Microhardness, chemical etching, SEM, AFM and SHG studies of novel nonlinear optical crystal – l-threonine formate

The crystal l-threonine formate, an organic NLO crystal was synthesized from aqueous solution by slow evaporation technique. The grown crystal surface has been analyzed by scanning electron microscopy (SEM), chemical etching and atomic force microscopy (AFM). SEM analysis reveals pyramidal shaped minute crystallites on the growth surface. The etching study indicates the occurrence of etch pit patterns like striations and step like pattern. The mechanical properties of LTF crystals were evaluated by mechanical testing which reveals certain mechanical characteristics like elastic stiffness constant (C11) and youngʹs modulus (E). The Vickers and Knoop microhardness studies have been carried out on LTF crystals over a range of 10–50 g. Hardness anisotropy has been observed in accordance with the orientation of the crystal. AFM image shows major hillock on growth surface. The second harmonic generation (SHG) efficiency has been tested by the Kurtz powder technique using Nd:YAG laser and found to be about 1.21 times in comparison with standard potassium dihydrogen phosphate (KDP) crystals.