Polarized photoluminescence of $nc$-Si–SiO$_{x}$ nanostructures

The effect of photoluminescence polarization memory in $nc$-Si–SiO$_{x}$ light-emitting structures containing Si nanoparticles ($nc$-Si) in an oxide matrix is for the first time studied. The polarization properties of continuous and porous nanostructures passivated in HF vapors (or solutions) are studied. It is established that the polarization memory effect is manifested only after treatment of the structures in HF. The effect is also accompanied by a shift of the photoluminescence peak to shorter wavelengths and by a substantial increase in the photoluminescence intensity. It is found that, in anisotropic $nc$-Si–SiO$_{x}$ samples produced by oblique deposition in vacuum, the degree of linear photoluminescence polarization in the sample plane exhibits a noticeable orientation dependence and correlates with the orientation of SiO$_x$ nanocolumns forming the structure of the porous layer. These effects are attributed to the transformation of symmetrically shaped Si nanoparticles into asymmetric elongated $nc$-Si particles upon etching in HF. In continuous layers, $nc$-Si particles are oriented randomly, whereas in porous structures, their preferential orientation coincides with the orientation of oxide nanocolumns.