Recent progress on BEEM

Abstract

The application of ballistic-electron-emission microscopy (BEEM) and spectroscopy (BEES) to epitaxial CoSi 2/Si interfaces is reviewed. Dislocations in 2–3 nm thick CoSi 2(0 0 1)/Si(0 0 1) films with Burgers vectors b = a/4〈1 1 1〉 are shown to lower the barrier height measured at 77 K by almost 0.1 eV. This corresponds to a decrease of the Schottky barrier height at the metallurgical interface from the value of Φ B=0.74±0.03 eV, characteristic for defect-free regions, to near zero within the range of their strain field of a few nanometers. By contrast, the dislocations of type b = a/6 〈1 1 2 ̄ 〉 present at CoSi 2/Si(1 1 1) interfaces do not affect the barrier height. Films of CoSi 2/Si(1 1 1) are more suitable for studying interfacial scattering by BEEM because of their simpler surface structure and because of band structure effects. Here individual point defects can be resolved. Their spatial distribution indicates diffusion along the interface during film growth. By analysing the shape of BEES spectra obtained on isolated point defects, and by making use of the projected band structure predicting the BEES current to set in ∼0.2 eV above the Schottky barrier, it may be concluded that the defects are located at the interface.