Diffusion and isotope effect in bulk-metallic glass-forming Pd–Cu–Ni–P alloys from the glass to the equilibrium melt

2003 ◽  
Vol 18 (11) ◽  
pp. 2688-2696 ◽  
Author(s):  
Volker Zöllmer ◽  
Klaus Raätzke ◽  
Franz Faupel

We report on radiotracer diffusion measurements in metallic bulk-glass-forming Pd-Cu-Ni-P alloys. The Pd-Cu-Ni-P system, with its high stability against crystallization, allows diffusion measurements from the glassy state to the equilibrium melt for the first time. Serial sectioning was performed by grinding and ion-beam sputtering. The time and temperature as well as mass dependence, expressed in terms of the isotope effect E, of codiffusion were investigated. In the glassy state as well as in the deeply supercooled state below the critical temperature Tc, where the mode-coupling theory predicts a freezing-in of liquidlike motion, the measured very small isotope effects indicated a highly collective hopping mechanism. Below Tc, the temperature dependence showed Arrhenius-type behavior. Above Tc, the onset of liquidlike motion was evidenced by a gradual drop of the effective activation energy, resulting from the decay of hopping barriers, and by the validity of the Stokes-Einstein equation, which was found to break down below Tc. This strongly supports the mode-coupling scenario. Isotope effect measurements, which have never been carried out near Tc in any material, showed atomic transport up to the equilibrium melt to be far away from the hydrodynamic regime of uncorrelated binary collisions. The latter appears to be a prerequisite of excellent glass-forming abilities.

2007 ◽  
Vol 266 ◽  
pp. 109-118
Author(s):  
Klaus Rätzke ◽  
V. Zöllmer ◽  
A. Bartsch ◽  
Andreas Meyer ◽  
Franz Faupel

Since the discovery of bulk metallic glasses there has been considerable research effort on these systems, in particular with respect to mass transport. Now the undercooled melt between the melting temperature and the caloric glass transition temperature, which has not been accessible before due to the rapid onset of crystallization, can be investigated and theories can be tested. Here we report on radiotracer diffusion measurements in metallic bulk-glass-forming Pd-Cu-Ni-P alloys. Serial sectioning was performed by grinding and ion-beam sputtering. The time, temperature as well as the mass dependence, expressed in terms of the isotope effect E, of Co-diffusion were investigated. The Co isotope effect measurements, which have never been carried out near Tc in any material, show atomic transport up to the equilibrium melt to be far away from the hydrodynamic regime of uncorrelated binary collisions. In the glassy state as well as in the deeply supercooled state below the critical temperature Tc, where the mode coupling theory predicts a freezing-in of liquid-like motion, the experimentally determined very small isotope effects indicate a highly collective hopping mechanism involving some ten atoms. Below Tc the temperature dependence shows Arrhenius-type behavior with an effective activation enthalpy of 3.2 eV. Above Tc the onset of liquid-like motion is evidenced by a gradual drop of the effective activation energy and by the validity of the Stokes-Einstein equation, which is found to break down below Tc. Although having strong covalent bonding tendencies, Phosphorous diffusion is only slightly slower than Co diffusion, indicating that it does not determine the overall viscosity below Tc. The Stokes-Einstein equation is presently tested for other constituents of the alloy.


Author(s):  
J. S. Maa ◽  
Thos. E. Hutchinson

The growth of Ag films deposited on various substrate materials such as MoS2, mica, graphite, and MgO has been investigated extensively using the in situ electron microscopy technique. The three stages of film growth, namely, the nucleation, growth of islands followed by liquid-like coalescence have been observed in both the vacuum vapor deposited and ion beam sputtered thin films. The mechanisms of nucleation and growth of silver films formed by ion beam sputtering on the (111) plane of silicon comprise the subject of this paper. A novel mode of epitaxial growth is observed to that seen previously.The experimental arrangement for the present study is the same as previous experiments, and the preparation procedure for obtaining thin silicon substrate is presented in a separate paper.


Author(s):  
A.E.M. De Veirman ◽  
F.J.G. Hakkens ◽  
W.M.J. Coene ◽  
F.J.A. den Broeder

There is currently great interest in magnetic multilayer (ML) thin films (see e.g.), because they display some interesting magnetic properties. Co/Pd and Co/Au ML systems exhibit perpendicular magnetic anisotropy below certain Co layer thicknesses, which makes them candidates for applications in the field of magneto-optical recording. It has been found that the magnetic anisotropy of a particular system strongly depends on the preparation method (vapour deposition, sputtering, ion beam sputtering) as well as on the substrate, underlayer and deposition temperature. In order to get a better understanding of the correlation between microstructure and properties a thorough cross-sectional transmission electron microscopy (XTEM) study of vapour deposited Co/Pd and Co/Au (111) MLs was undertaken (for more detailed results see ref.).The Co/Pd films (with fixed Pd thickness of 2.2 nm) were deposited on mica substrates at substrate temperatures Ts of 20°C and 200°C, after prior deposition of a 100 nm Pd underlayer at 450°C.


2003 ◽  
Vol 762 ◽  
Author(s):  
Z.B. Zhou ◽  
G.M. Hadi ◽  
R.Q. Cui ◽  
Z.M. Ding ◽  
G. Li

AbstractBased on a small set of selected publications on the using of nanocrystalline silicon films (nc-Si) for solar cell from 1997 to 2001, this paper reviews the application of nc-Si films as intrinsic layers in p-i-n solar cells. The new structure of nc-Si films deposited at high chamber pressure and high hydrogen dilution have characters of nanocrystalline grains with dimension about several tens of nanometer embedded in matrix of amorphous tissue and a high volume fraction of crystallinity (60~80%). The new nc-Si material have optical gap of 1.89 eV. The efficiency of this single junction solar cell reaches 8.7%. This nc-Si layer can be used not only as an intrinsic layer and as a p-type layer. Also nanocrystalline layer may be used as a seed layer for the growth of polycrystalline Si films at a low temperature.We used single ion beam sputtering methods to synthesize nanocrystalline silicon films successfully. The films were characterized with the technique of X-ray diffraction, Atomic Force Micrographs. We found that the films had a character of nc-amorphous double phase structure. Conductivity test at different temperatures presented the transportation of electrons dominated by different mechanism within different temperature ranges. Photoconductivity gains of the material were obtained in our recent investigation.


2003 ◽  
Vol 775 ◽  
Author(s):  
Suk-Ho Choi ◽  
Jun Sung Bae ◽  
Kyung Jung Kim ◽  
Dae Won Moon

AbstractSi/SiO2 multilayers (MLs) have been prepared under different deposition temperatures (TS) by ion beam sputtering. The annealing at 1200°C leads to the formation of Si nanocrystals in the Si layer of MLs. The high resolution transmission electron microscopy images clearly demonstrate the existence of Si nanocrystals, which exhibit photoluminescence (PL) in the visible range when TS is ≥ 300°C. This is attributed to well-separation of nanocrystals in the higher-TS samples, which is thought to be a major cause for reducing non-radiative recombination in the interface between Si nanocrystal and surface oxide. The visible PL spectra are enhanced in its intensity and are shifted to higher energy by increasing TS. These PL behaviours are consistent with the quantum confinement effect of Si nanocrystals.


1996 ◽  
Vol 8 (1/2) ◽  
pp. 27-28
Author(s):  
Mitsuhiro WADA ◽  
Yoshihito MATSUMURA ◽  
Hirohisa UCHIDA ◽  
Haru-Hisa UCHIDA ◽  
Hideo KANEKO

1988 ◽  
Vol 23 (8) ◽  
pp. 3026-3030 ◽  
Author(s):  
Takeyuki Suzuki ◽  
Tsutomu Yamazaki ◽  
Harunobu Oda

2019 ◽  
Vol 682 ◽  
pp. 109-120 ◽  
Author(s):  
Wjatscheslaw Sakiew ◽  
Stefan Schrameyer ◽  
Marco Jupé ◽  
Philippe Schwerdtner ◽  
Nick Erhart ◽  
...  

Sign in / Sign up

Export Citation Format

Share Document