PREDICTION OF UNUSUAL ELECTRONIC-PROPERTIES OF SI QUANTUM FILMS

Direct pseudopotential band structure calculations of thin Si(001) films reveal a number of features that are unexpected on the basis of conventional quantum confinement models: (i) The energies of some valence-band states exhibit oscillations when the number of monolayers in the film changes from even to odd, (ii) certain film wave functions have a cosine (rather than sine) envelope function, and (iii) the energy of the highest occupied film state remains pinned at a constant value for all even-layered film. We demonstrate a simple alternative to the effective-mass model which explains these results.