Study of space charge layer in silver bromide microcrystals by means of ultraviolet photoelectron spectroscopy

Ultraviolet photoelectron spectroscopy has been successfully used to measur e the heights of the tops of the valence bands of the surfaces of AgBr laye rs on Ag substrates for the verification of the space charge layer model. A ccording to this model, the positive space charge layer (composed of negati ve charges with excess negative kink sites on the surface and corresponding positive charges with interstitial silver ions in the interior) is formed in silver halides, causing the difference in the electronic energy levels b etween their surface and interior. The depression of the positive space cha rge layer of AgBr caused by such adsorbates as photographic stabilizers and antifoggants was estimated from the decrease in the ionic conductivity of cubic AgBr microcrystals by the adsorbates. It was confirmed by the decreas e in the heights of the tops of the valence bands of the surfaces of AgBr l ayers caused by the adsorbates in the presence of thin gelatin membranes on their surfaces. This result provided the explanation for the fact that the adsorbates increased the number of the microcrystals which formed latent i mage centers on the surface and decreased the number of the microcrystals, which formed latent image centers in the interior. (C) 2000 American Instit ute of Physics. [S0021-8979(00)01517-6].