Eﬀect of swift heavy ion irradiation on the surface morphology of highly c-axis oriented LSMO thin ﬁlms grown by pulsed laser deposition M.S. Sahasrabudhe a , Deepak N. Bankar a , A.G. Banpurkar a , S.I. Patil a , K.P. Adhi a, * , Ravi Kumar b a Center for Advanced Studies in Materials Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune 411 007, India b Nuclear Science Center, Aruna Asaf Ali Marg, New Delhi 110 067, India Received 26 February 2007 Available online 6 July 2007 Abstract A detailed investigation of the surface morphology of the pristine and swift heavy ion (SHI) irradiated La 0.7 Sr 0.3 MnO 3 (LSMO) thin ﬁlm using atomic force microscope (AFM) is presented. Highly c-axis oriented LSMO thin ﬁlms were grown on LaAlO 3 (1 0 0) (LAO) substrates by the pulsed laser deposition (PLD) technique. The ﬁlms were annealed at 800 °C for 12 h in air (pristine ﬁlms) and subse- quently, irradiated with SHI of oxygen and silver. The incident ﬂuence was varied from 1 · 10 12 to 1 · 10 14 ions/cm 2 and 1 · 10 11 to 1 · 10 12 ions/cm 2 for oxygen and silver ions, respectively. X-ray diﬀraction (XRD) studies reveal that the irradiated ﬁlms are strained. From the AFM images, various details pertaining to the surface morphology such as rms roughness (r), the surface rms roughness aver- aged over an inﬁnite large image (r 1 ), fractal dimension (D F ) and the lateral coherence length (n) were estimated using the length depen- dent variance measurements. In case of irradiated ﬁlms, the surface morphology shows drastic modiﬁcations, which is dependent on the nature of ions and the incident ﬂuence. However, the surface is found to remain self-aﬃne in each case. In case of oxygen ion irradiated ﬁlms both, r 1 and D F are observed to increase with ﬂuence up to a dose value of 1 · 10 13 ions/cm 2 . With further increase in dose value both r 1 and D F decreases. In case of silver ion irradiated ﬁlms, r 1 and D F decrease with increase in ﬂuence value in the range studied. Ó 2007 Elsevier B.V. All rights reserved. PACS: 75.47.Gk; 61.80.x; 61.80.Jn Keywords: Radiation damage; CMR manganites; Ion radiation eﬀects; Surface roughness 1. Introduction The study of surface roughness of the deposited thin ﬁlms is of paramount interest from both academic as well as technological perspective. The smoothness or roughness of the ﬁnal growth front of the thin ﬁlm forming an inter- face with adjacent material, i.e. either contacts or other thin ﬁlm in bi-layer or multi-layers, inﬂuence the perfor- mance of the devices realized. For instance Saito et al. [1] have studied the eﬀects of the remote surface roughness, which is the roughness between the polycrystalline silicon gate and gate dielectric, on the inversion carrier mobility of metal–insulator–semiconductor ﬁeld-eﬀect-transistors with ultrathin gate dielectrics. Breemen et al. [2] have stud- ied the large area liquid crystal mono-domain ﬁeld eﬀect transistors. Berndt et al. [3] have investigated the eﬀect of surface roughness on the magnetic properties of LSMO thin ﬁlms etc. Apposite control of the surface properties requires an understanding of the underlying growth mech- anism, which can be achieved by detailed analysis of sur- faces prepared under various growth conditions. We have selected La 0.7 Sr 0.3 MnO 3 (LSMO) thin ﬁlms as a vehicle in our study for various reasons. With a high Curie tempera- ture T C of 370 K, LSMO is an attractive material for 0168-583X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2007.06.030 * Corresponding author. Tel.: +91 20 2569 2678; fax: +91 20 2569 1684. E-mail address: kpa@physics.unipune.ernet.in (K.P. Adhi). www.elsevier.com/locate/nimb Nuclear Instruments and Methods in Physics Research B 263 (2007) 407–413 NIM B Beam Interactions with Materials & Atoms