Surface Electronic States Induced High Terahertz Conductivity of Co3 O4 Microhollow Structure

ACS Applied Materials & Interfaces
Rupali RakshitD S Rana

Abstract

Herein, we report the observation of unusual electronic and magnetic phases in traditional antiferromagnetic Co3O4 micromaterials and modulation of their properties on a temperature scale. In particular, we demonstrate a comparative low-energy carrier dynamics of Co3O4 microflower and microhollow flower (MHF) structures of same average size of 2 μm to unravel the ground-state information induced by surface electronics across the insulator-semiconductor transition using terahertz (THz) time domain spectroscopy. Interestingly, the THz optical constants of these structures are found to exhibit remarkably distinct features both as a function of frequency and temperature. Detailed study reveals that the partial metallization through large two-dimensional surface electronic states of MHF structure enables to achieve significantly higher carrier dynamics in contrast to its wide-band-gap solid counterparts and the magnetic measurements reconfirm the presence of these surface states by indicating ferromagnetism in Co3O4 MHF structures. Moreover, the simultaneous existence of insulator-semiconductor and antiferromagnetic-paramagnetic transitions near the Néel temperature points out the significant role of magnetically active Co2+ ions at...Continue Reading

References

Nov 17, 2006·The Journal of Physical Chemistry. B·Hyun-Jeong NamNaoto Koshizaki
Mar 27, 2010·Science·Hidenori Takagi, Harold Y Hwang
Sep 25, 2010·Nature Materials·Craig J Fennie, Darrell G Schlom

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