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The ability of a national standards laboratory to disseminate a temperature scale relies entirely on the stability of available secondary temperature standards. For many years, germanium resistance thermometers (GRTs) were the accepted secondary thermometer of choice below 27.5 K. Rhodium-iron resistance thermometers (RIRTs) have supplanted their use in many standards laboratories, but GRTs are still preferred in some applications due to their smaller size and high sensitivity. Following a trend over the past few decades, high quality thermometer standards for the cryogenic temperature range, including GRTs and RIRTs, have become harder to both produce and procure. Currently, outside of national standards laboratories work, the 1 K to 27 K temperature is most often served by Cernox® resistance thermometers (CxRTs). This work examines historical data to compare GRT and CxRT thermometers' performance over the 1 K to 27 K temperature range. In short term stability tests at 4.2 K, data show that GRTs are stable to the ±0.5 mK level while CxRTs are stable to the ±0.75 mK level. Over extended periods of repeated thermal cycling to room temperature, GRTs remain stable to about ±2 mK below 10 K and ±5 mK above 10 K. While the average stability of a test group of CxRTs is on par with the GRT stability, the individual device stability has greater variability. [ABSTRACT FROM AUTHOR]

Armchair (5, 5) carbon nanotubes doped with germanium atoms (Ge, n = 1-4) were explored theoretically in this work. Density functional theory (DFT) with hybrid functional Becke 3-parameter Lee–Yang–Parr (B3LYP) and a basis set 6-31G* were used to investigate the structural and electronic properties of the resulting nanotubes. The stability of the substitutional Ge atoms was thus studied and explained in terms of the binding energy per dopant atom. The density of state and HOMO-LUMO gap showed that electrical conductivity increases gradually with the number of dopants. The ionization potential, electron affinity, chemical hardness and softness, and chemical potential were also calculated. [ABSTRACT FROM AUTHOR]

One of the essential values in Profile Distribution Models (PDM) is the coefficient profile shape (h0) parameter; on the other hand, h0 has an interlink to relaxation length (λ). Both its function is critical, but unfortunately, the h0 parameter studies are still limited. The main aim of this study was to investigate the total inventory of 137Cs and 210Pbex on profile shape and obtain h0 and λ values on seven undisturbed lands. Soil samples were taken from seven locations of Undisturbed Land (UL) on three watersheds using scrapping, each location was grabbed at intervals of 2 cm to a depth of 20, and continued with a coring tool to 30 cm of depth for 10 cm intervals; a totally of 77 soil samples were analyzed. Samples have been prepared well and measured using Low Energy Germanium (LEGe) gamma spectroscopy. The total inventory was analyzed by Pearson correlation. Meanwhile, the exponential fitting line defined h0 and λ values. This study found that the total inventory of 210Pbex at a depth of 0 to 30 cm ranged from 2799.189±349.952 (UL6) to 7873.290±241.158 Bq m−2 (UL4). Meanwhile, 137Cs is 92.912±4.528 (UL3) to 265.114±10.519 Bq m-2 (UL5). On the other hand, a 20 to 30 cm depth showed the concentration of 137Cs at UL1, and 210Pbex at UL3 was below MDA level. Inventory profile of FRN present; (1) a good 210Pbex exponential shape for all UL; (2) except for UL6 and 7, profile of 137Cs in the five ULs is not exponential shape, indicates UL 6 and 7 had been tillage after 1964's (the highest fallout of 137Cs period), but the land has not experienced significant disturbance or erosion is minimal. Whereas, in UL 1 to UL 5 the profile is not following the exponential theory, thus, the area can be considered cultivated or disturbed land. Parameter h0 of 137Cs was obtained greater than 210Pbex within the range 150.644 (UL6) – 1666.667 (UL1) kg m−2. However, there is no correlation between h0 137Cs and 210Pbex. The highest λ value of 137Cs and 210Pbex were obtained at 13.177 and 198.125 cm, respectively [ABSTRACT FROM AUTHOR]

An environmental study based on comparing the results of measurements of soil and plant samples taken from inside destructive nuclear sites such as the Russian reactor, July 14, and the Italian fuel site and comparing them with models taken from the areas around the Tuwaitha nuclear site using the gamma spectrum system (high purity germanium gamma spectroscopy) to determine the real effects of the destroyed nuclear sites on the surrounding areas. Most of the samples taken from the site were contaminated with isotopes of Cs-137, Co-60, and K-40, where the highest concentration of Cs-137 activity was (1847 ± 40.6) Bq/Kg and K-40 was (758 ± 40) Bq/Kg. The off-site radioactivity of the samples Cs-137 was (0.891 ± 0.01) Bq/Kg and K-40 was (587.420 ± 10.6) Bq/Kg. [ABSTRACT FROM AUTHOR]

We present the surface evolution of the single crystal germanium substrates bombarded with 200 keV Kr ions at a constant fluence of 5.0 × 1017 ions/cm2 at various off-normal ion incident angles, viz. 40°, 50°, 60°, and 70°. The surface morphologies of the irradiated samples were obtained by scanning the surface of size 10 × 10 µm2, using Atomic Force Microscopy (AFM). The data acquisition and off-line analysis of AFM micro images were done by WSxM and Nanoscope software. The statistical surface data points were analysed by the Fractal method to obtain the surface parameters, and for comparative study, the roughness exponent was also obtained from the power spectral density method. The self-affine nature of the samples and the evolution of the ripple pattern are both clearly visible in the fractal correlation plots. [ABSTRACT FROM AUTHOR]

The nuclear properties of 74-80Ge isotopes, energy levels, electromagnetic transitions B(E2), B(M1), and the potential energy surface (PES) were studied. Finally, all of these structures are classified. The results are in good agreement with the available experimental data. [ABSTRACT FROM AUTHOR]

In this study, the molten method was used to prepare the chalcogenide compound Ge35−S65-X−CdX. Five samples were obtained by partial replacement of sulfur with cadmium in the weight ratios x = 0, 5, 10, 15and 20, respectively. The materials were mixed separately, ground, placed in quartz ampoules, and heated to 900 degrees Celsius. After conducting several operations on the samples, their insulating properties were studied, represented by the real dielectric constant and the imaginary dielectric constant. The loss remained in a frequency range ranging from (50_1000000 Hz). It was found that partial replacement plays an important role in enhancing the insulating properties. [ABSTRACT FROM AUTHOR]

In this study, metal induced crystallization technique is used in to obtain the lower temperature point in crystallization. Two different metals with one non-metal configuration as a baseline i.e. SiGe/Ni, SiGe/Cu and SiGe. A simple metal-assisted chemical etching method is used to fabricate the Si nanopillar, with Ag acting as a catalyst. Following by deposition of metal namely nickel (Ni) and copper (Cu) then undergo thermal annealing from 200 ℃ until 1000 ℃ to improve the crystallinity of the Ge layer. Morphological studies of surface area were conducted using scanning electron microscopy (SEM). The results show that the crystallization temperature of SiGe with Ni was obtained at 400 ℃ while the crystallization temperature of SiGe without any metal was obtained at 600 ℃. Meanwhile the crystallinity, for SiGe/Cu only occurs in very low level where the structure did not change until the annealing was conducted at 600 ℃. Based from these result, it is proved that the metal can help lowering the crystallization temperature and improving the defects of SiGe [ABSTRACT FROM AUTHOR]

A low-background, hyper-pure germanium (HPGe) gamma-ray spectroscopy system was used to measure uranium (238U) and a thorium (232Th) concentrations in Amman's drinking water. Drinking water samples were collected from sixteen different places in Amman, Jordan, using polyethylene bottles. In drinking water, the activity of 226Ra and 228Ra ranged from 0.345 ± 0.066 to 0.668 ± 0.166 BqL−1, with a mean value of 0.517 ± 0.108 BqL−1 and 0.017 ± 0.009 to 0.378 ± 0.046 BqL−1, with a mean value of 0.227 ± 0.035 BqL−1, respectively. In this study, the average total radium (226Ra +228Ra) activity in the drinking water was 0.747 ± 0.203 BqL−1, which is less than the WHO's, 2017 MRL of 1.1 BqL−1. The mean radium ratio (228Ra/226Ra) is 0.469 ± 0.045 BqL−1, which is approximately five times higher than the WHO's 2017 minimum recommended limits (MRLs) of 0.1 BqL−1. In all drinking water samples, uranium (238U ̶ 226Ra) concentrations were found to be higher than thorium (232Th ̶ 228Ra) concentrations. All of the results of this study were compared to the international minimum recommended limits (IMRLs) and previous experimental results from around the world. [ABSTRACT FROM AUTHOR]

Although germanium cells present attractive advantages for its use in thermophotovoltaic (TPV) devices, their limited below-bandgap reflectance and the set thickness of these type of cells favors free carrier absorption (FCA) and the loss of unused infrared photons. To circumvent these problems, we have developed a fast and isotropic chemical thinning process of Ge wafers, which helps reducing the impact that FCA may have on the performance of our devices. Additionally, to increase the IR reflection, an Al back contact and diffused p+ doped back surface field (BSF) structure is proposed as a mean of obtaining a high-quality back mirror for both IR photons and minority carriers. To optimize the properties of this structure, Ge TPV cells were fabricated using different annealing temperatures to modify the opto-electronic behavior of the combined back mirror and BSF layers. EQE, reflectivity and I-V curves were measured for all devices and results were modelled using a classic analytic model based on Hovel's equations, confirming that the opto-electronic changes can be explained through changes in the characteristics of the rear IR mirror and BSF structure. An optimal trade-off between optical and electrical properties was found for TPV cells annealed at 400 °C. [ABSTRACT FROM AUTHOR]

The efficiency of pulse-shape-discrimination (PSD) methods for rejection of α-ray-induced events in high purity germanium detectors of the BEGe-like (BEGe standing for Broad Energy Germanium) type was studied. A high number of α-ray events was obtained by placing a gold foil with deposited 209Po on the p+ contact of the detector. Investigated classification methods were trained exclusively on γ-ray events from a 228Th source (using the so-called single-site and multi-site γ-ray events) and applied to α-ray events. The aim of this work was to test if a PSD classifier trained and calibrated solely on γ rays can also efficiently remove α-ray events with no further adaptation. The ROOT/TMVA projective-likelihood estimator, a multi-layer-perceptron (MLP) artificial neural network, and A/E methods were all studied. For the tested BEGe-like detector, the projective likelihood showed the best performance, rejecting α-ray background events by more than a factor of 104 (limited by statistics), while maintaining a high survival probability of about 89% for single-site γ-ray events. [ABSTRACT FROM AUTHOR]

The phenomenon of dezincification is responsible for brass's low corrosion resistance in certain situations. A trace amount addition of arsenic to α--brasses prevent dezincification, whereas heat treatment to convert more susceptible (α +ß) brasses to single-phase α -brasses is occasionally used to solve the problem. The disadvantages of these procedures include the fact that arsenic is only effective on α -phase brasses and the ineffective cost of the heat treatment. Tin and Germanium were tested as corrosion inhibitors for less expensive hot-stampable (α +ß) brasses in this study. The goal of the research was to figure out what the ideal amounts of these elements are, as well as to figure out how the inhibition works. While tin alone was shown to be an effective corrosion inhibitor, it was discovered that when germanium was added, the inhibition was even better. This is due to an increase in toughness and ductility, as well as improved adhesion and oxide plasticity. [ABSTRACT FROM AUTHOR]

The morphology of the surfaces of single-crystal germanium, corresponding to the crystallographic planes {111}, {100}, {110}, after laser heat treatment was investigated. We used repetitively pulsed radiation of a nanosecond UV laser (wavelength is 355 nm, duration is 10 ns, energy density∼0.5 – 1.3 J/cm2) of pre-threshold intensity. It was confirmed that on the {111} plane, as a result of impact to radiation, etching pits appear, which are identical to those, that appear during selective chemical etching. It was first discovered, that on the {100} plane etching results, having a crystallographic nature, can also appear. On the {110} plane, traces of the impact of laser radiation were also observed. However, the crystallographic orientation of the plane in the traces of impact to radiation did not manifest itself explicitly. [ABSTRACT FROM AUTHOR]

Validation of HPGe efficiency modeling by MCNP5 for volume source has been carried out in this study. Monte Carlo code is commonly used to estimate the detector efficiency replacing standard radioactive source. In this work, validation of HPGe efficiency was performed by comparing the result of MCNP modeling with the measurement data from two different types of sample, which are point-like source and liquid source. The germanium crystal (dead layer) was optimized correspond to relative efficiency as well as absolute efficiency of a point standard source Co-60 and Eu-152 obtained by experiment. The modeling validation was carried out by using the standard volume source, which is a liquid source containing Eu-152 radioactive material. The result shows that the discrepancy for both point source as well as liquid source are not larger than 7%. It means that the modeling using the MCNP5 code is still satisfying the experiment data. However, for the future work, the validation of this model using another type of standard sources, such as soil source and charcoal source containing standard radioactive material is absolutely needed. [ABSTRACT FROM AUTHOR]

The results of investigations of relaxation processes of donor bound electrons in the germanium doped by arsenic at cryogenic temperatures are presented. The lifetimes of p-type excited states of a donor were measured by pump-probe technique utilizing THz radiation from free-electron laser NovoFEL. The uniaxial stress along [111] axis was applied to the crystal to modify the energy spectrum of the impurity and intervalley relaxation processes. The analysis of experimental for p-type excited states allows to get the upper limit for the relaxation time of lowest 1s excited state. The comparison of obtained experimental results with the theoretical estimates for the interaction with TA phonons indicates on the enhancement of the interaction with the phonons having wavenumbers corresponding to the flat part of the dispersion. [ABSTRACT FROM AUTHOR]

Phosphoric acid/hydrogen peroxide (H3PO4/H2O2) oxidizer mixture is used to grow films on high purity germanium (HPGe) crystals in Hydrofluoric acid with an objective to passivate the inter-contact region of HPGe detectors. The bonding characteristics have been investigated by IR transmission. The native oxide films consist of Ge-O bonding in cristalobite atomic configuration where both hexagonal and tetragonal germanium oxide signatures are present. Raman spectroscopy data indicate the amorphous nature of grown films. Scanning electron microscopy (SEM) clearly reveals formation of a porous layer that is Ge–Hx terminated as indicated by FTIR spectroscopy when high peroxide concentrations are employed for growth. On the other hand smooth and dense films appear at low H2O2 concentration with no Ge-H bonding signature. The chemically grown films are quite stable in HF unlike the unstable nature of native oxides of Ge. HPGe diode has been fabricated using lithium diffused and Pd surface barrier contacts. The inter-contact region is passivated using chemically grown oxide film. The film offers high resistive properties and inhibit surface leakage problem of the fabricated diodes. [ABSTRACT FROM AUTHOR]

In this work, we investigate graphene field-effect phototransistor based on photogating. We discuss the theory of this effect and predict such characteristics as the dependence of photoresponse on the gate voltage. To verify our considerations, we fabricate devices on different semiconductor substrates (silicon, germanium or gallium arsenide) and measure their properties. We demonstrate that photogating reveals opportunities for the development of highly sensitive broadband photodetectors from ultraviolet to mid-infrared ranges. [ABSTRACT FROM AUTHOR]

Silicon germanium nanowire has varieties of applications in nanoelectronics and optoelectronics due to technological advances. Nowadays, Computational Material Science is evolving because computer simulation is a tool to get insight about the properties of materials at atomic or molecular level which is used to predict and/or verify experiments. This is considered as a bridge between theory and experiment. In this paper, silicon germanium square nanowire having simulation length of 97.74 A0 is simulated by Nonequilibrium molecular dynamics simulation. Empirical interatomic potential used is Stillinger Weber potential. For canonical ensemble, effect of temperatures on thermal conductivity of silicon germanium square nanowire is studied [ABSTRACT FROM AUTHOR]

Currently, solar simulators demand component solar cells, also named isotypes, in order to equilibrate their spectrum and match the required norm. Each architecture of cell needs a specific set of isotypes and each one of them need calibration in order to assess the incident power coming from the solar simulator in its spectral range. In this article, pseudo-isotypes are proposed in order to ease the spectral balance of new architectures of multijunction solar cells (MJSC). Pseudo-isotypes are silicon and germanium photodiodes filtered with filters reproducing the cut-on and the cut-off of each MJSC subcell. The use of pseudo-isotypes requires the development of a simple and accurate calibration in order to obtain the constants associated with these references without sending it to a certified laboratory. An indoor calibration method is described and its accuracy is assessed. IV characteristics of 3J MJSC under a solar simulator are carried out with different sets of references: i) isotypes calibrated outdoor, ii) isotypes calibrated indoor, and iii) pseudo-isotypes calibrated indoor. [ABSTRACT FROM AUTHOR]

The outstanding electrical properties of the single crystal chemical vapourdeposition (scCVD) and poly crystal chemical vapour deposition (pcCVD) diamond play an important role for the use of radiation detection. A diamond radiation detector was fabricated using diamond grown on diamond substrate as a basic source material. The detector was tested by Optical Microscope, X-ray diffraction, Raman spectroscopy &(I-V) characteristics. Optical microscope confirms the surface morphology as well as grain boundaries of the diamond films. XRD confirms crystallinity and long range ordered of the film. Raman shows the good content of Sp³ bonds. The measured leakage current was very low ~2.3pA and ~40pA of substrate and grown diamond film and is in good agreement with the reported values by various research groups. The comparison study of silicon, germanium, gallium Arsenide and diamond confirms that diamond isradiation hard than other materials. It causes due to high atomic displacement energy i.e., energy required to displace a carbon atom from its lattice site [ABSTRACT FROM AUTHOR]

Motivated by the recent theoretical prediction of “Quantum Spin Liquids and the Metal-Insulator Transition (MIT) in Doped Semiconductors”[1], In this work, we have investigated for a possible spin liquid state in boron doped germanium polycrystalline samples at four different concentrations. We have realized the transition from insulating state (pure germanium) to the metallic state by doping of boron in fine steps. It is predicted that a quantum spin liquid state can appear as an intermediate phase between the metal and the Anderson-Mott insulator. Therefore a signature of spin liquid behavior in doped semiconductors can be probed by a careful and doping dependent study of thermal transport near the MIT. A spinon Fermi liquid character in this disordered and correlated phase would lead to thermal conductivity κ ~ T for low T, as predicted by theory [1]. In addition, the effect of concentration of boron doping on the electrical resistivity, carrier concentration, and thermal conductivity has been studied. [ABSTRACT FROM AUTHOR]

Using first principle calculation, we investigate the structural, electronic and magnetic properties of both armchair and zigzag germanium carbide nanoribbon. It has been observed that the electronic and magnetic properties of the investigated germanium carbide nanoribbon can be tuned by using different types of H-termination. The Ge-C and Ge-H bond are ionic while C-H bond is found covalent. In zigzag germanium carbide nanoribbon (ZGeCNR), bare or one the edges H-termination turns the ribbon magnetic. Bare armchair germanium carbide nanoribbon (AGeCNR) is nonmagnetic semiconductor while both side or one side H-terminated turn it to semiconducting. ZGeCNR are conductors, however, magnetic behavior is induced with hydrogen termination. Also bare ZGeCNR shows half metallic bebavour, which suggests its applications in spintronics. [ABSTRACT FROM AUTHOR]

Naturally and anthropogenic radionuclides are present in various degrees in all different geological formations in the environment. Among these formations, sediment plays an important role in aquatic radioecology, since it acts as a medium of migration for the transfer of radionuclides to the biological systems. In this study, the content of natural radionuclides (238U, 232Th, 40K) and anthropogenic (137Cs) in sediment collected from different location a long Rhumel River were determined using a coaxial hyper pure germanium (HPGe) detector with an aim of evaluating the radiation hazard. These results are compared with internationally approved values and the recommended safety limits. Also, frequency distribution of the specific activities and their radiological parameters were studied, analyzed and found to be the asymmetrical distribution. [ABSTRACT FROM AUTHOR]

In this work, results of research of spectral characteristics for idealized n+-p-p+(t)n+-p-p+(t) ... n+-p-p+ structures have been presented that correspond to conditions of negligibly low rate of bulk and surface recombination of charge carriers in photoactive p-layers of the structure. Upper-limit efficient cascade photoelectric converters on the base of such structures in semiconductor materials like silicon and germanium have been described. [ABSTRACT FROM AUTHOR]

Removal of 210Po from copper, stainless steel and germanium was studied by using a standard, semiconductor-based- and a large-surface, low-background alpha spectrometer. Electropolishing and etching were applied as the surface cleaning techniques. Application of a "dynamical" process resulted for the first time in an effective 210Po removal from copper surface by etching. According to the performed measurements weak (natural) specific activities of polonium were also reduced after electropolishing of copper and stainless steel samples. An example of a bulk 210Po measurement in Titanium and deconvolution of the bulk and surface contributions to the registered spectrum is also discussed. [ABSTRACT FROM AUTHOR]

The observation of neutrinoless double-beta decay (0νββ) would show that lepton number is violated, reveal that neutrinos are Majorana particles, and provide information on neutrino mass. A discovery-capable experiment covering the inverted ordering region, with effective Majorana neutrino masses of 15 − 50 meV, will require a tonne-scale experiment with excellent energy resolution and extremely low backgrounds, at the level of ∼0.1 count /(FWHM·t·yr) in the region of the signal. The current generation 76Ge experiments GERDA and the Majorana Demonstrator, utilizing high purity Germanium detectors with an intrinsic energy resolution of 0.12%, have achieved the lowest backgrounds by over an order of magnitude in the 0νββ signal region of all 0νββ experiments. Building on this success, the LEGEND collaboration has been formed to pursue a tonne-scale 76Ge experiment. The collaboration aims to develop a phased 0νββ experimental program with discovery potential at a half-life approaching or at 1028 years, using existing resources as appropriate to expedite physics results. [ABSTRACT FROM AUTHOR]

Within mechanisms involving light and heavy Majorana neutrinos, the nuclear transition matrix elements (NTMEs) for the neutrinoless double-β decay of 76Ge and 82Se isotopes are calculated. Uncertainties in the average NTMEs M(0ν) and M(0N) due to the exchange of light and heavy Majorana neutrinos, respectively, turn out to be about 10% and 37%, respectively. Limits on the effective mass of light Majorana neutrino , heavy Majorana neutrino and Majoron-neutrino coupling constant of classical Majoron model are extracted. [ABSTRACT FROM AUTHOR]

Solar neutrinos interact within double-beta decay (ββ) detectors and contribute to backgrounds for ββ experiments. Background contributions due to charge-current solar neutrino interactions with ββ nuclei of 76Ge, 82Se, 100Mo, 130Te, 136Xe, and 150Nd are evaluated. They are shown to be significant for future high-sensitivity ββ experiments that may search for Majorana neutrino masses in the inverted-hierarchy mass region. The impact of solar neutrino backgrounds and their reduction are discussed for future ββ experiments. [ABSTRACT FROM AUTHOR]

As scaling of device dimensions has continued, it has become necessary to replace traditional SiO2 with high dielectric constant materials in the conventional CMOS devices. In addition, use of metal gate electrodes and Germanium substrates may have to be used in order to address leakage and mobility issues. Al2O3 is one of the potential candidates both for CMOS and as a blocking dielectric for Flash memory applications owing to its low leakage. In this study, the effects of sputtering conditions and post-deposition annealing conditions on the electrical and reliability characteristics of MOS capacitors using Al2O3 films on Si and Ge substrates with Aluminium gate electrodes have been presented. It was observed that higher sputtering power resulted in larger flat-band voltage (Vfb) shifts, more hysteresis, higher interface state density (Dit) and a poorer reliability. Wit was also found that while a short duration high temperature annealing improves film characteristics, a long duration anneal even at 800C was found to be detrimental to MOS characteristics. Finally, the electronic conduction mechanism in Al2O3 films was also studied. It was observed that the conduction mechanism varied depending on the annealing condition, thickness of film and electric field. [ABSTRACT FROM AUTHOR]

This paper focuses on the properties of nanoparticles obtained in pulsed spark discharge by erosion of silicon and germanium electrodes in inert atmosphere. A distinctive feature of the obtained particles is a small primary particle size of 10-20 nm and a low degree of agglomeration. Due to the small size of the particles and the presence of residual oxygen in a chamber the particles are oxidized. Silicon nanoparticles are oxidized more actively than germanium ones under identical conditions of synthesis. Some of the synthesized nanoparticles are found to have a core-shell structure, a pure semiconductor core and shell of the oxide, which opens wide possibilities for practical use in electronics. [ABSTRACT FROM AUTHOR]

Germanium (Ge) on Silicon (Si) has the potential to produce a wide variety of devices, including sensors, solar cells and transistors. Modification of these materials so that a suspended membrane layer is formed, through removing regions of the Si substrate, offers the potential for sensors with a more rapid response and higher sensitivity. Such membranes are a very simple micro-electronic mechanical system (MEMS). It is essential to ensure that the membranes are robust against shock and vibration, with well-characterised resonant frequencies, prior to any practical application. We present work using laser interferometry to characterise the resonant modes of membranes produced from Ge or silicon carbide (SiC) on a Si substrate, with the membranes typically having around 1 mm lateral dimensions. Two dimensional scanning of the sample enables visualisation of each mode. The stress measured from the resonant frequencies agrees well with that calculated from the growth conditions. SiC provides a more robust platform for electronics, while Ge offers better resonant properties. This offers a potential technique for characterising production quality or lifetime testing for the MEMS produced. [ABSTRACT FROM AUTHOR]

We have measured the collisional excitation cross sections for the 3d→4f and 3d→5f excitations in Au ions near the Ni-like charge state by using beam plasmas created in the Livermore electron beam ion trap EBIT-I. The cross sections have been experimentally determined at approximately 1, 2 and 3 keV above the threshold energy, ET, for the 3d→4f excitations (ET ~ 2.5 keV) and at approximately 0.1, 1 and 2 keV above the threshold energy for the 3d→5f excitations (ET ~ 3.3 keV). The cross section measurements were made possible by using the GSFC x-ray microcalorimeter at the Livermore EBIT facility. The absolute cross sections are determined from the ratio of the intensity of the collisionally excited bound-bound transitions to the intensity of the radiative recombination lines produced in EBIT-I plasmas. The effects of polarization and Auger decay channels are accounted for in the cross section determination. Measured cross sections are compared with those from HULLAC, DWS and FAC calculations. The measurements demonstrate that some errors exist in the calculated excitation cross sections. [ABSTRACT FROM AUTHOR]

We present the analysis of X-ray emission spectra of copper, germanium and rubidium plasmas measured at the Phelix laser facility. The laser intensity was around 6x1014 W.cm-2. The analysis is based on the hypothesis of an homogeneous plasma in local thermodynamic equilibrium using an effective temperature. This temperature is deduced from hydrodynamic simulations and collisional-radiative computations. Spectra are then calculated using the LTE opacity codes OPAMCDF and SCO-RCG and compared to experimental data. [ABSTRACT FROM AUTHOR]

The optimal measurement counting time for gamma-ray spectrometry analysis using HPGe detectors was determined in our laboratory by comparing twelve hours measurement counting time at day and twelve hours measurement counting time at night. The day spectrum does not fully cover the night spectrum for the same sample. It is observed that the perturbation come to the sun-light. After several investigations became clearer: to remove all effects of radiation from outside (earth, the sun, and universe) our system, it is necessary to measure the background for 24, 48 or 72 hours. In the same way, the samples have to be measured for 24, 48 or 72 hours to be safe to be purified the measurement (equality of day and night measurement). It is also possible to not use the background of the winter in summer. Depend on to the energy of radionuclide we seek, it is clear that the most important steps of a gamma spectrometry measurement are the preparation of the sample and the calibration of the detector. [ABSTRACT FROM AUTHOR]

A new experimental procedure to overcome luminescent coupling effect in a multi-junction solar cell is proposed. The procedure was used to obtain the true (hereinafter the actual) external quantum efficiency EQE(λ) values of Ge subcell, and consists of the following steps: 1) photon-coupled characteristic determination; 2) initial EQE(λ) measurement conditions choice and fixation; 3) EQE(λ) measurement with the conventional method; 4) actual EQE(λ) data search with use of photon-coupled characteristic. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

I propose a model for the upper-part of pf-shell, which consists of p1/2, p3/2, f5/2 and g9/2 single-particle orbits. While the pf-subshell (or d˜s-subshell, i.e. η˜ = 2, s˜1/2, d˜3/2, d˜5/2) is governed by the SU˜S¯T (4) ⊗ UL¯ (6) symmetry, the g9/2 intruder state is governed by the seniority model. The nuclear states of 76Ge and 76Se are expressed as direct products of the d˜s subshell component and the g-subshell one. The five-dimensional quasispin formalism with seniority zero restriction is used for a classification in the g-subshell. In the d˜s-subshell, for each configuration [Mπ, Mν]d˜s I choose only the most symmetric U˜L¯ (6) representations with total pseudo-spin S˜ = 0. Therefore, all the configurations are given by (0Y0˜) {4P˜ 2Y} and (0Y˜-20) {4P+1˜ 2Y-2} for 76Ge and 76Se, respectively with Y = 6 - (nν - nπ)/2 and P = (4 - nπ)/2. I derive an explicit expression for the NME of the 2νββ(0+ → 0+) in the closure approximation. [ABSTRACT FROM AUTHOR]

The GERDA experiment is designed to search for neutrinoless double beta (0vββ) decay of 76Ge. In Phase I of the experiment a background index of 10-2 cts/(ke.kg.yr) was reached. A lower limit on the half-life of the 0vββ decay of 76Ge was set to 2.1‧1025 yr (at 90% C.L.). The aim of Phase II is to reach a sensitivity of the half-life of about 1026 yr. To increase the exposure thirty new Broad Energy Germanium (BEGe) detectors have been produced. These detectors are distinct for their improved energy resolution and enhanced pulse shape discrimination of signal from background events. Further background reduction will be reached by a light instrumentation to read out argon scintillation light. In April 2015 the light instrumentation together with eight BEGe detectors has been successfully deployed in the GERDA cryostat. In a commissioning run it was shown that two of the major background components, external γ-rays from 214Bi and 208Tl decays, were suppressed up to two orders of magnitude. We are confident to reach a background index of 10-3 cts/(keV.kg.yr) which is the design goal for GERDA Phase II. [ABSTRACT FROM AUTHOR]

The CoGeNT detector, located in the Soudan Underground Laboratory in Northern Minnesota, consists of a 475 grams (fiducial mass of 330 grams) target mass of p-type point contact germanium detector that measures the ionization charge created by nuclear recoils. This detector has searched for recoils created by dark matter since December of 2009. We analyze the public dataset from the CoGeNT experiment to search for evidence of dark matter interactions with the detector. We perform an unbinned maximum likelihood fit to the data and compare the significance of different WIMP hypotheses relative to each other and the null hypothesis of no WIMP interactions. This work presents the current status of the analysis. [ABSTRACT FROM AUTHOR]

High mobility materials are being considered to replace Si in the channel to achieve higher drive currents and switching speeds. Ge is one of new attractive channel materials that require CMOS scaling For future technology nodes and future high performance P-MOSFETS, we have studied a nanoscale SOI DG MOSFETs using quantum simulation approach on DG MOSFETs within the variation of Ge channel concentration and in the presence of source and drain doping by replacing Silicon in the channel by Ge using various dielectric constant. The use of high mobility channel (like Ge) to maximize the MOSFET IDsat and simultaneously circumvent the poor electrostatic control to suppress short-channel effects and enhance source injection velocity. The leakage current (Ioff) can be controlled by different gates oxide thickness more ever the required threshold voltage (VTH) can be achieved by keeping gate work function and altering the doping channel. [ABSTRACT FROM AUTHOR]

Germanium nanocrystals with tetragonal (ST-12) and diamond like cubic (Ge-I) phases have been selectively grown by controlling the ionization and electrostatic potential of Ge clusters in an ion cluster beam deposition system. Predominantly tetragonal nanocrystals were obtained when grown using neutral clusters. The percentage of cubic phase increased when grown by ionizing the clusters and accelerating them towards substrates by applying electrostatic bias in the range of 1.5 - 2.5 kV. Raman spectroscopic measurement showed strong peak at 275cm-1and 300 cm-1for tetragonal and cubic Ge nanocrystals, respectively. TEM measurements showed crystalline lattice fringes of both type of the nanocrystals. The selected area electron diffraction patterns showed (111) and (210) as the dominating lattice planes for tetragonal nanocrystals while the cubic phases had (111), (311) and (331) as the prominent lattice planes. The optical absorption edge redshifted from 1.75 to 1.55 eV as the percentage of the cubic phases increased in the NC composition in the composite film. [ABSTRACT FROM AUTHOR]

Perovskite-type CH3NH3PbI3-based photovoltaic devices were fabricated and characterized. Doping effects of thallium (Tl), indium (In), or germanium (Ge) element on the photovoltaic properties and surface structures of the perovskite phase were investigated. The open circuit voltage increased by Ge addition, and fill factors were improved by adding a small amount of Ge, Tl or In. In addition, the wavelength range of incident photon conversion efficiencies was expanded by the Tl addition. [ABSTRACT FROM AUTHOR]

In this work we discuss the surface roughness of Si interface impact to the tunneling current of the Si/Si1- xGex/Si heterojunction bipolar transistor. The Si interface surface roughness can be analyzed from electrical characteristics through the transversal electron velocity obtained as fitting parameter factor. The results showed that surface roughness increase as Ge content of virtual substrate increase This model can be used to investigate the effect of Ge content of the virtual substrate to the interface surface condition through current-voltage characteristic. [ABSTRACT FROM AUTHOR]

Uranium ore can be easily detected due to various gamma-ray energies emitted from uranium daughters particularly from 238U daughters such as 214Bi, 214Pb and 226Ra. After uranium is extracted from uranium ore, only low energy gamma-rays emitted from 235U may be detected if the detector is placed in close contact to the specimen. In this research, identification and characterization of uranium bearing materials is experimentally investigated using direct measurement of gamma-rays from 235U in combination with the x-ray fluorescence (XRF) technique. Measurement of gamma-rays can be conducted by using high purity germanium (HPGe) detector or cadmium telluride (CdTe) detector while a 57Coradioisotope-excited XRF spectrometer using CdTe detector is used for elemental analysis. The proposed technique was tested with various uranium bearing specimens containing natural, depleted and enriched uranium in both metallic and powder forms. [ABSTRACT FROM AUTHOR]

Removal of the long-lived 222Rn daughters (210Pb, 210Bi and 210Po) from copper, stainless steel and germanium surfaces was investigated. As cleaning techniques etching and electro-polishing was applied to samples in a form of discs exposed earlier to a strong radon source. Reduction of the 210Pb activity was tested using a HPGe spectrometer, for 210Bi a beta spectrometer and for 210Po an alpha spectrometer was used. According to the conducted measurements electropolishing was always more efficient compared to etching and in case of copper the activity reduction factors for 210Pb, 210Bi and 210Po were between 200 and 400. Etching does not remove 210Po from copper but works very efficiently from germanium. Results obtained for 210Pb and 210Bi for etched stainless steel were worse but still slightly better than those achieved for copper. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Exposing food to radiation can improve hygiene quality, germination control, retard sprouting, and enhance physical attributes of the food product. To provide for food safety, radiation dosimetry in irradiated food is required. Herein, fabricated germanium doped (Ge-doped) optical fibres have been used. The fibres have been irradiated using a gamma source irradiator, doses in the range 1 kGy to 10 kGy being delivered. Using Ge-doped optical fibres of variable size, type and dopant concentration, study has been made of linearity, reproducibility, and fading. The thermoluminescence (TL) yield of the fibres were obtained and compared. The fibres exhibit a linear dose response over the investigated range of doses, with mean reproducibility to within 2.69% to 8.77%, exceeding the dose range of all commercial dosimeters used in evaluating high doses for the food irradiation industry. TL fading of the Ge-doped flat fibres has been found to be < 13%. [ABSTRACT FROM AUTHOR]

In this paper, a new heterostructure based on GaAs/Ge impact ionization avalanche transit time diode (IMPATT) is investigated at 94 GHz design frequency, with an emphasis on the optimized current density. A complete theoretical simulation with validatation of experimental results found that this type of structure is possible for high efficiency near about 13.5 % as compared to Ge (13 %) and GaAs (11 %) homostructure devices. But the rf power in case of GaAs is higher of about 788 mW as compared to other diodes because of due to high breakdown voltage. The result shows that heterostructure based IMPATT diode gives high efficiency with moderate power. The available experimental methods and the simulation results will be suitable for high efficiency diode used for communication. [ABSTRACT FROM AUTHOR]

In this paper we present the results of optically stimulated electron emission (OSEE) investigation of thin SiO2 films implanted with Ge+ ions. The emission models of Urbach rule and power Kane-dependence are used to fit OSEE spectra at different excitation energy ranges. The materials under study may find a number of technological applications in optical devices and ultraviolet sensors. Samples attestation was performed by electron microscopy and x-ray photoelectron spectroscopy (XPS). XPS data revealed strong dependence between the Si, Ge and O atoms state and annealing time. Observed correlations between parameter values of Urbach- and Kane-related models suggest the implantation-induced changeover of both the vibronic subsystem and energy band structure. [ABSTRACT FROM AUTHOR]

Atomic structure and localized vibrations of a-SiO2:Ge are studied using computer modeling techniques. The simulation was carried out by the lattice dynamics calculation of the local density of vibrational states. Local structures parameters are calculated, localized symmetrized vibrations frequency caused by Ge impurity in different charge states are defined. The movements of atoms located near Ge impurity are analyzed and their contribution into localized vibrations of different type is evaluated [ABSTRACT FROM AUTHOR]