STM, STS, and local work function study of Cs/p-GaAs(110)

Various surface configurations of Cs/p-GaAs(1 1 0) have been studied by sca nning tunneling microscopy and scanning tunneling spectroscopy with an inte rest in relation to the photoelectron emission. The local work function is found to be 4.8, 3.3, and 3.3 eV from clean p-GaAs(1 1 0), Cs one-dimension al (1D) lines (Cs coverage of 0.23 ML), and partially-ordered Cs polygons ( Cs coverage of 0.5 ML), respectively. It is understood that only a coherent ly c(4 x 4)-ordered Cs-polygon surface (Cs coverage of 0.6 and 0.7 ML) can emit photoelectrons due to a sufficient reduction of the local work functio n down to 1.3 eV to get the negative electron affinity state. The local wor k function image shows that the boundary of Cs atoms has a lower local work function than at the top of Cs atoms. (C) 2001 Elsevier Science B.V. All r ights reserved.