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Determining and acting on thermo-physical properties at the nanoscale is essential for understanding/managing heat distribution in micro/nanostructured materials and miniaturized devices. Adequate thermal nano-characterization techniques are required to address thermal issues compromising device performance. Scanning thermal microscopy (SThM) is a probing and acting technique based on atomic force microscopy using a nano-probe designed to act as a thermometer and resistive heater, achieving high spatial resolution. Enabling direct observation and mapping of thermal properties such as thermal conductivity, SThM is becoming a powerful tool with a critical role in several fields, from material science to device thermal management. We present an overview of the different thermal probes, followed by the contribution of SThM in three currently significant research topics. First, in thermal conductivity contrast studies of graphene monolayers deposited on different substrates, SThM proves itself a reliable technique to clarify the intriguing thermal properties of graphene, which is considered an important contributor to improve the performance of downscaled devices and materials. Second, SThM's ability to perform sub-surface imaging is highlighted by thermal conductivity contrast analysis of polymeric composites. Finally, an approach to induce and study local structural transitions in ferromagnetic shape memory alloy Ni-Mn-Ga thin films using localized nano-thermal analysis is presented.

Thermoelectric conversion may take a significant share in future energy technologies. Oxide‐based thermoelectric composite ceramics attract attention for promising routes for control of electrical and thermal conductivity for enhanced thermoelectric performance. However, the variability of the composite properties responsible for the thermoelectric performance, despite nominally identical preparation routes, is significant, and this cannot be explained without detailed studies of thermal transport at the local scale. Scanning thermal microscopy (SThM) is a scanning probe microscopy method providing access to local thermal properties of materials down to length scales below 100 nm. To date, realistic quantitative SThM is shown mostly for topographically very smooth materials. Here, methods for SThM imaging of bulk ceramic samples with relatively rough surfaces are demonstrated. “Jumping mode” SThM (JM‐SThM), which serves to preserve the probe integrity while imaging rough surfaces, is developed and applied. Experiments with real thermoelectric ceramics show that the JM‐SThM can be used for meaningful quantitative imaging. Quantitative imaging is performed with the help of calibrated finite‐elements model of the SThM probe. The modeling reveals non‐negligible effects associated with the distributed nature of the resistive SThM probes used; corrections need to be made depending on probe‐sample contact thermal resistance and probe current frequency.

Low temperature (400°C) deposition of ferromagnetic Ni-Mn-Ga thin films is successfully performed via rf magnetron sputtering technique using co-deposition of two targets Ni50Mn50 and Ni50Ga50 on sapphire (0001) and Si (100) substrates. The films are in part amorphous with significant degree of crystallinity. The obtained crystallographic structure is shown to be substrate-dependent. Films on both substrates are ferromagnetic at room temperature (Curie temperature ∼ 332.5K) with well-defined hysteresis loops, low coercivity (∼ 100 Oe) and a saturation magnetization of ∼ 200 emu/cc. At low temperature (5 K), both films show increased magnetization value with wider hysteresis loops having higher coercivity and remanent magnetization. The process is therefore effective in achieving the appropriate thermodynamic conditions to deposit thin films of the Ni-Mn-Ga austenitic phase (highly magnetic at room temperature) at relatively low substrate temperature without the need for post-deposition annealing or further thermal treatment, which is prerequisite for the device fabrication.

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