Y(Ni, Mn)O3 epitaxial thin films prepared by pulsed laser deposition

High–quality epitaxial YNixMn1-xO3 thin films have been successfully grown on SrTiO3 (100) (STO) by pulsed laser deposition. X-ray diffraction studies showed that the films deposited on STO are fully c-axis oriented and exhibit in-plane alignment. The magnetic transition temperatures (Tc) of the films (both x=0.33 and 0.5) are equivalent to the values of the corresponding bulk samples. However, when x=0.5, the films show magnetic properties quite different from those of bulk samples. This difference may be caused by the structure distortion in these films.Comment: 14 pages, 4 figures. to be publishe

Surface excitonic emission and quenching effects in ZnO nanowire/nanowall systems: limiting effects on device potential.

We report ZnO nanowire/nanowall growth using a two-step vapour phase transport method on a-plane sapphire. X-ray diffraction and scanning electron microscopy data establish that the nanostructures are vertically well-aligned with c-axis normal to the substrate, and have a very low rocking curve width. Photoluminescence data at low temperatures demonstrate the exceptionally high optical quality of these structures, with intense emission and narrow bound exciton linewidths. We observe a high energy excitonic emission at low temperatures close to the band-edge which we assign to the surface exciton in ZnO at ~ 3.366 eV, the first time this feature has been reported in ZnO nanorod systems. This assignment is consistent with the large surface to volume ratio of the nanowire systems and indicates that this large ratio has a significant effect on the luminescence even at low temperatures. The band-edge intensity decays rapidly with increasing temperature compared to bulk single crystal material, indicating a strong temperature-activated non-radiative mechanism peculiar to the nanostructures. No evidence is seen of the free exciton emission due to exciton delocalisation in the nanostructures with increased temperature, unlike the behaviour in bulk material. The use of such nanostructures in room temperature optoelectronic devices appears to be dependent on the control or elimination of such surface effects

Control of ZnO nanowire arrays by nanosphere lithography (NSL) on laser-produced ZnO substrates

Nanosphere lithography (NSL) is a successful technique for fabricating highly ordered arrays of ZnO nanowires typically on sapphire and GaN substrates. In this work, we investigate the use of thin ZnO films deposited on Si by pulsed laser deposition (PLD) as the substrate. This has a number of advantages over the alternatives above, including cost and potential scalability of production and it removes any issue of inadvertent n-type doping of nanowires by diffusion from the substrate. We demonstrate ordered arrays of ZnO nanowires, on ZnO-coated substrates by PLD, using a conventional NSL technique with gold as the catalyst. The nanowires were produced by Vapor Phase Transport (VPT) growth in a tube furnace system and grew only on the areas pre-patterned by Au. We have also investigated the growth of ZnO nanowires using ZnO catalyst points deposited by PLD through an NSL mask on a bare silicon substrate

Control of composition and structure of ferroelectric oxide thin films grown by pulsed laser deposition

Phys. Stat. Sol. (c), 2008, 5(10), 3293-329

Simple Method to Estimate Fractional Numbers of Eu 3+ Ions in Different Phases in Highly Luminescent ZrO 2 –SiO 2 Nanocomposites

International audienceLuminescent, transparent nanocomposites incorporating very tiny crystals in glassy host matrix are a strategy to control a local structure with low phonon energy and/or adjustable band structure, and the charge‐transfer state of luminescent centers such as rare‐earth ions, resulting in their high photoluminescence (PL) efficiency and controllable absorption–emission route mechanism. For this purpose, it is important to know how many luminescent dopants can be incorporated into the nanocrystal domains. Herein, Eu 3+ ‐doped ZrO 2 –SiO 2 nanocomposites are considered as a test case, together with the starting gel thermal evolution. The progressive sol–gel chemistry enables the preferential introduction of Eu 3+ ions into the ZrO 2 nanocrystals. An analytical method using the Eu 3+ PL decay curves quantitatively reveals for the first time that the number of Eu 3+ ions doped in the ZrO 2 crystalline nanodomains, which is obtained above 900 °C, exceeds 60%, and increases to 76% when the thermal treatment temperature is 1100 °C. The fractional number of Eu 3+ ions and the local asymmetry ratio of Λ = I( 5 D 0 − 7 F 2 )/I( 5 D 0 − 7 F 1 ) for each region are estimated as Λ = 2.1–2.9, Λ ≈ 15, and Λ = 4.6–7.4 for the ZrO 2 , boundary, and SiO 2 ‐rich glass phases, depending on the heat‐treatment temperature

SrBi2Nb2O9 thin films epitaxially grown on Pt epitaxial bottom layers: structural characteristics and nanoscale characterization of the ferroelectric behaviour by AFM

SrBi2Nb2O9 (SBN) films were grown by pulsed laser deposition on (400) and (110) Pt epitaxial bottom layers. In both cases x-ray diffraction evidenced the epitaxial growth of SBN in spite of the coexistence of mainly two orientations. SBN films on (100) Pt present usually a dominant (001) orientation with the (115) one. AFM piezoresponse images agree with the crystallographic data, i.e. only the (115) oriented grains show a piezoelectric contrast. The SBN films grown on (I 10) Pt lead to a more homogenous piezoresponse imaging, in agreement with the preferential (116) orientation and the microstructure. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Exploring the optical properties of the 1.53 μm emission in Er3+-doped glass, anti-glass and ceramic in TeO2 - Ta2O5 - Bi2O3 system

International audienceA series of 80TeO2 - 10Ta2O5 – 10Bi2O3 glasses, anti-glasses and ceramics doped with different concentrations of Er₂O₃, ranging from 0.25 % to 2 % mol, were synthesized to explore their structural transformation and optical properties. The maximum solubility of Er₂O₃ was identified at 1.25 % mol, beyond which the glass transitioned from an amorphous to a crystalline structure. The anti-glasses and ceramics obtained from the heat treatment of the parent glasses were also studied to gain insights into their optical properties. This study reveals a direct relationship between Er3+ ions concentration and full width at half maximum (FWHM) of photoluminescence spectra. The increase in Er3+ ions concentration correlates with a rise in FWHM, indicative of spectral broadening. Anti-glass exhibits a higher emission intensity, followed by ceramic and then glass, reflecting their distinct structural properties. Anti-glass doped with 1 % mol Er2O3 shows an FWHM over 130 nm under 578 mW pumping. The lifetime of the excited state 4I13/2 increases with the Er2O3 content in the anti-glass and the ceramic, with a notable decrease at 1 % mol Er2O3 ions for both materials, while in glass, the decrease is observed at 0.5 %. Emission cross-sections decrease with increasing Er3+ ions concentration and power, influenced by factors like thermal effects and saturation. The Judd-Ofelt theory highlights structural differences, with glasses having a more disordered structure and with an increase in the Ω₆ parameter across all materials, implying enhanced electric dipole line strength and spontaneous emission probability with higher Er₂O₃ content. Overall, this comprehensive study provides valuable insights into the optical behavior of Er3+ ions in these materials, essential for applications in laser design and optical amplifiers