Correlation between ion beam parameters and physical characteristics of nanostructures fabricated by focused ion beam Sarvesh K. Tripathi, Neeraj Shukla, Vishwas N. Kulkarni * Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208 016, India Received 25 September 2007; received in revised form 13 December 2007 Available online 1 February 2008 Abstract We report a study of the physical characteristics of the pillars of C, Pt and W grown by 10–30 keV Ga focused ion beam (FIB) as a function of Ga ion flux, and present a quantitative analysis of the elements using energy-dispersive analysis of X-rays (EDAX). All the FIB grown pillars exhibit a rough morphology with whisker like protrusions on the cylindrical surface and broadening of the base as compared to the nominal size. For a constant fluence, the height of the pillar initially increases and then reduces after going through a maximum as a function of ion flux in all the cases. The compositional analysis shows good metallic quality for Pt structures but reveals significant contamination of Ga in C and Ga and C in W structures at higher ion fluxes. Explanation to all these observations has been sought in the light of secondary ion and electron effects and the different processes involved which lead to the FIB induced deposition. Ó 2008 Elsevier B.V. All rights reserved. PACS: 81.15.Jj; 81.16.ÀCj; 41.75.Ài; 52.59.Àf Keywords: Focused ion beam; Nano structure fabrication; EDAX; SEM 1. Introduction Nanostructures of precise dimensions are required for the manufacturing of nano-sensors, actuators, micro and nano-electro-mechanical systems (MEMS and NEMS) and structures for biological applications. Focused ion beam (FIB) assisted process, which was initially used for photomask repair, failure analysis of circuits and devices in semiconductor industry, site specific TEM sample prep- aration, etc., is now emerging as a powerful and unique way to fabricate rapid prototypes of a variety of 3-D nano- structures [1,2]. Fabrication of several unique 3-D struc- tures viz, hanging beams, cantilevers, tubes, hollow pyramids, etc., has been reported in the literature [1]. The physical, mechanical, electrical and other properties of FIB made nanostructures which have potential applica- tions in the fabrication of a variety of sensors, MEMS and NEMS get strongly influenced by the energy and flux of the incident ions. For example, Fujita et al. have shown that Young’s modulus of Ga FIB grown carbon pillars reduces by about six times when the growth rate is increased by about four times [3]. In another work, the FIB deposited platinum films have shown resistivity depen- dence on the growth conditions [4]. These findings are unexpected because the growth process depends on the phenomena of cracking of molecules under ion impact and on the release of the volatile components with residue remaining on the surface as the grown material. During the deposition process, the primary ions and the components of the precursor gas mainly carbon can also get trapped in the grown layer. Strategies to either reduce the Ga incor- poration or to remove it after deposition have been sug- gested in the literature [5]. In the literature, the studies concerning FIB induced growth are rather limited as com- pared to the studies on the aspects related to micro-compo- nents and structures made by FIB milling. In this paper, we 0168-583X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2007.12.071 * Corresponding author. Tel.: +91 512 2597985/2597986; fax: +91 512 2590914/2590103. E-mail address: vnk@iitk.ac.in (V.N. Kulkarni). www.elsevier.com/locate/nimb Available online at www.sciencedirect.com Nuclear Instruments and Methods in Physics Research B 266 (2008) 1468–1474 NIM B Beam Interactions with Materials & Atoms