Phase transitions and excitation spectrum of submonolayer potassium on graphite
- 16 September 1991
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 67 (12) , 1562-1565
- https://doi.org/10.1103/physrevlett.67.1562
Abstract
We have investigated both the structures and the excitation spectra produced by submonolayer adsorption of potassium on the surface of graphite at 90 K, using high-resolution low-energy electron diffraction in conjunction with high-resolution electron-energy-loss spectroscopy. We show that at very low coverages a dispersed potassium phase is formed with a giant K-K spacing (around 60 Å); this phase continuously compresses with increasing adatom density until a critical coverage where a close-packed structure nucleates. Below the critical coverage, charge is redistributed between the alkali and the substrate to increase the frequency of the substrate plasmon mode; above the critical coverage, excitations attributed to metallic potassium are observed.Keywords
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