Epitaxial growth of CaSi<sub>2</sub> on Si(111)

Schöpke, A.; Würz, R.; Schmidt, M.

doi:10.1002/sia.1339

Cited by 11 publications

(9 citation statements)

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“…In contrast, the x-ray photon spectroscopy ͑XPS͒ results for calcium silicides, 26,27,[29][30][31] and in particular CaSi, are ambiguous because of the surface sensitivity of this method. These results have been obtained mainly for the silicide films on Si surfaces with a Ca deposition.…”

Section: Resultsmentioning

confidence: 80%

“…At the initial stage of the film's growth, the Si 2p photoelectron spectra showed a larger negative chemical shift ͑1.1-1.45 eV͒, while a smaller negative chemical shift ͑0.3-0.4 eV͒ was observed after the CaSi 2 films formed. 26,27 Schöpke et al 27 concluded that a larger chemical shift arose from the formation of the Ca-rich silicides, such as Ca 2 Si and CaSi. The local structure of the Si atoms in CaSi, however, resembles that of CaSi 2 rather than Ca 2 Si, where the nearest-neighbor atoms of Si are Ca atoms, because the nearest-neighbor atom of Si in CaSi 2 is not Ca but Si.…”

Section: Resultsmentioning

confidence: 99%

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Effective charge on silicon atom in the metal silicidesMg2Siand CaSi

et al. 2005

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The effective charges of Si in both magnesium ͑Mg 2 Si͒ and calcium silicides ͑CaSi and Ca 2 Si͒ have been investigated by measuring high-resolution Si K␣ x-ray fluorescence spectra. CaSi showed small but positive chemical shifts ͑+0.03 eV͒, while the chemical shift of Mg 2 Si was negative ͑−0.14 eV͒, as expected from their electronegativity ͑Ca: 1.00; Mg: 1.31; Si: 1.90͒. The similarity of the chemical shift for the Fe silicides and the calculations for the free single Si atom suggested that the effective charge of Si for CaSi was positive. From the observations the effective charges on Si in CaSi and Mg 2 Si were estimated to be +0.1 and −0.3 electrons. The discrete variation Hatree-Fock-Slater calculations for Mg 2 Si and CaSi also showed opposite chemical shifts and effective charges: −0.09 eV and −0.35 electrons for Mg 2 Si and +0.09 eV and +0.26 electrons for CaSi, respectively. The composition of the nearest-neighbor atoms of Si, which are Si in CaSi and Mg in Mg 2 Si, cause the opposite effective charges between the two silicides.

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Section: Resultsmentioning

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Effective charge on silicon atom in the metal silicidesMg2Siand CaSi

et al. 2005

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“…It has been reported that CaSi 2 epitaxial films were grown on Si substrates by solid-phase epitaxy (SPE) [10][11][12][13] and reactive deposition epitaxy (RDE). [9,[14][15] The epitaxial relationship is CaSi 2 (0001)/Si{111} [14] with the lowest lattice mismatch of 0.4 %.…”

Section: Introductionmentioning

confidence: 99%

Ordered CaSi₂ Microwall Arrays on Si Substrates Induced by the Kirkendall Effect

Meng

Ueki

Tatsuoka

et al. 2017

Chemistry A European J

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We have specified the synthetic conditions to obtain one-directionally ordered CaSi microwall arrays vertically grown on a Si substrate. Our basic concept is based on the utilization of the Kirkendall effect for reactive deposition epitaxy (RDE). We found for the first time that: 1) a much larger Ca vapor supply on the Si substrate than the conventional RDE, 2) the adoption of a two-step heating process, and 3) the selection of the crystal axis of the Si surface are the keys to control the microstructures of CaSi on the Si substrate. The CaSi phase was first formed on Si, then the CaSi phase was formed at the CaSi/Si interface. Based on the Kirkendall effect, the interdiffusion of Ca and Si was enhanced in the vertical direction rather than in the parallel direction to the Si surface. CaSi tends to grow along four equivalent Si{111} planes, however, the specific orientation of the Si surface resulted in CaSi microwalls grown along its Si(111‾ ) plane, the only plane directing nearly vertical to the surface among the Si{111} planes. These results suggest that the Kirkendall effect under asymmetric growth of target materials would be a rational strategy to obtain their ordered microstructures.

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“…Unfortunately, methods for fabricating epitaxial films of calcium silicides on silicon are limited to the evaporation of calcium metal onto Si wafers followed by an anneal to produce CaSi 2 . [10][11][12] In addition, CaSi 2 and CaSi melts, prepared by heating of Ca and Si in stoichiometric proportion, exhibit superconducting behavior at high pressures, 13,14 and show potential for reversible hydrogen storage, 15 respectively.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of calcium disilicide‐induced calcification of crystalline silicon surfaces in simulated body fluid under zero bias

Seregin

Coffer

2007

J Biomedical Materials Res

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A dry-etch spark ablation method was used to produce calcium disilicide (CaSi2/Si) layers on silicon surfaces, and their biomineralization under zero bias was followed by means of scanning electron microscopy, X-ray energy dispersive analysis, and Raman spectroscopy. CaSi2/Si wafers are bioinert at 25 degrees C and bioactive at 37 degrees C. Mechanistic insights regarding biomineralization were derived from an analysis of film growth morphology and chemical composition after various soaking periods in standard simulated body fluid (SBF). Changes in CaSi2/Si calcification behavior as a function of reaction temperature and pH, SBF concentration, and various surface modification processes were also employed for this purpose. During CaSi2/Si calcification under zero bias, calcium phosphate (CaP) growth is strongly dependent on the structural degradation of CaSi2/Si grains. Surface silanol groups, initially present on the as-prepared material, cannot induce CaP nucleation, which begins only upon delamination of CaSi2/Si layers. The calcium phosphate phases, which are present during various growth stages, possibly include a combination of Mg-substituted whitlockite, monetite, and tricalcium phosphate.

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Epitaxial growth of CaSi₂ on Si(111)

Cited by 11 publications

References 9 publications

Effective charge on silicon atom in the metal silicidesMg2Siand CaSi

Effective charge on silicon atom in the metal silicidesMg2Siand CaSi

Ordered CaSi₂ Microwall Arrays on Si Substrates Induced by the Kirkendall Effect

Mechanism of calcium disilicide‐induced calcification of crystalline silicon surfaces in simulated body fluid under zero bias

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Epitaxial growth of CaSi2 on Si(111)

Cited by 11 publications

References 9 publications

Effective charge on silicon atom in the metal silicidesMg2Siand CaSi

Effective charge on silicon atom in the metal silicidesMg2Siand CaSi

Ordered CaSi2 Microwall Arrays on Si Substrates Induced by the Kirkendall Effect

Mechanism of calcium disilicide‐induced calcification of crystalline silicon surfaces in simulated body fluid under zero bias

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Epitaxial growth of CaSi₂ on Si(111)

Ordered CaSi₂ Microwall Arrays on Si Substrates Induced by the Kirkendall Effect