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Molecular Spintronics Gabriel Aeppli 1 , Andrew Fisher 1 , Nicholas Harrison 2 , Sandrine Heutz 3 , Tim Jones 4 , Chris Kay 5 and Des McMorrow 1 1 Department of Physics and Astronomy, London Centre for Nanotechnology, University College London, London WC1E 6BT, U.K. 2 Department of Chemistry, London Centre for Nanotechnology, Imperial College London, London SW7 2AZ, U.K. 3 Department of Materials, London Centre for Nanotechnology, Imperial College London, London SW7 2AZ, U.K. 4 Department of Chemistry, University of Warwick, Coventry, CV4 7AL, U.K. 5 Department of Biology, London Centre for Nanotechnology, University College London, London WC1E 6BT, UK. • Funded through the Basic Technology programme • November 2008 start, duration 4 years. • Includes 3 institutions (Warwick, UCL and Imperial) and 7 investigators. • Crossing boundaries: PIs experts in different branches of Science (Chemistry, Physics, Biology) and Engineering (Materials, EE). • Directly employs 4 PDRAs and 3 PhD students • Project extends boundaries: Additional academics (a.o. Hirjibehedin, Curson, Nathan, Ryan), more than 7 PhD students and PDRAs closely linked to the project Combine cheap organic electronics and high performance spintronics to develop molecular spintronics with outcomes in IT and biosensing. Use expertise in small molecule film growth, magnetism, theory, optoelectronics, device engineering and spin resonance applied to biology. Molecular Electronics OPV, OLED, Transistors Semicond. polymers and molecules Spintronics GMR, MRAM Magnetic HJ Magnetic Semiconductors Organic Spintronics Molecular films as tunnelling layers Molecules on magn. surfaces Molecular Magnetism Magnetic switching, spin-crossover Molecular powder, e.g. Prussian Blue BT Molecular Spintronics Unique combination of properties Xiong, Nature 04 Baibich, PRL88 Verdaguer, Science 96 Nelson, Durrant (IC), Forrest Applications in IT Combine magnetic centre (Q-bit) with semiconducting ring (control) N N - N N - N N N N Cu 2+ Exploit spin and magnetism in optoelectronic devices based on organometallics Applications in Biosensing Label-free detection based on specific spin relaxation Key Publications and Patents • A Novel Route for the Inclusion of Metal Dopants in Silicon, Nanotechnology 21 (2010) 035304. • Ultralong copper phthalocyanine nanowires with new crystal structure and broad optical absorption, ACS Nano 4 (2010) 3921-3926. • Morphology and Structure Transitions of Copper Hexadecafluorophthalocyanine (F 16 CuPc) Thin Films, J. Phys. Chem. C 114 (2010) 1057. • Theoretical modeling of exchange interactions in Cu(II)Pc one- dimensional chain, Phys Rev B (2011) – in press. • Spin-based diagnostic of nanostructure in films of a common molecular semiconductor – submitted. • Patent: A Novel Route for the Inclusion of Metal Dopants in Silicon (GB0908254.6). Further funding Project is a platform for further funding, including EPSRC-NSFC grant in Foundations of Molecular Nanospintronics. Key issue: efficiency of organic devices strongly depends on molecular orientation. However, diffraction cannot always be applied in poorly crystallised systems. Objectives: use spin resonance lineshapes and positions to determine local order and orientation of dye molecules in test systems and apply to rationalisation of solar cells Film B perp ( = 90°) B parallel ( = 0°) On glass g ┴ g // and g ┴ Templated g // g ┴ B “parallel” ( = 90°) B “perpendicular” ( = 90°) g // g perp g perp g // CuPc on glass CuPc templated Top view of molecules on substrate g-factors observed Field (mT) Orientation ( ) 250 260 270 280 290 300 310 320 330 340 350 360 370 380 390 400 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 Field (mT) Orientation ( ) 250 260 270 280 290 300 310 320 330 340 350 360 370 380 390 400 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 Field (mT) Orientation ( ) 250 260 270 280 290 300 310 320 330 340 350 360 370 380 390 400 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 Film on glass Templated CuPc:C 60 mixed Unexpected benefit of BT project for energy sector: • molecular spins as an inexpensive in-line quality control tool to measure mol. orientation • clustering and preferential orientation with molecules perp to substrate in mixed CuPc:C 60 • unfavourable orientation of molecules in mixed solar cells, points to path for increased efficiency Main Milestones Nanowire film and FET Set of rules for correlation between molecular parameters and exchange couplings EPR Hamiltonian • Thin film Tc above 77K • Optical control of exchange interactions • EPR detection of biomolecules based on antibody/antigen interactions • Magneto-optic phenomenology and EPR Hamiltonian for bioassay 400 nm 1 cm N 2 20 nm d 001 Nanowires and films are essential for miniaturisation of spintronic device and efficient spin transport through single crystal domains CuPc by Organic Vapour Phase Deposition Based on molecules in a 3-zone furnace and inert carrier gas wires with new crystal structure, high flexibility and aspect ratios approaching CNTs alpha wire beta 0 1 2 3 4 5 6 7 0.0 0.2 0.4 0.6 0.8 1.0 Normalised magnetisation m 0 H (Tesla) Magnetic properties show that wires have antiferromagnetic coupling, as rationalised by theoretical calculations. High orbital overlap along long axis should mediate high anisotropic conductivity. Increasing Tc using different transition metal derivatives Project Organisation Engineering Application: new route to determine local order in organic solar cells Visibility and Outcomes Science Application: molecular magnetic wires and films from vapour Project Summary and Context Thin films grown using organic molecular beam deposition 0 20 40 60 80 0.0 3.0x10 7 6.0x10 7 9.0x10 7 1.2x10 8 1.5x10 8 -1 (Oe/emu) Magnetisation Ferromagnetic film with Tc ~26 K -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 -1.0 -0.5 0.0 0.5 1.0 -0.10 -0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08 0.10 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 m 0 H (Tesla) m 0 H (Tesla) M normalised at 7T
