Photoelectron holography applied to surface structural determination
- Univ. of California, Berkeley, CA (United States)
Photoemitted electron waves are used as coherent source waves for angstrom-scale holographic imaging of local atomic geometry at surfaces. Electron angular distribution patterns are collected above a sample surface and serve as a record of the interference between source wave and waves scattered from surrounding ion cores. Using a mathematical imaging integral transformation, the three-dimensional structural information is obtained directly from these collected patterns. Patterns measured with different electron kinetic energies are phase-summed for image improvement. Pt (111) surface is used as a model system. A pattern 9.6Å-1 (351 eV) is used to generate a full 3-D image of atom locations around an emitter with nearest neighbors within 0.lÅ of the expected bulk positions. Atoms several layers beyond the nearest neighbors are also apparent. Twin-image reduction and artifact suppression is obtained by phase-summing eight patterns measured from 8.8 to 10.2Å-1 (295 to 396 eV). 32 were measured in 0.2Å-1 steps from 6.0 to 12.2Å-1 (137 to 567 eV) are presented here. Simple models of two-slit interference are compared with electron scattering to illuminate understanding of holographic recording of the structural information. This also shows why it sometimes fails due to destructive interferences. Simple theoretical models of electron scattering are compared to experiment to show the origin of the structural information and the differences that result from atomic scattering and from the source wave. Experimental parameters and their relation to imaging is discussed. Comparison is made to the Pt pattern measured at 351 eV using the simple theoretical model. The remaining data set is also modeled, and the eight appropriate theoretical patterns are used to regenerate the multiple-wavenumber experimental result. A clean Cu (001) surface is also measured and imaged.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC03-76SF00098; AC02-76CH00016; W-7405-ENG-48
- OSTI ID:
- 113807
- Report Number(s):
- LBL--37309; ON: DE96000111
- Country of Publication:
- United States
- Language:
- English
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