Salts and comparable structures consist of ions. In a solid state,
they form ion
lattices. Vibrations
of ion crystals
account, inter alia, for heat
transfer and the diffusion
of sound. Controlling vibrations may enable control of material properties
of crystals. Conceivable innovative applications include thermoelectric nanoelements
that could render human body heat usable as power supply of wearable
electronic devices, or wafer-thin
structures to create sound-proof chambers.
Now, a cooperation of Rutgers
University, a center of nanobiology,
and the University of Graz,
Austria, relying on latest-generation electron microscopy, made ion lattice
vibrations visible for the first time in ultra-high atomic and energetic
resolution in both spatial and spectral dimension, compared to earlier experiments.
The ion lattice of a crystal nanocube was caused to vibrate by targeting it
with an electron
beam. Depending on the spot on the cube hit by the electron, it can trigger
different modes. The more powerful the ion trigger, the more energy is drawn
from the electron beam. The individual modes of vibration can be determined
from the measured loss of energy.
By causing the electron beam to cover the entire
sample, vibrations
of the ion lattice could be determined with topological resolution in the
nanometer scale and with a very high frequency in the Terahertz range. The
phenomena observed under the electron microscope were computer-simulated, which
showed for the first time how ions vibrate at different locations on the cube.
This may open the door to revolutionary developments in steering sound and heat
with heretofore unknown precision.
