Ge Targets Research Articles

Effects of the chemical bonding on the optical and mechanical properties for germaniumcarbide films used as antireflection and protection coating of ZnS windows

Germanium carbide (Ge1−xCx) films have been prepared by RF reactive sputtering a pure Ge(111) target at different flow rate ratiosof CH4/(CH4+Ar) in aCH4/Ar mixturedischarge, and it has been found that the composition, chemical bonding, optical and mechanical propertiesof Ge1−xCx films are remarkably influenced by the flow rate ratio ofCH4/(CH4+Ar). The effects of the chemical bonding on the optical and mechanical properties of theGe1−xCx films have been explored. In addition, an antireflectionGe1−xCx double-layer coating deposited on both sides of the ZnS substratewafer has been developed for application as an infrared window. It isshown that the transmittance in the wavelength region between 8 and12 µm and the hardness of the ZnS substrate have been significantly improved by the double-layercoating.

Charge-changing interactions of ultrarelativistic In nuclei

We present experimental results of nuclear-charge changing interactions for 158A-GeV ultrarelativistic In ions in Si, Ge, Sn, W, and Pb targets. Calculations based on the abrasion-ablation model for hadronic interaction and the RELDIS model for electromagnetic dissociation are compared to the data.

Influence of Ge addition on the morphology and properties of TiN thin films deposited by magnetron sputtering

Thin films of TM–X–N (TM stands for early transition metal and X = Si, Al, etc.) are used as protective coatings. The most investigated among the ternary composite systems is Ti–Si–N. The system Ti–Ge–N has been chosen to extend the knowledge about the formation of nanocomposite films. Ti–Ge–N thin films were deposited by reactive magnetron sputtering on Si and WC–Co substrates at T s = 240 °C, from confocal Ti and Ge targets in mixed Ar/N 2 atmosphere. The nitrogen partial pressure and the power on the Ti target were kept constant, while the power on the Ge target was varied in order to obtain various Ge concentrations in the films. No presence of Ge–N bonds was detected, while X-ray photoelectron spectroscopy measurements revealed the presence of Ti–Ge bonds. Transmission Electron Microscopy investigations have shown important changes induced by Ge addition in the morphology and structure of Ti–Ge–N films. Electron Energy-Loss Spectrometry study revealed a significant increase of Ge content at the grain boundaries. The segregation of Ge atoms to the TiN crystallite surface appears to be responsible for limitation of crystal growth and formation of a TiGe y amorphous phase.

Structural and chemical properties of sputter-deposited Ti–Ge–N thin films

Ti–Ge–N single-layer and TiN/GeN-multilayer thin films were deposited by reactive magnetron sputtering on Si and WC–Co substrates at constant temperature T s = 240 °C, from confocal Ti and Ge targets in a mixed Ar/N 2 atmosphere. The nitrogen partial pressure, the TiN deposition time t Ti and the power on the Ti and Ge targets were kept constant. In order to obtain various GeN layer thicknesses in the films, the deposition time ratio t Ge/ t Ti was varied. TiN/GeN multilayer films with TiN thickness ∼ 5 nm and various GeN thicknesses between 0.5 and 5 nm were deposited. A nanocrystalline multilayer film is formed, where the suppression of crystal growth is controlled by the successive deposition of two phases. TEM investigations revealed important changes induced by GeN x thickness variation: the columnar single-layer morphology switches into a multilayer morphology. The critical GeN thickness for changing the type of morphology is controlled by the diffusion of Ge atoms at the TiN crystallite boundaries. The morphology modification from single-layer to multilayer type determines the film hardening. Electron probe microanalyses (EPMA), scanning tunneling microscopy (STM), transmission electron microscopy (TEM), nanoindentation and X-ray diffraction (XRD) techniques were employed to characterize single- and multilayer films. The properties of alternate-deposited films are compared to those of co-deposited ones and interpreted.

837 POSTER PSA bouncing after short-term androgen deprivation and 3-D conformal radiotherapy for localized prostate adenocarcinoma and the relationship with the kinetics of testosterone

In preparation to change treatment planning systems for gynecological intracavitary insertion dosimetry, 3 patients were planned on 3 systems. The GE Target II, BrachyVision, and ADAC Pinnacle were the systems used. The dose distributions to several points of interest were calculated and compared. We analyzed the data sets to assess the differences and found that they were insignificant, mostly due to human error during digitization and calculation rounding.

835 POSTER Similar effect on rectal dose reduction despite different displacement kits during high dose rate brachytherapy for prostate cancer

In preparation to change treatment planning systems for gynecological intracavitary insertion dosimetry, 3 patients were planned on 3 systems. The GE Target II, BrachyVision, and ADAC Pinnacle were the systems used. The dose distributions to several points of interest were calculated and compared. We analyzed the data sets to assess the differences and found that they were insignificant, mostly due to human error during digitization and calculation rounding.

A study of electron beams extracted from a plasma produced by laser interaction with a solid target

In this work, wave formation in laser-produced plasma is investigated by an analysis of time-of-flight signal of the electron pulse. Electrons are extracted from a non-equilibrium plasma, generated by pulsed laser ablation on a solid Ge target. The process is represented by ion-acoustic waves, which are generated from an external perturbation, given by the positive bias voltage of a Faraday cup. The characteristics of the waves depend substantially on the geometry of the plasma expansion chamber and on laser fluence, but are independent on bias potential. A KrF excimer UV laser was employed for plasma generation. Measurements were performed at two different laser fluences, 4 and 7 J/cm2. The plasma created propagates with a mean velocity of about 1.1 × 104 m/s. A movable Faraday cup was employed in order to collect electrons at different bias voltage values.

836 POSTER HDR brachytherapy as boost combined with external radiotherapy for localised prostate cancer. Long term follow-up compared to nomogram

In preparation to change treatment planning systems for gynecological intracavitary insertion dosimetry, 3 patients were planned on 3 systems. The GE Target II, BrachyVision, and ADAC Pinnacle were the systems used. The dose distributions to several points of interest were calculated and compared. We analyzed the data sets to assess the differences and found that they were insignificant, mostly due to human error during digitization and calculation rounding.

Analytical and numerical calculations of the temperature distribution in Si and Ge targets irradiated by excimer lasers

The calculations of the temperature distribution induced by excimer lasers in silicon and germanium by using different mathematical approaches are presented. In this work, the heat conduction differential equation is solved by: (i) conventional analytical method, where the thermal parameters, i.e., thermal conductivity, specific heat and density are temperature independent; (ii) the Kirchhoff transformation method, that incorporates the dependence of the thermal conductivity with the temperature through a polynomial function; (iii) a numerical approach, by using the finite elements method (ANSYS program), which allows the incorporation of all temperature dependent parameters and the phase changes of the material using the enthalpy function. A comparison of the temperature profile versus depth obtained for semi-infinite amorphous germanium and crystalline silicon materials when irradiated with an ArF excimer laser (193 nm, 20 ns) is presented. The melting depth for a given energy density is also evaluated by the different mathematical methods. The validity of these results and the reliability and advantages of the numerical methods is discussed.

スパッタ法によるａ‐ＧｅＣ：Ｈ薄膜の微結晶化

GeC:H films have been deposited by a reactive rf magnetron sputtering of Ge target in argon-methane and helium gas mixtures. The effect of helium partial pressure ratio R on the structural, optical and electrical properties of the films was investigated. The films shows the amorphous nature in the low R range up to 60%. With increasing R above 70%, the peak of X-ray diffraction appears, the bonding configuration concerning carbon bonds in IR spectra increases, the optical bandgap decreases, and the dark conductivity increases rapidly. It is found from these data that the microcrystallization of GeC:H films could be achieved by introducing hellium in the sputtering process.

Formation, structure, and phonon confinement effect of nanocrystalline Si1−xGex in SiO2-Si-Ge cosputtered films

Using magnetron cosputtering of SiO2, Ge, and Si targets, Si-based SiO2:Ge:Si films were fabricated for exploring the influence of Si target proportion (PSi) and annealing temperature (Ta) on formation, local structure, and phonon properties of nanocrystalline Si1−xGex (nc-Si1−xGex). At low PSi and Ta higher than 800°C, no nc-Si1−xGex but a kind of composite nanocrystal consisting of a Ge core, GeSi shell, and amorphous Si outer shell is formed in the SiO2 matrix. At moderate PSi, nc-Si1−xGex begins to be formed at Ta=800°C and coexists with nc-Ge at Ta=1100°C. At high PSi, it was disclosed that both optical phonon frequency and lattice spacing of nc-Si1−xGex increase with raising Ta. The possible origin of this phenomenon is discussed by considering three factors, the phonon confinement, strain effect, and composition variation of nc-Si1−xGex. This work will be helpful in understanding the growth process of ternary GeSiO films and beneficial to further investigations on optical properties of nc-Ge1−xSix in the ternary matrix.

Chemical bonding of a-Ge1−xCx:H films grown by RF reactive sputtering

Amorphous hydrogenated germanium-carbon (a-Ge1−xCx:H) films were deposited by RF reactive sputtering pure Ge (111) target at different flow rate ratios of CH4/(CH4+Ar) in a discharge Ar/CH4, and their composition and chemical bonding were investigated using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). XPS and FTIR results showed the content of germanium in the films decreased with the increase of the flow rate ratio CH4/(Ar+CH4), and the Ge–C, Ge–H, C–H bonds were formed in the films. The fraction of Ge–C, Ge–H, and C–H bonds was strongly dependent on the flow rate ratio. Raman results indicated that the films also contain both Ge–Ge and C–C bonding. Based on the change of the chemical bonding of a-Ge1−xCx:H films with the flow rate ratio CH4/(CH4+Ar), an optimal experimental condition for the application of infrared windows was obtained.

Comparison of three brachytherapy gynecological intercavitary treatment planning systems

In preparation to change treatment planning systems for gynecological intracavitary insertion dosimetry, 3 patients were planned on 3 systems. The GE Target II, BrachyVision, and ADAC Pinnacle were the systems used. The dose distributions to several points of interest were calculated and compared. We analyzed the data sets to assess the differences and found that they were insignificant, mostly due to human error during digitization and calculation rounding.

Fluoride complexation of element 104, rutherfordium.

Fluoride complexation of element 104, rutherfordium (Rf), produced in the 248Cm(18O,5n)261Rf reaction has been studied by anion-exchange chromatography on an atom-at-a-time scale. The anion-exchange chromatographic behavior of Rf was investigated in 1.9-13.9 M hydrofluoric acid together with those of the group-4 elements Zr and Hf produced in the 18O-induced reactions on Ge and Gd targets, respectively. It was found that the adsorption behavior of Rf on anion-exchange resin is quite different from those of Zr and Hf, suggesting the influence of relativistic effects on the fluoride complexation of Rf.

Strong violet–blue photoluminescence from Ge oxide films by magnetron sputtering

Strong violet–blue photoluminescence (PL) band peaked at around 410 nm was obtained in Ge oxide films fabricated using magnetron sputtering of single crystal Ge target in diluted O 2. The peak position of this band remains unchanged with annealing temperature, but its intensity has a maximum in the sample annealed at 600 °C and almost vanishes in the samples annealed over 700 °C. PL excitation spectral examinations reveal that the origin of this band is different from that of the violet 395 nm PL band, which was frequently observed in Ge oxide and attributed to GeO color centers. The experimental results from Raman scattering and X-ray diffraction spectroscopy suggest that the 410 nm PL band arises from optical transition in the Ge neutral oxygen vacancy centers. Our experiments provide effective arguments for judging the existence of the neutral oxygen vacancy centers.

Fabrication of Germanium‐Filled Silica Nanotubes and Aligned Silica Nanofibers

Germanium‐filled SiO2 nanotubes and aligned SiO2 nanofibers are synthesized via a two‐stage process: thermal evaporation of SiO powder, followed by laser ablation of a Ge target. The nanotubes are either partially filled with Ge nanoparticles/nanorods or completely filled with Ge nanowires, forming Ge/SiO2 nanocables (see Figure). The products were characterized using a variety of spectroscopic techniques.

Raman scattering and x-ray absorption studies of Ge–Si nanocrystallization

We have studied the local structure of GeSi nanocrystals embedded in SiO2 prepared by co-sputtering of Ge, Si, and SiO2 targets onto a Si(100) substrate. From Raman scattering, we conclude that the formation of the isotropic crystalline Ge phase starts at about 800 °C followed by the formation of a GeSi phase at higher temperatures. The formed nanocrystals, whose size depends on the annealing temperature, are randomly oriented. The local structure of the nanocrystals has been studied by x-ray absorption fine structure spectroscopy. They are found to consist of a relaxed Ge core with a typical diameter of ∼4 nm and the Ge–Ge bond length of 2.45 Å and of a GeSi outer shell, the Ge–Si bond length being 2.39 Å. The average composition of the grown nanocrystals is estimated to be Ge0.75Si0.25.

Deposition and characterization of Ge–Sb–Te layers for applications in optical data storage

Ge–Sb–Te films for optical data storage applications were deposited by magnetron sputtering of separate Ge, Sb, and Te targets on Si(1 1 1) wafers in a dc argon plasma. To investigate the influence of the chemical composition of the phase change material on its optical properties, films with lateral compositional gradients of up to 30 at.% were deposited. The composition and structure of the films were investigated by X-ray photoelectron spectroscopy (XPS), electron probe microanalysis (EPMA) and X-ray diffraction (XRD) on plain Si wafers, whereas the phase change velocity of Ge–Sb–Te as a re-writable optical data storage medium was determined on Si/Al/SiO 2/Ge–Sb–Te multilayers near to technical conditions. The phase change of Ge–Sb–Te films was induced and characterized with a static tester consisting of an optical microscope with an integrated high power laser diode. The change in reflectivity induced by the laser pulses was measured by a high sensitivity photodetector. Depending on the composition, the crystallization time was determined between 220 and 500 ns, while the amorphization time was between 20 and 120 ns.

Physical properties of thin GeO 2 films produced by reactive DC magnetron sputtering

We have studied optical and structural properties of GeO x films produced by reactive DC magnetron sputtering of Ge targets in an Ar/O 2-mixture. Optical spectroscopy measurements of reflectance and transmittance of the films were employed to determine optical properties. The film structure was determined by X-ray diffraction measurements, while X-ray reflectometry was used to determine the thickness, density, and roughness of the films. The film topography was additionally characterized by atomic force microscopy. For appropriate oxygen flows highly transmitting GeO x films can be grown at rates up to 3 nm/s for power density of 2.6 W/cm 2. Optical and structural properties of the films are closely correlated and can be controlled by the oxygen flow. With increasing oxygen flow an increasing growth rate of the oxide films is initially observed. The resulting films above 20 sccm and below 25 sccm O 2 are transparent in the visible range, have a negligible roughness and are amorphous. A further rise in oxygen flow leads to a pronounced decrease in growth rate above 25 sccm and a further increase in the bandgap of the germanium oxide up to more than 48000 cm −1 (5.95 eV). This transition in film growth is accompanied by an increase in roughness and a structural transition leading to polycrystalline films of α-GeO 2 (quartz-structure). Nevertheless, the film density is hardly affected by the structural change and remains rather constant around 3.65 g/cm 3, which is 85% of the density of single crystalline α-GeO 2. A model is presented which can account for the change of film properties.

Synthesis and properties of Si and Ge nanoclusters produced by pulsed laser ablation

We show that conventional pulsed laser ablation (PLA) of Si and Ge targets in inert buffer gases is an efficient method of nanocluster synthesis. From a photoluminescence study of Si and Ge nanoclusters produced by PLA we have demonstrated the possibility of tuning the luminescence band from the near infrared to the near ultraviolet regions. The stabilization of the properties of Si nanoclusters by reactive (H2 gas) PLA synthesis was proved by photoluminescence measurements. Finally, we report a photoluminescence study of gas-suspended Ge nanoclusters during their preparation. They exhibit a broad luminescence spectrum extended from UV to the blue-green region and modulated by a molecule-like structure. We propose an interpretation of the vibronic structure involving Ge-O-Ge vibrations at the surface of photo-excited clusters. To the best of our knowledge, we report here the first observation of vibrational effects from gas-suspended Ge nanoclusters.