Search results for "Laser deposition"

Ceramics and Thin Films of Some New Pb(B 3+ ,Nb)TiO 3 -PbTiO 3 Systems

2003

The structure, dielectric, and electromechanical properties of (1 m x )Pb(B 3+ ,Nb)TiO 3 - x PbTiO 3 binary systems (B = Lu, Er, Tb, Ho) are reported. The crystallographic features at the morphotropic phase boundary (MPB) between tetragonal P4mm and pseudo-monoclinic M phases are discussed with respect to electro-mechanical properties. Doping effect (with La 3+ ) on the properties of ceramic samples of pseudobinary Pb(Lu 1/2 Nb 1/2 )O 3 -PbTiO 3 (PLuNT) system has been investigated. Pb(Mg 1/3 Nb 2/3 )-PbTiO 3 (PT) solid solutions were studied under different processing conditions for obtaining ceramics of 100% perovskite structure with sufficient high j T EC ∼ 1 K near room temperature. The…

Epitaxial growth and properties of (001)-oriented TbBaCo2O6−δ films

2008

Thin epitaxial films of TbBaCo2O6−δ cobaltites have been synthesized using pulsed laser deposition. It was found that the film properties are extremely sensitive to the oxygen pressure during deposition, temperature of the substrate, and the cooling rate. Growth parameters were optimized for δ≈0.5 films with ordered Tb and Ba ions, as well as oxygen vacancies. The properties of these c-axis oriented films are similar to bulk TbBaCo2O5.5: they show a metal-insulator phase transition at TMI≈350 K, ferromagnetic order below TC=285 K, and antiferromagnetism at T<Ti≈230 K.

Spectroscopic ellipsometry applied to phase transitions in solids: possibilities and limitations

2009

The possibilities of in situ spectroscopic ellipsometry applied to phase transitions investigation in oxide thin films and crystals are examined in this work, along with the use of various parameters calculated from ellipsometric data (band gap energy Eg, refractive index n and surface roughness) together with the directly measured main ellipsometric angles psi and Delta, for the detection of phase transitions. The efficiency of spectroscopic ellipsometry on "surface" phase transition and its sensitivity to surface defects are also demonstrated.

Erroneous p-type assignment by Hall effect measurements in annealed ZnO films grown on InP substrate

2013

We report on incorrect carrier type identification achieved by Hall effect measurements performed on ZnO films grown by pulsed laser deposition on InP substrates and subsequently annealed for 1 h at 600 C in air. While Hall measurements, after post-growth annealing, reveal a change in the electrical properties of the films, from n-type to p-type, both photocurrent-based and standard C V measurements performed on the same samples show no change in the native n-type doping of the ZnO films. A possible interpretation of the two results is reported. In particular, p-type conductivity observed by Hall effect may be ascribed to a highly conductive thin layer formed during the annealing process at…

Optical properties of thin films of ZnO prepared by pulsed laser deposition

2004

In this paper we report on the structural features and optical properties of wurtzite ZnO films epitaxially grown on sapphire, fluorite and mica substrates by means of pulsed laser deposition (PLD). Post-deposition annealing results in a clear improvement of the film quality, reflected by the small width of the exciton-related lines in both the absorption and the photoluminescence spectra. Photoluminescence spectra revealed a multi-line structure which is identified in term of free excitons and excitons complexes with neutral donors and deep centers. The relative intensity of the PL lines mainly depends on the nature of the substrate used. Concerning optoelectronic applications it is especi…

Photocatalysis of rhodamine B and methyl orange degradation under solar light on ZnO and Cu2O thin films

2020

We report the photocatalytic properties of ZnO and Cu2O thin films deposited on glass substrates at room temperature by DC sputtering and pulsed laser deposition. The photoactivity of the films was investigated through the degradation of rhodamine B (RhB) and methyl orange (MO) under solar light. In order to select the most suitable film of ZnO for the of RhB and MO degradation, the relationship between the characteristics (e.g. energy levels and defects concentration) of ZnO films and their effectiveness in the photocatalytic yield of RhB and MO been studied, where several films were deposited by using different oxygen partial pressures (PO2: 0.05–1.3 mbar), while Cu2O films were grown und…

2008

ZnO doped with a few per cent (<10%) of magnetic ions such as Co exhibit room temperature (RT) ferromagnetism, transforming it into a very promising candidate for future spin electronic applications. We present x-ray magnetic circular dichroism (XMCD) spectroscopy, which has been used in total electron yield, total fluorescence yield, and reflection mode to investigate the origin of ferromagnetism in such diluted magnetic semiconductor materials in a surface, bulk and interface sensitive way, respectively. We investigated three different types of samples: ZnO doped with 5% Co, artificially layered films, and layered films with additional co-doping of 10% Li. These films are prepared by puls…

Rogue waves among noiselike-pulse laser emission: An experimental investigation

2014

We investigate experimental conditions in a fiber ring laser where noiselike-pulse emission fulfills the rogue wave criteria, highlighting the influence of the chromatic dispersion sign as well as the pivotal role of the pulse measurement design. While pulse-energy rogue waves are exclusively detected in the anomalous dispersion regime, spectral rogue waves are recorded for both positive and negative dispersions. To reveal $\mathsf{L}\text{-shaped}$ statistical series compatible with the generation of spectral rogue wave events, the dispersive Fourier-transform method is implemented to study the shot-to-shot spectral fluctuations of the laser output.

Pulsed laser deposition of ZnO and VO2 films for memristor fabrication

2015

Memristors are resistive switching memory devices which have attracted much attention over the last years for high-density memory applications because of their simple structure, small cell size, high speed, low power consumption, potential for 3-D stacking and excellent compatibility with the complementary metal-oxide-semiconductor (CMOS) technology [1]. Beside nonvolatile memory applications, memristors have been also proposed for other different applications including biosensors [2] and neuromorphic [3] circuits. The device structure is simply an oxide material sandwiched between two metal electrodes. The switching behavior is not only dependent on the oxide material but also on the choic…

Density of States characterization of TiO2 films deposited by Pulsed Laser Deposition for Heterojunction solar cells

2021

The application of titanium dioxide (TiO2) in the photovoltaic field is gaining traction as this material can be deployed in doping-free heterojunction solar cells with the role of electron selective contact. For modeling-based optimization of such contact, knowledge of the titanium oxide defect density of states is crucial. In this paper, we report a method to extract the defect density through nondestructive optical measures, including the contribution given by small polaron optical transitions. The presence of both related to oxygen-vacancy defects and polarons is supported by the results of optical characterizations and the evaluation of previous observations resulting in a defect band …