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Sample records for 14-crystal germanium array

  1. GERmanium detector array, GERDA

    The GERmanium Detector Array, GERDA, is designed to search for 'neutrinoless double beta decay' (0ν2β) in 76Ge. The high-purity segmented Ge detectors will be directly submerged and operated in liquid N2 or Ar. The measurement of the half-life time of 0ν2β decay will provide information about the absolute neutrino mass scale and indirectly, the hierarchy. The design goal of GERDA is to reach a sensitivity of 0.2 eV on the effective Majorana neutrino mass (mββ). The GERDA experiment is located in hall A of the Grand Sasso national lab (LNGS) and the construction will start in 2006

  2. A Low Noise 64x64 Germanium Array for Far IR Astronomy Project

    National Aeronautics and Space Administration — We propose to develope a 64x64 far infrared germanium focal-plane array with the following key design features: 1- Four top-illuminated, 32x32 germanium sub-arrays...

  3. Performance of a compact multi-crystal high-purity germanium detector array for measuring coincident gamma-ray emissions

    The Multi-sensor Airborne Radiation Survey (MARS) detector is a 14-crystal array of high-purity germanium (HPGe) detectors housed in a single cryostat. The array was used to measure the astrophysical S-factor for the 14N(p,γ)15O⁎ reaction for several transition energies at an effective center-of-mass energy of 163 keV. Owing to the granular nature of the MARS detector, the effect of gamma-ray summing was greatly reduced in comparison to past experiments which utilized large, single-crystal detectors. The new S-factor values agree within their uncertainties with the past measurements. Details of the analysis and detector performance are presented

  4. Performance of a compact multi-crystal high-purity germanium detector array for measuring coincident gamma-ray emissions

    Howard, Chris; Daigle, Stephen; Buckner, Matt [University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 (United States); Triangle Universities Nuclear Laboratory, Durham, NC 27708 (United States); Erikson, Luke E.; Runkle, Robert C. [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Stave, Sean C., E-mail: Sean.Stave@pnnl.gov [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Champagne, Arthur E.; Cooper, Andrew; Downen, Lori [University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 (United States); Triangle Universities Nuclear Laboratory, Durham, NC 27708 (United States); Glasgow, Brian D. [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Kelly, Keegan; Sallaska, Anne [University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 (United States); Triangle Universities Nuclear Laboratory, Durham, NC 27708 (United States)

    2015-05-21

    The Multi-sensor Airborne Radiation Survey (MARS) detector is a 14-crystal array of high-purity germanium (HPGe) detectors housed in a single cryostat. The array was used to measure the astrophysical S-factor for the {sup 14}N(p,γ){sup 15}O{sup ⁎} reaction for several transition energies at an effective center-of-mass energy of 163 keV. Owing to the granular nature of the MARS detector, the effect of gamma-ray summing was greatly reduced in comparison to past experiments which utilized large, single-crystal detectors. The new S-factor values agree within their uncertainties with the past measurements. Details of the analysis and detector performance are presented.

  5. A Low Noise 64x64 Germanium Array for Far IR Astronomy Project

    National Aeronautics and Space Administration — We propose to investigate the feasibility of developing a 64x64 far infrared germanium focal-plane array with the following key design features: 1- Four...

  6. A Silicon-Germanium Single Chip Receiver for S-band Phased Array Radars

    Heij, W. de; Boer, A. de; Hek, A.P. de; Vliet, F.E. van

    2011-01-01

    A Silicon-Germanium single chip receiver has been developed for S-band phased array radars with 2-D digital beamforming. The complete receiver chain from the S-band RF input up to the low-IF output has been integrated on a single SiGe chip. The only external components required to complete the recei

  7. Initial Component Testing for a Germanium Array Cryostat

    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.

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

    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.

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

    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.

  10. The constellation-X focal plane microcalorimeter array: An NTD-germanium solution

    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 spectrometers. Details of construction are presented

  11. The GERmanium Detector Array (Gerda) for the search of neutrinoless ββ decays of 76Ge at LNGS

    This paper describes the proposed Gerda experiment, the GERmanium Detector Array for the search of neutrinoless ββ decays of 76Ge at LNGS. The goal of the Gerda project is to operate bare germanium diodes enriched in 76Ge in an (optional active) cryogenic fluid shield with a sensitivity for neutrinoless ββ decay of T1/2>2-bar 1026 years after an exposure of 100 kg -bar years

  12. First results of neutrinoless double beta decay search with the GERmanium Detector Array "GERDA"

    Janicskó Csáthy, József

    2014-06-01

    The study of neutrinoless double beta decay is the most powerful approach to the fundamental question if the neutrino is a Majorana particle, i.e. its own anti-particle. The observation of the lepton number violating neutrinoless double beta decay would establish the Majorana nature of the neutrino. Until now neutrinoless double beta decay was not observed. The GERmanium Detector Array, GERDA is a double beta decay experiment located at the INFN Gran Sasso National Laboratory, Italy. GERDA operates bare Ge diodes enriched in 76Ge in liquid argon supplemented by a water shield. The exposure accumulated adds up to 21.6 kg· yr with a background level of 1.8 · 10-2 cts/(keV·kg·yr). The results of the Phase I of the experiment are presented and the preparation of the Phase II is briefly discussed.

  13. Broadband absorptance enhancement of silicon nanowire arrays with germanium as the substrate

    Wang, Han; Xia, Xin-Lin

    2013-08-01

    A composite structure with silicon nanowire arrays on germanium substrate is proposed as a good candidate for highly efficient solar cells. The Bruggeman approximation considering anisotropic wave propagating in uniaxial media is employed to calculate the radiative properties. Meantime, finite-difference time-domain (FDTD) method is used to verify for both normal and oblique incidence. It is found that the composite structure has superior absorption characteristics over thin Si film, particularly near the bandgap. With a thickness only of 4 μm, the composite structure improved the absorptance to above 0.6 across the whole wavelength band with the lattice constant of 100 nm, and the ultimate efficiency about 10% is higher than that of infinite bulk silicon, owing to the combined effects of suppressed reflection and high light trapping capability. To better understand the absorption enhancement process in the composite structure, the photogeneration profiles are provided by using FDTD method.

  14. Segmented Monolithic Germanium Detector Arrays for X-ray Absorption Spectroscopy. Final Report

    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.

  15. Status of the Germanium Detector Array (GERDA) in the search of neutrinoless ββ decays of 76Ge at LNGS

    The Germanium Detector Array (GERDA) in the search for neutrinoless ββ decays of 76Ge at LNGS will operate bare germanium diodes enriched in 76Ge in an (optional active) cryogenic fluid shield to investigate neutrinoless ββ decay with a sensitivity of T1/2 > 2 x 1026 yr after an exposure of 100 kg yr. Recent progress includes the installation of the first underground infrastructures at Gran Sasso, the completion of the enrichment of 37.5 kg of germanium material for detector construction, prototyping of low-mass detector support and contacts, and front-end and DAQ electronics, as well as the preparation for construction of the cryogenic vessel and water tank

  16. Germanium Collimating micro-Channel Arrays For High Resolution, High Energy Confocal X-ray Fluorescence Microscopy

    Agyeman-Budu, David N; Coulthard, Ian; Gordon, Robert; Hallin, Emil; Woll, Arthur R

    2016-01-01

    Confocal x-ray fluorescence microscopy (CXRF) allows direct detection of x-ray fluorescence from a micron-scale 3D volume of an extended, unthinned sample. We have previously demonstrated the use of a novel collection optic, fabricated from silicon, that improves the spatial resolution of this approach by an order of magnitude over CXRF using polycapillaries. The optic, called a collimating channel array (CCA), consists of micron-scale, lithographically-fabricated arrays of collimating channels, all directed towards a single source position. Due to the limited absorbing power of silicon, the useful energy range of these optics was limited to fluorescence emission below about 10 keV. Here, we report fabrication of CCAs from germanium substrates, and demonstrate their practical use for CXRF up to 20 keV. Specifically we demonstrate a nearly energy-independent critical spatial resolution $d_R$ of 2.1$\\pm$0.17 \\um from 2-20 keV, as well as excellent background reduction compared to silicon-based CCAs throughout t...

  17. A 32x32 Direct Hybrid Germanium Photoconductor Array with CTIA Readout Multiplexer Project

    National Aeronautics and Space Administration — This proposal introduces an innovative concept aimed to develop, for the first time, a 1k pixel far infrared focal-plane array with the following key design...

  18. A 32x32 Direct Hybrid Germanium Photoconductor Array with CTIA Readout Multiplexer Project

    National Aeronautics and Space Administration — We propose to investigate the feasibility of developing a two-dimensional far infrared photoconductor array with the following key design features: 1- A...

  19. Large area germanium detector arrays for lung counting: what is the optimum number of detectors?

    Kramer, Gary H; Hauck, Barry M

    2007-01-01

    Using the Lawrence Livermore National Laboratory (LLNL) torso phantom to calibrate a lung counting system can lead to the conclusion that three large area (i.e. >70 mm diameter) Ge detectors will outperform a four-detector array and provide a lower MDA as a four-detector array of large area Ge detectors covers a significant portion of inactive tissue (i.e. non-lung tissue). The lungs of the LLNL phantom, which are approximately 10 cm too short compared with real lungs, also suggests that a two-detector array could be used under limited circumstances. When tested with modified lungs that are more human-like, it was found that the four-detector array showed the best counting efficiency and the lowest MDA. Fortunately, these findings indicate that, although the LLNL phantom's lungs are too short, there is no adverse impact on the calibration of a lung counter. PMID:17151008

  20. Gamma-ray observations of SN 1987A with an array of high-purity germanium detectors

    A balloon borne gamma-ray spectrometer comprising an array of high-purity n-type germanium (HPGe) detectors having geometric area 119 cm2, resolution 2.5 keV at 1.0 MeV, surrounded by an active NaI (Tl) collimator and Compton suppressing anticoincidence shield nominally 10 cm thick, was flown from Alice Springs, Northern Territory, Australia, on May 29--30, 1987, 96 days after the observed neutrino pulse. The average column depth of residual atmosphere in the direction of SN 1987A at float altitude was 6.3 g cm-2 during the observation. SN 1987A was within the 22-deg full-width-half-maximum (FWHM) field of view for about 3300 s during May 29.9--30.3 UT. No excess gamma rays were observed at energies appropriate to the Ni(56)-Co(56) decay chain or from other lines in the energy region from 0.1 to 3.0 MeV. With 80% of the data analyzed, the 3-sigma upper limit obtained for the 1238-keV line from Co(56) at the instrument resolution (about 3 keV) is 1.3 x 10-3 photons cm-2 s-1

  1. GERDA, a GERmanium Detector Array for the search for neutrinoless ββ decay in 76Ge

    The GERDA project, searching for neutrinoless double beta-decay of 76Ge with enriched germanium detectors submerged in a cryogenic bath, has been approved for installation at the Gran Sasso National Laboratory (LNGS), Italy. The GERDA technique is aiming at a dramatic reduction of the background due to radioactive contaminations of the materials surrounding the detectors. This will lead to a sensitivity of about 1026 years on the half-life of neutrinoless double beta decay. Already in the first phase of the experiment, GERDA will be able to investigate with high statistical significance the claimed evidence for neutrinoless double beta decay of 76Ge based on the data of the Heidelberg-Moscow experiment

  2. Improved germanium well detectors

    Germanium well detectors with metal surface barrier contact are comparable for general use with conventional germanium coaxial detectors. They offer very high sensitivity, the highest presently available

  3. Effect of an aerosol deposition pattern in the lung on the counting efficiency of a large area germanium detector array.

    Kramer, Gary H; Hauck, Barry M

    2008-01-01

    The Human Monitoring Laboratory has extended the use of sliced lungs containing planar sources to simulate heterogeneous radionuclide deposition patterns. This work examined two deposition patterns and their effect on the counting efficiency of low-energy photons. The results have shown that heterogenous distributions can be difficult to detect in some cases and can still lead to large uncertainties (up to a factor of 2.5) in the activity estimate, especially at low photon energies. At higher energies ( approximately 60 keV), the effect of the heterogeneous distribution is greatly reduced and errors in the activity estimate reduced to approximately 25%. The presence of a heterogenous distribution can be detected by comparing the ratio of the individual detector counts with the expected values obtained from measuring multiple lungs sets that contained a homogeneous distribution. The distributions tested in this paper were detectable (at 2sigma) as heterogeneous by two of the four detectors in the counting array. PMID:18003713

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

    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.

  5. Neutron Interactions as Seen by A Segmented Germanium Detector

    Abt, I.; A. Caldwell; Kroeninger, K.; Liu, J.; Liu, X.; Majorovits, B.

    2007-01-01

    The GERmanium Detector Array, GERDA, is designed for the search for ``neutrinoless double beta decay'' (0-nu-2-beta) with germanium detectors enriched in Ge76. An 18-fold segmented prototype detector for GERDA Phase II was exposed to an AmBe neutron source to improve the understanding of neutron induced backgrounds. Neutron interactions with the germanium isotopes themselves and in the surrounding materials were studied. Segment information is used to identify neutron induced peaks in the rec...

  6. Deep-inelastic heavy-ion collisions at the Tandem accelerator in Orsay - Gamma spectroscopy of fp-shell neutron-rich nuclei with the ORGAM germanium array detector

    The work presented here aimed at producing neutron rich fp shell nuclei through heavy ion collisions at the Tandem accelerator of IPN, and to study them using gamma spectroscopy. For this purpose, a germanium gamma array called ORGAM, and dedicated to high resolution gamma spectroscopy, was set up at the Tandem accelerator. During the year 2008/2009, the individual germanium detectors were tested and repaired, as well as their ancillary anti-Compton shielding. At the same time, the liquid nitrogen auto-fill system was improved for better reliability. The array was finally set up on a beam line of the accelerator.The first experiment using the ORGAM array was performed in July 2009. This experiment aimed to study fully damped deep-inelastic collisions between a 36S beam accelerated to 154 MeV, and a 70Zn target. An additional charged particle detection system was used to detect interesting fragments emitted at backward angles. It was not possible to separate these fragments from the background induced by backscattered ions from the beam. Nevertheless, the study of gamma-gamma coincidences detected with the ORGAM array allowed to identify gamma cascades de-exciting nuclei potentially produced through the mechanism of interest. Data accumulated during another experiment performed at the tandem accelerator in 2005 were analyzed. Fusion-evaporation reaction between a 25 MeV, 14C beam focused on a 48Ca target produced the 57Cr and 59Mn nuclei, whose energy spectra were established up to 3 MeV. We attempted to study theoretically odd Chromium isotopes with a simple model based on the intermediate coupling scheme. This model, which does not take into account correlations between valence nucleons, described in satisfactory way the semi-magic + 1 neutron, 53Cr, but failed to do so for mid-shell nuclei 55Cr and 57Cr. (author)

  7. Germanium and gallium

    Present article is devoted to germanium and gallium content in fluorite. The literature data on germanium and gallium content was analysed. The literature data on germanium and gallium distribution in fluorite of various geologic deposits and ores of Kazakhstan, Uzbekistan, Tajikistan and some geologic deposits of Russia were studied. The germanium and gallium content in fluorite of geologic deposits of various mineralogical and genetic type was defined.

  8. Germanium detector studies in the framework of the GERDA experiment

    Budjáš, D.

    2009-01-01

    The GERmanium Detector Array (GERDA) is an ultra-low background experiment under construction at Laboratori Nazionali del Gran Sasso. GERDA will search for Ge-76 neutrinoless double beta decay with an aim for 100-fold reduction in background compared to predecessor experiments. This ambition necessitates innovative design approaches, strict selection of low-radioactivity materials, and novel techniques for active background suppression. The core feature of GERDA is its array of germanium dete...

  9. Germanium Detectors in Homeland Security at PNNL

    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.

  10. Calibration of a large hyperpure germanium array for in-vivo detection of the actinides with a tissue-equivalent torso phantom

    For calibration of the array for internally deposited 238Pu, 239Pu, and 241Am, a tissue-equivalent anthropomorphic phantom, was used for efficiency determinations at the ORNL facility. This phantom consists of a tissue-equivalent torso into which is imbedded an adult male skeleton, interchangeable organs containing a homogeneous distribution of various radionuclides, and two sets of chest overlay plates for simulation of progressively thicker tissue over the chest, as well as differing thoracic fat contents

  11. Mesostructured metal germanium sulfides

    MacLachlan, M.J.; Coombs, N.; Bedard, R.L.; White, S.; Thompson, L.K.; Ozin, G.A.

    1999-12-29

    A new class of mesostructured metal germanium sulfide materials has been prepared and characterized. The synthesis, via supramolecular assembly of well-defined germanium sulfide anionic cluster precursors and transition-metal cations in formamide, represents a new strategy for the formation of this class of solids. A variety of techniques were employed to examine the structure and composition of the materials. Structurally, the material is best described as a periodic mesostructured metal sulfide-based coordination framework akin to periodic hexagonal mesoporous silica, MCM-41. At the molecular scale, the materials strongly resemble microstructured metal germanium sulfides, in which the structure of the [Ge{sub 4}S{sub 10}]{sup 4{minus}} cluster building-blocks are intact and linked via {mu}-S-M-S bonds. Evidence for a metal-metal bond in mesostructured Cu/Ge{sub 4}S{sub 10} is also provided.

  12. Neutron Interactions as Seen by A Segmented Germanium Detector

    Abt, I; Kroeninger, K; Liu, J; Liu, X; Majorovits, B

    2007-01-01

    The GERmanium Detector Array, GERDA, is designed for the search for ``neutrinoless double beta decay'' (0-nu-2-beta) with germanium detectors enriched in Ge76. An 18-fold segmented prototype detector for GERDA Phase II was exposed to an AmBe neutron source to improve the understanding of neutron induced backgrounds. Neutron interactions with the germanium isotopes themselves and in the surrounding materials were studied. Segment information is used to identify neutron induced peaks in the recorded energy spectra. The Geant4 based simulation package MaGe is used to simulate the experiment. Though many photon peaks from germanium isotopes excited by neutrons are correctly described by Geant4, some physics processes were identified as being incorrectly treated or even missing.

  13. Calibration of germanium detectors

    The process of determining the energy-dependent detection probability with measurements using Ge (Li) and high-grade germanium detectors is described. The paper explains which standards are best for a given purpose and given requirements as to accuracy, and how to assess measuring geometry variations and summation corrections. (DG)

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

    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

  15. Identification of photons in double beta-decay experiments using segmented germanium detectors - studies with a GERDA Phase II prototype detector

    Abt, I.; Caldwell, A.; Kröninger, K.; Liu, J; X. Liu; Majorovits, B.

    2007-01-01

    The sensitivity of experiments searching for neutrinoless double beta-decay of germanium was so far limited by the background induced by external gamma-radiation. Segmented germanium detectors can be used to identify photons and thus reduce this background component. The GERmanium Detector Array, GERDA, will use highly segmented germanium detectors in its second phase. The identification of photonic events is investigated using a prototype detector. The results are compared with Monte Carlo d...

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

    119Sn and 129Te (129I) Moessbauer spectroscopy showed that chalcogen-enriched Ge100-yXy (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.

  17. Experience from operating germanium detectors in GERDA

    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.

  18. Pulse shapes and surface effects in segmented germanium detectors

    Lenz, Daniel

    2010-03-24

    It is well established that at least two neutrinos are massive. The absolute neutrino mass scale and the neutrino hierarchy are still unknown. In addition, it is not known whether the neutrino is a Dirac or a Majorana particle. The GERmanium Detector Array (GERDA) will be used to search for neutrinoless double beta decay of {sup 76}Ge. The discovery of this decay could help to answer the open questions. In the GERDA experiment, germanium detectors enriched in the isotope {sup 76}Ge are used as source and detector at the same time. The experiment is planned in two phases. In the first, phase existing detectors are deployed. In the second phase, additional detectors will be added. These detectors can be segmented. A low background index around the Q value of the decay is important to maximize the sensitivity of the experiment. This can be achieved through anti-coincidences between segments and through pulse shape analysis. The background index due to radioactive decays in the detector strings and the detectors themselves was estimated, using Monte Carlo simulations for a nominal GERDA Phase II array with 18-fold segmented germanium detectors. A pulse shape simulation package was developed for segmented high-purity germanium detectors. The pulse shape simulation was validated with data taken with an 19-fold segmented high-purity germanium detector. The main part of the detector is 18-fold segmented, 6-fold in the azimuthal angle and 3-fold in the height. A 19th segment of 5mm thickness was created on the top surface of the detector. The detector was characterized and events with energy deposited in the top segment were studied in detail. It was found that the metalization close to the end of the detector is very important with respect to the length of the of the pulses observed. In addition indications for n-type and p-type surface channels were found. (orig.)

  19. Germanium detector studies in the framework of the GERDA experiment

    Budjas, Dusan

    2009-05-06

    The GERmanium Detector Array (GERDA) is an ultra-low background experiment under construction at Laboratori Nazionali del Gran Sasso. GERDA will search for {sup 76}Ge neutrinoless double beta decay with an aim for 100-fold reduction in background compared to predecessor experiments. This ambition necessitates innovative design approaches, strict selection of low-radioactivity materials, and novel techniques for active background suppression. The core feature of GERDA is its array of germanium detectors for ionizing radiation, which are enriched in {sup 76}Ge. Germanium detectors are the central theme of this dissertation. The first part describes the implementation, testing, and optimisation of Monte Carlo simulations of germanium spectrometers, intensively involved in the selection of low-radioactivity materials. The simulations are essential for evaluations of the gamma ray measurements. The second part concerns the development and validation of an active background suppression technique based on germanium detector signal shape analysis. This was performed for the first time using a BEGe-type detector, which features a small read-out electrode. As a result of this work, BEGe is now one of the two detector technologies included in research and development for the second phase of the GERDA experiment. A suppression of major GERDA backgrounds is demonstrated, with (0.93{+-}0.08)% survival probability for events from {sup 60}Co, (21{+-}3)% for {sup 226}Ra, and (40{+-}2)% for {sup 228}Th. The acceptance of {sup 228}Th double escape events, which are analogous to double beta decay, was kept at (89{+-}1)%. (orig.)

  20. Pulse shapes and surface effects in segmented germanium detectors

    It is well established that at least two neutrinos are massive. The absolute neutrino mass scale and the neutrino hierarchy are still unknown. In addition, it is not known whether the neutrino is a Dirac or a Majorana particle. The GERmanium Detector Array (GERDA) will be used to search for neutrinoless double beta decay of 76Ge. The discovery of this decay could help to answer the open questions. In the GERDA experiment, germanium detectors enriched in the isotope 76Ge are used as source and detector at the same time. The experiment is planned in two phases. In the first, phase existing detectors are deployed. In the second phase, additional detectors will be added. These detectors can be segmented. A low background index around the Q value of the decay is important to maximize the sensitivity of the experiment. This can be achieved through anti-coincidences between segments and through pulse shape analysis. The background index due to radioactive decays in the detector strings and the detectors themselves was estimated, using Monte Carlo simulations for a nominal GERDA Phase II array with 18-fold segmented germanium detectors. A pulse shape simulation package was developed for segmented high-purity germanium detectors. The pulse shape simulation was validated with data taken with an 19-fold segmented high-purity germanium detector. The main part of the detector is 18-fold segmented, 6-fold in the azimuthal angle and 3-fold in the height. A 19th segment of 5mm thickness was created on the top surface of the detector. The detector was characterized and events with energy deposited in the top segment were studied in detail. It was found that the metalization close to the end of the detector is very important with respect to the length of the of the pulses observed. In addition indications for n-type and p-type surface channels were found. (orig.)

  1. Germanium detector studies in the framework of the GERDA experiment

    The GERmanium Detector Array (GERDA) is an ultra-low background experiment under construction at Laboratori Nazionali del Gran Sasso. GERDA will search for 76Ge neutrinoless double beta decay with an aim for 100-fold reduction in background compared to predecessor experiments. This ambition necessitates innovative design approaches, strict selection of low-radioactivity materials, and novel techniques for active background suppression. The core feature of GERDA is its array of germanium detectors for ionizing radiation, which are enriched in 76Ge. Germanium detectors are the central theme of this dissertation. The first part describes the implementation, testing, and optimisation of Monte Carlo simulations of germanium spectrometers, intensively involved in the selection of low-radioactivity materials. The simulations are essential for evaluations of the gamma ray measurements. The second part concerns the development and validation of an active background suppression technique based on germanium detector signal shape analysis. This was performed for the first time using a BEGe-type detector, which features a small read-out electrode. As a result of this work, BEGe is now one of the two detector technologies included in research and development for the second phase of the GERDA experiment. A suppression of major GERDA backgrounds is demonstrated, with (0.93±0.08)% survival probability for events from 60Co, (21±3)% for 226Ra, and (40±2)% for 228Th. The acceptance of 228Th double escape events, which are analogous to double beta decay, was kept at (89±1)%. (orig.)

  2. Neutron interactions with segmented germanium detectors studies with a GERDA Phase II prototype detector

    The GERmanium Detector Array, GERDA, is designed to search for ''neutrinoless double beta decay'' (0ν2β) with Germanium detectors enriched in 76Ge. The estimate of neutron induced background relies purely on Geant4 simulations. In order to study neutron interactions with the Germanium itself as well as the surrounding materials, a prototype detector for GERDA Phase II with 18 segments was exposed to an AmBe neutron source. The simulated results from the Geant4-based MaGe MC package agree in general with the measurements, thus verifying the MC used. The Geant4 package is able to simulate most de-excitation photons from the Germanium isotopes and the nuclei recoil process after interacting with neutrons. However, some physics processes are missing in the simulation. (orig.)

  3. Vapor pressure of germanium precursors

    Pangrác, Jiří; Fulem, Michal; Hulicius, Eduard; Melichar, Karel; Šimeček, Tomislav; Růžička, K.; Morávek, Pavel; Růžička, V.; Rushworth, S. A.

    2008-01-01

    Roč. 310, č. 23 (2008), s. 4720-4723. ISSN 0022-0248 R&D Projects: GA ČR GA203/08/0217 Institutional research plan: CEZ:AV0Z10100521 Keywords : characterization * phase equilibria * metalorganic vapor phase epitaxy * germanium compounds Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.757, year: 2008

  4. Structural, electronic, and linear optical properties of organic photovoltaic PBTTT-C14 crystal

    Li, Long-Hua; Kontsevoi, Oleg Y.; Rhim, S. H.; Freeman, Arthur J.

    2013-04-01

    Poly(2,5-bis(3-tetradecylthiophen-2yl)thieno(3,2-b)thiophene) (PBTTT-C14) is an important electro-optical polymer, whose three-dimensional crystal structure is somewhat ambiguous and the fundamental electronic and linear optical properties are not well known. We carried out first-principles calculations to model the crystal structure and to study the effect of side-chains on the physical structure and electronic properties. Our calculations suggest that the patterns of side-chain has little direct effect on the valence band maximum and conduction band minimum but they do have impact on the bandgap through changing the π-π stacking distance. By examining the band structure and wave functions, we conclude that the fundamental bandgap of the PBTTT-C14 crystal is determined by the conduction band energy at the Q point. The calculations indicate that the bandgap of PBTTT-C14 crystal may be tunable by introducing different side-chains. The significant peak in the imaginary part of the dielectric function arises from transitions along the polymer backbone axis, as determined by the critical-point analysis and the large optical transition matrix elements in the direction of the backbone.

  5. Laser synthesis of germanium tin alloys on virtual germanium

    Stefanov, S; Conde, J. C.; Chiussi, S; De Benedetti, A.; Serra, C.; Werner, J.; Oehme, M.; Schulze, J.; Buca, D.; Holländer, B; Mantl, S.

    2012-01-01

    Synthesis of heteroepitaxial germanium tin (GeSn) alloys using excimer laser processing of a thin 4 nm Sn layer on Ge has been demonstrated and studied. Laser induced rapid heating, subsequent melting, and re-solidification processes at extremely high cooling rates have been experimentally achieved and also simulated numerically to optimize the processing parameters. "In situ" measured sample reflectivity with nanosecond time resolution was used as feedback for the simulations and directly co...

  6. The GALATEA test facility and a first study of alpha-induced surface events in a Germanium detector

    Irlbeck, Sabine

    2014-01-01

    Germanium detectors are a choice technology in fundamental research. They are suitable for the search for rare events due to their high sensitivity and excellent energy resolution. As an example, the GERDA (GERmanium Detector Array) experiment searching for neutrinoless double beta decay is described. The observation of this decay would resolve the fundamental question whether the neutrino is its own antiparticle. Especially adapted detector technologies and low background rates n...

  7. Radiation damage of germanium detectors

    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.

  8. Harmonic Lattice Dynamics of Germanium

    The phonon dispersion relations of the Δ-, Λ-, and Σ-directions of germanium at 80 K are analysed in terms of current harmonic lattice dynamical models. On the basis of this experience, a new model is proposed which gives a unified account of the strong points of the previous models. The principal elements of the presented theory are quasiparticle bond charges combined with a valence force field

  9. Germanium Microsphere High-Q Resonator

    Wang, Pengfei; Lee, Timothy; Ding, Ming; Dhar, Anirban; Hawkins, Thomas; Foy, Paul; Semenova, Yuliya; Wu, Qiang; Sahu, Jayanta; Farrell, Gerald; Ballato, John; Brambilla, Gilberto

    2012-01-01

    In this Letter, the fabrication and characterization of a microsphere resonator from the semiconductor germanium is demonstrated. Whispering gallery modes are excited in a 46 μm diameter germanium microsphere resonator using evanescent coupling from a tapered silica optical fiber with a waist diameter of 2 μm. Resonances with Q factors as high as 3.8×104 at wavelengths near 2 μm are observed. Because of their ultrahigh optical nonlinearities and extremely broad transparency window, germanium ...

  10. Study on the local atomic structure of germanium in organic germanium compounds by EXAFS

    1999-01-01

    Organic germanium compounds have been extensively applied in medicine as tonics,In this paper,the local structures of two organic germanium compounds,carboxyethylgermanium sesquioxide and polymeric germanium glutamate,were determined by EXAFS.The structure parameters including coordination numbers and bond lengths were reported,and possible structure patterns were discussed.

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

    Schubert, A G; Avignone, F T; Back, H O; Barabash, A S; Bergevin, M; Bertrand, F E; Boswell, M; Brudanin, V; Busch, M; Chan, Y-D; Christofferson, C D; Collar, J I; Combs, D C; Cooper, R J; Detwiler, J A; Leon, J; Doe, P J; Efremenko, Yu; Egorov, V; Ejiri, H; Elliott, S R; Esterline, J; Fast, J E; Fields, N; Finnerty, P; Fraenkle, F M; Gehman, V M; Giovanetti, G K; Green, M P; Guiseppe, V E; Gusey, K; Hallin, A L; Hazama, R; Henning, R; Hime, A; Hoppe, E W; Horton, M; Howard, S; Howe, M A; Johnson, R A; Keeter, K J; Keillor, M E; Keller, C; Kephart, J D; Kidd, M F; Knecht, A; Kochetov, O; Konovalov, S I; Kouzes, R T; LaFerriere, B; LaRoque, B H; Leviner, L E; Loach, J C; MacMullin, S; Marino, M G; Martin, R D; Mei, D -M; Merriman, J; Miller, M L; Mizouni, L; Nomachi, M; Orrell, J L; Overman, N; Phillips, D G; Poon, A W P; Perumpilly, G; Prior, G; Radford, D C; Rielage, K; Robertson, R G H; Ronquest, M C; Shima, T; Shirchenko, M; Snavely, K J; Sobolev, V; Steele, D; Strain, J; Thomas, K; Timkin, V; Tornow, W; Vanyushin, I; Varner, R L; Vetter, K; Vorren, K; Wilkerson, J F; Wolfe, B A; Yakushev, E; Young, A R; Yu, C ?H; Yumatov, V; Zhan, C

    2011-01-01

    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 76-Ge. The DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76-Ge. 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 76-Ge neutrinoless double-beta decay Q-value of 2039 keV.

  12. Interfacial properties of germanium nitride dielectric layers in germanium

    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.

  13. Zone refining high-purity germanium

    The effects of various parameters on germanium purification by zone refining have been examined. These parameters include the germanium container and container coatings, ambient gas and other operating conditions. Four methods of refining are presented which reproducibly yield 3.5 kg germanium ingots from which high purity (vertical barN/sub A/ - N/sub D/vertical bar less than or equal to2 x 1010 cm-3) single crystals can be grown. A qualitative model involving binary and ternary complexes of Si, O, B, and Al is shown to account for the behavior of impurities at these low concentrations

  14. Solution synthesis of germanium nanocrystals

    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.

  15. Silicon Germanium Quantum Well Solar Cell Project

    National Aeronautics and Space Administration — Quantum-well structures embodied on single crystal silicon germanium drastically enhanced carrier mobilities.  The cell-to-cell circuits of quantum-well PV...

  16. Metal induced crystallization of silicon germanium alloys

    Gjukic, M.

    2007-05-15

    In the framework of this thesis the applicability of the aluminium-induced layer exchange on binary silicon germanium alloys was studied. It is here for the first time shown that polycrstalline silicon-germanium layers can be fabricated over the whole composition range by the aluminium-induced layer exchange. The experimental results prove thet the resulting material exhibits a polycrystalline character with typocal grain sizes of 10-100 {mu}m. Raman measurements confirm that the structural properties of the resulting layers are because of the large crystallites more comparable with monocrystalline than with nano- or microcrystalline silicon-germanium. The alloy ratio of the polycrystalline layer correspondes to the chemical composition of the amorphous starting layer. The polycrystalline silicon-germanium layers possess in the range of the interband transitions a reflection spectrum, as it is otherwise only known from monocrystalline reference layers. The improvement of the absorption in the photovoltaically relevant spectral range aimed by the application of silicon-germanium could be also proved by absorption measurments. Strongly correlated with the structural properties of the polycrystalline layers and the electronic band structure resulting from this are beside the optical properties also the electrical properties of the material, especially the charge-carrier mobility and the doping concentration. For binary silicon-germanium layers the hole concentration of about 2 x 10{sup 18} cm{sup -3} for pure silicon increrases to about 5 x 10{sup 20} cm{sub -3} for pure germanium. Temperature-resolved measurements were applied in order to detect doping levels respectively semiconductor-metal transitions. In the last part of the thesis the hydrogen passivation of polycrystalline thin silicon-germanium layers, which were fabricated by means of aluminium-induced layer exchange, is treated.

  17. Germanium Resistance Thermometer For Subkelvin Temperatures

    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.

  18. Sensitive germanium thermistors for cryogenic thermal detector of Tokyo dark matter search programme

    Ootani, Wataru; Ito, Yutaka; Nishigaki, Keiji; Kishimoto, Yasuhiro; Minowa, Makoto; Ootuka, Youiti

    1995-01-01

    Sensitive n-type and p-type germanium thermistors were fabricated by the melt doping technique and by the neutron transmutation doping (NTD) technique, respectively, aiming at a use for the cryogenic thermal detector, or bolometer of Tokyo dark matter search programme. We report on the measurements of the sensitivities of these thermistors. In particular, the p-type thermistors are sensitive enough to scale up our existing prototype LiF bolometer and realize a multiple array of the bolometers...

  19. Recovering germanium from coal ash by chlorination with ammonium chloride

    2002-01-01

    A new process of enriching germanium from coal ash was developed. The process involves in mixing the coal ash and ammonium chloride and then roasting the mixture to produce germanium chloride that is then absorbed by dilute hydrochloric acid and hydrolyzed to germanium oxide. The germanium recovery reached to 80.2% at the optimum condition: mass ratio of NH4Cl/coal ash is 0.15, roasting temperature 400℃ and roasting time 90 min.

  20. electrocatalytic nitrate reduction on palladium based catalysts activated with germanium

    Gootzen, J.F.E.; Lefferts, L.; Veen, van J.A.R.

    1999-01-01

    The electrocatalytic reduction of nitrate has been studied with electrochemical methods on palladium and palladium–platinum electrodes activated with germanium. The formation of a palladium–germanium alloy that occurs at germanium coverage above 0.2 has a strong enhancing effect on the rate of nitra

  1. Film germanium strain gauges for cryogenic temperatures

    Strain-measuring characteristics of strain gauges (SG) based on germanium films on gallium arsenide designed for operation in 4-100 K temperature interval and strain range ε∼(±0.3%) are presented. SG are characterized by weak temperature dependences of resistance and strain sensitivity in the temperature range measured. It is shown that in the low-temperature region SG based on heteroepitaxial germanium films on gallium arsenide are no worse than the best domestic and foreign semiconducting and metal SG and are perspective for cryogenic object diagnostics under magnetic field effect

  2. Germanium-Based Nanomaterials for Rechargeable Batteries.

    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

  3. Germanium-overcoated niobium Dayem bridges

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

    1976-01-01

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

  4. The GALATEA test facility and a first study of α-induced surface events in a germanium detector

    Germanium detectors are a choice technology in fundamental research. They are suitable for the search for rare events due to their high sensitivity and excellent energy resolution. As an example, the GERDA (GERmanium Detector Array) experiment searching for neutrinoless double beta decay is described. The observation of this decay would resolve the fundamental question whether the neutrino is its own antiparticle. Especially adapted detector technologies and low background rates needed to detect very rare events such as neutrinoless double beta decays are discussed. The identification of backgrounds originating from the interaction of radiation, especially α-particles, is a focus of this thesis. Low background experiments face problems from α-particles due to unavoidable surface contaminations of the germanium detectors. The segmentation of detectors is used to obtain information about the special characteristics of selected events. The high precision test stand GALATEA was especially designed for surface scans of germanium detectors. As part of this work, GALATEA was completed and commissioned. The final commissioning required major upgrades of the original design which are described in detail. Collimator studies with two commercial germanium detectors are presented. Different collimation levels for a β-source were investigated and crystal axis effects were examined. The first scan with an α-source of the passivated end-plate of a special 19-fold segmented prototype detector mounted in GALATEA is described. The α-induced surface events were studied and characterized. Crosstalk and mirror pulses seen in the segments of the germanium detector were analyzed. The detector studies presented in this thesis will help to further improve the design of germanium detectors for low background experiments.

  5. The GALATEA test facility and a first study of α-induced surface events in a germanium detector

    Irlbeck, Sabine

    2014-01-30

    Germanium detectors are a choice technology in fundamental research. They are suitable for the search for rare events due to their high sensitivity and excellent energy resolution. As an example, the GERDA (GERmanium Detector Array) experiment searching for neutrinoless double beta decay is described. The observation of this decay would resolve the fundamental question whether the neutrino is its own antiparticle. Especially adapted detector technologies and low background rates needed to detect very rare events such as neutrinoless double beta decays are discussed. The identification of backgrounds originating from the interaction of radiation, especially α-particles, is a focus of this thesis. Low background experiments face problems from α-particles due to unavoidable surface contaminations of the germanium detectors. The segmentation of detectors is used to obtain information about the special characteristics of selected events. The high precision test stand GALATEA was especially designed for surface scans of germanium detectors. As part of this work, GALATEA was completed and commissioned. The final commissioning required major upgrades of the original design which are described in detail. Collimator studies with two commercial germanium detectors are presented. Different collimation levels for a β-source were investigated and crystal axis effects were examined. The first scan with an α-source of the passivated end-plate of a special 19-fold segmented prototype detector mounted in GALATEA is described. The α-induced surface events were studied and characterized. Crosstalk and mirror pulses seen in the segments of the germanium detector were analyzed. The detector studies presented in this thesis will help to further improve the design of germanium detectors for low background experiments.

  6. Vacancy-hydrogen complexes in germanium

    Coomer, B.J.; Leary, P.; Jones, R. [Exeter Univ. (United Kingdom). Dept. of Physics; Budde, M.; Bech Nielsen, B. [Institute of Physics and Astronomy, Aarhus University, DK-80000, Aarhus (Denmark); Oeberg, S. [Department of Mathematics, University of Luleaa, Luleaa, S95 187 (Sweden); Briddon, P.R. [Department of Physics, The University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU (United Kingdom)

    1999-02-12

    Local-density-functional pseudopotential theory is used to investigate the structural, electronic and vibrational properties of vacancy-hydrogen complexes in germanium. The results are compared with recent infrared absorption data from proton and deuteron implanted Ge. The acceptor and donor levels of the VH{sub n} defects are derived semi-empirically from the relaxed structures. (orig.) 7 refs.

  7. Electron tunnelling into amorphous germanium and silicon.

    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.

  8. Method for copper staining of germanium crystals

    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.

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

    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.

  10. gamma-ray tracking in germanium the backtracking method

    Marel, J V D

    2002-01-01

    In the framework of a European TMR network project the concept for a gamma-ray tracking array is being developed for nuclear physics spectroscopy in the energy range of approx 10 keV up to several MeV. The tracking array will consist of a large number of position-sensitive germanium detectors in a spherical geometry around a target. Due to the high segmentation, a Compton scattered gamma-ray will deposit energy in several different segments. A method has been developed to reconstruct the tracks of multiple coincident gamma-rays and to find their initial energies. By starting from the final point the track can be reconstructed backwards to the origin with the help of the photoelectric and Compton cross-sections and the Compton scatter formula. Every reconstructed track is given a figure of merit, thus allowing suppression of wrongly reconstructed tracks and gamma-rays that have scattered out of the detector system. This so-called backtracking method has been tested on simulated events in a shell-like geometry ...

  11. Constraining neutrino electromagnetic properties by germanium detectors

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

    2014-01-01

    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. Using existing data with sub-keV thresholds, limits on reactor antineutrino's millicharge, magnetic moment, and charge radius squared are derived. The projected sensitivities for next generation experiments are also given and discussed.

  12. Vacancy-indium clusters in implanted germanium

    Chroneos, Alexander I.

    2010-04-01

    Secondary ion mass spectroscopy measurements of heavily indium doped germanium samples revealed that a significant proportion of the indium dose is immobile. Using electronic structure calculations we address the possibility of indium clustering with point defects by predicting the stability of indium-vacancy clusters, InnVm. We find that the formation of large clusters is energetically favorable, which can explain the immobility of the indium ions. © 2010 Elsevier B.V. All rights reserved.

  13. Bottom-up assembly of metallic germanium

    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.

  14. Next Generation Germanium Systems for Safeguards Applications

    We are developing the latest generation of highly portable, mechanically cooled germanium systems for safeguard applications. In collaboration with our industrial partner, Ph.D.s Co, we have developed the Germanium Gamma Ray Imager (GeGI), an imager with a 2π field of view. This instrument has been thoroughly field tested in a wide range of environments and have performed reliably even in the harshest conditions. The imaging capability of GeGI complements existing safeguards techniques by allowing for the spatial detection, identification, and characterization of nuclear material. Additionally, imaging can be used in design information verification activities to address potential material diversions. Measurements conducted at the Paducah Gaseous Diffusion Plant highlight the advantages this instrument offers in the identification and localization of LEU, HEU and Pu holdup. GeGI has also been deployed to the Savannah River Site for the measurement of radioactive waste canisters, providing information valuable for waste characterization and inventory accountancy. Measuring 30 x 15 x 23 cm and weighing approximately 15 kg, this instrument is the first portable germanium-based imager. GeGI offers high reliability with the convenience of mechanical cooling, making this instrument ideal for the next generation of safeguards instrumentation. (author)

  15. Formation of Germanium Nitride Nanowires on the Surface of Crystalline Germanium

    We report on the growth mechanisms of germanium nitride nanowires on the surface of crystalline Ge annealed in hydrazine vapor at different temperatures. In spite of the presence of water (and hence oxygen precursors) in hydrazine, the pure germanium nitride single crystal nanowires were produced in the temperature range of 480-580 degree C. At temperatures below 520 degree C, the GeOx clusters were formed first at the Ge surface, followed by the nucleation and growth of nanowires through the Vapor-Liquid-Solid mechanism. The Vapor-Solid growth mechanism was observed at temperatures exceeding 520 degree C, and Ge3N4 nanobelts were produced instead of nanowires with circular cross-sections. All nanostructures have the alpha germanium nitride structure; however, at the nucleation stage, the presence of beta Ge3N4 phase was also observed in the roots of nanowires.

  16. Low Power Silicon Germanium Electronics for Microwave Radiometers

    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.

  17. Separation of radioarsenic from a germanium dioxide target

    A procedure for the separation and recovery of arsenic radionuclides from a germanium oxide target using a liquid-liquid extraction technique is described. The effects of target material and preparation were investigated. The effects of hydrochloric acid and hydrogen peroxide concentration on germanium recovery were determined. The efficacy of various reducing agents were evaluated for recovery of arsenic. In addition, the effects of hydrochloric acid and reducing agent concentration were evaluated for optimum arsenic extraction conditions. The germanium oxide target material was recovered in greater than 99% radiochemical yield with less than 1% crossover contamination of germanium radionuclides. (author)

  18. Development of segmented germanium detectors for neutrinoless double beta decay experiments

    The results from neutrino oscillation experiments indicate that at least two neutrinos have mass. However, the value of the masses and whether neutrinos and anti-neutrinos are identical, i.e., Majorana particles, remain unknown. Neutrinoless double beta decay experiments can help to improve our understanding in both cases and are the only method currently possible to tackle the second question. The GERmanium Detector Array (GERDA) experiment, which will search for the neutrinoless double beta decay of 76Ge, is currently under construction in Hall A of the INFN Gran Sasso National Laboratory (LNGS), Italy. In order to achieve an extremely low background level, segmented germanium detectors are considered to be operated directly in liquid argon which serves simultaneously as cooling and shielding medium. Several test cryostats were built at the Max-Planck-Institut fuer Physik in Muenchen to operate segmented germanium detectors both in vacuum and submerged in cryogenic liquid. The performance and the background discrimination power of segmented germanium detectors were studied in detail. It was proven for the first time that segmented germanium detectors can be operated stably over long periods submerged in a cryogenic liquid. It was confirmed that the segmentation scheme employed does well in the identification of photon induced background and demonstrated for the first time that also neutron interactions can be identified. The C++ Monte Carlo framework, MaGe (Majorana-GERDA), is a joint development of the Majorana and GERDA collaborations. It is based on GEANT4, but tailored especially to simulate the response of ultra-low background detectors to ionizing radiation. The predictions of the simulation were veri ed to be accurate for a wide range of conditions. Some shortcomings were found and corrected. Pulse shape analysis is complementary to segmentation in identifying background events. Its efficiency can only be correctly determined using reliable pulse shape

  19. Development of segmented germanium detectors for neutrinoless double beta decay experiments

    Liu, Jing

    2009-06-09

    The results from neutrino oscillation experiments indicate that at least two neutrinos have mass. However, the value of the masses and whether neutrinos and anti-neutrinos are identical, i.e., Majorana particles, remain unknown. Neutrinoless double beta decay experiments can help to improve our understanding in both cases and are the only method currently possible to tackle the second question. The GERmanium Detector Array (GERDA) experiment, which will search for the neutrinoless double beta decay of {sup 76}Ge, is currently under construction in Hall A of the INFN Gran Sasso National Laboratory (LNGS), Italy. In order to achieve an extremely low background level, segmented germanium detectors are considered to be operated directly in liquid argon which serves simultaneously as cooling and shielding medium. Several test cryostats were built at the Max-Planck-Institut fuer Physik in Muenchen to operate segmented germanium detectors both in vacuum and submerged in cryogenic liquid. The performance and the background discrimination power of segmented germanium detectors were studied in detail. It was proven for the first time that segmented germanium detectors can be operated stably over long periods submerged in a cryogenic liquid. It was confirmed that the segmentation scheme employed does well in the identification of photon induced background and demonstrated for the first time that also neutron interactions can be identified. The C++ Monte Carlo framework, MaGe (Majorana-GERDA), is a joint development of the Majorana and GERDA collaborations. It is based on GEANT4, but tailored especially to simulate the response of ultra-low background detectors to ionizing radiation. The predictions of the simulation were veri ed to be accurate for a wide range of conditions. Some shortcomings were found and corrected. Pulse shape analysis is complementary to segmentation in identifying background events. Its efficiency can only be correctly determined using reliable pulse

  20. Performance of bare high-purity germanium detectors in liquid argon for the GERDA experiment

    Heider, Marik Barnabé; Chkvorets, Oleg; Di Vacri, Assunta; Gusev, Konstantin; Schönert, Stefan; Shirchenko, Mark

    2008-01-01

    The GERmanium Detector Array, GERDA, will search for neutrinoless double beta decay in 76Ge at the National Gran Sasso Laboratory of the INFN. Bare high-purity germanium detectors enriched in 76Ge will be submerged in liquid argon serving simultaneously as a shield against external radioactivity and as a cooling medium. In GERDA Phase-I, reprocessed enriched-Ge detectors, which were previously operated by the Heidelberg-Moscow and IGEX collaborations, will be redeployed. Before operating the enriched detectors, tests are performed with non-enriched bare HPGe detectors in the GERDA underground Detector Laboratory to test the Phase-I detector assembly, the detector handling protocols, the refurbishment technology and to study the long-term stability in liquid argon. The leakage currents in liquid argon and liquid nitrogen have been extensively studied under varying gamma irradiation conditions. In total three non-enriched high-purity p-type prototype germanium detectors have been operated successfully. The dete...

  1. AGATA - Advanced Gamma Tracking Array

    Akkoyun, S; Alikhani, B; Ameil, F; de Angelis, G; Arnold, L; Astier, A; Ataç, A; Aubert, Y; Aufranc, C; Austin, A; Aydin, S; Azaiez, F; Badoer, S; Balabanski, D L; Barrientos, D; Baulieu, G; Baumann, R; Bazzacco, D; Beck, F A; Beck, T; Bednarczyk, P; Bellato, M; Bentley, M A; Benzoni, G; Berthier, R; Berti, L; Beunard, R; Bianco, G Lo; Birkenbach, B; Bizzeti, P G; Bizzeti-Sona, A M; Blanc, F Le; Blasco, J M; Blasi, N; Bloor, D; Boiano, C; Borsato, M; Bortolato, D; Boston, A J; Boston, H C; Bourgault, P; Boutachkov, P; Bouty, A; Bracco, A; Brambilla, S; Brawn, I P; Brondi, A; Broussard, S; Bruyneel, B; Bucurescu, D; Burrows, I; Bürger, A; Cabaret, S; Cahan, B; Calore, E; Camera, F; Capsoni, A; Carrió, F; Casati, G; Castoldi, M; Cederwall, B; Cercus, J -L; Chambert, V; Chambit, M El; Chapman, R; Charles, L; Chavas, J; Clément, E; Cocconi, P; Coelli, S; Coleman-Smith, P J; Colombo, A; Colosimo, S; Commeaux, C; Conventi, D; Cooper, R J; Corsi, A; Cortesi, A; Costa, L; Crespi, F C L; Cresswell, J R; Cullen, D M; Curien, D; Czermak, A; Delbourg, D; Depalo, R; Descombes, T; Désesquelles, P; Detistov, P; Diarra, C; Didierjean, F; Dimmock, M R; Doan, Q T; Domingo-Pardo, C; Doncel, M; Dorangeville, F; Dosme, N; Drouen, Y; Duchêne, G; Dulny, B; Eberth, J; Edelbruck, P; Egea, J; Engert, T; Erduran, M N; Ertürk, S; Fanin, C; Fantinel, S; Farnea, E; Faul, T; Filliger, M; Filmer, F; Finck, Ch; de France, G; Gadea, A; Gast, W; Geraci, A; Gerl, J; Gernhäuser, R; Giannatiempo, A; Giaz, A; Gibelin, L; Givechev, A; Goel, N; González, V; Gottardo, A; Grave, X; Grȩbosz, J; Griffiths, R; Grint, A N; Gros, P; Guevara, L; Gulmini, M; Görgen, A; Ha, H T M; Habermann, T; Harkness, L J; Harroch, H; Hauschild, K; He, C; Hernández-Prieto, A; Hervieu, B; Hess, H; Hüyük, T; Ince, E; Isocrate, R; Jaworski, G; Johnson, A; Jolie, J; Jones, P; Jonson, B; Joshi, P; Judson, D S; Jungclaus, A; Kaci, M; Karkour, N; Karolak, M; Kaşkaş, A; Kebbiri, M; Kempley, R S; Khaplanov, A; Klupp, S; Kogimtzis, M; Kojouharov, I; Korichi, A; Korten, W; Kröll, Th; Krücken, R; Kurz, N; Ky, B Y; Labiche, M; Lafay, X; Lavergne, L; Lazarus, I H; Leboutelier, S; Lefebvre, F; Legay, E; Legeard, L; Lelli, F; Lenzi, S M; Leoni, S; Lermitage, A; Lersch, D; Leske, J; Letts, S C; Lhenoret, S; Lieder, R M; Linget, D; Ljungvall, J; Lopez-Martens, A; Lotodé, A; Lunardi, S; Maj, A; van der Marel, J; Mariette, Y; Marginean, N; Marginean, R; Maron, G; Mather, A R; Mȩczyński, W; Mendéz, V; Medina, P; Melon, B; Menegazzo, R; Mengoni, D; Merchan, E; Mihailescu, L; Michelagnoli, C; Mierzejewski, J; Milechina, L; Million, B; Mitev, K; Molini, P; Montanari, D; Moon, S; Morbiducci, F; Moro, R; Morrall, P S; Möller, O; Nannini, A; Napoli, D R; Nelson, L; Nespolo, M; Ngo, V L; Nicoletto, M; Nicolini, R; Noa, Y Le; Nolan, P J; Norman, M; Nyberg, J; Obertelli, A; Olariu, A; Orlandi, R; Oxley, D C; Özben, C; Ozille, M; Oziol, C; Pachoud, E; Palacz, M; Palin, J; Pancin, J; Parisel, C; Pariset, P; Pascovici, G; Peghin, R; Pellegri, L; Perego, A; Perrier, S; Petcu, M; Petkov, P; Petrache, C; Pierre, E; Pietralla, N; Pietri, S; Pignanelli, M; Piqueras, I; Podolyak, Z; Pouhalec, P Le; Pouthas, J; Pugnére, D; Pucknell, V F E; Pullia, A; Quintana, B; Raine, R; Rainovski, G; Ramina, L; Rampazzo, G; La Rana, G; Rebeschini, M; Recchia, F; Redon, N; Reese, M; Reiter, P; Regan, P H; Riboldi, S; Richer, M; Rigato, M; Rigby, S; Ripamonti, G; Robinson, A P; Robin, J; Roccaz, J; Ropert, J -A; Rossé, B; Alvarez, C Rossi; Rosso, D; Rubio, B; Rudolph, D; Saillant, F; Şahin, E; Salomon, F; Salsac, M -D; Salt, J; Salvato, G; Sampson, J; Sanchis, E; Santos, C; Schaffner, H; Schlarb, M; Scraggs, D P; Seddon, D; Şenyiğit, M; Sigward, M -H; Simpson, G; Simpson, J; Slee, M; Smith, J F; Sona, P; Sowicki, B; Spolaore, P; Stahl, C; Stanios, T; Stefanova, E; Stézowski, O; Strachan, J; Suliman, G; Söderström, P -A; Tain, J L; Tanguy, S; Tashenov, S; Theisen, Ch; Thornhill, J; Tomasi, F; Toniolo, N; Touzery, R; Travers, B; Triossi, A; Tripon, M; Tun-Lanoë, K M M; Turcato, M; Unsworth, C; Ur, C A; Valiente-Dobon, J J; Vandone, V; Vardaci, E; Venturelli, R; Veronese, F; Veyssiere, Ch; Viscione, E; Wadsworth, R; Walker, P M; Warr, N; Weber, C; Weisshaar, D; Wells, D; Wieland, O; Wiens, A; Wittwer, G; Wollersheim, H J; Zocca, F; Zamfir, N V; Ziȩbliński, M; Zucchiatti, A

    2011-01-01

    The Advanced GAmma Tracking Array (AGATA) is a European project to develop and operate the next generation gamma-ray spectrometer. AGATA is based on the technique of gamma-ray energy tracking in electrically segmented high-purity germanium crystals. This technique requires the accurate determination of the energy, time and position of every interaction as a gamma ray deposits its energy within the detector volume. Reconstruction of the full interaction path results in a detector with very high efficiency and excellent spectral response. The realization of gamma-ray tracking and AGATA is a result of many technical advances. These include the development of encapsulated highly-segmented germanium detectors assembled in a triple cluster detector cryostat, an electronics system with fast digital sampling and a data acquisition system to process the data at a high rate. The full characterization of the crystals was measured and compared with detector-response simulations. This enabled pulse-shape analysis algorith...

  2. Optical Activation of Germanium Plasmonic Antennas in the Mid-Infrared.

    Fischer, Marco P; Schmidt, Christian; Sakat, Emilie; Stock, Johannes; Samarelli, Antonio; Frigerio, Jacopo; Ortolani, Michele; Paul, Douglas J; Isella, Giovanni; Leitenstorfer, Alfred; Biagioni, Paolo; Brida, Daniele

    2016-07-22

    Impulsive interband excitation with femtosecond near-infrared pulses establishes a plasma response in intrinsic germanium structures fabricated on a silicon substrate. This direct approach activates the plasmonic resonance of the Ge structures and enables their use as optical antennas up to the mid-infrared spectral range. The optical switching lasts for hundreds of picoseconds until charge recombination redshifts the plasma frequency. The full behavior of the structures is modeled by the electrodynamic response established by an electron-hole plasma in a regular array of antennas. PMID:27494498

  3. Heterostructures of germanium nanowires and germanium-silicon oxide nanotubes and growth mechanisms

    Huang, J Q; Chim, W K [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, 117576 (Singapore); Chiam, S Y; Wong, L M; Wang, S J, E-mail: elecwk@nus.edu.s [Institute of Materials Research and Engineering, A-STAR (Agency for Science, Technology and Research), 3 Research Link, 117602 (Singapore)

    2009-10-21

    We report on a method to fabricate one-dimensional heterostructures of germanium nanowires (GeNWs) and germanium-silicon oxide nanotubes (GeSiO{sub x}NTs). The synthesis of the wire-tube heterostructures is carried out using a simple furnace set-up with germanium tetraiodide and germanium powders as growth precursors, gold-dotted silicon wafers as substrates and by controlling the temperature ramp rate/sequence of the growth precursors. Two types of wire-tube heterostructures resulting from distinct growth mechanisms are obtained. The type-1 heterostructure consists of a GeNW, grown via a gold-catalyzed vapour-liquid-solid process, at the lower end and a GeSiO{sub x}NT at the upper end. In contrast, the type-2 heterostructure is made up of a solid wire at the upper end and a hollow tube at the lower end. The solid wire portion of the type-2 heterostructure is formed through an oxide-assisted growth process.

  4. Heterostructures of germanium nanowires and germanium-silicon oxide nanotubes and growth mechanisms

    We report on a method to fabricate one-dimensional heterostructures of germanium nanowires (GeNWs) and germanium-silicon oxide nanotubes (GeSiOxNTs). The synthesis of the wire-tube heterostructures is carried out using a simple furnace set-up with germanium tetraiodide and germanium powders as growth precursors, gold-dotted silicon wafers as substrates and by controlling the temperature ramp rate/sequence of the growth precursors. Two types of wire-tube heterostructures resulting from distinct growth mechanisms are obtained. The type-1 heterostructure consists of a GeNW, grown via a gold-catalyzed vapour-liquid-solid process, at the lower end and a GeSiOxNT at the upper end. In contrast, the type-2 heterostructure is made up of a solid wire at the upper end and a hollow tube at the lower end. The solid wire portion of the type-2 heterostructure is formed through an oxide-assisted growth process.

  5. Ultraviolet-light-induced processes in germanium-doped silica

    Kristensen, Martin

    2001-01-01

    A model is presented for the interaction of ultraviolet (UV) light with germanium-doped silica glass. It is assumed that germanium sites work as gates for transferring the excitation energy into the silica. In the material the excitation induces forbidden transitions to two different defect state...

  6. Silicon germanium mask for deep silicon etching

    Serry, Mohamed

    2014-07-29

    Polycrystalline silicon germanium (SiGe) can offer excellent etch selectivity to silicon during cryogenic deep reactive ion etching in an SF.sub.6/O.sub.2 plasma. Etch selectivity of over 800:1 (Si:SiGe) may be achieved at etch temperatures from -80 degrees Celsius to -140 degrees Celsius. High aspect ratio structures with high resolution may be patterned into Si substrates using SiGe as a hard mask layer for construction of microelectromechanical systems (MEMS) devices and semiconductor devices.

  7. Tensile strain mapping in flat germanium membranes

    Rhead, S. D., E-mail: S.Rhead@warwick.ac.uk; Halpin, J. E.; Myronov, M.; Patchett, D. H.; Allred, P. S.; Wilson, N. R.; Leadley, D. R. [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom); Shah, V. A. [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom); Department of Engineering, University of Warwick, Coventry, CV4 7AL (United Kingdom); Kachkanov, V.; Dolbnya, I. P. [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE (United Kingdom); Reparaz, J. S. [ICN2 - Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, 08193 Bellaterra (Barcelona) (Spain); Sotomayor Torres, C. M. [ICN2 - Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, 08193 Bellaterra (Barcelona) (Spain)

    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.

  8. Tensile strain mapping in flat germanium membranes

    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

  9. Silicon/Germanium Molecular Beam Epitaxy

    Ericsson, Leif

    2006-01-01

    Molecular Beam Epitaxy (MBE) is a well-established method to grow low-dimensional structures for research applications. MBE has given many contributions to the rapid expanding research-area of nano-technology and will probably continuing doing so. The MBE equipment, dedicated for Silicon/Germanium (Si/Ge) systems, at Karlstads University (Kau) has been studied and started for the first time. In the work of starting the system, all the built in interlocks has been surveyed and connected, and t...

  10. Electromechanically cooled germanium radiation detector system

    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++, GAMANL, GRPANL and MGAU, 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 . 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

  11. High-purity germanium crystal growing

    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 1010cm-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

  12. Experimental test of the background rejection, through imaging capability, of a highly segmented AGATA germanium detector

    Doncel, M., E-mail: doncel@usal.e [Laboratorio de Radiaciones Ionizantes, Universidad de Salamanca (Spain); Recchia, F. [INFN sezione di Padova, Padova (Italy); Quintana, B. [Laboratorio de Radiaciones Ionizantes, Universidad de Salamanca (Spain); Gadea, A. [IFIC Valencia, Valencia (Spain); INFN Laboratori Nazionali di Legnaro, Legnaro (Italy); Farnea, E. [INFN sezione di Padova, Padova (Italy)

    2010-10-21

    The development of highly segmented germanium detectors as well as the algorithms to identify the position of the interaction within the crystal opens the possibility to locate the {gamma}-ray source using Compton imaging algorithms. While the Compton-suppression shield, coupled to the germanium detector in conventional arrays, works also as an active filter against the {gamma} rays originated outside the target, the new generation of position sensitive {gamma}-ray detector arrays has to fully rely on tracking capabilities for this purpose. In specific experimental conditions, as the ones foreseen at radioactive beam facilities, the ability to discriminate background radiation improves the sensitivity of the gamma spectrometer. In this work we present the results of a measurement performed at the Laboratori Nazionali di Legnaro (LNL) aiming the evaluation of the AGATA detector capabilities to discriminate the origin of the {gamma} rays on an event-by-event basis. It will be shown that, exploiting the Compton scattering formula, it is possible to track back {gamma} rays coming from different positions, assigning them to specific emitting locations. These imaging capabilities are quantified for a single crystal AGATA detector.

  13. Effects of Germanium on Movement of Dislocations in p-Type Czochralski Silicon

    2006-01-01

    By indentation at room temperature followed by annealing at high temperatures, the pinning effect of germanium on dislocations in germanium-doped Czochralski silicon was investigated. Experimental results show that the dislocations in germanium-doped Czochralski silicon move shorter and slower than those in Czochralski silicon undoping with germanium when the concentration of germanium is over 1×1018 cm-3. The retarding velocity of dislocations is contributed to the dislocations pinning effect of the strain field introduced by the high concentration germanium, and the Ge4B cluster and the oxygen precipitation those are preferred to form at higher concentration germanium.

  14. Oxygen defect processes in silicon and silicon germanium

    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

  15. Oxygen defect processes in silicon and silicon germanium

    Chroneos, A., E-mail: alexander.chroneos@imperial.ac.uk [Faculty of Engineering and Computing, Coventry University, Priory Street, Coventry CV1 5FB (United Kingdom); Department of Materials, Imperial College London, London SW7 2BP (United Kingdom); Sgourou, E. N.; Londos, C. A. [Solid State Section, Physics Department, University of Athens, Panepistimiopolis, Zografos, 157 84 Athens (Greece); Schwingenschlögl, U. [PSE Division, KAUST, Thuwal 23955-6900 (Saudi Arabia)

    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.

  16. Oxygen defect processes in silicon and silicon germanium

    Chroneos, A.

    2015-06-18

    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.

  17. Germanium detectors and natural radioactivity in food

    Potassium is a very important mineral for many physiological processes, like fluid balance, protein synthesis and signal transmission in nerves. Many aliments like raisins, bananas or chocolate contain potassium. Natural potassium contains 0.012% of the radioactive isotope Potassium 40. This isotope decays via β+ decay into a metastable state of Argon 40, which reaches its ground state emitting a gamma of 1460 keV. A commercially produced Germanium detector has been used to measure the energy spectra of different selected food samples. It was calibrated with KCl and potassium contents were extracted. Results verify the high potassium content of commonly recommended food samples. However, the measurement quantitatively differ from the expectations in several cases. One of the most interesting results concerns chocolate bars with different percentages of cacao.

  18. Germanium detectors and natural radioactivity in food

    Garbini, Lucia [Max-Planck-Institut fuer Physik, Muenchen (Germany); Collaboration: GeDet-Collaboration

    2013-07-01

    Potassium is a very important mineral for many physiological processes, like fluid balance, protein synthesis and signal transmission in nerves. Many aliments like raisins, bananas or chocolate contain potassium. Natural potassium contains 0.012% of the radioactive isotope Potassium 40. This isotope decays via β{sup +} decay into a metastable state of Argon 40, which reaches its ground state emitting a gamma of 1460 keV. A commercially produced Germanium detector has been used to measure the energy spectra of different selected food samples. It was calibrated with KCl and potassium contents were extracted. Results verify the high potassium content of commonly recommended food samples. However, the measurement quantitatively differ from the expectations in several cases. One of the most interesting results concerns chocolate bars with different percentages of cacao.

  19. Synthesis of silicon and germanium nanowires.

    Clement, Teresa J. (Arizona State University); 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.

  20. Interactions of germanium atoms with silica surfaces

    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.

  1. Interactions of germanium atoms with silica surfaces

    GeH4 is thermally cracked over a hot filament depositing 0.7-15 ML Ge onto 2-7 nm SiO2/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 GeO2 desorption is monitored through temperature programmed desorption in the temperature range 300-1000 K. Low temperature desorption features are attributed to GeO and GeH4. No GeO2 desorption is observed, but GeO2 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 SiO2 surfaces are proposed

  2. Electron paramagnetic resonance at dislocations in germanium

    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.

  3. Lattice site and thermal stability of transition metals in germanium

    Augustyns, Valérie; Pereira, Lino

    Although the first transistor was based on germanium, current chip technology mainly uses silicon due to its larger abundance, a lower price and higher quality silicon-oxide. However, a very important goal in microelectronics is to obtain faster integrated circuits. The advantages of germanium compared to silicon (e.g. a higher mobility of the charge carriers) motivates further research on germanium based materials. Semiconductor doping (e.g. introducing impurities into silicon and germanium in order to alter - and control - their properties) can be done by ion implantation or by in situ doping, whereby the host material is doped during growth. This thesis focuses on introducing dopants by ion implantation. The implantation as well as the subsequent measurements were performed in ISOLDE (CERN) using the emission channeling technique. Although ion implantation generates undesired defects in the host material (e.g. vacancies), such damage can be reduced by performing the implantation at an elevated temperature....

  4. Protective infrared antireflection coating based on sputtered germanium carbide

    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. Consistency check of pulse shape discrimination for broad energy germanium detectors using double beta decay data

    The Gerda (GERmanium Detector Array) experiment was built to study fundamental neutrino properties via neutrinoless double beta decay (0νββ). 0νββ events are single-site events (SSE) confined to a scale about millimeter. However, most of backgrounds are multi-site events (MSE). Broad Energy Germanium detectors (BEGes) offer the potential merits of improved pulse shape recognition efficiencies of SSE/MSE. They allow us to reach the goal of Phase II with a background index of 10-3 cts/(keV.kg.yr) in the ROI. BEGe detectors with a total target mass of 3.63 kg have been installed to the Gerda setup in the Laboratori Nazionali del Gran Sasso (LNGS) in July 2012 and are collecting data since. A consistency check of the pulse shape discrimination (PSD) efficiencies by comparison of calibration data and 2νββ data will be presented. The PSD power of these detectors is demonstrated.

  6. Consistency check of pulse shape discrimination for broad energy germanium detectors using double beta decay data

    Liao, Heng-Ye [Max-Planck-Institut fuer Physik, Muenchen (Germany); Collaboration: GERDA-Collaboration

    2013-07-01

    The Gerda (GERmanium Detector Array) experiment was built to study fundamental neutrino properties via neutrinoless double beta decay (0νββ). 0νββ events are single-site events (SSE) confined to a scale about millimeter. However, most of backgrounds are multi-site events (MSE). Broad Energy Germanium detectors (BEGes) offer the potential merits of improved pulse shape recognition efficiencies of SSE/MSE. They allow us to reach the goal of Phase II with a background index of 10{sup -3} cts/(keV.kg.yr) in the ROI. BEGe detectors with a total target mass of 3.63 kg have been installed to the Gerda setup in the Laboratori Nazionali del Gran Sasso (LNGS) in July 2012 and are collecting data since. A consistency check of the pulse shape discrimination (PSD) efficiencies by comparison of calibration data and 2νββ data will be presented. The PSD power of these detectors is demonstrated.

  7. Astroparticle physics with a customized low-background broad energy Germanium detector

    Aalseth, Craig E.; Amman, M.; Avignone, Frank T.; Back, Henning O.; Barabash, Alexander S.; Barbeau, P. S.; Bergevin, M.; Bertrand, F.; Boswell, M.; Brudanin, V.; Bugg, William; Burritt, Tom H.; Busch, Matthew; Capps, Greg L.; Chan, Yuen-Dat; Collar, J. I.; Cooper, R. J.; Creswick, R.; Detwiler, Jason A.; Diaz, J.; Doe, Peter 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 M.; Giovanetti, G. K.; Guiseppe, Vincente; Gusey, K.; Hallin, A. L.; Harper, Gregory; 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; Knecht, A.; Kochetov, Oleg; Konovalov, S.; Kouzes, Richard T.; Leviner, L.; Loach, J. C.; Luke, P.; MacMullin, S.; Marino, Michael G.; Martin, R. D.; Mei, Dong-Ming; Miley, Harry S.; Miller, M. L.; Mizouni, Leila; Myers, Allan W.; Nomachi, Masaharu; Orrell, John L.; Peterson, David; Phillips, D.; Poon, Alan; Prior, Gersende; Qian, J.; Radford, D. C.; Rielage, Keith; Robertson, R. G. H.; Rodriguez, Larry; Rykaczewski, Krzysztof P.; Salazar, Harold; Schubert, Alexis G.; Shima, T.; Shirchenko, M.; Steele, David; Strain, J.; Swift, Gary; Thomas, K.; Timkin, V.; Tornow, W.; Van Wechel, T. D.; Vanyushin, I.; Varner, R. L.; Vetter, Kai; Wilkerson, J. F.; Wolfe, B. A.; Xiang, W.; Yakushev, E.; Yaver, Harold; Young, A.; Yu, Chang-Hong; Yumatov, Vladimir; Zhang, C.; Zimmerman, S.

    2011-10-01

    The Majorana Collaboration is building the Majorana Demonstrator, a 60 kg array of high purity germanium detectors housed in an ultra-low background shield at the Sanford Underground Laboratory in Lead, SD. The Majorana Demonstrator will search for neutrinoless double-beta decay of 76Ge while demonstrating the feasibility of a tonne-scale experiment. It may also carry out a dark matter search in the 1-10 GeV/c² mass range. We have found that customized Broad Energy Germanium (BEGe) detectors produced by Canberra have several desirable features for a neutrinoless double-beta decay experiment, including low electronic noise, excellent pulse shape analysis capabilities, and simple fabrication. We have deployed a customized BEGe, the Majorana Low-Background BEGe at Kimballton (MALBEK), in a low-background cryostat and shield at the Kimballton Underground Research Facility in Virginia. This paper will focus on the detector characteristics and measurements that can be performed with such a radiation detector in a low-background environment.

  8. Astroparticle Physics with a Customized Low-Background Broad Energy Germanium Detector

    Aalseth, C E; Avignone, F T; Back, H O; Barabash, A S; Barbeau, P S; Bergevin, M; Bertrand, F E; Boswell, M; Brudanin, V; Bugg, W; Burritt, T H; Busch, M; Capps, G; Chan, Y-D; Collar, J I; Cooper, R J; Creswick, R; Detwiler, J A; Diaz, J; Doe, P J; Efremenko, Yu; Egorov, V; Ejiri, H; Elliott, S R; Ely, J; Esterline, J; Farach, H; Fast, J E; Fields, N; Finnerty, P; Fujikawa, B; Fuller, E; Gehman, V M; Giovanetti, G K; Guiseppe, V E; Gusey, K; Hallin, A L; Harper, G C; Hazama, R; Henning, R; Hime, A; Hoppe, E W; Hossbach, T W; Howe, M A; Johnson, R A; Keeter, K J; Keillor, M; Keller, C; Kephart, J D; Kidd, M F; Knecht, A; Kochetov, O; Konovalov, S I; Kouzes, R T; Leviner, L; Loach, J C; Luke, P N; MacMullin, S; Marino, M G; Martin, R D; Mei, D -M; Miley, H S; Miller, M L; Mizouni, L; Meyers, A W; Nomachi, M; Orrell, J L; Peterson, D; Phillips, D G; Poon, A W P; Prior, G; Qian, J; Radford, D C; Rielage, K; Robertson, R G H; Rodriguez, L; Rykaczewski, K P; Salazar, H; Schubert, A G; Shima, T; Shirchenko, M; Steele, D; Strain, J; Swift, G; Thomas, K; Timkin, V; Tornow, W; Van Wechel, T D; Vanyushin, I; Varner, R L; Vetter, K; Wilkerson, J F; Wolfe, B A; Xiang, W; Yakushev, E; Yaver, H; Young, A R; Yu, C -H; Yumatov, V; Zhang, C; Zimmerman, S

    2010-01-01

    The MAJORANA Collaboration is building the MAJORANA DEMONSTRATOR, a 60 kg array of high purity germanium detectors housed in an ultra-low background shield at the Sanford Underground Laboratory in Lead, SD. The MAJORANA DEMONSTRATOR will search for neutrinoless double-beta decay of 76Ge while demonstrating the feasibility of a tonne-scale experiment. It may also carry out a dark matter search in the 1-10 GeV/c^2 mass range. We have found that customized Broad Energy Germanium (BEGe) detectors produced by Canberra have several desirable features for a neutrinoless double-beta decay experiment, including low electronic noise, excellent pulse shape analysis capabilities, and simple fabrication. We have deployed a customized BEGe, the MAJORANA Low-Background BEGe at Kimballton (MALBEK), in a low-background cryostat and shield at the Kimballton Underground Research Facility in Virginia. This paper will focus on the detector characteristics and measurements that can be performed with such a radiation detector in a ...

  9. Focusing of a new germanium counter type : the composite detector. Uses of the TREFLE detector in the EUROGAM multidetector

    The aim of this thesis is the development of new types of germanium detectors: the composite detectors. Two types of prototypes are then conceived: the stacked planar detector (EDP) and the assembly of coaxial diodes (TREFLE). They are designed for the multidetector EUROGAM destined to the research of nuclear structure at high angular momentum. The four planar diodes of EDP detector were of 7 cm diameter and of 15 to 20 mm thick. The difference between the calculated and measured photopic efficiency is observed. The importance of surface channel induces a weak resistance of neutron damages. The sputtering method for the surface treatment reducing the germanium dead layer as well as a rule of selection concerning the impurity concentration and the thickness of crystal is helpful for the later production of germanium detector. The CLOVER detector consist of for mean size crystals in the same cryostat. The photopic efficiency is much larger than that of the greatest monocrystal detector. And the granulation of composite detector allowed the Doppler broadening correction of gamma ray observed in the nuclear reaction where the recoil velocity is very high. This new type of detector enable the linear polarization measurement of gamma ray. Twenty-four CLOVER detector are actually mounted in the EUROGAM array. The characteristics measured in source as well as in beam, reported in this thesis, meet exactly the charge account. (author). 47 refs., 61 figs., 18 tabs

  10. Nanoindentation of ion-implanted crystalline germanium

    Most indentation studies to date on crystalline germanium (c-Ge) and related covalent semiconductors have been carried out on pristine defect-free material. This paper addresses the paucity of studies on imperfect crystalline materials by exploring the impact of defects generated by ion implantation, prior to contact damage, upon the mechanical properties of c-Ge. Implantation with Ge ions is carried out to generate a layer of highly defective but still-crystalline Ge. Under nanoindentation with a sharp diamond tip, enhanced plasticity is observed relative to pristine material. Characterization by cross-sectional transmission electron microscopy, atomic force microscopy, and load curve analysis shows softening, quasiductile extrusion, and cracking suppression taking place. These changes can be explained by the high density of defects, and dangling bonds in particular, created by ion implantation and revealed by positron-annihilation spectroscopy, and are proportional to the fraction of 'missing bonds' or vacancies in the material. A thermal annealing step at 200 deg. C is sufficient to restore the mechanical response of pristine material, despite incomplete recovery of the original pristine crystal structure.

  11. Low background germanium detector technology from Canberra

    Full text: Since Eurisys Mesures and Canberra merged into one company under the wings of Cogema-Areva in February 2001, decades of know-how and experience in building Germanium detectors for low level gamma ray analysis have been brought together. This vast experience means that Canberra can offer a large variety of 'low level detectors' depending on the application. The complexity and cost of these detectors increase with the decreasing detection limits that our customers want to obtain. In this paper we give a short overview of the various categories of 'low level HP Ge detectors' that we produce. We present some examples of detection limits that can be obtained with each of these and we show what measures are taken to come to the next lower limit of detection. The spectroscopist should be aware, however, that the detection limit that can be obtained with a particular source and isotope mix depends in the first place on the choice of the detector element geometry and size, and on the geometry of the cryostat and source. Reference discusses this aspect of the optimum counting conditions. The choice of the shielding and the location of the detector-shield combination (above or below ground level) comes in second place. The precise design and choice of materials for the cryostat -- the subject of this paper -- are generally only the third factor of importance. The simplest low level gamma counting system that we consider in this paper consists of a standard high purity germanium detector in a standard lead shield. The cryostat materials used for these standard detectors are selected mainly for their mechanical properties and cost. Selection of the cryostat materials for their radio-purity comes only in the second place. The contribution of their activities to the background in the spectrum is neglectable since the measuring times are usually limited (typically 1 hour) and the background coming from the room and from the sample is generally higher. Detection limits

  12. Low background Germanium detector technology from Canberra

    Full text: Since Eurisys Mesures and Canberra merged into one company under the wings of Cogema-Areva in February 2001, decades of know-how and experience in building Germanium detectors for low level gamma ray analysis have been brought together. This vast experience means that Canberra can offer a large variety of 'low level detectors' depending on the application. The complexity and cost of these detectors increase with the decreasing detection limits that our customers want to obtain. In this paper we give a short overview of the various categories of 'low level HP Ge detectors' that we produce. We present some examples of detection limits that can be obtained with each of these and we show what measures are taken to come to the next lower limit of detection. The spectroscopist should be aware, however, that the detection limit that can be obtained with a particular source and isotope mix depends in the first place on the choice of the detector element geometry and size, and on the geometry of the cryostat and source. Reference discusses this aspect of the optimum counting conditions. The choice of the shielding and the location of the detector-shield combination (above or below ground level) comes in second place. The precise design and choice of materials for the cryostat - the subject of this paper - are generally only the third factor of importance. The simplest low level gamma counting system that we consider in this paper consists of a standard high purity germanium detector in a standard lead shield. The cryostat materials used for these standard detectors are selected mainly for their mechanical properties and cost. Selection of the cryostat materials for their radio-purity comes only in second place. The contribution of their activities to the background in the spectrum is negligible since the measuring times are usually limited (typically 1 hour) and the background coming from the room and the sample is generally higher. Detection limits that are

  13. Anisotropic Optical Properties of Layered Germanium Sulfide

    Tan, Dezhi; Wang, Feijiu; Mohamed, Nur Baizura; Mouri, Shinichiro; Sandhaya, Koirala; Zhang, Wenjing; Miyauchi, Yuhei; Ohfuchi, Mari; Matsuda, Kazunari

    2016-01-01

    Two-dimensional (2D) layered materials, transition metal dichalcogenides and black phosphorus, have attracted much interest from the viewpoints of fundamental physics and device applications. The establishment of new functionalities in anisotropic layered 2D materials is a challenging but rewarding frontier, owing to their remarkable optical properties and prospects for new devices. Here, we report the anisotropic optical properties of layered 2D monochalcogenide of germanium sulfide (GeS). Three Raman scattering peaks corresponding to the B3g, A1g, and A2g modes with strong polarization dependence are demonstrated in the GeS flakes, which validates polarized Raman spectroscopy as an effective method for identifying the crystal orientation of anisotropic layered GeS. Photoluminescence (PL) is observed with a peak at around 1.66 eV that originates from the direct optical transition in GeS at room temperature. Moreover, determination of the polarization dependent characteristics of the PL and absorption reveals...

  14. Erbium in silicon-germanium quantum wells

    Strained Si1-xGex/Si quantum wells have been doped with erbium by implantation. A comparison is made with strained Si1-xGex/Si quantum wells and relaxed Si1-xGex, with x between 10% and 25%, doped with erbium during MBE growth. The erbium concentration was between 1x1018 and 5x1018 cm-3 throughout the active regions. Transmission electron microscopy, X-ray diffraction, and photoluminescence studies indicate that good regrowth can been achieved after full amorphisation by implantation of the strained quantum wells. The erbium luminescence is more intense in the Si1-xGex/Si layers, but erbium-implanted samples containing Si1-xGex exhibit defect luminescence in the region of 0.9-1.0 eV. These defects are also present when Si1-xGex/Si quantum wells are implanted with an amorphising dose of silicon, and then regrown. They are attributed to small germanium-rich platelets, rather than to erbium-related defects. Electroluminescence is presented from a forward biased erbium-implanted Si0.87Ge0.13/Si structure at a drive current density of only 1.8 mA/cm2. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  15. Development of a low-temperature germanium detector via mechanical cooling with a compact pulse-tube refrigerator

    Koike, T., E-mail: tkoike@lambda.phys.tohoku.ac.jp [Department of Physics, Tohoku University, Sendai 980-7858 (Japan); Chiga, N. [Department of Physics, Tohoku University, Sendai 980-7858 (Japan); Haruyama, T. [Institute of Particle and Nuclear Studies, KEK, Tsukuba 305-0801 (Japan); Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo, Kashiwa 277-8583 (Japan); Hosomi, K. [Department of Physics, Tohoku University, Sendai 980-7858 (Japan); Advance Science Research Center, JAEA, Ibaraki 319-1195 (Japan); Ichinohe, H. [Fuji Electric Co. Ltd., Hino 191-8502 (Japan); Kasami, K. [Institute of Particle and Nuclear Studies, KEK, Tsukuba 305-0801 (Japan); Matsushita, T.; Mizoguchi, Y. [Fuji Electric Co. Ltd., Hino 191-8502 (Japan); Ono, H. [SEIKO EG and G Co. Ltd., Matsudo 270-2222 (Japan); Shirotori, K. [Department of Physics, Tohoku University, Sendai 980-7858 (Japan); Research Center for Nuclear Physics, Ibaraki 567-0047 (Japan); Takeuchi, T. [Fuji Electric Co. Ltd., Hino 191-8502 (Japan); Tamura, H.; Yamamoto, T.O. [Department of Physics, Tohoku University, Sendai 980-7858 (Japan)

    2015-01-11

    We have developed a new germanium (Ge) detector unit for hypernuclear γ-ray spectroscopy at J-PARC, which comprises a new Ge detector array Hyperball-J. A compact pulse-tube refrigerator is coupled to a coaxial Ge detector in order to achieve lower crystal temperatures as a means to increase radiation hardness. The obtained crystal temperature is 72 K, while an energy resolution is maintained at (FWHM) 3.1(1) keV for 1.33 MeV γ rays using a gate-integrated shaping amplifier (ORTEC 973U). Gain shifts with changing crystal temperature are also confirmed for the Ge detector.

  16. Development of a low-temperature germanium detector via mechanical cooling with a compact pulse-tube refrigerator

    We have developed a new germanium (Ge) detector unit for hypernuclear γ-ray spectroscopy at J-PARC, which comprises a new Ge detector array Hyperball-J. A compact pulse-tube refrigerator is coupled to a coaxial Ge detector in order to achieve lower crystal temperatures as a means to increase radiation hardness. The obtained crystal temperature is 72 K, while an energy resolution is maintained at (FWHM) 3.1(1) keV for 1.33 MeV γ rays using a gate-integrated shaping amplifier (ORTEC 973U). Gain shifts with changing crystal temperature are also confirmed for the Ge detector

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

    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

  18. Germanium, Arsenic, and Selenium Abundances in Metal-Poor Stars

    Roederer, Ian U

    2012-01-01

    The elements germanium (Ge, Z=32), arsenic (As, Z=33), and selenium (Se, Z=34) span the transition from charged-particle or explosive synthesis of the iron-group elements to neutron-capture synthesis of heavier elements. Among these three elements, only the chemical evolution of germanium has been studied previously. Here we use archive observations made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope and observations from several ground-based facilities to study the chemical enrichment histories of seven stars with metallicities -2.6 < [Fe/H] < -0.4. We perform a standard abundance analysis of germanium, arsenic, selenium, and several other elements produced by neutron-capture reactions. When combined with previous derivations of germanium abundances in metal-poor stars, our sample reveals an increase in the [Ge/Fe] ratios at higher metallicities. This could mark the onset of the weak s-process contribution to germanium. In contrast, the [As/Fe] and [Se/Fe] ratios rema...

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

    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

  20. Anisotropy of thermal expansion and electric resistance of cermet germanium telluride

    Anisotropies of thermal expansion α and electric resistance ρ of cermet germanium telluride were investigated depending on pressing conditions. It is shown that anisotropy of cermet germanium telluride depends sufficiently on pressing conditions with respect to thermal expansion and electric resistance. It was established that anisotropy of the cermet germanium telluride was strongly affected by pressing force and temperature. Anisotropy of the cermet germanium telluride also depends with respect to α and ρ on the material and size of the mould

  1. Porous structure formation in ion irradiated germanium

    The ion beam induced modification of amorphous germanium is characterised by the formation of voids close to the sample surface and the transformation into a sponge-like porous surface layer at high ion fluences. This extreme structural modification of the sample surface is independent of the (heavy) ion species used and accompanied by a strong volume expansion. Nevertheless, recently it was demonstrated that buried voids (and buried sponge-like layers) can be formed in the depth of the projected ion range, however, only for the irradiation with I-ions at high ion fluences. Thus, the ion species and their chemical properties seem to play an important role in the structural modification around the projected ion range. In this paper we investigate the influence of the ion species on the ion beam induced void formation in Ge for room temperature irradiation with 380 keV I- and Au-ions as a function of the ion fluence. Independent of the ion species, a strong volume expansion is observed caused by void formation and the transformation into a sponge-like porous surface layer. For both ion species used, the final porous layers are structurally identical as established by cross section and plan view electron microscopy investigations. Further ion irradiation of the sponge-like porous structure, however, leads to significant differences in the ion beam induced structural evolution. For the Au-ion irradiation the porous layer remains nearly unchanged, whereas for the irradiation with I-ions a transformation from sponge-like to netlike porous layers occurs which is accompanied again by an extreme volume expansion. The underlying mechanism will be discussed based on chemical properties of the implanted ions

  2. Liquid phase epitaxial growth and characterization of germanium far infrared blocked impurity band detectors

    Bandaru, Jordana

    2001-05-12

    Germanium Blocked Impurity Band (BIB) detectors require a high purity blocking layer (< 10{sup 13} cm{sup -3}) approximately 1 mm thick grown on a heavily doped active layer ({approx} 10{sup 16} cm{sup -3}) approximately 20 mm thick. Epilayers were grown using liquid phase epitaxy (LPE) of germanium out of lead solution. The effects of the crystallographic orientation of the germanium substrate on LPE growth modes were explored. Growth was studied on substrates oriented by Laue x-ray diffraction between 0.02{sup o} and 10{sup o} from the {l_brace}111{r_brace} toward the {l_brace}100{r_brace}. Terrace growth was observed, with increasing terrace height for larger misorientation angles. It was found that the purity of the blocking layer was limited by the presence of phosphorus in the lead solvent. Unintentionally doped Ge layers contained {approx}10{sup 15} cm{sup -3} phosphorus as determined by Hall effect measurements and Photothermal Ionization Spectroscopy (PTIS). Lead purification by vacuum distillation and dilution reduced the phosphorus concentration in the layers to {approx} 10{sup 14} cm{sup -3} but further reduction was not observed with successive distillation runs. The graphite distillation and growth components as an additional phosphorus source cannot be ruled out. Antimony ({approx}10{sup 16} cm{sup -3}) was used as a dopant for the active BIB layer. A reduction in the donor binding energy due to impurity banding was observed by variable temperature Hall effect measurements. A BIB detector fabricated from an Sb-doped Ge layer grown on a pure substrate showed a low energy photoconductive onset ({approx}6 meV). Spreading resistance measurements on doped layers revealed a nonuniform dopant distribution with Sb pile-up at the layer surface, which must be removed by chemomechanical polishing. Sb diffusion into the pure substrate was observed by Secondary Ion Mass Spectroscopy (SIMS) for epilayers grown at 650 C. The Sb concentration at the interface

  3. Liquid phase epitaxial growth and characterization of germanium far infrared blocked impurity band detectors

    Germanium Blocked Impurity Band (BIB) detectors require a high purity blocking layer ( and lt; 10(sup 13) cm(sup -3)) approximately 1 mm thick grown on a heavily doped active layer ((approx) 10(sup 16) cm(sup -3)) approximately 20 mm thick. Epilayers were grown using liquid phase epitaxy (LPE) of germanium out of lead solution. The effects of the crystallographic orientation of the germanium substrate on LPE growth modes were explored. Growth was studied on substrates oriented by Laue x-ray diffraction between 0.02(sup o) and 10(sup o) from the(lbrace)111(rbrace) toward the(lbrace)100(rbrace). Terrace growth was observed, with increasing terrace height for larger misorientation angles. It was found that the purity of the blocking layer was limited by the presence of phosphorus in the lead solvent. Unintentionally doped Ge layers contained(approx)10(sup 15) cm(sup -3) phosphorus as determined by Hall effect measurements and Photothermal Ionization Spectroscopy (PTIS). Lead purification by vacuum distillation and dilution reduced the phosphorus concentration in the layers to(approx) 10(sup 14) cm(sup -3) but further reduction was not observed with successive distillation runs. The graphite distillation and growth components as an additional phosphorus source cannot be ruled out. Antimony ((approx)10(sup 16) cm(sup -3)) was used as a dopant for the active BIB layer. A reduction in the donor binding energy due to impurity banding was observed by variable temperature Hall effect measurements. A BIB detector fabricated from an Sb-doped Ge layer grown on a pure substrate showed a low energy photoconductive onset ((approx)6 meV). Spreading resistance measurements on doped layers revealed a nonuniform dopant distribution with Sb pile-up at the layer surface, which must be removed by chemomechanical polishing. Sb diffusion into the pure substrate was observed by Secondary Ion Mass Spectroscopy (SIMS) for epilayers grown at 650 C. The Sb concentration at the interface dropped

  4. Field emission measured from nanostructured germanium and silicon thin films

    We have prepared nanostructured thin films of germanium and silicon. The films were grown by an ion beam sputtering technique followed by a rapid annealing step using an electron beam annealer. The annealing temperature is a comparatively low 500 deg. C, resulting in well defined nano-islands on the film surface. Electron field emission has been measured from the surfaces under high vacuum. The threshold electric field value for significant current flow was measured as 2.5 V μm-1 for a silicon thin film which is comparable to other silicon technologies. A value of 0.5 V μm-1 for a germanium thin film represents an order of magnitude improvement for related germanium nanostructured systems.

  5. Investigation of the performance of various germanium detectors in a Compton suppression shield

    The performance of four germanium detectors with different geometries inside an escape suppression shield have been investigated. The measurements show that the use of escape suppression shields give an improved detection system. The best results were obtained for the biggest germanium detector used and there is also evidence that detectors with less inactive germanium layers give better results. (U.K.)

  6. Epitaxial growth of group IV materials by chemical vapor deposition for Germanium Metal Oxide Semiconductor devices

    Vincent, Benjamin; Loo, Roger; Caymax, Matty [imec, Kapeldreef 75, B-3001 Leuven (Belgium)

    2011-07-01

    Over the past 5-10 years, germanium has attracted a lot of interest to replace Silicon as a high carrier mobility material in future p-Metal Oxide Semiconductors transistors. This paper reviews developments of epitaxial Group IV materials (silicon, germanium, tin and alloys) by means of Reduced Pressure Chemical Vapor Deposition for use as Channel, Gate stack and Source/Drain in high performance Germanium transistors. We first describe Germanium growth on standard Silicon wafers. Selective epitaxial growth within Shallow Trench Isolation structures allows seamless integration of Germanium channels in Si platform with a significant defect reduction down to levels required for state-of-the-art VLSI technology. Next we focus on the most successful passivation approach for Germanium MOS interfaces by means of ultrathin epitaxial Si capping layers. This moves the problem of gate stack formation from a germanium surface to a silicon surface. We discuss novel extremely low temperature CVD processes involving innovative precursors, and impacts of point defects, strain relaxation and Silicon-Germanium intermixing on Germanium device performance. Finally, the implementation of Germanium-Tin alloys in embedded Source/Drain regions in Germanium transistors is proposed as an innovative architecture to implement strain in Germanium channels.

  7. Formation of non-equilibrium germanium-based solid solutions in al-ge-alloys

    O.Yu. Bereza

    2012-08-01

    Full Text Available This article is devoted to the investigation of phase composition and microstructure of the higher cooled aluminum-germanium alloys. The formation of non-equilibrium germanium solid solutions is shown. The influence of the rate of cooling and the germanium percentage on the phase composition of alloys is shown.

  8. Atomic ionization of germanium due to neutrino magnetic moments

    Chen, Jiunn-Wei; Huang, Keh-Ning; Liu, C -P; Shiao, Hao-Tse; Singh, Lakhwinder; Wong, Henry T; Wu, Chih-Liang; Wu, Chih-Pan

    2013-01-01

    An ab initio calculation of atomic ionization of germanium (Ge) by neutrinos was carried out in the framework of multiconfiguration relativistic random phase approximation. The main goal is to provide a more accurate cross section formula than the conventional one, which is based on the free electron approximation, for searches of neutrino magnetic moments with Ge detectors whose threshold is reaching down to the sub-keV regime. Limits derived with both methods are compared, using reactor neutrino data taken with low threshold germanium detectors.

  9. Phase transformations in two-layer germanium-tellurium condensates

    Investigation results of phase transformations, occuring in thin two-layer films germanium-tellurium with bilayer thickness of 20-30 up to 70-80 mm are presented. Two-layer films were produced by vacuum precipitation. Amorphous germanium and polycrystalline tellurium layer is detected in the initial films. Condensate warm-up by the electron beam leads to formation of a homogeneous amorphous GeTe film. It is ascertained, that the free energy of the formed compound film is lower than the free energy of thetw-layer condensate, i.e. condensate amorphization appears to be an energetically bemfitial process

  10. Ionization Efficiency Study for Low Energy Nuclear Recoils in Germanium

    Barker, D; Mei, D -M; Zhang, C

    2013-01-01

    We used the internal conversion ($E_0$ transition) of germanium-72 to indirectly measure the low energy nuclear recoils of germanium. Together with a reliable Monte Carlo package, in which we implement the internal conversion process, the data was compared to the Lindhard ($k$=0.159) and Barker-Mei models. A shape analysis indicates that both models agree well with data in the region of interest within 4%. The most probable value (MPV) of the nuclear recoils obtained from the shape analysis is 17.5 keV with an average path-length of 0.014 $\\mu$m.

  11. The GALATEA test-facility for High Purity Germanium Detectors

    Abt, I; Doenmez, B; Garbini, L; Irlbeck, S; Majorovits, B; Palermo, M; Schulz, O; Seitz, H; Stelzer, F

    2014-01-01

    GALATEA is a test facility designed to investigate bulk and surface effects in high purity germanium detectors. A vacuum tank houses an infrared screened volume with a cooled detector inside. A system of three 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 as well as of a laser beam to study surface effects. A 19-fold segmented true-coaxial germanium detector was used for commissioning.

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

    Abt, I.; Caldwell, A.; Dönmez, B.; Garbini, L.; Irlbeck, S.; Majorovits, B.; Palermo, M., E-mail: palermo@mpp.mpg.de; Schulz, O.; Seitz, H.; Stelzer, F.

    2015-05-11

    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.

  13. Program LEPS to addition of gamma spectra from germanium detectors

    The LEP program, written in FORTRAN IV, performs the addition of two spectra, collected with different detectors, from the same sample. This application, adds the two gamma spectra obtained from two opposite LEPS Germanium Detectors (Low Energy Photon Spectrometer), correcting the differences (channel/energy) between both two spectra, and fitting them before adding. The total-spectrum is recorded at the computer memory as a single spectrum. The necessary equipment, to run this program is: - Two opposite germanium detectors, with their associate electronics. - Multichannel analyzer (2048 memory channel minimum) - Computer on-line interfacing to multichannel analyzer. (Author) 4 refs

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

    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).

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

    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.

  16. AGATA - Advanced GAmma Tracking Array

    The Advanced GAmma Tracking Array (AGATA) is a European project to develop and operate the next generation γ-ray spectrometer. AGATA is based on the technique of γ-ray energy tracking in electrically segmented high-purity germanium crystals. This technique requires the accurate determination of the energy, time and position of every interaction as a γ ray deposits its energy within the detector volume. Reconstruction of the full interaction path results in a detector with very high efficiency and excellent spectral response. The realisation of γ-ray tracking and AGATA is a result of many technical advances. These include the development of encapsulated highly segmented germanium detectors assembled in a triple cluster detector cryostat, an electronics system with fast digital sampling and a data acquisition system to process the data at a high rate. The full characterisation of the crystals was measured and compared with detector-response simulations. This enabled pulse-shape analysis algorithms, to extract energy, time and position, to be employed. In addition, tracking algorithms for event reconstruction were developed. The first phase of AGATA is now complete and operational in its first physics campaign. In the future AGATA will be moved between laboratories in Europe and operated in a series of campaigns to take advantage of the different beams and facilities available to maximise its science output. The paper reviews all the achievements made in the AGATA project including all the necessary infrastructure to operate and support the spectrometer.

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

    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

  18. Direct observations of the vacancy and its annealing in germanium

    Slotte, J.; Kilpeläinen, S.; Tuomisto, F.;

    2011-01-01

    K. This is identified as the positron lifetime in a germanium monovacancy. Annealing experiments in the temperature interval 35–300 K reveal two annealing stages. The first at 100 K is tentatively associated with the annealing of the Frenkel pair, the second at 200 K with the annealing of the...

  19. Chemical Route for Si/C Coated Germanium Nanowires

    Dřínek, Vladislav; Šubrt, Jan; Klementová, Mariana; Fajgar, Radek

    2010-01-01

    Roč. 89, č. 2 (2010), s. 255-260. ISSN 0165-2370 R&D Projects: GA ČR GA203/09/1088 Institutional research plan: CEZ:AV0Z40720504; CEZ:AV0Z40320502 Keywords : nanowire * germanium * germylene Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.234, year: 2010

  20. Photomask technique for fabricating high purity germanium strip detectors

    A new technology for germanium strip detectors has been developed. This technique uses a photomask process which needs no growing and etching and allows all kinds of segmented electrodes. Typically we have obtained 1.2 keV FWHM on the 122 keV line of 57Co and a X-Y detector having 20 strips in each side. (orig.)

  1. Development of revitalisation technique for impaired lithium doped germanium detector

    Semiconductor detectors play very significant role in photon detection and are important tools in the field of gamma spectroscopy. Lithium doped germanium detectors belong to this category. The development of revitalisation technique for these impaired detectors are discussed in this report

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

    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

  3. Composite germanium monochromators - results for the TriCS

    Schefer, J.; Fischer, S.; Boehm, M.; Keller, L.; Horisberger, M.; Medarde, M.; Fischer, P. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    Composite germanium monochromators are in the beginning of their application in neutron diffraction. We show here the importance of the permanent quality control with neutrons on the example of the 311 wafers which will be used on the single crystal diffractometer TriCS at SINQ. (author) 2 figs., 3 refs.

  4. Discovery of Gallium, Germanium, Lutetium, and Hafnium Isotopes

    J.L. Gross; Thoennessen, M

    2011-01-01

    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 discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

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

    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.

  6. The nitrogen pair in silicon and germanium microstructure and interaction

    The objective of the present work has been to study the microstructure of nitrogen defects in silicon and germanium, especially the nitrogen pair defect which is the dominant nitrogen defect in both materials. The interaction of nitrogen with other impurities as oxygen, boron and phosphorus have also been studied. A number of different experimental techniques have been used especially ion channeling and Fourier Transformation Infra-Red absorption spectroscopy. Although several references to theory are given, this thesis is concerned with the experimental investigations carried out on nitrogen in silicon and germanium. Monocrystals implanted by nitrogen contained typically 6,5x1019 cm-3. After implantation the samples were annealed at 700 deg. C in order to produce the expected nitrogen defects. The structure of nitrogen pair in silicon and germanium by channeling measurements and infrared absorption has been studied. A new model of the pair defect has been proposed. Uniaxial stress on the nitrogen pair in silicon and germanium has been analyzed. A direct theoretical prediction within the antiparallel model regarding the splitting under [001] stress is confirmed experimentally. (EG) 38 refs

  7. Characteristics of germanium thin film thermometers at low temperatures

    Germanium thin films as resistance thermometers have been tested at liquid helium temperature. Germanium is deposited in vacuum on insulated substrates and then silver onto the germanium films as ohmic contacts. The thermometers with desired resistances and suitable sensitivities can be easily fabricated by choosing proper deposition conditions. The purpose of this work is to develop a thermometer with a fast response time for heat transfer experiments in liquid helium. The characteristics of a typical thermometer are as follows. The film resistance can be expressed as a function of temperature by a simple correlation, log R=C+m log T, between 4.2K and 20K. The sensitivity is approximately 20Ω/K. After 50 thermal cyclings, the increase rate of the resistance at liquid helium temperature is within 0,8%. An estimated heat capacity of the film is 2x10-8 J/K, and a thermal relaxation time is of the order of 10-12 s at 4.2K. These results prove that the germanium thin film thermometers are promising to measure transient surface temperature near 4.2K. A stainless steel foil with the thermometers is heated by a direct current in a liquid helium bath, and the surface temperature of the foil are measured. Large temperature fluctuations due to occasional liquid solid contacts are observed. (author)

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

    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

  9. Plasmonic Nanoslit Array Enhanced Metal-Semiconductor-Metal Optical Detectors

    Eryilmaz, Sukru Burc; Okyay, Ali K

    2014-01-01

    Metallic nanoslit arrays integrated on germanium metal-semiconductor-metal photodetectors show many folds of absorption enhancement for transverse-magnetic polarization in the telecommunication C-band. Such high enhancement is attributed to resonant interference of surface plasmon modes at the metal-semiconductor interface. Horizontal surface plasmon modes were reported earlier to inhibit photodetector performance. We computationally show, however, that horizontal modes enhance the efficiency of surface devices despite reducing transmitted light in the far field.

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

    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

  11. Titania-germanium nanocomposite for photo-thermo-electric application

    The introduction of germanium (Ge) into titania (TiO2) creates an attractive semiconductor. The new semiconductor is named titania-germanium (TiO2-Ge). Ge dots are dispersed in the distorted TiO2 matrix of TiO2-Ge. The quantum Bohr radius of Ge is 24.3 nm, and hence the properties of the Ge dot can be varied by tailoring its size if it is smaller than its Bohr radius due to the quantum confinement effect (QCE). Therefore, simply by changing the Ge concentration, the morphology of TiO2-Ge can be varied within a wide range. Consequently, the optical, electronic and thermal properties of TiO2-Ge can be tailored. TiO2-Ge becomes a promising material for the next generation of photovoltaics as well as thermoelectric devices. It could also be used for photo-thermo-electric applications

  12. Mechanically-cooled germanium detector using two stirling refrigerators

    In this paper, we present a developed mechanically-cooled germanium gamma-ray detector using Stirling refrigerators. Two Stirling refrigerators having cooling faculty of 1.5W at 80K were used to cool down a germanium detector element to 77K instead of a dewar containing liquid nitrogen. An 145cm3 (56.0mmf x 59.1 mml) closed-end Ge(I) detector having relative detection efficiency of 29.4% was attached at the refrigerators. The size of the detector was 60cml x 15cmh x 15cmw. The lowest cooling temperature, 70K was obtained after 8 hours operation. The energy resolutions for 1.33MeV gamma-rays and for pulser signals were 2.43keV and 1.84keV at an amplifier shaping time of 2μsec, respectively

  13. Limits on dark matter from the St. Gotthard germanium detector

    A search for the presence of galactic cold dark matter has been performed using a single 140 cm3 (0.7 kg) germanium crystal. A low background germanium detectors installed in the St. Gotthard tunnel for the purpose of studying 76Ge double beta decay may serve as a sensitive detector for cold galactic dark matter. It is assumed that the dark matter consists of heavy Dirac neutrinos. A low detection threshold of 1.5 keV has been achieved, making the detector sensitive to Dirac neutrinos with masses above 12 GeV and a halo density of 0.30 GeV cm-3 at Earth. (R.P.) 5 refs.; 2 figs

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

    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.

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

    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 (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

  16. Diffusion of n-type dopants in germanium

    Chroneos, A., E-mail: alexander.chroneos@imperial.ac.uk [Engineering and Innovation, The Open University, Milton Keynes MK7 6AA (United Kingdom); Department of Materials, Imperial College, London SW7 2AZ (United Kingdom); Bracht, H., E-mail: bracht@uni-muenster.de [Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Strasse 10, D-48149 Münster (Germany)

    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.

  17. Diffusion of n-type dopants in germanium

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

  18. Hole mobility in germanium irradiated with large fluences of fast neutrons

    The Hall mobility of holes in germanium irradiated with large fluences of fast neutrons 1014 cm-219 cm-2 is studied over a wide range of temperature 7 K14 cm-3RD17 cm-3. After irradiation the original samples became p-type, low-resistance samples. Electrical properties of neutron irradiated germanium are determined by acceptor-like radiation defects with energy levels of EV+0.016 eV. It is found that at temperatures above 100 K the hole mobility in neutron irradiated germanium and in germanium doped by gallium changes with temperature by general laws, and their values are comparable. The main scattering mechanisms inherent to homogeneous doped crystalline semiconductors are established also in neutron irradiated germanium. The results give rise to conclude that germanium irradiated with large fluences of fast neutrons can be assumed as crystalline with a homogeneous radiation defect distribution. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

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

    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.

  20. Synthesis and characterization of Germanium quantum dots for thermoelectric applications

    Hojabri, arash

    2015-01-01

    Energy resources are a main factor for the development of industry and human life, however, the use of fusil fuels as energy is harmful to the environment. Taking these two matters into consideration, the use of waste energy is a good response. The thermoelectric phenomena, which was, discovered in the 18th century plays a main role in converting waste heat energy to electricity and vice-versa. Germanium quantum dots (Ge QDs) have received special attention due to their unusual electrical and...

  1. Impacts of Atomistic Coating on Thermal Conductivity of Germanium Nanowires

    Chen, Jie; Zhang, Gang; Li, Baowen

    2012-01-01

    By using non-equilibrium molecular dynamics simulations, we demonstrated that thermal conductivity of Germanium nanowires can be reduced more than 25% at room temperature by atomistic coating. There is a critical coating thickness beyond which thermal conductivity of the coated nanowire is larger than that of the host nanowire. The diameter dependent critical coating thickness and minimum thermal conductivity are explored. Moreover, we found that interface roughness can induce further reducti...

  2. Environmental applications for an intrinsic germanium well detector

    The overall performance of an intrinsic germanium well detector for 125I measurements was investigated in a program of environmental surveillance. Concentrations of 125I and 131I were determined in thyroids of road-killed deer showing the highest activities of 125I 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

  3. Diffusion of tin in germanium: A GGA+U approach

    Tahini, H. A.

    2011-10-18

    Density functional theory calculations are used to investigate the formation and diffusion of tin-vacancy pairs (SnV) in germanium(Ge). Depending upon the Fermi energy, SnV pairs can form in neutral, singly negative, or doubly negative charged states. The activation energies of diffusion, also as function of the Fermi energy, are calculated to lie between 2.48-3.65 eV, in agreement with and providing an interpretation of available experimental work.

  4. Growth rate and crystal habit of germanium telluride

    Controlling steps of GeTe crystal growth under different experimental conditions were determined. Diffusion coefficient of GeTe molecules in argon was found, and condensation coefficient was evaluated. Influence of mass transfer rate in a gas on crystal habit was studied: crystals have round faces at low rates and dendritic growth is observed at high rates. Optimal conditions of growing edged crystals of germanium telluride of α-3 mm size were determined

  5. Strain-induced changes to the electronic structure of germanium

    Tahini, H. A.

    2012-04-17

    Density functional theory calculations (DFT) are used to investigate the strain-induced changes to the electronic structure of biaxially strained (parallel to the (001), (110) and (111) planes) and uniaxially strained (along the [001], [110] and [111] directions) germanium (Ge). It is calculated that a moderate uniaxial strain parallel to the [111] direction can efficiently transform Ge to a direct bandgap material with a bandgap energy useful for technological applications. © 2012 IOP Publishing Ltd.

  6. Average resonance parameters of germanium and selenium nuclei

    Full sets of average resonance parameters S0, S1, R0', R1', S1,3/2 for germanium and selenium nuclei with natural isotope content are determined. Parameters are received from the analysis of experimental neutron elastic scattering cross sections at energy region up to 440 keV with the help of the method developed by the authors. The analysis of recommended parameters and some literature data is fulfilled as well.

  7. HEROICA: an Underground Facility for the Fast Screening of Germanium Detectors

    Andreotti, E.; Garfagnini, A.; Maneschg, W.; Barros, N.; Benato, G.; Brugnera, R.; Costa, F.; Falkenstein, R.; Guthikonda, K.; A. Hegai; Hemmer, S.(Dipartimento di Fisica e Astronomia dell‘Università di Padova, Padua, Italy); Hult, M.; Jaenner, K.; Kihm, T.; Lehnert, B.

    2013-01-01

    An infrastructure to characterize germanium detectors has been designed and constructed at the HADES Underground Research Laboratory, located in Mol (Belgium). Thanks to the 223m 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 sp...

  8. Monte Carlo simulation of the X-ray response of a germanium microstrip detector with energy and position resolution

    Rossi, G; Fajardo, P; Morse, J

    1999-01-01

    We present Monte Carlo computer simulations of the X-ray response of a micro-strip germanium detector over the energy range 30-100 keV. The detector consists of a linear array of lithographically defined 150 mu m wide strips on a high purity monolithic germanium crystal of 6 mm thickness. The simulation code is divided into two parts. We first consider a 10 mu m wide X-ray beam striking the detector surface at normal incidence and compute the interaction processes possible for each photon. Photon scattering and absorption inside the detector crystal are simulated using the EGS4 code with the LSCAT extension for low energies. A history of events is created of the deposited energies which is read by the second part of the code which computes the energy histogram for each detector strip. Appropriate algorithms are introduced to account for lateral charge spreading occurring during charge carrier drift to the detector surface, and Fano and preamplifier electronic noise contributions. Computed spectra for differen...

  9. Ion-beam induced structure modifications in amorphous germanium; Ionenstrahlinduzierte Strukturmodifikationen in amorphem Germanium

    Steinbach, Tobias

    2012-05-03

    Object of the present thesis was the systematic study of ion-beam induced structure modifications in amorphous germanium (a-Ge) layers due to low- (LEI) and high-energetic (SHI) ion irradiation. The LEI irradiation of crystalline Ge (c-Ge) effects because the dominating nuclear scattering of the ions on the solid-state atoms the formation of a homogeneous a-Ge Layer. Directly on the surface for fluences of two orders of magnitude above the amorphization fluence the formation of stable cavities independently on the irradiation conditions was observed. For the first time for the ion-beam induced cavity formation respectively for the steady expansion of the porous layer forming with growing fluence a linear dependence on the energy {epsilon}{sub n} deposed in nuclear processes was detected. Furthermore the formation of buried cavities was observed, which shows a dependence on the type of ions. While in the c-Ge samples in the range of the high electronic energy deposition no radiation defects, cavities, or plastic deformations were observed, the high electronic energy transfer in the 3.1 {mu}m thick pre-amorphized a-Ge surface layers leads to the formation of randomly distributed cavities. Basing on the linear connection between cavity-induced vertical volume expansion and the fluence determined for different energy transfers for the first time a material-specific threshold value of {epsilon}{sub e}{sup HRF}=(10.5{+-}1.0) kev nm{sup -1} was determined, above which the ion-beam induced cavity formation in a-Ge sets on. The anisotropic plastic deformation of th a-Ge layer superposed at inclined SHI irradiation on the cavity formation was very well described by an equation derived from the viscoelastic Maxwell model, but modified under regardment of the experimental results. The positive deformation yields determined thereby exhibit above a threshold value for the ion-beam induced plastic deformation {epsilon}{sub e}{sup S{sub a}}=(12{+-}2) keV nm{sup -1} for the first

  10. Transfer-less flexible and transparent high-κ/metal gate germanium devices on bulk silicon (100)

    Nassar, Joanna M.

    2014-08-01

    Flexible wearable electronics have been of great interest lately for the development of innovative future technology for various interactive applications in the field of consumer electronics and advanced healthcare, offering the promise of low-cost, lightweight, and multifunctionality. In the pursuit of this trend, high mobility channel materials need to be investigated on a flexible platform, for the development of flexible high performance devices. Germanium (Ge) is one of the most attractive alternatives for silicon (Si) for high-speed computational applications, due its higher hole and electron mobility. Thus, in this work we show a cost effective CMOS compatible process for transforming conventional rigid Ge metal oxide semiconductor capacitors (MOSCAPS) into a mechanically flexible and semi-transparent platform. Devices exhibit outstanding bendability with a bending radius of 0.24 cm, and semi-transparency up to 30 %, varying with respect to the diameter size of the release holes array.

  11. Developments in large gamma-ray detector arrays

    Lee, I Y; Vetter, K

    2003-01-01

    Gamma-ray spectroscopy was revolutionized with the introduction of high energy-resolution semiconductor germanium (Ge) detectors in the early 1960s. This led to the large increase in sensitivity realized by today's arrays of Compton-suppressed Ge detectors. A still larger increase in sensitivity is expected by implementing the new concept of tracking. A tracking array consists of highly segmented Ge detectors (that can cover the full 4 pi solid-angle) in which gamma rays will be identified by measuring and tracking every gamma ray interaction. This article reviews the physics motivation for such detectors and the development of the new technologies involved. The concept of tracking is explained using the example of a proposed array called gamma-ray energy tracking array (GRETA).

  12. Array tomography: imaging stained arrays.

    Micheva, Kristina D; O'Rourke, Nancy; Busse, Brad; Smith, Stephen J

    2010-11-01

    Array tomography is a volumetric microscopy method based on physical serial sectioning. Ultrathin sections of a plastic-embedded tissue are cut using an ultramicrotome, bonded in an ordered array to a glass coverslip, stained as desired, and imaged. The resulting two-dimensional image tiles can then be reconstructed computationally into three-dimensional volume images for visualization and quantitative analysis. The minimal thickness of individual sections permits high-quality rapid staining and imaging, whereas the array format allows reliable and convenient section handling, staining, and automated imaging. Also, the physical stability of the arrays permits images to be acquired and registered from repeated cycles of staining, imaging, and stain elution, as well as from imaging using multiple modalities (e.g., fluorescence and electron microscopy). Array tomography makes it possible to visualize and quantify previously inaccessible features of tissue structure and molecular architecture. However, careful preparation of the tissue is essential for successful array tomography; these steps can be time-consuming and require some practice to perfect. In this protocol, tissue arrays are imaged using conventional wide-field fluorescence microscopy. Images can be captured manually or, with the appropriate software and hardware, the process can be automated. PMID:21041399

  13. Array tomography: production of arrays.

    Micheva, Kristina D; O'Rourke, Nancy; Busse, Brad; Smith, Stephen J

    2010-11-01

    Array tomography is a volumetric microscopy method based on physical serial sectioning. Ultrathin sections of a plastic-embedded tissue are cut using an ultramicrotome, bonded in an ordered array to a glass coverslip, stained as desired, and imaged. The resulting two-dimensional image tiles can then be reconstructed computationally into three-dimensional volume images for visualization and quantitative analysis. The minimal thickness of individual sections permits high-quality rapid staining and imaging, whereas the array format allows reliable and convenient section handling, staining, and automated imaging. Also, the physical stability of the arrays permits images to be acquired and registered from repeated cycles of staining, imaging, and stain elution, as well as from imaging using multiple modalities (e.g., fluorescence and electron microscopy). Array tomography makes it possible to visualize and quantify previously inaccessible features of tissue structure and molecular architecture. However, careful preparation of the tissue is essential for successful array tomography; these steps can be time consuming and require some practice to perfect. This protocol describes the sectioning of embedded tissues and the mounting of the serial arrays. The procedures require some familiarity with the techniques used for ultramicrotome sectioning for electron microscopy. PMID:21041397

  14. Dead Layer Measurement in P-type Point Contact Germanium Detectors for the Majorana Demonstrator

    Elia, Sophia; Majorana Collaboration

    2015-10-01

    The Majorana Demonstrator will search for the neutrinoless double beta decay (0 νββ) of the isotope 76Ge. In anticipation of the future large-scale experiments, its goal is to demonstrate a path forward to a background rate of one cnt/(ROI-t-y) in a 4 keV region around the Q-value of the 76Ge 0 νββ . The Majorana Demonstrator consists of an array of high purity germanium detectors arranged in strings. Before installation in the cryostat, each string has been characterized. A vertical scan along the string (Z-scan) using radioactive sources is performed to measure the dead layer of each detector while an azimuthal scan is taken to measure the orientation of the crystal axes, useful for axion physics. Understanding the dead layer of the crystals is crucial to precisely determine the effective mass of the detectors. This poster presents Z-scan measurements and data analysis. The dead layer determination obtained through detailed comparison of simulation and data will be discussed.

  15. Demonstration of Surface Electron Rejection with Interleaved Germanium Detectors for Dark Matter Search

    Agnese, R; Balakishiyeva, D; Thakur, R Basu; Bauer, D A; Borgland, A; Brandt, D; Brink, P L; Bunker, R; Cabrera, B; Caldwell, D O; Cerdeno, D G; Chagani, H; Cherry, M; Cooley, J; Cornell, B; Crewdson, C H; Cushman, P; Daal, M; Di Stefano, P C F; Silva, E Do Couto E; Doughty, T; Esteban, L; Fallows, S; Figueroa-Feliciano, E; Fox, J; Fritts, M; Godfrey, G L; Golwala, S R; Hall, J; Harris, H R; Hasi, J; Hertel, S A; Hines, B A; Hofer, T; Holmgren, D; Hsu, L; Huber, M E; Jastram, A; Kamaev, O; Kara, B; Kelsey, M H; Kenany, S A; Kennedy, A; Kenney, C J; Kiveni, M; Koch, K; Loer, B; Asamar, E Lopez; Mahapatra, R; Mandic, V; Martinez, C; McCarthy, K A; Mirabolfathi, N; Moffatt, R A; Moore, D C; Nadeau, P; Nelson, R H; Novak, L; Page, K; Partridge, R; Pepin, M; Phipps, A; Prasad, K; Pyle, M; Qiu, H; Radpour, R; Rau, W; Redl, P; Reisetter, A; Resch, R W; Ricci, Y; Saab, T; Sadoulet, B; Sander, J; Schmitt, R; Schneck, K; Schnee, R W; Scorza, S; Seitz, D; Serfass, B; Shank, B; Speller, D; Tomada, A; Villano, A N; Welliver, B; Wright, D H; Yellin, S; Yen, J J; Young, B A; Zhang, J

    2013-01-01

    SuperCDMS, a direct search for WIMPs, is currently operating a 9-kg array of cryogenic germanium (Ge) detectors in the Soudan Underground Laboratory. These detectors, known as iZIPs, use ionization and phonon sensors placed symmetrically on both sides of a Ge crystal to measure both charge and athermal phonons from each particle interaction. The information from each event provides excellent discrimination between electron recoils and nuclear recoils, as well as discrimination between events on the detector surface and those in the interior. To demonstrate the surface electron rejection capabilities, two $^{210}$Pb sources were installed facing detectors, producing $\\sim$130 beta decays/hr. In $\\sim$800 live hours, no events leaked into the WIMP signal region in the recoil energy range 8--115 keVr, providing an upper limit to the surface event leakage fraction of $1.7 \\times 10^{-5}$ at 90% C.L. This rejection factor demonstrates that surface electrons would produce $< 0.6$ event background in the 0.3 ton-...

  16. A micro-strip germanium detector for position sensitive X-ray spectroscopy

    For the current X-ray spectroscopy program at the ESR storage ring (GSI-Darmstadt) a position sensitive germanium detector system has been completed. The position sensitive structure of the detector has been realized on an area of 47 mm x 23.4 mm by an array of 200 strips (200 μm wide and 23.4 mm long) separated by 35 μm wide grooves etched through boron implanted contact. The thickness of the detector inclusive a 0.6 mm thick Li-diffused rear contact amounts to 4.1 mm. Each strip has been joined to a preamplifier placed outside the cryostat with printed leads inside the flexible Kapton foil. The energy resolution of the strips has been about 1.8 keV [FWHM] for 60 keV photons. Coincidences between neighbouring strips were measured whereby a time resolution of 70 ns [FWHM] was obtained. First preliminary results obtained with the detector mounted at the transmission X-ray spectrometer FOCAL demonstrated that an energy resolution better than 100 eV is achievable together with a high detection efficiency. Along with a new kind of X-ray spectrometer this detector may play a keyrole for the next step of high precision X-ray experiments, aiming on a precise test of quantum electrodynamics in the heaviest one-electron systems such as hydrogenlike uranium. (orig.)

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

    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.

  18. DFT normal coordinate analysis of the vibrational spectra of iron and germanium corroles

    Zakharieva, O.; Veeger, C.

    2005-01-01

    DFT calculations on the vibrational modes of [FeCl(OECorr)], [FeCl(TPCorr)], [FeC6H5(OECorr)] and the corresponding germanium systems, [GeCl(OECorr)], [GeCl(TPCorr)] and [GeC6H 5(OECorr)] are for the first time presented. In addition DFT calculations on the electronic structure of the germanium corr

  19. Electonic properties of hydrogenated amorphous silicon-germanium alloys

    Bullot, J.; Galin, M.; Gauthier, M. (Universite de Paris-Sud, Orsay (France)); Bourdon, B. (CIT-Alcatel Transmission, Marcoussis (France))

    1983-06-01

    The electronic properties of some binary hydrogenated amorphous silicon-germanium alloys a-Sisub(x)Gesub(1-x):H in the silicon rich region (x > 0.6) are investigated. Experimental evidence is presented of photo-induced effects similar to those described in Si:H (Staebler-Wronski effect). The electronic properties are then studied from the dual point of view of the germanium content dependence and of the photo and thermal histories of the films. The dark conductivity changes between the annealed state and the light-soaked state are interpreted in terms of the variation of the temperature coefficient of the Fermi level. The photoconductivity efficiency is shown to remain close to that of a-Si:H for 1 > x >= 0.9 and to strongly decrease when the germanium content is further increased: the photoresponse of the Sisub(0.62)Gesub(0.38) alloy is 10/sup 4/ times smaller than that of a-Si:H. This deterioration of the photoconductive properties is explained in terms of the increase of the density of gap states following Ge substitution. This conclusion is based on the study of the width of the exponential absorption edge and on the results of photoconductivity time response studies. The latter data are interpreted by means of the model of Rose of trapping and recombination kinetics and it is found that for x approximately 0.6 the density of states at 0.4-0.5 eV below the mobility edge is 7 x 10/sup 17/ eV/sup -1/ cm/sup -3/ as compared to 2.4 x 10/sup 16/ eV/sup -1/ cm/sup -3/ for x = 0.97.

  20. Germanium Lift-Off Masks for Thin Metal Film Patterning

    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.

  1. GERDA: a germanium detector array to search for neutrinoless double beta decay

    The GERDA, a new experiment to search for the double beta decay of 76Ge, is being installed at Laboratori Nazionali del Gran Sasso. The potentialities of this experiment as well the status of the project are reviewed

  2. Search for neutrinoless double beta decay of Ge-76 with the GERmanium Detector Array '' GERDA ''

    The study of neutrinoless double beta decay (DBD) is the most powerful approach to the fundamental question if the neutrino is a Majorana particle, i.e. its own anti-particle. The observation of neutrinoless DBD would not only establish the Majorana nature of the neutrino but also represent a determination of its effective mass if the nuclear matrix element is given. So far, the most sensitive results have been obtained with Ge-76, and the group of Klapdor-Kleingrothaus has made a claim of discovery. Future experiments have to reduce radioactive backgrounds to increase the sensitivity. '' GERDA '' is a new double beta-decay experiment which is currently under construction in the INFN Gran Sasso National Laboratory, Italy. It is implementing a new shielding concept by operating bare Ge diodes - enriched in Ge-76 - in high purity liquid argon supplemented by a water shield. The aim of '' GERDA '' is to verify or refute the recent claim of discovery, and, in a second phase, to achieve a two orders of magnitude lower background index than recent experiments, increasing the sensitive mass and reaching exposure of 100 kg yr. It be will discuss design, physics reach, and status of construction of '' GERDA '', and present results from various R efforts including long term stability of bare Ge diodes in cryogenic liquids, material screening, cryostat performance, detector segmentation, cryogenic precision electronics, safety aspects, and Monte Carlo simulations. (author)

  3. Search for Neutrinoless Double Beta Decay of 76Ge with the GERmanium Detector Array "gerda"

    Garfagnini, Alberto

    2011-10-01

    The study of neutrinoless double beta decay (DBD) is the only presently known approach to the fundamental question if the neutrino is a Majorana particle, i.e. its own anti-particle. The observation of neutrinoless DBD would not only establish the Majorana nature of the neutrino but also represent a determination of its effective mass if the nuclear matrix element is given. So far, the most sensitive results have been obtained with 76Ge, and the group of Klapdor-Kleingrothaus has made a claim of discovery. Future experiments have to reduce radioactive backgrounds to increase the sensitivity. GERDA is a new DBD experiment which is currently under construction in the INFN Gran Sasso National Laboratory, Italy. It is implementing a new shielding concept by operating bare Ge diodes - enriched in 76Ge - in high purity liquid argon supplemented by a water shield. The aim of GERDA is to scrutinize the recent claim of discovery, and, in a second phase, to achieve a two orders of magnitude lower background index than recent experiments, increasing the sensitive mass and reaching an exposure of 100 kg yr. The paper will discuss design, physics reach, and status of construction of GERDA.

  4. Ultra-low noise mechanically cooled germanium detector

    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.

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

    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.

  6. Germanium waveguide photodetectors integrated on silicon with MBE

    A near infrared germanium waveguide photodetector for high speed operation is grown monolithically integrated on Si with molecular beam epitaxy (MBE). With a special virtual substrate concept the lattice mismatch between Si and Ge is accommodated. For high speed operation the active device consists of a Ge p-i-n structure with very high-doped contact layers. The challenges on the MBE growth are the abrupt doping transitions over more than 4 orders of magnitudes among p-contact, intrinsic region and the n-contact

  7. Mechanism of Germanium-Induced Perimeter Crystallization of Amorphous Silicon

    Hakim, M. M. A.; Ashburn, P.

    2007-01-01

    We report a study aimed at highlighting the mechanism of a new amorphous silicon crystallization phenomenon that originates from the perimeter of a germanium layer during low-temperature annealing (500°C). Results are reported on doped and undoped amorphous silicon films, with thicknesses in the range 40–200 nm, annealed at a temperature of 500 or 550°C. A comparison is made of crystallization arising from Ge and SiGe layers and the role of damage from a high-dose fluorine implant is investig...

  8. Effect of pressure on arsenic diffusion in germanium

    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

  9. Synthesis and characterization of Germanium quantum dots for thermoelectric applications

    Hojabri, arash

    2015-01-01

    Energy resources are a main factor for the development of industry and human life, however, the use of fusil fuels as energy is harmful to the environment. Taking these two matters into consideration, the use of waste energy is a good response. The thermoelectric phenomena, which was, discovered in the 18th century plays a main role in converting waste heat energy to electricity and vice-versa.  Germanium quantum dots (Ge QDs) have received special attention due to their unusual electrical an...

  10. Role of hydrogen at germanium/dielectric interfaces

    Hydrogen is an indispensable ingredient in integrated-circuit fabrication, since it is used to passivate defects at the Si/SiO2 interface present in every CMOS transistor. Hydrogen will likely play an equally important role for the novel channel materials and dielectrics that are currently being investigated. We show that first-principles calculations can produce fundamental information about the behavior of hydrogen in relevant semiconductors and oxides. We point out the link between the electronic structure of hydrogen and the band-alignment problem, and specifically highlight why hydrogen at interfaces with germanium will exhibit a very different behavior from what is known to happen in silicon

  11. Phonon Quasidiffusion in Cryogenic Dark Matter Search Large Germanium Detectors

    Leman, S W; McCarthy, K A; Pyle, M; Resch, R; Sadoulet, B; Sundqvist, K M; Brink, P L; Cherry, M; Silva, E Do Couto E; Figueroa-Feliciano, E; Mirabolfathi, N; Serfass, B; Tomada, A

    2011-01-01

    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.

  12. Ultra-Low Noise Mechanically Cooled Germanium Detector

    Barton, Paul; Martin, Ryan; Vetter, Kai

    2015-01-01

    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. Low capacitance large volume shaped-field germanium detector

    A large volume (150 cm3) germanium detector with a full- depletion capacitance of only ∼1 pf has been fabricated. The effect of impurity space-charge was utilized to obtain an appropriate electric field distribution in the detector so that carriers are collected on a small area electrode. Detectors based on this principle are capable of very low noise operation and have immediate applications in direct detection dark matter particle experiments. Detector pulse shapes and carrier trapping effects were also examined for possible applications involving higher energy radiations. 9 refs., 10 figs

  14. Recycling effect of germanium on ECR ion source

    Leherissier, P.; Barué, C.; Canet, C; Dubois, M.; Dupuis, M.; Flambard, J.L.; Gaubert, G.; Jardin, P.; Lecesne, N.; Lemagnen, F.; R. LEROY; Pacquet, J.Y.

    2003-01-01

    After running for three weeks with a 76Ge beam provided by the ECR-4 ion source at GANILwe have investigated the recycling effect of an SF6 plasma. The initial beam was produced bythe classical method, using germanium dioxide in our micro-oven and helium as support gas.The overall ionization efficiency was measured and found to be around 3%. Without theoven, and using SF6 instead of helium, the ECR-4 ion source has been able to produce a verystable beam during a two-week period. The intensity...

  15. Cryostat for Ultra-low-energy Threshold Germanium Spectrometers

    Aalseth, Craig E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Bonicalzi, Ricco [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Fast, James E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Hossbach, Todd W. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Orrell, John L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Overman, Cory T. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); VanDevender, Brent A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2013-04-01

    This paper presents progress on the development of a cryostat intended to improve upon the low-energy threshold (below 0.5 keV) of p-type point contact germanium gamma-ray spectrometers. Ultra-low energy thresholds are important in the detection of low-energy nuclear recoils, an event class relevant to both dark matter direct detection and measurement of coherent neutrino-nucleus scattering. The cryostat design, including a thermal and electrical-field model, is presented. A prototype cryostat has been assembled and data acquired to evaluate its vacuum and thermal performance.

  16. Cryostat for Ultra-low-energy Threshold Germanium Spectrometers

    Aalseth, Craig E; Fast, James E; Hossbach, Todd W; Orrell, John L; Overman, Cory T; Vandevender, Brent A

    2012-01-01

    This paper presents progress on the development of a cryostat intended to improve upon the low-energy threshold (below 0.5 keV) of p-type point contact germanium gamma-ray spectrometers. Ultra-low energy thresholds are important in the detection of low-energy nuclear recoils, an event class relevant to both dark matter direct detection and measurement of coherent neutrino-nucleus scattering. The cryostat design, including a thermal and electrical-field model, is given. A prototype cryostat has been assembled and data acquired to evaluate its vacuum and thermal performance.

  17. Silicon-germanium nanostructures for on-chip optical interconnects

    Tsybeskov, L.; Lee, E.K.; Chang, H.Y. [New Jersey Institute of Technology, Department of Electrical and Computer Engineering, Newark, NJ (United States); Lockwood, D.J.; Baribeau, J.M.; Wu, X. [National Research Council, Institute for Microstructural Sciences, Ottawa (Canada); Kamins, T.I. [Hewlett-Packard Laboratories, Information and Quantum Systems Laboratory, Palo Alto, CA (United States)

    2009-06-15

    Silicon-germanium epitaxially grown on silicon in the form of two-dimensional (quantum wells) and three-dimensional (quantum dots) nanostructures exhibits photoluminescence and electroluminescence in the technologically important spectral range of 1.3-1.6 {mu}m. Until recently, the major roadblocks for practical applications of these devices were strong thermal quenching of the luminescence quantum efficiency, and a long carrier radiative lifetime. This paper summarizes recent progress in the understanding of carrier recombination in Si/SiGe nanostructures and presents a potential new route toward CMOS compatible light emitters for on-chip optical interconnects. (orig.)

  18. Point defect engineering strategies to retard phosphorous diffusion in germanium

    Tahini, H. A.

    2013-01-01

    The diffusion of phosphorous in germanium is very fast, requiring point defect engineering strategies to retard it in support of technological application. Density functional theory corroborated with hybrid density functional calculations are used to investigate the influence of the isovalent codopants tin and hafnium in the migration of phosphorous via the vacancy-mediated diffusion process. The migration energy barriers for phosphorous are increased significantly in the presence of oversized isovalent codopants. Therefore, it is proposed that tin and in particular hafnium codoping are efficient point defect engineering strategies to retard phosphorous migration. © the Owner Societies 2013.

  19. Neutronenaktivierung von Germanium : Sensitivitätsstudie und Wirkungsquerschnittsmessung

    Lier, Alisa

    2013-01-01

    Mithilfe einer (n,γ)-Aktivierung von Germanium am Forschungsreaktor TRIGA in Mainz wurde zum einen in Hinblick auf zukünftige Experiment an der NIF eine Sensitivitätsstudie durchgeführt. Zum anderen wurden die thermischen Neutroneneinfangquerschnitte von 74Ge und 76Ge jeweils für den Einfang in den Isomer- und Grundzustand gemessen, um die Abweichungen der Daten von [Hol93] und [Mug06] zu klären. Zusätzlich wurden die Halbwertszeiten der betrachteten radioaktiven Ge-Isotope bestimmt.

  20. HEROICA: an Underground Facility for the Fast Screening of Germanium Detectors

    Andreotti, E; Maneschg, W; Barros, N; Benato, G; Brugnera, R; Costa, F; Falkenstein, R; Guthikonda, K K; Hegai, A; Hemmer, S; Hult, M; Jaenner, 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

    2013-01-01

    An infrastructure to characterize germanium detectors has been designed and constructed at the HADES Underground Research Laboratory, located in Mol (Belgium). Thanks to the 223m 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 30km from the underground test site. Therefore, HADES is used both for storage of the crystals over night...

  1. Femtosecond Laser Processing of Germanium: An Ab Initio Molecular Dynamics Study

    Ji, Pengfei

    2016-01-01

    An ab initio molecular dynamics study of femtosecond laser processing of germanium is presented in this paper. The method based on the finite temperature density functional theory is adopted to probe the structural change, thermal motion of the atoms, dynamic property of the velocity autocorrelation, and the vibrational density of states. Starting from a cubic system at room temperature (300 K) containing 64 germanium atoms with an ordered arrangement of 1.132 nm in each dimension, the femtosecond laser processing is simulated by imposing the Nose Hoover thermostat to the electronic subsystem lasting for ~100 fs and continuing with microcanonical ensemble simulation of ~200 fs. The simulation results show solid, liquid and gas phases of germanium under adjusted intensities of the femtosecond laser irradiation. We find the irradiated germanium distinguishes from the usual germanium crystal by analyzing their melting and dynamic properties.

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

    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.

  3. Focusing of a new germanium counter type : the composite detector. Uses of the TREFLE detector in the EUROGAM multidetector; Mise au point d`un nouveau type de compteur germanium: le detecteur composite. Utilisation du detecteur TREFLE dans le multidetecteur EUROGAM

    Han, L.

    1995-05-01

    The aim of this thesis is the development of new types of germanium detectors: the composite detectors. Two types of prototypes are then conceived: the stacked planar detector (EDP) and the assembly of coaxial diodes (TREFLE). They are designed for the multidetector EUROGAM destined to the research of nuclear structure at high angular momentum. The four planar diodes of EDP detector were of 7 cm diameter and of 15 to 20 mm thick. The difference between the calculated and measured photopic efficiency is observed. The importance of surface channel induces a weak resistance of neutron damages. The sputtering method for the surface treatment reducing the germanium dead layer as well as a rule of selection concerning the impurity concentration and the thickness of crystal is helpful for the later production of germanium detector. The CLOVER detector consist of for mean size crystals in the same cryostat. The photopic efficiency is much larger than that of the greatest monocrystal detector. And the granulation of composite detector allowed the Doppler broadening correction of gamma ray observed in the nuclear reaction where the recoil velocity is very high. This new type of detector enable the linear polarization measurement of gamma ray. Twenty-four CLOVER detector are actually mounted in the EUROGAM array. The characteristics measured in source as well as in beam, reported in this thesis, meet exactly the charge account. (author). 47 refs., 61 figs., 18 tabs.

  4. Cost-Efficient Thermophotovoltaic Cells based on Germanium (Kostefficiënte thermofotovoltaïsche cellen gebaseerd op germanium)

    van der Heide, Johan

    2009-01-01

    This thesis describes the realisation of cost-efficient thermophotovolta ic cells based on germanium substrates. Because the majority of the incoming phot ons will have a long wavelength it is important to apply optical confinement on the TPV cell. In this thesis this has been done by using a highly reflective rear contact. Electrical contact has been created at the rear with a laser (LFC) such that the metal is locally heated and contact is formed at the rear of the cel l. This applicat...

  5. Germanium-76 Isotope Separation by Cryogenic Distillation. Final Report

    The current separation method for Germanium isotopes is electromagnetic separation using Calutrons. The Calutrons have the disadvantage of having a low separation capacity and a high energy cost to achieve the separation. Our proposed new distillation method has the advantage that larger quantities of Germanium isotopes can be separated at a significantly lower cost and in a much shorter time. After nine months of operating the column that is 1.5 meter in length, no significant separation of the isotopes has been measured. We conclude that the length of the column we have been using is too short. In addition, other packing material than the 0.16 inch Propak, 316 ss Protruded metal packing that we used in the column, should be evaluated which may have a better separation factor than the 0.16 inch Propak, 316 ss Protruded metal packing that has been used. We conclude that a much longer column - a minimum of 50 feet length - should be built and additional column packing should be tested to verify that isotopic separation can be achieved by cryogenic distillation. Even a longer column than 50 feet would be desirable.

  6. Performance of a Small Anode Germanium Well detector

    Adekola, A.S., E-mail: aderemi.adekola@canberra.com; Colaresi, J.; Douwen, J.; Mueller, W.F.; Yocum, K.M.

    2015-06-01

    The performance of Small Anode Germanium (SAGe) Well detector [1] has been evaluated for a range of sample sizes and geometries counted inside the well, on the end cap or in Marinelli beakers. The SAGe Well is a new type of low capacitance germanium well detector manufactured using small anode technology. The detector has similar energy resolution performance to semi-planar detectors, and offers significant improvement over the Coaxial and existing Well detectors. Resolution performance of 0.75 keV Full Width at Half Maxiumum (FWHM) at 122 keV γ-ray energy and resolution of 2.0–2.3 keV FWHM at 1332 keV γ-ray energy are guaranteed. Such outstanding resolution performance will benefit environmental applications in revealing the detailed radionuclide content of samples, particularly at low energy, and will enhance the detection sensitivity resulting in reduced counting time. This paper reports the counting performance of SAGe Well detector for range of sample sizes and geometries and how it compares to other detector types.

  7. Silicon-germanium Single-heterojunction Bipolar Transistor

    G.M. Khanduri

    2006-04-01

    Full Text Available The cutoff frequency performance of an NPN Si/SiGe/SiGe single-heterojunction bipolartransistor (SiGe SHBT at high collector current densities has been analysed using a 2-D MEDICIdevice simulator. A conventional NPN Si/SiGe/Si double-heterojunction bipolar transistor(SiGe DHBT having uniform 20 atomic per cent of germanium in the base region has beeninvestigated for comparison. The analysis shows the formation of a retarding potential barrierfor minority carrier electrons at the base-collector heterojunction of the DHBT structure. Whereas,the base-collector homojunction of the SiGe SHBT structure, having a uniform 15 atomic percent of germanium profile in its base and collector, inhibits the formation of such a retardingpotential barrier, the SHBT structure with a base-collector homojunction shows an improvedcutoff frequency at high collector current density in comparison with conventional SiGe DHBT,which makes it more promising for high speed, scaled down, field-specific applications.

  8. Evaluating a new segmented germanium detector contact technology

    Jackson, E. G.; Lister, C. J.; Chowdhury, P.; Hull, E.; Pehl, R.

    2012-10-01

    New technologies for making gamma ray detectors position sensitive have many applications in space science, medical imaging, homeland security, and in nuclear structure research. One promising approach uses high-purity germanium wafers with the planar surfaces segmented into orthogonal strip patterns forming a Double-Sided Strip Detector (DSSD). The combination of data from adjoining strips, or pixels, is physics-rich for Compton image formation and polarization studies. However, sensitivity to charge loss and various kinds of cross-talk [1] have limited the usefulness of first generation devices. We are investigating new contact technologies, developed by PhDs Co [2], based on amorphous-germanium and yttrium contacts RF sputter deposited to a thickness of ˜ 1000 å. New techniques allow both physical and photolithographic segmentation of the contacts with inter-strip gap widths of 0.25 mm. These modifications should improve all aspects of charge collection. The new detector technology employs the same material and fabrication technique for both the n- and p- contacts, thus removing artificial asymmetry in the data. Results from tests of cross-talk, charge collection, and scattering asymmetry will be presented and compared with older technologies. This mechanically cooled counter, NP-7, seems to represent a breakthrough.[4pt] [1] S. Gros et al., Nucl. Inst. Meth. A 602, 467 (2009).[0pt] [2] E. Hull et al Nucl Inst Meth A 626, 39 (2011)

  9. Materials and Fabrication Issues for Large Machined Germanium Immersion Gratings

    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.

  10. Advances in fractal germanium micro/nanoclusters induced by gold: microstructures and properties.

    Chen, Zhiwen; Shek, Chan-Hung; Wu, C M Lawrence; Lai, Joseph K L

    2014-02-01

    Germanium materials are a class of unique semiconductor materials with widespread technological applications because of their valuable semiconducting, electrical, optical, and thermoelectric power properties in the fields of macro/mesoscopic materials and micro/nanodevices. In this review, we describe the efforts toward understanding the microstructures and various properties of the fractal germanium micro/nanoclusters induced by gold prepared by high vacuum thermal evaporation techniques, highlighting contributions from our laboratory. First, we present the integer and non-integer dimensional germanium micro/nanoclusters such as nanoparticles, nanorings, and nanofractals induced by gold and annealing. In particular, the nonlinear electrical behavior of a gold/germanium bilayer film with the interesting nanofractal is discussed in detail. In addition, the third-order optical nonlinearities of the fractal germanium nanocrystals embedded in gold matrix will be summarized by using the sensitive and reliable Z-scan techniques aimed to determine the nonlinear absorption coefficient and nonlinear refractive index. Finally, we emphasize the thermoelectric power properties of the gold/germanium bilayer films. The thermoelectric power measurement is considered to be a more effective method than the conductivity for investigating superlocalization in a percolating system. This research may provide a novel insight to modulate their competent performance and promote rational design of micro/nanodevices. Once mastered, germanium thin films with a variety of fascinating micro/nanoclusters will offer vast and unforeseen opportunities in the semiconductor industry as well as in other fields of science and technology. PMID:24749428

  11. Germanium ion implantation to Improve Crystallinity during Solid Phase Epitaxy and the effect of AMU Contamination

    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 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

  12. Discrimination of nuclear and electronic recoil events using plasma effect in germanium detectors

    Wei, W -Z; Mei, D -M

    2016-01-01

    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.

  13. The development of novel analytical methods for the determination of germanium in foodstuffs

    McMahon, Michael

    2006-01-01

    This work represents the development of novel methods of analysis for a wide range of metals, in particular germanium. This research has identified a range of foodstuffs and supplements containing low level concentrations o f germanium. In total germanium was quantified in 28 samples including vegetables such as beetroot (3 23/g)> garlic (2 78^ig/g) and potato (1 85|ng/g) and tablet formulations such as aloe vera tablet (20 83 jug/g), ginger tablet (9 96^g/g) and ginseng tablet (5 48|j.g/g). ...

  14. Analysis of Silicon Germanium Standards for the Quantification of SiGe Microelectronic Devices using AES

    Watts, JF; Mallinson, CF; Littlejohns, CG; Gardes, FY; Castle, JE

    2015-01-01

    Four samples of well-defined silicon-germanium alloys were used as standards for calibration purposes to allow accurate quantification of silicon-germanium-on-insulator (SGOI) microelectronic devices using Auger electron spectroscopy. Narrow Si KLL and the Ge LMM, high resolution Si KL_2,3L_2,3 and Ge L_3M_4,5M_4,5 together with survey spectra were collected and are presented from each sample. A matrix effect was observed for silicon in germanium and calculated as 0.85 and 0.95 for the Ge77.5...

  15. Features of Stress State of Germanium Nanocrystals in SiOx Matrix

    V.V. Kuryliuk

    2015-03-01

    Full Text Available Features of mechanical stress in germanium nanocrystals synthesised in amorphous SiОx matrix with SixNy buffer layer were studied by means of Fourier transform infrared absorption spectroscopy, Raman scattering and computer modeling. It was found that the germanium nanocrystals are under significant compressive stress with a magnitude of up to 2.9 GPa. Such a high strain value can be explained by a partial penetration of the nanocrystals in the silicon substrate. In this case the principal source of mechanical stress is the lattice mismatch between silicon and germanium.

  16. Muonium in ultra-pure and Si-doped germanium

    The influence of the isoelectronic impurity silicon ([Si] = 1012 - 1018 cm-3) on the spin precession signals of positive muons in ultra-pure germanium crystals is investigated between 5 and 340 K in transverse magnetic fields of 0.5 to 27.5 mT. Normal ('isotropic') muonium atoms Mu are formed in all samples with about the same probability (approx. 0.7). Down to quite low temperatures (20 K) Mu is found to diffuse very rapidly through the Ge matrix and to become ionized by interaction with the Si atoms. Another ionization process, presumably due to the screening of the μ+ by the increasing number of free charge carriers, sets in at about 180 K. (Auth.)

  17. Optimization of the geometry of broad energy germanium detectors

    Broad energy germanium (BEGe) detectors are employed in many different scientific experiments and widely used in industrial applications. A circular contact is implanted on a base of the cylindrical shaped detector. This circular contact is used as a read out electrode and is surrounded by a passivated groove that separates it from the high voltage electrode, which spans over the remaining surface. The size of the read out electrode and the groove geometry are assumed to have a major impact onto the energy resolution, pulse shape discrimination and energy threshold. To quantify the impact of the detectors geometry on its performance, the read out contacts size of two BEGe detectors was modified several times. The geometry of the detector was optimized prior to each reprocessing step through the use of simulations. For each configuration, the detectors performance was analysed through distinct measurements. Some general consideration about analysis tools, simulation libraries and first results of this study are presented in this talk.

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

    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.

  19. Anomalous compression behavior of germanium during phase transformation

    Yan, Xiaozhi [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China); Tan, Dayong [Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China); Guangzhou Institute of Geochemistry, Chinese Academic of Sciences, Guangzhou 510640 (China); Ren, Xiangting [Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China); Yang, Wenge, E-mail: yangwg@hpstar.ac.cn, E-mail: duanweihe@scu.edu.cn [Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China); High Pressure Synergetic Consortium (HPSynC), Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States); He, Duanwei, E-mail: yangwg@hpstar.ac.cn, E-mail: duanweihe@scu.edu.cn [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Institute of Fluid Physics and National Key Laboratory of Shockwave and Detonation Physic, China Academy of Engineering Physics, Mianyang 621900 (China); Mao, Ho-Kwang [Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China); High Pressure Synergetic Consortium (HPSynC), Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States); Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015 (United States)

    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.

  20. Anomalous compression behavior of germanium during phase transformation

    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. Submicron fabrication by local anodic oxidation of germanium thin films

    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.

  2. Specific features of phase transformations in germanium monotelluride

    Phase transformations in germanium monotelluride are studied . using DRON-0.5 and DRON-1 plants with high-temperature chamber GPVT-1500 at Cu, Ksub(α) radiation. It is shown that in the whole homogeneity range α GeTe is a metastable phase which is formed under the conditions of fast cooling of alloy from temperatures >=Tsub(cub) (temperature of transition in cubic crystal system). An equilibrium γ-phase is obtained by annealing of dispersed powders and metal-ceramic specimens of alloys with 50.3; 50.6; 50.9 at % Te. Lattice parameters of rhombic γ-phase do not depend on tellurium content in initial α- phase. α→γ transformation is observed at any temperature less than Tsub(cub) with the change of alloy composition, namely tellurium precipitation. γ-phase transforms into β at higher temperatures than α-phase

  3. Core and valence thermal vibrations in diamond, silicon, and germanium

    Saravanan, R. (School of Physics, Madurai Kamaraj Univ. (India)); Balamurugan, P. (School of Physics, Madurai Kamaraj Univ. (India)); Mohanlal, S.K. (School of Physics, Madurai Kamaraj Univ. (India))

    1994-08-01

    An analysis is made using published X-ray data, for the thermal vibrations in diamond, silicon, and germanium. The overall thermal vibration is split into core and valence contributions, because valence electrons can oscillate with different phase and amplitude than core electrons due to bond polarizability. Using indigenously developed computer programs the published data are analyzed. In the first phase, the overall Debye-Waller factor of diamond, Si, and Ge together with scaling and extinction factors are refined using the method of least squares. In the second phase, the core and valence contributions of the harmonic temperature factor are evaluated. Finally, in the third phase, the core and valence contributions of the anharmonic temperature factor are evaluated. The error in the fitting procedure is less than 1% for Si and Ge and about 3% for diamond. (orig.)

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

    Neufeld, K.W.; Ruhter, W.D.

    1995-05-01

    We have integrated a small, highly-reliable, electro-mechanical cryo-cooler with a high-resolution germanium detector for portable/field applications. The system weighs 6.8 kg and requires 40 watts of power to operate once the detector is cooled to its operating temperature. the detector is a 500 mm{sup 2} by 20-mm thick low-energy configuration that gives a full-width at half maximum (FWHM) energy resolution of 523 eV at 122 keV, when cooled with liquid nitrogen. The energy resolution of the detector, when cooled with the electro-mechanical cooler, is 570 eV at 122 keV. We have field tested this system in measurements of plutonium and uranium for isotopic and enrichment information using the MGA and MGAU analysis programs without any noticeable effects on the results.

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

    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

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

    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.

  7. Characteristics of GRIFFIN high-purity germanium clover detectors

    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.

  8. Buried Porous Silicon-Germanium Layers in Monocrystalline Silicon Lattices

    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.

  9. Radiation-enhanced self- and boron diffusion in germanium

    Schneider, S.; Bracht, H.; Klug, J.N.;

    2013-01-01

    We report experiments on proton radiation-enhanced self- and boron (B) diffusion in germanium (Ge) for temperatures between 515 ∘ C and 720 ∘ C. Modeling of the experimental diffusion profiles measured by means of secondary ion mass spectrometry is achieved on the basis of the Frenkel pair reaction...... and the interstitialcy and dissociative diffusion mechanisms. The numerical simulations ascertain concentrations of Ge interstitials and B-interstitial pairs that deviate by several orders of magnitude from their thermal equilibrium values. The dominance of self-interstitial related defects under...... irradiation leads to an enhanced self- and B diffusion in Ge. Analysis of the experimental profiles yields data for the diffusion of self-interstitials (I ) and the thermal equilibrium concentration of BI pairs in Ge. The temperature dependence of these quantities provides the migration enthalpy of I and...

  10. Optimization of the geometry of broad energy germanium detectors

    Salathe, Marco [Max Planck Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany)

    2015-07-01

    Broad energy germanium (BEGe) detectors are employed in many different scientific experiments and widely used in industrial applications. A circular contact is implanted on a base of the cylindrical shaped detector. This circular contact is used as a read out electrode and is surrounded by a passivated groove that separates it from the high voltage electrode, which spans over the remaining surface. The size of the read out electrode and the groove geometry are assumed to have a major impact onto the energy resolution, pulse shape discrimination and energy threshold. To quantify the impact of the detectors geometry on its performance, the read out contacts size of two BEGe detectors was modified several times. The geometry of the detector was optimized prior to each reprocessing step through the use of simulations. For each configuration, the detectors performance was analysed through distinct measurements. Some general consideration about analysis tools, simulation libraries and first results of this study are presented in this talk.

  11. Hydrogen concentration and distribution in high-purity germanium crystals

    High-purity germanium crystals used for making nuclear radiation detectors are usually grown in a hydrogen ambient from a melt contained in a high-purity silica crucible. The benefits and problems encountered in using a hydrogen ambient are reviewed. A hydrogen concentration of about 2 x 1015cm-3 has been determined by growing crystals in hydrogen spiked with tritium and counting the tritium β-decays in detectors made from these crystals. Annealing studies show that the hydrogen is strongly bound, either to defects or as H2 with a dissociation energy > 3 eV. This is lowered to 1.8 eV when copper is present. Etching defects in dislocation-free crystals grown in hydrogen have been found by etch stripping to have a density of about 1 x 107 cm-3 and are estimated to contain 108 H atoms each

  12. An aeronomical application of a germanium near infrared (NIR) detector

    A collaboration between Boston University and the Aerospace corporation has resulted in a germanium based detector used in conjunction with an infrared optimized Fabry-Perot spectrometer. Gold plated mirrors were installed and the appropriate transmissive optics are used in the Fabry-Perot to optimize the NIR transmission. The detector is a germanium PIN diode coated with a layer of silicon-nitride. Current produced by the detector is measured by using a Capacitive Trans-Impedance Amplifier (CITA). An A/D converter samples the amplified capacitor voltage and outputs a 12 bit word that is then passed on to the controlling computer system. The detector, amplifier, and associated electronics are mounted inside a standard IR dewar and operated at 77 K. The authors have operated this detector and spectrometer system at Millstone Hill for about 6 months. Acceptable noise characteristics, a NEP of 10-17 watts, and a QE of 90% at 1.2 microm, have been achieved with an amplifier gain of 200. The system is currently configured for observations of thermospheric helium, and has made the first measurement of the He 10,830 angstrom nightglow emission isolated from OH contamination. In an effort to both increase the sensitivity of the Fabry-Perot in the visible and to adapt it for planetary astronomy the authors have entered into a collaboration with CIDTEC. A Charge Injection Detector or CID has some unique capabilities that distinguish it from a CCD and the authors are evaluating it as a detector for the Hadinger fringe pattern produced by a Fabry-Perot. The CID allows non-destructive readout and random access of individual pixels with in the entire frame, this allows for both ''electronic masking'' of bright objects and allows each fringe to be observed without having to readout a large number of dark pixels

  13. Sensitivity comparison of intrinsic germanium detectors with various efficiencies

    Scientists today are being asked to measure concentrations of radionuclides at increasingly lower levels. This creates a demand for better resolution detectors with larger efficiencies that can provide the necessary sensitivity to accurately determine low levels of radioactivity. This study has acquired a large volume of empirical data for a wide range of relative efficiency germanium detectors. The purpose was to determine the sensitivity of various efficiency high-purity (P-type) germanium detectors produced by a single manufacturer. Selecting efficiency as the only variable and essentially all other variables remaining constant narrowed the field of detectors to 30. This investigation compares the response for the lower limit of detection (LLD), figure-of-merit (FOM), and minimum detectable activity (MDA) versus efficiency. In addition to the efficiency, the resolution, background, peak-to-Compton (P/C), and crystal shape of a p-type detector are of particular importance when considering the parameters of a detectors performance. A concise summary of the results is that the detector of choice for low energy measurements would be a 25% detector with resolution better than 1.8 keV FWHM for the 1.332 keV energy of Co-60. The detector of choice for energy levels greater than 500 keV would be a high efficiency low background detector. If the entire energy range is of interest, then a 70% low background detector with a high P/C and a resolution better than 1.9 keV would yield the lowest MDA and assure the most efficient counting times. 9 refs., 25 figs., 6 tabs

  14. A study on the forms of existence of germanium in uranium-bearing coals of Bangmai basin of Yunnan

    The Bangmai basin is an asymmetrical intermontane synclinal basin with a Hercynian-Yenshan granitic body (γ33-γ52) as its basement. Its overlying strata are made up of the N1 of coal-bearing clastic rocks of Neogene period. Germanium ore mostly occur within the N12 coal-seam. Uranium, germanium-bearing coals are mainly lignites of low grade in coalation and belong to semidurain, semiclarain, duroclarain and clarodurain. In order to probe into the forms of existence of germanium in coal, six kinds of analytical methods (electronic probe analysis, separation of heavy liquid, grain-size analysis, electric osmosis, chemical extraction and grade-extraction) have been adopted. A simulated test of humic complex germanium in the laboratory was carried out. According to infrared spectral analysis, it is found that 1700 cm-1 wavecrest almost disappears, 1250 cm-1 peak weakens and 1600 cm-1 peak strengthens, 1400 cm-1 peak slightly strengthens. No doubt, these illustrate the formatiion of humic germanium complex. Afterward, through differential thermal analysis and measurement of pH variation of media, it futher proves the presence of humic germanium complex. It is considered that the forms of existence of germanium in uranium-bearing coals mainly are: (1) In close chemical combination with organic matter, usually in the form of humic germanium complex and germanium organic compound; (2) In the state of adsorption, germanium is adsorbed by some organic matter, clay minerals and limonite etc.; (3) A very rare part occurring as isomorphous form

  15. Contribution of a germanium detector in mobile gamma-ray spectrometry. Spectral analysis and performance

    Gutierrez, S; Bourgeois, C

    2002-01-01

    The sensitivity of the germanium semi-conductor detector is 30 times lower than that of the sodium iodide (NaI) detectors frequently used in airborne spectrometry. Its energy resolution however, is 20 times better, giving more accurate identification of radionuclides, especially when complex spectra are involved. The use of the germanium detector in mobile gamma-ray spectrometry provides a large amount of qualitative and quantitative information. In post-accident situations a germanium detector will be sufficient, and should therefore be used in preference to a NaI detector. An algorithm for detecting the total absorption peaks by studying the variations in the spectral profile of germanium gamma-ray spectra has been developed at the CEA. The use of digital filters that take into account the characteristics of the absorption peaks reduces the statistical fluctuations, making possible detection based on the analysis of the first and second derivatives. The absorption peak is then estimated by subtracting the b...

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

    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.

  17. Thermal recrystallization of physical vapor deposition based germanium thin films on bulk silicon (100)

    Hussain, Aftab M.

    2013-08-16

    We demonstrate a simple, low-cost, and scalable process for obtaining uniform, smooth surfaced, high quality mono-crystalline germanium (100) thin films on silicon (100). The germanium thin films were deposited on a silicon substrate using plasma-assisted sputtering based physical vapor deposition. They were crystallized by annealing at various temperatures ranging from 700 °C to 1100 °C. We report that the best quality germanium thin films are obtained above the melting point of germanium (937 °C), thus offering a method for in-situ Czochralski process. We show well-behaved high-κ /metal gate metal-oxide-semiconductor capacitors (MOSCAPs) using this film. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Methods and software for predicting germanium detector absolute full-energy peak efficiencies

    High-purity germanium (HPGe) and lithium drifted germanium (Ge(Li)) detectors have been the detector of choice for high resolution gamma-ray spectroscopy for many years. This is primarily due to the superior energy resolution that germanium detectors present over other gamma-ray detectors. In order to perform quantitative analyses with germanium detectors, such as activity determination or nuclide identification, one must know the absolute full-energy peak efficiency at the desired gamma-ray energy. Many different methods and computer codes have been developed throughout history in an effort to predict these efficiencies using minimal or no experimental observations. A review of these methods and the computer codes that utilize them is presented. (author)

  19. An Implant-Passivated Blocked Impurity Band Germanium Detector for the Far Infrared Project

    National Aeronautics and Space Administration — We propose to fabricate a germanium blocked-impurity-band (BIB) detector using a novel process which will enable us to: 1- fabricate a suitably-doped active layer...

  20. An Implant-Passivated Blocked Impurity Band Germanium Detector for the Far Infrared Project

    National Aeronautics and Space Administration — We propose to investigate the feasibility of fabricating a germanium blocked-impurity-band (BIB) detector using a novel process which will enable us to: 1-...

  1. Operation of a high purity germanium crystal in liquid argon as a Compton suppressed radiation spectrometer

    Orrell, J L; Amsbaugh, J F; Doe, P J; Hossbach, T W; Orrell, John L.; Aalseth, Craig E.; Amsbaugh, John F.; Doe, Peter J.; Hossbach, Todd W.

    2007-01-01

    A high purity germanium crystal was operated in liquid argon as a Compton suppressed radiation spectrometer. Spectroscopic quality resolution of less than 1% of the full-width half maximum of full energy deposition peaks was demonstrated. The construction of the small apparatus used to obtain these results is reported. The design concept is to use the liquid argon bath to both cool the germanium crystal to operating temperatures and act as a scintillating veto. The scintillation light from the liquid argon can veto cosmic-rays, external primordial radiation, and gamma radiation that does not fully deposit within the germanium crystal. This technique was investigated for its potential impact on ultra-low background gamma-ray spectroscopy. This work is based on a concept initially developed for future germanium-based neutrinoless double-beta decay experiments.

  2. Influence of reductant and germanium concentration on the growth and stress development of germanium nanocrystals in silicon oxide matrix

    Germanium (Ge) nanocrystals have been synthesized by annealing co-sputtered SiO2-Ge samples in N2 or forming gas (90% N2+10% H2) at temperatures ranging from 700 to 1000 deg. C. We concluded that the annealing ambient, temperature and Ge concentration have a significant influence on the formation and evolution of the nanocrystals. We showed that a careful selective etching of the annealed samples in hydrofluoric acid solution enabled the embedded Ge nanocrystals to be liberated from the SiO2 matrix. From the Raman results of the as-grown and the liberated nanocrystals, we established that the nanocrystals generally experienced compressive stress in the oxide matrix and the evolution of these stress states was intimately linked to the distribution, density, size and quality of the Ge nanocrystals

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

    Wang, Dong, E-mail: wang.dong.539@m.kyushu-u.ac.jp; Maekura, Takayuki; Kamezawa, Sho [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580 (Japan); Yamamoto, Keisuke; Nakashima, Hiroshi [Art, Science and Technology Center for Cooperative Research, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580 (Japan)

    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.

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

    Andreotti, Erica [Universität Tübingen, Auf der Morgenstelle 14, 72076 Tübingen (Germany); 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.

  5. Tuning the Electro-optical Properties of Germanium Nanowires by Tensile Strain

    Greil, J.; Lugstein, A.; Zeiner, C.; G STRASSER; Bertagnolli, E.

    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 tem...

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

    Andreotti, Erica; Gerda Collaboration

    2013-08-01

    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.

  7. Germanium isotopic systematics in Ge-rich coal from the Lincang Ge deposit, Yunnan, Southwestern China

    Qi, Hua-wen; Rouxel, Olivier; Hu, Rui-zhong; Bi, Xian-wu; Wen, Han-jie

    2011-01-01

    Organic matter plays an important role in the transport and precipitation of germanium (Ge) in coal-hosted Ge deposits. In this paper. Ge isotopes of coal samples and their combustion products were analyzed in order to investigate the potential use of Ge isotopes as tracers of Ge sources and enrichment mechanisms in coal. Germanium isotopic composition of various samples (mainly Ge-rich lignite) from the Lincang Ge deposit, Yunnan, Southwest China was analyzed using a continuous flow hydride ...

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

    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.

  9. Automation of the Characterization of High Purity Germanium Detectors

    Dugger, Charles ``Chip''

    2014-09-01

    Neutrinoless double beta decay is a rare hypothesized process that may yield valuable insight into the fundamental properties of the neutrino. Currently there are several experiments trying to observe this process, including the Majorana DEMONSTRAOR experiment, which uses high purity germanium (HPGe) detectors to generate and search for these events. Because the event happens internally, it is essential to have the lowest background possible. This is done through passive detector shielding, as well as event discrimination techniques that distinguish between multi-site events characteristic of gamma-radiation, and single-site events characteristic of neutrinoless double beta decay. Before fielding such an experiment, the radiation response of the detectors must be characterized. A robotic arm is being tested for future calibration of HPGe detectors. The arm will hold a source at locations relative to the crystal while data is acquired. Several radioactive sources of varying energy levels will be used to determine the characteristics of the crystal. In this poster, I will present our work with the robot, as well as the characterization of data we took with an underground HPGe detector at the WIPP facility in Carlsbad, NM (2013). Neutrinoless double beta decay is a rare hypothesized process that may yield valuable insight into the fundamental properties of the neutrino. Currently there are several experiments trying to observe this process, including the Majorana DEMONSTRAOR experiment, which uses high purity germanium (HPGe) detectors to generate and search for these events. Because the event happens internally, it is essential to have the lowest background possible. This is done through passive detector shielding, as well as event discrimination techniques that distinguish between multi-site events characteristic of gamma-radiation, and single-site events characteristic of neutrinoless double beta decay. Before fielding such an experiment, the radiation response of

  10. Performance of the Fully Digital FPGA-based Front-End Electronics for the GALILEO Array

    Barrientos, D; Bazzacco, D; Bortolato, D; Cocconi, P; Gadea, A; González, V; Gulmini, M; Isocrate, R; Mengoni, D; Pullia, A; Recchia, F; Rosso, D; Sanchis, E; Toniolo, N; Ur, C A; Valiente-Dobón, J J

    2014-01-01

    In this work we present the architecture and results of a fully digital Front End Electronics (FEE) read out system developed for the GALILEO array. The FEE system, developed in collaboration with the Advanced Gamma Tracking Array (AGATA) collaboration, is composed of three main blocks: preamplifiers, digitizers and preprocessing electronics. The slow control system contains a custom Linux driver, a dynamic library and a server implementing network services. The digital processing of the data from the GALILEO germanium detectors has demonstrated the capability to achieve an energy resolution of 1.53 per mil at an energy of 1.33 MeV.

  11. Study on the increase of inactive germanium layer in a high-purity germanium detector after a long time operation applying MCNP code

    Huy, N.Q. [Faculty of Fundamental Sciences, Ho Chi Minh City University of Industry, 12 Nguyen Van Bao Street, Ward 4, Go Vap District, Ho Chi Minh City (Viet Nam)]. E-mail: hlchau@hcm.vnn.vn; Binh, D.Q. [Center for Nuclear Techniques Ho Chi Minh City, 217 Nguyen Trai Street, District 1, Ho Chi Minh City (Viet Nam); An, V.X. [Faculty of Fundamental Sciences, Ho Chi Minh City University of Industry, 12 Nguyen Van Bao Street, Ward 4, Go Vap District, Ho Chi Minh City (Viet Nam)

    2007-04-11

    This study aims at finding an explanation for the decrease in the efficiency of an HPGe detector and evaluating a change in the detector inactive germanium layer during its operation. Monte Carlo calculations using the MCNP4C2 code were performed to evaluate the detector efficiency for different values of the inactive germanium layer. Comparison of the experimental and calculated data shows that the inactive germanium layer of the detector changed its thickness from 0.35 to 1.16 mm after an operating time of 9 years. Measurements for determining the reduction of the detector efficiency were carried out two times, one after 3 years and another after 9 years of operation. Experimental result shows that the detector efficiency was reduced about 8% in this period. The increase of inactive germanium layer can be considered as the main reason for explaining the reduction of detector efficiency of about 13% at the {gamma} energies from 200 to 1800 keV during 9 years of detector operation, in which 5% for the 3 first years and 8% for the 6 last years.

  12. Study on the increase of inactive germanium layer in a high-purity germanium detector after a long time operation applying MCNP code

    This study aims at finding an explanation for the decrease in the efficiency of an HPGe detector and evaluating a change in the detector inactive germanium layer during its operation. Monte Carlo calculations using the MCNP4C2 code were performed to evaluate the detector efficiency for different values of the inactive germanium layer. Comparison of the experimental and calculated data shows that the inactive germanium layer of the detector changed its thickness from 0.35 to 1.16 mm after an operating time of 9 years. Measurements for determining the reduction of the detector efficiency were carried out two times, one after 3 years and another after 9 years of operation. Experimental result shows that the detector efficiency was reduced about 8% in this period. The increase of inactive germanium layer can be considered as the main reason for explaining the reduction of detector efficiency of about 13% at the γ energies from 200 to 1800 keV during 9 years of detector operation, in which 5% for the 3 first years and 8% for the 6 last years

  13. Enhanced plasma current collection from weakly conducting solar array blankets

    Hillard, G. Barry

    1993-05-01

    Among the solar cell technologies to be tested in space as part of the Solar Array Module Plasma Interactions Experiment (SAMPIE) will be the Advanced Photovoltaic Solar Array (APSA). Several prototype twelve cell coupons were built for NASA using different blanket materials and mounting techniques. The first conforms to the baseline design for APSA which calls for the cells to be mounted on a carbon loaded Kapton blanket to control charging in GEO. When deployed, this design has a flexible blanket supported around the edges. A second coupon was built with the cells mounted on Kapton-H, which was in turn cemented to a solid aluminum substrate. A final coupon was identical to the latter but used germanium coated Kapton to control atomic oxygen attack in LEO. Ground testing of these coupons in a plasma chamber showed considerable differences in plasma current collection. The Kapton-H coupon demonstrated current collection consistent with exposed interconnects and some degree of cell snapover. The other two coupons experienced anomalously large collection currents. This behavior is believed to be a consequence of enhanced plasma sheaths supported by the weakly conducting carbon and germanium used in these coupons. The results reported here are the first experimental evidence that the use of such materials can result in power losses to high voltage space power systems.

  14. Proton-induced radiation damage in germanium detectors

    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.

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

    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.

  16. The impact of heavy Ga doping on superconductivity in germanium

    We report new experimental results on how superconductivity in gallium-doped germanium (Ge:Ga) is influenced by hole concentration and microstructure. Ion implantation and subsequent flash-lamp annealing at various temperatures have been utilized to prepare highly p-doped thin films consisting of nanocrystalline and epitaxially grown sublayers with Ga-peak concentrations of up to 8 at.%. Successive structural investigations were carried out by means of Rutherford-backscattering spectrometry in combination with ion channelling, secondary ion- mass spectrometry, and high-resolution cross-sectional transmission electron microscopy. Hole densities of 1.8·1020 to 5.3 · 1020 cm-3 (0.4 to 1.2 at.%) were estimated via Hall-effect measurements revealing that only a fraction of the incorporated gallium has been activated electrically to generate free charge carriers. The coincidence of a sufficiently high hole and Ga concentration is required for the formation of a superconducting condensate. Our data reflect a critical hole concentration of around 0.4 at.%. Higher concentrations lead to an increase of Tc from 0.24 to 0.43 K as characterized by electrical-transport measurements. A short mean-free path indicates superconductivity in the dirty limit. In addition, small critical-current densities of max. 20 kA/m2 point to a large impact of the microstructure.

  17. The ACCUSCAN-II vertical scanning germanium whole body counter

    The ACCUSCAN-II is manufactured by Canberra Industries, and represents a new generation of WBC systems. One or two Germanium detectors are used for precise nuclide identification. The detectors scan the total body and can accurately quantify radioactive material anywhere in the body. The shield is a full 4'' thick steel or 2'' lead and weighs about 9000 lbs. The subject can be counted standing for full body scans, or seated for longer counting times of limited portions of the body. Optional electronics also generate a count rate vs. body position profile, as an aid to interpretation of the dose implications of the count. Typical LLD's are 5 - 10 nCi for a 5 minute total body count and 0.5 - 0.7 nCi for a 5 minute long screening count. The system is available in several flavors. The manual version is an inexpensive system intended for universities, hospitals and small industrial facilities. The automatic system includes a MicroVAX-II computer and runs ABACOS0-II Body Burden Software, and is ideal for facilities with large numbers of people to count and where automated analysis of the data is desirable

  18. An Ab Initio Study on Silicon and Germanium Nanotubes

    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.

  19. Comparison of Germanium and Sodium Iodide: In Vivo Measurement Systems

    The experience several investigators have had with lithium-drifted germanium. Ge(Li), and lithium-drifted silicon, Si (Li), counting systems for in vivo measurements is compared with conventional scintillator detector systems in similar configurations. Measurements of plutonium and americium in lungs, other organs, and wounds using coaxial and planar-drift detectors are presented. A proposed large area planar Ge(Li) lung counter system is compared to two- and four-crystal sodium iodide counters (130 cm2 by 9 mm thick) currently used for uranium and plutonium lung measurements. A large Ge(Li) detector system being employed at Battelle-Northwest Laboratory to make whole-body measurements of radionuclide deposits in humans consists of four coaxial detectors, each 40 cm3 in volume (total 160 cm3). The individual detectors are enclosed in separate cryostats but mounted in a common 30 litre liquid nitrogen dewar of the ''chicken feeder'' design. The system is compared to the standard 23 cm diameter by 10 cm thick sodium iodide scintillator in the standard chair position. (author)

  20. Etching of germanium-tin using ammonia peroxide mixture

    The wet etching of germanium-tin (Ge1-xSnx) 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 Ge1-xSnx 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 Ge1-xSnx 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 Ge0.918Sn0.082 samples. Both root-mean-square roughness and undulation periods of the Ge1-xSnx surface were observed to increase with increasing t. This work provides further understanding of the wet etching of Ge1-xSnx using APM and may be used for the fabrication of Ge1-xSnx-based electronic and photonic devices

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

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

    2014-08-13

    From signal transduction of living cells to oxidation and corrosion of metals, mechanical stress intimately couples with chemical reactions, regulating these biological and physiochemical processes. The coupled effect is particularly evident in the electrochemical lithiation/delithiation cycling of high-capacity electrodes, such as silicon (Si), where on the one hand lithiation-generated stress mediates lithiation kinetics and on the other the electrochemical reaction rate regulates stress generation and mechanical failure of the electrodes. Here we report for the first time the evidence on the controlled lithiation in germanium nanowires (GeNWs) through external bending. Contrary to the symmetric core-shell lithiation in free-standing GeNWs, we show bending the GeNWs breaks the lithiation symmetry, speeding up lithaition at the tensile side while slowing down at the compressive side of the GeNWs. The bending-induced symmetry breaking of lithiation in GeNWs is further corroborated by chemomechanical modeling. In the light of the coupled effect between lithiation kinetics and mechanical stress in the electrochemical cycling, our findings shed light on strain/stress engineering of durable high-rate electrodes and energy harvesting through mechanical motion. PMID:25025296

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

    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. Impurity complex formation in ultra-pure germanium

    Several unknown, hydrogenic acceptors and donors were recently discovered in ultra-pure germanium by photoelectric spectroscopy. These centers are not created by elemental impurities. Comparative analysis of a large number of crystals grown under various conditions lead to the conclusion that copper, a fast diffusing multivalent acceptor, together with lithium and/or hydrogen, is responsible for several of the unknown centers. This is the first time that hydrogen has been recognized as playing the role of a donor pairing with an acceptor. Hall effect measurements complementing the photoelectric spectroscopy results lead to a tentative assignment of the following energy levels: (Cu, Li) complexes: E/sub V/ + 20.5 meV/super */, E/sub V/ + 25.0 meV/super */, E/sub V/ + 275 meV(/super */hydrogenic acceptor); (Cu, H) complexes: E/sub V/ + 17.0 meV/super */, E/sub V/ + 17.5 meV/super */, E/sub V/ + 175 meV. Experiments which may help determine the structure of the complexes are proposed

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

    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

  5. Etching of germanium-tin using ammonia peroxide mixture

    Dong, Yuan; Ong, Bin Leong; Wang, Wei; Gong, Xiao; Liang, Gengchiau; Yeo, Yee-Chia, E-mail: yeo@ieee.org [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); Zhang, Zheng; Pan, Jisheng [Institute of Material Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, #08-03, Innovis, Singapore 138634 (Singapore); Tok, Eng-Soon [Department of Physics, National University of Singapore, Singapore 117551 (Singapore)

    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.

  6. Low background germanium planar detector for gamma-ray spectrometry

    A new ultra-low background planar germanium spectrometer has been developed. The planar geometry improves the sensitivity and energy resolution below 600 keV. The integral background counting rate in the Laboratoire Souterrain de Modane (4800 m water equivalent) in the energy range from 20 to 1500 keV for the planar Ge (mass=800 g) is 140 count/day. After 40 days of statistics, the background counting rates for all expected single lines are below 0.5 count/day with the exception of 210Pb(46-keV line) which was measured to be (1.76±0.25) count/day. Monte Carlo simulations have been performed to explain the origin of the remaining background and to calculate the detection efficiencies. Sensitivities around 1 mBq/kg are obtained within few days of statistics for 226Ra and 228Th. The main achievement is the high sensitivities for 210Pb (46-keV line) and 238U (234Th: 63 and 93 keV lines). For an aluminium sample (mass=1 kg) the limits obtained in 15 days are 210Pb238U<3mBq/kg.

  7. Electrical and structural properties of superconducting layers in gallium-doped silicon and germanium; Elektrische und strukturelle Eigenschaften von supraleitenden Schichten in Galliumimplantiertem Silizium und Germanium

    Fiedler, Jan

    2013-08-21

    In this work, a pioneering attempt to analyze in detail the influence of superconducting gallium-rich precipitates on the electrical transport properties of heavily-doped silicon and germanium layers is presented. An innovative, highly-promising path for the fabrication of superconducting layers in commercial silicon and germanium wafers by ion implantation and short term annealing is successfully demonstrated. Up to date, no reports on superconducting gallium-doped germanium unequivocally confirming the source of superconductivity - high doping or gallium precipitates - were available. Consequently, the results presented herein provide a valuable help on how to explain the superconducting state in gallium-doped germanium. Ion implantation via a thin SiO{sub 2} or Si{sub 3}N{sub 4} cover layer was used to introduce a gallium concentration far above the equilibrium solid solubility limit into the silicon and germanium layers. To initiate the reconstruction of the damaged lattice and the redistribution of the implanted gallium, rapid thermal annealing was subsequently employed. A detailed analysis of the microstructure performed by means of transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy, has revealed the presence of gallium-rich precipitates in the implanted layers. The redistribution of the gallium was investigated by Rutherford backscattering spectrometry and Auger electron spectroscopy. The obtained results were then discussed with respect to the literature. For the first time, the formation of 10 nm thin gallium-rich layers at the cover layer/semiconducting interface was observed. A new model describing the redistribution mechanism was proposed. In addition to the investigations on heavily-doped semiconductors available in the literature, the fabricated gallium-rich interface layers were used to analyze the electrical properties of semiconductors with a high density of precipitates. It has been observed, that for gallium

  8. Techniques to distinguish between electron and photon induced events using segmented germanium detectors

    Kroeninger, K.

    2007-06-05

    Two techniques to distinguish between electron and photon induced events in germanium detectors were studied: (1) anti-coincidence requirements between the segments of segmented germanium detectors and (2) the analysis of the time structure of the detector response. An 18-fold segmented germanium prototype detector for the GERDA neutrinoless double beta-decay experiment was characterized. The rejection of photon induced events was measured for the strongest lines in {sup 60}Co, {sup 152}Eu and {sup 228}Th. An accompanying Monte Carlo simulation was performed and the results were compared to data. An overall agreement with deviations of the order of 5-10% was obtained. The expected background index of the GERDA experiment was estimated. The sensitivity of the GERDA experiment was determined. Special statistical tools were developed to correctly treat the small number of events expected. The GERDA experiment uses a cryogenic liquid as the operational medium for the germanium detectors. It was shown that germanium detectors can be reliably operated through several cooling cycles. (orig.)

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

    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.

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

    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.

  11. Techniques to distinguish between electron and photon induced events using segmented germanium detectors

    Two techniques to distinguish between electron and photon induced events in germanium detectors were studied: (1) anti-coincidence requirements between the segments of segmented germanium detectors and (2) the analysis of the time structure of the detector response. An 18-fold segmented germanium prototype detector for the GERDA neutrinoless double beta-decay experiment was characterized. The rejection of photon induced events was measured for the strongest lines in 60Co, 152Eu and 228Th. An accompanying Monte Carlo simulation was performed and the results were compared to data. An overall agreement with deviations of the order of 5-10% was obtained. The expected background index of the GERDA experiment was estimated. The sensitivity of the GERDA experiment was determined. Special statistical tools were developed to correctly treat the small number of events expected. The GERDA experiment uses a cryogenic liquid as the operational medium for the germanium detectors. It was shown that germanium detectors can be reliably operated through several cooling cycles. (orig.)

  12. Determination of trace impurities in germanium dioxide by ICP-OES, ICP-MS and ETAAS after matrix volatilization: a long-run performance of the method.

    Niemelä, Matti; Kola, Harri; Perämäki, Paavo

    2014-01-01

    High-purity germanium compounds (e.g. germanium dioxide) are used these days in several applications (e.g. germanium-based detectors, semiconductors, fiber-optic systems). Thus, reliable methods for the routine determination of trace element impurities from germanium compounds must be developed. In this study, inductively coupled plasma mass spectrometry, inductively coupled plasma optical emission spectrometry and/or electrothermal atomic-absorption spectrometry was used for the determination of fifteen impurity elements in germanium dioxide. Possible interference effects due to a germanium matrix were eliminated/minimized by a simple open-vessel volatilization of germanium tetra chloride before the determinations. The results, based on the data gathered over a period of one year, showed that the long-run performance of the method is good, and it can be used for routine analysis of impurity elements in high-purity germanium dioxide. PMID:25007932

  13. Automatic energy calibration of germanium detectors using fuzzy set theory

    With the advent of multi-detector arrays, many tasks that are usually performed by physicists, such as energy calibration, become very time consuming. There is therefore a need to develop more and more complex algorithms able to mimic human expertise. Fuzzy logic proposes a theoretical framework to build algorithms that are close to the human way of thinking. In this paper we apply fuzzy set theory in order to develop an automatic procedure for energy calibration. The algorithm, based on fuzzy concepts, has been tested on data taken with the EUROBALL IV γ-ray array

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

    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

  15. Trace radioactive measurement in foodstuffs using high purity germanium detector

    Trace radioactivity in food has been seriously considered sources of potential harm after the accidental radioactive releases in the last decades which led to contamination of the food chain. Countermeasures are being used to reduce the radiological health risk to the population and to ensure that public safety and international commitments are met. Investigation of radioactive traces in foods was carried out by gamma-ray spectrometry. The radionuclides being measured were fission products 137Cs and 134Cs and naturally occurring 40Κ. Gamma-ray measurements were performed using a hybrid gamma-ray counting system with coaxial p-type Tennelec High Purity Germanium (HPGe) detector with relative efficiency of 18.4%. Channels were calibrated to energies using a standard check source with 137Cs and 60Co present. Self-shielding within samples was taken into account by comparing directly with reference standards of similar matrix and geometry. Efficiencies of radionuclides of interests were accounted in calculating the activity concentrations in the samples. Efficiency calibration curve was generated using an in-house validated program called FINDPEAK, a least-square method that fits a polynomial up to sixth-order of equation. Lower Limits of Detection (LLD) obtained for both 137Cs and 134Cs ranges from 1-6 Bq/Kg depending on the sample matrix. In the last five years, there have been no foodstuffs analyzed exceeded the local and international regulatory limit of 1000Bq/Kg for the summed activities of 137Cs and 134Cs. (author)

  16. Electronic and magnetic properties of perfect and defected germanium nanoribbons

    Highlights: · Perfect AGeNRs are NM semiconductor with three-branch band gaps and decaying profiles. · Perfect ZGeNRs are AFM semiconductor with a decreasing band gap as width increases. · The band gap of AGeNRs can be tuned by mono- or di-vacancy at different positions. · Metallization can be realized in ZGeNRs by mono- or di-vacancy at different positions. · Magnetic properties of ZGeNRs depend closely upon the vacancy positions. - Abstract: The electronic and magnetic properties of both perfect and defected germanium nanoribbons (GeNRs) are investigated by using projector-augmented wave method based on density-functional theory. All the GeNRs with different edge shapes (armchair or zigzag) and widths are cut from the buckled Ge hexagonal sheet which is found to be semi-metallic as the planar graphene sheet. The results show that the perfect armchair GeNRs are nonmagnetic semiconductors and their band gaps exhibit three branches with decaying profiles, while the perfect zigzag GeNRs show the stable antiferromagnetic semiconducting ground state and their band gaps monotonously decrease with increasing ribbon width. These properties of the GeNRs are similar to graphene nanoribbons and should be important for designing new functional Ge-based nanodevices. The effects of the monovacancy or divacancy on the electronic and magnetic properties of the GeNRs are also considered. We found that the band gap of armchair GeNRs can be easily tuned by a monovancancy or divacancy at different positions, which provides a way of band gap engineering of armchair GeNRs for actual applications. Different from the defected armchair GeNRs, the metallization can be realized in zigzag GeNRs by a monovacancy or a divacancy, however, their magnetic properties depend closely upon the vacancy positions.

  17. Large microcalorimeter arrays for high-resolution X- and gamma-rayspectroscopy

    Hoover, A.S., E-mail: ahoover@lanl.gov [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Hoteling, N.; Rabin, M.W. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Ullom, J.N.; Bennett, D.A. [National Institute of Standards and Technology, Boulder, CO 80305 (United States); Karpius, P.J.; Vo, D.T. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Doriese, W.B.; Hilton, G.C.; Horansky, R.D.; Irwin, K.D.; Kotsubo, V. [National Institute of Standards and Technology, Boulder, CO 80305 (United States); Lee, D.W. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Vale, L.R. [National Institute of Standards and Technology, Boulder, CO 80305 (United States)

    2011-10-01

    Microcalorimeter detectors provide unprecedented energy resolution for the measurement of X-rays and soft gamma-rays. Energy resolution in the 100 keV region can be up to an order of magnitude better than planar high-purity germanium (HPGe) detectors. The technology is well-suited to analysis of materials with complex spectra presenting closely spaced photopeaks. One application area is the measurement and assay of nuclear materials for safeguards and fuel cycle applications. In this paper, we discuss the operation and performance of a 256-pixel array, and present results of a head-to-head comparison of isotopic determination measurements with high-purity germanium using a plutonium standard. We show that the uncertainty of a single measurement is smaller for the microcalorimeter data compared to the HPGe data when photopeak areas are equal. We identify several key areas where analysis codes can be optimized that will likely lead to improvement in the microcalorimeter performance.

  18. Large microcalorimeter arrays for high-resolution X- and gamma-rayspectroscopy

    Microcalorimeter detectors provide unprecedented energy resolution for the measurement of X-rays and soft gamma-rays. Energy resolution in the 100 keV region can be up to an order of magnitude better than planar high-purity germanium (HPGe) detectors. The technology is well-suited to analysis of materials with complex spectra presenting closely spaced photopeaks. One application area is the measurement and assay of nuclear materials for safeguards and fuel cycle applications. In this paper, we discuss the operation and performance of a 256-pixel array, and present results of a head-to-head comparison of isotopic determination measurements with high-purity germanium using a plutonium standard. We show that the uncertainty of a single measurement is smaller for the microcalorimeter data compared to the HPGe data when photopeak areas are equal. We identify several key areas where analysis codes can be optimized that will likely lead to improvement in the microcalorimeter performance.

  19. Hybrid Array of Gamma Ray Detectors (HAGRiD)

    Smith, Karl; Grzywacz, R.; Jones, K. L.; Munoz, S.; Baugher, T.; Cizewski, J. A.; Ratkiewicz, A.; Pain, S. D.

    2015-10-01

    Transfer reactions and beta-decay studies are powerful tools to study nuclear structure and to provide insight into astrophysically important reactions that may be difficult to measure directly. Both types of studies are enhanced immensely by measuring a particle-gamma coincidence. For transfer reactions, gamma-ray measurements improve the resolution, aid in channel selection and lifetime measurements. To achieve these coincidences the Hybrid Array of Gamma Ray Detectors (HAGRiD) is being designed and constructed. This array would be coupled with the Oak Ridge Rutgers Barrel Array (ORRUBA) of silicon detectors, the Versatile Array of Neutron Detectors at Low Energy (VANDLE) and beta detection scintillators. Detector systems providing a particle-gamma coincidence have previously compromised the charged-particle angular resolution due to compact geometries used to increase the gamma efficiency. HAGRiD will be coupled with ORRUBA such that resolution is not sacrificed, requiring the new array to provide improved resolution and efficiency over NaI and increased portability and flexibility over germanium detectors; therefore, we have chosen to use LaBr3(Ce) crystals. We demonstrate the advantages of a coupled detector system and discuss the current status of the project.

  20. Impurity diffusion, point defect engineering, and surface/interface passivation in germanium

    Chroneos, Alexander I.

    2012-01-26

    In recent years germanium has been emerging as a mainstream material that could have important applications in the microelectronics industry. The principle aim of this study is to review investigations of the diffusion of technologically important p- and n-type dopants as well as surface and interface passivation issues in germanium. The diffusion of impurities in germanium is interrelated to the formation of clusters whenever possible, and possibilities for point defect engineering are discussed in view of recent results. The importance of electrically active defects on the Ge surface and interfaces is addressed considering strategies to suppress them and to passivate the surfaces/interfaces, bearing in mind their importance for advanced devices. © 2012 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Determination of Shear Deformation Potentials from the Free-Carrier Piezobirefringence in Germanium and Silicon

    Riskaer, Sven

    1966-01-01

    The present investigations of the free-carrier piezobirefringence phenomenon verify that in n-type germanium and silicon as well as in p-type silicon this effect can be ascribed to intraband transitions of the carriers. It is demonstrated how a combined investigation of the low-stress and high......-stress piezobirefringence in these materials provides a direct and independent method for determining deformation-potential constants. For n-type germanium we obtain Ξu=18.0±0.5 eV, for n-type silicon Ξu=8.5±0.4 eV; for p-type silicon a rather crude analytical approximation yields b=-3.1 eV and d=-8.3 eV. Finally......, experimental evidence is given to support the assumption, that in p-type germanium intraband transitions alone cannot account for the free-carrier piezobirefringence....

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

    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

  3. Germanium field-effect transistor made from a high-purity substrate

    Field effect transistors have been fabricated on high-purity germanium substrates using low-temperature technology. The aim of this work is to preserve the low density of trapping centers in high-quality starting material by low-temperature (0C) processing. The use of germanium promises to eliminate some of the traps which cause generation-recombination noise in silicon field-effect transistors (FET's) at low temperatures. Typically, the transconductance (g/sub m/) in the germanium FET's is 10 mA/V and the gate leakage can be less than 10-12 A. Present devices exhibit a large 1/f noise component and most of this noise must be eliminated if they are to be competitive with silicon FET's commonly used in high-resolution nuclear spectrometers

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

    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

  5. Silicon-germanium (Sige) nanostructures production, properties and applications in electronics

    Usami, N

    2011-01-01

    Nanostructured silicon-germanium (SiGe) provides the prospect of novel and enhanced electronic device performance. This book reviews the materials science and technology of SiGe nanostructures, including crystal growth, fabrication of nanostructures, material properties and applications in electronics.$bNanostructured silicon-germanium (SiGe) opens up the prospects of novel and enhanced electronic device performance, especially for semiconductor devices. Silicon-germanium (SiGe) nanostructures reviews the materials science of nanostructures and their properties and applications in different electronic devices. The introductory part one covers the structural properties of SiGe nanostructures, with a further chapter discussing electronic band structures of SiGe alloys. Part two concentrates on the formation of SiGe nanostructures, with chapters on different methods of crystal growth such as molecular beam epitaxy and chemical vapour deposition. This part also includes chapters covering strain engineering and mo...

  6. A novel approach for justification of box-triangular germanium profile in SiGe HBTs

    This work presents a unique and robust approach for validation of using the box-triangular germanium profile in the base of SiGe heterojunction bipolar transistors, where the methodology considers the simultaneous optimization of the p-type base doping profile in conjunction with the germanium profile in the base. The study analyses the electron motion across the SiGe base in SiGe HBTs, owing to different accelerating electric fields. The analysis first presents a figure of merit, to achieve the minimum electron transit time across the base in conjunction with the increased current gain in n—p—n-SiGe HBTs, which shows a general trend vis-à-vis the advantage of a trapezoid germanium profile, but with additional accuracy as we considered simultaneously optimized p-type base doping. The effect of minority carrier velocity saturation is then included to make the study more detailed. The analysis then investigates the shifted germanium profile in the base to further minimize the base transit time. Finally, it is shown that a shifted germanium profile eventually evolves into a box-triangular Ge-profile in the SiGe base, which could simultaneously minimize the base transit time and reduce emitter delay by virtue of the high current gain. The analysis verifies that for an average Ge-dose of 7.5% Ge across the base, a box-triangular germanium profile in conjunction with an optimum base doping profile has an approximately identical base transit time and a 30% higher current gain, in comparison with an optimum base doping and triangular Ge-profile across the whole base. (semiconductor devices)

  7. Time-resolved spectroscopy of plasma resonances in highly excited silicon and germanium

    The dynamics of the electron-hole plasma in silicon and germanium samples irradiated by 20 ps. 532 nm laser pulses has been investigated in the near infrared by the time-resolved picosecond optical spectroscopy. The experimental reflectivities and transmission are compared with the predictions of the thermal model for degenerate carrier distributions through the Drude formalism. Above a certain fluence, a significant deviation between measured and calculated values indicates a strong increase of the recombination rate as soon as the plasma resonances become comparable with the band gaps. These new plasmon-aided recombination channels are particularly pronounced in germanium. 15 refs., 8 figs

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

    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.

  9. GIOVE - A New Detector Setup for High Sensitivity Germanium Spectroscopy At Shallow Depth

    Heusser, Gerd; Hakenmüller, Janina; Laubenstein, Matthias; Lindner, Manfred; Maneschg, Werner; Simgen, Hardy; Stolzenburg, Dominik; Strecker, Herbert

    2015-01-01

    We report on the development and construction of the high-purity germanium spectrometer setup GIOVE (Germanium Inner Outer Veto), recently built and now operated at the shallow underground laboratory of the Max-Planck-Institut f\\"ur Kernphysik, Heidelberg. Particular attention was paid to the design of a novel passive and active shield, aiming at efficient rejection of environmental and muon induced radiation backgrounds. The achieved sensitivity level of <100 {\\mu}Bq/kg for primordial radionuclides from U and Th in typical {\\gamma} ray sample screening measurements is unique among instruments located at comparably shallow depths and can compete with instruments at far deeper underground sites.

  10. GIOVE: a new detector setup for high sensitivity germanium spectroscopy at shallow depth

    Heusser, G.; Weber, M.; Hakenmueller, J.; Lindner, M.; Maneschg, W.; Simgen, H.; Stolzenburg, D.; Strecker, H. [Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany); Laubenstein, M. [Laboratori Nazionali del Gran Sasso, Assergi (Italy)

    2015-11-15

    We report on the development and construction of the high-purity germanium spectrometer setup GIOVE (Germanium Inner Outer VEto), recently built and now operated at the shallow underground laboratory of the Max-Planck-Institut fuer Kernphysik, Heidelberg. Particular attention was paid to the design of a novel passive and active shield, aiming at efficient rejection of environmental and muon induced radiation backgrounds. The achieved sensitivity level of ≤ 100μBq kg{sup -1} for primordial radionuclides from U and Th in typical γ ray sample screening measurements is unique among instruments located at comparably shallow depths and can compete with instruments at far deeper underground sites. (orig.)

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

    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. (orig.)

  12. Temperature-dependent hyperfine interactions at {sup 111}Cd-C complex in germanium

    Mola, Genene Tessema [University of Kwazulu-Natal, School Chemistry and Physics, Pietermaritzburg Campus, Private Bag X01, Scottsville (South Africa)

    2013-09-15

    The temperature dependent nuclear hyperfine interaction of {sup 111}Cd-carbon complex in germanium has been studied using the perturbed {gamma}-{gamma} angular correlation (PAC) method. The parameters of the hyperfine interaction representing substitutional carbon-cadmium complex in germanium ({nu} {sub Q1}=207(1) MHz ({eta}=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. (orig.)

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

    Wang, Wei; Li, Lingzi; Yeo, Yee-Chia, E-mail: yeo@ieee.org [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); Tok, Eng Soon [Department of Physics, National University of Singapore, Singapore 117551 (Singapore)

    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.

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

    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

  15. Characterization of Segmented Large Volume, High Purity Germanium Detectors

    Bruyneel, Bart

    2006-01-01

    Gamma ray tracking in future HPGe arrays like AGATA will rely on pulse shape analysis (PSA) of multiple Gamma interactions. For this purpose, a simple and fast procedure was developed which enabled the first full characterization of a segmented large volume HPGe detector. An analytical model for the hole mobility in a Ge crystal lattice was developed to describe the hole drift anisotropy with experimental velocity values along the crystal axis as parameters. The new model is based on the drif...

  16. Wafer-level radiometric performance testing of uncooled microbolometer arrays

    Dufour, Denis G.; Topart, Patrice; Tremblay, Bruno; Julien, Christian; Martin, Louis; Vachon, Carl

    2014-03-01

    A turn-key semi-automated test system was constructed to perform on-wafer testing of microbolometer arrays. The system allows for testing of several performance characteristics of ROIC-fabricated microbolometer arrays including NETD, SiTF, ROIC functionality, noise and matrix operability, both before and after microbolometer fabrication. The system accepts wafers up to 8 inches in diameter and performs automated wafer die mapping using a microscope camera. Once wafer mapping is completed, a custom-designed quick insertion 8-12 μm AR-coated Germanium viewport is placed and the chamber is pumped down to below 10-5 Torr, allowing for the evaluation of package-level focal plane array (FPA) performance. The probe card is electrically connected to an INO IRXCAM camera core, a versatile system that can be adapted to many types of ROICs using custom-built interface printed circuit boards (PCBs). We currently have the capability for testing 384x288, 35 μm pixel size and 160x120, 52 μm pixel size FPAs. For accurate NETD measurements, the system is designed to provide an F/1 view of two rail-mounted blackbodies seen through the Germanium window by the die under test. A master control computer automates the alignment of the probe card to the dies, the positioning of the blackbodies, FPA image frame acquisition using IRXCAM, as well as data analysis and storage. Radiometric measurement precision has been validated by packaging dies measured by the automated probing system and re-measuring the SiTF and Noise using INO's pre-existing benchtop system.

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

    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.

  18. Reaction studies of hot silicon and germanium radicals. Progress report, February 1, 1982-July 31, 1984

    The experimental approach toward attaining the goals of this research program is briefly outlined, and the progress made in the 1982 to 1984 period is reviewed in sections entitled: (1) Recoil atom experiments, (2) Studies of thermally and photochemically generated silicon and germanium radicals, and (3) Ion-molecule reaction studies

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

    LIN Li-Xia; CHEN Jia-He; WU Peng; ZENG Yu-Heng; MA Xiang-Yang; YANG De-Ren

    2011-01-01

    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.

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

    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.

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

    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. Luminescence decay dynamics of self-assembled germanium islands in silicon

    Julsgaard, Brian; Balling, Peter; Hansen, John Lundsgaard;

    2011-01-01

    The dynamics of the luminescence decay from self-assembled germanium islands embedded in crystalline silicon has been studied for temperatures varied between 16 K and room temperature. We separate the time scale for various dynamical processes by time-resolved emission spectroscopy and identify...

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

    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

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

    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

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

    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.

  6. Applications of new organometallic derivatives of germanium and silicon in chemical radioprotection

    This work deals with the synthesis and study of the radioprotective activity of organometallic structures of the types: metallathiazolidines, metalladithioacetals, germocanes, oxathiagermolanes, germoxanes and germathianes derived from n-substituted cysteamine and methyl-cysteamine, from 1-thio-ethyl-2-(1-naphtylmethyl)-2-imidazoline, from 2,2'-oxidiethanethiol and from 2,2'-thiodiethanethiol. These organometallic compounds have shown a net increase of the radioprotective activity and a significant abatement of the acute toxicity, in comparison with the basic organic structure. These results demonstrate the interest of the presence of metallic hetero-elements, like silicon or germanium, which deeply modify the electronic structure and the chemical and biological behaviour of these molecules. 62 silicon-based, germanium-based and purely organic compounds have been synthesized, among which 13 silicon or germanium-based compounds lead to interesting dose reduction factors (DRF) comprised between 1.4 and 1.7. The low toxicity of these silicon or germanium-based structures, the absence of accumulation phenomena, and their easy elimination by the organism allow to consider their systematic use without important drawbacks. Some organo-silicon compounds are today commercialized as drugs. This work represent an interesting development in the domain of organometallic functional compounds from group 14 elements. Even if all these organometallic compounds are active in chemical radioprotection of animals, their study in human clinical radioprotection has never been carried out but can be considered. (J.S.)

  7. Conceptual design of a hybrid Ge:Ga detector array

    Parry, C. M.

    1984-01-01

    For potential applications in space infrared astronomy missions such as the Space Infrared Telescope Facility and the Large Deployable Reflector, integrated arrays of long-wavelength detectors are desired. The results of a feasibility study which developed a design for applying integrated array techniques to a long-wavelength (gallium-doped germanium) material to achieve spectral coverage between 30 and 200 microns are presented. An approach which builds up a two-dimensional array by stacking linear detector modules is presented. The spectral response of the Ge:Ga detectors is extended to 200 microns by application of uniaxial stress to the stack of modules. The detectors are assembled with 1 mm spacing between the elements. Multiplexed readout of each module is accomplished with integration sampling of a metal-oxide-semiconductor (MOS) switch chip. Aspects of the overall design, including the anticipated level of particle effects on the array in the space environment, a transparent electrode design for 200 microns response, estimates of optical crosstalk, and mechanical stress design calculations are included.

  8. Contribution of a germanium detector in mobile gamma-ray spectrometry. Spectral analysis and performance

    The sensitivity of the germanium semi-conductor detector is 30 times lower than that of the sodium iodide (NaI) detectors frequently used in airborne spectrometry. Its energy resolution however, is 20 times better, giving more accurate identification of radionuclides, especially when complex spectra are involved. The use of the germanium detector in mobile gamma-ray spectrometry provides a large amount of qualitative and quantitative information. In post-accident situations a germanium detector will be sufficient, and should therefore be used in preference to a NaI detector. An algorithm for detecting the total absorption peaks by studying the variations in the spectral profile of germanium gamma-ray spectra has been developed at the CEA. The use of digital filters that take into account the characteristics of the absorption peaks reduces the statistical fluctuations, making possible detection based on the analysis of the first and second derivatives. The absorption peak is then estimated by subtracting the background noise modelled in the detection window. This method of analysis offers the advantage of not requiring prior knowledge of the number or nature of the radionuclides to be detected. A study has been carried out to assess the specific performances of this detection software in different situations: average background noise in France and detection of artificial sources with varying activity levels. This analysis showed that the performance of our detection algorithm is very close to the theoretical detection limits, for both natural and artificial radionuclides. This algorithm is therefore well suited to the germanium type of spectral profile and to low count rates

  9. Average Energy Expended Per e-h Pair and Energy Scale Function for Germanium-Based Dark Matter Experiments

    Wei, W -Z; Mei, D -M

    2016-01-01

    We report a new method to determine the temperature-dependent average energy expended per electron-hole (e-h) pair, $\\varepsilon$, for germanium detectors. As a result, the Fano factor and $\\varepsilon$ can be determined separately. Subsequently, we illustrate the variation of $\\varepsilon$ as a function of temperature. The impact of $\\varepsilon$ on the energy threshold and energy scale for germanium detectors at a given temperature is evaluated. We demonstrate an absolute energy scale function of low-energy recoils for germanium detectors in the direct detection of dark matter particles.

  10. Fabrication and characteristics of high-K HfO2 gate dielectrics on n-germanium

    Han De-Dong; Kang Jin-Feng; Liu Xiao-Yan; Sun Lei; Luo Hao; Han Ru-Qi

    2007-01-01

    This paper reports that the high-K HfO2 gate dielectrics are fabricated on n-germanium substrates by sputtering Hf on Ge and following by a furnace annealing. The impacts of sputtering ambient, annealing ambient and annealing temperature on the electrical properties of high-K HfO2 gate dielectrics on germanium substrates are investigated.Experimental results indicate that high-K HfO2 gate dielectrics on germanium substrates with good electrical characteristics are obtained, the electrical properties of high-K HfO2 gate dielectrics is strongly correlated with sputtering ambient, annealing ambient and annealing temperature.

  11. Graphical Environment Tools for Application to Gamma-Ray Energy Tracking Arrays

    Todd, Richard A. [RIS Corp.; Radford, David C. [ORNL Physics Div.

    2013-12-30

    Highly segmented, position-sensitive germanium detector systems are being developed for nuclear physics research where traditional electronic signal processing with mixed analog and digital function blocks would be enormously complex and costly. Future systems will be constructed using pipelined processing of high-speed digitized signals as is done in the telecommunications industry. Techniques which provide rapid algorithm and system development for future systems are desirable. This project has used digital signal processing concepts and existing graphical system design tools to develop a set of re-usable modular functions and libraries targeted for the nuclear physics community. Researchers working with complex nuclear detector arrays such as the Gamma-Ray Energy Tracking Array (GRETA) have been able to construct advanced data processing algorithms for implementation in field programmable gate arrays (FPGAs) through application of these library functions using intuitive graphical interfaces.

  12. Electrical and structural properties of superconducting layers in gallium-doped silicon and germanium

    In this work, a pioneering attempt to analyze in detail the influence of superconducting gallium-rich precipitates on the electrical transport properties of heavily-doped silicon and germanium layers is presented. An innovative, highly-promising path for the fabrication of superconducting layers in commercial silicon and germanium wafers by ion implantation and short term annealing is successfully demonstrated. Up to date, no reports on superconducting gallium-doped germanium unequivocally confirming the source of superconductivity - high doping or gallium precipitates - were available. Consequently, the results presented herein provide a valuable help on how to explain the superconducting state in gallium-doped germanium. Ion implantation via a thin SiO2 or Si3N4 cover layer was used to introduce a gallium concentration far above the equilibrium solid solubility limit into the silicon and germanium layers. To initiate the reconstruction of the damaged lattice and the redistribution of the implanted gallium, rapid thermal annealing was subsequently employed. A detailed analysis of the microstructure performed by means of transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy, has revealed the presence of gallium-rich precipitates in the implanted layers. The redistribution of the gallium was investigated by Rutherford backscattering spectrometry and Auger electron spectroscopy. The obtained results were then discussed with respect to the literature. For the first time, the formation of 10 nm thin gallium-rich layers at the cover layer/semiconducting interface was observed. A new model describing the redistribution mechanism was proposed. In addition to the investigations on heavily-doped semiconductors available in the literature, the fabricated gallium-rich interface layers were used to analyze the electrical properties of semiconductors with a high density of precipitates. It has been observed, that for gallium concentrations at the

  13. Aerosol assisted chemical vapour deposition of germanium thin films using organogermanium carboxylates as precursors and formation of germania films

    Alpa Y Shah; Amey Wadawale; Vijaykumar S Sagoria; Vimal K Jain; C A Betty; S Bhattacharya

    2012-06-01

    Diethyl germanium bis-picolinate, [Et2Ge(O2CC5H4N)2], and trimethyl germanium quinaldate, [Me3Ge(O2CC9H6N)], have been used as precursors for deposition of thin films of germanium by aerosol assisted chemical vapour deposition (AACVD). The thermogravimetric analysis revealed complete volatilization of complexes under nitrogen atmosphere. Germanium thin films were deposited on silicon wafers at 700°C employing AACVD method. These films on oxidation under an oxygen atmosphere at 600°C yield GeO2. Both Ge and GeO2 films were characterized by XRD, SEM and EDS measurements. Their electrical properties were assessed by current–voltage (–) characterization.

  14. Study of the effect of neutron and electron irradiations on the low temperature thermal conductivity of germanium and silicon

    The main results obtained from this work are the following: 1 Neutron irradiation (at 300 deg. K) produces lattice defects in germanium and silicon, and a corresponding very large lowering of the thermal conductivity is observed in the low temperature region (4-300 ). The results obtained have been explained with the help of the following hypotheses: for silicon a scattering of phonons by the stress fields produced by the defects; for germanium, a supplementary scattering of the electron phonon type. 2 Annealing treatments carried out on these materials above 373 deg. K restored the thermal conductivity over the whole temperature range of the measurements (4-300 deg. K); in the case of both germanium and silicon there were two steps in the annealing process. 3 A study of the thermal conductivity of germanium (initially P or N) after an electronic irradiation showed that the scattering of phonons could depend on the state of charge of the defects thus produced. (author)

  15. Temperature Dependence of the Average Energy Expended Per e-h Pair for Germanium-Based Dark Matter Experiments

    Wei, W. -Z.; Wang, L.; Mei, D.-M.

    2016-01-01

    We report a new method to determine the temperature-dependent average energy expended per electron-hole (e-h) pair, $\\varepsilon$, for germanium detectors. As a result, the Fano factor and $\\varepsilon$ can be determined separately. Subsequently, we illustrate the variation of $\\varepsilon$ as a function of temperature. The impact of $\\varepsilon$ on the energy threshold and energy scale for germanium detectors at a given temperature is evaluated.

  16. Monte Carlo simulation study of the impact of strain and substrate orientation on hole mobility in Germanium

    The use of alternative channel materials to maintain device performance with scaling for CMOS technology is an active area of research, with Germanium offering an extremely attractive possibility for pMOSFETs in CMOS. In this paper we use full band Monte Carlo transport simulations to investigate the impact of substrate orientation and biaxial strain on hole mobility in bulk Germanium helping to establish a preferential substrate channel orientation that can maximize carrier mobility for these devices.

  17. Monte Carlo simulation study of the impact of strain and substrate orientation on hole mobility in Germanium

    Riddet, Craig; Watling, Jeremy R; Chan, Kah Hou; Asenov, Asen, E-mail: c.riddet@elec.gla.ac.u [Device Modelling Group, Department of Electronics and Electrical Engineering, University of Glasgow, Glasgow, G12 8LT, Scotland (United Kingdom)

    2010-07-01

    The use of alternative channel materials to maintain device performance with scaling for CMOS technology is an active area of research, with Germanium offering an extremely attractive possibility for pMOSFETs in CMOS. In this paper we use full band Monte Carlo transport simulations to investigate the impact of substrate orientation and biaxial strain on hole mobility in bulk Germanium helping to establish a preferential substrate channel orientation that can maximize carrier mobility for these devices.

  18. Super phase array

    Wee, W H; Pendry, J B [Condensed Matter Theory Group Department of Physics Imperial College London London SW7 2AZ (United Kingdom)], E-mail: w.wee07@imperial.ac.uk

    2010-03-15

    For a long time phase arrays have been used in a variety of wave transmission applications because of their simplicity and versatility. Conventionally there is a trade-off between the compactness of a phase array and its directivity. In this paper we demonstrate how by embedding a normal phase array within a superlens (made of negative refractive index material) we can overcome this constraint and create compact phase arrays with a virtual extent much larger than the physical size of the array. In this paper we also briefly discuss the apparent unphysical field divergences in superlenses and how to resolve this issue.

  19. Super phase array

    For a long time phase arrays have been used in a variety of wave transmission applications because of their simplicity and versatility. Conventionally there is a trade-off between the compactness of a phase array and its directivity. In this paper we demonstrate how by embedding a normal phase array within a superlens (made of negative refractive index material) we can overcome this constraint and create compact phase arrays with a virtual extent much larger than the physical size of the array. In this paper we also briefly discuss the apparent unphysical field divergences in superlenses and how to resolve this issue.

  20. The impact of radiation on semiconducting characteristics of monocrystalline silicon and germanium

    Obrenović Marija D.

    2016-01-01

    Full Text Available The paper examines the effects of radiation on the electrical characteristics of monocrystalline silicon and germanium. Samples of monocrystalline silicon and germanium are irradiated under controlled laboratory conditions in the field of neutron, X- and g-radiation. Change of the samples' specific resistance was measured dependent on the radiation dose with the type of radiation as a parameter. Next, the dependence of the samples resistance on temperature was recorded (in the impurities region and in intrinsic region with the previously absorbed dose as a parameter. The results were statistically analyzed and explained on the basis of radiation effects in solids. The results are compared with those obtained by using Monte Carlo method. A good agreement was confirmed by the mentioned experimental investigation. [Projekat Ministarstva nauke Republike Srbije, br. 171007

  1. Development of a customized leading-edge discriminator for a planar-type segmented germanium detector

    A customized leading-edge discriminator has been developed for picking up information on the position and the time for a planar-type segmented germanium detector. The discriminator consisted of three stages: a differentiating amplifier, a voltage comparator, and a mono-stable multivibrator. With the present discriminator modules, we examined spectral characteristics for the segmented germanium detector by using uncollimated 662-keV gamma rays. Anode energy spectra in coincidence with cathodes showed that better peak-to-total ratios could be obtained with increasing coincidence fold. Further, a salient feature of the exponential decay in the time difference spectrum between the anode and cathodes was observed to a fair extent

  2. A Low-noise Germanium Ionization Spectrometer for Low-background Science

    Aalseth, Craig E; Colaresi, Jim; Fast, James E; Hossbach, Todd W; Orrell, John L; Overman, Cory T; Scholz, Bjorn; VanDevender, Brent A; Yocum, K Michael

    2016-01-01

    Recent progress on the development of very low noise high purity germanium ionization spectrometers has produced an instrument of 1.2 kg mass and excellent noise performance. The detector was installed in a low-background cryostat intended for use in a direct detection search for low mass, WIMP dark matter. This Transaction reports the thermal characterization of the cryostat, specifications of the newly prepared 1.2 kg p-type point contact germanium detector, and the spectroscopic performance of the integrated system. The integrated detector and low background cryostat achieved full-width-at-half-maximum noise performance of 98 eV for an electronic pulse generator peak and 1.9 keV for the 1332 keV Co-60 gamma ray.

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

    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.

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

    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.

  5. Hybrid continuum–atomistic modelling of swift heavy ion radiation damage in germanium

    The response of germanium to swift heavy ion irradiation is simulated using a hybrid continuum–atomistic approach. The continuum part of the model, which characterises the electronic excitations is an extension of the inelastic thermal spike based on an approximation to the Boltzmann transport equation; while the atomistic part is represented with molecular dynamics. This integrated method can realistically account for the non-equilibrium carrier dynamics in band-gap materials under irradiation, unlike earlier developments based on the two-temperature approach. The model is used to obtain temporal and spatial evolution of carrier density, electronic temperature and lattice temperature for germanium irradiated with carbon cluster ions. Good agreement with experimental data of amorphised latent track radii for different stopping powers is obtained by fitting a constant value for the electron–phonon coupling strength – the only parameter treated as free in the model

  6. Effects of Germanium Tetrabromide Addition to Zinc Tetraphenyl Porphyrin / Fullerene Bulk Heterojunction Solar Cells

    Atsushi Suzuki

    2014-03-01

    Full Text Available The effects of germanium tetrabromide addition to tetraphenyl porphyrin zinc (Zn-TPP/fullerene (C60 bulk heterojunction solar cells were characterized. The light-induced charge separation and charge transfer were investigated by current density and optical absorption. Addition of germanium tetrabromide inserted into active layer of Zn-TPP/C60 as bulk heterojunction had a positive effect on the photovoltaic and optical properties. The photovoltaic mechanism of the solar cells was discussed by experimental results. The photovoltaic performance was due to light-induced exciton promoted by insert of GeBr4 and charge transfer from HOMO of Zn-TPP to LUMO of C60 in the active layer.

  7. Monte Carlo simulation of complex germanium detector systems and Compton suppression spectrometers

    The performance of Germanium detectors and Compton suppression spectrometers is calculated using the Monte Carlo method in the energy range that is of interest for nuclear γ-ray spectroscopy. The calculated properties are: intrinsic peak efficiencies, peak/total and peak/Compton ratios as well as the Compton suppression factor for single gamma rays and high multiplicity gamma cascades. The reliability of the calculation is checked by comparison with the observed properties of existing devices. Then, response functions are predicted for new spectrometers. In particular, a new symmetric Compton suppression configuration using three Germanium crystals, which is capable of achieving an excellent performance, is proposed. This detector has been constructed and the experimental results are compared with the calculation. (orig.)

  8. Production of stable silicon and germanium isotopes via their enriched volatile compounds

    The paper considers two main approaches discussed in literature for conversion of gaseous fluorides SiF4, GeF4 and hydrogen-containing compound of germanium, i.e., GeH4, isotopic enriched by centrifugal method, into target products-stable isotopes of silicon and germanium in the form of bulk polycrystals and thin layers. In the first two-step (chemical) approach the fluorides are converted into intermediate compounds which are further subjected either to pyrolysis or to reduction by hydrogen. In the second single-step (plasma-chemical) approach the gaseous fluorides are reduced by hydrogen in plasma sustained by the discharges of different types. (author)

  9. GIOVE: a new detector setup for high sensitivity germanium spectroscopy at shallow depth

    Heusser, G., E-mail: gerd.heusser@mpi-hd.mpg.de; Weber, M., E-mail: marc.weber@mpi-hd.mpg.de; Hakenmüller, J. [Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117, Heidelberg (Germany); Laubenstein, M. [Laboratori Nazionali del Gran Sasso, Via G. Acitelli 22, 67100, Assergi, AQ (Italy); Lindner, M.; Maneschg, W.; Simgen, H.; Stolzenburg, D.; Strecker, H. [Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117, Heidelberg (Germany)

    2015-11-09

    We report on the development and construction of the high-purity germanium spectrometer setup GIOVE (Germanium Inner Outer VEto), recently built and now operated at the shallow underground laboratory of the Max-Planck-Institut für Kernphysik, Heidelberg. Particular attention was paid to the design of a novel passive and active shield, aiming at efficient rejection of environmental and muon induced radiation backgrounds. The achieved sensitivity level of ≤100 μBq kg{sup -1} for primordial radionuclides from U and Th in typical γ ray sample screening measurements is unique among instruments located at comparably shallow depths and can compete with instruments at far deeper underground sites.

  10. Study on dislocation multiplication in the head of Germanium single crystal

    LI Nan; FENG Deshen; YIN Shiping; SU Xiaoping; YANG Hai; YU Yunqi; MI Jianjun

    2006-01-01

    The high strength, radiation hardness and cost-effectiveness make Germanium the substrate of choice for high-efficiency multi-junction solar cells for space applications.Numerical modeling and large-scale simulation are important and indispensable tools in the analysis and development of crystal growth process.In this study, germanium single crystals with low dislocation density were produced by Czochralski method by applying the necking technique.Chemical etching pits method was used to measure the dislocation density, and a professional modeling software CrysVUn was used to obtain the thermal-stress distribution.The results show that the thermal-stress of the sample with diameter of 15 mm is nearly equal to that of other samples, so the thermal-stress does not influence the dislocation multiplication.Based on the result, the dislocation density must be strangely increased caused by gravity.

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

    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

  12. Dependence of photon interaction depth on linear attenuation coefficient in high pure germanium detectors

    The present work is concerned with the construction of a semiempirical function de (μ, Eγ) of the effective photon interaction depth depending upon both the linear attenuation coefficient of Ge and γ-ray energy. The interaction depth results obtained from the measurements in two high purity germanium crystals, which nearly equal in volume, have been fitted by using a function. The semiempirical function agrees with the measured interaction depth values on the average to within 3-4%. The knowledge of effective interaction depth of γ-rays in germanium detector is a useful parameter in order to calculate the absolute efficiency for any source-to-detector distance on the particular detector. (Author)

  13. Bibliographical study on the high-purity germanium radiation detectors used in gamma and X spectrometry

    The germanium or silicon lithium-drifted detectors, Ge(Li) or Si(Li), and high-purity germanium detectors, HP Ge (impurity concentration approximately 1010cm-3), are the most commonly used at the present time as gamma and X-ray spectrometers. The HP Ge detectors for which room temperature storage is the main characteristic can be obtained with a large volume and a thin window, and are used as the Ge(Li) in γ ray spectrometry or the Si(Li) in X-ray spectrometry. This publication reviews issues from 1974 to 1978 on the state of the art and applications of the HP Ge semiconductor detectors. 101 bibliographical notices with French summaries are presented. An index for authors, documents and periodicals, and subjects is included

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

    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

  15. Study of the creep of germanium bi-crystals by X ray topography and electronic microscopy

    This research thesis addresses the study of the microscopic as well as macroscopic aspect of the role of grain boundary during deformation, by studying the creep of Germanium bi-crystals. The objective was to observe interactions of network dislocations with the boundary as well as the evolution of dislocations in each grain. During the first stages of deformation, samples have been examined by X ray topography, a technique which suits well the observation of low deformed samples, provided their initial dislocation density is very low. At higher deformation, more conventional techniques of observation of sliding systems and electronic microscopy have been used. After some general recalls, the definition of twin boundaries and of their structure in terms of dislocation, a look at germanium deformation, and an overview of works performed on bi-crystals deformation, the author presents the experimental methods and apparatuses. He reports and discusses the obtained results at the beginning of deformation as well as during next phases

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

    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.

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

    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.

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

    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.

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

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

    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.

  1. Measurement of the isotopic composition of germanium by k{sub 0}-INAA and INAA

    Vermaercke, P., E-mail: pvermaer@sckcen.b [SCK-CEN, Belgian Nuclear Research Centre, Boeretang 200, B-2400 Mol (Belgium); Hult, M. [EC-JRC-IRMM, Institute for Reference Materials and Measurements, Retieseweg, B-2440 Geel (Belgium); Verheyen, L.; Farina Arbocco, F. [SCK-CEN, Belgian Nuclear Research Centre, Boeretang 200, B-2400 Mol (Belgium)

    2010-10-11

    In experiments searching for neutrinoless double {beta}-decay high-purity Germanium detectors enriched in {sup 76}Ge will be used. Due to the nature of these experiments the isotopic composition of the enriched germanium is an important parameter. In order to determine the {sup 76}Ge/{sup 74}Ge isotopic ratio in this new material, but also in natural and depleted samples, the feasibility of using k{sub 0}- and relative standardisation neutron activation analysis for the determination of isotopic ratios was investigated. The paper will discuss the accuracy and the estimated uncertainty of both methods in general. It was found that both techniques are useful for the determination of isotopic ratios. The analysis also demonstrated that the k{sub 0}-data for Ge should be re-evaluated.

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

    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

  3. Estimation of decrease in efficiency of the high purity Germanium detector after a long time operation

    In many recent years, the gamma spectrometry using the high purity germanium (HPGe) detector have come into widespread use to determine the activity of radioactive samples. However, the decrease in detector efficiency remarkably influences on the result of measured gamma spectra. In this work, we estimated the decrease in efficiency of the GC1518 HPGe detector made in Canberra Industries, Inc. and located at the Center for HCMC Nuclear Techniques. It was found that the detector efficiency reduces to 8% within 6 years from October 1999 to August 2005. The decrease in efficiency can be explained by increase in the thickness of an inactive germanium layer based on using the Monte Carlo simulation. (author)

  4. Measurement of the temperature dependence of pulse lengths in an n-type germanium detector

    Germanium detectors are operated at liquid nitrogen temperatures to reduce the number of electrons in the conduction band. The mobility of the charge carriers is temperature dependent and thus also the rise time of the pulses induced by the drifting charge carriers. The temperature, T, dependence of the pulse lengths for an 18-fold segmented n-type germanium detector was measured in the temperature range of 77-120 K. The interactions of 122 keV photons originating from 152Eu were selected and pulses as observed on the core and segment electrodes were studied. In both cases, the T dependence can be well described by an eκ/T ansatz, where κ is a fit parameter.

  5. Metastable phase formation during chemical vapor deposition of niobium-germanium films

    Regularities of different metastable phase formation during chemical vapor deposition of niobium-germanium coatings were investigated. These coatings were deposited on wire and band metal substrates by method of chemical transport reactions with the use of iodine as transporting agent. It was shown that it was possible to deposite the metastable Nb5Ge3 phase with structure of T2 type and X phase with cubic structure and hypothetical Nb2Ge composition during iodide process using Nb3Ge alloy as initial material together with phases existing at state diagram. Metastable T2 and X phases are formed only at high total pressure (more 250-500 Pa) and deposition rate less 1 μm/min. Coatings on the base of Nb3Ge with germanium content from 11 to 23 at.% were obtained

  6. Neutrino and dark matter physics with sub-keV germanium detectors

    Arun Kumar Soma; Lakhwinder Singh; Manoj Kumar Singh; Venktesh Singh; Henry T Wong; on behalf of the TEXONO Collaboration

    2014-11-01

    Germanium detectors with sub-keV sensitivities open a window to study neutrino physics to search for light weakly interacting massive particle (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. Highlights of the physics motivation, our R&D programme, as well as the status and plans are presented.

  7. Reaction studies of hot silicon and germanium radicals. Progress report, September 1, 1978-August 31, 1979

    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; (b) Thermally induced silylene and germylene reactions; (c) Silicon free radical chemistry; (d) The role of ionic reactions in the chemistry of recoiling silicon atoms

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

    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.

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

    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-}.

  10. Enhanced nonlinearity in photonic crystal fiber by germanium doping in the core region

    Tingting Sun; Guiyun Kai; Zhi Wang; Shuzhong Yuan; Xiaoyi Dong

    2008-01-01

    Germanium doping in silica can be used as a method for nonlinearity enhancement.Properties of the enhanced nonlinearity in photonic crystal fiber(PCF)with a GeO2-doped core are investigated theoretically by using all-vector finite element method.Numerical result shows that the nonlinear coefficient of PCF is greatly enhanced with increasing doping concentration,furthermore,optimal radius of the doped region should be considered for the desired operating wavelength.

  11. MATHEMATICAL MODELING OF THE DISSOLUTION PROCESS OF SILICON INTO GERMANIUM MELT

    , Mahfoud Kadja

    2011-01-01

    Numerical simulations were carried out to study the thermosolutal and flow structures observed in the dissolution experiments of silicon into a germanium melt. The dissolution experiments utilized a material configuration similar to that used in the Liquid Phase Diffusion (LPD) and Melt-Replenishment Czochralski (Cz) crystal growth systems. In the present model, the computational domain was assumed axisymmetric. Governing equations of the liquid phase (Si-Ge mixture), namely the equations of ...

  12. Measurement of the temperature dependence of pulse lengths in an -type germanium detector

    Abt, I; CALDWELL A.; J. Liu; Majorovits, B.; Volynets, O.

    2011-01-01

    Abstract The temperature dependence of the pulse length was measured for an 18-fold segmented n-type germanium detector in the temperature range of 77?120 K. The interactions of 122 keV photons originating from a 152Eu source were selected and pulses as observed on the core and segment electrodes were studied. In both cases, the temperature dependence can be well described by a Boltzmann-like ansatz.

  13. Calibration curve for germanium spectrometers from solutions calibrated by liquid scintillation counting

    The beta-gamma emitters ''60Co, ''137 Cs, ''131 I, ''210 Pb y ''129 Iare radionuclides for which the calibration by the CIEMAT/NIST method ispossible with uncertainties less than 1%. We prepared, from standardized solutions of these radionuclides, samples in vials of 20 ml. We obtained the calibration curves, efficiency as a function of energy, for two germanium detectors. (Author) 5 refs

  14. Transient response in doped germanium photoconductors under very low background operation

    Church, S. E.; Price, M.C.; Haegel, N. M.; Griffin, M. J.; Ade, P.A.R.

    1996-01-01

    Doped germanium photoconductors are the most sensitive detectors for astronomy in the wavelength range 40–240 μm. Under the extremely low background conditions encountered in cooled satellite instruments, these devices exhibit a number of transient effects, such as slow relaxation after a step change in illumination or bias, and spontaneous spiking at high signal levels. Such behavior can degrade the excellent instantaneous sensitivity of these detectors and create calibration uncertainties. ...

  15. Performance Analysis of Silicon and Germanium Nanowire Transistor using Crystal Orientation and Oxide Thickness

    P.Theres Mary; N.B. BALAMURUGAN

    2014-01-01

    Nanowire Transistors have attracted attention due to the probable high performance and excellent controllability of device current. In this paper, we investigate the performance analysis of nanowire transistors made of silicon and germanium materials. The nanowire transistor has a 3D distribution of electron density and electrostatic potential, therefore self-consistent 3D simulations are used. Nanowire (tool) is 3D Poisson self-consistent simulator which can study the 3D transport in nanowir...

  16. Importance of frequency-dependent grain boundary scattering in nanocrystalline silicon and silicon-germanium thermoelectrics

    Hua, Chengyun; Minnich, Austin J.

    2014-01-01

    Nanocrystalline silicon and silicon-germanium alloys are promising thermoelectric materials that have achieved substantially improved figure of merits compared to their bulk counterparts. This enhancement is typically attributed to a reduction in lattice thermal conductivity by phonon scattering at grain boundaries. However, further improvements are difficult to achieve because grain boundary scattering is poorly understood, with recent experimental observations suggesting that the phonon tra...

  17. High-purity germanium detector ionization pulse shapes of nuclear recoils, gamma interactions and microphonism

    Baudis, L.; Hellmig, J.; Klapdor-Kleingrothaus, H. V.; Ramachers, Y.; Hammer, J. W.; Mayer, A.

    1999-01-01

    Nuclear recoil measurements with high-purity Germanium detectors are very promising to directly detect dark matter candidates. The main background sources in such experiments are natural radioactivity and microphonic noise. Digital pulse shape analysis is an encouraging approach to reduce the background originating from the latter. To study the pulse shapes of nuclear recoil events we performed a neutron scattering experiment, which covered the ionization energy range from 20 to 80 keV. We ha...

  18. A Segmented, Enriched N-type Germanium Detector for Neutrinoless Double Beta-Decay Experiments

    Leviner, L. E.; Aalseth, C. E.; Ahmed, M. W.; Avignone III, F. T.; Back, H. O.; Barabash, A. S.; Boswell, M.(Los Alamos National Laboratory, Los Alamos, NM 87545, USA); L. De Braeckeleer(Washington U., Seattle); Brudanin, V. B.; Chan, Y-D.; Egorov, V. G.; Elliott, S. R.; Gehman, V. M.; Hossbach, T. W.; Kephart, J. D.

    2013-01-01

    We present data characterizing the performance of the first segmented, N-type Ge detector, isotopically enriched to 85% $^{76}$Ge. This detector, based on the Ortec PT6x2 design and referred to as SEGA (Segmented, Enriched Germanium Assembly), was developed as a possible prototype for neutrinoless double beta-decay measurements by the {\\sc Majorana} collaboration. We present some of the general characteristics (including bias potential, efficiency, leakage current, and integral cross-talk) fo...

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

    Yamauchi, Jun [Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522 (Japan); Yoshimoto, Yoshihide [Department of Applied Mathematics and Physics, Graduate School of Engineering, Tottori University, 4-101 Koyama-Minami, Tottori, 680-8552 (Japan); Suwa, Yuji [Central Research Laboratory, Hitachi, Ltd., Hatoyama, Saitama 350-0395 (Japan)

    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.

  20. Thermally stable low current consuming gallium and germanium chalcogenides for consumer and automotive memory applications

    Hewak, D. W.; Huang, C. C.; Gholipour, B.; K Knight; Guerin, S.; Hayden, B.; Purdy, G

    2011-01-01

    The phase change technology behind rewritable optical disks and the latest generation of electronic memories has provided clear commercial and technological advances for the field of data storage, by virtue of the many well known attributes, in particular scaling, cycling endurance and speed, that chalcogenide materials offer. While the switching power and current consumption of established germanium antimony telluride based memory cells are a major factor in chip design in real world applica...

  1. A single layer hydrogen silsesquioxane (HSQ) based lift-off process for germanium and platinum

    Passi, Vikram; Lecestre, Aurélie; Krzeminski, Christophe; Larrieu, Guilhem; Dubois, Emmanuel; Raskin, Jean-Pierre

    2009-01-01

    Primarily used as etch mask, single layer hydrogen silsesquioxane has never been investigated for lift-off technique. In this article, we propose a new technique where a single layer of hydrogen silsesquioxane, a negative tone electron beam resist, is used to make lift-off of germanium and platinum. Removal of exposed hydrogen silsesquioxane is tested for various concentrations of hydrofluoric acid. Ultrasonic agitation is also used to reduce the formation of flakes due to accumulation of mat...

  2. Temperature dependence of the pulse properties and the leakage current of germanium detectors

    Caldwell, Allen; Lenz, Daniel; Liu, Jing; Liu, Xiang; Majorovitz, Bela; Volynets, Oleksandr [Max-Planck-Institute for Physics, Munich (Germany)

    2010-07-01

    High-purity germanium detectors are used in neutrinoless double-beta decay experiments like Gerda as they have very good resolution and act as the detector and the source simultaneously. Germanium detectors are operated at liquid nitrogen temperatures to reduce the number of electrons in the conduction band. The mobility of the charge carriers is temperature dependent and thus also the rise time of the pulses induced by the drifting charge carriers. Therefore pulse shapes analysis has to take into account possible temperature variations. Measurements of the temperature dependence of the pulses were made using a high-purity n-type segmented germanium detector. The detector was installed in a vacuum cryostat and cooled through a copper cooling finger submerged in liquid nitrogen. A collimated {sup 152}Eu source located at two different positions along the crystal axes 100 and 110 was used. The temperature was monitored using a PT100 resistor installed at the closest possible point to the detector. The pulse properties in the temperature range from 93 to 99 K and the temperature dependence of the leakage current in the temperature range from 85 to 112 K are discussed.

  3. Defect Density Comparison of Detached versus Attached Bridgman Grown Germanium Crystals

    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.

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

    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

  5. Boron doping compensation of hydrogenated amorphous and polymorphous germanium thin films for infrared detection applications

    Moreno, M., E-mail: mmoreno@inaoep.mx [National Institute of Astrophysics, Optics and Electronics, INAOE, P.O. Box 51 and 216, Puebla, Z. P. 72840 Puebla (Mexico); Delgadillo, N. [Universidad Autónoma de Tlaxcala, Av. Universidad No. 1, Z. P. 90006 Tlaxcala (Mexico); Torres, A. [National Institute of Astrophysics, Optics and Electronics, INAOE, P.O. Box 51 and 216, Puebla, Z. P. 72840 Puebla (Mexico); Ambrosio, R. [Technology and Engineering Institute, Ciudad Juarez University UACJ, Av. Del Charro 450N, Z. P. 32310 Chihuahua (Mexico); Rosales, P.; Kosarev, A.; Reyes-Betanzo, C.; Hidalga-Wade, J. de la; Zuniga, C.; Calleja, W. [National Institute of Astrophysics, Optics and Electronics, INAOE, P.O. Box 51 and 216, Puebla, Z. P. 72840 Puebla (Mexico)

    2013-12-02

    In this work we have studied boron doping of hydrogenated amorphous germanium a-Ge:H and polymorphous germanium (pm-Ge:H) in low regimes, in order to compensate the material from n-type (due to oxygen contamination that commonly occurs during plasma deposition) to intrinsic, and in this manner improve the properties that are important for infrared (IR) detection, as activation energy (E{sub a}) and temperature coefficient of resistance (TCR). Electrical, structural and optical characterization was performed on the films produced. Measurements of the temperature dependence of conductivity, room temperature conductivity (σ{sub RT}), E{sub a} and current–voltage characteristics under IR radiation were performed in the compensated a-Ge:H and pm-Ge:H films. Our results demonstrate that, effectively, the values of E{sub a}, TCR and IR detection are improved on the a-Ge:H/pm-Ge:H films, using boron doping in low regimes, which results of interest for infrared detectors. - Highlights: • We reported boron doping compensation of amorphous and polymorphous germanium. • The films were deposited by plasma enhanced chemical vapor deposition. • The aim is to use the films as thermo-sensing elements in un-cooled microbolometers. • Those films have advantages over boron doped a-Si:H used in commercial detectors.

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

    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

  7. Effect of normal processes on thermal conductivity of germanium, silicon and diamond

    Banashree Saikai; Anil Kumar

    2008-07-01

    The effect of normal scattering processes is considered to redistribute the phonon momentum in (a) the same phonon branch – KK-S model and (b) between different phonon branches – KK-H model. Simplified thermal conductivity relations are used to estimate the thermal conductivity of germanium, silicon and diamond with natural isotopes and highly enriched isotopes. It is observed that the consideration of the normal scattering processes involving different phonon branches gives better results for the temperature dependence of the thermal conductivity of germanium, silicon and diamond with natural and highly enriched isotopes. Also, the estimation of the lattice thermal conductivity of germanium and silicon for these models with the consideration of quadratic form of frequency dependences of phonon wave vector leads to the conclusion that the splitting of longitudinal and transverse phonon modes, as suggested by Holland, is not an essential requirement to explain the entire temperature dependence of lattice thermal conductivity whereas KK-H model gives a better estimation of the thermal conductivity without the splitting of the acoustic phonon modes due to the dispersive nature of the phonon dispersion curves.

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

    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.

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

    Moffatt, R. A., E-mail: rmoffatt@stanford.edu; Cabrera, B.; Corcoran, B. M.; Kreikebaum, J. M.; Redl, P.; Shank, B.; Yen, J. J. [Department of Physics, Stanford University, Stanford, California 94305 (United States); Young, B. A. [Department of Physics, Stanford University, Stanford, California 94305 (United States); Department of Physics, Santa Clara University, Santa Clara, California 95053 (United States); Brink, P. L.; Cherry, M.; Tomada, A. [SLAC National Accelerator Facility, Menlo Park, California 94025 (United States); Phipps, A.; Sadoulet, B.; Sundqvist, K. M. [Department of Physics, University of California, Berkeley, California 94720 (United States)

    2016-01-11

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

    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.

  11. CDEX-1 1 kg point-contact germanium detector for low mass dark matter searches

    The CDEX collaboration has been established for direct detection of light dark matter particles, using ultra-low energy threshold point-contact p-type germanium detectors, in China JinPing underground Laboratory (CJPL). The first 1 kg point-contact germanium detector with a sub-keV energy threshold has been tested in a passive shielding system located in CJPL. The outputs from both the point-contact P+ electrode and the outside N+ electrode make it possible to scan the lower energy range of less than 1 keV and at the same time to detect the higher energy range up to 3 MeV. The outputs from both P+ and N+ electrode may also provide a more powerful method for signal discrimination for dark matter experiment. Some key parameters, including energy resolution, dead time, decay times of internal X-rays, and system stability, have been tested and measured. The results show that the 1 kg point-contact germanium detector, together with its shielding system and electronics, can run smoothly with good performances. This detector system will be deployed for dark matter search experiments. (authors)

  12. Carbon nanotube nanoelectrode arrays

    Ren, Zhifeng; Lin, Yuehe; Yantasee, Wassana; Liu, Guodong; Lu, Fang; Tu, Yi

    2008-11-18

    The present invention relates to microelectode arrays (MEAs), and more particularly to carbon nanotube nanoelectrode arrays (CNT-NEAs) for chemical and biological sensing, and methods of use. A nanoelectrode array includes a carbon nanotube material comprising an array of substantially linear carbon nanotubes each having a proximal end and a distal end, the proximal end of the carbon nanotubes are attached to a catalyst substrate material so as to form the array with a pre-determined site density, wherein the carbon nanotubes are aligned with respect to one another within the array; an electrically insulating layer on the surface of the carbon nanotube material, whereby the distal end of the carbon nanotubes extend beyond the electrically insulating layer; a second adhesive electrically insulating layer on the surface of the electrically insulating layer, whereby the distal end of the carbon nanotubes extend beyond the second adhesive electrically insulating layer; and a metal wire attached to the catalyst substrate material.

  13. Study of adsorption of germanium on β-SnO2 sorbent

    Full text: Tin dioxide (β -SnO2) is used as adsorbent for preparation of 68Ga generator. Commercial adsorbent of β -SnO2 is a little available and rare reagent. At present the only firm 'Carlo-Erba' (Italy) is its producer. Therefore we tried to prepare this adsorbent and to study of adsorption of germanium on the obtained β -SnO2. The main objective was to obtain good adsorption performance towards germanium. Another important feature is the separation of gallium from germanium to find best conditions for separation of the pair elements. The radioactive tracer technique was used for determination of the distributions coefficients (KD). Both 77Ge and 72Ga radionuclides were produced by irradiation of pure metals in WWR-SM nuclear reactor at a thermal neutron flux of 5 x 1013 n/cm2/s for 20-24 hours. The dissolution of the metal tin in concentrated nitric acid was used for preparation of β-SnO2. It is shown that the adsorption properties of β-SnO2 greatly depended on conditions of treatment after dissolution of tin. Extremely high distribution coefficients for 77Ge radionuclide and the more high separation factor of Ge-Ga were achieved in 1 M HCl for β -SnO2 sample dried at 180-200o C. Adsorption of germanium was quantitative (99.5-99.7 %) from hydrochloric acid solutions (0.1-1.4 M). The dynamic capacity before the breakthrough of germanium was 20 mg of Ge per gram of β -SnO2. The obtained adsorbent β-SnO2 was tested for separation of 68Ge-68Ga radionuclide chain. The optimal separation of the daughter 68Ga from parent 68Ge can be achieved by using 1 M HCl as eluent. It is shown that the tin dioxide - 1 M HCl generator system provides high yields of 68Ga (75-80%) with low levels of breakthrough of 68Ge (2 x10-4%)

  14. Characterization of segmented large volume, high purity germanium detectors

    γ-ray tracking in future HPGe arrays like AGATA will rely on pulse shape analysis (PSA) of multiple γ-interactions. For this purpose, a simple and fast procedure was developed which enabled the first full characterization of a segmented large volume HPGe detector. An analytical model for the hole mobility in a Ge crystal lattice was developed to describe the hole drift anisotropy with experimental velocity values along the crystal axis as parameters. The new model is based on the drifted Maxwellian hole distribution in Ge. It is verified by reproducing successfully experimental longitudinal hole anisotropy data. A comparison between electron and hole mobility shows large differences for the longitudinal and tangential velocity anisotropy as a function of the electrical field orientation. Measurements on a 12 fold segmented, n-type, large volume, irregular shaped HPGe detector were performed in order to determine the parameters of anisotropic mobility for electrons and holes as charge carriers created by γ-ray interactions. To characterize the electron mobility the complete outer detector surface was scanned in small steps employing photopeak interactions at 60 keV. A precise measurement of the hole drift anisotropy was performed with 356 keV rays. The drift velocity anisotropy and crystal geometry cause considerable rise time differences in pulse shapes depending on the position of the spatial charge carrier creation. Pulse shapes of direct and transient signals are reproduced by weighting potential calculations with high precision. The measured angular dependence of rise times is caused by the anisotropic mobility, crystal geometry, changing field strength and space charge effects. Preamplified signals were processed employing digital spectroscopy electronics. Response functions, crosstalk contributions and averaging procedures were taken into account implying novel methods due to the segmentation of the Ge-crystal and the digital electronics. The results are

  15. Characterization of segmented large volume, high purity germanium detectors

    Bruyneel, B. [Koeln Univ. (Germany). Inst. fuer Kernphysik

    2006-07-01

    {gamma}-ray tracking in future HPGe arrays like AGATA will rely on pulse shape analysis (PSA) of multiple {gamma}-interactions. For this purpose, a simple and fast procedure was developed which enabled the first full characterization of a segmented large volume HPGe detector. An analytical model for the hole mobility in a Ge crystal lattice was developed to describe the hole drift anisotropy with experimental velocity values along the crystal axis as parameters. The new model is based on the drifted Maxwellian hole distribution in Ge. It is verified by reproducing successfully experimental longitudinal hole anisotropy data. A comparison between electron and hole mobility shows large differences for the longitudinal and tangential velocity anisotropy as a function of the electrical field orientation. Measurements on a 12 fold segmented, n-type, large volume, irregular shaped HPGe detector were performed in order to determine the parameters of anisotropic mobility for electrons and holes as charge carriers created by {gamma}-ray interactions. To characterize the electron mobility the complete outer detector surface was scanned in small steps employing photopeak interactions at 60 keV. A precise measurement of the hole drift anisotropy was performed with 356 keV rays. The drift velocity anisotropy and crystal geometry cause considerable rise time differences in pulse shapes depending on the position of the spatial charge carrier creation. Pulse shapes of direct and transient signals are reproduced by weighting potential calculations with high precision. The measured angular dependence of rise times is caused by the anisotropic mobility, crystal geometry, changing field strength and space charge effects. Preamplified signals were processed employing digital spectroscopy electronics. Response functions, crosstalk contributions and averaging procedures were taken into account implying novel methods due to the segmentation of the Ge-crystal and the digital electronics

  16. ISS Solar Array Management

    Williams, James P.; Martin, Keith D.; Thomas, Justin R.; Caro, Samuel

    2010-01-01

    The International Space Station (ISS) Solar Array Management (SAM) software toolset provides the capabilities necessary to operate a spacecraft with complex solar array constraints. It monitors spacecraft telemetry and provides interpretations of solar array constraint data in an intuitive manner. The toolset provides extensive situational awareness to ensure mission success by analyzing power generation needs, array motion constraints, and structural loading situations. The software suite consists of several components including samCS (constraint set selector), samShadyTimers (array shadowing timers), samWin (visualization GUI), samLock (array motion constraint computation), and samJet (attitude control system configuration selector). It provides high availability and uptime for extended and continuous mission support. It is able to support two-degrees-of-freedom (DOF) array positioning and supports up to ten simultaneous constraints with intuitive 1D and 2D decision support visualizations of constraint data. Display synchronization is enabled across a networked control center and multiple methods for constraint data interpolation are supported. Use of this software toolset increases flight safety, reduces mission support effort, optimizes solar array operation for achieving mission goals, and has run for weeks at a time without issues. The SAM toolset is currently used in ISS real-time mission operations.

  17. Array for detecting microbes

    Andersen, Gary L.; DeSantis, Todd D.

    2014-07-08

    The present embodiments relate to an array system for detecting and identifying biomolecules and organisms. More specifically, the present embodiments relate to an array system comprising a microarray configured to simultaneously detect a plurality of organisms in a sample at a high confidence level.

  18. Micromachined electrode array

    Okandan, Murat (Edgewood, NM); Wessendorf, Kurt O. (Albuquerque, NM)

    2007-12-11

    An electrode array is disclosed which has applications for neural stimulation and sensing. The electrode array, in certain embodiments, can include a plurality of electrodes each of which is flexibly attached to a common substrate using a plurality of springs to allow the electrodes to move independently. In other embodiments of the electrode array, the electrodes can be fixed to the substrate. The electrode array can be formed from a combination of bulk and surface micromachining, and can include electrode tips having an electroplated metal (e.g. platinum, iridium, gold or titanium) or a metal oxide (e.g. iridium oxide) for biocompatibility. The electrode array can be used to form a part of a neural prosthesis, and is particularly well adapted for use in an implantable retinal prosthesis.

  19. Diode Laser Arrays

    Botez, Dan; Scifres, Don R.

    1994-08-01

    This book provides a comprehensive overview of the fundamental principles and applications of semiconductor diode laser arrays. All of the major types of arrays are discussed in detail, including coherent, incoherent, edge- and surface-emitting, horizontal- and vertical-cavity, individually addressed, lattice- matched and strained-layer systems. The initial chapters cover such topics as lasers, amplifiers, external-cavity control, theoretical modeling, and operational dynamics. Spatially incoherent arrays are then described in detail, and the uses of vertical-cavity surface emitter and edge-emitting arrays in parallel optical-signal processing and multi-channel optical recording are discussed. Researchers and graduate students in solid state physics and electrical engineering studying the properties and applications of such arrays will find this book invaluable.

  20. Microfabricated ion trap array

    Blain, Matthew G.; Fleming, James G.

    2006-12-26

    A microfabricated ion trap array, comprising a plurality of ion traps having an inner radius of order one micron, can be fabricated using surface micromachining techniques and materials known to the integrated circuits manufacturing and microelectromechanical systems industries. Micromachining methods enable batch fabrication, reduced manufacturing costs, dimensional and positional precision, and monolithic integration of massive arrays of ion traps with microscale ion generation and detection devices. Massive arraying enables the microscale ion traps to retain the resolution, sensitivity, and mass range advantages necessary for high chemical selectivity. The reduced electrode voltage enables integration of the microfabricated ion trap array with on-chip circuit-based rf operation and detection electronics (i.e., cell phone electronics). Therefore, the full performance advantages of the microfabricated ion trap array can be realized in truly field portable, handheld microanalysis systems.

  1. Evaluation of chemical and structural properties of germanium-carbon coatings deposited by plasma enhanced chemical vapor deposition

    Jamali, Hossein, E-mail: h.jamali@mut-es.ac.ir; Mozafarinia, Reza; Eshaghi, Akbar

    2015-10-15

    Germanium-carbon coatings were deposited on silicon and glass substrates by plasma enhanced chemical vapor deposition (PECVD) using three different flow ratios of GeH{sub 4} and CH{sub 4} precursors. Elemental analysis, structural evaluation and microscopic investigation of coatings were performed using laser-induced breakdown spectroscopy (LIBS), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM), respectively. Based on the results, the coatings exhibited a homogeneous and dense structure free of pores with a very good adhesion to substrate. The structural evaluation revealed that the germanium-carbon coatings were a kind of a Ge-rich composite material containing the amorphous and crystalline germanium and amorphous carbon with the mixture of Ge–Ge, Ge–C, C–C, Ge–H and C–H bonds. The result suggested that the amorphisation of the coatings could be increased with raising CH{sub 4}:GeH{sub 4} flow rate ratio and subsequently increasing C amount incorporated into the coating. - Highlights: • Germanium-carbon coatings were prepared by PECVD technique. • The germanium-carbon coatings were a kind of composite material. • The amorphisation of the coatings were increased with raising CH{sub 4}:GeH{sub 4} flow ratio.

  2. Methods to improve and understand the sensitivity of high purity germanium detectors for searches of rare events

    Volynets, Oleksandr

    2012-07-27

    Observation of neutrinoless double beta-decay could answer fundamental questions on the nature of neutrinos. High purity germanium detectors are well suited to search for this rare process in germanium. Successful operation of such experiments requires a good understanding of the detectors and the sources of background. Possible background sources not considered before in the presently running GERDA high purity germanium detector experiment were studied. Pulse shape analysis using artificial neural networks was used to distinguish between signal-like and background-like events. Pulse shape simulation was used to investigate systematic effects influencing the efficiency of the method. Possibilities to localize the origin of unwanted radiation using Compton back-tracking in a granular detector system were examined. Systematic effects in high purity germanium detectors influencing their performance have been further investigated using segmented detectors. The behavior of the detector response at different operational temperatures was studied. The anisotropy effects due to the crystallographic structure of germanium were facilitated in a novel way to determine the orientation of the crystallographic axes.

  3. Methods to improve and understand the sensitivity of high purity germanium detectors for searches of rare events

    Observation of neutrinoless double beta-decay could answer fundamental questions on the nature of neutrinos. High purity germanium detectors are well suited to search for this rare process in germanium. Successful operation of such experiments requires a good understanding of the detectors and the sources of background. Possible background sources not considered before in the presently running GERDA high purity germanium detector experiment were studied. Pulse shape analysis using artificial neural networks was used to distinguish between signal-like and background-like events. Pulse shape simulation was used to investigate systematic effects influencing the efficiency of the method. Possibilities to localize the origin of unwanted radiation using Compton back-tracking in a granular detector system were examined. Systematic effects in high purity germanium detectors influencing their performance have been further investigated using segmented detectors. The behavior of the detector response at different operational temperatures was studied. The anisotropy effects due to the crystallographic structure of germanium were facilitated in a novel way to determine the orientation of the crystallographic axes.

  4. Evaluation of chemical and structural properties of germanium-carbon coatings deposited by plasma enhanced chemical vapor deposition

    Germanium-carbon coatings were deposited on silicon and glass substrates by plasma enhanced chemical vapor deposition (PECVD) using three different flow ratios of GeH4 and CH4 precursors. Elemental analysis, structural evaluation and microscopic investigation of coatings were performed using laser-induced breakdown spectroscopy (LIBS), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM), respectively. Based on the results, the coatings exhibited a homogeneous and dense structure free of pores with a very good adhesion to substrate. The structural evaluation revealed that the germanium-carbon coatings were a kind of a Ge-rich composite material containing the amorphous and crystalline germanium and amorphous carbon with the mixture of Ge–Ge, Ge–C, C–C, Ge–H and C–H bonds. The result suggested that the amorphisation of the coatings could be increased with raising CH4:GeH4 flow rate ratio and subsequently increasing C amount incorporated into the coating. - Highlights: • Germanium-carbon coatings were prepared by PECVD technique. • The germanium-carbon coatings were a kind of composite material. • The amorphisation of the coatings were increased with raising CH4:GeH4 flow ratio

  5. Study of high K isomers and shape coexistence in sup 1 sup 8 sup 8 Pb Nuclei; Germanium detector; RITU; JUROSPHERE

    Moore, C J P

    2002-01-01

    An experiment was designed to produce sup 1 sup 8 sup 8 Pb nuclei using the sup 1 sup 5 sup 0 Sm( sup 4 sup 2 Ca,4n) sup 1 sup 8 sup 8 Pb reaction at an energy of 200 MeV. It was performed at the University of Jyvaeskylae, Finland, using the gas-filled recoil separator RITU with JUROSPHERE at the target position and an array of quadrant detectors around the implantation strip detector. There was also the GSI Super Clover germanium detector at the focal plane with its 4 crystals being treated as individual spectrometers. Using a prompt-delayed coincidence technique the gamma rays above a 1.2 mu s isomer can be elucidated by tagging on the subsequently delayed transitions. Transitions above this isomer have been discovered for the first time and a tentative decay scheme has been constructed. From gamma-ray intensities, (g sub K -g sub R)/Q sub 0 ratios have been calculated for this isomer and it has been allocated a nu left brace 9/2 sup + [624] x 7/2 sup - [514]right brace configuration with a spin and parity ...

  6. A small diameter, flexible, all attitude, self-contained germanium spectrometer. Operator's manual

    The end of the Cold War has brought about tremendous changes in the nuclear complex of the Department of Energy. One of the many changes has been the shutdown or decommissioning of many facilities that performed nuclear work. One of the steps in the process of decommissioning a facility involves the decontamination or removal of drain lines or pipes that may have carried radioactive materials at one time. The removal of all these pipes and drain lines to a nuclear disposal facility could be quite costly. It was suggested by Pacific Northwest National Laboratory (PNNL) that a germanium spectrometer could be built that could fit through straight pipes with a diameter as small as 5.08 cm (2 inches) and pass through curved pipes with a diameter as small as 7.6 cm (3 inches) such as that of a 3-inch p-trap in a drain line. The germanium spectrometer could then be used to simultaneously determine all gamma-ray emitting radionuclides in or surrounding the pipe. By showing the absence of any gamma-ray emitting radionuclides, the pipes could then be reused in place or disposed of as non-radioactive material, thus saving significantly in disposal costs. A germanium spectrometer system has been designed by PNNL and fabricated by Princeton Gamma Tech (PGT) that consists of three segments, each 4.84 cm in diameter and about 10 cm in length. Flexible stainless steel bellows were used to connect the segments. Segment 1 is a small liquid nitrogen reservoir. The reservoir is filled with a sponge-like material which enables the detector to be used in any orientation. A Stirling cycle refrigerator is under development which can replace the liquid nitrogen reservoir to provide continuous cooling and operation

  7. A small diameter, flexible, all attitude, self-contained germanium spectrometer. Operator`s manual

    Bordzindki, R.L.; Lepel, E.A.; Reeves, J.H. [Battelle, Pacific Northwest National Lab., Richland, WA (United States); Kohli, R. [Battelle, Columbus Lab., OH (United States)

    1997-05-01

    The end of the Cold War has brought about tremendous changes in the nuclear complex of the Department of Energy. One of the many changes has been the shutdown or decommissioning of many facilities that performed nuclear work. One of the steps in the process of decommissioning a facility involves the decontamination or removal of drain lines or pipes that may have carried radioactive materials at one time. The removal of all these pipes and drain lines to a nuclear disposal facility could be quite costly. It was suggested by Pacific Northwest National Laboratory (PNNL) that a germanium spectrometer could be built that could fit through straight pipes with a diameter as small as 5.08 cm (2 inches) and pass through curved pipes with a diameter as small as 7.6 cm (3 inches) such as that of a 3-inch p-trap in a drain line. The germanium spectrometer could then be used to simultaneously determine all gamma-ray emitting radionuclides in or surrounding the pipe. By showing the absence of any gamma-ray emitting radionuclides, the pipes could then be reused in place or disposed of as non-radioactive material, thus saving significantly in disposal costs. A germanium spectrometer system has been designed by PNNL and fabricated by Princeton Gamma Tech (PGT) that consists of three segments, each 4.84 cm in diameter and about 10 cm in length. Flexible stainless steel bellows were used to connect the segments. Segment 1 is a small liquid nitrogen reservoir. The reservoir is filled with a sponge-like material which enables the detector to be used in any orientation. A Stirling cycle refrigerator is under development which can replace the liquid nitrogen reservoir to provide continuous cooling and operation.

  8. Structural and optical properties of 200 mm germanium-on-insulator (GeOI) substrates for silicon photonics applications

    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.

  9. Efficiency enhancements in crystalline silicon solar cells by alloying with germanium

    Healy, S.A.; Green, M.A. (New South Wales Univ., Kensington (Australia). Centre for Photovoltaic Devices and Systems)

    1992-12-01

    Thin-film crystalline silicon (c-Si) offers the promise of high performance photovoltaic cells at low cost. The incorporation of a region alloyed with germanium into a thin-film c-Si cell offers an enhancement in the near infrared response via the reduced bandgap of this region. This proposition is validated via theoretical analyses and computer device modelling which show that significant gains in cell efficiencies can be obtained as a result of realistic surface restraints on cell voltage. Fabrication techniques are examined with particular emphasis on liquid phase epitaxy and future possible implementations are postulated. (orig.).

  10. A New Expression for the Full Energy Peak Efficiency of a High Pure Germanium Detector

    Medhat, M E; Awaad, Z

    2001-01-01

    An empirical expression for the full energy photo-peak efficiency in terms of gamma-ray energy (E) and the vertical distance from the detector surface (d) (i.e. efficiency = function (d,E)) has been obtained for a high pure germanium detector (HPGe) using different standard sources. Comparison of the calculated efficiencies and the experimentally measured values for the energy range from 59.5-1332.2 keV and a source-to-detector distance of 5-30 cm showed that the theoretical values agree with the experiment.

  11. Co-doping with antimony to control phosphorous diffusion in germanium

    Tahini, H. A.

    2013-02-15

    In germanium, phosphorous and antimony diffuse quickly and as such their transport must be controlled in order to design efficient n-typed doped regions. Here, density functional theory based calculations are used to predict the influence of double donor co-doping on the migration activation energies of vacancy-mediated diffusion processes. The migration energy barriers for phosphorous and antimony were found to be increased significantly when larger clusters involving two donor atoms and a vacancy were formed. These clusters are energetically stable and can lead to the formation of even larger clusters involving a number of donor atoms around a vacancy, thereby affecting the properties of devices.

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

    Koleśnik-Gray, Maria M.; Krstić, Vojislav, E-mail: vojislav.krstic@fau.de [Department of Physics, Chair for Applied Physics, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Staudtstr. 7, 91058 Erlangen (Germany); Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), and AMBER at CRANN, Trinity College Dublin, College Green, Dublin 2 (Ireland); School of Physics, Trinity College Dublin, College Green, Dublin 2 (Ireland); Sorger, Christian; Weber, Heiko B. [Department of Physics, Chair for Applied Physics, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Staudtstr. 7, 91058 Erlangen (Germany); Biswas, Subhajit; Holmes, Justin D. [Materials Chemistry and Analysis Group, Department of Chemistry, Tyndall Institute, University College Cork, Cork (Ireland); Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), and AMBER at CRANN, Trinity College Dublin, College Green, Dublin 2 (Ireland)

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

    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

  14. Simulation of gamma-ray current pulse shapes produced in a high purity germanium detector

    Bambford, G.J.; Rester, A.C.; Coldwell, R.L. (Inst. for Astrophysics and Planetary Exploration, Univ. of Florida, Alachua, FL (United States))

    1992-08-01

    In this paper, the authors present results of a simulation of gamma-ray interactions in a high purity germanium detector (HPGe). Gamma-ray interactions have been divided into Compton events which leave only part of their energy in the detector and full energy events which leave all their energy in the detector. The current pulse shapes from the detector were examined on a pulse by pulse basis. the simulation shows that rejecting all waveforms with trailing edges less than 50 ns improves the peak to Compton ratio by a factor of two and in addition, flattens the remaining Compton edges.

  15. Simulation of gamma-ray current pulse shapes produced in a high purity germanium detector

    In this paper, the authors present results of a simulation of gamma-ray interactions in a high purity germanium detector (HPGe). Gamma-ray interactions have been divided into Compton events which leave only part of their energy in the detector and full energy events which leave all their energy in the detector. The current pulse shapes from the detector were examined on a pulse by pulse basis. the simulation shows that rejecting all waveforms with trailing edges less than 50 ns improves the peak to Compton ratio by a factor of two and in addition, flattens the remaining Compton edges

  16. Experimental Search for Solar Axions via Coherent Primakoff Conversion in a Germanium Spectrometer

    Avignone, F T; Brodzinski, R; Collar, J I; Creswick, R J; Di Gregorio, D E; Farach, H A; Gattone, A O; Guérard, C K; Hasenbalg, F; Huck, H; Miley, H S; Morales, A; Morales, J; Nussinov, S; De Solorzano, A O; Reeves, J H; Villar, J; Zioutas, Konstantin

    1998-01-01

    Results are reported of an experimental search for the unique, rapidly varying temporal pattern of solar axions coherently converting into photons via the Primakoff effect in a single crystal germanium detector. This conversion is predicted when axions are incident at a Bragg angle with a crystalline plane. The analysis of approximately 1.94 kg.yr of data from the 1 kg DEMOS detector in Sierra Grande, Argentina, yields a new laboratory bound on axion-photon coupling of $g_{a\\gamma \\gamma} < 2.7\\cdot 10^{-9}$ GeV$^{-1}$, independent of axion mass up to ~ 1 keV.

  17. Diffusion of E centers in germanium predicted using GGA+U approach

    Tahini, H. A.

    2011-08-17

    Density functional theory calculations (based on GGA+U approach) are used to investigate the formation and diffusion of donor-vacancy pairs (E centers) in germanium. We conclude that depending upon the Fermi energy,E centers that incorporate for phosphorous and arsenic can form in their neutral, singly negatively or doubly negatively charged states whereas with antimony only the neutral or doubly negatively charged states are predicted. The activation energies of diffusion are compared with recent experimental work and support the idea that smaller donor atoms exhibit higher diffusionactivation energies.

  18. Low-energy neutrino and dark matter physics with sub-keV germanium detectors

    A K Soma; L Singh; M K Singh; V Singh; H T Wong

    2012-11-01

    The TEXONO-CDEX Collaboration (Taiwan experiment on neutrino–China dark matter experiment) explores high-purity germanium (HPGe) detection technology to develop a sub-keV threshold detector for pursuing studies on low mass weakly interacting massive particles (WIMPs), properties of neutrino and the possibilities of neutrino-nucleus coherent scattering observation. This article will introduce the facilities of newly established China Jing-Ping Underground Laboratory (CJPL), preliminary result of cosmic ray background studies at CJPL, the dark matter studies pursued at Kuo-Sheng Neutrino Laboratory (KSNL) and research efforts to accomplish our physics goals.

  19. Ion implanted N-type contract for high-purity germanium radiation detectors

    Thin large-area n+ contacts on high-purity germanium detectors have been produced by implantation of 25 keV phosphorous ions. The contacts show leakage current of less than 10-9 A up to fields of greater than 2000 V/cm. Unannealed lattice damage may still limit the maximum applied field, but proper surface treatment prior to implantation and subsequent annealing steps have resulted in a dramatic improvement in the applied field. Spectra are presented which demonstrate that the n+ window is thin and the spectrometer performance is excellent

  20. Advanced characterization of carrier profiles in germanium using micro-machined contact probes

    Clarysse, T.; Konttinen, M.; Parmentier, B.;

    2012-01-01

    The accurate determination of the sheet resistance and carrier depth profile, i.e. active dopant profile, of shallow junction isolated structures involving new high mobility materials, such as germanium, is a crucial topic for future CMOS development. In this work, we discuss the capabilities of...... use of only two probes, a spreading resistance like setup is obtained with small spacing and drastically reduced electrical contact radii (~10 nm) leading to a substantial reduction of the correction factors which are normally required for converting spreading resistance profiles. We demonstrate the...

  1. Separation of no-carrier-added arsenic-77 from neutron irradiated germanium

    Arsenic-77 (T1/2 = 1.6 d) was produced by irradiating natural germanium in Pakistan Research Reactor-1. The nuclear reaction 76Ge(n, γ-) produces 77Ge, which decays by emission of β particles into 77As. The neutron irradiated target was dissolved in aqua regia, excess of acid was removed by evaporation and finally the solution in basic media was passed through hydrous zirconium oxide (HZO) column. The Ge was quantitatively retained on HZO, while 77As was present in the effluent. More than 90% 77As was recovered. The chemical impurity of Ge in 77As was < 0.01 μg/mL. (orig.)

  2. Ultra compact 45 GHz CMOS compatible Germanium waveguide photodiode with low dark current.

    DeRose, Christopher T; Trotter, Douglas C; Zortman, William A; Starbuck, Andrew L; Fisher, Moz; Watts, Michael R; Davids, Paul S

    2011-12-01

    We present a compact 1.3 × 4 μm2 Germanium waveguide photodiode, integrated in a CMOS compatible silicon photonics process flow. This photodiode has a best-in-class 3 dB cutoff frequency of 45 GHz, responsivity of 0.8 A/W and dark current of 3 nA. The low intrinsic capacitance of this device may enable the elimination of transimpedance amplifiers in future optical data communication receivers, creating ultra low power consumption optical communications. PMID:22273883

  3. Evaluations of the commercial spectrometer systems for safeguards applications using the germanium detectors

    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

  4. Determination of mean inner potential of germanium using off-axis electron holography.

    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

  5. Experiments towards size and dopant control of germanium quantum dots for solar applications

    Brittany L. Oliva-Chatelain; Barron, Andrew R.

    2015-01-01

    While the literature for the doping of silicon quantum dots (QDs) and nanocrystals (NCs) is extensive, reports of doping their germanium analogs are sparse. We report a range of attempts to dope Ge QDs both during and post-synthesis. The QDs have been characterized by TEM, XPS, and I/V measurements of SiO2 coated QD thin films in test cells using doped Si substrates. The solution synthesis of Ge QDs by the reduction of GeCl4 with LiAlH4 results in Ge QDs with a low level of chlorine atoms on ...

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

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

  7. Spectral studies on germanium pin-photovoltaic cells for thermophotovoltaic conversion. Technical report

    Kittl, E.; Guazzoni, G.

    1975-05-01

    The results of an experimental investigation on a newly-developed germanium PIN-photovoltaic cell are reported, covering measured data on the spectral response of this cell. Also reported are experimental data on the optical surface reflectance and an analysis of its influence on the true spectral response of the cell. Measurements of the cell's output performance are reported for three different sources of chromatic radiation. These results are then compared to theoretical expectations derived from a computer analysis. (GRA)

  8. Ab initio modeling of defects in silicon, germanium and SiGe alloys

    Torres, V. J. B.; Coutinho, J.; Carvalho, A; Barroso, M.; Almeida, Luís; Pinto, H.; Ribeiro, R. M.

    2005-01-01

    Understanding the most elemental defects in semiconductors is a fundamental step to grasp the countless solid-state reactions that may occur during crystal growth, device processing and operation stages. The higher carrier mobilitity in SiGe alloys and germanium, when compared with silicon, and the necessity to a higher K dielectric than SiO2 makes these semiconductors the most contendors to a new generation of electronic devices. Our aim is to model self and impurity point defects in SiGe a...

  9. Search of axions from a nuclear power reactor with a high-purity germanium detector

    This article reports the first study of possible emissions of axions from power reactors using Primakoff and Compton conversions as the detection mechanisms. The expected experimental signatures are mono-energetic lines produced by their Primakoff or Compton conversions at a high-purity germanium (HPGe) detector. No evidence of axion emissions were observed and constraints on axion couplings versus axion mass within the framework of invisible axion models were placed. This experimental approach provides a unique probe for axion mass at the keV-MeV range not accessible to the other techniques

  10. Experimental Search for Solar Axions via Coherent Primakoff Conversion in a Germanium Spectrometer

    Avignone, F. T.; Abriola, D.; Brodzinski, R. L.; J. I. Collar; Creswick, R.J.; DiGregorio, D. E.; Farach, H. A.; Gattone, A. O.; Guerard, C. K.; Hasenbalg, F.; Huck, H.; Miley, H. S.; Morales, A.; MORALES, J., CRUZ, D., DELGADO, P., LIZANA, M., LÓPEZ, V.; Nussinov, S.

    1997-01-01

    Results are reported of an experimental search for the unique, rapidly varying temporal pattern of solar axions coherently converting into photons via the Primakoff effect in a single crystal germanium detector. This conversion is predicted when axions are incident at a Bragg angle with a crystalline plane. The analysis of approximately 1.94 kg.yr of data from the 1 kg DEMOS detector in Sierra Grande, Argentina, yields a new laboratory bound on axion-photon coupling of $g_{a\\gamma \\gamma} < 2...

  11. Experimental Search for Solar Axions via Coherent Primakoff Conversion in a Germanium Spectrometer

    Results are reported of an experimental search for the unique, rapidly varying temporal pattern of solar axions coherently converting into photons via the Primakoff effect in a single crystal germanium detector when axions are incident at a Bragg angle with a crystalline plane. The analysis of 1.94kgyr of data from the 1kg DEMOS detector in Sierra Grande, Argentina, yields a new laboratory bound by an axion-photon coupling of gaγγ-9 GeV-1 , independent of axion mass up to ∼1 keV . copyright 1998 The American Physical Society

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

    Wang, X.; Tsybeskov, L., E-mail: tsybesko@njit.edu [ECE Department, New Jersey Institute of Technology, Newark, New Jersey 07102 (United States); Kamins, T. I. [Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Wu, X.; Lockwood, D. J. [National Research Council, Ottawa, Ontario K1A 0R6 (Canada)

    2015-12-21

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

  13. Electric-Field Ionization of Gallium Acceptors in Germanium Induced by Single-cycle Terahertz Pulses

    Mukai, Y; Tanaka, K

    2013-01-01

    The electric field ionization of gallium acceptors in germanium was studied by using terahertz time-domain spectroscopy after single-cycle terahertz pulse excitation. As the peak electric field of the excitation pulse increases, the distinct absorptions due to acceptor transitions centered at 2.0 and 2.2 THz decrease, and simultaneously, absorption emerges in the lower frequency region. These behaviors clearly show that the terahertz pulse ionizes neutral acceptors. The electric field dependence of the released hole density is well reproduced by a model assuming direct field-assisted tunneling of acceptors.

  14. Surface Passivation of Germanium Using NH3 Ambient in RTP for High Mobility MOS Structure

    Anil G. Khairnar; Y.S. Mhaisagar; A.M. Mahajan

    2013-01-01

    Ge CMOS is very striking for the post Si-CMOS technology. However, we have to attempt a number of challenges with regard to materials and their interface control. In this paper we have investigated the control of the interfacial properties of SiO2 / Ge gate stack structures by the thermal nitridation technique. Structural and electrical properties of SiO2 gate-dielectric metal-oxide-semiconductor (MOS) capacitors deposited by sputtering on germanium are studied. The structural characterizatio...

  15. Electric and magnetic dipolar response of Germanium spheres: Interference effects, scattering anisotropy and optical forces

    Gómez-Medina, Raquel; Suárez-Lacalle, Irene; González, Francisco; Moreno, Fernando; Nieto-Vesperinas, Manuel; Sáenz, Juan J

    2011-01-01

    We address the scattering cross sections, and their consequences, for submicrometer Germanium spheres. It is shown that there is a wide window in the near infrared where light scattering by these particles is fully described by their induced electric and magnetic dipoles. In this way, we observe remarkable anisotropic scattering angular distributions, as well as zero forward or backward scattered intensities, which until recently was theoretically demonstrated only for hypothetically postulated magnetodielectric spheres. Also, interesting new effects of the optical forces exerted on these objects are now obtained.

  16. Design and Development of Binary Diffractive Germanium Lens by Thin Film Deposition

    Alshami, M.; Wabby, A.; Mousselly, M. F.

    2015-11-01

    The design and development of infrared (λ: [8]-[12] μm) binary diffractive germanium lens (BDGL) by two - steps thin film deposition (Physical vapor deposition (PVD) technique) is presented. The optical design of the required elements using the optical design code Zemax, the design of the 4 steps binary surface and its required metallic masks using the programming language Delphi, the procedures of fabrication, and the measurement of the resulting profile, were presented. The comparison between the refractive/diffractive lenses by measuring the minimum resolvable temperature difference (MRTD) shows the advantages of binary diffractive surface.

  17. Feasibility of organo-beryllium target mandrels using organo-germanium PECVD as a surrogate

    Inertial Confinement Fusion capsules incorporating beryllium are becoming attractive for use in implosion experiments designed for modest energy gain. This paper explores the feasibility of chemical vapor deposition of organo-beryllium precursors to form coating materials of interest as ablators and fuel containers. Experiments were performed in a surrogate chemical system utilizing tetramethylgermane as the organometallic precursor. Coatings with up to 60 mole percent germanium were obtained. These coatings compare favorably with those previously reported in the literature and provide increasing confidence that a similar deposition process with an organo-beryllium precursor would be successful

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

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

    2016-06-01

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

  19. High-precision efficiency calibration of a high-purity co-axial germanium detector

    A high-purity co-axial germanium detector has been calibrated in efficiency to a precision of about 0.15% over a wide energy range. High-precision scans of the detector crystal and γ-ray source measurements have been compared to Monte-Carlo simulations to adjust the dimensions of a detector model. For this purpose, standard calibration sources and short-lived online sources have been used. The resulting efficiency calibration reaches the precision needed e.g. for branching ratio measurements of super-allowed β decays for tests of the weak-interaction standard model

  20. Germanium thermometers in the temperature range .1000K to 4.20K

    The sensitivity characteristics of two germanium thermometers that proved to be convenient sensors in the temperature range from .1000K to 4.20K, are described. Their resistances change from about 8 x 105 ohms at .1000K to about 100 ohms at 4.20K. The calibration curves were fitted to natural spline functions of order 3 in the whole range of temperatures. These functions give less than half millidegree standard dispersion against 15 millidegree standard dispersion when usual polynomial interpolations are used. It is discussed what spline functions are, and compare the goodness of spline interpolation with polynomial methods

  1. Synthesis and characterization of germanium monosulphide (GeS) single crystals grown using different transporting agents

    G K Solanki; Dipika B Patel; Sandip Unadkat; M K Agarwal

    2010-05-01

    This paper reports the growth of germanium monosulphide (GeS) single crystals by vapour phase technique using different transporting agents. The single crystallinity and composition of the grown crystals have been verified by transmission electron microscopy (TEM) and energy dispersive analysis of X-rays (EDAX) respectively. Resistivity measurements have been carried out in different temperature ranges. Transport parameters, e.g. resistivity, Hall coefficient, carrier concentration and mobility have been measured at varying magnetic fields. All the experimental results have been explained.

  2. Introduction to adaptive arrays

    Monzingo, Bob; Haupt, Randy

    2011-01-01

    This second edition is an extensive modernization of the bestselling introduction to the subject of adaptive array sensor systems. With the number of applications of adaptive array sensor systems growing each year, this look at the principles and fundamental techniques that are critical to these systems is more important than ever before. Introduction to Adaptive Arrays, 2nd Edition is organized as a tutorial, taking the reader by the hand and leading them through the maze of jargon that often surrounds this highly technical subject. It is easy to read and easy to follow as fundamental concept

  3. Conceptual design of a high resolution Ge array with tracking and imaging capabilities for the DESPEC (FAIR) experiment

    We present results of Monte Carlo simulations for the conceptual design of the high-resolution DESPEC Germanium Array Spectrometer (DEGAS) proposed for the Facility for Ion and Antiproton Research (FAIR) under construction at Darmstadt, Germany. The project is carried out in three phases, although only results for the two first phases will be addressed in this work. The first phase will consist of a re-arrangement of the EUROBALL cluster detectors previously used in the RISING campaign at GSI. The second phase is based on coupling AGATA-type triple-cluster detectors with EUROBALL cluster detectors in a compact geometry around the active ion implantation target of DESPEC

  4. Physical characteristics of germanium to be considered in the radiation shielding calculation for the prompt gamma rays facility analysis

    Physical characteristics of germanium (gamma detector material) to be considered in the shielding design have been researched for the prompt gammas rays facility. Reports on gamma spectrum analysis produced by neutronic capture show that an important factor to be considered are those produced by inelastic collisions with the detector material, the germanium. These collisions tend to damage the crystal and consequently, the resolution and life of detector. A research has been done concerning which energies should be considered using graphics of efficient sections existing at internet and with the MCNP calculation code

  5. Determination of the free carrier concentration in atomic-layer doped germanium thin films by infrared spectroscopy

    Novel silicon photonics applications requiring heavy n-type doping have recently driven a great deal of interest towards the phosphorous doping of germanium. In this work we report on infrared reflectance spectroscopy measurements of the electron density in heavily n-type doped germanium layers obtained by stacking multiple phosphorous δ-layers. Here, we demonstrate that the conventional Drude model of the electrodynamic response of free carriers in metals can be adapted to describe heavily doped semiconductor thin films. Consequently, the effect of the electron density on the plasma frequency, scattering rate and complex permittivity can be investigated. (special issue article)

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

    Hille, P., E-mail: Pascal.Hille@physik.uni-giessen.de; Müßener, J.; Becker, P.; Teubert, J.; Schörmann, J.; Eickhoff, M. [I. Physikalisches Institut, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392 Gießen (Germany); Mata, M. de la [Institut de Ciencia de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, CAT (Spain); Rosemann, N.; Chatterjee, S. [Faculty of Physics and Materials Science Center, Philipps Universität Marburg, Renthof 5, 35032 Marburg (Germany); Magén, C. [Laboratorio de Microscopías Avanzadas, Instituto de Nanociencia de Aragon-ARAID, Universidad de Zaragoza, 50018 Zaragoza (Spain); Arbiol, J. [Institut de Ciencia de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, CAT (Spain); Institucio Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, CAT (Spain)

    2014-03-10

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

  7. Determination of Trace Germanium in Marine Sediments by Hydride Generation-Atomic Fluorescence Spectrometry (HG-AFS)

    LI Jing; ZHAO Shilan; ZHANG Zhaohui; ZENG Xianjie

    2004-01-01

    A method for the analysis of trace germanium in marine sediments by HG-AFS has been investigated. The experimental conditions such as the acidity of reduction reaction, the amount of sodium boro-hydride, the carrier gas flow rate, etc., were tested and optimized by using a kind of orthogonal design. The detection limit of the presented method is 0.95 μg L-1 for germanium. The calibration curve shows a satisfactory line in the concentration range 0-320 μg L-1 Ge with a variation coefficient of ±2.1%.

  8. The MPIR 100 mK bolometer array for 2 mm continuum observations

    We are developing bolometer arrays for continuum detection in millimeter and submillimeter astronomy [1]. For the 2 mm atmospheric window, where the transmission is comparatively high, a bolometer temperature of about 100 mK is necessary in order to avoid being limited by the system noise. Our new 2 mm array is cooled by a 3He/4He-dilution refrigerator with a base temperature of 30 mK. The substrate for the 19 channel bolometer array consists of a single-crystal silicon wafer with silicon-nitride membranes. Radiation is collected by a single-mode horn array in front of the wafer and coupled into efficient absorbers in the center of the membranes. Resulting temperature changes of the absorbers are measured with NTD-germanium thermistors. In the first stage of the read out electronics, we use JFETs working at 150 K. Cold RF-filters prevent RF interference from entering the bolometer array cavity. The combination of several mesh filters and a short piece of cylindrical waveguide at the end of each horn defines the bandpass for the incoming radiation, which is matched to the 2 mm atmospheric window

  9. Protein Functionalized Nanodiamond Arrays

    Liu YL

    2010-01-01

    Full Text Available Abstract Various nanoscale elements are currently being explored for bio-applications, such as in bio-images, bio-detection, and bio-sensors. Among them, nanodiamonds possess remarkable features such as low bio-cytotoxicity, good optical property in fluorescent and Raman spectra, and good photostability for bio-applications. In this work, we devise techniques to position functionalized nanodiamonds on self-assembled monolayer (SAMs arrays adsorbed on silicon and ITO substrates surface using electron beam lithography techniques. The nanodiamond arrays were functionalized with lysozyme to target a certain biomolecule or protein specifically. The optical properties of the nanodiamond-protein complex arrays were characterized by a high throughput confocal microscope. The synthesized nanodiamond-lysozyme complex arrays were found to still retain their functionality in interacting with E. coli.

  10. Permutations of cubical arrays

    The structure constants of an algebra determine a cube called the cubical array associated with the algebra. The permuted indices of the cubical array associated with a finite semifield generate new division algebras. We do not not require that the algebra be finite and ask 'Is it possible to choose a basis for the algebra such any permutation of the indices of the structure constants leaves the algebra unchanged?' What are the associated algebras? Author shows that the property 'weakly quadratic' is invariant under all permutations of the indices of the corresponding cubical array and presents two algebras for which the cubical array is invariant under all permutations of the indices.

  11. Flexible retinal electrode array

    Okandan, Murat (Albuquerque, NM); Wessendorf, Kurt O. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)

    2006-10-24

    An electrode array which has applications for neural stimulation and sensing. The electrode array can include a large number of electrodes each of which is flexibly attached to a common substrate using a plurality of springs to allow the electrodes to move independently. The electrode array can be formed from a combination of bulk and surface micromachining, with electrode tips that can include an electroplated metal (e.g. platinum, iridium, gold or titanium) or a metal oxide (e.g. iridium oxide) for biocompatibility. The electrode array can be used to form a part of a neural prosthesis, and is particularly well adapted for use in an implantable retinal prosthesis where the electrodes can be tailored to provide a uniform gentle contact pressure with optional sensing of this contact pressure at one or more of the electrodes.

  12. Expandable LED array interconnect

    Yuan, Thomas Cheng-Hsin; Keller, Bernd

    2011-03-01

    A light emitting device that can function as an array element in an expandable array of such devices. The light emitting device comprises a substrate that has a top surface and a plurality of edges. Input and output terminals are mounted to the top surface of the substrate. Both terminals comprise a plurality of contact pads disposed proximate to the edges of the substrate, allowing for easy access to both terminals from multiple edges of the substrate. A lighting element is mounted to the top surface of the substrate. The lighting element is connected between the input and output terminals. The contact pads provide multiple access points to the terminals which allow for greater flexibility in design when the devices are used as array elements in an expandable array.

  13. Aligators for arrays

    Henzinger, Thomas A.; Hottelier, Thibaud; Kovács, Laura; Rybalchenko, Andrey

    2010-01-01

    This paper presents Aligators, a tool for the generation of universally quantified array invariants. Aligators leverages recurrence solving and algebraic techniques to carry out inductive reasoning over array content. The Aligators’ loop extraction module allows treatment of multi-path loops by exploiting their commutativity and serializability properties. Our experience in applying Aligators on a collection of loops from open source software projects indicates the applicability of recurren...

  14. RFID array sensing

    Capdevila Cascante, Santiago; Jofre Roca, Lluís; Romeu Robert, Jordi; Bolomey, J.Ch

    2010-01-01

    In this paper the use of RFID tags for the measurement of physical parameters in a distributed set of points is presented. Experimental results for two different scenarios are presented; the first uses a 2D RFID array to measure the field distribution of a radiating aperture, while the second detects the change in the close environment of an array of RFID tags to determine the water level of a container.

  15. Microphone arrays fundamentals

    Embrechts, Jean-Jacques

    2011-01-01

    Microphone arrays are essentially directional sensors. They are therefore mainly used for locating, identifying, isolating, measuring and recording individual sound sources. The main principles governing the directivity of microphone arrays are reviewed: phase differences between signals create constructive and destructive interferences, depending on the direction of the sound source. Moreover, signal processing is applied to provide “beamforming”, i.e. beam shaping and steering. Contrary to ...

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

    Pulci Olivia

    2010-01-01

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

  17. Efficient one-pot synthesis of monodisperse alkyl-terminated colloidal germanium nanocrystals

    An efficient one-pot method for fabricating alkyl-capped germanium nanocrystals (Ge NCs) is reported. Ge NCs with a size of 3.9 ± 0.5 nm, are formed by co-reduction of germanium tetrachloride in the presence of n-butyltrichlorogermane, producing NCs with butyl-terminated surfaces. The advantage of this method is that it allows rapid synthesis and functionalisation of NCs with minimal post-synthetic purification requirements. TEM imaging showed that the Ge NCs are monodisperse and highly crystalline, while EDX and SAED confirmed the chemical identity and crystal phase of the NCs. FTIR and XPS confirmed that the Ge NCs were well passivated, with some oxidation of the nanocrystal surface. Optical spectroscopy of the NCs showed a strong absorbance in the UV region and an excitation wavelength dependent photoluminescence in the UV/violet. Time resolved photoluminescence measurements showed the presence of two nanosecond lifetime components, consistent with recombination of photogenerated excitons at low lying energy states present at the nanocrystal surface. Photoluminescence quantum yields were determined to be 37 %, one of the highest values reported for organically terminated Ge NCs

  18. Efficient one-pot synthesis of monodisperse alkyl-terminated colloidal germanium nanocrystals

    Carolan, Darragh, E-mail: darragh.carolan@tyndall.ie; Doyle, Hugh, E-mail: hugh.doyle@tyndall.ie [University College Cork, Tyndall National Institute (Ireland)

    2014-12-15

    An efficient one-pot method for fabricating alkyl-capped germanium nanocrystals (Ge NCs) is reported. Ge NCs with a size of 3.9 ± 0.5 nm, are formed by co-reduction of germanium tetrachloride in the presence of n-butyltrichlorogermane, producing NCs with butyl-terminated surfaces. The advantage of this method is that it allows rapid synthesis and functionalisation of NCs with minimal post-synthetic purification requirements. TEM imaging showed that the Ge NCs are monodisperse and highly crystalline, while EDX and SAED confirmed the chemical identity and crystal phase of the NCs. FTIR and XPS confirmed that the Ge NCs were well passivated, with some oxidation of the nanocrystal surface. Optical spectroscopy of the NCs showed a strong absorbance in the UV region and an excitation wavelength dependent photoluminescence in the UV/violet. Time resolved photoluminescence measurements showed the presence of two nanosecond lifetime components, consistent with recombination of photogenerated excitons at low lying energy states present at the nanocrystal surface. Photoluminescence quantum yields were determined to be 37 %, one of the highest values reported for organically terminated Ge NCs.

  19. Inter-electrode charge collection in high-purity germanium detectors with amorphous semiconductor contacts

    High-purity germanium (HPGe) radiation detectors with segmented signal readout electrodes combine excellent energy resolution with fine spatial resolution, opening exciting possibilities in radiation imaging applications. Segmenting the electrodes provides the ability to determine the positions of radiation interactions in the detector, but it also brings potential challenges that can inhibit performance. A challenge unique to segmented electrode detectors is collection of charge carriers to the gap between adjacent electrodes rather than to the electrodes themselves, which gives a deficit in the summed energy. While amorphous semiconductor electrical contacts have enabled a simplified fabrication process capable of fine electrode segmentation, the amorphous semiconductor passivation layer between electrodes is prone to inter-electrode charge collection. This article presents a study of the impact of fabrication process parameters on the energy deficit due to inter-electrode charge collection for double-sided strip detectors. Eight double-sided strip HPGe detectors were fabricated with amorphous germanium (a-Ge) and amorphous silicon (a-Si) contacts formed by sputter deposition. Each detector was evaluated for inter-electrode charge collection performance, using as a metric the deficit in the summed signal of two adjacent electrodes. It is demonstrated that both a-Ge and a-Si contacts can be produced with nearly non-existent inter-electrode charge collection when the appropriate combination of sputter gas hydrogen content and gas pressure are selected

  20. A three-dimensional silicon photonic crystal nanocavity with enhanced emission from embedded germanium islands

    We report the realization of a silicon three-dimensional photonic crystal nanocavity containing self-assembled germanium-island emitters. The three-dimensional woodpile photonic crystal was assembled layer by layer by micromanipulation using silicon plates grown by molecular beam epitaxy. An optical nanocavity was formed in the center of the photonic crystal by introducing a point defect into one of the plates. Measurements of the filtered spontaneous emission from the Ge islands in the active plate through the localized modes of the structure directly reveal information on the evolution of the frequency and Q-factor as upper cladding plates are sequentially added. An exponential increase of the cavity-Q is observed when the number of upper cladding plates is increased up to a maximum of ten. The emission of germanium-islands within the cavity reveals several strongly polarized cavity modes with quality-factors up to ≈13 600. The emission intensity of the cavity modes is enhanced by large factors up to ≈58× as compared with the active plate outside the photonic environment. (paper)

  1. Surface passivation of high-purity germanium gamma-ray detector

    The experimental work consists of two parts. The first involves fabrication of hyper-pure germanium gamma ray detectors using standard surface treatment, chemical etchings and containment in a suitable cryostat. Then, after cooling the detectors to 77 K, γ-ray emissions from radioisotopes are resolved, resolution, depletion depth, VR versus IR characteristics and /NA -ND/ of the germanium are measured. The second part of the work involves investigation of surface states in an effort to achieve long-term stability of operating characteristics. Several methods are used: plasma hydrogenation, a-Si and a-Ge pinch-off effect and simple oxidation. A-Ge and a-Si thicknesses were measured using Rutherford backscattering techniques; surface states were measured with deep level transient spectroscopy and diode reverse current versus reverse voltage plots. Some scanning electron microscope measurements were used in determining major film contaminants during backscattering of a-Si and a-Ge films. Surface passivation studies revealed unexpected hole trapping defects generated when a-Ge:H film is applied. The a-Si:H films were found to be mechanically strong, no defect traps were found and preliminary results suggest that such films will be good passivants. 14 refs., 2 tabs., 7 figs., 13 ills

  2. Excitation functions of longer lived radionuclides formed by deuteron irradiation of germanium

    The cross sections of nuclear reactions induced by deuteron particles on natural germanium were investigated by using the stacked target technique, activation method and standard high resolution gamma spectrometry. Targets were natural germanium, vacuum evaporated onto 25 micron thick polyimide (kapton) foils with nominal thickness of about 2 μm. The stack was composed of 26 kapton–Ge–Ge–kapton sandwich targets foils and 24 aluminum and 25 titanium foils with nominal thickness of 50 and 11 μm respectively. The Al foils served as monitors and at the same time as energy degraders in the high energy part of the stack. Ti foils were included in the stack to monitor the beam parameters in the low energy region. The irradiation was done with 50 MeV deuteron particles with a beam current of about 50 nA for about 1 h. Activation cross sections were determined for production of the 70,71,72,73,74,76As, 69,75,77Ge and 66,67,73Ga radionuclides. The deduced experimental cross sections were compared to the results of theoretical calculations taken from the TENDL-2013 data library based on the TALYS computer code. A comparison was made with available experimental data measured earlier. Thick target yields were deduced from the experimental cross sections and were compared with the data published before. The possible production routes of arsenic radioisotopes are discussed

  3. Excitation functions of longer lived radionuclides formed by deuteron irradiation of germanium

    Takács, S., E-mail: stakacs@atomki.hu [Institute for Nuclear Research, Hungarian Academy of Sciences, 4026 Debrecen (Hungary); Takács, M.P. [Institute for Nuclear Research, Hungarian Academy of Sciences, 4026 Debrecen (Hungary); Institute of Physics, University of Debrecen, 4026 Debrecen (Hungary); Hermanne, A. [Cyclotron Laboratory, Vrije Universiteit Brussel, Brussels 1090 Belgium (Belgium); Tárkányi, F. [Institute for Nuclear Research, Hungarian Academy of Sciences, 4026 Debrecen (Hungary); Adam-Rebeles, R. [Cyclotron Laboratory, Vrije Universiteit Brussel, Brussels 1090 Belgium (Belgium)

    2014-10-01

    The cross sections of nuclear reactions induced by deuteron particles on natural germanium were investigated by using the stacked target technique, activation method and standard high resolution gamma spectrometry. Targets were natural germanium, vacuum evaporated onto 25 micron thick polyimide (kapton) foils with nominal thickness of about 2 μm. The stack was composed of 26 kapton–Ge–Ge–kapton sandwich targets foils and 24 aluminum and 25 titanium foils with nominal thickness of 50 and 11 μm respectively. The Al foils served as monitors and at the same time as energy degraders in the high energy part of the stack. Ti foils were included in the stack to monitor the beam parameters in the low energy region. The irradiation was done with 50 MeV deuteron particles with a beam current of about 50 nA for about 1 h. Activation cross sections were determined for production of the {sup 70,71,72,73,74,76}As, {sup 69,75,77}Ge and {sup 66,67,73}Ga radionuclides. The deduced experimental cross sections were compared to the results of theoretical calculations taken from the TENDL-2013 data library based on the TALYS computer code. A comparison was made with available experimental data measured earlier. Thick target yields were deduced from the experimental cross sections and were compared with the data published before. The possible production routes of arsenic radioisotopes are discussed.

  4. Excitation functions of longer lived radionuclides formed by deuteron irradiation of germanium

    Takács, S.; Takács, M. P.; Hermanne, A.; Tárkányi, F.; Adam-Rebeles, R.

    2014-10-01

    The cross sections of nuclear reactions induced by deuteron particles on natural germanium were investigated by using the stacked target technique, activation method and standard high resolution gamma spectrometry. Targets were natural germanium, vacuum evaporated onto 25 micron thick polyimide (kapton) foils with nominal thickness of about 2 μm. The stack was composed of 26 kapton-Ge-Ge-kapton sandwich targets foils and 24 aluminum and 25 titanium foils with nominal thickness of 50 and 11 μm respectively. The Al foils served as monitors and at the same time as energy degraders in the high energy part of the stack. Ti foils were included in the stack to monitor the beam parameters in the low energy region. The irradiation was done with 50 MeV deuteron particles with a beam current of about 50 nA for about 1 h. Activation cross sections were determined for production of the 70,71,72,73,74,76As, 69,75,77Ge and 66,67,73Ga radionuclides. The deduced experimental cross sections were compared to the results of theoretical calculations taken from the TENDL-2013 data library based on the TALYS computer code. A comparison was made with available experimental data measured earlier. Thick target yields were deduced from the experimental cross sections and were compared with the data published before. The possible production routes of arsenic radioisotopes are discussed.

  5. On the understanding of irradiation effects in germanium, silicon and gallium arsenide semi-conductors

    We have studied the behaviour of germanium, silicon and gallium arsenide semiconductors irradiated by different projectiles (heavy ions, protons, electrons and fullerenes). At low doses, thanks to deep level transient spectroscopy (DLTS) and Hall effect electrical measurements, we were able to explicit the nature of the defects present in germanium after irradiation at room temperature. For different projectiles, we have determined the defect creation kinetics. At higher doses, the electrical measurements have brought to the fore the presence of a specific defect created only after an heavy ion (or proton) irradiation. Moreover, positron annihilation spectroscopy (PAS) measurements show that size of this specific defect increases with the fluence. The damage has also been quantified by channeling Rutherford backscaterring (RBS-C) measurements. At first sight, the obtained defect creation rates are normalized by the nuclear collisions. This normalization is also present in the inverse of the gain evolution in silicon bipolar transistors. Meanwhile, an extensive study shows an efficiency decrease of the defect creation at intermediate values of the electronic energy loss Se, then, at the opposite, an increasing at higher values of Se. In the three semiconductors, we have observed track formation after fullerenes irradiation. These tracks are amorphous cylinders which have been characterized by transmission and high resolution electronic microscopy. They are due to the very high values of the electronic energy density which can be deposited by fullerenes owing to their low velocity. (author)

  6. Thermodynamic calculations of self- and hetero-diffusion parameters in germanium

    In the present work, the diffusion coefficients of n- and p-type dopants (P, As, Sb, Al) and self-diffusion in crystalline germanium are calculated from the bulk elastic properties of the host material based on the cBΩ thermodynamic model. The calculated diffusion coefficients as a function of temperature and the activation enthalpies prove to be in full agreement with the reported experimental results. Additional point defect parameters such as activation entropy, activation volume and activation Gibbs free energy are also calculated for each diffusing element. The pressure dependence of self-diffusion coefficients in germanium is also verified at high temperatures (876 K–1086 K), in agreement with reported results ranging from ambient pressure up to 600 MPa and is further calculated at pressures up to 3 GPa, where the phase transition to Ge II occurs. - Highlights: • Calculation of diffusivities of n- and p-type dopants in Ge from elastic properties. • Calculation of point defect parameters according to the cBΩ thermodynamic model. • Prediction of the pressure dependence of self-diffusion coefficients in Ge

  7. Chemical Bonding, Interfaces and Defects in Hafnium Oxide/Germanium Oxynitride Gate Stacks on Ge (100)

    Oshima, Yasuhiro; /Stanford U., Materials Sci. Dept.; Sun, Yun; /SLAC, SSRL; Kuzum, Duygu; /Stanford U.; Sugawara, Takuya; Saraswat, Krishna C.; Pianetta, Piero; /SLAC, SSRL; McIntyre, Paul C.; /Stanford U., Materials Sci. Dept.

    2008-10-31

    Correlations among interface properties and chemical bonding characteristics in HfO{sub 2}/GeO{sub x}N{sub y}/Ge MIS stacks were investigated using in-situ remote nitridation of the Ge (100) surface prior to HfO{sub 2} atomic layer deposition (ALD). Ultra thin ({approx}1.1 nm), thermally stable and aqueous etch-resistant GeO{sub x}N{sub y} interfaces layers that exhibited Ge core level photoelectron spectra (PES) similar to stoichiometric Ge{sub 3}N{sub 4} were synthesized. To evaluate GeO{sub x}N{sub y}/Ge interface defects, the density of interface states (D{sub it}) was extracted by the conductance method across the band gap. Forming gas annealed (FGA) samples exhibited substantially lower D{sub it} ({approx} 1 x 10{sup 12} cm{sup -2} eV{sup -1}) than did high vacuum annealed (HVA) and inert gas anneal (IGA) samples ({approx} 1x 10{sup 13} cm{sup -2} eV{sup -1}). Germanium core level photoelectron spectra from similar FGA-treated samples detected out-diffusion of germanium oxide to the HfO{sub 2} film surface and apparent modification of chemical bonding at the GeO{sub x}N{sub y}/Ge interface, which is related to the reduced D{sub it}.

  8. Exploration Of Activity Measurements And Equilibrium Checks For Sediment Dating Using Thick-Window Germanium Detectors

    Warner, Jacob A.; Fitzsimmons, Kathryn E.; Reynolds, Eva M.; Gladkis, Laura G.; Timmers, Heiko

    2011-06-01

    Activity measurements on sediment samples for trapped-charge geological dating using gamma-ray spectroscopy are an important verification of the field-site dose rate determination. Furthermore gamma-ray spectroscopy can check if the natural decay series are in secular equilibrium which is a crucial assumption in such dating. Typically the activities of leading members of the Thorium and Uranium decay series are measured, which requires Germanium detectors with thin windows and good energy resolution in order to effectively detect the associated low energy gamma-rays. Such equipment is not always readily available. The potential of conventional Germanium detectors with thick entrance window has been explored towards routine gamma-ray spectroscopy of sediment samples using higher energy gamma-rays. Alternative isotopes, such as Ac-228 and Pb-212 for the Thorium series, and Pa-234m, Ra-226 and Bi-214 for the Uranium series, have been measured in order to determine the mass-specific activity for the respective series and possibly provide a check of secular equilibrium. In addition to measurements of the K-40 activity, with the alternative approach, the activities of both decay series can be accurately determined. The secular equilibrium condition may be tested for the Thorium series. Measurement accuracy for Pa-234m is, however, not sufficient to permit also a reliable check of equilibrium for the Uranium series.

  9. Optimizing Chemical Sensor Array Sizes

    Optimal selection of array sensors for a chemical sensing application is a nontrivial task. It is commonly believed that ''more is better'' when choosing the number of sensors required to achieve good chemical selectivity. However, cost and system complexity issues point towards the choice of small arrays. A quantitative array optimization is carried out to explore the selectivity of arrays of partially-selective chemical sensors as a function of array size. It is shown that modest numbers (dozens) of target analytes are completely distinguished with a range of arrays sizes. However, the array selectivity and the robustness against sensor sensitivity variability are significantly degraded if the array size is increased above a certain number of sensors, so that relatively small arrays provide the best performance. The results also suggest that data analyses for very large arrays of partially-selective sensors will be optimized by separately anal yzing small sensor subsets

  10. Imaging antenna arrays

    Rutledge, D. B.; Muha, M. S.

    1982-01-01

    Many millimeter and far-infrared imaging systems are limited in sensitivity and speed because they depend on a single scanned element. Because of recent advances in planar detectors such as Schottky diodes, superconducting tunnel junctions, and microbolometers, an attractive approach to this problem is a planar antenna array with integrated detectors. A planar line antenna array and optical system for imaging has been developed. The significant advances are a 'reverse-microscope' optical configuration and a modified bow-tie antenna design. In the 'reverse-microscope' configuration, a lens is attached to the bottom of the substrate containing the antennas. Imaging is done through the substrate. This configuration eliminates the troublesome effects of substrate surface waves. The substrate lens has only a single refracting surface, making possible a virtually aplanatic system, with little spherical aberration or coma. The array is characterized by an optical transfer function that is easily measured. An array with 19 dB crosstalk levels between adjacent antennas has been tested and it was found that the array captured 50 percent of the available power. This imaging system was diffraction limited.

  11. High-speed recovery of germanium in a convection-aided mode using functional porous hollow-fiber membranes.

    Ozawa, I; Saito, K; Sugita, K; Sato, K; Akiba, M; Sugo, T

    2000-08-01

    A porous hollow-fiber membrane capable of recovery of germanium from a liquid stream was prepared by radiation-induced graft polymerization of an epoxy-group-containing vinyl monomer, glycidyl methacrylate, and subsequent functionalization with 2,2'-iminodiethanol, di-2-propanolamine, N-methylglucamine, and 3-amino-1,2-propanediol. The functional group density was as high as 1.4 mol per kg of the resultant hollow fiber. The polymer chains containing functional groups surrounding the pores enabled a high-speed recovery of germanium during permeation of a germanium oxide (GeO2) solution through the pores of the hollow fiber. Because of a negligible diffusional mass-transfer resistance, germanium concentration changes with the effluent volume, i.e., breakthrough curves, overlapped irrespective of the residence time of the solution, which ranged from 0.37 to 3.7 s across the hollow fiber. After repeated use of adsorption and elution, the adsorption capacity did not deteriorate. PMID:10949471

  12. Antireflection coating formed by plasma-enhanced chemical-vapor deposition for terahertz-frequency germanium optics

    Hosako, Iwao

    2003-07-01

    A method of manufacturing optical coatings for germanium optics used at terahertz frequencies has been developed. The various optical coatings used at terahertz frequencies are difficult to manufacture conventionally because these coatings must be as thick as several tens of micrometers, which is far thicker than those used in the optical region. One way to overcome this problem is to form a silicon oxide layer through plasma-enhanced chemical-vapor deposition, with silane (SiH4) as a source gas. Using this method, I formed 21-μm-thick silicon oxide films as antireflection (AR) layers for germanium optics and obtained low reflection at 1.7 THz (wavelength, λ = 175 μm). This method is easily applied to large-aperture optics and micro-optics as well as to optics with a complex surface form. The AR coatings can also be formed for photoconductive detectors made from germanium doped with gallium at a low temperature (160 °C) this low temperature ensures that the doped impurities in the germanium do not diffuse. Fabrication of optical coatings upon substrates that have refractive indices of 3.84-11.7 may also be possible by control of the refractive indices of the deposited layers.

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

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

    2014-12-01

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

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

    Tanaka, H., E-mail: tanaka@semicon.kuee.kyoto-u.ac.jp; Mori, S.; Morioka, N.; Suda, J.; Kimoto, T. [Department of Electronic Science and Engineering, Kyoto University, Kyoto 615-8510 (Japan)

    2014-12-21

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

  15. Equation of state, nonlinear elastic response, and anharmonic properties of diamond-cubic silicon and germanium. First-principles investigation

    Wang, Chenju [Sichuan Univ., Chengdu (China). Inst. of Atomic and Molecular Physics; Institute of Fluid Physics, Sichuan (China). National Key Laboratory of Shock Wave and Detonation Physics; Gu, Jianbing [Institute of Fluid Physics, Sichuan (China). National Key Laboratory of Shock Wave and Detonation Physics; Sichuan Univ., Chengdu (China). College of Physical Science and Technology; Kuang, Xiaoyu [Sichuan Univ., Chengdu (China). Inst. of Atomic and Molecular Physics; Xiang, Shikai [Institute of Fluid Physics, Sichuan (China). National Key Laboratory of Shock Wave and Detonation Physics

    2015-10-01

    Nonlinear elastic properties of diamond-cubic silicon and germanium have not been investigated sufficiently to date. Knowledge of these properties not only can help us to understand nonlinear mechanical effects but also can assist us to have an insight into the related anharmonic properties, so we investigate the nonlinear elastic behaviour of single silicon and germanium by calculating their second- and third-order elastic constants. All the results of the elastic constants show good agreement with the available experimental data and other theoretical calculations. Such a phenomenon indicates that the present values of the elastic constants are accurate and can be used to further study the related anharmonic properties. Subsequently, the anharmonic properties such as the pressure derivatives of the second-order elastic constants, Grueneisen constants of long-wavelength acoustic modes, and ultrasonic nonlinear parameters are explored. All the anharmonic properties of silicon calculated in the present work also show good agreement with the existing experimental results; this consistency not only reveals that the calculation method of the anharmonic properties is feasible but also illuminates that the anharmonic properties obtained in the present work are reliable. For the anharmonic properties of germanium, since there are no experimental result and other theoretical data till now, we hope that the anharmonic properties of germanium first offered in this work would serve as a reference for future studies.

  16. Nonlinear strain dependences in highly strained germanium micromembranes for on-chip light source applications (Conference Presentation)

    Guilloy, Kevin; Gassenq, Alban; Pauc, Nicolas; Escalante Fernandez, Jose Maria; Duchemin, Ivan; Niquet, Yann-Michel; Tardif, Samuel; Rieutord, Francois; Gentile, Pascal; Osvaldo Dias, Guilherme; Rouchon, Denis; Widiez, Julie; Hartmann, Jean-Michel; Fowler, Daivid; Chelnokov, Alexei; Geiger, Richard; Zabel, Thomas; Sigg, Hans C.; Faist, Jérôme; Reboud, Vincent; Calvo, Vincent

    2016-05-01

    Germanium is a strong candidate as a laser source for silicon photonics. Despite the indirect nature of its bandgap, the application of several percent of tensile strain reduces the energy difference between its direct and indirect bandgaps [1]. It has been predicted that above a certain strain threshold, germanium transforms into an actual direct bandgap material [2]. However, the properties of this material at unprecedented levels of strain still raise issues. A recently introduced strain technology based on prestressed germanium layers [3] enables to fabricate micro-membranes at such high strain. We present here both a theoretical and experimental study of the band edge and Raman shift at such high strain level. For above reasons, we start from slightly tensile-strained germanium-on-insulator (GeOI) substrates obtained by the Smart CutTM technology [4]. By etching adequate pattern in the germanium layer, both uniaxial and biaxial stress conditions were obtained after etching away the sacrificial buried oxide underneath the germanium layer. We performed x-ray diffraction measurements at the ESRF synchrotron using Laue in combinations with rainbow filtering techniques on the micro-membranes revealing strain values of 4.9 % for the uniaxial strain and 1.9 % for the biaxial strain [5-6]. We then studied the relationship between strain and Raman shift. While the relationship remained linear for biaxial stress condition, a significant deviation from the linear behavior behavior was observed above 2.5 % uniaxial strain. Such nonlinearity becomes dominant at very high strain levels; indeed a 9.9 cm-1 Raman shift corresponds to 4.9 % strain instead of the 6.5 % predicted by the linear extrapolation [5]. We performed simulations of the band structure of germanium under various stress conditions using a tight-binding model. For uniaxial stress, the relation between the energy positions of the band edges differed significantly from the deformation potential models in [1

  17. FEL phased array configurations

    Shellan, Jeffrey B.

    1986-01-01

    The advantages and disadvantages of various phased array and shared aperture concepts for FEL configurations are discussed. Consideration is given to the characteristics of intra- and inter-micropulse phasing; intra-macropulse phasing; an internal coupled resonator configuration; and an injection locked oscillator array. The use of a master oscillator power amplifier (MOPA) configuration with multiple or single master oscillators for FELs is examined. The venetian blind, rotating plate, single grating, and grating rhomb shared aperture concepts are analyzed. It is noted that the shared aperture approach using a grating rhomb and the MOPA concept with a single master oscillator and a coupled resonator are useful for FEL phased array configurations; and the MOPA concept is most applicable.

  18. Comparison of ultrasonic-assisted and regular leaching of germanium from by-product of zinc metallurgy.

    Zhang, Libo; Guo, Wenqian; Peng, Jinhui; Li, Jing; Lin, Guo; Yu, Xia

    2016-07-01

    A major source of germanium recovery and also the source of this research is the by-product of lead and zinc metallurgical process. The primary purpose of the research is to investigate the effects of ultrasonic assisted and regular methods on the leaching yield of germanium from roasted slag containing germanium. In the study, the HCl-CaCl2 mixed solution is adopted as the reacting system and the Ca(ClO)2 used as the oxidant. Through six single factor (leaching time, temperature, amount of Ca(ClO)2, acid concentration, concentration of CaCl2 solution, ultrasonic power) experiments and the comparison of the two methods, it is found the optimum collective of germanium for ultrasonic-assisted method is obtained at temperature 80 °C for a leaching duration of 40 min. The optimum concentration for hydrochloric acid, CaCl2 and oxidizing agent are identified to be 3.5 mol/L, 150 g/L and 58.33 g/L, respectively. In addition, 700 W is the best ultrasonic power and an over-high power is adverse in the leaching process. Under the optimum condition, the recovery of germanium could reach up to 92.7%. While, the optimum leaching condition for regular leaching method is same to ultrasonic-assisted method, except regular method consume 100 min and the leaching rate of Ge 88.35% is lower about 4.35%. All in all, the experiment manifests that the leaching time can be reduced by as much as 60% and the leaching rate of Ge can be increased by 3-5% with the application of ultrasonic tool, which is mainly thanks to the mechanical action of ultrasonic. PMID:26964934

  19. Atacama Compact Array Antennas

    Saito, Masao; Inatani, Junji; Nakanishi, Kouichiro; Naoi, Takahiro; Yamada, Masumi; Saito, Hiro; Ikenoue, Bungo; Kato, Yoshihiro; Morita, Kou-ichiro; Mizuno, Norikazu; Iguchi, Satoru

    2011-01-01

    We report major performance test results of the Atacama Compact Array (ACA) 7-m and 12-m antennas of ALMA (Atacama Large Millimeter/submillimeter Array). The four major performances of the ACA antennas are all-sky pointing (to be not more than 2.0 arcsec), offset pointing (to be < 0.6 arcsec) surface accuracy (< 25(20) micrometer for 12(7)m-antenna), stability of path-length (15 micrometer over 3 min), and high servo capability (6 degrees/s for Azimuth and 3 degrees/s for Elevation). The high...

  20. Wire Array Photovoltaics

    Turner-Evans, Dan

    Over the past five years, the cost of solar panels has dropped drastically and, in concert, the number of installed modules has risen exponentially. However, solar electricity is still more than twice as expensive as electricity from a natural gas plant. Fortunately, wire array solar cells have emerged as a promising technology for further lowering the cost of solar. Si wire array solar cells are formed with a unique, low cost growth method and use 100 times less material than conventional Si cells. The wires can be embedded in a transparent, flexible polymer to create a free-standing array that can be rolled up for easy installation in a variety of form factors. Furthermore, by incorporating multijunctions into the wire morphology, higher efficiencies can be achieved while taking advantage of the unique defect relaxation pathways afforded by the 3D wire geometry. The work in this thesis shepherded Si wires from undoped arrays to flexible, functional large area devices and laid the groundwork for multijunction wire array cells. Fabrication techniques were developed to turn intrinsic Si wires into full p-n junctions and the wires were passivated with a-Si:H and a-SiNx:H. Single wire devices yielded open circuit voltages of 600 mV and efficiencies of 9%. The arrays were then embedded in a polymer and contacted with a transparent, flexible, Ni nanoparticle and Ag nanowire top contact. The contact connected >99% of the wires in parallel and yielded flexible, substrate free solar cells featuring hundreds of thousands of wires. Building on the success of the Si wire arrays, GaP was epitaxially grown on the material to create heterostructures for photoelectrochemistry. These cells were limited by low absorption in the GaP due to its indirect bandgap, and poor current collection due to a diffusion length of only 80 nm. However, GaAsP on SiGe offers a superior combination of materials, and wire architectures based on these semiconductors were investigated for multijunction

  1. Constraints on Millicharged Neutrinos via Atomic Ionizations with Germanium Detectors at sub-keV Sensitivities

    Chen, Jiunn-Wei; Li, Hau-Bin; Liu, C -P; Singh, Lakhwinder; Wong, Henry T; Wu, Chih-Liang; Wu, Chih-Pan

    2014-01-01

    With the advent of detectors with sub-keV sensitivities, atomic ionization has been identified as a promising avenue to probe possible neutrino electromagnetic properties. The interaction cross-sections induced by millicharged neutrinos are evaluated with the ab-initio multi-configuration relativistic random-phase approximation. There is significant enhancement at atomic binding energies compared to that when the electrons are taken as free particles. Positive signals would distinctly manifest as peaks at specific energies with known intensity ratios. Selected reactor neutrino data with germanium detectors at analysis threshold as low as 300 eV are studied. No such signatures are observed, and a combined limit on the neutrino charge fraction of $| \

  2. An Experimental Study of the Accuracy of Compensation in Lithium Drifted Germanium Detectors

    The nature and magnitude of the space charge existing in the compensated layer of lithium drifted germanium detectors has been studied as a function of drifted depth and of the electric field applied during drift. Experimental values were obtained from the dependence of detector capacitance on applied bias. In most cases there was a linear space charge gradient in the compensated layer. When small electric fields were applied to deep compensated layers, the space charge became constant throughout a large part of the compensated layer. There is some evidence for a strong decrease of mobile carrier recombination lifetime with increasing drifted depth, possibly down to a few microseconds for drifted depths of the order of 7 mm. The experimental results of the investigation are to a large extent in good agreement with theory

  3. Common mistakes associated with absolute full energy peak efficiency measurements using high pure germanium detectors

    The present work focuses on the uncertainties associated with absolute full energy peak efficiency (AFEPE) when measurements of calibration point sources conducted at various distances from two high pure germanium detectors (HPGe) from Ortec and Eurisys. A set consists of 11 point sources from Amersham were used. The measurements were performed at different source to detector distances. All the spectra were unfolded and analyzed using Emc plus MCA card from Silena. Full energy peak efficiency for each energy was then calculated using the well-know formula. The first approach was to fit the experimental data using least square fitting. Following that, a comparison between the experimental and calculated results was performed. The scattering data due to measurements of the multi-energetic sources specially when measurements carried out at very close distances from the detector were plotted and discussed.(author)

  4. Pulse shape analysis with a broad-energy germanium detector for the gerda experiment

    To reduce background in experiments looking for rare events, such as the GERDA double beta decay experiment, it is necessary to employ active background-suppression techniques. One of such techniques is the pulse shape analysis of signals induced by the interaction of radiation with the detector. Analysis of the time-development of the impulses can distinguish between an interaction of an electron and an interaction of a multiple-scattered photon inside the detector. This information can be used to eliminate unwanted events from the recorded data. In this talk, results of a pulse-shape analysis of signals from a commercially available broad-energy germanium detector will be presented. The background rejection capability of such detector configuration and the potential for its use in ultralow-background experiments are discussed.

  5. Pulse Shape Analysis with a Broad-Energy Germanium Detector for the GERDA experiment

    Budjá?, Du?an; Chkvorets, Oleg; Schönert, Stefan; Khanbekov, Nikita

    2008-01-01

    To reduce background in experiments looking for rare events, such as the GERDA double beta decay experiment, it is necessary to employ active background-suppression techniques. One of such techniques is the pulse shape analysis of signals induced by the interaction of radiation with the detector. Analysis of the time-development of the impulses can distinguish between an interaction of an electron and an interaction of a multiple-scattered photon inside the detector. This information can be used to eliminate background events from the recorded data. Results of pulse-shape analysis of signals from a commercially available broad-energy germanium detector are presented and the pulse-shape discrimination capability of such detector configuration for use in low-background experiments is discussed.

  6. Germanium-tin multiple quantum well on silicon avalanche photodiode for photodetection at two micron wavelength

    Dong, Yuan; Wang, Wei; Lee, Shuh Ying; Lei, Dian; Gong, Xiao; Khai Loke, Wan; Yoon, Soon-Fatt; Liang, Gengchiau; Yeo, Yee-Chia

    2016-09-01

    We report the demonstration of a germanium-tin multiple quantum well (Ge0.9Sn0.1 MQW)-on-Si avalanche photodiode (APD) for light detection near the 2 μm wavelength range. The measured spectral response covers wavelengths from 1510 to 2003 nm. An optical responsivity of 0.33 A W‑1 is achieved at 2003 nm due to the internal avalanche gain. In addition, a thermal coefficient of breakdown voltage is extracted to be 0.053% K‑1 based on the temperature-dependent dark current measurement. As compared to the traditional 2 μm wavelength APDs, the Si-based APD is promising for its small excess noise factor, less stringent demand on temperature stability, and its compatibility with silicon technology.

  7. The germanium isotopes production rate in background process in SAGE experiment

    The analysis of the direct determination of systematics connected with the germanium isotopes generation of in background processes in radiochemical SAGE experiments on measuring solar neutrinos is described. The found 68Ge generation rate is 6.5 (1 ± 1.0) times higher than expected; the generation rate of 69Ge does not exceed preliminary evaluations. The result on 68Ge corresponds to the systematic of cosmic ray muons of 5.8% (4.5 SNU) for the measured capture rate of solar neutrino of 77.0 SNU. To check the cosmic-ray muon influence of the SAGE systematic one suggests the experiment in place of underground scintillation telescope of the Baksan neutrino observatory on the Institute for Nuclear Research of the RAS

  8. Rate of germanium-isotope production by background processes in the SAGE experiment

    Data on a direct determination of systematic uncertainties caused by the background production of germanium isotopes in the radiochemical SAGE experiment measuring the solar-neutrino flux are analyzed. The result obtained for the rate of 68Ge production is 6.5(1±1.0) times greater than the expected one; the rate of 69Ge production does not exceed preliminary estimates. The above result for 68Ge corresponds to the systematic uncertainty that is caused by the interaction of cosmic-ray muons and which is equal to 5.8% (4.5 SNU) at a solar-neutrino-capture rate of 77.0 SNU. An experiment is proposed that would test the effect of cosmic-ray muon influence on the SAGE systematic uncertainty and which would be performed at the location of the underground scintillation telescope facilities of the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences)

  9. Pulse shape analysis for segmented germanium detectors implemented in graphics processing units

    Calore, Enrico, E-mail: enrico.calore@lnl.infn.it [INFN Laboratori Nazionali di Legnaro, Viale Dell' Università 2, I-35020 Legnaro, Padova (Italy); Bazzacco, Dino, E-mail: dino.bazzacco@pd.infn.it [INFN Sezione di Padova, Via Marzolo 8, I-35131 Padova (Italy); Recchia, Francesco, E-mail: francesco.recchia@pd.infn.it [INFN Sezione di Padova, Via Marzolo 8, I-35131 Padova (Italy); Dipartimento di Fisica e Astronomia dell' Università di Padova, Via Marzolo 8, I-35131 Padova (Italy)

    2013-08-11

    Position sensitive highly segmented germanium detectors constitute the state-of-the-art of the technology employed for γ-spectroscopy studies. The operation of large spectrometers composed of tens to hundreds of such detectors demands enormous amounts of computing power for the digital treatment of the signals. The use of Graphics Processing Units (GPUs) has been evaluated as a cost-effective solution to meet such requirements. Different implementations and the hardware constraints limiting the performance of the system are examined. -- Highlights: • We implemented the grid-search algorithm in OpenCL in order to be run on GPUs. • We compared its performances in respect to an optimized CPU implementation in C++. • We analyzed the results highlighting the most probable factors limiting their speed. • We propose some solutions to overcome their speed limits.

  10. Germanium-on-silicon Vernier-effect photonic microcavities for the mid-infrared.

    Troia, Benedetto; Penades, Jordi Soler; Khokhar, Ali Z; Nedeljkovic, Milos; Alonso-Ramos, Carlos; Passaro, Vittorio M N; Mashanovich, Goran Z

    2016-02-01

    We present Vernier-effect photonic microcavities based on a germanium-on-silicon technology platform, operating around the mid-infrared wavelength of 3.8 μm. Cascaded racetrack resonators have been designed to operate in the second regime of the Vernier effect, and typical Vernier comb-like spectra have been successfully demonstrated with insertion losses of ∼5  dB, maximum extinction ratios of ∼23  dB, and loaded quality factors higher than 5000. Furthermore, an add-drop racetrack resonator designed for a Vernier device has been characterized, exhibiting average insertion losses of 1 dB, extinction ratios of up to 18 dB, and a quality factor of ∼1700. PMID:26907436

  11. Ab initio calculation of the formation energy of charged vacancies in germanium

    Density functional theory (DFT) with local density approximation (LDA) has been used to calculate the formation energy (Ef) of the neutral and charged vacancies in germanium single crystal. The standard (four valence electrons) and harder (which treat the semicore 3d states of Ge as valence) projector augmented wave (PAW) potentials were used. Additionally, the effect of including on-site Coulomb interaction, U, for Ge semicore d states within the LDA+U approach was investigated. The LDA+U method improves the LDA band gap which allows investigating the dependence of formation energy of charged vacancies on Fermi level position in the band gap. It was shown that the calculated formation energies of the neutral and charged vacancies are in good agreement with published experimental data

  12. Neutrino and dark matter experiments with sub-keV Germanium detectors

    Germanium ionization detectors with sensitivities as low as 100 eVee open new windows for the studies of neutrino and dark matter physics. Sensitivities and dynamic ranges on several important research programs in neutrino and dark matter physics can be significantly enhanced with low energy physics signal detection at sub-keV region. This motivates efforts to characterize detector behaviour and to devise optimal analysis methods in the sub-keV energy region where the physics signals is comparable to the electronic noise. Various experimental issues have to be addressed before the promises of this new detector technique can be fully exploited. The theme of TEXONO (Taiwan EXperiment On NeutrinO) is to develop detectors with modular mass of Ø (1 kg), physics threshold of Ø(100 eVee) and background level at threshold of Ø (1kg-1 keV-1 day-1)

  13. Enrichment determinations on uranium dioxide powders and pellets using hyperpure germanium detectors in field conditions

    The purpose of this study was to investigate the capabilities of hyperpure germanium detectors for enrichment determinations on low enrichment uranium oxide in production lines. The measurements were effected using two detectors in two geometries : with and without collimator on reference samples which fulfilled the ''infinite thickness'' condition. An external source of Eu-152 was used to define the counting time and to verify the stability of the instrument. Powders and pellets of uranium oxide with enrichment varying from 1.9 up to 4.2 % were measured in the ''Franco-Belge de Fabrication de Combustibles'' (FBFC), Dessel, Belgium. Estimations of systematic and random errors and background corrections are given for the two cases with and without collimation. Tests of the sample homogeneity and detection power of enrichment change versus declared value are fully discussed. (author)

  14. Doping profile and Ge-dose optimization for silicon–germanium heterojunction bipolar transistors

    The speed of silicon–germanium (SiGe) heterojunction bipolar transistors (HBTs) has been dramatically increased. It is known that the speed of HBTs is dominated by the base transit time, which could be influenced by the doping profile in the base region and the Ge concentration. In this study, the design of the doping profile and Ge-dose concentration for SiGe HBTs are mathematically formulated and solved by a technique of geometric programming (GP). The solution calculated by the GP method is guaranteed to be a global optimal. The accuracy of the adopted numerical optimization technique is first confirmed by comparing with two-dimensional device simulation. The result of this study shows that a 23% Ge fraction may maximize the current gain; furthermore, a 12.5% Ge may maximize the cut-off frequency for the explored device, where a 254 GHz cut-off frequency is achieved

  15. The impact of neutral impurity concentration on charge drift mobility in germanium

    Mei, H; Wang, G -J; Yang, G

    2016-01-01

    We report a new result of the neutral impurity scattering of electrons and holes that has impact on the charge drift mobility in high purity germanium crystals at 77 Kelvin. The charge carrier concentration, mobility and resistivity are measured by Hall Effect system at 77 Kelvin. We investigated the contribution to the total charge drift mobility from ionized impurity scattering, lattice scattering, and neutral impurity scattering with the best theoretical models and experimental data. Several samples with measured Hall mobility from the grown crystals are used for this investigation. With the measured Hall mobility and ionized impurity concentration as well as the theoretical models, we calculated the neutral impurity concentration by the Matthiessen's rule. As a result, the distributions of the neutral impurity concentrations with respect to the radius of the crystals are obtained. Consequently, we demonstrate that neutral impurity scattering is a significant contribution to the charge drift mobility, whic...

  16. Doping dependence of self-diffusion in germanium and the charge states of vacancies

    Südkamp, T.; Bracht, H.; Impellizzeri, G.;

    2013-01-01

    into account the dominance of doubly negatively charged vacancies under donor doping, the doping dependence of self-diffusion is best described with an inverse level ordering for singly and doubly negatively charged vacancies for all doping conditions. The level ordering explains the dominance of......Self-diffusion in boron-doped germanium has been studied at temperatures between 526 and 749 °C with secondary ion mass spectrometry. Self-diffusion under acceptor doping is retarded compared to intrinsic conditions. This demonstrates the contribution of charged vacancies in self-diffusion. Taking...... doubly charged vacancies under donor doping and their decreasing contribution with increasing acceptor doping until neutral vacancies mediate self-diffusion...

  17. Performance Analysis of Silicon and Germanium Nanowire Transistor using Crystal Orientation and Oxide Thickness

    P.Theres Mary

    2014-09-01

    Full Text Available Nanowire Transistors have attracted attention due to the probable high performance and excellent controllability of device current. In this paper, we investigate the performance analysis of nanowire transistors made of silicon and germanium materials. The nanowire transistor has a 3D distribution of electron density and electrostatic potential, therefore self-consistent 3D simulations are used. Nanowire (tool is 3D Poisson self-consistent simulator which can study the 3D transport in nanowire transistor considering phonon scattering based on the effective-mass approximation. The output characteristics of the nanowire transistors are studied in detail for both Si and Ge materials for different transport orientation (i.e., 100,110,111 and varying the oxide thickness.

  18. Gamma-Ray Assay with Lithium-Drifted Germanium Semiconductor Nuclear Detectors

    The characteristics and applications of the semiconductor nuclear radiation detectors which have been fabricated from germanium and compensated to high resistivity by the Pell lithium-drift method to obtain a large sensitive volume for gamma-ray detection are presented. Detector thicknesses of 1 mm to 4 mm are readily fabricated whereas 6 mm and greater are low-yield devices. Areas of 1 cm2 to 6 cm2 are available but the yield depends inversely upon the area. Gamma-ray resolutions of less than 10 keV are obtainable under standard laboratory conditions and less than 3 keV under ideal conditions. Such high resolutions will have immediate effect on gamma-ray assay as it may prove possible in many applications to remove the need for chemical separation. Results with 207Bi, 166Ho and other sources are given. (author)

  19. Strained silicon/silicon germanium heterojunction n-channel metal oxide semiconductor field effect transistors

    Olsen, S H

    2002-01-01

    Investigations into the performance of strained silicon/silicon-germanium (Si/SiGe) n-channel metal-oxide-semiconductor field effect transistors (MOSFETs) have been carried out. Theoretical predictions suggest that use of a strained Si/SiGe material system with advanced material properties compared with conventional silicon allows enhanced MOSFET device performance. This study has therefore investigated the practical feasibility of obtaining superior electrical performance using a Si/SiGe material system. The MOSFET devices consisted of a strained Si surface channel and were fabricated on relaxed SiGe material using a reduced thermal budget process in order to preserve the strain. Two batches of strained Si/SiGe devices fabricated on material grown by differing methods have been analysed and both showed good transistor action. A correlation of electrical and physical device data established that the electrical device behaviour was closely related to the SiGe material quality, which differed depending on growt...

  20. A model for thickness effect on the band gap of amorphous germanium film

    Wang, Xiao-Dong; Wang, Hai-Feng; Chen, Bo; Li, Yun-Peng; Ma, Yue-Ying

    2013-05-01

    A Mott-Davis-Paracrystalline model was proposed to interpret thickness effect of the band gap for amorphous germanium (a-Ge). We believe that a-Ge has a semiconductor-alloy-like structure, it may contain medium-range order (MRO) and continuous random network (CRN) simultaneously and there is a dependence of MRO/CRN ratio on film thickness and preparation methods/parameters. For MRO is dominant, thickness effect can be described by one-dimensional quantum confinement (ODQC) effect of nanocrystals and strain-induced shrinkage of the band gap; For CRN is dominant, thickness dependence can be interpreted by changes in the quality of a CRN and ODQC effect of nanoamorphous phase.

  1. Quantitative assessment of molecular dynamics-grown amorphous silicon and germanium films on silicon (111)

    Käshammer, Peter; Borgardt, Nikolai I.; Seibt, Michael; Sinno, Talid

    2016-09-01

    Molecular dynamics based on the empirical Tersoff potential was used to simulate the deposition of amorphous silicon and germanium on silicon(111) at various deposition rates and temperatures. The resulting films were analyzed quantitatively by comparing one-dimensional atomic density profiles to experimental measurements. It is found that the simulations are able to capture well the structural features of the deposited films, which exhibit a gradual loss of crystalline order over several monolayers. A simple mechanistic model is used to demonstrate that the simulation temperature may be used to effectively accelerate the surface relaxation processes during deposition, leading to films that are consistent with experimental samples grown at deposition rates many orders-of-magnitude slower than possible in a molecular dynamics simulation.

  2. Synthesis and characterization of nano/micro structured crystalline germanium dioxide with novel morphology

    WANG XiaoYan; DUAN Lian; DONG GuiFang; WEI Peng; WANG Wei; WANG LiDuo; QIU Yong

    2009-01-01

    Nano/micro-structured germanium oxide (GeO2) was prepared using GeCl4 and KOH by a simple solution method in alkalic alcoholic solution.Different morphologies of GeO2 were obtained by changing the reaction conditions.The effects of the reaction time,the concentration of the reactants,the reaction temperature and the dispersant upon the morphology of the deposited GeO2 have been investigated.The products were detected by X-ray diffraction (XRD),atomic force microscope (AFM),scanning electron microscope (SEM) and transmission electron microscope (TEM).Novel cross-like structures were obtained by using n-butylamine as the dispersant.The formation of the cross-like structures has been discussed and a solution-liquid-solid (SLS) mechanism was proposed.

  3. Analytical modeling and simulation of germanium single gate silicon on insulator TFET

    This paper proposes a new two dimensional (2D) analytical model for a germanium (Ge) single gate silicon-on-insulator tunnel field effect transistor (SG SOI TFET). The parabolic approximation technique is used to solve the 2D Poisson equation with suitable boundary conditions and analytical expressions are derived for the surface potential, the electric field along the channel and the vertical electric field. The device output tunnelling current is derived further by using the electric fields. The results show that Ge based TFETs have significant improvements in on-current characteristics. The effectiveness of the proposed model has been verified by comparing the analytical model results with the technology computer aided design (TCAD) simulation results and also comparing them with results from a silicon based TFET. (semiconductor devices)

  4. Determination of Hot-Carrier Distribution Functions in Uniaxially Stressed p-Type Germanium

    Christensen, Ove

    1973-01-01

    This paper gives a description of an experimental determination of distribution functions in k→ space of hot holes in uniaxially compressed germanium. The hot-carrier studies were made at 85°K at fields up to 1000 V/cm and uniaxial stresses up to 11 800 kg/cm2. The field and stress were always in...... the 〈111〉 direction. For the highest stresses, the maximum fields were close to the threshold for current oscillations. The distribution functions were obtained from experimental modulation of intervalence-band absorption of infrared radiation. In order to interpret the results, a parametrized...... performed in thermal equilibrium. The average carrier energy calculated from the distribution function shows a fast increase with stress and almost saturates when the strain splitting of the two p3 / 2 levels reaches the optical-phonon energy. This saturation is interpreted in terms of the change in...

  5. THE PATHOGENESIS OF EXPERIMENTAL MODEL OF MITOCHONDRIAL MYOPATHY INDUCED BY GERMANIUM DIOXIDE

    李晓东; 高枫; 陈清棠

    2001-01-01

    Objective. The purpose of the study was to build up an animal model of mitochondrial myopathy in order to analyse the pathogenesis of the disease.Methods. The skeletal muscles from Wistar rats treated with germanium dioxide for 24 weeks were analysed by histopathologic and electron-microscopic studies. A quantitative analysis was carried out in mitochondrial DNAs of these samples. The biological function of the model was determined.``Results. An animal model of mitochondrial myopathy was built up, in which oxygen free radicals were increased and mitochondrial DNA copies were decreased contrasted with controls.``Conclusion. It suggested that environmental toxin may play a role in the pathogenesis of mitochondrial myopathy. The increase of oxygen free radicals is an important link causing the disease.

  6. THE PATHOGENESIS OF EXPERIMENTAL MODEL OF MITOCHONDRIAL MYOPATHY INDUCED BY GERMANIUM DIOXIDE

    李晓东; 高枫; 陈清棠

    2001-01-01

    Objective. The purpose of the study was to build up an animal model of mitochondrial myopathy in order to analyse the pathogenesis of the disease. Methods. The skeletal muscles from Wistar rats treated with germanium dioxide for 24 weeks were analysed by histopathologic and electron-microscopic studies. A quantitative analysis was carried out in mitochondrial DNAs of these samples. The biological function of the model was determined. Results. An animal model of mitochondrial myopathy was built up, in which oxygen free radicals were increased and mitochondrial DNA copies were decreased contrasted with controls. Conclusion. It suggested that environmental toxin may play a role in the pathogenesis of mitochondrial myopathy. The increase of oxygen free radicals is an important link causing the disease.

  7. Observation of Impact Ionization of Shallow States in Sub-Kelvin, High-Purity Germanium

    Phipps, A.; Sadoulet, B.; Sundqvist, K. M.

    2016-07-01

    We report on the observation of impact ionization processes involving shallow impurity states in a sub-Kelvin, high-purity n-type germanium detector similar to those used by direct detection dark matter experiments such as the Cryogenic Dark Matter Search. An optical fiber is used to generate packets of charge carriers near one surface of the detector. The charge carriers drift to the opposite surface by application of an electric field. The resulting drift current is measured by a high-speed charge amplifier. The onset of impact ionization for both electron and hole transport is clearly observed in the drift current as the applied electric field is increased above ≈ 5 V/cm. We present the effective charge collection efficiency and trapping length as a function of applied electric field for electrons and holes. We estimate the impact ionization cross section to be on the order of 5× 10^{-13} mathrm {cm}^2.

  8. Observation of Impact Ionization of Shallow States in Sub-Kelvin, High-Purity Germanium

    Phipps, A.; Sadoulet, B.; Sundqvist, K. M.

    2016-01-01

    We report on the observation of impact ionization processes involving shallow impurity states in a sub-Kelvin, high-purity n-type germanium detector similar to those used by direct detection dark matter experiments such as the Cryogenic Dark Matter Search. An optical fiber is used to generate packets of charge carriers near one surface of the detector. The charge carriers drift to the opposite surface by application of an electric field. The resulting drift current is measured by a high-speed charge amplifier. The onset of impact ionization for both electron and hole transport is clearly observed in the drift current as the applied electric field is increased above ≈ 5 V/cm. We present the effective charge collection efficiency and trapping length as a function of applied electric field for electrons and holes. We estimate the impact ionization cross section to be on the order of 5× 10^{-13} {cm}^2.

  9. High-purity germanium detector ionization pulse shapes of nuclear recoils, gamma interactions and microphonism

    Baudis, L; Klapdor-Kleingrothaus, H V; Ramachers, Y; Hammer, J W; Mayer, A

    1998-01-01

    Nuclear recoil measurements with high-purity Germanium detectors are very promising to directly detect dark matter candidates. The main background sources in such experiments are natural radioactivity and microphonic noise. Digital pulse shape analysis is an encouraging approach to reduce the background originating from the latter. To study the pulse shapes of nuclear recoil events we performed a neutron scattering experiment, which covered the ionization energy range from 20 to 80 keV. We have measured ionization efficiencies as well and found an excellent agreement with the theory of Lindhard. In a further experiment we measured pulse shapes of a radioactive gamma-source and found no difference to nuclear recoil pulse shapes. Pulse shapes originating from microphonics of a HPGe-detector are presented for the first time. A microphonic noise suppression method, crucial for dark matter direct detection experiments, can therefore be calibrated with pulse shapes from gamma-sources.

  10. Recent results from the canfranc dark matter search with germanium detectors

    Irastorza, I. G.; Morales, A.; Aalseth, C. E.; Avignone III, F. T.; Brodzinski, R. L.; Cebrian, S.; Garcia, E.; Gonzalez, D; Hensley, W. K.; Miley, H. S.; MORALES, J., CRUZ, D., DELGADO, P., LIZANA, M., LÓPEZ, V.; de Solorzano, A. Ortiz; Puimedon, J.; Reeves, J. H.; Sarsa, M. L.(Laboratorio de Física Nuclear y Astropartículas, Universidad de Zaragoza, Calle Pedro Cerbuna 12, 50009, Zaragoza, Spain)

    2000-01-01

    Two germanium detectors are currently operating in the Canfranc Underground Laboratory at 2450 m.w.e looking for WIMP dark matter. One is a 2 kg 76Ge IGEX detector (RG-2) which has an energy threshold of 4 keV and a low-energy background rate of about 0.3 c/keV/kg/day. The other is a small (234 g) natural abundance Ge detector (COSME), of low energy threshold (2.5 keV) and an energy resolution of 0.4 keV at 10 keV which is looking for WIMPs and for solar axions. The analysis of 73 kg-days of ...

  11. Wetting Angle and Surface Tension of Germanium Melts on Different Substrate Materials

    Kaiser, N.; Croell, A.; Szofran, F. R.; Benz, K. W.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    The sessile drop technique has been used to measure the wetting angle and the surface tension of molten germanium (Ge) on various substrate materials. Sapphire, fused silica, glassy carbon, graphite, SiC, carbon-based aerogel, pyrolytic boron nitride (pBN), AlN, Si3N4, and CVD diamond were used as substrate materials. In addition, the effects of different cleaning procedures and surface treatments on the wetting behavior were investigated. The highest wetting angles with values around 170 deg. were found for pBN substrates under active vacuum or with a slight overpressure of 5N Argon or forming gas (2% Hydrogen in 5N Argon). The measurement of the surface tension and its temperature dependence for Ge under a forming gas atmosphere resulted in gamma(T) = 591 - 0.077 (T-T(sub m).

  12. Separation of no-carrier-added arsenic-77 from neutron irradiated germanium

    Bokhari, T.H. [Isotope Production Div., Pakistan Inst. of Nuclear Science and Technology, Islamabad (Pakistan); Dept. of Chemistry, Government Coll. Univ., Lahore (Pakistan); Mushtaq, A. [Isotope Production Div., Pakistan Inst. of Nuclear Science and Technology, Islamabad (Pakistan); Khan, I.U. [Dept. of Chemistry, Government Coll. Univ., Lahore (Pakistan)

    2009-09-15

    Arsenic-77 (T{sub 1/2} = 1.6 d) was produced by irradiating natural germanium in Pakistan Research Reactor-1. The nuclear reaction {sup 76}Ge(n, {gamma}{sup -}) produces {sup 77}Ge, which decays by emission of {beta} particles into {sup 77}As. The neutron irradiated target was dissolved in aqua regia, excess of acid was removed by evaporation and finally the solution in basic media was passed through hydrous zirconium oxide (HZO) column. The Ge was quantitatively retained on HZO, while {sup 77}As was present in the effluent. More than 90% {sup 77}As was recovered. The chemical impurity of Ge in {sup 77}As was < 0.01 {mu}g/mL. (orig.)

  13. Measurement of the cosmogenic activation of germanium detectors in EDELWEISS-III

    Armengaud, E; Augier, C; Benoît, A; Bergé, L; Billard, J; Blümer, J; de Boissière, T; Broniatowski, A; Camus, P; Cazes, A; Chapellier, M; Charlieux, F; De Jésus, M; Dumoulin, L; Eitel, K; Foerster, N; Gascon, J; Giuliani, A; Gros, M; Hehn, L; Heuermann, G; Jin, Y; Juillard, A; Kéfélian, C; Kleifges, M; Kozlov, V; Kraus, H; Kudryavtsev, V A; Le-Sueur, H; Marnieros, S; Navick, X -F; Nones, C; Olivieri, E; Pari, P; Paul, B; Piro, M -C; Poda, D; Queguiner, E; Rozov, S; Sanglard, V; Schmidt, B; Scorza, S; Siebenborn, B; Tcherniakhovski, D; Vagneron, L; Weber, M; Yakushev, E

    2016-01-01

    We present a measurement of the cosmogenic activation in the germanium cryogenic detectors of the EDELWEISS III direct dark matter search experiment. The decay rates measured in detectors with different exposures to cosmic rays above ground are converted into production rates of different isotopes. The measured production rates in units of nuclei/kg/day are 82 $\\pm$ 21 for $^3$H, 2.8 $\\pm$ 0.6 for $^{49}$V, 4.6 $\\pm$ 0.7 for $^{55}$Fe, and 106 $\\pm$ 13 for $^{65}$Zn. These results are the most accurate for these isotopes. A lower limit on the production rate of $^{68}$Ge of 74 nuclei/kg/day is also presented. They are compared to model predictions present in literature and to estimates calculated with the ACTIVIA code.

  14. Tensile-Strained Germanium-on-Insulator Substrate Fabrication for Silicon-Compatible Optoelectronics

    Jain, J Raja; Balram, Krishna C; White, Justin S; Brongersma, Mark L; Miller, David A B; Howe, Roger T

    2011-01-01

    We present a method to fabricate tensile-strained germanium-on-insulator (GOI) substrates using heteroepitaxy and layer transfer techniques. The motivation is to obtain a high-quality wafer-scale GOI platform suitable for silicon-compatible optoelectronic device fabrication. Crystal quality is assessed using X-Ray Diffraction (XRD) and Transmission Electron Microscopy. A biaxial tensile film strain of 0.16% is verified by XRD. Suitability for device manufacturing is demonstrated through fabrication and characterization of metal-semiconductor-metal photodetectors that exhibit good responsivity beyond 1.55 {\\mu}m. The substrate fabrication process is compatible with complementary metal-oxide-semiconductor manufacturing and represents a potential route to wafer-scale integration of silicon-compatible optoelectronics.

  15. Atomic transport during solid-phase epitaxial recrystallization of amorphous germanium

    The atomic mixing of matrix atoms during solid-phase epitaxy (SPE) is studied by means of isotopically enriched germanium (Ge) multilayer structures that were amorphized by Ge ion implantation up to a depth of 1.5 μm. Recrystallization of the amorphous structure is performed at temperatures between 350 °C and 450 °C. Secondary-ion-mass-spectrometry is used to determine the concentration-depth profiles of the Ge isotope before and after SPE. An upper limit of 0.5 nm is deduced for the displacement length of the Ge matrix atoms by the SPE process. This small displacement length is consistent with theoretical models and atomistic simulations of SPE, indicating that the SPE mechanism consists of bond-switching with nearest-neighbours across the amorphous-crystalline (a/c) interface

  16. Mapping Brazilian radioactive minerals by gamma-ray spectrometry and using a germanium detector

    This paper has as scope the organization of a catalogue of the main uranium and/or thorium minerals using their gamma-ray spectra registered by their natural radioactivity with a pure germanium detector. The objective is to accumulate data for the radiometric identification for a posterior comparative study of minerals of same procedence or from new uranium and thorium occurrences. On the respective spectra are marked the main peaks, their energies and the correspondent radioisotopes. An estimative of their radioactive equilibrium state is included. As additional information the decay of the descendents of the natural series of 235U, 238U and 232Th, their gamma-ray energies and, finally, a table of the main uranium and thorium ores are presented. (Author)

  17. Measurement of 238U muonic x-rays with a germanium detector setup

    Esch, Ernst I [Los Alamos National Laboratory; Jason, Andrew [Los Alamos National Laboratory; Miyadera, Haruo [Los Alamos National Laboratory; Hoteling, Nathan J [Los Alamos National Laboratory; Heffner, Robert H [Los Alamos National Laboratory; Adelmann, Andreas [PAUL SCHERRER INSTITUT; Stocki, Trevor [HEALTH CANADA; Mitchell, Lee [NAVAL RESEARCH LAB

    2009-01-01

    In the field of nuclear non-proliferation muon interactions with materials are of great interest. This paper describes an experiment conducted at the Paul Scherrer Institut (PSI) in Switzerland where a muon beam is stopped in a uranium target. The muons produce characteristic muonic x-rays. Muons will penetrate shielding easily and the produced characteristic x-rays can be used for positive isotope identification. Furthermore, the x-rays for uranium isotopes lie in the energy range of 6-7 MeV, which allows them to have an almost optimal mean free path in heavy shielding such as lead or steel. A measurement was conducted at PSI to prove the feasibility of detecting muonic x-rays from a large sample of depleted uranium (several kilograms) with a germanium detector. In this paper, the experimental setup and analysis of the measurement itself is presented.

  18. Measurement of the dead layer thickness in a p-type point contact germanium detector

    Jiang, H; Li, Y L; Kang, K J; Li, Y J; Li, J; Lin, S T; Liu, S K; Ma, H; Ma, J L; Su, J; Wong, H T; Yang, L T; Zhao, W; Zeng, Z

    2016-01-01

    A 994g mass p-type PCGe detector was deployed by the first phase of the China Dark matter EXperiment aiming at the direct searches of light weakly interacting massive particles. Measuring the thickness of the dead layer of a p-type germanium detector is an issue of major importance since it determines the fiducial mass of the detector. This work reports a method using an uncollimated 133Ba source to determine the dead layer thickness. The experimental design, data analysis and Monte Carlo simulation processes, as well as the statistical and systematic errors are described. An agreement between the experimental data and simulation results was achieved to derive the thickness of the dead layer of 1.02 mm.

  19. Structural, elastic and thermodynamic properties of the tetragonal structure of germanium carbonitride

    Xing, Mengjiang; Li, Binhua; Yu, Zhengtao; Chen, Qi

    2016-04-01

    The structural, mechanical, electronic and thermodynamic properties of the tetragonal structure germanium carbonitride (t-GeCN) were first investigated using the density function theory with the ultrasoft psedopotential scheme in the frame of the generalized gradient approximation and the local density approximation. The elastic constants have confirmed that the t-GeCN is mechanically stable and phonon spectra have confirmed that the t-GeCN is dynamically stable. The anisotropy studies show that t-GeCN exhibits a larger anisotropy in its Poisson's ratio, Young's modulus, shear modulus, sound velocities and universal elastic anisotropy index. Electronic structure study shows that t-GeCN is an indirect semiconductor with band gap of 0.628 eV. The thermodynamic properties of t-GeCN, including Debye temperature, heat capacity, Grüneisen parameter and thermal expansion coefficient are investigated utilizing the quasi-harmonic Debye model.

  20. Canister cryogenic system for cooling germanium semiconductor detectors in borehole and marine probes

    Boynton, G.R.

    1975-01-01

    High resolution intrinsic and lithium-drifted germanium gamma-ray detectors operate at about 77-90 K. A cryostat for borehole and marine applications has been designed that makes use of prefrozen propane canisters. Uses of such canisters simplifies cryostat construction, and the rapid exchange of canisters greatly reduces the time required to restore the detector to full holding-time capability and enhances the safety of a field operation where high-intensity 252Cf or other isotopic sources are used. A holding time of 6 h at 86 K was achieved in the laboratory in a simulated borehole probe in which a canister 3.7 cm diameter by 57 cm long was used. Longer holding times can be achieved by larger volume canisters in marine probes. ?? 1975.