Fabrication of LSS bottom electrode by PLD M.S. Awan a, * , A.S. Bhatti a , S. Qing b , C.K. Ong b a Center for Micro and Nano Devices, Department of Physics, Park Road, Near Tramaree Chowk, COMSATS Institute of Information Technology, Islamabad, Pakistan b Center for Superconducting and Magnetic Materials, Department of Physics, National University of Singapore,117542 Singapore, Singapore article info Article history: Received 13 October 2009 Received in revised form 23 March 2010 Accepted 25 March 2010 Keywords: Polycrystalline Pulsed laser ablation Buffer layer Multiferroic Conductive electrode abstract Polycrystalline LaNiO 3 /SrTiO 3 /Si(100) (LSS) conducting substrates were fabricated by pulsed laser deposition (PLD) technique. LSS substrate is a potential candidate for the multiferroic materials for use as bottom electrode. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) equipped with EDX system, atomic force microscopy (AFM) and electrical resistivity were employed to characterize the films. Buffer layer SrTiO 3 (STO) deposited at 700  C resulted in dense, smooth and with crack free features. XRD studies confirmed bi-crystalline [(100), (110)] growth of STO on Si(100) substrate. Deposition of bottom electrode LaNiO 3 (LNO) epitaxially followed the buffer layer. EDX anal- yses determined the chemical composition of the films. The role of oxygen partial pressure during deposition affecting the crystallinity and resistivity of the films was explored in detail. Atomic force microscopy revealed the atomic scale features of the films desirable for functional devices. Resistivity of the conducting film (LNO) was w10 4 U cm at room temperature. Thus it is demonstrated that LNO/STO/ Si(100) is a suitable conducting substrate for growth of the multiferroic functional materials. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction In recent years, multiferroic materials have received consider- able attention for their potential applications in integrated circuits and functional devices [1]. These applications require fabrication of high quality ferroelectric and magnetic thin films on suitable electrodes, such as metal or conducting oxides. Electrodes are required to have certain properties, such as high metallic conduc- tivity, sufficient resistance against oxidation and good adhesion to the films [2]. Therefore, platinum (Pt), one of the few metals satisfying these requirements, has been used as a bottom electrode in high dielectric constant thin film capacitors [3]. However, Pt as an electrode poses a challenge to obtain a good quality thin film on it due to large lattice mismatch with most of the perovskite oxide materials. Moreover, Pt electrodes often result in the formation of hillocks, which may lead to the degradation of dielectric properties. Also the electrical properties of capacitors (like Pt/PZT/Pt) easily degrade in a hydrogen-containing or plasma environment [4]. As an alternative material, conducting perovskite oxides such as LaSrMnO (LSMO), La 0.5 Sr 0.5 CoO 3 (LSCO), YBa 2 Cu 3 O 7 (YBCO), SrRuO 3 (SRO) and LaNiO 3 (LNO) have been tried as bottom electrode [5e8] for the determination of electrical properties of the multiferroic thin films. Among all these conductive oxides LaNiO 3 (LNO) is the most attractive contender for electrode material. This is because of its simple crystal structure, uncomplicated synthesis at low temperatures compared to other metal oxides. For multilayers containing LNO, the diffusion of ions into the material (YBCO) during fabrication may be smaller than with the multilayers of other materials. Finally, LNO has only two metal ions in it and its composition is thus easier to reproduce. It has a pseudo-cubic perovskite crystal structure with lattice parameter a ¼ 3.84  A and electrical resistivity <10 3 U cm at room temperature [9]. LNO has been used as the bottom contact for the study of ferroelectric materials BaSrTiO 3 (BST), Pb(ZrTi)O 3 (PZT), BaTiO 3 (BTO) [10e13]. The (100) and/or (110) oriented perovskite thin films have been shown good multiferroic properties [14]. Thus in order to have good electrical contact, the bottom electrode is preferred to have the same orientation with excellent electrical properties. Significant understanding of LNO has been developed through numerous experimental and theoretical analyses [15e17]. PLD has been applied [18e20] to grow LNO and/or functional materials on variety of substances. However, their growth on silicon substrate is still a challenge due to large lattice mismatch. The complexity of lattice mismatch between LNO and Si substrate is addressed by introducing a buffer layer. This paper focuses on the fabrication of conducting LNO thin film on STO buffered Si(100) substrate by PLD. Insulating behavior and low chemical reactivity of STO makes it ideal candidate for buffer layer. Furthermore it has crystallographic similarity with the multiferroic (BFO) materials. Intentionally (100 and/or 110) phases of STO were preferred for growth on Si substrate to facilitate the epitaxial growth of (LNO and BFO) films. * Corresponding author. Tel.: þ92 34 55112329. E-mail address: sss_awan@yahoo.com (M.S. Awan). Contents lists available at ScienceDirect Vacuum journal homepage: www.elsevier.com/locate/vacuum 0042-207X/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.vacuum.2010.03.011 Vacuum 85 (2010) 55e59