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An in situ study of the activating layer on GaAs (CS, 0) photocathodes has been made using Auger electron spectroscopy, relative work function, photo-emission and spatial resolution measuring techniques.The layer thickness, composition and work function reduction have been measured for both single-and two-temperature activations. In order to account for the electron transmission probability and the transverse energy of the emitted photo-electrons it is necessary to consider both the work function lowering and the scattering properties of the activating layer. Further it has been shown that neither the heterojunction or dipole models provide an adequate explanation of the properties of the layer which are more consistent with the cluster model of Burt and Heine.

A study has been made of the relationship between the facetting and surface structure observed upon (111)B and (100)GaAs photocathode surfaces and the mean transverse emission energy of the photoelectrons emitted from these cathodes. It is concluded that the mean transverse emission is largely independent of the degree of facetting and the presence of surface structure; however, a relationship exists between the temperature at which the cathode surface is cleaned and the mean transverse emission energy.

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A negative bias applied to a nondiamond substrate at the initiation of microwave plasma-enhanced chemical-vapor deposition of thin-film diamond can lead to diamond nucleation, high crystalline density, and an improved level of crystallographic alignment. In this work, optical emission spectroscopy has been used to study changes in the chemical species within the plasma that occur as a result the applied bias to a tungsten substrate. The ratio of C2 to CH species detected changes considerably as does the atomic hydrogen intensity as the bias is applied. Both effects appear to be greatest near the substrate surface. The results are discussed in terms of possible origins for the bias-enhanced nucleation process.