The interaction of alkoxysilanes with nanoscaled giant polyoxoclusters is a challenging route for efficiently building blocks for supramolecular smart-tune design. 3-aminopropyltrimethoxysilane (APTMS) treatment grafts amino groups onto the surface of...

No abstract

information storage, [1,2] memristors based on tunneling, [3,4] energy storage devices, [5] etc. Tailoring the defect structure permits fine tuning of the functional properties of ferroelectrics. [6][7][8][9][10] The surfaces and interfaces are directly influenced by the nearby defects, and bulk properties are rendered by the defects via multiple mechanisms. [11,12] Up to date, the number of techniques allowing studies of defects with a high spatial resolution is limited, and they are mainly based on local monitoring of the crystalline structure or chemical composition. [13][14][15][16] Most of these local compositional methods like transmission electron microscopy, X-ray tomography, electron holography, etc. do not have a high enough sensitivity or need challenging sample preparation. [13] The optical method of second harmonic generation can be used to monitor the defect concentration and off-stoichiometry, [16] however it is limited in resolving the type of charged defects and yields only micrometer-scale spatial resolution. Thus, the novel experimental approaches allowing accurate measurement of the defect concentration and/or corresponded functional properties at the nanoscale are highly desirable.In ferroelectrics, charged defects affect polarization reversal as they directly participate in the screening of the depolarization electric field [8,[17][18][19][20] since they can become mobile Monitoring the charged defect concentration at the nanoscale is of critical importance for both the fundamental science and applications of ferroelectrics. However, up-to-date, high-resolution study methods for the investigation of structural defects, such as transmission electron microscopy, X-ray tomography, etc., are expensive and demand complicated sample preparation. With an example of the lanthanum-doped bismuth ferrite ceramics, a novel method is proposed based on the switching spectroscopy piezoresponse force microscopy (SSPFM) that allows probing the electric potential from buried subsurface charged defects in the ferroelectric materials with a nanometer-scale spatial resolution. When compared with the compositionsensitive methods, such as neutron diffraction, X-ray photoelectron spectroscopy, and local time-of-flight secondary ion mass spectrometry, the SSPFM sensitivity to the variation of the electric potential from the charged defects is shown to be equivalent to less than 0.3 at% of the defect concentration. Additionally, the possibility to locally evaluate dynamics of the polarization screening caused by the charged defects is demonstrated, which is of significant interest for further understanding defect-mediated processes in ferroelectrics.

No abstract

The core-shell morphology study is crucial for composite materials, comprised of a low conductive core with a highly conductive thin carbon shell. The study analyzed carbon morphology evolution for the two series of Li 4 Ti 5 O 12 /C samples with carbon content increasing from 0.9 to 5.6 wt%. The conventional X-Ray Photoelectron Spectroscopy (XPS) study allowed us to conclude about the efficiency threshold of carbon layer growth over lithium titanate core for two carbon deposition methods-both sucrose and acetylene decompositions. Although the carbon layer thickness is increasing with carbon concentration growth in LTO/C composites, the efficiency of carbon coverage was shown to decrease with the threshold carbon concentrations about 1-2%. The chemical bonding analysis based on the same XPS data was used for C@LTO interface characterization. The proposed approach can be used for optimization of producing different composites with core-shell structure (carbon-based composites, materials with protective layers, and materials with gradient core-shell structure).