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The ternary carbides and nitrides referred to as the MAX phases exhibit properties combining typical ceramic attributes such as resistance to oxidation and thermal shock with electrical resistivity values that are typically low for a ceramic material. These merits suggest many application areas for MAX phases both in the form of bulk material, such as heating elements and gas nozzles, as well as functional thin films in sensors and microelectronics. The synthesis of well-defined epitaxial thin films has progressed lately by the development of a magnetron sputtering process from elemental sources. For industrial conditions however, growth from compound targets is generally preferred.
In this study, we present the synthesis of Ti-Al-C films on Al2O3 (0001), using dc magnetron sputtering from a Ti2AlC (MAXTHAL® 211) target. The films were synthesized at substrate temperatures ranging from ambient to 1000 °C and with different target-to-substrate distances.
Mass spectrometry measurements of the growth flux from the target show three main constituents, Ti, Al and C, while no compound ions such as TiC where detected.
Ion beam analysis revealed that all films, irrespective of temperature, exhibited carbon content higher than the Ti2AlC stoichiometry. The excess of carbon in the films restricts the deposition of Ti2AlC as seen by a competitive growth of TiC. At temperatures above 700 °C the films are also depleted in Al due to the onset of Al evaporation, which also favor TiC growth.
Co-sputtering of Ti2AlC with Ti, however, offers a route to synthesize Ti2AlC containing films. Four-point probe measurements of films grown from the compound target and at temperatures above 700 °C show resistivity values in the range of 190 to 480 µΩcm with the lowest value obtained for a film deposited at 1000 °C.
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