STUDY OF SURFACE PHASE TRANSITION BY HIGH-RESOLUTION

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Angle-resolved high-resolution electron energy loss spectroscopy (HREELS) has been widely applied for the study of energy dispersion curves of surface phonons and surface plasmons. However, wide acceptance angles and the limited angular scanning in a 1 dimensional manner in conventional high-resolution electron energy loss spectrometers has been hindering the detailed studies of phonon anomalies during phase transitions as well as low-dimensional plasmon modes (sheet plasmons, wire plasmons). Also, in situ studies of surface phase transitions during temperature change or during molecular beam epitaxy (MBE) are difficult using the electron beams of conventional HREELS.Here in this project, we have developed a new version of an electron energy loss spectrometer which is capable of measuring high-resolution EELspectra as well as high-resolution diffraction by use of monochromatised slow electron beams during MBE and sample heating [reference 1]. Comprehensive study of phase transition will be performed by correlating possible phonon anomalies with the spot profile/intensity analyses of the diffraction patterns. Also, energy dispersion curves of low-dimensional plasmon modes, which are impossible to measure with conventional spectrometers, can be studied by utilizing its high momentum resolution [reference 2].