Giovanni A. Battiston

Influence of substrate on structural properties of TiO2 thin films obtained via MOCVD

Abstract Among the techniques developed for depositing thin films, metal-organic chemical vapor deposition is one of the most promising. In the present work, the deposition of TiO2 thin films on stainless steel, titanium, barium borosilicate glass and alumina substrates, using titanium tetraisopropoxide as a precursor, was investigated. The films were deposited at 420 °C. The resulting film phase, checked by X-ray powder diffraction, was found to be polycrystalline anatase and was oriented with the a axis perpendicular to the substrate surface, except for alumina substrates where titania films were randomly oriented. Some considerations on texture and crystallite size as a function of film thickness are reported. Annealing up to 1100 °C induced the complete anatase-rutile transformation on alumina substrates.

Chemical vapour deposition and characterization of gallium oxide thin films

Abstract Gallium oxide thin films were deposited on alumina and TiO2 substrates by metal organic chemical vapour deposition using gallium trishexafluoroacetylacetonate (Ga(hfac)3) as precursor in the presence of oxygen. The depositions were carried out at 470°C and 2.6 kPa leading to a growth rate of 0.7 μm h−1. As-grown films appeared black, smooth and well adherent to the substrates. X-Ray photoelectron spectroscopy (XPS) analysis revealed stoichiometric Ga2O3 with a low carbon content (less than 5%) and almost undetectable fluorine. As-deposited Ga2O3 films were X-ray amorphous, but the onset of a crystallization process was evident after annealing in dry air at 700 °C. Moreover, after thermal treatment, the films became carbon free and transparent in the visible range. The effect of annealing at different temperatures on the film structure was investigated by X-ray diffraction. A phase modification from amorphous to polycrystalline Ga2O3 was observed after thermal treatment at temperatures from 600 to 1000 °C. As shown by secondary ion mass spectrometry (SIMS) studies, Al diffusion into Ga2O3 films was detected after annealing at 1000 °C when pure Al2O3 was used as substrate; this diffusion was completely inhibited using a TiO2 film as buffer layer with a thickness of at least 4 μm.

Zirconium Dioxide Thin Films Characterized by XPS

In this work we use x-ray photoelectron spectroscopy (XPS) to analyze the principal core levels of a ZrO2 thin film deposited on glass using Zr(OPri)3(dpm) (OPri=isopropoxy; hdpm=2,2,6,6-tetramethyl-3,5-heptanedione) as precursor. Besides the general survey, charge corrected binding energies for the Zr 3d5/2, Zr 3d3/2, O 1s, and C 1s photoelectrons are reported. Deconvolution of the O 1s signal reveals the presence of –OH groups and adsorbed water, whose presence can be related to the air exposure of the film between its preparation and XPS analysis.

Structure and volatility of copper complexes containing pyrazolyl-based ligands

Abstract Volatility studies, electrospray mass spectra and IR in vapour phase were carried out for a series of Cu(I) and Cu(II) complexes containing anionic pyrazole-based ligands such as 4-acyl-5-pyrazolonates and poly(pyrazolyl)borates. The volatility has been related to structural features and molecular parameters of the copper complexes. The crystal structures of [Cu(Q′)2(bipy)]·(acetone)1.5 (Q′=1-phenyl-3-methyl-4-benzoyl-pyrazolon-5-ato, bipy=2,2′-bipyridyl) and [Cu(QF)2(phen)]·EtOH (QF=1-phenyl-3-methyl-4-trifluoroacetyl-pyrazolon-5-ato, phen=1,10-phenanthroline), have been also determined. In these complexes the copper atom is in a tetragonally distorted octahedral arrangement of the four O-atoms of pyrazolones with N2-donor ligand in equatorial position. Two sets of CuO distances, the longer being in axial positions, have been found. XRD data of films obtained from metal organic chemical vapour deposition MOCVD experiments on [Cu(poly(pyrazolyl)borate)(PR3)] complexes have also been reported.

Spectroscopic and structural studies on volatile gallium β-diketonates as potential precursors for MOCVD

Abstract The complexes Ga(hfac) 3 (Hhfac=hexafluoroacetylacetone) and Ga(dpm) 3 (Hdpm=dipivaloylmethane) have been studied by solid and gas phase IR, mass spectrometry, 1 H and 13 C NMR, in order to prove their suitability as precursors for Ga 2 O 3 deposition via metalorganic chemical vapor deposition (MOCVD). The crystal structure of Ga(hfac)3 was also determined. The complex crystallizes in the monoclinic space group P 2 1 / n with a =9.034(3), b =13.399(3), c =19.100(4) A, β=92.19(3)° for Z =4. The final R factor was 0.048. The Ga(III) ion exhibits a regular octahedral coordination with GaO bond distance of 1.954(5) A (av. value). The X-ray, IR and MS studies showed the presence of identical monomeric species both in the solid and in the gas phase. Ga(hfac) 3 was used in preliminary MOCVD experiments to grow Ga 2 O 3 films.

The use of 210Pb and 137Cs in the study of sediment pollution in the Lagoon of Venice

The activity of 137Cs per unit area in sediments of the central part of the Lagoon of Venice was determined with the aim of identifying boundaries of homogeneous depositional zones. The 210Pb dating technique was used to date vertical profiles of cores from the same area. A comparison of the total amounts of 137Cs and non-supported 210Pb present in each core and the atmospheric input allows us to identify different depositional areas inside the basin and to outline the possible drainage effect of industrial solid wastes used in past reclaiming operations.

Infrared spectroscopic studies on metal carbonyl compounds. XX. Assignment in the CO stretching region of the binuclear mixed carbonyl compound MnRe(CO)10; force and interaction constants calculation by a parametric rotational method☆☆☆

Abstract The infrared spectrum and complete assignment of the reinvestigated mixed carbonyl MnRe(CO)10, in the CO stretching region is reported, with special emphasis on the weak isotopic bands. The frequencies and assignment are compared with those of the homo-nuclear compounds M2(CO)10 (M = Mn, Tc and Re)3. The force and interaction constants have been calculated in a CO factored force field by a parametric rotational method4 applied for the presence of a species of fourth order, with the introduction of constraints in the eigenvector matrix.

Structural and infrared spectroscopic characterization of Co6C(CO)12S2: a high-nuclearity carbido carbonyl cluster spontaneously formed from dicobalt octacarbonyl and carbon disulphide

Abstract Co6C(CO)12S2 (I) has been isolated in crystalline form from the mixture of more than a dozen of carbonyl products formed when Co2(CO)8 reacts at room temperature with CS2. Crystals of I are monoclinic with space group Cc, and lattice constants a  16.250(5), b  9.413(4), c  16.036(5) A, β  116.77(4)°. Structure refinement gave R  0.034 for 1974 reflections. The CCo6S2 core of the molecule possesses idealized D3h geometry. It is composed of a Co6 trigonal prism, enclosing a C atom in the centre, and the triangular faces are capped symmetrically by the two S atoms. The core contains two sorts od CoCo distances: short one (2.432 A) along the triangular edges, and long ones (2.669 A) along the lateral edges. The average CoC distance is 1.94 A, and the average CoS distance 2.192 A. 13CO-enriched samples were prepared photochemically and their IR spectra used in the assignment of the CO stretching frequencies. The CO stretching force constant was calculated to be 1670(2) Nm-1. By the use of 13CS2, I has also been obtained in a selectively carbido-13C-labelled form. The vibrational frequencies of the carbide atom were observed, and that at 819 cm-1 (13C: 790 cm-1) assigned to the species , and that at 548 cm-1 (13C: 535.5 cm-1) to species E′. For the Co-C(carbide) force constant a value of 155 Nm-1 was calculated. The cobalt—sulphur stretching frequencies were found at 309 cm-1 ( ) and 239 cm-1 (E′). The CoS stretching force constant, 78 Nm-1, is considerably lower than that obtained for SCo3-(CO)9, viz. 112 Nm-1.

MOCVD of Al2O3 Films Using New Dialkylaluminum Acetylacetonate Precursors: Growth Kinetics and Process Yields

Dimethyl, diethyl, and di-iso-butyl aluminum acetylacetonate compounds were synthesized to deposit Al 2 O 3 thin films by low-pressure metal-organic (LP-MO)CVD. Alumina films were grown in the temperature range 400-520°C under an oxygen or water vapor atmosphere. A kinetic model was applied to analyze the experimental data and to compare the properties of the three precursors. The model, supported by in-line Fourier transform infrared (FTIR) measurements, clearly distinguished the rate-determining steps of the heterogeneous process, with kinetic constants correlated to the molecular structure of the precursors. A method of optimizing deposition conditions, on the basis of the uniformity of the obtained thin films, is discussed.

Chemical Vapor Deposited Fe2O3 Thin Films Analyzed by XPS

In the present study, x-ray photoelectron spectroscopy (XPS) was employed to investigate the principal core levels of a Fe2O3 thin film. The sample was deposited on glass in a N2+O2 atmosphere by chemical vapor deposition (CVD), using Fe(acac)3 (Hacac = 2,4-pentanedione) as the source compound. XPS surface data for the Fe 2p3/2, O 1s, and C 1s photoelectrons, obtained by an Al Kα monochromatized excitation source, are reported. Deconvolution of the O 1s signal revealed the presence of –OH groups along with the major component ascribed to lattice oxygen. The relatively high carbon content in the film indicated an incomplete decomposition of the used precursor.