Pulsed laser ablation of indium tin oxide in the nano and femtosecond regime: Characterization of transient species A. De Bonis b , A. Galasso b , V. Marotta a , S. Orlando a , A. Santagata a , R. Teghil b , S. Veronesi c , P. Villani b,a , A. Giardini a,c, * a CNR – Istituto di Metodologie Inorganiche e dei Plasmi – Sezione di Potenza, Zona Industriale, I-85050 Tito Scalo (PZ), Italy b Dipartimento di Chimica, Universita’ della Basilicata, Via N. Sauro, 85, I-85100 Potenza, Italy c Dipartimento di Chimica, Universita’ di Roma ‘‘La Sapienza’’, P. le Aldo Moro, 5, I-00185 Roma, Italy Received 3 May 2005; accepted 15 July 2005 Available online 14 November 2005 Abstract Tin doped indium oxide (ITO) is a n-type highly degenerate, wide band-gap semiconductor that is extensively used for many engineering applications. Pulsed laser ablation of indium tin oxide in the nano and femtosecond regime has been performed in our laboratory. Plume diagnostics has been carried out by means of a fast Intensified Coupled Charge Device (ICCD) camera. Optical emission spectroscopy has been applied to characterize the transient species produced in the nano and femtosecond regime. The time evolution of emission lines, in the femto and nanosecond regime, have been compared and discussed. In the mass spectrometry, of the ionized species, the presence of mixed metal oxide clusters has been detected. This fact is an indication that chemical reactions can occur during the plasma expansion or on the ITO surface. # 2005 Elsevier B.V. All rights reserved. Keywords: Pulsed laser ablation; Indium tin oxide; Transient species 1. Introduction Tin doped indium oxide (ITO) is a n-type highly degenerate, wide band-gap semiconductor that is extensively used for many engineering applications. In particular, thin ITO films is used for electronical and photoelectronical applications such as liquid crystal displays, solar cells and gas sensors. Electron beam, evaporation, sputtering and more recently reactive pulsed laser ablation are methods commonly used to produce thin films of ITO [1–7]. Pulsed laser ablation of various targets is well known to produce material removal which usually forms luminous plasma above the solid surface hit by laser [7–9]. Many aspects of the interaction process and plasma characteristics are strongly influenced by experimental parameters such as laser beam properties, laser pulse duration, surrounding atmosphere and property of the material itself. In the past, the influence of the pulse duration was studied. Ultra short pulses can induce processes which can be treated by different approaches such as the two-temperature model, Coulomb explosion and non- thermal heating [10–16]. The knowledge of the type, concentration and distribution of laser formed species is of great interest for the application of laser ablation techniques to thin film production [6–13]. Formation of intermediate complexes in gas-phase is observed and analysed by a TOF mass spectrometer [17–21]. In this paper, we are mainly concerned on plume diagnostics of ITO material and we report on an analysis of the plasma produced by laser ablation of an ITO target in vacuum in both nanosecond (ns) and femtosecond (fs) regime. These studies aim to compare the plasma characteristics in the two regimes and to give information on the possibility to produce very thin films (around 100 nm) of ITO on a glass substrate which can be used as sensors for toxic gases. www.elsevier.com/locate/apsusc Applied Surface Science 252 (2006) 4632–4636 * Corresponding author. Tel.: +39 06 49913984; fax: +39 06 490324. E-mail address: anna.giardini@uniroma1.it (A. Giardini). 0169-4332/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2005.07.100