Alkali co-adsorption and surface coverage effects on electron-stimulated desorption (ESD): CO and NO on Ni(111)

✍ Scribed by F. Bozso; Ph. Avouris

• Publisher: Elsevier Science
• Year: 1986
• Tongue: English
• Weight: 628 KB
• Volume: 125
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(86)87093-2

✦ Synopsis

We present results on the effect of potassium co-adsorption on the ESD from CO and NO on Ni(ll1) at 90 K. K co-adsorption strongly affects the yields of positive ions and alters their electron beam energy dependence. At a K-coverage of 6, = 0.25 and saturation coverages of CO or NO, the strong O+ ESD threshold associated with 0 Is ionization is eliminated. We attribute this to increased metal + C0(2~*) electron back-donation upon K addition which screens the 0 1s hole, and reduces the excitation probability of shake-off/shake-up processes responsible for O+ ESD. For fixed K-coverage, the ESD yields depend on adsorbate coverage. For 8, = 0.25 and CO or NO exposures < 1 L the adsorbate state is ESD inactive at both valence-and core-excitation energies.