Control of Iron Disilicide Crystal Structure by Using Liquid Phase Obtained by Au-Si Eutectic Reaction
- PDF / 2,767,454 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 84 Downloads / 182 Views
Control of Iron Disilicide Crystal Structure by Using Liquid Phase Obtained by Au-Si Eutectic Reaction Kensuke Akiyama1,2, Yuu Motoizumi1 and Hiroshi Funakubo2 1 Kanagawa Industrial Technology Center, 705-1 Shimoimaizumi, Ebina, Kanagawa 2430435, Japan 2 Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502, Japan.
ABSTRACT The Au-Si liquid phase was obtained by melting the Si surface via Au-Si eutectic reaction, which contributed to the formation of semiconducting iron disilicide (β-FeSi2), on Au-coated Si(100) substrates. By coating a substrate with an Au layer of 60 nm or more, the Au-Si liquid phase covered the entire Si substrate surface, and single-phase β-FeSi2 was grown on Si(100) substrates. A clear photoluminescence spectrum of β-FeSi2 indicated the formation of highquality crystals with a low density of the non-radiative recombination center in the grains. INTRODUCTION Semiconducting iron disilicide (β-FeSi2) has been extensively investigated due to its great potential for a wide range of applications including thermoelectric device, photovoltaics, and optoelectronics. [1,2] For example, its photoluminescence (PL) at 1.54 μm and high optical absorption coefficient (higher than 105 cm-1 above 1.0 eV) has attracted interest over the past ten years for silicon-based optoelectronic applications and photovoltaic devices [2]. However, lightemitting-diode and photodiode devices using β-FeSi2 exhibit an emission efficiency of about 0.1 and 0.01%, respectively [3,4]. It has been pointed out that the improvement in these properties can be attributed to the decrease in the density of crystal defects, e.g., non-radiative recombination center, in β-FeSi2 [5,6]. Thus, decreasing these crystal defects during β-FeSi2 growth leads to sufficient optical properties. We previously reported on the emission of a strong PL spectrum intensity from β-FeSi2, suggesting the low density of the non-radiative recombination center by depositing it on a Au-coated Si substrates [7]. However, a mixture of metallic iron disilicide (αFeSi2) and β-FeSi2 phases was grown on Si(100) with a 40-nm-thick Au layer. Thus, controlling the FeSi2 crystal structure and achieving the formation of single-phase β-FeSi2 are expected. In this paper, we report on the formation of single-phase β-FeSi2 by coating Si(100) substrates with an Au layer of 60 nm or more. The PL properties from β-FeSi2 indicated the low density of the non-radiative recombination center. EXPERIMENT
Gold layers were evaporated onto Si(100) substrates at room temperature in vacuum (below 5×10-6 Torr). Iron silicides were deposited by co-sputtering Fe and Si by using the rfmagnetron sputtering method in an argon atmosphere at various deposition temperatures between 550 and 800°C. The chamber pressure during deposition was kept constant at 3×10-3 Torr, and the deposition rate was set to 1.7 nm/min during the deposition time of 120 min. A 2-inch Fe-Si alloy disk with silicon tips was used as a target. The Si/Fe at
Data Loading...
