Abstract
Nickel oxide (NiO) nanocrystals epitaxially grown on (001) strontium titanate (SrTiO3) single crystal substrates were characterized to investigate interface morphology and chemistry. Aberration corrected high angle annular dark field scanning transmission electron microscopy reveals the interface between the NiO nanocrystals and the underlying SrTiO3 substrate to be rough, irregular, and have a lower average atomic number than the substrate or the nanocrystal. Energy dispersive x-ray spectroscopy and electron energy loss spectroscopy confirm both chemical disorder and a shift of the energy of the Ti L2,3 peaks. Analysis of the O K edge profiles in conjunction with this shift, implies the presence of oxygen vacancies at the interface. This sheds light into the origin of the previously postulated minority carriers’ model to explain resistive switching in NiO [J. Sullaphen, K. Bogle, X. Cheng, J. M. Gregg, and N. Valanoor, Appl. Phys. Lett. 100, 203115 (2012)].
Highlights
Nickel oxide (NiO) has been widely investigated for its optical,[2] ferromagnetic,[3,4] and electrochromic properties.[5,6,7] It was recently found to have resistive switching (RS) properties, switching from a high resistance (OFF) state to a low resistive (ON) state by successive application of electric fields of opposite polarity.[8]
It can be said that detailed interface characterization is necessary for any nanoelectronic device that is based on metal oxides
032109-3 Cheng et al FIG. 1. (a) Three-dimensional atomic force microscope (AFM) image shows morphology of the NiO nanocrystals grown on the SrTiO3 substrate. (b) High angle annular dark field (HAADF) scanning transmission electron microscope (STEM) image shows a cross-sectional specimen of NiO-SrTiO3. (c) Bright field (BF) transmission electron microscope (TEM) image and selected area electron diffraction (SAED) pattern of the area show that the NiO nanocrystal is bound by {111} and {113} facets. (d) A HAADF-scanning transmission electron microscopy (STEM) image shows the rough interface with atomic resolution
Summary
Nickel oxide (NiO) has been widely investigated for its optical,[2] (anti-) ferromagnetic,[3,4] and electrochromic properties.[5,6,7] It was recently found to have resistive switching (RS) properties, switching from a high resistance (OFF) state to a low resistive (ON) state (and back to OFF) by successive application of electric fields of opposite polarity.[8]. Role of interface structure and chemistry in resistive switching of NiO nanocrystals on SrTiO3
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