Scanning thermal microscopy: A review

Abstract

Fundamental research and continued miniaturization of materials, components and systems have raised the need for the development of thermal-investigation methods enabling ultra-local measurements of surface temperature and thermophysical properties in many areas of science and applicative fields. Scanning thermal microscopy (SThM) is a promising technique for nanometer-scale thermal measurements, imaging, and study of thermal transport phenomena. This review focuses on fundamentals and applications of SThM methods. It inventories the main scanning probe microscopy-based techniques developed for thermal imaging with nanoscale spatial resolution. It describes the approaches currently used to calibrate the SThM probes in thermometry and for thermal conductivity measurement. In many cases, the link between the nominal measured signal and the investigated parameter is not straightforward due to the complexity of the micro/nanoscale interaction between the probe and the sample. Special attention is given to this interaction that conditions the tip-sample interface temperature. Examples of applications of SThM are presented, which include the characterization of operating devices, the measurements of the effective thermal conductivity of nanomaterials and local phase transition temperatures. Finally, future challenges and opportunities for SThM are discussed.

Quantification of probe–sample interactions of a scanning thermal microscope using a nanofabricated calibration sample having programmable size

“…This is compounded by the fact that, in passive mode, the probe temperature is always lower than that of the sample as a result of the thermal resistance of the tip-sample contact [1][11] [12].…”

Topography-free sample for thermal spatial response measurement of scanning thermal microscopy

“…The contact thermal resistance, R int , represents thermal interaction between the tip and the sample and is a combination of many factors; however, solid to solid contact (R ss ), water meniscus (R w ), and air (R air ) conduction are generally believed to dominate over heat transfer through radiation (R rad ). 28,33,53 Gorbunov et al 54 proved that heat dissipation to the sample from a heated tip is a function of the tip-sample contact radius as well as the sample materials being scanned. This has been investigated by Gotsmann 29 who indicated that the contact thermal conductance is dependent on the pressure when the contact radius is constant.…”

“…Hence, the tip-sample force was kept 20 nN during our experiment. These thermal interactions have been recently discussed in detail by King et al 55 and Gomès et al 28 As the geometry and materials comprising the Si 3 N 4 tip will not change significantly, the thermal resistance of tip, R t , is regarded as a constant value.…”

“…Furthermore, the SiN x film thickness of 400 nm makes it unnecessary to consider boundary scattering effects. Thus, the thermal spreading resistance of the SiNx can be given by 28,34 …”

“…However, advanced scanning methods such as the "double-scan technique" 24 and "topography-correction technique" 23 have been demonstrated a) Electronic mail: y.ge.1@research.gla.ac.uk to effectively diminish this artifact. Another major artifact, induced by the topography of the sample, is hard to eliminate due to its complexity [25][26][27][28] and it is this example that will be considered here. The heat transfer between the probe tip and the sample has been proven to occur through a combination of pathways, including thermal conduction through the solid-solid contact, water meniscus, and air and thermal radiation (in near and far fields) when performing measurement under ambient conditions.…”