Single-Layer Graphene/Germanium Interface Representing a Schottky Junction Studied by Photoelectron Spectroscopy.

We investigated the interfacial electronic structure of the bidimensional interface of single-layer graphene on a germanium substrate. The procedure followed a well-established approach using ultraviolet (UPS) and X-ray (XPS) photoelectron spectroscopy. The direct synthesis of the single-layer graphene on the surface of (110) undoped Ge substrates was conducted via chemical vapor deposition (CVD). The main graphitic properties of the systems were identified, and it was shown that the Ge substrate affected the electronic structure of the single-layer graphene, indicating the electronic coupling between the graphene and the Ge substrate. Furthermore, the relevant features associated with the Schottky contact's nature, the energy level's alignments, and the energy barrier's heights for electron and hole injection were obtained in this work. The results are useful, given the possible integration of single-layer graphene on a Ge substrate with the complementary metal-oxide-semiconductor (CMOS) technology.

Measured low-energy x-ray spectra of interest in diagnostic radiology and mammography.

Objective.In cities situated at high-altitude, the measured x-ray spectra are required to calculate the absorbed dose to water in radiobiology and medical dosimetry because of the air-density effect. This work aims to measure, in a high-altitude city, a set of x-ray spectra from an x-ray tube with tungsten anode generated at potentials of the M-series x-ray beams from NIST in the range of 20 and 150 kV as well as other beam qualities that have been characterized and used for dosimetry study in our group called W-series. To also measure some spectra of mammography interest in the energy range of 25 and 35 kV using additional filtration of rhodium (Rh), molybdenum (Mo) and silver (Ag).Approach.A tungsten anode x-ray tube with potential between 10 to and 160 kV was used. A high-purity germanium (HPGe) detector associated with a DSPEC Jr 2.0TMdigital signal processing module has been used for the spectra measurements. Prior the spectra measurements, the HPGe detector has been characterized and calibrated using several radioactive sources. Mainresults.The M80 spectrum was compared to a mathematically filtered beam from Physicalisch Technische Bundesanstalt corresponding to the same potential finding a difference of 0.7% in the average energy. So, the mathematically filtered beam from PTB matches very well our M80 beam. The beams M80, M100 and M120 were also compared with calculations for the corresponding kilovoltage from an executable that calculates x-ray spectra from tungsten anode x-ray tubes in the energy range between 40 to 300 kV called SpekCalc. The SpekCalc reproduces qualitatively the experimental spectra, but not quantitatively, mainly for M100 and M120 beams.Significance.These spectra can be used to simulate the patient dose as well as image quality using Monte Carlo (MC) codes or to evaluate the absorbed dose in dosimetry studies.

Effects of lithium on the electronic properties of porous Ge as anode material for batteries.

Recently, the need of improvement of energy storage has led to the development of Lithium batteries with porous materials as electrodes. Porous Germanium (pGe) has shown promise for the development of new generation Li-ion batteries due to its excellent electronic, and chemical properties, however, the effect of lithium in its properties has not been studied extensively. In this contribution, the effect of surface and interstitial Li on the electronic properties of pGe was studied using a first-principles density functional theory scheme. The porous structures were modeled by removing columns of atoms in the [001] direction and the surface dangling bonds were passivated with H atoms, and then replaced with Li atoms. Also, the effect of a single interstitial Li in the Ge was analyzed. The transition state and the diffusion barrier of the Li in the Ge structure were studied using a quadratic synchronous transit scheme.

Fabrication of Microbolometer Arrays Based on Polymorphous Silicon-Germanium.

This work reports the development of arrays of infrared sensors (microbolometers) using a hydrogenated polymorphous silicon-germanium alloy (pm-SixGe1-x:H). Basically, polymorphous semiconductors consist of an amorphous semiconductor matrix with embedded nanocrystals of about 2-3 nm. The pm-SixGe1-x:H alloy studied has a high temperature coefficient of resistance (TCR) of 4.08%/K and conductivity of 1.5 × 10-5 S∙cm-1. Deposition of thermosensing film was made by plasma-enhanced chemical vapor deposition (PECVD) at 200 °C, while the area of the devices is 50 × 50 µm2 with a fill factor of 81%. Finally, an array of 19 × 20 microbolometers was packaged for electrical characterization. Voltage responsivity values were obtained in the range of 4 × 104 V/W and detectivity around 2 × 107 cm∙Hz1/2/W with a polarization current of 70 µA at a chopper frequency of 30 Hz. A minimum value of 2 × 10-10 W/Hz1/2 noise equivalent power was obtained at room temperature. In addition, it was found that all the tested devices responded to incident infrared radiation, proving that the structure and mechanical stability are excellent.

Study of Si and Ge Atoms Termination Using H-Dilution in SiGe:H Alloys Deposited by Radio Frequency (13.56 MHz) Plasma Discharge at Low Temperature.

In this work, we present the study of the atomic composition in amorphous SiXGeY:HZ films deposited by radio frequency (RF-13.56 MHz) plasma discharge at low deposition temperature. A study and control of Si and Ge atoms termination using H-dilution in SiGe:H alloys deposited by RF plasma discharge was conducted and we made a comparison with low-frequency plasma discharge studies. Solid contents of the main elements and contaminants were determined by SIMS technique. It was found that for low dilution rates from RH = 9 to 30, the germanium content in the solid phase strongly depends on the hydrogen dilution and varies from Y = 0.49 to 0.68. On the other hand, with a higher presence of hydrogen in the mixture, the germanium content does not change and remains close to the value of Y = 0.69. The coefficient of Ge preferential incorporation depended on RH and varied from PGe = 0.8 to 4.3. Also, the termination of Si and Ge atoms with hydrogen was studied using FTIR spectroscopy. Preferential termination of Si atoms was observed in the films deposited with low RH < 20, while preferential termination of Ge atoms was found in the films deposited with high RH > 40. In the range of 20 < RH < 40, hydrogen created chemical bonds with both Si and Ge atoms without preference.

Stabilization of the GeO2/Ge Interface by Nitrogen Incorporation in a One-Step NO Thermal Oxynitridation.

The thermal instability of GeO2/Ge structures lasts as a barrier against the development of Ge-based metal-oxide-semiconductor devices. In the present work, stabilization was achieved through the incorporation of nitrogen into the oxide layer by thermally growing GeOxNy films in NO. With this approach, a stable layer is obtained in a single step as opposed to other nitridation techniques (like plasma immersion) which require additional processing. Significant reduction of GeO desorption from the surface and a strong barrier against additional substrate oxidation were obtained by the insertion of a small amount of nitrogen content (N/O ≈ 10%). Nuclear reaction analysis and profiling showed that nitrogen incorporation and removal occur simultaneously during film growth, yielding N to be distributed throughout the whole film, without accumulation in any particular region. Both the oxidation barrier and the lower GeO desorption rate are explained by a reduction of vacancy diffusivity inside the dielectric. This is not caused by the densification of the oxide, but is a consequence of nitrogen blockage of oxygen vacancy diffusion paths.

SU-E-I-65: Magnetic Resonance Spectroscopy of the Prostate: A Phantom Study of Metabolite Concentrations.

PURPOSE: Magnetic Resonance Spectroscopy (MRS) of the prostate is not used in radiotherapy departments on a regular basis due to a number of issues. The indication and severity of prostate cancer is related to the presence of choline in the prostate, in particular, the ratio of choline (plus creatine) to citrate. In-vivo data supports this theory only marginally but lacks strong correlation with biopsy data. The situation is further complicated by the lack of precise spatial information in biopsy, variation of magnetic susceptibility, and spatial dependence of MRS data on the distance from the endo-rectal coil. The latter also cause low signal-to-noise ratio (SNR). We intend to understand how the level of metabolite concentrations and spatial dependences determine what is observed in MRS. METHODS: A spherical phantom is filled with water solutions containing various amounts of metabolites. It is placed on top of an endo-rectal coil with the balloon filled with per fluorocarbon. MRS data is acquired on a GE 1.5 T MR scanner. The metabolite values, their ratios etc as reported in GE software, FuncTool are studied as functions of metabolite concentrations in the phantom. RESULTS: Analysis of the phantom data indicates that the metabolite ratio reported in FuncTool is approximately linearly correlated to the metabolite concentrations used in the phantom to a certain point and then saturates whereas the largest metabolite value is well correlated with its concentration in the phantom. All metabolite values become weaker and SNR lower as we move away from the coil. CONCLUSIONS: This work indicates the potential of using metabolite values directly provided their spatial dependences on the distance of the voxels from the endo-rectal coil can be accommodated.

SU-E-I-13: Evaluation of CT Number with Changing Scan Parameters for Nucletron Simulix Evolution CBCT.

PURPOSE: To quantify the variation in CT number generated by the Simulix Evolution CBCT with changes in scan length and phantom thickness. METHODS: Three phantoms were used in this study: CIRS Model 610 AAPM CT Phantom, Gammex 467 Tissue Characterization Phantom, and Catphan 600 phantom. The AAPM Phantom was used to assess the variation of HU with phantom thickness. Scans were acquired with two field size settings (full- and half-beam) with and without a 3.5 cm thick ring. The Catphan and Gammex phantoms were used to assess the Simulix's capability of producing a consistent CT-to-ED conversion table with different scan lengths, ranging from 1 cm (very thin) to 20 cm (clinical use). The data were also compared to data acquired with our in-house CT Sim (GE HiLite LightSpeed 16 slice). RESULTS: The AAPM phantom scans with and without the ring yielded an average difference in HU of 145 HU (full-beam) and 74 HU (half-beam) for each of five inserts. The HU for Cortical Bone (SB3) [largest Gammex electron density insert; 1.69] ranged from 923 to 1170 HU for the 4 cm and 1 cm scan lengths, respectively. The HU for Teflon [largest Catphan electron density insert; 1.867] ranged from 657 to 951 for the 20 cm and 1 cm scan lengths, respectively. The HU for air in Catphan ranged from -749 to -905, and the HU for LDPE [electron density 0.944] ranged from -82 to -42, for the 20 cm and 1 cm scan lengths, respectively. CONCLUSIONS: Results show a large variability in the calculated CT number with differences in phantom thickness, as evidenced by the results with the AAPM phantom. In addition, there appears to be a dependence on scan length, attributed to increased scatter contribution. Further tests will be done to evaluate the appropriateness of the use of the Simulix CBCT unit for heterogeneity corrected external beam treatment planning. The author has received no funding during the course of this research.

Determinación de germanio en muestras de exudado de Aloe vera (L.) Burm f. (zábila), mediante la espectrometría de absorción atómica con atomización electrotérmica / Determination of germanium in leaves exudate samples of Aloe vera (L.) Burm f. (zábila), by electrothermal atomic absorption spectrometry

Esta investigación trata sobre la determinación de germanio en exudado de hojas de zábila, mediante la técnica ana lítica espectrometría de absorción atómica con atomización electrotérmica (ETAAS). El exudado de las hojas de zábila es el líquido amarillo y de sabor amargo que emana de las hojas de la planta cortadas en la base. Es también conocido como zumo o látex. Ha sido utilizado en el tratamiento de diversas afecciones tales como: tratamiento de heridas, infecciones bucales, irritaciones de la piel, otras. El germanio es un oligoelemento que ha sido utilizado como inmunoestimulante y en pacientes con neoplasia. La concentración del germanio presente en el exudado de Aloe vera (L.) Burm.f. fue de 7.42 ± 2.33 μg/g. La metodología empleada fue validada por estudio de recuperación, ubicándose en un valor promedio de 97.43 ± 2.22%. La desviación estándar relativa fue de 2.88%, lo que es un indicativo de la precisión. El método utilizado para la determinación del elemento en cuestión es exacto, preciso y libre de interferencias.

The objective of this work was to determine the concentration of germanium in Aloe vera (zábila) from leaves exudated, using the electrothermal atomic absorption spectrometry analytical technic (ETAAS). The exudated is a yellow and bitter liquid, used in wounds healing, skin irritations, mouth infections, etc. The germanium is a trace element used as immunestimulant in patients with tumour. A concentration of 7.42 ± 2.33 μg/g was found. The method for the determination of germanium was validated by recovery studies, a value of 97.43 ± 2.22% was obtained for germanium, and the relative standar deviation (RSD%) was 2.88%. The method was exact, precise and free from interferences.