Monitoring crystal dissolution at nanometer resolution using laser reflectometry

Laser reflectometry has been used for the first time as an in situ real-tim e monitor of the dissolution of the (0 0 1) face of KClO3 crystals into aqu eous solution. During the dissolution process the reflected light was subje ct to constructive and destructive interference caused by the movement of c rystal boundaries. This produced Fabry-Perot oscillations similar to the wi dely exploited phenomenon used in the laser reflectometry-based metrology o f semiconductor surfaces. The method is adapted and theoretical fits to the observed data are presented. The quality of the data allows dissolution ra tes of 100 nm s(-1) to be measured accurately. Data gained by this method w as used to verify the concentration dependence of the dissolution rate and confirm it as a diffusion-controlled mechanism. The hydrodynamic radius of the diffusing ions was found to be 0.224 nm, in agreement with literature v alues. The potential of laser reflectometry for use as an effective probe s ensitive to changes in crystal surface morphology during dissolution has al so been demonstrated. (C) 2000 Elsevier Science B.V. All rights reserved.