We used direct imaging of diffusion fields in photoemission electron microscopy to study the diffusion (an)isotropy of Ag on flat and vicinal Si(001) surfaces with miscut angles between 0.2° and 4° in the [110] direction. While the diffusion field, represented by its iso-coverage zone, is isotropic on flat Si(001), it becomes elongated on the vicinal surface. The aspect ratio of the iso-coverage zone is used as a measure of the effective diffusion anisotropy on the surface. The aspect ratio of the iso-coverage zone increases continuously with the miscut angle, up to the maximum miscut that was studied. For the 4° miscut surface we find that the shape of the diffusion field is independent of the kink density of the substrate. From the temperature dependence of the aspect ratio, we determine an effective energy of ΔEani ∼ 0.7 eV for the activation energy responsible for the anisotropy.

We have developed a mirror electron microscope (MEM) for inspecting fine processed flat surfaces. This apparatus can detect nanometer-sized particles and scratches on very flat surfaces. Its sensitivity for electric charge distribution is useful for detecting failures in microdevice patterns. In observation of an insulator surface with the MEM, complex features caused by small amount of charge distribution were observed in the images. We believe that the MEM can provide different methods for characterization of electrical behavior on insulator surfaces.

Commercial scandium oxide doped thermionic cathodes have demonstrated current densities over 100 A/cm2. In order to understand the effect of Sc- and Ba- oxides on the emissivity of these cathodes we have imaged thin films of scandium oxide and barium oxide on tungsten foils using photoelectron emission microscopy and thermionic emission microscopy. Arrays of 100 um × 100 um squares of scandium and 25 um × 25 um squares of barium, 200 nm thick, were sputter deposited onto 50 um thick sheets of tungsten foil. Imaging squares of different sizes gives an unequivocal identification of each material and a completely consistent comparison of each material and cathode structure under identical conditions in one image.

The metal squares oxidize in air before imaging. Each sample was heated in situ in a Bauer-Telieps style LEEM/PEEM used primarily in the ThEEM mode. The barium oxide squares emit below 875 K, and diffuse over the scandium below 875 K. Thermionic emission from scandium oxide squares is observed at temperatures significantly larger than 875 K. Failure of the barium oxide film cathode is through barium desorption. AES spectra show that the Sc does not desorb.

While the origin of reduced emission temperature is commonly believed to be a result of a low work function monolayer of Ba and Sc oxides, in our study, the benefits of a combined Ba/Sc cathode are present in a thick (multi-layer), layered structure of barium oxide on top of a thick scandium oxide layer.

A novel low energy electron microscope (LEEM) aimed at improving the throughput and extending the applications for semiconductor devices has been developed. A dual beam approach, where two beams with different landing energies illuminate the field of view, is used to mitigate the charging effects when the LEEM is used to image semiconductor substrates with insulating or composite (insulator, semiconductor, metal) surfaces. We have experimentally demonstrated this phenomenon by imaging a variety of semiconductor device wafers without deleterious charging effects. Results from several important semiconductor device layers will be illustrated in detail.