The Design And Characterization Of β-FeSi₂Type Multicomponent Amorphous Alloys

Research shows that amorphous FeSi2has semiconductive properties with0.89-0.90eV direct band-gap at room temperature, similar to β-FeSi2. Moreover, the long-range disordered structure of amorphous FeSi2helps to eliminate the problems like lattice mismatch and defects, hence large areas of uniform film can be easily obtained. Based on these properties, amorphous FeSi2is expected to replace β-FeSi2and be applied extensively in the field of energy.Because the electro-optical property of FeSi2relies on the short-range order structure very much, samples with different composition were designed based on the cluster-plus-glue-atom-model in this work. Fe4Si8-xMx(M=Sn, C, Al) alloy rods were prepared by suction casting process. Fe3M1Six(M=B, Cr, Ni, Co) and Fe-Si-Al thin films were then prepared on Si(100) and Al2O3(0001) using magnetron sputtering. In order to select the proper third alloying elements and find out the method to enhance the amorphous formation ability and amorphous stability, thereby lay the foundation for the synthesis and application of amorphous FeSi2, some conclusions were made as follows.1. Due to the low cooling rate, there were multiphase coexistences in as-cast alloy rods and even segregation in samples added C and Sn. After annealing at850℃for12h, more β-phase can be observed in the alloy rods and the segregated SiC was slightly dissolved. Uniform microstructure may be obtained after further annealing. However, it is impracticable to prepare β-phase by Sn because the segregated Sn was still there after annealing.2. The as-deposited films were all amorphous and the films with B, Cr. Al as the third elements had semiconduetive properties. Furthermore, the variations of the band-gap were different with the third elements:0～0.65eV in Fe3Cr1Six(3.8≤x≤17.3) films,0.65-0.60eV in Fe3B1Six(5.4≤x≤9.9) and0～0.60eV while adding Al. According to the Hall results, the mobility and the carrier concentration of the films with the third elements B or Al were close to those of the binary β-FeSi2films.3. The Fe3M1Six films with different M(M=B, Cr, Ni. Co) showed different crystallization process after annealing at850℃for4hours. Among them, the single-β phase Fe2.7Si8.4B0.9film showed the most prominent semiconductor performance, with a resistivity of0.17Ω·cm, a sheet carrier concentration of2.8×1020cm-3, a mobility of0.13cm2/V·s and a band-gap width of0.65eV. It was confirmed that doping a proper third component can expand the (3phase zone exhibiting similar semiconductor property as binary β-FeSi2.