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Sample records for ntd germanium thermistors

  1. Neutron Transmutation Doped (NTD) germanium thermistors for sub-mm bolometer applications

    NASA Technical Reports Server (NTRS)

    Haller, E. E.; Itoh, K. M.; Beeman, J. W.

    1996-01-01

    Recent advances in the development of neutron transmutation doped (NTD) semiconductor thermistors fabricated from natural and controlled isotopic composition germanium are reported. The near ideal doping uniformity that can be achieved with the NTD process, the device simplicity of NTD Ge thermistors and the high performance of cooled junction field effect transistor preamplifiers led to the widespread acceptance of these thermal sensors in ground-based, airborne and spaceborne radio telescopes. These features made possible the development of efficient bolometer arrays.

  2. Neutron transmutation doped (Ntd) germanium thermistors for sub-Mm bolometer applications

    SciTech Connect

    Haller, E.E. |; Itoh, K.M.; Beeman, J.W.

    1996-09-01

    The authors report on recent advances in the development of Neutron Transmutation Doped (NTD) semiconductor thermistors fabricated from germanium of natural and controlled isotopic composition. The near ideal doping uniformity which can be achieved with the NTD process, the device simplicity of NTD Ge thermistors and the high performance of cooled junction field effect transistor (FET) preamplifiers have led to the widespread acceptance of these thermal sensors in many radiotelescopes operating on the ground, on high altitude aircraft and on spaceborne satellites. These features also have made possible the development of efficient bolometer arrays which are beginning to produce exciting results.

  3. Microcalorimeters with NTD and Expitaxial Germanium Thermistors for High Resolution X-Ray Spectroscopy

    NASA Technical Reports Server (NTRS)

    Silver, Eric; Brinton, John C. (Technical Monitor)

    2004-01-01

    This is a progress report for the second year of a three year SR&T grant to continue the advancement of NTD-based microcalorimeters. We reported last year that we re-prioritized certain aspects of the statement of work and chose to emphasize issues of array development in the first year rather than wait until year two. Consequently, some of the projects scheduled for the first year were delayed to the second year and we report on those topics here. These include: a) Measurements that map out JFET , thermistor, l/f and feedback resistor noise; b) Investigations that evaluate the limits of the JFET preamplifier circuitry as it pertains to stability at the 2 eV level; The results of a) and b) have led to preliminary measurements that demonstrate 3.08 eV resolution at 6 keV. c) Calculations that can predict the current performance.

  4. Micro-Calorimeters with NTD and Epitaxial Germanium Thermistors for High Resolution X-Ray Spectroscopy. Revised

    NASA Technical Reports Server (NTRS)

    Brinton, John (Technical Monitor); Silver, Eric

    2005-01-01

    This is a progress report for the third year of a three year SR&T grant to continue the advancement of NTD-based microcalorimeters. We highlight our progress to date that allowed us to garner an additional three years of funding for this work.

  5. The Constellation-X Focal Plane Microcalorimeter Array: An NTD-Germanium Solution

    NASA Technical Reports Server (NTRS)

    Beeman, J.; Silver, E.; Bandler, S.; Schnopper, H.; Murray, S.; Madden, N.; Landis, D.; Haller, E. E.; Barbera, M.

    2001-01-01

    The hallmarks of Neutron Transmutation Doped (NTD) germanium cryogenic thermistors include high reliability, reproducibility, and long term stability of bulk carrier transport properties. Using micro-machined NTD Ge thermistors with integral 'flying' leads, we can now fabricate two-dimensional arrays that are built up from a series of stacked linear arrays. We believe that this modular approach of building, assembling, and perhaps replacing individual modules of detectors is essential to the successful fabrication and testing of large multi-element instruments. Details of construction are presented.

  6. X-Ray and Gamma-Ray Astronomy with NTD Germanium-based Microcalorimeters

    NASA Technical Reports Server (NTRS)

    Silver, E.; Bandler, S.; Schnopper, H.; Murray, S.; Madden, N.; Landis, D.; Goulding, F.; Beeman, J.; Haller, E. E.; Barbera, M.

    2003-01-01

    We report on the performance of our NTD-Ge microcalorimeters. To date, the spectral resolution for x-ray and gamma-ray lines from radioactive sources and laboratory plasmas is 4.8 eV in the entire 1 - 6 keV band and 52 eV at 60 keV. Technical details responsible for this performance are presented as well as an innovative electro-thermal approach for enhancing count-rate capability.

  7. Microcalorimeters with Germanium Thermistors for High Resolution Soft and Hard X-ray Astronomy

    NASA Technical Reports Server (NTRS)

    Silver, Eric

    2005-01-01

    This is a progress report for the third year of a three year SR&T grant to continue the advancement of NTD-based microcalorimeters. We highlight our progress to date that allowed us to garner an additional three years of funding for this work.

  8. Development of Thin Film Germanium-Gold Thermistors for Calorimetric Detection of Nuclear Radiation.

    NASA Astrophysics Data System (ADS)

    Wang, Xunxie

    1995-01-01

    The present work is to produce thin film semiconductor thermistors which can be directly fabricated on radiation absorbers to act as ultra low-mass, highly sensitive cryogenic phonon sensors for detecting single nuclear radiation interaction invents. The specific application envisioned for these devices is in the search for galactic Dark Matter, which is proposed to exist in the form of weakly interacting massive particles in the galaxy. Thin film Au doped Ge thermistors were directly fabricated on single crystal silicon absorbers using vacuum filament evaporation and microfabrication techniques. The fabrication procedure developed in the present work gives micron-scale thin film GeAu thermistors with highly reproducible characteristics. Electrical and thermal properties of thin film Ge_{rm 1-x}Au _{rm x} for 0.019 < x < 0.17 were studied between room temperature and 0.019K and in magnetic fields up to 4.0T. Measurements indicated that variable-range-hopping dominates the conductivity of GeAu thin film at temperatures below 10K. Metal-insulator transition of the film is found to occur for x > 0.17. The observed magnetoresistance is explained by using a field-dependent hopping exponent proposed in the present work combined with Mott's hopping conductivity theory. A new treatment of electrical field-induced nonlinearity in variable-range-hopping is also given which quantitatively reproduced the observed nonlinear resistivity. Electrical heat pulse and particle detection measurements showed that the total effective heat capacity of the device was dominated by the silicon absorber substrate at a bath temperature of 1.5 K and by electron system of the thermistor itself of the device when the bath temperatures were below 100 mK. Excellent responsivity of GeAu thin film calorimeters has been demonstrated in AC electrical pulse and nuclear radiation detection experiments. At optimal bias power, the responsivity (|DeltaV/ DeltaE|) of the present devices reaches 10^8 V/J at

  9. Microcalorimeters with Germanium Thermistors for High Resolution Soft and Hard X-ray Astronomy

    NASA Technical Reports Server (NTRS)

    Silver, E.

    2003-01-01

    This is a progress report for the first year of a three year Space Research and Technology (SR&T) grant to continue the advancement of neutron transmutation doped (NTD-based) microcalorimeters. We have re-prioritized certain aspects of the statement of work and chose to emphasize issues of array development in the first year rather than wait until year two. Consequently, some of the projects scheduled for the first year were delayed to the second year. Here we report on our progress to: a) Build and test a 1 x 4 element array and to investigate electrical and thermal cross-talk; b) Build a multiplexed 4 channel analog pulse processor; c) Build a digital pulse processor that can accommodate 4 channels with independent triggers; d) Develop a proportional thermal baseline restoration system compatible with the constant voltage mode of microcalorimeter operation.

  10. NTD-GE Based Microcalorimeter Performance

    NASA Technical Reports Server (NTRS)

    Bandler, Simon; Silver, Eric; Schnopper, Herbert; Murray, Stephen; Barbera, Marco; Madden, Norm; Landis, Don; Beeman, Jeff; Haller, Eugene; Tucker, Greg

    2000-01-01

    Our group has been developing x-ray microcalorimeters consisting of neutron transmutation doped (NTD) germanium thermistors attached to superconducting tin absorbers. We discuss the performance of single pixel x-ray detectors, and describe an array technology. In this paper we describe the read-out circuit that allows us to measure fast signals in our detectors as this will be important in understanding the primary cause of resolution broadening. We describe briefly a multiplexing scheme that allows a number of different calorimeters to be read out using a single JFET. We list the possible causes of broadening and give a description of the experiment which best demonstrates the cause of the primary broadening source. We mention our strategy for finding a suitable solution to this problem and describe briefly a technology for building arrays of these calorimeters.

  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. 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.

  13. Particle detection with semiconductor thermistors at low temperatures

    SciTech Connect

    Wang, N.; Beeman, J.; Cleland, A.N.; Cummings, A.; Lange, A.; Ross, R.; Sadoulet, B.; Steiner, H.; Shutt, T.; Wellstood, F.C.

    1988-11-01

    We have studied the use of neutron transmutation doped (NTD) Ge thermistors as phonon sensors at dilution refrigerator temperatures. In addition to measuring their thermal and electrical properties, we have observed pulses generated by X-rays incident on a thermistor thermally well-clamped to a heat sink. We find that during these pulses the lattice temperature of the thermistor apparently does not change. This surprising result is interpreted as evidence of a strong coupling between the high energy phonons generated by the interaction and the charge carriers in the thermistor. Additionally, these phonons appear to be absorbed within a fraction of a millimeter. We conclude that these thermistors have several desirable properties for a good high energy phonon sensor. It remains to be seen, however, if a composite detector consisting of a large crystal and attached phonon sensors can be developed. 15 refs., 9 figs.

  14. Thermistor Characteristics and Stability.

    ERIC Educational Resources Information Center

    Fricker, H. S.

    1987-01-01

    Discusses the uses of thermistors in teaching electronics and semiconductors. Describes how to experimentally measure and graph the characteristics of a thermistor. Suggests one possible approach to understand the shapes of the characteristics. (CW)

  15. Thermistor mount efficiency calibration

    SciTech Connect

    Cable, J.W.

    1980-05-01

    Thermistor mount efficiency calibration is accomplished by use of the power equation concept and by complex signal-ratio measurements. A comparison of thermistor mounts at microwave frequencies is made by mixing the reference and the reflected signals to produce a frequency at which the amplitude and phase difference may be readily measured.

  16. SSPX thermistor system

    SciTech Connect

    Thomassen, K I

    2000-11-29

    The SSPX Thermistor is a glass encapsulated bead thermistor made by Thermometrics, a BR 14 P A 103 J. The BR means ruggedized bead structure, 14 is the nominal bead diameter in mils, P refers to opposite end leads, A is the material system code letter, 103 refers to its 10 k{Omega} zero-power resistance at 25 C, and the tolerance letter J indicates {+-} 5% at 25 C. It is football shaped, with height ->, and is viewed through a slot of height h = 0.01 inches. The slot is perpendicular to the long axis of the bead, and is a distance s {approx} 0.775 cm in front of the thermistor. So plasma is viewed over a large angle along the slot, but over a small angle {alpha} perpendicular to the slot. The angle {alpha} is given by 2s tan{alpha} = -> + h.

  17. A Thermistor Interface.

    ERIC Educational Resources Information Center

    Kamin, Gary D.; Dowden, Edward

    1987-01-01

    Describes the use of a precalibrated stainless steel thermistor, interfaced with an Apple computer, in chemistry experiments. Discusses the advantages of "instant" temperature readings in experiments requiring that readings be taken at certain intervals. Outlines such an experiment which investigates freezing point depressions. (TW)

  18. X-ray microcalorimeters with germanium resistance thermometers

    SciTech Connect

    Labov, S.; Silver, E.; Pfafman, T.; Wai, Y. ); Beeman, J.; Goulding, F.; Landis, D.; Madden, N.; Haller, E. )

    1990-08-13

    We report on the current of our work on x-ray microcalorimeters for use as high resolution x-ray spectrometers. To maximize the x-ray collecting area and the signal to noise ratio, the total heat capacity of the device must be minimized. This is best achieved if the calorimeter is divided into two components, a thermal sensor and an x-ray absorber. The thermal sensor is a neutron transmutation doped (NTD) germanium resistor made as small as possible to minimize the heat capacity of the calorimeter. The thermistor can be attached to a thin x-ray absorber with large area and low heat capacity fabricated from superconducting materials such as niobium. We discuss results from our most recent studies of such superconducting absorbers and present the x-ray spectra obtained with these composite microcalorimeters at a temperature of 0.1 K. An energy resolution of 19 eV FWHM has been measured. 14 refs., 3 figs.

  19. The NTD Nanoscope: potential applications and implementations

    PubMed Central

    2011-01-01

    Background Nanopore transduction detection (NTD) offers prospects for a number of highly sensitive and discriminative applications, including: (i) single nucleotide polymorphism (SNP) detection; (ii) targeted DNA re-sequencing; (iii) protein isoform assaying; and (iv) biosensing via antibody or aptamer coupled molecules. Nanopore event transduction involves single-molecule biophysics, engineered information flows, and nanopore cheminformatics. The NTD Nanoscope has seen limited use in the scientific community, however, due to lack of information about potential applications, and lack of availability for the device itself. Meta Logos Inc. is developing both pre-packaged device platforms and component-level (unassembled) kit platforms (the latter described here). In both cases a lipid bi-layer workstation is first established, then augmentations and operational protocols are provided to have a nanopore transduction detector. In this paper we provide an overview of the NTD Nanoscope applications and implementations. The NTD Nanoscope Kit, in particular, is a component-level reproduction of the standard NTD device used in previous research papers. Results The NTD Nanoscope method is shown to functionalize a single nanopore with a channel current modulator that is designed to transduce events, such as binding to a specific target. To expedite set-up in new lab settings, the calibration and troubleshooting for the NTD Nanoscope kit components and signal processing software, the NTD Nanoscope Kit, is designed to include a set of test buffers and control molecules based on experiments described in previous NTD papers (the model systems briefly described in what follows). The description of the Server-interfacing for advanced signal processing support is also briefly mentioned. Conclusions SNP assaying, SNP discovery, DNA sequencing and RNA-seq methods are typically limited by the accuracy of the error rate of the enzymes involved, such as methods involving the polymerase

  20. Computed Tomography For Inspection Of Thermistors

    NASA Technical Reports Server (NTRS)

    Schaefer, Lloyd A.

    1991-01-01

    Computed tomography (CT) enables identification of cracked thermistors without disassembly of equipment containing them. CT unit used to scan equipment and locate thermistors. Further scans made in various radial orientations perpendicular to plane of devices to find cracks. Cracks invisible in conventional x-radiographs seen.

  1. MEMS Flow Sensors Based on Self-Heated aGe-Thermistors in a Wheatstone Bridge.

    PubMed

    Talic, Almir; Cerimovic, Samir; Beigelbeck, Roman; Kohl, Franz; Sauter, Thilo; Keplinger, Franz

    2015-01-01

    A thermal flow transduction method combining the advantages of calorimetric and hot-film transduction principles is developed and analyzed by Finite Element Method (FEM) simulations and confirmed experimentally. The analyses include electrothermal feedback effects of current driven NTC thermistors. Four thin-film germanium thermistors acting simultaneously as heat sources and as temperature sensors are embedded in a micromachined silicon-nitride membrane. These devices form a self-heated Wheatstone bridge that is unbalanced by convective cooling. The voltage across the bridge and the total dissipated power are exploited as output quantities. The used thin-film thermistors feature an extremely high temperature sensitivity. Combined with properly designed resistance values, a power demand in sub-1mW range enables efficient gas-flow transduction, as confirmed by measurements. Two sensor configurations with different arrangements of the membrane thermistors were examined experimentally. Moreover, we investigated the influence of different layouts on the rise time, the sensitivity, and the usable flow range by means of two-dimensional finite element simulations. The simulation results are in reasonable agreement with corresponding measurement data confirming the basic assumptions and modeling approach. PMID:25928062

  2. MEMS Flow Sensors Based on Self-Heated aGe-Thermistors in a Wheatstone Bridge

    PubMed Central

    Talic, Almir; Cerimovic, Samir; Beigelbeck, Roman; Kohl, Franz; Sauter, Thilo; Keplinger, Franz

    2015-01-01

    A thermal flow transduction method combining the advantages of calorimetric and hot-film transduction principles is developed and analyzed by Finite Element Method (FEM) simulations and confirmed experimentally. The analyses include electrothermal feedback effects of current driven NTC thermistors. Four thin-film germanium thermistors acting simultaneously as heat sources and as temperature sensors are embedded in a micromachined silicon-nitride membrane. These devices form a self-heated Wheatstone bridge that is unbalanced by convective cooling. The voltage across the bridge and the total dissipated power are exploited as output quantities. The used thin-film thermistors feature an extremely high temperature sensitivity. Combined with properly designed resistance values, a power demand in sub-1mW range enables efficient gas-flow transduction, as confirmed by measurements. Two sensor configurations with different arrangements of the membrane thermistors were examined experimentally. Moreover, we investigated the influence of different layouts on the rise time, the sensitivity, and the usable flow range by means of two-dimensional finite element simulations. The simulation results are in reasonable agreement with corresponding measurement data confirming the basic assumptions and modeling approach. PMID:25928062

  3. Translational Activities to Enable NTD Vaccines.

    PubMed

    Gray, S A; Coler, R N; Carter, D; Siddiqui, A A

    2016-01-01

    There is an urgent need to develop new vaccines for tuberculosis, HIV/AIDS, and malaria, as well as for chronic and debilitating infections known as neglected tropical diseases (NTDs). The term "NTD" emerged at the beginning of the new millennium to describe a set of diseases that are characterized as (1) poverty related, (2) endemic to the tropics and subtropics, (3) lacking public health attention and inadequate industrial investment, (4) having poor research funding and a weak research and development (R&D) pipeline, (5) usually associated with high morbidity but low mortality, and (6) often having no safe and long-lasting treatment available. Many additional challenges to the current control and elimination programs for NTDs exist. These include inconsistent performance of diagnostic tests, regional differences in access to treatment and in treatment outcome, lack of integrated surveillance and vector/intermediate host control, and impact of ecological climatic changes particularly in regions where new cases are increasing in previously nonendemic areas. Moreover, the development of NTD vaccines, including those for schistosomiasis, leishmaniasis, leprosy, hookworm, and Chagas disease are being led by nonprofit product development partnerships (PDPs) working in partnership with academic and industrial partners, contract research organizations, and in some instances vaccine manufacturers in developing countries. In this review, we emphasize global efforts to fuel the development of NTD vaccines, the translational activities needed to effectively move promising vaccine candidates to Phase-I clinical trials and some of the hurdles to ensuring their availability to people in the poorest countries of Africa, Asia, Latin America, and the Caribbean. PMID:27571699

  4. Stretchable graphene thermistor with tunable thermal index.

    PubMed

    Yan, Chaoyi; Wang, Jiangxin; Lee, Pooi See

    2015-02-24

    Stretchable graphene thermistors with intrinsic high stretchability were fabricated through a lithographic filtration method. Three-dimensional crumpled graphene was used as the thermal detection channels, and silver nanowires were used as electrodes. Both the detection channel and electrodes were fully embedded in an elastomer matrix to achieve excellent stretchability. Detailed temperature sensing properties were characterized at different strains up to 50%. It is evident that the devices can maintain their functionalities even at high stretched states. The devices demonstrated strain-dependent thermal indices, and the sensitivity of the thermistors can be effectively tuned using strain. The unique tunable thermal index is advantageous over conventional rigid ceramic thermistors for diverse and adaptive applications in wearable electronics. PMID:25671368

  5. Thermistor holder for skin-temperature measurements

    NASA Technical Reports Server (NTRS)

    Greenleaf, J. E.; Williams, B. A.

    1974-01-01

    Sensing head of thermistor probe is supported in center area of plastic ring which has tabs so that it can be anchored in place by rubber bands or adhesive tapes. Device attaches probes to human subjects practically, reliably, and without affecting characteristics of skin segment being measured.

  6. Development of NTD Ge Sensors for Superconducting Bolometer

    NASA Astrophysics Data System (ADS)

    Garai, A.; Mathimalar, S.; Singh, V.; Dokania, N.; Nanal, V.; Pillay, R. G.; Ramakrishnan, S.; Shrivastava, A.; Jagadeesan, K. C.; Thakare, S. V.

    2016-08-01

    Neutron transmutation-doped (NTD) Ge sensors have been prepared by irradiating device-grade Ge with thermal neutrons at Dhruva reactor, BARC, Mumbai. These sensors are intended to be used for the study of neutrinoless double beta decay in ^{124}Sn with a superconducting Tin bolometer. Resistance measurements are performed on NTD Ge sensors in the temperature range 100-350 mK. The observed temperature dependence is found to be consistent with the variable-range hopping mechanism.

  7. An Inexpensive Thermistor Thermometer for Beginning Chemistry Laboratories.

    ERIC Educational Resources Information Center

    Srivastava, Shyam B.; Meloan, Clifton E.

    1984-01-01

    The design and use of an inexpensive thermistor thermometer is described. In addition to providing a rugged thermometer, using the instruments offers an opportunity to have students become familiar with new principles and techniques, such as principles of thermistors, the Wheatstone bridge, and the concept of calibration. (JN)

  8. Preliminary estimates of radiosonde thermistor errors

    NASA Technical Reports Server (NTRS)

    Schmidlin, F. J.; Luers, J. K.; Huffman, P. D.

    1986-01-01

    Radiosonde temperature measurements are subject to errors, not the least of which is the effect of long- and short-wave radiation. Methods of adjusting the daytime temperatures to a nighttime equivalent are used by some analysis centers. Other than providing consistent observations for analysis this procedure does not provide a true correction. The literature discusses the problem of radiosonde temperature errors but it is not apparent what effort, if any, has been taken to quantify these errors. To accomplish the latter, radiosondes containing multiple thermistors with different coatings were flown at Goddard Space Flight Center/Wallops Flight Facility. The coatings employed had different spectral characteristics and, therefore, different adsorption and emissivity properties. Discrimination of the recorded temperatures enabled day and night correction values to be determined for the US standard white-coated rod thermistor. The correction magnitudes are given and a comparison of US measured temperatures before and after correction are compared with temperatures measured with the Vaisala radiosonde. The corrections are in the proper direction, day and night, and reduce day-night temperature differences to less than 0.5 C between surface and 30 hPa. The present uncorrected temperatures used with the Viz radiosonde have day-night differences that exceed 1 C at levels below 90 hPa. Additional measurements are planned to confirm these preliminary results and determine the solar elevation angle effect on the corrections. The technique used to obtain the corrections may also be used to recover a true absolute value and might be considered a valuable contribution to the meteorological community for use as a reference instrument.

  9. Used to Calibrate Thermistors on In Situ Permeable Flow Sensors

    Energy Science and Technology Software Center (ESTSC)

    1996-12-01

    The software package is comprised of three programs which together are used to calibrate thermistors in an In Situ Permable Flow Sensor. TBATH controls a temperature controlled bath/circulator. The code monitors the temperature of a set of previously calibrated thermistors located in a tank through which the fluid from the bath is circulated. After the temperature has reached and maintained thermal equilibrium for a specified period of time, the bath/circulator is instructed by the programmore » to change the temperature set point to the next specified temperature. An arbitrary number of temperature calibration points can be specified allowing thermistors to be calibrated on a continuous basis without human intervention. CALIB is used to merge two data files that are collected during a temperature calibration run. During calibration of the thermistors on an In Situ Permeable Flow Sensor, the known temperatures in the temperaure controlled tank are recorded in one computer file in one format while the electrical resistance of the thermistors being calibrated is collected in a different file with a different format. This software reads in the two files and writes out a third file with all of the data in it that is required to calculate the calibration coefficients of the thermistors on the probe. POLYFIT is used to calculate the calibration coefficients which permit the temperature of a thermistor to ba calculated from its electrical resistance. During calibration of a thermistor, the electrical resistance of the thermistor is measured at four or more known temperatures and the data sent to this software. The program calculates the coefficients of a fourth order polynomial relating the inverse of the absolute temperature to the natural log of the electrical resistance. Once these coefficients are known, the polynomial can be evaluated with any measured electrical resistance to calculate the equivalent temperature.« less

  10. Laboratory Astrophysics and Microanalysis with NTD-Germanium-Based X-Ray Microcalorimeter

    NASA Technical Reports Server (NTRS)

    Silver, E.; Schnopper, H.; Bandler, S.; Murray, S.; Madden, N.; Landis, D.; Beeman, J.; Haller, E.; Barbera, M.; Tucker, G.

    2000-01-01

    With the ability to create cosmic plasma conditions in the laboratory it is possible to investigate the dependencies of key diagnostic X-ray lines on density, temperature, and excitation conditions that exist in astrophysical sources with X-ray optics and a high resolution x-ray microcalorimeter. The same instrumentation can be coupled to scanning electron microscopes or x-ray fluorescence probes to analyze the elemental and chemical composition of electronic, biological, geological and particulate materials. We describe how our microcalorimeter and x-ray optics provide significantly improved capabilities for laboratory astrophysics and microanalysis.

  11. Flexible miniaturized nickel oxide thermistor arrays via inkjet printing technology.

    PubMed

    Huang, Chun-Chih; Kao, Zhen-Kai; Liao, Ying-Chih

    2013-12-26

    In this study, an inkjet printing process was developed to produce thermistor arrays for temperature sensing applications. First, a formulation process was carefully performed to generate a stable nanoparticle ink for nickel oxide, a material with a large temperature coefficient of resistance. The thermistor was then fabricated by printing a square NiO thin film in between two parallel silver conductive tracks on either glass plates or polyimide films. The printed thermistor, which has an adjustable dimension with a sub-millimeter scale, can operate over a wide range from room temperature to 200 °C with great sensitivity (B values ~4300 K) without hysteretic effects. When printed on polyimide films, the thermistors can also be bent or attached to curved surfaces to provide accurate and reliable temperature measurements. Moreover, the thermistor responds quickly to small temperature changes and provides an effective tool for transient temperature measurements. Finally, a thermistor array was fabricated to show the flexibility of this inkjet printing process and to demonstrate the applicability of the printed devices for temperature sensing applications. PMID:24298996

  12. Thermistors Used in Climatic Chamber at High Temperature and Humidity

    NASA Astrophysics Data System (ADS)

    van Geel, J. L. W. A.; Bosma, R.; van Wensveen, J.; Peruzzi, A.

    2015-03-01

    In 2011, VSL initiated the development of a facility for a relative humidity between and for calibrating high-temperature relative humidity sensors at pressures other than atmospheric. The setup for calculating the relative humidity uses the dew-point temperature, measured by a chilled mirror hygrometer, and the temperature distribution in the chamber, measured by a series of thermistors. This paper describes the results of thermal tests performed on the thermistors to ensure that they meet the requirements of the humidity calibration facility. Different types of thermistors were evaluated up to , and the selected type showed a short-term drift of less than 2 mK. Exposure of these thermistors to temperatures up to gave an initial hysteresis of 40 mK, but after this initial hysteresis, the hysteresis, over the range from up to , was less than 10 mK. Use of a digital multimeter, with a low-power option, limited the self-heating of the thermistors, over the range from up to , to less than 5 mK. During use in the new setup, the thermistors were exposed to changing humidities between 1 %Rh and 90 %Rh and temperatures up to , showing drifts of less than 10 mK.

  13. Development of NTD-Ge Cryogenic Sensors in LUMINEU

    NASA Astrophysics Data System (ADS)

    Navick, Xavier-Francois; Bachelet, Cyril; Bouville, David; Coron, Noel; Devoyon, Laurent; Giuliani, Andrea; Gray, David; Hervé, Serge; Humbert, Vincent; Lemaitre, Mathieu; Loidl, Martin; de Marcillac, Pierre; Nones, Claudia; Pénichot, Yves; Redon, Thierry; René, Alexis; Rodrigues, Matias

    2016-07-01

    One of the goals of LUMINEU is to develop NTD-Ge sensors for various applications. The steps are to produce NTD-Ge sensors first, then to study the dependence of their performance on the production parameters, and finally to optimize their electric contacts. In this paper, we present the different possibilities for estimating and measuring the real neutron fluence received by each Ge wafer irradiated in a thermal neutron reactor. Measurements of their resistivity at 300 K indicate a fluence discrepancy from the expected value and confirm the homogeneity of the doping throughout the volume. In addition, we present a method allowing an improved estimation of the impedance below 30 mK just by measuring the ratio of the NTDs' resistivity at 77 and 4 K.

  14. Construction and Characterization of NTC Thermistors at Low Temperature

    NASA Astrophysics Data System (ADS)

    Lan, Yuqi; Yu, Lihong; Chen, Guangming; Yang, Sifeng; Chang, Aimin

    2010-09-01

    Nano-powder of a negative temperature coefficient (NTC) ceramic with a spinel structure of Mn-Ni-Cu-Co-La-O composition was prepared by the Pechini method. A type of NTC thermistor sensor (3.0 mm diameter × 1.5 mm high) was designed by the in situ lead wire attachment method (ISAM) and made using the synthesized powder. NTC thermistors were packed in the glass-sealed package. Six independent NTC thermistors were calibrated using a cryostat, a standard platinum resistance thermometer, and a Fluke 1590 super thermometer meter over the temperature range from 18 K to 120 K. The data were interpolated to obtain calibration tables at 2 K intervals from 18 K to 30 K, and at 5 K intervals from 30 K to 120 K. These tables were fitted with the equation: 1/ T = A 0 + A 1 ln( R/ R ref) + A 2 ln( R/ R ref)2 + A 3 ln( R/ R ref)3 + A 4 ln( R/ R ref)4. Aging, thermometric characteristics, fitting of calibrated data, stability of NTC thermistors, and the effect of a magnetic field on NTC thermistors were investigated.

  15. Temperature Errors in Linearizing Resistance Networks for Thermistors

    NASA Astrophysics Data System (ADS)

    White, D. R.

    2015-12-01

    It is well known that a single negative-temperature-coefficient thermistor can be linearized over a narrow temperature range by connecting a single resistor in parallel with the thermistor. With the linearizing resistor properly chosen for the operating temperature, the residual errors are proportional to the cube of the temperature range and have a peak value of about 0.2° C for a 30° C range. A greater range of temperatures can be covered or greater linearity be achieved by cascading thermistor-resistor combinations. This paper investigates the limits of the linearity performance of such networks by using interpolation to model their behavior. A simple formula is derived for estimating the residual non-linearity as a function of the number of thermistors, the temperature range covered by the network, and the constant characterizing the exponential temperature dependence of the thermistors. Numerical simulations are used to demonstrate the validity of the formula. Guidelines are also given for circuit topologies for realizing the networks, for optimizing the design of the networks, and for calculating the sensitivities to relative errors in the component values.

  16. Additive chemistry and distributions in NTD photoresist thin films

    NASA Astrophysics Data System (ADS)

    Thackeray, James; Hong, Chang-Young; Clark, Michael B.

    2016-03-01

    The lithographic performance of photoresists is a function of the vertical distribution of formulation components, such as photoacid generator (PAG) molecules, in photoresist thin films and how these components undergo chemical modification and migrate within the film during the lithography processing steps. This paper will discuss how GCIB-SIMS depth profiles were used to monitor the PAG and quencher base distributions before and after exposure and post-exposure bake processing steps for different PAG/photoresist formulations. The authors show that the use of surface active quencher in an NTD photoresist leads to better resist profiles, superior DOF and better OPC performance.

  17. Mechanical Equivalent of Heat--Software for a Thermistor

    ERIC Educational Resources Information Center

    Boleman, Michael

    2008-01-01

    The Mechanical Equivalent of Heat Apparatus from PASCO scientific provides the means for doing a simple experiment to determine the mechanical equivalent of heat, "J." A necessary step of this experiment is to determine the temperature of an aluminum cylinder. By measuring the resistance of a thermistor embedded in the cylinder, one is able to…

  18. A Hydrazine Leak Sensor Based on Chemically Reactive Thermistors

    NASA Technical Reports Server (NTRS)

    Davis, Dennis D.; Mast, Dion J.; Baker, David L.

    1999-01-01

    Leaks in the hydrazine supply system of the Shuttle APU can result in hydrazine ignition and fire in the aft compartment of the Shuttle. Indication of the location of a leak could provide valuable information required for operational decisions. WSTF has developed a small, single use sensor for detection of hydrazine leaks. The sensor is composed of a thermistor bead coated with copper(II) oxide (CuO) dispersed in a clay or alumina binder. The CuO-coated thermistor is one of a pair of closely located thermistors, the other being a reference. On exposure to hydrazine the CuO reacts exothermically with the hydrazine and increases the temperature of the coated-thermistor by several degrees. The temperature rise is sensed by a resistive bridge circuit and an alarm registered by data acquisition software. Responses of this sensor to humidity changes, hydrazine concentration, binder characteristics, distance from a liquid leak, and ambient pressure levels as well as application of this sensor concept to other fluids are presented.

  19. Conjugated polymer/graphene oxide nanocomposite as thermistor

    SciTech Connect

    Joshi, Girish M. Deshmukh, Kalim

    2015-06-24

    We demonstrated the synthesis and measurement of temperature dependent electrical resistivity of graphene oxide (GO) reinforced poly (3, 4 - ethylenedioxythiophene) - tetramethacrylate (PEDOTTMA)/Polymethylmethacrylate (PMMA) based nanocomposites. Negative temperature coefficient (NTC) was observed for 0.5, 1 % GO loading and the positive temperature coefficient (PTC) was observed for 1.5 and 2 % Go loading in the temperature (40 to 120 °C). The GO inducted nanocomposite perform as an excellent thermistor and suitable for electronic and sensor domain.

  20. Conjugated polymer/graphene oxide nanocomposite as thermistor

    NASA Astrophysics Data System (ADS)

    Joshi, Girish M.; Deshmukh, Kalim

    2015-06-01

    We demonstrated the synthesis and measurement of temperature dependent electrical resistivity of graphene oxide (GO) reinforced poly (3, 4 - ethylenedioxythiophene) - tetramethacrylate (PEDOTTMA)/Polymethylmethacrylate (PMMA) based nanocomposites. Negative temperature coefficient (NTC) was observed for 0.5, 1 % GO loading and the positive temperature coefficient (PTC) was observed for 1.5 and 2 % Go loading in the temperature (40 to 120 °C). The GO inducted nanocomposite perform as an excellent thermistor and suitable for electronic and sensor domain.

  1. Status of NTD Ge bolometer material and devices

    NASA Technical Reports Server (NTRS)

    Haller, E. E.; Haegel, N. M.; Park, I. S.

    1986-01-01

    The first IR Detector Technology Workshop took place at NASA Ames Research Center on July 12 and 13, 1983. The conclusions presented at that meeting are still valid. More was learned about the physics of hopping conduction at very low temperatures which will be important for bolometer design and operation at ever decreasing temperatures. Resistivity measurements were extended down to 50 mK. At such low temperatures, precise knowledge of the neutron capture cross sections sigma (sub n) of the various Ge isotopes is critical if one is to make an accurate prediction of the dopant concentrations and compensation, and therefore resistivity, that will result from a given irradiation. An empirical approach for obtaining the desired resistivity material is described and the process of conducting a set of experiments which will improve the knowledge of the effective sigma (sub n) values for a given location in a particular reactor is discussed. A wider range of NTD Ge samples is now available. Noise measurements on bolometers with ion implanted contacts show the no 1/f noise component appears down to 1 Hz and probably lower.

  2. Mechanistic insights into folate supplementation from Crooked tail and other NTD-prone mutant mice.

    PubMed

    Gray, Jason D; Ross, M Elizabeth

    2009-04-01

    Despite two decades of research since Smithells and colleagues began exploring its benefits, the mechanisms through which folic acid supplementation supports neural tube closure and early embryonic development are still unclear. The greatest progress toward a molecular-genetic understanding of folate effects on neural tube defect (NTD) pathogenesis has come from animal models. The number of NTD-associated mouse mutants accumulated and studied over the past decade has illuminated the complexity of both genetic factors contributing to NTDs and also NTD-gene interactions with folate metabolism. This article discusses insights gained from mouse models into how folate supplementation impacts neurulation. A case is made for renewed efforts to systematically screen the folate responsiveness of the scores of NTD-associated mouse mutations now identified. Designed after Crooked tail, supplementation studies of additional mouse mutants could build the molecular network maps that will ultimately enable tailoring of therapeutic regimens to individual families. PMID:19067399

  3. Unipolar memristive switching in bulk positive temperature coefficient ceramic thermistor

    NASA Astrophysics Data System (ADS)

    Wu, Hongya; Wang, Caihui; Fu, Hua; Zhou, Ji; Zheng, Shuzhi

    2016-01-01

    A memristive switching phenomena was investigated in macroscale bulk positive temperature coefficient (PTC) thermosensitive ceramics. (BaxSr1-x)TiO3, which is a well-known PTC thermistor, was taken as an example to analyze the memristive behavior of those macroscale bulk ceramics. Hysteretic current-voltage (I-V) characteristics, which are the features of memristor were obtained. The origin of the effect is attributed to the PTC thermosensitive characteristic of the bulk ceramics, and a switching mechanism driven by competing field-driven heat generation and heat dissipation was proposed.

  4. Investigation of electrical noise in selenium-immersed thermistor bolometers

    NASA Technical Reports Server (NTRS)

    Tarpley, J. L.; Sarmiento, P. D.

    1980-01-01

    The selenium immersed, thermistor bolometer, IR detector failed due to spurious and escalating electrical noise outburst as a function of time at elevated temperatures during routine ground based testing in a space simulated environment. Spectrographic analysis of failed bolometers revealed selenium pure zones in the insulating selenium arsenic (Se-As) glass film which surrounds the active sintered Mn, Ni, Co oxide flake. The selenium pure film was identified as a potentially serious failure mechanism. Significant changes were instituted in the manufacturing techniques along with more stringent process controls which eliminated the selenium pure film and successfully produced 22study bolometers.

  5. Novel DDR process and materials for front-edge NTD process

    NASA Astrophysics Data System (ADS)

    Shigaki, Shuhei; Takeda, Satoshi; Shibayama, Wataru; Onishi, Ryuji; Nakajima, Makoto; Sakamoto, Rikimaru

    2016-03-01

    We developed the novel process and material which can prevent the pattern collapse issue perfectly. The process was Dry Development Rinse (DDR) process, and the material used in this process was DDR Material (DDRM). DDRM was containing siloxane polymer which could be replaced the space area of the photo resist pattern. And finally, the reversed pattern would be created by dry etching process without any pattern collapse issue. This novel process was useful not only in positive tone development (PTD) process but also in negative tone development (NTD) process. We newly developed DDRM for NTD process. Novel DDRM consist of special polymer and it used organic solvent system. So, new DDRM showed no mixing property with NTD photo resist and it has enough etch selectivity against NTD photo resist. Image reversal was successfully achieved by combination of NTD process and DDR process keeping good pattern quality. Tone reverse pattern below hp 18nm was obtained without any pattern collapse issue, which couldn't be created by just using normal NTD process.

  6. Evaluation of lens heating effect in high transmission NTD processes at the 20nm technology node

    NASA Astrophysics Data System (ADS)

    Jeon, Bumhwan; Lee, Sam; Subramany, Lokesh; Li, Chen; Pal, Shyam; Meyers, Sheldon; Mehta, Sohan; Wei, Yayi; Cho, David R.

    2014-04-01

    The NTD (Negative Tone Developer) process has been embraced as a viable alternative to traditionally, more conventional, positive tone develop processes. Advanced technology nodes have necessitated the adopting of NTD processes to achieve such tight design specifications in critical dimensions. Dark field contact layers are prime candidates for NTD processing due to its high imaging contrast. However, reticles used in NTD processes are highly transparent. The transmission rate of those masks can be over 85%. Consequently, lens heating effects result in a non-trivial impact that can limit NTD usability in a high volume mass production environment. At the same time, Source Mask Optimized (SMO) freeform pupils have become popular. This can also result in untoward lens heating effects which are localized in the lens. This can result in a unique drift behavior with each Zernike throughout the exposing of wafers. In this paper, we present our experience and lessons learned from lens heating with NTD processes. The results of this study indicate that lens heating makes impact on drift behavior of each Zernike during exposure while source pupil shape make an impact on the amplitude of Zernike drift. Existing lens models should be finely tuned to establish the correct compensation for drift. Computational modeling for lens heating can be considered as one of these opportunities. Pattern shapes, such as dense and iso pattern, can have different drift behavior during lens heating.

  7. 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.

  8. 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.

  9. Thermistor based, low velocity isothermal, air flow sensor

    NASA Astrophysics Data System (ADS)

    Cabrita, Admésio A. C. M.; Mendes, Ricardo; Quintela, Divo A.

    2016-03-01

    The semiconductor thermistor technology is applied as a flow sensor to measure low isothermal air velocities (<2 ms-1). The sensor is subjected to heating and cooling cycles controlled by a multifunctional timer. In the heating stage, the alternating current of a main AC power supply source guarantees a uniform thermistor temperature distribution. The conditioning circuit assures an adequate increase of the sensors temperature and avoids the thermal disturbance of the flow. The power supply interruption reduces the consumption from the source and extends the sensors life time. In the cooling stage, the resistance variation of the flow sensor is recorded by the measuring chain. The resistive sensor parameters proposed vary significantly and feature a high sensitivity to the flow velocity. With the aid of a computer, the data transfer, storage and analysis provides a great advantage over the traditional local anemometer readings. The data acquisition chain has a good repeatability and low standard uncertainties. The proposed method measures isothermal air mean velocities from 0.1 ms-1 to 2 ms-1 with a standard uncertainty error less than 4%.

  10. Positive temperature coefficient thermistors based on carbon nanotube/polymer composites

    NASA Astrophysics Data System (ADS)

    Zeng, You; Lu, Guixia; Wang, Han; Du, Jinhong; Ying, Zhe; Liu, Chang

    2014-10-01

    In order to explore availability of carbon nanotube (CNT)-based positive temperature coefficient (PTC) thermistors in practical application, we prepared carbon nanotube (CNT) filled high density polyethylene (HDPE) composites by using conventional melt-mixing methods, and investigated their PTC effects in details. The CNT-based thermistors exhibit much larger hold current and higher hold voltage, increasing by 129% in comparison with the commercial carbon black (CB) filled HDPE thermistors. Such high current-bearing and voltage-bearing capacity for the CNT/HDPE thermistors is mainly attributed to high thermal conductivity and heat dissipation of entangled CNT networks. Moreover, the CNT/HDPE thermistors exhibit rapid electrical response to applied voltages, comparable to commercial CB-based thermistors. In light of their high current-bearing capacity and quick response, the CNT-based thermistors have great potential to be used as high-performance thermistors in practical application, especially in some critical circumstances of high temperature, large applied currents, and high applied voltages.

  11. Effects of inositol supplementation in a cohort of mothers at risk of producing an NTD pregnancy.

    PubMed

    Cavalli, Pietro; Tonni, Gabriele; Grosso, Enrico; Poggiani, Carlo

    2011-11-01

    Neural tube defects (NTDs), most commonly spina bifida and anencephaly, can be prevented with periconceptional intake of folic acid in about 70% of cases. Recurrence of NTDs despite supplementation of high dose of folic acid further suggests that a proportion of NTD cases might be resistant to folic acid. Moreover, heterogeneity of NTDs has been suggested in animal studies, indicating that only some sub-type of NTDs should be considered sensitive to folate intake. Inositol isomers (particularly myo- and chiro-inositol) can prevent folate-resistant NTDs in the curly-tail mutant mouse, suggesting that some cases of human NTDs might benefit from inositol supplementation. In humans, lower inositol blood concentration was found in pregnant women carrying NTD fetuses, whereas a periconceptional combination therapy with folic acid associated with inositol has been linked to normal live births, despite high NTD recurrence risk. Fifteen pregnancies from 12 Caucasian women from different parts of Italy with at least one previous NTD-affected pregnancy underwent periconceptional combined myo-inositol and folic acid supplementation. Maternal serum α-feto-protein levels were found in the normal range, and normal results on ultrasound examination were found in all the pregnancies that followed. No collateral effects or intense uterine contractions were demonstrated in this pilot study in any of the pregnancies after inositol supplementation, and seventeen babies were born without any type of NTD. PMID:21956977

  12. 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.

  13. Assessing female sexual arousal with the labial thermistor: response specificity and construct validity.

    PubMed

    Prause, N; Heiman, J R

    2009-05-01

    The labial thermistor offers several potential psychometric advantages over existing measures of female sexual response; however, the thermistor lacked data to support these presumed advantages, especially with respect to its discriminant validity. In this study, both the labial thermistor was worn simultaneously with the vaginal photoplethysmograph as women viewed films. They also indicated their level of subjective sexual arousal using a lever. The labial thermistor discriminated sexual from nonsexual arousing stimuli and was sensitive to different levels of sexual arousal. The correspondence of the instrument with subjective sexual arousal, measured using a continuous lever, was lower during the mildly arousing sexual film and higher during the maximally sexual arousing film. One woman reported that the labial thermistor was very uncomfortable, while others indicated no or mild discomfort from each instrument. The vaginal photoplethysmograph largely replicated the effects documented by the labial thermistor, although it did not discriminate sexual stimuli of different intensity nor correspond with women's continuous lever responses as closely during the more arousing stimulus. Difficulties recording simultaneously with these instruments are noted. The labial thermistor adequately discriminates between generally arousing and sexually arousing stimuli, increasing its utility as a measure for between-subject study designs. PMID:19041673

  14. Evaluation of insulated miniature thermistors for skin temperature measurement in the rat

    NASA Astrophysics Data System (ADS)

    Szlyk, Patricia C.; Sils, Ingrid V.; Ferguson, June D.; Matthew, William T.; Hubbard, Roger W.

    1986-08-01

    A miniature thermistor modified by covering its outer surface with insulating foam was evaluated as a temperature sensor at three skin sites in the adult male laboratory rat. A high precision thermistor was modified by covering the outer epoxy surface with about 1/4 inch of a commercially available insulating foam. Such foam thickness provided sufficient insulation to reduce the influence of ambient temperature on the thermistor reading yet contributed minimal additional probe weight. Results indicate that compared to the insulated thermistor, the uninsulated probe underestimated skin temperature measured at the midscapular region of the back, ventral surface of the foot, and dorsal base of the tail at cool ambient temperature (25c) and overestimated temperature at the back and tail skin sites at high ambient temperature (42c). The differences in temperature measured by the insulated and uninsulated thermistors were greastest at the back skin site, which was the only fur-covered and the least vascularized area of the rat that we studied. Using an insulated miniature thermistor to reduce the influence of environmental temperature on thermistor readings when measuring skin temperature in a furred laboratory animal is recommended.

  15. Fit for purpose: do we have the right tools to sustain NTD elimination?

    PubMed Central

    2015-01-01

    Priorities for NTD control programmes will shift over the next 10-20 years as the elimination phase reaches the ‘end game’ for some NTDs, and the recognition that the control of other NTDs is much more problematic. The current goal of scaling up programmes based on preventive chemotherapy (PCT) will alter to sustaining NTD prevention, through sensitive surveillance and rapid response to resurgence. A new suite of tools and approaches will be required for both PCT and Intensive Disease Management (IDM) diseases in this timeframe to enable disease endemic countries to: 1. Sensitively and sustainably survey NTD transmission and prevalence in order to identify and respond quickly to resurgence. 2. Set relevant control targets based not only on epidemiological indicators but also entomological and ecological metrics and use decision support technology to help meet those targets. 3. Implement verified and cost-effective tools to prevent transmission throughout the elimination phase. Liverpool School of Tropical Medicine (LSTM) and partners propose to evaluate and implement existing tools from other disease systems as well as new tools in the pipeline in order to support endemic country ownership in NTD decision-making during the elimination phase and beyond.

  16. Time-Separating Heating and Sensor Functions of Thermistors in Precision Thermal Control Applications

    NASA Technical Reports Server (NTRS)

    Cho, Hyung J.; Sukhatme, Kalyani G.; Mahoney, John C.; Penanen, Konstantin Penanen; Vargas, Rudolph, Jr.

    2010-01-01

    A method allows combining the functions of a heater and a thermometer in a single device, a thermistor, with minimal temperature read errors. Because thermistors typically have a much smaller thermal mass than the objects they monitor, the thermal time to equilibrate the thermometer to the temperature of the object is typically much shorter than the thermal time of the object to change its temperature in response to an external perturbation.

  17. Thin metal thermistors for shock temperature measurements of polymers

    NASA Astrophysics Data System (ADS)

    Taylor, N. E.; Williamson, D. M.; Picard, A.; Cunningham, L. K.; Jardine, A. P.

    2015-06-01

    Equations of state can be used to predict the relationship between pressure, volume and temperature. However, in shock physics, they are usually only constrained by experimental observations of pressure and volume. Direct observation of temperature in a shock is therefore valuable in constraining equations of state. Bloomquist and Sheffield (1980, 1981) and Rosenberg and Partom (1984) have attempted such observations in poly(methyl methacrylate) (PMMA). However, their results disagree strongly above 2 GPa shock pressure. The present authors previously presented an improved fabrication technique, to examine this outstanding issue. This technique made use of the fact that the electrical resistivity of most metals is a known function of both pressure and temperature. By fabricating a thin metal thermistor gauge and measuring its change in resistance during a shock experiment of known pressure, its temperature can be recovered. Heat transfer into the gauge depends strongly on the gauge dimensions and the thermal conductivity of the shocked PMMA. Here we present several improvements to the technique. By varying the gauge thickness over the range 100 nm to 10 μ m we assess the heat transfer into the gauge.

  18. 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.

  19. Electrical properties of neutron-transmutation-doped germanium

    SciTech Connect

    Rodder, M.

    1982-08-01

    Electrical properties of neutron-transmutation-doped germanium (NTD Ge) and nearly uncompensated gallium-doped germanium have been measured as functions of net-impurity concentration (2 x 10/sup 15/cm/sup -3/ less than or equal to N/sub A/ - N/sub D/ less than or equal to 5 x 10/sup 16/cm/sup -3/) and temperature (0.3 K less than or equal to T less than or equal to 300 K). The method of impurity conduction as a function of carrier concentration and compensation was investigated in the low temperature hopping regime. For nearest neighbor hopping, the resistivity is expected to vary as rho = rho/sub 0/exp(..delta../T) while Mott's theory of variable range hopping predicts that rho = rho/sub 0/exp(..delta../T)/sup 1/4/ in the low temperature limit. In contrast, our results show that the resistivity can best be approximated by rho = rho/sub 0/exp(..delta../T)/sup 1/2/ in the hopping regime down to 0.3 K.

  20. 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.

  1. Attractive mechanical properties of a lightweight highly sensitive bi layer thermistor: polycarbonate/organic molecular conductor

    NASA Astrophysics Data System (ADS)

    Laukhina, E.; Lebedev, V.; Rovira, C.; Laukhin, V.; Veciana, J.

    2016-03-01

    The paper covers some of the basic mechanical characteristics of a recently developed bi layer thermistor: polycarbonate/(001) oriented layer of organic molecular conductor α’-(BEDT-TTF)2IxBr3-x, were BEDT-TTF=bis(ethylenedithio)tetrathiafulvalen. The nano and macro mechanical properties have been studied in order to use this flexible, low cost thermistor in sensing applications by proper way. The nano-mechanical properties of the temperature sensitive semiconducting layer of α’-(BEDT-TTF)2IxBr3-x were tested using nanoindentation method. The value of Young's modulus in direction being perpendicular to the layer plan was found as 9.0 ±1.4 GPa. The macro mechanical properties of the thermistor were studied using a 5848 MicroTester. The tensile tests showed that basic mechanical characteristics of the thermistor are close to those of polycarbonate films. This indicates a good mechanical strength of the developed sensor. Therefore, the thermistor can be used in technologies that need to be instrumented with highly robustness lightweight low cost temperature sensors. The paper also reports synthetic details on fabricating temperature sensing e-textile. As the temperature control is becoming more and more important in biomedical technologies like healthcare monitoring, this work strongly contributes on the ongoing research on engineering sensitive conducting materials for biomedical applications.

  2. Advanced patterning approaches based on negative-tone development (NTD) process for further extension of 193nm immersion lithography

    NASA Astrophysics Data System (ADS)

    Shirakawa, Michihiro; Inoue, Naoki; Furutani, Hajime; Yamamoto, Kei; Goto, Akiyoshi; Fujita, Mitsuhiro

    2015-03-01

    Two approaches which achieve the further evolution of NTD (Negative Tone Development) process are shown in this article. One is ACCEL (Advanced Chemical Contrast Enhancement Layer) process that can improve the lithography performance and the other is DTD (Dual Tone Development) process that can shrink patterning pitch below the limit of single exposure process. ACCEL is an additionally provided layer which is coated on a surface of NTD resist film before exposure and removed by NTD developer. ACCEL can enhance the acid distribution and dissolution contrast of the NTD resist. In fact, lithography performances such as exposure latitude (EL) and DOF improved dramatically by applying ACCEL compared to the NTD resist without ACCEL. We consider that suppression of excessive acid diffusion and material transfer between the resist layer and the ACCEL layer are the causes of the contrast enhancement. DTD process is one of the simplest pitch shrink method which is achieved by repeating PTD and NTD process. Feasibility study of DTD patterning has been demonstrated so far. However, Exposure latitude margin and CDU performance were not sufficient for applying DTD to HVM. We developed the novel DTD specific resist under a new concept, and 32 nm half pitch (hp) contact hole (CH) pattern was successfully formed with enough margins. DTD line and space (L/S) patterning are also demonstrated and 24 nm hp L/S pattern can be resolved. k1 factors of DTD CH and L/S patterns reach to 0.20 and 0.15, respectively.

  3. A Simple Experiment to Determine the Characteristics of an NTC Thermistor for Low-Temperature Measurement Applications

    ERIC Educational Resources Information Center

    Mawire, A.

    2012-01-01

    A simple low-cost experiment for undergraduate students to determine the characteristics of a negative temperature coefficient of resistance thermistor is presented. The experiment measures the resistance-temperature and voltage-temperature characteristics of the thermistor. Results of the resistance-temperature experiment are used to determine…

  4. 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.

  5. Conceptual design of experimental equipment for large-diameter NTD-Si.

    PubMed

    Yagi, M; Watanabe, M; Ohyama, K; Yamamoto, K; Komeda, M; Kashima, Y; Yamashita, K

    2009-01-01

    An irradiation-experimental equipment for 12in neutron transmutation doping silicon (NTD-Si) was designed conceptually by using MCNP5 in order to improve the neutron flux distribution of the radial direction. As a result of the calculations, the neutron absorption reaction ratio of the circumference to the center could be limited within 1.09 using a thermal neutron filter that covers the surface of the silicon ingot. The uniformity of the (30)Si neutron absorption was less than 5.3%. PMID:19299158

  6. Design and Development of Thermistor based Power Meter at 140 GHz Frequency Band

    NASA Astrophysics Data System (ADS)

    Roy, Rajesh; Kush, Abhimanyue Kumar; Dixit, Rajendra Prasad

    2011-12-01

    Design and development of thermistor based power meter at 140 gigahertz (GHz) frequency band have been presented. Power meter comprises power sensor, amplifier circuit and dialog based graphical user interface in visual C++ for the average power measurement. The output power level of a component or system is very critical design factor. Thus there was a need of a power meter for the development of millimeter wave components at 140 GHz frequency band. Power sensor has been designed and developed using NTC (Negative Temperature Coefficient) thermistors. The design aims at developing a direct, simple and inexpensive power meter that can be used to measure absolute power at 140 GHz frequency band. Due to absorption of 140 GHz frequencies, resistance of thermistor changes to a new value. This change in resistance of thermistor can be converted to a dc voltage change and amplified voltage change can be fed to computer through data acquisition card. Dialog based graphical user interface (GUI) has been developed in visual C++ language for average power measurement in dBm. WR6 standard rectangular waveguide is the input port for the sensor of power meter. Temperature compensation has been achieved. Moderate sensor return loss greater than 20 dB has been found over the frequency range 110 to 170 GHz. The response time of the power sensor is 10 second. Average power accuracy is better than ±0.25 dB within the power range from -10 to 10 dBm at 140 GHz frequency band.

  7. A Low-Cost Thermistor Device for Measurements of Metabolic Heat in Yeast Cells in Suspension.

    ERIC Educational Resources Information Center

    Keeling, Richard P.

    1980-01-01

    Provides illustrated directions for the construction and use of a low-cost thermistor device. Attached to a servo-type millivolt chart recorder, the device will record minute temperature changes and will simulate data obtained from an oxygen polarograph. Includes results of experiments with baker's yeast. (Author/CS)

  8. The Influence of Thermistor Location on Temperature Measurement from a Photonic Package

    NASA Astrophysics Data System (ADS)

    Eason, Cormac; Rensing, Marc; Lee, Jun Su; O'Brien, Peter

    2014-07-01

    This paper begins by describing some commonly used photonic packages. The requirements for optical connections to these packages are then discussed. Photonic packages are different to most electronic packages in that the thermal management requirements usually include maintaining the Photonic Integrated Circuit (PIC) at a fixed, sometimes below ambient, operating temperature rather than with keeping the temperature of a package below an upper limit as with most electronic packages. This means that an active Thermoelectric Module (TEM) based cooling system is required. A thermistor is fitted within the package to provide thermal feedback to the TEM controller. This paper uses finite element modelling to investigate whether there is a good match between the target temperature for the PIC and the temperature registered by the thermistor. The results of the modelling show that the model results are quite stable even with large variations in convection and thermistor thermal properties. The thermistor location influences the temperature measured from the package and its thermal response time, but follows the device temperature well enough to provide the TEM controller with adequate feedback to maintain the PIC at a steady temperature in steady state running conditions.

  9. Germanium: An aqueous processing review

    SciTech Connect

    Lier, R.J.M. van; Dreisinger, D.B.

    1995-08-01

    In industrial aqueous solutions, germanium generally occurs in trace amounts amid high concentrations of other metals, such as zinc, copper and iron. Separation of germanium from these metals as well as its isolation from gallium and indium pose a real challenge to the hydrometallurgist. After a brief discussion of the aqueous chemistry of germanium, this paper reviews the flowsheet of the Apex Mine in Utah. The Apex property was the only mine in the world to be operated primarily for production of gallium and germanium, but apparently closed due to great operating difficulties. Several process variants proposed for the treatment of the Apex ore, including bioleaching methods, are addressed. Following a more general description of the behavior of germanium in hydrometallurgical zinc processing streams, available technology for its recovery from aqueous solutions is summarized. Precipitation, solvent extraction, ion exchange, electrowinning, ion flotation and liquid-membrane separation are all outlined in terms of the aqueous chemistry of germanium. Finally, the production of high purity germanium dioxide and metal is briefly discussed. 61 refs.

  10. 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

  11. 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.

  12. The Structure of NtdA, a Sugar Aminotransferase Involved in the Kanosamine Biosynthetic Pathway in Bacillus subtilis, Reveals a New Subclass of Aminotransferases*

    PubMed Central

    van Straaten, Karin E.; Ko, Jong Bum; Jagdhane, Rajendra; Anjum, Shazia; Palmer, David R. J.; Sanders, David A. R.

    2013-01-01

    NtdA from Bacillus subtilis is a sugar aminotransferase that catalyzes the pyridoxal phosphate-dependent equatorial transamination of 3-oxo-α-d-glucose 6-phosphate to form α-d-kanosamine 6-phosphate. The crystal structure of NtdA shows that NtdA shares the common aspartate aminotransferase fold (Type 1) with residues from both monomers forming the active site. The crystal structures of NtdA alone, co-crystallized with the product α-d-kanosamine 6-phosphate, and incubated with the amine donor glutamate reveal three key structures in the mechanistic pathway of NtdA. The structure of NtdA alone reveals the internal aldimine form of NtdA with the cofactor pyridoxal phosphate covalently attached to Lys-247. The addition of glutamate results in formation of pyridoxamine phosphate. Co-crystallization with kanosamine 6-phosphate results in the formation of the external aldimine. Only α-d-kanosamine 6-phosphate is observed in the active site of NtdA, not the β-anomer. A comparison of the structure and sequence of NtdA with other sugar aminotransferases enables us to propose that the VIβ family of aminotransferases should be divided into subfamilies based on the catalytic lysine motif. PMID:24097983

  13. 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

  14. Nitrogen in germanium

    NASA Astrophysics Data System (ADS)

    Chambouleyron, I.; Zanatta, A. R.

    1998-07-01

    The known properties of nitrogen as an impurity in, and as an alloy element of, the germanium network are reviewed in this article. Amorphous and crystalline germanium-nitrogen alloys are interesting materials with potential applications for protective coatings and window layers for solar conversion devices. They may also act as effective diffusion masks for III-V electronic devices. The existing data are compared with similar properties of other group IV nitrides, in particular with silicon nitride. To a certain extent, the general picture mirrors the one found in Si-N systems, as expected from the similar valence structure of both elemental semiconductors. However, important differences appear in the deposition methods and alloy composition, the optical properties of as grown films, and the electrical behavior of nitrogen-doped amorphous layers. Structural studies are reviewed, including band structure calculations and the energies of nitrogen-related defects, which are compared with experimental data. Many important aspects of the electronic structure of Ge-N alloys are not yet completely understood and deserve a more careful investigation, in particular the structure of defects associated with N inclusion. The N doping of the a-Ge:H network appears to be very effective, the activation energy of the most effectively doped samples becoming around 120 meV. This is not the case with N-doped a-Si:H, the reasons for the difference remaining an open question. The lack of data on stoichiometric β-Ge3N4 prevents any reasonable assessment on the possible uses of the alloy in electronic and ceramic applications.

  15. 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.

  16. Are infrared and thermistor thermometers interchangeable for measuring localized skin temperature?

    PubMed

    Kelechi, Teresa J; Michel, Yvonne; Wiseman, Jan

    2006-01-01

    Localized skin temperature must be measured by accurate and reliable thermometers to effectively evaluate treatment outcomes, monitor changes, and predict potential complications. This study compared localized skin temperature measurements with a contact thermistor thermometer used as a reference standard and a noncontact infrared (IR) skin thermometer to determine their interchangeability with calculated Bland-Altman limits of agreement. Fifty-five adults ages 50 to 89 participated in the study in which data were collected in a climate-controlled room over 3 measurement periods, 1 week apart. The thermistor and IR thermometers were interchangeable with a limit of agreement of +/- 1.5 degrees C. This limit of agreement is acceptable as a reference standard for IR thermometers to measure localized skin temperature in clinical settings. PMID:16764175

  17. Measurement of isotope separation factors in the palladium-hydrogen system using a thermistor technique

    SciTech Connect

    Ortiz, T.M.

    1998-05-01

    The range of available data on separation factors in the palladium-hydrogen/deuterium system has been extended. A matched pair of glass-coated bead thermistors was used to measure gas phase compositions. The compositions of the input gas--assumed also to be the solid phase composition--were measured independently be mass spectrometry as being within 0.5 mole% of the values used to calibrate the thermistors. This assumption is based on the fact that > 99% of the input gas is absorbed into the solid. Separation factors were measured for 175 K {le} T {le} 389 K and for 0.195 {le} x{sub H} {le} 0.785.

  18. Determination of the detection threshold for Polyethylene Terephthalate (PET) Nuclear Track Detector (NTD)

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, R.; Dey, S.; Ghosh, Sanjay K.; Maulik, A.; Raha, Sibaji; Syam, D.

    2016-03-01

    In this work we investigated the detection threshold of the polymer material Polyethylene Terephthalate (PET) intended to be used as Nuclear Track Detector (NTD) in the search for rare events (e.g. strangelets) in cosmic rays. 11 MeV 12C and 2 MeV proton beams from the accelerator at the Institute of Physics (IOP), Bhubaneswar were utilized for this study. The results show that the PET detector has a much higher detection threshold (Z / β ∼ 140) compared to many other commercially available and widely used detector materials like CR-39 (Z / β ∼ 6-20) or Makrofol (Z / β ∼ 57). This makes PET a particularly suitable detector material for testing certain phenomenological models which predict the presence of strangelets as low energy, heavily ionizing particles in cosmic radiation at high mountain altitudes.

  19. The ability to create NTD silicon technology in the IRT-T reactor in a horizontal experimental channel with one-side access

    NASA Astrophysics Data System (ADS)

    Varlachev, V. A.; Golovatsky, A. V.; Emets, E. G.; Butko, Ya A.

    2016-06-01

    The article shows the ability of creation of neutron transmutation doping (NTD) of monocrystalline silicon technology in the reactor's channel, which has a one-side access. In the article a distribution of thermal neutron flux through the length of channel and it's radius, neutron spectrum were obtained which confirmed that horizontal experimental channel HEC-1 is suitable for NTD.

  20. 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. PMID:20230043

  1. Investigation of the difficulties associated with the use of lead telluride and other II - IV compounds for thin film thermistors

    NASA Technical Reports Server (NTRS)

    Mclennan, W. D.

    1975-01-01

    The fabrication of thermistors was investigated for use as atmospheric temperature sensors in meteorological rocket soundings. The final configuration of the thin film thermistor is shown. The composition and primary functions of the six layers of the sensor are described. A digital controller for thin film deposition control is described which is capable of better than .1 A/sec rate control. The computer program modules for digital control of thin film deposition processing are included.

  2. [Expiratory ventilation and carbon dioxide production measured with a thermistor flow-through system].

    PubMed

    Nagashima, T

    1996-03-01

    A thermistor flow-through system for measuring expiratory volume without a mouthpiece and a nose clip was developed. First, a thermostat and a large syringe were connected to a box used to stimulate a subject's head. A carbon dioxide (CO2) gas mixture was driven through the box, while the output of a thermistor sensor of the thermistor flow-through system was recorded. The correlation between the area under the temperature-time curve and the actual volume of gas driven through the box was computed. Second, the effects of driving time, gas temperature, and room temperature on the area under the temperature-time curve were measured. Third, corrections for expiratory time and for the temperature of exhaled gas were derived from regression analysis of the relation between the time taken to drive the CO2 gas mixture and the area under the temperature-time curve, and between the temperature of the CO2 gas mixture and the area under the temperature-time curve, respectively. Fourth, CO2 production was computed from the area under the CO2 concentration-time curve (obtained at the same time as the temperature-time curve). To measure the temperature-time curve and the CO2-time curve for the simulator, the box was placed under the transparent hood of the thermistor flow-through system. To measure the temperature-time and CO2-time curves for a subject, the head was placed in the hood while the subject was supine. The subject breathed with the mouth held slightly open, and the mixture of room air and expired gas was continuously drawn at a constant flow through an outlet at the top of the hood. The outlet was connected to a flow meter and to a constant-speed blower. The CO2 concentration and the temperature in the hood exhaust were measured at the outlet, and were continuously recorded with a chart recorder. To measure the actual volume of CO2, a Douglas bag was also used, and was connected to the blower. Increases in the driving time and in gas temperature caused increases in

  3. 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.

  4. 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.

  5. Layout optimization of DRAM cells using rigorous simulation model for NTD

    NASA Astrophysics Data System (ADS)

    Jeon, Jinhyuck; Kim, Shinyoung; Park, Chanha; Yang, Hyunjo; Yim, Donggyu; Kuechler, Bernd; Zimmermann, Rainer; Muelders, Thomas; Klostermann, Ulrich; Schmoeller, Thomas; Do, Mun-hoe; Choi, Jung-Hoe

    2014-03-01

    DRAM chip space is mainly determined by the size of the memory cell array patterns which consist of periodic memory cell features and edges of the periodic array. Resolution Enhancement Techniques (RET) are used to optimize the periodic pattern process performance. Computational Lithography such as source mask optimization (SMO) to find the optimal off axis illumination and optical proximity correction (OPC) combined with model based SRAF placement are applied to print patterns on target. For 20nm Memory Cell optimization we see challenges that demand additional tool competence for layout optimization. The first challenge is a memory core pattern of brick-wall type with a k1 of 0.28, so it allows only two spectral beams to interfere. We will show how to analytically derive the only valid geometrically limited source. Another consequence of two-beam interference limitation is a "super stable" core pattern, with the advantage of high depth of focus (DoF) but also low sensitivity to proximity corrections or changes of contact aspect ratio. This makes an array edge correction very difficult. The edge can be the most critical pattern since it forms the transition from the very stable regime of periodic patterns to non-periodic periphery, so it combines the most critical pitch and highest susceptibility to defocus. Above challenge makes the layout correction to a complex optimization task demanding a layout optimization that finds a solution with optimal process stability taking into account DoF, exposure dose latitude (EL), mask error enhancement factor (MEEF) and mask manufacturability constraints. This can only be achieved by simultaneously considering all criteria while placing and sizing SRAFs and main mask features. The second challenge is the use of a negative tone development (NTD) type resist, which has a strong resist effect and is difficult to characterize experimentally due to negative resist profile taper angles that perturb CD at bottom characterization by

  6. Th and U fuel photofission study by NTD for AD-MSR subcritical assembly

    NASA Astrophysics Data System (ADS)

    Sajo-Bohus, Laszlo; Greaves, Eduardo D.; Davila, Jesus; Barros, Haydn; Pino, Felix; Barrera, Maria T.; Farina, Fulvio

    2015-07-01

    During the last decade a considerable effort has been devoted for developing energy generating systems based on advanced nuclear technology within the design concepts of GEN-IV. Thorium base fuel systems such as accelerator driven nuclear reactors are one of the often mentioned attractive and affordable options. Several radiotherapy linear accelerators are on the market and due to their reliability, they could be employed as drivers for subcritical liquid fuel assemblies. Bremsstrahlung photons with energies above 5.5MeV, induce (γ,n) and (e,e'n) reactions in the W-target. Resulting gamma radiation and photo or fission neutrons may be absorbed in target materials such as thorium and uranium isotopes to induce sustained fission or nuclear transmutation in waste radioactive materials. Relevant photo driven and photo-fission reaction cross sections are important for actinides 232Th, 238U and 237Np in the radiotherapy machines energy range of 10-20 MV. In this study we employ passive nuclear track detectors (NTD) to determine fission rates and neutron production rates with the aim to establish the feasibility for gamma and photo-neutron driven subcritical assemblies. To cope with these objectives a 20 MV radiotherapy machine has been employed with a mixed fuel target. Results will support further development for a subcritical assembly employing a thorium containing liquid fuel. It is expected that acquired technological knowledge will contribute to the Venezuelan nuclear energy program.

  7. Th and U fuel photofission study by NTD for AD-MSR subcritical assembly

    SciTech Connect

    Sajo-Bohus, Laszlo; Greaves, Eduardo D.; Barros, Haydn; Pino, Felix; Barrera, Maria T.; Farina, Fulvio; Davila, Jesus

    2015-07-23

    During the last decade a considerable effort has been devoted for developing energy generating systems based on advanced nuclear technology within the design concepts of GEN-IV. Thorium base fuel systems such as accelerator driven nuclear reactors are one of the often mentioned attractive and affordable options. Several radiotherapy linear accelerators are on the market and due to their reliability, they could be employed as drivers for subcritical liquid fuel assemblies. Bremsstrahlung photons with energies above 5.5MeV, induce (γ,n) and (e,e’n) reactions in the W-target. Resulting gamma radiation and photo or fission neutrons may be absorbed in target materials such as thorium and uranium isotopes to induce sustained fission or nuclear transmutation in waste radioactive materials. Relevant photo driven and photo-fission reaction cross sections are important for actinides {sup 232}Th, {sup 238}U and {sup 237}Np in the radiotherapy machines energy range of 10-20 MV. In this study we employ passive nuclear track detectors (NTD) to determine fission rates and neutron production rates with the aim to establish the feasibility for gamma and photo-neutron driven subcritical assemblies. To cope with these objectives a 20 MV radiotherapy machine has been employed with a mixed fuel target. Results will support further development for a subcritical assembly employing a thorium containing liquid fuel. It is expected that acquired technological knowledge will contribute to the Venezuelan nuclear energy program.

  8. Thermistor guided radiofrequency ablation of atrial insertion sites in patients with accessory pathways.

    PubMed

    Tracy, C M; Moore, H J; Solomon, A J; Rodak, D J; Fletcher, R D

    1995-11-01

    Radiofrequency ablation has gained acceptance in the treatment of patients with symptomatic Wolff-Parkinson-White syndrome. The purpose of this study was to characterize the relation between temperature and other electroconductive parameters in patients undergoing atrial insertion accessory pathway ablation utilizing a thermistor equipped catheter. The mean temperature and power at sites of atrial insertion ablation are lower than has been previously associated with creation of radiofrequency lesions in the ventricle. While high cavitary blood flow in the atrium may result in cooling, the thinner atrial tissue may require less energy to achieve adequate heating than ventricular myocardium. PMID:8552513

  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. The NTD-CTD intersubunit interface plays a critical role in assembly and stabilization of the HIV-1 capsid

    PubMed Central

    2013-01-01

    Background Lentiviruses exhibit a cone-shaped capsid composed of subunits of the viral CA protein. The intrinsic stability of the capsid is critical for HIV-1 infection, since both stabilizing and destabilizing mutations compromise viral infectivity. Structural studies have identified three intersubunit interfaces in the HIV-1 capsid, two of which have been previously studied by mutational analysis. In this present study we analyzed the role of a third interface, that which is formed between the amino terminal domain (NTD) and carboxyl terminal domain (CTD) of adjacent subunits. Results We provided evidence for the presence of the NTD-CTD interface in HIV-1 particles by engineering intersubunit NTD-CTD disulfide crosslinks, resulting in accumulation of disulfide-linked oligomers up to hexamers. We also generated and characterized a panel of HIV-1 mutants containing substitutions at this interface. Some mutants showed processing defects and altered morphology from that of wild type, indicating that the interface is important for capsid assembly. Analysis of these mutants by transmission electron microscopy corroborated the importance of this interface in assembly. Other mutants exhibited quantitative changes in capsid stability, many with unstable capsids, and one mutant with a hyperstable capsid. Analysis of the mutants for their capacity to saturate TRIMCyp-mediated restriction in trans confirmed that the unstable mutants undergo premature uncoating in target cells. All but one of the mutants were markedly attenuated in replication owing to impaired reverse transcription in target cells. Conclusions Our results demonstrate that the NTD-CTD intersubunit interface is present in the mature HIV-1 capsid and is critical for proper capsid assembly and stability. PMID:23497318

  11. X-Ray Micro-Calorimeter Based on Si Thermistors for X-Ray Astronomy: Design and First Measurements

    NASA Astrophysics Data System (ADS)

    Aliane, A.; de Moro, F.; Pigot, C.; Agnese, P.; de La Broïse, X.; Gasse, A.; Navick, X.-F.; Karolak, M.; Ribot, H.; Sauvageot, J.-L.; Szeflinski, V.; Gobil, Y.; Renaud, D.; Rivallin, P.; Geoffray, H.

    2008-04-01

    X-ray Astronomy provides a unique window on a wide variety of astrophysical phenomena. The currently operating X-ray space observatories perform X-ray spectral imaging with the use of CCDs. When available, cryogenic X-ray microcalorimeter arrays will far outperform CCDs in terms of spectral resolution, energy bandwidth and count rate. Experience has been gained with Infra-Red bolometer arrays at CEA-LETI (Grenoble) in collaboration with the CEA-SAp (Saclay); taking advantage of this background, we are now developing an X-ray spectro-imaging camera for the next generation space astronomy missions, using silicon technology (implanted and high temperature diffused thermistors). Each pixel of this array detector is made of a tantalum absorber bound, by indium bump hybridization, to a silicon thermistor. The absorber array is bound to the thermistor array in a single automatic step. The thermo-mechanical link, provided by hybridization, is being improved in terms of thermal capacitance. Finally, our main effort is in developing arrays of silicon thermistors with negligible excess 1/ f noise. The thermistor has been simulated with the 2D simulator ATHENA (SILVACO International). We studied the effects of the implants and their thermal treatment on both vertical and lateral dopant distributions at the edges of the thermistor. Prototypes have been created following the procedure optimized by the ATHENA simulation. We present the status of the development and results of measurements performed on these four main building blocks required to create a detector array up to 32×32 pixels in size.

  12. Radiation damage of germanium detectors

    NASA Technical Reports Server (NTRS)

    Pehl, R. H.

    1978-01-01

    Energetic particles can produce interstitial-vacancy pairs in a crystal by knocking the atoms from their normal positions. Detectors are unique among semiconductor devices in depending on very low concentrations of electrically active impurities, and also on efficient transport of holes and electrons over relatively large distances. Because the dense regions of damage produced by energetic particles may result in donors and/or acceptors, and also provide trapping sites for holes and electrons, detectors are very sensitive to radiation damage. In addition to these effects occurring within the detector, radiation may also change the characteristics of the exposed surfaces causing unpredictable effects on the detector leakage current. Radiation-induced surface degradation has rarely, if ever, been observed for germanium detectors. The possibility of minimizing hole trapping in charge collection by the use of a high-purity germanium coaxial detector configured with the p (+) contact on the coaxial periphery is discussed.

  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. 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.

  15. 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.

  16. 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.

  17. High performance LWIR microbolometer with Si/SiGe quantum well thermistor and wafer level packaging

    NASA Astrophysics Data System (ADS)

    Roer, Audun; Lapadatu, Adriana; Bring, Martin; Wolla, Erik; Hohler, Erling; Kittilsland, Gjermund

    2011-11-01

    An uncooled microbolometer with peak responsivity in the long wave infrared region of the electromagnetic radiation is developed at Sensonor Technologies. It is a 384 x 288 focal plane array with a pixel pitch of 25μm, based on monocrystalline Si/SiGe quantum wells as IR sensitive material. The high sensitivity (TCR) and low 1/f noise are the main performance characteristics of the product. The frame rate is maximum 60Hz and the output interface is digital (LVDS). The quantum well thermistor material is transferred to the read-out integrated circuit (ROIC) by direct wafer bonding. The ROIC wafer containing the released pixels is bonded in vacuum with a silicon cap wafer, providing hermetic encapsulation at low cost. The resulting wafer stack is mounted in a standard ceramic package. In this paper the architecture of the pixels and the ROIC, the wafer packaging and the electro-optical measurement results are presented.

  18. Thermal conductivity and diffusivity of biomaterials measured with self-heated thermistors

    NASA Astrophysics Data System (ADS)

    Valvano, J. W.; Cochran, J. R.; Diller, K. R.

    1985-05-01

    This paper presents an experimental method to measure the thermal conductivity and thermal diffusivity of biomaterials. Self-heated thermistor probes, inserted into the tissue of interest, are used to deliver heat as well as to monitor the rate of heat removal. An empirical calibration procedure allows accurate thermal-property measurements over a wide range of tissue temperatures. Operation of the instrument in three media with known thermal properties shows the uncertainty of measurements to be about 2%. The reproducibility is 0.5% for the thermal-conductivity measurements and 2% for the thermal-diffusivity measurements. Thermal properties were measured in dog, pig, rabbit, and human tissues. The tissues included kidney, spleen, liver, brain, heart, lung, pancreas, colon cancer, and breast cancer. Thermal properties were measured for 65 separate tissue samples at 3, 10, 17, 23, 30, 37, and 45°C. The results show that the temperature coefficient of biomaterials approximates that of water.

  19. 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.

  20. APPLICATION OF GERMANIUM DETECTORS TO ENVIRONMENTAL MONITORING

    EPA Science Inventory

    Gamma-ray spectroscopy is one of the most economical and wide-ranging tools for monitoring the environment for radiological impact. This report examines the problems involved in applying germanium detectors to the analysis of environmental samples. All aspects of germanium spectr...

  1. Reactions of germanium tetrahalides with ketene acetals

    SciTech Connect

    Efimova, I.V.; Kazankova, M.A.; Lutsenko, I.F.

    1985-05-01

    Recently, the authors reported that alkyl vinyl ethers and terminal alkynes are readily germylated by germanium tetrahalides in the presence of a tertiary amine. To extend the range of applicability of this reaction and to obtain additional information on its mechanism, the authors study reactions of ketene acetals with germanium tetrachloride and tetrabromide in the presence of triethylamine.

  2. Study of the mask materials for PTD process and NTD process in practical ArF immersion lithography

    NASA Astrophysics Data System (ADS)

    Adachi, Takashi; Tani, Ayako; Hayano, Katsuya; Takamizawa, Hideyoshi

    2014-07-01

    In this report, we compared the lithographic performances between the conventional positive tone development (PTD) process and the negative tone development (NTD) process, using the lithography simulation. We selected the MoSi-binary mask and conventional 6% attenuated phase shift mask as mask materials. The lithographic performance was evaluated and compared after applying the optical proximity correction (OPC). The evaluation items of lithographic performance were the aerial image profile, the aerial image contrast, normalized image log slope (NILS), mask error enhancement factor (MEEF), and the bossung curves, etc. The designs for the evaluation were selected the simple contact hole and the metal layer sample design.

  3. 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

  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. MAJORANA Collaboration's experience with germanium detectors

    DOE PAGESBeta

    Mertens, S.; Abgrall, N.; Avignone, F. T.; Barabash, A. S.; Bertrand, F. E.; Brudanin, V.; Busch, M.; Buuck, M.; Byram, D.; Caldwell, A. S.; et al

    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

  6. Epstein-Barr virus nuclear protein 3C binds to the N-terminal (NTD) and beta trefoil domains (BTD) of RBP/CSL; Only the NTD interaction is essential for lymphoblastoid cell growth

    SciTech Connect

    Calderwood, Michael A.; Lee, Sungwook; Holthaus, Amy M.; Blacklow, Stephen C.; Kieff, Elliott; Johannsen, Eric

    2011-05-25

    Association of EBV nuclear proteins EBNA2, EBNA3A and EBNA3C with RBP/CSL, is essential for lymphoblastoid cell line (LCL) proliferation. Conserved residues in the EBNA3 homology domain, required for RBP/CSL interaction, lack the W{Phi}P motif that mediates EBNA2 and Notch binding to the RBP/CSL beta-trefoil domain (BTD). We map RBP/CSL interacting residues within EBNA3A(aa128-204) and EBNA3C(aa211-233). The EBNA3A results are consistent with an earlier report (aa125-222), but the EBNA3C domain is unexpectedly small and includes a 'WTP' sequence. This EBNA3C WTP motif confers RBP/CSL binding in vitro, in yeast, and in mammalian cells. Further, an EBNA3C WTP {yields} STP(W227S) mutation impaired BTD binding whereas EBNA3 homology domain mutations disrupted RBP/CSL N-terminal domain (NTD) binding. WTP was not essential for EBNA3C repression of EBNA2 in reporter assays or for maintenance of LCL growth. Our results indicate that EBNA3 proteins interact with multiple RBP/CSL domains, but only NTD interactions are required for LCL growth.

  7. Interfacial properties of germanium nitride dielectric layers in germanium

    NASA Astrophysics Data System (ADS)

    Meiners, L. G.

    The first year's effort on this project has been primarily devoted to the design and construction of a low-pressure chemical vapor deposition system for growth of the germanium nitride layers. The gas manifold layout is shown schematically, as is the reactor assembly, and the vacuum pumping assembly. The generator-cavity system is capable of delivering 0-600 W of microwave power at 2.45 GHz. The power generating section has been constructed from components contained in a portable home microwave oven and the cavity was assembled from easily machinable pieces. The cw magnetron source was mounted directly on a cylindrical microwave cavity. The plasma was contained in an on-axis 20-mm o.d. quartz tube. Design tradeoffs and operating information are discussed.

  8. Solution synthesis of germanium nanocrystals

    DOEpatents

    Gerung, Henry; Boyle, Timothy J.; Bunge, Scott D.

    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.

  9. 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%.

  10. High efficiency germanium immersion gratings

    NASA Astrophysics Data System (ADS)

    Kuzmenko, Paul J.; Davis, Pete J.; Little, Steve L.; Little, Liesl M.; Bixler, Jay V.

    2006-06-01

    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 104. Scatter should be low based upon the surface roughness. Measurement of the spectral line profile of a CO II laser sets an upper bound on total integrated scatter of 0.5%.

  11. Germanium: giving microelectronics an efficiency boost

    USGS Publications Warehouse

    Mercer, Celestine N.

    2015-01-01

    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.

  12. An instrument for measuring endometrial blood flow in the uterus, using two thermistor probes.

    PubMed

    Hansson, G A; Hauksson, A; Strömberg, P; Akerlund, M

    1987-01-01

    An instrument was developed for continuous measurement of thermal conductance reflecting blood flow locally in the endometrium. The probe consists of two small thermistors, one sensing the tissue temperature, and the other working at 5 degrees C elevated temperature, sensing the heat loss caused by thermal conduction mainly due to the blood flow. The power needed to keep this temperature difference was recorded as a measure of flow. When the instrument was tested in model experiments, for measurement of flows at temperatures of 35 to 40 degrees C, stable recordings with high sensitivity were obtained and no influence of the surrounding temperature was observed. Recordings were also made in vivo in non-pregnant women by applying the instrument to the endometrium of the uterine fundus. Intrauterine pressure was recorded simultaneously. The blood flow recordings were stable over long periods in spite of changes in body temperature, but with fluctuations of up to 0.1 mW concomitant with uterine contractions. Pulse-syncronous variations in flow were recorded, indicating a high sensitivity and a short time constant of the instrument. The blood flow effects of vasoactive substances, i.e. vasopressin and a vasopressin antagonist, could readily be distinguished. It is concluded that this instrument can be used for semi-quantitative recordings of blood flow in cavities of the body, for example the uterus, which can be reached by small probes and that changes of body temperature do not effect the measurements. PMID:3585951

  13. Thin film metal thermistors with microsecond time response for shock temperature measurements of polymers

    NASA Astrophysics Data System (ADS)

    Taylor, Nicholas; Williamson, David; Jardine, Andrew

    2013-06-01

    Equations of state can be used to predict the relationship between pressure, volume and temperature. However, in shock physics, they are usually only constrained by experimental observations of pressure and volume. Direct observation of temperature in a shock is therefore valuable in constraining equations of state. Bloomquist and Sheffield (1980, 1981) and Rosenberg and Partom (1984) have attempted such observations in PMMA. However, their results disagree strongly above 2 GPa shock pressure. Here we present an improved fabrication technique, to examine this outstanding issue. We make use of the fact that the electrical resistivity of most metals is a known function of both pressure and temperature. If the change in resistance of a thin metal thermistor gauge is measured during a shock experiment of known pressure, the temperature can be calculated directly. The time response is limited by the time taken for the gauge to reach thermal equilibrium with the medium in which it is embedded. Gold gauges of thickness up to 200 nm have been produced by evaporation, and fully embedded in PMMA. These reach thermal equilibrium with the host material in under 1 μs, allowing temperature measurement within the duration of a plate impact experiment.

  14. Steps toward thin film metal thermistors with microsecond time response for shock temperature measurements of polymers

    NASA Astrophysics Data System (ADS)

    Taylor, N. E.; Williamson, D. M.; Jardine, A. P.

    2014-05-01

    Equations of state can be used to predict the relationship between pressure, volume and temperature. However, in shock physics, they are usually only constrained by experimental observations of pressure and volume. Direct observation of temperature in a shock is therefore valuable in constraining equations of state. Bloomquist and Sheffield (1980, 1981) and Rosenberg and Partom (1984) have attempted such observations in poly(methyl methacrylate) (PMMA). However, their results disagree strongly above 2GPa shock pressure. Here we present an improved fabrication technique, to examine this outstanding issue. We make use of the fact that the electrical resistivity of most metals is a known function of both pressure and temperature. If the change in resistance of a thin metal thermistor gauge is measured during a shock experiment of known pressure, the temperature can be calculated directly. The time response is limited by the time taken for the gauge to reach thermal equilibrium with the medium in which it is embedded. Gold gauges of thickness up to 200 nm have been produced by thermal evaporation, and fully embedded in PMMA. These reach thermal equilibrium with the host material in under 1 us, allowing temperature measurement within the duration of a plate impact experiment.

  15. 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.

  16. Dangling bonds and vacancies in germanium

    NASA Astrophysics Data System (ADS)

    Weber, J. R.; Janotti, A.; Van de Walle, C. G.

    2013-01-01

    The quest for metal-oxide-semiconductor field-effect transistors (MOSFETs) with higher carrier mobility has triggered great interest in germanium-based MOSFETs. Still, the performance of germanium-based devices lags significantly behind that of their silicon counterparts, possibly due to the presence of defects such as dangling bonds (DBs) and vacancies. Using screened hybrid functional calculations we investigate the role of DBs and vacancies in germanium. We find that the DB defect in germanium has no levels in the band gap; it acts as a negatively charged acceptor with the (0/-1) transition level below the valence-band maximum (VBM). This explains the absence of electron-spin-resonance observations of DBs in germanium. The vacancy in germanium has a much lower formation energy than the vacancy in silicon and is stable in a number of charge states, depending on the position of the Fermi level. We find the (0/-1) and (-1/-2) transition levels at 0.16 and 0.38 eV above the VBM; the spacing of these levels is explained based on the strength of intraorbital repulsion. We compare these results with calculations for silicon, as well as with available experimental data.

  17. An enzyme thermistor-based assay for total and free cholesterol.

    PubMed

    Raghavan, V; Ramanathan, K; Sundaram, P V; Danielsson, B

    1999-11-01

    A method to evaluate the free (FC) and total cholesterol (TC) in human serum, bile and gallstone extract using an enzyme thermistor (ET)-based flow injection analysis (FIA) is presented. The cholesterol in high-density (HDL-C) and low density lipoprotein (LDL-C) have also been evaluated. A heparin functionalized Sepharose column was employed for the isolation of HDL and LDL fractions from serum. The estimation of cholesterol and its esters was based on their reaction with cholesterol oxidase (CO), cholesterol esterase (CE) and catalase (CAT). Three different enzyme columns, i.e. co-immobilized CO/CAT (column A), only CE (column B) and co-immobilized CO/CE/CAT (column C) were prepared by cross-linking the enzymes on glass beads using glutaraldehyde. Column A was used for estimating FC and column C was used for estimating total cholesterol (cholesterol plus esterified cholesterol). Column B was used as a pre-column which could be switched 'in' or 'out' in conjunction with column A for the estimation of TC or FC, respectively. A calibration between 1.0 and 8.0 mmol/l for FC and 0. 25 and 4.0 mmol/l for TC was obtained. For more than 2000 assays with the ET device a C.V. of less than 4% was obtained. The assay time was approximately 4 min per assay. The cholesterol estimations on the ET correlated well with similar estimations using a commercially available cholesterol diagnostic kit. PMID:10556661

  18. 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.

  19. Recovery of germanium-68 from irradiated targets

    SciTech Connect

    Phillips, D.R.; Jamriska, D.J. Sr.; Hamilton, V.T.

    1992-12-31

    This invention is comprised of 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.

  20. Recovery of germanium-68 from irradiated targets

    SciTech Connect

    Phillips, D.R.; Jamriska, D.J. Sr.; Hamilton, V.T.

    1993-03-02

    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.

  1. 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

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. Germanium-Based Nanomaterials for Rechargeable Batteries.

    PubMed

    Wu, Songping; Han, Cuiping; Iocozzia, James; Lu, Mingjia; Ge, Rongyun; Xu, Rui; Lin, Zhiqun

    2016-07-01

    Germanium-based nanomaterials have emerged as important candidates for next-generation energy-storage devices owing to their unique chemical and physical properties. In this Review, we provide a review of the current state-of-the-art in germanium-based materials design, synthesis, processing, and application in battery technology. The most recent advances in the area of Ge-based nanocomposite electrode materials and electrolytes for solid-state batteries are summarized. The limitations of Ge-based materials for energy-storage applications are discussed, and potential research directions are also presented with an emphasis on commercial products and theoretical investigations. PMID:27281435

  7. Reliability and validity of skin temperature measurement by telemetry thermistors and a thermal camera during exercise in the heat.

    PubMed

    James, C A; Richardson, A J; Watt, P W; Maxwell, N S

    2014-10-01

    New technologies afford convenient modalities for skin temperature (TSKIN) measurement, notably involving wireless telemetry and non-contact infrared thermometry. The purpose of this study was to investigate the validity and reliability of skin temperature measurements using a telemetry thermistor system (TT) and thermal camera (TC) during exercise in a hot environment. Each system was compared against a certified thermocouple, measuring the surface temperature of a metal block in a thermostatically controlled waterbath. Fourteen recreational athletes completed two incremental running tests, separated by one week. Skin temperatures were measured simultaneously with TT and TC compared against a hard-wired thermistor system (HW) throughout rest and exercise. Post hoc calibration based on waterbath results displayed good validity for TT (mean bias [MB]=-0.18 °C, typical error [TE]=0.18 °C) and reliability (MB=-0.05 °C, TE=0.31 °C) throughout rest and exercise. Poor validity (MB=-1.4 °C, TE=0.35 °C) and reliability (MB=-0.65 °C, TE=0.52 °C) was observed for TC, suggesting it may be best suited to controlled, static situations. These findings indicate TT systems provide a convenient, valid and reliable alternative to HW, useful for measurements in the field where traditional methods may be impractical. PMID:25436963

  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. Dopant precipitation in silicon-germanium alloys.

    NASA Technical Reports Server (NTRS)

    Raag, V.

    1972-01-01

    The model commonly used to describe dopant precipitation in silicon-germanium alloys is discussed. The results of an experimental program are fit to the model in order to determine the long-term behavior of the thermoelectric properties of the n-type 80 at. % Si/20 at. % Ge alloy. Thermoelectric property projections to twelve years of operating time are given.

  10. Method for copper staining of germanium crystals

    NASA Technical Reports Server (NTRS)

    Rivet, E. J.

    1969-01-01

    Proper conditions for copper staining of germanium crystals include a low solution temperature of 3 degrees C, illumination of the sample by infrared light, and careful positioning of the light source relative to the sample so as to minimize absorption of the infrared light.

  11. Hydrogenated amorphous silicon-germanium alloys

    SciTech Connect

    Luft, W.

    1988-02-01

    This report describes the effects of the germanium fraction in hydrogenated amorphous silicon-germanium alloys on various parameters, especially those that are indicators of film quality, and the impact of deposition methods, feedgas mixtures, and other deposition parameters on a SiGe:H and a-SiGe:H:F film characteristics and quality. Literature data show the relationship between germanium content, hydrogen content, deposition method (various glow discharges and CVD), feedgas lmixture, and other parameters and properties, such as optical band gap, dark and photoconductivities, photosensitivity, activation energy, Urbach parameter, and spin density. Some of these are convenient quality indicators; another is the absence of microstructure. Examining RF glow discharge with both a diode and triode geometry, DC proximity glow discharge, microwave glow discharge, and photo-CVD, using gas mixtures such as hydrogen-diluted and undiluted mixtures of silane/germane, disilane/germane, silane/germaniumtetrafluoride, and others, it was observed that hydrogen dilution (or inert gas dilution) is essential in achieving high photosensitivity in silicon-germanium alloys (in contradistinction to amorphous hydrogenated silicon). Hydrogen dilution results in a higher photosensitivity than do undiluted gas mixtures. 81 refs., 42 figs., 7 tabs.

  12. 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).

  13. The effect of sintering temperature on electrical characteristics of Fe2TiO5/Nb2O5 ceramics for NTC thermistor

    NASA Astrophysics Data System (ADS)

    Wiendartun, Risdiana, Fitrilawati, Siregar, R. E.

    2016-02-01

    A study on the fabrication of Iron Titanium Oxide (Fe2TiO5) ceramics for negative temperature coefficient (NTC) thermistors has been carried out, in order to know the effect of sintering temperature on the electrical characteristic of 1.0 % mole Nb2O5 doped Fe2TiO5 ceramics.These ceramics were made by mixing commercial powders of Fe2O3, TiO2 and Nb2O5 with proportional composition to produce Fe2TiO5 based ceramic. The raw pellet was sintered at 1000 °C, 1100 °C and 1200 °C temperature for 2 hours in air. Analysis of the microstructure and crystal structure were performed by using a scanning electron microscope (SEM) and x-ray diffraction (XRD) respectively. XRD spectra showed that the crystal structure of all ceramics of Fe2TiO5 made at various sintering temperatures are orthorhombic. The SEM images showed that the grain size of pellet ceramics increase with increasing sintering temperatures. From electrical resistances data that was measured at temperature 30-300 °C, it is found that the value of thermistor constant (B), activation energy (Ea), thermistor sensitivity (α) and room temperature resistance (RRT) decreases with respect to the increasing of sintering temperature. The fabricated Fe2TiO5 ceramics have thermistor constants (B = 6394-6959 K). This can be applied as temperature sensor, and will fulfill the market requirement.

  14. Spin transport in p-type germanium.

    PubMed

    Rortais, F; Oyarzún, S; Bottegoni, F; Rojas-Sánchez, J-C; Laczkowski, P; Ferrari, A; Vergnaud, C; Ducruet, C; Beigné, C; Reyren, N; Marty, A; Attané, J-P; Vila, L; Gambarelli, S; Widiez, J; Ciccacci, F; Jaffrès, H; George, J-M; Jamet, M

    2016-04-27

    We report on the spin transport properties in p-doped germanium (Ge-p) using low temperature magnetoresistance measurements, electrical spin injection from a ferromagnetic metal and the spin pumping-inverse spin Hall effect method. Electrical spin injection is carried out using three-terminal measurements and the Hanle effect. In the 2-20 K temperature range, weak antilocalization and the Hanle effect provide the same spin lifetime in the germanium valence band (≈1 ps) in agreement with predicted values and previous optical measurements. These results, combined with dynamical spin injection by spin pumping and the inverse spin Hall effect, demonstrate successful spin accumulation in Ge. We also estimate the spin Hall angle θ(SHE) in Ge-p (6-7 x 10(-4) at room temperature, pointing out the essential role of ionized impurities in spin dependent scattering. PMID:26988255

  15. Constraining neutrino electromagnetic properties by germanium detectors

    NASA Astrophysics Data System (ADS)

    Chen, Jiunn-Wei; Chi, Hsin-Chang; Huang, Keh-Ning; Li, Hau-Bin; Liu, C.-P.; Singh, Lakhwinder; Wong, Henry T.; Wu, Chih-Liang; Wu, Chih-Pan

    2015-01-01

    The electromagnetic properties of neutrinos, which are either trivial or negligible in the context of the Standard Model, can probe new physics and have significant implications in astrophysics and cosmology. The current best direct limits on the neutrino millicharges and magnetic moments are both derived from data taken with germanium detectors with low thresholds at keV levels. In this paper, we discuss in detail a robust, ab initio method: the multiconfiguration relativistic random-phase approximation, that enables us to reliably understand the germanium detector response at the sub-keV level, where atomic many-body physics matters. By using existing data with sub-keV thresholds, limits on the reactor antineutrino's millicharge, magnetic moment, and charge radius squared are derived. The projected sensitivities for next-generation experiments are also given and discussed.

  16. A Germanium-Based, Coded Aperture Imager

    SciTech Connect

    Ziock, K P; Madden, N; Hull, E; William, C; Lavietes, T; Cork, C

    2001-10-31

    We describe a coded-aperture based, gamma-ray imager that uses a unique hybrid germanium detector system. A planar, germanium strip detector, eleven millimeters thick is followed by a coaxial detector. The 19 x 19 strip detector (2 mm pitch) is used to determine the location and energy of low energy events. The location of high energy events are determined from the location of the Compton scatter in the planar detector and the energy is determined from the sum of the coaxial and planar energies. With this geometry, we obtain useful quantum efficiency in a position-sensitive mode out to 500 keV. The detector is used with a 19 x 17 URA coded aperture to obtain spectrally resolved images in the gamma-ray band. We discuss the performance of the planar detector, the hybrid system and present images taken of laboratory sources.

  17. Spin transport in p-type germanium

    NASA Astrophysics Data System (ADS)

    Rortais, F.; Oyarzún, S.; Bottegoni, F.; Rojas-Sánchez, J.-C.; Laczkowski, P.; Ferrari, A.; Vergnaud, C.; Ducruet, C.; Beigné, C.; Reyren, N.; Marty, A.; Attané, J.-P.; Vila, L.; Gambarelli, S.; Widiez, J.; Ciccacci, F.; Jaffrès, H.; George, J.-M.; Jamet, M.

    2016-04-01

    We report on the spin transport properties in p-doped germanium (Ge-p) using low temperature magnetoresistance measurements, electrical spin injection from a ferromagnetic metal and the spin pumping-inverse spin Hall effect method. Electrical spin injection is carried out using three-terminal measurements and the Hanle effect. In the 2-20 K temperature range, weak antilocalization and the Hanle effect provide the same spin lifetime in the germanium valence band (≈1 ps) in agreement with predicted values and previous optical measurements. These results, combined with dynamical spin injection by spin pumping and the inverse spin Hall effect, demonstrate successful spin accumulation in Ge. We also estimate the spin Hall angle {θ\\text{SHE}} in Ge-p (6-7× {{10}-4} ) at room temperature, pointing out the essential role of ionized impurities in spin dependent scattering.

  18. The first spectroscopic observation of germanium carbide

    NASA Astrophysics Data System (ADS)

    Ruiz, Jose I.

    Electronic spectroscopy was used to obtain gas phase spectrum of the germanium carbide molecule in emission from a corona excited supersonic expansion source. The (2) 3pi -- X 3pi electronic transition was observed around the 21250 cm-1 region. In this system, vibrational bands and the rotational lines of the O = 0, 1, and 2 components were obtained and analyzed. The equilibrium transition energy is found at 21120.3 cm-1 and the fundamental vibrational frequency for the lowest energy ground state O = 2 component is 795.3 cm -1. This is the first spectroscopic observation of germanium carbide. An unsuccessful attempt to obtain the first electronic emission spectrum of aluminum boride is also described.

  19. Energetic semiconductor bridge device incorporating Al/MoOx multilayer nanofilms and negative temperature coefficient thermistor chip

    NASA Astrophysics Data System (ADS)

    Zhu, Peng; Jiao, Jianshe; Shen, Ruiqi; Ye, Yinghua; Fu, Shuai; Li, Dongle

    2014-05-01

    The design, fabrication, and characterization of an energetic semiconductor bridge device are presented. The device consists of a semiconductor bridge heating element, which has been selectively coated with Al/MoOx multilayer nanofilms to enhance ignition of a conventional pyrotechnics. Integrated negative temperature coefficient thermistor chip provides protection against electromagnetic and electrostatic discharge events. The device was specifically configured to allow ease of interconnection by wire bonds and silver-filled conductive epoxy. Extensive design validation testing was performed. The device has demonstrated low, predictable firing energy and insensitivity. Al/MoOx multilayer nanofilms have no distinct influence on the electrical properties of semiconductor bridge. Nanothermite reaction provides reliable ignition by being able to ignite across a gap.

  20. High-performance LWIR microbolometer with Si/SiGe quantum well thermistor and wafer level packaging

    NASA Astrophysics Data System (ADS)

    Roer, Audun; Lapadatu, Adriana; Wolla, Erik; Kittilsland, Gjermund

    2013-06-01

    An uncooled microbolometer with peak responsivity in the long wave infrared region of the electromagnetic radiation is developed at Sensonor AS. It is a 384 x 288 focal plane array with a pixel pitch of 25µm, based on monocrystalline Si/SiGe quantum wells as IR sensitive material. The high sensitivity (TCR) and low 1/f-noise are the main performance characteristics of the product. The frame rate is maximum 60Hz and the output interface is digital (LVDS). The quantum well thermistor material is transferred to the read-out integrated circuit (ROIC) by direct wafer bonding. The ROIC wafer containing the released pixels is bonded in vacuum with a silicon cap wafer, providing hermetic encapsulation at low cost. The resulting wafer stack is mounted in a standard ceramic package. In this paper the architecture of the pixels and the ROIC, the wafer packaging and the electro-optical measurement results are presented.

  1. Electronic structure of intrinsic defects in crystalline germanium telluride.

    SciTech Connect

    Thompson, Aidan Patrick; Pineda, Andrew C.; Umrigar, Cyrus J.; Hjalmarson, Harold Paul; Schultz, Peter Andrew; Edwards, Arthur H.; Martin, Marcus Gary

    2005-05-01

    Germanium telluride undergoes rapid transition between polycrystalline and amorphous states under either optical or electrical excitation. While the crystalline phases are predicted to be semiconductors, polycrystalline germanium telluride always exhibits p-type metallic conductivity. We present a study of the electronic structure and formation energies of the vacancy and antisite defects in both known crystalline phases. We show that these intrinsic defects determine the nature of free-carrier transport in crystalline germanium telluride. Germanium vacancies require roughly one-third the energy of the other three defects to form, making this by far the most favorable intrinsic defect. While the tellurium antisite and vacancy induce gap states, the germanium counterparts do not. A simple counting argument, reinforced by integration over the density of states, predicts that the germanium vacancy leads to empty states at the top of the valence band, thus giving a complete explanation of the observed p-type metallic conduction.

  2. Xenon Filled Silicon Germanium Thermoelectric Generators

    NASA Technical Reports Server (NTRS)

    Dewinter, F.

    1972-01-01

    An analysis is presented that shows the desirability and feasibility of using a xenon fill in the initial stages of operation of a silicon-germanium radioisotope thermoelectric generator to be used in outer-planetary exploration. The xenon cover gas offers protection against oxidation and against material sublimation, and allows the generator to deliver required power throughout the prelaunch and launch phases. The protective mechanisms afforded by the xenon cover gas and the mechanization of a xenon supply system are also discussed.

  3. Germanium films by polymer-assisted deposition

    SciTech Connect

    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.

  4. 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.

  5. On the geological availability of germanium

    NASA Astrophysics Data System (ADS)

    Frenzel, Max; Ketris, Marina P.; Gutzmer, Jens

    2014-04-01

    Based on a detailed statistical analysis of chemical data published in the scientific literature, estimates were made of the minimum amounts of recoverable Ge contained within sulphidic zinc ores and coals, given current processing technologies. It is expected that at least 119 kt (˜7 kt in zinc ores and ˜112 kt in coal) of recoverable germanium exist within proven reserves (at present stage of knowledge) at grades in excess of 100 ppm in sphalerite and 200 ppm in coal, while at least 440 kt (˜50 kt in zinc ores and ˜390 kt in coal) should become recoverable in the future, being associated to coal reserves at 8-200 ppm Ge and zinc resources containing in excess of 100 ppm Ge in sphalerite. Mississippi Valley Type (MVT) deposits are expected to be the most important hosts of germanium-rich sphalerite, while both brown and hard coals are expected to be equally important as hosts of germanium. The approach taken in this publication shows that reliable minimum estimates for the availability of by-product metals lacking suitable reserve/resource data may be attained by using robust statistical methods and geochemical data published in the scientific literature

  6. 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

  7. 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.

  8. Bottom-up assembly of metallic germanium

    NASA Astrophysics Data System (ADS)

    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.

    2015-08-01

    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.

  9. Synthesis and characterization of germanium nanowires and germanium/silicon radially heterostructured nanowires

    NASA Astrophysics Data System (ADS)

    Goldthorpe, Irene Anne

    Semiconductor nanowires offer new opportunities to study physical phenomena in low-dimensional nanostructures. They also possess technologically useful properties for applications in electronics, optics, sensing, and thermoelectrics. Germanium nanowires are of particular interest, because of germanium's compatibility with standard silicon integrated circuit fabrication processes, its high electronic carrier mobilities, and the low temperature required for germanium nanowire growth. In this work, epitaxially-aligned germanium nanowires are grown on silicon substrates by chemical vapor deposition through the vapor-liquid-solid mechanism. Uniform nanowire diameters between 5 and 50 nm are obtained through the use of monodisperse gold colloids as catalysts. The crystallographic orientation of the nanowires, their strain, and their heteroepitaxial relationship with the substrate are characterized with transmission electron microscopy (TEM) and x-ray diffraction (XRD). A process for removing the gold catalysts from the tips of the germanium nanowires is demonstrated. Silicon shells are then heteroepitaxially deposited around the wires to fabricate radial heterostructures. These shells passivate the germanium nanowire surface, create electronic band offsets to confine holes away the surface where they can scatter or recombine, and induce strain which could allow for the engineering of properties such as band gap and carrier mobilities. However, analogous to planar heteroepitaxy, surface roughening and misfit dislocations can relax this strain. The effects of coaxial dimensions on strain relaxation in these structures are analyzed quantitatively by TEM and synchrotron XRD, and these results are related to continuum elasticity models. Lessons learned generated two successful strategies for synthesizing coherent core-shell nanowires with large misfit strain: chlorine surface passivation and growth of nanowires with low-energy sidewall facets. Both approaches avoid the strain

  10. Anisotropy-Driven Spin Relaxation in Germanium

    NASA Astrophysics Data System (ADS)

    Li, Pengke; Li, Jing; Qing, Lan; Dery, Hanan; Appelbaum, Ian

    2013-12-01

    A unique spin depolarization mechanism, induced by the presence of g-factor anisotropy and intervalley scattering, is revealed by spin-transport measurements on long-distance germanium devices in a magnetic field longitudinal to the initial spin orientation. The confluence of electron-phonon scattering (leading to Elliott-Yafet spin flips) and this previously unobserved physics enables the extraction of spin lifetime solely from spin-valve measurements, without spin precession, and in a regime of substantial electric-field-generated carrier heating. We find spin lifetimes in Ge up to several hundreds of nanoseconds at low temperature, far beyond any other available experimental results.

  11. 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.

  12. 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.

  13. The first spectroscopic observation of germanium carbide

    NASA Astrophysics Data System (ADS)

    Brazier, Christopher R.; Ruiz, José I.

    2011-11-01

    The gas phase spectrum of the germanium carbide radical has been observed at low temperature in emission from a corona excited supersonic expansion source. Many vibrational bands involving the Ω = 0, 1, and 2 components of the (2) 3Π-X 3Π system were recorded and analyzed. The equilibrium transition energy is found at 21120.3 cm -1, in good agreement with theoretical predictions. The fundamental vibrational frequency for the lowest energy ground state Ω = 2 component is 795.3 cm -1.

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

    DOE PAGESBeta

    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 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

  15. Investigation of intrinsic gettering for germanium doped Czochralski silicon wafer

    NASA Astrophysics Data System (ADS)

    Chen, Jiahe; Yang, Deren; Ma, Xiangyang; Wang, Weiyan; Zeng, Yuheng; Que, Duanlin

    2007-06-01

    The intrinsic gettering (IG) effects in a germanium-doped Czochralski (GCz) silicon wafer have been investigated through a processing simulation of dynamic random access memory making and an evaluation on IG capability for copper contamination. It has been suggested that both the good quality defect-free denuded zones (DZs) and the high-density bulk microdefect (BMD) regions could be generated in GCz silicon wafer during device fabrication. Meanwhile, it was also indicated that the tiny oxygen precipitates were hardly presented in DZs of silicon wafer with the germanium doping. Furthermore, it was found in GCz silicon wafer that the BMDs were higher in density but smaller in size in contrast to that in conventional Cz silicon wafer. Promoted IG capability for metallic contamination was therefore induced in the germanium-doped Cz silicon wafer. A mechanism of the germanium doping on oxygen precipitation in Cz silicon was discussed, which was based on the hypothesis of germanium-related complexes.

  16. Germanium resistance thermometer calibration at superfluid helium temperatures

    SciTech Connect

    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.

  17. 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

    2016-03-01

    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. PMID:26796765

  18. Experience from operating germanium detectors in GERDA

    NASA Astrophysics Data System (ADS)

    Palioselitis, Dimitrios; GERDA Collaboration

    2015-05-01

    Phase I of the Germanium Detector Array (GERDA) experiment, searching for the neutrinoless double beta (0νββ) decay of 76Ge, was completed in September 2013. The most competitive half-life lower limit for the 0νββ decay of 76Ge was set (T-0ν1/2 > 2.1 · 1025 yr at 90% C.L.). GERDA operates bare Ge diodes immersed in liquid argon. During Phase I, mainly refurbished semi-coaxial high purity Ge detectors from previous experiments were used. The experience gained with handling and operating bare Ge diodes in liquid argon, as well as the stability and performance of the detectors during GERDA Phase I are presented. Thirty additional new enriched BEGe-type detectors were produced and will be used in Phase II. A subgroup of these detectors has already been used successfully in GERDA Phase I. The present paper gives an overview of the production chain of the new germanium detectors, the steps taken to minimise the exposure to cosmic radiation during manufacturing, and the first results of characterisation measurements in vacuum cryostats.

  19. 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.

  20. 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.

  1. Preparation and characterization of hydrogenated amorphous germanium and hydrogenated amorphous germanium carbide thin films

    NASA Astrophysics Data System (ADS)

    Wu, Hai-Sheng

    1989-02-01

    Hydrogenated amorphous germanium (a-Ge:H) and germanium carbide (a-Ge(1-x)Cx:H) films were prepared by rf sputtering of a polycrystalline Ge target in a vacuum approximately 4 x 10 to the 7th Torr at various rf power 50 less than or equal to P less than or equal to 600 W (0.27 to 3.3 W/sq cm), target-substrate distance 1 less than or equal to d less than or equal to 7 minutes, varying partial pressures of Ar, H2, and C3H8, and flow rates f. The vibrational and opto-electronic properties such as infrared (IR) absorption, optical gap, electron-spin-resonance (ESR) signals, and conductivities vary with deposition conditions. The photoconductivity sigma sub ph, in particular, was carefully monitored as a function of the deposition conditions to optimize it.

  2. Oxygen defect processes in silicon and silicon germanium

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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.

  3. Sputtered germanium/silicon devices for photonics applications

    NASA Astrophysics Data System (ADS)

    Nujhat, N.; Papouloute, J.-P.; DeBerry, M.; Jiang, L.; Korivi, N. S.

    2015-08-01

    We report on the ongoing investigation of magnetron sputtered germanium on silicon for photonics applications. Direct current (DC) magnetron sputtering has been used to deposit germanium layers on silicon at low growth temperatures and medium range vacuum levels. Standard photolithography has been used to make germanium photodetectors for the 1550 nm wavelength range. Electrical characterization, more specifically current-voltage measurements indicate that the devices function as intended. Sputtered silicon waveguides have also been fabricated and evaluated for possible applications in photonics integration. The sputtering-based developments in our present research are expected to provide for a flexible and economically viable manufacturing process for such devices.

  4. 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.

  5. 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.

  6. 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.

  7. Interactions of germanium atoms with silica surfaces

    NASA Astrophysics Data System (ADS)

    Stanley, Scott K.; Coffee, Shawn S.; Ekerdt, John G.

    2005-11-01

    GeH 4 is thermally cracked over a hot filament depositing 0.7-15 ML Ge onto 2-7 nm SiO 2/Si(1 0 0) at substrate temperatures of 300-970 K. Ge bonding changes are analyzed during annealing with X-ray photoelectron spectroscopy. Ge, GeH x, GeO, and GeO 2 desorption is monitored through temperature programmed desorption in the temperature range 300-1000 K. Low temperature desorption features are attributed to GeO and GeH 4. No GeO 2 desorption is observed, but GeO 2 decomposition to Ge through high temperature pathways is seen above 750 K. Germanium oxidization results from Ge etching of the oxide substrate. With these results, explanations for the failure of conventional chemical vapor deposition to produce Ge nanocrystals on SiO 2 surfaces are proposed.

  8. Electron paramagnetic resonance at dislocations in germanium

    SciTech Connect

    Pakulis, E.J.

    1982-06-01

    The first observation of the paramagnetic resonance of electrons at dislocations in germanium single crystals is reported. Under subband gap optical excitation, two sets of lines are detected: four lines about the <111> axes with g/sub perpendicular to/ = 0.34 and g/sub parallel/ = 1.94, and 24 lines with g/sub perpendicular to/ = 0.73 and g/sub parallel/ = 1.89 about <111> axes with the six-fold 1.2/sup 0/ distortion. This represents the first measurement of the disortion angle of a dislocation dangling bond. The possibility that the distortion results from a Peierls transition along the dislocation line is discussed.

  9. Thermodynamic properties of germanium/carbon microclusters

    NASA Astrophysics Data System (ADS)

    Wielgus, Pawel; Roszak, Szczepan; Majumdar, Devashis; Leszczynski, Jerzy

    2005-12-01

    Theoretical studies on the GenCm (n =1,2; m =1-3) microclusters have been performed using the state of the art calculations. Several alternative structures of these clusters were studied to locate the lowest-energy isomers. It is observed that the structures of the complexes result from the competition between ionic Ge-C, conjugated covalent C-C, and metallic Ge-Ge bonds. The ionization of the molecules enhances the ionic character of the Ge-C bond and has significant structural consequences. Using theoretically determined partition functions, thermodynamic data are computed and experimental enthalpies are enhanced. The ab initio atomization energies of germanium carbides compare well with corrected experimental functions. The experimental appearance potentials are well reproduced by the theoretical ionization potentials.

  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

    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.

  12. Germanium detectors in homeland security at PNNL

    DOE PAGESBeta

    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

  13. Tin impurity centers in glassy germanium chalcogenides

    SciTech Connect

    Bordovsky, G. A.; Gladkikh, P. V.; Kozhokar, M. Yu.; Marchenko, A. V.; Seregin, P. P.; Terukov, E. I.

    2011-10-15

    Tin atoms produced by radioactive decay of {sup 119mm}Sn and {sup 119}Sn impurity atoms in the structure of Ge{sub x}S{sub 1-x} and Ge{sub x}Se{sub 1-x} glasses are stabilized in the form of Sn{sup 2+} and Sn{sup 4+} ions and correspond to ionized states of the amphoteric two-electron center with negative correlation energy (Sn{sup 2+} is an ionized acceptor, and Sn{sup 4+} is an ionized donor), whereas the neutral state of the Sn{sup 3+} center appears to be unstable. {sup 119}Sn atoms produced by radioactive decay of {sup 119m}Te impurity atoms in the structure of Ge{sub x}S{sub 1-x} and Ge{sub x}Se{sub 1-x} glasses are stabilized at both chalcogen sites (they are electrically inactive) and germanium sites.

  14. 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.

  15. 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

  16. Spectral Characterizations of the Clouds and the Earth's Radiant Energy System (CERES) Thermistor Bolometers using Fourier Transform Spectrometer (FTS) Techniques

    NASA Technical Reports Server (NTRS)

    Thornhill, K. Lee; Bitting, Herbert; Lee, Robert B., III; Paden, Jack; Pandey, Dhirendra K.; Priestley, Kory J.; Thomas, Susan; Wilson, Robert S.

    1998-01-01

    Fourier Transform Spectrometer (FTS) techniques are being used to characterize the relative spectral response, or sensitivity, of scanning thermistor bolometers in the infrared (IR) region (2 - >= 100-micrometers). The bolometers are being used in the Clouds and the Earth's Radiant Energy System (CERES) program. The CERES measurements are designed to provide precise, long term monitoring of the Earth's atmospheric radiation energy budget. The CERES instrument houses three bolometric radiometers, a total wavelength (0.3- >= 150-micrometers) sensor, a shortwave (0.3-5-micrometers) sensor, and an atmospheric window (8-12-micrometers) sensor. Accurate spectral characterization is necessary for determining filtered radiances for longwave radiometric calibrations. The CERES bolometers spectral response's are measured in the TRW FTS Vacuum Chamber Facility (FTS - VCF), which uses a FTS as the source and a cavity pyroelectric trap detector as the reference. The CERES bolometers and the cavity detector are contained in a vacuum chamber, while the FTS source is housed in a GN2 purged chamber. Due to the thermal time constant of the CERES bolometers, the FTS must be operated in a step mode. Data are acquired in 6 IR spectral bands covering the entire longwave IR region. In this paper, the TRW spectral calibration facility design and data measurement techniques are described. Two approaches are presented which convert the total channel FTS data into the final CERES spectral characterizations, producing the same calibration coefficients (within 0.1 percent). The resulting spectral response curves are shown, along with error sources in the two procedures. Finally, the impact of each spectral response curve on CERES data validation will be examined through analysis of filtered radiance values from various typical scene types.

  17. Synthesis and thermoluminescence of boron-doped germanium nanowires

    NASA Astrophysics Data System (ADS)

    Zahedifar, M.; Hosseinmardi, F.; Eshraghi, L.; Ganjipour, B.

    2011-03-01

    Boron doped germanium nanowires were synthesized using chemical vapor deposition (CVD) with Au nanoparticles as nucleating centers, germanium tetrachloride as the source of germanium and B 2H 6 gas as source of boron impurity. Au nanoparticles were deposited on Si using 3-aminopropyltriethylsilane (APTES). The single crystal Ge nanowires with diameters ranging from 19 to 200 nm were grown in a controllable manner. Effects of Au nanoparticle size, argon gas flow, temperature and duration of growth on diameter and length of nanowires were investigated. This is the first report on thermoluminescence (TL) properties of boron doped germanium nanowires. Glow curves were fitted using computerized glow curve deconvolution program and seven overlapped peaks were obtained. Further the response of synthesized nanowires to different dose levels of UV was studied and linear response regime was determined.

  18. Transport Phenomena in Liquid Phase Diffusion Growth of Silicon Germanium

    NASA Astrophysics Data System (ADS)

    Armour, Neil Alexander

    Silicon Germanium, SiGe, is an important emerging semiconductor material. In order to optimize growth techniques for SiGe production, such as Liquid Phase Diffusion, LPD, or Melt Replenishment Czochralski, a good understanding of the transport phenomena in the melt is required. In the context of the Liquid Phase Diffusion growth technique, the transport phenomena of silicon in a silicon-germanium melt has been explored. Experiments isolating the dissolution and transport of silicon into a germanium melt have been conducted under a variety of flow conditions. Preliminary modeling of these experiments has also been conducted and agreement with experiments has been shown. In addition, full LPD experiments have also been conducted under varying flow conditions. Altered flow conditions were achieved through the application of a variety of magnetic fields. Through the experimental and modeling work better understanding of the transport mechanisms at work in a silicon-germanium melt has been achieved.

  19. Reaction studies of hot silicon, germanium and carbon atoms

    SciTech Connect

    Gaspar, P.P.

    1986-11-15

    Research has been continued on hot silicon, germanium and carbon atoms. Progress in the period November 16, 1985 to November 15, 1986 is reviewed in the following areas: (1) Recoil atom reaction studies. (2) Reactions of thermally generated free atoms.

  20. 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.

  1. 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.

  2. 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

  3. Modified silicon-germanium alloys with improved performance. [thermoelectric material

    NASA Technical Reports Server (NTRS)

    Pisharody, R. K.; Garvey, L. P.

    1978-01-01

    This paper discusses the results of a program on the modification of silicon-germanium alloys by means of small extraneous material additions in order to improve their figures-of-merit. A review of the properties that constitute the figure-of-merit indicates that it is the relatively high thermal conductivity of silicon-germanium alloys that is responsible for their low values of figure-of-merit. The intent of the effort discussed in this paper is therefore the reduction of the thermal conductivity of silicon-germanium alloys by minor alloy additions and/or changes in the basic structure of the material. Because Group III and V elements are compatible with silicon and germanium, the present effort in modifying silicon-germanium alloys has concentrated on additions of gallium phosphide. A significant reduction in thermal conductivity, approximately 40 to 50 percent, has been demonstrated while the electrical properties are only slightly affected as a result. The figure-of-merit of the resultant material is enhanced over that of silicon-germanium alloys and when fully optimized is potentially better than that of any other presently available thermoelectric material.

  4. Protective infrared antireflection coating based on sputtered germanium carbide

    NASA Astrophysics Data System (ADS)

    Gibson, Des; Waddell, Ewan; Placido, Frank

    2011-09-01

    This paper describes optical, durablility and environmental performance of a germanium carbide based durable antireflection coating. The coating has been demonstrated on germanium and zinc selenide infra-red material however is applicable to other materials such as zinc sulphide. The material is deposited using a novel reactive closed field magnetron sputtering technique, offering significant advantages over conventional evaporation processes for germanium carbide such as plasma enhanced chemical vapour deposition. The sputtering process is "cold", making it suitable for use on a wide range of substrates. Moreover, the drum format provide more efficient loading for high throughput production. The use of the closed field and unbalanced magnetrons creates a magnetic confinement that extends the electron mean free path leading to high ion current densities. The combination of high current densities with ion energies in the range ~30eV creates optimum thin film growth conditions. As a result the films are dense, spectrally stable, supersmooth and low stress. Films incorporate low hydrogen content resulting in minimal C-H absorption bands within critical infra-red passbands such as 3 to 5um and 8 to 12um. Tuning of germanium carbide (Ge(1-x)Cx) film refractive index from pure germanium (refractive index 4) to pure germanium carbide (refractive index 1.8) will be demonstrated. Use of film grading to achieve single and dual band anti-reflection performance will be shown. Environmental and durability levels are shown to be suitable for use in harsh external environments.

  5. 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.

  6. Optical properties of colloidal germanium nanocrystals

    SciTech Connect

    WILCOXON,JESS P.; PROVENCIO,PAULA P.; SAMARA,GEORGE A.

    2000-05-01

    Highly crystalline germanium (Ge) nanocrystals in the size range 2--10 nm were grown in inverse micelles and purified and size-separated by high pressure liquid chromatography with on-line optical and electrical diagnostics. The nanocrystals retain the diamond structure of bulk Ge down to at least 2.0 nm (containing about 150 Ge atoms). The background- and impurity-free extinction and photoluminescence (PL) spectra of these nanocrystals revealed rich structure which was interpreted in terms of the bandstructure of Ge shifted to higher energies by quantum confinement. The shifts ranged from {minus}0.1 eV to over 1 eV for the various transitions. PL in the range 350--700 nm was observed from nanocrystals 2--5 nm in size. The 2.0 nm nanocrystals yielded the most intense PL (at 420 nm) which is believed to be intrinsic and attributed to direct recombination at {Gamma}. Excitation at high energy (250 nm) populates most of the conduction bands resulting in competing recombination channels and the observed broad PL spectra.

  7. 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.

  8. 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.

  9. Preparation and characterization of hydrogenated amorphous germanium and hydrogenated amorphous germanium carbide thin films

    SciTech Connect

    Wu, Hai-Sheng

    1989-02-01

    Hydrogenated amorphous germanium (a-Ge:H) and germanium carbide (a-Ge/sub 1-x/C/sub x/:H) films were prepared by rf sputtering of a polycrystalline Ge target in a vacuum /approximately/ 4 /times/ 10/sup /minus/7/ Torr at various rf power 50 less than or equal to P less than or equal to 600 W (0. 27-3.3 W/cm/sup 2/), target-substrate distance 1 less than or equal to d less than or equal to 7'', varying partial pressures of Ar, H/sub 2/, and C/sub 3/H/sub 8/, and flow rates f. The vibrational and opto-electronic properties such as infrared (IR) absorption, optical gap, electron-spin-resonance (ESR) signals, and conductivities vary with deposition conditions. The photoconductivity sigma/sub ph/, in particular, was carefully monitored as a function of the deposition conditions to optimize it. 96 refs., 49 figs., 7 tabs.

  10. Preparation and characterization of hydrogenated amorphous germanium and hydrogenated amorphous germanium-carbide thin films

    SciTech Connect

    Wu, H.S.

    1988-01-01

    Hydrogenated amorphous germanium (a-Ge:H) and germanium carbide (a-Ge{sub 1{minus}x}C{sub x}:H) films were prepared by rf sputtering of a polycrystalline Ge target in a vacuum {approximately}4 {times} 10{sup {minus}7} Torr at various rf power, target-substrate distance, varying partial pressures of Ar, H{sub 2}, and C{sub 3}H{sub 8}, and flow rates. The vibrational and opto-electronic properties such as infrared (IR) absorption, optical gap, electron-spin-resonance (ESR) signals, and conductivities vary with deposition conditions. The photoconductivity, in particular, was carefully monitored as a function of the deposition conditions to optimize it. The concentration of Ge-H bonds and the optical gap generally decrease as P is increased. Results of annealing showed the enhanced segregation effect of Ge-C bonds {ge} 300{degree}C. The evolution of bonded hydrogen with temperature is studied. Deposition rates of a-Ge:H films are estimated and compared. The thermalization curve for a Ge target is constructed. Deposition rate was found to decrease exponentially with increasing target-substrate distances to decrease with increasing partial pressures of H{sub 2} and C{sub 3}H{sub 8} and increasing flow rates. Hydrogen incorporation markedly increased photoconductivity.

  11. 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.

  12. Single-molecule conductance in atomically precise germanium wires.

    PubMed

    Su, Timothy A; Li, Haixing; Zhang, Vivian; Neupane, Madhav; Batra, Arunabh; Klausen, Rebekka S; Kumar, Bharat; Steigerwald, Michael L; Venkataraman, Latha; Nuckolls, Colin

    2015-09-30

    While the electrical conductivity of bulk-scale group 14 materials such as diamond carbon, silicon, and germanium is well understood, there is a gap in knowledge regarding the conductivity of these materials at the nano and molecular scales. Filling this gap is important because integrated circuits have shrunk so far that their active regions, which rely so heavily on silicon and germanium, begin to resemble ornate molecules rather than extended solids. Here we unveil a new approach for synthesizing atomically discrete wires of germanium and present the first conductance measurements of molecular germanium using a scanning tunneling microscope-based break-junction (STM-BJ) technique. Our findings show that germanium and silicon wires are nearly identical in conductivity at the molecular scale, and that both are much more conductive than aliphatic carbon. We demonstrate that the strong donor ability of C-Ge σ-bonds can be used to raise the energy of the anchor lone pair and increase conductance. Furthermore, the oligogermane wires behave as conductance switches that function through stereoelectronic logic. These devices can be trained to operate with a higher switching factor by repeatedly compressing and elongating the molecular junction. PMID:26373928

  13. Application of germanium carbide in durable multilayer IR coatings

    NASA Astrophysics Data System (ADS)

    Kelly, Chris J.; Orr, James S.; Gordon, H.; Traub, Leonard T.; Lettington, Alan H.

    1990-08-01

    Infrared transparent amorphous hydrogenated alloys of germanium and carbon (germanium carbide) have been deposited by plasma assisted chemical vapour deposition (PACVD) using germane (GeH4 ) and butane (C 4Hid as the feedstocks and by reactive sputtering of germanium with a CH1g-Ar plasma. The effects of varying various deposition conditions have been assessed on a number of coating properties . Germanium Carbide has good environmental durability and can be deposited in thick layers. Using PACVD it can be deposited with any refractive index in the range 2 to 4 while the sputtering process is limited to indices in the range 3 to 4 . One advantage of the sputtering process is the high deposition rates achievable which can be up to '-lOum/h compared with lum/h for the PACVD process. When used in conjunction with "diamond-like" carbon (a-'C:H) , germanium carbide offers the prospect of rnultilayer antireflection coatings for 8 to 12 urn optics with durabilities which hitherto have been impossible to achieve. Antireflection coatings for zinc sulphide windows which are subject to hostile environmental conditions have been investigated and the performance of the coatings is presented. The factors affecting the practical realisation of these coatings on a production scale are discussed.

  14. Low temperature exfoliation process in hydrogen-implanted germanium layers

    NASA Astrophysics Data System (ADS)

    Ferain, I. P.; Byun, K. Y.; Colinge, C. A.; Brightup, S.; Goorsky, M. S.

    2010-03-01

    The feasibility of transferring hydrogen-implanted germanium to silicon with a reduced thermal budget is demonstrated. Germanium samples were implanted with a splitting dose of 5×1016 H2+ cm-2 at 180 keV and a two-step anneal was performed. Surface roughness and x-ray diffraction pattern measurements, combined with cross-sectional TEM analysis of hydrogen-implanted germanium samples were carried out in order to understand the exfoliation mechanism as a function of the thermal budget. It is shown that the first anneal performed at low temperature (≤150 °C for 22 h) enhances the nucleation of hydrogen platelets significantly. The second anneal is performed at 300 °C for 5 min and is shown to complete the exfoliation process by triggering the formation of extended platelets. Two key results are highlighted: (i) in a reduced thermal budget approach, the transfer of hydrogen-implanted germanium is found to follow a mechanism similar to the transfer of hydrogen-implanted InP and GaAs, (ii) such a low thermal budget (<300 °C) is found to be suitable for directly bonded heterogeneous substrates, such as germanium bonded to silicon, where different thermal expansion coefficients are involved.

  15. Investigation of germanium Raman lasers for the mid-infrared.

    PubMed

    De Leonardis, Francesco; Troia, Benedetto; Soref, Richard A; Passaro, Vittorio M N

    2015-06-29

    In this paper we present a detailed theoretical investigation of integrated racetrack Raman lasers based on the germanium material system operating in the mid-infrared beyond the germanium two-photon absorption cut-off wavelength of 3.17 μm. The effective Raman gain has been estimated in waveguides based on germanium-on-silicon, germanium-on-SOI and germanium-on-Si3N4 technology platforms as a function of their crystallographic orientations. Furthermore, general design guidelines have been determined by means of a comparative analysis of Raman laser performance, i.e. the threshold power, polarization and directionality of the excited Stokes signals as a function of racetrack cavity length and directional-coupler dimensions. Finally, the emitted Raman laser power has been evaluated as a function of overall propagation losses and operative wavelengths up to 3.8 μm, while the time dynamics of Raman lasers has been simulated assuming continuous and pulse waves as input pump signals. PMID:26191733

  16. Reaction studies of hot silicon, germanium and carbon atoms

    SciTech Connect

    Gaspar, P.P.

    1990-11-01

    The goal of this project was to increase the authors understanding of the interplay between the kinetic and electronic energy of free atoms and their chemical reactivity by answering the following questions: (1) what is the chemistry of high-energy carbon silicon and germanium atoms recoiling from nuclear transformations; (2) how do the reactions of recoiling carbon, silicon and germanium atoms take place - what are the operative reaction mechanisms; (3) how does the reactivity of free carbon, silicon and germanium atoms vary with energy and electronic state, and what are the differences in the chemistry of these three isoelectronic atoms This research program consisted of a coordinated set of experiments capable of achieving these goals by defining the structures, the kinetic and internal energy, and the charge states of the intermediates formed in the gas-phase reactions of recoiling silicon and germanium atoms with silane, germane, and unsaturated organic molecules, and of recoiling carbon atoms with aromatic molecules. The reactions of high energy silicon, germanium, and carbon atoms created by nuclear recoil were studied with substrates chosen so that their products illuminated the mechanism of the recoil reactions. Information about the energy and electronic state of the recoiling atoms at reaction was obtained from the variation in end product yields and the extent of decomposition and rearrangement of primary products (usually reactive intermediates) as a function of total pressure and the concentration of inert moderator molecules that remove kinetic energy from the recoiling atoms and can induce transitions between electronic spin states. 29 refs.

  17. First-principles calculations of multivacancies in germanium

    NASA Astrophysics Data System (ADS)

    Sholihun; Ishii, Fumiyuki; Saito, Mineo

    2016-01-01

    We carry out density-functional-theory calculations to study the stability of germanium multivacancies. We use supercells containing 216 atomic sites and simulate two configurations called the “part of hexagonal ring” (PHR) and fourfold configurations of the tri-, tetra-, and pentavacancies. We find that the fourfold configurations of the tetra- and pentavacancies are the most stable and these configurations are also the most stable in the case of silicon. However, we find that the PHR and fourfold configurations have similar energies in the case of the germanium trivacancy. These results are in contrast to those of the silicon trivacancy; the fourfold configuration has substantially lower energy than the PHR configuration. This difference between germanium and silicon is expected to originate from the fact that the four bonds in the fourfold configurations in the germanium trivacancy are weaker than those in the silicon one. By calculating dissociation energies, we find that the silicon tetravacancy is not easy to dissociate, whereas the germanium tetravacancy is not very stable compared with the silicon one.

  18. POSITION SENSITIVE GERMANIUM DETECTORS FOR GAMMA-RAY IMAGING AND SPECTROSCOPY

    EPA Science Inventory

    Gamma-ray imaging with position-sensitive germanium detectors offers the advantages of excellent energy resolution, high detection efficiency, and potentially good sptial resolution. The development of the amorphous-semiconductor electrical contact technology for germanium detec...

  19. Growth mode and properties of Mn-Co-Ni-O NTC thermistor thin films deposited on MgO (100) substrate by laser MBE

    NASA Astrophysics Data System (ADS)

    Xie, Yahong; Kong, Wenwen; Ji, Guang; Gao, Bo; Yao, Jincheng; Chang, Aimin

    2014-12-01

    Mn1.56Co0.96Ni0.48O4-δ thin films were deposited on MgO (100) substrate using laser molecular beam epitaxy (LMBE) technique at the temperature range of 300-600°C under oxygen partial pressure of 5 × 10-3 Pa. The effect of growth temperature on microstructure and electrical properties as well as the growth mode were studied using XRD, RHEED, AFM and resistance-temperature measurements. The results showed that all prepared thin films underwent epitaxial growth along the single-(100) orientation direction of the MgO substrate from 3D-island mode to 2D layer-by-layer mode, and exhibited good crystallinity and NTC thermistor behavior. Their resistance at room temperature can be in the range of 10-50 MΩ together with a B-value of about 3300 K, which are desirable for a wide range of practical applications of the NTC thermistors.

  20. Hydrogenated nanocrystalline silicon germanium thin films

    NASA Astrophysics Data System (ADS)

    Yusoff, A. R. M.; Syahrul, M. N.; Henkel, K.

    2007-08-01

    Hydrogenated nanocrystalline silicon germanium thin films (nc-SiGe:H) is an interesting alternative material to replace hydrogenated nanocrystalline silicon (nc-Si:H) as the narrow bandgap absorber in an a-Si/a-SiGe/nc-SiGe(nc-Si) triple-junction solar cell due to its higher optical absorption in the wavelength range of interest. In this paper, we present results of optical, structural investigations and electrical characterization of nc-SiGe:H thin films made by hot-wire chemical vapor deposition (HWCVD) with a coil-shaped tungsten filament and with a disilane/germane/hydrogen gas mixture. The optical band gaps of a-SiGe:H and nc-SiGe:H thin-films, which are deposited with the same disilane/germane/hydrogen gas mixture ratio of 3.4:1.7:7, are about 1.58 eV and 2.1 eV, respectively. The nc-SiGe:H thin film exhibits a larger optical absorption coefficient of about 2-4 in the 600-900 nm range when compared to nc-Si:H thin film. Therefore, a thinner nc-SiGe:H layer of sim500 nm thickness may be sufficient for the narrow bandgap absorber in an a-Si based multiple-junction solar cell. We enhanced the transport properties as measured by the photoconductivity frequency mixing technique. These improved alloys do not necessarily show an improvement in the degree of structural heterogeneity on the nanometer scale as measured by small-angle X-ray scattering. Decreasing both the filament temperature and substrate temperature produced a film with relatively low structural heterogeneity while photoluminescence showed an order of magnitude increase in defect density for a similar change in the process.

  1. 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

  2. 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

  3. Simulations for Tracking Cosmogenic Activation in Germanium and Copper

    SciTech Connect

    Aguayo, Estanislao; Kouzes, Richard T.; Orrell, John L.

    2011-11-01

    High-purity germanium (HPGe) detectors housed in copper cryostats and shielding materials are used in measurements of the extraordinarily rare nuclear decay process, neutrinoless double-beta decay (0νββ), and for dark matter searches. Cosmogenic production of 68Ge and 60Co in the germanium and copper represent an irreducible background to these experiments as the subsequent decays of these isotopes can mimic the signals of interest. These radioactive isotopes can be removed by chemical and/or isotopic separation, but begin to grow-in to the material after separation until the material is moved deep underground. This work is motivated by the need to have a reliable, experimentally benchmarked simulation tool for evaluating shielding materials used during transportation and near-surface manufacturing of experiment components. The resulting simulations tool has been used to enhance the effectiveness of an existing transport shield used to ship enriched germanium from the separations facility to the detector manufacturing facility.

  4. 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.

  5. 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.

  6. 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

  7. Silicon-germanium technology program of the Jet Propulsion Laboratory.

    NASA Technical Reports Server (NTRS)

    De Winter, F.; Stapfer, G.

    1972-01-01

    The outer planetary exploration missions studied by the Jet Propulsion Laboratory require silicon-germanium radioisotope thermoelectric generators (RTGs) in which the factors of safety are as low as is compatible with the reliable satisfaction of the power needs. Work on silicon germanium sublimation performed at the Jet Propulsion Laboratory is presented. Analytical modeling work on the solid-diffusion process involved in the steady-state (free) sublimation of silicon germanium is described. Analytical predictions are made of the sublimation suppression which can be achieved by using a cover gas. A series of accelerated (high-temperature) tests which were performed on simulated hardware (using four SiGe couples) to study long-term sublimation and reaction mechanisms are also discussed.

  8. 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...

  9. 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...

  10. 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...

  11. 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...

  12. 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...

  13. Deposition and characterizations of ultrasmooth silver thin films assisted with a germanium wetting layer

    NASA Astrophysics Data System (ADS)

    Zhang, Junce; Fryauf, David M.; Diaz Leon, Juan J.; Garrett, Matthew; VJ, Logeeswaran; Islam, Saif M.; Kobayashi, Nobuhiko P.

    2015-08-01

    In this paper, silver thin films deposited on SiO2 substrates with a germanium wetting layer fabricated by electron-beam evaporation were studied. The characterization methods of XTEM, FTIR, XRD and XRR were used to study the structural properties of silver thin films with various thicknesses of germanium layers. Silver films deposited with very thin (1-5nm) germanium wetting layers show about one half of improvement in the crystallite sizes comparing silver films without germanium layer. The surface roughness of silver thin films significantly decrease with a thin germanium wetting layer, reaching a roughness minimum around 1-5nm of germanium, but as the germanium layer thickness increases, the silver thin film surface roughness increases. The relatively higher surface energy of germanium and bond dissociation energy of silver-germanium were introduced to explain the effects the germanium layer made to the silver film deposition. However, due to the Stranski-Krastanov growth mode of germanium layer, germanium island formation started with increased thickness (5-15nm), which leads to a rougher surface of silver films. The demonstrated silver thin films are very promising for large-scale applications as molecular anchors, optical metamaterials, plasmonic devices, and several areas of nanophotonics.

  14. Nanocrystal Inks without Ligands: Stable Colloids of Bare Germanium Nanocrystals

    SciTech Connect

    Holman, Zachary C.; Kortshagen, Uwe R.

    2011-05-11

    Colloidal semiconductor nanocrystals typically have ligands attached to their surfaces that afford solubility in common solvents but hinder charge transport in nanocrystal films. Here, an alternative route is explored in which bare germanium nanocrystals are solubilized by select solvents to form stable colloids without the use of ligands. A survey of candidate solvents shows that germanium nanocrystals are completely solubilized by benzonitrile, likely because of electrostatic stabilization. Films cast from these dispersions are uniform, dense, and smooth, making them suitable for device applications without postdeposition treatment.

  15. Characterisation of two AGATA asymmetric high purity germanium capsules

    NASA Astrophysics Data System (ADS)

    Colosimo, S. J.; Moon, S.; Boston, A. J.; Boston, H. C.; Cresswell, J. R.; Harkness-Brennan, L.; Judson, D. S.; Lazarus, I. H.; Nolan, P. J.; Simpson, J.; Unsworth, C.

    2015-02-01

    The AGATA spectrometer is an array of highly segmented high purity germanium detectors. The spectrometer uses pulse shape analysis in order to track Compton scattered γ-rays to increase the efficiency of nuclear spectroscopy studies. The characterisation of two high purity germanium detector capsules for AGATA of the same A-type has been performed at the University of Liverpool. This work will examine the uniformity of performance of the two capsules, including a comparison of the resolution and efficiency as well as a study of charge collection. The performance of the capsules shows good agreement, which is essential for the efficient operation of the γ-ray tracking array.

  16. LETTER TO THE EDITOR: Structure of densified amorphous germanium dioxide

    NASA Astrophysics Data System (ADS)

    Micoulaut, Matthieu

    2004-03-01

    Classical molecular dynamics simulations are used to study the structure of densified germanium dioxide (GeO2). It is found that the coordination number of germanium changes with increasing density (pressure) while pressure released systems exhibit only a marked angular change in local structure as compared to the virgin system. The structural modification with pressure appears to be stepwise and gradually affects long-range (through the reduction of the long-range correlations as seen from the shift of the first sharp diffraction peak), intermediate-range (by angular reduction) and finally short-range structure (by tetrahedron distortion).

  17. 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.

  18. 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.

  19. Large-size germanium crystal growth for rare event physics

    NASA Astrophysics Data System (ADS)

    Mei, Dongming; Wang, Guojian; Mei, Hao; Guan, Yutong; Yang, Gang; Govani, Jayesh; Cubed Collaboration

    2014-09-01

    Cosmogenic production in germanium crystals grown on the surface can limit the sensitivity for the next generation deep underground experiments in searching for rare event physics beyond the Standard Model. One of the best solutions to eliminate unwanted cosmogenics is to produce the germanium crystals and detectors in an underground environment. The goal of this project is to create state-of-the-art detectors to advance neutrinoless double-beta decay and dark matter exploration research and technology while simultaneously paving the way for infrastructure to support an underground laboratory for zone refining, crystal growth, and detector fabrication. The greatest challenge in the growth of germanium crystals is a lack of precise control of individual crystal properties such as the impurity distribution, the dislocation density, and the crystalline structure. With knowledge gained from the pioneers in the field of crystal growth, the researchers have developed a novel technique to grow detector-grade crystals. In this paper, we will report detector-grade large-size germanium crystal growth at the University of South Dakota. Cosmogenic production in germanium crystals grown on the surface can limit the sensitivity for the next generation deep underground experiments in searching for rare event physics beyond the Standard Model. One of the best solutions to eliminate unwanted cosmogenics is to produce the germanium crystals and detectors in an underground environment. The goal of this project is to create state-of-the-art detectors to advance neutrinoless double-beta decay and dark matter exploration research and technology while simultaneously paving the way for infrastructure to support an underground laboratory for zone refining, crystal growth, and detector fabrication. The greatest challenge in the growth of germanium crystals is a lack of precise control of individual crystal properties such as the impurity distribution, the dislocation density, and the

  20. Tensile-strained germanium microdisks with circular Bragg reflectors

    NASA Astrophysics Data System (ADS)

    El Kurdi, M.; Prost, M.; Ghrib, A.; Elbaz, A.; Sauvage, S.; Checoury, X.; Beaudoin, G.; Sagnes, I.; Picardi, G.; Ossikovski, R.; Boeuf, F.; Boucaud, P.

    2016-02-01

    We demonstrate the combination of germanium microdisks tensily strained by silicon nitride layers and circular Bragg reflectors. The microdisks with suspended lateral Bragg reflectors form a cavity with quality factors up to 2000 around 2 μm. This represents a key feature to achieve a microlaser with a quasi-direct band gap germanium under a 1.6% biaxial tensile strain. We show that lowering the temperature significantly improves the quality factor of the quasi-radial modes. Linewidth narrowing is observed in a range of weak continuous wave excitation powers. We finally discuss the requirements to achieve lasing with these kind of structures.

  1. 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.

  2. 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.

  3. 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.

  4. Dark Matter Physics with SUB-keV Germanium Detectors

    NASA Astrophysics Data System (ADS)

    Wong, Henry T.

    2015-03-01

    Germanium detectors with sub-keV sensitivities open a window to study neutrino physics to search for light WIMP dark matter. We summarize the recent results on spin-independent couplings of light WIMPs from the TEXONO experiment at the Kuo-Sheng Reactor Neutrino Laboratory.

  5. Strained-layer epitaxy of germanium-silicon alloys.

    PubMed

    Bean, J C

    1985-10-11

    Despite the dominant position of silicon in semiconductor electronics, its use is ultimately limited by its incompatibility with other semiconducting materials. Strained-layer epitaxy overcomes problems of crystallographic compatibility and produces high-quality heterostructures of germanium-silicon layers on silicon. This opens the door to a range of electronic and photonic devices that are based on bandstructure physics. PMID:17842673

  6. 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.

  7. 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.

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

    SciTech Connect

    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.

  9. 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.

  10. 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). PMID:26695261

  11. 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.

  12. 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.

  13. Broad Band Antireflection Coatings for Silicon and Germanium Substrates.

    NASA Astrophysics Data System (ADS)

    Bezuidenhout, Dirk Francois

    Infrared antireflection coatings for silicon and germanium substrates and some of the associated problems are addressed in this thesis. One of the first problems identified and investigated was that of the adhesion of ZnS films to germanium substrates. The cleaning of the Ge discs was evaluated by means of Auger spectroscopy. The main contaminant species found were carbon, oxygen and in the case of germanium substrates sulphur. No sulphur was found on silicon substrates. A wash in a series of organic solutions followed by a bake inside the vacuum chamber lead to much improved though still not acceptable adhesion of ZnS films to germanium substrates. The influence of a contact layer between the substrate and ZnS was investigated. Firstly, metal contact layers (Ni, Cr, Cu) were tried to improve the adhesion of the ZnS films. These samples (germanium-metal-zinc sulphide) were annealed in air in order to transfer the germanium -metal film to a germanide region and thus high optical transmission at long wave-lengths. Slight absorption still results even after the annealing of these samples. A dielectric material, Y_2O_3 , was therefore tested replacing the metal films. The system Ge-Y_2O_3 -ZnS in conjunction with an organic wash and vacuum bake lead to excellent adhesion of the ZnS layers to the germanium substrates. The next problem area addressed was that of a low refractive index material replacement for ThF _4. Four materials were investigated, i.e. ZnS, PbF_2, Y_2O _3 and YF_3. The refractive indices found for these compounds in thin film form at a wavelength of 10 μm is 2,18 for ZnS, 1,7 for PbF_2, 1,42 for Y_2O_3 and 1,3 for YF_3. From these results YF_3 was chosen as low refractive index material in the coating designs. Multi-layer coatings incorporating ZnS, Ge and YF_3 films were designed and evaporated. Measured reflectance values below 0,2% were obtained from 9 μm to 11 mum. These systems were stable and robust. Finally, a silicon ball lens was

  14. Respiratory monitoring system based on the nasal pressure technique for the analysis of sleep breathing disorders: Reduction of static and dynamic errors, and comparisons with thermistors and pneumotachographs

    NASA Astrophysics Data System (ADS)

    Alves de Mesquita, Jayme; Lopes de Melo, Pedro

    2004-03-01

    Thermally sensitive devices—thermistors—have usually been used to monitor sleep-breathing disorders. However, because of their long time constant, these devices are not able to provide a good characterization of fast events, like hypopneas. Nasal pressure recording technique (NPR) has recently been suggested to quantify airflow during sleep. It is claimed that the short time constants of the devices used to implement this technique would allow an accurate analysis of fast abnormal respiratory events. However, these devices present errors associated with nonlinearities and acoustic resonance that could reduce the diagnostic value of the NPR. Moreover, in spite of the high scientific and clinical potential, there is no detailed description of a complete instrumentation system to implement this promising technique in sleep studies. In this context, the purpose of this work was twofold: (1) describe the development of a flexible NPR device and (2) evaluate the performance of this device when compared to pneumotachographs (PNTs) and thermistors. After the design details are described, the system static accuracy is evaluated by a comparative analysis with a PNT. This analysis revealed a significant reduction (p<0.001) of the static error when system nonlinearities were reduced. The dynamic performance of the NPR system was investigated by frequency response analysis and time constant evaluations and the results showed that the developed device response was as good as PNT and around 100 times faster (τ=5,3 ms) than thermistors (τ=512 ms). Experimental results obtained in simulated clinical conditions and in a patient are presented as examples, and confirmed the good features achieved in engineering tests. These results are in close agreement with physiological fundamentals, supplying substantial evidence that the improved dynamic and static characteristics of this device can contribute to a more accurate implementation of medical research projects and to improve the

  15. 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

  16. Low temperature carrier transport properties in isotopically controlled germanium

    SciTech Connect

    Itoh, K.

    1994-12-01

    Investigations of electronic and optical properties of semiconductors often require specimens with extremely homogeneous dopant distributions and precisely controlled net-carrier concentrations and compensation ratios. The previous difficulties in fabricating such samples are overcome as reported in this thesis by growing high-purity Ge single crystals of controlled {sup 75}Ge and {sup 70}Ge isotopic compositions, and doping these crystals by the neutron transmutation doping (NTD) technique. The resulting net-impurity concentrations and the compensation ratios are precisely determined by the thermal neutron fluence and the [{sup 74}Ge]/[{sup 70}Ge] ratios of the starting Ge materials, respectively. This method also guarantees unprecedented doping uniformity. Using such samples the authors have conducted four types of electron (hole) transport studies probing the nature of (1) free carrier scattering by neutral impurities, (2) free carrier scattering by ionized impurities, (3) low temperature hopping conduction, and (4) free carrier transport in samples close to the metal-insulator transition.

  17. Improving Memory Characteristics of Hydrogenated Nanocrystalline Silicon Germanium Nonvolatile Memory Devices by Controlling Germanium Contents.

    PubMed

    Kim, Jiwoong; Jang, Kyungsoo; Phu, Nguyen Thi Cam; Trinh, Thanh Thuy; Raja, Jayapal; Kim, Taeyong; Cho, Jaehyun; Kim, Sangho; Park, Jinjoo; Jung, Junhee; Lee, Youn-Jung; Yi, Junsin

    2016-05-01

    Nonvolatile memory (NVM) with silicon dioxide/silicon nitride/silicon oxynitride (ONO(n)) charge trap structure is a promising flash memory technology duo that will fulfill process compatibility for system-on-panel displays, down-scaling cell size and low operation voltage. In this research, charge trap flash devices were fabricated with ONO(n) stack gate insulators and an active layer using hydrogenated nanocrystalline silicon germanium (nc-SiGe:H) films at a low temperature. In this study, the effect of the interface trap density on the performance of devices, including memory window and retention, was investigated. The electrical characteristics of NVM devices were studied controlling Ge content from 0% to 28% in the nc-SiGe:H channel layer. The optimal Ge content in the channel layer was found to be around 16%. For nc-SiGe:H NVM with 16% Ge content, the memory window was 3.13 V and the retention data exceeded 77% after 10 years under the programming condition of 15 V for 1 msec. This showed that the memory window increased by 42% and the retention increased by 12% compared to the nc-Si:H NVM that does not contain Ge. However, when the Ge content was more than 16%, the memory window and retention property decreased. Finally, this research showed that the Ge content has an effect on the interface trap density and this enabled us to determine the optimal Ge content. PMID:27483856

  18. 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. PMID:27015376

  19. Gamma Ray Interactions in Planar Germanium Strip Detectors

    NASA Astrophysics Data System (ADS)

    Jackson, E. G.; Lakshmi, S.; Chowdhury, P.; Deo, A. Y.; Guess, C. J.; Hota, S.; Lister, C. J.

    2011-10-01

    The position resolution of the interaction point of a gamma ray within the volume of a planar germanium crystal is under investigation. A 16x16 planar double-sided strip detector of high-purity germanium, measuring 92×92×20 mm, with 16 horizontal strips on one face and 16 vertical strips on the other, is used. Comparing the strongest strip signal from each side of the detector allows for a X-Y pixelation of the gamma ray interaction in the crystal. Energy and efficiency calibrations are performed with standard 152Eu and 133Ba sources placed at fixed distances from the detector face. The measured efficiency of each pixel is compared to calculated geometric efficiencies. Next steps involve the analysis of two-pixel events which pick out Compton scatters within the planar crystal. Results and status report will be presented. Work supported by the U.S. Department of Energy.

  20. 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.

  1. 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.

  2. High temperature material interactions of thermoelectric systems using silicon germanium.

    NASA Technical Reports Server (NTRS)

    Stapfer, G.; Truscello, V. C.

    1973-01-01

    The efficient use of silicon germanium thermoelectric material for radioisotope thermoelectric generators (RTG) is achieved by operation at relatively high temperatures. The insulation technique which is most appropriate for this application uses multiple layers of molybdenum foil and astroquartz. Even so, the long term operation of these materials at elevated temperatures can cause material interaction to occur within the system. To investigate these material interactions, the Jet Propulsion Laboratory is currently testing a number of thermoelectric modules which use four silicon germanium thermoelectric couples in conjunction with the multifoil thermal insulation. The paper discusses the results of the ongoing four-couple module test program and correlates test results with those of a basic material test program.

  3. 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.

  4. 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.

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

    SciTech Connect

    Nathan Robert Classen

    2002-12-31

    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 {beta} C-H insertion mechanism.

  6. P-type Modified Electrode Germanium Detector Impurity Profiles

    NASA Astrophysics Data System (ADS)

    Kephart, Jeremy

    2008-04-01

    Germanium detectors with unprecedented capabilities are needed for detecting ultra-rare events in future neutrinoless double-beta decay experiments, searches for dark matter, environmental monitoring programs, national security applications, and potentially neutrino astrophysics. An ideal detector would combine ultra-low background capabilities, minimal electronic instrumentation, extremely low energy threshold, and the ability to perform event reconstruction to determine the interaction type or the spatial distribution of ionization following an interaction. A germanium detector with a special, very low capacitance, contact geometry and presumably a deliberately contrived impurity profile could provide all these capabilities. We present an analysis of the detector impurity concentration profiles and their impact on the depletion voltage, capacitance and charge collection times for such detectors.

  7. Environmental applications for an intrinsic germanium well detector

    SciTech Connect

    Stegnar, P.; Eldridge, J.S.; Teasley, N.A.; Oakes, T.W.

    1983-01-01

    The overall performance of an intrinsic germanium well detector for /sup 125/I measurements was investigated in a program of environmental surveillance. Concentrations of /sup 125/I and /sup 131/I were determined in thyroids of road-killed deer showing the highest activities of /sup 125/I in the animals from the near vicinity of Oak Ridge National Laboratory. This demonstrates the utility of road-killed deer as a bioindicator for radioiodine around nuclear facilities. 6 refs., 2 figs., 3 tabs.

  8. 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.

  9. Fabrication techniques for reverse electrode coaxial germanium nuclear radiation detectors

    SciTech Connect

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

    1980-11-01

    Germanium detectors with reverse polarity coaxial electrodes have been shown to exhibit improved resistance to radiation damage as compared with conventional electrode devices. However, the production of reverse electrode devices involves the development of new handling and fabrication techniques which has limited their wider application. We have developed novel techniques which lead to a device which is simple to fabricate, environmentally passivated and surface state adjusted.

  10. Preparation and Characterization of Hydrogenated Amorphous Germanium and Hydrogenated Amorphous Germanium - Thin Films.

    NASA Astrophysics Data System (ADS)

    Wu, Hai-Sheng

    Hydrogenated amorphous germanium (a-Ge:H) and germanium carbide (a-Ge_{rm 1 -x}C_{rm x} :H) films were prepared by rf sputtering of a polycrystalline Ge target in a vacuum ~4 times 10^{-7} Torr at various rf power 50 <=q P <=q 600 W (0.27-3.3 W/cm ^2), target-substrate distance 1 <=q d <=q 7 ^{''}, varying partial pressures of Ar, H_2, and C_3H_8, and flow rates f. The vibrational and opto-electronic properties such as infrared (IR) absorption, optical gap, electron -spin-resonance (ESR) signals, and conductivities vary with deposition conditions. The photoconductivity sigma_{rm ph}, in particular, was carefully monitored as a function of the deposition conditions to optimize it. The concentration of Ge-H bonds and the optical gap (E_{rm g}), generally decrease as P is increased. E_ {rm g} of the a-Ge_ {rm 1-x}C_{ rm x}:H films range from 0.85-2.3 eV. The ESR results range from 2 times 10 ^{17} to 2 times 10^{19}^ins/cm ^3. Results of annealing showed the enhanced segregation effect of Ge-C bonds >=q300^circC. The evolution of bonded hydrogen with temperature is studied. Deposition rates (R_{rm d}) of a-Ge:H films are estimated and compared. The thermalization curve for a Ge target is constructed. R _{rm d} was found to decrease exponentially with increasing d, to decrease with increasing partial pressures of H_2 and C_3H_8 and increasing flow rates. R_{ rm d} is maximal at some P_ {rm Ar} and is relatively insensitive to the substrate temperature T_{rm s}, and rises linearly with the rf power. Hydrogen incorporation markedly increased sigma_{rm ph}. The dark conductivity sigma_{rm d} and sigma_{rm ph} increase with increasing d, up to an optimal value at d ~ 6^ {''}, increase at f < 1 sccm, and increase with P and T _{rm s}. Incorporation of significant amounts of carbon sharply reduces sigma_{rm ph}. However, a small amount has little effect on sigma _{rm ph}. Although all increases in sigma_{rm ph} are significant relative to those of previously reported rf

  11. Synthesis and characterization of silicon and germanium nanowires, silica nanotubes, and germanium telluride/tellurium nanostructures

    NASA Astrophysics Data System (ADS)

    Tuan, Hsing-Yu

    A supercritical fluid-liquid solid (SFLS) nanowire growth process using alkanethiol-coated Au nanoparticles to seed silicon nanowires was developed for synthesizing silicon nanowires in solution. The organic solvent was found to significantly influence the silicon precursor decomposition in solution. 46.8 mg of silicon nanowires with 63% yield of silicon nanowire synthesis were achieved while using benzene as a solvent. The most widely used metal for seeding Si and Ge nanowires is Au. However, Au forms deep trap in both Si and Ge and alternative metal seeds are more desirable for electronic applications. Different metal nanocrystals were studied for Si and Ge nanowire synthesis, including Co, Ni, CuS, Mn, Ir, MnPt 3, Fe2O3, and FePt. All eight metals have eutectic temperatures with Si and Ge that are well above the nanowire growth temperature. Unlike Au nanocrystals, which seed nanowire growth through the formation of a liquid Au:Si (Au:Ge) alloy, these other metals seed nanowires by forming solid silicide alloys, a process we have called "supercritical fluid-solid-solid" (SFSS) growth. Moreover, Co and Ni nanoparticles were found to catalyze the decomposition of various silane reactants that do not work well to make Si nanowires using Au seeds. In addition to seeding solid nanowires, CuS nanoparticles were found to seed silica nanotubes via a SFSS like mechanism. 5% of synthesized silica nanotubes were coiled. Heterostructured nanomaterials are interesting since they merge the properties of the individual materials and can be used in diverse applications. GeTe/Te heterostructures were synthesized by reacting diphenylgermane (DPG) and TOP-Te in the presence of organic surfactants. Aligned Te nanorods were grown on the surface facets of micrometer-size germanium telluride particles.

  12. 3D positioning germanium detectors for gamma-ray astronomy

    NASA Astrophysics Data System (ADS)

    Coburn, Wayne; Amrose, Susan; Boggs, Steven E.; Lin, Robert P.; Amman, Mark S.; Burks, Morgan T.; Hull, Ethan L.; Luke, Paul N.; Madden, Norman W.

    2003-01-01

    We have developed germanium detector technologies for use in the Nuclear Compton Telescope (NCT) - a balloon-borne soft γ-ray (0.2-10 MeV) telescope to study astrophysical sources of nuclear line emission and polarization. The heart of NCT is an array of twelve large volume cross strip germanium detectors, designed to provide 3-D positions for each photon interaction with ~1mm resolution while maintaining the high spectral resolution of germanium. Here we discuss the detailed performance of our prototype 19x19 strip detector, including laboratory tests, calibrations, and numerical simulations. In addition to the x and y positions provided by the orthogonal strips, the interaction depth (z-position) in the detector is measured using the relative timing of the anode and cathode charge collection signals. We describe laboratory calibrations of the depth discrimination using collimated sources with different characteristic energies, and compare the measurements to detailed Monte Carlo simulations and charge collection routines tracing electron-hole pairs from the interaction site to the electrodes. We have also investigated the effects of charge sharing and loss between electrodes, and present these in comparison to charge collection simulations. Detailed analysis of strip-to-strip uniformity in both efficiency and spectral resolution are also presented.

  13. 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.

  14. 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}.

  15. High purity germanium crystal growth at the University of South Dakota

    NASA Astrophysics Data System (ADS)

    Wang, Guojian; Mei, Hao; Mei, Dongming; Guan, Yutong; Yang, Gang

    2015-05-01

    High-purity germanium crystal growth is challenging work, requiring the control of individual crystal properties such as the impurity distribution, the dislocation density, and the crystalline structure. Currently, we grow high-purity germanium crystals by the Czochralski method in our laboratory in order to understand the details of the growing process, especially for large diameter crystals. In this paper, we report the progress of detector-grade germanium crystal growth at the University of South Dakota.

  16. 3D microoptical elements formed in a photostructurable germanium silicate by direct laser writing

    NASA Astrophysics Data System (ADS)

    Malinauskas, M.; Žukauskas, A.; Purlys, V.; Gaidukevičiu¯tė, A.; Balevičius, Z.; Piskarskas, A.; Fotakis, C.; Pissadakis, S.; Gray, D.; Gadonas, R.; Vamvakaki, M.; Farsari, M.

    2012-12-01

    We present our investigations into the fabrication of three-dimensional microoptical elements by the direct femtosecond laser writing of a germanium-silicon photosensitive hybrid material. Germanium glass composites are very interesting for optical applications as they are photosensitive, and maintain high optical transparency in the visible and near-infrared bands of the spectrum. Here, we have used a germanium containing hybrid material to make nanophotonic structures and microoptical elements such as photonic crystal templates, prisms and spatial polarization plates, both on flat surfaces and fiber tips. Our results show that this germanium silicate composite is an excellent material for microoptics fabrication.

  17. Tin-germanium alloys as anode materials for sodium-ion batteries.

    PubMed

    Abel, Paul R; Fields, Meredith G; Heller, Adam; Mullins, C Buddie

    2014-09-24

    The sodium electrochemistry of evaporatively deposited tin, germanium, and alloys of the two elements is reported. Limiting the sodium stripping voltage window to 0.75 V versus Na/Na+ improves the stability of the tin and tin-rich compositions on repeated sodiation/desodiation cycles, whereas the germanium and germanium-rich alloys were stable up to 1.5 V. The stability of the electrodes could be correlated to the surface mobility of the alloy species during deposition suggesting that tin must be effectively immobilized in order to be successfully utilized as a stable electrode. While the stability of the alloys is greatly increased by the presence of germanium, the specific Coulombic capacity of the alloy decreases with increasing germanium content due to the lower Coulombic capacity of germanium. Additionally, the presence of germanium in the alloy suppresses the formation of intermediate phases present in the electrochemical sodiation of tin. Four-point probe resistivity measurements of the different compositions show that electrical resistivity increases with germanium content. Pure germanium is the most resistive yet exhibited the best electrochemical performance at high current densities which indicates that electrical resistivity is not rate limiting for any of the tested compositions. PMID:25158125

  18. 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

  19. Synthesis of silicon and germanium nanowires and silicon/germanium nanowire heterostructures

    NASA Astrophysics Data System (ADS)

    Clement, Teresa J.

    2007-12-01

    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. Thermal annealing of the deposited gold seeds prior to nanowire growth is shown to lead to ripening of the gold seeds and the formation of pillars several nanometers in height under the seeds. These pillars are demonstrated to result from the catalytic collection of surface Si adatoms and provide a method to obtain 100% vertical growth of nanowires on Si (111) substrates. The growth of nanowire heterostructures has also been investigated with specific attention paid to the strain induced within these structures. Strain in axial and core-shell Si/Ge nanowire heterostructures provides a unique opportunity for modifying bandstructures of specific nanoscale heterostructures. Specific precursor selection adds an additional control by which we are able to grow specific heterostructures---axial or core-shell. Axial heterowires form more easily by catalyzing silane at the Au eutectic seed, while core-shell heterowires grow more easily by stabilizing lateral growth using disilane or digermane. Strain mapping of nanowires based on geometric phase analysis of high-resolution transmission electron microscopy lattice imaging reveals large strains present in core-shell Si

  20. Using in-situ thermistor string measurements in the Arctic sea ice to validate total surface energy flux in ERA-Interrim.

    NASA Astrophysics Data System (ADS)

    Thorn Ljungdahl, Mathilde; Kaas, Eigil; Toudal Pedersen, Leif

    2016-04-01

    We have used thermistor string measurements from two Ice Mass Balance (IMB) buoys to first infer the Arctic Sea Ice heat diffusivity, and then use these to estimate the near surface total heat flux in the ice during the winter season 2012-13. This flux is then compared with the corresponding total surface energy flux (i.e. sensible heat, latent heat, net short and long wave radiation) in the ERA-Interrim re-analysis data interpolated in time and space to the location of the buoys. It is found that difference between the ERA-interrim total flux (upward) and the corresponding flux in the upper part of the ice varies during the winter. We hypothesise that this varying bias in the ERA-Interrim is related to the treatment of sea ice in the IFS model. In the version used for ERA-Interrim, sea ice is enforced to have a fixed thickness of 1.5m whereas there is considerable seasonal variation in the actual thick thickness.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Heterogeneity of indium antimonide doped with tellurium, germanium, cadmium, and silicon

    SciTech Connect

    Gromova T.I.; Fridshtand, E.S.; Kevorkov, M.N.; Popkov, A.N.; Yorova, E.S.

    1986-05-01

    This paper investigates the heterogeneity of crystals of n- and p-type conductivity with a carrier concentration above 1014 cm-/sup 3/ at 77 K, that are doped with tellurium, germanium, cadmium, and silicon. Cadmium is the weak acceptor, whereas germanium and silicon show amphoteric properties, being located mainly at the sublattice points of the Group V element.

  6. 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.

  7. 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.

  8. 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.

  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. 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.

  11. 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.

  12. 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.

  13. Electric current induced modification of germanium nanowire NEM switch contact

    NASA Astrophysics Data System (ADS)

    Meija, R.; Kosmaca, J.; Jasulaneca, L.; Petersons, K.; Biswas, S.; Holmes, J. D.; Erts, D.

    2015-05-01

    We present an investigation of contact properties of a germanium (Ge) nanowire based nanoelectromechanical (NEM) switch in its ON state. The contact stiffness in the ON state was evaluated by detecting the nanowire’s resonance frequency. It was found that the resonance frequency increases when electric current flows through the nanowire/counter electrode contact area. The reason for modification in the contact area is referred to as electric-current-induced processes in the native oxide layer covering the nanowires. The presented resonance shift method is a simple way to indicate strengthening of the nanowire/counter electrode contact area without disassembling the contact.

  14. Electric current induced modification of germanium nanowire NEM switch contact.

    PubMed

    Meija, R; Kosmaca, J; Jasulaneca, L; Petersons, K; Biswas, S; Holmes, J D; Erts, D

    2015-05-15

    We present an investigation of contact properties of a germanium (Ge) nanowire based nanoelectromechanical (NEM) switch in its ON state. The contact stiffness in the ON state was evaluated by detecting the nanowire's resonance frequency. It was found that the resonance frequency increases when electric current flows through the nanowire/counter electrode contact area. The reason for modification in the contact area is referred to as electric-current-induced processes in the native oxide layer covering the nanowires. The presented resonance shift method is a simple way to indicate strengthening of the nanowire/counter electrode contact area without disassembling the contact. PMID:25902759

  15. 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.

  16. Germanium wrap-around photodetectors on Silicon photonics.

    PubMed

    Going, Ryan; Seok, Tae Joon; Loo, Jodi; Hsu, Kyle; Wu, Ming C

    2015-05-01

    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). PMID:25969287

  17. 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.

  18. 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.

  19. Preparation of freestanding germanium nanocrystals by ultrasonic aerosol pyrolysis

    NASA Astrophysics Data System (ADS)

    Stoldt, Conrad R.; Haag, Michael A.; Larsen, Brian A.

    2008-07-01

    This letter reports a synthetic route adaptable for the continuous, large-scale production of germanium (Ge) nanocrystals for emerging electronic and optoelectronic applications. Using an ultrasonic aerosol pyrolysis approach, diamond cubic Ge nanocrystals with dense, spherical morphologies and sizes ranging from 3to14nm are synthesized at 700°C from an ultrasonically generated aerosol of tetrapropylgermane (TPG) precursor and toluene solvent. The ultimate crystal size demonstrates a near linear relationship within the range of TPG concentrations investigated, while the shape of the measured size distributions predicts multiple particle formation mechanisms during aerosol decomposition and condensation.

  20. Reaction studies of hot silicon, germanium and carbon atoms

    SciTech Connect

    Gaspar, P.P.

    1989-02-01

    Research has been continued on hot silicon, germanium and carbon atoms. The results of experiments directed toward attaining the goals of this research program are briefly presented for the period September 1, 1987 to January 31, 1989 in sections entitled: (1) The mechanism of hydrogen acquisition by high energy silicon atoms. (2) The mechanism of disilene formation in the reactions of recoiling silicon atoms with silane. (3) The contribution of ionic processes to the primary reactions of recoiling silicon atoms. (4) The role of phosphine in hydrogen acquisition by recoiling silicon atoms. (5) Mechanism of reaction of recoiling carbon atoms with aromatic molecules.

  1. 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.

  2. Synthesis and Characterization of Functional Iron and Germanium Nanomaterials

    NASA Astrophysics Data System (ADS)

    Hoffman, Melanie

    Germanium nanomaterials have many potential applications based on their size-tunable optical and electronic properties, for example in photodetectors, photovoltaics and non-volatile memory. In this work, the synthesis of Ge nanoparticles by two different methods based on tailorability through the substituent chemistry of the Ge precursors is explored. In Chapter Two, the effect of the organic substituent upon thermal decomposition of organogermanium oxides (RGeO1.5)n to yield oxide-embedded germanium nanocrystals (Ge-NCs) is investigated. Substituents with stable radical formation or the presence of beta-hydrogen are found to facilitate NC formation at lower temperatures. Lower temperature limits germanium production to a pathway based on disproportionation only, and not -- as previously -- also on hydrogen reduction of germanium oxides. The organic substituent also introduces tailorability of organogermanium oxide properties, such as melting points. For R = n-butyl, benzyl, these are lowered below the disproportionation temperature, yielding melts containing Ge-NCs. The knowledge gained in the substituent study is applied to solution synthesis of Ge-NCs in Chapter Three. The n-butyl substituent, which formed Ge-NC from (nBuGeO1.5)n at 300 °C, can eliminate by radical and beta-hydride elimination pathways. In the molecular compounds nBuxGeH4-x (x = 1-4), reductive elimination also becomes possible. We propose this leads to the decrease in decomposition temperature of nBu xGeH4-x from x = 4 to x = 1. In the second section of this thesis, Chapter Four, the catalytic activity of metal-decorated iron/iron-oxide core-shell nanoparticles (M/Fe Fe xOy) in Heck and Suzuki couplings is investigated. Electroless deposition of noble metals on Fe FexOy generates the catalyst. The catalytic activity of Pd/Fe FexOy is improved over standard heterogeneous catalysts (e.g., Pd/C) in Heck coupling of styrene and bromobenzene. Leaching studies in Suzuki coupling of bromobenzene with

  3. 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.

  4. Germanium-on-SOI waveguides for mid-infrared wavelengths.

    PubMed

    Younis, Usman; Vanga, Sudheer K; Lim, Andy Eu-Jin; Lo, Patrick Guo-Qiang; Bettiol, Andrew A; Ang, Kah-Wee

    2016-05-30

    We report on the development of Germanium-on-SOI waveguides for mid-infrared wavelengths. The strip waveguides have been formed in 0.85 and 2 μm thick Ge grown on SOI substrate with 220 nm thick Si overlayer. The propagation loss for various waveguide widths has been measured using the Fabry-Perot method with temperature tuning. The minimum loss of ~8 dB/cm has been achieved for 0.85 μm thick Ge core using 3.682 μm laser excitation. The transparency of these waveguides has been measured up to at least 3.82 μm. PMID:27410120

  5. Effect of pressure on arsenic diffusion in germanium

    SciTech Connect

    Mitha, S.; Theiss, S.D.; Aziz, M.J.; Schiferl, D.; Poker, D.B.

    1994-01-01

    We report preliminary results of a study of the activation volume for diffusion of arsenic in germanium. High-temperature high-pressure anneals were performed in a liquid argon pressure medium in a diamond anvil cell capable of reaching 5 GPa and 750 C,l which is externally heated for uniform and repeatable temperature profiles. Broadening of an ion-implanted arsenic profile was measured by Secondary Ion Mass Spectrometry. Hydrostatic pressure retards the diffusivity at 575 C, characterized by an activation volume that is +15% of the atomic volume of Ge. Implications for diffusion mechanisms are discussed.

  6. 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.

  7. Suspended germanium cross-shaped microstructures for enhancing biaxial tensile strain

    NASA Astrophysics Data System (ADS)

    Ishida, Satomi; Kako, Satoshi; Oda, Katsuya; Ido, Tatemi; Iwamoto, Satoshi; Arakawa, Yasuhiko

    2016-04-01

    We fabricate a suspended germanium cross-shaped microstructure to biaxially enhance residual tensile strain using a germanium epilayer directly grown on a silicon-on-insulator substrate. Such a suspended germanium system with enhanced biaxial tensile strain will be a promising platform for incorporating optical cavities toward the realization of germanium lasers. We demonstrate systematic control over biaxial tensile strain and photoluminescence peaks by changing structural geometry. The photoluminescence peaks corresponding to the direct recombination between the conduction Γ valley and two strain-induced separated valence bands have been clearly assigned. A maximum biaxial strain of 0.8% has been achieved, which is almost half of that required to transform germanium into a direct band-gap semiconductor.

  8. Direct Bandgap Light Emission from Strained Germanium Nanowires Coupled with High-Q Nanophotonic Cavities.

    PubMed

    Petykiewicz, Jan; Nam, Donguk; Sukhdeo, David S; Gupta, Shashank; Buckley, Sonia; Piggott, Alexander Y; Vučković, Jelena; Saraswat, Krishna C

    2016-04-13

    A silicon-compatible light source is the final missing piece for completing high-speed, low-power on-chip optical interconnects. In this paper, we present a germanium nanowire light emitter that encompasses all the aspects of potential low-threshold lasers: highly strained germanium gain medium, strain-induced pseudoheterostructure, and high-Q nanophotonic cavity. Our nanowire structure presents greatly enhanced photoluminescence into cavity modes with measured quality factors of up to 2000. By varying the dimensions of the germanium nanowire, we tune the emission wavelength over more than 400 nm with a single lithography step. We find reduced optical loss in optical cavities formed with germanium under high (>2.3%) tensile strain. Our compact, high-strain cavities open up new possibilities for low-threshold germanium-based lasers for on-chip optical interconnects. PMID:26907359

  9. Thin film germanium on silicon created via ion implantation and oxide trapping

    NASA Astrophysics Data System (ADS)

    Anthony, R.; Knights, A. P.

    2015-06-01

    We present a novel process for integrating germanium with silicon-on-insulator (SOI) wafers. Germanium is implanted into SOI which is then oxidized, trapping the germanium between the two oxide layers (the grown oxide and the buried oxide). With careful control of the implantation and oxidation conditions this process creates a thin layer (current experiments indicate up to 20-30nm) of almost pure germanium. The layer can be used potentially for fabrication of integrated photo-detectors sensitive to infrared wavelengths, or may serve as a seed for further germanium growth. Results are presented from electron microscopy and Rutherford back-scattering analysis, as well as preliminary modelling using an analytical description of the process.

  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. Mechanical stresses and crystallization of lithium phosphorous oxynitride-coated germanium electrodes during lithiation and delithiation

    NASA Astrophysics Data System (ADS)

    Al-Obeidi, Ahmed; Kramer, Dominik; Mönig, Reiner; Thompson, Carl V.

    2016-02-01

    The evolution of mechanical stresses during the cycling of lithium phosphorous oxynitride (LiPON) coated germanium thin film electrodes was monitored using substrate curvature measurements. By coating germanium thin films with LiPON, morphology evolution, e.g. crack and island formation, can be strongly suppressed. LiPON-coated germanium thin film electrodes can retain their planar form during cycling, resulting in a clear and reproducible stress response originating primarily from the electrochemical processes occurring during lithiation and delithiation. Together with the electrochemical data, stress measurements were used to infer mechanisms underlying the alloying of lithium with germanium. The stress signatures associated with individual phases, crystallization, and amorphization of lithium-germanium alloys are reported and discussed.

  12. 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.

  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. 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%.

  15. 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.

  16. Materials and fabrication issues for large machined germanium immersion gratings

    NASA Astrophysics Data System (ADS)

    Kuzmenko, Paul J.; Davis, Pete J.; Little, Steve L.; Hale, Layton C.

    2006-06-01

    LLNL has successfully fabricated small (1.5 cm2 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 63.4° 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.

  17. 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)

  18. Background Reduction For Germanium Double Beta Decay Experiments

    SciTech Connect

    Gomez, H.; Cebrian, S.; Morales, J.; Villar, J. A.

    2007-03-28

    The new generation experiments to search for the neutrinoless double beta decay of 76Ge (Q{beta}{beta}=2039keV) using enriched germanium detectors, need to reach a background level of {approx}10-3 c keV-1 kg-1 y-1 in the Region of Interest (RoI: 2-2.1 MeV) that would have, for 70 kg of germanium enriched to 86% in 76Ge, 3 keV of FWHM and 5 years of measuring time, a sensitivity on the effective neutrino mass of {<=} 40 meV. To reduce the background level close to the value needed, we have to combine several techniques. Three of the most important points to study are: segmentation and granularity of the crystal and spatial resolution of the detector directly correlated with an offline Pulse Shape Analysis (PSA). Preliminary studies about these strategies for background reduction were developed during last months, obtaining some promising results.

  19. 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.

  20. Monte Carlo of Cryogenic Dark Matter Search large germanium detectors

    NASA Astrophysics Data System (ADS)

    Leman, Steven; McCarty, Kevin; Cabrera, Blas; Pyle, Matthew; Sundqvist, Kyle; Sadoulet, Bernard

    2010-02-01

    A description of the Cryogenic Dark Matter Search (CDMS) detector Monte Carlo (MC) is given along with a comparison to calibration data obtained in 3" diameter, 1" thick [100] germanium crystals. Prompt phonons are generated from electron-recoil interactions along with Luke phonons created by charges as they drift through the crystal via our ionization channels' electric field. The MC phonon transport is described by quasidiffusion, which includes anisotropic propagation, isotope scattering and anharmonic decay, until the phonons are absorbed in either the Transition Edge Sensor based phonon channels or lost in surface interactions. Charge creation is a powerful discriminator for electron-recoil and nuclear-recoil events and also surface interaction rejection. Unlike holes, electrons transports obliquely to the electric field in our detectors due to the germanium [100] crystal orientation and the indirect semiconductor band structure. We are improving the agreement between MC and calibration data in different detector designs, which provides a powerful consistency test of our phonon and charge models. )

  1. 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.

  2. 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

  3. 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.

  4. Formation of germanium oxide microcrystals on the surface of Te-implanted Ge

    NASA Astrophysics Data System (ADS)

    Perrin Toinin, J.; Rudzevich, Y.; Hoummada, K.; Texier, M.; Bernardini, S.; Portavoce, A.; Chow, L.

    2015-12-01

    The formation of voids on the surface of heavily implanted germanium has been known for more than 30 years. Recently there is a renewed interest in germanium due to its potential application in the complementary metal oxide semiconductor (CMOS) devices. Here we report the observation of germanium oxide microcrystals formed on the surface of tellurium implanted into a germanium substrate. The Ge target used was a (1 0 0) polished single crystalline germanium wafer and the implantation was carried out at room temperature with Te ions at 180 keV and a fluence of 3.6 × 1015 at/cm2. Under scanning electron microscope (SEM), the surface of the Ge substrate is evenly covered by microcrystals with a diameter about 1-2 μm and a coverage density of ∼107 particles/cm2. The initially smooth surface of the polished germanium substrate becomes very rough and mostly consists of voids with an average diameter of 40-60 nm, which is consistent with reports of heavily implanted germanium. The composition of the microcrystals was studied using energy dispersive X-ray analysis (EDX) and atom probe tomography (APT) and will be presented. Preliminary results indicate that tellurium is not detected in the microcrystals. The origin of the microcrystals will be discussed.

  5. 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

  6. 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.

  7. 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.

  8. Characterization of three planar germanium detectors fabricated with the crystals grown at USD

    NASA Astrophysics Data System (ADS)

    Nazir, Hossain; Huang, Mianliang; Khizar, Muhammad; Mei, Dongming; Wang, Guojian; Mei, Hao; Guan, Yutong; University of South Dakota Team

    2014-03-01

    We characterized the performance of planar germanium detectors developed in the University of South Dakota (USD). The planar detectors were made from high purity germanium crystals with amorphous germanium contacts. These detectors were developed possible for the neutrinoless double beta-decay measurements and dark matter search underground. They were tested in a temporary cryostat to investigate the depletion voltage, leakage current, efficiency and resolution using a 60Co γ ray source. This work is supported by DOE grant DE-FG02-10ER46709 and the state of South Dakota.

  9. Improving Thick Germanium Detectors: Cryogenic Dark Matter Search

    NASA Astrophysics Data System (ADS)

    Epstein, Paulette; Mahapatra, Rupak; CDMS at Texas A&M University Team

    2011-10-01

    Texas A&M University is working on improving the current production rate, quality, and reproducibility of fabricated detectors, specifically for the Cryogenic Dark Matter Search (CDMS) to detect particles called WIMPs (Weakly Interacting Massive Particles). An automated sputtering system is used to deposit amorphous silicon and high quality tungsten and aluminum thin-films on 3 inch by 1 inch germanium substrates to demonstrate repeatable depositions with desired properties, such as, accurate thickness, desirable critical temperature, and good sensitivity at low energy. These techniques can then be used in the future to improve detectors, not only for the search for Dark Matter, but for other areas of research in nuclear and particle physics. Funded by DOE and NSF-REU Program.

  10. Germanium-Vacancy Single Color Centers in Diamond

    PubMed Central

    Iwasaki, Takayuki; Ishibashi, Fumitaka; Miyamoto, Yoshiyuki; Doi, Yuki; Kobayashi, Satoshi; Miyazaki, Takehide; Tahara, Kosuke; Jahnke, Kay D.; Rogers, Lachlan J.; Naydenov, Boris; Jelezko, Fedor; Yamasaki, Satoshi; Nagamachi, Shinji; Inubushi, Toshiro; Mizuochi, Norikazu; Hatano, Mutsuko

    2015-01-01

    Atomic-sized fluorescent defects in diamond are widely recognized as a promising solid state platform for quantum cryptography and quantum information processing. For these applications, single photon sources with a high intensity and reproducible fabrication methods are required. In this study, we report a novel color center in diamond, composed of a germanium (Ge) and a vacancy (V) and named the GeV center, which has a sharp and strong photoluminescence band with a zero-phonon line at 602 nm at room temperature. We demonstrate this new color center works as a single photon source. Both ion implantation and chemical vapor deposition techniques enabled fabrication of GeV centers in diamond. A first-principles calculation revealed the atomic crystal structure and energy levels of the GeV center. PMID:26250337

  11. Portable electro-mechanically cooled high-resolution germanium detector

    NASA Astrophysics Data System (ADS)

    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(exp 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.

  12. Reliability assessment of germanium gate stacks with promising initial characteristics

    NASA Astrophysics Data System (ADS)

    Lu, Cimang; Lee, Choong Hyun; Nishimura, Tomonori; Nagashio, Kosuke; Toriumi, Akira

    2015-02-01

    This work reports on the reliability assessment of germanium (Ge) gate stacks with promising initial electrical properties, with focus on trap generation under a constant electric stress field (Estress). Initial Ge gate stack properties do not necessarily mean highly robust reliability when it is considered that traps are newly generated under high Estress. A small amount of yttrium- or scandium oxide-doped GeO2 (Y-GeO2 or Sc-GeO2, respectively) significantly reduces trap generation in Ge gate stacks without deterioration of the interface. This is explained by the increase in the average coordination number (Nav) of the modified GeO2 network that results from the doping.

  13. Band Anticrossing in Dilute Germanium Carbides Using Hybrid Density Functionals

    NASA Astrophysics Data System (ADS)

    Stephenson, Chad A.; O'brien, William A.; Qi, Meng; Penninger, Michael; Schneider, William F.; Wistey, Mark A.

    2016-04-01

    Dilute germanium carbides (Ge1- x C x ) offer a direct bandgap for compact silicon photonics, but widely varying properties have been reported. This work reports improved band structure calculations for Ge1- x C x using ab initio simulations that employ the HSE06 exchange-correlation density functional. Contrary to Vegard's law, the conduction band minimum at Γ is consistently found to decrease with increasing C content, while L and X valleys change much more slowly. The calculated Ge bandgap is within 11% of experimental values. A decrease in energy at the Γ conduction band valley of (170 meV ± 50)/%C is predicted, leading to a direct bandgap for x > 0.008. These results indicate a promising material for Group IV lasers.

  14. 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.

  15. Giant pop-ins and amorphization in germanium during indentation

    NASA Astrophysics Data System (ADS)

    Oliver, David J.; Bradby, Jodie E.; Williams, Jim S.; Swain, Michael V.; Munroe, Paul

    2007-02-01

    Sudden excursions of unusually large magnitude (>1 μm), "giant pop-ins," have been observed in the force-displacement curve for high load indentation of crystalline germanium (Ge). A range of techniques including Raman microspectroscopy, focused ion-beam cross sectioning, and transmission electron microscopy, are applied to study this phenomenon. Amorphous material is observed in residual indents following the giant pop-in. The giant pop-in is shown to be a material removal event, triggered by the development of shallow lateral cracks adjacent to the indent. Enhanced depth recovery, or "elbowing," observed in the force-displacement curve following the giant pop-in is explained in terms of a compliant response of plates of material around the indent detached by lateral cracking. The possible causes of amorphization are discussed, and the implications in light of earlier indentation studies of Ge are considered.

  16. 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.

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

    DOE PAGESBeta

    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.

  18. 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.

  19. Tunable split-ring resonators using germanium telluride

    NASA Astrophysics Data System (ADS)

    Kodama, C. H.; Coutu, R. A.

    2016-06-01

    We demonstrate terahertz (THz) split-ring resonator (SRR) designs with incorporated germanium telluride (GeTe) thin films. GeTe is a chalcogenide that undergoes a nonvolatile phase change from the amorphous to crystalline state at approximately 200 °C, depending on the film thickness and stoichiometry. The phase change also causes a drop in the material's resistivity by six orders of magnitude. In this study, two GeTe-incorporated SRR designs were investigated. The first was an SRR made entirely out of GeTe and the second was a gold SRR structure with a GeTe film incorporated into the gap region of the split ring. These devices were characterized using THz time-domain spectroscopy and were heated in-situ to determine the change in the design operation with varying temperatures.

  20. 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.

  1. Towards monolithic integration of germanium light sources on silicon chips

    NASA Astrophysics Data System (ADS)

    Saito, Shinichi; Zaher Al-Attili, Abdelrahman; Oda, Katsuya; Ishikawa, Yasuhiko

    2016-04-01

    Germanium (Ge) is a group-IV indirect band gap semiconductor, and therefore bulk Ge cannot emit light efficiently. However, the direct band gap energy is close to the indirect one, and significant engineering efforts are being made to convert Ge into an efficient gain material monolithically integrated on a Si chip. In this article, we will review the engineering challenges of developing Ge light sources fabricated using nano-fabrication technologies compatible with complementary metal-oxide-semiconductor processes. In particular, we review recent progress in applying high-tensile strain to Ge to reduce the direct band gap. Another important technique is doping Ge with donor impurities to fill the indirect band gap valleys in the conduction band. Realization of carrier confinement structures and suitable optical cavities will be discussed. Finally, we will discuss possible applications of Ge light sources in potential photonics-electronics convergent systems.

  2. 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.

  3. Dislocation distribution in large high-purity germanium crystal

    NASA Astrophysics Data System (ADS)

    Mei, Hao; Wang, Guojian; Mei, Dongming; Huang, Mianliang; Yang, Gang; Guan, Yutong; Cubed Collaboration

    2014-03-01

    We investigated the impacts of growth rate, time-temperature profile, thermal gradient on the dislocation distribution in large high-purity germanium crystal (12 cm in diameter) grown via Czochralski along <100>orientation. The time-temperature profiles of the crystal grown at different input power were investigated using direct measurements and computational modeling. The effect of crystallization speed on dislocation density is discussed from the context of thermal gradient during growth. Several samples from the grown crystals were used for this investigation. We measured dislocation density across the entire cross-section of the grown crystal through the microscope. By measuring and calculating the dislocation density, we were able to identify the denseness and the type of dislocation, which allows us to study how the thermal stress impacts the dislocation generation and distribution across the large grown crystals. This work is supported by DOE grant DE-FG02-10ER46709 and the state of South Dakota.

  4. Submicron fabrication by local anodic oxidation of germanium thin films

    NASA Astrophysics Data System (ADS)

    Oliveira, A. B.; Medeiros-Ribeiro, G.; Azevedo, A.

    2009-08-01

    Here we describe a lithography scheme based on the local anodic oxidation of germanium film by a scanning atomic force microscope in a humidity-controlled atmosphere. The oxidation kinetics of the Ge film were investigated by a tapping mode, in which a pulsed bias voltage was synchronized and applied with the resonance frequency of the cantilever, and by a contact mode, in which a continuous voltage was applied. In the tapping mode we clearly identified two regimes of oxidation as a function of the applied voltage: the trench width increased linearly during the vertical growth and increased exponentially during the lateral growth. Both regimes of growth were interpreted taking into consideration the Cabrera-Mott mechanism of oxidation applied to the oxide/Ge interface. We also show the feasibility of the bottom-up fabrication process presented in this work by showing a Cu nanowire fabricated on top of a silicon substrate.

  5. Isotopically enriched germanium detectors for astrophysical gamma-ray spectroscopy

    NASA Technical Reports Server (NTRS)

    Gehrels, Neil

    1990-01-01

    A study is presented of the instrumental background in astrophysical gamma-ray spectrometers using isotopically enriched germanium detectors. Calculations show that the beta-decay background, which is the largest component between approximately 0.1 and 1.0 MeV in balloonborne and satellite spectrometers, is dominated by the activation of Ge-74. This component can be reduced by an order of magnitude using detectors enriched to more than 80 percent in (Ge-70). The predicted reduction in the total background for current balloonborne instruments is more than a factor of 1.7 between 0.2 and 1.0 MeV. For future satellite instruments, the reduction in this energy range is by more than a factor of 5.

  6. Germanium-Vacancy Single Color Centers in Diamond.

    PubMed

    Iwasaki, Takayuki; Ishibashi, Fumitaka; Miyamoto, Yoshiyuki; Doi, Yuki; Kobayashi, Satoshi; Miyazaki, Takehide; Tahara, Kosuke; Jahnke, Kay D; Rogers, Lachlan J; Naydenov, Boris; Jelezko, Fedor; Yamasaki, Satoshi; Nagamachi, Shinji; Inubushi, Toshiro; Mizuochi, Norikazu; Hatano, Mutsuko

    2015-01-01

    Atomic-sized fluorescent defects in diamond are widely recognized as a promising solid state platform for quantum cryptography and quantum information processing. For these applications, single photon sources with a high intensity and reproducible fabrication methods are required. In this study, we report a novel color center in diamond, composed of a germanium (Ge) and a vacancy (V) and named the GeV center, which has a sharp and strong photoluminescence band with a zero-phonon line at 602 nm at room temperature. We demonstrate this new color center works as a single photon source. Both ion implantation and chemical vapor deposition techniques enabled fabrication of GeV centers in diamond. A first-principles calculation revealed the atomic crystal structure and energy levels of the GeV center. PMID:26250337

  7. Electron temperature and density measurements of laser induced germanium plasma

    NASA Astrophysics Data System (ADS)

    Shakeel, Hira; Arshad, Saboohi; Haq, S. U.; Nadeem, Ali

    2016-05-01

    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/cm2) 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.

  8. Bridgman Growth of Germanium Crystals in a Rotating Magnetic Field

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Szofran, F. R.; Cobb, S. D.; Schweizer, M.; Walker, J. S.

    2005-01-01

    A series of (100)-oriented gallium-doped germanium crystals has been grown by the vertical Bridgman method and under the influence of a rotating magnetic field (RMF). Time-dependent flow instabilities occur when the critical magnetic Taylor number (Tm(sup c)) is exceeded, and this can be observed by noting the appearance of striations in the grown crystals. Tm(sup c) decreases as the aspect ratio of the melt increases, and approaches the theoretical limit expected for an infinite cylinder. Intentional interface demarcations are introduced by pulsing the RMF on and off The RMF has a marked affect on the interface shape, changing it from concave to nearly flat as the RMF strength is increased.

  9. Comparison of Germanium Telluride (GeTe) Crystals

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Comparison of Germanium Telluride (GeTe) Crystals grown on Earth (left) and in space (right) during the Skylab SL-3 mission. These crystals were grown using a vapor transport crystal growth method in the Multipurpose Electric Furnace System (MEFS). Crystals grown on earth are needles and platelettes with distorted surfaces and hollow growth habits. The length of the ground-based needle is approximately 2 mm and the average lenth of the platelets is 1 mm. The dull appearance of the Skylab crystals resulted from condensation of the transport agent during the long cooling period dictated by the Skylab furnace. In a dedicated process, this would be prevented by removing the ampoule from the furnace and quenching the vapor source.

  10. Noise performance of high-efficiency germanium quantum dot photodetectors

    NASA Astrophysics Data System (ADS)

    Siontas, Stylianos; Liu, Pei; Zaslavsky, Alexander; Pacifici, Domenico

    2016-08-01

    We report on the noise analysis of high performance germanium quantum dot (Ge QD) photodetectors with responsivity up to ˜2 A/W and internal quantum efficiency up to ˜400%, over the 400-1100 nm wavelength range and at a reverse bias of -10 V. Photolithography was performed to define variable active-area devices that show suppressed dark current, leading to a higher signal-to-noise ratio, up to 105, and specific detectivity D * ≃ 6 × 10 12 cm Hz 1 / 2 W-1. These figures of merit suggest Ge QDs as a promising alternative material for high-performance photodetectors working in the visible to near-infrared spectral range.

  11. Bridgman Growth of Germanium Crystals in a Rotating Magnetic Field

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    A series of (100)-oriented gallium-doped germanium crystals have been grown by the Bridgman method and under the influence of a rotating magnetic field (RMF). The RMF has a marked affect on the interface shape, changing it from concave to nearly flat. The onset of time-dependent flow instabilities occurs when the critical magnetic Taylor number is exceeded, and this can be observed by noting the appearance of striations in the grown crystals. The critical magnetic Taylor number is a sensitive function of the aspect ratio and, as the crystal grows under a constant applied magnetic field, the induced striations change from nonperiodic to periodic, undergo a period-doubling transition, and then cease to exist. Also, by pulsing the RMF on and off, it is shown that intentional interface demarcations can be introduced.

  12. A pseudo-single-crystalline germanium film for flexible electronics

    SciTech Connect

    Higashi, H.; Yamada, S.; Kanashima, T.; Hamaya, K.; Kasahara, K.; Park, J.-H.; Miyao, M.; Kudo, K.; Okamoto, H.; Moto, K.; Tsunoda, I.

    2015-01-26

    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 Al{sub 2}O{sub 3} 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.

  13. Bridgman Growth of Germanium Crystals in a Rotating Magnetic Field

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Walker, J. S.; Schweizer, M.; Cobb, S. D.; Szofran, F. R.

    2004-01-01

    A series of (100)-oriented gallium-doped germanium crystals have been grown by the Bridgman method and under the influence of a rotating magnetic field (RMF). Time-dependent flow instabilities occur when the critical magnetic Taylor number (Tm(sup c) is exceeded, and this can be observed by noting the appearance of striations in the grown crystals. The experimental data indicate that Tm(sup c) increases as the aspect ratio of the melt decreases. Modeling calculations predicting Tm(sup c) as a function of aspect ratio are in reasonable agreement with the experimental data. The RMF has a marked affect on the interface shape, changing it from concave to nearly flat as the RMF strength is increased. Also, by pulsing the RMF on and off, it is shown that intentional interface demarcations can be introduced.

  14. 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.

  15. 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.

  16. Development of silicon-germanium visible-near infrared arrays

    NASA Astrophysics Data System (ADS)

    Zeller, John W.; Rouse, Caitlin; Efstathiadis, Harry; Haldar, Pradeep; Lewis, Jay S.; Dhar, Nibir K.; Wijewarnasuriya, Priyalal; Puri, Yash R.; Sood, Ashok K.

    2016-05-01

    Photodetectors based on germanium which do not require cooling and can provide good near-infrared (NIR) detection performance offer a low-cost alternative to conventional infrared sensors based on material systems such as InGaAs, InSb, and HgCdTe. As a result of the significant difference in thermal expansion coefficients between germanium and silicon, tensile strain incorporated into Ge epitaxial layers deposited on Si utilizing specialized growth processes can extend the operational range of detection to 1600 nm and longer wavelengths. We have fabricated Ge based PIN photodetectors on 300 mm diameter Si wafers to take advantage of high throughput, large-area complementary metal-oxide semiconductor (CMOS) technology. This device fabrication process involves low temperature epitaxial deposition of Ge to form a thin p+ (boron) Ge seed/buffer layer, and subsequent higher temperature deposition of a thicker Ge intrinsic layer. This is followed by selective ion implantation of phosphorus of various concentrations to form n+ Ge regions, deposition of a passivating oxide cap, and then top copper contacts to complete the PIN detector devices. Various techniques including transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS) have been employed to characterize the material and structural properties of the epitaxially grown layers and fabricated detector devices, and these results are presented. The I-V response of the photodetector devices with and without illumination was also measured, for which the Ge based photodetectors consistently exhibited low dark currents of around ~1 nA at -1 V bias.

  17. The time and temperature dependence of the thermoelectric properties of silicon-germanium alloy

    NASA Technical Reports Server (NTRS)

    Raag, V.

    1975-01-01

    Experimental data on the electrical resistivity and Seebeck coefficient of n-type and p-type silicon-germanium alloys are analyzed in terms of a solid-state dopant precipitation model proposed by Lifshitz and Slyozov (1961). Experimental findings on the time and temperature dependence of the thermal conductivity of these two types of alloy indicate that the thermal conductivity of silicon-germanium alloys changes with time, contrary to previous hypothesis. A preliminary model is presented which stipulates that the observed thermal conductivity decrease in silicon-germanium alloys is due partly to dopant precipitation underlying the electrical property changes and partly to enhanced alloying of the material. It is significant that all three properties asymptotically approach equilibrium values with time. Total characterization of these properties will enable the time change to be fully compensated in the design of a thermoelectric device employing silicon-germanium alloys.

  18. Self-assembled asymmetric membrane containing micron-size germanium for high capacity lithium ion batteries

    DOE PAGESBeta

    Byrd, Ian; Chen, Hao; Webber, Theron; Li, Jianlin; Wu, Ji

    2015-10-23

    We report the formation of novel asymmetric membrane electrode containing micron-size (~5 μm) germanium powders through a self-assembly phase inversion method for high capacity lithium ion battery anode. 850 mA h g-1 capacity (70%) can be retained at a current density of 600 mA g-1 after 100 cycles with excellent rate performance. Such a high retention rate has rarely been seen for pristine micron-size germanium anodes. Moreover, scanning electron microscope studies reveal that germanium powders are uniformly embedded in a networking porous structure consisting of both nanopores and macropores. It is believed that such a unique porous structure can efficientlymore » accommodate the ~260% volume change during germanium alloying and de-alloying process, resulting in an enhanced cycling performance. Finally, these porous membrane electrodes can be manufactured in large scale using a roll-to-roll processing method.« less

  19. IR absorption and Raman spectra of single crystals of stable germanium isotopes

    NASA Astrophysics Data System (ADS)

    Gavva, V. A.; Kotereva, T. V.; Lipskiy, V. A.; Nezhdanov, A. V.

    2016-02-01

    The Raman and IR absorption spectra of single crystals of germanium isotopes 72Ge, 73Ge, 74Ge, and 76Ge in the region of phonon absorption and interband electronic transitions are studied at room temperature. The dependence of the Raman peak position on the atomic mass has the form ν ~ M -1/2. The shifts of the phonon absorption peaks of individual isotopes with respect to germanium of natural isotopic composition natGe are determined. With increasing average atomic mass of germanium, these peaks shift to longer wavelengths. In the region of interband electronic transitions, the intrinsic absorption edge of 76Ge is observed to shift by 1 meV to higher energies with respect to Ge of natural isotopic composition. For isotopes with atomic masses close to that of natural germanium (72Ge,73Ge, 74Ge), we found no significant difference in the band gap width at room temperature.

  20. Impurity distribution in high purity germanium crystal and its impact on the detector performance

    NASA Astrophysics Data System (ADS)

    Wang, Guojian; Amman, Mark; Mei, Hao; Mei, Dongming; Irmscher, Klaus; Guan, Yutong; Yang, Gang

    High-purity germanium crystals were grown in a hydrogen atmosphere using the Czochralski method. The axial and radial distributions of impurities in the crystals were measured by Hall effect and Photo-thermal ionization spectroscopy (PTIS). Amorphous semiconductor contacts were deposited on the germanium crystals to make detectors. Three planar detectors were fabricated from three crystals with different net carrier concentrations (1.7, 7.9 and 10x1010 cm-3). We evaluated the electrical and spectral performance of three detectors. Measurements of gamma-ray spectra from 137Cs, 241Am and 60Co sources demonstrate that the detectors have excellent energy resolution. The relationship between the impurities and detector's energy resolution was analyzed. Keywords: High-purity germanium crystal, High-purity germanium detector This work is supported by DOE grant DE-FG02-10ER46709 and the state of South Dakota..

  1. Jet thinning of germanium for TEM using automatic termination of polishing

    SciTech Connect

    Kestel, B.J.

    1993-01-01

    This report describes an automated jet electropolishing technique, using modified commercial equipment, for the production of germanium TEM specimens. This technique allows rapid and reliable thinning of large areas and results in clean surfaces.

  2. Electronic and magnetic properties of Fe and Mn doped two dimensional hexagonal germanium sheets

    SciTech Connect

    Soni, Himadri R. Jha, Prafulla K.

    2014-04-24

    Using first principles density functional theory calculations, the present paper reports systematic total energy calculations of the electronic properties such as density of states and magnetic moment of pristine and iron and manganese doped two dimensional hexagonal germanium sheets.

  3. Induced Radioactivity Measured in a Germanium Detector After a Long Duration Balloon Flight

    NASA Technical Reports Server (NTRS)

    Starr, R.; Evans, L. G.; Floyed, S. R.; Drake, D. M.; Feldman, W. C.; Squyres, S. W.; Rester, A. C.

    1997-01-01

    A 13-day long duration balloon flight carrying a germanium detector was flown from Williams Field, Antartica in December 1992. After recovery of the payload the activity induced in the detector was measured.

  4. Self-assembled asymmetric membrane containing micron-size germanium for high capacity lithium ion batteries

    SciTech Connect

    Byrd, Ian; Chen, Hao; Webber, Theron; Li, Jianlin; Wu, Ji

    2015-10-23

    We report the formation of novel asymmetric membrane electrode containing micron-size (~5 μm) germanium powders through a self-assembly phase inversion method for high capacity lithium ion battery anode. 850 mA h g-1 capacity (70%) can be retained at a current density of 600 mA g-1 after 100 cycles with excellent rate performance. Such a high retention rate has rarely been seen for pristine micron-size germanium anodes. Moreover, scanning electron microscope studies reveal that germanium powders are uniformly embedded in a networking porous structure consisting of both nanopores and macropores. It is believed that such a unique porous structure can efficiently accommodate the ~260% volume change during germanium alloying and de-alloying process, resulting in an enhanced cycling performance. Finally, these porous membrane electrodes can be manufactured in large scale using a roll-to-roll processing method.

  5. Mechanically Cooled Large-Volume Germanium Detector Systems for Neclear Explosion Monitoring DOENA27323-2

    SciTech Connect

    Hull, E.L.

    2006-10-30

    Compact maintenance free mechanical cooling systems are being developed to operate large volume high-resolution gamma-ray detectors for field applications. To accomplish this we are utilizing a newly available generation of Stirling-cycle mechanical coolers to operate the very largest volume germanium detectors with no maintenance. The user will be able to leave these systems unplugged on the shelf until needed. The maintenance-free operating lifetime of these detector systems will exceed 5 years. Three important factors affect the operation of mechanically cooled germanium detectors: temperature, vacuum, and vibration. These factors will be studied in the laboratory at the most fundamental levels to insure a solid understanding of the physical limitations each factor places on a practical mechanically cooled germanium detector system. Using this knowledge, mechanically cooled germanium detector prototype systems will be designed and fabricated.

  6. Mechanically Cooled Large-Volume Germanium Detector Systems for Nuclear Explosion Monitoring DOENA27323-1

    SciTech Connect

    Hull, E.L.

    2006-07-28

    Compact maintenance free mechanical cooling systems are being developed to operate large volume germanium detectors for field applications. To accomplish this we are utilizing a newly available generation of Stirling-cycle mechanical coolers to operate the very largest volume germanium detectors with no maintenance. 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 5 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. 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 reliably utilized.

  7. Direct band gap electroluminescence from bulk germanium at room temperature using an asymmetric fin type metal/germanium/metal structure

    SciTech Connect

    Wang, Dong Maekura, Takayuki; Kamezawa, Sho; Yamamoto, Keisuke; Nakashima, Hiroshi

    2015-02-16

    We demonstrated direct band gap (DBG) electroluminescence (EL) at room temperature from n-type bulk germanium (Ge) using a fin type asymmetric lateral metal/Ge/metal structure with TiN/Ge and HfGe/Ge contacts, which was fabricated using a low temperature (<400 °C) process. Small electron and hole barrier heights were obtained for TiN/Ge and HfGe/Ge contacts, respectively. DBG EL spectrum peaked at 1.55 μm was clearly observed even at a small current density of 2.2 μA/μm. Superlinear increase in EL intensity was also observed with increasing current density, due to superlinear increase in population of elections in direct conduction band. The efficiency of hole injection was also clarified.

  8. HEROICA: A fast screening facility for the characterization of germanium detectors

    SciTech Connect

    Andreotti, Erica; Collaboration: GERDA Collaboration

    2013-08-08

    In the course of 2012, a facility for the fast screening of germanium detectors called HEROICA (Hades Experimental Research Of Intrinsic Crystal Appliances) has been installed at the HADES underground laboratory in the premises of the Belgian Nuclear Research Centre SCK•CEN, in Mol (Belgium). The facility allows performing a complete characterization of the critical germanium detectors' operational parameters with a rate of about two detectors per week.

  9. Design of a Prototype Cryogenic Chamber and Characterization of a High Purity Germanium Detector

    NASA Astrophysics Data System (ADS)

    Hossain, Abu Hena Muhammad Nazir

    Germanium detectors are the best choice for gamma ray spectrometry because of their good energy resolution and high efficiency compared to any other gamma rays spectrometers. Due to their high sensitivity and good energy resolution, these kinds of detector have a range of application. There is a significant number of particles detection experiments going on which used germanium detectors all around the world. These also have applications in non-proliferation and medical diagnosis. Thus, germanium detectors have a wide range of applications both research and industry. The Center for Ultra-Low Background Experiment in the Dakotas (CUBED) at the University of South Dakota is developing the facilities to fabricate germanium detectors. It is requires to characterize the germanium detector properties, especially electrical properties. In this project I design and developed a cryogenic chamber for the CUBED group which is able to rest any type of radiation detectors of different sizes and shapes. The cryostat chamber is able to provide low pressure and low temperature for the testing of the germanium detector sample. Leakage current measurements have been done for several detector samples by using this cryostat chamber. Several kinds of electrical properties such as depletion voltage, breakdown voltage, electronics noise, impurity concentration etc. can be derived from these experiments in the future.

  10. The Primary and Secondary Production of Germanium: A Life-Cycle Assessment of Different Process Alternatives

    NASA Astrophysics Data System (ADS)

    Robertz, Benedicte; Verhelle, Jensen; Schurmans, Maarten

    2015-02-01

    Germanium is a semiconducting metalloid element used in optical fibers, catalysis, infrared optics, solar cells, and light-emitting diodes. The need for Ge in these markets is considered to increase by a steady ~1% on a yearly basis. Its economic importance, coupled with the identified supply risks, has led to the classification of germanium as a critical raw material within Europe. Since the early 1950s, Umicore Electro-Optic Materials has supplied germanium-based materials solutions to its markets around the world. Umicore extracts germanium from a wide range of refining and recycling feeds. The main objectives of this study were to quantify the potential environmental impacts of the production of germanium from production scraps from the photovoltaic industry and to compare them with the potential impacts of the primary production of germanium from coal. The data related to the secondary production are Umicore-specific data. Environmental impact scores have been calculated for the impact categories recommended by the International reference life cycle data system. The comparison of the primary and secondary production highlights the benefit linked to the recycling of metals.

  11. Maximizing Tensile Strain in Germanium Nanomembranes for Enhanced Optoelectronic Properties

    NASA Astrophysics Data System (ADS)

    Sanchez Perez, Jose Roberto

    Silicon, germanium, and their alloys, which provide the leading materials platform of microelectronics, are extremely inefficient light emitters because of their indirect fundamental energy band gap. This basic materials property has so far hindered the development of group-IV photonic-active devices, including light emitters and diode lasers, thereby significantly limiting our ability to integrate electronic and photonic functionalities at the chip level. Theoretical studies have predicted that tensile strain in Ge lowers the direct energy band gap relative to the indirect one, and that, with sufficient strain, Ge becomes direct-band gap, thus enabling facile interband light emission and the fabrication of Group IV lasers. It has, however, not been possible to impart sufficient strain to Ge to reach the direct-band gap goal, because bulk Ge fractures at much lower strains. Here it is shown that very thin sheets of Ge(001), called nanomembranes (NMs), can be used to overcome this materials limitation. Germanium nanomembranes (NMs) in the range of thicknesses from 20nm to 100nm were fabricated and then transferred and mounted to a flexible substrate [a polyimide (PI) sheet]. An apparatus was developed to stress the PI/NM combination and provide for in-situ Raman measurements of the strain as a function of applied stress. This arrangement allowed for the introduction of sufficient biaxial tensile strain (>1.7%) to transform Ge to a direct-band gap material, as determined by photoluminescence (PL) measurements and theory. Appropriate shifts in the emission spectrum and increases in PL intensities were observed. The advance in this work was nanomembrane fabrication technology; i.e., making thin enough Ge sheets to accept sufficiently high levels of strain without fracture. It was of interest to determine if the strain at which fracture ultimately does occur can be raised, by evaluating factors that initiate fracture. Attempts to assess the effect of free edges (enchant

  12. HEROICA: an underground facility for the fast screening of germanium detectors

    NASA Astrophysics Data System (ADS)

    Andreotti, E.; Garfagnini, A.; Maneschg, W.; Barros, N.; Benato, G.; Brugnera, R.; Costa, F.; Falkenstein, R.; Guthikonda, K. K.; Hegai, A.; Hemmer, S.; Hult, M.; Jänner, K.; Kihm, T.; Lehnert, B.; Liao, H.; Lubashevskiy, A.; Lutter, G.; Marissens, G.; Modenese, L.; Pandola, L.; Reissfelder, M.; Sada, C.; Salathe, M.; Schmitt, C.; Schulz, O.; Schwingenheuer, B.; Turcato, M.; Ur, C.; von Sturm, K.; Wagner, V.; Westermann, J.

    2013-06-01

    HEROICA (Hades Experimental Research Of Intrinsic Crystal Appliances) is an infrastructure to characterize germanium detectors and has been designed and constructed at the HADES Underground Research Laboratory, located in Mol (Belgium). Thanks to the 223 m overburden of clay and sand, the muon flux is lowered by four orders of magnitude. This natural shield minimizes the exposure of radio-pure germanium material to cosmic radiation resulting in a significant suppression of cosmogenic activation in the germanium detectors. The project has been strongly motivated by a special production of germanium detectors for the GERDA experiment. GERDA, currently collecting data at the Laboratori Nazionali del Gran Sasso of INFN, is searching for the neutrinoless double beta decay of 76Ge. In the near future, GERDA will increase its mass and sensitivity by adding new Broad Energy Germanium (BEGe) detectors. The production of the BEGe detectors is done at Canberra in Olen (Belgium), located about 30 km from the underground test site. Therefore, HADES is used both for storage of the crystals over night, during diode production, and for the characterization measurements. A full quality control chain has been setup and tested on the first seven prototype detectors delivered by the manufacturer at the beginning of 2012. The screening capabilities demonstrate that the installed setup fulfills a fast and complete set of measurements on the diodes and it can be seen as a general test facility for the fast screening of high purity germanium detectors. The results are of major importance for a future massive production and characterization chain of germanium diodes foreseen for a possible next generation 1-tonne double beta decay experiment with 76Ge.

  13. Development of a new type of germanium detector for dark matter searches

    NASA Astrophysics Data System (ADS)

    Wei, Wenzhao

    Monte Carlo simulation is an important tool used to develop a better understanding of important physical processes. This thesis describes three Monte Carlo simulations used to understand germanium detector response to low energy nuclear recoils and radiogenic backgrounds for direct dark matter searches. The first simulation is the verification of Barker-Mei model, a theoretical model for calculating the ionization efficiency for germanium detector for the energy range of 1 - 100 keV. Utilizing the shape analysis, a bin-to-bin comparison between simulation and experimental data was performed for verifying the accuracy of the Barker-Mei model. A percentage difference within 4% was achieved between data and simulation, which showed the validity of the Barker-Mei model. The second simulation is the study of a new type of germanium detector for n/gamma discrimination at 77 K with plasma time difference in pulse shape. Due to the poor time resolution, conventional P-type Point Contact (PPC) and coaxial germanium detectors are not capable of discriminating nuclear recoils from electron recoils. In this thesis, a new idea of using great detector granularity and plasma time difference in pulse shape to discriminate nuclear recoils from electron recoils with planar germanium detectors in strings was discussed. The anticipated sensitivity of this new detector array is shown for detecting dark matter. The last simulation is a study of a new type of germanium-detector array serving as a PMT screening facility for ultra-low background dark matter experiments using noble liquid xenon as detector material such LUX/LZ and XENON100/XENON1T. A well-shaped germanium detector array and a PMT were simulated to study the detector response to the signal and background for a better understanding of the radiogenic gamma rays from PMTs. The detector efficiency and other detector performance were presented in this work.

  14. Point defect states in Sb-doped germanium

    SciTech Connect

    Patel, Neil S. Monmeyran, Corentin; Agarwal, Anuradha; Kimerling, Lionel C.

    2015-10-21

    Defect states in n-type Sb-doped germanium were investigated by deep-level transient spectroscopy. Cobalt-60 gamma rays were used to generate isolated vacancies and interstitials which diffuse and react with impurities in the material to form four defect states (E{sub 37}, E{sub 30}, E{sub 22}, and E{sub 21}) in the upper half of the bandgap. Irradiations at 77 K and 300 K as well as isothermal anneals were performed to characterize the relationships between the four observable defects. E{sub 37} is assigned to the Sb donor-vacancy associate (E-center) and is the only vacancy containing defect giving an estimate of 2 × 10{sup 11 }cm{sup −3} Mrad{sup −1} for the uncorrelated vacancy-interstitial pair introduction rate. The remaining three defect states are interstitial associates and transform among one another. Conversion ratios between E{sub 22}, E{sub 21}, and E{sub 30} indicate that E{sub 22} likely contains two interstitials.

  15. Etching of germanium-tin using ammonia peroxide mixture

    SciTech Connect

    Dong, Yuan; Ong, Bin Leong; Wang, Wei; Gong, Xiao; Liang, Gengchiau; Yeo, Yee-Chia; Zhang, Zheng; Pan, Jisheng; Tok, Eng-Soon

    2015-12-28

    The wet etching of germanium-tin (Ge{sub 1-x}Sn{sub x}) alloys (4.2% < x < 16.0%) in ammonia peroxide mixture (APM) is investigated. Empirical fitting of the data points indicates that the etch depth of Ge{sub 1-x}Sn{sub x} is proportional to the square root of the etch time t and decreases exponentially with increasing x for a given t. In addition, X-ray photoelectron spectroscopy results show that increasing t increases the intensity of the Sn oxide peak, whereas no obvious change is observed for the Ge oxide peak. This indicates that an accumulation of Sn oxide on the Ge{sub 1-x}Sn{sub x} surface decreases the amount of Ge atoms exposed to the etchant, which accounts for the decrease in etch rate with increasing etch time. Atomic force microscopy was used to examine the surface morphologies of the Ge{sub 0.918}Sn{sub 0.082} samples. Both root-mean-square roughness and undulation periods of the Ge{sub 1-x}Sn{sub x} surface were observed to increase with increasing t. This work provides further understanding of the wet etching of Ge{sub 1-x}Sn{sub x} using APM and may be used for the fabrication of Ge{sub 1-x}Sn{sub x}-based electronic and photonic devices.

  16. Characterization of germanium stripe x-ray lasers

    SciTech Connect

    Wan, A.S.; Moreno, J.C.; MacGowan, B.J.

    1993-07-01

    One method of improving the transverse spatial coherence of x-ray lasers (XRLS) is by adaptive spatial filtering of XRL apertures using geometric shaping in the form of bowtie or wedge XRLS. However, we must maintain the desired geometric shapes in exploding foil or slab configurations during the lasing period. As a first step toward understanding Lasing in such geometries we study the behavior of simple stripe XRLs. Past experience with stripe XRLs deposited on thick plastic substrates resulted in significantly weaker laser intensities as compared to line-focused slab XRLs. Possible reasons for this intensity reduction of stripe XRLs could include mixing at the laser boundary, and changes in plasma, kinetics, and hydrodynamic properties which affect laser gains and propagation. We will present experimental and theoretical characterizations of germanium line-focused and stripe XRLs. Key experimental parameters we will study include images of emission profiles of the laser blow-off, angular divergences, XRL output intensities, and ionization balances as we vary XRL designs. We will compare the experimental results with two-dimensional (2-D) laser deposition and hydrodynamics simulations using LASNEX, and study the changes in ionization balances and level populations from post-processing LASNEX results.

  17. An Ab Initio Study on Silicon and Germanium Nanotubes

    NASA Astrophysics Data System (ADS)

    Pradhan, Prachi

    2005-03-01

    First principles calculations using hybrid density functional theory have been performed to examine the electronic and geometric structure properties of single-walled silicon (SWSiNT) and germanium (SWGeNT) nanotubes. Finite clusters XmHn^ (X = Si or Ge) are used to model the nanotubes (e.g. the smallest SWSiNT is modeled as Si60H12). Hydrogen termination is done to simulate the effect of longer tubes as well as to take care of end effects. A pseudopotential basis set has been used for the silicon atoms^1 and complete geometry optimizations of the structures has been carried out using the Gaussian 03 suite of programs.^2 Computer simulations predict that the existence and stability of the nanotubes are highly dependent on the ratio of the sp^2 to sp^3 hybridization. Results will be presented on cohesive energies, HOMO- LUMO gaps, and other electronic structure properties and their dependence on the tube diameter. We will discuss the density of states (DOS) to explain the possible metallic or semi-conducting character of the tubes. Detailed comparisons with published data in the literature will also be presented. * Work supported, in part, by the Welch Foundation, Houston, Texas (Grant No. Y-1525). ^1 P. J. Hay and W. R. Wadt, J. Chem. Phys. 82, 270 (1985). ^2 Gaussian03, Revision A.1, M. J. Frisch et al., Gaussian Inc., Pittsburgh, PA , 2003.

  18. Atomic layer deposition of hafnium oxide on germanium substrates

    NASA Astrophysics Data System (ADS)

    Delabie, Annelies; Puurunen, Riikka L.; Brijs, Bert; Caymax, Matty; Conard, Thierry; Onsia, Bart; Richard, Olivier; Vandervorst, Wilfried; Zhao, Chao; Heyns, Marc M.; Meuris, Marc; Viitanen, Minna M.; Brongersma, Hidde H.; de Ridder, Marco; Goncharova, Lyudmila V.; Garfunkel, Eric; Gustafsson, Torgny; Tsai, Wilman

    2005-03-01

    Germanium combined with high-κ dielectrics has recently been put forth by the semiconductor industry as potential replacement for planar silicon transistors, which are unlikely to accommodate the severe scaling requirements for sub-45-nm generations. Therefore, we have studied the atomic layer deposition (ALD) of HfO2 high-κ dielectric layers on HF-cleaned Ge substrates. In this contribution, we describe the HfO2 growth characteristics, HfO2 bulk properties, and Ge interface. Substrate-enhanced HfO2 growth occurs: the growth per cycle is larger in the first reaction cycles than the steady growth per cycle of 0.04nm. The enhanced growth goes together with island growth, indicating that more than a monolayer coverage of HfO2 is required for a closed film. A closed HfO2 layer is achieved after depositing 4-5HfO2 monolayers, corresponding to about 25 ALD reaction cycles. Cross-sectional transmission electron microscopy images show that HfO2 layers thinner than 3nm are amorphous as deposited, while local epitaxial crystallization has occurred in thicker HfO2 films. Other HfO2 bulk properties are similar for Ge and Si substrates. According to this physical characterization study, HfO2 can be used in Ge-based devices as a gate oxide with physical thickness scaled down to 1.6nm.

  19. Proton-induced radiation damage in germanium detectors

    NASA Technical Reports Server (NTRS)

    Brueckner, J.; Koerfer, M.; Waenke, H.; Schroeder, A. N. F.; Filges, D.; Dragovitsch, P.; Englert, P. A. J.; Starr, R.; Trombka, J. I.

    1991-01-01

    High-purity germanium (HPGe) detectors will be used in future space missions for gamma-ray measurements and will be subject to interactions with energetic particles. To simulate this process, several large-volume n-type HPGe detectors were incrementally exposed to a particle fluence of up to 10 to the 8th protons/sq cm (proton energy: 1.5 GeV) at different operating temperatures (90 to 120 K) to induce radiation damage. Basic scientific and engineering data on detector performance were collected. During the incremental irradiation, the peak shape produced by the detectors showed a significant change from a Gaussian shape to a broad complex structure. After the irradiation, all detectors were thoroughly characterized by measuring many parameters. To remove the accumulated radiation damage, the detectors were stepwise-annealed at temperatures below 110 C, while kept in their specially designed cryostats. This study shows that n-type HPGe detectors can be used in charged-particle environments as high-energy resolution devices until a certain level of radiation damage is accumulated and that the damage can be removed at moderate annealing temperatures and the detector returned to operating condition.

  20. Radiation damage of the HEAO C-1 germanium detectors

    NASA Technical Reports Server (NTRS)

    Mahoney, W. A.; Ling, J. C.; Jacobson, A. S.

    1981-01-01

    The effects of radiation damage from proton bombardment of the four HEAO C-1 high purity germanium detectors have been measured and compared to predictions. Because of the presence of numerous gamma-ray lines in the detector background spectra and because of the relatively long exposure time of the HEAO 3 satellite to cosmic-ray and trapped protons, it has been possible to measure both the energy and time dependence of radiation damage. After 100 d in orbit, each of the four detectors has been exposed to approximately 3 x 10 to the 7th protons/sq cm, and the average energy resolution at 1460 keV had degraded from 3.2 keV fwhm to 8.6 keV fwhm. The lines were all broadened to the low energy side although the line profile was different for each of the four detectors. The damage-related contribution to the degradation in energy resolution was found to be linear in energy and proton influence.

  1. Spatial resolution attainable in germanium detectors by pulse shape analysis

    SciTech Connect

    Blair, J., Bechtel, NV; Beckedahl, D.; Kammeraad, J.; Schmid, G., LLNL

    1998-05-01

    There are several applications for which it is desirable to calculate the locations and energies of individual gamma-ray interactions within a high purity germanium (HPGe) detector. These include gamma-ray imaging and Compton suppression. With a segmented detector this can be accomplished by analyzing the pulse shapes of the signals from the various segments. We examine the fundamental limits to the spatial resolution attainable with this approach. The primary source of error is the series noise of the field effect transistors (FETs) at the inputs of the charge amplifiers. We show how to calculate the noise spectral density at the output of the charge amplifiers due to an optimally selected FET. This calculation is based only on the detector capacitance and a noise constant for the FET technology. We show how to use this spectral density to calculate the uncertainties in parameters, such as interaction locations and energies, that are derived from pulse shape analysis using maximum likelihood estimation (MLE) applied to filtered and digitized recordings of the charge signals. Example calculations are given to illustrate our approach. Experimental results are given that demonstrate that one can construct complete systems, from detector through data analysis, that come near the theoretical limits.

  2. 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.

  3. Ductile-regime turning of germanium and silicon

    NASA Technical Reports Server (NTRS)

    Blake, Peter N.; Scattergood, Ronald O.

    1989-01-01

    Single-point diamond turning of silicon and germanium was investigated in order to clarify the role of cutting depth in coaxing a ductile chip formation in normally brittle substances. Experiments based on the rapid withdrawal of the tool from the workpiece have shown that microfracture damage is a function of the effective depth of cut (as opposed to the nominal cutting depth). In essence, damage created by the leading edge of the tool is removed several revolutions later by lower sections of the tool edge, where the effective cutting depth is less. It appears that a truly ductile cutting response can be achieved only when the effective cutting depth, or critical chip thickness, is less than about 20 nm. Factors such as tool rake angle are significant in that they will affect the actual value of the critical chip thickness for transition from brittle to ductile response. It is concluded that the critical chip thickness is an excellent parameter for measuring the effects of machining conditions on the ductility of the cut and for designing tool-workpiece geometry in both turning and grinding.

  4. Spin Qubits in Germanium Structures with Phononic Gap

    NASA Technical Reports Server (NTRS)

    Smelyanskiy, V. N.; Vasko, F. T.; Hafiychuk, V. V.; Dykman, M. I.; Petukhov, A. G.

    2014-01-01

    We propose qubits based on shallow donor electron spins in germanium structures with phononic gap. We consider a phononic crystal formed by periodic holes in Ge plate or a rigid cover / Ge layer / rigid substrate structure with gaps approximately a few GHz. The spin relaxation is suppressed dramatically, if the Zeeman frequency omegaZ is in the phononic gap, but an effective coupling between the spins of remote donors via exchange of virtual phonons remains essential. If omegaZ approaches to a gap edge in these structures, a long-range (limited by detuning of omegaZ) resonant exchange interaction takes place. We estimate that ratio of the exchange integral to the longitudinal relaxation rate exceeds 10(exp 5) and lateral scale of resonant exchange 0.1 mm. The exchange contribution can be verified under microwave pumping through oscillations of spin echo signal or through the differential absorption measurements. Efficient manipulation of spins due to the Rabi oscillations opens a new way for quantum information applications.

  5. Proton-induced radiation damage in germanium detectors

    SciTech Connect

    Bruckner, J.; Korfer, M.; Wanke, H. , Mainz ); Schroeder, A.N.F. ); Figes, D.; Dragovitsch, P. ); Englert, P.A.J. ); Starr, R.; Trombka, J.I. . Goddard Space Flight Center); Taylor, I. ); Drake, D.M.; Shunk, E.R. )

    1991-04-01

    High-purity germanium (HPGe) detectors will be used in future space missions for gamma-ray measurements and will be subject to interactions with energetic particles. To simulate this process several large-volume n-type HPGe detectors were incrementally exposed to a particle fluence of up to 10{sub 8} protons cm{sup {minus}2} (proton energy: 1.5 GeV) at different operating temperatures (90 to 120 K) to induce radiation damage. Basic scientific as well as engineering data on detector performance were collected. During the incremental irradiation, the peak shape produced by the detectors showed a significant change from a Gaussian shape to a broad complex structure. After the irradiation all detectors were thoroughly characterized by measuring many parameters. To remove the accumulated radiation damage the detectors were stepwise annealed at temperatures T {le} 110{degrees}C while staying specially designed cryostats. This paper shows that n-type HPGe detectors can be used in charged particles environments as high-energy resolution devices until a certain level of radiation damage is accumulated and that the damage can be removed at moderate annealing temperatures and the detector returned to operating condition.

  6. Comparison of CDMS [100] and [111] Oriented Germanium Detectors

    SciTech Connect

    Leman, S.W.; Hertel, S.A.; Kim, P.; Cabrera, B.; Do Couto E.Silva, E.; Figueroa-Feliciano, E.; McCarthy, K.A.; Resch, R.; Sadoulet, B.; Sundqvist, K.M.; /UC, Berkeley

    2012-09-14

    The Cryogenic Dark Matter Search (CDMS) utilizes large mass, 3-inch diameter x 1-inch thick target masses as particle detectors. The target is instrumented with both phonon and ionization sensors and comparison of energy in each channel provides event-by-event classification of electron and nuclear recoils. Fiducial volume is determined by the ability to obtain good phonon and ionization signal at a particular location. Due to electronic band structure in germanium, electron mass is described by an anisotropic tensor with heavy mass aligned along the symmetry axis defined by the [111] Miller index (L valley), resulting in large lateral component to the transport. The spatial distribution of electrons varies significantly for detectors which have their longitudinal axis orientations described by either the [100] or [111] Miller indices. Electric fields with large fringing component at high detector radius also affect the spatial distribution of electrons and holes. Both effects are studied in a 3 dimensional Monte Carlo and the impact on fiducial volume is discussed.

  7. Germanium Detector Crystal Axis Orientation for the MAJORANA Demonstrator

    NASA Astrophysics Data System (ADS)

    Letourneau, Hannah

    2013-10-01

    The MAJORANA Demonstrator, currently being constructed at Sanford Underground Research Facility in Lead, South Dakota, is an array of germanium detectors which will be used to search for neutrinoless double beta decay, which would demonstrate that neutrinos have a Majorana mass term and lepton number is not conserved. An important characteristic of semiconductor detectors is the crystal axis orientation, because the propagation of electromagnetic signals is attenuated by the location of the interaction relative to the axis of the crystal. Conventionally, a goniometer is used to position a collimated low energy gamma source in many small increments around the detector to measure the rise time at each position. However, due to physical constraints from the casing of the Demonstrator, a different method must be developed. At the University of Washington this summer, I worked with a 76 Ge point-contact detector. I found the crystal axis orientation first with Americium 241, a lower energy gamma source. Then, I used a higher energy source, Thorium 232, in conjunction with the only a few angular reference points to also calculate rise time. Also, I wrote code to process the data. The success of this method will be evaluated and discussed. NSF

  8. Spin pumping and inverse spin Hall effect in germanium

    NASA Astrophysics Data System (ADS)

    Rojas Sanchez, Juan-Carlos; Vergnaud, C.; Vila, L.; Attane, J.-P.; Marty, A.; Jaffres, Henri; Jamet, Matthieu; George, Jean-Marie

    2014-03-01

    We have measured the inverse spin Hall effect (ISHE) in n-Ge at room temperature. The spin current in germanium was generated by spin pumping from a CoFeB/MgO magnetic tunnel junction in order to prevent the impedance mismatch issue. A clear electromotive force was measured in Ge at the ferromagnetic resonance of CFB. The same study was then carried out on several test samples, in particular, we have investigated the influence of the MgO tunnel barrier and sample annealing on the ISHE signal. The reference CFB/MgO bilayer grown on SiO2 exhibits a clear electromotive force due to anisotropic magnetoresistance and anomalous Hall effect, which is dominated by an asymmetric contribution with respect to the resonance field. We also found that the MgO tunnel barrier is essential to observe ISHE in Ge and that sample annealing systematically leads to an increase of the signal. We propose a theoretical model based on the presence of localized states at the interface to account for these observations. Finally, all of our results are fully consistent with the observation of ISHE in heavily doped n-Ge with a spin Hall angle around 0.001. JCRS acknowledges the Eurotalent CEA program.

  9. Isotopic germanium targets for high beam current applications at GAMMASPHERE.

    SciTech Connect

    Greene, J. P.; Lauritsen, T.

    2000-11-29

    The creation of a specific heavy ion residue via heavy ion fusion can usually be achieved through a number of beam and target combinations. Sometimes it is necessary to choose combinations with rare beams and/or difficult targets in order to achieve the physics goals of an experiment. A case in point was a recent experiment to produce {sup 152}Dy at very high spins and low excitation energy with detection of the residue in a recoil mass analyzer. Both to create the nucleus cold and with a small recoil-cone so that the efficiency of the mass analyzer would be high, it was necessary to use the {sup 80}Se on {sup 76}Ge reaction rather than the standard {sup 48}Ca on {sup 108}Pd reaction. Because the recoil velocity of the {sup 152}Dy residues was very high using this symmetric reaction (5% v/c), it was furthermore necessary to use a stack of two thin targets to reduce the Doppler broadening. Germanium targets are fragile and do not withstand high beam currents, therefore the {sup 76}Ge target stacks were mounted on a rotating target wheel. A description of the {sup 76}Ge target stack preparation will be presented and the target performance described.

  10. Measurement of Compton scattering in phantoms by germanium detectors

    SciTech Connect

    Zasadny, K.R.; Koral, K.F. . Medical Center); Floyd, C.E. Jr.; Jaszczak, R.J. . Dept. of Radiology)

    1990-04-01

    Quantitative Anger-camera tomography requires correction for Compton scattering. The Anger camera spectral-fitting technique can measure scatter fractions at designated positions in an image allowing for correction. To permit verification of those measurements for {sup 131}I, the authors have determined scatter fractions with a high-purity germanium (HPGe) detector and various phantom configurations. The scatter fraction values for {sup 99m}Tc were also measured and are compared to results from Monte Carlo simulation. The phantom consisted of a 22.2 cm diameter {times} 18.6 cm high cylinder filled with water and a 6 cm diameter water-filled sphere placed at various locations inside the cylinder. Radioisotope is added to either the sphere or the cylinder. The source is collimated by an Anger camera collimator and the active area of the HPGe detector is defined by a 0.6 cm diameter hole in a lead shielding mask. Corrections include accounting for the HPGe detector efficiency as a function of gamma-ray energy, the finite energy resolution of detector and the HPGe detector energy resolution compared to that for a NaI(Tl) Anger camera.

  11. Environmental Radioactivity: Gamma Ray Spectroscopy with Germanium detector

    NASA Astrophysics Data System (ADS)

    Vyas, Gargi; Beausang, Cornelius; Hughes, Richard; Tarlow, Thomas; Gell, Kristen; University of Richmond Physics Team

    2013-10-01

    A CF-1000BRL series portable Air Particle Sampler with filter paper as filter media was placed in one indoor and one outdoor location at 100 LPM flow rate on six dates under alternating rainy and warm weather conditions over the course of sixteen days in May 2013. The machine running times spanned between 6 to 69 hours. Each filter paper was then put in a germanium gamma ray detector, and the counts ranged from 93000 to 250000 seconds. The spectra obtained were analyzed by the CANBERRA Genie 2000 software, corrected using a background spectrum, and calibrated using a 20.27 kBq activity multi-nuclide source. We graphed the corrected counts (from detector analysis time)/second (from air sampler running time)/liter (from the air sampler's flow rate) of sharp, significantly big peaks corresponding to a nuclide in every sample against the sample number along with error bars. The graphs were then used to compare the samples and they showed a similar trend. The slight differences were usually due to the different running times of the air sampler. The graphs of about 22 nuclides were analyzed. We also tried to recognize the nuclei to which several gamma rays belonged that were displayed but not recognized by the Genie 2000 software.

  12. What is the thermal conductivity limit of silicon germanium alloys?

    PubMed

    Lee, Yongjin; Pak, Alexander J; Hwang, Gyeong S

    2016-07-20

    The lowest possible thermal conductivity of silicon-germanium (SiGe) bulk alloys achievable through alloy scattering, or the so-called alloy limit, is important to identify for thermoelectric applications. However, this limit remains a subject of contention as both experimentally-reported and theoretically-predicted values tend to be widely scattered and inconclusive. In this work, we present a possible explanation for these discrepancies by demonstrating that the thermal conductivity can vary significantly depending on the degree of randomness in the spatial arrangement of the constituent atoms. Our study suggests that the available experimental data, obtained from alloy samples synthesized using ball-milling techniques, and previous first-principles calculations, restricted by small supercell sizes, may not have accessed the alloy limit. We find that low-frequency anharmonic phonon modes can persist unless the spatial distribution of Si and Ge atoms is completely random at the atomic scale, in which case the lowest possible thermal conductivity may be achieved. Our theoretical analysis predicts that the alloy limit of SiGe could be around 1-2 W m(-1) K(-1) with an optimal composition around 25 at% Ge, which is substantially lower than previously reported values from experiments and first-principles calculations. PMID:27398924

  13. Defect Density Characterization of Detached-Grown Germanium Crystals

    NASA Technical Reports Server (NTRS)

    Schweizer, M.; Cobb, S. D.; Volz, M. P.; Szoke, J.; Szofran, F. R.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Several (111)-oriented, Ga-doped germanium crystals were grown in pyrolytic boron nitride (pBN) containers by the Bridgman and the detached Bridgman growth techniques. Growth experiments in closed-bottom pBN containers resulted in nearly completely detached-grown crystals, because the gas pressure below the melt can build up to a higher pressure than above the melt. With open-bottom tubes the gas pressure above and below the melt is balanced during the experiment, and thus no additional force supports the detachment. In this case the crystals grew attached to the wall. Etch pit density (EPD) measurements along the axial growth direction indicated a strong improvement of the crystal quality of the detached-grown samples compared to the attached samples. Starting in the seed with an EPD of 6-8 x 10(exp 3)/square cm it decreased in the detached-grown crystals continuously to about 200-500/square cm . No significant radial difference between the EPD on the edge and the middle of the crystal exists. In the attached grown samples the EPD increases up to a value of about 2-4 x 10(exp 4)/square cm (near the edge) and up to 1 x 10(exp 4)/square cm in the middle of the sample. Thus the difference between the detached- and the attached-grown crystals with respect to the EPD is approximately two orders of magnitude.

  14. X-ray Characterization of Detached-Grown Germanium Crystals

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Schweizer, M.; Raghothamachar, B.; Dudley, M.; Szoke, J.; Cobb, S. D.; Szofran, F. R.

    2005-01-01

    Germanium (111)-oriented crystals have been grown by the vertical Bridgman technique, in both detached and attached configurations. Microstructural characterization of these crystals has been performed using synchrotron white beam x-ray topography (SWBXT) and double axis x-ray diffraction. Dislocation densities were measured from x-ray topographs obtained using the reflection geometry. For detached-grown crystals, the dislocation density is 4-6 x 10(exp 4) per square centimeter in the seed region, and decreases in the direction of growth to less than 10(exp 3) per square centimeter, and in some crystals reaches less than 10(exp 2) per square centimeter. For crystals grown in the attached configuration, dislocation densities were on the order of 10(exp 4) per square centimeter in the middle of the crystals, increasing to greater than 10(exp 5) per square centimeter near the edge. The measured dislocation densities are in excellent agreement with etch pit density results. The rocking curve linewidths were relatively insensitive to the dislocation densities. However, broadening and splitting of the rocking curves were observed in the vicinity of subgrain boundaries identified by x-ray topography in some of the attached-grown crystals.

  15. Thermal detectors as single photon X-ray spectrometers

    NASA Technical Reports Server (NTRS)

    Moseley, S. H.; Kelley, R. L.; Mather, J. C.; Mushotzky, R. F.; Szymkowiak, A. E.; Mccammon, D.

    1985-01-01

    In a thermal detector employed for X-ray spectroscopy applications, the energy of an X-ray is converted to heat in a small mass, and the energy of that X-ray inferred from the size of the temperature rise. The present investigation is concerned with the possibility to make an extremely low heat capacity calorimeter which can be employed as a thermal detector. Several types of calorimeters were fabricated and tested at temperatures as low as approximately 0.05 K. The obtained devices make use of thermistors constructed of melt-doped silicon, nuclear transmutation doped (NTD) germanium, and ion-implanted silicon with a variety of materials for the support and electrical leads. The utility of these microcalorimeters as X-ray spectrometers could be verified.

  16. Increasing sp3 hybridized carbon atoms in germanium carbide films by increasing the argon ion energy and germanium content

    NASA Astrophysics Data System (ADS)

    Hu, C. Q.; Zheng, B.; Zhu, J. Q.; Han, J. C.; Zheng, W. T.; Guo, L. F.

    2010-04-01

    We have prepared germanium carbide (Ge1-xCx) films on Si(0 0 1) by radio frequency (RF) reactive sputtering a pure Ge(1 1 1) target in a CH4/Ar mixture discharge, and found that the sp3 hybridized carbon atoms in the Ge1-xCx film can be significantly increased in two ways. One is by increasing the Ge content via increasing the RF power during the film deposition, which can lead to a transition from sp2 C-C to sp3 C-Ge bonding in the film. Another is by increasing the Ar ion energy in a discharge Ar/CH4 gas by applying the negative bias voltage, which plays an important role in inducing the compressive stress in film. We find that when the compressive stress increases above a critical value of 2.2 GPa, an abrupt transition from sp2 C-C to sp3 C-C bonding occurs in the Ge1-xCx film, which is a consequence of energy minimization.

  17. 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. PMID:25629917

  18. Analysis of optical gain threshold in n-doped and tensile-strained germanium heterostructure diodes

    NASA Astrophysics Data System (ADS)

    Prost, M.; El Kurdi, M.; Aniel, F.; Zerounian, N.; Sauvage, S.; Checoury, X.; BÅ`uf, F.; Boucaud, P.

    2015-09-01

    The optical emission of germanium-based luminescent and/or laser devices can be enhanced by tensile strain and n-type doping. In this work, we study by simulation the interplay between electrical transport and optical gain in highly n-doped and intrinsic germanium p-n heterostructure diodes under tensile strain. The effects of strain and doping on carrier mobilities and energy distribution are taken into account. Whereas the n-doping of Ge enhances the filling of the indirect L and Brillouin zone-center conduction band states, the n-doping also reduces the carrier injection efficiency, which is detrimental for the achievement of optical gain at reduced current densities. For applied biaxial strains larger than 1.25%, i.e., far before reaching the cross-over from indirect to direct band gap regime, undoped germanium exhibits a lower optical gain threshold as compared to doped germanium. We also show that the threshold current needed to reach transparency in germanium heterostructures has been significantly underestimated in the previous works.

  19. Integrated analysis and design optimization of germanium purification process using zone-refining technique

    NASA Astrophysics Data System (ADS)

    Wang, Sen; Fang, H. S.; Jin, Z. L.; Zhao, C. J.; Zheng, L. L.

    2014-12-01

    Germanium (Ge) is a preferred material in the fabrication of high-performance gamma radiation detector for spectroscopy in nuclear physics. To maintain an intrinsic region in which electrons and holes reach the contacts to produce a spectroscopic signal, germanium crystals are usually doped with lithium (Li) ions. Consequently, hyperpure germanium (HPGe) should be prepared before the doping process to eliminate the interference of unexpected impurities in the Li dopant. Zone-refining technique, widely used in purification of ultra-pure materials, is chosen as one of the purification steps during detector-grade germanium production. In the paper, numerical analysis has been conducted to analyze heat transfer, melt flow and impurity segregation during a multi-pass zone-refining process of germanium in a Cyberstar mirror furnace. By modifying the effective redistribution coefficients, axial segregations of various impurities are investigated. Marangoni convection is found dominant in the melt. It affects the purification process through modifying the boundary layer thickness. Impurity distributions along the ingot are obtained with different conditions, such as pass number, zone travel rate, initial impurity concentration, segregation coefficient, and hot-zone length. Based on the analysis, optimization of the purification process design is proposed.

  20. Biallelic and Genome Wide Association Mapping of Germanium Tolerant Loci in Rice (Oryza sativa L.)

    PubMed Central

    Talukdar, Partha; Douglas, Alex; Price, Adam H.; Norton, Gareth J.

    2015-01-01

    Rice plants accumulate high concentrations of silicon. Silicon has been shown to be involved in plant growth, high yield, and mitigating biotic and abiotic stresses. However, it has been demonstrated that inorganic arsenic is taken up by rice through silicon transporters under anaerobic conditions, thus the ability to efficiently take up silicon may be considered either a positive or a negative trait in rice. Germanium is an analogue of silicon that produces brown lesions in shoots and leaves, and germanium toxicity has been used to identify mutants in silicon and arsenic transport. In this study, two different genetic mapping methods were performed to determine the loci involved in germanium sensitivity in rice. Genetic mapping in the biparental cross of Bala × Azucena (an F6 population) and a genome wide association (GWA) study with 350 accessions from the Rice Diversity Panel 1 were conducted using 15 μM of germanic acid. This identified a number of germanium sensitive loci: some co-localised with previously identified quantitative trait loci (QTL) for tissue silicon or arsenic concentration, none co-localised with Lsi1 or Lsi6, while one single nucleotide polymorphism (SNP) was detected within 200 kb of Lsi2 (these are genes known to transport silicon, whose identity was discovered using germanium toxicity). However, examining candidate genes that are within the genomic region of the loci detected above reveals genes homologous to both Lsi1 and Lsi2, as well as a number of other candidate genes, which are discussed. PMID:26356220

  1. Hydrometallurgical recovery of germanium from coal gasification fly ash: pilot plant scale evaluation

    SciTech Connect

    Arroyo, F.; Fernandez-Pereira, C.; Olivares, J.; Coca, P.

    2009-04-15

    In this article, a hydrometallurgical method for the selective recovery of germanium from fly ash (FA) has been tested at pilot plant scale. The pilot plant flowsheet comprised a first stage of water leaching of FA, and a subsequent selective recovery of the germanium from the leachate by solvent extraction method. The solvent extraction method was based on Ge complexation with catechol in an aqueous solution followed by the extraction of the Ge-catechol complex (Ge(C{sub 6}H{sub 4}O{sub 2}){sub 3}{sup 2-}) with an extracting organic reagent (trioctylamine) diluted in an organic solvent (kerosene), followed by the subsequent stripping of the organic extract. The process has been tested on a FA generated in an integrated gasification with combined cycle (IGCC) process. The paper describes the designed 5 kg/h pilot plant and the tests performed on it. Under the operational conditions tested, approximately 50% of germanium could be recovered from FA after a water extraction at room temperature. Regarding the solvent extraction method, the best operational conditions for obtaining a concentrated germanium-bearing solution practically free of impurities were as follows: extraction time equal to 20 min; aqueous phase/organic phase volumetric ratio equal to 5; stripping with 1 M NaOH, stripping time equal to 30 min, and stripping phase/organic phase volumetric ratio equal to 5. 95% of germanium were recovered from water leachates using those conditions.

  2. PREFACE: 2nd Workshop on Germanium Detectors and Technologies

    NASA Astrophysics Data System (ADS)

    Abt, I.; Majorovits, B.; Keller, C.; Mei, D.; Wang, G.; Wei, W.

    2015-05-01

    The 2nd workshop on Germanium (Ge) detectors and technology was held at the University of South Dakota on September 14-17th 2014, with more than 113 participants from 8 countries, 22 institutions, 15 national laboratories, and 8 companies. The participants represented the following big projects: (1) GERDA and Majorana for the search of neutrinoless double-beta decay (0νββ) (2) SuperCDMS, EDELWEISS, CDEX, and CoGeNT for search of dark matter; (3) TEXONO for sub-keV neutrino physics; (4) AGATA and GRETINA for gamma tracking; (5) AARM and others for low background radiation counting; (5) as well as PNNL and LBNL for applications of Ge detectors in homeland security. All participants have expressed a strong desire on having better understanding of Ge detector performance and advancing Ge technology for large-scale applications. The purpose of this workshop was to leverage the unique aspects of the underground laboratories in the world and the germanium (Ge) crystal growing infrastructure at the University of South Dakota (USD) by brining researchers from several institutions taking part in the Experimental Program to Stimulate Competitive Research (EPSCoR) together with key leaders from international laboratories and prestigious universities, working on the forefront of the intensity to advance underground physics focusing on the searches for dark matter, neutrinoless double-beta decay (0νββ), and neutrino properties. The goal of the workshop was to develop opportunities for EPSCoR institutions to play key roles in the planned world-class research experiments. The workshop was to integrate individual talents and existing research capabilities, from multiple disciplines and multiple institutions, to develop research collaborations, which includes EPSCor institutions from South Dakota, North Dakota, Alabama, Iowa, and South Carolina to support multi-ton scale experiments for future. The topic areas covered in the workshop were: 1) science related to Ge

  3. Detached Solidification of Germanium-Silicon Crystals on the ISS

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Mazuruk, K.; Croell, A.

    2016-01-01

    A series of Ge(sub 1-x) Si(sub x) crystal growth experiments are planned to be conducted in the Low Gradient Furnace (LGF) onboard the International Space Station. 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. The existence of this meniscus depends on the ratio of the strength of gravity to capillary forces. On Earth, this ratio is large and stable detached growth can only be obtained over limited conditions. Crystals grown detached on the ground exhibited superior structural quality as evidenced by measurements of etch pit density, synchrotron white beam X-ray topography and double axis X-ray diffraction.

  4. Low Power Silicon Germanium Electronics for Microwave Radiometers

    NASA Technical Reports Server (NTRS)

    Doiron, Terence A.; Krebs, Carolyn (Technical Monitor)

    2001-01-01

    Space-based radiometric observations of key hydrological parameters (e.g., soil moisture) at the spatial and temporal scales required in the post-2002 era face significant technological challenges. These measurements are based on relatively low frequency thermal microwave emission (at 1.4 GHz for soil moisture and salinity, 10 GHz and up for precipitation, and 19 and 37 GHz for snow). The long wavelengths at these frequencies coupled with the high spatial and radiometric resolutions required by the various global hydrology communities necessitate the use of very large apertures (e.g., greater than 20 m at 1.4 GHz) and highly integrated stable RF electronics on orbit. Radio-interferometric techniques such as Synthetic Thinned Array Radiometry (STAR), using silicon germanium (SiGe) low power radio frequency integrated circuits (RFIC), is one of the most promising technologies to enable very large non-rotating apertures in space. STAR instruments are composed of arrays of small antenna/receiving elements that are arranged so that the collecting area is smaller than an equivalent real aperture system, allowing very high packing densities for launch. A 20 meter aperture at L-band, for example, will require greater than 1000 of these receiving elements. SiGe RFIC's reduce power consumption enough to make an array like this possible in the power-limited environment of space flight. An overview of the state-of-the-art will be given, and current work in the area of SiGe radiometer development for soil moisture remote sensing will be discussed.

  5. Germanium and Silicon Nanocrystal Thin-Film Field-Effect Transistors from Solution

    SciTech Connect

    Holman, Zachary C.; Liu, Chin-Yi; Kortshagen, Uwe R.

    2010-07-09

    Germanium and silicon have lagged behind more popular II-VI and IV-VI semiconductor materials in the emerging field of semiconductor nanocrystal thin film devices. We report germanium and silicon nanocrystal field-effect transistors fabricated by synthesizing nanocrystals in a plasma, transferring them into solution, and casting thin films. Germanium devices show n-type, ambipolar, or p-type behavior depending on annealing temperature with electron and hole mobilities as large as 0.02 and 0.006 cm2 V-1 s-1, respectively. Silicon devices exhibit n-type behavior without any postdeposition treatment, but are plagued by poor film morphology.

  6. Present growth technology of silicon germanium alloys and possible advantages of microgravity growth

    NASA Technical Reports Server (NTRS)

    Stafsudd, O. M.

    1981-01-01

    The growth technology of Silicon-germanium (Si-Ge) alloys and the possible advantages of growth in microgravity is reviewed. The Si-Ge alloys have a continuous variation of bandgap energy from the germanium bandgap to the silicon bandgap. The unusual two slope behavior of Eg versus composition is due to the differences in the conduction band structure between Si and Ge. Below 17% (atomic), the germanium band structure dominates; and above it, the bands are "silicon like". It is found that the growth of Si-Ge alloys in microgravity is very attractive. In particular, the float zone method, in which a liquid zone of controlled starting composition, used to grow a large amount of useful alloy crystal. Large temperature gradients and relatively flat growth interfaces are necessary to obtain homogeneous crystal growth.

  7. Chromatographic separation of germanium and arsenic for the production of high purity (77)As.

    PubMed

    Gott, Matthew D; DeGraffenreid, Anthony J; Feng, Yutian; Phipps, Michael D; Wycoff, Donald E; Embree, Mary F; Cutler, Cathy S; Ketring, Alan R; Jurisson, Silvia S

    2016-04-01

    A simple column chromatographic method was developed to isolate (77)As (94±6% (EtOH/HCl); 74±11 (MeOH)) from germanium for potential use in radioimmunotherapy. The separation of arsenic from germanium was based on their relative affinities for different chromatographic materials in aqueous and organic environments. Using an organic or mixed mobile phase, germanium was selectively retained on a silica gel column as germanate, while arsenic was eluted from the column as arsenate. Subsequently, enriched (76)Ge (98±2) was recovered for reuse by elution with aqueous solution (neutral to basic). Greater than 98% radiolabeling yield of a (77)As-trithiol was observed from methanol separated [(77)As]arsenate [17]. PMID:26947162

  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. PMID:25616130

  9. Investigation of influential parameters for zone-refinement of germanium crystals

    NASA Astrophysics Data System (ADS)

    Yang, Gang; Govani, Jayesh; Guan, Yutong; Huang, Mianliang; Mei, Hao; Wang, Guojian; Mei, Dongming

    2014-03-01

    In zone-refining of high-purity germanium crystals, the influential parameters include vacuum level, container of germanium ingot, ambient gases, zone travel speed, zone length, etc. In the present work, the influences of zone length and zone travel speed on the purity level of the zone-refined ingot have been investigated with many experiments. The impurity level in the zone-refined ingot was characterized by van der pauw hall measurement. The shallow impurities are measured with a photothermal ionization spectroscopy (PTIS), which identifies existence of boron, aluminum and phosphor as three main impurities, in the zone-refined germanium ingot. Utilizing the multiple experiments, we have optimized the zone length and zone travel speed. We demonstrate our experimental results with solidification theory of metals.

  10. The MAJORANA DEMONSTRATOR: A Search for Neutrinoless Double-beta Decay of Germanium-76

    SciTech Connect

    Schubert, Alexis G.; Aguayo, Estanislao; Avignone, F. T.; Zhang, C.; Back, Henning O.; Barabash, Alexander S.; Bergevin, M.; Bertrand, F.; Boswell, M.; Brudanin, V.; Busch, Matthew; Chan, Yuen-Dat; Christofferson, Cabot-Ann; Collar, J. I.; Combs, Dustin C.; Cooper, R. J.; Detwiler, Jason A.; Leon, Jonathan D.; Doe, Peter J.; Efremenko, Yuri; Egorov, Viatcheslav; Ejiri, H.; Elliott, S. R.; Esterline, James H.; Fast, James E.; Fields, N.; Finnerty, P.; Fraenkle, Florian; Gehman, Victor M.; Giovanetti, G. K.; Green, M.; Guiseppe, Vincente; Gusey, K.; Hallin, A. L.; Hazama, R.; Henning, Reyco; Hime, Andrew; Hoppe, Eric W.; Horton, Mark; Howard, Stanley; Howe, Mark; Johnson, R. A.; Keeter, K.; Keillor, Martin E.; Keller, C.; Kephart, Jeremy D.; Kidd, M. F.; Knecht, A.; Kochetov, Oleg; Konovalov, S.; Kouzes, Richard T.; LaFerriere, Brian D.; LaRoque, B. H.; Leviner, L.; Loach, J. C.; MacMullin, S.; Marino, Michael G.; Martin, R. D.; Mei, Dong-Ming; Merriman, Jason H.; Miller, M. L.; Mizouni, Leila; Nomachi, Masaharu; Orrell, John L.; Overman, Nicole R.; Phillips, D.; Poon, Alan; Perumpilly, Gopakumar; Prior, Gersende; Radford, D. C.; Rielage, Keith; Robertson, R. G. H.; Ronquest, M. C.; Shima, T.; Shirchenko, M.; Snavely, Kyle J.; Sobolev, V.; Steele, David; Strain, J.; Thomas, K.; Timkin, V.; Tornow, Werner; Vanyushin, I.; Varner, R. L.; Vetter, Kai; Vorren, Kris R.; Wilkerson, J. F.; Wolfe, B. A.; Yakushev, E.; Young, A.; Yu, Chang-Hong; Yumatov, Vladimir

    2012-09-28

    The observation of neutrinoless double-beta decay would determine whether the neutrino is a Majorana particle and provide information on the absolute scale of neutrino mass. The MAJORANA Collaboration is constructing the DEMONSTRATOR, an array of germanium detectors, to search for neutrinoless double-beta decay of 76Ge. The DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76Ge. The DEMONSTRATOR will be deployed deep underground in an ultra-low-background shielded environment. Operation of the DEMONSTRATOR aims to determine whether a future tonne-scale germanium experiment can achieve a background goal of one count per tonne-year in a 4-keV region of interest around the 76Ge neutrinoless double-beta decay Q-value of 2039 keV.

  11. Segmentation of the Outer Contact on P-Type Coaxial Germanium Detectors

    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.

    2006-09-21

    Germanium detector arrays are needed for low-level counting facilities. The practical applications of such user facilities include characterization of low-level radioactive samples. In addition, the same detector arrays can also perform important fundamental physics measurements including the search for rare events like neutrino-less double-beta decay. Coaxial germanium detectors having segmented outer contacts will provide the next level of sensitivity improvement in low background measurements. The segmented outer detector contact allows performance of advanced pulse shape analysis measurements that provide additional background reduction. Currently, n-type (reverse electrode) germanium coaxial detectors are used whenever a segmented coaxial detector is needed because the outer boron (electron barrier) contact is thin and can be segmented. Coaxial detectors fabricated from p-type germanium cost less, have better resolution, and are larger than n-type coaxial detectors. However, it is difficult to reliably segment p-type coaxial detectors because thick (~1 mm) lithium-diffused (hole barrier) contacts are the standard outside contact for p-type coaxial detectors. During this Phase 1 Small Business Innovation Research (SBIR) we have researched the possibility of using amorphous germanium contacts as a thin outer contact of p-type coaxial detectors that can be segmented. We have developed amorphous germanium contacts that provide a very high hole barrier on small planar detectors. These easily segmented amorphous germanium contacts have been demonstrated to withstand several thousand volts/cm electric fields with no measurable leakage current (<1 pA) from charge injection over the hole barrier. We have also demonstrated that the contact can be sputter deposited around and over the curved outside surface of a small p-type coaxial detector. The amorphous contact has shown good rectification properties on the outside of a small p-type coaxial detector. These encouraging

  12. Doping of germanium and silicon crystals with non-hydrogenic acceptors for far infrared lasers

    DOEpatents

    Haller, Eugene E.; Brundermann, Erik

    2000-01-01

    A method for doping semiconductors used for far infrared lasers with non-hydrogenic acceptors having binding energies larger than the energy of the laser photons. Doping of germanium or silicon crystals with beryllium, zinc or copper. A far infrared laser comprising germanium crystals doped with double or triple acceptor dopants permitting the doped laser to be tuned continuously from 1 to 4 terahertz and to operate in continuous mode. A method for operating semiconductor hole population inversion lasers with a closed cycle refrigerator.

  13. Probing the Electronic Density of States of Germanium Nanoparticles: A Method for Determining Atomic Structure

    SciTech Connect

    Williamson, A; Bostedt, C; van Buuren, T; Willey, T; Terminello, L; Galli, G; Pizzagalli, L

    2004-03-31

    We present first principles electronic structure calculations and photoemission measurements of the change in the valence band DOS of germanium as its dimensions are reduced from the bulk to the nanoscale. By comparing the calculated broadening of the s and s--p band peaks and the energy of surface dangling bonds to the measured DOS we identify the most likely structure of these nanoparticles. We propose that, in contrast to recent interpretations, small 2-3 nm germanium nanoparticles prepared by gas phase aggregation have a distorted diamond structure core and a thermally disordered surface.

  14. Optimization of the Transport Shield for Neutrinoless Double Beta-decay Enriched Germanium

    SciTech Connect

    Aguayo Navarrete, Estanislao; Kouzes, Richard T.; Orrell, John L.; Reid, Douglas J.; Fast, James E.

    2012-04-15

    This document presents results of an investigation of the material and geometry choice for the transport shield of germanium, the active detector material used in 76Ge neutrinoless double beta decay searches. The objective of this work is to select the optimal material and geometry to minimize cosmogenic production of radioactive isotopes in the germanium material. The design of such a shield is based on the calculation of the cosmogenic production rate of isotopes that are known to cause interfering backgrounds in 76Ge neutrinoless double beta decay searches.

  15. Reaction between defects in germanium doubly doped with aluminum and antimony

    SciTech Connect

    Akopyan, R.A.; Mamedova, S.K.; Salaev, D.E.

    1987-12-01

    Microhardness and Hall effect are investigated in germanium crystals, doped with donor- and acceptor-type elements at different ratios of the doping components. In the constructed composition-property diagrams, the presence of singular points is revealed, which corresponds to an equiatomic ratio between the donors and acceptors. From a comparison of the results with data, obtained earlier on complexly doped semiconductors (Ge, Si, InP, InAs), the possibility of the formation of donor-acceptor clusters of the (AlSb) type is demonstrated in a germanium-based solid solution.

  16. Investigation into Methods to Improve Ion Source Life for Germanium Implantation

    NASA Astrophysics Data System (ADS)

    Sweeney, Joseph; Sergi, Steven; Tang, Ying; Byl, Oleg; Yedave, Sharad; Kaim, Robert; Bishop, Steve

    2011-01-01

    Germanium tetrafluoride has long been the standard dopant gas of choice for germanium implantation processes. While this material maintains several positive attributes (e.g., it is a nonflammable gas that is easily delivered to an ion source), its use can result in extremely short ion source lifetimes. This is especially the case for the situation when an ion implanter runs solely or predominantly GeF4. Presented here is an examination of various potential solutions to the short source life problem, some of which enable significant improvement.

  17. Strain distribution in single, suspended germanium nanowires studied using nanofocused x-rays.

    PubMed

    Keplinger, Mario; Grifone, Raphael; Greil, Johannes; Kriegner, Dominik; Persson, Johan; Lugstein, Alois; Schülli, Tobias; Stangl, Julian

    2016-02-01

    Within the quest for direct band-gap group IV materials, strain engineering in germanium is one promising route. We present a study of the strain distribution in single, suspended germanium nanowires using nanofocused synchrotron radiation. Evaluating the probed Bragg reflection for different illumination positions along the nanowire length results in corresponding strain components as well as the nanowire's tilting and bending. By using these findings we determined the complete strain state with the help of finite element modelling. The resulting information provides us with the possibility of evaluating the validity of the strain investigations following from Raman scattering experiments which are based on the assumption of purely uniaxial strain. PMID:26753909

  18. Microstructures of niobium-germanium alloys processed in inert gas in the 100 meter drop tube

    NASA Technical Reports Server (NTRS)

    Bayuzick, R. J.; Robinson, M. B.; Hofmeister, W. H.; Evans, N. D.

    1986-01-01

    The 100 meter drop tube at NASA's Marshall Space Flight Center has been used for a series of experiments with niobium-germanium alloys. These experiments were conducted with electromagnetic levitation melting in a 200 torr helium environment. Liquid alloys experienced large degrees of undercooling prior to solidification in the drop tube. Several interesting metastable structures were observed. However, the recalescence event prevented extended solid solubility of germanium in the A-15 beta phase. Liquids of eutectic composition were found to undercool in the presence of solid alpha and solid Nb5Ge3.

  19. Ionization Measurements of SuperCDMS SNOLAB 100 mm Diameter Germanium Crystals

    SciTech Connect

    Chagani, H.; Bauer, D.A.; Brandt, D.; Brink, P.L.; Cabrera, B.; Cherry, M.; Silva, E.Do Couto e; Godfrey, G.G.; Hall, J.; Hansen, S.; Hasi, J.; Kelsey, M.; Kenney, C.J.; Mandic, V.; Nagasawa, D.; Novak, L.; Mirabolfathi, N.; Partridge, R.; Radpour, R.; Resch, R.; Sadoulet, B.; /UC, Berkeley /Stanford U. /SLAC /Stanford U. /Santa Clara U. /Minnesota U.

    2012-06-12

    Scaling cryogenic Germanium-based dark matter detectors to probe smaller WIMP-nucleon cross-sections poses significant challenges in the forms of increased labor, cold hardware, warm electronics and heat load. The development of larger crystals alleviates these issues. The results of ionization tests with two 100 mm diameter, 33 mm thick cylindrical detector-grade Germanium crystals are presented here. Through these results the potential of using such crystals in the Super Cryogenic Dark Matter Search (SuperCDMS) SNOLAB experiment is demonstrated.

  20. Ordered growth of germanium hut islands on Si (001) molecular bonded substrates

    SciTech Connect

    Poydenot, V.; Dujardin, R.; Rouviere, J.L.; Barski, A.; Fournel, F.

    2004-12-06

    Ordered germanium hut islands are grown by molecular-beam epitaxy on high twist angle molecular bonded silicon (001) substrates (twist angle higher than 20 deg.). We show that the growth organization is induced by an array of interfacial tilt dislocations. Plan-view transmission electron microscopy and atomic force microscopy observations show that the orientation and period of the tilt dislocation array determine the orientation, period, and length of elongated germanium hut islands. The strain field generated by an array of tilt dislocations is proposed as the driving force of the reported organization.

  1. Removal of the long-lived {sup 222}Rn daughters from steel and germanium surfaces

    SciTech Connect

    Wojcik, Marcin; Zuzel, Grzegorz; Majorovits, Bela

    2011-04-27

    Removal of the long-lived {sup 222}Rn daughters ({sup 210}Pb, {sup 210}Bi and {sup 210}Po) from stainless steel and germanium surfaces was investigated. As cleaning technique etching was applied to samples in a form of discs exposed earlier to a strong radon source. Reduction of the {sup 210}Pb activity was tested using a HPGe spectrometer, for {sup 210}Bi a beta spectrometer and for {sup 210}Po an alpha spectrometer was used. According to the conducted measurements all the isotopes were removed very efficiently from germanium. Results obtained for stainless steel were worse but still better than those achieved for copper.

  2. Temperature-dependent hyperfine interactions at 111Cd-C complex in germanium

    NASA Astrophysics Data System (ADS)

    Mola, Genene Tessema

    2013-09-01

    The temperature dependent nuclear hyperfine interaction of 111Cd-carbon complex in germanium has been studied using the perturbed γ- γ angular correlation (PAC) method. The parameters of the hyperfine interaction representing substitutional carbon-cadmium complex in germanium ( ν Q1=207(1) MHz ( η=0.16)) shows dependence on temperature. The formation and thermal stability of the complex has been reported by the same author earlier. It was found in this study that the quadrupole coupling constant of the interaction increases at sample temperature below 293 K. The results are encouraging toward better understanding of the complex in the host matrix.

  3. Self-assembly of tin wires via phase transformation of heteroepitaxial germanium-tin on germanium substrate

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Li, Lingzi; Tok, Eng Soon; Yeo, Yee-Chia

    2015-06-01

    This work demonstrates and describes for the first time an unusual strain-relaxation mechanism by the formation and self-assembly of well-ordered tin wires during the thermal annealing of epitaxial Ge0.83Sn0.17-on-Ge(001) substrate. Fully strained germanium-tin alloys (Ge0.83Sn0.17) were epitaxially grown on Ge(001) substrate by molecular beam epitaxy. The morphological and compositional evolution of Ge0.83Sn0.17 during thermal annealing is studied by atomic force microscopy, X-ray diffraction, transmission electron microscopy. Under certain annealing conditions, the Ge0.83Sn0.17 layer decomposes into two stable phases, and well-defined Sn wires that are preferentially oriented along two orthogonal ⟨100⟩ azimuths are formed. The formation of the Sn wires is related to the annealing temperature and the Ge0.83Sn0.17 thickness, and can be explained by the nucleation of a grain with Sn islands on the outer front, followed by grain boundary migration. The Sn wire formation process is found to be thermally activated, and an activation enthalpy (Ec) of 0.41 eV is extracted. This thermally activated phase transformation, i.e., 2D epitaxial layer to 3D wires, occurs via a mechanism akin to "cellular precipitation." This synthesis route of Sn wires opens new possibilities for creation of nanoscale patterns at high-throughput without the need for lithography.

  4. Self-assembly of tin wires via phase transformation of heteroepitaxial germanium-tin on germanium substrate

    SciTech Connect

    Wang, Wei; Li, Lingzi; Yeo, Yee-Chia; Tok, Eng Soon

    2015-06-14

    This work demonstrates and describes for the first time an unusual strain-relaxation mechanism by the formation and self-assembly of well-ordered tin wires during the thermal annealing of epitaxial Ge{sub 0.83}Sn{sub 0.17}-on-Ge(001) substrate. Fully strained germanium-tin alloys (Ge{sub 0.83}Sn{sub 0.17}) were epitaxially grown on Ge(001) substrate by molecular beam epitaxy. The morphological and compositional evolution of Ge{sub 0.83}Sn{sub 0.17} during thermal annealing is studied by atomic force microscopy, X-ray diffraction, transmission electron microscopy. Under certain annealing conditions, the Ge{sub 0.83}Sn{sub 0.17} layer decomposes into two stable phases, and well-defined Sn wires that are preferentially oriented along two orthogonal 〈100〉 azimuths are formed. The formation of the Sn wires is related to the annealing temperature and the Ge{sub 0.83}Sn{sub 0.17} thickness, and can be explained by the nucleation of a grain with Sn islands on the outer front, followed by grain boundary migration. The Sn wire formation process is found to be thermally activated, and an activation enthalpy (E{sub c}) of 0.41 eV is extracted. This thermally activated phase transformation, i.e., 2D epitaxial layer to 3D wires, occurs via a mechanism akin to “cellular precipitation.” This synthesis route of Sn wires opens new possibilities for creation of nanoscale patterns at high-throughput without the need for lithography.

  5. Germanium and Rare Earth Element accumulation in woody bioenergy crops

    NASA Astrophysics Data System (ADS)

    Hentschel, Werner

    2016-04-01

    Germanium and REEs are strategic elements that are used for high tech devices and engineered systems, however these elements are hardly concentrated into mineable ore deposits. Since these elements occur widely dispersed in the earth crust with concentrations of several mgṡkg‑1 (Ge 1.6 mgṡkg‑1, Nd 25 mgṡkg‑1) a new possibility to gain these elements could be phytomining, a technique that uses plants to extract elements from soils via their roots. Since knowledge about accumulating plant species is quite limited we conducted research on the concentrations of strategic elements in wood and leaves of fast growing tree species (Salix spec., Populus spec., Betula pendula, Alnus glutinosa, Fraxinus excelsior, Acer pseudoplatanus). In total 35 study sites were selected in the mining affected area around Freiberg (Saxony, Germany), differing in their species composition and degree of contamination with toxic trace metals (Pb, As, Cd). On each site plant tissues (wood and leaves, respectively) of different species were sampled. In addition soil samples were taken from a soil depth of 0 - 30 cm and 30 - 60 cm. The aim of our work was to investigate correlations between the concentrations of the target elements in plant tissues and soil characteristics like pH, texture, nutrients and concentrations in six operationally defined soil fractions (mobile, acid soluble, oxidizable, amorphic oxides, crystalline oxides, residual or siliceous). Concentrations of elements in soil extracts and plant tissues were measured with ICP-MS. The element Nd was selected as representative for the group of REEs, since this element showed a high correlation with the concentrations of the other REE We found that the concentration of Nd in the leaves (0.31 mgṡkg‑1Nd) were several times higher than in herbaceous species (0.05 mgṡkg‑1 Nd). The concentration of Ge in leaves were ten times lower than that of Nd whereas in herbaceous species Nd and Ge were in equal magnitude. Within

  6. High bit rate germanium single photon detectors for 1310nm

    NASA Astrophysics Data System (ADS)

    Seamons, J. A.; Carroll, M. S.

    2008-04-01

    There is increasing interest in development of high speed, low noise and readily fieldable near infrared (NIR) single photon detectors. InGaAs/InP Avalanche photodiodes (APD) operated in Geiger mode (GM) are a leading choice for NIR due to their preeminence in optical networking. After-pulsing is, however, a primary challenge to operating InGaAs/InP single photon detectors at high frequencies1. After-pulsing is the effect of charge being released from traps that trigger false ("dark") counts. To overcome this problem, hold-off times between detection windows are used to allow the traps to discharge to suppress after-pulsing. The hold-off time represents, however, an upper limit on detection frequency that shows degradation beginning at frequencies of ~100 kHz in InGaAs/InP. Alternatively, germanium (Ge) single photon avalanche photodiodes (SPAD) have been reported to have more than an order of magnitude smaller charge trap densities than InGaAs/InP SPADs2, which allowed them to be successfully operated with passive quenching2 (i.e., no gated hold off times necessary), which is not possible with InGaAs/InP SPADs, indicating a much weaker dark count dependence on hold-off time consistent with fewer charge traps. Despite these encouraging results suggesting a possible higher operating frequency limit for Ge SPADs, little has been reported on Ge SPAD performance at high frequencies presumably because previous work with Ge SPADs has been discouraged by a strong demand to work at 1550 nm. NIR SPADs require cooling, which in the case of Ge SPADs dramatically reduces the quantum efficiency of the Ge at 1550 nm. Recently, however, advantages to working at 1310 nm have been suggested which combined with a need to increase quantum bit rates for quantum key distribution (QKD) motivates examination of Ge detectors performance at very high detection rates where InGaAs/InP does not perform as well. Presented in this paper are measurements of a commercially available Ge APD

  7. Quantum devices in silicon/silicon germanium heterostructures

    NASA Astrophysics Data System (ADS)

    Slinker, Keith A.

    This thesis presents the fabrication and characterization of silicon/silicon-germanium quantum wells, quantum dots, and quantum point contacts. These systems are promising for quantum computing applications due to the long predicted spin lifetimes. In addition, the valley states in Si/SiGe two-dimensional electron gases (2DEGs) are a novel phenomenon in regards to nanostructures, and characterizing these states is also necessary for potential computing applications. However, working with these heterostructures---especially in regards to metal Schottky gating---has proved historically challenging such that single electron transistors had not been achieved at the onset of this research. The first quantum dots in Si/SiGe are presented, defined completely by CF4 reactive ion etch without the use of metal gates. Etch-defined 2DEG side gates are used to modulate the potential of the quantum dot. Results for various metal gating schemes are also presented, culminating in the first Schottky-gated quantum dots in Si/SiGe. Differing from the etch-defined dots, the tunnel junctions of the metal-etch hybrid dot are fully tunable by the voltage applied to the top gates. Hall measurements of multiple heterostructures are presented, providing evidence that many of the challenges associated with gating Si/SiGe can be attributed to undepleted dopants in the supply layer. These dopants screen the top gates but can be detected as a parallel conduction channel in Hall measurements taken at a 2 K. A fully top-gate defined quantum dot was fabricated on an optimized Si/SiGe heterostructure, and the single particle excited states were resolved for the first time in Si/SiGe. Finally, quantum point contacts were defined by metal top gates, and the conduction was mapped out over a large range of magnetic field and voltages on the gates. The positions of the conductance steps are used to extract the valley splitting---a quantity that had been measured in a bulk 2DEG but not in a nanostructure

  8. Measurement of acousto-optic interaction in germanium in the far infrared

    SciTech Connect

    Duerr, W.; Schmidt, W.

    1985-10-01

    Acoustooptic interaction in a germanium Bragg cell, which was operated as an acoustic resonator, was measured at 119 microns relative to 10.6 microns. The figure of merit of the material was found to be approximately 20 percent higher in the far infrared. The performance of various acoustooptic materials in the far infrared is briefly discussed. 5 references.

  9. Germanium determination by flame atomic absorption spectrometry: an increased vapor pressure-chloride generation system.

    PubMed

    Kaya, Murat; Volkan, Mürvet

    2011-03-15

    A new chloride generation system was designed for the direct, sensitive, rapid and accurate determination of the total germanium in complex matrices. It was aimed to improve the detection limit of chloride generation technique by increasing the vapor pressure of germanium tetrachloride (GeCl(4)). In order to do so, a novel joint vapor production and gas-liquid separation unit equipped with a home-made oven was incorporated to an ordinary nitrous oxide-acetylene flame atomic absorption spectrometer. Several variables such as reaction time, temperature and acid concentration have been investigated. The linear range for germanium determination was 0.1-10 ng mL(-1) for 1 mL sampling volume with a detection limit (3s) of 0.01 ng mL(-1). The relative standard deviation (RSD) was 2.4% for nine replicates of a 1 ng mL(-1) germanium solution. The method was validated by the analysis of one non-certified and two certified geochemical reference materials, respectively, CRM GSJ-JR-2 (Rhyolite), and GSJ-JR-1 (Rhyolite), and GBW 07107 (Chinese Rock). Selectivity of the method was investigated for Cd(2+), Co(2+), Cu(2+), Fe(3+), Ga(3+), Hg(2+), Ni(2+), Pb(2+), Sn(2+), and Zn(2+) ions and ionic species of As(III), Sb(III), Te(IV), and Se(IV). PMID:21315908

  10. Evaluation of semiconductor specimens by X-ray analysis. [considering germanium and gallium arsenide structures

    NASA Technical Reports Server (NTRS)

    Walter, H. U.

    1975-01-01

    Germanium and GaAs crystals were investigated for studies on photovoltaic effects, chemical etching and epitaxial growth according to the overall objective to assess the defect structure of single crystalline materials. A brief survey of basic theory and topographical techniques is provided; examples of topographs are presented.

  11. Probing the structural evolution of ruthenium doped germanium clusters: Photoelectron spectroscopy and density functional theory calculations.

    PubMed

    Jin, Yuanyuan; Lu, Shengjie; Hermann, Andreas; Kuang, Xiaoyu; Zhang, Chuanzhao; Lu, Cheng; Xu, Hongguang; Zheng, Weijun

    2016-01-01

    We present a combined experimental and theoretical study of ruthenium doped germanium clusters, RuGen(-) (n = 3-12), and their corresponding neutral species. Photoelectron spectra of RuGen(-) clusters are measured at 266 nm. The vertical detachment energies (VDEs) and adiabatic detachment energies (ADEs) are obtained. Unbiased CALYPSO structure searches confirm the low-lying structures of anionic and neutral ruthenium doped germanium clusters in the size range of 3 ≤ n ≤ 12. Subsequent geometry optimizations using density functional theory (DFT) at PW91/LANL2DZ level are carried out to determine the relative stability and electronic properties of ruthenium doped germanium clusters. It is found that most of the anionic and neutral clusters have very similar global features. Although the global minimum structures of the anionic and neutral clusters are different, their respective geometries are observed as the low-lying isomers in either case. In addition, for n > 8, the Ru atom in RuGen(-/0) clusters is absorbed endohedrally in the Ge cage. The theoretically predicted vertical and adiabatic detachment energies are in good agreement with the experimental measurements. The excellent agreement between DFT calculations and experiment enables a comprehensive evaluation of the geometrical and electronic structures of ruthenium doped germanium clusters. PMID:27439955

  12. Enhanced Third Harmonic Generation in Single Germanium Nanodisks Excited at the Anapole Mode.

    PubMed

    Grinblat, Gustavo; Li, Yi; Nielsen, Michael P; Oulton, Rupert F; Maier, Stefan A

    2016-07-13

    We present an all-dielectric germanium nanosystem exhibiting a strong third order nonlinear response and efficient third harmonic generation in the optical regime. A thin germanium nanodisk shows a pronounced valley in its scattering cross section at the dark anapole mode, while the electric field energy inside the disk is maximized due to high confinement within the dielectric. We investigate the dependence of the third harmonic signal on disk size and pump wavelength to reveal the nature of the anapole mode. Each germanium nanodisk generates a high effective third order susceptibility of χ((3)) = 4.3 × 10(-9) esu, corresponding to an associated third harmonic conversion efficiency of 0.0001% at an excitation wavelength of 1650 nm, which is 4 orders of magnitude greater than the case of an unstructured germanium reference film. Furthermore, the nonlinear conversion via the anapole mode outperforms that via the radiative dipolar resonances by about 1 order of magnitude, which is consistent with our numerical simulations. These findings open new possibilities for the optimization of upconversion processes on the nanoscale through the appropriate engineering of suitable dielectric materials. PMID:27331867

  13. Probing the structural evolution of ruthenium doped germanium clusters: Photoelectron spectroscopy and density functional theory calculations

    PubMed Central

    Jin, Yuanyuan; Lu, Shengjie; Hermann, Andreas; Kuang, Xiaoyu; Zhang, Chuanzhao; Lu, Cheng; Xu, Hongguang; Zheng, Weijun

    2016-01-01

    We present a combined experimental and theoretical study of ruthenium doped germanium clusters, RuGen− (n = 3–12), and their corresponding neutral species. Photoelectron spectra of RuGen− clusters are measured at 266 nm. The vertical detachment energies (VDEs) and adiabatic detachment energies (ADEs) are obtained. Unbiased CALYPSO structure searches confirm the low-lying structures of anionic and neutral ruthenium doped germanium clusters in the size range of 3 ≤ n ≤ 12. Subsequent geometry optimizations using density functional theory (DFT) at PW91/LANL2DZ level are carried out to determine the relative stability and electronic properties of ruthenium doped germanium clusters. It is found that most of the anionic and neutral clusters have very similar global features. Although the global minimum structures of the anionic and neutral clusters are different, their respective geometries are observed as the low-lying isomers in either case. In addition, for n > 8, the Ru atom in RuGen−/0 clusters is absorbed endohedrally in the Ge cage. The theoretically predicted vertical and adiabatic detachment energies are in good agreement with the experimental measurements. The excellent agreement between DFT calculations and experiment enables a comprehensive evaluation of the geometrical and electronic structures of ruthenium doped germanium clusters. PMID:27439955

  14. Chemical synthesis of germanium nanoparticles with uniform size as anode materials for lithium ion batteries.

    PubMed

    Wang, Liangbiao; Bao, Keyan; Lou, Zhengsong; Liang, Guobing; Zhou, Quanfa

    2016-02-21

    A simple Mg-thermal reduction reaction is reported to synthesize germanium (Ge) nanoparticles with a uniform size at a low temperature of 400 °C in an autoclave. The as-prepared Ge nanoparticles exhibit promising anode applications in lithium ion batteries with high capacity and excellent cycling stability. PMID:26813100

  15. Multidimensional Germanium-Based Materials as Anodes for Lithium-Ion Batteries.

    PubMed

    Qin, Jinwen; Cao, Minhua

    2016-04-20

    Metallic germanium is an ideal anode for lithium-ion batteries (LIBs), owing to its high theoretical capacity (1624 mA h g(-1) ) and low operating voltage. Herein, we highlight recent advances in the development of Ge-based anodes in LIBs, although improvements in their coulombic efficiency (CE), capacity retention, and rate performance are still required. One of the major concerns facing the development of Ge anodes is the controlled formation of microstructures. In this Focus Review, we summarize Ge-based materials with different structural dimensions, that is, zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), three-dimensional (3D), and even monolithic and macroscale structures. Moreover, the design of Ge-based oxide materials, as an effective route for achieving higher Li-storage capacities and cycling performance, is also discussed. Finally, we briefly summarize new types of Ge-based materials, such as ternary germanium oxides, germanium sulfides, and germanium phosphides, and predict that they will bring about a reformation in the field of LIBs. PMID:26990878

  16. Reaction studies of hot silicon and germanium radicals. Progress report, September 1, 1979-August 31, 1980

    SciTech Connect

    Gaspar, P.P.

    1980-08-31

    The experimental approach to attaining the goals of this research program is briefly outlined and the progress made in the last year is reviewed in sections entitled: (a) primary steps in the reaction of recoiling silicon and germanium atoms and the identification of reactive intermediates in the recoil reactions; (b) thermally induced silylene and germylene reactions; (c) ion-molecule reaction studies.

  17. Denuded Zone Formation in Germanium Codoped Heavily Phosphorus-Doped Czochralski Silicon

    NASA Astrophysics Data System (ADS)

    Lin, Li-Xia; Chen, Jia-He; Wu, Peng; Zeng, Yu-Heng; Ma, Xiang-Yang; Yang, De-Ren

    2011-03-01

    The formation of a denuded zone (DZ) by conventional furnace annealing (CFA) and rapid thermal annealing (RTA) based denudation processing is investigated and the gettering of copper (Cu) atoms in germanium co-doped heavily phosphorus-doped Czochralski (GHPCZ) silicon wafers is evaluated. It is suggested that both a good quality defect-free DZ with a suitable width in the sub-surface area and a high density bulk micro-defect (BMD) region could be formed in heavily phosphorus-doped Czochralski (HPCZ) silicon and GHPCZ silicon wafers. This is ascribed to the formation of phosphorus-vacancy (P-V) related complexes and germanium-vacancy (GeV) related complexes. Compared with HPCZ silicon, the DZ width is wider in the GHPCZ silicon sample with CFA-based denudation processing but narrower in the one with two-step RTA pretreatments. These phenomena are ascribed to the enhancing effect of germanium on oxygen out-diffusion movement and oxygen precipitate nucleation, respectively. Furthermore, fairly clean DZs near the surface remain in both the HPCZ and GHPCZ silicon wafers after Cu in-diffusion, except for the HPCZ silicon wafer which underwent denudation processing with a CFA pretreatment, suggesting that germanium doping could improve the gettering of Cu contamination.

  18. High-resolution imaging gamma-ray spectroscopy with externally segmented germanium detectors

    NASA Technical Reports Server (NTRS)

    Callas, J. L.; Mahoney, W. A.; 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. An angular resolution of 0.2 deg becomes practical by combining position-sensitive germanium detectors having a segment thickness of a few millimeters with a one-dimensional coded aperture located about a meter from the detectors. Correspondingly higher angular resolutions are possible with larger separations between the detectors and the coded aperture. Two-dimensional images can be obtained by rotating the instrument. Although the basic concept is similar to optical or X-ray coded-aperture imaging techniques, several complicating effects arise because of the penetrating nature of gamma rays. The complications include partial transmission through the coded aperture elements, Compton scattering in the germanium detectors, and high background count rates. Extensive electron-photon Monte Carlo modeling of a realistic detector/coded-aperture/collimator system has been performed. Results show that these complicating effects can be characterized and accounted for with no significant loss in instrument sensitivity.

  19. Germanium detectors for nuclear spectroscopy: Current research and development activity at LNL

    NASA Astrophysics Data System (ADS)

    Napoli, D. R.; Maggioni, G.; Carturan, S.; Eberth, J.; Gelain, M.; Grimaldi, M. G.; Tatí, S.; Riccetto, S.; Mea, G. Della

    2016-07-01

    High-purity Germanium (HPGe) detectors have reached an unprecedented level of sophistication and are still the best solution for high-resolution gamma spectroscopy. In the present work, we will show the results of the characterization of new surface treatments for the production of these detectors, studied in the framework of our multidisciplinary research program in HPGe detector technologies.

  20. Rigorous theory of the radiative and gain characteristics of silicon and germanium lasing media

    NASA Astrophysics Data System (ADS)

    Wen, Hanqing; Bellotti, Enrico

    2015-01-01

    A generalized numerical model for the phonon-assisted optical interband transition based on the Green's function formalism was developed and implemented to investigate optical processes in germanium and silicon media intended for on-chip light emitter and laser applications. High-fidelity full band structures obtained from the empirical pseudopotential method, self-energies, and the corresponding spectral density functions for the phonon-perturbed electron and holes have been computed numerically as a function of strain, temperature, and doping level. Validation has been carried out by showing the model's ability to accurately reproduce the measured temperature dependent absorption coefficient data for both germanium and silicon. Absorption coefficients, radiative recombination rates of germanium and silicon active media were investigated with different biaxial tensile strain, doping concentrations and injection conditions. Furthermore, when the model is employed to compute the optical gain in strained germanium, we find that the use of tensile strain and high injection are the preferable approaches to obtain population inversion. At the same time, strong absorption from the spin-orbit to the heavy-hole band limits the maximum injection density that can be applied. Finally, when applied to study silicon, the proposed model also successfully reproduces the experimentally observed radiative recombination peak due to the two-phonon process.

  1. Fabrication and performance of intrinsic germanium photodiodes. [for atmospheric IR spectroscopy

    NASA Technical Reports Server (NTRS)

    Beiting, E. J., III; Feldman, P. D.

    1977-01-01

    The paper presents fabrication details for an intrinsic germanium photodiode developed for study of atmospheric constituents, the airglow and auroras in the 1-2 micron spectral range. Attention is given to cutting of the single crystal, spreading of the lithium dispersion, sputtering of a gold coating, and surface passivation. A wavelength response curve is presented.

  2. Thermophysical Properties of Molten Germanium Measured by the High Temperature Electrostatic Levitator

    NASA Technical Reports Server (NTRS)

    Rhim, W. K.; Ishikawa, T.

    1998-01-01

    Thermophysical properties of molten germanium such as the density, the thermal expansion coefficient, the hemisphereical total emissivity, the constant pressure specific heat capacity, the surface tension, and the electrical resistivity have been measured using the High Temperature Electrostatic Levitator at JPL.

  3. The Preparation of Complexes of Germanone from a Germanium μ-Oxo Dimer.

    PubMed

    Sinhababu, Soumen; Yadav, Dhirendra; Karwasara, Surendar; Sharma, Mahendra Kumar; Mukherjee, Goutam; Rajaraman, Gopalan; Nagendran, Selvarajan

    2016-06-27

    Complexes of germanone containing formal Ge=O→M bonds (M=Zn, B, Ge, Sn) were isolated and characterized. The compounds were prepared through a novel synthetic route using a germanium μ-oxo dimer 3 as the starting material. This method circumvents the need to employ germanones to prepare complexes of germanones. PMID:27238633

  4. Probing the structural evolution of ruthenium doped germanium clusters: Photoelectron spectroscopy and density functional theory calculations

    NASA Astrophysics Data System (ADS)

    Jin, Yuanyuan; Lu, Shengjie; Hermann, Andreas; Kuang, Xiaoyu; Zhang, Chuanzhao; Lu, Cheng; Xu, Hongguang; Zheng, Weijun

    2016-07-01

    We present a combined experimental and theoretical study of ruthenium doped germanium clusters, RuGen‑ (n = 3–12), and their corresponding neutral species. Photoelectron spectra of RuGen‑ clusters are measured at 266 nm. The vertical detachment energies (VDEs) and adiabatic detachment energies (ADEs) are obtained. Unbiased CALYPSO structure searches confirm the low-lying structures of anionic and neutral ruthenium doped germanium clusters in the size range of 3 ≤ n ≤ 12. Subsequent geometry optimizations using density functional theory (DFT) at PW91/LANL2DZ level are carried out to determine the relative stability and electronic properties of ruthenium doped germanium clusters. It is found that most of the anionic and neutral clusters have very similar global features. Although the global minimum structures of the anionic and neutral clusters are different, their respective geometries are observed as the low-lying isomers in either case. In addition, for n > 8, the Ru atom in RuGen‑/0 clusters is absorbed endohedrally in the Ge cage. The theoretically predicted vertical and adiabatic detachment energies are in good agreement with the experimental measurements. The excellent agreement between DFT calculations and experiment enables a comprehensive evaluation of the geometrical and electronic structures of ruthenium doped germanium clusters.

  5. Growth of epitaxial silicon and germanium nanowires using the gold catalyzed vapor-liquid-solid mechanism

    NASA Astrophysics Data System (ADS)

    Dailey, Eric J.

    The growth of silicon and germanium nanowires and their nanowire heterostructures has been investigated using the gold catalyzed vapor-liquid-solid (VLS) mechanism. The Au catalyst particles were deposited under ultra high vacuum (UHV) conditions onto vicinal Si(111) surfaces using physical vapor deposition. Nanowires were grown in a home built UHV-chemical vapor deposition (CVD) chamber using silane, disilane, germane, and digermane as gas precursors. Silicon nanowire morphology was determined to be dependent on the stability of the gold catalyst particle at the tip of the nanowire. Specifically, silicon nanowires grow along <111> orientations when gold wets the nanowire sidewalls and along <112> orientations when gold does not wet the nanowire sidewalls except under a very narrow pressure range. The dependence of gold coverage on CVD parameters on the sidewalls of <111> and <112> silicon nanowires was also determined revealing a liquid metal wetting of cylinders phenomenon. A new "seedless" VLS mechanism for nanowire growth was also determined in which the Stranski-Krastanov planar gold layer on Si(111) dewets under certain CVD conditions resulting in 15 nm diameter gold seeds that then form nanowires via the VLS mechanism. Both core/shell and axial nanowire heterostructures were also investigated with a focus on the effect of nanowire orientation on heterostructure formation. For core/shell heterostructures, only the <110> germanium core/silicon shell heterostructures were determined to form with smooth shell deposition while all other orientations underwent shell roughening. Various germanium core diameters and silicon shell thicknesses for <110> germanium core/silicon shell heterostructures were analyzed to determine the effect of nanowire diameter on shell coherency limits and to determine the strain within the nanowire heterostructures. Lastly, axial nanowire heterostructures were investigated to determine the ability to form axial heterostructures using

  6. The Construction and Characterization of Native Insulators on Gallium-Arsenide and Germanium

    NASA Astrophysics Data System (ADS)

    Crisman, Everett Earle

    Because of the excellent electrical properties that are obtained at the interfaces between silicon and thermally grown "native" oxides and nitrides, metal-insulator -semiconductor field effect transistors (MISFET's) have become the basic elements in fast high density computer memories as well as a primary structure for probing semiconductor surface charge transport phenomena. As silicon surface mobilities approach the bulk mobility a physical constraint is also being approached with respect to speed and density. Other semiconductors with higher bulk mobilities have, therefore, been suggested as replacements for silicon: gallium arsenide because of its very high room temperature electron mobility and germanium because it is one of the few well studied semiconductors with electron and hole mobilities of nearly the same magnitude. Unlike silicon, Ge and GaAs do not react readily wit oxygen or nitrogen to form uniform layers of interface passivating "native" insulators. In this study, techniques are reported for making native insulators on gallium arsenide and germanium. On gallium arsenide, the insulator is an oxide formed by a plasma oxidation technique (POX). On germanium, oxides have been formed by a high pressure oxidation technique (HPO) and these subsequently have been converted to nitrides (or oxynitride) by reaction with ammonia gas. Details of the formation techniques and basic characterization of the insulators and insulator/semiconductor interface electrical properties are present. Surface mobilities of about 20% of the bulk values were measured for MISFET's constructed on both GaAs and Ge using native oxides as the insulator. Fixed interface charge density in the low to mid 10('11)/cm('2) and midgap densities of states in the high 10('11)/cm('2)-eV range were also measured on similar MIS capacitors. On germanium nitride structures fixed surface charge density and interface density of states were both measured to be on the order of 10('10). Characterization

  7. Removal and deposition efficiencies of the long-lived 222Rn daughters during etching of germanium surfaces

    NASA Astrophysics Data System (ADS)

    Zuzel, G.; Wójcik, M.; Majorovits, B.; Lampert, M. O.; Wendling, P.

    2012-06-01

    Removal and deposition efficiencies of the long-lived 222Rn daughters during etching from and onto surfaces of standard and high purity germanium were investigated. The standard etching procedure of Canberra-France used during production of high purity n-type germanium diodes was applied to germanium discs, which have been exposed earlier to a strong radon source for deposition of its progenies. An uncontaminated sample was etched in a solution containing 210Pb, 210Bi and 210Po. All isotopes were measured before and after etching with appropriate detectors. In contrast to copper and stainless steel, they were removed from germanium very efficiently. However, the reverse process was also observed. Considerable amounts of radioactive lead, bismuth and polonium isotopes present initially in the artificially polluted etchant were transferred to the clean high purity surface during processing of the sample.

  8. Anomalous small angle x-ray scattering studies of amorphous metal-germanium alloys

    SciTech Connect

    Rice, M.

    1993-12-01

    This dissertation addresses the issue of composition modulation in sputtered amorphous metal-germanium thin films with the aim of understanding the intermediate range structure of these films as a function of composition. The investigative tool used in this work is anomalous small-angle X-ray scattering (ASAXS). The primary focus of this investigation is the amorphous iron-germanium (a-Fe{sub x}Ge{sub 100-x}) system with particular emphasis on the semiconductor-rich regime. Brief excursions are made into the amorphous tungsten-germanium (a-W{sub x}Ge{sub 100-x}) and the amorphous molybdenum-germanium (a-Mo{sub x}Ge{sub 100-x}) systems. All three systems exhibit an amorphous structure over a broad composition range extending from pure amorphous germanium to approximately 70 atomic percent metal when prepared as sputtered films. Across this composition range the structures change from the open, covalently bonded, tetrahedral network of pure a-Ge to densely packed metals. The structural changes are accompanied by a semiconductor-metal transition in all three systems as well as a ferromagnetic transition in the a-Fe{sub x}Ge{sub 100-x} system and a superconducting transition in the a-Mo{sub x}Ge{sub 100-x} system. A long standing question, particularly in the a-Fe{sub x}Ge{sub 100-x} and the a-Mo{sub x}Ge{sub 100-x} systems, has been whether the structural changes (and therefore the accompanying electrical and magnetic transitions) are accomplished by homogeneous alloy formation or phase separation. The application of ASAXS to this problem proves unambiguously that fine scale composition modulations, as distinct from the simple density fluctuations that arise from cracks and voids, are present in the a-Fe{sub x}Ge{sub 100-x}, a-W{sub x}Ge{sub 100-x}, and a-Mo{sub x}Ge{sub 100-x} systems in the semiconductor-metal transition region. Furthermore, ASAXS shows that germanium is distributed uniformly throughout each sample in the x<25 regime of all three systems.

  9. Thermal cycling properties of a lead-free positive temperature coefficient thermistor in the Ba0.97(Bi0.5Na0.5)0.03TiO3 system

    NASA Astrophysics Data System (ADS)

    Choi, Hyoung-Seuk; Choi, Soon-Mok; Choi, Duck-Kyun

    2016-01-01

    A Pb-free PTC (positive temperature coefficient thermistor) heater was developed in the Ba0.97(Bi0.5Na0.5)0.03TiO3 system especially for automotive part applications. The reliability was verified by using a thermal cycling test designed on the basis of the result from a quality function deployment (QFD) analysis. We compared the thermal cycling test results from the newly-developed Pb-free PTC heaters with the results from PTC heaters currently on the market, namely, PTC heaters containing Pb. Life prediction and stress-strength relationships were analyzed together with a thermal diffusivity evaluation. We discuss the potential failure mechanisms during the thermal cycling test, focusing on the fact that electrical degradation in PTC materials is closely related to mechanical degradation due to the internal stress in the materials that comes from repeated phase changes. Different grain size distributions on the sintered bulks were considered to a key factor for explaining the different results of the reliability tests between the new Pb-free PTC heaters developed in this study and the commercial PTC heaters containing Pb.

  10. Deposition of HfO2 on germanium and the impact of surface pretreatments

    NASA Astrophysics Data System (ADS)

    Van Elshocht, S.; Brijs, B.; Caymax, M.; Conard, T.; Chiarella, T.; De Gendt, S.; De Jaeger, B.; Kubicek, S.; Meuris, M.; Onsia, B.; Richard, O.; Teerlinck, I.; Van Steenbergen, J.; Zhao, C.; Heyns, M.

    2004-10-01

    The deposition behavior of HfO2 by metalorganic chemical vapor deposition on germanium has been investigated. HfO2 films can be deposited on Ge with equally good quality as compared to high-k growth on silicon. Surface preparation is very important: compared to an HF-last, NH3 pretreatments result in smoother films with strongly reduced diffusion of germanium in the HfO2 film, resulting in a much better electrical performance. We clearly show that much thinner interfacial layers can be obtained, approximately half the thickness of what is typically found for depositions on silicon, suggesting the possibility of more aggressive equivalent oxide thickness/leakage scaling.

  11. Numerical evaluation of Auger recombination coefficients in relaxed and strained germanium

    NASA Astrophysics Data System (ADS)

    Dominici, Stefano; Wen, Hanqing; Bertazzi, Francesco; Goano, Michele; Bellotti, Enrico

    2016-05-01

    The potential applications of germanium and its alloys in infrared silicon-based photonics have led to a renewed interest in their optical properties. In this letter, we report on the numerical determination of Auger coefficients at T = 300 K for relaxed and biaxially strained germanium. We use a Green's function based model that takes into account all relevant direct and phonon-assisted processes and perform calculations up to a strain level corresponding to the transition from indirect to direct energy gap. We have considered excess carrier concentrations ranging from 1016 cm-3 to 5 × 1019 cm-3. For use in device level simulations, we also provide fitting formulas for the calculated electron and hole Auger coefficients as functions of carrier density.

  12. Research and Development Supporting a Next Generation Germanium Double Beta Decay Experiment

    NASA Astrophysics Data System (ADS)

    Rielage, Keith; Elliott, Steve; Chu, Pinghan; Goett, Johnny; Massarczyk, Ralph; Xu, Wenqin

    2015-10-01

    To improve the search for neutrinoless double beta decay, the next-generation experiments will increase in source mass and continue to reduce backgrounds in the region of interest. A promising technology for the next generation experiment is large arrays of Germanium p-type point contact detectors enriched in 76-Ge. The experience, expertise and lessons learned from the MAJORANA DEMONSTRATOR and GERDA experiments naturally lead to a number of research and development activities that will be useful in guiding a future experiment utilizing Germanium. We will discuss some R&D activities including a hybrid cryostat design, background reduction in cabling, connectors and electronics, and modifications to reduce assembly time. We acknowledge the support of the U.S. Department of Energy through the LANL/LDRD Program.

  13. Current experiments in germanium 0 ν β β search -- GERDA and MAJORANA

    NASA Astrophysics Data System (ADS)

    von Sturm, K.

    2015-01-01

    There are unanswered questions regarding neutrino physics that are of great interest for the scientific community. For example the absolute masses, the mass hierarchy and the nature of neutrinos are unknown up to now. The discovery of neutrinoless double beta decay (0νββ) would prove the existence of a Majorana mass, which would be linked to the half-life of the decay, and would in addition provide an elegant solution for the small mass of the neutrinos via the seesaw mechanism. Because of an existing discovery claim of 0νββ of 76Ge and the excellent energy resolution achievable, germanium is of special interest in the search for 0νββ . In this article the state of the art of germanium 0νββ search, namely the GERDA experiment and MAJORANA demonstrator, is presented. In particular, recent results of the GERDA collaboration, which strongly disfavour the above mentioned claim, are discussed.

  14. Density functional calculation of the structural and electronic properties of germanium quantum dots

    SciTech Connect

    Anas, M. M.; Gopir, G.

    2015-04-24

    We apply first principles density functional computational methods to study the structures, densities of states (DOS), and higher occupied molecular orbital (HOMO) – lowest unoccupied molecular orbital (LUMO) gaps of selected free-standing Ge semiconductor quantum dots up to 1.8nm. Our calculations are performed using numerical atomic orbital approach where linear combination of atomic orbital was applied. The surfaces of the quantum dots was passivized by hydrogen atoms. We find that surface passivation does affect the electronic properties associated with the changes of surface state, electron localization, and the energy gaps of germanium nanocrystals as well as the confinement of electrons inside the quantum dots (QDs). Our study shows that the energy gaps of germanium quantum dots decreases with the increasing dot diameter. The size-dependent variations of the computed HOMO-LUMO gaps in our quantum dots model were found to be consistent with the effects of quantum confinement reported in others theoretical and experimental calculation.

  15. Production of pristine, sulfur-coated and silicon-alloyed germanium nanoparticles via laser pyrolysis.

    PubMed

    Kim, Seongbeom; Yi Park, Song; Jeong, Jaeki; Kim, Gi-Hwan; Rohani, Parham; Suk Kim, Dong; Swihart, Mark T; Young Kim, Jin

    2015-07-31

    Here we demonstrate production of three types of germanium containing nanoparticles (NPs) by laser pyrolysis of GeH4 and characterize their sizes, structures and composition. Pristine Ge NPs were fabricated with 50 standard cubic centimeter per minute (sccm) of GeH4 and 25 sccm of SF6 as a photosensitizer gas, while sulfur-coated Ge NPs were produced with 25 sccm of GeH4 and 50 sccm of SF6. The laser pyrolysis of SiH4/GeH4 mixtures produced Si1-xGex alloy NPs. Effects of key process parameters including laser intensity and gas flow rates on NP properties have been investigated. The ability of the laser pyrolysis technique to flexibly produce a variety of germanium-containing NPs, as illustrated in this study shows promise for commercial-scale production of new nanomaterials as high purity dry powders. PMID:26152899

  16. Enhanced light emission from germanium microdisks on silicon by surface passivation through thermal oxidation

    NASA Astrophysics Data System (ADS)

    Xu, Xuejun; Hashimoto, Hideaki; Sawano, Kentarou; Nohira, Hiroshi; Maruizumi, Takuya

    2016-05-01

    We have observed enhanced direct-gap light emission from undoped and n-doped germanium microdisks on silicon. The enhancement is attributed mainly to increased carrier density due to surface passivation of the dry-etched sidewall. The enhancement factor increases as the disk size decreases, approaching 4 for microdisks with radii of 1 µm. To achieve maximum enhancement and not modify the geometric structure of resonators, 450-500 °C is found to be the best temperature window. Thermal oxidation is also effective for the degraded interface induced by sputtered Al2O3. These results indicate that thermal oxidation is a promising method suitable for fabrication of low-threshold germanium lasers.

  17. Passivation of micro-strip gas chambers with an interstitial germanium coating

    SciTech Connect

    Miyamoto, J.; Knoll, G.F.; Amos, N.

    1996-12-31

    Micro-strip gas chambers (MSGCs) were constructed in the Solid-State Electronics Laboratory of the University of Michigan and their performance was studied. Many efforts have been made in the past to construct MSGCs that yield high absolute gas gain and stable gas gain. Introducing a thin germanium layer has been effective for passivation but difficulties associated with the poor adhesiveness of the thin layer have been a serious obstacle. This paper reports on a new method used to overcome these difficulties. Unlike the conventional coating method the thin germanium layer was successfully deposited between the strip lines. This technique requires a careful geometric alignment of a second photomask with the original micro-strip structure. The resulting detector performance was noteworthy and an absolute gas gain of 2 {center_dot} 10{sup 4} was easily achieved by the new chamber. The chamber`s gain instability was also reduced significantly compared with those without interstitial coating.

  18. Germanium detectors with sub-keV sensitivities for neutrino and dark matter physics

    NASA Astrophysics Data System (ADS)

    Soma, Arun Kumar; Tsz-King Wong, Henry; TEXONO Collaboration

    2015-05-01

    A detector of O(1 kg) modular mass with O(100 eV) threshold at O(1 kg-1keV-1day-1) background level finds tremendous application in the field of neutrino and dark matter physics. This novel detector demands overcoming several challenges at both hardware and software levels. The collaboration is exploring Germanium detection technology and highlights of the R & D program are presented. The salient features of various detector configuration and the applied analysis methodologies are discussed. In particular the differentiation of surface and bulk events by pulse shape analysis in point contact Germanium detector is described. These advances pave the way for new detector technique to be fully exploited.

  19. Wideband antireflection coatings on germanium and filters for second optical window

    NASA Astrophysics Data System (ADS)

    Ciosek, Jerzy; Firak, Jozef; Stanislawek, Urszula; Kwasny, Miroslaw; Kopczynski, Krzysztof

    2003-10-01

    The investigation results of wideband (8-12 μm) antireflection coatings on germanium substrate and spectral characteristics of interference wideband filter for spectral range of 8-12 μm are presented. For design of filters and antireflection coatings the following layer materials were used: Ge, ZnS and Mira, and substrate materials such as: Ge for antireflection coatings and ZnSe for interference filters. Wideband filter for the range of 8-12 μm requires application of additional two filters cutting off radiation from the range of 1-7 μm. The cutting off filters are interference filters for which construction germanium, Mira, and ZnS were used. The constructions of basic and cutting off filters were designed considering technical possibilities of vacuum device BAK 550 of the Balzers firm.

  20. Production of pristine, sulfur-coated and silicon-alloyed germanium nanoparticles via laser pyrolysis

    NASA Astrophysics Data System (ADS)

    Kim, Seongbeom; Park, Song Yi; Jeong, Jaeki; Kim, Gi-Hwan; Rohani, Parham; Kim, Dong Suk; Swihart, Mark T.; Kim, Jin Young

    2015-07-01

    Here we demonstrate production of three types of germanium containing nanoparticles (NPs) by laser pyrolysis of GeH4 and characterize their sizes, structures and composition. Pristine Ge NPs were fabricated with 50 standard cubic centimeter per minute (sccm) of GeH4 and 25 sccm of SF6 as a photosensitizer gas, while sulfur-coated Ge NPs were produced with 25 sccm of GeH4 and 50 sccm of SF6. The laser pyrolysis of SiH4/GeH4 mixtures produced Si1-xGex alloy NPs. Effects of key process parameters including laser intensity and gas flow rates on NP properties have been investigated. The ability of the laser pyrolysis technique to flexibly produce a variety of germanium-containing NPs, as illustrated in this study shows promise for commercial-scale production of new nanomaterials as high purity dry powders.

  1. Dissolution chemistry and biocompatibility of silicon- and germanium-based semiconductors for transient electronics.

    PubMed

    Kang, Seung-Kyun; Park, Gayoung; Kim, Kyungmin; Hwang, Suk-Won; Cheng, Huanyu; Shin, Jiho; Chung, Sangjin; Kim, Minjin; Yin, Lan; Lee, Jeong Chul; Lee, Kyung-Mi; Rogers, John A

    2015-05-01

    Semiconducting materials are central to the development of high-performance electronics that are capable of dissolving completely when immersed in aqueous solutions, groundwater, or biofluids, for applications in temporary biomedical implants, environmentally degradable sensors, and other systems. The results reported here include comprehensive studies of the dissolution by hydrolysis of polycrystalline silicon, amorphous silicon, silicon-germanium, and germanium in aqueous solutions of various pH values and temperatures. In vitro cellular toxicity evaluations demonstrate the biocompatibility of the materials and end products of dissolution, thereby supporting their potential for use in biodegradable electronics. A fully dissolvable thin-film solar cell illustrates the ability to integrate these semiconductors into functional systems. PMID:25867894

  2. Extension of long wavelength response by modulation doping in extrinsic germanium infrared detectors

    NASA Technical Reports Server (NTRS)

    Hadek, V.; Farhoomand, J.; Beichman, C. A.; Watson, D. M.; Jack, M. D.

    1985-01-01

    A new concept for infrared detectors based on multilayer epitaxy and modulation doping has been investigated. This permits a high doping concentration and lower excitation energy in the photodetecting layer as is necessary for longer wavelength response, without incurring the detrimental effects of increased dark current and noise as would be the case with conventional detector designs. Germanium photodetectors using conventional materials and designs have a long wavelength cutoff in the infrared at 138 microns, which can only be extended through the inconvenient application of mechanical stress or magnetic fields. As a result of this approach which was arrived at from theoretical considerations and subsequently demonstrated experimentally, the long wavelength cutoff for germanium extrinsic detectors was extended beyond 200 microns, as determined by direct infrared optical measurements.

  3. Purification of Germanium Crystals by Zone Refinement: Theoretical and Experimental Approaches

    NASA Astrophysics Data System (ADS)

    Yang, Gang; Guan, Yutong; Wang, Guojian; Mei, Hao; Jian, Fanyi; Mei, Dongming; Crystal Growth Team

    2015-03-01

    The results of single germanium crystals grown from zone-refined germanium ingots, identified by photon thermal ionization spectroscopy (PTIS), show that there are four main impurities, aluminum (Al), phosphor (P), boron (B) and gallium (Ga) in the crystals. Based the PTIS results, we investigated the influences of zone speed, zone width and the number of passes on effective segregation coefficient of Al, P and Ga in the process of zone refinement, then the further calculation of distribution of Al, P and Ga along the zone refined ingots has been conducted. In terms of trend of impurity distribution, the calculated results have a very good agreement with the experimental results. We report both the theoretical calculations and the experimental results. This work is supported by DOE grant DE-FG02-10ER46709 and the state of South Dakota.

  4. Low-loss germanium strip waveguides on silicon for the mid-infrared.

    PubMed

    Chang, Yu-Chi; Paeder, Vincent; Hvozdara, Lubos; Hartmann, Jean-Michel; Herzig, Hans Peter

    2012-07-15

    Mid-infrared photonics in silicon needs low-loss integrated waveguides. While monocrystalline germanium waveguides on silicon have been proposed, experimental realization has not been reported. Here we demonstrate a germanium strip waveguide on a silicon substrate. It is designed for single mode transmission of light in transverse magnetic (TM) polarization generated from quantum cascade lasers at a wavelength of 5.8 μm. The propagation losses were measured with the Fabry-Perot resonance method. The lowest achieved propagation loss is 2.5 dB/cm, while the bending loss is measured to be 0.12 dB for a 90° bend with a radius of 115 μm. PMID:22825166

  5. Analog Readout and Analysis Software for the Ultra-High Rate Germanium (UHRGe) Project

    SciTech Connect

    Fast, James E.; Aguayo Navarrete, Estanislao; Evans, Allan T.; VanDevender, Brent A.; Rodriguez, Douglas C.; Wood, Lynn S.

    2011-09-01

    High-resolution high-purity germanium (HPGe) spectrometers are needed for Safeguards applications such as spent fuel assay and uranium hexafluoride cylinder verification. In addition, these spectrometers would be applicable to other high-rate applications such as non-destructive assay of nuclear materials using nuclear resonance fluorescence. Count-rate limitations of today's HPGe technologies, however, lead to concessions in their use and reduction in their efficacy. Large-volume, very high-rate HPGe spectrometers are needed to enable a new generation of nondestructive assay systems. The Ultra-High Rate Germanium (UHRGe) project is developing HPGe spectrometer systems capable of operating at unprecedented rates, 10 to 100 times those available today. This report documents current status of developments in the analog electronics and analysis software.

  6. NMR Study on Type-I Copper-doped Germanium Clathrate

    NASA Astrophysics Data System (ADS)

    Gou, Weiping; Li, Yang; Ross, Joseph H.

    2002-10-01

    NMR Study on Type-I Copper-doped Germanium Clathrate Weiping Gou, Yang Li and Joseph H. Ross, Jr. Department of Physics, Texas A University, College Station, TX 77843-4242 Germanium clathrates are new materials containing a network of nanometer-size cages, in which a wide variety of electronic and magnetic behavior is observed. We have prepared a single-phase clathrate of the composition Ba8Ge44Cu2, Ba8Ge42Cu4 and Ba8Ge40Cu6. From 63Cu nuclear magnetic resonance (NMR) we have identified two distinct sites, and we associate these sites with random occupancy of 6c sites on the Ge network, giving different local environments for Cu atoms. We identify a large paramagnetic Knight shift for these NMR lines, and a measure of the spin-lattice relaxation time (T1) shows that the Korringa ratio is obeyed. We will discuss the current understanding of this behavior.

  7. Empirical Correction of Crosstalk in a Low-Background Germanium γ–γ Analysis System

    SciTech Connect

    Keillor, Martin E.; Erikson, Luke E.; Aalseth, Craig E.; Day, Anthony R.; Fuller, Erin S.; Glasgow, Brian D.; Hoppe, Eric W.; Hossbach, Todd W.; Mizouni, Leila K.; Myers, Allan W.; Overman, Cory T.; Seifert, Allen; Stavenger, Timothy J.

    2013-05-01

    ABSTRACT The Pacific Northwest National Laboratory is currently developing a custom software suite capable of automating many of the tasks required to accurately analyze coincident signals within gamma spectrometer arrays. During the course of this work, significant crosstalk was identified in the energy determination for spectra collected with a new low-background intrinsic germanium (HPGe) array at PNNL. The HPGe array is designed for high detection efficiency, ultra-low-background performance, and sensitive gamma gamma coincidence detection. The first half of the array, a single cryostat containing 7 HPGe crystals, was recently installed into a new shallow underground laboratory facility. This update will present a brief review of the germanium array, describe the observed crosstalk, and present a straight-forward empirical correction that significantly reduces the impact of this crosstalk on the spectroscopic performance of the system.

  8. Characterization of a high-purity germanium detector for small-animal SPECT

    PubMed Central

    Johnson, Lindsay C; Campbell, Desmond L; Hull, Ethan L; Peterson, Todd E

    2011-01-01

    We present an initial evaluation of a mechanically-cooled, high-purity germanium double-sided strip detector as a potential gamma camera for small-animal SPECT. It is 90 mm in diameter and 10 mm thick with two sets of 16 orthogonal strips that have a 4.5 mm width with a 5 mm pitch. We found an energy resolution of 0.96% at 140 keV, an intrinsic efficiency of 43.3% at 122 keV and a FWHM spatial resolution of approximately 1.5 mm. We demonstrated depth-of-interaction estimation capability through comparison of pinhole acquisitions with a point source on and off axis. Finally, a flood-corrected-flood image exhibited a strip-level uniformity of less than 1%. This high-purity germanium offers many desirable properties for small-animal SPECT. PMID:21852723

  9. Tilt boundary induced heteroepitaxy in chemically grown dendritic silver nanostructures on germanium and their optical properties.

    PubMed

    Ghosh, Tanmay; Das, Pabitra; Chini, Tapas Kumar; Ghosh, Tapas; Satpati, Biswarup

    2014-08-21

    Dendritic silver nanostructures were prepared by a simple dip-and-rinse galvanic displacement reaction directly on germanium surfaces. The formation and evolution of these dendrites were investigated using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDX). The present results clearly show a new type of heteroepitaxy, where the large lattice mismatch between silver and germanium is accommodated at the interface by the formation of low-energy asymmetric tilt boundaries. The overgrown samples reduce the strain by introducing crystal defects. Additionally, by employing cathodoluminescence (CL) spectroscopy and imaging with a field emission gun scanning electron microscope (FEG-SEM), we provide information on the surface plasmon assisted photon emission of a stack of Ag hexagonal nanostructures. Surface enhanced Raman scattering (SERS) studies show the suitability of such Ag nanodendritic structures as SERS active substrates. PMID:25000224

  10. Investigation of mid-infrared second harmonic generation in strained germanium waveguides.

    PubMed

    De Leonardis, Francesco; Troia, Benedetto; Soref, Richard A; Passaro, Vittorio M N

    2016-05-16

    In this paper we present a detailed theoretical investigation of second harmonic generation in strained germanium waveguides operating at the mid infrared pump wavelength of 4 μm. The effective second order susceptibility has been estimated through a multiphysics approach considering the residual stress of the SiNx cladding film. Furthermore, general physical features have been investigated by means of a comparative analysis of SHG performance as a function of input pump power, linear and nonlinear phase mismatching, effective recombination carrier lifetime, and temperature, taking into account both continuous and pulsed regimes. Finally, periodically poled germanium devices have been explored with the aim to improve the SHG efficiency. In the same operative conditions, efficiencies of 0.6% and 0.0018% have been obtained in poled and not-poled waveguides, respectively. PMID:27409935

  11. One-pot synthesis of functionalized germanium nanocrystals from a single source precursor

    NASA Astrophysics Data System (ADS)

    Purkait, Tapas K.; Swarnakar, Anindya K.; de Los Reyes, Glenda B.; Hegmann, Frank A.; Rivard, Eric; Veinot, Jonathan G. C.

    2015-01-01

    One-pot syntheses of surface functionalized germanium nanocrystals (GeNCs) based upon traditional hot injection and microwave-assisted heating of a Ge(ii) dihydride single source precursor have been developed. The reported procedures offer in situ hydrogermylation-based covalent attachment of alkene/alkyne derived surface moieties that give access to hydrophobic or hydrophilic GeNCs.One-pot syntheses of surface functionalized germanium nanocrystals (GeNCs) based upon traditional hot injection and microwave-assisted heating of a Ge(ii) dihydride single source precursor have been developed. The reported procedures offer in situ hydrogermylation-based covalent attachment of alkene/alkyne derived surface moieties that give access to hydrophobic or hydrophilic GeNCs. Electronic supplementary information (ESI) available: Experimental details, FTIR, TEM images and XPS of thermally functionalized GeNCs. See DOI: 10.1039/c4nr05125d

  12. Recommendations for a Static Cosmic Ray Shield for Enriched Germanium Detectors

    SciTech Connect

    Aguayo Navarrete, Estanislao; Orrell, John L.; Ankney, Austin S.; Berguson, Timothy J.

    2011-09-21

    This document provides a detailed study of cost and materials that could be used to shield the detector material of the international Tonne-scale germanium neutrinoless double-beta decay experiment from hadronic particles from cosmic ray showers at the Earth's surface. This work was motivated by the need for a shield that minimizes activation of the enriched germanium during storage; in particular, when the detector material is being worked on at the detector manufacturer's facility. This work considers two options for shielding the detector material from cosmic ray particles. One option is to use a pre-existing structure already located near the detector manufacturer, such as Canberra Industries in Meriden, Connecticut. The other option is to build a shield onsite at a detector manufacturer's site. This paper presents a cost and efficiency analysis of such construction.

  13. Nanorods of Silicon and Germanium with Well-Defined Shapes and Sizes

    SciTech Connect

    Slavi C. Sevov

    2012-05-03

    We have made number of important discoveries along the major goals of the project, namely i) electrodeposition of germanium thin films from clusters, ii) synthesis of cluster-based surfactants with long hydrocarbon chains and micelles made of them, iii) grafting of Ge{sub 9}-clusters onto self assembled films of siloxanes attached to glass substrates, iv) doping of Ge{sub 9}-clusters, and v) expanding the clusters to ten-atom cages of Ge{sub 10}{sup 2-}.

  14. An improved matrix separation method for characterization of ultrapure germanium (8N).

    PubMed

    Reddy, M A; Shekhar, R; Jai Kumar, Sunil

    2016-10-01

    An improved matrix separation method has been described to characterize ultrapure germanium of 8N (99.999999%) purity. In this method, temperature of the reaction vessel in which in-situ generated chlorine gas reacts with germanium solid material directly is optimized to quantitatively remove Ge matrix from all its impurities. Optimized reaction temperature has been found to be 230±5°C. Recovery studies on more than 60 elements have been carried out at the optimized temperature. Recoveries of all the analytes except As, Se, Sn, Hg, Tl are found to be quantitative. The method has been examined for various amounts of Ge material and found to be suitable even for 10g of Ge sample and provides low parts per billion and trillion levels of process blanks. Determination of concentrations of impurities has been done by inductively coupled plasma quadrupole mass spectrometer (ICP-QMS) and high resolution continuum source graphite furnace atomic absorption spectrometer (HR-CS-GFAAS). In the absence of certified reference materials for ultrapure germanium, accuracy of the proposed method is established by spike recovery tests. Precision of this method is found to vary from 7% to 50% for concentrations between 4 and 0.004ngg(-1). Limits of detection (LOD) for the target analytes are found to be between 6 and 0.011ngmL(-1) or 1.8-0.003ngg(-1) for the proposed procedure. The method has been successfully applied for that characterization of ultrapure germanium material of 8N purity. PMID:27474273

  15. A first-principles core-level XPS study on the boron impurities in germanium crystal

    SciTech Connect

    Yamauchi, Jun; Yoshimoto, Yoshihide; Suwa, Yuji

    2013-12-04

    We systematically investigated the x-ray photoelectron spectroscopy (XPS) core-level shifts and formation energies of boron defects in germanium crystals and compared the results to those in silicon crystals. Both for XPS core-level shifts and formation energies, relationship between defects in Si and Ge is roughly linear. From the similarity in the formation energy, it is expected that the exotic clusters like icosahedral B12 exist in Ge as well as in Si.

  16. Spatially resolved Raman spectroscopy on indium-catalyzed core-shell germanium nanowires: size effects.

    PubMed

    Xiang, Y; Zardo, I; Cao, L Y; Garma, T; Heiss, M; Morante, J R; Arbiol, J; Brongersma, M L; Fontcuberta I Morral, A

    2010-03-12

    The structure of indium-catalyzed germanium nanowires is investigated by atomic force microscopy, scanning confocal Raman spectroscopy and transmission electron microscopy. The nanowires are formed by a crystalline core and an amorphous shell. We find that the diameter of the crystalline core varies along the nanowire, down to few nanometers. Phonon confinement effects are observed in the regions where the crystalline region is the thinnest. The results are consistent with the thermally insulating behavior of the core-shell nanowires. PMID:20154375

  17. Tunability of the dielectric function of heavily doped germanium thin films for mid-infrared plasmonics

    NASA Astrophysics Data System (ADS)

    Frigerio, Jacopo; Ballabio, Andrea; Isella, Giovanni; Sakat, Emilie; Pellegrini, Giovanni; Biagioni, Paolo; Bollani, Monica; Napolitani, Enrico; Manganelli, Costanza; Virgilio, Michele; Grupp, Alexander; Fischer, Marco P.; Brida, Daniele; Gallacher, Kevin; Paul, Douglas J.; Baldassarre, Leonetta; Calvani, Paolo; Giliberti, Valeria; Nucara, Alessandro; Ortolani, Michele

    2016-08-01

    Heavily doped semiconductor thin films are very promising for application in mid-infrared plasmonic devices because the real part of their dielectric function is negative and broadly tunable in the 5 to 50 μ m wavelength range at least. In this work, we investigate the electrodynamics of heavily n -type-doped germanium epilayers at infrared frequencies beyond the assumptions of the Drude model. The films are grown on silicon and germanium substrates, are in situ doped with phosphorous in the 1017 to 1019 cm-3 range, then screened plasma frequencies in the 100 to 1200 cm-1 range were observed. We employ infrared spectroscopy, pump-probe spectroscopy, and dc transport measurements to determine the tunability of the plasma frequency. Although no plasmonic structures have been realized in this work, we derive estimates of the decay time of mid-infrared plasmons and of their figures of merit for field confinement and for surface plasmon propagation. The average electron scattering rate increases almost linearly with excitation frequency, in agreement with quantum calculations based on a model of the ellipsoidal Fermi surface at the conduction band minimum of germanium accounting for electron scattering with optical phonons and charged impurities. Instead, we found weak dependence of plasmon losses on neutral impurity density. In films where a transient plasma was generated by optical pumping, we found significant dependence of the energy relaxation times in the few-picosecond range on the static doping level of the film, confirming the key but indirect role played by charged impurities in energy relaxation. Our results indicate that underdamped mid-infrared plasma oscillations are attained in n -type-doped germanium at room temperature.

  18. A first-principles core-level XPS study on the boron impurities in germanium crystal

    NASA Astrophysics Data System (ADS)

    Yamauchi, Jun; Yoshimoto, Yoshihide; Suwa, Yuji

    2013-12-01

    We systematically investigated the x-ray photoelectron spectroscopy (XPS) core-level shifts and formation energies of boron defects in germanium crystals and compared the results to those in silicon crystals. Both for XPS core-level shifts and formation energies, relationship between defects in Si and Ge is roughly linear. From the similarity in the formation energy, it is expected that the exotic clusters like icosahedral B12 exist in Ge as well as in Si.

  19. High-capacity nanostructured germanium-containing materials and lithium alloys thereof

    DOEpatents

    Graetz, Jason A.; Fultz, Brent T.; Ahn, Channing; Yazami, Rachid

    2010-08-24

    Electrodes comprising an alkali metal, for example, lithium, alloyed with nanostructured materials of formula Si.sub.zGe.sub.(z-1), where 0germanium exhibit a combination of improved capacities, cycle lives, and/or cycling rates compared with similar electrodes made from graphite. These electrodes are useful as anodes for secondary electrochemical cells, for example, batteries and electrochemical supercapacitors.

  20. Experimental investigation of boron diffusion in silicon/silicon germanium heterostructures

    NASA Astrophysics Data System (ADS)

    Kuo, Paohua

    Silicon (Si) is the most widely used semiconductor material in the electronics industry today. Incorporating germanium (Ge) into silicon adds bandgap engineering capability to the advanced technology base and manufacturing economies of silicon. Many researchers have recently demonstrated the potential of Si 1-xGex alloys for extending the performance limits of silicon-based devices including bipolar transistors as well as field-effect transistors. One of the most studied devices is the n-Si/p-Si1-x Gex/n-Si heterojunction bipolar transistor which includes a boron-doped Si1-xGex base layer. For optimal device and fabrication process design, it is important to have an understanding of boron diffusion in the Si/Si1-xGex heterostructure. The objectives of this work are the experimental characterization and modeling of boron diffusion in Si/Si1-xGex heterostructures. Boron diffusion in Si/Si1-xGex was characterized as a function of various processing parameters (anneal temperature, time, and ambient) and materials parameters (germanium content x, boron concentration, and macroscopic strain). Boron diffusivity in strained Si1-xGe x was observed, in general, to decrease with increasing germanium content for all annealing conditions and over large ranges of boron concentration investigated. Furthermore, boron diffusion was shown to depend primarily on germanium content rather than macroscopic strain. The segregation phenomenon across a Si/Si1-xGex heterointerface was also characterized and models for boron diffusion in Si1-x Gex are proposed.

  1. Reaction studies of hot silicon and germanium radicals. Progress report, September 1, 1980-August 31, 1981

    SciTech Connect

    Gaspar, P.P.

    1981-08-31

    The experimental approach to attaining the goals of this research program is briefly outlined and the progress made in the last year is reviewed in sections entitled: a. Primary steps in the reaction of recoiling silicon and germanium atoms and the identification of reactive intermediates in the recoil reactions; b. Thermally and photochemically induced silylene and germylene reactions and the reactions of thermally evaporated silicon atoms.

  2. An aluminum-germanium eutectic structure for silicon wafer bonding technology

    NASA Astrophysics Data System (ADS)

    Perez-Quintana, I.; Ottaviani, G.; Tonini, R.; Felisari, L.; Garavaglia, M.; Oggioni, L.; Morin, D.

    2005-08-01

    An aluminum-germanium eutectic bonding technology has been used to uniformly bond two silicon wafers for MEMS packaging at temperatures as low as 450 °C, well below the aluminum-silicon eutectic temperature (577 °C). A device silicon wafer has been put in contact with a cap wafer where an aluminum film covered by a germanium film has been thermally evaporated. The annealing has been performed in a vacuum furnace under uniaxial pressure variable from 1.8 up to 30 kbar. The samples have been analyzed with various analytical techniques. 4He+ MeV Rutherford Backscattering Spectrometry (RBS) has been used to measure the thicknesses of the deposited films and to follow the aluminum-germanium intermixing, Scanning Acoustic Microscope (SAM) to control the uniformity of the bonding, Scanning Electron Microscope (SEM) associated with electron induced X-ray fluorescence to analyze composition, morphology and elements distribution in the film between the two bonded wafers. The temperatures for the annealing were selected above and below the Ge-Al the eutectic temperature. At temperatures below the eutectic no-bonding has been obtained for any applied pressure. Above the eutectic bonding occurs. The formation of a liquid film is mandatory to obtain a reproducible and robust bonding. The pressure is necessary to improve the contacts between the two wafers; its role in the metallurgy of the bonding needs to be explored.

  3. The mineralogical deportment of germanium in the Clarksville Electrolytic Zinc Plant of Savage Zinc Inc.

    SciTech Connect

    Dutrizac, J.E.; Chen, T.T.; Longton, R.J.

    1996-08-01

    Germanium is a strategic element which is widely used for infrared night vision systems, fiber optics, gamma-ray detectors, semiconductors, catalysts, and phosphors. Germanium is recovered from the dusts and residues generated during the processing of certain complex Zn-Cu-Pb sulfide ores or low-temperature sphalerite ores. A mineralogical study was carried out on the neutral leach residue and weak acid leach residue generated from Gordonsville zinc concentrate at the Clarksville Electrolytic Zinc Plant of Savage Zinc Inc. The intent was to characterize the mineral forms and associations of germanium. The Gordonsville zinc concentrate consists mostly of sphalerite which has a solid solution Ge content of {approximately} 400 ppm; the sphalerite is the dominant, if not only, Ge carrier in the concentrate. The major Ge carrier in the neutral residue is the iron gel-silica gel phase, but modest amounts of Ge are present in the ZnO, ZnFe{sub 2}O{sub 4}, sphalerite, and Zn-Fe-Pb silicate phases. The major Ge carrier in the acid residue is the iron gel-silica gel phase which contains up to 1.7% Ge and accounts for {approximately} 70% of the total Ge content of this residue. The remaining Ge is carried by the Zn-Fe-Pb silicate, ZnFe{sub 2}O{sub 4}, and some of the rare Mn-Pb-Fe oxide phases.

  4. Germanium and uranium in coalified wood from Upper Devonian black shale

    USGS Publications Warehouse

    Breger, Irving A.; Schopf, James M.

    1954-01-01

    Microscopic study of black, vitreous, carbonaceous material occurring in the Chattanooga shale in Tennessee and in the Cleveland member of the Ohio shale in Ohio has revealed coalified woody plant tissue. Some samples have shown sufficient detail to be identified with the genus Callixylon. Similar material has been reported in the literature as "bituminous" or "asphaltic" stringers. Spectrographic analyses of the ash from the coalified wood have shown unusually high percentages of germanium, uranium, vanadium, and nickel. The inverse relationship between uranium and germanium in the ash and the ash content of various samples shows an association of these elements with the organic constituents of the coal. On the basis of geochemical considerations, it seems most probable that the wood or coalified wood was germanium-bearing at the time logs or woody fragments were floated into the basins of deposition of the Chattanooga shale and the Cleveland member of the Ohio shale. Once within the marine environment, the material probably absorbed uranium with the formation of organo-uranium compounds such as have been found to exist in coals. It is suggested that a more systematic search for germaniferous coals in the vicinity of the Chattanooga shale and the Cleveland member of the Ohio shale might be rewarding.

  5. Germanium and uranium in coalified wood bom upper Devonian black shale

    USGS Publications Warehouse

    Breger, I.A.; Schopf, J.M.

    1955-01-01

    Microscopic study of black, vitreous, carbonaceous material occurring in the Chattanooga shale in Tennessee and in the Cleveland member of the Ohio shale in Ohio has revealed coalified woody plant tissue. Some samples have shown sufficient detail to be identified with the genus Cauixylon. Similar material has been reported in the literature as "bituminous" or "asphaltic" stringers. Spectrographic analyses of the ash from the coalified wood have shown unusually high percentages of germanium, uranium, vanadium, and nickel. The inverse relationship between uranium and germanium in the ash and the ash content of various samples shows an association of these elements with the organic constituents of the coal. On the basis of geochemical considerations, it seems most probable that the wood or coalified wood was germanium-bearing at the time logs or woody fragmenta were floated into the basins of deposition of the Chattanooga shale and the Cleveland member of the Ohio shale. Once within the marine environment, the material probably absorbed uranium with the formation of organo-uranium compounds such as exist in coals. It is suggested that a more systematic search for germaniferous coals in the vicinity of the Chattanooga shale and the Cleveland member of the Ohio shale might be rewarding. ?? 1955.

  6. Germanium: a new catalyst for diamond synthesis and a new optically active impurity in diamond.

    PubMed

    Palyanov, Yuri N; Kupriyanov, Igor N; Borzdov, Yuri M; Surovtsev, Nikolay V

    2015-01-01

    Diamond attracts considerable attention as a versatile and technologically useful material. For many demanding applications, such as recently emerged quantum optics and sensing, it is important to develop new routes for fabrication of diamond containing defects with specific optical, electronic and magnetic properties. Here we report on successful synthesis of diamond from a germanium-carbon system at conditions of 7 GPa and 1,500-1,800 °C. Both spontaneously nucleated diamond crystals and diamond growth layers on seeds were produced in experiments with reaction time up to 60 h. We found that diamonds synthesized in the Ge-C system contain a new optical centre with a ZPL system at 2.059 eV, which is assigned to germanium impurities. Photoluminescence from this centre is dominated by zero-phonon optical transitions even at room temperature. Our results have widened the family of non-metallic elemental catalysts for diamond synthesis and demonstrated the creation of germanium-related optical centres in diamond. PMID:26435400

  7. Ion-beam mixing in silicon and germanium at low temperatures

    SciTech Connect

    Clark, G.J.; Marwick, A.D.; Poker, D.B.

    1982-01-01

    Ion-beam mixing of thin marker layers in amorphous silicon and germanium was studied using irradiations with Xe ions at temperatures of 34k and 77k. The marker species, ion energies and doses were: in silicon, markers of Ge and Pt irradiated with 200-keV Xe up to 2.7x10/sup 16/ ions cm/sup -2/; and in germanium, markers of Al and Si bombarded with 295-keV Xe up to 1.63x10/sup 16/ ions cm/sup -2/. In silicon, Pt markers were found to broaden at about the same rate at 34k and 77k; and the rate of broadening was similar to that found by other workers when expressed as an efficiency of mixing, i.e., when dependence on ion dose and deposited energy was factored out. However, a Ge marker irradiated at 34k did not broaden from its original thickness. In germanium, markers of both Al and Si were mixed by irradiation at 34k, but at 77k only the Al marker broadened; the Si marker did not. The broadening of the markers is ascribed to ballistic mixing, while the cases where no broadening occurred are explicable if diffusion by a defect mechanism transported displaced marker atoms back to traps near their original sites.

  8. Segmented Monolithic Germanium Detector Arrays for X-ray Absorption Spectroscopy

    SciTech Connect

    Dr. Ethan L. Hull

    2011-03-27

    The experimental results from the Phase I effort were extremely encouraging. During Phase I PHDs Co. made the first strides toward a new detector technology that could have great impact on synchrotron x-ray absorption (XAS) measurements, and x-ray detector technology in general. Detector hardware that allowed critical demonstration measurements of our technology was designed and fabricated. This new technology allows good charge collection from many pixels on a single side of a multi-element monolithic germanium planar detector. The detector technology provides “dot-like” collection electrodes having very low capacitance. The detector technology appears to perform as anticipated in the Phase I proposal. In particular, the 7-pixel detector studied showed remarkable properties; making it an interesting example of detector physics. The technology is enabled by the use of amorphous germanium contact technology on germanium planar detectors. Because of the scalability associated with the fabrication of these technologies at PHDs Co., we anticipate being able to supply larger detector systems at significantly lower cost than systems made in the conventional manner.

  9. Imaging the oblique propagation of electrons in germanium crystals at low temperature and low electric field

    NASA Astrophysics Data System (ADS)

    Moffatt, R. A.; Cabrera, B.; Corcoran, B. M.; Kreikebaum, J. M.; Redl, P.; Shank, B.; Yen, J. J.; Young, B. A.; Brink, P. L.; Cherry, M.; Tomada, A.; Phipps, A.; Sadoulet, B.; Sundqvist, K. M.

    2016-01-01

    Excited electrons in the conduction band of germanium collect into four energy minima, or valleys, in momentum space. These local minima have highly anisotropic mass tensors which cause the electrons to travel in directions which are oblique to an applied electric field at sub-Kelvin temperatures and low electric fields, in contrast to the more isotropic behavior of the holes. This experiment produces a full two-dimensional image of the oblique electron and hole propagation and the quantum transitions of electrons between valleys for electric fields oriented along the [0,0,1] direction. Charge carriers are excited with a focused laser pulse on one face of a germanium crystal and then drifted through the crystal by a uniform electric field of strength between 0.5 and 6 V/cm. The pattern of charge density arriving on the opposite face is used to reconstruct the trajectories of the carriers. Measurements of the two-dimensional pattern of charge density are compared in detail with Monte Carlo simulations developed for the Cryogenic Dark Matter Search (SuperCDMS) to model the transport of charge carriers in high-purity germanium detectors.

  10. Novel Germanium/Polypyrrole Composite for High Power Lithium-ion Batteries

    PubMed Central

    Gao, Xuanwen; Luo, Wenbin; Zhong, Chao; Wexler, David; Chou, Shu-Lei; Liu, Hua-Kun; Shi, Zhicong; Chen, Guohua; Ozawa, Kiyoshi; Wang, Jia-Zhao

    2014-01-01

    Nano-Germanium/polypyrrole composite has been synthesized by chemical reduction method in aqueous solution. The Ge nanoparticles were directly coated on the surface of the polypyrrole. The morphology and structural properties of samples were determined by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Thermogravimetric analysis was carried out to determine the polypyrrole content. The electrochemical properties of the samples have been investigated and their suitability as anode materials for the lithium-ion battery was examined. The discharge capacity of the Ge nanoparticles calculated in the Ge-polypyrrole composite is 1014 mAh g−1 after 50 cycles at 0.2 C rate, which is much higher than that of pristine germanium (439 mAh g−1). The composite also demonstrates high specific discharge capacities at different current rates (1318, 1032, 661, and 460 mAh g−1 at 0.5, 1.0, 2.0, and 4.0 C, respectively). The superior electrochemical performance of Ge-polypyrrole composite could be attributed to the polypyrrole core, which provides an efficient transport pathway for electrons. SEM images of the electrodes have demonstrated that polypyrrole can also act as a conductive binder and alleviate the pulverization of electrode caused by the huge volume changes of the nanosized germanium particles during Li+ intercalation/de-intercalation. PMID:25168783

  11. Epitaxial Growth of Perovskite Strontium Titanate on Germanium via Atomic Layer Deposition.

    PubMed

    Lin, Edward L; Edmondson, Bryce I; Hu, Shen; Ekerdt, John G

    2016-01-01

    Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and conformality by taking advantage of self-limiting reactions between vapor-phase precursors and the growing film. Perovskite oxides present potential for next-generation electronic materials, but to-date have mostly been deposited by physical methods. This work outlines a method for depositing SrTiO3 (STO) on germanium using ALD. Germanium has higher carrier mobilities than silicon and therefore offers an alternative semiconductor material with faster device operation. This method takes advantage of the instability of germanium's native oxide by using thermal deoxidation to clean and reconstruct the Ge (001) surface to the 2×1 structure. 2-nm thick, amorphous STO is then deposited by ALD. The STO film is annealed under ultra-high vacuum and crystallizes on the reconstructed Ge surface. Reflection high-energy electron diffraction (RHEED) is used during this annealing step to monitor the STO crystallization. The thin, crystalline layer of STO acts as a template for subsequent growth of STO that is crystalline as-grown, as confirmed by RHEED. In situ X-ray photoelectron spectroscopy is used to verify film stoichiometry before and after the annealing step, as well as after subsequent STO growth. This procedure provides framework for additional perovskite oxides to be deposited on semiconductors via chemical methods in addition to the integration of more sophisticated heterostructures already achievable by physical methods. PMID:27501462

  12. Spin-dependent intravalley and intervalley electron-phonon scatterings in germanium

    NASA Astrophysics Data System (ADS)

    Liu, Z.; Nestoklon, M. O.; Cheng, J. L.; Ivchenko, E. L.; Wu, M. W.

    2013-08-01

    The spin-dependent electron-phonon scattering in the L and Γ valleys of germanium crystals has been investigated theoretically. For this purpose, the 16 × 16 k · p Hamiltonian correctly describing the electron dispersion in the vicinity of the L point of the Brillouin zone in germanium in the lowest conduction bands and the highest valence bands has been constructed. This Hamiltonian facilitates the analysis of the spin-dependent properties of conduction electrons. Then, the electron scatterings by phonons in the L and Γ valleys, i.e., intra- L valley, intra-Γ valley, inter- L-Γ valley, and inter- L-L valley scatterings, have been considered successively. The scattering matrix expanded in powers of the electron wave vectors counted from the centers of the valleys has been constructed using the invariant method for each type of processes. The numerical coefficients in these matrices have been found by the pseudopotential method. The partial contributions of the Elliott and Yafet mechanisms to the spin-dependent electron scattering have been analyzed. The obtained results can be used in studying the optical orientation and relaxation of hot electrons in germanium.

  13. Rain erosion behavior of germanium carbide films grown on ZnS substrates

    NASA Astrophysics Data System (ADS)

    Mackowski, Jean-Marie; Cimma, B.; Pignard, R.; Colardelle, P.; Laprat, Patrice

    1992-12-01

    Thick germanium carbine films (GeC) are successfully grown on various Zinc Sulfide and Germanium substrates at temperatures up to 350 degree(s)C by two methods: Plasma Enhanced Chemical Vapor Deposition (PECVD) in gas mixtures of methane and germane and by Reactive Radio-Frequency Sputtering (RRFS) starting from a germanium target in a sputtering medium of methane and argon. The optical and mechanical properties of the GeC coatings depend on the composition determined by the deposition parameters. The refractive index at 633 nm varies from 4.9 to 4.3 for a carbon content ranging from 3 to 25% and the correlated refractive index in the 8 to 12 micrometers range is found to be between 3.96 and 3.1. For these coatings, the absorption coefficient is ranging from 270 to 40 cm-1. All films are amorphous in nature with domains ranging from 13 to 20 angstroms. The hydrogen content varies from 2 to 25% coming from C:H, Ge:H and C:Ge:H bonding. The XPS analysis shows the Ge:C precipitation kinetic for high deposition temperature or annealed films. The rain erosion resistance of GeC films and GeC with a protective diamond like-carbon (DLC) coating on top is measured for 1.2 mm water drop with an impact velocity ranging from 210 to 265 m/s on the Saab-Scania whirling-arm rig (Linkoping, Sweden).

  14. Defect Density Comparison of Detached versus Attached Bridgman Grown Germanium Crystals

    NASA Technical Reports Server (NTRS)

    Schweizer, M.; Cobb, S. D.; Volz, M. P.; Szofran, F. R.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Semiconductor Bridgman growth without contact between the growing crystal and the growth ampoule has been observed on Earth in the last few years during several experiments. Previously, this so-called detached or dewetted growth phenomenon occurred preferentially under microgravity conditions due to the absence of the hydrostatic pressure. Many theoretical as well as experimental investigations helped to provide a better understanding of the mechanism and to identify the parameters leading to the detachment. Thus, recent attempts to get stable detached growth under terrestrial conditions by Duffar et al. growing III-V compounds and our own group with germanium and germanium-silicon alloys were frequently successful. At this conference we present the results of several germanium growth experiments performed in pyrolytic boron nitride containers. To exert an influence on the pressure ratio above and below the melt we used closed-bottom and open-bottom containers. This resulted in mainly detached-grown single crystals with the closed-bottom crucibles and attached single crystals with the open-bottom tubes. Evidence of detached growth is obtained from the crystal surface with a combination of axial profilometer scans and optical and electron microscopy. Detailed investigations of the defect structure, which is the main focus of this presentation, have shown an improvement of the crystal quality in the detached-grown samples, with a strong reduction of the etch pit density by about two orders of magnitude.

  15. Tuning the Electro-optical Properties of Germanium Nanowires by Tensile Strain

    PubMed Central

    2012-01-01

    In this Letter we present the electrical and electro-optical characterization of single crystalline germanium nanowires (NWs) under tensile strain conditions. The measurements were performed on vapor–liquid–solid (VLS) grown germanium (Ge) NWs, monolithically integrated into a micromechanical 3-point strain module. Uniaxial stress is applied along the ⟨111⟩ growth direction of individual, 100 nm thick Ge NWs while at the same time performing electrical and optical characterization at room temperature. Compared to bulk germanium, an anomalously high and negative-signed piezoresistive coefficient has been found. Spectrally resolved photocurrent characterization on strained NWs gives experimental evidence on the strain-induced modifications of the band structure. Particularly we are revealing a rapid decrease in resistivity and a red-shift in photocurrent spectra under high strain conditions. For a tensile strain of 1.8%, resistivity decreased by a factor of 30, and the photocurrent spectra shifted by 88 meV. Individual stressed NWs are recognized as an ideal platform for the exploration of strain-related electronic and optical effects and may contribute significantly to the realization of novel optoelectronic devices, strain-enhanced field-effect transistors (FETs), or highly sensitive strain gauges. PMID:23146072

  16. Germanium: a new catalyst for diamond synthesis and a new optically active impurity in diamond

    PubMed Central

    Palyanov, Yuri N.; Kupriyanov, Igor N.; Borzdov, Yuri M.; Surovtsev, Nikolay V.

    2015-01-01

    Diamond attracts considerable attention as a versatile and technologically useful material. For many demanding applications, such as recently emerged quantum optics and sensing, it is important to develop new routes for fabrication of diamond containing defects with specific optical, electronic and magnetic properties. Here we report on successful synthesis of diamond from a germanium-carbon system at conditions of 7 GPa and 1,500–1,800 °C. Both spontaneously nucleated diamond crystals and diamond growth layers on seeds were produced in experiments with reaction time up to 60 h. We found that diamonds synthesized in the Ge-C system contain a new optical centre with a ZPL system at 2.059 eV, which is assigned to germanium impurities. Photoluminescence from this centre is dominated by zero-phonon optical transitions even at room temperature. Our results have widened the family of non-metallic elemental catalysts for diamond synthesis and demonstrated the creation of germanium-related optical centres in diamond. PMID:26435400

  17. Molecular dynamics simulation of shock-induced phase transition in Germanium

    NASA Astrophysics Data System (ADS)

    Lane, J. Matthew D.; Thompson, Aidan P.

    2009-06-01

    Results from shock-wave and ramp-wave uniaxial loading of Germanium will be presented. Germanium is known to transition from ambient cubic diamond (cd) phase to the high-pressure body-centered tetragonal (bct) or β-tin phase at pressures between 10 and 12 GPa. Large-scale molecular dynamics (MD) simulations were used to study the phase transition in single-crystal Germanium under uniaxial compression along several different crystal axes. We observed that the transition from the cd phase to the bct phase nucleates through shear banding and advances to relieve uniaxial strain. The macroscopic properties are compared with experimental results for both the Modified Embedded Atom Method (MEAM) and Tersoff potentials. Simulation techniques included standard non-equilibrium MD, as well as alternative computational methods, such as the Continuous Hugoniot Method and homogeneous uniaxial ramp methods. [4pt] This work is supported by the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  18. Synthesis, Electronic Structure, and Reactivity Studies of a 4-Coordinate Square Planar Germanium(IV) Cation.

    PubMed

    Fang, Huayi; Jing, Huize; Zhang, Aixi; Ge, Haonan; Yao, Zhengmin; Brothers, Penelope J; Fu, Xuefeng

    2016-06-22

    A tetra-coordinate, square planar germanium(IV) cation [(TPFC)Ge](+) (TPFC = tris(pentafluorophenyl)corrole) was synthesized quantitatively by the reaction of (TPFC)Ge-H with [Ph3C](+)[B(C6F5)4](¯). The highly reactive [(TPFC)Ge](+) cation reacted with benzene to form phenyl complex (TPFC)Ge-C6H5 through an electrophilic pathway. The key intermediate, a σ-type germylium-benzene adduct, [(TPFC)Ge(η(1)-C6H6)](+), was isolated and characterized by single-crystal X-ray diffraction. Deprotonation of [(TPFC)Ge(η(1)-C6H6)](+) cation led to the formation of (TPFC)Ge-C6H5. [(TPFC)Ge](+) also reacted with ethylene and cyclopropane in benzene at room temperature to form (TPFC)Ge-CH2CH2C6H5 and (TPFC)Ge-CH2CH2CH2C6H5, respectively. The observed electrophilic reactivity is ascribed to the highly exposed cationic germanium center with novel frontier orbitals comprising two vacant sp-hybridized orbitals that are not conjugated to π-system. The three electron-withdrawing pentafluorophenyl groups on the corrole ligand also enhance the electrophilicity of the cationic germanium corrole. PMID:27243114

  19. Reactivity of divalent germanium alkoxide complexes is in sharp contrast to the heavier tin and lead analogues.

    PubMed

    Ferro, Lorenzo; Hitchcock, Peter B; Coles, Martyn P; Fulton, J Robin

    2012-02-01

    The chemistry of β-diketiminate germanium alkoxide complexes has been examined and shown to be in sharp contrast to its heavier congeners. For instance, (BDI)GeOR (BDI = [{N(2,6-(i)Pr(2)C(6)H(3))C(Me)}(2)CH], R = (i)Pr, (s)Bu, (t)Bu) does not react with carbon dioxide to form a metal carbonate complex. Addition of aliphatic electrophiles, such as methyl iodide or methyl triflate, results in the net oxidative addition to the germanium, giving cationic tetravalent germanium complexes, [(BDI)Ge(Me)OR][X] (X = I, OTf). An examination of the contrasting reactivities of the alkoxide ligand and the germanium loan pair with Lewis acids yielded the unusual germanium(II)-copper(I) adduct, {μ(2)-Cu(2)I(2)}[(BDI)GeO(t)Bu](2). This complex not only displays a rare example of a divalent Ge-Cu bond, but is the first example in which a planar Cu(2)I(2) diamond core possesses a three-coordinate copper bound to another metal center. PMID:22242862

  20. Delivery of Erbium:YAG laser radiation through side-firing germanium oxide optical fibers

    NASA Astrophysics Data System (ADS)

    Ngo, Anthony K.; Fried, Nathaniel M.

    2006-02-01

    The Erbium:YAG laser is currently being tested experimentally for endoscopic applications in urology, including more efficient laser lithotripsy and more precise incision of urethral strictures than the Holmium:YAG laser. While side-firing silica fibers are available for use with the Ho:YAG laser in urology, no such fibers exist for use with the Er:YAG laser. These applications may benefit from the availability of a side-firing, mid-infrared optical fiber capable of delivering the laser radiation at a 90-degree angle to the tissue. The objective of this study is to describe the simple construction and characterization of a side-firing germanium oxide fiber for potential use in endoscopic laser surgery. Side-firing fibers were constructed from 450-micron-core germanium oxide fibers of 1.45-m-length by polishing the distal tip at a 45-degree angle and placing a 1-cm-long protective quartz cap over the fiber tip. Er:YAG laser radiation with a wavelength of 2.94 microns, pulse duration of 300 microseconds, pulse repetition rate of 3 Hz, and pulse energies of from 5 to 550 mJ was coupled into the fibers. The fiber transmission rate and damage threshold measured 48 +/- 4 % and 149 +/- 37 mJ, respectively (n = 6 fibers). By comparison, fiber transmission through normal germanium oxide trunk fibers measured 66 +/- 3 %, with no observed damage (n = 5 fibers). Sufficient pulse energies were transmitted through the side-firing fibers for contact tissue ablation. Although these initial tests are promising, further studies will need to be conducted, focusing on assembly of more flexible, smaller diameter fibers, fiber bending transmission tests, long-term fiber reliability tests, and improvement of the fiber output spatial beam profile.

  1. Biological insertion of nanostructured germanium and titanium oxides into diatom biosilica

    NASA Astrophysics Data System (ADS)

    Jeffryes, Clayton S.

    There is significant interest in titanium oxide and germanium-silicon oxide nanocomposites for optoelectronic, photocatalytic, and solar cell applications. The ability of the marine diatom Pinnularia sp. to uptake soluble metal oxides from cell culture medium, and incorporate them into the micro- and nano-structure of their amorphous silica cell walls, called frustules, was evaluated using an engineered photobioreactor system. The effects of metal oxides on the structural and elemental properties of the frustule were also evaluated. Diatom cell cultures grown in 5 L photobioreactors were initially charged with 0.5 mM of soluble silicon, Si(OH)4, an obligate substrate required for frustule fomation. Upon exhaustion of Si(OH)4 cells were exposed to the mixed pulse-addition of soluble silicon and germanium or co-perfusion addition of soluble silicon and titanium, which were incorporated into the frustules. Metals composition of the cell culture medium, diatom biomass and purified frustules were measured, as was the local elemental composition within the frustule pores and the metal oxide crystallinity. Diatom frustules having a germanium composition of 1.6 wt % were devoid of the native intra-pore structures and possessed enhanced photoluminescence and electroluminescence when compared to frustules without Ge. Diatoms cultivated in the presence of soluble titanium incorporated amorphous titania into the frustule, which maintained native structure even when local TiO2 concentrations within the nanopores approached 60 wt. %. Titanium oxide could also be biomimetically deposited directly within the diatom nanopores by adsorbing poly-L-lysine to the diatom biosilica where it catalyzed the soluble titanium precursor Ti-BALDH into amorphous titania nanoparticles. Both biogenic and biomimetic titania could be converted to anatase titanium by thermal annealing. It was determined that nanostructured metal oxide composites can be fabricated biomimetically or in cell culture to

  2. Electronic transport in nanocrystalline germanium/hydrogenated amorphous silicon composite thin films

    NASA Astrophysics Data System (ADS)

    Bodurtha, Kent Edward

    Recent interest in composite materials based on hydrogenated amorphous silicon (a-Si:H) stems in part from its potential for technical applications in thin film transistors and solar cells. Previous reports have shown promising results for films of a-Si:H with embedded silicon nanocrystals, with the goal of combining the low cost, large area benefits of hydrogenated amorphous silicon with the superior electronic characteristics of crystalline material. These materials are fabricated in a dual-chamber plasma-enhanced chemical vapor deposition system in which the nanocrystals are produced separately from the amorphous film, providing the flexibility to independently tune the growth parameters of each phase; however, electronic transport through these and other similar materials is not well understood. This thesis reports the synthesis and characterization of thin films composed of germanium nanocrystals embedded in a-Si:H. The results presented here describe detailed measurements of the conductivity, photoconductivity and thermopower which reveal a transition from conduction through the a-Si:H for samples with few germanium nanocrystals, to conduction through the nanocrystal phase as the germanium crystal fraction XGe is increased. These films display reduced photosensitivity as XGe is increased, but an unexpected increase in the dark conductivity is found in samples with X Ge > 5% after long light exposures. Detailed studies of the conductivity temperature dependence in these samples exposes a subtle but consistent deviation from the standard Arrhenius expression; the same departure is found in samples of pure a-Si:H; a theoretical model is presented which accurately describes the actual conductivity temperature dependence.

  3. Analysis of high-purity germanium dioxide by ETV-ICP-AES with preliminary concentration of trace elements.

    PubMed

    Medvedev, Nickolay S; Shaverina, Anastasiya V; Tsygankova, Alphiya R; Saprykin, Anatoly I

    2016-08-01

    The paper presents a combined technique of germanium dioxide analysis by inductively coupled plasma atomic emission spectrometry (ICP-AES) with preconcentration of trace elements by distilling off matrix and electrothermal (ETV) introduction of the trace elements concentrate into the ICP. Evaluation of metrological characteristics of the developed technique of high-purity germanium dioxide analysis was performed. The limits of detection (LODs) for 25 trace elements ranged from 0.05 to 20ng/g. The accuracy of proposed technique is confirmed by "added-found" («or spiking») experiment and comparing the results of ETV-ICP-AES and ICP-AES analysis of high purity germanium dioxide samples. PMID:27216693

  4. Structural and optical properties of 200 mm germanium-on-insulator (GeOI) substrates for silicon photonics applications

    NASA Astrophysics Data System (ADS)

    Reboud, Vincent; Widiez, Julie; Hartmann, Jean Michel; Osvaldo Dias, Guilherme; Fowler, Daivid; Chelnokov, Alexei; Gassenq, Alban; Guilloy, Kevin; Pauc, Nicolas; Calvo, Vincent; Geiger, Richard; Zabel, T.; Faist, Jérôme; Sigg, Hans

    2015-02-01

    Integrated laser sources compatible with microelectronics represent currently one of the main challenges for silicon photonics. Using the Smart CutTM technology, we have fabricated for the first time 200 mm optical Germanium-On-Insulator (GeOI) substrates which consist of a thick layer of germanium (typically greater than 500 nm) on top of a thick buried oxide layer (around 1 µm). From this, we fabricated suspended microbridges with efficient Bragg mirror cavities. The high crystalline quality of the Ge layer should help to avoid mechanical failure when fabricating suspended membranes with amounts of tensile strain high enough to transform Ge into a direct bandgap material. Optical GeOI process feasibility has successfully been demonstrated, opening the way to waferscale fabrication of new light emitting devices based on highly-tensely strained (thanks to suspended membranes) and/or doped germanium.

  5. The MAJORANA DEMONSTRATOR: An R and D project towards a tonne-scale germanium neutrinoless double-beta decay search

    SciTech Connect

    Aalseth, C. E.; Ely, J.; Fast, J. E.; Fuller, E.; Hoppe, E. W.; Keillor, M.; Kouzes, R. T.; Miley, H. S.; Orrell, J. L.; Thompson, R.; Warner, R.; Amman, M.; Bergevin, M.; Chan, Y.-D.; Detwiler, J. A.; Fujikawa, B.; Loach, J. C.; Luke, P. N.; Poon, A. W. P; Prior, G.

    2009-12-17

    The MAJORANA collaboration is pursuing the development of the so-called MAJORANA DEMONSTRATOR. The DEMONSTRATOR is intended to perform research and development towards a tonne-scale germanium-based experiment to search for the neutrinoless double-beta decay of {sup 76}Ge. The DEMONSTRATOR can also perform a competitive direct dark matter search for light WIMPs in the 1-10 GeV/c{sup 2} mass range. It will consist of approximately 60 kg of germanium detectors in an ultra-low background shield located deep underground at the Sanford Underground Laboratory in Lead, SD. The DEMONSTRATOR will also perform background and technology studies, and half of the detector mass will be enriched germanium. This talk will review the motivation, design, technology and status of the Demonstrator.

  6. Differential analysis of band-edge photoluminescence spectra of germanium single crystals with different orientations under biaxial tensile strains

    NASA Astrophysics Data System (ADS)

    Emel'yanov, A. M.

    2016-06-01

    The previously published photoluminescence spectra of bulk germanium single crystals with orientations (100), (110), and (111) under different biaxial tensile strains have been investigated using the differential method proposed by the author for the analysis of luminescence spectra of semiconductors. An increase in the strain for all these orientations of the single crystals leads to a shift in the maxima of the differential spectra in the region of direct radiative transitions toward lower photon energies due to the narrowing of the germanium direct band gap. At the same time, the positions of the maxima of the differential spectra in the region of indirect radiative transitions remain almost unchanged. This indicates that the germanium indirect band gap does not depend on the tensile strains, at least for their values of ˜0.2-0.3%.

  7. The MAJORANA DEMONSTRATOR: An R&D project towards a tonne-scale germanium neutrinoless double-beta decay search

    SciTech Connect

    Aalseth, Craig E; Amman, M; Amsbaugh, John F; Avignone, F. T.; Back, Henning O; Barabash, A; Barbeau, Phil; Beene, Jim; Bergevin, M; Bertrand, F; Boswell, M; Brudanin, V; Bugg, William; Burritt, Tom H; Chan, Yuen-Dat; Collar, J I; Cooper, R J; Creswick, R; Detwiler, Jason A; Doe, P J; Efremenko, Yuri; Egorov, Viatcheslav; Ejiri, H; Elliott, Steven R; Ely, James H; Esterline, James H; Farach, H A; Fast, James E; Fields, N; Finnerty, P; Fujikawa, Brian; Fuller, Erin S; Gehman, Victor; Giovanetti, G K; Guiseppe, Vincente; Gusey, K; Hallin, A L; Hazama, R; Henning, Reyco; Hime, Andrew; Hoppe, Eric W; Hossbach, Todd W; Howe, M A; Johnson, R A; Keeter, K; Keillor, Martin E; Keller, C; Kephart, Jeremy D; Kidd, Mary; Kochetov, Oleg; Konovalov, S; Kouzes, Richard T; Lesko, Kevin; Leviner, L; Loach, J C; Luke, P; MacMullin, S; Marino, Michael G; Mei, Dong-Ming; Miley, Harry S; Miller, M; Mizouni, Leila K; Montoya, A; Myers, A W; Nomachi, Masaharu; Odom, Brian; Orrell, John L; Phillips, D; Poon, Alan; Prior, Gersende; Qian, J; Radford, D C; Rielage, Keith; Robertson, R G. H.; Rodriguez, Larry; Rykaczewski, Krzysztof P; Schubert, Alexis G; Shima, T; Shirchenko, M; Strain, J; Thomas, K; Thompson, Robert C; Timkin, V; Tornow, W; Van Wechel, T D; Vanyushin, I; Vetter, Kai; Warner, Ray A; Wilkerson, J; Wouters, Jan; Yakushev, E; Young, A; Yu, Chang-Hong; Yumatov, Vladimir; Zhang, C L; Zimmerman, S

    2009-12-17

    The MAJORANA collaboration is pursuing the development of the so-called MAJORANA DEMONSTRATOR. The DEMONSTRATOR is intended to perform research and development towards a tonne-scale germanium-based experiment to search for the neutrinoless double-beta decay of 76Ge. The DEMONSTRATOR can also perform a competitive direct dark matter search for light WIMPs in the 1-10GeV/c2 mass range. It will consist of approximately 60 kg. of germanium detectors in an ultra-low background shield located deep underground at the Sanford Underground Laboratory in Lead, SD. The DEMONSTRATOR will also perform background and technology studies, and half of the detector mass will be enriched germanium. This talk will review the motivation, design, technology and status of the Demonstrator.

  8. Monte Carlo analysis of germanium detector performance in slow positron beam experiments

    NASA Astrophysics Data System (ADS)

    Heikinheimo, J.; Tuominen, R.; Tuomisto, F.

    2016-01-01

    Positron annihilation Doppler broadening spectroscopy is one of the most popular positron annihilation vacancy characterization techniques in experimental materials research. The measurements are often carried out with a slow positron beam setup, which enables depth profiling of the samples. The key measurement devices of Doppler broadening spectroscopy setups are high-purity germanium detectors. Since Doppler broadening spectroscopy is one of the standard techniques in defect characterization, there is a demand to evaluate different kinds of factors that might have an effect on the results. Here we report the results of Monte Carlo simulations of detector response in different geometries and compare the data to experiments.

  9. Lattice dynamics and thermoelectric properties of nanocrystalline silicon-germanium alloys

    SciTech Connect

    Claudio, Tania; Stein, Niklas; Peterman, Nils; Stroppa, Daniel; Koza, Michael M.; Wiggers, Hartmut; Klobes, B.; Schierning, Gabi; Hermann, Raphael P.

    2015-10-26

    The lattice dynamics and thermoelectric properties of sintered phosphorus-doped nanostructured silicon- germanium alloys obtained by gas-phase synthesis were studied. Measurements of the density of phonon states by inelastic neutron scattering were combined with measurements of the elastic constants and the low- temperature heat capacity. A strong influence of nanostructuring and alloying on the lattice dynamics was observed. The thermoelectric transport properties of samples with different doping as well as samples sintered at different temperature were characterized between room temperature and 1000C. A peak figure of merit zT = 0:88 at 900C is observed and comparatively insensitive to the aforementioned param- eter variations.

  10. Thermophysical properties of germanium for thermal analysis of growth from the melt

    NASA Technical Reports Server (NTRS)

    Crouch, R. K.; Fripp, A. L.; Debnam, W. J.; Taylor, R. E.; Groot, H.

    1982-01-01

    The thermal diffusivity of Ge has been measured over a temperature range from 300 C to 1010 C which includes values for the melt. Specific heat has been measured from room temperature to 727 C. Thermal conductivity has been calculated over the same temperature range as the diffusivity measurements. These data are reported along with the best values from the literature for the other parameters which are required to calculate the temperature and convective fields for the growth of germanium by the Bridgman method. These parameters include the specific heat, the viscosity, the emissivity, and the density as a function of temperature.

  11. Nanoscale dry etching of germanium by using inductively coupled CF4 plasma

    NASA Astrophysics Data System (ADS)

    Shim, Kyu-Hwan; Yang, Ha Yong; Kil, Yeon-Ho; Yang, Hyeon Deok; Yang, Jong-Han; Hong, Woong-Ki; Kang, Sukill; Jeong, Tae Soo; Kim, Taek Sung

    2012-08-01

    The nanoscale dry etching of germanium was investigated by using inductively coupled CF4 plasma and electron-beam lithography. The optimal dose of PMMA as E-beam lithography resist was ˜200 mC/cm2. When ICP Power was 200W, CF4 gas flow rate was 40 sccm, and process pressure was 20 mTorr, it had a smooth surface and good etch rate. The etching selectivity of Ge wafer to PMMA resist was as low as ˜1.5. Various sub-100 nm dry-etching patterns have been obtained. SEM pictures showed good profile qualities with a smooth etching sidewall and ultrasmall etching features.

  12. 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.

  13. Impact of minority carrier lifetime on the performance of strained germanium light sources

    NASA Astrophysics Data System (ADS)

    Sukhdeo, David S.; Gupta, Shashank; Saraswat, Krishna C.; Dutt, Birendra (Raj); Nam, Donguk

    2016-04-01

    We theoretically investigate the impact of the defect-limited carrier lifetime on the performance of germanium (Ge) light sources. For Ge LEDs, we show that improving the material quality can offer even greater enhancements than techniques such as tensile strain, the leading approach for enhancing Ge light emission. For Ge lasers, we show that the defect-limited lifetime becomes increasing important as tensile strain is introduced, and that defect-limited lifetime must be improved if the full benefits of strain are to be realized. We conversely show that improving the material quality supersedes much of the utility of n-type doping for Ge lasers.

  14. Mechanisms of optical losses in fibres with a high concentration of germanium dioxide

    SciTech Connect

    Likhachev, M E; Bubnov, M M; Semenov, S L; Shvetsov, V V; Dianov, Evgenii M; Khopin, V F; Gur'yanov, A N

    2003-07-31

    The mechanisms of optical losses determining the scattering of light in single-mode fibres with a high germanium-dioxide content in a core are investigated. The coefficients of the Rayleigh scattering in fibres with a high level of doping (a molar concentration of GeO{sub 2} of up to 30 %) are measured for the first time. The investigations of the angular distribution of the intensity of light scattered from the fibre have revealed the presence of an additional, anomalous scattering of light besides the Rayleigh scattering. The nature of this phenomenon is discussed. (special issue devoted to the memory of academician a m prokhorov)

  15. Neutrino and dark matter physics with sub-KeV Germanium detectors

    NASA Astrophysics Data System (ADS)

    Li, Hau Bin; (TEXONO collaboration

    2016-05-01

    Germanium detectors with sub-keV sensitivities [1, 2, 3] offer a unique opportunity to study neutrino interactions and properties [4] as well as to search for light WIMP Dark Matter [5, 6]. The TEXONO and CDEX Collaborations have been pursuing this research program at the Kuo-Sheng Neutrino Laboratory in Taiwan and in the China Jinping Underground Laboratory in China. We will present highlights of the detector R&D program which allow us to experimental probe this new energy window. The results, status and plans of our neutrino physics program will be discussed, with focus on the quest on neutrino-nucleus coherent scattering.

  16. Germanium-catalyzed growth of single-crystal GaN nanowires

    NASA Astrophysics Data System (ADS)

    Saleem, Umar; Wang, Hong; Peyrot, David; Olivier, Aurélien; Zhang, Jun; Coquet, Philippe; Ng, Serene Lay Geok

    2016-04-01

    We report the use of Germanium (Ge) as catalyst for Gallium Nitride (GaN) nanowires growth. High-yield growth has been achieved with Ge nanoparticles obtained by dewetting a thin layer of Ge on a Si (100) substrate. The nanowires are long and grow straight with very little curvature. The GaN nanowires are single-crystalline and show a Wurtzite structure growing along the [0001] axis. The growth follows a metal-free Vapor-Liquid-Solid (VLS) mechanism, further allowing a CMOS technology compatibility. The synthesis of nanowires has been done using an industrial Low Pressure Chemical Vapor Deposition (LPCVD) system.

  17. Determination of mean inner potential of germanium using off-axis electron holography.

    PubMed

    Li; McCartney; Dunin-Borkowski; Smith

    1999-07-01

    Off-axis electron holography has been used to determine the mean inner potential of germanium using cleaved 90 degrees wedge samples, where the wedge thickness profiles were checked by weak-beam dark-field extinction fringes. Dynamical contributions to the phase of the image were minimized by tilting to weakly diffracting conditions, as confirmed by reference to convergent-beam electron diffraction patterns. Small residual corrections were determined using multislice calculations. From a total of 18 separate measurements, it is concluded that the value of the mean inner potential is 14.3(2) V, which agrees with recent theoretical calculations to within experimental error. PMID:10927276

  18. Evaluations of the commercial spectrometer systems for safeguards applications using the germanium detectors

    SciTech Connect

    Vo, D.T.

    1998-12-31

    Safeguards applications require the best spectrometer systems with excellent resolution, stability, and throughput. Instruments must perform well in all the situations and environments. Data communication to the computer should be convenient, fast, and reliable. The software should have all the necessary tools and be ease to use. Portable systems should be small in size, lightweight, and have a long battery life. Nine commercially available spectrometer systems are tested with both the planar and coaxial germanium detectors. Considering the performance of the Digital Signal Processors (DSP), digital-based spectroscopy may be the future of gamma-ray spectroscopy.

  19. An IR modulator based on the self-assembly of gold nanoparticles on germanium.

    PubMed

    Ghosh, Harekrishna; Bouhekka, Ahmed; Bürgi, Thomas

    2014-09-28

    By using a polyelectrolyte layer gold nanoparticles have been assembled onto a Ge internal reflection element. Upon illumination with visible and near infrared light strong infrared absorption has been observed, which can be traced to intervalence band transitions in Ge. This reveals the existence of holes in the Ge near its valence band edge. The switching between light and dark states is faster than 160 μs and the device acts as an infrared modulator. The effect develops with a peculiar kinetics, which may indicate the development of an interfacial layer between germanium and gold that allows efficient electron transfer upon illumination. PMID:25102024

  20. Formation and thermodynamics of gaseous germanium and tin vanadates: a mass spectrometric and quantum chemical study.

    PubMed

    Shugurov, S M; Panin, A I; Lopatin, S I; Emelyanova, K A

    2015-06-01

    The stabilities of gaseous germanium and tin vanadates were confirmed by high temperature mass spectrometry, and its structures were determined by quantum chemical calculations. A number of gas-phase reactions involving these gaseous salts were studied. On the basis of the equilibrium constants, the standard formation enthalpies of gaseous GeV2O6 (-1520 ± 42 kJ mol(-1)) and SnV2O6 (-1520 ± 43 kJ mol(-1)) were determined at a temperature of 298 K. PMID:25947046