摘要:

In contrast to elemental materials, sputtering of alkali halides occurs due to few distinct mechanisms which, in general, can be classified as electronic- and cascade-type processes. In recent years these processes have been the subject of numerous experimental studies. In this paper we review the available experimental data and present current views on the mechanisms leading to the emission of ground- and excited-state neutral particles and ions during low-energy ion-stimulated desorption of alkali halides.

ISSN:1042-0150    

DOI:10.1080/10420159408218861

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Sputtering of CeF3and LaF3surfaces by singly charged rare gas ions (Ar+, He+, Xe+) with impact energies between 100 and 1500 eV has been performed. The emission of Ce+, La+and F+was measured by quadrupole mass spectrometer. The yield of Ce+, La+decreases with decreasing impact energies; under ∼160 eV this decrease becomes very rapid compared with the decrease of F+yield. For He+bombardment a higher yield of F+was observed than for Ar+bombardment. The F+yield for Xe+bombardment is even lower than for Ar+. Therefore an electronic effect has to be assumed as a cause of the F+emission enhancement as in the case of LiF. The quantitative differences between the data on LaF3, CeF3and on LiF have been explained using our results on valence band measurements of rare earth trifluorides by XPS method.

ISSN:1042-0150    

DOI:10.1080/10420159408218862

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Recent advances in photon- and electron-stimulated desorption of excited alkali-metal atoms and CN molecules are discussed. The role of defects created by photon and electron irradiation leading to surface metalization is particularly emphasized in the desorption mechanisms. Two mechanisms are proposed for the creation of excited alkali-metal atoms: (1) appropriate to the low-temperature regime, the first mechanism assumes that surface exoergic reactions between alkali-metal dimers and halogen atoms produce desorbed excited alkali-metal atoms, the surface reactants being formed by radiation-initiated defect processes, and (2) the second mechanism assumes that the gas-phase excitation of ground-state alkali-metal atoms by primary electrons produce the excited alkali-metal atoms. The mechanism responsible for CN desorption may be described in three steps: (1) pre-irradiation produces alkali-metal rich surfaces via defect-mediated processes, (2) when the surface is exposed to CO2and N2, surface reactions generate CN molecules bound to the alkali-rich surface, and (3) electron or photon bombardment induces the desorption of excited CN molecules from the surface by direct bond-breaking.

ISSN:1042-0150    

DOI:10.1080/10420159408218863

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The electronic structure of thin LiF adlayers deposited on W(110) at room temperature is studied by ion impact electron spectroscopy (IIES) with He+ions, metastable impact electron spectroscopy (MIES) with He* atoms, ultraviolet photoelectron spectroscopy (UPS), and to some extent with electron energy loss spectroscopy (EELS). The transition from the electronic structure of single adsorbed molecules to the emergence of the bulk structure could be studied by following the emergence of bulk properties, in particular the bandgap, as a function of the LiF exposure. The first step in the layer growth is molecular absorption of LiF. The next step is the formation of islands formed by the LiF molecules.

ISSN:1042-0150    

DOI:10.1080/10420159408218864

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:1042-0150    

DOI:10.1080/10420159408218850

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor