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Mn+1AXn (MAX) phases are novel structural and functional materials with a layered crystal structure. Their unique properties such as good machinability, high electrical conductivity, low friction, and corrosion resistance are appealing for many engineering applications. Herein, Ti2AlC and Ti3AlC2 MAX thin films are synthesized by magnetron sputtering and subsequent thermal annealing. A multilayer approach is used to deposit single‐element nanolayers of titanium, aluminum, and carbon onto silicon substrates with a double‐layer‐diffusion barrier of SiO2 and SixNy. Ti2AlC and Ti3AlC2 thin films (thickness ≈500 nm) are formed via rapid thermal annealing and verified by X‐Ray diffraction. Nanoindentation tests show hardness values of about 11.6 and 5.3 GPa for Ti2AlC and Ti3AlC2, respectively. The tribological behavior of the Ti2AlC and Ti3AlC2 thin films against AISI 52100 steel balls under dry sliding conditions is studied using ball‐on‐flat tribometry. The resulting coefficient of friction (CoF) for Ti2AlC and Ti3AlC2 ranges between 0.21–0.42 and 0.64–0.91, respectively. The better tribological behavior observed for Ti2AlC thin films is ascribed to its smaller grain size, reduced surface roughness, and higher hardness. [ABSTRACT FROM AUTHOR]

The knowledge of pre-exponential factors and activation energies for low temperatures and short annealing times in nanoscaled systems is important for the downscaling of thermal processes. Here, the diffusion coefficients in aluminum-nickel, aluminum-titanium, titanium-silicon, and aluminum-copper bilayers were determined using rapid thermal annealing. The annealing time was set to 500 s and the investigated bilayer thin film thicknesses were 2 µm. The temperatures ranged from 389 to 613 K depending on the bilayer system. For the various material combinations, the diffusion coefficients were determined by elemental depth profiling and compared to literature values. For the aluminum-copper system, a good agreement with literature and a single set of values was found, whereas for aluminum-nickel, aluminum-titanium, and titanium-silicon two or more sets of values were observed. [ABSTRACT FROM AUTHOR]

In the last years, M n + 1 AX n (MAX) phases came into the focus of functional thin film research. Potential fields of application for MAX phases are structural materials for high temperatures, tribological protective coatings, electrical contacts in aggressive environments, and as sensing materials in sensor technology. This paper focuses on the tribological behavior of Ti 3 SiC 2 , Ti 2 AlN and Cr 2 AlC phase thin films against a counterpart bearing steel 1.3505. The MAX films are deposited by magnetron sputtering of elemental multilayers and a rapid thermal annealing synthesis. The formation of the MAX phases is investigated by X-ray diffraction and transmission electron microscopy. The reciprocating micro-tribological sliding against steel balls, scanning electron microscopy and energy dispersive X-ray spectroscopy revealed an adhesive wear mechanism for Cr 2 AlC and Ti 2 AlN with friction coefficients in the range of 0.30 to 0.70 and 0.15 to 0.50, respectively. The best friction and wear behavior were observed for Ti 3 SiC 2 with a friction coefficient in the range of 0.15 to 0.25. Furthermore, for all MAX phases, hypotheses for the wear mechanisms are formulated. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cr2AlC were produced by magnetron sputtering of multilayers from elemental targets and subsequent rapid thermal annealing. [•] MEMS like structures were prepared in the shape of freestanding doubly clamped beams and cantilevers. [•] The vibrational mechanical properties were investigated using electrostatical excitation and analysis by Laser Doppler Vibrometer. [•] A model of calculating the Young's modulus of the structures and therefore also of the thin film was postulated leading from the vibrational measurements of the doubly clamped beams and the cantilevers. [ABSTRACT FROM AUTHOR]

Highlights • DC-magnetron sputtering on flat and nanostructured borosilicate glass was employed • XRD shows crystalline peaks corresponding to hexagonal wurtzite structure of ZnO. • Film thickness, film roughness, interface roughness and density are studied by XRR • AZO thin films were found to be highly transparent in the visible to NIR region. • The power conversion efficiency of cells with AZO on the flat substrate is 2.24%. Abstract Transparent conductive aluminum-doped zinc oxide (AZO) thin films were deposited on a flat and nanostructured borosilicate glass substrates by using DC-magnetron sputtering. The aluminum doping concentration was kept at 3.3 wt% and the film thickness (100–400 nm) was varied. The thin films were then annealed at 250 °C for 1 h in nitrogen and/or argon atmosphere, respectively. AZO thin films exhibited hexagonal wurtzite structure of ZnO with an intense (0 0 2) diffraction peak, indicating that they have c-axis preferred orientation. Optical transmittance was observed to be greater than 80% in the visible range for films deposited on both flat and nanostructured glass substrates. The lowest resistivity of 9.7 × 10−4 Ω cm was observed for AZO film of 400 nm thickness on flat glass substrate, annealed in Nitrogen atmosphere. The power conversion efficiency (PCE) of 0.27% and 2.24% were recorded for organic solar cell devices based on AZO deposited on nanostructured and flat borosilicate glass, respectively. In comparison with the latter, the PCE of ITO based device was recorded to be 3.17%. Due to their good optical and electrical properties, AZO thin films are promising candidates as transparent electrodes in organic solar cells. [ABSTRACT FROM AUTHOR]

This work analyzes the photoluminescence emission of Yb3+ and Tb3+ ions in co-doped silicon oxycarbide thin films, their activation by thermal treatment, and reveals their luminescent properties regarding the energy transfer between them. Three samples of silicon oxycarbide were prepared by rf magnetron sputtering from SiC, Yb and Tb targets in an oxygen/argon atmosphere. The first one is the undoped silicon oxycarbide sample, the second one is Tb single doped, and the last one is the Yb-Tb co-doped sample. All three samples are identified as silicon oxycarbides with a low carbon content using energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. The latter shows the presence of the vibrational modes of Si–C and Si–O bonds. Subsequent annealing treatments up to temperatures of 750 °C led to the rare earths optical activation in the samples. For each annealing step, we present the photoluminescence spectra using an above-bandgap excitation of 325 nm. The Tb3+ and Yb3+ -related luminescence lines were identified. The Yb3+ ions luminescence for the co-doped sample shows concentration quenching above annealing temperatures of 500 °C whereas the Tb3+ ions luminescence intensity remains almost constant. The analysis of the photoluminescence excitation spectra shows the direct excitation of the Tb3+ ions in the Tb-doped samples. A high suppression of the direct excitation of the Tb3+ ions in the Yb-Tb co-doped samples was observed. The energy transfer from Tb3+ to Yb3+ ions in co-doped samples is evidenced, first, by the decrease of the Tb3+ photoluminescence intensity in the co-doped compared to the Tb doped sample. Second, a change from nearly single exponential to nonexponential decay in the Tb3+ photoluminescence decay curves and third, by the reduction of the Tb3+ decay time from 1.2 ms in the Tb-doped sample to 0.5 ms in the Yb-Tb co-doped sample. • The Yb3+ and Tb3+ luminescence were identified in Yb-Tb co-doped silicon oxycarbide. • The quenching process in Yb3+ ions was observed above 500 °C in co-doped silicon oxycarbide. • Indications of energy transfer from Tb3+ to Yb3+ were found by PL decay curves. [ABSTRACT FROM AUTHOR]

• Synthesis of Ti 2 AlC & Ti 3 AlC 2 MAX-phases by annealing of the same multilayer system. • The multilayer system is a sequence of pure elemental layers deposited by sputtering. • Study of temperature influence on the stoichiometry of the MAX-phase. • Evaluation of elastic modulus and hardness due to the MAX-phase transformation. • Effect of the grain growth and MAX-phase transformation on the mechanical properties. MAX phase thin films have been synthesized by thermal treatment of a Ti-Al-C multilayer system. The preparation of the multilayer system was carried out via magnetron sputtering. Based on the thickness ratio among the individual nanoscale monolayers (Ti, Al, C), the resulting MAX phase stoichiometry can be controlled. This paper describes the synthesis of both Ti 2 AlC and Ti 3 AlC 2 MAX phases from the same precursor multilayer system which is composed of a sequence of Ti/Al/C pure elemental single layers with thicknesses of 14, 6, and 3.5 nm, respectively. This sequence is repeated 22 times with a total thickness of around 500 nm. Rapid thermal treatment tests were performed to study the phase development. The Ti 2 AlC MAX phase forms in a temperature range below 850 °C, whereas the Ti 3 AlC 2 MAX phase starts to form at temperatures above 850 °C and reaches its highest phase purity at 950 °C. The thin film structures were studied by X-ray diffraction and Raman spectroscopy. Furthermore, the electrical and mechanical properties were investigated to gain more insights regarding the phase transformation and their influence on the thin film properties. [ABSTRACT FROM AUTHOR]