Pulsed laser deposition of KNbO₃ thin films

The laser ablation of stationary KNbO3 single crystal targets induces a Nb enrichment of the target surface. In rotated targets this effect is observed only in those areas irradiated with low laser fluence. The composition of the plasma formed close to the target surface is congruent with the target composition; however, at further distances K-deficient films are formed due to the preferential backscattering of K in the plasma. This loss may be compensated for by using K-rich ceramic targets. Best results so far have been obtained with [K]/[Nb] = 2.85 target composition, and crystalline KNbO3 films are formed when heating the substrates to 650 °C. Films formed on (100)MgO single crystals are usually single phase and oriented with the (110) film plane parallel to the (100) substrate surface. (100)NbO may coexist with KNbO3 on (100)MgO. At substrate temperatures higher than 650 °C, niobium diffuses into MgO forming Mg4Nb2O9 and NbO, leading to K evaporation from the film. Films formed on (001) alpha-Al2O3 (sapphire) show the coexistence of (111), (110), and (001) orientations of KNbO3, and the presence of NbO2 is also observed. KNbO3 films deposited on (001)LiNbO3 crystallize with the (111) plane of the film parallel to the substrate surface. For the latter two substrates the Nb diffusion into the substrate is lower than in MgO and consequently the K concentration retained in the film is comparatively larger

Ab Initio Calculation of the Lattice Distortions induced by Substitutional Ag- and Cu- Impurities in Alkali Halide Crystals

An ab initio study of the doping of alkali halide crystals (AX: A = Li, Na, K, Rb; X = F, Cl, Br, I) by ns2 anions (Ag- and Cu-) is presented. Large active clusters with 179 ions embedded in the surrounding crystalline lattice are considered in order to describe properly the lattice relaxation induced by the introduction of substitutional impurities. In all the cases considered, the lattice distortions imply the concerted movement of several shells of neighbors. The shell displacements are smaller for the smaller anion Cu-, as expected. The study of the family of rock-salt alkali halides (excepting CsF) allows us to extract trends that might be useful at a predictive level in the study of other impurity systems. Those trends are presented and discussed in terms of simple geometric arguments.Comment: LaTeX file. 8 pages, 3 EPS pictures. New version contains calculations of the energy of formation of the defects with model clusters of different size

Pulsed laser deposition of KNbO₃

The Handbook of Thin Film Deposition is a comprehensive reference focusing on thin film technologies and applications used in the semiconductor industry and the closely related areas of thin film deposition, thin film micro properties, photovoltaic solar energy applications, new materials for memory applications and methods for thin film optical processes. In a major restructuring, this edition of the handbook lays the foundations with an up-to-date treatment of lithography, contamination and yield management, and reliability of thin films. The established physical and chemical deposition processes and technologies are then covered, the last section of the book being devoted to more recent technological developments such as microelectromechanical systems, photovoltaic applications, digital cameras, CCD arrays, and optical thin films.• A practical survey of thin film technologies aimed at engineers and managers involved in all stages of the process: design, fabrication, quality assurance and applications. • Covers core processes and applications in the semiconductor industry and new developments in the photovoltaic and optical thin film industries. • The new edition takes covers the transition taking place in the semiconductor world from Al/SiO2 to copper interconnects with low-k dielectrics.• Written by acknowledged industry experts from key companies in the semiconductor industry including Intel and IBM.• Foreword by Gordon E. Moore, co-founder of Intel and formulator of the renowned ‘Moore’s Law’ relating to the technology development cycle in the semiconductor industry

BIREFRINGENGE INDUCED BY SPATIAL DISPERSION IN ALKALI HALIDES

L'anisotropie optique induite par la dispersion spatiale des cristaux de KI, CsI et KBr proche à leur bord d'absorption a été mesurée par des experiments de transmission optique. La biréfringence a une grande dispersion proche au bord d'absorption de ces matériaux. En ajustant les résultats avec un modèle microscopique on obtient le paramètre de courbure anisotropique (warping) γ2 - γ3. Le paramètre de warping est beaucoup plus petit pour le KBr que pour les iodures.Optical anisotropy induced by spatial dispersion of KI, CsI and KBr single crystals near their absorption edge has been measured by means of optical transmision experiments. The birefringence has strong dispersion near the absorption edge of these materials. By fitting the results with a microscopical model one obtains the warping parameter γ2 - γ3. The warping parameter is much more smaller in KBr than for iodides