Structural Investigation of Electrochemically Etched Silicon

Abstract

Small-angle neutron scattering (SANS) measurements of four electrochemically etched, porous silicon (PS) samples have been performed over a wide wavevector transfer (Q) range. The intermediate to high Q results can be modeled with a non-particulate, random phase model. Correlation length scales on the order of 1 to 2 nm thought to characterize the PS skeleton have been deduced from the SANS data. The microstructural anisotropy was studied tilting two of the samples with respect to the neutron beam. These samples exhibited an asymmetric scattering pattern at intermediate Q (0.1 ≤ Q ≤ 0.6 nm⁻¹) in this condition. Photoluminescence spectra from all four samples have been recorded as well. A correlation appears to exist between the SANS and photoluminescence measurements. An x-ray diffraction measurement of one sample demonstrates that the PS layer retains the silicon lattice structure. Significant peak broadening is observed that we interpreted as a quasi-particle size effect The PS particle size calculated from the x-ray diffraction measurement is equal to the correlation length obtained in the SANS measurement.