Iron silicides grown by solid phase epitaxy on aSi(111)surface: Schematic phase diagram

Abstract

We have determined the schematic phase diagram in detail with high reliability for Fe silicides grown by solid phase epitaxy ͑SPE͒ on a Si͑111͒7 ϫ 7 surface at wide Fe coverage ͑0.2-56 monolayers͒ and subsequent annealing temperatures from 300 to 800°C. In the SPE growth, ␦-7 ϫ 7, 1 ϫ 1, bcc-Fe͑111͒1 ϫ 1, 2 ϫ 2, c͑8 ϫ 4͒, 3D-2 ϫ 2 ͑␣-FeSi 2 ͒, ͱ 3 ϫ ͱ 3-R30°, ␤-FeSi 2 , and fine polycrystalline phases are formed on the Si͑111͒ surface depending on Fe coverage and annealing temperature. We have characterized the surface periodic structures and morphologies of all the above Fe silicide phases using low-energy electron diffraction and scanning tunneling microscopy. Reflection high-energy electron diffraction also has been used to determine three-dimensional structures. Based on the overall view regarding the formations and changes of Fe silicide phases on a Si͑111͒ surface, we discuss the growth mechanisms.

Variety of iron silicides grown on Si(001) surfaces by solid phase epitaxy: Schematic phase diagram

“…At higher θ F e the cluster size became larger, and was about several nm at θ F e = 16 ML and T a = RT, where neither steps in STM nor spots in LEED were observed. These surfaces at both lower and higher θ F e did not change drastically after annealing at T a = 200 • C. RHEED also showed amorphous patterns for as-deposited surfaces at θ F e = 12.5 and 25 ML, while they showed broad transmission spots (indicating a fiber structure with bcc- form under further annealing inducing massive mixture in surface and substrate layers [4]. In this sense, β-FeSi 2 is appropriate for 3D layered islands (D), and for 3D dome-like islands (E) though they are not pinned (not epitaxially grown).…”

“…Since plural silicides can co-exist on surfaces, local structure analyses such as scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) are the most powerful methods to study the silicide formation, in addition to averaged structure analyses such as low-energy electron diffraction (LEED), reflection high-energy electron diffraction (RHEED), X-ray photoelectron diffraction (XPD), X-ray photoelectron spectroscopy (XPS), ultra-violet photoelectron spectroscopy (UPS), and so on. STM results have been reported for many studies of silicides grown by SPE on Si(111), but in restricted preparation conditions, and recently, progress has been made in establishing a schematic phase diagram [4]. For silicides on Si(001) there are few STM works [5][6][7] which have reported in very restricted conditions, and there is no detailed phase diagram, even though works using averaged structure analysis [8,9] have suggested rough phase diagrams.…”

Study of the Interface Structure of Epitaxial Ultra-Thin Film by an X-Ray Holographic Imaging Method

“…Recently fabrication of iron silicides on Si(111) by solid phase epitaxy (SPE) growth was systematically studied for the conditions of the amount of deposited Fe and subsequent annealing temperature [8]. In the region of a few monolayer deposition, thin films with 1×1, 2×2 and c(8×4) periodicity, observed by LEED, RHEED, STM etc., are fabricated almost separately.…”

Self-consistent mapping: Effect of local environment on formation of magnetic moment in α−FeSi2

“…The growth of Fe-silicides on silicon has been widely studied in recent years because, depending on their phase, crystal structure and composition, they can be semiconducting, metallic and/or ferromagnetic, and hence offer a large variety of potential applications when integrated into silicon-based devices [4]- [6]. To this day, several Fe-silicide structures have been reported.…”