Quantum Effects in Low-Energy Electron
Microscopy: a 3-D Probe of Nanostructure
Michael Altman Department of
Physics Hong Kong University of Science andTechnology
The physical properties of thin films exhibit remarkable quantum
size effects due to the discrete quantum well (QW) states that are
caused by electron confinement. Measurements of the elastically
reflected electrons from thin films often reveal intensity peaks at
very low energy that are associated with QW resonances above the
vacuum level. In direct correspondence with the binding energies of QW
states below vacuum, the energies of QW resonances are very sensitive
to film thickness. This talk will focus on the three-dimensional view
of thin film nanostructure that is obtained from highly laterally
resolved measurements of QW resonances in low energy electron
microscopy. Details of the buried interface and strained layer
spacings in coherently strained Ag films on the W(110) surface are
determined accurately by dynamical theory analysis of the intensity
peaks associated with QW resonances. Information on unoccupied
band structure is also obtained from a phase accumulation model
analysis of QW resonances in Ag films on the Fe(100) surface. The
surface morphology of these films following thermal decomposition is
found to be governed by minima in the global energy landscape that are
defined by QW states at the belly of the Ag Fermi surface in the [100]
direction. In collaboration with C.T. Chan, W.F. Chung, Y.J. Feng, K.L. Man,
H.C. Poon, S.Y. Tong, and Z.Q. Qiu