ADSORPTION OF Cs ON Si(111)-(7 × 7) SURFACES: SITE PREFERENCE AND THE NEAR-METALLIC STATE OF Cs

Author:

PAPAGEORGOPOULOS A. C.1,KAMARATOS M.1

Affiliation:

1. Department of Physics, University of Ioannina, PO Box 1186, GR-451 10 Ioannina, Greece

Abstract

This study involves the adsorption of Cs on Si (111)-(7 × 7) surfaces at room and elevated temperatures, with increasing coverage of Cs to saturation, in ultrahigh vacuum (UHV) conditions. The techniques of low energy electron diffraction (LEED), Auger electron spectroscopy (AES), thermal desorption spectroscopy (TDS) and work function (WF) measurements were utilized. A WF change at the minimum, found to be Δϕ=-3.2 eV at an approximate 0.23 ML Cs coverage, corresponds to half the saturation coverage. We propose that, at that coverage, the adatom dangling bonds of the Si (111)-(7 × 7) substrate are completely filled. At saturation coverage (0.47 ML), Cs forms a single saturation layer in a near-metallic surface state, where the atomic radius of the Cs adatoms is likely to be 2.2× 10-8 cm. The surface exhibits a high degree of disorder with 0.47 ML of adsorbed Cs, and it is likely that the adsorbate remains in cluster-like domains within the center of the disordered 7×7 unit cells, instead of evenly covering the Si surface. Saturation coverage of Cs on Si (111)-(7 × 7) surfaces exhibits a WF value 0.5 eV less than that of pure metallic Cs. Cesium adatoms form a stronger bond to the Si (111)-(7 × 7) surface than to Ni(100), with a calculated energy of 1.64 eV/atom. The induced surface disorder and strong binding energy are evidence of the strong Cs–Si interaction, which most likely prevents the formation of a purely metallic Cs overlayer.

Publisher

World Scientific Pub Co Pte Lt

Subject

Materials Chemistry,Surfaces, Coatings and Films,Surfaces and Interfaces,Condensed Matter Physics

Cited by 4 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

1. Unravelling the secrets of Cs controlled secondary ion formation: Evidence of the dominance of site specific surface chemistry, alloying and ionic bonding;Surface Science Reports;2013-03

2. On the understanding of positive and negative ionization processes during ToF-SIMS depth profiling by co-sputtering with cesium and xenon;Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms;2009-02

3. Cesium/xenon co-sputtering at different energies during ToF-SIMS depth profiling;Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms;2008-12

4. Calculation of the surface binding energy for ion sputtered particles;Applied Surface Science;2005-01

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