Scanning probe microscopes (SPM’s) are indispensable in modern nanoscale science but ability of SPM’s to look below the surface is unavoidably limited. In spite of developments based on Ultrasonic Force Microscopy (UFM) a true subsurface imaging in stiff solid state nanostructures has yet to be reliably demonstrated. Moreover, some misconceptions still exist as to how the wave propagation of ultrasonic waves contributes to the imaging. In this paper we produce first unambiguous UFM imaging of internal morphology of two high stiffness solid state nanostructures – 50 nm thick graphite slabs and iii-v InAs/GaAs semiconductor quantum dot structures under atomically flat GaAs capping layer. Furthermore, we show that the imaging mechanism in reported so far subsurface imaging methods is indeed the elastic field produced by the indention of dynamically stiffened cantilever-tip system, with detection due to the nonlinear tip-surface interaction, and lateral resolution for subsurface imaging is on the same order as the depth of subsurface feature. We show that phase information available in HFM for subsurface mapping produces only a minute correction due to a very large scale difference of ultrasonic wavelengths (~mm) and the imaged volumes (~100 nm). http: www.nano-science.com.
Journal: TechConnect Briefs
Volume: 1, Nanotechnology 2012: Advanced Materials, CNTs, Particles, Films and Composites (Volume 1)
Published: June 18, 2012
Pages: 24 - 26
Industry sector: Advanced Materials & Manufacturing
Topics: Materials Characterization & Imaging