Pattern formation in SiSb system

Abstract

Thermal annealing of Si/Si 1-x Sb x /Si amorphous thin film tri-layer samples (x=18 and 24 at%Sb) under 100 bar Ar pressure results in an interesting pattern formation. In pictures, taken by means of cross-sectional transmission electron microscopy (TEM), stripe-shaped contrast, with three maxima, parallel with the interfaces can be seen. Secondary neutral mass spectrometer (SNMS) measurements revealed that the regions with different contrasts correspond to Sb-rich and Sb-depleted regions. Furthermore, the Sb concentration peaks in the Sb-rich regions, especially at longer annealing times, are different: the peak developed at the Si/SiSb interface closer to the free surface decays faster than that of the inner one closer to the substrate. The pattern formation is interpreted by segregation-initiated spinodal-like decomposition, while the difference of the Sb concentration peaks is explained by the resultant Sb transport to and evaporation from the free surface. The possible role of formation of nanocrystalline grains, in the explanation of the fast transport under pressure as compared to vacuum is also discussed.

Investigation of Sb diffusion in amorphous silicon

“…It was showed that sample with 5% Sb concentration annealed lower then 823 K remains 6 in amorphous state. From the time evaluation of SNMS concentration profile D Sb ≈1•10 -21 m 2 /s diffusion coefficient was calculated for Sb diffusion in amorphous Si at 823 K. As it was described in our present and previous works [5,6] in annealed samples the diffusion and decomposition processes significantly enhanced by the applying small (100 bar) hydrostatic pressure. The effect of hydrostatic pressure is not clear and need further investigation.…”

“…), which means that Sb diffused out from SiSb layer into amorphous Si. However, in contrast to heated samples in 100 bar Ar with higher Sb concentration (13-26 at%) [6], where the SiSb layer underwent a spinodal-like decomposition resulting three Sb-rich stripes parallel to the original interfaces, morphological changes were not detected. Electron diffraction measurements also showed that the samples heat treated at 823 K remained in amorphous state.…”

“…In our previous works [5,6] the diffusion and transformation processes in amorphous Si 1-x Sb x mono-, Si/Si 1-x Sb x /Si tri-and Si/Si 1-x Sb x multilayer systems with different composition (x=13-26 %) were investigated. After annealing the samples the most interesting result was that under hydrostatic pressure (100 bar-4,7 kbar Ar) in the Si/SiSb/Si trilayers (and only in this type of samples and only under hydrostatic pressures) the SiSb layer underwent a spinodal-like decomposition, resulting in three Sb-rich stripes parallel to the interfaces.…”

Effects of annealing on amorphous GdxSi1−x near the metal-insulator transition

“…%, where insulators are defined as having zero conductivity with an activated temperature dependence in the limit as T goes to zero and metals have finite, nonzero conductivity, and power law dependence in the same limit. [7][8][9][10] In a recent paper, 11 we showed that annealed a-Nb-Si develops Nb-rich clusters within a Nb-depleted amorphous matrix, causing the resistivity to increase dramatically and leading to improvements in the technological use of a-Nb-Si resistance thermometers. % Gd; 2-6 this alloy also shows dramatic magnetic and magnetotransport effects, including enormous ͑many orders of magnitude͒ negative magnetoresistance 3,4 ͑MR͒ below a characteristic temperature T * .…”