PHOTOEMISSION-STUDY OF CS ON A-SI-H

We report a photoemission study of Cs on hydrogenated amorphous silico n (a-Si:H) at room temperature. The alkali adsorbate bonds covalently with the amorphous substrate, but remains neutral at all time. The Cs/ a-Si covalent bonding is strong, in contrast to the crystalline counte rpart where the bonding is weak, and highly polarized. Surface disorde ring facilities in this strong covalent bonding further lessens the ad sorbate-adsorbate interaction, resulting in the absence of Fermi emiss ion.