Iron Silicide Formation from Fe Thin-Film Electrodeposition on Hydrogen-Terminated Si(111)

Abstract

We report on the surface morphology, crystalline, and electronic properties of Fe thin films potentiostatically eletrodeposited on hydrogen-terminated Si(111) substrates. Spontaneous reaction between Fe deposits and hydrogen-terminated Si surfaces have been observed at room temperature with formation of polycrystalline silicides normalFe2Si and normalFe5normalSi3 , together with metallic Fe having a body-centered cubic structure. X-ray photoemission spectroscopy and X-ray diffraction measurements have been performed to investigate the thermal stability between Fe and Si under high-vacuum thermal treatments up to 300°C .

Morphology, structure, and magnetism of FeCo thin films electrodeposited on hydrogen-terminated Si(111) surfaces

“…The absence of a systematic evolution of the potentiostatic current transients suggests random nucleation at reaction sites followed by diffusion-limited aggregation of the ions, as already reported in other works [18,22]. In other words, diffusion-limited steady currents are attained after a nucleation mode between instantaneous and progressive nucleation, as described by Scharifker and Hills [28].…”

“…At the end of the cyclic voltammogram, i.e., in the potential region of −900 to 0 mV, an anodic current is observed. As previously described, this anodic region can be assigned with oxidation of Fe to Fe 2+ and Fe 2+ to Fe 3+ (or Fe to Fe 3+ in some part) [22,24]. The reduction wave, as well as cathodic and anodic current peaks, becomes larger and more intense with addition of Co.…”

“…In contrast, different reports on the electrodeposition of Fe on Si reveal oxide formation, except Kim et al [21] using methanolic chloride solutions. Zarpellon et al [22] reported that the Fe films electrodeposited on a Si(111) substrate exhibit submicrometer grains with slightly flat terraces on the surface, along with the presence of iron silicides. Lee et al [23] have shown that α-Fe(110) films with nearly monosized nanostructures of spherical shapes on an n-type Si(111) substrate could be grown by pulsed electrodeposition in a nonaqueous solution, and Zhao et al [24] reported the synthesis of near-monosized Fe oval-shaped nanorod particles and spherical nanoparticles using electrodeposition on a hydrogen-terminated Si(100) surface from aqueous FeCl 3 solutions.…”

“…Besides, it is well known that the Fe/Si interface is very reactive and unstable even at room temperature, favoring the formation of Fe clusters and Fe silicides [22].…”

“…In order to minimize these problems, we investigate the influence of cobalt on Fe electrodeposition from the same aqueous ammonium sulfate solution used in a previous work of our group [22]. In this work, we report that the addition of small amounts of Co, in order to limit electroactive species in the electrolyte solution and keep deposit composition with less then 10 at% Co, is sufficient to induce significant changes in the morphology and crystalline structure, as well as the magnetic and electronic properties of Fe deposits on Si, resulting in thin films with a metallic character.…”