Atomic excitations during ion beam sputtering of YBa 2 Cu 3 O 7 targets A.H. Dogar a , A. Qayyum b, * a Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad, Pakistan b Physics Research Division, Pakistan Institute of Nuclear Science and Technology, P.O. Nilore, Islamabad, Pakistan Received 29 November 2005; received in revised form 23 January 2006 Available online 9 March 2006 Abstract YBa 2 Cu 3 O 7 targets were bombarded with 1–10 keV Ar + beam, and excitation of the sputtered particles was studied with the help of optical spectroscopy in 300–700 nm wavelength range. Intense emission from several YI, BaI and CuI transitions was observed, but essentially no emission from sputtered excited atomic and molecular oxygen. Photon yields of various emission lines were measured as a function of the ion energy and results were compared with a model based on the collision cascade sputtering mechanism and an excitation process that depend on velocity of the ejected particle. Moreover, we observed decrease of the photon emission with ion flu- ence that may be due to depletion of the oxygen in surface region. Ó 2006 Elsevier B.V. All rights reserved. PACS: 79.20.m; 34.50.Dy Keywords: Ion-induced photon emission; Sputtering; YBa 2 Cu 3 O 7 1. Introduction It is well established that the interaction of the energetic ions with solid surfaces results in the release of excited neu- trals and ions from the target. The subsequent decay of these excited particles in vicinity of the target surface results in the emission of photons [1,2]. This phenomenon has been given the name of ion-induced photon emission (IPE). Although a large amount of work has been reported on the emission from elemental and composite targets but understanding of the IPE is far from being complete. Addi- tionally, excitation in sputtering is much more complicated and even less understood in case of composite targets. Explanations of the excited state populations in terms of direct excitation in atom–atom collisions in the cascade, atom–surface electron transfer, bond breaking and the local thermal equilibrium processes have been proposed so far [3]. None of these models can independently explain majority of the experimental findings. On experimental front, beside strong influence of the matrix on excitation efficiency [4], development of IPE as a standard analytical technique is hindered by the weak photon emission that is due to non-radiative de-excitations of the sputtered par- ticles [2]. In this work the projectile energy dependence of the line radiation emitted during sputtering of YBa 2 Cu 3 O 7 by 1–10 Ar + ions is studied and results are discussed in terms of a model [5], which assumes that the dominating effect in the production of excited atoms and ions is the electron exchange mechanism between sputtered particle and surface. The presented result will provide more in sights to the processes of excitation and survival of the excited particle during sputtering. 2. Experimental setup The experimental setup has been previously described in detail [6], only a brief description is given here. The 0168-583X/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2006.01.058 * Corresponding author. Tel.: +92 51 5957460; fax: +92 51 9290275. E-mail address: qayyum@pinstech.org.pk (A. Qayyum). www.elsevier.com/locate/nimb Nuclear Instruments and Methods in Physics Research B 247 (2006) 290–294 NIM B Beam Interactions with Materials & Atoms