48
3 Probing Methods: STM/S, PES, APECS, XAS, ZPS
chemisorption, the initially empty DOS peaking at 0.5~1.8 eV above E F is partially occupied by the Cu
P electrons, which weakens the intensity of the unoccupied
states. Meanwhile, the lone pair of O
2− creates additional DOS features at −2.0 eV.
The presence of the lone pair and the dipole states is the same to that detected using
angular-resolved PES and using the de-excitation spectroscopy of metastable atoms
of the same surface [8].
3.3 PES and AES: Valence- and Core-Band Shift
3.3.1 General Description
Angular-resolved PES means the PES data collection by changing the azimuth angle
between the incident beam and often the <10> directional reference in the real lattice
space or the X direction in the Brillouin zone, as shown in Fig. 3.3. The angular
variation only resolves the anisotropy of the crystal structure and the valence electrons
distributed in real space, particularly for the reconstructed surfaces. This technique
has formed the state-of-art means for investigating the electronic structure of high-T C
superconductors and topological insulators [9, 10].
Fig. 3.3 Angle-resolved photoemission spectroscopy (ARPES): a the geometry of an ARPES
experiment in which the emission direction of the photoelectron is specified by the polar (θ) and
the azimuthal (φ) angles and b the Brillouin zones of a two dimensional square reciprocal lattice,
which has the same symmetry of the real lattice [11]
3 Probing Methods: STM/S, PES, APECS, XAS, ZPS
chemisorption, the initially empty DOS peaking at 0.5~1.8 eV above E F is partially occupied by the Cu
P electrons, which weakens the intensity of the unoccupied
states. Meanwhile, the lone pair of O
2− creates additional DOS features at −2.0 eV.
The presence of the lone pair and the dipole states is the same to that detected using
angular-resolved PES and using the de-excitation spectroscopy of metastable atoms
of the same surface [8].
3.3 PES and AES: Valence- and Core-Band Shift
3.3.1 General Description
Angular-resolved PES means the PES data collection by changing the azimuth angle
between the incident beam and often the <10> directional reference in the real lattice
space or the X direction in the Brillouin zone, as shown in Fig. 3.3. The angular
variation only resolves the anisotropy of the crystal structure and the valence electrons
distributed in real space, particularly for the reconstructed surfaces. This technique
has formed the state-of-art means for investigating the electronic structure of high-T C
superconductors and topological insulators [9, 10].
Fig. 3.3 Angle-resolved photoemission spectroscopy (ARPES): a the geometry of an ARPES
experiment in which the emission direction of the photoelectron is specified by the polar (θ) and
the azimuthal (φ) angles and b the Brillouin zones of a two dimensional square reciprocal lattice,
which has the same symmetry of the real lattice [11]