The Preparation And Characterization Of Fe₃Si₈M Type Bulk Ternary Alloys And Amorphous Thin Films

Researchs show that amorphous FeSi2 has semiconductive properties with 0.89-0.90eV direct band-gap at room temperature, similar toβ-FeSi2 phase. This finding greatly improved the practical application value of this material. The amorphous FeSi2 possessing semiconductive properties will have more promising perspective.Out of the consideration of promising perspective for semiconductor amorphous FeSi2, the ternary alloying research was made on the base of the structure of (3-FeSi2, and phase composition of ternary alloys and formation of amorphous were investigates in this paper. Ternary Fe3SigM (M= B, Cr, Ni, Cu, Co, Al) series of alloy rods and ribbons were prepared using high vacuum suction casting and melt spinning methods. On the base of the formation rule ofβ-FeSi2 phase in (Fe, M)Si2 ternary alloys, Fe-Si-M (M= Cr, Co, Ni, B) system amorphous thin films were prepared by megnatron sputtering on the Si(100) wafers. The reaults are as follows:(1). The alloy rods are crystal states with several phase coexisted. Phase separation exists in all samples, but the samples with B and Cr elements as the third component respectively have slighter phase separation, and the composition are close to the design composition. The (3-phase has different dissolve ability of the third element, it could dissolve 15-20at% Ni, 4-13at% Cu,7-10at% Co and 7-10at% Cr. However in contrary to the designed formula, the added Al replaced Si in stead of Fe. It is infeasible to prepareβ-phase by adding Al element in this modle.(2). The alloy ribbons are also crystal state with several phase coexisted, but the main phase isβ-phase. There are trace amounts of amorphous particles in Fe3Si8B and Fe3Si8Cr ribbon samples, which show under the rapid cooling conditions, the additions of B and Cr are favorable for the amorphous phase formation. There are a, P and Si crystal grains in the Fe3SigAl sample, it shows that the addited Al element relaced the site of Si again.(3). The thin films are amorphous state, with high brightness, good adhesiveness and high reflectivity. On the right of designed composition point, sheet resistance decreases with the composition closing to the composition designed. For the Fe-Si-Cr samples, the smallest sheet resistance and resistivity are obtained at the point of designed composition. The results of Hall measurements show that adding Cr and Ni as glue atoms, samples present mostly p-semiconductor, adding B as glue atom, samples present mostly n-type. But the conductive type is not obvious with adding Co as glue atom. The values of Hall mobility are between 10-5cm2/V·s and 10cm2/V·s, and the sheet carrier concentration are higher(1015～1018cm-2). Photo-absorption measurements show the band gaps of these amorphous thin films are narrower thanβ-FeSi2.