Properties of CrSi2 nanocrystallites grown in a silicon matrix

Semiconducting CrSi2 nanocrystallites (NCs) were grown by reactive deposition epitaxy. The NCs were covered by 100 nm of epitaxial silicon. Their structure, morphology and optical properties were investigated by transmission electron microscopy (TEM), atomic force microscopy (AFM), ultraviolet photoelectron spectroscopy (UPS) and optical reflectance spectroscopy (ORS). The preservation of the CrSi2 phase has been justified by UPS, by ORS, and by TEM measurements. The distribution of Cr was investigated by Rutherford backscattering (RBS). The electrically active defects were investigated by deep level transient spectroscopy (DLTS). The crystal structure of the NCs nucleated near the deposition depth is identified by high-resolution TEM as hexagonal CrSi2. Energy filtered TEM shows that most of the Cr is localized in the three-dimensional (3D) NCs. RBS shows that the concentration of Cr is appropriate for the deposited quantity. In the 0.1 nm Cr sample most of the Cr is localized near the surface; in the 0.6 nm Cr sample the concentration increases at the depth of Cr deposition, while in the 1.5 nm Cr sample the excess Cr is localized near the deposition depth. DLTS Arrhenius plots give activation energies of the defects appropriate for Cr contamination, however these defects may be related to the CrSi2 NCs.