Abstract:The InAs quantum structures were formed in silicon by sequential ion implantation and subsequent thermal annealing. Two kinds of crystalline InAs nanostructures were successfully synthesized: nanodots (NDs) and nanopyramids (NPs). The peaks at 215 and 235 cm −1 , corresponding to the transverse optical (TO) and longitudinal optical (LO) InAs single-phonon modes, respectively, are clearly visible in the Raman spectra. Moreover, the PL band at around 1.3 µm, due to light emission from InAs NDs with an average diameter 7 ± 2 nm, was observed. The InAs NPs were found only in samples annealed for 20 ms at temperatures ranging from 1000 up to 1200°C. The crystallinity and pyramidal shape of InAs quantum structures were confirmed by HRTEM and XRD techniques. The average size of the NPs is 50 nm base and 50 nm height, and they are oriented parallel to the Si (001) planes. The lattice parameter of the NPs increases from 6.051 to 6.055 Å with the annealing temperature increasing from 1100 to 1200°C, due to lattice relaxation. Energy dispersive spectroscopy (EDS) shows almost stoichiometric composition of the InAs NPs. PACS

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The structure of porous Si samples prepared by conventional photoexcited electrochemical etching in hydrofluoric acid solution is presented. Strain enhanced cracking was evidenced at the surface of the sample, which was synthesized at higher incidence angle of light. Combined modes of carbon-fluorine and/or oxygen related impurities, and silicon-oxides are revealed from Fourier transform infrared investigation. A resonant feature at ∼467 nm, originating from a strong coupling of localized excitons at the Si/SiO2 interfacial states and Si–O vibrational modes, is examined during photoluminescence measurements for an excitation wavelength of 320 nm. Furthermore, the appearance of luminescence bands in the range 378–412 nm is discussed in the light of a quantum confinement assisted radiative recombination of electrons and holes at impurity related defects or at the vacancies of neutral oxygen.