Temperature distribution in a thin-film chip utilized for advanced nanocalorimetry

Abstract

High sensitivity and fast calorimeters based on silicon nitride thin-film technology are used to study thermal properties of sub-micron samples and transition kinetics on a millisecond time scale. A commercially available thin-film sensor was utilized in our previous works for fast-scanning calorimetric measurements. A non-adiabatic condition allows not only fast heating but also fast cooling at rates up to 10 000 K s−1. Heat transfer from the sub-micron membrane was realized through an ambient gas. In order to justify the calibration procedure utilized in non-adiabatic thin-film calorimetry, the temperature distributions in the membrane and in the ambient gas have been studied. Results from an analytical solution of the heat-transfer problem have been compared with the temperature profiles obtained by fast infrared thermographic measurements under static and oscillating heating–cooling conditions. A theoretical background for ultra-fast-cooling experiments has been formulated. Actually, the best cooling medium for the ultra-fast thin-film cooling calorimetry is a gas at a reduced pressure. The thermal conductivity of a gas is not a limiting factor for the ultra-fast-cooling experiments.

Platinum Micro-Hotplates on Thermal Insulated Structure for Micro-Thermoelectric Gas Sensor

“…As the active part of the micro-hotplate (meander) has dimensions less than 1 mm, the convection is not the main dispersion path for the heat (12) . The silicon heat spreader has a thickness of 70 µm so that the heat conduction and the radiative emission can not be negligible (13) .…”

In situ investigation of vapor-deposited glasses of toluene and ethylbenzene via alternating current chip-nanocalorimetry

“…This value has to be split reasonably to the 16 low passes. The inner part of the membrane shows a homogeneous temperature distribution for the DC case [100] which allows for the assumption of constant thermal resistance per unit volume. The electrical resistance for the outer rings decreases like 1/r with r being the radius vector.…”

“…Only the solid phase III-to-plastic phase II transition can be measured in vacuum since sublimation occurs at higher temperature. Backfilling the chamber with nitrogen gas up to 300 mbar avoids sublimation but allows heat loss through the gas, in addition to the heat loss through the membrane, which may influence the temperature distribution in the membrane [100]. To check the influence of the gas, the temperatures of the solid phase III-to-plastic crystal II transition measured in vacuum and in nitrogen gas were compared.…”

A scanning AC calorimetry technique for the analysis of nano-scale quantities of materials

“…15 In this device, the applied AC frequency is limited to approximately 100 Hz because the distance between the sample and the temperature sensor dampens the temperature response of the sensor. 16 Moreover, the scan rate cannot exceed 5 K/min because of considerations of temperature uniformity across the sample and accuracy of the temperature measurements. 15 In this paper, we present a scanning AC nanocalorimetry method that enables AC measurements at heating and cooling rates that vary from isothermal to 2 × 10 3 K/s (and possibly higher) -in terms of scan rate, the technique bridges the gap between nanocalorimetry and traditional scanning calorimetry of bulk materials.…”