%0 Journal Article
%T Surface Electronic States Induced High Terahertz Conductivity of Co3O4 Microhollow Structure
%J -
%D 2018
%R https://doi.org/10.1021/acsami.8b02925
%X 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 ¦Ìm to unravel the ground-state information induced by surface electronics across the insulator¨Csemiconductor 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¨Csemiconductor and antiferromagnetic¨Cparamagnetic transitions near the N¨¦el temperature points out the significant role of magnetically active Co2+ ions at the tetrahedral site of Co3O4 normal spinel structure in determining the conduction dynamics instead of 3d band related to Co3+ ions at octahedral site. Finally, we demonstrate that the continuous modulation of temperature-controlled charge transport coupled with intrinsic phase transition in Co3O4 microstructures has the potential to design efficient analog-like THz modulator, filter, and sensor. We believe that these outcomes can stimulate new opportunities toward next-generation caloritronics-based ultrafast energy-efficient transition-metal oxide electronics having both economic and environmental significance
%U https://pubs.acs.org/doi/10.1021/acsami.8b02925