Defect Engineered Tialn Thin Films

This thesis investigates the effect of point defects (nitrogen vacancies and interstitials) and multilayering ((Ti,Al)N/TiN) on the phase transformations in cathodic arc-evaporated cubic (Ti,Al)N thin films at elevated temperatures. Special attention is paid to the evolution of the beneficial spinodal decomposition into c-TiN and c-AlN, the detrimental formation of wurtzite AlN and the potential application as hard coating in cutting tools. c-(Ti1-xAlx)Ny thin films with varying Al fractions and N content (y = 0.93 to 0.75) show a delay in the spinodal decomposition when increasing the amount of N vacancies. This results in a 300 °C upshift in the age hardening and a delay in the w-AlN formation, while additions of self-interstitials enhance phase separation. High temperature interaction between hard metal substrates and thin films is more pronounced when increasing N deficiency through diffusion of substrate elements into the film. Low N content films (y = 0.58 to 0.40) showed formation of additional phases such as Ti4AlN3, Ti2AlN, Al5Ti2 and Al3Ti during annealing and a transformation from Ti2AlN to Ti4AlN3 via intercalation. The multilayer structure of TiN/TiAlN results in surfacedirected spinodal decomposition that affects the decomposition behavior. Careful use of these effects appears as a promising method to improve cutting tool performance. Diese Arbeit untersucht den Effekt von Punktdefekten (Stickstoffleerstellen und Zwischengitteratome) und Multilagen ((Ti,Al)N/TiN) auf die Phasenumwandlung in lichtbogenverdampften kubischen (Ti,Al)N-Dünnschichten bei erhöhten Temperaturen. Besonderes Augenmerk liegt auf der Entwicklung der vorteilhaften spinodalen Entmischung in c-TiN und c-AlN und der nachteiligen Bildung von Wurtzit-AlN, sowie der möglichen Anwendung als Hartstoffbeschichtung von Schneidwerkzeugen. c-(Ti1-xAlx)Ny mit unterschiedlichem Al-Anteil und N-Gehalten von y = 0,93 bis 0,75 zeigt mit zunehmenden Stickstoffleerstellen eine Verzögerung der spinodalen Entmischung. Dadurch verschiebt sich die Ausscheidungshärtung um 300 °C zu höheren Temperaturen und die w-AlN-Bildung wird verzögert, während der Einbau von Eigenzwischengitteratomen die Entmischung beschleunigt. Die Hochtemperaturwechselwirkung zwischen Hartmetallsubstrat und Dünnschicht durch Diffusion von Substratelementen in die Schicht nimmt mit steigendem Stickstoffdefizit zu. Stickstoffarme Schichten (y = 0,58 bis 0,40) zeigen während der Wärmebehandlung zusätzliche Phasen wie Ti4AlN3, Ti2AlN, Al5Ti2 und Al3Ti und eine Umwandlung von Ti2AlN in Ti4AlN3 durch Interkalation. Die Multischichtstruktur von TiN/TiAlN führt zu einer oberflächengerichteten spinodalen Entmischung, die das Entmischungsverhalten beeinflusst. Ein gezielter Einsatz dieser Effekte erscheint als ein vielsprechender Weg, um die Leistungsfähigkeit von Schneidwerkzeugen zu verbessern. I denna avhandling behandlas inverkan av punktdefekter (kvävevakanser och interstitialer) och multilagring ((Ti,Al)N/TiN) på högtemperaturfasomvandlingar i tunna arcförångade skikt av kubiska (Ti,Al)N. Störst vikt har lagts på utvecklingen av det fördelaktiga spinodala sönderfallet till c-TiN och c-AlN, den ofördelaktiga omvandlingen till w-AlN och potentialen som hårda skikt i verktygstillämpningar. Tunna c-(Ti1-xAlx)Ny skikt med olika Al-andel och en N-halt mellan (y = 0.93 och 0.75) uppvisar ökad undertryckning av det spinodala sönderfallet med ökat kvävevakanshalt. Detta resulterar i bildandet av w-AlN skiftas upp i temperatur vilket gör att åldershärdningen höjs med 300 °C. Däremot medför närvaron av självinterstitialer ett snabbare sönderfall. Växelverkan mellan hårdmetallsubstraten och de tunna skikten vid hög temperatur ökar med minskad kvävehalt i skiten genom diffusion av atomer från substratet in i filmen. Filmer med låg kvävehalt (y = 0.58 till 0.40) bildar även andra faser så som Ti4AlN3, Ti2AlN, Al5Ti2 och Al3Ti under värmebehandling och fasomvandlingen från Ti2AlN till Ti4AlN3 sker via en mekanism kallad intercalation. Multilagring av TiN/TiAlN resulterar i ett ytriktad spinodalt sönderfall vilket påverkar det totala sönderfallsförloppet. Nyttjande av dessa resultat syns som lovande vägar till förbättrade verktygsegenskaper.

Thin film mechanical behavior and stress presents a technological challenge for materials scientists, physicists and engineers. This book provides a comprehensive coverage of the major issues and topics dealing with stress, defect formation, surface evolution and allied effects in thin film materials. Physical phenomena are examined from the continuum down to the sub-microscopic length scales, with the connections between the structure of the material and its behavior described. Theoretical concepts are underpinned by discussions on experimental methodology and observations. Fundamental scientific concepts are embedded through sample calculations, a broad range of case studies with practical applications, thorough referencing, and end of chapter problems. With solutions to problems available on-line, this book will be essential for graduate courses on thin films and the classic reference for researchers in the field.

This study highlights the role of nitrogen vacancies and defect structures in engineering hard coatings with enhanced phase stability and mechanical properties for high temperature applications. Titanium aluminum nitride (Ti,Al)N based materials in the form of thin coatings has remained as an outstanding choice for protection of metal cutting tools due to its superior oxidation resistance and high-temperature wear resistance. High-temperature spinodal decomposition of metastable (Ti,Al)N into coherent c-TiN and c-AlN nm-sized domains results in high hardness at elevated temperatures. Even higher thermal input leads to transformation of c-AlN to w-AlN, which is detrimental to the mechanical properties of the coating. One mean to delay this transformation is to introduce nitrogen vacancies. In this thesis, I show that by combining a reduction of the overall N-content of the c-(Ti,Al)Ny (y < 1) coating with a low substrate bias voltage during cathodic arc deposition an even more pronounced delay of the c-AlN to w-AlN phase transformation is achieved. Under such condition, age hardening is retained until 1100 ?C, which is the highest temperature reported for (Ti,Al)N films. During cutting operations, the wear mechanism of the cathodicarc-deposited c-(Ti0.52Al0.48)Ny with N-contents of y = 0.92, 0.87, and 0.75 films are influenced by the interplay of nitrogen vacancies, microstructure, and chemical reactions with the workpiece material. The y = 0.75 coating contains the highest number of macroparticles and has an inhomogeneous microstructure after machining, which lower its flank and crater wear resistance. Age hardening of the y = 0.92 sample causes its superior flank wear resistance while the dense structure of the y = 0.87 sample prevents chemical wear that results in excellent crater wear resistance. Heteroepitaxial c-(Ti1-x,Alx)Ny (y = 0.92, 0.79, and0.67) films were grown on MgO(001) and (111) substrates using magnetron putter deposition to examine the details of their defect structures during spinodal decomposition. At 900 ?C, the films decompose to form coherent c-AlN- and c-TiN- rich domains with elongated shape along the elastically soft <001> direction. Deformation maps show that most strains occur near the interface of the segregated domains and inside the c-TiN domains. Dislocations favorably aggregate in c-TiN rather than c-AlN because the later has stronger directionality of covalent chemical bonds. At elevated temperature, the domain size of (001) and (111)- oriented c-(Ti,Al)Ny films increases with the nitrogen content. This indicates that there is a delay in coarsening due to the presence of more N vacancies in the film. The structural and functional properties (Ti1-x,Alx)Ny are also influenced by its Al content (x). TiN and (Ti1-x,Alx)Ny (y = 1, x = 0.63 and x = 0.77) thin films were grown on MgO(111) substrates using magnetron sputtering technique. Both TiN and Ti0.27Al0.63N films are single crystals with cubic structure. (Ti0.23,Al0.77)N film has epitaxial cubic structure only in the first few atomic layers then it transitions to an epitaxial wurtzite layer, with an orientation relationship of c-(Ti0.23,Al0.77)N(111)[1-10]??w-(Ti0.23,Al0.77)N(0001)[11-20]. The w-(Ti0.23,Al0.77)N shows phase separation of coherent nm-sized domains with varying chemical composition during growth. After annealing at high temperature, the domains in w-(Ti0.23,Al0.77)N have coarsened. The domains in w-(Ti0.23,Al0.77)N are smaller compared to the domains in c-(Ti0.27,Al0.63)N film that has undergone spinodal decomposition. The results that emerged from this thesis are of great importance in the cutting tool industry and also in the microelectronics industry, because the layers examined have properties that are well suited for diffusion barriers.

This volume comprises the expert contributions from the invited speakers at the 17th International Conference on Thin Films (ICTF 2017), held at CSIR-NPL, New Delhi, India. Thin film research has become increasingly important over the last few decades owing to the applications in latest technologies and devices. The book focuses on current advances in thin film deposition processes and characterization including thin film measurements. The chapters cover different types of thin films like metal, dielectric, organic and inorganic, and their diverse applications across transistors, resistors, capacitors, memory elements for computers, optical filters and mirrors, sensors, solar cells, LED's, transparent conducting coatings for liquid crystal display, printed circuit board, and automobile headlamp covers. This book can be a useful reference for students, researchers as well as industry professionals by providing an up-to-date knowledge on thin films and coatings.

Focuses on the development of fundamental knowledge with the aim of understanding materials phenomena, transformation and processing of knowledge-based multifunctional materials, surface engineering, and support for materials development and knowledge-based higher performance materials for macro-scale applications.

This book is a compilation of research work in the interdisciplinary areas of electronics, communication, and computing. This book is specifically targeted at students, research scholars and academicians. The book covers the different approaches and techniques for specific applications, such as particle-swarm optimization, Otsu’s function and harmony search optimization algorithm, triple gate silicon on insulator (SOI)MOSFET, micro-Raman and Fourier Transform Infrared Spectroscopy (FTIR) analysis, high-k dielectric gate oxide, spectrum sensing in cognitive radio, microstrip antenna, Ground-penetrating radar (GPR) with conducting surfaces, and digital image forgery detection. The contents of the book will be useful to academic and professional researchers alike.

This 3e, edited by Peter M. Martin, PNNL 2005 Inventor of the Year, is an extensive update of the many improvements in deposition technologies, mechanisms, and applications. This long-awaited revision includes updated and new chapters on atomic layer deposition, cathodic arc deposition, sculpted thin films, polymer thin films and emerging technologies. Extensive material was added throughout the book, especially in the areas concerned with plasma-assisted vapor deposition processes and metallurgical coating applications.