Biomedical subjects

Hongzhou Ma

Publications and source records attributed to Hongzhou Ma.

2 recordsLinked to original sources

PubMed2006

GHz apertureless near-field scanning optical microscopy of ferroelectric nanodomain dynamics.

Nanoscale domain dynamics of (Ba,Sr)TiO(3) thin films are investigated at microwave frequencies with a home-developed GHz-frequency apertureless near-field scanning optical microscope (GHz-ANSOM). Using a microwave phase-modulation technique, we decoupled topographic artifacts from the optical signal, providing an enhanced and background-free temporal response. Interleaved acquisition of images taken at sequential time intervals provides amplitude and phase information about the electrooptic response at <50 nm spatial resolution and <10 ps temporal resolution. The local microwave response is highly nonuniform in both the amplitude and the phase.

Journal Article↗

PubMed2003

Lattice-scale domain wall dynamics in ferroelectrics.

Ferroelectric domain walls are atomically thin, and consequently their dynamics are sensitive to the periodic potential of the underlying lattice. Despite their central role in domain dynamics, lattice-scale effects have never been directly observed. We investigate local domain dynamics in thin film ferroelectrics using atomic-force microscopy. Upon combined dc and ac electric driving, fluctuations in the local piezoresponse are observed. Fourier analysis of the fluctuations reveals the presence of narrow band and broad band noise, and Barkhausen jumps. The narrow band noise is attributed to dynamics associated with lattice-scale pinning and is reproduced by a simple physical model.

Journal Article↗