Aninvestigationofcobaltoxidebasednanocrystalline thin®lmsbysecondaryionmassspectrometry Simona Barison 1 , Davide Barreca 2 , Sergio Daolio 1 , Monica Fabrizio 1 * and Eugenio Tondello 2 1 Istituto di Polarografia ed Elettrochimica Preparativa, CNR Corso Stati Uniti 4 I- 35127 Padova, Italy 2 Dipartimento di Chimica Inorganica, Metallorganica ed Analitica, Universita ` di Padova, Centro di Studio sulla Stabilita ` e Reattivita ` dei Composti di Coordinazione del CNR, Via Marzolo 1, I- 35131, Padova, Italy; Via Loredan 4 I- 35131 Padova, Italy Received 26 February 2001; Revised 22 June 2001; Accepted 22 June 2001 An investigation of cobalt oxide based nanocrystalline thin films by secondary ion mass spec- trometry SIMS) is presented. The coatings, whose composition ranged between CoO and Co 3 O 4 , weresynthesizedbychemicalvapordepositionCVD)onindiumtinoxideITO)substrates,using cobaltII) b-diketonateasprecursor.TheSIMSanalysisrevealedasatisfactoryprecursorconversion into the oxides and allowed distinction of regions in the films at different compositions. Film- substrate intermixing phenomena were evidenced and studied as a function of deposition temperature, film thickness and composition. Copyright # 2001JohnWiley&Sons,Ltd. Oxide-based materials show a broad spectrum of charac- teristics ranging from insulating to metallic, through optical, catalytic and superconducting properties 1 and, in this widespread context, nanocrystalline oxide based thin films have attracted a markedly growing interest in recent years. Nanocrystalline materials are usually defined as polycrystal- line solids with particle diameters or grain sizes ranging from sub-nanometers up to 100 nm. As the crystal size decreases, there is a continuous transition from bulk to molecular properties with a number of effects being attributed to quantum confinement or more generally to restricted geometry. 2 These size effects are undoubtedly of outstanding importance in the fields of catalysis, gas sensors and semiconductor devices, whose functional properties are affected by various features, i.e. composition, grain size distribution, grain-grain and grain-substrate mutual inter- actions. 3 Cobalt oxide namely CoO and Co 3 O 4 ) nanocrystalline thin films are attractive candidates for various applications, such as electrochromic devices, 4 energy storage compo- nents, 5 heterogeneous catalysts, 6 optical sensors, 7 thermal absorbers, protective layers and magneto-optical recording media. 8 In order to exploit the potential of these materials and to obtain the necessary basis for thin films engineering, many techniques have to be used to attain a deeper insight into the structure-properties relations. With this aim, an extensive study has been devoted to the characterization of CoO- and Co 3 O 4 -based films obtained by chemical vapor deposition CVD) from a CoII) b-diketonate, Codpm) 2 Hdpm = 2,2-6,6-tetramethyl-3,5-heptanedione) by means of XRD X-ray diffraction), optical absorption, XPS X-ray photoelectron spectroscopy), XE-AES X-ray excited auger electron spectroscopy) and AFM atomic force micro- scopy). 9,10 In this work, a SIMS investigation is described, which enabled us i) to verify the conversion degree of the organometallic precursor under the adopted conditions; ii) to establish the composition and homogeneity of mixed deposits; iii) to investigate the influence of the substrate material and the preparation conditions on the composition and thickness of the interface regions; and iv) to detect eventual impurities due to film-substrate intermixing phenomena or to an unclean decomposition pattern of the employed precursor. SIMS, in fact, is a powerful and versatile analytical tool, as often demonstrated in the characterization of several oxide thin films. 11 EXPERIMENTAL Film preparation Nanocrystalline cobalt oxide thin films were deposited in a cold-wall low-pressure custom-built CVD reactor using O 2 as the carrier gas as well as the oxidizing agent. The ITO substrate indium tin oxide, In 2 O 3 :Sn, r = 10 O/square) preparation and cleaning procedure has been reported elsewhere. Codpm) 2 Hdpm = 2,2-6,6-tetramethyl-3,5-hep- tanedione) was used as precursor. 9 In order to investigate the influence of process parameters on the film characteristics, two sample sets were prepared: I) pO 2 ) = 10 mbar, O 2 flow rate = 150 sccm; II) pO 2 )= 2 mbar, O 2 flow rate = 50 sccm. In both cases, four different deposition temperatures were used: 350, 400, 450 and 500 °C. The deposit thickness see below) was evaluated between 200 and 1300 nm and the AFM surface roughness, 9 calcu- lated between 5 and 30 nm, increased on increasing the temperature for both sample sets I and II. The average crystallite sizes were estimated by applying the Scherrer *Correspondence to : M. Fabrizio, Istituto di Polarogra®a ed Elettrochimica Preparativa, CNR, Corso Stati Uniti 4, I- 35127 Padova, Italy. E-mail: m.fabrizio@ipelp.pd.cnr.it DOI:10.1002/rcm.397 Copyright # 2001 John Wiley & Sons, Ltd. RAPID COMMUNICATIONS IN MASS SPECTROMETRY Rapid Commun. Mass Spectrom. 2001; 15: 1621±1624