Appl Phys A (2010) 101: 753–758 DOI 10.1007/s00339-010-5988-2 Electrical and optical properties of ITO and ITO/Cr-doped ITO films A.P. Caricato · M. Cesaria · A. Luches · M. Martino · G. Maruccio · D. Valerini · M. Catalano · A. Cola · M.G. Manera · M. Lomascolo · A. Taurino · R. Rella Received: 22 November 2009 / Accepted: 15 June 2010 / Published online: 31 August 2010 © Springer-Verlag 2010 Abstract In this paper we report on the effects of the inser- tion of Cr atoms on the electrical and optical properties of indium tin oxide (ITO) films to be used as electrodes in spin- polarized light-emitting devices. ITO films and ITO(80 nm)/ Cr-doped ITO(20 nm) bilayers and Cr-doped ITO films with a thickness of 20 nm were grown by pulsed ArF excimer laser deposition. The optical, structural, morpho- logical and electrical properties of ITO films and ITO/Cr- doped structures were characterized by UV–Visible trans- mission and reflection spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM) and Hall-effect analysis. For the different investigations, the samples were deposited on different substrates like silica and carbon coated Cu grids. ITO films with a thickness of 100 nm, a resistivity as low as ∼4 × 10 −4  cm, an en- ergy gap of ∼4.3 eV and an atomic scale roughness were deposited at room temperature without any post-deposition process. The insertion of Cr into the ITO matrix in the upper 20 nm of the ITO matrix induced variations in the physical properties of the structure like an increase of average rough- ness (∼0.4–0.5 nm) and resistivity (up to ∼8 × 10 −4  cm). A.P. Caricato ( ) · M. Cesaria · A. Luches · M. Martino · D. Valerini Physics Department, University of Salento, Via Arnesano, 73100 Lecce, Italy e-mail: caricato@le.infn.it Fax: +39-0832297505 G. Maruccio Scuola Superiore Isufi, University of Salento, Via Arnesano, 73100 Lecce, Italy M. Catalano · A. Cola · M.G. Manera · M. Lomascolo · A. Taurino · R. Rella Institute for Microelectronics and Microsystems, IMM-CNR, Via Monteroni, 73100 Lecce, Italy These variations were correlated to the microstructure of the Cr-doped ITO films with particular attention to the upper 20 nm. 1 Introduction Indium tin oxide (ITO) is a very interesting and studied ma- terial because of its properties are appealing for different applications, like solar cells [1], heat-reflecting mirrors [2], antireflection coatings [3], gas sensors [4] and flat panel dis- plays [5]. In fact, ITO is a highly degenerate n-type semi- conductor with a wide band gap (∼3.5–4.3 eV) and low electrical resistivity (1–3 × 10 −4  cm). Moreover, it ex- hibits high transmission (∼90%) in the visible and high re- flectance in the infrared region [6]. Furthermore, since ITO films allow for an efficient hole injection into organic ma- terials, they were widely utilized as the anode contacts in organic light-emitting diodes (OLED) [7, 8]. Very recently, both theoretical and experimental studies suggested that degenerate wide band gap oxide semicon- ductors can be one of the most favorable host compounds for dilute magnetic semiconductors (DMS) with high Curie temperature [9–12]. This finding opened new possible appli- cations for these materials, like in transparent semiconduc- tor spin electronic devices operable at room temperature. At the moment, wide research efforts are in particular devoted to induce ferromagnetism in semiconductors by doping with 3d transition elements, from Sc d 0 to Cu d 8 [13–24]. Several studies deal with the effects of doping on struc- tural, electrical and optical properties of transparent conduc- tive oxides, depending on the choice of both content and type of dopant as well as deposition technique [25, 26]. However, only few papers report experimental and theoret- ical analyses of doped ITO films, as concerns the ability to