Ion beam energy effects on structure and properties of diamond like carbon films deposited by closed drift ion source S ˇ . Mes ˇkinis a, * , V. Kopustinskas a , A. Tamulevic ˇien _ e a , S. Tamulevic ˇius a , G. Niaura b , J. Jankauskas a , R. Gudaitis a a Institute of Physical Electronics of Kaunas University of Technology, Savanori˛ u 271, LT-50131 Kaunas, Lithuania b Institute of Chemistry, A. Gos ˇtauto 9, LT-01108 Vilnius, Lithuania article info Article history: Received 19 October 2009 Received in revised form 21 January 2010 Accepted 24 January 2010 Keywords: Diamond like carbon Closed drift (anode layer) ion source Ion beam deposition Structure Optical properties Electrical properties abstract In the present study DLC films deposited from acetylene gas by a closed drift ion source were investi- gated. Ion beam energy effects on structure as well as optical and electrical properties of the synthesized films were studied. Non-monotonic dependence of structure of the DLC films on ion beam energy was observed. The highest sp 3 /sp 2 ratio as well as highest optical transparency was observed in the case of the films synthesized by 500 eV energy ion beam. However, the bandgap of the DLC films synthesized by 500 eV energy ion beam was the lowest between all investigated samples, while resistivity non- monotonically decreased with increase of the ion beam energy. These results were explained by changes of the sp 3 /sp 2 ratio, structure of sp 2 bonded clusters as well as hydrogen content in the film due to the competition between the increased (decreased) ion beam energy and decreased (increased) ion/ neutral ratio. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Diamond like carbon (DLC) is an umbrella term that refers to films of amorphous carbon materials that display some of the unique properties of natural diamond [1]. DLC films received significant interest due to their outstanding mechanical, chemical, optical, and electrical properties as well as room temperature deposition possibility [1]. Besides the numerous tribological applications, possibility to use diamond like carbon films for optical and electronic applications such as antireflective coatings for solar cells, transparent protective films for optical storage disks [2] and IR windows [3], and passivating films for high power diodes [4] were considered. Recently discovered piezoresistive properties of the diamond like carbon [5–7] in combination with exceptional hard- ness, high Young’s modulus, and low friction coefficient [1] make this material very attractive for different microelectromechanical (MEMS) sensors applications. Numerous deposition methods (plasma enhanced chemical vapor deposition, magnetron sputtering, ion beam sputtering, ion beam deposition, laser ablation, filtered vacuum arc deposition, and others) were used for synthesis of the both hydrogen-free and hydrogenated DLC films. Particularly, ion beam deposition has some advantages over the other methods of the synthesis of the hydrogenated DLC films. Parameters of the thin film growth process such as ion beam energy, plasma power, substrate temperature, angle of ion beam incidence, system pressure, gas composition, and flow rate can be autonomously and precisely controlled over a wide range of process conditions. Films can be deposited both onto the electrically conductive and insulating materials. Among all the ion sources used for DLC synthesis closed drift (anode layer) method is notable for easy of the maintenance and reliability due to the griddles and electrodeless design as well as large area deposition possibility [8,9]. Closed drift ion sources are widely used in industry. However, peculiarities of the DLC films deposited by closed drift ion source and dependence of their properties on technological process conditions are less investigated comparing with hydrogenated DLC films deposition by PECVD or plasma beam source [7,9–16]. It should be noted that contradictory results were reported on the influence of the ion beam energy on the properties of DLC films synthesized by closed drift ion source [9,10], while ion energy is the main parameter in diamond like carbon film synthesis process [1]. Therefore, in the present study effects of the ion beam energy on the structure, electrical, optical, and piezoresistive properties as well as residual stress level of hydrogenated DLC films were investigated. * Corresponding author. Tel.: þ370 37 327605; fax.: þ370 37 314423. E-mail address: sarunas.meskinis@ktu.lt (S ˇ . Mes ˇkinis). Contents lists available at ScienceDirect Vacuum journal homepage: www.elsevier.com/locate/vacuum ARTICLE IN PRESS 0042-207X/$ – see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.vacuum.2010.01.047 Vacuum xxx (2010) 1–5 Please cite this article in press as: S ˇ Mes ˇkinisKopustinskas V, et al., Ion beam energy effects on structure and properties of diamond like carbon films..., Vacuum (2010), doi:10.1016/j.vacuum.2010.01.047