Self-organization during Growth of ZrN/SiNx Multilayers by Epitaxial Lateral Overgrowth

ZrN/SiNx nanoscale multilayers were deposited on ZrN seed layers grown on top of MgO(001) substrates by dc magnetron sputtering with a constant ZrN thickness of 40 Å and with an intended SiNx thickness of 2, 4, 6, 8, and 15 Å at a substrate temperature of 800 °C and 6 Å at 500 °C. The films were investigated by X-ray diffraction, high-resolution scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy. The investigations show that the SiNx is amorphous and that the ZrN layers are crystalline. Growth of epitaxial cubic SiNx – known to take place on TiN(001) – on ZrN(001) is excluded to the monolayer resolution of this study. During the course of SiNx deposition, the material segregates to form surface precipitates in discontinuous layers for SiNx thicknesses ≤ 6 Å that coalesce into continuous layers for 8 and 15 Å thickness at 800 °C, and for 6 Å at 500 °C. The SiNx precipitates are aligned vertically. The ZrN layers in turn grow by epitaxial lateral overgrowth on the discontinuous SiNx in samples deposited at 800 °C with up to 6 Å thick SiNx layers. Effectively a self-organized nanostructure can be grown consisting of strings of 1-3 nm large SiNx precipitates along apparent column boundaries in the epitaxial ZrN

Low-temperature growth of dense and hard Ti0.41Al0.51Ta0.08N films via hybrid HIPIMS/DC magnetron co-sputtering with synchronized metal-ion irradiation

Hard Ti1-xAlxN thin films are of importance for metal-cutting applications. The hardness, thermal stability, and oxidation resistance of these coatings can be further enhanced by alloying with TaN. We use a hybrid high-power pulsed and dc magnetron co-sputtering (HIPIMS/DCMS) technique to grow dense and hard Ti0.41Al0.51Ta0.08N alloys without external heating (T-s amp;lt; 150 degrees C). Separate Ti and Al targets operating in the DCMS mode maintain a deposition rate of similar to 50 nm/min, while irradiation of the growing film by heavy Ta+/Ta2+ ions from the HIPIMS-powered Ta target, using dc bias synchronized to the metal-ion-rich part of each HIPIMS pulse, provides effective near-surface atomic mixing resulting in densification. The substrate is maintained at floating potential between the short bias pulses to minimize Ar+ bombardment, which typically leads to high compressive stress. Transmission and scanning electron microscopy analyses reveal dramatic differences in the microstructure of the co-sputtered HIPIMS/DCMS films (Ta-HIPIMS) compared to films with the same composition grown at floating potential with all targets in the DCMS mode (Ta-DCMS). The Ta-DCMS alloy films are only similar to 70% dense due to both inter-and intra-columnar porosity. In contrast, the Ta-HIPIMS layers exhibit no inter-columnar porosity and are essentially fully dense. The mechanical properties of Ta-HIPIMS films are significantly improved with hardness and elastic modulus values of 28.0 and 328 GPa compared to 15.3 and 289 GPa for reference Ta-DCMS films. Published by AIP Publishing.Funding Agencies|Swedish Research Council VR Grant [2013-4018, 2014-5790]; VINN Excellence Center Functional Nanoscale Materials (FunMat); Aforsk Foundation Grant [16-359]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU 2009-00971]; Knut and Alice Wallenberg Foundation [2011.0143]</p