Abstract
The effect of L-methionine additive on the crystal growth of L-alanine crystal was investigated by atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS) and time of flight-secondary ion mass spectrometry (TOF-SIMS). The crystal was grown in the presence of L-methionine (5 mol % with respect to L-alanine concentration) at a supercooling ΔT=2K. The growth rate of (120) face was almost suppressed and that of (011) face was only relatively inhibited. The surface topography of each face was also observed by AFM and they showed to be different. From the XPS depth profile results, sulfur atoms were detected only outer surface of the (120) face, but in the case of (011) face, sulfur atoms were detected not only outer surface but also in side of the crystalline lattice. In addition, from the TOF-SIMS results, L-methionine molecule and L-alanine molecule were dotted each other on the surface of (011) face, but in the case of (120) face, L-methionine molecule was present only on local part of surface, on which L-alanine molecule won't. It was considered that L-methionine molecule which exist in outermost surface of (120) face hinder the growth of that face of L-alanine and that which exist in the surface of (011) face don't prevent the growth. The difference of growth suppression effect on each face by L-methionine additive was confirmed by XPS analysis and TOF-SIMS analysis.
