Papers by Keyword: Germanium

Abstract: Ge p-i-n photodetectors with and without graphene on active area fabricated and investigated the graphene effects on opto-electrical properties of photodetectors. The photodetectors were characterized with respect to their dark, photocurrents and responsivities in the wavelength range between 1530-1630 nm. For a 250 um-diameter device at room temperature, it was found that dark current of p-i-n photodetector with graphene were reduced significantly compared with photodetector without graphene. This improvement is attributed to the passivation of the graphene layers that leads to the efficient light detection. Therefore, it is noted that the uniform coverage of graphene onto the Ge surface plays a significant role in advancing their opto-electrical performance of photodetector.

Abstract: The phase equilibrium in the Fe-Ge-O system is investigated by measuring EMF of galvanic elements with solid oxygen-conductive electrolytes. The samples for investigation were prepared by the solid phase reaction at 900 °C. The samples were analyzed to determine the total and phase composition. The gross composition of the samples was refined by chemical analysis. The iron content was determined by the standard method of bichromatometric titration, while that of germanium was determined by the photometric method, which is based on measuring the optical density of the colored colloid solution of germanium phenyl fluoronate, which is formed upon the interaction of germanium dioxide with phenylfluorone in the acidic medium. The phase composition was established using X-ray diffractometry and electron probe microanalysis using a DRON-3 diffractometer and a JEOL JSM-6460LV computer controlled scanning (raster) microscope. The experimental function of EMF galvanic elements of temperature is formulated. After processing the obtained data, the equilibrium oxygen pressures over the samples were calculated, the solubility of germanium in iron monoxide (wustite) was determined, the phase composition of the regions bordering the wustite region was established, the isothermal sections of the state diagram of the system were constructed at 1173 and 1273 K in the equilibrium region of the wustite solution with metallic and spinel phases

Abstract: The effects of Si and/or Ge addition on the microstructure and creep properties at 650°C and 137 MPa were investigated in near-α Ti–Al–Sn–Zr–Mo alloys. Si and/or Ge addition decreased the minimum creep strain rate owing to the solid solution of Si and Ge in the matrix and the precipitation of silicide, germanide, and their solid solutions. The decrease in the minimum creep strain rate in the alloy with 1 wt% Ge without Si was the most significant because of the formation of very fine germanide precipitates. In addition, a marked shift in the lattice parameters of the α and β phases was detected for the alloy with 4 wt% Ge. The Moiré fringe patterns at the α/β interfaces in the alloys were investigated using high-resolution transmission electron micrographs to discuss the alloying effect on the structure of the interfaces.

Abstract: An experimental study is reported to characterise the femtosecond (FS) laser grooving process for Germanium (Ge) substrates. The effects of process parameters, including laser fluence, pulse repetition rate and scan speed, on the groove characteristics, material removal rate (MRR) and heat affected zone (HAZ) size are discussed. It is shown that with properly selected process parameters, high quality micro-grooves can be obtained on Ge wafers. Recommendations are finally made on the selection of the most appropriate process parameters for FS micro-grooving of Ge substrates.

Abstract: Tristrimethylsilylgermane, (Me₃Si)₃GeH, was employed as a molecular model compound for hydrogen terminated Ge(111) surfaces. Time and temperature dependent NMR spectroscopy yielded rate constants for the reaction between (Me₃Si)₃GeH and elemental sulfur and allowed for the determination of the activation energy for this molecular model reaction to mimic germanium surface passivation.

Abstract: A sessile drop experiment involving slow heating and cooling of lead-free solder alloys under inert gas revealed segregation of trace elements to the sample surface. Addition of germanium or gallium to Sn-0.7Cu-0.05Ni alloys promoted a metallic lustre in samples, in contrast with the blue/purple colour of the parent alloy. Alloys with Ge or Ga additions showed oxidation resistance. Depth profiling of surfaces of sample alloys with Ge or Ga showed a significant concentration of these elements within the oxide film, which may be responsible for oxidation resistance of these alloys.

Abstract: The wettability of Sn-Cu-Ni with Germanium (Ge) additions of 0 ppm, 10 ppm, 60 ppm, 100 ppm and 200 ppm were investigated with Gen3 machine. The range of the wettability shows the lowest and the highest reading of wetting time and maximum force. Three different conditions were investigated which consist of as soldered, reflowed and aged. Further interfacial IMC observation was done for 0 ppm and 60 ppm of Ge to investigate the growth of interfacial IMC after thermal aging. From the measurement, the thickness of IMC for 0 ppm Ge is 2.075μm, 3.936μm and 4.502μm with aging time at 24,120 and 240 hours respectively. While for 60 ppm Ge, the IMC thickness are much lower with 1.8μm, 3.11μm and 4.154μm at the same aging time with 0ppm Ge. The results indicate that 60 ppm of Ge in Sn-Cu-Ni has the lowest wetting time, higher maximum force and slow IMC growth.

Abstract: Thin Mg₂Ge films were grown using two methods: a co-deposition of Ge and Mg on Si substrate kept at room temperature followed by annealing at 200 °C (solid phase epitaxy – SPE) and reactive deposition epitaxy (RDE) of Ge and Mg on Si at 200 °C. Optical properties of these structures were investigated in the photon energy range of 0.02–6.2 eV. Based on optical functions calculation, it was shown that SPE growth results in formation of a crystalline layer of Mg₂Si, which exhibits a strong optical phonon originated from the substrate-film interface. In the case of RDE growth, the amount of Mg₂Si is sufficiently lower, but Mg‑Si-Ge compound phonon appears. The estimate of a fundamental indirect transition value in the film is 0.72 eV for SPE growth method and 0.56 eV for RDE due to the ternary compound Mg-Ge-Si at the film-substrate interface.

Abstract: Ion-beam deposition of amorphous Ge layers on different substrates (silicon and quartz) has been performed. Deposited amorphous Ge layers were subjected to pulsed laser annealing (λ = 0.69 μm, τ = 80 ns). Simultaneously the optical probing of the Ge surface was carried out. The computer simulation of heating processes and phase transitions was performed taking into account the temperature dependences of film and substrates’ parameters and phase transition energies. The results of the dynamics of heating, melting, crystallization and plasma formation processes are well described by simulation data. It is shown that the threshold values for radiation power density and phase transition rates are determined mainly by thermophysical parameters of the substrates and thermal contact between Ge melt and substrate.

Abstract: A technique for ordered fabrication of periodic freestanding micro/nanostructures on the crystalline germanium (Ge) <100> surfaces with 1064 nm wavelength ultrashort laser pulses under ambient conditions is presented. The laser radiation fluence used for obtaining the structures is close to the melting threshold (0.1 J/cm²) of Ge. The dimensions of structures range from hundreds of nanometres to a few microns. The orientation of the periodic surface structures depends on laser beam polarization direction. Arrays of structures are formed in rows parallel to the sample movement direction for samples machined with s-polarized laser pulses, but formed in the direction perpendicular to the movement for p-polarized pulses. The structures are fabricated under variable temperatures on sample surface owing to the changed interference between incident and reflected laser beams. A micro-Raman analysis of the processed surfaces shows a minor change in the spectral intensity as compared to the unprocessed surface and the material retains its crystallinity after laser irradiation.