In-Situ investigation of surface processes on AlGaAs/GaAs cleavage edges

In-situ observations of surface processes on a freshly cleaved multiquantum well (MQW) cleavage edge allow to obtain chemical information in addition to the surface topography primarily seen in AFM images. Under air the cleavage surface shows a corrugation of about 0.5 nm due to a varying degree of oxidation on the different layers. This oxidation process could be avoided by preparing and imaging the cleavage surface under inert toluene without any contact to ambient atmosphere. After removing the toluene and purging the cell with air, oxidation products developed along the expected AlGaAs layers. A treatment of the oxidized surface with 1 and 10 mmol/L HCl has led to crater formation, which was more pronounced in areas of chemical inhomogeneities and crystallographic defects. 0.1 mol/L HCl has led to an inversion of the original contrast over the whole investigated area, which could be monitored directly in the AFM liquid cell.