Varandani Deepak, Agarwal Khushboo, Brugger Juergen, Mehta Bodh Raj
Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India.
Ecole Polytechnique Fédérale de Lausanne, Lausanne CH-1015, Switzerland.
Rev Sci Instrum. 2016 Aug;87(8):084903. doi: 10.1063/1.4960332.
A commercial scanning thermal microscope has been upgraded to facilitate its use in estimating the radial thermal diffusivity of thin films close to room temperature. The modified setup includes a microcontroller driven microhotplate coupled with a Bluetooth module for wireless control. The microcontroller board (Arduino Leonardo) is used to generate a bias of suitable voltage amplitude and pulse duration which is applied across the microhotplate contact pads. A corresponding heat pulse from the Pt heating element (1 mm(2)) embedded within the microhotplate is delivered to the lower surface of the thin film (25 mm(2)) deposited over it. The large difference in the dimensions of the heating source and the thin film surface causes heat to flow radially outwards on the top surface of the latter. The decay of this radial heat wave as it flows outwards is recorded by the scanning thermal microscope in terms of temperature-time (T-t) profiles at varying positions around the central heating zone. A fitting procedure is suggested to extract the thermal diffusivity value from the array of T-t profiles. The efficacy of the above setup has been established by evaluating the thermal diffusivities of Bi2Te3 and Bi2Te3:Si thin film samples. Further, with only minor alterations in design the capabilities of the above setup can be extended to estimate the axial thermal diffusivity and specific heat of thin films, as a function of temperature.
一台商用扫描热显微镜已进行升级，以便于在接近室温的条件下估算薄膜的径向热扩散率。改进后的装置包括一个由微控制器驱动的微热板，并配有蓝牙模块用于无线控制。微控制器板（Arduino Leonardo）用于产生合适电压幅度和脉冲持续时间的偏置电压，该电压施加在微热板的接触垫上。来自嵌入微热板内的铂加热元件（1平方毫米）的相应热脉冲被传递到沉积在其上的薄膜（25平方毫米）的下表面。加热源和薄膜表面尺寸的巨大差异导致热量在薄膜的顶表面径向向外流动。扫描热显微镜通过记录围绕中央加热区不同位置的温度 - 时间（T - t）曲线，来记录这种径向热波向外流动时的衰减情况。建议采用一种拟合程序从T - t曲线阵列中提取热扩散率值。通过评估Bi2Te3和Bi2Te3:Si薄膜样品的热扩散率，已证实上述装置的有效性。此外，只需对设计进行微小改动，上述装置的功能就可以扩展到估算薄膜的轴向热扩散率和比热容随温度的变化情况。
