Scanning AC nanocalorimetry combined with in-situ x-ray diffraction

Abstract

Micromachined nanocalorimetry sensors have shown excellent performance for high-temperature and high-scanning rate calorimetry measurements. Here, we combine scanning AC nanocalorimetry with in-situ x-ray diffraction (XRD) to facilitate interpretation of the calorimetry measurements. Time-resolved XRD during in-situ operation of nanocalorimetry sensors using intense, high-energy synchrotron radiation allows unprecedented characterization of thermal and structural material properties. We demonstrate this experiment with detailed characterization of the melting and solidification of elemental Bi, In, and Sn thin-film samples, using heating and cooling rates up to 300 K/s. Our experiments show that the solidification process is distinctly different for each of the three samples. The experiments are performed using a combinatorial device that contains an array of individually addressable nanocalorimetry sensors. Combined with XRD, this device creates a new platform for high-throughput mapping of the composition dependence of solid-state reactions and phase transformations. V C 2013 AIP Publishing LLC.

Scanning AC Nanocalorimetry and Its Applications

“…Thanks to the wide time-scale of measurements, the technique can also be combined with in-situ X-ray diffraction (XRD) to obtain structural information of phase transition during calorimetry scans [26].…”

“…Immediately after deposition, the Bi film was coated with a 30 nm layer of silicon nitride by RF sputtering. During initial melting, the Bi film broke up into a stable dispersion of small, individual islands, as expected for a liquid film that does not wet the substrate [26]. Optical micrographs of the sample (Figure 4.2a) were analyzed using digital image processing tools to yield the size distribution of the droplets (Figure 4.2b), …”

“…In a typical measurement, a thin-film sample is deposited in the shaded area between the two voltage sensing leads and an electric current is applied to the tungsten heating element, which, in turn, heats the sample. The measured values of current and voltage are used to determine the power supplied to the sample, while the temperature of the sample is determined from the resistance of the heating element, which is calibrated to temperature using a standard procedure described in detail in references [22,26]. The nanocalorimetry sensor is installed in a probe card that is mounted inside a high vacuum furnace, with a base pressure of 10 -7 Torr.…”

“…For the DC measurements, both the temperature of the sample and the power supplied to it were determined directly from the sensor as described earlier. For the AC measurements, the in-phase and out-of-phase response of the sample was determined by dividing measured voltage and current signals into segments consisting of an integer number of AC oscillation periods, and applying a discrete Fourier transform (DFT) to every segment as described elsewhere [22,26].…”

“…We perform calorimetry measurements using a nanocalorimeter sensor derived from an original design by Allen and coworkers [3,15], which has negligible thermal lag between sample and temperature sensor thus enabling accurate temperature measurement at very high scanning rates. This nanocalorimeter sensor combined with the appropriate AC-technique [22] is also capable of making accurate measurements at medium to slow scan rates where heat loss to the environment makes DC measurements not practical [81], even allowing in-situ XRD measurements during the scans [26]. By combining AC and DC techniques we have performed measurements on undercooled Bi samples at cooling rates from 10 1 to 10 4 K/s and use classical nucleation theory to interpret the experimental results.…”