Nanoscale phase transformation in Ge₂ Sb₂ Te ₅ using encapsulated scanning probes and retraction force microscopy

Abstract

Encapsulated conducting probes that can sustain high currents are used to study the nanoscale properties of thin-film stacks comprising of a phase-change chalcogenide, Ge2 Sb2 Te5. Scaling studies on this promising candidate for random-access memory devices had thus far required extensive lithography and nanoscale growth. This seriously hampers rapid materials characterization. This article describes the use of two key techniques, an encapsulated conductive probe and its use in retraction mode, whereby the attractive force between tip and sample is used to maintain electrical contact. The effective transformation of nanoscale dots of amorphous Ge2 Sb2 Te5 into the crystalline state is achieved and the electrical conductivity of the transformed structures is probed. The use of retraction force microscopy in a robust manner is demonstrated by reading the conductivity of the crystalline dots. Both these techniques could enable rapid electrical characterization of nanoscale materials, without extensive nanopatterning, thus reducing material development cycles. © 2009 American Institute of Physics.