X-ray study of the modulated structure in as-grown Ga2Te3 crystals with the defect zinc-blende lattice

Ga2Te3 crystallizes in the zinc-blende structure, where one third of the cation sites are vacant. Single crystal X-ray diffraction studies were done on as-grown Ga2Te3 crystals. The diffraction measurements show, other than the zinc-blende type main reflections, satellite reflections at q ≈1/20(210)c , where the subscript c means the cubic sub-lattice. The analysis of the satellite reflections shows that the crystal contains a two-dimensional modulation with q 1≈1/20(210)c and View the MathML sourceq1′≈1/20(21¯0)c. The modulated structure is composed of a coupled mode of the amplitude type modulation caused by Ga vacancies and the accompanying displacive modulation of surrounding Te atoms, which has the polarization vector along the [001]c direction. The nature of the atomic modulations is argued and the origin of the modulation is ascribed to the local distortion around a Ga vacancy.