Nanoscale imaging of permittivity in giant-κ CaCu3Ti4O12 grains

Abstract

The possibility to image the local permittivity in giant-dielectrics by scanning probe microscopy was demonstrated. In particular, the microstructure and the dielectric properties of CaCu 3 Ti 4 O 12 ͑CCTO͒ films grown on ͑001͒ LaAlO 3 substrates were studied. CCTO amorphous layers obtained by metal-organic chemical vapor deposition have been crystallized by subsequent rapid thermal treatments at 1100°C. X-ray diffraction measurements demonstrated the growth of CCTO and CaTiO 3 phases. As a novelty, large square CCTO grains ͑a few microns͒ were formed with a very high permittivity. The local impedance modulus, phase, and morphology were simultaneously acquired, and the local permittivity ͑around 8000 at 90 kHz͒ of each isolated CCTO grain was calculated.

Control of Heteroepitaxial Growth of CaCu3Ti4O12 Films on SrTiO3 Substrates by MOCVD

“…In fact, the lattice mismatch Full Paper between CCTO and LaAlO 3 is higher (2.5%) than that of CTO/LaAlO 3 (0.7%), nevertheless the formation of a CTO/ CCTO mixture has been observed only at high temperatures. [37] In particular, the formation of the CCTO/CTO mixture has been observed after rapid thermal annealing treatments, (kinetic-driven process) at 1000-1100 8C, of the amorphous matrix obtained during the two-step process, [36] while one-step depositions give rise to CCTO films. In order to provide an immediate overview, a scheme summarizing all the performed deposition/annealing processes and the related results is shown in Figure 7.…”

“…Nevertheless, in previous papers, [33,37] we have already reported a full dielectric characterization of CCTO films deposited by our MOCVD approaches. We established that two main mechanisms can be proposed for the explanation of the extrinsic colossal permittivity response.…”

Conductive Atomic Force Microscopy and Scanning Impedance Microscopy for the Imaging of Electrical Domain in CaCu3Ti4O12 Perovskite Oxide

“…Obviously, they cannot be reduced with superficial treatments. The electrical contact quality between the probe and the sample surface has been checked using the Scanning Impedance Microscopy (SIM) in order to exclude the presence of electrical features as fixed or mobile charges and also the presence of surface states [5,9,10] Figure 3 shows the dC/dV (C= capacitance and V= Voltage) versus voltage curves acquired on both the treated (blue curve) and untreated (red curve) CCTO surfaces. Figure 2 clearly shows the strong PSD(k) surface roughness reduction at high frequency (green circle) and the exponential decay vs. k after the 0.1 µm diamond paste treatment, reaching roughness values comparable to an atomic flat sample (RMS ~ 1 nm in regions which do not include any void) in 10x10 µm 2 scanned regions.…”

Scanning Probe Microscopy on heterogeneous CaCu3Ti4O12 thin films

“…Standard experiments were carried out using Nanoworld boron doped diamond tips [19-22]. Laser off measurements have been also carried out to exclude the influence of the laser on the reported electrical measurements at nanoscale.…”