Guest Editorial: Nanostructured Thin Films

Abstract

Nanostructured thin films (NSTF) are providing enormous scope for advances in optical, electronic and optoelectronic engineering and underpinning key developments in nanoscience. From a scientific perspective they embody numerous challenges and opportunities: covering concepts, models, growth, structure and characterization. Emerging technologies which depend on NSTF include photonics and plasmonics for information processing and communications; semiconductor and molecular electronics; display and lighting; single molecule bio-sensing, proteomics, advanced medical therapies, diagnostics and imaging; large scale, low cost approaches to energy efficiency, renewable energy and energy storage; and material surfaces which are durable, self-repair, self-clean, and have the ability to sense, change color, and to modulate reflectance, transmittance or thermal emittance. Nanometal based composites are known from antiquity and featured as coatings in stunning luster's on Renaissance pottery [1]. Relevant nano-optics science dates back over a century and includes the classic 1857 paper by Faraday [2], and the resonant model of Maxwell Garnett (MG) [3], which is able to describe the spectral response of many of today’s thin films, either in its original form or with various enhancements. For an excellent historical overview of the evolution of this subject from the middle of the 19 th century until the mid1990’s I recommend the collection of facsimiles of landmark original papers put together by Lakhtakia [4]. Technological and scientific interest in spectral control using nano-composite cermet coatings blossomed during the oil crises in the 1970’s for spectrally selective solar absorbers [5]. Gold black layers made much earlier [6] provided one interesting test for the emerging models in that period as the simple models such as (MG) could not handle touching or close nanoparticles. (Vacuum deposition at elevated pressure of gold black coatings exemplifies how early stage NSTF studies can lead to broader developments, in that case mass producing nanoparticles in vacuum). In the 1980’s energy efficient spectrally selective windows based on nano-thin strongly plasmonic metal in insulator/metal/insulator multilayers evolved to become one of the first commodity scale high technology plasmonic thin film products. Dense silver films in these multilayers are produced today on the 60 million m 2 per