TOP-SEEDED SOLUTION GROWTH OF MONOMETHYLUREA SINGLE-CRYSTALS

It was previously reported on the growth of monomethylurea (NMU) singl e crystals from methanol solution by a mechanical limitation-direction (MLD) technique in which long (100) oriented seeds, capped on their e xtremities, were employed. The crystals obtained by this technique, in spite of their good structural and optical quality, presented their c ore region, in which the seed was located, with a higher density of st ructural defects and henceforth a reduced cross section useful for opt ical applications. It is here referred to a new, top-seeded growth con figuration. devised on the basis of a preliminary PBC analysis for ass essing the morphological importance of the crystal faces experimentall y observed during crystal growth, which allows to grow NMU crystals in which the defected core region is removed for almost the entire lengt h of the crystal.