  We demonstrate that an applied electric field causes piezoelectric distortion
across single molecular monolayers of oligopeptides. We deposited
self-assembled monolayers ~1.5 nm high onto smooth gold surfaces. These
monolayers exhibit strong piezoelectric response that varies linearly with
applied bias (1-3V), measured using piezoresponse force microscopy (PFM). The
response is markedly greater than control experiments with rigid alkanethiols
and correlates with surface spectroscopy and theoretical predictions of
conformational change from applied electric fields. Unlike existing
piezoelectric oxides, our peptide monolayers are intrinsically flexible, easily
fabricated, aligned and patterned without poling.
