Cathodoluminescence Study of Indented ZnO Crystals
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0957-K06-03
Cathodoluminescence Study of Indented ZnO Crystals Julio Mass1,2, Manuel Avella1, Juan Jiménez1, Tomás Rodríguez3, Michael Callahan4, E. Grant4, K. Rakes4, David Bliss4, and Buguo Wang5 1 Física de la Materia Condensada, Universidad de Valladolid, E.T.S.I.I, Paseo del Cauce s/n, Valladolid, 47011, Spain 2 Dpto. Matemáticas y Física, UniNorte, UniNorte, Km 5, Barranquilla, Colombia 3 Tecnología Electrónica, Universidad Politécnica de Madrid, ETSIT, Ciudad Universitaria, Madrid, 28028, Spain 4 Sensors Directorate, Air Force Research Laboratory, Hanscom AFB, MA, MA 01731 5 Solid State Scientific Corporation, Hollis, NH, NH 03049 ABSTRACT Vickers indentations of ZnO crystals grown by the hydrothermal method were studied by cathodoluminescence. The plastic deformation induced defects, which have influence on the luminescence spectrum. The main changes in the luminescence response concern the generation of non radiative recombination centers, but also a band close to the first order phonon replica of the free exciton is observed to appear in the regions deformed by the indentation. Besides, deep levels are also generated. The result of this is a relative increase of the defect related bands respect to the dominant bound exciton emission. INTRODUCTION ZnO is a wide bandgap semiconductor with potential application for UV optoelectronics. It offers several advantageous properties for UV based optoelectronics, such as a large direct band gap (3.3 eV), a large exciton binding energy (60 meV) that allows efficient excitonic emission at room temperature, and the existence of high quality large area crystals suitable for homoepitaxy (1). However, the problem of stable p-type doping is not yet resolved (2). To advance in the improvement of ZnO, a better comprehension of the crystal defects is necessary. The luminescence spectrum of ZnO has proven to be very sensitive to the growth conditions and to the surface properties; in particular, the luminescence spectrum of ZnO reveals significant differences from sample to sample, from one surface termination to other, and a strong dependence on the polishing procedure (3). During polishing, but also during other handling operations, plastic deformations can take place, and the interaction between the dislocations generated by the deformation and the crystal matrix introduces point defects or their complexes, which can affect the local properties of ZnO. Microindentation is a way to achieve plastic deformation in a controlled way. Previous reports on the indentation of ZnO using both microindenters and nanoindenters focused on the description of the slip system responsible for the dislocation rosette around the indentation (4,5). However, an exhaustive study of the influence of the indentation on the luminescence spectrum is still lacking. We present herein a spectrally resolved cathodoluminescence (CL) study of the spectral changes induced locally in the luminescence spectrum by Vickers microindentation. SAMPLES AND EXPERIMENTAL SET-UP The samples were cut from hydrothermal
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