Alkali adsorption

Figure 2.5. Potassium (a) and sodium (b) induced work function changes for adsorption at 100 K (open circles) and after annealing to 350 K or upon alkali adsorption at 350 K (open triangles) on Al single crystals.23 Reprinted with permission from the American Vacuum Society.

S. Surnev, and M. Kiskinova, Formation of Patchy Surface Overlayers Alkali Adsorption and Alkali Cabon Monoxide and oxygen coadsorption on Ru(001) and Ru(10l 0 Appl. Phys. 46, 323-329 (1988). 

Finally, DFT calculations [83] for different alkali coverages also provided an explanation for another unexpected property of alkali adsorption on aluminum, namely that many of the structure develop by island growth, even when no intermixing occurs with the substrate [51]. It was found that depolarisation of the adsorbate dipoles occurs already at quite low coverages, thereby reducing the tendency to form dispersed structures. 

Alkali Adsorption and Co-Adsorption with Alkalis on Metal Surfaces... 

ALKALI ADSORPTION AND CO-ADSORPTION WITH ALKALIS ON METAL SURFACES... 

Figure 2.72. Free-electron model of alkali adsorption.

Lang, N.D. "Theory of Alkali Adsorption on Metal Surfaces", in Physics and Chemistry of Alkali Metal Adsorptioa Bonzel, H P., Bradshaw, A.M., Ertl, G. (eds.), Amsterdam Elsevier, 1989, p. 11-24. 

On other surfaces, notably Pt(l 11), Pd(l 11) and K on Rh(l 11), the adsorption site is hep for both the p(2x2) and the (V3xV3)R30° phases. In the case of Pt(111), DFT calculations [98M1] have suggested that the origin for the hep site preference is due to the tilting of the electron density due to the J-states toward the hep sites, leading to an added attraction in those sites which is not present for the fee sites. This picture is consistent with the results for alkali adsorption on Rh(lll) and Pd(lll), where hep sites are also occupied in the p(2x2) structure. It is also consistent with the observations of fcc-site occupation for the p(2x2) structure in the systems of K and Rb on Ru(OOOl), and K, Rb and Cs on Ag(lll), where the effect of the J-electrons may be significantly less. 

More complex multilayer intermixed structures have also been observed and characterized for alkali adsorption on the (100) surfaces of Cu, Ag, Af Ni and Au, and the (111) surfaces of A1 and Cu [98T1]. The fcc(llO) surfaces of many metals also have been observed to undergo significant reconstructions upon alkali adsorption, and the geometries of many of these substrate reconstructions have been measured [96D1,98T1]. 

Alkali adsorption systems which undergo condensation. The information given iiKludes the coverages at which they eondense, the stracture they condense into, and the temperature. LT denotes a low... 

Alkali metals on certain metal surfaces have a propensity to intermix with the substrate surface atoms, often producing complex surface alloy stractures. A recent review of the conplex structures formed by alkali adsorption on fee surfaces describes many of these systems [98T1]. These stractures will be discussed in chapter 4.1 in this volume here we provide a smnmary. The intermixed stractures that have been observed are all activated stractures i.e. their formation requires some thermal energy. The temperatures required to form these stractures range fi om about 200 K to 400 K. Some general features of the intermixed structures studied thus far were smnmarized in Reference [98T1] as ... 

Zirl DM, Garofalini SH (1989) Mechanism of alkali adsorption on silica surfaces. Phys Chem of Glass 30 155-159... 

Y., and Somorjai, G. (1986). Studies of alkali adsorption on Rh(lll) using optical second-harmonic generation. Surface Science, 172 466 - 476. 

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