M. Morales Rodriguez

Comparative investigation of photoluminescence of silicon wire structures and silicon oxide films

Photoluminescence spectra and their dependence on temperature as well as Raman scattering spectra and Atomic Force Microscopy investigations have been used to study the peculiarities of the red photoluminescence band in low-dimensional Si structures, such as porous silicon and silicon oxide films. It has been shown that the red photoluminescence band of porous silicon is complex and can be decomposed into two elementary bands. It was discovered that elementary band intensities depend very much on surface morphology of porous silicon. The same positions of the photoluminescence bands are also observed in silicon oxide films for different oxide composition. Comparative investigation of the PL temperature dependences in porous silicon and silicon oxide films indicates that silicon-oxide defect related mechanisms of some elementary photoluminescence bands are involved.

Ballistic effect and photoluminescence excitation in porous silicon

Abstract This article presents experimental results supporting the role of the ballistic transport in strong “red” photoluminescence (PL) of porous silicon (PSi). It is shown that this PL band connects with emission of oxide-related defects at the Si/SiO x interface. The dependence of an intensity of interface-defect related photoluminescence on morphology and the average size of Si nano-crystallites on porous silicon surface has been investigated. The peculiarities of Raman and PL excitation spectra in dependence on the average size of Si nano-crystallites have been studied as well. Confirmation of ballistic effect role is important for understanding the photoluminescence mechanism in Si nano-crystallites and successful application of silicon low-dimensional structures in optoelectronics.

Ballistic regime and photoluminescence excitation in Si wires and dots

Abstract This article presents the experimental results supporting the role of the ballistic effect in strong “red” photoluminescence (PL) of silicon low-dimensional structures: wires and dots. The peculiarities of the PL and PL excitation spectra in dependence on the morphology of porous silicon layers and the size of Si nano-crystallites have been investigated. The porous silicon layers with different morphology were created by the variation of preparation regimes. The size of Si nano-crystallites is estimated using the atomic force microscopy and Raman scattering methods. The mechanisms of PL and PL excitation in Si low-dimensional structures are discussed as well.

Si Wire Light Emission Changes During Si/SiO x Interface Formation

Photoluminescence (PL), PL excitation, Raman scattering, IR absorption spectra as well as PSi surface morphology, have been studied as a function of Si/SiO x interface formation during PSi ageing in ambient air with the aim to reveal a PL mechanism. It is shown that fresh- prepared PSi layers created at low values of the anodization current Ia is characterized by “red” emission band centered at 1.72 eV, while the samples prepared at higher values of Ia have “orange” PL band centered at 2.00 eV. During oxidation in ambient air two processes take place at the PSi ageing: the oxidation of small size Si nano-crystallites up to their disappearing and the change of silicon oxide composition at the Si/SiO x crystallite surface. These processes initiate changes in PL and PL excitation spectra. The peak position of “red” PL band shifts to the high-energy up to 1.80-1.85 eV while the “orange” band does not change essentially.