Gas Sensing Materials Based on TiO2 Thin Films

Ti O 2 thin films were prepared by spray pyrolysis using a solution of titanium tetrachloride and ethyl alcohol. The deposition was performed onto different substrates (silicon, quartz, glass) maintained at the same temperature, 270 ° C . After annealing, a predominant rutile structure is obtained for films deposited onto silicon and quartz substrates, as revealed by x-ray diffraction patterns. The Ti O 2 films were exposed to different gases, at different temperatures, in order to evaluate their gas sensitivity. The optimum operating temperatures, showing the highest gas sensitivity, were determined for some gases (acetone, ethanol, methane, and liquefied petroleum gas)

Reversible Martensitic Phase Transition in Yttrium-Stabilized ZrO2 Nanopowders by Adsorption of Water

Funding: This work was supported by H2020/MSCA/RISE/SSHARE number 871284 project and the RO-JINR Grant No. 367/2021 item 27 and RO-JINR Projects № 366/2021 items 57, 61, 83, 85. Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.The present study was aimed at revealing the influence of the mechanical stress induced by water molecule adsorption on the composition of crystalline phases in the ZrO2 + 3 mol% Y2O3-nanoparticles. Three basic methods were used to determine the phase transition: Neutron diffraction, Raman microspectroscopic scanning, and X-ray diffraction. The fact of reversible phase-structural β → α transformation and the simultaneous presence of two polymorphic structural modifications (β is the phase of the tetragonal syngony and α of monoclinic syngony in nanosized particles (9 nm)) under normal physical conditions was established by these methods. An assumption was made regarding the connection of the physical mechanism of transformation of the extremely nonequilibrium surface of nanoparticles with electronic exchange of the material of the near-surface layer of nanoparticles with the adsorption layer through donor-acceptor interaction. The principal possibility of creating direct-acting hydroelectric converters based on nanoscale YSZ (Yttria-Stabilized Zirconia) systems due to the reversible character of the considered effect was shown.publishersversionpublishe

Polaronic transport in TiO2 thin films with increasing Nb content

WOS: 000298585300009The temperature dependence of the charge transport in TiO2 films was investigated to establish the correlation between the Nb content and electrical properties. It was identified that temperature-dependent conductivity of the films is dominated by a phonon-assisted small polaron hopping model in the non-adiabatic regime. Applying the polaron hopping models of Mott, Schnakenberg and Emin to describe the observed behavior, temperature-dependent conductivity data of the films were analyzed. A detailed analysis in terms of small polaron hopping parameters in the investigated temperature regime was used to correlate electrical properties with the percentage of Nb.CNCSISConsiliul National al Cercetarii Stiintifice din Invatamantul Superior (CNCSIS) [PCCE-ID_76/2010]We thank Professor M. Girtan from Photonics Laboratory, Angers University, Angers, France, for sample preparation. This work was supported by the CNCSIS via contract no. PCCE-ID_76/2010

Polaron transport in TiO2 thin films

WOS: 000283745100059Undoped and Fe-doped TiO2 thin films were obtained by rf-sputtering technique onto heated glass substrates (250 degrees C) covered with indium tin oxide. The temperature dependence of the electrical conductivity was investigated in the temperature range 13-320 K, and it shows that the conduction mechanism in the studied samples is described by small-polaron hopping (SPH) at temperatures higher than half of the Debye temperature (theta(D)). It was found that the magnitude of the SPH coupling increases by Fe doping in TiO2 thin films. With decreasing temperature, the conduction behavior transited from SPH conduction to variable-range hopping (VRH) conduction. In the intermediate temperature domain (200 K<T<theta(D)/2), the VRH conduction was found to be dominant, while a temperature-independent conductivity behavior was observed in the lower temperature range (T<200 K). (C) 2010 American Institute of Physics. [doi: 10.1063/1.3493742]CNCSISConsiliul National al Cercetarii Stiintifice din Invatamantul Superior (CNCSIS) [PCCE-ID_76, 12128/2008]One of the authors (D. Mardare) is grateful to Professor F. Levy from Institute of Applied Physics, Polytechnic Federal School of Lausanne, Switzerland for providing the necessary laboratory facilities to carry out a part of this investigation. This work was supported by CNCSIS Contract No. PCCE-ID_76 and by Grant No. 12128/2008

PHOTOINDUCED WETTABILITY OF TITANIUM OXIDE THIN FILMS

WOS: 000284612100007We present here the results of a systematic investigation of the influence of the main deposition parameters (substrate temperature, deposition time, reactive gas composition, etc.) on the hydrophilic properties of DC sputtered titania films, grown on heated glass substrates (463-573 K), using water vapors as the reactive gas. Reference samples prepared in standard oxygen-based deposition conditions were used to compare the results. All the investigated samples were polycrystalline, with either pure anatase or mixed anatase-rutile nano-phase mixtures, depending on substrate temperature and film thickness. The surface wettability, evaluated from contact angle data during UV irradiation and in the back-reaction conditions, is discussed in terms of the synergic effects of materials structure, surface morphology, elemental composition, and electronic properties.CNCSISConsiliul National al Cercetarii Stiintifice din Invatamantul Superior (CNCSIS) [PCCE-ID_76]; Turkish national research scholarshipTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [2218]The financial support from the CNCSIS Contract PCCE-ID_76 is acknowledged by D. Mardare, A. Manole and D. Luca. A. Yildiz acknowledges the 2218-coded Turkish national research scholarship. D. Mardare is grateful to Prof. F. Levy from the Polytechnic Federal School of Lausanne, Switzerland, for ensuring the access to deposition facilities

The thickness effect on the electrical conduction mechanism in titanium oxide thin films

WOS: 000276054200054In this paper we made a study on the effect of films thickness on the electrical conduction properties of nanostructured TiO(2) thin films deposited by d.c. reactive sputtering. The deposition was performed on heated (573 K) glass substrates, using water vapor as reactive gas. The electrical conductivity of the films was investigated in the temperature range 13-320K. The temperature dependence of electrical conductivity between 80 and 320 K indicated that electrical conductivity in the films was controlled by potential barriers caused by depletion of carriers at grain boundaries in the material. Values of grain barrier heights and surface trap density at the grain boundaries were extracted from the high temperature data for the investigated samples. Both the grain barrier heights and surface trap density at the grain boundaries were found to depend significantly on film thickness into the deposition process. The low-temperature (T < 80 K) conductivity of the films was described in terms of variable-range hopping (VRH) conduction. Characteristic parameters describing the low-temperature conductivity, such as the hopping distance, hopping energy and density of states were determined, and their values as a function of film thickness were discussed in the light of variable-range hopping conduction model. (C) 2009 Elsevier B.V. All rights reserved.TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK); ANCSTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [TBAG-U/220 (107T584), 17CB/2008]; BiDEBTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK)One of the authors (D. Mardare) is very indebted to Professor F. Levy from Institute of Applied Physics, Polytechnic Federal School of Lausanne, Switzerland for providing the necessary laboratory facilities to carry out a part of this investigation. The authors would also like to thank N. Cornei and G.I. Rusu from "Al.I.. Cuza" University, Iasi, Romania. This work was supported by TUBITAK and ANCS under project no. TBAG-U/220 (107T584) and 17CB/2008. Abdullah Yildiz acknowledges 2218 coded national research scholarship from BiDEB

Undoped and Cr-doped TiO2 thin films obtained by spray pyrolysis

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Surface wettability of titania thin films with increasing Nb content Surface wettability of titania thin films with increasing Nb content

Multi-scale order in amorphous transparent oxide thin films J. Appl. Phys. 112, 054907 (2012) Growth of continuous and ultrathin platinum films on tungsten adhesion layers using atomic layer deposition techniques Appl. Phys. Lett. 101, 111601 (2012) Effect of tip polarity on Kelvin probe force microscopy images of thin insulator CaF2 films on Si(111) Appl. Phys. Lett. 101, 083119 (2012) Epitaxial growth and metal-insulator transition of vanadium oxide thin films with controllable phases Appl. Phys. Lett. 101, 071902 (2012) Additional information on J. Appl. Phys. TiO 2 and TiO 2 /Nb amorphous thin films were grown on glass substrates by a sol-gel technique (spin coating). Films&apos; surface composition, structure, and morphology were derived from x-ray photoelectron spectroscopy, x-ray diffraction, and atomic force microscopy data. The investigated films showed a smooth surface (roughness values below 5 nm). A separate surface wettability investigation showed that by increasing the Nb amount in pristine titania films results in a decrease of contact angle (CA) values from 40 to nearly 0 , thus, indicating a super-hydrophilic conversion under UV illumination. This conversion rate is greatly enhanced by increasing the Nb content, the surface super-hydrophilic behavior occurring after a couple of minutes in the TiO 2 /Nb samples, but after 4 h in the pristine titania specimen. The current results are discussed in terms of the optical band gap shift towards higher energies, by increasing the Nb content in the films, a process explained based on small polaron hopping model. V C 2012 American Institute of Physics