Diffusion of Li into Ag

298 to 353 K. That author also claimed that the diffusion of Li 

Ignatiev that Li diffuses into graphite even at liquid nitrogen temperature to leave only a submonolayer of Li on the surface. Diffusion of other alkali metals (Na, K, and Rb) into silver has also been observed by Lambert and co-workers but is significant only at high temperatures ( 870 K). Li diffuses more readily because of its small size. The atomic radii for Li, Na, K, Rb and Cs are 1.55, 1.90, 2.35, 2.48 and 2.67 A respectively. 

It was also observed in this work that Li and/or Li oxides appeared red under Ar ion bombardment. In the energy range of 500 to 2000 eV, the brightness of the red color increased with the ion energy. This provided another means to detect the presence of Li (or Li oxide). In one experiment, a clean Ag substrate was covered by a multilayer Li film (95% by AES) and then exposed to THF at 110 K. After about two hours (one hour for sample warm-up and the other for XPS characterization of the surface), the sample was placed under the Ar ion beam for cleaning. It took about 2 minutes to eliminate the Li layer (or Li oxide layer) on the surface by Ar ion bombardment 

B) (next page) The same spectrum as that for 293 K but shown In a larger scale. The features pointed with arrows were due to plasmon loss. 

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Much attention was paid to diffusion of Li into the silver substrate. Figure 5.5 shows a plot of Auger signal intensity of the Li 52 eV KW peak as a function of temperature for the Ag sample exposed to Li vapor at 113 K. The shape of the curve is similar to that for potassium on Ag(lll). A fast decrease of Li signal occurs at about 330 K, only 30 K higher chan that observed for potassium on Ag(lll). However it is very difficult to attribute this to Li desorption as has been proposed for potassium. This is because the vapor pressure of Ll at 300 K is about 10 Corr, ° four orders of magnitude smaller Chan that of potassium (2 x 10 torr) at the same temperature. A reasonable explanation for the sharp decrease may be due to the diffusion of Li into the Ag bulk. Diffusion of Li into Ag(lll)... 

Although Ag was inert to THF and Li, the diffusion of Li into Ag was significant. Therefore a better substrate is required for future study. There are two possibilities. One is to saturate the Ag by Li. The other is to use a bulk Li sample. But the problem with the latter is that TPD can not be used above 450 K, the melting point of Li. 

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