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Stability and chemical composition of thermally grown iridium-oxide thin filmsThe effect of thermal growth conditions on the morphology and surface work function of iridium oxide thin films grown by annealing Ir thin films in an O 2 ambient is presented. The samples were analyzed using x-ray diffraction, x-ray photoelectron spectroscopy, atomic force microscopy, and photoelectric work function measurements. It is found that, with increasing temperature, IrO 2 changes from ͑110͒ oriented to a mixture of ͑110͒ and ͑200͒ during the oxide growth. This is manifested as a sharpening of the photoelectric energy distributions at 800°C. The surface work function was determined to be 4.23 eV using ultraviolet photoelectron spectroscopy. X-ray photoelectron spectroscopy analysis shows that IrO 2 starts to form at 600°C accompanied by surface roughening. Annealing the Ir film at 900°C in O 2 ambient leads to almost complete desorption of the film.

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We report the spontaneous formation of uniformly distributed arrays of "tips" (tall conical hillocks) upon oxidation of palladium (Pd) thin films. The formation of the palladium oxide tips depended on the thickness and granularity of the Pd film and on annealing and oxidation conditions. As the Pd film thickness increased from 40 to 200 nanometers, the average height of the tips increased from 0.5 to 1.2 micrometers, their height distribution became broader, and their density decreased from 55 x 10(6) to 12 x 10(6) per square centimeter. Enhanced photoelectron emission from locations corresponding to the tips suggests their possible use in field emission applications.

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As revolutionary as microelectronics has been as a technology, there are functions that it does not address. Microelectronics focuses on ever-smaller integrated circuits (ICs) in ever-fewer square millimeters of space to increase clock speeds and decrease the power required for computer processing functions. However, applications requiring control, communications, computing, and sensing over a large area are difficult or costprohibitive to achieve because of the material incompatibilities of traditional ICs with structures, materials, and manufacturing technology. Macroelectronics addresses these applications with the aim of providing active control circuitry in situ over areas of many square meters for displays, solar panels, x-ray imagers, surface measurements, structural shape control, vehicle health monitoring, and other large-system applications. The materials challenges of macroelectronics integrated circuits (MEICs) reviewed in this issue include lightweight flexible substrates, thin-film transistors (TFTs) with IC or near-IC performance, modeling, and manufacturing technology. Compatible component materials, flexible substrates, processing conditions, host system composition, and functionality provide grand challenges that are just beginning to be addressed by researchers.

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