Applied Surface Science 256 (2010) 5602–5605 Contents lists available at ScienceDirect Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc Fabrication of diamond nanorods for gas sensing applications Marina Davydova a,b,∗ , Alexander Kromka a , Bohuslav Rezek a , Oleg Babchenko a , Martin Stuchlik c , Karel Hruska a a Institute of Physics, Academy of Science of the Czech Republic, Cukrovarnicka 10, 16200 Prague, Czech Republic b Department of Physics, Faculty of Civil Engineering, CTU in Prague, Thakurova 7, 16629 Prague, Czech Republic c Department of Chemistry, TU Liberec, Studentska 2, 46117 Liberec, Czech Republic article info Article history: Available online 11 March 2010 PACS: 73.63.Bd 61.46.Km 81.05.ug 81.15.Gh 68.55.A Keywords: Nanocrystalline diamond Diamond nanorods Surface conductivity Gas sensor SEM abstract Diamond nanorods were fabricated for a sensing device by utilizing reactive ion etching in CF 4 /O 2 radio frequency plasma. The length of the nanorods has been controlled by the ion etching time. The obtained morphologies were investigated by scanning electron microscopy. The gas sensing properties of the H- terminated diamond-based sensor structures are indicating that we have achieved high sensitivity to detect phosgene gas. Also, our sensor exhibited good selectivity between humid air and phosgene gas if the measurement is conducted at elevated temperatures, such as 140 ◦ C. Furthermore, such sensor response rating could reach as high value as 4344 for the phosgene gas, which was evaluated for the sample consisting of the longest nanorods (up to 200 nm). © 2010 Elsevier B.V. All rights reserved. 1. Introduction Recently, one-dimensional nanostructures such as nanowires, nanotubes, nanocones and nanorods, respectively, have becom- ing widespread [1–4]. These structures are being used in a large number of electronic and gas sensing devices among others. It has been found that the one-dimensional nanostructures, among many possible geometrical configurations, exhibit distinctive fea- tures that are not present in the bulk films, for instance [5]. The main difference between the two sensing nanostructures, i.e. nanorods and thin films, is in the higher surface-to-volume ratio values in nanorods as compared to thin films, which has significant impact on the number of possible reaction sites. In comparison to common sensitive materials, such as SnO 2 , Ga 2 O 3 , TiO 2 , etc., diamond is very attractive material for this field due to its inherent physical and chemical properties [6–8]. The geometrical diversity of 1D diamond structures has been already fabricated using reactive ion etching and by employing various chemistries [9,10]. For example, Rakha et al. [11] demonstrated ∗ Corresponding author at: Institute of Physics, Academy of Science of the Czech Republic, Cukrovarnicka 10, 16200 Prague, Czech Republic. Tel.: +420 220 318 511; fax: +420 233 343 184. E-mail address: davydova@fzu.cz (M. Davydova). fabrication of diamond nanorods (DNRs) by hydrogen plasma post- treatment of nanocrystalline diamond (NCD) films, where their “top surface” diameter was approx. 5 nm. Nanorods of single crystalline diamond with a diameter of ∼200 nm have also been produced combining a microwave plasma treatment with a reactive ion etch- ing method [4]. A uniform diamond nanocones array was formed with a density of 2 × 10 8 cones/cm 2 by using selective ion sputter- ing process [3]. We have pointed out in our previous publication that the increased surface-to-volume ratio in the porous-like structure for- mations is playing a crucial role in enhancing the sensitivity of such systems [12]. In this work, we are presenting routes for fabrication of diamond nanorods using a dry plasma etching process. We are investigating the impacts of the etching time on the surface geom- etry of the formed diamond nanorods and on their gas sensing properties. The gas sensing properties of the H-terminated dia- mond device are examined using various probe gases. The influence of the probe gas concentration and the sensor operation tempera- ture is also investigated. 2. Experimental The process of fabricating diamond nanorods was carried out in the following steps: First, before NCD growth, the Ti/Au electrodes 0169-4332/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2010.03.034