Direct nanoscale 3D characterisation of Ge-Sb-Te and Ge-Te phase change films

I. Grishin, O.V. Kolosov
Lancaster University, UK

Keywords: phase change materials, ultrasonic force microscopy, SPM, BEXP, ion beam


DC magnetron sputter-deposited Ge-Sb-Te and Ge-Te based phase change thin films were investigated via a variety of Scanning Probe Microscopy techniques. Micron and sub-micron crystalline and amorphous bit patterns were induced with laser heating and conductive probe microscopy. Due to the probe-sample surface contact constriction a novel Beam Exit X-Section Polishing Technique, or BEXP, was implemented to produce atomically flat sections of the different phase films in order to enable sub-surface, or 3D, profiling and property mapping of these bits. A PMMA Ion Beam masking concept allowed for 2-5 nm in-depth resolution to be achieved for the studied films. The geometric arrangement of the processed sample surface and section prevents any damage to be dealt to the bits, thus allowing for simultaneous surface and sub-surface investigation of the same area. Results on local nanomechanical elasticity and morphology are provided by sub-sequent Ultrasonic Force Microscopy (UFM) imaging.