Structural phase changes in a titanium-silicon system modified by high-current electron beams and compression plasma flows

Abstract

Structural phase changes in a titanium-silicon system treated by low energy high current elec tron beams (HCEBs) and compression plasma flows (CPFs) with the duration 100 µs and the energy density 12-15 J/cm 2 are studied. Scanning electron microscopy, X ray diffraction and electron microprobe analysis are used in this work. The formation of a titanium doped silicon layer 10-25 µm thick, titanium silicides (TiSi 2 under HCEBs and Ti 5 Si 3 under CPF treatment), silicon dendrites, and needle like eutectics (typical size of precipitates is about 50 nm) is revealed. It is shown via the results of numerical simulation that the thickness of the metal doped layer is mainly controlled by the power density value and the surface nonuni formity of the heat flow over the target surface. The thermodynamic regularities of phase formation are dis cussed, taking into account heat transfer between the silicide nuclei and solid silicon.

Effect of Compressed Plasma Flow on Tantalum-Titanium Thin Layer Deposited on Silicon Substrate

“…In addition, a high cooling rate (~10 7 K/s) and a maximum temperature gradient (~10 7 K/m) were estimated. However, an investigation on Ti-Si system under CPF treatment [20], confirmed that, under the impact of anuniform heat flux (without convection), the melting process starts at the threshold energy density 12 J/cm also showed that by doubling the energy density, the thickness of the molten alloy layer becomes 15 times thicker. It should be mentioned that the calorimetric experiment gives the average value of the energy density, and because of the inhomogeneity of the heat flux, the density of the plasma energy in local areas may be much greater than calculated values.…”

“…Thermal, mechanical, and radiation effects of CPF pulses provide nonequilibrium conditions for structural and phase transformations and the formation of novel low-dimensional structures in the surface layers of solids. CPF treatment of a thin metal layer (e.g., Fe, Ti, Ni, Zr, Mo) on a silicon substrate successfully made it possible to form metal silicides in the near-surface layer [16,[19][20][21].…”