Imaging nanostructures with coherent phonon pulses

We demonstrate submicron resolution imaging using picosecond acoustic phonon pulses. High-frequency acoustic pulses are generated by impulsive thermoelastic excitation of a patterned 15-nm15-nm-thick metal film on a crystalline substrate using ultrafast optical pulses. The spatiotemporal diffracted acoustic strain field is measured on the opposite side of the substrate, and this field is used in a time-reversal algorithm to reconstruct the object. The image resolution is characterized using lithographically defined 1-micron1-micron-period Al structures on Si. Straightforward technical improvements should lead to resolution approaching 45 nm45nm, extending the resolution of acoustic microscopy into the nanoscale regime.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71146/2/APPLAB-84-25-5180-1.pd