Photonic QCAPhotonically Addressed Zero Current Logic through Nano-Assembly of Functionalised Nanoparticles to Quantum Dot
Cellular Automata
Donald Lupo (PC)Department of Electronics and Communications Engineering
Mircea Guina (PI)Optoelectronics Research Centre
Nikolai Tkachenko (PI)Department of Chemistry and Bioengineering
Tampere University of Technology
17.11.2015
Outline
• Introduction
• Epitaxial quantum dots
• Positioning of quantum dots• Photonic control of quantum dot charge• Quantum dot self-assembling
• Conclusions
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Quantum Dot Cellular Automata (QCA)
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Advantages:+ no current consumption+ fast operation+ small size
Requirements:- electronic coupling between QD- no charge dissipation
C. G. Smith, Computation without current, Science (1999) 284 (5412), 274.
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Quantum Dot Cellular Automata (QCA)
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Advantages:+ no current consumption+ fast operation+ small size
Requirements:- electronic coupling between QD- no charge dissipation
Problems:x these are single electron devicesx requires small QD (<10 nm at RT)x QD must be at short distancex addressing individual QDx reading out the state of QD
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PhotonicQCA: Hypothesis and Objectives
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Hypothesis: organic functionalization of quantum dot nanoparticles can enable photonically mediated charge injection into and charge transfer between quantum dots forming a QCA cell as a path to fully optically addressable zero current architecture.
Objectives:1. Fabrication and positioning of semiconductor QDs into QCA compatible
arrays using nanofabrication and self-assembly techniques; ← completed2. Demonstration of photon-induced vectorial charge transfer from a ligand to
a QD; ← completed3. Demonstration of charge transfer between QDs coupled by a photo- and
electro-active chemical linker and triggered by light; ← in progress4. Assembly of a QD cell functionalized with ligands to enable optically
mediated charge transfer; ← in progress5. Demonstration of simple logic in a nanofabricated QCA device. ← still
approaching
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Epitaxial Quantum Dots:Properties and Positioning
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• Site-controlled InAs QD were grown by molecular beam epitaxy (MBE) into the nanolithographically defined pits on GaAs wafers.
• Patterning can be done using either nanoimprint or electron beam lithography. Pits are dry etched into the GaAs wafer: (a) device structure, (b) wafer image, (c) large scale SEM image, (d) QD AFM image.
• Possibility to fabricate QCA logic circuits in the wafer scale was demonstrated by modelling NOT gate structure (e).
• Typical epitaxial QD size is 30 nm.
(d)
(e)
Device structure Microscope image
QD arrays Single QDs
NOT gate structure
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Epitaxial Quantum Dots:Voltage Controlled Photoluminiscence
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• InAs QDs buried into the Schottky-diode structure.
• QD photoluminescense can be quenched by the external voltage.
• Energy bands are altered to allow carrier tunneling out of the QDs
– PL is quenched– Photon induced charge in QD
PL spectra as function of bias voltage
Exciton (X) and biexciton (XX) intensity from InGa QDs as function of bias voltage.
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Colloidal Quantum Dot-Organic Dye hybrids:Solution Study
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HNNH
N
N
N N
NN
O O
OO
COOH HOOC
O O
OO
OO
HOOC
Pc
C60
Compounds (dyes) Hybrids
+COOH
=
Emission decay of QD is quenched on increased concentration of the electron acceptor, C
60
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Vectorial Electron Transfer from QD: Transient Absorption Spectroscopy Study
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anion C60
−
QD:CdSe/ZnS core/shelldiameter: 4-10 nmabsorption: 510-650 nm
QD - C60
hv
QD+-C60
−
QD - C60
C60
OO
OO
HOOC
~100 ps
2-12 ns
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cation Pc+
QD - Pc
hv
QD−-Pc+
QD - PcT
30-100 ps
~1 ns
QD:CdSe corediameter: 4-8 nmabs.: 510-650 nm
HNNH
N
N
N N
NN
O O
OO
COOH HOOC
O O
Pc:
Vectorial Electron Transfer to QD: Transient Absorption Spectroscopy Study
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Functionalization of QD immobilized on a surface
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SdSe NH2
NH2
NH2
NH2
NH2
NH2
NH2
NH2
substrate (e.g. quartz)
SiOO
O
SH
SiOO
O
S
SiOO
O
SH
SiOO
O
SH
SiOO
O
SH
SiOO
O
S
SiOO
O
SH
SdSe NH2
NH2
NH2
NH2
NH2
NH2
NH2
NH2
OO
OO
HOOC
OO
OO
HOOC
Emission of self-assembled monolayer of CdSe QDs is quenched after immersion of the substrate into fullerene solution.
QDs can be positioned by employing imprint nanolithography and functionalized by organic photo-ligands.
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Publications
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Full papers (peer-review):1. J. Tommila, A. Schramm, T. V. Hakkarainen, M. Dumitrescu, M. Guina, Nanotechnology
(2013) 23, 1.2. T. V. Hakkarainen, E. Luna, J. Tommila, A. Schramm, M. Guina, J. Appl. Phys. (2013) 114,
174304.3. D. Sirbu, C. Turta, A. C. Benniston, F. Abou-Chahine, H. Lemmetyinen, N. V. Tkachenko, C.
Woodd and E. Gibson,RCS Adv. (2014) 4, 22733–22742.4. K. Stranius, L. George, A. Efimov, T.-P. Ruoko, J. Pohjola, N. V. Tkachenko, Langmuir (2014)
31, 944–952.5. Tommila, V. V. Belykh, T. V. Hakkarainen, E. Heinonen, N. N. Sibeldin, A. Schramm, and M.
Guina, Appl. Phys. Lett. (2014) 104, 213104.6. F. Abou-Chahine, D. Fujii, H. Imahori, H. Nakano, N. V. Tkachenko, Y. Matano, H.
Lemmetyinen, J. Phys. Chem. B (2015) 119, 7328-7337.7. 212. B. Pelado, F. Abou-Chahine, J. Calbo, R. Caballero, P. de la Cruz, J. M. Junquera-
Hernández, E. Ortí, N. V. Tkachenko, F. Langa, Chem. Europ. J. (2015) 21, 5814-5825.8. K. Virkki, S. Demir, H. Lemmetyinen, N. V. Tkachenko, J. Phys. Chem. C (2015) 119,
17561−17572.9. Schramm, T. V. Hakkarainen, J. Tommila, and M. Guina, Nanoscale Res. Lett. (2015) 10, 242.
One manuscript is under review and another will be submitted within one week.
Results were reported at four national and eight international meetings and conferences.
17.11.2015
Conclusions: Current Status
Hypothesis 1: Semiconductor QD can be positioned by nanofabrication, scanning probe techniques and through chemically mediated self-assembly into regular arrays ← proven with nanofabrication
Hypothesis 2: Chemical functionalization of semiconductor QD structures with appropriate electron donor/acceptor (phthalocyanine/fullerene, respectively) ligands can enable electron injection to/from QDs through absorption of a photon ← proven by bi-directional charge transfer in QD-dye hybrids
Hypothesis 3: Semiconductor QDs can be chemically linked by electron donor-acceptor molecules that through absorption of a photon can enable alternatively directed charge transfer between QDs ← work in progress with hybrid SAMs of QD and organic ligands
Hypothesis 4: Functionalized semiconductor QDs can be arranged into regular arrays to form QCAs ← work in progress at stage of adding functionality to QD arrays
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