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O rganic Spintronics

O rganic Spintronics. Current team members Franklyn Burke (graduate student, 2007-) Huesyin Tokuc (graduate student, 2008-) Prof. Greg Szulczewski SFI Walton Fellow 2008-2009 “Spin Electronics with Organic Materials”. Research Acitivities.

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O rganic Spintronics

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  1. Organic Spintronics Current team members Franklyn Burke (graduate student, 2007-) Huesyin Tokuc (graduate student, 2008-) Prof. Greg Szulczewski SFI Walton Fellow 2008-2009 “Spin Electronics with Organic Materials” MANSE Midterm Review

  2. Research Acitivities • Growth of organic microcrystals and nanowires by physical vapor deposition • Characterization of organic wires by SEM, TEM, XRD, PL, EPR, FT-IR, and SQUID magnetometery • Fabrication of nanogap electrodes • Set-up high impedance probe for magnetotransport studies on crystalline organic semiconductors • Construction of UHV chamber for spin valve growth • Transport measurements on Alq3 based MTJs MANSE Midterm Review

  3. Organic Crystal Growth Al doped 8-hydroxyquinoline Physical vapor deposition Alq3 Cu phthalocyanine (CuPc) rubrene MANSE Midterm Review

  4. SQUID Magnetometery of Alq3 Al-doped 8-hydroxyquinoline nanowires The concentration of paramagnetic (S= ½) defect centers in Alq3 is estimated to be: 4 x10-4/formula unit. This yield an average defect separation of ~ 11 nm. Unshaved material scavenges Fe from the stainless steel die! MANSE Midterm Review

  5. Alignment of crystals on electrodes Al-doped 8-hydroxquinoline rubrene a = 24.936 Å, b = 28.551 Å, c = 3.787 Åa = 14.44 Å, b = 7.18 Å, c = 26.97 Å Largest μ along B axis Nano gap MANSE Midterm Review

  6. Fabrication of nano gap electrodes UV optical lithography to prepare Deposit Pt contacts on nanowire Hall bar by electron beam deposition Focused–ion beam etching to produce trench MANSE Midterm Review

  7. Magnetotransport in organic nanowires Al-doped 8-hydroxyquinoline NiFe electrodes Au electrodes Tunneling VRH NNH MANSE Midterm Review

  8. Rubrene crystals on NiFe electrodes Semiconducting behavior σ = σo exp[-(TM/T)1/(1+d) d =1 and TM ~ 235 K 280nm gap MANSE Midterm Review

  9. Magnetotransport for rubrene on NiFe 300nm gap MR proportional to T-2.25 70 K Negative MR scales linearly at high H Positive MR seen at low H Negative MR is predicted to scale as T-1.5 for 1D VRH* *Nguyen et al. JETP 1985, 62, 1021 No MR observed using Au electrodes MANSE Midterm Review

  10. TMR characteristics of 24 x 24μm2junctions The MTJ Stack: SiO2/Ta(30)/CoFe(5)/Barrier/CoFe(3)/IrMn(10)/Ta(5)/Pt(5) 2.5 nm Al2O3/ 1nm Alq3 2.5 nm Al2O3 MANSE Midterm Review

  11. On-going work • Metal phthalocyanine (MPc) films and crystal growth M= Mn, Fe, Co, Ni, Cu, and Zn • Deposition of vertical spin valves in new UHV chamber MANSE Midterm Review

  12. Future work • Fabricate lateral spin valves with different coercivity electrodes and gap separation • Vertical spin valves with crystalline MPc’s e.g. CoFe/MgO/MPc/LiF/Co • Magnetometery, spectroscopy, and microscopy of FM/organic and organic/FM interfaces MANSE Midterm Review

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