Atomic force microscopy and scanning electron microscopy study of MgO(110) surface faceting

Phosphoric- and nitric-acid etching of the MgO(110) surface generates vicinal faceting in both the 〈001〉 and 〈110〉 directions. Vacuum annealing (to 1000°C) does not introduce thermal faceting, and does not alter the chemical-etch morphology. Three types of acid-induced faceting (early-stage pits, later-stage grooves, and inverted trapezoidal pyramids) are seen as a function of etching time. Facet-angle analysis by atomic force microscopy (AFM) and scanning electron microscopy (SEM) shows the etch morphology to be vicinal, with angles in the range of 9° to 23°, not the low-energy {100} planes expected from minimization of surface energy.