In search of perfection: understanding the highly defect-selective chemistry of anisotropic etching.

Anisotropic etchants selectively reveal a specific crystallographic plane. Although prized industrially, these etchants are poorly understood because they target specific defect sites on a surface. New methods, which rely on a combination of scanning tunneling microscopy, kinetic Monte Carlo simulations, and infrared spectroscopy, have been developed to quantify these reactions. By correlating the measured reaction rates with the structure of the defects, information about reaction mechanisms can be obtained. These techniques have also been extended to allow for the quantification of impurity reactions such as the reaction of dissolved O2, and of nonetching additives, such as alcohols. A complementary macroscopic technique, which utilizes microfabricated arrays of miscut surfaces to measure orientation-dependent kinetics, is also described.