Theoretical study on spin-polarized injection of electrical currents into polymer semiconductors

다국어 초록 (Multilingual Abstract)

Different from electrons and holes in traditional inorganic semiconductors, the charge carriers in polymer semiconductors are spin polarons and spinless bipolarons. In this paper, a theoretical model is presented to describe the spin-polarized injection of electrical currents from a ferromagnetic contact into a non-magnetic polymer semiconductor. In this model, a new relation of conductivity to concentration polarization for polymer semiconductors is introduced based on a three-channel model to describe the spin polarized injection of electrical currents under large electrical current densities. The calculated results of the model reveal the effects of the polaron ratio, the carrier concentration polarization, the interfacial conductance, the bulk conductivity of materials, and the electrical current density, etc. on the spin polarization of electrical currents. As conclusions, the large and matched bulk conductivity of materials, the small spin-dependent interfacial conductance, the thin polymer thickness and the large enough electrical current are critical factors for upgrading the spin polarization of electrical currents in polymer semiconductors. Particularly, when the polaron ratio in polymer semiconductors approaches the concentration polarization of the ferromagnetic contact, a modest concentration polarization is sufficient for achieving a nearly complete spin-polarized injection of electrical currents.

참고문헌 (Reference)

1 J.H. Wei, "YiJing Yan, Conductance switching, hysteresis, and magnetoresistance in organic semiconductors" 8 (8): 487-497, 2007

2 P.P. Ruden, "Theory of spin injection into conjugated organic semiconductors" 95 (95): 4898-4904, 2004

3 S.A. Wolf, "Spintronics: a spin-based electronics vision for the future" 294 (294): 1488-1495, 2001

4 J.F. Ren, "Spin polarized injection and transport in organic polymers" 155 (155): 611-614, 2005

5 C. Gould, "Spin injection into semiconductors using dilute magnetic semiconductors" 190 (190): 395-402, 2002

6 W. Van Roy, "Spin injection in LED’s and in unipolar devices" 126 (126): 155-163, 2006

7 A.J. Heeger, "Solitons in conducting polymers" 60 (60): 781-850, 1988

8 V. Dediu, "Room temperature spin polarized injection in organic semiconductor" 122 (122): 181-184, 2002

9 A. Hayer, "Polymer light-emitting diodes with spin-polarised charge injection" 147 (147): 155-158, 2004

10 X. Sun, "Photoinduced polarization inversion in a polymeric molecule" 84 (84): 2830-2832, 2000

11 Sheng Li, "Photoinduced carrier fission in polymers with a nondegenerate ground state" 70 (70): 075201-, 2004

12 Sheng Li, "Photoexcitation of bipolaron in conducting polymers" 19 (19): 657-658, 2002

13 F.J. Wang, "Organic spintronics: the case of Fe/Alq3/Co spin-valve devices[J]" 155 (155): 172-175, 2005

14 Wesley C. Pirkle, "Nontraditional Architectures and Spin Processes in Organic Light Emitting Devices, Doctor dissertation"

15 R.J. Soulen Jr, "Measuring the spin polarization of a metal with a superconducting point contact" 282 (282): 85-88, 1998

16 Z.H. Xiong, "Jing Shi, Giant magnetoresistance in organic spin-valves" 427 (427): 821-824, 2004

17 R. Fiederling, "Injection and detection of a spin-polarized current in a lightemitting diode" 402 (402): 787-790, 1999

18 Saori Kashiwada, "Feasibility study of a semiconductor quantum bit structure based on a spin FET embedded with self-assembled InAs quantum dots" 301 : 758-788, 2007

19 J.C. Scott, "Electron-spin-resonance studies of pyrrole polymers: evidence for bipolarons" 28 (28): 2140-2145, 1983

20 Emmanuel I. Rashba, "Electron spin operation by electrical fields: spin dynamics and spin injection" 20 (20): 189-195, 2004

21 D.L. Smith, "Electrical spin injection into semiconductors" 64 (64): 045323-, 2001

22 J.F. Ren, "Diffusion theory of spin injection into organic polymers" 17 (17): 2341-2347, 2005

23 G. Schmidt, "Concepts for spin injection into semiconductors – a review" 38 (38): 107-122, 2005

24 V.I. Krinichnyi, "2-mm Waveband electron paramagnetic resonance spectroscopy of conducting polymers" 108 (108): 173-222, 2000