Ftouni Hossein, Tainoff Dimitri, Richard Jacques, Lulla Kunal, Guidi Jean, Collin Eddy, Bourgeois Olivier
Institut NÉEL, CNRS-UJF, 25 avenue des Martyrs, 38042 Grenoble Cedex 9, France.
Rev Sci Instrum. 2013 Sep;84(9):094902. doi: 10.1063/1.4821501.
We present a specific heat measurement technique adapted to thin or very thin suspended membranes from low temperature (8 K) to 300 K. The presented device allows the measurement of the heat capacity of a 70 ng silicon nitride membrane (50 or 100 nm thick), corresponding to a heat capacity of 1.4 × 10(-10) J/K at 8 K and 5.1 × 10(-8) J/K at 300 K. Measurements are performed using the 3ω method coupled to the Völklein geometry. This configuration allows the measurement of both specific heat and thermal conductivity within the same experiment. A transducer (heater/thermometer) is used to create an oscillation of the heat flux on the membrane; the voltage oscillation appearing at the third harmonic which contains the thermal information is measured using a Wheatstone bridge set-up. The heat capacity measurement is performed by measuring the variation of the 3ω voltage over a wide frequency range and by fitting the experimental data using a thermal model adapted to the heat transfer across the membrane. The experimental data are compared to a regular Debye model; the specific heat exhibits features commonly seen for glasses at low temperature.
我们展示了一种适用于从低温（8K）到300K的薄或极薄悬浮膜的比热测量技术。所展示的装置能够测量70ng氮化硅膜（50或100nm厚）的热容量，在8K时对应热容量为1.4×10⁻¹⁰J/K，在300K时为5.1×10⁻⁸J/K。测量使用与Völklein几何结构耦合的3ω方法进行。这种配置允许在同一实验中测量比热和热导率。一个换能器（加热器/温度计）用于在膜上产生热流振荡；使用惠斯通电桥装置测量出现在包含热信息的三次谐波处的电压振荡。通过在很宽的频率范围内测量3ω电压的变化，并使用适合跨膜热传递的热模型拟合实验数据来进行热容量测量。将实验数据与常规德拜模型进行比较；比热在低温下呈现出玻璃常见的特征。
