PNNL-13501 - Pacific Northwest National Laboratory

Spontaneous Formation of Cu2O Nano-Corrals
In addition to Cu2O quantum dots, we have also
developed a process for growth of Cu2O nano-corrals on
SrTiO3 substrates. These were grown by first depositing a
layer of copper metal on a SrTiO3 substrate, then
subsequently annealing the Cu/SrTiO3 in oxygen plasma
at elevated temperatures. The resulting surface exhibited
corrals with diameters ranging from approximately 50 nm
to 80 nm, as shown in Figure 3. The chemical state of
copper was examined by x-ray photoelectron
spectroscopy. Results confirmed that copper at the
surface was copper (I) instead of copper (II), suggesting
these corrals consisted of Cu2O instead of a CuO phase.
The importance of this finding is that these nanoscale ring
structures can exhibit artificial magnetic and conducting
properties, as was predicted by Laudauer et al. (1985) and
Figure 3. An atomic force microscopy image of Cu 2O nanocorrals
formed on a SrTiO 3 substrate surface
recently confirmed by Lorke et al. (2000) on InAs. The
driving force for the formation of these nano-corrals is
currently unclear. We speculate that they are due to stress
relaxation and subsequent dislocation formation at the
Cu2O/SrTiO3 interface.
Photoluminescence Behavior of Cu2O Quantum Dots
One potential application of the Cu2O/SrTiO3 quantumdot
system is photocatalysis. It is important to
characterize the optical properties of this system. We
conducted photoluminescence measurements on
Cu2O/SrTiO3. Results are shown in Figure 4. The
photoluminescence spectrum shows a broad distribution
Figure 4. Photoluminescence spectrum of Cu 2O quantum
dots showing typical luminescence behavior from quantum
dots. The spectrum was taken at 18 K to eliminate photon
scattering effects.
with a peak centered around 480 nm. The breadth of the
spectrum is due to the size distribution of quantum dots,
as has been demonstrated in other quantum dots systems
(Bimberg et al. 1999). The fact that these Cu2O quantum
dots exhibit photoluminescence under above-gap
irradiation suggests that the defect density of this system
is low. It would otherwise show no photoluminescence
because of scattering and recombinations mediated by
defects.
References
Bimberg D, M Grundmann, and N Ledentsov. 1999.
Quantum dot heterostructure. John Wiley & Sons, New
York.
Laudauer R et al. 1985. Phys. Lett. 96A, 365.
Lorke A, RJ Luyken, AO Govorov, and JP Kotthaus.
2000. “Spectroscopy of nanoscopic semiconductor
rings.” Phys. Rev. Lett. 84, 2223.
Presentation
Liang Y, D McCready, S Lea, S Chambers, and S Gan.
November 2000. “A novel stable quantum dot system for
electron-hole pair separation: self-assembled Cu2O
quantum dots on SrTiO3(001).” Material Research
Society Meeting, Boston.
Micro/Nano Technology 355