Intermetallic Thin Films Research Articles

Synthesis of Ti–Al Intermetallic Compound Films by Intense Pulsed Ion Beam Evaporation

In order to examine the possibility of the synthesis of an intermetallic compound thin film by intense, pulsed, ion beam evaporation (IBE), the synthesis of thin films of Ti–Al system intermetallic compound was attempted. The crystal structure and composition of the films were evaluated. By using a combination target of Ti and Al, thin films of single phase could not be synthesized, while the Ti3Al film was found to be successfully synthesized by using a Ti/Al sintered target. The Ti3Al film was orientated in the 002 plane.

Microstructure and growth modes of stoichiometric NiAl and Ni3Al thin films deposited by r.f.-magnetron sputtering

Intermetallic thin films of stoichiometric NiAl and Ni3Al have been deposited onto n-type silicon (100) and nickel (110) substrates using r.f.-magnetron co-sputtering. The morphology and crystal structure of the thin films have been studied by transmission electron microscopy from planar-view and cross-sectional samples. Chemical order has been assessed using nano-diffraction techniques. Superlattice reflections confirm a fully ordered structure in both intermetallics. These NiAl and Ni3Al thin films are nanoscaled with an average grain size ranging from 50 to 100 nm and exhibit fiber textures in the 〈110〉 and 〈111〉 directions when deposited onto silicon. Granular- and heteroepitaxial relations have been observed when sputtering onto nickel at high substrate temperature. A granular-heteroepitaxial mode of growth exhibiting the inverse Nishiyama–Wassermann relation (2̄11)[2̄11]B2∥(1̄10)[1̄10]fcc is observed in NiAl for the first time, whereas a single-crystalline heteroepitaxial growth relation of (1̄10)[1̄10]L12∥(1̄10)[1̄10]fcc is achieved in Ni3Al. The interface chemistry and surface topography have been studied by secondary ion mass spectroscopy and scanning tunneling microscopy, respectively, indicating an oxygen-free layer of very low surface roughness. The influence of the lattice matching and the deposition parameters on the thin film microstructure and orientation are discussed.

ChemInform Abstract: Thermal Phase Evolution of Pt—Si Intermetallic Thin Films Prepared by the Activated Adsorption of SiH4 on Pt(100) and Comparison to Known Structural Models.

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Morphological and Compositional Evolution of Pt−Si Intermetallic Thin Films Prepared by the Activated Adsorption of SiH4on Pt(111)

We have investigated using scanning tunneling microscopy (STM) and Auger electron spectroscopy (AES) the growth and structural evolution of Pt−Si intermetallic phases formed via a chemical vapor deposition (CVD) mediated process. The Pt silicide thin films were prepared though the exposure of a Pt(111) crystal to silane (SiH4) followed by various annealing treatments. The deposition of Si via the decomposition of silane at room temperature preferentially forms clusters at step edges that avoid the centers of Pt terraces. The sizes and coverages of the clusters increases with silane exposure. The clusters are of intermetallic character (composed of both Si and Pt) and coarsen to give cluster heights much larger than a Pt(111) step height. These observations implicitly establish that Si interdiffusion in the near-surface region is weakly activated. Studies performed as a function of the silane exposure and annealing temperature reveal a complicated phase behavior that incorporates seven separate atomically ...

Thermal Phase Evolution of Pt−Si Intermetallic Thin Films Prepared by the Activated Adsorption of SiH4on Pt(100) and Comparison to Known Structural Models

We have investigated the growth, morphology, and phase evolution of Pt−Si intermetallic thin films using scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and Auger electron spectroscopy (AES). These materials were formed through an “inverted” CVD deposition process that involves the exposure of a Pt(100) crystal to silane (SiH4) followed by flash annealing treatments. Structural studies performed as a function of the annealing temperature reveal a complicated phase behavior that involves the sequential formation of four atomically ordered phases with multilevel character. The nature of this process is analyzed to obtain information about the primary structure-determining interactions responsible for the phase transformations seen in this system. We describe the structure-determining influences seen on the Pt(100) surface and provide a comparison with earlier results obtained on Pt(111) and Ni surfaces. The substrate effects are marked and the differences between the results obtained on Pt(100) and Pt(111) are discussed in detail. A model is presented that relates the structure of the phases obtained on the Pt(100) surface to known bulk Pt silicide phases. Of particular interest is the finding that “inverted” CVD via the thermolytic decomposition of SiH4 on the Pt(100) substrate yields, upon suitable thermal treatment, a (√17×√17)R14.0° overlayer structure exhibiting two chiral surface domains. This multilayer structure is well described by a termination of the bulk Pt−Si intermetallic phase that is isomorphic with the well-known Ni12P5 structure.

An investigation into the fabrication and properties of Ni 3Al thin coatings on nickel substrates

Thin film intermetallic aluminides are being studied for use as interconnects in microelectronics, working coatings in alloys and matrix in composite materials because of their good corrosion resistance, low oxide inclusions and high bond strength with substrates. In aerospace applications, nickel-base superalloys are being used in turbine blades which operate as temperatures u to 1000 C or higher. Their main requirements are corrosion and oxidation resistance, high temperature strength, and resistance to thermal shock and fatigue. One obvious way to improve the resistance to corrosion and surface wear of superalloy blades at high temperatures is to apply protective coatings on the blades. In this respect, it is well known that the intermetallic compound Ni{sub 3}Al possesses advantageous high-temperature properties. It exhibits the so-called flow stress anomaly, which means that the strength of the material gets higher as temperature increases up to about 650 C. It is also interesting to note that Ni{sub 3}Al and nickel share similar physical properties such as thermal expansion coefficients and melting temperatures. Together with their equivalent fcc lattice structures and low theoretical lattice mismatch (1.3%) at their interface, a Ni{sub 3}Al intermetallic thin film is therefore expected to exhibit excellent adhesion with a supporting Nimore » substrate, while providing the latter with improved resistance to mechanical wear, chemical corrosion and high temperature oxidation. On this consideration, the aim of this work is to synthesize Ni-Al thin films with the 3Ni/1Al stoichiometry by the sputter technique on nickel substrates and to study the oxidation and wear resistance of the Ni{sub 3}Al coating-nickel substrate system.« less

Coordination of alane and aluminum alkyls to the N-donor atom of side chain functionalized cyclopentadienyl iron and nickel complexes; structure of {[(C 5H 5)(C 5H 4CH 2NMe 2)]Fe} 2AlH 3

The synthesis of iron and nickel complexes with interaction of aiane and trialkylaluminum compounds to the amino group is described. Treatment of [2-( N,N-dimethyIamino)methyl] ferrocene {[(C 5H 5)(C 5H 4CH 2NMe 2)]Fe ( 1) with trimethylaminealane (H 3AlNMe 3), leads to the formation of the iron alane complex {[(C 5H 5)(C 5H 4CH 2NMe 2)]Fe} 2AlH 3 ( 2), with a five-coordinated aluminum center. The structure of 2 has been determined by single-crystal X-ray diffraction. The reaction of FeCl 2 with two equivalents of {(C 5H 4CH 2CH 2NMe 2)Li} leads to the formation of [(C 5H 4CH 2CH 2CH 2NMe 2) 2Fe] ( 3). Complex 3 reacts quantitatively with two equivalents of trimethylaluminum to the compound [(C 5H 4CH 2CH 2NMe 2) 2Fe](AlMe 3) 2 ( 4). Addition of trimethylaluminum or triethylaluminum to the nickel complex [(C 5H 4CH 2CH 2NMe 2) 2Ni]Ni ( 5) give the paramagnetie nickel aluminum compounds [(C 5H 4CH,CH 2NMe 2) 2Ni](AlMe 3) 2 ( 6a) and [(C 5H 4CH 2CH 2NMe 2) 2Ni](AlEt 3) 2 ( 6b), respectively. These compounds were characterized by 1H, 13C and 27Al NMR, elemental analysis and mass spectroscopy. Studies to deposit intermetallic thin films using these compounds as bimetallic single source precursors revealed that aluminum was deposited, only.

Point defects and texture of Pd1 − xInx sputtered intermetallic thin films

Pd1 − xInx thin films (0.4 < x < 0.56) were prepared by radio frequency sputtering from a multi-zone target. The properties of these Hume-Rothery alloys were studied by X-ray diffractometry, electron probe microanalysis and scanning tunneling microscopy. The diffraction spectra were analyzed to obtain the intensity ratio of the (100) superlattice line to the (200) normal line, together with the variations of the lattice constant. The results are explained quantitatively by a model based on point defects, i.e. Pd vacancies in In-rich films and Pd antisite atoms in Pd-rich films. In-rich films grow preferentially in the [100] direction while Pd-rich films grow preferentially in the [110] direction. The grains in indium-rich sputtered films appear to be enclosed in an atomically thick, indium-rich layer. The role of texture and the influence of point defects on electrical resistivity is also reported.

The synthesis of nickel aluminides by multilayer self-propagating combustion

The synthesis of Ni-Al intermetallic thin films by self-propagating combustion reactions was investigated for the 1:1 and 3:1 Ni/Al stoichiometries. The dependence of the combustion wave velocity on the individual layer thickness was determined. The marked decrease in velocity with layer thickness was consistent with results of modeling studies on multilayer systems. Activation energies for the synthesis of NiAl were determined to be in the range 127.9 to 149.8 kJ · mol−1, and those for the synthesis of Ni3Al were found to be in the range 133.8 to 146.3 kJ · mol−1. In the case of NiAl, the experimental value is attributed to a diffusion process of Al in NiAl. Differential thermal analysis (DTA) showed the sequence of steps in the formation of NiAl and Ni3Al. The dependence of the thermal peaks on the heating rate for both cases was found to be consistent with theory. The activation energies obtained from the DTA analysis were compared to previous results obtained with relatively thin layers.

ZrAl3 Intermetallic Compound Thin Film as a Diffusion Barrier between Al and Au Layers

A layer of intermetallic compound ZrAl3 of 100 nm thickness functioning as a diffusion barrier between Al and Au thin films was investigated. The performance of the barrier was characterized by in situ monitoring of electrical resistance during heating under vacuum. The value of sheet resistance remained constant up to about 340° C; then it increased gradually to a maximum at about 550° C. The increase of resistance reflected the occurrence of interactions between thin films. With the aid of Auger electron spectroscopy depth profile and X-ray diffraction analyses, it was found that the degradation of the ZrAl3 barrier layer was mainly attributed to the diffusion of Al through ZrAl3 grain boundaries, reacting with Au to form Au5Al2 initially on the surface at 300° C. As temperature was increased further, AuAl2 was found at the Au/ZrAl3 interface.

Magnetic and Magneto-Optic Properties of PtFe (001) and PtCo (001) Thin Films

ABSTRACTWe report on the magnetic and Magneto-optical properties of PtFe and PtCo intermetallic thin films when they have the CuAu(I) tetragonal structure and their crystallographic C axis is oriented out of the film plane. These films possess large perpendicular magnetic anisotropy energies. We observe changes in the Magneto-optic Kerr rotations of Pt-Fe and Pt-Co alloys associated with the formation of the uniaxial CuAu(I) crystal structure. In particular, we report the observation of up to 60% enhancement in the Magneto-optic Ken-rotation for ordered, epitaxial PtFe intermetallic alloy over that of the random face centered cubic alloy. This enhancement is wavelength dependent, with a peak in the visible light range at 2.0 eV.

Reactivity of intermetallic thin films formed by the surface mediated decomposition of main group organometallic compounds

We have observed that by the reaction of silane with clean Ni, Rh, Pt, Mo, Ta, W, Cu, and Au surfaces at elevated temperatures, thin alloy and intermetallic compound phases can be prepared. For example, SiH4 reacts with atomically clean nickel surfaces to give a &amp;gt;50 Å surface film of predominantly Ni2Si. Subsequent reaction with oxygen leads to the formation of a thin passivating layer of SiO2; structurally similar materials were also obtained from the direct reaction of silane with oxidized nickel surfaces. Our results from studies on a wide variety of metal surfaces suggest a general procedure for the preparation of passivating, non-native oxide thin films. The scope of this methodology as regards applicable metals and reactive gases, and the physical and chemical properties of several representative materials is discussed.