Science.gov

Sample records for intrinsic semiconductors based

  1. Near-infrared-to-visible highly selective thermal emitters based on an intrinsic semiconductor.

    PubMed

    Asano, Takashi; Suemitsu, Masahiro; Hashimoto, Kohei; De Zoysa, Menaka; Shibahara, Tatsuya; Tsutsumi, Tatsunori; Noda, Susumu

    2016-12-01

    Control of the thermal emission spectra of emitters will result in improved energy utilization efficiency in a broad range of fields, including lighting, energy harvesting, and sensing. In particular, it is challenging to realize a highly selective thermal emitter in the near-infrared-to-visible range, in which unwanted thermal emission spectral components at longer wavelengths are significantly suppressed, whereas strong emission in the near-infrared-to-visible range is retained. To achieve this, we propose an emitter based on interband transitions in a nanostructured intrinsic semiconductor. The electron thermal fluctuations are first limited to the higher-frequency side of the spectrum, above the semiconductor bandgap, and are then enhanced by the photonic resonance of the structure. Theoretical calculations indicate that optimized intrinsic Si rod-array emitters with a rod radius of 105 nm can convert 59% of the input power into emission of wavelengths shorter than 1100 nm at 1400 K. It is also theoretically indicated that emitters with a rod radius of 190 nm can convert 84% of the input power into emission of <1800-nm wavelength at 1400 K. Experimentally, we fabricated a Si rod-array emitter that exhibited a high peak emissivity of 0.77 at a wavelength of 790 nm and a very low background emissivity of <0.02 to 0.05 at 1100 to 7000 nm, under operation at 1273 K. Use of a nanostructured intrinsic semiconductor that can withstand high temperatures is promising for the development of highly efficient thermal emitters operating in the near-infrared-to-visible range.

  2. Near-infrared–to–visible highly selective thermal emitters based on an intrinsic semiconductor

    PubMed Central

    Asano, Takashi; Suemitsu, Masahiro; Hashimoto, Kohei; De Zoysa, Menaka; Shibahara, Tatsuya; Tsutsumi, Tatsunori; Noda, Susumu

    2016-01-01

    Control of the thermal emission spectra of emitters will result in improved energy utilization efficiency in a broad range of fields, including lighting, energy harvesting, and sensing. In particular, it is challenging to realize a highly selective thermal emitter in the near-infrared–to–visible range, in which unwanted thermal emission spectral components at longer wavelengths are significantly suppressed, whereas strong emission in the near-infrared–to–visible range is retained. To achieve this, we propose an emitter based on interband transitions in a nanostructured intrinsic semiconductor. The electron thermal fluctuations are first limited to the higher-frequency side of the spectrum, above the semiconductor bandgap, and are then enhanced by the photonic resonance of the structure. Theoretical calculations indicate that optimized intrinsic Si rod-array emitters with a rod radius of 105 nm can convert 59% of the input power into emission of wavelengths shorter than 1100 nm at 1400 K. It is also theoretically indicated that emitters with a rod radius of 190 nm can convert 84% of the input power into emission of <1800-nm wavelength at 1400 K. Experimentally, we fabricated a Si rod-array emitter that exhibited a high peak emissivity of 0.77 at a wavelength of 790 nm and a very low background emissivity of <0.02 to 0.05 at 1100 to 7000 nm, under operation at 1273 K. Use of a nanostructured intrinsic semiconductor that can withstand high temperatures is promising for the development of highly efficient thermal emitters operating in the near-infrared–to–visible range. PMID:28028532

  3. Intrinsic spin dynamics in semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Valín-Rodríguez, Manuel

    2005-12-01

    We investigate the characteristic spin dynamics corresponding to semiconductor quantum dots within the multiband envelope function approximation (EFA). By numerically solving an 8 × 8 k·p Hamiltonian we treat systems based on different III-V semiconductor materials. It is shown that, even in the absence of an applied magnetic field, these systems show intrinsic spin dynamics governed by intraband and interband transitions leading to characteristic spin frequencies ranging from THz to optical frequencies.

  4. Intrinsic DX Centers in Ternary Chalcopyrite Semiconductors

    SciTech Connect

    Lany, S.; Zunger, A.

    2008-01-01

    In III-V and II-VI semiconductors, certain nominally electron-donating impurities do not release electrons but instead form deep electron-traps known as 'DX centers.' While in these compounds, such traps occur only after the introduction of foreign impurity atoms, we find from first-principles calculations that in ternary I-III-VI{sub 2} chalcopyrites like CuInSe{sub 2} and CuGaSe{sub 2}, DX-like centers can develop without the presence of any extrinsic impurities. These intrinsic DX centers are suggested as a cause of the difficulties to maintain high efficiencies in CuInSe{sub 2}-based thin-film solar-cells when the band gap is increased by addition of Ga.

  5. Acoustically induced stark effect for excitons in intrinsic semiconductors.

    PubMed

    Ivanov, A L; Littlewood, P B

    2001-09-24

    A Stark effect for excitons parametrically driven by coherent acoustic phonons is proposed. Our scheme refers to a low-temperature intrinsic semiconductor or semiconductor nanostructure pumped by an acoustic wave (frequency band nu(ac) approximately equal to 1-40 GHz and intensity range I(ac) approximately equal to 10(-2)-10(2) W/cm(2)) and probed by low-intensity light. Tunable optical band gaps, which strongly change the spectral shape of the exciton line, are induced in the polariton spectrum by acoustic pumping. We develop an exactly solvable model of the acoustic Stark effect and apply our results to GaAs driven by bulk or surface acoustic waves.

  6. Intrinsic charge trapping in organic and polymeric semiconductors: a physical chemistry perspective

    SciTech Connect

    Kaake, Loren; Barbara, Paul F.; Zhu, Xiaoyang

    2010-01-12

    We aim to understand the origins of intrinsic charge carrier traps in organic and polymeric semiconductor materials from a physical chemistry perspective. In crystalline organic semiconductors, we point out some of the inadequacies in the description of intrinsic charge traps using language and concepts developed for inorganic semiconductors. In π-conjugated polymeric semiconductors, we suggest the presence of a two-tier electronic energy landscape, a bimodal majority landscape due to two dominant structural motifs and a minority electronic energy landscape from intrinsic charged defects. The bimodal majority electronic energy landscape results from a combination of amorphous domains and microcrystalline or liquid-crystalline domains. The minority tier of the electronic density of states is comprised of deep Coulomb traps embedded in the majority electronic energy landscape. This minority electronic energy landscape may dominate transport properties at low charge carrier densities, such as those expected for organic photovoltaic devices, while the bimodal majority electronic energy landscape becomes significant at high carrier densities, that is, in organic field effect transistors.

  7. New concept to break the intrinsic properties of organic semiconductors for optical sensing applications

    NASA Astrophysics Data System (ADS)

    Choy, Wallace C. H.

    2015-09-01

    As the intrinsic electrostatic limit, space charge limit (SCL) for photocurrent is a universal phenomenon which is fundamental important for organic semiconductors. We will demonstrate SCL breaking by a new plasmonic-electrical concept. As a proof-ofconcept, organic solar cells (OSCs) comprising metallic planar and grating electrodes are studied. Interestingly, although strong plasmonic resonances induce abnormally dense photocarriers around a grating anode, the grating incorporated inverted OSC is exempt from space charge accumulation (limit) and degradation of electrical properties. The plasmonic-electrical concept will open up a new way to manipulate both optical and electrical properties of semiconductor devices simultaneously.

  8. Thienoacene-based organic semiconductors.

    PubMed

    Takimiya, Kazuo; Shinamura, Shoji; Osaka, Itaru; Miyazaki, Eigo

    2011-10-11

    Thienoacenes consist of fused thiophene rings in a ladder-type molecular structure and have been intensively studied as potential organic semiconductors for organic field-effect transistors (OFETs) in the last decade. They are reviewed here. Despite their simple and similar molecular structures, the hitherto reported properties of thienoacene-based OFETs are rather diverse. This Review focuses on four classes of thienoacenes, which are classified in terms of their chemical structures, and elucidates the molecular electronic structure of each class. The packing structures of thienoacenes and the thus-estimated solid-state electronic structures are correlated to their carrier transport properties in OFET devices. With this perspective of the molecular structures of thienoacenes and their carrier transport properties in OFET devices, the structure-property relationships in thienoacene-based organic semiconductors are discussed. The discussion provides insight into new molecular design strategies for the development of superior organic semiconductors.

  9. Intrinsic delay of permeable base transistor

    SciTech Connect

    Chen, Wenchao; Guo, Jing; So, Franky

    2014-07-28

    Permeable base transistors (PBTs) fabricated by vacuum deposition or solution process have the advantages of easy fabrication and low power operation and are a promising device structure for flexible electronics. Intrinsic delay of PBT, which characterizes the speed of the transistor, is investigated by solving the three-dimensional Poisson equation and drift-diffusion equation self-consistently using finite element method. Decreasing the emitter thickness lowers the intrinsic delay by improving on-current, and a thinner base is also preferred for low intrinsic delay because of fewer carriers in the base region at off-state. The intrinsic delay exponentially decreases as the emitter contact Schottky barrier height decreases, and it linearly depends on the carrier mobility. With an optimized emitter contact barrier height and device geometry, a sub-nano-second intrinsic delay can be achieved with a carrier mobility of ∼10 cm{sup 2}/V/s obtainable in solution processed indium gallium zinc oxide, which indicates the potential of solution processed PBTs for GHz operations.

  10. Intrinsic coherent acoustic phonons in the indirect band gap semiconductors Si and GaP

    NASA Astrophysics Data System (ADS)

    Ishioka, Kunie; Rustagi, Avinash; Höfer, Ulrich; Petek, Hrvoje; Stanton, Christopher J.

    2017-01-01

    We report on the intrinsic optical generation and detection of coherent acoustic phonons at (001)-oriented bulk Si and GaP without metallic phonon transducer structures. Photoexcitation by a 3.1-eV laser pulse generates a normal strain pulse within the ˜100 -nm penetration depth in both semiconductors. The subsequent propagation of the strain pulse into the bulk is detected with a delayed optical probe as a periodic modulation of the optical reflectivity. Our theoretical model explains quantitatively the generation of the acoustic pulse via the deformation potential electron-phonon coupling and detection in terms of the spatially and temporally dependent photoelastic effect for both semiconductors. Comparison with our theoretical model reveals that the experimental strain pulses have finite buildup times of 1.2 and 0.4 ps for GaP and Si, which are comparable with the time required for the photoexcited electrons to transfer to the lowest X valley through intervalley scattering. The deformation potential coupling related to the acoustic pulse generation for GaP is estimated to be twice as strong as that for Si from our experiments, in agreement with a previous theoretical prediction.

  11. Photogenerated Intrinsic Free Carriers in Small-molecule Organic Semiconductors Visualized by Ultrafast Spectroscopy

    PubMed Central

    He, Xiaochuan; Zhu, Gangbei; Yang, Jianbing; Chang, Hao; Meng, Qingyu; Zhao, Hongwu; Zhou, Xin; Yue, Shuai; Wang, Zhuan; Shi, Jinan; Gu, Lin; Yan, Donghang; Weng, Yuxiang

    2015-01-01

    Confirmation of direct photogeneration of intrinsic delocalized free carriers in small-molecule organic semiconductors has been a long-sought but unsolved issue, which is of fundamental significance to its application in photo-electric devices. Although the excitonic description of photoexcitation in these materials has been widely accepted, this concept is challenged by recently reported phenomena. Here we report observation of direct delocalized free carrier generation upon interband photoexcitation in highly crystalline zinc phthalocyanine films prepared by the weak epitaxy growth method using ultrafast spectroscopy. Transient absorption spectra spanning the visible to mid-infrared region revealed the existence of short-lived free electrons and holes with a diffusion length estimated to cross at least 11 molecules along the π−π stacking direction that subsequently localize to form charge transfer excitons. The interband transition was evidenced by ultraviolet-visible absorption, photoluminescence and electroluminescence spectroscopy. Our results suggest that delocalized free carriers photogeneration can also be achieved in organic semiconductors when the molecules are packed properly. PMID:26611323

  12. Intrinsic point defects and complexes in the quaternary kesterite semiconductor Cu2ZnSnS4

    NASA Astrophysics Data System (ADS)

    Chen, Shiyou; Yang, Ji-Hui; Gong, X. G.; Walsh, Aron; Wei, Su-Huai

    2010-06-01

    Current knowledge of the intrinsic defect properties of Cu2ZnSnS4 (CZTS) is limited, which is hindering further improvement of the performance of CZTS-based solar cells. Here, we have performed first-principles calculations for a series of intrinsic defects and defect complexes in CZTS, from which we have the following observations. (i) It is important to control the elemental chemical potentials during crystal growth to avoid the formation of secondary phases such as ZnS, CuS, and Cu2SnS3 . (ii) The intrinsic p -type conductivity is attributed to the CuZn antisite which has a lower formation energy and relatively deeper acceptor level compared to the Cu vacancy. (iii) The low formation energy of many of the acceptor defects will lead to the intrinsic p -type character, i.e., n -type doping is very difficult in this system. (iv) The role of electrically neutral defect complexes is predicted to be important, because they have remarkably low formation energies and electronically passivate deep levels in the band gap. For example, [CuZn-+ZnCu+] , [VCu-+ZnCu+] , and [ZnSn2-+2ZnCu+] may form easily in nonstoichiometric samples. The band alignment between Cu2ZnSnS4 , CuInSe2 and the solar-cell window layer CdS has also been calculated, revealing that a type-II band alignment exists for the CdS/Cu2ZnSnS4 heterojunction. The fundamental differences between CZTS and CuInSe2 for use in thin-film photovoltaics are discussed. The results are expected to be relevant to other I2-II-IV-VI4 semiconductors.

  13. Intrinsic ferromagnetic properties in Cr-doped ZnO diluted magnetic semiconductors

    SciTech Connect

    Liu Yang; Yang Yanting; Yang Jinghai; Guan Qingfeng; Liu Huilian; Yang Lili; Zhang Yongjun; Wang Yaxin; Wei Maobin; Liu Xiaoyan; Fei Lianhua; Cheng Xin

    2011-05-15

    The Cr-doped zinc oxide (Zn{sub 1-x}Cr{sub x}O, 0{<=}x{<=}0.08) diluted magnetic semiconductors have been synthesized successfully by the sol-gel method. Investigations on magnetic, optical and structural properties of the produced samples have been done. Energy dispersive spectroscopy (EDS) shows the existence of Cr ion in the Cr-doped ZnO. The results of X-ray diffraction (XRD), the transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) indicate that the Cr ions are at least partially substitutionally incorporated into the crystal lattice of ZnO. The produced samples show good high-T{sub c} (Curie temperature) ferromagnetism (FM) in Cr-doped ZnO nanoparticles with Cr concentration of less than 5 at%. The results of photoluminescence (PL) further testify that FM is an intrinsic property of the Cr-doped ZnO nanoparticles. And the occurrence of FM should mainly contribute to the Cr doping. -- Graphical Abstract: As can be seen from the magnetic hysteresis loops of Zn{sub 1-x}Cr{sub x}O (x=0.01, 0.03, 0.05, and 0.08) at room temperature under 10 KOe, the samples show good high-T{sub c} ferromagnetism with Cr concentration of less than 5 at%. Display Omitted Highlights: {yields} Zn{sub 1-x}Cr{sub x}O(0{<=}x{<=}0.08) nanoparticles are successfully synthesized by sol-gel method. {yields} The Cr ions are substitutionally incorporated into the crystal lattice of ZnO. {yields} The Cr-doped ZnO nanoparticles show good high-T{sub c} ferromagnetism. {yields} The ferromagnetism is an intrinsic property of the Cr-doped ZnO nanoparticles.

  14. 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.

  15. Cytotoxicity of semiconductor nanoparticles in A549 cells is attributable to their intrinsic oxidant activity

    NASA Astrophysics Data System (ADS)

    Escamilla-Rivera, Vicente; Uribe-Ramirez, Marisela; Gonzalez-Pozos, Sirenia; Velumani, Subramaniam; Arreola-Mendoza, Laura; De Vizcaya-Ruiz, Andrea

    2016-04-01

    Copper indium gallium diselenide (CIGS) and cadmium sulfide (CdS) nanoparticles (NP) are next generation semiconductors used in photovoltaic cells (PV). They possess high quantum efficiency, absorption coefficient, and cheaper manufacturing costs compared to silicon. Due to their potential for an industrial development and the lack of information about the risk associated in their use, we investigated the influence of the physicochemical characteristics of CIGS (9 nm) and CdS (20 nm) in relation to the induction of cytotoxicity in human alveolar A549 cells through ROS generation and mitochondrial dysfunction. CIGS induced cytotoxicity in a dose dependent manner in lower concentrations than CdS; both NP were able to induce ROS in A549. Moreover, CIGS interact directly with mitochondria inducing depolarization that leads to the induction of apoptosis compared to CdS. Antioxidant pretreatment significantly prevented the loss of mitochondrial membrane potential and cytotoxicity, suggesting ROS generation as the main cytotoxic mechanism. These results demonstrate that semiconductor characteristics of NP are crucial for the type and intensity of the cytotoxic effects. Our work provides relevant information that may help guide the production of a safer NP-based PV technologies, and would be a valuable resource on future risk assessment for a safer use of nanotechnology in the development of clean sources of renewable energy.

  16. 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.

  17. Neutron hardness of silicon-based semiconductor devices

    SciTech Connect

    Baratta, A.J.; Kenney, E.S.

    1988-01-01

    The effects of radiation on silicon-based semiconductor devices have been the subject of research for many years. In an effort to understand these effects, a series of experiments was conducted on gamma-hardened MOSFETs. Experiments concentrated on MOSFETs in rad-hard form and on off-the-shelf items. Because of the need to maintain bias voltages at set levels to enhance damage and because of concerns over possible rapid annealing, active testing during irradiation was performed. In general, MOSFETs are expected to perform well in fast neutron environments. With the advances in rad-hard technologies, exposures to several-megarad gamma rays can be tolerated. In nuclear systems, the normal concurrent neutron fluence can reach over 10{sup 16} n/cm{sup 2}. At these levels, current research indicates that the devices fail. Such failure is not altogether unexpected, although the degree of induced structural disorder in the semiconductor's crystalline makeup is still small. However, the damage done appears to carry the silicon back to a nearly intrinsic state. Knowing that each primary knock-on atom causes 10 to 6000 secondary atomic dislocations, the fluences of 10{sup 16}/cm{sup 2} are clearly at a level able to markedly change semiconductor dopant-induced behavior. Thus, one can conclude that for current devices, the gamma dose in a mixed neutron gamma field may no longer be limiting.

  18. 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

  19. Estimation of entropy rate in a fast physical random-bit generator using a chaotic semiconductor laser with intrinsic noise.

    PubMed

    Mikami, Takuya; Kanno, Kazutaka; Aoyama, Kota; Uchida, Atsushi; Ikeguchi, Tohru; Harayama, Takahisa; Sunada, Satoshi; Arai, Ken-ichi; Yoshimura, Kazuyuki; Davis, Peter

    2012-01-01

    We analyze the time for growth of bit entropy when generating nondeterministic bits using a chaotic semiconductor laser model. The mechanism for generating nondeterministic bits is modeled as a 1-bit sampling of the intensity of light output. Microscopic noise results in an ensemble of trajectories whose bit entropy increases with time. The time for the growth of bit entropy, called the memory time, depends on both noise strength and laser dynamics. It is shown that the average memory time decreases logarithmically with increase in noise strength. It is argued that the ratio of change in average memory time with change in logarithm of noise strength can be used to estimate the intrinsic dynamical entropy rate for this method of random bit generation. It is also shown that in this model the entropy rate corresponds to the maximum Lyapunov exponent.

  20. Semiconductor nanocrystal-based phagokinetic tracking

    SciTech Connect

    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.

  1. Mechanical properties of organic semiconductors for mechanically stable and intrinsically stretchable solar cells (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Lipomi, Darren J.

    2016-09-01

    This presentation describes my group's efforts to understand the molecular and microstructural basis for the mechanical properties of organic semiconductors for organic photovoltaic (OPV) devices. Our work is motivated by two goals. The first goal is to mitigate mechanical forms of degradation of printed modules during roll-to-roll fabrication, installation, and environmental forces—i.e., wind, rain, snow, and thermal expansion and contraction. Mechanical stability is a prerequisite for inexpensive processing on flexible substrates: to encapsulate devices in glass is to surrender this advantage. The second goal is to enable the next generation of ultra-flexible and stretchable solar cells for collapsible, portable, and wearable applications, and as low-cost sources of energy—"solar tarps"—for disaster relief and for the developing world. It may seem that organic semiconductors, due to their carbon framework, are already sufficiently compliant for these applications. We have found, however, that the mechanical properties (stiffness and brittleness) occupy a wide range of values, and can be difficult to predict from molecular structure alone. We are developing an experimental and theoretical framework for how one can combine favorable charge-transport properties and mechanical compliance in organic semiconductor films. In particular, we have explored the roles of the backbone, alkyl side chain, microstructural order, the glass transition, molecular packing with fullerenes, plasticizing effects of additives, extent of separation of [60]PCBM and [70]PCBM, structural randomness in low-bandgap polymers, and reinforcement by encapsulation, on the mechanical compliance. We are exploring the applicability of semi-empirical "back-of-the-envelope" models, along with multi-scale molecular dynamics simulations, with the ultimate goal of designing electroactive organic materials whose mechanical properties can be dialed-in. We have used the insights we have developed to

  2. Intrinsic feature-based pose measurement for imaging motion compensation

    DOEpatents

    Baba, Justin S.; Goddard, Jr., James Samuel

    2014-08-19

    Systems and methods for generating motion corrected tomographic images are provided. A method includes obtaining first images of a region of interest (ROI) to be imaged and associated with a first time, where the first images are associated with different positions and orientations with respect to the ROI. The method also includes defining an active region in the each of the first images and selecting intrinsic features in each of the first images based on the active region. Second, identifying a portion of the intrinsic features temporally and spatially matching intrinsic features in corresponding ones of second images of the ROI associated with a second time prior to the first time and computing three-dimensional (3D) coordinates for the portion of the intrinsic features. Finally, the method includes computing a relative pose for the first images based on the 3D coordinates.

  3. Reaction-diffusion optoelectronics based on dispersed semiconductors

    NASA Astrophysics Data System (ADS)

    Gradov, O. V.; Gradova, M. A.

    2015-11-01

    Since many dispersed semiconductors are capable of light energy conversion and possess photocatalytic and luminescent properties, and any discreet light-sensitive medium can be applied for the positional-sensitive light flux registration (similar to pixels and voxels in semiconductor-based image recording), the use of chemically active dispersed semiconductors allows to perform a direct signal / image registration based on light-sensitive reaction-diffusion redox systems without conventional CCD / CMOS devices. The image capturing in this case will correspond to the formation of the metastable dissipative structures in the active medium, with their morphological properties determined by the flux gradient and provided by the corresponding dispersed semiconductor medium sensitivity.

  4. Teacher and Student Intrinsic Motivation in Project-Based Learning

    ERIC Educational Resources Information Center

    Lam, Shui-fong; Cheng, Rebecca Wing-yi; Ma, William Y. K.

    2009-01-01

    In this study we examined the relationship between teacher and student intrinsic motivation in project-based learning. The participants were 126 Hong Kong secondary school teachers and their 631 students who completed evaluation questionnaires after a semester-long project-based learning program. Both teachers and students were asked to indicate…

  5. Thiazole-based organic semiconductors for organic electronics.

    PubMed

    Lin, Yuze; Fan, Haijun; Li, Yongfang; Zhan, Xiaowei

    2012-06-19

    Over the past two decades, organic semiconductors have been the subject of intensive academic and commercial interests. Thiazole is a common electron-accepting heterocycle due to electron-withdrawing nitrogen of imine (C=N), several moieties based on thiazole have been widely introduced into organic semiconductors, and yielded high performance in organic electronic devices. This article reviews recent developments in the area of thiazole-based organic semiconductors, particularly thiazole, bithiazole, thiazolothiazole and benzobisthiazole-based small molecules and polymers, for applications in organic field-effect transistors, solar cells and light-emitting diodes. The remaining problems and challenges, and the key research direction in near future are discussed.

  6. Biological semiconductor based on electrical percolation.

    PubMed

    Yang, Minghui; Bruck, Hugh Alan; Kostov, Yordan; Rasooly, Avraham

    2010-05-01

    We have developed a novel biological semiconductor (BSC) based on electrical percolation through a multilayer three-dimensional carbon nanotube-antibody bionanocomposite network, which can measure biological interactions directly and electronically. In electrical percolation, the passage of current through the conductive network is dependent upon the continuity of the network. Molecular interactions, such as binding of antigens to the antibodies, disrupt the network continuity causing increased resistance of the network. A BSC is fabricated by immobilizing a prefunctionalized single-walled carbon nanotubes (SWNTs)-antibody bionanocomposite directly on a poly(methyl methacrylate) (PMMA) surface (also known as plexiglass or acrylic). We used the BSC for direct (label-free) electronic measurements of antibody-antigen binding, showing that, at slightly above the electrical percolation threshold of the network, binding of a specific antigen dramatically increases the electrical resistance. Using anti-staphylococcal enterotoxin B (SEB) IgG as a "gate" and SEB as an "actuator", we demonstrated that the BSC was able to detect SEB at concentrations of 1 ng/mL. The new BSCs may permit assembly of multiple sensors on the same chip to create "biological central processing units (CPUs)" with multiple BSC elements, capable of processing and sorting out information on multiple analytes simultaneously.

  7. Identification of intrinsic deep level defects responsible for electret behavior in TlGaSe2 layered semiconductor

    NASA Astrophysics Data System (ADS)

    Seyidov, MirHasan Yu.; Mikailzade, Faik A.; Uzun, Talip; Odrinsky, Andrei P.; Yakar, Emin; Aliyeva, Vafa B.; Babayev, Sardar S.; Mammadov, Tofig G.

    2016-02-01

    Unusual behavior of pyroelectric current signal polarity near the Curie point (Tc) was observed for TlGaSe2 a ferroelectric-semiconductor. It has been revealed that the polarity of the spontaneous polarization near Tc depends on the sample poling prehistory. In particular, applying an external electric field only in the temperature range of the paraelectric state during cooling regime in darkness brought to the depolarization current at Tc with the sign opposite to the external field polarity. Otherwise, if the sample was poled in the temperature interval of the incommensurate phase, pyroelectric current exhibits a peak at Tc with the polarity that is the same as for the external poling electric field. These observations indicate that internal electric field is present in the bulk and near-surface layer regions of the electrically poled single crystal TlGaSe2. Possible mechanisms and origins responsible for the internal electric fields in TlGaSe2 are discussed. It is shown that the formation of internal electric fields in TlGaSe2 is due to charging of intrinsic native defects during the poling process. Characteristics of electrically active intrinsic defects in TlGaSe2 were investigated by using of Photo-Induced Current Transient Spectroscopy (PICTS) technique. Six deep defect levels in the band gap of TlGaSe2 were determined, which were localized both in the bulk and on the surface of the sample and could be electrically charged. The correlation between polarization effects and PICTS results has been established. It was shown that native deep defects (A3-A6) localized in the bulk of crystal are responsible for hetero-charge formation and negative sign of the pyroelectric current peak observed around the Curie temperature after poling the sample in the temperature intervals well above Tc. It was also shown that the positive sign pyrocurrent observed near the Curie point is attributed to the homo-charge formed by native A2-trapping centers which are localized near

  8. Toward intrinsically stretchable organic semiconductors: mechanical properties of high-performance conjugated polymers

    NASA Astrophysics Data System (ADS)

    Sawyer, Eric J.; Savagatrup, Suchol; O'Connor, Timothy F.; Makaram, Aditya S.; Burke, Daniel J.; Zaretski, Aliaksandr V.; Printz, Adam D.; Lipomi, Darren J.

    2014-10-01

    This paper describes several approaches to understanding and improving the response of π-conjugated (semiconducting) polymers to tensile strain. Our principal goal was to establish the design criteria for introducing elasticity and ductility in conjugated (semiconducting) polymers through a rigorous analysis of the structural determinants of the mechanical properties of this type of material. We elucidated the details of the effect of the alkyl side chain length on the mechanical properties of regioregular polythiophene and used this analysis to select materials for stretching and transfer printing of organic solar cells to hemispherical substrates. This demonstration represents the first time that a conjugated polymer device has ever been stretched and conformally bonded to a complex 3D surface (i.e., other than a cone or cylinder, for which flexibility—as opposed to stretchability—is sufficient). We then further explored the details of the dependence of the mechanical properties on the side chain of a semiconducting polymer by synthesizing a series of hybrid materials (block and random copolymers) containing both short and long side chains. This analysis revealed the unusual semiconducting polymer, poly(3-heptylthiophene), as having an excellent combination of mechanical and electronic properties. In parallel, we explored a new method of producing "blocky" copolymers using a new procedure based on random segmentation of conjugated monomers. We found that introduction of structural randomness increased the elasticity without having detrimental effects on the photovoltaic performance. We also describe methods of synthesizing large volumes of conjugated polymers in environmentally benign ways that were amenable to manufacturing.

  9. Graphene-based lateral heterostructure transistors exhibit better intrinsic performance than graphene-based vertical transistors as post-CMOS devices

    NASA Astrophysics Data System (ADS)

    Logoteta, Demetrio; Fiori, Gianluca; Iannaccone, Giuseppe

    2014-10-01

    We investigate the intrinsic performance of vertical and lateral graphene-based heterostructure field-effect transistors, currently considered the most promising options to exploit graphene properties in post-CMOS electronics. We focus on three recently proposed graphene-based transistors, that in experiments have exhibited large current modulation. Our analysis is based on device simulations including the self-consistent solution of the electrostatic and transport equations within the Non-Equilibrium Green's Function formalism. We show that the lateral heterostructure transistor has the potential to outperform CMOS technology and to meet the requirements of the International Technology Roadmap for Semiconductors for the next generation of semiconductor integrated circuits. On the other hand, we find that vertical heterostructure transistors miss these performance targets by several orders of magnitude, both in terms of switching frequency and delay time, due to large intrinsic capacitances, and unavoidable current/capacitance tradeoffs.

  10. Graphene-based lateral heterostructure transistors exhibit better intrinsic performance than graphene-based vertical transistors as post-CMOS devices

    PubMed Central

    Logoteta, Demetrio; Fiori, Gianluca; Iannaccone, Giuseppe

    2014-01-01

    We investigate the intrinsic performance of vertical and lateral graphene-based heterostructure field-effect transistors, currently considered the most promising options to exploit graphene properties in post-CMOS electronics. We focus on three recently proposed graphene-based transistors, that in experiments have exhibited large current modulation. Our analysis is based on device simulations including the self-consistent solution of the electrostatic and transport equations within the Non-Equilibrium Green's Function formalism. We show that the lateral heterostructure transistor has the potential to outperform CMOS technology and to meet the requirements of the International Technology Roadmap for Semiconductors for the next generation of semiconductor integrated circuits. On the other hand, we find that vertical heterostructure transistors miss these performance targets by several orders of magnitude, both in terms of switching frequency and delay time, due to large intrinsic capacitances, and unavoidable current/capacitance tradeoffs. PMID:25328156

  11. Semiconductor nanostructure-based photovoltaic solar cells.

    PubMed

    Zhang, Genqiang; Finefrock, Scott; Liang, Daxin; Yadav, Gautam G; Yang, Haoran; Fang, Haiyu; Wu, Yue

    2011-06-01

    Substantial efforts have been devoted to design, synthesize, and integrate various semiconductor nanostructures for photovoltaic (PV) solar cells. In this article, we will review the recent progress in this exciting area and cover the material chemistry and physics related to all-inorganic nanostructure solar cells, hybrid inorganic nanostructure-conductive polymer composite solar cells, and dye-sensitized solar cells.

  12. Semiconductor nanostructure-based photovoltaic solar cells

    NASA Astrophysics Data System (ADS)

    Zhang, Genqiang; Finefrock, Scott; Liang, Daxin; Yadav, Gautam G.; Yang, Haoran; Fang, Haiyu; Wu, Yue

    2011-06-01

    Substantial efforts have been devoted to design, synthesize, and integrate various semiconductor nanostructures for photovoltaic (PV) solar cells. In this article, we will review the recent progress in this exciting area and cover the material chemistry and physics related to all-inorganic nanostructure solar cells, hybrid inorganic nanostructure-conductive polymer composite solar cells, and dye-sensitized solar cells.

  13. All-semiconductor metamaterial-based optical circuit board at the microscale

    NASA Astrophysics Data System (ADS)

    Min, Li; Huang, Lirong

    2015-07-01

    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.

  14. 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.

  15. Doped semiconductor nanocrystal based fluorescent cellular imaging probes.

    PubMed

    Maity, Amit Ranjan; Palmal, Sharbari; Basiruddin, S K; Karan, Niladri Sekhar; Sarkar, Suresh; Pradhan, Narayan; Jana, Nikhil R

    2013-06-21

    Doped semiconductor nanocrystals such as Mn doped ZnS, Mn doped ZnSe and Cu doped InZnS, are considered as new classes of fluorescent biological probes with low toxicity. Although the synthesis in high quality of such nanomaterials is now well established, transforming them into functional fluorescent probes remains a challenge. Here we report a fluorescent cellular imaging probe made of high quality doped semiconductor nanocrystals. We have identified two different coating approaches suitable for transforming the as synthesized hydrophobic doped semiconductor nanocrystals into water-soluble functional nanoparticles. Following these approaches we have synthesized TAT-peptide- and folate-functionalized nanoparticles of 10-80 nm hydrodynamic diameter and used them as a fluorescent cell label. The results shows that doped semiconductor nanocrystals can be an attractive alternative for conventional cadmium based quantum dots with low toxicity.

  16. Doped semiconductor nanocrystal based fluorescent cellular imaging probes

    NASA Astrophysics Data System (ADS)

    Maity, Amit Ranjan; Palmal, Sharbari; Basiruddin, Sk; Karan, Niladri Sekhar; Sarkar, Suresh; Pradhan, Narayan; Jana, Nikhil R.

    2013-05-01

    Doped semiconductor nanocrystals such as Mn doped ZnS, Mn doped ZnSe and Cu doped InZnS, are considered as new classes of fluorescent biological probes with low toxicity. Although the synthesis in high quality of such nanomaterials is now well established, transforming them into functional fluorescent probes remains a challenge. Here we report a fluorescent cellular imaging probe made of high quality doped semiconductor nanocrystals. We have identified two different coating approaches suitable for transforming the as synthesized hydrophobic doped semiconductor nanocrystals into water-soluble functional nanoparticles. Following these approaches we have synthesized TAT-peptide- and folate-functionalized nanoparticles of 10-80 nm hydrodynamic diameter and used them as a fluorescent cell label. The results shows that doped semiconductor nanocrystals can be an attractive alternative for conventional cadmium based quantum dots with low toxicity.Doped semiconductor nanocrystals such as Mn doped ZnS, Mn doped ZnSe and Cu doped InZnS, are considered as new classes of fluorescent biological probes with low toxicity. Although the synthesis in high quality of such nanomaterials is now well established, transforming them into functional fluorescent probes remains a challenge. Here we report a fluorescent cellular imaging probe made of high quality doped semiconductor nanocrystals. We have identified two different coating approaches suitable for transforming the as synthesized hydrophobic doped semiconductor nanocrystals into water-soluble functional nanoparticles. Following these approaches we have synthesized TAT-peptide- and folate-functionalized nanoparticles of 10-80 nm hydrodynamic diameter and used them as a fluorescent cell label. The results shows that doped semiconductor nanocrystals can be an attractive alternative for conventional cadmium based quantum dots with low toxicity. Electronic supplementary information available: Characterization details of coating and

  17. Incremental learning of skill collections based on intrinsic motivation

    PubMed Central

    Metzen, Jan H.; Kirchner, Frank

    2013-01-01

    Life-long learning of reusable, versatile skills is a key prerequisite for embodied agents that act in a complex, dynamic environment and are faced with different tasks over their lifetime. We address the question of how an agent can learn useful skills efficiently during a developmental period, i.e., when no task is imposed on him and no external reward signal is provided. Learning of skills in a developmental period needs to be incremental and self-motivated. We propose a new incremental, task-independent skill discovery approach that is suited for continuous domains. Furthermore, the agent learns specific skills based on intrinsic motivation mechanisms that determine on which skills learning is focused at a given point in time. We evaluate the approach in a reinforcement learning setup in two continuous domains with complex dynamics. We show that an intrinsically motivated, skill learning agent outperforms an agent which learns task solutions from scratch. Furthermore, we compare different intrinsic motivation mechanisms and how efficiently they make use of the agent's developmental period. PMID:23898265

  18. Incremental learning of skill collections based on intrinsic motivation.

    PubMed

    Metzen, Jan H; Kirchner, Frank

    2013-01-01

    Life-long learning of reusable, versatile skills is a key prerequisite for embodied agents that act in a complex, dynamic environment and are faced with different tasks over their lifetime. We address the question of how an agent can learn useful skills efficiently during a developmental period, i.e., when no task is imposed on him and no external reward signal is provided. Learning of skills in a developmental period needs to be incremental and self-motivated. We propose a new incremental, task-independent skill discovery approach that is suited for continuous domains. Furthermore, the agent learns specific skills based on intrinsic motivation mechanisms that determine on which skills learning is focused at a given point in time. We evaluate the approach in a reinforcement learning setup in two continuous domains with complex dynamics. We show that an intrinsically motivated, skill learning agent outperforms an agent which learns task solutions from scratch. Furthermore, we compare different intrinsic motivation mechanisms and how efficiently they make use of the agent's developmental period.

  19. 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.

  20. 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%.

  1. 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.

  2. Changing the Environment Based on Empowerment as Intrinsic Motivation

    NASA Astrophysics Data System (ADS)

    Salge, Christoph; Glackin, Cornelius; Polani, Daniel

    2014-05-01

    One aspect of intelligence is the ability to restructure your own environment so that the world you live in becomes more beneficial to you. In this paper we investigate how the information-theoretic measure of agent empowerment can provide a task-independent, intrinsic motivation to restructure the world. We show how changes in embodiment and in the environment change the resulting behaviour of the agent and the artefacts left in the world. For this purpose, we introduce an approximation of the established empowerment formalism based on sparse sampling, which is simpler and significantly faster to compute for deterministic dynamics. Sparse sampling also introduces a degree of randomness into the decision making process, which turns out to beneficial for some cases. We then utilize the measure to generate agent behaviour for different agent embodiments in a Minecraft-inspired three dimensional block world. The paradigmatic results demonstrate that empowerment can be used as a suitable generic intrinsic motivation to not only generate actions in given static environments, as shown in the past, but also to modify existing environmental conditions. In doing so, the emerging strategies to modify an agent's environment turn out to be meaningful to the specific agent capabilities, i.e., de facto to its embodiment.

  3. 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.

  4. Tantalum-based semiconductors for solar water splitting.

    PubMed

    Zhang, Peng; Zhang, Jijie; Gong, Jinlong

    2014-07-07

    Solar energy utilization is one of the most promising solutions for the energy crises. Among all the possible means to make use of solar energy, solar water splitting is remarkable since it can accomplish the conversion of solar energy into chemical energy. The produced hydrogen is clean and sustainable which could be used in various areas. For the past decades, numerous efforts have been put into this research area with many important achievements. Improving the overall efficiency and stability of semiconductor photocatalysts are the research focuses for the solar water splitting. Tantalum-based semiconductors, including tantalum oxide, tantalate and tantalum (oxy)nitride, are among the most important photocatalysts. Tantalum oxide has the band gap energy that is suitable for the overall solar water splitting. The more negative conduction band minimum of tantalum oxide provides photogenerated electrons with higher potential for the hydrogen generation reaction. Tantalates, with tunable compositions, show high activities owning to their layered perovskite structure. (Oxy)nitrides, especially TaON and Ta3N5, have small band gaps to respond to visible-light, whereas they can still realize overall solar water splitting with the proper positions of conduction band minimum and valence band maximum. This review describes recent progress regarding the improvement of photocatalytic activities of tantalum-based semiconductors. Basic concepts and principles of solar water splitting will be discussed in the introduction section, followed by the three main categories regarding to the different types of tantalum-based semiconductors. In each category, synthetic methodologies, influencing factors on the photocatalytic activities, strategies to enhance the efficiencies of photocatalysts and morphology control of tantalum-based materials will be discussed in detail. Future directions to further explore the research area of tantalum-based semiconductors for solar water splitting

  5. 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.

  6. Nanophotonics Based on Semiconductor-Photonic Crystal/Quantum Dot and Metal-/Semiconductor-Plasmonics

    NASA Astrophysics Data System (ADS)

    Asakawa, Kiyoshi; Sugimoto, Yoshimasa; Ikeda, Naoki; Tsuya, Daiju; Koide, Yasuo; Watanabe, Yoshinori; Ozaki, Nobuhiko; Ohkouchi, Shunsuke; Nomura, Tsuyoshi; Inoue, Daisuke; Matsui, Takayuki; Miura, Atsushi; Fujikawa, Hisayoshi; Sato, Kazuo

    This paper reviews our recent activities on nanophotonics based on a photonic crystal (PC)/quantum dot (QD)-combined structure for an all-optical device and a metal/semiconductor composite structure using surface plasmon (SP) and negative refractive index material (NIM). The former structure contributes to an ultrafast signal processing component by virtue of new PC design and QD selective-area-growth technologies, while the latter provides a new RGB color filter with a high precision and optical beam-steering device with a wide steering angle.

  7. Low-voltage organic electronics based on a gate-tunable injection barrier in vertical graphene-organic semiconductor heterostructures.

    PubMed

    Hlaing, Htay; Kim, Chang-Hyun; Carta, Fabio; Nam, Chang-Yong; Barton, Rob A; Petrone, Nicholas; Hone, James; Kymissis, Ioannis

    2015-01-14

    The vertical integration of graphene with inorganic semiconductors, oxide semiconductors, and newly emerging layered materials has recently been demonstrated as a promising route toward novel electronic and optoelectronic devices. Here, we report organic thin film transistors based on vertical heterojunctions of graphene and organic semiconductors. In these thin heterostructure devices, current modulation is accomplished by tuning of the injection barriers at the semiconductor/graphene interface with the application of a gate voltage. N-channel devices fabricated with a thin layer of C60 show a room temperature on/off ratio >10(4) and current density of up to 44 mAcm(-2). Because of the ultrashort channel intrinsic to the vertical structure, the device is fully operational at a driving voltage of 200 mV. A complementary p-channel device is also investigated, and a logic inverter based on two complementary transistors is demonstrated. The vertical integration of graphene with organic semiconductors via simple, scalable, and low-temperature fabrication processes opens up new opportunities to realize flexible, transparent organic electronic, and optoelectronic devices.

  8. Uniform Doping in Quantum-Dots-Based Dilute Magnetic Semiconductor.

    PubMed

    Saha, Avijit; Shetty, Amitha; Pavan, A R; Chattopadhyay, Soma; Shibata, Tomohiro; Viswanatha, Ranjani

    2016-07-07

    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.

  9. Method of plasma etching Ga-based compound semiconductors

    DOEpatents

    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.

  10. Semiconductor wire array structures, and solar cells and photodetectors based on such structures

    SciTech Connect

    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.

  11. Method of plasma etching GA-based compound semiconductors

    DOEpatents

    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.

  12. 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.

  13. 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.

  14. Intrinsic spin and momentum relaxation in organic single-crystalline semiconductors probed by ESR and Hall measurements

    NASA Astrophysics Data System (ADS)

    Tsurumi, Junto; Häusermann, Roger; Watanabe, Shun; Mitsui, Chikahiko; Okamoto, Toshihiro; Matsui, Hiroyuki; Takeya, Jun

    Spin and charge momentum relaxation mechanism has been argued among organic semiconductors with various methods, devices, and materials. However, little is known in organic single-crystalline semiconductors because it has been hard to obtain an ideal organic crystal with an excellent crystallinity and controllability required for accurate measurements. By using more than 1-inch sized single crystals which are fabricated via contentious edge-casting method developed by our group, we have successfully demonstrated a simultaneous determination of spin and momentum relaxation time for gate-induced charges of 3,11-didecyldinaphtho[2,3- d:2',3'- d']benzo[1,2- b:4,5- b']dithiophene, by combining electron spin resonance (ESR) and Hall effect measurements. The obtained temperature dependences of spin and momentum relaxation times are in good agreement in terms of power law with a factor of approximately -2. It is concluded that Elliott-Yafet spin relaxation mechanism can be dominant at room temperature regime (200 - 300 K). Probing characteristic time scales such as spin-lattice, spin-spin, and momentum relaxation times, demonstrated in the present work, would be a powerful tool to elucidate fundamental spin and charge transport mechanisms. We acknowledge the New Energy and Industrial Technology Developing Organization (NEDO) for financial support.

  15. 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.

  16. 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.

  17. Spin-Seebeck Effect in III-V Based Semiconductors

    NASA Astrophysics Data System (ADS)

    Jaworski, Christopher M.; Myers, Roberto C.; Heremans, Joseph P.

    2012-02-01

    The spin-Seebeck effect has now been observed in metals^1 (NiFe), semiconductors^2 (GaMnAs), and insulators^3 (YIG). It consists of a thermally generated spin distribution that is phonon driven. Here we extend our measurements of the spin-Seebeck effect to other group III-V based magnetic semiconductors and present measurements of conventional thermomagnetic and galvanomagnetic properties as well as the spin-Seebeck effect. Work supported by the National Science Foundation, NSF-CBET-1133589 1. K. Uchida, et al., Nature 455 778 (2008) 2. C.M. Jaworski et al., Nature Materials 8 898 (2010), Phys. Rev. Lett. 106 186601 (2011) 3. K. Uchida, et al., Nature Materials 8 893 (2010)

  18. Content-Based Image Retrieval for Semiconductor Process Characterization

    NASA Astrophysics Data System (ADS)

    Tobin, Kenneth W.; Karnowski, Thomas P.; Arrowood, Lloyd F.; Ferrell, Regina K.; Goddard, James S.; Lakhani, Fred

    2002-12-01

    Image data management in the semiconductor manufacturing environment is becoming more problematic as the size of silicon wafers continues to increase, while the dimension of critical features continues to shrink. Fabricators rely on a growing host of image-generating inspection tools to monitor complex device manufacturing processes. These inspection tools include optical and laser scattering microscopy, confocal microscopy, scanning electron microscopy, and atomic force microscopy. The number of images that are being generated are on the order of 20,000 to 30,000 each week in some fabrication facilities today. Manufacturers currently maintain on the order of 500,000 images in their data management systems for extended periods of time. Gleaning the historical value from these large image repositories for yield improvement is difficult to accomplish using the standard database methods currently associated with these data sets (e.g., performing queries based on time and date, lot numbers, wafer identification numbers, etc.). Researchers at the Oak Ridge National Laboratory have developed and tested a content-based image retrieval technology that is specific to manufacturing environments. In this paper, we describe the feature representation of semiconductor defect images along with methods of indexing and retrieval, and results from initial field-testing in the semiconductor manufacturing environment.

  19. Metal-optic and Plasmonic Semiconductor-based Nanolasers

    NASA Astrophysics Data System (ADS)

    Lakhani, Amit Manmohan

    Over the past few decades, semiconductor lasers have relentlessly followed the path towards miniaturization. Smaller lasers are more energy efficient, are cheaper to make, and open up new applications in sensing and displays, among many other things. Yet, up until recently, there was a fundamental problem with making lasers smaller: purely semiconductor lasers couldn't be made smaller than the diffraction limit of light. In recent years, however, metal-based lasers have been demonstrated in the nanoscale that have shattered the diffraction limit. As optical materials, metals can be used to either reflect light (metal-optics) or convert light to electrical currents (plasmonics). In both cases, metals have provided ways to squeeze light beyond the diffraction limit. In this dissertation, I experimentally demonstrated one nanolaser based on plasmonic transduction and another laser based on metal-optic reflection. To create coherent plasmons, I designed a nanolaser based on a plasmonic bandgap defect state inside a surface plasmonic crystal. In a one-dimensional periodic semiconductor beam, I was able to confine surface plasmons by interrupting the periodicity of the crystal. These confined surface plasmons then underwent laser oscillations in effective mode volumes as small as 0.007 cubic wavelengths. At this electromagnetic volume, energy was squeezed 10 times smaller than those possible in similar photonic crystals that do not utilize metal. This demonstration should pave the way for achieving engineered nanolasers with deep-subwavelength mode volumes and enable plasmonic crystals to become attractive platforms for designing plasmons. After achieving large reductions in electromagnetic mode volumes, I switched to a metal-optics-based nanolaser design to further reduce the physical volumes of small light sources. The semiconductor nanopatch laser achieved laser oscillations with subwavelength-scale physical dimensions (0.019 cubic wavelengths) and effective mode

  20. Antimonide-Based Compound Semiconductors for Low-Power Electronics

    DTIC Science & Technology

    2013-01-01

    bipolar transistors [3], heterostructure barrier varactors for use as frequency multipliers [4], and p-n diodes for THz mixer applications [5...In0.69Al0.31As0.41Sb0.59/In0.27Ga0.73Sb double-heterojunction bipolar transistors with InAs0.66Sb0.34 contact layers. Electron Lett. 2010;46: 1333-5. [4] Champlain JG...Quantum wells formed from antimonide-based compound semiconductors are exploited in n-channel field-effect transistors (FETs) operating at high speeds

  1. 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.

  2. The Relationships among Measures of Intrinsic Motivation, Instructional Design, and Learning in Computer-Based Instruction.

    ERIC Educational Resources Information Center

    Rezabek, Randy

    The intent of this study was to explore the intrinsic aspects of motivation, and to see if the design of instruction could positively affect learners' levels of intrinsic motivation toward the subject matter. The following questions were addressed: (1) Will different computer-based instructional treatments which have been designed to reflect…

  3. Improving low-temperature performance of infrared thin-film interference filters utilizing the intrinsic properties of IV-VI narrow-gap semiconductors.

    PubMed

    Li, Bin; Zhang, S; Jiang, J; Fan, B; Zhang, F

    2004-02-09

    Pb(1) (-x)Ge(x)Te is a pseudobinary alloy of IV-VI narrow-gap semiconductor, of which maximum refractive index corresponds to the ferroelectric phase transition. Since the temperature coefficient of refractive index can be tunable from negative to positive by changing the Ge composition, it is possible to utilize the intrinsic property in the fabrication of infrared thin-film interference filters. In this letter, we report a narrow-bandpass filter, in which Pb(0.94)Ge(0.06)Te was substituted for PbTe. It found that the low-temperature stability of the filter is obviously improved: in the temperature range of 80-300K, the shift of center wavelength with temperature is reduced from 0.48nm.K(-1) to 0.23nm K(-1); furthermore, the peak transmittance of filter fabricated with Pb(0.94)Ge(0.06)Te is ~3% over that fabricated with PbTe.

  4. Unusual electronic transport and magnetism in titanium oxide based semiconductors and metals

    NASA Astrophysics Data System (ADS)

    Zhang, Shixiong

    The main objective of this thesis was to explore the structural, electrical, magnetic and optical properties of titanium based novel oxide thin films, such as transparent conducting oxides (TCOs) and diluted magnetic semiconductors (DMSs), so as to be able to realize optoelectronics and spintronics applications. I demonstrated that niobium doped titanium dioxide (TiO2) in its epitaxial anatase phase grown at certain condition is an intrinsic transparent conducting oxide, with both its conductivity and transparency comparable to that of the commercial transparent electrode In-Sn-O being widely used in current optoelectronic devices. I investigated the growth parameter dependence of structure and conductivity of this material. It was found that the growth temperature is a crucial parameter for the structural quality as well as the electron mobility, while the oxygen partial pressure is essential for the conduction electron concentration. The excellent conductivity of niobium doped TiO2 should be attributed to the extremely high solubility of niobium in the TiO2 matrix as well as a very shallow donor level created in the TiO2 band gap. I investigated several important oxide based DMS systems, such as niobium and cobalt dual doped TiO2, transition metal (TM) element doped SrTiO3 etc. I found that niobium dual doping is an effective way to introduce carriers into the classical Co: TiO2 system, which provides the feasibility of studying the RKKY interaction in this system by chemical doping. Our detailed characterization of TM doped SrTiO3 questioned the intrinsic nature of the ferromagnetism observed by other groups. By a systematic study of Hall effect on superparamagnetic Co-(La,Sr)TiO 3 thin films, I was able to demonstrate that the magnitude of the anomalous Hall effect is a way to distinguish between intrinsic and extrinsic DMS. A Kondo effect was observed in niobium doped TiO2 grown at certain condition. The origin of magnetic moments in this system was suggested

  5. Sapphire-fiber-based intrinsic Fabry-Perot interferometer

    NASA Technical Reports Server (NTRS)

    Wang, Anbo; Gollapudi, Sridhar; Murphy, Kent A.; May, Russell G.; Claus, Richard O.

    1992-01-01

    A sapphire optical fiber intrinsic Fabry-Perot interferometric sensor is demonstrated. A length of multimode sapphire fiber that functions as a Fabry-Perot cavity is spliced to a silica single-mode fiber. The interferometric signals of this sensor are produced by the interference between the reflection from the silica-sapphire fiber splice and the reflection from the free end face of the sapphire fiber. This sensor has been demonstrated for temperature measurement. A resolution of 0.2 C has been obtained over a measurement range of 310 C to 976 C.

  6. Hybrid photovoltaics based on semiconductor nanocrystals and amorphous silicon.

    PubMed

    Sun, Baoquan; Findikoglu, Alp T; Sykora, Milan; Werder, Donald J; Klimov, Victor I

    2009-03-01

    Semiconductor nanocrystals (NCs) are promising materials for applications in photovoltaic (PV) structures that could benefit from size-controlled tunability of absorption spectra, the ease of realization of various tandem architectures, and, perhaps, increased conversion efficiency in the ultraviolet region through carrier multiplication. The first practical step toward utilization of the unique properties of NCs in PV technologies could be through their integration into traditional silicon-based solar cells. Here, we demonstrate an example of such hybrid PV structures that combine colloidal NCs with amorphous silicon. In these structures, NCs and silicon are electronically coupled, and the regime of this coupling can be tuned by altering the alignment of NC energy states with regard to silicon band edges. For example, using wide-gap CdSe NCs we demonstrate a photoresponse which is exclusively due to the NCs. On the other hand, in devices comprising narrow-gap PbS NCs, both the NCs and silicon contribute to photocurrent, which results in PV response extending from the visible to the near-infrared region. The hybrid silicon/PbS NC solar cells show external quantum efficiencies of approximately 7% at infrared energies and 50% in the visible and a power conversion efficiency of up to 0.9%. This work demonstrates the feasibility of hybrid PV devices that combine advantages of mature silicon fabrication technologies with the unique electronic properties of semiconductor NCs.

  7. 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.

  8. Photonic crystal waveguides based on wide-gap semiconductor alloys

    NASA Astrophysics Data System (ADS)

    Martin, Aude; Combrié, Sylvain; De Rossi, Alfredo

    2017-03-01

    This review is devoted to integrated photonic platforms based on large band-gap semiconductors, alternatives to silicon photonics. The large electronic band gap of the material employed is chosen to address the specific needs of nonlinear optics, and, in particular, lower nonlinear losses and the capability of handling larger optical power densities. Moreover, these new platforms offer broader transmission spectra, extending to the visible spectral region, which is also required for other applications, particularly sensing and bio-related photonics. The focus is on nanoscale patterned waveguiding structures, which, owing to the tight confinement of light, have demonstrated a large nonlinear response. The third-order nonlinear response and the related parametric interactions will be considered here, encompassing four-wave mixing, phase-sensitive amplification, wavelength conversion, and also nonlinear pulse propagation and soliton dynamics. The comparison between different materials and waveguide design highlights specific features of photonic crystal waveguides.

  9. 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

  10. Supramolecular luminescence from oligofluorenol-based supramolecular polymer semiconductors.

    PubMed

    Zhang, Guang-Wei; Wang, Long; Xie, Ling-Hai; Lin, Jin-Yi; Huang, Wei

    2013-11-13

    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.

  11. Optical properties of semiconductor microcavities

    NASA Astrophysics Data System (ADS)

    Son, Joong-Kon

    Thanks to the difference in energy gap between two semiconductors and to their different indices of refraction, semiconductor heterostructures can confine electrons as well as photons. This property makes it possible to build semiconductor-based optical resonators (microcavities) with a radiation dipole (a quantum well) in its midst to investigate the coupling between the optical modes of the microcavity with the exciton modes of the quantum well. Such an interaction, besides its intrinsic interest, is relevant to vertically-emitting semiconductor lasers, based on the quantum well- microcavity system. In this thesis, we will present experimental evidence of temperature and electric-field dependent exciton-cavity coupling in GaAs-GaAlAs microcavities.

  12. Optical Properties and Wave Propagation in Semiconductor-Based Two-Dimensional Photonic Crystals

    SciTech Connect

    Agio, Mario

    2002-12-31

    This work is a theoretical investigation on the physical properties of semiconductor-based two-dimensional photonic crystals, in particular for what concerns systems embedded in planar dielectric waveguides (GaAs/AlGaAs, GaInAsP/InP heterostructures, and self-standing membranes) or based on macro-porous silicon. The photonic-band structure of photonic crystals and photonic-crystal slabs is numerically computed and the associated light-line problem is discussed, which points to the issue of intrinsic out-of-lane diffraction losses for the photonic bands lying above the light line. The photonic states are then classified by the group theory formalism: each mode is related to an irreducible representation of the corresponding small point group. The optical properties are investigated by means of the scattering matrix method, which numerically implements a variable-angle-reflectance experiment; comparison with experiments is also provided. The analysis of surface reflectance proves the existence of selection rules for coupling an external wave to a certain photonic mode. Such rules can be directly derived from symmetry considerations. Lastly, the control of wave propagation in weak-index contrast photonic-crystal slabs is tackled in view of designing building blocks for photonic integrated circuits. The proposed designs are found to comply with the major requirements of low-loss propagation, high and single-mode transmission. These notions are then collected to model a photonic-crystal combiner for an integrated multi-wavelength-source laser.

  13. Surface plasmon based engineering of semiconductor nanowire optics

    NASA Astrophysics Data System (ADS)

    Aspetti, Carlos Octavio

    Semiconductor nanowires combine the material properties of semiconductors, which are ubiquitous in modern technology, with nanoscale dimensions and as such, are firmly poised at the forefront of nanotechnology research. The rich physics of semiconductor nanowire optics, in particular, arises from the increased interaction between light and matter that occurs when light is confined to dimensions below the size of its wavelength, in other words, when the nanowire serves as a light trapping optical cavity, which itself is also a source of light. Light confinement is taken to new extremes by coupling to the surface plasmon modes of metallic nanostructures, where light acquires mixed photonic and electronic character, and which may focus light to deep-subwavelength regions amenable to the dimensions of the electron wave. This thesis examines how the integration of "plasmonic optical cavities" and semiconductor nanowires leads to substantial modification (and enhancement) of the optical properties of the same, resulting in orders-of-magnitude faster and more efficient light emission with colors that may be tuned as a function of optical cavity geometry. Furthermore, this method is applied to nanowires composed of both direct and indirect bandgap semiconductor materials resulting in applications such as light emission from high-energy states in light emitting materials, highly enhanced broadband light emission from nominally non-light emitting (dark) materials, and broadband (and anomalous) enhancement of light absorption in various materials, all the while maintaining the unifying theme of employing integrated plasmonic-semiconductor optical cavities to achieve tailored optical properties. We begin with a review of the electromagnetic properties of optical cavities, surface plasmon-enhanced light emission in semiconductors, and the key physical properties of semiconductor nanowires. It goes without saying that this thesis work resides at the interface between optical

  14. Bismuth-based oxide semiconductors: Mild synthesis and practical applications

    NASA Astrophysics Data System (ADS)

    Timmaji, Hari Krishna

    In this dissertation study, bismuth based oxide semiconductors were prepared using 'mild' synthesis techniques---electrodeposition and solution combustion synthesis. Potential environmental remediation and solar energy applications of the prepared oxides were evaluated. Bismuth vanadate (BiVO4) was prepared by electrodeposition and solution combustion synthesis. A two step electrosynthesis strategy was developed and demonstrated for the first time. In the first step, a Bi film was first electrodeposited on a Pt substrate from an acidic BiCl3 medium. Then, this film was anodically stripped in a medium containing hydrolyzed vanadium precursor, to generate Bi3+, and subsequent BiVO4 formation by in situ precipitation. The photoelectrochemical data were consistent with the in situ formation of n-type semiconductor films. In the solution combustion synthesis procedure, BiVO4 powders were prepared using bismuth nitrate pentahydrate as the bismuth precursor and either vanadium chloride or vanadium oxysulfate as the vanadium precursor. Urea, glycine, or citric acid was used as the fuel. The effect of the vanadium precursor on the photocatalytic activity of combustion synthesized BiVO 4 was evaluated in this study. Methyl orange was used as a probe to test the photocatalytic attributes of the combustion synthesized (CS) samples, and benchmarked against a commercial bismuth vanadate sample. The CS samples showed superior activity to the commercial benchmark sample, and samples derived from vanadium chloride were superior to vanadium oxysulfate counterparts. The photoelectrochemical properties of the various CS samples were also studied and these samples were shown to be useful both for environmental photocatalytic remediation and water photooxidation applications. Silver bismuth tungstate (AgBiW2O8) nanoparticles were prepared for the first time by solution combustion synthesis by using silver nitrate, bismuth nitrate, sodium tungstate as precursors for Ag, Bi, and W

  15. Electrical and Optical Characterization of Nanowire based Semiconductor Devices

    NASA Astrophysics Data System (ADS)

    Ayvazian, Talin

    This research project is focused on a new strategy for the creation of nanowire based semiconductor devices. The main goal is to understand and optimize the electrical and optical properties of two types of nanoscale devices; in first type lithographically patterned nanowire electrodeposition (LPNE) method has been utilized to fabricate nanowire field effect transistors (NWFET) and second type involved the development of light emitting semiconductor nanowire arrays (NWLED). Field effect transistors (NWFETs) have been prepared from arrays of polycrystalline cadmium selenide (pc-CdSe) nanowires using a back gate configuration. pc-CdSe nanowires were fabricated using the lithographically patterned nanowire electrode- position (LPNE) process on SiO2 /Si substrates. After electrodeposition, pc-CdSe nanowires were thermally annealed at 300 °C x 4 h either with or without exposure to CdCl 2 in methanol a grain growth promoter. The influence of CdCl2 treatment was to increase the mean grain diameter as determined by X-ray diffraction pattern and to convert the crystal structure from cubic to wurtzite. Transfer characteristics showed an increase of the field effect mobility (mu eff) by an order of magnitude and increase of the Ion/I off ratio by a factor of 3-4. Light emitting devices (NW-LED) based on lithographically patterned pc-CdSe nanowire arrays have been investigated. Electroluminescence (EL) spectra of CdSe nanowires under various biases exhibited broad emission spectra centered at 750 nm close to the band gap of CdSe (1.7eV). To enhance the intensity of the emitted light and the external quantum efficiency (EQE), the distance between the contacts were reduced from 5 mum to less than 1 mum which increased the efficiency by an order of magnitude. Also, increasing the annealing temperature of nanowires from 300 °C x4 h to 450 This research project is focused on a new strategy for the creation of nanowire based semiconductor devices. The main goal is to understand

  16. Ratiometric fluorescence, electrochemiluminescence, and photoelectrochemical chemo/biosensing based on semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Wu, Peng; Hou, Xiandeng; Xu, Jing-Juan; Chen, Hong-Yuan

    2016-04-01

    Ratiometric fluorescent sensors, which can provide built-in self-calibration for correction of a variety of analyte-independent factors, have attracted particular attention for analytical sensing and optical imaging with the potential to provide a precise and quantitative analysis. A wide variety of ratiometric sensing probes using small fluorescent molecules have been developed. Compared with organic dyes, exploiting semiconductor quantum dots (QDs) in ratiometric fluorescence sensing is even more intriguing, owing to their unique optical and photophysical properties that offer significant advantages over organic dyes. In this review, the main photophysical mechanism for generating dual-emission from QDs for ratiometry is discussed and categorized in detail. Typically, dual-emission can be obtained either with energy transfer from QDs to dyes or with independent dual fluorophores of QDs and dye/QDs. The recent discovery of intrinsic dual-emission from Mn-doped QDs offers new opportunities for ratiometric sensing. Particularly, the signal transduction of QDs is not restricted to fluorescence, and electrochemiluminescence and photoelectrochemistry from QDs are also promising for sensing, which can be made ratiometric for correction of interferences typically encountered in electrochemistry. All these unique photophysical properties of QDs lead to a new avenue of ratiometry, and the recent progress in this area is addressed and summarized here. Several interesting applications of QD-based ratiometry are presented for the determination of metal ions, temperature, and biomolecules, with specific emphasis on the design principles and photophysical mechanisms of these probes.

  17. Towards the generation of random bits at terahertz rates based on a chaotic semiconductor laser

    NASA Astrophysics Data System (ADS)

    Kanter, Ido; Aviad, Yaara; Reidler, Igor; Cohen, Elad; Rosenbluh, Michael

    2010-06-01

    Random bit generators (RBGs) are important in many aspects of statistical physics and crucial in Monte-Carlo simulations, stochastic modeling and quantum cryptography. The quality of a RBG is measured by the unpredictability of the bit string it produces and the speed at which the truly random bits can be generated. Deterministic algorithms generate pseudo-random numbers at high data rates as they are only limited by electronic hardware speed, but their unpredictability is limited by the very nature of their deterministic origin. It is widely accepted that the core of any true RBG must be an intrinsically non-deterministic physical process, e.g. measuring thermal noise from a resistor. Owing to low signal levels, such systems are highly susceptible to bias, introduced by amplification, and to small nonrandom external perturbations resulting in a limited generation rate, typically less than 100M bit/s. We present a physical random bit generator, based on a chaotic semiconductor laser, having delayed optical feedback, which operates reliably at rates up to 300Gbit/s. The method uses a high derivative of the digitized chaotic laser intensity and generates the random sequence by retaining a number of the least significant bits of the high derivative value. The method is insensitive to laser operational parameters and eliminates the necessity for all external constraints such as incommensurate sampling rates and laser external cavity round trip time. The randomness of long bit strings is verified by standard statistical tests.

  18. A surface intrinsic feature based method (SIFBM) for the characterization of optical microstructure

    NASA Astrophysics Data System (ADS)

    Cheung, C. F.; Kong, L. B.; Lee, W. B.; To, S.

    2008-12-01

    Optical microstructures are small scale topologies which are generally classified as grooves, pyramids, microlens arrays, lenticulations, echells, etc. They are widely used in advanced optics applications. Currently, there is lack of methods for the characterization of surface quality for optical microstructures with sub-micromenter form accuracy and surface finish in the nanometer range. This paper presents a Surface Intrinsic Feature Based Method (SIFBM) which makes use of surface intrinsic properties such as curvatures, normal vectors, torsion, intrinsic frames, etc. They are mapped as special images and image processing techniques are then employed to conduct image registration or correspondences searching by some algorithms such as correlation functions. The surface matching is optimized by corresponding vectors deviations. In the present study, a prototype surface characterization system has been built based on the SIFBM. Primary experimental work has been conducted to validate the proposed method. The results demonstrate that the SIFBM has potential advantages over existing methods.

  19. Exploration of oxide-based diluted magnetic semiconductors toward transparent spintronics

    NASA Astrophysics Data System (ADS)

    Fukumura, T.; Yamada, Y.; Toyosaki, H.; Hasegawa, T.; Koinuma, H.; Kawasaki, M.

    2004-02-01

    A review is given for the recent progress of research in the field of oxide-based diluted magnetic semiconductor (DMS), which was triggered by combinatorial discovery of transparent ferromagnet. The possible advantages of oxide semiconductor as a host of DMS are described in comparison with conventional compound semiconductors. Limits and problems for identifying novel ferromagnetic DMS are described in view of recent reports in this field. Several characterization techniques are proposed in order to eliminate unidentified ferromagnetism of oxide-based DMS unidentified ferromagnetic oxide (UFO). Perspectives and possible devices are also given.

  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. All optical logic operations using semiconductor optical amplifier based devices

    NASA Astrophysics Data System (ADS)

    Wang, Qiang

    High-speed optical processing technologies are essential for the construction of all-optical networks in the information era. In this Ph. D. thesis dissertation, essential mechanisms related to the semiconductor optical amplifier (SOA) based device such as the gain and phase dynamics when a short pulse in propagating inside SOA, and, all-optical Boolean function, XOR, AND and OR have been studied. In order to realize the all-optical logic using SOA, the nonlinear gain and phase dynamics in SOA need to be studied first. The experimental results of 10--90% gain recovery curve have been presented. The recovery time is related to the carrier lifetime of the SOA and it varies with gain compression and bias current. For pulse width of a few picosecond, intraband effects need to be considered. In the SOA, phase change is also induced when a short pulse is propagating inside SOA. Unlike the conventional way of estimating the phase shift using alpha factor, the maximum phase shift is obtained first, then the effective alpha factor is calculated. The experimental results of all optical Boolean function XOR and OR at 80 Gb/s are presented using SOA-MZI-DI and SOA-DI respectively. These are the highest operating speed that has been reported. The all optical AND operation at 40 Gb/s using SOA-MZI have also been reported here. The numerical simulation shows that the performance of these all-optical Boolean operations is limited by the carrier lifetime of the SOA. The Boolean functions are the first step towards all optical circuits. The designs of a parity checker and a pseudo-random binary sequence (PRBS) generator are demonstrated. The error analysis using quality factor and eye-diagram is also presented.

  2. Study of intrinsic anchoring in nematic liquid crystals based on modified Gruhn Hess pair potential

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi-Dong; Zhang, Yan-Jun

    2008-01-01

    A nematic liquid crystal slab composed of N molecular layers is investigated using a simple cubic lattice model, based upon the molecular pair potential which is spatially anisotropic and dependent on elastic constants of liquid crystals. A perfect nematic order is assumed in the theoretical treatment, which means the orientation of the molecular long axis coincides with the director of liquid crystal and the total free energy equals to the total interaction energy. We present a modified Gruhn Hess model, which is relative to the splay-bend elastic constant K. Furthermore, we have studied the free nematic interfacial behavior (intrinsic anchoring) by this model in the assumption of the perfect nematic order. We find that the preferred orientation at the free interface and the intrinsic anchoring strength change with the value of modification, and that the director profile can be determined by the competition of the intrinsic anchoring with external forces present in the system. Also we simulate the intrinsic anchoring at different temperatures using Monte Carlo method and the simulation results show that the intrinsic anchoring favors planar alignment and the free interface is more disordered than the bulk.

  3. A game theoretic framework for incentive-based models of intrinsic motivation in artificial systems.

    PubMed

    Merrick, Kathryn E; Shafi, Kamran

    2013-01-01

    An emerging body of research is focusing on understanding and building artificial systems that can achieve open-ended development influenced by intrinsic motivations. In particular, research in robotics and machine learning is yielding systems and algorithms with increasing capacity for self-directed learning and autonomy. Traditional software architectures and algorithms are being augmented with intrinsic motivations to drive cumulative acquisition of knowledge and skills. Intrinsic motivations have recently been considered in reinforcement learning, active learning and supervised learning settings among others. This paper considers game theory as a novel setting for intrinsic motivation. A game theoretic framework for intrinsic motivation is formulated by introducing the concept of optimally motivating incentive as a lens through which players perceive a game. Transformations of four well-known mixed-motive games are presented to demonstrate the perceived games when players' optimally motivating incentive falls in three cases corresponding to strong power, affiliation and achievement motivation. We use agent-based simulations to demonstrate that players with different optimally motivating incentive act differently as a result of their altered perception of the game. We discuss the implications of these results both for modeling human behavior and for designing artificial agents or robots.

  4. Flexible OFDM-based access systems with intrinsic function of chromatic dispersion compensation

    NASA Astrophysics Data System (ADS)

    Konishi, Tsuyoshi; Murakawa, Takuya; Nagashima, Tomotaka; Hasegawa, Makoto; Shimizu, Satoshi; Hattori, Kuninori; Okuno, Masayuki; Mino, Shinji; Himeno, Akira; Uenohara, Hiroyuki; Wada, Naoya; Cincotti, Gabriella

    2015-12-01

    Cost-effective and tunable chromatic dispersion compensation in a fiber link are still an open issue in metro and access networks to cope with increasing costs and power consumption. Intrinsic chromatic dispersion compensation functionality of optical fractional orthogonal frequency division multiplexing is discussed and experimentally demonstrated using dispersion-tunable transmitter and receiver based on wavelength selective switching devices.

  5. Stimulating Students' Intrinsic Motivation for Learning Chemistry through the Use of Context-Based Learning Modules

    ERIC Educational Resources Information Center

    Vaino, Katrin; Holbrook, Jack; Rannikmae, Miia

    2012-01-01

    This paper introduces a research project in which five chemistry teachers, working in cooperation with university researchers, implemented a new teaching approach using context-based modules specially designed to stimulate the intrinsic motivation of students. The intention was to induce change in chemistry teachers' teaching approach from more…

  6. Redox characterization of semiconductors based on electrochemical measurements combined with UV-Vis diffuse reflectance spectroscopy.

    PubMed

    Świętek, Elżbieta; Pilarczyk, Kacper; Derdzińska, Justyna; Szaciłowski, Konrad; Macyk, Wojciech

    2013-09-14

    Several techniques can be applied to characterize redox properties of wide bandgap semiconductors, however some of them are of limited use. In this paper we propose a new modification of the old spectroelectrochemical method developed two decades ago. A procedure based on measurements of the reflectance changes as a function of potential applied to the electrode coated with the studied material appears to be a very convenient tool for characterizing redox properties of semiconductors, forming either transparent or opaque films at a platinum electrode. A discussion on the measured redox parameters of semiconductor films concludes with a definition of a new term, the absorption onset potential of the material.

  7. 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.

  8. Subpicosecond Carrier Dynamics in Semiconductor Lasers and Lasers Based on Intersubband Transition.

    NASA Astrophysics Data System (ADS)

    Sung, Chun-Yung

    Recently, research for semiconductor lasers has proceeded in two directions. One direction is towards faster modulation speed for greater optical communication capacity. The second direction is towards long wavelength (10-100 mun) coherent radiation from the novel quantum well laser structures. In both cases, a fundamental understanding of carrier dynamics in the subpicosecond time scale is extremely important. This thesis explores the ultrafast carrier relaxation dynamics in several important optoelectronic semiconductor structures, with an emphasis on intersubband relaxation dynamics. Amplified femtosecond pulses are used for the generation of a femtosecond white light continuum, which has been used for the femtosecond differential transmission spectroscopy. We extensively studied the carrier relaxation for both low and high density excitation. The carrier capture, which is the intrinsic limit to the highest modulation bandwidth for SCH quantum well semiconductor lasers, has been time-resolved via femtosecond differential transmission spectroscopy. Strong capture resonances have been observed. Since the capture experiments reported to date do not directly measure the capture under conditions of laser operation, we have extended a three-pulse technique to remove carriers from the gain region of an inverted quantum well and monitor the gain recovery. This yields capture and relaxation times more appropriate for comparison with modulated laser operation. The gain recovery in a separate-confinement quantum-well structure limited by the carrier capture is directly time-resolved as well as spectral hole burning. Long carrier capture times are observed in the case of high density excitation due to Pauli-exclusion principle. The carrier tunneling dynamics in the new developed high speed tunneling injection laser (TIL) are also spectrally and temporally resolved. The measured ultrafast tunneling times confirm the TIL's potential for high speed applications. Ultrafast

  9. Controlled assembly and electronics in semiconductor nanocrystal-based devices

    NASA Astrophysics Data System (ADS)

    Drndic, Marija

    2006-03-01

    I will discuss the assembly of semiconductor nanocrystals (CdSe and PbSe) into electronic devices and the basic mechanisms of charge transport in nanocrystal arrays [1-4]. Spherical CdSe nanocrystals show robust memory effects that can be exploited for memory applications [1]. Nanocrystal memory can be erased electrically or optically and is rewritable. In PbSe nanocrystal arrays, as the interdot coupling is increased, the system evolves from an insulating regime dominated by Coulomb blockade to a semiconducting regime, where hopping conduction is the dominant transport mechanism [2]. Two-dimensional CdSe nanorod arrays show striking and anomalous transport properties, including strong and reproducible non-linearities and current oscillations with dc-voltage [4]. I will also discuss imaging of the charge transport in nanocrystal-based electronic devices. Nanocrystal arrays were investigated using electrostatic force microscopy (EFM) and transmission electron microscopy (TEM) [3]. Changes in lattice and transport properties upon annealing in vacuum were revealed. Local charge transport was directly imaged by EFM and correlated to nanopatterns observed with TEM. This work shows how charge transport in complex nanocrystal networks can be identified with nm resolution [3]. This work was supported by the ONR grant N000140410489, the NSF grants DMR-0449553 and MRSEC DMR00-79909, and the ACS PRF grant 41256-G10. References:1) Fischbein M. D. and Drndic M., ``CdSe nanocrystal quantum-dot memory,'' Applied Physics Letters, 86 (19), 193106, 2005.2) H. E. Romero and Drndic M., ``Coulomb blockade and hopping conduction in PbSe quantum dots,'' Physical Review Letters 95, 156801, 2005.3) Hu Z., Fischbein M. D. and Drndic M., ``Local charge transport in two-dimensional PbSe nanocrystal arrays studied by electrostatic force microscopy",'' Nano Letters 5 (7), 1463, 2005.4) Romero H.E., Calusine G. and Drndic M., ``Current oscillations, switching and hysteresis in CdSe nanorod

  10. Strain-based control of crystal anisotropy for perovskite oxides on semiconductor-based material

    DOEpatents

    McKee, Rodney Allen; Walker, Frederick Joseph

    2000-01-01

    A crystalline structure and a semiconductor device includes a substrate of a semiconductor-based material and a thin film of an anisotropic crystalline material epitaxially arranged upon the surface of the substrate so that the thin film couples to the underlying substrate and so that the geometries of substantially all of the unit cells of the thin film are arranged in a predisposed orientation relative to the substrate surface. The predisposition of the geometries of the unit cells of the thin film is responsible for a predisposed orientation of a directional-dependent quality, such as the dipole moment, of the unit cells. The predisposed orientation of the unit cell geometries are influenced by either a stressed or strained condition of the lattice at the interface between the thin film material and the substrate surface.

  11. Assessing Online Textual Feedback to Support Student Intrinsic Motivation Using a Collaborative Text-Based Dialogue System: A Qualitative Study

    ERIC Educational Resources Information Center

    Shroff, Ronnie H.; Deneen, Christopher

    2011-01-01

    This paper assesses textual feedback to support student intrinsic motivation using a collaborative text-based dialogue system. A research model is presented based on research into intrinsic motivation, and the specific construct of feedback provides a framework for the model. A qualitative research methodology is used to validate the model.…

  12. X-ray Characterization of Oxide-based Magnetic Semiconductors

    NASA Astrophysics Data System (ADS)

    Idzerda, Yves

    2008-05-01

    Although the evidence for magnetic semiconductors (not simply semiconductors which are ferromagnetic) is compelling, there is much uncertainty in the mechanism for the polarization of the carriers, suggesting that it must be quite novel. Recent experimental evidence suggests that this mechanism is similar to the polaron percolation theory proposed by Kaminski and Das Sarma,ootnotetextKaminski and S. Das Sarma, Physical Review Letters 88, 247202 (2002). which was recently applied specifically to doped oxides by Coey et al.ootnotetextJ. M. D. Coey, M. Venkatesan, and C. B. Fitzgerald, Nature Materials 4, 173 (2005). where the ferromagnetism is driven by the percolation of polarons generated by defects or dopants. We have used X-ray absorption spectroscopy at the L-edges and K-edges for low concentrations transition metal (TM) doped magnetic oxides (including TiO2, La1-xSrxO3, HfO2, and In2O3). We have found that in most cases, the transition metal assumes a valence consistent with being at a substitutional, and not interstitial site. We have also measured the X-ray Magnetic Circular Dichroism spectra. Although these materials show strong bulk magnetization, we are unable to detect a robust dichroism feature associated with magnetic elements in the host semiconductor. In the cases where a dichroism signal was observed, it was very weak and could be ascribed to a distinct ferromagnetic phase (TM metal cluster, TM oxide particulate, etc.) separate from the host material. This fascinating absence of a dichroic signal and its significant substantiation of important features of the polaron percolation model may help to finally resolve the issue of ferromagnetism in magnetically doped oxides.

  13. 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.

  14. Anhydrous crystals of DNA bases are wide gap semiconductors.

    PubMed

    Maia, F F; Freire, V N; Caetano, E W S; Azevedo, D L; Sales, F A M; Albuquerque, E L

    2011-05-07

    We present the structural, electronic, and optical properties of anhydrous crystals of DNA nucleobases (guanine, adenine, cytosine, and thymine) found after DFT (Density Functional Theory) calculations within the local density approximation, as well as experimental measurements of optical absorption for powders of these crystals. Guanine and cytosine (adenine and thymine) anhydrous crystals are predicted from the DFT simulations to be direct (indirect) band gap semiconductors, with values 2.68 eV and 3.30 eV (2.83 eV and 3.22 eV), respectively, while the experimentally estimated band gaps we have measured are 3.83 eV and 3.84 eV (3.89 eV and 4.07 eV), in the same order. The electronic effective masses we have obtained at band extremes show that, at low temperatures, these crystals behave like wide gap semiconductors for electrons moving along the nucleobases stacking direction, while the hole transport are somewhat limited. Lastly, the calculated electronic dielectric functions of DNA nucleobases crystals in the parallel and perpendicular directions to the stacking planes exhibit a high degree of anisotropy (except cytosine), in agreement with published experimental results.

  15. Chasing equilibrium: measuring the intrinsic solubility of weak acids and bases.

    PubMed

    Stuart, Martin; Box, Karl

    2005-02-15

    A novel procedure is described for rapid (20-80 min) measurement of intrinsic solubility values of organic acids, bases, and ampholytes. In this procedure, a quantity of substance was first dissolved at a pH where it exists predominantly in its ionized form, and then a precipitate of the neutral (un-ionized) species was formed by changing the pH. Subsequently, the rate of change of pH due to precipitation or dissolution was monitored and strong acid and base titrant were added to adjust the pH to discover its equilibrium conditions, and the intrinsic solubility of the neutral form of the compound could then be determined. The procedure was applied to a variety of monoprotic and diprotic pharmaceutical compounds. The results were highly repeatable and had a good correlation to available published values. Data collected during the procedure provided good diagnostic information. Kinetic solubility data were also collected but provided a poor guide to the intrinsic solubility.

  16. 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.

  17. Thermodynamic properties of semiconductor compounds studied based on Debye-Waller factors

    NASA Astrophysics Data System (ADS)

    Van Hung, Nguyen; Toan, Nguyen Cong; Ba Duc, Nguyen; Vuong, Dinh Quoc

    2015-08-01

    Thermodynamic properties of semiconductor compounds have been studied based on Debye-Waller factors (DWFs) described by the mean square displacement (MSD) which has close relation with the mean square relative displacement (MSRD). Their analytical expressions have been derived based on the statistical moment method (SMM) and the empirical many-body Stillinger-Weber potentials. Numerical results for the MSDs of GaAs, GaP, InP, InSb, which have zinc-blende structure, are found to be in reasonable agreement with experiment and other theories. This paper shows that an elements value for MSD is dependent on the binary semiconductor compound within which it resides.

  18. Ultrafast switching based on field optical bistability in nano-film of semiconductor

    NASA Astrophysics Data System (ADS)

    Trofimov, Vyacheslav A.; Egorenkov, Vladimir A.; Loginova, Maria M.

    2016-09-01

    Using computer simulation, we show a possibility of ultrafast switching between stable states of an optical bistable device based on nano-film of semiconductor. Optical bistability occurs because of nonlinear dependence of semiconductor absorption coefficient on electric field potential. Electric field is induced by a laser pulse due to charged particles generation. The main feature of this bistable element is low absorption energy, which is necessary for switching, in comparison with bistable element based on other physical mechanism of laser energy absorption. For computer simulation of a problem under consideration a new finite-difference scheme is proposed using the original iterative process.

  19. Semiconductor meta-surface based perfect light absorber.

    PubMed

    Liu, Guiqiang; Nie, Yiyou; Fu, Guolan; Liu, Xiaoshan; Liu, Yi; Tang, Li; Liu, Zhengqi

    2017-04-21

    We numerically proposed and demonstrated a semiconductor meta-surface light absorber, which consists of a silicon patches array on a silicon thin-film and an opaque silver substrate. The Mie resonances of the silicon patches and the fundamental cavity mode of the ultra-thin silicon film couple strongly to the incident optical field, leading to a multi-band perfect absorption. The maximal absorption is above 99.5% and the absorption is polarization-independent. Moreover, the absorption behavior is scalable in the frequency region via tuning the structural parameters. These features hold the absorber platform with wide applications in optoelectronics such as hot-electron excitation and photo-detection.

  20. Strong vibration nonlinearity in semiconductor-based nanomechanical systems

    NASA Astrophysics Data System (ADS)

    Moskovtsev, Kirill; Dykman, M. I.

    2017-02-01

    We study the effect of the electron-phonon coupling on vibrational eigenmodes of nano- and micromechanical systems made of semiconductors with equivalent energy valleys. We show that the coupling can lead to a strong mode nonlinearity. The mechanism is the lifting of the valley degeneracy by the strain. The redistribution of the electrons between the valleys is controlled by a large ratio of the electron-phonon coupling constant to the electron chemical potential or temperature. We find the quartic in the strain terms in the electron free energy, which determine the amplitude dependence of the mode frequencies. This dependence is calculated for silicon microsystems. It is significantly different for different modes and the crystal orientation, and can vary nonmonotonously with the electron density and temperature.

  1. Novel semiconductor radiation detector based on mercurous halides

    NASA Astrophysics Data System (ADS)

    Chen, Henry; Kim, Joo-Soo; Amarasinghe, Proyanthi; Palosz, Withold; Jin, Feng; Trivedi, Sudhir; Burger, Arnold; Marsh, Jarrod C.; Litz, Marc S.; Wiejewarnasuriya, Priyalal S.; Gupta, Neelam; Jensen, Janet; Jensen, James

    2015-08-01

    The three most important desirable features in the search for room temperature semiconductor detector (RTSD) candidate as an alternative material to current commercially off-the-shelf (COTS) material for gamma and/or thermal neutron detection are: low cost, high performance and long term stability. This is especially important for pager form application in homeland security. Despite years of research, no RTSD candidate so far can satisfy the above 3 features simultaneously. In this work, we show that mercurous halide materials Hg2X2 (X= I, Cl, Br) is a new class of innovative compound semiconductors that is capable of delivering breakthrough advances to COTS radiation detector materials. These materials are much easier to grow thicker and larger volume crystals. They can detect gamma and potentially neutron radiation making it possible to detect two types of radiation with just one crystal material. The materials have wider bandgaps (compared to COTS) meaning higher resistivity and lower leakage current, making this new technology more compatible with available microelectronics. The materials also have higher atomic number and density leading to higher stopping power and better detector sensitivity/efficiency. They are not hazardous so there are no environmental and health concerns during manufacturing and are more stable making them more practical for commercial deployment. Focus will be on Hg2I2. Material characterization and detector performance will be presented and discussed. Initial results show that an energy resolution better than 2% @ 59.6 keV gamma from Am-241 and near 1% @ 662 keV from Cs-137 source can be achieved at room temperature.

  2. Skull base tumours Part II. Central skull base tumours and intrinsic tumours of the bony skull base.

    PubMed

    Borges, Alexandra

    2008-06-01

    With the advances of cross-sectional imaging radiologists gained an increasing responsibility in the management of patients with skull base pathology. As this anatomic area is hidden to clinical exam, surgeons and radiation oncologists have to rely on imaging studies to plan the most adequate treatment. To fulfil these endeavour radiologists need to be knowledgeable about skull base anatomy, about the main treatment options available, their indications and contra-indications and needs to be aware of the wide gamut of pathologies seen in this anatomic region. This article will provide a radiologists' friendly approach to the central skull base and will review the most common central skull base tumours and tumours intrinsic to the bony skull base.

  3. 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.

  4. Solar-blind UV detectors based on wide band gap semiconductors

    NASA Astrophysics Data System (ADS)

    Schuhle, Udo; Hochedez, Jean-Francois

    Solid-state photon detectors based on semiconductors other than silicon are not yet considered mature technology but their current development opens new possibilities, also for space observations. Such devices are especially attractive for ultraviolet radiation detection, as semiconductor materials with band gaps larger than that of silicon can be produced and used as "visible-blind" or "solar-blind" detectors that are not affected by daylight. Here we evaluate the advantages of such detectors compared to silicon-based devices and report on the semiconductor detectors that have been fabricated in recent years with materials having large band-gap energies. We describe the most common pixel designs and characterize their general properties.

  5. Two-Dimensional Semiconductor Optoelectronics Based on van der Waals Heterostructures

    PubMed Central

    Lee, Jae Yoon; Shin, Jun-Hwan; Lee, Gwan-Hyoung; Lee, Chul-Ho

    2016-01-01

    Two-dimensional (2D) semiconductors such as transition metal dichalcogenides (TMDCs) and black phosphorous have drawn tremendous attention as an emerging optical material due to their unique and remarkable optical properties. In addition, the ability to create the atomically-controlled van der Waals (vdW) heterostructures enables realizing novel optoelectronic devices that are distinct from conventional bulk counterparts. In this short review, we first present the atomic and electronic structures of 2D semiconducting TMDCs and their exceptional optical properties, and further discuss the fabrication and distinctive features of vdW heterostructures assembled from different kinds of 2D materials with various physical properties. We then focus on reviewing the recent progress on the fabrication of 2D semiconductor optoelectronic devices based on vdW heterostructures including photodetectors, solar cells, and light-emitting devices. Finally, we highlight the perspectives and challenges of optoelectronics based on 2D semiconductor heterostructures. PMID:28335321

  6. An assignment of intrinsically disordered regions of proteins based on NMR structures.

    PubMed

    Ota, Motonori; Koike, Ryotaro; Amemiya, Takayuki; Tenno, Takeshi; Romero, Pedro R; Hiroaki, Hidekazu; Dunker, A Keith; Fukuchi, Satoshi

    2013-01-01

    Intrinsically disordered proteins (IDPs) do not adopt stable three-dimensional structures in physiological conditions, yet these proteins play crucial roles in biological phenomena. In most cases, intrinsic disorder manifests itself in segments or domains of an IDP, called intrinsically disordered regions (IDRs), but fully disordered IDPs also exist. Although IDRs can be detected as missing residues in protein structures determined by X-ray crystallography, no protocol has been developed to identify IDRs from structures obtained by Nuclear Magnetic Resonance (NMR). Here, we propose a computational method to assign IDRs based on NMR structures. We compared missing residues of X-ray structures with residue-wise deviations of NMR structures for identical proteins, and derived a threshold deviation that gives the best correlation of ordered and disordered regions of both structures. The obtained threshold of 3.2Å was applied to proteins whose structures were only determined by NMR, and the resulting IDRs were analyzed and compared to those of X-ray structures with no NMR counterpart in terms of sequence length, IDR fraction, protein function, cellular location, and amino acid composition, all of which suggest distinct characteristics. The structural knowledge of IDPs is still inadequate compared with that of structured proteins. Our method can collect and utilize IDRs from structures determined by NMR, potentially enhancing the understanding of IDPs.

  7. Intrinsic functional connectivity pattern-based brain parcellation using normalized cut

    NASA Astrophysics Data System (ADS)

    Cheng, Hewei; Song, Dandan; Wu, Hong; Fan, Yong

    2012-02-01

    In imaging data based brain network analysis, a necessary precursor for constructing meaningful brain networks is to identify functionally homogeneous regions of interest (ROIs) for defining network nodes. For parcellating the brain based on resting state fMRI data, normalized cut is one widely used clustering algorithm which groups voxels according to the similarity of functional signals. Due to low signal to noise ratio (SNR) of resting state fMRI signals, spatial constraint is often applied to functional similarity measures to generate smooth parcellation. However, improper spatial constraint might alter the intrinsic functional connectivity pattern, thus yielding biased parcellation results. To achieve reliable and least biased parcellation of the brain, we propose an optimization method for the spatial constraint to functional similarity measures in normalized cut based brain parcellation. Particularly, we first identify the space of all possible spatial constraints that are able to generate smooth parcellation, then find the spatial constraint that leads to the brain parcellation least biased from the intrinsic function pattern based parcellation, measured by the minimal Ncut value calculated based on the functional similarity measure of original functional signals. The proposed method has been applied to the parcellation of medial superior frontal cortex for 20 subjects based on their resting state fMRI data. The experiment results indicate that our method can generate meaningful parcellation results, consistent with existing functional anatomy knowledge.

  8. Rainflow Algorithm-Based Lifetime Estimation of Power Semiconductors in Utility Applications

    SciTech Connect

    GopiReddy, Lakshmi Reddy; Tolbert, Leon M.; Ozpineci, Burak; Pinto, Joao O. P.

    2015-07-15

    Rainflow algorithms are one of the popular counting methods used in fatigue and failure analysis in conjunction with semiconductor lifetime estimation models. However, the rain-flow algorithm used in power semiconductor reliability does not consider the time-dependent mean temperature calculation. The equivalent temperature calculation proposed by Nagode et al. is applied to semiconductor lifetime estimation in this paper. A month-long arc furnace load profile is used as a test profile to estimate temperatures in insulated-gate bipolar transistors (IGBTs) in a STATCOM for reactive compensation of load. In conclusion, the degradation in the life of the IGBT power device is predicted based on time-dependent temperature calculation.

  9. Multilayer hybrid LEDs based on colloidal inorganic semiconductors nanocrystal and PIN technology

    NASA Astrophysics Data System (ADS)

    Rizzo, Aurora; Mazzeo, Marco; Gigli, Giuseppe

    2008-04-01

    Light emitting devices (LEDs) based on colloidal semiconductor nanocrystals represent a matter of technological interest for the development of flat panel display and lighting systems. The appealing features of these materials are the high fluorescence efficiency, narrow ban edge emission, potential chemical stability, and tunable light emission across the visible spectrum. However the integration of these materials in the very promising PIN technology is still challenging due to the lack of an appropriate QD deposition technique. So far only wet deposition methods such as spin-coating and drop-casting have been exploited to realize QD thin film. Moreover QD thermal evaporation is not possible because of their high molecular weight. In this scenario we developed a dry, simple, and inexpensive deposition technique to transfer semiconductor QDs on organic semiconductor materials. We exploited this technique to fabricated an organic/inorganic hybrid red emitting device whit a doped hole transport layer.

  10. Spin selector based on periodic diluted-magnetic-semiconductor/nonmagnetic-barrier superlattices

    SciTech Connect

    Yang, Ping-Fan; Guo, Yong; Zhu, Rui

    2015-07-15

    We propose a spin selector based on periodic diluted-magnetic-semiconductor/nonmagnetic-barrier (DMS/NB) superlattices subjected to an external magnetic field. We find that the periodic DMS/NB superlattices can achieve 100% spin filtering over a dramatically broader range of incident energies than the diluted-magnetic-semiconductor/semiconductor (DMS/S) case studied previously. And the positions and widths of spin-filtering bands can be manipulated effectively by adjusting the geometric parameters of the system or the strength of external magnetic field. Such a compelling filtering feature stems from the introduction of nonmagnetic barrier and the spin-dependent giant Zeeman effect induced by the external magnetic field. We also find that the external electric field can exert a significant influence on the spin-polarized transport through the DMS/NB superlattices.

  11. Organic Semiconductors based on Dyes and Color Pigments.

    PubMed

    Gsänger, Marcel; Bialas, David; Huang, Lizhen; Stolte, Matthias; Würthner, Frank

    2016-05-01

    Organic dyes and pigments constitute a large class of industrial products. The utilization of these compounds in the field of organic electronics is reviewed with particular emphasis on organic field-effect transistors. It is shown that for most major classes of industrial dyes and pigments, i.e., phthalocyanines, perylene and naphthalene diimides, diketopyrrolopyrroles, indigos and isoindigos, squaraines, and merocyanines, charge-carrier mobilities exceeding 1 cm(2) V(-1) s(-1) have been achieved. The most widely investigated molecules due to their n-channel operation are perylene and naphthalene diimides, for which even values close to 10 cm(2) V(-1) s(-1) have been demonstrated. The fact that all of these π-conjugated colorants contain polar substituents leading to strongly quadrupolar or even dipolar molecules suggests that indeed a much larger structural space shows promise for the design of organic semiconductor molecules than was considered in this field traditionally. In particular, because many of these dye and pigment chromophores demonstrate excellent thermal and (photo-)chemical stability in their original applications in dyeing and printing, and are accessible by straightforward synthetic protocols, they bear a particularly high potential for commercial applications in the area of organic electronics.

  12. Computational molecular design of polyhedral oligomeric silsesquioxane based organic-inorganic hybrid semiconductors

    NASA Astrophysics Data System (ADS)

    Qi, Feng

    processability, cubic molecular symmetry, and the three-dimensional conjugation. The computationally designed octa(2,5-diiodophenyl)-SQ (ODIPS) shows a calculated conduction band structure similar to that of 1,4-diiodobenzene (DIB), whose high hole mobility is known from experiment. Electronic band structure calculations indicate that the SQ cages, which are by themselves insulators, contribute to the electronic transport process in these hybrid molecules, and enhance the intrinsic electronic properties of the organic semiconductor functional groups.

  13. An All Fiber Intrinsic Fabry-Perot Interferometer Based on an Air-Microcavity

    PubMed Central

    Jáuregui-Vázquez, Daniel; Estudillo-Ayala, Julián M.; Rojas-Laguna, Roberto; Vargas-Rodríguez, Everardo; Sierra-Hernández, Juan M.; Hernández-García, Juan C.; Mata-Chávez, Ruth I.

    2013-01-01

    In this work an Intrinsic Fabry-Perot Interferometer (IFPI) based on an air-microcavity is presented. Here the air microcavity, with silica walls, is formed at a segment of a hollow core photonic crystal fiber (HCPCF), which is fusion spliced with a single mode fiber (SMF). Moreover, the spectral response of the IFPI is experimentally characterized and some results are provided. Finally, the viability to use the IFPI to implement a simple, compact size, and low cost refractive index sensor is briefly analyzed. PMID:23673676

  14. Shared Reading: assessing the intrinsic value of a literature-based health intervention.

    PubMed

    Longden, Eleanor; Davis, Philip; Billington, Josie; Lampropoulou, Sofia; Farrington, Grace; Magee, Fiona; Walsh, Erin; Corcoran, Rhiannon

    2015-12-01

    Public health strategies have placed increasing emphasis on psychosocial and arts-based strategies for promoting well-being. This study presents preliminary findings for a specific literary-based intervention, Shared Reading, which provides community-based spaces in which individuals can relate with both literature and one another. A 12-week crossover design was conducted with 16 participants to compare benefits associated with six sessions of Shared Reading versus a comparison social activity, Built Environment workshops. Data collected included quantitative self-report measures of psychological well-being, as well as transcript analysis of session recordings and individual video-assisted interviews. Qualitative findings indicated five intrinsic benefits associated with Shared Reading: liveness, creative inarticulacy, the emotional, the personal and the group (or collective identity construction). Quantitative data additionally showed that the intervention is associated with enhancement of a sense of 'Purpose in Life'. Limitations of the study included the small sample size and ceiling effects created by generally high levels of psychological well-being at baseline. The therapeutic potential of reading groups is discussed, including the distinction between instrumental and intrinsic value within arts-and-health interventions.

  15. Semiconductor-based, large-area, flexible, electronic devices on {110}<100> oriented substrates

    SciTech Connect

    Goyal, Amit

    2014-08-05

    Novel articles and methods to fabricate the same resulting in flexible, oriented, semiconductor-based, electronic devices on {110}<100> textured substrates 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.

  16. [100] or [110] aligned, semiconductor-based, large-area, flexible, electronic devices

    DOEpatents

    Goyal, Amit

    2015-03-24

    Novel articles and methods to fabricate the same resulting in flexible, large-area, [100] or [110] textured, 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.

  17. High-mobility pyrene-based semiconductor for organic thin-film transistors.

    PubMed

    Cho, Hyunduck; Lee, Sunyoung; Cho, Nam Sung; Jabbour, Ghassan E; Kwak, Jeonghun; Hwang, Do-Hoon; Lee, Changhee

    2013-05-01

    Numerous conjugated oligoacenes and polythiophenes are being heavily studied in the search for high-mobility organic semiconductors. Although many researchers have designed fused aromatic compounds as organic semiconductors for organic thin-film transistors (OTFTs), pyrene-based organic semiconductors with high mobilities and on-off current ratios have not yet been reported. Here, we introduce a new pyrene-based p-type organic semiconductor showing liquid crystal behavior. The thin film characteristics of this material are investigated by varying the substrate temperature during the deposition and the gate dielectric condition using the surface modification with a self-assembled monolayer, and systematically studied in correlation with the performances of transistor devices with this compound. OTFT fabricated under the optimum deposition conditions of this compound, namely, 1,6-bis(5'-octyl-2,2'-bithiophen-5-yl)pyrene (BOBTP) shows a high-performance transistor behavior with a field-effect mobility of 2.1 cm(2) V(-1) s(-1) and an on-off current ratio of 7.6 × 10(6) and enhanced long-term stability compared to the pentacene thin-film transistor.

  18. The determination of the intrinsic and extrinsic parameters of virtual camera based on OpenGL

    NASA Astrophysics Data System (ADS)

    Li, Suqi; Zhang, Guangjun; Wei, Zhenzhong

    2006-11-01

    OpenGL is the international standard of 3D image. The 3D image generation by OpenGL is similar to the shoot by camera. This paper focuses on the application of OpenGL to computer vision, the OpenGL 3D image is regarded as virtual camera image. Firstly, the imaging mechanism of OpenGL has been analyzed in view of perspective projection transformation of computer vision camera. Then, the relationship between intrinsic and extrinsic parameters of camera and function parameters in OpenGL has been analysed, the transformation formulas have been deduced. Thereout the computer vision simulation has been realized. According to the comparison between the actual CCD camera images and virtual camera images(the parameters of actual camera are the same as virtual camera's) and the experiment results of stereo vision 3D reconstruction simulation, the effectiveness of the method with which the intrinsic and extrinsic parameters of virtual camera based on OpenGL are determined has been verified.

  19. Pixelated CdTe detectors to overcome intrinsic limitations of crystal based positron emission mammographs

    NASA Astrophysics Data System (ADS)

    De Lorenzo, G.; Chmeissani, M.; Uzun, D.; Kolstein, M.; Ozsahin, I.; Mikhaylova, E.; Arce, P.; Cañadas, M.; Ariño, G.; Calderón, Y.

    2013-01-01

    A positron emission mammograph (PEM) is an organ dedicated positron emission tomography (PET) scanner for breast cancer detection. State-of-the-art PEMs employing scintillating crystals as detection medium can provide metabolic images of the breast with significantly higher sensitivity and specificity with respect to standard whole body PET scanners. Over the past few years, crystal PEMs have dramatically increased their importance in the diagnosis and treatment of early stage breast cancer. Nevertheless, designs based on scintillators are characterized by an intrinsic deficiency of the depth of interaction (DOI) information from relatively thick crystals constraining the size of the smallest detectable tumor. This work shows how to overcome such intrinsic limitation by substituting scintillating crystals with pixelated CdTe detectors. The proposed novel design is developed within the Voxel Imaging PET (VIP) Pathfinder project and evaluated via Monte Carlo simulation. The volumetric spatial resolution of the VIP-PEM is expected to be up to 6 times better than standard commercial devices with a point spread function of 1 mm full width at half maximum (FWHM) in all directions. Pixelated CdTe detectors can also provide an energy resolution as low as 1.5% FWHM at 511 keV for a virtually pure signal with negligible contribution from scattered events.

  20. Pixelated CdTe detectors to overcome intrinsic limitations of crystal based positron emission mammographs.

    PubMed

    De Lorenzo, G; Chmeissani, M; Uzun, D; Kolstein, M; Ozsahin, I; Mikhaylova, E; Arce, P; Cañadas, M; Ariño, G; Calderón, Y

    2013-01-01

    A positron emission mammograph (PEM) is an organ dedicated positron emission tomography (PET) scanner for breast cancer detection. State-of-the-art PEMs employing scintillating crystals as detection medium can provide metabolic images of the breast with significantly higher sensitivity and specificity with respect to standard whole body PET scanners. Over the past few years, crystal PEMs have dramatically increased their importance in the diagnosis and treatment of early stage breast cancer. Nevertheless, designs based on scintillators are characterized by an intrinsic deficiency of the depth of interaction (DOI) information from relatively thick crystals constraining the size of the smallest detectable tumor. This work shows how to overcome such intrinsic limitation by substituting scintillating crystals with pixelated CdTe detectors. The proposed novel design is developed within the Voxel Imaging PET (VIP) Pathfinder project and evaluated via Monte Carlo simulation. The volumetric spatial resolution of the VIP-PEM is expected to be up to 6 times better than standard commercial devices with a point spread function of 1 mm full width at half maximum (FWHM) in all directions. Pixelated CdTe detectors can also provide an energy resolution as low as 1.5% FWHM at 511 keV for a virtually pure signal with negligible contribution from scattered events.

  1. Pixelated CdTe detectors to overcome intrinsic limitations of crystal based positron emission mammographs

    PubMed Central

    De Lorenzo, G.; Chmeissani, M.; Uzun, D.; Kolstein, M.; Ozsahin, I.; Mikhaylova, E.; Arce, P.; Cañadas, M.; Ariño, G.; Calderón, Y.

    2013-01-01

    A positron emission mammograph (PEM) is an organ dedicated positron emission tomography (PET) scanner for breast cancer detection. State-of-the-art PEMs employing scintillating crystals as detection medium can provide metabolic images of the breast with significantly higher sensitivity and specificity with respect to standard whole body PET scanners. Over the past few years, crystal PEMs have dramatically increased their importance in the diagnosis and treatment of early stage breast cancer. Nevertheless, designs based on scintillators are characterized by an intrinsic deficiency of the depth of interaction (DOI) information from relatively thick crystals constraining the size of the smallest detectable tumor. This work shows how to overcome such intrinsic limitation by substituting scintillating crystals with pixelated CdTe detectors. The proposed novel design is developed within the Voxel Imaging PET (VIP) Pathfinder project and evaluated via Monte Carlo simulation. The volumetric spatial resolution of the VIP-PEM is expected to be up to 6 times better than standard commercial devices with a point spread function of 1 mm full width at half maximum (FWHM) in all directions. Pixelated CdTe detectors can also provide an energy resolution as low as 1.5% FWHM at 511 keV for a virtually pure signal with negligible contribution from scattered events. PMID:23750176

  2. Amygdala-based intrinsic functional connectivity and anxiety disorders in adolescents and young adults.

    PubMed

    Toazza, Rudineia; Franco, Alexandre Rosa; Buchweitz, Augusto; Molle, Roberta Dalle; Rodrigues, Danitsa Marcos; Reis, Roberta Sena; Mucellini, Amanda Brondani; Esper, Nathalia Bianchini; Aguzzoli, Cristiano; Silveira, Patrícia Pelufo; Salum, Giovanni Abrahão; Manfro, Gisele Gus

    2016-11-30

    Anxiety disorders (AD) are the most prevalent group of psychiatric disorders in adolescents and young adults. Nevertheless, the pathophysiology of anxiety disorders is still poorly understood. This study investigated differences in the functional connectivity of intrinsic amygdala-based networks of participants with and without AD. Resting state fMRI data were obtained from 18 participants with an AD and 19 healthy comparison individuals. Psychiatric diagnosis was assessed using standardized structured interviews. The comparison between groups was carried out using functional connectivity maps from six seed regions defined using probabilistic maps bilaterally within the amygdala (basolateral, superficial and centromedial amygdala). We found significant between-group differences in five clusters, which showed aberrant functional connectivity with the left basolateral amygdala: right precentral gyrus, right cingulate gyrus, bilateral precuneus, and right superior frontal gyrus in subjects with AD as compared with the comparison subjects. For the comparison subjects, the correlations between the amygdala and the five clusters were either non-significant, or negative. The present study suggests there is an intrinsic disruption in the communication between left basolateral amygdala and a network of brain regions involved with emotion regulation, and with the default mode network in adolescents and young adults with anxiety disorders.

  3. High performance field-effect ammonia sensors based on a structured ultrathin organic semiconductor film.

    PubMed

    Li, Liqiang; Gao, Peng; Baumgarten, Martin; Müllen, Klaus; Lu, Nan; Fuchs, Harald; Chi, Lifeng

    2013-07-05

    High performance organic field-effect transistor (OFET)-based ammonia sensors are demonstrated with ultrathin (4-6 molecular layers) dendritic microstripes of an organic semiconductor prepared via dip-coating. These sensors exhibit high sensitivity, fast response/recovery rate, good selectivity, low concentration detection ability, and reliable reversibility, as well as stability. Such a performance represents great progress in the field of OFET-based sensors.

  4. Laser apparatus for surgery and force therapy based on high-power semiconductor and fibre lasers

    SciTech Connect

    Minaev, V P

    2005-11-30

    High-power semiconductor lasers and diode-pumped lasers are considered whose development qualitatively improved the characteristics of laser apparatus for surgery and force therapy, extended the scope of their applications in clinical practice, and enhanced the efficiency of medical treatment based on the use of these lasers. The characteristics of domestic apparatus are presented and their properties related to the laser emission wavelength used in them are discussed. Examples of modern medical technologies based on these lasers are considered. (invited paper)

  5. Intrinsic interference mitigating coordinated beamforming for the FBMC/OQAM based downlink

    NASA Astrophysics Data System (ADS)

    Cheng, Yao; Li, Peng; Haardt, Martin

    2014-12-01

    In this work, we propose intrinsic interference mitigating coordinated beamforming (IIM-CBF)-based transmission strategies for the downlink of multi-user multiple-input-multiple-out (MIMO) systems and coordinated multi-point (CoMP) systems where filter bank based multi-carrier with offset quadrature amplitude modulation (FBMC/OQAM) is employed. Our goal is to alleviate the dimensionality constraint imposed on the state-of-the-art solutions for FBMC/OQAM-based space division multiple access that the total number of receive antennas of the users must not exceed the number of transmit antennas at the base station. First, two IIM-CBF algorithms are developed for a single-cell multi-user MIMO downlink system. The central idea is to jointly and iteratively calculate the precoding matrix and decoding matrix for each subcarrier to mitigate the multi-user interference as well as the intrinsic interference inherent in FBMC/OQAM-based systems. Second, for a CoMP downlink scenario where partial coordination among the base stations is considered, the application of coordinated beamforming-based transmission schemes is further investigated. An appropriate IIM-CBF technique is proposed. Simulation results show that when the number of transmit antennas at the base station is equal to the total number of receive antennas of the users, the proposed IIM-CBF algorithm outperforms the existing transmission strategies for FBMC/OQAM-based multi-user MIMO downlink systems. Moreover, we evaluate the performances of the IIM-CBF schemes in the downlink of multi-user MIMO systems and CoMP systems where the total number of receive antennas of users exceeds the number of transmit antennas at the base station. It is observed that by employing the IIM-CBF techniques, FBMC/OQAM systems achieve a similar bit error rate (BER) performance as its orthogonal frequency division multiplexing with the cyclic prefix insertion (CP-OFDM)-based counterpart while exhibiting superiority in terms of a higher

  6. Unimolecular, soluble semiconductor nanoparticle-based biosensors for thrombin using charge/electron transfer.

    PubMed

    Swain, Marla D; Octain, Jashain; Benson, David E

    2008-12-01

    Duplex DNA was attached to semiconductor nanoparticles providing selective detection of thrombin. Using the method reported here, semiconductor nanoparticles can have selective sensory functions for a host of additional analytes in the future. The system uses one DNA strand that selectively binds an analyte (thrombin), while the complementary DNA strand contains a redox-active metal complex. The accessibility of the metal complex to the nanoparticle surface is increased upon thrombin binding due to unravelling of the duplex DNA secondary structure. Increased interactions between the metal complex and the nanoparticle surface will decrease nanoparticle emission intensity, through charge transfer. Initially, water-soluble nanoparticles with carboxylate-terminated monolayers showed thrombin-specific responses in emission intensity (-30% for 1:1 nanoparticle to DNA, +50% for 1:5). Despite the selective responses, the thrombin binding isotherms indicated multiple binding equilibria and more than likely nanoparticle aggregation. The need for a nonaggregative system comes from the potential employment of these sensors in live cell or living system fluorescence assays. By changing the nanoparticle capping ligand to provide an ethylene glycol-terminated monolayer, the binding isotherms fit a two-state binding model with a thrombin dissociation constant of 3 nM in a physiologically relevant buffer. This article demonstrates the need to consider capping ligand effects in designing biosensors based on semiconductor nanoparticles and demonstrates an initial DNA-attached semiconductor nanoparticle system that uses DNA-analyte binding interactions (aptamers).

  7. Hybrid Solar Cells with Prescribed Nanoscale Morphologies Based onHyperbranched Semiconductor Nanocrystals

    SciTech Connect

    Gur, Ilan; Fromer, Neil A.; Chen, Chih-Ping; Kanaras, AntoniosG.; Alivisatos, A. Paul

    2006-09-09

    In recent years, the search to develop large-area solar cells at low cost has led to research on photovoltaic (PV) systems based on nanocomposites containing conjugated polymers. These composite films can be synthesized and processed at lower costs and with greater versatility than the solid state inorganic semiconductors that comprise today's solar cells. However, the best nanocomposite solar cells are based on a complex architecture, consisting of a fine blend of interpenetrating and percolating donor and acceptor materials. Cell performance is strongly dependent on blend morphology, and solution-based fabrication techniques often result in uncontrolled and irreproducible blends, whose composite morphologies are difficult to characterize accurately. Here we incorporate 3-dimensional hyper-branched colloidal semiconductor nanocrystals in solution-processed hybrid organic-inorganic solar cells, yielding reproducible and controlled nanoscale morphology.

  8. Density functional theory calculations of III-N based semiconductors with mBJLDA

    NASA Astrophysics Data System (ADS)

    Gürel, Hikmet Hakan; Akıncı, Özden; Ünlü, Hilmi

    2017-02-01

    In this work, we present first principles calculations based on a full potential linear augmented plane-wave method (FP-LAPW) to calculate structural and electronic properties of III-V based nitrides such as GaN, AlN, InN in a zinc-blende cubic structure. First principles calculation using the local density approximation (LDA) and generalized gradient approximation (GGA) underestimate the band gap. We proposed a new potential called modified Becke-Johnson local density approximation (MBJLDA) that combines modified Becke-Johnson exchange potential and the LDA correlation potential to get better band gap results compared to experiment. We compared various exchange-correlation potentials (LSDA, GGA, HSE, and MBJLDA) to determine band gaps and structural properties of semiconductors. We show that using MBJLDA density potential gives a better agreement with experimental data for band gaps III-V nitrides based semiconductors.

  9. Electronic Biosensors Based on III-Nitride Semiconductors.

    PubMed

    Kirste, Ronny; Rohrbaugh, Nathaniel; Bryan, Isaac; Bryan, Zachary; Collazo, Ramon; Ivanisevic, Albena

    2015-01-01

    We review recent advances of AlGaN/GaN high-electron-mobility transistor (HEMT)-based electronic biosensors. We discuss properties and fabrication of III-nitride-based biosensors. Because of their superior biocompatibility and aqueous stability, GaN-based devices are ready to be implemented as next-generation biosensors. We review surface properties, cleaning, and passivation as well as different pathways toward functionalization, and critically analyze III-nitride-based biosensors demonstrated in the literature, including those detecting DNA, bacteria, cancer antibodies, and toxins. We also discuss the high potential of these biosensors for monitoring living cardiac, fibroblast, and nerve cells. Finally, we report on current developments of covalent chemical functionalization of III-nitride devices. Our review concludes with a short outlook on future challenges and projected implementation directions of GaN-based HEMT biosensors.

  10. Electronic Biosensors Based on III-Nitride Semiconductors

    NASA Astrophysics Data System (ADS)

    Kirste, Ronny; Rohrbaugh, Nathaniel; Bryan, Isaac; Bryan, Zachary; Collazo, Ramon; Ivanisevic, Albena

    2015-07-01

    We review recent advances of AlGaN/GaN high-electron-mobility transistor (HEMT)-based electronic biosensors. We discuss properties and fabrication of III-nitride-based biosensors. Because of their superior biocompatibility and aqueous stability, GaN-based devices are ready to be implemented as next-generation biosensors. We review surface properties, cleaning, and passivation as well as different pathways toward functionalization, and critically analyze III-nitride-based biosensors demonstrated in the literature, including those detecting DNA, bacteria, cancer antibodies, and toxins. We also discuss the high potential of these biosensors for monitoring living cardiac, fibroblast, and nerve cells. Finally, we report on current developments of covalent chemical functionalization of III-nitride devices. Our review concludes with a short outlook on future challenges and projected implementation directions of GaN-based HEMT biosensors.

  11. Fundamental Understanding of the Intrinsic Ductility in Nickel-Base L1 sub 2 Type Alloys

    DTIC Science & Technology

    1988-06-30

    AD-A197 605 FR-20424 "Gm-Two 88 U ,7 FUNDAMENTAL UNDERSTANDING OF THE INTRINSIC DUCTILITY IN NICKEL-BASE L12 TYPE ALLOYS C Lav D.M. Shah,. Un United...ntrlns’c Ductility In *11 :,’ A:- F1 f4I Report - ..,..4e - ,., C .we f tfort. FRC20424"’ I-.. a.-. 4nl jQ’rfU ePA a v,P 3 F orw tr a: we he rqVi t ;6tamit...ixtcen Copfol of tN 14Aac Pratt W to vAu C . C . Law Program Manager cc: Administrative Contracting IJ,’fcev Air Force Plant Representative OJf9--e UTC

  12. Computational design of intrinsic molecular rectifiers based on asymmetric functionalization of N-phenylbenzamide

    SciTech Connect

    Ding, Wendu; Koepf, Matthieu; Koenigsmann, Christopher; Batra, Arunabh; Venkataraman, Latha; Negre, Christian F. A.; Brudvig, Gary W.; Crabtree, Robert H.; Schmuttenmaer, Charles A.; Batista, Victor S.

    2015-11-03

    Here, we report a systematic computational search of molecular frameworks for intrinsic rectification of electron transport. The screening of molecular rectifiers includes 52 molecules and conformers spanning over 9 series of structural motifs. N-Phenylbenzamide is found to be a promising framework with both suitable conductance and rectification properties. A targeted screening performed on 30 additional derivatives and conformers of N-phenylbenzamide yielded enhanced rectification based on asymmetric functionalization. We demonstrate that electron-donating substituent groups that maintain an asymmetric distribution of charge in the dominant transport channel (e.g., HOMO) enhance rectification by raising the channel closer to the Fermi level. These findings are particularly valuable for the design of molecular assemblies that could ensure directionality of electron transport in a wide range of applications, from molecular electronics to catalytic reactions.

  13. Intrinsic memory function of carbon nanotube-based ferroelectric field-effect transistor.

    PubMed

    Fu, Wangyang; Xu, Zhi; Bai, Xuedong; Gu, Changzhi; Wang, Enge

    2009-03-01

    We demonstrate the intrinsic memory function of ferroelectric field-effect transistors (FeFETs) based on an integration of individual single-walled carbon nanotubes (SWCNTs) and epitaxial ferroelectric films. In contrast to the previously reported "charge-storage" CNT-FET memories, whose operations are haunted by a lack of control over the "charge traps", the present CNT-FeFETs exhibit a well-defined memory hysteresis loop induced by the reversible remnant polarization of the ferroelectric films. Large memory windows approximately 4 V, data retention time up to 1 week, and ultralow power consumption (energy per bit) of femto-joule, are highlighted in this report. Further simulations and experimental results show that the memory device is valid under operation voltage less than 1 V due to an electric-field enhancement effect induced by the ultrathin SWCNTs.

  14. Novel methods based on 13C detection to study intrinsically disordered proteins

    NASA Astrophysics Data System (ADS)

    Felli, Isabella C.; Pierattelli, Roberta

    2014-04-01

    Intrinsically disordered proteins (IDPs) are characterized by highly flexible solvent exposed backbones and can sample many different conformations. These properties confer them functional advantages, complementary to those of folded proteins, which need to be characterized to expand our view of how protein structural and dynamic features affect function beyond the static picture of a single well defined 3D structure that has influenced so much our way of thinking. NMR spectroscopy provides a unique tool for the atomic resolution characterization of highly flexible macromolecules in general and of IDPs in particular. The peculiar properties of IDPs however have profound effects on spectroscopic parameters. It is thus worth thinking about these aspects to make the best use of the great potential of NMR spectroscopy to contribute to this fascinating field of research. In particular, after many years of dealing with exclusively heteronuclear NMR experiments based on 13C direct detection, we would like here to address their relevance when studying IDPs.

  15. Computational design of intrinsic molecular rectifiers based on asymmetric functionalization of N-phenylbenzamide

    DOE PAGES

    Ding, Wendu; Koepf, Matthieu; Koenigsmann, Christopher; ...

    2015-11-03

    Here, we report a systematic computational search of molecular frameworks for intrinsic rectification of electron transport. The screening of molecular rectifiers includes 52 molecules and conformers spanning over 9 series of structural motifs. N-Phenylbenzamide is found to be a promising framework with both suitable conductance and rectification properties. A targeted screening performed on 30 additional derivatives and conformers of N-phenylbenzamide yielded enhanced rectification based on asymmetric functionalization. We demonstrate that electron-donating substituent groups that maintain an asymmetric distribution of charge in the dominant transport channel (e.g., HOMO) enhance rectification by raising the channel closer to the Fermi level. These findingsmore » are particularly valuable for the design of molecular assemblies that could ensure directionality of electron transport in a wide range of applications, from molecular electronics to catalytic reactions.« less

  16. 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.

  17. Impact of Mindfulness-Based Stress Reduction training on intrinsic brain connectivity.

    PubMed

    Kilpatrick, Lisa A; Suyenobu, Brandall Y; Smith, Suzanne R; Bueller, Joshua A; Goodman, Trudy; Creswell, J David; Tillisch, Kirsten; Mayer, Emeran A; Naliboff, Bruce D

    2011-05-01

    The beneficial effects of mindful awareness and mindfulness meditation training on physical and psychological health are thought to be mediated in part through changes in underlying brain processes. Functional connectivity MRI (fcMRI) allows identification of functional networks in the brain. It has been used to examine state-dependent activity and is well suited for studying states such as meditation. We applied fcMRI to determine if Mindfulness-Based Stress Reduction (MBSR) training is effective in altering intrinsic connectivity networks (ICNs). Healthy women were randomly assigned to participate in an 8-week Mindfulness-Based Stress Reduction (MBSR) training course or an 8-week waiting period. After 8 weeks, fMRI data (1.5T) was acquired while subjects rested with eyes closed, with the instruction to pay attention to the sounds of the scanner environment. Group independent component analysis was performed to investigate training-related changes in functional connectivity. Significant MBSR-related differences in functional connectivity were found mainly in auditory/salience and medial visual networks. Relative to findings in the control group, MBSR subjects showed (1) increased functional connectivity within auditory and visual networks, (2) increased functional connectivity between auditory cortex and areas associated with attentional and self-referential processes, (3) stronger anticorrelation between auditory and visual cortex, and (4) stronger anticorrelation between visual cortex and areas associated with attentional and self-referential processes. These findings suggest that 8 weeks of mindfulness meditation training alters intrinsic functional connectivity in ways that may reflect a more consistent attentional focus, enhanced sensory processing, and reflective awareness of sensory experience.

  18. Antimonide-Based Compound Semiconductors for Electronic Devices: A Review

    DTIC Science & Technology

    2005-04-01

    currents, apparently due to exten- sive interface recombination [137]. Dodd et al. fabricated npn InAs bipolar transistors on InP in an attempt to achieve...Demonstration of npn InAs bipolar transistors with inverted base doping. IEEE Electron Dev Lett 1996;17(4):166–8. [139] Moran PD, Chow D, Hunter A, Kuech TF...based electronic devices: high electron mobility transistors (HEMTs), resonant tunneling diodes (RTDs), and heterojunction bipolar transistors (HBTs

  19. Physically-Based Assessment of Intrinsic Groundwater Resource Vulnerability in AN Urban Catchment

    NASA Astrophysics Data System (ADS)

    Graf, T.; Therrien, R.; Lemieux, J.; Molson, J. W.

    2013-12-01

    Several methods exist to assess intrinsic groundwater (re)source vulnerability for the purpose of sustainable groundwater management and protection. However, several methods are empirical and limited in their application to specific types of hydrogeological systems. Recent studies suggest that a physically-based approach could be better suited to provide a general, conceptual and operational basis for groundwater vulnerability assessment. A novel method for physically-based assessment of intrinsic aquifer vulnerability is currently under development and tested to explore the potential of an integrated modelling approach, combining groundwater travel time probability and future scenario modelling in conjunction with the fully integrated HydroGeoSphere model. To determine the intrinsic groundwater resource vulnerability, a fully coupled 2D surface water and 3D variably-saturated groundwater flow model in conjunction with a 3D geological model (GoCAD) has been developed for a case study of the Rivière Saint-Charles (Québec/Canada) regional scale, urban watershed. The model has been calibrated under transient flow conditions for the hydrogeological, variably-saturated subsurface system, coupled with the overland flow zone by taking into account monthly recharge variation and evapotranspiration. To better determine the intrinsic groundwater vulnerability, two independent approaches are considered and subsequently combined in a simple, holistic multi-criteria-decision analyse. Most data for the model comes from an extensive hydrogeological database for the watershed, whereas data gaps have been complemented via field tests and literature review. The subsurface is composed of nine hydrofacies, ranging from unconsolidated fluvioglacial sediments to low permeability bedrock. The overland flow zone is divided into five major zones (Urban, Rural, Forest, River and Lake) to simulate the differences in landuse, whereas the unsaturated zone is represented via the model

  20. S2DS: Physics-based compact model for circuit simulation of two-dimensional semiconductor devices including non-idealities

    NASA Astrophysics Data System (ADS)

    Suryavanshi, Saurabh V.; Pop, Eric

    2016-12-01

    We present a physics-based compact model for two-dimensional (2D) field-effect transistors (FETs) based on monolayer semiconductors such as MoS2. A semi-classical transport approach is appropriate for the 2D channel, enabling simplified analytical expressions for the drain current. In addition to intrinsic FET behavior, the model includes contact resistance, traps and impurities, quantum capacitance, fringing fields, high-field velocity saturation, and self-heating, the latter being found to play an important role. The model is calibrated with state-of-the-art experimental data for n- and p-type 2D-FETs, and it can be used to analyze device properties for sub-100 nm gate lengths. Using the experimental fit, we demonstrate the feasibility of circuit simulations using properly scaled devices. The complete model is implemented in SPICE-compatible Verilog-A, and a downloadable version is freely available at the nanoHUB.org.

  1. 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.

  2. 1×2 Multimode interference couplers based on semiconductor hollow waveguides formed from omnidirectional reflectors

    NASA Astrophysics Data System (ADS)

    Lo, Shih-Shou; Chen, Chii-Chang

    2007-07-01

    A 1×2 hollow multimode interference (MMI) coupler based on semiconductor hollow waveguides formed from omnidirectional reflectors (SHOW-ODR) is demonstrated. The device has a shorter coupling length than a conventional silicon-on-insulator MMI coupler. A 2 dB uniformity was achieved at operating wavelengths between 1520 and 1562 nm. The device exhibited a weak polarization dependence in the TE and TM modes.

  3. Copper-based ternary and quaternary semiconductor nanoplates: templated synthesis, characterization, and photoelectrochemical properties.

    PubMed

    Wu, Xue-Jun; Huang, Xiao; Qi, Xiaoying; Li, Hai; Li, Bing; Zhang, Hua

    2014-08-18

    Two-dimensional (2D) copper-based ternary and quaternary semiconductors are promising building blocks for the construction of efficient solution-processed photovoltaic devices at low cost. However, the facile synthesis of such 2D nanoplates with well-defined shape and uniform size remains a challenge. Reported herein is a universal template-mediated method for preparing copper-based ternary and quaternary chalcogenide nanoplates, that is, CuInS2, CuIn(x)Ga(1-x)S2, and Cu2ZnSnS4, by using a pre-synthesized CuS nanoplate as the starting template. The various synthesized nanoplates are monophasic with uniform thickness and lateral size. As a proof of concept, the Cu2ZnSnS4 nanoplates were immobilized on a Mo/glass substrate and used as semiconductor photoelectrode, thus showing stable photoelectrochemical response. The method is general and provides future opportunities for fabrication of cost-effective photovoltaic devices based on 2D semiconductors.

  4. An experimental study of GFP-based FRET, with application to intrinsically unstructured proteins

    PubMed Central

    Ohashi, Tomoo; Galiacy, Stephane D.; Briscoe, Gina; Erickson, Harold P.

    2007-01-01

    We have experimentally studied the fluorescence resonance energy transfer (FRET) between green fluorescent protein (GFP) molecules by inserting folded or intrinsically unstructured proteins between CyPet and Ypet. We discovered that most of the enhanced FRET signal previously reported for this pair was due to enhanced dimerization, so we engineered a monomerizing mutation into each. An insert containing a single fibronectin type III domain (3.7 nm end-to-end) gave a moderate FRET signal while a two-domain insert (7.0 nm) gave no FRET. We then tested unstructured proteins of various lengths, including the charged-plus-PQ domain of ZipA, the tail domain of α-adducin, and the C-terminal tail domain of FtsZ. The structures of these FRET constructs were also studied by electron microscopy and sedimentation. A 12 amino acid linker and the N-terminal 33 amino acids of the charged domain of the ZipA gave strong FRET signals. The C-terminal 33 amino acids of the PQ domain of the ZipA and several unstructured proteins with 66–68 amino acids gave moderate FRET signals. The 150 amino acid charged-plus-PQ construct gave a barely detectable FRET signal. FRET efficiency was calculated from the decreased donor emission to estimate the distance between donor and acceptor. The donor–acceptor distance varied for unstructured inserts of the same length, suggesting that they had variable stiffness (persistence length). We conclude that GFP-based FRET can be useful for studying intrinsically unstructured proteins, and we present a range of calibrated protein inserts to experimentally determine the distances that can be studied. PMID:17586775

  5. Active devices based on organic semiconductors for wearable applications.

    PubMed

    Barbaro, Massimo; Caboni, Alessandra; Cosseddu, Piero; Mattana, Giorgio; Bonfiglio, Annalisa

    2010-05-01

    Plastic electronics is an enabling technology for obtaining active (transistor based) electronic circuits on flexible and/or nonplanar surfaces. For these reasons, it appears as a perfect candidate to promote future developments of wearable electronics toward the concept of fabrics and garments made by functional (in this case, active electronic) yarns. In this paper, a panoramic view of recent achievements and future perspectives is given.

  6. Passivation of III-V Compound Semiconductor Based Devices

    DTIC Science & Technology

    1993-11-29

    approximately 60 A/s. The AES, Rutherford Backscattering, FIIR and stress measurements were also carried out. This work was done in collaboration with Dr ...begun to collaborate with us on the project. A brief description of these projects are listed below: 8 a) HP Research Laboratory ( Drs . S. Camnitz, K. L...DC characterization of devices. b) University of California. Santa Barbara ( Drs . B. Young, L. A. Coldren and V. Malhotra): Passivation of GaAs-based

  7. Cascadable all-optical inverter based on a nonlinear vertical-cavity semiconductor optical amplifier.

    PubMed

    Zhang, Haijiang; Wen, Pengyue; Esener, Sadik

    2007-07-01

    We report, for the first time to our knowledge, the operation of a cascadable, low-optical-switching-power(~10 microW) small-area (~100 microm(2)) high-speed (80 ps fall time) all-optical inverter. This inverter employs cross-gain modulation, polarization gain anisotropy, and highly nonlinear gain characteristics of an electrically pumped vertical-cavity semiconductor optical amplifier (VCSOA). The measured transfer characteristics of such an optical inverter resemble those of standard electronic metal-oxide semiconductor field-effect transistor-based inverters exhibiting high noise margin and high extinction ratio (~9.3 dB), making VCSOAs an ideal building block for all-optical logic and memory.

  8. Anisotropy of the electron g factor in quantum wells based on cubic semiconductors

    SciTech Connect

    Alekseev, P. S.

    2013-09-15

    A new mechanism for the spin splitting of electron levels in asymmetric quantum wells based on GaAs-type semiconductors relative to rotations of the magnetic field in the well plane is suggested. It is demonstrated that the anisotropy of the Zeeman splitting (linear in a magnetic field) arises in asymmetric quantum wells due to the interface spin-orbit terms in the electron Hamiltonian. In the case of symmetric quantum wells, it is shown that the anisotropy of the Zeeman splitting is a cubic function of the magnitude of the magnetic field, depends on the direction of the magnetic field in the interface plane as the fourth-order harmonic, and is governed by the spin-orbit term of the fourth order by the kinematic momentum in the electron Hamiltonian of a bulk semiconductor.

  9. Expanding the Scope of Thiophene Based Semiconductors: Perfluoroalkylated Materials and Fused Thienoacenes

    NASA Astrophysics Data System (ADS)

    Black, Hayden Thompson

    Thiophene based semiconductors with new molecular and macromolecular structures were explored for applications in field effect transistors. Perfluoroalkylation was studied both as a means for controlling the self-assembly properties of polythiophenes, as well as modifying the molecular orbital energies of a series of oligothiophenes. End-perfluoroalkylation of poly(3-hexylthiophene) resulted in interesting self-assembly of the polymer into a bilayer vesicle. Similar fluorophilic assembly may be useful for controlling blend morphologies in heterojunction based devices. On the other hand, perfluoroalkylation of small molecule thiophene semiconductors leads to low lying LUMO levels, and can be used to promote electron injection for n-type transistor devices. This strategy was employed in combination with a pi-electron deficient benzothiadiazole to afford a new n-type semiconductor with an exceptionally low LUMO. Monoperfluoroalkylated oligothiophenes were also synthesized and studied in field effect transistors for the first time. In addition, two new fused thienoacene compounds were synthesized and their crystal structures were analyzed. The fused compounds showed exceptional pi-pi stacking and assembled into well defined one-dimensional microcrystals from the vapor phase. Field effect transistors were fabricated employing the new thienoacenes, showing p-type conductivity with equivalent charge carrier mobilities.

  10. UXO detection and identification based on intrinsic target polarizabilities: A case history

    SciTech Connect

    Gasperikova, E.; Smith, J.T.; Morrison, H.F.; Becker, A.; Kappler, K.

    2008-07-15

    Electromagnetic induction data parameterized in time dependent object intrinsic polarizabilities allow discrimination of unexploded ordnance (UXO) from false targets (scrap metal). Data from a cart-mounted system designed for discrimination of UXO with 20 mm to 155 mm diameters are used. Discrimination of UXO from irregular scrap metal is based on the principal dipole polarizabilities of a target. A near-intact UXO displays a single major polarizability coincident with the long axis of the object and two equal smaller transverse polarizabilities, whereas metal scraps have distinct polarizability signatures that rarely mimic those of elongated symmetric bodies. Based on a training data set of known targets, object identification was made by estimating the probability that an object is a single UXO. Our test survey took place on a military base where both 4.2-inch mortar shells and scrap metal were present. The results show that we detected and discriminated correctly all 4.2-inch mortars, and in that process we added 7%, and 17%, respectively, of dry holes (digging scrap) to the total number of excavations in two different survey modes. We also demonstrated a mode of operation that might be more cost effective than the current practice.

  11. ZnCdMgSe-Based Semiconductors for Intersubband Devices

    SciTech Connect

    Tamargo, Maria C.

    2008-11-13

    This paper presents a review of recent results on the application of ZnCdMgSe-based wide bandgap II-VI compounds to intersubband devices such as quantum cascade lasers and quantum well infrared photodetectors operating in the mid-infrared region. The conduction band offset of ZnCdSe/ZnCdMgSe quantum well structures was determined from contactless electroreflectance measurements to be as high as 1.12 eV. FT-IR was used to measure intersubband absorption in multi-quantum well structures in the mid-IR range. Electroluminescence at 4.8 {mu}m was observed from a quantum cascade emitter structure made from these materials. Preliminary results are also presented on self assembled quantum dots of CdSe on ZnCdMgSe, and novel quantum well structures with metastable binary MgSe barriers.

  12. 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.

  13. Symmetry-Based Tight Binding Modeling of Halide Perovskite Semiconductors.

    PubMed

    Boyer-Richard, Soline; Katan, Claudine; Traoré, Boubacar; Scholz, Reinhard; Jancu, Jean-Marc; Even, Jacky

    2016-10-06

    On the basis of a general symmetry analysis, this paper presents an empirical tight-binding (TB) model for the reference Pm-3m perovskite cubic phase of halide perovskites of general formula ABX3. The TB electronic band diagram, with and without spin orbit coupling effect of MAPbI3 has been determined based on state of the art density functional theory results including many body corrections (DFT+GW). It affords access to various properties, including distorted structures, at a significantly reduced computational cost. This is illustrated with the calculation of the band-to-band absorption spectrum, the variation of the band gap under volumetric strain, as well as the Rashba effect for a uniaxial symmetry breaking. Compared to DFT approaches, this empirical model will help to tackle larger issues, such as the electronic band structure of large nanostructures, including many-body effects, or heterostructures relevant to perovskite device modeling suited to the description of atomic-scale features.

  14. Multiple Exciton Generation in Semiconductor Nanostructures: DFT-based Computation

    NASA Astrophysics Data System (ADS)

    Mihaylov, Deyan; Kryjevski, Andrei; Kilin, Dmitri; Kilina, Svetlana; Vogel, Dayton

    Multiple exciton generation (MEG) in nm-sized H-passivated Si nanowires (NWs), and quasi 2D nanofilms depends strongly on the degree of the core structural disorder as shown by the perturbation theory calculations based on the DFT simulations. In perturbation theory, we work to the 2nd order in the electron-photon coupling and in the (approximate) RPA-screened Coulomb interaction. We also include the effect of excitons for which we solve Bethe-Salpeter Equation. To describe MEG we calculate exciton-to-biexciton as well as biexciton-to-exciton rates and quantum efficiency (QE). We consider 3D arrays of Si29H36 quantum dots, NWs, and quasi 2D silicon nanofilms, all with both crystalline and amorphous core structures. Efficient MEG with QE of 1.3 up to 1.8 at the photon energy of about 3Egap is predicted in these nanoparticles except for the crystalline NW and film where QE ~=1. MEG in the amorphous nanoparticles is enhanced by the electron localization due to structural disorder. The exciton effects significantly red-shift QE vs. photon energy curves. Nm-sized a-Si NWs and films are predicted to have effective MEG within the solar spectrum range. Also, we find efficient MEG in the chiral single-wall Carbon nanotubes and in a perovskite nanostructure.

  15. Analytical modelling of a refractive index sensor based on an intrinsic micro Fabry-Perot interferometer.

    PubMed

    Vargas-Rodriguez, Everardo; Guzman-Chavez, Ana D; Cano-Contreras, Martin; Gallegos-Arellano, Eloisa; Jauregui-Vazquez, Daniel; Hernández-García, Juan C; Estudillo-Ayala, Julian M; Rojas-Laguna, Roberto

    2015-10-15

    In this work a refractive index sensor based on a combination of the non-dispersive sensing (NDS) and the Tunable Laser Spectroscopy (TLS) principles is presented. Here, in order to have one reference and one measurement channel a single-beam dual-path configuration is used for implementing the NDS principle. These channels are monitored with a couple of identical optical detectors which are correlated to calculate the overall sensor response, called here the depth of modulation. It is shown that this is useful to minimize drifting errors due to source power variations. Furthermore, a comprehensive analysis of a refractive index sensing setup, based on an intrinsic micro Fabry-Perot Interferometer (FPI) is described. Here, the changes over the FPI pattern as the exit refractive index is varied are analytically modelled by using the characteristic matrix method. Additionally, our simulated results are supported by experimental measurements which are also provided. Finally it is shown that by using this principle a simple refractive index sensor with a resolution in the order of 2.15 × 10(-4) RIU can be implemented by using a couple of standard and low cost photodetectors.

  16. Analytical Modelling of a Refractive Index Sensor Based on an Intrinsic Micro Fabry-Perot Interferometer

    PubMed Central

    Vargas-Rodriguez, Everardo; Guzman-Chavez, Ana D.; Cano-Contreras, Martin; Gallegos-Arellano, Eloisa; Jauregui-Vazquez, Daniel; Hernández-García, Juan C.; Estudillo-Ayala, Julian M.; Rojas-Laguna, Roberto

    2015-01-01

    In this work a refractive index sensor based on a combination of the non-dispersive sensing (NDS) and the Tunable Laser Spectroscopy (TLS) principles is presented. Here, in order to have one reference and one measurement channel a single-beam dual-path configuration is used for implementing the NDS principle. These channels are monitored with a couple of identical optical detectors which are correlated to calculate the overall sensor response, called here the depth of modulation. It is shown that this is useful to minimize drifting errors due to source power variations. Furthermore, a comprehensive analysis of a refractive index sensing setup, based on an intrinsic micro Fabry-Perot Interferometer (FPI) is described. Here, the changes over the FPI pattern as the exit refractive index is varied are analytically modelled by using the characteristic matrix method. Additionally, our simulated results are supported by experimental measurements which are also provided. Finally it is shown that by using this principle a simple refractive index sensor with a resolution in the order of 2.15 × 10−4 RIU can be implemented by using a couple of standard and low cost photodetectors. PMID:26501277

  17. GaN nanostructure-based light emitting diodes and semiconductor lasers.

    PubMed

    Viswanath, Annamraju Kasi

    2014-02-01

    GaN and related materials have received a lot of attention because of their applications in a number of semiconductor devices such as LEDs, laser diodes, field effect transistors, photodetectors etc. An introduction to optical phenomena in semiconductors, light emission in p-n junctions, evolution of LED technology, bandgaps of various semiconductors that are suitable for the development of LEDs are discussed first. The detailed discussion on photoluminescence of GaN nanostructures is made, since this is crucial to develop optical devices. Fabrication technology of many nanostructures of GaN such as nanowires, nanorods, nanodots, nanoparticles, nanofilms and their luminescence properties are given. Then the optical processes including ultrafast phenomena, radiative, non-radiative recombination, quantum efficiency, lifetimes of excitons in InGaN quantum well are described. The LED structures based on InGaN that give various important colors of red, blue, green, and their design considerations to optimize the output were highlighted. The recent efforts in GaN technology are updated. Finally the present challenges and future directions in this field are also pointed out.

  18. Graphene-based hybrid structures combined with functional materials of ferroelectrics and semiconductors

    NASA Astrophysics Data System (ADS)

    Jie, Wenjing; Hao, Jianhua

    2014-05-01

    Fundamental studies and applications of 2-dimensional (2D) graphene may be deepened and broadened via combining graphene sheets with various functional materials, which have been extended from the traditional insulator of SiO2 to a versatile range of dielectrics, semiconductors and metals, as well as organic compounds. Among them, ferroelectric materials have received much attention due to their unique ferroelectric polarization. As a result, many attractive characteristics can be shown in graphene/ferroelectric hybrid systems. On the other hand, graphene can be integrated with conventional semiconductors and some newly-discovered 2D layered materials to form distinct Schottky junctions, yielding fascinating behaviours and exhibiting the potential for various applications in future functional devices. This review article is an attempt to illustrate the most recent progress in the fabrication, operation principle, characterization, and promising applications of graphene-based hybrid structures combined with various functional materials, ranging from ferroelectrics to semiconductors. We focus on mechanically exfoliated and chemical-vapor-deposited graphene sheets integrated in numerous advanced devices. Some typical hybrid structures have been highlighted, aiming at potential applications in non-volatile memories, transparent flexible electrodes, solar cells, photodetectors, and so on.

  19. Semiconductor heterostructure

    NASA Technical Reports Server (NTRS)

    Hovel, Harold John (Inventor); Woodall, Jerry MacPherson (Inventor)

    1978-01-01

    A technique for fabricating a semiconductor heterostructure by growth of a ternary semiconductor on a binary semiconductor substrate from a melt of the ternary semiconductor containing less than saturation of at least one common ingredient of both the binary and ternary semiconductors wherein in a single temperature step the binary semiconductor substrate is etched, a p-n junction with specific device characteristics is produced in the binary semiconductor substrate by diffusion of a dopant from the melt and a region of the ternary semiconductor of precise conductivity type and thickness is grown by virtue of a change in the melt characteristics when the etched binary semiconductor enters the melt.

  20. Semiconductor structure

    NASA Technical Reports Server (NTRS)

    Hovel, Harold J. (Inventor); Woodall, Jerry M. (Inventor)

    1979-01-01

    A technique for fabricating a semiconductor heterostructure by growth of a ternary semiconductor on a binary semiconductor substrate from a melt of the ternary semiconductor containing less than saturation of at least one common ingredient of both the binary and ternary semiconductors wherein in a single temperature step the binary semiconductor substrate is etched, a p-n junction with specific device characteristics is produced in the binary semiconductor substrate by diffusion of a dopant from the melt and a region of the ternary semiconductor of precise conductivity type and thickness is grown by virtue of a change in the melt characteristics when the etched binary semiconductor enters the melt.

  1. 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.

  2. Photonic Bell-state analysis based on semiconductor-superconductor structures

    NASA Astrophysics Data System (ADS)

    Sabag, Evyatar; Bouscher, Shlomi; Marjieh, Raja; Hayat, Alex

    2017-03-01

    We propose a compact and highly efficient scheme for complete Bell-state analysis using two-photon absorption in a superconducting proximity region of a semiconductor avalanche photodiode. One-photon transitions to the superconducting Cooper-pair based condensate in the conduction band are forbidden, whereas two-photon transitions are allowed and are strongly enhanced by superconductivity. This Cooper-pair based two-photon absorption results in a strong detection preference of a specified entangled state. Our analysis shows high detection purity of the desired Bell state with negligible false detection probability. The theoretically demonstrated concept can pave the way towards practical realizations of advanced quantum information schemes.

  3. Dithienocoronenediimide-based copolymers as novel ambipolar semiconductors for organic thin-film transistors.

    PubMed

    Usta, Hakan; Newman, Christopher; Chen, Zhihua; Facchetti, Antonio

    2012-07-17

    A new class of ambipolar donor-acceptor π-conjugated polymers based on a dithienocoronenediimide core is presented. Solution-processed top-gate/bottom-contact thin film transistors (TFTs) exhibit electron and hole mobilities of up to 0.30 cm(2)/V·s and 0.04 cm(2)/V·s, respectively, which are the highest reported to date for an ambipolar polymer in ambient conditions. The polymers presented here are the first examples of coronenediimide-based semiconductors showing high organic TFT performances.

  4. Figures of merit for microwave photonic phase shifters based on semiconductor optical amplifiers.

    PubMed

    Sancho, Juan; Lloret, Juan; Gasulla, Ivana; Sales, Salvador; Capmany, José

    2012-05-07

    We theoretically and experimentally compare the performance of two fully tunable phase shifter structures based on semiconductor optical amplifiers (SOA) by means of several figures of merit common to microwave photonic systems. A single SOA stage followed by a tailored notch filter is compared with a cascaded implementation comprising three SOA-based phase shifter stages. Attention is focused on the assessment of the RF net gain, noise figure and nonlinear distortion. Recommendations on the performance optimization of this sort of approaches are detailed.

  5. Study of magnetism in dilute magnetic semiconductors based on III-V nitrides

    NASA Astrophysics Data System (ADS)

    Rajaram, Rekha

    Spin based electronics, commonly referred to as "spintronics", seeks to expand the functionalities of microelectronic devices by introducing the ability to manipulate the carrier's spin, in addition to or instead of its charge. Key steps in spintronic devices include the injection, manipulation and detection of the carrier's spin. Metal-based spintronic devices such as spin valves have already found applications in high capacity hard disk drive read heads and have potential in non-volatile solid state memories. However, in order to realize the full potential of spintronics, spin manipulation must be introduced into semiconductor devices. This in turn, requires the development of magnetic semiconductors. Dilute magnetic semiconductors (DMS) are a class of magnetic semiconductors in which a fraction of the cations are substitutionally replaced by magnetic ions. The exchange interaction between the spin of the dopant atoms and the carriers in the semiconductor host is expected to bring about global ferromagnetic order in the entire lattice in these materials. The search for novel DMS candidates has been driven by two cardinal requirements - a material system with well-developed growth technology, and a high Curie temperature. In this work, we have investigated the growth and characteristics of one such promising candidate, transition-metal doped InN. InN films were deposited on c-sapphire substrates by molecular beam epitaxy, employing GaN underlayers to reduce the lattice mismatch between the film and substrate. The films were doped from 0.1-6% Cr with no noticeable trace of crystalline secondary phases detected by X-ray diffraction. However, Mn-doping led to segregation of manganese nitride. Hall effect measurements revealed n-type behavior in both undoped as well as Cr-doped films. A magnetic hysteresis, with a small remanence and coercivity was observed in Cr:InN up to room temperature, confirming long-range magnetic order in this material. X-ray magnetic circular

  6. A detailed, conductance-based computer model of intrinsic sensory neurons of the gastrointestinal tract.

    PubMed

    Chambers, Jordan D; Bornstein, Joel C; Gwynne, Rachel M; Koussoulas, Katerina; Thomas, Evan A

    2014-09-01

    Intrinsic sensory neurons (ISNs) of the enteric nervous system respond to stimuli such as muscle tension, muscle length, distortion of the mucosa, and the chemical content in the lumen. ISNs form recurrent networks that probably drive many intestinal motor patterns and reflexes. ISNs express a large number of voltage- and calcium-gated ion channels, some of which are modified by inflammation or repeated physiological stimuli, but how interactions between different ionic currents in ISNs produce both normal and pathological behaviors in the intestine remains unclear. We constructed a model of ISNs including voltage-gated sodium and potassium channels, N-type calcium channels, big conductance calcium-dependent potassium (BK) channels, calcium-dependent nonspecific cation channels (NSCa), intermediate conductance calcium-dependent potassium (IK) channels, hyperpolarization-activated cation (Ih) channels, and internal calcium dynamics. The model was based on data from the literature and our electrophysiological studies. The model reproduced responses to short or long depolarizing current pulses and responses to long hyperpolarizing current pulses. Sensitivity analysis showed that Ih, IK, NSCa, and BK have the largest influence on the number of action potentials observed during prolonged depolarizations. The model also predicts that changes to the voltage of activation for Ih have a large influence on excitability, but changes to the time constant of activation for Ih have a minor effect. Our model identifies how interactions between different iconic currents influence the excitability of ISNs and highlights an important role for Ih in enteric neuroplasticity resulting from disease.

  7. Colorimetric detection of Shewanella oneidensis based on immunomagnetic capture and bacterial intrinsic peroxidase activity

    NASA Astrophysics Data System (ADS)

    Wen, Junlin; Zhou, Shungui; Chen, Junhua

    2014-06-01

    Rapid detection and enumeration of target microorganisms is considered as a powerful tool for monitoring bioremediation process that typically involves cleaning up polluted environments with functional microbes. A novel colorimetric assay is presented based on immunomagnetic capture and bacterial intrinsic peroxidase activity for rapidly detecting Shewanella oneidensis, an important model organism for environmental bioremediation because of its remarkably diverse respiratory abilities. Analyte bacteria captured on the immunomagnetic beads provided a bacterial out-membrane peroxidase-amplified colorimetric readout of the immunorecognition event by oxidizing 3, 3', 5, 5'-tetramethylbenzidine (TMB) in the present of hydrogen peroxide. The high-efficiency of immunomagnetic capture and signal amplification of peroxidase activity offers an excellent detection performance with a wide dynamic range between 5.0 × 103 and 5.0 × 106 CFU/mL toward target cells. Furthermore, this method was demonstrated to be feasible in detecting S. oneidensis cells spiked in environmental samples. The proposed colorimetric assay shows promising environmental applications for rapid detection of target microorganisms.

  8. The Effects of Project-Based Learning Activities on Intrinsic Motivation and Skill Acquisition of Rural Middle School Math Students

    ERIC Educational Resources Information Center

    Yancy, Yuri G.

    2012-01-01

    This study was conducted in a middle school math class and investigated the effects of project-based activities on the middle school math students' skill acquisition and intrinsic motivation. After math-related project activities were implemented and completed, an analysis of how the students were affected in the areas of math skills and…

  9. Understanding the Influence of Intrinsic and Extrinsic Factors on Inquiry-Based Science Education at Township Schools in South Africa

    ERIC Educational Resources Information Center

    Ramnarain, Umesh

    2016-01-01

    This mixed-methods research investigated teachers' perceptions of intrinsic factors (personal attributes of the teacher) and extrinsic factors (environmental) influencing the implementation of inquiry-based science learning at township (underdeveloped urban area) high schools in South Africa. Quantitative data were collected by means of an adapted…

  10. Imaging performance comparison between a LaBr{sub 3}:Ce scintillator based and a CdTe semiconductor based photon counting compact gamma camera

    SciTech Connect

    Russo, P.; Mettivier, G.; Pani, R.; Pellegrini, R.; Cinti, M. N.; Bennati, P.

    2009-04-15

    The authors report on the performance of two small field of view, compact gamma cameras working in single photon counting in planar imaging tests at 122 and 140 keV. The first camera is based on a LaBr{sub 3}:Ce scintillator continuous crystal (49x49x5 mm{sup 3}) assembled with a flat panel multianode photomultiplier tube with parallel readout. The second one belongs to the class of semiconductor hybrid pixel detectors, specifically, a CdTe pixel detector (14x14x1 mm{sup 3}) with 256x256 square pixels and a pitch of 55 {mu}m, read out by a CMOS single photon counting integrated circuit of the Medipix2 series. The scintillation camera was operated with selectable energy window while the CdTe camera was operated with a single low-energy detection threshold of about 20 keV, i.e., without energy discrimination. The detectors were coupled to pinhole or parallel-hole high-resolution collimators. The evaluation of their overall performance in basic imaging tasks is presented through measurements of their detection efficiency, intrinsic spatial resolution, noise, image SNR, and contrast recovery. The scintillation and CdTe cameras showed, respectively, detection efficiencies at 122 keV of 83% and 45%, intrinsic spatial resolutions of 0.9 mm and 75 {mu}m, and total background noises of 40.5 and 1.6 cps. Imaging tests with high-resolution parallel-hole and pinhole collimators are also reported.

  11. Monolithic in-based III-V compound semiconductor focal plane array cell with single stage CCD output

    NASA Technical Reports Server (NTRS)

    Fossum, Eric R. (Inventor); Cunningham, Thomas J. (Inventor); Krabach, Timothy N. (Inventor); Staller, Craig O. (Inventor)

    1995-01-01

    A monolithic semiconductor imager includes an indium-based III-V compound semiconductor monolithic active layer of a first conductivity type, an array of plural focal plane cells on the active layer, each of the focal plane cells including a photogate over a top surface of the active layer, a readout circuit dedicated to the focal plane cell including plural transistors formed monolithically with the monolithic active layer and a single-stage charge coupled device formed monolithically with the active layer between the photogate and the readout circuit for transferring photo-generated charge accumulated beneath the photogate during an integration period to the readout circuit. The photogate includes thin epitaxial semiconductor layer of a second conductivity type overlying the active layer and an aperture electrode overlying a peripheral portion of the thin epitaxial semiconductor layer, the aperture electrode being connectable to a photogate bias voltage.

  12. Monolithic in-based III-V compound semiconductor focal plane array cell with single stage CCD output

    NASA Technical Reports Server (NTRS)

    Fossum, Eric R. (Inventor); Cunningham, Thomas J. (Inventor); Krabach, Timothy N. (Inventor); Staller, Craig O. (Inventor)

    1994-01-01

    A monolithic semiconductor imager includes an indium-based III-V compound semiconductor monolithic active layer of a first conductivity type, an array of plural focal plane cells on the active layer, each of the focal plane cells including a photogate over a top surface of the active layer, a readout circuit dedicated to the focal plane cell including plural transistors formed monolithically with the monolithic active layer and a single-stage charge coupled device formed monolithically with the active layer between the photogate and the readout circuit for transferring photo-generated charge accumulated beneath the photogate during an integration period to the readout circuit. The photogate includes thin epitaxial semiconductor layer of a second conductivity type overlying the active layer and an aperture electrode overlying a peripheral portion of the thin epitaxial semiconductor layer, the aperture electrode being connectable to a photogate bias voltage.

  13. Time-of-flight analysis of charge mobility in a Cu-phthalocyanine-based discotic liquid crystal semiconductor

    NASA Astrophysics Data System (ADS)

    Fujikake, Hideo; Murashige, Takeshi; Sugibayashi, Makiko; Ohta, Kazuchika

    2004-10-01

    We used a time-of-flight method to study the charge carrier mobility properties of a molecular-aligned discotic liquid crystal semiconductor based on Cu-phthalocyanine. The heated isotropic-phase semiconductor material was sandwiched between transparent electrodes coated onto glass substrates without conventional alignment layers. This was then cooled, and a discotic liquid crystal semiconductor cell was obtained, which we used to make mobility measurements. The material had a fixed molecular alignment due to the supercooling of the hexagonal columnar mesophase. It was clarified that the carrier mobility for electrons was as high as it was for holes at room temperature. The maximum value of negative charge mobility reached 2.60×10-3cm2/Vs, although negative carrier mobility is often much lower than positive carrier mobility in other organic semiconductors, including conventional Cu-phthalocyanine vacuum-deposited films.

  14. Fast gain and phase recovery of semiconductor optical amplifiers based on submonolayer quantum dots

    SciTech Connect

    Herzog, Bastian Owschimikow, Nina; Kaptan, Yücel; Kolarczik, Mirco; Switaiski, Thomas; Woggon, Ulrike; Schulze, Jan-Hindrik; Rosales, Ricardo; Strittmatter, André; Bimberg, Dieter; Pohl, Udo W.

    2015-11-16

    Submonolayer quantum dots as active medium in opto-electronic devices promise to combine the high density of states of quantum wells with the fast recovery dynamics of self-assembled quantum dots. We investigate the gain and phase recovery dynamics of a semiconductor optical amplifier based on InAs submonolayer quantum dots in the regime of linear operation by one- and two-color heterodyne pump-probe spectroscopy. We find an as fast recovery dynamics as for quantum dot-in-a-well structures, reaching 2 ps at moderate injection currents. The effective quantum well embedding the submonolayer quantum dots acts as a fast and efficient carrier reservoir.

  15. 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.

  16. A New Class of Chemical Sensors for Gases Based on Photoluminescence from Semiconductor-Derived Interfaces.

    DTIC Science & Technology

    1987-07-08

    02 962 At N CLASS OF CHEMICAL SENSORS FOR GASES ESCFO N PI4OTOLUMINESCENCE FROM U)MCONSIU!V-MWISON DEPT OF CHEMISTRY G EYER ET RL 6S8 JUL 87...4134003 4 Technical Report No. UWIS/DC/TR-87/5 A New Class of Chemical Sensors for Gases Based on Photoluminescence from Semiconductor-Derived Interfaces...volume devoted to chemical sensors ) FTIS GRA&I DTIC TAB N University of Wisconsin Unannounced 0 Department of Chemistry Justification Madison, Wisconsin

  17. Photonic processing and realization of an all-optical digital comparator based on semiconductor optical amplifiers

    NASA Astrophysics Data System (ADS)

    Singh, Simranjit; Kaur, Ramandeep; Kaler, Rajinder Singh

    2015-01-01

    A module of an all-optical 2-bit comparator is analyzed and implemented using semiconductor optical amplifiers (SOAs). By employing SOA-based cross phase modulation, the optical XNOR logic is used to get an A=B output signal, where as AB¯ and A¯B> logics operations are used to realize A>B and A

  18. Electronic modification of Cu-based chalcopyrite semiconductors induced by lattice deformation and composition alchemy

    NASA Astrophysics Data System (ADS)

    Jiang, F. D.; Feng, J. Y.

    2008-02-01

    Using first principles calculation, we systematically investigate the electronic modification of Cu-based chalcopyrite semiconductors induced by lattice deformation and composition alchemy. It is shown that the optical band gap Eg is remarkably sensitive to the anion displacement μ, resulting from the opposite shifts of conduction band minimum and valence band maximum. Meanwhile, the dependence of structural parameters of alloyed compounds on alloy composition x is demonstrated for both cation and anion alloying. The d orbitals of group-III cations are found to be of great importance in the calculation. Abnormal changes in the optical band gap Eg induced by anion alloying are addressed.

  19. Large ordered arrays of single photon sources based on II-VI semiconductor colloidal quantum dot.

    PubMed

    Zhang, Qiang; Dang, Cuong; Urabe, Hayato; Wang, Jing; Sun, Shouheng; Nurmikko, Arto

    2008-11-24

    In this paper, we developed a novel and efficient method of deterministically organizing colloidal particles on structured surfaces over macroscopic areas. Our approach utilizes integrated solution-based processes of dielectric encapsulation and electrostatic-force-mediated self-assembly, which allow precisely controlled placement of sub-10nm sized particles at single particle resolution. As a specific demonstration, motivated by application to single photon sources, highly ordered 2D arrays of single II-VI semiconductor colloidal quantum dots (QDs) were created by this method. Individually, the QDs display triggered single photon emission at room temperature with characteristic photon antibunching statistics, suggesting a pathway to scalable quantum optical radiative systems.

  20. Charge carrier coherence and Hall effect in organic semiconductors.

    PubMed

    Yi, H T; Gartstein, Y N; Podzorov, V

    2016-03-30

    Hall effect measurements are important for elucidating the fundamental charge transport mechanisms and intrinsic mobility in organic semiconductors. However, Hall effect studies frequently reveal an unconventional behavior that cannot be readily explained with the simple band-semiconductor Hall effect model. Here, we develop an analytical model of Hall effect in organic field-effect transistors in a regime of coexisting band and hopping carriers. The model, which is supported by the experiments, is based on a partial Hall voltage compensation effect, occurring because hopping carriers respond to the transverse Hall electric field and drift in the direction opposite to the Lorentz force acting on band carriers. We show that this can lead in particular to an underdeveloped Hall effect observed in organic semiconductors with substantial off-diagonal thermal disorder. Our model captures the main features of Hall effect in a variety of organic semiconductors and provides an analytical description of Hall mobility, carrier density and carrier coherence factor.

  1. Optically induced current in molecular conduction nanojunctions with semiconductor contacts

    NASA Astrophysics Data System (ADS)

    Fainberg, Boris D.; Seideman, Tamar

    2013-06-01

    We propose a new approach to coherent control of transport via molecular junctions, which bypasses several of the hurdles to experimental realization of optically manipulated nanoelectronics noted in the previous literature. The method is based on the application of intrinsic semiconductor contacts and optical frequencies below the semiconductor bandgap. To explore the coherently controlled electronic dynamics, we introduce a density matrix formalism that accounts for both the discrete molecular state and the semiconductor quasicontinua within a single master equation and offers analytically soluble limits for a single and two-site molecular bridge. Our analytical theory predicts a new phenomenon, referred to as coherent destruction of induced tunnelling, which extends the phenomenon of coherent destruction of tunnelling frequently discussed in the previous literature. Our results illustrate the potential of semiconductor contacts in coherent control of photocurrent.

  2. Charge carrier coherence and Hall effect in organic semiconductors

    SciTech Connect

    Yi, H. T.; Gartstein, Y. N.; Podzorov, V.

    2016-03-30

    Hall effect measurements are important for elucidating the fundamental charge transport mechanisms and intrinsic mobility in organic semiconductors. However, Hall effect studies frequently reveal an unconventional behavior that cannot be readily explained with the simple band-semiconductor Hall effect model. Here, we develop an analytical model of Hall effect in organic field-effect transistors in a regime of coexisting band and hopping carriers. The model, which is supported by the experiments, is based on a partial Hall voltage compensation effect, occurring because hopping carriers respond to the transverse Hall electric field and drift in the direction opposite to the Lorentz force acting on band carriers. We show that this can lead in particular to an underdeveloped Hall effect observed in organic semiconductors with substantial off-diagonal thermal disorder. Lastly, our model captures the main features of Hall effect in a variety of organic semiconductors and provides an analytical description of Hall mobility, carrier density and carrier coherence factor.

  3. Charge carrier coherence and Hall effect in organic semiconductors

    PubMed Central

    Yi, H. T.; Gartstein, Y. N.; Podzorov, V.

    2016-01-01

    Hall effect measurements are important for elucidating the fundamental charge transport mechanisms and intrinsic mobility in organic semiconductors. However, Hall effect studies frequently reveal an unconventional behavior that cannot be readily explained with the simple band-semiconductor Hall effect model. Here, we develop an analytical model of Hall effect in organic field-effect transistors in a regime of coexisting band and hopping carriers. The model, which is supported by the experiments, is based on a partial Hall voltage compensation effect, occurring because hopping carriers respond to the transverse Hall electric field and drift in the direction opposite to the Lorentz force acting on band carriers. We show that this can lead in particular to an underdeveloped Hall effect observed in organic semiconductors with substantial off-diagonal thermal disorder. Our model captures the main features of Hall effect in a variety of organic semiconductors and provides an analytical description of Hall mobility, carrier density and carrier coherence factor. PMID:27025354

  4. Extended-Gate Metal Oxide Semiconductor Field Effect Transistor-Based Biosensor for Detection of Deoxynivalenol

    NASA Astrophysics Data System (ADS)

    Kwon, Insu; Lee, Hee-Ho; Choi, Jinhyeon; Shin, Jang-Kyoo; Seo, Sang-Ho; Choi, Sung-Wook; Chun, Hyang Sook

    2011-06-01

    In this work, we present an extended-gate metal oxide semiconductor field effect transistor (MOSFET)-based biosensor for the detection of deoxynivalenol using a null-balancing circuit. An extended-gate MOSFET-based biosensor was fabricated by a standard complementary metal oxide semiconductor (CMOS) process and its characteristics were measured. A null-balancing circuit was used to measure the output voltage of the sensor directly, instead of measuring the drain current of the sensor. Au was used as the gate metal, which has a chemical affinity with thiol, which leads to the immobilization of a self-assembled monolayer (SAM) of mercaptohexadecanoic acid (MHDA). The SAM was used to immobilize the anti-deoxynivalenol antibody. The carboxyl group of the SAM was bound to the anti-deoxynivalenol antibody. The anti-deoxynivalenol antibody and deoxynivalenol were bound by their antigen-antibody reaction. The measurements were performed in phosphate buffered saline (PBS; pH 7.4) solution. A standard Ag/AgCl electrode was employed as a reference electrode. The bindings of a SAM, anti-deoxynivalenol antibody, and deoxynivalenol caused a variation in the output voltage of the extended-gate MOSFET-based biosensor. Surface plasmon resonance (SPR) measurement was performed to verify the interaction among the SAM, deoxynivalenol-antibody, and deoxynivalenol.

  5. A design of atmospheric laser communication system based on semiconductor laser

    NASA Astrophysics Data System (ADS)

    Rao, Jionghui; Yao, Wenming; Wen, Linqiang

    2016-01-01

    This paper uses semiconductor laser with 905nm wave length as light source to design a set of short-distance atmospheric laser communication system. This system consists of laser light source, launch modulation circuit, detector, receiving and amplifying circuit and so on. First, this paper analyzes the factors which lead to the decrease of luminous power of laser communication link under the applicable environment-specific sea level, then this paper elicits the relationship of luminous power of receiving optical systems and distance, slant angle and divergence angle which departures from the laser beam axis by using gaussian beam geometric attenuation mode. Based on the two reasons that PPM modulation theory limits the transmission rate of PPM modulation, that is, this paper makes an analysis on repetition frequency and pulse width of laser, makes theoretical calculation for typical parameters of semiconductor laser and gets the repetition frequency which is 10KHz, pulse width is50ns, the transmission rate is 71.66 Kb/s, at this time, modulation digit is 9; then this paper selects frame synchronization code of PPM modulation and provides implementation method for test; lastly, programs language based on Verilog, uses the FPGA development board to realize PPM modulation code and does simulation test and hardware test. This paper uses APD as the detector of receiving and amplifying circuit. Then this paper designs optical receiving circuit such as amplifying circuit, analog-digital conversion circuit based on the characteristics of receipt.

  6. Sensitivity of intrinsic mode functions of Lorenz system to initial values based on EMD method

    NASA Astrophysics Data System (ADS)

    Zou, Ming-Wei; Feng, Guo-lin; Gao, Xin-Quan

    2006-06-01

    Extreme sensitivity to initial values is an intrinsic character of chaotic systems. The evolution of a chaotic system has a spatiotemporal structure containing quasi-periodic changes of different spatiotemporal scales. This paper uses an empirical mode decomposition (EMD) method to decompose and compare the evolution of the time-dependent evolutions of the x-component of the Lorenz system. The results indicate that the sensitivity of intrinsic mode function (IMF) component is dependent on initial values, which provides some scientific evidence for the possibility of long-range climatic prediction.

  7. Quantitative biomarkers of colonic dysplasia based on intrinsic second-harmonic generation signal

    NASA Astrophysics Data System (ADS)

    Zhuo, Shuangmu; Zhu, Xiaoqin; Wu, Guizhu; Chen, Jianxin; Xie, Shusen

    2011-12-01

    Most colorectal cancers arise from dysplastic lesions, such as adenomatous polyps, and these lesions are difficult to be detected by the current endoscopic screening approaches. Here, we present the use of an intrinsic second-harmonic generation (SHG) signal as a novel means to differentiate between normal and dysplastic human colonic tissues. We find that the SHG signal can quantitatively identify collagen change associated with colonic dysplasia that is indiscernible by conventional pathologic techniques. By comparing normal with dysplastic mucosa, there were significant differences in collagen density and collagen fiber direction, providing substantial potential to become quantitative intrinsic biomarkers for in vivo clinical diagnosis of colonic dysplasia.

  8. 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.

  9. Semiconductor optical amplifier-based heterodyning detection for resolving optical terahertz beat-tone signals from passively mode-locked semiconductor lasers

    SciTech Connect

    Latkowski, Sylwester; Maldonado-Basilio, Ramon; Carney, Kevin; Parra-Cetina, Josue; Philippe, Severine; Landais, Pascal

    2010-08-23

    An all-optical heterodyne approach based on a room-temperature controlled semiconductor optical amplifier (SOA) for measuring the frequency and linewidth of the terahertz beat-tone signal from a passively mode-locked laser is proposed. Under the injection of two external cavity lasers, the SOA acts as a local oscillator at their detuning frequency and also as an optical frequency mixer whose inputs are the self-modulated spectrum of the device under test and the two laser beams. Frequency and linewidth of the intermediate frequency signal (and therefore, the beat-tone signal) are resolved by using a photodiode and an electrical spectrum analyzer.

  10. Vertical 2D/3D Semiconductor Heterostructures Based on Epitaxial Molybdenum Disulfide and Gallium Nitride.

    PubMed

    Ruzmetov, Dmitry; Zhang, Kehao; Stan, Gheorghe; Kalanyan, Berc; Bhimanapati, Ganesh R; Eichfeld, Sarah M; Burke, Robert A; Shah, Pankaj B; O'Regan, Terrance P; Crowne, Frank J; Birdwell, A Glen; Robinson, Joshua A; Davydov, Albert V; Ivanov, Tony G

    2016-03-22

    When designing semiconductor heterostructures, it is expected that epitaxial alignment will facilitate low-defect interfaces and efficient vertical transport. Here, we report lattice-matched epitaxial growth of molybdenum disulfide (MoS2) directly on gallium nitride (GaN), resulting in high-quality, unstrained, single-layer MoS2 with strict registry to the GaN lattice. These results present a promising path toward the implementation of high-performance electronic devices based on 2D/3D vertical heterostructures, where each of the 3D and 2D semiconductors is both a template for subsequent epitaxial growth and an active component of the device. The MoS2 monolayer triangles average 1 μm along each side, with monolayer blankets (merged triangles) exhibiting properties similar to that of single-crystal MoS2 sheets. Photoluminescence, Raman, atomic force microscopy, and X-ray photoelectron spectroscopy analyses identified monolayer MoS2 with a prominent 20-fold enhancement of photoluminescence in the center regions of larger triangles. The MoS2/GaN structures are shown to electrically conduct in the out-of-plane direction, confirming the potential of directly synthesized 2D/3D semiconductor heterostructures for vertical current flow. Finally, we estimate a MoS2/GaN contact resistivity to be less than 4 Ω·cm(2) and current spreading in the MoS2 monolayer of approximately 1 μm in diameter.

  11. Extracting Intrinsic Functional Networks with Feature-Based Group Independent Component Analysis

    ERIC Educational Resources Information Center

    Calhoun, Vince D.; Allen, Elena

    2013-01-01

    There is increasing use of functional imaging data to understand the macro-connectome of the human brain. Of particular interest is the structure and function of intrinsic networks (regions exhibiting temporally coherent activity both at rest and while a task is being performed), which account for a significant portion of the variance in…

  12. Prospects of IMPATT devices based on wide bandgap semiconductors as potential terahertz sources

    NASA Astrophysics Data System (ADS)

    Acharyya, Aritra; Banerjee, J. P.

    2014-01-01

    In this paper the potentiality of impact avalanche transit time (IMPATT) devices based on different semiconductor materials such as GaAs, Si, InP, 4H-SiC and Wurtzite-GaN (Wz-GaN) has been explored for operation at terahertz frequencies. Drift-diffusion model is used to design double-drift region (DDR) IMPATTs based on different materials at millimeter-wave (mm-wave) and terahertz (THz) frequencies. The performance limitations of these devices are studied from the avalanche response times at different mm-wave and THz frequencies. Results show that the upper cut-off frequency limits of GaAs and Si DDR IMPATTs are 220 GHz and 0.5 THz, respectively, whereas the same for InP and 4H-SiC DDR IMPATTs is 1.0 THz. Wz-GaN DDR IMPATTs are found to be excellent candidate for generation of RF power at THz frequencies of the order of 5.0 THz with appreciable DC to RF conversion efficiency. Further, it is observed that up to 1.0 THz, 4H-SiC DDR IMPATTs excel Wz-GaN DDR IMPATTs as regards their RF power outputs. Thus, the wide bandgap semiconductors such as Wz-GaN and 4H-SiC are highly suitable materials for DDR IMPATTs at both mm-wave and THz frequency ranges.

  13. Active photonic devices based on colloidal semiconductor nanocrystals and organometallic halide perovskites

    NASA Astrophysics Data System (ADS)

    Suárez Alvarez, Isaac

    2016-10-01

    Semiconductor nanocrystals have arisen as outstanding materials to develop a new generation of optoelectronic devices. Their fabrication under simple and low cost colloidal chemistry methods results in cheap nanostructures able to provide a wide range of optical functionalities. Their attractive optical properties include a high absorption cross section below the band gap, a high quantum yield emission at room temperature, or the capability of tuning the band-gap with the size or the base material. In addition, their solution process nature enables an easy integration on several substrates and photonic structures. As a consequence, these nanoparticles have been extensively proposed to develop several photonic applications, such as detection of light, optical gain, generation of light or sensing. This manuscript reviews the great effort undertaken by the scientific community to construct active photonic devices based on these nanoparticles. The conditions to demonstrate stimulated emission are carefully studied by comparing the dependence of the optical properties of the nanocrystals with their size, shape and composition. In addition, this paper describes the design of different photonic architectures (waveguides and cavities) to enhance the generation of photoluminescence, and hence to reduce the threshold of optical gain. Finally, semiconductor nanocrystals are compared to organometallic halide perovskites, as this novel material has emerged as an alternative to colloidal nanoparticles.

  14. Cyclopentadithiophene-Based Organic Semiconductors: Effect of Fluorinated Substituents on Electrochemical and Charge Transport Properties

    SciTech Connect

    Reddy, J. Sreedhar; Kale, Tejaswini; Balaji, Ganapathy; Chandrasekaran, A.; Thayumanavan, S.

    2011-03-17

    Thiophene-based semiconductors are often hole conductors that have been converted to electron-transporting materials by incorporation of electron-withdrawing groups at terminal positions, such as fluorinated substituents. This conversion of an otherwise p-type material to n-type material is often attributed to the lowering of the lowest unoccupied molecular orbital (LUMO) energy level due to the increased electron affinity in the molecule. Yet, it is not clear if lowering of LUMO energy level is a sufficient condition for yielding n-type material. Herein, we report small-molecule semiconductors based on cyclopentadithiophene (CPD), which can be orthogonally functionalized at two different positions, which allows us to tune the frontier orbital energy levels. We find that simply lowering the LUMO energy level, without inclusion of fluoro groups, does not result in conversion of the otherwise p-type material to n-type material, whereas incorporation of fluorinated substituents does. This indicates that charge transport behavior is not an exclusive function of the frontier orbital energy levels.

  15. [Study of immobilization and properties of urease for creation of a biosensor based on semiconductor structures].

    PubMed

    Bubriak, O A; Khustochka, L N; Soldatkin, A P; Starodub, N F

    1992-01-01

    Many-sided investigations of urease immobilization methods were carried out to create the biosensor devices on the base of semiconductor structures. Special attention was concentrated on the biomembrane formation by means of urease and bovine serum albumin (BSA) cross-linking by gaseous glutaraldehyde. Optimal conditions for the formation process were selected which preserve about 20% of total urease activity after the cross-linking. The properties of enzyme immobilized by the above-mentioned method have been comprehensively studied. They included the urease activity dependence on pH, ionic strength, incubation buffer capacity as well as the enzyme stability during its functioning, storing and thermoinactivation. As was shown, for immobilized ureas Km value for urea at pH 7.0 and 20 degrees C is 1.65 time less than for free enzyme. In the presence of EDTA (1 mM) the enzyme activity in the biomembrane is practically unchanged under a month storing. Biomembrane possesses good adhesion to silicon surface and its swelling level under different conditions does not exceed 35%. The conclusion is made about the prospects of the used method of biomembrane formation for biosensor technology based on semiconductor structures.

  16. Web-based interactive educational software introducing semiconductor laser dynamics: Sound of Lasers (SOL)

    NASA Astrophysics Data System (ADS)

    Consoli, Antonio; Sanchez, Jorge R.; Horche, Paloma R.; Esquivias, Ignacio

    2014-07-01

    presented. The proposed tool is addressed to the students of optical communication courses, encouraging self consolidation of the subjects learned in lectures. The semiconductor laser model is based on the well known rate equations for the carrier density, photon density and optical phase. The direct modulation of the laser is considered with input parameters which can be selected by the user. Different options for the waveform, amplitude and frequency of the injected current are available, together with the bias point. Simulation results are plotted for carrier density and output power versus time. Instantaneous frequency variations of the laser output are numerically shifted to the audible frequency range and sent to the computer loudspeakers. This results in an intuitive description of the "chirp" phenomenon due to amplitude-phase coupling, typical of directly modulated semiconductor lasers. In this way, the student can actually listen to the time resolved spectral content of the laser output. By changing the laser parameters and/or the modulation parameters, consequent variation of the laser output can be appreciated in intuitive manner. The proposed educational tool has been previously implemented by the same authors with locally executable software. In the present manuscript, we extend our previous work to a web based platform, offering improved distribution and allowing its use to the wide audience of the web.

  17. Multianalyte biosensor based on pH-sensitive ZnO electrolyte–insulator–semiconductor structures

    SciTech Connect

    Haur Kao, Chyuan; Chun Liu, Che; Ueng, Herng-Yih; Chen, Hsiang Cheng Chu, Yu; Jie Chen, Yu; Ling Lee, Ming; Ming Chang, Kow

    2014-05-14

    Multianalyte electrolyte–insulator–semiconductor (EIS) sensors with a ZnO sensing membrane annealed on silicon substrate for use in pH sensing were fabricated. Material analyses were conducted using X-ray diffraction and atomic force microscopy to identify optimal treatment conditions. Sensing performance for various ions of Na{sup +}, K{sup +}, urea, and glucose was also tested. Results indicate that an EIS sensor with a ZnO membrane annealed at 600 °C exhibited good performance with high sensitivity and a low drift rate compared with all other reported ZnO-based pH sensors. Furthermore, based on well-established pH sensing properties, pH-ion-sensitive field-effect transistor sensors have also been developed for use in detecting urea and glucose ions. ZnO-based EIS sensors show promise for future industrial biosensing applications.

  18. Multianalyte biosensor based on pH-sensitive ZnO electrolyte-insulator-semiconductor structures

    NASA Astrophysics Data System (ADS)

    Haur Kao, Chyuan; Chen, Hsiang; Ling Lee, Ming; Chun Liu, Che; Ueng, Herng-Yih; Cheng Chu, Yu; Jie Chen, Yu; Ming Chang, Kow

    2014-05-01

    Multianalyte electrolyte-insulator-semiconductor (EIS) sensors with a ZnO sensing membrane annealed on silicon substrate for use in pH sensing were fabricated. Material analyses were conducted using X-ray diffraction and atomic force microscopy to identify optimal treatment conditions. Sensing performance for various ions of Na+, K+, urea, and glucose was also tested. Results indicate that an EIS sensor with a ZnO membrane annealed at 600 °C exhibited good performance with high sensitivity and a low drift rate compared with all other reported ZnO-based pH sensors. Furthermore, based on well-established pH sensing properties, pH-ion-sensitive field-effect transistor sensors have also been developed for use in detecting urea and glucose ions. ZnO-based EIS sensors show promise for future industrial biosensing applications.

  19. [Medical professionals on the subject of their core values: the importance of practice-based stories and intrinsic motivation].

    PubMed

    Witman, Yolande; van den Kerkhof, Peter C M; Braat, Didi D M

    2013-01-01

    In the current system for guaranteeing quality of care, emphasis is placed firmly on external control of professionals. We looked for a way to appeal to the intrinsic motivation of medical professionals and to discover what they mean by 'good work'. This was achieved with the aid of reflective sessions using the toolkit 'Good Work': in four sessions three different groups of medical professionals (medical department chairs, residents and interns) from a Dutch university hospital reflected on the topics 'excellence', 'moral responsibility' and 'personal engagement'. The participants exchanged practice-based stories during the sessions. The most important theme was moral responsibility, with its accompanying dilemmas. The sessions gave rise to feelings of mutual acknowledgement, recognition, inspiration and motivation. Sharing meaningful practice-based stories can be considered as a 'moment of learning', strengthening professional identity and stimulating intrinsic motivation. More space for this form of reflection might restore the balance with external control systems.

  20. Room-temperature terahertz detectors based on semiconductor nanowire field-effect transistors.

    PubMed

    Vitiello, Miriam S; Coquillat, Dominique; Viti, Leonardo; Ercolani, Daniele; Teppe, Frederic; Pitanti, Alessandro; Beltram, Fabio; Sorba, Lucia; Knap, Wojciech; Tredicucci, Alessandro

    2012-01-11

    The growth of semiconductor nanowires (NWs) has recently opened new paths to silicon integration of device families such as light-emitting diodes, high-efficiency photovoltaics, or high-responsivity photodetectors. It is also offering a wealth of new approaches for the development of a future generation of nanoelectronic devices. Here we demonstrate that semiconductor nanowires can also be used as building blocks for the realization of high-sensitivity terahertz detectors based on a 1D field-effect transistor configuration. In order to take advantage of the low effective mass and high mobilities achievable in III-V compounds, we have used InAs nanowires, grown by vapor-phase epitaxy, and properly doped with selenium to control the charge density and to optimize source-drain and contact resistance. The detection mechanism exploits the nonlinearity of the transfer characteristics: the terahertz radiation field is fed at the gate-source electrodes with wide band antennas, and the rectified signal is then read at the output in the form of a DC drain voltage. Significant responsivity values (>1 V/W) at 0.3 THz have been obtained with noise equivalent powers (NEP) < 2 × 10(-9) W/(Hz)(1/2) at room temperature. The large existing margins for technology improvements, the scalability to higher frequencies, and the possibility of realizing multipixel arrays, make these devices highly competitive as a future solution for terahertz detection.

  1. TOPICAL REVIEW: Ferromagnetic nitride-based semiconductors doped with transition metals and rare earths

    NASA Astrophysics Data System (ADS)

    Bonanni, A.

    2007-09-01

    This review summarizes the state-of-the-art in the search for room temperature ferromagnetic semiconductors based on transition-metal- and rare-earth-doped nitrides. The major methods of synthesis are reported, together with an overview of the magnetic, structural, electrical and optical characterization of the materials systems, where available. The controversial experimental results concerning the actual value of the apparent Curie temperature in magnetically doped nitrides are highlighted, the inadequacy of standard characterization methods alone and the necessity of a possibly exhaustive structural investigation of the systems are proven and underlined. Furthermore, the dependence on the fabrication parameters of the magnetic ions incorporation into the semiconductor matrix is discussed, with special attention to the fundamental concepts of solubility limit and spinodal decomposition. It is argued that high-temperature ferromagnetic features in magnetically doped nitrides result from the presence of nanoscale regions containing a high concentration of the magnetic constituents. Various functionalities of these multicomponent systems are listed. Moreover, we give an extensive overview on the properties of single magnetic-impurity states in the nitride host. The understanding of this limit is crucial when considering the most recent suggestions for the control of the magnetic ion distribution—and consequently of the magnetic response—through the Fermi level engineering as well as to indicate roads for achieving high-temperature ferromagnetism in the systems containing a uniform distribution of magnetic ions.

  2. Potential for spin-based information processing in a thin-film molecular semiconductor

    NASA Astrophysics Data System (ADS)

    Warner, Marc; Din, Salahud; Tupitsyn, Igor; Morley, Gavin; Stoneham, Marshall; Gardener, Jules; Wu, Zhenlin; Fisher, Andrew; Heutz, Sandrine; Kay, Christopher; Aeppli, Gabriel

    2014-03-01

    Organic semiconductors are studied intensively for applications in electronics and optics, and even spin-based information technology, or spintronics. Fundamental quantities in spintronics are the population relaxation time (T1) and the phase memory time (T2) : T1 measures the lifetime of a classical bit, in this case embodied by a spin oriented either parallel or antiparallel to an external magnetic field, and T2 measures the corresponding lifetime of a quantum bit, encoded in the phase of the quantum state. Here we establish that these times are surprisingly long for a common, low-cost and chemically modifiable organic semiconductor, the blue pigment copper phthalocyanine, in easily processed thin-film form of the type used for device fabrication. At 5 K, a temperature reachable using inexpensive closed-cycle refrigerators, T1 and T2 are respectively 59 ms and 2.6 ms, and at 80 K, which is just above the boiling point of liquid nitrogen, they are respectively 10 ms and 1 ms, demonstrating that the performance of thin-film copper phthalocyanine is superior to that of single-molecule magnets over the same temperature range.

  3. Semiconductor-based photoelectrochemical water splitting at the limit of very wide depletion region

    SciTech Connect

    Liu, Mingzhao; Lyons, John L.; Yan, Danhua H.; Hybertsen, Mark S.

    2015-11-23

    In semiconductor-based photoelectrochemical (PEC) water splitting, carrier separation and delivery largely relies on the depletion region formed at the semiconductor/water interface. As a Schottky junction device, the trade-off between photon collection and minority carrier delivery remains a persistent obstacle for maximizing the performance of a water splitting photoelectrode. Here, it is demonstrated that the PEC water splitting efficiency for an n-SrTiO3 (n-STO) photoanode is improved very significantly despite its weak indirect band gap optical absorption (α < 10⁴ cm⁻¹), by widening the depletion region through engineering its doping density and profile. Graded doped n-SrTiO3 photoanodes are fabricated with their bulk heavily doped with oxygen vacancies but their surface lightly doped over a tunable depth of a few hundred nanometers, through a simple low temperature re-oxidation technique. The graded doping profile widens the depletion region to over 500 nm, thus leading to very efficient charge carrier separation and high quantum efficiency (>70%) for the weak indirect transition. As a result, this simultaneous optimization of the light absorption, minority carrier (hole) delivery, and majority carrier (electron) transport by means of a graded doping architecture may be useful for other indirect band gap photocatalysts that suffer from a similar problem of weak optical absorption.

  4. Semiconductor-based photoelectrochemical water splitting at the limit of very wide depletion region

    DOE PAGES

    Liu, Mingzhao; Lyons, John L.; Yan, Danhua H.; ...

    2015-11-23

    In semiconductor-based photoelectrochemical (PEC) water splitting, carrier separation and delivery largely relies on the depletion region formed at the semiconductor/water interface. As a Schottky junction device, the trade-off between photon collection and minority carrier delivery remains a persistent obstacle for maximizing the performance of a water splitting photoelectrode. Here, it is demonstrated that the PEC water splitting efficiency for an n-SrTiO3 (n-STO) photoanode is improved very significantly despite its weak indirect band gap optical absorption (α < 10⁴ cm⁻¹), by widening the depletion region through engineering its doping density and profile. Graded doped n-SrTiO3 photoanodes are fabricated with their bulkmore » heavily doped with oxygen vacancies but their surface lightly doped over a tunable depth of a few hundred nanometers, through a simple low temperature re-oxidation technique. The graded doping profile widens the depletion region to over 500 nm, thus leading to very efficient charge carrier separation and high quantum efficiency (>70%) for the weak indirect transition. As a result, this simultaneous optimization of the light absorption, minority carrier (hole) delivery, and majority carrier (electron) transport by means of a graded doping architecture may be useful for other indirect band gap photocatalysts that suffer from a similar problem of weak optical absorption.« less

  5. Potential for spin-based information processing in a thin-film molecular semiconductor

    NASA Astrophysics Data System (ADS)

    Warner, Marc; Din, Salahud; Tupitsyn, Igor S.; Morley, Gavin W.; Stoneham, A. Marshall; Gardener, Jules A.; Wu, Zhenlin; Fisher, Andrew J.; Heutz, Sandrine; Kay, Christopher W. M.; Aeppli, Gabriel

    2013-11-01

    Organic semiconductors are studied intensively for applications in electronics and optics, and even spin-based information technology, or spintronics. Fundamental quantities in spintronics are the population relaxation time (T1) and the phase memory time (T2): T1 measures the lifetime of a classical bit, in this case embodied by a spin oriented either parallel or antiparallel to an external magnetic field, and T2 measures the corresponding lifetime of a quantum bit, encoded in the phase of the quantum state. Here we establish that these times are surprisingly long for a common, low-cost and chemically modifiable organic semiconductor, the blue pigment copper phthalocyanine, in easily processed thin-film form of the type used for device fabrication. At 5K, a temperature reachable using inexpensive closed-cycle refrigerators, T1 and T2 are respectively 59ms and 2.6μs, and at 80K, which is just above the boiling point of liquid nitrogen, they are respectively 10μs and 1μs, demonstrating that the performance of thin-film copper phthalocyanine is superior to that of single-molecule magnets over the same temperature range. T2 is more than two orders of magnitude greater than the duration of the spin manipulation pulses, which suggests that copper phthalocyanine holds promise for quantum information processing, and the long T1 indicates possibilities for medium-term storage of classical bits in all-organic devices on plastic substrates.

  6. Investigation of laser radar systems based on mid-infrared semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Rybaltowski, Adam

    This dissertation deals with the possibility of utilizing mid-infrared semiconductor lasers in systems of optical remote sensing with range resolution, called laser radar or lidar. The main subject investigated in this dissertation is two-fold: firstly, an analysis of the signal-to-noise ratio (SNR) and related maximum sensing range calculations in this type of lidar based on available system components, and---secondly---improvements in the Random-Modulation Continuous-Wave (RM-CW) lidar technique to better utilize available mid-infrared semiconductor lasers. As far as the SNR analysis is concerned, an appropriate framework has been constructed to analyze post-demodulation noise in mid-infrared direct-detection RM-CW lidar. It is based on a generalization of the Wiener-Khintchine theorem; noise is assumed to be additive, stationary, and have an arbitrary power spectrum. This is in contrast to the SNR analysis in the literature on this subject, which is inadequate for mid-infrared RM-CW lidar as it only considers Poissonian fluctuations of the number of detected photons. In addition to regular SNR analysis, the framework derived in this dissertation allows treatment of singularities such as demodulation with an unbalanced sequence in 1/f noise. To calculate maximum lidar sensing range, the following detection limits have been considered: signal shot noise, background blackbody radiation shot noise based on the Background-Limited Photodetection (BLIP) detectivity limit, and minimum-size detector noise given by diffraction-limited focusing. The latter is found to be of greatest practical interest. Furthermore, a lidar figure of merit has been introduced, and all quantities related to lidar performance and its detection limits have been presented graphically. Since pseudo-random sequences discussed in the literature have been found highly non-optimal for most applications of RM-CW lidar, a framework for the construction of new pseudo-random sequences of desired

  7. An HEMT-Based Cryogenic Charge Amplifier for Sub-kelvin Semiconductor Radiation Detectors

    NASA Astrophysics Data System (ADS)

    Phipps, A.; Sadoulet, B.; Juillard, A.; Jin, Y.

    2016-07-01

    We present the design and noise performance of a fully cryogenic (T=4 K) high-electron mobility transistor (HEMT)-based charge amplifier for readout of sub-kelvin semiconductor radiation detectors. The amplifier is being developed for use in direct detection dark matter searches such as the cryogenic dark matter search and will allow these experiments to probe weakly interacting massive particle masses below 10 GeV/c^2 while retaining background discrimination. The amplifier dissipates ≈ 1 mW of power and provides an open loop voltage gain of several hundreds. The measured noise performance is better than that of JFET-based charge amplifiers and is dominated by the noise of the input HEMT. An optimal filter calculation using the measured closed loop noise and typical detector characteristics predicts a charge resolution of σ _q=106 eV (35 electrons) for leakage currents below 4 × 10^{-15} A.

  8. Reconfigurable Optical Signal Processing Based on a Distributed Feedback Semiconductor Optical Amplifier.

    PubMed

    Li, Ming; Deng, Ye; Tang, Jian; Sun, Shuqian; Yao, Jianping; Azaña, José; Zhu, Ninghua

    2016-01-27

    All-optical signal processing has been considered a solution to overcome the bandwidth and speed limitations imposed by conventional electronic-based systems. Over the last few years, an impressive range of all-optical signal processors have been proposed, but few of them come with reconfigurability, a feature highly needed for practical signal processing applications. Here we propose and experimentally demonstrate an analog optical signal processor based on a phase-shifted distributed feedback semiconductor optical amplifier (DFB-SOA) and an optical filter. The proposed analog optical signal processor can be reconfigured to perform signal processing functions including ordinary differential equation solving and temporal intensity differentiation. The reconfigurability is achieved by controlling the injection currents. Our demonstration provitdes a simple and effective solution for all-optical signal processing and computing.

  9. Diode-Laser Pumped Far-Infrared Local Oscillator Based on Semiconductor Quantum Wells

    NASA Technical Reports Server (NTRS)

    Kolokolov, K.; Li, J.; Ning, C. Z.; Larrabee, D. C.; Tang, J.; Khodaparast, G.; Kono, J.; Sasa, S.; Inoue, M.; Biegel, Bryan A. (Technical Monitor)

    2002-01-01

    The contents include: 1) Tetrahertz Field: A Technology Gap; 2) Existing THZ Sources and Shortcomings; 3) Applications of A THZ Laser; 4) Previous Optical Pumped LW Generations; 5) Optically Pumped Sb based Intersubband Generation Whys; 6) InGaAs/InP/AlAsSb QWs; 7) Raman Enhanced Optical Gain; 8) Pump Intensity Dependence of THZ Gain; 9) Pump-Probe Interaction Induced Raman Shift; 10) THZ Laser Gain in InGaAs/InP/AlAsSb QWs; 11) Diode-Laser Pumped Difference Frequency Generation (InGaAs/InP/AlAsSb QWs); 12) 6.1 Angstrom Semiconductor Quantum Wells; 13) InAs/GaSb/AlSb Nanostructures; 14) InAs/AlSb Double QWs: DFG Scheme; 15) Sb-Based Triple QWs: Laser Scheme; and 16) Exciton State Pumped THZ Generation. This paper is presented in viewgraph form.

  10. Reconfigurable Optical Signal Processing Based on a Distributed Feedback Semiconductor Optical Amplifier

    PubMed Central

    Li, Ming; Deng, Ye; Tang, Jian; Sun, Shuqian; Yao, Jianping; Azaña, José; Zhu, Ninghua

    2016-01-01

    All-optical signal processing has been considered a solution to overcome the bandwidth and speed limitations imposed by conventional electronic-based systems. Over the last few years, an impressive range of all-optical signal processors have been proposed, but few of them come with reconfigurability, a feature highly needed for practical signal processing applications. Here we propose and experimentally demonstrate an analog optical signal processor based on a phase-shifted distributed feedback semiconductor optical amplifier (DFB-SOA) and an optical filter. The proposed analog optical signal processor can be reconfigured to perform signal processing functions including ordinary differential equation solving and temporal intensity differentiation. The reconfigurability is achieved by controlling the injection currents. Our demonstration provitdes a simple and effective solution for all-optical signal processing and computing. PMID:26813252

  11. Imitation learning based on an intrinsic motivation mechanism for efficient coding.

    PubMed

    Triesch, Jochen

    2013-01-01

    A hypothesis regarding the development of imitation learning is presented that is rooted in intrinsic motivations. It is derived from a recently proposed form of intrinsically motivated learning (IML) for efficient coding in active perception, wherein an agent learns to perform actions with its sense organs to facilitate efficient encoding of the sensory data. To this end, actions of the sense organs that improve the encoding of the sensory data trigger an internally generated reinforcement signal. Here it is argued that the same IML mechanism might also support the development of imitation when general actions beyond those of the sense organs are considered: The learner first observes a tutor performing a behavior and learns a model of the the behavior's sensory consequences. The learner then acts itself and receives an internally generated reinforcement signal reflecting how well the sensory consequences of its own behavior are encoded by the sensory model. Actions that are more similar to those of the tutor will lead to sensory signals that are easier to encode and produce a higher reinforcement signal. Through this, the learner's behavior is progressively tuned to make the sensory consequences of its actions match the learned sensory model. I discuss this mechanism in the context of human language acquisition and bird song learning where similar ideas have been proposed. The suggested mechanism also offers an account for the development of mirror neurons and makes a number of predictions. Overall, it establishes a connection between principles of efficient coding, intrinsic motivations and imitation.

  12. Diagnostics of gear faults based on EMD and automatic selection of intrinsic mode functions

    NASA Astrophysics Data System (ADS)

    Ricci, Roberto; Pennacchi, Paolo

    2011-04-01

    Signal processing is an important tool for diagnostics of mechanical systems. Many different techniques are available to process experimental signals, among others: FFT, wavelet transform, cepstrum, demodulation analysis, second order ciclostationarity analysis, etc. However, often hypothesis about data and computational efforts restrict the application of some techniques. In order to overcome these limitations, the empirical mode decomposition has been proposed. The outputs of this adaptive approach are the intrinsic mode functions that are treated with the Hilbert transform in order to obtain the Hilbert-Huang spectrum. Anyhow, the selection of the intrinsic mode functions used for the calculation of Hilbert-Huang spectrum is normally done on the basis of user's experience. On the contrary, in the paper a merit index is introduced that allows the automatic selection of the intrinsic mode functions that should be used. The effectiveness of the improvement is proven by the result of the experimental tests presented and performed on a test-rig equipped with a spiral bevel gearbox, whose high contact ratio made difficult to diagnose also serious damages of the gears. This kind of gearbox is normally never employed for benchmarking diagnostics techniques. By using the merit index, the defective gearbox is always univocally identified, also considering transient operating conditions.

  13. Intrinsic and metal-doped gallium oxide based high-temperature oxygen sensors for combustion processes

    NASA Astrophysics Data System (ADS)

    Rubio, Ernesto Javier

    films were evaluated as a function of W-content. The structural analyses indicate the formation of monoclinic beta-phase 2O3 in as-grown W-doped 2O3 films for all W-content. Thermally induced secondary phase (W-oxide) formation was observed after the annealing process. Chemical analysis demonstrates the increasing W atomic percentage in the films with increasing sputtering power, whereas the main metallic ionic species for the films are W6+ and Ga3+. Evidence of W interdiffusion due to the annealing process is presented, and the mechanism of diffusion is discussed. Surface morphology of the films is also discussed, and the transition to mesoporous surface is observed after annealing. Finally, the oxygen sensor performance evaluation demonstrated that the W-incorporated 2O3 exhibits improved response time compared to intrinsic 2O3 based oxygen sensors.

  14. Semiconductor device PN junction fabrication using optical processing of amorphous semiconductor material

    SciTech Connect

    Sopori, Bhushan; Rangappan, Anikara

    2014-11-25

    Systems and methods for semiconductor device PN junction fabrication are provided. In one embodiment, a method for fabricating an electrical device having a P-N junction comprises: depositing a layer of amorphous semiconductor material onto a crystalline semiconductor base, wherein the crystalline semiconductor base comprises a crystalline phase of a same semiconductor as the amorphous layer; and growing the layer of amorphous semiconductor material into a layer of crystalline semiconductor material that is epitaxially matched to the lattice structure of the crystalline semiconductor base by applying an optical energy that penetrates at least the amorphous semiconductor material.

  15. Semiconductor polymer-based rf MEMS and its applications to microwave systems

    NASA Astrophysics Data System (ADS)

    Varadan, Vijay K.; Jose, K. A.; Vinoy, K. J.; Varadan, Vasundara V.

    2000-06-01

    During the past decade, several new fabrication techniques have evolved which helped popularize micro-electromechanical systems (MEMS), and numerous novel devices have been reported in diverse areas of engineering and science. One such area is microwave and millimeter wave systems. MEMS technology for microwave applications should solve many intriguing problems of high frequency technology for wireless communications. The recent and dramatic developments of personal communication devices forced the market to acquire miniaturized efficient devices, which is possible only by the development of RF MEMS. Semiconductor- polymer based sensor use silicon use silicon or compound semiconductors as inorganic parts with sensitive polymers as insulating, semiconducting or conductive materials. Organic thin film transistor has also been fabricated using this concept. These devices may allow control circuitry to be integrated with 2D or 3D MEMS. Interdigital type RF-MEMS can be designed and fabricated with Interdigital Electrodes (IDE) deposited on either polymer or an inorganic material such as Barium Strontium Titanate (BST). In the case of polymer-based device, we study the capacitance change and calibrate it for desired sensing application. In the inorganic case, we make use of the change in dielectric properties of BST as a function of DC bias. IDE will act like a RF filter and oscillator just like the comb-type RF MEMS devices. These polymeric based devices can be integrated with organic thin film transistors. RF switches, tuners and filters are some of the initial applications of RF MEMS although many others are still under development. In this paper we present the design and development of few devices such as phase shifters, switches and IDT capacitors. It is observed that, dielectric constant of BST thin film changes by more than 50 percent with an applied bias voltage of 25 V dc, which could therefore be easily implemented in RF switch.

  16. III-antimonide/nitride based semiconductors for optoelectronic materials and device studies : LDRD 26518 final report.

    SciTech Connect

    Kurtz, Steven Ross; Hargett, Terry W.; Serkland, Darwin Keith; Waldrip, Karen Elizabeth; Modine, Normand Arthur; Klem, John Frederick; Jones, Eric Daniel; Cich, Michael Joseph; Allerman, Andrew Alan; Peake, Gregory Merwin

    2003-12-01

    The goal of this LDRD was to investigate III-antimonide/nitride based materials for unique semiconductor properties and applications. Previous to this study, lack of basic information concerning these alloys restricted their use in semiconductor devices. Long wavelength emission on GaAs substrates is of critical importance to telecommunication applications for cost reduction and integration into microsystems. Currently InGaAsN, on a GaAs substrate, is being commercially pursued for the important 1.3 micrometer dispersion minima of silica-glass optical fiber; due, in large part, to previous research at Sandia National Laboratories. However, InGaAsN has not shown great promise for 1.55 micrometer emission which is the low-loss window of single mode optical fiber used in transatlantic fiber. Other important applications for the antimonide/nitride based materials include the base junction of an HBT to reduce the operating voltage which is important for wireless communication links, and for improving the efficiency of a multijunction solar cell. We have undertaken the first comprehensive theoretical, experimental and device study of this material with promising results. Theoretical modeling has identified GaAsSbN to be a similar or potentially superior candidate to InGaAsN for long wavelength emission on GaAs. We have confirmed these predictions by producing emission out to 1.66 micrometers and have achieved edge emitting and VCSEL electroluminescence at 1.3 micrometers. We have also done the first study of the transport properties of this material including mobility, electron/hole mass, and exciton reduced mass. This study has increased the understanding of the III-antimonide/nitride materials enough to warrant consideration for all of the target device applications.

  17. Semiconductor-based superlens for subwavelength resolution below the diffraction limit at extreme ultraviolet frequencies

    NASA Astrophysics Data System (ADS)

    Vincenti, M. A.; D'Orazio, A.; Cappeddu, M. G.; Akozbek, Neset; Bloemer, M. J.; Scalora, M.

    2009-05-01

    We theoretically demonstrate negative refraction and subwavelength resolution below the diffraction limit in the UV and extreme UV ranges using semiconductors. The metal-like response of typical semiconductors such as GaAs or GaP makes it possible to achieve negative refraction and superguiding in resonant semiconductor/dielectric multilayer stacks, similar to what has been demonstrated in metallodielectric photonic band gap structures. The exploitation of this basic property in semiconductors raises the possibility of yet-untapped applications in the UV and soft x-ray ranges.

  18. Influences of semiconductor laser on fibre-optic distributed disturbance sensor based on Mach-Zehnder interferometer

    NASA Astrophysics Data System (ADS)

    Liang, Sheng; Zhang, Chun-Xi; Lin, Bo; Lin, Wen-Tai; Li, Qin; Zhong, Xiang; Li, Li-Jing

    2010-12-01

    This paper investigates the influences of a semiconductor laser with narrow linewidth on a fibre-optic distributed disturbance sensor based on Mach-Zehnder interferometer. It establishes an effective numerical model to describe the noises and linewidth of a semiconductor laser, taking into account their correlations. Simulation shows that frequency noise has great influences on location errors and their relationship is numerically investigated. Accordingly, there is need to determine the linewidth of the laser less than a threshold and obtain the least location errors. Furthermore, experiments are performed by a sensor prototype using three semiconductor lasers with different linewidths, respectively, with polarization maintaining optical fibres and couplers to eliminate the polarization induced noises and fading. The agreement of simulation with experimental results means that the proposed numerical model can make a comprehensive description of the noise behaviour of a semiconductor laser. The conclusion is useful for choosing a laser source for fibre-optic distributed disturbance sensor to achieve optimized location accuracy. What is more, the proposed numerical model can be widely used for analysing influences of semiconductor lasers on other sensing, communication and optical signal processing systems.

  19. All-optical flip-flop based on vertical cavity semiconductor optical amplifiers.

    PubMed

    Song, Deqiang; Gauss, Veronica; Zhang, Haijiang; Gross, Matthias; Wen, Pengyue; Esener, Sadik

    2007-10-15

    We report the operation of an all-optical set-reset (SR) flip-flop based on vertical cavity semiconductor optical amplifiers (VCSOAs). This flip-flop is cascadable, has low optical switching power (~10 microW), and has the potential to be integrated on a small footprint (~100 microm(2)). The flip-flop is composed of two cross-coupled electrically pumped VCSOA inverters and uses the principles of cross-gain modulation, polarization gain anisotropy, and highly nonlinear gain characteristics to achieve flip-flop functionality. We believe that, when integrated on chip, this type of all-optical flip-flop opens new prospects for implementing all-optical fast memories and timing regeneration circuits.

  20. Quantitative analysis of uranium in aqueous solutions using a semiconductor laser-based spectroscopic method.

    PubMed

    Cho, Hye-Ryun; Jung, Euo Chang; Cha, Wansik; Song, Kyuseok

    2013-05-07

    A simple analytical method based on the simultaneous measurement of the luminescence of hexavalent uranium ions (U(VI)) and the Raman scattering of water, was investigated for determining the concentration of U(VI) in aqueous solutions. Both spectra were measured using a cw semiconductor laser beam at a center wavelength of 405 nm. The empirical calibration curve for the quantitative analysis of U(VI) was obtained by measuring the ratio of the luminescence intensity of U(VI) at 519 nm to the Raman scattering intensity of water at 469 nm. The limit of detection (LOD) in the parts per billion range and a dynamic range from the LOD up to several hundred parts per million were achieved. The concentration of uranium in groundwater determined by this method is in good agreement with the results determined by kinetic phosphorescence analysis and inductively coupled plasma mass spectrometry.

  1. Solid-state semiconductor optical cryocooler based on CdS nanobelts.

    PubMed

    Li, Dehui; Zhang, Jun; Wang, Xinjiang; Huang, Baoling; Xiong, Qihua

    2014-08-13

    We demonstrate the laser cooling of silicon-on-insulator (SOI) substrate using CdS nanobelts. The local temperature change of the SOI substrate exactly beneath the CdS nanobelts is deduced from the ratio of the Stokes and anti-Stokes Raman intensities from the Si layer on the top of the SOI substrate. We have achieved a 30 and 20 K net cooling starting from 290 K under a 3.8 mW 514 nm and a 4.4 mW 532 nm pumping, respectively. In contrast, a laser heating effect has been observed pumped by 502 and 488 nm lasers. Theoretical analysis based on the general static heat conduction module in the Ansys program package is conducted, which agrees well with the experimental results. Our investigations demonstrate the laser cooling capability of an external thermal load, suggesting the applications of II-VI semiconductors in all-solid-state optical cryocoolers.

  2. Development and Electrochemical Investigations of an EIS- (Electrolyte-Insulator-Semiconductor) based Biosensor for Cyanide Detection

    PubMed Central

    Turek, Monika; Ketterer, Lothar; Claβen, Melanie; Berndt, Heinz K.; Elbers, Gereon; Krüger, Peter; Keusgen, Michael; Schöning, Michael J.

    2007-01-01

    A cyanide biosensor based on a pH-sensitive p-doped electrolyte-insulator-semiconductor (EIS) structure with an immobilised enzyme (cyanidase) is realised at the laboratory scale. The immobilisation of the cyanidase is performed in two distinct steps: first, the covalent coupling of cyanidase to an N-hydroxysuccinimide- (NHS) activated Sepharose™ gel and then, the physical entrapment of NHS-activated Sepharose™ with the immobilised cyanidase in a dialysis membrane onto the EIS structure. The immobilisation of the cyanidase to the NHS-activated Sepharose™ is studied by means of gel electrophoresis measurements and investigations using an ammonia- (NH3) selective electrode. For the electrochemical characterisation of the cyanide biosensor, capacitance/voltage and constant capacitance measurements, respectively, have been carried out. A differential measurement procedure is presented to evaluate the cyanide concentration-dependent biosensor signals.

  3. Model-based non-destructive investigation methods in semiconductor industry

    NASA Astrophysics Data System (ADS)

    Bilski, B.; Paz, V. Ferreras; Frenner, K.; Osten, W.

    2013-05-01

    Scatterometry is an investigation method that is gaining in importance in semiconductor industry. As an optical method it has distinct advantages that its competitor-methods do not possess: the ability for a quick and non-destructive measurement of fine features fabricated by modern generations of lithography machines. Scatterometry is very distinct from other measurement techniques also in this respect that it is a model-based method. As such it relies heavily on simulation and is essentially solving an inverse problem. In a forward optical measurement an imaging system processes the object information losing some fraction of information in the process. The measurement process in scatterometry follows the same pattern. The measurement result however is now compared against multiple simulated direct problems. The best fit between the simulation and the measurement is assumed to reconstruct the measured object.

  4. Simple and compact tunable semiconductor lasers based on novel half-wave coupler

    NASA Astrophysics Data System (ADS)

    He, Jian-Jun; Xiong, Xiaohai; Meng, Jianjun; Wu, Lin; Zhang, Sen; Liao, Xiaolu; Zou, Li

    2015-02-01

    Widely tunable semiconductor lasers based on a novel half-wave coupler are presented. They have been implemented in the form of half-wave coupled V-cavity and ring-FP cavities. By using the novel half-wave coupler, single-mode lasing with high side-mode-suppression-ratio is achieved. Single-electrode controlled wide-band wavelength tuning with Vernier effect is demonstrated. The full-band tuning of 50 channels with 100GHz spacing is realized by further employing temperature induced gain spectrum shift. The laser is packaged into a small-form-factor 9-pin box TOSA, and the electronic driver has been developed for the wavelength tuning and direct modulation. The advantages of compactness, fabrication simplicity, easy wavelength control and direct modulation allow the tunable lasers to be used in low-cost access and datacenter networks, as well as in portable devices for spectroscopic analysis.

  5. Characterization of TiO2-based semiconductors for photocatalysis by electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Ângelo, Joana; Magalhães, Pedro; Andrade, Luísa; Mendes, Adélio

    2016-11-01

    The photocatalytic activity of a commercial titanium dioxide (P25) and of an in-house prepared P25/graphene composite is assessed according to standard ISO 22197-1:2007. The photoactivity performances of bare and composite TiO2-based materials were further studied by electrochemical impedance spectroscopy (EIS) technique to better understand the function of the graphene in the composite. EIS experiments were performed using a three-electrode configuration, which allows obtaining more detailed information about the complex charge transfer phenomena at the semiconductor/electrolyte interface. The Randles equivalent circuit was selected as the most suitable for modelling the present photocatalysts. The use of the graphene composite allows a more effective charge separation with lower charge transfer resistance and less e-/h+ recombination on the composite photocatalyst, reflected in the higher values of NO conversion.

  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

    2016-07-12

    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.

  7. 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.

  8. Synchronized 4 × 12 GHz hybrid harmonically mode-locked semiconductor laser based on AWG.

    PubMed

    Liu, S; Lu, D; Zhang, R; Zhao, L; Wang, W; Broeke, R; Ji, C

    2016-05-02

    We report a monolithically integrated synchronized four wavelength channel mode-locked semiconductor laser chip based on arrayed waveguide grating and fabricated in the InP material system. Device fabrication was completed in a multiproject wafer foundry run on the Joint European Platform for Photonic Integration of Components and Circuits. The integrated photonic chip demonstrated 5th harmonic electrical hybrid mode-locking operation with four 400 GHz spacing wavelength channels and synchronized to a 12.7 GHz RF clock, for nearly transform-limited optical pulse trains from a single output waveguide. A low timing jitter of 0.349 ps, and RF frequency locking range of ~50 MHz were also achieved.

  9. All-optical sampling based on quantum-dot semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Wu, Chen; Wang, Yongjun; Wang, Lina

    2016-11-01

    In recent years, the all-optical signal processing system has become a hot research field of optical communication. This paper focused on the basic research of quantum-dot (QD) semiconductor optical amplifier (SOA) and studied its practical application to all-optical sampling. A multi-level dynamic physical model of QD-SOA is established, and its ultrafast dynamic characteristics are studied through theoretical and simulation research. For further study, an all-optical sampling scheme based on the nonlinear polarization rotation (NPR) effect of QD-SOA is also proposed. This paper analyzed the characteristics of optical switch window and investigated the influence of different control light pulses on switch performance. The presented optical sampling method has an important role in promoting the improvement of all-optical signal processing technology.

  10. Photodetectors Based on Two-Dimensional Layer-Structured Hybrid Lead Iodide Perovskite Semiconductors.

    PubMed

    Zhou, Jiachen; Chu, Yingli; Huang, Jia

    2016-10-05

    Hybrid lead iodide perovskite semiconductors have attracted intense research interests recently because of their easy fabrication processes and high power conversion efficiencies in photovoltaic applications. Layer-structured materials have interesting properties such as quantum confinement effect and tunable band gap due to the unique two-dimensional crystalline structures. ⟨100⟩-oriented layer-structured perovskite materials are inherited from three-dimensional ABX3 perovskite materials with a generalized formula of (RNH3)2(CH3NH3)n-1MnX3n+1, and adopt the Ruddlesden-Popper type crystalline structure. Here we report the synthesis and investigation of three layer-structured perovskite materials with different layer numbers: (C4H9NH3)2PbI4 (n = 1, one-layered perovskite), (C4H9NH3)2(CH3NH3)Pb2I7 (n = 2, two-layered perovskite) and (C4H9NH3)2(CH3NH3)2Pb3I10 (n = 3, three-layered perovskite). Their photoelectronic properties were investigated in related to their molecular structures. Photodetectors based on these two-dimensional (2D) layer-structured perovskite materials showed tunable photoresponse with short response time in milliseconds. The photodetectors based on three-layered perovskite showed better performances than those of the other two devices, in terms of output current, responsivity, Ilight/Idark ratio, and response time, because of its smaller optical band gap and more condensed microstructure comparing the other two materials. These results revealed the relationship between the molecular structures, film microstructures and the photoresponse properties of 2D layer-structured hybrid perovskites, and demonstrated their potentials as flexible, functional, and tunable semiconductors in optoelectronic applications, by taking advantage of their tunable quantum well molecular structure.

  11. Semiconductor detectors with proximity signal readout

    SciTech Connect

    Asztalos, Stephen J.

    2014-01-30

    Semiconductor-based radiation detectors are routinely used for the detection, imaging, and spectroscopy of x-rays, gamma rays, and charged particles for applications in the areas of nuclear and medical physics, astrophysics, environmental remediation, nuclear nonproliferation, and homeland security. Detectors used for imaging and particle tracking are more complex in that they typically must also measure the location of the radiation interaction in addition to the deposited energy. In such detectors, the position measurement is often achieved by dividing or segmenting the electrodes into many strips or pixels and then reading out the signals from all of the electrode segments. Fine electrode segmentation is problematic for many of the standard semiconductor detector technologies. Clearly there is a need for a semiconductor-based radiation detector technology that can achieve fine position resolution while maintaining the excellent energy resolution intrinsic to semiconductor detectors, can be fabricated through simple processes, does not require complex electrical interconnections to the detector, and can reduce the number of required channels of readout electronics. Proximity electrode signal readout (PESR), in which the electrodes are not in physical contact with the detector surface, satisfies this need.

  12. Fast-response humidity-sensing films based on methylene blue aggregates formed on nanoporous semiconductor films

    NASA Astrophysics Data System (ADS)

    Ishizaki, Ryota; Katoh, Ryuzi

    2016-05-01

    We prepared fast-response colorimetric humidity-sensing (vapochromic) films based on methylene blue adsorption onto nanoporous semiconductor (TiO2, Al2O3) films. Color changes caused by changes of humidity could be easily identified visually. A characteristic feature of the vapochromic films was their fast response to changes of humidity. We found that the response began to occur within 10 ms. The response was rapid because all the methylene blue molecules attached to the nanoporous semiconductor surface were directly exposed to the environment. We also deduced that the color changes were caused by structural changes of the methylene blue aggregates on the surface.

  13. Terrylenediimide-Based Intrinsic Theranostic Nanomedicines with High Photothermal Conversion Efficiency for Photoacoustic Imaging-Guided Cancer Therapy.

    PubMed

    Zhang, Shaobo; Guo, Weisheng; Wei, Jie; Li, Chan; Liang, Xing-Jie; Yin, Meizhen

    2017-03-21

    Activatable theranostic nanomedicines involved in photothermal therapy (PTT) have received constant attention as promising alternatives to traditional therapies in clinic. However, the theranostic nanomedicines widely suffer from instability and complicated nanostructures, which hamper potential clinical applications. Herein, we demonstrated a terrylenediimide (TDI)-poly(acrylic acid) (TPA)-based nanomedicine (TNM) platform used as an intrinsic theranostic agent. As an exploratory paradigm in seeking biomedical applications, TDI was modified with poly(acrylic acid)s (PAAs), resulting in eight-armed, star-like TPAs composed of an outside hydrophilic PAA corona and an inner hydrophobic TDI core. TNMs were readily fabricated via spontaneous self-assembly. Without additional vehicle and cargo, the as-prepared TNMs possessed a robust nanostructure and high photothermal conversion efficiency up to approximately 41%. The intrinsic theranostic properties of TNMs for use in photoacoustic (PA) imaging by a multispectral optoacoustic tomography system and in mediating photoinduced tumor ablation were intensely explored. Our results suggested that the TNMs could be successfully exploited as intrinsic theranostic agents for PA imaging-guided efficient tumor PTT. Thus, these TNMs hold great potential for (pre)clinical translational development.

  14. Intrinsic Geodesy

    DTIC Science & Technology

    1952-03-01

    Variation with the Height of the Principal Radii of Curvature in Somigliana’s Theory"), Bollettino di Geodesia e Scienze Affini, anno VIII, 1950 46...MARUSSI, A., "Principi di Geodesia Intrinseca applicati al campo di Somigliana" ("Principles of Intrinsic Geodesy Applied to Somigliana’s Field...34), Bollettino di Geodesia e Scienze Affini, anno VIII, 1950; and also Atti della XLII Riunione _dela Socie&Ljtsjjganaper il Progresso delle Scienze, Roma

  15. Intrinsic motivation factors based on the self-determinant theory for regular breast cancer screening.

    PubMed

    Jung, Su Mi; Jo, Heui-Sug

    2014-01-01

    The purpose of this study was to identify factors of intrinsic motivation that affect regular breast cancer screening and contribute to development of a program for strategies to improve effective breast cancer screening. Subjects were residing in South Korea Gangwon-Province and were female over 40 and under 69 years of age. For the investigation, the Intrinsic Motivation Inventory (IMI) was modified to the situation of cancer screening and was used to survey 905 inhabitants. Multinominal logistic regression analyses were conducted for regular breast cancer screening (RS), one-time breast cancer screening (OS) and non-breast cancer screening (NS). For statistical analysis, IBM SPSS 20.0 was utilized. The determinant factors between RS and NS were "perceived effort and choice" and "stress and strain" - internal motivations related to regular breast cancer screening. Also, determinant factors between RS and OS are "age" and "perceived effort and choice" for internal motivation related to cancer screening. To increase regular screening, strategies that address individual perceived effort and choice are recommended.

  16. Modeling photoinduced fluorescence enhancement in semiconductor nanocrystal arrays

    NASA Astrophysics Data System (ADS)

    Maenosono, Shinya

    2003-07-01

    Photoinduced fluorescence enhancement (PFE) in semiconductor nanocrystal (NC) arrays is modeled based on the rate equations for ground-state, excited-state and photoionized NCs in the array. The photoionization process is broken down into fast and slow ionization processes, which are expected to relate to blinking and darkening phenomena, respectively. Consequently, PFE behavior is found to change drastically, as it depends on both the intrinsic properties of NCs, and on external conditions, such as surface-capping molecules and atmosphere.

  17. Toward printed integrated circuits based on unipolar or ambipolar polymer semiconductors.

    PubMed

    Baeg, Kang-Jun; Caironi, Mario; Noh, Yong-Young

    2013-08-21

    For at least the past ten years printed electronics has promised to revolutionize our daily life by making cost-effective electronic circuits and sensors available through mass production techniques, for their ubiquitous applications in wearable components, rollable and conformable devices, and point-of-care applications. While passive components, such as conductors, resistors and capacitors, had already been fabricated by printing techniques at industrial scale, printing processes have been struggling to meet the requirements for mass-produced electronics and optoelectronics applications despite their great potential. In the case of logic integrated circuits (ICs), which constitute the focus of this Progress Report, the main limitations have been represented by the need of suitable functional inks, mainly high-mobility printable semiconductors and low sintering temperature conducting inks, and evoluted printing tools capable of higher resolution, registration and uniformity than needed in the conventional graphic arts printing sector. Solution-processable polymeric semiconductors are the best candidates to fulfill the requirements for printed logic ICs on flexible substrates, due to their superior processability, ease of tuning of their rheology parameters, and mechanical properties. One of the strongest limitations has been mainly represented by the low charge carrier mobility (μ) achievable with polymeric, organic field-effect transistors (OFETs). However, recently unprecedented values of μ ∼ 10 cm(2) /Vs have been achieved with solution-processed polymer based OFETs, a value competing with mobilities reported in organic single-crystals and exceeding the performances enabled by amorphous silicon (a-Si). Interestingly these values were achieved thanks to the design and synthesis of donor-acceptor copolymers, showing limited degree of order when processed in thin films and therefore fostering further studies on the reason leading to such improved charge

  18. Mobility anisotropy of two-dimensional semiconductors

    NASA Astrophysics Data System (ADS)

    Lang, Haifeng; Zhang, Shuqing; Liu, Zhirong

    2016-12-01

    The carrier mobility of anisotropic two-dimensional semiconductors under longitudinal acoustic phonon scattering was theoretically studied using deformation potential theory. Based on the Boltzmann equation with the relaxation time approximation, an analytic formula of intrinsic anisotropic mobility was derived, showing that the influence of effective mass on mobility anisotropy is larger than those of deformation potential constant or elastic modulus. Parameters were collected for various anisotropic two-dimensional materials (black phosphorus, Hittorf's phosphorus, BC2N , MXene, TiS3, and GeCH3) to calculate their mobility anisotropy. It was revealed that the anisotropic ratio is overestimated by the previously described method.

  19. 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.

  20. {100}<100> or 45.degree.-rotated {100}<100>, semiconductor-based, large-area, flexible, electronic devices

    SciTech Connect

    Goyal, Amit

    2012-05-15

    Novel articles and methods to fabricate the same resulting in flexible, {100}<100> or 45.degree.-rotated {100}<100> oriented, 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.

  1. Process simulation of carbon-based nanostructures in next-generation semiconductor integrated elements

    NASA Astrophysics Data System (ADS)

    Zempo, Yasunari; Ohno, Takahisa

    2013-03-01

    The trend in semiconductor devices leads us to develop new materials such as CNT and graphene from the point of high electric conductivity, new CMOS channel and interconnect, and low-voltage operation. To realize the carbon-based nano device, we have established HPCI carbon-based nano structure material consortium with industries, universities and institutions, aiming for R&D of nano electric fabrication. Our research is oriented to process simulations of nano structure manufacturing for optimal process design, property analyses for comprehensive assessment of the device applications, and providing industry-friendly environment that combines first principles and other methods (semi-empirical and classical). To promote device manufacturing with the help of HPCI (K computer), PHASE is our key software for electronic structure calculations based on DFT using plane wave base, which is not only wide applicable to various materials, and involves analytical tools for dielectric response, vibrational analysis, STM simulation, etc. but also compatible to wide range of platforms from note PC to SC, with well optimized parallel computation. Some of applications will be presented together with the scalability on K computer such as SiC defects, graphene growth, and conductivity analysis

  2. Recent Advances in Inorganic Nanoparticle-Based NIR Luminescence Imaging: Semiconductor Nanoparticles and Lanthanide Nanoparticles.

    PubMed

    Kim, Dokyoon; Lee, Nohyun; Park, Yong Il; Hyeon, Taeghwan

    2017-01-18

    Several types of nanoparticle-based imaging probes have been developed to replace conventional luminescent probes. For luminescence imaging, near-infrared (NIR) probes are useful in that they allow deep tissue penetration and high spatial resolution as a result of reduced light absorption/scattering and negligible autofluorescence in biological media. They rely on either an anti-Stokes or a Stokes shift process to generate luminescence. For example, transition metal-doped semiconductor nanoparticles and lanthanide-doped inorganic nanoparticles have been demonstrated as anti-Stokes shift-based agents that absorb NIR light through two- or three-photon absorption process and upconversion process, respectively. On the other hand, quantum dots (QDs) and lanthanide-doped nanoparticles that emit in NIR-II range (∼1000 to ∼1350 nm) were suggested as promising Stokes shift-based imaging agents. In this topical review, we summarize and discuss the recent progress in the development of inorganic nanoparticle-based luminescence imaging probes working in NIR range.

  3. Quantitative optical biomarkers of lung cancer based intrinsic two-photon excited fluorescence signal

    NASA Astrophysics Data System (ADS)

    Li, Jingwen; Zhan, Zhenlin; Lin, Hongxin; Zuo, Ning; Zhu, Xiaoqin; Xie, Shusen; Chen, Jianxin; Zhuo, Shuangmu

    2016-10-01

    Alterations in the elastic fibers have been implicated in lung cancer. However, the label-free, microscopic imaging of elastic fibers in situ remains a major challenge. Here, we present the use of intrinsic two-photon excited fluorescence (TPEF) signal as a novel means for quantification of the elastic fibers in intact fresh human lung tissues. We obtained the TPEF images of elastic fibers from ex vivo the human lung tissues. We found that three features, including the elastic fibers area, the elastic fibers orientation, the elastic fibers structure, provide the quantitative identification of lung cancer and the direct visual cues for cancer versus non-cancer areas. These results suggest that the TPEF signal can be used as the label-free optical biomarkers for rapid clinical lung diagnosis and instant image-guided surgery.

  4. Proton Conduction in a Phosphonate-Based Metal-Organic Framework Mediated by Intrinsic "Free Diffusion inside a Sphere".

    PubMed

    Pili, Simona; Argent, Stephen P; Morris, Christopher G; Rought, Peter; García-Sakai, Victoria; Silverwood, Ian P; Easun, Timothy L; Li, Ming; Warren, Mark R; Murray, Claire A; Tang, Chiu C; Yang, Sihai; Schröder, Martin

    2016-05-25

    Understanding the molecular mechanism of proton conduction is crucial for the design of new materials with improved conductivity. Quasi-elastic neutron scattering (QENS) has been used to probe the mechanism of proton diffusion within a new phosphonate-based metal-organic framework (MOF) material, MFM-500(Ni). QENS suggests that the proton conductivity (4.5 × 10(-4) S/cm at 98% relative humidity and 25 °C) of MFM-500(Ni) is mediated by intrinsic "free diffusion inside a sphere", representing the first example of such a mechanism observed in MOFs.

  5. Semiconductor ultraviolet photodetectors based on ZnO and MgxZn1-xO

    NASA Astrophysics Data System (ADS)

    Hou, Yaonan; Mei, Zengxia; Du, Xiaolong

    2014-07-01

    It is indispensable to develop wide-band-gap based ultraviolet (UV) photodetectors (PDs), which are one of the basic building blocks of solid state UV optoelectronic devices. In the last two decades, we have witnessed the renaissance of ZnO as a wide-band-gap semiconductor and an enormous development of ZnO-based UV PDs as a result of its superb optical and electronic properties. Since the first demonstration, a great variety of UV PDs based on ZnO and its related materials have been proposed and demonstrated. These PDs, with diverse device geometries, exhibit either high performance or multiple functions, reflecting a state-of-the-art technology of UV optoelectronics. In this review, we study the latest progress of UV PDs made on ZnO and MgxZn1-xO, which is a representative alloy of ZnO for band-gap engineering techniques. The discussion focuses on the device performance and the behind device physics according to the architecture of UV PDs.

  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. Metal-oxide-semiconductor based gas sensors: screening, preparation, and integration.

    PubMed

    Zhang, Jian; Qin, Ziyu; Zeng, Dawen; Xie, Changsheng

    2017-03-01

    Metal-oxide-semiconductor (MOS) based gas sensors have been considered a promising candidate for gas detection over the past few years. However, the sensing properties of MOS-based gas sensors also need to be further enhanced to satisfy the higher requirements for specific applications, such as medical diagnosis based on human breath, gas detection in harsh environments, etc. In these fields, excellent selectivity, low power consumption, a fast response/recovery rate, low humidity dependence and a low limit of detection concentration should be fulfilled simultaneously, which pose great challenges to the MOS-based gas sensors. Recently, in order to improve the sensing performances of MOS-based gas sensors, more and more researchers have carried out extensive research from theory to practice. For a similar purpose, on the basis of the whole fabrication process of gas sensors, this review gives a presentation of the important role of screening and the recent developments in high throughput screening. Subsequently, together with the sensing mechanism, the factors influencing the sensing properties of MOSs involved in material preparation processes were also discussed in detail. It was concluded that the sensing properties of MOSs not only depend on the morphological structure (particle size, morphology, pore size, etc.), but also rely on the defect structure and heterointerface structure (grain boundaries, heterointerfaces, defect concentrations, etc.). Therefore, the material-sensor integration was also introduced to maintain the structural stability in the sensor fabrication process, ensuring the sensing stability of MOS-based gas sensors. Finally, the perspectives of the MOS-based gas sensors in the aspects of fundamental research and the improvements in the sensing properties are pointed out.

  8. Feature analysis and classification of manufacturing signatures based on semiconductor wafermaps

    SciTech Connect

    Tobin, K.W.; Gleason, S.S.; Karnowski, T.P.; Cohen, S.L.

    1997-02-01

    Automated tools for semiconductor wafer defect analysis are becoming more necessary as device densities and wafer sizes continue to increase. Trends towards larger wafer formats and smaller critical dimensions have caused an exponential increase in the volume of defect data which must be analyzed and stored. To accommodate these changing factors, automatic analysis tools are required that can efficiently and robustly process the increasing amounts of data, and thus quickly characterize manufacturing processes and accelerate yield learning. During the first year of this cooperative research project between SEMATECH and the Oak Ridge National Laboratory, a robust methodology for segmenting signature events prior to feature analysis and classification was developed. Based on the results of this segmentation procedure, a feature measurement strategy has been designed based on interviews with process engineers coupled with the analysis of approximately 1500 electronic wafermap files. In this paper, the authors represent an automated procedure to rank and select relevant features for use with a fuzzy pair-wise classifier and give examples of the efficacy of the approach taken. Results of the feature selection process are given for two uniquely different types of class data to demonstrate a general improvement in classifier performance.

  9. A 6 GW nanosecond solid-state generator based on semiconductor opening switch

    NASA Astrophysics Data System (ADS)

    Gusev, A. I.; Pedos, M. S.; Rukin, S. N.; Timoshenkov, S. P.; Tsyranov, S. N.

    2015-11-01

    In this paper, a nanosecond all solid-state generator providing peak power of up to 6 GW, output voltage of 500-900 kV, pulse length (full width at half maximum) of ˜7 ns across external loads of 40-100 Ω, and pulse repetition frequency up to 1 kHz in burst operation mode is described. The output pulse is generated by a semiconductor opening switch (SOS). A new SOS pumping circuit based on a double forming line (DFL) is proposed and its implementation described. As compared with a lumped capacitors-based pumping circuit, the DFL allows minimization of the inductance and stray capacitance of the reverse pumping circuit, and thus, an increase in the SOS cutoff current amplitude and generator output peak power as a whole. The pumping circuit provides a reverse current increasing through the SOS up to 14 kA within ˜12 ns. The SOS cuts off the current in ˜2 ns; the current cutoff rate reaches 7 kA/ns. The SOS braking power (the product of peak voltage and cutoff current) for an external load above 100 Ω is 13 GW.

  10. An Ultrafast Switchable Terahertz Polarization Modulator Based on III-V Semiconductor Nanowires.

    PubMed

    Baig, Sarwat A; Boland, Jessica L; Damry, Djamshid A; Tan, H Hoe; Jagadish, Chennupati; Joyce, Hannah J; Johnston, Michael B

    2017-04-12

    Progress in the terahertz (THz) region of the electromagnetic spectrum is undergoing major advances, with advanced THz sources and detectors being developed at a rapid pace. Yet, ultrafast THz communication is still to be realized, owing to the lack of practical and effective THz modulators. Here, we present a novel ultrafast active THz polarization modulator based on GaAs semiconductor nanowires arranged in a wire-grid configuration. We utilize an optical pump-terahertz probe spectroscopy system and vary the polarization of the optical pump beam to demonstrate ultrafast THz modulation with a switching time of less than 5 ps and a modulation depth of -8 dB. We achieve an extinction of over 13% and a dynamic range of -9 dB, comparable to microsecond-switchable graphene- and metamaterial-based THz modulators, and surpassing the performance of optically switchable carbon nanotube THz polarizers. We show a broad bandwidth for THz modulation between 0.1 and 4 THz. Thus, this work presents the first THz modulator which combines not only a large modulation depth but also a broad bandwidth and picosecond time resolution for THz intensity and phase modulation, making it an ideal candidate for ultrafast THz communication.

  11. A micromachined thermo-optical light modulator based on semiconductor-to-metal phase transition

    NASA Astrophysics Data System (ADS)

    Jiang, Lijun

    In this research, a micromachined thermo-optical light modulator was realized based on the semiconductor-to-metal phase transition of vanadium dioxide (VO2) thin film. VO2 undergoes a reversible phase transition at approximately 68°C, which is accompanied with drastic changes in its electrical and optical properties. The sharp electrical resistivity change can be as great as five orders. Optically, VO2 film will switch from a transparent semiconductor phase to a reflective metal phase upon the phase transition. The light modulator in this research exploits this phase transition related optical switching by using surface micromachined low-thermal-mass pixels to achieve good thermal isolations, which ensures that each pixel can be individually switched without cross talking. In operation, the pixel temperature was controlled by integrated resistor on each pixel or spatially addressed thermal radiation sources. Active VO2 thin film was synthesized by thermal oxidation of e-beam evaporated vanadium metal film. The oxidized film exhibits a phase transition at ˜65°C with a hysteresis of about 15°C. A transmittance switching from ˜90% to ˜30% in the near infrared and a reflectance switching from ˜50% to ˜15% in the visible have been achieved. The surface microstructure was studied and correlated to its optical properties. A study on the hysteresis loop reveals that the VO2 can be repetitively switched between the "on" and "off" states. The micromachined thermal isolation pixel was a bridge-like silicon dioxide platform suspended with narrow supporting legs. The pixel design was optimized with both thermal and optical simulations. The VO2 light modulator was fabricated by surface micromachining based on dry processing. Silicon dioxide was deposited on a polyimide sacrificial layer by PECVD and patterned to form the structural pixel. Vanadium film was e-beam evaporated and patterned with lift-off process. It was thermally oxidized into VO2 at 390°C. The thermal

  12. A polyaniline based intrinsically conducting coating for corrosion protection of structural steels.

    PubMed

    Pan, Tongyan; Wang, Zhaoyang

    2013-11-01

    Among the various corrosion protection strategies for structural steels, coating techniques provide the most cost-effective protection and have been used as the primary mode of corrosion protection. Existing coating techniques however have been used mainly for their barrier capability and therefore all have a limited service life due to oxidation aging, electrolytic degradation, or various inadvertent defects and flaws occurred in and after coating applications. This work investigated the anti-corrosion potential of a π-conjugated polymer-polyaniline (PANi), which was doped into an intrinsically conducting polymer and then included in a two-layer coating system as a primer layer. To achieve a long service life, the primer layer was made by mixing the conductive PANi in a waterborne poly-vinyl butyral solution to provide strong adhesion to steel surface, and then topcoated with a layer of elastomer-modified polyethylene to obtain extra mechanical and barrier protections. Two ASTM standard tests were conducted to evaluate the corrosion durability and tensile adhesion of the two-layer system, in which the system demonstrated superior performance. The Scanning Kelvin Probe Force Microscopy (SKPFM) was used to provide the microscopic evidences for the outstanding performance.

  13. SS-Stabilizing Proteins Rationally: Intrinsic Disorder-Based Design of Stabilizing Disulphide Bridges in GFP.

    PubMed

    Melnik, Bogdan S; Povarnitsyna, Tatiana V; Glukhov, Anatoly S; Melnik, Tatyana N; Uversky, Vladimir N; Sarma, Ramaswamy H

    2012-01-01

    Abstract The most attractive and methodologically convenient way to enhance protein stability is via the introduction of disulphide bond(s). However, the effect of the artificially introduced SS-bond on protein stability is often quite unpredictable. This raises the question of how to choose the protein sites in an intelligent manner, so that the 'fastening' of these sites by the SS-bond(s) would provide maximal protein stability. We hypothesize that the successful design of a stabilizing SS-bond requires finding highly mobile protein regions. Using GFP as an illustrative example, we demonstrate that the knowledge of the peculiarities of the intramolecular hydrophobic interactions, combined with the understanding of the local intrinsic disorder propensities (that can be evaluated by various disorder predictors, e.g., PONDRFIT), is sufficient to find the candidate sites for the introduction of stabilizing SS-bridge(s). In fact, our analysis revealed that the insertion of the engineered SS-bridge between two highly flexible regions of GFP noticeably increased the conformational stability of this protein toward the thermal and chemical unfolding. Therefore, our study represents a novel approach for the rational design of stabilizing disulphide bridges in proteins.

  14. Determination of localized trap parameters in organic semiconductors using charge based deep level transient spectroscopy (Q-DLTS)

    NASA Astrophysics Data System (ADS)

    Nguyen, T. P.; Ip, J.; Gaudin, O.; Jackman, R. B.

    2004-07-01

    In organic light emitting diodes (OLEDs), localized traps within the band gap of the organic semiconductor play a fundamental role in the light emission process. Trapped charge carriers cannot recombine efficiently and therefore do not contribute to the emission. The determination of the trap parameters in the emitting layer is especially important in the evaluation of the efficiency of such devices. We have investigated the trap parameters in some organic semiconductors using the Charge-Based Deep Level Transient Spectroscopy (Q-DLTS) technique. Examples are given in poly(p phenylene vinylene) or PPV and 4, 4'-bis(4-dimethylaminostryryl) or DMASB, for which the trap level, the trap density, and the capture cross section were determined. In addition, it was possible to identify the carrier type (minority and majority) traps in these semiconductors. The results were compared with those obtained in similar materials by other techniques such as conventional DLTS, thermally stimulated currents (TSC), impedance measurements. Q-DLTS appears to be a powerful tool for studying defects in organic semiconductors.

  15. Exploring the intrinsic differences among breast tumor subtypes defined using immunohistochemistry markers based on the decision tree

    PubMed Central

    Li, Yang; Tang, Xu-Qing; Bai, Zhonghu; Dai, Xiaofeng

    2016-01-01

    Exploring the intrinsic differences among breast cancer subtypes is of crucial importance for precise diagnosis and therapeutic decision-making in diseases of high heterogeneity. The subtypes defined with several layers of information are related but not consistent, especially using immunohistochemistry markers and gene expression profiling. Here, we explored the intrinsic differences among the subtypes defined by the estrogen receptor, progesterone receptor and human epidermal growth factor receptor 2 based on the decision tree. We identified 30 mRNAs and 7 miRNAs differentially expressed along the tree’s branches. The final signature panel contained 30 mRNAs, whose performance was validated using two public datasets based on 3 well-known classifiers. The network and pathway analysis were explored for feature genes, from which key molecules including FOXQ1 and SFRP1 were revealed to be densely connected with other molecules and participate in the validated metabolic pathways. Our study uncovered the differences among the four IHC-defined breast tumor subtypes at the mRNA and miRNA levels, presented a novel signature for breast tumor subtyping, and identified several key molecules potentially driving the heterogeneity of such tumors. The results help us further understand breast tumor heterogeneity, which could be availed in clinics. PMID:27786176

  16. The intrinsic periodic fluctuation of forest: a theoretical model based on diffusion equation

    NASA Astrophysics Data System (ADS)

    Zhou, J.; Lin, G., Sr.

    2015-12-01

    Most forest dynamic models predict the stable state of size structure as well as the total basal area and biomass in mature forest, the variation of forest stands are mainly driven by environmental factors after the equilibrium has been reached. However, although the predicted power-law size-frequency distribution does exist in analysis of many forest inventory data sets, the estimated distribution exponents are always shifting between -2 and -4, and has a positive correlation with the mean value of DBH. This regular pattern can not be explained by the effects of stochastic disturbances on forest stands. Here, we adopted the partial differential equation (PDE) approach to deduce the systematic behavior of an ideal forest, by solving the diffusion equation under the restricted condition of invariable resource occupation, a periodic solution was gotten to meet the variable performance of forest size structure while the former models with stable performance were just a special case of the periodic solution when the fluctuation frequency equals zero. In our results, the number of individuals in each size class was the function of individual growth rate(G), mortality(M), size(D) and time(T), by borrowing the conclusion of allometric theory on these parameters, the results perfectly reflected the observed "exponent-mean DBH" relationship and also gave a logically complete description to the time varying form of forest size-frequency distribution. Our model implies that the total biomass of a forest can never reach a stable equilibrium state even in the absence of disturbances and climate regime shift, we propose the idea of intrinsic fluctuation property of forest and hope to provide a new perspective on forest dynamics and carbon cycle research.

  17. All-solid-state repetitive semiconductor opening switch-based short pulse generator.

    PubMed

    Ding, Zhenjie; Hao, Qingsong; Hu, Long; Su, Jiancang; Liu, Guozhi

    2009-09-01

    The operating characteristics of a semiconductor opening switch (SOS) are determined by its pumping circuit parameters. SOS is still able to cut off the current when pumping current duration falls to the order of tens of nanoseconds and a short pulse forms simultaneously in the output load. An all-solid-state repetitive SOS-based short pulse generator (SPG100) with a three-level magnetic pulse compression unit was successfully constructed. The generator adopts magnetic pulse compression unit with metallic glass and ferrite cores, which compresses a 600 V, 10 mus primary pulse into short pulse with forward pumping current of 825 A, 60 ns and reverse pumping current of 1.3 kA, 30 ns. The current is sent to SOS in which the reverse pumping current is interrupted. The generator is capable of providing a pulse with the voltage of 120 kV and duration of 5-6 ns while output load being 125 Omega. The highest repetition rate is up to 1 kHz.

  18. Artificial Neuron Based on Integrated Semiconductor Quantum Dot Mode-Locked Lasers

    PubMed Central

    Mesaritakis, Charis; Kapsalis, Alexandros; Bogris, Adonis; Syvridis, Dimitris

    2016-01-01

    Neuro-inspired implementations have attracted strong interest as a power efficient and robust alternative to the digital model of computation with a broad range of applications. Especially, neuro-mimetic systems able to produce and process spike-encoding schemes can offer merits like high noise-resiliency and increased computational efficiency. Towards this direction, integrated photonics can be an auspicious platform due to its multi-GHz bandwidth, its high wall-plug efficiency and the strong similarity of its dynamics under excitation with biological spiking neurons. Here, we propose an integrated all-optical neuron based on an InAs/InGaAs semiconductor quantum-dot passively mode-locked laser. The multi-band emission capabilities of these lasers allows, through waveband switching, the emulation of the excitation and inhibition modes of operation. Frequency-response effects, similar to biological neural circuits, are observed just as in a typical two-section excitable laser. The demonstrated optical building block can pave the way for high-speed photonic integrated systems able to address tasks ranging from pattern recognition to cognitive spectrum management and multi-sensory data processing. PMID:27991574

  19. Artificial Neuron Based on Integrated Semiconductor Quantum Dot Mode-Locked Lasers.

    PubMed

    Mesaritakis, Charis; Kapsalis, Alexandros; Bogris, Adonis; Syvridis, Dimitris

    2016-12-19

    Neuro-inspired implementations have attracted strong interest as a power efficient and robust alternative to the digital model of computation with a broad range of applications. Especially, neuro-mimetic systems able to produce and process spike-encoding schemes can offer merits like high noise-resiliency and increased computational efficiency. Towards this direction, integrated photonics can be an auspicious platform due to its multi-GHz bandwidth, its high wall-plug efficiency and the strong similarity of its dynamics under excitation with biological spiking neurons. Here, we propose an integrated all-optical neuron based on an InAs/InGaAs semiconductor quantum-dot passively mode-locked laser. The multi-band emission capabilities of these lasers allows, through waveband switching, the emulation of the excitation and inhibition modes of operation. Frequency-response effects, similar to biological neural circuits, are observed just as in a typical two-section excitable laser. The demonstrated optical building block can pave the way for high-speed photonic integrated systems able to address tasks ranging from pattern recognition to cognitive spectrum management and multi-sensory data processing.

  20. Artificial Neuron Based on Integrated Semiconductor Quantum Dot Mode-Locked Lasers

    NASA Astrophysics Data System (ADS)

    Mesaritakis, Charis; Kapsalis, Alexandros; Bogris, Adonis; Syvridis, Dimitris

    2016-12-01

    Neuro-inspired implementations have attracted strong interest as a power efficient and robust alternative to the digital model of computation with a broad range of applications. Especially, neuro-mimetic systems able to produce and process spike-encoding schemes can offer merits like high noise-resiliency and increased computational efficiency. Towards this direction, integrated photonics can be an auspicious platform due to its multi-GHz bandwidth, its high wall-plug efficiency and the strong similarity of its dynamics under excitation with biological spiking neurons. Here, we propose an integrated all-optical neuron based on an InAs/InGaAs semiconductor quantum-dot passively mode-locked laser. The multi-band emission capabilities of these lasers allows, through waveband switching, the emulation of the excitation and inhibition modes of operation. Frequency-response effects, similar to biological neural circuits, are observed just as in a typical two-section excitable laser. The demonstrated optical building block can pave the way for high-speed photonic integrated systems able to address tasks ranging from pattern recognition to cognitive spectrum management and multi-sensory data processing.

  1. Effective coupled optoelectrical design method for fully infiltrated semiconductor nanowires based hybrid solar cells.

    PubMed

    Wu, Dan; Tang, Xiaohong; Wang, Kai; Li, Xianqiang

    2016-10-31

    We present a novel coupled design method that both optimizes light absorption and predicts electrical performance of fully infiltrated inorganic semiconductor nanowires (NWs) based hybrid solar cells (HSC). This method provides a thorough insight of hybrid photovoltaic process as a function of geometrical parameters of NWs. An active layer consisting of GaAs NWs as acceptor and poly(3-hexylthiophene-2,5-diyl) (P3HT) as donor were used as a design example. Absorption spectra features were studied by the evolution of the leaky modes and Fabry-Perot resonance with wavelength focusing firstly on the GaAs/air layer before extending to GaAs/P3HT hybrid active layer. The highest absorption efficiency reached 39% for the hybrid active layer of 2 μm thickness under AM 1.5G illumination. Combined with the optical absorption analysis, our method further codesigns the energy harvesting to predict electrical performance of HSC considering exciton dissociation efficiencies within both inorganic NWs and a polymeric shell of 20 nm thickness. The validity of the simulation model was also proved by the well agreement of the simulation results with the published experimental work indicating an effective guidance for future high performance HSC design.

  2. Large anomalous Hall effect in a silicon-based magnetic semiconductor.

    PubMed

    Manyala, Ncholu; Sidis, Yvan; DiTusa, John F; Aeppli, Gabriel; Young, David P; Fisk, Zachary

    2004-04-01

    Magnetic semiconductors are attracting great interest because of their potential use for spintronics, a new technology that merges electronics with the manipulation of conduction electron spins. (GaMn)As and (GaMn)N have recently emerged as the most popular materials for this new technology, and although their Curie temperatures are rising towards room temperature, these materials can only be fabricated in thin-film form, are heavily defective, and are not obviously compatible with Si. We show here that it is productive to consider transition metal monosilicides as potential alternatives. In particular, we report the discovery that the bulk metallic magnets derived from doping the narrow-gap insulator FeSi with Co share the very high anomalous Hall conductance of (GaMn)As, while displaying Curie temperatures as high as 53 K. Our work opens up a new arena for spintronics, involving a bulk material based only on transition metals and Si, which displays large magnetic-field effects on its electrical properties.

  3. A physics-based model of threshold voltage for amorphous oxide semiconductor thin-film transistors

    NASA Astrophysics Data System (ADS)

    Chen, Chi-Le; Chen, Wei-Feng; Zhou, Lei; Wu, Wei-Jing; Xu, Miao; Wang, Lei; Peng, Jun-Biao

    2016-03-01

    In the application of the Lambert W function, the surface potential for amorphous oxide semiconductor thin-film transistors (AOS TFTs) under the subthreshold region is approximated by an asymptotic equation only considering the tail states. While the surface potential under the above-threshold region is approximated by another asymptotic equation only considering the free carriers. The intersection point between these two asymptotic equations represents the transition from the weak accumulation to the strong accumulation. Therefore, the gate voltage corresponding to the intersection point is defined as threshold voltage of AOS TFTs. As a result, an analytical expression for the threshold voltage is derived from this novel definition. It is shown that the threshold voltage achieved by the proposed physics-based model is agreeable with that extracted by the conventional linear extrapolation method. Furthermore, we find that the free charge per unit area in the channel starts increasing sharply from the threshold voltage point, where the concentration of the free carriers is a little larger than that of the localized carriers. The proposed model for the threshold voltage of AOS TFTs is not only physically meaningful but also mathematically convenient, so it is expected to be useful for characterizing and modeling AOS TFTs.

  4. PRECISION CLEANING OF SEMICONDUCTOR SURFACES USING CARBON DIOXIDE-BASED FLUIDS

    SciTech Connect

    J. RUBIN; L. SIVILS; A. BUSNAINA

    1999-07-01

    The Los Alamos National Laboratory, on behalf of the Hewlett-Packard Company, is conducting tests of a closed-loop CO{sub 2}-based supercritical fluid process, known as Supercritical CO{sub 2} Resist Remover (SCORR). We have shown that this treatment process is effective in removing hard-baked, ion-implanted photoresists, and appears to be fully compatible with metallization systems. We are now performing experiments on production wafers to assess not only photoresist removal, but also residual surface contamination due to particulate and trace metals. Dense-phase (liquid or supercritical) CO{sub 2}, since it is non-polar, acts like an organic solvent and therefore has an inherently high volubility for organic compounds such as oils and greases. Also, dense CO{sub 2} has a low-viscosity and a low dielectric constant. Finally, CO{sub 2} in the liquid and supercritical fluid states can solubilize metal completing agents and surfactants. This combination of properties has interesting implications for the removal not only of organic films, but also trace metals and inorganic particulate. In this paper we discuss the possibility of using CO{sub 2} as a precision-cleaning solvent, with particular emphasis on semiconductor surfaces.

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

    PubMed Central

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

    2008-01-01

    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

  6. Semiconductor and carbon-based fluorescent nanodots: the need for consistency.

    PubMed

    Cayuela, A; Soriano, M L; Carrillo-Carrión, C; Valcárcel, M

    2016-01-25

    Fluorescent nanodots have become increasingly prevalent in a wide variety of applications with special interest in analytical and biomedical fields. The present overview focuses on three main aspects: (i) a systematic description and reasonable classification of the most relevant types of fluorescent nanodots according to their nature, quantum confinement and crystalline structure is provided, starting with a clear distinction between semiconductor and carbon-based dots (graphene quantum dots, carbon quantum dots and carbon nanodots). A new set of abbreviations and definitions for them to avoid contradictions found in literature is also proposed; (ii) a rational classification allows the establishment of clear-cut differences and similarities among them. From a basic point of view, the origins of the photoluminescence of the different nanodots are also established, which is a relevant contribution of this overview. Additionally, the most outstanding similarities and differences in a great variety of criteria (i.e. year of discovery, synthesis, the physico-chemical characteristics like structure, nature, shape, size, quantum confinement, toxicity and solubility, the optical characteristics including the quantum yield and lifetime, limitations, applications as well as the evolution of publications) are thoroughly outlined; and (iii) finally, the promising future of fluorescent nanodots in both analytical and biomedical fields is discussed using selected examples of relevant applications.

  7. Band gaps by design: Tailoring ZnO based semiconductor alloy films

    NASA Astrophysics Data System (ADS)

    Che, Hui

    This dissertation presents the research on the synthesis of ZnO based ternary semiconductor alloy films with tailored band gaps and the studies in their structural and optical properties. MgxZn1-xO alloys expanded the band gaps from 3.20 eV to deeper UV region of 5.67 eV. While ZnSxO1-x reduced the band gaps into the visible region of 2.9 eV. The alloy films were grown via reactive sputtering deposition, which is a cost effective and environment-friendly technique. An analytical method was developed for accurately determining the band gaps of alloys via transmission spectroscopy. The structural inhomogeneity issues in the Mg xZn1-xO alloys were studied via Selective Resonant Raman Scattering. Urbach energy analysis and Raman spectral line width analysis indicated that structural defects and alloy composition fluctuations in the MgxZn1-xO alloy films are the dominant origins of the localized electronic tail states and the Raman line broadening. While the Raman line broadening due to the anharmonicity of the alloys is not significant. The achievement of ZnSxO1-x alloy films with reduced band gaps paved the way for further research on band gap engineering of ZnO in the visible region.

  8. Multi-immunosensors based on electrolite-insulator-semiconductor structures for determination of some herbicides

    NASA Astrophysics Data System (ADS)

    Starodub, Nickolaj F.; Starodub, Valentyna M.; Krivenchuk, Vladimir E.; Shapovalenko, Valentyna F.

    2002-02-01

    New type of the multi-immune sensor was elaborated. It is based on electrolyte-insulator-semiconductors structures and intended for determination of such herbicides as simazine, atrazine and 2,4-D. The specific antibodies were immobilized on nitrocellulose disks, which were placed in measuring cells. The analysis was fulfilled by sequential saturation of antibodies, left unbound after their exposure to native herbicide in investigated sample, with labelled herbicide. If horse radish peroxidase (HRP) was used as label the sensitivity of this multi-immune sensor was about 5 and 1.25 (mu) g/L for simazine and 2,4-D, respectively. At the changing of HRP by (beta) -glucose oxidase the sensitivity of analysis of these herbicides increased approximately in 5 times. The linear plots of the registered concentrations were in the range of 1,0-150,0 and 0,25-150,0 ng/mL for simazine and 2,4-D respectively. It was recommended to use the developed immune sensor for wide screening of herbicides in environment. The ways for increasing of its sensitivity were proposed.

  9. 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.

  10. Silicon-on-insulator-based complementary metal oxide semiconductor integrated optoelectronic platform for biomedical applications

    NASA Astrophysics Data System (ADS)

    Mujeeb-U-Rahman, Muhammad; Scherer, Axel

    2016-12-01

    Microscale optical devices enabled by wireless power harvesting and telemetry facilitate manipulation and testing of localized biological environments (e.g., neural recording and stimulation, targeted delivery to cancer cells). Design of integrated microsystems utilizing optical power harvesting and telemetry will enable complex in vivo applications like actuating a single nerve, without the difficult requirement of extreme optical focusing or use of nanoparticles. Silicon-on-insulator (SOI)-based platforms provide a very powerful architecture for such miniaturized platforms as these can be used to fabricate both optoelectronic and microelectronic devices on the same substrate. Near-infrared biomedical optics can be effectively utilized for optical power harvesting to generate optimal results compared with other methods (e.g., RF and acoustic) at submillimeter size scales intended for such designs. We present design and integration techniques of optical power harvesting structures with complementary metal oxide semiconductor platforms using SOI technologies along with monolithically integrated electronics. Such platforms can become the basis of optoelectronic biomedical systems including implants and lab-on-chip systems.

  11. 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.

  12. 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.

  13. 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.

  14. A FRET-Based Method for Probing the Conformational Behavior of an Intrinsically Disordered Repeat Domain from Bordetella pertussis Adenylate Cyclase

    DTIC Science & Technology

    2009-10-22

    2003) Designing repeat proteins: Well-expressed, soluble and stable proteins from combinatorial libraries of consensus ankyrin repeat proteins. J. Mol...A FRET-Based Method for Probing the Conformational Behavior of an Intrinsically Disordered Repeat Domain from Bordetella pertussis Adenylate Cyclase...changes exhibited by intrinsically disordered proteins is necessary as we continue to unravel their myriad biological functions. In repeats in toxin

  15. Relaxivity of Gd-based contrast agents on X nuclei with long intrinsic relaxation times in aqueous solutions

    PubMed Central

    van Heeswijk, Ruud B.; Laus, Sabrina; Morgenthaler, Florence D.; Gruetter, Rolf

    2007-01-01

    The relaxivity of commercially available gadolinium-based contrast agents was studied for X-nuclei resonances with long intrinsic relaxation times ranging between 6 and several hundred seconds. Omniscan in pure 13C formic acid had a relaxivity of 2.9 mM-1 s-1, whereas its relaxivity on glutamate C1 and C5 in aqueous solution was ∼0.5 mM-1 s-1. Both relaxivities allow the preparation of solutions with a predetermined short T1 suggest that in vitro substantial sensitivity gains in their measurement can be achieved. 6Li has a long intrinsic relaxation time, on the order of several minutes, which was strongly affected by the contrast agents. Relaxivity ranged from ∼0.1 mM-1 s-1 for Omniscan to 0.3 for Magnevist, whereas the relaxivity of Gd-DOTP was at 11 mM-1 s-1 two orders of magnitude higher. Overall these experiments suggest that the presence of 0.1-10 μM contrast agents should be detectable, provided sufficient sensitivity is available, such as that afforded by hyperpolarization, recently introduced to in vivo imaging. PMID:17448617

  16. Facing the sunrise: cultural worldview underlying intrinsic-based encoding of absolute frames of reference in aymara.

    PubMed

    Núñez, Rafael E; Cornejo, Carlos

    2012-08-01

    The Aymara of the Andes use absolute (cardinal) frames of reference for describing the relative position of ordinary objects. However, rather than encoding them in available absolute lexemes, they do it in lexemes that are intrinsic to the body: nayra ("front") and qhipa ("back"), denoting east and west, respectively. Why? We use different but complementary ethnographic methods to investigate the nature of this encoding: (a) linguistic expressions and speech-gesture co-production, (b) linguistic patterns in the distinct regional Spanish-based variety Castellano Andino (CA), (c) metaphorical extensions of CA's spatial patterns to temporal ones, and (d) layouts of traditional houses. Findings indicate that, following fundamental principles of Aymara cosmology, people, objects, and land--as a whole--are conceived as having an implicit canonical orientation facing east, a primary landmark determined by the sunrise. The above bodily based lexicalizations are thus linguistic manifestations of a broader macro-cultural worldview and its psycho-cognitive reality.

  17. Rhombohedral cubic semiconductor materials on trigonal substrate with single crystal properties and devices based on such materials

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); Choi, Sang Hyouk (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor)

    2012-01-01

    Growth conditions are developed, based on a temperature-dependent alignment model, to enable formation of cubic group IV, group II-V and group II-VI crystals in the [111] orientation on the basal (0001) plane of trigonal crystal substrates, controlled such that the volume percentage of primary twin crystal is reduced from about 40% to about 0.3%, compared to the majority single crystal. The control of stacking faults in this and other embodiments can yield single crystalline semiconductors based on these materials that are substantially without defects, or improved thermoelectric materials with twinned crystals for phonon scattering while maintaining electrical integrity. These methods can selectively yield a cubic-on-trigonal epitaxial semiconductor material in which the cubic layer is substantially either directly aligned, or 60 degrees-rotated from, the underlying trigonal material.

  18. Temperature Dependence of Density, Viscosity and Electrical Conductivity for Hg-Based II-VI Semiconductor Melts

    NASA Technical Reports Server (NTRS)

    Li, C.; Ban, H.; Lin, B.; Scripa, R. N.; Su, C.-H.; Lehoczky, S. L.

    2004-01-01

    The relaxation phenomenon of semiconductor melts, or the change of melt structure with time, impacts the crystal growth process and the eventual quality of the crystal. The thermophysical properties of the melt are good indicators of such changes in melt structure. Also, thermophysical properties are essential to the accurate predication of the crystal growth process by computational modeling. Currently, the temperature dependent thermophysical property data for the Hg-based II-VI semiconductor melts are scarce. This paper reports the results on the temperature dependence of melt density, viscosity and electrical conductivity of Hg-based II-VI compounds. The melt density was measured using a pycnometric method, and the viscosity and electrical conductivity were measured by a transient torque method. Results were compared with available published data and showed good agreement. The implication of the structural changes at different temperature ranges was also studied and discussed.

  19. A next generation semiconductor based sequencing approach for the identification of meat species in DNA mixtures.

    PubMed

    Bertolini, Francesca; Ghionda, Marco Ciro; D'Alessandro, Enrico; Geraci, Claudia; Chiofalo, Vincenzo; Fontanesi, Luca

    2015-01-01

    The identification of the species of origin of meat and meat products is an important issue to prevent and detect frauds that might have economic, ethical and health implications. In this paper we evaluated the potential of the next generation semiconductor based sequencing technology (Ion Torrent Personal Genome Machine) for the identification of DNA from meat species (pig, horse, cattle, sheep, rabbit, chicken, turkey, pheasant, duck, goose and pigeon) as well as from human and rat in DNA mixtures through the sequencing of PCR products obtained from different couples of universal primers that amplify 12S and 16S rRNA mitochondrial DNA genes. Six libraries were produced including PCR products obtained separately from 13 species or from DNA mixtures containing DNA from all species or only avian or only mammalian species at equimolar concentration or at 1:10 or 1:50 ratios for pig and horse DNA. Sequencing obtained a total of 33,294,511 called nucleotides of which 29,109,688 with Q20 (87.43%) in a total of 215,944 reads. Different alignment algorithms were used to assign the species based on sequence data. Error rate calculated after confirmation of the obtained sequences by Sanger sequencing ranged from 0.0003 to 0.02 for the different species. Correlation about the number of reads per species between different libraries was high for mammalian species (0.97) and lower for avian species (0.70). PCR competition limited the efficiency of amplification and sequencing for avian species for some primer pairs. Detection of low level of pig and horse DNA was possible with reads obtained from different primer pairs. The sequencing of the products obtained from different universal PCR primers could be a useful strategy to overcome potential problems of amplification. Based on these results, the Ion Torrent technology can be applied for the identification of meat species in DNA mixtures.

  20. A semiconductor-based, frequency-stabilized mode-locked laser using a phase modulator and an intracavity etalon.

    PubMed

    Davila-Rodriguez, Josue; Ozdur, Ibrahim; Williams, Charles; Delfyett, Peter J

    2010-12-15

    We report a frequency-stabilized semiconductor-based mode-locked laser that uses a phase modulator and an intracavity Fabry-Perot etalon for both active mode-locking and optical frequency stabilization. A twofold multiplication of the repetition frequency of the laser is inherently obtained in the process. The residual timing jitter of the mode-locked pulse train is 13 fs (1 Hz to 100 MHz), measured after regenerative frequency division of the photodetected pulse train.

  1. Features of the spectral dependences of transmittance of organic semiconductors based on tert-butyl substituted lutetium phthalocyanine molecules

    SciTech Connect

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

    2011-11-15

    Vibronic properties of organic semiconductors based on tert-butyl substituted phthalocyanine lutetium diphthalocyanine molecules are studied by IR and Raman spectroscopy. It is shown that substitution of several carbon atoms in initial phthalocyanine (Pc) ligands with {sup 13}C isotope atoms causes a spectral shift in the main absorption lines attributed to benzene, isoindol, and peripheral C-H groups. A comparison of spectral characteristics showed that the shift can vary from 3 to 1 cm{sup -1}.

  2. Synthesis of Perylene Imide Diones as Platforms for the Development of Pyrazine Based Organic Semiconductors.

    PubMed

    de Echegaray, Paula; Mancheño, María J; Arrechea-Marcos, Iratxe; Juárez, Rafael; López-Espejo, Guzmán; López Navarrete, J Teodomiro; Ramos, María Mar; Seoane, Carlos; Ortiz, Rocío Ponce; Segura, José L

    2016-11-18

    There is a great interest in peryleneimide (PI)-containing compounds given their unique combination of good electron accepting ability, high abosorption in the visible region, and outstanding chemical, thermal, and photochemical stabilities. Thus, herein we report the synthesis of perylene imide derivatives endowed with a 1,2-diketone functionality (PIDs) as efficient intermediates to easily access peryleneimide (PI)-containing organic semiconductors with enhanced absorption cross-section for the design of tunable semiconductor organic materials. Three processable organic molecular semiconductors containing thiophene and terthiophene moieties, PITa, PITb, and PITT, have been prepared from the novel PIDs. The tendency of these semiconductors for molecular aggregation have been investigated by NMR spectroscopy and supported by quantum chemical calculations. 2D NMR experiments and theoretical calculations point to an antiparallel π-stacking interaction as the most stable conformation in the aggregates. Investigation of the optical and electrochemical properties of the materials is also reported and analyzed in combination with DFT calculations. Although the derivatives presented here show modest electron mobilities of ∼10(-4) cm(2)V(-1)s(-1), these preliminary studies of their performance in organic field effect transistors (OFETs) indicate the potential of these new building blocks as n-type semiconductors.

  3. Tailoring the Spectroscopic Properties of Semiconductor Nanowires via Surface-Plasmon-Based Optical Engineering

    PubMed Central

    2014-01-01

    Semiconductor nanowires, due to their unique electronic, optical, and chemical properties, are firmly placed at the forefront of nanotechnology research. The rich physics of semiconductor nanowire optics arises due to the enhanced light–matter interactions at the nanoscale and coupling of optical modes to electronic resonances. Furthermore, confinement of light can be taken to new extremes via coupling to the surface plasmon modes of metal nanostructures integrated with nanowires, leading to interesting physical phenomena. This Perspective will examine how the optical properties of semiconductor nanowires can be altered via their integration with highly confined plasmonic nanocavities that have resulted in properties such as orders of magnitude faster and more efficient light emission and lasing. The use of plasmonic nanocavities for tailored optical absorption will also be discussed in order to understand and engineer fundamental optical properties of these hybrid systems along with their potential for novel applications, which may not be possible with purely dielectric cavities. PMID:25396030

  4. Rainflow Algorithm-Based Lifetime Estimation of Power Semiconductors in Utility Applications

    DOE PAGES

    GopiReddy, Lakshmi Reddy; Tolbert, Leon M.; Ozpineci, Burak; ...

    2015-07-15

    Rainflow algorithms are one of the popular counting methods used in fatigue and failure analysis in conjunction with semiconductor lifetime estimation models. However, the rain-flow algorithm used in power semiconductor reliability does not consider the time-dependent mean temperature calculation. The equivalent temperature calculation proposed by Nagode et al. is applied to semiconductor lifetime estimation in this paper. A month-long arc furnace load profile is used as a test profile to estimate temperatures in insulated-gate bipolar transistors (IGBTs) in a STATCOM for reactive compensation of load. In conclusion, the degradation in the life of the IGBT power device is predicted basedmore » on time-dependent temperature calculation.« less

  5. Intrinsic Polarization and Tunable Color of Electroluminescence from Organic Single Crystal-based Light-Emitting Devices

    PubMed Central

    Ding, Ran; Feng, Jing; Zhou, Wei; Zhang, Xu-Lin; Fang, Hong-Hua; Yang, Tong; Wang, Hai-Yu; Hotta, Shu; Sun, Hong-Bo

    2015-01-01

    A single crystal-based organic light-emitting device (OLED) with intrinsically polarized and color-tunable electroluminescence (EL) has been demonstrated without any subsequent treatment. The polarization ratio of 5:1 for the transversal-electric (TE) and transversal-magnetic (TM) polarization at the emission peak of 575 nm, and 4.7:1 for the TM to TE polarization at the emission peak of 635 nm, respectively, have been obtained. The emitting color is tunable between yellow, yellow-green and orange by changing the polarization angle. The polarized EL and the polarization-induced color tunability can be attributed to the anisotropic microcavity formed by the BP3T crystal with uniaxial alignment of the molecules. PMID:26207723

  6. Multistrip synthetic single-crystal-diamond photodiode based on a p-type/intrinsic/Schottky metal transverse configuration

    NASA Astrophysics Data System (ADS)

    Ciancaglioni, I.; Marinelli, Marco; Milani, E.; Prestopino, G.; Verona, C.; Verona-Rinati, G.; Angelone, M.; Pillon, M.; Dolbnya, I.; Sawhney, K.; Tartoni, N.

    2011-04-01

    A synthetic multistrip single-crystal-diamond detector based on a p-type/intrinsic diamond/Schottky metal transverse configuration, operating at zero-bias voltage, was developed. The device was characterized at the Diamond Light Source synchrotron in Harwell (UK) under monochromatic high-flux X-ray beams from 6 to 20 keV and a micro-focused 10 keV beam with a spot size of ~3 μm. No significant pixel-to-pixel variation of both spectral responsivity and time response, high spatial resolution and good signal uniformity along each strip were found, suggesting the tested device structure as a promising sensor for X-ray and UV radiation imaging.

  7. Intrinsic carrier mobility extraction based on a new quasi-analytical model for graphene field-effect transistors

    NASA Astrophysics Data System (ADS)

    Wang, Shaoqing; Jin, Zhi; Muhammad, Asif; Peng, Songang; Huang, Xinnan; Zhang, Dayong; Shi, Jingyuan

    2016-10-01

    The most common method of mobility extraction for graphene field-effect transistors is proposed by Kim. Kim’s method assumes a constant mobility independent of carrier density and gets the mobility by fitting the transfer curves. However, carrier mobility changes with the carrier density, leading to the inaccuracy of Kim’s method. In our paper, a new and more accurate method is proposed to extract mobility by fitting the output curves at a constant gate voltage. The output curves are fitted using several kinds of current-voltage models. Besides the models in the literature, we present a modified model, which takes into account not only the quantum capacitance, contact resistance, but also a modified drift velocity-field relationship. Comparing with the other models, this new model can fit better with our experimental data. The dependence of carrier intrinsic mobility on carrier density is obtained based on this model.

  8. Raman scattering in organic semiconductors based on erbium biphthalocyanine molecules and chlorine-containing europium-lutetium triphthalocyanine molecules

    SciTech Connect

    Belogorokhov, I. A.; Mamichev, D. A.; Dronov, M. A.; Pushkarev, V. E.; Tomilova, L. G.; Khokhlov, D. R.

    2010-08-15

    The Raman spectra of semiconductor structures based on erbium biphthalocyanine molecules and chlorine-substituted europium-lutetium triphthalocyanine molecules are studied on excitation with Ar{sup +} laser radiation at the wavelength 514 nm. The data on the spectral position of Raman intensity peaks related to vibronic states of the basic molecular groups forming the semiconductor are obtained. Raman lines irrelevant to the known vibronic states of the basic phthalocyanine molecular groups are observed in the ranges 100-500 and 500-900 cm{sup -1}. It is shown that, in the spectra of triphthalocyanine, some lines are structurally complex and shifted with respect to the characteristic lines of molecular groups by several inverse centimeters.

  9. 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.

  10. Highly Stretchable Fully-Printed CNT-Based Electrochemical Sensors and Biofuel Cells: Combining Intrinsic and Design-Induced Stretchability.

    PubMed

    Bandodkar, Amay J; Jeerapan, Itthipon; You, Jung-Min; Nuñez-Flores, Rogelio; Wang, Joseph

    2016-01-13

    We present the first example of an all-printed, inexpensive, highly stretchable CNT-based electrochemical sensor and biofuel cell array. The synergistic effect of utilizing specially tailored screen printable stretchable inks that combine the attractive electrical and mechanical properties of CNTs with the elastomeric properties of polyurethane as a binder along with a judiciously designed free-standing serpentine pattern enables the printed device to possess two degrees of stretchability. Owing to these synergistic design and nanomaterial-based ink effects, the device withstands extremely large levels of strains (up to 500% strain) with negligible effect on its structural integrity and performance. This represents the highest stretchability offered by a printed device reported to date. Extensive electrochemical characterization of the printed device reveal that repeated stretching, torsional twisting, and indenting stress has negligible impact on its electrochemical properties. The wide-range applicability of this platform to realize highly stretchable CNT-based electrochemical sensors and biofuel cells has been demonstrated by fabricating and characterizing potentiometric ammonium sensor, amperometric enzyme-based glucose sensor, enzymatic glucose biofuel cell, and self-powered biosensor. Highly stretchable printable multianalyte sensor, multifuel biofuel cell, or any combination thereof can thus be realized using the printed CNT array. Such combination of intrinsically stretchable printed nanomaterial-based electrodes and strain-enduring design patterns holds considerable promise for creating an attractive class of inexpensive multifunctional, highly stretchable printed devices that satisfy the requirements of diverse healthcare and energy fields wherein resilience toward extreme mechanical deformations is mandatory.

  11. Changes induced in a ZnS:Cr-based electroluminescent waveguide structure by intrinsic near-infrared laser radiation

    SciTech Connect

    Vlasenko, N. A. Oleksenko, P. F.; Mukhlyo, M. A.; Veligura, L. I.

    2013-08-15

    The causes of changes that occur in a thin-film electroluminescent metal-insulator-semiconductor-insulator-metal waveguide structure based on ZnS:Cr (Cr concentration of {approx}4 Multiplication-Sign 10{sup 20} cm{sup -3}) upon lasing ({lambda} Almost-Equal-To 2.6 {mu}m) and that induce lasing cessation are studied. It is established that lasing ceases because of light-scattering inhomogeneities formed in the structure and, hence, optical losses enhance. The origin of the inhomogeneities and the causes of their formation are clarified by studying the surface topology and the crystal structure of constituent layers of the samples before and after lasing. The studies are performed by means of atomic force microscopy and X-ray radiography. It is shown that a substantial increase in the sizes of grains on the surface of the structure is the manifestation of changes induced in the ZnS:Cr film by recrystallization. Recrystallization is initiated by local heating by absorbed laser radiation in existing Cr clusters and quickened by a strong electric field (>1 MV cm{sup -1}). The changes observed in the ZnS:Cr film are as follows: the textured growth of ZnS crystallites, an increase in the content of Cr clusters, and the appearance of some CrS and a rather high ZnO content. Some ways for improving the stability of lasing in the ZnS:Cr-based waveguide structures are proposed.

  12. Thermal and Optical Modulation of the Carrier Mobility in OTFTs Based on an Azo-anthracene Liquid Crystal Organic Semiconductor.

    PubMed

    Chen, Yantong; Li, Chao; Xu, Xiuru; Liu, Ming; He, Yaowu; Murtaza, Imran; Zhang, Dongwei; Yao, Chao; Wang, Yongfeng; Meng, Hong

    2017-03-01

    One of the most striking features of organic semiconductors compared with their corresponding inorganic counterparts is their molecular diversity. The major challenge in organic semiconductor material technology is creating molecular structural motifs to develop multifunctional materials in order to achieve the desired functionalities yet to optimize the specific device performance. Azo-compounds, because of their special photoresponsive property, have attracted extensive interest in photonic and optoelectronic applications; if incorporated wisely in the organic semiconductor groups, they can be innovatively utilized in advanced smart electronic applications, where thermal and photo modulation is applied to tune the electronic properties. On the basis of this aspiration, a novel azo-functionalized liquid crystal semiconductor material, (E)-1-(4-(anthracen-2-yl)phenyl)-2-(4-(decyloxy)phenyl)diazene (APDPD), is designed and synthesized for application in organic thin-film transistors (OTFTs). The UV-vis spectra of APDPD exhibit reversible photoisomerizaton upon photoexcitation, and the thin films of APDPD show a long-range orientational order based on its liquid crystal phase. The performance of OTFTs based on this material as well as the effects of thermal treatment and UV-irradiation on mobility are investigated. The molecular structure, stability of the material, and morphology of the thin films are characterized by thermal gravimetric analysis (TGA), polarizing optical microscopy (POM), (differential scanning calorimetry (DSC), UV-vis spectroscopy, atomic force microscopy (AFM), and scanning tunneling microscopy (STM). This study reveals that our new material has the potential to be applied in optical sensors, memories, logic circuits, and functional switches.

  13. Laser beam shaping optical system design methods and their application in edge-emitting semiconductor laser-based LIDAR systems

    NASA Astrophysics Data System (ADS)

    Serkan, Mert

    LIDAR (Light Detection And Ranging) systems are employed for numerous applications such as remote sensing, military applications, optical data storage, display technology, and material processing. Furthermore, they are superior to other active remote sensing tools such as RADAR systems, considering their higher accuracy and more precise resolution due to their much shorter wavelengths and narrower beamwidth. Several types of lasers can be utilized as the radiation source of several LIDAR systems. Semiconductor laser-based LIDAR systems have several advantages such as low cost, compactness, broad range of wavelengths, and high PRFs (Pulse Repetition Frequency). However, semiconductor lasers have different origins and angles of divergence in the two transverse directions, resulting in the inherent astigmatism and elliptical beam shape. Specifically, elliptical beam shape is not desirable for several laser-based applications including LIDAR systems specifically designed to operate in the far-field region. In this dissertation, two mirror-based and two lens-based beam shapers are designed to circularize, collimate, and expand an edge-emitting semiconductor laser beam to a desired beam diameter for possible application in LIDAR systems. Additionally, most laser beams including semiconductor laser beams have Gaussian irradiance distribution. For applications that require uniform illumination of an extended target area, Gaussian irradiance distribution is undesirable. Therefore, a specific beam shaper is designed to transform the irradiance distribution from Gaussian to uniform in addition to circularizing, collimating, and expanding the semiconductor laser beam. For the design of beam shapers, aperture sizes of the surfaces are preset for desired power transmission and allowed diffraction level, surface parameters of the optical components and the distances between these surfaces are determined. Design equations specific to these beam shaping optical systems are

  14. Resistance transition assisted geometry enhanced magnetoresistance in semiconductors

    SciTech Connect

    Luo, Zhaochu; Zhang, Xiaozhong

    2015-05-07

    Magnetoresistance (MR) reported in some non-magnetic semiconductors (particularly silicon) has triggered considerable interest owing to the large magnitude of the effect. Here, we showed that MR in lightly doped n-Si can be significantly enhanced by introducing two diodes and proper design of the carrier path [Wan, Nature 477, 304 (2011)]. We designed a geometrical enhanced magnetoresistance (GEMR) device whose room-temperature MR ratio reaching 30% at 0.065 T and 20 000% at 1.2 T, respectively, approaching the performance of commercial MR devices. The mechanism of this GEMR is: the diodes help to define a high resistive state (HRS) and a low resistive state (LRS) in device by their openness and closeness, respectively. The ratio of apparent resistance between HRS and LRS is determined by geometry of silicon wafer and electrodes. Magnetic field could induce a transition from LRS to HRS by reshaping potential and current distribution among silicon wafer, resulting in a giant enhancement of intrinsic MR. We expect that this GEMR could be also realized in other semiconductors. The combination of high sensitivity to low magnetic fields and large high-field response should make this device concept attractive to the magnetic field sensing industry. Moreover, because this MR device is based on a conventional silicon/semiconductor platform, it should be possible to integrate this MR device with existing silicon/semiconductor devices and so aid the development of silicon/semiconductor-based magnetoelectronics. Also combining MR devices and semiconducting devices in a single Si/semiconductor chip may lead to some novel devices with hybrid function, such as electric-magnetic-photonic properties. Our work demonstrates that the charge property of semiconductor can be used in the magnetic sensing industry, where the spin properties of magnetic materials play a role traditionally.

  15. Intrinsic Functional Connectivity of Amygdala-Based Networks in Adolescent Generalized Anxiety Disorder

    ERIC Educational Resources Information Center

    Roy, Amy K.; Fudge, Julie L.; Kelly, Clare; Perry, Justin S. A.; Daniele, Teresa; Carlisi, Christina; Benson, Brenda; Castellanos, F. Xavier; Milham, Michael P.; Pine, Daniel S.; Ernst, Monique

    2013-01-01

    Objective: Generalized anxiety disorder (GAD) typically begins during adolescence and can persist into adulthood. The pathophysiological mechanisms underlying this disorder remain unclear. Recent evidence from resting state functional magnetic resonance imaging (R-fMRI) studies in adults suggests disruptions in amygdala-based circuitry; the…

  16. SIMULATION OF INTRINSIC BIOREMEDIATION PROCESSES AT WURTSMITH AIR FORCE BASE, MICHIGAN

    EPA Science Inventory

    In October, 1988, a KC-135 aircraft crashed at Wurtsmith Air Force base (AFB), Oscoda, Michigan during an attempted landing. Approximately 3000 gallons of jet fuel (JP-4) were spilled onto the ground, with a large portion of the fuel entering the subsurface. Previous investigat...

  17. Versatile Soft Grippers with Intrinsic Electroadhesion Based on Multifunctional Polymer Actuators.

    PubMed

    Shintake, Jun; Rosset, Samuel; Schubert, Bryan; Floreano, Dario; Shea, Herbert

    2016-01-13

    A highly versatile soft gripper that can handle an unprecedented range of object types is developed based on a new design of dielectric elastomer actuators employing an interdigitated electrode geometry, simultaneously maximizing both electroadhesion and electrostatic actuation while incorporating self-sensing. The multifunctionality of the actuator leads to a highly integrated, lightweight, fast, soft gripper with simplified structure and control.

  18. Nanoassemblies Based on Semiconductor Quantum Dots and Dye Molecules:. Single Objects Detection and Related Interface Dynamics

    NASA Astrophysics Data System (ADS)

    Zenkevich, E.; von Borczyskowski, C.; Kowerko, D.

    2013-05-01

    Single molecule spectroscopy of QD-dye nanoassemblies is shown that single functionalized dye molecules (perylene-bisimides and meso-pyridyl porphyrins) can be considered as extremely sensitive probes for studying exciton and relaxation processes in semiconductor CdSe/ZnS quantum dots.

  19. A lysinated thiophene-based semiconductor as a multifunctional neural bioorganic interface.

    PubMed

    Bonetti, Simone; Pistone, Assunta; Brucale, Marco; Karges, Saskia; Favaretto, Laura; Zambianchi, Massimo; Posati, Tamara; Sagnella, Anna; Caprini, Marco; Toffanin, Stefano; Zamboni, Roberto; Camaioni, Nadia; Muccini, Michele; Melucci, Manuela; Benfenati, Valentina

    2015-06-03

    Lysinated molecular organic semiconductors are introduced as valuable multifunctional platforms for neural cells growth and interfacing. Cast films of quaterthiophene (T4) semiconductor covalently modified with lysine-end moieties (T4Lys) are fabricated and their stability, morphology, optical/electrical, and biocompatibility properties are characterized. T4Lys films exhibit fluorescence and electronic transport as generally observed for unsubstituted oligothiophenes combined to humidity-activated ionic conduction promoted by the charged lysine-end moieties. The Lys insertion in T4 enables adhesion of primary culture of rat dorsal root ganglion (DRG), which is not achievable by plating cells on T4. Notably, on T4Lys, the number on adhering neurons/area is higher and displays a twofold longer neurite length than neurons plated on glass coated with poly-l-lysine. Finally, by whole-cell patch-clamp, it is shown that the biofunctionality of neurons cultured on T4Lys is preserved. The present study introduces an innovative concept for organic material neural interface that combines optical and iono-electronic functionalities with improved biocompatibility and neuron affinity promoted by Lys linkage and the softness of organic semiconductors. Lysinated organic semiconductors could set the scene for the fabrication of simplified bioorganic devices geometry for cells bidirectional communication or optoelectronic control of neural cells biofunctionality.

  20. Optical logic and signal processing using a semiconductor laser diode-based optical bistability device

    NASA Astrophysics Data System (ADS)

    Zhang, Yuancheng; Song, Qian; He, Shaowei

    1995-02-01

    Using an optical fibre-coupled semiconductor laser diode OBD with output feedback pumping operation in 5 modes (differential gain, bistability, zero-bias, inverted differential gain, and inverted bistability) has been realized respectively, and 5 elementary optical logic functions (AND, OR, NOT, NAND, and NOR) and some optical signal processing such as limiting, reshaping, and triggering have been implemented.

  1. Electric Conduction in Semiconductors: A Pedagogical Model Based on the Monte Carlo Method

    ERIC Educational Resources Information Center

    Capizzo, M. C.; Sperandeo-Mineo, R. M.; Zarcone, M.

    2008-01-01

    We present a pedagogic approach aimed at modelling electric conduction in semiconductors in order to describe and explain some macroscopic properties, such as the characteristic behaviour of resistance as a function of temperature. A simple model of the band structure is adopted for the generation of electron-hole pairs as well as for the carrier…

  2. The Relational-Behavior Model: The Relationship between Intrinsic Motivational Instruction and Extrinsic Motivation in Psychologically Based Instruction

    ERIC Educational Resources Information Center

    Chandler, Donald S., Jr.

    2008-01-01

    This pilot study examined the relational-behavior model (RBM) as a method of intrinsic motivational instruction in psychology courses. Among a sample of 33 college students enrolled in two undergraduate psychology courses, a Spearman rho analysis revealed a significant relationship between the intrinsic motivational factors (e.g. student/class…

  3. Semiconductor sensors

    NASA Technical Reports Server (NTRS)

    Gatos, Harry C. (Inventor); Lagowski, Jacek (Inventor)

    1977-01-01

    A semiconductor sensor adapted to detect with a high degree of sensitivity small magnitudes of a mechanical force, presence of traces of a gas or light. The sensor includes a high energy gap (i.e., .about. 1.0 electron volts) semiconductor wafer. Mechanical force is measured by employing a non-centrosymmetric material for the semiconductor. Distortion of the semiconductor by the force creates a contact potential difference (cpd) at the semiconductor surface, and this cpd is determined to give a measure of the force. When such a semiconductor is subjected to illumination with an energy less than the energy gap of the semiconductors, such illumination also creates a cpd at the surface. Detection of this cpd is employed to sense the illumination itself or, in a variation of the system, to detect a gas. When either a gas or light is to be detected and a crystal of a non-centrosymmetric material is employed, the presence of gas or light, in appropriate circumstances, results in a strain within the crystal which distorts the same and the distortion provides a mechanism for qualitative and quantitative evaluation of the gas or the light, as the case may be.

  4. B-DNA structure is intrinsically polymorphic: even at the level of base pair positions

    SciTech Connect

    Maehigashi, Tatsuya; Hsiao, Chiaolong; Woods, Kristen Kruger; Moulaei, Tinoush; Hud, Nicholas V.; Williams, Loren Dean

    2012-10-23

    Increasingly exact measurement of single crystal X-ray diffraction data offers detailed characterization of DNA conformation, hydration and electrostatics. However, instead of providing a more clear and unambiguous image of DNA, highly accurate diffraction data reveal polymorphism of the DNA atomic positions and conformation and hydration. Here we describe an accurate X-ray structure of B-DNA, painstakingly fit to a multistate model that contains multiple competing positions of most of the backbone and of entire base pairs. Two of ten base-pairs of CCAGGCCTGG are in multiple states distinguished primarily by differences in slide. Similarly, all the surrounding ions are seen to fractionally occupy discrete competing and overlapping sites. And finally, the vast majority of water molecules show strong evidence of multiple competing sites. Conventional resolution appears to give a false sense of homogeneity in conformation and interactions of DNA. In addition, conventional resolution yields an average structure that is not accurate, in that it is different from any of the multiple discrete structures observed at high resolution. Because base pair positional heterogeneity has not always been incorporated into model-building, even some high and ultrahigh-resolution structures of DNA do not indicate the full extent of conformational polymorphism.

  5. Band offset formation at semiconductor heterojunctions through density-based minimization of interface energy

    NASA Astrophysics Data System (ADS)

    Tung, Raymond T.; Kronik, Leeor

    2016-08-01

    It is well known that the magnitude of band offset (BO) at any semiconductor heterojunction is directly derivable from the distribution of charge at that interface and that the latter is decided by a minimization of total energy. However, the fact that BO formation is governed by energy minimization has not been explicitly used in theoretical BO models, likely because the equilibrium charge densities at heterojunction interfaces appear difficult to predict, except via explicit calculation. In this paper, electron densities at a large number of (100), (110), and (111) oriented heterojunctions between lattice-matched, isovalent semiconductors with the zinc blende (ZB) structure have been calculated by first-principles methods and analyzed in detail for possible common characteristics among energy-minimized densities. Remarkably, the heterojunction electron density was found to largely depend only on the immediate, local atomic arrangement. In fact, it is so much so that a juxtaposition of local electron-densities generated in oligo-cells (LEGOs) accurately reproduced the charge densities that minimize the energy for the heterojunctions. Furthermore, the charge distribution for each bulk semiconductor was found to display a striking separability of its electrostatic effect into two neutral parts, associated with the cation and the anion, which are approximately transferrable among semiconductors. These discoveries form the basis of a neutral polyhedra theory (NPT) that approximately predicts the equilibrium charge density and BO of relaxed heterojunctions from the energy minimization requirement. Well-known experimentally observed characteristics of heterojunctions, such as the insensitivity of BO to heterojunction orientation and the identity of interface bonds, the transitivity rule, etc., are all in good agreement with the NPT. Therefore, energy minimization, which essentially decides the electronic properties of all other solid and molecular systems, also governs

  6. Dual emissions from MnS clusters confined in the sodalite nanocage of a chalcogenide-based semiconductor zeolite.

    PubMed

    Hu, Dandan; Zhang, Yingying; Lin, Jian; Hou, Yike; Li, Dongsheng; Wu, Tao

    2017-03-21

    A new host-guest hybrid system with MnS clusters confined in a chalcogenide-based semiconductor zeolite was for the first time constructed and its photoluminescence (PL) properties were also investigated. The existence of MnS clusters in the nanopores of the semiconductor zeolite was revealed by UV-Vis absorption spectroscopy, steady-state fluorescence analysis, Raman as well as Fourier transform infrared (FTIR) spectroscopy. The aggregation state of the entrapped MnS clusters at different measurement temperatures was probed by electron paramagnetic resonance (EPR) spectroscopy. Of significant importance is the fact that the entrapped MnS clusters displayed dual emissions at 518 nm (2.39 eV) and 746 nm (1.66 eV), respectively, and the long-wavelength emission has never been observed in other MnS-confined host-guest systems. These two emission peaks displayed tunable PL intensity affected by the loading level and measurement temperature. This can be explained by the different morphologies of MnS clusters with different aggregation states at the corresponding loading level or measurement temperature. The current study opens a new avenue to construct inorganic chalcogenide cluster involved host-guest systems with a semiconductor zeolite as the host matrix.

  7. Electrical properties of BaTiO3 based - MFIS heterostructure: Role of semiconductor channel carrier concentration

    NASA Astrophysics Data System (ADS)

    Vagadia, Megha; Ravalia, Ashish; Solanki, P. S.; Pandey, Parul; Asokan, K.; Kuberkar, D. G.

    2014-05-01

    Effect of semiconductor channel carrier concentration on the modifications in the electrical properties of Ag/BaTiO3/SrTiO3/ZnO Metal-Ferroelectric-Insulator-Semiconductor (MFIS) heterostructure has been investigated. Under 4 V applied voltage, low leakage current density ˜3.2 × 10-6 A/cm2, has been observed in ZnO based MFIS heterostructure, which becomes ˜5.0 × 10-6 A/cm2 for MFIS with Al:ZnO channel. Observation of counterclockwise butterfly shaped C-V behavior confirms that, hysteresis in C-V is due to spontaneous ferroelectric polarization and field effect. A device with ZnO semiconductor exhibit ˜2700% modulation which decreases to ˜800% for Al: ZnO channel with good retention behavior. Pulse induced write/erase repeatability of source/drain current confirms the usefulness of the presently studied devices for non-volatile switching memory application.

  8. Intrinsic Motivation and Engagement as "Active Ingredients" in Garden-Based Education: Examining Models and Measures Derived from Self-Determination Theory

    ERIC Educational Resources Information Center

    Skinner, Ellen A.; Chi, Una

    2012-01-01

    Building on self-determination theory, this study presents a model of intrinsic motivation and engagement as "active ingredients" in garden-based education. The model was used to create reliable and valid measures of key constructs, and to guide the empirical exploration of motivational processes in garden-based learning. Teacher- and…

  9. Thin film solar cell including a spatially modulated intrinsic layer

    DOEpatents

    Guha, Subhendu; Yang, Chi-Chung; Ovshinsky, Stanford R.

    1989-03-28

    One or more thin film solar cells in which the intrinsic layer of substantially amorphous semiconductor alloy material thereof includes at least a first band gap portion and a narrower band gap portion. The band gap of the intrinsic layer is spatially graded through a portion of the bulk thickness, said graded portion including a region removed from the intrinsic layer-dopant layer interfaces. The band gap of the intrinsic layer is always less than the band gap of the doped layers. The gradation of the intrinsic layer is effected such that the open circuit voltage and/or the fill factor of the one or plural solar cell structure is enhanced.

  10. Variability in the Intrinsic UV Absorption in Mrk 279 based on HST/COS Spectra

    NASA Astrophysics Data System (ADS)

    Schmachtenberger, Benjamin R.; Gabel, Jack; Crenshaw, D. Michael; Kraemer, Steven B.

    2015-01-01

    We present an analysis of the variability of the mass outflow systems in the Seyfert 1 galaxy Mrk 279 based on spectra obtained with the Cosmic Origin Spectrograph (COS) aboard the Hubble Space Telescope in 2011, compared with observations in 2002 and 2003 obtained with the Space Telescope Imaging Spectrograph (STIS). The continuum flux dropped by a factor of fifteen in 2011 compared to 2003, similar to the low flux level observed in 2002. We measure covering factors and ionic column densities for the outflow systems, treating three distinct emission components - continuum, broad line region (BLR) and intermediate line region (ILR). We find that the column densities of C IV and N V have increased in both the low and high velocity kinematic components (radial velocities -265 km/s and -460 km/s), and Si IV has appeared in the former. Based on photoionization models using CLOUDY, we find the column density variations in both components are consistent with a response of the outflow to the drop in ionizing flux. We also find that the covering factor of the ILR in the low velocity component has increased in the 2011 spectrum, while the covering factors in the high velocity component are stable across the three epochs. We use these results to constrain the geometry and physical conditions of the outflows in Mrk 279.

  11. A Carbonaceous Membrane based on a Polymer of Intrinsic Microporosity (PIM-1) for Water Treatment.

    PubMed

    Kim, Hee Joong; Kim, Dong-Gyun; Lee, Kyuchul; Baek, Youngbin; Yoo, Youngjae; Kim, Yong Seok; Kim, Byoung Gak; Lee, Jong-Chan

    2016-10-26

    As insufficient access to clean water is expected to become worse in the near future, water purification is becoming increasingly important. Membrane filtration is the most promising technologies to produce clean water from contaminated water. Although there have been many studies to prepare highly water-permeable carbon-based membranes by utilizing frictionless water flow inside the carbonaceous pores, the carbon-based membranes still suffer from several issues, such as high cost and complicated fabrication as well as relatively low salt rejection. Here, we report for the first time the use of microporous carbonaceous membranes via controlled carbonization of polymer membranes with uniform microporosity for high-flux nanofiltration. Further enhancement of membrane performance is observed by O2 plasma treatment. The optimized membrane exhibits high water flux (13.30 LMH Bar(-1)) and good MgSO4 rejection (77.38%) as well as antifouling properties. This study provides insight into the design of microporous carbonaceous membranes for water purification.

  12. A Carbonaceous Membrane based on a Polymer of Intrinsic Microporosity (PIM-1) for Water Treatment

    NASA Astrophysics Data System (ADS)

    Kim, Hee Joong; Kim, Dong-Gyun; Lee, Kyuchul; Baek, Youngbin; Yoo, Youngjae; Kim, Yong Seok; Kim, Byoung Gak; Lee, Jong-Chan

    2016-10-01

    As insufficient access to clean water is expected to become worse in the near future, water purification is becoming increasingly important. Membrane filtration is the most promising technologies to produce clean water from contaminated water. Although there have been many studies to prepare highly water-permeable carbon-based membranes by utilizing frictionless water flow inside the carbonaceous pores, the carbon-based membranes still suffer from several issues, such as high cost and complicated fabrication as well as relatively low salt rejection. Here, we report for the first time the use of microporous carbonaceous membranes via controlled carbonization of polymer membranes with uniform microporosity for high-flux nanofiltration. Further enhancement of membrane performance is observed by O2 plasma treatment. The optimized membrane exhibits high water flux (13.30 LMH Bar‑1) and good MgSO4 rejection (77.38%) as well as antifouling properties. This study provides insight into the design of microporous carbonaceous membranes for water purification.

  13. A Carbonaceous Membrane based on a Polymer of Intrinsic Microporosity (PIM-1) for Water Treatment

    PubMed Central

    Kim, Hee Joong; Kim, Dong-Gyun; Lee, Kyuchul; Baek, Youngbin; Yoo, Youngjae; Kim, Yong Seok; Kim, Byoung Gak; Lee, Jong-Chan

    2016-01-01

    As insufficient access to clean water is expected to become worse in the near future, water purification is becoming increasingly important. Membrane filtration is the most promising technologies to produce clean water from contaminated water. Although there have been many studies to prepare highly water-permeable carbon-based membranes by utilizing frictionless water flow inside the carbonaceous pores, the carbon-based membranes still suffer from several issues, such as high cost and complicated fabrication as well as relatively low salt rejection. Here, we report for the first time the use of microporous carbonaceous membranes via controlled carbonization of polymer membranes with uniform microporosity for high-flux nanofiltration. Further enhancement of membrane performance is observed by O2 plasma treatment. The optimized membrane exhibits high water flux (13.30 LMH Bar−1) and good MgSO4 rejection (77.38%) as well as antifouling properties. This study provides insight into the design of microporous carbonaceous membranes for water purification. PMID:27782212

  14. Intrinsic fiber optical gas sensor based on surface plasmon resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Niggemann, Matthias; Katerkamp, Andreas; Pellmann, Maria; Bolsmann, Peter; Reinbold, Joerg; Cammann, Karl

    1995-09-01

    A miniaturized fiber optical sensor based on surface plasmon resonance spectroscopy is investigated in view of the detection of organic solvent vapors, particularly tetrachloroethene. Surface plasmons are excited on a silver coated multimode fiber by polychromatic light, and the resonant excitation is detected as a resonant absorption band in the measured output spectrum. When the analyte is absorbed in a thin gas-sensitive polysiloxane film deposited on the silver layer the polymer film changes its thickness and its refractive index. These changes result in a wavelength shift of the resonant curve depending on the analyte gas concentration. Theoretical considerations about the sensing effect are made and resonance curves were computer-simulated. Based on this simulation the layout of all sensor parameters was optimized. The sensor shows an excellent response to tetrachloroethene with a response time of two seconds and high reporducibility. Using self-assembling monolayers on the silver surface a long-term stability of more than three months is obtained. The sensor shows low cross sensitivities less than 1% to other solvent vapors like aceton and ethanol, furthermore, the influence of humidity is very low. This miniaturized fiber optical sensor in combination with an easy-to-handle and non-sophisticated measuring and evaluation unit is excellently suitable for the remote sensing of special organic solvent vapors.

  15. Switchable dual-wavelength fiber laser based on semiconductor optical amplifier and polarization-maintaining fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Feng, Suchun; Xu, Ou; Lu, Shaohua; Ren, Wenhua; Jian, Shuisheng

    2008-12-01

    Switchable dual-wavelength with orthogonal polarizations fiber laser based on semiconductor optical amplifier (SOA) and polarization-maintaining fiber Bragg grating (PMFBG) at room temperature is proposed. Owing to the polarization dependent loss of the PMFBG, the laser can be designed to operate in stable dual-wavelength or wavelength-switching modes with a wavelength spacing of 0.336 nm at room temperature by adjusting the polarization controller (PC). The amplitude variation in nearly half an hour is less than 0.1 dB for both wavelengths, which is more stable than that of erbium doped fiber (EDF)-based laser with similar configuration.

  16. Study of self-compliance behaviors and internal filament characteristics in intrinsic SiOx-based resistive switching memory

    NASA Astrophysics Data System (ADS)

    Chang, Yao-Feng; Fowler, Burt; Zhou, Fei; Chen, Ying-Chen; Lee, Jack C.

    2016-01-01

    Self-compliance characteristics and reliability optimization are investigated in intrinsic unipolar silicon oxide (SiOx)-based resistive switching (RS) memory using TiW/SiOx/TiW device structures. The program window (difference between SET voltage and RESET voltage) is dependent on external series resistance, demonstrating that the SET process is due to a voltage-triggered mechanism. The program window has been optimized for program/erase disturbance immunity and reliability for circuit-level applications. The SET and RESET transitions have also been characterized using a dynamic conductivity method, which distinguishes the self-compliance behavior due to an internal series resistance effect (filament) in SiOx-based RS memory. By using a conceptual "filament/resistive gap (GAP)" model of the conductive filament and a proton exchange model with appropriate assumptions, the internal filament resistance and GAP resistance can be estimated for high- and low-resistance states (HRS and LRS), and are found to be independent of external series resistance. Our experimental results not only provide insights into potential reliability issues but also help to clarify the switching mechanisms and device operating characteristics of SiOx-based RS memory.

  17. Semiconductor P-I-N detector

    DOEpatents

    Sudharsanan, Rengarajan; Karam, Nasser H.

    2001-01-01

    A semiconductor P-I-N detector including an intrinsic wafer, a P-doped layer, an N-doped layer, and a boundary layer for reducing the diffusion of dopants into the intrinsic wafer. The boundary layer is positioned between one of the doped regions and the intrinsic wafer. The intrinsic wafer can be composed of CdZnTe or CdTe, the P-doped layer can be composed of ZnTe doped with copper, and the N-doped layer can be composed of CdS doped with indium. The boundary layers is formed of an undoped semiconductor material. The boundary layer can be deposited onto the underlying intrinsic wafer. The doped regions are then typically formed by a deposition process or by doping a section of the deposited boundary layer.

  18. Polarization sensitive optical coherence tomography of melanin provides intrinsic contrast based on depolarization

    PubMed Central

    Baumann, Bernhard; Baumann, Stefan O.; Konegger, Thomas; Pircher, Michael; Götzinger, Erich; Schlanitz, Ferdinand; Schütze, Christopher; Sattmann, Harald; Litschauer, Marco; Schmidt-Erfurth, Ursula; Hitzenberger, Christoph K.

    2012-01-01

    Polarization sensitive optical coherence tomography (PS-OCT) is a functional extension of OCT. In addition to imaging based on tissue reflectivity, PS-OCT also enables depth-resolved mapping of sample polarization properties such as phase-retardation, birefringent axis orientation, Stokes vectors, and degree of polarization uniformity (DOPU). In this study, PS-OCT was used to investigate the polarization properties of melanin. In-vitro measurements in samples with varying melanin concentrations revealed polarization scrambling, i.e. depolarization of backscattered light. Polarization scrambling in the PS-OCT images was more pronounced for higher melanin concentrations and correlated with the concentration of the melanin granules in the phantoms. Moreover, in-vivo PS-OCT was performed in the retinas of normal subjects and individuals with albinism. Unlike in the normal eye, polarization scrambling in the retinal pigment epithelium (RPE) was less pronounced or even not observable in PS-OCT images of albinos. These results indicate that the depolarizing appearance of pigmented structures like, for instance, the RPE is likely to be caused by the melanin granules contained in these cells. PMID:22808437

  19. Diagnosis of cervical cells based on fractal and Euclidian geometrical measurements: Intrinsic Geometric Cellular Organization

    PubMed Central

    2014-01-01

    Background Fractal geometry has been the basis for the development of a diagnosis of preneoplastic and neoplastic cells that clears up the undetermination of the atypical squamous cells of undetermined significance (ASCUS). Methods Pictures of 40 cervix cytology samples diagnosed with conventional parameters were taken. A blind study was developed in which the clinic diagnosis of 10 normal cells, 10 ASCUS, 10 L-SIL and 10 H-SIL was masked. Cellular nucleus and cytoplasm were evaluated in the generalized Box-Counting space, calculating the fractal dimension and number of spaces occupied by the frontier of each object. Further, number of pixels occupied by surface of each object was calculated. Later, the mathematical features of the measures were studied to establish differences or equalities useful for diagnostic application. Finally, the sensibility, specificity, negative likelihood ratio and diagnostic concordance with Kappa coefficient were calculated. Results Simultaneous measures of the nuclear surface and the subtraction between the boundaries of cytoplasm and nucleus, lead to differentiate normality, L-SIL and H-SIL. Normality shows values less than or equal to 735 in nucleus surface and values greater or equal to 161 in cytoplasm-nucleus subtraction. L-SIL cells exhibit a nucleus surface with values greater than or equal to 972 and a subtraction between nucleus-cytoplasm higher to 130. L-SIL cells show cytoplasm-nucleus values less than 120. The rank between 120–130 in cytoplasm-nucleus subtraction corresponds to evolution between L-SIL and H-SIL. Sensibility and specificity values were 100%, the negative likelihood ratio was zero and Kappa coefficient was equal to 1. Conclusions A new diagnostic methodology of clinic applicability was developed based on fractal and euclidean geometry, which is useful for evaluation of cervix cytology. PMID:24742118

  20. A Fragment-Based Method of Creating Small-Molecule Libraries to Target the Aggregation of Intrinsically Disordered Proteins.

    PubMed

    Joshi, Priyanka; Chia, Sean; Habchi, Johnny; Knowles, Tuomas P J; Dobson, Christopher M; Vendruscolo, Michele

    2016-03-14

    The aggregation process of intrinsically disordered proteins (IDPs) has been associated with a wide range of neurodegenerative disorders, including Alzheimer's and Parkinson's diseases. Currently, however, no drug in clinical use targets IDP aggregation. To facilitate drug discovery programs in this important and challenging area, we describe a fragment-based approach of generating small-molecule libraries that target specific IDPs. The method is based on the use of molecular fragments extracted from compounds reported in the literature to inhibit of the aggregation of IDPs. These fragments are used to screen existing large generic libraries of small molecules to form smaller libraries specific for given IDPs. We illustrate this approach by describing three distinct small-molecule libraries to target, Aβ, tau, and α-synuclein, which are three IDPs implicated in Alzheimer's and Parkinson's diseases. The strategy described here offers novel opportunities for the identification of effective molecular scaffolds for drug discovery for neurodegenerative disorders and to provide insights into the mechanism of small-molecule binding to IDPs.

  1. Evaluation of a CdTe semiconductor based compact gamma camera for sentinel lymph node imaging

    SciTech Connect

    Russo, Paolo; Curion, Assunta S.; Mettivier, Giovanni; Esposito, Michela; Aurilio, Michela; Caraco, Corradina; Aloj, Luigi; Lastoria, Secondo

    2011-03-15

    Purpose: The authors assembled a prototype compact gamma-ray imaging probe (MediPROBE) for sentinel lymph node (SLN) localization. This probe is based on a semiconductor pixel detector. Its basic performance was assessed in the laboratory and clinically in comparison with a conventional gamma camera. Methods: The room-temperature CdTe pixel detector (1 mm thick) has 256x256 square pixels arranged with a 55 {mu}m pitch (sensitive area 14.08x14.08 mm{sup 2}), coupled pixel-by-pixel via bump-bonding to the Medipix2 photon-counting readout CMOS integrated circuit. The imaging probe is equipped with a set of three interchangeable knife-edge pinhole collimators (0.94, 1.2, or 2.1 mm effective diameter at 140 keV) and its focal distance can be regulated in order to set a given field of view (FOV). A typical FOV of 70 mm at 50 mm skin-to-collimator distance corresponds to a minification factor 1:5. The detector is operated at a single low-energy threshold of about 20 keV. Results: For {sup 99m}Tc, at 50 mm distance, a background-subtracted sensitivity of 6.5x10{sup -3} cps/kBq and a system spatial resolution of 5.5 mm FWHM were obtained for the 0.94 mm pinhole; corresponding values for the 2.1 mm pinhole were 3.3x10{sup -2} cps/kBq and 12.6 mm. The dark count rate was 0.71 cps. Clinical images in three patients with melanoma indicate detection of the SLNs with acquisition times between 60 and 410 s with an injected activity of 26 MBq {sup 99m}Tc and prior localization with standard gamma camera lymphoscintigraphy. Conclusions: The laboratory performance of this imaging probe is limited by the pinhole collimator performance and the necessity of working in minification due to the limited detector size. However, in clinical operative conditions, the CdTe imaging probe was effective in detecting SLNs with adequate resolution and an acceptable sensitivity. Sensitivity is expected to improve with the future availability of a larger CdTe detector permitting operation at shorter

  2. Chaos synchronization based on a continuous chaos control method in semiconductor lasers with optical feedback.

    PubMed

    Murakami, A; Ohtsubo, J

    2001-06-01

    Chaos synchronization using a continuous chaos control method was studied in two identical chaotic laser systems consisting of semiconductor lasers and optical feedback from an external mirror. Numerical calculations for rate equations indicate that the stability of chaos synchronization depends significantly on the external mirror position. We performed a linear stability analysis for the rate equations. Our results show that the stability of the synchronization is much influenced by the mode interaction between the relaxation oscillation frequency of the semiconductor laser and the external cavity frequency. Due to this interaction, an intensive mode competition between the two frequencies destroys the synchronization, but stable synchronization can be achieved when the mode competition is very weak.

  3. Semiconductor nanoparticle-based hydrogels prepared via self-initiated polymerization under sunlight, even visible light

    PubMed Central

    Zhang, Da; Yang, Jinhu; Bao, Song; Wu, Qingsheng; Wang, Qigang

    2013-01-01

    Since ancient times, people have used photosynthesized wood, bamboo, and cotton as building and clothing materials. The advantages of photo polymerization include the mild and easy process. However, the direct use of available sunlight for the preparation of materials is still a challenge due to its rather dilute intensity. Here, we show that semiconductor nanoparticles can be used for initiating monomer polymerization under sunlight and for cross-linking to form nanocomposite hydrogels with the aid of clay nanosheets. Hydrogels are an emerging multifunctional platform because they can be easily prepared using solar energy, retain semiconductor nanoparticle properties after immobilization, exhibit excellent mechanical strength (maximum compressive strength of 4.153 MPa and tensile strength 1.535 MPa) and high elasticity (maximum elongation of 2784%), and enable recyclable photodegradation of pollutants. This work suggests that functional nanoparticles can be immobilized in hydrogels for their collective application after combining their mechanical and physiochemical properties. PMID:23466566

  4. Semiconductor laser self-mixing micro-vibration measuring technology based on Hilbert transform

    NASA Astrophysics Data System (ADS)

    Tao, Yufeng; Wang, Ming; Xia, Wei

    2016-06-01

    A signal-processing synthesizing Wavelet transform and Hilbert transform is employed to measurement of uniform or non-uniform vibrations in self-mixing interferometer on semiconductor laser diode with quantum well. Background noise and fringe inclination are solved by decomposing effect, fringe counting is adopted to automatic determine decomposing level, a couple of exact quadrature signals are produced by Hilbert transform to extract vibration. The tempting potential of real-time measuring micro vibration with high accuracy and wide dynamic response bandwidth using proposed method is proven by both simulation and experiment. Advantages and error sources are presented as well. Main features of proposed semiconductor laser self-mixing interferometer are constant current supply, high resolution, simplest optical path and much higher tolerance to feedback level than existing self-mixing interferometers, which is competitive for non-contact vibration measurement.

  5. Highly Stretchable Fully-Printed CNT-based Electrochemical Sensors and Biofuel Cells: Combining Intrinsic and Design-induced Stretchability

    PubMed Central

    Bandodkar, Amay J.; Jeerapan, Itthipon; You, Jung-Min; Nuñez-Flores, Rogelio; Wang, Joseph

    2015-01-01

    We present the first example of an all-printed, inexpensive, highly stretchable CNT-based electrochemical sensor and biofuel cell array. The synergistic effect of utilizing specially tailored screen printable stretchable inks that combine the attractive electrical and mechanical properties of CNTs with the elastomeric properties of polyurethane as a binder along with a judiciously designed free-standing serpentine pattern enables the printed device to possess two degrees of stretchability. Owing to these synergistic design and nanomaterial-based ink effects, the device withstands extremely large levels of strains (upto 500% strain) with negligible effect on its structural integrity and performance. This represents the highest stretchability offered by a printed device reported to date. Extensive electrochemical characterization of the printed device reveal that repeated stretching, torsional twisting and indenting stress has negligible impact on its electrochemical properties. The wide-range applicability of this platform to realize highly stretchable CNT-based electrochemical sensors and biofuel cells has been demonstrated by fabricating and characterizing potentiometric ammonium sensor, amperometric enzyme-based glucose sensor, enzymatic glucose biofuel cell and self-powered biosensor. Highly stretchable printable multi-analyte sensor, multi-fuel biofuel cell or any combination thereof can thus be realized using the printed CNT array. Such combination of intrinsically-stretchable printed nanomaterial-based electrodes and strain-enduring design patterns holds considerable promise for creating an attractive class of inexpensive multi-functional, highly stretchable printed devices that satisfy the requirements of diverse healthcare and energy fields wherein resilience towards extreme mechanical deformations is mandatory. PMID:26694819

  6. Device and Circuit Codesign Strategy for Application to Low-Noise Amplifier Based on Silicon Nanowire Metal-Oxide-Semiconductor Field Effect Transistors

    NASA Astrophysics Data System (ADS)

    Seongjae Cho,; Hee-Sauk Jhon,; Jung Hoon Lee,; Se Hwan Park,; Hyungcheol Shin,; Byung-Gook Park,

    2010-04-01

    In this study, a full-range approach from device level to circuit level design is performed for RF application of silicon nanowire (SNW) metal-oxide-semiconductor field effect transistors (MOSFETs). Both DC and AC analyses have been conducted to confirm the advantages of an SNW MOSFET over the conventional planar (CPL) MOSFET device having dimensional equivalence. Besides the intrinsic characteristic parameters, the extrinsic resistance and capacitance caused by wiring components are extracted from each device. On the basis of these intrinsic and extrinsic parameters, a multi-fingered 5.8 GHz low-noise amplifier (LNA) design adopting SNW MOSFETs has been achieved, which shows an improved gain of 17.5 dB and a noise figure of 3.1 dB over a CPL MOSFET LNA.

  7. Seeing diabetes: visual detection of glucose based on the intrinsic peroxidase-like activity of MoS2 nanosheets

    NASA Astrophysics Data System (ADS)

    Lin, Tianran; Zhong, Liangshuang; Guo, Liangqia; Fu, Fengfu; Chen, Guonan

    2014-09-01

    Molybdenum disulfide (MoS2) has attracted increasing research interest recently due to its unique physical, optical and electrical properties, correlated with its 2D ultrathin atomic-layered structure. Until now, however, great efforts have focused on its applications such as lithium ion batteries, transistors, and hydrogen evolution reactions. Herein, for the first time, MoS2 nanosheets are discovered to possess an intrinsic peroxidase-like activity and can catalytically oxidize 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to produce a color reaction. The catalytic activity follows the typical Michaelis-Menten kinetics and is dependent on temperature, pH, H2O2 concentration, and reaction time. Based on this finding, a highly sensitive and selective colorimetric method for H2O2 and glucose detection is developed and applied to detect glucose in serum samples. Moreover, a simple, inexpensive, instrument-free and portable test kit for the visual detection of glucose in normal and diabetic serum samples is constructed by utilizing agarose hydrogel as a visual detection platform.Molybdenum disulfide (MoS2) has attracted increasing research interest recently due to its unique physical, optical and electrical properties, correlated with its 2D ultrathin atomic-layered structure. Until now, however, great efforts have focused on its applications such as lithium ion batteries, transistors, and hydrogen evolution reactions. Herein, for the first time, MoS2 nanosheets are discovered to possess an intrinsic peroxidase-like activity and can catalytically oxidize 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to produce a color reaction. The catalytic activity follows the typical Michaelis-Menten kinetics and is dependent on temperature, pH, H2O2 concentration, and reaction time. Based on this finding, a highly sensitive and selective colorimetric method for H2O2 and glucose detection is developed and applied to detect glucose in serum samples. Moreover, a simple, inexpensive

  8. Device Concepts Based on Spin-dependent Transmission in Semiconductor Heterostructures

    NASA Technical Reports Server (NTRS)

    Ting, David Z. - Y.; Cartoixa, X.

    2004-01-01

    We examine zero-magnetic-field spin-dependent transmission in nonmagnetic semiconductor heterostructures with structural inversion asymmetry (SIA) and bulk inversion asymmetry (BIA), and report spin devices concepts that exploit their properties. Our modeling results show that several design strategies could be used to achieve high spin filtering efficiencies. The current spin polarization of these devices is electrically controllable, and potentially amenable to highspeed spin modulation, and could be integrated in optoelectronic devices for added functionality.

  9. Highly Efficient Oxygen-Storage Material with Intrinsic Coke Resistance for Chemical Looping Combustion-Based CO2 Capture.

    PubMed

    Imtiaz, Qasim; Kurlov, Alexey; Rupp, Jennifer Lilia Marguerite; Müller, Christoph Rüdiger

    2015-06-22

    Chemical looping combustion (CLC) and chemical looping with oxygen uncoupling (CLOU) are emerging thermochemical CO2 capture cycles that allow the capture of CO2 with a small energy penalty. Here, the development of suitable oxygen carrier materials is a key aspect to transfer these promising concepts to practical installations. CuO is an attractive material for CLC and CLOU because of its high oxygen-storage capacity (20 wt %), fast reaction kinetics, and high equilibrium partial pressure of oxygen at typical operating temperatures (850-1000 °C). However, despite its promising characteristics, its low Tammann temperature requires the development of new strategies to phase-stabilize CuO-based oxygen carriers. In this work, we report a strategy based on stabilization by co-precipitated ceria (CeO2-x ), which allowed us to increase the oxygen capacity, coke resistance, and redox stability of CuO-based oxygen carriers substantially. The performance of the new oxygen carriers was evaluated in detail and compared to the current state-of-the-art materials, that is, Al2 O3 -stabilized CuO with similar CuO loadings. We also demonstrate that the higher intrinsic oxygen uptake, release, and mobility in CeO2-x -stabilized CuO leads to a three times higher carbon deposition resistance compared to that of Al2 O3 -stabilized CuO. Moreover, we report a high cyclic stability without phase intermixing for CeO2-x -supported CuO. This was accompanied by a lower reduction temperature compared to state-of-the-art Al2 O3 -supported CuO. As a result of its high resistance towards carbon deposition and fast oxygen uncoupling kinetics, CeO2-x -stabilized CuO is identified as a very promising material for CLC- and CLOU-based CO2 capture architectures.

  10. Third generation photovoltaics based on multiple exciton generation in quantum confined semiconductors.

    PubMed

    Beard, Matthew C; Luther, Joseph M; Semonin, Octavi E; Nozik, Arthur J

    2013-06-18

    Improving the primary photoconversion process in a photovoltaiccell by utilizing the excess energy that is otherwise lost as heat can lead to an increase in the overall power conversion efficiency (PCE). Semiconductor nanocrystals (NCs) with at least one dimension small enough to produce quantum confinement effects provide new ways of controlling energy flow not achievable in thin film or bulk semiconductors. Researchers have developed various strategies to incorporate these novel structures into suitable solar conversion systems. Some of these methods could increase the PCE past the Shockley-Queisser (SQ) limit of ∼33%, making them viable "third generation photovoltaic" (TGPV) cell architectures. Surpassing the SQ limit for single junction solar cells presents both a scientific and a technological challenge, and the use of semiconductor NCs to enhance the primary photoconversion process offers a promising potential solution. The NCs are synthesized via solution phase chemical reactions producing stable colloidal solutions, where the reaction conditions can be modified to produce a variety of shapes, compositions, and structures. The confinement of the semiconductor NC in one dimension produces quantum films, wells, or discs. Two-dimensional confinement leads to quantum wires or rods (QRs), and quantum dots (QDs) are three-dimensionally confined NCs. The process of multiple exciton generation (MEG) converts a high-energy photon into multiple electron-hole pairs. Although many studies have demonstrated that MEG is enhanced in QDs compared with bulk semiconductors, these studies have either used ultrafast spectroscopy to measure the photon-to-exciton quantum yields (QYs) or theoretical calculations. Implementing MEG in a working solar cell has been an ongoing challenge. In this Account, we discuss the status of MEG research and strategies towards implementing MEG in working solar cells. Recently we showed an external quantum efficiency for photocurrent of greater

  11. Sol-gel derived precursors to Group 14 semiconductor nanocrystals - Convenient materials for enabling nanocrystal-based applications

    NASA Astrophysics Data System (ADS)

    Veinot, Jonathan G. C.; Henderson, Eric J.; Hessel, Colin M.

    2009-11-01

    Semiconductor nanocrystals are intriguing because of their electronic, optical, and chemical characteristics. Silicon nanocrystals (Si-NCs) of sub-5 nm dimension are of particular interest due to their intense photoluminescent response and the promise of linking silicon photonics and electronics. Other related nanomaterials of technological importance include SiC and Ge. The following contribution describes key experimental findings pertaining to synthetic methodology, investigation of nanodomain formation and growth, as determined by X-ray powder diffraction (XRD) and photoluminescence (PL) spectroscopy for a series of sol-gel derived prepolymers suitable for preparing Group 14 based nanocrystal containing composites.

  12. An upstream reach-extender for 10Gb/s PON applications based on an optimized semiconductor amplifier cascade.

    PubMed

    Porto, Stefano; Antony, Cleitus; Ossieur, Peter; Townsend, Paul D

    2012-01-02

    We present a reach-extender for the upstream transmission path of 10Gb/s passive optical networks based on an optimised cascade of two semiconductor optical amplifiers (SOAs). Through careful optimisation of the bias current of the second stage SOA, over 19dB input dynamic range and up to 12dB compression of the output dynamic range were achieved without any dynamic control. A reach of 70km and split up to 32 were demonstrated experimentally using an ac-coupled, continuous-mode receiver with a reduced 56ns ac-coupling constant.

  13. Effect of Electron-Beam Irradiation on Organic Semiconductor and Its Application for Transistor-Based Dosimeters.

    PubMed

    Kim, Jae Joon; Ha, Jun Mok; Lee, Hyeok Moo; Raza, Hamid Saeed; Park, Ji Won; Cho, Sung Oh

    2016-08-03

    The effects of electron-beam irradiation on the organic semiconductor rubrene and its application as a dosimeter was investigated. Through the measurements of photoluminescence and the ultraviolet photoelectron spectroscopy, we found that electron-beam irradiation induces n-doping of rubrene. Additionally, we fabricated rubrene thin-film transistors with pristine and irradiated rubrene, and discovered that the decrease in transistor properties originated from the irradiation of rubrene and that the threshold voltages are shifted to the opposite directions as the irradiated layers. Finally, a highly sensitive and air-stable electron dosimeter was fabricated based on a rubrene transistor.

  14. Ground-based research of crystal growth of II-VI compound semiconductors by physical vapor transport

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Gillies, D. C.; Szofran, F. R.; Lehoczky, S. L.; Su, Ching-Hua; Sha, Yi-Gao; Zhou, W.; Dudley, M.; Liu, Hao-Chieh; Brebrick, R. F.; Wang, J. C.

    1994-01-01

    Ground-based investigation of the crystal growth of II-VI semiconductor compounds, including CdTe, CdS, ZnTe, and ZnSe, by physical vapor transport in closed ampoules was performed. The crystal growth experimental process and supporting activities--preparation and heat treatment of starting materials, vapor partial pressure measurements, and transport rate measurements are reported. The results of crystal characterization, including microscopy, microstructure, optical transmission photoluminescence, synchrotron radiation topography, and chemical analysis by spark source mass spectrography, are also discussed.

  15. Optimisation of 40 Gb/s wavelength converters based on four-wave mixing in a semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Schulze, K.; Petersen, M. N.; Herrera, J.; Ramos, F.; Marti, J.

    2007-08-01

    The optimum operating powers and wavelengths for a 40 Gb/s wavelength converter based on four-wave mixing in a semiconductor optical amplifier are inferred from experimental results. From these measurements, some general rules of thumb are derived for this kind of devices. Generally, the optimum signal power should be 10 dB lower than the pump power (-16 dB conversion efficiency) whereas the wavelength separation between the signal and the pump carrier should not be lower than about four times the signal bitrate (1.3 nm for 40 Gb/s RZ signals).

  16. First-principle study on some new spin-gapless semiconductors: The Zr-based quaternary Heusler alloys

    NASA Astrophysics Data System (ADS)

    Gao, Qiang; Xie, Huan-Huan; Li, Lei; Lei, Gang; Deng, Jian-Bo; Hu, Xian-Ru

    2015-09-01

    Employing first-principle calculations, we have investigated electronic and magnetic properties of the Zr-based quaternary Heusler alloys: ZrCoVIn, ZrFeVGe, ZrCoFeP, ZrCoCrBe and ZrFeCrZ (Z = In and Ga). Our calculation results show that all the alloys are (or nearly) spin-gapless semiconductors. The Slater-Pauling behaviours of these alloys are discussed as well. The cohesion energy and formation energy of these alloys have also been discussed, and the results indicate the studied alloys are stable.

  17. Application of semiconductor optical amplifier for mobile radio communications networks based on radio-over-fiber systems

    NASA Astrophysics Data System (ADS)

    Andreev, Vladimir A.; Burdin, Vladimir A.; Volkov, Kirill A.; Dashkov, Michael V.; Bukashkin, Sergei A.; Buzov, Alexander L.; Procopiev, Vladimir I.; Zharkov, Alexander D.

    2016-03-01

    The analysis of semiconductor optical amplifier applications in Radio-over-Fiber systems of telecommunication networks is given. In such systems semiconductor optical amplifier can be used for either amplification, modulation or detection, and also as an universal device.

  18. A New Polymer Nanoprobe Based on Chemiluminescence Resonance Energy Transfer for Ultrasensitive Imaging of Intrinsic Superoxide Anion in Mice.

    PubMed

    Li, Ping; Liu, Lu; Xiao, Haibin; Zhang, Wei; Wang, Lulin; Tang, Bo

    2016-03-09

    Despite significant developments in optical imaging of superoxide anion (O2(•-)) as the preliminary reactive oxygen species, novel visualizing strategies that offer ultrahigh sensitivity are still imperative. This is mainly because intrinsic concentrations of O2(•-) are extremely low in living systems. Herein, we present the rational design and construction of a new polymer nanoprobe PCLA-O2(•-) for detecting O2(•-) based on chemiluminescence (CL) resonance energy transfer without an external excitation source. Structurally, PCLA-O2(•-) contains two moieties linked covalently, namely imidazopyrazinone that is capable of CL triggered by O2(•-) as the energy donor and conjugated polymers with light-amplifying property as the energy acceptor. Experiment results demonstrate that PCLA-O2(•-) exhibits ultrahigh sensitivity at the picomole level, dramatically prolonged luminescence time, specificity, and excellent biocompatibility. Without exogenous stimulation, this probe for the first time in situ visualizes O2(•-) level differences between normal and tumor tissues of mice. These exceptional features ensure that PCLA-O2(•-) as a self-luminescing probe is an alternative in vivo imaging approach for ultralow level O2(•-).

  19. Flow focussing of particles and cells based on their intrinsic properties using a simple diamagnetic repulsion setup.

    PubMed

    Rodríguez-Villarreal, Angeles Ivón; Tarn, Mark D; Madden, Leigh A; Lutz, Julia B; Greenman, John; Samitier, Josep; Pamme, Nicole

    2011-04-07

    The continuous flow focussing and manipulation of particles and cells are important factors in microfluidic applications for performing accurate and reproducible procedures downstream. Many particle focussing methods require complex setups or channel designs that can limit the process and its applications. Here, we present diamagnetic repulsion as a simple means of focussing objects in continuous flow, based only on their intrinsic properties without the requirement of any label. Diamagnetic polystyrene particles were suspended in a paramagnetic medium and pumped through a capillary between a pair of permanent magnets, whereupon the particles were repelled by each magnet into the central axis of the capillary, thus achieving focussing. By investigating this effect, we found that the focussing was greatly enhanced with (i) increased magnetic susceptibility of the medium, (ii) reduced flow rate of the suspension, (iii) increased particle size, and (iv) increased residence time in the magnetic field. Furthermore, we applied diamagnetic repulsion to the flow focussing of living, label-free HaCaT cells.

  20. Electrodes for Semiconductor Gas Sensors.

    PubMed

    Lee, Sung Pil

    2017-03-25

    The electrodes of semiconductor gas sensors are important in characterizing sensors based on their sensitivity, selectivity, reversibility, response time, and long-term stability. The types and materials of electrodes used for semiconductor gas sensors are analyzed. In addition, the effect of interfacial zones and surface states of electrode-semiconductor interfaces on their characteristics is studied. This study describes that the gas interaction mechanism of the electrode-semiconductor interfaces should take into account the interfacial zone, surface states, image force, and tunneling effect.

  1. Alterations of Intrinsic Brain Connectivity Patterns in Depression and Bipolar Disorders: A Critical Assessment of Magnetoencephalography-Based Evidence.

    PubMed

    Alamian, Golnoush; Hincapié, Ana-Sofía; Combrisson, Etienne; Thiery, Thomas; Martel, Véronique; Althukov, Dmitrii; Jerbi, Karim

    2017-01-01

    Despite being the object of a thriving field of clinical research, the investigation of intrinsic brain network alterations in psychiatric illnesses is still in its early days. Because the pathological alterations are predominantly probed using functional magnetic resonance imaging (fMRI), many questions about the electrophysiological bases of resting-state alterations in psychiatric disorders, particularly among mood disorder patients, remain unanswered. Alongside important research using electroencephalography (EEG), the specific recent contributions and future promise of magnetoencephalography (MEG) in this field are not fully recognized and valued. Here, we provide a critical review of recent findings from MEG resting-state connectivity within major depressive disorder (MDD) and bipolar disorder (BD). The clinical MEG resting-state results are compared with those previously reported with fMRI and EEG. Taken together, MEG appears to be a promising but still critically underexploited technique to unravel the neurophysiological mechanisms that mediate abnormal (both hyper- and hypo-) connectivity patterns involved in MDD and BD. In particular, a major strength of MEG is its ability to provide source-space estimations of neuromagnetic long-range rhythmic synchronization at various frequencies (i.e., oscillatory coupling). The reviewed literature highlights the relevance of probing local and interregional rhythmic synchronization to explore the pathophysiological underpinnings of each disorder. However, before we can fully take advantage of MEG connectivity analyses in psychiatry, several limitations inherent to MEG connectivity analyses need to be understood and taken into account. Thus, we also discuss current methodological challenges and outline paths for future research. MEG resting-state studies provide an important window onto perturbed spontaneous oscillatory brain networks and hence supply an important complement to fMRI-based resting-state measurements in

  2. Alterations of Intrinsic Brain Connectivity Patterns in Depression and Bipolar Disorders: A Critical Assessment of Magnetoencephalography-Based Evidence

    PubMed Central

    Alamian, Golnoush; Hincapié, Ana-Sofía; Combrisson, Etienne; Thiery, Thomas; Martel, Véronique; Althukov, Dmitrii; Jerbi, Karim

    2017-01-01

    Despite being the object of a thriving field of clinical research, the investigation of intrinsic brain network alterations in psychiatric illnesses is still in its early days. Because the pathological alterations are predominantly probed using functional magnetic resonance imaging (fMRI), many questions about the electrophysiological bases of resting-state alterations in psychiatric disorders, particularly among mood disorder patients, remain unanswered. Alongside important research using electroencephalography (EEG), the specific recent contributions and future promise of magnetoencephalography (MEG) in this field are not fully recognized and valued. Here, we provide a critical review of recent findings from MEG resting-state connectivity within major depressive disorder (MDD) and bipolar disorder (BD). The clinical MEG resting-state results are compared with those previously reported with fMRI and EEG. Taken together, MEG appears to be a promising but still critically underexploited technique to unravel the neurophysiological mechanisms that mediate abnormal (both hyper- and hypo-) connectivity patterns involved in MDD and BD. In particular, a major strength of MEG is its ability to provide source-space estimations of neuromagnetic long-range rhythmic synchronization at various frequencies (i.e., oscillatory coupling). The reviewed literature highlights the relevance of probing local and interregional rhythmic synchronization to explore the pathophysiological underpinnings of each disorder. However, before we can fully take advantage of MEG connectivity analyses in psychiatry, several limitations inherent to MEG connectivity analyses need to be understood and taken into account. Thus, we also discuss current methodological challenges and outline paths for future research. MEG resting-state studies provide an important window onto perturbed spontaneous oscillatory brain networks and hence supply an important complement to fMRI-based resting-state measurements in

  3. Widely tunable lasers based on mode-hop-free semiconductor laser array

    NASA Astrophysics Data System (ADS)

    Kurobe, T.; Kimoto, T.; Muranushi, K.; Mukaihara, T.; Ariga, M.; Kagimoto, T.; Kagi, N.; Matsuo, N.; Kasukawa, A.

    2007-11-01

    Integration of mode-hop-free tunable laser array and a semiconductor optical amplifier is most reliable approach to realize widely tunable lasers. We have developed two types of tunable lasers, one is a thermally tunable DFB laser array for DWDM tunable transponders, which has shown high power and wide tunability covering Cband or L-band, housing in compact butterfly packages with robust wavelength locker. Another is a short-cavity DBR laser array for optical burst switching, whose lasing frequency can be monotonously tuned and locked on the ITU grid within 5 microseconds. Both lasers have demonstrated superior performances in system experiments.

  4. Room-temperature fabrication of light-emitting thin films based on amorphous oxide semiconductor

    SciTech Connect

    Kim, Junghwan Miyokawa, Norihiko; Ide, Keisuke; Toda, Yoshitake; Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio

    2016-01-15

    We propose a light-emitting thin film using an amorphous oxide semiconductor (AOS) because AOS has low defect density even fabricated at room temperature. Eu-doped amorphous In-Ga-Zn-O thin films fabricated at room temperature emitted intense red emission at 614 nm. It is achieved by precise control of oxygen pressure so as to suppress oxygen-deficiency/excess-related defects and free carriers. An electronic structure model is proposed, suggesting that non-radiative process is enhanced mainly by defects near the excited states. AOS would be a promising host for a thin film phosphor applicable to flexible displays as well as to light-emitting transistors.

  5. Optical clock division based on dual-wavelength mode-locked semiconductor fiber ring laser.

    PubMed

    Zhang, Weiwei; Sun, Junqiang; Wang, Jian; Zhang, Xingliang; Huang, Dexiu

    2008-07-21

    We have reported the optical clock division utilizing an injected mode-locked fiber ring laser incorporating semiconductor optical amplifiers (SOAs) and a dispersion compensation fiber (DCF). The clock division is mainly caused by the modulation competition between two wavelength components while both of them satisfy the harmonic mode-locking condition at the newly generated frequency. Stable second, third, and fourth clock divisions are obtained by properly adjusting the polarization controllers inside the ring cavity when a 10-GHz clock signal without any sub-harmonic frequency component is injected into the cavity. The radio-frequency spectra show good qualities of the obtained clock division trains.

  6. Excitability in optically injected semiconductor lasers: Contrasting quantum- well- and quantum-dot-based devices

    NASA Astrophysics Data System (ADS)

    Kelleher, B.; Bonatto, C.; Huyet, G.; Hegarty, S. P.

    2011-02-01

    Excitability is a generic prediction for an optically injected semiconductor laser. However, the details of the phenomenon differ depending on the type of device in question. For quantum-well lasers very complicated multipulse trajectories can be found, while for quantum-dot lasers the situation is much simpler. Experimental observations show the marked differences in the pulse shapes while theoretical considerations reveal the underlying mechanism responsible for the contrast, identifying the increased stability of quantum-dot lasers to perturbations as the root.

  7. Excitability in optically injected semiconductor lasers: contrasting quantum-well- and quantum-dot-based devices.

    PubMed

    Kelleher, B; Bonatto, C; Huyet, G; Hegarty, S P

    2011-02-01

    Excitability is a generic prediction for an optically injected semiconductor laser. However, the details of the phenomenon differ depending on the type of device in question. For quantum-well lasers very complicated multipulse trajectories can be found, while for quantum-dot lasers the situation is much simpler. Experimental observations show the marked differences in the pulse shapes while theoretical considerations reveal the underlying mechanism responsible for the contrast, identifying the increased stability of quantum-dot lasers to perturbations as the root.

  8. GUARD RING SEMICONDUCTOR JUNCTION

    DOEpatents

    Goulding, F.S.; Hansen, W.L.

    1963-12-01

    A semiconductor diode having a very low noise characteristic when used under reverse bias is described. Surface leakage currents, which in conventional diodes greatly contribute to noise, are prevented from mixing with the desired signal currents. A p-n junction is formed with a thin layer of heavily doped semiconductor material disposed on a lightly doped, physically thick base material. An annular groove cuts through the thin layer and into the base for a short distance, dividing the thin layer into a peripheral guard ring that encircles the central region. Noise signal currents are shunted through the guard ring, leaving the central region free from such currents. (AEC)

  9. All oxide semiconductor-based bidirectional vertical p-n-p selectors for 3D stackable crossbar-array electronics

    NASA Astrophysics Data System (ADS)

    Bae, Yoon Cheol; Lee, Ah Rahm; Baek, Gwang Ho; Chung, Je Bock; Kim, Tae Yoon; Park, Jea Gun; Hong, Jin Pyo

    2015-08-01

    Three-dimensional (3D) stackable memory devices including nano-scaled crossbar array are central for the realization of high-density non-volatile memory electronics. However, an essential sneak path issue affecting device performance in crossbar array remains a bottleneck and a grand challenge. Therefore, a suitable bidirectional selector as a two-way switch is required to facilitate a major breakthrough in the 3D crossbar array memory devices. Here, we show the excellent selectivity of all oxide p-/n-type semiconductor-based p-n-p open-based bipolar junction transistors as selectors in crossbar memory array. We report that bidirectional nonlinear characteristics of oxide p-n-p junctions can be highly enhanced by manipulating p-/n-type oxide semiconductor characteristics. We also propose an associated Zener tunneling mechanism that explains the unique features of our p-n-p selector. Our experimental findings are further extended to confirm the profound functionality of oxide p-n-p selectors integrated with several bipolar resistive switching memory elements working as storage nodes.

  10. All oxide semiconductor-based bidirectional vertical p-n-p selectors for 3D stackable crossbar-array electronics

    PubMed Central

    Bae, Yoon Cheol; Lee, Ah Rahm; Baek, Gwang Ho; Chung, Je Bock; Kim, Tae Yoon; Park, Jea Gun; Hong, Jin Pyo

    2015-01-01

    Three-dimensional (3D) stackable memory devices including nano-scaled crossbar array are central for the realization of high-density non-volatile memory electronics. However, an essential sneak path issue affecting device performance in crossbar array remains a bottleneck and a grand challenge. Therefore, a suitable bidirectional selector as a two-way switch is required to facilitate a major breakthrough in the 3D crossbar array memory devices. Here, we show the excellent selectivity of all oxide p-/n-type semiconductor-based p-n-p open-based bipolar junction transistors as selectors in crossbar memory array. We report that bidirectional nonlinear characteristics of oxide p-n-p junctions can be highly enhanced by manipulating p-/n-type oxide semiconductor characteristics. We also propose an associated Zener tunneling mechanism that explains the unique features of our p-n-p selector. Our experimental findings are further extended to confirm the profound functionality of oxide p-n-p selectors integrated with several bipolar resistive switching memory elements working as storage nodes. PMID:26289565

  11. All oxide semiconductor-based bidirectional vertical p-n-p selectors for 3D stackable crossbar-array electronics.

    PubMed

    Bae, Yoon Cheol; Lee, Ah Rahm; Baek, Gwang Ho; Chung, Je Bock; Kim, Tae Yoon; Park, Jea Gun; Hong, Jin Pyo

    2015-08-20

    Three-dimensional (3D) stackable memory devices including nano-scaled crossbar array are central for the realization of high-density non-volatile memory electronics. However, an essential sneak path issue affecting device performance in crossbar array remains a bottleneck and a grand challenge. Therefore, a suitable bidirectional selector as a two-way switch is required to facilitate a major breakthrough in the 3D crossbar array memory devices. Here, we show the excellent selectivity of all oxide p-/n-type semiconductor-based p-n-p open-based bipolar junction transistors as selectors in crossbar memory array. We report that bidirectional nonlinear characteristics of oxide p-n-p junctions can be highly enhanced by manipulating p-/n-type oxide semiconductor characteristics. We also propose an associated Zener tunneling mechanism that explains the unique features of our p-n-p selector. Our experimental findings are further extended to confirm the profound functionality of oxide p-n-p selectors integrated with several bipolar resistive switching memory elements working as storage nodes.

  12. Study of Fused Thiophene Based Organic Semiconductors and Interfacial Self-Assembled Monolayer (SAM) for Thin-Film Transistor (TFT) Application

    NASA Astrophysics Data System (ADS)

    Youn, Jangdae

    , the role of a thiol SAM on top of the gold electrode is investigated in terms of semiconductor film structure and OTFT performance in the bottom-contact/ bottom-gate TFT structure by using one of the most successful small molecule based n-type organic semiconductors, α,ω-diperfluorohexylquarterthiophene (DFH-4T) and N,N' bis(n-octyl)-dicyanoperylene-3,4:9,10-bis(dicarb-oximide) (PDI-8CN2). The study of semiconductor film morphogy shows that the semiconductor molecules at the gold/SAM/semiconductor interface are aligned normal to the substrate, facilitating charge transport at the interfacial region. As a result, contact resistance was minimized, and the OTFT device performance was improved. When it comes to semiconductor-dielectric interface, it is important because the charge transport layer of the OTFTs is formed within several monolayers of semiconductor films right above the gate dielectric. The physical and chemical nature of the dielectric surface significantly influences charge flow. For example, the surface of a SiO2 dielectric contains a large number of SiOH functional groups in air. After depositing semiconductor material on top of the SiO2 surface, those SiOH functional groups play a role of charge traps. One of the most effective ways of circumventing this problem is to introduce organic self-assembled monolayers (SAMs) on the SiO 2 dielectric surface. The SAMs in the semiconductor-dielectric interface not only minimize the charge traps but also improve the crystallinity of top semiconductor layers. Furthermore, the improvement of the semiconductor film microstructure depends on the structure of the SAM. When the SAM is disorganized, the size and density of crystalline domains in the semiconductor film decline. Meanwhile, the domain size and population density of crystalline domains expand when the SAM is tightly packed and vertically aligned. In this thesis, a humidity control method of fabricating high quality octadecyltrichlorosilane (OTS) SAM on SiO2

  13. The Narrow-Band Model and Semi-Conductor Theory

    ERIC Educational Resources Information Center

    Tanner, B. K.

    1976-01-01

    Applies the narrow-band model to the instruction of intrinsic and extrinsic semiconductors along with the phenomenon of compensation. Advocates the model for undergraduate instruction due to its intuitive appeal and mathematical simplicity. (CP)

  14. Optical waveguide beam splitters based on hybrid metal-dielectric-semiconductor nanostructures

    NASA Astrophysics Data System (ADS)

    Li, Yunyun; Liang, Junwu; Zhang, Qinglin; Zhou, Zidong; Li, Honglai; Fan, Xiaopeng; Wang, Xiaoxia; Fan, Peng; Yang, Yankun; Guo, Pengfei; Zhuang, Xiujuan; Zhu, Xiaoli; Liao, Lei; Pan, Anlian

    2015-11-01

    Miniature integration is desirable for the future photonics circuit. Low-dimensional semiconductor and metal nanostructures is the potential building blocks in compact photonic circuits for their unique electronic and optical properties. In this work, a hybrid metal-dielectric-semiconductor nanostructure is designed and fabricated to realizing a nano-scale optical waveguide beam splitter, which is constructed with the sandwiched structure of a single CdS nanoribbon/HfO2 thin film/Au nanodisk arrays. Micro-optical investigations reveal that the guided light outputting at the terminal end of the CdS ribbon is well separated into several light spots. Numerical simulations further demonstrate that the beam splitting mechanism is attributed to the strong electromagnetic coupling between the Au nanodisks and light guided in the nanoribbon. The number of the split beams (light spots) at the terminal end of the nanoribbon is mainly determined by the number of the Au nanodisk rows, as well as the distance of the blank region between the nanodisks array and the end of the CdS ribbon, owing to the interference between the split beams. These optical beam splitters may find potential applications in high-density integrated photonic circuits and systems.

  15. Dense Plasma Focus-Based Nanofabrication of III–V Semiconductors: Unique Features and Recent Advances

    PubMed Central

    Mangla, Onkar; Roy, Savita; Ostrikov, Kostya (Ken)

    2015-01-01

    The hot and dense plasma formed in modified dense plasma focus (DPF) device has been used worldwide for the nanofabrication of several materials. In this paper, we summarize the fabrication of III–V semiconductor nanostructures using the high fluence material ions produced by hot, dense and extremely non-equilibrium plasma generated in a modified DPF device. In addition, we present the recent results on the fabrication of porous nano-gallium arsenide (GaAs). The details of morphological, structural and optical properties of the fabricated nano-GaAs are provided. The effect of rapid thermal annealing on the above properties of porous nano-GaAs is studied. The study reveals that it is possible to tailor the size of pores with annealing temperature. The optical properties of these porous nano-GaAs also confirm the possibility to tailor the pore sizes upon annealing. Possible applications of the fabricated and subsequently annealed porous nano-GaAs in transmission-type photo-cathodes and visible optoelectronic devices are discussed. These results suggest that the modified DPF is an effective tool for nanofabrication of continuous and porous III–V semiconductor nanomaterials. Further opportunities for using the modified DPF device for the fabrication of novel nanostructures are discussed as well.

  16. 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.

  17. 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.

  18. REVIEW ARTICLE: Harmonically mode-locked semiconductor-based lasers as high repetition rate ultralow noise pulse train and optical frequency comb sources

    NASA Astrophysics Data System (ADS)

    Quinlan, F.; Ozharar, S.; Gee, S.; Delfyett, P. J.

    2009-10-01

    Recent experimental work on semiconductor-based harmonically mode-locked lasers geared toward low noise applications is reviewed. Active, harmonic mode-locking of semiconductor-based lasers has proven to be an excellent way to generate 10 GHz repetition rate pulse trains with pulse-to-pulse timing jitter of only a few femtoseconds without requiring active feedback stabilization. This level of timing jitter is achieved in long fiberized ring cavities and relies upon such factors as low noise rf sources as mode-lockers, high optical power, intracavity dispersion management and intracavity phase modulation. When a high finesse etalon is placed within the optical cavity, semiconductor-based harmonically mode-locked lasers can be used as optical frequency comb sources with 10 GHz mode spacing. When active mode-locking is replaced with regenerative mode-locking, a completely self-contained comb source is created, referenced to the intracavity etalon.

  19. Thin Film Transistor Gas Sensors Incorporating High-Mobility Diketopyrrolopyrole-Based Polymeric Semiconductor Doped with Graphene Oxide.

    PubMed

    Cheon, Kwang Hee; Cho, Jangwhan; Kim, Yun-Hi; Chung, Dae Sung

    2015-07-01

    In this work, we fabricated a diketopyrrolopyrole-based donor-acceptor copolymer composite film. This is a high-mobility semiconductor component with a functionalized-graphene-oxide (GO) gas-adsorbing dopant, used as an active layer in gas-sensing organic-field-effect transistor (OFET) devices. The GO content of the composite film was carefully controlled so that the crystalline orientation of the semiconducting polymer could be conserved, without compromising its gas-adsorbing ability. The resulting optimized device exhibited high mobility (>1 cm(2) V(-1) s(-1)) and revealed sensitive response during programmed exposure to various polar organic molecules (i.e., ethanol, acetone, and acetonitrile). This can be attributed to the high mobility of polymeric semiconductors, and also to their high surface-to-volume ratio of GO. The operating mechanism of the gas sensing GO-OFET is fully discussed in conjunction with charge-carrier trap theory. It was found that each transistor parameter (e.g., mobility, threshold voltage), responds independently to each gas molecule, which enables high selectivity of GO-OFETs for various gases. Furthermore, we also demonstrated practical GO-OFET devices that operated at low voltage (<1.5 V), and which successfully responded to gas exposure.

  20. Optimization of the thermoelectric figure of merit of fine-grained semiconductor materials based upon lead telluride

    NASA Astrophysics Data System (ADS)

    Rowe, D. M.

    1986-02-01

    Lead telluride type semiconductors are used in the fabrication of thermoelectric modules. This report covers the programme to produce materials based upon lead telluride with improved figures of merit and hence greater thermoelectric conversion efficiency. One way of improving the figure of merit is by reducing the lattice thermal conductivity of the material. This can be achieved by increasing phonon grain boundary scattering. A realistic theoretical model has been developed for lead telluride and used to investigate the lattice thermal conductivity as a function of grain size and level of doping. In optimally doped material with a grain size of 1 micrometer, the reduction in lattice thermal conductivity was predicted to be 4-6 percent compared with equivalent single crystal. Thermal diffusivity measurements on small grained compacts supported this prediction. Phonon grain boundary scattering is enhanced in semiconductor alloys because of the presence of disorder scattering and the theoretical model was extended to take this factor into account. PbSnTe and PbGeTe were identified as alloys whose lattice thermal conductivity could be significantly decreased by a reduction in grain size and in optimally doped compacted material with a grain size of 0.5 micrometer the reduction compared to equivalent single crystal material was estimated to be 11 and 14 percent respectively.

  1. Characteristic of energetic semiconductor bridge based on Al/MoOx energetic multilayer nanofilms with different modulation periods

    NASA Astrophysics Data System (ADS)

    Xu, Jianbing; Tai, Yu; Ru, Chengbo; Dai, Ji; Shen, Yun; Ye, Yinghua; Shen, Ruiqi; Fu, Shuai

    2017-03-01

    Three types of energetic semiconductor bridges (ESCBs) through integrating different Al/MoOx energetic multilayer nanofilms on a semiconductor bridge have been investigated in this study. The relationships among the critical firing energy, critical firing time, total firing time, and ignition energy as well as the input energy utilization efficiency of these initiators were analyzed. The principal component analysis (PCA) was utilized in the experiments to evaluate the output energy magnitude based on the ignition duration, the maximum flame area, reaction ratio, and other parameters. The results obtained were as follows: (1) The critical firing energy is positively proportional to the modulation periods of nanofilms for the initiators discharged with identical voltage, while the total firing energy and the input energy utilization efficiency do not change significantly; (2) by using PCA, the composite score of the ESCB/50 nm, ESCB/150 nm, ESCB/1500 nm, and SCB is measured at 3.025, 0.250, -1.433, and -1.842, respectively, discharge with 30 V/47 μF, which indicated that the output energy of ESCBs can be increased significantly by decreasing the modulation periods of nanofilms.

  2. Creating semiconductor metafilms with designer absorption spectra

    PubMed Central

    Kim, Soo Jin; Fan, Pengyu; Kang, Ju-Hyung; Brongersma, Mark L.

    2015-01-01

    The optical properties of semiconductors are typically considered intrinsic and fixed. Here we leverage the rapid developments in the field of optical metamaterials to create ultrathin semiconductor metafilms with designer absorption spectra. We show how such metafilms can be constructed by placing one or more types of high-index semiconductor antennas into a dense array with subwavelength spacings. It is argued that the large absorption cross-section of semiconductor antennas and their weak near-field coupling open a unique opportunity to create strongly absorbing metafilms whose spectral absorption properties directly reflect those of the individual antennas. Using experiments and simulations, we demonstrate that near-unity absorption at one or more target wavelengths of interest can be achieved in a sub-50-nm-thick metafilm using judiciously sized and spaced Ge nanobeams. The ability to create semiconductor metafilms with custom absorption spectra opens up new design strategies for planar optoelectronic devices and solar cells. PMID:26184335

  3. Nonvolatile Memory Effect in Indium Gallium Arsenide-Based Metal-Oxide-Semiconductor Devices Using II-VI Tunnel Insulators

    NASA Astrophysics Data System (ADS)

    Chan, P.-Y.; Gogna, M.; Suarez, E.; Karmakar, S.; Al-Amoody, F.; Miller, B. I.; Jain, F. C.

    2011-08-01

    This paper reports the successful use of ZnSe/ZnS/ZnMgS/ZnS/ZnSe as a gate insulator stack for an InGaAs-based metal-oxide-semiconductor (MOS) device, and demonstrates the threshold voltage shift required in nonvolatile memory devices using a floating gate quantum dot layer. An InGaAs-based nonvolatile memory MOS device was fabricated using a high- κ II-VI tunnel insulator stack and self-assembled GeO x -cladded Ge quantum dots as the charge storage units. A Si3N4 layer was used as the control gate insulator. Capacitance-voltage data showed that, after applying a positive voltage to the gate of a MOS device, charges were being stored in the quantum dots. This was shown by the shift in the flat-band/threshold voltage, simulating the write process of a nonvolatile memory device.

  4. Optical absorption enhancement of hybrid-plasmonic-based metal-semiconductor-metal photodetector incorporating metal nanogratings and embedded metal nanoparticles.

    PubMed

    Tan, Chee Leong; Karar, Ayman; Alameh, Kamal; Lee, Yong Tak

    2013-01-28

    We propose and numerically demonstrate a high absorption hybrid-plasmonic-based metal semiconductor metal photodetector (MSM-PD) comprising metal nanogratings, a subwavelength slit and amorphous silicon or germanium embedded metal nanoparticles (NPs). Simulation results show that by optimizing the metal nanograting parameters, the subwavelength slit and the embedded metal NPs, a 1.3 order of magnitude increase in electric field is attained, leading to 28-fold absorption enhancement, in comparison with conventional MSM-PD structures. This is 3.5 times better than the absorption of surface plasmon polariton (SPP) based MSM-PD structures employing metal nanogratings and a subwavelength slit. This absorption enhancement is due to the ability of the embedded metal NPs to enhance their optical absorption and scattering properties through light-stimulated resonance aided by the conduction electrons of the NPs.

  5. Facing the Sunrise: Cultural Worldview Underlying Intrinsic-Based Encoding of Absolute Frames of Reference in Aymara

    ERIC Educational Resources Information Center

    Nunez, Rafael E.; Cornejo, Carlos

    2012-01-01

    The Aymara of the Andes use absolute (cardinal) frames of reference for describing the relative position of ordinary objects. However, rather than encoding them in available absolute lexemes, they do it in lexemes that are intrinsic to the body: "nayra" ("front") and "qhipa" ("back"), denoting east and west,…

  6. BRIDGE21--Exploring the Potential to Foster Intrinsic Student Motivation through a Team-Based, Technology-Mediated Learning Model

    ERIC Educational Resources Information Center

    Lawlor, John; Marshall, Kevin; Tangney, Brendan

    2016-01-01

    It is generally accepted that intrinsic student motivation is a critical requirement for effective learning but formal learning in school places a huge reliance on extrinsic motivation to focus the learner. This reliance on extrinsic motivation is driven by the pressure on formal schooling to "deliver to the test." The experience of the…

  7. Charge carrier coherence and Hall effect in organic semiconductors

    DOE PAGES

    Yi, H. T.; Gartstein, Y. N.; Podzorov, V.

    2016-03-30

    Hall effect measurements are important for elucidating the fundamental charge transport mechanisms and intrinsic mobility in organic semiconductors. However, Hall effect studies frequently reveal an unconventional behavior that cannot be readily explained with the simple band-semiconductor Hall effect model. Here, we develop an analytical model of Hall effect in organic field-effect transistors in a regime of coexisting band and hopping carriers. The model, which is supported by the experiments, is based on a partial Hall voltage compensation effect, occurring because hopping carriers respond to the transverse Hall electric field and drift in the direction opposite to the Lorentz force actingmore » on band carriers. We show that this can lead in particular to an underdeveloped Hall effect observed in organic semiconductors with substantial off-diagonal thermal disorder. Lastly, our model captures the main features of Hall effect in a variety of organic semiconductors and provides an analytical description of Hall mobility, carrier density and carrier coherence factor.« less

  8. Semiconductor films on flexible iridium substrates

    DOEpatents

    Goyal, Amit

    2005-03-29

    A laminate semiconductor article includes a flexible substrate, an optional biaxially textured oxide buffer system on the flexible substrate, a biaxially textured Ir-based buffer layer on the substrate or the buffer system, and an epitaxial layer of a semiconductor. Ir can serve as a substrate with an epitaxial layer of a semiconductor thereon.

  9. Band gap narrowing in zinc oxide-based semiconductor thin films

    SciTech Connect

    Kumar, Jitendra E-mail: akrsri@gmail.com; Kumar Srivastava, Amit E-mail: akrsri@gmail.com

    2014-04-07

    A simple expression is proposed for the band gap narrowing (or shrinkage) in semiconductors using optical absorption measurements of spin coated 1 at. % Ga-doped ZnO (with additional 0–1.5 at. % zinc species) thin films as ΔE{sub BGN} = Bn{sup 1/3} [1 − (n{sub c}/n){sup 1/3}], where B is the fitting parameter, n is carrier concentration, and n{sub c} is the critical density required for shrinkage onset. Its uniqueness lies in not only describing variation of ΔE{sub BGN} correctly but also allowing deduction of n{sub c} automatically for several M-doped ZnO (M: Ga, Al, In, B, Mo) systems. The physical significance of the term [1 − (n{sub c}/n){sup 1/3}] is discussed in terms of carrier separation.

  10. Selection of modes in transverse-mode waveguides for semiconductor lasers based on asymmetric heterostructures

    SciTech Connect

    Slipchenko, S. O. Bondarev, A. D.; Vinokurov, D. A.; Nikolaev, D. N.; Fetisova, N. V.; Sokolova, Z. N.; Pikhtin, N. A.; Tarasov, I. S.

    2009-01-15

    Asymmetric Al{sub 0.3}Ga{sub 0.7}As/GaAs/InGaAs heterostructures with a broadened waveguide produced by the method of MOCVD epitaxy are studied. It is established that the precision shift of the active region to one of the cladding layers ensures the generation of the chosen mode of high order in the transverse broadened waveguide. It is experimentally established that this shift brings about an increase in internal optical losses and a decrease in the internal quantum efficiency of stimulated emission. It is shown experimentally that the shift of the active region to the n-type cladding layer governs the sublinear form of the power-current characteristic for semiconductor lasers; in the case of a shift of the active region towards the p-type cladding layer, the laser diodes demonstrated a linear dependence of optical power on the pump current in the entire range of pump currents.

  11. Spin polarized state filter based on semiconductor–dielectric–iron–semiconductor multi-nanolayer device

    SciTech Connect

    Makarov, Vladimir I.; Khmelinskii, Igor

    2015-04-15

    Highlights: • Development of a new spintronics device. • Development of quantum spin polarized filters. • Development of theory of quantum spin polarized filter. - Abstract: Presently we report spin-polarized state transport in semiconductor–dielectric–iron–semiconductor (SDIS) four-nanolayer sandwich devices. The exchange-resonance spectra in such devices are quite specific, differing also from spectra observed earlier in other three-nanolayer devices. The theoretical model developed earlier is extended and used to interpret the available experimental results. A detailed ab initio analysis of the magnetic-field dependence of the output magnetic moment is also performed. The model predicts an exchange spectrum comprising a series of peaks, with the spectral structure determined by several factors, discussed in the paper.

  12. 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.

  13. Metal-semiconductor-metal neutron detectors based on hexagonal boron nitride epitaxial layers

    NASA Astrophysics Data System (ADS)

    Majety, S.; Li, J.; Cao, X. K.; Dahal, R.; Lin, J. Y.; Jiang, H. X.

    2012-10-01

    Hexagonal boron nitride (hBN) possesses extraordinary potential for solid-state neutron detector applications. This stems from the fact that the boron-10 (10B) isotope has a capture cross-section of 3840 barns for thermal neutrons that is orders of magnitude larger than other isotopes. Epitaxial layers of hBN have been synthesized by metal organic chemical vapor deposition (MOCVD). Experimental measurements indicated that the thermal neutron absorption coefficient and length of natural hBN epilayers are about 0.0036 μm-1 and 277 μm, respectively. To partially address the key requirement of long carrier lifetime and diffusion length for a solid-state neutron detector, micro-strip metal-semiconductor-metal detectors were fabricated and tested. A good current response was generated in these detectors using continuous irradiation with a thermal neutron beam, corresponding to an effective conversion efficiency approaching ~80% for absorbed neutrons.

  14. Accelerator-based electron beam technologies for modification of bipolar semiconductor devices

    NASA Astrophysics Data System (ADS)

    Pavlov, Y. S.; Surma, A. M.; Lagov, P. B.; Fomenko, Y. L.; Geifman, E. M.

    2016-09-01

    Radiation processing technologies for static and dynamic parameters modification of silicon bipolar semiconductor devices implemented. Devices of different classes with wide range of operating currents (from a few mA to tens kA) and voltages (from a few volts to 8 kV) were processed in large scale including power diodes and thyristors, high-frequency bipolar and IGBT transistors, fast recovery diodes, pulsed switching diodes, precise temperature- compensated Zener diodes (in general more than fifty 50 device types), produced by different enterprises. The necessary changes in electrical parameters and characteristics of devices caused by formation in the device structures of electrically active and stable in the operating temperature range sub-nanoscale recombination centres. Technologies implemented in the air with high efficiency and controllability, and are an alternative to diffusion doping of Au or Pt, γ-ray, proton and low-Z ion irradiation.

  15. Dissolution chemistry and biocompatibility of silicon- and germanium-based semiconductors for transient electronics.

    PubMed

    Kang, Seung-Kyun; Park, Gayoung; Kim, Kyungmin; Hwang, Suk-Won; Cheng, Huanyu; Shin, Jiho; Chung, Sangjin; Kim, Minjin; Yin, Lan; Lee, Jeong Chul; Lee, Kyung-Mi; Rogers, John A

    2015-05-06

    Semiconducting materials are central to the development of high-performance electronics that are capable of dissolving completely when immersed in aqueous solutions, groundwater, or biofluids, for applications in temporary biomedical implants, environmentally degradable sensors, and other systems. The results reported here include comprehensive studies of the dissolution by hydrolysis of polycrystalline silicon, amorphous silicon, silicon-germanium, and germanium in aqueous solutions of various pH values and temperatures. In vitro cellular toxicity evaluations demonstrate the biocompatibility of the materials and end products of dissolution, thereby supporting their potential for use in biodegradable electronics. A fully dissolvable thin-film solar cell illustrates the ability to integrate these semiconductors into functional systems.

  16. New unorthodox semiconductor devices

    NASA Astrophysics Data System (ADS)

    Board, K.

    1985-12-01

    A range of new semiconductor devices, including a number of structures which rely entirely upon new phenomena, are discussed. Unipolar two-terminal devices, including impurity-controlled barriers and graded composition barriers, are considered, as are new transistor structures, including the hot-electron camel transistor, the planar-doped barrier transistor, the thermionic emission transistor, and the permeable base transistor. Regenerative switching devices are addressed, including the metal-tunnel insulator-semiconductor switch, the polysilicon switch, MIS, and MISIM switching structures, and the triangular-barrier switch. Heterostructure devices are covered, including the heterojunction bipolar transistor, the selectively doped heterojunction transistor, heterojunction lasers, and quantum-well structures.

  17. Ferromagnets based on diamond-like semiconductors GaSb, InSb, Ge, and Si supersaturated with manganese or iron impurities during laser-plasma deposition

    SciTech Connect

    Demidov, E. S.; Podol'skii, V. V.; Lesnikov, V. P.; Sapozhnikov, M. V.; Druzhnov, D. M.; Gusev, S. N.; Gribkov, B. A.; Filatov, D. O.; Stepanova, Yu. S.; Levchuk, S. A.

    2008-01-15

    Properties of thin (30-100 nm) layers of diluted magnetic semiconductors based on diamond-like compounds III-V (InSb and GaSb) and elemental semiconductors Ge and Si doped with 3d impurities of manganese and iron up to 15% were measured and discussed. The layers were grown by laser-plasma deposition onto heated single-crystal gallium arsenide or sapphire substrates. The ferromagnetism of layers with the Curie temperature up to 500 K appeared in observations of the ferromagnetic resonance, anomalous Hall effect, and magneto-optic Kerr effect. The carrier mobility of diluted magnetic semiconductors is a hundred times larger than that of the previously known highest temperature magnetic semiconductors, i.e., copper and chromium chalcogenides. The difference between changes in the magnetization with temperature in diluted semiconductors based on III-V, Ge, and Si was discussed. A complex structure of the ferromagnetic resonance spectrum in Si:Mn/GaAs was observed. The results of magnetic-force microscopy showed a weak correlation between the surface relief and magnetic inhomogeneity, which suggests that the ferromagnetism is caused by the 3d-impurity solid solution, rather than ferromagnetic phase inclusions.

  18. Diode having trenches in a semiconductor region

    DOEpatents

    Palacios, Tomas Apostol; Lu, Bin; Matioli, Elison de Nazareth

    2016-03-22

    An electrode structure is described in which conductive regions are recessed into a semiconductor region. Trenches may be formed in a semiconductor region, such that conductive regions can be formed in the trenches. The electrode structure may be used in semiconductor devices such as field effect transistors or diodes. Nitride-based power semiconductor devices are described including such an electrode structure, which can reduce leakage current and otherwise improve performance.

  19. Semiconductor devices having a recessed electrode structure

    DOEpatents

    Palacios, Tomas Apostol; Lu, Bin; Matioli, Elison de Nazareth

    2015-05-26

    An electrode structure is described in which conductive regions are recessed into a semiconductor region. Trenches may be formed in a semiconductor region, such that conductive regions can be formed in the trenches. The electrode structure may be used in semiconductor devices such as field effect transistors or diodes. Nitride-based power semiconductor devices are described including such an electrode structure, which can reduce leakage current and otherwise improve performance.

  20. Nonlinear theory of surface-helical instability of a semiconductor plasma. III. Analysis of nonlinear effects

    NASA Astrophysics Data System (ADS)

    Karavaev, F. G.; Uspenskii, B. A.; Chuprikov, N. L.

    1980-05-01

    Results obtained earlier in [1, 2] are used to calculate the nonlinear parameters of the helical instability of a semiconductor plasma that fills a half-space. It is found that in semiconductors with intrinsic or almost intrinsic conduction an “explosive” type of instability development occurs, this being due to the effect of the electric self-field of the wave.

  1. Wide-Bandgap Semiconductors

    SciTech Connect

    Chinthavali, M.S.

    2005-11-22

    With the increase in demand for more efficient, higher-power, and higher-temperature operation of power converters, design engineers face the challenge of increasing the efficiency and power density of converters [1, 2]. Development in power semiconductors is vital for achieving the design goals set by the industry. Silicon (Si) power devices have reached their theoretical limits in terms of higher-temperature and higher-power operation by virtue of the physical properties of the material. To overcome these limitations, research has focused on wide-bandgap materials such as silicon carbide (SiC), gallium nitride (GaN), and diamond because of their superior material advantages such as large bandgap, high thermal conductivity, and high critical breakdown field strength. Diamond is the ultimate material for power devices because of its greater than tenfold improvement in electrical properties compared with silicon; however, it is more suited for higher-voltage (grid level) higher-power applications based on the intrinsic properties of the material [3]. GaN and SiC power devices have similar performance improvements over Si power devices. GaN performs only slightly better than SiC. Both SiC and GaN have processing issues that need to be resolved before they can seriously challenge Si power devices; however, SiC is at a more technically advanced stage than GaN. SiC is considered to be the best transition material for future power devices before high-power diamond device technology matures. Since SiC power devices have lower losses than Si devices, SiC-based power converters are more efficient. With the high-temperature operation capability of SiC, thermal management requirements are reduced; therefore, a smaller heat sink would be sufficient. In addition, since SiC power devices can be switched at higher frequencies, smaller passive components are required in power converters. Smaller heat sinks and passive components result in higher-power-density power converters

  2. Kansas Advanced Semiconductor Project

    SciTech Connect

    Baringer, P.; Bean, A.; Bolton, T.; Horton-Smith, G.; Maravin, Y.; Ratra, B.; Stanton, N.; von Toerne, E.; Wilson, G.

    2007-09-21

    KASP (Kansas Advanced Semiconductor Project) completed the new Layer 0 upgrade for D0, assumed key electronics projects for the US CMS project, finished important new physics measurements with the D0 experiment at Fermilab, made substantial contributions to detector studies for the proposed e+e- international linear collider (ILC), and advanced key initiatives in non-accelerator-based neutrino physics.

  3. 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…

  4. A novel approach for generating flat optical frequency comb based on externally injected gain-switching distributed feedback semiconductor laser

    NASA Astrophysics Data System (ADS)

    Zhu, Huatao; Wang, Rong; Pu, Tao; Xiang, Peng; Zheng, Jilin; Fang, Tao

    2017-02-01

    In this paper, a novel approach for generating flat optical frequency comb (OFC) based on externally injected gain-switched distributed feedback (DFB) semiconductor laser is proposed and experimentally demonstrated. In the proposed system, the flatness, the number of OFC spectral lines, and the spectral line to background noise ratio can be tuned to their optimized values by adjusting the current of the modulation signal, the injection ratio and the detuning frequency. Since the frequency of the modulation signal decides the frequency spacing of the output spectral lines, OFC spectral lines of different spacing can be achieved. In the experiment, 10 spectral lines with 1.5 dB power variation are demonstrated to verify the proposed approach. In addition, the expansion of the spectral line is investigated.

  5. High responsivity A-plane GaN-based metal-semiconductor-metal photodetectors for polarization-sensitive applications

    SciTech Connect

    Navarro, A.; Rivera, C.; Pereiro, J.; Munoz, E.; Imer, B.; DenBaars, S. P.; Speck, J. S.

    2009-05-25

    The fabrication and characterization of metal-semiconductor-metal polarization-sensitive photodetectors based on A-plane GaN grown on R-plane sapphire substrates is reported. These photodetectors take advantage of the in-plane crystal anisotropy, which results in linear dichroism near the band gap energy. The high resistivity of the A-plane GaN material leads to extremely low dark currents. For an optimized finger spacing of 1 {mu}m, dark current density and responsivity at 30 V are 0.3 nA/mm{sup 2} and 2 A/W, respectively. A maximum polarization sensitivity ratio of 1.8 was determined. In a differential configuration, the full width at half maximum of the polarization-sensitive region is 8.5 nm.

  6. 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.

  7. 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

    2014-02-07

    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.

  8. Photonic generation of ultra-wideband doublet pulse using a semiconductor-optical-amplifier based polarization-diversified loop.

    PubMed

    Luo, Bowen; Dong, Jianji; Yu, Yuan; Yang, Ting; Zhang, Xinliang

    2012-06-15

    We propose and demonstrate a novel scheme of ultra-wideband (UWB) doublet pulse generation using a semiconductor optical amplifier (SOA) based polarization-diversified loop (PDL) without any assistant light. In our scheme, the incoming gaussian pulse is split into two parts by the PDL, and each of them is intensity modulated by the other due to cross-gain modulation (XGM) in the SOA. Then, both parts are recombined with incoherent summation to form a UWB doublet pulse. Bi-polar UWB doublet pulse generation is demonstrated using an inverted gaussian pulse injection. Moreover, pulse amplitude modulation of UWB doublet is also experimentally demonstrated. Our scheme shows some advantages, such as simple implementation without assistant light and single optical carrier operation with good fiber dispersion tolerance.

  9. TUNABLE RING LASER BASED ON A SEMICONDUCTOR OPTICAL AMPLIFIER AT 1300 NM USING A SIMPLE WAVELENGTH SELECTION FILTER

    PubMed Central

    Jeon, Mansik; Kim, Jeehyun; Song, Jae-Won; Lee, Ho; Choi, Sanghoon; Nelson, J. Stuart

    2009-01-01

    A simple, compact, and low cost tunable ring laser with a commercial semiconductor optical amplifier (SOA) was demonstrated. The tunable ring laser is based on an external wavelength filter cavity that is analogous with the Littman configuration with a diffraction grating, a mirror, and a simple slit. The unique structural advantage of this new system is that the slit is displaced to select a desired wavelength instead of tilting the mirror as in the Littman configuration. This allows easy control over the selected wavelength by the translating action of the slit. The full width half maximum (FWHM) wavelength turning range is 45 nm, and the wavelength resolution is about 2 pm. The demonstrated tunable ring laser has 2 mW output power. The side mode suppression ratios is 70–73 dB. PMID:20539831

  10. Frequency-modulated, tunable, semiconductor-optical-amplifier-based fiber ring laser for linewidth and line shape control.

    PubMed

    Girard, Simon Lambert; Chen, Hongxin; Schinn, Gregory W; Piché, Michel

    2008-08-15

    We report how the linewidth and line shape of a tunable semiconductor-optical-amplifier-based fiber ring laser can be actively adjusted by applying an intracavity frequency modulation to the laser. Frequency-modulated laser operation is achieved by driving the phase modulator frequency close to the cavity axial-mode spacing, leading to a constant-amplitude laser output having a periodically varying instantaneous frequency. The resulting linewidth varies proportionally with the inverse of the frequency detuning, and it is adjustable from submegahertz to over more than 5 GHz. By appropriate selection of the modulating waveform we have synthesized a near-Gaussian output line shape; other line shapes can be produced by modifying the modulating waveform. Experimental observations are in good agreement with a simple model.

  11. Physics with isotopically controlled semiconductors

    SciTech Connect

    Haller, E. E.

    2010-07-15

    This paper is based on a tutorial presentation at the International Conference on Defects in Semiconductors (ICDS-25) held in Saint Petersburg, Russia in July 2009. The tutorial focused on a review of recent research involving isotopically controlled semiconductors. Studies with isotopically enriched semiconductor structures experienced a dramatic expansion at the end of the Cold War when significant quantities of enriched isotopes of elements forming semiconductors became available for worldwide collaborations. Isotopes of an element differ in nuclear mass, may have different nuclear spins and undergo different nuclear reactions. Among the latter, the capture of thermal neutrons which can lead to neutron transmutation doping, is the most prominent effect for semiconductors. Experimental and theoretical research exploiting the differences in all the properties has been conducted and will be illustrated with selected examples.

  12. First order reversal curves and intrinsic parameter determination for magnetic materials; limitations of hysteron-based approaches in correlated systems

    NASA Astrophysics Data System (ADS)

    Ruta, Sergiu; Hovorka, Ondrej; Huang, Pin-Wei; Wang, Kangkang; Ju, Ganping; Chantrell, Roy

    2017-03-01

    The generic problem of extracting information on intrinsic particle properties from the whole class of interacting magnetic fine particle systems is a long standing and difficult inverse problem. As an example, the Switching Field Distribution (SFD) is an important quantity in the characterization of magnetic systems, and its determination in many technological applications, such as recording media, is especially challenging. Techniques such as the first order reversal curve (FORC) methods, were developed to extract the SFD from macroscopic measurements. However, all methods rely on separating the contributions to the measurements of the intrinsic SFD and the extrinsic effects of magnetostatic and exchange interactions. We investigate the underlying physics of the FORC method by applying it to the output predictions of a kinetic Monte-Carlo model with known input parameters. We show that the FORC method is valid only in cases of weak spatial correlation of the magnetisation and suggest a more general approach.

  13. First order reversal curves and intrinsic parameter determination for magnetic materials; limitations of hysteron-based approaches in correlated systems

    PubMed Central

    Ruta, Sergiu; Hovorka, Ondrej; Huang, Pin-Wei; Wang, Kangkang; Ju, Ganping; Chantrell, Roy

    2017-01-01

    The generic problem of extracting information on intrinsic particle properties from the whole class of interacting magnetic fine particle systems is a long standing and difficult inverse problem. As an example, the Switching Field Distribution (SFD) is an important quantity in the characterization of magnetic systems, and its determination in many technological applications, such as recording media, is especially challenging. Techniques such as the first order reversal curve (FORC) methods, were developed to extract the SFD from macroscopic measurements. However, all methods rely on separating the contributions to the measurements of the intrinsic SFD and the extrinsic effects of magnetostatic and exchange interactions. We investigate the underlying physics of the FORC method by applying it to the output predictions of a kinetic Monte-Carlo model with known input parameters. We show that the FORC method is valid only in cases of weak spatial correlation of the magnetisation and suggest a more general approach. PMID:28338056

  14. Two-step fabrication of self-catalyzed Ga-based semiconductor nanowires on Si by molecular-beam epitaxy.

    PubMed

    Yu, Xuezhe; Li, Lixia; Wang, Hailong; Xiao, Jiaxing; Shen, Chao; Pan, Dong; Zhao, Jianhua

    2016-05-19

    For the epitaxial growth of Ga-based III-V semiconductor nanowires (NWs) on Si, Ga droplets could provide a clean and compatible solution in contrast to the common Au catalyst. However, the use of Ga droplets is rather limited except for that in Ga-catalyzed GaAs NW studies in a relatively narrow growth temperature (Ts) window around 620 °C on Si. In this paper, we have investigated the two-step growth of Ga-catalyzed III-V NWs on Si (111) substrates by molecular-beam epitaxy. First, by optimizing the surface oxide, vertically aligned GaAs NWs with a high yield are obtained at Ts = 620 °C. Then a two-temperature procedure is adopted to preserve Ga droplets at lower Ts, which leads to an extension of Ts down to 500 °C for GaAs NWs. Based on this procedure, systematic morphological and structural studies for Ga-catalyzed GaAs NWs in the largest Ts range could be presented. Then within the same growth scheme, for the first time, we demonstrate Ga-catalyzed GaAs/GaSb heterostructure NWs. These GaSb NWs are axially grown on the GaAs NW sections and are pure zinc-blende single crystals. Compositional measurements confirm that the catalyst particles indeed mainly consist of Ga and GaSb sections are of high purity but with a minor composition of As. In the end, we present GaAsSb NW growth with a tunable Sb composition. Our results provide useful information for the controllable synthesis of multi-compositional Ga-catalyzed III-V semiconductor NWs on Si for heterogeneous integration.

  15. Tunable and switchable multi-wavelength fiber laser based on semiconductor optical amplifier and twin-core photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Kim, Bongkyun; Han, Jihee; Chung, Youngjoo

    2012-02-01

    Multi-wavelength fiber lasers have attracted a lot of interest, recently, because of their potential applications in wavelength-division-multiplexing (WDM) systems, optical fiber sensing, and fiber-optics instruments, due to their numerous advantages such as multiple wavelength operation, low cost, and compatibility with the fiber optic systems. Semiconductor optical amplifier (SOA)-based multi-wavelength fiber lasers exhibit stable operation because of the SOA has the property of primarily inhomogeneous broadening and thus can support simultaneous oscillation of multiple lasing wavelengths. In this letter, we propose and experimentally demonstrate a switchable multi-wavelength fiber laser employing a semiconductor optical amplifier and twin-core photonic crystal fiber (TC-PCF) based in-line interferometer comb filter. The fabricated two cores are not symmetric due to the associated fiber fabrication process such as nonuniform heat gradient in furnace and asymmetric microstructure expansion during the gas pressurization which results in different silica strut thickness and core size. The induced asymmetry between two cores considerably alters the linear power transfer, by seriously reducing it. These nominal twin cores form effective two optical paths and associated effective refractive index difference. The in-fiber comb filter is effectively constructed by splicing a section of TC-PCF between two single mode fibers (SMFs). The proposed laser can be designed to operate in stable multi-wavelength lasing states by adjusting the states of the polarization controller (PC). The lasing modes are switched by varying the state of PC and the change is reversible. In addition, we demonstrate a tunable multi-wavelength fiber laser operation by applying temperature changes to TC-PCF in the multi-channel filter.

  16. Search for effective spin injection heterostructures based on half-metal Heusler alloys/gallium arsenide semiconductors: A theoretical investigation

    NASA Astrophysics Data System (ADS)

    Sivakumar, Chockalingam

    Efficient electrical spin injection from half-metal (HM) electrodes into semiconducting (SC) channel material is a desirable aspect in spintronics, but a challenging one. Half-metals based on the Heusler alloy family are promising candidates as spin sources due to their compatibility with compound SCs, and very high Curie temperatures. Numerous efforts were made in the past two decades to grow atomically abrupt interfaces between HM_Heusler and SC heterostructures. However, diffusion of magnetic impurities into the semiconductor, defects and disorder near the interface, and formation of reacted phases were great challenges. A number of theoretical efforts were undertaken to understand the role of such material defects in destroying the half-metallicity and also to propose promising half-metal/SC heterostructures based on first principles. This dissertation summarizes the investigations undertaken to decode the complexity of, and to understand the various physical properties of, a number of real-world Heusler/SC heterostructure samples, based on the ab initio density functional theory (DFT) approach. In addition, it summarizes various results from the first principles-based search for promising half-metal/SC heterostructures. First, I present results from DFT-based predictive models of actual Co 2MnSi (CMS)/GaAs heterostructures grown in (001) texture. I investigate the physical, chemical, electronic, and magnetic properties to understand the complexity of these structures and to pinpoint the origin of interfacial effects, when present. Based on the investigations of such models, I discuss the utility of those actual samples in spintronic applications. Next, I summarise the results from an ab initio DFT-based survey of 6 half-Heusler half-metal/GaAs heterostructure models in (110) texture, since compound semiconductors such as GaAs have very long spin lifetime in (110) layering. I show 3 half-Heusler alloys (CoVAs, NiMnAs, and RhFeGe), that when interfaced with Ga

  17. Fast optical source for quantum key distribution based on semiconductor optical amplifiers.

    PubMed

    Jofre, M; Gardelein, A; Anzolin, G; Amaya, W; Capmany, J; Ursin, R; Peñate, L; Lopez, D; San Juan, J L; Carrasco, J A; Garcia, F; Torcal-Milla, F J; Sanchez-Brea, L M; Bernabeu, E; Perdigues, J M; Jennewein, T; Torres, J P; Mitchell, M W; Pruneri, V

    2011-02-28

    A novel integrated optical source capable of emitting faint pulses with different polarization states and with different intensity levels at 100 MHz has been developed. The source relies on a single laser diode followed by four semiconductor optical amplifiers and thin film polarizers, connected through a fiber network. The use of a single laser ensures high level of indistinguishability in time and spectrum of the pulses for the four different polarizations and three different levels of intensity. The applicability of the source is demonstrated in the lab through a free space quantum key distribution experiment which makes use of the decoy state BB84 protocol. We achieved a lower bound secure key rate of the order of 3.64 Mbps and a quantum bit error ratio as low as 1.14×10⁻² while the lower bound secure key rate became 187 bps for an equivalent attenuation of 35 dB. To our knowledge, this is the fastest polarization encoded QKD system which has been reported so far. The performance, reduced size, low power consumption and the fact that the components used can be space qualified make the source particularly suitable for secure satellite communication.

  18. Characterization of wavelength-swept active mode locking fiber laser based on reflective semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Lee, Hwi Don; Lee, Ju Han; Yung Jeong, Myung; Kim, Chang-Seok

    2011-07-01

    The static and dynamic characteristics of a wavelength-swept active mode locking (AML) fiber laser are presented in both the time-region and wavelength-region. This paper shows experimentally that the linewidth of a laser spectrum and the bandwidth of the sweeping wavelength are dependent directly on the length and dispersion of the fiber cavity as well as the modulation frequency and sweeping rate under the mode-locking condition. To achieve a narrower linewidth, a longer length and higher dispersion of the fiber cavity as well as a higher order mode locking condition are required simultaneously. For a broader bandwidth, a lower order of the mode locking condition is required using a lower modulation frequency. The dynamic sweeping performance is also analyzed experimentally to determine its applicability to optical coherence tomography imaging. It is shown that the maximum sweeping rate can be improved by the increased free spectral range from the shorter length of the fiber cavity. A reflective semiconductor optical amplifier (RSOA) was used to enhance the modulation and dispersion efficiency. Overall a triangular electrical signal can be used instead of the sinusoidal signal to sweep the lasing wavelength at a high sweeping rate due to the lack of mechanical restrictions in the wavelength sweeping mechanism.

  19. Design of Semiconductor-Based Back Reflectors for High Voc Monolithic Multijunction Solar Cells: Preprint

    SciTech Connect

    Garcia, I.; Geisz, J.; Steiner, M.; Olson, J.; Friedman, D.; Kurtz, S.

    2012-06-01

    State-of-the-art multijunction cell designs have the potential for significant improvement before going to higher number of junctions. For example, the Voc can be substantially increased if the photon recycling taking place in the junctions is enhanced. This has already been demonstrated (by Alta Devices) for a GaAs single-junction cell. For this, the loss of re-emitted photons by absorption in the underlying layers or substrate must be minimized. Selective back surface reflectors are needed for this purpose. In this work, different architectures of semiconductor distributed Bragg reflectors (DBR) are assessed as the appropriate choice for application in monolithic multijunction solar cells. Since the photon re-emission in the photon recycling process is spatially isotropic, the effect of the incident angle on the reflectance spectrum is of central importance. In addition, the DBR structure must be designed taking into account its integration into the monolithic multijunction solar cells, concerning series resistance, growth economics, and other issues. We analyze the tradeoffs in DBR design complexity with all these requirements to determine if such a reflector is suitable to improve multijunction solar cells.

  20. Simulation of plasma based semiconductor processing using block structured locally refined grids

    SciTech Connect

    Wake, D.D.

    1998-01-01

    We have described a new numerical method for plasma simulation. Calculations have been presented which show that the method is accurate and suggest the regimes in which the method provides savings in CPU time and memory requirements. A steady state simulation of a four centimeter domain was modeled with sheath scale (150 microns) resolution using only 40 grid points. Simulations of semiconductor processing equipment have been performed which imply the usefulness of the method for engineering applications. It is the author`s opinion that these accomplishments represent a significant contribution to plasma simulation and the efficient numerical solution of certain systems of non-linear partial differential equations. More work needs to be done, however, for the algorithm to be of practical use in an engineering environment. Despite our success at avoiding the dielectric relaxation timestep restrictions the algorithm is still conditionally stable and requires timesteps which are relatively small. This represents a prohibitive runtime for steady state solutions on high resolution grids. Current research suggests that these limitations may be overcome and the use of much larger timesteps will be possible.

  1. Solar cells based on block copolymer semiconductor nanowires: effects of nanowire aspect ratio.

    PubMed

    Ren, Guoqiang; Wu, Pei-Tzu; Jenekhe, Samson A

    2011-01-25

    The solution-phase self-assembly of nanowires (NWs) from diblock copolymer semiconductors, poly(3-butylthiophene)-block-poly(3-octylthiophene), of different block compositions gave crystalline NWs of similar width (13-16 nm) but a tunable average aspect ratio (length/width) of 50-260. The power conversion efficiency of bulk heterojunction solar cells comprising the diblock copolythiophene NWs and PC(71)BM was found to increase with increasing aspect ratio, reaching 3.4% at the highest average aspect ratio of 260. The space charge limited current mobility of holes in neat films of the copolymer NWs and in copolymer NWs/PC(71)BM films (∼1.0 × 10(-4) cm(2)/(V s)) was invariant with aspect ratio, reflecting the parallel orientation of the NWs to the substrate. The enhancement of photovoltaic efficiency with increasing aspect ratio of NWs was explained in terms of increased exciton and charge photogeneration and collection in the bulk heterojunction solar cells.

  2. Analysis of Interface Charge Densities for High-k Dielectric Materials based Metal Oxide Semiconductor Devices

    NASA Astrophysics Data System (ADS)

    Maity, N. P.; Thakur, R. R.; Maity, Reshmi; Thapa, R. K.; Baishya, S.

    2016-10-01

    In this paper, the interface charge densities (Dit) are studied and analyzed for ultra thin dielectric metal oxide semiconductor (MOS) devices using different high-k dielectric materials such as Al2O3, ZrO2 and HfO2. The Dit have been calculated by a new approach using conductance method and it indicates that by reducing the thickness of the oxide, the Dit increases and similar increase is also found by replacing SiO2 with high-k. For the same oxide thickness, SiO2 has the lowest Dit and found to be the order of 1011cm-2eV-1. Linear increase in Dit has been observed as the dielectric constant of the oxide increases. The Dit is found to be in good agreement with published fabrication results at p-type doping level of 1×1017cm-3. Numerical calculations and solutions are performed by MATLAB and device simulation is done by ATLAS.

  3. Fast optical source for quantum key distribution based on semiconductor optical amplifiers

    NASA Astrophysics Data System (ADS)

    Jofre, M.; Gardelein, A.; Anzolin, G.; Amaya, W.; Campmany, J.; Ursin, R.; Penate, L.; Lopez, D.; San Juan, J. L.; Carrasco, J. A.; Garcia, F.; Torcal-Milla, F. J.; Sanchez-Brea, L. M.; Bernabeu, E.; Perdigues, J. M.; Jennewein, T.; Torres, J. P.; Mitchell, M. W.; Pruneri, V.

    2011-02-01

    A novel integrated optical source capable of emitting faint pulses with different polarization states and with different intensity levels at 100 MHz has been developed. The source relies on a single laser diode followed by four semiconductor optical amplifiers and thin film polarizers, connected through a fiber network. The use of a single laser ensures high level of indistinguishability in time and spectrum of the pulses for the four different polarizations and three different levels of intensity. The applicability of the source is demonstrated in the lab through a free space quantum key distribution experiment which makes use of the decoy state BB84 protocol. We achieved a lower bound secure key rate of the order of 3.64 Mbps and a quantum bit error ratio as low as $1.14\\times 10^{-2}$ while the lower bound secure key rate became 187 bps for an equivalent attenuation of 35 dB. To our knowledge, this is the fastest polarization encoded QKD system which has been reported so far. The performance, reduced size, low power consumption and the fact that the components used can be space qualified make the source particularly suitable for secure satellite communication.

  4. Bio Organic-Semiconductor Field-Effect Transistor (BioFET) Based on Deoxyribonucleic Acid (DNA) Gate Dielectric

    DTIC Science & Technology

    2010-03-31

    floating gate devices and metal-insulator-oxide-semiconductor (MIOS) devices. First attempts to use polarizable gate insulators in combination with...organic semiconductors. The field effect transistors showed floating gate effects, but the potential for organic memories was not realized. Recently...

  5. Multi-gas interaction modeling on decorated semiconductor interfaces: A novel Fermi distribution-based response isotherm and the inverse hard/soft acid/base concept

    NASA Astrophysics Data System (ADS)

    Laminack, William; Gole, James

    2015-12-01

    A unique MEMS/NEMS approach is presented for the modeling of a detection platform for mixed gas interactions. Mixed gas analytes interact with nanostructured decorating metal oxide island sites supported on a microporous silicon substrate. The Inverse Hard/Soft acid/base (IHSAB) concept is used to assess a diversity of conductometric responses for mixed gas interactions as a function of these nanostructured metal oxides. The analyte conductometric responses are well represented using a combination diffusion/absorption-based model for multi-gas interactions where a newly developed response absorption isotherm, based on the Fermi distribution function is applied. A further coupling of this model with the IHSAB concept describes the considerations in modeling of multi-gas mixed analyte-interface, and analyte-analyte interactions. Taking into account the molecular electronic interaction of both the analytes with each other and an extrinsic semiconductor interface we demonstrate how the presence of one gas can enhance or diminish the reversible interaction of a second gas with the extrinsic semiconductor interface. These concepts demonstrate important considerations in the array-based formats for multi-gas sensing and its applications.

  6. Real-time and noninvasive monitoring of respiration activity of fertilized ova using semiconductor-based biosensing devices.

    PubMed

    Sakata, Toshiya; Makino, Izumi; Kita, Sayaka

    2011-05-01

    In this report, we propose a novel evaluation method of embryo activity, describing the real-time and noninvasive electrical monitoring of embryo activity, caused by fertilization of the sea urchin, using a biologically-coupled field-effect transistor (bio-FET) comprised of semiconductor-based biosensing devices. The detection principle of bio-FET is based on the potentiometric detection of charge density change at the gate insulator, which includes changes of hydrogen ion concentration corresponding to pH variation. The surface potential at the gate surface of the bio-FET increased after the introduction of sperms into the ova, resulting in fertilization on the gate sensing area. The positive shift of surface potential indicates the increase of positive charges of hydrogen ions generated by dissolved carbon dioxide in artificial sea water based on respiration activity of the embryo. Moreover, the electrical signal of embryo activity is suppressed due to the inhibition of cytokinesis by introduction of cytochalasin B. The platform based on the bio-FET is expected to be a real-time, label-free and noninvasive detection system, not only in fundamental studies of embryo activity but also in the evaluation of embryo quality for in vitro fertilization.

  7. A portable and wide energy range semiconductor-based neutron spectrometer

    NASA Astrophysics Data System (ADS)

    Hoshor, C. B.; Oakes, T. M.; Myers, E. R.; Rogers, B. J.; Currie, J. E.; Young, S. M.; Crow, J. A.; Scott, P. R.; Miller, W. H.; Bellinger, S. L.; Sobering, T. J.; Fronk, R. G.; Shultis, J. K.; McGregor, D. S.; Caruso, A. N.

    2015-12-01

    Hand-held instruments that can be used to passively detect and identify sources of neutron radiation-either bare or obscured by neutron moderating and/or absorbing material(s)-in real time are of interest in a variety of nuclear non-proliferation and health physics applications. Such an instrument must provide a means to high intrinsic detection efficiency and energy-sensitive measurements of free neutron fields, for neutrons ranging from thermal energies to the top end of the evaporation spectrum. To address and overcome the challenges inherent to the aforementioned applications, four solid-state moderating-type neutron spectrometers of varying cost, weight, and complexity have been designed, fabricated, and tested. The motivation of this work is to introduce these novel human-portable instruments by discussing the fundamental theory of their operation, investigating and analyzing the principal considerations for optimal instrument design, and evaluating the capability of each of the four fabricated spectrometers to meet the application needs.

  8. Intrinsic absolute bioavailability prediction in rats based on in situ absorption rate constants and/or in vitro partition coefficients: 6-fluoroquinolones.

    PubMed

    Sánchez-Castaño, G; Ruíz-García, A; Bañón, N; Bermejo, M; Merino, V; Freixas, J; Garriguesx, T M; Plá-Delfina, J M

    2000-11-01

    A preliminary study attempting to predict the intrinsic absolute bioavailability of a group of antibacterial 6-fluoroquinolones-including true and imperfect homologues as well as heterologues-was carried out. The intrinsic absolute bioavailability of the test compounds, F, was assessed on permanently cannulated conscious rats by comparing the trapezoidal normalized areas under the plasma concentration-time curves obtained by intravenous and oral routes (n = 8-12). The high-performance liquid chromatography analytical methods used for plasma samples are described. Prediction of the absolute bioavailability of the compounds was based on their intrinsic rat gut in situ absorption rate constant, k(a). The working equation was: where T represents the mean absorbing time. A T value of 0.93 (+/-0.06) h provides the best correlation between predicted and experimentally obtained bioavailabilities (F' and F, respectively) when k(a) values are used (slope a = 1.10; intercept b = -0.05; r = 0.991). The k(a) values can also be expressed in function of the in vitro partition coefficients, P, between n-octanol and a phosphate buffer. In this case, theoretical k(a) values can be determined with the parameters of a standard k(a)/P correlation previously established for a group of model compounds. When P values are taken instead of k(a) values, reliable bioavailability predictions can also be made. These and other relevant features of the method are discussed.

  9. Joint amplitude and frequency demodulation analysis based on intrinsic time-scale decomposition for planetary gearbox fault diagnosis

    NASA Astrophysics Data System (ADS)

    Feng, Zhipeng; Lin, Xuefeng; Zuo, Ming J.

    2016-05-01

    Planetary gearbox vibration signals feature complex modulations, thus leading to intricate sideband structure and resulting in difficulty in fault characteristic frequency identification. Intrinsic time-scale decomposition has unique merits, such as high adaptability to changes in signals, low computational complexity, good capability to suppress mode mixing and to preserve temporal information of transients, and excellent suitability for mono-component decomposition of complex multi-component signals. In order to address the issue with planetary gearbox fault diagnosis due to the multiple modulation sources, a joint amplitude and frequency demodulation analysis method is proposed, by exploiting the merits of intrinsic time-scale decomposition. The signal is firstly decomposed into a series of mono-component proper rotational components. Then the one with its instantaneous frequency fluctuating around the gear meshing frequency or its harmonics is selected as the sensitive component. Next, Fourier transformation is applied to the instantaneous amplitude and instantaneous frequency of the sensitive component to obtain the amplitude and frequency demodulated spectra respectively. Finally, a planetary gearbox fault is diagnosed by matching the peaks in the amplitude and frequency demodulated spectra with the theoretical gear fault characteristic frequencies. The proposed method is illustrated by a numerical simulated signal, and further validated by lab experimental signals of a planetary gearbox. The localized faults of sun, planet and ring gears are diagnosed, showing the effectiveness of the method.

  10. Novel all-optical switches based on traveling-wave semiconductor optical amplifiers

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaoxing

    1997-08-01

    In this work, novel all-optical switches, which can provide both high-speed and broad-bandwidth switching simultaneously for future telecommunication networks, have been proposed and demonstrated in traveling-wave semiconductor optical amplifiers (TW-SOA). The design, fabrication and characterization of anti- reflection coating for TW-SOA were presented. Guided mode approach was used to optimize the coating conditions. High quality TW-SOA were fabricated with 21 dB small- signal gain, 0.2 dB gain ripple and 5× 10-5 residual reflectivity. The study showed careful selection of the laser wavelength was necessary in order to match the amplifier's operating wavelength. A new class of an all-optical packet switch-the wavelength recognizing switch (WRS)-was proposed. The device uses a control signal to sense the wavelength of the input data packet and taps the packet to the appropriate output port. The underlying mechanism is nearly-degenerate four-wave mixing (FWM). The implementation of the WRS in a broad-area TW-SOA provided +8.2 dB switching efficiency, -28.8 dB crosstalk and 32.9 dB signal-to-noise ratio. The switching bandwidth was 42 nm, while the recognition bandwidth was 0.03 A. Completely filter-free FWM wavelength conversion was also proposed and demonstrated for the first time. The noncollinear configuration provided 29 dB suppression of the straight-through converter beam from the converted signal. Further suppression of the strong pump beam from the converted signal was realized by using an orthogonal polarization technique, with isolation ratio of 19.2 dB achieved. A high conversion efficiency of 4.9 dB, together with a wide efficiency bandwidth of 40 nm and a large signal-to-noise ratio of 28 dB was obtained. Important material parameters were investigated for the optimization of devices' performance. Ambipolar diffusion coefficient of 8.0 cm2/s and carrier lifetime of 1.33 ns were directly measured. The diffusion coefficient decreased as the current

  11. Squeezing of phonoritons in semiconductors

    NASA Astrophysics Data System (ADS)

    Huong, N. Q.; Hau, N. N.; Birman, J. L.

    2007-12-01

    If a semiconductor sample is illuminated by hight-intensity electro-magnetic radiation near the resonance, the occupation number of polaritons in the same mode is large and the interaction between polaritons and phonons become very important. This interaction leads to the formation of a new kind of elementary excitation called phonoriton, which actually is a coherent superposition of excitons, photons, and longitudinal acoustic phonons under Brillouin scattering of an intense polariton. The phonoritons have been studied theoretically and experimentally and have been found in Cu2O. In this work we discuss the squeezing of phonoritons inside semiconductors from a theoretical point of view. We found the squeezed states, or so called 'low-noise' states- the states of reduced quantum noise with reducing effect of vacuum fluctuation, for phonoritons. It shows that the phonoritons are intrinsically squeezed. From our results we also have the possibility to tune the squeeze amplitude, what is important both theoretically and experimentally.

  12. 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.

  13. 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.

  14. Optical implementation of neural learning algorithms based on cross-gain modulation in a semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Li, Qiang; Wang, Zhi; Le, Yansi; Sun, Chonghui; Song, Xiaojia; Wu, Chongqing

    2016-10-01

    Neuromorphic engineering has a wide range of applications in the fields of machine learning, pattern recognition, adaptive control, etc. Photonics, characterized by its high speed, wide bandwidth, low power consumption and massive parallelism, is an ideal way to realize ultrafast spiking neural networks (SNNs). Synaptic plasticity is believed to be critical for learning, memory and development in neural circuits. Experimental results have shown that changes of synapse are highly dependent on the relative timing of pre- and postsynaptic spikes. Synaptic plasticity in which presynaptic spikes preceding postsynaptic spikes results in strengthening, while the opposite timing results in weakening is called antisymmetric spike-timing-dependent plasticity (STDP) learning rule. And synaptic plasticity has the opposite effect under the same conditions is called antisymmetric anti-STDP learning rule. We proposed and experimentally demonstrated an optical implementation of neural learning algorithms, which can achieve both of antisymmetric STDP and anti-STDP learning rule, based on the cross-gain modulation (XGM) within a single semiconductor optical amplifier (SOA). The weight and height of the potentitation and depression window can be controlled by adjusting the injection current of the SOA, to mimic the biological antisymmetric STDP and anti-STDP learning rule more realistically. As the injection current increases, the width of depression and potentitation window decreases and height increases, due to the decreasing of recovery time and increasing of gain under a stronger injection current. Based on the demonstrated optical STDP circuit, ultrafast learning in optical SNNs can be realized.

  15. 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.

  16. Materials Science and Technology, Volume 4, Electronic Structure and Properties of Semiconductors

    NASA Astrophysics Data System (ADS)

    Schröter, Wolfgang

    1996-12-01

    This volume spans the field of semiconductor physics, with particular emphasis on concepts relevant to semiconductor technology. From the Contents: Lannoo: Band Theory Applied to Semiconductors. Ulbrich: Optical Properties and Charge Transport. Watkins: Intrinsic Point Defects in Semiconductors. Feichtinger: Deep Centers in Semiconductors. Gösele/Tan: Equilibria, Nonequilibria, Diffusion, and Precipitation. Alexander/Teichler: Dislocations. Thibault/Rouvière/Bourret: Grain Boundaries in Semiconductors. Ourmazd/Hull/Tung: Interfaces. Chang: The Hall Effect in Quantum Wires. Street/Winer: Material Properties of Hydrogenated Amorphous Silicon. Schröter/Seibt/Gilles: High-Temperature Properties of 3d Transition Elements in Silicon.

  17. Biomimetic fiber mesh scaffolds based on gelatin and hydroxyapatite nano-rods: Designing intrinsic skills to attain bone reparation abilities.

    PubMed

    Sartuqui, Javier; Gravina, A Noel; Rial, Ramón; Benedini, Luciano A; Yahia, L'Hocine; Ruso, Juan M; Messina, Paula V

    2016-09-01

    Intrinsic material skills have a deep effect on the mechanical and biological performance of bone substitutes, as well as on its associated biodegradation properties. In this work we have manipulated the preparation of collagenous derived fiber mesh frameworks to display a specific composition, morphology, open macroporosity, surface roughness and permeability characteristics. Next, the effect of the induced physicochemical attributes on the scaffold's mechanical behavior, bone bonding potential and biodegradability were evaluated. It was found that the scaffold microstructure, their inherent surface roughness, and the compression strength of the gelatin scaffolds can be modulated by the effect of the cross-linking agent and, essentially, by mimicking the nano-scale size of hydroxyapatite in natural bone. A clear effect of bioactive hydroxyapatite nano-rods on the scaffolds skills can be appreciated and it is greater than the effect of the cross-linking agent, offering a huge perspective for the upcoming progress of bone implant technology.

  18. Probing the intrinsic failure mechanism of fluorinated amorphous carbon film based on the first-principles calculations

    PubMed Central

    Zhang, Ren-hui; Wang, Li-ping; Lu, Zhi-bin

    2015-01-01

    Fluorinated amorphous carbon films exhibit superlow friction under vacuum, but are prone to catastrophic failure. Thus far, the intrinsic failure mechanism remains unclear. A prevailing view is that the failure of amorphous carbon film results from the plastic deformation of substrates or strong adhesion between two contacted surfaces. In this paper, using first-principles and molecular dynamics methodology, combining with compressive stress-strain relation, we firstly demonstrate that the plastic deformation induces graphitization resulting in strong adhesion between two contacted surfaces under vacuum, which directly corresponds to the cause of the failure of the films. In addition, sliding contact experiments are conducted to study tribological properties of iron and fluorinated amorphous carbon surfaces under vacuum. The results show that the failure of the film is directly attributed to strong adhesion resulting from high degree of graphitization of the film, which are consistent with the calculated results. PMID:25803202

  19. Proton Conduction in a Phosphonate-Based Metal–Organic Framework Mediated by Intrinsic “Free Diffusion inside a Sphere”

    PubMed Central

    2016-01-01

    Understanding the molecular mechanism of proton conduction is crucial for the design of new materials with improved conductivity. Quasi-elastic neutron scattering (QENS) has been used to probe the mechanism of proton diffusion within a new phosphonate-based metal–organic framework (MOF) material, MFM-500(Ni). QENS suggests that the proton conductivity (4.5 × 10–4 S/cm at 98% relative humidity and 25 °C) of MFM-500(Ni) is mediated by intrinsic “free diffusion inside a sphere”, representing the first example of such a mechanism observed in MOFs. PMID:27182787

  20. New Semiconductor Devices

    NASA Astrophysics Data System (ADS)

    Balestra, F.

    2008-11-01

    A review of recently emerging semiconductor devices for nanoelectronic applications is given. For the end of the international technology roadmap for semiconductors, very innovative materials, technologies and nanodevice architectures will be needed. Silicon on insulator-based devices seem to be the best candidates for the ultimate integration of integrated circuits on silicon. The flexibility of the silicon on insulator-based structure and the possibility to realize new device architectures allow to obtain optimum electrical properties for low power and high performance circuits. These transistors are also very interesting for high frequency and memory applications. The performance and physical mechanisms are addressed in single- and multi-gate thin film Si, SiGe and Ge metal-oxide-semiconductor field-effect-transistors. The impact of tensile or compressive uniaxial and biaxial strains in the channel, of high k materials and metal gates as well as metallic Schottky source-drain architectures are discussed. Finally, the interest of advanced beyond-CMOS (complementary MOS) nanodevices for long term applications, based on nanowires, carbon electronics or small slope switch structures are presented.

  1. Ordering-induced direct-to-indirect band gap transition in multication semiconductor compounds

    NASA Astrophysics Data System (ADS)

    Park, Ji-Sang; Yang, Ji-Hui; Kanevce, Ana; Choi, Sukgeun; Repins, Ingrid L.; Wei, Su-Huai

    2015-02-01

    Using first-principles calculations and symmetry analysis, we show that as cation atoms in a zinc blende-based semiconductor are replaced through atomic mutation (e.g., evolve from ZnSe to CuGaS e2 to C u2ZnGeS e4 ), the band gaps of the semiconductors will become more and more indirect because of the band splitting at the zone boundary, and in some cases will even form the segregating states. For example, although ZnSe is a direct band gap semiconductor, quaternary compounds C u2ZnGeS e4 and C u2ZnSnS e4 can be indirect band gap semiconductors if they form the primitive mixed CuAu ordered structures. We also find that the stability and the electronic structure of the quaternary polytypes with different atomic ordering are almost negative-linearly correlated. We suggest that these intrinsic properties of the multication semiconductors can have a large influence on the design and device performance of these materials.

  2. Large-signal characterizations of DDR IMPATT devices based on group III-V semiconductors at millimeter-wave and terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Acharyya, Aritra; Mallik, Aliva; Banerjee, Debopriya; Ganguli, Suman; Das, Arindam; Dasgupta, Sudeepto; Banerjee, J. P.

    2014-08-01

    Large-signal (L-S) characterizations of double-drift region (DDR) impact avalanche transit time (IMPATT) devices based on group III-V semiconductors such as wurtzite (Wz) GaN, GaAs and InP have been carried out at both millimeter-wave (mm-wave) and terahertz (THz) frequency bands. A L-S simulation technique based on a non-sinusoidal voltage excitation (NSVE) model developed by the authors has been used to obtain the high frequency properties of the above mentioned devices. The effect of band-to-band tunneling on the L-S properties of the device at different mm-wave and THz frequencies are also investigated. Similar studies are also carried out for DDR IMPATTs based on the most popular semiconductor material, i.e. Si, for the sake of comparison. A comparative study of the devices based on conventional semiconductor materials (i.e. GaAs, InP and Si) with those based on Wz-GaN shows significantly better performance capabilities of the latter at both mm-wave and THz frequencies.

  3. Continuous Monitoring of Electrical Activity of Pancreatic β-Cells Using Semiconductor-Based Biosensing Devices

    NASA Astrophysics Data System (ADS)

    Sakata, Toshiya; Sugimoto, Haruyo

    2011-02-01

    The electrical activity of rat pancreatic β-cells caused by introduction of glucose was directly and noninvasively detected using a cell-based field-effect transistor (FET). Rat pancreatic β-cells were adhered to the gate sensing surface of the cell-based FET. The principle of cell-based FETs is based on the detection of charge density changes such as pH variation at the interface between the cell membrane and the gate surface. The gate surface potential of pancreatic β-cell-based FET increased continuously after introduction of glucose at a high concentration of 10 mg/ml. This result indicates that the electrical activity of β-cells was successfully monitored on the basis of pH changes, i.e., increase in the concentration of hydrogen ions, at the cell/gate interface using the pancreatic β-cell-based FET. We assume that the pH variation based on hydrogen ion accumulation at the cell/gate interface was induced by activation of respiration accompanied by insulin secretion process following glucose addition. The platform based on the field-effect devices is suitable for application in a real-time, noninvasive, and label-free detection system for cell functional analyses.

  4. Fiber-based multiple-beam reflection interferometer for single-longitudinal-mode generation in fiber laser based on semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Terentyev, V. S.; Simonov, V. A.; Babin, S. A.

    2017-02-01

    A technique of single-longitudinal-mode selection in a fiber laser by means of a fiber multiple-beam reflection interferometer (FRI) has been experimentally demonstrated for the first time. The laser is based on a semiconductor optical amplifier placed in a linear fiber cavity formed by a fiber Bragg grating (FBG), and the FRI generates at 1529.24 nm with output power of 1 mW in single-frequency regime with a linewidth of about 217 kHz and polarization extinction ratio of  >30 dB. The FRI technique potentially enables fast tuning (within the FBG bandwidth of ~0.9 nm in our case) by varying the base length of the FRI that can be used in a number of practical applications.

  5. Tunable high-power narrow-linewidth semiconductor laser based on an external-cavity tapered amplifier.

    PubMed

    Chi, Mingjun; Jensen, Ole Bjarlin; Holm, Jesper; Pedersen, Christian; Andersen, Peter Eskil; Erbert, Götz; Sumpf, Bernd; Petersen, Paul Michael

    2005-12-26

    A high-power narrow-linewidth laser system based on a tapered semiconductor optical amplifier in external cavity is demonstrated. The external cavity laser system uses a new tapered amplifier with a super-large optical-cavity (SLOC) design that leads to improved performance of the external cavity diode lasers. The laser system is tunable over a 29 nm range centered at 802 nm. As high as 1.95 W output power is obtained at 803.84 nm, and an output power above 1.5 W is achieved from 793 to 812 nm at operating current of 3.0 A. The emission linewidth is below 0.004 nm and the beam quality factor M2 is below 1.3 over the 29 nm tunable range. As an example of application, the laser system is used as a pump source for the generation of 405 nm blue light by single-pass frequency doubling in a periodically poled KTiOPO4. An output power of 24 mW at 405 nm, corresponding to a conversion efficiency of 0.83%/W is attained.

  6. Device modeling of perovskite solar cells based on structural similarity with thin film inorganic semiconductor solar cells

    NASA Astrophysics Data System (ADS)

    Minemoto, Takashi; Murata, Masashi

    2014-08-01

    Device modeling of CH3NH3PbI3-xCl3 perovskite-based solar cells was performed. The perovskite solar cells employ a similar structure with inorganic semiconductor solar cells, such as Cu(In,Ga)Se2, and the exciton in the perovskite is Wannier-type. We, therefore, applied one-dimensional device simulator widely used in the Cu(In,Ga)Se2 solar cells. A high open-circuit voltage of 1.0 V reported experimentally was successfully reproduced in the simulation, and also other solar cell parameters well consistent with real devices were obtained. In addition, the effect of carrier diffusion length of the absorber and interface defect densities at front and back sides and the optimum thickness of the absorber were analyzed. The results revealed that the diffusion length experimentally reported is long enough for high efficiency, and the defect density at the front interface is critical for high efficiency. Also, the optimum absorber thickness well consistent with the thickness range of real devices was derived.

  7. New time-space-time optical packet switching node based on nonlinear polarization rotation of a semiconductor optical amplifier.

    PubMed

    Yongjun, Wang; Qinghua, Tian; Zhi, Wang; Xiaoqing, Zhu; Chen, Wu; Chao, Shang; Xin, Xiangjun

    2016-03-10

    In this paper, we establish a simple model to analyze the semiconductor optical amplifier's (SOA) nonlinear polarization rotation (NPR) and acquire the variable curves of phase difference between TE and TM modes with bias current, pump power, probe power, and linewidth enhancement factor (LEF). The results indicate that the optical switch based on the SOA's NPR can be realized by changing the pump's optical power and the main operating parameters, such as bias current and hold beam power, and then the pump power can be determined. On this basis, a time-space-time (T-S-T) optical packet switching node is proposed, in which the SOA's NPR switch is the basic element. Then, the T-S and S-T experimental systems are set up, and the experimental results demonstrate that the proposed switch scheme can implement the optical switching function in accordance with the routing requirement. The signal-to-noise ratio (SNR) exceeds 20 dB, and the extinction ratio (ER) is more than 10 dB after being delayed and switched in the node.

  8. Integrated Semiconductor-based Diagnostics System for Multiplexed Genomic Amplification and Electrochemical Detection of Biothreat Agents

    DTIC Science & Technology

    2009-01-01

    contract effort focused on the development of an automated, cartridge-based genotyping system that integrates a multiplex polymerase chain reaction...REPORT b.ABSTRACT c. THIS PAGE ABSTRACT OF PAGES Kristian Roth $X u U U SAR 19b. TELEPHONE NUMBER 425-493-2368 Standard Form 298 (Rev 8/98...Biothreat Agents Report Title ABSTRACT This contract effort focused on the development of an automated, cartridge-based genotyping system that integrates a

  9. Stretchable Organic Semiconductor Devices.

    PubMed

    Qian, Yan; Zhang, Xinwen; Xie, Linghai; Qi, Dianpeng; Chandran, Bevita K; Chen, Xiaodong; Huang, Wei

    2016-11-01

    Stretchable electronics are essential for the development of intensely packed collapsible and portable electronics, wearable electronics, epidermal and bioimplanted electronics, 3D surface compliable devices, bionics, prosthesis, and robotics. However, most stretchable devices are currently based on inorganic electronics, whose high cost of fabrication and limited processing area make it difficult to produce inexpensive, large-area devices. Therefore, organic stretchable electronics are highly attractive due to many advantages over their inorganic counterparts, such as their light weight, flexibility, low cost and large-area solution-processing, the reproducible semiconductor resources, and the easy tuning of their properties via molecular tailoring. Among them, stretchable organic semiconductor devices have become a hot and fast-growing research field, in which great advances have been made in recent years. These fantastic advances are summarized here, focusing on stretchable organic field-effect transistors, light-emitting devices, solar cells, and memory devices.

  10. A Radio-Based Search finds no evidence for intrinsically weak TGFs in the Fermi GBM Data

    NASA Astrophysics Data System (ADS)

    Briggs, Michael; Omar, Kareem

    2016-04-01

    We analyze gamma-ray data from the Fermi Gamma-ray Burst Monitor (GBM) around the times of VLF radio sferics. The gamma-ray photons are time-aligned to the times of radio sferics, with correction for the light travel time to Fermi, and accumulated. Gamma-ray photons from TGFs already known from the standard GBM TGF offline search are excluded from the accumulation. We use sferic signals from both the World Wide Lightning Location Network (WWLLN) and the Earth Networks Total Lightning Network (ENTLN). No excess signal is found in the accumulation of the gamma-ray data for sferics within 400 km of the Fermi nadir. However, an excess of gamma-rays is found in the co-aligned signal for sferics between 400 and 800 km of the Fermi nadir. Our interpretation of this distance-dependent non-detection / detection pattern is that the standard GBM offline search for TGFs is missing some TGFs that are weak at Fermi due to distance from Fermi and that there is no evidence for a population of TGFs that are intrinsically fainter than the threshold of the search.

  11. Long-term stability of underground operated CZT detectors based on the analysis of intrinsic 113Cd β--decay

    NASA Astrophysics Data System (ADS)

    Ebert, J.; Gößling, C.; Gehre, D.; Hagner, C.; Heidrich, N.; Klingenberg, R.; Kröninger, K.; Nitsch, C.; Oldorf, C.; Quante, T.; Rajek, S.; Rebber, H.; Rohatsch, K.; Tebrügge, J.; Temminghoff, R.; Theinert, R.; Timm, J.; Wonsak, B.; Zatschler, S.; Zuber, K.

    2016-06-01

    The COBRA collaboration operates a demonstrator setup at the underground facility Laboratori Nazionali del Gran Sasso (LNGS, located in Italy) to prove the technological capabilities of this concept for the search for neutrinoless double beta-decay. The setup consists of 64 (1×1×1) cm3 Cadmium-Zinc-Telluride (CZT) detectors in Coplanar-Grid (CPG) configuration. One purpose of this demonstrator is to test if reliable long-term operation of CZT-CPG detectors in such a setup is possible. The demonstrator has been operated under ultra low-background conditions for more than three years and collected data corresponding to a total exposure of 218 kg days. The presented study focuses on the long-term stability of CZT detectors by analyzing the intrinsic, fourfold forbidden non-unique 113Cd single beta-decay. It can be shown that CZT detectors can be operated stably for long periods of time and that the 113Cd single beta-decay can be used as an internal monitor of the detector performance during the runtime of the experiment.

  12. An optimized Npro-based method for the expression and purification of intrinsically disordered proteins for an NMR study

    PubMed Central

    Goda, Natsuko; Matsuo, Naoki; Tenno, Takeshi; Ishino, Sonoko; Ishino, Yoshizumi; Fukuchi, Satoshi; Ota, Motonori; Hiroaki, Hidekazu

    2015-01-01

    Intrinsically disordered proteins (IDPs) are an emerging concept. IDPs have high flexibility in their polypeptide chains, lacking a stable 3-dimensional structure. Because of the difficulty in performing X-ray crystallography for IDPs, nuclear magnetic resonance (NMR) spectroscopy is the first choice for atomic-level investigation of their nature. Given that isotopically labeled IDP samples are necessary for NMR study, a robust and cost-effective protocol for bacterial expression and purification of IDP is also needed. We employed the Npro (EDDIE)-autoprotease fusion protein system. Although IDPs are believed to be readily degraded by endogenous proteases when expressed in Escherichia coli, Npro-fused IDPs showed excellent resistance to degradation. Seven IDPs of uncharacterized function sampled from the human genome as well as 3 constructs from IDP regions derived from human FancM and Thermococcus kodakarensis Hef were prepared. We improved the protocol of refolding of Npro (EDDIE) to use dialysis, which is convenient for subsequent purification using reversed-phase (RP) HPLC. The method is robust and widely applicable to any IDP sample, promoting the acquisition of experimental data for IDPs in a high-throughput manner.

  13. An optimized N(pro)-based method for the expression and purification of intrinsically disordered proteins for an NMR study.

    PubMed

    Goda, Natsuko; Matsuo, Naoki; Tenno, Takeshi; Ishino, Sonoko; Ishino, Yoshizumi; Fukuchi, Satoshi; Ota, Motonori; Hiroaki, Hidekazu

    2015-01-01

    Intrinsically disordered proteins (IDPs) are an emerging concept. IDPs have high flexibility in their polypeptide chains, lacking a stable 3-dimensional structure. Because of the difficulty in performing X-ray crystallography for IDPs, nuclear magnetic resonance (NMR) spectroscopy is the first choice for atomic-level investigation of their nature. Given that isotopically labeled IDP samples are necessary for NMR study, a robust and cost-effective protocol for bacterial expression and purification of IDP is also needed. We employed the N(pro) (EDDIE)-autoprotease fusion protein system. Although IDPs are believed to be readily degraded by endogenous proteases when expressed in Escherichia coli, N(pro)-fused IDPs showed excellent resistance to degradation. Seven IDPs of uncharacterized function sampled from the human genome as well as 3 constructs from IDP regions derived from human FancM and Thermococcus kodakarensis Hef were prepared. We improved the protocol of refolding of N(pro) (EDDIE) to use dialysis, which is convenient for subsequent purification using reversed-phase (RP) HPLC. The method is robust and widely applicable to any IDP sample, promoting the acquisition of experimental data for IDPs in a high-throughput manner.

  14. In vitro intrinsic clearance-based optimization of N3-phenylpyrazinones as corticotropin-releasing factor-1 (CRF1) receptor antagonists.

    PubMed

    Hartz, Richard A; Ahuja, Vijay T; Rafalski, Maria; Schmitz, William D; Brenner, Allison B; Denhart, Derek J; Ditta, Jonathan L; Deskus, Jeffrey A; Yue, Eddy W; Arvanitis, Argyrios G; Lelas, Snjezana; Li, Yu-Wen; Molski, Thaddeus F; Wong, Harvey; Grace, James E; Lentz, Kimberley A; Li, Jianqing; Lodge, Nicholas J; Zaczek, Robert; Combs, Andrew P; Olson, Richard E; Mattson, Ronald J; Bronson, Joanne J; Macor, John E

    2009-07-23

    A series of pyrazinone-based heterocycles was identified as potent and orally active corticotropin-releasing factor-1 (CRF(1)) receptor antagonists. Selected compounds proved efficacious in an anxiety model in rats; however, pharmacokinetic properties were not optimal. In this article, we describe an in vitro intrinsic clearance-based approach to the optimization of pyrazinone-based CRF(1) receptor antagonists wherein sites of metabolism were identified by incubation with human liver microsomes. It was found that the rate of metabolism could be decreased by incorporation of appropriate substituents at the primary sites of metabolism. This led to the discovery of compound 12x, a highly potent (IC(50) = 1.0 nM) and selective CRF(1) receptor antagonist with good oral bioavailability (F = 52%) in rats and efficacy in the defensive withdrawal anxiety test in rats.

  15. SEMICONDUCTOR TECHNOLOGY: Material removal rate in chemical-mechanical polishing of wafers based on particle trajectories

    NASA Astrophysics Data System (ADS)

    Jianxiu, Su; Xiqu, Chen; Jiaxi, Du; Renke, Kang

    2010-05-01

    Distribution forms of abrasives in the chemical mechanical polishing (CMP) process are analyzed based on experimental results. Then the relationships between the wafer, the abrasive and the polishing pad are analyzed based on kinematics and contact mechanics. According to the track length of abrasives on the wafer surface, the relationships between the material removal rate and the polishing velocity are obtained. The analysis results are in accord with the experimental results. The conclusion provides a theoretical guide for further understanding the material removal mechanism of wafers in CMP.

  16. SEMICONDUCTOR TECHNOLOGY: Wafer level hermetic packaging based on Cu-Sn isothermal solidification technology

    NASA Astrophysics Data System (ADS)

    Yuhan, Cao; Le, Luo

    2009-08-01

    A novel wafer level bonding method based on Cu-Sn isothermal solidification technology is established. A multi-layer sealing ring and the bonding processing are designed, and the amount of solder and the bonding parameters are optimized based on both theoretical and experimental results. Verification shows that oxidation of the solder layer, voids and the scalloped-edge appearance of the Cu6Sn5 phase are successfully avoided. An average shear strength of 19.5 MPa and an excellent leak rate of around 1.9 × 10-9 atm cc/s are possible, meeting the demands of MIL-STD-883E.

  17. Intrinsically motivated action-outcome learning and goal-based action recall: a system-level bio-constrained computational model.

    PubMed

    Baldassarre, Gianluca; Mannella, Francesco; Fiore, Vincenzo G; Redgrave, Peter; Gurney, Kevin; Mirolli, Marco

    2013-05-01

    Reinforcement (trial-and-error) learning in animals is driven by a multitude of processes. Most animals have evolved several sophisticated systems of 'extrinsic motivations' (EMs) that guide them to acquire behaviours allowing them to maintain their bodies, defend against threat, and reproduce. Animals have also evolved various systems of 'intrinsic motivations' (IMs) that allow them to acquire actions in the absence of extrinsic rewards. These actions are used later to pursue such rewards when they become available. Intrinsic motivations have been studied in Psychology for many decades and their biological substrates are now being elucidated by neuroscientists. In the last two decades, investigators in computational modelling, robotics and machine learning have proposed various mechanisms that capture certain aspects of IMs. However, we still lack models of IMs that attempt to integrate all key aspects of intrinsically motivated learning and behaviour while taking into account the relevant neurobiological constraints. This paper proposes a bio-constrained system-level model that contributes a major step towards this integration. The model focusses on three processes related to IMs and on the neural mechanisms underlying them: (a) the acquisition of action-outcome associations (internal models of the agent-environment interaction) driven by phasic dopamine signals caused by sudden, unexpected changes in the environment; (b) the transient focussing of visual gaze and actions on salient portions of the environment; (c) the subsequent recall of actions to pursue extrinsic rewards based on goal-directed reactivation of the representations of their outcomes. The tests of the model, including a series of selective lesions, show how the focussing processes lead to a faster learning of action-outcome associations, and how these associations can be recruited for accomplishing goal-directed behaviours. The model, together with the background knowledge reviewed in the paper

  18. CaTiO.sub.3 Interfacial template structure on semiconductor-based material and the growth of electroceramic thin-films in the perovskite class

    DOEpatents

    McKee, Rodney Allen; Walker, Frederick Joseph

    1998-01-01

    A structure including a film of a desired perovskite oxide which overlies and is fully commensurate with the material surface of a semiconductor-based substrate and an associated process for constructing the structure involves the build up of an interfacial template film of perovskite between the material surface and the desired perovskite film. The lattice parameters of the material surface and the perovskite of the template film are taken into account so that during the growth of the perovskite template film upon the material surface, the orientation of the perovskite of the template is rotated 45.degree. with respect to the orientation of the underlying material surface and thereby effects a transition in the lattice structure from fcc (of the semiconductor-based material) to the simple cubic lattice structure of perovskite while the fully commensurate periodicity between the perovskite template film and the underlying material surface is maintained. The film-growth techniques of the invention can be used to fabricate solid state electrical components wherein a perovskite film is built up upon a semiconductor-based material and the perovskite film is adapted to exhibit ferroelectric, piezoelectric, pyroelectric, electro-optic or large dielectric properties during use of the component.

  19. Fast pixelated sensors for radiation detection and imaging based on quantum confined structures in III/V semiconductors

    NASA Astrophysics Data System (ADS)

    Tortora, M.; Biasiol, G.; Cautero, G.; Menk, R. H.; Plaisier, J. R.; Antonelli, M.

    2017-03-01

    In order to improve the characterisation of the delivered beams in many types of photon sources, innovative beam profilers based on III/V semiconductor materials (InGaAs/InAlAs) have been deeply investigated. Owing to a tunable and direct band gap these devices allow radiation detection in a wide spectral range. In order to increase the sensitivity of the device in radiation detection charge amplification on the sensor level is implemented. This is obtained by exploiting In0.75Ga0.25As/In0.75Al0.25As quantum wells (QW) hosting a two-dimensional electron gas (2DEG) through molecular beam epitaxy (MBE). Internal charge-amplification mechanism can be achieved for very low applied voltages, while the high carrier mobility allows the design of very fast photon detectors with sub-nanosecond response times. This technology has been preliminarily exploited to fabricate prototype beam profilers with a strip geometry (with 50-μm-wide strips). Tests were carried out both with conventional X-ray tubes and at the Elettra synchrotron facility. The results testify how these profilers are capable of reconstructing the shape of the beam, as well as estimating the position of the beam centroid with a precision of about 400 nm. Further measurements with different samples of decreasing thickness have shown how this precision could be further improved by an optimised microfabrication. For this reason a new design, based on a membrane-photodetector, is proposed. Results regarding the spatial resolution as function of the sensor thickness will be presented and discussed.

  20. Solar-fuel synthesis based on colloidal and particulate semiconductors. Annual report, August 1, 1987-July 31, 1988

    SciTech Connect

    Frank, A.J.; Graetzel, M.

    1988-08-15

    The properties of a new and very active oxygen-evolving dimeric complex L2(H2O)Ru-O-Ru(H2O))L2 (where L = 2,2'-bipyridyl-4,4'-dicarboxylate) were scrutinized. Stable and very reactive H2-evolving photosystems based on the linear-chain complex (Pt(bpy)2)(Pt(CN)4) were characterized. The scale-up of one photosystem produced significant quantities of gas. The pathway of room temperature methanation of CO2 on TiO2-supported mixed Ru/RuO2 catalyst was studied by FTIR spectroscopy. The same material was found to enhance drastically the Boudard disproportionation and the conversion of NO and CO to CO2 and N2O. A MoO3/TiO2 catalyst was discovered that displays high activity in the photoactivation of methane at 40 deg C. An efficient room temperature photocatalyst Pt(bpy)-TiO2 was also discovered for selectively oxidizing methanol to formaldehyde, a valuable chemical feedstock. An unprecedented light-to-current conversion efficiency of 91% was achieved in sensitizing fractal-type semiconductor oxide films. Regenerative photoelectrochemical cells based on Al-doped anatase films and the Br(1-)/Br2 redox couple were scaled up to 32 sq cm surface area. An open-circuit voltage of 1.05 V, a fill factor of 73% and a polychromatic light-to-power conversion efficiency of 3.5% were obtained with the system.

  1. Spin-Photon Entanglement in Semiconductor Quantum Dots: Towards Solid-State-Based Quantum Repeaters

    NASA Astrophysics Data System (ADS)

    De Greve, Kristiaan; Yamamoto, Yoshihisa

    `In this chapter, we introduced and analyze techniques that allow truly secure secret key sharing over long distances, using public, open channels, where the laws of quantum mechanics ensure the security of the long distance key sharing - an idea generally referred to as the essence of a quantum repeater. We describe several proof-of-principle experiments where technology based on self-assembled quantum dots is used as the backbone of a future quantum repeater.'

  2. Benzothienobenzothiophene-based conjugated oligomers as semiconductors for stable organic thin-film transistors.

    PubMed

    Yu, Han; Li, Weili; Tian, Hongkun; Wang, Haibo; Yan, Donghang; Zhang, Jingping; Geng, Yanhou; Wang, Fosong

    2014-04-09

    Two benzothienobenzothiophene (BTBT)-based conjugated oligomers, i.e., 2,2'-bi[1]benzothieno[3,2-b][1]benzothiophene (1) and 5,5'-bis([1]benzothieno[3,2-b][1]benzothiophen-2-yl)-2,2'-bithiophene (2), were prepared and characterized. Both oligomers exhibit excellent thermal stability, with 5% weight-loss temperatures (T(L)) above 370 °C; no phase transition was observed before decomposition. The highest occupied molecular orbital (HOMO) levels of 1 and 2 are -5.3 and -4.9 eV, respectively, as measured by ultraviolet photoelectron spectroscopy. Thin-film X-ray diffraction and atomic force microscopy characterizations indicate that both oligomers form highly crystalline films with large domain sizes on octadecyltrimethoxysilane-modified substrates. Organic thin-film transistors with top-contact and bottom-gate geometry based on 1 and 2 exhibited mobilities up to 2.12 cm(2)/V·s for 1 and 1.39 cm(2)/V·s for 2 in an ambient atmosphere. 1-based devices exhibited great air and thermal stabilities, as evidenced by the slight performance degradation after 2 months of storage under ambient conditions and after thermal annealing at temperatures below 250 °C.

  3. Synthesis, characterization and apoptotic activity of quinazolinone Schiff base derivatives toward MCF-7 cells via intrinsic and extrinsic apoptosis pathways

    PubMed Central

    Zahedifard, Maryam; Lafta Faraj, Fadhil; Paydar, Mohammadjavad; Yeng Looi, Chung; Hajrezaei, Maryam; Hasanpourghadi, Mohadeseh; Kamalidehghan, Behnam; Abdul Majid, Nazia; Mohd Ali, Hapipah; Ameen Abdulla, Mahmood

    2015-01-01

    The current study investigated the cytotoxic effect of 3-(5-chloro-2-hydroxybenzylideneamino)-2-(5-chloro-2-hydroxyphenyl)-2,3-dihydroquinazolin-41(H)-one (A) and 3-(5-nitro-2-hydroxybenzylideneamino)-2-(5-nitro-2-hydroxyphenyl)-2,3-dihydroquinazolin-4(1H)-one (B) on MCF-7, MDA-MB-231, MCF-10A and WRL-68 cells. The mechanism involved in apoptosis was assessed to evaluate the possible pathways induced by compound A and B. MTT assay results using A and B showed significant inhibition of MCF-7 cell viability, with IC50 values of 3. 27 ± 0.171 and 4.36 ± 0.219 μg/mL, respectively, after a 72 hour treatment period. Compound A and B did not demonstrate significant cytotoxic effects towards MDA-MB-231, WRL-68 and MCF-10A cells. Acute toxicity tests also revealed an absence of toxic effects on mice. Fluorescent microscopic studies confirmed distinct morphological changes (membrane blebbing and chromosome condensation) corresponding to typical apoptotic features in treated MCF-7 cells. Using Cellomics High Content Screening (HCS), we found that compound A and B could trigger the release of cytochrome c from mitochondria to the cytosol. The release of cytochrome c activated the expression of caspases-9 and then stimulated downstream executioner caspase-3/7. In addition, caspase-8 showed remarkable activity, followed by inhibition of NF-κB activation in A-and B-treated MCF-7 cells. The results indicated that A and B could induce apoptosis via a mechanism that involves either extrinsic or intrinsic pathways. PMID:26108872

  4. Intrinsic Connectivity Network-Based Classification and Detection of Psychotic Symptoms in Youth With 22q11.2 Deletions.

    PubMed

    Schreiner, Matthew; Forsyth, Jennifer K; Karlsgodt, Katherine H; Anderson, Ariana E; Hirsh, Nurit; Kushan, Leila; Uddin, Lucina Q; Mattiacio, Leah; Coman, Ioana L; Kates, Wendy R; Bearden, Carrie E

    2017-04-05

    22q11.2 Deletion syndrome (22q11DS) is a genetic disorder associated with numerous phenotypic consequences and is one of the greatest known risk factors for psychosis. We investigated intrinsic-connectivity-networks (ICNs) as potential biomarkers for patient and psychosis-risk status in 2 independent cohorts, UCLA (33 22q11DS-participants, 33 demographically matched controls), and Syracuse (28 22q11DS, 28 controls). After assessing group connectivity differences, ICNs from the UCLA cohort were used to train classifiers to distinguish cases from controls, and to predict psychosis risk status within 22q11DS; classifiers were subsequently tested on the Syracuse cohort. In both cohorts we observed significant hypoconnectivity in 22q11DS relative to controls within anterior cingulate (ACC)/precuneus, executive, default mode (DMN), posterior DMN, and salience networks. Of 12 ICN-derived classifiers tested in the Syracuse replication-cohort, the ACC/precuneus, DMN, and posterior DMN classifiers accurately distinguished between 22q11DS and controls. Within 22q11DS subjects, connectivity alterations within 4 networks predicted psychosis risk status for a given individual in both cohorts: the ACC/precuneus, DMN, left executive, and salience networks. Widespread within-network-hypoconnectivity in large-scale networks implicated in higher-order cognition may be a defining characteristic of 22q11DS during adolescence and early adulthood; furthermore, loss of coherence within these networks may be a valuable biomarker for individual prediction of psychosis-risk in 22q11DS.

  5. Semiconductor Ion Implanters

    NASA Astrophysics Data System (ADS)

    MacKinnon, Barry A.; Ruffell, John P.

    2011-06-01

    In 1953 the Raytheon CK722 transistor was priced at 7.60. Based upon this, an Intel Xeon Quad Core processor containing 820,000,000 transistors should list at 6.2 billion! Particle accelerator technology plays an important part in the remarkable story of why that Intel product can be purchased today for a few hundred dollars. Most people of the mid twentieth century would be astonished at the ubiquity of semiconductors in the products we now buy and use every day. Though relatively expensive in the nineteen fifties they now exist in a wide range of items from high-end multicore microprocessors like the Intel product to disposable items containing `only' hundreds or thousands like RFID chips and talking greeting cards. This historical development has been fueled by continuous advancement of the several individual technologies involved in the production of semiconductor devices including Ion Implantation and the charged particle beamlines at the heart of implant machines. In the course of its 40 year development, the worldwide implanter industry has reached annual sales levels around 2B, installed thousands of dedicated machines and directly employs thousands of workers. It represents in all these measures, as much and possibly more than any other industrial application of particle accelerator technology. This presentation discusses the history of implanter development. It touches on some of the people involved and on some of the developmental changes and challenges imposed as the requirements of the semiconductor industry evolved.

  6. Semiconductor Ion Implanters

    SciTech Connect

    MacKinnon, Barry A.; Ruffell, John P.

    2011-06-01

    In 1953 the Raytheon CK722 transistor was priced at $7.60. Based upon this, an Intel Xeon Quad Core processor containing 820,000,000 transistors should list at $6.2 billion. Particle accelerator technology plays an important part in the remarkable story of why that Intel product can be purchased today for a few hundred dollars. Most people of the mid twentieth century would be astonished at the ubiquity of semiconductors in the products we now buy and use every day. Though relatively expensive in the nineteen fifties they now exist in a wide range of items from high-end multicore microprocessors like the Intel product to disposable items containing 'only' hundreds or thousands like RFID chips and talking greeting cards. This historical development has been fueled by continuous advancement of the several individual technologies involved in the production of semiconductor devices including Ion Implantation and the charged particle beamlines at the heart of implant machines. In the course of its 40 year development, the worldwide implanter industry has reached annual sales levels around $2B, installed thousands of dedicated machines and directly employs thousands of workers. It represents in all these measures, as much and possibly more than any other industrial application of particle accelerator technology. This presentation discusses the history of implanter development. It touches on some of the people involved and on some of the developmental changes and challenges imposed as the requirements of the semiconductor industry evolved.

  7. Isotopically controlled semiconductors

    SciTech Connect

    Haller, Eugene E.

    2006-06-19

    The following article is an edited transcript based on the Turnbull Lecture given by Eugene E. Haller at the 2005 Materials Research Society Fall Meeting in Boston on November 29, 2005. The David Turnbull Lectureship is awarded to recognize the career of a scientist who has made outstanding contributions to understanding materials phenomena and properties through research, writing, and lecturing, as exemplified by the life work of David Turnbull. Haller was named the 2005 David Turnbull Lecturer for his 'pioneering achievements and leadership in establishing the field of isotopically engineered semiconductors; for outstanding contributions to materials growth, doping and diffusion; and for excellence in lecturing, writing, and fostering international collaborations'. The scientific interest, increased availability, and technological promise of highly enriched isotopes have led to a sharp rise in the number of experimental and theoretical studies with isotopically controlled semiconductor crystals. This article reviews results obtained with isotopically controlled semiconductor bulk and thin-film heterostructures. Isotopic composition affects several properties such as phonon energies, band structure, and lattice constant in subtle, but, for their physical understanding, significant ways. Large isotope-related effects are observed for thermal conductivity in local vibrational modes of impurities and after neutron transmutation doping. Spectacularly sharp photoluminescence lines have been observed in ultrapure, isotopically enriched silicon crystals. Isotope multilayer structures are especially well suited for simultaneous self- and dopant-diffusion studies. The absence of any chemical, mechanical, or electrical driving forces makes possible the study of an ideal random-walk problem. Isotopically controlled semiconductors may find applications in quantum computing, nanoscience, and spintronics.

  8. Study of the properties of silicon-based semiconductor converters for betavoltaic cells

    SciTech Connect

    Polikarpov, M. A.; Yakimov, E. B.

    2015-06-15

    Silicon p-i-n diodes are studied in a scanning electron microscope under conditions simulating the β-radiation from a radioactive Ni{sup 63} source with an activity of 10 mCi/cm{sup 2}. The attainable parameters of β-voltaic cells with a source of this kind and a silicon-based converter of β-particle energy to electric current are estimated. It is shown that the power of elements of this kind can reach values of ∼10 nW/cm{sup 2} even for a cell with an area of one centimeter, which is rather close to the calculated value.

  9. Operating principles of vertical transistors based on monolayer two-dimensional semiconductor heterojunctions

    SciTech Connect

    Lam, Kai Tak; Seol, Gyungseon; Guo, Jing

    2014-07-07

    A vertical transistor based on a double gated, atomically thin heterojunction is theoretically examined. Both p-type and n-type transistor operations can be conveniently achieved by using one of the two gates as the switching gate. The transistor shows excellent saturation of output I-V characteristics due to drain-induced depletion and lack of tunneling barrier layers. The subthreshold slope could be below the thermionic limit due to band filtering as the switching mechanism. The atomically thin vertical PN heterojunction can be electrostatically modulated from a type II heterojunction to a broken bandgap alignment, which is preferred for maximizing the on-current.

  10. Highly Effective Polarized Electron Sources Based on Strained Semiconductor Superlattice with Distributed Bragg Reflector

    SciTech Connect

    Gerchikov, L.G.; Aulenbacher, K.; Clendenin, J.E.; Kuz'michev, V.V.; Mamaev, Yu.A.; Maruyama, T.; Mikhrin, V.S.; Roberts, J.S.; Utstinov, V.M.; Vasiliev, D.A.; Vasiliev, A.P.; Yashin, Yu.P.; Zhukov, A.E.; /St. Petersburg Polytechnic Inst. /Mainz U., Inst. Kernphys. /SLAC /Ioffe Phys. Tech. Inst. /Sheffield U.

    2007-11-28

    Resonance enhancement of the quantum efficiency of new polarized electron photocathodes based on a short-period strained superlattice structures is reported. The superlattice is a part of an integrated Fabry-Perot optical cavity. We demonstrate that the Fabry-Perot resonator enhances the quantum efficiency by the order of magnitude in the wavelength region of the main polarization maximum. The high structural quality implied by these results points to the very promising application of these photocathodes for spin-polarized electron sources.

  11. Ion-beam amorphization of semiconductors: A physical model based on the amorphous pocket population

    SciTech Connect

    Mok, K.R.C.; Jaraiz, M.; Martin-Bragado, I.; Rubio, J.E.; Castrillo, P.; Pinacho, R.; Barbolla, J.; Srinivasan, M.P.

    2005-08-15

    We introduce a model for damage accumulation up to amorphization, based on the ion-implant damage structures commonly known as amorphous pockets. The model is able to reproduce the silicon amorphous-crystalline transition temperature for C, Si, and Ge ion implants. Its use as an analysis tool reveals an unexpected bimodal distribution of the defect population around a characteristic size, which is larger for heavier ions. The defect population is split in both size and composition, with small, pure interstitial and vacancy clusters below the characteristic size, and amorphous pockets with a balanced mixture of interstitials and vacancies beyond that size.

  12. Highly Effective Polarized Electron Sources Based on Strained Semiconductor Superlattice with Distributed Bragg Reflector

    SciTech Connect

    Gerchikov, L. G.; Kuz'michev, V. V.; Mamaev, Yu. A.; Vasiliev, D. A.; Yashin, Yu. P.; Aulenbacher, K.; Clendenin, J. E.; Maruyama, T.; Mikhrin, V. S.; Ustinov, V. M.; Vasiliev, A. P.; Zhukov, A. E.; Roberts, J. S.

    2008-02-06

    Resonance enhancement of the quantum efficiency of new polarized electron photocathodes based on a short-period strained superlattice structures is reported. The superlattice is a part of an integrated Fabry-Perot optical cavity. We demonstrate that the Fabry-Perot resonator enhances the quantum efficiency by the order of magnitude in the wavelength region of the main polarization maximum. The high structural quality implied by these results points to the very promising application of these photocathodes for spin-polarized electron sources.

  13. Investigating the effects of capping layer on optical gain of nitride based semiconductor nanostructure lasers

    NASA Astrophysics Data System (ADS)

    Annabi Milani, E.; Mohadesi, V.; Asgari, A.

    2017-04-01

    In this study, the effects of GaN capping layer on the behaviour of AlGaN/GaN nanostructure based laser is considered. We have employed the self-consistent solution of Poisson and Schrodinger equations for calculation of the energy levels, wave functions and conduction and valance bands profile. The impact of different thicknesses of the capping layer has been studied for sheet carrier density, then on optical gain. The results indicate that, by increasing the thickness of the cap layer, the optical gain decreases.

  14. Spin-based single-photon transistor, dynamic random access memory, diodes, and routers in semiconductors

    NASA Astrophysics Data System (ADS)

    Hu, C. Y.

    2016-12-01

    The realization of quantum computers and quantum Internet requires not only quantum gates and quantum memories, but also transistors at single-photon levels to control the flow of information encoded on single photons. Single-photon transistor (SPT) is an optical transistor in the quantum limit, which uses a single photon to open or block a photonic channel. In sharp contrast to all previous SPT proposals which are based on single-photon nonlinearities, here I present a design for a high-gain and high-speed (up to THz) SPT based on a linear optical effect: giant circular birefringence induced by a single spin in a double-sided optical microcavity. A gate photon sets the spin state via projective measurement and controls the light propagation in the optical channel. This spin-cavity transistor can be directly configured as diodes, routers, DRAM units, switches, modulators, etc. Due to the duality as quantum gate and transistor, the spin-cavity unit provides a solid-state platform ideal for future Internet: a mixture of all-optical Internet with quantum Internet.

  15. From computational modelling of the intrinsic apoptosis pathway to a systems-based analysis of chemotherapy resistance: achievements, perspectives and challenges in systems medicine

    PubMed Central

    Würstle, M L; Zink, E; Prehn, J H M; Rehm, M

    2014-01-01

    Our understanding of the mitochondrial or intrinsic apoptosis pathway and its role in chemotherapy resistance has increased significantly in recent years by a combination of experimental studies and mathematical modelling. This combined approach enhanced the quantitative and kinetic understanding of apoptosis signal transduction, but also provided new insights that systems-emanating functions (i.e., functions that cannot be attributed to individual network components but that are instead established by multi-component interplay) are crucial determinants of cell fate decisions. Among these features are molecular thresholds, cooperative protein functions, feedback loops and functional redundancies that provide systems robustness, and signalling topologies that allow ultrasensitivity or switch-like responses. The successful development of kinetic systems models that recapitulate biological signal transduction observed in living cells have now led to the first translational studies, which have exploited and validated such models in a clinical context. Bottom-up strategies that use pathway models in combination with higher-level modelling at the tissue, organ and whole body-level therefore carry great potential to eventually deliver a new generation of systems-based diagnostic tools that may contribute to the development of personalised and predictive medicine approaches. Here we review major achievements in the systems biology of intrinsic apoptosis signalling, discuss challenges for further model development, perspectives for higher-level integration of apoptosis models and finally discuss requirements for the development of systems medical solutions in the coming years. PMID:24874730

  16. 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.

  17. Triazine-based graphitic carbon nitride: a two-dimensional semiconductor.

    PubMed

    Algara-Siller, Gerardo; Severin, Nikolai; Chong, Samantha Y; Björkman, Torbjörn; Palgrave, Robert G; Laybourn, Andrea; Antonietti, Markus; Khimyak, Yaroslav Z; Krasheninnikov, Arkady V; Rabe, Jürgen P; Kaiser, Ute; Cooper, Andrew I; Thomas, Arne; Bojdys, Michael J

    2014-07-14

    Graphitic carbon nitride has been predicted to be structurally analogous to carbon-only graphite, yet with an inherent bandgap. We have grown, for the first time, macroscopically large crystalline thin films of triazine-based, graphitic carbon nitride (TGCN) using an ionothermal, interfacial reaction starting with the abundant monomer dicyandiamide. The films consist of stacked, two-dimensional (2D) crystals between a few and several hundreds of atomic layers in thickness. Scanning force and transmission electron microscopy show long-range, in-plane order, while optical spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations corroborate a direct bandgap between 1.6 and 2.0 eV. Thus TGCN is of interest for electronic devices, such as field-effect transistors and light-emitting diodes.

  18. A novel single-stranded DNA detection method based on organic semiconductor heterojunction

    NASA Astrophysics Data System (ADS)

    Gu, Wen; Liu, Hongbo; Zhang, Xia; Zhang, Hao; Chen, Xiong; Wang, Jun

    2016-12-01

    We demonstrate a novel DNA detection method with low-cost and disposable advantages by utilizing F16CuPc/CuPc planar organic heterojunction device. Single-stranded DNA (ssDNA) molecules have been well immobilized on the surface of CuPc film observed by atomic force microscopy, producing an obvious electrical response of the device. The conductivity of the organic heterojunction film was significantly increased by ssDNA immobilization because ssDNA molecules brought additional positive charges at heterojunction interface. Furthermore, the thickness dependence of CuPc upper layer on the electrical response was studied to optimize the sensitivity. This study will be helpful for the development of organic heterojunction based biosensors.

  19. Trends and techniques for space base electronics. [mathematical models, ion implantation, and semiconductors

    NASA Technical Reports Server (NTRS)

    Gassaway, J. D.; Mahmood, Q.; Trotter, J. D.

    1978-01-01

    A system was developed for depositing aluminum and aluminum alloys by the D.C. sputtering technique. This system which was designed for a high level of cleanliness and ion monitoring the deposition parameters during film preparation is ready for studying the deposition and annealing parameters upon double level metal preparation. The finite element method was studied for use in the computer modeling of two dimensional MOS transistor structures. An algorithm was developed for implementing a computer study which is based upon the finite difference method. The program was modified and used to calculate redistribution data for boron and phosphorous which had been predeposited by ion implantation with range and straggle conditions typical of those used at MSFC. Data were generated for 111 oriented SOS films with redistribution in N2, dry O2 and steam ambients. Data are given showing both two dimensional effects and the evolution of the junction depth, sheet resistance and integrated dose with redistribution time.

  20. Intrinsic Nilpotent Approximation.

    DTIC Science & Technology

    1985-06-01

    RD-A1II58 265 INTRINSIC NILPOTENT APPROXIMATION(U) MASSACHUSETTS INST 1/2 OF TECH CAMBRIDGE LAB FOR INFORMATION AND, DECISION UMCLRSSI SYSTEMS C...TYPE OF REPORT & PERIOD COVERED Intrinsic Nilpotent Approximation Technical Report 6. PERFORMING ORG. REPORT NUMBER LIDS-R-1482 7. AUTHOR(.) S...certain infinite-dimensional filtered Lie algebras L by (finite-dimensional) graded nilpotent Lie algebras or g . where x E M, (x,,Z) E T*M/O. It

  1. PLGA-PLL-PEG-Tf-based targeted nanoparticles drug delivery system enhance antitumor efficacy via intrinsic apoptosis pathway

    PubMed Central

    Bao, Wen; Liu, Ran; Wang, Yonglu; Wang, Fei; Xia, Guohua; Zhang, Haijun; Li, Xueming; Yin, Haixiang; Chen, Baoan

    2015-01-01

    Chemotherapy offers a systemic cancer treatment; however, it is limited in clinical administration due to its serious side effects. In cancer medicine, the use of nanoparticles (NPs) drug delivery system (DDS) can sustainedly release anticancer drug at the specific site and reduce the incidence of toxicity in normal tissues. In the present study, we aimed to evaluate the benefit of a novel chemotherapeutic DDS and its underlying mechanisms. Daunorubicin (DNR) was loaded into poly (lactic-co-glycolic acid) (PLGA)-poly-l-lysine (PLL)-polyethylene glycol (PEG)-transferrin (Tf) NPs to construct DNR-PLGA-PLL-PEG-Tf-NPs (DNR-loaded NPs) as a DDS. After incubating with PLGA-PLL-PEG-Tf-NPs, DNR, and DNR-loaded NPs, the leukemia K562 cells were collected and the intracellular concentration of DNR was detected by flow cytometry, respectively. Furthermore, the effect of drugs on the growth of tumors in K562 xenografts was observed and the relevant toxicity of therapeutic drugs on organs was investigated in vivo. Meanwhile, cell apoptosis in the excised xenografts was measured by transferase-mediated dUTP nick-end labeling assay, and the expression of apoptosis-related proteins, including Bcl-2, Bax, Caspase-9, Caspase-3, and cleaved-PARP, was determined by Western blotting analysis. Results showed that DNR-loaded NPs increased intracellular concentration of DNR in K562 cells in vitro and induced a remarkable improvement in anticancer activity in the xenografts in vivo. The expression of Bcl-2 protein was downregulated and that of Bax, Caspase-9, Caspase-3, and cleaved-PARP proteins were obviously upregulated in the DNR-loaded NPs group than that in other ones. Interestingly, pathological assessment showed no apparent damage to the main organs. In summary, the results obtained from this study showed that the novel NPs DDS could improve the efficacy of DNR in the treatment of leukemia and induce apoptosis via intrinsic pathway. Thus, it can be inferred that the new drug

  2. Comprehensive Molecular Profiling of Archival Bone Marrow Trephines Using a Commercially Available Leukemia Panel and Semiconductor-Based Targeted Resequencing

    PubMed Central

    Bartels, Stephan; Schipper, Elisa; Kreipe, Hans Heinrich; Lehmann, Ulrich

    2015-01-01

    replacing Sanger sequencing by this semiconductor-based targeted resequencing approach. PMID:26222071

  3. Ab initio-based approach to structural change of compound semiconductor surfaces during MBE growth

    NASA Astrophysics Data System (ADS)

    Ito, Tomonori; Akiyama, Toru; Nakamura, Kohji

    2009-01-01

    Phase diagrams of GaAs and GaN surfaces are systematically investigated by using our ab initio-based approach in conjunction with molecular beam epitaxy (MBE). The phase diagrams are obtained as a function of growth parameters such as temperature and beam equivalent pressure (BEP). The versatility of our approach is exemplified by the phase diagram calculations for GaAs(0 0 1) surfaces, where the stable phases and those phase boundaries are successfully determined as functions of temperature and As 2 and As 4 BEPs. The initial growth processes are clarified by the phase diagram calculations for GaAs(1 1 1)B-(2×2). The calculated results demonstrate that the As-trimer desorption on the GaAs(1 1 1)B-(2×2) with Ga adatoms occurs beyond 500-700 K while the desorption without Ga adatoms does beyond 800-1000 K. This self-surfactant effect induced by Ga adsorption crucially affects the initial growth of GaAs on the GaAs(1 1 1)B-(2×2). Furthermore, the phase diagram calculations for GaN(0 0 0 1) suggests that Ga adsorption or desorption during GaN MBE growth can easily change the pseudo-(1×1) to the (2×2)-Ga via newly found (1×1) and vice versa. On the basis of this finding, the possibility of ghost island formation during MBE growth is discussed.

  4. Charge carrier mobilities in organic semiconductor crystals based on the spectral overlap.

    PubMed

    Stehr, Vera; Fink, Reinhold F; Deibel, Carsten; Engels, Bernd

    2016-09-05

    The prediction of substance-related charge-transport properties is important for the tayloring of new materials for organic devices, such as organic solar cells. Assuming a hopping process, the Marcus theory is frequently used to model charge transport. Here another approach, which is already widely used for exciton transport, is adapted to charge transport. It is based on the spectral overlap of the vibrational donor and acceptor spectra. As the Marcus theory it is derived from Fermi's Golden rule, however, it contains less approximations, as the molecular vibrations are treated quantum mechanically. In contrast, the Marcus theory reduces all vibrational degrees of freedom to one and treats its influence classically. The approach is tested on different acenes and predicts most of the experimentally available hole mobilities in these materials within a factor of 2. This represents a significant improvement to values obtained from Marcus theory which is qualitatively correct but frequently overestimates the mobilities by factors up to 10. Furthermore, the charge-transport properties of two derivatives of perylene bisimide are investigated. © 2016 Wiley Periodicals, Inc.

  5. N-bits all-optical circular shift register based on semiconductor optical amplifier buffer

    NASA Astrophysics Data System (ADS)

    Lazzeri, Emma; Berrettini, Gianluca; Meloni, Gianluca; Bogoni, Antonella; Potì, Luca

    2011-03-01

    In the perspective of a future all-optical communication network optical shift register will play an important role especially for what concerns several binary functions, such as serial to parallel conversion and cyclic operations, that are involved in techniques allowing error detection and correction as parity check, or cyclic redundancy check. During the last decades, several attempts of realizing circulating memories or shift register in the optical domain were made, with some limits in terms of functionality, number of bit to be stored (under three), scalability or photonic integrability. In this paper, we present a new approach to realize a circulating optical shift register consisting on an SOA-based optical buffer (OB) and a bit selecting circuit (BSC). The OB is potentially integrable and is able to store a finite number of bit at high bit rate. The BSC returns consecutive bits at a lower clock rate, achieving proper shift register function. The bit selection is realized by means of four wave mixing (FWM) in a Kerr medium, and the sequence cancellation is allowed to enable new sequence storing. Experimental validation of the scheme for fB=59MHz and fB=236MHz shows optical signal to noise ratio per bit penalty of 5.6dB at BER=10-9.

  6. Development of compact high efficiency microstructured semiconductor neutron detectors

    NASA Astrophysics Data System (ADS)

    McGregor, D. S.; Bellinger, S. L.; Fronk, R. G.; Henson, L.; Huddleston, D.; Ochs, T.; Shultis, J. K.; Sobering, T. J.; Taylor, R. D.

    2015-11-01

    Semiconductor diode detectors coated with neutron reactive materials are generally fashioned as planar diodes coated with 10B, 6LiF, or Gd. Planar detectors coated with 10B or 6LiF are limited to less than 5% intrinsic thermal neutron detection efficiency. Detectors coated with Gd can achieve higher efficiencies, but the low-energy signatures are problematic in the presence of background radiations. Microstructured semiconductor neutron detectors (MSNDs) can now achieve a tenfold increase in neutron detection efficiency over the planar diode designs. These semiconductor neutron detectors are fashioned with a matrix of microstructured patterns etched deeply into the semiconductor substrate and, subsequently, backfilled with neutron reactive materials. Intrinsic thermal-neutron detection efficiencies exceeding 35% have been achieved with devices no thicker than 1 mm while operating on less than 5 V, now allowing for instrumentation to be realized with similar performance as 3He gas-filled detectors.

  7. Intrinsic Friction Microscopy

    NASA Astrophysics Data System (ADS)

    Knorr, Daniel; Overney, Rene

    2008-03-01

    A novel scanning probe methodology based on lateral force microscopy is presented wherein kinetic friction measurements, obtained as a function of velocity for various temperatures, are used to deduce apparent Arrhenius-type activation energies for surface and subsurface molecular mobilities. Depending on the coupling strength (cooperativity) between molecular mobilities involved the dissipation energy can carry a significant entropic energy contribution, accounting for the majority of the apparent Arrhenius activation energy. The intrinsic friction methodology also provides a means of directly separating enthalpic energy contributions from entropic ones by employing absolute rate theory. As such, the degree of cooperativity in the system is readily apparent. This methodology is illustrated with nanoscale tribological experiments on two systems, (1) monodisperse, atactic polystyrene and (2) self assembling molecular glassy chromophores. In polystyrene, dissipation was found to be a discrete function of loading, where the γ-relaxation (phenyl group rotation) was recovered for ultra low loads and the β-relaxation (local backbone translation) for higher loads in the same temperature range, indicating sensitivity to surface and subsurface mobilities. For self assembling glassy chromophores, the degree of intermolecular cooperativity was deduced using the methodology, resulting in an increased understanding of the interactions between self assembling molecules.

  8. Intrinsically irreversible heat engine

    DOEpatents

    Wheatley, J.C.; Swift, G.W.; Migliori, A.

    1984-01-01

    A class of heat engines based on an intrinsically irreversible heat transfer process is disclosed. In a typical embodiment the engine comprises a compressible fluid that is cyclically compressed and expanded while at the same time being driven in reciprocal motion by a positive displacement drive means. A second thermodynamic medium is maintained in imperfect thermal contact with the fluid and bears a broken thermodynamic symmetry with respect to the fluid. The second thermodynamic medium is a structure adapted to have a low fluid flow impedance with respect to the compressible fluid, and which is further adapted to be in only moderate thermal contact with the fluid. In operation, thermal energy is pumped along the second medium due to a phase lag between the cyclical heating and cooling of the fluid and the resulting heat conduction between the fluid and the medium. In a preferred embodiment the engine comprises an acoustical drive and a housing containing a gas which is driven at a resonant frequency so as to be maintained in a standing wave. Operation of the engine at acoustic frequencies improves the power density and coefficient of performance. The second thermodynamic medium can be coupled to suitable heat exchangers to utilize the engine as a simple refrigeration device having no mechanical moving parts. Alternatively, the engine is reversible in function so as to be utilizable as a prime mover by coupling it to suitable sources and sinks of heat.

  9. Intrinsically irreversible heat engine

    DOEpatents

    Wheatley, J.C.; Swift, G.W.; Migliori, A.

    1984-12-25

    A class of heat engines based on an intrinsically irreversible heat transfer process is disclosed. In a typical embodiment the engine comprises a compressible fluid that is cyclically compressed and expanded while at the same time being driven in reciprocal motion by a positive displacement drive means. A second thermodynamic medium is maintained in imperfect thermal contact with the fluid and bears a broken thermodynamic symmetry with respect to the fluid. The second thermodynamic medium is a structure adapted to have a low fluid flow impedance with respect to the compressible fluid, and which is further adapted to be in only moderate thermal contact with the fluid. In operation, thermal energy is pumped along the second medium due to a phase lag between the cyclical heating and cooling of the fluid and the resulting heat conduction between the fluid and the medium. In a preferred embodiment the engine comprises an acoustical drive and a housing containing a gas which is driven at a resonant frequency so as to be maintained in a standing wave. Operation of the engine at acoustic frequencies improves the power density and coefficient of performance. The second thermodynamic medium can be coupled to suitable heat exchangers to utilize the engine as a simple refrigeration device having no mechanical moving parts. Alternatively, the engine is reversible in function so as to be utilizable as a prime mover by coupling it to suitable sources and sinks of heat. 11 figs.

  10. Intrinsically irreversible heat engine

    DOEpatents

    Wheatley, John C.; Swift, Gregory W.; Migliori, Albert

    1984-01-01

    A class of heat engines based on an intrinsically irreversible heat transfer process is disclosed. In a typical embodiment the engine comprises a compressible fluid that is cyclically compressed and expanded while at the same time being driven in reciprocal motion by a positive displacement drive means. A second thermodynamic medium is maintained in imperfect thermal contact with the fluid and bears a broken thermodynamic symmetry with respect to the fluid. the second thermodynamic medium is a structure adapted to have a low fluid flow impedance with respect to the compressible fluid, and which is further adapted to be in only moderate thermal contact with the fluid. In operation, thermal energy is pumped along the second medium due to a phase lag between the cyclical heating and cooling of the fluid and the resulting heat conduction between the fluid and the medium. In a preferred embodiment the engine comprises an acoustical drive and a housing containing a gas which is driven at a resonant frequency so as to be maintained in a standing wave. Operation of the engine at acoustic frequencies improves the power density and coefficient of performance. The second thermodynamic medium can be coupled to suitable heat exchangers to utilize the engine as a simple refrigeration device having no mechanical moving parts. Alternatively, the engine is reversible in function so as to be utilizable as a prime mover by coupling it to suitable sources and sinks of heat.

  11. Theory Of An Electro-Optic Modulator Based On Quantum Wells In A Semiconductor etalon

    NASA Astrophysics Data System (ADS)

    Guy, D. R. P.; Apsley, N.; Taylor, L. L.; Bass, S. J.; Klipstein, P. C.

    1987-08-01

    We present the design of an electro-optic modulator which is based on the quantum-confined Stark effect (QCSE) in GaAs quantum wells contained within the central layer of a Fabry-Perot etalon. The etalon mirrors are quarter wave stacks of Ga0.7A10.3As and AlAs, eliminating the need for the application of anti-reflection coatings. p-i-n-doping is employed with the undoped Or stack sandwiched between doped mirrors, enabling electric fields of the order of 105Vcm-1 to be readily developed across the quantum wells. Placing a multiple quantum well structure within an etalon resonant cavity gives flexibility of design in terms of operating wavelength and mode: Light incident perpendicular to the QW stack is modulated through the operation of the QCSE on the QW excitons, either electro-refractively by a change in the real part of the QW refractive index producing a wavelength modulation of the narrow-band Fabry-Perot transmission resonance or in electro-absorptive mode. The semi-empirical theory uses conventional multilayer optical matrix methods together with a recent theory of the QCSE which has been tested against the results of electro-reflectance experiments. In electro-absorption mode we find a ratio of 19:1 on:off at 857.5nm for 8 quantum wells. In electro-refractive mode, using 32 wells, we predict modulation from 10% to 76% reflection at 883nm. These figures exclude substrate effects. Extension of the theory to other materials systems is readily accomplished. We present the reflectivity spectrum of a high quality etalon in In0.53Ga0.47As/InP and find good agreement with the predictions of the optical matrix model.

  12. Oxide-based method of making compound semiconductor films and making related electronic devices

    DOEpatents

    Kapur, Vijay K.; Basol, Bulent M.; Leidholm, Craig R.; Roe, Robert A.

    2000-01-01

    A method for forming a compound film includes the steps of preparing a source material, depositing the source material on a base and forming a preparatory film from the source material, heating the preparatory film in a suitable atmosphere to form a precursor film, and providing suitable material to said precursor film to form the compound film. The source material includes oxide-containing particles including Group IB and IIIA elements. The precursor film includes non-oxide Group IB and IIIA elements. The compound film includes a Group IB-IIIA-VIA compound. The oxides may constitute greater than about 95 molar percent of the Group IB elements and greater than about 95 molar percent of the Group IIIA elements in the source material. Similarly, non-oxides may constitute greater than about 95 molar percent of the Group IB elements and greater than about 95 molar percent of the Group IIIA elements in the precursor film. The molar ratio of Group IB to Group IIIA elements in the source material may be greater than about 0.6 and less than about 1.0, or substantially greater that 1.0, in which case this ratio in the compound film may be reduced to greater than about 0.6 and less than about 1.0. The source material may be prepared as an ink from particles in powder form. The oxide-containing particles may include a dopant, as may the compound film. Compound films including a Group IIB-IVA-VA compound may be substituted using appropriate substitutions in the method. The method, also, is applicable to fabrication of solar cells and other electronic devices.

  13. Toward a national semiconductor strategy, volume 1

    NASA Astrophysics Data System (ADS)

    1991-02-01

    Updated here are key market data showing trends in the U.S. semiconductor industry's world market position. New information is given on three emerging semiconductor-based technologies: broadband communications, advanced display systems, and intelligent vehicles and highways. These are examples of important, high-volume markets that will consume significant numbers of semiconductor components and that must be addressed in a national semiconductor strategy. New recommendations and a summary of all Committee recommendations to date are given as well as a summary of comments received at a public forum held in Silicon Valley in may 1990.

  14. Taming excitons in II-VI semiconductor nanowires and nanobelts

    NASA Astrophysics Data System (ADS)

    Xu, Xinlong; Zhang, Qing; Zhang, Jun; Zhou, Yixuan; Xiong, Qihua

    2014-10-01

    Excitons are one of the most important fundamental quasi-particles, and are involved in a variety of processes forming the basis of a wide range of opto-electronic and photonic devices based on II-VI semiconductor nanowires and nanobelts, such as light-emitting diodes, photovoltaic cells, photodetectors and nanolasers. A clear understanding of their properties and unveiling the potential engineering for excitons is of particular importance for the design and optimization of nanoscale opto-electronic and photonic devices. Herein, we present a comprehensive review on discussing the fundamental behaviours of the excitons in one-dimensional (1D) II-VI semiconductor nanomaterials (nanowires and nanobelts). We will start with a focus on the unique properties (origin, generation, etc) and dynamics of excitons and exciton complexes in the II-VI semiconductor nanowires and nanobelts. Then we move to the recent progress on the excitonic response in 1D nanomaterials and focus on the tailoring and engineering of excitonic properties through rational controlling of the physical parameters and conditions, intrinsically and extrinsically. These include (1) exciton-exciton interaction, which is important for 1D nanomaterial nanolasing; (2) exciton-phonon interaction, which has interesting applications for laser cooling; and (3) exciton-plasmon interaction, which is the cornerstone towards the realization of plasmonic lasers. The potential of electric field, morphology and size control for excitonic properties is also discussed. Unveiling and controlling excitonic properties in II-VI semiconductor nanowires and nanobelts would promote the development of 1D nanoscience and nanotechnology.

  15. A 1.33 µm picosecond pulse generator based on semiconductor disk mode-locked laser and bismuth fiber amplifier.

    PubMed

    Heikkinen, Juuso; Gumenyuk, Regina; Rantamäki, Antti; Leinonen, Tomi; Melkumov, Mikhail; Dianov, Evgeny M; Okhotnikov, Oleg G

    2014-05-19

    We demonstrate that a combination of ultrafast wafer bonded semiconductor disk laser and a bismuth-doped fiber amplifier provides an attractive design for high power 1.33 µm tandem hybrid systems. Over 0.5 W of average output power was achieved at a repetition rate of 827 MHz that corresponds to a pulse energy of 0.62 nJ.

  16. Electronic structure of defects in III-VI and II-VI semiconductors and novel ytterbium-based intermetallics

    NASA Astrophysics Data System (ADS)

    Rak, Zsolt

    In recent years there has been a revival of interest in the III-VI family of semiconductors (GaS, GaSe, GaTe and InSe) due to their exciting nonlinear optical properties and their possible application in detector devices. These materials crystallize in layered crystal structure and their physical properties display a quasi two-dimensional character. An important characteristic of these systems is the existence of Ga-Ga (or In-In) dimers. It is well known that defects control the physical properties of semiconductors. In this thesis, we have carried out electronic structure calculations to study the nature of defect states in these materials. The defects we have studied include substitutional impurities at the cation and the anion sites as well as cationic and anionic vacancies. The failure of the hydrogenic effective mass approximation (EMA) to reproduce the experimental binding energies for the substitutional Cd and Sn defect states in GaSe, indicates the presence of large central cell corrections and the necessity of incorporating short range interactions in the calculation of defect binding energy. This has been done using a supercell model and self-consistent ab initio electronic structure method within density functional theory (DFT), which is known to be quite successful in tackling the problem of defects in semiconductors. Analyzing the defects from first-principles, we have been able to explain the detailed microscopic mechanism of the formation of Ga-site defects in GaSe and GaTe. When Ga is replaced by an impurity or when it is removed from the system to create a vacancy, the Ga dimer states can be strongly perturbed and this perturbation can give rise to defect states in the band gap. Defect formation energy calculations, based on total energy differences between the pure and defect containing systems, can give valuable insight into the solubility of different impurities in a host compound. The formation energies of Ge and Sn impurities reveal that under

  17. Treatability Study in Support of Intrinsic Remediation for the Hangar 10 Site. Elmendorf Air Force Base, Anchorage, Alaska

    DTIC Science & Technology

    1995-03-01

    ANCHORAGE , ALASKA March 1995 D Prepared for: I * AIR FORCE CENTER FOR ENVIRONMENTAL EXCELLENCE TECHNOLOGY TRANSFER DIVISION BROOKS AIR FORCE BASE SAN...ANTONIO, TEXAS AND ELMENDORF AIR FORCE BASE ANCHORAGE , ALASKA I Prepared by: I Parsons Engineering Science, Inc. 1700 Broadway, Suite 900 Denver, Colorado...Wnrinsic Remediation TS Elmendorf Air Force Base Anchorage . Alaska 0 125250 500 1000 MENARSNSEIGUINE N FEET Denver, Colorado 5-31

  18. Theoretical Study of the Noble Metals on Semiconductor Surfaces and Titanium-Base Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Ding, Yungui

    The electronic and structural properties of the (sqrt3 x sqrt3) R30^circ Ag/Si(111) and ( sqrt3 x sqrt3) R30^ circ 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 (sqrt3 x sqrt3) R30^circ 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 (sqrt3 x sqrt3) R30^circ 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 (sqrt3 x sqrt3) R30^circ 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. Calculations are also done for Ti in bcc structure and hypothetical B2-structured TiAl, TiAg, and TiCu. Our results show correlation between the

  19. Understanding the acid-base properties of adenosine: the intrinsic basicities of N1, N3 and N7.

    PubMed

    Kapinos, Larisa E; Operschall, Bert P; Larsen, Erik; Sigel, Helmut

    2011-07-11

    Adenosine (Ado) can accept three protons, at N1, N3, and N7, to give H(3) (Ado)(3+) , and thus has three macro acidity constants. Unfortunately, these constants do not reflect the real basicity of the N sites due to internal repulsions, for example, between (N1)H(+) and (N7)H(+). However, these macroconstants are still needed for the evaluations and the first two are taken from our own earlier work, that is, pK(H)(H(3))((Ado)) = -4.02 and pK(H)(H(2))((Ado)) = -1.53; the third one was re-measured as pK(H)(H)((Ado)) = 3.64 ± 0.02 (25 °C; I=0.5 M, NaNO(3)), because it is the main basis for evaluating the intrinsic basicities of N7 and N3. Previously, contradicting results had been published for the micro acidity constant of the (N7)H(+) site; this constant has now been determined in an unequivocal manner, and that of the (N3)H(+) site was obtained for the first time. The micro acidity constants, which describe the release of a proton from an (N)H(+) site under conditions for which the other nitrogen atoms are free and do not carry a proton, decrease in the order pk(N7-N1)(N7(Ado)N1·H)) = 3.63 ± 0.02 > pk(N7-N1)(H·N7(Ado)N1) = 2.15 ± 0.15 > pk(N3-N1,N7)(H·N3(Ado)N1,N7) =1.5 ± 0.3, reflecting the decreasing basicity of the various nitrogen atoms, that is, N1>N7>N3. Application of the above-mentioned microconstants allows one to calculate the percentages (formation degrees) of the tautomers formed for monoprotonated adenosine, H(Ado)(+) , in aqueous solution; the results are 96.1, 3.2, and 0.7% for N7(Ado)N1·H(+), (+)H·N7(Ado)N1, and (+)H·N3(Ado)N1,N7, respectively. These results are in excellent agreement with theoretical DFT calculations. Evidently, H(Ado)(+) exists to the largest part as N7(Ado)N1·H(+) having the proton located at N1; the two other tautomers are minority species, but they still form. These results are not only meaningful for adenosine itself, but are also of relevance for nucleic acids and adenine nucleotides, as they help to understand

  20. Quasar redshifts: the intrinsic component

    NASA Astrophysics Data System (ADS)

    Hansen, Peter M.

    2016-09-01

    The large observed redshift of quasars has suggested large cosmological distances and a corresponding enormous energy output to explain the brightness or luminosity as seen at earth. Alternative or complementary sources of redshift have not been identified by the astronomical community. This study examines one possible source of additional redshift: an intrinsic component based on the plasma characteristics of high temperature and high electron density which are believed to be present.

  1. Engineering optical properties of semiconductor metafilm superabsorbers

    NASA Astrophysics Data System (ADS)

    Kim, Soo Jin; Fan, Pengyu; Kang, Ju-Hyung; Brongersma, Mark L.

    2016-04-01

    Light absorption in ultrathin layer of semiconductor has been considerable interests for many years due to its potential applications in various optical devices. In particular, there have been great efforts to engineer the optical properties of the film for the control of absorption spectrums. Whereas the isotropic thin films have intrinsic optical properties that are fixed by materials' properties, metafilm that are composed by deep subwavelength nano-building blocks provides significant flexibilities in controlling the optical properties of the designed effective layers. Here, we present the ultrathin semiconductor metafilm absorbers by arranging germanium (Ge) nanobeams in deep subwavelength scale. Resonant properties of high index semiconductor nanobeams play a key role in designing effective optical properties of the film. We demonstrate this in theory and experimental measurements to build a designing rule of efficient, controllable metafilm absorbers. The proposed strategy of engineering optical properties could open up wide range of applications from ultrathin photodetection and solar energy harvesting to the diverse flexible optoelectronics.

  2. rf-microwave switches based on reversible semiconductor-metal transition of VO2 thin films synthesized by pulsed-laser deposition

    NASA Astrophysics Data System (ADS)

    Dumas-Bouchiat, F.; Champeaux, C.; Catherinot, A.; Crunteanu, A.; Blondy, P.

    2007-11-01

    Microwave switching devices based on the semiconductor-metal transition of VO2 thin films were developped on two types of substrates (C-plane sapphire and SiO2/Si), and in both shunt and series configurations. Under thermal activation, the switches achieved up to 30-40dB average isolation of the radio-frequency (rf) signal on 500MHz -35GHz frequency band with weak insertion losses. These VO2-based switches can be electrically activated with commutation times less than 100ns, which make them promising candidates for realizing efficient and simple rf switches.

  3. Semiconductor Terahertz Technology

    DTIC Science & Technology

    2009-06-15

    COVERED (From - To) 15-June-2009 Final Report 12 Apr 07 - 15 Apr 09 4. TITLE AND SUBTITLE Sa. CONTRACT NUMBER FA8718-07-C-0030 Semiconductor Terahertz ...and the other for the phononic waveguides. 15. SUBJECT TERMS Quantum cascade laser, gennanium, gennanium-tin, terahertz 16. SECURITY CLASStFICATION OF...7 Figure 7 lllustration of a GaAs-based active region waveguide with either Ga or Au as cladding operating in the Restrahlen band of GaN . 10 Figure 8

  4. Chemically Derivatized Semiconductor Photoelectrodes.

    DTIC Science & Technology

    1982-01-04

    as Si, Ge, and GaAs derivatized with reagents based on ferrocene such as those represented by I and II. Work with p-type semiconductor photoelectrode...Concerning n-type Si it was found that EtOH/0.1 M En-Bu4N)C104 solutions containing A = ferrocene and A+ = ferri-- cinium result in a constant output of...electrical energy from an illuminated photoelectrochemical device configured as in Scheme II.(20) The ferrocene captures the photogenerated h+ at a rate -4

  5. A synaptic device built in one diode-one resistor (1D-1R) architecture with intrinsic SiOx-based resistive switching memory

    NASA Astrophysics Data System (ADS)

    Chang, Yao-Feng; Fowler, Burt; Chen, Ying-Chen; Zhou, Fei; Pan, Chih-Hung; Chang, Kuan-Chang; Tsai, Tsung-Ming; Chang, Ting-Chang; Sze, Simon M.; Lee, Jack C.

    2016-04-01

    We realize a device with biological synaptic behaviors by integrating silicon oxide (SiOx) resistive switching memory with Si diodes to further minimize total synaptic power consumption due to sneak-path currents and demonstrate the capability for spike-induced synaptic behaviors, representing critical milestones for the use of SiO2-based materials in future neuromorphic computing applications. Biological synaptic behaviors such as long-term potentiation, long-term depression, and spike-timing dependent plasticity are demonstrated systemically with comprehensive investigation of spike waveform analyses and represent a potential application for SiOx-based resistive switching materials. The resistive switching SET transition is modeled as hydrogen (proton) release from the (SiH)2 defect to generate the hydrogenbridge defect, and the RESET transition is modeled as an electrochemical reaction (proton capture) that re-forms (SiH)2. The experimental results suggest a simple, robust approach to realize programmable neuromorphic chips compatible with largescale complementary metal-oxide semiconductor manufacturing technology.

  6. Photoelectrosynthesis at semiconductor electrodes

    SciTech Connect

    Nozik, A. J.

    1980-12-01

    The general principles of photoelectrochemistry and photoelectrosynthesis are reviewed and some new developments in photoelectrosynthesis are discussed. Topics include energetics of semiconductor-electrolyte interfaces(band-edge unpinning); hot carrier injection at illuminated semiconductor-electrolyte junctions; derivatized semiconductor electrodes; particulate photoelectrochemical systems; layered compounds and other new materials; and dye sensitization. (WHK)

  7. Epitaxy of highly ordered organic semiconductor crystallite networks supported by hexagonal boron nitride

    PubMed Central

    Matković, Aleksandar; Genser, Jakob; Lüftner, Daniel; Kratzer, Markus; Gajić, Radoš; Puschnig, Peter; Teichert, Christian

    2016-01-01

    This study focuses on hexagonal boron nitride as an ultra-thin van der Waals dielectric substrate for the epitaxial growth of highly ordered crystalline networks of the organic semiconductor parahexaphenyl. Atomic force microscopy based morphology analysis combined with density functional theory simulations reveal their epitaxial relation. As a consequence, needle-like crystallites of parahexaphenyl grow with their long axes oriented five degrees off the hexagonal boron nitride zigzag directions. In addition, by tuning the deposition temperature and the thickness of hexagonal boron nitride, ordered networks of needle-like crystallites as long as several tens of micrometers can be obtained. A deeper understanding of the organic crystallites growth and ordering at ultra-thin van der Waals dielectric substrates will lead to grain boundary-free organic field effect devices, limited only by the intrinsic properties of the organic semiconductors. PMID:27929042

  8. Gate-modulated transport properties and mechanism for nanowire cross junction based on SnO2 semiconductor

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Tong, Yanhong; Wang, Guorui; Tang, Qingxin; Liu, Yichun

    2015-12-01

    The transport properties and mechanism of the three-terminal field-effect nanowire cross junction have been systematically investigated. An interesting phenomenon, such as applied voltage bias on nanowire cross junction makes the ON/OFF current ratio of the transistor improved by over 2 orders of magnitude, has been observed. Different from the two-terminal nanowire cross junctions, the cross junction induced potential barrier in three-terminal counterparts is found to be capable to prevent the current of the top semiconductor nanowire from injecting into the bottom nanowire at off state, while to make the current of the top semiconductor nanowire contribute to the current of the bottom nanowire at on state, resulting in the current switch between on state and off state by the gate voltage modulation.

  9. Electrical properties of zinc-oxide-based thin-film transistors using strontium-oxide-doped semiconductors

    NASA Astrophysics Data System (ADS)

    Wu, Shao-Hang; Zhang, Nan; Hu, Yong-Sheng; Chen, Hong; Jiang, Da-Peng; Liu, Xing-Yuan

    2015-10-01

    Strontium-zinc-oxide (SrZnO) films forming the semiconductor layers of thin-film transistors (TFTs) are deposited by using ion-assisted electron beam evaporation. Using strontium-oxide-doped semiconductors, the off-state current can be dramatically reduced by three orders of magnitude. This dramatic improvement is attributed to the incorporation of strontium, which suppresses carrier generation, thereby improving the TFT. Additionally, the presence of strontium inhibits the formation of zinc oxide (ZnO) with the hexagonal wurtzite phase and permits the formation of an unusual phase of ZnO, thus significantly changing the surface morphology of ZnO and effectively reducing the trap density of the channel. Project supported by the National Natural Science Foundation of China (Grant No. 6140031454) and the Innovation Program of Chinese Academy of Sciences and State Key Laboratory of Luminescence and Applications.

  10. Near-field thermal radiation transfer between semiconductors based on thickness control and introduction of photonic crystals

    NASA Astrophysics Data System (ADS)

    Inoue, Takuya; Asano, Takashi; Noda, Susumu

    2017-03-01

    We numerically investigate the spectral control of near-field thermal radiation transfer using interband absorption in semiconductors and the band-folding effect in photonic crystals (PCs) for highly efficient thermophotovoltaics. We reveal that the near-field coupling between two semiconductors (Si and GaSb) realizes frequency-selective thermal radiation transfer concentrated above their bandgap energy when their thicknesses are optimized considering their absorption coefficient spectra. Moreover, we elucidate the role of PC structures in the near-field thermal radiation transfer and demonstrate that the band-folding effect in PCs can further increase both the radiation power and frequency selectivity of the near-field thermal radiation transfer.

  11. Experience of development and employment of portative x-ray radiometric instrument on the base of cooled semiconductor detection units

    SciTech Connect

    Klyutchinsky, Yu.; Veits, B.; Efremov, Yu.

    1993-12-31

    The results of development and employment of field X-ray radiometric insrtuments intended for the determination of different element mass fractions from calcium to uranium in various mediums under industrial conditions are considered in this report. The portable semiconductor units for detecting x ray radiation with high energy resolution are used as a detector. The applications to ore testing and environmental monitoring are described.

  12. Analysis of Intrinsic Peptide Detectability via Integrated Label-Free and SRM-Based Absolute Quantitative Proteomics.

    PubMed

    Jarnuczak, Andrew F; Lee, Dave C H; Lawless, Craig; Holman, Stephen W; Eyers, Claire E; Hubbard, Simon J

    2016-09-02

    Quantitative mass spectrometry-based proteomics of complex biological samples remains challenging in part due to the variability and charge competition arising during electrospray ionization (ESI) of peptides and the subsequent transfer and detection of ions. These issues preclude direct quantification from signal intensity alone in the absence of a standard. A deeper understanding of the governing principles of peptide ionization and exploitation of the inherent ionization and detection parameters of individual peptides is thus of great value. Here, using the yeast proteome as a model system, we establish the concept of peptide F-factor as a measure of detectability, closely related to ionization efficiency. F-factor is calculated by normalizing peptide precursor ion intensity by absolute abundance of the parent protein. We investigated F-factor characteristics in different shotgun proteomics experiments, including across multiple ESI-based LC-MS platforms. We show that F-factors mirror previously observed physicochemical predictors as peptide detectability but demonstrate a nonlinear relationship between hydrophobicity and peptide detectability. Similarly, we use F-factors to show how peptide ion coelution adversely affects detectability and ionization. We suggest that F-factors have great utility for understanding peptide detectability and gas-phase ion chemistry in complex peptide mixtures, selection of surrogate peptides in targeted MS studies, and for calibration of peptide ion signal in label-free workflows. Data are available via ProteomeXchange with identifier PXD003472.

  13. Exploiting the intrinsic microbial degradative potential for field-based in situ dechlorination of trichloroethene contaminated groundwater.

    PubMed

    Adetutu, Eric M; Gundry, Taylor D; Patil, Sayali S; Golneshin, Aida; Adigun, Joy; Bhaskarla, Vijay; Aleer, Samuel; Shahsavari, Esmaeil; Ross, Elizabeth; Ball, Andrew S

    2015-12-30

    Bioremediation of trichloroethene (TCE) polluted groundwater is challenging, with limited next generation sequencing (NGS) derived information available on microbial community dynamics associated with dechlorination. Understanding these dynamics is important for designing and improving TCE bioremediation. In this study, biostimulation (BS), biostimulation-bioaugmentation (BS-BA) and monitored natural attenuation (MNA) approaches were applied to contaminated groundwater wells resulted in ≥ 95% dechlorination within 7 months. Vinyl chloride's final concentrations in stimulated wells were between 1.84 and 1.87 μg L(-1), below the US EPA limit of 2.0 μg L(-1), compared to MNA (4.3 μg L(-1)). Assessment of the groundwater microbial community with qPCR showed up to ∼ 50-fold increase in the classical dechlorinators' (Geobacter and Dehalococcoides sp.) population post-treatment. Metagenomic assays revealed shifts from Gammaproteobacteria (pre-treatment) to Epsilonproteobacteria and Deltaproteobacteria (post-treatment) only in stimulated wells. Although stimulated wells were functionally distinct from MNA wells post-treatment, substantial dechlorination in all the wells implied some measure of redundancy. This study, one of the few NGS-based field studies on TCE bioremediation, provides greater insights into dechlorinating microbial community dynamics which should be useful for future field-based studies.

  14. Study of self-compliance behaviors and internal filament characteristics in intrinsic SiO{sub x}-based resistive switching memory

    SciTech Connect

    Chang, Yao-Feng Zhou, Fei; Chen, Ying-Chen; Lee, Jack C.; Fowler, Burt

    2016-01-18

    Self-compliance characteristics and reliability optimization are investigated in intrinsic unipolar silicon oxide (SiO{sub x})-based resistive switching (RS) memory using TiW/SiO{sub x}/TiW device structures. The program window (difference between SET voltage and RESET voltage) is dependent on external series resistance, demonstrating that the SET process is due to a voltage-triggered mechanism. The program window has been optimized for program/erase disturbance immunity and reliability for circuit-level applications. The SET and RESET transitions have also been characterized using a dynamic conductivity method, which distinguishes the self-compliance behavior due to an internal series resistance effect (filament) in SiO{sub x}-based RS memory. By using a conceptual “filament/resistive gap (GAP)” model of the conductive filament and a proton exchange model with appropriate assumptions, the internal filament resistance and GAP resistance can be estimated for high- and low-resistance states (HRS and LRS), and are found to be independent of external series resistance. Our experimental results not only provide insights into potential reliability issues but also help to clarify the switching mechanisms and device operating characteristics of SiO{sub x}-based RS memory.

  15. Wide band gap semiconductor templates

    DOEpatents

    Arendt, Paul N.; Stan, Liliana; Jia, Quanxi; DePaula, Raymond F.; Usov, Igor O.

    2010-12-14

    The present invention relates to a thin film structure based on an epitaxial (111)-oriented rare earth-Group IVB oxide on the cubic (001) MgO terminated surface and the ion-beam-assisted deposition ("IBAD") techniques that are amendable to be over coated by semiconductors with hexagonal crystal structures. The IBAD magnesium oxide ("MgO") technology, in conjunction with certain template materials, is used to fabricate the desired thin film array. Similarly, IBAD MgO with appropriate template layers can be used for semiconductors with cubic type crystal structures.

  16. Unitary lens semiconductor device

    DOEpatents

    Lear, K.L.

    1997-05-27

    A unitary lens semiconductor device and method are disclosed. The unitary lens semiconductor device is provided with at least one semiconductor layer having a composition varying in the growth direction for unitarily forming one or more lenses in the semiconductor layer. Unitary lens semiconductor devices may be formed as light-processing devices such as microlenses, and as light-active devices such as light-emitting diodes, photodetectors, resonant-cavity light-emitting diodes, vertical-cavity surface-emitting lasers, and resonant cavity photodetectors. 9 figs.

  17. Unitary lens semiconductor device

    DOEpatents

    Lear, Kevin L.

    1997-01-01

    A unitary lens semiconductor device and method. The unitary lens semiconductor device is provided with at least one semiconductor layer having a composition varying in the growth direction for unitarily forming one or more lenses in the semiconductor layer. Unitary lens semiconductor devices may be formed as light-processing devices such as microlenses, and as light-active devices such as light-emitting diodes, photodetectors, resonant-cavity light-emitting diodes, vertical-cavity surface-emitting lasers, and resonant cavity photodetectors.

  18. Diamagnetic excitons in semiconductors (Review)

    NASA Astrophysics Data System (ADS)

    Seisyan, R. P.

    2016-05-01

    Optical properties of semiconductor crystals in the presence of a high magnetic field have been considered. The field turn-on gives rise to oscillations of the optical-absorption edge or, more specifically, the formation of a complex absorption spectrum with a periodic structure, referred to as the spectrum of "diamagnetic excitons." Such spectra appear a source of the most accurate knowledge about the band structure of semiconductors. Moreover, these spectra can be used for simulating the low-dimensional state in semiconductors and possible interpretation of the emission spectra of neutron stars. The proposed analytical review is based on extensive experimental and theoretical data contained mostly in cited original works of the author with colleagues.

  19. Predicting Intrinsic Motivation

    ERIC Educational Resources Information Center

    Martens, Rob; Kirschner, Paul A.

    2004-01-01

    Intrinsic motivation can be predicted from participants' perceptions of the social environment and the task environment (Ryan & Deci, 2000)in terms of control, relatedness and competence. To determine the degree of independence of these factors 251 students in higher vocational education (physiotherapy and hotel management) indicated the extent to…

  20. [Intrinsic cardiac ganglia].

    PubMed

    Birand, Ahmet

    2008-12-01

    Heart has been considered as the source and the seat of emotions, passion and love. But from the dawn of XIXth century, scientists have emphasized that the heart, though life depends on its ceaseless activity, is merely a electromechanical pump, pumping oxygenated blood. Nowadays, we all know that heart pumps blood commensurate with the needs of the body and this unending toil, and its regulation depends on the intrinsic properties of the myocardium, Frank-Starling Law and neurohumoral contribution. It has been understood, though not clearly enough, that these time-tensions may cause structural or functional cardiac impairments and arrhythmias are related to the autonomic nervous system. Less well known and less taken in account in daily cardiology practice is the fact that heart has an intrinsic cardiac nervous system, or "heart brain" consisting of complex ganglia, intrinsic cardiac ganglia containing afferent (receiving), local circuit (interneurons) and efferent (transmitting) sympathetic and parasympathetic neurons. This review enlightens structural and functional aspects of intrinsic cardiac ganglia as the very first step in the regulation of cardiac function. This issue is important for targets of pharmacological treatment and techniques of cardiac surgery interventions as repair of septal defects, valvular interventions and congenital corrections.