LAUSR

ABSTRACT: In this paper, the structural, optical and thermal properties of n-type (100), p-type (100) and (111) mesoporous silicon (MePSi) are reported. The mesoporous silicon was prepared by an electrochemical process from bulk silicon wafer. Depending on the etching depth, analyses show that the porosity of p-type (111) increased by 32 to 40% compared to p (100) which, in turn, increased by 22 to 48% compared to n-type (100). The structure morphology and the abundance of Si-Ox and Si-Hy also depended heavily on the type and crystal orientation of MePSi. The thermal properties of the MePSi layers such as thermal conductivity (κ), volumetric heat capacity (ρCp) and thermal contact resistance (Rth) were determined using the pulsed photothermal method. The thermal conductivity of bulk silicon dropped sharply after etching, decreasing by more than twenty-fold in the case of n-type (100) and by over forty-five fold for p-type (100) and (111). According to the percolation model depending on both porosity and phonon confinement, the drop in thermal conductivity was mainly due to the nanostructure formation after etching. Thermal investigations showed that the volumetric heat capacity (ρCp) followed the barycentric model which depends mainly on the porosity. The thermal contact resistances of MePSi layers were estimated to be in the range of 1x10-8 to 1x10-7 K⋅m2⋅W-1.