Contactless processing of SiGe-melts in EML under reduced gravity

The processing of semiconductors based on electromagnetic levitation is a challenge, because this kind of materials shows a poor electrical conductivity. Here, we report the results of measurements of the thermophysical properties obtained recently from highly doped semiconductors Si1-x Ge x under microgravity conditions in the framework of parabola flight campaigns. Due to the limited time of about 20 s of microgravity especially Ge-rich samples with low melting temperatures were investigated. The measurements were performed contactlessly by video techniques with subsequent digital image processing. Linear and volume thermal expansion coefficients were measured hereby from image data. An anomaly of volume changes near the solidus temperature is visible. Viscosity and surface tension were determined by the oscillating drop technique using optic and electronic data. It was observed that the alloying of Si into Ge increases the surface tension of the melts. The viscosity is following an Arrhenius equation and shows a crossover temperature which separates simple liquid at high temperatures from cooperative liquid at low temperatures

Examining the influence of turbulence on viscosity measurements of molten germanium under reduced gravity

The thermophysical properties of liquid germanium were recently measured both in parabolic flight experiments and on the ISS in the ISS-EML facility. The viscosity measurements differed between the reduced gravity experiments and the literature values. Since the oscillating drop method has been widely used in EML, further exploration into this phenomenon was of interest. Models of the magnetohydrodynamic flow indicated that turbulence was present during the measurement in the ISS-EML facility, which accounts for the observed difference

Structural, magnetotransport, and micromagnetic properties of sputtered Ir(111)/Co superlattices

Structural, magnetotransport, and micromagnetic properties of sputtered Ir(111)/Co superlattices / Yuansu Luo ... - In: Journal of applied physics. 87. 2000. S. 2479-248

Giant magnetoresistance and interlayer coupling in Cu(111)/Ag67Co33 granular multilayers

Giant magnetoresistance and interlayer coupling in Cu(111)/Ag67Co33 granular multilayers / Y. Luo ... - In: Journal of applied physics. 81. 1997. S. 4589- 459

Oscillations of giant magnetoresistance in Cu/AgCo granularmultilayers

Oscillations of giant magnetoresistance in Cu/AgCo granularmultilayers / Y. Luo ... - In: Europhysics letters. 37. 1997. S. 225-23

Interlayer coupling and magnetoresistance in Ir/Co multilayers

Interlayer coupling and magnetoresistance in Ir/Co multilayers / Y. Luo ; M. Moske and K. Samwer. - In: Europhysics letters. 42. 1998. S. 565-57

Untersuchungen zur Struktur, Phasenbildung und Supraleitung der A15-Phase in gesputterten NbAl-Duennfilmen

Available from TIB Hannover: H93B1328 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Superconductive spin-valve effect in CoFeHf/Pb/CoFeHf layered structures

(CoFe)75Hf25/Pb/(CoFe)75Hf25 spin-valve–like structures were investigated to show an influence from the relative orientation of ferromagnetic layers on the superconductivity of the Pb space layer, where (CoFe)75Hf25 is amorphous and thus soft ferromagnetic. The Pb layer deposited at 77 K is super smooth as indicated by X-ray diffraction. A proximity effect arises from the ferromagnetic layers and destroys the superconductivity of Pb with a layer thickness ds<35 nm. In order to minimize the proximity effect, thin oxide layers of CoFeHfO (1 nm) were inserted at relevant interfaces. The superconductivity of Pb is alive then even for layered samples with ds=4 nm, showing a sharp superconductive transition at the critical temperature Tc=6 K. A shift of ΔTc∼30 mK was observed by switching the ferromagnetic layers from parallel to antiparallel

Thermophysical properties of a Si50Ge50 melt measured on board the International Space Station

Thermophysical properties of highly doped Si50Ge50 melt were measured contactlessly in the electromagnetic levitation facility ISSEML on board the International Space Station. The sample could be melted, overheated by about 375 K, and cooled down in 350 mbar Argon atmosphere. A large undercooling of about 240 K was observed and a quasi-homogeneous nucleation on the droplet surface occurred. During the cooling phase, high-resolution videos were taken from the side and the top. The density and thermal expansion were evaluated with digital image processing; the viscosity and the surface tension were measured by means of the oscillating drop technique. Inductive measurements of the electrical resistivity were conducted by a dedicated electronics. All data were taken as a function of temperature T from the overheated melt down to the undercooled range. We found a nonlinear thermal expansion, suggesting a many body effect in the liquid beyond the regular pair interaction, an enhanced damping of surface oscillations likely related to an internal turbulent flow, and an increment of the electrical resistivity with decreased T in the undercooled range regarding a demixing of the components