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Growth stress in tungsten carbide-diamond-like carbon coatings, sputter deposited in a reactive argon/acetylene plasma, has been studied as a function of the acetylene partial pressure. Stress and microstructure have been investigated by wafer curvature and transmission electron microscopy (TEM) whereas composition and energy distribution functions of positive ions were obtained by electron probe microanalyzer, elastic recoil detection analysis, and mass-energy analyzer (MEA). It has been observed that the compressive stress decreases with increasing acetylene partial pressure, showing an abrupt change from -5.0 to -1.6 GPa at an acetylene partial pressure of 0.012 Pa. TEM micrographs show that by increasing the acetylene partial pressure in the plasma from 0 to 0.012 Pa, the microstructure of the coating changes from polycrystalline to amorphous. MEA results show that the most probable energy of positive ions bombarding the substrate during deposition in pure argon and argon/acetylene atmosphere is the same. Based on the results, it is concluded that the huge variation in the compressive stress at low acetylene partial pressures is due to a change in the microstructure of the coating from polycrystalline to amorphous and not to the energy of positive ions bombarding the film. [ABSTRACT FROM AUTHOR]

Stress in hard films is the net sum of tensile stress generated at the grain boundaries, compressive stress due to ion peening, and thermal stress due to the difference in thermal expansion of the coating and substrate. The tensile part due to grain boundaries is thickness dependent. The other two contributions are not thickness dependent. Summation of the three components leads to a stress gradient in the coating. In the present paper it is demonstrated that adding the three contributions mentioned above yields a good description of the observed dependence of stress on thickness in CrN coatings. [ABSTRACT FROM AUTHOR]

We developed and demonstrate an analysis method in which we calibrate the intensity scale of cross-sectional transmission electron microscopy (TEM) using Cu Kα reflectometry. This results in quantitative in-depth density profiles of multilayer structures. Only three free parameters are needed to obtain the calibrated profiles, corresponding to three TEM image intensity levels. Additionally, the optical indices of the two multilayer materials used and the assumption that the layers are laterally homogeneous are used in the model. The power and the general usefulness of the method is demonstrated using experimental data of W/Si and Mo/Si multilayer systems with sharp interfaces as well as multilayers of which the interfaces were deliberately intermixed. [ABSTRACT FROM AUTHOR]

We studied the tensile stress and grain-width evolution in sputter-deposited Cr films with thickness from 20 nm to 2.7 μm. Films were deposited in an industrial Hauzer 750 physical vapor deposition machine at 50–80 °C. The films exhibited a columnar microstructure. A power law behavior of the tensile stress as well as of the average grain width with thickness was observed. Both power exponents were strongly dependent on the Ar pressure during deposition. The power exponent α for stress varied from 0.26 to 0.79 for the range of Ar pressures used (5×10-3–2×10-2 mbar). The mechanism of tensile stress generation is the shrinkage of the grain boundaries. Assuming the same shrinkage of the grain boundaries all through the layer, the stress and the grain width would be inversely proportional. Indeed, the grain width followed the same power law as the stress at low Ar pressure [α=0.3(1)], but not at high Ar pressure [α=0.58(3)]. Transmission electron microscopy showed the formation of numerous voids. At higher Ar pressure the void fraction is significantly higher than at low pressure, thereby diminishing stress generation. [ABSTRACT FROM AUTHOR]

PbZrO[sub 3] (PZ) films of different thicknesses have been grown by metalorganic chemical vapor deposition on SrTiO[sub 3] (STO) substrates. The structure of the films was determined by x-ray diffraction and transmission electron microscopy. At the deposition temperature, the growth is cube on cube and is therefore heteroepitaxial. During cool down, PZ goes through a phase transformation from paraelectric to antiferroelectric at the Curie temperature and its cubic structure is stretched to orthorhombic. This results in domain formation in the PZ films corresponding to the different stretching directions. At room temperature, the thin PZ film consists of at least two different (120) domain variants and the thin-film-substrate relation can be described as (120)[002]PZ//(100) [00&1macr;-] STO for one of these variants. By etching down a thick film, it was observed that ∼260 nm is the threshold thickness, above which two additional different (002) domain variants appear in addition to the (120) domain variants. For one of the (002) domain variants, the thin-film-substrate relation can be described as (002)[100]PZ//(100)[011] STO. The surface morphology of the thick films, studied by scanning electron and atomic force microscopy, is partly covered with pyramids. These pyramids can originate from both (120) or (002) domains and are due to a higher growth rate of these two planes compared to the rest of the layer. A suggestion is made for pyramid-facet indexing for both domains. [ABSTRACT FROM AUTHOR]

The growth kinetics and mechanisms of thin aluminum-oxide films formed by the dry, thermal oxidation of a bare Al(431) substrate at a partial oxygen pressure of 1.33 × 10[sup -4] Pa in the temperature range of 373-773 K were studied using x-ray photoelectron spectroscopy. The initial oxidation of the bare Al substrate proceeds by an island-by-layer growth mechanism, involving the lateral diffusion over the bare Al substrate surface of mobile oxygen species. At low temperatures (T ≤ 573 K), an amorphous oxide film develops that attains a limiting (uniform) thickness. At high temperatures (T>573 K), growth is not impeded at a limiting thickness. Kinetic analysis established the occurrences of two different oxide-film growth regimes: an initial regime of very fast oxide-film growth and a second, much slower oxidation stage that is observed only at T > 573 K. These results could be discussed in terms of electric-field controlled, interstitial, outward transport of Al cations through a close packing of O anions in the amorphous films, and inward diffusion of O along grain boundaries in the crystalline films, respectively. For the electric-field controlled Al cation motion, a value of 2.6 eV was determined for the rate-limiting energy barrier, which is located at the metal/oxide interface. This corresponds with a Mott potential of -1.6 V. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) etching has been used to study defects in heteroepitaxial GaN layers. In Ga-polar layers PEC etching reveals only dislocations in the form of filamentary etch features (whiskers). Transmission electron microscopy (TEM) confirmed a one-to-one correspondence between the whiskers and straight threading dislocations, which are mainly of edge and mixed type. In N-polar layers, apart from dislocations, inversion domains (IDs) also give rise to the formation of more complex etch features that also have been confirmed by TEM. IDs of nanometer diameter result in formation of whiskers similar to the dislocation-related ones. However, when the diameter of IDs exceeds a critical size (about 100 nm), crater-like deep etch features are formed during PEC etching. Based on the mechanism of PEC etching of GaN in aqueous KOH solutions, it is argued that inversion domain boundaries are electrically active defects. [ABSTRACT FROM AUTHOR]

A chemical protocol to design robust hybrid [Fe(Htrz)2(trz)](BF4)@SiO2 nanoparticles (NPs) with sizes as small as 28 nm and ultrathin silica shells below 3 nm has been developed. These NPs present a characteristic abrupt spin transition with a subsequent decrease in the width of the thermal hysteresis upon reducing the NP size. [ABSTRACT FROM AUTHOR]