Effect of Growth Temperature and Atmosphere Exposure Time on Impurity Incorporation in Sputtered Mg, Al, and Ca Thin Films

Abstract

Impurities can be incorporated during thin film deposition, but also can originate from atmosphere exposure. As impurities can strongly affect the composition—structure—property relations in magnetron sputter deposited thin films, it is important to distinguish between both incorporation channels. Therefore, the impurity incorporation by atmosphere exposure into sputtered Mg, Al, and Ca thin films is systematically studied by a variation of the deposition temperatures and atmosphere exposure times. Deposition temperature variation results in morphological modifications explained by considering surface and bulk diffusion as well as grain boundary motion and evaporation. The film morphologies exhibiting the lowest oxygen concentrations, as measured by energy dispersive X-ray spectroscopy, are obtained at a homologous temperature of 0.4 for both Mg and Al thin films. For Ca, preventing atmosphere exposure is essential to hinder impurity incorporation: By comparing the impurity concentration in Al-capped and uncapped thin films, it is demonstrated that Ca thin films are locally protected by Al-capping, while Mg (and Al) form native passivation layers. Furthermore, it can be learned that the capping (or self-passivation) efficiency in terms of hindering further oxidation of the films in atmosphere is strongly dependent on the underlying morphology, which in turn is defined by the growth temperature.

Effect of Substrate Bias Voltage on Microstructure and Mechanical Properties of Cr-Nb-Ti-Zr-N-O Ceramic Thin Films Produced by Reactive Sputtering

“…%. However, because of the inadequate vacuum or residual gas and ambient air [43], in the present experiments, the oxygen percentage is high enough (more than 8.6 at. %) to assume as a principal component.…”

CALPHAD-Based Modelling of the Temperature–Composition–Structure Relationship during Physical Vapor Deposition of Mg-Ca Thin Films

“…Upon a further increase in the Mg/Ca ratio, the fcc Ca peak vanished and the formation of phase-pure Mg 2 Ca was obtained through XRD. It needs to be considered, however, that due to the high reactivity of the fcc Ca with the atmosphere (an exposure that was required for the XRD analysis), the formation of nanocrystalline/amorphous Ca(OH) 2 is expected [ 12 , 27 ]. Hence, no attempt is conducted here to determine a composition limit for the formation of the pure Mg 2 Ca phase on the Ca-rich side.…”

“…To further investigate the stoichiometry range of the Mg 2 Ca (C14) Laves phase experimentally, combinatorial Mg-Ca thin films were synthesized in a high-vacuum laboratory-scale deposition chamber by direct-current magnetron sputtering using circular elemental Mg (99.95% purity) and Ca (99.5% purity) targets with a diameter of 50 mm at base pressures below 2 × 10 −5 Pa. The Ca-target-cleaning procedure is described elsewhere [ 27 ]. Thin films were synthesized at room temperature (without intentional heating) at an Ar pressure of 0.4 Pa onto stationary Si (100) substrates, resulting in the formation of a composition gradient along the substrate.…”

Compositional defects in a MoAlB MAB phase thin film grown by high-power pulsed magnetron sputtering

“…11 However, densification of the film through employment of HPPMS causes a significantly lower oxygen content of ∼2 at% vs. ∼4 at% obtained after DC sputtering; this densification reduces oxygen incorporation through atmospheric exposure, which is also governed by the film morphology. 25 The ERDA depth profile is provided in the ESI (Fig. S4 †).…”