Electron microscope observations of twinning and phase transformations in indium sulfide crystals

Thin crystals of indium sulfide with the crystal structures corresponding to the compositions InS and In6S7 have been grown by means of a chemical transport reaction. Phase transitions have been induced by beam heating in the electron microscope and have been identified by electron diffraction. Crystals of InS occasionally contain twins when examined in the electron microscope. The twins presumably originate during the growth process. On subjecting these crystals to high intensity electron irradiation in the electron microscope large numbers of twins are nucleated. On continued electron irradiation structural transformations occur in these crystals. Crystals with the orthorhombic InS structure transform to the monoclinic In6S7 structure and on further electron irradiation a further transformation to the tetragonal In2S3 structure occurs. When crystals with the monoclinic In6S7 structure are subjected to high electron beam intensities in the electron microscope, a structural transformation also occurs and the crystals transform to the tetragonal In2S3 structure.