The challenging measurements of thermal properties are of fundamental importance in the evolution of modern technology and direct quantification of nanoscale features is a crucial step in this development. Exploring confined systems from monolayer to bulk, we performed scanning thermal microscopy (SThM) on graphene, MoS2 and Bi2Se3 and correlated the outcomes with finite elements (FE) simulations.

SThM is a scanning probe microscopy technique derived from the well-known Atomic Force Microscope where a self-heated probe is used as a thermosensor while scanning the sample; during probe-sample contact the corresponding drop in probe temperature can be electronically monitored and directly related to changes in the thermal properties as represented on Fig. 1 where a 5±1 nm flake of each materials mentioned on a SiO2 substrate is thermally measured. FE simulations were realized to correlate the measured properties of our systems varying several parameters such as graphene’s isotropy and anisoptropy as well as substrate interactions.

We have investigated how these properties change as a function of sample number of layers on substrates of both high and low thermal conductivities. We observe well defined values of thermal conductance for monolayer and near monolayer thicknesses, however when increasing multilayers most materials conductance does not scale linearly with thickness as in some cases the conductance increases whilst in others a decrease is observed. We discuss and compare experimental considerations and simulation outputs in order to construct a thermal conductance models to explain these interesting results.