Epitaxy of fluorite-structure silicides: metastable cubic FeSi2 on Si(111)

Phase transformation in FeSi2 nanowires

“…Indeed, this is implied by the observation that the transformation temperature depends on film thickness for extended overlayers [16]. For example, a 14-Å -thick film transforms at 500 1C while a 300-Å -thick film transforms at $200 1C [16]. The thickness dependence indicates that the metastable phase has a lower interface energy than the b-phase.…”

“…In the present case, both structures are epitaxial, and hence it is expected that the phase stabilities may be affected by strain energies. Indeed, this is implied by the observation that the transformation temperature depends on film thickness for extended overlayers [16]. For example, a 14-Å -thick film transforms at 500 1C while a 300-Å -thick film transforms at $200 1C [16].…”

“…g-FeSi 2 has a CaF 2 lattice and was first reported by Onda in 1992 [16]. This phase was predicted to exist and to be ferromagnetic, based on band-structure calculations [6].…”

Stress evolution during the growth of ultrathin layers of iron and iron silicide on Si(111)

“…9 This leaves the semiconducting ␤-FeSi 2 as the phase formed. We obtain the same AES signal ratio after annealing a 4 nm Fe layer, deposited at 160 or 300 K, for 20 min at 600 K. This silicide formation at a rather low temperature indicates the high mobility of Si in the deposited Fe film.…”

“…The semiconducting ␤-FeSi 2 attracted special interest due to its reported direct energy gap of 0.89 eV. 1,2 To name a few techniques, low energy diffraction ͑LEED͒, 3-7 reflection high energy electron diffraction ͑RHEED͒ [8][9][10][11] Auger electron spectroscopy ͑AES͒ combined with electron energy loss spectroscopy ͑EELS͒, [12][13][14][15][16] Rutherford backscattering spectroscopy ͑RBS͒, 17 transmission electron microscopy ͑TEM͒, 18,19 photoelectron spectroscopy, [20][21][22][23] and recently scanning tunneling microscopy ͑STM͒ 24,25 experiments have been performed to characterize the structural and electronic properties of the Fe/Si system. To elucidate the issues of lattice distortion between silicon and silicide, 3,8 we measured the film stress with submonolayer sensitivity during the growth of Fe on Si at temperatures between 160 and 600 K. Our results support the more recent scenarios for the growth of Fe on Si proposed by Alvarez et al, 24 favoring a reactive Fe/Si interface even at 300 K.…”