Abstract
Ballistic-electron-emission microscopy (BEEM) has been performed on epitaxial CoSi 2 /Si(111) and CoSi 2 /Si(100) films, and on CoSi 2 /Si/Ge/Si(100) heterostructures containing buried Ge quantum dots. At CoSi 2 /n-Si(111) and CoSi 2 /p-Si(111) interfaces the spatial variation of hot carrier transmission is dominated by scattering at dislocations and point defects, while the Schottky barrier height is not measurably affected by defects. The excellent spatial resolution of 1.3 nm, achieved for films as thick as 5 nm on n-Si(111) and of 1.6 nm on p-Si(111) can be explained only by taking into account the theoretically predicted focussing effect of the hot electron beam, induced by the special constant energy surfaces of CoSi 2 . Scanning tunneling spectroscopy (STS) studies of Ge quantum dots buried in a Si matrix have revealed a substantial lowering of the Si surface band gap due to the strain imposed by the dots. In CoSi 2 /Si/Ge/Si(100) heterostructures the Ge-induced strain has been found to modify the defect structure at the CoSi 2 /Si interface, leading to pronounced contrast variations in BEEM images. The BEEM contrast gives direct evidence for the rotation of Ge islands by 45° during capping with epitaxial Si.
Published Version
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