Papers by Keyword: PLD

Abstract: SnO2 thin films have been grown on Si3N4 substrates and also on Al2O3 sensor substrates with Pt interdigitated electrodes by the pulsed excimer laser deposition (PLD). Palladium doped SnO2 thin film was also prepared by the PLD method combined with the DC sputtering process. The substrate temperature and the oxygen gas pressure were changed from 300 to 500°C and from 100 to 300 mTorr, respectively during deposition. The morphology and structural properties of the prepared thin films have been studied by AFM and XRD. The gas sensing properties of the SnO2 sensor to NO gas was evaluated by measuring electrical resistance between interdigitated electrodes. The highest sensitivity of the undoped SnO2 and Pd doped sensor was found to be around 9.5 and 42, respectively.

Abstract: High-quality transparent conductive Al-doped ZnO (AZO) thin films were deposited by pulsed laser deposition on quartz glass substrates at room temperature. We varied the growth condition in terms of oxygen pressure. The structure
and electrical and optical properties of the as-grown AZO films were mainly investigated. The AZO films formed at room temperature showed a low electrical resistivity of 3.01×10-4 ) cm, a carrier concentration of 1.12×1021 cm-3 and a carrier mobility of 18.59 cm2/Vs at an oxygen pressure of 10 mTorr. A visible transmittance of above 83% was obtained. The present results suggest that optimized AZO films should be very useful and effective for flexible display, top emission type of OLEDs and for various other kinds of optoelectronic devices such as flexible solar cell or passive photo device.

Abstract: Superconducting YBa2Cu3O7-δ
(YBCO) films were grown on MgO single crystalline substrates using a BaZrO3 (BZO) buffer layer deposited by a pulsed laser deposition (PLD). Deposition condition has been optimized to obtain good epitaxial BZO film followed by deposition of YBCO superconducting films. The crystallinity and microstructure of epitaxial YBCO/ BZO/ MgO (00l) films were investigated by a two-dimensional x-ray diffraction and a field emission scanning electron microscope. The in-plane (φ-scan) measurements for the BZO films (200 ~ 500 nm thick) grown on MgO substrates revealed a narrow full width half maximum (0φ = 2o). The XRD results exhibited that YBCO films with a BZO buffer layer were well oriented in the [00l] direction perpendicular to the substrate surface. The BZO films also showed homogeneous and dense surface morphologies. By the deposition of a subsequent BZO buffer layer, YBCO was grown epitaxially on MgO with results showing a critical current density (Jc) of ~ 3.3 × 106 A/cm2 and a critical temperature (Tc) of 86 K.

Abstract: Samarium doped ceria exhibits relative high conductivity of 0.1 S/cm at 700 °C and has been considered to be an attractive electrolyte for solid oxide fuel cells operating at the temperature range between 500 to 600 °C. Although the material exhibits better chemical and structural compatibility with electrodes as well as higher ionic conductivity than Yttria-stabilized Zirconia, the reduction of Ce4+ to Ce3+ induces n-type electronic conduction which tends to decrease power output of solid oxide fuel cells. The problem can be eliminated by using a barrier of thin Zr0.9Sc0.1O2 layer deposited over SDC layer as an alternative electrolyte to improve the stability of Samarium doped ceria under reducing atmosphere. In this work, we will report the results on the development of the Pulsed Laser Deposition (PLD) process to fabricate Sm0.2Ce0.8O1.9/Zr0.9Sc0.1O2 bilayer films. Bilayer films with controlled microstructures, density, and interfacial properties were successfully grown by the PLD at various deposition temperatures on Si(100) substartes. X-ray diffraction was used to determine their crystal structures, while the cross section images of the film-film and film-substrate interfaces were examined by field-emission SEM. The film density was calculated from the index of reflection data determined by a fiber-optic spectrophotometer.

Abstract: Atomic-scale smooth Pt electrode films have been deposited on MgO/TiN buffered Si (100) by the pulsed laser deposition (PLD) technique. The whole growth process of the multilayer films was monitored by using in-situ reflection high energy electron diffraction (RHEED) apparatus. The Pt/MgO/TiN/Si(100) stacked structure was also characterized by X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The HREED observations show that the growth mode of the Pt electrode film is 2D layer-by-layer growth. It is found that the (111)-oriented Pt electrode film has a crystallinity comparable to that of monocrystals. The achievement of the quasi-single-crystal Pt electrode film with an atomic-scale smooth surface is ascribed to the improved crystalline quality of the MgO film.

Abstract: The aim of this paper is the residual stress evaluation in dental implants and the improvement of adherence at the metal-ceramic interface. This study is focused on the development of a multi-layer system model of Hydroxyapatite/TiO2/Ti components. Our aim is to validate new methods of laser ablation deposition and sol-gel, by controlling the residual stresses and actual adherence to titanium substrates. We present a report of the growth of hydroxyapatite layers by PLD (pulsed laser deposition) and sol-gel deposition, and the measurement of their residual stresses.

Abstract: Pb(Zr0.05Ti0.95)O3/(La,Sr)CoO3 thin films were prepared by pulsed laser deposition (PLD) on SrTiO3(001) substrates. Phase transition behavior of Pb(Zr0.05Ti0.95)O3 (PZT) was investigated using high temperature X-ray diffraction (HT-XRD) and high-temperature electrical measurement. The phase transition temperature of PZT thin film is larger than bulk one. In 100 and 200nm-thickness epitaxial PZT thin films, the phase transition temperatures obtained from X-ray diffraction measurement and electrical property measurement are in good agreement.

Abstract: In this study, BiFeO3 (BFO) epitaxial film was deposited on SrRuO3 (100)/SrTiO3 (100) substrates using pulsed laser deposition (PLD). Phase pure BFO thin film was obtained. Introducing a mask between the target and substrate in PLD improved the surface roughness from 47.8 nm (RMS, without mask) to 7.7 nm (RMS, with mask). The composition and electrical properties of BFO thin film were assessed after annealing for 1 h in Ar, N2, or O2 atmosphere at 600°C. The P-E hysteresis properties improved only in the O2 atmosphere. After annealing under O2 atmosphere, the leakage current decreased from 6.1 × 10-2 A/cm to 2.9 × 10-2 A/cm at 200 kV/cm, as in the other annealing atmospheres, but 2Pr increased from 35 BC/cm2 to 50 BC/cm2.

Abstract: There is a need to develop new tough bioactive materials capable to withstand high loads when implanted in the body and with improved fixation, which led to the production of bioactive coatings on metallic substrates. A new approach, which consists of biomorphic silicon carbide (SiC) coated with bioactive glass, was recently presented. This new material joins the high mechanical strength, lightness and porosity of biomorphic SiC, and the bioactive properties of PLD glass films. In this work, a multiple evaluation in terms of biocompatibility of this new material was carried out starting from the biomorphic SiC morphology and porosity, following with the bioactivity of the coatings in simulated body fluid, and ending with a deep biocompatibility study with MG-63 cells. Different ranges of porosity and pore size were offered by the biomorphic SiC depending on the starting wood. The PLD glassy coatings had a high bioactivity in vitro and both the biomorphic SiC coated and uncoated presented high levels of biocompatibility.

Abstract: Polycrystalline ZrO2 and yttria-stablilized ZrO2 thin films have been deposited on Pt/Ti/SiO2/Si substrates by pulsed laser deposition methods. Pt/ZrO2/Pt and Pt/YSZ/Pt capacitor structures show giant conductivity switching behaviors which can be utilized for nonvolatile memory devices. Maximum on/off ratio of 106 and good endurance even after 105 times conductivity switching are observed in a typical Pt/ZrO2/Pt whose ZrO2 film has been deposited at 100 °C and an oxygen pressure of 50 mTorr. The Pt/ZrO2/Pt structure exhibits two ohmic behaviors in the low voltage region (V < 1.4 V) depending on the value of previously applied high voltage and Schottky-type conduction in the high voltage region (1.4 V < V < 8.9 V). It seems that conductivity switching behaviors in our Pt/ZrO2/Pt structure result from the changes in both the Schottky barrier and the bulk conductivity controlled by applied voltages. A Pt/YSZ/Pt capacitor structure has more stable reset voltage and current state than a Pt/ZrO2/Pt capacitor structure. Moreover, a Pt/YSZ/Pt capacitor structure shows higher Conductivity than a Pt/ZrO2/Pt capacitor structure, which may result from substitution of Y3+ ions for Zr4+ ions.