The influence of the Mn content on the elastic properties of face centered cubic Fe-Mn alloys was studied using the combinatorial approach. Fe-Mn thin films with a graded chemical composition were synthesized. Nanoindentation experiments were carried out to investigate the elastic properties as a function of the Mn content. As the Mn content increases from similar to 23 to similar to 39 at.%, the average bulk modulus varies from 143 to 105 GPa. Ab initio calculations served to probe the impact of magnetic effects on the elastic properties. The magnetic state description with disordered local moments yields the best agreement with the experimental results, whereas with non-magnetic and antiferromagnetic configurations the bulk modulus is overestimated. The strong impact of the magnetic configuration may be understood based on the differences in the chemical bonding and the magnetovolume effect. It is suggested that, owing to minute energy differences of competing antiferromagnetic configurations, a mixture of these with a "notional magnetic disorder" is present, which is in fact well described by the disordered local moments model. These results show that the combinatorial thin film synthesis with subsequent nanoindentation is an appropriate tool for investigating the elastic properties of Fe-Mn alloys systematically as a function of the chemical composition, to validate theoretical models.

We have studied the influence of the Mn content on the elastic properties of Fe–Mn random alloys (space group of Fmm) using ab initio calculations. The magnetic effects in Fe–Mn alloys have a strong influence on the elastic properties, even above the Néel temperature. As the Mn content is increased from 5  to  40  at.  %, the C₄₄ elastic constant is unaffected, while C₁₁ and C₁₂ decrease. This behavior can be understood based on the magnetovolume effect which softens the lattice. Since the amplitude of local magnetic moments is less sensitive to volume conserving distortions, the softening is not present during shearing.

The thermal stability of Ti₃SiC₂(0 0 0 1) thin films is studied by in situ X-ray diffraction analysis during vacuum furnace annealing in combination with X-ray photoelectron spectroscopy, transmission electron microscopy and scanning transmission electron microscopy with energy dispersive X-ray analysis. The films are found to be stable during annealing at temperatures up to ∼1000 °C for 25 h. Annealing at 1100–1200 °C results in the rapid decomposition of Ti₃SiC₂ by Si out-diffusion along the basal planes via domain boundaries to the free surface with subsequent evaporation. As a consequence, the material shrinks by the relaxation of the Ti₃C₂ slabs and, it is proposed, by an in-diffusion of O into the empty Si-mirror planes. The phase transformation process is followed by the detwinning of the as-relaxed Ti₃C₂ slabs into (1 1 1)-oriented TiC_0.67 layers, which begin recrystallizing at 1300 °C. Ab initio calculations are provided supporting the presented decomposition mechanisms.

The influence of ion energy on the hydrogen incorporation has been investigated for alumina thin films, deposited by reactive magnetron sputtering in an Ar/O-2/H2O environment. Ar+ with an average kinetic energy of similar to 5 eV was determined to be the dominating species in the plasma. The films were analyzed with x-ray diffraction, x-ray photoelectron spectroscopy, and elastic recoil detection analysis, demonstrating evidence for amorphous films with stoichiometric O/Al ratio. As the substrate bias potential was increased from -15 V (floating potential) to -100 V, the hydrogen content decreased by similar to 70%, from 9.1 to 2.8 at. %. Based on ab initio calculations, these results may be understood by thermodynamic principles, where a supply of energy enables surface diffusion, H-2 formation, and desorption [Rosen , J. Phys.: Condens. Matter 17, L137 (2005)]. These findings are of importance for the understanding of the correlation between ion energy and film composition and also show a pathway to reduce impurity incorporation during film growth in a high vacuum ambient.

The effect of energy supplied to the growing alumina film on the composition and structure has been investigated by varying substrate temperature and substrate bias potential. The constitution and composition were studied by X-ray diffraction and elastic recoil detection analysis, respectively. Increasing the substrate bias potential from -50 to -100 V caused the amorphous or weakly crystalline films to evolve into stoichiometric, crystalline films with a mixture of the alpha- and gamma-phase above 700 degrees C, and. gamma-phase dominated films at temperatures as low as 200 degrees C. All films had a grain size of less than 10 nm. The combined constitution and grain size data is consistent with previous work stating that. - alumina is thermodynamically stable at grain sizes less than 12 nm [McHale et al., Science 277, 788 ( 1997)]. In order to correlate phase formation with synthesis conditions, the plasma chemistry and ion energy distributions were measured at synthesis conditions. These results indicate that for a substrate bias potential of - 50V, ion energies in excess of 100 eV are attained, both from a high energy tail and the accelerated ions with charge greater than 1. These results are of importance for an increased understanding of the evolution of film composition and microstructure, also providing a pathway to. - alumina growth at temperatures as low as 200 degrees C.

We have synthesized Ta thin films on Si substrates placed along a wall of a 2-cm-deep and 1-cm-wide trench, using both a mostly neutral Ta flux by conventional dc magnetron sputtering (dcMS) and a mostly ionized Ta flux by high-power pulsed magnetron sputtering (HPPMS). Structure of the grown films was evaluated by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The Ta thin film grown by HPPMS has a smooth surface and a dense crystalline structure with grains oriented perpendicular to the substrate surface, whereas the film grown by dcMS exhibits a rough surface, pores between the grains, and an inclined columnar structure. The improved homogeneity achieved by HPPMS is a direct consequence of the high ion fraction of sputtered species.

The effect of chemical composition on the elastic and electrical properties is studied for the BOxYz system with 0.27less than or equal toxless than or equal to1.14 and 0.36less than or equal tozless than or equal to0.08. We use ab initio calculations to obtain the elastic constants and density of states for BO1.5 and the BOY phase (yttrium substituting for oxygen in the boron suboxide structure). For decreasing x values, the elastic modulus is predicted to increase from 11 to 340 GPa, while electronic structure calculations suggest a shift in electrical properties from insulating to metallic. Thin films in the B-O-Y system are grown by reactive rf magnetron sputtering. As x decreases from 1.14 to 0.27, the elastic modulus increases from 12 to 282 GPa, which is a factor of 24, while resistivity decreases from 7.6+/-0.4 to (3.8+/-0.1)x10(-2) Omegam. The observed shifts in elasticity and resistivity are shown to be induced by the associated changes in chemical bonding from van der Waals type in BO1.5 to icosahedral type in the BOY phase.

Thin films of (Na,K)NbO_x (NKN) were grown by reactive RF magnetron sputtering on polycrystalline Pt₈₀Ir₂₀ substrates, at relatively low growth temperatures between 300°C and 450°C. The results show that the electrical performance and the microstructure of the films are a strong function of the substrate temperature. X-ray diffraction of films grown up to 400°C revealed the formation of only one crystalline NKN-phase with a preferred (0 0 2)-orientation. However, a mixed orientation together with a secondary, paraelectric potassium niobate phase, were observed for NKN films deposited at 450°C. The differences in the microstructure explains the variations in the dielectric constants and losses: The single phase NKN films displayed a dielectric constant and a dielectric loss of 506 and 0.011, respectively, while the films with mixed phases exhibited values of 475 and 0.022, respectively. The possibility of fabricating NKN films with relatively high dielectric properties at low growth temperatures, as demonstrated here, is of high technological importance.

Boron suboxide (BOx, x< 1.5) is a promising material for a wide range of applications. The elastic modulus (E) of 473 GPa has been reported for crystalline BO0.17, which tends to exhibit ultra-low friction as a direct consequence of boric acid (H3BO3) formation. When thin films are formed, they are reported to be amorphous with E<300 GPa. The objective of this work was to understand the formation of crystalline BOx based films. The methodology applied was to study the correlation between composition, structure, and properties of this material with experimental and theoretical means. The growth technique used was reactive RF magnetron sputtering in an Ar/O2 ambient and the characterization included a wide range of analytical techniques. The theoretical tools employed were classical molecular dynamics and ab initio calculations. Two distinctive approaches were used to find a pathway for crystalline film synthesis: firstly extensive ion bombardment during film growth and secondly control of chemical composition as well as quantum design. When films were bombarded with Ar+ ions, they remained amorphous and E (55-248 GPa) was found to be a strong function of film density (p=1.5-2.3 g/cm3) at constant chemical composition. On the other hand, when the chemical composition was varied, the behavior of E was more complex. Firstly, it was established that the role of O in amorphous films is different than in crystalline BO0.17, where O shortens the chemical bonds. As x in BOx increased from 0.08 to 0.60, the fraction of long B-O bonds increased resulting in E decreasing from 273 to 15 GPa. Secondly, H incorporation (up to 4.7 at.%) reduced E, most likely due to a H3BO3 formation. Thirdly, C incorporation (up to 0.6 at.%) shortened the average bond length, increasing p and E, but decreasing the relative dielectric constant (19.2-0.9). Based on ab initio calculations investigating the effect of alloying metals with BO0.17, the formation of a crystalline Y containing phase was predicted. This so-called BOY phase was calculated to be 0.36 eV/atom more stable than BO0.17 and B-B were 4.9% shorter. Experimentally, this phase was synthesized and properties were determined. The measured E of 316 GPa was consistent with the prediction based on elastic constants. Moreover, the BOY phase was found to be thermally stable at temperatures up to 1000 °C and exhibited a resistivity of 3.8 Ωcm.

Elastic modulus of amorphous boron suboxide thin films was studied by theoretical and experimental methods. It was shown that the increase of x in the a-BOx films from 0.08 to 0.18 decreased the magnitude of the elastic modulus from 273 to 231 GPa. The decrease of the elastic modulus with an increasing amount of O was correlated to the presence of the long B-O bonds with ionic contribution and the reduction of the film density.