Journal
NANO LETTERS
Volume 8, Issue 12, Pages 4404-4409Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nl802277k
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- Max Planck Institute of Microstructure Physics (Germany)
- EU STREP Multiceral.
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We report intense terahertz emission from lead zirconate titanate (PZT) tubular nanostructures, which have a wall thickness around 40 nm and protrude on n-type Si substrates. Such emission is totally absent in flat PZT films or bulk; hence the effect is attributed to the nanoscale geometry of the tubes. The terahertz radiation is emitted within 0.2 ps, and the spectrum exhibits a broad peak from 2 to 8 THz. This is a gap in the frequency spectrum of conventional semiconductor terahertz devices, such as ZnTe, and an order of magnitude higher frequency peak than that in the well-studied p-InAs, due to the abnormally large carrier concentration gradient in the nanostructured PZT. The inferred mechanism is optical rectification within a surface accumulation layer, rather than the Dember effect. The terahertz emission is optically pumped, but since the tubes exhibit ferroelectric switching, electrically driven emission may also be possible. EPR reveals O-2 molecules adsorbed onto the nanotubes, which may play some role in the emission.
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