A review is given of ceramic and single-crystal thin film ferroelectric oxides, emphasizing perovskite phases, together with some new developments on hafnia films. It is shown that singlecrystal barium titanate films behave as bulk down to at least 77 nm, with no finite size effects, no phase transition temperature shifts, and no dielectric peak broadening or change from first-to second-order transitions, suggesting that the gradient defect model of Bratkovsky and Levanyuk correctly describes such effects as extrinsic in experimental studies of equally thin ceramic thin films. In ceramic barium-strontium titanate (BST) thin films, it is shown that there is also no intrinsic broadening or shifts in phase transitions, with sharp, unshifted, bulk-like transitions observed only as re-entrant upon warming from cryogenic temperatures; this shows that phase transitions in ceramic thin films are dominated by kinetics and not thermodynamics and are definitely not equilibrium measurements. At high fields (41 GV/m), the films exhibit space charge-limited conduction; no variable-range hopping is observed, contrary to recent studies on SrTiO 3 . Some novel, unconventional switching processes are discussed, comparing the ''perimeter effect'' (non-equilibrium, ballistic) with Molotskii's equilibrium model. Theory and experiment are described for [3D] nanotubes, nanorods, and nanoribbons (or micro-ribbons). The layered-structure-perovskitepyrochlore conversion in bismuth titanate is described together with the PbO1TiO 2 phase separation in lead zirconate titanate during electrical breakdown, as are novel HfO 2 precursors that demonstrate enhanced temperature crystallization from the amorphous state and hence commercial advantages for frontend processing. II. [2D] SystemsIn planar structures, both fine-grained ceramics and single crystals offer intriguing materials science in the 4-100 nm thickness regime. Several authors 2-4 have indicated that thin films might exhibit second-order phase transitions that, in bulk form, are first order; then, the question is exactly what thicknesses constitute ''thin''? Although the International FRAM ''Roadmap'' suggests 5 that FRAM structures must become [3D] by 2007 to accommodate requisite capacitance, at present, all FRAMs are planar-stacked devices. Therefore, we begin with the [2D] systems' materials science. J ournal

Deposition of SrTiO3 (STO) thin films by radio-frequency magnetron sputtering in an ultrahigh vacuum system at a low substrate temperature (∼200 °C) was performed in order to produce high-quality STO/p-Si (100) interfaces and STO insulator layers with dielectric constants of high magnitude. The STO films were identified as polycrystalline by x-ray diffraction, and were approximated with a layered structure according to the best fitting results of raw data from both Rutherford backscattering spectroscopy and variable angle spectroscopic ellipsometry. Room-temperature current–voltage and capacitance–voltage (C–V) measurements on Al/STO/p-Si diodes clearly revealed metal–insulator–semiconductor behavior, and the STO/p-Si interface state densities were of the order of 1011 eV−1 cm−2. The dielectric constant of the STO film was 65, and the dielectric loss factor varied between 0.05 and 0.55 for a frequency range of 1 kHz–10 MHz. For a 387 nm thick STO film, the dielectric breakdown field was 0.31 MV cm−1, and the charge storage capacity was 2.1 μC cm−2. These results indicate that STO films are suitable for applications as insulator layers in dynamic random access memories or as cladding layers in electroluminescent devices.

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Articles you may be interested inGrowth of fullerene-like carbon nitride thin solid films by reactive magnetron sputtering; role of low-energy ion irradiation in determining microstructure and mechanical properties J. Appl. Phys. 93, 3002 (2003); 10.1063/1.1538316 Elastic modulus of amorphous boron suboxide thin films studied by theoretical and experimental methods J. Appl. Phys. 93, 940 (2003); 10.1063/1.1531811 Formation of hydrogenated carbon nitride films by reactive sputtering Synthesis and mechanical properties of boron suboxide thin filmsBoron suboxide thin films, with controlled carbon content, were grown by rf dual magnetron sputtering of boron and carbon targets in an argon-oxygen atmosphere. Film composition, structure, mechanical, and electrical properties were evaluated with x-ray photoelectron spectroscopy, Auger electron spectroscopy, x-ray diffraction, transmission electron microscopy, nanoindentation, and high-frequency capacitance-voltage measurements. X-ray amorphous B-O-C films (O/Bϭ0.02) showed an increase in density from 2.0 to 2.4 g/cm 3 as C content was increased from 0 to 0.6 at. % and the film with the highest density had nanocrystalline inclusions. The density increase occurred most likely due to the formation of B-C bonds, which are shorter than B-B bonds. All measured material properties were found to depend strongly on the C content and thus film density. The elastic modulus increased from 188 to 281 GPa with the increasing C content, while the relative dielectric constant decreased from 19.2 to 0.9. Hence, B-O-C films show a potential for protective coatings and even for application in electronic and optical devices.