Deposition And Characterization Of Thin Films Of Metals And Compounds

This book is about thin films; what they are, how they are prepared, how they are characterized, and what they are used for. The contents of this book not only showcase the diversity of thin films, but also reveals the commonality among the work performed in a variety of areas. The chapters in this volume are based on invited papers presented by prominent researchers in the field at a Symposium on "Thin Films: Preparation, Characterization, Applications" at the 221st National Meeting of the American Chemical Society held in San Diego, California. The coverage of the symposium was extensive; topics ranged from highly-ordered metal adlayers on well-defined electrode surfaces to bio-organic films on non-metallic nanoparticles. An objective of this book is for the readers to be able to draw from the experience and results of others in order to improve and expand the understanding of the science and technology of their own thin films systems.

This up-to-date handbook covers the main topics of preparation, characterization and properties of complex metal-based layer systems. The authors -- an outstanding group of researchers -- discuss advanced methods for structure, chemical and electronic state characterization with reference to the properties of thin functional layers, such as metallization and barrier layers for microelectronics, magnetoresistive layers for GMR and TMR, sensor and resistance layers. As such, the book addresses materials specialists in industry, especially in microelectronics, as well as scientists, and can also be recommended for advanced studies in materials science, analytics, surface and solid state science.

"Preparation of Thin Films provides a comprehensive account of various deposition techniques for the preparation of thin films of elements, compounds, alloys, ceramics, and semiconductors - emphasizing inorganic compound thin films and discussing high vacuum and chemical deposition methods used for preparing high temperature superconducting oxide thin films. "

Thin Film Coatings: Properties, Deposition, and Applications discusses the holistic subject of conventional and emerging thin film technologies without bias to a specific technology based on the existing literature. It covers properties and delves into the various methods of thin film deposition, including the most recent techniques and a direction for future developments. It also discusses the cutting-edge applications of thin film coatings such as self-healing and smart coatings, biomedical, hybrid, and scalable thin films. Finally, the concept of Industry 4.0 in thin film coating technology is examined. This book: Explores a wide range and is not specific to material and method of deposition Demonstrates the application of thin film coatings in nearly all sectors, such as energy and anti-microbial applications Details the preparation and properties of hybrid and scalable (ultra) thin materials for advanced applications Provides detailed bibliometric analyses on applications of thin film coatings Discusses Industry 4.0 and 3D printing in thin film technology With its broad coverage, this comprehensive reference will appeal to a wide audience of materials scientists and engineers and others studying and developing advanced thin film technologies.

This thesis is devoted towards physical vapor deposition (PVD) of thin films of transition-metal (TM) diborides, focused on the material system TiBx, Ti1-xAlxB2-y and CrBx. The metal diborides are a large family of compounds with both metallic and ceramic properties, due to its bonding nature being a mix of covalent and ionic bonds. Their characteristics include, e.g., good mechanical, electrical and thermal properties, while an improved oxidation and corrosion resistance are currently sought after. Furthermore, while the ideal composition of these diborides is TMB2, i.e. with a B to metal ratio of 2, the stoichiometry in the PVD deposited films typically diverges from this ratio. TiBx is often reported to be overstoichiometric, with x well above 2. One of the most known and commonly used member of the TM diboride family is TiBx, primarily used in hard-coating applications such as tools for machining Al. However, the material displays a fracture toughness and oxidation resistance that ideally needs to be improved. The films presented in this thesis were deposited by high power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS). Using both methods facilitates an improved control of both microstructure and composition, and hence the materials properties. With HiPIMS, understoichiometric TiBx films were grown and it was shown that these films can match and even exceed the overstoichiometric counterpart, deposited with DCMS, in terms of mechanical properties. The hardness and fracture toughness for TiB1.43 films were measured at 43.9±0.9 GPa and 4.2±0.1 MPa√m, compared to TiB2.70 films at 37.7±0.8 GPa and 3.1±0.1 MPa√m. Furthermore, the understoichiometric films significantly improve the oxidation resistance. Air annealing of TiB1.43, TiB2.20, and TiB2.70 films at 400 °C showed an average oxidation rate of 2.9±1.5, 7.1±1.0, and 20.0±5.0 nm/h, respectively, explained by the microstructural difference between over- and understoichiometric material. In TiBx films where x > 2, there is a B-rich tissue phase in the grain boundaries which is suggested to enhance oxidation. The hydroscopic nature of B2O3 causes more rapid oxidation and evaporation thus providing an easy oxidation pathway in B-rich regions. However, understoichiometric films where x < 2 do not show any significant boundary phases. Instead, the B deficiency is presented as planar defects with Ti-rich stacking faults. Hence the absence of the B-rich tissue phase has strongly contributed to increasing the oxidation resistance. Oxidation resistance and mechanical properties were also investigated for understoichiometric Ti1-xAlxB2-y coatings with varying Ti:Al and B:M ratios, obtained from both HiPIMS and DCMS depositions. Al alloying of the TM diboride TiBx significantly enhances the oxidation resistance. However, incorporating too much Al is at the expense of the excellent hardness seen in the pure TiBx, going from 46.2±1.1 GPa to 22.6±1.1 GPa for Ti0.9Al0.1B1.3 and Ti0.3Al0.7B1.3, respectively. Hence, a reduction in the Al content is needed to retain the mechanical properties. The boundary phase in this material consists of a Ti1-xAlxB2-y tissue phase, rich in either Al or B depending on the x and y values. An improved oxidation resistance in Ti1-xAlxB2-y was seen with reduced Al and B content, proposed to be due to absence of tissue phase in the grain boundaries, in line with the observations for TiBx. The oxide scale thickness of Ti0.9Al0.1B1.3 and Ti0.9Al0.1B1.9 after air annealing at 600 °C for 10 h was measured to be 205 nm and 320 nm, respectively. Moreover, the trends indicate a reduced oxidation rate as the oxide scale grows thicker. A systematical study of DCMS deposited CrBx coatings, 1.90 ≤ x 2.08, was also performed, motivated by CrBx being a material of interest for providing potential corrosion resistance. All films, irrespectable of the deposition conditions, exhibited (001) texture, with epitaxial growth observed when increasing temperature from 500 °C to 900 °C. Higher density (5.2 g/cm3) and smoother surfaces was seen in films grown at lower pressure, 5 mTorr (0.67 Pa), compared to higher pressure, 20 mTorr (2.67 Pa), and was explained by less gas scattering leading to more energetic particles impinging on the surface. CrBx film composition show no apparent dependence on substrate temperature, and has a slight dependence on deposition pressure for the samples deposited at 900 °C, with reduced B content for increasing pressure. Overstoichiometric CrB2.08 films showed the presence of large B-rich inclusions, and B deficiency in CrB1.90 films presented as planar defects with Cr-rich stacking faults, similar to understoichiometric TiBx. The thorough investigations of all the systems in this thesis are aimed towards improving the understanding of the correlation between the thin film synthesis process and the resulting composition and microstructure, which in turn dictates the properties of thin films. A particular emphasis is put on control of composition. I den här avhandlingen fokuserar jag på beläggningar av tunna filmer, dvs. tunna lager av material som läggs på en yta för att ge ytan vissa specifika egenskaper. Jag genomför metodiska analyser av de filmer jag får från två olika beläggningsmetoder; ”high-power impulse magnetron sputtering” (HiPIMS) och den mer konventionella metoden ”directcurrent magnetron sputtering” (DCMS). Dessa metoder skiljer sig främst åt i antal parametrar man kan variera för att kontrollera processen som styr vilket material som bildas, där HiPIMS är den metod med flest parametrar. Anledningen till att HiPIMS inte har sett ett större användningsområde till dags dato är att det är en relativt ny process jämfört med DCMS, och på grund av den komplexitet som tillkommer när man utökar mängden tillväxtparametrar. För båda processerna är en grundläggande förståelse av både processen och materialet önskvärt för att få ett optimerat material, med specifika önskade egenskaper. Material i fokus i denna avhandling är TiBx, Ti1-xAlxB2-y och CrBx, även kallade övergångsmetall-diborider, där Ti står för titan, Al för aluminium, Cr för krom, B för bor, och x/y står för variabler i sammansättningen av materialet. Dessa diborider bär med sig unika egenskaper från respektive element och innehåller en blandning av kovalenta bindningar och jon-bindningar. Beroende på sammansättningen av atomer så kan vi se olika mekaniska, elektriska och termiska egenskaper samt olika grad av oxidering- och eroderings-resistans. TiBx är till exempel välkänt för sina tillämpningar inom skärande bearbetning, men har inte lika lovande egenskaper när det kommer till beständighet mot oxidering. Det här är delvis en konsekvens av att man idag kommersiellt använder sig främst av DCMS för tillväxt av dessa beläggningar, då denna metod typiskt genererar överstökiometriska tunna filmer av TiBx (x > 2), vilket i sin tur påverkar beständigheten mot oxidering negativt. Med hjälp av HiPIMS kan man kontrollera stökiometrin av filmen i större grad, och kan således generera understökiometrisk TiBx (x < 2) som jag visar på har bättre mekaniska egenskaper, bland annat högre hårdhet, bättre brottseghet och förbättrad beständighet mot oxidering, kontra den överstökiometriska motsvarigheten. Hur mikrostrukturen i överstökiometriska TiBx filmer ser ut är välkänt, där överflödigt B ansamlas i korngränserna och bilder en s.k. ”B-rik vävnadsfas”. Jag har påvisat hur motsvarande mikrostruktur ser ut för understökiometrisk TiBx filmer, något som fram tills nu varit okänt. I dessa faser saknas vävnadsfas i korngränserna, och istället hittas överskottet av Ti som plandefekter i de kolumnära TiB2-strukturerna i filmen. Jag visar på att avsaknaden av vävnadsfas i korngränserna tydligt förbättrar beständigheten mot oxidering, vilket troligtvis beror på att just korngränserna, och deras innehåll, agerar som en katalys for oxidering. På samma sätt undersöker jag hur materialsystemet Ti1-xAlxBy-2 beter sig med varierande Ti:Al förhållande och även B:M förhållande (bor till metall), i filmer skapade med både DCMS och HiPIMS. Målet med inkluderingen av Al är just att förbättra beständighet mot oxidering, och samtidigt bevara de åtråvärda mekaniska egenskaperna som filmer av TiBx har. Korngränserna i det här materialet består av en vävnadsfasblandning, rik på antingen Al eller B, beroende på förhållandet mellan x och y i Ti1- xAlxBy-2. Jag visar på att en reducering av denna vävnadsfas även här förbättrar beständigheten mot oxidering. Det påvisas genom att reducera Al- och B-innehållet i filmerna, vilket minskar vävnadsfasen i korngränserna, och således förbättras beständigheten mot oxidering. En systematisk undersökning av tunna filmer av CrBx, belagda med DCMS, har genomförts, då detta är ett materialsystem med potential för beständighet mot korrosion. Både lätt över- och understökiometriska filmer växtes, och fick sin mikrostruktur och lokala sammansättning undersökt. Alla filmer påvisade en (001) textur, med epitaxiell tillväxt när temperaturen ökade från 500 C° till 900 C°. Högre densitet (~5.2 g/cm3) och jämnare ytor sågs för filmer belagda vid lägre tryck, 5 mTorr (0.67 Pa), jämfört med högre tryck, 20 mTorr (2.67 Pa). Kompositionen för CrBx filmerna påvisade inte ett temperaturberoende, men visade ett marginellt beroende på beläggningstryck för prover växta vid 900 C°. Även observerat för understökiometriska CrB1.90 filmer är att underskottet av B presenteras som plandefekter med Cr-rika plan i de kolumnära CrB2- strukturerna i filmen, precis som i understökiometrisk TiBx. I överstökiometriska CrB2.08 filmer så visades stora inneslutningar av ansamlat B.

The explosive growth in the semiconductor industry has caused a rapid evolution of thin film materials that lend themselves to the fabrication of state-of-the-art semiconductor devices. Early in the 1960s an old research technique named chemical vapour phase deposition (CVD), which has several unique advantages, developed into the most widely used technique for thin film preparation in electronics technology. In the last 25 years, tremendous advances have been made in the science and technology of thin films prepared by means of CVD. This book presents in a single volume, an up-to-date overview of the important field of CVD processes which has never been completely reviewed previously. Contents: Part I. 1. Evolution of CVD Films. Introductory remarks. Short history of CVD thin films. II. Fundamentals. 2. Techniques of Preparing Thin Films. Electrolytic deposition techniques. Vacuum deposition techniques. Plasma deposition techniques. Liquid-phase deposition techniques. Solid-phase deposition techniques. Chemical vapour conversion of substrate. Chemical vapour deposition. Comparison between CVD and other thin film deposition techniques. 3. Chemical Processes Used in CVD. Introduction. Description of chemical reactions used in CVD. 4. Thermodynamics of CVD. Feasibility of a CVD process. Techniques for equilibrium calculations in CVD systems. Examples of thermodynamic studies of CVD systems. 5. Kinetics of CVD. Steps and control type of a CVD heterogeneous reaction. Influence of experimental parameters on thin film deposition rate. Continuous measurement of the deposition rate. Experimental methods for studying CVD kinetics. Role of homogeneous reactions in CVD. Mechanism of CVD processes. Kinetics and mechanism of dopant incorporation. Transport phenomena in CVD. Status of kinetic and mechanism investigations in CVD systems. 6. Measurement of Thin Film Thickness. Mechanical methods. Mechanical-optical methods. Optical methods. Electrical methods. Miscellaneous methods. 7. Nucleation and Growth of CVD Films. Stages in the nucleation and growth mechanism. Regimes of nucleation and growth. Nucleation theory. Dependence of nucleation on deposition parameters. Heterogeneous nucleation and CVD film structural forms. Homogeneous nucleation. Experimental techniques. Experimental results of CVD film nucleation. 8. Thin Film Structure. Techniques for studying thin film structure. Structural defects in CVD thin films. 9. Analysis of CVD Films. Analysis techniques of thin film bulk. Analysis techniques of thin film surfaces. Film composition measurement. Depth concentration profiling. 10. Properties of CVD Films. Mechanical properties. Thermal properties. Optical properties. Photoelectric properties. Electrical properties. Magnetic properties. Chemical properties. Part III. 11. Equipment and Substrates. Equipment for CVD. Safety in CVD. Substrates. 12. Preparation and Properties of Semiconducting Thin Films. Homoepitaxial semiconducting films. Heteroepitaxial semiconducting films. 13. Preparation and Properties of Amorphous Insulating Thin Films. Oxides. Nitrides and Oxynitrides. Polymeric thin films. 14. Preparation and Properties of Conductive Thin Films. Metals and metal alloys. Resistor materials. Transparent conducting films. Miscellaneous materials. 15. Preparation and Properties of Superconducting and Magnetic Thin Films. Superconducting materials. Magnetic materials. 16. Uses of CVD Thin Films. Applications in electronics and microelectronics. Applications in the field of microwaves and optoelectronics. Miscellaneous applications. Artificial heterostructures (Quantum wells, superlattices, monolayers, two-dimensional electron gases). Part V. 17. Present and Future Importance of CVD Films. Present status and future trends in CVD films. References. Index of Acronyms and Abbreviations. Author Index. CVD Film Index. Subject Index. Supplier Index.

Prepared as a textbook complete with problems after each chapter, specifically intended for classroom use in universities.

This is the first text to cover all aspects of solution processed functional oxide thin-films. Chemical Solution Deposition (CSD) comprises all solution based thin- film deposition techniques, which involve chemical reactions of precursors during the formation of the oxide films, i. e. sol-gel type routes, metallo-organic decomposition routes, hybrid routes, etc. While the development of sol-gel type processes for optical coatings on glass by silicon dioxide and titanium dioxide dates from the mid-20th century, the first CSD derived electronic oxide thin films, such as lead zirconate titanate, were prepared in the 1980’s. Since then CSD has emerged as a highly flexible and cost-effective technique for the fabrication of a very wide variety of functional oxide thin films. Application areas include, for example, integrated dielectric capacitors, ferroelectric random access memories, pyroelectric infrared detectors, piezoelectric micro-electromechanical systems, antireflective coatings, optical filters, conducting-, transparent conducting-, and superconducting layers, luminescent coatings, gas sensors, thin film solid-oxide fuel cells, and photoelectrocatalytic solar cells. In the appendix detailed “cooking recipes” for selected material systems are offered.