Semiconducting nanocrystalline iron disilicide thin films prepared by pulsed-laser ablation

Yoshitake, Tsuyoshi; Yatabe, M.; Itakura, Masaru; Kuwano, Noriyuki; Tomokiyo, Yoshitsugu; Nagayama, Kazuaki

doi:10.1063/1.1617374

Cited by 50 publications

(44 citation statements)

References 11 publications

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“…10,12,18 However, when a highly energetic pulsed laser deposition technique is used, 8,19 the films grow in the form of a nanocrystalline ␤-FeSi 2 phase already at RT. In the studies of this technique for deposition of ␤-FeSi 2 it was suggested 19 that diffusivity of Si atoms is dominant for substrate temperatures ജ400°C, and diffusivity of Fe atoms is enhanced for substrate temperatures ജ700°C.…”

Section: Discussionmentioning

confidence: 99%

“…7 Amorphous FeSi 2 is also a direct gap semiconductor with a band gap of 0.88-0.90 eV, close to that of the crystalline ␤ phase, and with a similar photoabsorption efficiency. More recently, 8 it was reported that very fine ͑3-5 nm͒ nanocrystalline ␤-FeSi 2 films also exhibit a direct band gap behavior. As their structure is somewhere at the boundary between a fully grown crystalline and the amorphous FeSi 2 phase, the measured E g = 0.85-0.95 eV confirms similar band gap values for these two phases.…”

Section: Introductionmentioning

confidence: 99%

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Transition from amorphous to crystalline beta phase in co-sputtered FeSi2 films as a function of temperature

Milosavljević

Shao

Lourenço

et al. 2005

Journal of Applied Physics

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A study of the stability of amorphous FeSi 2 films and their transition to a crystalline phase as a function of deposition or annealing temperature is presented. Stoichiometric FeSi 2 films, 300-400 nm thick, were deposited on ͑100͒ Si substrates by co-sputtering of Fe and Si. It was found that the films grow in an amorphous form for the substrate temperature ranging from room temperature to 200°C, while from 300-700°C, they grow in form of a crystalline ␤-FeSi 2 phase. In a postdeposition 30 min heat treatments, the layers retain the amorphous structure up to 400°C, transforming to the crystalline ␤ phase at 500-700°C. The results are discussed in the frame of the existing models, and compared to those found in the literature. It is shown that in as-deposited films, the growth is controlled by surface diffusion, the crystalline layers growing in a columnar structure strongly correlated to the Si substrate. Postdeposition treatments induce a random crystallization controlled by bulk diffusion, the resulting structure not being influenced by the substrate. The results of this work contribute to a better understanding of the processes involved in a transition of amorphous FeSi 2 films to a crystalline phase, and provide a basis to determine the processing parameters in potential applications of this promising semiconducting material.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Transition from amorphous to crystalline beta phase in co-sputtered FeSi2 films as a function of temperature

Milosavljević

Shao

Lourenço

et al. 2005

Journal of Applied Physics

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“…As already mentioned in the Introduction, amorphous semiconducting Fe disilicide can be grown, e.g., by sputter deposition. Fe-Si bonds are identified via XPS measurements or electron diffraction [18,[44][45][46][47][48][49].…”

Section: Fe Ni Mo and W Surfactantsmentioning

confidence: 99%

“…Pronounced phase separation also takes place in ion beam irradiation induced cone formation on compound semiconductors like InSb or GaSb [42,43]. Usually, metal silicides are considered as crystalline phases, however, amorphous Fe disilicide has attracted attention as a semiconducting material with a band gap of 0.9 eV with potential applications as photovoltaic material [44][45][46]. The identification of amorphous metal silicides can be done on the basis of X-ray photoelectron spectroscopy (XPS) or an analysis of atom pair distribution function measured with electron diffraction [18,[47][48][49].…”

Section: Introductionmentioning

confidence: 99%

The role of phase separation for self-organized surface pattern formation by ion beam erosion and metal atom co-deposition

et al. 2012

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We investigate the ripple pattern formation on Si surfaces at room temperature during normal incidence ion beam erosion under simultaneous deposition of different metallic co-deposited surfactant atoms. The co-deposition of small amounts of metallic atoms, in particular Fe and Mo, is known to have a tremendous impact on the evolution of nanoscale surface patterns on Si. In previous work on ion erosion of Si during co-deposition of Fe atoms, we proposed that chemical interactions between Fe and Si atoms of the steady-state mixed Fe x Si surface layer formed during ion beam erosion is a dominant driving force for self-organized pattern formation. In particular, we provided experimental evidence for the formation of amorphous iron disilicide. To confirm and generalize such chemical effects on the pattern formation, in particular the tendency for phase separation, we have now irradiated Si surfaces with normal incidence 5 keV Xe ions under simultaneous gracing incidence co-deposition of Fe, Ni, Cu, Mo, W, Pt, and Au surfactant atoms. The selected metals in the two groups (Fe, Ni, Cu) and (W, Pt, Au) are very similar regarding their collision cascade behavior, but strongly differ regarding their tendency to silicide formation. We find pronounced ripple pattern formation only for those co deposited metals (Fe, Mo, Ni, W, and Pt), which are prone to the formation of mono and disilicides. In contrast, for Cu and Au co-deposition the surface remains very flat, even after irradiation at high ion fluence. Because of the very different behavior of Cu compared to Fe, Ni and Au compared to W, Pt, phase separation toward amorphous metal silicide phases is seen as the relevant pro-

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“…[23][24][25] Milosavljevic presented a thermodynamic calculation, which indicates, that amorphous FeSi 2 is in metastable equilibrium with Si and should have a nearly constant stoichiometry of Fe/Si ≈ 1/2. 24 However, little work has yet been done to reveal the atomistic structure of amorphous FeSi 2 .…”

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confidence: 99%

Sharp transition from ripple patterns to a flat surface for ion beam erosion of Si with simultaneous co-deposition of iron

2012

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We investigate pattern formation on Si by sputter erosion under simultaneous co-deposition of Fe atoms, both at off-normal incidence, as function of the Fe surface coverage. The patterns obtained for 5 keV Xe ion irradiation at 30° incidence angle are analyzed with atomic force microscopy. Rutherford backscattering spectroscopy of the local steady state Fe content of the Fe-Si surface layer allows a quantitative correlation between pattern type and Fe coverage. With increasing Fe coverage the patterns change, starting from a flat surface at low coverage (< 2×1015 Fe/cm2) over dot patterns (2-8×1015 Fe/cm2), ripples patterns (8-17×1015 Fe/cm2), pill bug structures (1.8×1016 Fe/cm2) and a rather flat surface with randomly distributed weak pits at high Fe coverage (>1.8×1016 Fe/cm2). Our results confirm the observations by Macko for 2 keV Kr ion irradiation of Si with Fe co-deposition. In particular, we also find a sharp transition from pronounced ripple patterns with large amplitude (rms roughness ∼ 18 nm) to a rather flat surface (rms roughness ∼ 0.5 nm). Within this transition regime, we also observe the formation of pill bug structures, i.e. individual small hillocks with a rippled structure on an otherwise rather flat surface. The transition occurs within a very narrow regime of the steady state Fe surface coverage between 1.7 and 1.8×1016 Fe/cm2, where the composition of the mixed Fe-Si surface layer of about 10 nm thickness reaches the stoichiometry of FeSi2. Phase separation towards amorphous iron silicide is assumed as the major contribution for the pattern formation at lower Fe coverage and the sharp transition from ripple patterns to a flat surface

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Semiconducting nanocrystalline iron disilicide thin films prepared by pulsed-laser ablation

Cited by 50 publications

References 11 publications

Transition from amorphous to crystalline beta phase in co-sputtered FeSi2 films as a function of temperature

Transition from amorphous to crystalline beta phase in co-sputtered FeSi2 films as a function of temperature

The role of phase separation for self-organized surface pattern formation by ion beam erosion and metal atom co-deposition

Sharp transition from ripple patterns to a flat surface for ion beam erosion of Si with simultaneous co-deposition of iron

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