Combinatorial nanocalorimetry
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The parallel nano-scanning calorimeter (PnSC) is a silicon-based micromachined device for calorimetric measurement of nanoscale materials in a high-throughput methodology. The device contains an array of nanocalorimeters. Each nanocalorimeter consists of a silicon nitride membrane and a tungsten heating element that also serves as a temperature gauge. The small mass of the individual nanocalorimeters enables measurements on samples as small as a few hundred nanograms at heating rates up to 104 K/s. The sensitivity of the device is demonstrated through the analysis of the melting transformation of a 25-nm indium film. To demonstrate the combinatorial capabilities, the device is used to analyze a Ni–Ti–Zr sample library. The as-deposited amorphous samples are crystallized by local heating in a process that lasts just tens of milliseconds. The martensite–austenite transformation in the Ni–Ti–Zr shape memory alloy system is analyzed and the dependence of transformation temperature and specific heat on composition is revealed. I. INTRODUCTION
As materials scientists strive to optimize the performance of materials, often the best performers are found in complex materials systems, i.e., materials systems with three components or more. This class of materials systems is still largely unexplored. The reason why complex materials systems remain unexplored is twofold: first, the scope of the problem is vast and second, conventional measurement methods are too slow. For example, considering ternary and quaternary combinations of elements lead to over four million materials systems of which less than 1% are well known.1 Conventional measurement methods consider just one composition of one material system at a time. This approach is insufficient to explore the vast materials space in a reasonable amount of time. The dependence of materials properties on temperature, scale, and processing conditions further increases the scope of the problem. Clearly, high-throughput techniques can improve the efficiency of materials discovery and property optimization. This work introduces an instrument, the parallel nanoscanning calorimeter (PnSC), which combines techniques from combinatorics and nanocalorimetry to create a useful tool for materials research and discovery.2 More specifically, the PnSC allows high-throughput measurement of enthalpy-related materials properties in thin-film samples. The design of the PnSC allows for fast synthesis of sample libraries by conventional thin-film growth techniques. Samples can range from nanometer to micrometer a)
Address all correspondence to this author. e-mail: [email protected]. DOI: 10.1557/JMR.2010.0286
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http://journals.cambridge.org
J. Mater. Res., Vol. 25, No. 11, Nov 2010 Downloaded: 20 Mar 2015
thickness and libraries can vary by composition, thickness, temperature history, etc. Once created, the entire sample library is measured sequentially with millisecond measurement times, allowing fast sample analysis over a wide range of temperatures. Combinatorial materials science
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