Phase contrast imaging of nanocomposites and molecularly thick lubricant films inmagnetic media

Abstract

The sources of phase angle contrast in measurements using atomic forcemicroscopy and the effect of free amplitude and setpoint on phase angle contrastimages of several nanocomposites and molecularly thick lubricant films have beenstudied. Phase angle contrast depends on viscoelastic properties and interfacialadhesion, as well as on the selection of free amplitude and setpoint. Phase anglecontrast is a stronger function of viscoelastic properties with increasing freeamplitude or setpoint. However, the effect of adhesion on phase anglecontrast becomes more dominant at low free amplitudes or setpoints. As aresult of competition between viscoelasticity and adhesion, the phase anglecontrast may flip with changes in free amplitude and setpoint. A comparisonbetween topographic, friction and phase angle images shows that phase angleimages give information that cannot be obtained from topographic orfriction images. By optimizing free amplitude and setpoint, the phase anglecontrast imaging technique can be used to detect changes in compositionacross polymer nanocomposites and molecularly thick lubricated surfaces.