Oxidation effects on cleaved multiple quantum well surfaces in air observed by scanning probe microscopy

Publisher Website
Google Scholar
Abstract
Atomic force microscopy (AFM) and scanning tunneling microscopy (STM) of quantum well structures can give an independent method of measuring superlattice spacing and uniformity without having to resort to more involved techniques requiring intricate sample preparation. We present the first AFM images of cleaved InGaAs/InP multiple quantum wells and compare them with STM images taken of the same heterostructure. The images were stable in air for over a day. Based on our results, we propose that the mechanism for contrast in our images is due to an oxide layer that grows primarily on the InGaAs wells and not on the InP barriers. Both STM and AFM clearly resolve the individual wells of the heterostructure, although STM measured a larger corrugation than an AFM. STM also exhibited superior lateral resolution of about 2 nm while AFM had a lateral resolution of approximately 6 nm.