STEM Electron Diffraction from Areas less than 30Å; Application to Amorphous Films

Abstract

A technique of selective micro-area transmission electron diffraction has been developed using the Philips 301 TEM with a scanning (STEM) attachment. With this technique we are able to obtain electron diffraction patterns from selected areas less than 30 Å in diameter or about 103 atoms! This is to be compared with the best published results which show selected area diffraction (SAD) from areas at least 100 Å in diameter, approximately 105 atoms, or the conventional SAD techniques applicable to areas down to 2000 Å diameter, approximately 5 x 106 atoms. (The number of atoms was calculated assuming a 50 Å thick film of a f.c.c. structure with ao = 5 Å.) The selected micro-area capability was proven by experimentally obtaining discrete single crystal diffraction patterns from an array of evaporated gold particles some less than 30 Å diameter and separated by 30 Å or less, Fig. 1.