| AVS 60th International Symposium and Exhibition | |
| Surface Science | Tuesday Sessions |
| Session SS-TuP |
| Session: | Surface Science Poster Session |
| Presenter: | A.A. Padama, Osaka University, Japan |
| Authors: | A.A. Padama, Osaka University, Japan W.A. Diño, Osaka University, Japan H. Kasai, Osaka University, Japan |
| Correspondent: | Click to Email |
In surface systems, work function is an important property that indicates the required energy necessary to remove an electron from solid to vacuum. This property is essential for different applications that require electron emission such as in optoelectronic and thermionic devices and in ion productions for plasma application [1-3]. Low work function system is desired and is usually realized by introducing adsorbate which can modify the electronic properties of the surface under investigation [4-6]. It is therefore fundamental to understand the work function lowering and establish indicators that could possibly predict the changes in work function among materials.
In this present work, we investigated the variation of work function in alkali metal (Li, Na, K, Rb, Cs) / W(110) surface systems at different alkali metal coverage by performing density functional theory-based calculations. For all cases, work function rapidly decreases and reaches minimum value at an optimum coverage and rises again with further increase in alkali metal coverage (Fig. 1). The variation of work function values was analyzed using the density of states projected on the adsorbed alkali metal atoms. For K, Rb, and Cs, we observed that the minimum work function is achieved when the states corresponding to the interaction of the adsorbed alkali metals are partially occupied. Further increase in the coverage shifts the states to the occupied region and signifies the interaction among the adsorbed alkali metals which causes the increase in work function. For Li and Na which have smaller atomic radius, work function starts to increase when these states begin to shift in the occupied region. We conclude that the electronic profile of the system is a simple yet good indicator in predicting work function variation in alkali metal – W(110). The details of our work will be presented in the symposium.
References:
[1] D. Otálvaro, T. Veening, G. Brocks, J. Phys. Chem. C 116 (2012) 7826-7837.
[2] M. Bacal, Chem. Phys. 398 (2012) 3-6.
[3] M. Lin, R. Jao, W. Lin, J. Vac.Sci. Technol. B 26 (2008) 821-825.
[4] H. Nakanishi, H. Kasai and A. Okiji, Surf. Sci. 197, 515 (1988).
[5] H. Nakanishi, H. Kasai and A. Okiji, Surf. Sci. 216, 249 (1989).
[6] H. Ishida and K. Terakura, Phys. Rev B 36, 4510 (1987).