Spontaneous ordering of oxide nanostructures

We report the spontaneous formation of uniformly distributed arrays of "tip s" (tall conical hillocks) upon oxidation of palladium (Pd) thin films. The formation of the palladium oxide tips depended on the thickness and granul arity of the Pd film and on annealing and oxidation conditions. As the Pd f ilm thickness increased from 40 to 200 nanometers, the average height of th e tips increased from 0.5 to 1.2 micrometers, their height distribution bec ame broader, and their density decreased from 55 X 10(6) to 12 X 10(6) per square centimeter. Enhanced photoelectron emission from locations correspon ding to the tips suggests their possible use in field emission applications .