Partial charge injection from surface and adsorbate states into semiconductor space charge layers

A182 iron spectra, and the form and number of crystalhtes as a function of deposition tune and temperature At high temperatures, Ts > 200°C, the sdver grows defmitwely in a Stranskl Krastanov (layer plus island) growth mode, with a very strong dependence of the island density on the deposition temperature, varying from ~106 to ~1010 cm -2 between Ts = 500 and 200°C The crystals have more or less regular hexagonal forms with (111) and (111) faces predominating with a height to width ratio which decreases with deposition time in the range 0 1 - 0 6 At temperatures below 200°C, the island density Is too high to be observed directly by SEM, and silver appears to grow m a F r a n k - v a n der Merwe (layer by layer) mode However, this uniform deposit is unstable on heating above 200°C, and annealed deposits recreate rather similar islands An analysis of published Auger a m p l i t u d e - t i m e curves is made to estimate the initial island density produced by depositions below Ts = 200°C, and it is shown that these densities constitute a very reasonable extrapolation of the higher temperature SEM values A model of Stranski-Krastanov growth is gwen in outline and applied to Ag/Sffl 11) It is argued that the island density is determined largely by island mstabihty at high temperatures, even though condensatlon is complete At low temperatures it is argued that Stranskl-Krastanov growth becomes essentially equivalent to F r a n k - v a n der Merwe growth for high enough island density, for kinetic rather than thermodynamic reasons, without any change in the basic StransklKrastanov mechanism

Surface Science 95 (1980) 4 3 1 - 4 4 6 © North-Holland Publishing Company PARTIAL CHARGE INJECTION FROM SURFACE AND ADSORBATE STATES INTO SEMICONDUCTOR SPACE CHARGE LAYERS W. L O R E N Z a n d C. E N G L E R

Sektton Chemte, Karl-Marx-Umversttat, Leipzig, GDR Received 7 December 1979; accepted for publication 28 January 1980 Chemisorption processes on semiconductor interfaces are generally coupled with partial charge rejection into a space charge layer. A computational approach of this phenomenon Is closely related to the problem of discriminating surface and space charges on semiconductors. We report on the present state of model computations of partial charge injection, based on a local density of states treatment of semiconductor surfaces and on a superpositron approximation of local chemical states and macroscopic band bending. Relation to macroscopic dynamic theory of interface reactrons is indicated. As examples, ideal and (1 × 1) reconstructed GaAs(110) surfaces and chemlsorption of a L1 atom are discussed in some detail.

Surface Science 95 (1980) 4 4 7 - 4 6 4 © North-Holland Pubhsinng Company Q U A N T I T A T I V E P R E D I C T I O N S OF TIlE H E A T OF A D S O R P T I O N OF METALS ON METALLIC SUBSTRATES A . R M I E D E M A a n d J.W.F. D O R L E I J N

Phtlips Research Laboratories and Phihps Lighting Division. Eindhoven, The Netherlands Received 4 December 1979; accepted for publication 19 February 1980 The enthalpy of adsorption of metal atoms on metalhc substrates can be calculated by means of a semi-empirical model in which metal atoms are treated as if they were macroscopic pieces of metal In this model the enthalpy of adsorption of a metal A on a substrate B can be