By expanding the limit of miniaturisation to achieve superior materials and devices properties, nanoscience and nanotechnology create new challenges to understand materials behaviour at the nanometre length scales. New phenomena require matching tools that in turn open new investigation perspectives, themselves launching platforms for new discoveries. Amongst the vast realm of nanoresearch, thermal properties have gained interest in the past decades due their crucial importance in technological developments, ranging from mainstream semiconductor microelectronics to cutting edge quantum technologies.
Whereas major standard techniques to measure thermal properties are not efficient for studying nanosstructured materials, Scanning Thermal Microscopy (SThM) offers both sensitivity to nanoscale thermal transport and a spatial resolution down to a few nanometres. This thesis develops fundamental aspects of the SThM technique by increasing its reproducibility and developing an experimental and analytical framework to analyse experimental data.
These developments are then applied to produce quantitative measurements of a wide range of materials from vertically aligned carbon nanotubes to metal covered block copolymers. In brief, we probed the 3D thermal properties distribution of isotropic and anisotropic materials, such as optoelectronic thin film. We also measured low dimensional systems of 2D materials heterostructures from franckeite and graphene on MoS2. Thermoelectric properties of graphene nanoconstrictions are unveiled using a combined three-terminal approach. Additionally, cryoSThM is introduced as a new tool with the ability to measure at temperatures below 150K.
The research presented in this thesis has a two-fold impact. On one hand, major technical SThM challenges are answered and efficient solutions developed. In this respect, cryoSThM and 3D nanothermal probing of materials open radically new routes for further investigations. On the other hand, new insights are gained from the extraction of materials properties and the observation of new phenomena. The knowledge gained through this research leads to innovative keys to develop applications in various fields, ranging from heat management to thermoelectric energy conversion.