process of surface back-relaxation. Model calculations for metal/GaAs interfaces show a weak dependence of the Fermi level pinning on the thickness of metal deposited at room temperature. This weak dependence indicates a strong dependence of the defect formation energy on the Fermi level, a unique feature of amphoteric native defects. This result is in very good agreement with experimental data. It is shown that a very distinct asymmetry in the Fermi level pinning on p- and n-type GaAs observed at liquid nitrogen temperatures can be understood in terms of much different recombination rates for amphoteric native defects in those two types of materials. Also, it is demonstrated that the Fermi level stabilization energy, a central concept of the amphoteric defect system, plays a fundamental role in other phenomena in semiconductors such as semiconductor/semiconductor heterointerface intermixing and saturation of free carrier concentration. 33 refs., 6 figs.

  4. Monolayer MXenes: promising half-metals and spin gapless semiconductors

    NASA Astrophysics Data System (ADS)

    Gao, Guoying; Ding, Guangqian; Li, Jie; Yao, Kailun; Wu, Menghao; Qian, Meichun

    2016-04-01

    Half-metals and spin gapless semiconductors are promising candidates for spintronic applications due to the complete (100%) spin polarization of electrons around the Fermi level. Based on recent experimental and theoretical findings of graphene-like monolayer transition metal carbides and nitrides (also known as MXenes), we demonstrate using first-principles calculations that monolayers Ti2C and Ti2N exhibit nearly half-metallic ferromagnetism with the magnetic moments of 1.91 and 1.00μB per formula unit, respectively, while monolayer V2C is a metal with unstable antiferromagnetism, and monolayer V2N is a nonmagnetic metal. Interestingly, under a biaxial strain, there is a phase transition from a nearly half-metal to truly half-metal, spin gapless semiconductor, and metal for monolayer Ti2C. Monolayer Ti2N is still a nearly half-metal under a suitable biaxial strain. Large magnetic moments can be induced by the biaxial tensile and compressive strains for monolayer V2C and V2N, respectively. We also show that the structures of these four monolayer MXenes are stable according to the calculated formation energy and phonon spectrum. Our investigations suggest that, unlike monolayer graphene, monolayer MXenes Ti2C and Ti2N without vacancy, doping or external electric field exhibit intrinsic magnetism, especially the half-metallic ferromagnetism and spin gapless semiconductivity, which will stimulate further studies on possible spintronic applications for new two-dimensional materials of MXenes.

  5. Monolayer MXenes: promising half-metals and spin gapless semiconductors.

    PubMed

    Gao, Guoying; Ding, Guangqian; Li, Jie; Yao, Kailun; Wu, Menghao; Qian, Meichun

    2016-04-28

    Half-metals and spin gapless semiconductors are promising candidates for spintronic applications due to the complete (100%) spin polarization of electrons around the Fermi level. Based on recent experimental and theoretical findings of graphene-like monolayer transition metal carbides and nitrides (also known as MXenes), we demonstrate using first-principles calculations that monolayers Ti2C and Ti2N exhibit nearly half-metallic ferromagnetism with the magnetic moments of 1.91 and 1.00μB per formula unit, respectively, while monolayer V2C is a metal with unstable antiferromagnetism, and monolayer V2N is a nonmagnetic metal. Interestingly, under a biaxial strain, there is a phase transition from a nearly half-metal to truly half-metal, spin gapless semiconductor, and metal for monolayer Ti2C. Monolayer Ti2N is still a nearly half-metal under a suitable biaxial strain. Large magnetic moments can be induced by the biaxial tensile and compressive strains for monolayer V2C and V2N, respectively. We also show that the structures of these four monolayer MXenes are stable according to the calculated formation energy and phonon spectrum. Our investigations suggest that, unlike monolayer graphene, monolayer MXenes Ti2C and Ti2N without vacancy, doping or external electric field exhibit intrinsic magnetism, especially the half-metallic ferromagnetism and spin gapless semiconductivity, which will stimulate further studies on possible spintronic applications for new two-dimensional materials of MXenes. PMID:27074402

  6. Synthesis and characterization of three-dimensional transition metal ions doped zinc oxide based dilute magnetic semiconductor thin films

    NASA Astrophysics Data System (ADS)

    Samanta, Kousik

    Dilute magnetic semiconductors (DMS), especially 3d-transition metal (TM) doped ZnO based DMS materials are the most promising candidates for optoelectronics and spintronics applications; e.g. in spin light emitting diode (SLED), spin transistors, and spin field effect transistors (SFET), etc. In the present dissertation, thin films of Zn1-xTMxO (TM = Co2+, Cu2+, and Mn2+) were grown on (0001) oriented Al2O3 substrates by pulsed laser deposition (PLD) technique. The films were highly c-axis oriented, nearly single crystalline, and defects free for a limited concentration of the dilution of transition metal ions. In particular, we have obtained single crystalline phases of Zn1-xTMxO thin films for up to 10, 3, and 5 stoichiometric percentages of Co2+, Cu2+, and Mn2+ respectively. Raman micro-probe system was used to understand the structural and lattice dynamical properties at different physical conditions. The confinement of optical phonons in the disorder lattice was explained by alloy potential fluctuation (APF) using a spatial correlation (SC) model. The detailed analysis of the optical phonon behavior in disorder lattice confirmed the substitution of the transition metal ions in Zn 2+ site of the ZnO host lattice. The secondary phases of ZnCo 2O4, CuO, and ZnMn2O4 were detected in higher Co, Cu, and Mn doped ZnO thin films respectively; where as, XRD did not detect these secondary phases in the same samples. Room temperature ferromagnetism was observed in Co2+ and Cu2+ ions doped ZnO thin films with maximum saturation magnetization (Ms) of 1.0 and 0.76 muB respectively. The origin of the observed ferromagnetism in Zn1-xCoxO thin films was tested by the controlled introduction of shallow donors (Al) in Zn0.9-x Co0.1O:Alx (x = 0.005 and 0.01) thin films. The saturation magnetization for the 10% Co-doped ZnO (1.0 muB /Co) at 300K reduced (˜0.25 muB/Co) due to Al doping. The observed ferromagnetism and the reduction due to Al doping can be explained by the Bound

  7. A Customized Metal Oxide Semiconductor-Based Gas Sensor Array for Onion Quality Evaluation: System Development and Characterization

    PubMed Central

    Konduru, Tharun; Rains, Glen C.; Li, Changying

    2015-01-01

    A gas sensor array, consisting of seven Metal Oxide Semiconductor (MOS) sensors that are sensitive to a wide range of organic volatile compounds was developed to detect rotten onions during storage. These MOS sensors were enclosed in a specially designed Teflon chamber equipped with a gas delivery system to pump volatiles from the onion samples into the chamber. The electronic circuit mainly comprised a microcontroller, non-volatile memory chip, and trickle-charge real time clock chip, serial communication chip, and parallel LCD panel. User preferences are communicated with the on-board microcontroller through a graphical user interface developed using LabVIEW. The developed gas sensor array was characterized and the discrimination potential was tested by exposing it to three different concentrations of acetone (ketone), acetonitrile (nitrile), ethyl acetate (ester), and ethanol (alcohol). The gas sensor array could differentiate the four chemicals of same concentrations and different concentrations within the chemical with significant difference. Experiment results also showed that the system was able to discriminate two concentrations (196 and 1964 ppm) of methlypropyl sulfide and two concentrations (145 and 1452 ppm) of 2-nonanone, two key volatile compounds emitted by rotten onions. As a proof of concept, the gas sensor array was able to achieve 89% correct classification of sour skin infected onions. The customized low-cost gas sensor array could be a useful tool to detect onion postharvest diseases in storage. PMID:25587975

  8. A customized metal oxide semiconductor-based gas sensor array for onion quality evaluation: system development and characterization.

    PubMed

    Konduru, Tharun; Rains, Glen C; Li, Changying

    2015-01-01

    A gas sensor array, consisting of seven Metal Oxide Semiconductor (MOS) sensors that are sensitive to a wide range of organic volatile compounds was developed to detect rotten onions during storage. These MOS sensors were enclosed in a specially designed Teflon chamber equipped with a gas delivery system to pump volatiles from the onion samples into the chamber. The electronic circuit mainly comprised a microcontroller, non-volatile memory chip, and trickle-charge real time clock chip, serial communication chip, and parallel LCD panel. User preferences are communicated with the on-board microcontroller through a graphical user interface developed using LabVIEW. The developed gas sensor array was characterized and the discrimination potential was tested by exposing it to three different concentrations of acetone (ketone), acetonitrile (nitrile), ethyl acetate (ester), and ethanol (alcohol). The gas sensor array could differentiate the four chemicals of same concentrations and different concentrations within the chemical with significant difference. Experiment results also showed that the system was able to discriminate two concentrations (196 and 1964 ppm) of methlypropyl sulfide and two concentrations (145 and 1452 ppm) of 2-nonanone, two key volatile compounds emitted by rotten onions. As a proof of concept, the gas sensor array was able to achieve 89% correct classification of sour skin infected onions. The customized low-cost gas sensor array could be a useful tool to detect onion postharvest diseases in storage. PMID:25587975

  9. Method of physical vapor deposition of metal oxides on semiconductors

    DOEpatents

    Norton, David P.

    2001-01-01

    A process for growing a metal oxide thin film upon a semiconductor surface with a physical vapor deposition technique in a high-vacuum environment and a structure formed with the process involves the steps of heating the semiconductor surface and introducing hydrogen gas into the high-vacuum environment to develop conditions at the semiconductor surface which are favorable for growing the desired metal oxide upon the semiconductor surface yet is unfavorable for the formation of any native oxides upon the semiconductor. More specifically, the temperature of the semiconductor surface and the ratio of hydrogen partial pressure to water pressure within the vacuum environment are high enough to render the formation of native oxides on the semiconductor surface thermodynamically unstable yet are not so high that the formation of the desired metal oxide on the semiconductor surface is thermodynamically unstable. Having established these conditions, constituent atoms of the metal oxide to be deposited upon the semiconductor surface are directed toward the surface of the semiconductor by a physical vapor deposition technique so that the atoms come to rest upon the semiconductor surface as a thin film of metal oxide with no native oxide at the semiconductor surface/thin film interface. An example of a structure formed by this method includes an epitaxial thin film of (001)-oriented CeO.sub.2 overlying a substrate of (001) Ge.

  10. Monte Carlo calculations for metal-semiconductor hot-electron injection via tunnel-junction emission

    NASA Astrophysics Data System (ADS)

    Appelbaum, Ian; Narayanamurti, V.

    2005-01-01

    We present a detailed description of a scheme to calculate the injection current for metal-semiconductor systems using tunnel-junction electron emission. We employ a Monte Carlo framework for integrating over initial free-electron states in a metallic emitter and use interfacial scattering at the metal-semiconductor interface as an independent parameter. These results have implications for modeling metal-base transistors and ballistic electron emission microscopy and spectroscopy.

  11. New Concentric Electrode Metal-Semiconductor-Metal Photodetectors

    NASA Technical Reports Server (NTRS)

    Towe, Elias

    1996-01-01

    A new metal-semiconductor-metal (MSM) photodetector geometry is proposed. The new device has concentric metal electrodes which exhibit a high degree of symmetry and a design flexibility absent in the conventional MSM device. The concentric electrodes are biased to alternating potentials as in the conventional interdigitated device. Because of the high symmetry configuration, however, the new device also has a lower effective capacitance. This device and the conventional MSM structure are analyzed within a common theoretical framework which allows for the comparison of the important performance characteristics.

  12. Design and control of Ge-based metal-oxide-semiconductor interfaces for high-mobility field-effect transistors with ultrathin oxynitride gate dielectrics

    NASA Astrophysics Data System (ADS)

    Minoura, Yuya; Kasuya, Atsushi; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji

    2013-07-01

    High-quality Ge-based metal-oxide-semiconductor (MOS) stacks were achieved with ultrathin oxynitride (GeON) gate dielectrics. An in situ process based on plasma nitridation of the base germanium oxide (GeO2) surface and subsequent metal electrode deposition was proven to be effective for suppressing electrical deterioration induced by the reaction at the metal/insulator interface. The electrical properties of the bottom GeON/Ge interface were further improved by both low-temperature oxidation for base GeO2 formation and high-temperature in situ vacuum annealing after plasma nitridation of the base oxide. Based on the optimized in situ gate stack fabrication process, very high inversion carrier mobility (μhole: 445 cm2/Vs, μelectron: 1114 cm2/Vs) was demonstrated for p- and n-channel Ge MOSFETs with Al/GeON/Ge gate stacks at scaled equivalent oxide thickness down to 1.4 nm.

  13. Nanoscale Metal Oxide Semiconductors for Gas Sensing

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Evans, Laura; Xu, Jennifer C.; VanderWal, Randy L.; Berger, Gordon M.; Kulis, Michael J.

    2011-01-01

    A report describes the fabrication and testing of nanoscale metal oxide semiconductors (MOSs) for gas and chemical sensing. This document examines the relationship between processing approaches and resulting sensor behavior. This is a core question related to a range of applications of nanotechnology and a number of different synthesis methods are discussed: thermal evaporation- condensation (TEC), controlled oxidation, and electrospinning. Advantages and limitations of each technique are listed, providing a processing overview to developers of nanotechnology- based systems. The results of a significant amount of testing and comparison are also described. A comparison is made between SnO2, ZnO, and TiO2 single-crystal nanowires and SnO2 polycrystalline nanofibers for gas sensing. The TECsynthesized single-crystal nanowires offer uniform crystal surfaces, resistance to sintering, and their synthesis may be done apart from the substrate. The TECproduced nanowire response is very low, even at the operating temperature of 200 C. In contrast, the electrospun polycrystalline nanofiber response is high, suggesting that junction potentials are superior to a continuous surface depletion layer as a transduction mechanism for chemisorption. Using a catalyst deposited upon the surface in the form of nanoparticles yields dramatic gains in sensitivity for both nanostructured, one-dimensional forms. For the nanowire materials, the response magnitude and response rate uniformly increase with increasing operating temperature. Such changes are interpreted in terms of accelerated surface diffusional processes, yielding greater access to chemisorbed oxygen species and faster dissociative chemisorption, respectively. Regardless of operating temperature, sensitivity of the nanofibers is a factor of 10 to 100 greater than that of nanowires with the same catalyst for the same test condition. In summary, nanostructure appears critical to governing the reactivity, as measured by electrical

  14. High power semiconductor disk laser with a semiconductor-dielectric-metal compound mirror

    NASA Astrophysics Data System (ADS)

    Rantamäki, A.; Saarinen, E. J.; Lyytikäinen, J.; Lahtonen, K.; Valden, M.; Okhotnikov, O. G.

    2014-03-01

    We present optically pumped semiconductor disk lasers with a thin dielectric layer placed between the semiconductor distributed Bragg reflector and the metallization interface. The approach is shown to enhance the reflectivity of the semiconductor mirror while introducing a negligible penalty to the thermal resistance of the device. The design has potential for improving the performance of semiconductor disk lasers by avoiding highly pump-absorbing metal layers and allowing thinner mirror structures. The advantages are expected to be especially prominent for material systems that employ thick thermally insulating semiconductor mirrors.

  15. Metal oxide semiconductor thin-film transistors for flexible electronics

    NASA Astrophysics Data System (ADS)

    Petti, Luisa; Münzenrieder, Niko; Vogt, Christian; Faber, Hendrik; Büthe, Lars; Cantarella, Giuseppe; Bottacchi, Francesca; Anthopoulos, Thomas D.; Tröster, Gerhard

    2016-06-01

    The field of flexible electronics has rapidly expanded over the last decades, pioneering novel applications, such as wearable and textile integrated devices, seamless and embedded patch-like systems, soft electronic skins, as well as imperceptible and transient implants. The possibility to revolutionize our daily life with such disruptive appliances has fueled the quest for electronic devices which yield good electrical and mechanical performance and are at the same time light-weight, transparent, conformable, stretchable, and even biodegradable. Flexible metal oxide semiconductor thin-film transistors (TFTs) can fulfill all these requirements and are therefore considered the most promising technology for tomorrow's electronics. This review reflects the establishment of flexible metal oxide semiconductor TFTs, from the development of single devices, large-area circuits, up to entirely integrated systems. First, an introduction on metal oxide semiconductor TFTs is given, where the history of the field is revisited, the TFT configurations and operating principles are presented, and the main issues and technological challenges faced in the area are analyzed. Then, the recent advances achieved for flexible n-type metal oxide semiconductor TFTs manufactured by physical vapor deposition methods and solution-processing techniques are summarized. In particular, the ability of flexible metal oxide semiconductor TFTs to combine low temperature fabrication, high carrier mobility, large frequency operation, extreme mechanical bendability, together with transparency, conformability, stretchability, and water dissolubility is shown. Afterward, a detailed analysis of the most promising metal oxide semiconducting materials developed to realize the state-of-the-art flexible p-type TFTs is given. Next, the recent progresses obtained for flexible metal oxide semiconductor-based electronic circuits, realized with both unipolar and complementary technology, are reported. In particular

  16. Lattice matched semiconductor growth on crystalline metallic substrates

    DOEpatents

    Norman, Andrew G; Ptak, Aaron J; McMahon, William E

    2013-11-05

    Methods of fabricating a semiconductor layer or device and said devices are disclosed. The methods include but are not limited to providing a metal or metal alloy substrate having a crystalline surface with a known lattice parameter (a). The methods further include growing a crystalline semiconductor alloy layer on the crystalline substrate surface by coincident site lattice matched epitaxy. The semiconductor layer may be grown without any buffer layer between the alloy and the crystalline surface of the substrate. The semiconductor alloy may be prepared to have a lattice parameter (a') that is related to the lattice parameter (a). The semiconductor alloy may further be prepared to have a selected band gap.

  17. Development of new generation of perovskite based noble metal/semiconductor photocatalysts for visible-light-driven hydrogen production

    NASA Astrophysics Data System (ADS)

    Shen, Peichuan

    In recent decades, semiconductor photocatalysis has attracted a growing attention as a possible alternative to existing methods of hydrogen production, hydrocarbon conversion and organic compound oxidation. Many types of photocatalysts have been developed and tested for photocatalytic applications. However, most of them do not have notable activity in visible light region, which limits their practical applications. Development of photocatalysts, which can be activated by visible light provides a promising way forward to utilize both UV and visible portions of solar spectrum. In this thesis, two main methods to advance visible light driven photocatalysis, such as bandgap modification through doping and co-catalyst development, are investigated. The photocatalysts studied in this thesis included CdS and SrTiO3, which were extensively investigated and characterized. Rhodium doped strontium titanate was synthesized through different preparation methods. The synthesized samples have been investigated by various characterization techniques including XRD, TEM, STEM, XPS and UV-Vis spectroscopy. The effect of preparation conditions, such as doping concentration, calcination temperature and pH have been investigated and optimized. In addition, the photocatalytic activities for hydrogen production of the samples synthesized by different preparation methods were also studied. Among the preparation methods, polymerizable complex (PC) method was found to be the most effective synthesis method for SrTiO3: Rh. The samples prepared by PC method had higher photocatalytic activity as compared to that of samples synthesized by solid state reaction method and hydrothermal method. The reasons might be attributed to more effective doping and higher surface area. The results of this work suggest that PC method can also be applied to develop other perovskite materials for photocatalytic applications. Co-catalyst development for enhancement of photocatalytic hydrogen production is also

  18. Leakage Current Mechanism of InN-Based Metal-Insulator-Semiconductor Structures with Al2O3 as Dielectric Layers.

    PubMed

    Wang, X; Zhang, G Z; Xu, Y; Gan, X W; Chen, C; Wang, Z; Wang, Y; Wang, J L; Wang, T; Wu, H; Liu, C

    2016-12-01

    InN-based metal-insulator-semiconductor (MIS) structures were prepared with Al2O3 as the gate oxides. Surface morphologies of InN films are improved with increasing Mg doping concentrations. At high frequencies, the measured capacitance densities deviate from the real ones with turning frequencies inversely proportional to series resistances. An ultralow leakage current density of 1.35 × 10(-9) A/cm(2) at 1 V is obtained. Fowler-Nordheim tunneling is the main mechanism of the leakage current at high fields, while Schottky emission dominates at low fields. Capacitance densities shift with different biases, indicating that the InN-based MIS structures can serve as potential candidates for MIS field-effect transistors. PMID:26759357

  19. Leakage Current Mechanism of InN-Based Metal-Insulator-Semiconductor Structures with Al2O3 as Dielectric Layers

    NASA Astrophysics Data System (ADS)

    Wang, X.; Zhang, G. Z.; Xu, Y.; Gan, X. W.; Chen, C.; Wang, Z.; Wang, Y.; Wang, J. L.; Wang, T.; Wu, H.; Liu, C.

    2016-01-01

    InN-based metal-insulator-semiconductor (MIS) structures were prepared with Al2O3 as the gate oxides. Surface morphologies of InN films are improved with increasing Mg doping concentrations. At high frequencies, the measured capacitance densities deviate from the real ones with turning frequencies inversely proportional to series resistances. An ultralow leakage current density of 1.35 × 10-9 A/cm2 at 1 V is obtained. Fowler-Nordheim tunneling is the main mechanism of the leakage current at high fields, while Schottky emission dominates at low fields. Capacitance densities shift with different biases, indicating that the InN-based MIS structures can serve as potential candidates for MIS field-effect transistors.

  20. GaAs metal-oxide-semiconductor based non-volatile flash memory devices with InAs quantum dots as charge storage nodes

    NASA Astrophysics Data System (ADS)

    Islam, Sk Masiul; Chowdhury, Sisir; Sarkar, Krishnendu; Nagabhushan, B.; Banerji, P.; Chakraborty, S.; Mukherjee, Rabibrata

    2015-06-01

    Ultra-thin InP passivated GaAs metal-oxide-semiconductor based non-volatile flash memory devices were fabricated using InAs quantum dots (QDs) as charge storing elements by metal organic chemical vapor deposition technique to study the efficacy of the QDs as charge storage elements. The grown QDs were embedded between two high-k dielectric such as HfO2 and ZrO2, which were used for tunneling and control oxide layers, respectively. The size and density of the QDs were found to be 5 nm and 1.8×1011 cm-2, respectively. The device with a structure Metal/ZrO2/InAs QDs/HfO2/GaAs/Metal shows maximum memory window equivalent to 6.87 V. The device also exhibits low leakage current density of the order of 10-6 A/cm2 and reasonably good charge retention characteristics. The low value of leakage current in the fabricated memory device is attributed to the Coulomb blockade effect influenced by quantum confinement as well as reduction of interface trap states by ultra-thin InP passivation on GaAs prior to HfO2 deposition.

  1. GaAs metal-oxide-semiconductor based non-volatile flash memory devices with InAs quantum dots as charge storage nodes

    SciTech Connect

    Islam, Sk Masiul Chowdhury, Sisir; Sarkar, Krishnendu; Nagabhushan, B.; Banerji, P.; Chakraborty, S.

    2015-06-24

    Ultra-thin InP passivated GaAs metal-oxide-semiconductor based non-volatile flash memory devices were fabricated using InAs quantum dots (QDs) as charge storing elements by metal organic chemical vapor deposition technique to study the efficacy of the QDs as charge storage elements. The grown QDs were embedded between two high-k dielectric such as HfO{sub 2} and ZrO{sub 2}, which were used for tunneling and control oxide layers, respectively. The size and density of the QDs were found to be 5 nm and 1.8×10{sup 11} cm{sup −2}, respectively. The device with a structure Metal/ZrO{sub 2}/InAs QDs/HfO{sub 2}/GaAs/Metal shows maximum memory window equivalent to 6.87 V. The device also exhibits low leakage current density of the order of 10{sup −6} A/cm{sup 2} and reasonably good charge retention characteristics. The low value of leakage current in the fabricated memory device is attributed to the Coulomb blockade effect influenced by quantum confinement as well as reduction of interface trap states by ultra-thin InP passivation on GaAs prior to HfO{sub 2} deposition.

  2. Growth and characterization of rutile TiO2 nanorods on various substrates with fabricated fast-response metal-semiconductor-metal UV detector based on Si substrate

    NASA Astrophysics Data System (ADS)

    Selman, Abbas M.; Hassan, Z.

    2015-07-01

    Rutile-phase titanium dioxide nanorods (NRs) were synthesized successfully on p-type silicon (Si) (1 1 1), c-plane sapphire (Al2O3), glass coated with fluorine-doped tin oxide (FTO), glass, and quartz substrates via chemical bath deposition method. All substrates were seeded with a TiO2 seed layer synthesized with a radio frequency reactive magnetron sputtering system prior to NRs growth. The effect of substrate type on structural, morphological, and optical properties of rutile TiO2 NRs was studied. X-ray diffraction, Raman spectroscopy, and field-emission scanning electron microscopy analyses showed the tetragonal rutile structure of the synthesized TiO2 NRs. Optical properties were examined with photoluminescence (PL) spectroscopy of the grown rutile NRs on all substrates, with the spectra exhibiting one strong ultraviolet emission peak intensity compared with broad visible peak. The optimal sample of rutile NRs was grown on Si substrate. Thus, a fast-response metal-semiconductor-metal ultraviolet (UV) detector was fabricated. Upon exposure to 365 nm light (2.3 mW/cm2) at 5 V bias, the device displays 2.62 × 10-5 A photocurrent, and the response and recovery times are calculated as 18.5 and 19.1 ms, respectively. These results demonstrate that the fabricated high-quality photodiode is a promising candidate as a low-cost UV photodetector for commercially integrated photoelectronic applications.

  3. Metal-Insulator-Semiconductor Nanowire Network Solar Cells.

    PubMed

    Oener, Sebastian Z; van de Groep, Jorik; Macco, Bart; Bronsveld, Paula C P; Kessels, W M M; Polman, Albert; Garnett, Erik C

    2016-06-01

    Metal-insulator-semiconductor (MIS) junctions provide the charge separating properties of Schottky junctions while circumventing the direct and detrimental contact of the metal with the semiconductor. A passivating and tunnel dielectric is used as a separation layer to reduce carrier recombination and remove Fermi level pinning. When applied to solar cells, these junctions result in two main advantages over traditional p-n-junction solar cells: a highly simplified fabrication process and excellent passivation properties and hence high open-circuit voltages. However, one major drawback of metal-insulator-semiconductor solar cells is that a continuous metal layer is needed to form a junction at the surface of the silicon, which decreases the optical transmittance and hence short-circuit current density. The decrease of transmittance with increasing metal coverage, however, can be overcome by nanoscale structures. Nanowire networks exhibit precisely the properties that are required for MIS solar cells: closely spaced and conductive metal wires to induce an inversion layer for homogeneous charge carrier extraction and simultaneously a high optical transparency. We experimentally demonstrate the nanowire MIS concept by using it to make silicon solar cells with a measured energy conversion efficiency of 7% (∼11% after correction), an effective open-circuit voltage (Voc) of 560 mV and estimated short-circuit current density (Jsc) of 33 mA/cm(2). Furthermore, we show that the metal nanowire network can serve additionally as an etch mask to pattern inverted nanopyramids, decreasing the reflectivity substantially from 36% to ∼4%. Our extensive analysis points out a path toward nanowire based MIS solar cells that exhibit both high Voc and Jsc values. PMID:27172429

  4. Gate voltage dependent 1/f noise variance model based on physical noise generation mechanisms in n-channel metal-oxide-semiconductor field-effect transistors

    NASA Astrophysics Data System (ADS)

    Arai, Yukiko; Aoki, Hitoshi; Abe, Fumitaka; Todoroki, Shunichiro; Khatami, Ramin; Kazumi, Masaki; Totsuka, Takuya; Wang, Taifeng; Kobayashi, Haruo

    2015-04-01

    1/f noise is one of the most important characteristics for designing analog/RF circuits including operational amplifiers and oscillators. We have analyzed and developed a novel 1/f noise model in the strong inversion, saturation, and sub-threshold regions based on SPICE2 type model used in any public metal-oxide-semiconductor field-effect transistor (MOSFET) models developed by the University of California, Berkeley. Our model contains two noise generation mechanisms that are mobility and interface trap number fluctuations. Noise variability dependent on gate voltage is also newly implemented in our model. The proposed model has been implemented in BSIM4 model of a SPICE3 compatible circuit simulator. Parameters of the proposed model are extracted with 1/f noise measurements for simulation verifications. The simulation results show excellent agreements between measurement and simulations.

  5. Origin of the performances degradation of two-dimensional-based metal-oxide-semiconductor field effect transistors in the sub-10 nm regime: A first-principles study

    NASA Astrophysics Data System (ADS)

    Lu, Anh Khoa Augustin; Pourtois, Geoffrey; Agarwal, Tarun; Afzalian, Aryan; Radu, Iuliana P.; Houssa, Michel

    2016-01-01

    The impact of the scaling of the channel length on the performances of metal-oxide-semiconductor field effect transistors, based on two-dimensional (2D) channel materials, is theoretically investigated, using density functional theory combined with the non-equilibrium Green's function method. It is found that the scaling of the channel length below 10 nm leads to strong device performance degradations. Our simulations reveal that this degradation is essentially due to the tunneling current flowing between the source and the drain in these aggressively scaled devices. It is shown that this electron tunneling process is modulated by the effective mass of the 2D channel material, and sets the limit of the scaling in future transistor designs.

  6. (Plasmonic Metal Core)/(Semiconductor Shell) Nanostructures

    NASA Astrophysics Data System (ADS)

    Fang, Caihong

    Over the past several years, integration of metal nanocrystals that can support localized surface plasmon has been demonstrated as one of the most promising methods to the improvement of the light-harvesting efficiency of semiconductors. Ag and Au nanocrystals have been extensively hybridized with semiconductors by either deposition or anchoring. However, metal nanocrystals tend to aggregate, reshape, detach, or grow into large nanocrystals, leading to a loss of the unique properties seen in the original nanocrystals. Fortunately, core/shell nanostructures, circumventing the aforementioned problems, have been demonstrated to exhibit superior photoactivities. To further improve the light-harvesting applications of (plasmonic metal core)/(semiconductor shell) nanostructures, it is vital to understand the plasmonic and structural evolutions during the preparation processes, design novel hybrid nanostructures, and improve their light-harvesting performances. In this thesis, I therefore studied the plasmonic and structural evolutions during the formation of (Ag core)/(Ag2S shell) nanostructures. Moreover, I also prepared (noble metal core)/(TiO2 shell) nanostructures and investigated their plasmonic properties and photon-harvesting applications. Clear understanding of the sulfidation process can enable fine control of the plasmonic properties as well as the structural composition of Ag/Ag 2S nanomaterials. Therefore, I investigated the plasmonic and structural variations during the sulfidation process of Ag nanocubes both experimentally and numerically. The sulfidation reactions were carried out at both the ensemble and single-particle levels. Electrodynamic simulations were also employed to study the variations of the plasmonic properties and plasmon modes. Both experiment and simulation results revealed that sulfidation initiates at the vertices of Ag nanocubes. Ag nanocubes are then gradually truncated and each nanocube becomes a nanosphere eventually. The cubic

  7. Vibronic states in organic semiconductors based on non-metal naphthalocyanine. Detection of heterocyclic phthalocyanine compounds in a flexible dielectric matrix

    SciTech Connect

    Belogorokhov, I. A.; Tikhonov, E. V.; Dronov, M. A.; Belogorokhova, L. I.; Ryabchikov, Yu. V.; Tomilova, L. G.; Khokhlov, D. R.

    2012-01-15

    The vibronic properties of semiconductor structures based on non-metal naphthalocyanine molecules are studied using IR and Raman spectroscopy methods. New absorption lines in the transmission spectra of such materials are detected and identified. Three transmission lines are observed in the range 2830-3028 cm{sup -1}, which characterize carbon-hydrogen bonds of peripheral molecular groups. Their spectral positions are 2959, 2906, and 2866 cm{sup -1}. It is detected that the phthalocyanine ring can also exhibit its specific vibronic properties in the Raman spectra at 767, 717, and 679 cm{sup -1}. The naphthalocyanine molecule in the organic dielectric matrix of microfibers is described using IR spectroscopy. It is shown that the set of vibrations characterizing the isoindol group, pyrrole ring, naphtha group, and C-H bonds, allows an accurate enough description of the vibronic states of the naphthalocyanine complex in complex heterostructures to be made. The spectral range with fundamental modes, characterizing a naphthalocyanine semiconductor in a heterostructure, is 600-1600 cm{sup -1}. A comparison of the compositions of complex systems with a similar heterostructure containing lutetium diphthalocyanine demonstrated few errors.

  8. Valorization of GaN based metal-organic chemical vapor deposition dust a semiconductor power device industry waste through mechanochemical oxidation and leaching: A sustainable green process.

    PubMed

    Swain, Basudev; Mishra, Chinmayee; Lee, Chan Gi; Park, Kyung-Soo; Lee, Kun-Jae

    2015-07-01

    Dust generated during metal organic vapor deposition (MOCVD) process of GaN based semiconductor power device industry contains significant amounts of gallium and indium. These semiconductor power device industry wastes contain gallium as GaN and Ga0.97N0.9O0.09 is a concern for the environment which can add value through recycling. In the present study, this waste is recycled through mechanochemical oxidation and leaching. For quantitative recovery of gallium, two different mechanochemical oxidation leaching process flow sheets are proposed. In one process, first the Ga0.97N0.9O0.09 of the MOCVD dust is leached at the optimum condition. Subsequently, the leach residue is mechanochemically treated, followed by oxidative annealing and finally re-leached. In the second process, the MOCVD waste dust is mechanochemically treated, followed by oxidative annealing and finally leached. Both of these treatment processes are competitive with each other, appropriate for gallium leaching and treatment of the waste MOCVD dust. Without mechanochemical oxidation, 40.11 and 1.86 w/w% of gallium and Indium are leached using 4M HCl, 100°C and pulp density of 100 kg/m(3,) respectively. After mechanochemical oxidation, both these processes achieved 90 w/w% of gallium and 1.86 w/w% of indium leaching at their optimum condition. PMID:26094059

  9. Transient absorption microscopy studies of single metal and semiconductor nanostructures

    NASA Astrophysics Data System (ADS)

    Johns, Paul; Sajini-Devadas, Mary; Hartland, Gregory V.

    2015-08-01

    Transient absorption microscopy is an experimental technique that allows nanomaterials to be studied with ultrafast time resolution and diffraction limited spatial resolution. This paper describes recent results from using transient absorption microscopy to investigate energy relaxation processes in single metal and semiconductor nanowires. The processes that have been examined include charge carrier trapping in semiconductor nanostructures, the motion of surface plasmon polaritons in metal nanowires, and the damping of the acoustic breathing modes of metal nanowires by high viscosity solvents.

  10. Metal-oxide-semiconductor photocapacitor for sensing surface plasmon polaritons

    NASA Astrophysics Data System (ADS)

    Khalilzade-Rezaie, Farnood; Peale, Robert E.; Panjwani, Deep; Smith, Christian W.; Nath, Janardan; Lodge, Michael; Ishigami, Masa; Nader, Nima; Vangala, Shiva; Yannuzzi, Mark; Cleary, Justin W.

    2015-09-01

    An electronic detector of surface plasmon polaritons (SPP) is reported. SPPs optically excited on a metal surface using a prism coupler are detected by using a close-coupled metal-oxide-semiconductor capacitor. Semitransparent metal and graphene gates function similarly. We report the dependence of the photoresponse on substrate carrier type, carrier concentration, and back-contact biasing.

  11. Large Lateral Photovoltaic Effect in Metal-(Oxide-) Semiconductor Structures

    PubMed Central

    Yu, Chongqi; Wang, Hui

    2010-01-01

    The lateral photovoltaic effect (LPE) can be used in position-sensitive detectors to detect very small displacements due to its output of lateral photovoltage changing linearly with light spot position. In this review, we will summarize some of our recent works regarding LPE in metal-semiconductor and metal-oxide-semiconductor structures, and give a theoretical model of LPE in these two structures. PMID:22163463

  12. Thermoelectric Performance Enhancement by Surrounding Crystalline Semiconductors with Metallic Nanoparticles

    NASA Technical Reports Server (NTRS)

    Kim, Hyun-Jung; King, Glen C.; Park, Yeonjoon; Lee, Kunik; Choi, Sang H.

    2011-01-01

    Direct conversion of thermal energy to electricity by thermoelectric (TE) devices may play a key role in future energy production and utilization. However, relatively poor performance of current TE materials has slowed development of new energy conversion applications. Recent reports have shown that the dimensionless Figure of Merit, ZT, for TE devices can be increased beyond the state-of-the-art level by nanoscale structuring of materials to reduce their thermal conductivity. New morphologically designed TE materials have been fabricated at the NASA Langley Research Center, and their characterization is underway. These newly designed materials are based on semiconductor crystal grains whose surfaces are surrounded by metallic nanoparticles. The nanoscale particles are used to tailor the thermal and electrical conduction properties for TE applications by altering the phonon and electron transport pathways. A sample of bismuth telluride decorated with metallic nanoparticles showed less thermal conductivity and twice the electrical conductivity at room temperature as compared to pure Bi2Te3. Apparently, electrons cross easily between semiconductor crystal grains via the intervening metallic nanoparticle bridges, but phonons are scattered at the interfacing gaps. Hence, if the interfacing gap is larger than the mean free path of the phonon, thermal energy transmission from one grain to others is reduced. Here we describe the design and analysis of these new materials that offer substantial improvements in thermoelectric performance.

  13. Fabrication of porous materials (metal, metal oxide and semiconductor) through an aerosol-assisted route

    NASA Astrophysics Data System (ADS)

    Sohn, Hiesang

    Porous materials have gained attraction owing to their vast applications in catalysts, sensors, energy storage devices, bio-devices and other areas. To date, various porous materials were synthesized through soft and hard templating approaches. However, a general synthesis method for porous non-oxide materials, metal alloys and semiconductors with tunable structure, composition and morphology has not been developed yet. To address this challenge, this thesis presents an aerosol method towards the synthesis of such materials and their applications for catalysis, hydrogen storage, Li-batteries and photo-catalysis. The first part of this thesis presents the synthesis of porous metals, metal oxides, and semiconductors with controlled pore structure, crystalline structure and morphology. In these synthesis processes, metal salts and organic ligands were employed as precursors to create porous metal-carbon frameworks. During the aerosol process, primary metal clusters and nanoparticles were formed, which were coagulated/ aggregated forming the porous particles. Various porous particles, such as those of metals (e.g., Ni, Pt, Co, Fe, and Ni xPt(1-x)), metal oxides (e.g., Fe3O4 and SnO2) and semiconductors (e.g., CdS, CuInS2, CuInS 2x-ZnS(1-x), and CuInS2x-TiO2(1-x)) were synthesized. The morphology, porous structure and crystalline structure of the particles were regulated through both templating and non-templating methods. The second part of this thesis explores the applications of these materials, including propylene hydrogenation and H2 uptake capacity of porous Ni, NiPt alloys and Ni-Pt composites, Li-storage of Fe3O4 and SnO2, photodegradation of CuInS2-based semiconductors. The effects of morphology, compositions, and porous structure on the device performance were systematically investigated. Overall, this dissertation work unveiled a simple synthesis approach for porous particles of metals, metal alloys, metal oxides, and semiconductors with controlled

  14. Growth of metal and semiconductor nanostructures using localized photocatalysts

    SciTech Connect

    Shelnutt, John A; Wang, Zhongchun; Medforth, Craig J

    2006-03-08

    Our overall goal has been to understand and develop a light-driven approach to the controlled growth of novel metal and semiconductor nanostructures and nanomaterials. In this photochemical process, bio-inspired porphyrin-based photocatalysts reduce metal salts in aqueous solutions at ambient temperatures when exposed to visible light, providing metal nucleation and growth centers. The photocatalyst molecules are pre-positioned at the nanoscale to control the location of the deposition of metal and therefore the morphology of the nanostructures that are grown. Self-assembly, chemical confinement, and molecular templating are some of the methods we are using for nanoscale positioning of the photocatalyst molecules. When exposed to light, each photocatalyst molecule repeatedly reduces metal ions from solution, leading to deposition near the photocatalyst and ultimately the synthesis of new metallic nanostructures and nanostructured materials. Studies of the photocatalytic growth process and the resulting nanostructures address a number of fundamental biological, chemical, and environmental issues and draw on the combined nanoscience characterization and multi-scale simulation capabilities of the new DOE Center for Integrated Nanotechnologies at Sandia National Laboratories and the University of Georgia. Our main goals are to elucidate the processes involved in the photocatalytic growth of metal nanomaterials and provide the scientific basis for controlled nanosynthesis. The nanomaterials resulting from these studies have applications in nanoelectronics, photonics, sensors, catalysis, and micromechanical systems. Our specific goals for the past three years have been to understand the role of photocatalysis in the synthesis of dendritic metal (Pt, Pd, Au) nanostructures grown from aqueous surfactant solutions under ambient conditions and the synthesis of photocatalytic porphyrin nanostructures (e.g., nanotubes) as templates for fabrication of photo-active metal

  15. Room-temperature electrically pumped near-infrared random lasing from high-quality m-plane ZnO-based metal-insulator-semiconductor devices.

    PubMed

    Chen, Chao; Wang, Ti; Wu, Hao; Zheng, He; Wang, Jianbo; Xu, Yang; Liu, Chang

    2015-01-01

    Epitaxial m-plane ZnO thin films have been deposited on m-plane sapphire substrates at a low temperature of 200°C by atomic layer deposition. A 90° in-plane rotation is observed between the m-plane ZnO thin films and the sapphire substrates. Moreover, the residual strain along the ZnO [-12-10] direction is released. To fabricate metal-insulator-semiconductor devices, a 50-nm Al2O3 thin film is deposited on the m-plane ZnO thin films. It is interesting to observe the near-infrared random lasing from the metal-insulator-semiconductor devices. PMID:25852396

  16. Room-temperature electrically pumped near-infrared random lasing from high-quality m-plane ZnO-based metal-insulator-semiconductor devices

    NASA Astrophysics Data System (ADS)

    Chen, Chao; Wang, Ti; Wu, Hao; Zheng, He; Wang, Jianbo; Xu, Yang; Liu, Chang

    2015-03-01

    Epitaxial m-plane ZnO thin films have been deposited on m-plane sapphire substrates at a low temperature of 200°C by atomic layer deposition. A 90° in-plane rotation is observed between the m-plane ZnO thin films and the sapphire substrates. Moreover, the residual strain along the ZnO [-12-10] direction is released. To fabricate metal-insulator-semiconductor devices, a 50-nm Al2O3 thin film is deposited on the m-plane ZnO thin films. It is interesting to observe the near-infrared random lasing from the metal-insulator-semiconductor devices.

  17. Nanowires and Nanobelts: Volume 1, Metal and Semiconductor Nanowires

    NASA Astrophysics Data System (ADS)

    Wang, Zhong Lin

    This two volume reference, Nanowires and Nanobelts: Materials, Properties and Devices, provides a comprehensive introduction to the field and reviews the current state of the research. Volume 1, Metal and Semiconductor Nanowires covers a wide range of materials systems, from noble metals (such as Au, Ag, Cu), single element semiconductors (such as Si and Ge), compound semiconductors (such as InP, CdS and GaAs as well as heterostructures), nitrides (such as GaN and Si3N4) to carbides (such as SiC).

  18. Metal oxide semiconductor structure using oxygen-terminated diamond

    NASA Astrophysics Data System (ADS)

    Chicot, G.; Maréchal, A.; Motte, R.; Muret, P.; Gheeraert, E.; Pernot, J.

    2013-06-01

    Metal-oxide-semiconductor structures with aluminum oxide as insulator and p-type (100) mono-crystalline diamond as semiconductor have been fabricated and investigated by capacitance versus voltage and current versus voltage measurements. The aluminum oxide dielectric was deposited using low temperature atomic layer deposition on an oxygenated diamond surface. The capacitance voltage measurements demonstrate that accumulation, depletion, and deep depletion regimes can be controlled by the bias voltage, opening the route for diamond metal-oxide-semiconductor field effect transistor. A band diagram is proposed and discussed.

  19. The MSFC complementary metal oxide semiconductor (including multilevel interconnect metallization) process handbook

    NASA Technical Reports Server (NTRS)

    Bouldin, D. L.; Eastes, R. W.; Feltner, W. R.; Hollis, B. R.; Routh, D. E.

    1979-01-01

    The fabrication techniques for creation of complementary metal oxide semiconductor integrated circuits at George C. Marshall Space Flight Center are described. Examples of C-MOS integrated circuits manufactured at MSFC are presented with functional descriptions of each. Typical electrical characteristics of both p-channel metal oxide semiconductor and n-channel metal oxide semiconductor discrete devices under given conditions are provided. Procedures design, mask making, packaging, and testing are included.

  20. Gate-control efficiency and interface state density evaluated from capacitance-frequency-temperature mapping for GaN-based metal-insulator-semiconductor devices

    SciTech Connect

    Shih, Hong-An; Kudo, Masahiro; Suzuki, Toshi-kazu

    2014-11-14

    We present an analysis method for GaN-based metal-insulator-semiconductor (MIS) devices by using capacitance-frequency-temperature (C-f-T) mapping to evaluate the gate-control efficiency and the interface state density, both exhibiting correlations with the linear-region intrinsic transconductance. The effectiveness of the method was exemplified by application to AlN/AlGaN/GaN MIS devices to elucidate the properties of AlN-AlGaN interfaces depending on their formation processes. Using the C-f-T mapping, we extract the gate-bias-dependent activation energy with its derivative giving the gate-control efficiency, from which we evaluate the AlN-AlGaN interface state density through the Lehovec equivalent circuit in the DC limit. It is shown that the gate-control efficiency and the interface state density have correlations with the linear-region intrinsic transconductance, all depending on the interface formation processes. In addition, we give characterization of the AlN-AlGaN interfaces by using X-ray photoelectron spectroscopy, in relation with the results of the analysis.

  1. Note: A disposable x-ray camera based on mass produced complementary metal-oxide-semiconductor sensors and single-board computers

    NASA Astrophysics Data System (ADS)

    Hoidn, Oliver R.; Seidler, Gerald T.

    2015-08-01

    We have integrated mass-produced commercial complementary metal-oxide-semiconductor (CMOS) image sensors and off-the-shelf single-board computers into an x-ray camera platform optimized for acquisition of x-ray spectra and radiographs at energies of 2-6 keV. The CMOS sensor and single-board computer are complemented by custom mounting and interface hardware that can be easily acquired from rapid prototyping services. For single-pixel detection events, i.e., events where the deposited energy from one photon is substantially localized in a single pixel, we establish ˜20% quantum efficiency at 2.6 keV with ˜190 eV resolution and a 100 kHz maximum detection rate. The detector platform's useful intrinsic energy resolution, 5-μm pixel size, ease of use, and obvious potential for parallelization make it a promising candidate for many applications at synchrotron facilities, in laser-heating plasma physics studies, and in laboratory-based x-ray spectrometry.

  2. Note: A disposable x-ray camera based on mass produced complementary metal-oxide-semiconductor sensors and single-board computers.

    PubMed

    Hoidn, Oliver R; Seidler, Gerald T

    2015-08-01

    We have integrated mass-produced commercial complementary metal-oxide-semiconductor (CMOS) image sensors and off-the-shelf single-board computers into an x-ray camera platform optimized for acquisition of x-ray spectra and radiographs at energies of 2-6 keV. The CMOS sensor and single-board computer are complemented by custom mounting and interface hardware that can be easily acquired from rapid prototyping services. For single-pixel detection events, i.e., events where the deposited energy from one photon is substantially localized in a single pixel, we establish ∼20% quantum efficiency at 2.6 keV with ∼190 eV resolution and a 100 kHz maximum detection rate. The detector platform's useful intrinsic energy resolution, 5-μm pixel size, ease of use, and obvious potential for parallelization make it a promising candidate for many applications at synchrotron facilities, in laser-heating plasma physics studies, and in laboratory-based x-ray spectrometry. PMID:26329247

  3. Three-Dimensional Flexible Complementary Metal-Oxide-Semiconductor Logic Circuits Based On Two-Layer Stacks of Single-Walled Carbon Nanotube Networks.

    PubMed

    Zhao, Yudan; Li, Qunqing; Xiao, Xiaoyang; Li, Guanhong; Jin, Yuanhao; Jiang, Kaili; Wang, Jiaping; Fan, Shoushan

    2016-02-23

    We have proposed and fabricated stable and repeatable, flexible, single-walled carbon nanotube (SWCNT) thin film transistor (TFT) complementary metal-oxide-semiconductor (CMOS) integrated circuits based on a three-dimensional (3D) structure. Two layers of SWCNT-TFT devices were stacked, where one layer served as n-type devices and the other one served as p-type devices. On the basis of this method, it is able to save at least half of the area required to construct an inverter and make large-scale and high-density integrated CMOS circuits easier to design and manufacture. The 3D flexible CMOS inverter gain can be as high as 40, and the total noise margin is more than 95%. Moreover, the input and output voltage of the inverter are exactly matched for cascading. 3D flexible CMOS NOR, NAND logic gates, and 15-stage ring oscillators were fabricated on PI substrates with high performance as well. Stable electrical properties of these circuits can be obtained with bending radii as small as 3.16 mm, which shows that such a 3D structure is a reliable architecture and suitable for carbon nanotube electrical applications in complex flexible and wearable electronic devices. PMID:26768020

  4. Note: A disposable x-ray camera based on mass produced complementary metal-oxide-semiconductor sensors and single-board computers

    SciTech Connect

    Hoidn, Oliver R.; Seidler, Gerald T.

    2015-08-15

    We have integrated mass-produced commercial complementary metal-oxide-semiconductor (CMOS) image sensors and off-the-shelf single-board computers into an x-ray camera platform optimized for acquisition of x-ray spectra and radiographs at energies of 2–6 keV. The CMOS sensor and single-board computer are complemented by custom mounting and interface hardware that can be easily acquired from rapid prototyping services. For single-pixel detection events, i.e., events where the deposited energy from one photon is substantially localized in a single pixel, we establish ∼20% quantum efficiency at 2.6 keV with ∼190 eV resolution and a 100 kHz maximum detection rate. The detector platform’s useful intrinsic energy resolution, 5-μm pixel size, ease of use, and obvious potential for parallelization make it a promising candidate for many applications at synchrotron facilities, in laser-heating plasma physics studies, and in laboratory-based x-ray spectrometry.

  5. Mn-based ferromagnetic semiconductors

    NASA Astrophysics Data System (ADS)

    Dietl, Tomasz; Sawicki, Maciej

    2003-07-01

    The present status of research and prospects for device applications of ferromagnetic (diluted magnetic) semiconductors (DMS) is presented. We review the nature of the electronic states and the mechanisms of the carrier-mediated exchange interactions (mean-field Zener model) in p-type Mn-based III-V and II-VI compounds, highlighting a good correspondence of experimental findings and theoretical predictions. An account of the latest progress on the road of increasing the Currie point to above the room temperature is given for both families of compounds. We comment on a possibility of obtaining ferromagnetism in n-type materials, taking (Zn,Mn)O:Al as the example. Concerning technologically important issue of easy axis and domain engineering, we present theoretical predictions and experimental results on the temperature and carrier concentration driven change of magnetic anisotropy in (Ga,Mn)As.

  6. Ultrathin metal-semiconductor-metal resonator for angle invariant visible band transmission filters

    SciTech Connect

    Lee, Kyu-Tae; Seo, Sungyong; Yong Lee, Jae; Jay Guo, L.

    2014-06-09

    We present transmission visible wavelength filters based on strong interference behaviors in an ultrathin semiconductor material between two metal layers. The proposed devices were fabricated on 2 cm × 2 cm glass substrate, and the transmission characteristics show good agreement with the design. Due to a significantly reduced light propagation phase change associated with the ultrathin semiconductor layer and the compensation in phase shift of light reflecting from the metal surface, the filters show an angle insensitive performance up to ±70°, thus, addressing one of the key challenges facing the previously reported photonic and plasmonic color filters. This principle, described in this paper, can have potential for diverse applications ranging from color display devices to the image sensors.

  7. Metal-doped semiconductor nanoparticles and methods of synthesis thereof

    NASA Technical Reports Server (NTRS)

    Ren, Zhifeng (Inventor); Chen, Gang (Inventor); Poudel, Bed (Inventor); Kumar, Shankar (Inventor); Wang, Wenzhong (Inventor); Dresselhaus, Mildred (Inventor)

    2009-01-01

    The present invention generally relates to binary or higher order semiconductor nanoparticles doped with a metallic element, and thermoelectric compositions incorporating such nanoparticles. In one aspect, the present invention provides a thermoelectric composition comprising a plurality of nanoparticles each of which includes an alloy matrix formed of a Group IV element and Group VI element and a metallic dopant distributed within the matrix.

  8. Integrated photo-responsive metal oxide semiconductor circuit

    NASA Technical Reports Server (NTRS)

    Jhabvala, Murzban D. (Inventor); Dargo, David R. (Inventor); Lyons, John C. (Inventor)

    1987-01-01

    An infrared photoresponsive element (RD) is monolithically integrated into a source follower circuit of a metal oxide semiconductor device by depositing a layer of a lead chalcogenide as a photoresistive element forming an ohmic bridge between two metallization strips serving as electrodes of the circuit. Voltage from the circuit varies in response to illumination of the layer by infrared radiation.

  9. Metal-doped semiconductor nanoparticles and methods of synthesis thereof

    DOEpatents

    Ren, Zhifeng; Chen, Gang; Poudel, Bed; Kumar, Shankar; Wang, Wenzhong; Dresselhaus, Mildred

    2009-09-08

    The present invention generally relates to binary or higher order semiconductor nanoparticles doped with a metallic element, and thermoelectric compositions incorporating such nanoparticles. In one aspect, the present invention provides a thermoelectric composition comprising a plurality of nanoparticles each of which includes an alloy matrix formed of a Group IV element and Group VI element and a metallic dopant distributed within the matrix.

  10. GaAs metal-oxide-semiconductor based nonvolatile memory devices embedded with ZnO quantum dots

    NASA Astrophysics Data System (ADS)

    Kundu, Souvik; Rao Gollu, Sankara; Sharma, Ramakant; Halder, Nripendra. N.; Biswas, Pranab; Banerji, P.; Gupta, D.

    2013-08-01

    Ultrathin InP passivated GaAs non-volatile memory devices were fabricated with chemically synthesized 5 nm ZnO quantum dots embedded into ZrO2 high-k oxide matrix deposited through metal organic chemical vapor deposition. In these memory devices, the memory window was found to be 6.10 V and the obtained charge loss was only 15.20% after 105 s. The superior retention characteristics and a wide memory window are achieved due to presence of ZnO quantum dots between tunneling and control oxide layers. Room temperature Coulomb blockade effect was found in these devices and it was ascertained to be the main reason for low leakage. Electronic band diagram with program and erase operations were described on the basis of electrical characterizations.

  11. High temperature behavior of multi-region direct current current-voltage spectroscopy and relationship with shallow-trench-isolation-based high-voltage laterally diffused metal-oxide-semiconductor field-effect-transistors reliability

    NASA Astrophysics Data System (ADS)

    He, Yandong; Zhang, Ganggang; Zhang, Xing

    2014-01-01

    With the process compatibility with the mainstream standard complementary metal-oxide-semiconductor (CMOS), shallow trench isolation (STI) based laterally diffused metal-oxide-semiconductor (LDMOS) devices have become popular for its better tradeoff between breakdown voltage and performance, especially for smart power applications. A multi-region direct current current-voltage (MR-DCIV) technique with spectroscopic features was demonstrated to map the interface state generation in the channel, accumulation and STI drift regions. High temperature behavior of MR-DCIV spectroscopy was analyzed and a physical model was verified. Degradation of STI-based LDMOS transistors under high temperature reverse bias (HTRB) stress is experimentally studied by MR-DCIV spectroscopy. The impact of interface state location on device electrical characteristics was investigated. Our results show that the major contribution to HTRB degradation, in term of the on-resistance degradation, was attributed to interface state generation under STI drift region.

  12. Spin-dependent transport properties of a GaMnAs-based vertical spin metal-oxide-semiconductor field-effect transistor structure

    SciTech Connect

    Kanaki, Toshiki Asahara, Hirokatsu; Ohya, Shinobu Tanaka, Masaaki

    2015-12-14

    We fabricate a vertical spin metal-oxide-semiconductor field-effect transistor (spin-MOSFET) structure, which is composed of an epitaxial single-crystal heterostructure with a ferromagnetic-semiconductor GaMnAs source/drain, and investigate its spin-dependent transport properties. We modulate the drain-source current I{sub DS} by ∼±0.5% with a gate-source voltage of ±10.8 V and also modulate I{sub DS} by up to 60% with changing the magnetization configuration of the GaMnAs source/drain at 3.5 K. The magnetoresistance ratio is more than two orders of magnitude higher than that obtained in the previous studies on spin MOSFETs. Our result shows that a vertical structure is one of the hopeful candidates for spin MOSFET when the device size is reduced to a sub-micron or nanometer scale.

  13. Valorization of GaN based metal-organic chemical vapor deposition dust a semiconductor power device industry waste through mechanochemical oxidation and leaching: A sustainable green process

    SciTech Connect

    Swain, Basudev; Mishra, Chinmayee; Lee, Chan Gi; Park, Kyung-Soo; Lee, Kun-Jae

    2015-07-15

    Dust generated during metal organic vapor deposition (MOCVD) process of GaN based semiconductor power device industry contains significant amounts of gallium and indium. These semiconductor power device industry wastes contain gallium as GaN and Ga{sub 0.97}N{sub 0.9}O{sub 0.09} is a concern for the environment which can add value through recycling. In the present study, this waste is recycled through mechanochemical oxidation and leaching. For quantitative recovery of gallium, two different mechanochemical oxidation leaching process flow sheets are proposed. In one process, first the Ga{sub 0.97}N{sub 0.9}O{sub 0.09} of the MOCVD dust is leached at the optimum condition. Subsequently, the leach residue is mechanochemically treated, followed by oxidative annealing and finally re-leached. In the second process, the MOCVD waste dust is mechanochemically treated, followed by oxidative annealing and finally leached. Both of these treatment processes are competitive with each other, appropriate for gallium leaching and treatment of the waste MOCVD dust. Without mechanochemical oxidation, 40.11 and 1.86 w/w% of gallium and Indium are leached using 4 M HCl, 100 °C and pulp density of 100 kg/m{sup 3,} respectively. After mechanochemical oxidation, both these processes achieved 90 w/w% of gallium and 1.86 w/w% of indium leaching at their optimum condition. - Highlights: • Waste MOCVD dust is treated through mechanochemical leaching. • GaN is hardly leached, and converted to NaGaO{sub 2} through ball milling and annealing. • Process for gallium recovery from waste MOCVD dust has been developed. • Thermal analysis and phase properties of GaN to Ga{sub 2}O{sub 3} and GaN to NaGaO{sub 2} is revealed. • Solid-state chemistry involved in this process is reported.

  14. Self-aligned metallization on organic semiconductor through 3D dual-layer thermal nanoimprint

    NASA Astrophysics Data System (ADS)

    Jung, Y.; Cheng, X.

    2014-09-01

    High-resolution patterning of metal structures on organic semiconductors is important to the realization of high-performance organic transistors for organic integrated circuit applications. The traditional shadow mask technique has a limited resolution, precluding sub-micron metal structures on organic semiconductors. Thus organic transistors cannot benefit from scaling into the deep sub-micron region to improve their dc and ac performances. In this work, we report an efficient multiple-level metallization on poly (3-hexylthiophene) (P3HT) with a deep sub-micron lateral gap. By using a 3D nanoimprint mold in a dual-layer thermal nanoimprint process, we achieved self-aligned two-level metallization on P3HT. The 3D dual-layer thermal nanoimprint enables the first metal patterns to have suspending side-wings that can clearly define a distance from the second metal patterns. Isotropic and anisotropic side-wing structures can be fabricated through two different schemes. The process based on isotropic side-wings achieves a lateral-gap in the order of 100 nm (scheme 1). A gap of 60 nm can be achieved from the process with anisotropic side-wings (scheme 2). Because of the capability of nanoscale metal patterning on organic semiconductors with high overlay accuracy, this self-aligned metallization technique can be utilized to fabricate high-performance organic metal semiconductor field-effect transistor.

  15. Nanodiamond-based nanostructures for coupling nitrogen-vacancy centres to metal nanoparticles and semiconductor quantum dots.

    PubMed

    Gong, Jianxiao; Steinsultz, Nat; Ouyang, Min

    2016-01-01

    The ability to control the interaction between nitrogen-vacancy centres in diamond and photonic and/or broadband plasmonic nanostructures is crucial for the development of solid-state quantum devices with optimum performance. However, existing methods typically employ top-down fabrication, which restrict scalable and feasible manipulation of nitrogen-vacancy centres. Here, we develop a general bottom-up approach to fabricate an emerging class of freestanding nanodiamond-based hybrid nanostructures with external functional units of either plasmonic nanoparticles or excitonic quantum dots. Precise control of the structural parameters (including size, composition, coverage and spacing of the external functional units) is achieved, representing a pre-requisite for exploring the underlying physics. Fine tuning of the emission characteristics through structural regulation is demonstrated by performing single-particle optical studies. This study opens a rich toolbox to tailor properties of quantum emitters, which can facilitate design guidelines for devices based on nitrogen-vacancy centres that use these freestanding hybrid nanostructures as building blocks. PMID:27273426

  16. Nanodiamond-based nanostructures for coupling nitrogen-vacancy centres to metal nanoparticles and semiconductor quantum dots

    PubMed Central

    Gong, Jianxiao; Steinsultz, Nat; Ouyang, Min

    2016-01-01

    The ability to control the interaction between nitrogen-vacancy centres in diamond and photonic and/or broadband plasmonic nanostructures is crucial for the development of solid-state quantum devices with optimum performance. However, existing methods typically employ top-down fabrication, which restrict scalable and feasible manipulation of nitrogen-vacancy centres. Here, we develop a general bottom-up approach to fabricate an emerging class of freestanding nanodiamond-based hybrid nanostructures with external functional units of either plasmonic nanoparticles or excitonic quantum dots. Precise control of the structural parameters (including size, composition, coverage and spacing of the external functional units) is achieved, representing a pre-requisite for exploring the underlying physics. Fine tuning of the emission characteristics through structural regulation is demonstrated by performing single-particle optical studies. This study opens a rich toolbox to tailor properties of quantum emitters, which can facilitate design guidelines for devices based on nitrogen-vacancy centres that use these freestanding hybrid nanostructures as building blocks. PMID:27273426

  17. Nanodiamond-based nanostructures for coupling nitrogen-vacancy centres to metal nanoparticles and semiconductor quantum dots

    DOE PAGESBeta

    Gong, Jianxiao; Steinsultz, Nat; Ouyang, Min

    2016-06-08

    The ability to control the interaction between nitrogen-vacancy centres in diamond and photonic and/or broadband plasmonic nanostructures is crucial for the development of solid-state quantum devices with optimum performance. However, existing methods typically employ top-down fabrication, which restrict scalable and feasible manipulation of nitrogen-vacancy centres. Here, we develop a general bottom-up approach to fabricate an emerging class of freestanding nanodiamond-based hybrid nanostructures with external functional units of either plasmonic nanoparticles or excitonic quantum dots. Precise control of the structural parameters ( including size, composition, coverage and spacing of the external functional units) is achieved, representing a pre-requisite for exploring themore » underlying physics. Fine tuning of the emission characteristics through structural regulation is demonstrated by performing single-particle optical studies. Lastly, this study opens a rich toolbox to tailor properties of quantum emitters, which can facilitate design guidelines for devices based on nitrogenvacancy centres that use these freestanding hybrid nanostructures as building blocks.« less

  18. Nanodiamond-based nanostructures for coupling nitrogen-vacancy centres to metal nanoparticles and semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Gong, Jianxiao; Steinsultz, Nat; Ouyang, Min

    2016-06-01

    The ability to control the interaction between nitrogen-vacancy centres in diamond and photonic and/or broadband plasmonic nanostructures is crucial for the development of solid-state quantum devices with optimum performance. However, existing methods typically employ top-down fabrication, which restrict scalable and feasible manipulation of nitrogen-vacancy centres. Here, we develop a general bottom-up approach to fabricate an emerging class of freestanding nanodiamond-based hybrid nanostructures with external functional units of either plasmonic nanoparticles or excitonic quantum dots. Precise control of the structural parameters (including size, composition, coverage and spacing of the external functional units) is achieved, representing a pre-requisite for exploring the underlying physics. Fine tuning of the emission characteristics through structural regulation is demonstrated by performing single-particle optical studies. This study opens a rich toolbox to tailor properties of quantum emitters, which can facilitate design guidelines for devices based on nitrogen-vacancy centres that use these freestanding hybrid nanostructures as building blocks.

  19. Ferromagnetic Resonance Spin Pumping and Electrical Spin Injection in Silicon-Based Metal-Oxide-Semiconductor Heterostructures.

    PubMed

    Pu, Y; Odenthal, P M; Adur, R; Beardsley, J; Swartz, A G; Pelekhov, D V; Flatté, M E; Kawakami, R K; Pelz, J; Hammel, P C; Johnston-Halperin, E

    2015-12-11

    We present the measurement of ferromagnetic resonance (FMR-)driven spin pumping and three-terminal electrical spin injection within the same silicon-based device. Both effects manifest in a dc spin accumulation voltage V_{s} that is suppressed as an applied field is rotated to the out-of-plane direction, i.e., the oblique Hanle geometry. Comparison of V_{s} between these two spin injection mechanisms reveals an anomalously strong suppression of FMR-driven spin pumping with increasing out-of-plane field H_{app}^{z}. We propose that the presence of the large ac component to the spin current generated by the spin pumping approach, expected to exceed the dc value by 2 orders of magnitude, is the origin of this discrepancy through its influence on the spin dynamics at the oxide-silicon interface. This convolution, wherein the dynamics of both the injector and the interface play a significant role in the spin accumulation, represents a new regime for spin injection that is not well described by existing models of either FMR-driven spin pumping or electrical spin injection. PMID:26705647

  20. Ferromagnetic Resonance Spin Pumping and Electrical Spin Injection in Silicon-Based Metal-Oxide-Semiconductor Heterostructures

    NASA Astrophysics Data System (ADS)

    Pu, Y.; Odenthal, P. M.; Adur, R.; Beardsley, J.; Swartz, A. G.; Pelekhov, D. V.; Flatté, M. E.; Kawakami, R. K.; Pelz, J.; Hammel, P. C.; Johnston-Halperin, E.

    2015-12-01

    We present the measurement of ferromagnetic resonance (FMR-)driven spin pumping and three-terminal electrical spin injection within the same silicon-based device. Both effects manifest in a dc spin accumulation voltage Vs that is suppressed as an applied field is rotated to the out-of-plane direction, i.e., the oblique Hanle geometry. Comparison of Vs between these two spin injection mechanisms reveals an anomalously strong suppression of FMR-driven spin pumping with increasing out-of-plane field Happz . We propose that the presence of the large ac component to the spin current generated by the spin pumping approach, expected to exceed the dc value by 2 orders of magnitude, is the origin of this discrepancy through its influence on the spin dynamics at the oxide-silicon interface. This convolution, wherein the dynamics of both the injector and the interface play a significant role in the spin accumulation, represents a new regime for spin injection that is not well described by existing models of either FMR-driven spin pumping or electrical spin injection.

  1. Practical anti-reflection coating for metal semiconductor solar cells

    NASA Technical Reports Server (NTRS)

    Yeh, Y.-C. M.; Stirn, R. J.

    1975-01-01

    The metal-semiconductor solar cell is a possible candidate for converting solar to electrical energy for terrestrial application. A method is given for obtaining optical parameters of practical antireflection coatings for the metal-semiconductor solar cell. This method utilizes the measured refractive index obtained from ellipsometry since the surface to be AR coated has a multilayer structure. Both the experimental results and theoretical calculation of optical parameters for Ta2O5 antireflection coatings on Au-GaAs and Au-GaAs(0.78)P(0.22) solar cells are presented for comparison.

  2. GaN Metal Oxide Semiconductor Field Effect Transistors

    SciTech Connect

    Ren, F.; Pearton, S.J.; Abernathy, C.R.; Baca, A.; Cheng, P.; Shul, R.J.; Chu, S.N.G.; Hong, M.; Lothian, J.R.; Schurman, M.J.

    1999-03-02

    A GaN based depletion mode metal oxide semiconductor field effect transistor (MOSFET) was demonstrated using Ga{sub 2}O{sub 3}(Gd{sub 2}O{sub 3}) as the gate dielectric. The MOS gate reverse breakdown voltage was > 35V which was significantly improved from 17V of Pt Schottky gate on the same material. A maximum extrinsic transconductance of 15 mS/mm was obtained at V{sub ds} = 30 V and device performance was limited by the contact resistance. A unity current gain cut-off frequency, f{sub {tau}}, and maximum frequency of oscillation, f{sub max} of 3.1 and 10.3 GHz, respectively, were measured at V{sub ds} = 25 V and V{sub gs} = {minus}20 V.

  3. Modeling of Metal-Ferroelectric-Semiconductor Field Effect Transistors

    NASA Technical Reports Server (NTRS)

    Duen Ho, Fat; Macleod, Todd C.

    1998-01-01

    The characteristics for a MFSFET (metal-ferroelectric-semiconductor field effect transistor) is very different than a conventional MOSFET and must be modeled differently. The drain current has a hysteresis shape with respect to the gate voltage. The position along the hysteresis curve is dependent on the last positive or negative polling of the ferroelectric material. The drain current also has a logarithmic decay after the last polling. A model has been developed to describe the MFSFET drain current for both gate voltage on and gate voltage off conditions. This model takes into account the hysteresis nature of the MFSFET and the time dependent decay. The model is based on the shape of the Fermi-Dirac function which has been modified to describe the MFSFET's drain current. This is different from the model proposed by Chen et. al. and that by Wu.

  4. Metal-semiconductor transition of graphene nanoribbons with different addends

    NASA Astrophysics Data System (ADS)

    Zhang, X. W.; Dai, B.; Liu, J. S.; Yang, G. W.

    2012-02-01

    Using a LCAO method, which is based on spinless sp3 scheme, we have studied the electronic properties of graphene nanoribbons with zigzag edges (ZGNRs) terminated partially by methylene groups. Metal-semiconductor transition is proved when the H atoms at both sides of ZGNRs are partially substituted by methylene groups. Furthermore, when one-third of H atoms are substituted and the distribution of methylenes is symmetric, the band gap comes to about 0.59 eV, which is the widest energy gap in this work. Otherwise, when the addends at both sides are of asymmetric distribution, a band gap of only 0.21 eV is obtained. These results suggest that the addends at the edge of ZGNRs play an important role in modifying the electronic properties.

  5. Bulk and interface trapping in the gate dielectric of GaN based metal-oxide-semiconductor high-electron-mobility transistors

    NASA Astrophysics Data System (ADS)

    Ťapajna, M.; Jurkovič, M.; Válik, L.; Haščík, Š.; Gregušová, D.; Brunner, F.; Cho, E.-M.; Kuzmík, J.

    2013-06-01

    The trapping phenomena in GaN metal-oxide-semiconductor high-electron mobility transistor structures with 10 and 20-nm thick Al2O3 gate dielectric grown by metal-organic chemical vapor deposition were deeply investigated using comprehensive capacitance-voltage measurements. By controlling the interface traps population, substantial electron trapping in the dielectric bulk was identified. Separation between the trapping process and the interface traps emission allowed us to determine distribution of interface trap density in a wide energy range. Temperature dependence of the trapping process indicates thermionic field emission of electrons from the gate into traps with a sheet density of ~1013 cm-2, located a few nm below the gate.

  6. Bulk and interface trapping in the gate dielectric of GaN based metal-oxide-semiconductor high-electron-mobility transistors

    NASA Astrophysics Data System (ADS)

    Ťapajna, M.; Jurkovič, M.; Válik, L.; Haščík, Š.; Gregušová, D.; Brunner, F.; Cho, E.-M.; Kuzmík, J.

    2013-06-01

    The trapping phenomena in GaN metal-oxide-semiconductor high-electron mobility transistor structures with 10 and 20-nm thick Al2O3 gate dielectric grown by metal-organic chemical vapor deposition were deeply investigated using comprehensive capacitance-voltage measurements. By controlling the interface traps population, substantial electron trapping in the dielectric bulk was identified. Separation between the trapping process and the interface traps emission allowed us to determine distribution of interface trap density in a wide energy range. Temperature dependence of the trapping process indicates thermionic field emission of electrons from the gate into traps with a sheet density of ˜1013 cm-2, located a few nm below the gate.

  7. Ultrafast photoinduced charge separation in metal-semiconductor nanohybrids.

    PubMed

    Mongin, Denis; Shaviv, Ehud; Maioli, Paolo; Crut, Aurélien; Banin, Uri; Del Fatti, Natalia; Vallée, Fabrice

    2012-08-28

    Hybrid nano-objects formed by two or more disparate materials are among the most promising and versatile nanosystems. A key parameter in their properties is interaction between their components. In this context we have investigated ultrafast charge separation in semiconductor-metal nanohybrids using a model system of gold-tipped CdS nanorods in a matchstick architecture. Experiments are performed using an optical time-resolved pump-probe technique, exciting either the semiconductor or the metal component of the particles, and probing the light-induced change of their optical response. Electron-hole pairs photoexcited in the semiconductor part of the nanohybrids are shown to undergo rapid charge separation with the electron transferred to the metal part on a sub-20 fs time scale. This ultrafast gold charging leads to a transient red-shift and broadening of the metal surface plasmon resonance, in agreement with results for free clusters but in contrast to observation for static charging of gold nanoparticles in liquid environments. Quantitative comparison with a theoretical model is in excellent agreement with the experimental results, confirming photoexcitation of one electron-hole pair per nanohybrid followed by ultrafast charge separation. The results also point to the utilization of such metal-semiconductor nanohybrids in light-harvesting applications and in photocatalysis. PMID:22792998

  8. Plasmonic nanostructured metal-oxide-semiconductor reflection modulators.

    PubMed

    Olivieri, Anthony; Chen, Chengkun; Hassan, Sa'ad; Lisicka-Skrzek, Ewa; Tait, R Niall; Berini, Pierre

    2015-04-01

    We propose a plasmonic surface that produces an electrically controlled reflectance as a high-speed intensity modulator. The device is conceived as a metal-oxide-semiconductor capacitor on silicon with its metal structured as a thin patch bearing a contiguous nanoscale grating. The metal structure serves multiple functions as a driving electrode and as a grating coupler for perpendicularly incident p-polarized light to surface plasmons supported by the patch. Modulation is produced by charging and discharging the capacitor and exploiting the carrier refraction effect in silicon along with the high sensitivity of strongly confined surface plasmons to index perturbations. The area of the modulator is set by the area of the incident beam, leading to a very compact device for a strongly focused beam (∼2.5 μm in diameter). Theoretically, the modulator can operate over a broad electrical bandwidth (tens of gigahertz) with a modulation depth of 3 to 6%, a loss of 3 to 4 dB, and an optical bandwidth of about 50 nm. About 1000 modulators can be integrated over a 50 mm(2) area producing an aggregate electro-optic modulation rate in excess of 1 Tb/s. We demonstrate experimentally modulators operating at telecommunications wavelengths, fabricated as nanostructured Au/HfO2/p-Si capacitors. The modulators break conceptually from waveguide-based devices and belong to the same class of devices as surface photodetectors and vertical cavity surface-emitting lasers. PMID:25730698

  9. Semiconductor-based optical refrigerator

    DOEpatents

    Epstein, Richard I.; Edwards, Bradley C.; Sheik-Bahae, Mansoor

    2002-01-01

    Optical refrigerators using semiconductor material as a cooling medium, with layers of material in close proximity to the cooling medium that carries away heat from the cooling material and preventing radiation trapping. In addition to the use of semiconducting material, the invention can be used with ytterbium-doped glass optical refrigerators.

  10. Metal/Semiconductor hybrid nanostructures for plasmon-enhanced applications.

    PubMed

    Jiang, Ruibin; Li, Benxia; Fang, Caihong; Wang, Jianfang

    2014-08-20

    Hybrid nanostructures composed of semiconductor and plasmonic metal components are receiving extensive attention. They display extraordinary optical characteristics that are derived from the simultaneous existence and close conjunction of localized surface plasmon resonance and semiconduction, as well as the synergistic interactions between the two components. They have been widely studied for photocatalysis, plasmon-enhanced spectroscopy, biotechnology, and solar cells. In this review, the developments in the field of (plasmonic metal)/semiconductor hybrid nanostructures are comprehensively described. The preparation of the hybrid nanostructures is first presented according to the semiconductor type, as well as the nanostructure morphology. The plasmonic properties and the enabled applications of the hybrid nanostructures are then elucidated. Lastly, possible future research in this burgeoning field is discussed. PMID:24753398

  11. High-temperature Complementary Metal Oxide Semiconductors (CMOS)

    NASA Technical Reports Server (NTRS)

    Mcbrayer, J. D.

    1981-01-01

    The results of an investigation into the possibility of using complementary metal oxide semiconductor (CMOS) technology for high temperature electronics are presented. A CMOS test chip was specifically developed as the test bed. This test chip incorporates CMOS transistors that have no gate protection diodes; these diodes are the major cause of leakage in commercial devices.

  12. Abrupt Depletion Layer Approximation for the Metal Insulator Semiconductor Diode.

    ERIC Educational Resources Information Center

    Jones, Kenneth

    1979-01-01

    Determines the excess surface change carrier density, surface potential, and relative capacitance of a metal insulator semiconductor diode as a function of the gate voltage, using the precise questions and the equations derived with the abrupt depletion layer approximation. (Author/GA)

  13. Different effects of electronic excitation on metals and semiconductors

    NASA Astrophysics Data System (ADS)

    Yan, Gai-Qin; Cheng, Xin-Lu; Zhang, Hong; Zhu, Zhi-Yang; Ren, Da-Hua

    2016-06-01

    We study the electronic excitation effect upon ultrafast and intense laser irradiation on the stability of target materials, using density functional perturbation theory. The target materials include metals (Li, Na, Mg, Al, K, W, Au), Bi as a semimetal, and Si as a semiconductor. We found that the electronic excitation had different effects on the two distinct materials. For metals, the electronic pressure induces an increase in the shear modulus and presents a negative effect on the phonon entropy, which increases the lattice vibration frequency and melting temperature, leading to a higher stability for the close-packed structure (Al, Au, Mg). Conversely, the electronic pressure induces a decreasing trend in all these quantities, leading to a lower degree of stability and even a structural destabilization in the case of bcc-structured metals (W, Na, K, and Li). For semimetals and semiconductors, the internal pressure induces a completely opposite behavior with respect to close-packed structure metals. This can lead to structural destabilization for semimetals and even collapse for semiconductors. Finally, a shift of the Raman and infrared active modes is revealed for semimetals and semiconductors.

  14. Metal Insulator Semiconductor Structures on Gallium Arsenide.

    NASA Astrophysics Data System (ADS)

    Connor, Sean Denis

    Available from UMI in association with The British Library. The compound semiconductor gallium arsenide and its associated aluminium alloys have been the subject of intensive research in recent years. These materials offer the advantage of high electron mobilities coupled with the ability to be 'barrier engineered' leading to high injection efficiencies in bipolar devices. From a technological viewpoint however these materials are difficult to work with and device realisation is a major problem. Both thermal and anodic oxidation of these materials fail to produce a dielectric of sufficient quality for device applications and as a result devices tend to be complex non planar, mesa structures. A technique is proposed whereby the electrical interface is separated from the dielectric by means of a thin layer of AlGaAs, carrier confinement in the active GaAs region being maintained by the potential barriers to holes and electrons formed by the GaAs-AlGaAs junction. The integrity of these barriers is maintained by the provision of a suitable 'capping' dielectric. The electrical characteristics of various dielectric systems on GaAs have been investigated by means of current -voltage, capacitance-voltage and electronic breakdown measurements. Transport mechanisms for leakage current through these systems are identified and the interface properties (viz Fermi level pinning etc.) assessed by means of a direct comparison between experimental capacitance-voltage curves and theoretical data obtained from classical theory. As a technique for producing a convenient, in house 'capping' dielectric with good electrical and mechanical properties, the plasma anodisation of deposited aluminium films has been investigated. The anodisation parameters have been optimised for oxidation of these films in a microwave sustained oxygen plasma to give alumina films of around 500 A. A qualitative model for the anodisation process, involving linear and parabolic growth kinetics is proposed and

  15. Asymmetrically contacted germanium photodiode using a metal-interlayer-semiconductor-metal structure for extremely large dark current suppression.

    PubMed

    Zang, Hwan-Jun; Kim, Gwang-Sik; Park, Gil-Jae; Choi, Yong-Soo; Yu, Hyun-Yong

    2016-08-15

    In this study, we proposed germanium (Ge) metal-interlayer-semiconductor-metal (MISM) photodiodes (PD), with an anode of a metal-interlayer-semiconductor (MIS) contact and a cathode of a metal-semiconductor (MS) contact, to efficiently suppress the dark current of Ge PD. We selected titanium dioxide (TiO2) as an interlayer material for the MIS contact, due to its large valence band offset and negative conduction band offset to Ge. We significantly suppress the dark current of Ge PD by introducing the MISM structure with a TiO2 interlayer, as this enhances the hole Schottky barrier height, and thus acts as a large barrier for holes. In addition, it collects photo-generated carriers without degradation, due to its negative conduction band offset to Ge. This reduces the dark current of Ge MISM PDs by ×8000 for 7-nm-thick TiO2 interlayer, while its photo current is still comparable to that of Ge metal-semiconductor-metal (MSM) PDs. Furthermore, the proposed Ge PD shows ×6,600 improvement of the normalized photo-to-dark-current ratio (NPDR) at a wavelength of 1.55 μm. The proposed Ge MISM PD shows considerable promise for low power and high sensitivity Ge-based optoelectronic applications. PMID:27519063

  16. High-temperature MEMS Heater Platforms: Long-term Performance of Metal and Semiconductor Heater Materials

    PubMed Central

    Spannhake, Jan; Schulz, Olaf; Helwig, Andreas; Krenkow, Angelika; Müller, Gerhard; Doll, Theodor

    2006-01-01

    Micromachined thermal heater platforms offer low electrical power consumption and high modulation speed, i.e. properties which are advantageous for realizing non-dispersive infrared (NDIR) gas- and liquid monitoring systems. In this paper, we report on investigations on silicon-on-insulator (SOI) based infrared (IR) emitter devices heated by employing different kinds of metallic and semiconductor heater materials. Our results clearly reveal the superior high-temperature performance of semiconductor over metallic heater materials. Long-term stable emitter operation in the vicinity of 1300 K could be attained using heavily antimony-doped tin dioxide (SnO2:Sb) heater elements.

  17. Trap Profiling Based on Frequency Varied Charge Pumping Method for Hot Carrier Stressed Thin Gate Oxide Metal Oxide Semiconductors Field Effect Transistors.

    PubMed

    Choi, Pyungho; Kim, Hyunjin; Kim, Sangsub; Kim, Soonkon; Javadi, Reza; Park, Hyoungsun; Choi, Byoungdeog

    2016-05-01

    In this study, pulse frequency and reverse bias voltage is modified in charge pumping and advanced technique is presented to extract oxide trap profile in hot carrier stressed thin gate oxide metal oxide semiconductor field effect transistors (MOSFETs). Carrier trapping-detrapping in a gate oxide was analyzed after hot carrier stress and the relationship between trapping depth and frequency was investigated. Hot carrier induced interface traps appears in whole channel area but induced border traps mainly appears in above pinch-off region near drain and gradually decreases toward center of the channel. Thus, hot carrier stress causes interface trap generation in whole channel area while most border trap generation occurs in the drain region under the gate. Ultimately, modified charge pumping method was performed to get trap density distribution of hot carrier stressed MOSFET devices, and the trapping-detrapping mechanism is also analyzed. PMID:27483833

  18. 1.2-17.6 GHz Ring-Oscillator-Based Phase-Locked Loop with Injection Locking in 65 nm Complementary Metal Oxide Semiconductor

    NASA Astrophysics Data System (ADS)

    Lee, Sang-yeop; Ito, Hiroyuki; Amakawa, Shuhei; Tanoi, Satoru; Ishihara, Noboru; Masu, Kazuya

    2012-02-01

    A wide-frequency-range phase-locked loop (PLL) with subharmonic injection locking is proposed. The PLL is equipped with a wide tunable ring-type voltage-controlled oscillator (ring VCO), frequency dividers, and a doubler in order to the widen injection-locked tuning range (ILTR). In addition, high-frequency injection signals are used to improve phase noise, which is supposed to be generated by a reference PLL. The proposed circuit is fabricated by using a 65 nm Si complementary metal oxide semiconductor (CMOS) process. The measured frequency tuning range is from 1.2 to 17.6 GHz with a frequency doubler and dividers. The phase noise at 14.4 GHz (=32×450 MHz) with injection locking was -109 dBc/Hz, which shows a 21-dB reduction compared with that in the case without injection locking.

  19. 0.1 V 13 GHz Transformer-Based Quadrature Voltage-Controlled Oscillator with a Capacitor Coupling Technique in 90 nm Complementary Metal Oxide Semiconductor

    NASA Astrophysics Data System (ADS)

    Kamimura, Tatsuya; Lee, Sang-yeop; Tanoi, Satoru; Ito, Hiroyuki; Ishihara, Noboru; Masu, Kazuya

    2012-04-01

    A low power-supply voltage and high-frequency quadrature voltage-controlled oscillator (QVCO) using a combination of capacitor coupling and transformer feedback techniques is presented. The capacitor coupling technique can boost the transconductance of the LC-VCO core and coupling transconductance of QVCO at high frequency. Also, this technique can improve the quality factor of the QVCO at high frequency with low power-supply voltage, compared with the conventional QVCO. In addition, the capacitor coupling QVCO with transformer feedback can improve the quality factor of QVCO. Using this topology, the QVCO is able to operate at over 10 GHz with lower power-supply voltage. Implemented in the 90 nm complementary metal oxide semiconductor (CMOS) process, the proposed QVCO measures 1-MHz-offset phase noise of -94 dBc/Hz at 13 GHz while consuming 0.68 mW from a 0.1 V power-supply.

  20. P-Channel InGaN/GaN heterostructure metal-oxide-semiconductor field effect transistor based on polarization-induced two-dimensional hole gas

    NASA Astrophysics Data System (ADS)

    Zhang, Kexiong; Sumiya, Masatomo; Liao, Meiyong; Koide, Yasuo; Sang, Liwen

    2016-03-01

    The concept of p-channel InGaN/GaN heterostructure field effect transistor (FET) using a two-dimensional hole gas (2DHG) induced by polarization effect is demonstrated. The existence of 2DHG near the lower interface of InGaN/GaN heterostructure is verified by theoretical simulation and capacitance-voltage profiling. The metal-oxide-semiconductor FET (MOSFET) with Al2O3 gate dielectric shows a drain-source current density of 0.51 mA/mm at the gate voltage of ‑2 V and drain bias of ‑15 V, an ON/OFF ratio of two orders of magnitude and effective hole mobility of 10 cm2/Vs at room temperature. The normal operation of MOSFET without freeze-out at 8 K further proves that the p-channel behavior is originated from the polarization-induced 2DHG.

  1. P-Channel InGaN/GaN heterostructure metal-oxide-semiconductor field effect transistor based on polarization-induced two-dimensional hole gas.

    PubMed

    Zhang, Kexiong; Sumiya, Masatomo; Liao, Meiyong; Koide, Yasuo; Sang, Liwen

    2016-01-01

    The concept of p-channel InGaN/GaN heterostructure field effect transistor (FET) using a two-dimensional hole gas (2DHG) induced by polarization effect is demonstrated. The existence of 2DHG near the lower interface of InGaN/GaN heterostructure is verified by theoretical simulation and capacitance-voltage profiling. The metal-oxide-semiconductor FET (MOSFET) with Al2O3 gate dielectric shows a drain-source current density of 0.51 mA/mm at the gate voltage of -2 V and drain bias of -15 V, an ON/OFF ratio of two orders of magnitude and effective hole mobility of 10 cm(2)/Vs at room temperature. The normal operation of MOSFET without freeze-out at 8 K further proves that the p-channel behavior is originated from the polarization-induced 2DHG. PMID:27021054

  2. The empirical dependence of radiation-induced charge neutralization on negative bias in dosimeters based on the metal-oxide-semiconductor field-effect transistor

    SciTech Connect

    Benson, Chris; Albadri, Abdulrahman; Joyce, Malcolm J.; Price, Robert A.

    2006-08-15

    The dependence of radiation-induced charge neutralization (RICN) has been studied in metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters. These devices were first exposed to x rays under positive bias and then to further dose increments at a selection of reverse bias levels. A nonlinear empirical trend has been established that is consistent with that identified in the data obtained in this work. Estimates for the reverse bias level corresponding to the maximum rate of RICN have been extracted from the data. These optimum bias levels appear to be independent of the level of initial absorbed dose under positive bias. The established models for threshold voltage change have been considered and indicate a related nonlinear trend for neutralization cross section {sigma}{sub N} as a function of oxide field. These data are discussed in the context of dose measurement with MOSFETs and within the framework of statistical mechanics associated with neutral traps and their field dependence.

  3. Nanoscale High-Speed Metal-Semiconductor Photodetectors

    NASA Astrophysics Data System (ADS)

    Liu, Mark Yue

    This thesis work studies the design, fabrication and characterization of nanoscale high-speed metal-semiconductor -metal (MSM) photodetectors. Smallest, fastest MSM photodetectors will be presented. Important design issues such as carrier transit time, carrier recombination time, light penetration depth, and device parasitic elements are investigated. Carrier transport in nanoscale detectors is studied using a Monte Carlo method. Based on the theoretical and experimental data, scaling rules for high-speed operation of MSM photodetectors are proposed. Nanoscale MSM photodetectors are fabricated using a custom-built ultra-high-resolution electron beam lithography system and a lift-off process. Different resist schemes and accurate dose control are essential to produce desired nanoscale structures. MSM photodetectors with finger spacing and width as small as 25 nm are fabricated on GaAs, Si and silicon-on-insulator (SOI) substrate. To our knowledge, they represent the smallest ever reported to date. Sub-picosecond characterization of the detectors' impulse response is performed using an electro-optic system and a femtosecond laser. The fastest MSM photodetectors have a response time and a 3-dB bandwidth of, respectively, 0.87 ps and 510 GHz on low-temperature-grown GaAs, 1.5 ps and 300 GHz on bulk GaAs, 3.7 ps and 110 GHz on bulk Si, and 3.2 ps and 140 GHz on SOI. They are, to the best of our knowledge, the fastest photodetectors of their kind. MSM photodetectors on GaAs and Si can also be used at 1.3 to 1.55 μm wavelength range, based on the internal emission of carriers at the metal-semiconductor interface. The performance of the GaAs and Si detector at 1.3 μm wavelength, including the dependence of responsivity on finger size, optical power, and applied bias, will be presented in this thesis. Finally, we will propose a new silicon Fabry-Perot planar waveguide modulator structure consisting of two Bragg mirrors, which are nanoscale trenches in the waveguide

  4. Metal Semiconductor Heterostructures for Photocatalytic Conversion of Light Energy.

    PubMed

    Dutta, Sumit Kumar; Mehetor, Shyamal Kumar; Pradhan, Narayan

    2015-03-19

    For fast separation of the photogenerated charge carriers, metal semiconductor heterostructures have emerged as one of the leading materials in recent years. Among these, metal Au coupled with low bandgap semiconductors remain as ideal materials where both can absorb the solar light in the visible region. It is also established that on excitation, the plasmonic state of gold interacts with excited state of semiconductor and helps for the delocalization of the photogenerated electrons. Focusing these materials where electron transfer preferably occurs from semiconductor to metal Au on excitation, in this Perspective, we report the latest developments in the synthetic chemistry in designing such nano heterostructures and discuss their photocatalytic activities in organic dye degradation/reduction and/or photocatalytic water splitting for generation of hydrogen. Among these, materials such as Au-CZTS, Au-SnS, Au-Bi2S3, Au-ZnSe, and so forth are emphasized, and their formation chemistry as well as their photocatalytic activities are discussed in this Perspective. PMID:26262849

  5. Metal-insulator transition in films of doped semiconductor nanocrystals.

    PubMed

    Chen, Ting; Reich, K V; Kramer, Nicolaas J; Fu, Han; Kortshagen, Uwe R; Shklovskii, B I

    2016-03-01

    To fully deploy the potential of semiconductor nanocrystal films as low-cost electronic materials, a better understanding of the amount of dopants required to make their conductivity metallic is needed. In bulk semiconductors, the critical concentration of electrons at the metal-insulator transition is described by the Mott criterion. Here, we theoretically derive the critical concentration nc for films of heavily doped nanocrystals devoid of ligands at their surface and in direct contact with each other. In the accompanying experiments, we investigate the conduction mechanism in films of phosphorus-doped, ligand-free silicon nanocrystals. At the largest electron concentration achieved in our samples, which is half the predicted nc, we find that the localization length of hopping electrons is close to three times the nanocrystals diameter, indicating that the film approaches the metal-insulator transition. PMID:26618885

  6. Metal-insulator transition in films of doped semiconductor nanocrystals

    NASA Astrophysics Data System (ADS)

    Chen, Ting; Reich, K. V.; Kramer, Nicolaas J.; Fu, Han; Kortshagen, Uwe R.; Shklovskii, B. I.

    2016-03-01

    To fully deploy the potential of semiconductor nanocrystal films as low-cost electronic materials, a better understanding of the amount of dopants required to make their conductivity metallic is needed. In bulk semiconductors, the critical concentration of electrons at the metal-insulator transition is described by the Mott criterion. Here, we theoretically derive the critical concentration nc for films of heavily doped nanocrystals devoid of ligands at their surface and in direct contact with each other. In the accompanying experiments, we investigate the conduction mechanism in films of phosphorus-doped, ligand-free silicon nanocrystals. At the largest electron concentration achieved in our samples, which is half the predicted nc, we find that the localization length of hopping electrons is close to three times the nanocrystals diameter, indicating that the film approaches the metal-insulator transition.

  7. High performance high-κ/metal gate complementary metal oxide semiconductor circuit element on flexible silicon

    NASA Astrophysics Data System (ADS)

    Torres Sevilla, G. A.; Almuslem, A. S.; Gumus, A.; Hussain, A. M.; Cruz, M. E.; Hussain, M. M.

    2016-02-01

    Thinned silicon based complementary metal oxide semiconductor (CMOS) electronics can be physically flexible. To overcome challenges of limited thinning and damaging of devices originated from back grinding process, we show sequential reactive ion etching of silicon with the assistance from soft polymeric materials to efficiently achieve thinned (40 μm) and flexible (1.5 cm bending radius) silicon based functional CMOS inverters with high-κ/metal gate transistors. Notable advances through this study shows large area of silicon thinning with pre-fabricated high performance elements with ultra-large-scale-integration density (using 90 nm node technology) and then dicing of such large and thinned (seemingly fragile) pieces into smaller pieces using excimer laser. The impact of various mechanical bending and bending cycles show undeterred high performance of flexible silicon CMOS inverters. Future work will include transfer of diced silicon chips to destination site, interconnects, and packaging to obtain fully flexible electronic systems in CMOS compatible way.

  8. Cosmic Ray Measurements by Scintillators with Metal Resistor Semiconductor Avalanche Photo Diodes

    ERIC Educational Resources Information Center

    Blanco, Francesco; La Rocca, Paola; Riggi, Francesco; Akindinov, Alexandre; Mal'kevich, Dmitry

    2008-01-01

    An educational set-up for cosmic ray physics experiments is described. The detector is based on scintillator tiles with a readout through metal resistor semiconductor (MRS) avalanche photo diode (APD) arrays. Typical measurements of the cosmic angular distribution at sea level and a study of the East-West asymmetry obtained by such a device are…

  9. Formation and properties of metallic nanoparticles on compound semiconductor surfaces

    NASA Astrophysics Data System (ADS)

    Kang, Myungkoo

    When electromagnetic radiation is incident upon metallic nanoparticles (NPs), a collective oscillation, termed a surface plasmon resonance (SPR), is generated. Recently, metallic NPs on semiconductor surfaces have enabled the generation of SPR, promising for enhanced light emission, efficient solar energy harvesting, biosensing, and metamaterials. Metallic NPs have been fabricated by focused ion beam (FIB) which has an advantage of cost-effectiveness over conventional lithography process requiring multi-step processes. Here, we report formation and properties of FIB-induced metallic NPs on compound semiconductor surfaces. Results presented in this thesis study suggest that FIB-induced Ga NPs can be a promising alternative plasmonic material. In particular, using a combined experimental-computational approach, we discovered a universal mechanism for ion-induced NP formation, which is governed by the sputtering yield of semiconductor surfaces. We also discovered a governing mechanism for ion-induced NP motion, which is driven by thermal fluctuation and anisotropic mass transport. Furthermore, we demonstrated Ga NP arrays with plasmon resonances with performance comparable to those of traditionally-used silver and gold NPs. We then finally demonstrated the Ga NP plasmoninduced enhancement of light emission from GaAs, which is the first ever combination of a new plasmonic material (Ga) and a new fabrication method (FIB) for the plasmon-enhanced light emission.

  10. Strong and highly asymmetrical optical absorption in conformal metal-semiconductor-metal grating system for plasmonic hot-electron photodetection application

    PubMed Central

    Wu, Kai; Zhan, Yaohui; Zhang, Cheng; Wu, Shaolong; Li, Xiaofeng

    2015-01-01

    We propose an architecture of conformal metal-semiconductor-metal (MSM) device for hot-electron photodetection by asymmetrical alignment of the semiconductor barrier relative to the Fermi level of metals and strong energy localization through plasmonic resonances. Compared with the conventional grating design, the multi-layered grating system under conformal configuration is demonstrated to possess both optical and electrical advantages for high-sensitivity hot-electron photodetection. Finite-element simulation reveals that a strong and highly asymmetrical optical absorption (top metal absorption >99%) can be realized under such a conformal arrangement. An analytical probability-based electrical simulation verifies the strong unidirectional photocurrent, by taking advantage of the extremely high net absorption and a low metal/semiconductor barrier height, and predicts that the corresponding photoresponsivity can be ~3 times of that based on the conventional grating design in metal-insulator-metal (MIM) configuration. PMID:26387836

  11. Strong and highly asymmetrical optical absorption in conformal metal-semiconductor-metal grating system for plasmonic hot-electron photodetection application.

    PubMed

    Wu, Kai; Zhan, Yaohui; Zhang, Cheng; Wu, Shaolong; Li, Xiaofeng

    2015-01-01

    We propose an architecture of conformal metal-semiconductor-metal (MSM) device for hot-electron photodetection by asymmetrical alignment of the semiconductor barrier relative to the Fermi level of metals and strong energy localization through plasmonic resonances. Compared with the conventional grating design, the multi-layered grating system under conformal configuration is demonstrated to possess both optical and electrical advantages for high-sensitivity hot-electron photodetection. Finite-element simulation reveals that a strong and highly asymmetrical optical absorption (top metal absorption >99%) can be realized under such a conformal arrangement. An analytical probability-based electrical simulation verifies the strong unidirectional photocurrent, by taking advantage of the extremely high net absorption and a low metal/semiconductor barrier height, and predicts that the corresponding photoresponsivity can be ~3 times of that based on the conventional grating design in metal-insulator-metal (MIM) configuration. PMID:26387836

  12. Superabsorbing, Artificial Metal Films Constructed from Semiconductor Nanoantennas.

    PubMed

    Kim, Soo Jin; Park, Junghyun; Esfandyarpour, Majid; Pecora, Emanuele F; Kik, Pieter G; Brongersma, Mark L

    2016-06-01

    In 1934, Wilhelm Woltersdorff demonstrated that the absorption of light in an ultrathin, freestanding film is fundamentally limited to 50%. He concluded that reaching this limit would require a film with a real-valued sheet resistance that is exactly equal to R = η/2 ≈ 188.5Ω/□, where [Formula: see text] is the impedance of free space. This condition can be closely approximated over a wide frequency range in metals that feature a large imaginary relative permittivity εr″, that is, a real-valued conductivity σ = ε0εr″ω. A thin, continuous sheet of semiconductor material does not facilitate such strong absorption as its complex-valued permittivity with both large real and imaginary components preclude effective impedance matching. In this work, we show how a semiconductor metafilm constructed from optically resonant semiconductor nanostructures can be created whose optical response mimics that of a metallic sheet. For this reason, the fundamental absorption limit mentioned above can also be reached with semiconductor materials, opening up new opportunities for the design of ultrathin optoelectronic and light harvesting devices. PMID:27149008

  13. Computational Study of Metal Contacts to Monolayer Transition-Metal Dichalcogenide Semiconductors

    NASA Astrophysics Data System (ADS)

    Kang, Jiahao; Liu, Wei; Sarkar, Deblina; Jena, Debdeep; Banerjee, Kaustav

    2014-07-01

    Among various 2D materials, monolayer transition-metal dichalcogenide (mTMD) semiconductors with intrinsic band gaps (1-2 eV) are considered promising candidates for channel materials in next-generation transistors. Low-resistance metal contacts to mTMDs are crucial because currently they limit mTMD device performances. Hence, a comprehensive understanding of the atomistic nature of metal contacts to these 2D crystals is a fundamental challenge, which is not adequately addressed at present. In this paper, we report a systematic study of metal-mTMD contacts with different geometries (top contacts and edge contacts) by ab initio density-functional theory calculations, integrated with Mulliken population analysis and a semiempirical van der Waals dispersion potential model (which is critical for 2D materials and not well treated before). Particularly, In, Ti, Au, and Pd, contacts to monolayer MoS2 and WSe2 as well as Mo-MoS2 and W-WSe2 contacts are evaluated and categorized, based on their tunnel barriers, Schottky barriers, and orbital overlaps. Moreover, going beyond Schottky theory, new physics in such contact interfaces is revealed, such as the metallization of mTMDs and abnormal Fermi level pinning. Among the top contacts to MoS2, Ti and Mo show great potential to form favorable top contacts, which are both n-type contacts, while for top contacts to WSe2, W or Pd exhibits the most advantages as an n- or p-type contact, respectively. Moreover, we find that edge contacts can be highly advantageous compared to top contacts in terms of electron injection efficiency. Our formalism and the results provide guidelines that would be invaluable for designing novel 2D semiconductor devices.

  14. Single-photon imaging in complementary metal oxide semiconductor processes

    PubMed Central

    Charbon, E.

    2014-01-01

    This paper describes the basics of single-photon counting in complementary metal oxide semiconductors, through single-photon avalanche diodes (SPADs), and the making of miniaturized pixels with photon-counting capability based on SPADs. Some applications, which may take advantage of SPAD image sensors, are outlined, such as fluorescence-based microscopy, three-dimensional time-of-flight imaging and biomedical imaging, to name just a few. The paper focuses on architectures that are best suited to those applications and the trade-offs they generate. In this context, architectures are described that efficiently collect the output of single pixels when designed in large arrays. Off-chip readout circuit requirements are described for a variety of applications in physics, medicine and the life sciences. Owing to the dynamic nature of SPADs, designs featuring a large number of SPADs require careful analysis of the target application for an optimal use of silicon real estate and of limited readout bandwidth. The paper also describes the main trade-offs involved in architecting such chips and the solutions adopted with focus on scalability and miniaturization. PMID:24567470

  15. Single-photon imaging in complementary metal oxide semiconductor processes.

    PubMed

    Charbon, E

    2014-03-28

    This paper describes the basics of single-photon counting in complementary metal oxide semiconductors, through single-photon avalanche diodes (SPADs), and the making of miniaturized pixels with photon-counting capability based on SPADs. Some applications, which may take advantage of SPAD image sensors, are outlined, such as fluorescence-based microscopy, three-dimensional time-of-flight imaging and biomedical imaging, to name just a few. The paper focuses on architectures that are best suited to those applications and the trade-offs they generate. In this context, architectures are described that efficiently collect the output of single pixels when designed in large arrays. Off-chip readout circuit requirements are described for a variety of applications in physics, medicine and the life sciences. Owing to the dynamic nature of SPADs, designs featuring a large number of SPADs require careful analysis of the target application for an optimal use of silicon real estate and of limited readout bandwidth. The paper also describes the main trade-offs involved in architecting such chips and the solutions adopted with focus on scalability and miniaturization. PMID:24567470

  16. Photonics and optoelectronics of 2D semiconductor transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Mak, Kin Fai; Shan, Jie

    2016-04-01

    Recent advances in the development of atomically thin layers of van der Waals bonded solids have opened up new possibilities for the exploration of 2D physics as well as for materials for applications. Among them, semiconductor transition metal dichalcogenides, MX2 (M = Mo, W; X = S, Se), have bandgaps in the near-infrared to the visible region, in contrast to the zero bandgap of graphene. In the monolayer limit, these materials have been shown to possess direct bandgaps, a property well suited for photonics and optoelectronics applications. Here, we review the electronic and optical properties and the recent progress in applications of 2D semiconductor transition metal dichalcogenides with emphasis on strong excitonic effects, and spin- and valley-dependent properties.

  17. Finite Element Simulation of Metal-Semiconductor-Metal Photodetector

    SciTech Connect

    Guarino, G.; Donaldson, W.R.; Mikulics, M.; Marso, M.; Kordos, P.; Sobolewski, R.

    2009-08-19

    The successful application of finite element analysis to ultrafast optoelectronic devices is demonstrated. Finite element models have been developed for both an alloyed- and surface-contact metal–semiconductor–metal photodetectors. The simulation results agree with previously reported experimental data. The alloyed device, despite having a somewhat larger capacitance, has a non-illuminated region of lower resistance with a more-uniform and deeper-penetrating electric field and carrier transport current. The latter explains, in terms of the equivalent lumped parameters, the experimentally observed faster response of the alloyed device. The model is further used to predict improved responsivity, based on electrode spacing and antireflective coating. We project that increasing the depth of the alloyed contact beyond approximately half of the optical penetration depth will not yield significantly improved responsivity.

  18. Light sources based on semiconductor current filaments

    DOEpatents

    Zutavern, Fred J.; Loubriel, Guillermo M.; Buttram, Malcolm T.; Mar, Alan; Helgeson, Wesley D.; O'Malley, Martin W.; Hjalmarson, Harold P.; Baca, Albert G.; Chow, Weng W.; Vawter, G. Allen

    2003-01-01

    The present invention provides a new type of semiconductor light source that can produce a high peak power output and is not injection, e-beam, or optically pumped. The present invention is capable of producing high quality coherent or incoherent optical emission. The present invention is based on current filaments, unlike conventional semiconductor lasers that are based on p-n junctions. The present invention provides a light source formed by an electron-hole plasma inside a current filament. The electron-hole plasma can be several hundred microns in diameter and several centimeters long. A current filament can be initiated optically or with an e-beam, but can be pumped electrically across a large insulating region. A current filament can be produced in high gain photoconductive semiconductor switches. The light source provided by the present invention has a potentially large volume and therefore a potentially large energy per pulse or peak power available from a single (coherent) semiconductor laser. Like other semiconductor lasers, these light sources will emit radiation at the wavelength near the bandgap energy (for GaAs 875 nm or near infra red). Immediate potential applications of the present invention include high energy, short pulse, compact, low cost lasers and other incoherent light sources.

  19. Conduction properties of metal/organic monolayer/semiconductor heterostructures

    SciTech Connect

    Li, D.; Bishop, A.; Gim, Y.; Shi, X.B.; Fitzsimmons, M.R.; Jia, Q.X.

    1998-11-01

    We have fabricated and characterized rectifying devices made of metal/organic monolayer/semiconductor heterostructures. The devices consist of an organic barrier layer sandwiched between an aluminum (Al) metal contact and a {ital p}-type Si semiconductor. The barrier materials were chosen from three types of self-assembled monolayers (SAMs) with different electronic properties: (1) wide-band gap poly(diallydimethyl ammonium) chloride (PDDA), (2) narrow-band gap PDDA/NiPc (nickel phthalocyanine tetrasulfonate), and (3) donor type PDDA/PPP (poly {ital p}-quaterphenylene-disulfonic-dicarboxylic acid). From current{endash}voltage (I{endash}V) measurements at room temperature, we have found the turn-on voltage of the devices can be tuned by varying the structure, hence electronic properties, of the organic monolayers, and that there exists a power-law dependence of {ital I} on V, I{proportional_to}V{sup {alpha}}, with the exponent {alpha}=2.2 for PDDA, 2.7 for PDDA/NiPc, and 1.44 for PDDA/PPP as the barrier layer, respectively. Our results imply that the transport properties are controlled by both the electronic properties of the SAMs and those of the metal and semiconductor, as indicated by the power-law dependence of the I{endash}V characteristics. {copyright} {ital 1998 American Institute of Physics.}

  20. Metal Oxide Semi-Conductor Gas Sensors in Environmental Monitoring

    PubMed Central

    Fine, George F.; Cavanagh, Leon M.; Afonja, Ayo; Binions, Russell

    2010-01-01

    Metal oxide semiconductor gas sensors are utilised in a variety of different roles and industries. They are relatively inexpensive compared to other sensing technologies, robust, lightweight, long lasting and benefit from high material sensitivity and quick response times. They have been used extensively to measure and monitor trace amounts of environmentally important gases such as carbon monoxide and nitrogen dioxide. In this review the nature of the gas response and how it is fundamentally linked to surface structure is explored. Synthetic routes to metal oxide semiconductor gas sensors are also discussed and related to their affect on surface structure. An overview of important contributions and recent advances are discussed for the use of metal oxide semiconductor sensors for the detection of a variety of gases—CO, NOx, NH3 and the particularly challenging case of CO2. Finally a description of recent advances in work completed at University College London is presented including the use of selective zeolites layers, new perovskite type materials and an innovative chemical vapour deposition approach to film deposition. PMID:22219672

  1. Photoinduced electron transfer from phycoerythrin to colloidal metal semiconductor nanoparticles

    NASA Astrophysics Data System (ADS)

    Kathiravan, A.; Chandramohan, M.; Renganathan, R.; Sekar, S.

    2009-04-01

    Phycoerythrin is a water soluble pigment which absorbs in the visible region at 563 nm. The interaction of phycoerythrin with colloidal metal semiconductors was studied by absorption, FT-IR and fluorescence spectroscopy. Phycoerythrin adsorbed strongly on the surface of TiO 2 nanoparticles, the apparent association constant for the association between colloidal metal-TiO 2 nanoparticles and phycoerythrin was determined from fluorescence quenching data. The free energy change (Δ Get) for electron transfer process has been calculated by applying Rehm-Weller equation.

  2. Scalability of Schottky barrier metal-oxide-semiconductor transistors

    NASA Astrophysics Data System (ADS)

    Jang, Moongyu

    2016-05-01

    In this paper, the general characteristics and the scalability of Schottky barrier metal-oxide-semiconductor field effect transistors (SB-MOSFETs) are introduced and reviewed. The most important factors, i.e., interface-trap density, lifetime and Schottky barrier height of erbium-silicided Schottky diode are estimated using equivalent circuit method. The extracted interface trap density, lifetime and Schottky barrier height for hole are estimated as 1.5 × 1013 traps/cm2, 3.75 ms and 0.76 eV, respectively. The interface traps are efficiently cured by N2 annealing. Based on the diode characteristics, various sizes of erbium-silicided/platinum-silicided n/p-type SB-MOSFETs are manufactured and analyzed. The manufactured SB-MOSFETs show enhanced drain induced barrier lowering (DIBL) characteristics due to the existence of Schottky barrier between source and channel. DIBL and subthreshold swing characteristics are comparable with the ultimate scaling limit of double gate MOSFETs which shows the possible application of SB-MOSFETs in nanoscale regime.

  3. Investigation of Hot Carrier Degradation in Shallow-Trench-Isolation-Based High-Voltage Laterally Diffused Metal-Oxide-Semiconductor Field-Effect Transistors by a Novel Direct Current Current-Voltage Technique

    NASA Astrophysics Data System (ADS)

    He, Yandong; Zhang, Ganggang

    2012-04-01

    Shallow trench isolation (STI) based laterally diffused metal-oxide-semiconductor (LDMOS) devices have become popular with its better tradeoff between breakdown voltage and on-resistance and its compatibility with the standard complementary metal-oxide-semiconductor (CMOS) process. A novel direct current current-voltage (DCIV) technique demonstrated with multiple sharp peak signals is proposed to characterize interface state generation in the channel and in the STI drift regions separately. Degradation of STI-based LDMOS transistors in various hot-carrier stress modes is investigated experimentally by proposed technique. A two-dimensional numerical device simulation is performed to obtain insight into the proposed technique and device degradation characteristics under hot-carrier stress conditions. The impact of interface state location on device electrical characteristics is analyzed from measurement and simulation. Our results show that the maximum Isub stress becomes the worst hot-carrier degradation mode in term of the on-resistance degradation, which is attributed to interface state generation under STI drift region.

  4. Fabrication and characterization of metal-semiconductor-metal nanorod using template synthesis

    SciTech Connect

    Kim, Kyohyeok; Kwon, Namyong; Hong, Junki; Chung, Ilsub

    2009-07-15

    The authors attempted to fabricate and characterize one dimensional metal-semiconductor-metal (MSM) nanorod using a template. Cadmium selenide (CdSe) and polypyrrole (Ppy) were chosen as n-type and p-type semiconductor materials, respectively, whereas Au was chosen as a metal electrode. The fabrication of the nanorod was achieved by ''template synthesis'' method using polycarbonate membrane. The structure of the fabricated nanorod was analyzed using scanning electron microscopy and energy dispersive spectroscopy. In addition, the electrical properties of MSM nanorods were characterized using scanning probe microscopy (Seiko Instruments, SPA 300 HV) by probing with a conductive cantilever. I-V characteristics as a function of the temperature give the activation energy, as well as the barrier height of a metal-semiconductor contact, which is useful to understand the conduction mechanism of MSM nanorods.

  5. P-Channel InGaN/GaN heterostructure metal-oxide-semiconductor field effect transistor based on polarization-induced two-dimensional hole gas

    PubMed Central

    Zhang, Kexiong; Sumiya, Masatomo; Liao, Meiyong; Koide, Yasuo; Sang, Liwen

    2016-01-01

    The concept of p-channel InGaN/GaN heterostructure field effect transistor (FET) using a two-dimensional hole gas (2DHG) induced by polarization effect is demonstrated. The existence of 2DHG near the lower interface of InGaN/GaN heterostructure is verified by theoretical simulation and capacitance-voltage profiling. The metal-oxide-semiconductor FET (MOSFET) with Al2O3 gate dielectric shows a drain-source current density of 0.51 mA/mm at the gate voltage of −2 V and drain bias of −15 V, an ON/OFF ratio of two orders of magnitude and effective hole mobility of 10 cm2/Vs at room temperature. The normal operation of MOSFET without freeze-out at 8 K further proves that the p-channel behavior is originated from the polarization-induced 2DHG. PMID:27021054

  6. Amorphous metallizations for high-temperature semiconductor device applications

    NASA Technical Reports Server (NTRS)

    Wiley, J. D.; Perepezko, J. H.; Nordman, J. E.; Kang-Jin, G.

    1981-01-01

    The initial results of work on a class of semiconductor metallizations which appear to hold promise as primary metallizations and diffusion barriers for high temperature device applications are presented. These metallizations consist of sputter-deposited films of high T sub g amorphous-metal alloys which (primarily because of the absence of grain boundaries) exhibit exceptionally good corrosion-resistance and low diffusion coefficients. Amorphous films of the alloys Ni-Nb, Ni-Mo, W-Si, and Mo-Si were deposited on Si, GaAs, GaP, and various insulating substrates. The films adhere extremely well to the substrates and remain amorphous during thermal cycling to at least 500 C. Rutherford backscattering and Auger electron spectroscopy measurements indicate atomic diffussivities in the 10 to the -19th power sq cm/S range at 450 C.

  7. Growth and characterization of an In0.53Ga0.47As-based Metal-Oxide-Semiconductor Capacitor (MOSCAP) structure on 300 mm on-axis Si (001) wafers by MOCVD

    NASA Astrophysics Data System (ADS)

    Orzali, Tommaso; Vert, Alexey; Kim, Tae-Woo; Hung, P. Y.; Herman, Joshua L.; Vivekanand, Saikumar; Huang, Gensheng; Kelman, Max; Karim, Zia; Hill, Richard J. W.; Rao, Satyavolu S. Papa

    2015-10-01

    We report on the development of a metamorphic In0.53Ga0.47As-based heterostructure grown on 300 mm on-axis Si (001) wafers by metal-organic chemical vapor deposition (MOCVD), and the fabrication of a Metal-Oxide-Semiconductor Capacitor (MOSCAP) with C-V characteristics and interfacial trap density (Dit) values comparable to those of an equivalent structure grown on an InP substrate. A 1.15 μm thick GaAs/InP buffer with a defect density in the low 109 cm-2 range and a surface roughness rms value <2 nm was used to accommodate the large lattice mismatch between In0.53Ga0.47As and Si.

  8. Radiation hardening of metal-oxide semi-conductor (MOS) devices by boron

    NASA Technical Reports Server (NTRS)

    Danchenko, V.

    1974-01-01

    Technique using boron effectively protects metal-oxide semiconductor devices from ionizing radiation without using shielding materials. Boron is introduced into insulating gate oxide layer at semiconductor-insulator interface.

  9. How many electrons make a semiconductor nanocrystal film metallic

    NASA Astrophysics Data System (ADS)

    Reich, Konstantin; Chen, Ting; Kramer, Nicolaas; Fu, Han; Kortshagen, Uwe; Shklovskii, Boris

    For films of semiconductor nanocrystals to achieve their potential as novel, low-cost electronic materials, a better understanding of their doping to tune their conductivity is required. So far, it not known how many dopants will turn a nanocrystal film from semiconducting to metallic. In bulk semiconductors, the critical concentration nM of electrons at the metal-insulator transition is described by the famous Mott criterion: nMaB3 ~= 0 . 02 , where aB is the effective Bohr radius. We show theoretically that in a dense NC film, where NCs touch each other by small facets, the concentration of electrons nc >>nM at the metal-insulator transition satisfies the condition: ncρ3 ~= 0 . 3 , where ρ is a radius of contact facets. In the accompanying experiments, we investigate the conduction mechanism in films of phosphorus-doped, ligand-free silicon nanocrystals. At the largest electron concentration achieved in our samples, which is half the predicted nc, we find that the localization length of hopping electrons is close to three times the nanocrystals diameter, indicating that the film approaches the metal-insulator transition. This work was supported primarily by the National Science Foundation through the University of Minnesota MRSEC under Award No. DMR-1420013.

  10. ``Electric growth`` of metal overlayers on semiconductor substrates

    SciTech Connect

    Zhang, Z.; Cho, J.H. |; Niu, Q.; Shih, C.K.; Suo, Z.

    1998-02-01

    In this article, the authors present the main results from their recent studies of metal overlayer growth on semiconductor substrates. They show that a variety of novel phenomena can exist in such systems, resulting from several competing interactions. The confined motion of the conduction electrons within the metal overlayer can mediate a surprisingly long-range repulsive force between the metal-semiconductor interface and the growth front, acting to stabilize the overlayer. Electron transfer from the overlayer to the substrate leads to an attractive force between the two interfaces, acting to destabilize the overlayer. Interface-induced Friedel oscillations in electron density can further impose an oscillatory modulation onto the two previous interactions. These three competing factors, of all electronic nature, can make a flat metal overlayer critically, marginally, or magically stable, or totally unstable against roughening. The authors further show that, for many systems, these electronic effects can easily win over the effect of stress. First-principles studies of a few representative systems support the main features of the present electronic growth concept.

  11. Defect production and annealing kinetics in elemental metals and semiconductors

    NASA Astrophysics Data System (ADS)

    de la Rubia, T. Diaz; Soneda, N.; Caturla, M. J.; Alonso, E. A.

    1997-11-01

    We present a review of recent results of molecular dynamics (MD) and kinetic Monte Carlo (KMC) simulations of defect production and annealing in irradiated metals and semiconductors. The MD simulations describe the primary damage state in elemental metals Fe, V and Au, and in an elemental semiconductor Si. We describe the production of interstitial and vacancy clusters in the cascades and highlight the differences among the various materials. In particular, we discuss how covalent bonding in Si affects defect production and amorphization resulting in a very different primary damage state from the metals. We also use MD simulations to extract prefactors and activation energies for migration of point defects, as well as to investigate the energetics, geometry and diffusivity of small vacancy and interstitial clusters. We show that, in the metals, small interstitial clusters are highly mobile and glide in one dimension along the direction of the Burger's vector. In silicon, we show that, in contrast to the metals, the neutral vacancy diffuses faster than the neutral self-interstitial. The results for the primary damage state and for the defect energetics and kinetics are then combined and used in a kinetic Monte Carlo simulation to investigate the escape efficiency of defects from their nascent cascade in metals, and the effect of dose rate on damage accumulation and amorphization in silicon. We show that in fee metals Au and Pb at or above stage V the escape probability is approximately 40% for 30 keV recoils so that the freely migrating defect fraction is approximately 10% of the dpa standard. In silicon, we show that damage accumulation at room temperature during light ion implantation can be significantly reduced by decreasing the dose rate. The results are compared to scanning tunneling microscopy experiments.

  12. All-Graphene Planar Self-Switching MISFEDs, Metal-Insulator-Semiconductor Field-Effect Diodes

    PubMed Central

    Al-Dirini, Feras; Hossain, Faruque M.; Nirmalathas, Ampalavanapillai; Skafidas, Efstratios

    2014-01-01

    Graphene normally behaves as a semimetal because it lacks a bandgap, but when it is patterned into nanoribbons a bandgap can be introduced. By varying the width of these nanoribbons this band gap can be tuned from semiconducting to metallic. This property allows metallic and semiconducting regions within a single Graphene monolayer, which can be used in realising two-dimensional (2D) planar Metal-Insulator-Semiconductor field effect devices. Based on this concept, we present a new class of nano-scale planar devices named Graphene Self-Switching MISFEDs (Metal-Insulator-Semiconductor Field-Effect Diodes), in which Graphene is used as the metal and the semiconductor concurrently. The presented devices exhibit excellent current-voltage characteristics while occupying an ultra-small area with sub-10 nm dimensions and an ultimate thinness of a single atom. Quantum mechanical simulation results, based on the Extended Huckel method and Nonequilibrium Green's Function Formalism, show that a Graphene Self-Switching MISFED with a channel as short as 5 nm can achieve forward-to-reverse current rectification ratios exceeding 5000. PMID:24496307

  13. Nonequilibrium carrier dynamics in transition metal dichalcogenide semiconductors

    NASA Astrophysics Data System (ADS)

    Steinhoff, A.; Florian, M.; Rösner, M.; Lorke, M.; Wehling, T. O.; Gies, C.; Jahnke, F.

    2016-09-01

    When exploring new materials for their potential in (opto)electronic device applications, it is important to understand the role of various carrier interaction and scattering processes. In atomically thin transition metal dichalcogenide semiconductors, the Coulomb interaction is known to be much stronger than in quantum wells of conventional semiconductors like GaAs, as witnessed by the 50 times larger exciton binding energy. The question arises, whether this directly translates into equivalently faster carrier–carrier Coulomb scattering of excited carriers. Here we show that a combination of ab initio band-structure and many-body theory predicts Coulomb-mediated carrier relaxation on a sub-100 fs time scale for a wide range of excitation densities, which is less than an order of magnitude faster than in quantum wells.

  14. Rare Earth Metal/semiconductor Interfaces and Compounds

    NASA Astrophysics Data System (ADS)

    Nogami, Jun

    Interfaces formed at room temperature by incremental deposition of rare earth metals onto semiconductor substrates have been studied with surface sensitive soft X-ray photoelectron spectroscopy. The trends in core level lineshape and intensity with increasing metal coverage have been used to deduce an outline of the evolution and the final morphology of the interfacial region on a microscopic scale. Measurements were taken for Ytterbium (Yb) on Silicon (Si), Germanium, and Gallium Arsenide, and for Gadolinium (Gd) and Europium (Eu) on Silicon. The Yb/Si interface work was supported by comparable measurements of bulk Yb silicide samples of known composition and crystal structure. In a general sense, the behavior of all the systems studied is similar. At very low metal coverages, the metal atoms chemisorb and are weakly bonded to the substrate. The 4f core levels indicate that the metal-metal atom coordination is relatively low at this stage. The interaction with the substrate strengthens with increasing coverage, culminating in the formation of a strongly reacted phase at between 1 and 3 monolayers (ML). The strong reaction is limited to a narrow region at room temperature. At less than 10 ML coverage, the surface of the sample is almost indistinguishable from the pure metal. Details of the behavior such as the reactivity at low coverage, the compounds formed at the interface, the morphology at the surface at intermediate coverages, the final interfacial width, and the amount of substrate atom outdiffusion and surface segregation can all vary from system to system. It is in explaining the causes of some of these differences that insight about what governs the behavior of all of these rare earth metal/semiconductor systems has been obtained. The divalent metals (Yb, Eu) are significantly less reactive than trivalent Gd at sub-monolayer coverages. For the divalent metals the formation of a metal-rich phase is strongly favored in the reaction at the interface, whereas

  15. Ultraviolet GaN photodetectors on Si via oxide buffer heterostructures with integrated short period oxide-based distributed Bragg reflectors and leakage suppressing metal-oxide-semiconductor contacts

    SciTech Connect

    Szyszka, A. E-mail: adam.szyszka@pwr.wroc.pl; Haeberlen, M.; Storck, P.; Thapa, S. B.; Schroeder, T.

    2014-08-28

    Based on a novel double step oxide buffer heterostructure approach for GaN integration on Si, we present an optimized Metal-Semiconductor-Metal (MSM)-based Ultraviolet (UV) GaN photodetector system with integrated short-period (oxide/Si) Distributed Bragg Reflector (DBR) and leakage suppressing Metal-Oxide-Semiconductor (MOS) electrode contacts. In terms of structural properties, it is demonstrated by in-situ reflection high energy electron diffraction and transmission electron microscopy-energy dispersive x-ray studies that the DBR heterostructure layers grow with high thickness homogeneity and sharp interface structures sufficient for UV applications; only minor Si diffusion into the Y{sub 2}O{sub 3} films is detected under the applied thermal growth budget. As revealed by comparative high resolution x-ray diffraction studies on GaN/oxide buffer/Si systems with and without DBR systems, the final GaN layer structure quality is not significantly influenced by the growth of the integrated DBR heterostructure. In terms of optoelectronic properties, it is demonstrated that—with respect to the basic GaN/oxide/Si system without DBR—the insertion of (a) the DBR heterostructures and (b) dark current suppressing MOS contacts enhances the photoresponsivity below the GaN band-gap related UV cut-off energy by almost up to two orders of magnitude. Given the in-situ oxide passivation capability of grown GaN surfaces and the one order of magnitude lower number of superlattice layers in case of higher refractive index contrast (oxide/Si) systems with respect to classical III-N DBR superlattices, virtual GaN substrates on Si via functional oxide buffer systems are thus a promising robust approach for future GaN-based UV detector technologies.

  16. Role of direct electron-phonon coupling across metal-semiconductor interfaces in thermal transport via molecular dynamics

    SciTech Connect

    Lin, Keng-Hua; Strachan, Alejandro

    2015-07-21

    Motivated by significant interest in metal-semiconductor and metal-insulator interfaces and superlattices for energy conversion applications, we developed a molecular dynamics-based model that captures the thermal transport role of conduction electrons in metals and heat transport across these types of interface. Key features of our model, denoted eleDID (electronic version of dynamics with implicit degrees of freedom), are the natural description of interfaces and free surfaces and the ability to control the spatial extent of electron-phonon (e-ph) coupling. Non-local e-ph coupling enables the energy of conduction electrons to be transferred directly to the semiconductor/insulator phonons (as opposed to having to first couple to the phonons in the metal). We characterize the effect of the spatial e-ph coupling range on interface resistance by simulating heat transport through a metal-semiconductor interface to mimic the conditions of ultrafast laser heating experiments. Direct energy transfer from the conduction electrons to the semiconductor phonons not only decreases interfacial resistance but also increases the ballistic transport behavior in the semiconductor layer. These results provide new insight for experiments designed to characterize e-ph coupling and thermal transport at the metal-semiconductor/insulator interfaces.

  17. Dual-probe scanning tunneling microscope for study of nanoscale metal-semiconductor interfaces

    NASA Astrophysics Data System (ADS)

    Yi, W.; Kaya, I. I.; Altfeder, I. B.; Appelbaum, I.; Chen, D. M.; Narayanamurti, V.

    2005-06-01

    Using a dual-probe scanning tunneling microscope, we have performed three-terminal ballistic electron emission spectroscopy on Au /GaAs(100) by contacting the patterned metallic thin film with one tip and injecting ballistic electrons with another tip. The collector current spectra agree with a Monte-Carlo simulation based on modified planar tunneling theory. Our results suggest that it is possible to study nanoscale metal-semiconductor interfaces without the requirement of an externally-contacted continuous metal thin film.

  18. Electrostatic analysis of n-doped SrTiO3 metal-insulator-semiconductor systems

    NASA Astrophysics Data System (ADS)

    Kamerbeek, A. M.; Banerjee, T.; Hueting, R. J. E.

    2015-12-01

    Electron doped SrTiO3, a complex-oxide semiconductor, possesses novel electronic properties due to its strong temperature and electric-field dependent permittivity. Due to the high permittivity, metal/n-SrTiO3 systems show reasonably strong rectification even when SrTiO3 is degenerately doped. Our experiments show that the insertion of a sub nanometer layer of AlOx in between the metal and n-SrTiO3 interface leads to a dramatic reduction of the Schottky barrier height (from around 0.90 V to 0.25 V). This reduces the interface resistivity by 4 orders of magnitude. The derived electrostatic analysis of the metal-insulator-semiconductor (n-SrTiO3) system is consistent with this trend. When compared with a Si based MIS system, the change is much larger and mainly governed by the high permittivity of SrTiO3. The non-linear permittivity of n-SrTiO3 leads to unconventional properties such as a temperature dependent surface potential non-existent for semiconductors with linear permittivity such as Si. This allows tuning of the interfacial band alignment, and consequently the Schottky barrier height, in a much more drastic way than in conventional semiconductors.

  19. Analysis of Carbon Nanotube Metal-Semiconductor Diode Device

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Biegel, Bryan (Technical Monitor)

    2002-01-01

    We study recently reported drain current Id-drain voltage Vd characteristics of a carbon nanotube metal semiconductor diode device with the gate voltage Vg applied to modulate the carrier density in the nanotube. The diode was kink-shaped at the metal-semiconductor interface. It was shown that (1) larger negative Vg blocked Id more effectively in the negative Vd region, resulting in the rectifying Id-Vd characteristics, and that (2) positive Vg allowed Id in the both Vd polarities, resulting in the non-rectifying characteristics. The negative Vd was the Schottky reverse direction, judging from the negligible Id behavior for a wide region of -4 V less than Vd less than 0 V, with Vg = -4 V. Such negative Vg would attract positive charges from the metallic electrodes (charge reservoir) to the nanotube and lower the nanotube Fermi energy (EF). With larger negative Vg, the experiment showed that the Schottky forward direction (Vd greater than 0) had a smaller turn-on voltage and the Schottky reverse direction (Vd less than 0) was more resistant to the tunneling breakdown. Therefore, the majority carriers in the transport would be electrons since they can see a lower tunneling barrier (shallower built-in potential) in the forward direction when EF is lowered, and a thicker tunneling barrier (Schottky barrier) in the reverse direction due to the reduction in the electron density when EF is lowered.

  20. Effects of radiation and temperature on gallium nitride (GaN) metal-semiconductor-metal ultraviolet photodetectors

    NASA Astrophysics Data System (ADS)

    Chiamori, Heather C.; Angadi, Chetan; Suria, Ateeq; Shankar, Ashwin; Hou, Minmin; Bhattacharya, Sharmila; Senesky, Debbie G.

    2014-06-01

    The development of radiation-hardened, temperature-tolerant materials, sensors and electronics will enable lightweight space sub-systems (reduced packaging requirements) with increased operation lifetimes in extreme harsh environments such as those encountered during space exploration. Gallium nitride (GaN) is a ceramic, semiconductor material stable within high-radiation, high-temperature and chemically corrosive environments due to its wide bandgap (3.4 eV). These material properties can be leveraged for ultraviolet (UV) wavelength photodetection. In this paper, current results of GaN metal-semiconductor-metal (MSM) UV photodetectors behavior after irradiation up to 50 krad and temperatures of 15°C to 150°C is presented. These initial results indicate that GaN-based sensors can provide robust operation within extreme harsh environments. Future directions for GaN-based photodetector technology for down-hole, automotive and space exploration applications are also discussed.

  1. A Unique Ternary Semiconductor-(Semiconductor/Metal) Nano-Architecture for Efficient Photocatalytic Hydrogen Evolution.

    PubMed

    Zhuang, Tao-Tao; Liu, Yan; Sun, Meng; Jiang, Shen-Long; Zhang, Ming-Wen; Wang, Xin-Chen; Zhang, Qun; Jiang, Jun; Yu, Shu-Hong

    2015-09-21

    It has been a long-standing demand to design hetero-nanostructures for charge-flow steering in semiconductor systems. Multi-component nanocrystals exhibit multifunctional properties or synergistic performance, and are thus attractive materials for energy conversion, medical therapy, and photoelectric catalysis applications. Herein we report the design and synthesis of binary and ternary multi-node sheath hetero-nanorods in a sequential chemical transformation procedure. As verified by first-principles simulations, the conversion from type-I ZnS-CdS heterojunction into type-II ZnS-(CdS/metal) ensures well-steered collections of photo-generated electrons at the exposed ZnS nanorod stem and metal nanoparticles while holes at the CdS node sheaths, leading to substantially improved photocatalytic hydrogen-evolution performance. PMID:26276905

  2. Spinodal nanodecomposition in semiconductors doped with transition metals

    NASA Astrophysics Data System (ADS)

    Dietl, T.; Sato, K.; Fukushima, T.; Bonanni, A.; Jamet, M.; Barski, A.; Kuroda, S.; Tanaka, M.; Hai, Pham Nam; Katayama-Yoshida, H.

    2015-10-01

    This review presents the recent progress in computational materials design, experimental realization, and control methods of spinodal nanodecomposition under three- and two-dimensional crystal-growth conditions in spintronic materials, such as magnetically doped semiconductors. The computational description of nanodecomposition, performed by combining first-principles calculations with kinetic Monte Carlo simulations, is discussed together with extensive electron microscopy, synchrotron radiation, scanning probe, and ion beam methods that have been employed to visualize binodal and spinodal nanodecomposition (chemical phase separation) as well as nanoprecipitation (crystallographic phase separation) in a range of semiconductor compounds with a concentration of transition metal (TM) impurities beyond the solubility limit. The role of growth conditions, codoping by shallow impurities, kinetic barriers, and surface reactions in controlling the aggregation of magnetic cations is highlighted. According to theoretical simulations and experimental results the TM-rich regions appear in the form of either nanodots (the dairiseki phase) or nanocolumns (the konbu phase) buried in the host semiconductor. Particular attention is paid to Mn-doped group III arsenides and antimonides, TM-doped group III nitrides, Mn- and Fe-doped Ge, and Cr-doped group II chalcogenides, in which ferromagnetic features persisting up to above room temperature correlate with the presence of nanodecomposition and account for the application-relevant magneto-optical and magnetotransport properties of these compounds. Finally, it is pointed out that spinodal nanodecomposition can be viewed as a new class of bottom-up approach to nanofabrication.

  3. Thin-film transistors based on organic conjugated semiconductors

    NASA Astrophysics Data System (ADS)

    Garnier, Francis

    1998-02-01

    The use of organic semiconductors as active layers in thin-film transistors has raised in the recent years a large interest, both for the fundamental understanding of the charge transport processes in organic materials, and also for the potential applications of these devices in the new field of flexible electronics. Short conjugated oligomers have been shown to possess much higher field-effect mobilities than their parent conjugated polymers. The origin of such increase in the efficiency of charge transport is mainly attributed to the close-packing and long-range structural organization displayed in thin films of conjugated oligomers. The various routes for controlling this organization are described, which allow to realize liquid crystal-like two-dimensional structures for these semiconductors, whose carrier mobility has now become equivalent to that of amorphous silicon. It is also shown that the effect of conjugation length on carrier mobility is not as critical as previously thought, but the associated increase of the band gap energy effects the efficiency of charge injection at the metal/semiconductor interface. This problem can be answered by realizing a local doping of the semiconductor, which allows the injection of charge to operate through an efficient tunneling mechanism. Organic-based thin-film transistors have now become viable devices.

  4. Broadband terahertz generation using the semiconductor-metal transition in VO2

    NASA Astrophysics Data System (ADS)

    Charipar, Nicholas A.; Kim, Heungsoo; Mathews, Scott A.; Piqué, Alberto

    2016-01-01

    We report the design, fabrication, and characterization of broadband terahertz emitters based on the semiconductor-metal transition in thin film VO2 (vanadium dioxide). With the appropriate geometry, picosecond electrical pulses are generated by illuminating 120 nm thick VO2 with 280 fs pulses from a femtosecond laser. These ultrafast electrical pulses are used to drive a simple dipole antenna, generating broadband terahertz radiation.

  5. Stability of amorphous metal films on semiconductor substrates

    NASA Astrophysics Data System (ADS)

    Perepezko, J. H.; Wiley, J. D.

    In the culmination of work which began in June 1984, goals of this research have been as follows: Investigation of the stability of amorphous alloy films during diffusion and interdiffusion treatments. The atomic transport measurements will be conducted by a combination of RBS and AES techniques as explained in earlier reports. X-ray diffraction and transmission electron microscopy will be used for structural examination. Investigation of the electrical behavior of amorphous metal/semiconductor contacts, including both the interfacial electrical (Schottky barrier and Ohmic) behavior and the stability of the amorphous metallization against current-induced degradation by electromigration. Fundamental studies of the electromigration process itself will be conducted in this broader context. Examination of structural relaxation during post-depression annealing will also take place.

  6. Synthesis and catalytic properties of metal and semiconductor nanoclusters

    SciTech Connect

    Wilcoxon, J.P.; Martino, T.; Klavetter, E.; Sylwester, A.P.

    1993-08-01

    Synthesis of metal or semiconductor nanoclusters in microheterogeneous oil-continuous inverse micelle systems is discussed. We focus on synthesis and catalytic properties of palladium, iron, and iron sulfide nanoclusters. Cluster size-control is achieved by changing the micelle size which is determined by small angle neutron scattering (SANS) and chosen to produce cluster in size range of 1-20 nm. Cluster sizes were determined by either transmission electron microscopy (TEM) or small-angle x-ray scattering (SAXS). Cluster structure was determined by either x-ray or electron diffraction. In the case of Fe nanoclusters the crystal structure depended on the chemical nature of the surfactant micelle used in the synthesis, illustrating the important role of the surfactant during the growth process. Results of in-situ pyrene hydrogenation using size-selected Pd clusters show a significant increase in activity/total surface area as the size decreases. These clusters also proved effective as unsupported catalysts for direct coal hydropyrolysis, even at very low metal concentrations. Synthesis and optical features of a new semiconductor cluster material, FeS{sub 2}, is discussed with regard to its use in photocatalysis. Application of FeS{sub 2} in coal hydrogenolysis reactions has improved yields of short chain hydrocarbons significantly compared to conventional FeS{sub 2} powders.

  7. High-performance GaAs-based metal-oxide-semiconductor heterostructure field-effect transistors with atomic-layer-deposited Al2O3 gate oxide and in situ AlN passivation by metalorganic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Aoki, Takeshi; Fukuhara, Noboru; Osada, Takenori; Sazawa, Hiroyuki; Hata, Masahiko; Inoue, Takayuki

    2014-10-01

    GaAs-based metal-oxide-semiconductor heterostructure field-effect transistors (MOSHFETs) with Al2O3 gate oxide and in situ AlN passivation were investigated. Passivation with AlN improved the quality of the MOS interfaces, leading to good control of the gate. The devices had a sufficiently small subthreshold swing of 84 mV decade-1 in the drain current vs gate voltage curves, as well as negligible frequency dispersions and nearly zero hysteresis in the gate capacitance vs gate voltage curves. A maximum drain current of 630 mA/mm and a peak effective mobility of 6720 cm2 V-1 s-1 at a sheet carrier density of 3 × 1012 cm-2 were achieved.

  8. EDITORIAL: Frontiers in semiconductor-based devices Frontiers in semiconductor-based devices

    NASA Astrophysics Data System (ADS)

    Krishna, Sanjay; Phillips, Jamie; Ghosh, Siddhartha; Ma, Jack; Sabarinanthan, Jayshri; Stiff-Roberts, Adrienne; Xu, Jian; Zhou, Weidong

    2009-12-01

    This special cluster of Journal of Physics D: Applied Physics reports proceedings from the Frontiers in Semiconductor-Based Devices Symposium, held in honor of the 60th birthday of Professor Pallab Bhattacharya by his former doctoral students. The symposium took place at the University of Michigan, Ann Arbor on 6-7 December 2009. Pallab Bhattacharya has served on the faculty of the Electrical Engineering and Computer Science Department at the University of Michigan, Ann Arbor for 25 years. During this time, he has made pioneering contributions to semiconductor epitaxy, characterization of strained heterostructures, self-organized quantum dots, quantum-dot optoelectronic devices, and integrated optoelectronics. Professor Bhattacharya has been recognized for his accomplishments by membership of the National Academy of Engineering, by chaired professorships (Charles M Vest Distinguished University Professor and James R Mellor Professor of Engineering), and by selection as a Fellow of the IEEE, among numerous other honors and awards. Professor Bhattacharya has also made remarkable contributions in education, including authorship of the textbook Semiconductor Optoelectronic Devices (Prentice Hall, 2nd edition) and the production of 60 PhD students (and counting). In fact, this development of critical human resources is one of the biggest impacts of Professor Bhattacharya's career. His guidance and dedication have shaped the varied professional paths of his students, many of whom currently enjoy successful careers in academia, industry, and government around the world. This special cluster acknowledges the importance of Professor Bhattacharya's influence as all of the contributions are from his former doctoral students. The symposium reflects the significant impact of Professor Bhattacharya's research in that the topics span diverse, critical research areas, including: semiconductor lasers and modulators, nanoscale quantum structure-based devices, flexible CMOS-based

  9. Spin-based logic in semiconductors for reconfigurable large-scale circuits

    NASA Astrophysics Data System (ADS)

    Dery, H.; Dalal, P.; Cywiński, Ł.; Sham, L. J.

    2007-05-01

    Research in semiconductor spintronics aims to extend the scope of conventional electronics by using the spin degree of freedom of an electron in addition to its charge. Significant scientific advances in this area have been reported, such as the development of diluted ferromagnetic semiconductors, spin injection into semiconductors from ferromagnetic metals and discoveries of new physical phenomena involving electron spin. Yet no viable means of developing spintronics in semiconductors has been presented. Here we report a theoretical design that is a conceptual step forward-spin accumulation is used as the basis of a semiconductor computer circuit. Although the giant magnetoresistance effect in metals has already been commercially exploited, it does not extend to semiconductor/ferromagnet systems, because the effect is too weak for logic operations. We overcome this obstacle by using spin accumulation rather than spin flow. The basic element in our design is a logic gate that consists of a semiconductor structure with multiple magnetic contacts; this serves to perform fast and reprogrammable logic operations in a noisy, room-temperature environment. We then introduce a method to interconnect a large number of these gates to form a `spin computer'. As the shrinking of conventional complementary metal-oxide-semiconductor (CMOS) transistors reaches its intrinsic limit, greater computational capability will mean an increase in both circuit area and power dissipation. Our spin-based approach may provide wide margins for further scaling and also greater computational capability per gate.

  10. A model for the C-V characteristics of the metal-ferroelectric-insulator-semiconductor structure

    NASA Astrophysics Data System (ADS)

    Zhang, Jun Jie; Sun, Jing; Zheng, Xue Jun

    2009-02-01

    A model is developed to describe the characteristics of the metal-ferroelectric-insulator-semiconductor (MFIS) structure based on the dipole switching theory (DST) and the silicon physics of metal-oxide-semiconductor (MOS) structure. The ferroelectric dipole distribution function is used to simulate the history-dependent electric field effect of the ferroelectric layer. Using the model, the thickness effects of the ferroelectric and insulator layers on the capacitance-voltage ( C-V) characteristic and the memory window were investigated for Pt/SBT/ZrO 2/Si and Pt/BLT/MgO/Si structures. All the simulation results show good agreement with the experimental results, indicating that the model is suitable for simulating the C-V characteristic and the memory window of MFIS structure. In addition, the mathematical description is simple and can be easily integrated into the electronic design automation (EDA) software for circuit simulation.

  11. Analysis of Carbon Nanotube Metal-Semiconductor Diode Device

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Biegel, Bryan (Technical Monitor)

    2001-01-01

    We study recently reported drain current I(sub d)-drain voltage V(sub d) characteristics of a carbon nanotube metal-semiconductor diode device with the gate voltage V(sub g) applied to modulate the carrier density in the nanotube. The diode was kink-shaped at the metal-semiconductor interface. It was shown that (1) larger negative V(sub g) blocked I(sub d) more effectively in the negative V(sub d) region, resulting in the rectifying I(sub d)-V(sub d) characteristics, and that (2) positive V(sub g) allowed I(sub d) in the both V(sub d) polarities, resulting in the non-rectifying characteristics. The negative V(sub d) was the Schottky reverse direction, judging from the negligible I(sub d) behavior for a wide region of -4 V (is less than) V(sub d) (is less than) 0 V, with V(sub g) = -4 V. Such negative V(sub g) would attract positive charges from the metallic electrodes (charge reservoir) to the nanotube and lower the nanotube Fermi energy (E(sub F)). With larger negative V(sub g), the experiment showed that the Schottky forward direction (V(sub d) (is greater than) 0) had a smaller turn-on voltage and the Schottky reverse direction (V(sub d) (is less than) 0) was more resistant to the tunneling breakdown. Therefore, the majority carriers in the transport would be electrons since they can see a lower tunneling barrier (shallower built-in potential) in the forward direction when E(sub F) is lowered, and a thicker tunneling barrier (Schottky barrier) in the reverse direction due to the reduction in the electron density when E(sub F) is lowered.

  12. Generalized Electron Counting in Determination of Metal-Induced Reconstruction of Compound Semiconductor Surfaces

    SciTech Connect

    Zhang, Lixin; Wang, E. G.; Xue, Qi-Kun; Zhang, S. B.; Zhang, Zhenyu

    2006-01-01

    Based on theoretical analysis, first-principles calculations, and experimental observations, we establish a generic guiding principle, embodied in generalized electron counting (GEC), that governs the surface reconstruction of compound semiconductors induced by different metal adsorbates. Within the GEC model, the adsorbates serve as an electron bath, donating or accepting the right number of electrons as the host surface chooses a specific reconstruction that obeys the classic electron-counting model. The predictive power of the GEC model is illustrated for a wide range of metal adsorbates.

  13. Progress in ion torrent semiconductor chip based sequencing.

    PubMed

    Merriman, Barry; Rothberg, Jonathan M

    2012-12-01

    In order for next-generation sequencing to become widely used as a diagnostic in the healthcare industry, sequencing instrumentation will need to be mass produced with a high degree of quality and economy. One way to achieve this is to recast DNA sequencing in a format that fully leverages the manufacturing base created for computer chips, complementary metal-oxide semiconductor chip fabrication, which is the current pinnacle of large scale, high quality, low-cost manufacturing of high technology. To achieve this, ideally the entire sensory apparatus of the sequencer would be embodied in a standard semiconductor chip, manufactured in the same fab facilities used for logic and memory chips. Recently, such a sequencing chip, and the associated sequencing platform, has been developed and commercialized by Ion Torrent, a division of Life Technologies, Inc. Here we provide an overview of this semiconductor chip based sequencing technology, and summarize the progress made since its commercial introduction. We described in detail the progress in chip scaling, sequencing throughput, read length, and accuracy. We also summarize the enhancements in the associated platform, including sample preparation, data processing, and engagement of the broader development community through open source and crowdsourcing initiatives. PMID:23208921

  14. Quantifying coherent and incoherent cathodoluminescence in semiconductors and metals

    SciTech Connect

    Brenny, B. J. M.; Coenen, T.; Polman, A.

    2014-06-28

    We present a method to separate coherent and incoherent contributions to cathodoluminescence from bulk materials by using angle-resolved cathodoluminescence spectroscopy. Using 5 and 30 keV electrons, we measure the cathodoluminescence spectra for Si, GaAs, Al, Ag, Au, and Cu and determine the angular emission distributions for Al, GaAs, and Si. Aluminium shows a clear dipolar radiation profile due to coherent transition radiation, while GaAs shows incoherent luminescence characterized by a Lambertian angular distribution. Silicon shows both transition radiation and incoherent radiation. From the angular data, we determine the ratio between the two processes and decompose their spectra. This method provides a powerful way to separate different radiative cathodoluminescence processes, which is useful for material characterization and in studies of electron- and light-matter interaction in metals and semiconductors.

  15. Nonlinear optical properties of metal and semiconductor nanoparticles

    NASA Astrophysics Data System (ADS)

    Whelan, Aine M.; Benrezzak, Sakina; Brennan, Margaret E.; Kelly, John M.; Blau, Werner J.

    2003-03-01

    The synthesis of metal (Au,Ag) and semiconductor (PbS) nanoparticles of specific morphology and shape is reported. The shape of PbS nanoparticles has been varied from spherical to oval to cubic, by use of poly(vinyl alcohol) (PVA), DNA and ethylene glycol as stabilisers respectively. For the first time, a seeding method has been used to successfully prepare PVA stabilised gold and silver nanoparticles. Characterisation of the third order optical nonlinearity of the nanoparticles has been carried out using the Z-scan technique with values of Im ÷ (3) as large as 10-10. Modulation of the magnitude of the nonlinear optical response with morphology in the case of the PbS nanoparticles is presented.

  16. Tunnel based spin injection devices for semiconductor spintronics

    NASA Astrophysics Data System (ADS)

    Jiang, Xin

    This dissertation summarizes the work on spin-dependent electron transport and spin injection in tunnel based spintronic devices. In particular, it focuses on a novel three terminal hot electron device combining ferromagnetic metals and semiconductors---the magnetic tunnel transistor (MTT). The MTT has extremely high magnetic field sensitivity and is a useful tool to explore spin-dependent electron transport in metals, semiconductors, and at their interfaces over a wide energy range. In Chap. 1, the basic concept and fabrication of the MTT are discussed. Two types of MTTs, with ferromagnetic single and spin-valve base layers, respectively, are introduced and compared. In the following chapters, the transport properties of the MTT are discussed in detail, including the spin-dependent hot electron attenuation lengths in CoFe and NiFe thin films on GaAs (Chap. 2), the bias voltage dependence of the magneto-current (Chap. 3), the giant magneto-current effect in MTTs with a spin-valve base (Chap. 4), and the influence of non-magnetic seed layers on magneto-electronic properties of MTTs with a Si collector (Chap. 5). Chap. 6 concentrates on electrical injection of spin-polarized electrons into semiconductors, which is an essential ingredient in semiconductor spintronics. Two types of spin injectors are discussed: an MTT injector and a CoFe/MgO tunnel injector. The spin polarization of the injected electron current is detected optically by measuring the circular polarization of electroluminescence from a quantum well light emitting diode. Using an MTT injector a spin polarization of ˜10% is found for injection electron energy of ˜2 eV at 1.4K. This moderate spin polarization is most likely limited by significant electron spin relaxation at high energy. Much higher spin injection efficiency is obtained by using a CoFe/MgO tunnel injector with spin polarization values of ˜50% at 100K. The temperature and bias dependence of the electroluminescence polarization provides

  17. Semiconductor nanocrystal-based phagokinetic tracking

    DOEpatents

    Alivisatos, A Paul; Larabell, Carolyn A; Parak, Wolfgang J; Le Gros, Mark; Boudreau, Rosanne

    2014-11-18

    Methods for determining metabolic properties of living cells through the uptake of semiconductor nanocrystals by cells. Generally the methods require a layer of neutral or hydrophilic semiconductor nanocrystals and a layer of cells seeded onto a culture surface and changes in the layer of semiconductor nanocrystals are detected. The observed changes made to the layer of semiconductor nanocrystals can be correlated to such metabolic properties as metastatic potential, cell motility or migration.

  18. High-speed, efficient metal - semiconductor - metal photodetectors

    SciTech Connect

    Collin, St; Pardo, F; Bardou, N; Pelouard, J.-L.; Averin, S V

    2010-08-03

    Design principles and the fabrication technique of highly efficient, high-speed photodetectors based on MSM nanostructures are developed. To efficiently confine light in the region of the strong field as well as to decrease light losses due to reflection from the diode contacts, use is made of a nanoscale interdigital diffraction grating and a multilayer Bragg grating. Measurements of the reflection coefficients and the quantum efficiency for a multilayer structure are in good agreement with theoretical estimates. A record-high quantum efficiency (QE = 46 %) is obtained for high speed MSM photodetectors. The detector has a high spectral selectivity ({Delta}{lambda}{sub 1/2} = 17 nm) at a wavelength of 800 nm. Taking into account the diode capacitance and the drift time of photogenerated carriers, the performance of the detectors under study is {approx} 500 GHz. The low level of the dark current density in the structures under study (j={sup 1} pA {mu}m{sup -2}) makes it possible to realise on their basis highly sensitive, high-speed selective detectors of optical radiation.

  19. Characterization of silicon carbide metal oxide semiconductor capacitors

    NASA Astrophysics Data System (ADS)

    Marinella, Matthew J.

    Only a few years after the invention of the transistor, William Shockley considered silicon carbide (SiC) an excellent material for high temperature semiconductor devices. Over a half century later, SiC technology is nearly mature enough that it may be considered for use in commercial electronic devices. Furthermore, since SiC has the ability to grow thermal silicon dioxide, significant research has been directed toward the creation of a commercial SiC metal oxide semiconductor field effect transistor (MOSFET). However, a number of significant hurdles still must be overcome before SiC devices can become commercially competitive, including the relatively high cost and low quality of materials. Another significant problem is the lack of understanding of factors which limit the minority carrier lifetime. The primary purpose of this work was to use the pulsed metal oxide semiconductor capacitor (MOS-C) technique to measure generation lifetime in SiC materials. It was found that many nonidealities corrupt the results obtained by this technique. One very interesting nonideality was negative bias temperature instability (NBTI), which has also been widely studied by the silicon industry in recent years. Methods to understand and minimize the effect of these nonidealities were developed. Furthermore, these methods allowed for further study of the oxide properties, such as leakage current. Even after accounting for nonidealities, generation lifetimes showed several peculiarities, such as a variation of as much as a factor of 1000 within a square cm area. In addition, the ratio of generation to recombination lifetime is less than unity, which is not predicted by classic theory, nor typically observed in silicon devices. Possible explanations are put forth to explain these observations. In addition, to further investigate these abnormalities, Schottky diodes were fabricated and characterized. When applied to the SiC MOS capacitor, the pulsed MOS-C technique involves

  20. Coaxial metal-oxide-semiconductor (MOS) Au/Ga2O3/GaN nanowires.

    PubMed

    Hsieh, Chin-Hua; Chang, Mu-Tung; Chien, Yu-Jen; Chou, Li-Jen; Chen, Lih-Juann; Chen, Chii-Dong

    2008-10-01

    Coaxial metal-oxide-semiconductor (MOS) Au-Ga2O3-GaN heterostructure nanowires were successfully fabricated by an in situ two-step process. The Au-Ga2O3 core-shell nanowires were first synthesized by the reaction of Ga powder, a mediated Au thin layer, and a SiO2 substrate at 800 degrees C. Subsequently, these core-shell nanowires were nitridized in ambient ammonia to form a GaN coating layer at 600 degrees C. The GaN shell is a single crystal, an atomic flat interface between the oxide and semiconductor that ensures that the high quality of the MOS device is achieved. These novel 1D nitride-based MOS nanowires may have promise as building blocks to the future nitride-based vertical nanodevices. PMID:18778107

  1. Hybrid Integration of Graphene Analog and Silicon Complementary Metal-Oxide-Semiconductor Digital Circuits.

    PubMed

    Hong, Seul Ki; Kim, Choong Sun; Hwang, Wan Sik; Cho, Byung Jin

    2016-07-26

    We demonstrate a hybrid integration of a graphene-based analog circuit and a silicon-based digital circuit in order to exploit the strengths of both graphene and silicon devices. This mixed signal circuit integration was achieved using a three-dimensional (3-D) integration technique where a graphene FET multimode phase shifter is fabricated on top of a silicon complementary metal-oxide-semiconductor field-effect transistor (CMOS FET) ring oscillator. The process integration scheme presented here is compatible with the conventional silicon CMOS process, and thus the graphene circuit can successfully be integrated on current semiconductor technology platforms for various applications. This 3-D integration technique allows us to take advantage of graphene's excellent inherent properties and the maturity of current silicon CMOS technology for future electronics. PMID:27403730

  2. Photocatalytic Reactive Oxygen Species Formation by Semiconductor-Metal Hybrid Nanoparticles. Toward Light-Induced Modulation of Biological Processes.

    PubMed

    Waiskopf, Nir; Ben-Shahar, Yuval; Galchenko, Michael; Carmel, Inbal; Moshitzky, Gilli; Soreq, Hermona; Banin, Uri

    2016-07-13

    Semiconductor-metal hybrid nanoparticles manifest efficient light-induced spatial charge separation at the semiconductor-metal interface, as demonstrated by their use for hydrogen generation via water splitting. Here, we pioneer a study of their functionality as efficient photocatalysts for the formation of reactive oxygen species. We observed enhanced photocatalytic activity forming hydrogen peroxide, superoxide, and hydroxyl radicals upon light excitation, which was significantly larger than that of the semiconductor nanocrystals, attributed to the charge separation and the catalytic function of the metal tip. We used this photocatalytic functionality for modulating the enzymatic activity of horseradish peroxidase as a model system, demonstrating the potential use of hybrid nanoparticles as active agents for controlling biological processes through illumination. The capability to produce reactive oxygen species by illumination on-demand enhances the available peroxidase-based tools for research and opens the path for studying biological processes at high spatiotemporal resolution, laying the foundation for developing novel therapeutic approaches. PMID:27224678

  3. Plasmonically-enhanced mid-infrared photoluminescence in a metal/narrow-gap semiconductor structure

    NASA Astrophysics Data System (ADS)

    Lu, Pengqi; Cai, Chunfeng; Zhang, Bingpo; Liu, Bozhi; Wu, Huizhen; Bi, Gang; Si, Jianxiao

    2016-05-01

    We report the enhancement of the mid-infrared (MIR) luminescence intensity in a nanoscale metal/semiconductor structure by the coupling of surface plasmon polaritons (SPPs) with excitons in a narrow-gap semiconductor. The SPPs are efficiently excited by the total internal reflection photons at a metal/semiconductor interface. The intense electric field induced by SPPs, in turn, greatly changes the radiative recombination rates of the excitons generated by the pumping laser and thus the MIR luminescence intensity. The finding avails the understanding of fundamental science of SPs in narrow-gap semiconductors and the development of novel MIR devices.

  4. Electrode dependent interfacial layer variation in metal-oxide-semiconductor capacitor

    NASA Astrophysics Data System (ADS)

    Park, I.-S.; Jung, Y. C.; Lee, M.; Seong, S.; Ahn, J.

    2014-03-01

    The interfacial layer between oxide and semiconductor in metal-oxide-semiconductor (MOS) capacitors depends on the metal electrode material. The metal/HfO2/Si and metal/HfO2/Ge capacitor were made using an atomic layer deposited HfO2 dielectric films and Mo, Ru, and Pt electrodes above Si substrate and Ti, Ru, and Pt electrodes above Ge substrate. The measured saturation capacitance was varied with electrode and evaluated to capacitance equivalent thickness (CET). In Si-based MOS capacitor, the CET value of the capacitor with Pt electrode is larger than those with Mo and Ru electrode. In addition, the CET is 27.4 A, 38.2 A, and 30.8 A for Ti, Ru, and Pt electrode, respectively, for Ge-based MOS capacitors. The CET variation with electrode is attributed the variation of dielectric constant of HfO2 dielectric and the difference of interfacial layer. The CET variation is well in agreement with the interfacial layer thickness taken by a transmission electron microscopy. The thickness variation of interfacial layer results from the oxygen gettering ability of the electrode even though they are apart.

  5. Multiple percolation tunneling staircase in metal-semiconductor nanoparticle composites

    SciTech Connect

    Mukherjee, Rupam; Huang, Zhi-Feng; Nadgorny, Boris

    2014-10-27

    Multiple percolation transitions are observed in a binary system of RuO{sub 2}-CaCu{sub 3}Ti{sub 4}O{sub 12} metal-semiconductor nanoparticle composites near percolation thresholds. Apart from a classical percolation transition, associated with the appearance of a continuous conductance path through RuO{sub 2} metal oxide nanoparticles, at least two additional tunneling percolation transitions are detected in this composite system. Such behavior is consistent with the recently emerged picture of a quantum conductivity staircase, which predicts several percolation tunneling thresholds in a system with a hierarchy of local tunneling conductance, due to various degrees of proximity of adjacent conducting particles distributed in an insulating matrix. Here, we investigate a different type of percolation tunneling staircase, associated with a more complex conductive and insulating particle microstructure of two types of non-spherical constituents. As tunneling is strongly temperature dependent, we use variable temperature measurements to emphasize the hierarchical nature of consecutive tunneling transitions. The critical exponents corresponding to specific tunneling percolation thresholds are found to be nonuniversal and temperature dependent.

  6. Simulation of Submicronmeter Metal-Semiconductor-Metal Ultraviolet Photodiodes no Gallium Nitride

    SciTech Connect

    Li, J.; Donaldson, W.R.; Hsiang, T.Y.

    2004-09-15

    Ultrafast metal Semiconductor metal ultraviolet photodetectors on GaN with 0.3-mm finger width and spacing were fabricated and packaged with a specially designed fast circuit. The assembly was simulated using a distributed circuit approach with optical illumination at l = 270 nm. This is the first theoretical simulation report of this effect in ultrafast ultraviolet photodetectors on GaN. Comparison of simulations and measurements was made in a wide range of optical energies, and a close agreement was achieved with a single energy-scaling factor.

  7. Unusual nonlinear current-voltage characteristics of a metal-intrinsic semiconductor-metal barrierless structure

    NASA Astrophysics Data System (ADS)

    Meriuts, A. V.; Gurevich, Yu. G.

    2015-03-01

    A nonlinear model for the electric current in a metal-intrinsic semiconductor-metal structure without potential barriers in contacts is considered using a drift diffusion approach. An analytical solution of the continuity equations and the current-voltage characteristic for various recombination rates in the contacts are obtained. It is shown that the current-voltage characteristics of such a structure exhibit not only linear behavior, corresponding to Ohm's law, but may also possess properties of current-voltage characteristics of the rectifier diode. It is also possible current-voltage characteristics with saturation in both forward and backward directions. Physical model that explains the obtained results is proposed.

  8. Analysis of aluminum nano-gratings assisted light reflection reduction in GaAs metal-semiconductor-metal photodetectors

    NASA Astrophysics Data System (ADS)

    Fan, Zhenzhu; Su, Yahui; Zhang, Huayong; Han, Xiaohu; Ren, Feifei

    2015-09-01

    Plasmonics-based GaAs metal-semiconductor-metal photodetector (MSM-PD) with aluminum nano-gratings was proposed. A detailed numerical study of subwavelength nanogratings behavior to reduce the light reflection is performed by finite-difference time domain (FDTD) algorithm. The geometric parameters of nano-gratings, such as aperture width, the nano-gratings height, the duty cycles are optimized for subwavelength metal nanogratings on GaAs substrate and their impact on light reflection below the conventional MSM-PD is confirmed. Simulation results show that a light reflection factor around 15% can be obtained near the wavelength of 900 nm with optimized MSM-PDs, and in visible light spectrum, the Al nano-gratings show better performance than Au nano-gratings.

  9. Electrical properties of hybrid (ferromagnetic metal)-(layered semiconductor) Ni/p-GaSe structures

    SciTech Connect

    Bakhtinov, A. P. Vodopyanov, V. N.; Kovalyuk, Z. D.; Netyaga, V. V.; Lytvyn, O. S.

    2010-02-15

    Two-barrier Ni/n-Ga2Se3/p-GaSe structures with nanoscale Ni-alloy grains caused by reactions at the 'metal-layered semiconductor' interface were formed after growing Ni layers on the p-GaSe (0001) surface. Current-voltage and capacitance-voltage characteristics of hybrid structures were studied in the temperature range of 220-350 K. The dependence of the impedance spectra on the bias voltage was studied at various temperatures. The frequency dependences of the impedance at high frequencies (f = 10{sup 6} Hz) are discussed in terms of the phenomena of spin injection and extraction in structures with an ultrathin spin-selective Ni/n-Ga{sub 2}Se{sub 3} barrier and the effects of spin diffusion and relaxation in the semiconductor substrate. The room-temperature phenomena of the Coulomb blockade and negative differential capacitance were detected. These phenomena are explained based on an analysis of transport processes in a narrow region near the 'ferromagnetic metal-semiconductor' interface, where nanoscale grains are arranged.

  10. Semiconductor-Nanowire-Based Superconducting Qubit.

    PubMed

    Larsen, T W; Petersson, K D; Kuemmeth, F; Jespersen, T S; Krogstrup, P; Nygård, J; Marcus, C M

    2015-09-18

    We introduce a hybrid qubit based on a semiconductor nanowire with an epitaxially grown superconductor layer. Josephson energy of the transmonlike device ("gatemon") is controlled by an electrostatic gate that depletes carriers in a semiconducting weak link region. Strong coupling to an on-chip microwave cavity and coherent qubit control via gate voltage pulses is demonstrated, yielding reasonably long relaxation times (~0.8 μs) and dephasing times (~1 μs), exceeding gate operation times by 2 orders of magnitude, in these first-generation devices. Because qubit control relies on voltages rather than fluxes, dissipation in resistive control lines is reduced, screening reduces cross talk, and the absence of flux control allows operation in a magnetic field, relevant for topological quantum information. PMID:26431009

  11. Optical switches based on semiconductor optical amplifiers

    NASA Astrophysics Data System (ADS)

    Kalman, Robert F.; Dias, Antonio R.; Chau, Kelvin K.; Goodman, Joseph W.

    1991-12-01

    Fiber-optic switching systems typically exhibit large losses associated with splitting and combining of the optical power, and with excess component losses. These losses increase quickly with switch size. To obtain acceptable signal-to-noise performance through large optical switching, optical amplifiers can be used. In applications requiring optical switching, semiconductor optical amplifiers (SOAs) are preferred over erbium-doped fiber amplifiers due to their fast switching speeds and the possibility of their integration in monolithic structures with passive waveguides and electronics. We present a general analysis of optical switching systems utilizing SOAs. These systems, in which the gain provided by SOAs is distributed throughout the optical system, are referred to as distributed optical gain (DOG) systems. Our model predicts the performance and achievable sizes of switches based on the matrix-vector multiplier crossbar and Benes network. It is found that for realistic SOA parameters optical switches accommodating extremely large numbers of nodes are, in principle, achievable.

  12. Adjustable metal-semiconductor transition of FeS thin films by thermal annealing

    SciTech Connect

    Fu Ganhua; Polity, Angelika; Volbers, Niklas; Meyer, Bruno K.; Mogwitz, Boris; Janek, Juergen

    2006-12-25

    FeS polycrystalline thin films were prepared on float glass at 500 deg. C by radio-frequency reactive sputtering. The influence of vacuum annealing on the metal-semiconductor transition of FeS films was investigated. It has been found that with the increase of the annealing temperature from 360 to 600 deg. C, the metal-semiconductor transition temperature of FeS films first decreases and then increases, associated with first a reduction and then an enhancement of hysteresis width. The thermal stress is considered to give rise to the abnormal change of the metal-semiconductor transition of the FeS film during annealing.

  13. Electrical properties of GaN-based metal-insulator-semiconductor structures with Al2O3 deposited by atomic layer deposition using water and ozone as the oxygen precursors

    NASA Astrophysics Data System (ADS)

    Kubo, Toshiharu; Freedsman, Joseph J.; Iwata, Yasuhiro; Egawa, Takashi

    2014-04-01

    Al2O3 deposited by atomic layer deposition (ALD) was used as an insulator in metal-insulator-semiconductor (MIS) structures for GaN-based MIS-devices. As the oxygen precursors for the ALD process, water (H2O), ozone (O3), and both H2O and O3 were used. The chemical characteristics of the ALD-Al2O3 surfaces were investigated by x-ray photoelectron spectroscopy. After fabrication of MIS-diodes and MIS-high-electron-mobility transistors (MIS-HEMTs) with the ALD-Al2O3, their electrical properties were evaluated by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The threshold voltage of the C-V curves for MIS-diodes indicated that the fixed charge in the Al2O3 layer is decreased when using both H2O and O3 as the oxygen precursors. Furthermore, MIS-HEMTs with the H2O + O3-based Al2O3 showed good dc I-V characteristics without post-deposition annealing of the ALD-Al2O3, and the drain leakage current in the off-state region was suppressed by seven orders of magnitude.

  14. Surface enhanced Raman spectroscopic studies of the metal-semiconductor interface in organic field effect transistors

    NASA Astrophysics Data System (ADS)

    Adil, Danish; Guha, Suchi

    2012-02-01

    The performance of organic field-effect transistors (FETs) largely depends on the nature of interfaces of dissimilar materials. Metal-semiconductor interfaces, in particular, play a critical role in the charge injection process. Here, Raman spectroscopy is used to investigate the nature of the Au-semiconductor interface in pentacene based FETs. A large enhancement in the Raman intensity (SERS) is observed from the pentacene film under the Au layer. The enhancement is evidence of a nano-scale roughness in the morphology of the interface, which is further confirmed by electron microscopy images. The morphology of the interface is investigated by SERS as a function of the pentacene layer thickness and the Au layer thickness. The Raman spectra are found to be extremely sensitive in detecting small changes in the morphology of the interface in the sub-nanometer range. Changes in the Raman spectra are further tracked after biasing and ageing the devices. Evolution of these Raman spectra is correlated with degradation in device performance. Finally, FETs based on other donor-acceptor semiconductors are probed by Raman scattering and contrasted with those of the pentacene-based devices.

  15. Factors for the polarization lifetime in metal-ferroelectric-insulator-semiconductor capacitors

    NASA Astrophysics Data System (ADS)

    Xiao, Y. G.; Xiong, Y.; Tang, M. H.; Li, J. C.; Gu, X. C.; Cheng, C. P.; Jiang, B.; Tang, Z. H.; Lv, X. S.; Cai, H. Q.; He, J.

    2012-07-01

    Depolarization field in metal-ferroelectric-insulator-semiconductor (MFIS) capacitors with a ferroelectric-electrode interface layer was derived theoretically in this work. The polarization relaxation characteristics were investigated in details based on Lou's polarization retention model. It is found that the retention time of ferroelectric field-effect transistors (FETs) can be affected significantly by the dielectric constant and the thickness of ferroelectric thin film, and by the interface layer thickness. The results may provide some insights into the design and the retention property improvement of MFIS-FET as nonvolatile memory.

  16. Metal-oxide-semiconductor field effect transistor humidity sensor using surface conductance

    NASA Astrophysics Data System (ADS)

    Song, Seok-Ho; Yang, Hyun-Ho; Han, Chang-Hoon; Ko, Seung-Deok; Lee, Seok-Hee; Yoon, Jun-Bo

    2012-03-01

    This letter presents a metal-oxide-semiconductor field effect transistor based humidity sensor which does not use any specific materials to sense the relative humidity. We simply make use of the low pressure chemical vapor deposited (LPCVD) silicon dioxide's surface conductance change. When the gate is biased and then floated, the electrical charge in the gate is dissipated through the LPCVD silicon dioxide's surface to the surrounding ground with a time constant depending on the surface conductance which, in turn, varies with humidity. With this method, extremely high sensitivity was achieved—the charge dissipation speed increased thousand times as the relative humidity increased.

  17. Defect-induced semiconductor to metal transition in graphene monoxide.

    PubMed

    Woo, Jungwook; Yun, Kyung-Han; Cho, Sung Beom; Chung, Yong-Chae

    2014-07-14

    This study investigates the influence of point defects on the geometric and electronic structure of graphene monoxide (GMO) via density functional theory calculations. In aspects of defect formation energy, GMOs with oxygen vacancies and bridge interstitial defects are more likely to form when compared to GMOs with defects such as carbon vacancies and hollow interstitial defects. It was also found that the oxygen vacancy or the hollow interstitial defect induces local tensile strain around the defective site and this strain increases the band gap energy of the defective GMO. In addition, the band gaps of GMO with carbon vacancies or bridge interstitial defects decreased mainly due to the dangling bonds, not due to the strain effect. It is noted that the dangling bond derived from the defects forms the defect-level in the band gap of GMO. The semiconductor to metal transition by the band gap change (0-0.7 eV) implies the possibility for band gap engineering of GMO by vacancies and interstitial defects. PMID:24886723

  18. Molecular Dynamics Modeling of Heat Transport in Metals and Semiconductors

    SciTech Connect

    Narumanchi, S.; Kim, K.

    2010-01-01

    Interfacial thermal transport is of great importance in a number of practical applications where interfacial resistance between layers is frequently a major bottleneck to effective heat dissipation. For example, efficient heat transfer at silicon/aluminum and silicon/copper interfaces is very critical in power electronics packages used in hybrid electric vehicle applications. It is therefore important to understand the factors that govern and impact thermal transport at semiconductor/metal interfaces. Hence, in this study, we use classical molecular dynamics modeling to understand and study thermal transport in silicon and aluminum, and some preliminary modeling to study thermal transport at the interface between silicon and aluminum. A good match is shown between our modeling results for thermal conductivity in silicon and aluminum and the experimental data. The modeling results from this study also match well with relevant numerical studies in the literature for thermal conductivity. In addition, preliminary modeling results indicate that the interfacial thermal conductance for a perfect silicon/aluminum interface is of the same order as experimental data in the literature as well as diffuse mismatch model results accounting for realistic phonon dispersion curves.

  19. Growth and characterization of metal/semiconductor superlattices

    NASA Astrophysics Data System (ADS)

    Henz, J.; Ospelt, M.; Von Känel, H.

    1989-04-01

    Thanks to recent advances in the growth of CoSi 2-layers on Si(111) it has become possible for the first time to fabricate metal/semiconductor superlattices. This is achieved by a combination of solid phase epitaxy (SPE) and molecular beam epitaxy (MBE). We briefly explain the growth of thin ( < 100 Å) type B oriented (i.e. rotated by 180° with respect to the substrate) CoSi 2 layers. We show the effect of the two different surface structures of CoSi 2 on the morphology of the films. Silicon with a reasonable crystal quality can be grown on top of CoSi 2 by using low substrate temperatures for the first few monolayers of growth. We always find the orientation of Si to be the same as the one of the underlying suicide, when the latter is of high quality. Superlattices of CoSi 2 and Si have two periods, one being given by the different materials and the other by the alternating crystal orientations. We show some TEM cross section images as well as first X-ray investigations of these structures.

  20. Nanostructured target fabrication with metal and semiconductor nanoparticles

    NASA Astrophysics Data System (ADS)

    Barberio, M.; Antici, P.

    2015-10-01

    The development of ultra-intense high-energy (≫1 J) short (<1 ps) laser pulses in the last decade has enabled the acceleration of high-energy short-pulse proton beams. A key parameter for enhancing the acceleration regime is the laser-to-target absorption, which heavily depends on the target structure and material. In this work, we present the realization of a nanostructured target with a sub-laser wavelength nano-layer in the front surface as a possible candidate for improving the absorption. The nanostructured film was realized by a simpler and cheaper method than using conventional lithographic techniques: A colloidal solution of metallic or semiconductor nanoparticles (NPs) was produced by laser ablation and, after a heating and sonication process, was spray-dried on the front surface of an aluminum target. The obtained nanostructured film with a thickness of 1 μm appears, at morphological and chemical analysis, uniformly nanostructured and distributed on the target surface without the presence of oxides or external contaminants. Finally, the size of the NPs can be tuned from tens to hundreds of nanometers simply by varying the growth parameters (i.e., irradiation time, fluence, and laser beam energy).

  1. Fabrication of Metal-Semiconductor Heterostructures in Silicon Nanowires

    NASA Astrophysics Data System (ADS)

    Yang, Luyun

    The increasing demand for fossil fuels and the need to reduce greenhouse gases require clean energy sources and more efficient utilization of energy. Thermoelectric materials provide a means toward achieving these goals since they convert heat, including waste heat, directly into an electric potential difference. Metal-semiconductor heterostructures can work as Schottky barriers in thermoelectric materials to increase thermoelectric efficiency. In this project, nickel silicide phases were introduced into silicon nanowires (SiNWs) to build up the Schottky barrier. SiNW arrays were fabricated using a metal-assisted chemical process, creating SiNWs about 200 nm in diameter and 30im in length. Different methods were adopted for nickel deposition: electroless nickel deposition, electro nickel deposition, E-beam deposition, and thermal evaporation. The samples were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that depositing nickel on SiNWs in an aqueous solution without electricity is a simple way to deposit nickel particles, and the morphology of nickel particles depends on the concentration of the deposition bath. However, an aqueous solution will cause oxidation of the SiNWs and hinder the formation of nickel silicide. To solve this problem, depositing nickel on SiNWs in organic solutions inside an oxygen-free glove box is a way to prevent oxidation, and nickel can diffuse into silicon substrates easily via annealing when there no oxidation layer on the surface of SiNWs. The dominant phase formed in these samples is NiSi2 after being annealed at 650°C for one hour in a tube furnace.

  2. General atomistic approach for modeling metal-semiconductor interfaces using density functional theory and nonequilibrium Green's function

    NASA Astrophysics Data System (ADS)

    Stradi, Daniele; Martinez, Umberto; Blom, Anders; Brandbyge, Mads; Stokbro, Kurt

    2016-04-01

    Metal-semiconductor contacts are a pillar of modern semiconductor technology. Historically, their microscopic understanding has been hampered by the inability of traditional analytical and numerical methods to fully capture the complex physics governing their operating principles. Here we introduce an atomistic approach based on density functional theory and nonequilibrium Green's function, which includes all the relevant ingredients required to model realistic metal-semiconductor interfaces and allows for a direct comparison between theory and experiments via I -Vbias curve simulations. We apply this method to characterize an Ag/Si interface relevant for photovoltaic applications and study the rectifying-to-Ohmic transition as a function of the semiconductor doping. We also demonstrate that the standard "activation energy" method for the analysis of I -Vbias data might be inaccurate for nonideal interfaces as it neglects electron tunneling, and that finite-size atomistic models have problems in describing these interfaces in the presence of doping due to a poor representation of space-charge effects. Conversely, the present method deals effectively with both issues, thus representing a valid alternative to conventional procedures for the accurate characterization of metal-semiconductor interfaces.

  3. Cytotoxicity of metal and semiconductor nanoparticles indicated by cellular micromotility.

    PubMed

    Tarantola, Marco; Schneider, David; Sunnick, Eva; Adam, Holger; Pierrat, Sebastien; Rosman, Christina; Breus, Vladimir; Sönnichsen, Carsten; Basché, Thomas; Wegener, Joachim; Janshoff, Andreas

    2009-01-27

    In the growing field of nanotechnology, there is an urgent need to sensitively determine the toxicity of nanoparticles since many technical and medical applications are based on controlled exposure to particles, that is, as contrast agents or for drug delivery. Before the in vivo implementation, in vitro cell experiments are required to achieve a detailed knowledge of toxicity and biodegradation as a function of the nanoparticles' physical and chemical properties. In this study, we show that the micromotility of animal cells as monitored by electrical cell-substrate impedance analysis (ECIS) is highly suitable to quantify in vitro cytotoxicity of semiconductor quantum dots and gold nanorods. The method is validated by conventional cytotoxicity testing and accompanied by fluorescence and dark-field microscopy to visualize changes in the cytoskeleton integrity and to determine the location of the particles within the cell. PMID:19206269

  4. Role of the dielectric for the charging dynamics of the dielectric/barrier interface in AlGaN/GaN based metal-insulator-semiconductor structures under forward gate bias stress

    SciTech Connect

    Lagger, P.; Steinschifter, P.; Reiner, M.; Stadtmüller, M.; Denifl, G.; Ostermaier, C.; Naumann, A.; Müller, J.; Wilde, L.; Sundqvist, J.; Pogany, D.

    2014-07-21

    The high density of defect states at the dielectric/III-N interface in GaN based metal-insulator-semiconductor structures causes tremendous threshold voltage drifts, ΔV{sub th}, under forward gate bias conditions. A comprehensive study on different dielectric materials, as well as varying dielectric thickness t{sub D} and barrier thickness t{sub B}, is performed using capacitance-voltage analysis. It is revealed that the density of trapped electrons, ΔN{sub it}, scales with the dielectric capacitance under spill-over conditions, i.e., the accumulation of a second electron channel at the dielectric/AlGaN barrier interface. Hence, the density of trapped electrons is defined by the charging of the dielectric capacitance. The scaling behavior of ΔN{sub it} is explained universally by the density of accumulated electrons at the dielectric/III-N interface under spill-over conditions. We conclude that the overall density of interface defects is higher than what can be electrically measured, due to limits set by dielectric breakdown. These findings have a significant impact on the correct interpretation of threshold voltage drift data and are of relevance for the development of normally off and normally on III-N/GaN high electron mobility transistors with gate insulation.

  5. Thermoelectric properties of HfN/ScN metal/semiconductor superlattices: a first-principles study

    NASA Astrophysics Data System (ADS)

    Saha, Bivas; Sands, Timothy D.; Waghmare, Umesh V.

    2012-10-01

    Nitride-based metal/semiconductor superlattices are promising candidates for high-temperature thermoelectric applications. Motivated by recent experimental studies, we perform first-principles density functional theory based analysis of electronic structure, vibrational spectra and transport properties of HfN/ScN metal/semiconductor superlattices for their potential applications in thermoelectric and thermionic energy conversion devices. Our results suggest (a) an asymmetric linearly increasing density of states and (b) flattening of conduction bands along the cross-plane Γ-Z direction near the Fermi energy of these superlattices, as is desirable for a large power factor. The n-type Schottky barrier height of 0.13 eV at the metal/semiconductor interface is estimated by the microscopic averaging technique of the electrostatic potential. Vibrational spectra of these superlattices show softening of transverse acoustic phonon modes and localization of ScN phonons in the vibrational energy gap between the HfN (metal) and ScN (semiconductor) states. Our estimates of lattice thermal conductivity within the Boltzmann transport theory suggests up to two orders of magnitude reduction in the cross-plane lattice thermal conductivity of these superlattices compared to their individual bulk components.

  6. Ultraviolet random lasing from asymmetrically contacted MgZnO metal-semiconductor-metal device

    SciTech Connect

    Morshed, Muhammad M.; Suja, Mohammad; Zuo, Zheng; Liu, Jianlin

    2014-11-24

    Nitrogen-doped Mg{sub 0.12}Zn{sub 0.88}O nanocrystalline thin film was grown on c-plane sapphire substrate. Asymmetric Ni/Au and Ti/Au Schottky contacts and symmetric Ni/Au contacts were deposited on the thin film to form metal-semiconductor-metal (MSM) laser devices. Current-voltage, photocurrent, and electroluminescence characterizations were performed. Evident random lasing with a threshold current of ∼36 mA is demonstrated only from the asymmetric MSM device. Random lasing peaks are mostly distributed between 340 and 360 nm and an output power of 15 nW is measured at 43 mA injection current. The electron affinity difference between the contact metal and Mg{sub 0.12}Zn{sub 0.88}O:N layer plays an important role for electron and hole injection and subsequent stimulated random lasing.

  7. Rectification and Photoconduction Mapping of Axial Metal-Semiconductor Interfaces Embedded in GaAs Nanowires

    NASA Astrophysics Data System (ADS)

    Orrù, Marta; Piazza, Vincenzo; Rubini, Silvia; Roddaro, Stefano

    2015-10-01

    Semiconductor nanowires have emerged as an important enabling technology and are today used in many advanced device architectures, with an impact both for what concerns fundamental science and in view of future applications. One of the key challenges in the development of nanowire-based devices is the fabrication of reliable nanoscale contacts. Recent developments in the creation of metal-semiconductor junctions by thermal annealing of metallic electrodes offer promising perspectives. Here, we analyze the optoelectronic properties of nano-Schottky barriers obtained thanks to the controlled formation of metallic AuGa regions in GaAs nanowire. The junctions display a rectifying behavior and their transport characteristics are analyzed to extract the average ideality factor and barrier height in the current architecture. The presence, location, and properties of the Schottky junctions are cross-correlated with spatially resolved photocurrent measurements. Broadband light emission is reported in the reverse breakdown regime; this observation, combined with the absence of electroluminescence at forward bias, is consistent with the device unipolar nature.

  8. Hydrogen Gas Sensors Based on Semiconductor Oxide Nanostructures

    PubMed Central

    Gu, Haoshuang; Wang, Zhao; Hu, Yongming

    2012-01-01

    Recently, the hydrogen gas sensing properties of semiconductor oxide (SMO) nanostructures have been widely investigated. In this article, we provide a comprehensive review of the research progress in the last five years concerning hydrogen gas sensors based on SMO thin film and one-dimensional (1D) nanostructures. The hydrogen sensing mechanism of SMO nanostructures and some critical issues are discussed. Doping, noble metal-decoration, heterojunctions and size reduction have been investigated and proved to be effective methods for improving the sensing performance of SMO thin films and 1D nanostructures. The effect on the hydrogen response of SMO thin films and 1D nanostructures of grain boundary and crystal orientation, as well as the sensor architecture, including electrode size and nanojunctions have also been studied. Finally, we also discuss some challenges for the future applications of SMO nanostructured hydrogen sensors. PMID:22778599

  9. GaN metal-semiconductor-metal UV sensor with multi-layer graphene as Schottky electrodes

    NASA Astrophysics Data System (ADS)

    Lee, Chang-Ju; Kang, Sang-Bum; Cha, Hyeon-Gu; Won, Chul-Ho; Hong, Seul-Ki; Cho, Byung-Jin; Park, Hongsik; Lee, Jung-Hee; Hahm, Sung-Ho

    2015-06-01

    We fabricated a GaN-based metal-semiconductor-metal (MSM)-type UV sensor using a multilayer graphene as transparent Schottky electrodes. The fabricated GaN MSM UV sensor showed a high photo-to-dark current contrast ratio of 3.9 × 105 and a UV-to-visible rejection ratio of 1.8 × 103 at 7 V. The as-fabricated GaN MSM UV sensor with graphene electrodes has a low bias dependence of maximum photoresponsivity and a noise-like response at a visible wavelength in the 500 nm region. These problems were successfully solved by treatment with a buffered oxide etcher (BOE), and the photoresponse characteristics of the fabricated GaN MSM UV sensor after the treatment were better than those before the treatment.

  10. Metallization and packaging of compound semiconductor devices at Sandia National Laboratories

    SciTech Connect

    Seigal, P.K.; Armendariz, M.G.; Rieger, D.J.; Lear, K.L.; Sullivan, C.T.

    1996-11-01

    Recent advances in compound semiconductor technology utilize a variety of metal thin films fabricated by thermal and electron-beam evaporation, and electroplating. An overview of metal processes used by Sandia`s Compound Semiconductor Research Laboratory is presented. Descriptions of electrical n-type and p-type ohmic contact alloys, interconnect metal, and metal layers specifically included for packaging requirements are addressed. Several illustrations of devices incorporating gold plated air bridges are included. ``Back-end`` processes such as flip-chip under bump metallurgy with fluxless solder reflow and plated solder processes are mentioned as current research areas.

  11. Recent progress in III-V based ferromagnetic semiconductors: Band structure, Fermi level, and tunneling transport

    SciTech Connect

    Tanaka, Masaaki; Ohya, Shinobu Nam Hai, Pham

    2014-03-15

    Spin-based electronics or spintronics is an emerging field, in which we try to utilize spin degrees of freedom as well as charge transport in materials and devices. While metal-based spin-devices, such as magnetic-field sensors and magnetoresistive random access memory using giant magnetoresistance and tunneling magnetoresistance, are already put to practical use, semiconductor-based spintronics has greater potential for expansion because of good compatibility with existing semiconductor technology. Many semiconductor-based spintronics devices with useful functionalities have been proposed and explored so far. To realize those devices and functionalities, we definitely need appropriate materials which have both the properties of semiconductors and ferromagnets. Ferromagnetic semiconductors (FMSs), which are alloy semiconductors containing magnetic atoms such as Mn and Fe, are one of the most promising classes of materials for this purpose and thus have been intensively studied for the past two decades. Here, we review the recent progress in the studies of the most prototypical III-V based FMS, p-type (GaMn)As and its heterostructures with focus on tunneling transport, Fermi level, and bandstructure. Furthermore, we cover the properties of a new n-type FMS, (In,Fe)As, which shows electron-induced ferromagnetism. These FMS materials having zinc-blende crystal structure show excellent compatibility with well-developed III-V heterostructures and devices.

  12. Recent progress in III-V based ferromagnetic semiconductors: Band structure, Fermi level, and tunneling transport

    NASA Astrophysics Data System (ADS)

    Tanaka, Masaaki; Ohya, Shinobu; Nam Hai, Pham

    2014-03-01

    Spin-based electronics or spintronics is an emerging field, in which we try to utilize spin degrees of freedom as well as charge transport in materials and devices. While metal-based spin-devices, such as magnetic-field sensors and magnetoresistive random access memory using giant magnetoresistance and tunneling magnetoresistance, are already put to practical use, semiconductor-based spintronics has greater potential for expansion because of good compatibility with existing semiconductor technology. Many semiconductor-based spintronics devices with useful functionalities have been proposed and explored so far. To realize those devices and functionalities, we definitely need appropriate materials which have both the properties of semiconductors and ferromagnets. Ferromagnetic semiconductors (FMSs), which are alloy semiconductors containing magnetic atoms such as Mn and Fe, are one of the most promising classes of materials for this purpose and thus have been intensively studied for the past two decades. Here, we review the recent progress in the studies of the most prototypical III-V based FMS, p-type (GaMn)As and its heterostructures with focus on tunneling transport, Fermi level, and bandstructure. Furthermore, we cover the properties of a new n-type FMS, (In,Fe)As, which shows electron-induced ferromagnetism. These FMS materials having zinc-blende crystal structure show excellent compatibility with well-developed III-V heterostructures and devices.

  13. Structural and optical properties of silicon metal-oxide-semiconductor light-emitting devices

    NASA Astrophysics Data System (ADS)

    Xu, Kaikai; Zhang, Zhengyuan; Zhang, Zhengping

    2016-01-01

    A silicon p-channel metal oxide semiconductor field-effect transistor (Si-PMOSFET) that is fully compatible with the standard complementary metal oxide semiconductor process is investigated based on the phenomenon of optical radiation observed in the reverse-biased p-n junction in the Si-PMOSFET device. The device can be used either as a two-terminal silicon diode light-emitting device (Si-diode LED) or as a three-terminal silicon gate-controlled diode light-emitting device (Si gate-controlled diode LED). It is seen that the three-terminal operating mode could provide much higher power transfer efficiency than the two-terminal operating mode. A new solution based on the concept of a theoretical quantum efficiency model combined with calculated results is proposed for interpreting the evidence of light intensity reduction at high operating voltages. The Si-LED that can be easily integrated into CMOS fabrication process is an important step toward optical interconnects.

  14. Synthesis of a nano-silver metal ink for use in thick conductive film fabrication applied on a semiconductor package.

    PubMed

    Yung, Lai Chin; Fei, Cheong Choke; Mandeep, Js; Binti Abdullah, Huda; Wee, Lai Khin

    2014-01-01

    The success of printing technology in the electronics industry primarily depends on the availability of metal printing ink. Various types of commercially available metal ink are widely used in different industries such as the solar cell, radio frequency identification (RFID) and light emitting diode (LED) industries, with limited usage in semiconductor packaging. The use of printed ink in semiconductor IC packaging is limited by several factors such as poor electrical performance and mechanical strength. Poor adhesion of the printed metal track to the epoxy molding compound is another critical factor that has caused a decline in interest in the application of printing technology to the semiconductor industry. In this study, two different groups of adhesion promoters, based on metal and polymer groups, were used to promote adhesion between the printed ink and the epoxy molding substrate. The experimental data show that silver ink with a metal oxide adhesion promoter adheres better than silver ink with a polymer adhesion promoter. This result can be explained by the hydroxyl bonding between the metal oxide promoter and the silane grouping agent on the epoxy substrate, which contributes a greater adhesion strength compared to the polymer adhesion promoter. Hypotheses of the physical and chemical functions of both adhesion promoters are described in detail. PMID:24830317

  15. Synthesis of a Nano-Silver Metal Ink for Use in Thick Conductive Film Fabrication Applied on a Semiconductor Package

    PubMed Central

    Yung, Lai Chin; Fei, Cheong Choke; Mandeep, JS; Binti Abdullah, Huda; Wee, Lai Khin

    2014-01-01

    The success of printing technology in the electronics industry primarily depends on the availability of metal printing ink. Various types of commercially available metal ink are widely used in different industries such as the solar cell, radio frequency identification (RFID) and light emitting diode (LED) industries, with limited usage in semiconductor packaging. The use of printed ink in semiconductor IC packaging is limited by several factors such as poor electrical performance and mechanical strength. Poor adhesion of the printed metal track to the epoxy molding compound is another critical factor that has caused a decline in interest in the application of printing technology to the semiconductor industry. In this study, two different groups of adhesion promoters, based on metal and polymer groups, were used to promote adhesion between the printed ink and the epoxy molding substrate. The experimental data show that silver ink with a metal oxide adhesion promoter adheres better than silver ink with a polymer adhesion promoter. This result can be explained by the hydroxyl bonding between the metal oxide promoter and the silane grouping agent on the epoxy substrate, which contributes a greater adhesion strength compared to the polymer adhesion promoter. Hypotheses of the physical and chemical functions of both adhesion promoters are described in detail. PMID:24830317

  16. Metal semiconductor phase transition in vanadium dioxide nanocrystals

    NASA Astrophysics Data System (ADS)

    Lopez Noriega, Rene

    The goal of this research was to improve the understanding of the submicron VO2 formation in the near surface of a host material and to explore the possibility of size effects in the mechanics of the semiconductor to metal phase transition as well as in the optical properties of VO2. By means of ion implantation and thermal processing, we were able to produce variable-sized nanoscale VO2 precipitates embedded in SiO 2. The transition temperatures were found to be correlated with the size of the precipitates, in such a way that for smaller particles, both transitions were thermally delayed. A review of the energy barriers and other features involved in the transition, led us to conclude that regardless of that exact mechanism, the phase transition must proceed in a heterogeneous fashion. Smaller particles were expected to have a lower chance of containing a nucleation site and thus, they need a greater thermal driving force in order to activate them. VO2 precipitates were not only controlled in size but as an unexpected result they turned out to be produced in elongated shapes oriented mainly along the implanted surface. This morphology, which was explained in terms of the Bravais-Friedel law of crystal growth, allowed us to understand the optical properties of the precipitates. We concluded that the optical behavior shown by the particles in the SiO2 matrix, was result of a surface plasmon resonance due to the dielectric confinement and metallic character of the VO2 in the high temperature phase. Beside these contributions to material and physical sciences, we have shown that established results for VO2 doping can be applicable to our submicron particles. We were able to successfully control the width of the hysteresis loop by adding Ti ions before the precipitation. We also reached lower switching temperatures by implanting small quantities of W. Ion implantation also proved to be an easy and convenient way to incorporate VO2 nanoparticles into an optical fiber

  17. The dispersion in accumulation at InGaAs-based metal/oxide/semiconductor gate stacks with a bi-layered dielectric structure

    NASA Astrophysics Data System (ADS)

    Krylov, Igor; Ritter, Dan; Eizenberg, Moshe

    2015-08-01

    InGaAs gate stacks comprising the moderate dielectric constant (k) Al2O3 have a significantly lower dispersion in accumulation in comparison to stacks with the high-k HfO2 of the same physical thickness. As a result, a HfO2/Al2O3 bi-layer structure seems attractive in terms of both high effective dielectric constant and low dispersion in accumulation. The influence of Al2O3 thickness on the dispersion was investigated in metal/HfO2/Al2O3/InGaAs gate stacks with a fixed overall dielectric thickness. An effective suppression of the dispersion with the increase of the Al2O3 thickness was observed. However, the Al2O3 thickness required for passivation of the dispersion in accumulation was significantly higher in comparison to both the border traps related tunneling distance in Al2O3 and the minimal thickness required for the Al2O3/InGaAs band offset stabilization. The phenomenon can be explained by the lower dielectric constant of Al2O3 film (compared to the subsequently deposited HfO2 layer), where Al2O3 dielectric constant dependence on the film thickness enhances the dispersion intensity. As a result, the guidelines for the passivation layer engineering are: maximization of both majority carriers band offsets and of the dielectric constant of the passivation layer.

  18. Density functional studies on wurtzite piezotronic transistors: influence of different semiconductors and metals on piezoelectric charge distribution and Schottky barrier

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    The mechanical–electrical coupling properties of piezoelectric semiconductors endow these materials with novel device applications in microelectromechanical systems, sensors, human–computer interfaces, etc. When an applied strain is exerted on a piezoelectric semiconductor, piezoelectric charges are generated at the surface or interface of the semiconductor, which can be utilized to control the electronic transport characteristics. This is the fundamental working mechanism of piezotronic devices, called the piezotronic effect. In the present report, a series of piezotronic transistors composed of different electrode metals and semiconductors is examined using density functional theory calculation. It is found that the influence of semiconductors on the piezotronic effect is larger than the impact of metals, and GaN and CdS are promising candidates for piezotronic and piezo-phototronic devices, respectively. The width of the piezoelectric charge distribution obtained in the present study can be used as a parameter in classical finite-element-method based simulations, which provide guidance on designing high-performance piezotronic devices.

  19. Density functional studies on wurtzite piezotronic transistors: influence of different semiconductors and metals on piezoelectric charge distribution and Schottky barrier.

    PubMed

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

    2016-05-20

    The mechanical-electrical coupling properties of piezoelectric semiconductors endow these materials with novel device applications in microelectromechanical systems, sensors, human-computer interfaces, etc. When an applied strain is exerted on a piezoelectric semiconductor, piezoelectric charges are generated at the surface or interface of the semiconductor, which can be utilized to control the electronic transport characteristics. This is the fundamental working mechanism of piezotronic devices, called the piezotronic effect. In the present report, a series of piezotronic transistors composed of different electrode metals and semiconductors is examined using density functional theory calculation. It is found that the influence of semiconductors on the piezotronic effect is larger than the impact of metals, and GaN and CdS are promising candidates for piezotronic and piezo-phototronic devices, respectively. The width of the piezoelectric charge distribution obtained in the present study can be used as a parameter in classical finite-element-method based simulations, which provide guidance on designing high-performance piezotronic devices. PMID:27053577

  20. Lossless propagation in metal-semiconductor-metal plasmonic waveguides using quantum dot active medium.

    PubMed

    Sheikhi, K; Granpayeh, N; Ahmadi, V; Pahlavan, S

    2015-04-01

    In this paper, we analyze and simulate the lossless propagation of lightwaves in the active metal-semiconductor-metal plasmonic waveguides (MSMPWs) at the wavelength range of 1540-1560 nm using a quantum dot (QD) active medium. The Maxwell's equations are solved in the waveguide, and the required gains for achieving lossless propagation are derived. On the other hand, the rate equations in quantum dot active regions are solved by using the Runge-Kutta method, and the achievable optical gain is derived. The analyses results show that the required optical gain for lossless propagation in MSMPWs is achievable using the QD active medium. Also, by adjusting the active medium parameters, the MSMPWs loss can be eliminated in a specific bandwidth, and the propagation length increases obviously. PMID:25967191

  1. High detectivity GaN metal semiconductor metal UV photodetectors with transparent tungsten electrodes

    NASA Astrophysics Data System (ADS)

    Wang, C. K.; Chang, S. J.; Su, Y. K.; Chiou, Y. Z.; Chang, C. S.; Lin, T. K.; Liu, H. L.; Tang, J. J.

    2005-06-01

    GaN metal-semiconductor-metal (MSM) ultraviolet photodetectors with transparent tungsten (W) electrodes were fabricated and characterized. It was found that the 10 nm thick W film deposited with a 250 W RF power could provide a reasonably high transmittance of 68.3% at 360 nm, a low resistivity of 1.5 × 10-3 Ω cm and an effective Schottky barrier height of 0.777 eV on u-GaN. We also achieved a peak responsivity of 0.15 A W-1 and a quantum efficiency of 51.8% at 360 nm from the GaN MSM UV photodetector with W electrodes. With a 2 V applied bias, it was found that the minimum noise equivalent power (NEP) and the maximum D* of our detector were 1.745 × 10-10 W and 7.245 × 109 cm Hz0.5 W-1, respectively.

  2. DOE/BES/NSET annual report on growth of metal and semiconductor nanostructures using localized photocatalysts.

    SciTech Connect

    Haddad, Raid Edward; Brinker, C. Jeffrey; Shelnutt, John Allen; Yang, Yi; Nuttall, H. Eric; Watt, Richard K.; Singl, Anup K.; Challa, Sivakumar R.; Wang, Zhongchun; van Swol, Frank B.; Pereira, Eulalia; Qiu, Yan; Jiang, Ying-Bing; Xu, Huifang; Medforth, Craig J.; Song, Yujiang

    2003-10-01

    Our overall goal is to understand and develop a novel light-driven approach to the controlled growth of unique metal and semiconductor nanostructures and nanomaterials. In this photochemical process, bio-inspired porphyrin-based photocatalysts reduce metal salts in aqueous solutions at ambient temperatures to provide metal nucleation and growth centers. Photocatalyst molecules are pre-positioned at the nanoscale to control the location and morphology of the metal nanostructures grown. Self-assembly, chemical confinement, and molecular templating are some of the methods used for nanoscale positioning of the photocatalyst molecules. When exposed to light, the photocatalyst molecule repeatedly reduces metal ions from solution, leading to deposition and the synthesis of the new nanostructures and nanostructured materials. Studies of the photocatalytic growth process and the resulting nanostructures address a number of fundamental biological, chemical, and environmental issues and draw on the combined nanoscience characterization and multi-scale simulation capabilities of the new DOE Center for Integrated Nanotechnologies, the University of New Mexico, and Sandia National Laboratories. Our main goals are to elucidate the processes involved in the photocatalytic growth of metal nanomaterials and provide the scientific basis for controlled synthesis. The nanomaterials resulting from these studies have applications in nanoelectronics, photonics, sensors, catalysis, and micromechanical systems. The proposed nanoscience concentrates on three thematic research areas: (1) the creation of nanoscale structures for realizing novel phenomena and quantum control, (2) understanding nanoscale processes in the environment, and (3) the development and use of multi-scale, multi-phenomena theory and simulation. Our goals for FY03 have been to understand the role of photocatalysis in the synthesis of dendritic platinum nanostructures grown from aqueous surfactant solutions under ambient

  3. Electrostatic analysis of n-doped SrTiO{sub 3} metal-insulator-semiconductor systems

    SciTech Connect

    Kamerbeek, A. M. Banerjee, T.; Hueting, R. J. E.

    2015-12-14

    Electron doped SrTiO{sub 3}, a complex-oxide semiconductor, possesses novel electronic properties due to its strong temperature and electric-field dependent permittivity. Due to the high permittivity, metal/n-SrTiO{sub 3} systems show reasonably strong rectification even when SrTiO{sub 3} is degenerately doped. Our experiments show that the insertion of a sub nanometer layer of AlO{sub x} in between the metal and n-SrTiO{sub 3} interface leads to a dramatic reduction of the Schottky barrier height (from around 0.90 V to 0.25 V). This reduces the interface resistivity by 4 orders of magnitude. The derived electrostatic analysis of the metal-insulator-semiconductor (n-SrTiO{sub 3}) system is consistent with this trend. When compared with a Si based MIS system, the change is much larger and mainly governed by the high permittivity of SrTiO{sub 3}. The non-linear permittivity of n-SrTiO{sub 3} leads to unconventional properties such as a temperature dependent surface potential non-existent for semiconductors with linear permittivity such as Si. This allows tuning of the interfacial band alignment, and consequently the Schottky barrier height, in a much more drastic way than in conventional semiconductors.

  4. Transmission line based short pulse generation circuits in a 0.13 μm complementary metal-oxide-semiconductor technology

    NASA Astrophysics Data System (ADS)

    Zou, Huan; Geng, Yongtao; Wang, Pingshan

    2011-02-01

    A few traditional pulse forming circuits are implemented and compared in a commercial 0.13 μm digital CMOS technology. Standard on-chip transmission lines are used as pulse forming lines (PFLs), while CMOS transistors are used as switches. The shortest output pulses of these circuits are analyzed and compared through Cadence Spectre simulations. All the CMOS circuits are fabricated in the commercial technology. Pulses of ˜170 ps durations and 120-400 mV amplitudes are obtained when the power supply is tuned from 1.2 to 2 V. The results show that these traditional PFL based circuits can be implemented in standard CMOS technology for high power short pulse generations. Furthermore, the PFL circuits significantly extend the short pulse generation capabilities of CMOS technologies.

  5. Irradiation effects of graphene-enhanced gallium nitride (GaN) metal-semiconductor-metal (MSM) ultraviolet photodetectors

    NASA Astrophysics Data System (ADS)

    Chiamori, Heather C.; Miller, Ruth; Suria, Ateeq; Broad, Nicholas; Senesky, Debbie G.

    2015-05-01

    Ultraviolet (UV) photodetectors are used for applications such as flame detection, space navigation, biomedical and environmental monitoring. Robust operation within large ranges of temperatures, radiation, salinity and/or corrosive chemicals require sensor materials with the ability to withstand and function reliably within these extreme harsh environments. For example, spacecraft can utilize a sun sensor (light-based sensor) to assist with determination of orientation and may be exposed to both ionizing radiation and extreme temperature swings during operation. Gallium nitride (GaN), a wide bandgap semiconductor material, has material properties enabling visible-blindness, tunable cutoff wavelength selection based on ternary alloy mole fraction, high current density, thermal/chemical stability and high radiation tolerance due to the strength of the chemical bond. Graphene, with outstanding electrical, optical and mechanical properties and a flat absorption spectrum from 300 to 2,500 nm, has potential use as a transparent conductor for GaN-based metal-semiconductor-metal (MSM) photodetectors. Here, graphene-enhanced MSM UV photodetectors are fabricated with transparent and conductive graphene interdigitated electrodes on thin film GaN-on-sapphire substrates serving as back-to-back Schottky contacts. We report on the irradiation response of graphene/GaN-based MSM UV photodetectors up to 750 krad total ionizing dose (TID) then tested under dark and UV light (365 nm) conditions. In addition, based on current-voltage measurements from 75 krad to 750 krad TID, calculated photodetector responsivity values change slightly by 25% and 11% at -5 V and -2 V, respectively. These initial findings suggest that graphene/GaN MSM UV photodetectors could potentially be engineered to reliably operate within radiation environments.

  6. Magnetic-field-induced photocurrent in metal-dielectric-semiconductor heterostructures based on cobalt nanoparticles SiO2(Co)/GaAs

    NASA Astrophysics Data System (ADS)

    Pavlov, V. V.; Lutsev, L. V.; Usachev, P. A.; Astretsov, A. A.; Stognij, A. I.; Novitskii, N. N.; Pisarev, R. V.

    2016-02-01

    Magnetic-field influence on photocurrent in heterostructures of silicon dioxide films with cobalt nanoparticles SiO2(Co) grown on gallium arsenide GaAs substrate has been studied in the avalanche regime at room temperature. High values of magnetic-field-induced photocurrent were found in the vicinity and above the GaAs bandgap of ∼1.4 eV. For photon energies E > 1.4 eV the photocurrent significantly increases, while the avalanche process is suppressed by the magnetic field, and the current flowing through the heterostructure decreases. The photocurrent is enhanced in the SiO2(Co 60 at%)/GaAs heterostructure at the magnetic field H=1.65 kOe by factor of about 10 for the photon energy E=1.5 eV. This phenomenon is explained by a model based on electronic transitions in magnetic fields with the spin-dependent recombination process at deep impurity centers in the SiO2(Co)/GaAs interface region.

  7. Optimal metal domain size for photocatalysis with hybrid semiconductor-metal nanorods.

    PubMed

    Ben-Shahar, Yuval; Scotognella, Francesco; Kriegel, Ilka; Moretti, Luca; Cerullo, Giulio; Rabani, Eran; Banin, Uri

    2016-01-01

    Semiconductor-metal hybrid nanostructures offer a highly controllable platform for light-induced charge separation, with direct relevance for their implementation in photocatalysis. Advances in the synthesis allow for control over the size, shape and morphology, providing tunability of the optical and electronic properties. A critical determining factor of the photocatalytic cycle is the metal domain characteristics and in particular its size, a subject that lacks deep understanding. Here, using a well-defined model system of cadmium sulfide-gold nanorods, we address the effect of the gold tip size on the photocatalytic function, including the charge transfer dynamics and hydrogen production efficiency. A combination of transient absorption, hydrogen evolution kinetics and theoretical modelling reveal a non-monotonic behaviour with size of the gold tip, leading to an optimal metal domain size for the most efficient photocatalysis. We show that this results from the size-dependent interplay of the metal domain charging, the relative band-alignments, and the resulting kinetics. PMID:26783194

  8. Optimal metal domain size for photocatalysis with hybrid semiconductor-metal nanorods

    PubMed Central

    Ben-Shahar, Yuval; Scotognella, Francesco; Kriegel, Ilka; Moretti, Luca; Cerullo, Giulio; Rabani, Eran; Banin, Uri

    2016-01-01

    Semiconductor-metal hybrid nanostructures offer a highly controllable platform for light-induced charge separation, with direct relevance for their implementation in photocatalysis. Advances in the synthesis allow for control over the size, shape and morphology, providing tunability of the optical and electronic properties. A critical determining factor of the photocatalytic cycle is the metal domain characteristics and in particular its size, a subject that lacks deep understanding. Here, using a well-defined model system of cadmium sulfide-gold nanorods, we address the effect of the gold tip size on the photocatalytic function, including the charge transfer dynamics and hydrogen production efficiency. A combination of transient absorption, hydrogen evolution kinetics and theoretical modelling reveal a non-monotonic behaviour with size of the gold tip, leading to an optimal metal domain size for the most efficient photocatalysis. We show that this results from the size-dependent interplay of the metal domain charging, the relative band-alignments, and the resulting kinetics. PMID:26783194

  9. Optimal metal domain size for photocatalysis with hybrid semiconductor-metal nanorods

    NASA Astrophysics Data System (ADS)

    Ben-Shahar, Yuval; Scotognella, Francesco; Kriegel, Ilka; Moretti, Luca; Cerullo, Giulio; Rabani, Eran; Banin, Uri

    2016-01-01

    Semiconductor-metal hybrid nanostructures offer a highly controllable platform for light-induced charge separation, with direct relevance for their implementation in photocatalysis. Advances in the synthesis allow for control over the size, shape and morphology, providing tunability of the optical and electronic properties. A critical determining factor of the photocatalytic cycle is the metal domain characteristics and in particular its size, a subject that lacks deep understanding. Here, using a well-defined model system of cadmium sulfide-gold nanorods, we address the effect of the gold tip size on the photocatalytic function, including the charge transfer dynamics and hydrogen production efficiency. A combination of transient absorption, hydrogen evolution kinetics and theoretical modelling reveal a non-monotonic behaviour with size of the gold tip, leading to an optimal metal domain size for the most efficient photocatalysis. We show that this results from the size-dependent interplay of the metal domain charging, the relative band-alignments, and the resulting kinetics.

  10. Photoluminescence mechanisms of metallic Zn nanospheres, semiconducting ZnO nanoballoons, and metal-semiconductor Zn/ZnO nanospheres

    PubMed Central

    Lin, Jin-Han; Patil, Ranjit A.; Devan, Rupesh S.; Liu, Zhe-An; Wang, Yi-Ping; Ho, Ching-Hwa; Liou, Yung; Ma, Yuan-Ron

    2014-01-01

    We utilized a thermal radiation method to synthesize semiconducting hollow ZnO nanoballoons and metal-semiconductor concentric solid Zn/ZnO nanospheres from metallic solid Zn nanospheres. The chemical properties, crystalline structures, and photoluminescence mechanisms for the metallic solid Zn nanospheres, semiconducting hollow ZnO nanoballoons, and metal-semiconductor concentric solid Zn/ZnO nanospheres are presented. The PL emissions of the metallic Zn solid nanospheres are mainly dependent on the electron transitions between the Fermi level (EF) and the 3d band, while those of the semiconducting hollow ZnO nanoballoons are ascribed to the near band edge (NBE) and deep level electron transitions. The PL emissions of the metal-semiconductor concentric solid Zn/ZnO nanospheres are attributed to the electron transitions across the metal-semiconductor junction, from the EF to the valence and 3d bands, and from the interface states to the valence band. All three nanostructures are excellent room-temperature light emitters. PMID:25382186

  11. Nonvolatile and tunable switching of lateral photo-voltage triggered by laser and electric pulse in metal dusted metal-oxide-semiconductor structures.

    PubMed

    Zhou, Peiqi; Gan, Zhikai; Huang, Xu; Mei, Chunlian; Huang, Meizhen; Xia, Yuxing; Wang, Hui

    2016-01-01

    Owing to the innate stabilization of built-in potential in p-n junction or metal-oxide-semiconductor structure, the sensitivity and linearity of most lateral photovoltaic effect (LPE) devices is always fixed after fabrication. Here we report a nonvolatile and tunable switching effect of lateral photo-voltage (LPV) in Cu dusted ultrathin metal-oxide-semiconductor structure. With the stimulation of electric pulse and local illumination, the sensitivity and linearity of LPV can be adjusted up and down in a nonvolatile manner. This phenomenon is attributed to a controllable change of the Schottky barrier formed between the metal layer and silicon substrate, including the consequent change of film resistivity. This work may widely improve the performance of existing LPE-based devices and suggest new applications for LPE in other areas. PMID:27535351

  12. Nonvolatile and tunable switching of lateral photo-voltage triggered by laser and electric pulse in metal dusted metal-oxide-semiconductor structures

    PubMed Central

    Zhou, Peiqi; Gan, Zhikai; Huang, Xu; Mei, Chunlian; Huang, Meizhen; Xia, Yuxing; Wang, Hui

    2016-01-01

    Owing to the innate stabilization of built-in potential in p–n junction or metal-oxide-semiconductor structure, the sensitivity and linearity of most lateral photovoltaic effect (LPE) devices is always fixed after fabrication. Here we report a nonvolatile and tunable switching effect of lateral photo-voltage (LPV) in Cu dusted ultrathin metal-oxide-semiconductor structure. With the stimulation of electric pulse and local illumination, the sensitivity and linearity of LPV can be adjusted up and down in a nonvolatile manner. This phenomenon is attributed to a controllable change of the Schottky barrier formed between the metal layer and silicon substrate, including the consequent change of film resistivity. This work may widely improve the performance of existing LPE-based devices and suggest new applications for LPE in other areas. PMID:27535351

  13. Metal-semiconductor hybrid thin films in field-effect transistors

    SciTech Connect

    Okamura, Koshi Dehm, Simone; Hahn, Horst

    2013-12-16

    Metal-semiconductor hybrid thin films consisting of an amorphous oxide semiconductor and a number of aluminum dots in different diameters and arrangements are formed by electron beam lithography and employed for thin-film transistors (TFTs). Experimental and computational demonstrations systematically reveal that the field-effect mobility of the TFTs enhances but levels off as the dot density increases, which originates from variations of the effective channel length that strongly depends on the electric field distribution in a transistor channel.

  14. Novel diluted magnetic semiconductor materials based on zinc oxide

    NASA Astrophysics Data System (ADS)

    Chakraborti, Deepayan

    The primary aim of this work was to develop a ZnO based diluted magnetic semiconductor (DMS) materials system which displays ferromagnetism above room temperature and to understand the origin of long-range ferromagnetic ordering in these systems. Recent developments in the field of spintronics (spin based electronics) have led to an extensive search for materials in which semiconducting properties can be integrated with magnetic properties to realize the objective of successful fabrication of spin-based devices. For these devices we require a high efficiency of spin current injection at room temperature. Diluted magnetic semiconductors (DMS) can serve this role, but they should not only display room temperature ferromagnetism (RTFM) but also be capable of generating spin polarized carriers. Transition metal doped ZnO has proved to be a potential candidate as a DMS showing RTFM. The origin of ferromagnetic ordering in ZnO is still under debate. However, the presence of magnetic secondary phases, composition fluctuations and nanoclusters could also explain the observation of ferromagnetism in the DMS samples. This encouraged us to investigate Cu-doped(+ spin in the 2+ valence state) ZnO system as a probable candidate exhibiting RTFM because neither metallic Cu nor its oxides (Cu2O or CuO) are ferromagnetic. The role of defects and free carriers on the ferromagnetic ordering of Cu-doped ZnO thin films was studied to ascertain the origin of ferromagnetism in this system. A novel non-equilibrium Pulsed Laser Deposition technique has been used to grow high quality epitaxial thin films of Cu:ZnO and (Co,Cu):ZnO on c-plane Sapphire by domain matching epitxay. Both the systems showed ferromagnetic ordering above 300K but Cu ions showed a much stronger ferromagnetic ordering than Co, especially at low concentrations (1-2%) of Cu where we realized near 100% polarization. But, the incorporation of Cu resulted in a 2-order of magnitude rise in the resistivity from 10-1 to 101

  15. Organic-on-silicon complementary metal-oxide-semiconductor colour image sensors.

    PubMed

    Lim, Seon-Jeong; Leem, Dong-Seok; Park, Kyung-Bae; Kim, Kyu-Sik; Sul, Sangchul; Na, Kyoungwon; Lee, Gae Hwang; Heo, Chul-Joon; Lee, Kwang-Hee; Bulliard, Xavier; Satoh, Ryu-Ichi; Yagi, Tadao; Ro, Takkyun; Im, Dongmo; Jung, Jungkyu; Lee, Myungwon; Lee, Tae-Yon; Han, Moon Gyu; Jin, Yong Wan; Lee, Sangyoon

    2015-01-01

    Complementary metal-oxide-semiconductor (CMOS) colour image sensors are representative examples of light-detection devices. To achieve extremely high resolutions, the pixel sizes of the CMOS image sensors must be reduced to less than a micron, which in turn significantly limits the number of photons that can be captured by each pixel using silicon (Si)-based technology (i.e., this reduction in pixel size results in a loss of sensitivity). Here, we demonstrate a novel and efficient method of increasing the sensitivity and resolution of the CMOS image sensors by superposing an organic photodiode (OPD) onto a CMOS circuit with Si photodiodes, which consequently doubles the light-input surface area of each pixel. To realise this concept, we developed organic semiconductor materials with absorption properties selective to green light and successfully fabricated highly efficient green-light-sensitive OPDs without colour filters. We found that such a top light-receiving OPD, which is selective to specific green wavelengths, demonstrates great potential when combined with a newly designed Si-based CMOS circuit containing only blue and red colour filters. To demonstrate the effectiveness of this state-of-the-art hybrid colour image sensor, we acquired a real full-colour image using a camera that contained the organic-on-Si hybrid CMOS colour image sensor. PMID:25578322

  16. Reaction Current Phenomenon in Bifunctional Catalytic Metal-Semiconductor Nanostructures

    NASA Astrophysics Data System (ADS)

    Hashemian, Mohammad Amin

    Energy transfer processes accompany every elementary step of catalytic chemical processes on material surface including molecular adsorption and dissociation on atoms, interactions between intermediates, and desorption of reaction products from the catalyst surface. Therefore, detailed understanding of these processes on the molecular level is of great fundamental and practical interest in energy-related applications of nanomaterials. Two main mechanisms of energy transfer from adsorbed particles to a surface are known: (i) adiabatic via excitation of quantized lattice vibrations (phonons) and (ii) non-adiabatic via electronic excitations (electron/hole pairs). Electronic excitations play a key role in nanocatalysis, and it was recently shown that they can be efficiently detected and studied using Schottky-type catalytic nanostructures in the form of measureable electrical currents (chemicurrents) in an external electrical circuit. These nanostructures typically contain an electrically continuous nanocathode layers made of a catalytic metal deposited on a semiconductor substrate. The goal of this research is to study the direct observations of hot electron currents (chemicurrents) in catalytic Schottky structures, using a continuous mesh-like Pt nanofilm grown onto a mesoporous TiO2 substrate. Such devices showed qualitatively different and more diverse signal properties, compared to the earlier devices using smooth substrates, which could only be explained on the basis of bifunctionality. In particular, it was necessary to suggest that different stages of the reaction are occurring on both phases of the catalytic structure. Analysis of the signal behavior also led to discovery of a formerly unknown (very slow) mode of the oxyhydrogen reaction on the Pt/TiO2(por) system occurring at room temperature. This slow mode was producing surprisingly large stationary chemicurrents in the range 10--50 microA/cm2. Results of the chemicurrent measurements for the bifunctional

  17. Alloyed 2D Metal-Semiconductor Atomic Layer Junctions.

    PubMed

    Kim, Ah Ra; Kim, Yonghun; Nam, Jaewook; Chung, Hee-Suk; Kim, Dong Jae; Kwon, Jung-Dae; Park, Sang Won; Park, Jucheol; Choi, Sun Young; Lee, Byoung Hun; Park, Ji Hyeon; Lee, Kyu Hwan; Kim, Dong-Ho; Choi, Sung Mook; Ajayan, Pulickel M; Hahm, Myung Gwan; Cho, Byungjin

    2016-03-01

    Heterostructures of compositionally and electronically variant two-dimensional (2D) atomic layers are viable building blocks for ultrathin optoelectronic devices. We show that the composition of interfacial transition region between semiconducting WSe2 atomic layer channels and metallic NbSe2 contact layers can be engineered through interfacial doping with Nb atoms. WxNb1-xSe2 interfacial regions considerably lower the potential barrier height of the junction, significantly improving the performance of the corresponding WSe2-based field-effect transistor devices. The creation of such alloyed 2D junctions between dissimilar atomic layer domains could be the most important factor in controlling the electronic properties of 2D junctions and the design and fabrication of 2D atomic layer devices. PMID:26839956

  18. Strong coupling among semiconductor quantum dots induced by a metal nanoparticle

    PubMed Central

    2012-01-01

    Based on cavity quantum electrodynamics (QED), we investigate the light-matter interaction between surface plasmon polaritons (SPP) in a metal nanoparticle (MNP) and the excitons in semiconductor quantum dots (SQDs) in an SQD-MNP coupled system. We propose a quantum transformation method to strongly reveal the exciton energy shift and the modified decay rate of SQD as well as the coupling among SQDs. To obtain these parameters, a simple system composed of an SQD, an MNP, and a weak signal light is designed. Furthermore, we consider a model to demonstrate the coupling of two SQDs mediated by SPP field under two cases. It is shown that two SQDs can be entangled in the presence of MNP. A high concurrence can be achieved, which is the best evidence that the coupling among SQDs induced by SPP field in MNP. This scheme may have the potential applications in all-optical plasmon-enhanced nanoscale devices. PMID:22297024

  19. Photoconduction efficiencies of metal oxide semiconductor nanowires: The material's inherent properties

    NASA Astrophysics Data System (ADS)

    Chen, R. S.; Wang, W. C.; Chan, C. H.; Lu, M. L.; Chen, Y. F.; Lin, H. C.; Chen, K. H.; Chen, L. C.

    2013-11-01

    The photoconduction (PC) efficiencies of various single-crystalline metal oxide semiconductor nanowires (NWs) have been investigated and compared based on the materials' inherent properties. The defined PC efficiency (normalized gain) of SnO2 NWs is over one to five orders of magnitude higher than that of its highly efficient counterparts such as ZnO, TiO2, WO3, and GaN. The inherent property of the material allowed the photoconductive gain of an SnO2 single-NW photodetector to easily reach 8 × 108 at a low bias of 3.0 V and a low light intensity of 0.05 Wm-2, which is the optimal reported value so far for the single-NW photodetectors. The probable physical origins, such as charged surface state density and surface band bending, that caused the differences in PC efficiencies and carrier lifetimes are also discussed.

  20. Flexible complementary metal oxide semiconductor microelectrode arrays with applications in single cell characterization

    NASA Astrophysics Data System (ADS)

    Pajouhi, H.; Jou, A. Y.; Jain, R.; Ziabari, A.; Shakouri, A.; Savran, C. A.; Mohammadi, S.

    2015-11-01

    A highly flexible microelectrode array with an embedded complementary metal oxide semiconductor (CMOS) instrumentation amplifier suitable for sensing surfaces of biological entities is developed. The array is based on ultrathin CMOS islands that are thermally isolated from each other and are interconnected by meandered nano-scale wires that can adapt to cellular surfaces with micro-scale curvatures. CMOS temperature sensors are placed in the islands and are optimally biased to have high temperature sensitivity. While no live cell thermometry is conducted, a measured temperature sensitivity of 0.15 °C in the temperature range of 35 to 40 °C is achieved by utilizing a low noise CMOS lock-in amplifier implemented in the same technology. The monolithic nature of CMOS sensors and amplifier circuits and their versatile flexible interconnecting wires overcome the sensitivity and yield limitations of microelectrode arrays fabricated in competing technologies.

  1. Drift-diffusion equation for ballistic transport in nanoscale metal-oxide-semiconductor field effect transistors

    NASA Astrophysics Data System (ADS)

    Rhew, Jung-Hoon; Lundstrom, Mark S.

    2002-11-01

    We develop a drift-diffusion equation that describes ballistic transport in a nanoscale metal-oxide-semiconductor field effect transistor (MOSFET). We treat injection from different contacts separately, and describe each injection with a set of extended McKelvey one-flux equations [Phys. Rev. 123, 51 (1961); 125, 1570 (1962)] that include hierarchy closure approximations appropriate for high-field ballistic transport and degenerate carrier statistics. We then reexpress the extended one-flux equations in a drift-diffusion form with a properly defined Einstein relationship. The results obtained for a nanoscale MOSFET show excellent agreement with the solution of the ballistic Boltzmann transport equation with no fitting parameters. These results show that a macroscopic transport model based on the moments of the Boltzmann transport equation can describe ballistic transport.

  2. Electronic-Structure Theory of Organic Semiconductors: Charge-Transport Parameters and Metal/Organic Interfaces

    NASA Astrophysics Data System (ADS)

    Coropceanu, Veaceslav; Li, Hong; Winget, Paul; Zhu, Lingyun; Brédas, Jean-Luc

    2013-07-01

    We focus this review on the theoretical description, at the density functional theory level, of two key processes that are common to electronic devices based on organic semiconductors (such as organic light-emitting diodes, field-effect transistors, and solar cells), namely charge transport and charge injection from electrodes. By using representative examples of current interest, our main goal is to introduce some of the reliable theoretical methodologies that can best depict these processes. We first discuss the evaluation of the microscopic parameters that determine charge-carrier transport in organic molecular crystals, i.e., electronic couplings and electron-vibration couplings. We then examine the electronic structure at interfaces between an organic layer and a metal or conducting oxide electrode, with an emphasis on the work-function modifications induced by the organic layer and on the interfacial energy-level alignments.

  3. The friction behavior of semiconductors Si and GaAs in contact with pure metals

    NASA Technical Reports Server (NTRS)

    Mishina, H.

    1984-01-01

    The friction behavior of the semiconductors silicon and gallium arsenide in contact with pure metals was studied. Five transition and two nontransition metals, titanium, tantalum, nickel, palladium, platinum, copper, and silver, slid on a single crystal silicon (111) surface. Four metals, indium, nickel, copper and silver, slid on a single crystal gallium arsenide (100) surface. Experiments were conducted in room air and in a vacuum of 10 to the minus 7th power N/sq cm (10 to the minus 9th power torr). The results indicate that the sliding of silicon on the transition metals exhibits relatively higher friction than for the nontransition metals in contact with silicon. There is a clear correlation between friction and Schottky barrier height formed at the metal silicon interface for the transition metals. Transition metals with a higher barrier height on silicon had a lower friction. The same effect of barrier height was found for the friction of gallium arsenide in contact with metals.

  4. Giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor

    NASA Astrophysics Data System (ADS)

    Ugeda, Miguel M.; Bradley, Aaron J.; Shi, Su-Fei; da Jornada, Felipe H.; Zhang, Yi; Qiu, Diana Y.; Ruan, Wei; Mo, Sung-Kwan; Hussain, Zahid; Shen, Zhi-Xun; Wang, Feng; Louie, Steven G.; Crommie, Michael F.

    2014-12-01

    Two-dimensional (2D) transition metal dichalcogenides (TMDs) are emerging as a new platform for exploring 2D semiconductor physics. Reduced screening in two dimensions results in markedly enhanced electron-electron interactions, which have been predicted to generate giant bandgap renormalization and excitonic effects. Here we present a rigorous experimental observation of extraordinarily large exciton binding energy in a 2D semiconducting TMD. We determine the single-particle electronic bandgap of single-layer MoSe2 by means of scanning tunnelling spectroscopy (STS), as well as the two-particle exciton transition energy using photoluminescence (PL) spectroscopy. These yield an exciton binding energy of 0.55 eV for monolayer MoSe2 on graphene—orders of magnitude larger than what is seen in conventional 3D semiconductors and significantly higher than what we see for MoSe2 monolayers in more highly screening environments. This finding is corroborated by our ab initio GW and Bethe-Salpeter equation calculations which include electron correlation effects. The renormalized bandgap and large exciton binding observed here will have a profound impact on electronic and optoelectronic device technologies based on single-layer semiconducting TMDs.

  5. Study of gain phenomenon in lateral metal-semiconductor-metal detectors for indirect conversion medical imaging

    NASA Astrophysics Data System (ADS)

    Abbaszadeh, Shiva; Allec, Nicholas; Wang, Kai; Chen, Feng; Karim, Karim S.

    2011-03-01

    Previously, metal-semiconductor-metal (MSM) lateral amorphous selenium (a-Se) detectors have been proposed for indirect detector medical imaging applications. These detectors have raised interest due to their high-speed and photogain. The gain measured from these devices was assumed to have been photoconductive gain; however the origin of this gain was not fully understood. In addition, whether or not there was any presence of photocurrent multiplication gain was not investigated. For integration-type applications photocurrent multiplication gain is desirable since the total collected charge can be greater than the total number of absorbed photons. In order to fully appreciate the value of MSM devices and their benefit for different applications, whether it is counting or integration applications, we need to investigate the responsible mechanisms of the observed response. In this paper, we systematically study, through experimental and theoretical means, the nature of the photoresponse and its responsible mechanisms. This study also exposes the possible means to increase the performance of the device and under what conditions it will be most beneficial.

  6. Effect of realistic metal electronic structure on the lower limit of contact resistivity of epitaxial metal-semiconductor contacts

    SciTech Connect

    Hegde, Ganesh Chris Bowen, R.

    2014-08-04

    The effect of realistic metal electronic structure on the lower limit of resistivity in [100] oriented n-Si is investigated using full band Density Functional Theory and Semi-Empirical Tight Binding calculations. It is shown that the “ideal metal” assumption may fail in some situations and, consequently, underestimate the lower limit of contact resistivity in n-Si by at least an order of magnitude at high doping concentrations. The mismatch in transverse momentum space in the metal and the semiconductor, the so-called “valley filtering effect,” is shown to be sensitive to the details of the transverse boundary conditions for the unit cells used. The results emphasize the need for explicit inclusion of the metal atomic and electronic structure in the atomistic modeling of transport across metal-semiconductor contacts.

  7. Semiconductor-to-metallic flipping in a ZnFe{sub 2}O{sub 4}–graphene based smart nano-system: Temperature/microwave magneto-dielectric spectroscopy

    SciTech Connect

    Ameer, Shahid; Gul, Iftikhar Hussain; Mahmood, Nasir; Mujahid, Muhammad

    2015-01-15

    Zn-(FeO{sub 2}){sub 2}–graphene smart nano-composites were synthesized using a novel modified solvothermal synthesis with different percentages of graphene. The structure of the nanocomposite was confirmed through X-ray diffraction, micro-Raman scattering spectroscopy, Ultraviolet–Visible spectroscopy, and Fourier transform infrared spectroscopy. The structural growth and morphological aspects were analyzed using scanning/transmission electron microscopy, revealing marvelous micro-structural features of the assembled nano-system resembling a maple leaf. To determine the composition, energy dispersive spectroscopy and X-ray photoelectron spectroscopy were used. Microwave magneto-dielectric spectroscopy revealed the improved dielectric properties of the nano-composite compared to those of the parent functional nanocrystals. Temperature gradient dielectric spectroscopy was used over the spectral range from 100 Hz to 5 MHz to reveal the phenomenological effect that the nanosystem flips from its usual semiconductor nature to a metallic nature with sensing temperature. Electrical conductivity and dielectric analysis indicated that the dielectric loss and the dielectric permittivity increased at room temperature. This extraordinary switching capability of the functionalized graphene nanosystem opens up a new dimension for engineering advanced and efficient smart composite materials. - Graphical abstract: Display Omitted - Highlights: • Zn-(FeO{sub 2}){sub 2}–graphene smart nano-composites were synthesized using a novel modified solvothermal synthesis. • The synthesized nano-system exhibits marvelous leaf like microstructure. • These nano-composites show improved magneto dielectric response. • This engineered smart nano-system shows phenomenological flipping from semiconductor like nature to metallic behavior.

  8. Ag-based semiconductor photocatalysts in environmental purification

    NASA Astrophysics Data System (ADS)

    Li, Jiade; Fang, Wen; Yu, Changlin; Zhou, Wanqin; zhu, Lihua; Xie, Yu

    2015-12-01

    Over the past decades, with the fast development of global industrial development, various organic pollutants discharged in water have become a major source of environmental pollution in waste fields. Photocatalysis, as green and environmentally friendly technology, has attracted much attention in pollutants degradation due to its efficient degradation rate. However, the practical application of traditional semiconductor photocatalysts, e.g. TiO2, ZnO, is limited by their weak visible light adsorption due to their wide band gaps. Nowadays, the study in photocatalysts focuses on new and narrow band gap semiconductors. Among them, Ag-based semiconductors as promising visible light-driven photocatalysts have aroused much interesting due to their strong visible light responsibility. Most of Ag-based semiconductors could exhibit high initial photocatalytic activity. But they easy suffer from poor stability because of photochemical corrosion. Design heterojunction, increasing specific surface area, enriching pore structure, regulating morphology, controlling crystal facets, and producing plasmonic effects were considered as the effective strategies to improve the photocatalytic performance of Ag-based photocatalyts. Moreover, combining the superior properties of carbon materials (e.g. carbon quantum dots, carbon nano-tube, carbon nanofibers, graphene) with Ag-based semiconductor could produce high efficient composite photocatalyts.

  9. Long-term research in Japan: amorphous metals, metal oxide varistors, high-power semiconductors and superconducting generators

    SciTech Connect

    Hane, G.J.; Yorozu, M.; Sogabe, T.; Suzuki, S.

    1985-04-01

    The review revealed that significant activity is under way in the research of amorphous metals, but that little fundamental work is being pursued on metal oxide varistors and high-power semiconductors. Also, the investigation of long-term research program plans for superconducting generators reveals that activity is at a low level, pending the recommendations of a study currently being conducted through Japan's Central Electric Power Council.

  10. Semiconductor photoelectrochemistry

    NASA Technical Reports Server (NTRS)

    Buoncristiani, A. M.; Byvik, C. E.

    1983-01-01

    Semiconductor photoelectrochemical reactions are investigated. A model of the charge transport processes in the semiconductor, based on semiconductor device theory, is presented. It incorporates the nonlinear processes characterizing the diffusion and reaction of charge carriers in the semiconductor. The model is used to study conditions limiting useful energy conversion, specifically the saturation of current flow due to high light intensity. Numerical results describing charge distributions in the semiconductor and its effects on the electrolyte are obtained. Experimental results include: an estimate rate at which a semiconductor photoelectrode is capable of converting electromagnetic energy into chemical energy; the effect of cell temperature on the efficiency; a method for determining the point of zero zeta potential for macroscopic semiconductor samples; a technique using platinized titanium dioxide powders and ultraviolet radiation to produce chlorine, bromine, and iodine from solutions containing their respective ions; the photoelectrochemical properties of a class of layered compounds called transition metal thiophosphates; and a technique used to produce high conversion efficiency from laser radiation to chemical energy.

  11. Modeling of metal-ferroelectric-insulator-semiconductor structure considering the effects of interface traps

    NASA Astrophysics Data System (ADS)

    Sun, Jing; Shi, Xiao Rong; Zheng, Xue Jun; Tian, Li; Zhu, Zhe

    2015-06-01

    An improved model, in which the interface traps effects are considered, is developed by combining with quantum mechanical model, dipole switching theory and silicon physics of metal-oxide-semiconductor structure to describe the electrical properties of metal-ferroelectric-insulator-semiconductor (MFIS) structure. Using the model, the effects of the interface traps on the surface potential (ϕSi) of the semiconductor, the low frequency (LF) capacitance-voltage (C-V) characteristics and memory window of MFIS structure are simulated, and the results show that the ϕSi- V and LF C-V curves are shifted toward the positive-voltage direction and the memory window become worse as the density of the interface trap states increases. This paper is expected to provide some guidance to the design and performance improvement of MFIS structure devices. In addition, the improved model can be integrated into electronic design automation (EDA) software for circuit simulation.

  12. Future of Semiconductor Based Thermal Neutron Detectors

    SciTech Connect

    Nikolic, R J; Cheung, C L; Reinhardt, C E; Wang, T F

    2006-02-22

    Thermal neutron detectors have seen only incremental improvements over the last decades. In this paper we overview the current technology of choice for thermal neutron detection--{sup 3}He tubes, which suffer from, moderate to poor fieldability, and low absolute efficiency. The need for improved neutron detection is evident due to this technology gap and the fact that neutrons are a highly specific indicator of fissile material. Recognizing this need, we propose to exploit recent advances in microfabrication technology for building the next generation of semiconductor thermal neutron detectors for national security requirements, for applications requiring excellent fieldability of small devices. We have developed an innovative pathway taking advantage of advanced processing and fabrication technology to produce the proposed device. The crucial advantage of our Pillar Detector is that it can simultaneously meet the requirements of high efficiency and fieldability in the optimized configuration, the detector efficiency could be higher than 70%.

  13. Optical Design of Plant Canopy Measurement System and Fabrication of Two-Dimensional High-Speed Metal-Semiconductor-Metal Photodetector Arrays

    NASA Technical Reports Server (NTRS)

    Sarto, Anthony; VanZeghbroeck, Bart; Vanderbilt, Vern C.

    1996-01-01

    Electrical and optical designs for the prototype plant canopy architecture measurement system, including specified component and parts lists, are presented. Six single Metal-Semiconductor-Metal (MSM) detectors are mounted in high-speed packages.

  14. Observation of quantum oscillation of work function in ultrathin-metal/semiconductor junctions

    SciTech Connect

    Takhar, Kuldeep; Meer, Mudassar; Khachariya, Dolar; Ganguly, Swaroop; Saha, Dipankar

    2015-09-15

    Quantization in energy level due to confinement is generally observed for semiconductors. This property is used for various quantum devices, and it helps to improve the characteristics of conventional devices. Here, the authors have demonstrated the quantum size effects in ultrathin metal (Ni) layers sandwiched between two large band-gap materials. The metal work function is found to oscillate as a function of its thickness. The thermionic emission current bears the signature of the oscillating work function, which has a linear relationship with barrier heights. This methodology allows direct observation of quantum oscillations in metals at room temperature using a Schottky diode and electrical measurements using source-measure-units. The observed phenomena can provide additional mechanism to tune the barrier height of metal/semiconductor junctions, which are used for various electronic devices.

  15. Low resistance barrier layer for isolating, adhering, and passivating copper metal in semiconductor fabrication

    DOEpatents

    Weihs, Timothy P.; Barbee, Jr., Troy W.

    2002-01-01

    Cubic or metastable cubic refractory metal carbides act as barrier layers to isolate, adhere, and passivate copper in semiconductor fabrication. One or more barrier layers of the metal carbide are deposited in conjunction with copper metallizations to form a multilayer characterized by a cubic crystal structure with a strong (100) texture. Suitable barrier layer materials include refractory transition metal carbides such as vanadium carbide (VC), niobium carbide (NbC), tantalum carbide (TaC), chromium carbide (Cr.sub.3 C.sub.2), tungsten carbide (WC), and molybdenum carbide (MoC).

  16. Thermoelectric figure of merit of a material consisting of semiconductor or metal particles

    SciTech Connect

    Kharlamov, V. F.

    2013-07-15

    It is found that the dimensionless thermoelectric figure of merit of a material consisting of a large number of ball-shaped semiconductor or metal particles can be much more than unity. The introduction of an insulator into the space between the particles is shown to sharply increase the power of the converter of heat energy into electric current energy.

  17. Ultrahigh quality factor in a metal-embedded semiconductor microdisk cavity.

    PubMed

    Kurosawa, Hiroyuki; Kumano, Hidekazu; Suemune, Ikuo

    2015-12-15

    We numerically and theoretically investigate electrodynamics of a metal-embedded semiconductor microdisk cavity. The electrodynamics of a cavity mode is discussed from the viewpoint of quantum mechanics, which clarifies the condition for high Q factor. Using numerical calculations, we optimize the cavity structure and show that the Q factor can be increased up to 1,700,000. Our study suggests that the metal-embedded cavity is a promising candidate for cavity quantum electrodynamics (QED) devices. PMID:26670507

  18. Is DNA a metal, semiconductor or insulator? A theoretical approach

    NASA Astrophysics Data System (ADS)

    Rey-Gonzalez, Rafael; Fonseca-Romero, Karen; Plazas, Carlos; Grupo de Óptica e Información Cuántica Team

    Over the last years, scientific interest for designing and making low dimensional electronic devices with traditional or novel materials has been increased. These experimental and theoretical researches in electronic properties at molecular scale are looking for developing efficient devices able to carry out tasks which are currently done by silicon transistors and devices. Among the new materials DNA strands are highlighted, but the experimental results have been contradictories pointing to behaviors as conductor, semiconductor or insulator. To contribute to the understanding of the origin of the disparity of the measurements, we perform a numerical calculation of the electrical conductance of DNA segments, modeled as 1D disordered finite chains. The system is described into a Tight binding model with nearest neighbor interactions and a s orbital per site. Hydration effects are included as random variations of self-energies. The electronic current as a function of applied bias is calculated using Launder formalism, where the transmission probability is determined into the transfer matrix formalism. We find a conductor-to-semiconductor-to-insulator transition as a function of the three effects taken into account: chain size, intrinsic disorder, and hydration We thank Fundación para la Promoción de la Investigación y la Tecnología, Colombia, and Dirección de Investigación de Bogotá, Universidad Nacional de Colombia, for partial financial support.

  19. Semiconductor-based DNA sequencing of histone modification states.

    PubMed

    Cheng, Christine S; Rai, Kunal; Garber, Manuel; Hollinger, Andrew; Robbins, Dana; Anderson, Scott; Macbeth, Alyssa; Tzou, Austin; Carneiro, Mauricio O; Raychowdhury, Raktima; Russ, Carsten; Hacohen, Nir; Gershenwald, Jeffrey E; Lennon, Niall; Nusbaum, Chad; Chin, Lynda; Regev, Aviv; Amit, Ido

    2013-01-01

    The recent development of a semiconductor-based, non-optical DNA sequencing technology promises scalable, low-cost and rapid sequence data production. The technology has previously been applied mainly to genomic sequencing and targeted re-sequencing. Here we demonstrate the utility of Ion Torrent semiconductor-based sequencing for sensitive, efficient and rapid chromatin immunoprecipitation followed by sequencing (ChIP-seq) through the application of sample preparation methods that are optimized for ChIP-seq on the Ion Torrent platform. We leverage this method for epigenetic profiling of tumour tissues. PMID:24157732

  20. Semiconductor-based DNA sequencing of histone modification states

    PubMed Central

    Cheng, Christine S.; Rai, Kunal; Garber, Manuel; Hollinger, Andrew; Robbins, Dana; Anderson, Scott; Macbeth, Alyssa; Tzou, Austin; Carneiro, Mauricio O.; Raychowdhury, Raktima; Russ, Carsten; Hacohen, Nir; Gershenwald, Jeffrey E.; Lennon, Niall; Nusbaum, Chad; Chin, Lynda; Regev, Aviv; Amit, Ido

    2013-01-01

    The recent development of a semiconductor-based, non-optical DNA sequencing technology promises scalable, low-cost and rapid sequence data production. The technology has previously been applied mainly to genomic sequencing and targeted re-sequencing. Here we demonstrate the utility of Ion Torrent semiconductor-based sequencing for sensitive, efficient and rapid chromatin immunoprecipitation followed by sequencing (ChIP-seq) through the application of sample preparation methods that are optimized for ChIP-seq on the Ion Torrent platform. We leverage this method for epigenetic profiling of tumour tissues. PMID:24157732

  1. Key techniques for space-based solar pumped semiconductor lasers

    NASA Astrophysics Data System (ADS)

    He, Yang; Xiong, Sheng-jun; Liu, Xiao-long; Han, Wei-hua

    2014-12-01

    In space, the absence of atmospheric turbulence, absorption, dispersion and aerosol factors on laser transmission. Therefore, space-based laser has important values in satellite communication, satellite attitude controlling, space debris clearing, and long distance energy transmission, etc. On the other hand, solar energy is a kind of clean and renewable resources, the average intensity of solar irradiation on the earth is 1353W/m2, and it is even higher in space. Therefore, the space-based solar pumped lasers has attracted much research in recent years, most research focuses on solar pumped solid state lasers and solar pumped fiber lasers. The two lasing principle is based on stimulated emission of the rare earth ions such as Nd, Yb, Cr. The rare earth ions absorb light only in narrow bands. This leads to inefficient absorption of the broad-band solar spectrum, and increases the system heating load, which make the system solar to laser power conversion efficiency very low. As a solar pumped semiconductor lasers could absorb all photons with energy greater than the bandgap. Thus, solar pumped semiconductor lasers could have considerably higher efficiencies than other solar pumped lasers. Besides, solar pumped semiconductor lasers has smaller volume chip, simpler structure and better heat dissipation, it can be mounted on a small satellite platform, can compose satellite array, which can greatly improve the output power of the system, and have flexible character. This paper summarizes the research progress of space-based solar pumped semiconductor lasers, analyses of the key technologies based on several application areas, including the processing of semiconductor chip, the design of small and efficient solar condenser, and the cooling system of lasers, etc. We conclude that the solar pumped vertical cavity surface-emitting semiconductor lasers will have a wide application prospects in the space.

  2. Π Band Dispersion along Conjugated Organic Nanowires Synthesized on a Metal Oxide Semiconductor.

    PubMed

    Vasseur, Guillaume; Abadia, Mikel; Miccio, Luis A; Brede, Jens; Garcia-Lekue, Aran; de Oteyza, Dimas G; Rogero, Celia; Lobo-Checa, Jorge; Ortega, J Enrique

    2016-05-01

    Surface-confined dehalogenation reactions are versatile bottom-up approaches for the synthesis of carbon-based nanostructures with predefined chemical properties. However, for devices generally requiring low-conductivity substrates, potential applications are so far severely hampered by the necessity of a metallic surface to catalyze the reactions. In this work we report the synthesis of ordered arrays of poly(p-phenylene) chains on the surface of semiconducting TiO2(110) via a dehalogenative homocoupling of 4,4″-dibromoterphenyl precursors. The supramolecular phase is clearly distinguished from the polymeric one using low-energy electron diffraction and scanning tunneling microscopy as the substrate temperature used for deposition is varied. X-ray photoelectron spectroscopy of C 1s and Br 3d core levels traces the temperature of the onset of dehalogenation to around 475 K. Moreover, angle-resolved photoemission spectroscopy and tight-binding calculations identify a highly dispersive band characteristic of a substantial overlap between the precursor's π states along the polymer, considered as the fingerprint of a successful polymerization. Thus, these results establish the first spectroscopic evidence that atomically precise carbon-based nanostructures can readily be synthesized on top of a transition-metal oxide surface, opening the prospect for the bottom-up production of novel molecule-semiconductor devices. PMID:27115554

  3. Π Band Dispersion along Conjugated Organic Nanowires Synthesized on a Metal Oxide Semiconductor

    PubMed Central

    2016-01-01

    Surface-confined dehalogenation reactions are versatile bottom-up approaches for the synthesis of carbon-based nanostructures with predefined chemical properties. However, for devices generally requiring low-conductivity substrates, potential applications are so far severely hampered by the necessity of a metallic surface to catalyze the reactions. In this work we report the synthesis of ordered arrays of poly(p-phenylene) chains on the surface of semiconducting TiO2(110) via a dehalogenative homocoupling of 4,4″-dibromoterphenyl precursors. The supramolecular phase is clearly distinguished from the polymeric one using low-energy electron diffraction and scanning tunneling microscopy as the substrate temperature used for deposition is varied. X-ray photoelectron spectroscopy of C 1s and Br 3d core levels traces the temperature of the onset of dehalogenation to around 475 K. Moreover, angle-resolved photoemission spectroscopy and tight-binding calculations identify a highly dispersive band characteristic of a substantial overlap between the precursor’s π states along the polymer, considered as the fingerprint of a successful polymerization. Thus, these results establish the first spectroscopic evidence that atomically precise carbon-based nanostructures can readily be synthesized on top of a transition-metal oxide surface, opening the prospect for the bottom-up production of novel molecule–semiconductor devices. PMID:27115554

  4. Development of transition-metal doped copper oxide and zinc oxide dilute magnetic semiconductors

    NASA Astrophysics Data System (ADS)

    Ivill, Mathew P.

    The field of spintronics has recently attracted much attention because of its potential to provide new functionalities and enhanced performance in conventional electronic devices. Oxide materials provide a convenient platform to study the spin-based functionality in host semiconducting material. Recent theoretical treatments predict that wide band-gap semiconductors, including ZnO, can exhibit high temperature ferromagnetic ordering when doped with transition metals. This work focused on the possibility of using wide band-gap oxide semiconductors as potential spintronic materials. The structure, magnetic, and electronic transport properties of transition-metal doped ZnO and Cu 2O were investigated. Mn and Co were used as transition metal dopants. Thin films of these materials were fabricated using pulsed laser deposition (PLD). The Mn solubility in Cu2O was found to be small and the precipitation of Mn-oxides was favored at high growth temperatures. Phase pure Mn-doped Cu2O samples were found to be non-magnetic. Samples were p-type with carrier concentrations on the order of 1014-10 16 cm-3. The effects of carrier concentration on the magnetic properties of Mn-doped ZnO were studied using Sn and P as electronic codopants. Sn acts as an n-type dopant providing extra electrons to the ZnO. P acts as a p-type dopant that supplies excess holes to compensate the native electron concentration in ZnO. The electron concentration was decreased using P, but the films remained n-type. An inverse correlation was found between the ferromagnetism and the electron concentration; the ferromagnetic coupling between Mn spins increased with decreasing electron concentration. The nature of ferromagnetism in Co-doped ZnO was also investigated. Ferromagnetism was found in films deposited at 400°C in vacuum, while films deposited in oxygen or at higher temperatures were non-magnetic. Films deposited under vacuum had rather high electron concentrations and were presumably doped with

  5. Chemical reactions at metallic and metal/semiconductor interfaces stimulated by pulsed laser annealing

    NASA Astrophysics Data System (ADS)

    Petit, E. J.; Caudano, R.

    1992-01-01

    Multilayer Al/Sb thin films have been evaporated on GaSb single crystals in ultra-high vacuum and pulsed-laser irradiated in-situ above the energy density threshold for surface melting. Superficial and interfacial chemical reactions have been characterized in-situ by Auger electron spectroscopy; and later, by X-ray photoelectron spectroscopy profiling, Rutherford backscattering spectrometry and scanning electron microscopy. The chemical reaction between the Al and Sb films is considered as a model reaction for laser-assisted synthesis of high-purity intermetallic compounds. The observation of a strong interfacial reaction between the melted film and the substrate is also a subject of great concern for optical data recording and laser alloying of ohmic contacts on semiconductors. We show that a suitable choice of the substrate and adding a low surface tension element into the metallic film can improve its stability during melting, and prevent inhomogeneous reaction and formation of holes, cracks and particles. Finally, other solutions are suggested to improve the control of these reactions.

  6. Anisotropy-based crystalline oxide-on-semiconductor material

    DOEpatents

    McKee, Rodney Allen; Walker, Frederick Joseph

    2000-01-01

    A semiconductor structure and device for use in a semiconductor application utilizes a substrate of semiconductor-based material, such as silicon, and a thin film of a crystalline oxide whose unit cells are capable of exhibiting anisotropic behavior overlying the substrate surface. Within the structure, the unit cells of the crystalline oxide are exposed to an in-plane stain which influences the geometric shape of the unit cells and thereby arranges a directional-dependent quality of the unit cells in a predisposed orientation relative to the substrate. This predisposition of the directional-dependent quality of the unit cells enables the device to take beneficial advantage of characteristics of the structure during operation. For example, in the instance in which the crystalline oxide of the structure is a perovskite, a spinel or an oxide of similarly-related cubic structure, the structure can, within an appropriate semiconductor device, exhibit ferroelectric, piezoelectric, pyroelectric, electro-optic, ferromagnetic, antiferromagnetic, magneto-optic or large dielectric properties that synergistically couple to the underlying semiconductor substrate.

  7. Ring resonator based narrow-linewidth semiconductor lasers

    NASA Technical Reports Server (NTRS)

    Ksendzov, Alexander (Inventor)

    2005-01-01

    The present invention is a method and apparatus for using ring resonators to produce narrow linewidth hybrid semiconductor lasers. According to one embodiment of the present invention, the narrow linewidths are produced by combining the semiconductor gain chip with a narrow pass band external feedback element. The semi conductor laser is produced using a ring resonator which, combined with a Bragg grating, acts as the external feedback element. According to another embodiment of the present invention, the proposed integrated optics ring resonator is based on plasma enhanced chemical vapor deposition (PECVD) SiO.sub.2 /SiON/SiO.sub.2 waveguide technology.

  8. Features of high-frequency measurements of the impedance of metal-insulator-semiconductor structures with an ultrathin oxide

    SciTech Connect

    Goldman, E. I.; Levashova, A. I.; Levashov, S. A.; Chucheva, G. V.

    2015-04-15

    The possibilities of using the data of high-frequency measurements of the impedance of metal-oxide-semiconductor structures with an ultrathin insulating layer for determining the parameters of the semiconductor and the tunneling characteristics of the insulator are considered. If the accuracy of the experiment makes it possible to record both the active and reactive impedance components, the thickness of the surface depletion layer, the resistance of the semiconductor base portion, the differential tunnel conductivity of the insulating layer, and the differential tunneling-stimulated current of the generation of electron-hole pairs are calculated using the values of the capacitance and conduction of the structure measured at two frequencies. In the case, where the values of the active component of the impedance is beyond the accuracy of measurements, analysis of the parameters is possible upon four-frequency organization of the experiment from the values of only the capacitances with an increased accuracy of their measurements. A test for the necessary accuracy of data of such an experiment is formulated. If the test fails, it is possible to determine only the capacitance of the surface depletion layer in the semiconductor and, in this case, it is sufficient to implement only the single-frequency experiment.

  9. Self-aligned epitaxial metal-semiconductor hybrid nanostructures for plasmonics

    SciTech Connect

    Urbanczyk, Adam; Otten, Frank W. M. van; Noetzel, Richard

    2011-06-13

    We demonstrate self-alignment of epitaxial Ag nanocrystals on top of low-density near-surface InAs quantum dots (QDs) grown by molecular beam epitaxy. The Ag nanocrystals support a surface plasmon resonance that can be tuned to the emission wavelength of the QDs. Photoluminescence measurements of such hybrid metal-semiconductor nanostructures reveal large enhancement of the emission intensity. Our concept of epitaxial self-alignment enables the integration of plasmonic functionality with electronic and photonic semiconductor devices operating down to the single QD level.

  10. Enhanced adhesion of films to semiconductors or metals by high energy bombardment

    NASA Technical Reports Server (NTRS)

    Tombrello, Thomas A. (Inventor); Qiu, Yuanxun (Inventor); Mendenhall, Marcus H. (Inventor)

    1985-01-01

    Films (12) of a metal such as gold or other non-insulator materials are firmly bonded to other non-insulators such as semiconductor substrates (10), suitably silicon or gallium arsenide by irradiating the interface with high energy ions. The process results in improved adhesion without excessive doping and provides a low resistance contact to the semiconductor. Thick layers can be bonded by depositing or doping the interfacial surfaces with fissionable elements or alpha emitters. The process can be utilized to apply very small, low resistance electrodes (78) to light-emitting solid state laser diodes (60) to form a laser device 70.

  11. MBE Growth of Ferromagnetic Metal/Compound Semiconductor Heterostructures for Spintronics

    ScienceCinema

    Palmstrom, Chris [University of California, Santa Barbara, California, United States

    2010-01-08

    Electrical transport and spin-dependent transport across ferromagnet/semiconductor contacts is crucial in the realization of spintronic devices. Interfacial reactions, the formation of non-magnetic interlayers, and conductivity mismatch have been attributed to low spin injection efficiency. MBE has been used to grow epitaxial ferromagnetic metal/GA(1-x)AL(x)As heterostructures with the aim of controlling the interfacial structural, electronic, and magnetic properties. In situ, STM, XPS, RHEED and LEED, and ex situ XRD, RBS, TEM, magnetotransport, and magnetic characterization have been used to develop ferromagnetic elemental and metallic compound/compound semiconductor tunneling contacts for spin injection. The efficiency of the spin polarized current injected from the ferromagnetic contact has been determined by measuring the electroluminescence polarization of the light emitted from/GA(1-x)AL(x)As light-emitting diodes as a function of applied magnetic field and temperature. Interfacial reactions during MBE growth and post-growth anneal, as well as the semiconductor device band structure, were found to have a dramatic influence on the measured spin injection, including sign reversal. Lateral spin-transport devices with epitaxial ferromagnetic metal source and drain tunnel barrier contacts have been fabricated with the demonstration of electrical detection and the bias dependence of spin-polarized electron injection and accumulation at the contacts. This talk emphasizes the progress and achievements in the epitaxial growth of a number of ferromagnetic compounds/III-V semiconductor heterostructures and the progress towards spintronic devices.

  12. MBE Growth of Ferromagnetic Metal/Compound Semiconductor Heterostructures for Spintronics

    SciTech Connect

    Palmstrom, Chris

    2009-07-01

    Electrical transport and spin-dependent transport across ferromagnet/semiconductor contacts is crucial in the realization of spintronic devices. Interfacial reactions, the formation of non-magnetic interlayers, and conductivity mismatch have been attributed to low spin injection efficiency. MBE has been used to grow epitaxial ferromagnetic metal/GA(1-x)AL(x)As heterostructures with the aim of controlling the interfacial structural, electronic, and magnetic properties. In situ, STM, XPS, RHEED and LEED, and ex situ XRD, RBS, TEM, magnetotransport, and magnetic characterization have been used to develop ferromagnetic elemental and metallic compound/compound semiconductor tunneling contacts for spin injection. The efficiency of the spin polarized current injected from the ferromagnetic contact has been determined by measuring the electroluminescence polarization of the light emitted from/GA(1-x)AL(x)As light-emitting diodes as a function of applied magnetic field and temperature. Interfacial reactions during MBE growth and post-growth anneal, as well as the semiconductor device band structure, were found to have a dramatic influence on the measured spin injection, including sign reversal. Lateral spin-transport devices with epitaxial ferromagnetic metal source and drain tunnel barrier contacts have been fabricated with the demonstration of electrical detection and the bias dependence of spin-polarized electron injection and accumulation at the contacts. This talk emphasizes the progress and achievements in the epitaxial growth of a number of ferromagnetic compounds/III-V semiconductor heterostructures and the progress towards spintronic devices.

  13. Electrical Characterization of Metal-Ferroelectric-Insulator- Semiconductor having Double Layered Insulator for Memory Applications

    NASA Astrophysics Data System (ADS)

    Ismail, L. N.; Wahid, M. H.; Habibah, Z.; Herman, S. H.; Rozana, M. D.; Rusop, M.

    2014-08-01

    Metal-ferroelectric-insulator-semiconductor (MFIS) devices were successfully fabricated using poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) and poly (methyl methacrylate): titanium dioxide (PMMA:TiO2) nanocomposite as ferroelectric and insulator films, respectively on n-type silicon (n-Si) substrate. Both ferroelectric and insulator films were prepared by sol-gel spin coating method. The electrical behaviour of metal-ferroelectric-metal (MFM) structure with PVDF-TrFE film and metal-insulator- metal (MIM) structure PMMA:TiO2 film exhibited different current characteristics. The capacitance of the MFIS devices was found to be 0.42 and 0.29 nF at frequency of 1kHz and 1 MHz respectively. Meanwhile, the dielectric loss values are constant (~60 × 10-3) in the frequency range from 100 Hz to 100 kHz. I-V results for MFIS are much higher than MIM and MFM is due to there is a trapped holes/electron located at the semiconductor- insulator interface which contributes to high leakage current in the MFIS device. We conclude, although interposing the PMMA :TiO2 nanocomposite insulator layer between the semiconductor and Al electrodes degrades the MFIS performance, nevertheless, they remain sufficiently good for use in organic electronic devices.

  14. Semiconductor-metal transition of Se in Ru-Se Catalyst Nanoparticles

    NASA Astrophysics Data System (ADS)

    Babu, P. K.; Lewera, Adam; Oldfield, Eric; Wieckowski, Andrzej

    2009-03-01

    Ru-Se composite nanoparticles are promising catalysts for the oxygen reduction reaction (ORR) in fuel cells. Though the role of Se in enhancing the chemical stability of Ru nanoparticles is well established, the microscopic nature of Ru-Se interaction was not clearly understood. We carried out a combined investigation of ^77Se NMR and XPS on Ru-Se nanoparticles and our results indicate that Se, a semiconductor in elemental form, becomes metallic when interacting with Ru. ^77Se spin-lattice relaxation rates are found to be proportional to T, the well-known Korringa behavior characteristic of metals. The NMR results are supported by the XPS binding energy shifts which suggest that a possible Ru->Se charge transfer could be responsible for the semiconductor->metal transition of Se which also makes Ru less susceptible to oxidation during ORR.

  15. Using a Semiconductor-to-Metal Transition to Control Optical Transmission through Subwavelength Hole Arrays

    DOE PAGESBeta

    Donev, E. U.; Suh, J. Y.; Lopez, R.; Feldman, L. C.; Haglund, R. F.

    2008-01-01

    We describe a simple configuration in which the extraordinary optical transmission effect through subwavelength hole arrays in noble-metal films can be switched by the semiconductor-to-metal transition in an underlying thin film of vanadium dioxide. In these experiments, the transition is brought about by thermal heating of the bilayer film. The surprising reverse hysteretic behavior of the transmission through the subwavelength holes in the vanadium oxide suggest that this modulation is accomplished by a dielectric-matching condition rather than plasmon coupling through the bilayer film. The results of this switching, including the wavelength dependence, are qualitatively reproduced by a transfer matrix model.more » The prospects for effecting a similar modulation on a much faster time scale by using ultrafast laser pulses to trigger the semiconductor-to-metal transition are also discussed.« less

  16. One-dimensional quantum transport in hybrid metal-semiconductor nanotube systems

    NASA Astrophysics Data System (ADS)

    Gelin, Maxim; Bondarev, Igor

    We study the inter-play between the intrinsic 1D conductance of metallic atomic wires (AWs) and plasmon mediated near-field effects for semiconducting single wall carbon nanotubes (CNs) that encapsulate AWs of finite length. We use the matrix Green's functions formalism to develop an electron transfer theory for such a hybrid quasi-1D metal-semiconductor nanotube system. The theory predicts Fano resonances in electron transmission through the system. That is the AW-CN near-field interaction blocks some of the pristine AW transmission band channels to open up new coherent channels in the CN forbidden gap outside the pristine AW transmission band. This makes the entire hybrid system transparent in the energy domain where neither of the individual pristine constituents, neither AW nor CN, are transparent. The effect can be used to control electron charge transfer in semiconducting CN based devices for nanoscale energy conversion, separation and storage. Nsf-ECCS-1306871 (M.G.), DOE-DE-SC0007117 (I.B.).

  17. Hopping conductivity and insulator-metal transition in films of touching semiconductor nanocrystals

    NASA Astrophysics Data System (ADS)

    Fu, Han; Reich, K. V.; Shklovskii, B. I.

    2016-03-01

    This paper is focused on the variable-range hopping of electrons in semiconductor nanocrystal (NC) films below the critical doping concentration nc at which it becomes metallic. The hopping conductivity is described by the Efros-Shklovskii law, which depends on the localization length of electrons. We study how the localization length grows with the doping concentration n in the film of touching NCs. For that we calculate the electron transfer matrix element t (n ) between neighboring NCs for two models when NCs touch by small facets or just one point. We study two sources of disorder: variations of NC diameters and random Coulomb potentials originating from random numbers of donors in NCs. We use the ratio of t (n ) to the disorder-induced NC level dispersion to find the localization length of electrons due to the multistep elastic co-tunneling process. We found three different phases at n base, and (3) "blinking metal" where the localization length periodically diverges. The first two phases were seen experimentally and we discuss how one can see the more exotic third one. In all three, the localization length diverges at n =nc . This allows us to find nc.

  18. Theoretical analysis of hot electron injection from metallic nanotubes into a semiconductor interface.

    PubMed

    Kumarasinghe, Chathurangi S; Premaratne, Malin; Gunapala, Sarath D; Agrawal, Govind P

    2016-07-21

    Metallic nanostructures under optical illumination can generate a non-equilibrium high-energy electron gas (also known as hot electrons) capable of being injected into neighbouring media over a potential barrier at particle boundaries. The nature of this process is highly nanoparticle shape and size dependent. Here, we have derived an analytical expression for the frequency dependent rate of injection of these energetic electrons from a metallic nanotube into a semiconductor layer in contact with its inner boundary. In our derivation, we have considered the quantum mechanical motion of the electron gas confined by the particle boundaries in determining the electron energy spectrum and wave functions. We present a comprehensive theoretical analysis of how different geometric parameters such as the outer to inner radius ratio, length and thickness of a nanotube and illumination frequency affect the hot electron injection and internal quantum efficiency of the nanotube. We reveal that longer nanotubes with thin shells and high inner to outer radius ratios show better performance at visible and infrared frequencies. Our derivations and results provide the much needed theoretical insight for optimization of thin nanotubes for different hot electron based applications. PMID:27332556

  19. A high pressure low temperature study on rare earth compounds: Semiconductor to metal transition

    NASA Astrophysics Data System (ADS)

    Neuenschwander, J.; Wachter, P.

    1990-01-01

    This work studies the pressure induced semiconductor to metal transition (SMT) in several rare earth compounds. This SMT is accompanied by a valence instability. Single crystalline semiconducting TmSe 1- xTe x, Tm 1- xEu xSe and SmS 1- xSe x alloys are investigated under high pressure at low temperatures. Measurements of electrical resistivity, magnetic susceptibility, neutron diffraction, volume and optical properties are presented and discussed. A very unusual peak structure in the resistivity-pressure relation of TmSe 1- xTe x at low temperatures is observed. A discussion of the novel feature involves the concept of the excitonic insulator and f-d hybridization. The magnetic behavior of the Tm and Eu based compounds is significantly influenced by the SMT. This is thought to be mainly due to the additional coupling between the rare earth moments via free carriers which are present in the metallic state. In SmS 1- xSe x a considerable softening of the lattice is observed before the valence transition occurs. It is speculated that Poisson's ratio might become negative already in the semiconducting state.

  20. A high pressure low temperature study on rare earth compounds: Semiconductor to metal transition

    NASA Astrophysics Data System (ADS)

    Neuenschwander, J.; Wachter, P.

    1989-12-01

    This work studies the pressure induced semiconductor to metal transition (SMT) in several rare earth compounds. This SMT is accompanied by a valence instability. Single crystalline semiconducting TmSe1-xTex, Tm1-xEuxSe and SmS1-xSex alloys are investigated under high pressure at low temperatures. Measurements of electrical resistivity, magnetic susceptibility, neutron diffraction, volume and optical properties are presented and discussed. A very unusual peak structure in the resistivity-pressure relation of TmSe1-xTex at low temperatures is observed. A discussion of the novel feature involves the concept of the excitonic insulator and f-d hybridization. The magnetic behavior of the Tm and Eu based compounds is significantly influenced by the SMT. This is thought to be mainly due to the additional coupling between the rare earth moments via free carriers which are present in the metallic state. In SmS1-xSex a considerable softening of the lattice is observed before the valence transition occurs. It is speculated that Poisson's ratio might become negative already in the semiconducting state.

  1. Space-division optical switches based on semiconductor optical amplifiers

    NASA Astrophysics Data System (ADS)

    Kalman, Robert F.; Kazovsky, Leonid G.; Goodman, Joseph W.

    Benes and distributed gain matrix-vector multiplier (MVM) switches larger than 10 exp 10 x 10 exp can, in principle, be achieved by using semiconductor optical amplifiers (SOA's). In contrast, lumped gain SOA-based MVM switches are limited in size to less than 100 x 100.

  2. Hybrid metal-semiconductor mirror for high power VECSEL

    NASA Astrophysics Data System (ADS)

    Laurain, Alexandre; Gbele, Kokou; Hader, Jorg; Stolz, Wolfgang; Koch, Stephan; Ruiz Perez, Antje; Moloney, Jerome V.

    2016-03-01

    We demonstrate a low thermal impedance hybrid mirror VECSEL. We used only 14 pairs of AlGaAs/AlAs, transparent at the pump wavelength, and we used a patterned mask to deposit pure gold on areas of the chip to be pumped, and Ti/Au on other area to circumvent the poor adhesion of gold on GaAs. A higher gain is observed on an area metallized with pure gold and an output power of 4W was obtained, showing the effectiveness of the metallic mirror and validating the bonding quality. Chip processing and laser characteristics are studied in detail and compared to simulations.

  3. Semiconductor-based, large-area, flexible, electronic devices

    DOEpatents

    Goyal, Amit

    2011-03-15

    Novel articles and methods to fabricate the same resulting in flexible, large-area, triaxially textured, single-crystal or single-crystal-like, semiconductor-based, electronic devices are disclosed. Potential applications of resulting articles are in areas of photovoltaic devices, flat-panel displays, thermophotovoltaic devices, ferroelectric devices, light emitting diode devices, computer hard disc drive devices, magnetoresistance based devices, photoluminescence based devices, non-volatile memory devices, dielectric devices, thermoelectric devices and quantum dot laser devices.

  4. Electrochemistry of Prussian blue films on metal and semiconductor electrodes

    SciTech Connect

    Viehbeck, A.; DeBerry, D.W.

    1985-06-01

    The electrochemical properties of Prussian blue films on Pt and spark anodized n-type TiO/sub 2/ electrodes were investigated. Evidence for four redox states for Prussian blue was obtained. While the oxidation of Everitt's salt to Prussian blue involves the high spin iron atoms, the oxidation of Prussian blue to Berlin green and Berlin green to Prussian yellow involves the low spin hexacyanoferrate groups. The Prussian blue/Everitt's salt redox system (E/sub 0/ = +0.2V vs. SCE) is the most stable and reversible couple. The diffusion coefficients for reduction and oxidation of this redox couple are 5.0 x 10/sup -9/ and 2.7 x 10/sup -9/ cm/sup 2//S, respectively. The photoelectrochromic behavior of Prussian blue on semiconductor TiO/sub 2/ electrodes is discussed. The films deposited on TiO/sub 2/ have short-circuit memory, and lateral color spreading through the film is slow. A light addressable electrochromic display is described.

  5. Passivation of impurities in semiconductors by hydrogen and light metal ions

    NASA Astrophysics Data System (ADS)

    Gislason, Hafliði P.

    1997-01-01

    Books as well as numerous articles have been written about hydrogen passivation in classical semiconductors such as Si and GaAs. The subject has gained a renewed interest recently since hydrogen is widely considered to saturate the hole conductivity of the wide bandgap semiconductors GaN and ZnSe which are currently most promising for blue light emitting devices. Other group-I impurities are capable of compensating the electrical conductivity of semiconductors both through directly neutralising (passivating) the impurity or providing space charge of polarity opposite to that of the dominating one. The paper reviews the similarities and differences between hydrogen and its light metallic neighbour in the periodic table, lithium. Also we provide a comparison with the heavier interstitial copper which is known for its ability to passivate shallow acceptors. Finally fundamental differences between shallow-level and deep level passivation will be addressed.

  6. Fast optical recording media based on semiconductor nanostructures for image recording and processing

    SciTech Connect

    Kasherininov, P. G. Tomasov, A. A.

    2008-11-15

    Fast optical recording media based on semiconductor nanostructures (CdTe, GaAs) for image recording and processing with a speed to 10{sup 6} cycle/s (which exceeds the speed of known recording media based on metal-insulator-semiconductor-(liquid crystal) (MIS-LC) structures by two to three orders of magnitude), a photosensitivity of 10{sup -2}V/cm{sup 2}, and a spatial resolution of 5-10 (line pairs)/mm are developed. Operating principles of nanostructures as fast optical recording media and methods for reading images recorded in such media are described. Fast optical processors for recording images in incoherent light based on CdTe crystal nanostructures are implemented. The possibility of their application to fabricate image correlators is shown.

  7. A Generic Guiding Principle for the Prediction of Metal-Induced Reconstructions of Compound Semiconductor Surfaces

    SciTech Connect

    Yang, Shenyuan; Zhang, Lixin; Chen, Hua; Wang, Enge; Zhang, Zhenyu

    2008-01-01

    We have performed extensive and systematical ab initio calculations to substantiate a recently proposed generalized electron counting (GEC) rule that governs the rich patterns of compound semiconductor reconstruction induced by metal adsorption. In this rule, the metal adsorbates serve as an electron bath, either donating or accepting the right number of electrons, with which the binary host system chooses a specific reconstruction under the classical electron counting rule, and meanwhile, the adsorbates stay in their optimal valency. The GEC rule is applied to different GaAs surfaces deposited by various classes of metal adsorbates, leading to a number of possible reconstructions, which can be further confirmed by first-principles calculations and/or experiments. The alkali metal adsorption on the GaAs(110) surface up to the saturate coverage is a perfect example of the GEC rule. The application of the GEC rule to the prototype system of Mn/GaAs(001) not only predicts possible reconstruction patterns over a wide range of coverage, but also provides an underlying link between the reconstruction structures and the local magnetic moments of the metal adsorbates. In Au/GaAs(100), we demonstrate the application of the GEC rule to those systems where metal adsrobates form covalent bonds with the substrate. The GEC rule, as a generic principle, is expected to be applicable to more metal-adsorbed compound semiconductor surfaces. PACS numbers: 68.35.-p, 68.43.Bc, 75.70.-i

  8. The local metallicity of gadolinium doped compound semiconductors

    NASA Astrophysics Data System (ADS)

    Colón Santana, J. A.; Liu, Pan; Wang, Xianjie; Tang, J.; McHale, S. R.; Wooten, D.; McClory, J. W.; Petrosky, J. C.; Wu, J.; Palai, R.; Losovjy, Ya B.; Dowben, P. A.

    2012-11-01

    The local metallicities of Hf0.97Gd0.03O2, Ga0.97Gd0.03N, Eu0.97Gd0.04O and EuO films were studied through a comparison of the findings from constant initial state spectroscopy using synchrotron light. Resonant enhancements, corresponding to the 4d → 4f transitions of Eu and Gd, were observed in some of the valence band photoemission features. The resonant photoemission intensity enhancements for the Gd 4f photoemission features are far stronger for the more insulating host systems than for the metallic system Eu0.96Gd0.04O. The evidence seems to suggest a correlation between the effective screening in the films and the resonant photoemission process.

  9. A comprehensive study of charge trapping in organic field-effect devices with promising semiconductors and different contact metals by displacement current measurements

    NASA Astrophysics Data System (ADS)

    Bisoyi, Sibani; Rödel, Reinhold; Zschieschang, Ute; Kang, Myeong Jin; Takimiya, Kazuo; Klauk, Hagen; Tiwari, Shree Prakash

    2016-02-01

    A systematic and comprehensive study on the charge-carrier injection and trapping behavior was performed using displacement current measurements in long-channel capacitors based on four promising small-molecule organic semiconductors (pentacene, DNTT, C10-DNTT and DPh-DNTT). In thin-film transistors, these semiconductors showed charge-carrier mobilities ranging from 1.0 to 7.8 cm2 V-1 s-1. The number of charges injected into and extracted from the semiconductor and the density of charges trapped in the device during each measurement were calculated from the displacement current characteristics and it was found that the density of trapped charges is very similar in all devices and of the order 1012 cm-2, despite the fact that the four semiconductors show significantly different charge-carrier mobilities. The choice of the contact metal (Au, Ag, Cu, Pd) was also found to have no significant effect on the trapping behavior.

  10. Semiconductor-halfmetal-metal transition and magnetism of bilayer graphene nanoribbons/hexagonal boron nitride heterostructure

    NASA Astrophysics Data System (ADS)

    Ilyasov, V. V.; Meshi, B. C.; Nguyen, V. C.; Ershov, I. V.; Nguyen, D. C.

    2014-12-01

    The paper presents the results of ab initio study of electronic structure modulation and edge magnetism in the antiferromagnetic (AF) bilayer zigzag graphene nanoribbons (AF-BZGNR)/hexagonal boron nitride (h-BN(0001)) semiconductor heterostructure induced with transverse external electric field (Eext) and nanomechanical compression (extension), performed within the framework of the density functional theory using Grimme's DFT(PBE)-D2 scheme. For the first time we established critical values of Eext and interlayer distance in the bilayer for the BZGNR/h-BN(0001) heterostructure providing for semiconductor-halfmetal-metal phase transition for one of the electron spin configurations. We discovered the effect of preserved local magnetic moment (0.3μB) of edge carbon atoms of the lower (buffer) graphene nanoribbon during nanomechanical uniaxial compression (or extension) of the BZGNR/h-BN(0001) semiconductor heterostructure. It has been demonstrated that magnetic properties of the AF-BZGNR/h-BN(0001) semiconductor heterostructure can be controlled using Eext. In particular, the local magnetic moment of edge carbon atoms decreases by 10% at a critical value of the positive potential. We have established that local magnetic moments and band gaps can be altered in a wide range using nanomechanical uniaxial compression and Eext, thus making the AF-BZGNR/h-BN(0001) semiconductor heterostructure potentially promising for nanosensors, spin filters, and spintronics applications.

  11. Theoretical maximum efficiency of solar energy conversion in plasmonic metal-semiconductor heterojunctions.

    PubMed

    Cushing, Scott K; Bristow, Alan D; Wu, Nianqiang

    2015-11-28

    Plasmonics can enhance solar energy conversion in semiconductors by light trapping, hot electron transfer, and plasmon-induced resonance energy transfer (PIRET). The multifaceted response of the plasmon and multiple interaction pathways with the semiconductor makes optimization challenging, hindering design of efficient plasmonic architectures. Therefore, in this paper we use a density matrix model to capture the interplay between scattering, hot electrons, and dipole-dipole coupling through the plasmon's dephasing, including both the coherent and incoherent dynamics necessary for interactions on the plasmon's timescale. The model is extended to Shockley-Queisser limit calculations for both photovoltaics and solar-to-chemical conversion, revealing the optimal application of each enhancement mechanism based on plasmon energy, semiconductor energy, and plasmon dephasing. The results guide application of plasmonic solar-energy harvesting, showing which enhancement mechanism is most appropriate for a given semiconductor's weakness, and what nanostructures can achieve the maximum enhancement. PMID:26497739

  12. Modeling of Total Ionizing Dose Effects in Advanced Complementary Metal-Oxide-Semiconductor Technologies

    NASA Astrophysics Data System (ADS)

    Sanchez Esqueda, Ivan

    2011-12-01

    The increased use of commercial complementary metal-oxide-semiconductor (CMOS) technologies in harsh radiation environments has resulted in a new approach to radiation effects mitigation. This approach utilizes simulation to support the design of integrated circuits (ICs) to meet targeted tolerance specifications. Modeling the deleterious impact of ionizing radiation on ICs fabricated in advanced CMOS technologies requires understanding and analyzing the basic mechanisms that result in buildup of radiation-induced defects in specific sensitive regions. Extensive experimental studies have demonstrated that the sensitive regions are shallow trench isolation (STI) oxides. Nevertheless, very little work has been done to model the physical mechanisms that result in the buildup of radiation-induced defects and the radiation response of devices fabricated in these technologies. A comprehensive study of the physical mechanisms contributing to the buildup of radiation-induced oxide trapped charges and the generation of interface traps in advanced CMOS devices is presented in this dissertation. The basic mechanisms contributing to the buildup of radiation-induced defects are explored using a physical model that utilizes kinetic equations that captures total ionizing dose (TID) and dose rate effects in silicon dioxide (SiO2). These mechanisms are formulated into analytical models that calculate oxide trapped charge density (Not) and interface trap density (Nit) in sensitive regions of deep-submicron devices. Experiments performed on field-oxide-field-effect-transistors (FOXFETs) and metal-oxide-semiconductor (MOS) capacitors permit investigating TID effects and provide a comparison for the radiation response of advanced CMOS devices. When used in conjunction with closed-form expressions for surface potential, the analytical models enable an accurate description of radiation-induced degradation of transistor electrical characteristics. In this dissertation, the incorporation

  13. Controlled metal-semiconductor sintering/alloying by one-directional reverse illumination

    DOEpatents

    Sopori, Bhushan L.

    1993-01-01

    Metal strips deposited on a top surface of a semiconductor substrate are sintered at one temperature simultaneously with alloying a metal layer on the bottom surface at a second, higher temperature. This simultaneous sintering of metal strips and alloying a metal layer on opposite surfaces of the substrate at different temperatures is accomplished by directing infrared radiation through the top surface to the interface of the bottom surface with the metal layer where the radiation is absorbed to create a primary hot zone with a temperature high enough to melt and alloy the metal layer with the bottom surface of the substrate. Secondary heat effects, including heat conducted through the substrate from the primary hot zone and heat created by infrared radiation reflected from the metal layer to the metal strips, as well as heat created from some primary absorption by the metal strips, combine to create secondary hot zones at the interfaces of the metal strips with the top surface of the substrate. These secondary hot zones are not as hot as the primary hot zone, but they are hot enough to sinter the metal strips to the substrate.

  14. Superatoms and Metal-Semiconductor Motifs for Cluster Materials

    SciTech Connect

    Castleman, A. W.

    2013-10-11

    A molecular understanding of catalysis and catalytically active materials is of fundamental importance in designing new substances for applications in energy and fuels. We have performed reactivity studies and ultrafast ionization and coulomb explosion studies on a variety of catalytically-relevant materials, including transition metal oxides of Fe, Co, Ni, Cu, Ti, V, Nb, and Ta. We demonstrate that differences in charge state, geometry, and elemental composition of clusters of such materials determine chemical reactivity and ionization behavior, crucial steps in improving performance of catalysts.

  15. Metal-free ferromagnetic metal and intrinsic spin semiconductor: two different kinds of SWCNT functionalized BN nanoribbons.

    PubMed

    Lou, Ping

    2015-03-28

    Two different kinds of SWCNT functionalized zigzag edge BN nanoribbons with n chains (n-ZBNNRs), namely, (a) B-edge functionalized by (m,m)SWCNT and N-edge modified with H (nZBNNR-B-(m,m)SWCNTs); and (b) the B-edge modified with H and the N-edge functionalized by (m,m)SWCNT (nZBNNR-N-(m,m)SWCNTs), have been predicted. Amazingly, we find that unlike the semiconducting and nonmagnetic H-modified n-ZBNNRs, the nZBNNR-B-(m,m)SWCNTs are intrinsic ferromagnetic metals, regardless of ribbon widths n and tube diameters (m,m). At a given (m,m), their local magnetic moments, at first, exhibit oscillation with increasing n, whereas when n is larger than 5, they are independent of n. In contrast, unlike the metallic and nonmagnetic (m,m)SWCNTs, the nZBNNR-N-(m,m)SWCNTs are ferromagnetic intrinsic spin-semiconductors with direct band gaps, regardless of n and (m,m). Their local magnetic moments and band gaps are independent of n and (m,m). The DFT calculations reveal that the process of SWCNT functionalization of the n-ZBNNRs does not need any activation energy. Moreover, the formation energies of the SWCNT functionalized n-ZBNNRs are always less than zero. Therefore, the SWCNT functionalized n-ZBNNRs are not only stable, but can also be spontaneously formed. Furthermore, compared with n-ZBNNRs, the SWCNT functionalized n-ZBNNRs show significant improvements in their thermal and mechanical stabilities. Thus, (m,m)SWCNT functionalization of n-ZBNNRs may open new routes toward practical nanoelectronic and optoelectronic as well as spintronic devices based on BNC-based materials. PMID:25721493

  16. Mechanistic Studies of Charge Injection from Metallic Electrodes into Organic Semiconductors Mediated by Ionic Functionalities: Final Report

    SciTech Connect

    Nguyen, Thuc-Quyen; Bazan, Guillermo; Mikhailovsky, Alexander

    2014-04-15

    Metal-organic semiconductor interfaces are important because of their ubiquitous role in determining the performance of modern electronics such as organic light emitting diodes (OLEDs), fuel cells, batteries, field effect transistors (FETs), and organic solar cells. Interfaces between metal electrodes required for external wiring to the device and underlying organic structures directly affect the charge carrier injection/collection efficiency in organic-based electronic devices primarily due to the mismatch between energy levels in the metal and organic semiconductor. Environmentally stable and cost-effective electrode materials, such as aluminum and gold typically exhibit high potential barriers for charge carriers injection into organic devices leading to increased operational voltages in OLEDs and FETs and reduced charge extraction in photovoltaic devices. This leads to increased power consumption by the device, reduced overall efficiency, and decreased operational lifetime. These factors represent a significant obstacle for development of next generation of cheap and energy-efficient components based on organic semiconductors. It has been noticed that introduction of organic materials with conjugated backbone and ionic pendant groups known as conjugated poly- and oligoelectrolytes (CPEs and COEs), enables one to reduce the potential barriers at the metal-organic interface and achieve more efficient operation of a device, however exact mechanisms of the phenomenon have not been understood. The goal of this project was to delineate the function of organic semiconductors with ionic groups as electron injection layers. The research incorporated a multidisciplinary approach that encompassed the creation of new materials, novel processing techniques, examination of fundamental electronic properties and the incorporation of the resulting knowledgebase into development of novel organic electronic devices with increased efficiency, environmental stability, and reduced

  17. Uniform Doping in Quantum-Dots-Based Dilute Magnetic Semiconductor.

    PubMed

    Saha, Avijit; Shetty, Amitha; Pavan, A R; Chattopadhyay, Soma; Shibata, Tomohiro; Viswanatha, Ranjani

    2016-07-01

    Effective manipulation of magnetic spin within a semiconductor leading to a search for ferromagnets with semiconducting properties has evolved into an important field of dilute magnetic semiconductors (DMS). Although a lot of research is focused on understanding the still controversial origin of magnetism, efforts are also underway to develop new materials with higher magnetic temperatures for spintronics applications. However, so far, efforts toward quantum-dots(QDs)-based DMS materials are plagued with problems of phase separation, leading to nonuniform distribution of dopant ions. In this work, we have developed a strategy to synthesize highly crystalline, single-domain DMS system starting from a small magnetic core and allowing it to diffuse uniformly inside a thick CdS semiconductor matrix and achieve DMS QDs. X-ray absorption fine structure (XAFS) spectroscopy and energy-dispersive X-ray spectroscopy-scanning transmission electron microscopy (STEM-EDX) indicates the homogeneous distribution of magnetic impurities inside the semiconductor QDs leading to superior magnetic property. Further, the versatility of this technique was demonstrated by obtaining ultra large particles (∼60 nm) with uniform doping concentration as well as demonstrating the high quality magnetic response. PMID:27295453

  18. Metal-inducd assembly of a semiconductor-island lattice: Getruncated pyramids on Au-patterned Si

    SciTech Connect

    Robinson, J.T.; Liddle, J.A.; Minor, A.; Radmilovic, V.; Yi,D.O.; Greaney, P.A.; Long, K.N.; Chrzan, D.C.; Dubon, O.D.

    2005-08-28

    We report the two-dimensional alignment of semiconductor islands using rudimentary metal patterning to control nucleation and growth. In the Ge on Si system, a square array of sub-micron Au dots on the Si (001) surface induces the assembly of deposited Ge adatoms into an extensive island lattice. Remarkably, these highly ordered Ge islands form between the patterned Au dots and are characterized by a unique truncated pyramidal shape. A model based on patterned diffusion barriers explains the observed ordering and establishes general criteria for the broader applicability of such a directed assembly process to quantum dot ordering.

  19. Metal-induced assembly of a semiconductor island lattice: Ge truncated pyramids on Au-patterned Si.

    PubMed

    Robinson, J T; Liddle, J A; Minor, A; Radmilovic, V; Yi, D O; Greaney, P Alex; Long, K N; Chrzan, D C; Dubon, O D

    2005-10-01

    We report the two-dimensional alignment of semiconductor islands using rudimentary metal patterning to control nucleation and growth. In the Ge on Si system, a square array of submicron Au dots on the Si (001) surface induces the assembly of deposited Ge adatoms into an extensive island lattice. Remarkably, these highly ordered Ge islands form between the patterned Au dots and are characterized by a unique truncated pyramidal shape. A model based on patterned diffusion barriers explains the observed ordering and establishes general criteria for the broader applicability of such a directed assembly process to quantum dot ordering. PMID:16218739

  20. Silicon Metal-oxide-semiconductor Quantum Dots for Single-electron Pumping.

    PubMed

    Rossi, Alessandro; Tanttu, Tuomo; Hudson, Fay E; Sun, Yuxin; Möttönen, Mikko; Dzurak, Andrew S

    2015-01-01

    As mass-produced silicon transistors have reached the nano-scale, their behavior and performances are increasingly affected, and often deteriorated, by quantum mechanical effects such as tunneling through single dopants, scattering via interface defects, and discrete trap charge states. However, progress in silicon technology has shown that these phenomena can be harnessed and exploited for a new class of quantum-based electronics. Among others, multi-layer-gated silicon metal-oxide-semiconductor (MOS) technology can be used to control single charge or spin confined in electrostatically-defined quantum dots (QD). These QD-based devices are an excellent platform for quantum computing applications and, recently, it has been demonstrated that they can also be used as single-electron pumps, which are accurate sources of quantized current for metrological purposes. Here, we discuss in detail the fabrication protocol for silicon MOS QDs which is relevant to both quantum computing and quantum metrology applications. Moreover, we describe characterization methods to test the integrity of the devices after fabrication. Finally, we give a brief description of the measurement set-up used for charge pumping experiments and show representative results of electric current quantization. PMID:26067215

  1. Integrating Partial Polarization into a Metal-Ferroelectric-Semiconductor Field Effect Transistor Model

    NASA Technical Reports Server (NTRS)

    MacLeod, Todd C.; Ho, Fat Duen

    1999-01-01

    The ferroelectric channel in a Metal-Ferroelectric-Semiconductor Field Effect Transistor (MFSFET) can partially change its polarization when the gate voltage near the polarization threshold voltage. This causes the MFSFET Drain current to change with repeated pulses of the same gate voltage near the polarization threshold voltage. A previously developed model [11, based on the Fermi-Dirac function, assumed that for a given gate voltage and channel polarization, a sin-le Drain current value would be generated. A study has been done to characterize the effects of partial polarization on the Drain current of a MFSFET. These effects have been described mathematically and these equations have been incorporated into a more comprehensive mathematical model of the MFSFET. The model takes into account the hysteresis nature of the MFSFET and the time dependent decay as well as the effects of partial polarization. This model defines the Drain current based on calculating the degree of polarization from previous gate pulses, the present Gate voltage, and the amount of time since the last Gate volta-e pulse.

  2. Progress in complementary metal-oxide-semiconductor silicon photonics and optoelectronic integrated circuits

    NASA Astrophysics Data System (ADS)

    Hongda, Chen; Zan, Zhang; Beiju, Huang; Luhong, Mao; Zanyun, Zhang

    2015-12-01

    Silicon photonics is an emerging competitive solution for next-generation scalable data communications in different application areas as high-speed data communication is constrained by electrical interconnects. Optical interconnects based on silicon photonics can be used in intra/inter-chip interconnects, board-to-board interconnects, short-reach communications in datacenters, supercomputers and long-haul optical transmissions. In this paper, we present an overview of recent progress in silicon optoelectronic devices and optoelectronic integrated circuits (OEICs) based on a complementary metal-oxide-semiconductor-compatible process, and focus on our research contributions. The silicon optoelectronic devices and OEICs show good characteristics, which are expected to benefit several application domains, including communication, sensing, computing and nonlinear systems. Project supported by the National Basic Research Program of China (No. 2011CBA00608), the National Natural Science Foundation of China (Nos. 61178051, 61321063, 61335010, 61178048, 61275169), and the National High Technology Research and Development Program of China (Nos. 2013AA013602, 2013AA031903, 2013AA032204).

  3. Vertically integrated, three-dimensional nanowire complementary metal-oxide-semiconductor circuits.

    PubMed

    Nam, SungWoo; Jiang, Xiaocheng; Xiong, Qihua; Ham, Donhee; Lieber, Charles M

    2009-12-15

    Three-dimensional (3D), multi-transistor-layer, integrated circuits represent an important technological pursuit promising advantages in integration density, operation speed, and power consumption compared with 2D circuits. We report fully functional, 3D integrated complementary metal-oxide-semiconductor (CMOS) circuits based on separate interconnected layers of high-mobility n-type indium arsenide (n-InAs) and p-type germanium/silicon core/shell (p-Ge/Si) nanowire (NW) field-effect transistors (FETs). The DC voltage output (V(out)) versus input (V(in)) response of vertically interconnected CMOS inverters showed sharp switching at close to the ideal value of one-half the supply voltage and, moreover, exhibited substantial DC gain of approximately 45. The gain and the rail-to-rail output switching are consistent with the large noise margin and minimal static power consumption of CMOS. Vertically interconnected, three-stage CMOS ring oscillators were also fabricated by using layer-1 InAs NW n-FETs and layer-2 Ge/Si NW p-FETs. Significantly, measurements of these circuits demonstrated stable, self-sustained oscillations with a maximum frequency of 108 MHz, which represents the highest-frequency integrated circuit based on chemically synthesized nanoscale materials. These results highlight the flexibility of bottom-up assembly of distinct nanoscale materials and suggest substantial promise for 3D integrated circuits. PMID:19940239

  4. Silicon Metal-oxide-semiconductor Quantum Dots for Single-electron Pumping

    PubMed Central

    Rossi, Alessandro; Tanttu, Tuomo; Hudson, Fay E.; Sun, Yuxin; Möttönen, Mikko; Dzurak, Andrew S.

    2015-01-01

    As mass-produced silicon transistors have reached the nano-scale, their behavior and performances are increasingly affected, and often deteriorated, by quantum mechanical effects such as tunneling through single dopants, scattering via interface defects, and discrete trap charge states. However, progress in silicon technology has shown that these phenomena can be harnessed and exploited for a new class of quantum-based electronics. Among others, multi-layer-gated silicon metal-oxide-semiconductor (MOS) technology can be used to control single charge or spin confined in electrostatically-defined quantum dots (QD). These QD-based devices are an excellent platform for quantum computing applications and, recently, it has been demonstrated that they can also be used as single-electron pumps, which are accurate sources of quantized current for metrological purposes. Here, we discuss in detail the fabrication protocol for silicon MOS QDs which is relevant to both quantum computing and quantum metrology applications. Moreover, we describe characterization methods to test the integrity of the devices after fabrication. Finally, we give a brief description of the measurement set-up used for charge pumping experiments and show representative results of electric current quantization. PMID:26067215

  5. Method of plasma etching Ga-based compound semiconductors

    SciTech Connect

    Qiu, Weibin; Goddard, Lynford L.

    2012-12-25

    A method of plasma etching Ga-based compound semiconductors includes providing a process chamber and a source electrode adjacent to the process chamber. The process chamber contains a sample comprising a Ga-based compound semiconductor. The sample is in contact with a platen which is electrically connected to a first power supply, and the source electrode is electrically connected to a second power supply. The method includes flowing SiCl.sub.4 gas into the chamber, flowing Ar gas into the chamber, and flowing H.sub.2 gas into the chamber. RF power is supplied independently to the source electrode and the platen. A plasma is generated based on the gases in the process chamber, and regions of a surface of the sample adjacent to one or more masked portions of the surface are etched to create a substantially smooth etched surface including features having substantially vertical walls beneath the masked portions.

  6. Metal-Insulator-Semiconductor Diode Consisting of Two-Dimensional Nanomaterials.

    PubMed

    Jeong, Hyun; Oh, Hye Min; Bang, Seungho; Jeong, Hyeon Jun; An, Sung-Jin; Han, Gang Hee; Kim, Hyun; Yun, Seok Joon; Kim, Ki Kang; Park, Jin Cheol; Lee, Young Hee; Lerondel, Gilles; Jeong, Mun Seok

    2016-03-01

    We present a novel metal-insulator-semiconductor (MIS) diode consisting of graphene, hexagonal BN, and monolayer MoS2 for application in ultrathin nanoelectronics. The MIS heterojunction structure was fabricated by vertically stacking layered materials using a simple wet chemical transfer method. The stacking of each layer was confirmed by confocal scanning Raman spectroscopy and device performance was evaluated using current versus voltage (I-V) and photocurrent measurements. We clearly observed better current rectification and much higher current flow in the MIS diode than in the p-n junction and the metal-semiconductor diodes made of layered materials. The I-V characteristic curve of the MIS diode indicates that current flows mainly across interfaces as a result of carrier tunneling. Moreover, we observed considerably high photocurrent from the MIS diode under visible light illumination. PMID:26886870

  7. Field-induced activation of metal oxide semiconductor for low temperature flexible transparent electronic device applications

    NASA Astrophysics Data System (ADS)

    Pudasaini, Pushpa Raj; Noh, Joo Hyon; Wong, Anthony; Haglund, Amada; Ward, Thomas Zac; Mandrus, David; Rack, Philip

    Amorphous metal-oxide semiconductors have been extensively studied as an active channel material in thin film transistors due to their high carrier mobility, and excellent large-area uniformity. Here, we report the athermal activation of amorphous indium gallium zinc oxide semiconductor channels by an electric field-induced oxygen migration via gating through an ionic liquid. Using field-induced activation, a transparent flexible thin film transistor is demonstrated on a polyamide substrate with transistor characteristics having a current ON-OFF ratio exceeding 108, and saturation field effect mobility of 8.32 cm2/(V.s) without a post-deposition thermal treatment. This study demonstrates the potential of field-induced activation as an athermal alternative to traditional post-deposition thermal annealing for metal oxide electronic devices suitable for transparent and flexible polymer substrates. Materials Science and Technology Division, ORBL, Oak Ridge, TN 37831, USA.

  8. Intrinsic Perturbation of the Landau Levels in Metals and Semiconductors at Low Temperatures

    NASA Astrophysics Data System (ADS)

    Awobode, Ayodeji

    2009-03-01

    The de Haas--van Alphen effect in non-superconducting metals and semiconductors at very low temperatures is proposed as a test of an intrinsic perturbative term which appears in the Landau equation sequel to the modification of the Pauli equation. Corrections to the frequency (or period) of the de Haas--van Alphen oscillation in metals is calculated and shown to depend on the Fermi energy and the measured anomalous part of the electron magnetic moment. Precision measurement of the magneto-optical properties which arise from the motion of electrons in binary semiconductors placed in a weak magnetic field is also proposed as a means of observing very small changes in the.

  9. DNA detection using a complementary metal-oxide semiconductor ring oscillator circuit

    NASA Astrophysics Data System (ADS)

    Kocanda, Martin; Abdel-Motaleb, Ibrahim

    2010-10-01

    A DNA detection scheme has been implemented that utilizes a simple complementary metal-oxide semiconductor (CMOS) ring oscillator circuit. The detector oscillates at a fundamental frequency when using a nonhybridized single-strand DNA probe layer. Upon hybridization with a complimentary DNA strand, the oscillator output exhibits an increased frequency shift, indicating a genetic match. The probe assembly consists of a p-GaAs substrate containing a pulsed laser deposition-applied barium strontium titanate layer and an overlying sodium dodecyl sulfate lipid layer that serves to anchor a functionalized oligonucleotide probe. The oscillator circuit consisting of cascaded discrete complimentary n-channel and p-channel metal-oxide-semiconductor field-effect transistors was implemented using passive components arranged in a T-network to provide the associated fundamental time constant.

  10. INSTRUMENTS AND METHODS OF INVESTIGATION: Scanning tunneling microscopy of fullerenes on metal and semiconductor surfaces

    NASA Astrophysics Data System (ADS)

    Bakhtizin, Raouf Z.; Hashizume, T.; Wang, W.-D.; Sakurai, Toshio

    1997-03-01

    The current state of the ultra-high vacuum scanning tunneling microscopy (STM) of fullerene molecules is reviewed with the use of the authors' work. We focus our work on absorption and reaction of the C60 and C70 fullerenes, separately or in mixture, with semiconductor [Si(111)-7×7 and Si(100)-2×1] and metal [Cu(111)-1×1 and Ag(111)-1×1] surfaces. By using the STM, the adsorption geometry and the corresponding reconstruction are directly observed on these surfaces, and the intramolecular structures are revealed in high resolution STM images which are analyzed theoretically within the local charge distribution model. Results on the ordered growth of fullerene films on metal and semiconductor surfaces are presented and discussed.

  11. Effect of Temperature on GaGdO/GaN Metal Oxide Semiconductor Field Effect Transistors

    SciTech Connect

    Abernathy, C.R.; Baca, A.; Chu, S.N.G.; Hong, M.; Lothian, J.R.; Marcus, M.A.; Pearton, S.J.; Ren, F.; Schurman, M.J.

    1998-10-14

    GaGdO was deposited on GaN for use as a gate dielectric in order to fabricate a depletion metal oxide semiconductor field effect transistor (MOSFET). This is the fmt demonstration of such a device in the III-Nitride system. Analysis of the effect of temperature on the device shows that gate leakage is significantly reduced at elevated temperature relative to a conventional metal semiconductor field effeet transistor (MESFET) fabricated on the same GaN layer. MOSFET device operation in fact improved upon heating to 400 C. Modeling of the effeet of temperature on contact resistance suggests that the improvement is due to a reduction in the parasitic resistances present in the device.

  12. All-semiconductor metamaterial-based optical circuit board at the microscale

    SciTech Connect

    Min, Li; Huang, Lirong

    2015-07-07

    The newly introduced metamaterial-based optical circuit, an analogue of electronic circuit, is becoming a forefront topic in the fields of electronics, optics, plasmonics, and metamaterials. However, metals, as the commonly used plasmonic elements in an optical circuit, suffer from large losses at the visible and infrared wavelengths. We propose here a low-loss, all-semiconductor metamaterial-based optical circuit board at the microscale by using interleaved intrinsic GaAs and doped GaAs, and present the detailed design process for various lumped optical circuit elements, including lumped optical inductors, optical capacitors, optical conductors, and optical insulators. By properly combining these optical circuit elements and arranging anisotropic optical connectors, we obtain a subwavelength optical filter, which can always hold band-stop filtering function for various polarization states of the incident electromagnetic wave. All-semiconductor optical circuits may provide a new opportunity in developing low-power and ultrafast components and devices for optical information processing.

  13. Decoration of diatom biosilica with noble metal and semiconductor nanoparticles (<10 nm): assembly, characterization, and applications.

    PubMed

    Jantschke, Anne; Herrmann, Anne-Kristin; Lesnyak, Vladimir; Eychmüller, Alexander; Brunner, Eike

    2012-01-01

    Diatom-templated noble metal (Ag, Pt, Au) and semiconductor (CdTe) nanoparticle arrays were synthesized by the attachment of prefabricated nanoparticles of defined size. Two different attachment techniques-layer-by-layer deposition and covalent linking-could successfully be applied. The synthesized arrays were shown to be useful for surface-enhanced Raman spectroscopy (SERS) of components, for catalysis, and for improved image quality in scanning electron microscopy (SEM). PMID:22102484

  14. Modular synthesis of a dual metal-dual semiconductor nano-heterostructure

    SciTech Connect

    Amirav, Lilac; Oba, Fadekemi; Aloni, Shaul; Alivisatos, A. Paul

    2015-04-29

    Reported is the design and modular synthesis of a dual metal-dual semiconductor heterostructure with control over the dimensions and placement of its individual components. Analogous to molecular synthesis, colloidal synthesis is now evolving into a series of sequential synthetic procedures with separately optimized steps. Here we detail the challenges and parameters that must be considered when assembling such a multicomponent nanoparticle, and their solutions.

  15. 1/f noise in semiconductor and metal nanocrystal solids

    SciTech Connect

    Liu, Heng Lhuillier, Emmanuel Guyot-Sionnest, Philippe

    2014-04-21

    Electrical 1/f noise is measured in thin films of CdSe, CdSe/CdS, ZnO, HgTe quantum dots and Au nanocrystals. The 1/f noise, normalized per nanoparticle, shows no systematic dependence on the nanoparticle material and the coupling material. However, over 10 orders of magnitude, it correlates well with the nearest neighbor conductance suggesting some universal magnitude of the 1/f noise in these granular conductors. In the hopping regime, the main mechanism of 1/f noise is determined to be mobility fluctuated. In the metallic regime obtained with gold nanoparticle films, the noise drops to a similar level as bulk gold films and with a similar temperature dependence.

  16. Electronic Characterization of Au/DNA/ITO Metal-Semiconductor-Metal Diode and Its Application as a Radiation Sensor.

    PubMed

    Al-Ta'ii, Hassan Maktuff Jaber; Periasamy, Vengadesh; Amin, Yusoff Mohd

    2016-01-01

    Deoxyribonucleic acid or DNA molecules expressed as double-stranded (DSS) negatively charged polymer plays a significant role in electronic states of metal/silicon semiconductor structures. Electrical parameters of an Au/DNA/ITO device prepared using self-assembly method was studied by using current-voltage (I-V) characteristic measurements under alpha bombardment at room temperature. The results were analyzed using conventional thermionic emission model, Cheung and Cheung's method and Norde's technique to estimate the barrier height, ideality factor, series resistance and Richardson constant of the Au/DNA/ITO structure. Besides demonstrating a strongly rectifying (diode) characteristic, it was also observed that orderly fluctuations occur in various electrical parameters of the Schottky structure. Increasing alpha radiation effectively influences the series resistance, while the barrier height, ideality factor and interface state density parameters respond linearly. Barrier height determined from I-V measurements were calculated at 0.7284 eV for non-radiated, increasing to about 0.7883 eV in 0.036 Gy showing an increase for all doses. We also demonstrate the hypersensitivity phenomena effect by studying the relationship between the series resistance for the three methods, the ideality factor and low-dose radiation. Based on the results, sensitive alpha particle detectors can be realized using Au/DNA/ITO Schottky junction sensor. PMID:26799703

  17. Electronic Characterization of Au/DNA/ITO Metal-Semiconductor-Metal Diode and Its Application as a Radiation Sensor

    PubMed Central

    Al-Ta’ii, Hassan Maktuff Jaber; Periasamy, Vengadesh; Amin, Yusoff Mohd

    2016-01-01

    Deoxyribonucleic acid or DNA molecules expressed as double-stranded (DSS) negatively charged polymer plays a significant role in electronic states of metal/silicon semiconductor structures. Electrical parameters of an Au/DNA/ITO device prepared using self-assembly method was studied by using current–voltage (I-V) characteristic measurements under alpha bombardment at room temperature. The results were analyzed using conventional thermionic emission model, Cheung and Cheung’s method and Norde’s technique to estimate the barrier height, ideality factor, series resistance and Richardson constant of the Au/DNA/ITO structure. Besides demonstrating a strongly rectifying (diode) characteristic, it was also observed that orderly fluctuations occur in various electrical parameters of the Schottky structure. Increasing alpha radiation effectively influences the series resistance, while the barrier height, ideality factor and interface state density parameters respond linearly. Barrier height determined from I–V measurements were calculated at 0.7284 eV for non-radiated, increasing to about 0.7883 eV in 0.036 Gy showing an increase for all doses. We also demonstrate the hypersensitivity phenomena effect by studying the relationship between the series resistance for the three methods, the ideality factor and low-dose radiation. Based on the results, sensitive alpha particle detectors can be realized using Au/DNA/ITO Schottky junction sensor. PMID:26799703

  18. Effect of barrier height on friction behavior of the semiconductors silicon and gallium arsenide in contact with pure metals

    NASA Technical Reports Server (NTRS)

    Mishina, H.; Buckley, D. H.

    1984-01-01

    Friction experiments were conducted for the semiconductors silicon and gallium arsenide in contact with pure metals. Polycrystalline titanium, tantalum, nickel, palladium, and platinum were made to contact a single crystal silicon (111) surface. Indium, nickel, copper, and silver were made to contact a single crystal gallium arsenide (100) surface. Sliding was conducted both in room air and in a vacuum of 10 to the minus 9th power torr. The friction of semiconductors in contact with metals depended on a Schottky barrier height formed at the metal semiconductor interface. Metals with a higher barrier height on semiconductors gave lower friction. The effect of the barrier height on friction behavior for argon sputtered cleaned surfaces in vacuum was more specific than that for the surfaces containing films in room air. With a silicon surface sliding on titanium, many silicon particles back transferred. In contrast, a large quantity of indium transferred to the gallium arsenide surface.

  19. Modeling electrochemical deposition inside nanotubes to obtain metal-semiconductor multiscale nanocables or conical nanopores.

    PubMed

    Lebedev, Konstantin; Mafé, Salvador; Stroeve, Pieter

    2005-08-01

    Nanocables with a radial metal-semiconductor heterostructure have recently been prepared by electrochemical deposition inside metal nanotubes. First, a bare nanoporous polycarbonate track-etched membrane is coated uniformly with a metal film by electroless deposition. The film forms a working electrode for further deposition of a semiconductor layer that grows radially inside the nanopore when the deposition rate is slow. We propose a new physical model for the nanocable synthesis and study the effects of the deposited species concentration, potential-dependent reaction rate, and nanopore dimensions on the electrochemical deposition. The problem involves both axial diffusion through the nanopore and radial transport to the nanopore surface, with a surface reaction rate that depends on the axial position and the time. This is so because the radial potential drop across the deposited semiconductor layer changes with the layer thickness through the nanopore. Since axially uniform nanocables are needed for most applications, we consider the relative role of reaction and axial diffusion rates on the deposition process. However, in those cases where partial, empty-core deposition should be desirable (e.g., for producing conical nanopores to be used in single nanoparticle detection), we give conditions where asymmetric geometries can be experimentally realized. PMID:16852830

  20. Cu2O-based solar cells using oxide semiconductors

    NASA Astrophysics Data System (ADS)

    Minami, Tadatsugu; Nishi, Yuki; Miyata, Toshihiro

    2016-01-01

    We describe significant improvements of the photovoltaic properties that were achieved in Al-doped ZnO (AZO)/n-type oxide semiconductor/p-type Cu2O heterojunction solar cells fabricated using p-type Cu2O sheets prepared by thermally oxidizing Cu sheets. The multicomponent oxide thin film used as the n-type semiconductor layer was prepared with various chemical compositions on non-intentionally heated Cu2O sheets under various deposition conditions using a pulsed laser deposition method. In Cu2O-based heterojunction solar cells fabricated using various ternary compounds as the n-type oxide thin-film layer, the best photovoltaic performance was obtained with an n-ZnGa2O4 thin-film layer. In most of the Cu2O-based heterojunction solar cells using multicomponent oxides composed of combinations of various binary compounds, the obtained photovoltaic properties changed gradually as the chemical composition was varied. However, with the ZnO-MgO and Ga2O3-Al2O3 systems, higher conversion efficiencies (η) as well as a high open circuit voltage (Voc) were obtained by using a relatively small amount of MgO or Al2O3, e.g., (ZnO)0.91-(MgO)0.09 and (Ga2O3)0.975-(Al2O3)0.025, respectively. When Cu2O-based heterojunction solar cells were fabricated using Al2O3-Ga2O3-MgO-ZnO (AGMZO) multicomponent oxide thin films deposited with metal atomic ratios of 10, 60, 10 and 20 at.% for the Al, Ga, Mg and Zn, respectively, a high Voc of 0.98 V and an η of 4.82% were obtained. In addition, an enhanced η and an improved fill factor could be achieved in AZO/n-type multicomponent oxide/p-type Cu2O heterojunction solar cells fabricated using Na-doped Cu2O (Cu2O:Na) sheets that featured a resistivity controlled by optimizing the post-annealing temperature and duration. Consequently, an η of 6.25% and a Voc of 0.84 V were obtained in a MgF2/AZO/n-(Ga2O3-Al2O3)/p-Cu2O:Na heterojunction solar cell fabricated using a Cu2O:Na sheet with a resistivity of approximately 10 Ω·cm and a (Ga0.975Al0

  1. Thermoelectric properties of zinc based pnictide semiconductors

    NASA Astrophysics Data System (ADS)

    Sreeparvathy, P. C.; Kanchana, V.; Vaitheeswaran, G.

    2016-02-01

    We report a detailed first principles density functional calculations to understand the electronic structure and transport properties of Zn-based pnictides ZnXPn2 (X: Si, Ge, and Sn; Pn: P and As) and ZnSiSb2. The electronic properties calculated using Tran-Blaha modified Becke-Johnson functional reveals the semi-conducting nature, and the resulting band gaps are in good agreement with experimental and other theoretical reports. We find a mixture of heavy and light bands in the band structure which is an advantage for good thermoelectric (TE) properties. The calculated transport properties unveils the favour p-type conduction in ZnXP2 (X: Si, Ge, and Sn) and n-type conduction in ZnGeP2 and ZnSiAs2. Comparison of transport properties of Zn-based pnictides with the prototype chalcopyrite thermoelectric materials implies that the thermopower values of the investigated compounds to be higher when compared with the prototype chalcopyrite thermoelectric materials, together with the comparable values for electrical conductivity scaled by relaxation time. In addition to this, Zn-based pnictides are found to possess higher thermopower than well known traditional TE materials at room temperature and above which motivates further research in these compounds.

  2. Method of plasma etching GA-based compound semiconductors

    SciTech Connect

    Qiu, Weibin; Goddard, Lynford L.

    2013-01-01

    A method of plasma etching Ga-based compound semiconductors includes providing a process chamber and a source electrode adjacent thereto. The chamber contains a Ga-based compound semiconductor sample in contact with a platen which is electrically connected to a first power supply, and the source electrode is electrically connected to a second power supply. SiCl.sub.4 and Ar gases are flowed into the chamber. RF power is supplied to the platen at a first power level, and RF power is supplied to the source electrode. A plasma is generated. Then, RF power is supplied to the platen at a second power level lower than the first power level and no greater than about 30 W. Regions of a surface of the sample adjacent to one or more masked portions of the surface are etched at a rate of no more than about 25 nm/min to create a substantially smooth etched surface.

  3. Semiconductor-Nanocrystals-Based White Light-Emitting Diodes

    SciTech Connect

    Dai, Quanqin; Duty, Chad E; Hu, Michael Z.

    2010-01-01

    In response to the demands for energy and the concerns of global warming and climate change, energy efficient and environmentally friendly solid-state lighting, such as white lightemitting diodes (WLEDs), is considered to be the most promising and suitable light source. Because of their small size, high efficiency, and long lifetime, WLEDs based on colloidal semiconductor nanocrystals (or quantum dots) are emerging as a completely new technology platform for the development of flat-panel displays and solid-state lighting, exhibiting the potential to replace the conventionally used incandescent and fluorescent lamps. This replacement can cut the ever-increasing level of energy consumption, solve the problem of rapidly depleting fossil fuel reserves, and improve the quality of the global environment. In this review, the recent progress in semiconductor-nanocrystals-based WLEDs is highlighted, the different approaches for generating white light are compared, and the benefits and challenges of the solid-state lighting technology are discussed.

  4. Semiconductor Nanocrystals-Based White Light Emitting Diodes

    SciTech Connect

    Dai, Quanqin; Hu, Michael Z.; Duty, Chad E

    2010-01-01

    In response to the demands for energy and the concerns of global warming and climate change, energy efficient and environmentally friendly solid state lighting, such as white light emitting diodes (WLEDs), is considered to be the most promising and suitable light source. Because of their small size, high efficiency, and long lifetime, WLEDs based on colloidal semiconductor nanocrystals (or quantum dots) are emerging as a completely new technology platform for the development of flat-panel displays and solid state lighting, exhibiting the potential to replace the conventionally used incandescent and fluorescent lamps. This replacement could cut the ever-increasing energy consumption, solve the problem of rapidly depleting fossil fuel reserves, and improve the quality of the global environment. In this review, we highlight the recent progress in semiconductor nanocrystals-based WLEDs, compare different approaches for generating white light, and discuss the benefits and challenges of the solid state lighting technology.

  5. A Low-Leakage Epitaxial High-κ Gate Oxide for Germanium Metal-Oxide-Semiconductor Devices.

    PubMed

    Hu, Chengqing; McDaniel, Martin D; Jiang, Aiting; Posadas, Agham; Demkov, Alexander A; Ekerdt, John G; Yu, Edward T

    2016-03-01

    Germanium (Ge)-based metal-oxide-semiconductor field-effect transistors are a promising candidate for high performance, low power electronics at the 7 nm technology node and beyond. However, the availability of high quality gate oxide/Ge interfaces that provide low leakage current density and equivalent oxide thickness (EOT), robust scalability, and acceptable interface state density (Dit) has emerged as one of the most challenging hurdles in the development of such devices. Here we demonstrate and present detailed electrical characterization of a high-κ epitaxial oxide gate stack based on crystalline SrHfO3 grown on Ge (001) by atomic layer deposition. Metal-oxide-Ge capacitor structures show extremely low gate leakage, small and scalable EOT, and good and reducible Dit. Detailed growth strategies and postgrowth annealing schemes are demonstrated to reduce Dit. The physical mechanisms behind these phenomena are studied and suggest approaches for further reduction of Dit. PMID:26859048

  6. Van der Waals metal-semiconductor junction: Weak Fermi level pinning enables effective tuning of Schottky barrier

    DOE PAGESBeta

    Liu, Yuanyue; Stradins, Paul; Wei, Su -Huai

    2016-04-22

    Two-dimensional (2D) semiconductors have shown great potential for electronic and optoelectronic applications. However, their development is limited by a large Schottky barrier (SB) at the metal-semiconductor junction (MSJ), which is difficult to tune by using conventional metals because of the effect of strong Fermi level pinning (FLP). We show that this problem can be overcome by using 2D metals, which are bounded with 2D semiconductors through van der Waals (vdW) interactions. This success relies on a weak FLP at the vdW MSJ, which is attributed to the suppression of metal-induced gap states. Consequently, the SB becomes tunable and can vanishmore » with proper 2D metals (for example, H-NbS2). This work not only offers new insights into the fundamental properties of heterojunctions but also uncovers the great potential of 2D metals for device applications.« less

  7. Van der Waals metal-semiconductor junction: Weak Fermi level pinning enables effective tuning of Schottky barrier

    PubMed Central

    Liu, Yuanyue; Stradins, Paul; Wei, Su-Huai

    2016-01-01

    Two-dimensional (2D) semiconductors have shown great potential for electronic and optoelectronic applications. However, their development is limited by a large Schottky barrier (SB) at the metal-semiconductor junction (MSJ), which is difficult to tune by using conventional metals because of the effect of strong Fermi level pinning (FLP). We show that this problem can be overcome by using 2D metals, which are bounded with 2D semiconductors through van der Waals (vdW) interactions. This success relies on a weak FLP at the vdW MSJ, which is attributed to the suppression of metal-induced gap states. Consequently, the SB becomes tunable and can vanish with proper 2D metals (for example, H-NbS2). This work not only offers new insights into the fundamental properties of heterojunctions but also uncovers the great potential of 2D metals for device applications. PMID:27152360

  8. Modeling small-signal response of GaN-based metal-insulator-semiconductor high electron mobility transistor gate stack in spill-over regime: Effect of barrier resistance and interface states

    NASA Astrophysics Data System (ADS)

    Capriotti, M.; Lagger, P.; Fleury, C.; Oposich, M.; Bethge, O.; Ostermaier, C.; Strasser, G.; Pogany, D.

    2015-01-01

    We provide theoretical and simulation analysis of the small signal response of SiO2/AlGaN/GaN metal insulator semiconductor (MIS) capacitors from depletion to spill over region, where the AlGaN/SiO2 interface is accumulated with free electrons. A lumped element model of the gate stack, including the response of traps at the III-N/dielectric interface, is proposed and represented in terms of equivalent parallel capacitance, Cp, and conductance, Gp. Cp -voltage and Gp -voltage dependences are modelled taking into account bias dependent AlGaN barrier dynamic resistance Rbr and the effective channel resistance. In particular, in the spill-over region, the drop of Cp with the frequency increase can be explained even without taking into account the response of interface traps, solely by considering the intrinsic response of the gate stack (i.e., no trap effects) and the decrease of Rbr with the applied forward bias. Furthermore, we show the limitations of the conductance method for the evaluation of the density of interface traps, Dit, from the Gp/ω vs. angular frequency ω curves. A peak in Gp/ω vs. ω occurs even without traps, merely due to the intrinsic frequency response of gate stack. Moreover, the amplitude of the Gp/ω vs. ω peak saturates at high Dit, which can lead to underestimation of Dit. Understanding the complex interplay between the intrinsic gate stack response and the effect of interface traps is relevant for the development of normally on and normally off MIS high electron mobility transistors with stable threshold voltage.

  9. Modeling small-signal response of GaN-based metal-insulator-semiconductor high electron mobility transistor gate stack in spill-over regime: Effect of barrier resistance and interface states

    SciTech Connect

    Capriotti, M. E-mail: dionyz.pogany@tuwien.ac.at; Fleury, C.; Oposich, M.; Bethge, O.; Strasser, G.; Pogany, D. E-mail: dionyz.pogany@tuwien.ac.at; Lagger, P.; Ostermaier, C.

    2015-01-14

    We provide theoretical and simulation analysis of the small signal response of SiO{sub 2}/AlGaN/GaN metal insulator semiconductor (MIS) capacitors from depletion to spill over region, where the AlGaN/SiO{sub 2} interface is accumulated with free electrons. A lumped element model of the gate stack, including the response of traps at the III-N/dielectric interface, is proposed and represented in terms of equivalent parallel capacitance, C{sub p}, and conductance, G{sub p}. C{sub p} -voltage and G{sub p} -voltage dependences are modelled taking into account bias dependent AlGaN barrier dynamic resistance R{sub br} and the effective channel resistance. In particular, in the spill-over region, the drop of C{sub p} with the frequency increase can be explained even without taking into account the response of interface traps, solely by considering the intrinsic response of the gate stack (i.e., no trap effects) and the decrease of R{sub br} with the applied forward bias. Furthermore, we show the limitations of the conductance method for the evaluation of the density of interface traps, D{sub it}, from the G{sub p}/ω vs. angular frequency ω curves. A peak in G{sub p}/ω vs. ω occurs even without traps, merely due to the intrinsic frequency response of gate stack. Moreover, the amplitude of the G{sub p}/ω vs. ω peak saturates at high D{sub it}, which can lead to underestimation of D{sub it}. Understanding the complex interplay between the intrinsic gate stack response and the effect of interface traps is relevant for the development of normally on and normally off MIS high electron mobility transistors with stable threshold voltage.

  10. Ultrasensitive NO2 Sensor Based on Ohmic Metal-Semiconductor Interfaces of Electrolytically Exfoliated Graphene/Flame-Spray-Made SnO2 Nanoparticles Composite Operating at Low Temperatures.

    PubMed

    Tammanoon, Nantikan; Wisitsoraat, Anurat; Sriprachuabwong, Chakrit; Phokharatkul, Ditsayut; Tuantranont, Adisorn; Phanichphant, Sukon; Liewhiran, Chaikarn

    2015-11-01

    In this work, flame-spray-made undoped SnO2 nanoparticles were loaded with 0.1-5 wt % electrolytically exfoliated graphene and systematically studied for NO2 sensing at low working temperatures. Characterizations by X-ray diffraction, transmission/scanning electron microscopy, and Raman and X-ray photoelectron spectroscopy indicated that high-quality multilayer graphene sheets with low oxygen content were widely distributed within spheriodal nanoparticles having polycrystalline tetragonal SnO2 phase. The 10-20 μm thick sensing films fabricated by spin coating on Au/Al2O3 substrates were tested toward NO2 at operating temperatures ranging from 25 to 350 °C in dry air. Gas-sensing results showed that the optimal graphene loading level of 0.5 wt % provided an ultrahigh response of 26,342 toward 5 ppm of NO2 with a short response time of 13 s and good recovery stabilization at a low optimal operating temperature of 150 °C. In addition, the optimal sensor also displayed high sensor response and relatively short response time of 171 and 7 min toward 5 ppm of NO2 at room temperature (25 °C). Furthermore, the sensors displayed very high NO2 selectivity against H2S, NH3, C2H5OH, H2, and H2O. Detailed mechanisms for the drastic NO2 response enhancement by graphene were proposed on the basis of the formation of graphene-undoped SnO2 ohmic metal-semiconductor junctions and accessible interfaces of graphene-SnO2 nanoparticles. Therefore, the electrolytically exfoliated graphene-loaded FSP-made SnO2 sensor is a highly promising candidate for fast, sensitive, and selective detection of NO2 at low operating temperatures. PMID:26479951

  11. Identifying airborne metal particles sources near an optoelectronic and semiconductor industrial park

    NASA Astrophysics Data System (ADS)

    Chen, Ho-Wen; Chen, Wei-Yea; Chang, Cheng-Nan; Chuang, Yen-Hsun; Lin, Yu-Hao

    2016-06-01

    The recently developed Central Taiwan Science Park (CTSP) in central Taiwan is home to an optoelectronic and semiconductor industrial cluster. Therefore, exploring the elemental compositions and size distributions of airborne particles emitted from the CTSP would help to prevent pollution. This study analyzed size-fractionated metal-rich particle samples collected in upwind and downwind areas of CTSP during Jan. and Oct. 2013 by using micro-orifice uniform deposited impactor (MOUDI). Correlation analysis, hierarchical cluster analysis and particle mass-size distribution analysis are performed to identify the source of metal-rich particle near the CTSP. Analyses of elemental compositions and particle size distributions emitted from the CTSP revealed that the CTSP emits some metals (V, As, In Ga, Cd and Cu) in the ultrafine particles (< 1 μm). The statistical analysis combines with the particle mass-size distribution analysis could provide useful source identification information. In airborne particles with the size of 0.32 μm, Ga could be a useful pollution index for optoelectronic and semiconductor emission in the CTSP. Meanwhile, the ratios of As/Ga concentration at the particle size of 0.32 μm demonstrates that humans near the CTSP would be potentially exposed to GaAs ultrafine particles. That is, metals such as Ga and As and other metals that are not regulated in Taiwan are potentially harmful to human health.

  12. THz semiconductor-based front-end receiver technology for space applications

    NASA Technical Reports Server (NTRS)

    Mehdi, Imran; Siegel, Peter

    2004-01-01

    Advances in the design and fabrication of very low capacitance planar Schottky diodes and millimeter-wave power amplifiers, more accurate device and circuit models for commercial 3-D electromagnetic simulators, and the availability of both MEMS and high precision metal machining, have enabled RF engineers to extend traditional waveguide-based sensor and source technologies well into the TI-Iz frequency regime. This short paper will highlight recent progress in realizing THz space-qualified receiver front-ends based on room temperature semiconductor devices.

  13. Monolithically Integrated Metal/Semiconductor Tunnel Junction Nanowire Light-Emitting Diodes.

    PubMed

    Sadaf, S M; Ra, Y H; Szkopek, T; Mi, Z

    2016-02-10

    We have demonstrated for the first time an n(++)-GaN/Al/p(++)-GaN backward diode, wherein an epitaxial Al layer serves as the tunnel junction. The resulting p-contact free InGaN/GaN nanowire light-emitting diodes (LEDs) exhibited a low turn-on voltage (∼2.9 V), reduced resistance, and enhanced power, compared to nanowire LEDs without the use of Al tunnel junction or with the incorporation of an n(++)-GaN/p(++)-GaN tunnel junction. This unique Al tunnel junction overcomes some of the critical issues related to conventional GaN-based tunnel junction designs, including stress relaxation, wide depletion region, and light absorption, and holds tremendous promise for realizing low-resistivity, high-brightness III-nitride nanowire LEDs in the visible and deep ultraviolet spectral range. Moreover, the demonstration of monolithic integration of metal and semiconductor nanowire heterojunctions provides a seamless platform for realizing a broad range of multifunctional nanoscale electronic and photonic devices. PMID:26812264

  14. GMAG Dissertation Award Talk: Zero-moment Half-Metallic Ferrimagnetic Semiconductors

    NASA Astrophysics Data System (ADS)

    Jamer, Michelle E.

    2015-03-01

    Low- and zero-moment half-metallic ferrimagnetic semiconductors have been proposed for advanced applications, such as nonvolatile RAM memory and quantum computing. These inverse-Heusler materials could be used to generate spin-polarized electron or hole currents without the associated harmful fringing magnetic fields. Such materials are expected to exhibit low to zero magnetic moment at room temperature, which makes them well-positioned for future spin-based devices. However, these compounds have been shown to suffer from disorder. This work focuses on the synthesis of these compounds and the investigation of their structural, magnetic, and transport properties. Cr2CoGa and Mn3Al thin films were synthesized by molecular beam epitaxy, and V3Al and Cr2CoAl were synthesized via arc-melting. Rietveld analysis was used to determine the degree of ordering in the sublattices as a function of annealing. The atomic moments were measured by X-ray magnetic circular and linear dichroism confirmed antiferromagnetic alignment of sublattices and the desired near-zero moment in several compounds. In collaboration with George E. Sterbinsky, Photon Sciences Directorate, Brookhaven National Laboratory; Dario Arena Photon Sciences Directorate, Brookhaven National Laboratory; Laura H. Lewis, Chemical Engineering, Northeastern University; and Don Heiman, Physics, Northeastern University. NSF-ECCS-1402738, NSF-DMR-0907007.

  15. Origin of microwave noise from an n-channel metal-oxide-semiconductor field effect transistor

    NASA Astrophysics Data System (ADS)

    Pantisano, Luigi; Cheung, K. P.

    2002-12-01

    The physics of noise is a complex subject. It is often difficult to clearly identify the physical origin of the observed noise. Electronic noise at microwave frequencies is technologically very important and has been extensively studied. While it is well known that many physical phenomena give rise to output current fluctuations (i.e., noise) in a metal-oxide-semiconductor field effect transistor (MOSFET), few physical phenomena have a time constant that can contribute in the microwave range. Current physical models of MOSFET microwave noise are all based on thermal agitation of electrons (thermal noise). However, what is the correct temperature (lattice or electron) to use in the noise calculation is an ongoing debate in the literature. All the modeling efforts have been using noise measured from pristine devices as a test for validity. In this work, we studied the n-MOSFET microwave noise as a function of electrical stress induced degradation. Our experiments thus introduced a new dimension in the noise behavior study. The results of our experiments cannot be explained by any of the current existing models. All existing models discounted flicker noise as being too small at microwave frequency. Our experimental results compel us to reexamine the validity of this common assumption. While we are not quite able to prove conclusively, our evidences are clearly leaning toward defect-induced fluctuation (flicker noise) as the origin of microwave noise in a n-MOSFET

  16. Fabrication of Back-Side Illuminated Complementary Metal Oxide Semiconductor Image Sensor Using Compliant Bump

    NASA Astrophysics Data System (ADS)

    Naoya Watanabe,; Isao Tsunoda,; Takayuki Takao,; Koichiro Tanaka,; Tanemasa Asano,

    2010-04-01

    We fabricated a back-side illuminated (BSI) complementary metal oxide semiconductor (CMOS) image sensor in which a very-thin BSI photodiode array chip was stacked on a CMOS read-out circuit chip by compliant bumps. Cone-shaped bumps made of Au were prepared as the compliant bumps. The base diameter was 10-12 μm and the height was 9-10 μm. To fabricate the BSI CMOS image sensor, we developed a novel thin-chip assembly process. The key features of the process are as follows: preparation of a photodiode array wafer and a CMOS read-out circuit wafer, Au cone bump formation, bonding to support glass, thinning of the photodiode array wafer to 21 μm, through silicon via (TSV) formation using Cu electroplating, formation of back-side electrodes, transfer of the photodiode array wafer to a polymer support tape, dicing of the photodiode array wafer, separation of support tape, formation of Ni-Au bumps, dicing of CMOS read-out circuit wafer, and three-dimensional (3D) chip-stacking. The BSI CMOS image sensor thus fabricated has the following specifications: number of active pixels is 16,384 (128 × 128), photodiode size is approximately 18 μm square, photodiode pitch is 24 μm, and fill factor is approximately 55%. No defects were observed in the obtained image frames.

  17. Fabrication of Back-Side Illuminated Complementary Metal Oxide Semiconductor Image Sensor Using Compliant Bump

    NASA Astrophysics Data System (ADS)

    Watanabe, Naoya; Tsunoda, Isao; Takao, Takayuki; Tanaka, Koichiro; Asano, Tanemasa

    2010-04-01

    We fabricated a back-side illuminated (BSI) complementary metal oxide semiconductor (CMOS) image sensor in which a very-thin BSI photodiode array chip was stacked on a CMOS read-out circuit chip by compliant bumps. Cone-shaped bumps made of Au were prepared as the compliant bumps. The base diameter was 10-12 µm and the height was 9-10 µm. To fabricate the BSI CMOS image sensor, we developed a novel thin-chip assembly process. The key features of the process are as follows: preparation of a photodiode array wafer and a CMOS read-out circuit wafer, Au cone bump formation, bonding to support glass, thinning of the photodiode array wafer to 21 µm, through silicon via (TSV) formation using Cu electroplating, formation of back-side electrodes, transfer of the photodiode array wafer to a polymer support tape, dicing of the photodiode array wafer, separation of support tape, formation of Ni-Au bumps, dicing of CMOS read-out circuit wafer, and three-dimensional (3D) chip-stacking. The BSI CMOS image sensor thus fabricated has the following specifications: number of active pixels is 16,384 (128 ×128), photodiode size is approximately 18 µm square, photodiode pitch is 24 µm, and fill factor is approximately 55%. No defects were observed in the obtained image frames.

  18. Novel optoelectronic devices based on single semiconductor nanowires (nanobelts)

    PubMed Central

    2012-01-01

    Semiconductor nanowires (NWs) or nanobelts (NBs) have attracted more and more attention due to their potential application in novel optoelectronic devices. In this review, we present our recent work on novel NB photodetectors, where a three-terminal metal–semiconductor field-effect transistor (MESFET) device structure was exploited. In contrast to the common two-terminal NB (NW) photodetectors, the MESFET-based photodetector can make a balance among overall performance parameters, which is desired for practical device applications. We also present our recent work on graphene nanoribbon/semiconductor NW (SNW) heterojunction light-emitting diodes (LEDs). Herein, by taking advantage of both graphene and SNWs, we have fabricated, for the first time, the graphene-based nano-LEDs. This achievement opens a new avenue for developing graphene-based nano-electroluminescence devices. Moreover, the novel graphene/SNW hybrid devices can also find use in other applications, such as high-sensitivity sensor and transparent flexible devices in the future. PMID:22501032

  19. Semiconductor wire array structures, and solar cells and photodetectors based on such structures

    DOEpatents

    Kelzenberg, Michael D.; Atwater, Harry A.; Briggs, Ryan M.; Boettcher, Shannon W.; Lewis, Nathan S.; Petykiewicz, Jan A.

    2014-08-19

    A structure comprising an array of semiconductor structures, an infill material between the semiconductor materials, and one or more light-trapping elements is described. Photoconverters and photoelectrochemical devices based on such structure also described.

  20. Cross-plane thermal conductivity of (Ti,W)N/(Al,Sc)N metal/semiconductor superlattices

    NASA Astrophysics Data System (ADS)

    Saha, Bivas; Koh, Yee Rui; Comparan, Jonathan; Sadasivam, Sridhar; Schroeder, Jeremy L.; Garbrecht, Magnus; Mohammed, Amr; Birch, Jens; Fisher, Timothy; Shakouri, Ali; Sands, Timothy D.

    2016-01-01

    Reduction of cross-plane thermal conductivity and understanding of the mechanisms of heat transport in nanostructured metal/semiconductor superlattices are crucial for their potential applications in thermoelectric and thermionic energy conversion devices, thermal management systems, and thermal barrier coatings. We have developed epitaxial (Ti,W)N/(Al,Sc)N metal/semiconductor superlattices with periodicity ranging from 1 nm to 240 nm that show significantly lower thermal conductivity compared to the parent TiN/(Al,Sc)N superlattice system. The (Ti,W)N/(Al,Sc)N superlattices grow with [001] orientation on the MgO(001) substrates with well-defined coherent layers and are nominally single crystalline with low densities of extended defects. Cross-plane thermal conductivity (measured by time-domain thermoreflectance) decreases with an increase in the superlattice interface density in a manner that is consistent with incoherent phonon boundary scattering. Thermal conductivity values saturate at 1.7 W m-1K-1 for short superlattice periods possibly due to a delicate balance between long-wavelength coherent phonon modes and incoherent phonon scattering from heavy tungsten atomic sites and superlattice interfaces. First-principles density functional perturbation theory based calculations are performed to model the vibrational spectrum of the individual component materials, and transport models are used to explain the interface thermal conductance across the (Ti,W)N/(Al,Sc)N interfaces as a function of periodicity. The long-wavelength coherent phonon modes are expected to play a dominant role in the thermal transport properties of the short-period superlattices. Our analysis of the thermal transport properties of (Ti,W)N/(Al,Sc)N metal/semiconductor superlattices addresses fundamental questions about heat transport in multilayer materials.

  1. An electrodeposited inhomogeneous metal-insulator-semiconductor junction for efficient photoelectrochemical water oxidation.

    PubMed

    Hill, James C; Landers, Alan T; Switzer, Jay A

    2015-11-01

    The photoelectrochemical splitting of water into hydrogen and oxygen requires a semiconductor to absorb light and generate electron-hole pairs, and a catalyst to enhance the kinetics of electron transfer between the semiconductor and solution. A crucial question is how this catalyst affects the band bending in the semiconductor, and, therefore, the photovoltage of the cell. We introduce a simple and inexpensive electrodeposition method to produce an efficient n-Si/SiOx/Co/CoOOH photoanode for the photoelectrochemical oxidation of water to oxygen. The photoanode functions as a solid-state, metal-insulator-semiconductor photovoltaic cell with spatially non-uniform barrier heights in series with a low overpotential water-splitting electrochemical cell. The barrier height is a function of the Co coverage; it increases from 0.74 eV for a thick, continuous film to 0.91 eV for a thin, inhomogeneous film that has not reached coalescence. The larger barrier height leads to a 360 mV photovoltage enhancement relative to a solid-state Schottky barrier. PMID:26366847

  2. An electrodeposited inhomogeneous metal-insulator-semiconductor junction for efficient photoelectrochemical water oxidation

    NASA Astrophysics Data System (ADS)

    Hill, James C.; Landers, Alan T.; Switzer, Jay A.

    2015-11-01

    The photoelectrochemical splitting of water into hydrogen and oxygen requires a semiconductor to absorb light and generate electron-hole pairs, and a catalyst to enhance the kinetics of electron transfer between the semiconductor and solution. A crucial question is how this catalyst affects the band bending in the semiconductor, and, therefore, the photovoltage of the cell. We introduce a simple and inexpensive electrodeposition method to produce an efficient n-Si/SiOx/Co/CoOOH photoanode for the photoelectrochemical oxidation of water to oxygen. The photoanode functions as a solid-state, metal-insulator-semiconductor photovoltaic cell with spatially non-uniform barrier heights in series with a low overpotential water-splitting electrochemical cell. The barrier height is a function of the Co coverage; it increases from 0.74 eV for a thick, continuous film to 0.91 eV for a thin, inhomogeneous film that has not reached coalescence. The larger barrier height leads to a 360 mV photovoltage enhancement relative to a solid-state Schottky barrier.

  3. High-temperature ferromagnetism in transition metal implanted wide-bandgap semiconductors

    NASA Astrophysics Data System (ADS)

    Raley, Jeremy A.

    The field of spin transport electronics (spintronics) is a viable candidate for advancing computing and communication technologies. Material with both semiconductor and magnetic properties, which is commonly called a dilute magnetic semiconductor (DMS), will prove most useful in the fabrication of spintronic devices. In order to produce a DMS at above room temperature, transition metals (TMs) were implanted into host semiconductors of p-GaN, Al0.35Ga0.65N, or ZnO. Magnetic hysteresis measurements using a superconducting quantum interference device (SQUID) magnetometer show that some of the material combinations clearly exhibit ferromagnetism above room temperature. The most promising materials for creating spintronic devices using ion implantation are p-GaN:Mn, Al0.35Ga0.65N:Cr, and Fe-implanted ZnO nanotips on Al2O3. Temperature-dependent magnetization measurements confirm that indications of ferromagnetism are due to DMS behavior. Photo- and cathodoluminescence measurements show that implantation damage is recovered and the implanted TMs are incorporated into the semiconductor. As progress is made toward realizing practical spintronic devices, the work reported here will be useful for determining material combinations and implantation conditions that will yield the needed materials.

  4. Charge transport and mobility engineering in two-dimensional transition metal chalcogenide semiconductors.

    PubMed

    Li, Song-Lin; Tsukagoshi, Kazuhito; Orgiu, Emanuele; Samorì, Paolo

    2016-01-01

    Two-dimensional (2D) van der Waals semiconductors represent the thinnest, air stable semiconducting materials known. Their unique optical, electronic and mechanical properties hold great potential for harnessing them as key components in novel applications for electronics and optoelectronics. However, the charge transport behavior in 2D semiconductors is more susceptible to external surroundings (e.g. gaseous adsorbates from air and trapped charges in substrates) and their electronic performance is generally lower than corresponding bulk materials due to the fact that the surface and bulk coincide. In this article, we review recent progress on the charge transport properties and carrier mobility engineering of 2D transition metal chalcogenides, with a particular focus on the markedly high dependence of carrier mobility on thickness. We unveil the origin of this unique thickness dependence and elaborate the devised strategies to master it for carrier mobility optimization. Specifically, physical and chemical methods towards the optimization of the major factors influencing the extrinsic transport such as electrode/semiconductor contacts, interfacial Coulomb impurities and atomic defects are discussed. In particular, the use of ad hoc molecules makes it possible to engineer the interface with the dielectric and heal the vacancies in such materials. By casting fresh light on the theoretical and experimental studies, we provide a guide for improving the electronic performance of 2D semiconductors, with the ultimate goal of achieving technologically viable atomically thin (opto)electronics. PMID:26593874

  5. Optically induced transport through semiconductor-based molecular electronics

    SciTech Connect

    Li, Guangqi; Seideman, Tamar; Fainberg, Boris D.

    2015-04-21

    A tight binding model is used to investigate photoinduced tunneling current through a molecular bridge coupled to two semiconductor electrodes. A quantum master equation is developed within a non-Markovian theory based on second-order perturbation theory with respect to the molecule-semiconductor electrode coupling. The spectral functions are generated using a one dimensional alternating bond model, and the coupling between the molecule and the electrodes is expressed through a corresponding correlation function. Since the molecular bridge orbitals are inside the bandgap between the conduction and valence bands, charge carrier tunneling is inhibited in the dark. Subject to the dipole interaction with the laser field, virtual molecular states are generated via the absorption and emission of photons, and new tunneling channels open. Interesting phenomena arising from memory are noted. Such a phenomenon could serve as a switch.

  6. Optically induced transport through semiconductor-based molecular electronics

    NASA Astrophysics Data System (ADS)

    Li, Guangqi; Fainberg, Boris D.; Seideman, Tamar

    2015-04-01

    A tight binding model is used to investigate photoinduced tunneling current through a molecular bridge coupled to two semiconductor electrodes. A quantum master equation is developed within a non-Markovian theory based on second-order perturbation theory with respect to the molecule-semiconductor electrode coupling. The spectral functions are generated using a one dimensional alternating bond model, and the coupling between the molecule and the electrodes is expressed through a corresponding correlation function. Since the molecular bridge orbitals are inside the bandgap between the conduction and valence bands, charge carrier tunneling is inhibited in the dark. Subject to the dipole interaction with the laser field, virtual molecular states are generated via the absorption and emission of photons, and new tunneling channels open. Interesting phenomena arising from memory are noted. Such a phenomenon could serve as a switch.

  7. Dilute Magnetic Semiconductor and Half-Metal Behaviors in 3d Transition-Metal Doped Black and Blue Phosphorenes: A First-Principles Study.

    PubMed

    Yu, Weiyang; Zhu, Zhili; Niu, Chun-Yao; Li, Chong; Cho, Jun-Hyung; Jia, Yu

    2016-12-01

    We present first-principles density-functional calculations for the structural, electronic, and magnetic properties of substitutional 3d transition metal (TM) impurities in two-dimensional black and blue phosphorenes. We find that the magnetic properties of such substitutional impurities can be understood in terms of a simple model based on the Hund's rule. The TM-doped black phosphorenes with Ti, V, Cr, Mn, Fe, and Ni impurities show dilute magnetic semiconductor (DMS) properties while those with Sc and Co impurities show nonmagnetic properties. On the other hand, the TM-doped blue phosphorenes with V, Cr, Mn, and Fe impurities show DMS properties, with Ni impurity showing half-metal properties, whereas Sc- and Co-doped systems show nonmagnetic properties. We identify two different regimes depending on the occupation of the hybridized electronic states of TM and phosphorous atoms: (i) bonding states are completely empty or filled for Sc- and Co-doped black and blue phosphorenes, leading to nonmagnetic; (ii) non-bonding d states are partially occupied for Ti-, V-, Cr-, Mn-, Fe- and Ni-doped black and blue phosphorenes, giving rise to large and localized spin moments. These results provide a new route for the potential applications of dilute magnetic semiconductor and half-metal in spintronic devices by employing black and blue phosphorenes. PACS numbers: 73.22.-f, 75.50.Pp, 75.75. + a. PMID:26858159

  8. Dilute Magnetic Semiconductor and Half-Metal Behaviors in 3 d Transition-Metal Doped Black and Blue Phosphorenes: A First-Principles Study

    NASA Astrophysics Data System (ADS)

    Yu, Weiyang; Zhu, Zhili; Niu, Chun-Yao; Li, Chong; Cho, Jun-Hyung; Jia, Yu

    2016-02-01

    We present first-principles density-functional calculations for the structural, electronic, and magnetic properties of substitutional 3 d transition metal (TM) impurities in two-dimensional black and blue phosphorenes. We find that the magnetic properties of such substitutional impurities can be understood in terms of a simple model based on the Hund's rule. The TM-doped black phosphorenes with Ti, V, Cr, Mn, Fe, and Ni impurities show dilute magnetic semiconductor (DMS) properties while those with Sc and Co impurities show nonmagnetic properties. On the other hand, the TM-doped blue phosphorenes with V, Cr, Mn, and Fe impurities show DMS properties, with Ni impurity showing half-metal properties, whereas Sc- and Co-doped systems show nonmagnetic properties. We identify two different regimes depending on the occupation of the hybridized electronic states of TM and phosphorous atoms: (i) bonding states are completely empty or filled for Sc- and Co-doped black and blue phosphorenes, leading to nonmagnetic; (ii) non-bonding d states are partially occupied for Ti-, V-, Cr-, Mn-, Fe- and Ni-doped black and blue phosphorenes, giving rise to large and localized spin moments. These results provide a new route for the potential applications of dilute magnetic semiconductor and half-metal in spintronic devices by employing black and blue phosphorenes. PACS numbers: 73.22.-f, 75.50.Pp, 75.75. + a

  9. Barrier height enhancement of metal/semiconductor contact by an enzyme biofilm interlayer

    NASA Astrophysics Data System (ADS)

    Ocak, Yusuf Selim; Gul Guven, Reyhan; Tombak, Ahmet; Kilicoglu, Tahsin; Guven, Kemal; Dogru, Mehmet

    2013-06-01

    A metal/interlayer/semiconductor (Al/enzyme/p-Si) MIS device was fabricated using α-amylase enzyme as a thin biofilm interlayer. It was observed that the device showed an excellent rectifying behavior and the barrier height value of 0.78 eV for Al/α-amylase/p-Si was meaningfully larger than the one of 0.58 eV for conventional Al/p-Si metal/semiconductor (MS) contact. Enhancement of the interfacial potential barrier of Al/p-Si MS diode was realized using enzyme interlayer by influencing the space charge region of Si semiconductor. The electrical properties of the structure were executed by the help of current-voltage and capacitance-voltage measurements. The photovoltaic properties of the structure were executed under a solar simulator with AM1.5 global filter between 40 and 100 mW/cm2 illumination conditions. It was also reported that the α-amylase enzyme produced from Bacillus licheniformis had a 3.65 eV band gap value obtained from optical method.

  10. III-V Nanowire Complementary Metal-Oxide Semiconductor Transistors Monolithically Integrated on Si.

    PubMed

    Svensson, Johannes; Dey, Anil W; Jacobsson, Daniel; Wernersson, Lars-Erik

    2015-12-01

    III-V semiconductors have attractive transport properties suitable for low-power, high-speed complementary metal-oxide-semiconductor (CMOS) implementation, but major challenges related to cointegration of III-V n- and p-type metal-oxide-semiconductor field-effect transistors (MOSFETs) on low-cost Si substrates have so far hindered their use for large scale logic circuits. By using a novel approach to grow both InAs and InAs/GaSb vertical nanowires of equal length simultaneously in one single growth step, we here demonstrate n- and p-type III-V MOSFETs monolithically integrated on a Si substrate with high I(on)/I(off) ratios using a dual channel, single gate-stack design processed simultaneously for both types of transistors. In addition, we demonstrate fundamental CMOS logic gates, such as inverters and NAND gates, which illustrate the viability of our approach for large scale III-V MOSFET circuits on Si. PMID:26595174

  11. Ionic Liquid Activation of Amorphous Metal-Oxide Semiconductors for Flexible Transparent Electronic Devices

    DOE PAGESBeta

    Pudasaini, Pushpa Raj; Noh, Joo Hyon; Wong, Anthony T.; Ovchinnikova, Olga S.; Haglund, Amanda V.; Dai, Sheng; Ward, Thomas Zac; Mandrus, David; Rack, Philip D.

    2016-02-09

    To begin this abstract, amorphous metal-oxide semiconductors offer the high carrier mobilities and excellent large-area uniformity required for high performance, transparent, flexible electronic devices; however, a critical bottleneck to their widespread implementation is the need to activate these materials at high temperatures which are not compatible with flexible polymer substrates. The highly controllable activation of amorphous indium gallium zinc oxide semiconductor channels using ionic liquid gating at room temperature is reported. Activation is controlled by electric field-induced oxygen migration across the ionic liquid-semiconductor interface. In addition to activation of unannealed devices, it is shown that threshold voltages of a transistormore » can be linearly tuned between the enhancement and depletion modes. Finally, the first ever example of transparent flexible thin film metal oxide transistor on a polyamide substrate created using this simple technique is demonstrated. Finally, this study demonstrates the potential of field-induced activation as a promising alternative to traditional postdeposition thermal annealing which opens the door to wide scale implementation into flexible electronic applications.« less

  12. Anomalous quantum efficiency for photoconduction and its power dependence in metal oxide semiconductor nanowires

    NASA Astrophysics Data System (ADS)

    Chen, R. S.; Wang, W. C.; Lu, M. L.; Chen, Y. F.; Lin, H. C.; Chen, K. H.; Chen, L. C.

    2013-07-01

    The quantum efficiency and carrier lifetime that decide the photoconduction (PC) efficiencies in the metal oxide semiconductor nanowires (NWs) have been investigated. The experimental result surprisingly shows that the SnO2, TiO2, WO3, and ZnO NWs reveal extraordinary quantum efficiencies in common, which are over one to three orders of magnitude lower than the theoretical expectation. The surface depletion region (SDR)-controlled photoconductivity is proposed to explain the anomalous quantum efficiency and its power dependence. The inherent difference between the metal oxide nanostructures such as carrier lifetime, carrier concentration, and dielectric constant leading to the distinct PC performance and behavior are also discussed.The quantum efficiency and carrier lifetime that decide the photoconduction (PC) efficiencies in the metal oxide semiconductor nanowires (NWs) have been investigated. The experimental result surprisingly shows that the SnO2, TiO2, WO3, and ZnO NWs reveal extraordinary quantum efficiencies in common, which are over one to three orders of magnitude lower than the theoretical expectation. The surface depletion region (SDR)-controlled photoconductivity is proposed to explain the anomalous quantum efficiency and its power dependence. The inherent difference between the metal oxide nanostructures such as carrier lifetime, carrier concentration, and dielectric constant leading to the distinct PC performance and behavior are also discussed. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr01635h

  13. Hydrogen Doped Metal Oxide Semiconductors with Exceptional and Tunable Localized Surface Plasmon Resonances.

    PubMed

    Cheng, Hefeng; Wen, Meicheng; Ma, Xiangchao; Kuwahara, Yasutaka; Mori, Kohsuke; Dai, Ying; Huang, Baibiao; Yamashita, Hiromi

    2016-07-27

    Heavily doped semiconductors have recently emerged as a remarkable class of plasmonic alternative to conventional noble metals; however, controlled manipulation of their surface plasmon bands toward short wavelengths, especially in the visible light spectrum, still remains a challenge. Here we demonstrate that hydrogen doped given MoO3 and WO3 via a facile H-spillover approach, namely, hydrogen bronzes, exhibit strong localized surface plasmon resonances in the visible light region. Through variation of their stoichiometric compositions, tunable plasmon resonances could be observed in a wide range, which hinge upon the reduction temperatures, metal species, the nature and the size of metal oxide supports in the synthetic H2 reduction process as well as oxidation treatment in the postsynthetic process. Density functional theory calculations unravel that the intercalation of hydrogen atoms into the given host structures yields appreciable delocalized electrons, enabling their plasmonic properties. The plasmonic hybrids show potentials in heterogeneous catalysis, in which visible light irradiation enhanced catalytic performance toward p-nitrophenol reduction relative to dark condition. Our findings provide direct evidence for achieving plasmon resonances in hydrogen doped metal oxide semiconductors, and may allow large-scale applications with low-price and earth-abundant elements. PMID:27384437

  14. High-efficiency photovoltaics based on semiconductor nanostructures

    SciTech Connect

    Yu, Paul K.L.; Yu, Edward T.; Wang, Deli

    2011-10-31

    The objective of this project was to exploit a variety of semiconductor nanostructures, specifically semiconductor quantum wells, quantum dots, and nanowires, to achieve high power conversion efficiency in photovoltaic devices. In a thin-film device geometry, the objectives were to design, fabricate, and characterize quantum-well and quantum-dot solar cells in which scattering from metallic and/or dielectric nanostructures was employed to direct incident photons into lateral, optically confined paths within a thin (~1-3um or less) device structure. Fundamental issues concerning nonequilibrium carrier escape from quantum-confined structures, removal of thin-film devices from an epitaxial growth substrate, and coherent light trapping in thin-film photovoltaic devices were investigated. In a nanowire device geometry, the initial objectives were to engineer vertical nanowire arrays to optimize optical confinement within the nanowires, and to extend this approach to core-shell heterostructures to achieve broadspectrum absorption while maintaining high opencircuit voltages. Subsequent work extended this approach to include fabrication of nanowire photovoltaic structures on low-cost substrates.

  15. Profiling Photoinduced Carrier Generation in Semiconductor Microwire Arrays via Photoelectrochemical Metal Deposition.

    PubMed

    Dasog, Mita; Carim, Azhar I; Yalamanchili, Sisir; Atwater, Harry A; Lewis, Nathan S

    2016-08-10

    Au was photoelectrochemically deposited onto cylindrical or tapered p-Si microwires on Si substrates to profile the photoinduced charge-carrier generation in individual wires in a photoactive semiconductor wire array. Similar experiments were repeated for otherwise identical Si microwires doped to be n-type. The metal plating profile was conformal for n-type wires, but for p-type wires was a function of distance from the substrate and was dependent on the illumination wavelength. Spatially resolved charge-carrier generation profiles were computed using full-wave electromagnetic simulations, and the localization of the deposition at the p-type wire surfaces observed experimentally correlated well with the regions of enhanced calculated carrier generation in the volumes of the microwires. This technique could potentially be extended to determine the spatially resolved carrier generation profiles in a variety of mesostructured, photoactive semiconductors. PMID:27322391

  16. Modeling of n-InAs metal oxide semiconductor capacitors with high-κ gate dielectric

    NASA Astrophysics Data System (ADS)

    Babadi, A. S.; Lind, E.; Wernersson, L. E.

    2014-12-01

    A qualitative analysis on capacitance-voltage and conductance data for high-κ/InAs capacitors is presented. Our measured data were evaluated with a full equivalent circuit model, including both majority and minority carriers, as well as interface and border traps, formulated for narrow band gap metal-oxide-semiconductor capacitors. By careful determination of interface trap densities, distribution of border traps across the oxide thickness, and taking into account the bulk semiconductor response, it is shown that the trap response has a strong effect on the measured capacitances. Due to the narrow bandgap of InAs, there can be a large surface concentration of electrons and holes even in depletion, so a full charge treatment is necessary.

  17. Stark spectroscopy of CuPc organic semiconductor with a submicron metal-electrode grating

    NASA Astrophysics Data System (ADS)

    Blinov, L. M.; Lazarev, V. V.; Yudin, S. G.; Palto, S. P.

    2016-02-01

    The optical and electro-optical properties of organic copper phthalocyanine semiconductor (α- CuPc) have been investigated by Stark (electroabsorption) spectroscopy using a metal electrode grating with a submicron (0.88 μm) interelectrode distance. Differences between dipole moments (Δμ) and polarizabilities (Δα) in the excited and ground states of α-CuPc are measured for a nanoscale semiconductor film. It is concluded that the extremely high values of Δμ and Δα are in principle not parameters of individual α-CuPc molecules: they are determined by exciton effects specifically in the polycrystalline medium with a characteristic morphology of hyperfine films, which depends on the structure of the samples and their fabrication technology.

  18. Hydrogenated Graphene Nanoflakes: Semiconductor to Half-Metal Transition and Remarkable Large Magnetism

    SciTech Connect

    Zhou, Yungang; Wang, Zhiguo; Yang, Ping; Sun, Xin; Zu, Xiaotao; Gao, Fei

    2012-03-08

    The electronic and magnetic properties of graphene nanoflakes (GNFs) can be tuned by patterned adsorption of hydrogen. Controlling the H coverage from bare GNFs to half hydrogenated and then to fully hydrogenated GNFs, the transformation of small-gap semiconductor {yields} half-metal {yields} wide-gap semiconductor occurs, accompanied by a magnetic {yields} magnetic {yields} nonmagnetic transfer and a nonmagnetic {yields} magnetic {yields} nonmagnetic transfer for triangular and hexagonal nanoflakes, respectively. The half hydrogenated GNFs, associated with strong spin polarization around the Fermi level, exhibit the unexpected large spin moment that is scaled squarely with the size of flakes. The induced spin magnetizations of these nanoflakes align parallel and lead to a substantial collective character, enabling the half hydrogenated GNFs to be spin-filtering flakes. These hydrogenation-dependent behaviors are then used to realize an attractive approach to engineer the transport properties, which provides a new route to facilitate the design of tunable spin devices.

  19. Modeling of n-InAs metal oxide semiconductor capacitors with high-κ gate dielectric

    SciTech Connect

    Babadi, A. S. Lind, E.; Wernersson, L. E.

    2014-12-07

    A qualitative analysis on capacitance-voltage and conductance data for high-κ/InAs capacitors is presented. Our measured data were evaluated with a full equivalent circuit model, including both majority and minority carriers, as well as interface and border traps, formulated for narrow band gap metal-oxide-semiconductor capacitors. By careful determination of interface trap densities, distribution of border traps across the oxide thickness, and taking into account the bulk semiconductor response, it is shown that the trap response has a strong effect on the measured capacitances. Due to the narrow bandgap of InAs, there can be a large surface concentration of electrons and holes even in depletion, so a full charge treatment is necessary.

  20. Charging and exciton-mediated decharging of metal nanoparticles in organic semiconductor matrices

    SciTech Connect

    Ligorio, Giovanni; Vittorio Nardi, Marco Christodoulou, Christos; Florea, Ileana; Ersen, Ovidiu; Monteiro, Nicolas-Crespo; Brinkmann, Martin; Koch, Norbert

    2014-04-21

    Gold nanoparticles (Au-NPs) were deposited on the surface of n- and p-type organic semiconductors to form defined model systems for charge storage based electrically addressable memory elements. We used ultraviolet photoelectron spectroscopy to study the electronic properties and found that the Au-NPs become positively charged because of photoelectron emission, evidenced by spectral shifts to higher binding energy. Upon illumination with light that can be absorbed by the organic semiconductors, dynamic charge neutrality of the Au-NPs could be re-established through electron transfer from excitons. The light-controlled charge state of the Au-NPs could add optical addressability to memory elements.

  1. Ferroelectric switching of poly(vinylidene difluoride-trifluoroethylene) in metal-ferroelectric-semiconductor non-volatile memories with an amorphous oxide semiconductor

    NASA Astrophysics Data System (ADS)

    Gelinck, G. H.; van Breemen, A. J. J. M.; Cobb, B.

    2015-03-01

    Ferroelectric polarization switching of poly(vinylidene difluoride-trifluoroethylene) is investigated in different thin-film device structures, ranging from simple capacitors to dual-gate thin-film transistors (TFT). Indium gallium zinc oxide, a high mobility amorphous oxide material, is used as semiconductor. We find that the ferroelectric can be polarized in both directions in the metal-ferroelectric-semiconductor (MFS) structure and in the dual-gate TFT under certain biasing conditions, but not in the single-gate thin-film transistors. These results disprove the common belief that MFS structures serve as a good model system for ferroelectric polarization switching in thin-film transistors.

  2. Ferroelectric switching of poly(vinylidene difluoride-trifluoroethylene) in metal-ferroelectric-semiconductor non-volatile memories with an amorphous oxide semiconductor

    SciTech Connect

    Gelinck, G. H.; Breemen, A. J. J. M. van; Cobb, B.

    2015-03-02

    Ferroelectric polarization switching of poly(vinylidene difluoride-trifluoroethylene) is investigated in different thin-film device structures, ranging from simple capacitors to dual-gate thin-film transistors (TFT). Indium gallium zinc oxide, a high mobility amorphous oxide material, is used as semiconductor. We find that the ferroelectric can be polarized in both directions in the metal-ferroelectric-semiconductor (MFS) structure and in the dual-gate TFT under certain biasing conditions, but not in the single-gate thin-film transistors. These results disprove the common belief that MFS structures serve as a good model system for ferroelectric polarization switching in thin-film transistors.

  3. Understanding the Electronic Structure of Metal/SAM/Organic−Semiconductor Heterojunctions

    PubMed Central

    2009-01-01

    Computational modeling is used to describe the mechanisms governing energy level alignment between an organic semiconductor (OSC) and a metal covered by various self-assembled monolayers (SAMs). In particular, we address the question to what extent and under what circumstances SAM-induced work-function modifications lead to an actual change of the barriers for electron and hole injection from the metal into the OSC layer. Depending on the nature of the SAM, we observe clear transitions between Fermi level pinning and vacuum-level alignment regimes. Surprisingly, although in most cases the pinning occurs only when the metal is present, it is not related to charge transfer between the electrode and the organic layer. Instead, charge rearrangements at the interface between the SAM and the OSC are observed, accompanied by a polarization of the SAM. PMID:19891441

  4. Interfacial thermal conductance across metal-insulator/semiconductor interfaces due to surface states

    NASA Astrophysics Data System (ADS)

    Lu, Tingyu; Zhou, Jun; Nakayama, Tsuneyoshi; Yang, Ronggui; Li, Baowen

    2016-02-01

    We point out that the effective channel for the interfacial thermal conductance, the inverse of Kapitza resistance, of metal-insulator/semiconductor interfaces is governed by the electron-phonon interaction mediated by the surface states allowed in a thin region near the interface. Our detailed calculations demonstrate that the interfacial thermal conductance across Pb/Pt/Al/Au-diamond interfaces are only slightly different among these metals, and reproduce well the experimental results of the interfacial thermal conductance across metal-diamond interfaces observed by Stoner et al. [Phys. Rev. Lett. 68, 1563 (1992), 10.1103/PhysRevLett.68.1563] and most recently by Hohensee et al. [Nat. Commun. 6, 6578 (2015), 10.1038/ncomms7578].

  5. Chemically Derivatized Semiconductor Photoelectrodes.

    ERIC Educational Resources Information Center

    Wrighton, Mark S.

    1983-01-01

    Deliberate modification of semiconductor photoelectrodes to improve durability and enhance rate of desirable interfacial redox processes is discussed for a variety of systems. Modification with molecular-based systems or with metals/metal oxides yields results indicating an important role for surface modification in devices for fundamental study…

  6. Insulator charging limits direct current across tunneling metal-insulator-semiconductor junctions

    NASA Astrophysics Data System (ADS)

    Vilan, Ayelet

    2016-01-01

    Molecular electronics studies how the molecular nature affects the probability of charge carriers to tunnel through the molecules. Nevertheless, transport is also critically affected by the contacts to the molecules, an aspect that is often overlooked. Specifically, the limited ability of non-metallic contacts to maintain the required charge balance across the fairly insulating molecule often have dramatic effects. This paper shows that in the case of lead/organic monolayer-silicon junctions, a charge balance is responsible for an unusual current scaling, with the junction diameter (perimeter), rather than its area. This is attributed to the balance between the 2D charging at the metal/insulator interface and the 3D charging of the semiconductor space-charge region. A derivative method is developed to quantify transport across tunneling metal-insulator-semiconductor junctions; this enables separating the tunneling barrier from the space-charge barrier for a given current-voltage curve, without complementary measurements. The paper provides practical tools to analyze specific molecular junctions compatible with existing silicon technology, and demonstrates the importance of contacts' physics in modeling charge transport across molecular junctions.

  7. Surface plasmon assisted hot electron collection in wafer-scale metallic-semiconductor photonic crystals.

    PubMed

    Chou, Jeffrey B; Li, Xin-Hao; Wang, Yu; Fenning, David P; Elfaer, Asmaa; Viegas, Jaime; Jouiad, Mustapha; Shao-Horn, Yang; Kim, Sang-Gook

    2016-09-01

    Plasmon assisted photoelectric hot electron collection in a metal-semiconductor junction can allow for sub-bandgap optical to electrical energy conversion. Here we report hot electron collection by wafer-scale Au/TiO2 metallic-semiconductor photonic crystals (MSPhC), with a broadband photoresponse below the bandgap of TiO2. Multiple absorption modes supported by the 2D nano-cavity structure of the MSPhC extend the photon-metal interaction time and fulfill a broadband light absorption. The surface plasmon absorption mode provides access to enhanced electric field oscillation and hot electron generation at the interface between Au and TiO2. A broadband sub-bandgap photoresponse centered at 590 nm was achieved due to surface plasmon absorption. Gold nanorods were deposited on the surface of MSPhC to study localized surface plasmon (LSP) mode absorption and subsequent injection to the TiO2 catalyst at different wavelengths. Applications of these results could lead to low-cost and robust photo-electrochemical applications such as more efficient solar water splitting. PMID:27607726

  8. Interface Schottky barrier engineering via strain in metal-semiconductor composites.

    PubMed

    Ma, Xiangchao; Dai, Ying; Yu, Lin; Huang, Baibiao

    2016-01-21

    The interfacial carrier transfer property, which is dominated by the interface Schottky barrier height (SBH), plays a crucial role in determining the performance of metal-semiconductor heterostructures in a variety of applications. Therefore, artificially controlling the interface SBH is of great importance for their industrial applications. As a model system, the Au/TiO2 (001) heterostructure is studied using first-principles calculations and the tight-binding method in the present study. Our investigation demonstrates that strain can be an effective way to decrease the interface SBH and that the n-type SBH can be more effectively decreased than the p-type SBH. Astonishingly, strain affects the interface SBH mainly by changing the intrinsic properties of Au and TiO2, whereas the interfacial potential alignment is almost independent of strain due to two opposite effects, which are induced by strain at the interfacial region. These observed trends can be understood on the basis of the general free-electron gas model of typical metals, the tight-binding theory and the crystal-field theory, which suggest that similar trends may be generalized for many other metal-semiconductor heterostructures. Given the commonness and tunability of strain in typical heterostructures, we anticipate that the tunability of the interface SBH with strain described here can provide an alternative effective way for realizing more efficient applications of relevant heterostructures. PMID:26511292

  9. Metal-oxide-semiconductor-compatible ultra-long-range surface plasmon modes

    NASA Astrophysics Data System (ADS)

    Durfee, C. G.; Furtak, T. E.; Collins, R. T.; Hollingsworth, R. E.

    2008-06-01

    Long-range surface plasmons traveling on thin metal films have demonstrated promising potential in subwavelength waveguide applications. In work toward device applications that can leverage existing silicon microelectronics technology, it is of interest to explore the propagation of surface plasmons in a metal-oxide-semiconductor geometry. In such a structure, there is a high refractive index contrast between the semiconductor (n ≈3.5 for silicon) and the insulating oxide (typically n ≈1.5-2.5). However, the introduction of dielectrics with disparate refractive indices is known to strongly affect the guiding properties of surface plasmons. In this paper, we analyze the implications of high index contrast in 1D layered surface plasmon structures. We show that it is possible to introduce a thin dielectric layer with a low refractive index positioned next to the metal without adversely affecting the guiding quality. In fact, such a configuration can dramatically increase the propagation length of the conventional long-range mode. While this study is directed at silicon-compatible waveguides working at telecommunications wavelengths, this configuration has general implications for surface plasmon structure design using other materials and operating at alternative wavelengths.

  10. Amorphous silicon enhanced metal-insulator-semiconductor contacts for silicon solar cells

    NASA Astrophysics Data System (ADS)

    Bullock, J.; Cuevas, A.; Yan, D.; Demaurex, B.; Hessler-Wyser, A.; De Wolf, S.

    2014-10-01

    Carrier recombination at the metal-semiconductor contacts has become a significant obstacle to the further advancement of high-efficiency diffused-junction silicon solar cells. This paper provides the proof-of-concept of a procedure to reduce contact recombination by means of enhanced metal-insulator-semiconductor (MIS) structures. Lightly diffused n+ and p+ surfaces are passivated with SiO2/a-Si:H and Al2O3/a-Si:H stacks, respectively, before the MIS contacts are formed by a thermally activated alloying process between the a-Si:H layer and an overlying aluminum film. Transmission/scanning transmission electron microscopy (TEM/STEM) and energy dispersive x-ray spectroscopy are used to ascertain the nature of the alloy. Idealized solar cell simulations reveal that MIS(n+) contacts, with SiO2 thicknesses of ˜1.55 nm, achieve the best carrier-selectivity producing a contact resistivity ρc of ˜3 mΩ cm2 and a recombination current density J0c of ˜40 fA/cm2. These characteristics are shown to be stable at temperatures up to 350 °C. The MIS(p+) contacts fail to achieve equivalent results both in terms of thermal stability and contact characteristics but may still offer advantages over directly metallized contacts in terms of manufacturing simplicity.

  11. Quantum random number generator based on photonic emission in semiconductors.

    PubMed

    Stipcević, M; Rogina, B Medved

    2007-04-01

    We report upon the realization of a novel fast nondeterministic random number generator whose randomness relies on the intrinsic randomness of the quantum physical processes of photonic emission in semiconductors and subsequent detection by the photoelectric effect. Timing information of detected photons is used to generate binary random digits-bits. The bit extraction method based on the restartable clock method theoretically eliminates both bias and autocorrelation while reaching efficiency of almost 0.5 bits per random event. A prototype has been built and statistically tested. PMID:17477690

  12. Microwave photonic interference mitigation filter based on semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Xu, Enming; Zhang, Xinliang; Zhou, Lina; Zhang, Yu; Yu, Yuan; Wang, Fei; Huang, Dexiu

    2009-11-01

    A microwave photonic interference mitigation filter is proposed and experimentally demonstrated. The structure is based on a recirculating delay line loop comprising a semiconductor optical amplifier (SOA) and a tunable narrowband optical filter. Converted signal used as negative tap is generated through wavelength conversion employing cross-gain modulation of amplified spontaneous emission spectrum of the SOA. The converted signal circulating in the RDL loop realizes a high quality factor (Q) response after photo-detection. A bandpass response with negative coefficients combined with a broadband allpass response achieves a notch response with flat passband.

  13. Solar hydrogen production with semiconductor metal oxides: new directions in experiment and theory.

    PubMed

    Valdés, Álvaro; Brillet, Jeremie; Grätzel, Michael; Gudmundsdóttir, Hildur; Hansen, Heine A; Jónsson, Hannes; Klüpfel, Peter; Kroes, Geert-Jan; Le Formal, Florian; Man, Isabela C; Martins, Rafael S; Nørskov, Jens K; Rossmeisl, Jan; Sivula, Kevin; Vojvodic, Aleksandra; Zäch, Michael

    2012-01-01

    An overview of a collaborative experimental and theoretical effort toward efficient hydrogen production via photoelectrochemical splitting of water into di-hydrogen and di-oxygen is presented here. We present state-of-the-art experimental studies using hematite and TiO(2) functionalized with gold nanoparticles as photoanode materials, and theoretical studies on electro and photo-catalysis of water on a range of metal oxide semiconductor materials, including recently developed implementation of self-interaction corrected energy functionals. PMID:22083224

  14. Complementary metal-oxide-semiconductor compatible 1060 nm photodetector with ultrahigh gain under low bias.

    PubMed

    Hall, David; Li, Baoxia; Liu, Yu-Hsin; Yan, Lujiang; Lo, Yu-Hwa

    2015-10-01

    Falling on the tail of the absorption spectrum of silicon, 1060 nm Si detectors often suffer from low responsivity unless an exceedingly thick absorption layer is used, a design that requires high operation voltage and high purity epitaxial or substrate material. We report an all-silicon 1060 nm detector with ultrahigh gain to allow for low operation voltage (<4  V) and thin (200 nm) effective absorption layer, using the recently discovered cycling excitation process. With 1% external quantum efficiency, a responsivity of 93 A/W was demonstrated in a p/n junction device compatible with the complementary metal-oxide-semiconductor process. PMID:26421551

  15. Ultrasensitive mass sensor fully integrated with complementary metal-oxide-semiconductor circuitry

    SciTech Connect

    Forsen, E.; Abadal, G.; Ghatnekar-Nilsson, S.; Teva, J.; Verd, J.; Sandberg, R.; Svendsen, W.; Perez-Murano, F.; Esteve, J.; Figueras, E.; Campabadal, F.; Montelius, L.; Barniol, N.; Boisen, A.

    2005-07-25

    Nanomechanical resonators have been monolithically integrated on preprocessed complementary metal-oxide-semiconductor (CMOS) chips. Fabricated resonator systems have been designed to have resonance frequencies up to 1.5 MHz. The systems have been characterized in ambient air and vacuum conditions and display ultrasensitive mass detection in air. A mass sensitivity of 4 ag/Hz has been determined in air by placing a single glycerine drop, having a measured weight of 57 fg, at the apex of a cantilever and subsequently measuring a frequency shift of 14.8 kHz. CMOS integration enables electrostatic excitation, capacitive detection, and amplification of the resonance signal directly on the chip.

  16. Trace explosive sensor devices based on semiconductor nanomaterials

    NASA Astrophysics Data System (ADS)

    Wang, Danling

    This dissertation discusses an explosive sensing device based on semiconductor nanomaterials. Here, we mainly focus on two kinds of materials: titanium dioxide nanowires and silicon nanowires to detect explosive trace vapor. Herein, methods for the synthesis, fabrication, design of nanostructured sensing materials using low-cost hydrothermal process are present. In addition, the nanomaterials have been systemically tested on different explosive. The first part of dissertation is focused on the fabrication of TiO2(B) dominant nanowires and testing the response to explosives. It was found that the high porous TiO2(B) nanowires when mixed anatase TiO2, exhibit a very fast and highly sensitive response to nitro-containing explosives. The second part of dissertation has studied the basic sensing mechanism of TiO2(B) nanowire sensor to detect explosives. It shows the specific surface characteristics of TiO2 responsible for the nitro-containing explosives. This information is then used to propose a method using UV illumination to reduce the effect of water vapor on TiO2(B) nanowires. The third part discussed an explosive sensor based on silicon nanowires. We analyzed the mechanism of silicon nanowires to detect nitro-related explosive compounds. In order to further investigate the sensing mechanism of TiO2, the fourth part of dissertation studies the effect on sensor performance by using different crystal phases of TiO2, different microstructure of TiO2, surface modification of TiO2, and different kinds of nanostructured semiconductors such as ZnO nanowires, TiO2 coated ZnO nanowires, V2O5 nanowires, and CdS nanowires to detect explosives. It is found that only TiO2 related semiconductor shows good response to explosives.

  17. Alloy Engineering of Defect Properties in Semiconductors: Suppression of Deep Levels in Transition-Metal Dichalcogenides

    NASA Astrophysics Data System (ADS)

    Huang, Bing; Yoon, Mina; Sumpter, Bobby G.; Wei, Su-Huai; Liu, Feng

    2015-09-01

    Developing practical approaches to effectively reduce the amount of deep defect levels in semiconductors is critical for their use in electronic and optoelectronic devices, but this still remains a very challenging task. In this Letter, we propose that specific alloying can provide an effective means to suppress the deep defect levels in semiconductors while maintaining their basic electronic properties. Specifically, we demonstrate that for transition-metal dichalcogenides, such as MoSe2 and WSe2 , where anion vacancies are the most abundant defects that can induce deep levels, the deep levels can be effectively suppressed in Mo1 -xWx Se2 alloys at low W concentrations. This surprising phenomenon is associated with the fact that the band edge energies can be substantially tuned by the global alloy concentration, whereas the defect level is controlled locally by the preferred locations of Se vacancies around W atoms. Our findings illustrate a concept of alloy engineering and provide a promising approach to control the defect properties of semiconductors.

  18. Alloy Engineering of Defect Properties in Semiconductors: Suppression of Deep Levels in Transition-Metal Dichalcogenides

    NASA Astrophysics Data System (ADS)

    Huang, Bing; Yoon, Mina; Sumpter, Bobby; Wei, Suhuai; Liu, Feng

    Developing practical approaches to effectively reduce the amount of deep defect levels in semiconductors is critical for their use in electronic and optoelectronic devices, but this still remains a very challenging task. In this talk, we propose that specific alloying can provide an effective means to suppress the deep defect levels in semiconductors while maintaining their basic electronic properties. Specifically, we demonstrate that for transition-metal dichalcogenides, such as MoSe2 and WSe2, where anion vacancies are the most abundant defects that can induce deep levels, the deep levels can be effectively suppressed in MoWSe2 alloys at low W concentrations. This surprising phenomenon is associated with the fact that the band edge energies can be substantially tuned by the global alloy concentration, whereas the defect level is controlled locally by the preferred locations of Se vacancies around W atoms. Our findings illustrate a concept of alloy engineering and provide a promising approach to control the defect properties of semiconductors.

  19. Low-temperature grown GaAs heterojunction metal-semiconductor-metal photodetectors improve speed and efficiency

    NASA Astrophysics Data System (ADS)

    Currie, Marc; Quaranta, Fabio; Cola, Adriano; Gallo, Eric M.; Nabet, Bahram

    2011-11-01

    Low-temperature-grown GaAs (LT-GaAs) has a picosecond recombination lifetime, making a fast photodetector material but limiting carrier mobility and collection efficiency. Here, a metal-semiconductor-metal photodetector with a thin channel of regular-temperature GaAs (RT-GaAs) above LT-GaAs provides fast transit between contacts. A p-type delta doping layer below these layers produces a vertical electric field forcing optically generated electrons towards the channel. The AlGaAs/RT-GaAs heterojunction increases Schottky contacts, and the resulting 8-22 μm pitch photodetectors have low (<1-nA) dark current, 12-ps (oscilloscope-limited) pulsewidth, and 0.15-A/W responsivity. The devices demonstrate that fast LT-GaAs pulses are achievable with responsivity similar to RT-GaAs.

  20. Metal Schottky Source/Drain Technology for Ultrathin Silicon-on-Thin-Box Metal Oxide Semiconductor Field Effect Transistors

    NASA Astrophysics Data System (ADS)

    Shima, Akio; Sugii, Nobuyuki; Mise, Nobuyuki; Hisamoto, Digh; Takeda, Ken-ichi; Torii, Kazuyoshi

    2011-04-01

    This paper reports novel, non-epitaxial raised source/drain (S/D) approaches to decrease the parasitic external resistance in complementary metal-oxide-semiconductor field-effect transistors (CMOSFETs) fabricated on ultrathin silicon on insulator (UTSOI). This technique utilizes a metal Schottky S/D process with dopant segregation. Selectively formed NiSi2 with dopant segregation fabricated by laser-spike annealing (LSA) significantly lowered effective Shottky-barrier height and, thereby, lowered contact resistance (ρc). Satisfying the requirements of UTSOI MOSFETs in the 32-nm node for low stand-by power (LSTP) application, external parasitic resistance was reduced to 140 (NMOS) and 350 (PMOS) Ω µm. Our results show that ρc is an important component of parasitic resistance in terms of improving device performance of UTSOI MOSFETs.

  1. Process for producing chalcogenide semiconductors

    DOEpatents

    Noufi, R.; Chen, Y.W.

    1985-04-30

    A process for producing chalcogenide semiconductor material is disclosed. The process includes forming a base metal layer and then contacting this layer with a solution having a low pH and containing ions from at least one chalcogen to chalcogenize the layer and form the chalcogenide semiconductor material.

  2. Process for producing chalcogenide semiconductors

    DOEpatents

    Noufi, Rommel; Chen, Yih-Wen

    1987-01-01

    A process for producing chalcogenide semiconductor material is disclosed. The process includes forming a base metal layer and then contacting this layer with a solution having a low pH and containing ions from at least one chalcogen to chalcogenize the layer and form the chalcogenide semiconductor material.

  3. Non-noble metal based metallization systems

    NASA Technical Reports Server (NTRS)

    Garcia, A., III

    1983-01-01

    The results of efforts to produce a nonsilver metallization system for silicon photovoltaic cells are given. The system uses a metallization system based on molybdenum, tin, and titanium hydride. The initial work in this system was done using the MIDFILM process. The MIDFILM process attains a line resolution comparable to photoresist methods with a process related to screen printing. The surface to be processed is first coated with a thin layer of photopolymer material. Upon exposure to ultraviolet light through a suitable mask, the polymer in the non-pattern area crosslinks and becomes hard. The unexposed pattern areas remain tacky. The conductor material is then applied in the form of a dry mixture of metal which adheres to the tacky pattern area. The assemblage is then fired to ash the photopolymer and sinter the conductor powder.

  4. The design criteria of hybrid waveguides using semiconductor gain to compensate the metal loss towards nano-scale lasers with high plasmonicity

    NASA Astrophysics Data System (ADS)

    Yang, Wei; Zong, Hua; Ji, Qingbin; Yan, Tongxing; Hu, Xiaodong

    2014-07-01

    In this Letter, we report on the design criteria of plasmonic nano-lasers based on hybrid waveguides using semiconductor gain to compensate for the metal loss. A quantitative measure of the plasmonic-like character in nano-lasers was discussed with the distance of operation wavelength to plasmon resonance, herein defined as "plasmonicity" ( Θ = ω / ω sp). We found that the effective index (confinement) increased with plasmonicity rapidly when approaching resonance and the associated giant modal loss prohibited lasing. We further studied the design criteria of a practicable green nano-laser, based on a vertical p-n junction combined with a lateral semiconductor/dielectric/metal core-shell structure. The influence of thickness and permittivity of dielectric spacer and also the critical thickness of the active region were investigated numerically. The approach proposed here will shed light on the future fabrication of electrical injection nano-lasers with high plasmonicity.

  5. Direct observation of both contact and remote oxygen scavenging of GeO{sub 2} in a metal-oxide-semiconductor stack

    SciTech Connect

    Fadida, S. Shekhter, P.; Eizenberg, M.; Cvetko, D.; Floreano, L.; Verdini, A.; Kymissis, I.

    2014-10-28

    In the path to incorporating Ge based metal-oxide-semiconductor into modern nano-electronics, one of the main issues is the oxide-semiconductor interface quality. Here, the reactivity of Ti on Ge stacks and the scavenging effect of Ti were studied using synchrotron X-ray photoelectron spectroscopy measurements, with an in-situ metal deposition and high resolution transmission electron microscopy imaging. Oxygen removal from the Ge surface was observed both in direct contact as well as remotely through an Al{sub 2}O{sub 3} layer. The scavenging effect was studied in situ at room temperature and after annealing. We find that the reactivity of Ti can be utilized for improved scaling of Ge based devices.

  6. A model for the frequency dispersion of the high-k metal-oxide-semiconductor capacitance in accumulation

    NASA Astrophysics Data System (ADS)

    Yao, B.; Fang, Z. B.; Zhu, Y. Y.; Ji, T.; He, G.

    2012-05-01

    High-frequency capacitance-voltage measurements have been made on metal-oxide-semiconductor capacitors by using single crystalline Er2O3 high-k gate dielectrics. Based on our analysis, it has been found that frequency dispersion of Er2O3 capacitance in accumulation decreases consistently with the increase of the frequency. A correction model is proposed to explain these frequency dispersion phenomena and the capacitance-frequency equations are obtained from the impedance expression of the equivalent circuit. Based on the simulated capacitance-frequency, it can be concluded that frequency dispersion of Er2O3 capacitance in accumulation originates from the existence of the parasitic resistances, the series resistances, and the formed SiOx interfacial layer.

  7. Semiconductor-nanocrystals-based white light-emitting diodes.

    PubMed

    Dai, Quanqin; Duty, Chad E; Hu, Michael Z

    2010-08-01

    In response to the demands for energy and the concerns of global warming and climate change, energy efficient and environmentally friendly solid-state lighting, such as white light-emitting diodes (WLEDs), is considered to be the most promising and suitable light source. Because of their small size, high efficiency, and long lifetime, WLEDs based on colloidal semiconductor nanocrystals (or quantum dots) are emerging as a completely new technology platform for the development of flat-panel displays and solid-state lighting, exhibiting the potential to replace the conventionally used incandescent and fluorescent lamps. This replacement can cut the ever-increasing level of energy consumption, solve the problem of rapidly depleting fossil fuel reserves, and improve the quality of the global environment. In this review, the recent progress in semiconductor-nanocrystals-based WLEDs is highlighted, the different approaches for generating white light are compared, and the benefits and challenges of the solid-state lighting technology are discussed. PMID:20602425

  8. Semiconductor product analysis challenges based on the 1999 ITRS

    SciTech Connect

    JOSEPH,THOMAS W.; ANDERSON,RICHARD E.; GILFEATHER,GLEN; LECLAIRE,CAROLE; YIM,DANIEL

    2000-05-30

    One of the most significant challenges for technology characterization and future analysis is to keep instrumentation and techniques in step with the development of technology itself. Not only are dimensions shrinking and new materials being employed, but the rate of change is increasing. According to the 1999 International Technology Roadmap for Semiconductors (ITRS) the number and difficulty of the technical challenges continue to increase as technology moves forward. It could be argued that technology cannot be developed without appropriate analytical technique, nevertheless while much effort is being directed at materials and processes, only a small proportion is being directed at analysis. Whereas previous versions of the Semiconductor Industry Association roadmap contained a small number of implicit references to characterization and analysis, the 1999 ITRS contains many explicit references. It is clear that characterization is now woven through the roadmap, and technology developers in all areas appreciate the fact that new instrumentation and techniques will be required to sustain the rate of development the semiconductor industry has seen in recent years. Late in 1999, a subcommittee of the Sematech Product Analysis Forum reviewed the ITRS and identified a top-ten list of challenges which the failure analysis community will face as present technologies are extended and future technologies are developed. This paper discusses the PAF top-ten list of challenges, which is based primarily on the Difficult Challenges tables from each ITRS working group. Eight of the top-ten are challenges of significant technical magnitude, only two could be considered non-technical in nature. Most of these challenges cut across several working group areas and could be considered common threads in the roadmap, ranging from fault simulation and modeling to imaging small features, from electrical defect isolation to reprocessing.

  9. One-dimensional transport in hybrid metal-semiconductor nanotube systems

    NASA Astrophysics Data System (ADS)

    Gelin, M. F.; Bondarev, I. V.

    2016-03-01

    We develop an electron transport theory for the hybrid system of a semiconducting carbon nanotube that encapsulates a one-atom-thick metallic wire. The theory predicts Fano resonances in electron transport through the system, whereby the interaction of electrons on the wire with nanotube plasmon generated near fields blocks some of the wire transmission channels to open up the new coherent plasmon-mediated channel in the nanotube forbidden gap outside the wire transmission band. Such a channel makes the entire hybrid system transparent in the energy domain where neither wire nor nanotube is individually transparent. This effect can be used to control and optimize charge transfer in hybrid nanodevices built on metal-semiconductor nanotube systems.

  10. Application of the exact exchange potential method for half metallic intermediate band alloy semiconductor.

    PubMed

    Fernández, J J; Tablero, C; Wahnón, P

    2004-06-01

    In this paper we present an analysis of the convergence of the band structure properties, particularly the influence on the modification of the bandgap and bandwidth values in half metallic compounds by the use of the exact exchange formalism. This formalism for general solids has been implemented using a localized basis set of numerical functions to represent the exchange density. The implementation has been carried out using a code which uses a linear combination of confined numerical pseudoatomic functions to represent the Kohn-Sham orbitals. The application of this exact exchange scheme to a half-metallic semiconductor compound, in particular to Ga(4)P(3)Ti, a promising material in the field of high efficiency solar cells, confirms the existence of the isolated intermediate band in this compound. PMID:15268104

  11. Anomalous quantum efficiency for photoconduction and its power dependence in metal oxide semiconductor nanowires.

    PubMed

    Chen, R S; Wang, W C; Lu, M L; Chen, Y F; Lin, H C; Chen, K H; Chen, L C

    2013-08-01

    The quantum efficiency and carrier lifetime that decide the photoconduction (PC) efficiencies in the metal oxide semiconductor nanowires (NWs) have been investigated. The experimental result surprisingly shows that the SnO2, TiO2, WO3, and ZnO NWs reveal extraordinary quantum efficiencies in common, which are over one to three orders of magnitude lower than the theoretical expectation. The surface depletion region (SDR)-controlled photoconductivity is proposed to explain the anomalous quantum efficiency and its power dependence. The inherent difference between the metal oxide nanostructures such as carrier lifetime, carrier concentration, and dielectric constant leading to the distinct PC performance and behavior are also discussed. PMID:23779084

  12. Novel photoinduced phase transitions in transition metal oxides and diluted magnetic semiconductors

    PubMed Central

    2012-01-01

    Some transition metal oxides have frustrated electronic states under multiphase competition due to strongly correlated d electrons with spin, charge, and orbital degrees of freedom and exhibit drastic responses to external stimuli such as optical excitation. Here, we present photoemission studies on Pr0.55(Ca1 − ySry)0.45MnO3 (y = 0.25), SrTiO3, and Ti1 − xCoxO2 (x = 0.05, 0.10) under laser illumination and discuss electronic structural changes induced by optical excitation in these strongly correlated oxides. We discuss the novel photoinduced phase transitions in these transition metal oxides and diluted magnetic semiconductors on the basis of polaronic pictures such as orbital, ferromagnetic, and ferroelectric polarons. PMID:23092248

  13. Photoelectrochemical water splitting enhanced by self-assembled metal nanopillars embedded in an oxide semiconductor photoelectrode.

    PubMed

    Kawasaki, Seiji; Takahashi, Ryota; Yamamoto, Takahisa; Kobayashi, Masaki; Kumigashira, Hiroshi; Yoshinobu, Jun; Komori, Fumio; Kudo, Akihiko; Lippmaa, Mikk

    2016-01-01

    Production of chemical fuels by direct solar energy conversion in a photoelectrochemical cell is of great practical interest for developing a sustainable energy system. Various nanoscale designs such as nanowires, nanotubes, heterostructures and nanocomposites have been explored to increase the energy conversion efficiency of photoelectrochemical water splitting. Here we demonstrate a self-organized nanocomposite material concept for enhancing the efficiency of photocarrier separation and electrochemical energy conversion. Mechanically robust photoelectrodes are formed by embedding self-assembled metal nanopillars in a semiconductor thin film, forming tubular Schottky junctions around each pillar. The photocarrier transport efficiency is strongly enhanced in the Schottky space charge regions while the pillars provide an efficient charge extraction path. Ir-doped SrTiO3 with embedded iridium metal nanopillars shows good operational stability in a water oxidation reaction and achieves over 80% utilization of photogenerated carriers under visible light in the 400- to 600-nm wavelength range. PMID:27255209

  14. Controlling the metal to semiconductor transition of MoS2 and WS2 in solution

    DOE PAGESBeta

    Chou, Stanley Shihyao; Yi-Kai Huang; Kim, Jaemyung; Kaehr, Bryan James; Foley, Brian M.; Lu, Ping; Conner Dykstra; Hopkins, Patrick E.; Brinker, C. Jeffrey; Jiaxing Huang; et al

    2015-01-22

    Lithiation-exfoliation produces single to few-layered MoS2 and WS2 sheets dispersible in water. However, the process transforms them from the pristine semiconducting 2H phase to a distorted metallic phase. Recovery of the semiconducting properties typically involves heating of the chemically exfoliated sheets at elevated temperatures. Therefore, it has been largely limited to sheets deposited on solid substrates. We report the dispersion of chemically exfoliated MoS2 sheets in high boiling point organic solvents enabled by surface functionalization and the controllable recovery of their semiconducting properties directly in solution. Ultimately, this process connects the scalability of chemical exfoliation with the simplicity of solutionmore » processing, enabling a facile method for tuning the metal to semiconductor transitions of MoS2 and WS2 within a liquid medium.« less

  15. Photoelectrochemical water splitting enhanced by self-assembled metal nanopillars embedded in an oxide semiconductor photoelectrode

    NASA Astrophysics Data System (ADS)

    Kawasaki, Seiji; Takahashi, Ryota; Yamamoto, Takahisa; Kobayashi, Masaki; Kumigashira, Hiroshi; Yoshinobu, Jun; Komori, Fumio; Kudo, Akihiko; Lippmaa, Mikk

    2016-06-01

    Production of chemical fuels by direct solar energy conversion in a photoelectrochemical cell is of great practical interest for developing a sustainable energy system. Various nanoscale designs such as nanowires, nanotubes, heterostructures and nanocomposites have been explored to increase the energy conversion efficiency of photoelectrochemical water splitting. Here we demonstrate a self-organized nanocomposite material concept for enhancing the efficiency of photocarrier separation and electrochemical energy conversion. Mechanically robust photoelectrodes are formed by embedding self-assembled metal nanopillars in a semiconductor thin film, forming tubular Schottky junctions around each pillar. The photocarrier transport efficiency is strongly enhanced in the Schottky space charge regions while the pillars provide an efficient charge extraction path. Ir-doped SrTiO3 with embedded iridium metal nanopillars shows good operational stability in a water oxidation reaction and achieves over 80% utilization of photogenerated carriers under visible light in the 400- to 600-nm wavelength range.

  16. Tunable surface plasmon polaritons in metal-strip waveguides with magnetized semiconductor substrates in Voigt configuration

    NASA Astrophysics Data System (ADS)

    Mathew, Gishamol; Mathew, Vincent

    2012-05-01

    The properties of surface plasmon polaritons (SPPs) in a magnetically tunable strip waveguide geometry comprising of a metal film of finite width deposited on a magnetized semiconductor and covered by an isotropic dielectric material were studied in Voigt configuration. The method of lines was used to compute the dispersion relation of fundamental modes, and the dependence of the propagation constant on metal film dimensions, material parameters and biasing magnetic field was considered. The bounded SPPs are nonreciprocal with respect to the direction of the biasing magnetic field, producing a nonreciprocal phase shift of the order of 2-18 rad mm-1 at a wavelength of excitation 1.55 μm. Moreover, controlled propagation of SPP modes and their effective tuning are possible in this strip geometry, which enables the design and development of tunable optoelectronic devices.

  17. Photoelectrochemical water splitting enhanced by self-assembled metal nanopillars embedded in an oxide semiconductor photoelectrode

    PubMed Central

    Kawasaki, Seiji; Takahashi, Ryota; Yamamoto, Takahisa; Kobayashi, Masaki; Kumigashira, Hiroshi; Yoshinobu, Jun; Komori, Fumio; Kudo, Akihiko; Lippmaa, Mikk

    2016-01-01

    Production of chemical fuels by direct solar energy conversion in a photoelectrochemical cell is of great practical interest for developing a sustainable energy system. Various nanoscale designs such as nanowires, nanotubes, heterostructures and nanocomposites have been explored to increase the energy conversion efficiency of photoelectrochemical water splitting. Here we demonstrate a self-organized nanocomposite material concept for enhancing the efficiency of photocarrier separation and electrochemical energy conversion. Mechanically robust photoelectrodes are formed by embedding self-assembled metal nanopillars in a semiconductor thin film, forming tubular Schottky junctions around each pillar. The photocarrier transport efficiency is strongly enhanced in the Schottky space charge regions while the pillars provide an efficient charge extraction path. Ir-doped SrTiO3 with embedded iridium metal nanopillars shows good operational stability in a water oxidation reaction and achieves over 80% utilization of photogenerated carriers under visible light in the 400- to 600-nm wavelength range. PMID:27255209

  18. Strains and photovoltaic response in Ta-sputtered Si metal-insulator-semiconductor solar cells

    NASA Astrophysics Data System (ADS)

    Lalevic, B.; Murty, K.; Ito, T.; Kalman, Z. H.; Weissmann, S.

    1981-07-01

    Deformation by bending of Si or Si-SiO2 wafers is achieved by sputter deposition of tantalum films. Strains induced at Si-SiO2 interface and in Ta films are investigated using a combination of X-ray diffraction, electron diffraction, and transmission electron microscopy. Thin Ta film deposits are found to have predominantly a fcc structure, while thicker films have the normal bcc structure with certain admixture of fcc. Film strains generated by the coexistence of the polymorph structure are accommodated by formation of misfit dislocations at the film-Si substrate interface. The effect of the induced stress on the electronic parameters characterizing the Si-SiO2 interface is studied in the metal-oxide-semiconductor structure, and for the effect on photovoltaic response a metal-insulator-semiconductor solar cell configuration is used. Large changes with increasing stress are observed in the values of recombination time, capture cross section, and diffusion length and in sharply decreased conversion efficiency, fill factor, open-circuit voltage, and short-circuit current.

  19. Fabrication of Smooth Patterned Structures of Refractory Metals, Semiconductors, and Oxides via Template Stripping

    PubMed Central

    2013-01-01

    The template-stripping method can yield smooth patterned films without surface contamination. However, the process is typically limited to coinage metals such as silver and gold because other materials cannot be readily stripped from silicon templates due to strong adhesion. Herein, we report a more general template-stripping method that is applicable to a larger variety of materials, including refractory metals, semiconductors, and oxides. To address the adhesion issue, we introduce a thin gold layer between the template and the deposited materials. After peeling off the combined film from the template, the gold layer can be selectively removed via wet etching to reveal a smooth patterned structure of the desired material. Further, we demonstrate template-stripped multilayer structures that have potential applications for photovoltaics and solar absorbers. An entire patterned device, which can include a transparent conductor, semiconductor absorber, and back contact, can be fabricated. Since our approach can also produce many copies of the patterned structure with high fidelity by reusing the template, a low-cost and high-throughput process in micro- and nanofabrication is provided that is useful for electronics, plasmonics, and nanophotonics. PMID:24001174

  20. Strain-induced programmable half-metal and spin-gapless semiconductor in an edge-doped boron nitride nanoribbon

    NASA Astrophysics Data System (ADS)

    Zhu, Shuze; Li, Teng

    2016-03-01

    The search for half-metals and spin-gapless semiconductors has attracted extensive attention in material design for spintronics. Existing progress in such a search often requires peculiar atomistic lattice configuration and also lacks active control of the resulting electronic properties. Here we reveal that a boron nitride nanoribbon with a carbon-doped edge can be made a half-metal or a spin-gapless semiconductor in a programmable fashion. The mechanical strain serves as the on/off switches for functions of half-metal and spin-gapless semiconductor to occur. Our findings shed light on how the edge doping combined with strain engineering can affect electronic properties of two-dimensional materials.

  1. Space division switches based on semiconductor optical amplifiers

    NASA Astrophysics Data System (ADS)

    Kalman, R. F.; Kazovsky, L. G.; Goodman, J. W.

    Semiconductor optical amplifiers (SOA's) can be used in space-division (SD) switches to provide both switching and optical gain. We present a general analysis of optical switches using SOA's, considering noise and saturation effects associated with amplified spontaneous emission. Based on this analysis, we derive size limitations of SD switches. Three specific SD switching architectures are considered. For a lumped gain matrix vector multiplier (MVM) switch, switch sizes are limited to the range of 3000 x 3000 for SOA's with saturation output powers of 100 mW. Based on the effects considered in our analysis, distributed gain MVM switches and Benes switches are not limited by signal-to noise ratio and saturation up to sizes of 10 exp 80 x 10 exp 80 for SOA's with saturation output powers of 100 mW.

  2. Chemoelectronic circuits based on metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Yan, Yong; Warren, Scott C.; Fuller, Patrick; Grzybowski, Bartosz A.

    2016-07-01

    To develop electronic devices with novel functionalities and applications, various non-silicon-based materials are currently being explored. Nanoparticles have unique characteristics due to their small size, which can impart functions that are distinct from those of their bulk counterparts. The use of semiconductor nanoparticles has already led to improvements in the efficiency of solar cells, the processability of transistors and the sensitivity of photodetectors, and the optical and catalytic properties of metal nanoparticles have led to similar advances in plasmonics and energy conversion. However, metals screen electric fields and this has, so far, prevented their use in the design of all-metal nanoparticle circuitry. Here, we show that simple electronic circuits can be made exclusively from metal nanoparticles functionalized with charged organic ligands. In these materials, electronic currents are controlled by the ionic gradients of mobile counterions surrounding the ‘jammed’ nanoparticles. The nanoparticle-based electronic elements of the circuitry can be interfaced with metal nanoparticles capable of sensing various environmental changes (humidity, gas, the presence of various cations), creating electronic devices in which metal nanoparticles sense, process and ultimately report chemical signals. Because the constituent nanoparticles combine electronic and chemical sensing functions, we term these systems ‘chemoelectronic’. The circuits have switching times comparable to those of polymer electronics, selectively transduce parts-per-trillion chemical changes into electrical signals, perform logic operations, consume little power (on the scale of microwatts), and are mechanically flexible. They are also ‘green’, in the sense that they comprise non-toxic nanoparticles cast at room temperature from alcohol solutions.

  3. Chemoelectronic circuits based on metal nanoparticles.

    PubMed

    Yan, Yong; Warren, Scott C; Fuller, Patrick; Grzybowski, Bartosz A

    2016-07-01

    To develop electronic devices with novel functionalities and applications, various non-silicon-based materials are currently being explored. Nanoparticles have unique characteristics due to their small size, which can impart functions that are distinct from those of their bulk counterparts. The use of semiconductor nanoparticles has already led to improvements in the efficiency of solar cells, the processability of transistors and the sensitivity of photodetectors, and the optical and catalytic properties of metal nanoparticles have led to similar advances in plasmonics and energy conversion. However, metals screen electric fields and this has, so far, prevented their use in the design of all-metal nanoparticle circuitry. Here, we show that simple electronic circuits can be made exclusively from metal nanoparticles functionalized with charged organic ligands. In these materials, electronic currents are controlled by the ionic gradients of mobile counterions surrounding the 'jammed' nanoparticles. The nanoparticle-based electronic elements of the circuitry can be interfaced with metal nanoparticles capable of sensing various environmental changes (humidity, gas, the presence of various cations), creating electronic devices in which metal nanoparticles sense, process and ultimately report chemical signals. Because the constituent nanoparticles combine electronic and chemical sensing functions, we term these systems 'chemoelectronic'. The circuits have switching times comparable to those of polymer electronics, selectively transduce parts-per-trillion chemical changes into electrical signals, perform logic operations, consume little power (on the scale of microwatts), and are mechanically flexible. They are also 'green', in the sense that they comprise non-toxic nanoparticles cast at room temperature from alcohol solutions. PMID:26974958

  4. Impact of Reducing Shallow Trench Isolation Mechanical Stress on Active Length for 40 nm n-Type Metal-Oxide-Semiconductor Field-Effect Transistors

    NASA Astrophysics Data System (ADS)

    Huang, Yao-Tsung; Wu, San-Lein; Lin, Hau-Yu; Kuo, Cheng-Wen; Chang, Shoou-Jinn; Hong, De-Gong; Wu, Chung-Yi; Huang, Cheng-Tung; Cheng, Osbert

    2011-04-01

    We report an improved densification annealing process for sub atmospheric chemical vapor deposition (SACVD)-based shallow trench isolation (STI) to enhance n-type metal-oxide-semiconductor field-effect transistor (nMOSFET) performance for 40 nm node and beyond. Experimental results show that this improved STI densification process leads to lower compressive stress in the small active area compared with the standard STI process. This is beneficial to electron mobility and leads to an enhancement of on-current (ION). Moreover, comparable drain induced barrier lowering (DIBL) and subthreshold swing (SS) characteristics for both devices indicate that the improved densification process would no significant influences on process variations or dopant diffusions. Hence, the improved STI process can be adopted in 40 nm complementary metal-oxide-semiconductor (CMOS) technology and beyond.

  5. Semiconductor to metallic type transition in Ni1.5Fe1.5O4 ferrite

    NASA Astrophysics Data System (ADS)

    Aneeshkumar K., S.; Bhowmik, R. N.

    2016-05-01

    We have investigated electrical properties of Ni1.5Fe1.5O4 ferrite. The sample has been prepared by chemical coprecipitation route. The dc limit of conductivity has been derived from the fitting of ac conductivity data using Johnscher power law and Cole-Cole plot of impedance spectrum. The temperature dependence of dc conductivity data indicated a semiconductor to metallic type transition at 373K and metallic to semiconductor transition at 413K. Such electrical transition may be attributed to the effect of localization and de-localization of charge carriers in the hopping paths (Fe3+-O-Fe3+) and (Ni2+-O-Ni3+).

  6. Characterization of Interface State in Silicon Carbide Metal Oxide Semiconductor Capacitors

    NASA Astrophysics Data System (ADS)

    Kao, Wei-Chieh

    Silicon carbide (SiC) has always been considered as an excellent material for high temperature and high power devices. Since SiC is the only compound semiconductor whose native oxide is silicon dioxide (SiO2), it puts SiC in a unique position. Although SiC metal oxide semiconductor (MOS) technology has made significant progress in recent years, there are still a number of issues to be overcome before more commercial SiC devices can enter the market. The prevailing issues surrounding SiC MOSFET devices are the low channel mobility, the low quality of the oxide layer and the high interface state density at the SiC/SiO2 interface. Consequently, there is a need for research to be performed in order to have a better understanding of the factors causing the poor SiC/SiO2 interface properties. In this work, we investigated the generation lifetime in SiC materials by using the pulsed metal oxide semiconductor (MOS) capacitor method and measured the interface state density distribution at the SiC/SiO2 interface by using the conductance measurement and the high-low frequency capacitance technique. These measurement techniques have been performed on n-type and p-type SiC MOS capacitors. In the course of our investigation, we observed fast interface states at semiconductor-dielectric interfaces in SiC MOS capacitors that underwent three different interface passivation processes, such states were detected in the nitrided samples but not observed in PSG-passivated samples. This result indicate that the lack of fast states at PSG-passivated interface is one of the main reasons for higher channel mobility in PSG MOSFETs. In addition, the effect of mobile ions in the oxide on the response time of interface states has been investigated. In the last chapter we propose additional methods of investigation that can help elucidate the origin of the particular interface states, enabling a more complete understanding of the SiC/SiO2 material system.

  7. Semiconductor to metal transition by tuning the location of N{sub 2}{sup AA} in armchair graphene nanoribbons

    SciTech Connect

    Chen, Tong; Wang, Ling-Ling Li, Quan; Luo, Kai-Wu; Xu, Liang; Li, Xiao-Fei; Zhang, Xiang-Hua

    2014-02-07

    The electronic band structures and transport properties of N{sub 2}{sup AA}-doped armchair graphene nanoribbons (aGNRs) with two quasi-adjacent substitutional nitrogen atoms incorporated in pairs of neighboring carbon atoms in the same sublattice A are investigated by using non-equilibrium Green function formalism in combination with density functional theory. The results show that the coupling effect between the Pz orbitals of carbon and nitrogen atoms plays an important role in the transition between semiconductor and metal by different locations of N{sub 2}{sup AA}-doped aGNRs. And the striking negative differential resistance behaviors can be found in such devices. These tremendous properties suggest potential application of N{sub 2}{sup AA}-doped aGNRs in graphene-based nanoelectronic devices.

  8. A complementary metal-oxide-semiconductor compatible monocantilever 12-point probe for conductivity measurements on the nanoscale

    NASA Astrophysics Data System (ADS)

    Gammelgaard, L.; Bøggild, P.; Wells, J. W.; Handrup, K.; Hofmann, Ph.; Balslev, M. B.; Hansen, J. E.; Petersen, P. R. E.

    2008-09-01

    We present a complementary metal-oxide-semiconductor compatible, nanoscale 12-point-probe based on TiW electrodes placed on a SiO2 monocantilever. Probes are mass fabricated on Si wafers by a combination of electron beam and UV lithography, realizing TiW electrode tips with a width down to 250nm and a probe pitch of 500nm. In-air four-point measurements have been performed on indium tin oxide, ruthenium, and titanium-tungsten, showing good agreement with values obtained by other four-point probes. In-vacuum four-point resistance measurements have been performed on clean Bi(111) using different probe spacings. The results show the expected behavior for bulk Bi, indicating that the contribution of electronic surface states to the transport properties is very small.

  9. Semiconductor-metal phase transition of vanadium dioxide nanostructures on silicon substrate: Applications for thermal control of spacecraft

    NASA Astrophysics Data System (ADS)

    Leahu, G. L.; Li Voti, R.; Larciprete, M. C.; Belardini, A.; Mura, F.; Fratoddi, I.; Sibilia, C.; Bertolotti, M.

    2014-06-01

    We present a detailed infrared study of the semiconductor-to-metal transition (SMT) in a vanadium dioxide (VO2) film deposited on silicon wafer. The VO2 phase transition is studied in the mid-infrared (MIR) region by analyzing the transmittance and the reflectance measurements, and the calculated emissivity. The temperature behaviour of the emissivity during the SMT put into evidence the phenomenon of the anomalous absorption in VO2 which has been explained by applying the Maxwell Garnett effective medium approximation theory, together with a strong hysteresis phenomenon, both useful to design tunable thermal devices to be applied for the thermal control of spacecraft. We have also applied the photothermal radiometry in order to study the changes in the modulated emissivity induced by laser. Experimental results show how the use of these techniques represent a good tool for a quantitative measurement of the optothermal properties of vanadium dioxide based structures.

  10. Slow and fast traps in metal-oxide-semiconductor capacitors fabricated on recessed AlGaN/GaN heterostructures

    NASA Astrophysics Data System (ADS)

    Fiorenza, Patrick; Greco, Giuseppe; Iucolano, Ferdinando; Patti, Alfonso; Roccaforte, Fabrizio

    2015-04-01

    In this letter, slow and fast trap states in metal-oxide-semiconductor (MOS) capacitors fabricated on recessed AlGaN/GaN heterostructures were studied by frequency dependent conductance measurements. In particular, the comparison of devices before and after annealing in forming gas allowed to ascribe the fast states (with characteristic response time in the range of 5-50 μs) to SiO2/GaN "interface traps," and the slow states (50-100 μs) to "border traps" located few nanometers inside the SiO2 layer. These results can be important to predict and optimize the threshold voltage stability of hybrid MOS-based transistors on GaN.

  11. Semiconductor-metal phase transition of vanadium dioxide nanostructures on silicon substrate: Applications for thermal control of spacecraft

    SciTech Connect

    Leahu, G. L. Li Voti, R. Larciprete, M. C. Belardini, A. Mura, F. Sibilia, C.; Bertolotti, M.; Fratoddi, I.

    2014-06-19

    We present a detailed infrared study of the semiconductor-to-metal transition (SMT) in a vanadium dioxide (VO2) film deposited on silicon wafer. The VO2 phase transition is studied in the mid-infrared (MIR) region by analyzing the transmittance and the reflectance measurements, and the calculated emissivity. The temperature behaviour of the emissivity during the SMT put into evidence the phenomenon of the anomalous absorption in VO2 which has been explained by applying the Maxwell Garnett effective medium approximation theory, together with a strong hysteresis phenomenon, both useful to design tunable thermal devices to be applied for the thermal control of spacecraft. We have also applied the photothermal radiometry in order to study the changes in the modulated emissivity induced by laser. Experimental results show how the use of these techniques represent a good tool for a quantitative measurement of the optothermal properties of vanadium dioxide based structures.

  12. Anisotropy of piezoresistance in n-channel inversion layers of metal-oxide-semiconductor transistors on (001)Si

    NASA Astrophysics Data System (ADS)

    Maruyama, T.; Zaima, S.; Koide, Y.; Kanda, Y.; Yasuda, Y.

    1990-12-01

    The crystallographic orientation dependence of piezoresistance of n-channel inversion layers in metal-oxide-semiconductor field-effect transistors on p-type (001)Si has been studied by using a diaphragm at room temperature. The experimental results have been compared with self-consistent calculations based on a surface quantization effect. The main feature of the crystallographic orientation dependence can be explained by an electron repopulation effect induced by applied strain and an effective mass anisotropy. It can be found that the difference between longitudinal and transverse piezoresistance in the devices nearly along the [110] directions is mainly due to an orthorhombic distortion of Si, and the shear deformation coefficients Ξu is determined to be 5.8 eV from comparing the experimental results with the calculated ones. An expression of the shear piezoresistance component π44 is also derived.

  13. A compact quantum correction model for symmetric double gate metal-oxide-semiconductor field-effect transistor

    SciTech Connect

    Cho, Edward Namkyu; Shin, Yong Hyeon; Yun, Ilgu

    2014-11-07

    A compact quantum correction model for a symmetric double gate (DG) metal-oxide-semiconductor field-effect transistor (MOSFET) is investigated. The compact quantum correction model is proposed from the concepts of the threshold voltage shift (ΔV{sub TH}{sup QM}) and the gate capacitance (C{sub g}) degradation. First of all, ΔV{sub TH}{sup QM} induced by quantum mechanical (QM) effects is modeled. The C{sub g} degradation is then modeled by introducing the inversion layer centroid. With ΔV{sub TH}{sup QM} and the C{sub g} degradation, the QM effects are implemented in previously reported classical model and a comparison between the proposed quantum correction model and numerical simulation results is presented. Based on the results, the proposed quantum correction model can be applicable to the compact model of DG MOSFET.

  14. Electron Transport Behavior on Gate Length Scaling in Sub-50 nm GaAs Metal Semiconductor Field Effect Transistors

    NASA Astrophysics Data System (ADS)

    Han, Jaeheon

    2011-12-01

    Short channel GaAs Metal Semiconductor Field Effect Transistors (MESFETs) have been fabricated with gate length to 20 nm, in order to examine the characteristics of sub-50 nm MESFET scaling. Here the rise in the measured transconductance is mainly attributed to electron velocity overshoot. For gate lengths below 40 nm, however, the transconductance drops suddenly. The behavior of velocity overshoot and its degradation is investigated and simulated by using a transport model based on the retarded Langevin equation (RLE). This indicates the existence of a minimum acceleration length needed for the carriers to reach the overshoot velocity. The argument shows that the source resistance must be included as an internal element, or appropriate boundary condition, of relative importance in any model where the gate length is comparable to the inelastic mean free path of the carriers.

  15. Extraction of Channel Length Independent Series Resistance for Deeply Scaled Metal-Oxide-Semiconductor Field-Effect Transistors

    NASA Astrophysics Data System (ADS)

    Ma, Li-Juan; Ji, Xiao-Li; Chen, Yuan-Cong; Xia, Hao-Guang; Zhu, Chen-Xin; Guo, Qiang; Yan, Feng

    2014-09-01

    The recently developed four Rsd extraction methods from a single device, involving the constant-mobility method, the direct Id—Vgs method, the conductance method and the Y-function method, are evaluated on 32 nm n-channel metal-oxide-semiconductor field-effect transistors (nMOSFETs). It is found that Rsd achieved from the constant-mobility method exhibits the channel length independent characteristics. The L-dependent Rsd extracted from the other three methods is proven to be associated with the gate-voltage-induced mobility degradation in the extraction procedures. Based on L-dependent behaviors of Rsd, a new method is proposed for accurate series resistance extraction on deeply scaled MOSFETs.

  16. Energy-band diagram configuration of Al2O3/oxygen-terminated p-diamond metal-oxide-semiconductor

    NASA Astrophysics Data System (ADS)

    Maréchal, A.; Aoukar, M.; Vallée, C.; Rivière, C.; Eon, D.; Pernot, J.; Gheeraert, E.

    2015-10-01

    Diamond metal-oxide-semiconductor capacitors were prepared using atomic layer deposition at 250 °C of Al2O3 on oxygen-terminated boron doped (001) diamond. Their electrical properties were investigated in terms of capacitance and current versus voltage measurements. Performing X-ray photoelectron spectroscopy based on the measured core level energies and valence band maxima, the interfacial energy band diagram configuration of the Al2O3/O-diamond is established. The band diagram alignment is concluded to be of type I with valence band offset Δ E v of 1.34 ± 0.2 eV and conduction band offset Δ E c of 0.56 ± 0.2 eV considering an Al2O3 energy band gap of 7.4 eV. The agreement with electrical measurement and the ability to perform a MOS transistor are discussed.

  17. Interface Schottky barrier engineering via strain in metal-semiconductor composites

    NASA Astrophysics Data System (ADS)

    Ma, Xiangchao; Dai, Ying; Yu, Lin; Huang, Baibiao

    2016-01-01

    The interfacial carrier transfer property, which is dominated by the interface Schottky barrier height (SBH), plays a crucial role in determining the performance of metal-semiconductor heterostructures in a variety of applications. Therefore, artificially controlling the interface SBH is of great importance for their industrial applications. As a model system, the Au/TiO2 (001) heterostructure is studied using first-principles calculations and the tight-binding method in the present study. Our investigation demonstrates that strain can be an effective way to decrease the interface SBH and that the n-type SBH can be more effectively decreased than the p-type SBH. Astonishingly, strain affects the interface SBH mainly by changing the intrinsic properties of Au and TiO2, whereas the interfacial potential alignment is almost independent of strain due to two opposite effects, which are induced by strain at the interfacial region. These observed trends can be understood on the basis of the general free-electron gas model of typical metals, the tight-binding theory and the crystal-field theory, which suggest that similar trends may be generalized for many other metal-semiconductor heterostructures. Given the commonness and tunability of strain in typical heterostructures, we anticipate that the tunability of the interface SBH with strain described here can provide an alternative effective way for realizing more efficient applications of relevant heterostructures.The interfacial carrier transfer property, which is dominated by the interface Schottky barrier height (SBH), plays a crucial role in determining the performance of metal-semiconductor heterostructures in a variety of applications. Therefore, artificially controlling the interface SBH is of great importance for their industrial applications. As a model system, the Au/TiO2 (001) heterostructure is studied using first-principles calculations and the tight-binding method in the present study. Our investigation

  18. Characterization of metal-functionalized flax orbitide as a new candidate for light-emitting semiconductor

    NASA Astrophysics Data System (ADS)

    Bauer, Robert; Bazylewski, Paul; Jadhav, Pramodkumar; Shen, Jianheng; Paskal Okinyo-Owiti, Denis; Yang, Jian; Chang, Gap Soo; Reaney, Martin; Sammynaiken, Ramaswami

    2015-06-01

    Organic materials display promise in numerous electronic applications, complimentary to traditional semi-conducting materials. Cyclolinopeptides show promise in light-emitting applications as an organic semiconductor. Photoluminescence measurements indicate charge transfer between the peptide and the metal, resulting in an increase in intensity of the emission from around the metal in the Cyclolinopeptide complex. Complementary X-ray absorption near-edge spectroscopy (XANES) shows a change in occupation of energy states in the peptide when complexed with the metal, indicating charge transfer, but peak positions show the peptide is not chemically changed by the metal. Combining X-ray emission and XANES provides element specific partial density of states, to estimate the element specific energy gap which is the proposed emission range for the peptide material. Organic light emitting diode devices have been fabricated, although no measurable emission has been seen as of yet. The devices have diode like current-voltage characteristics showing the peptide is semi-conducting with a threshold voltage of approximately 2.5 V.

  19. Evaluation of a dual bias dual metal oxide-silicon semiconductor field effect transistor detector as radiation dosimeter.

    PubMed

    Soubra, M; Cygler, J; Mackay, G

    1994-04-01

    A new type of direct reading semiconductor dosimeter has been investigated as a radiation detector for photon and electron therapy beams of various energies. The operation of this device is based on the measurement of the threshold voltage shift in a custom-built metal oxide-silicon semiconductor field effect transistor (MOSFET). This voltage is a linear function of absorbed dose. The extent of the linearity region is dependent on the voltage controlled operation during irradiation. Operating two MOSFETS at two different biases simultaneously during irradiation will result in sensitivity (V/Gy) reproducibility better than +/- 3% over a range in dose of 100 Gy and at a dose per fraction greater than 20 x 10(-2) Gy. The modes of operation give this device many advantages, such as continuous monitoring during irradiation, immediate reading, and permanent storage of total dose after irradiation. The availability and ease of use of these MOSFET detectors make them very promising in clinical dosimetry. PMID:8058024

  20. Schottky or Ohmic metal-semiconductor contact: influence on photocatalytic efficiency of Ag/ZnO and Pt/ZnO model systems.

    PubMed

    Yan, Fengpo; Wang, Yonghao; Zhang, Jiye; Lin, Zhang; Zheng, Jinsheng; Huang, Feng

    2014-01-01

    The relationship between the contact type in metal-semiconductor junctions and their photocatalytic efficiencies is investigated. Two metal-semiconductor junctions, silver on zinc oxide (Ag/ZnO) and platinum on zinc oxide (Pt/ZnO) serve as model system for Ohmic and Schottky metal-semiconductor contact, respectively. Ag/ZnO, with Ohmic contact, exhibits a higher photocatalytic efficiency than Pt/ZnO, with Schottky contact. The direction of electric fields within the semiconductor is found to play a crucial role in the separation of photogenerated charges, and thus strongly influences the photocatalytic efficiency. PMID:24458735

  1. Amorphous silicon enhanced metal-insulator-semiconductor contacts for silicon solar cells

    SciTech Connect

    Bullock, J. Cuevas, A.; Yan, D.; Demaurex, B.; Hessler-Wyser, A.; De Wolf, S.

    2014-10-28

    Carrier recombination at the metal-semiconductor contacts has become a significant obstacle to the further advancement of high-efficiency diffused-junction silicon solar cells. This paper provides the proof-of-concept of a procedure to reduce contact recombination by means of enhanced metal-insulator-semiconductor (MIS) structures. Lightly diffused n{sup +} and p{sup +} surfaces are passivated with SiO{sub 2}/a-Si:H and Al{sub 2}O{sub 3}/a-Si:H stacks, respectively, before the MIS contacts are formed by a thermally activated alloying process between the a-Si:H layer and an overlying aluminum film. Transmission/scanning transmission electron microscopy (TEM/STEM) and energy dispersive x-ray spectroscopy are used to ascertain the nature of the alloy. Idealized solar cell simulations reveal that MIS(n{sup +}) contacts, with SiO{sub 2} thicknesses of ∼1.55 nm, achieve the best carrier-selectivity producing a contact resistivity ρ{sub c} of ∼3 mΩ cm{sup 2} and a recombination current density J{sub 0c} of ∼40 fA/cm{sup 2}. These characteristics are shown to be stable at temperatures up to 350 °C. The MIS(p{sup +}) contacts fail to achieve equivalent results both in terms of thermal stability and contact characteristics but may still offer advantages over directly metallized contacts in terms of manufacturing simplicity.

  2. Geometric and electronic structure of mixed metal-semiconductor clusters from global optimization.-

    NASA Astrophysics Data System (ADS)

    Hagelberg, Frank; Wu, Jianhua

    2006-03-01

    In addition to pure metal and semiconductor clusters, hybrid species that contain both types of constituents occur at the metal-semiconductor interface. Thus, clusters of the form Cu(x)Si(y) were detected by mass spectrometry [1]. In this contribution, the geometric and energetic features of Me(m)Si(7-m) (Me=Cu and Li) clusters are discussed. The choice of these systems is motivated by the structural similarity of the pure Si(7), Li(7), and Cu(7) systems which all stabilize in D(5h) symmetry. On the other hand, Li and Cu, representing the alkali group (IA) and the noble metal group (IB) of the periodic system, are expected to display strongly differing behavior when integrated into a Si(n) cluster, resulting in different ground state geometries for the cases Me = Li and Me = Cu. Addressing this problem by means of geometry optimization requires, in view of the large number of possible atomic permutations for Me(m)Si(7-m) with 0 < m < 7, the use of a global search algorithm. Equilibrium geometries are obtained by simulated annealing within the Nose' thermostat frame. It is observed that Cu(m)Si(7-m) clusters with m < 6 tend towards ground state geometries derived from the D(5h) prototype. For Li(m)Si(7-m), the Li(m) subsystem is found to adsorb on the framework of the Si(7-m) dianion. [1] J.J. Scherer, J.B. Pau, C.P. Collier, A. O'Keefe, and R.J. Saykally, J. Chem. Phys. 103, 9187 (1995).

  3. Detection of Infrared Photons Using the Electronic Stress in Metal-Semiconductor Interfaces

    SciTech Connect

    Datskos, P.G.; Datskou, I.; Egert, C.M.; Rjic, S.

    1999-04-05

    It is well known that the work function of metals decreases when they are placed in a nonpolar liquid. A similar decrease occurs when the metal is placed into contact with a semiconductor forming a Schottky barrier. We report on a new method for detecting photons using the stress caused by photo-electrons emitted from a metal film surface in contact with a semiconductor microstructure. The photoelectrons diffuse into the microstructure and produce an electronic stress. The photon detection results from the measurement of the photo-induced bending of the microstructure. Internal photoemission has been used in the past to detect photons, however, in those cases the detection was accomplished by measuring the current due to photoelectrons and not due to electronic stress. Small changes in position (displacement) of microstructures are routinely measured in atomic force microscopy (AFM) where atomic imaging of surfaces relies on the measurement of small changes (< l0{sup -9} m) in the bending of microcantilevers. In the present work we studied the photon response of Si microcantilevers coated with a thin film of Pt. The Si microcantilevers were 500 nm thick and had a 30 nm layer of Pt. Photons with sufficient energies produce electrons from the platinum-silicon interface which diffuse into the Si and produce an electronic stress. Since the excess charge carriers cause the Si microcantilever to contract in length but not the Pt layer, the bimaterial microcantilever bends. In our present studies we used the optical detection technique to measure the photometric response of Pt-Si microcantilevers as a function of photon energy. The charge carriers responsible for the photo-induced stress in Si, were produced via internal photoemission using a diode laser with wavelength {lambda} = 1550 nm.

  4. Flexible non-volatile memory devices based on organic semiconductors

    NASA Astrophysics Data System (ADS)

    Cosseddu, Piero; Casula, Giulia; Lai, Stefano; Bonfiglio, Annalisa

    2015-09-01

    The possibility of developing fully organic electronic circuits is critically dependent on the ability to realize a full set of electronic functionalities based on organic devices. In order to complete the scene, a fundamental element is still missing, i.e. reliable data storage. Over the past few years, a considerable effort has been spent on the development and optimization of organic polymer based memory elements. Among several possible solutions, transistor-based memories and resistive switching-based memories are attracting a great interest in the scientific community. In this paper, a route for the fabrication of organic semiconductor-based memory devices with performances beyond the state of the art is reported. Both the families of organic memories will be considered. A flexible resistive memory based on a novel combination of materials is presented. In particular, high retention time in ambient conditions are reported. Complementary, a low voltage transistor-based memory is presented. Low voltage operation is allowed by an hybrid, nano-sized dielectric, which is also responsible for the memory effect in the device. Thanks to the possibility of reproducibly fabricating such device on ultra-thin substrates, high mechanical stability is reported.

  5. Supramolecular Luminescence from Oligofluorenol-Based Supramolecular Polymer Semiconductors

    PubMed Central

    Zhang, Guang-Wei; Wang, Long; Xie, Ling-Hai; Lin, Jin-Yi; Huang, Wei

    2013-01-01

    Supramolecular luminescence stems from non-covalent exciton behaviors of active π-segments in supramolecular entities or aggregates via intermolecular forces. Herein, a π-conjugated oligofluorenol, containing self-complementary double hydrogen bonds, was synthesized using Suzuki coupling as a supramolecular semiconductor. Terfluorenol-based random supramolecular polymers were confirmed via concentration-dependent nuclear magnetic resonance (NMR) and dynamic light scattering (DLS). The photoluminescent spectra of the TFOH-1 solution exhibit a green emission band (g-band) at approximately ~520 nm with reversible features, as confirmed through titration experiments. Supramolecular luminescence of TFOH-1 thin films serves as robust evidence for the aggregates of g-band. Our results suggest that the presence of polyfluorene ketone defects is a sufficient condition, rather than a sufficient-necessary condition for the g-band. Supramolecular electroluminescence will push organic devices into the fields of supramolecular optoelectronics, spintronics, and mechatronics. PMID:24232455

  6. Optimization algorithm based characterization scheme for tunable semiconductor lasers.

    PubMed

    Chen, Quanan; Liu, Gonghai; Lu, Qiaoyin; Guo, Weihua

    2016-09-01

    In this paper, an optimization algorithm based characterization scheme for tunable semiconductor lasers is proposed and demonstrated. In the process of optimization, the ratio between the power of the desired frequency and the power except of the desired frequency is used as the figure of merit, which approximately represents the side-mode suppression ratio. In practice, we use tunable optical band-pass and band-stop filters to obtain the power of the desired frequency and the power except of the desired frequency separately. With the assistance of optimization algorithms, such as the particle swarm optimization (PSO) algorithm, we can get stable operation conditions for tunable lasers at designated frequencies directly and efficiently. PMID:27607701

  7. (Hafnium zirconium) nitride/scandium nitride metal/semiconductor superlattices for thermionic energy conversion

    NASA Astrophysics Data System (ADS)

    Schroeder, Jeremy Leroy

    Nitride metal/semiconductor superlattices are a promising materials system for high temperature (>800K) thermionic energy conversion devices. This dissertation specifically investigates various properties of the (HfxZr 1-x)N/ScN metal/semiconductor materials system and introduces a novel approach for fabricating bulk-like thermoelectric devices. (HfxZr 1-x)N/ScN superlattices were deposited on magnesium oxide, sapphire, and silicon substrates by reactive DC magnetron sputtering and characterized by field emission scanning electron microscopy, high resolution x-ray diffraction, and transmission electron microscopy. Magnesium oxide and sapphire substrates produce epitaxial superlattice, whereas films deposited on silicon are characterized as textured-polycrystalline with superlattices within each grain. In addition to thin film characterization, a novel laminate approach was developed that allows for bulk-like devices to be fabricated from nanostructured superlattices, bridging the nano/micro divide. The laminate approach provides a means to simultaneously characterize all of the thermoelectric parameters, (Seebeck coefficient, electrical conductivity, thermal conductivity) of superlattices via a Z-meter characterization system and also provides a scalable process for industrial applications. Parasitic analysis of laminates revealed that low electrical contact resistivity contacts (<2·10-8 Ω-cm 2) are a critical factor for successful implementation of laminate metal/semiconductor superlattice devices. Electrical contact resistivity values for various contact schemes were characterized by the transfer length method, with values as low as 4·10-8 Ω-cm2 achieved. The high uncertainty in the characterization of contacts with low electrical contact resistivity is a challenging roadblock that can be partially overcome through careful design of the transfer length method pattern. Temperature dependent thermal conductivity analysis of HfN/ScN, (Hf 0.5Zr0.5)N/ScN, and Zr

  8. Two-dimensional transition metal dichalcogenides as atomically thin semiconductors: opportunities and challenges.

    PubMed

    Duan, Xidong; Wang, Chen; Pan, Anlian; Yu, Ruqin; Duan, Xiangfeng

    2015-12-21

    The discovery of graphene has ignited intensive interest in two-dimensional layered materials (2DLMs). These 2DLMs represent a new class of nearly ideal 2D material systems for exploring fundamental chemistry and physics at the limit of single-atom thickness, and have the potential to open up totally new technological opportunities beyond the reach of existing materials. In general, there are a wide range of 2DLMs in which the atomic layers are weakly bonded together by van der Waals interactions and can be isolated into single or few-layer nanosheets. The van der Waals interactions between neighboring atomic layers could allow much more flexible integration of distinct materials to nearly arbitrarily combine and control different properties at the atomic scale. The transition metal dichalcogenides (TMDs) (e.g., MoS2, WSe2) represent a large family of layered materials, many of which exhibit tunable band gaps that can undergo a transition from an indirect band gap in bulk crystals to a direct band gap in monolayer nanosheets. These 2D-TMDs have thus emerged as an exciting class of atomically thin semiconductors for a new generation of electronic and optoelectronic devices. Recent studies have shown exciting potential of these atomically thin semiconductors, including the demonstration of atomically thin transistors, a new design of vertical transistors, as well as new types of optoelectronic devices such as tunable photovoltaic devices and light emitting devices. In parallel, there have also been considerable efforts in developing diverse synthetic approaches for the rational growth of various forms of 2D materials with precisely controlled chemical composition, physical dimension, and heterostructure interface. Here we review the recent efforts, progress, opportunities and challenges in exploring the layered TMDs as a new class of atomically thin semiconductors. PMID:26479493

  9. Silicon carbide: A unique platform for metal-oxide-semiconductor physics

    SciTech Connect

    Liu, Gang; Tuttle, Blair R.; Dhar, Sarit

    2015-06-15

    A sustainable energy future requires power electronics that can enable significantly higher efficiencies in the generation, distribution, and usage of electrical energy. Silicon carbide (4H-SiC) is one of the most technologically advanced wide bandgap semiconductor that can outperform conventional silicon in terms of power handling, maximum operating temperature, and power conversion efficiency in power modules. While SiC Schottky diode is a mature technology, SiC power Metal Oxide Semiconductor Field Effect Transistors are relatively novel and there is large room for performance improvement. Specifically, major initiatives are under way to improve the inversion channel mobility and gate oxide stability in order to further reduce the on-resistance and enhance the gate reliability. Both problems relate to the defects near the SiO{sub 2}/SiC interface, which have been the focus of intensive studies for more than a decade. Here we review research on the SiC MOS physics and technology, including its brief history, the state-of-art, and the latest progress in this field. We focus on the two main scientific problems, namely, low channel mobility and bias temperature instability. The possible mechanisms behind these issues are discussed at the device physics level as well as the atomic scale, with the support of published physical analysis and theoretical studies results. Some of the most exciting recent progress in interface engineering for improving the channel mobility and fundamental understanding of channel transport is reviewed.

  10. Interface effects on the characteristics of metal-ferroelectric-insulator-semiconductor field-effect transistor

    NASA Astrophysics Data System (ADS)

    Sun, Jing; Zheng, Xue Jun; Cao, Juan; Li, Wen

    2011-09-01

    The interface effects on the electrical characteristics of metal-ferroelectric-insulator- semiconductor field-effect transistor (MFIS-FET) are studied using an improved model in which the expressions for interface and the mobility model are incorporated into Lue model. The interface layer between the ferroelectric and the electrode and the SiO2 layer between the insulator and the semiconductor have been investigated. Capacitance-gate voltage (C-VG) and drain current-gate voltage (ID-VGS) characteristics are modeled with fixed interface layer and SiO2 layer thicknesses and show good agreement with the experiments, verifying the validity of the improved model and the existence of the interface in the transistor. The characteristics, such as C-VG, ID-VGS and drain current-drain voltage (ID-VDS), are modeled respectively with various interface layer and SiO2 layer thicknesses. The thicker the interface layer and SiO2 layer are, the worse the transistor characteristics become. Similar characteristics can be observed at the specific thickness of the two layers, indicating that both interface layer and SiO2 layer should be considered when the characteristics of MFIS-FETs degrade. In addition, the type of the interfaces can be distinguished by comparing the capacitance in the accumulation region. It is expected that this work can offer some useful guidance to the design and performance improvement of MFIS structure devices.

  11. Enhanced terahertz emission by coherent optical absorption in ultrathin semiconductor films on metals.

    PubMed

    Ramakrishnan, Gopakumar; Ramanandan, Gopika K P; Adam, Aurèle J L; Xu, Man; Kumar, Nishant; Hendrikx, Ruud W A; Planken, Paul C M

    2013-07-15

    We report on the surprisingly strong, broadband emission of coherent terahertz pulses from ultrathin layers of semiconductors such as amorphous silicon, germanium and polycrystalline cuprous oxide deposited on gold, upon illumination with femtosecond laser pulses. The strength of the emission is surprising because the materials are considered to be bad (amorphous silicon and polycrystalline cuprous oxide) or fair (amorphous germanium) terahertz emitters at best. We show that the strength of the emission is partly explained by cavity-enhanced optical absorption. This forces most of the light to be absorbed in the depletion region of the semiconductor/metal interface where terahertz generation occurs. For an excitation wavelength of 800 nm, the strongest terahertz emission is found for a 25 nm thick layer of amorphous germanium, a 40 nm thick layer of amorphous silicon and a 420 nm thick layer of cuprous oxide, all on gold. The emission from cuprous oxide is similar in strength to that obtained with optical rectification from a 300 μm thick gallium phosphide crystal. As an application of our findings we demonstrate how such thin films can be used to turn standard optical components, such as paraboloidal mirrors, into self-focusing terahertz emitters. PMID:23938530

  12. Study of indium antimonide metal-oxide-semiconductor structure prepared by direct photochemical-vapor deposition

    NASA Astrophysics Data System (ADS)

    Su, Y. K.; Liaw, U. H.

    1994-10-01

    Silicon dioxide (SiO2) insulator layers on indium antimonide (InSb) have been prepared by direct phtochemical-vapor deposition at low temperature below 200 C using 2537 A UV light. Ellipsometric studies prove that the refractive index and deposition rate of the photo-oxide films depend on the substrate temperature and gas ratio. The films evaluated by Auger electron spectroscopy (AES) depth profile showed that composition atoms were distributed uniformly throughout the oxide film. The AES analysis found the dominant components of the oxide film are silicon and oxygen. Fourier transform infrared spectroscopy absorption shows that the grown film has strong Si-O bonds with few Si-H bonds. The chemical x-ray photoelectron spectroscopy depth profile shows that the constituents of the semiconductors' outdiffusion into the oxide are few. Metal-oxide-semiconductor (MOS) capacitors were constructed on InSb substrates. Capacitance voltage (C-V) characteristics of the MOS capacitors were measured at 77 K. The interface-state density is of the order of 10(exp 11)/sq cm/eV, and distributed in a very good U shape within the midgap. C-V curves showed almost no hysteresis and smaller flatband voltage. The current-voltage curve shows the leakage current is about 1 nA at 0.8 V, and the breakdown voltage is about 0.8 MV/cm.

  13. Study of indium antimonide metal-oxide-semiconductor structure prepared by direct photochemical-vapor deposition

    NASA Astrophysics Data System (ADS)

    Su, Y. K.; Liaw, U. H.

    1994-10-01

    Silicon dioxide (SiO2) insulator layers on indium antimonide (InSb) have been prepared by direct photochemical-vapor deposition at low temperature below 200 °C using 2537 Å UV light. Ellipsometric studies prove that the refractive index and deposition rate of the photo-oxide films depend on the substrate temperature and gas ratio. The films evaluated by Auger electron spectroscopy (AES) depth profile showed that composition atoms were distributed uniformly throughout the oxide film. The AES analysis found the dominant components of the oxide film are silicon and oxygen. Fourier transform infrared spectroscopy absorption shows that the grown film has strong Si—O bonds with few Si—H bonds. The chemical x-ray photoelectron spectroscopy depth profile shows that the constituents of the semiconductors' outdiffusion into the oxide are few. Metal-oxide-semiconductor (MOS) capacitors were constructed on InSb substrates. Capacitance voltage (C-V) characteristics of the MOS capacitors were measured at 77 K. The interface-state density is of the order of 1011 cm-2 eV-1, and distributed in a very good U shape within the midgap. C-V curves showed almost no hysteresis and smaller flatband voltage. The current-voltage curve shows the leakage current is about 1 nA at 0.8 V, and the breakdown voltage is about 0.8 MV/cm.

  14. Silicon carbide: A unique platform for metal-oxide-semiconductor physics

    NASA Astrophysics Data System (ADS)

    Liu, Gang; Tuttle, Blair R.; Dhar, Sarit

    2015-06-01

    A sustainable energy future requires power electronics that can enable significantly higher efficiencies in the generation, distribution, and usage of electrical energy. Silicon carbide (4H-SiC) is one of the most technologically advanced wide bandgap semiconductor that can outperform conventional silicon in terms of power handling, maximum operating temperature, and power conversion efficiency in power modules. While SiC Schottky diode is a mature technology, SiC power Metal Oxide Semiconductor Field Effect Transistors are relatively novel and there is large room for performance improvement. Specifically, major initiatives are under way to improve the inversion channel mobility and gate oxide stability in order to further reduce the on-resistance and enhance the gate reliability. Both problems relate to the defects near the SiO2/SiC interface, which have been the focus of intensive studies for more than a decade. Here we review research on the SiC MOS physics and technology, including its brief history, the state-of-art, and the latest progress in this field. We focus on the two main scientific problems, namely, low channel mobility and bias temperature instability. The possible mechanisms behind these issues are discussed at the device physics level as well as the atomic scale, with the support of published physical analysis and theoretical studies results. Some of the most exciting recent progress in interface engineering for improving the channel mobility and fundamental understanding of channel transport is reviewed.

  15. 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

  16. 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

  17. 3-D perpendicular assembly of single walled carbon nanotubes for complimentary metal oxide semiconductor interconnects.

    PubMed

    Kim, Tae-Hoon; Yilmaz, Cihan; Somu, Sivasubramanian; Busnaina, Ahmed

    2014-05-01

    Due to their superior electrical properties such as high current density and ballistic transport, carbon nanotubes (CNT) are considered as a potential candidate for future Very Large Scale Integration (VLSI) interconnects. However, direct incorporation of CNTs into Complimentary Metal Oxide Semiconductor (CMOS) architecture by conventional chemical vapor deposition (CVD) growth method is problematic since it requires high temperatures that might damage insulators and doped semiconductors in the underlying CMOS circuits. In this paper, we present a directed assembly method to assemble aligned CNTs into pre-patterned vias and perpendicular to the substrate. A dynamic electric field with a static offset is applied to provide the force needed for directing the SWNT assembly. It is also shown that by adjusting assembly parameters the density of the assembled CNTs can be significantly enhanced. This highly scalable directed assembly method is conducted at room temperature and pressure and is accomplished in a few minutes. I-V characterization of the assembled CNTs was conducted using a Zyvex nanomanipulator in a scanning electron microscope (SEM) and the measured value of the resistance is found to be 270 komega s. PMID:24734611

  18. Structural Design Principle of Small-Molecule Organic Semiconductors for Metal-Free, Visible-Light-Promoted Photocatalysis.

    PubMed

    Wang, Lei; Huang, Wei; Li, Run; Gehrig, Dominik; Blom, Paul W M; Landfester, Katharina; Zhang, Kai A I

    2016-08-01

    Herein, we report on the structural design principle of small-molecule organic semiconductors as metal-free, pure organic and visible light-active photocatalysts. Two series of electron-donor and acceptor-type organic semiconductor molecules were synthesized to meet crucial requirements, such as 1) absorption range in the visible region, 2) sufficient photoredox potential, and 3) long lifetime of photogenerated excitons. The photocatalytic activity was demonstrated in the intermolecular C-H functionalization of electron-rich heteroaromates with malonate derivatives. A mechanistic study of the light-induced electron transport between the organic photocatalyst, substrate, and the sacrificial agent are described. With their tunable absorption range and defined energy-band structure, the small-molecule organic semiconductors could offer a new class of metal-free and visible light-active photocatalysts for chemical reactions. PMID:27378555

  19. Newtype single-layer magnetic semiconductor in transition-metal dichalcogenides VX2 (X = S, Se and Te).

    PubMed

    Fuh, Huei-Ru; Chang, Ching-Ray; Wang, Yin-Kuo; Evans, Richard F L; Chantrell, Roy W; Jeng, Horng-Tay

    2016-01-01

    We present a newtype 2-dimensional (2D) magnetic semiconductor based on transition-metal dichalcogenides VX2 (X = S, Se and Te) via first-principles calculations. The obtained indirect band gaps of monolayer VS2, VSe2, and VTe2 given from the generalized gradient approximation (GGA) are respectively 0.05, 0.22, and 0.20 eV, all with integer magnetic moments of 1.0 μB. The GGA plus on-site Coulomb interaction U (GGA + U) enhances the exchange splittings and raises the energy gap up to 0.38~0.65 eV. By adopting the GW approximation, we obtain converged G0W0 gaps of 1.3, 1.2, and 0.7 eV for VS2, VSe2, and VTe2 monolayers, respectively. They agree very well with our calculated HSE gaps of 1.1, 1.2, and 0.6 eV, respectively. The gap sizes as well as the metal-insulator transitions are tunable by applying the in-plane strain and/or changing the number of stacking layers. The Monte Carlo simulations illustrate very high Curie-temperatures of 292, 472, and 553 K for VS2, VSe2, and VTe2 monolayers, respectively. They are nearly or well beyond the room temperature. Combining the semiconducting energy gap, the 100% spin polarized valence and conduction bands, the room temperature TC, and the in-plane magnetic anisotropy together in a single layer VX2, this newtype 2D magnetic semiconductor shows great potential in future spintronics. PMID:27601195

  20. A Pt-Ti-O gate Si-metal-insulator-semiconductor field-effect transistor hydrogen gas sensor

    NASA Astrophysics Data System (ADS)

    Usagawa, Toshiyuki; Kikuchi, Yota

    2010-10-01

    A hydrogen gas sensor based on platinum-titanium-oxygen (Pt-Ti-O) gate silicon-metal-insulator-semiconductor field-effect transistors (Si-MISFETs) was developed. The sensor has a unique gate structure composed of titanium and oxygen accumulated around platinum grains on top of a novel mixed layer of nanocrystalline TiOx and superheavily oxygen-doped amorphous titanium formed on SiO2/Si substrates. The FET hydrogen sensor shows high reliability and high sensing amplitude (Δ Vg) defined by the magnitude of the threshold voltage shift. Δ Vg is well fitted by a linear function of the logarithm of air-diluted hydrogen concentration C (ppm), i.e., Δ Vg(V) =0.355 log C(ppm ) -0.610 , between 100 ppm and 1%. This high gradient coefficient of Δ Vg for the wide sensing range demonstrates that the sensor is suitable for most hydrogen-safety-monitoring sensor systems. The Pt-Ti-O structures of the sensor are typically realized by annealing Pt (15 nm)/Ti (5 nm)-gate Si-metal-oxide-semiconductor structures in air at 400 °C for 2 h. The Pt-Ti-O gate MIS structures were analyzed by transmission electron microscope (TEM), x-ray diffraction, Auger electron spectroscopy, and TEM energy dispersive x-ray spectroscopy. From the viewpoint of practical sensing applications, hydrogen postannealing of the Pt-Ti-O gate Si-MISFETs is necessary to reduce the residual sensing amplitudes with long tailing profiles.

  1. Newtype single-layer magnetic semiconductor in transition-metal dichalcogenides VX2 (X = S, Se and Te)

    PubMed Central

    Fuh, Huei-Ru; Chang, Ching-Ray; Wang, Yin-Kuo; Evans, Richard F. L.; Chantrell, Roy W.; Jeng, Horng-Tay

    2016-01-01

    We present a newtype 2-dimensional (2D) magnetic semiconductor based on transition-metal dichalcogenides VX2 (X = S, Se and Te) via first-principles calculations. The obtained indirect band gaps of monolayer VS2, VSe2, and VTe2 given from the generalized gradient approximation (GGA) are respectively 0.05, 0.22, and 0.20 eV, all with integer magnetic moments of 1.0 μB. The GGA plus on-site Coulomb interaction U (GGA + U) enhances the exchange splittings and raises the energy gap up to 0.38~0.65 eV. By adopting the GW approximation, we obtain converged G0W0 gaps of 1.3, 1.2, and 0.7 eV for VS2, VSe2, and VTe2 monolayers, respectively. They agree very well with our calculated HSE gaps of 1.1, 1.2, and 0.6 eV, respectively. The gap sizes as well as the metal-insulator transitions are tunable by applying the in-plane strain and/or changing the number of stacking layers. The Monte Carlo simulations illustrate very high Curie-temperatures of 292, 472, and 553 K for VS2, VSe2, and VTe2 monolayers, respectively. They are nearly or well beyond the room temperature. Combining the semiconducting energy gap, the 100% spin polarized valence and conduction bands, the room temperature TC, and the in-plane magnetic anisotropy together in a single layer VX2, this newtype 2D magnetic semiconductor shows great potential in future spintronics. PMID:27601195

  2. Trion-based Optical Processes in Semiconductor Quantum Wells

    NASA Astrophysics Data System (ADS)

    Baldwin, Thomas Kendrick

    In a semiconductor, negative charge is carried by conduction-band electrons and positive charge is carried by valence-band holes. While charge transport properties can be understood by considering the motion of these carriers individually, the optical properties are largely determined by their mutual interaction. The hydrogen-like bound state of an electron with a hole, or exciton, is the fundamental optical excitation in direct-gap materials such as gallium arsenide and cadmium telluride. In this dissertation, we consider charged excitons, or trions. A bound state of an exciton with a resident electron or hole, trions are a relatively pure manifestation of the three-body problem which can be studied experimentally. This is a subject of practical as well as academic interest: Since the trion is the elementary optical excitation of a resident free carrier, the related optical processes can open pathways for manipulating carrier spin and carrier transport. We present three experimental investigations of trion-based optical processes in semiconductor quantum wells. In the first, we demonstrate electromagnetically induced transparency via the electron spin coherence made possible by the trion transition. We explore the practical limits of this technique in high magnetic fields. In the second, we present a direct measurement of trion and exciton oscillator strength at high magnetic fields. These data reveal insights about the structure of the trion's three-body wavefunction relative to that of its next excited state, the triplet trion. In the last, we investigate the mechanism underlying exciton-correlated tunneling, an optically-controllable transport process in mixed-type quantum wells. Extensive experimental studies indicate that it is due to a local, indirect interaction between an exciton and a hole, forming one more example of a trion-mediated optical process. This dissertation includes previously published co-authored material.

  3. Deep-subwavelength hybrid plasmonic waveguide with metal-semiconductor ribs for nanolaser applications

    NASA Astrophysics Data System (ADS)

    Li, Zhiquan; Piao, Ruiqi; Zhao, Jingjing; Meng, Xiaoyun; Li, Wenchao; Niu, Liyong; Gu, Erdan

    2015-12-01

    We propose a novel hybrid plasmonic waveguide with metal-semiconductor ribs. We investigated the modal properties of the proposed structure and the threshold property for plasmonic nanolaser applications by using the finite element method. The results reveal that the structure enables deep-subwavelength mode confinement with low propagation loss and low threshold. By optimizing the geometric parameters of the structure, the mode area can reach 0.000 29λ 2 with a threshold of 700.9/cm at the wavelength of 1.55 μm. Compared to the previously studied hybrid plasmonic waveguide, tighter mode confinement and lower propagation loss is simultaneously achieved for the structure with the same geometric parameters. The designed structure can be used as a low-threshold nanolaser and has promising potential for applications in active plasmonic systems and optoelectronic integrated circuits.

  4. High-Performance WSe2 Complementary Metal Oxide Semiconductor Technology and Integrated Circuits.

    PubMed

    Yu, Lili; Zubair, Ahmad; Santos, Elton J G; Zhang, Xu; Lin, Yuxuan; Zhang, Yuhao; Palacios, Tomás

    2015-08-12

    Because of their extraordinary structural and electrical properties, two-dimensional materials are currently being pursued for applications such as thin-film transistors and integrated circuit. One of the main challenges that still needs to be overcome for these applications is the fabrication of air-stable transistors with industry-compatible complementary metal oxide semiconductor (CMOS) technology. In this work, we experimentally demonstrate a novel high performance air-stable WSe2 CMOS technology with almost ideal voltage transfer characteristic, full logic swing and high noise margin with different supply voltages. More importantly, the inverter shows large voltage gain (∼38) and small static power (picowatts), paving the way for low power electronic system in 2D materials. PMID:26192468

  5. A Novel Metal-Ferroelectric-Semiconductor Field-Effect Transistor Memory Cell Design

    NASA Technical Reports Server (NTRS)

    Phillips, Thomas A.; Bailey, Mark; Ho, Fat Duen

    2004-01-01

    The use of a Metal-Ferroelectric-Semiconductor Field-Effect Transistor (MFSFET) in a resistive-load SRAM memory cell has been investigated A typical two-transistor resistive-load SRAM memory cell architecture is modified by replacing one of the NMOS transistors with an n-channel MFSFET. The gate of the MFSFET is connected to a polling voltage pulse instead of the other NMOS transistor drain. The polling voltage pulses are of sufficient magnitude to saturate the ferroelectric gate material and force the MFSFET into a particular logic state. The memory cell circuit is further modified by the addition of a PMOS transistor and a load resistor in order to improve the retention characteristics of the memory cell. The retention characteristics of both the "1" and "0" logic states are simulated. The simulations show that the MFSFET memory cell design can maintain both the "1" and "0" logic states for a long period of time.

  6. Size and shape dependent melting temperature and thermal expansivity of metallic and semiconductor nanoparticles

    NASA Astrophysics Data System (ADS)

    Patel, Ghanshyam R.; Thakar, Nilesh A.; Pandya, Tushar C.

    2016-05-01

    Liquid drop model is used to predict the size dependent melting temperature of low dimensional systems. In the present work we have modified liquid drop model for predicting shape and size dependent melting temperature of nanoparticles of Pb and Si. The new modified liquid drop model gives good agreement between calculated and experimental data which demonstrate the validity of the present work. It is found that the particle shape can affect the melting temperature of nanoparticles and this effect on the melting temperature becomes larger with decreasing of particle size. In the present study relationship for size and shape dependent of thermal expansivity is deduced for metallic and semiconductor nanoparticles. The present relationship for thermal expansivity may be used to predict the coefficient of thermal expansion for nanoparticles.

  7. Complementary Metal Oxide Semiconductor-Compatible Back-Side-Illuminated Photodiode for Optoelectronic Integrated Circuit Devices

    NASA Astrophysics Data System (ADS)

    Shin, Sang-Baie; Sekiguchi, Hiroto; Okada, Hiroshi; Wakahara, Akihiro

    2013-04-01

    In this study, the prototype optoelectronic integrated circuits (OEICs) operating with optical input signals were designed and fabricated. A back-side-illuminated (BSI) photodiode was designed and demonstrated by a newly proposed practical method, utilizing micro-electromechanical systems (MEMS) and postcomplement metal oxide semiconductor (CMOS) processes. Additional fabrication processes for the BSI photodiode were proposed and described in detail in this paper. The operational amplifier for amplification of the optical current by the BSI photodiode as the transimpedance amplifier was designed and fabricated. And the pulse width modulation (PWM) wave generator was implemented for modulating optical signals as the prototype OEIC device. The maximum quantum efficiency of 28.4% was obtained from the fabricated BSI photodiode. Output signals of PWM were successfully controlled by the generated optical current of the BSI photodiode.

  8. Strongly modified four-wave mixing in a coupled semiconductor quantum dot-metal nanoparticle system

    SciTech Connect

    Paspalakis, Emmanuel; Evangelou, Sofia; Kosionis, Spyridon G.; Terzis, Andreas F.

    2014-02-28

    We study the four-wave mixing effect in a coupled semiconductor quantum dot-spherical metal nanoparticle structure. Depending on the values of the pump field intensity and frequency, we find that there is a critical distance that changes the form of the spectrum. Above this distance, the four-wave mixing spectrum shows an ordinary three-peaked form and the effect of controlling its magnitude by changing the interparticle distance can be obtained. Below this critical distance, the four-wave mixing spectrum becomes single-peaked; and as the interparticle distance decreases, the spectrum is strongly suppressed. The behavior of the system is explained using the effective Rabi frequency that creates plasmonic metaresonances in the hybrid structure. In addition, the behavior of the effective Rabi frequency is explained via an analytical solution of the density matrix equations.

  9. Energy harvesting thermoelectric generators manufactured using the complementary metal oxide semiconductor process.

    PubMed

    Yang, Ming-Zhi; Wu, Chyan-Chyi; Dai, Ching-Liang; Tsai, Wen-Jung

    2013-01-01

    This paper presents the fabrication and characterization of energy harvesting thermoelectric micro generators using the commercial complementary metal oxide semiconductor (CMOS) process. The micro generator consists of 33 thermocouples in series. Thermocouple materials are p-type and n-type polysilicon since they have a large Seebeck coefficient difference. The output power of the micro generator depends on the temperature difference in the hot and cold parts of the thermocouples. In order to increase this temperature difference, the hot part of the thermocouples is suspended to reduce heat-sinking. The micro generator needs a post-CMOS process to release the suspended structures of hot part, which the post-process includes an anisotropic dry etching to etch the sacrificial oxide layer and an isotropic dry etching to remove the silicon substrate. Experiments show that the output power of the micro generator is 9.4 mW at a temperature difference of 15 K. PMID:23396193

  10. Studies of Thermophysical Properties of Metals and Semiconductors by Containerless Processing Under Microgravity

    NASA Technical Reports Server (NTRS)

    Seidel, A.; Soellner, W.; Stenzel, C.

    2012-01-01

    Electromagnetic levitation under microgravity provides unique opportunities for the investigation of liquid metals, alloys and semiconductors, both above and below their melting temperatures, with minimized disturbances of the sample under investigation. The opportunity to perform such experiments will soon be available on the ISS with the EML payload which is currently being integrated. With its high-performance diagnostics systems EML allows to measure various physical properties such as heat capacity, enthalpy of fusion, viscosity, surface tension, thermal expansion coefficient, and electrical conductivity. In studies of nucleation and solidification phenomena the nucleation kinetics, phase selection, and solidification velocity can be determined. Advanced measurement capabilities currently being studied include the measurement and control of the residual oxygen content of the process atmosphere and a complementary inductive technique to measure thermophysical properties.

  11. Influence of graphene oxide on metal-insulator-semiconductor tunneling diodes

    PubMed Central

    2012-01-01

    In recent years, graphene studies have increased rapidly. Graphene oxide, which is an intermediate product to form graphene, is insulating, and it should be thermally reduced to be electrically conductive. We herein describe an attempt to make use of the insulating properties of graphene oxide. The graphene oxide layers are deposited onto Si substrates, and a metal-insulator-semiconductor tunneling structure is formed and its optoelectronic properties are studied. The accumulation dark current and inversion photocurrent of the graphene oxide device are superior to the control device. The introduction of graphene oxide improves the rectifying characteristic of the diode and enhances its responsivity as a photodetector. At 2 V, the photo-to-dark current ratio of the graphene oxide device is 24, larger than the value of 15 measured in the control device. PMID:22734469

  12. Semiconductor- to metallic-like behavior in Bi thin films on KCl substrate

    NASA Astrophysics Data System (ADS)

    Bui, Thanh Nhan; Raskin, Jean-Pierre; Hackens, Benoit

    2016-04-01

    Bi thin films, with a thickness of 100 nm, are deposited by electron-beam evaporation on a freshly cleaved (100) KCl substrate. The substrate temperature during film growth (Tdep) ranges from room temperature up to 170 °C. Films deposited at room temperature exhibit a maze-like microstructure typical of the rhombohedral (110) texture, as confirmed by X-ray diffraction. For Tdep above 80 °C, a different microstructure appears, characterized by concentric triangular shapes corresponding to the trigonal (111) texture. Temperature dependence of the resistivity shows a transition from a semiconductor-like behavior for films deposited at room temperature to a metallic-like behavior for Tdep above 80 °C. From magnetoresistance measurements between room temperature and 1.6 K, we extract the electron and hole mobilities, concentrations, and mean free paths, which allow to draw a complete picture of the transport properties of both types of films.

  13. Magnetic ordering in digital alloys of group-IV semiconductors with 3d-transition metals

    SciTech Connect

    Otrokov, M. M.; Tugushev, V. V.; Ernst, A.; Ostanin, S. A.; Kuznetsov, V. M.; Chulkov, E. V.

    2011-04-15

    The ab initio investigation of the magnetic ordering in digital alloys consisting of monolayers of 3d-transition metals Ti, V, Cr, Mn, Fe, Co, and Ni introduced into the Si, Ge, and Si{sub 0.5}Ge{sub 0.5} semiconductor hosts is reported. The calculations of the parameters of the exchange interactions and total-energy calculations indicate that the ferromagnetic order appears only in the manganese monolayers, whereas the antiferromagnetic order is more probable in V, Cr, and Fe monolayers, and Ti, Co, and Ni monolayers are nonmagnetic. The stability of the ferromagnetic phase in digital alloys containing manganese monolayers has been analyzed using the calculations of magnon spectra.

  14. Optimal design of an electret microphone metal-oxide-semiconductor field-effect transistor preamplifier.

    PubMed

    van der Donk, A G; Bergveld, P

    1992-04-01

    A theoretical noise analysis of the combination of a capacitive microphone and a preamplifier containing a metal-oxide-semiconductor field-effect transistor (MOSFET) and a high-value resistive bias element is given. It is found that the output signal-to-noise ratio for a source follower and for a common-source circuit is almost the same. It is also shown that the output noise can be reduced by making the microphone capacitance as well as the bias resistor as large as possible, and furthermore by keeping the parasitic gate capacitances as low as possible and finally by using an optimum value for the gate area of the MOSFET. The main noise source is the thermal noise of the gate leakage resistance of the MOSFET. It is also shown that short-channel MOSFETs produce more thermal channel noise than longer channel devices. PMID:1597614

  15. Sharp semiconductor-to-metal transition of VO{sub 2} thin films on glass substrates

    SciTech Connect

    Jian, Jie; Chen, Aiping; Zhang, Wenrui; Wang, Haiyan

    2013-12-28

    Outstanding phase transition properties of vanadium dioxide (VO{sub 2}) thin films on amorphous glass were achieved and compared with the ones grown on c-cut sapphire and Si (111) substrates, all by pulsed laser deposition. The films on glass substrate exhibit a sharp semiconductor-to-metal transition (∼4.3 °C) at a near bulk transition temperature of ∼68.4 °C with an electrical resistance change as high as 3.2 × 10{sup 3} times. The excellent phase transition properties of the films on glass substrate are correlated with the large grain size and low defects density achieved. The phase transition properties of VO{sub 2} films on c-cut sapphire and Si (111) substrates were found to be limited by the high defect density.

  16. Control of Nanostructures and Interfaces of Metal Oxide Semiconductors for Quantum-Dots-Sensitized Solar Cells.

    PubMed

    Tian, Jianjun; Cao, Guozhong

    2015-05-21

    Nanostructured metal oxide semiconductors (MOS), such as TiO2 and ZnO, have been regarded as an attractive material for the quantum dots sensitized solar cells (QDSCs), owing to their large specific surface area for loading a large amount of quantum dots (QDs) and strong scattering effect for capturing a sufficient fraction of photons. However, the large surface area of such nanostructures also provides easy pathways for charge recombination, and surface defects and connections between adjacent nanoparticles may retard effective charge injection and charge transport, leading to a loss of power conversion efficiency. Introduction of the surface modification for MOS or QDs has been thought an effective approach to improve the performance of QDSC. In this paper, the recent advances in the control of nanostructures and interfaces in QDSCs and prospects for the further development with higher power conversion efficiency (PCE) have been discussed. PMID:26263261

  17. Metal-Insulator-Semiconductor (MIS) Structure with AlN Dielectric

    SciTech Connect

    Mahyuddin, A.; Hassan, Z.; Cheong, K. Y.

    2009-06-01

    In this paper, we present the study of the structural and electrical properties of AlN/GaN thin films grown on Si (111) substrates by plasma-assisted molecular beam epitaxy (RF-MBE) with AlN buffer layer. The performance of aluminum nitride (AlN) as insulator and aluminum (Al) contacts is presented. The thickness of GaN film and AlN insulating film as seen from SEM cross section are about 357.3 nm and 63.38 nm respectively. The presence of Ga, Al and N are confirmed by energy dispersive X-ray (EDX) measurement. The X-ray diffraction (XRD) measurement reveals that the samples are all wurtzite hexagonal AlN and GaN structure. The fabricated metal-insulator-semiconductor (MIS) structure was characterized using capacitance-voltage (C-V) measurements.

  18. Technology of GaAs metal-oxide-semiconductor solar cells

    NASA Technical Reports Server (NTRS)

    Stirn, R. J.; Yeh, Y. C. M.

    1977-01-01

    The growth of an oxide interfacial layer was recently found to increase the open-circuit voltage (OCV) and efficiency by up to 60 per cent in GaAs metal-semiconductor solar cells. Details of oxidation techniques to provide the necessary oxide thickness and chemical structure and using ozone, water-vapor-saturated oxygen, or oxygen gas discharges are described, as well as apparent crystallographic orientation effects. Preliminary results of the oxide chemistry obtained from X-ray, photoelectron spectroscopy are given. Ratios of arsenic oxide to gallium oxide of unity or less seem to be preferable. Samples with the highest OVC predominantly have As(+3) in the arsenic oxide rather than As(+5). A major difficulty at this time is a reduction in OCV by 100-200 mV when the antireflection coating is vacuum deposited.

  19. Design issues for lateral double-diffused metal-oxide-semiconductor with higher breakdown voltage.

    PubMed

    Sung, Kunsik; Won, Taeyoung

    2013-05-01

    In this paper, we discuss a new High-Side nLDMOSFET whose breakdown voltage is over 100 V while meeting the thermal budget for the conventional process. The proposed n-channel lateral double-diffused metal-oxide-semiconductor field-effect transistor (LDMOSFET) has a feature in that the structure comprises a gap of 5 microm between the DEEP N-WELL and the center of the source, the surface of which is implanted by the NADJUST-layer for high breakdown voltage and simultaneously the low specific on-resistance. The computer simulation of the proposed High-Side nLDMOS exhibits BVdss of 126 V and R(ON,sp) of as low as 2.50 m(omega) x cm2. The NBL, which plays a significant role as a blocking layer against the punch-through seems to function as a hurdle for increasing the breakdown voltage. PMID:23858840

  20. Modeling of quasi-ballistic transport in nanowire metal-oxide-semiconductor field-effect transistors

    NASA Astrophysics Data System (ADS)

    Lee, Yeonghun; Kakushima, Kuniyuki; Natori, Kenji; Iwai, Hiroshi

    2015-10-01

    We developed a semi-analytical quasi-ballistic transport model for the nanowire metal-oxide-semiconductor field-effect transistors, dealing with finite lengths of source, channel, and drain. For the modeling, we used a combination of one-flux scattering matrices and analytical solutions of Boltzmann transport equations. The developed model was in quantitatively good agreement with numerical results, and well represented intermediate-scaled devices. In addition, we illustrated that the finite source seriously affect the distribution function of the carriers injected from the source, and the finite drain does for the backscattering into the channel from the drain. Finally, our model and results would help to understand physical aspects regarding quasi-ballistic transport in nanoscale devices.