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