Ti0.5Al0.5N alloy films, typically 1.5 μm thick, were grown on MgO(001) at temperatures Ts between 400 and 850 °C by ultra-high-vacuum reactive magnetron sputtering in pure N2. Films grown at Ts between ≂480 and 560 °C were single crystals in which the lattice misfit strain was partially relieved by glide of 〈001〉 misfit dislocations, with Burgers vector =a0/2〈011〉, on {011̄} planes. Cross-sectional transmission electron microscopy investigation showed no evidence of residual extended defects in the films until thicknesses of ≂150 nm at which point threading dislocations, oriented along the [001] growth direction, were observed. Surface-initiated spinodal decomposition, resulting in the formation of compositionally modulated NaCl-structure platelets along [001] with width ≂1 nm, occurred over a narrow growth temperature range between 540 and 560 °C as a precursor to bulk phase separation of wurtzite-structure AlN at Ts≥560 °C. The alloy was continuously depleted of AlN at higher growth temperatures until the equilibrium two-phase structure, cubic TiN and wurtzite AlN, was obtained at Ts≥750 °C.

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Abstract.A simple and cost effective approach to stabilize the sputtering process in the transition zone during reactive high-power impulse magnetron sputtering (HiPIMS) is proposed. The method is based on real-time monitoring and control of the discharge current waveforms. To stabilize the process conditions at a given set point, a feedback control system was implemented that automatically regulates the pulse frequency, and thereby the average sputtering power, to maintain a constant maximum discharge current. In the present study, the variation of the pulse current waveforms over a wide range of reactive gas flows and pulse frequencies during a reactive HiPIMS process of Hf-N in an Ar-N 2 atmosphere illustrates that the discharge current waveform is a an excellent indicator of the process conditions. Activating the reactive HiPIMS peak current regulation, stable process conditions were maintained when varying the N 2 flow from 2.1 to 3.5 sccm by an automatic adjustment of the pulse frequency from 600 Hz to 1150 Hz and consequently an increase of the average power from 110 to 270 W. Hf-N films deposited using peak current regulation exhibited a stable stoichiometry, a nearly constant power-normalized deposition rate, and a polycrystalline cubic phase Hf-N with (111)-preferred orientation over the entire reactive gas flow range investigated. The physical reasons for the change in the current pulse waveform for different process conditions are discussed in some detail.

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