Self Limiting Growth Of Aluminum Oxide Thin Films By Pulsed Plasma Enhanced Chemical Vapor Deposition

Medical Coatings and Deposition Technologies is an important new addition to the libraries of medical device designers and manufacturers. Coatings enable the properties of the surface of a device to be controlled independently from the underlying bulk properties; they are often critical to the performance of the device and their use is rapidly growing. This book provides an introduction to many of the most important types of coatings used on modern medical devices as well as descriptions of the techniques by which they are applied and methods for testing their efficacy. Developers of new medical devices and those responsible for producing them will find it an important reference when deciding if a particular functionality can be provided by a coating and what limitations may apply in a given application. Written as a practical guide and containing many specific coating examples and a large number of references for further reading, the book will also be useful to students in materials science & engineering with an interest in medical devices. Chapters on antimicrobial coatings as well as coatings for biocompatibility, drug delivery, radiopacity and hardness are supported by chapters describing key liquid coating processes, plasma-based processes and chemical vapor deposition. Many types of coatings can be applied by more than one technique and the reader will learn the tradeoffs given the relevant design, manufacturing and economic constraints. The chapter on regulatory considerations provides important perspectives regarding the marketing of these coatings and medical devices.

Atomic layer deposition (ALD) is a self-limiting subset of chemical vapor deposition that has become widely popular in materials science applications such as device packaging, semiconductor passivation, transistor gate dielectrics, optical coatings, and protective barriers. ALD is capable of uniformly coating high-aspect ratio features, such as 1-dimensional nanostructures or pinhole-sized vias, across a macroscopic distance which is expected to only be limited by the size of the deposition chamber. This work reviews several applications of ALD used to deposit thin conformal layers of dielectric material which specifically capitalize on the precise, conformal nature of the deposition process. Semiconductor nanowire networks coated with aluminum oxide (AlOx) by plasma enhanced ALD (PEALD) show blue-shifted photoluminescence with increasing AlOx thickness. Novel memristor 0́edge0́+ devices fabricated with an active switching layer of titanium dioxide deposited by PEALD yield an active device cross-section two orders of magnitude smaller than what is possible with conventional 2-dimensional thin film devices fabricated by similar photolithography methods. Protected silver mirrors coated with AlOx deposited by PEALD have superior durability when compared to mirrors coated with an identical layer of AlOx deposited by conventional physical vapor deposition. All of these applications benefit from the robust uniform coating properties of the ALD growth mechanism. Additional studies of dielectric barrier overlayers deposited by ALD on silver mirrors are discussed, and a figure of merit is proposed for judging overall mirror performance.

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.

Atomic layer deposition, formerly called atomic layer epitaxy, was developed in the 1970s to meet the needs of producing high-quality, large-area fl at displays with perfect structure and process controllability. Nowadays, creating nanomaterials and producing nanostructures with structural perfection is an important goal for many applications in nanotechnology. As ALD is one of the important techniques which offers good control over the surface structures created, it is more and more in the focus of scientists. The book is structured in such a way to fi t both the need of the expert reader (due to the systematic presentation of the results at the forefront of the technique and their applications) and the ones of students and newcomers to the fi eld (through the first part detailing the basic aspects of the technique). This book is a must-have for all Materials Scientists, Surface Chemists, Physicists, and Scientists in the Semiconductor Industry.

In the first part of this work, thin films of Al2O3 deposited via atomic layer deposition (ALD) are demonstrated to improve the thermal stability of cellulose nanocrystal (CNC) aerogels. ALD is a chemical vapor deposition (CVD) like method in which sequential precursor exposures and self-limited surface reactions produce a conformal thin film with precise thickness control. The conformal nature of ALD is well suited to coating the porous microstructure of aerogels. SEM micrographs of coating thickness depth profiles are shown to agree with trends predicted by precursor penetration models. Thermogravimetric analysis shows samples coated with ALD Al2O3 have increased decomposition temperatures. In the second part of this work, ALD zinc tin oxide (ZTO) is used to demonstrate a technique for measuring the substrate inhibited growth in multicomponent and laminate ALD systems. The thickness control of ALD makes it attractive for multicomponent and laminate systems. However, the surface reactions of ALD mean that the first few cycles, while the film nucleates, may have a different growth per cycle (GPC) than when the film is growing on itself in a bulk growth regime. A model for the substrate inhibited ALD of ZTO is derived from two complementary sets of laminates. The thickness and composition predictions of our model are tested against the bulk GPC of ZnO and SnO2. In the final part of this work, prompt inorganic condensation (PIC) is explored as a potentially more environmentally friendly alternative to ALD for planar thin film applications. Whereas ALD requires expensive vacuum systems and has low precursor utilization, solution based methods, such as PIC, allow atmospheric processing and precursor recycling. The water based PIC solutions use nitrate counter ions which evaporate at low temperatures. Combined with the low energy required to convert the hydroxide precursor clusters into an oxide film makes PIC a promising low temperature route to dense solution processed thin films. The dielectric performance of PIC Al2O3 is shown to be comparable to ALD Al2O3 films on Si though a large interfacial SiO2 layer is found to be dominating the behavior of the PIC films. This interfacial layer is shown to form very quickly (≤ 2 min) at low temperatures (≤ 50°C). This low temperature interfacial oxide growth could be a benefit in passivating solar cells.