It has been reported that very thin films of metastable γ-FeSi2 phase with a cubic CaF2 structure [8, 9], FeSi1+x (0 ≤ x ≤ 1) phase with a defect CsCl structure [10, 11] and a new silicide phase with a c (4 × 8) surface periodicity [2, 12, 13] can be grown on Si (111) substrate by solid-phase epitaxy (SPE), which was realized by depositing iron on the silicon substrate at room temperature and then annealing the film at an elevated temperature. Despite the interesting properties and potential Sotrastaurin in vivo applications, it is

challenging to control the silicide reaction at the Fe/Si interface and grow a flat and single-phase thin film of iron silicide with the demanded structure. Due to the variety of existing compounds and the complexity of growth kinetics, the iron silicide GSK2118436 clinical trial thin films usually grow into a mixture of different phases with heterogeneous morphology [2, 5, 13]. Different from the silicide reaction in SPE, which is realized under iron-rich condition, reactive deposition epitaxy (RDE) (deposition of iron on the silicon substrate heated to a determined temperature) most probably involves diffusion of monomers on the surface, which may lead to the formation of unusual silicide structures. It has

been reported that RDE favors the production of Si-rich phases and single crystalline epitaxial structures [14, 15]. In this paper, we performed a scanning tunneling microscope (STM) study on the reactive epitaxial growth of iron silicides on Si (111)-(7 × 7) surface at different temperatures. We found that a thicker homogeneous and crystalline c (4 × 8) iron silicide thin film can be formed on the Si (111) surface with an extremely low deposition rate. The thickness of the film can be up to approximately 6.3 Å, which is significantly larger than that obtained previously by RDE method. This film could be used in the optoelectronic devices or serve as a precursor surface applicable in magnetic technological

fields. Methods Iron silicide thin films were grown on Si (111) substrates by using an ultrahigh vacuum (UHV) molecular beam epitaxy-STM system (Multiprobe XP, Omicron, Taunusstein, Germany) with a base pressure of less than 5.0 × 10−11 mbar. P-doped, n-type Si (111) substrates with resistivity of approximately 1 Ω cm were cleaned in UHV by the well-established annealing Niclosamide and flashing procedures [16]. Iron was deposited on the clean substrates by heating iron lumps (purity 99.998%) in a Mo crucible with electron bombardment. The iron flux was monitored by an internal ion collector mounted near the evaporation source. During deposition, the substrates were heated by direct current and the temperatures were measured using an infrared pyrometer. The deposition rate was controlled from approximately 0.01 to 0.07 ML min−1 (1 ML = 1 iron atom per 1 × 1 surface mesh = 7.8 × 1014 atoms cm−2) [13]. An electrochemically etched tungsten tip was used for scanning.