Silicon carbide layers were fabricated using self-propagating high-temperature synthesis of binary silicon-carbon based reactive multilayers. The silicon and carbon bilayers were fabricated with two different bilayer thicknesses. They are deposited by magnetron sputtering in an alternating layer system with a total thickness of 1 μm. The entire system is annealed by rapid thermal annealing at different temperatures ranging from 500 to 1100 °C. From XRD analysis we could find that the formation of the silicon carbide phase was initiated from 700 °C. With increasing bilayer thickness the silicon carbide phase formation was partially suppressed by the silicon recrystallization due to resulting lower carbon diffusion into silicon. The transformation process proceeds in a four-step process: densification/recrystallization, interdiffusion, nucleation and transformation. From this, it was noted that when compared to low bilayer thickness samples, the formation of the silicon carbide phase is delayed with increasing bilayer thickness and needs higher reaction initiation temperatures.
Graphical abstract
Al−AlN composite thin films with surface nanostructures possessing excellent broad-band antireflection properties can be simply fabricated by using a simple sputtering-based method, namely, limited reactive sputtering at elevated temperature. A mixture of Ar and N 2 gases with limited gas flow of N 2 is used. During the process, the limited amount of the N ions and radicals can only consume some of the sputtered Al atoms for the formation of AlN, so that the Al−AlN composite thin film can finally be deposited on the substrate. Compared to the traditional cosputtering for composite deposition, which works necessarily with two or more targets simultaneously, here only a single Al target is required. When the substrate temperature is higher than 100 °C, surface nanostructures can be evolved because of the different diffusion kinetics of Al and AlN. The total reflection was reduced drastically (<10%) in the spectral range 300−2000 nm. The Al−AlN composite thin films exhibit also a good electric conductivity.
An alternative low thermal budget silicon carbide syntheses route is presented. The method is based on self-propagating high-temperature synthesis of binary silicon-carbon-based reactive multilayers. With this technique, it is possible to obtain cubic polycrystalline silicon carbide at relatively low annealing temperatures by a solid state reaction. The reaction starts above 600 °C. The transformation process proceeds in a four-step process. The reaction enthalpy was determined to be (-70 ± 4) kJ/mol.
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