Linköping Studies in Science and Technology Dissertation No. 1472 Inside The Miscibility Gap Nanostructuring and Phase Transformations in Hard Nitride Coatings Lars Johnson Thin Film Physics Division Department of Physics, Chemistry, and Biology (IFM) Linköping University SE-581 83 Linköping, Sweden Linköping 2012 © Lars Johnson Except for papers 1-3 © Elsevier B.V., used with permission. ISBN 978-91-7519-809-5 ISSN 0345-7524 Typeset using LATEX Printed by LiU-Tryck, Linköping 2012 II ABSTRACT This thesis is concerned with self-organization phenomena in hard and wear resistant transition-metal nitride coatings, both during growth and during post-deposition thermal annealing. The uniting physical principle in the studied systems is the immiscibility of their constituent parts, which leads, under certain conditions, to structural variations on the nanoscale. The study of such structures is challenging, and during this work atom probe to- mography (apt) was developed as a viable tool for their study. Ti0.33Al0.67N was observed to undergo spinodal decomposition upon annealing to 900 °C, by the use of apt in combination with electron microscopy. The addition of C to TiSiN was found to promote and refine the feather-like microstructure common in the system, with an ensuing decrease in thermal stability. An age-hardening of 36 % was measured in arc evaporated Zr0.44Al0.56N1.20, which was a nanocomposite of cubic, hexagonal, and amorphous phases. Magnetron sputtering of Zr0.64Al0.36N at 900 °C resulted in a self-organized and highly ordered growth of a two-dimensional two-phase labyrinthine structure of cubic ZrN and wurtzite AlN. The structure was analyzed and recovered by apt, although the ZrN phase suffered from severe trajectory aberrations, rendering only the Al signal useable. The initiation of the orga- nized growth was found to occur by local nucleation at 5-8 nm from the sub- strate, before which random fluctuations in Al/Zr content increased steadily from the substrate. Finally, the decomposition of solid-solution TiB0.33N0.67 was found, by apt, to progress through the nucleation of TiB0.5N0.5 and TiN, followed by the transformation of the former into hexagonal TiB2. III INUTILÖSLIGHETSLUCKAN nanostrukturering och fasomvandlingar i hårda nitridskikt Populärvetenskaplig Sammanfattning Den här doktorsavhandlingen behandlar mätningen och förståelsen av nanostrukturering och fasomvandlingar i hårda nitridskikt. Skikt, eller tunna filmer, används idag i stor omfattning, i allt från deko- rativa beläggningar på husgeråd till komplexa lager i halvledarindustrin. Vanligtvis görs tunna filmer genom kondensation av en ånga på ytan som ska beläggas, och genom att endast lägga ett tunt lager kan material med vitt skilda egenskaper från de som förekommer i tjockare former skapas. Detta gör tunna filmer viktiga, då man genom att kombinera en film med ett sub- stratmaterial kan åstadkomma egenskaper som inte går att uppå på något annat sätt. Av speciellt intresse för den här avhandlingen är nötningståliga skikt, vilka i industrin används som beläggningar på skärande verktyg för metallbearbetning. Egenskaper som hårdhet kan förbättras ytterligare om filmen har en struktur på nanometerskalan. Ett sätt att åstadkomma sådana strukturer är att belägga en yta med två material som är olösliga i varandra, t.ex. titanni- trid (TiN) och aluminiumnitrid (AlN), som då kommer att försöka separera om atomerna har tillräcklig rörlighet, d.v.s. om temperaturen är tillräckligt hög. Nanostrukturering kan ske antingen vid själva beläggningen, eller vid värmebehandling i efterhand. Det är detaljerna i sådana separationsprocesser som har studerats i det här arbetet, med sikte på atomär avbildning, där mekanismerna för fasomvandling i TiAlN och TiBN har identifierats som spinodalt sönder- fall och icke-klassisk kärnbildning och tillväxt i de respektive fallen. En två- dimensionell labyrintisk struktur i ZrAlN har upptäckts, och förklarats så- som orsakad av en balans mellan ytenergi och elastisk energi på tillväxtytan. Den viktigaste tekniken för studierna har varit Atomsondstomografi, där man mäter ett prov atom för atom, och sedan återskapar det i tre dimen- sioner. Då tillämpningen på hårda skikt är ny har det inspirerat till att en metodutveckling som också ingår i avhandlingen. V PREFACE This thesis is the result of my doctoral studies in the Thin Film Physics Di- vision at the Department of Physics, Chemistry, and Biology at Linköping University between 2007 and 2012. The main body of the work was done under the auspices of the Vinnex Center for Functional Nanoscale Materi- als (FunMat), in collaboration with Sandvik Coromant, SECO Tools, and Ionbond Sweden. I have also been visiting the Microscopy and Microanaly- sis group at Chalmers University of Technology, and the Nanostructured Materials group at Montanuniversität Leoben. I would like to thank my supervisors Lars Hultman, Magnus Odén, Krystyna Stiller, and Mattias Thuvander; my co-authors and the members of Theme 2 of FunMat; and my friends and colleagues, especially the coffee club, at the department. Lars Johnson Linköping, September 2012 VII INCLUDEDPAPERS I Spinodal Decomposition of Ti0.33Al0.67N Thin Films Studied by Atom Probe Tomography L.J.S. Johnson, M. Thuvander, K. Stiller, M. Odén, L. Hultman Thin Solid Films 520 (2012) 4362. II Microstructure Evolution and Age Hardening in (Ti,Si)(C,N) Thin Films Deposited by Cathodic Arc Evaporation L.J.S. Johnson, L. Rogström, M.P. Johansson, M. Odén, L. Hultman Thin Solid Films 519 (2010) 1397. III Age Hardening in Arc-evaporated ZrAlN Thin Films L. Rogström, L.J.S. Johnson, M.P. Johansson, M. Ahlgren, L. Hultman, M. Odén Scripta Materialia 62 (2010) 739. IV Self-organized Labyrinthine Nanostructure in Zr0.64Al0.36N Thin Films N. Ghafoor, L.J.S Johnson, L. Hultman, M. Odén In manuscript. V Self-organized Nanostructuring in Zr0.64Al0.36N Thin Films Studied by Atom Probe Tomography L.J.S Johnson, N. Ghafoor, M. Thuvander, K. Stiller, M. Odén, L. Hultman In manuscript. VI Phase Transformation of Ti(B,N) into TiB2 and TiN Studied by Atom Probe Tomography L.J.S Johnson, R. Rachbauer, P.O.Å. Persson, L. Hultman, P.H. Mayrhofer In manuscript. The Author’s Contributions I Did all experimental work, and wrote the paper. II Did most of the experimental work, and wrote the paper. III Took part in the experimental work, and in writing the paper. IV Took part in the experimental work, and wrote the paper. V Did most of the experimental work, and wrote the paper. VI Took part in the experimental work, and wrote the paper. IX CONTENTS INTRODUCTION TO THE FIELD 3 1 Introduction 5 2 Materials 9 2.1 Immiscible Nitride Systems 9 2.2 Ti-Al-N 10 2.3 Zr-Al-N 11 2.4 Ti-Si-C-N 12 2.5 Ti-B-N 14 3 Deposition 19 3.1 Physical Vapour Deposition 19 3.2 Film Growth 21 4 Phase Transformations 25 4.1 Diffusion 26 4.2 Immiscibility 27 5 Thin Film Characterization 33 5.1 X-ray Diffraction 33 5.2 Transmission Electron Microscopy 34 5.3 Elastic Recoil Detection Analysis 41 5.4 Nanoindentation 41 6 Atom Probe Tomography 43 6.1 History 43 6.2 Principle of Operation 45 6.3 Tomographic Reconstruction 48 6.4 Visualization and Data Analysis 51 6.5 Sample Preparation 52 6.6 APT of Hard Coatings 53 6.7 Development of a Blind Deconvolution method for APT Mass Spectra 54 7 Contributions to the Field 67 X PAPERS 71 I Spinodal Decomposition of Ti0.33Al0.67N Thin Films Studied by Atom Probe Tomography 73 1 Introduction 75 2 Experimental Details 76 3 Data Analysis 76 4 Results 78 5 Discussion 85 6 Conclusions 89 II Microstructure Evolution and Age Hardening in (Ti,Si)(C,N) Thin Films Deposited by Cathodic Arc Evapora- tion 93 1 Introduction 95 2 Experimental Details 96 3 Results and Discussion 97 4 Conclusions 106 III Age Hardening in Arc-evaporated ZrAlN Thin Films 109 IV Self-organized Labyrinthine Nanostructure in Zr0.64Al0.36N Thin Films 117 V Self-organized Nanostructuring in Zr0.64Al0.36N Thin Films Stud- ied by Atom Probe Tomography 127 1 Introduction 129 2 Experimental Details 130 3 Results and Discussion 130 4 Conclusions 138 VI Phase Transformation of Ti(B,N) into TiB2 and TiN Studied by Atom Probe Tomography 141 1 Introduction 143 2 Experimental Details 143 3 Results 144 4 Discussion 150 5 Conclusions 152 XI ACRONYMS apt atom probe tomography cbed convergent-beam electron diffraction ctf contrast transfer function cvd chemical vapour deposition ed electron diffraction edx energy-dispersive X-ray spectroscopy eels electron energy loss spectroscopy erda elastic recoil detection analysis fcc face centered cubic fib focussed ion beam microscopy fim field ion microscopy fwhm full-width at half maximum haadf high angle annular dark field stem hcp hexagonal close packed hrtem high-resolution tem icf image compression factor leap local-electrode atom probe pvd physical vapour deposition rbs rutherford backscattering spectroscopy rdf radial distribution function saed selected area electron diffraction sem scanning electron microscopy stem scanning transmission electron microscopy XII szm structure zone model tem transmission electron microscopy tof time-of-flight uhv ultra-high vacuum xps X-ray photoelectron spectroscopy xrd X-ray diffractometry XIII The Tao that can be told is not the eternal Tao; The name that can be named is not the eternal name. The nameless is the beginning of heaven and earth. The named is the mother of ten thousand things. Ever desireless, one can see the mystery. Ever desiring, one can see the manifestations. These two spring from the same source but differ in name; This appears as darkness. Darkness within darkness. The gate to all mystery. Tao Te Ching, Gia-Fu Feng & Jane English transl. Skulle jag sörja då wore jag tokot Fast än thet ginge mig aldrig så slätt Lyckan min kan fulla synas gå krokot Wackta på Tijden hon lär full gå rätt; All Werlden älskar Ju hwad som är brokot Mången mått liwa som eij äter skrätt.