Open AccessNanoscale crystallization of phase change Ge 2 Sb 2 Te 5 film with AFM lithography
Author(s) -
Kim JunHo
Publication year - 2010
Publication title -
scanning
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.359
H-Index - 47
eISSN - 1932-8745
pISSN - 0161-0457
DOI - 10.1002/sca.20201
Subject(s) - materials science , crystallization , lithography , amorphous solid , nanoscopic scale , optoelectronics , electric field , nanotechnology , nanowire , crystallography , chemistry , physics , organic chemistry , quantum mechanics
We have made nanoindents on Ge 2 Sb 2 Te 5 (GST) films using electric field‐assisted atomic force microscope (AFM) lithography. GST shows increase of material density and electric conductivity as it changes from amorphous to crystalline phases. By applying electric field between AFM probe‐tip and GST surface, nanoscale crystallization could be induced on tip contact area. As the crystallized GST exhibits increase of material density, that is to say depression of volume, nanoindented surface with crystallization is created on host amorphous GST ( a ‐GST) film. For the AFM lithography, a highly conductive tip, which showed voltage‐switching characteristics in current–voltage spectroscopy of GST film, was found to be very suitable for recording and sensing crystallized nanoindents on the GST film. By varying sample bias voltages, we performed nanoscale crystallization, and measured the nanostructured film in AFM conductance‐image ( C ‐image) mode and topography‐image ( T ‐image) mode, simultaneously. Two types of crystallized wires were fabricated on ( a ‐GST) film. Type‐I was sensed in only C ‐image, whereas Type‐II was sensed in both C ‐image and T ‐image. These nanowires are discussed in terms of crystallization of GST and sensitivity of current (or topography) sensing. By repeated lithography, larger size of nanoindented wires were also produced, which indicates line‐dimension controllability of AFM lithography. SCANNING 32: 320–326, 2010. © 2010 Wiley Periodicals, Inc.