Mechanical microthinning: An alternative to chemical or ion-beam thinning for TEM specimen preparation

Abstract

Recent publications(1-3) have indicated a number of cautions to be observed when interpreting electron transparent foils prepared by ion beam thinning. Some of the cited problems which could be encountered are: atom rearrangement creating new concentration gradients, final foil thickness variations due to original surface irregularities, specimen inhomogenieties or selective rates of etching by the ion beam, and blind side redeposition of matter when single gun ion beam thinning is employed to thin from the reverse side to preserve surface coated layers. Publications 2 and 3 both indicate that mechanical ‘prethinning’ the specimen discs to ≤20/μm prior to ion thinning in a device called a Dimpler(VCR Group, San Francisco, Cal.) would eliminate or highly retard many of the stated problems.