Atomic layer deposition: A versatile technique for plasmonics and nanobiotechnology
- PDF / 532,102 Bytes
- 9 Pages / 584.957 x 782.986 pts Page_size
- 107 Downloads / 307 Views
Although atomic layer deposition (ALD) has been used for many years as an industrial manufacturing method for microprocessors and displays, this versatile technique is finding increased use in the emerging fields of plasmonics and nanobiotechnology. In particular, ALD coatings can modify metallic surfaces to tune their optical and plasmonic properties, to protect them against unwanted oxidation and contamination, or to create biocompatible surfaces. Furthermore, ALD is unique among thin film deposition techniques in its ability to meet the processing demands for engineering nanoplasmonic devices, offering conformal deposition of dense and ultrathin films on high-aspect-ratio nanostructures at temperatures below 100 °C. In this review, we present key features of ALD and describe how it could benefit future applications in plasmonics, nanosciences, and biotechnology.
I. INTRODUCTION
Atomic layer deposition (ALD) is a variant of chemical vapor deposition (CVD) techniques capable of angstromresolution, layer-by-layer growth of compound films.1–4 ALD can deposit these ultrathin films in a conformal manner over a wide range of materials and high-aspect-ratio topographies. It has been used extensively in commercial production, most notably for high-permittivity gate insulators in 45-nm-node silicon transistors.5,6 Beyond its adoption by the microelectronics industry, this versatile technique finds broad application in surface modification, lithographic patterning, optical tuning, layer-by-layer optical characterization, and protection and encapsulation of various nanostructures. This review focuses on these new and emerging applications, particularly in plasmonics and nanobiotechnology, and summarizes some recent researches. In a typical ALD reaction for depositing a binary compound film, the precursors “A” and “B” are sequentially introduced into a reaction chamber with an inert purging step in between: A/purge/B/purge/A/purge, etc. until the desired thickness is reached. An archetypical ALD process is the deposition of Al2O3 from trimethylaluminum (TMA) and H2O, which consists of four steps3: (i) inject the first precursor (TMA) until its binding sites on the reaction surface are saturated, (ii) purge the chamber with inert gas and remove unbound precursor, (iii) inject the second precursor (H2O) and form a monolayer of hydroxyl (OH) groups on the surface, and (iv) purge. Each a)
Address all correspondence to this author. e-mail: [email protected] This paper has been selected as an Invited Feature Paper. DOI: 10.1557/jmr.2011.434 J. Mater. Res., Vol. 27, No. 4, Feb 28, 2012
http://journals.cambridge.org
Downloaded: 24 Jun 2014
growth step self-saturates when the surface binding sites are occupied; thus, the deposited film thickness after each cycle is highly reproducible. The total film thickness can be tuned in a stepwise manner by the total number of each atomically thick ALD cycle. Importantly, the film thickness can be precisely controlled over a large area, regardless of the underlying topography, because the self-saturating gr
Data Loading...
