Science.gov

Sample records for metal-dielectric-semiconductor germanium nanowires

  1. Electrodeposited germanium nanowires.

    PubMed

    Mahenderkar, Naveen K; Liu, Ying-Chau; Koza, Jakub A; Switzer, Jay A

    2014-09-23

    Germanium (Ge) is a group IV semiconductor with superior electronic properties compared with silicon, such as larger carrier mobilities and smaller effective masses. It is also a candidate anode material for lithium-ion batteries. Here, a simple, one-step method is introduced to electrodeposit dense arrays of Ge nanowires onto indium tin oxide (ITO) substrates from aqueous solution. The electrochemical reduction of ITO produces In nanoparticles that act as a reduction site for aqueous Ge(IV) species, and as a solvent for the crystallization of Ge nanowires. Nanowires deposited at 95 °C have an average diameter of 100 nm, whereas those deposited at room temperature have an average diameter of 35 nm. Both optical absorption and Raman spectroscopy suggest that the electrodeposited Ge is degenerate. The material has an indirect bandgap of 0.90-0.92 eV, compared with a value of 0.67 eV for bulk, intrinsic Ge. The blue shift is attributed to the Moss-Burstein effect, because the material is a p-type degenerate semiconductor. On the basis of the magnitude of the blue shift, the hole concentration is estimated to be 8 × 10(19) cm(-3). This corresponds to an In impurity concentration of about 0.2 atom %. The resistivity of the wires is estimated to be 4 × 10(-5) Ω·cm. The high conductivity of the wires should make them ideal for lithium-ion battery applications.

  2. Surface Passivation of Germanium Nanowires

    SciTech Connect

    Adhikari, Hemant; Sun, Shiyu; Pianetta, Piero; Chidsey, Chirstopher E.D.; McIntyre, Paul C.; /SLAC, SSRL

    2005-05-13

    The surface of single crystal, cold-wall CVD-grown germanium nanowires was studied by synchrotron radiation photoemission spectroscopy (SR-PES) and also by conventional XPS. The as-grown germanium nanowires seem to be hydrogen terminated. Exposure to laboratory atmosphere leads to germanium oxide growth with oxidation states of Ge{sup 1+}, Ge{sup 2+}, Ge{sup 3+}, while exposure to UV light leads to a predominance of the Ge{sup 4+} oxidation state. Most of the surface oxide could be removed readily by aqueous HF treatment which putatively leaves the nanowire surface hydrogen terminated with limited stability in air. Alternatively, chlorine termination could be achieved by aq. HCl treatment of the native oxide-coated nanowires. Chlorine termination was found to be relatively more stable than the HF-last hydrogen termination.

  3. A review on germanium nanowires.

    PubMed

    Pei, Li Z; Cai, Zheng Y

    2012-01-01

    Ge nanowires exhibit wide application potential in the fields of nanoscale devices due to their excellently optical and electrical properties. This article reviews the recent progress and patents of Ge nanowires. The recent progress and patents for the synthesis of Ge nanowires using chemical vapor deposition, laser ablation, thermal evaporation, template method and supercritical fluid-liquid-solid method are demonstrated. Amorphous germanium oxide layer and defects existing in Ge nanowires result in poor Ohmic contact between Ge nanowires and electrodes. Therefore, Ge nanowires should be passivated in order to deposit connecting electrodes before applied in nanoelectronic devices. The experimental progress and patents on the application of Ge nanowires as field effect transistors, lithium batteries, photoresistors, memory cell and fluid sensors are discussed. Finally, the future development of Ge nanowires for the synthesis and practical application is also discussed.

  4. Synthesis of silicon and germanium nanowires.

    SciTech Connect

    Clement, Teresa J.; Hsu, Julia W. P.

    2007-11-01

    The vapor-liquid-solid growth process for synthesis of group-IV semiconducting nanowires using silane, germane, disilane and digermane precursor gases has been investigated. The nanowire growth process combines in situ gold seed formation by vapor deposition on atomically clean silicon (111) surfaces, in situ growth from the gaseous precursor(s), and real-time monitoring of nanowire growth as a function of temperature and pressure by a novel optical reflectometry technique. A significant dependence on precursor pressure and growth temperature for the synthesis of silicon and germanium nanowires is observed, depending on the stability of the specific precursor used. Also, the presence of a nucleation time for the onset of nanowire growth has been found using our new in situ optical reflectometry technique.

  5. Smooth germanium nanowires prepared by a hydrothermal deposition process

    SciTech Connect

    Pei, L.Z.; Zhao, H.S.; Tan, W.; Yu, H.Y.; Chen, Y.W.; Fan, C.G.; Zhang, Qian-Feng

    2009-11-15

    Smooth germanium nanowires were prepared using Ge and GeO{sub 2} as the starting materials and Cu sheet as the substrate by a simple hydrothermal deposition process. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations show that the germanium nanowires are smooth and straight with uniform diameter of about 150 nm in average and tens of micrometers in length. X-ray diffraction (XRD) and Raman spectrum of the germanium nanowires display that the germanium nanowires are mainly composed of cubic diamond phase. PL spectrum shows a strong blue light emission at 441 nm. The growth mechanism is also discussed.

  6. Uniform phosphorus doping of untapered germanium nanowires.

    PubMed

    Guilloy, K; Pauc, N; Gentile, P; Robin, E; Calvo, V

    2016-12-02

    One of the major challenges in the growth of vapor-liquid-solid (VLS) nanowires is the control of dopant incorporation in the structures. In this work, we study the n-type doping and morphology of nanowires grown by chemical vapor deposition when HCl is introduced. We obtain fully untapered nanowires with a growth temperature up to 410 °C and measure their resistivity using the 4-probe technique to be 2.0 mΩ cm. We perform energy dispersive x-ray measurements showing a concentration of dopants in the (5-7) × 10(18) cm(-3) range, being radially and axially uniform. The combination of these two measurements shows that the mobility is the same as for bulk germanium, demonstrating that the VLS mechanism has no detrimental effect for the electron transport in these nanowires.

  7. Promoting Cell Proliferation Using Water Dispersible Germanium Nanowires

    PubMed Central

    Bezuidenhout, Michael; Liu, Pai; Singh, Shalini; Kiely, Maeve

    2014-01-01

    Group IV Nanowires have strong potential for several biomedical applications. However, to date their use remains limited because many are synthesised using heavy metal seeds and functionalised using organic ligands to make the materials water dispersible. This can result in unpredicted toxic side effects for mammalian cells cultured on the wires. Here, we describe an approach to make seedless and ligand free Germanium nanowires water dispersible using glutamic acid, a natural occurring amino acid that alleviates the environmental and health hazards associated with traditional functionalisation materials. We analysed the treated material extensively using Transmission electron microscopy (TEM), High resolution-TEM, and scanning electron microscope (SEM). Using a series of state of the art biochemical and morphological assays, together with a series of complimentary and synergistic cellular and molecular approaches, we show that the water dispersible germanium nanowires are non-toxic and are biocompatible. We monitored the behaviour of the cells growing on the treated germanium nanowires using a real time impedance based platform (xCELLigence) which revealed that the treated germanium nanowires promote cell adhesion and cell proliferation which we believe is as a result of the presence of an etched surface giving rise to a collagen like structure and an oxide layer. Furthermore this study is the first to evaluate the associated effect of Germanium nanowires on mammalian cells. Our studies highlight the potential use of water dispersible Germanium Nanowires in biological platforms that encourage anchorage-dependent cell growth. PMID:25237816

  8. Promoting cell proliferation using water dispersible germanium nanowires.

    PubMed

    Bezuidenhout, Michael; Liu, Pai; Singh, Shalini; Kiely, Maeve; Ryan, Kevin M; Kiely, Patrick A

    2014-01-01

    Group IV Nanowires have strong potential for several biomedical applications. However, to date their use remains limited because many are synthesised using heavy metal seeds and functionalised using organic ligands to make the materials water dispersible. This can result in unpredicted toxic side effects for mammalian cells cultured on the wires. Here, we describe an approach to make seedless and ligand free Germanium nanowires water dispersible using glutamic acid, a natural occurring amino acid that alleviates the environmental and health hazards associated with traditional functionalisation materials. We analysed the treated material extensively using Transmission electron microscopy (TEM), High resolution-TEM, and scanning electron microscope (SEM). Using a series of state of the art biochemical and morphological assays, together with a series of complimentary and synergistic cellular and molecular approaches, we show that the water dispersible germanium nanowires are non-toxic and are biocompatible. We monitored the behaviour of the cells growing on the treated germanium nanowires using a real time impedance based platform (xCELLigence) which revealed that the treated germanium nanowires promote cell adhesion and cell proliferation which we believe is as a result of the presence of an etched surface giving rise to a collagen like structure and an oxide layer. Furthermore this study is the first to evaluate the associated effect of Germanium nanowires on mammalian cells. Our studies highlight the potential use of water dispersible Germanium Nanowires in biological platforms that encourage anchorage-dependent cell growth.

  9. Doping of germanium nanowires grown in presence of PH3

    NASA Astrophysics Data System (ADS)

    Tutuc, E.; Chu, J. O.; Ott, J. A.; Guha, S.

    2006-12-01

    The authors study the Au-catalyzed chemical vapor growth of germanium (Ge) nanowires in the presence of phosphine (PH3), used as a dopant precursor. The device characteristics of the ensuing nanowire field effect transistors (FETs) indicate n-type, highly doped nanowires. Using a combination of different nanowire growth sequences and their FET characteristics, the authors determine that phosphorus incorporates predominately via the conformal growth, which accompanies the acicular, nanowire growth. As such, the Ge nanowires grown in the presence of PH3 contain a phosphorus doped shell and an undoped core. The authors determine the doping level in the shell to be ≃(1-4)×1019cm-3.

  10. Solution-Processed Germanium Nanowire-Positioned Schottky Solar Cells

    DTIC Science & Technology

    2011-04-01

    available soon. Solution-processed germanium nanowire-positioned Schottky solar cells Nanoscale Research Letters 2011, 6:287 doi:10.1186/1556-276X-6-287 Ju...DATES COVERED 00-00-2011 to 00-00-2011 4. TITLE AND SUBTITLE Solution-processed germanium nanowire-positioned Schottky solar cells 5a. CONTRACT...nanowire (GeNW)-positioned Schottky solar cell was fabricated by a solution process. A GeNW-containing solution was spread out onto asymmetric metal

  11. 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.

  12. Developing Germanium on Nothing (GON) Nanowire Arrays

    NASA Astrophysics Data System (ADS)

    Thomas, Paul M.

    Advanced crystal growth techniques enable novel devices and circuit designs to further scale and integrate heterogeneous structures for CMOS, MEMS/NEMS, and optoelectronic applications. In particular, nanowires (NW) are among the promising structures derived from these developments. Research has demonstrated the utility of NWs as a channel material for gate-all-around transistors, high sensitivity biological/chemical sensors, photodetectors, as well as a whole spectrum of LEDs and lasers. However, NW based devices are not without their fabrication challenges. Relatively simple structures for CMOS or MEMS/NEMS processes are difficult to reproduce when many NW based devices rely on a dropcast process. This thesis demonstrates a method for producing Germanium on Nothing (GON) NW arrays on a Si substrate that forgoes dropcasting and, instead, creates NWs via selective material removal methods commonly utilized by industry. GON NW arrays are formed through the sequential use of E-beam lithography, selective wet chemical etching, and reactive ion etching. Global oxide thinning in BOE leaves a thin masking layer that protects the underlying Si, preventing etching in a TMAH solution. GON regions are defined by E-beam lithography and are subject to a RIE which creates release points in the remaining SiO 2. Unmasked Si is then etched by a TMAH solution, undercutting the Ge lines, leaving an array of suspended Ge wires. NW dimensions are reached by thinning the Ge wire diameter with a H2O2 solution. NWs with ˜50 nm diameters and ˜ 200 nm lengths, as well as 10 microm by 10 microm membranes of Ge/SiO2, have been demonstrated in this thesis.

  13. Germanium nanowire growth controlled by surface diffusion effects

    SciTech Connect

    Schmidtbauer, Jan; Bansen, Roman; Heimburger, Robert; Teubner, Thomas; Boeck, Torsten; Fornari, Roberto

    2012-07-23

    Germanium nanowires (NWs) were grown onto Ge(111) substrates by the vapor-liquid-solid process using gold droplets. The growth was carried out in a molecular beam epitaxy chamber at substrate temperatures between 370 Degree-Sign C and 510 Degree-Sign C. The resulting nanowire growth rate turns out to be highly dependent on the substrate temperature exhibiting the maximum at T = 430 Degree-Sign C. The temperature dependence of growth rate can be attributed to surface diffusion both along the substrate and nanowire sidewalls. Analyzing the diffusive material transport yields a diffusion length of 126 nm at a substrate temperature of 430 Degree-Sign C.

  14. Impacts of atomistic coating on thermal conductivity of germanium nanowires.

    PubMed

    Chen, Jie; Zhang, Gang; Li, Baowen

    2012-06-13

    By using nonequilibrium molecular dynamics simulations, we demonstrated that thermal conductivity of germanium nanowires can be reduced more than 25% at room temperature by atomistic coating. There is a critical coating thickness beyond which thermal conductivity of the coated nanowire is larger than that of the host nanowire. The diameter-dependent critical coating thickness and minimum thermal conductivity are explored. Moreover, we found that interface roughness can induce further reduction of thermal conductivity in coated nanowires. From the vibrational eigenmode analysis, it is found that coating induces localization for low-frequency phonons, while interface roughness localizes the high-frequency phonons. Our results provide an available approach to tune thermal conductivity of nanowires by atomic layer coating.

  15. Investigation of factors affecting electrical contacts on single germanium nanowires

    NASA Astrophysics Data System (ADS)

    Sett, Shaili; Das, K.; Raychaudhuri, A. K.

    2017-03-01

    We report an experimental investigation of the quality of electrical contacts made on single Germanium nanowires (grown using Au catalyst from vapor) using Cr/Au contact pads. The nanowires are single crystalline and have a thin layer of oxide on them. We find that a low specific contact resistivity of 10-6 Ω cm2 can be obtained in nanowires with low resistance and the contact resistance enhances almost linearly with the nanowire resistivity. The metal semiconductor junction shows an ideality factor close to unity. A low barrier height of 0.15 eV can be obtained in nanowires of lower resistivities which increase to nearly 0.3 eV for nanowires of higher resistivity. The experiments were carried down to 10 K, and junction characteristics as a function of temperature were evaluated. The specific contact resistance increases on cooling but the barrier shows suppression as the nanowire is cooled, along with an enhancement of the ideality factor. We analyze the temperature dependence of these parameters using a model that assumes a Gaussian distribution of barrier heights in the contact region. The temperature dependence predicted by the model was observed, and the relevant parameters were obtained from the data.

  16. Electrodeposition at room temperature of amorphous silicon and germanium nanowires in ionic liquid

    NASA Astrophysics Data System (ADS)

    Martineau, F.; Namur, K.; Mallet, J.; Delavoie, F.; Endres, F.; Troyon, M.; Molinari, M.

    2009-11-01

    The electrodeposition at room temperature of silicon and germanium nanowires from the air- and water-stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (P1,4) containing SiCl4 as Si source or GeCl4 as Ge source is investigated by cyclic voltammetry. By using nanoporous polycarbonate membranes as templates, it is possible to reproducibly grow pure silicon and germanium nanowires of different diameters. The nanowires are composed of pure amorphous silicon or germanium. The nanowires have homogeneous cylindrical shape with a roughness of a few nanometres on the wire surfaces. The nanowires' diameters and lengths well match with the initial membrane characteristics. Preliminary photoluminescence experiments exhibit strong emission in the near infrared for the amorphous silicon nanowires.

  17. In situ monitoring of Joule heating effects in germanium nanowires by μ-Raman spectroscopy.

    PubMed

    Lugstein, Alois; Mijić, Mario; Burchhart, Thomas; Zeiner, Clemens; Langegger, Rupert; Schneider, Michael; Schmid, Ulrich; Bertagnolli, Emmerich

    2013-02-15

    We explored a noninvasive optical method to determine the Joule heating of individual germanium nanowires. Using confocal μ-Raman spectroscopy, variations in the optical phonon frequency, in detail the downshifting of the first-order Stokes Raman band, are correlated to the temperature increase of vapor-liquid-solid grown germanium nanowires under an applied electrical bias. The germanium nanowires were found to handle high threshold current densities of more than 10(6) A cm(-2) before sustaining immediate deterioration. Failure of single crystalline germanium nanowires was directly observed when the applied electric field reached the breakdown point of 1.25 × 10(5) V cm(-1).

  18. Young’s modulus of [111] germanium nanowires

    SciTech Connect

    Maksud, M.; Yoo, J.; Harris, C. T.; Palapati, N. K. R.; Subramanian, A.

    2015-11-02

    Our paper reports a diameter-independent Young’s modulus of 91.9 ± 8.2 GPa for [111] Germanium nanowires (Ge NWs). When the surface oxide layer is accounted for using a core-shell NW approximation, the YM of the Ge core approaches a near theoretical value of 147.6 ± 23.4 GPa. The ultimate strength of a NW device was measured at 10.9 GPa, which represents a very high experimental-to-theoretical strength ratio of ~75%. Furthermore, with increasing interest in this material system as a high-capacity lithium-ion battery anode, the presented data provide inputs that are essential in predicting its lithiation-induced stress fields and fracture behavior.

  19. Young’s modulus of [111] germanium nanowires

    SciTech Connect

    Maksud, M.; Palapati, N. K. R.; Subramanian, A.; Yoo, J.; Harris, C. T.

    2015-11-01

    This paper reports a diameter-independent Young’s modulus of 91.9 ± 8.2 GPa for [111] Germanium nanowires (Ge NWs). When the surface oxide layer is accounted for using a core-shell NW approximation, the YM of the Ge core approaches a near theoretical value of 147.6 ± 23.4 GPa. The ultimate strength of a NW device was measured at 10.9 GPa, which represents a very high experimental-to-theoretical strength ratio of ∼75%. With increasing interest in this material system as a high-capacity lithium-ion battery anode, the presented data provide inputs that are essential in predicting its lithiation-induced stress fields and fracture behavior.

  20. Young’s modulus of [111] germanium nanowires

    DOE PAGES

    Maksud, M.; Yoo, J.; Harris, C. T.; ...

    2015-11-02

    Our paper reports a diameter-independent Young’s modulus of 91.9 ± 8.2 GPa for [111] Germanium nanowires (Ge NWs). When the surface oxide layer is accounted for using a core-shell NW approximation, the YM of the Ge core approaches a near theoretical value of 147.6 ± 23.4 GPa. The ultimate strength of a NW device was measured at 10.9 GPa, which represents a very high experimental-to-theoretical strength ratio of ~75%. Furthermore, with increasing interest in this material system as a high-capacity lithium-ion battery anode, the presented data provide inputs that are essential in predicting its lithiation-induced stress fields and fracture behavior.

  1. Schottky contacts in germanium nanowire network devices synthesized from nickel seeds

    NASA Astrophysics Data System (ADS)

    Gouveia, R. C.; Rodrigues, A. D.; Leite, E. R.; Chiquito, A. J.

    2016-10-01

    This paper presents reliable process to the synthesis of germanium nanowires by the vapor-liquid-solid method using nickel as an alternative catalyst to gold, the most commonly used metal, without toxic gas precursors. The structural study showed single-crystalline germanium nanowires with diamond structure, lengths of tens of microns and diameters smaller than 40 nm. The reduced dimensions of the nanowires led to phonons localization effect, with correlation lengths of the same order of the nanowires diameters. Additionally, the analysis of electronic properties of metal-nanowire-metal devices indicated the presence of Schottky barriers, whose values depend linearly on temperature. This linear dependence was assigned to the tunneling process through an insulator layer (mostly GeOx) at the metal-semiconductor interface. These results point to the existence of another channel for electrons transference from metal to semiconductor being very significant to electronic devices fabrication.

  2. Diameter-dependent dopant location in silicon and germanium nanowires

    PubMed Central

    Xie, Ping; Hu, Yongjie; Fang, Ying; Huang, Jinlin; Lieber, Charles M.

    2009-01-01

    We report studies defining the diameter-dependent location of electrically active dopants in silicon (Si) and germanium (Ge) nanowires (NWs) prepared by nanocluster catalyzed vapor-liquid-solid (VLS) growth without measurable competing homogeneous decomposition and surface overcoating. The location of active dopants was assessed from electrical transport measurements before and after removal of controlled thicknesses of material from NW surfaces by low-temperature chemical oxidation and etching. These measurements show a well-defined transition from bulk-like to surface doping as the diameter is decreased <22–25 nm for n- and p-type Si NWs, although the surface dopant concentration is also enriched in the larger diameter Si NWs. Similar diameter-dependent results were also observed for n-type Ge NWs, suggesting that surface dopant segregation may be general for small diameter NWs synthesized by the VLS approach. Natural surface doping of small diameter semiconductor NWs is distinct from many top-down fabricated NWs, explains enhanced transport properties of these NWs and could yield robust properties in ultrasmall devices often dominated by random dopant fluctuations. PMID:19706402

  3. Bending-induced symmetry breaking of lithiation in germanium nanowires.

    PubMed

    Gu, Meng; Yang, Hui; Perea, Daniel E; Zhang, Ji-Guang; Zhang, Sulin; Wang, Chong-Min

    2014-08-13

    From signal transduction of living cells to oxidation and corrosion of metals, mechanical stress intimately couples with chemical reactions, regulating these biological and physiochemical processes. The coupled effect is particularly evident in the electrochemical lithiation/delithiation cycling of high-capacity electrodes, such as silicon (Si), where on the one hand lithiation-generated stress mediates lithiation kinetics and on the other the electrochemical reaction rate regulates stress generation and mechanical failure of the electrodes. Here we report for the first time the evidence on the controlled lithiation in germanium nanowires (GeNWs) through external bending. Contrary to the symmetric core-shell lithiation in free-standing GeNWs, we show bending the GeNWs breaks the lithiation symmetry, speeding up lithaition at the tensile side while slowing down at the compressive side of the GeNWs. The bending-induced symmetry breaking of lithiation in GeNWs is further corroborated by chemomechanical modeling. In the light of the coupled effect between lithiation kinetics and mechanical stress in the electrochemical cycling, our findings shed light on strain/stress engineering of durable high-rate electrodes and energy harvesting through mechanical motion.

  4. Bending-induced Symmetry Breaking of Lithiation in Germanium Nanowires

    SciTech Connect

    Gu, Meng; Yang, Hui; Perea, Daniel E.; Zhang, Jiguang; Zhang, Sulin; Wang, Chong M.

    2014-08-01

    From signal transduction of living cells to oxidation and corrosion of metals, mechanical stress intimately couples with chemical reactions, regulating these biological and physiochemical processes. The coupled effect is particularly evident in electrochemical lithiation/delithiation cycling of high-capacity electrodes, such as silicon (Si), where on one hand lithiation-generated stress mediates lithiation kinetics, and on the other electrochemical reaction rate regulates stress generation and mechanical failure of the electrodes. Here we report for the first time the evidence on the controlled lithiation in germanium nanowires (GeNWs) through external bending. Contrary to the symmetric core-shell lithiation in free-standing GeNWs, we show bending GeNWs breaks the lithiation symmetry, speeding up lithaition at the tensile side while slowing down at the compressive side of the GeNWs. The bending-induced symmetry breaking of lithiation in GeNWs is further corroborated by chemomechanical modeling. In the light of the coupled effect between lithiation kinetics and mechanical stress in the electrochemical cycling, our findings shed light on strain/stress engineering of durable high-rate electrodes and energy harvesting through mechanical motion.

  5. Stress induced half-metallicity in surface defected germanium nanowires.

    PubMed

    Sk, Mahasin Alam; Ng, Man-Fai; Yang, Shuo-Wang; Lim, Kok Hwa

    2012-01-21

    Germanium nanowires (GeNWs) with single, double, quadruple and octuple surface dangling bonds (SDBs) are investigated using density-functional-theory calculations. We show that single SDB defected GeNWs remain semiconducting as their non-defected form while double or multiple SDB defects result in either semiconducting or metallic GeNWs, depending on the defect's locations on the surface. More importantly, we show that the electronic properties of surface defected GeNWs can also be fine-tuned by applying tensile and compressive strains. Upon the right loading, the surface defected GeNWs become half-metallic. In addition, we determine that the surface defected GeNWs can be classified into three classes: (1) GeNWs with zero magnetic moment, which are either metallic or semiconducting; (2) GeNWs with net magnetic moments equal to the number of SDBs, which are semiconducting with distinct spin-up and spin-down configurations; and (3) GeNWs with net magnetic moments significantly lower than the number of SDBs. We also find that only the defected GeNWs that fall under (3) are potentially half-metallic. Our results predict that half-metallic GeNWs can be obtained via engineering of the surface defects and the structures without the presence of impurity dopants.

  6. Silicon and germanium nanowire electronics: physics of conventional and unconventional transistors.

    PubMed

    Weber, Walter M; Mikolajick, Thomas

    2017-06-01

    Research in the field of electronics of 1D group-IV semiconductor structures has attracted increasing attention over the past 15 years. The exceptional combination of the unique 1D electronic transport properties with the mature material know-how of highly integrated silicon and germanium technology holds the promise of enhancing state-of-the-art electronics. In addition of providing conduction channels that can bring conventional field effect transistors to the uttermost scaling limits, the physics of 1D group IV nanowires endows new device principles. Such unconventional silicon and germanium nanowire devices are contenders for beyond complementary metal oxide semiconductor (CMOS) computing by virtue of their distinct switching behavior and higher expressive value. This review conveys to the reader a systematic recapitulation and analysis of the physics of silicon and germanium nanowires and the most relevant CMOS and CMOS-like devices built from silicon and germanium nanowires, including inversion mode, junctionless, steep-slope, quantum well and reconfigurable transistors.

  7. Silicon and germanium nanowire electronics: physics of conventional and unconventional transistors

    NASA Astrophysics Data System (ADS)

    Weber, Walter M.; Mikolajick, Thomas

    2017-06-01

    Research in the field of electronics of 1D group-IV semiconductor structures has attracted increasing attention over the past 15 years. The exceptional combination of the unique 1D electronic transport properties with the mature material know-how of highly integrated silicon and germanium technology holds the promise of enhancing state-of-the-art electronics. In addition of providing conduction channels that can bring conventional field effect transistors to the uttermost scaling limits, the physics of 1D group IV nanowires endows new device principles. Such unconventional silicon and germanium nanowire devices are contenders for beyond complementary metal oxide semiconductor (CMOS) computing by virtue of their distinct switching behavior and higher expressive value. This review conveys to the reader a systematic recapitulation and analysis of the physics of silicon and germanium nanowires and the most relevant CMOS and CMOS-like devices built from silicon and germanium nanowires, including inversion mode, junctionless, steep-slope, quantum well and reconfigurable transistors.

  8. Operando X-ray scattering and spectroscopic analysis of germanium nanowire anodes in lithium ion batteries.

    PubMed

    Silberstein, Katharine E; Lowe, Michael A; Richards, Benjamin; Gao, Jie; Hanrath, Tobias; Abruña, Héctor D

    2015-02-17

    X-ray diffraction (XRD) and Fourier transform extended X-ray absorption fine structure (EXAFS) analysis of X-ray absorption spectroscopy (XAS) measurements have been employed to determine structural and bonding changes, as a function of the lithium content/state of charge, of germanium nanowires used as the active anode material within lithium ion batteries (LIBs). Our data, collected throughout the course of battery cycling (operando), indicate that lithium incorporation within the nanostructured germanium occurs heterogeneously, preferentially into amorphous regions over crystalline domains. Maintenance of the molecular structural integrity within the germanium nanowire is dependent on the depth of discharge. Discharging to a shallower cutoff voltage preserves partial crystallinity for several cycles.

  9. Structural and optical properties of axial silicon-germanium nanowire heterojunctions

    SciTech Connect

    Wang, X.; Tsybeskov, L.; Kamins, T. I.; Wu, X.; Lockwood, D. J.

    2015-12-21

    Detailed studies of the structural and optical properties of axial silicon-germanium nanowire heterojunctions show that despite the 4.2% lattice mismatch between Si and Ge they can be grown without a significant density of structural defects. The lattice mismatch induced strain is partially relieved due to spontaneous SiGe intermixing at the heterointerface during growth and lateral expansion of the Ge segment of the nanowire. The mismatch in Ge and Si coefficients of thermal expansion and low thermal conductivity of Si/Ge nanowire heterojunctions are proposed to be responsible for the thermally induced stress detected under intense laser radiation in photoluminescence and Raman scattering measurements.

  10. Size Dependent Pore Formation in Germanium Nanowires Undergoing Reversible Delithiation Observed by In Situ TEM

    SciTech Connect

    Lu, Xiaotang; He, Yang; Mao, Scott X.; Wang, Chong-min; Korgel, Brian A.

    2016-12-22

    Germanium (Ge) nanowires coated with an amorphous silicon (Si) shell undergoing lithiation and delithiation were studied using in situ transmission electron microscopy (TEM). Delithiation creates pores in nanowires with diameters larger than ~25 nm, but not in smaller diameter nanowires. The formation of pores in Ge nanowires undergoing delithiation has been observed before in in situ TEM experiments, but there has been no indication that a critical diameter exists below which pores do not form. Pore formation occurs as a result of fast lithium diffusion compared to vacancy migration. We propose that a short diffusion path for vacancies to the nanowire surface plays a role in limiting pore formation even when lithium diffusion is fast.

  11. Germanium

    SciTech Connect

    Major-Sosias, M.A.

    1996-01-01

    Germanium is an important semiconductor material, or metalloid which, by definition, is a material whose electrical properties are halfway between those of metallic conductors and electrical insulators. This paper describes the properties, sources, and market for germanium.

  12. Modifying the band gap and optical properties of Germanium nanowires by surface termination

    NASA Astrophysics Data System (ADS)

    Legesse, Merid; Fagas, Giorgos; Nolan, Michael

    2017-02-01

    Semiconductor nanowires, based on silicon (Si) or germanium (Ge) are leading candidates for many ICT applications, including next generation transistors, optoelectronics, gas and biosensing and photovoltaics. Key to these applications is the possibility to tune the band gap by changing the diameter of the nanowire. Ge nanowires of different diameter have been studied with H termination, but, using ideas from chemistry, changing the surface terminating group can be used to modulate the band gap. In this paper we apply the generalised gradient approximation of density functional theory (GGA-DFT) and hybrid DFT to study the effect of diameter and surface termination using -H, -NH2 and -OH groups on the band gap of (001), (110) and (111) oriented germanium nanowires. We show that the surface terminating group allows both the magnitude and the nature of the band gap to be changed. We further show that the absorption edge shifts to longer wavelength with the -NH2 and -OH terminations compared to the -H termination and we trace the origin of this effect to valence band modifications upon modifying the nanowire with -NH2 or -OH. These results show that it is possible to tune the band gap of small diameter Ge nanowires over a range of ca. 1.1 eV by simple surface chemistry.

  13. Solution synthesis of lead seeded germanium nanowires and branched nanowire networks and their application as Li-ion battery anodes

    NASA Astrophysics Data System (ADS)

    Flynn, Grace; Palaniappan, Kumaranand; Sheehan, Martin; Kennedy, Tadhg; Ryan, Kevin M.

    2017-06-01

    Herein, we report the high density growth of lead seeded germanium nanowires (NWs) and their development into branched nanowire networks suitable for application as lithium ion battery anodes. The synthesis of the NWs from lead seeds occurs simultaneously in both the liquid zone (solution-liquid-solid (SLS) growth) and solvent rich vapor zone (vapor-liquid-solid (VLS) growth) of a high boiling point solvent growth system. The reaction is sufficiently versatile to allow for the growth of NWs directly from either an evaporated catalyst layer or from pre-defined nanoparticle seeds and can be extended to allowing extensive branched nanowire formation in a secondary reaction where these seeds are coated onto existing wires. The NWs are characterized using TEM, SEM, XRD and DF-STEM. Electrochemical analysis was carried out on both the single crystal Pb-Ge NWs and the branched Pb-Ge NWs to assess their suitability for use as anodes in a Li-ion battery. Differential capacity plots show both the germanium wires and the lead seeds cycle lithium and contribute to the specific capacity that is approximately 900 mAh g-1 for the single crystal wires, rising to approximately 1100 mAh g-1 for the branched nanowire networks.

  14. In operandi observation of dynamic annealing: A case study of boron in germanium nanowire devices

    SciTech Connect

    Koleśnik-Gray, Maria M.; Krstić, Vojislav; Sorger, Christian; Weber, Heiko B.; Biswas, Subhajit; Holmes, Justin D.

    2015-06-08

    We report on the implantation of boron in individual, electrically contacted germanium nanowires with varying diameter and present a technique that monitors the electrical properties of a single device during implantation of ions. This method gives improved access to study the dynamic annealing ability of the nanowire at room temperature promoted by its quasi-one-dimensional confinement. Based on electrical data, we find that the dopant activation efficiency is nontrivially diameter dependent. As the diameter decreases, a transition from a pronounced dynamic-annealing to a radiation-damage dominated regime is observed.

  15. Electric field effect thermoelectric transport in individual silicon and germanium/silicon nanowires

    NASA Astrophysics Data System (ADS)

    Brovman, Yuri M.; Small, Joshua P.; Hu, Yongjie; Fang, Ying; Lieber, Charles M.; Kim, Philip

    2016-06-01

    We have simultaneously measured conductance and thermoelectric power (TEP) of individual silicon and germanium/silicon core/shell nanowires in the field effect transistor device configuration. As the applied gate voltage changes, the TEP shows distinctly different behaviors while the electrical conductance exhibits the turn-off, subthreshold, and saturation regimes, respectively. At room temperature, peak TEP value of ˜300 μ V/K is observed in the subthreshold regime of the Si devices. The temperature dependence of the saturated TEP values is used to estimate the carrier doping of Si nanowires.

  16. Enabling Energy Efficiency and Polarity Control in Germanium Nanowire Transistors by Individually Gated Nanojunctions.

    PubMed

    Trommer, Jens; Heinzig, André; Mühle, Uwe; Löffler, Markus; Winzer, Annett; Jordan, Paul M; Beister, Jürgen; Baldauf, Tim; Geidel, Marion; Adolphi, Barbara; Zschech, Ehrenfried; Mikolajick, Thomas; Weber, Walter M

    2017-02-28

    Germanium is a promising material for future very large scale integration transistors, due to its superior hole mobility. However, germanium-based devices typically suffer from high reverse junction leakage due to the low band-gap energy of 0.66 eV and therefore are characterized by high static power dissipation. In this paper, we experimentally demonstrate a solution to suppress the off-state leakage in germanium nanowire Schottky barrier transistors. Thereto, a device layout with two independent gates is used to induce an additional energy barrier to the channel that blocks the undesired carrier type. In addition, the polarity of the same doping-free device can be dynamically switched between p- and n-type. The shown germanium nanowire approach is able to outperform previous polarity-controllable device concepts on other material systems in terms of threshold voltages and normalized on-currents. The dielectric and Schottky barrier interface properties of the device are analyzed in detail. Finite-element drift-diffusion simulations reveal that both leakage current suppression and polarity control can also be achieved at highly scaled geometries, providing solutions for future energy-efficient systems.

  17. Theoretical Investigation of Biaxially Tensile-Strained Germanium Nanowires

    NASA Astrophysics Data System (ADS)

    Zhu, Zhongyunshen; Song, Yuxin; Chen, Qimiao; Zhang, Zhenpu; Zhang, Liyao; Li, Yaoyao; Wang, Shumin

    2017-07-01

    We theoretically investigate highly tensile-strained Ge nanowires laterally on GaSb. Finite element method has been used to simulate the residual elastic strain in the Ge nanowire. The total energy increment including strain energy, surface energy, and edge energy before and after Ge deposition is calculated in different situations. The result indicates that the Ge nanowire on GaSb is apt to grow along 〈100〉 rather than 〈110〉 in the two situations and prefers to be exposed by {105} facets when deposited a small amount of Ge but to be exposed by {110} when the amount of Ge exceeds a critical value. Furthermore, the conduction band minima in Γ-valley at any position in both situations exhibits lower values than those in L-valley, leading to direct bandgap transition in Ge nanowire. For the valence band, the light hole band maxima at Γ-point is higher than the heavy hole band maxima at any position and even higher than the conduction band minima for the hydrostatic strain more than ˜5.0%, leading to a negative bandgap. In addition, both electron and hole mobility can be enhanced by owing to the decrease of the effective mass under highly tensile strain. The results suggest that biaxially tensile-strained Ge nanowires hold promising properties in device applications.

  18. Solution-grown germanium nanowire anodes for lithium-ion batteries.

    PubMed

    Chockla, Aaron M; Klavetter, Kyle C; Mullins, C Buddie; Korgel, Brian A

    2012-09-26

    Solution-grown germanium (Ge) nanowires were tested as high capacity anodes in lithium ion (Li-ion) batteries. Nanowire films were formulated and cast as slurries with conductive carbon (7:1 Ge:C w/w), PVdF binder and 1.0 M LiPF(6) dissolved in various solvents as electrolyte. The addition of fluorethylene carbonate (FEC) to the electrolyte was critical to achieving stable battery cycling and reversible capacities as high as 1248 mA h g(-1) after 100 cycles, which is close to the theoretical capacity of 1,384 mA h g(-1). Ge nanowire anodes also exhibited high rate capability, with reversible cycling above 600 mA h g(-1) for 1200 cycles at a rate of 1C. The batteries could also be discharged at 10C with a capacity of 900 mA h g(-1) when charged at 1C.

  19. Solution Synthesis of Germanium Nanowires Using a Ge+2 Alkoxide Precursor

    PubMed Central

    Gerung, Henry; Boyle, Timothy J.; Tribby, Louis J.; Bunge, Scott D.; Brinker, C. Jeffrey; Han, Sang M.

    2008-01-01

    A simple solution synthesis of germanium (Ge0) nanowires under mild conditions (<400 °C and 1 atm) was demonstrated using germanium 2,6 dibutylphenoxide Ge(DBP)2 (1) as the precursor where DBP = OC6H3(C(CH3)3)2–2,6. Compound 1, synthesized from Ge(NR2)2 where R = SiMe3 and two equivalents of DBP-H, was characterized as a mononuclear species by single crystal X-ray diffraction. Dissolution of 1 in oleylamine, followed by rapid injection into a 1-octadecene solution heated to 300 °C under an atmosphere of Ar, led to the formation of Ge0 nanowires. The Ge0 nanowires were characterized by transmission electron microscopy (TEM), X-ray diffraction analysis, and Fourier transform infrared spectroscopy. These characterizations revealed that the nanowires are single crystalline in the cubic phase and coated with oleylamine surfactant. We also observed that the nanowire length (0.1 to 10 µm) increases with increasing temperature (285 to 315 °C) and time (5 to 60 min). Two growth mechanisms are proposed based on the TEM images intermittently taken during the growth process as a function of time: (1) self-seeding mechanism where one of two overlapping nanowires serves as a seed, while the other continues to grow as a wire and (2) self-assembly mechanism where an aggregate of small rods (< 50 nm in diameter) recrystallize on the tip of a longer wire, extending its length. PMID:16608360

  20. Thermal Conductivity Suppression in Nanostructured Silicon and Germanium Nanowires

    NASA Astrophysics Data System (ADS)

    Özden, Ayberk; Kandemir, Ali; Ay, Feridun; Perkgöz, Nihan Kosku; Sevik, Cem

    2016-03-01

    The inherent low lattice thermal conductivity (TC) of semiconductor nanowires (s-NW) due to one-dimensional phonon confinement might provide a solution for the long-lasting figure-of-merit problem for highly efficient thermoelectric (TE) applications. Standalone diameter modulation or alloying of s-NW serve as a toolkit for TC control, but realizing the full potential of nanowires requires new atomic-scale designs, growth, characterization, and understanding of the physical mechanisms behind the structure-property (TC) relationship. Before undertaking time-consuming and expensive experimental work, molecular dynamics (MD) simulations serve as an excellent probe to investigate new designs and understand how nanostructures affect thermal transport properties through their capability to capture various phenomena such as phonon boundary scattering, phonon coherence resonance, and phonon backscattering. On the other hand, because different research groups use different structural and MD parameters in their simulations, it is rather difficult to make comparisons between different nanostructures and select appropriate ones for potential TE applications. Therefore, in this work, we systematically investigated pristine, core-shell (C-S), holey (H-N), superlattice (SL), sawtooth (ST), and superlattice sawtooth (SL-ST) nanowires with identical structural parameters. Specifically, we aim to compare the relative TC reduction achieved by these nanostructures with respect to pristine nanowires in order to propose the best structural design with the lowest lattice TC, using Green-Kubo method-based equilibrium molecular dynamics simulations at 300 K. Our results show that the TC can be minimized by changing specific parameters such as the core diameter and monolayer separation for C-S, H-N, and ST structures. In the case of SL structures, the TC is found to be independent of these parameters. However, surface roughness in the form of a ST morphology provides a TC value below 2 W

  1. Geometrical and band-structure effects on phonon-limited hole mobility in rectangular cross-sectional germanium nanowires

    NASA Astrophysics Data System (ADS)

    Tanaka, H.; Mori, S.; Morioka, N.; Suda, J.; Kimoto, T.

    2014-12-01

    We calculated the phonon-limited hole mobility in rectangular cross-sectional [001], [110], [111], and [112]-oriented germanium nanowires, and the hole transport characteristics were investigated. A tight-binding approximation was used for holes, and phonons were described by a valence force field model. Then, scattering probability of holes by phonons was calculated taking account of hole-phonon interaction atomistically, and the linearized Boltzmann's transport equation was solved to calculate the hole mobility at low longitudinal field. The dependence of the hole mobility on nanowire geometry was analyzed in terms of the valence band structure of germanium nanowires, and it was found that the dependence was qualitatively reproduced by considering an average effective mass and the density of states of holes. The calculation revealed that [110] germanium nanowires with large height along the [001] direction show high hole mobility. Germanium nanowires with this geometry are also expected to exhibit high electron mobility in our previous work, and thus they are promising for complementary metal-oxide-semiconductor (CMOS) applications.

  2. Geometrical and band-structure effects on phonon-limited hole mobility in rectangular cross-sectional germanium nanowires

    SciTech Connect

    Tanaka, H. Mori, S.; Morioka, N.; Suda, J.; Kimoto, T.

    2014-12-21

    We calculated the phonon-limited hole mobility in rectangular cross-sectional [001], [110], [111], and [112]-oriented germanium nanowires, and the hole transport characteristics were investigated. A tight-binding approximation was used for holes, and phonons were described by a valence force field model. Then, scattering probability of holes by phonons was calculated taking account of hole-phonon interaction atomistically, and the linearized Boltzmann's transport equation was solved to calculate the hole mobility at low longitudinal field. The dependence of the hole mobility on nanowire geometry was analyzed in terms of the valence band structure of germanium nanowires, and it was found that the dependence was qualitatively reproduced by considering an average effective mass and the density of states of holes. The calculation revealed that [110] germanium nanowires with large height along the [001] direction show high hole mobility. Germanium nanowires with this geometry are also expected to exhibit high electron mobility in our previous work, and thus they are promising for complementary metal-oxide-semiconductor (CMOS) applications.

  3. Electronic states of lithium passivated germanium nanowires: An ab-initio study

    NASA Astrophysics Data System (ADS)

    Trejo, A.; Carvajal, E.; Vázquez-Medina, R.; Cruz-Irisson, M.

    2014-05-01

    A study of the electronic and structural properties of germanium nanowires (GeNWs) was performed using the ab-initio Density Functional Theory within the generalized gradient approximation where electron-ion interactions are described by ultrasoft pseudopotentials. To study the effects of the lithium in the surface of the GeNWs we compare the electronic band structures of Hydrogen passivated GeNWs with those of partial and totally Li passivated GeNWs. The nanowires were constructed in the [001], [111] and [110] directions, using the supercell model to create different wire diameters. The results show that in the case of partial Li passivation there are localized orbitals near the valence band maximum, which would create a p-doped-kind of state. The total Li passivation created metallic states for all the wires.

  4. Electronic states of lithium passivated germanium nanowires: An ab-initio study

    SciTech Connect

    Trejo, A.; Carvajal, E.; Vázquez-Medina, R.; Cruz-Irisson, M.

    2014-05-15

    A study of the electronic and structural properties of germanium nanowires (GeNWs) was performed using the ab-initio Density Functional Theory within the generalized gradient approximation where electron-ion interactions are described by ultrasoft pseudopotentials. To study the effects of the lithium in the surface of the GeNWs we compare the electronic band structures of Hydrogen passivated GeNWs with those of partial and totally Li passivated GeNWs. The nanowires were constructed in the [001], [111] and [110] directions, using the supercell model to create different wire diameters. The results show that in the case of partial Li passivation there are localized orbitals near the valence band maximum, which would create a p-doped-kind of state. The total Li passivation created metallic states for all the wires.

  5. Directed synthesis of germanium oxide nanowires by vapor-liquid-solid oxidation.

    PubMed

    Gunji, M; Thombare, S V; Hu, S; McIntyre, P C

    2012-09-28

    We report on the directed synthesis of germanium oxide (GeO(x)) nanowires (NWs) by locally catalyzed thermal oxidation of aligned arrays of gold catalyst-tipped germanium NWs. During oxygen anneals conducted above the Au-Ge binary eutectic temperature (T > 361 °C), one-dimensional oxidation of as-grown Ge NWs occurs by diffusion of Ge through the Au-Ge catalyst droplet, in the presence of an oxygen containing ambient. Elongated GeO(x) wires grow from the liquid catalyst tip, consuming the adjoining Ge NWs as they grow. The oxide NWs' diameter is dictated by the catalyst diameter and their alignment generally parallels that of the growth direction of the initial Ge NWs. Growth rate comparisons reveal a substantial oxidation rate enhancement in the presence of the Au catalyst. Statistical analysis of GeO(x) nanowire growth by ex situ transmission electron microscopy and scanning electron microscopy suggests a transition from an initial, diameter-dependent kinetic regime, to diameter-independent wire growth. This behavior suggests the existence of an incubation time for GeO(x) NW nucleation at the start of vapor-liquid-solid oxidation.

  6. Significant thermal conductivity reduction of silicon nanowire forests through discrete surface doping of germanium

    SciTech Connect

    Pan, Ying; Hong, Guo; Raja, Shyamprasad N.; Zimmermann, Severin; Poulikakos, Dimos; Tiwari, Manish K.

    2015-03-02

    Silicon nanowires (SiNWs) are promising materials for the realization of highly-efficient and cost effective thermoelectric devices. Reduction of the thermal conductivity of such materials is a necessary and viable pathway to achieve sufficiently high thermoelectric efficiencies, which are inversely proportional to the thermal conductivity. In this article, vertically aligned forests of SiNW and germanium (Ge)-doped SiNW with diameters around 100 nm have been fabricated, and their thermal conductivity has been measured. The results show that discrete surface doping of Ge on SiNW arrays can lead to 23% reduction in thermal conductivity at room temperature compared to uncoated SiNWs. Such reduction can be further enhanced to 44% following a thermal annealing step. By analyzing the binding energy changes of Ge-3d and Si-2p using X-ray photoelectron spectroscopy, we demonstrate that surface doped Ge interacts strongly with Si, enhancing phonon scattering at the Si-Ge interface as has also been shown in non-equilibrium molecular dynamics studies of single nanowires. Overall, our results suggest a viable pathway to improve the energy conversion efficiency of nanowire-forest thermoelectric nanomaterials.

  7. Ionic liquid electrodeposition of strain-released Germanium nanowires as stable anodes for lithium ion batteries.

    PubMed

    Hao, Jian; Yang, Yu; Zhao, Jiupeng; Liu, Xusong; Endres, Frank; Chi, Caixia; Wang, Binsheng; Liu, Xiaoxu; Li, Yao

    2017-06-22

    With the growing demand for portable and wearable electronic devices, it is imperative to develop high performance Li-ion batteries with long life times. Germanium-based materials have recently demonstrated excellent lithium-ion storage ability and are being considered as the most promising candidates for the anodes of lithium-ion batteries. Nevertheless, the practical implementation of Ge-based materials to Li-ion batteries is greatly hampered by the poor cycling ability that resulted from the huge volume variation during lithiation/delithiation processes. Herein, we develop a simple and efficient method for the preparation of Ge nanowires without catalyst nanoparticles and templates, using ionic liquid electrodeposition with subsequent annealing treatment. The Ge nanowire anode shows improved electrochemical performance compared with the Ge dense film anode. A capacity of ∼1200 mA h g(-1) after 200 cycles at 0.1 C is obtained, with an initial coulombic efficiency of 81.3%. In addition, the Ge nanowire anode demonstrates superior rate capability with excellent capacity retention and stability (producing highly stable discharge capacities of about 620 mA h g(-1) at 5 C). The improved electrochemical performance is the result of the enhanced electron migration and electron transport paths of the nanowires, and sufficient elasticity to buffer the volume expansion. This approach encompasses a low energy processing method where all the material is electrochemically active and binder free. The improved cycling stability and rate performance characteristics make these anodes highly attractive for the most demanding lithium-ion applications.

  8. Screening of the quantum-confined Stark effect in AlN/GaN nanowire superlattices by germanium doping

    SciTech Connect

    Hille, P. Müßener, J.; Becker, P.; Teubert, J.; Schörmann, J.; Eickhoff, M.; Mata, M. de la; Rosemann, N.; Chatterjee, S.; Magén, C.; Arbiol, J.

    2014-03-10

    We report on electrostatic screening of polarization-induced internal electric fields in AlN/GaN nanowire heterostructures with germanium-doped GaN nanodiscs embedded between AlN barriers. The incorporation of germanium at concentrations above 10{sup 20} cm{sup –3} shifts the photoluminescence emission energy of GaN nanodiscs to higher energies accompanied by a decrease of the photoluminescence decay time. At the same time, the thickness-dependent shift in emission energy is significantly reduced. In spite of the high donor concentration, a degradation of the photoluminescence properties is not observed.

  9. Screening of the quantum-confined Stark effect in AlN/GaN nanowire superlattices by germanium doping

    NASA Astrophysics Data System (ADS)

    Hille, P.; Müßener, J.; Becker, P.; de la Mata, M.; Rosemann, N.; Magén, C.; Arbiol, J.; Teubert, J.; Chatterjee, S.; Schörmann, J.; Eickhoff, M.

    2014-03-01

    We report on electrostatic screening of polarization-induced internal electric fields in AlN/GaN nanowire heterostructures with germanium-doped GaN nanodiscs embedded between AlN barriers. The incorporation of germanium at concentrations above 1020 cm-3 shifts the photoluminescence emission energy of GaN nanodiscs to higher energies accompanied by a decrease of the photoluminescence decay time. At the same time, the thickness-dependent shift in emission energy is significantly reduced. In spite of the high donor concentration, a degradation of the photoluminescence properties is not observed.

  10. Strongly Enhanced THz Emission caused by Localized Surface Charges in Semiconducting Germanium Nanowires

    PubMed Central

    Lee, Woo-Jung; Ma, Jin Won; Bae, Jung Min; Jeong, Kwang-Sik; Cho, Mann-Ho; Kang, Chul; Wi, Jung-Sub

    2013-01-01

    A principal cause of THz emission in semiconductor nanostructures is deeply involved with geometry, which stimulates the utilization of indirect bandgap semiconductors for THz applications. To date, applications for optoelectronic devices, such as emitters and detectors, using THz radiation have focused only on direct bandgap materials. This paper reports the first observation of strongly enhanced THz emission from Germanium nanowires (Ge NWs). The origin of THz generation from Ge NWs can be interpreted using two terms: high photoexcited electron-hole carriers (Δn) and strong built-in electric field (Eb) at the wire surface based on the relation . The first is related to the extensive surface area needed to trigger an irradiated photon due to high aspect ratio. The second corresponds to the variation of Fermi-level determined by confined surface charges. Moreover, the carrier dynamics of optically excited electrons and holes give rise to phonon emission according to the THz region. PMID:23760467

  11. Germanium doping of self-assembled GaN nanowires grown by plasma-assisted molecular beam epitaxy

    SciTech Connect

    Schörmann, Jörg; Hille, Pascal; Schäfer, Markus; Müßener, Jan; Becker, Pascal; Klar, Peter J.; Hofmann, Detlev M.; Teubert, Jörg; Eickhoff, Martin; Kleine-Boymann, Matthias; Rohnke, Marcus; Mata, Maria de la; Arbiol, Jordi

    2013-09-14

    Germanium doping of GaN nanowires grown by plasma-assisted molecular beam epitaxy on Si(111) substrates is studied. Time of flight secondary ion mass spectrometry measurements reveal a constant Ge-concentration along the growth axis. A linear relationship between the applied Ge-flux and the resulting ensemble Ge-concentration with a maximum content of 3.3×10{sup 20} cm{sup −3} is extracted from energy dispersive X-ray spectroscopy measurements and confirmed by a systematic increase of the conductivity with Ge-concentration in single nanowire measurements. Photoluminescence analysis of nanowire ensembles and single nanowires reveals an exciton localization energy of 9.5 meV at the neutral Ge-donor. A Ge-related emission band at energies above 3.475 eV is found that is assigned to a Burstein-Moss shift of the excitonic emission.

  12. Germanium doping of self-assembled GaN nanowires grown by plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Schörmann, Jörg; Hille, Pascal; Schäfer, Markus; Müßener, Jan; Becker, Pascal; Klar, Peter J.; Kleine-Boymann, Matthias; Rohnke, Marcus; de la Mata, Maria; Arbiol, Jordi; Hofmann, Detlev M.; Teubert, Jörg; Eickhoff, Martin

    2013-09-01

    Germanium doping of GaN nanowires grown by plasma-assisted molecular beam epitaxy on Si(111) substrates is studied. Time of flight secondary ion mass spectrometry measurements reveal a constant Ge-concentration along the growth axis. A linear relationship between the applied Ge-flux and the resulting ensemble Ge-concentration with a maximum content of 3.3×1020 cm-3 is extracted from energy dispersive X-ray spectroscopy measurements and confirmed by a systematic increase of the conductivity with Ge-concentration in single nanowire measurements. Photoluminescence analysis of nanowire ensembles and single nanowires reveals an exciton localization energy of 9.5 meV at the neutral Ge-donor. A Ge-related emission band at energies above 3.475 eV is found that is assigned to a Burstein-Moss shift of the excitonic emission.

  13. Weak localization and the approach to metal-insulator transition in single crystalline germanium nanowires

    NASA Astrophysics Data System (ADS)

    Sett, Shaili; Das, K.; Raychaudhuri, A. K.

    2017-03-01

    We study the low-temperature electronic transport properties of single germanium nanowires (NWs) with diameters down to 45 nm to investigate the weak localization (WL) behavior and approach to metal-insulator transition (MIT) within them. The NWs (single crystalline) we investigate lie on the metallic side of the MIT with an extrapolated zero temperature conductivity {σ0} in the range 23 to 1790 (Ω cm)-1 and show a temperature-dependent conductivity which below 30 K can be described by a 3D WL behavior with Thouless length {{L}\\text{Th}}˜ {{T}-\\frac{p{2}}} and p˜ 4 . From the observed value of {σ0} and the value of the critical carrier concentration n c, it is observed that the approach to MIT can be described by the scaling equation {σ0}˜ {{≤ft(n-{{n}\\text{c}}\\right)}ν} with ν ≈ 0.6 , which is a value expected for an uncompensated system. The investigation establishes a NW size limit for the applicability of 3D scaling theories.

  14. Weak localization and the approach to metal-insulator transition in single crystalline germanium nanowires.

    PubMed

    Sett, Shaili; Das, K; Raychaudhuri, A K

    2017-03-22

    We study the low-temperature electronic transport properties of single germanium nanowires (NWs) with diameters down to 45 nm to investigate the weak localization (WL) behavior and approach to metal-insulator transition (MIT) within them. The NWs (single crystalline) we investigate lie on the metallic side of the MIT with an extrapolated zero temperature conductivity [Formula: see text] in the range 23 to 1790 [Formula: see text] cm)(-1) and show a temperature-dependent conductivity which below 30 K can be described by a 3D WL behavior with Thouless length [Formula: see text] and [Formula: see text]. From the observed value of [Formula: see text] and the value of the critical carrier concentration n c, it is observed that the approach to MIT can be described by the scaling equation [Formula: see text] with [Formula: see text], which is a value expected for an uncompensated system. The investigation establishes a NW size limit for the applicability of 3D scaling theories.

  15. Investigation of sub-10nm cylindrical surrounding gate germanium nanowire field effect transistor with different cross-section areas

    NASA Astrophysics Data System (ADS)

    Bayani, Amir Hossein; Dideban, Daryoosh; Voves, Jan; Moezi, Negin

    2017-05-01

    In this paper, germanium nanowires (GeNWs) with different cross-sectional areas are considered as the channel of a cylindrical surrounding gate field effect transistors (CSG-FETs) and the electronic properties of them are calculated through the density functional method and Slater-Koster (SK) tight binding model. The corresponding transistor parameters are obtained using Non-equilibrium Green's function (NEGF) combined by SK model. We find that SK model predicts the well-nigh same bandgap value compared to meta-GGA-DFT approximation, while GGA-DFT underestimates the value of the bandgap. CSG-GeNW-FETs Transistor figure of merit shows a supreme Ion/Ioff ratio which is equal to 1012 for one of the considered structures with a circular cross-section. The obtained sub-threshold swing (SS) values for the FETs illustrate an increment trend when the supercell size of the germanium nanowire increases whereas the transconductance and ON-current of the FETs decrease when the GeNW supercell size scales down due to the declining of the density of states and electron transmission spectrum.

  16. Inherent control of growth, morphology, and defect formation in germanium nanowires.

    PubMed

    Biswas, Subhajit; Singha, Achintya; Morris, Michael A; Holmes, Justin D

    2012-11-14

    The use of bimetallic alloy seeds for growing one-dimensional nanostructures has recently gained momentum among researchers. The compositional flexibility of alloys provides the opportunity to manipulate the chemical environment, reaction kinetics, and thermodynamic behavior of nanowire growth, in both the eutectic and the subeutectic regimes. This Letter describes for the first time the role of Au(x)Ag(1-x) alloy nanoparticles in defining the growth characteristics and crystal quality of solid-seeded Ge nanowires via a supercritical fluid growth process. The enhanced diffusivity of Ge in the alloy seeds, compared to pure Ag seeds, and slow interparticle diffusion of the alloy nanoparticles allows the realization of high-aspect ratio nanowires with diameters below 10 nm, via a seeded bottom-up approach. Also detailed is the influence the alloyed seeds have on the crystalline features of nanowires synthesized from them, that is, planar defects. The distinctive stacking fault energies, formation enthalpies, and diffusion chemistries of the nanocrystals result in different magnitudes of {111} stacking faults in the seed particles and the subsequent growth of <112>-oriented nanowires with radial twins through a defect transfer mechanism, with the highest number twinned Ge nanowires obtained using Ag(0.75)Au(0.25) growth seeds. Employing alloy nanocrystals for intrinsically dictating the growth behavior and crystallinity of nanowires could open up the possibility of engineering nanowires with tunable structural and physical properties.

  17. Effects of temperature on the ion-induced bending of germanium and silicon nanowires

    NASA Astrophysics Data System (ADS)

    Camara, Osmane; Hanif, Imran; Tunes, Matheus; Harrison, Robert; Greaves, Graeme; Donnelly, Stephen; Hinks, Jonathan

    2017-07-01

    Nanowires can be manipulated using an ion beam via a phenomenon known as ion-induced bending (IIB). While the mechanisms behind IIB are still the subject of debate, accumulation of point defects or amorphisation are often cited as possible driving mechanisms. Previous results in the literature on IIB of Ge and Si nanowires have shown that after irradiation the aligned nanowires are fully amorphous. Experiments were recently reported in which crystalline seeds were preserved in otherwise-amorphous ion-beam-bent Si nanowires which then facilitated solid-phase epitaxial growth (SPEG) during subsequent annealing. However, the ion-induced alignment of the nanowires was lost during the SPEG. In this work, in situ ion irradiations in a transmission electron microscope at 400 °C and 500 °C were performed on Ge and Si nanowires, respectively, to supress amorphisation and the build-up of point defects. Both the Ge and Si nanowires were found to bend during irradiation thus drawing into question the role of mechanisms based on damage accumulation under such conditions. These experiments demonstrate for the first time a simple way of realigning single-crystal Ge and Si nanowires via IIB whilst preserving their crystal structure.

  18. The influence of covering a germanium nanowire with a single wall carbon nanotube on mechanical properties: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Abdollahi, M.; Davoodi, J.

    2017-07-01

    Semiconductor nanowires are potential candidates for applications in quantum information processing, Josephson junctions, and field-effect transistors. Therefore, this study focused on the effects of covering a germanium nanowire (GeNW) with a single wall carbon nanotube (CNT) on the stress-strain diagram, failure points, and Young's modulus using molecular dynamics simulations. To describe the interactions between atoms in the system, we used Tersoff potential. Also, a Nose-Hoover thermostat was employed to control temperature of the system. The stress-strain curves of GeNW and GeNW inside CNT (CNT-GeNW) were obtained at various temperatures, radii, and strain velocities. It was found that coverage of GeNW with CNT led to 2-6 fold improved Young's modulus. It was also determined that a significant part of the Young's modulus in CNT-GeNW is due to the presence of CNT. Moreover, we defined the behavior of Young's modulus of GeNW as well as CNT-GeNW in the [100], [110], and [111] crystallography direction and found that Young's modulus decreased with increasing temperature. In addition, by increasing strain velocity, Young's modulus decreased for GeNW but increased for CNT-GeNW. Finally, we observed that when a GeNW is covered by a CNT, its failure point increased as compared with GeNW.

  19. Synthesis of silicon-germanium axial nanowire heterostructures in a solvent vapor growth system using indium and tin catalysts.

    PubMed

    Mullane, E; Geaney, H; Ryan, K M

    2015-03-14

    Here we describe a relatively facile synthetic protocol for the formation of Si-Ge and Si-Ge-Si1-xGex axial nanowire heterostructures. The wires are grown directly on substrates with an evaporated catalytic layer placed in the vapour zone of a high boiling point solvent with the silicon and germanium precursors injected as liquids sequentially. We show that these heterostructures can be formed using either indium or tin as the catalyst seeds which form in situ during the thermal anneal. There is a direct correlation between growth time and segment length allowing good control over the wire composition. The formation of axial heterostructures of Si-Ge-Si1-xGex nanowires using a triple injection is further discussed with the alloyed Si1-xGex third component formed due to residual Ge precursor and its greater reactivity in comparison to silicon. It was found that the degree of tapering at each hetero-interface varied with both the catalyst type and composition of the NW. The report shows the versatility of the solvent vapour growth system for the formation of complex Si-Ge NW heterostructures.

  20. Effects of surface oxide formation on germanium nanowire band-edge photoluminescence

    SciTech Connect

    Minaye Hashemi, Fatemeh Sadat; Thombare, Shruti; Brongersma, Mark L.; Morral, Anna Fontcuberta i; McIntyre, Paul C.

    2013-06-24

    The effect of intentional surface oxide formation on band-edge photoluminescence (PL) of Ge nanowires was investigated. Thermal oxidation in molecular O{sub 2} was used to produce a surface oxide layer on assemblies of single crystal nanowires grown by the vapor-liquid-solid method. With increasing oxidation of the wires, the band-edge PL associated with the indirect gap transition becomes more intense. X-ray photoelectron spectroscopy confirms the formation of an increasingly GeO{sub 2}-like surface oxide under annealing conditions that enhance the indirect-gap PL, consistent with surface oxide passivation of nonradiative recombination centers initially present on the nanowire surface.

  1. Fabrication and optical properties of (I) Erbium-doped nanowires containing germanium and/or zinc oxide and (II) Porous germanium nanowires

    NASA Astrophysics Data System (ADS)

    Huang, Xuezhen

    Nanomaterials have attracted great attention in the past two decades due to their superior mechanical, thermal, chemical, electrical and optical properties entirely different from bulk materials, which lead to numerous potential applications in nanodevices and nanoelectronics, such as FETs, LEDs, single electron memory devices, spin polarized electronics, quantum computing, sensors, photonic crystals/devices, solar cells etc. Based on the previous work on Er-doped GeNWs, a core-shell nanostructure was built by introducing Zn/ZnO shell onto Er-doped GeNWs. It was found that Zn sources and corresponding surface modification processes (CVD and PVD) have important impact on Er3+ PL and ZnO UV/visible PL due to Zn2GeO4 formation, which were confirmed by HRTEM and XRD measurements. In another work, Ge and Er were used to modify the surface of ZnO tetrapods. Both strong ZnO visible PL and Er3+ PL were observed; considerable enhancement of Er3+ PL was made possible by Ge deposition as a sensitizer layer. The Zn2GeO4 phase observed could either separate from the ZnO phase or mix uniformly with the ZnO phase. As a control system, Er/GeOx/ZnO nanofibers were fabricated by electrospinning of selected sol-gel precursor solutions. These types of nanofibers exhibited strong Er3+ near IR PL at 1.54 mum after annealing to remove the polymer template. XRD spectra indicate that the Er/Ge/Zn mixture likely forms a disordered phase, especially with high Er3+ concentrations, which contributes to the strong Er 3+ PL with the reduction of Er-Er interactions. In another work, the fabrication of F-doped ZnO nanowires was investigated on different substrates with or without carrier gas (Ar). ZnO UV/visible PL spectra indicate that F-doping diminished the intensity of defect light emission at ˜2.4 eV. Furthermore, ZnO/F-doped ZnO core-shell NWs were fabricated either by PVD or CVD processes; the PVD method provides better crystalline shell structures after annealing. The last work describes

  2. Theoretical approach to the phonon modes and specific heat of germanium nanowires

    NASA Astrophysics Data System (ADS)

    Trejo, A.; López-Palacios, L.; Vázquez-Medina, R.; Cruz-Irisson, M.

    2014-11-01

    The phonon modes and specific heat of Ge nanowires were computed using a first principles density functional theory scheme with a generalized gradient approximation and finite-displacement supercell algorithms. The nanowires were modeled in three different directions: [001], [111], and [110], using the supercell technique. All surface dangling bonds were saturated with Hydrogen atoms. The results show that the specific heat of the GeNWs at room temperature increases as the nanowire diameter decreases, regardless the orientation due to the phonon confinement and surface passivation. Also the phonon confinement effects could be observed since the highest optical phonon modes in the Ge vibration interval shifted to a lower frequency compared to their bulk counterparts.

  3. Atomically abrupt silicon-germanium axial heterostructure nanowires synthesized in a solvent vapor growth system.

    PubMed

    Geaney, Hugh; Mullane, Emma; Ramasse, Quentin M; Ryan, Kevin M

    2013-04-10

    The growth of Si/Ge axial heterostructure nanowires in high yield using a versatile wet chemical approach is reported. Heterostructure growth is achieved using the vapor zone of a high boiling point solvent as a reaction medium with an evaporated tin layer as the catalyst. The low solubility of Si and Ge within the Sn catalyst allows the formation of extremely abrupt heterojunctions of the order of just 1-2 atomic planes between the Si and Ge nanowire segments. The compositional abruptness was confirmed using aberration corrected scanning transmission electron microscopy and atomic level electron energy loss spectroscopy. Additional analysis focused on the role of crystallographic defects in determining interfacial abruptness and the preferential incorporation of metal catalyst atoms near twin defects in the nanowires.

  4. Analysis of ballistic and quasi-ballistic hole transport properties in germanium nanowires based on an extended "Top of the Barrier" model

    NASA Astrophysics Data System (ADS)

    Tanaka, Hajime; Suda, Jun; Kimoto, Tsunenobu

    2016-09-01

    The ballistic hole transport properties in rectangular cross-sectional germanium nanowire transistors with various geometries were studied based on the "Top of the Barrier" model. Then, by an extension of this model, the quasi-ballistic hole transport was discussed taking into account phonon and surface roughness scattering in the channel and source-to-drain direct tunneling. Among several nanowire geometries targeted in this study, the [1 1 0]-oriented nanowire with large height along [1 1 bar 0] ([1 1 0]/(1 1 bar 0) NW) exhibited the largest ballistic current. This was understood from its large density of states and resulting high hole density. Large density of states, however, enhances backscattering in the channel. An approximation analysis of quasi-ballistic transport suggested that the [1 1 0]/(0 0 1) NW with higher mobility can outperform [1 1 0]/(1 1 bar 0) NW when scattering and tunneling are considered.

  5. Nanoheteroepitaxy of gallium arsenide on strain-compliant silicon-germanium nanowires

    NASA Astrophysics Data System (ADS)

    Chin, Hock-Chun; Gong, Xiao; Ng, Tien Khee; Loke, Wan Khai; Wong, Choun Pei; Shen, Zexiang; Wicaksono, Satrio; Yoon, Soon Fatt; Yeo, Yee-Chia

    2010-07-01

    Heterogeneous integration of high-quality GaAs on Si-based substrates using a selective migration-enhanced epitaxy (MEE) of GaAs on strain-compliant SiGe nanowires was demonstrated for the first time. The physics of compliance in nanoscale heterostructures was captured and studied using finite-element simulation. It is shown that nanostructures can provide additional substrate compliance for strain relief and therefore contribute to the formation of defect-free GaAs on SiGe. Extensive characterization using scanning electron microscopy and cross-sectional transmission electron microscopy was performed to illustrate the successful growth of GaAs on SiGe nanowire. Raman and Auger electron spectroscopy measurements further confirmed the quality of the GaAs grown and the high growth selectivity of the MEE process.

  6. Nanoheteroepitaxy of gallium arsenide on strain-compliant silicon-germanium nanowires

    SciTech Connect

    Chin, Hock-Chun; Gong, Xiao; Yeo, Yee-Chia; Ng, Tien Khee; Loke, Wan Khai; Wicaksono, Satrio; Yoon, Soon Fatt; Wong, Choun Pei; Shen, Zexiang

    2010-07-15

    Heterogeneous integration of high-quality GaAs on Si-based substrates using a selective migration-enhanced epitaxy (MEE) of GaAs on strain-compliant SiGe nanowires was demonstrated for the first time. The physics of compliance in nanoscale heterostructures was captured and studied using finite-element simulation. It is shown that nanostructures can provide additional substrate compliance for strain relief and therefore contribute to the formation of defect-free GaAs on SiGe. Extensive characterization using scanning electron microscopy and cross-sectional transmission electron microscopy was performed to illustrate the successful growth of GaAs on SiGe nanowire. Raman and Auger electron spectroscopy measurements further confirmed the quality of the GaAs grown and the high growth selectivity of the MEE process.

  7. Gold-catalyzed vapor-liquid-solid germanium-nanowire nucleation on porous silicon.

    PubMed

    Koto, Makoto; Marshall, Ann F; Goldthorpe, Irene A; McIntyre, Paul C

    2010-05-07

    Nanoporous Si(111) substrates are used to study the effects of Au catalyst coarsening on the nucleation of vapor-liquid-solid-synthesized epitaxial Ge nanowires (NWs) at temperatures less than 400 degrees C. Porous Si substrates, with greater effective interparticle separations for Au surface diffusion than nonporous Si, inhibit catalyst coarsening and agglomeration prior to NW nucleation. This greatly reduces the variation in wire diameter and length and increases the yield compared to nucleation on identically prepared nonporous Si substrates.

  8. The impact of erbium incorporation on the structure and photophysics of silicon-germanium nanowires.

    PubMed

    Wu, Ji; Wieligor, Monika; Zerda, T Waldek; Coffer, Jeffery L

    2010-12-01

    In this paper, we report multi-step processes for the fabrication of Er3+-doped SiGe nanowires (NWs) and characterization of their emissive properties. Three different alloyed architectures are obtained by altering the deposition sequences of Si and Er3+ on a Ge core NW, each involving a fixed concentration of these three elements. The deposition of Si onto the Ge NW core, followed by an Er3+-rich layer on the outermost surface, permits facile formation of a SiGe alloy given the lack of an erbium diffusion barrier; yet clustering of the erbium centers on the NW surface produces the weakest emitter. For nanowires prepared by co-depositing Si and Er3+ on top of the Ge core, the presence of impurity Er3+ ions greatly reduces the alloying rate of Si and Ge such that less Si can diffuse into the Ge core. For this structure, the reduction of Er-Er interactions by a polycrystalline Si shell results in the strongest emission at 1540 nm. If an Er3+ layer is inserted between the Ge and Si layers (a sandwich structure), it is found that Er3+ ions diffuse preferentially into the SiGe core instead of the silicon-rich shell, with a correspondingly weaker luminescence intensity. A combination of high resolution transmission electron microscopy, energy dispersive X-ray mapping, micro-Raman spectroscopy, and photoluminescence spectroscopy are employed to derive these conclusions.

  9. On demand shape-selective integration of individual vertical germanium nanowires on a Si(111) substrate via laser-localized heating.

    PubMed

    Ryu, Sang-Gil; Kim, Eunpa; Yoo, Jae-Hyuck; Hwang, David J; Xiang, Bin; Dubon, Oscar D; Minor, Andrew M; Grigoropoulos, Costas P

    2013-03-26

    Semiconductor nanowire (NW) synthesis methods by blanket furnace heating produce structures of uniform size and shape. This study overcomes this constraint by applying laser-localized synthesis on catalytic nanodots defined by electron beam lithography in order to accomplish site- and shape-selective direct integration of vertically oriented germanium nanowires (GeNWs) on a single Si(111) substrate. Since the laser-induced local temperature field drives the growth process, each NW could be synthesized with distinctly different geometric features. The NW shape was dialed on demand, ranging from cylindrical to hexagonal/irregular hexagonal pyramid. Finite difference time domain analysis supported the tunability of the light absorption and scattering spectra via controlling the GeNW shape.

  10. Growth and electrical rectification in axial in-situ doped p-n junction germanium nanowires

    SciTech Connect

    Picraux, Samuel T; Dayeh, Shadi; Zaslavsky, Alexander; Le, Son T

    2009-01-01

    In this work, we demonstrate the vapor-liquid-solid (VLS) growth and electrical properties of axial in-situ doped p-n junction Ge nanowires (NWs). In-situ doping of the NWs was accomplished by introducing dopant gases (diborane and phosphine) together with GeH{sub 4} in the growth process. By changing dopant sources during growth, a p-n junction can be realized along the axis of the NWs. Metal contacts to the wires were defined using e-beam lithography patterning, followed by 100 nm Ni sputter deposition and lift-off. Four-point measurements of the fabricated devices at room temperature and at 77 K clearly show rectification with on/off current ratio up to two orders of magnitude when the bias is applied across the p-n junction. The ideality factor of the junction current points to a significant generation-recombination contribution. The Ohmic characteristics in the p and n regions outside the junction make it possible to estimate the doping levels. We also observed backgate control of the NW junction current.

  11. Strain-induced structural defects and their effects on the electrochemical performances of silicon core/germanium shell nanowire heterostructures

    SciTech Connect

    Lin, Yung-Chen; Kim, Dongheun; Li, Zhen; Nguyen, Binh-Minh; Li, Nan; Zhang, Shixiong; Yoo, Jinkyoung

    2016-12-14

    Here we report on strain-induced structural defect formation in core Si nanowire of Si/Ge core/shell nanowire heterostructure and influences of the structural defects on the electrochemical performances in lithium-ion battery anodes based on Si/Ge core/shell nanowire heterostructures. The induced structural defects consisting of stacking faults and dislocations in the core Si nanowire were observed for the first time. The generation of stacking faults in Si/Ge core/shell nanowire heterostructure is observed to prefer settling in either only Ge shell region or in both Ge shell and Si core regions and is associated with the increase of the shell volume fraction. The relax of misfit strain in [112] oriented core/shell nanowire heterostructure leads to subsequent gliding of Shockley partial dislocations, preferentially forming the twins. The observation of cross-over defect formation is of great importance for the understanding of heteroepitaxy in radial heterostructures at nanoscale and building the three dimensional heterostructures for the various applications. In addition, the effect of the defect formation on nanomaterial’s functionality is investigated by electrochemical performance test. The Si/Ge core/shell nanowire heterostructures enhance the gravimetric capacity of lithium ion battery anodes under fast charging/discharging rates compared to Si nanowires. However, the induced structural defects hamper lithiation of the Si/Ge core/shell nanowire heterostructure.

  12. Strain-induced structural defects and their effects on the electrochemical performances of silicon core/germanium shell nanowire heterostructures

    DOE PAGES

    Lin, Yung-Chen; Kim, Dongheun; Li, Zhen; ...

    2016-12-14

    Here we report on strain-induced structural defect formation in core Si nanowire of Si/Ge core/shell nanowire heterostructure and influences of the structural defects on the electrochemical performances in lithium-ion battery anodes based on Si/Ge core/shell nanowire heterostructures. The induced structural defects consisting of stacking faults and dislocations in the core Si nanowire were observed for the first time. The generation of stacking faults in Si/Ge core/shell nanowire heterostructure is observed to prefer settling in either only Ge shell region or in both Ge shell and Si core regions and is associated with the increase of the shell volume fraction. Themore » relax of misfit strain in [112] oriented core/shell nanowire heterostructure leads to subsequent gliding of Shockley partial dislocations, preferentially forming the twins. The observation of cross-over defect formation is of great importance for the understanding of heteroepitaxy in radial heterostructures at nanoscale and building the three dimensional heterostructures for the various applications. In addition, the effect of the defect formation on nanomaterial’s functionality is investigated by electrochemical performance test. The Si/Ge core/shell nanowire heterostructures enhance the gravimetric capacity of lithium ion battery anodes under fast charging/discharging rates compared to Si nanowires. However, the induced structural defects hamper lithiation of the Si/Ge core/shell nanowire heterostructure.« less

  13. Strain-induced structural defects and their effects on the electrochemical performances of silicon core/germanium shell nanowire heterostructures.

    PubMed

    Lin, Yung-Chen; Kim, Dongheun; Li, Zhen; Nguyen, Binh-Minh; Li, Nan; Zhang, Shixiong; Yoo, Jinkyoung

    2017-01-19

    We report on strain-induced structural defect formation in core Si nanowires of a Si/Ge core/shell nanowire heterostructure and the influence of the structural defects on the electrochemical performances in lithium-ion battery anodes based on Si/Ge core/shell nanowire heterostructures. The induced structural defects consisting of stacking faults and dislocations in the core Si nanowire were observed for the first time. The generation of stacking faults in the Si/Ge core/shell nanowire heterostructure is observed to prefer settling in either only the Ge shell region or in both the Ge shell and Si core regions and is associated with the increase of the shell volume fraction. The relaxation of the misfit strain in the [112] oriented core/shell nanowire heterostructure leads to subsequent gliding of Shockley partial dislocations, preferentially forming the twins. The observation of crossover of defect formation is of great importance for understanding heteroepitaxy in radial heterostructures at the nanoscale and for building three dimensional heterostructures for the various applications. Furthermore, the effect of the defect formation on the nanomaterial's functionality is investigated using electrochemical performance tests. The Si/Ge core/shell nanowire heterostructures enhance the gravimetric capacity of lithium ion battery anodes under fast charging/discharging rates compared to Si nanowires. However, the induced structural defects hamper lithiation of the Si/Ge core/shell nanowire heterostructure.

  14. Non-equilibrium induction of tin in germanium: towards direct bandgap Ge(1-x)Sn(x) nanowires.

    PubMed

    Biswas, Subhajit; Doherty, Jessica; Saladukha, Dzianis; Ramasse, Quentin; Majumdar, Dipanwita; Upmanyu, Moneesh; Singha, Achintya; Ochalski, Tomasz; Morris, Michael A; Holmes, Justin D

    2016-04-20

    The development of non-equilibrium group IV nanoscale alloys is critical to achieving new functionalities, such as the formation of a direct bandgap in a conventional indirect bandgap elemental semiconductor. Here, we describe the fabrication of uniform diameter, direct bandgap Ge(1-x)Sn(x) alloy nanowires, with a Sn incorporation up to 9.2 at.%, far in excess of the equilibrium solubility of Sn in bulk Ge, through a conventional catalytic bottom-up growth paradigm using noble metal and metal alloy catalysts. Metal alloy catalysts permitted a greater inclusion of Sn in Ge nanowires compared with conventional Au catalysts, when used during vapour-liquid-solid growth. The addition of an annealing step close to the Ge-Sn eutectic temperature (230 °C) during cool-down, further facilitated the excessive dissolution of Sn in the nanowires. Sn was distributed throughout the Ge nanowire lattice with no metallic Sn segregation or precipitation at the surface or within the bulk of the nanowires. The non-equilibrium incorporation of Sn into the Ge nanowires can be understood in terms of a kinetic trapping model for impurity incorporation at the triple-phase boundary during growth.

  15. Non-equilibrium induction of tin in germanium: towards direct bandgap Ge1-xSnx nanowires

    NASA Astrophysics Data System (ADS)

    Biswas, Subhajit; Doherty, Jessica; Saladukha, Dzianis; Ramasse, Quentin; Majumdar, Dipanwita; Upmanyu, Moneesh; Singha, Achintya; Ochalski, Tomasz; Morris, Michael A.; Holmes, Justin D.

    2016-04-01

    The development of non-equilibrium group IV nanoscale alloys is critical to achieving new functionalities, such as the formation of a direct bandgap in a conventional indirect bandgap elemental semiconductor. Here, we describe the fabrication of uniform diameter, direct bandgap Ge1-xSnx alloy nanowires, with a Sn incorporation up to 9.2 at.%, far in excess of the equilibrium solubility of Sn in bulk Ge, through a conventional catalytic bottom-up growth paradigm using noble metal and metal alloy catalysts. Metal alloy catalysts permitted a greater inclusion of Sn in Ge nanowires compared with conventional Au catalysts, when used during vapour-liquid-solid growth. The addition of an annealing step close to the Ge-Sn eutectic temperature (230 °C) during cool-down, further facilitated the excessive dissolution of Sn in the nanowires. Sn was distributed throughout the Ge nanowire lattice with no metallic Sn segregation or precipitation at the surface or within the bulk of the nanowires. The non-equilibrium incorporation of Sn into the Ge nanowires can be understood in terms of a kinetic trapping model for impurity incorporation at the triple-phase boundary during growth.

  16. Non-equilibrium induction of tin in germanium: towards direct bandgap Ge1−xSnx nanowires

    PubMed Central

    Biswas, Subhajit; Doherty, Jessica; Saladukha, Dzianis; Ramasse, Quentin; Majumdar, Dipanwita; Upmanyu, Moneesh; Singha, Achintya; Ochalski, Tomasz; Morris, Michael A.; Holmes, Justin D.

    2016-01-01

    The development of non-equilibrium group IV nanoscale alloys is critical to achieving new functionalities, such as the formation of a direct bandgap in a conventional indirect bandgap elemental semiconductor. Here, we describe the fabrication of uniform diameter, direct bandgap Ge1−xSnx alloy nanowires, with a Sn incorporation up to 9.2 at.%, far in excess of the equilibrium solubility of Sn in bulk Ge, through a conventional catalytic bottom-up growth paradigm using noble metal and metal alloy catalysts. Metal alloy catalysts permitted a greater inclusion of Sn in Ge nanowires compared with conventional Au catalysts, when used during vapour–liquid–solid growth. The addition of an annealing step close to the Ge-Sn eutectic temperature (230 °C) during cool-down, further facilitated the excessive dissolution of Sn in the nanowires. Sn was distributed throughout the Ge nanowire lattice with no metallic Sn segregation or precipitation at the surface or within the bulk of the nanowires. The non-equilibrium incorporation of Sn into the Ge nanowires can be understood in terms of a kinetic trapping model for impurity incorporation at the triple-phase boundary during growth. PMID:27095012

  17. Advances in the Application of Silicon and Germanium Nanowires for High-Performance Lithium-Ion Batteries.

    PubMed

    Kennedy, Tadhg; Brandon, Michael; Ryan, Kevin M

    2016-07-01

    Li-alloying materials such as Si and Ge nanowires have emerged as the forerunners to replace the current, relatively low-capacity carbonaceous based Li-ion anodes. Since the initial report of binder-free nanowire electrodes, a vast body of research has been carried out in which the performance and cycle life has significantly progressed. The study of such electrodes has provided invaluable insights into the cycling behavior of Si and Ge, as the effects of repeated lithiation/delithiation on the material can be observed without interference from conductive additives or binders. Here, some of the key developments in this area are looked at, focusing on the problems encountered by Li-alloying electrodes in general (e.g., pulverization, loss of contact with current collector etc.) and how the study of nanowire electrodes has overcome these issues. Some key nanowire studies that have elucidated the consequences of the alloying/dealloying process on the morphology of Si and Ge are also considered, in particular looking at the impact that effects such as pore formation and lithium-assisted welding have on performance. Finally, the challenges for the practical implementation of nanowire anodes within the context of the current understanding of such systems are discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Nanowire Heterostructures Comprising Germanium Stems and Silicon Branches as High-Capacity Li-Ion Anodes with Tunable Rate Capability.

    PubMed

    Kennedy, Tadhg; Bezuidenhout, Michael; Palaniappan, Kumaranand; Stokes, Killian; Brandon, Michael; Ryan, Kevin M

    2015-07-28

    Here we report the rational design of a high-capacity Li-ion anode material comprising Ge nanowires with Si branches. The unique structure provides an electrode material with tunable properties, allowing the performance to be tailored for either high capacity or high rate capability by controlling the mass ratio of Si to Ge. The binder free Si-Ge branched nanowire heterostructures are grown directly from the current collector and exhibit high capacities of up to ∼1800 mAh/g. Rate capability testing revealed that increasing the Ge content within the material boosted the performance of the anode at fast cycling rates, whereas a higher Si content was optimal at slower rates of charge and discharge. Using ex-situ electron microscopy, Raman spectroscopy and energy dispersive X-ray spectroscopy mapping, the composition of the material is shown to be transient in nature, transforming from a heterostructure to a Si-Ge alloy as a consequence of repeated lithiation and delithiation.

  19. Design and analysis of nanowire p-type MOSFET coaxially having silicon core and germanium peripheral channel

    NASA Astrophysics Data System (ADS)

    Yu, Eunseon; Cho, Seongjae

    2016-11-01

    In this work, a nanowire p-type metal-oxide-semiconductor field-effect transistor (PMOSFET) coaxially having a Si core and a Ge peripheral channel is designed and characterized by device simulations. Owing to the high hole mobility of Ge, the device can be utilized for high-speed CMOS integrated circuits, with the effective confinement of mobile holes in Ge by the large valence band offset between Si and Ge. Source/drain doping concentrations and the ratio between the Si core and Ge channel thicknesses are determined. On the basis of the design results, the channel length is aggressively scaled down by evaluating the primary DC parameters in order to confirm device scalability and low-power applicability in sub-10-nm technology nodes.

  20. Nanowire Photovoltaic Devices

    NASA Technical Reports Server (NTRS)

    Forbes, David

    2015-01-01

    Firefly Technologies, in collaboration with the Rochester Institute of Technology and the University of Wisconsin-Madison, developed synthesis methods for highly strained nanowires. Two synthesis routes resulted in successful nanowire epitaxy: direct nucleation and growth on the substrate and a novel selective-epitaxy route based on nanolithography using diblock copolymers. The indium-arsenide (InAs) nanowires are implemented in situ within the epitaxy environment-a significant innovation relative to conventional semiconductor nanowire generation using ex situ gold nanoparticles. The introduction of these nanoscale features may enable an intermediate band solar cell while simultaneously increasing the effective absorption volume that can otherwise limit short-circuit current generated by thin quantized layers. The use of nanowires for photovoltaics decouples the absorption process from the current extraction process by virtue of the high aspect ratio. While no functional solar cells resulted from this effort, considerable fundamental understanding of the nanowire epitaxy kinetics and nanopatterning process was developed. This approach could, in principle, be an enabling technology for heterointegration of dissimilar materials. The technology also is applicable to virtual substrates. Incorporating nanowires onto a recrystallized germanium/metal foil substrate would potentially solve the problem of grain boundary shunting of generated carriers by restricting the cross-sectional area of the nanowire (tens of nanometers in diameter) to sizes smaller than the recrystallized grains (0.5 to 1 micron(exp 2).

  1. Solution synthesis of germanium nanocrystals

    DOEpatents

    Gerung, Henry [Albuquerque, NM; Boyle, Timothy J [Kensington, MD; Bunge, Scott D [Cuyahoga Falls, OH

    2009-09-22

    A method for providing a route for the synthesis of a Ge(0) nanometer-sized material from. A Ge(II) precursor is dissolved in a ligand heated to a temperature, generally between approximately 100.degree. C. and 400.degree. C., sufficient to thermally reduce the Ge(II) to Ge(0), where the ligand is a compound that can bond to the surface of the germanium nanomaterials to subsequently prevent agglomeration of the nanomaterials. The ligand encapsulates the surface of the Ge(0) material to prevent agglomeration. The resulting solution is cooled for handling, with the cooling characteristics useful in controlling the size and size distribution of the Ge(0) materials. The characteristics of the Ge(II) precursor determine whether the Ge(0) materials that result will be nanocrystals or nanowires.

  2. TRIFLUOROMETHYL COMPOUNDS OF GERMANIUM

    DTIC Science & Technology

    FLUORIDES, *GERMANIUM COMPOUNDS, *HALIDES, *ORGANOMETALLIC COMPOUNDS, ALKYL RADICALS, ARSENIC COMPOUNDS, CHEMICAL BONDS, CHEMICAL REACTIONS ...CHLORIDES, CHLORINE COMPOUNDS, HYDROLYSIS, IODIDES, METHYL RADICALS, POTASSIUM COMPOUNDS, PYROLYSIS, STABILITY, SYNTHESIS, TIN COMPOUNDS.

  3. Mineral commodity profiles: Germanium

    USGS Publications Warehouse

    Butterman, W.C.; Jorgenson, John D.

    2005-01-01

    Overview -- Germanium is a hard, brittle semimetal that first came into use a half-century ago as a semiconductor material in radar units and as the material from which the first transistor was made. Today it is used principally as a component of the glass in telecommunications fiber optics; as a polymerization catalyst for polyethylene terephthalate (PET), a commercially important plastic; in infrared (IR) night vision devices; and as a semiconductor and substrate in electronics circuitry. Most germanium is recovered as a byproduct of zinc smelting, although it also has been recovered at some copper smelters and from the fly ash of coal-burning industrial powerplants. It is a highly dispersed element, associated primarily with base-metal sulfide ores. In the United States, germanium is recovered from zinc smelter residues and manufacturing scrap and is refined by two companies at four germanium refineries. One of the four refineries is dedicated to processing scrap. In 2000, producers sold zone-refined (high-purity) germanium at about $1,250 per kilogram and electronic-grade germanium dioxide (GeO2) at $800 per kilogram. Domestic refined production was valued at $22 million. Germanium is a critical component in highly technical devices and processes. It is likely to remain in demand in the future at levels at least as high as those of 2000. U.S. resources of germanium are probably adequate to meet domestic needs for several decades.

  4. Germanium detector passivated with hydrogenated amorphous germanium

    DOEpatents

    Hansen, William L.; Haller, Eugene E.

    1986-01-01

    Passivation of predominantly crystalline semiconductor devices (12) is provided for by a surface coating (21) of sputtered hydrogenated amorphous semiconductor material. Passivation of a radiation detector germanium diode, for example, is realized by sputtering a coating (21) of amorphous germanium onto the etched and quenched diode surface (11) in a low pressure atmosphere of hydrogen and argon. Unlike prior germanium diode semiconductor devices (12), which must be maintained in vacuum at cryogenic temperatures to avoid deterioration, a diode processed in the described manner may be stored in air at room temperature or otherwise exposed to a variety of environmental conditions. The coating (21) compensates for pre-existing undesirable surface states as well as protecting the semiconductor device (12) against future impregnation with impurities.

  5. Lithium drifted germanium system

    NASA Technical Reports Server (NTRS)

    Fjarlie, E. J.

    1969-01-01

    General characteristics of the lithium-drifted germanium photodiode-Dewar-preamplifier system and particular operating instructions for the device are given. Information is included on solving operational problems.

  6. Generalized Redox-Responsive Assembly of Carbon-Sheathed Metallic and Semiconducting Nanowire Heterostructures.

    PubMed

    Choi, Sinho; Kim, Jieun; Hwang, Dae Yeon; Park, Hyungmin; Ryu, Jaegeon; Kwak, Sang Kyu; Park, Soojin

    2016-02-10

    One-dimensional metallic/semiconducting materials have demonstrated as building blocks for various potential applications. Here, we report on a unique synthesis technique for redox-responsive assembled carbon-sheathed metal/semiconducting nanowire heterostructures that does not require a metal catalyst. In our approach, germanium nanowires are grown by the reduction of germanium oxide particles and subsequent self-catalytic growth during the thermal decomposition of natural gas, and simultaneously, carbon sheath layers are uniformly coated on the nanowire surface. This process is a simple, reproducible, size-controllable, and cost-effective process whereby most metal oxides can be transformed into metallic/semiconducting nanowires. Furthermore, the germanium nanowires exhibit stable chemical/thermal stability and outstanding electrochemical performance including a capacity retention of ∼96% after 1200 cycles at the 0.5-1C rate as lithium-ion battery anode.

  7. Bridgman Growth of Germanium

    NASA Technical Reports Server (NTRS)

    Szofran, F. R.; Volz, M. P.; Cobb, S. D.; Motakef, S.

    1997-01-01

    The high-magnetic-field crystal growth facility at the Marshall Space Flight Center will be briefly described. This facility has been used to grow bulk germanium by the Bridgman technique in magnetic fields up to 5 Tesla. The results of investigations of ampoule material on the interface shape and thermal field applied to the melt on stability against convection will be discussed.

  8. Segmented nanowires displaying locally controllable properties

    DOEpatents

    Sutter, Eli Anguelova; Sutter, Peter Werner

    2013-03-05

    Vapor-liquid-solid growth of nanowires is tailored to achieve complex one-dimensional material geometries using phase diagrams determined for nanoscale materials. Segmented one-dimensional nanowires having constant composition display locally variable electronic band structures that are determined by the diameter of the nanowires. The unique electrical and optical properties of the segmented nanowires are exploited to form electronic and optoelectronic devices. Using gold-germanium as a model system, in situ transmission electron microscopy establishes, for nanometer-sized Au--Ge alloy drops at the tips of Ge nanowires (NWs), the parts of the phase diagram that determine their temperature-dependent equilibrium composition. The nanoscale phase diagram is then used to determine the exchange of material between the NW and the drop. The phase diagram for the nanoscale drop deviates significantly from that of the bulk alloy.

  9. Vapor pressure of germanium precursors

    NASA Astrophysics Data System (ADS)

    Pangrác, J.; Fulem, M.; Hulicius, E.; Melichar, K.; Šimeček, T.; Růžička, K.; Morávek, P.; Růžička, V.; Rushworth, S. A.

    2008-11-01

    The vapor pressure of two germanium precursors tetrakis(methoxy)germanium (Ge(OCH 3) 4, CASRN 992-91-6) and tetrakis(ethoxy)germanium (Ge(OC 2H 5) 4, CASRN 14165-55-0) was determined using a static method in the temperature range 259-303 K. The experimental vapor pressure data were fit with the Antoine equation. The mass spectra before and after degassing by vacuum distillation at low temperature are also reported and discussed.

  10. Germanium detector vacuum encapsulation

    NASA Technical Reports Server (NTRS)

    Madden, N. W.; Malone, D. F.; Pehl, R. H.; Cork, C. P.; Luke, P. N.; Landis, D. A.; Pollard, M. J.

    1991-01-01

    This paper describes an encapsulation technology that should significantly improve the viability of germanium gamma-ray detectors for a number of important applications. A specialized vacuum chamber has been constructed in which the detector and the encapsulating module are processed in high vacuum. Very high vacuum conductance is achieved within the valveless encapsulating module. The detector module is then sealed without breaking the chamber vacuum. The details of the vacuum chamber, valveless module, processing, and sealing method are presented.

  11. Germanium detector vacuum encapsulation

    NASA Technical Reports Server (NTRS)

    Madden, N. W.; Malone, D. F.; Pehl, R. H.; Cork, C. P.; Luke, P. N.; Landis, D. A.; Pollard, M. J.

    1991-01-01

    This paper describes an encapsulation technology that should significantly improve the viability of germanium gamma-ray detectors for a number of important applications. A specialized vacuum chamber has been constructed in which the detector and the encapsulating module are processed in high vacuum. Very high vacuum conductance is achieved within the valveless encapsulating module. The detector module is then sealed without breaking the chamber vacuum. The details of the vacuum chamber, valveless module, processing, and sealing method are presented.

  12. Monocrystalline germanium film on sapphire

    NASA Astrophysics Data System (ADS)

    Godbey, David J.; Qadri, Syed B.

    1993-04-01

    A monocrystalline germanium film is grown on a sapphire substrate with a (I 102) orientation. The substrate is first pretreated to restructure the (1102) surface plane. Typically, restructuring is accomplished by either an anneal at high temperature or ion bombardment. A monocrystalline germanium layer is grown on the pretreated surface by a vapor deposition process such as molecular beam epitaxy or chemical vapor deposition.

  13. Germanium-76 Sample Analysis

    SciTech Connect

    Kouzes, Richard T.; Engelhard, Mark H.; Zhu, Zihua

    2011-04-01

    The MAJORANA DEMONSTRATOR is a large array of ultra-low background high-purity germanium detectors, enriched in 76Ge, designed to search for zero-neutrino double-beta decay (0νββ). The DEMONSTRATOR will utilize 76Ge from Russia, and the first one gram sample was received from the supplier for analysis on April 24, 2011. The Environmental Molecular Sciences facility, a DOE user facility at PNNL, was used to make the required isotopic and chemical purity measurements that are essential to the quality assurance for the MAJORANA DEMONSTRATOR. The results of this first analysis are reported here.

  14. Slow Crack Growth of Germanium

    NASA Technical Reports Server (NTRS)

    Salem, Jon

    2016-01-01

    The fracture toughness and slow crack growth parameters of germanium supplied as single crystal beams and coarse grain disks were measured. Although germanium is anisotropic (A=1.7), it is not as anisotropic as SiC, NiAl, or Cu, as evidence by consistent fracture toughness on the 100, 110, and 111 planes. Germanium does not exhibit significant slow crack growth in distilled water. (n=100). Practical values for engineering design are a fracture toughness of 0.7 MPam and a Weibull modulus of m=6+/-2. For well ground and reasonable handled coupons, fracture strength should be greater than 30 MPa.

  15. Nanowires enabling strained photovoltaics

    SciTech Connect

    Greil, J.; Bertagnolli, E.; Lugstein, A.; Birner, S.

    2014-04-21

    Photovoltaic nano-devices have largely been relying on charge separation in conventional p-n junctions. Junction formation via doping, however, imposes major challenges in process control. Here, we report on a concept for photovoltaic energy conversion at the nano scale without the need for intentional doping. Our approach relies on charge carrier separation in inhomogeneously strained germanium nanowires (Ge NWs). This concept utilizes the strain-induced gradient in bandgap along tapered NWs. Experimental data confirms the feasibility of strain-induced charge separation in individual vapor-liquid-solid grown Ge NW devices with an internal quantum efficiency of ∼5%. The charge separation mechanism, though, is not inherently limited to a distinct material. Our work establishes a class of photovoltaic nano-devices with its opto-electronic properties engineered by size, shape, and applied strain.

  16. Germanium geochemistry and mineralogy

    USGS Publications Warehouse

    Bernstein, L.R.

    1985-01-01

    Germanium is enriched in the following geologic environments: 1. (1) iron meteorites and terrestrial iron-nickel; 2. (2) sulfide ore deposits, particularly those hosted by sedimentary rocks; 3. (3) iron oxide deposits; 4. (4) oxidized zones of Ge-bearing sulfide deposits; 5. (5) pegmatites, greisens, and skarns; and 6. (6) coal and lignitized wood. In silicate melts, Ge is highly siderophile in the presence of native iron-nickel; otherwise, it is highly lithophile. Among silicate minerals, Ge is concentrated in those having less polymerized silicate tetrahedra such as olivine and topaz. In deposits formed from hydrothermal solutions, Ge tends to be enriched mostly in either sulfides or in fluorine-bearing phases; it is thus concentrated both in some hydrothermal sulfide deposits and in pegmatites, greisens, and skarns. In sulfide deposits that formed from solutions having low to moderate sulfur activity, Ge is concentrated in sphalerite in amounts up to 3000 ppm. Sulfide deposits that formed from solutions having higher sulfur activity allowed Ge to either form its own sulfides, particularly with Cu, or to substitute for As, Sn, or other metals in sulfosalts. The Ge in hydrothermal fluids probably derives from enrichment during the fractional crystallization of igneous fluids, or is due to the incorporation of Ge from the country rocks, particularly from those containing organic material. Germanium bonds to lignin-derivative organic compounds that are found in peat and lignite, accounting for its common concentration in coals and related organic material. Germanium is precipitated from water together with iron hydroxide, accounting for its concentration in some sedimentary and supergene iron oxide deposits. It also is able to substitute for Fe in magnetite in a variety of geologic environments. In the oxidized zone of Ge-bearing sulfide deposits, Ge is concentrated in oxides, hydroxides, and hydroxy-sulfates, sometimes forming its own minerals. It is particularly

  17. Hafnium germanium telluride

    PubMed Central

    Jang, Gyung-Joo; Yun, Hoseop

    2008-01-01

    The title hafnium germanium telluride, HfGeTe4, has been synthesized by the use of a halide flux and structurally characterized by X-ray diffraction. HfGeTe4 is isostructural with stoichiometric ZrGeTe4 and the Hf site in this compound is also fully occupied. The crystal structure of HfGeTe4 adopts a two-dimensional layered structure, each layer being composed of two unique one-dimensional chains of face-sharing Hf-centered bicapped trigonal prisms and corner-sharing Ge-centered tetra­hedra. These layers stack on top of each other to complete the three-dimensional structure with undulating van der Waals gaps. PMID:21202163

  18. Germanium requirements for national defense

    NASA Astrophysics Data System (ADS)

    Fink, Donald A.; Culver-Hopper, Julia

    1991-07-01

    Germanium, one of the most important of the advanced electronic materials, is used in semiconductor devices, fiber optic systems, and infrared sensors for ships, aircraft, missiles, tanks and anti-tank units. Because of its importance in these applications, germanium was added to the National Defense Stockpile in the early 1980s. This study estimates the appropriate amount of germanium to be held in the stockpile, given DoD's current assumptions for stockpile planning. Because of the dearth of publicly available data on germanium supplies and demands, the analysts based these estimates on data gathered from Service Program Offices and industry and company officials throughout North America. The study was conducted in support of DoD's ongoing effort to review and update the requirements for strategic and critical materials.

  19. Sulfur Nanowires

    NASA Astrophysics Data System (ADS)

    Carvajal, Eliel; Santiago, Patricia; Escudero, Roberto; Mendoza, Doroteo

    2000-03-01

    We have synthetized sulfur nanowires by a template approach using nanoporous anodic alumina. High resolution electron microscopy shows that isolated sulfur nanowires (15 nanometers of diameter) present crystalline structure different to that observed in the stable bulk allotrope (orthorhombic alfa-sulfur). Melting behavior of the sulfur nanowires embedded into the nanoporous alumina matrix was studied by differential scanning calorimetry, showing again very different behavior of the nanowires compared to that of the bulk sulfur. On the other hand, in order to study the bonding configuration of the sulfur atoms in the nanowires, we will present infrared spectroscopy characterization of the nanowires confined into the nanoporous alumina. Finally, on the base of the experimental observations, we will present a structural model for the sulfur nanowires.

  20. Local structure of germanium-sulfur, germanium-selenium, and germanium-tellurium vitreous alloys

    SciTech Connect

    Bordovsky, G. A.; Terukov, E. I.; Anisimova, N. I.; Marchenko, A. V.; Seregin, P. P.

    2009-09-15

    {sup 119}Sn and {sup 129}Te ({sup 129}I) Moessbauer spectroscopy showed that chalcogen-enriched Ge{sub 100-y}X{sub y} (X = S, Se, Te) glasses are constructed of structural units including two-coordinated chalcogen atoms in chains such as Ge-X-Ge- and Ge-X-X-Ge-. Germanium in these glasses is only tetravalent and four-coordinated, and only chalcogen atoms are in the local environment of germanium atoms. Chalcogen-depleted glasses are constructed of structural units including two-coordinated (in Ge-X-Ge- chains) and three-coordinated chalcogen atoms (in -Ge-X-Ge- chains). Germanium in these glasses stabilizes in both the tetravalent four-coordinated and divalent three-coordinated states, and only chalcogen atoms are in the local environment of germanium atoms.

  1. Stable and metastable nanowires displaying locally controllable properties

    DOEpatents

    Sutter, Eli Anguelova; Sutter, Peter Werner

    2014-11-18

    Vapor-liquid-solid growth of nanowires is tailored to achieve complex one-dimensional material geometries using phase diagrams determined for nanoscale materials. Segmented one-dimensional nanowires having constant composition display locally variable electronic band structures that are determined by the diameter of the nanowires. The unique electrical and optical properties of the segmented nanowires are exploited to form electronic and optoelectronic devices. Using gold-germanium as a model system, in situ transmission electron microscopy establishes, for nanometer-sized Au--Ge alloy drops at the tips of Ge nanowires (NWs), the parts of the phase diagram that determine their temperature-dependent equilibrium composition. The nanoscale phase diagram is then used to determine the exchange of material between the NW and the drop. The phase diagram for the nanoscale drop deviates significantly from that of the bulk alloy.

  2. Resonant germanium nanoantenna photodetectors.

    PubMed

    Cao, Linyou; Park, Joon-Shik; Fan, Pengyu; Clemens, Bruce; Brongersma, Mark L

    2010-04-14

    On-chip optical interconnection is considered as a substitute for conventional electrical interconnects as microelectronic circuitry continues to shrink in size. Central to this effort is the development of ultracompact, silicon-compatible, and functional optoelectronic devices. Photodetectors play a key role as interfaces between photonics and electronics but are plagued by a fundamental efficiency-speed trade-off. Moreover, engineering of desired wavelength and polarization sensitivities typically requires construction of space-consuming components. Here, we demonstrate how to overcome these limitations in a nanoscale metal-semiconductor-metal germanium photodetector for the optical communications band. The detector capitalizes on antenna effects to dramatically enhance the photoresponse (>25-fold) and to enable wavelength and polarization selectivity. The electrical design featuring asymmetric metallic contacts also enables ultralow dark currents (approximately 20 pA), low power consumption, and high-speed operation (>100 GHz). The presented high-performance photodetection scheme represents a significant step toward realizing integrated on-chip communication and manifests a new paradigm for developing miniaturized optoelectronics components.

  3. Germananes: Germanium Graphane Analogues

    NASA Astrophysics Data System (ADS)

    Goldberger, Joshua

    2014-03-01

    Graphene's success has shown that it is not only possible to create stable, single-atom thick sheets from a crystalline solid, but that these materials have fundamentally different properties than the parent material. Our interest focuses on the synthesis and properties of Group IV graphane analogues. We have synthesized for the first time, mm-scale crystals of a hydrogen-terminated germanium multilayered graphane analogue (germanane, GeH) from the topochemical deintercalation of CaGe2. This layered van der Waals solid is analogous to multilayered graphane. The surface layer of GeH only slowly oxidizes in air over the span of five months, while the underlying layers are resilient to oxidation. We demonstrate that it is possible to covalently terminate the external surface with organic substituents to tune the electronic structure, and enhance the stability. These materials represent a new class of covalently terminated graphane analogues having great potential for a wide range of optoelectronic and sensing applications, especially since theory predicts a direct band gap of 1.53 eV and an electron mobility of 18,000 cm2/Vs which is five times higher than that of bulk Ge.

  4. OCCURRENCE OF GERMANIUM AND ARSENIC IN METEORITES.

    PubMed

    Papish, J; Hanford, Z M

    1930-03-07

    1. Spectroscopic evidence has been obtained of the occurrence of germanium in certain siderites, siderolites and aerolites. 2. Judging from the number and intensity of spectral lines the germanium in these meteorites is present in traces. 3. Germanium has been extracted from Toluca and Welland siderites. 4. Arsenic has been extracted from Toluca and Welland siderites.

  5. The Germanium Dichotomy in Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Humayun, M.; Yang, S.; Righter, K.; Zanda, B.; Hewins, R. H.

    2016-01-01

    Germanium is a moderately volatile and siderophile element that follows silicon in its compatibility during partial melting of planetary mantles. Despite its obvious usefulness in planetary geochemistry germanium is not analyzed routinely, with there being only three prior studies reporting germanium abundances in Martian meteorites. The broad range (1-3 ppm) observed in Martian igneous rocks is in stark contrast to the narrow range of germanium observed in terrestrial basalts (1.5 plus or minus 0.1 ppm). The germanium data from these studies indicates that nakhlites contain 2-3 ppm germanium, while shergottites contain approximately 1 ppm germanium, a dichotomy with important implications for core formation models. There have been no reliable germanium abundances on chassignites. The ancient meteoritic breccia, NWA 7533 (and paired meteorites) contains numerous clasts, some pristine and some impact melt rocks, that are being studied individually. Because germanium is depleted in the Martian crust relative to chondritic impactors, it has proven useful as an indicator of meteoritic contamination of impact melt clasts in NWA 7533. The germanium/silicon ratio can be applied to minerals that might not partition nickel and iridium, like feldspars. We report germanium in minerals from the 3 known chassignites, 2 nakhlites and 5 shergottites by LAICP- MS using a method optimized for precise germanium analysis.

  6. Dermal absorption of inorganic germanium in rats.

    PubMed

    Yokoi, Katsuhiko; Kawaai, Takae; Konomi, Aki; Uchida, Yuka

    2008-11-01

    So-called germanium 'health' products including dietary supplements, cosmetics, accessories, and warm bath service containing germanium compounds and metalloid are popular in Japan. Subchronic and chronic oral exposure of germanium dioxide (GeO(2)), popular chemical form of inorganic germanium causes severe germanium toxicosis including death and kidney dysfunction in humans and experimental animals. Intestinal absorption of neutralized GeO(2) or germanate is almost complete in humans and animals. However, it is not known whether germanium is cutaneously absorbed. We tested dermal absorption of neutralized GeO(2) or germanate using male F344/N rats. Three groups of rats were treated with a 3-h topical application of hydrophilic ointment containing graded level of neutralized GeO(2) (pH 7.4): 0, 0.21 and 0.42 mg GeO(2)/g. Germanium concentration in blood and tissues sampled from rats after topical application of inorganic germanium was measured by inductively coupled plasma-mass spectrometry. Animals topically applied 0.42 mg GeO(2)/g ointment had significantly higher germanium concentrations in plasma, liver, and kidney than those of rats that received no topical germanium. The results indicate that skin is permeable to inorganic germanium ion or germanate and recurrent exposure of germanium compounds may pose a potential health hazard.

  7. [Effects of Germanium Concentrations on Germanium Accumulation and Biotransformation of Polysaccarified Germanium in Cordyceps militaris].

    PubMed

    Wang, Ju-feng; Li, Hu-ming; Yang, Dao-de

    2015-11-01

    To study the effects of Germanium (Ge) concentration on Ge accumulation and biotransformation of polysaccarified Ge (PG) in Cordyceps militaris. Solid and liquid culture were used in this study. In the solid culture conditions, when the Ge concentration of medium was 200 mg/L, the sporophore biomass of Cordyceps militaris was the maximum; and when Ge concentration was 300 mg/L,the amount of biotransformation of PG in sporophore was the highest; and when the Ge concentration is 250 mg/L, conversion rate of organic germanium (OG) in sporophore reached the highest value. In the liquid culture conditions, when the Ge concentration was 250 mg/L, the mycelium biomass of Cordyceps militaris was the maximum; and when Ge concentration was 150 mg/L, the amount of organic conversion of PG in mycelium was the most; and conversion rate of OG in mycelium was the highest in media with the Ge concentration of 200 mg/L. This study showed the germanium concentrations in 150 - 300 mg/L was more suitable for Ge accumulation and biotransformation of PG in Cordyceps militaris. In general, the biotransformation capacity to germanium of sporophore was stronger than that of mycelium of Cordyceps militaris. Germanium can significantly affect Ge accumulation and biotransformation of PG in Cordyceps militaris (P < 0.05) at different concentration. This result has practical value for Ge enriched cultivation of fruiting body in Cordyceps militaris.

  8. Germanium Multiphase Equation of State

    NASA Astrophysics Data System (ADS)

    Crockett, Scott; Kress, Joel; Rudin, Sven; de Lorenzi-Venneri, Giulia

    2013-06-01

    A new SESAME multiphase Germanium equation of state (EOS) has been developed utilizing the best experimental data and theoretical calculations. The equilibrium EOS includes the GeI (diamond), GeII (beta-Sn) and liquid phases. We will also explore the meta-stable GeIII (tetragonal) phase of germanium. The theoretical calculations used in constraining the EOS are based on quantum molecular dynamics and density functional theory phonon calculations. We propose some physics rich experiments to better understand the dynamics of this element.

  9. Germanium Nanocrystal Solar Cells

    NASA Astrophysics Data System (ADS)

    Holman, Zachary Charles

    Greenhouse gas concentrations in the atmosphere are approaching historically unprecedented levels from burning fossil fuels to meet the ever-increasing world energy demand. A rapid transition to clean energy sources is necessary to avoid the potentially catastrophic consequences of global warming. The sun provides more than enough energy to power the world, and solar cells that convert sunlight to electricity are commercially available. However, the high cost and low efficiency of current solar cells prevent their widespread implementation, and grid parity is not anticipated to be reached for at least 15 years without breakthrough technologies. Semiconductor nanocrystals (NCs) show promise for cheap multi-junction photovoltaic devices. To compete with photovoltaic materials that are currently commercially available, NCs need to be inexpensively cast into dense thin films with bulk-like electrical mobilities and absorption spectra that can be tuned by altering the NC size. The Group II-VI and IV-VI NC communities have had some success in achieving this goal by drying and then chemically treating colloidal particles, but the more abundant and less toxic Group IV NCs have proven more challenging. This thesis reports thin films of plasma-synthesized Ge NCs deposited using three different techniques, and preliminary solar cells based on these films. Germanium tetrachloride is dissociated in the presence of hydrogen in a nonthermal plasma to nucleate Ge NCs. Transmission electron microscopy and X-ray diffraction indicate that the particles are nearly monodisperse (standard deviations of 10-15% the mean particle diameter) and the mean diameter can be tuned from 4-15 nm by changing the residence time of the Ge NCs in the plasma. In the first deposition scheme, a Ge NC colloid is formed by reacting nanocrystalline powder with 1-dodecene and dispersing the functionalized NCs in a solvent. Films are then formed on substrates by drop-casting the colloid and allowing it to dry

  10. Nanowire Lasers

    NASA Astrophysics Data System (ADS)

    Couteau, C.; Larrue, A.; Wilhelm, C.; Soci, C.

    2015-05-01

    We review principles and trends in the use of semiconductor nanowires as gain media for stimulated emission and lasing. Semiconductor nanowires have recently been widely studied for use in integrated optoelectronic devices, such as light-emitting diodes (LEDs), solar cells, and transistors. Intensive research has also been conducted in the use of nanowires for subwavelength laser systems that take advantage of their quasione- dimensional (1D) nature, flexibility in material choice and combination, and intrinsic optoelectronic properties. First, we provide an overview on using quasi-1D nanowire systems to realize subwavelength lasers with efficient, directional, and low-threshold emission. We then describe the state of the art for nanowire lasers in terms of materials, geometry, andwavelength tunability.Next,we present the basics of lasing in semiconductor nanowires, define the key parameters for stimulated emission, and introduce the properties of nanowires. We then review advanced nanowire laser designs from the literature. Finally, we present interesting perspectives for low-threshold nanoscale light sources and optical interconnects. We intend to illustrate the potential of nanolasers inmany applications, such as nanophotonic devices that integrate electronics and photonics for next-generation optoelectronic devices. For instance, these building blocks for nanoscale photonics can be used for data storage and biomedical applications when coupled to on-chip characterization tools. These nanoscale monochromatic laser light sources promise breakthroughs in nanophotonics, as they can operate at room temperature, can potentially be electrically driven, and can yield a better understanding of intrinsic nanomaterial properties and surface-state effects in lowdimensional semiconductor systems.

  11. Epitaxial Deposition Of Germanium Doped With Gallium

    NASA Technical Reports Server (NTRS)

    Huffman, James E.

    1994-01-01

    Epitaxial layers of germanium doped with gallium made by chemical vapor deposition. Method involves combination of techniques and materials used in chemical vapor deposition with GeH4 or GeCl4 as source of germanium and GaCl3 as source of gallium. Resulting epitaxial layers of germanium doped with gallium expected to be highly pure, with high crystalline quality. High-quality material useful in infrared sensors.

  12. Epitaxial Deposition Of Germanium Doped With Gallium

    NASA Technical Reports Server (NTRS)

    Huffman, James E.

    1994-01-01

    Epitaxial layers of germanium doped with gallium made by chemical vapor deposition. Method involves combination of techniques and materials used in chemical vapor deposition with GeH4 or GeCl4 as source of germanium and GaCl3 as source of gallium. Resulting epitaxial layers of germanium doped with gallium expected to be highly pure, with high crystalline quality. High-quality material useful in infrared sensors.

  13. Calibration of Germanium Resistance Thermometers

    NASA Technical Reports Server (NTRS)

    Ladner, D.; Urban, E.; Mason, F. C.

    1987-01-01

    Largely completed thermometer-calibration cryostat and probe allows six germanium resistance thermometers to be calibrated at one time at superfluid-helium temperatures. In experiments involving several such thermometers, use of this calibration apparatus results in substantial cost savings. Cryostat maintains temperature less than 2.17 K through controlled evaporation and removal of liquid helium from Dewar. Probe holds thermometers to be calibrated and applies small amount of heat as needed to maintain precise temperature below 2.17 K.

  14. Mineral resource of the month: germanium

    USGS Publications Warehouse

    Guberman, David

    2010-01-01

    The article provides information on germanium, an element with electrical properties between those of a metal and an insulator. Applications of germanium include its use as a component of the glass in fiber-optic cable, in infrared optics devices and as a semiconductor and substrate used in electronic and solar applications. Germanium was first isolated by German chemist Clemens Winkler in 1886 and was named after Winkler's native country. In 2008, the leading sources of primary germanium from coal or zinc include Canada, China and Russia.

  15. Hydrothermal synthesis of bismuth germanium oxide

    DOEpatents

    Boyle, Timothy J.

    2016-12-13

    A method for the hydrothermal synthesis of bismuth germanium oxide comprises dissolving a bismuth precursor (e.g., bismuth nitrate pentahydrate) and a germanium precursor (e.g., germanium dioxide) in water and heating the aqueous solution to an elevated reaction temperature for a length of time sufficient to produce the eulytite phase of bismuth germanium oxide (E-BGO) with high yield. The E-BGO produced can be used as a scintillator material. For example, the air stability and radioluminescence response suggest that the E-BGO can be employed for medical applications.

  16. Structural Design Parameters for Germanium

    NASA Technical Reports Server (NTRS)

    Salem, Jon; Rogers, Richard; Baker, Eric

    2017-01-01

    The fracture toughness and slow crack growth parameters of germanium supplied as single crystal beams and coarse grain disks were measured. Although germanium is anisotropic (A* 1.7), it is not as anisotropic as SiC, NiAl, or Cu. Thus the fracture toughness was similar on the 100, 110, and 111 planes, however, measurements associated with randomly oriented grinding cracks were 6 to 30 higher. Crack extension in ring loaded disks occurred on the 111 planes due to both the lower fracture energy and the higher stresses on stiff 111 planes. Germanium exhibits a Weibull scale effect, but does not exhibit significant slow crack growth in distilled water. (n 100), implying that design for quasi static loading can be performed with scaled strength statistics. Practical values for engineering design are a fracture toughness of 0.69 0.02 MPam (megapascals per square root meter) and a Weibull modulus of m 6 2. For well ground and reasonable handled coupons, average fracture strength should be greater than 40 megapascals. Aggregate, polycrystalline elastic constants are Epoly 131 gigapascals, vpoly 0.22.

  17. Germanium recycling in the United States in 2000

    USGS Publications Warehouse

    Jorgenson, John D.

    2006-01-01

    This report describes the recycling flow of germanium in the United States in 2000, as well as other germanium material flow streams. Germanium was recycled mostly from new scrap that was generated during the manufacture of germanium-containing fiber optic cables and from new and old scrap products of germanium-containing infrared imaging devices. In 2000, about 11.5 metric tons of germanium was recycled, about 40 percent of which was derived from old scrap. The germanium recycling rate was estimated to be 50 percent, and germanium scrap recycling efficiency, 76 percent.

  18. Dimensionality Effects in FeGe2 Nanowires: Enhanced Anisotropic Magnetization and Anomalous Electrical Transport

    DOE PAGES

    Tang, Siwei; Kravchenko, Ivan; Ward, T. Z.; ...

    2017-08-02

    Here, we report the synthesis of single-crystal iron germanium nanowires via chemical vapor deposition without the assistance of any catalysts. The assembly of single-crystal FeGe2 nanowires with tetragonal C16 crystal structure shows anisotropic magnetic behavior along the radial direction or the growth axial direction, with both antiferromagnetic and ferromagnetic orders. Single FeGe2 nanowire devices were fabricated using e-beam lithography. Electronic transport measurement in these devices show two resistivity anomalies near 250 K and 200 K which are likely signatures of the two spin density wave states in FeGe2.

  19. Self-organized growth of germanium nanocolumns

    NASA Astrophysics Data System (ADS)

    Mussabek, G. K.; Yermukhamed, D.; Dikhanbayev, K. K.; Schleusener, A.; Mathur, S.; Sivakov, V.

    2017-03-01

    The crystalline germanium nanostructures were obtained on a silicon surface by the chemical vapor deposition technique using a germanium (IV) iso-propoxide ([Ge(OiPr)4]) metalorganic precursor as a germanium source. As was observed, the one-dimensional (1D) germanium nanostructures on the silicon surface form without using a metal catalyst, meaning that the formation of 1D nanostructures is based not on a vapor-liquid-solid (VLS) growth mechanism, but on self-organization processes which take place on the silicon surfaces during the CVD process of germanium iso-propoxide pyrolysis. Our observation suggests that the non-catalytic growth of germanium nanocolumns is strongly dependent on the CVD process temperature. The germanium phase composition and morphology have been investigated by x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS), and high resolution scanning electron microscopy (HRSEM), respectively. Our results provide a new way to grow 1D germanium nanostructures without contamination by a catalyst, which the vapor-liquid-solid growth mechanism is known to cause, allowing for the application of such materials in micro- and optoelectronics.

  20. Mineral resource of the month: germanium

    USGS Publications Warehouse

    Jorgenson, John D.

    2003-01-01

    Germanium is a hard, brittle semimetal that first came into use over a half-century ago as a semiconductor material in radar units and in the first transistor ever made. Most germanium is recovered as a byproduct of zinc smelting, but it has also been recovered at some copper smelters and from the fly ash of coal-burning industrial power plants.

  1. High efficiency germanium-assisted grating coupler.

    PubMed

    Yang, Shuyu; Zhang, Yi; Baehr-Jones, Tom; Hochberg, Michael

    2014-12-15

    We propose a fiber to submicron silicon waveguide vertical coupler utilizing germanium-on-silicon gratings. The germanium is epitaxially grown on silicon in the same step for building photodetectors. Coupling efficiency based on FDTD simulation is 76% at 1.55 µm and the optical 1dB bandwidth is 40 nm.

  2. The Reactivity of Germanium Phosphanides with Chalcogens.

    PubMed

    Harris, Lisa M; Tam, Eric C Y; Cummins, Struan J W; Coles, Martyn P; Fulton, J Robin

    2017-03-06

    The reactivity of germanium phosphanido complexes with elemental chalcogens is reported. Addition of sulfur to [(BDI)GePCy2] (BDI = CH{(CH3)CN-2,6-iPr2C6H3}2) results in oxidation at germanium to form germanium(IV) sulfide [(BDI)Ge(S)PCy2] and oxidation at both germanium and phosphorus to form germanium(IV) sulfide dicylohexylphosphinodithioate complex [(BDI)Ge(S)SP(S)Cy2], whereas addition of tellurium to [(BDI)GePCy2] only gives the chalcogen inserted product, [(BDI)GeTePCy2]. This reactivity is different from that observed between [(BDI)GePCy2] and selenium. Addition of selenium to the diphenylphosphanido germanium complex, [(BDI)GePPh2], results in insertion of selenium into the Ge-P bond to form [(BDI)GeSePCy2] as well as the oxidation at phosphorus to give [(BDI)GeSeP(Se)Ph2]. In contrast, addition of selenium to the bis(trimethylsilyl)phosphanido germanium complex, [(BDI)GeP(SiMe3)2], yields the germanium(IV) selenide [(BDI)Ge(Se)P(SiMe3)2].

  3. MAJORANA Collaboration's experience with germanium detectors

    DOE PAGES

    Mertens, S.; Abgrall, N.; Avignone, F. T.; ...

    2015-05-01

    The goal of the Majorana Demonstrator project is to search for 0νββ decay in 76Ge. Of all candidate isotopes for 0νββ, 76Ge has some of the most favorable characteristics. Germanium detectors are a well established technology, and in searches for 0νββ, the high purity germanium crystal acts simultaneously as source and detector. Furthermore, p-type germanium detectors provide excellent energy resolution and a specially designed point contact geometry allows for sensitive pulse shape discrimination. This paper will summarize the experiences the MAJORANA collaboration made with enriched germanium detectors manufactured by ORTEC®®. The process from production, to characterization and integration in MAJORANAmore » mounting structure will be described. A summary of the performance of all enriched germanium detectors will be given.« less

  4. MAJORANA Collaboration's experience with germanium detectors

    SciTech Connect

    Mertens, S.; Abgrall, N.; Avignone, F. T.; Barabash, A. S.; Bertrand, F. E.; Brudanin, V.; Busch, M.; Buuck, M.; Byram, D.; Caldwell, A. S.; Chan, Y. -D.; Christofferson, C. D.; Cuesta, C.; Detwiler, J. A.; Efremenko, Yu; Ejiri, H.; Elliott, S. R.; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guinn, I.; Guiseppe, V. E.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Jasinski, B. R.; Keeter, K. J.; Kidd, M. F.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; MacMullin, J.; Martin, R. D.; Meijer, S. J.; Orrell, J. L.; O'Shaughnessy, C.; Overman, N. R.; Poon, A. W. P.; Radford, D. C.; Rager, J.; Rielage, K.; Robertson, R. G. H.; Romero-Romero, E.; Ronquest, M. C.; Shanks, B.; Shirchenko, M.; Snyder, N.; Tedeschi, D.; Trimble, J. E.; Varner, R. L.; Vasilyev, S.; Vetter, K.; Vorren, K.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Yu, C. -H.; Yumatov, V.

    2015-05-01

    The goal of the Majorana Demonstrator project is to search for 0νββ decay in 76Ge. Of all candidate isotopes for 0νββ, 76Ge has some of the most favorable characteristics. Germanium detectors are a well established technology, and in searches for 0νββ, the high purity germanium crystal acts simultaneously as source and detector. Furthermore, p-type germanium detectors provide excellent energy resolution and a specially designed point contact geometry allows for sensitive pulse shape discrimination. This paper will summarize the experiences the MAJORANA collaboration made with enriched germanium detectors manufactured by ORTEC®®. The process from production, to characterization and integration in MAJORANA mounting structure will be described. A summary of the performance of all enriched germanium detectors will be given.

  5. Black Germanium fabricated by reactive ion etching

    NASA Astrophysics Data System (ADS)

    Steglich, Martin; Käsebier, Thomas; Kley, Ernst-Bernhard; Tünnermann, Andreas

    2016-09-01

    A reactive ion etching technique for the preparation of statistical "Black Germanium" antireflection surfaces, relying on self-organization in a Cl2 etch chemistry, is presented. The morphology of the fabricated Black Germanium surfaces is the result of a random lateral distribution of pyramidal etch pits with heights around (1450 ± 150) nm and sidewall angles between 80° and 85°. The pyramids' base edges are oriented along the <110> crystal directions of Germanium, indicating a crystal anisotropy of the etching process. In the Vis-NIR, the tapered Black Germanium surface structure suppresses interface reflection to <2.5 % for normal incidence and still to <6 % at an angle of incidence of 70°. The presented Black Germanium might find applications as low-cost AR structure in optoelectronics and IR optics.

  6. MAJORANA Collaboration's Experience with Germanium Detectors

    SciTech Connect

    Mertens, S.; Abgrall, N.; Avignone, III, F. T.; Bertrand, F. E.; Efremenko, Yuri; Galindo-Uribarri, A; Radford, D. C.; Romero-Romero, E.; White, B. R.; Wilkerson, J. F.; Majorana,

    2015-01-01

    The goal of the Majorana Demonstrator project is to search for 0v beta beta decay in Ge-76. Of all candidate isotopes for 0v beta beta, Ge-76 has some of the most favorable characteristics. Germanium detectors are a well established technology, and in searches for 0v beta beta, the high purity germanium crystal acts simultaneously as source and detector. Furthermore, p-type germanium detectors provide excellent energy resolution and a specially designed point contact geometry allows for sensitive pulse shape discrimination. This paper will summarize the experiences the MAJORANA collaboration made with enriched germanium detectors manufactured by ORTEC (R)(R). The process from production, to characterization and integration in MAJORANA mounting structure will be described. A summary of the performance of all enriched germanium detectors will be given.

  7. Microstrutured fibers with germanium doped core components

    NASA Astrophysics Data System (ADS)

    Kobelke, J.; Schuster, K.; Schwuchow, A.; Wang, Y.; Brückner, S.; Becker, M.; Rothhardt, M.; Kirchhof, J.; Ecke, W.; Willsch, R.; Bartelt, H.

    2009-05-01

    The paper reports preparation and applicative aspects of two types of index guiding microstructured fibers (MOFs) with germanium doped cores. The first fiber type has a solid core with graded germanium profile. It shows a high photosensitivity compared to pure silica MOFs. We inscribed high-quality Bragg gratings with a reflectivity of 73% without hydrogen loading. The solid core germanium doped MOF was spliced with standard silica fiber. The minimum splice loss was about 1 dB at 1550 μm wavelength. A more complex MOF type was prepared with germanium doped holey core in a silica holey cladding. The germanium doped core area includes seven holes in hexagonal arrangement with equal diameter and pitch sizes. The holey core propagates a large area annulus mode. We show the suitability of this MOF for chemical gas sensing by filling the core cavities with hydrocarbon analytes.

  8. Germanium multiphase equation of state

    SciTech Connect

    Crockett, Scott D.; Lorenzi-Venneri, Giulia De; Kress, Joel D.; Rudin, Sven P.

    2014-05-07

    A new SESAME multiphase germanium equation of state (EOS) has been developed using the best available experimental data and density functional theory (DFT) calculations. The equilibrium EOS includes the Ge I (diamond), the Ge II (β-Sn) and the liquid phases. The foundation of the EOS is based on density functional theory calculations which are used to determine the cold curve and the Debye temperature. Results are compared to Hugoniot data through the solid-solid and solid-liquid transitions. We propose some experiments to better understand the dynamics of this element

  9. Germanium multiphase equation of state

    DOE PAGES

    Crockett, Scott D.; Lorenzi-Venneri, Giulia De; Kress, Joel D.; ...

    2014-05-07

    A new SESAME multiphase germanium equation of state (EOS) has been developed using the best available experimental data and density functional theory (DFT) calculations. The equilibrium EOS includes the Ge I (diamond), the Ge II (β-Sn) and the liquid phases. The foundation of the EOS is based on density functional theory calculations which are used to determine the cold curve and the Debye temperature. Results are compared to Hugoniot data through the solid-solid and solid-liquid transitions. We propose some experiments to better understand the dynamics of this element

  10. Germanium multiphase equation of state

    NASA Astrophysics Data System (ADS)

    Crockett, S. D.; De Lorenzi-Venneri, G.; Kress, J. D.; Rudin, S. P.

    2014-05-01

    A new SESAME multiphase germanium equation of state (EOS) has been developed utilizing the best available experimental data and density functional theory (DFT) calculations. The equilibrium EOS includes the Ge I (diamond), the Ge II (β-Sn) and the liquid phases. The foundation of the EOS is based on density functional theory calculations which are used to determine the cold curve and the Debye temperature. Results are compared to Hugoniot data through the solid-solid and solid-liquid transitions. We propose some experiments to better understand the dynamics of this element.

  11. Electronic considerations for externally segmented germanium detectors

    NASA Technical Reports Server (NTRS)

    Madden, N. W.; Landis, D. A.; Goulding, F. S.; Pehl, R. H.; Cork, C. P.; Luke, P. N.; Malone, D. F.; Pollard, M. J.

    1991-01-01

    The dominant background source for germanium gamma ray detector spectrometers used for some astrophysics observations is internal beta decay. Externally segmented germanium gamma ray coaxial detectors can identify beta decay by localizing the event. Energetic gamma rays interact in the germanium detector by multiple Compton interactions while beta decay is a local process. In order to recognize the difference between gamma rays and beta decay events, the external electrode (outside of detector) is electrically partitioned. The instrumentation of these external segments and the consequence with respect to the spectrometer energy signal is examined.

  12. Binding of germanium of Pseudomonas putida cells

    SciTech Connect

    Klapcinska, B.; Chmielowski, J.

    1986-05-01

    The binding of germanium to Pseudomonas putida ATCC 33015 was investigated by using whole intact cells grown in a medium supplemented with GeO/sub 2/ and catechol or acetate. Electron-microscopic examination of the control and metal-loaded samples revealed that germanium was bound within the cell envelope. A certain number of small electron-dense deposits of the bound element were found in the cytoplasm when the cells were grown in the presence of GeO/sub 2/ and catechol. The study of germanium distribution in cellular fractions revealed that catechol facilitated the intracellular accumulation of this element.

  13. Patterning NHS-terminated SAMs on germanium.

    PubMed

    Morris, Carleen J; Shestopalov, Alexander A; Gold, Brian H; Clark, Robert L; Toone, Eric J

    2011-05-17

    Here we report a simple, robust approach to patterning functional SAMs on germanium. The protocol relies on catalytic soft-lithographic pattern transfer from an elastomeric stamp bearing pendant immobilized sulfonic acid moieties to an NHS-functionalized bilayer molecular system comprising a primary ordered alkyl monolayer and a reactive ester secondary overlayer. The catalytic polyurethane-acrylate stamp was used to form micrometer-scale features of chemically distinct SAMs on germanium. The methodology represents the first example of patterned SAMs on germanium, a semiconductor material.

  14. Electronic considerations for externally segmented germanium detectors

    NASA Technical Reports Server (NTRS)

    Madden, N. W.; Landis, D. A.; Goulding, F. S.; Pehl, R. H.; Cork, C. P.; Luke, P. N.; Malone, D. F.; Pollard, M. J.

    1991-01-01

    The dominant background source for germanium gamma ray detector spectrometers used for some astrophysics observations is internal beta decay. Externally segmented germanium gamma ray coaxial detectors can identify beta decay by localizing the event. Energetic gamma rays interact in the germanium detector by multiple Compton interactions while beta decay is a local process. In order to recognize the difference between gamma rays and beta decay events, the external electrode (outside of detector) is electrically partitioned. The instrumentation of these external segments and the consequence with respect to the spectrometer energy signal is examined.

  15. Silicon and Germanium Nanostructures for Photovoltaic Applications: Ab-Initio Results

    PubMed Central

    2010-01-01

    Actually, most of the electric energy is being produced by fossil fuels and great is the search for viable alternatives. The most appealing and promising technology is photovoltaics. It will become truly mainstream when its cost will be comparable to other energy sources. One way is to significantly enhance device efficiencies, for example by increasing the number of band gaps in multijunction solar cells or by favoring charge separation in the devices. This can be done by using cells based on nanostructured semiconductors. In this paper, we will present ab-initio results of the structural, electronic and optical properties of (1) silicon and germanium nanoparticles embedded in wide band gap materials and (2) mixed silicon-germanium nanowires. We show that theory can help in understanding the microscopic processes important for devices performances. In particular, we calculated for embedded Si and Ge nanoparticles the dependence of the absorption threshold on size and oxidation, the role of crystallinity and, in some cases, the recombination rates, and we demonstrated that in the case of mixed nanowires, those with a clear interface between Si and Ge show not only a reduced quantum confinement effect but display also a natural geometrical separation between electron and hole. PMID:21076696

  16. High Efficiency Germanium Immersion Gratings

    SciTech Connect

    Kuzmenko, P J; Davis, P J; Little, S L; Little, L M; Bixler, J V

    2006-05-01

    We have fabricated several germanium immersion gratings by single crystal, single point diamond flycutting on an ultra-precision lathe. Use of a dead sharp tool produces groove corners less than 0.1 micron in radius and consequently high diffraction efficiency. We measured first order efficiencies in immersion of over 80% at 10.6 micron wavelength. Wavefront error was low averaging 0.06 wave rms (at 633 nm) across the full aperture. The grating spectral response was free of ghosts down to our detection limit of 1 part in 10{sup 4}. Scatter should be low based upon the surface roughness. Measurement of the spectral line profile of a CO{sub 2} laser sets an upper bound on total integrated scatter of 0.5%.

  17. Germanium: giving microelectronics an efficiency boost

    USGS Publications Warehouse

    Mercer, Celestine N.

    2015-07-30

    Germanium is an essentially nontoxic element, with the exception of only a few compounds. However, if dissolved concentrations in drinking water are as high as one or more parts per million chronic diseases may occur.

  18. Tough germanium nanoparticles under electrochemical cycling.

    PubMed

    Liang, Wentao; Yang, Hui; Fan, Feifei; Liu, Yang; Liu, Xiao Hua; Huang, Jian Yu; Zhu, Ting; Zhang, Sulin

    2013-04-23

    Mechanical degradation of the electrode materials during electrochemical cycling remains a serious issue that critically limits the capacity retention and cyclability of rechargeable lithium-ion batteries. Here we report the highly reversible expansion and contraction of germanium nanoparticles under lithiation-delithiation cycling with in situ transmission electron microscopy (TEM). During multiple cycles to the full capacity, the germanium nanoparticles remained robust without any visible cracking despite ∼260% volume changes, in contrast to the size-dependent fracture of silicon nanoparticles upon the first lithiation. The comparative in situ TEM study of fragile silicon nanoparticles suggests that the tough behavior of germanium nanoparticles can be attributed to the weak anisotropy of the lithiation strain at the reaction front. The tough germanium nanoparticles offer substantial potential for the development of durable, high-capacity, and high-rate anodes for advanced lithium-ion batteries.

  19. Germanium Resistance Thermometer For Subkelvin Temperatures

    NASA Technical Reports Server (NTRS)

    Castles, Stephen H.

    1993-01-01

    Improved germanium resistance thermometer measures temperatures as small as 0.01 K accurately. Design provides large area for electrical connections (to reduce electrical gradients and increase sensitivity to changes in temperatures) and large heat sink (to minimize resistance heating). Gold pads on top and bottom of germanium crystal distribute electrical current and flow of heat nearly uniformly across crystal. Less expensive than magnetic thermometers or superconducting quantum interference devices (SQUID's) otherwise used.

  20. WIMP Searches at Canfranc with Germanium Detectors

    NASA Astrophysics Data System (ADS)

    Morales, Angel

    2001-04-01

    An overview of the searches for Weak Interacting Massive Particles (WIMPs) through their scattering off Germanium nuclei carried out in the Canfranc Tunnel Astroparticle Laboratory (at 2450 metres of water equivalent (m.w.e.)) in a collaboration between the Universities of South Carolina and Zaragoza is given. The main experimental results are sketched both for natural abundance (COSME) and 76Ge enriched (IGEX) Germanium detector experiments are summarized and a briefing on the GEDEON project is also presented.

  1. Germanium Resistance Thermometer For Subkelvin Temperatures

    NASA Technical Reports Server (NTRS)

    Castles, Stephen H.

    1993-01-01

    Improved germanium resistance thermometer measures temperatures as small as 0.01 K accurately. Design provides large area for electrical connections (to reduce electrical gradients and increase sensitivity to changes in temperatures) and large heat sink (to minimize resistance heating). Gold pads on top and bottom of germanium crystal distribute electrical current and flow of heat nearly uniformly across crystal. Less expensive than magnetic thermometers or superconducting quantum interference devices (SQUID's) otherwise used.

  2. Nanowire Optoelectronics

    NASA Astrophysics Data System (ADS)

    Wang, Zhihuan; Nabet, Bahram

    2015-12-01

    Semiconductor nanowires have been used in a variety of passive and active optoelectronic devices including waveguides, photodetectors, solar cells, light-emitting diodes (LEDs), lasers, sensors, and optical antennas. We review the optical properties of these nanowires in terms of absorption, guiding, and radiation of light, which may be termed light management. Analysis of the interaction of light with long cylindrical/hexagonal structures with subwavelength diameters identifies radial resonant modes, such as Leaky Mode Resonances, or Whispering Gallery modes. The two-dimensional treatment should incorporate axial variations in "volumetric modes,"which have so far been presented in terms of Fabry-Perot (FP), and helical resonance modes. We report on finite-difference timedomain (FDTD) simulations with the aim of identifying the dependence of these modes on geometry (length, width), tapering, shape (cylindrical, hexagonal), core-shell versus core-only, and dielectric cores with semiconductor shells. This demonstrates how nanowires (NWs) form excellent optical cavities without the need for top and bottommirrors. However, optically equivalent structures such as hexagonal and cylindrical wires can have very different optoelectronic properties meaning that light management alone does not sufficiently describe the observed enhancement in upward (absorption) and downward transitions (emission) of light inNWs; rather, the electronic transition rates should be considered. We discuss this "rate management" scheme showing its strong dimensional dependence, making a case for photonic integrated circuits (PICs) that can take advantage of the confluence of the desirable optical and electronic properties of these nanostructures.

  3. Inverting polar domains via electrical pulsing in metallic germanium telluride.

    PubMed

    Nukala, Pavan; Ren, Mingliang; Agarwal, Rahul; Berger, Jacob; Liu, Gerui; Johnson, A T Charlie; Agarwal, Ritesh

    2017-04-12

    Germanium telluride (GeTe) is both polar and metallic, an unusual combination of properties in any material system. The large concentration of free-carriers in GeTe precludes the coupling of external electric field with internal polarization, rendering it ineffective for conventional ferroelectric applications and polarization switching. Here we investigate alternate ways of coupling the polar domains in GeTe to external electrical stimuli through optical second harmonic generation polarimetry and in situ TEM electrical testing on single-crystalline GeTe nanowires. We show that anti-phase boundaries, created from current pulses (heat shocks), invert the polarization of selective domains resulting in reorganization of certain 71(o) domain boundaries into 109(o) boundaries. These boundaries subsequently interact and evolve with the partial dislocations, which migrate from domain to domain with the carrier-wind force (electrical current). This work suggests that current pulses and carrier-wind force could be external stimuli for domain engineering in ferroelectrics with significant current leakage.

  4. Inverting polar domains via electrical pulsing in metallic germanium telluride

    PubMed Central

    Nukala, Pavan; Ren, Mingliang; Agarwal, Rahul; Berger, Jacob; Liu, Gerui; Johnson, A. T. Charlie; Agarwal, Ritesh

    2017-01-01

    Germanium telluride (GeTe) is both polar and metallic, an unusual combination of properties in any material system. The large concentration of free-carriers in GeTe precludes the coupling of external electric field with internal polarization, rendering it ineffective for conventional ferroelectric applications and polarization switching. Here we investigate alternate ways of coupling the polar domains in GeTe to external electrical stimuli through optical second harmonic generation polarimetry and in situ TEM electrical testing on single-crystalline GeTe nanowires. We show that anti-phase boundaries, created from current pulses (heat shocks), invert the polarization of selective domains resulting in reorganization of certain 71o domain boundaries into 109o boundaries. These boundaries subsequently interact and evolve with the partial dislocations, which migrate from domain to domain with the carrier-wind force (electrical current). This work suggests that current pulses and carrier-wind force could be external stimuli for domain engineering in ferroelectrics with significant current leakage. PMID:28401949

  5. Inverting polar domains via electrical pulsing in metallic germanium telluride

    NASA Astrophysics Data System (ADS)

    Nukala, Pavan; Ren, Mingliang; Agarwal, Rahul; Berger, Jacob; Liu, Gerui; Johnson, A. T. Charlie; Agarwal, Ritesh

    2017-04-01

    Germanium telluride (GeTe) is both polar and metallic, an unusual combination of properties in any material system. The large concentration of free-carriers in GeTe precludes the coupling of external electric field with internal polarization, rendering it ineffective for conventional ferroelectric applications and polarization switching. Here we investigate alternate ways of coupling the polar domains in GeTe to external electrical stimuli through optical second harmonic generation polarimetry and in situ TEM electrical testing on single-crystalline GeTe nanowires. We show that anti-phase boundaries, created from current pulses (heat shocks), invert the polarization of selective domains resulting in reorganization of certain 71o domain boundaries into 109o boundaries. These boundaries subsequently interact and evolve with the partial dislocations, which migrate from domain to domain with the carrier-wind force (electrical current). This work suggests that current pulses and carrier-wind force could be external stimuli for domain engineering in ferroelectrics with significant current leakage.

  6. Germanium-silicon solid solutions

    NASA Technical Reports Server (NTRS)

    Zemskov, V. S.; Kubasov, V. N.; Belokurova, I. N.; Titkov, A. N.; Shulpina, I. L.; Safarov, V. I.; Guseva, N. B.

    1977-01-01

    An experiment on melting and directional crystallization of an antimony (Sb) doped germanium silicon (GeSi) solid solution was designed for the Apollo-Soyuz Test Project (ASTP) to study the possibility of using zero-g conditions for obtaining solid-solution monocrystals with uniformly distributed components. Crystallization in the zero-g environment did not occur under ideal stationary growth and segregation conditions. Crystallization under zero-g conditions revealed the heterogeneous nature of Si and Sb distribution in the cross sections of crystals. The presence of the radial thermal gradient in the multipurpose furnace could be one of the reasons for such Si and Sb distribution. The structure of space-grown crystals correlates with the nature of heterogeneities of Si and Sb distribution in crystals. The type of surface morphology and the contour observed in space-grown crystals were never observed in ground-based crystals and indicate the absence of wetting of the graphitized walls of the ampoule by the melt during melting and crystallization.

  7. Germanium anode with excellent lithium storage performance in a germanium/lithium-cobalt oxide lithium-ion battery.

    PubMed

    Li, Xiuwan; Yang, Zhibo; Fu, Yujun; Qiao, Li; Li, Dan; Yue, Hongwei; He, Deyan

    2015-02-24

    Germanium is a highly promising anode material for lithium-ion batteries as a consequence of its large theoretical specific capacity, good electrical conductivity, and fast lithium ion diffusivity. In this work, Co3O4 nanowire array fabricated on nickel foam was designed as a nanostructured current collector for Ge anode. By limiting the voltage cutoff window in an appropriate range, the obtained Ge anode exhibits excellent lithium storage performance in half- and full-cells, which can be mainly attributed to the designed nanostructured current collector with good conductivity, enough buffering space for the volume change, and shortened ionic transport length. More importantly, the assembled Ge/LiCoO2 full-cell shows a high energy density of 475 Wh/kg and a high power density of 6587 W/kg. A high capacity of 1184 mA h g(-1) for Ge anode was maintained at a current density of 5000 mA g(-1) after 150 cycles.

  8. Silicon-germanium photodetectors for optical telecommunications

    NASA Astrophysics Data System (ADS)

    Ali, Dyan

    This thesis investigates the design and growth of silicon-germanium p-i-n photodetectors for optical telecommunications applications. Two types of heterostructures are considered: strained silicon-germanium layers grown directly on silicon substrates, and strain-balanced silicon-germanium/silicon superlattice grown on relaxed buffer layers. The heterostructures are designed using existing band structure models and are grown using solid source molecular beam epitaxy (SS-MBE). To facilitate these growths, an atomic absorption spectroscopy- based flux monitor for the silicon source is developed and calibrated. In addition, the development of a substrate preparation procedure for relaxed buffer layers that is compatible with SS-MBE is developed and allows the growth of epitaxial films with low defect densities. P-i-n diodes processed from these films are shown to have low reverse leakage currents densities compared to other competing devices. Photocurrent spectroscopy is used to characterize these structures. A clear reduction in the bandgap of the heterostructures over that of the constituent alloys due to exploitation of the Type-II band offsets in the silicon-germanium material system is demonstrated in both, the strained and strain-balanced photodetectors. Finally, the low leakage current densities are exploited to fabricate devices with noise equivalent powers comparable to or better than competing approaches based on the growth of germanium on silicon substrates.

  9. Recovery of germanium-68 from irradiated targets

    DOEpatents

    Phillips, Dennis R.; Jamriska, Sr., David J.; Hamilton, Virginia T.

    1993-01-01

    A process for selective separation of germanium-68 from proton irradiated molybdenum targets is provided and includes dissolving the molybdenum target in a hydrogen peroxide solution to form a first ion-containing solution, contacting the first ion-containing solution with a cationic resin whereby ions selected from the group consisting of molybdenum, niobium, technetium, selenium, vanadium, arsenic, germanium, zirconium and rubidium remain in a second ion-containing solution while ions selected from the group consisting of rubidium, zinc, beryllium, cobalt, iron, manganese, chromium, strontium, yttrium and zirconium are selectively adsorbed by the first resin, adjusting the pH of the second ion-containing solution to within a range of from about 0.7 to about 3.0, adjusting the soluble metal halide concentration in the second ion-containing solution to a level adapted for subsequent separation of germanium, contacting the pH-adjusted, soluble metal halide-containing second ion-containing solution with a dextran-based material whereby germanium ions are separated by the dextran-based material, and recovering the germanium from the dextran-based material, preferably by distillation.

  10. Quasiballistic quantum transport through Ge/Si core/shell nanowires

    NASA Astrophysics Data System (ADS)

    Kotekar-Patil, D.; Nguyen, B.-M.; Yoo, J.; Dayeh, S. A.; Frolov, S. M.

    2017-09-01

    We study signatures of ballistic quantum transport of holes through Ge/Si core/shell nanowires at low temperatures. We observe Fabry–Pérot interference patterns as well as conductance plateaus at integer multiples of 2e 2/h at zero magnetic field. Magnetic field evolution of these plateaus reveals relatively large effective Landé g-factors. Ballistic effects are observed in nanowires with silicon shell thickness of 1–3 nm, but not in bare germanium wires. These findings inform the future development of spin and topological quantum devices which rely on ballistic sub-band-resolved transport.

  11. Quasiballistic quantum transport through Ge/Si core/shell nanowires.

    PubMed

    Kotekar-Patil, D; Nguyen, B-M; Yoo, J; Dayeh, S A; Frolov, S M

    2017-09-20

    We study signatures of ballistic quantum transport of holes through Ge/Si core/shell nanowires at low temperatures. We observe Fabry-Pérot interference patterns as well as conductance plateaus at integer multiples of 2e (2)/h at zero magnetic field. Magnetic field evolution of these plateaus reveals relatively large effective Landé g-factors. Ballistic effects are observed in nanowires with silicon shell thickness of 1-3 nm, but not in bare germanium wires. These findings inform the future development of spin and topological quantum devices which rely on ballistic sub-band-resolved transport.

  12. Sn-induced low-temperature growth of Ge nanowire electrodes with a large lithium storage capacity

    NASA Astrophysics Data System (ADS)

    Ko, Young-Dae; Kang, Jin-Gu; Lee, Gwang-Hee; Park, Jae-Gwan; Park, Kyung-Soo; Jin, Yun-Ho; Kim, Dong-Wan

    2011-08-01

    We herein present the synthesis of germanium (Ge) nanowires on Au-catalyzed low-temperature substrates using a simple thermal Ge/Sn co-evaporation method. Incorporation of a low-melting point metal (Sn) enables the efficient delivery of Ge vapor to the substrate, even at a source temperature below 600 °C. The as-synthesized nanowires were found to be a core/shell heterostructure, exhibiting a uniform single crystalline Ge sheathed within a thin amorphous germanium suboxide (GeOx) layer. Furthermore, these high-density Ge nanowires grown directly on metal current collectors can offer good electrical connection and easy strain relaxation due to huge volume expansion during Li ion insertion/extraction. Therefore, the self-supported Ge nanowire electrodes provided excellent large capacity with little fading upon cycling (a capacity of ~900 mA h g-1 at 1C rate).We herein present the synthesis of germanium (Ge) nanowires on Au-catalyzed low-temperature substrates using a simple thermal Ge/Sn co-evaporation method. Incorporation of a low-melting point metal (Sn) enables the efficient delivery of Ge vapor to the substrate, even at a source temperature below 600 °C. The as-synthesized nanowires were found to be a core/shell heterostructure, exhibiting a uniform single crystalline Ge sheathed within a thin amorphous germanium suboxide (GeOx) layer. Furthermore, these high-density Ge nanowires grown directly on metal current collectors can offer good electrical connection and easy strain relaxation due to huge volume expansion during Li ion insertion/extraction. Therefore, the self-supported Ge nanowire electrodes provided excellent large capacity with little fading upon cycling (a capacity of ~900 mA h g-1 at 1C rate). Electronic supplementary information (ESI) available: Binary phase diagram of Ge-Sn, SEM images of Ge nanowires grown at various source temperatures, typical TEM image and EDS intensity profile of Ge nanowires, HAADF STEM image and EDS intensity profile of

  13. Extrinsic germanium Blocked Impurity Bank (BIB) detectors

    NASA Technical Reports Server (NTRS)

    Krabach, Timothy N.; Huffman, James E.; Watson, Dan M.

    1989-01-01

    Ge:Ga blocked-impurity-band (BIB) detectors with long wavelength thresholds greater than 190 microns and peak quantum efficiencies of 4 percent, at an operating temperature of 1.8 K, have been fabricated. These proof of concept devices consist of a high purity germanium blocking layer epitaxially grown on a Ga-doped Ge substrate. This demonstration of BIB behavior in germanium enables the development of far infrared detector arrays similar to the current silicon-based devices. Present efforts are focussed on improving the chemical vapor deposition process used to create the blocking layer and on the lithographic processing required to produce monolithic detector arrays in germanium. Approaches to test the impurity levels in both the blocking and active layers are considered.

  14. Front End Spectroscopy ASIC for Germanium Detectors

    NASA Astrophysics Data System (ADS)

    Wulf, Eric

    Large-area, tracking, semiconductor detectors with excellent spatial and spectral resolution enable exciting new access to soft (0.2-5 MeV) gamma-ray astrophysics. The improvements from semiconductor tracking detectors come with the burden of high density of strips and/or pixels that require high-density, low-power, spectroscopy quality readout electronics. CMOS ASIC technologies are a natural fit to this requirement and have led to high-quality readout systems for all current semiconducting tracking detectors except for germanium detectors. The Compton Spectrometer and Imager (COSI), formerly NCT, at University of California Berkeley and the Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS) at Goddard Space Flight Center utilize germanium cross-strip detectors and are on the forefront of NASA's Compton telescope research with funded missions of long duration balloon flights. The development of a readout ASIC for germanium detectors would allow COSI to replace their discrete electronics readout and would enable the proposed Gamma-Ray Explorer (GRX) mission utilizing germanium strip-detectors. We propose a 3-year program to develop and test a germanium readout ASIC to TRL 5 and to integrate the ASIC readout onto a COSI detector allowing a TRL 6 demonstration for the following COSI balloon flight. Our group at NRL led a program, sponsored by another government agency, to produce and integrate a cross-strip silicon detector ASIC, designed and fabricated by Dr. De Geronimo at Brookhaven National Laboratory. The ASIC was designed to handle the large (>30 pF) capacitance of three 10 cm^2 detectors daisy-chained together. The front-end preamplifier, selectable inverter, shaping times, and gains make this ASIC compatible with a germanium cross-strip detector as well. We therefore have the opportunity and expertise to leverage the previous investment in the silicon ASIC for a new mission. A germanium strip detector ASIC will also require precise timing of the signals at

  15. Gamma-ray imaging with germanium detectors

    NASA Astrophysics Data System (ADS)

    Mahoney, W. A.; Callas, J. L.; Ling, J. C.; Radocinski, R. G.; Skelton, R. T.; Varnell, L. S.; Wheaton, W. A.

    1993-01-01

    Externally segmented germanium detectors promise a breakthrough in gamma-ray imaging capabilities while retaining the superb energy resolution of germanium spectrometers. By combining existing position-sensitive detectors with an appropriate code aperture, two-dimensional imaging with 0.2-deg angular resolution becomes practical for a typical balloon experiment. Much finer resolutions are possible with larger separations between detectors and the coded aperture as would be applicable for space-based or lunar-based observatories. Two coaxial germanium detectors divided into five external segments have been fabricated and have undergone extensive performance evaluation and imaging testing in our laboratory. These tests together with detailed Monte Carlo modeling calculations have demonstrated the great promise of this sensor technology for future gamma-ray missions.

  16. Gamma-ray imaging with germanium detectors

    NASA Technical Reports Server (NTRS)

    Mahoney, W. A.; Callas, J. L.; Ling, J. C.; Radocinski, R. G.; Skelton, R. T.; Varnell, L. S.; Wheaton, W. A.

    1993-01-01

    Externally segmented germanium detectors promise a breakthrough in gamma-ray imaging capabilities while retaining the superb energy resolution of germanium spectrometers. By combining existing position-sensitive detectors with an appropriate code aperture, two-dimensional imaging with 0.2-deg angular resolution becomes practical for a typical balloon experiment. Much finer resolutions are possible with larger separations between detectors and the coded aperture as would be applicable for space-based or lunar-based observatories. Two coaxial germanium detectors divided into five external segments have been fabricated and have undergone extensive performance evaluation and imaging testing in our laboratory. These tests together with detailed Monte Carlo modeling calculations have demonstrated the great promise of this sensor technology for future gamma-ray missions.

  17. Chalcogenide and germanium hybrid optics

    NASA Astrophysics Data System (ADS)

    Cogburn, Gabriel

    2011-11-01

    When choosing a material to design infrared optics, an optical designer has to decide which material properties are most important to what they are trying to achieve. Factors include; cost, optical performance, index of material, sensor format, manufacturability, mechanical mounting and others. This paper will present an optical design that is made for a 640×480, 17μm sensor and is athermalized by using the material properties of chalcogenide glass and Germanium (Ge). The optical design will be a 3-element, f1.0 optic with an EFL of 20mm at 10μm. It consists of two Ge spherical lenses and a middle chalcogenide aspheric element. By using Ge and chalcogenide, this design utilizes the high index of Ge and combines it with the lower dn/dt of chalcogenide glass to provide an athermalized design without the use of additional electro-optical compensation inside the assembly. This study will start from the optical design process and explain the mechanical and optical properties of the design, then show the manufacturing process of molding an aspheric chalcogenide element. After the three elements are manufactured, they will be assembled and tested throughout the temperature range of -40 to 85°C to compare optical performance to design expectations. Ultimately, this paper will show that a high performance, athermalized optical assembly is possible to manufacture at a lower cost with the use of combining different infrared materials that allow for spherical Ge lenses and only one aspherical chalcogenide element which can be produced in higher volumes at lower costs through glass molding technology.

  18. Germanium-overcoated niobium Dayem bridges

    NASA Technical Reports Server (NTRS)

    Holdeman, L. B.; Peters, P. N.

    1976-01-01

    Overcoating constriction microbridges with semiconducting germanium provides additional thermal conductivity at liquid-helium temperatures to reduce the effects of self-heating in these Josephson junctions. Microwave-induced steps were observed in the I-V characteristics of an overcoated Dayem bridge fabricated in a 15-nm-thick niobium film; at least 20 steps could be counted at 4.2 K. No steps were observed in the I-V characteristics of the bridge prior to overcoating. In addition, the germanium overcoat can protect against electrical disturbances at room temperature.

  19. Silicon and germanium nanocrystals: properties and characterization

    PubMed Central

    Carvalho, Alexandra; Coutinho, José

    2014-01-01

    Summary Group-IV nanocrystals have emerged as a promising group of materials that extends the realm of application of bulk diamond, silicon, germanium and related materials beyond their traditional boundaries. Over the last two decades of research, their potential for application in areas such as optoelectronic applications and memory devices has been progressively unraveled. Nevertheless, new challenges with no parallel in the respective bulk material counterparts have arisen. In this review, we consider what has been achieved and what are the current limitations with regard to growth, characterization and modeling of silicon and germanium nanocrystals and related materials. PMID:25383290

  20. Atomic scale dynamics of ultrasmall germanium clusters.

    PubMed

    Bals, S; Van Aert, S; Romero, C P; Lauwaet, K; Van Bael, M J; Schoeters, B; Partoens, B; Yücelen, E; Lievens, P; Van Tendeloo, G

    2012-06-12

    Starting from the gas phase, small clusters can be produced and deposited with huge flexibility with regard to composition, materials choice and cluster size. Despite many advances in experimental characterization, a detailed morphology of such clusters is still lacking. Here we present an atomic scale observation as well as the dynamical behaviour of ultrasmall germanium clusters. Using quantitative scanning transmission electron microscopy in combination with ab initio calculations, we are able to characterize the transition between different equilibrium geometries of a germanium cluster consisting of less than 25 atoms. Seven-membered rings, trigonal prisms and some smaller subunits are identified as possible building blocks that stabilize the structure.

  1. Atomic scale dynamics of ultrasmall germanium clusters

    PubMed Central

    Bals, S.; Van Aert, S.; Romero, C.P.; Lauwaet, K.; Van Bael, M.J.; Schoeters, B.; Partoens, B.; Yücelen, E.; Lievens, P.; Van Tendeloo, G.

    2012-01-01

    Starting from the gas phase, small clusters can be produced and deposited with huge flexibility with regard to composition, materials choice and cluster size. Despite many advances in experimental characterization, a detailed morphology of such clusters is still lacking. Here we present an atomic scale observation as well as the dynamical behaviour of ultrasmall germanium clusters. Using quantitative scanning transmission electron microscopy in combination with ab initio calculations, we are able to characterize the transition between different equilibrium geometries of a germanium cluster consisting of less than 25 atoms. Seven-membered rings, trigonal prisms and some smaller subunits are identified as possible building blocks that stabilize the structure. PMID:22692540

  2. Neutron-transmutation-doped germanium bolometers

    NASA Technical Reports Server (NTRS)

    Palaio, N. P.; Rodder, M.; Haller, E. E.; Kreysa, E.

    1983-01-01

    Six slices of ultra-pure germanium were irradiated with thermal neutron fluences between 7.5 x 10 to the 16th and 1.88 x 10 to the 18th per sq cm. After thermal annealing the resistivity was measured down to low temperatures (less than 4.2 K) and found to follow the relationship rho = rho sub 0 exp(Delta/T) in the hopping conduction regime. Also, several junction FETs were tested for noise performance at room temperature and in an insulating housing in a 4.2 K cryostat. These FETs will be used as first stage amplifiers for neutron-transmutation-doped germanium bolometers.

  3. Germanium-overcoated niobium Dayem bridges

    NASA Technical Reports Server (NTRS)

    Holdeman, L. B.; Peters, P. N.

    1976-01-01

    Overcoating constriction microbridges with semiconducting germanium provides additional thermal conductivity at liquid-helium temperatures to reduce the effects of self-heating in these Josephson junctions. Microwave-induced steps were observed in the I-V characteristics of an overcoated Dayem bridge fabricated in a 15-nm-thick niobium film; at least 20 steps could be counted at 4.2 K. No steps were observed in the I-V characteristics of the bridge prior to overcoating. In addition, the germanium overcoat can protect against electrical disturbances at room temperature.

  4. Silver nano-inukshuks on germanium.

    PubMed

    Aizawa, Masato; Cooper, Anne M; Malac, Marek; Buriak, Jillian M

    2005-05-01

    The integration of metallic nanostructures with semiconductors is important for a variety of technological applications. Through an efficient galvanic displacement reaction on germanium, complex silver nanostructures form spontaneously in aqueous conditions at room temperature. The structures, termed nano-inukshuks, are based on stacks of hexagonal metallic structures that grow, initially, parallel to the surface normal of the germanium. TEM, SEM, XPS, XRD, and EDS indicate that the structures are crystalline silver and, based on open cell potential studies, that their nucleation takes place in the first 100 s, followed by growth of the silver structures, most likely through Volmer-Weber growth.

  5. Nanowire-based detector

    DOEpatents

    Berggren, Karl K; Hu, Xiaolong; Masciarelli, Daniele

    2014-06-24

    Systems, articles, and methods are provided related to nanowire-based detectors, which can be used for light detection in, for example, single-photon detectors. In one aspect, a variety of detectors are provided, for example one including an electrically superconductive nanowire or nanowires constructed and arranged to interact with photons to produce a detectable signal. In another aspect, fabrication methods are provided, including techniques to precisely reproduce patterns in subsequently formed layers of material using a relatively small number of fabrication steps. By precisely reproducing patterns in multiple material layers, one can form electrically insulating materials and electrically conductive materials in shapes such that incoming photons are redirected toward a nearby electrically superconductive materials (e.g., electrically superconductive nanowire(s)). For example, one or more resonance structures (e.g., comprising an electrically insulating material), which can trap electromagnetic radiation within its boundaries, can be positioned proximate the nanowire(s). The resonance structure can include, at its boundaries, electrically conductive material positioned proximate the electrically superconductive nanowire such that light that would otherwise be transmitted through the sensor is redirected toward the nanowire(s) and detected. In addition, electrically conductive material can be positioned proximate the electrically superconductive nanowire (e.g. at the aperture of the resonant structure), such that light is directed by scattering from this structure into the nanowire.

  6. High Duty Cycle Germanium Lasers and Continuous Terahertz Emission from Germanium

    DTIC Science & Technology

    2000-09-29

    which allows one to construct crystal volume. The set of three lines relatively arbitrary shapes because the generated photons corresponds to an...measured laser emission from contacts of the lasers. However, the heat conductivity of beryllium-doped germanium crystals with small inter- this...conventional, continuously excited beryllium-doped germanium crystals with a volume of 0.5 mm 3 . Experimental and theoretical investigations of Table 1

  7. Novel metastable metallic and semiconducting germaniums.

    PubMed

    Selli, Daniele; Baburin, Igor A; Martoňák, Roman; Leoni, Stefano

    2013-01-01

    Group-IVa elements silicon and germanium are known for their semiconducting properties at room temperature, which are technologically critical. Metallicity and superconductivity are found at higher pressures only, Ge β-tin (tI4) being the first high-pressure metallic phase in the phase diagram. However, recent experiments suggest that metallicity in germanium is compatible with room conditions, calling for a rethinking of our understanding of its phase diagram. Missing structures can efficiently be identified based on structure prediction methods. By means of ab initio metadynamics runs we explored the lower-pressure region of the phase diagram of germanium. A monoclinic germanium phase (mC16) with four-membered rings, less dense than diamond and compressible into β-tin phase (tI4) was found. Tetragonal bct-5 appeared between diamond and tI4. mC16 is a narrow-gap semiconductor, while bct-5 is metallic and potentially still superconducting in the very low pressure range. This finding may help resolving outstanding experimental issues.

  8. Electron tunnelling into amorphous germanium and silicon.

    NASA Technical Reports Server (NTRS)

    Smith, C. W.; Clark, A. H.

    1972-01-01

    Measurements of tunnel conductance versus bias, capacitance versus bias, and internal photoemission were made in the systems aluminum-oxide-amorphous germanium and aluminium-oxide-amorphous silicon. A function was extracted which expresses the deviation of these systems from the aluminium-oxide-aluminium system.

  9. Improving CMOS-compatible Germanium photodetectors.

    PubMed

    Li, Guoliang; Luo, Ying; Zheng, Xuezhe; Masini, Gianlorenzo; Mekis, Attila; Sahni, Subal; Thacker, Hiren; Yao, Jin; Shubin, Ivan; Raj, Kannan; Cunningham, John E; Krishnamoorthy, Ashok V

    2012-11-19

    We report design improvements for evanescently coupled Germanium photodetectors grown at low temperature. The resulting photodetectors with 10 μm Ge length manufactured in a commercial CMOS process achieve >0.8 A/W responsivity over the entire C-band, with a device capacitance of <7 fF based on measured data.

  10. Germanium JFET for Cryogenic Readout Electronics

    NASA Technical Reports Server (NTRS)

    Das, N. C.; Monroy, C.; Jhabvala, M.; Shu, P.

    1999-01-01

    The n-channel Germanium junction field effect transistor (Ge-JFET) was designed and fabricated for cryogenic applications. The Ge-JFET exhibits superior noise performance at liquid nitrogen temperature (77 K). From the device current voltage characteristics of n-channel JFETs, it is seen that transconductance increases monotonically with the lowering of temperature to 4.2 K (liquid helium temperature).

  11. Novel metastable metallic and semiconducting germaniums

    PubMed Central

    Selli, Daniele; Baburin, Igor A.; Martoňák, Roman; Leoni, Stefano

    2013-01-01

    Group-IVa elements silicon and germanium are known for their semiconducting properties at room temperature, which are technologically critical. Metallicity and superconductivity are found at higher pressures only, Ge β-tin (tI4) being the first high-pressure metallic phase in the phase diagram. However, recent experiments suggest that metallicity in germanium is compatible with room conditions, calling for a rethinking of our understanding of its phase diagram. Missing structures can efficiently be identified based on structure prediction methods. By means of ab initio metadynamics runs we explored the lower-pressure region of the phase diagram of germanium. A monoclinic germanium phase (mC16) with four-membered rings, less dense than diamond and compressible into β-tin phase (tI4) was found. Tetragonal bct-5 appeared between diamond and tI4. mC16 is a narrow-gap semiconductor, while bct-5 is metallic and potentially still superconducting in the very low pressure range. This finding may help resolving outstanding experimental issues. PMID:23492980

  12. Fabrication of multilayer nanowires

    SciTech Connect

    Kaur, Jasveer Singh, Avtar; Kumar, Davinder; Thakur, Anup; Kaur, Raminder

    2016-05-06

    Multilayer nanowires were fabricated by potentiostate ectrodeposition template synthesis method into the pores of polycarbonate membrane. In present work layer by layer deposition of two different metals Ni and Cu in polycarbonate membrane having pore size of 600 nm were carried out. It is found that the growth of nanowires is not constant, it varies with deposition time. Scanning electron microscopy (SEM) is used to study the morphology of fabricated multilayer nanowires. An energy dispersive X-ray spectroscopy (EDS) results confirm the composition of multilayer nanowires. The result shows that multilayer nanowires formed is dense.

  13. Germanium as a Sodium Ion Battery Material: In Situ TEM Reveals Fast Sodiation Kinetics with High Capacity

    SciTech Connect

    Lu, Xiaotang; Adkins, Emily R.; He, Yang; Zhong, Li; Luo, Langli; Mao, Scott X.; Wang, Chong M.; Korgel, Brian A.

    2016-01-29

    Amorphous germanium (a-Ge) nanowires have great potential for application as anodes in Na-ion batteries. However, the Na-Ge reaction is much less studied and understood compared with other metal alloy anodes. Here, in situ transmission electron microscopy (TEM) is used to study the sodiation/desodiation behavior of a-Ge nanowires. Unexpectedly, our experiments revealed that a-Ge nanowires can be charged at a very fast rate and the final sodiation product, with over 300% volume expansion, is close to Na3Ge instead of NaGe which was considered as the ultimate sodiation state that Ge could achieve. Porous structure was observed in desodiation and, in contrast to delithiation, Na extraction is more likely to create pores in the nanowires due to the much larger radius of the Na ion. This porous structure has demonstrated excellent robustness upon cycling: it could recover flawlessly from the giant pores that were created during experimentation. These results show that the potential of a-Ge for Na-ion battery applications may have been previously underestimated.

  14. Spin-Charge Conversion Phenomena in Germanium

    NASA Astrophysics Data System (ADS)

    Oyarzún, Simón; Rortais, Fabien; Rojas-Sánchez, Juan-Carlos; Bottegoni, Federico; Laczkowski, Piotr; Vergnaud, Céline; Pouget, Stéphanie; Okuno, Hanako; Vila, Laurent; Attané, Jean-Philippe; Beigné, Cyrille; Marty, Alain; Gambarelli, Serge; Ducruet, Clarisse; Widiez, Julie; George, Jean-Marie; Jaffrès, Henri; Jamet, Matthieu

    2017-01-01

    The spin-orbit coupling relating the electron spin and momentum allows for spin generation, detection and manipulation. It thus fulfils the three basic functions of the spin field-effect-transistor made of semiconductors. In this paper, we review our recent results on spin-charge conversion in bulk germanium and at the Ge(111) surface. We used the spin pumping technique to generate pure spin currents to be injected into bulk germanium and at the Fe/Ge(111) interface. The mechanism for spin-charge conversion in bulk germanium is the spin Hall effect and we could experimentally determine the spin Hall angle θSHE, i.e., the spin-charge conversion efficiency, in heavily doped n-type and p-type germanium. We found very small values at room temperature: θSHE ≈ (1-2) × 10-3 in n-Ge and θSHE ≈ (6-7) × 10-4 in p-Ge. Moreover, we pointed out the essential role of spin dependent scattering on ionized impurities in the spin Hall effect mechanism. We concluded that the spin Hall effect in bulk germanium is too weak to produce large spin currents, whereas a large Rashba effect (>100 meV) at Ge(111) surfaces covered with heavy metals could generate spin polarized currents. We could indeed demonstrate a giant spin-to-charge conversion in metallic states at the Fe/Ge(111) interface due to the Rashba coupling. We generated very large charge currents by direct spin pumping into the interface states from 20 K to room temperature. By this, we raise a new paradigm: the possibility to use the spin-orbit coupling for the development of the spin-field-effect-transistor.

  15. Multiphase separation of copper nanowires.

    PubMed

    Qian, Fang; Lan, Pui Ching; Olson, Tammy; Zhu, Cheng; Duoss, Eric B; Spadaccini, Christopher M; Han, T Yong-Jin

    2016-09-22

    This communication reports a new method to purify copper nanowires with nearly 100% yield from undesired copper nanoparticle side-products formed during batch processes of copper nanowire synthesis. This simple separation method can yield large quantities of long, uniform, high-purity copper nanowires to meet the requirements of nanoelectronics applications as well as provide an avenue for purifying copper nanowires in the industrial scale synthesis of copper nanowires, a key step for commercialization and application of nanowires.

  16. Multiphase separation of copper nanowires

    DOE PAGES

    Qian, Fang; Lan, Pui Ching; Olson, Tammy; ...

    2016-01-01

    This communication reports a new method to purify copper nanowires with nearly 100% yield from undesired copper nanoparticle side-products formed during batch processes of copper nanowire synthesis. This simple separation method can yield large quantities of long, uniform, high-purity copper nanowires to meet the requirements of nanoelectronics applications as well as provide an avenue for purifying copper nanowires in the industrial scale synthesis of copper nanowires, a key step for commercialization and application of nanowires.

  17. Multiphase separation of copper nanowires

    SciTech Connect

    Qian, Fang; Lan, Pui Ching; Olson, Tammy; Zhu, Cheng; Duoss, Eric B.; Spadaccini, Christopher M.; Han, T. Yong-Jin

    2016-09-01

    Here, this communication reports a new method to purify copper nanowires with nearly 100% yield from undesired copper nanoparticle side-products formed during batch processes of copper nanowire synthesis. Also, this simple separation method can yield large quantities of long, uniform, high-purity copper nanowires to meet the requirements of nanoelectronics applications as well as provide an avenue for purifying copper nanowires in the industrial scale synthesis of copper nanowires, a key step for commercialization and application of nanowires.

  18. Comparison of organic and inorganic germanium compounds in cellular radiosensitivity and preparation of germanium nanoparticles as a radiosensitizer.

    PubMed

    Lin, Ming-Hsing; Hsu, Tzu-Sheng; Yang, Pei-Ming; Tsai, Meng-Yen; Perng, Tsong-Pyng; Lin, Lih-Yuan

    2009-03-01

    The aim of this work is to compare the radiosensitizing effect between organic and inorganic germanium compounds and to investigate whether nanometer-sized germanium particles can act as radiosensitizers. Bis (2-carboxyethylgermanium) sesquioxide (Ge-132), germanium oxide (GeO(2)) and germanium nanoparticles were used in this study. Cell viability was determined by clonogenic survival assay. Cellular DNA damage was evaluated by alkaline comet assay, confocal microscopy and the cellular level of phospho-histone H2AX (gamma-H2AX). Nanometer-sized germanium particles were fabricated. They have a similar radiosensitizing effect as that of GeO(2). Conversely, Ge-132 did not enhance the radiosensitivity of cells. Comet assay was employed to evaluate the level of DNA damage and confirmed that inorganic germanium compounds enhanced cellular radiosensitivity. Notably, the comet assay indicated that the nanoparticle itself caused a higher level of DNA damage. The possibility that germanium nanoparticles per se caused DNA damage was ruled out when the cellular level of gamma-H2AX was examined. We demonstrated that inorganic but not organic germanium compounds exerted radiosensitizing effect in cells. Nanometer-sized germanium particles were fabricated and were able to enhance the radiosensitivity of cells. Confounding effect may occur when comet assay is used to estimate the level of DNA damage in the presence of germanium nanoparticles.

  19. Germanium Metal - Insulator - Semiconductor Field Effect Transistors Utilizing a Germanium Nitride Gate Insulator.

    NASA Astrophysics Data System (ADS)

    Rosenberg, James Jordan

    The work presented in this thesis provides new information on three distinct but related topics. Firstly, it describes a technique for growing thin films of germanium nitride on germanium--a previously unexplored semiconductor -insulator system. Secondly, it describes electrical measurements made on metal-Ge(,3)N(,4)-Ge capacitors which demonstrate that this metal-insulator-semiconductor (MIS) system is of high quality. Thirdly, it describes a process by which n-channel germanium metal-insulator-semiconductor field effect transistors (MISFETs) have been fabricated. The motivations for exploring this new MIS system (e.g. basic physics of germanium inversion layers, higher performance MISFETs, etc.) are also described. The growth technique described here and the films produced by it possess several distinct advantages over previous methods of obtaining insulating films on germanium. The growth technique itself is simple. It involves no elaborate or expensive equipment, and is essentially identical in its execution (although not in its chemical process) to conventional techniques for obtaining an insulator on silicon (i.e. thermal oxidation of silicon). The film growth technique yields very reproducible results (in terms of film thickness and refractive index) from wafer to wafer. The physical properties of the film itself are also attractive. It is far more chemically stable than germanium oxide, and is quite process compatible. It is resistant to many chemicals encountered in typical processing cycles, but also can be readily patterned in hot phosphoric acid, which does not appreciably attack germanium. Electrical measurements on MIS capacitors indicate that the density of fast states at the germanium-germanium nitride interface is quite low. The interface state density is less than or equal to 1 x 10('11)/cm('2)-eV from midgap to within 0.15 eV of the conduction band edge, as determined by variable frequency capacitance measurements. The MISFETs fabricated for this

  20. A simple route to the synthesis of single crystalline copper metagermanate nanowires

    SciTech Connect

    Pei, L.Z.; Zhao, H.S.; Tan, W.; Yu, H.Y.; Chen, Y.W.; Zhang Qianfeng; Fan, C.G.

    2009-12-15

    Single crystalline copper metagermanate (CuGeO{sub 3}) nanowires with the diameter of 30-300 nm and length of longer than 100 {mu}m have been prepared by a simple hydrothermal deposition route. X-ray diffraction (XRD), selected area electron diffraction (SAED), high-resolution transmission electron microscopy (HRTEM) and Raman analyses confirm that the nanowires are orthorhombic single crystals with a main growth direction along <101>. Room temperature photoluminescence (PL) measurement shows a strong blue emission peak at 442 nm with a broad emission band. The blue emission may be ascribed to radiative recombination of oxygen vacancies and oxygen-germanium vacancies. The formation process of CuGeO{sub 3} nanowires is also discussed.

  1. Optical Detection Properties of Silicon-Germanium Quantum Well Structures

    DTIC Science & Technology

    1996-10-18

    AFIT/DS/ENP/96-07 OPTICAL DETECTION PROPERTIES OF SILICON-GERMANIUM QUANTUM WELL STRUCTURES DISSERTATION Michael R. Gregg, Captain, USAF AFIT/DS/ENP...96 Approved for public release; distribution unlimited DTC Qr. ~r AFIT/DS/ENP/96-07 Optical Detection Properties of Silicon-Germanium Quantum Well ...release; distribution unlimited AFIT/DS/ENP/96-07 Optical Detection Properties of Silicon-Germanium Quantum Well Structures Michael R. Gregg, BA, MS

  2. High-fidelity chemical patterning on oxide-free germanium.

    PubMed

    Hohman, J Nathan; Kim, Moonhee; Lawrence, Jeffrey A; McClanahan, Patrick D; Weiss, Paul S

    2012-04-25

    Oxide-free germanium can be chemically patterned directly with self-assembled monolayers of n-alkanethiols via submerged microcontact printing. Native germanium dioxide is water soluble; immersion activates the germanium surface for self-assembly by stripping the oxide. Water additionally provides an effective diffusion barrier that prevents undesired ink transport. Patterns are stable with respect to molecular exchange by carboxyl-functionalized thiols.

  3. Advances in nanowire bioelectronics

    NASA Astrophysics Data System (ADS)

    Zhou, Wei; Dai, Xiaochuan; Lieber, Charles M.

    2017-01-01

    Semiconductor nanowires represent powerful building blocks for next generation bioelectronics given their attractive properties, including nanometer-scale footprint comparable to subcellular structures and bio-molecules, configurable in nonstandard device geometries readily interfaced with biological systems, high surface-to-volume ratios, fast signal responses, and minimum consumption of energy. In this review article, we summarize recent progress in the field of nanowire bioelectronics with a focus primarily on silicon nanowire field-effect transistor biosensors. First, the synthesis and assembly of semiconductor nanowires will be described, including the basics of nanowire FETs crucial to their configuration as biosensors. Second, we will introduce and review recent results in nanowire bioelectronics for biomedical applications ranging from label-free sensing of biomolecules, to extracellular and intracellular electrophysiological recording.

  4. Multicolored Vertical Silicon Nanowires

    SciTech Connect

    Seo, Kwanyong; Wober, Munib; Steinvurzel, P.; Schonbrun, E.; Dan, Yaping; Ellenbogen, T.; Crozier, K. B.

    2011-04-13

    We demonstrate that vertical silicon nanowires take on a surprising variety of colors covering the entire visible spectrum, in marked contrast to the gray color of bulk silicon. This effect is readily observable by bright-field microscopy, or even to the naked eye. The reflection spectra of the nanowires each show a dip whose position depends on the nanowire radii. We compare the experimental data to the results of finite difference time domain simulations to elucidate the physical mechanisms behind the phenomena we observe. The nanowires are fabricated as arrays, but the vivid colors arise not from scattering or diffractive effects of the array, but from the guided mode properties of the individual nanowires. Each nanowire can thus define its own color, allowing for complex spatial patterning. We anticipate that the color filter effect we demonstrate could be employed in nanoscale image sensor devices.

  5. Crucible-free pulling of germanium crystals

    NASA Astrophysics Data System (ADS)

    Wünscher, Michael; Lüdge, Anke; Riemann, Helge

    2011-03-01

    Commonly, germanium crystals are grown after the Czochralski (CZ) method. The crucible-free pedestal and floating zone (FZ) methods, which are widely used for silicon growth, are hardly known to be investigated for germanium. The germanium melt is more than twice as dense as liquid silicon, which could destabilize a floating zone. Additionally, the lower melting point and the related lower radiative heat loss is shown to reduce the stability especially of the FZ process with the consequence of a screw-like crystal growth. We found that the lower heat radiation of Ge can be compensated by the increased convective cooling of a helium atmosphere instead of the argon ambient. Under these conditions, the screw-like growth could be avoided. Unfortunately, the helium cooling deteriorates the melting behavior of the feed rod. Spikes appear along the open melt front, which touch on the induction coil. In order to improve the melting behavior, we used a lamp as a second energy source as well as a mixture of Ar and He. With this, we found a final solution for growing stable crystals from germanium by using both gases in different parts of the furnace. The experimental work is accompanied by the simulation of the stationary temperature field. The commercially available software FEMAG-FZ is used for axisymmetric calculations. Another tool for process development is the lateral photo-voltage scanning (LPS), which can determine the shape of the solid-liquid phase boundary by analyzing the growth striations in a lateral cut of a grown crystal. In addition to improvements of the process, these measurements can be compared with the calculated results and, hence, conduce to validate the calculation.

  6. Improving Germanium Detector Resolution and Reliability

    DTIC Science & Technology

    2008-09-01

    layer and fast states in the oxide/germanium interfacial layer have been investigated by Bardeen et al. (1956). Because electrons are attracted to the...figure art work. REFERENCES Bardeen , J., R. E. Coovert, S. R. Morrison, J. R. Schrieffer, R. Sun (1956). Surface conductance and the field effect...Chapman, B. (1980). Glow Discharge Processes: Sputtering and Plasma Etching, John Wiley & Sons, Inc.. Dinger, R. J. (1975). Dead layers at the surface of

  7. Germanium films by polymer-assisted deposition

    DOEpatents

    Jia, Quanxi; Burrell, Anthony K.; Bauer, Eve; Ronning, Filip; McCleskey, Thomas Mark; Zou, Guifu

    2013-01-15

    Highly ordered Ge films are prepared directly on single crystal Si substrates by applying an aqueous coating solution having Ge-bound polymer onto the substrate and then heating in a hydrogen-containing atmosphere. A coating solution was prepared by mixing water, a germanium compound, ethylenediaminetetraacetic acid, and polyethyleneimine to form a first aqueous solution and then subjecting the first aqueous solution to ultrafiltration.

  8. Large Cryogenic Germanium Detector. Final Report

    SciTech Connect

    Mandic, Vuk

    2013-02-13

    The goal of this project was to investigate possible ways of increasing the size of cryogenic Ge detectors. This project identified two possible approaches to increasing the individual cryogenic Ge detector size. The first approach relies on using the existing technology for growing detector-grade (high-purity) germanium crystals of dislocation density 100-7000 cm{sup -2}. The second approach is to consider dislocation-free Ge crystals.

  9. Temperature dependent electrical transport in single Ge nanowires near insulator-metal transition

    NASA Astrophysics Data System (ADS)

    Raychaudhuri, Arup Kumar; Seth, Shaili; Das, Kaustuv

    We report low temperature (4K <= T <= 300K) electrical transport in single strands of Germanium Nanowires of radius well below 50 nm. The nanowires, grown from vapour phase with Au catalyst have carrier concentrations ranging from intrinsic to near the insulator-metal transition boundary. The nanowires were characterized extensively by High Resolution Transmission Electron Microscope and established their crystalline quality. A single nanowire dispersed on a Si/SiO2 substrate was connected by Cr/Au contacts made by electron beam lithography in 2-probe / 4-probe configurations. The undoped nanowires have a room temperature resistivity (ρ) of 2 ohm.cm or more (estimated carrier concentration ~1015/cm3) and below the 25K (where it shows carrier freeze out) the ρ rises to high value of 35 ohm.cm. For nanowires with ρ <= .01 ohm.cm at 300K , low temperature ρ becomes finite, signaling transition to a metallic state with negative temperature co-efficient of ρ. The critical composition for the insulator-metal transition is more than an order higher than that observed in the bulk. At low T (<25K) resistivity data in this regime can be fitted to weak-localization form ρ =ρ0 - aTp/2 with ρ0 the NW's ~ 0.5-3.5 mohm.cm, with the exponent p ~ 3-4 as expected from theoretical predictions. Acknowldge Financial Support from Department od Science and Technology, Government of India for Sponsored Project.

  10. Metal-seeded growth of III-V semiconductor nanowires: towards gold-free synthesis

    NASA Astrophysics Data System (ADS)

    Dick, Kimberly A.; Caroff, Philippe

    2014-02-01

    Semiconductor nanowires composed of III-V materials have enormous potential to add new functionality to electronics and optical applications. However, integration of these promising structures into applications is severely limited by the current near-universal reliance on gold nanoparticles as seeds for nanowire fabrication. Although highly controlled fabrication is achieved, this metal is entirely incompatible with the Si-based electronics industry. In this Feature we review the progress towards developing gold-free bottom-up synthesis techniques for III-V semiconductor nanowires. Three main categories of nanowire synthesis are discussed: selective-area epitaxy, self-seeding and foreign metal seeding, with main focus on the metal-seeded techniques. For comparison, we also review the development of foreign metal seeded synthesis of silicon and germanium nanowires. Finally, directions for future development and anticipated important trends are discussed. We anticipate significant development in the use of foreign metal seeding in particular. In addition, we speculate that multiple different techniques must be developed in order to replace gold and to provide a variety of nanowire structures and properties suited to a diverse range of applications.

  11. Joule heating in nanowires

    NASA Astrophysics Data System (ADS)

    Fangohr, Hans; Chernyshenko, Dmitri S.; Franchin, Matteo; Fischbacher, Thomas; Meier, Guido

    2011-08-01

    We study the effect of Joule heating from electric currents flowing through ferromagnetic nanowires on the temperature of the nanowires and on the temperature of the substrate on which the nanowires are grown. The spatial current density distribution, the associated heat generation, and diffusion of heat are simulated within the nanowire and the substrate. We study several different nanowire and constriction geometries as well as different substrates: (thin) silicon nitride membranes, (thick) silicon wafers, and (thick) diamond wafers. The spatially resolved increase in temperature as a function of time is computed. For effectively three-dimensional substrates (where the substrate thickness greatly exceeds the nanowire length), we identify three different regimes of heat propagation through the substrate: regime (i), where the nanowire temperature increases approximately logarithmically as a function of time. In this regime, the nanowire temperature is well described analytically by You [Appl. Phys. Lett.APPLAB0003-695110.1063/1.2399441 89, 222513 (2006)]. We provide an analytical expression for the time tc that marks the upper applicability limit of the You model. After tc, the heat flow enters regime (ii), where the nanowire temperature stays constant while a hemispherical heat front carries the heat away from the wire and into the substrate. As the heat front reaches the boundary of the substrate, regime (iii) is entered, where the nanowire and substrate temperature start to increase rapidly. For effectively two-dimensional substrates (where the nanowire length greatly exceeds the substrate thickness), there is only one regime in which the temperature increases logarithmically with time for large times, before the heat front reaches the substrate boundary. We provide an analytical expression, valid for all pulse durations, that allows one to accurately compute this temperature increase in the nanowire on thin substrates.

  12. Phonons in Ge nanowires

    NASA Astrophysics Data System (ADS)

    Peelaers, H.; Partoens, B.; Peeters, F. M.

    2009-09-01

    The phonon spectra of thin freestanding, hydrogen passivated, Ge nanowires are calculated by ab initio techniques. The effect of confinement on the phonon modes as caused by the small diameters of the wires is investigated. Confinement causes a hardening of the optical modes and a softening of the longitudinal acoustic modes. The stability of the nanowires, undoped or doped with B or P atoms, is investigated using the obtained phonon spectra. All considered wires were stable, except for highly doped, very thin nanowires.

  13. Germanium-76 Sample Analysis: Revision 3

    SciTech Connect

    Kouzes, Richard T.; Zhu, Zihua; Engelhard, Mark H.

    2011-09-19

    The MAJORANA DEMONSTRATOR is a large array of ultra-low background high-purity germanium detectors, enriched in 76Ge, designed to search for zero-neutrino double-beta decay (0{nu}{beta}{beta}). The DEMONSTRATOR will utilize 76Ge from Russia. The first one-gram sample was received from the supplier for analysis on April 24, 2011. The second one-gram sample was received from the supplier for analysis on July 12, 2011. The third sample, which came from the first large shipment of germanium from the vendor, was received from Oak Ridge National Laboratory (ORNL) on September 13, 2011. The Environmental Molecular Sciences facility, a DOE user facility at PNNL, was used to make the required isotopic and chemical purity measurements that are essential to the quality assurance for the MAJORANA DEMONSTRATOR. The results of these analyses are reported here. The isotopic composition of a sample of natural germanium was also measured twice. Differences in the result between these two measurements led to a re-measurement of the second 76Ge sample.

  14. Bottom-up assembly of metallic germanium

    PubMed Central

    Scappucci, Giordano; Klesse, Wolfgang M.; Yeoh, LaReine A.; Carter, Damien J.; Warschkow, Oliver; Marks, Nigel A.; Jaeger, David L.; Capellini, Giovanni; Simmons, Michelle Y.; Hamilton, Alexander R.

    2015-01-01

    Extending chip performance beyond current limits of miniaturisation requires new materials and functionalities that integrate well with the silicon platform. Germanium fits these requirements and has been proposed as a high-mobility channel material, a light emitting medium in silicon-integrated lasers, and a plasmonic conductor for bio-sensing. Common to these diverse applications is the need for homogeneous, high electron densities in three-dimensions (3D). Here we use a bottom-up approach to demonstrate the 3D assembly of atomically sharp doping profiles in germanium by a repeated stacking of two-dimensional (2D) high-density phosphorus layers. This produces high-density (1019 to 1020 cm−3) low-resistivity (10−4Ω · cm) metallic germanium of precisely defined thickness, beyond the capabilities of diffusion-based doping technologies. We demonstrate that free electrons from distinct 2D dopant layers coalesce into a homogeneous 3D conductor using anisotropic quantum interference measurements, atom probe tomography, and density functional theory. PMID:26256239

  15. Bottom-up assembly of metallic germanium.

    PubMed

    Scappucci, Giordano; Klesse, Wolfgang M; Yeoh, LaReine A; Carter, Damien J; Warschkow, Oliver; Marks, Nigel A; Jaeger, David L; Capellini, Giovanni; Simmons, Michelle Y; Hamilton, Alexander R

    2015-08-10

    Extending chip performance beyond current limits of miniaturisation requires new materials and functionalities that integrate well with the silicon platform. Germanium fits these requirements and has been proposed as a high-mobility channel material, a light emitting medium in silicon-integrated lasers, and a plasmonic conductor for bio-sensing. Common to these diverse applications is the need for homogeneous, high electron densities in three-dimensions (3D). Here we use a bottom-up approach to demonstrate the 3D assembly of atomically sharp doping profiles in germanium by a repeated stacking of two-dimensional (2D) high-density phosphorus layers. This produces high-density (10(19) to 10(20) cm(-3)) low-resistivity (10(-4)Ω · cm) metallic germanium of precisely defined thickness, beyond the capabilities of diffusion-based doping technologies. We demonstrate that free electrons from distinct 2D dopant layers coalesce into a homogeneous 3D conductor using anisotropic quantum interference measurements, atom probe tomography, and density functional theory.

  16. Structural characterization of nanowires and nanowire arrays

    NASA Astrophysics Data System (ADS)

    Becker, Catherine Rose

    Nanowires, which have diameter less than a few hundred nanometers and high aspect ratios, may have the same properties as their corresponding bulk materials, or may exhibit unique properties due to their confined dimensions and increased surface to volume ratios. They are a popular field of technological investigation in applications that depend on the transport of charge carriers, because of expectations that microcircuit miniaturization will lead to the next boom in the electronics industry. In this work, the high spatial resolution afforded by transmission electron microscopy (TEM) is used to study nanowires formed by electrochemical deposition into porous alumina templates. The goal is to determine the effect of the synthesis and subsequent processing on the microstructure and crystallinity of the wires. A thorough understanding of the microstructural features of a material is vital for optimizing its performance in a desired application. Two material systems were studied in this work. The first is bismuth telluride (Bi 2Te3), which is used in thermoelectric applications. The second is metallic copper, the electrochemical deposition of which is of interest for interconnects in semiconductor devices. The first part of this work utilized TEM to obtain a thorough characterization of the microstructural features of individual Bi2Te3 nanowires following release from the templates. As deposited, the nanowires are fine grained and exhibit significant lattice strain. Annealing increases the grain size and dislocations are created to accommodate the lattice strain. The degree of these microstructural changes depends on the thermal treatment. However, no differences were seen in the nanowire microstructure as a function of the synthetic parameters. The second part of this work utilized a modified dark field TEM technique in order to obtain a spatially resolved, semi-quantitative understanding of the evolution of preferred orientation as a function of the electrochemical

  17. Metallic nanowire networks

    DOEpatents

    Song, Yujiang; Shelnutt, John A.

    2012-11-06

    A metallic nanowire network synthesized using chemical reduction of a metal ion source by a reducing agent in the presence of a soft template comprising a tubular inverse micellar network. The network of interconnected polycrystalline nanowires has a very high surface-area/volume ratio, which makes it highly suitable for use in catalytic applications.

  18. Germanium: From Its Discovery to SiGe Devices

    SciTech Connect

    Haller, E.E.

    2006-06-14

    Germanium, element No.32, was discovered in 1886 by Clemens Winkler. Its first broad application was in the form of point contact Schottky diodes for radar reception during WWII. The addition of a closely spaced second contact led to the first all-solid-state electronic amplifier device, the transistor. The relatively low bandgap, the lack of a stable oxide and large surface state densities relegated germanium to the number 2 position behind silicon. The discovery of the lithium drift process, which made possible the formation of p-i-n diodes with fully depletable i-regions several centimeters thick, led germanium to new prominence as the premier gamma-ray detector. The development of ultra-pure germanium yielded highly stable detectors which have remained unsurpassed in their performance. New acceptors and donors were discovered and the electrically active role of hydrogen was clearly established several years before similar findings in silicon. Lightly doped germanium has found applications as far infrared detectors and heavily Neutron Transmutation Doped (NTD) germanium is used in thermistor devices operating at a few milliKelvin. Recently germanium has been rediscovered by the silicon device community because of its superior electron and hole mobility and its ability to induce strains when alloyed with silicon. Germanium is again a mainstream electronic material.

  19. Tunable porosity of 3D-networks with germanium nodes.

    PubMed

    Monnereau, Laure; Muller, Thierry; Lang, Mathias; Bräse, Stefan

    2016-01-11

    Eight hyper cross-linked polymers based on tetrakis(4-ethynylphenyl)germanium and tetrakis(4-ethynylphenyl)methane are presented. After investigation of their N2 adsorption properties at 77 K, the porosity of the germanium-based porous organic polymers (POPs) was modulated under acidic conditions, offering an easy and direct way, in a single step, to tune the adsorption properties.

  20. Josephson tunnel junction with polycrystalline silicon, germanium or silicon-germanium alloy tunneling barrier

    SciTech Connect

    Kroger, H.

    1980-09-02

    A Josephson tunnel junction device having niobium nitride superconductive electrodes includes a polycrystalline semiconductor tunnelling barrier therebetween comprised of silicon, germanium or an alloy thereof preferably deposited on the lower superconductive electrodes by chemical vapor deposition. The barrier height of the junction is precisely controlled by precision doping of the semiconductor material.

  1. Semiconductor nanowire lasers

    NASA Astrophysics Data System (ADS)

    Eaton, Samuel W.; Fu, Anthony; Wong, Andrew B.; Ning, Cun-Zheng; Yang, Peidong

    2016-06-01

    The discovery and continued development of the laser has revolutionized both science and industry. The advent of miniaturized, semiconductor lasers has made this technology an integral part of everyday life. Exciting research continues with a new focus on nanowire lasers because of their great potential in the field of optoelectronics. In this Review, we explore the latest advancements in the development of nanowire lasers and offer our perspective on future improvements and trends. We discuss fundamental material considerations and the latest, most effective materials for nanowire lasers. A discussion of novel cavity designs and amplification methods is followed by some of the latest work on surface plasmon polariton nanowire lasers. Finally, exciting new reports of electrically pumped nanowire lasers with the potential for integrated optoelectronic applications are described.

  2. All-Inorganic Germanium Nanocrystal Films by Cationic Ligand Exchange.

    PubMed

    Wheeler, Lance M; Nichols, Asa W; Chernomordik, Boris D; Anderson, Nicholas C; Beard, Matthew C; Neale, Nathan R

    2016-03-09

    We introduce a new paradigm for group IV nanocrystal surface chemistry based on room temperature surface activation that enables ionic ligand exchange. Germanium nanocrystals synthesized in a gas-phase plasma reactor are functionalized with labile, cationic alkylammonium ligands rather than with traditional covalently bound groups. We employ Fourier transform infrared and (1)H nuclear magnetic resonance spectroscopies to demonstrate the alkylammonium ligands are freely exchanged on the germanium nanocrystal surface with a variety of cationic ligands, including short inorganic ligands such as ammonium and alkali metal cations. This ionic ligand exchange chemistry is used to demonstrate enhanced transport in germanium nanocrystal films following ligand exchange as well as the first photovoltaic device based on an all-inorganic germanium nanocrystal absorber layer cast from solution. This new ligand chemistry should accelerate progress in utilizing germanium and other group IV nanocrystals for optoelectronic applications.

  3. All-inorganic Germanium nanocrystal films by cationic ligand exchange

    DOE PAGES

    Wheeler, Lance M.; Nichols, Asa W.; Chernomordik, Boris D.; ...

    2016-01-21

    In this study, we introduce a new paradigm for group IV nanocrystal surface chemistry based on room temperature surface activation that enables ionic ligand exchange. Germanium nanocrystals synthesized in a gas-phase plasma reactor are functionalized with labile, cationic alkylammonium ligands rather than with traditional covalently bound groups. We employ Fourier transform infrared and 1H nuclear magnetic resonance spectroscopies to demonstrate the alkylammonium ligands are freely exchanged on the germanium nanocrystal surface with a variety of cationic ligands, including short inorganic ligands such as ammonium and alkali metal cations. This ionic ligand exchange chemistry is used to demonstrate enhanced transport inmore » germanium nanocrystal films following ligand exchange as well as the first photovoltaic device based on an all-inorganic germanium nanocrystal absorber layer cast from solution. This new ligand chemistry should accelerate progress in utilizing germanium and other group IV nanocrystals for optoelectronic applications.« less

  4. REACTIVITY OF THE GERMANIUM SURFACE: Chemical Passivation and Functionalization

    NASA Astrophysics Data System (ADS)

    Loscutoff, Paul W.; Bent, Stacey F.

    2006-05-01

    With the rapidly changing materials needs of modern microelectronics, germanium provides an opportunity for future-generation devices. Controlling germanium interfaces will be essential for this purpose. We review germanium surface reactivity, beginning with a description of the most commonly used surfaces, Ge(100) and Ge(111). An analysis of oxide formation shows why the poor oxide properties have hindered practical use of germanium to date. This is followed by an examination of alternate means of surface passivation, with particular attention given to sulfide, chloride, and hydride termination. Specific tailoring of the interface properties is possible through organic functionalization. The few solution functionalization methods that have been studied are reviewed. Vacuum functionalization has been studied to a much greater extent, with dative bonding and cycloaddition reactions emerging as principle reaction mechanisms. These are reviewed through molecular reaction studies that demonstrate the versatility of the germanium surface.

  5. Germanium resistance thermometer calibration at superfluid helium temperatures

    NASA Technical Reports Server (NTRS)

    Mason, F. C.

    1985-01-01

    The rapid increase in resistance of high purity semi-conducting germanium with decreasing temperature in the superfluid helium range of temperatures makes this material highly adaptable as a very sensitive thermometer. Also, a germanium thermometer exhibits a highly reproducible resistance versus temperature characteristic curve upon cycling between liquid helium temperatures and room temperature. These two factors combine to make germanium thermometers ideally suited for measuring temperatures in many cryogenic studies at superfluid helium temperatures. One disadvantage, however, is the relatively high cost of calibrated germanium thermometers. In space helium cryogenic systems, many such thermometers are often required, leading to a high cost for calibrated thermometers. The construction of a thermometer calibration cryostat and probe which will allow for calibrating six germanium thermometers at one time, thus effecting substantial savings in the purchase of thermometers is considered.

  6. Germanium resistance thermometer calibration at superfluid helium temperatures

    NASA Technical Reports Server (NTRS)

    Mason, F. C.

    1985-01-01

    The rapid increase in resistance of high purity semi-conducting germanium with decreasing temperature in the superfluid helium range of temperatures makes this material highly adaptable as a very sensitive thermometer. Also, a germanium thermometer exhibits a highly reproducible resistance versus temperature characteristic curve upon cycling between liquid helium temperatures and room temperature. These two factors combine to make germanium thermometers ideally suited for measuring temperatures in many cryogenic studies at superfluid helium temperatures. One disadvantage, however, is the relatively high cost of calibrated germanium thermometers. In space helium cryogenic systems, many such thermometers are often required, leading to a high cost for calibrated thermometers. The construction of a thermometer calibration cryostat and probe which will allow for calibrating six germanium thermometers at one time, thus effecting substantial savings in the purchase of thermometers is considered.

  7. All-inorganic Germanium nanocrystal films by cationic ligand exchange

    SciTech Connect

    Wheeler, Lance M.; Nichols, Asa W.; Chernomordik, Boris D.; Anderson, Nicholas C.; Beard, Matthew C.; Neale, Nathan R.

    2016-01-21

    In this study, we introduce a new paradigm for group IV nanocrystal surface chemistry based on room temperature surface activation that enables ionic ligand exchange. Germanium nanocrystals synthesized in a gas-phase plasma reactor are functionalized with labile, cationic alkylammonium ligands rather than with traditional covalently bound groups. We employ Fourier transform infrared and 1H nuclear magnetic resonance spectroscopies to demonstrate the alkylammonium ligands are freely exchanged on the germanium nanocrystal surface with a variety of cationic ligands, including short inorganic ligands such as ammonium and alkali metal cations. This ionic ligand exchange chemistry is used to demonstrate enhanced transport in germanium nanocrystal films following ligand exchange as well as the first photovoltaic device based on an all-inorganic germanium nanocrystal absorber layer cast from solution. This new ligand chemistry should accelerate progress in utilizing germanium and other group IV nanocrystals for optoelectronic applications.

  8. Template-free preparation of crystalline Ge nanowire film electrodes via an electrochemical liquid-liquid-solid process in water at ambient pressure and temperature for energy storage.

    PubMed

    Gu, Junsi; Collins, Sean M; Carim, Azhar I; Hao, Xiaoguang; Bartlett, Bart M; Maldonado, Stephen

    2012-09-12

    The direct electrodeposition of crystalline germanium (Ge) nanowire film electrodes from an aqueous solution of dissolved GeO(2) using discrete 'flux' nanoparticles capable of dissolving Ge(s) has been demonstrated. Electrodeposition of Ge at inert electrode substrates decorated with small (<100 nm), discrete indium (In) nanoparticles resulted in crystalline Ge nanowire films with definable nanowire diameters and densities without the need for a physical or chemical template. The Ge nanowires exhibited strong polycrystalline character as-deposited, with approximate crystallite dimensions of 20 nm and a mixed orientation of the crystallites along the length of the nanowire. Energy dispersive spectroscopic elemental mapping of individual Ge nanowires showed that the In nanoparticles remained at the base of each nanowire, indicating good electrical communication between the Ge nanowire and the underlying conductive support. As-deposited Ge nanowire films prepared on Cu supports were used without further processing as Li(+) battery anodes. Cycling studies performed at 1 C (1624 mA g(-1)) indicated the native Ge nanowire films supported stable discharge capacities at the level of 973 mA h g(-1), higher than analogous Ge nanowire film electrodes prepared through an energy-intensive vapor-liquid-solid nanowire growth process. The cumulative data show that ec-LLS is a viable method for directly preparing a functional, high-activity nanomaterials-based device component. The work presented here is a step toward the realization of simple processes that make fully functional energy conversion/storage technologies based on crystalline inorganic semiconductors entirely through benchtop, aqueous chemistry and electrochemistry without time- or energy-intensive process steps.

  9. Analog/Digital System for Germanium Thermometer

    NASA Technical Reports Server (NTRS)

    Woodhouse, Christopher

    1988-01-01

    Electronic system containing analog and digital circuits makes high-precision, four-wire measurements of resistance of each germanium resistance thermometer (GRT) in array of devices, using alternating current (ac) of 1 micro-A. At end measurement interval, contents of negative register subtracted from positive one, resulting in very-narrow-band synchronous demodulation of carrier wave and suppression of out-of-band noise. Microprocessor free to perform other duties after measurement complete. Useful in noisy terrestrial environments encountered in factories.

  10. Simulated performance of a germanium Compton telescope

    NASA Astrophysics Data System (ADS)

    Boggs, Steven E.; Jean, Pierre

    2001-09-01

    To build upon the goals of the upcoming INTEGRAL mission, the next generation soft γ-ray (0.2-20 MeV) observatory will require improved sensitivity to nuclear line emission while maintaining high spectral resolution. We present the simulated performance of a germanium Compton telescope (GCT) design, which will allow a factor of ten improvement in sensitivity over INTEGRAL/SPI. We also discuss a number of issues concerning reconstruction techniques and event cuts, and demonstrate how these affect the overall performance of the telescope.

  11. Tensile strain mapping in flat germanium membranes

    SciTech Connect

    Rhead, S. D. Halpin, J. E.; Myronov, M.; Patchett, D. H.; Allred, P. S.; Wilson, N. R.; Leadley, D. R.; Shah, V. A.; Kachkanov, V.; Dolbnya, I. P.; Reparaz, J. S.; Sotomayor Torres, C. M.

    2014-04-28

    Scanning X-ray micro-diffraction has been used as a non-destructive probe of the local crystalline quality of a thin suspended germanium (Ge) membrane. A series of reciprocal space maps were obtained with ∼4 μm spatial resolution, from which detailed information on the strain distribution, thickness, and crystalline tilt of the membrane was obtained. We are able to detect a systematic strain variation across the membranes, but show that this is negligible in the context of using the membranes as platforms for further growth. In addition, we show evidence that the interface and surface quality is improved by suspending the Ge.

  12. Thermal conductivity modeling of core-shell and tubular nanowires.

    PubMed

    Yang, Ronggui; Chen, Gang; Dresselhaus, Mildred S

    2005-06-01

    The heteroepitaxial growth of crystalline core-shell nanostructures of a variety of materials has become possible in recent years, allowing the realization of various novel nanoscale electronic and optoelectronic devices. The increased surface or interface area will decrease the thermal conductivity of such nanostructures and impose challenges for the thermal management of such devices. In the meantime, the decreased thermal conductivity might benefit the thermoelectric conversion efficiency. In this paper, we present modeling results on the lattice thermal conductivity of core-shell and tubular nanowires along the wire axis direction using the phonon Boltzmann equation. We report the dependence of the thermal conductivity on the surface conditions and the core-shell geometry for silicon core-germanium shell and tubular silicon nanowires at room temperature. The results show that the effective thermal conductivity changes not only with the composition of the constituents but also with the radius of the nanowires and nanopores due to the nature of the ballistic phonon transport. The results in this work have implications for the design and operation of a variety of nanoelectronic devices, optoelectronic devices, and thermoelectric materials and devices.

  13. Nanowire-based thermoelectrics

    NASA Astrophysics Data System (ADS)

    Ali, Azhar; Chen, Yixi; Vasiraju, Venkata; Vaddiraju, Sreeram

    2017-07-01

    Research on thermoelectrics has seen a huge resurgence since the early 1990s. The ability of tuning a material’s electrical and thermal transport behavior upon nanostructuring has led to this revival. Nevertheless, thermoelectric performances of nanowires and related materials lag far behind those achieved with thin-film superlattices and quantum dot-based materials. This is despite the fact that nanowires offer many distinct advantages in enhancing the thermoelectric performances of materials. The simplicity of the strategy is the first and foremost advantage. For example, control of the nanowire diameters and their surface roughnesses will aid in enhancing their thermoelectric performances. Another major advantage is the possibility of obtaining high thermoelectric performances using simpler nanowire chemistries (e.g., elemental and binary compound semiconductors), paving the way for the fabrication of thermoelectric modules inexpensively from non-toxic elements. In this context, the topical review provides an overview of the current state of nanowire-based thermoelectrics. It concludes with a discussion of the future vision of nanowire-based thermoelectrics, including the need for developing strategies aimed at the mass production of nanowires and their interface-engineered assembly into devices. This eliminates the need for trial-and-error strategies and complex chemistries for enhancing the thermoelectric performances of materials.

  14. Purification of Germanium Crystals by Zone Refining

    NASA Astrophysics Data System (ADS)

    Kooi, Kyler; Yang, Gang; Mei, Dongming

    2016-09-01

    Germanium zone refining is one of the most important techniques used to produce high purity germanium (HPGe) single crystals for the fabrication of nuclear radiation detectors. During zone refining the impurities are isolated to different parts of the ingot. In practice, the effective isolation of an impurity is dependent on many parameters, including molten zone travel speed, the ratio of ingot length to molten zone width, and number of passes. By studying the theory of these influential factors, perfecting our cleaning and preparation procedures, and analyzing the origin and distribution of our impurities (aluminum, boron, gallium, and phosphorous) identified using photothermal ionization spectroscopy (PTIS), we have optimized these parameters to produce HPGe. We have achieved a net impurity level of 1010 /cm3 for our zone-refined ingots, measured with van der Pauw and Hall-effect methods. Zone-refined ingots of this purity can be processed into a detector grade HPGe single crystal, which can be used to fabricate detectors for dark matter and neutrinoless double beta decay detection. This project was financially supported by DOE Grant (DE-FG02-10ER46709) and the State Governor's Research Center.

  15. Germanium avalanche receiver for low power interconnects

    NASA Astrophysics Data System (ADS)

    Virot, Léopold; Crozat, Paul; Fédéli, Jean-Marc; Hartmann, Jean-Michel; Marris-Morini, Delphine; Cassan, Eric; Boeuf, Frédéric; Vivien, Laurent

    2014-09-01

    Recent advances in silicon photonics have aided the development of on-chip communications. Power consumption, however, remains an issue in almost all integrated devices. Here, we report a 10 Gbit per second waveguide avalanche germanium photodiode under low reverse bias. The avalanche photodiode scheme requires only simple technological steps that are fully compatible with complementary metal oxide semiconductor processes and do not need nanometre accuracy and/or complex epitaxial growth schemes. An intrinsic gain higher than 20 was demonstrated under a bias voltage as low as -7 V. The Q-factor relating to the signal-to-noise ratio at 10 Gbit per second was maintained over 20 dB without the use of a trans-impedance amplifier for an input optical power lower than -26 dBm thanks to an aggressive shrinkage of the germanium multiplication region. A maximum gain over 140 was also obtained for optical powers below -35 dBm. These results pave the way for low-power-consumption on-chip communication applications.

  16. Cryogenic readout techniques for germanium detectors

    SciTech Connect

    Benato, G.; Cattadori, C.; Di Vacri, A.; Ferri, E.

    2015-07-01

    High Purity Germanium detectors are used in many applications, from nuclear and astro-particle physics, to homeland security or environment protection. Although quite standard configurations are often used, with cryostats, charge sensitive amplifiers and analog or digital acquisition systems all commercially available, it might be the case that a few specific applications, e.g. satellites, portable devices, cryogenic physics experiments, etc. also require the development of a few additional or complementary techniques. An interesting case is for sure GERDA, the Germanium Detector Array experiment, searching for neutrino-less double beta decay of {sup 76}Ge at the Gran Sasso National Laboratory of INFN - Italy. In GERDA the entire detector array, composed of semi-coaxial and BEGe naked crystals, is operated suspended inside a cryostat filled with liquid argon, that acts not only as cooling medium and but also as an active shield, thanks to its scintillation properties. These peculiar circumstances, together with the additional requirement of a very low radioactive background from all the materials adjacent to the detectors, clearly introduce significant constraints on the design of the Ge front-end readout electronics. All the Ge readout solutions developed within the framework of the GERDA collaboration, for both Phase I and Phase II, will be briefly reviewed, with their relative strength and weakness compared together and with respect to ideal Ge readout. Finally, the digital processing techniques developed by the GERDA collaboration for energy estimation of Ge detector signals will be recalled. (authors)

  17. High-purity germanium crystal growing

    SciTech Connect

    Hansen, W.L.; Haller, E.E.

    1982-10-01

    The germanium crystals used for the fabrication of nuclear radiation detectors are required to have a purity and crystalline perfection which is unsurpassed by any other solid material. These crystals should not have a net electrically active impurity concentration greater than 10/sup 10/cm/sup -3/ and be essentially free of charge trapping defects. Such perfect crystals of germanium can be grown only because of the highly favorable chemical and physical properties of this element. However, ten years of laboratory scale and commercial experience has still not made the production of such crystals routine. The origin and control of many impurities and electrically active defect complexes is now fairly well understood but regular production is often interrupted for long periods due to the difficulty of achieving the required high purity or to charge trapping in detectors made from crystals seemingly grown under the required conditions. The compromises involved in the selection of zone refining and crystal grower parts and ambients is discussed and the difficulty in controlling the purity of key elements in the process is emphasized. The consequences of growing in a hydrogen ambient are discussed in detail and it is shown how complexes of neutral defects produce electrically active centers.

  18. Semiconductor Nanowires: What's Next?

    SciTech Connect

    Yang, Peidong; Yan, Ruoxue; Fardy, Melissa

    2010-04-28

    In this perspective, we take a critical look at the research progress within the nanowire community for the past decade. We discuss issues on the discovery of fundamentally new phenomena versus performance benchmarking for many of the nanowire applications. We also notice that both the bottom-up and top-down approaches have played important roles in advancing our fundamental understanding of this new class of nanostructures. Finally we attempt to look into the future and offer our personal opinions on what the future trends will be in nanowire research.

  19. Ultra High-Rate Germanium (UHRGe) Modeling Status Report

    SciTech Connect

    Warren, Glen A.; Rodriguez, Douglas C.

    2012-06-07

    The Ultra-High Rate Germanium (UHRGe) project at Pacific Northwest National Laboratory (PNNL) is conducting research to develop a high-purity germanium (HPGe) detector that can provide both the high resolution typical of germanium and high signal throughput. Such detectors may be beneficial for a variety of potential applications ranging from safeguards measurements of used fuel to material detection and verification using active interrogation techniques. This report describes some of the initial radiation transport modeling efforts that have been conducted to help guide the design of the detector as well as a description of the process used to generate the source spectrum for the used fuel application evaluation.

  20. Oxygen defect processes in silicon and silicon germanium

    SciTech Connect

    Chroneos, A.; Sgourou, E. N.; Londos, C. A.; Schwingenschlögl, U.

    2015-06-15

    Silicon and silicon germanium are the archetypical elemental and alloy semiconductor materials for nanoelectronic, sensor, and photovoltaic applications. The investigation of radiation induced defects involving oxygen, carbon, and intrinsic defects is important for the improvement of devices as these defects can have a deleterious impact on the properties of silicon and silicon germanium. In the present review, we mainly focus on oxygen-related defects and the impact of isovalent doping on their properties in silicon and silicon germanium. The efficacy of the isovalent doping strategies to constrain the oxygen-related defects is discussed in view of recent infrared spectroscopy and density functional theory studies.

  1. In-depth TEM characterization of block copolymer pattern transfer at germanium surfaces

    NASA Astrophysics Data System (ADS)

    Cummins, Cian; Collins, Timothy W.; Kelly, Roisin A.; McCarthy, Eoin K.; Morris, Michael A.

    2016-12-01

    Dry plasma etching for the pattern transfer of mask features is fundamental to semiconductor processing and the development of device and electrically conducting elements becomes more challenging as features reach the deep nanoscale regime. In this work, high resolution transmission electron microscopy (TEM) coupled with energy dispersive x-ray (EDX) characterization were used to analyze the pattern transfer of graphoepitaxially aligned block copolymer (BCP) features to germanium (Ge) substrates as a function of time. The BCP patterns were converted into metal oxide hardmasks in order to affect good aspect ratios of the transferred features. An unusual interface layer between metal oxide nanowires and the germanium-on-insulator substrate was observed. EDX analysis shows that the origin of this interface layer is a result of the presence of a negative tone e-beam resist material, HSQ (hydrogen silsesquioxane). HSQ was employed as a guiding material to align line-space features of poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP) BCP with 16 nm half-pitch topography. Additionally, the existence of a metal oxide layer (from the initial PS-b-P4VP film) is also shown through ex situ TEM and EDX characterization. Three dimensional modeling of features is also provided giving a unique insight into the arrangement and structure of BCP features prior to and after the pattern transfer process. The results presented in this article highlight the accuracy of high resolution electron microscopy and elemental mapping of BCP generated on-chip etch masks to observe and understand through-film features affecting pattern transfer.

  2. Porous silicon nanowires.

    PubMed

    Qu, Yongquan; Zhou, Hailong; Duan, Xiangfeng

    2011-10-05

    In this mini-review, we summarize recent progress in the synthesis, properties and applications of a new type of one-dimensional nanostructures-single crystalline porous silicon nanowires. The growth of porous silicon nanowires starting from both p- and n-type Si wafers with a variety of dopant concentrations can be achieved through either one-step or two-step reactions. The mechanistic studies indicate the dopant concentration of Si wafers, oxidizer concentration, etching time and temperature can affect the morphology of the as-etched silicon nanowires. The porous silicon nanowires are both optically and electronically active and have been explored for potential applications in diverse areas including photocatalysis, lithium ion batteries, gas sensors and drug delivery.

  3. Porous Silicon Nanowires

    PubMed Central

    Qu, Yongquan; Zhou, Hailong; Duan, Xiangfeng

    2011-01-01

    In this minreview, we summarize recent progress in the synthesis, properties and applications of a new type of one-dimensional nanostructures — single crystalline porous silicon nanowires. The growth of porous silicon nanowires starting from both p- and n-type Si wafers with a variety of dopant concentrations can be achieved through either one-step or two-step reactions. The mechanistic studies indicate the dopant concentration of Si wafers, oxidizer concentration, etching time and temperature can affect the morphology of the as-etched silicon nanowires. The porous silicon nanowires are both optically and electronically active and have been explored for potential applications in diverse areas including photocatalysis, lithium ion battery, gas sensor and drug delivery. PMID:21869999

  4. Nanowire Photonic Systems

    DTIC Science & Technology

    2009-12-22

    synthesis of silicon and gallium-indium nitride alloy nanowire heterostructures to provide building blocks for photonic devices that can span the...the Si-nanowire etching profile follows the order in which dopants were introduced during synthesis : First boron for p-type, no dopant for i-type... synthesis of nanoscale building blocks, (ii) characterization of fundamental physical properties of the building blocks, and (iii) assembly of

  5. Characterization of Nanowire Photodetectors

    DTIC Science & Technology

    2016-11-28

    SECURITY CLASSIFICATION OF: The funding of DURIP instrumentation proposal has enabled expansion of the electrical measurement capability in nanowires...Triangle Park, NC 27709-2211 Low frequency noise set up, nanowires, electrical characterization, pulsed laser source REPORT DOCUMENTATION PAGE 11. SPONSOR...person shall be subject to any oenalty for failing to comply with a collection of information if it does not display a currently valid OMB control

  6. Nanowire Electron Scattering Spectroscopy

    NASA Technical Reports Server (NTRS)

    Hunt, Brian; Bronikowsky, Michael; Wong, Eric; VonAllmen, Paul; Oyafuso, Fablano

    2009-01-01

    Nanowire electron scattering spectroscopy (NESS) has been proposed as the basis of a class of ultra-small, ultralow-power sensors that could be used to detect and identify chemical compounds present in extremely small quantities. State-of-the-art nanowire chemical sensors have already been demonstrated to be capable of detecting a variety of compounds in femtomolar quantities. However, to date, chemically specific sensing of molecules using these sensors has required the use of chemically functionalized nanowires with receptors tailored to individual molecules of interest. While potentially effective, this functionalization requires labor-intensive treatment of many nanowires to sense a broad spectrum of molecules. In contrast, NESS would eliminate the need for chemical functionalization of nanowires and would enable the use of the same sensor to detect and identify multiple compounds. NESS is analogous to Raman spectroscopy, the main difference being that in NESS, one would utilize inelastic scattering of electrons instead of photons to determine molecular vibrational energy levels. More specifically, in NESS, one would exploit inelastic scattering of electrons by low-lying vibrational quantum states of molecules attached to a nanowire or nanotube.

  7. Nanowire structures and electrical devices

    DOEpatents

    Bezryadin, Alexey; Remeika, Mikas

    2010-07-06

    The present invention provides structures and devices comprising conductive segments and conductance constricting segments of a nanowire, such as metallic, superconducting or semiconducting nanowire. The present invention provides structures and devices comprising conductive nanowire segments and conductance constricting nanowire segments having accurately selected phases including crystalline and amorphous states, compositions, morphologies and physical dimensions, including selected cross sectional dimensions, shapes and lengths along the length of a nanowire. Further, the present invention provides methods of processing nanowires capable of patterning a nanowire to form a plurality of conductance constricting segments having selected positions along the length of a nanowire, including conductance constricting segments having reduced cross sectional dimensions and conductance constricting segments comprising one or more insulating materials such as metal oxides.

  8. Transparent metal oxide nanowire transistors

    NASA Astrophysics Data System (ADS)

    Chen, Di; Liu, Zhe; Liang, Bo; Wang, Xianfu; Shen, Guozhen

    2012-05-01

    With the features of high mobility, a high electric on/off ratio and excellent transparency, metal oxide nanowires are excellent candidates for transparent thin-film transistors, which is one of the key technologies to realize transparent electronics. This article provides a comprehensive review of the state-of-the-art research activities that focus on transparent metal oxide nanowire transistors. It begins with the brief introduction to the synthetic methods for high quality metal oxide nanowires, and the typical nanowire transfer and printing techniques with emphasis on the simple contact printing methodology. High performance transparent transistors built on both single nanowires and nanowire thin films are then highlighted. The final section deals with the applications of transparent metal oxide nanowire transistors in the field of transparent displays and concludes with an outlook on the current perspectives and future directions of transparent metal oxide nanowire transistors.

  9. Transparent metal oxide nanowire transistors.

    PubMed

    Chen, Di; Liu, Zhe; Liang, Bo; Wang, Xianfu; Shen, Guozhen

    2012-05-21

    With the features of high mobility, a high electric on/off ratio and excellent transparency, metal oxide nanowires are excellent candidates for transparent thin-film transistors, which is one of the key technologies to realize transparent electronics. This article provides a comprehensive review of the state-of-the-art research activities that focus on transparent metal oxide nanowire transistors. It begins with the brief introduction to the synthetic methods for high quality metal oxide nanowires, and the typical nanowire transfer and printing techniques with emphasis on the simple contact printing methodology. High performance transparent transistors built on both single nanowires and nanowire thin films are then highlighted. The final section deals with the applications of transparent metal oxide nanowire transistors in the field of transparent displays and concludes with an outlook on the current perspectives and future directions of transparent metal oxide nanowire transistors.

  10. Germanium Detectors in Homeland Security at PNNL

    SciTech Connect

    Stave, Sean C.

    2015-05-01

    Neutron and gamma-ray detection is used for non-proliferation and national security applications. While lower energy resolution detectors such as NaI(Tl) have their place, high purity germanium (HPGe) also has a role to play. A detection with HPGe is often a characterization due to the very high energy resolution. However, HPGe crystals remain small and expensive leaving arrays of smaller crystals as an excellent solution. PNNL has developed two similar HPGe arrays for two very different applications. One array, the Multisensor Aerial Radiation Survey (MARS) detector is a fieldable array that has been tested on trucks, boats, and helicopters. The CASCADES HPGe array is an array designed to assay samples in a low background environment. The history of HPGe arrays at PNNL and the development of MARS and CASCADES will be detailed in this paper along with some of the other applications of HPGe at PNNL.

  11. Germanium detectors in homeland security at PNNL

    DOE PAGES

    Stave, S.

    2015-05-01

    Neutron and gamma-ray detection is used for non-proliferation and national security applications. While lower energy resolution detectors such as NaI(Tl) have their place, high purity germanium (HPGe) also has a role to play. A detection with HPGe is often a characterization due to the very high energy resolution. However, HPGe crystals remain small and expensive leaving arrays of smaller crystals as an excellent solution. PNNL has developed two similar HPGe arrays for two very different applications. One array, the Multisensor Aerial Radiation Survey (MARS) detector is a fieldable array that has been tested on trucks, boats, and helicopters. The CASCADESmore » HPGe array is an array designed to assay samples in a low background environment. The history of HPGe arrays at PNNL and the development of MARS and CASCADES will be detailed in this paper along with some of the other applications of HPGe at PNNL.« less

  12. Germanium detectors in homeland security at PNNL

    SciTech Connect

    Stave, S.

    2015-05-01

    Neutron and gamma-ray detection is used for non-proliferation and national security applications. While lower energy resolution detectors such as NaI(Tl) have their place, high purity germanium (HPGe) also has a role to play. A detection with HPGe is often a characterization due to the very high energy resolution. However, HPGe crystals remain small and expensive leaving arrays of smaller crystals as an excellent solution. PNNL has developed two similar HPGe arrays for two very different applications. One array, the Multisensor Aerial Radiation Survey (MARS) detector is a fieldable array that has been tested on trucks, boats, and helicopters. The CASCADES HPGe array is an array designed to assay samples in a low background environment. The history of HPGe arrays at PNNL and the development of MARS and CASCADES will be detailed in this paper along with some of the other applications of HPGe at PNNL.

  13. Background suppression techniques in germanium detectors

    NASA Technical Reports Server (NTRS)

    Gehrels, Neil; Cheung, Cynthia

    1992-01-01

    A new generation of astrophysical gamma ray spectrometers employing germanium solid state detectors for precise energy measurement are currently being planned for spaceflight in the late 1990's and the early 21st century. Because the observations of weak celestial sources are carried out in an intense radiation environment, the key objective of instrument design is to find ways to reduce the background. The current state of the knowledge in this field is reviewed and the new hardware techniques under design and test are discussed. Many of these techniques have already been flight tested on balloon platforms. Recent results from some of these tests are presented. By carefully applying these techniques it should be possible to achieve sensitivities that are factors of 3 to 10 better than would be obtained for a conventional instrument of similar weight.

  14. Germanium implantation into substrates for integrated optics

    NASA Astrophysics Data System (ADS)

    Poumellec, B.; Traverse, A.; Artigaud, S.; Hervo, J.

    1994-04-01

    Germanium and helium implantations have been performed in LiNbO 3, SiO 2 quartz and silica. The agreement between calculated and experimental doping profiles is excellent. The index profiles coincide with the calculated collision profiles but we have observed a surface effect in quartz and LiNbO 3. In the first material, Ge implantation yields a larger decrease of the refractive index at the surface than He, as it is predicted by calculation if we assume the refractive index and the disorder profile to be connected. In contrast, in LiNbO 3 a reverse observation is made with respect to the refractive index. It is accompanied by chemical perturbation which interferes with the structural modification at the origin of the refractive index change. One advantage of the method is that implanted Ge is in a reduced state.

  15. Fabrication and characteristics of porous germanium films

    PubMed Central

    Jing, Chengbin; Zhang, Chuanjian; Zang, Xiaodan; Zhou, Wenzheng; Bai, Wei; Lin, Tie; Chu, Junhao

    2009-01-01

    Porous germanium films with good adhesion to the substrate were produced by annealing GeO2 ceramic films in H2 atmosphere. The reduction of GeO2 started at the top of a film and resulted in a Ge layer with a highly porous surface. TEM and Raman measurements reveal small Ge crystallites at the top layer and a higher degree of crystallinity at the bottom part of the Ge film; visible photoluminescence was detected from the small crystallites. Porous Ge films exhibit high density of holes (1020 cm−3) and a maximum of Hall mobility at ∼225 K. Their p-type conductivity is dominated by the defect scattering mechanism. PMID:27877311

  16. Silicon germanium carbon heteroepitaxial growth on silicon

    NASA Astrophysics Data System (ADS)

    Mayer, James W.

    1993-10-01

    This project represents the initiation of band-gap engineering of Si-based devices at Arizona State University by James W. Mayer. While at Cornell, he directed the Microscience and Technology program supported by the Semiconductor Research Corporation. His Work on heteoepitaxy of SiGe on silicon convinced him that heteroepitaxy on Si was a viable technique for forming smaller band gap layers on silicon but the requirement was for larger energy-gap materials. In the fall of 1991, James Mayer visited Tom Picraux of Sandia National Laboratories and Clarence Tracy of Motorola Semiconductor Products to discuss the possibility of a joint program to investigate Silicon Germanium Carbon Heteroepitaxial Growth on Silicon. This represented a new research and development initiate for band gap engineering.

  17. Zirconia-germanium interface photoemission spectroscopy using synchrotron radiation

    SciTech Connect

    Chui, Chi On

    2005-04-05

    An ultrathin zirconia gate dielectric had been successfully incorporated into germanium metal-oxide-semiconductor (MOS) devices demonstrating very high permittivity gate stacks with no apparent interfacial layer. In this study, synchrotron radiation photoemission spectroscopy has been applied on the same gate stack to identify and quantify the presence of any interfacial germanium sub-oxide layer. By taking progressive core- level spectra during the layer-by-layer removal of the zirconia film, an oxidized germanium layer with sub-monolayer thickness was found possibly arising from an interfacial Zr-O-Ge bonding configuration. In addition, the offsets in the valence band spectra were also monitored and the energy band diagram of the zirconia-germanium heterostructure was constructed. Compared to high-{kappa} gate stacks on Si, the thinner interfacial layer and larger conduction band offset in high-{kappa} gate stacks on Ge suggest better scalability towards an ultimately higher MOS gate capacitance.

  18. Catalyst patterning for nanowire devices

    NASA Technical Reports Server (NTRS)

    Li, Jun (Inventor); Cassell, Alan M. (Inventor); Han, Jie (Inventor)

    2004-01-01

    Nanowire devices may be provided that are based on carbon nanotubes or single-crystal semiconductor nanowires. The nanowire devices may be formed on a substrate. Catalyst sites may be formed on the substrate. The catalyst sites may be formed using lithography, thin metal layers that form individual catalyst sites when heated, collapsible porous catalyst-filled microscopic spheres, microscopic spheres that serve as masks for catalyst deposition, electrochemical deposition techniques, and catalyst inks. Nanowires may be grown from the catalyst sites.

  19. All Nanowire Integrated Sensor Circuitry

    DTIC Science & Technology

    2008-04-01

    of single crystalline nanomaterials. Highly ordered and parallel arrays of optically active CdSe nanowires and high mobility Ge/Si nanowires are...for enabling the fabrication of the all- nanowire sensor circuitry. First, highly aligned CdSe and Ge/Si NW arrays were assembled at pre-defined...FETs (Tl and T2) amplifying the photoresponse of a CdSe nanosensor. (B) Schematic of the all- nanowire optical sensor circuit based on ordered

  20. Lipid nanotube or nanowire sensor

    DOEpatents

    Noy, Aleksandr [Belmont, CA; Bakajin, Olgica [San Leandro, CA; Letant, Sonia [Livermore, CA; Stadermann, Michael [Dublin, CA; Artyukhin, Alexander B [Menlo Park, CA

    2009-06-09

    A sensor apparatus comprising a nanotube or nanowire, a lipid bilayer around the nanotube or nanowire, and a sensing element connected to the lipid bilayer. Also a biosensor apparatus comprising a gate electrode; a source electrode; a drain electrode; a nanotube or nanowire operatively connected to the gate electrode, the source electrode, and the drain electrode; a lipid bilayer around the nanotube or nanowire, and a sensing element connected to the lipid bilayer.

  1. Lipid nanotube or nanowire sensor

    DOEpatents

    Noy, Aleksandr [Belmont, CA; Bakajin, Olgica [San Leandro, CA; Letant, Sonia [Livermore, CA; Stadermann, Michael [Dublin, CA; Artyukhin, Alexander B [Menlo Park, CA

    2010-06-29

    A sensor apparatus comprising a nanotube or nanowire, a lipid bilayer around the nanotube or nanowire, and a sensing element connected to the lipid bilayer. Also a biosensor apparatus comprising a gate electrode; a source electrode; a drain electrode; a nanotube or nanowire operatively connected to the gate electrode, the source electrode, and the drain electrode; a lipid bilayer around the nanotube or nanowire, and a sensing element connected to the lipid bilayer.

  2. Na-doped optical Germanium bulk crystals

    NASA Astrophysics Data System (ADS)

    Pekar, G. S.; Singaevsky, A. F.

    2012-09-01

    In an effort to develop a material for infrared (IR) optics with improved parameters, bulk crystals of optical germanium doped with Na have been first grown and studied. Single-crystalline and coarse-crystalline Ge:Na boules of different shapes and dimensions, up to 10 kg by weight, have been grown. Sodium was incorporated into the Ge crystal during the crystal growing from the melt. Despite the fact that Na contamination in the source material was not strictly controlled, the density of Na in the grown crystals determined by the neutron activation analysis as well as by the glow discharge mass spectrometry did not exceed 1015 cm-3. Just this value may be supposed to be close to the solubility limit of Na incorporated in Ge in the course of bulk crystal growth. A first demonstration of donor behavior of Na in bulk Ge crystals is made by means of a thermoelectric type of testing. An interstitial location of Na impurity has been verified by experiments on donor drift in the dc electric field. The crystals are grown with free electron density in the range from 5ṡ1013 to 4ṡ1014 cm-3 which is optimal for using Ge crystals as an optical material for fabricating passive elements of the IR technique. A comparison between the properties of Ge:Na crystals and Ge crystals doped with Sb, a conventional impurity in optical germanium, grown under the same technological conditions and from the same intrinsic Ge as a source material, revealed a number of advantages of Ge:Na crystals; among them, the higher transparency in the IR region, smaller radiation scattering and higher regular optical transmission, lower dislocation density, more uniform distribution of electrical and optical characteristics over the crystal volume, the identity of optical parameters in the single-crystalline, and coarse-crystalline boules. No degradation of optical elements fabricated from Ge:Na crystals was detected in the course of their commercial application, starting from 1998.

  3. Electromechanically cooled germanium radiation detector system

    NASA Astrophysics Data System (ADS)

    Lavietes, Anthony D.; Joseph Mauger, G.; Anderson, Eric H.

    1999-02-01

    We have successfully developed and fielded an electromechanically cooled germanium radiation detector (EMC-HPGe) at Lawrence Livermore National Laboratory (LLNL). This detector system was designed to provide optimum energy resolution, long lifetime, and extremely reliable operation for unattended and portable applications. For most analytical applications, high purity germanium (HPGe) detectors are the standard detectors of choice, providing an unsurpassed combination of high energy resolution performance and exceptional detection efficiency. Logistical difficulties associated with providing the required liquid nitrogen (LN) for cooling is the primary reason that these systems are found mainly in laboratories. The EMC-HPGe detector system described in this paper successfully provides HPGe detector performance in a portable instrument that allows for isotopic analysis in the field. It incorporates a unique active vibration control system that allows the use of a Sunpower Stirling cycle cryocooler unit without significant spectral degradation from microphonics. All standard isotopic analysis codes, including MGA and MGA++ [1], GAMANL [2], GRPANL [3]and MGAU [4], typically used with HPGe detectors can be used with this system with excellent results. Several national and international Safeguards organisations including the International Atomic Energy Agency (IAEA) and U.S. Department of Energy (DOE) have expressed interest in this system. The detector was combined with custom software and demonstrated as a rapid Field Radiometric Identification System (FRIS) for the U.S. Customs Service [5]. The European Communities' Safeguards Directorate (EURATOM) is field-testing the first Safeguards prototype in their applications. The EMC-HPGe detector system design, recent applications, and results will be highlighted.

  4. Reduction of Defects in Germanium-Silicon

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Crystals grown without contact with a container have far superior quality to otherwise similar crystals grown in direct contact with a container. In addition to float-zone processing, detached- Bridgman growth is a promising tool to improve crystal quality, without the limitations of float zoning or the defects introduced by normal Bridgman growth. Goals of this project include the development of the detached Bridgman process to be reproducible and well understood and to quantitatively compare the defect and impurity levels in crystals grown by these three methods. Germanium (Ge) and germanium-silicon (Ge-Si) alloys are being used. At MSFC, we are responsible for the detached Bridgman experiments intended to differentiate among proposed mechanisms of detachment, and to confirm or refine our understanding of detachment. Because the contact angle is critical to determining the conditions for detachment, the sessile drop method was used to measure the contact angles as a function of temperature and composition for a large number of substrates made of potential ampoule materials. Growth experiments have used pyrolytic boron nitride (pBN) and fused silica ampoules with the majority of the detached results occurring predictably in the pBN. Etch pit density (EPD) measurements of normal and detached Bridgman-grown Ge samples show a two order of magnitude improvement in the detached-grown samples. The nature and extent of detachment is determined by using profilometry in conjunction with optical and electron microscopy. The stability of detachment has been analyzed, and an empirical model for the conditions necessary to achieve sufficient stability to maintain detached growth for extended periods has been developed. We have investigated the effects on detachment of ampoule material, pressure difference above and below the melt, and Si concentration; samples that are nearly completely detached can be grown repeatedly in pBN. Current work is concentrated on developing a

  5. Electromechanically-cooled germanium radiation detector system

    SciTech Connect

    Lavietes, A. D., LLNL.

    1998-05-01

    We have successfully developed and fielded an electromechanically cooled germanium radiation detector (EMC-HPGe) at Lawrence Livermore National Laboratory (LLNL). This detector system was designed to provide optimum energy resolution, long lifetime, and extremely reliable operation for unattended and portable applications. For most analytical applications, high-purity germanium (HPGe) detectors are the standard detectors of choice, providing an unsurpassed combination of high energy resolution performance and exceptional detection efficiency. Logistical difficulties associated with providing the required liquid nitrogen (LN) for cooling is the primary reason that these systems are found mainly in laboratories. The EMC-HPGe detector system described in this paper successfully provides HPGe detector performance in a portable instrument that allows for isotopic analysis in the field. It incorporates a unique active vibration control system that allows the use of a Sunpower Stirling cycle cryocooler unit without significant spectral degradation from microphonics. All standard isotopic analysis codes, including MGA and MGA++[1], GAMANL[2], GRPANL[3] and MGAU[4], typically used with HPGe detectors can be used with this system with excellent results. Several national and international Safeguards organizations including the International Atomic Energy Agency (IAEA) and U.S. Department of Energy (DOE) have expressed interest in this system. The detector was combined with custom software and demonstrated as a rapid Field Radiometric Identification System (FRIS) for the U.S. Customs Service[5]. The European Communities' Safeguards Directorate (EURATOM) is field-testing the first Safeguards prototype in their applications. The EMC-HPGe detector system design, recent applications, and results will be highlighted.

  6. Nanowire Thermoelectric Devices

    NASA Technical Reports Server (NTRS)

    Borshchevsky, Alexander; Fleurial, Jean-Pierre; Herman, Jennifer; Ryan, Margaret

    2005-01-01

    Nanowire thermoelectric devices, now under development, are intended to take miniaturization a step beyond the prior state of the art to exploit the potential advantages afforded by shrinking some device features to approximately molecular dimensions (of the order of 10 nm). The development of nanowire-based thermoelectric devices could lead to novel power-generating, cooling, and sensing devices that operate at relatively low currents and high voltages. Recent work on the theory of thermoelectric devices has led to the expectation that the performance of such a device could be enhanced if the diameter of the wires could be reduced to a point where quantum confinement effects increase charge-carrier mobility (thereby increasing the Seebeck coefficient) and reduce thermal conductivity. In addition, even in the absence of these effects, the large aspect ratios (length of the order of tens of microns diameter of the order of tens of nanometers) of nanowires would be conducive to the maintenance of large temperature differences at small heat fluxes. The predicted net effect of reducing diameters to the order of tens of nanometers would be to increase its efficiency by a factor of .3. Nanowires made of thermoelectric materials and devices that comprise arrays of such nanowires can be fabricated by electrochemical growth of the thermoelectric materials in templates that contain suitably dimensioned pores (10 to 100 nm in diameter and 1 to 100 microns long). The nanowires can then be contacted in bundles to form devices that look similar to conventional thermoelectric devices, except that a production version may contain nearly a billion elements (wires) per square centimeter, instead of fewer than a hundred as in a conventional bulk thermoelectric device or fewer than 100,000 as in a microdevice. It is not yet possible to form contacts with individual nanowires. Therefore, in fabricating a nanowire thermoelectric device, one forms contacts on nanowires in bundles of the

  7. Near-infrared emission from mesoporous crystalline germanium

    SciTech Connect

    Boucherif, Abderraouf; Aimez, Vincent; Arès, Richard; Korinek, Andreas

    2014-10-15

    Mesoporous crystalline germanium was fabricated by bipolar electrochemical etching of Ge wafer in HF-based electrolyte. It yields uniform mesoporous germanium layers composed of high density of crystallites with an average size 5-7 nm. Subsequent extended chemical etching allows tuning of crystallites size while preserving the same chemical composition. This highly controllable nanostructure exhibits photoluminescence emission above the bulk Ge bandgap, in the near-infrared range (1095-1360nm) with strong evidence of quantum confinement within the crystallites.

  8. Method for using germanium thermometers in moderately high magnetic fields

    NASA Astrophysics Data System (ADS)

    Roy, A.; Buchanan, D. S.; Ginsberg, D. M.

    1985-03-01

    We have devised a simple method for extending the zero-field calibration of a germanium resistance thermometer to include the effects of magnetic fields up to 5 T. We describe the application of this method to the use of a germanium thermometer at liquid-helium temperatures. We outline a similar procedure to take into account the temperature variation of the calibration of a Hall probe.

  9. Near-infrared emission from mesoporous crystalline germanium

    NASA Astrophysics Data System (ADS)

    Boucherif, Abderraouf; Korinek, Andreas; Aimez, Vincent; Arès, Richard

    2014-10-01

    Mesoporous crystalline germanium was fabricated by bipolar electrochemical etching of Ge wafer in HF-based electrolyte. It yields uniform mesoporous germanium layers composed of high density of crystallites with an average size 5-7 nm. Subsequent extended chemical etching allows tuning of crystallites size while preserving the same chemical composition. This highly controllable nanostructure exhibits photoluminescence emission above the bulk Ge bandgap, in the near-infrared range (1095-1360nm) with strong evidence of quantum confinement within the crystallites.

  10. Hydrothermal germanium over the southern East pacific rise.

    PubMed

    Mortlock, R A; Froelich, P N

    1986-01-03

    Germanium enrichment in the oceanic water column above the southern axis of the East Pacific Rise results from hydrothermal solutions emanating from hot springs along the rise crest. This plume signature provides a new oceanic tracer of reactions between seawater and sea floor basalts during hydrothermal alteration. In contrast to the sharp plumes of (3)He and manganese, the germanium plume is broad and diffuse, suggesting the existence of pervasive venting of low-temperature solutions off the ridge axis.

  11. Optical gain in single tensile-strained germanium photonic wire.

    PubMed

    de Kersauson, M; El Kurdi, M; David, S; Checoury, X; Fishman, G; Sauvage, S; Jakomin, R; Beaudoin, G; Sagnes, I; Boucaud, P

    2011-09-12

    We have investigated the optical properties of tensile-strained germanium photonic wires. The photonic wires patterned by electron beam lithography (50 μm long, 1 μm wide and 500 nm thick) are obtained by growing a n-doped germanium film on a GaAs substrate. Tensile strain is transferred in the germanium layer using a Si₃N₄ stressor. Tensile strain around 0.4% achieved by the technique corresponds to an optical recombination of tensile-strained germanium involving light hole band around 1690 nm at room temperature. We show that the waveguided emission associated with a single tensile-strained germanium wire increases superlinearly as a function of the illuminated length. A 20% decrease of the spectral broadening is observed as the pump intensity is increased. All these features are signatures of optical gain. A 80 cm⁻¹ modal optical gain is derived from the variable strip length method. This value is accounted for by the calculated gain material value using a 30 band k · p formalism. These germanium wires represent potential building blocks for integration of nanoscale optical sources on silicon.

  12. Method of fabricating germanium and gallium arsenide devices

    NASA Technical Reports Server (NTRS)

    Jhabvala, Murzban (Inventor)

    1990-01-01

    A method of semiconductor diode fabrication is disclosed which relies on the epitaxial growth of a precisely doped thickness layer of gallium arsenide or germanium on a semi-insulating or intrinsic substrate, respectively, of gallium arsenide or germanium by either molecular beam epitaxy (MBE) or by metal-organic chemical vapor deposition (MOCVD). The method involves: depositing a layer of doped or undoped silicon dioxide on a germanium or gallium arsenide wafer or substrate, selectively removing the silicon dioxide layer to define one or more surface regions for a device to be fabricated thereon, growing a matched epitaxial layer of doped germanium or gallium arsenide of an appropriate thickness using MBE or MOCVD techniques on both the silicon dioxide layer and the defined one or more regions; and etching the silicon dioxide and the epitaxial material on top of the silicon dioxide to leave a matched epitaxial layer of germanium or gallium arsenide on the germanium or gallium arsenide substrate, respectively, and upon which a field effect device can thereafter be formed.

  13. Perovskite Nanowire Extrusion.

    PubMed

    Oener, Sebastian Z; Khoram, Parisa; Brittman, Sarah; Mann, Sander A; Zhang, Qianpeng; Fan, Zhiyong; Boettcher, Shannon W; Garnett, Erik C

    2017-10-10

    The defect tolerance of halide perovskite materials has led to efficient optoelectronic devices based on thin-film geometries with unprecedented speed. Moreover, it has motivated research on perovskite nanowires because surface recombination continues to be a major obstacle in realizing efficient nanowire devices. Recently, ordered vertical arrays of perovskite nanowires have been realized, which can benefit from nanophotonic design strategies allowing precise control over light propagation, absorption, and emission. An anodized aluminum oxide template is used to confine the crystallization process, either in the solution or in the vapor phase. This approach, however, results in an unavoidable drawback: only nanowires embedded inside the AAO are obtainable, since the AAO cannot be etched selectively. The requirement for a support matrix originates from the intrinsic difficulty of controlling precise placement, sizes, and shapes of free-standing nanostructures during crystallization, especially in solution. Here we introduce a method to fabricate free-standing solution-based vertical nanowires with arbitrary dimensions. Our scheme also utilizes AAO; however, in contrast to embedding the perovskite inside the matrix, we apply a pressure gradient to extrude the solution from the free-standing templates. The exit profile of the template is subsequently translated into the final semiconductor geometry. The free-standing nanowires are single crystalline and show a PLQY up to ∼29%. In principle, this rapid method is not limited to nanowires but can be extended to uniform and ordered high PLQY single crystalline perovskite nanostructures of different shapes and sizes by fabricating additional masking layers or using specifically shaped nanopore endings.

  14. Nanowire mesh solar fuels generator

    DOEpatents

    Yang, Peidong; Chan, Candace; Sun, Jianwei; Liu, Bin

    2016-05-24

    This disclosure provides systems, methods, and apparatus related to a nanowire mesh solar fuels generator. In one aspect, a nanowire mesh solar fuels generator includes (1) a photoanode configured to perform water oxidation and (2) a photocathode configured to perform water reduction. The photocathode is in electrical contact with the photoanode. The photoanode may include a high surface area network of photoanode nanowires. The photocathode may include a high surface area network of photocathode nanowires. In some embodiments, the nanowire mesh solar fuels generator may include an ion conductive polymer infiltrating the photoanode and the photocathode in the region where the photocathode is in electrical contact with the photoanode.

  15. The Mechanical Properties of Nanowires

    PubMed Central

    Wang, Shiliang; Shan, Zhiwei

    2017-01-01

    Applications of nanowires into future generation nanodevices require a complete understanding of the mechanical properties of the nanowires. A great research effort has been made in the past two decades to understand the deformation physics and mechanical behaviors of nanowires, and to interpret the discrepancies between experimental measurements and theoretical predictions. This review focused on the characterization and understanding of the mechanical properties of nanowires, including elasticity, plasticity, anelasticity and strength. As the results from the previous literature in this area appear inconsistent, a critical evaluation of the characterization techniques and methodologies were presented. In particular, the size effects of nanowires on the mechanical properties and their deformation mechanisms were discussed. PMID:28435775

  16. Selective formation of tungsten nanowires

    PubMed Central

    2011-01-01

    We report on a process for fabricating self-aligned tungsten (W) nanowires with polycrystalline silicon core. Tungsten nanowires as thin as 10 nm were formed by utilizing polysilicon sidewall transfer technology followed by selective deposition of tungsten by chemical vapor deposition (CVD) using WF6 as the precursor. With selective CVD, the process is self-limiting whereby the tungsten formation is confined to the polysilicon regions; hence, the nanowires are formed without the need for lithography or for additional processing. The fabricated tungsten nanowires were observed to be perfectly aligned, showing 100% selectivity to polysilicon and can be made to be electrically isolated from one another. The electrical conductivity of the nanowires was characterized to determine the effect of its physical dimensions. The conductivity for the tungsten nanowires were found to be 40% higher when compared to doped polysilicon nanowires of similar dimensions. PMID:21970543

  17. Selective formation of tungsten nanowires.

    PubMed

    Bien, Daniel Cs; Saman, Rahimah Mohd; Badaruddin, Siti Aishah Mohamad; Lee, Hing Wah

    2011-10-04

    We report on a process for fabricating self-aligned tungsten (W) nanowires with polycrystalline silicon core. Tungsten nanowires as thin as 10 nm were formed by utilizing polysilicon sidewall transfer technology followed by selective deposition of tungsten by chemical vapor deposition (CVD) using WF6 as the precursor. With selective CVD, the process is self-limiting whereby the tungsten formation is confined to the polysilicon regions; hence, the nanowires are formed without the need for lithography or for additional processing. The fabricated tungsten nanowires were observed to be perfectly aligned, showing 100% selectivity to polysilicon and can be made to be electrically isolated from one another. The electrical conductivity of the nanowires was characterized to determine the effect of its physical dimensions. The conductivity for the tungsten nanowires were found to be 40% higher when compared to doped polysilicon nanowires of similar dimensions.

  18. Piezoresistive boron doped diamond nanowire

    DOEpatents

    Sumant, Anirudha V.; Wang, Xinpeng

    2017-07-04

    A UNCD nanowire comprises a first end electrically coupled to a first contact pad which is disposed on a substrate. A second end is electrically coupled to a second contact pad also disposed on the substrate. The UNCD nanowire is doped with a dopant and disposed over the substrate. The UNCD nanowire is movable between a first configuration in which no force is exerted on the UNCD nanowire and a second configuration in which the UNCD nanowire bends about the first end and the second end in response to a force. The UNCD nanowire has a first resistance in the first configuration and a second resistance in the second configuration which is different from the first resistance. The UNCD nanowire is structured to have a gauge factor of at least about 70, for example, in the range of about 70 to about 1,800.

  19. Piezoresistive boron doped diamond nanowire

    DOEpatents

    Sumant, Anirudha V.; Wang, Xinpeng

    2016-09-13

    A UNCD nanowire comprises a first end electrically coupled to a first contact pad which is disposed on a substrate. A second end is electrically coupled to a second contact pad also disposed on the substrate. The UNCD nanowire is doped with a dopant and disposed over the substrate. The UNCD nanowire is movable between a first configuration in which no force is exerted on the UNCD nanowire and a second configuration in which the UNCD nanowire bends about the first end and the second end in response to a force. The UNCD nanowire has a first resistance in the first configuration and a second resistance in the second configuration which is different from the first resistance. The UNCD nanowire is structured to have a gauge factor of at least about 70, for example, in the range of about 70 to about 1,800.

  20. EDITORIAL: Nanowires for energy Nanowires for energy

    NASA Astrophysics Data System (ADS)

    LaPierre, Ray; Sunkara, Mahendra

    2012-05-01

    This special issue of Nanotechnology focuses on studies illustrating the application of nanowires for energy including solar cells, efficient lighting and water splitting. Over the next three decades, nanotechnology will make significant contributions towards meeting the increased energy needs of the planet, now known as the TeraWatt challenge. Nanowires in particular are poised to contribute significantly in this development as presented in the review by Hiralal et al [1]. Nanowires exhibit light trapping properties that can act as a broadband anti-reflection coating to enhance the efficiency of solar cells. In this issue, Li et al [2] and Wang et al [3] present the optical properties of silicon nanowire and nanocone arrays. In addition to enhanced optical properties, core-shell nanowires also have the potential for efficient charge carrier collection across the nanowire diameter as presented in the contribution by Yu et al [4] for radial junction a-Si solar cells. Hybrid approaches that combine organic and inorganic materials also have potential for high efficiency photovoltaics. A Si-based hybrid solar cell is presented by Zhang et al [5] with a photoconversion efficiency of over 7%. The quintessential example of hybrid solar cells is the dye-sensitized solar cell (DSSC) where an organic absorber (dye) coats an inorganic material (typically a ZnO nanostructure). Herman et al [6] present a method of enhancing the efficiency of a DSSC by increasing the hetero-interfacial area with a unique hierarchical weeping willow ZnO structure. The increased surface area allows for higher dye loading, light harvesting, and reduced charge recombination through direct conduction along the ZnO branches. Another unique ZnO growth method is presented by Calestani et al [7] using a solution-free and catalyst-free approach by pulsed electron deposition (PED). Nanowires can also make more efficient use of electrical power. Light emitting diodes, for example, will eventually become the

  1. Germanium ``hexa'' detector: production and testing

    NASA Astrophysics Data System (ADS)

    Sarajlić, M.; Pennicard, D.; Smoljanin, S.; Hirsemann, H.; Struth, B.; Fritzsch, T.; Rothermund, M.; Zuvic, M.; Lampert, M. O.; Askar, M.; Graafsma, H.

    2017-01-01

    Here we present new result on the testing of a Germanium sensor for X-ray radiation. The system is made of 3 × 2 Medipix3RX chips, bump-bonded to a monolithic sensor, and is called ``hexa''. Its dimensions are 45 × 30 mm2 and the sensor thickness was 1.5 mm. The total number of the pixels is 393216 in the matrix 768 × 512 with pixel pitch 55 μ m. Medipix3RX read-out chip provides photon counting read-out with single photon sensitivity. The sensor is cooled to ‑126°C and noise levels together with flat field response are measured. For ‑200 V polarization bias, leakage current was 4.4 mA (3.2 μ A/mm2). Due to higher leakage around 2.5% of all pixels stay non-responsive. More than 99% of all pixels are bump bonded correctly. In this paper we present the experimental set-up, threshold equalization procedure, image acquisition and the technique for bump bond quality estimate.

  2. Detached Growth of Germanium and Germaniumsilicon

    NASA Technical Reports Server (NTRS)

    Dold, P.; Schweizer, M.; Szofran, F.; Benz, K. W.

    1999-01-01

    Up to now, detached growth was observed mainly under microgravity, i.e. under the absence of hydrostatic pressure that hinders the formation of a free melt meniscus. the detached growth of germanium doped with gallium was obtained under 1 g conditions, the growth was performed in quartz-glass ampoule. Part of the crystal grew without wall contact, the detached growth was observed in-situ with a CCD-camera as well as after the growth process in form of growth lines and the formation of <111> facets on the crystal surface. GeSi crystal (oriientation: <111>, maximum silicon content: 4 at%, seed material: Ge) was grown in a pBN crucible (excluding the possibility of in-situ monitoring of the growth process). The grown crystal exhibits three growth facets, indicating also wall free growth. Surface analysis of the crystals (NDIC, SEM) and characterization of crystal segregation (EDAX, resistivity measurement) and defect structure (EPD, x-ray diffraction measurements) will be presented.

  3. Indirect absorption in germanium quantum wells

    NASA Astrophysics Data System (ADS)

    Schaevitz, R. K.; Ly-Gagnon, D. S.; Roth, J. E.; Edwards, E. H.; Miller, D. A. B.

    2011-09-01

    Germanium has become a promising material for creating CMOS-compatible optoelectronic devices, such as modulators and detectors employing the Franz-Keldysh effect (FKE) or the quantum-confined Stark effect (QCSE), which meet strict energy and density requirements for future interconnects. To improve Ge-based modulator design, it is important to understand the contributions to the insertion loss (IL). With indirect absorption being the primary component of IL, we have experimentally determined the strength of this loss and compared it with theoretical models. For the first time, we have used the more sensitive photocurrent measurements for determining the effective absorption coefficient in our Ge/SiGe quantum well material employing QCSE. This measurement technique enables measurement of the absorption coefficient over four orders of magnitude. We find good agreement between our thin Ge quantum wells and the bulk material parameters and theoretical models. Similar to bulk Ge, we find that the 27.7 meV LA phonon is dominant in these quantum confined structures and that the electroabsorption profile can be predicted using the model presented by Frova, Phys. Rev., 145 (1966).

  4. Detached Growth of Germanium and Germaniumsilicon

    NASA Technical Reports Server (NTRS)

    Dold, P.; Schweizer, M.; Szofran, F.; Benz, K. W.

    1999-01-01

    Up to now, detached growth was observed mainly under microgravity, i.e. under the absence of hydrostatic pressure that hinders the formation of a free melt meniscus. the detached growth of germanium doped with gallium was obtained under 1 g conditions, the growth was performed in quartz-glass ampoule. Part of the crystal grew without wall contact, the detached growth was observed in-situ with a CCD-camera as well as after the growth process in form of growth lines and the formation of <111> facets on the crystal surface. GeSi crystal (oriientation: <111>, maximum silicon content: 4 at%, seed material: Ge) was grown in a pBN crucible (excluding the possibility of in-situ monitoring of the growth process). The grown crystal exhibits three growth facets, indicating also wall free growth. Surface analysis of the crystals (NDIC, SEM) and characterization of crystal segregation (EDAX, resistivity measurement) and defect structure (EPD, x-ray diffraction measurements) will be presented.

  5. Growth and properties of nanocrystalline germanium films

    NASA Astrophysics Data System (ADS)

    Niu, Xuejun; Dalal, Vikram L.

    2005-11-01

    We report on the growth characteristics and structure of nanocrystalline germanium films using low-pressure plasma-assisted chemical vapor deposition process in a remote electron-cyclotron-resonance reactor. The films were grown from mixtures of germane and hydrogen at deposition temperatures varying between 130 °C and 310 °C. The films were measured for structure using Raman and x-ray spectroscopy. It is shown that the orientation of the film depends strongly upon the deposition conditions. Low-temperature growth leads to both <111> and <220> orientations, whereas at higher temperatures, the <220> grain strongly dominates. The Raman spectrum reveals a sharp crystalline peak at 300 cm-1 and a high ratio between crystalline and amorphous peak that is at 285 cm-1. The grain size in the films is a strong function of hydrogen dilution, with higher dilutions leading to smaller grain sizes. Growth temperature also has a strong influence on grain size, with higher temperatures yielding larger grain sizes. From these results, which are seen to be compatible with the growth of nanocrystalline Si films, it is seen that the natural growth direction for the film is <220>, and that bonded hydrogen interferes with the growth of <220> grains. High hydrogen dilutions lead to more random nucleation.

  6. Electrodeposition of germanium from supercritical fluids.

    PubMed

    Ke, Jie; Bartlett, Philip N; Cook, David; Easun, Timothy L; George, Michael W; Levason, William; Reid, Gillian; Smith, David; Su, Wenta; Zhang, Wenjian

    2012-01-28

    Several Ge(II) and Ge(IV) compounds were investigated as possible reagents for the electrodeposition of Ge from liquid CH(3)CN and CH(2)F(2) and supercritical CO(2) containing as a co-solvent CH(3)CN (scCO(2)) and supercritical CH(2)F(2) (scCH(2)F(2)). For Ge(II) reagents the most promising results were obtained using [NBu(n)(4)][GeCl(3)]. However the reproducibility was poor and the reduction currents were significantly less than the estimated mass transport limited values. Deposition of Ge containing films was possible at high cathodic potential from [NBu(n)(4)][GeCl(3)] in liquid CH(3)CN and supercritical CO(2) containing CH(3)CN but in all cases they were heavily contaminated by C, O, F and Cl. Much more promising results were obtained using GeCl(4) in liquid CH(2)F(2) and supercritical CH(2)F(2). In this case the reduction currents were consistent with mass transport limited reduction and bulk electrodeposition produced amorphous films of Ge. Characterisation by XPS showed the presence of low levels of O, F and C, XPS confirmed the presence of Ge together with germanium oxides, and Raman spectroscopy showed that the as deposited amorphous Ge could be crystallised by the laser used in obtaining the Raman measurements.

  7. The Germanium GAlactic Plane Patrol mission

    NASA Technical Reports Server (NTRS)

    Tueller, Jack; Gehrels, Neil; Leventhal, Marvin

    1992-01-01

    The goal of the Germanium GAlactic Plane Patrol mission (GGAPP) is to provide a continuous monitor of the Galactic Plane (GP) for variable sources of gamma-ray lines. Potentially interesting sources include black hole candidates, X-ray binary systems, pulsars, gamma-ray bursts, and solar flares. The GGAPP instrument is an array of Ge detectors cooled by a mechanical refrigerator to achieve a spectral resolution of 2 keV at 1 MeV (1/500). A bismuth germanate (BGO) shield will restrict the field-of-view (FOV) to within 20 deg of the GP, and a modulation collimator system will locate strong sources to less than 0.3 deg in galactic longitude, provide a direct means of subtracting background, and mapping the diffuse emission from the GP. The spacecraft will be rotationally stabilized with the spin axis perpendicular to the GP such that the modulator scans in galactic longitude. A HEO or L1 orbit will keep GGAPP far away from the strong background produced by the Earth. GGAPP will provide a natural bridge between GRO and future missions such as INTEGRAL/NAE.

  8. Tunnel current across linear homocatenated germanium chains

    SciTech Connect

    Matsuura, Yukihito

    2014-01-28

    The electronic transport properties of germanium oligomers catenating into linear chains (linear Ge chains) have been theoretically studied using first principle methods. The conduction mechanism of a Ge chain sandwiched between gold electrodes was analyzed based on the density of states and the eigenstates of the molecule in a two-probe environment. Like that of silicon chains (Si chains), the highest occupied molecular orbital of Ge chains contains the extended σ-conjugation of Ge 4p orbitals at energy levels close to the Fermi level; this is in contrast to the electronic properties of linear carbon chains. Furthermore, the conductance of a Ge chain is expected to decrease exponentially with molecular length L. The decay constant β, which is defined as e{sup −βL}, of a Ge chain is similar to that of a Si chain, whereas the conductance of the Ge chains is higher than that of Si chains even though the Ge–Ge bond length is longer than the Si–Si bond length.

  9. Determination of the Wetting Angle of Germanium and Germanium-Silicon Melts on Different Substrate Materials

    NASA Technical Reports Server (NTRS)

    Kaiser, Natalie; Croell, Arne; Szofran, F. R.; Cobb. S. D.; Dold, P.; Benz, K. W.

    1999-01-01

    During Bridgman growth of semiconductors detachment of the crystal and the melt meniscus has occasionally been observed, mainly under microgravity (microg) conditions. An important factor for detached growth is the wetting angle of the melt with the crucible material. High contact angles are more likely to result in detachment of the growing crystal from the ampoule wall. In order to achieve detached growth of germanium (Ge) and germanium-silicon (GeSi) crystals under 1g and microg conditions, sessile drop measurements were performed to determine the most suitable ampoule material as well as temperature dependence of the surface tension for GeSi. Sapphire, fused quartz, glassy carbon, graphite, SiC, pyrolytic Boron Nitride (pBN), AIN, and diamond were used as substrates. Furthermore, different cleaning procedures and surface treatments (etching, sandblasting, etc.) of the same substrate material and their effect on the wetting behavior were studied during these experiments. pBN and AIN substrates exhibited the highest contact angles with values around 170 deg.

  10. Determination of the Wetting Angle of Germanium and Germanium-Silicon Melts on Different Substrate Materials

    NASA Technical Reports Server (NTRS)

    Kaiser, Natalie; Croell, Arne; Szofran, F. R.; Cobb. S. D.; Dold, P.; Benz, K. W.

    1999-01-01

    During Bridgman growth of semiconductors detachment of the crystal and the melt meniscus has occasionally been observed, mainly under microgravity (microg) conditions. An important factor for detached growth is the wetting angle of the melt with the crucible material. High contact angles are more likely to result in detachment of the growing crystal from the ampoule wall. In order to achieve detached growth of germanium (Ge) and germanium-silicon (GeSi) crystals under 1g and microg conditions, sessile drop measurements were performed to determine the most suitable ampoule material as well as temperature dependence of the surface tension for GeSi. Sapphire, fused quartz, glassy carbon, graphite, SiC, pyrolytic Boron Nitride (pBN), AIN, and diamond were used as substrates. Furthermore, different cleaning procedures and surface treatments (etching, sandblasting, etc.) of the same substrate material and their effect on the wetting behavior were studied during these experiments. pBN and AIN substrates exhibited the highest contact angles with values around 170 deg.

  11. The role of oxidized germanium in the growth of germanium nanoparticles on hafnia

    NASA Astrophysics Data System (ADS)

    Winkenwerder, Wyatt A.; Ekerdt, John G.

    2008-08-01

    The role oxidized germanium (GeO x) plays in germanium (Ge) nanoparticle growth on hafnia is reported. Oxide islands, in the form of hafnium germinate, form on hafnia during the initial stages of growth. The Ge adatoms are oxidized by background oxidants, such as water, only when they are in contact with the hafnia surface. Once a sufficient amount of hafnium germinate has formed, Ge nanoparticles nucleate such that nanoparticle growth proceeds by Ge growth on GeO x. Nanoparticles are not deposited on the hafnia but only on the interfacial oxide islands formed early in the growth process. Annealing hafnia in a silane ambient after Ge nanoparticle growth reduces the amount of GeO x and appears to transform it into a hafnium silicate. Furthermore, the electronic and/or chemical interaction between the Ge nanoparticles and the hafnia substrate is changed by the silane annealing step as reflected in the binding energy shift in the Ge 2p signal and the increased retention time of metal-oxide-semiconductor capacitors made from Ge nanoparticles and hafnia. Pretreating hafnia in silane leads to hafnium silicate islands and subsequent Ge nanoparticle growth proceeds on the silicate islands.

  12. Germanium orthogonal strip detector system for gamma-ray imaging

    NASA Astrophysics Data System (ADS)

    Hull, Ethan L.; Burks, Morgan; Cork, Chris P.; Craig, William W.; Eckels, Del; Fabris, Lorenzo; Lavietes, Anthony D.; Luke, Paul N.; Madden, Norman W.; Pehl, Richard H.; Ziock, Klaus

    2001-12-01

    A germanium-detector based, gamma-ray imaging system has been designed, fabricated, and tested. The detector, cryostat, electronics, readout, and imaging software are discussed. An 11 millimeter thick, 2 millimeter pitch 19x19 orthogonal strip planar germanium detector is used in front of a coaxial detector to provide broad energy coverage. The planar detector was fabricated using amorphous germanium contacts. Each channel is read out with a compact, low noise external FET preamplifier specially designed for this detector. A bank of shaping amplifiers, fast amplifiers, and fast leading edge discriminators were designed and fabricated to process the signals from preamplifiers. The readout system coordinates time coincident x-y strip addresses with an x-strip spectroscopy signal and a spectroscopy signal from the coaxial detector. This information is sent to a computer where an image is formed. Preliminary shadow and pinhole images demonstrate the viability of a germanium based imaging system. The excellent energy resolution of the germanium detector system provides isotopic imaging.

  13. High-pressure viewports for infrared systems. Phase 1: Germanium

    NASA Astrophysics Data System (ADS)

    Stachiw, J. D.

    1980-09-01

    Spherical sectors fabricated from polycrystalline germanium can serve successfully as pressure-resistant windows in IR systems in the marine environment. Spherical sectors and included spherical angle withstood 100 pressure cycles from 0 to 20000 psi without cracking when tested hydrostatically in a compliant metallic mounting with an inclined seat protected by elastomeric gaskets. Nylon cloth-reinforced Neoprane and Kelvar-49-reinforced epoxy gaskets performed successfully provided that the bearing stress did not exceed 20000 psi for Neoprene and 60000 psi for epoxy gaskets. The average flexural and compressive short-term strengths of germanium under uniaxial loading were found to be in the 70000 to 15000 psi ranges, respectively. Germanium also exhibits static fatigue under sustained flexure loading in the marine environment. The static fatigue limit for sustained loading of 1000 hour duration in a seawater environment was found to be in the 8000 to 10000 psi range. Germanium was found to also to exhibit the Kaiser effect even though it is only a rather weak emitter of acoustic emissions under compressive loading. It appears that recording of acoustic emissions during a structural proof test could be incorporated into the quality assurance program for germanium lenses and windows where it would complement visual inspection for the presence of incipient cracks.

  14. 40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... primary and secondary germanium and gallium subcategory. 421.180 Section 421.180 Protection of Environment... POINT SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180 Applicability: Description of the primary and secondary germanium and gallium subcategory. The provisions of this subpart are...

  15. 40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... primary and secondary germanium and gallium subcategory. 421.180 Section 421.180 Protection of Environment... POINT SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180 Applicability: Description of the primary and secondary germanium and gallium subcategory. The provisions of this subpart are...

  16. 40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... primary and secondary germanium and gallium subcategory. 421.180 Section 421.180 Protection of Environment... POINT SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180 Applicability: Description of the primary and secondary germanium and gallium subcategory. The provisions of this subpart are...

  17. 40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... primary and secondary germanium and gallium subcategory. 421.180 Section 421.180 Protection of Environment... POINT SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180 Applicability: Description of the primary and secondary germanium and gallium subcategory. The provisions of this subpart are...

  18. 40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... primary and secondary germanium and gallium subcategory. 421.180 Section 421.180 Protection of Environment... POINT SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180 Applicability: Description of the primary and secondary germanium and gallium subcategory. The provisions of this subpart are...

  19. From Nanoislands to Nanowires: Growtth of Germanium on Gallium-Terminated Silicon Surfaces

    SciTech Connect

    Schmidt, T.; Flege, J; Speckmann, M; Clausen, T; Gangopadhyay, S; Locatelli, A; Mentes, T; Heum, S; Guo, F; et. al.

    2009-01-01

    The influence of Ga pre-adsorption on Si(111), Si(113) and Si(112) surfaces on Ge growth has been investigated by low-energy electron diffraction and microscopy as well as X-ray photoemission spectroscopy. On Si(111), step edges and substrate domain boundaries are decorated with Ga at high deposition temperatures, enabling selective growth and alignment of three-dimensional Ge islands on a chemically modulated surface. On Si(113), a morphological modulation is achieved by Ga saturation, as the Si substrate decomposes into an ordered array of (112) and (115) facets. This results in the growth of Ge islands aligned at the facets. These islands exhibit an anisotropy, as they are elongated along [1{bar 1}0]. Ga pre-adsorption on Si(112) smoothens the initially faceted bare surface, and subsequent Ge growth leads to the formation of nanoscale Ge wires. The results are discussed in terms of surface chemistry, as well as diffusion and strain relaxation anisotropy.

  20. Theoretical and experimental investigation of cosmogenic radioisotope production in germanium

    NASA Astrophysics Data System (ADS)

    Avignone, F. T.; Brodzinski, R. L.; Collar, J. I.; Miley, H. S.; Garcia, E.; Morales, A.; Morales, J.; Nuñez-Lagos, R.; Reeves, J. H.; Saenz, C.; Villar, J. A.

    1992-07-01

    Rates were calculated for the cosmic-ray-induced production of 3H, 54Mn, 57Ni, 57,58Co, 65,67Ga, 65Zn, and 68Ge in natural germanium using two experimental neutron spectra from the literature. Reaction excitation functions were computed with a nuclear spallation code. Experimental production rates of 54Mn, 57,58Co, 65Zn, 67Ga and 68Ge were derived from background spectra of natural isotopic abundance germanium detectors. The rate for 57Co was also derived from data taken with a detector fabricated from germanium isotopically enriched to 86% 76Ge and ˜14% 74Ge. The calculated and experimental data are in agreement within a factor of two and in many cases within 30%.

  1. Germanium implanted Bragg gratings in silicon on insulator waveguides

    NASA Astrophysics Data System (ADS)

    Loiacono, Renzo; Reed, Graham T.; Gwilliam, Russell; Mashanovich, Goran Z.; O'Faolain, Liam; Krauss, Thomas; Lulli, Giorgio; Jeynes, Chris; Jones, Richard

    2010-02-01

    Integrated Bragg gratings are an interesting candidate for waveguide coupling, telecommunication applications, and for the fabrication of integrated photonic sensors. These devices have a high potential for optical integration and are compatible with CMOS processing techniques if compared to their optical fibre counterpart. In this work we present design, fabrication, and testing of Germanium ion implanted Bragg gratings in silicon on insulator (SOI). A periodic refractive index modulation is produced in a 1μm wide SOI rib waveguide by implanting Germanium ions through an SiO2 hardmask. The implantation conditions have been analysed by 3D ion implantation modelling and the induced refractive index change has been investigated on implanted samples by Rutherford Backscattering Spectroscopy (RBS) and ellipsometry analysis. An extinction ratio of up to 30dB in transmission, around the 1.55μm wavelength, has been demonstrated for Germanium implanted gratings on SOI waveguides.

  2. Modeling of dislocation dynamics in germanium Czochralski growth

    NASA Astrophysics Data System (ADS)

    Artemyev, V. V.; Smirnov, A. D.; Kalaev, V. V.; Mamedov, V. M.; Sidko, A. P.; Podkopaev, O. I.; Kravtsova, E. D.; Shimansky, A. F.

    2017-06-01

    Obtaining very high-purity germanium crystals with low dislocation density is a practically difficult problem, which requires knowledge and experience in growth processes. Dislocation density is one of the most important parameters defining the quality of germanium crystal. In this paper, we have performed experimental study of dislocation density during 4-in. germanium crystal growth using the Czochralski method and comprehensive unsteady modeling of the same crystal growth processes, taking into account global heat transfer, melt flow and melt/crystal interface shape evolution. Thermal stresses in the crystal and their relaxation with generation of dislocations within the Alexander-Haasen model have been calculated simultaneously with crystallization dynamics. Comparison to experimental data showed reasonable agreement for the temperature, interface shape and dislocation density in the crystal between calculation and experiment.

  3. Academic and industry research progress in germanium nanodevices.

    PubMed

    Pillarisetty, Ravi

    2011-11-16

    Silicon has enabled the rise of the semiconductor electronics industry, but it was not the first material used in such devices. During the 1950s, just after the birth of the transistor, solid-state devices were almost exclusively manufactured from germanium. Today, one of the key ways to improve transistor performance is to increase charge-carrier mobility within the device channel. Motivated by this, the solid-state device research community is returning to investigating the high-mobility material germanium. Germanium-based transistors have the potential to operate at high speeds with low power requirements and might therefore be used in non-silicon-based semiconductor technology in the future. © 2011 Macmillan Publishers Limited. All rights reserved

  4. Germanium FCC structure from a colloidal crystal template

    SciTech Connect

    Miguez, H.; Meseguer, F.; Lopez, C.; Holgado, M.; Andreasen, G.; Mifsud, A.; Fornes, V.

    2000-05-16

    Here, the authors show a method to fabricate a macroporous structure in which the pores, essentially identical, arrange regularly in a face-centered cubic (FCC) lattice. The result is a network of air spheres in a germanium medium. This structure presents the highest dielectric contrast ({epsilon}{sub Ge}/{epsilon}{sub air} = 16) ever achieved in the optical regime in such periodic structures, which could result in important applications in photonics. The authors employ solid silica colloidal crystals (opals) as templates within which a cyclic germanium growth process is carried out. Thus, the three-dimensional periodicity of the host is inherited by the guest. Afterward, the silica is removed and a germanium opal replica is obtained.

  5. Next Generation Device Grade Silicon-Germanium on Insulator

    PubMed Central

    Littlejohns, Callum G.; Nedeljkovic, Milos; Mallinson, Christopher F.; Watts, John F.; Mashanovich, Goran Z.; Reed, Graham T.; Gardes, Frederic Y.

    2015-01-01

    High quality single crystal silicon-germanium-on-insulator has the potential to facilitate the next generation of photonic and electronic devices. Using a rapid melt growth technique we engineer tailored single crystal silicon-germanium-on-insulator structures with near constant composition over large areas. The proposed structures avoid the problem of laterally graded SiGe compositions, caused by preferential Si rich solid formation, encountered in straight SiGe wires by providing radiating elements distributed along the structures. This method enables the fabrication of multiple single crystal silicon-germanium-on-insulator layers of different compositions, on the same Si wafer, using only a single deposition process and a single anneal process, simply by modifying the structural design and/or the anneal temperature. This facilitates a host of device designs, within a relatively simple growth environment, as compared to the complexities of other methods, and also offers flexibility in device designs within that growth environment. PMID:25656076

  6. Moth's eye anti-reflection gratings on germanium freeform surfaces

    NASA Astrophysics Data System (ADS)

    Liu, Meng; Shultz, Jason A.; Owen, Joseph D.; Davies, Matthew A.; Suleski, Thomas J.

    2014-09-01

    Germanium is commonly used for optical components in the infrared, but the high refractive index of germanium causes significant losses due to Fresnel reflections. Anti-reflection (AR) surfaces based on subwavelength "moth's eye" gratings provide one means to significantly increase optical transmission. As found in nature, these gratings are conformal to the curved surfaces of lenslets in the eye of the moth. Engineered optical systems inspired by biological examples offer possibilities for increased performance and system miniaturization, but also introduce significant challenges to both design and fabrication. In this paper, we consider the design and fabrication of conformal moth's eye AR structures on germanium freeform optical surfaces, including lens arrays and Alvarez lenses. Fabrication approaches and limitations based on both lithography and multi-axis diamond machining are considered. Rigorous simulations of grating performance and approaches for simulation of conformal, multi-scale optical systems are discussed.

  7. Graphene-like monolayer low-buckled honeycomb germanium film

    NASA Astrophysics Data System (ADS)

    He, Yezeng; Luo, Haibo; Li, Hui; Sui, Yanwei; Wei, Fuxiang; Meng, Qingkun; Yang, Weiming; Qi, Jiqiu

    2017-04-01

    Molecular dynamics simulations have been performed to study the cooling process of two-dimensional liquid germanium under nanoslit confinement. The results clearly indicates that the liquid germanium undergoes an obvious liquid-solid phase transition to a monolayer honeycomb film with the decrease of temperature, accompanying the rapid change in potential energy, atomic volume, coordination number and lateral radial distribution function. During the solidification process, some hexagonal atomic islands first randomly emerge in the disordered liquid film and then grow up to stable crystal grains which keep growing and finally connect together to form a honeycomb polycrystalline film. It is worth noting that the honeycomb germanium film is low-buckled, quite different from the planar graphene.

  8. Silicon nanowire hot electron electroluminescence

    NASA Astrophysics Data System (ADS)

    du Plessis, Monuko; Joubert, Trudi-Heleen

    2016-02-01

    This paper investigates the avalanche electroluminescence characteristics of pn junctions formed in silicon nanowires fabricated in a silicon-on-insula*tor (SOI) technology. Since carriers are confined to the nanowires, it is possible to study the effect of electric field strength on device performance while the current density and carrier concentrations are kept constant. This is achieved by varying the nanowire length while keeping the bias current constant, eventually driving the pn junction into the reach-through bias condition. It is observed that photon emission for photon energies higher than 1.2 eV increases when the nanowire length is reduced, while photon emission with energies less than 1.2 eV decreases. The higher electric field in the nanowire at shorter nanowire lengths enhances the high-energy photon emission and attenuates the low energy photon emission.

  9. Ultralight Conductive Silver Nanowire Aerogels.

    PubMed

    Qian, Fang; Lan, Pui Ching; Freyman, Megan C; Chen, Wen; Kou, Tianyi; Olson, Tammy Y; Zhu, Cheng; Worsley, Marcus A; Duoss, Eric B; Spadaccini, Christopher M; Baumann, Ted; Han, T Yong-Jin

    2017-09-13

    Low-density metal foams have many potential applications in electronics, energy storage, catalytic supports, fuel cells, sensors, and medical devices. Here, we report a new method for fabricating ultralight, conductive silver aerogel monoliths with predictable densities using silver nanowires. Silver nanowire building blocks were prepared by polyol synthesis and purified by selective precipitation. Silver aerogels were produced by freeze-casting nanowire aqueous suspensions followed by thermal sintering to weld the nanowire junctions. As-prepared silver aerogels have unique anisotropic microporous structures, with density precisely controlled by the nanowire concentration, down to 4.8 mg/cm(3) and an electrical conductivity up to 51 000 S/m. Mechanical studies show that silver nanowire aerogels exhibit "elastic stiffening" behavior with a Young's modulus up to 16 800 Pa.

  10. Reduced Joule heating in nanowires

    NASA Astrophysics Data System (ADS)

    Léonard, François

    2011-03-01

    The temperature distribution in nanowires due to Joule heating is studied analytically using a continuum model and a Green's function approach. We show that the temperatures reached in nanowires can be much lower than that predicted by bulk models of Joule heating, due to heat loss at the nanowire surface that is important at nanoscopic dimensions, even when the thermal conductivity of the environment is relatively low. In addition, we find that the maximum temperature in the nanowire scales weakly with length, in contrast to the bulk system. A simple criterion is presented to assess the importance of these effects. The results have implications for the experimental measurements of nanowire thermal properties, for thermoelectric applications, and for controlling thermal effects in nanowire electronic devices.

  11. Ultralight Conductive Silver Nanowire Aerogels

    DOE PAGES

    Qian, Fang; Lan, Pui Ching; Freyman, Megan C.; ...

    2017-09-05

    Low-density metal foams have many potential applications in electronics, energy storage, catalytic supports, fuel cells, sensors, and medical devices. Here in this work, we report a new method for fabricating ultralight, conductive silver aerogel monoliths with predictable densities using silver nanowires. Silver nanowire building blocks were prepared by polyol synthesis and purified by selective precipitation. Silver aerogels were produced by freeze-casting nanowire aqueous suspensions followed by thermal sintering to weld the nanowire junctions. As-prepared silver aerogels have unique anisotropic microporous structures, with density precisely controlled by the nanowire concentration, down to 4.8 mg/cm3 and an electrical conductivity up to 51more » 000 S/m. Lastly, mechanical studies show that silver nanowire aerogels exhibit “elastic stiffening” behavior with a Young’s modulus up to 16 800 Pa.« less

  12. Stability of Detached Grown Germanium Single Crystals

    NASA Technical Reports Server (NTRS)

    Schweizer, M.; Volz, M. P.; Cobb, S. D.; Vujisic, L.; Szofran, F. R.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Detachment of the melt meniscus from the crucible during semiconductor Bridgman growth experiments has been observed in recent years, especially under microgravity experiments. Under earth conditions, the hydrostatic pressure counteracts the mechanism, whereby it is more difficult to achieve detached Bridgman growth. Attempts to get stable detached growth under terrestrial conditions have been discussed in the literature and have been the subject of recent experiments in our own group. The advantage of crystals grown without wall contact is obvious: In general, they possess a higher crystal quality than conventional Bridgman grown crystals with wall contact. However, due to the interaction of different parameters such as the wetting behavior of the melt with the crucible, and the dependence of the growth angle with the shape of the melt meniscus, the mechanism leading to detachment is very complicated and not completely understood. We have grown several doped and undoped Germanium crystals with the detached Bridgman and the normal Bridgman growth technique. Pyrolytic boron nitride containers were used for all growth experiments. In the detached grown crystals the typical gap thickness between the pBN crucible and the crystal is in the range of 10 to 100 micrometers, which was determined by performing profilometer measurements. Etch pit density measurements were also performed and a comparison between detached and attached grown crystals will be given. An interesting feature was detected on the surface of a detached grown crystal. Strong surface striations with an average axial distance of 0.5 mm were observed around the whole circumference. The maximum fluctuation of the gap thickness is in the range of 5-10 micrometers. These variations of the detached gap along the crystal axis can be explained by a kind of stiction of the melt/crucible interface and thus by a variation of the meniscus shape. This phenomenon leading to the fluctuation of the gap thickness will be

  13. Stability of Detached Grown Germanium Single Crystals

    NASA Technical Reports Server (NTRS)

    Schweizer, M.; Volz, M. P.; Cobb, S. D.; Motakef, S.; Szofran, F. R.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    Detachment of the melt meniscus from the crucible during semiconductor Bridgman growth experiments has been observed in recent years especially, under microgravity experiments. Under earth conditions, the hydrostatic pressure counteracts the mechanism, whereby it is more difficult to achieve detached Bridgman growth. Attempts to get stable detached growth under terrestrial conditions have been discussed in the literature and have been the subject of recent experiments in our own group. The advantage of crystals grown without wall contact is obvious: In general, they possess a higher crystal quality than conventional Bridgman grown crystals with wall contact. However, due to the interaction of different parameters such as the wetting behavior of the melt with the crucible, and the dependence of the growth angle with the shape of the melt meniscus, the mechanism leading to detachment is very complicated and not completely understood. We have grown several doped and undoped Germanium crystals with the detached Bridgman and the normal Bridgman growth technique. Pyrolytic boron nitride containers were used for all growth experiments. In the detached grown crystals the typical gap thickness between the pBN crucible and the crystal is in the range of 10 to 100 microns, which was determined by performing profilometer measurements. Etch pit density measurements were also performed and a comparison between detached and attached grown crystals will be given. An interesting feature was detected on the surface of a detached grown crystal. Strong surface striations with an average axial distance of 0.5mm were observed around the whole circumference. The maximum fluctuation of the gap thickness is in the range of 5-10 microns. These variations of the detached gap along the crystal axis can be explained by a kind of stiction of the melt/crucible interface and thus by a variation of the meniscus shape. This phenomenon leading to the fluctuation of the gap thickness will be

  14. Stability of Detached Grown Germanium Single Crystals

    NASA Technical Reports Server (NTRS)

    Schweizer, M.; Volz, M. P.; Cobb, S. D.; Motakef, S.; Szofran, F. R.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    Detachment of the melt meniscus from the crucible during semiconductor Bridgman growth experiments has been observed in recent years especially, under microgravity experiments. Under earth conditions, the hydrostatic pressure counteracts the mechanism, whereby it is more difficult to achieve detached Bridgman growth. Attempts to get stable detached growth under terrestrial conditions have been discussed in the literature and have been the subject of recent experiments in our own group. The advantage of crystals grown without wall contact is obvious: In general, they possess a higher crystal quality than conventional Bridgman grown crystals with wall contact. However, due to the interaction of different parameters such as the wetting behavior of the melt with the crucible, and the dependence of the growth angle with the shape of the melt meniscus, the mechanism leading to detachment is very complicated and not completely understood. We have grown several doped and undoped Germanium crystals with the detached Bridgman and the normal Bridgman growth technique. Pyrolytic boron nitride containers were used for all growth experiments. In the detached grown crystals the typical gap thickness between the pBN crucible and the crystal is in the range of 10 to 100 microns, which was determined by performing profilometer measurements. Etch pit density measurements were also performed and a comparison between detached and attached grown crystals will be given. An interesting feature was detected on the surface of a detached grown crystal. Strong surface striations with an average axial distance of 0.5mm were observed around the whole circumference. The maximum fluctuation of the gap thickness is in the range of 5-10 microns. These variations of the detached gap along the crystal axis can be explained by a kind of stiction of the melt/crucible interface and thus by a variation of the meniscus shape. This phenomenon leading to the fluctuation of the gap thickness will be

  15. Stability of Detached Grown Germanium Single Crystals

    NASA Technical Reports Server (NTRS)

    Schweizer, M.; Volz, M. P.; Cobb, S. D.; Vujisic, L.; Szofran, F. R.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Detachment of the melt meniscus from the crucible during semiconductor Bridgman growth experiments has been observed in recent years, especially under microgravity experiments. Under earth conditions, the hydrostatic pressure counteracts the mechanism, whereby it is more difficult to achieve detached Bridgman growth. Attempts to get stable detached growth under terrestrial conditions have been discussed in the literature and have been the subject of recent experiments in our own group. The advantage of crystals grown without wall contact is obvious: In general, they possess a higher crystal quality than conventional Bridgman grown crystals with wall contact. However, due to the interaction of different parameters such as the wetting behavior of the melt with the crucible, and the dependence of the growth angle with the shape of the melt meniscus, the mechanism leading to detachment is very complicated and not completely understood. We have grown several doped and undoped Germanium crystals with the detached Bridgman and the normal Bridgman growth technique. Pyrolytic boron nitride containers were used for all growth experiments. In the detached grown crystals the typical gap thickness between the pBN crucible and the crystal is in the range of 10 to 100 micrometers, which was determined by performing profilometer measurements. Etch pit density measurements were also performed and a comparison between detached and attached grown crystals will be given. An interesting feature was detected on the surface of a detached grown crystal. Strong surface striations with an average axial distance of 0.5 mm were observed around the whole circumference. The maximum fluctuation of the gap thickness is in the range of 5-10 micrometers. These variations of the detached gap along the crystal axis can be explained by a kind of stiction of the melt/crucible interface and thus by a variation of the meniscus shape. This phenomenon leading to the fluctuation of the gap thickness will be

  16. Alkanethiol-passivated ge nanowires as high-performance anode materials for lithium-ion batteries: the role of chemical surface functionalization.

    PubMed

    Yuan, Fang-Wei; Yang, Hong-Jie; Tuan, Hsing-Yu

    2012-11-27

    We demonstrate that dodecanethiol monolayer passivation can significantly enhance the anode performance of germanium (Ge) nanowires in lithium-ion batteries. The dodecanethiol-passivated Ge nanowires exhibit an excellent electrochemical performance with a reversible specific capacity of 1130 mAh/g at 0.1 C rate after 100 cycles. The functionalized Ge nanowires show high-rate capability having charge and discharge capacities of ∼555 mAh/g at high rates of 11 C. The functionalized Ge nanowires also performed well at 55 °C, showing their thermal stability at high working temperatures. Moreover, full cells using a LiFePO(4) cathode were assembled and the electrodes still have stable capacity retention. An aluminum pouch type lithium cell was also assembled to provide larger current (∼30 mA) for uses on light-emitting-diodes (LEDs) and audio devices. Investigation of the role of organic monolayer coating showed that the wires formed a robust nanowire/PVDF network through strong C-F bonding so as to maintain structure integrity during the lithiation/delithiation process. Organic monolayer-coated Ge nanowires represent promising Ge-C anodes with controllable low carbon content (ca. 2-3 wt %) for high capacity, high-rate lithium-ion batteries and are readily compatible with the commercial slurry-coating process for cell fabrication.

  17. Enhanced photothermal cooling of nanowires

    NASA Astrophysics Data System (ADS)

    Guccione, G.; Hosseini, M.; Mirzaei, A.; Slatyer, H. J.; Buchler, B. C.; Lam, P. K.

    2017-09-01

    We investigate the optomechanical interaction between light and metallic nanowires through the action of bolometric forces. We show that the response time of the photothermal forces induced on the nanowire is fast and the strength of the interaction can overcome the radiation pressure force. Furthermore, we suggest the photothermal forces can be enhanced by surface plasmon excitation to cool the sub-megahertz vibrational modes of the nanowires close to its quantum limit.

  18. Germanium terminated (1 0 0) diamond.

    PubMed

    Sear, Michael J; Schenk, Alex K; Tadich, Anton; Spencer, Benjamin J; Wright, Christopher A; Stacey, Alastair; Pakes, Chris I

    2017-04-12

    An ordered germanium terminated (1 0 0) diamond surface has been formed and characterised using a combination of low energy electron diffraction and synchrotron-based core level photoemission spectroscopy. A number of preparation methods are explored, in each case inducing a two domain [Formula: see text] surface reconstruction. The surface becomes saturated with bonded germanium such that each [Formula: see text] unit cell hosts 1.26 Ge atoms on average, and possesses a negative electron affinity of  -0.71 eV.

  19. Comparative infrared study of silicon and germanium nitrides

    NASA Astrophysics Data System (ADS)

    Baraton, M. I.; Marchand, R.; Quintard, P.

    1986-03-01

    Silicon and germanium nitride (Si 3N 4 and Ge 3N 4) are isomorphic compounds. They have been studied in the β-phase which crystallises in the hexagonal system. The space group is P6 3/m (C 6h2). The IR transmission spectra of these two nitrides are very similar but the absorption frequencies of germanium nitride are shifted to the lower values in comparison with silicon nitride. We noted that the atomic mass effect is the only cause of this shift for the streching modes but not for the bending modes.

  20. The Novel Synthesis of Silicon and Germanium Nanocrystallites

    SciTech Connect

    Kauzlarich, S M; Liu, Q; Yin, S C; Lee, W H; Taylor, B

    2001-04-03

    Interest in the synthesis of semiconductor nanoparticles has been generated by their unusual optical and electronic properties arising from quantum confinement effects. We have synthesized silicon and germanium nanoclusters by reacting Zintl phase precursors with either silicon or germanium tetrachloride in various solvents. Strategies have been investigated to stabilize the surface, including reactions with RLi and MgBrR (R = alkyl). This synthetic method produces group IV nanocrystals with passivated surfaces. These nanoparticle emit over a very large range in the visible region. These particles have been characterized using HRTEM, FTIR, UV-Vis, solid state NMR, and fluorescence. The synthesis and characterization of these nanoclusters will be presented.

  1. Germanium terminated (1 0 0) diamond

    NASA Astrophysics Data System (ADS)

    Sear, Michael J.; Schenk, Alex K.; Tadich, Anton; Spencer, Benjamin J.; Wright, Christopher A.; Stacey, Alastair; Pakes, Chris I.

    2017-04-01

    An ordered germanium terminated (1 0 0) diamond surface has been formed and characterised using a combination of low energy electron diffraction and synchrotron-based core level photoemission spectroscopy. A number of preparation methods are explored, in each case inducing a two domain ≤ft(3× 1\\right) surface reconstruction. The surface becomes saturated with bonded germanium such that each ≤ft(3× 1\\right) unit cell hosts 1.26 Ge atoms on average, and possesses a negative electron affinity of  ‑0.71 eV.

  2. Measurement and simulation of the segmented Germanium-Detector's Efficiency

    NASA Astrophysics Data System (ADS)

    Salem, Shadi

    This paper presents the methods to determine the detection efficiency of the segmented germanium detector. Two methods are given for the investigating the detection efficiency of the semiconductor segmented-germanium detector. Experimental measurements using radioactive sources are reported. The radioactive sources, which were involved, can give us the opportunity to cover the photon energy ranging up to hundreds of keV. A useful compilation is included of the latest values of the emission rates per decay for the following radioactive sources: 241Am and 133Ba. The second method, the simulation of the efficiency is involved for comparison purposes. A good agreement between the measurements and the simulation is obtained.

  3. Silicon germanium semiconductive alloy and method of fabricating same

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor)

    2008-01-01

    A silicon germanium (SiGe) semiconductive alloy is grown on a substrate of single crystalline Al.sub.2O.sub.3. A {111} crystal plane of a cubic diamond structure SiGe is grown on the substrate's {0001} C-plane such that a <110> orientation of the cubic diamond structure SiGe is aligned with a <1,0,-1,0> orientation of the {0001} C-plane. A lattice match between the substrate and the SiGe is achieved by using a SiGe composition that is 0.7223 atomic percent silicon and 0.2777 atomic percent germanium.

  4. High-Pressure Viewports for Infrared Systems. Phase 1. Germanium

    DTIC Science & Technology

    1980-09-01

    associated with a base metal ore, like ores of zinc,. o lead, or copper (table 2). - Although the germanium content of sphalerite is quite low, it...zinc smelting process takes place in three steps: (1) processing of zinc sulfide ores to obtain 8 Piedmont. JR. and JR Riordan, The Supply of...PPM Sphalerite ZnS 100-1850 Chalcopyrite CuFeS2 10-40 Enargite Cu3 AsS4 10-80 Cassiterite SnO 4 10 Table 2. Minerals containing germanium. zinc

  5. Servo System for the Athermalisation of a Germanium Lens,

    DTIC Science & Technology

    1982-11-01

    AD-A129 355 SERVO SYSTEM FOR THE ATHERMALISATION OF A GERMANIUM 1/I LENS(U) ROYAL SIGNALS AND RADAR ESTABLISHMENT MALVERN (ENGLAND) I C CARMICHAEL ET...St*%0AftS-,94-A .1 I.I ! / ,It ’IL"ITE Bi187081 RSRE MEMORANDUM No. 3527 ROYAL SIGNALS & RADAR ESTABLISHMENT SERVO SYSTEM FOR THE ATHERMALISATION OF...LA -4N ROYAL SIGNALS AND RADAR ESTABLISHMENT Memorandum 3527 Title: SERVO SYSTEM FOR THE ATHERMALISATION OF A GERMANIUM LENS Authors: I C Carmichael

  6. The GALATEA test-facility for high purity germanium detectors

    NASA Astrophysics Data System (ADS)

    Abt, I.; Caldwell, A.; Dönmez, B.; Garbini, L.; Irlbeck, S.; Majorovits, B.; Palermo, M.; Schulz, O.; Seitz, H.; Stelzer, F.

    2015-05-01

    GALATEA is a test facility designed to investigate bulk and surface effects in high purity germanium detectors. A vacuum tank houses a cold volume with the detector inside. A system of three precision motorized stages allows an almost complete scan of the detector. The main feature of GALATEA is that there is no material between source and detector. This allows the usage of alpha and beta sources to study surface effects. A 19-fold segmented true-coaxial germanium detector was used for commissioning. A first analysis of data obtained with an alpha source is presented here.

  7. Electrochemically Grown Single Nanowire Sensors

    NASA Technical Reports Server (NTRS)

    Yun, Minhee; Lee, Choonsup; Vasquez, Richard P.; Penner, Reginald; Bangar, Mangesh; Mulchandani, Ashok; Myung, Nosang V.

    2004-01-01

    We report a fabrication technique that is potentially capable of producing arrays of individually addressable nanowire sensors with controlled dimensions, positions, alignments, and chemical compositions. The concept has been demonstrated with electrodeposition of palladium wires with 75 nm to 350 nm widths. We have also fabricated single and double conducting polymer nanowires (polyaniline and polypyrrole) with 100nm and 200nm widths using electrochemical direct growth. Using single Pd nanowires, we have also demonstrated hydrogen sensing. It is envisioned that these are the first steps towards nanowire sensor arrays capable of simultaneously detecting multiple chemical species.

  8. Germanium-doped crystalline silicon: Effects of germanium doping on boron-related defects

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaodong; Yu, Xuegong; Yang, Deren

    2014-09-01

    Recently it has been recognized that germanium (Ge) doping can be used for microelectronics and photovoltaic devices. This article reviews the recent results about the effects of Ge doping on boron-related defects in crystalline silicon. Behavior of Ge interacting with the acceptor dopants is also discussed therein. In addition, the article provides a comprehensive review on the effect of Ge doping to the formation of iron-boron pairs and boron-oxygen defects that is responsible for the light induced degradation (LID) of the carrier lifetime. The improvement silicon-based solar cells application from Ge doping is discussed as well, including the increment of cell efficiency and the power output of corresponding modules under sunlight illumination.

  9. Detached Bridgman Growth of Germanium and Germanium-Silicon Alloy Crystals

    NASA Technical Reports Server (NTRS)

    Szofran, F. R.; Volz, M. P.; Schweizer, M.; Cobb, S. D.; Motakef, S.; Croell, A.; Dold, P.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    Earth based experiments on the science of detached crystal growth are being conducted on germanium and germanium-silicon alloys (2 at% Si average composition) in preparation for a series of experiments aboard the International Space Station (ISS). The purpose of the microgravity experiments includes differentiating among proposed mechanisms contributing to detachment, and confirming or refining our understanding of the detachment mechanism. Because large contact angle are critical to detachment, sessile drop measurements were used to determine the contact angles as a function of temperature and composition for a large number of substrates made of potential ampoule materials. Growth experiments have used pyrolytic boron nitride (pBN) and fused silica ampoules with the majority of the detached results occurring predictably in the pBN. The contact angles were 173 deg (Ge) and 165 deg (GeSi) for pBN. For fused silica, the contact angle decreases from 150 deg to an equilibrium value of 117 deg (Ge) or from 129 deg to an equilibrium value of 100 deg (GeSi) over the duration of the experiment. The nature and extent of detachment is determined by using profilometry in conjunction with optical and electron microscopy. The stability of detachment has been analyzed, and an empirical model for the conditions necessary to achieve sufficient stability to maintain detached growth for extended periods has been developed. Results in this presentation will show that we have established the effects on detachment of ampoule material, pressure difference above and below the melt, and silicon concentration; samples that are nearly completely detached can be grown repeatedly in pBN.

  10. Novel approach for n-type doping of HVPE gallium nitride with germanium

    NASA Astrophysics Data System (ADS)

    Hofmann, Patrick; Krupinski, Martin; Habel, Frank; Leibiger, Gunnar; Weinert, Berndt; Eichler, Stefan; Mikolajick, Thomas

    2016-09-01

    We present a novel method for germanium doping of gallium nitride by in-situ chlorination of solid germanium during the hydride vapour phase epitaxy (HVPE) process. Solid germanium pieces were placed in the doping line with a hydrogen chloride flow directed over them. We deduce a chlorination reaction taking place at 800 ° C , which leads to germanium chloroform (GeHCl3) or germanium tetrachloride (GeCl4). The reactor shows a germanium rich residue after in-situ chlorination experiments, which can be removed by hydrogen chloride etching. All gallium nitride crystals exhibit n-type conductivity, which shows the validity of the in-situ chlorination of germanium for doping. A complex doping profile is found for each crystal, which was assigned to a combination of localised supply of the dopant and sample rotation during growth and switch-off effects of the HVPE reactor.

  11. Microtubule-based gold nanowires and nanowire arrays.

    PubMed

    Zhou, Jing C; Gao, Yao; Martinez-Molares, Alfredo A; Jing, Xiaoye; Yan, Dong; Lau, Joseph; Hamasaki, Toshikazu; Ozkan, Cengiz S; Ozkan, Mihrimah; Hu, Evelyn; Dunn, Bruce

    2008-09-01

    Biological structures are attractive as templates to form nanoscale architectures for electronics because of their dimensions and the ability to interact with inorganic materials. In this study, we report the fabrication and electrical properties of microtubule (MT)-templated Au nanowires, and methods for assembling Au nanowire arrays based on these templates. The adsorption of MTs on silicon substrates is an effective means for preserving the conformation of the MT and provides a convenient platform for electrical measurements. To improve the metallization of MTs, a photochemical route for gold reduction is adapted, which leads to continuous coverage. The conductivity values measured on micrometer-long nanowires are similar to those reported for other biotemplated gold nanowires. A protocol for fabricating arrays of MT-templated gold nanowires is demonstrated.

  12. PHASE EQUILIBRIUM STUDIES OF GERMANIUM AND SILICON AT HIGH PRESSURES.

    DTIC Science & Technology

    phase Ge-IV with the body centered cubic structure . The triple point between Ge-I (diamond structure), Ge-III (body centered tetragonal) and Ge-IV (body...Another new phase with the simple cubic structure has been detected for the first time although its relations to the other polymorphs of germanium has

  13. Deformation potential constants of gallium impurity in germanium

    NASA Astrophysics Data System (ADS)

    Martin, A. D.; Fisher, P.; Freeth, C. A.; Salib, E. H.; Simmonds, P. E.

    1983-12-01

    The deformation potential constants and intensity parameters of some of the states and optically induced transitions of gallium impurity in germanium have been determined both experimentally and theoretically. The latter are based on the effective mass wavefunctions of Kohn and Schechter and of Mendelson and James. Reasonably good agreement is found between the experimental and theoretical results.

  14. Enhanced life ion source for germanium and carbon ion implantation

    SciTech Connect

    Hsieh, Tseh-Jen; Colvin, Neil; Kondratenko, Serguei

    2012-11-06

    Germanium and carbon ions represent a significant portion of total ion implantation steps in the process flow. Very often ion source materials that used to produce ions are chemically aggressive, especially at higher temperatures, and result in fast ion source performance degradation and a very limited lifetime [B.S. Freer, et. al., 2002 14th Intl. Conf. on Ion Implantation Technology Proc, IEEE Conf. Proc., p. 420 (2003)]. GeF{sub 4} and CO{sub 2} are commonly used to generate germanium and carbon beams. In the case of GeF{sub 4} controlling the tungsten deposition due to the de-composition of WF{sub 6} (halogen cycle) is critical to ion source life. With CO{sub 2}, the materials oxidation and carbon deposition must be controlled as both will affect cathode thermionic emission and anti-cathode (repeller) efficiencies due to the formation of volatile metal oxides. The improved ion source design Extended Life Source 3 (Eterna ELS3) together with its proprietary co-gas material implementation has demonstrated >300 hours of stable continuous operation when using carbon and germanium ion beams. Optimizing cogas chemistries retard the cathode erosion rate for germanium and carbon minimizes the adverse effects of oxygen when reducing gas is introduced for carbon. The proprietary combination of hardware and co-gas has improved source stability and the results of the hardware and co-gas development are discussed.

  15. Solution-processable white-light-emitting germanium nanocrystals

    SciTech Connect

    Shirahata, Naoto

    2014-06-01

    This paper describes an efficient chemical route for the synthesis of visible light emitting nanocrystals of germanium (ncGe). The synthesis started by heating Ge(II) iodide at 300 °C in argon atmosphere. Spectroscopic characterizations confirmed the formation of diamond cubic lattice structures of ncGe. By grafting hydrophobic chains on the ncGe surface, the dispersions in nonpolar solvents of the ncGe became very stable. The as-synthesized ncGe showed the bluish white photoluminescence (PL) feature, but it was found that the PL spectrum is composed of many different emission spectra. Therefore, the color-tuning of white light emission is demonstrated through the witting removal of extra ncGe with unfavorable emission feature by making full use of column chromatographic techniques. - Highlights: • Visible light emitting nanocrystals of germanium was synthesized by chemical reduction of germanium iodide. • White light emission was achieved by control over size distribution of germanium nanocrystals. • Tuning the color of white light was achieved by separation of nanocrystals by emission.

  16. Active noise canceling system for mechanically cooled germanium radiation detectors

    DOEpatents

    Nelson, Karl Einar; Burks, Morgan T

    2014-04-22

    A microphonics noise cancellation system and method for improving the energy resolution for mechanically cooled high-purity Germanium (HPGe) detector systems. A classical adaptive noise canceling digital processing system using an adaptive predictor is used in an MCA to attenuate the microphonics noise source making the system more deployable.

  17. Modified matrix volatilization setup for characterization of high purity germanium.

    PubMed

    Meruva, Adisesha Reddy; Raparthi, Shekhar; Kumar, Sunil Jai

    2016-01-01

    Modified matrix volatilization (MV) method has been described to characterize high purity germanium material of 7 N (99.99999%) purity. Transport of both, the chlorine gas generated in-situ in this method and the argon gas (carrier) is fine controlled by means of a mass flow controller. This enabled both uniform reaction of chlorine gas with the germanium matrix and smooth removal of germanium matrix as its chloride. This resulted in improvement in the reproducibility of the analytical results. The use of quartz reaction vessel has lead to the reduction in the process blank levels. The combined effect of these modifications in the MV setup has resulted in very consistent and low process blanks and hence improved detection limits of this method. Applicability of the method has been expanded to rare earth elements and other elements after examining their recoveries. The quantification is done by using inductively coupled plasma quadrupole mass spectrometer (ICP-QMS) and continuum source graphite furnace atomic absorption spectrometry (CS-GFAAS). In the absence of certified reference materials for high pure germanium, the accuracy of the method is established by spike recovery tests. The precision of the method has been found to vary from 1 to 30% for concentrations between 1 and 30 ng g(-1). The limits of detection (LOD) for the target analytes are found to be between 18 and 0.033 ng g(-1). Copyright © 2015 Elsevier B.V. All rights reserved.

  18. [Spectroscopic properties of Er3+-doped germanium bismuthate glass].

    PubMed

    Zhang, Yong; Ren, Guo-Zhong; Yang, Qi-Bin; Xu, Chang-Fu; Liu, Yun-Xin; Shang, Zhen-Gang

    2008-05-01

    Er(3+)-Doped Germanium Bismuthate Glass was fabricated and characterized. The absorption spectrum and up-conversion spectrum of glass were studied. The Judd-Oflet intensity parameters omega(t) (t = 2, 4, 6), determined based on Judd-Ofelt theory, were found to be omega2 = 3.35 x 10(-20) cm2, omega4 = 1.34 x 10(-20) cm2, omega6 = 0.67 x 10(-20) cm2. Frequency up-conversion of Er(3+)-doped germanium bismuthate glass has been investigated. The up-conversion mechanisms are discussed under 808 nm and 980 nm excitation. Stimulated emission cross-section of 4I(13/2) --> 4I(15/2) transition was calculated by McCumber theory. Compared to other host glasses, the emission property of Er(3+)-doped germanium bismuthate glasses has advantage over those of silicate, phosphate and germinate glasses. Er(3+)-doped germanium bismuth glasses are promising upconversion optical and optic-communication materials.

  19. Initial Results: An Ultra-Low-Background Germanium Crystal Array

    DTIC Science & Technology

    2010-09-01

    INITIAL RESULTS: AN ULTRA-LOW-BACKGROUND GERMANIUM CRYSTAL ARRAY Martin E. Keillor, Craig E. Aalseth, Anthony R. Day, Luke E. Erikson , James E. Fast...Brian D. Glasgow, Eric W. Hoppe, Todd W. Hossbach, Brian J. Hyronimus, Harry S. Miley, Allan W. Myers, and Allen Seifert Pacific Northwest

  20. Germanium accumulation-mode charge-injection-device process

    NASA Technical Reports Server (NTRS)

    Moore, T. G.

    1981-01-01

    Gallium doped germanium is suitable for applications in the detection of far infrared radiation. Measurements were made on experimental photoconductors (PCs), accumulation mode charge injection devices (AMCIDs), and the SSPC (a switched, sampled PC alternative to the AMCID). The results indicate that the SSPC, which had a responsivity near 1.5 amp/watt, is desirable for use in two dimensional detector arrays.

  1. The 100 micron detector development program. [gallium doped germanium photoconductors

    NASA Technical Reports Server (NTRS)

    Moore, W. J.

    1976-01-01

    An effort to optimize gallium-doped germanium photoconductors (Ge:Ga) for use in space for sensitive detection of far infrared radiation in the 100 micron region is described as well as the development of cryogenic apparatus capable of calibrating detectors under low background conditions.

  2. Discovery of gallium, germanium, lutetium, and hafnium isotopes

    SciTech Connect

    Gross, J.L.; Thoennessen, M.

    2012-09-15

    Currently, twenty-eight gallium, thirty-one germanium, thirty-five lutetium, and thirty-six hafnium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  3. Modeling of Boron and Phosphorus Implantation into (100) Germanium

    SciTech Connect

    Suh,Y.; Carroll, M.; Levy, R.; Sahiner, M.; Bisognin, G.; King, C.

    2005-01-01

    Boron and phosphorus implants into germanium and silicon with energies from 20 to 320 keV and ion doses from 5x10{sup 13} to 5x10{sup 16} cm{sup -2} were characterized using secondary ion mass spectrometry. The first four moments of all implants were calculated from the experimental data. Both the phosphorus and boron implants were found to be shallower in the germanium than in the silicon for the same implant parameters and high hole concentrations, as high as 2x10{sup 20} cm{sup -3}, were detected by spreading resistance profiling immediately after boron implants without subsequent annealing. Channeling experiments using nuclear reaction analysis also indicated high substitutional fractions ({approx}19%) even in the highest dose case immediately after implant. A greater straggle (second moment) is, however, observed in the boron implants in the germanium than in the silicon despite having a shorter projected range in the germanium. Implant profiles predicted by Monte Carlo simulations and Lindhard-Scharff-Schiott theory were calculated to help clarify the implant behavior. Finally, the experimentally obtained moments were used to calculate Pearson distribution fits to the boron and phosphorus implants for rapid simulation of nonamorphizing doses over the entire energy range examined.

  4. Ultrahigh-Density Nanowire Lattices and Circuits

    NASA Astrophysics Data System (ADS)

    Melosh, Nicholas A.; Boukai, Akram; Diana, Frederic; Gerardot, Brian; Badolato, Antonio; Petroff, Pierre M.; Heath, James R.

    2003-04-01

    We describe a general method for producing ultrahigh-density arrays of aligned metal and semiconductor nanowires and nanowire circuits. The technique is based on translating thin film growth thickness control into planar wire arrays. Nanowires were fabricated with diameters and pitches (center-to-center distances) as small as 8 nanometers and 16 nanometers, respectively. The nanowires have high aspect ratios (up to 106), and the process can be carried out multiple times to produce simple circuits of crossed nanowires with a nanowire junction density in excess of 1011 per square centimeter. The nanowires can also be used in nanomechanical devices; a high-frequency nanomechanical resonator is demonstrated.

  5. Graphene-based nanowire supercapacitors.

    PubMed

    Chen, Zhi; Yu, Dingshan; Xiong, Wei; Liu, Peipei; Liu, Yong; Dai, Liming

    2014-04-01

    We present a new type of electrochemical supercapacitors based on graphene nanowires. Graphene oxide (GO)/polypyrrole (PPy) nanowires are prepared via electrodepostion of GO/PPy composite into a micoroporous Al2O3 template, followed by the removal of template. PPy is electrochemically doped by oxygen-containing functional groups of the GO to enhance the charging/discharging rates of the supercapacitor. A high capacitance 960 F g(-1) of the GO/PPy nanowires is obtained due to the large surface area of the vertically aligned nanowires and the intimate contact between the nanowires and the substrate electrode. The capacitive performance remains stable after charging and discharging for 300 cycles. To improve the thermal stability and long-term charge storage, GO is further electrochemically reduced into graphene and PPy is subsequently thermally carbonized, leading to a high capacitance of 200 F g(-1) for the resultant pure reduced graphene oxide/carbon based nanowire supercapacitor. This value of capacitance (200 F g(-1)) is higher than that of conventional porous carbon materials while the reduced graphene oxide/carbon nanowires show a lower Faraday resistance and higher thermal stability than the GO/PPy nanowires.

  6. Development and Applications of Nanowire Nanophotonics

    DTIC Science & Technology

    2006-03-23

    Nanowire Nanophotonics G F49620-03-1-0063 6. AUTHOR(S) Charles. M. Lieber 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION...Release; distribution is unlimited. 13, ABSTRACT (Maximum 200 Words) The controlled and predictable synthesis of nanowires and nanowire heterostrucrures...nitride based nanowire materials, including radial nanowire heterostructures in which the composition and/or doping was modulated perpendicular to the

  7. An environmentally-friendly vacuum reduction metallurgical process to recover germanium from coal fly ash.

    PubMed

    Zhang, Lingen; Xu, Zhenming

    2016-07-15

    The demand for germanium in the field of semiconductor, electronics, and optical devices is growing rapidly; however, the resources of germanium are scarce worldwide. As a secondary material, coal fly ash could be further recycled to retrieve germanium. Up to now, the conventional processes to recover germanium have two problems as follows: on the one hand, it is difficult to be satisfactory for its economic and environmental effect; on the other hand, the recovery ratio of germanium is not all that could be desired. In this paper, an environmentally-friendly vacuum reduction metallurgical process (VRMP) was proposed to recover germanium from coal fly ash. The results of the laboratory scale experiments indicated that the appropriate parameters were 1173K and 10Pa with 10wt% coke addition for 40min, and recovery ratio germanium was 93.96%. On the basis of above condition, the pilot scale experiments were utilized to assess the actual effect of VRMP for recovery of germanium with parameter of 1473K, 1-10Pa and heating time 40min, the recovery ratio of germanium reached 94.64%. This process considerably enhances germanium recovery, meanwhile, eliminates much of the water usage and residue secondary pollution compared with other conventional processes. Copyright © 2016. Published by Elsevier B.V.

  8. Detached Bridgman Growth of Germanium and Germanium-Silicon Alloy Crystals

    NASA Technical Reports Server (NTRS)

    Szofran, F. R.; Volz, M. P.; Schweizer, M.; Kaiser, N.; Cobb, S. D.; Motakef, S.; Vujisic, L. J.; Croell, A.; Dold, P.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Earth based experiments on the science of detached crystal growth are being conducted on germanium and germanium-silicon alloys (2at% Si average composition) in preparation for a series of experiments aboard the International Space Station (ISS) to differentiate among proposed mechanisms contributing to detachment. Sessile drop measurements were first carried out for a large number of substrates made of potential ampoule materials to determine the contact angles and the surface tension as a function of temperature and composition. The process atmosphere and duration of the experiment (for some cases) were also found to have significant influence on the wetting angle. Growth experiments have used pyrolytic boron nitride (pBN) and fused silica ampoules with the majority of the detached results occurring predictably in the pBN. The contact angles were 173 deg (Ge) and 165 deg (GeSi) for pBN. For fused silica, the contact angle decreases to an equilibrium value with duration of measurement ranging from 150 to 117 deg (Ge), 129 to 100 deg (GeSi). Forming gas (Ar + 2% H2) and vacuum have been used in the growth ampoules. With gas in the ampoule, a variation of the temperature profile during growth has been used to control the pressure difference between the top of the melt and the volume below the melt caused by detachment of the growing crystal. The stability of detachment has been modeled and substantial insight has been gained into the reasons that detachment has most often been observed in reduced gravity but nonetheless has occurred randomly even there. An empirical model for the conditions necessary to achieve sufficient stability to maintain detached growth for extended periods has been developed and will be presented. Methods for determining the nature and extent of detachment include profilometry and optical and electron microscopy. This surface study is the subject of another presentation at this Congress. Results in this presentation will show that we have

  9. III-nitride nanowire lasers

    NASA Astrophysics Data System (ADS)

    Wright, Jeremy Benjamin

    In recent years there has been a tremendous interest in nanoscale optoelectronic devices. Among these devices are semiconductor nanowires whose diameters range from 10-100 nm. To date, nanowires have been grown using many semiconducting material systems and have been utilized as light emitting diodes, photodetectors, and solar cells. Nanowires possess a relatively large index contrast relative to their dielectric environment and can be used as lasers. A key figure of merit that allows for nanowire lasing is the relatively high optical confinement factor. In this work, I discuss the optical characterization of 3 types of III-nitride nanowire laser devices. Two devices were designed to reduce the number of lasing modes to achieve single-mode operation. The third device implements low-group velocity mode lasing with a photonic crystal constructed of an array of nanowires. Single-mode operation is necessary in any application where high beam quality and single frequency operation is required. III-Nitride nanowire lasers typically operate in a combined multi-longitudinal and multi-transverse mode state. Two schemes are introduced here for controlling the optical modes and achieving single-mode operation. The first method involves reducing the diameter of individual nanowires to the cut-off condition, where only one optical mode propagates in the wire. The second method employs distributed feedback (DFB) to achieve single-mode lasing by placing individual GaN nanowires onto substrates with etched gratings. The nanowire-grating substrate acted as a distributed feedback mirror producing single mode operation at 370 nm with a mode suppression ratio (MSR) of 17 dB. The usage of lasers for solid state lighting has the potential to further reduce U.S. lighting energy usage through an increase in emitter efficiency. Advances in nanowire fabrication, specifically a two-step top-down approach, have allowed for the demonstration of a multi-color array of lasers on a single chip

  10. III-Nitride Nanowire Lasers

    SciTech Connect

    Wright, Jeremy Benjamin

    2014-07-01

    In recent years there has been a tremendous interest in nanoscale optoelectronic devices. Among these devices are semiconductor nanowires whose diameters range from 10-100 nm. To date, nanowires have been grown using many semiconducting material systems and have been utilized as light emitting diodes, photodetectors, and solar cells. Nanowires possess a relatively large index contrast relative to their dielectric environment and can be used as lasers. A key gure of merit that allows for nanowire lasing is the relatively high optical con nement factor. In this work, I discuss the optical characterization of 3 types of III-nitride nanowire laser devices. Two devices were designed to reduce the number of lasing modes to achieve singlemode operation. The third device implements low-group velocity mode lasing with a photonic crystal constructed of an array of nanowires. Single-mode operation is necessary in any application where high beam quality and single frequency operation is required. III-Nitride nanowire lasers typically operate in a combined multi-longitudinal and multi-transverse mode state. Two schemes are introduced here for controlling the optical modes and achieving single-mode op eration. The rst method involves reducing the diameter of individual nanowires to the cut-o condition, where only one optical mode propagates in the wire. The second method employs distributed feedback (DFB) to achieve single-mode lasing by placing individual GaN nanowires onto substrates with etched gratings. The nanowire-grating substrate acted as a distributed feedback mirror producing single mode operation at 370 nm with a mode suppression ratio (MSR) of 17 dB. The usage of lasers for solid state lighting has the potential to further reduce U.S. lighting energy usage through an increase in emitter e ciency. Advances in nanowire fabrication, speci cally a two-step top-down approach, have allowed for the demonstration of a multi-color array of lasers on a single chip that emit

  11. Ultra-low Thermal Conductivity in Si/Ge Hierarchical Superlattice Nanowire

    PubMed Central

    Mu, Xin; Wang, Lili; Yang, Xueming; Zhang, Pu; To, Albert C.; Luo, Tengfei

    2015-01-01

    Due to interfacial phonon scattering and nanoscale size effect, silicon/germanium (Si/Ge) superlattice nanowire (SNW) can have very low thermal conductivity, which is very attractive for thermoelectrics. In this paper, we demonstrate using molecular dynamics simulations that the already low thermal conductivity of Si/Ge SNW can be further reduced by introducing hierarchical structure to form Si/Ge hierarchical superlattice nanowire (H-SNW). The structural hierarchy introduces defects to disrupt the periodicity of regular SNW and scatters coherent phonons, which are the key contributors to thermal transport in regular SNW. Our simulation results show that periodically arranged defects in Si/Ge H-SNW lead to a ~38% reduction of the already low thermal conductivity of regular Si/Ge SNW. By randomizing the arrangement of defects and imposing additional surface complexities to enhance phonon scattering, further reduction in thermal conductivity can be achieved. Compared to pure Si nanowire, the thermal conductivity reduction of Si/Ge H-SNW can be as large as ~95%. It is concluded that the hierarchical structuring is an effective way of reducing thermal conductivity significantly in SNW, which can be a promising path for improving the efficiency of Si/Ge-based SNW thermoelectrics. PMID:26568511

  12. Ultra-low Thermal Conductivity in Si/Ge Hierarchical Superlattice Nanowire.

    PubMed

    Mu, Xin; Wang, Lili; Yang, Xueming; Zhang, Pu; To, Albert C; Luo, Tengfei

    2015-11-16

    Due to interfacial phonon scattering and nanoscale size effect, silicon/germanium (Si/Ge) superlattice nanowire (SNW) can have very low thermal conductivity, which is very attractive for thermoelectrics. In this paper, we demonstrate using molecular dynamics simulations that the already low thermal conductivity of Si/Ge SNW can be further reduced by introducing hierarchical structure to form Si/Ge hierarchical superlattice nanowire (H-SNW). The structural hierarchy introduces defects to disrupt the periodicity of regular SNW and scatters coherent phonons, which are the key contributors to thermal transport in regular SNW. Our simulation results show that periodically arranged defects in Si/Ge H-SNW lead to a ~38% reduction of the already low thermal conductivity of regular Si/Ge SNW. By randomizing the arrangement of defects and imposing additional surface complexities to enhance phonon scattering, further reduction in thermal conductivity can be achieved. Compared to pure Si nanowire, the thermal conductivity reduction of Si/Ge H-SNW can be as large as ~95%. It is concluded that the hierarchical structuring is an effective way of reducing thermal conductivity significantly in SNW, which can be a promising path for improving the efficiency of Si/Ge-based SNW thermoelectrics.

  13. Germanium nanocrystals: Synthesis, characterization, and applications

    NASA Astrophysics Data System (ADS)

    Gerung, Henry

    The aim of this work was to demonstrate a simple synthesis route of Ge nanostructures (nanoparticles and nanowires), to characterize the physical and optical properties of Ge nanocrystal, and to demonstrate their biological and optoelectronics applications. The appropriate organometallic Ge 2+ precursors for the synthesis of Ge nanocrystals were identified. These precursors were used to develop a simple route that produced high quality Ge nanocrystals in high yield under mild conditions without using potentially contaminating catalysts and forming byproducts. The particle size was varied from 1 to 10 nm, depending on the reaction parameters. The relatively low-temperature, low-pressure nanocrystal synthesis condition allowed the use of organic solvents and surfactants. We also demonstrated morphological control over Ge nanocrystals via Ge2+ precursor reactivity modification. During synthesis, the surfactants passivate the nanocrystal surface and minimize surface oxidation. This synthesis method allowed optical characterization of Ge nanocrystals decoupled from contamination and oxidation. When excited with photons, Ge nanoparticles exhibit quantum confinement effect in both infrared and ultraviolet regions, as well as optical nonlinearity by the presence of two-photon absorption. These free-standing Ge nanocrystals could be further become integral elements in various optoelectronic devices. Herein, the production of water-soluble Ge nanoparticles was demonstrated as a proof of the effectiveness of our synthesis method. Addition of secondary layer surfactants such as cationic cetyltrimethylammonium bromide (CTAB) or functionalized polyethylene glycol (PEG), transforms the Ge nanoparticles to become water-soluble. The biocompatible, functionalized, water-soluble Ge nanoparticles were bound to extracellular receptors and also incorporated into the cells as a proof-of-concept demonstration for potential biomarker applications. In expectation of forming a 3-D

  14. Germanium, Arsenic, and Selenium Abundances in Metal-poor Stars

    NASA Astrophysics Data System (ADS)

    Roederer, Ian U.

    2012-09-01

    The elements germanium (Ge, Z = 32), arsenic (As, Z = 33), and selenium (Se, Z = 34) span the transition from charged-particle or explosive synthesis of the iron-group elements to neutron-capture synthesis of heavier elements. Among these three elements, only the chemical evolution of germanium has been studied previously. Here we use archive observations made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope and observations from several ground-based facilities to study the chemical enrichment histories of seven stars with metallicities -2.6 <= [Fe/H] <= -0.4. We perform a standard abundance analysis of germanium, arsenic, selenium, and several other elements produced by neutron-capture reactions. When combined with previous derivations of germanium abundances in metal-poor stars, our sample reveals an increase in the [Ge/Fe] ratios at higher metallicities. This could mark the onset of the weak s-process contribution to germanium. In contrast, the [As/Fe] and [Se/Fe] ratios remain roughly constant. These data do not directly indicate the origin of germanium, arsenic, and selenium at low metallicity, but they suggest that the weak and main components of the s-process are not likely sources. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This research made use of StarCAT, hosted by the Mikulski Archive at the Space Telescope Science Institute (MAST). These data are associated with Programs GO-7348, GO-7433, GO-8197, GO-9048, GO-9455, and GO-9804.Based on data obtained from the European Southern Observatory (ESO) Science Archive Facility. These data are associated with Programs 67.D-0439(A), 074.C-0364(A), 076.B-0055(A), and 080.D-0347(A).This research has made use of the Keck Observatory Archive (KOA), which is operated by

  15. Large-volume ultralow background germanium-germanium coincidence/anticoincidence gamma-ray spectrometer

    SciTech Connect

    Brodzinski, R.L.; Brown, D.P.; Evans, J.C. Jr.; Hensley, W.K.; Reeves, J.H.; Wogman, N.A.; Avignone, F.T. III; Miley, H.S.; Moore, R.S.

    1984-03-01

    A large volume (approx. 1440 cm/sup 3/), multicrystal, high resolution intrinsic germanium gamma-ray spectrometer has been designed based on 3 generations of experiments. The background from construction materials used in standard commercial configurations has been reduced by at least two orders of magnitude. Data taken with a 132 cm/sup 3/ prototype detector, installed in the Homestake Gold Mine, are presented. The first application of the full scale detector will be an ultrasensitive search for neutrinoless and two-neutrino double beta decay of /sup 76/Ge. The size and geometrical configuration of the crystals is chosen to optimize detection of double decay to the first excited state of /sup 76/Se with subsequent emission of a 559 keV gamma ray. The detector will be sufficiently sensitive for measuring the neutrinoless double beta decay to the ground state to establish a minimum half life of 1.4.10/sup 24/ y. Application of the large spectrometer system to the analysis of low level environmental and biological samples is discussed.

  16. Bioaccumulation of germanium by Pseudomonas putida in the presence of two selected substrates

    SciTech Connect

    Chmielowski, J.; Klapcinska, B.

    1986-05-01

    The uptake of germanium by Pseudomonas putida ATCC 33015 was studied in the presence of catechol or acetate or both as representative substrates differing in their ability to form complexes with this element. The bacteria were taken from a batch culture grown on acetate as the sole carbon source. Cells introduced into a medium containing germanium and either catechol or a mixture of catechol and acetate accumulated germanium in a biphasic way. After a lower level of accumulation that corresponded to the value obtained in the presence of acetate was reached, a further increase in the germanium content up to a higher saturation level was observed. The appearance of the second step of accumulation, which corresponded to the linear degradation of catechol, proved that catechol facilitated the transport of germanium into the cells through the nonspecific uptake of the germanium-catechol complex by an inducible catechol transport system.

  17. Nanowires for THz Spectroscopy

    DTIC Science & Technology

    2013-10-01

    03-D-0009 Mansoor Sheik- Bahae Prepared by: OVPR/ University Strategic Partnership MSC02 1660 1 University of New Mexico Albuquerque, New...Z39.18 00-10-2013 Technical 07/21/2010 - 04/30/2012 Nanowires for THz Spectroscopy HDTRA1-03-D-0009 Mansoor Sheik- Bahae 3 26 OVPR/University Strategic...kilogram (C/kg) second (s) kilogram (kg) kilo pascal (kPa) 3 TABLE OF CONTENTS: I . Introduction ………....…………………………………………………… 01 II

  18. Single nanowire extinction spectroscopy.

    PubMed

    Giblin, Jay; Vietmeyer, Felix; McDonald, Matthew P; Kuno, Masaru

    2011-08-10

    Here we show the first direct extinction spectra of single one-dimensional (1D) semiconductor nanostructures obtained at room temperature utilizing a spatial modulation approach. (1) For these materials, ensemble averaging in conventional extinction spectroscopy has limited our understanding of the interplay between carrier confinement and their electrostatic interactions. (2-4) By probing individual CdSe nanowires (NWs), we have identified and assigned size-dependent exciton transitions occurring across the visible. In turn, we have revealed the existence of room temperature 1D excitons in the narrowest NWs.

  19. Nanoantennas for nanowire photovoltaics

    SciTech Connect

    Alisafaee, Hossein; Fiddy, Michael A.

    2014-09-15

    We consider the use of plasmonic nanoantenna elements, hemispherical and cylindrical, for application in semiconductor nanowire (NW) vertical arrays. Using Mie theory and a finite element method, scattering and absorption efficiencies are obtained for the desired enhancement of interaction with light in the NWs. We find an optimal mixture of nanoantennae for efficient scattering of solar spectrum in the NW array. Spectral radiation patterns of scattered light are computed, and, for representing the total response of the nanoantenna-equipped NWs to the solar AM1.5G spectrum, the weighted average of scattering patterns for unpolarized normal incidence is obtained showing an advantageous overall directivity toward the NWs.

  20. Contact planarization of ensemble nanowires.

    PubMed

    Chia, A C E; LaPierre, R R

    2011-06-17

    The viability of four organic polymers (S1808, SC200, SU8 and Cyclotene) as filling materials to achieve planarization of ensemble nanowire arrays is reported. Analysis of the porosity, surface roughness and thermal stability of each filling material was performed. Sonication was used as an effective method to remove the tops of the nanowires (NWs) to achieve complete planarization. Ensemble nanowire devices were fully fabricated and I-V measurements confirmed that Cyclotene effectively planarizes the NWs while still serving the role as an insulating layer between the top and bottom contacts. These processes and analysis can be easily implemented into future characterization and fabrication of ensemble NWs for optoelectronic device applications.

  1. Single crystalline mesoporous silicon nanowires

    SciTech Connect

    Hochbaum, A.I.; Gargas, Daniel; Jeong Hwang, Yun; Yang, Peidong

    2009-08-04

    Herein we demonstrate a novel electroless etching synthesis of monolithic, single-crystalline, mesoporous silicon nanowire arrays with a high surface area and luminescent properties consistent with conventional porous silicon materials. These porous nanowires also retain the crystallographic orientation of the wafer from which they are etched. Electron microscopy and diffraction confirm their single-crystallinity and reveal the silicon surrounding the pores is as thin as several nanometers. Confocal fluorescence microscopy showed that the photoluminescence (PL) of these arrays emanate from the nanowires themselves, and their PL spectrum suggests that these arrays may be useful as photocatalytic substrates or active components of nanoscale optoelectronic devices.

  2. Thermal stability of strained nanowires.

    PubMed

    Nisoli, Cristiano; Abraham, Douglas; Lookman, Turab; Saxena, Avadh

    2009-06-19

    Stranski-Krastanow strained islands undergo a shape anisotropy transition as they grow in size, finally evolving toward nanowires. This effect has been explained until now via simple energetic models that neglect thermodynamics. We investigate theoretically the stability of strained nanowires under thermal fluctuations of the long side. We find phase transitions from nanowires back to nanoislands as the temperature is increased and as the height of the nanostructure is raised or lowered, and we predict regions of phase coexistence. Our results are general, but explain recent data on the growth of erbium silicide on a vicinal Si surface.

  3. Single crystalline mesoporous silicon nanowires.

    PubMed

    Hochbaum, Allon I; Gargas, Daniel; Hwang, Yun Jeong; Yang, Peidong

    2009-10-01

    Herein we demonstrate a novel electroless etching synthesis of monolithic, single-crystalline, mesoporous silicon nanowire arrays with a high surface area and luminescent properties consistent with conventional porous silicon materials. These porous nanowires also retain the crystallographic orientation of the wafer from which they are etched. Electron microscopy and diffraction confirm their single-crystallinity and reveal the silicon surrounding the pores is as thin as several nanometers. Confocal fluorescence microscopy showed that the photoluminescence (PL) of these arrays emanate from the nanowires themselves, and their PL spectrum suggests that these arrays may be useful as photocatalytic substrates or active components of nanoscale optoelectronic devices.

  4. Nanowire terahertz quantum cascade lasers

    SciTech Connect

    Grange, Thomas

    2014-10-06

    Quantum cascade lasers made of nanowire axial heterostructures are proposed. The dissipative quantum dynamics of their carriers is theoretically investigated using non-equilibrium Green functions. Their transport and gain properties are calculated for varying nanowire thickness, from the classical-wire regime to the quantum-wire regime. Our calculation shows that the lateral quantum confinement provided by the nanowires allows an increase of the maximum operation temperature and a strong reduction of the current density threshold compared to conventional terahertz quantum cascade lasers.

  5. Radiation Stability of Metal Nanowires

    NASA Astrophysics Data System (ADS)

    Bedin, S. A.; Makhin’ko, F. F.; Ovchinnikov, V. V.; Gerasimenko, N. N.; Zagorskiy, D. L.

    2017-01-01

    The aim of this work is to investigate the radiation stability of pure nickel and iron– nickel Fe0.56Ni0.44 alloy nanowires fabricated by matrix synthesis using polymer track membranes and Ar+ and Xe+ (E = 20 keV, j = 300 μA/cm2) beam irradiation. The dependence of the stability of nanowires on their diameter, fluence, and type of implanted ions is investigated. The assumption that the thermalized regions of dense cascades of atomic displacements (thermal spikes) play an important role in the nanowire structure change is made. These regions are nanosized zones of explosive energy release and heated to several thousands of degrees.

  6. Conducting polyaniline nanowire electrode junction

    NASA Astrophysics Data System (ADS)

    Gaikwad, Sumedh; Bodkhe, Gajanan; Deshmukh, Megha; Patil, Harshada; Rushi, Arti; Shirsat, Mahendra D.; Koinkar, Pankaj; Kim, Yun-Hae; Mulchandani, Ashok

    2015-03-01

    In this paper, a synthesis of conducting polyaniline nanowires electrode junction (CPNEJ) has been reported. Conducting polyaniline nanowires electrode junction on Si/SiO2 substrate (having 3 μm gap between two gold microelectrodes) is prepared. Polyaniline nanowires with diameter (ca. 140 nm to 160 nm) were synthesized by one step electrochemical polymerization using galvanostatic (constant current) technique to bridge this gap. The surface morphology of CPNEJ was studied by scanning electron microscope (SEM). The synthesized CPNEJ is an excellent platform for biosensor applications.

  7. Single-crystal germanium grown on (1-1 0 2) sapphire by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Godbey, D. J.; Qadri, S. B.; Twigg, M. E.; Richmond, E. D.

    1989-06-01

    Crystalline germanium films have been successfully grown on the (1-1 0 2) sapphire surface using molecular beam epitaxy. Growth at temperatures above 700 C and after preannealing the sapphire substrates above 1100 C resulted in germanium films with a (110) orientation. A 500 nm germanium film grown at 800 C after preannealing the sapphire substrate at 1400 C gave an X-ray rocking curve width that measured 317 arcsec at half maximum for the (220) reflection.

  8. Interactions between semiconductor nanowires and living cells.

    PubMed

    Prinz, Christelle N

    2015-06-17

    Semiconductor nanowires are increasingly used for biological applications and their small dimensions make them a promising tool for sensing and manipulating cells with minimal perturbation. In order to interface cells with nanowires in a controlled fashion, it is essential to understand the interactions between nanowires and living cells. The present paper reviews current progress in the understanding of these interactions, with knowledge gathered from studies where living cells were interfaced with vertical nanowire arrays. The effect of nanowires on cells is reported in terms of viability, cell-nanowire interface morphology, cell behavior, changes in gene expression as well as cellular stress markers. Unexplored issues and unanswered questions are discussed.

  9. Investigation of adatom adsorption on single layer buckled germanium selenide

    NASA Astrophysics Data System (ADS)

    Arkın, H.; Aktürk, E.

    2016-12-01

    A recent study of Hu et al. [1] predicted that 2D single layer of asymmetric washboard germanium selenide is found to be stable and display semiconducting properties. Motivating from this study, we have shown that another phase, which is 2D buckled honeycomb germanium selenide, is also stable. This phase exhibits semiconducting behavior with a band gap of 2.29 eV. Furthermore, on the basis of the first principles, spin-polarized density functional calculations, we investigate the effect of selected adatoms adsorption on the b-GeSe single layer. The adatoms Se, Ge, S, Si, C, Br and P are chemisorbed with significant binding energy where this effects modify the electronic structure of the single layer buckled GeSe locally by tuning the band gap. Net integer magnetic moment can be achieved and b-GeSe attains half metallicity through the adsorption of Si, Ge, P and Br.

  10. Development of neutron-transmutation-doped germanium bolometer material

    SciTech Connect

    Palaio, N.P.

    1983-08-01

    The behavior of lattice defects generated as a result of the neutron-transmutation-doping of germanium was studied as a function of annealing conditions using deep level transient spectroscopy (DLTS) and mobility measurements. DLTS and variable temperature Hall effect were also used to measure the activation of dopant impurities formed during the transmutation process. In additioon, a semi-automated method of attaching wires on to small chips of germanium (< 1 mm/sup 3/) for the fabrication of infrared detecting bolometers was developed. Finally, several different types of junction field effect transistors were tested for noise at room and low temperature (approx. 80 K) in order to find the optimum device available for first stage electronics in the bolometer signal amplification circuit.

  11. Synthesis and photoluminescence of ultra-pure germanium nanoparticles

    NASA Astrophysics Data System (ADS)

    Chivas, R.; Yerci, S.; Li, R.; Dal Negro, L.; Morse, T. F.

    2011-09-01

    We have used aerosol deposition to synthesize defect and micro-strain free, ultra-pure germanium nanoparticles. Transmission electron microscopy images show a core-shell configuration with highly crystalline core material. Powder X-ray diffraction measurements verify the presence of highly pure, nano-scale germanium with average crystallite size of 30 nm and micro-strain of 0.058%. X-ray photoelectron spectroscopy demonstrates that GeO x ( x ⩽ 2) shells cover the surfaces of the nanoparticles. Under optical excitation, these nanoparticles exhibit two separate emission bands at room temperature: a visible emission at 500 nm with 0.5-1 ns decay times and an intense near-infrared emission at 1575 nm with up to ˜20 μs lifetime.

  12. Characterization of the impurities in tungsten/silicon-germanium contacts

    SciTech Connect

    Gregg, H.A. Sr.

    1986-03-26

    Secondary ion mass spectrometry and Auger electron spectrometry depth profiling were used to determine impurity distributions in sputter deposited tungsten films over N-type and P-type 80/20 silicon-germanium elements of thermoelectric devices. These analyses showed that silicon, oxygen, sodium, boron, and phosphorous were present as impurities in the tungsten film. All these impurities except oxygen and sodium came from the substrate. Oxygen was gettered by the tungsten films, while sodium was possibly the result of sample handling. Further, the results from this study indicate that an oxide build-up, primarily at the tungsten/silicon-germanium interface of the N-type materials, is the major contributor to contact resistance in thermoelectric devices.

  13. Discovery of Photospheric Germanium in Hot DA White Dwarfs

    NASA Astrophysics Data System (ADS)

    Vennes, Stéphane; Chayer, Pierre; Dupuis, Jean

    2005-04-01

    We report the identification of Ge IV resonance lines in ultraviolet spectra of the hot DA white dwarfs Feige 24, G191-B2B, and GD 246. The lines originate in the stellar photosphere, and we measure low Ge/H abundance ratios ranging between -8.0 and -8.7. We also tentatively identify a resonance line of Sn IV blended with an Fe V line in the spectrum of G191-B2B. The presence of germanium extends our knowledge of the abundance pattern in hot white dwarfs beyond the iron group. The abundance ratio appears nearly solar, which implies either that the germanium abundance mixture in these stars has remained unaltered since leaving the main sequence or that diffusion processes (e.g., selective radiation pressure) are coincidentally reproducing a solar Ge/H ratio.

  14. Preconcentration of germanium on mercapto-modified silica gel

    NASA Astrophysics Data System (ADS)

    Göktürk, Gamze; Delzendeh, Mehrdad; Volkan, Mürvet

    2000-07-01

    A simple method for the determination of ultra-trace amounts of germanium in natural waters has been developed. Germanium was preconcentrated using silica having mercapto functional groups, namely mercapto silica and determined by hydride generation flame atomic absorption spectrometry (HGAAS). Utilising mercapto silica, satisfactory recovery values (>95%) were obtained at natural pH, for germanate concentrations as low as 50 ng l -1. Considering the highest preconcentration factor (400-fold) obtained, the sensitivity and 3s-detection limit of mercapto silica-HGAAS system can be expressed as 3.65 ng l -1/0.0044 AU and 0.813 ng l -1, respectively. Interference effects of diverse ions were investigated for HGAAS and mercapto silica-HGAAS systems.

  15. Metabolism of tellurium, antimony and germanium simultaneously administered to rats.

    PubMed

    Kobayashi, Akihiro; Ogra, Yasumitsu

    2009-06-01

    Recently, tellurium (Te), antimony (Sb) and germanium (Ge) have been used as an alloy in phase-change optical magnetic disks, such as digital versatile disk-random access memory (DVD-RAM) and DVD-recordable disk (DVD-RW). Although these metalloids, the so-called "exotic" elements, are known to be non-essential and harmful, little is known about their toxic effects and metabolism. Metalloid compounds, tellurite, antimonite and germanium dioxide, were simultaneously administered to rats. Their distributions metabolites were determined and identified by speciation. Te and Sb accumulated in red blood cells (RBCs): Te accumulated in RBCs in the dimethylated form, while Sb accumulated in the inorganic/non-methylated form. In addition, trimethyltelluronium (TMTe) was the urinary metabolite of Te, whereas Sb in urine was not methylated but oxidized. Ge was also not methylated in rats. These results suggest that each metalloid is metabolized via a unique pathway.

  16. Synthesis and Gas Phase Thermochemistry of Germanium-Containing Compounds

    SciTech Connect

    Classen, Nathan Robert

    2002-01-01

    The driving force behind much of the work in this dissertation was to gain further understanding of the unique olefin to carbene isomerization observed in the thermolysis of 1,1-dimethyl-2-methylenesilacyclobutane by finding new examples of it in other silicon and germanium compounds. This lead to the examination of a novel phenylmethylenesilacyclobut-2-ene, which did not undergo olefin to carbene rearrangement. A synthetic route to methylenegermacyclobutanes was developed, but the methylenegermacyclobutane system exhibited kinetic instability, making the study of the system difficult. In any case the germanium system decomposed through a complex mechanism which may not include olefin to carbene isomerization. However, this work lead to the study of the gas phase thermochemistry of a series of dialkylgermylene precursors in order to better understand the mechanism of the thermal decomposition of dialkylgermylenes. The resulting dialkylgermylenes were found to undergo a reversible intramolecular β C-H insertion mechanism.

  17. Diffusion of n-type dopants in germanium

    SciTech Connect

    Chroneos, A.; Bracht, H.

    2014-03-15

    Germanium is being actively considered by the semiconductor community as a mainstream material for nanoelectronic applications. Germanium has advantageous materials properties; however, its dopant-defect interactions are less understood as compared to the mainstream material, silicon. The understanding of self- and dopant diffusion is essential to form well defined doped regions. Although p-type dopants such as boron exhibit limited diffusion, n-type dopants such as phosphorous, arsenic, and antimony diffuse quickly via vacancy-mediated diffusion mechanisms. In the present review, we mainly focus on the impact of intrinsic defects on the diffusion mechanisms of donor atoms and point defect engineering strategies to restrain donor atom diffusion and to enhance their electrical activation.

  18. Electronic Structure of Germanium Nanocrystal Films Probed with Synchrotron Radiation

    SciTech Connect

    Bostedt, C

    2002-05-01

    The fundamental structure--property relationship of semiconductor quantum dots has been investigated. For deposited germanium nanocrystals strong quantum confinement effects have been determined with synchrotron radiation based x-ray absorption and photoemission techniques. The nanocrystals are condensed out of the gas phase with a narrow size distribution and subsequently deposited in situ onto various substrates. The particles are crystalline in the cubic phase with a structurally disordered surface shell and the resulting film morphology depends strongly on the substrate material and condition. The disordered surface region has an impact on the overall electronic structure of the particles. In a size-dependent study, the conduction and valence band edge of germanium nanocrystals have been measured for the first time and compared to the bulk crystal. The band edges move to higher energies as the particle size is decreased, consistent with quantum confinement theory. To obtain a more accurate analysis of confinement effects in the empty states, a novel analysis method utilizing an effective particle size for the x-ray absorption experiment, which allows a deconvolution of absorption edge broadening effects, has been introduced. Comparison of the present study to earlier studies on silicon reveals that germanium exhibits stronger quantum confinement effects than silicon. Below a critical particle size of 2.3 {+-} 0.7 nm, the band gap of germanium becomes larger than that of silicon--even if it is the opposite for bulk materials. This result agrees phenomenologically with effective mass and tight binding theories but contradicts the findings of recent pseudopotential calculations. The discrepancy between theory and experiments is attributed to the differences in the theoretical models and experimental systems. The experimentally observed structural disorder of the particle surface has to be included in the theoretical models.

  19. Optical properties of silicon germanium waveguides at telecommunication wavelengths.

    PubMed

    Hammani, Kamal; Ettabib, Mohamed A; Bogris, Adonis; Kapsalis, Alexandros; Syvridis, Dimitris; Brun, Mickael; Labeye, Pierre; Nicoletti, Sergio; Richardson, David J; Petropoulos, Periklis

    2013-07-15

    We present a systematic experimental study of the linear and nonlinear optical properties of silicon-germanium (SiGe) waveguides, conducted on samples of varying cross-sectional dimensions and Ge concentrations. The evolution of the various optical properties for waveguide widths in the range 0.3 to 2 µm and Ge concentrations varying between 10 and 30% is considered. Finally, we comment on the comparative performance of the waveguides, when they are considered for nonlinear applications at telecommunications wavelengths.

  20. Formation of a crystalline phase in amorphous hydrogenated carbon-germanium films by electron beam irradiation

    SciTech Connect

    Tyczkowski, J.; Pietrzyk, B.; Mazurczyk, R.; Polanski, K.; Balcerski, J.; Delamar, M.

    1997-11-01

    The influence of electron beam irradiation on morphology of plasma deposited amorphous hydrogenated carbon-germanium films produced from tetramethylgermanium in a three-electrode af reactor has been studied. It has been found that the insulating films are insensitive to this treatment, whereas a crystalline phase occurs in the semiconducting films. Although the molar content of germanium in these films amounts only to about 0.2, the crystalline phase is composed of pure germanium nanocrystals which contain about 70{percent} of the whole amount of germanium existing in the films. The nanocrystals are agglomerated in globules of 50{endash}500 nm in diameter. {copyright} {ital 1997 American Institute of Physics.}

  1. High-Purity Germanium Crystals Study for Underground Experiments

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Yang, Gang; Gavoni, Jayesh; Wang, Guojian; Mei, Hao; Mei, Dongming; Cubed Collaboration

    2013-10-01

    The main characterization is the measurement of electrical properties such as carrier concentration, carrier mobility, resistivity of germanium crystal, as well as to identify whether the crystal is n-type or p-type. Van der pauw Hall effect measurement is conducted at room temperature and 77 K separately for measuring electrical properties for shallow level impurities. The results show that the ionized impurity level of crystals grown in our lab has reached about 1010 /cm3. The accumulated data are applied with theoretical analysis. The study of mobility reveals the different scattering mechanisms involved with impurities and lattice vibrations of the crystal. Theoretical calculations have been performed with reasonable parameter assumption and then compared with experimental data. It is found that neutral impurity concentration constrains mobility at 77 K while ionized impurity is within the acceptable range (below 1012/cm3) in germanium crystals. Mobility can increase significantly when neutral impurity concentration is below 1014/cm3. Therefore, a large reduction of neutral impurity is a desirable approach for obtaining larger mobility, which would improve timing response of germanium detectors. Sponsored by Department of Energy- DE-FG02-10ER46709 and the State of South Dakota.

  2. Germanium on silicon to enable integrated photonic circuits

    NASA Astrophysics Data System (ADS)

    Hopkins, F. Kenneth; Walsh, Kevin M.; Benken, Alexander; Jones, John; Averett, Kent; Diggs, Darnell E.; Tan, Loon-Seng; Mou, Shin; Grote, James G.

    2013-09-01

    Electronic circuits alone cannot fully meet future requirements for speed, size, and weight of many sensor systems, such as digital radar technology and as a result, interest in integrated photonic circuits (IPCs) and the hybridization of electronics with photonics is growing. However, many IPC components such as photodetectors are not presently ideal, but germanium has many advantages to enable higher performance designs that can be better incorporated into an IPC. For example, Ge photodetectors offer an enormous responsivity to laser wavelengths near 1.55μm at high frequencies to 40GHz, and they can be easily fabricated as part of a planar silicon processing schedule. At the same time, germanium has enormous potential for enabling 1.55 micron lasers on silicon and for enhancing the performance of silicon modulators. Our new effort has begun by studying the deposition of germanium on silicon and beginning to develop methods for processing these films. In initial experiments comparing several common chemical solutions for selective etching under patterned positive photoresist, it was found that hydrogen peroxide (H2O2) at or below room temperature (20 C) produced the sharpest patterns in the Ge films; H2O2 at a higher temperature (50 C) resulted in the greatest lateral etching.

  3. Fluorine-enhanced boron diffusion in germanium-preamorphized silicon

    SciTech Connect

    Jacques, J.M.; Jones, K.S.; Robertson, L.S.; Li-Fatou, A.; Hazelton, C.M.; Napolitani, E.; Rubin, L.M.

    2005-10-01

    Silicon wafers were preamorphized with 60 keV Ge{sup +} or 70 keV Si{sup +} at a dose of 1x10{sup 15} atoms/cm{sup 2}. F{sup +} was then implanted into some samples at 6 keV at doses ranging from 1x10{sup 14} to 5x10{sup 15} atoms/cm{sup 2}, followed by {sup 11}B{sup +} implants at 500 eV, 1x10{sup 15} atoms/cm{sup 2}. Secondary-ion-mass spectrometry confirmed that fluorine enhances boron motion in germanium-preamorphized materials in the absence of annealing. The magnitude of boron diffusion scales with increasing fluorine dose. Boron motion in as-implanted samples occurs when fluorine is concentrated above 1x10{sup 20} atoms/cm{sup 3}. Boron atoms are mobile in as-implanted, amorphous material at concentrations up to 1x10{sup 19} atoms/cm{sup 3}. Fluorine directly influences boron motion only prior to activation annealing. During the solid-phase epitaxial regrowth process, fluorine does not directly influence boron motion, it simply alters the recrystallization rate of the silicon substrate. Boron atoms can diffuse in germanium-amorphized silicon during recrystallization at elevated temperatures without the assistance of additional dopants. Mobile boron concentrations up to 1x10{sup 20} atoms/cm{sup 3} are observed during annealing of germanium-preamorphized wafers.

  4. Metastable phases in mechanically alloyed aluminum germanium powders

    SciTech Connect

    Yvon, P.J.; Schwarz, R.B.

    1993-03-01

    Aluminum and germanium form a simple eutectic system with no stable intermetallic phase, and limited mutual solubility. We report the formation of a metastable rhombohedral,{gamma}{sub 1} phase by mechanically alloying aluminum and germanium powders. This phase, which appears for compositions between 20 and 50 at. % germanium, has also been observed in rapidly quenched alloys, but there is disagreement as to its composition. By measuring the heat of crystallization as a function of composition, we determined the composition of the {gamma}{sub 1} phase to be Al{sub 70}Ge{sub 30}. We also produced Al{sub 70}Ge{sub 30} by arc melting the pure elements, followed by splat-quenching at a cooling rate in the range of 10{sup 8} K s{sup {minus}1}. This method produced two metastable phases, one of which was found to be the {gamma}{sub 1} phase obtained by mechanical alloying. The other was a monoclinic phase reported earlier in the literature as {gamma}{sub 2}.

  5. Germanium-containing resist for bilayer resist process

    NASA Astrophysics Data System (ADS)

    Fujioka, Hirofumi; Nakajima, Hiroyuki H. N.; Kishimura, Shinji; Nagata, Hitoshi

    1990-06-01

    Germanium-containing resist material has been investigated as a new type of removable bilayer resist , since the oxide of germanium is soluble in conventional acids. The polymers derived from trimethylgermyl- styrene ( GeSt) show good resistance to 02 RIE , and their surface has been "determined to be converted into GeO, by XPS measurement before and after 02 RIE. The homopolymer of GeSt has been found to crosslink upon exposure to deep UV or electron beam radiation and to behave as a negative resist. The sensitivity is enhanced several times as high as that of the PGeSt by copolymerizing with 1 0 mol% chloromethyl-styrene ( CMSt) . The copolymer gives fine resist patterns with vertical sidewalls in a bilayer process. The germanium- containing resist pattern after 02 RIE is not completely dissolved in some acids such as H2 SO4 . This is due to the organic components remaining in the film. However, it has been found that it is perfectly dissolved in oxidizing acids such as fuming HNO and H2S04/H202(2/l) without a residue.

  6. Actuation of polypyrrole nanowires

    NASA Astrophysics Data System (ADS)

    Lee, Alexander S.; Peteu, Serban F.; Ly, James V.; Requicha, Aristides A. G.; Thompson, Mark E.; Zhou, Chongwu

    2008-04-01

    Nanoscale actuators are essential components of the NEMS (nanoelectromechanical systems) and nanorobots of the future, and are expected to become a major area of development within nanotechnology. This paper demonstrates for the first time that individual polypyrrole (PPy) nanowires with diameters under 100 nm exhibit actuation behavior, and therefore can potentially be used for constructing nanoscale actuators. PPy is an electroactive polymer which can change volume on the basis of its oxidation state. PPy-based macroscale and microscale actuators have been demonstrated, but their nanoscale counterparts have not been realized until now. The research reported here answers positively the fundamental question of whether PPy wires still exhibit useful volume changes at the nanoscale. Nanowires with a 50 nm diameter and a length of approximately 6 µm, are fabricated by chemical polymerization using track-etched polycarbonate membranes as templates. Their actuation response as a function of oxidation state is investigated by electrochemical AFM (atomic force microscopy). An estimate of the minimum actuation force is made, based on the displacement of the AFM cantilever.

  7. Actuation of polypyrrole nanowires.

    PubMed

    Lee, Alexander S; Peteu, Serban F; Ly, James V; Requicha, Aristides A G; Thompson, Mark E; Zhou, Chongwu

    2008-04-23

    Nanoscale actuators are essential components of the NEMS (nanoelectromechanical systems) and nanorobots of the future, and are expected to become a major area of development within nanotechnology. This paper demonstrates for the first time that individual polypyrrole (PPy) nanowires with diameters under 100 nm exhibit actuation behavior, and therefore can potentially be used for constructing nanoscale actuators. PPy is an electroactive polymer which can change volume on the basis of its oxidation state. PPy-based macroscale and microscale actuators have been demonstrated, but their nanoscale counterparts have not been realized until now. The research reported here answers positively the fundamental question of whether PPy wires still exhibit useful volume changes at the nanoscale. Nanowires with a 50 nm diameter and a length of approximately 6 µm, are fabricated by chemical polymerization using track-etched polycarbonate membranes as templates. Their actuation response as a function of oxidation state is investigated by electrochemical AFM (atomic force microscopy). An estimate of the minimum actuation force is made, based on the displacement of the AFM cantilever.

  8. Diamond Nanowire for UV Detection

    DTIC Science & Technology

    2010-02-28

    ten top physics stories of 2007” by the American Institute of Physics. Diamond, nanowire, ultraviolet, detector, nanotechnology, carbon, optics, nano ...material has been made, and resulted in a surprising discovery – bismuth when nano -patterned could undergo a phase transition from metallic to insulating...Sylvain Cloutier, Steven Palefsky, Jimmy Xu. Synthesis of Diamond Nanowires using Atmospheric-Pressure Chemical Vapor Deposition. (In review, at Nano

  9. Electrical Properties of Cu Nanowires

    DTIC Science & Technology

    2008-08-01

    attributed to the surface and size effects based on the further demonstrative analysis . I. INTRODUCTION Electrical properties of metallic nanowires...Walter, R. M. Penner, H. Liu, K. H. Ng, M. P. Zach, and F. Favier, "Sensors from electrodeposited metal nanowires," Surface And Interface Analysis , vol...and G. Dumpich, "Influence of the electron beam on electromigration measurements within a scanning electron microscope," Applied Physics Letters

  10. Functionalization of Mechanochemically Passivated Germanium Nanoparticles via "Click" Chemistry

    NASA Astrophysics Data System (ADS)

    Purkait, Tapas Kumar

    Germanium nanoparticles (Ge NPs) may be fascinating for their electronic and optoelectronic properties, as the band gap of Ge NPs can be tuned from the infrared into the visible range of solar spectru. Further functionalization of those nanoparticles may potentially lead to numerous applications ranging from surface attachment, bioimaging, drug delivery and nanoparticles based devices. Blue luminescent germanium nanoparticles were synthesized from a novel top-down mechanochemical process using high energy ball milling (HEBM) of bulk germanium. Various reactive organic molecules (such as, alkynes, nitriles, azides) were used in this process to react with fresh surface and passivate the surface through Ge-C or Ge-N bond. Various purification process, such as gel permeation chromatography (GPC), Soxhlet dailysis etc. were introduced to purify nanoparticles from molecular impurities. A size separation technique was developed using GPC. The size separated Ge NPs were characterize by TEM, small angle X-ray scattering (SAXS), UV-vis absorption and photoluminescence (PL) emission spectroscopy to investigate their size selective properties. Germanium nanoparticles with alkyne termini group were prepared by HEBM of germanium with a mixture of n-alkynes and alpha, o-diynes. Additional functionalization of those nanoparticles was achieved by copper(I) catalyzed azide-alkyne "click" reaction. A variety of organic and organometallic azides including biologically important glucals have been reacted in this manner resulting in nanopartilces adorned with ferrocenyl, trimethylsilyl, and glucal groups. Additional functionalization of those nanoparticles was achieved by reactions with various azides via a Cu(I) catalyzed azide-alkyne "click" reaction. Various azides, including PEG derivatives and cylcodextrin moiety, were grafted to the initially formed surface. Globular nanoparticle arrays were formed through interparticle linking via "click" chemistry or "host-guest" chemistry

  11. DNA-templated gold nanowires

    NASA Astrophysics Data System (ADS)

    Mohammadzadegan, Reza; Mohabatkar, Hassan; Sheikhi, Mohammad Hossein; Safavi, Afsaneh; Khajouee, Mahmood Barati

    2008-10-01

    We have developed simple methods of reproducibly creating deoxyribonucleic acid (DNA)-templated gold nanowires on silicon. First DNA nanowires were aligned on silicon surfaces. Briefly, modified silicon wafer was soaked in the DNA solution, and then the solution was removed using micropipettes; the surface tension at the moving air-solution interface is sufficient to align the DNA nanowires on the silicon wafer. In another attempt, an aqueous dispersion of sodium azide-stabilized gold nanoparticles was prepared. The nanoparticles aligned double-stranded λ-DNA to form a linear nanoparticle array. Continuous gold nanowires were obtained. The above nanowires were structurally characterized using scanning electron microscopy. The results of the characterizations show the wires to be 57-323 nm wide, to be continuous with a length of 2.8-9.5 μm. The use of DNA as a template for the self-assembly of conducting nanowires represents a potentially important approach in the fabrication of nanoscale interconnects.

  12. ZnO nanowire lasers.

    PubMed

    Vanmaekelbergh, Daniël; van Vugt, Lambert K

    2011-07-01

    The pathway towards the realization of optical solid-state lasers was gradual and slow. After Einstein's paper on absorption and stimulated emission of light in 1917 it took until 1960 for the first solid state laser device to see the light. Not much later, the first semiconductor laser was demonstrated and lasing in the near UV spectral range from ZnO was reported as early as 1966. The research on the optical properties of ZnO showed a remarkable revival since 1995 with the demonstration of room temperature lasing, which was further enhanced by the first report of lasing by a single nanowire in 2001. Since then, the research focussed increasingly on one-dimensional nanowires of ZnO. We start this review with a brief description of the opto-electronic properties of ZnO that are related to the wurtzite crystal structure. How these properties are modified by the nanowire geometry is discussed in the subsequent sections, in which we present the confined photon and/or polariton modes and how these can be investigated experimentally. Next, we review experimental studies of laser emission from single ZnO nanowires under different experimental conditions. We emphasize the special features resulting from the sub-wavelength dimensions by presenting our results on single ZnO nanowires lying on a substrate. At present, the mechanism of lasing in ZnO (nanowires) is the subject of a strong debate that is considered at the end of this review.

  13. Optical second harmonic generation from Pt nanowires

    NASA Astrophysics Data System (ADS)

    Hayashi, N.; Aratake, K.; Okushio, R.; Iwai, T.; Sugawara, A.; Sano, H.; Mizutani, G.

    2007-09-01

    We have measured optical second harmonic intensity from arrays of Pt nanowires of 20 nm and 9 nm average widths, as a function of the incident and output light polarizations, the azimuthal angle, and the excitation photon energy. The nanowires were fabricated through shadow deposition on self-organized NaCl(1 1 0) faceted templates. The anisotropy of the SH intensity from the Pt nanowires was found to be stronger than that from the Au nanowires reported previously. The effective nonlinear susceptibility element χ222(2), with the suffix 2 indicating the direction [1 1¯ 0], was observed for Pt nanowires, although it was not observed for Au nanowires. This difference is suggested to be due to the weaker suppression of the incident fundamental fields by the depolarization field in the Pt nanowires and the larger anisotropy in the nonlinearity of Pt nanowires due to the thinner widths.

  14. A silicon nanowire heater and thermometer

    NASA Astrophysics Data System (ADS)

    Zhao, Xingyan; Dan, Yaping

    2017-07-01

    In the thermal conductivity measurements of thermoelectric materials, heaters and thermometers made of the same semiconducting materials under test, forming a homogeneous system, will significantly simplify fabrication and integration. In this work, we demonstrate a high-performance heater and thermometer made of single silicon nanowires (SiNWs). The SiNWs are patterned out of a silicon-on-insulator wafer by CMOS-compatible fabrication processes. The electronic properties of the nanowires are characterized by four-probe and low temperature Hall effect measurements. The I-V curves of the nanowires are linear at small voltage bias. The temperature dependence of the nanowire resistance allows the nanowire to be used as a highly sensitive thermometer. At high voltage bias, the I-V curves of the nanowire become nonlinear due to the effect of Joule heating. The temperature of the nanowire heater can be accurately monitored by the nanowire itself as a thermometer.

  15. Do Twin Boundaries Always Strengthen Metal Nanowires?

    PubMed

    Zhang, Yongfeng; Huang, Hanchen

    2009-01-01

    It has been widely reported that twin boundaries strengthen nanowires regardless of their morphology-that is, the strength of nanowires goes up as twin spacing goes down. This article shows that twin boundaries do not always strengthen nanowires. Using classical molecular dynamics simulations, the authors show that whether twin boundaries strengthen nanowires depends on the necessary stress for dislocation nucleation, which in turn depends on surface morphologies. When nanowires are circular cylindrical, the necessary stress of dislocation nucleation is high and the presence of twin boundaries lowers this stress; twin boundaries soften nanowires. In contrast, when nanowires are square cylindrical, the necessary stress of dislocation nucleation is low, and a higher stress is required for dislocations to penetrate twin boundaries; they strengthen nanowires.

  16. Investigation of Nanowire Thickness and Enhancement Characteristics

    NASA Astrophysics Data System (ADS)

    Saylor, Cameron; Debu, Desalegn; Novak, Eric; Herzog, Joseph

    2015-03-01

    This work investigates of the effect of nanowire thickness on the optical enhancement of nanowire. We present a study that shows there is potential in altering the thickness of plasmonic structures to improve their optical field enhancement. The study was performed using a finite element method computational electromagnetic analysis, which allows for the thickness and width of the nanowire and wavelength of the incident light to be changed, and the corresponding effects on the optical enhancement characteristics of the structure to be measured. The nanowire was modeled using a two-dimensional cross-section that approximates the nanowire as being infinitely long, with the incident light polarized perpendicular to the length of the nanowire. Preliminary results suggest that lower nanowire thickness provide the highest optical enhancement. The effects of the material and thickness of the adhesion layer on the optical enhancement of the nanowire are also investigated.

  17. Nanoscale contact engineering for Silicon/Silicide nanowire devices

    NASA Astrophysics Data System (ADS)

    Lin, Yung-Chen

    attributed to the high compressive stress built-in in the core/shell NW structure that retards the diffusion of the nickel atom as well as limits the volume expansion of the metal-rich phases. As a result, the high stress at this finite scale hinders the continuous growth of Ni31Si 12 into the core/shell NWs and totally eliminates the formation of Ni 2Si in core/shell NWs with thick oxide shells (˜ 50 nm). Through these studies, we have demonstrated first time the phase formation sequences of nickel silicides in Si and Si/SiOx NW structures, which is of great importance for reliable contact engineering for Si NW devices. Furthermore, we have provided a clear picture of the hindered nickel silicide growth in confined nanoscale environment and showed the deviated behavior of silicides growth under stress. The information rendered here will be useful for Si NW device applications as well as for the silicon device engineering at nanoscale in general. To further investigate the oxide shell effect, Mn5Si 3 and Fe5Ge3 NW were grown within various oxide thickness to explore the nucleation and growth in the nanowire structure. A oxide shell exerted a compressive stress on the silicide or germanide materials will make those materials with single-crystal properties. Interestingly, single-crystal growth of contact materials can be also implemented for germanide materials. The iron-rich germanide, Fe5Ge3, was successfully grown with single-crystal properties. It shows ferromagnetic properties with a Curie temperature above the room temperature verified by magnetic force microscope (MFM). Two different epitaxial relations found at germanide/germanium interface due to the different sizes of the germanium NW templates. These two different crystal structures exhibited magnetic anisotropy in magnetic force microscope (MFM) measurement, showing differently preferred domain orientations. In-plane and out-of-plane magnetization in the Fe5Ge3 NWs are observed in our experiment. The crystal

  18. Electrochemical synthesis of highly crystalline copper nanowires

    SciTech Connect

    Kaur, Amandeep; Gupta, Tanish; Kumar, Akshay; Kumar, Sanjeev; Singh, Karamjeet; Thakur, Anup

    2015-05-15

    Copper nanowires were fabricated within the pores of anodic alumina template (AAT) by template synthesis method at pH = 2.9. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to investigate the structure, morphology and composition of fabricated nanowires. These characterizations revealed that the deposited copper nanowires were highly crystalline in nature, dense and uniform. The crystalline copper nanowires are promising in application of future nanoelectronic devices and circuits.

  19. Dual-Gate Operation and Carrier Transport in SiGe p-n Junction Nanowires.

    PubMed

    Delker, Collin J; Yoo, Jinkyoung; Bussmann, Ezra; Swartzentruber, Brian S; Harris, C T

    2017-10-05

    We investigate carrier transport in silicon-germanium nanowires with an axial p-n junction doping profile by fabricating these wires into transistors that feature separate top gates over each doping segment. By independently biasing each gate, carriers in the n- and p-side of the wire can be modulated. For these devices, which were fabricated with nickel source-drain electrical contacts, holes are the dominant charge carrier, with more favorable hole injection occurring on the p-side contact. Channel current exhibits greater sensitivity to the n-side gate, and in the reverse biased source-drain configuration, current is limited by the nickel/n-side Schottky contact. © 2017 IOP Publishing Ltd.

  20. Cobalt-doped cadmium selenide colloidal nanowires.

    PubMed

    Li, Zhen; Du, Ai Jun; Sun, Qiao; Aljada, Muhsen; Cheng, Li Na; Riley, Mark J; Zhu, Zhong Hua; Cheng, Zhen Xiang; Wang, Xiao Lin; Hall, Jeremy; Krausz, Elmars; Qiao, Shi Zhang; Smith, Sean C; Lu, Gao Qing Max

    2011-11-21

    Co(2+)-doped CdSe colloidal nanowires with tunable size and dopant concentration have been prepared by a solution-liquid-solid (SLS) approach for the first time. These doped nanowires exhibit anomalous photoluminescence temperature dependence in comparison with undoped nanowires.

  1. A light-driven supramolecular nanowire actuator.

    PubMed

    Lee, Junho; Oh, Seungwhan; Pyo, Jaeyeon; Kim, Jong-Man; Je, Jung Ho

    2015-04-21

    A single photomechanical supramolecular nanowire actuator with an azobenzene-containing 1,3,5-tricarboxamide derivative is developed by employing a direct writing method. Single nanowires display photoinduced reversible bending and the bending behavior follows first-order kinetics associated with azobenzene photoisomerization. A wireless photomechanical nanowire tweezers that remotely manipulates a single micro-particle is also demonstrated.

  2. Cutting ice: nanowire regelation.

    PubMed

    Hynninen, Teemu; Heinonen, Vili; Dias, Cristiano L; Karttunen, Mikko; Foster, Adam S; Ala-Nissila, Tapio

    2010-08-20

    Even below its normal melting temperature, ice melts when subjected to high pressure and refreezes once the pressure is lifted. A classic demonstration of this regelation phenomenon is the passing of a thin wire through a block of ice when sufficient force is exerted. Here we present a molecular-dynamics study of a nanowire cutting through ice to unravel the molecular level mechanisms responsible for regelation. In particular, we show that the transition from a stationary to a moving wire due to increased driving force changes from symmetric and continuous to asymmetric and discontinuous as a hydrophilic wire is replaced by a hydrophobic one. This is explained at the molecular level in terms of the wetting properties of the wire.

  3. Mechanical behaviors of nanowires

    NASA Astrophysics Data System (ADS)

    Chen, Yujie; An, Xianghai; Liao, Xiaozhou

    2017-09-01

    The mechanical behaviors of nanowires (NWs) are significantly different from those of their bulk materials because of their small dimensions. Determining the mechanical performance of NWs and understanding their deformation behavior are crucial for designing and manufacturing NW-based devices with predictable and reproducible operation. Owing to the difficulties to manipulate these nanoscale materials, nanomechanical testing of NWs is always challenging, and errors can be readily introduced in the measured mechanical data. Here, we survey the techniques that have been developed to quantify the mechanical properties and to understand the deformation mechanisms of NWs. We also provide a general review of the mechanical properties and deformation behaviors of NWs and discuss possible sources responsible for the discrepancy of measured mechanical properties. The effects of planar defects on the mechanical behavior of NWs are also reviewed.

  4. Nanowire Plasmon Resonators

    NASA Astrophysics Data System (ADS)

    de Leon, Nathalie; Shields, Brendan; Yu, Chun; Englund, Dirk; Akimov, Alexey; Lukin, Mikhail; Park, Hongkun

    2011-05-01

    Strong interactions between light and matter can be engineered by confining light to a small volume for an extended period of time. Nanoscale plasmonic structures can concentrate lighte well below the diffraction limit, but realization of small mode-volume plasmon cavities remains an outstanding challenge. We propose and demonstrate a new approach for realization of nanoscale plasmon resonators enabling strong light-matter interaction. In our approach, chemically synthesized silver nanowires are surrounded by patterned dielectric to create resonators with mode volumes that are two orders of magnitude below the diffraction limit and quality factors approaching 100. We show that they can be used to enhance spontaneous emission rates of CdSe quantum dots and single diamond nitrogen-vacancy centers by a factor larger than 20 at the cavity resonance.

  5. Metastable Ge1-xCx alloy nanowires.

    PubMed

    Kim, Byung-Sung; Lee, Jae-Hyun; Son, Kiseok; Hwang, Sung Woo; Choi, Byoung Lyong; Lee, Eun Kyung; Kim, Jong Min; Whang, Dongmok

    2012-02-01

    Carbon-containing alloy materials such as Ge(1-x)C(x) are attractive candidates for replacing silicon (Si) in the semiconductor industry. The addition of carbon to diamond lattice not only allows control over the lattice dimensions, but also enhances the electrical properties by enabling variations in strain and compositions. However, extremely low carbon solubility in bulk germanium (Ge) and thermodynamically unfavorable Ge-C bond have hampered the production of crystalline Ge(1-x)C(x) alloy materials in an equilibrium growth system. Here we successfully synthesized high-quality Ge(1-x)C(x) alloy nanowires (NWs) by a nonequilibrium vapor-liquid-solid (VLS) method. The carbon incorporation was controlled by NW growth conditions and the position of carbon atoms in the Ge matrix (at substitutional or interstitial sites) was determined by the carbon concentration. Furthermore, the shrinking of lattice spacing caused by substitutional carbon offered the promising possibility of band gap engineering for photovoltaic and optoelectronic applications.

  6. Naturally occurring vapor-liquid-solid (VLS) Whisker growth of germanium sulfide

    USGS Publications Warehouse

    Finkelman, R.B.; Larson, R.R.; Dwornik, E.J.

    1974-01-01

    The first naturally occurring terrestrial example of vapor-liquid-solid (VLS) growth has been observed in condensates from gases released by burning coal in culm banks. Scanning electron microscopy, X-ray diffraction, and energy dispersive analysis indicate that the crystals consist of elongated rods (??? 100 ??m) of germanium sulfide capped by bulbs depleted in germanium. ?? 1974.

  7. Oligogermanes as molecular precursors for germanium(0) nanoparticles: Size control and size-dependent fluorescence

    SciTech Connect

    Schrick, Aaron C.; Weinert, Charles S.

    2013-10-15

    Graphical abstract: Catenated germanium compounds are employed as molecular precursors for germanium(0) nanoparticles. The size of the nanoparticles, and their fluorescence spectra, depend on the number of catenated germanium atoms present in the precursor. - Highlights: • We have used oligogermanes for the size-specific synthesis of germanium(0) nanoparticles. • The size of the nanomaterials obtained depends directly on the degree of catenation present in the oligogermane precursor. • The nanoparticles are shown to exhibit size-dependent fluorescence. • Oligogermanes will function as useful precursors for the synthesis of a variety of nanomaterials. - Abstract: Germanium nanoparticles were synthesized in solution from novel oligogermane molecular precursors. The size of the nanoparticles obtained is directly related to the number of catenated germanium atoms present in the oligogermane precursor and the nanoparticles exhibit size-dependent fluorescence. The germanium nanoparticles were also characterized by TEM, powder XRD, FTIR, EDS and XPS methods. This method appears to be a promising new route for the synthesis of germanium nanoparticles since the size of the materials obtained can be controlled by the choice of the oligogermane used as the precursor.

  8. Oriented bottom-up growth of armchair graphene nanoribbons on germanium

    DOEpatents

    Arnold, Michael Scott; Jacobberger, Robert Michael

    2016-03-15

    Graphene nanoribbon arrays, methods of growing graphene nanoribbon arrays and electronic and photonic devices incorporating the graphene nanoribbon arrays are provided. The graphene nanoribbons in the arrays are formed using a scalable, bottom-up, chemical vapor deposition (CVD) technique in which the (001) facet of the germanium is used to orient the graphene nanoribbon crystals along the [110] directions of the germanium.

  9. Variable-Temperature Cryostat For Radiation-Damage Testing Of Germanium Detectors

    NASA Technical Reports Server (NTRS)

    Floyd, Samuel R.; Puc, Bernard P.

    1992-01-01

    Variable-temperature cryostats developed to study radiation damage to, and annealing of, germanium gamma-ray detectors. Two styles: one accommodates large single detector and one accommodates two medium-sized detectors. New cryostats allow complete testing of large-volume germanium gamma-ray detectors without breaking cryostat vacuum and removing detectors for annealing.

  10. Investigation of alginate binding to germanium and polystyrene substrata conditioned with mussel adhesive protein

    SciTech Connect

    Suci, P.A.; Geesey, G.G.

    1995-06-15

    Binding of alginate from Macrocystis pyrifera (kelp) to germanium and polystyrene substrata conditioned with mussel adhesive protein (MAP) from Mytilis edulis, to germanium substrata conditioned with bovine serum albumin (BSA) and polylysine, and to germanium substrata coated with aminopropyltriethoxysilane (APS) was investigated using attenuated total reflection Fourier transform infrared spectrometry. Binding of alginate to MAP appears to be proportional to surface coverage for levels tested. Distinct spectral features appear in the region associated with pyranose ring vibrations upon binding of alginate to MAP, polylysine, and APS, indicating that lysine residues play a prominent role in promoting irreversible adsorption with perturbation of pyranose ring atoms. BSA does not appear to enhance alginate adsorption over that observed on clean germanium and no new spectral features appear as a result of binding. The level of irreversible binding of alginate to germanium and polystyrene substrata conditioned with MAP is similar.

  11. Adhesion and friction behavior of group 4 elements germanium, silicon, tin, and lead

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1975-01-01

    Adhesion and friction studies were conducted with thin films of the group IV elements silicon, germanium, tin, and lead ion plated on the nickel (011) substrate. The mating surface was gold (111). Contacts were made for the elements in the clean state and with oxygen present. Adhesion and friction experiments were conducted at very light loads of 1 to 10 g. Sliding was at a speed of 0.7 mm/min. Friction results indicate that the more covalently bonded elements silicon and germanium exhibit lower adhesion and friction than the more metallic bonded tin and lead. The adhesion of gold to germanium was observed, and recrystallization of the transferred gold occurred. Plastic flow of germanium was seen with sliding. Oxygen reduced, but did not eliminate, the adhesion observed with germanium and silicon.

  12. Nanoindentation-induced phase transformation and structural deformation of monocrystalline germanium: a molecular dynamics simulation investigation

    PubMed Central

    2013-01-01

    Molecular dynamics simulations were conducted to study the nanoindentation of monocrystalline germanium. The path of phase transformation and distribution of transformed region on different crystallographic orientations were investigated. The results indicate the anisotropic behavior of monocrystalline germanium. The nanoindentation-induced phase transformation from diamond cubic structure to β-tin-Ge was found in the subsurface region beneath the tool when indented on the (010) plane, while direct amorphization was observed in the region right under the indenter when the germanium was loaded along the [101] and [111] directions. The transformed phases extend along the < 110 > slip direction of germanium. The depth and shape of the deformed layers after unloading are quite different according to the crystal orientation of the indentation plane. The study results suggest that phase transformation is the dominant mechanism of deformation of monocrystalline germanium film in nanoindentation. PMID:23947487

  13. Multilayers Diamond-Like Carbon Film with Germanium Buffer Layers by Pulsed Laser Deposition

    NASA Astrophysics Data System (ADS)

    Cheng, Y.; Lu, Y. M.; Guo, Y. L.; Huang, G. J.; Wang, S. Y.; Tian, F. T.

    Multilayer diamond-like carbon film with germanium buffer layers, which was composed of several thick DLC layers and thin germanium island “layers” and named as Ge-DLC film, was prepared on the germanium substrate by ultraviolet laser. The Ge-DLC film had almost same surface roughness as the pure DLC film. Hardness of the Ge-DLC film was above 48.1GPa, which was almost the same as that of pure DLC film. Meanwhile, compared to the pure DLC film, the critical load of Ge-DLC film on the germanium substrate increased from 81.6mN to 143.8mN. Moreover, Ge-DLC film on germanium substrates had no change after fastness tests. The results showed that Ge-DLC film not only kept high hardness but also had higher critical load than that of pure DLC film. Therefore, it could be used as practical protective films.

  14. Germanium CCDs for large-format SWIR and X-ray imaging

    NASA Astrophysics Data System (ADS)

    Leitz, C.; Rabe, S.; Prigozhin, I.; Burke, B.; Zhu, M.; Ryu, K.; Cooper, M.; Reich, R.; Johnson, K.; Hu, W. L.; Felton, B.; Cook, M.; Stull, C.; Suntharalingam, V.

    2017-05-01

    Germanium exhibits high sensitivity to short-wave infrared (SWIR) and X-ray radiation, making it an interesting candidate for imaging applications in these bands. Recent advances in germanium processing allow for high-quality charge-coupled devices (CCDs) to be realized in this material. In this article, we discuss our evaluation of germanium as an absorber material for CCDs via fabrication and analysis of discrete devices such as diodes, metal-insulator-semiconductor capacitors, and buried-channel metal-oxide-semiconductor field-effect transistors (MOSFETs). We then describe fabrication of our first imaging device on germanium, a 32 × 1 × 8.1 μm linear shift register. Based on this work, we find that germanium is a promising material for CCDs imaging in the SWIR and X-ray bands.

  15. Les alliages germanium-etain et silicium-germanium-etain: Croissance, proprietes structurales et stabilite thermique

    NASA Astrophysics Data System (ADS)

    Fournier-Lupien, Jean-Hughes

    Tin-containing group IV semiconductors present a rich playground for an independent control of bandgap and lattice parameter. The ability to grow these metastable alloys on silicon (Si) platform is a key step to achieve a new class of Si-compatible heterostructures and low dimensional systems relevant for applications in electronics and optoelectronics. With this perspective, this work focuses on understanding the structural properties of germanium-tin (GeSn) and silicon-germanium-tin (SiGeSn) alloys. Pseudomorphic layers (< 100 nm) of GeSn and SiGeSn have been grown on Si(001) substrate via low defect relaxed Ge virtual substrate in a reduced pressure chemical vapor deposition (RP-CVD) system. The precursors used during the growth are disilane (Si 2H6), digermane (Ge2H6) (10% diluted in H2), and tin tetrachloride (SnCl4) using N2 as carrier gas. Low temperature growth (between 350 and 475 °C) is used in order to prevent Sn segregation and clustering. Non-equilibrium growth allows Sn to crystallize into diamond cubic alpha-Sn structure and successfully be alloyed with group IV semiconductors leading to metastable alloys. The alloy composition range of SixGe1-x-ySn y and Ge1-zSnz sample is 0.04 ≤ x ≤ 0.19, 0.02 ≤ y ≤ 0.11 and 0.02 ≤ z ≤ 0.09. Post-growth structural analyses show that low growth temperature increases the incorporation of Sn in both binary and ternary alloys. Note that for the ternary alloy, increasing Sn composition leads a reduction in Si composition. This behavior is due to the fact that the cracking temperature of Si precursor is higher than that of Sn precursor. Raman spectroscopy has been used to characterize the as-grown layers and an empirical model has been established to quantify the composition and strain of the ternary alloy SiGeSn. Using three excitation wavelengths 532 nm, 633 nm and 785 nm, we found that 633 nm wavelength is the more appropriate to clearly identify all the vibrational modes in SiGeSn lattice. This

  16. Radiation Fluence dependent variation in Electrical conductivity of Cu nanowires

    SciTech Connect

    Gehlawat, Devender; Chauhan, R. P.; Sonkawade, R. G.

    2011-07-15

    Electrical conductivity of Cu nanowires varies with diameter of nanowires. However, keeping the diameter of nanowires constant, a variation in their electrical conductivity is observed after they irradiated with gamma rays and neutrons. On the basis of I-V characteristics drawn at room temperature, decrease in the conductivity of Cu nanowires is observed, as compared to that of pristine nanowires.

  17. Aluminum Nanowire Arrays via Directed Assembly.

    PubMed

    Nesbitt, Nathan T; Merlo, Juan M; Rose, Aaron H; Calm, Yitzi M; Kempa, Krzysztof; Burns, Michael J; Naughton, Michael J

    2015-11-11

    Freestanding and vertically-oriented metal nanowire arrays have potential utility in a number of applications, but presently lack a route to fabrication. Template-based techniques, such as electrodeposition into lithographically defined nanopore arrays, have produced well-ordered nanowire arrays with a maximum pitch of about 2 μm; such nanowires, however, tend to cluster due to local attractive forces. Here, we modify this template fabrication method to produce well-ordered, vertically-oriented, freestanding Al nanowire arrays, etched from an underlying Al substrate, with highly tunable pitch. In addition, optical measurements demonstrated that the nanowires support the propagation of surface plasmon polaritons.

  18. Conductive Nanowires Templated by Molecular Brushes.

    PubMed

    Raguzin, Ivan; Stamm, Manfred; Ionov, Leonid

    2015-10-21

    In this paper, we report the fabrication of conductive nanowires using polymer bottle brushes as templates. In our approach, we synthesized poly(2-dimethylamino)ethyl methacrylate methyl iodide quaternary salt brushes by two-step atom transfer radical polymerization, loaded them with palladium salt, and reduced them in order to form metallic nanowires with average lengths and widths of 300 and 20 nm, respectively. The obtained nanowires were deposited between conductive gold pads and were connected to them by sputtering of additional pads to form an electric circuit. We connected the nanowires in an electric circuit and demonstrated that the conductivity of these nanowires is around 100 S·m(-1).

  19. Mechanical characterization of a single gold nanowire.

    PubMed

    Chang, Ming; Liu, Xiaojun; Chang, Feng-Cheng; Deka, Juti R

    2013-08-01

    Mechanical properties of gold nanowires were individually determined in this investigation using a multifunctional nanomanipulator inside a scanning electron microscope (SEM). Gold nanowires were synthesized by an electrochemical deposition technique. Three different characterization techniques including tensile, buckling and bending tests were adapted to quantitatively determine Young's modulus, yield stress and failure stress of the gold nanowires. The mechanical characterizations show that the nanowires were highly flexible in nature. The excellent resilience and the ability to store elastic energy in these nanowires confirm their potential applications in nano electromechanical devices.

  20. Temperature-dependent Refractive Index of Silicon and Germanium

    NASA Technical Reports Server (NTRS)

    Frey, Bradley J.; Leviton, Douglas B.; Madison, Timothy J.

    2006-01-01

    Silicon and germanium are perhaps the two most well-understood semiconductor materials in the context of solid state device technologies and more recently micromachining and nanotechnology. Meanwhile, these two materials are also important in the field of infrared lens design. Optical instruments designed for the wavelength range where these two materials are transmissive achieve best performance when cooled to cryogenic temperatures to enhance signal from the scene over instrument background radiation. In order to enable high quality lens designs using silicon and germanium at cryogenic temperatures, we have measured the absolute refractive index of multiple prisms of these two materials using the Cryogenic, High-Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, as a function of both wavelength and temperature. For silicon, we report absolute refractive index and thermo-optic coefficient (dn/dT) at temperatures ranging from 20 to 300 K at wavelengths from 1.1 to 5.6 pin, while for germanium, we cover temperatures ranging from 20 to 300 K and wavelengths from 1.9 to 5.5 microns. We compare our measurements with others in the literature and provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures. Citing the wide variety of values for the refractive indices of these two materials found in the literature, we reiterate the importance of measuring the refractive index of a sample from the same batch of raw material from which final optical components are cut when absolute accuracy greater than k5 x 10" is desired.

  1. Germanium Lift-Off Masks for Thin Metal Film Patterning

    NASA Technical Reports Server (NTRS)

    Brown, Ari

    2012-01-01

    A technique has been developed for patterning thin metallic films that are, in turn, used to fabricate microelectronics circuitry and thin-film sensors. The technique uses germanium thin films as lift-off masks. This requires development of a technique to strip or undercut the germanium chemically without affecting the deposited metal. Unlike in the case of conventional polymeric lift-off masks, the substrate can be exposed to very high temperatures during processing (sputter deposition). The reason why polymeric liftoff masks cannot be exposed to very high temperatures (greater than 100 C) is because (a) they can become cross linked, making lift-off very difficult if not impossible, and (b) they can outgas nitrogen and oxygen, which then can react with the metal being deposited. Consequently, this innovation is expected to find use in the fabrication of transition edge sensors and microwave kinetic inductance detectors, which use thin superconducting films deposited at high temperature as their sensing elements. Transition edge sensors, microwave kinetic inductance detectors, and their circuitry are comprised of superconducting thin films, for example Nb and TiN. Reactive ion etching can be used to pattern these films; however, reactive ion etching also damages the underlying substrate, which is unwanted in many instances. Polymeric lift-off techniques permit thin-film patterning without any substrate damage, but they are difficult to remove and the polymer can outgas during thin-film deposition. The outgassed material can then react with the film with the consequence of altered and non-reproducible materials properties, which, in turn, is deleterious for sensors and their circuitry. The purpose of this innovation was to fabricate a germanium lift-off mask to be used for patterning thin metal films.

  2. Ballistic superconductivity in semiconductor nanowires

    PubMed Central

    Zhang, Hao; Gül, Önder; Conesa-Boj, Sonia; Nowak, Michał P.; Wimmer, Michael; Zuo, Kun; Mourik, Vincent; de Vries, Folkert K.; van Veen, Jasper; de Moor, Michiel W. A.; Bommer, Jouri D. S.; van Woerkom, David J.; Car, Diana; Plissard, Sébastien R; Bakkers, Erik P.A.M.; Quintero-Pérez, Marina; Cassidy, Maja C.; Koelling, Sebastian; Goswami, Srijit; Watanabe, Kenji; Taniguchi, Takashi; Kouwenhoven, Leo P.

    2017-01-01

    Semiconductor nanowires have opened new research avenues in quantum transport owing to their confined geometry and electrostatic tunability. They have offered an exceptional testbed for superconductivity, leading to the realization of hybrid systems combining the macroscopic quantum properties of superconductors with the possibility to control charges down to a single electron. These advances brought semiconductor nanowires to the forefront of efforts to realize topological superconductivity and Majorana modes. A prime challenge to benefit from the topological properties of Majoranas is to reduce the disorder in hybrid nanowire devices. Here we show ballistic superconductivity in InSb semiconductor nanowires. Our structural and chemical analyses demonstrate a high-quality interface between the nanowire and a NbTiN superconductor that enables ballistic transport. This is manifested by a quantized conductance for normal carriers, a strongly enhanced conductance for Andreev-reflecting carriers, and an induced hard gap with a significantly reduced density of states. These results pave the way for disorder-free Majorana devices. PMID:28681843

  3. Ballistic superconductivity in semiconductor nanowires

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Gül, Önder; Conesa-Boj, Sonia; Nowak, Michał P.; Wimmer, Michael; Zuo, Kun; Mourik, Vincent; de Vries, Folkert K.; van Veen, Jasper; de Moor, Michiel W. A.; Bommer, Jouri D. S.; van Woerkom, David J.; Car, Diana; Plissard, Sébastien R.; Bakkers, Erik P. A. M.; Quintero-Pérez, Marina; Cassidy, Maja C.; Koelling, Sebastian; Goswami, Srijit; Watanabe, Kenji; Taniguchi, Takashi; Kouwenhoven, Leo P.

    2017-07-01

    Semiconductor nanowires have opened new research avenues in quantum transport owing to their confined geometry and electrostatic tunability. They have offered an exceptional testbed for superconductivity, leading to the realization of hybrid systems combining the macroscopic quantum properties of superconductors with the possibility to control charges down to a single electron. These advances brought semiconductor nanowires to the forefront of efforts to realize topological superconductivity and Majorana modes. A prime challenge to benefit from the topological properties of Majoranas is to reduce the disorder in hybrid nanowire devices. Here we show ballistic superconductivity in InSb semiconductor nanowires. Our structural and chemical analyses demonstrate a high-quality interface between the nanowire and a NbTiN superconductor that enables ballistic transport. This is manifested by a quantized conductance for normal carriers, a strongly enhanced conductance for Andreev-reflecting carriers, and an induced hard gap with a significantly reduced density of states. These results pave the way for disorder-free Majorana devices.

  4. Photoelectrochemistry of Semiconductor Nanowire Arrays

    SciTech Connect

    Mallouk, Thomas E; Redwing, Joan M

    2009-11-10

    This project supported research on the growth and photoelectrochemical characterization of semiconductor nanowire arrays, and on the development of catalytic materials for visible light water splitting to produce hydrogen and oxygen. Silicon nanowires were grown in the pores of anodic aluminum oxide films by the vapor-liquid-solid technique and were characterized electrochemically. Because adventitious doping from the membrane led to high dark currents, silicon nanowire arrays were then grown on silicon substrates. The dependence of the dark current and photovoltage on preparation techniques, wire diameter, and defect density was studied for both p-silicon and p-indium phosphide nanowire arrays. The open circuit photovoltage of liquid junction cells increased with increasing wire diameter, reaching 350 mV for micron-diameter silicon wires. Liquid junction and radial p-n junction solar cells were fabricated from silicon nano- and microwire arrays and tested. Iridium oxide cluster catalysts stabilized by bidentate malonate and succinate ligands were also made and studied for the water oxidation reaction. Highlights of this project included the first papers on silicon and indium phosphide nanowire solar cells, and a new procedure for making ligand-stabilized water oxidation catalysts that can be covalently linked to molecular photosensitizers or electrode surfaces.

  5. Electrodeposited, Transverse Nanowire Electroluminescent Junctions.

    PubMed

    Qiao, Shaopeng; Xu, Qiang; Dutta, Rajen K; Le Thai, Mya; Li, Xiaowei; Penner, Reginald M

    2016-09-27

    The preparation by electrodeposition of transverse nanowire electroluminescent junctions (tn-ELJs) is described, and the electroluminescence (EL) properties of these devices are characterized. The lithographically patterned nanowire electrodeposition process is first used to prepare long (millimeters), linear, nanocrystalline CdSe nanowires on glass. The thickness of these nanowires along the emission axis is 60 nm, and the width, wCdSe, along the electrical axis is adjustable from 100 to 450 nm. Ten pairs of nickel-gold electrical contacts are then positioned along the axis of this nanowire using lithographically directed electrodeposition. The resulting linear array of nickel-CdSe-gold junctions produces EL with an external quantum efficiency, EQE, and threshold voltage, Vth, that depend sensitively on wCdSe. EQE increases with increasing electric field and also with increasing wCdSe, and Vth also increases with wCdSe and, therefore, the electrical resistance of the tn-ELJs. Vth down to 1.8(±0.2) V (for wCdSe ≈ 100 nm) and EQE of 5.5(±0.5) × 10(-5) (for wCdSe ≈ 450 nm) are obtained. tn-ELJs produce a broad EL emission envelope, spanning the wavelength range from 600 to 960 nm.

  6. Ballistic superconductivity in semiconductor nanowires.

    PubMed

    Zhang, Hao; Gül, Önder; Conesa-Boj, Sonia; Nowak, Michał P; Wimmer, Michael; Zuo, Kun; Mourik, Vincent; de Vries, Folkert K; van Veen, Jasper; de Moor, Michiel W A; Bommer, Jouri D S; van Woerkom, David J; Car, Diana; Plissard, Sébastien R; Bakkers, Erik P A M; Quintero-Pérez, Marina; Cassidy, Maja C; Koelling, Sebastian; Goswami, Srijit; Watanabe, Kenji; Taniguchi, Takashi; Kouwenhoven, Leo P

    2017-07-06

    Semiconductor nanowires have opened new research avenues in quantum transport owing to their confined geometry and electrostatic tunability. They have offered an exceptional testbed for superconductivity, leading to the realization of hybrid systems combining the macroscopic quantum properties of superconductors with the possibility to control charges down to a single electron. These advances brought semiconductor nanowires to the forefront of efforts to realize topological superconductivity and Majorana modes. A prime challenge to benefit from the topological properties of Majoranas is to reduce the disorder in hybrid nanowire devices. Here we show ballistic superconductivity in InSb semiconductor nanowires. Our structural and chemical analyses demonstrate a high-quality interface between the nanowire and a NbTiN superconductor that enables ballistic transport. This is manifested by a quantized conductance for normal carriers, a strongly enhanced conductance for Andreev-reflecting carriers, and an induced hard gap with a significantly reduced density of states. These results pave the way for disorder-free Majorana devices.

  7. Effect of germanium dioxide on growth of Spirulina platensis

    NASA Astrophysics Data System (ADS)

    Cao, Ji-Xiang

    1996-12-01

    This study on the effect of different concentrations of germanium dioxide (GeO2) on the specific growth rate (SGR), pigment contents, protein content and amino acid composition of Spirulina platensis showed that Ge was not the essential element of this alga; that GeO2 could speed up growth and raise protein content of S. platensis, and could possibly influence the photosynthesis system. The concentration range of GeO2 beneficial to growth of S. platensis is from 5 100mg/l. GeO2 is proposed to be utilized to remove contamination by Chlorella spp. usually occurring in the cultivation of Spirulina.

  8. Diffusion of iron, cobalt, and nickel in liquid germanium

    SciTech Connect

    Denisov, V.M.; Beletskii, V.V.

    1988-03-01

    To improve the processes employed for preparing single crystals with fixed electrophysical properties it is necessary to have information about the coefficients of diffusion of the impurities present in the melts. In this paper data on the diffusion of Fe, Co, and Ni in liquid germanium, starting from its melting point up to 1380/degree/K, are presented. The coefficients of diffusion of Fe, Co, and Ni in liquid Ge were determined by the capillary method. It was established that the change in the structure of liquid helium as a function of the temperature is responsible for the characteristic features of diffusion in the systems studied.

  9. Phonon Quasidiffusion in Cryogenic Dark Matter Search Large Germanium Detectors

    SciTech Connect

    Leman, S.W.; Cabrera, B.; McCarthy, K.A.; Pyle, M.; Resch, R.; Sadoulet, B.; Sundqvist, K.M.; Brink, P.L.; Cherry, M.; Do Couto E Silva, E.; Figueroa-Feliciano, E.; Mirabolfathi, N.; Serfass, B.; Tomada, A.; /Stanford U., Phys. Dept.

    2012-06-04

    We present results on quasidiffusion studies in large, 3 inch diameter, 1 inch thick [100] high purity germanium crystals, cooled to 50 mK in the vacuum of a dilution refrigerator, and exposed with 59.5 keV gamma-rays from an Am-241 calibration source. We compare data obtained in two different detector types, with different phonon sensor area coverage, with results from a Monte Carlo. The Monte Carlo includes phonon quasidiffusion and the generation of phonons created by charge carriers as they are drifted across the detector by ionization readout channels.

  10. Gallium-doped germanium, evaluation of photoconductors, part 1

    NASA Technical Reports Server (NTRS)

    Moore, W. J.

    1979-01-01

    Gallium-doped germanium far infrared detectors were evaluated at low temperatures and low background simulating the space environment. Signal and noise characteristics were determined for detector temperatures in the 2K to 4K range. Optimum performance occurs at about 2.5K for all devices tested. The minimum average NEP in the 40-130 micron region was found to be approximately 4 x 10 to the minus 17th power watt Hz(-1/2) at a frequency of 1 Hz.

  11. Three holes bound to a double acceptor - Be(+) in germanium

    NASA Technical Reports Server (NTRS)

    Haller, E. E.; Mcmurray, R. E., Jr.; Falicov, L. M.; Haegel, N. M.; Hansen, W. L.

    1983-01-01

    A double acceptor binding three holes has been observed for the first time with photoconductive far-infrared spectroscopy in beryllium-doped germanium single crystals. This new center, Be(+), has a hole binding energy of about 5 meV and is only present when free holes are generated by ionization of either neutral shallow acceptors or neutral Be double acceptors. The Be(+) center thermally ionizes above 4 K. It disappears at a uniaxial stress higher than about a billion dyn/sq cm parallel to (111) as a result of the lifting of the valence-band degeneracy.

  12. Integration of germanium waveguide photodetectors for intrachip optical interconnects

    NASA Astrophysics Data System (ADS)

    Rouviere, Mathieu; Halbwax, Mathieu; Cercus, Jean-Luc; Cassan, Eric; Vivien, Laurent; Pascal, Daniel; Heitzmann, Michel; Hartmann, Jean-Michel; Laval, Suzanne

    2005-07-01

    The main characteristics of germanium photodetectors integrated in silicon-on-insulator optical waveguides for intrachip optical interconnects are presented. The epitaxial Ge layers are grown on Si(001) by reduced-pressure chemical vapor deposition. The optical absorption of Ge layers is recorded from 1.2 to 1.7 µm and linked to the layer strain. The responsivity of an interdigitated metal-semiconductor-metal Ge photodetector has been measured. Light coupling from a slightly etched submicron rib silicon-on-insulator waveguide to a Ge photodetector is studied for two configurations: butt coupling and vertical coupling.

  13. Germanium photodetector with 60 GHz bandwidth using inductive gain peaking.

    PubMed

    Novack, Ari; Gould, Mike; Yang, Yisu; Xuan, Zhe; Streshinsky, Matthew; Liu, Yang; Capellini, Giovanni; Lim, Andy Eu-Jin; Lo, Guo-Qiang; Baehr-Jones, Tom; Hochberg, Michael

    2013-11-18

    Germanium-on-silicon photodetectors have been heavily investigated in recent years as a key component of CMOS-compatible integrated photonics platforms. It has previously been shown that detector bandwidths could theoretically be greatly increased with the incorporation of a carefully chosen inductor and capacitor in the photodetector circuit. Here, we show the experimental results of such a circuit that doubles the detector 3dB bandwidth to 60 GHz. These results suggest that gain peaking is a generally applicable tool for increasing detector bandwidth in practical photonics systems without requiring the difficult process of lowering detector capacitance.

  14. Infrared absorption study of neutron-transmutation-doped germanium

    NASA Technical Reports Server (NTRS)

    Park, I. S.; Haller, E. E.

    1988-01-01

    Using high-resolution far-infrared Fourier transform absorption spectroscopy and Hall effect measurements, the evolution of the shallow acceptor and donor impurity levels in germanium during and after the neutron transmutation doping process was studied. The results show unambiguously that the gallium acceptor level concentration equals the concentration of transmutated Ge-70 atoms during the whole process indicating that neither recoil during transmutation nor gallium-defect complex formation play significant roles. The arsenic donor levels appear at full concentration only after annealing for 1 h at 450 C. It is shown that this is due to donor-radiation-defect complex formation. Again, recoil does not play a significant role.

  15. A miniature temperature high germanium doped PCF interferometer sensor.

    PubMed

    Favero, F C; Spittel, R; Just, F; Kobelke, J; Rothhardt, M; Bartelt, H

    2013-12-16

    We report in this paper a high thermal sensitivity (78 pm/°C) modal interferometer using a very short Photonic Crystal Fiber stub with a shaped Germanium doped core. The Photonic Crystal Fiber is spliced between two standard fibers. The splice regions allow the excitation of the core and cladding modes in the PCF and perform an interferometric interaction of such modes. The device is proposed for sensitive temperature measurements in transmission, as well as in reflection operation mode with the same high temperature sensitivity.

  16. Photosensitivity of germanium-doped silica glass and fibers

    NASA Astrophysics Data System (ADS)

    Grubsky, Victor

    Germanium-doped silica glass changes its refractive index when it is exposed with UV light. This effect is caused by intrinsic defects of germanosilicate glass called germanium oxygen-deficient centers (GODC). The photosensitivity of glass allows fabrication of various refractive-index gratings in germanosilicate optical fibers. These gratings are basic elements used by the telecommunication industry. Nevertheless, the physical mechanisms causing the index change in glass are still unclear. In this thesis we discuss some aspects of the photosensitivity of germanium-doped glass and optical fibers. First, we present a historic overview of the previous work on defects in glass and their role for photosensitivity. The photoionization and densification theories of photosensitivity are reviewed. We then consider the transformations of defects in glass caused by UV radiation. We show that an index change can be produced by exciting either 240-nm or 330-nm absorption bands of GODC. We prove that the excitation of GODC to their triplet state is essential to produce a change in the glass structure. We also show that UV radiation forms a new defect with a luminescence band at 650 nm. We study the nature of the increase in glass photosensitivity caused by saturating glass with molecular hydrogen before exposing it to UV light. Hydrogen-loading the glass increases the saturated value of its index change by at least an order of magnitude and allows the use of high-coherence lasers at 275-305 nm for efficient and high-precision fiber grating fabrication. We also show that the stability of the refractive index change in hydrogen-loaded fibers is correlated with the water content of the glass. The difference between the spectral dependencies of photosensitivity in hydrogen-loaded and hydrogen-free glass suggests that different mechanisms are responsible for the index change in these two cases. We propose possible photoinduced reactions of hydrogen with germanium-doped glass

  17. A DONOR COMPLEX WITH TUNNELING HYDROGEN IN PURE GERMANIUM

    SciTech Connect

    Joos, B.; Haller, E.E.; Falicov, L.M.

    1980-02-01

    A shallow donor complex observed by several authors in ultrapure germanium grown in a hydrogen atmosphere is attributed to an oxygen-hydrogen system. Photoconductivity data under stress are presented. An abrupt transition in the spectra at a well-defined stress (2.1 x 10{sup 8} dyn cm{sup -2}) is found. It is explained by a theory which involves dynamic tunneling of the hydrogen in the vicinity of an oxygen center. The comparison with other complex donors and acceptors supports the model.

  18. Giant negative piezoresistance effect in copper-doped germanium

    SciTech Connect

    Dubon, O.D.; Haller, E.E. |; Walukiewicz, W.; Beeman, J.W.

    1996-09-01

    We have observed a stress-induced decrease of over ten orders of magnitude in the low-temperature electrical resistivity of copper- doped germanium single crystals. The application of large uniaxial stresses in a <001> direction leas to a change in the copper ground- state wavefunction from the highly localized (1s){sup 3} to the much more extended (1s){sup 2}(2s){sup 1} configuration. We attribute the decrease in the resistivity to impurity band conduction by the 2s - holes of the high pressure configuration.

  19. Ultra-low noise mechanically cooled germanium detector

    NASA Astrophysics Data System (ADS)

    Barton, P.; Amman, M.; Martin, R.; Vetter, K.

    2016-03-01

    Low capacitance, large volume, high purity germanium (HPGe) radiation detectors have been successfully employed in low-background physics experiments. However, some physical processes may not be detectable with existing detectors whose energy thresholds are limited by electronic noise. In this paper, methods are presented which can lower the electronic noise of these detectors. Through ultra-low vibration mechanical cooling and wire bonding of a CMOS charge sensitive preamplifier to a sub-pF p-type point contact HPGe detector, we demonstrate electronic noise levels below 40 eV-FWHM.

  20. Infrared absorption study of neutron-transmutation-doped germanium

    NASA Technical Reports Server (NTRS)

    Park, I. S.; Haller, E. E.

    1988-01-01

    Using high-resolution far-infrared Fourier transform absorption spectroscopy and Hall effect measurements, the evolution of the shallow acceptor and donor impurity levels in germanium during and after the neutron transmutation doping process was studied. The results show unambiguously that the gallium acceptor level concentration equals the concentration of transmutated Ge-70 atoms during the whole process indicating that neither recoil during transmutation nor gallium-defect complex formation play significant roles. The arsenic donor levels appear at full concentration only after annealing for 1 h at 450 C. It is shown that this is due to donor-radiation-defect complex formation. Again, recoil does not play a significant role.

  1. Performance of a 60 gram cryogenic germanium detector

    SciTech Connect

    Cummings, A.; Wang, N.; Shutt, T.; Barnes, P.; Lange, A.; Sadoulet, B.; Stubbs, C. . Dept. of Physics); Emes, J.; Ross, R.; Smith, G. ); Giraud-Heraud ); Haller, E.E. . Dept. of Materials Science and Mineral Engineering); Rich, J. )

    1991-04-01

    The authors have developed a 60 g particle detector which utilizes both the ionization and the photons produced by a particle interaction. Six NTD Ge thermistors are attached to a pure germanium crystal which has implanted contacts for drifting charge. The authors have operated our detector at 30 mK, and the authors have studied its response to irradiation by 18 and 60 keV photons from an 241 Am source. This paper presents an analysis of the resolution of our detector, considering the noise of the front end electronics, and signals from extraneous sources such as microphonics.

  2. Germanium wrap-around photodetectors on Silicon photonics.

    PubMed

    Going, Ryan; Seok, Tae Joon; Loo, Jodi; Hsu, Kyle; Wu, Ming C

    2015-05-04

    We present a novel waveguide coupling scheme where a germanium diode grown via rapid melt growth is wrapped around a silicon waveguide. A 4 fF PIN photodiode is demonstrated with 0.95 A/W responsivity at 1550 nm, 6 nA dark current, and nearly 9 GHz bandwidth. Devices with shorter intrinsic region exhibit higher bandwidth (30 GHz) and slightly lower responsivity (0.7 A/W). An NPN phototransistor is also demonstrated using the same design with 14 GHz f(T).

  3. Resonance-enhanced waveguide-coupled silicon-germanium detector

    NASA Astrophysics Data System (ADS)

    Alloatti, L.; Ram, R. J.

    2016-02-01

    A photodiode with 0.55 ± 0.1 A/W responsivity at a wavelength of 1176.9 nm has been fabricated in a 45 nm microelectronics silicon-on-insulator foundry process. The resonant waveguide photodetector exploits carrier generation in silicon-germanium within a microring which is compatible with high-performance electronics. A 3 dB bandwidth of 5 GHz at -4 V bias is obtained with a dark current of less than 20 pA.

  4. Germanium diffusion mechanisms in silicon from first principles

    NASA Astrophysics Data System (ADS)

    Caliste, Damien; Pochet, Pascal; Deutsch, Thierry; Lançon, Frédéric

    2007-03-01

    We present an extensive numerical study of the basic mechanisms that describe germanium diffusion in silicon mediated by point defects. This diffusion can be created by vacancies, interstitial atoms, or fourfold coordinated defects. All energies and elementary barriers have been precisely determined by ab initio calculations. The results for vacancies are compared with recently published values. The complex interstitial landscape is systematized and the key role of the hexagonal location is stressed as a halfway stable state between two, more stable, dumbbell [110] states. Finally, the mechanism of a concerted exchange linking two fourfold coordinated defects is fully calculated. Its activation energy is higher than for interstitial or vacancy mediated movements.

  5. Josephson tunnel junctions with chemically vapor deposited polycrystalline germanium barriers

    SciTech Connect

    Kroger, H.; Jillie, D.W.; Smith, L.N.; Phaneuf, L.E.; Potter, C.N.; Shaw, D.M.; Cukauskas, E.J.; Nisenoff, M.

    1984-03-01

    High quality Josephson tunnel junctions have been fabricated whose tunneling barrier is polycrystalline germanium chemically vapor deposited on a NbN base electrode and covered by a Nb counterelectrode. These junctions have excellent characteristics for device applications: values of V/sub m/ (the product of the critical current and the subgap resistance measured at 2 mV and 4.2 K) ranging between 35--48 mV, ideal threshold curves, a steep current rise at the gap voltage, and Josephson current densities from 100 to 1100 A/cm/sup 2/.

  6. Bulk and surface effects in segmented high purity germanium detectors

    NASA Astrophysics Data System (ADS)

    Abt, I.; Caldwell, A.; Dönmez, B.; Irlbeck, S.; Majorovits, B.; Volynets, O.

    2013-08-01

    Segmented high-purity germanium detectors have been developed for a variety of experiments. The segmentation is used to augment the excellent energy resolution of such a device with spatial information to disentangle event topologies. Several performance aspects of true-coaxial segmented detectors are presented, especially the effects due to the crystallographic axes and the problem of events close to the surfaces of the detector. A test stand and Monte Carlo tools developed to study such effects are introduced. The simulation tools can also be used to design novel detectors, such as segmented point-contact detectors. A particular design is presented and discussed.

  7. Single crystalline kinked semiconductor nanowire superstructures

    PubMed Central

    Tian, Bozhi; Xie, Ping; Kempa, Thomas J.; Bell, David C.; Lieber, Charles M.

    2009-01-01

    The ability to control and modulate the composition1–4, doping1,3–5, crystal structure6–8 and morphology9,10 of semiconductor nanowires during the synthesis process has allowed researchers to explore various applications of nanowires11–15. However, despite advances in nanowire synthesis, progress towards the ab initio design and growth of hierarchical nanostructures has been limited. Here we demonstrate a ‘nanotectonic’ approach that provides iterative control over the nucleation and growth of nanowires and use it to grow kinked or zigzag nanowires in which the straight sections are separated by triangular joints. Moreover, the lengths of the straight sections can be controlled and the growth direction remains coherent along the nanowire. We also grow dopant-modulated structures in which specific device functions, including p-n diodes and field-effect transistors, can be precisely localized at the kinked junctions in the nanowires. PMID:19893521

  8. Methods for synthesizing metal oxide nanowires

    DOEpatents

    Sunkara, Mahendra Kumar; Kumar, Vivekanand; Kim, Jeong H.; Clark, Ezra Lee

    2016-08-09

    A method of synthesizing a metal oxide nanowire includes the steps of: combining an amount of a transition metal or a transition metal oxide with an amount of an alkali metal compound to produce a mixture; activating a plasma discharge reactor to create a plasma discharge; exposing the mixture to the plasma discharge for a first predetermined time period such that transition metal oxide nanowires are formed; contacting the transition metal oxide nanowires with an acid solution such that an alkali metal ion is exchanged for a hydrogen ion on each of the transition metal oxide nanowires; and exposing the transition metal oxide nanowires to the plasma discharge for a second predetermined time period to thermally anneal the transition metal oxide nanowires. Transition metal oxide nanowires produced using the synthesis methods described herein are also provided.

  9. Fabrication and characterization of porous silicon nanowires

    NASA Astrophysics Data System (ADS)

    Jung, Daeyoon; Cho, Soo Gyeong; Moon, Taeho; Sohn, Honglae

    2016-01-01

    We report the synthesis of porous silicon nanowires through the metalassisted chemical etching of porous silicon in a solution of hydrofluoric acid and hydrogen peroxide. The morphology of porous silicon nanowires was characterized by scanning electron microscopy and transmission electron microscopy. The etch rate of the porous silicon nanowires was faster than that of silicon nanowires, but slower than that of porous silicon. The porous silicon nanowires distributed uniformly on the entire porous silicon layer and the tips of the porous silicon nanowires congregated together. The single crystalline and sponge-like porous structure with the pore diameters of less than 5 nm was confirmed for the porous silicon nanowires. [Figure not available: see fulltext.

  10. Patterned Fabrication of Zinc Oxide Nanowire Arrays

    NASA Astrophysics Data System (ADS)

    Khan, Sahar; Lamson, Thomas; Xu, Huizhong

    Zinc oxide nanowires possess desirable mechanical, thermodynamic, electrical, and optical properties. Although the hydrothermal growth process can be applied in tolerable growth conditions, the dimension and density of nanowires has a complex dependence on substrate pre-treatment, precursor concentrations, and growth conditions. Precise control of the geometry and density of nanowires as well as the location of nanowires would allow for the fabrication of useful nanowaveguide devices. In this work, we used electron beam lithography to pattern hole arrays in a polymer layer on gold-coated glass substrates and synthesized zinc oxide nanowires inside these holes. Arrays of nanowires with diameters ranging from 50 nm to 140 nm and various spacings were obtained. The transmission of light through these zinc oxide nanowire arrays in a silver film was also studied. This research was supported by the Seed Grant Program of St. John's University and the National Science Foundation under Grant No. CBET-0953645.

  11. The ultimate strength of glass silica nanowires.

    PubMed

    Brambilla, Gilberto; Payne, David N

    2009-02-01

    In the past decade nanowires have attracted an increase interest because of their extraordinary mechanical strength. In fact, material properties in the nanoregime are extremely different from those found in macroscopic samples: few crystalline materials have shown a tensile strength in excess of 10 GPa in the form of nanowires. Still the length of defect-free crystalline nanowires is limited to a few millimeters and the strength of long nanowires is compromised by defects. The strength of glass nanowires is less affected by single defects. In this paper we present the ultimate strength of glass silica nanowires manufactured by a top-down fabrication technique; this is the highest value reported for glass materials. The measured ultimate strength is in excess of 10 GPa and increases for decreasing nanowire diameters. Scanning electron micrographs of the broken fragments showed a fragile rupture.

  12. Electrically Injected UV-Visible Nanowire Lasers

    SciTech Connect

    Wang, George T.; Li, Changyi; Li, Qiming; Liu, Sheng; Wright, Jeremy Benjamin; Brener, Igal; Luk, Ting -Shan; Chow, Weng W.; Leung, Benjamin; Figiel, Jeffrey J.; Koleske, Daniel D.; Lu, Tzu-Ming

    2015-09-01

    There is strong interest in minimizing the volume of lasers to enable ultracompact, low-power, coherent light sources. Nanowires represent an ideal candidate for such nanolasers as stand-alone optical cavities and gain media, and optically pumped nanowire lasing has been demonstrated in several semiconductor systems. Electrically injected nanowire lasers are needed to realize actual working devices but have been elusive due to limitations of current methods to address the requirement for nanowire device heterostructures with high material quality, controlled doping and geometry, low optical loss, and efficient carrier injection. In this project we proposed to demonstrate electrically injected single nanowire lasers emitting in the important UV to visible wavelengths. Our approach to simultaneously address these challenges is based on high quality III-nitride nanowire device heterostructures with precisely controlled geometries and strong gain and mode confinement to minimize lasing thresholds, enabled by a unique top-down nanowire fabrication technique.

  13. Synthesis of nickel nanowires via electroless nanowire deposition on micropatterned substrates.

    PubMed

    Shi, Zhiwei; Walker, Amy V

    2011-09-20

    Electroless nanowire deposition on micropatterned substrates (ENDOM) is a promising new technique by which to direct the synthesis and precise placement of metallic nanowires. ENDOM is generally applicable to the preparation of metallic, semiconducting, and even insulating nanowires on technologically relevant substrates, is inexpensive, and can achieve high growth rates. The deposited nanowires are ultralong (centimeters) and can be patterned in arbitrary shapes. We demonstrate ENDOM using the growth of nickel nanowires. By controlling the deposition time, the width of the nanowires can be varied from 200 to 1000 nm and the height can be varied from 7 to 20 nm.

  14. Effect of ion-plated films of germanium and silicon on friction, wear, and oxidation of 52100 bearing steel

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.; Spalvins, T.

    1977-01-01

    Friction and wear experiments were conducted with ion plated films of germanium and silicon on the surface of 52100 bearing steel both dry and in the presence of mineral oil. Both silicon and germanium were found to reduce wear, with germanium being more effective than silicon. An optimum film thickness of germanium for minimum wear without surface crack formation was found to be approximately 400 nanometers (4000 A). The presence of silicon and germanium on the 52100 bearing steel surface improved resistance to oxidation.

  15. Synthesis and characterization of cadmium telluride nanowire.

    PubMed

    Kum, Maxwell C; Yoo, Bong Young; Rheem, Young Woo; Bozhilov, Krassimir N; Chen, Wilfred; Mulchandani, Ashok; Myung, Nosang V

    2008-08-13

    CdTe nanowires with controlled composition were cathodically electrodeposited using track-etched polycarbonate membrane as scaffolds and their material and electrical properties were systematically investigated. As-deposited CdTe nanowires show nanocrystalline cubic phase structures with grain sizes of up to 60 nm. The dark-field images of nanowires reveal that the crystallinity of nanowires was greatly improved from nanocrystalline to a few single crystals within nanowires upon annealing at 200 °C for 6 h in a reducing environment (5% H(2)+95% N(2)). For electrical characterization, a single CdTe nanowire was assembled across microfabricated gold electrodes using the drop-casting method. In addition to an increase in grain size, the electrical resistivity of an annealed single nanowire (a few 10(5) Ω cm) was one order of magnitude greater than in an as-deposited nanowire, indicating that crystallinity of nanowires improved and defects within nanowires were reduced during annealing. By controlling the dopants levels (e.g. Te content of nanowires), the resistivity of nanowires was varied from 10(4) to 10(0) Ω cm. Current-voltage (I-V) characteristics of nanowires indicated the presence of Schottky barriers at both ends of the Au/CdTe interface. Temperature-dependent I-V measurements show that the electron transport mode was determined by a thermally activated component at T>-50 °C and a temperature-independent component below -50 °C. Under optical illumination, the single CdTe nanowire exhibited enhanced conductance.

  16. Electrochemical synthesis of multisegmented nanowires

    SciTech Connect

    Kok, Kuan-Ying; Ng, Inn-Khuan; Saidin, Nur Ubaidah

    2012-11-27

    Electrochemical deposition has emerged as a promising route for nanostructure fabrication in recent years due to the many inherent advantages it possesses. This study focuses on the synthesis of high-aspect-ratio multisegmented Au/Ni nanowires using template-directed sequential electrochemical deposition techniques. By selectively removing the Ni segments in the nanowires, high-yield of pure gold nanorods of predetermined lengths was obtained. Alternatively, the sacrificial Ni segments in the nanowires can be galvanically displaced with Bi and Te to form barbells structures with Bi{sub x}Te{sub y} nanotubes attached to neighbouring gold segments. Detailed studies on the nanostructures obtained were carried out using various microscopy, diffraction and probebased techniques for structural, morphological and chemical characterizations.

  17. Controlled fabrication of nanowire sensors.

    SciTech Connect

    Leonard, Francois

    2007-10-01

    We present a simple top down approach based on nanoimprint lithography to create dense arrays of silicon nanowires over large areas. Metallic contacts to the nanowires and a bottom gate allow the operation of the array as a field-effect transistor with very large on/off ratios. When exposed to ammonia gas or cyclohexane solutions containing nitrobenzene or phenol, the threshold voltage of the field-effect transistor is shifted, a signature of charge transfer between the analytes and the nanowires. The threshold voltage shift is proportional to the Hammett parameter and the concentration of the nitrobenzene and phenol analytes. For the liquid analytes considered, we find binding energies of 400 meV, indicating strong physisorption. Such values of the binding energies are ideal for stable and reusable sensors.

  18. Optical absorption of silicon nanowires

    SciTech Connect

    Xu, T.; Lambert, Y.; Krzeminski, C.; Grandidier, B.; Stievenard, D.; Leveque, G.; Akjouj, A.; Pennec, Y.; Djafari-Rouhani, B.

    2012-08-01

    We report on simulations and measurements of the optical absorption of silicon nanowires (NWs) versus their diameter. We first address the simulation of the optical absorption based on two different theoretical methods: the first one, based on the Green function formalism, is useful to calculate the scattering and absorption properties of a single or a finite set of NWs. The second one, based on the finite difference time domain (FDTD) method, is well-adapted to deal with a periodic set of NWs. In both cases, an increase of the onset energy for the absorption is found with increasing diameter. Such effect is experimentally illustrated, when photoconductivity measurements are performed on single tapered Si nanowires connected between a set of several electrodes. An increase of the nanowire diameter reveals a spectral shift of the photocurrent intensity peak towards lower photon energies that allow to tune the absorption onset from the ultraviolet radiations to the visible light spectrum.

  19. Tunneling magnetoresistance in Si nanowires

    NASA Astrophysics Data System (ADS)

    Montes, E.; Rungger, I.; Sanvito, S.; Schwingenschlögl, U.

    2016-11-01

    We investigate the tunneling magnetoresistance of small diameter semiconducting Si nanowires attached to ferromagnetic Fe electrodes, using first principles density functional theory combined with the non-equilibrium Green’s functions method for quantum transport. Silicon nanowires represent an interesting platform for spin devices. They are compatible with mature silicon technology and their intrinsic electronic properties can be controlled by modifying the diameter and length. Here we systematically study the spin transport properties for neutral nanowires and both n and p doping conditions. We find a substantial low bias magnetoresistance for the neutral case, which halves for an applied voltage of about 0.35 V and persists up to 1 V. Doping in general decreases the magnetoresistance, as soon as the conductance is no longer dominated by tunneling.

  20. III-Nitride nanowire optoelectronics

    NASA Astrophysics Data System (ADS)

    Zhao, Songrui; Nguyen, Hieu P. T.; Kibria, Md. G.; Mi, Zetian

    2015-11-01

    Group-III nitride nanowire structures, including GaN, InN, AlN and their alloys, have been intensively studied in the past decade. Unique to this material system is that its energy bandgap can be tuned from the deep ultraviolet (~6.2 eV for AlN) to the near infrared (~0.65 eV for InN). In this article, we provide an overview on the recent progress made in III-nitride nanowire optoelectronic devices, including light emitting diodes, lasers, photodetectors, single photon sources, intraband devices, solar cells, and artificial photosynthesis. The present challenges and future prospects of III-nitride nanowire optoelectronic devices are also discussed.

  1. Reversible nanopore formation in Ge nanowires during lithiation-delithiation cycling: an in situ transmission electron microscopy study.

    PubMed

    Liu, Xiao Hua; Huang, Shan; Picraux, S Tom; Li, Ju; Zhu, Ting; Huang, Jian Yu

    2011-09-14

    Retaining the high energy density of rechargeable lithium ion batteries depends critically on the cycle stability of microstructures in electrode materials. We report the reversible formation of nanoporosity in individual germanium nanowires during lithiation-delithiation cycling by in situ transmission electron microscopy. Upon lithium insertion, the initial crystalline Ge underwent a two-step phase transformation process: forming the intermediate amorphous Li(x)Ge and final crystalline Li(15)Ge(4) phases. Nanopores developed only during delithiation, involving the aggregation of vacancies produced by lithium extraction, similar to the formation of porous metals in dealloying. A delithiation front was observed to separate a dense nanowire segment of crystalline Li(15)Ge(4) with a porous spongelike segment composed of interconnected ligaments of amorphous Ge. This front sweeps along the wire with a logarithmic time law. Intriguingly, the porous nanowires exhibited fast lithiation/delithiation rates and excellent mechanical robustness, attributed to the high rate of lithium diffusion and the porous network structure for facile stress relaxation, respectively. These results suggest that Ge, which can develop a reversible nanoporous network structure, is a promising anode material for lithium ion batteries with superior energy capacity, rate performance, and cycle stability.

  2. Silicon nanowires as intracellular devices

    NASA Astrophysics Data System (ADS)

    Zimmerman, John F.

    Semiconductor nanowire devices are an exciting class of materials for biomedical and electrophysiology applications, with current studies primarily delivering substrate bound devices through mechanical abrasion or electroporation. However, the ability to distribute these devices in a drug-like fashion is an important step in developing next-generation active therapeutic devices. In this work, we will discuss the interaction of label free Silicon nanowires (SiNWs) with cellular systems, showing that they can be internalized in multiple cell lines, and undergo an active 'burst-like' transport process. (Abstract shortened by ProQuest.).

  3. Single crystalline mesoporous silicon nanowires

    SciTech Connect

    Hochbaum, Allon; Dargas, Daniel; Hwang, Yun Jeong; Yang, Peidong

    2009-08-18

    Herein we demonstrate a novel electroless etching synthesis of monolithic, single-crystalline, mesoporous silicon nanowire arrays with a high surface area and luminescent properties consistent with conventional porous silicon materials. The photoluminescence of these nanowires suggest they are composed of crystalline silicon with small enough dimensions such that these arrays may be useful as photocatalytic substrates or active components of nanoscale optoelectronic devices. A better understanding of this electroless route to mesoporous silicon could lead to facile and general syntheses of different narrow bandgap semiconductor nanostructures for various applications.

  4. The effect of nanowire length and diameter on the properties of transparent, conducting nanowire films.

    PubMed

    Bergin, Stephen M; Chen, Yu-Hui; Rathmell, Aaron R; Charbonneau, Patrick; Li, Zhi-Yuan; Wiley, Benjamin J

    2012-03-21

    This article describes how the dimensions of nanowires affect the transmittance and sheet resistance of a random nanowire network. Silver nanowires with independently controlled lengths and diameters were synthesized with a gram-scale polyol synthesis by controlling the reaction temperature and time. Characterization of films composed of nanowires of different lengths but the same diameter enabled the quantification of the effect of length on the conductance and transmittance of silver nanowire films. Finite-difference time-domain calculations were used to determine the effect of nanowire diameter, overlap, and hole size on the transmittance of a nanowire network. For individual nanowires with diameters greater than 50 nm, increasing diameter increases the electrical conductance to optical extinction ratio, but the opposite is true for nanowires with diameters less than this size. Calculations and experimental data show that for a random network of nanowires, decreasing nanowire diameter increases the number density of nanowires at a given transmittance, leading to improved connectivity and conductivity at high transmittance (>90%). This information will facilitate the design of transparent, conducting nanowire films for flexible displays, organic light emitting diodes and thin-film solar cells.

  5. Superconductivity and unexpected chemistry of germanium hydrides under pressure

    NASA Astrophysics Data System (ADS)

    Davari Esfahani, M. Mahdi; Oganov, Artem R.; Niu, Haiyang; Zhang, Jin

    2017-04-01

    Following the idea that hydrogen-rich compounds might be high-Tc superconductors at high pressures, and the very recent breakthrough in predicting and synthesizing hydrogen sulfide with record-high Tc=203 K , an ab initio evolutionary algorithm for crystal structure prediction was employed to find stable germanium hydrides. In addition to the earlier structure of germane with space group Ama2, we propose a C2/m structure, which is energetically more favorable at pressures above 278 GPa (with inclusion of zero-point energy). Our calculations indicate that the C2/m phase of germane is a superconductor with Tc=67 K at 280 GPa. Germane is found to become thermodynamically unstable to decomposition to hydrogen and the compound Ge3H11 at pressures above 300 GPa. Ge3H11 with space group I 4 ¯m 2 is found to become stable at above 285 GPa with Tc=43 K . We find that the pressure-induced phase stability of germanium hydrides is distinct from analogous isoelectronic systems, e.g., Si hydrides and Sn hydrides. Superconductivity stems from large electron-phonon coupling associated with the wagging, bending, and stretching intermediate-frequency modes derived mainly from hydrogen.

  6. Materials and Fabrication Issues for Large Machined Germanium Immersion Gratings

    SciTech Connect

    Kuzmenko, P J; Davis, P J; Little, S L; Hale, L C

    2006-05-22

    LLNL has successfully fabricated small (1.5 cm{sup 2} area) germanium immersion gratings. We studied the feasibility of producing a large germanium immersion grating by means of single point diamond flycutting. Our baseline design is a 63.4o blaze echelle with a 6 cm beam diameter. Birefringence and refractive index inhomogeneity due to stresses produced by the crystal growth process are of concern. Careful selection of the grating blank and possibly additional annealing to relieve stress will be required. The Large Optics Diamond Turning Machine (LODTM) at LLNL is a good choice for the fabrication. It can handle parts up to 1.5 meter in diameter and 0.5 meter in length and is capable of a surface figure accuracy of better than 28 nm rms. We will describe the machine modifications and the machining process for a large grating. A next generation machine, the Precision Optical Grinder and Lathe (POGAL), currently under development has tighter specifications and could produce large gratings with higher precision.

  7. Characterisation of the SmartPET planar Germanium detectors

    NASA Astrophysics Data System (ADS)

    Boston, H. C.; Boston, A. J.; Cooper, R. J.; Cresswell, J.; Grint, A. N.; Mather, A. R.; Nolan, P. J.; Scraggs, D. P.; Turk, G.; Hall, C. J.; Lazarus, I.; Berry, A.; Beveridge, T.; Gillam, J.; Lewis, R.

    2007-08-01

    Small Animal Reconstruction PET (SmartPET) is a project funded by the UK medical research council (MRC) to demonstrate proof of principle that Germanium can be utilised in Positron Emission Tomography (PET). The SmartPET demonstrator consists of two orthogonal strip High Purity Germanium (HPGe) planar detectors manufactured by ORTEC. The aim of the project is to produce images of an internal source with sub mm 3 spatial resolution. Before this image can be achieved the detectors have to be fully characterised to understand the response at any given location to a γ-ray interaction. This has been achieved by probing the two detectors at a number of specified points with collimated sources of various energies and strengths. A 1 mm diameter collimated beam of photons was raster scanned in 1 mm steps across the detector. Digital pulse shape data were recorded from all the detector channels and the performance of the detector for energy and position determination has been assessed. Data will be presented for the first SmartPET detector.

  8. Evaluating a new segmented germanium detector contact technology

    NASA Astrophysics Data System (ADS)

    Jackson, E. G.; Lister, C. J.; Chowdhury, P.; Hull, E.; Pehl, R.

    2012-10-01

    New technologies for making gamma ray detectors position sensitive have many applications in space science, medical imaging, homeland security, and in nuclear structure research. One promising approach uses high-purity germanium wafers with the planar surfaces segmented into orthogonal strip patterns forming a Double-Sided Strip Detector (DSSD). The combination of data from adjoining strips, or pixels, is physics-rich for Compton image formation and polarization studies. However, sensitivity to charge loss and various kinds of cross-talk [1] have limited the usefulness of first generation devices. We are investigating new contact technologies, developed by PhDs Co [2], based on amorphous-germanium and yttrium contacts RF sputter deposited to a thickness of ˜ 1000 å. New techniques allow both physical and photolithographic segmentation of the contacts with inter-strip gap widths of 0.25 mm. These modifications should improve all aspects of charge collection. The new detector technology employs the same material and fabrication technique for both the n- and p- contacts, thus removing artificial asymmetry in the data. Results from tests of cross-talk, charge collection, and scattering asymmetry will be presented and compared with older technologies. This mechanically cooled counter, NP-7, seems to represent a breakthrough.[4pt] [1] S. Gros et al., Nucl. Inst. Meth. A 602, 467 (2009).[0pt] [2] E. Hull et al Nucl Inst Meth A 626, 39 (2011)

  9. Initial Component Testing for a Germanium Array Cryostat

    SciTech Connect

    Keillor, Martin E.; Aalseth, Craig E.; Day, Anthony R.; Fast, James E.; Hoppe, Eric W.; Hyronimus, Brian J.; Hossbach, Todd W.; Seifert, Allen

    2009-06-01

    This report describes progress on the construction of two ultra-low-background cryostats that are part of the NA-22 funded “Radionuclide Laboratories” (RN Labs) project. Each cryostat will house seven high-purity germanium crystals (HPGe). These cryostats are being built from a limited set of materials that are known to have very low levels of radioactive impurities. The RN Labs instrument is designed to take advantage of low background performance, high detection efficiency, and γ-γ coincidence signatures to provide unprecedented gamma spectroscopy sensitivity. The project is focused on improving gamma analysis capabilities for nuclear detonation detection (NDD) applications. The instrument also has the potential for basic nuclear physics research. Section 1 provides the background for the project. Section 2 discusses germanium crystal acceptance testing. Design problems were found after the first delivery of new detectors from the vendor, Canberra Semiconductors. The first four crystals were returned for repair, resulting in a delay in crystal procurement. Section 3 provides an update on copper electroforming. In general, electroforming parts for RN Labs has proceeded smoothly, but there have been recent problems in electroforming three large copper parts necessary for the project. Section 4 describes the first round of testing for the instrument: anti-cosmic scintillator testing, electronics testing, and initial vacuum testing. Section 5 concludes with an overall description of the state of the project and challenges that remain.

  10. Germanium electroabsorption devices on silicon for optical interconnects

    NASA Astrophysics Data System (ADS)

    Kuo, Yu-Hsuan; Miller, David A. B.; Harris, James S.

    2006-02-01

    Monolithic integration of both electronic and optic components into a silicon-based platform will provide high-speed optical interconnects and solve the power-bandwidth limitations. However, the lack of strong optical effects in silicon has limited the progress in the transmitter-end applications. Recently our research had demonstrated strong quantum-confined Stark effect (QCSE) in germanium quantum-well modulators on silicon. This first strong physical mechanism for group-IV photonics has a comparable behavior to III-V material systems. With proper quantum well structure design, we also demonstrated QCSE in C-band for long distance communications with CMOS-operational temperatures. The device fabrication is also compatible with standard silicon chip processes. Since the QCSE, a type of electroabsorption effect, requires much shorter optical length, it is suitable for device miniaturizations and possible for use in both lateral and vertical modulator configurations. Moreover, silicon-germanium electroabsorption modulators are inherently photodetectors, this advantage will enable efficient transmitter/receiver applications for optical interconnects.

  11. Reduction of phosphorus diffusion in germanium by fluorine implantation

    SciTech Connect

    El Mubarek, H. A. W.

    2013-12-14

    The control of phosphorus (P) diffusion in germanium (Ge) is essential for the realisation of ultrashallow n-type junctions in Ge. This work reports a detailed study of the effect of fluorine (F) co-implantation on P diffusion in Ge. P and F profiles were characterized by secondary ion mass spectroscopy. The ion implantation damage was investigated using cross sectional transmission electron microscopy. It is shown that F co-implantation reduces the implanted P profile width and reduces both intrinsic and extrinsic P diffusion in Ge. A defect mediated mechanism for the strong influence of F co-implantation on P diffusion in Ge is proposed and invokes the formation of F{sub n}V{sub m} clusters in the F-amorphized Ge layer. A fraction of these F{sub n}V{sub m} clusters decorate the interstitial type end-of-range defects in the re-grown Ge layer and the rest react during re-growth with interstitial germanium atoms diffusing back from the amorphous crystalline interface. The Ge vacancies are then annihilated and mobile interstitial F is released and out diffuses from the surface. This results in a re-grown Ge layer which has a low vacancy concentration and in which the P diffusion rate is reduced. These results open the way to the realization of enhanced Ge n-type devices.

  12. Intrinsic germanium detector used in borehole sonde for uranium exploration

    USGS Publications Warehouse

    Senftle, F.E.; Moxham, R.M.; Tanner, A.B.; Boynton, G.R.; Philbin, P.W.; Baicker, J.A.

    1976-01-01

    A borehole sonde (~1.7 m long; 7.3 cm diameter) using a 200 mm2 planar intrinsic germanium detector, mounted in a cryostat cooled by removable canisters of frozen propane, has been constructed and tested. The sonde is especially useful in measuring X- and low-energy gamma-ray spectra (40–400 keV). Laboratory tests in an artificial borehole facility indicate its potential for in-situ uranium analyses in boreholes irrespective of the state of equilibrium in the uranium series. Both natural gamma-ray and neutron-activation gamma-ray spectra have been measured with the sonde. Although the neutron-activation technique yields greater sensitivity, improvements being made in the resolution and efficiency of intrinsic germanium detectors suggest that it will soon be possible to use a similar sonde in the passive mode for measurement of uranium in a borehole down to about 0.1% with acceptable accuracy. Using a similar detector and neutron activation, the sonde can be used to measure uranium down to 0.01%.

  13. Crystal Growth of Germanium-Silicon Alloys on the ISS

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Mazuruk, K.; Croell, A.

    2015-01-01

    A series of Ge(1-x)Si(x) crystal growth experiments are planned to be conducted in the Low Gradient Furnace (LGF) onboard the International Space Station. The experiments are part of the investigation "Influence of Containment on the Growth of Silicon-Germanium" (ICESAGE). The primary objective of the research is to determine the influence of containment on the processing-induced defects and impurity incorporation in germanium-silicon alloy crystals. A comparison will be made between crystals grown by the normal and "detached" Bridgman methods and the ground-based float zone technique. Crystals grown without being in contact with a container have superior quality to otherwise similar crystals grown in direct contact with a container, especially with respect to impurity incorporation, formation of dislocations, and residual stress in crystals. "Detached" or "dewetted" Bridgman growth is similar to regular Bridgman growth in that most of the melt is in contact with the crucible wall, but the crystal is separated from the wall by a small gap, typically of the order of 10-100 microns. Long duration reduced gravity is essential to test the proposed theory of detached growth. Detached growth requires the establishment of a meniscus between the crystal and the ampoule wall. This meniscus can exist over a much larger range of processing parameters in microgravity and the meniscus is more stable under microgravity conditions. The plans for the flight experiments will be described.

  14. Crystallization of Electrodeposited Germanium Thin Film on Silicon (100)

    PubMed Central

    Abidin, Mastura Shafinaz Zainal; Matsumura, Ryo; Anisuzzaman, Mohammad; Park, Jong-Hyeok; Muta, Shunpei; Mahmood, Mohamad Rusop; Sadoh, Taizoh; Hashim, Abdul Manaf

    2013-01-01

    We report the crystallization of electrodeposited germanium (Ge) thin films on n-silicon (Si) (100) by rapid melting process. The electrodeposition was carried out in germanium (IV) chloride: propylene glycol (GeCl4:C3H8O2) electrolyte with constant current of 50 mA for 30 min. The measured Raman spectra and electron backscattering diffraction (EBSD) images show that the as-deposited Ge thin film was amorphous. The crystallization of deposited Ge was achieved by rapid thermal annealing (RTA) at 980 °C for 1 s. The EBSD images confirm that the orientations of the annealed Ge are similar to that of the Si substrate. The highly intense peak of Raman spectra at 300 cm−1 corresponding to Ge-Ge vibration mode was observed, indicating good crystal quality of Ge. An additional sub peak near to 390 cm−1 corresponding to the Si-Ge vibration mode was also observed, indicating the Ge-Si mixing at Ge/Si interface. Auger electron spectroscopy (AES) reveals that the intermixing depth was around 60 nm. The calculated Si fraction from Raman spectra was found to be in good agreement with the value estimated from Ge-Si equilibrium phase diagram. The proposed technique is expected to be an effective way to crystallize Ge films for various device applications as well as to create strain at the Ge-Si interface for enhancement of mobility. PMID:28788375

  15. Germanium nano-cluster films as humidity and hydrogen sensors

    NASA Astrophysics Data System (ADS)

    Mackenzie, D. M. A.; Brown, S. A.

    2012-10-01

    Films of germanium nano-clusters of 30 nm diameter were fabricated in a high-vacuum deposition apparatus utilizing an inert-gas-aggregation source. The germanium films readily formed an oxide layer in high vacuum along with a corresponding resistance increase, a process that accelerated when films were exposed to dry air. A decrease in resistance was observed when films were exposed to ambient air, and this was attributed to water vapour adsorbing on the surface. The effects of film-thickness were investigated. A reversible change in resistance of 2 orders of magnitude was observed for 99% humidity, with a response time of tens of minutes. It is proposed that the resistance-decrease occurs because water vapour creates surface defects which act as donors causing the electron concentration in the n-type film to increase. The films were also sensitive to hydrogen concentrations above 1% in dry air, with up to a factor of 25 decrease in resistance observed for 5% hydrogen concentration at room temperature. Unexpectedly, the sensitivity to hydrogen was only observed at temperatures below 100 °C, suggesting that surface moisture is necessary for films to show sensitivity to hydrogen.

  16. Metal silicide nanowires

    NASA Astrophysics Data System (ADS)

    Chen, Lih-Juann; Wu, Wen-Wei

    2015-07-01

    The growth, properties and applications of metal silicide nanowires (NWs) have been extensively investigated. The investigations have led to significant advance in the understanding of one-dimensional (1D) metal silicide systems. For example, CoSi is paramagnetic in bulk form, but ferromagnetic in NW geometry. In addition, the helimagnetic phase and skyrmion state in MnSi are stabilized by NW morphology. The influencing factors on the growth of silicide phase have been elucidated for Ni-Si, Pt-Si, and Mn-Si systems. Promising results were obtained for spintronics, non-volatile memories, field emitter, magnetoresistive sensor, thermoelectric generator and solar cells. However, the main thrust has been in microelectronic devices and integrated circuits. Transistors of world-record small size have been fabricated. Reconfigurable Si NW transistors, dually active Si NW transistors and circuits with equal electron and hole transport have been demonstrated. Furthermore, multifunctional devices and logic gates with undoped Si NWs were reported. It is foreseen that practical applications will be realized in the near future.

  17. Multimode silicon nanowire transistors.

    PubMed

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

    2014-11-12

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

  18. Multimode Silicon Nanowire Transistors

    PubMed Central

    2014-01-01

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

  19. Germanium Isotopic Fractionation in Iron Meteorites : Comparison with Experimental Data

    NASA Astrophysics Data System (ADS)

    Luais, B.; Toplis, M.; Tissandier, L.; Roskosz, M.

    2009-05-01

    Magmatic and non-magmatic iron meteorites are thought to be formed respectively by processes of metal- silicate segregation, and complex impacts on undifferentiated parent bodies. These processes are inferred from variations of siderophile element concentrations, such as Ge, Ni, Ir. Germanium is moderately siderophile, with metal-silicate partition coefficients which depend on oxygen fugacity. Germanium is also moderately volatile, and fractionation would be expected during high temperature processes. In order to investigate the extent of elemental and isotopic fractionation of germanium during metal-silicate equilibria and impact processes, we use a double approach including (1) Ge isotopic measurements of iron meteorites from non-magmatic and magmatic groups [1], and (2) experimental investigations of the isotopic fractionation associated with germanium transfer from an oxidized silicate liquid to a metallic phase under various fO2 conditions. Experiments were performed in a 1 atm vertical drop quench furnace, with starting materials corresponding to a glass of 1 bar An-Di euctectic composition doped with ˜ 4,000 ppm reference Ge standard, and pure Ni capsules as the metal phase. The assembly was heated at 1355°C for t =2 to 60 hrs over a range of fO2 from 4 log units below, to 2.5 log units above, the IW buffer. Metal and silicate phases were then mechanically separated. For isotopic measurements, the metal phase of these experiments and the selected iron meteorites were dissolved in high-purity dilute nitric acid. Chemical purification of Ge, and isotopic measurements using the Isoprobe MC-ICPMS follow Luais (2007). Germanium isotopic measurements of Fe-meteorites show that δ74Ge of magmatic irons are constant (δ74Ge=+1.77±0.22‰, 2σ), but heavier than non-magmatic irons (IAB : +1.15±0.2‰; IIE : -0.27 to +1.40±0.2‰). Time series experiments at the IW buffer show that there is a clear continuous increase in δ 74Ge in the metal as a function of time

  20. Hydrometallurgical recovery of germanium from coal gasification fly ash. Solvent extraction method

    SciTech Connect

    Arroyo, F.; Fernandez-Pereira, C.

    2008-05-15

    This article is concerned with a simple hydrometallurgical method for the selective recovery of germanium from fly ash (FA) generated in an integrated gasification with combined cycle (IGCC) process. The method is based on the leaching of FA with water and a subsequent concentration and selective separation of germanium by a solvent method. Regarding the leaching step, the different operational conditions studied were liquid/solid (L/S) ratio and time of contact. The solvent extraction method was based on germanium complexation with catechol (CAT) in an aqueous solution followed by the extraction of the Ge-CAT complex with an extracting organic reagent diluted in an organic solvent. The main factors examined during the extraction tests were aqueous phase/organic phase (AP/OP) volumetric ratio, aqueous phase pH, amounts of reagents, and time of contact. Germanium extraction yields were higher than 90%. Alkaline and acid stripping of organic extracts were studied obtaining the best results with 1M NaOH (85%). A high-purity germanium solution was obtained. Experimental data presented in this work show that the extraction of germanium by the solvent method designed can be selective toward germanium, and this element can be effectively separated from arsenic, molybdenum, nickel, antimony, vanadium, and zinc.

  1. Germanium-on-silicon nitride waveguides for mid-infrared integrated photonics

    NASA Astrophysics Data System (ADS)

    Li, Wei; Anantha, P.; Bao, Shuyu; Lee, Kwang Hong; Guo, Xin; Hu, Ting; Zhang, Lin; Wang, Hong; Soref, Richard; Tan, Chuan Seng

    2016-12-01

    A germanium-based platform with a large core-clad index contrast, germanium-on-silicon nitride waveguide, is demonstrated at mid-infrared wavelength. Simulations are performed to verify the feasibility of this structure. This structure is realized by first bonding a silicon-nitride-deposited germanium-on-silicon donor wafer onto a silicon substrate wafer, followed by the layer transfer approach to obtain germanium-on-silicon nitride structure, which is scalable to all wafer sizes. The misfit dislocations which initially form along the interface between germanium/silicon can be removed by chemical mechanical polishing after layer transfer process resulting in a high-quality germanium layer. At the mid-infrared wavelength of 3.8 μm, the germanium-on-silicon nitride waveguide has a propagation loss of 3.35 ± 0.5 dB/cm and a bend loss of 0.14 ± 0.01 dB/bend for a radius of 5 μm for the transverse-electric mode.

  2. Advances in fractal germanium micro/nanoclusters induced by gold: microstructures and properties.

    PubMed

    Chen, Zhiwen; Shek, Chan-Hung; Wu, C M Lawrence; Lai, Joseph K L

    2014-02-01

    Germanium materials are a class of unique semiconductor materials with widespread technological applications because of their valuable semiconducting, electrical, optical, and thermoelectric power properties in the fields of macro/mesoscopic materials and micro/nanodevices. In this review, we describe the efforts toward understanding the microstructures and various properties of the fractal germanium micro/nanoclusters induced by gold prepared by high vacuum thermal evaporation techniques, highlighting contributions from our laboratory. First, we present the integer and non-integer dimensional germanium micro/nanoclusters such as nanoparticles, nanorings, and nanofractals induced by gold and annealing. In particular, the nonlinear electrical behavior of a gold/germanium bilayer film with the interesting nanofractal is discussed in detail. In addition, the third-order optical nonlinearities of the fractal germanium nanocrystals embedded in gold matrix will be summarized by using the sensitive and reliable Z-scan techniques aimed to determine the nonlinear absorption coefficient and nonlinear refractive index. Finally, we emphasize the thermoelectric power properties of the gold/germanium bilayer films. The thermoelectric power measurement is considered to be a more effective method than the conductivity for investigating superlocalization in a percolating system. This research may provide a novel insight to modulate their competent performance and promote rational design of micro/nanodevices. Once mastered, germanium thin films with a variety of fascinating micro/nanoclusters will offer vast and unforeseen opportunities in the semiconductor industry as well as in other fields of science and technology.

  3. Inelasticity and precipitation of germanium from a solid solution in Al-Ge binary alloys

    NASA Astrophysics Data System (ADS)

    Kardashev, B. K.; Korchunov, B. N.; Nikanorov, S. P.; Osipov, V. N.

    2015-08-01

    The influence of precipitation of germanium atoms in a solid solution on the dependence of the inelasticity characteristics on the germanium content in aluminum-germanium alloys prepared by directional crystallization has been studied. It has been shown that the Young's modulus defect, the amplitude-dependent decrement, and the microplastic flow stress at a specified cyclic strain amplitude have extreme values at the eutectic germanium content in the alloy. The eutectic composition of the alloy undergoes a ductilebrittle transition. It has been found that there is a correlation between the dependences of the Young's modulus defect, amplitude-dependent decrement, microplastic flow stress, and specific entropy of the exothermal process of germanium precipitation on the germanium content in the hypoeutectic alloy. The concentration dependences of the inelasticity characteristics and their changes after annealing have been explained by the change in the resistance to the motion of intragrain dislocations due to different structures of the Guinier-Preston zones formed during the precipitation of germanium atoms.

  4. Crystal-originated particles in germanium-doped Czochralski silicon crystal

    NASA Astrophysics Data System (ADS)

    Chen, Jiahe; Yang, Deren; Li, Hong; Ma, Xiangyang; Tian, Daxi; Li, Liben; Que, Duainlin

    2007-08-01

    Grown-in distribution and annealing behavior of crystal-originated particles (COPs) in Czochralski silicon (Cz-Si) wafer with germanium doping have been investigated. It was found that COPs with high density but small sizes were inclined to generate in germanium-doped Cz-Si (GCz-Si) wafer. The increase of boron atoms in Cz-Si crystal with the germanium doping could benefit the formation of COPs while the oxygen interstitials in GCz-Si wafer could enhance the generation of COPs with small sizes. Meanwhile, it was suggested that the germanium doping in Cz-Si would result in the poor thermal stability of COPs. It is proposed that the combination between germanium atom and vacancy could reduce the free vacancy concentration and the onset temperature for void generation, thus forming denser but smaller void. While the stress compensation induced by boron and germanium atoms could increase the vacancy fluxes in heavy-boron doped GCz-Si crystal, the presence of oxygen atom in GCz-Si would incline to benefit the formation of inner oxide walls of void, especially with small sizes. Furthermore, thinner oxide walls within void for GCz-Si crystal are considered to be charged for the easy annihilation by the germanium doping.

  5. Germanium ion implantation to Improve Crystallinity during Solid Phase Epitaxy and the effect of AMU Contamination

    SciTech Connect

    Lee, K. S.; Yoo, D. H.; Son, G. H.; Lee, C. H.; Noh, J. H.; Han, J. J.; Yu, Y. S.; Hyung, Y. W.; Kim, Y. K.; Lee, S. C.; Lee, H. D.; Moon, J. T.; Yang, J. K.; Song, D. G.; Lim, T. J.

    2006-11-13

    Germanium ion implantation was investigated for crystallinity enhancement during solid phase epitaxial regrowth (SPE) using high current implantation equipment. Electron back-scatter diffraction(EBSD) measurement showed numerical increase of 19 percent of <100> signal, which might be due to pre-amorphization effect on silicon layer deposited by LPCVD process with germanium ion implantation. On the other hand, electrical property such as off-leakage current of NMOS transistor degraded in specific regions of wafers, which implied non-uniform distribution of donor-type impurities into channel area. It was confirmed that arsenic atoms were incorporated into silicon layer during germanium ion implantation. Since the equipment for germanium pre-amorphization implantation(PAI) was using several source gases such as BF3 and AsH3, atomic mass unit(AMU) contamination during PAI of germanium with AMU 74 caused the incorporation of arsenic with AMU 75 which resided in arc-chamber and other parts of the equipment. It was effective to use germanium isotope of AMU 72 to suppress AMU contamination, however it led serious reduction of productivity because of decrease in beam current by 30 percent as known to be difference in isotope abundance. It was effective to use enriched germanium source gas with AMU 72 in order to improve productivity. Spatial distribution of arsenic impurities in wafers was closely related to hardware configuration of ion implantation equipment.

  6. Atomic Layer Deposition Enabled Interconnect Technology for Vertical Nanowire Arrays

    DTIC Science & Technology

    2009-06-01

    nanowire light emitting diodes (LEDs), nanowire-based field effect transistors (FETs), resonators, batteries or biomedical applications. Keywords...various vertical nanowire-based devices, such as nanowire light emitting diodes (LEDs), nanowire-based field effect transistors (FETs), resonators...Silvija Gradecˇak, Yat Li, Cheng-Yen Wen, and Charles M. Lieber, “Core/Multishell Nanowire Heterostructures as Multicolor, High-Efficiency Light- Emitting

  7. Quantum optics with nanowires (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Zwiller, Val

    2017-02-01

    Nanowires offer new opportunities for nanoscale quantum optics; the quantum dot geometry in semiconducting nanowires as well as the material composition and environment can be engineered with unprecedented freedom to improve the light extraction efficiency. Quantum dots in nanowires are shown to be efficient single photon sources, in addition because of the very small fine structure splitting, we demonstrate the generation of entangled pairs of photons from a nanowire. By doping a nanowire and making ohmic contacts on both sides, a nanowire light emitting diode can be obtained with a single quantum dot as the active region. Under forward bias, this will act as an electrically pumped source of single photons. Under reverse bias, an avalanche effect can multiply photocurrent and enables the detection of single photons. Another type of nanowire under study in our group is superconducting nanowires for single photon detection, reaching efficiencies, time resolution and dark counts beyond currently available detectors. We will discuss our first attempts at combining semiconducting nanowire based single photon emitters and superconducting nanowire single photon detectors on a chip to realize integrated quantum circuits.

  8. Mechanically Cooled Large-Volume Germanium Detector Systems for Nuclear Explosion Monitoring

    SciTech Connect

    Hull, Ethan L.; Pehl, Richard H.; Lathrop, James R.; Martin, Gregory N.; Mashburn, R. B.; Miley, Harry S.; Aalseth, Craig E.; Hossbach, Todd W.; Bowyer, Ted W.

    2006-09-21

    Compact maintenance free mechanical cooling systems are being developed to operate large volume (~570 cm3, ~3 kg, 140% or larger) germanium detectors for field applications. We are using a new generation of Stirling-cycle mechanical coolers for operating the very largest volume germanium detectors with absolutely no maintenance or liquid nitrogen requirements. The user will be able to leave these systems unplugged on the shelf until needed. The flip of a switch will bring a system to life in ~1 hour for measurements. The maintenance-free operating lifetime of these detector systems will exceed five years. These features are necessary for remote long-duration liquid-nitrogen free deployment of large-volume germanium gamma-ray detector systems for Nuclear Explosion Monitoring (NEM). The Radionuclide Aerosol Sampler/Analyzer (RASA) will greatly benefit from the availability of such detectors by eliminating the need for liquid nitrogen at RASA sites while still allowing the very largest available germanium detectors to be utilized. These mechanically cooled germanium detector systems being developed here will provide the largest, most sensitive detectors possible for use with the RASA. To provide such systems, the appropriate technical fundamentals are being researched. Mechanical cooling of germanium detectors has historically been a difficult endeavor. The success or failure of mechanically cooled germanium detectors stems from three main technical issues: temperature, vacuum, and vibration. These factors affect one another. There is a particularly crucial relationship between vacuum and temperature. These factors will be experimentally studied both separately and together to insure a solid understanding of the physical limitations each factor places on a practical mechanically cooled germanium detector system for field use. Using this knowledge, a series of mechanically cooled germanium detector prototype systems are being designed and fabricated. Our collaborators

  9. Cellular manipulation and patterning using ferromagnetic nanowires

    NASA Astrophysics Data System (ADS)

    Hultgren, Anne

    Ferromagnetic nanowires are demonstrated as an effective tool to apply forces to living cells. Both magnetic cell separations and the magnetic patterning of cells on a substrate will be accomplished through the use of cell-nanowire interactions as well as nanowire-magnetic field interactions. When introduced into cultures of NIH-3T3 cells, the nanowires are internalized by cells via the integrin-mediated adhesion pathway without inflicting any toxic effects on the cell cycle over the course of several days. In addition, the length of the nanowires was found to have an effect on the cell-nanowire interactions when the cells were dissociated from the tissue culture dish. To compare the effectiveness of the nanowires as a means of manipulating cells to the current technology which is based on superparamagnetic beads, magnetic cell separations were performed with electrodeposited Ni nanowires 350 nm in diameter and 5--35 mum long in field gradients of 80 T/m. Single-pass separations of NIH-3T3 cells bound to nanowires achieve up to 81% purity with 85% yield, a dramatic improvement over the 55% purity and 20% yield obtained with the beads. The yield for the separations were found to be dependent on the length of the nanowires, and was maximized when the length of the nanowires equaled the diameter of the cells. This dependence was exploited to perform a size-selective magnetic separation. Substrates containing arrays of micro-magnets, fabricated using photolithography, were placed in cell cultures. These micro-magnet arrays create regions of locally strong magnetic field gradients to trap nanowires in specific locations on the substrate. These substrates were used in conjunction with fluid flow and a weak, externally applied magnetic field to create and control patterns of cells bound to nanowires. Controlled isolation of heterogeneous pairs and groups of cells will enable the study of the biochemistry of cell-cell contacts.

  10. Work Function Control of Germanium through Carborane-Carboxylic Acid Surface Passivation.

    PubMed

    Serino, Andrew C; Anderson, Mary E; Saleh, Liban M A; Dziedzic, Rafal M; Mills, Harrison; Heidenreich, Liv K; Spokoyny, Alexander M; Weiss, Paul S

    2017-10-02

    Self-assembled monolayers (SAMs) of carborane isomers with different dipole moments passivate germanium to modulate surface work function while maintaining chemical environment and surface energy. To identify head groups capable of monolayer formation on germanium surfaces, we studied thiol-, hydroxyl-, and carboxyl-terminated carboranes. These films were successfully formed with carboxylic acid head groups instead of the archetypal thiol, suggesting that the carborane cluster significantly affects headgroup reactivity. Film characterization included X-ray and ultraviolet photoelectron spectroscopies as well as contact angle goniometry. Using these carboranes, the germanium surface work function was tailored over 0.4 eV without significant changes to wetting properties.

  11. Discrimination of nuclear and electronic recoil events using plasma effect in germanium detectors

    NASA Astrophysics Data System (ADS)

    Wei, W.-Z.; Liu, J.; Mei, D.-M.

    2016-07-01

    We report a new method of using the plasma time difference, which results from the plasma effect, between the nuclear and electronic recoil events in high-purity germanium detectors to distinguish these two types of events in the search for rare physics processes. The physics mechanism of the plasma effect is discussed in detail. A numerical model is developed to calculate the plasma time for nuclear and electronic recoils at various energies in germanium detectors. It can be shown that under certain conditions the plasma time difference is large enough to be observable. The experimental aspects in realizing such a discrimination in germanium detectors is discussed.

  12. Influence of Containment on the Growth of Germanium-Silicon in Microgravity

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Mazuruk, K.; Croll, A.; Sorgenfrei, T.

    2017-01-01

    This investigation involves the comparison of results achieved from three types of crystal growth of germanium and germanium-silicon alloys: Float zone growth, Bridgman growth, and Detached Bridgman growth. The fundamental goal of the proposed research is to determine the influence of containment on the processing-induced defects and impurity incorporation in germanium-silicon (GeSi) crystals (silicon concentration in the solid up to 5%) for three different growth configurations in order to quantitatively assess the improvements of crystal quality possible by detached growth.

  13. Influence of Containment on the Growth of Silicon-Germanium: A Materials Science Flight Project

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Mazuruk, K.; Croell, A.

    2012-01-01

    This investigation involves the comparison of results achieved from three types of crystal growth of germanium and germanium-silicon alloys: (1) Float zone growth (2) Bridgman growth (3) Detached Bridgman growth crystal The fundamental goal of the proposed research is to determine the influence of containment on the processing-induced defects and impurity incorporation in germanium-silicon (GeSi) crystals (silicon concentration in the solid up to 5 at%) for three different growth configurations in order to quantitatively assess the improvements of crystal quality possible by detached growth.

  14. Tunneling and Transport in Nanowires

    SciTech Connect

    Goldman, Allen M.

    2016-08-16

    The goal of this program was to study new physical phenomena that might be relevant to the performance of conductive devices and circuits of the smallest realizable feature sizes possible using physical rather than biological techniques. Although the initial scientific work supported involved the use of scanning tunneling microscopy and spectroscopy to ascertain the statistics of the energy level distribution of randomly sized and randomly shaped quantum dots, or nano-crystals, the main focus was on the investigation of selected properties, including superconductivity, of conducting and superconducting nanowires prepared using electron-beam-lithography. We discovered a magnetic-field-restoration of superconductivity in out-of-equilibrium nanowires driven resistive by current. This phenomenon was explained by the existence of a state in which dissipation coexisted with nonvanishing superconducting order. We also produced ultra-small superconducting loops to study a predicted anomalous fluxoid quantization, but instead, found a magnetic-field-dependent, high-resistance state, rather than superconductivity. Finally, we developed a simple and controllable nanowire in an induced charged layer near the surface of a masked single-crystal insulator, SrTiO3. The layer was induced using an electric double layer transistor employing an ionic liquid (IL). The transport properties of the induced nanowire resembled those of collective electronic transport through an array of quantum dots.

  15. Single gallium nitride nanowire lasers.

    PubMed

    Johnson, Justin C; Choi, Heon-Jin; Knutsen, Kelly P; Schaller, Richard D; Yang, Peidong; Saykally, Richard J

    2002-10-01

    There is much current interest in the optical properties of semiconductor nanowires, because the cylindrical geometry and strong two-dimensional confinement of electrons, holes and photons make them particularly attractive as potential building blocks for nanoscale electronics and optoelectronic devices, including lasersand nonlinear optical frequency converters. Gallium nitride (GaN) is a wide-bandgap semiconductor of much practical interest, because it is widely used in electrically pumped ultraviolet-blue light-emitting diodes, lasers and photodetectors. Recent progress in microfabrication techniques has allowed stimulated emission to be observed from a variety of GaN microstructures and films. Here we report the observation of ultraviolet-blue laser action in single monocrystalline GaN nanowires, using both near-field and far-field optical microscopy to characterize the waveguide mode structure and spectral properties of the radiation at room temperature. The optical microscope images reveal radiation patterns that correlate with axial Fabry-Perot modes (Q approximately 10(3)) observed in the laser spectrum, which result from the cylindrical cavity geometry of the monocrystalline nanowires. A redshift that is strongly dependent on pump power (45 meV microJ x cm(-2)) supports the idea that the electron-hole plasma mechanism is primarily responsible for the gain at room temperature. This study is a considerable advance towards the realization of electron-injected, nanowire-based ultraviolet-blue coherent light sources.

  16. Surface physics of semiconducting nanowires

    NASA Astrophysics Data System (ADS)

    Amato, Michele; Rurali, Riccardo

    2016-02-01

    Semiconducting nanowires (NWs) are firm candidates for novel nanoelectronic devices and a fruitful playground for fundamental physics. Ultra-thin nanowires, with diameters below 10 nm, present exotic quantum effects due to the confinement of the wave functions, e.g. widening of the electronic band-gap, deepening of the dopant states. However, although several reports of sub-10 nm wires exist to date, the most common NWs have diameters that range from 20 to 200 nm, where these quantum effects are absent or play a very minor role. Yet, the research activity on this field is very intense and these materials still promise to provide an important paradigm shift for the design of emerging electronic devices and different kinds of applications. A legitimate question is then: what makes a nanowire different from bulk systems? The answer is certainly the large surface-to-volume ratio. In this article we discuss the most salient features of surface physics and chemistry in group-IV semiconducting nanowires, focusing mostly on Si NWs. First we review the state-of-the-art of NW growth to achieve a smooth and controlled surface morphology. Next we discuss the importance of a proper surface passivation and its role on the NW electronic properties. Finally, stressing the importance of a large surface-to-volume ratio and emphasizing the fact that in a NW the surface is where most of the action takes place, we discuss molecular sensing and molecular doping.

  17. Semiconductor nanowires: Controlled growth and thermal properties

    NASA Astrophysics Data System (ADS)

    Wu, Yiying

    This dissertation presents an experimental study of the controlled growth of semiconductor nanowires and their thermophysical properties. The synthesis of nanowires was based on the well-known Vapor-Liquid-Solid (VLS) mechanism in which the growth of nanowire is initiated by a nanosized liquid droplet. The prepared nanowires are single-crystalline with certain preferred growth direction. Nanowires with different compositions have been synthesized, including Si, Ge, boron and MgB2. The control of nanowire composition, diameter and orientation has also been achieved. In addition, a Pulsed Laser Ablation-Chemical Vapor Deposition (PLA-CVD) hybrid process was developed to synthesize Si/SiGe longitudinally superlattice nanowires. The thermal conductivity of individual pure Si nanowire and Si/SiGe nanowire was measured using a microfabricated suspended device over a temperature range of 20--320 K. The thermal conductivities of individual 22, 37, 56, and 115 nm diameter single crystalline intrinsic Si nanowires were much lower than the bulk value due to the strong phonon boundary scattering. Except for the 22 nm diameter nanowire, theoretical predictions using a modified Callaway model fit the experimental data very well. The data for the 22 nm diameter wire suggest that changes in phonon dispersion due to confinement can cause additional thermal conductivity reduction. The Si/SiGe superlattice nanowires with diameters of 83 run and 58 nm were also measured. Their thermal conductivities are smaller than pure Si nanowire with similar diameter, as well as Si/SiGe superlattice thin film with comparable period. Both the alloying scattering and the boundary scattering are believed to contribute to this reduction. Size dependent melting-recrystallization study of the carbon-sheathed semiconductor Ge nanowires was carried out in in-situ high temperature transmission electron microscope (TEM). Significant depression in melting temperature with decreasing size of the nanowires as

  18. Single gold nanowire electrodes and single Pt@Au nanowire electrodes: electrochemistry and applications.

    PubMed

    Zhang, Yaoyao; Xu, Shen; Xiao, Xiaoqing; Liu, Yong; Qian, Yuanyuan; Li, Yongxin

    2017-03-02

    Single Au nanowire electrodes and single Pt@Au nanowire electrodes showed steady-state voltammetric responses and a fast electron-transfer rate, which have been used to fabricate an E-DNA sensor and investigate the oxygen reduction reaction at the single nanowire level.

  19. Programmable nanowire circuits for nanoprocessors.

    PubMed

    Yan, Hao; Choe, Hwan Sung; Nam, SungWoo; Hu, Yongjie; Das, Shamik; Klemic, James F; Ellenbogen, James C; Lieber, Charles M

    2011-02-10

    A nanoprocessor constructed from intrinsically nanometre-scale building blocks is an essential component for controlling memory, nanosensors and other functions proposed for nanosystems assembled from the bottom up. Important steps towards this goal over the past fifteen years include the realization of simple logic gates with individually assembled semiconductor nanowires and carbon nanotubes, but with only 16 devices or fewer and a single function for each circuit. Recently, logic circuits also have been demonstrated that use two or three elements of a one-dimensional memristor array, although such passive devices without gain are difficult to cascade. These circuits fall short of the requirements for a scalable, multifunctional nanoprocessor owing to challenges in materials, assembly and architecture on the nanoscale. Here we describe the design, fabrication and use of programmable and scalable logic tiles for nanoprocessors that surmount these hurdles. The tiles were built from programmable, non-volatile nanowire transistor arrays. Ge/Si core/shell nanowires coupled to designed dielectric shells yielded single-nanowire, non-volatile field-effect transistors (FETs) with uniform, programmable threshold voltages and the capability to drive cascaded elements. We developed an architecture to integrate the programmable nanowire FETs and define a logic tile consisting of two interconnected arrays with 496 functional configurable FET nodes in an area of ∼960 μm(2). The logic tile was programmed and operated first as a full adder with a maximal voltage gain of ten and input-output voltage matching. Then we showed that the same logic tile can be reprogrammed and used to demonstrate full-subtractor, multiplexer, demultiplexer and clocked D-latch functions. These results represent a significant advance in the complexity and functionality of nanoelectronic circuits built from the bottom up with a tiled architecture that could be cascaded to realize fully integrated

  20. Synthesis and Characterization of Nanowires

    SciTech Connect

    Musket, R.G.; Felter, T.; Quong, A.

    2000-03-01

    With the dimensions of components in microelectronic circuits shrinking, the phenomena associated with electronic conduction through wires and with device operation can be expected to change. For example, as the length of electrical conductors is reduced, ballistic transport will become the main mode of conduction. Sufficient reduction in the cross sectional area of conductors can lead to quantum confinement effects. Prior knowledge of the phenomena associated with decreasing size should help guide the designers of future, smaller devices in terms of geometry and materials. However, prior knowledge requires the availability of sufficiently small nanowires for experiments. To date, the smallest nanowires that have been fabricated and investigated had diameters of 8 nm. We propose to extend the investigation of these size-related phenomena by synthesizing, using a novel version of nuclear, or ion, track lithography and characterizing, physically and electrically, nanowires with diameters D of 1 to 5 nm and lengths L of 2 to 250 nm. Thus, by varying the dimensions of the nanowires, we will be able to determine experimentally when the ideas of macroscopic conductance break down and the conductance becomes dominated by quantum and ballistic effects. In our approach the nature of the small-diameter nanostructure formed can be controlled: Nanowires are formed when L/D is large, and quantum dots are formed when both L and D are small. Theoretical calculations will be performed to both guide and understand the experimental studies. We have examined several aspects of this challenging problem and generated some promising results, but the project was not extended for the second year as planned. Thus, we did not have sufficient resources to complete the proof of concept.

  1. TOPICAL REVIEW: DNA nanowire fabrication

    NASA Astrophysics Data System (ADS)

    Gu, Qun; Cheng, Chuanding; Gonela, Ravikanth; Suryanarayanan, Shivashankar; Anabathula, Sathish; Dai, Kun; Haynie, Donald T.

    2006-01-01

    Deoxyribonucleic acid (DNA) has been a key building block in nanotechnology since the earliest work on what is now called DNA-templated self-assembly (Alivisatos et al 1996 Nature 382 609; Mirkin et al 1996 Nature 382 607; Braun et al 1998 Nature 391 775). A range of different nanoparticles and nanoclusters have been assembled on single DNA molecules for a variety of purposes (Braun et al 1998 Nature 391 775; Richter et al 2001 Appl. Phys. Lett. 78 536; Park et al 2002 Science 295 1503; Mirkin 2000 Inorg. Chem. 39 2258; Keren et al 2003 Science 302 1380). Electrically conductive silver (Braun et al 1998 Nature 391 775) and palladium (Richter et al 2001 Appl. Phys. Lett. 78 536) nanowires, for example, have been fabricated by DNA templating for the development of interconnection of nanoelectric elements, and field effect transistors have been built by assembly of a single carbon nanotube and DNA-templated nanowires (Keren et al 2003 Science 302 1380). DNA is well suited for nanowire assembly because of its size, well organized structure, and exquisite molecular-recognition-ability-specific base pairing. This property has been used to detect nucleic acids (Park et al 2002 Science 295 1503) and anthrax (Mirkin 2000 Inorg. Chem. 39 2258) with high sensitivity and specificity. Molecular recognition can also be used to localize nanowires in electronics. Various methods, for example molecular combing, electrophoretic stretching, and hydrodynamic stretching, have been developed to orient DNA molecules on a solid support. This review focuses on methods used to manipulate and metallize DNA in nanowire fabrication. A novel approach based on a single-stranded DNA template and molecular recognition is also discussed.

  2. Bacterial Nanowires Facilitate Extracellular Electron Transfer

    NASA Astrophysics Data System (ADS)

    Gorby, Y.

    2005-12-01

    Dissimilatory metal reducing bacteria, including Shewanella oneidensis and Geobacter sulfurreducens, produce electrically conductive nanowires that facilitate electron transfer to solid phase iron oxides. Nanowires produced by S. oneidensis strain MR-1 are functionalized by decaheme cytochromes MtrC and OmcA that are distributed along the length of the nanowires, as confirmed by immunolocalization experiments using peptide specific antibodies. Mutants lacking MtrC and OmcA produce nanowires that were poorly conductive, are unable to reduce solid phase iron oxides, and do not produce electric current in microbial fuel cells. Although less completely characterized, nanowires are also produced by organisms throughout a broad metabolic spectrum, from sulfate reducing bacteria to oxygenic, phototrophic cyanobacteria. Our research suggests that electrically conductive nanowires may be common throughout the microbial world and may serve as structures for efficient electron transfer and energy dissemination in complex communities such as microbial mats and biofilms.

  3. Photocatalytic Properties of Porous Silicon Nanowires.

    PubMed

    Qu, Yongquan; Zhong, Xing; Li, Yujing; Liao, Lei; Huang, Yu; Duan, Xiangfeng

    2010-01-01

    Porous silicon nanowires are synthesized through metal assisted wet-chemical etch of highly-doped silicon wafer. The resulted porous silicon nanowires exhibit a large surface area of 337 m(2)·g(-1) and a wide spectrum absorption across the entire ultraviolet, visible and near infrared regime. We further demonstrate that platinum nanoparticles can be loaded onto the surface of the porous silicon nanowires with controlled density. These combined advancements make the porous silicon nanowires an interesting material for photocatalytic applications. We show that the porous silicon nanowires and platinum nanoparticle loaded porous silicon nanowires can be used as effective photocatalysts for photocatalytic degradation of organic dyes and toxic pollutants under visible irradiation, and thus are of significant interest for organic waste treatment and environmental remediation.

  4. Improving Thermoelectric Properties of Nanowires Through Inhomogeneity

    NASA Astrophysics Data System (ADS)

    González, J. Eduardo; Sánchez, Vicenta; Wang, Chumin

    2016-10-01

    Inhomogeneity in nanowires can be present in the cross-section and/or by breaking the translational symmetry along the nanowire. In particular, the quasiperiodicity introduces an unusual class of electronic and phononic transport with a singular continuous eigenvalue spectrum and critically localized wave functions. In this work, the thermoelectricity in periodic and quasiperiodically segmented nanobelts and nanowires is addressed within the Boltzmann formalism by using a real-space renormalization plus convolution method developed for the Kubo-Greenwood formula, in which tight-binding and Born models are, respectively, used for the calculation of electric and lattice thermal conductivities. For periodic nanowires, we observe a maximum of the thermoelectric figure-of-merit (ZT) in the temperature space, as occurred in the carrier concentration space. This maximum ZT can be improved by introducing into nanowires periodically arranged segments and an inhomogeneous cross-section. Finally, the quasiperiodically segmented nanowires reveal an even larger ZT in comparison with the periodic ones.

  5. Improving Thermoelectric Properties of Nanowires Through Inhomogeneity

    NASA Astrophysics Data System (ADS)

    González, J. Eduardo; Sánchez, Vicenta; Wang, Chumin

    2017-05-01

    Inhomogeneity in nanowires can be present in the cross-section and/or by breaking the translational symmetry along the nanowire. In particular, the quasiperiodicity introduces an unusual class of electronic and phononic transport with a singular continuous eigenvalue spectrum and critically localized wave functions. In this work, the thermoelectricity in periodic and quasiperiodically segmented nanobelts and nanowires is addressed within the Boltzmann formalism by using a real-space renormalization plus convolution method developed for the Kubo-Greenwood formula, in which tight-binding and Born models are, respectively, used for the calculation of electric and lattice thermal conductivities. For periodic nanowires, we observe a maximum of the thermoelectric figure-of-merit ( ZT) in the temperature space, as occurred in the carrier concentration space. This maximum ZT can be improved by introducing into nanowires periodically arranged segments and an inhomogeneous cross-section. Finally, the quasiperiodically segmented nanowires reveal an even larger ZT in comparison with the periodic ones.

  6. Electronic Transport Control of Bi Nanowires

    DTIC Science & Technology

    2007-09-07

    TERMS night vision coolers, thermoelectrics, nanowires, bismuth, Aharonov Bohm , quantum, confinement Tito E. Huber Howard University Office Of...journals or in conference proceedings (N/A for none) Quantum Interference of Surface States in Bismuth Nanowires probed by the Aharonov - Bohm Oscillation of...indications that this in indeed the case because the nanowires exhibit Aharonov - Bohm oscillations that are generally observed in tubes or rings. 6

  7. Chemical reactivity of Ni-Rh nanowires.

    PubMed

    Schoiswohl, J; Mittendorfer, F; Surnev, S; Ramsey, M G; Andersen, J N; Netzer, F P

    2006-09-22

    The properties of bimetallic Ni-Rh nanowires, fabricated by decorating the steps of vicinal Rh(111) surfaces by stripes of self-assembled Ni adatoms, have been probed by STM, photoemission, and ab initio density functional theory calculations. These Ni-Rh nanowires have specific electronic properties that lead to a significantly enhanced chemical reactivity towards oxygen. As a result, the Ni-Rh nanowires can be oxidized exclusively, generating novel quasi-one-dimensional oxide structures.

  8. Characteristics of GRIFFIN high-purity germanium clover detectors

    NASA Astrophysics Data System (ADS)

    Rizwan, U.; Garnsworthy, A. B.; Andreoiu, C.; Ball, G. C.; Chester, A.; Domingo, T.; Dunlop, R.; Hackman, G.; Rand, E. T.; Smith, J. K.; Starosta, K.; Svensson, C. E.; Voss, P.; Williams, J.

    2016-06-01

    The Gamma-Ray Infrastructure For Fundamental Investigations of Nuclei, GRIFFIN, is a new experimental facility for radioactive decay studies at the TRIUMF-ISAC laboratory. The performance of the 16 high-purity germanium (HPGe) clover detectors that will make up the GRIFFIN spectrometer is reported. The energy resolution, efficiency, timing resolution, crosstalk and preamplifier properties of each crystal were measured using a combination of analog and digital data acquisition techniques. The absolute efficiency and add-back factors are determined for the energy range of 80-3450 keV. The detectors show excellent performance with an average over all 64 crystals of a FWHM energy resolution of 1.89(6) keV and relative efficiency with respect to a 3 in . × 3 in . NaI detector of 41(1)% at 1.3 MeV.

  9. Portable electro-mechanically cooled high-resolution germanium detector

    SciTech Connect

    Neufeld, K.W.; Ruhter, W.D.

    1995-05-01

    We have integrated a small, highly-reliable, electro-mechanical cryo-cooler with a high-resolution germanium detector for portable/field applications. The system weighs 6.8 kg and requires 40 watts of power to operate once the detector is cooled to its operating temperature. the detector is a 500 mm{sup 2} by 20-mm thick low-energy configuration that gives a full-width at half maximum (FWHM) energy resolution of 523 eV at 122 keV, when cooled with liquid nitrogen. The energy resolution of the detector, when cooled with the electro-mechanical cooler, is 570 eV at 122 keV. We have field tested this system in measurements of plutonium and uranium for isotopic and enrichment information using the MGA and MGAU analysis programs without any noticeable effects on the results.

  10. Method of manufacturing a niobium-aluminum-germanium superconductive material

    DOEpatents

    Wang, John L.; Pickus, Milton R.; Douglas, Kent E.

    1980-01-01

    A method for manufacturing flexible Nb.sub.3 (Al,Ge) multifilamentary superconductive material in which a sintered porous niobium compact is infiltrated with an aluminum-germanium alloy and thereafter deformed and heat treated in a series of steps at different successively higher temperatures preferably below 1000.degree. C. to produce filaments composed of Nb.sub.3 (Al,G3) within the compact. By avoiding temperatures in excess of 1000.degree. C. during the heat treatment, cladding material such as copper can be applied to facilitate a deformation step preceding the heat treatment and can remain in place through the heat treatment to also serve as a temperature stabilizer for supeconductive material produced. Further, these lower heat treatment temperatures favor formation of filaments with reduced grain size and, hence with more grain boundaries which in turn increase the current-carrying capacity of the superconductive material.

  11. Properties of silicon-germanium thermoelectric alloys with additives

    NASA Technical Reports Server (NTRS)

    Mclane, George; Raag, Valvo; Danielson, Lee; Wood, Charles; Vandersande, Jan

    1986-01-01

    The paper reports the results of measurements (Seebeck and Hall coefficients, electrical resistivity, and thermal conductivity) on silicon-germanium (Si-20 at. pct Ge) alloy with boron phosphide, B(6.5)P) as an additive, prepared as described by McLane et al. (1986). The power factor (Seebeck coefficient squared divided by electrical resistivity) and the thermal conductivity of SeGe/B(6.5)P material were found to be lower than for the 'standard' SiGe (Si-22 at. pct Ge) material. However, no net improvement was achieved in the figure-of-merit of the sample tested. It is suggested that structural inhomogeneities, revealed by a SEM examination, might be responsible for this lack of improvement.

  12. Experimental investigation on oxidation kinetics of germanium by ozone

    NASA Astrophysics Data System (ADS)

    Wang, Xiaolei; Zhao, Zhiqian; Xiang, Jinjuan; Wang, Wenwu; Zhang, Jing; Zhao, Chao; Ye, Tianchun

    2016-12-01

    Oxidation kinetics of germanium surface by ozone at low temperature (≤400 °C) is experimentally investigated. The growth process contains two regions: initial linear growth region and following parabolic growth region. The GeOx thickness vs. oxidation time plot obeys the well-known Deal-Grove or linear parabolic model. The linear growth region contains reaction of oxygen atoms with surface bond and back bonds of outmost Ge layer. And the activation energy is experimentally estimated to be 0.06 eV. Such small activation energy indicates that the linear growth region is nearly barrier-less. The parabolic growth region starts when the oxygen atoms diffuse into back bonds of second outmost Ge layers. And the activation energy for this process is found to be 0.54 eV. Furthermore, in the ozone oxidation it is not O3 molecules but O radicals that go through the GeOx film.

  13. Study on the Properties of High Purity Germanium Crystals

    NASA Astrophysics Data System (ADS)

    Yang, G.; Mei, H.; Guan, Y. T.; Wang, G. J.; Mei, D. M.; Irmscher, K.

    2015-05-01

    In the crystal growth lab of South Dakota University, we are growing high purity germanium (HPGe) crystals and using the grown crystals to make radiation detectors. As the detector grade HPGe crystals, they have to meet two critical requirements: an impurity level of ∼109 to 10 atoms /cm3 and a dislocation density in the range of ∼102 to 104 / cm3. In the present work, we have used the following four characterization techniques to investigate the properties of the grown crystals. First of all, an x-ray diffraction method was used to determine crystal orientation. Secondly, the van der Pauw Hall effect measurement was used to measure the electrical properties. Thirdly, a photo-thermal ionization spectroscopy (PTIS) was used to identify what the impurity atoms are in the crystal. Lastly, an optical microscope observation was used to measure dislocation density in the crystal. All of these characterization techniques have provided great helps to our crystal activities.

  14. FTIR and DFT studies of Novel Germanium-Carbon Clusters

    NASA Astrophysics Data System (ADS)

    Robbins, D. L.; Rittby, C. M. L.; Graham, W. R. M.

    2001-10-01

    The vibrational fundamentals and structures of germanium-carbon clusters formed by laser ablation and trapped in solid Ar are currently under investigation. The determination of the ground state geometries and vibrational fundamentals are facilitated by the comparison of frequencies and ^13C isotopic shifts measured by Fourier transform infrared spectroscopy with the predictions of density functional theory. The identification of the ν3 mode of linear GeC_3Ge (observed at 1920.7 cm-1 ) has been made.(D.L.Robbins, C.M.L. Rittby, and W.R.M. Graham J. Chem. Phys. 114, 3570 (2001).) The results of further calculations and assignments on larger species such as GeC4 and GeC9 will be reported.

  15. A pseudo-single-crystalline germanium film for flexible electronics

    NASA Astrophysics Data System (ADS)

    Higashi, H.; Kasahara, K.; Kudo, K.; Okamoto, H.; Moto, K.; Park, J.-H.; Yamada, S.; Kanashima, T.; Miyao, M.; Tsunoda, I.; Hamaya, K.

    2015-01-01

    We demonstrate large-area (˜600 μm), (111)-oriented, and high-crystallinity, i.e., pseudo-single-crystalline, germanium (Ge) films at 275 °C, where the temperature is lower than the softening temperature of a flexible substrate. A modulated gold-induced layer exchange crystallization method with an atomic-layer deposited Al2O3 barrier and amorphous-Ge/Au multilayers is established. From the Raman measurements, we can judge that the crystallinity of the obtained Ge films is higher than those grown by aluminum-induced-crystallization methods. Even on a flexible substrate, the pseudo-single-crystalline Ge films for the circuit with thin-film transistor arrays can be achieved, leading to high-performance flexible electronics based on an inorganic-semiconductor channel.

  16. Anomalous compression behavior of germanium during phase transformation

    SciTech Connect

    Yan, Xiaozhi; Tan, Dayong; Ren, Xiangting; Yang, Wenge E-mail: duanweihe@scu.edu.cn; He, Duanwei E-mail: duanweihe@scu.edu.cn; Mao, Ho-Kwang

    2015-04-27

    In this article, we present the abnormal compression and plastic behavior of germanium during the pressure-induced cubic diamond to β-tin structure transition. Between 8.6 GPa and 13.8 GPa, in which pressure range both phases are co-existing, first softening and followed by hardening for both phases were observed via synchrotron x-ray diffraction and Raman spectroscopy. These unusual behaviors can be interpreted as the volume misfit between different phases. Following Eshelby, the strain energy density reaches the maximum in the middle of the transition zone, where the switch happens from softening to hardening. Insight into these mechanical properties during phase transformation is relevant for the understanding of plasticity and compressibility of crystal materials when different phases coexist during a phase transition.

  17. Cryogenic performance of high-efficiency germanium immersion grating

    NASA Astrophysics Data System (ADS)

    Sarugaku, Yuki; Ikeda, Yuji; Kaji, Sayumi; Kobayashi, Naoto; Sukegawa, Takashi; Arasaki, Takayuki; Kondo, Sohei; Nakanishi, Kenshi; Yasui, Chikako; Kawakita, Hideyo

    2016-08-01

    Immersion gratings will play important roles for infrared astronomy in the next generation. We have been developing immersion gratings with a variety of kinds of materials and have succeeded in fabricating a high-efficiency germanium (Ge) immersion grating with both a reflection coating on the grating surface and an AR coating on the entrance surface. The grating will be installed in a K-, L-, and M-bands (2-5μm) high-resolution (R=80,000) spectrograph, VINROUGE, which is a prototype for the TMT MIR instrument. In this paper, we report the preliminary results on the evaluation of the Ge immersion grating. We confirmed that the peak absolute diffraction efficiency was in the range of 70-80%, which was as expected from the design, at both room and cryogenic temperatures.

  18. Exceptional transport property in a rolled-up germanium tube

    NASA Astrophysics Data System (ADS)

    Guo, Qinglei; Wang, Gang; Chen, Da; Li, Gongjin; Huang, Gaoshan; Zhang, Miao; Wang, Xi; Mei, Yongfeng; Di, Zengfeng

    2017-03-01

    Tubular germanium (Ge) resistors are demonstrated by rolling-up thin Ge nanomembranes (NMs, 50 nm in thickness) with electrical contacts. The strain distribution of rolled-up Ge microtubes along the radial direction is investigated and predicted by utilizing micro-Raman scattering spectroscopy with two different excitation lasers. Electrical properties are characterized for both unreleased GeNMs and released/rolled-up Ge microtubes. The conductivities of GeNMs significantly decrease after rolling-up into tubular structures, which can be attributed to surface charging states on the conductance, band bending, and piezo-resistance effect. When illuminated with a light source, facilitated by the suppressed dark current of rolled-up Ge tubes, the corresponding signal-to-noise ratio can be dramatically enhanced compared with that of planar GeNMs.

  19. Buried Porous Silicon-Germanium Layers in Monocrystalline Silicon Lattices

    NASA Technical Reports Server (NTRS)

    Fathauer, Robert W. (Inventor); George, Thomas (Inventor); Jones, Eric W. (Inventor)

    1998-01-01

    Monocrystalline semiconductor lattices with a buried porous semiconductor layer having different chemical composition is discussed and monocrystalline semiconductor superlattices with a buried porous semiconductor layers having different chemical composition than that of its monocrystalline semiconductor superlattice are discussed. Lattices of alternating layers of monocrystalline silicon and porous silicon-germanium have been produced. These single crystal lattices have been fabricated by epitaxial growth of Si and Si-Ge layers followed by patterning into mesa structures. The mesa structures are strain etched resulting in porosification of the Si-Ge layers with a minor amount of porosification of the monocrystalline Si layers. Thicker Si-Ge layers produced in a similar manner emitted visible light at room temperature.

  20. Electron temperature and density measurements of laser induced germanium plasma

    SciTech Connect

    Shakeel, Hira; Arshad, Saboohi; Haq, S. U. Nadeem, Ali

    2016-05-15

    The germanium plasma produced by the fundamental harmonics (1064 nm) of Nd:YAG laser in single and double pulse configurations have been studied spectroscopically. The plasma is characterized by measuring the electron temperature using the Boltzmann plot method for neutral and ionized species and electron number density as a function of laser irradiance, ambient pressure, and distance from the target surface. It is observed that the plasma parameters have an increasing trend with laser irradiance (9–33 GW/cm{sup 2}) and with ambient pressure (8–250 mbar). However, a decreasing trend is observed along the plume length up to 4.5 mm. The electron temperature and electron number density are also determined using a double pulse configuration, and their behavior at fixed energy ratio and different interpulse delays is discussed.