We used an atomic force microscope (AFM) to study the surface morphology of butterfly-like crystals of BaTiO3. Observations were made while varying the temperature from room temperature to 150°C and the annihilation process of the surface structure due to 90° domain boundaries was detected. The relationship between the surface gradient change at the domain boundaries and the tetragonal distortion was discussed.
The dielectric constants of the quantum paraelectrics SrTiO 3 and KTaO 3 are measured between 4 and 325 K. Their temperature dependences are analyzed on the basis of the Barrett and Vendik models. The former model deals with a ferroelectric optical mode coupled with other optical modes, whereas the latter deals with the mode coupled with acoustic modes.In addition, the latter contains a measure of the density of defects and inhomogeneity. The dielectric constants at low temperatures can be accurately described using Vendik's formula; however, they cannot be accurately described using Barrett's formula, even after the introduction of a measure of the density of defects and inhomogeneity. A critical quantum paraelectric region has been introduced recently between a classical region and a quantum paraelectric one. We point out that the critical region is where a low-temperature approximation is well realized for the model with the coupling between the ferroelectric and acoustic modes.
We demonstrate the results of a strain (stress) evaluation obtained from Raman spectroscopy measurements with the super-resolution method (the so-called super-resolution Raman spectroscopy) for a Si substrate with a patterned SiN film (serving as a strained Si sample). To improve the spatial resolution of Raman spectroscopy, we used the super-resolution method and a high-numerical-aperture immersion lens. Additionally, we estimated the spatial resolution by an edge force model (EFM) calculation. One- and two-dimensional stress distributions in the Si substrate with the patterned SiN film were obtained by super-resolution Raman spectroscopy. The results from both super-resolution Raman spectroscopy and the EFM calculation were compared and were found to correlate well. The best spatial resolution, 70 nm, was achieved by super-resolution Raman measurements with an oil immersion lens. We conclude that super-resolution Raman spectroscopy is a useful method for evaluating stress in miniaturized state-of-the-art transistors, and we believe that the super-resolution method will soon be a requisite technique.
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