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The chemical etching properties of ferroelectric LiTaO3 crystal in near-stoichiometric compositions were quantitatively investigated with various ratios of HF and HNO3 acid mixtures by scanning force microscopy in the nanoscale range. Along with congruent LiTaO3 crystal, the -Z surfaces of near-stoichiometric LiTaO3 crystal were etched preferentially with pure HF acid and mixtures of HF and HNO3 acids. The etching rates on the -Z surface of near-stoichiometric LiTaO3 crystal were slower than that of congruent LiTaO3 crystal. The roughness (peak to peak) of etched surfaces were about 2 nm after being etched in all ratios of HF and HNO3 acids to a 70-nm etch depth. The temperature dependence of the etch rate followed the Arrhenius law. By taking advantage of the chemical preferential etching properties, precision surface structures could be fabricated on near-stoichiometric LiTaO3 crystal. [ABSTRACT FROM AUTHOR]

Domain patterning thin ferroelectric films creates nonlinear optical devices. Unfortunately, pinholes cause conventional electrical domain-poling methods to short circuit when used on thin film. We have applied a focused ion beam (FIB) to pattern the ferroelectric domains of LiNbO3 single crystalline films with thicknesses of 800 nm–2 μm. FIB can fabricate domains 100 times faster than a scanning probe microscope and can be applied to irregular surface structures. Furthermore, FIB is compatible with semiconductor device processing techniques, which paves the way for monolithic nonlinear photonic integrated circuits in ferroelectrics. [ABSTRACT FROM AUTHOR]

We have investigated microscale to nanoscale ferroelectric domain and surface engineering of a near-stoichiometric LiNbO[SUB3] crystal by using scanning force microscopy. The single crystals LiNbO[SUB3] fixed on metal substrates were polished to a 5 μm thickness. Artificial patterns of inverted-domain structures were fabricated in the samples, where polarization directions of the domains were switched by scanning the samples with a conductive cantilever while applying voltages. Furthermore, the negatively polarized surfaces in the patterns were preferentially etched in HF solution. As a result, cavity and mound-shaped surfaces were fabricated; these structures could be used to create functional templates and devices. [ABSTRACT FROM AUTHOR]

The stability of periodically poled domain structures in near-stoichiometric lithium tantalite, LiTaO3, (SLT) crystals exhibiting a low coercive field has become an important issue in the use of quasiphase-matching (QPM) devices. Temperature-induced backswitching in inverted domain structures in a 1.0 mol % MgO-doped SLT-QPM device with a QPM period of 6.1 μm used for the second harmonic generation of 488-nm-wavelength light was investigated using scanning force microscopy. It was revealed that backswitching consistently occurred due to heat treatment and that the amount was dependent on the temperature history. We propose an effective method of suppressing backswitching in the inverted domain structures of SLT-QPM devices on the basis of systematically analyzing the backswitching phenomena. [ABSTRACT FROM AUTHOR]

The stability of domains engineered in near-stoichiometric and congruent composition LiTaO3 crystals was investigated after heat treatment using scanning force microscopy. Piezoresponse images of the domains showed that the heat treatment had induced backswitching in the near-stoichiometric crystals and that the degree of backswitching depended on the domain structure and heating temperature. No backswitching was observed in the congruent composition crystals after the same heat treatment. The thermal stability of engineered LiTaO3 domains thus depends on the number of nonstoichiometric defects, the domain wall energy, and the pyroelectric effect. [ABSTRACT FROM AUTHOR]