Surface Degradation during Separation of Crystals from Solution: Minimizing the Shut-off Effect

Deterioration of crystal surfaces during removal from solution prior to observation poses a problem for ex situ (atomic force) microscopy studies. We use potash alum (KAl(SO 4 ) 2 ·12H 2 O) crystals as a model system and investigate the variation of the following parameters: size, orientation, lifting rate, humidity, airflow, rinsing, and pollution. A model to describe the effects occurring during removal is developed and implications for other systems are presented to minimize the discrepancy between in situ and ex situ surfaces. This discrepancy is minimized for potash alum when a crystal is lifted slowly from its solution in a vertical position at a humidity below room humidity and in the absence of air flow.