Abstract
<P>With the miniaturization of a solid, quantum and interface effects
become increasingly important. As a result, the band structure of
a nanometric semiconductor changes: the band gap expands, the core
level shifts, the bandwidth revises, and the sublevel separation
within a band increases. Unfortunately, such a thorough change goes
beyond the scope of currently available models such as the `quantum
confinement' theory. A consistent understanding of the factors dominating
the band-structure change is highly desirable. Here we present a
new approach for the size-induced unusual change by adding the effect
of surface-coordination deficiency-induced bond contraction to the
convention of an extended solid of which the Hamiltonian contains
the intraatomic trapping interaction and the interatomic binding
interaction. Agreement between modelling predictions and the observed
size dependency in the photoluminescence of Si oxides and some nanometric
III-V and II-VI semiconductors, and in the core-level shift of Cu-O
nanosolids has been reached. Results indicate that the spontaneous
contraction of chemical bonds at a surface and the rise in the surface-to-volume
ratio with reducing particle size are responsible for the unusual
change of the band structure of a nanosolid.</P>
Users
Please
log in to take part in the discussion (add own reviews or comments).