Photoemission Study of Clean and Oxygen Covered Y(0001) Surfaces

• Main Authors: Chung-wei Wang, 王仲偉
• Other Authors: Ku-Ding Tsuei
• Format: Others
• Language: en_US
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/96660645057872794308

碩士 === 國立清華大學 === 物理學系 === 88 === I have performed an angle-resolved photoemission spectroscopy (ARPES) study on clean and oxygen covered Y(0001) single crystal surfaces. Low energy electron diffraction (LEED) and Auger electron spectroscopy (AES) were used to check surface ordering and cleanness. It’s found that a surface state at 0.5eV binding energy (BE) exists in the bulk projected band gap at the surface Brillouin zone center (gamma-bar ). The intensity of this surface state resonates at 38eV photon energy in the normal emission geometry. Its dispersion is nearly flat along gamma-bar M-bar direction and its intensity quickly drops away from the zone center. We assign it to dz2 orbital on top Y atoms. Near M-bar , two sharp peaks, one close to the Fermi level and another at 0.6eV BE, were observed, also showing minimal dispersion with intensity quickly dropping away from M-bar. These two states are in bulk-projected continuum and can be identified as bulk transitions. With successive dosage of oxygen, in addition to the usual large 6eV peak of oxygen 2p and 22eV peak of oxygen 2s, a small peak at 2.3eV grows at the expense of diminishing surface state intensity. This latter peak can be assigned due to oxygen adsorbed on the surface. At 30L dosage to saturate the surface, an additional small peak at 12eV BE can be observed. This peak is clearly related to the growth of Y2O3.