Thin films Epitaxial

Figure 6 High-resolution transmission electron microscopy image of an epitaxial thin film of Y Ba2Cu307 j, grown on LaAI03, shown in cross section. (Courtesy of T. E. MKchell, Los Alamos National Laboratory)...

Thin-film XRD is important in many technological applications, because of its abilities to accurately determine strains and to uniquely identify the presence and composition of phases. In semiconduaor and optical materials applications, XRD is used to measure the strain state, orientation, and defects in epitaxial thin films, which affect the film s electronic and optical properties. For magnetic thin films, it is used to identify phases and to determine preferred orientations, since these can determine magnetic properties. In metallurgical applications, it is used to determine strains in surfiice layers and thin films, which influence their mechanical properties. For packaging materials, XRD can be used to investigate diffusion and phase formation at interfaces... 

X rays and so that the angle between the difiracting plane and the incident X rays is equal to the Bragg angle For a single crystal or epitaxial thin film, there is only one specimen orientation for each (hkl) plane where these difiraction conditions are satisfied. 

Here Pyj is the structure factor for the (hkl) diffiaction peak and is related to the atomic arrangements in the material. Specifically, Fjjj is the Fourier transform of the positions of the atoms in one unit cell. Each atom is weighted by its form factor, which is equal to its atomic number Z for small 26, but which decreases as 2d increases. Thus, XRD is more sensitive to high-Z materials, and for low-Z materials, neutron or electron diffraction may be more suitable. The faaor e (called the Debye-Waller factor) accounts for the reduction in intensity due to the disorder in the crystal, and the diffracting volume V depends on p and on the film thickness. For epitaxial thin films and films with preferred orientations, the integrated intensity depends on the orientation of the specimen. 

Moustakas, T., Molecular Beam Epitaxy Thin Film Growth and... 

Epitaxial thin films, 24 742 Epitaxy, 22 152, 185. See also Epitaxial growth Heteroepitaxy in FET fabrication, 22 163-164 in HBT fabrication, 22 166, 167 in RTD fabrication, 22 170 silicon purification via, 22 496 197 vitreous silica in, 22 442 Epitaxy crystallization, ion-beam-induced, 14 447-448... 

Epitaxial thin films of silicon, to be deposited on crystalline silicon wafers, require no materials development. Other semi-conductor materials are possible, but silicon continues to be most cost-effective, principally due to the relatively... 

For industrial products, the remaining four steps are elucidated in Fig. 10.4-1. After the Concept Development step (see Fig. 10.3-2), preliminary product design occurs in the Feasibility step of the Stage-Gate process - which is not applicable for epitaxial thin films of silicon, as prototype thin films are normally not needed. 

Epitaxial thin films on MgO and SrTiOs have been obtained via both of these metal beam based techniques. 

In standard csd processing the aim is to produce dense polycrystalline, columnar or even epitaxial thin films. The above described csd precursor solution did not lead to satisfactory dense PbTi03 thin films. Nevertheless, the opposite of dense films, i.e. separated nanostructures are of great interest for studying intrinsic size effects. For this reason the before introduced PbTi03 precursor synthesis was modified. The flow chart in Figure 18.7 displays the main modifications of the basic csd route. 

Pertsev NA, Tagantsev AK, Setter N (2000) Phase transition and strain-induced ferroelectricity in SrTi03 epitaxial thin films. Phys Rev B 6LR825... 

Tyunina M, Narkilahti J, Plekh M, Qja R, Nieminen RM, Dejneka A, Trepakov V (2010) Evidence for strain-induced ferroelectric order in epitaxial thin-film KTa03. Phys Rev Lett 104 227601... 

Current-voltage (I-V) characteristics were also measured at different temperatures in magnetic fields applied perpendicularly to the surface of the substrate, i.e. parallel to the c-axis of the film. The critical current densities at T=2.1 K and in zero field are above 10 A/m. They have been defined by the electric field criterion E=Ec=10 V/cm. As an example, I-V characteristics for different values of the external magnetic field at T = 4.2 K are reported in Fig. 2. The values of the measured critical current density are slightly lower with respect to some others reported in the literature which, however, refer to epitaxial thin films in which Ce doping level was equal to its optimum value x = 0.15 [9]. We believe this is related to the reduced value of the critical temperature T in this system with respect to the optimally Ce-doped samples. 

Fig. 15.3 Preparation of epitaxial thin film model catalysts, (a) Electron micrograph of a Pt-AljOj model catalyst with a mean particle size of 5 nm the insets show the corresponding electron diffraction pattern and the (200) weak-beam dark-field image of a pyramidal Pt nanocrystal (b) an atomically resolved TEM micrograph of a slightly rectangular Pt particle. A structural model of a pyramidal Pt particle is presented in (c). To illustrate the epitaxial growth the NaCl substrate is also included...

Preparation and Nanoparticle Structure of Epitaxial Thin Film Model Catalysts... 

Apparently, epitaxial thin-film model catalysts provide a well-defined initial state for a systematic study of microstructural changes and structure-activity correlations. Model catalysts were prepared for various noble metal-oxide combinations, including Pt, Rh, Ir, Pd, Re supported by Al Oj, SiO, TiO, CeO, VO, Ga Oj, etc. The number density of the metal particles (island density particles per cm ) and their size can be controlled via the NaCl(OOl) substrate temperature during evaporation and the amount of metal deposited (as measured by a quartz microbalance), respectively (Pig. 15.4). 

Fig. 17.3 The preparation of epitaxial thin-film Ga O, oxide model catalysts, (a) Electron micrograph of a Ga O thin film prepared on NaCl(OOl) by the evaporation of Ga O in 10 Pa O at 623 K. The insets show the corresponding SAED pattern, (b) Electron micrograph of a Ga O thin film prepared on NaCl(OOl) in the absence of at 623 K and its corresponding SAED pattern (inset), (c) Ga2p XPS spectra obtained in the as-grown state and after different annealing treatments [26].

Table 9.3. Electrical properties of epitaxial thin films grown from Sn and In solvents...

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