The Field Emission Microscope has been extensively used in the study of metal and semiconductor surfaces. The process of Field Emission is, itself, of great interest and a considerable amount of both theoretical and experimental work has been carried out in this field. The Field Emission Microscope also yields useful information of a more practical nature, such as the nature of bulk and surface impurity, diffusion, chemisorption and surface potential barriers. It is essential that the surface to be studieg can be prepared in the form of a high curvature tip, with a radius of 10−5cm and can be cleaned sufficiently well for a symmetrical reproducible pattern to be observed.

Field Emission technique has been applied to study the behaviour of thin overlayers of gold on GaAs. Using Fowler-Nordheim plots, change in the work function φ, is examined for temperatures, T=77K and T=300K. φ changes slightly for low doses of gold and significantly for larger ones {φ=4.3 − 3.7 eV}. Desorption of gold is also examined and the results indicate two different adsorbed states in Au-overlayers formed at room temperature. Finally, a brief description of sample preparation is also included.