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Title of article :
Thin films of molecule-based charge transfer complex cobalt tetracyanoethylene: In situ X-ray photoemission study
Author/Authors :
Bhatt، نويسنده , , Pramod and Yusuf، نويسنده , , S.M.، نويسنده ,
Issue Information :
هفته نامه با شماره پیاپی سال 2011
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Abstract :
Thin films of molecule-based charge transfer magnet, cobalt tetracyanoethylene [Co(TCNE)x, x ~ 2] consisting of the transition metal Co, and an organic molecule viz. tetracyanoethylene (TCNE) have been deposited by using physical vapor deposition method under ultra-high vacuum conditions at room temperature. X-ray photoelectron spectroscopy (XPS) technique has been used extensively to investigate the electronic properties of the Co(TCNE)x thin films. The XPS measurements show that the prepared Co(TCNE)x films are clean, and oxygen free. The stoichiometries of the films, based on atomic sensitive factors, are obtained, and yields a ~ 1:2 ratio between metal Co and TCNE for all films. Interestingly, the positive shift of binding energy position for Co(2p), and negative shifts for C(1s) and N(1s) peaks suggest a charge-transfer from Co to TCNE, and cobalt is assigned to its Co(II) valence state. In the valence band investigation, the highest occupied molecular orbital (HOMO) of Co(TCNE)x is found to be at ~ 2.4 eV with respect to the Fermi level, and it is derived either from the TCNE− singly occupied molecular orbital (SOMO) or Co(3d) states. The peaks located at ~ 6.8 eV and ~ 8.8 eV are due to TCNE derived electronic states. The obtained core level and valence band results of Co(TCNE)x, films are compared with those of V(TCNE)x thin film magnet: a well known system of M(TCNE)x type of organic magnet, and important points regarding their electronic properties have been brought out.
Keywords :
Thin films , molecule-based magnets , X-ray photoelectron spectroscopy , physical vapor deposition
Journal title :
Surface Science
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