Signature of quasi one-dimensionality in the absorption spectra of electrochemically self-assembled nanowires

We have observed broad peaks in the room temperature absorption spectra of electrochemically self-assembled 10-nm diameter nanowires of CdSe and ZnS at photon energies close to the bandgap energy. They are believed to stem from the van Hove singularities in the quasi-one-dimensional electron–hole joint density of states. The absorption spectra of 50-nm diameter wires do not exhibit these peaks (their absorption increases monotonically with photon energy) since their diameter exceeds the thermal De-Broglie wavelength of the nanowires. That makes them behave as three-dimensional instead of quasi-one-dimensional structures. To our knowledge, this is the first observation of the signature of quasi-one-dimensional density of states in the absorption spectrum of electrochemically self-assembled nanowires.

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► Demonstration of quasi-one-dimensional density of states in self-assembled nanowires.
► Signature of quasi one-dimensional density of states is found in absorption peaks occurring at photon energies close to bandgap.
► Quasi-one-dimensionality requires nanowire diameters to be comparable to De-Broglie wavelength.
► Blue shift in absorption or photoluminescence spectra is not a definitive proof of quantum confinement.