Modification of the crystal structure of gadolinium gallium garnet by helium ion irradiation

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EAL STRUCTURE OF CRYSTALS

Modification of the Crystal Structure of Gadolinium Gallium Garnet by Helium Ion Irradiation B. K. Ostafiychuka, I. P. Yaremiya, S. I. Yaremiya, V. D. Fedoriva, U. O. Tomyna, M. M. Umantsiva, I. M. Fodchukb, and V. P. Kladkoc a

Vasyl Stefanyk Precarpathian National University, Shevchenko st. 57, IvanoFrankivsk 76018, Ukraine email: [email protected] b Fedkovych State University, Kotsyubinskogo st. 2, Chernivtsi 58012, Ukraine c Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, Nauki pr. 41, Kiev, 03028, Ukraine Received February 22, 2012

Abstract—The structure of gadolinium gallium garnet (GGG) single crystals before and after implantation by He+ ions has been investigated using highresolution Xray diffraction methods and the generalized dynamic theory of Xray scattering. The main types of growth defects in GGG single crystals and radiation induced defects in the ionimplanted layer have been determined. It is established that the concentration of dislocation loops in the GGG surface layer modified by ion implantation increases and their radius decreases with an increase in the implantation dose. DOI: 10.1134/S1063774513070122

INTRODUCTION Gadolinium gallium garnet (GGG, Gd3Ga5O12) single crystals are widely used as substrates for garnet ferrite films which are applied in microwave electron ics, magnetooptics, magnetic field sensors, optoelec tronics (phosphors for LEDs), and solidstate lasers in the IR and visible ranges. In addition, they are conve nient model samples with a complex basis for studying the physics of the processes occurring in their bulk and in the surface layer. Ion implantation is one of the most promising methods for affecting surface layers of single crystals in order to deliberately impart particular properties to them. In particular, implantation by He+ ions makes it possible to significantly increase the thickness of mod ified layer without its significant amorphization. A sur face waveguide layer is formed in GGG single crystals by ion implantation. Structural inhomogeneities caused by both growth and radiationinduced defects in GGG single crystals, as well as the kinetics of their interaction, have a deter mining influence on the operating characteristics of elements of GGGbased devices. Therefore, studying the defect subsystem in initial and modified GGG sin gle crystals is an urgent problem. EXPERIMENTAL The objects of study were GGG singlecrystal plates 0.49 mm thick grown by the Czochralski method in the (111) direction. The postgrowth treat ment of the plates included mechanical grinding and mechanical, mechanochemical, and chemical polish

ing; after the final treatment the surface had the 14th grade of finish. GGG single crystals were implanted by 100keV He+ ions under conditions excluding channeling (at an angle of ~7° with respect to the normal to the sur face). To minimize the selfannealing effect, the den sity of the ion current did not exceed 0.2 μA/cm2 dur ing implantation. The defect s

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