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The electronic structure and field effects of an organic-based room temperature magnetic semiconductor

Lincoln, Derek M.
http://rave.ohiolink.edu/etdc/view?acc_num=osu1193833038

Abstract Details

2007, Doctor of Philosophy, Ohio State University, Chemistry.
Vanadium tetracyanoethylene (V[TCNE]~2) is a magnetic semiconductor with an ordering temperature well above room temperature. Its highly disordered structure has hampered comprehensive descriptions of interactions between the V and TCNE sub-lattices that give rise to its magnetic and electrical properties. We report results of high-resolution x-ray absorption (XAS) and magnetic circular dichrosim (MCD) studies probing the electronic structure of V[TCNE]~2to elucidate the nature of these interactions. Included in this study are first reports of gas phase neutral TCNE XAS spectra as well as first reports of MCD spectra of the carbon and nitrogen absorption edges for V[TCNE]~2. The vanadium spectrum reveals a spin split L3and L2spectrum that is qualitatively modeled for V(II) using crystal field multiplet (CFM) theory except for a region of excess intensity on the high energy side of both the L3and L2absorption edges. We speculate the origin of this excess intensity is vanadium present in valence states higher than V(II) and antibonding states from hybridization of V and TCNE. Despite the localized nature of x-ray absorption, the C and N spectra of the TCNE suggest we are probing molecular final states of TCNE from different sites rather than atomically isolated states. In addition, the carbon and nitrogen absorption spectra reveal this molecular orbital structure remains largely intact in going from the gas phase to the condensed phase V[TCNE]~2. The value in high-resolution experimental data is exposed as new features are detected unveiling effects of magnetic exchange leading to spin splitting of the singly occupied molecular orbital of [TCNE]•−as revealed by carbon and nitrogen XAS and MCD spectra. Remarkable alignment of low photon energy features in vanadium, carbon, and nitrogen spectra reveal a strong hybridized structure between valence molecular orbitals of TCNE and vanadium 3d orbitals. Associated MCD spectra elucidate polarization associated with particular XAS features and we speculate on the mechanism of magnetic interaction between V and TCNE sub-lattices. We also report the first electric field effects of V[TCNE]~2. We construct field-effect devices and demonstrate the field effect and measure the current-voltage characteristics of these devices under varying applied gate voltages.
Arthur Epstein (Advisor)
148 p.
Organic magnet; Magnetic semiconductor; Vanadium tetracyanoethylene; Field effect transistor

Recommended Citations

Citations

  • Lincoln, D. M. (2007). The electronic structure and field effects of an organic-based room temperature magnetic semiconductor [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1193833038

    APA Style (7th edition)

  • Lincoln, Derek. The electronic structure and field effects of an organic-based room temperature magnetic semiconductor. 2007. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1193833038.

    MLA Style (8th edition)

  • Lincoln, Derek. "The electronic structure and field effects of an organic-based room temperature magnetic semiconductor." Doctoral dissertation, Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=osu1193833038

    Chicago Manual of Style (17th edition)

osu1193833038
949
© 2007, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.