Measuring thermal conductivity of thin films and coatings with the ultra-fast transient hot-strip technique

Abstract

This paper reports the ultra-fast transient hot-strip (THS) technique for determining the thermal conductivity of thin films and coatings of materials on substrates. The film thicknesses can vary between 10 nm and more than 10 µm. Precise measurement of thermal conductivity was performed with an experimental device generating ultra-short electrical pulses, and subsequent temperature increases were electrically measured on nanosecond and microsecond time scales. The electrical pulses were applied within metallized micro-strips patterned on the sample films and the temperature increases were analysed within time periods selected in the window [100 ns–10 µs]. The thermal conductivity of the films was extracted from the time-dependent thermal impedance of the samples derived from a three-dimensional heat diffusion model. The technique is described and its performance demonstrated on different materials covering a large thermal conductivity range. Experiments were carried out on bulk Si and thin films of amorphous SiO2 and crystallized aluminum nitride (AlN). The present approach can assess film thermal resistances as low as 10−8 K m2 W−1 with a precision of about 10%. This has never been attained before with the THS technique.

From diffusive to ballistic Stefan–Boltzmann heat transport in thin non-crystalline films

“…þT contact (8) here, DT max is the difference of temperature oscillation (T lm À T substrate ) max found in the limit of thick lms, r contact is the radius of the effective contact area of the probe, andT contact is the temperature offset caused by a constant thermal contact resistance, as r contact and the thermal contact resistance are constant for a certain range of sample thermal conductivity 33 which is typically neglected in eqn (6). Note, aside fromT contact , in the limit of ultra-thin lms (one-dimensional heat transport) eqn (8) becomes identical to eqn (6) (assuming w ¼ 2r contact and…”

“…There are steady state as well as transient techniques within the space and time/frequency domain to analyze thermal transport. [3][4][5][6][7] If the absorbed power in the sample is known, the thermal conductivity can be directly determined in steady state approaches. In the dynamic case, the density r as well as the specic heat c of the material must be considered.…”

Structural-dependent thermal conductivity of aluminium nitride produced by reactive direct current magnetron sputtering

“…We have developed this technique to carry-out accurate thermal conductivity measurements on thin-films and coatings exhibiting extremely small thermal resistance down to 10 À8 K m 2 /W. 12 The technique is described in Refs. around 50 nm was deposited by DC magnetron sputtering from a pure aluminum target in an argon plasma.…”

Thermal conductivity of polyimide/boron nitride nanocomposite films

“…Thermal conductivity measurements were carried out using a pulsed photothermal technique developed to determine the thermal properties of thin solid films and coatings . A gold (Au) “steamer” thin resistor (thickness 150 nm, strip length 64 mm, width 700 μm), used as a thermal sensor, was deposited by thermal evaporation on the surface of each sample with a total resistance of 20 Ω as shown in Figure .…”