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International audience; Novel adducts of lithium hexafluoroacetylacetonato {Li(hfa)} with polyethers (monoglyme = {CH3OCH2CH2OCH3}, diglyme = {CH3O(CH2CH2O)2CH3}, triglyme = {CH3O(CH2CH2O)3CH3} and tetraglyme {CH3O(CH2CH2O)4CH3} have been synthesized through a single step reaction and characterized by FT-IR spectroscopy, 1H, and 13C NMR, single crystal X-ray diffraction studies along with thermal analysis.

Gadolinium metal-organic frameworks (Gd-MOFs) and Eu-doped Gd-MOFs have been synthesized through a one-pot green approach using commercially available reagents. The 1,4-benzenedicarboxylic acid (H2-BDC) and 2,6-naphthalenedicarboxylic acid (H2-NDC) were chosen as ditopic organic linkers to build the 3D structure of the network. The Gd-MOFs were characterized using powder X-ray diffraction (XRD), FT-IR spectroscopy, field emission scanning electron microscopy (FE-SEM) and N2 adsorption–desorption analysis. The Gd-MOF structures were attributed comparing the XRD patterns, supported by the FT-IR spectra, with data reported in the literature for Ln-MOFs of similar lanthanide ionic radius. FE-SEM characterization points to the effect of the duration of the synthesis to a more crystalline and organized structure, with grain dimensions increasing upon increasing reaction time. The total surface area of the MOFs has been determined from the application of the Brunauer–Emmett–Teller method. The study allowed us to correlate the processing conditions and ditopic linker dimension to the network surface area. Both Gd-MOF and Eu-doped Gd-MOF have been tested for sensing of the inorganic ions such as Fe3+ and Cr2O72−.

Mild heating of the Zn(C5F6HO2)(2)center dot 2H(2)O center dot CH3(OCH2CH2)(2)OCH3 precursor allowed MOCVD deposition of ZnO films, in a low-pressure horizontal hot-wall reactor, on ITO substrates. The ZnO films were subsequently implanted with Sb ions. XRD measurements provided evidence that they consist of hexagonal, (002) and (101) oriented, crystals. UV-vis spectra showed that the transmittance of these films in the visible region is about 90%. The Sb implanted ZnO film showed a current-voltage characteristic that resembles that of a rectifying diode. This study represents the first example of Sb-implantation in ZnO films obtained by MOCVD.

A careful engineering of the central metal coordination spheres provides adducts with excellent properties for application as precursors in vapor phase and solution processes. The family of precursors under study concerns the fluorinated metal-organic β-diketonates of alkaline, alkaline-earth and rare-earth metals adducted with a polyether, with general formula M(hfa)n·L (M = Ca, Na, Y, Yb, Er, Tm; Hhfa = 1,1,1,5,5,5 hexafluoroacetylacetone, L = diglyme or tetraglyme). Mass transport properties, such as volatility and thermal stability, of these adducts have been deeply analyzed through thermogravimetric analysis and differential scanning calorimetric measurements. These properties are rationalized in relation to the metal coordination sphere in the precursors and their applications. In particular, the precursors under focus have been applied to metal organic chemical vapor deposition and a combined sol–gel/spin-coating approach. Both methods allow us to obtain selectively and reproducibly CaF2 and NaYF4 phases with several combinations of lanthanide doping ions, using a proper mixture of fluorinated precursors. A careful optimization of both synthetic strategies is the key point for the production of different lanthanide-doped binary and multicomponent fluoride films, i.e., CaF2:Yb3+,Er3+; CaF2:Yb3+,Tm3+; CaF2:Yb3+,Er3+,Tm3+ and NaYF4:Yb3+,Er3+; NaYF4:Yb3+,Tm3+, with suitable morphologies, compositions and crystalline structures. The films show very promising upconversion properties, thus pointing to their appealing applications in photovoltaic systems and white light emission devices.

Increasing awareness of environmental concerns has strongly pushed the scientific community towards the search for new solutions for efficient removal of oils and organic solvents from water. Here, we report the preparation of multifunctional TiO2-coated melamine-formaldehyde (MF) sponges as absorbent material for oils and organic solvents in water. TiO2-coated MF sponges were fabricated through an environmentally friendly approach, consisting in a simple immersion of the sponge into an oleic acid-capped TiO2 nanoparticles dispersion. The adhesion of TiOle coating to the sponge was then improved by the deposition of a low surface energy diamond-like carbon (DLC) thin layer. Our results highlighted that the modified MF sponges possess superhydrophobic and oleophilic behaviour, inertness to corrosive environment, good durability and reusability. Furthermore, the superhydrophobic DLC/TiO2@sponges showed (1) novel self-cleaning properties towards an absorbed commercial organic dye (IR-270BKA, chosen as representative) under visible light irradiation and (2) enhanced flame-retardant behaviour respect to the pristine MF sponge. These findings point out an important added value of DLC/TiOle@sponges making them promising candidates for wastewater treatments.

The present study evaluates the concept of permeable reactive barrier (PRB) coupled with microwaves (MWs) as in situ-regenerating technology with focus on Cs-contaminated water. Experimental and modelling results data from batch and column tests were carried out, evaluating several chemical-physical and environmental parameters. Main results showed a very rapid increase in GAC temperature during MW irradiation up to ∼680 °C. This highlights the GAC strong ability to transform MW power into heat due to GAC excellent dielectric properties (e′ = 13.8). Physical characterization revealed that GAC pore volume and specific surface area change with the number of regeneration cycles. GAC regeneration efficiency variation reflects this behaviour with a maximum value of ∼112% (5th cycle). The final GAC weight loss of ∼7% further demonstrates GAC life span preservation during MW irradiation. Results from column tests confirms that GAC can be regenerated by MW also in dynamic condition, due to sublimation/vaporization and vapour stripping Cs removal mechanisms and that the regeneration effectiveness is time-dependent. The breakthrough curve shape confirms significant benefits from MW irradiation. Overall, obtained finding demonstrated the feasibility of the proposed concept, also providing essential data to guide its scaling-up application.

Starting from fluorinated metal–organic β-diketonates, we report the synthesis of undoped and lanthanide-doped alkaline-earth fluoride (Er3+,Tm3+,Yb3+ tri-doped CaF2) thin films through two different chemical approaches: a metal–organic chemical vapor deposition (MOCVD) method and a combined sol–gel/spin-coating procedure. Both chemical approaches have the advantage of being very reliable and reproducible for the fast production of thin films with a high degree of uniformity over large areas. The fluorinated metal precursors act as a single-source in both processes, and an accurate control of the process parameters allows the optimization of the doped CaF2 films. X-ray diffraction, field emission scanning electron microscopy and energy dispersive X-ray analysis have been used to characterize the deposited films. Upconversion emission, typical of the lanthanide ions, in the visible and near infrared regions upon laser excitation at 980 nm is clearly observable. The emissions are in the central region of the CIE1931 color coordinate space.

A systematic study into the MOCVD of V-O films using the vanadyl-acetylacetonate [VO(acac)2] precursor is carried out. The films are prepared via low pressure MOCVD on Si(001) substrates. The nature and quality of films are examined by varying operational parameters, e.g., deposition temperature, precursor vaporization rate, and flow of oxygen reacting gas. X-ray diffraction data point to the formation of crystalline films in the range 200−550 °C. Outside of this temperature ranges amorphous phases were obtained. Field-emission scanning electron microscope (FESEM) images indicate very homogeneous surfaces with grain shape and dimensions depending on operational conditions. Energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) analyses point to the absence of any C contamination.

Pr1–xCaxMnO3 thin films have been deposited through an in situ metal organic chemical vapor deposition (MOCVD) process using a molten multi-metal source, consisting of the Pr(hfa)3·diglyme, Ca(hfa)2·tetraglyme, and Mn(tmhd)3 precursor mixture on single crystal substrates such as LaAlO3 (001) and MgO (001). Optimization of processing parameters has allowed the deposition of homogeneous thin films in morphology, composition, and thickness. The effect of substrate has been assessed in relation to structure and morphology. Field emission scanning electron microscope of a Pr0.7Ca0.3MnO3 film deposited at 1000 °C on MgO (001).

International audience; In Accumulated Low Schottky Barrier metal oxide semiconductor field effect transistors (MOSFET) on SOl structures, very thin silicide layers are used for ohmic contacts. Silicide contacts form due to metallurgical reaction of metal with semiconductor. In order to get a broad vision of the most interesting metal/silicide solution several material stacks were evaluated including platinum and iridium. In this work cross-sectional transmission electron microscopy was used to study the process of silicide formation in metal/Si and metal/SiGe/Si structures. Novel structure architectures have been developed. They are mainly based on the use of a very thin film SOl substrate with typical active silicon layer thicknesses ranging between 2 and 20 nm for 10-40 nm gate length MOSFETs. In Accumulation LowSchottky Barrier -SOI MOSFET structures very thin silicides are used for ohmic contacts. Silicide contacts form due to metallurgical reaction of metal with semiconductor.

The functionalization of piezoelectric/ferroelectric bismuth ferrite (BiFeO3, BFO) films and particles with bi-functional organic monolayers is reported. BFO films, grown by MOCVD adopting a bi-metallic mixed source, and BFO particles, synthetized by a sol-gel route, were functionalized either with the benzene-1,4-dicarboxylic acid (BDC) or with the phosphonobenzoic acid (PBA). The proposed functionalization route is based on an activation step of the BFO surface followed by the treatment with a BDC or PBA solution. The structural and morphological characterizations of functionalized BFO samples were carried out using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). The chemical composition and the anchoring mode of the grafted monolayers were investigated by X-ray photoelectron spectroscopy (XPS) and FT-IR. Comparison of XPS and FT-IR results, obtained from BDC and PBA functionalized surfaces, gave indications on the role of the nature of the anchoring group in the functionalization process. Finally, piezoresponse force microscopy (PFM) and PFM spectroscopy studies demonstrated that the ferroelectric properties of the material are retained after the functionalization.

The vapochromic and chemiresistive properties of a nanofibrillar molecular material composed of an amphiphilic ZnII Schiff-base complex, 1, are explored with the aim to obtain new materials with multifunctional properties. The solid 1 is characterized by the existence of two stable dimorphs, both exhibiting a nanofibrillar morphology. The thermal annealing of the ground solid 1 induces an irreversible lamellar-to-square columnar structural phase transition, as assessed by differential scanning calorimetry and X-ray diffraction analysis. When exposed to vapours of a Lewis base, spin coated films of the square columnar dimorph exhibit a marked change of both the optical absorption spectrum and the resistance, because of chemisorption of the Lewis base with the formation of 1·Lewis base adducts. The chemisorbed material is easily restored by thermal heating (150 °C), inducing desorption of the Lewis base. The changes of the properties are reproducible in successive cycles of exposure/restoring. Therefore, the present contribution provides new insights into the properties of this molecular material, potentially useful as a sensor for volatile organic Lewis bases.

In this work, we present all-oxide p-n junction core-shell nanowires (NWs) as fast and stable self-powered photodetectors. Hydrothermally grown n-type ZnO NWs were conformal covered by different thicknesses (up to 420 nm) of p-type copper oxide layers through metalorganic chemical vapor deposition (MOCVD). The ZnO NWs exhibit a single crystalline Wurtzite structure, preferentially grown along the [002] direction, and energy gap Eg = 3.24 eV. Depending on the deposition temperature, the copper oxide shell exhibits either a crystalline cubic structure of pure Cu2O phase (MOCVD at 250 °C) or a cubic structure of Cu2O with the presence of CuO phase impurities (MOCVD at 300 °C), with energy gap of 2.48 eV. The electrical measurements indicate the formation of a p-n junction after the deposition of the copper oxide layer. The core-shell photodetectors present a photoresponsivity at 0 V bias voltage up to 7.7 µA/W and time response ≤ 0.09 s, the fastest ever reported for oxide photodetectors in the visible range, and among the fastest including photodetectors with response limited to the UV region. The bare ZnO NWs have slow photoresponsivity, without recovery after the end of photo-stimulation. The fast time response for the core-shell structures is due to the presence of the p-n junctions, which enables fast exciton separation and charge extraction. Additionally, the suitable electronic structure of the ZnO-Cu2O heterojunction enables self-powering of the device at 0 V bias voltage. These results represent a significant advancement in the development of low-cost, high efficiency and self-powered photodetectors, highlighting the need of fine tuning the morphology, composition and electronic properties of p-n junctions to maximize device performances.

An innovative sol–gel process, using a mixture of Na(hfa)·tetraglyme and RE(hfa)3·diglyme (RE = Y, Yb, Tm) complexes, has been optimized to produce upconverting β-NaYF4:Yb3+/Tm3+ thin films. The X-ray diffraction (XRD) analysis confirms that the new sol–gel preparation route yields reproducibly and selectively the hexagonal Na(Y1.5Na0.5)F6 structure (β-NaYF4) without any impurity phases, since no peaks of the cubic NaYF4, YOF, Y2O3 or NaF phases were observed. This final goal has been achieved through an accurate optimization of the operative parameters such as the molar ratio of the precursor mixture, the aging time of the sol, the spin coating procedure and the annealing temperature. Field-emission scanning electron microscopy (FE-SEM) images indicate that the morphology of the surfaces, grain dimensions and thickness are strongly related to the processing parameters, with the hexagonal phase films having a very uniform morphology. Energy dispersive X-ray (EDX) analyses established the film composition in terms of dopant ions, which are responsible for the upconverting properties of the material. Luminescence measurements under laser excitation at 980 nm confirmed the promising upconversion properties of the β-NaYF4:Yb3+/Tm3+ films.

Epitaxial nickel oxide (NiO) thin films have been grown by Metal Organic Chemical Vapor Deposition on AlGaN/GaN heterostructures. Critical growth parameters have been studied in order to optimize the deposition process of NiO films suitable for applications in GaN-based devices. In particular, a second generation precursor has been used as nickel source, namely the N,N,N′,N′-tetramethylethylenediamine adduct of nickel bis 2-thenoyl-trifluoroacetonate, using different deposition temperatures and oxygen flow values. Optimized operative conditions allowed the growth of epitaxial thin films which exhibited a permittivity of 11.7, close to the bulk value. The electrical characterization of the obtained epitaxial films pointed out to promising dielectric properties for AlGaN/GaN transistor technology.

Metal-Organic Chemical Vapor Deposition (MOCVD) has been applied to the fabrication of lanthanum cobaltite (LaCoO 3 ) films on MgO (001) and LaAlO 3 (001) substrates. The films have been deposited using a multi-metal source, consisting of the La (hfa) 3 •diglyme and Co (tta) 2 •tmeda (H-hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; diglyme = CH 3 O-(CH 2 CH 2 O) 2 CH 3 , Htta = α-thenoyltrifluoroacetone; tmeda = N,N,N′,N′-tetramethyl-ethylendiammine) precursor mixture. Structural and morphological characterization of films, carried out using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), proved the present MOCVD approach a suitable effective route for the growth of pure LaCoO 3 films. Composition and purity has been assessed through energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) analyses.

Metal-Organic Chemical Vapor Deposition (MOCVD) has been applied to the fabrication of BiFeO 3 on dielectric SrTiO 3 and conducting SrTiO 3 :Nb (100) substrates. Films have been deposited using a mixed bi-metallic source, consisting of Bi(phenyl) 3 and Fe(tmhd) 3 , (phenyl = -C 6 H 5, H-tmhd = 2,2,6,6-tetramethyl-3,5-heptandione) precursor mixture. The chemical, structural and morphological characterizations of films have been carried out by energy dispersive X-ray analysis, X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Local piezoelectric properties have been investigated by piezoresponce force microscopy (PFM) and piezoelectric force spectroscopy (PFS). Structural and morphological characterizations point to the formation of homogeneous and flat surfaces for BiFeO 3 films. Different ferroelectric/piezoelectric domains have been observed depending on the structure/morphology of the samples.

This work reports two new silver metalorganic precursors for the chemical vapor deposition of Ag metallic coatings. Both precursors are based on β-diketonate adducts, namely, Ag(hfac)(L) (H-hfac = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione), where L is 1,10-phenanthroline (phen) or 2,5,8,11-tetraoxadodecane (triglyme). Using these ligands, the designed precursors have better solubility in alcoholic solvents and are less toxic and costly than previously reported ones. The new precursors have been characterized and their crystallographic structure solved. With the new triglyme precursor, [Ag(triglyme)2]+[Ag(hfac)2]−, pure metallic Ag coatings made of Ag nanoparticles about 20 nm in diameter were succesfully deposited on glass and Si substrates using Aerosol Assisted Metalorganic CVD (AA-CVD).

Calcium fluoride represents one of the most efficient hosts for up-conversion or down-conversion emissions. A simple metal organic chemical vapor deposition approach is applied to the fabrication of CaF2 nanostructured thin films using the fluorinated “second-generation” β-diketonate compound Ca(hfa)2•diglyme•H2O as a Ca-F single-source precursor. The versatility of the process is demonstrated for the fabrication of up-converting Yb/Er or Yb/Tm codoped CaF2 films on Si, quartz, and glass substrates. The Ln(hfa)3•diglyme (Ln = Tm, Er, Yb) precursors are used as sources of the doping ions. Structural, morphological, and compositional characterization of the films shows the formation of polycrystalline CaF2 films with a very uniform surface and suitable doping. In fact, an appropriate tuning of the mixture composition, i.e., the Ca:Ln ratio in the multicomponent source, permits the deposition of films with the desired stoichiometry. The films show promising up-conversion properties in the visible and near infrared regions upon laser excitation for both doping mixtures.

This paper reports on a structural and electrical analysis of nickel oxide (NiO) films grown both on AlGaN/GaN heterostructures and on 4H-SiC epilayers. The films were grown by metal organic chemical vapor deposition (MOCVD). The structural analysis showed epitaxially oriented films over the hexagonal substrates. The electrical characterization of simple devices onto AlGaN/GaN heterostructures enabled to demonstrate a dielectric constant of 11.7 and a reduction of the leakage current in insulated gate structures. On the other hand, epitaxial NiO films grown onto 4H-SiC epilayers exhibited the presence of an interfacial SiO2layer and twinned NiO grains, and a lower dielectric constant.

Thin films of CaCu3Ti4O12 (CCTO) are successfully deposited by metal-organic (MO)CVD on (001)SrTiO3 substrates. An interesting approach, based on a molten multi-component precursor source, is applied. The molten mixture consists of the Ca(hfa)2 center dot tetraglyme, Ti(tmhd)2(OiPr)2, and Cu(tmhd)2 [Hhfa?=?1,1,1,5,5,5-hexafluoro-2,4-pentanedione; tetraglyme?=?2,5,8,11,14-pentaoxapentadecane; Htmhd?=?2,2,6,6-tetramethyl-3,5-heptandione; OiPr?=?iso-propoxide] precursors. It is also found that, in the present case of a relatively large lattice mismatch (similar to 5%), the epitaxial growth can be achieved by a careful optimization of deposition parameters. Film structural and morphological characterization is carried out using several techniques; X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). A complete comparison between films deposited by two main processes is carried out in order to understand the kinetic and thermodynamic issues involved in the MOCVD epitaxial growth.

Metal-Organic Chemical Vapor Deposition (MOCVD) has been applied to the fabrication of BiFeO3 films undoped and doped with Ba or Ti on SrTiO3 (100) and YSZ (100) substrates. The films have been deposited using a multi-metal source, consisting of the Bi(phenyl)3, Fe(tmhd)3 and Ba(hfa)2 tetraglyme or Ti(tmhd)2(O-iPr)2 (phenyl = -C6H5, H-tmhd = 2,2,6,6-tetramethyl-3,5-heptandione; O-iPr = iso-propoxide; H-hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; tetraglyme = CH3O(CH2CH2O)4CH3) precursor mixture. The structural and morphological characterization of films has been carried out using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Chemical compositional studies have been performed by energy dispersive X-ray (EDX) analysis. Structural and morphological characterizations point to the formation of homogeneous and flat surfaces for both undoped and doped BiFeO3 films.

Magnesium fluoride (MgF2) films are fabricated via low pressure metal-organic (MO)CVD on glass or quartz substrates from the novel single-source precursor Mg(hfa)2 · 2H2O · 2diglyme. The nature and quality of films are scrutinized depending on relevant operational parameters, namely the deposition temperature, the precursor vaporization rate, and finally the flow of the oxygen reacting gas. Grazing incidence X-ray diffraction (GIXRD) data point to the formation of crystalline MgF2 films. Scanning electron microscope (SEM) images indicate very homogeneous surfaces with grain dimensions dependent upon operational conditions, while energy dispersive X-ray (EDX) analyses point to the absence of any C or O contaminants. Smooth and homogeneous surfaces can be obtained upon deposition under high oxygen flow. The MgF2 film deposited on glass at 400 °C under optimized conditions shows a ∼80% transmittance in the range 300 − 800 nm. The high crystalline and optical quality of the MgF2 films, deposited using mild deposition temperatures (< 450 °C) still confirms MOCVD as a versatile and competitive deposition technique.

Porous La0.8Sr0.2MnO3 (LSMO) films have been prepared by metal organic chemical vapor deposition (MOCVD) technique for solid oxide fuel cell (SOFC) applications. LSMO samples have been deposited on yttria-stabilized zirconia (YSZ) electrolyte pellets. The adopted in situ strategy involves a molten mixture consisting of the La(hfa)3·diglyme, Sr(hfa)2·tetraglyme, and Mn(tmhd)3 [Hhfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; diglyme = bis(2-methoxyethyl)ether; tetraglyme = 2,5,8,11,14-pentaoxapentadecane; Htmhd = 2,2,6,6-tetramethyl-3,5-heptandione] precursors. It has been shown that porous LSMO films can be obtained through an accurate tuning of processing parameters, which affect the nucleation and growth processes. The structural and compositional characterizations of these films, carried out by X-ray diffraction (XRD) and energy dispersive X-ray analysis, point to the formation of a single polycrystalline La0.8Sr0.2MnO3 phase. The field emission scanning electron microscopy (FE-SEM) images confirm the formation of porous films. To evaluate the electrochemical activity of the cathodic films, an investigation by impedance spectroscopy (IS) has been performed.

A new ligand, N, N, N', N'-tetramethylethylenediamine, has been used to grow ZnO nanorods on silicon substrates via a two steps approach. A preliminary seeding on silicon substrates has been combined with chemical bath deposition using a Zinc acetate - N, N, N', N'-tetramethylethylenediamine aqueous solution. The used diamino ligand has been selected as Zn(2+) complexing agent and the related hydrolysis generates the reacting ions (Zn(2-) and OH(-)) responsible for the ZnO growth. The seed layer has been annealed at low temperature (

Undoped and Europium-doped titania nanofibers have been fabricated by electrospinning technique, using a single multielement Titanium/Europium source. In this communication we present the synthesis, structural and spectroscopic characterisation of Eu-doped TiO2 nanofibers starting from polyvinylpyrrolidone, titanium tetraisopropoxide (Ti(OiPr)4) and Eu(hfa)3 x diglyme (Hhfa = 1,1,1,5,5,5-hexafluoroacetyacetone, diglyme = CH3O(CH2CH2O)2CH3). The chosen system allowed to investigate a wide compositional range, i.e., from 3 to 10% mol of Eu3+. Microstructure was studied by means of scanning electron microscopy (SEM), thermal behaviour followed by thermogravimetric and differential thermal analysis (TG-DTA). Phase analysis was performed by means of X-ray diffraction (XRD) and high temperature X-ray diffraction analysis (HT-XRD) up to 1100 degrees C. Luminescence properties were investigated by means of luminescence spectroscopy, using a laser excitation source at 395 nm. All electrospun materials consisted of randomly oriented nanofibers of fairly uniform diameter. The average fiber size was 80-100 nm and 40 nm for, respectively, Eu-doped and undoped TiO2 calcinated at 500 degrees C. The presence of Europium shifted toward higher values either the crystallization temperature of anatase and the anatase to rutile phase transition, the latter being accompanied by the formation of the Eu2Ti2O7 phase. The doped samples showed a strong luminescence of Eu3+ ions. The emission spectra were dominated by the 5D0 --> 7F2 emission, suggesting a notable distortion around the Eu3+ ions. The broadening of the bands pointed to the presence of a relevant inhomogeneous disorder around the Eu3+ sites. The Eu3+ doped TiO2 nanofibers showed a higher emission intensity with respect to the PVP/TiO2 ones.

La0.9Sr0.1MnO3 (LSMO) films are grown on LaAlO3(100) substrates through metal-organic (MO)CVD using ''second generation'' precursors of Sr, La, and Mn. An in-situ novel MOCVD strategy is adopted which involves the use of two different molten mixtures consisting of the La(hfa)3diglyme and Sr(hfa)2tetraglyme adducts as La and Sr sources, respectively, and Mn(hfa)2tmeda or Mn(tmhd)3 as Mn precursor [Hhfa ¼ 1,1,1,5,5,5-hexafluoro-2,4-pentanedione, digly- me ¼ bis(2-methoxyethyl)ether, tetraglyme ¼ 2,5,8,11,14-pentaoxapentadecane, tmeda ¼ N,N,N0 ,N0 -tetramethylethylendia- mine and H-tmhd ¼ 2,2,6,6-tetramethyl-3,5-heptandione]. The X-ray diffraction (XRD) patterns show that the films are c-axis oriented. Pole figures are applied as a simple non-invasive tool to assess the textural nature of these LSMO films. The morphology is investigated using the scanning electron microscopy (SEM) and atomic force microscopy (AFM) that reveal the presence of grains, 300 nm average dimensions, and a root mean square (rms) surface roughness of 21 nm. Chemical composition through energy-dispersive X-ray (EDX) analysis indicates that the films possess a stoichiometry of about 0.9:0.1:1 ratio, while X-ray photoelectron spectroscopy (XPS) depth profiles are used to assess the vertical compositional homogeneity. The ferromagnetic/paramagnetic and metallic/insulating transition temperatures are determined by standard four-contact resistivity versus temperature measurements.

High-k films of CaCu3Ti4O12 are of interest for industrial multifunctional electronics. For oriented flow High Vacuum CVD processes, precursors are needed that they can be safely transported in the gas phase without carrier gas. We investigated the vapor pressure, and transport rate and temporal stability of a potential Ca precursor [Ca(hfa)2tgte] (hfa: hexafluoroacetylacetonate, tgte: tetraethylene glycol dimethyl ether) under HV conditions by varying the evaporation temperature. At 115{degree sign}C, the transport rate for the Ca(hfa)2tgte precursor of 4.3 mmol per hour was achieved allowing for high film deposition rates.

Zinc oxide (ZnO) and ZnO:Al-doped films were deposited by metal organic chemical vapour deposition (MOCVD) using the Zn(tta)"2.tmeda (H-tta=2-thenoyltrifluoroacetone, tmeda=N,N,N',N'-tetramethylethylendiamine) and Al(acac)"3 (H-acac=acetylacetone) precursors on different substrates. The deposited layers were characterised by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). Film structure is strongly dependent on the substrate nature and deposition conditions. AFM and XRD measurements show a good film texture and a preferential orientation along the c-axis. The Al concentration of ZnO:Al film has been confirmed by energy dispersive X-ray (EDX) analysis. Optical transparency of these ZnO layers has been studied in order to evaluate their applications as a transparent conducting oxide (TCO) material.

Nanostructured ZnO thin films have been grown on quartz substrates by metal organic chemical vapor deposition. Zn(tta)2 center dot tmeda (H-tta = 2-thenoyltrifluoroacetone, tmeda = N,N,N',N'-tetramethylethylenediamine) has been used as Zn precursor. The impact of deposition temperature, in the range 400-750 degrees C, on film nanostructure and optical properties has been investigated. The X-ray diffraction patterns show that film crystallinity improves upon increasing the substrate temperature. This is consistent with morphologies observed through scanning electron microscopy (SEM) and atomic force microscopy (AFM), which indicate that grain dimensions increase ranging from 80 nm rounded grains at 400 degrees C to barlike grains of about 200-400 nm at the highest investigated temperature of 750 degrees C. The AFM investigation shows that the roughness is also a function of the substrate temperatures and parallels the grains size of ZnO films. The UV-vis transmission spectrum shows that ZnO films grown at 600 degrees C on quartz are highly transparent in the visible region. Furthermore, spectroscopic ellipsometry is used for investigating the dependence of the ZnO dielectric function and optical gap on film nanostructure.

The structural, morphological and optical properties of ZnO thin films grown by metal organic chemical vapor deposition (MOCVD) also plasma-assisted (PA-MOCVD) and Au-catalyst assisted (Au-MOCVD) are investigated. A new precursor Zn(TTA)2TMED (HTTA = 2-thenoyltrifluoroacetone, TMED = N,N,N′,N′-tetramethylethylendiamine) and O2 have been used to grow film on various substrates, including Si(1 0 0), α-Al2O3(0 0 0 1) and quartz. Spectroscopic ellipsometry is used for investigating the correlation between film nanostructure and optical properties (exciton of ZnO appears in dielectric function). It has been found that the O2 plasma assisted growth results in highly (0 0 0 1) oriented ZnO films on all investigated substrates, with better optical quality as indicated by a sharp and intense exciton in the dielectric function spectra. Conversely, highly textured and rough films are deposited by MOCVD and also using the Au-catalyst. In the latter case, coupling ZnO with Au nanoparticles used as catalyst results in an enhancement of the Au surface plasmon resonance peak at 2.2 eV.

International audience; Conventional and Pulsed Liquid Injection MOCVD processes (C-MOCVD and PLI-MOCVD) have been explored as synthetic routes for the growth of BaMgF4 on Si (100) and single crystalline SrTiO3 (100) substrates. For the two applied approaches, the volatile, thermally stable [small beta]-diketonate complexes Ba(hfa)2tetraglyme and Mg(hfa)2(diglyme)2(H2O)2 have been used as single precursors (C-MOCVD) or as a solution multimetal source (PLI-MOCVD). Structural characterization through X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM) analyses confirmed the formation of epitaxial BaMgF4 films on SrTiO3 substrates. Energy dispersive X-ray (EDX) analyses have been used to confirm composition and purity of deposited films. The impact of process parameters on film properties has been addressed, highlighting the strong influence of precursor ratio, deposition temperature and oxygen partial pressure on composition, microstructure and morphology of the films. Both methods appear well suited for the growth of the BaMgF4 phase, but while PLI-MOCVD yields a more straightforward control of the precursor composition that reflects on film stoichiometry, C-MOCVD provides an easier control of the degree of texturing as a function of temperature.

NiO thin films were grown through metalorganic chemical vapour deposition (MOCVD) on quartz and LaAlO3 (001) single crystal substrates. Two different volatile and thermally stable nickel β-diketonate adducts, Ni(hfa)2·tmeda and Ni(tta)2·tmeda [H-hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentandione; tmeda = N,N,N′,N′-tetramethylethylendiamine, Htta = 2-thenoyltrifluoroacetone], were applied as precursors for NiO film growth. The comprehensive study, applying two different precursors and changing the processing parameters, allowed for morphological control of the deposited NiO films. The AFM analyses indicated different values of roughness for NiO films obtained from the two different precursors and those from Ni(tta)2·tmeda showed a lower roughness. In addition, UV-Vis and ellipsometric measurements on NiO films grown from the Ni(tta)2·tmeda show higher transparency, fewer defects/impurities, better crystallinity and a higher refractive index than films deposited using the Ni(hfa)2·tmeda source. Raman spectroscopy confirmed the antiferromagnetic nature of the NiO layers. Work functions, around 5.1 eV, were measured by Kelvin Probe Force Microscopy for NiO films grown from Ni(tta)2·tmeda. The relationship between the precursor/substrate nature and film properties allowed us to define the best precursor and conditions for the MOCVD growth of good quality NiO films.

BaB2O4 thin films are deposited by metal-organic (MO)CVD using the barium(II) hydro-tri(1-pyrazolyl)borate, Ba[BH(PZ)(3)](2), complex, that is tested for the first time as a single-source precursor for the deposition of barium borate films. The related thermal analysis data reveal good volatility and high thermal stability with a low residue upon sublimation, despite the relatively high melting point (298.2 degrees C). Different BaB2O4 phases can be obtained depending on deposition temperatures. Films, deposited on Al2O3 (0001) substrates, are structurally and morphologically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS).

Praseodymium aluminum oxide (PrAlOx) thin films have been grown by metal organic chemical vapor deposition (MOCVD) using two different multimetal sources consisting of mixtures of aluminum acetylacetonate (Al(acac)3) with two praseodymium precursors, namely, the praseodymium hexafluoroacetylacetonate diglyme adduct (Pr(hfa)3âdiglyme) and the praseodymium tetramethylheptanedionate (Pr(tmhd)3). Smooth and amorphous films have been deposited on Si(100) substrates. Their chemical composition and microstructure, investigated by EDX measurements and TEM analyses, are deeply affected by the nature of the precursor mixture. Optimal structural and compositional properties are achieved with a Al(acac)3-Pr(hfa)3âdiglyme mixture. Annealing procedures at 900 °C under an inert ambient atmospher do not affect the film crystallization. Preliminary electrical characterizations indicate a dielectric constant of about 12.

Ordered homogeneous arrays of nickel (II) oxide nanotubes have been fabricated through an MOCVD template route using Ni(tta)(2)tmeda (Htta = 2 thenoyl-trifluoroacetone, tmeda = tetramethylendiamine) as a source. The X-ray diffraction pattern shows the formation of the NiO cubic phase. Scanning electron microscopy (SEM) images of the NiO nanotubes, after removing the template, indicate the formation of well ordered nanotube arrays. There is evidence, through transmission electron microscopy studies, that nanotubes are opened on both sides. The optical properties of NiO nanotubes, determined using spectroscopic ellipsometry, strongly depend on the polarization direction of the light electric field, indicating optical anisotropy that relates to the vertical alignment of nanotubes.

High- k polycrystalline Pr 2 O 3 and amorphous LaAlO 3 oxide thin films deposited on Si(0 0 1) are studied. The microstructure is investigated using X-ray diffraction and scanning electron microscopy. Optical properties are determined in the 0.75–6.5 eV photon energy range using spectroscopic ellipsometry. The polycrystalline Pr 2 O 3 films have an optical gap of 3.86 eV and a dielectric constant of 16–26, which increases with film thickness. Similarly, very thin amorphous LaAlO 3 films have the optical gap of 5.8 eV, and a dielectric constant below 14 which also increases with film thickness. The lower dielectric constant compared to crystalline material is an intrinsic characteristic of amorphous films.

ZnO thin films have been grown by metalorganic chemical vapor deposition (MOCVD) and plasma-assisted (PA) MOCVD on c-axis-oriented sapphire (0001) and Si (001) substrates using the novel Zn(2-thenoyltrifluoroacetonate)2·N,N,N′,N′-tetramethylethylendiamine precursor. The structural, morphological, and optical properties of ZnO films have been investigated. The results show that the O2 PA growth results in highly c-axis-oriented hexagonal ZnO thin films also on cubic substrates. PA-MOCVD ZnO films have good optical properties, as inferred by the presence of a sharp and intense exciton in the dielectric function.

A novel nickel beta-diketonate adduct, Ni(tta)2.tmeda, has been synthesized using 2-thenoyltrifluoroacetone as the beta-diketonate and N,N,N,'N'-tetramethylethylendiamine as the Lewis base. It has been characterized by elemental analyses, IR, 1H NMR, 13C NMR spectroscopy and single-crystal X-ray diffraction studies. Physical and thermal properties of Ni(tta)2.tmeda precursor have been also extensively investigated. Its efficacy as a metal-organic chemical vapour deposition (MOCVD) precursor for the growth of nickel oxide films has been fully tested by applying it to the deposition of NiO films on quartz substrate. NiO thin films have been characterized by X-ray diffraction (XRD), scanning electron microscopy and UV spectroscopy.

The effects of atomic hydrogen and nitrogen produced by remote r.f. H2 and N2 plasmas on the structure, morphology, and optical and electrical properties of Zn- and O-polar ZnO crystals and on ZnO thin films grown by metal–organic chemical vapour deposition (MOCVD) have been studied. It is found that the Zn-polar form is highly reactive with atomic hydrogen, while the O-polar form is almost inert. This difference in reactivity allows one to discern the O-polarity of the (0001) oriented ZnO thin films grown by MOCVD. A decrease of the resistivity of the grain-like MOCVD films is found upon atomic hydrogen treatment. Conversely, atomic nitrogen treatment results in p -type doping of the ZnO film and in an improvement of the surface morphology and microstructure.

Praseodymium-containing thin films have been deposited on Si(001) substrates by metal-organic chemical vapor deposition (MOCVD) from the Pr(tmhd) 3 (H-tmhd=2,2,6,6-tetramethyl-3,5-heptanedione) precursor. The structural, compositional, and morphological film characterization has been investigated using X-ray diffraction (XRD), angle-resolved X-ray photoelectron spectroscopy (AR-XPS), and transmission electron microscopy (TEM). Detalled studiess of the deposition parameters indicate that the MOCVD ptocess is governed by a kinetic regime and that some reactive phenomena occur at the film/substrate interface, forming a praseodymium silicate layer. A possible explanation for interfacial interaction has been proposed, taking into account the diffusions Si feom the substrate towards the bulk and that of oxygen from the film surface toward the substrate/ film interface. Finally, the electrical characterization of the praseodymium silicate layer has been carried out in order to evaluate its potential implementation as an alternative dielectric. Its dielectric constant has been evaluated to be ∼ 8.

We have investigated the effects of thermal annealing processes on Pr2O3/Pr-O-Si system grown using the metal organic chemical vapor deposition (MOCVD) technique from the Pr(tmhd)(3) [(H-tmhd = 2,2,6,6-tetramethylheptane-3,5-dione)] precursor. The influence of different atmospheres (Ar and O-2) during the annealing process has been investigated using transmission electron microscopy (TEM). The annealing processes have been carried out at two different temperatures, 800 and 900 degrees C, for 4 h. The praseodymium films have been found to be stable in argon atmosphere up to 800 degrees C whilst at 900 degrees C the film crystallization has been observed. On the other hand, in oxygen environment, evidence of crystallization processes has already been detected at 800 degrees C. The electron diffraction patterns of the crystallized films have shown some of the most intense reflections of the stoichiometric Pr8Si6O24 phase.

CeO2 nanostructured thin films have been deposited on Al2O3(1-102) and TiO2(001) single-crystal substrates through metal-organic chemical vapor deposition (MOCVD) using the Ce(III) 1,1,1,5,5,5-hexafluoro-2,4-pentanedionato diglyme adduct (Ce(hfa)(3).diglyme). Structural and morphological characterizations have been carried out by X-ray diffraction pattern (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM) measurements. It has been found that the deposition temperature and the lattice mismatch with the substrate have a strong impact on the film nanostructure. X-ray diffraction patterns of samples grown at low deposition temperature point to the formation of oriented CeO2 films, while films deposited at higher deposition temperatures have texture. Furthermore, SEM cross section images clearly point to relevant effects of deposition temperatures both on the structural alignment of CeO2 grains as well as on the film/substrate interfaces. Spectroscopic ellipsometric measurements provide a suitable rationalization of correlations between nanostructures and optical properties of the CeO2 films. Moreover, combination of SEM and spectroscopic ellipsometric measurements provide an in-depth interpretation of growth modes.