Suchergebnisse

Ti1-xSixN (0 less than= x less than= 0.26) thin films are grown in mixed Ar/N-2 discharges using hybrid high-power pulsed and dc magnetron co-sputtering (HIPIMS/DCMS). In the first set of experiments, the Si target is powered in HIPIMS mode and the Ti target in DCMS; the positions of the targets are then switched for the second set. In both cases, the Si concentration in co-sputtered films, deposited at T-s = 500 degrees C, is controlled by adjusting the average DCMS target power. A pulsed substrate bias of -60 V is applied in synchronous with the HIPIMS pulse. Depending on the type of pulsed metal-ion irradiation incident at the growing film, Ti+/Ti2+ vs. Si+/Si2+, completely different nanostructures are obtained. Ti+/Ti2+ irradiation during Ti-HIPIMS/Si-DCMS deposition leads to a phase-segregated nanocolumnar structure with TiN-rich grains encapsulated in a SiNz tissue phase, while Si+/Si2+ ion irradiation in the Si-HIPIMS/Ti-DCMS mode results in the formation of Ti1-xSixN solid solutions with x less than= 024. Film properties, including hardness, modulus of elasticity, and residual stress exhibit a dramatic dependence on the choice of target powered by HIPIMS. Ti-HIPIMS/Si-DCMS TiSiN nanocomposite films are superhard over a composition range of 0.04 less than= x less than= 0.26, which is significantly wider than previously reported. The hardness H of films with 0.13 less than= x less than= 0.26 is similar to 42 GPa; however, the compressive stress is also high, ranging from -6.7 to -8.5 GPa. Si-HIPIMS/Ti-DCMS films are softer at H similar to 14 GPa with 0.03 less than= x less than= 0.24, and essentially stress-free (sigma similar to 0.5 GPa). Mass spectroscopy analyses at the substrate position reveal that the doubly-to-singly ionized metal-ion flux ratio during HIPIMS pulses is 0.05 for Si and 029 for Ti due to the difference between the second ionization potentials of Si and Ti vs. the first ionization potential of the sputtering gas. The average momentum transfer to the film growth surface per deposited atom per pulse less than p(d)greater than is similar to 20 x higher during Ti-HIPIMS/Si-DCMS, which results in significantly higher adatom mean-free paths (mfps) leading, in turn, to a phase-segregated nanocolumnar structure. In contrast, relatively low less than p(d)greater than values during Si-HIPIMS/Ti-DCMS provide near-surface mixing with lower adatom mfps to form Ti1-xSixN solid solutions over a very wide composition range with x up to 0.24. Relaxed lattice constants decrease linearly, in agreement with ab-initio calculations for random Ti1-xSixN alloys, with increasing x. (C) 2015 Elsevier B.V. All rights reserved. ; Funding Agencies|European Research Council (ERC) [227754]; VINN Excellence Center Functional Nanoscale Materials (FunMat) Grant [2005-02666]; Knut and Alice Wallenberg Foundation Grant [2011.0143]; Swedish Government Strategic Faculty Grant in Materials Science; Swedish Research Council (VR) Project [2014-5790, 621-2011-4417, 330-2014-6336]

Bi nanocrystalline films were formed from perchlorate electrolyte (PE) on Cu substrate via electrochemical deposition with different duration and current densities. The microstructural, morphological properties, and elemental composition were studied using scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy-dispersive X-ray microanalysis (EDX). The optimal range of current densities for Bi electrodeposition in PE using polarization measurements was demonstrated. For the first time, it was shown and explained why, with a deposition duration of 1 s, co-deposition of Pb and Bi occurs. The correlation between synthesis conditions and chemical composition and microstructure for Bi films was discussed. The analysis of the microstructure evolution revealed the changing mechanism of the films' growth from pillar-like (for Pb-rich phase) to layered granular form (for Bi) with deposition duration rising. This abnormal behavior is explained by the appearance of a strong Bi growth texture and coalescence effects. The investigations of porosity showed that Bi films have a closely-packed microstructure. The main stages and the growth mechanism of Bi films in the galvanostatic regime in PE with a deposition duration of 1–30 s are proposed. © 2020 by the authors. Licensee MDPI, Basel, Switzerland. ; Government Council on Grants, Russian Federation ; 2.34 ; Funding: The work was performed with support of State Scientific and Technical Program "Nanotech" (task No. 2.34), Branch Scientific and Technical Program "Nanotechnology and Nanomaterials" (task No. 1), Act 211 of Government of Russian Federation (contract No. 02.A03.21.0011). Additionally, the work was partially supported by the Grant of World Federation of Scientists (Geneva, Switzerland).