Contact potential measurements of the adsorption of alkali metals on Ta(llO) and W(100) crystals

摘要: Abstract The adsorption of Cs, K, and Na on Ta(110) Cs K W(100) has been studied under ultrahigh vacuum conditions using an ion gun to deposit the alkali metals electron measure resulting change in work function, Δφ. Since iondeposition technique leads a quantitative determination n , number (coverage) atoms adsorbed per cm 2 it was possible obtain data Δφ versus . crystal at room temperature (≈ 300°K) during deposition measurements, but flashed ≈ 2500°K between runs desorb impurities. principal observations are: (i) initial dipole moments, micro O determined from slope limit → O, are fair agreement with those based classical image-potential model; (ii) for or Ta(110), minimum functions observed showed no apparent dependence substrate structure properties ; (iii) high coverage limit, approximately equal values corresponding bulk metal crystals; (iv) maximum coverages densities surface having same orientation as substrate. last two points suggest that, tend toward BCC surface, although adsorbate unit cell need not be coherent that