Understanding the microstructural evolution and mechanical properties of transparent Al-O-N and Al-Si-O-N films

Abstract

Optically transparent, colorless Al-O-N and Al-Si-O-N coatings with discretely varied O and Si contents were fabricated by reactive direct current magnetron sputtering (R-DCMS) from elemental Al and Si targets and O2 and N2 reactive gases. The Si/Al content was adjusted through the electrical power on the Si and Al targets, while the O/N content was controlled through the O2 flow piped to the substrate in addition to the N2 flow at the targets. The structure and morphology of the coatings were studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM), while the elemental composition was obtained from Rutherford backscattering spectrometry (RBS) and heavy ion elastic recoil detection analysis (ERDA). The chemical states of the elements in the coatings were analyzed by X-ray photoelectron spectroscopy (XPS). Based on analytical results, a model describing the microstructural evolution of the Al-O-N and also previously studied Al-Si-N [1, 2, 3, 4] coatings with O and Si content, respectively, is established. The universality of the microstructural evolution of these coatings with the concentration of the added element is attributed to the extra valence electron (e–) that must be incorporated into the AlN wurtzite host lattice. In the case of Al-O-N, this additional valence charge arises from the e – acceptor O replacing N in the AlN wurtzite lattice, while the e – donor Si substituting Al fulfills that role in the Al-Si-N system. In view of future applications of ternary Al-O-N and quaternary Al-Si-O-N transparent protective coatings, their mechanical properties such as residual stress (σ), hardness (HD) and Young’s modulus (E) were obtained from the curvature of films deposited onto thin substrates and by nanoindentation, respectively. Moderate compressive stress levels between −0.2 and −0.5 GPa, which suppress crack formation and film-substrate delamination, could be obtained together with HD values around 25 GPa.

Mapping the Structure of Oxygen-Doped Wurtzite Aluminum Nitride Coatings from Ab Initio Random Structure Search and Experiments

“…Similarly, in our most recent work, a lattice shrinkage was also observed for increasing O contents up to 8% in sputter-deposited Al-O-N films . While our XRD data suggests that up to 8% O can be incorporated into the AlN wurtzite lattice, Harris et al found that only up to 0.75% O can be incorporated into the wurtzite lattice of single-crystalline materials synthesized under thermal equilibrium conditions …”

“…At the threshold of 16% O, which separates (IIa) from (IIb), the residual film stress changes from tensile (in fiber textured nanocomposites) to compressive (nanocomposites containing crystallites of arbitrary orientations). Al-O-N with 30 – 60% O, regime (III), consists of an X-ray amorphous solid solution …”

Si-Al-N-O Multi-Layer Coatings with Increased Corrosion Resistance Deposited on Stainless Steel by Magnetron Sputtering

“…The amorphization of the oxide layer proceeds due to the incorporation of Si atoms into the crystal lattice of Al 2 O 3 [27]. The nitride layer transits into amorphous state as a result of introduction of oxygen ions into its crystal lattice the small amount of which presents after the change of gas environment in the vacuum chamber, as indicated by the authors [43,52] (during the process the microstructure evolves from crystalline to nanocrystalline and then to the amorphous microstructure). This is confirmed by the investigation of the elemental composition of coating layers in the multi-layer coating cross-section by EDXMA on the transmission electron microscope (Figure 1).…”

“…Therefore, the first layer of the coating is the amorphous aluminium-silicon oxynitride. This compound possesses higher hardness as compared to conventional silicon nitride [43][44][45][46][47][48][49][50][51][52][53][54][55][56]. Products based on aluminium-silicon oxynitride are used in the conditions of high mechanical loads, thermal shock, aggressive chemical and abrasive media, which is conditioned by their high strength, chemical stability, corrosion and thermal stability.…”

Degradation Processes in the Ai-Ti-Si System Under Thermal Shock

“…As a result, starting from a certain integration level of semiconductor devices, signal delays in the interconnections may exceed those in the structures themselves. In addition, as the semiconductor cross-sections decrease, the problems appear that are related to electromigration in thin metal films and contact ohmicity (Kang et al, 2008;Martineau et al, 2014;Macherzyński et al, 2016;De Rose et al, 2018;Homa and Sobczak, 2019;Eslami et al, 2019;Fischer et al, 2019;Chawla et al, 2019;Cruz et al, 2019;Yi et al, 2019). And technological complexities when making modern metallization systems (including the structures involving p-n junctions with small occurrence depth) should also be noted (Garosshen et al, 1985;Macherzyński et al, 2016).…”