THE ELECTRONIC-STRUCTURE OF NACL ADLAYERS ON W(110) STUDIED BY IONIZING-RADIATION

The electronic structure of thin NaCl adlayers deposited on W(110) at room temperature is studied with electron energy loss spectroscopy (EELS), ion impact electron spectroscopy (IIES) with He+ and He2+ ions, metastable impact electron spectroscopy (MIES) with He* atoms, ultraviolet photoelectron spectroscopy (UPS), and AES. It is concluded that NaCl adsorbs molecularly under the studied conditions. The transition from the electronic structure of single adsorbed NaCl molecules to the well-known bulk structure could be studied by following the emergence of bulk properties, such as interband transitions and excitonic excitations, as a function of the NaCl exposure. Our results are consistent with lateral growth of two-dimensional islands during the formation of the first adlayer. The electronic transition processes at the surface induced by electrons as well as He projectiles in different excitation and charge states, in particular the vacancy production in the Cl- 3p valence band, are studied. Their relevance for desorption induced by electronic transitions (DIET) is discussed.