One approach to further decreasing the operation temperatures while maintaining the power densities of SOFCs is to reduce the ohmic loss by employing a thinner electrolyte layer [9,10]. Very thin electrolyte layers (t ≤ 10µm) may be used if either the anode, cathode or the interconnect materials is employed as the structural support. It is for this reason that thin film deposition methods including pulsedlaserdeposition (PLD) are especially promising . Recently, PLD has been used to deposit thin dense SDC layers onto cathode substrates to fabricate bilayer oxide membranes [11,12].
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oxide ionic conductivity and good electronic conductiv- ity w1–3x. This makes them suitable candidates for applications such as solid oxide fuel cell cathodes, oxygen membranes and sensor materials. For sensor applications, the materials should be in either the thin or thick film state. It has been demonstrated that thin films of these types of materials may be grown by pulsedlaserdeposition (PLD) w4–10x. Dependingon the deposition conditions, PLD can yield both dense and porous films with metal stoichiometry equal to that of the target material.
Pulsed-laserdeposition has several attractive features, including stoichiometric transfer of material from the target, generation of energetic species, hypothermal reaction between the ablated cations and molecular oxygen in the ablation plasma, and compatibility with background pressures ranging from UHV to 100 Pa [ 7 ]. With appropriate deposition conditions, epitaxial oxide thin film can be deposited either with stoichiometric targets of the material of interest or with multiple targets for each element. Beside this, PLD also has some other key advantages, such as, the energy source being outside the vacuum chamber which provides a much greater degree of flexibility in material usage and geometrical arrangements, film growth rate can be controlled at atomic level, source material is evaporated only to the area defined by the laser focus, the ratios of the elemental components of the bulk and thin film remain same under optimal condition, and almost any condensed matter material can be ablated, etc.
Abstract—LiNi 0.5 Mn 1.5 O 4 thin films have been grown by
pulsedlaserdeposition (PLD) on stainless steel (SS) substrates. The crystallinity and structure of thin films were investigated by X-ray diffraction (XRD). The microstructure and surface morphology of thin films were examined using a field-emission scanning electron microscope (FESEM). The electrochemical properties of the thin films were studied with cyclic voltammetry (CV) and galvanostatic charge-discharge in the potential range between 3.0 and 4.9 V. The electrochemical behavior of LiNi 0.5 Mn 1.5 O 4 thin films showed
Experiments were conducted in a high vacuum chamber under an initial base pressure of 10 -7 -10 -8 mbar
stabilizing at a value of one decade order less after few minutes of ablation.
The targets used for the pulsedlaserdeposition were obtained from cutting Ti-Ni-Zr ingots further polished with SiC 1200 paper grid. The ingots were prepared by RF melting high purity metals under helium atmosphere in an induction furnace. Oxidation of Ti and Zr were prevented as far as it was possible by preparing them in an argon glove box. The targets presented as disks of 18 mm in diameter and 4 mm in thickness. The bulk materials were characterized by electron probe micro-analysis (EPMA) on a CAMECA SX 50 and Scanning Electron Microscopy (SEM) with a PHILIPS XL30G in order to check the composition of the ingots and more particularly that the size of the different phases present in the bulk target were far smaller than the used laser spot size. The same target was used for the preparation of several consecutive films, provided a standard polishing was performed prior to any film deposition. This polishing ensured among others the elimination of surface roughness of the target that usually produces non wanted droplets on the film. Following the same goal, combination of a non-linear motion of the laser beam through a computerized control of step by step motors  and a rotation of the target (11 r/min) was used to renew the irradiated area and to avoid crater formation.
Molecular Beam Epitaxy (MBE). However, for the integration of oxides with silicon the low deposition rate, application of only elemental sources and ﬂux monitoring issues make MBE a less ideal tool from the industrial point of view. An alternative technique that provides a tuneable deposition rate and has proven to be very successful in the growth of high-quality complex oxides is pulsedlaserdeposition (PLD)  . PLD is particularly useful when growing materials containing volatile species, for example PZT, which is the key enabler for piezo- MEMS technology  . Furthermore, the recent advances in large-area PLD  , have risen an interest to establish an all-PLD growth of complex oxides on Si.
Univ Orleans, UMR CNRS 7344, GREMI, 14 Rue Issoudun, F-45067 Orleans 2, France
National Institute for Lasers, Plasma and Radiation Physics, L22 PO Box MG-36, 77125 Bucharest, Romania
Pulsed-laserdeposition is known as a well-suited method for growing thin films of oxide compounds presenting a wide range of functional properties. A limitation of this method for industrial process is the very anisotropic expansion dynamics of the plasma plume, which induces difficulties to grow on large scale films with homogeneous thickness and composition. The specific aspect of the crystalline or orientation uniformity has not been investigated, despite its important role on oxide films proper- ties. In this work, the crystalline parameters and the texture of zinc oxide films are studied as a func- tion of position with respect to the central axis of the plasma plume. We demonstrate the existence of large non-uniformities in the films. The stoichiometry, the lattice parameter, and the distribution of crystallites orientations drastically depend on the position with respect to the plume axis, i.e., on the oblique incidence of the ablated species. The origin of these non-uniformities, in particular, the unexpected tilted orientation of the ZnO c-axis may be attributed to the combined effects of the oblique incidence and of the ratio between oxygen and zinc fluxes reaching the surface of the grow- ing film.
and lifetime studies for different Er 3+ concentrations have also been performed to find the optimal doping for a YSZ
2. Experimental details
Pulsedlaserdeposition (PLD) is a technique known to achieve high crystallinity in thin film oxides. In this regard, deposition of erbium-doped oxide thin layers grown by means of PLD was carried out in a high-vacuum stainless- steel chamber. KrF excimer laser pumping at 248 nm wavelength, a fluence of 3 J/cm², and at 5 Hz repetition rate ablates a sintered erbium-doped YSZ target with an incident angle of 45°. Rotating sintered ceramic targets of variable percentage in erbium-doped 8 mol% yttria-stabilized zirconia were placed at 50 mm from the substrate on a heated holder. Sapphire substrate was heated from room temperature to 800 °C at a rate of 10 °C/min at an initial pressure of 10 -6 Torr. The chamber receives a constant flux of oxygen at a pressure of 30 mTorr during deposition. Thereafter, the
Pulsed-laserdeposition (PLD) is a well suited deposition method for growing thin films of oxide compounds present- ing either the physical properties of their bulk counterparts or new ones by changes in stoichiometry. 1 Owing to the sim- plicity of the PLD process, oxide films can be deposited without sophisticated vacuum equipment, and the stoichio- metric transfer of the target material to the substrate may usually be achieved, even in the case of complex materials. A limitation of PLD in industrial process is the very aniso- tropic character of ablation, which leads to severe non- uniformities at large scale in film thickness and composi- tion, 2–7 resulting in non-uniformities in film properties. 8 Actually, without any additional technologies to improve the thickness and composition uniformity, the substrate surface covered by a nearly homogeneous film is only about 1 cm 2 . A lot of efforts have been devoted to homogenize the film thickness and composition through various modifications of the PLD process: controlled laser rastering on large diameter targets coupled with target and/or substrate movements, 1,9 inverse PLD 10 or off-axis deposition, 11 which in counterpart leads to a large decrease of the deposition rate. However, de- spite the important role of crystalline structure on oxide films properties, the specific aspect of structural uniformity of such large area films has not been widely studied.
temperature carbon reduction process. The successful re- moval of the oxysulfide phase was supported by the absence of sharp phonon modes associated with this noncubic phase in Raman scattering experiments. 4 In the past, several au- thors have reported the successful growth of LaS thin films using reactive planar magnetron sputtering, 6,7 multi-source vapor deposition, 8 and spray pyrolysis. 9 In this article, we report the successful growth of LaS thin films using pulsedlaserdeposition sPLDd. 10 The films grown here are typically 1/2 m m to 1 m m thick. The investigation of these thicker films is a crucial step prior to growing thinner sa few mono- layers thickd films of rare-earth sulfides as more stable alter- natives to cesiated surfaces to reach NEA at the surface of III-V semiconductor compounds.
As no precise description of the KNN system exists when the alkaline/niobium ratio is less than 1, an analogy with the KN system, chemically close to the KNN system has to be made to obtain the TTB phase. In such a system however, various phases are shown to exist with different alkaline/niobium ratios making the pure TTB phase hard to obtain. Nonetheless, the pulsedlaserdeposition (PLD) technique is suitable for this type of investigation. Indeed, if the method is known to be congruent in the absence of volatile cation, it offers also a great possibility to tune the composition of the films, either by the modification of the target one and/or by the modification of the deposition parameters. Therefore because of the high alkaline (especially potassium) volatility, a thorough investigation of the deposition parameters is requested to grow the pure phase .
The pulsedlaserdeposition (PLD) technique has been a common method to grow thin films such as solid electrolyte (SE). The effects of substrate temperature and laser fluence on the thin film properties and the device performance are analyzed. For the first time, a quantitative analytical model dealing with the energy conversion in the process when laser hits the target is presented, which provides a solution that is crucial in correlating the formation of high quality and uniform thin films to the experimental design. The migration speed of the ablated particles, which determines the quality of the deposited films, is found to be directly related with the laser fluence. Specifically, a threshold fluence is required to generate high purity single form thin film. This model provides the opportunities to improve experimental design and quality control.
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Large-area pulsedlaserdeposition of silicon carbide films
Yang, D.; Xue, L.; Mccague, C.M.; Norton, P.R.; Zhang, C.S.
mated that the intensity of the infrared laser light drops to 1 =e after pen- etrating ~ 80 μm into 0.5 wt.% Nb-doped STO. Thus, the IR beam is absorbed at the backside only and does not penetrate through the crystal, avoiding any risk of damaging the UHV chamber. [Transmission of IR light would be a problem when working with undoped insulating substrates.] It should be mentioned that direct heating of the substrate is essential for obtaining a uniform temperature pro ﬁle, with temperature differences over the whole sample of less than 5 °C. Heating sample plates with no hole — instead of directly heating the sample — resulted in differences of the sample temperature as high as 70 °C as a result of non-uniform thermal contact with the sample plate. At sample temperatures of up to 1000 °C, Ag paint to attach the sample onto the holder has to be avoided due to the high vapor pressure of Ag and risk of contamination by other components of the adhesive. Additionally, direct substrate heating is of advantage to preserve clean conditions in the PLD system as it avoids un- necessary heating of other parts. All temperatures mentioned in the pres- ent work were measured with an optical pyrometer (LumaSense Technologies; emissivity 80%) aimed at the substrate surface.
alkaline elements with a ratio of (K+Na)/Nb typically in the range ∼ 0.95-1. This lack of alkaline elements may lead to an oxygen deficiency for charge compensation. The related oxygen vacancies may be responsible for decreasing the piezoelectric and dielectric properties in some ferroelectric oxides . Here, the reported compositions are average values obtained from three measurements performed on different areas of each sample. The achievement of a standard deviation lower than 2% is affording evidence tending to prove the good homogeneity and reproducibility of the deposition method used. Nevertheless the overall accuracy of EDS technique itself is usually considered close to 10%, especially in the case of resistive materials in thin films. These results enable us to confirm the so-called KNN50/50 thin film composition close to K 0.5 Na 0.5 NbO 3 and that
earth-doped quaternary chalcogenide optical fibers with specific Ga-Ge-Sb-Se composition have also been suc- cessfully implemented in MWIR for gas sensing and for exploring the spectral range of LWIR using Tb 3+ , Dy 3+
and Sm 3+ 30 – 32 . Given the properties of these amorphous materials, one can recognize the potential for applica-
tions of this kind of materials as both efficient sensors and laser sources, particularly in integrated optics. In this work, we show an extensive study of erbium-doped Ga-Ge-Sb-S thin films fabricated by PLD and RF sputter- ing, comparing the two PVD methods and the effects that the deposition conditions have on their composition, morphology, topography and optical properties. Erbium ion doping was chosen, although this RE is relatively ineffective in generating an emission in the mid-IR spectral range except around 2.7 μm, given a very unfavorable branching ratio to allow an emission at 4.5 μm. On the other hand, erbium allows us to follow its spectroscopic characteristics in the near infrared in sulfide thin films and thus to obtain very valuable information on the man- ufacturing process of rare earth-doped chalcogenide films devoted to infrared emission. Thanks to the knowledge of these different chemical, optical or spectroscopic characteristics put into perspective in relation to the deposi- tion conditions, the aim of this study is to obtain a detailed understanding of the advantages of one PVD method over the other, and the possibilities of adapting the properties of the chalcogenide thin films by adjusting the set manufacturing parameters.
2.2 Atomic Force Microscopy (AFM) Chapter 2
2.2 Atomic Force Microscopy (AFM)
The Atomic Force Microscopy (AFM) is a scanning-probe microscopy tech- nique developed by Binning, Quate and Gerber in 1986, and it is largely applied in several research and industrial fields [53, 54]. The AFM is a non-destructive technique for the study of surface morphology at very high resolution. One of the peculiarity of this technique is the possibility to obtain 3D imaging of the surface. The surface is scanned using a sharp tip made of silicon or silicon nitride placed at the end of a small bar (cantilever) of about 100-400 µm length and of known elastic constant. The tip length is around few microns, and has a curvature that is generally below 10 nm. The sensibility of cantilever to forces ranging between 10-7 and 10-12 N allows to measure the breaking forces of singular chemical bonds. The tip size is important to acquire the real features of the surface and to ensure an atomic resolution. Thanks to the advances made in the piezoelectric transducers (PZT) is now possible to use the scanning probe microscopy (SPM) techniques to probe the surfaces with precisions below the Armstrong. The piezoelectric support, indeed, enables the movement of the cantilever along both z axis maintaining a constant force, and on the xy plane to analyse the sample surface. During the analysis, the cantilever is subjected to Van der Waals forces that are established between the tip and the sample. These forces determine special deflections and oscillation of the cantilever, whose amplitude can be measured through the reflection of a laser spot from the end of the cantilever to a PSDP detector constituted by a photo-diodes matrix capable to collect the (x, y) coordinates of the signal in each point. These signals are then elaborated in a 3D image by the computer connected to the AFM, providing information on the sample surface morphology. During the scan at fixed height, a feedback mechanism avoids the tip to break or get dirty on the sample surface. This feedback mechanism regulates the distance between the tip and the sample, keeping a constant force between them. The main operation methods are three: