Papers by Author: Béla Pécz

Abstract: Thick, thin films and island of Ca silicide have been grown by Ca deposition onto 500 °C Si (111)7x7 substrates. The crystal structure of the grown layers strongly differs from the known Ca silicides (Ca₂Si, CaSi, Ca₅Si₃, Ca₁₄Si₁₉, CaSi₂). The phonon peaks at 389 and 416 cm^-1 and the interband transition peaks (0.9-1.0, 1.3-1.7 and 2.0-2.5 eV) belongs to another silicide - Ca₃Si₄. Peculiarities of crystal, electronic, and phonon structure and optical properties of the grown Ca silicide films were measured by in situ and ex situ methods permit to state that the formed Ca silicide film has a composition Ca₃Si₄. Heterostructures with embedded Ca₃Si₄ films with different thicknesses have been formed atop the Ca₃Si₄ films by MBE and SPE at 500 °C. The observed density of pinholes with different sizes suggests the Si growth atop the Ca silicide follows a 3D mechanism. Photoluminescence was found first time in Si/Ca₃Si₄/Si (111) heterostructures.

Abstract: 3C-SiC layers were grown on Si substrates using standard precursors (SiH₄ and C3H₈) and by adding methyl trichloro silane (MTS) to the gas phase, with growth temperatures between 1200 and 1300 °C. Characterization of the 3C-SiC layers shows that 3C-SiC grown with MTS has higher polycrystalline and amorphous content as well as lower residual stress.

Abstract: In this work we report on the growth of cubic silicon carbide using CBr₄ and silane as precursors at different C₃H₈/CBr₄ flow ratios. The layers were deposited on 2’’ (001) Si wafers by means of the VPE technique in a horizontal cold-wall reactor with induction heating. The growths were performed at atmospheric pressure, in H₂ atmosphere and involved several steps: Si thermal etching; carburisation; epitaxial growth. Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were performed to observe the film morphology and defects and correlate them with the gas phase composition. Results show that the addition of CBr₄ to the standard SiH₄ and C₃H₈ precursor can change the crystalline nature and the morphology of the grown SiC.

Abstract: 3C-SiC films were grown on Si by VPE using CBr4 as the carbon source, at temperatures ranging between 1100 to 1250°C. XRD, TEM, AFM, and SEM results indicate that the epitaxy proceeds as a 3D growth of uncoalesced islands at low temperature, whereas a continuous layer with hillocks on top is obtained above 1200°C. The shape and faceting of the islands are analyzed by AFM, showing (311) preferred facets.