Abstract
Silicon nanocrystals and nanowires have been extensively studied because of their novel properties and their applications in electronic, optoelectronic, photovoltaic, thermoelectric and biological devices. Here we discuss results from ab initio calculations for undoped and doped Si nanocrystals and nanowires, showing how theory can aid and improve comprehension of the structural, electronic and optical properties of these systems.
Highlights
The scaling down of Si structures to nanometer size has opened up new chances to overcome the inability of bulk Si to be an efficient light emitter
With regards to the optoelectronic properties, we found that the GW corrections to the Density functional theory (DFT)-local density approximation (LDA) band gaps are much larger than those in the bulk case and
The stability of the impurities is slightly larger in the cubic phase, this means that there is not a clear preference of one phase with respect to the other. This nding is in contrast to what was found in the case of middle and large diameter NWs.[153]. This differing behaviour can be related to the different structural reorganization around the impurity that one can observe in ultrathin NWs
Summary
The scaling down of Si structures to nanometer size has opened up new chances to overcome the inability of bulk Si to be an efficient light emitter. The possibility of enhancing the electrical conductivity of nanosized systems has been attempted, for instance, by fabricating porous-Si from n- or p-doped bulk Si by means of electrochemical etching.[55] the etching process does not remove the impurities from the system,[56] a very low conductivity was measured, even for the larger mesoporous samples. This suggests that the ionization of the impurities at room temperature may be strongly quenched with respect to the bulk.
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