Journal of Electron Spectroscopy and Related Phenomena 180 (2010) 1–5 Contents lists available at ScienceDirect Journal of Electron Spectroscopy and Related Phenomena journal homepage: www.elsevier.com/locate/elspec Formation of self-organized Ta nano-structures by argon ion sputtering of Ta foil: XPS and AFM study V.R.R. Medicherla ∗ , S. Majumder, D. Paramanik, Shikha Varma Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005, India article info Article history: Received 15 May 2009 Received in revised form 25 January 2010 Accepted 11 February 2010 Available online 19 February 2010 PACS: 81.16.Rf 73.22.-f 77.55.+f 79.60.-i 07.79.Lh Keywords: Nano-structures High dielectric oxides Ion sputtering XPS Surface core level AFM Surface morphology abstract The nano-structured Ta has been prepared by 3 keV argon ion sputtering of the Ta foil. The XPS and AFM studies were carried out on samples sputtered for fluences ranging from 6.0×10 15 to 3.6×10 16 ions/cm 2 . The sample sputtered at lowest fluence showed the formation of dimples along with mild ripples which disappeared on further sputtering. After prolonged sputtering, clear ripple formation has been observed with a wave length of about 80 nm. Our XPS results indicated that Ta 4f of the Ta liberated after sput- tering is shifted to higher binding energy by 0.5 eV. The Ta 2 O 5 completely disappeared after prolonged sputtering for 60 min, but little amount of sub-Ta oxide (TaO x ) is still seen. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Tantalum and its compounds have extensively been studied due to their numerous technological applications such as thin film resistor materials with low temperature coefficient of resistivity [1], oxygen sensors [2], erosion and corrosion resistance coatings [3], and as a high dielectric (high k) material in metal-oxide- semiconductor devices [4]. Tantalum thin films are used as print head heaters [5], photo-catalysts [6] and hard coatings on tools [7], etc. Ta nano-structures have become very important both from tech- nological and fundamental point of view. Nano-scale tantalum powder has been widely studied for a variety of applications. For example, superfine and pliable tantalum powders can be utilized to improve the quality and reduce the package size of capacitors ∗ Corresponding author. Present Address: Department of Physics, Institute of Technical Education and Research Siksha ‘O’ Anusandhan University Jagamara, Bhubaneswar 751030, India. Tel.: +91 674 2350181; fax: +91 674 2351880. E-mail address: ramarao@iopb.res.in (V.R.R. Medicherla). used in memory devices. The super-conducting properties of Ta are expected to depend on the size of the nano-clusters. It would be a very challenging task to produce Ta nano-clusters without the interstitial impurities. Preparation of nano-tantalum by physical methods is extremely difficult due to its high melting point of 2996 ◦ C. Several chemical methods were used to synthesize tantalum powder of few micron size from TaCl 5 or K 2 TaF 7 [8]. In recent years many different meth- ods have been proposed and tested to produce nano-structures on solid surfaces [9]. A well ordered Ta surface with dimples of tens of nanometers in size has been observed by electropolishing the Ta foil [10]. The single crystalline nano-tantalum powder has been prepared by Wang et al. [11] using hydrogen arc plasma method. Among these methods, low energy ion bombardment has emerged as a simple and practical technique to produce nano-scale patterns on metallic surfaces [12]. The morphological evolution of the surface, during low energy ion sputtering is rather a complex issue. However, in nanotechnol- ogy, ion beam sputtering is frequently regarded as an alternative process for the formation of self-organized nano-patterns. This pat- tern formation is related to the surface instability between the 0368-2048/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.elspec.2010.02.006