Applied Surface Science 258 (2011) 147–150 Contents lists available at ScienceDirect Applied Surface Science j our nal ho me p age: www.elsevier.com/loc ate/apsusc Investigation of the surface properties of gold nanowire arrays Huijun Yao a,b,∗ , Dan Mo a , Jinglai Duan a , Yonghui Chen a , Jie Liu a,∗ , Youmei Sun a , Mingdong Hou a , Thomas Schäpers b a Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, PR China b Peter Grünberg Institute (PGI-9) and JARA-FIT Jülich-Aachen Research Alliance, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany a r t i c l e i n f o Article history: Received 11 October 2010 Received in revised form 3 August 2011 Accepted 3 August 2011 Available online 10 August 2011 Keywords: Gold nanowires Surface plasmon resonance (SPR) XPS a b s t r a c t Gold nanowire arrays with diameters ranging from 45 to 200 nm were obtained via electrochemical deposition within the ion-track templates. The morphology of gold nanowires was imaged by scanning electron microscopy (SEM). The surface properties were investigated by surface plasmon resonance (SPR) and X-ray photoelectron spectroscopy (XPS). The SPR peaks were observed as the gold nanowire arrays embedded in the templates and their intensity decreased after the sample exposed to the air for a certain time due to the formation of chemisorbed oxygen on nanowire surface. The positive binding energy shifts in Au core level was found when the gold nanowire arrays embodied in template and the initial- and finial-state effects were introduced to explain this phenomenon. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Gold is the much noble metal due to the lack of reactivity [1] and its unique properties, such as very good electrical and thermal conductivity, high ductility and chemical inertness, which make it useful for fabricating some electronic components used in semicon- ductor technology. For example, it is used in first- or second-level metallization and as a plating metal during the backside processing of GaAs devices [2]. When the gold size is in the nanometer regime, it will exhibit dif- ferent electronic properties [3,4] compared to the bulk. The effects of finite nano-size play an important role in the special electronic properties and are already intensively studied in the past [5,6]. Recent years, the nanotechnology has brought us many novel prop- erties about gold. Catalytic activity for example can be strongly enhanced for nanosized metals that normally do not or do only weakly show such behaviour as bulk material. Optical properties may be changed due to redistribution of valence band electrons [7]. The anti-Hall–Petch effect is found in the polycrystalline gold nanowires with grain size around 10 nm [8] and remarkably fail- ure current density as high as 4.94 × 10 8 A/cm 2 is observed in an individual gold nanowire [9]. Recently, several reports have shown that oxidation occurs when a gold film is exposed to highly reac- tive chemical environments, such as O 2 -plasma discharge or in UV/ozone [10,11], typically altering the electrical characteristics of ∗ Corresponding authors at: Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, PR China. Tel.: +86 931 4969334; fax: +86 931 4969334. E-mail addresses: Yaohuijun@impcas.ac.cn (H. Yao), J.liu@impcas.ac.cn (J. Liu). the material. As to gold nanowires, their surface states not only con- tribute to the electrical properties [12] but also play an important role in the optical properties. The X-ray photoelectron spectroscopy (XPS) is one of the most widely used experimental methods to identify metal oxide species in metal catalysts [13–15]. It can provide us additional informa- tion related to the electrical properties on the surface of the gold crystallites [16]. It is also evidenced that the oxygen element as a kind of hydrocarbon contamination adsorbed on the surface of the gold nanowires through XPS spectrum [17]. In this work, the gold nanowires were prepared in ion-track template with electrodepo- sition method which had been proved to be a kind of powerful tool to control nanowire’s shape, structure and density in nanowire preparing [7,8,18–20]. The changes of the extinction spectra related to gold nanowire surface properties were analyzed. The oxidation of gold nanowires had been conclusively elucidated and chemisorbed oxygen formed on the wire surface. The changing of surface elec- trical properties because of the initial- and final-state effects was also discussed. However, the relationship between the nobility of gold and the formation of its oxide and the effect of the oxide on the electrical, chemical and physical properties of gold metal still remained unclear. 2. Experiment The 30 m polycarbonate (PC) membranes (Makrofol N, Bayer Leverkusen) were irradiated at the UNILAC linear accelerator of GSI (Darmstadt, Germany) with Au ions (kinetic energy 11.4 MeV/u, fluence 1 × 10 8 ions/cm 2 ) in normal incidence. After irradiation, each side of the membrane was exposed to UV light for 2 h in 0169-4332/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2011.08.021