Growth and Optical Characterization of CrSi₂ Thin Films

Abstract

CrSi, thin films are grown by dc magnetron sputtering of Cr single layers on Si and Cr/Si multi-layer configurations on SiO, and subsequent external annealing. In the optical spectra around the band edge the phonon emission and the absorption branches of the indirect transition at 0.5 eV and the direct transition around 1 eV can be discerned. Spectral features in the reflectivity spectrum at higher energies are discussed on the basis of published density of states calculations. The reflectivity spectrum in the IR region exhibits pronounced structures which can be fitted by a six-oscillator model yielding the TO frequencies, oscillator strengths, and damping constants of the lattice modes. The Raman spectrum shows bands in the 310 to 410 cm-' wave number region.Es wurden CrSi,-Schichten durch Gleichstrom-Magnetron-Sputtern von Cr-Einzelschichten auf Si und Cr/Si-Schichten auf SiO, und nachfolgender externer Temperung hergestellt. In den optischen Spektren im Bereich der Bandkante wurden die Phonon-Emissions-und Absorptions-Zweige des indirekten Ubergangs bei 0,5 eV sowie der direkte Ubergang bei 1 eV erhalten. Die spektrale Abhangigkeit des Reflexionsvermogens bei hoherer Energie wird auf der Grundlage existierender ZustandsdichteBerechnungen diskutiert. Das Reflexionsspektrum im IR-Bereich weist ausgepragte Strukturen auf, die mit Hilfe eines Modells bestehend aus sechs Oszillatoren angepa5t werden konnten, woraus die TO-Frequenzen, Oszillatorstarken und Dampfungskonstanten der Gitterschwingungen ermittelt wurden. Das Raman-Spektrum weist Banden im Wellenzahlbereich von 310 bis 410 cm-' auf.

Revisited phonon assignment and electro-mechanical properties of chromium disilicide

“…17 The Cr 3d 5 4s 1 and Si 3s 2 3p 2 electronic states are considered as the valence states. This leads to an electronic band gap, E g ¼ 0.49 eV, which is consistent with the experimental values 1,2,19 reported between 0.35 and 0.55 eV in the literature. 18 Atomic relaxation is performed at the experimental lattice parameters (see previous section) until the maximum residual forces on each atom were less than 5 Â 10 À6 Ha per Bohr.…”

“…1,2 It crystallizes in a hexagonal C40 structure within the P6 2 22 space group with Cr and Si atoms in 3d and 6j special Wyckoff positions, respectively. 1,2 It crystallizes in a hexagonal C40 structure within the P6 2 22 space group with Cr and Si atoms in 3d and 6j special Wyckoff positions, respectively.…”

CVD diamond growth from nanodiamond seeds buried under a thin chromium layer

“…After 12 min of plasma exposure, phonon modes at 302 cm -1 , 349 cm -1 , 390 cm -1 and 409 cm -1 appear. These peaks are in a good agreement with those belonging to CrSi 2 reported in literature [27]. One can note that the Si phonon mode at 520.7 cm -1 gradually appears with CVD exposure time.…”

Synthesis and thermal stability of nanocrystalline chromium disilicide

“…Though chromium disilicide is an important material, studies on this material mainly referred to sintered specimens and polycrystalline films [8][9][10]. An arc plasma method [11] to prepare CrSi 2 nanocrystals by the direct evaporation of chromium in monosilane (SiH 4 ) atmosphere in a closed cycle was reported.…”