02764nas a2200253 4500008004100000022001400041245015000055210006900205260000800274300001200282490000800294520180700302653003902109653003502148653005102183653003602234100002302270700002002293700001902313700001502332700001502347700001802362856013002380 2018 eng d a1359-645400aReversible phase transformation phenomenon in titanium dioxide films: evidence beyond interface-nucleation and dissolution-precipitation kinetics0 aReversible phase transformation phenomenon in titanium dioxide f cMAR a253-2640 v1463 a

The re-crystallization kinetics and rutile to anatase reversible phase transformation (PT) in nano crystalline titanium dioxide (TiO2) are reported. Initially, an amorphous TiO2 film is used for the present study and in situ isothermal annealing dependent nucleation and growth kinetics of anatase and rutile phase is studied at low temperature (similar to 523 K) and well explained using Johnson Mehl AvramiKolmogorov (JMAK) model. The anatase nanocrystallite (NCs) transformation into rutile phase is reported with isothermal annealing for longer time and temperature dependent annealing in lower temperature range 523 K-673 K and explained using interface-nucleation mechanism. Furthermore, the thermodynamic stability of rutile NCs and lattice stress-induced reversible PT in nano-sized rutile TiO2 are confirmed in moderate temperature range (623 K- 973 K) and well explained using x-ray diffraction, micro-Raman spectroscopy and near edge x-ray absorption fine structure spectroscopy studies. However, annealing at higher temperature (1123 K- 1323 K) induces the growth of anatase NCs and their natural transform into rutile phase are explained by well-known dissolution precipitation mechanism. Activation energy of rutile PT is quantified and found higher for dissolution-precipitation mechanism than that for interface nucleation at earlier stage. Thus, overall PT kinetics at different temperature range is well understood by invoking in three step mechanism: 1) early stage anatase-to-rutile transformation is dominated by interface-nucleation, II) then intermediate stage reversible rutile-to-anatase PT and, Ill) at later stages, anatase-to-rutile PT is controlled by dissolution precipitation mechanism. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

10aDissolution-precipitation kinetics10aInterface-nucleation mechanism10aJohnson-Mehl-Avrami-Kolmogorov (JMAK) approach10aReversible phase transformation1 aGautam, Subodh, K.1 aSingh, Jitendra1 aShukla, D., K.1 aPippel, E.1 aPoddar, P.1 aSingh, Fouran uhttp://library.ncl.res.in/content/reversible-phase-transformation-phenomenon-titanium-dioxide-films-evidence-beyond-interface02144nas a2200265 4500008004100000022001400041245015500055210006900210260000800279300001400287490000700301520116100308653002601469653003001495653003501525653003501560653003301595100002601628700002001654700002201674700001801696700002201714700001801736856012401754 2019 eng d a0018-938300aIn situ study of radiation stability and associated conduction mechanisms of Nb-Doped TiO2/p-Si heterojunction diode under swift heavy ion irradiation0 aIn situ study of radiation stability and associated conduction m cMAR a1475-14810 v663 a

In situ current-voltage characteristics of Nb-doped TiO2/p-Si-based heterojunction diode have been studied under dense electronic excitations of 84-MeV Si6+ ions. The diode parameters such as ideality factor (eta), barrier height (phi(B)), reverse saturation current (J(s)), and series resistance (R-s) are found to be a strong function of ion irradiation fluence. The observed anomalies of fluence dependence of barrier height and ideality factor are explained in terms of irradiation-induced created defects complexes, modification of interface states and structural properties of Nbdoped-TiO2 (NTO) layer. Several mechanisms suchas barrier height inhomogeneity, donor defects-induced enchantment in n-NTO layer conductivity, and various current conduction mechanisms involved at different voltage ranges are discussed as a function of fluence with the help of constructed energy band diagram. Such in situ studies on n-NTO/p-Si heterojunction diode under radiation harsh environment are very appropriate for the better understanding of heterojunction interface properties and make it suitable for use in aerospace industry and nuclear reactors.

10aBarrier height tuning10an-NTO/p-Si heterojunction10aradiation stability of devices10asecondary electron irradiation10aspace-charge limited current1 aGautam, Subodh, Kumar1 aSingh, Jitendra1 aSingh, Ram, Gopal1 aGautam, Naina1 aTrivedi, Priyanka1 aSingh, Fouran uhttp://library.ncl.res.in/content/situ-study-radiation-stability-and-associated-conduction-mechanisms-nb-doped-tio2p-si02077nas a2200181 4500008004100000022001400041245018100055210006900236260000800305300001100313490000800324520136100332100001801693700001801711700002301729700001601752856012701768 2019 eng d a0021-897900aMicro-Raman investigations on zirconium oxide film during swift heavy ion irradiation to study crystalline-to-crystalline phase transformation kinetics by cascade overlap model0 aMicroRaman investigations on zirconium oxide film during swift h cJUL a0259010 v1263 a

In situ micro-Raman studies are reported to monitor the evolution of the tetragonal phase in a monoclinic zirconium oxide thin film under swift heavy ion irradiation with increasing ion fluences. Structural changes in the irradiated film are observed as compared to the virgin sample, evident from an evolution of the tetragonal phase beyond critical ion fluence. The interpretation of experimental data allows for an in-depth understanding of irradiation induced stiffening of phonon and crystalline-to-crystalline phase transformation in ZrO2 thin films. Irradiation induced peak broadening and uniform shifting of fundamental Raman modes are observed mainly in the anion (i. e., oxygen atom) dominant frequency region and give a direct indication of the accumulation of structural disorder in the oxygen sublattice of the ZrO2 film. A qualitative approach is followed to understand the kinetics of such a crystalline-to-crystalline phase transformation. Experimental results reveal that the cascade overlap model with the requirement of about six multiple ion impacts provides an excellent fit to data, and the same is further confirmed by x-ray diffraction data. Thus, this study suggests that such in situ studies envisage a better and more authentic insight into the kinetics of phase transformations under similar nonequilibrium conditions.

1 aSingh, Fouran1 aRawat, Mukesh1 aGautam, Subodh, K.1 aOjha, Sunil uhttp://library.ncl.res.in/content/micro-raman-investigations-zirconium-oxide-film-during-swift-heavy-ion-irradiation-study