Study of inhomogeneity in thickness of LR 115 detector with SEM and Form Talysurf

Long-term measurements of radon progeny concentrations using Solid-State nuclear tract detector are being actively explored. These measurements depend critically on the thickness of the removed layer during etching. Scanning electron microscope (SEM) observations have identified irregularities in etched LR 115 detectors, such as detachment of the active layer from the substrate and formation of air gaps in the substrate. After discarding these irregularities, by using 'Form Talysurf' surface profile measurements, the thickness of the active layers for the LR 115 detector are found to be 11.8±0.2 and 5.0±0.4 μm before and after 2 h of etching, respectively. The coefficient of variation has thus risen from 1.7% to 8.0% on etching. The increased inhomogeneity is explained by the formation of track-like damages, which have been observed using Form Talysurf, SEM, optical microscope and atomic force microscope. With this relative large coefficient of variation, the thickness of the active layer in the LR 115 detector cannot be assumed to be homogeneous in general, and the associated uncertainties should be considered carefully when the detector is used for alpha spectroscopy