| 1. |
- Boscarino, Diego, et al.
(författare)
-
Deposition of silica-silver nanocomposites by magnetron cosputtering
- 2005
-
Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 23:1, s. 11-19
-
Tidskriftsartikel (refereegranskat)abstract
- Thin films have been grown on silicon and silica substrates by cosputtering of silica and silver in Ar, Ar+2.5% O2, and Ar+5% O2 gas mixtures. Rutherford backscattering spectrometry showed that the films have Ag atomic fractions xAg in the range of ∼1 to ∼10 at. %, and, by valence considerations, that the fraction of oxidized Ag in the films deposited in presence of oxygen is limited. Transmission electron microscopy images revealed the presence of Ag nanoclusters, with a mean size diameter not larger than 5 nm. The clusters are preferentially arranged along columns. It is suggested that the columns are regions with diameter in the nanometer range in which the density of the dielectric matrix is lower, thus favoring the formation of metal clusters. In presence of O2, the clusters were observed to have a more regular spherical shape. The optical absorption spectra of films grown in presence of O2 are distinguished from those grown in Ar by specific features, which are attributed to oxidation at the cluster surface. © 2005 American Vacuum Society.
|
|
| 2. |
- Comini, Elisabetta, et al.
(författare)
-
Effects of Ta/Nb-doping on titania-based thin films for gas-sensing
- 2005
-
Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 108:1-2 SPEC. ISS., s. 21-28
-
Tidskriftsartikel (refereegranskat)abstract
- Thin films of titania with the addition of niobium and tantalum have been achieved by reactive sputtering process. Structural and morphological studies have been carried out by means of XRD, RBS, TEM and AFM in order to correlate the microstructural features to the sensing performance of the layers. The films proved sensitive to ethanol and carbon monoxide and ammonia. In the case of niobium addition, it was shown that annealing temperature and niobium content strongly influence the gas response of the films converting a n-type response, which is typical of pure TiO2 and of most of metal-oxide sensors, to a p-type response; this peculiarity is crucial for the discrimination of different gases. In the case of tantalum addition, the annealing treatment at 800 °C led only to a phase transformation that reduced the sensing performance of the layer. High sensitivity to CO is achieved with anatase or mixed anatase and rutile phases, while the rutile phase only exhibit a low gas sensitivity. © 2005 Elsevier B.V. All rights reserved.
|
|
| 3. |
- Guidi, Vincenzo, et al.
(författare)
-
Selective sublimation processing of thin films for gas sensing
- 2005
-
Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 108:1-2 SPEC. ISS., s. 15-20
-
Tidskriftsartikel (refereegranskat)abstract
- The selective sublimation processing (SSP) is a useful and easy method for production of semiconducting thin films via reactive sputtering for gas sensing. We have investigated the mechanism of film growth and processing for an insight into the main parameters that control the preparation methodology. A model based on diffusion equation, in the framework of a linear theory, has been proposed and compared to experimental evidences. Rutherford backscattering spectrometry has been extensively used as a tool for determination of concentration profiles in the layers. The model allowed a deeper understanding of film preparation with a physical description of the processes involved, which would open up the design of innovative nanostructured materials that rely on SSP. Titania thin films produced by this methodology and proved capable of sensing target gases of interest for many applications. © 2004 Elsevier B.V. All rights reserved.
|
|
| 4. |
- Maggioni, Gianluigi, et al.
(författare)
-
Effects of heat treatments on the properties of copper phthalocyanine films deposited by glow-discharge-induced sublimation
- 2006
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 18:17, s. 4195-4204
-
Tidskriftsartikel (refereegranskat)abstract
- Copper phthalocyanine films have been deposited by glow-discharge-induced sublimation. The films have undergone postdeposition heat treatments in air at 250 and 290°C for different times, ranging from 30 min to 14 h. The properties of as-deposited and heated films have been investigated by different techniques in order to determine the effects of heat treatments on the film properties. Fourier transform infrared analysis and UV-visible optical absorption analysis point out a gradual evolution of the film structure from a mixture of α and β polymorphs to the only β polymorph in the sample heated at 290°C for 14 h. A pronounced decrease of carbon and nitrogen atomic percentages against an oxygen increase in the heated films are shown by ion beam analyses (Rutherford backscattering spectrometry and nuclear reaction analysis) and X-ray photoelectron spectroscopy (XPS). X-ray absorption spectroscopy and XPS indicate that part of the copper phthalocyanine molecules decompose during heat treatments and the formation of copper oxide takes place. The replacement of copper phthalocyanine by copper oxide in the heated films accounts for the change of their surface electrical conductance and of their electrical response to NO 2. © 2006 American Chemical Society.
|
|
| 5. |
- Maggioni, Gianluigi, et al.
(författare)
-
Production and characterization of thin film materials for indoor optical gas sensing applications
- 2006
-
Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 41:1, s. 531-534
-
Tidskriftsartikel (refereegranskat)abstract
- Pure and Nile-Red-doped polyimide and porphyrin films have been deposited and their optical response to different organic vapours has been tested. Polyimide films were obtained by spin coating a solution containing 4, 4'-4, 4'-(hexafluoroisopropylidene) diphthalic anhydride and 2, 3, 5, 6-tetramethyl-1, 4-phenylenediamine. Free, cobalt and iron chloride 5, 10, 15, 20 meso-tetraphenyl porphyrin films were deposited by spin coating and by high vacuum evaporation. Exposure to water, ethanol and isopropanol vapours produce reversible changes of the fluorescence features of both pure and doped polyimide films. Exposure to methanol, ethanol and isopropanol vapours gives rise to changes of the optical absorption of porphyrin films. The results of the optical measurements point out that the synthesized films can be used for the detection of volatile organic compounds. © 2006 IOP Publishing Ltd.
|
|
| 6. |
- Rupertus, Volker, et al.
(författare)
-
Thickness of thin films on glass : A round robin test
- 2005
-
Ingår i: Glass Science and Technology. - : Verlag der Deutschen Glas Technischen Gesellschaft. - 0946-7475. ; 78:5, s. 212-217
-
Tidskriftsartikel (refereegranskat)abstract
- The film thicknesses of five different layer systems on glass substrates were analyzed and determined in a multi-method approach by eight different university and industrial laboratories. The total coating thicknesses varied between a few nm up to some 100 nm. The measurements give information about the chemical composition and cover a wide spectrum of typical coating application on glasses. The results of the different laboratories and methods are compared and the challenges and limits of the various analytical techniques are discussed.
|
|
| 7. |
- Scandale, Walter, et al.
(författare)
-
Double volume reflection of a proton beam by a sequence of two bent crystals
- 2008
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 658:4, s. 109-111
-
Tidskriftsartikel (refereegranskat)abstract
- The doubling of the angle of beam deflection due to volume reflection of protons by a sequence of two bent silicon crystals was experimentally observed at the 400 GeV proton beam of the CERN SPS. A similar sequence of short bent crystals can be used as an efficient primary collimator for the Large Hadron Collider.
|
|
| 8. |
- Scandale, W., et al.
(författare)
-
Multiple volume reflections of high-energy protons in a sequence of bent silicon crystals assisted by volume capture
- 2010
-
Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 688:4-5, s. 284-288
-
Tidskriftsartikel (refereegranskat)abstract
- Multiple volume reflections of the 400 GeV / c proton beam by the sequence of fourteen bent silicon strips has been studied at the CERN SPS. The sequence is close to be parallel that is the spread of the strip orientation angles is much smaller than their bend angle and eleven strips working coherently in the regime of volume reflections deflected the beam by 110 μrad with the efficiency 88%, which is significantly larger than the estimation based on independent reflections. The mechanism giving the efficiency increase has been studied by simulation. It appears that many particles volume captured in one of the strips take part in volume reflections in the subsequent ones. Such a crystal multi reflector can be successfully used as a primary collimator for the beam halo collimation of high-energy accelerators.
|
|
| 9. |
- Vomiero, Alberto, et al.
(författare)
-
Effects of thermal annealing on the structural properties of sputtered W-Si-N diffusion barriers
- 2004
-
Ingår i: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 7:4-6 SPEC. ISS., s. 325-330
-
Tidskriftsartikel (refereegranskat)abstract
- W-Si-N thin films were deposited via rf-magnetron sputtering from a W 5Si3 target in Ar/N2 reactive gas mixtures over a large range of compositions, obtained by varying the partial flow of nitrogen within the reaction chamber. The samples of each set were then thermally annealed in vacuum at different temperatures up to 980°C. Film composition was determined by Rutherford backscattering spectrometry (RBS), surface film morphology by scanning electron microscopy (SEM), micro-structure by transmission electron microscopy (TEM), vibrational properties by FT-IR absorption and Raman scattering spectroscopy, and electrical resistivity by four-point probe measurements. Independently of the deposition conditions, all the as-deposited films have an amorphous structure, while their composition varies, showing an increase of Si/W ratio from 0.1 up to 0.55 when the nitrogen concentration in the films increases from 0 to 60 at%. Thermal treatments in vacuum induce an important loss of nitrogen in the nitrogen-rich samples, especially at temperatures higher than 600°C. Samples with high nitrogen content preserve their amorphous structure even at the highest annealing temperature, despite the chemical bonding ordering observed by means of FTIR measurements. Raman spectroscopy of as-deposited films rich in nitrogen suggests the presence of an important amorphous silicon nitride component, but fails to detect any structural rearrangement either within the composite matrix of film or within silicon nitride component. Segregation of metallic tungsten was detected by TEM in the annealed sample with lowest nitrogen content (W 58Si21N21). Finally, the resistivity of the films increases with the N content, while the loss of nitrogen accompanies the decrease of resistivity especially of samples with high nitrogen content. © 2004 Elsevier Ltd. All rights reserved.
|
|
| 10. |
- Vomiero, Alberto, et al.
(författare)
-
Structural and functional characterization of W-Si-N sputtered thin films for copper metallizations
- 2004
-
Ingår i: Materials Research Society Symposium Proceedings. - 0272-9172 .- 1946-4274. ; 812, s. 153-158
-
Tidskriftsartikel (refereegranskat)abstract
- Ternary W-Si-N thin films have been reactively sputter-deposited from a W5Si3 target at different nitrogen partial pressures. The composition has been determined by 2.2 MeV 4He+ beam, the structure by x-ray diffraction and transmission electron microscope, the chemical bonds by Fourier transform - infrared spectroscopy and the surface morphology by scanning electron microscopy. Electrical resistivity was measured by four point probe technique on the as grown films. The film as-deposited is amorphous with the Si/W ratio increasing from about 0.1 up to 0.55 with the nitrogen content going from 0 to 60 at%. The heat treatments up to 980°C induce a loss of nitrogen in the nitrogen rich samples. Segregation of metallic tungsten occurs in the sample with low nitrogen content (W58Si 21N21). Samples with high nitrogen content preserve the amorphous structure, despite of the precipitation of a more ordered phase inferred by FT-IR absorbance spectrum of the layer treated at highest temperature. The surface morphology depends upon the nitrogen content; the loss of nitrogen induces the formation of blistering and in the most nitrogen rich sample the formation of holes. Electrical resistivity preliminary results on the as grown layers range between 500 and 4750 μΩcm passing from the lowest to the highest N concentration.
|
|
