Impact of Microstructure of Nanoscale Magnetron Sputtered Ru/Al Multilayers on Thermally Induced Phase Formation

In this study, we report on phase formation and microstructure evolution in multiscale magnetron sputtered Ru/Al multilayers upon thermal annealing in vacuum at slow heating rates of 10 K/min. By specifically adjusting the microstructure and design of the as-deposited multilayers, the formation of certain desired phases can be tuned. We demonstrate that the synthesis of single phase RuAl thin films is possible in a very controlled manner in a solid state only via thermal activation without initiating the self-propagating exothermic reactions of Ru/Al multilayers. To investigate phase formation sequences and the resulting microstructures, Ru/Al multilayers were designed via magnetron sputtering with systematic variation of bilayer modulation periods and subsequent vacuum annealing. Thin films samples were characterized by in situ high-temperature XRD, TEM imaging and diffraction. It is shown that different phase sequences appear in strong correlation with the modulation length. Depending on the multilayer design, the phase formation toward single-phase RuAl thin films happens as either a multi-step or single-step event. In particular, below a critical threshold of the modulation period, the multi-step phase formation can be suppressed, and only the desired RuAl target phase is obtained with a pronounced growth in a preferred orientation. This finding may be versatile for the targeted synthesis of intermetallic phases, contributing to further understanding of phase formation in such nanoscale multilayer systems.

[1]  A. Morozov,et al.  Heat-Resistant RuAl-Based Alloys: Part II. Powder Alloys—Preparation via Reaction Sintering , 2021, Inorganic Materials: Applied Research.

[2]  A. Morozov,et al.  Heat-Resistant RuAl-Based Alloys: Part I. Cast Alloys , 2020, Inorganic Materials: Applied Research.

[3]  F. Mücklich,et al.  Atomic-scale characterization of diffusion kinetics in Ru/Al multilayer thin films , 2019, Materials Letters.

[4]  F. Hodaj,et al.  The Competition of Intermediate Phases in the Diffusion Zone , 2019, Inorganic Materials: Applied Research.

[5]  F. Mücklich,et al.  Ignition in ternary Ru/Al-based reactive multilayers—Effects of chemistry and stacking sequence , 2018, Journal of Applied Physics.

[6]  Surendra Singh,et al.  Kinetics of interface alloy phase formation at nanometer length scale in ultra-thin films: X-ray and polarized neutron reflectometry , 2018, Progress in Materials Science.

[7]  L. Martinu,et al.  Review Article: Stress in thin films and coatings: Current status, challenges, and prospects , 2018 .

[8]  D Glocker,et al.  Handbook of Thin Film Process Technology: 98/2 Recipes for Optical Materials , 2017 .

[9]  Xuyang Zhou,et al.  Interrelationship of in situ growth stress evolution and phase transformations in Ti/W multilayered thin films , 2016 .

[10]  F. Mücklich,et al.  The role of transitional phase formation during ignition of reactive multilayers , 2015 .

[11]  David P. Adams,et al.  Reactive multilayers fabricated by vapor deposition. A critical review , 2015 .

[12]  T. Laurila,et al.  Thermodynamics, Diffusion and the Kirkendall Effect in Solids , 2014 .

[13]  F. Mücklich,et al.  Production of single-phase intermetallic films from Ru-Al multilayers , 2014 .

[14]  F. Mücklich,et al.  Phase formation of B2-RuAl during annealing of Ru/Al multilayers , 2010 .

[15]  F. Mücklich,et al.  RuAl and its alloys, Part II: Mechanical properties, environmental resistance and applications , 2008 .

[16]  F. Mücklich,et al.  Thin-Film Synthesis and Cyclic Oxidation Behavior of B2-RuAl , 2008 .

[17]  Lucille A. Giannuzzi,et al.  Introduction to Focused Ion Beams , 2005 .

[18]  F. Mücklich,et al.  RuAl and its alloys. Part I. Structure, physical properties, microstructure and processing , 2005 .

[19]  F. Hodaj,et al.  Suppression of intermediate phase nucleation in binary couples with metastable solubility , 2004 .

[20]  F. Mücklich,et al.  Effects of particle size and pressure on the reactive sintering of RuAl intermetallic compound , 2004 .

[21]  T. Pollock,et al.  Thermal expansion behavior of ruthenium aluminides , 2004 .

[22]  Lars Hultman,et al.  Microstructural evolution during film growth , 2003 .

[23]  David J. Srolovitz,et al.  Physical Origins of Intrinsic Stresses in Volmer-Weber Thin Films , 2002 .

[24]  C. Lang,et al.  Thermal conductivity of ruthenium aluminide (RuAl) , 1998 .

[25]  E. Altman,et al.  Intermetallic phase formation during annealing of Al/Ni multilayers , 1994 .

[26]  K. Barmak,et al.  A new model for grain boundary diffusion and nucleation in thin film reactions , 1994 .

[27]  R. Pretorius,et al.  Thin film compound phase formation sequence: An effective heat of formation model , 1993 .

[28]  C. Thompson.  On the role of diffusion in phase selection during reactions at interfaces , 1992 .

[29]  R. Fleischer.  Intermetallic Compounds for High-Temperature Structural Use UNIQUE IRIDIUM AND RUTHENIUM COMPOUNDS , 1992 .

[30]  F. W. Saris,et al.  Prediction of phase formation sequence and phase stability in binary metal-aluminum thin-film systems using the effective heat of formation rule , 1991 .

[31]  A. Laskar.  Diffusion in materials , 1990 .

[32]  Z. A. Munir,et al.  Self-propagating exothermic reactions: the synthesis of high-temperature materials by combustion , 1989 .

[33]  A. L. Greer.  Atomic diffusion and phase transformations in artificially layered thin films , 1986 .

[34]  C. Suryanarayana,et al.  Metastable phases in vapour-deposited Al-Ru alloys , 1982 .

[35]  R. Bene.  First nucleation rule for solid‐state nucleation in metal‐metal thin‐film systems , 1982 .

[36]  King-Ning Tu,et al.  Growth kinetics of planar binary diffusion couples: ’’Thin‐film case’’ versus ’’bulk cases’’ , 1982 .

[37]  John A. Thornton,et al.  Influence of apparatus geometry and deposition conditions on the structure and topography of thick sputtered coatings , 1974 .

[38]  J. E. Hilliard,et al.  Free Energy of a Nonuniform System. I. Interfacial Free Energy , 1958 .