Influence of Nanostructuration on the Vibrational, Electronic, and Optical Properties of CrSi₂ Thin Films

Abstract

We report a detailed experimental investigation of the influence of the formation of nanocrystallites on the vibrational, electronic and optical properties of CrSi 2 thin films. Both amorphous and nanostructured thin films were investigated by means of electrical resistivity, Hall effect measurements as well as Raman and infrared spectroscopies. We show that both types of films exhibit a semiconducting-like behavior, with the notable difference that the high defect concentrations in amorphous films act as hole donors, modifying the electronic band structure and optical constants. The effect of the film thickness on electrical properties is well captured by the Fuchs-Sondheimer model indicating a decrease in the charge carrier mean free path, likely due to the formation of amorphous/nano-crystallite interfaces that contribute to strongly scatter the charge carriers. Raman spectroscopy performed on nano-crystallized thin films evidences the presence of a Raman-active mode at 229 cm -1 and confirms DFT calculations predicting a mode at 248 cm -1 , the observation of which had remained elusive so far in polycrystalline CrSi 2 . Measurements of the refractive index and dielectric constants of amorphous thin films show a very high refractive index in the mid-IR range. Our results illustrate how the controlled growth of nano-crystallites can be used to tailor the electronic, vibrational and optical properties of amorphous thin films.

Ion implantation effects on the microstructure, electrical resistivity and thermal conductivity of amorphous CrSi2 thin films

“…These nanocrystallites introduce interfaces that can selectively scatter carriers. The increase in electrical resistivity in partially crystallized CrSi 2 thin films was also observed by Moll et al [57]. Its occurrence is also credited to an additional interface scattering mechanism produced by the presence of nanocrystallites.…”

Textured Stainless Steel as a Platform for Black Mg2Si/Si Heterojunction Solar Cells with Advanced Photovoltaic Performance

“…To clarify the role of Fe 3 O 4 in suppressing interdiffusion of Si, Cr and Fe atoms, Raman spectra were recorded for room-temperature deposited and high-temperature grown (up to 700 °C) Si layers on b-SS/Fe 3 O 4 templates. No Fe and Cr silicide-related phonon lines [ 43 , 44 , 45 ] were observed for all tested samples, as can be seen in Figure 3 d. Moreover, these measurements permitted optimization of the growth temperature for the Si cover layers. For instance, the higher the growth temperature, the fewer a-Si and polycrystalline fractions in deposited Si layers were observed.…”

Phases and Interfaces in the Cr–Fe–Si Ternary System: X-ray Diffraction and Electron Microscopy Study

“…See, for instance, the studies and syntheses [15][16][17][18][19][20][21][22][23]. It should be noted that the structure of binary iron or chromium silicides has been studied separately either at the micro-or nano-metric scale in the case of thin films or nanocrystals [24][25][26][27][28][29].…”