Thermal transport properties investigated through the 3¿-SThM

Trabajo presentado en el Nanotechnology Colombia-U.S. Workshop, celebrado en Bogotá (Colombia), los días 14 y 15 de febrero de 2017
Scanning thermal microscopy (SThM) has been implemented as a prominent technique that simultaneously measure topography and 3-omega voltage (3¿¿SThM); using a commercial probe of Pd coated on SiN at the end of the tip, it is possible to reach a lateral spatial resolution better than 100 nm [1]. The thermal images obtained with the 3¿ method are related to the heat variations of the samples due to their thermal conductivity [2]. Its characteristics make of this scanning probe a very important technique for nanoscale thermal transport investigations, which have a wide applicability in areas from biomedical, electronic industry and nano-device, solar cells among others[3]. This powerful technique is also of great interest for thermal conductivity measurements in thermoelectric materials. Actually, copper selenide Cu2Se and silver selenide Ag2Se have a promising efficiency although some issue regarding copper seggegation must be studied. Due to that copper segregation the thermal properties of these materials are highly affected. This segregation seems to occur as nanoparticle so it is interesting to see the effect at the nanoscale. However, the thermal conductivity measurements at the nanoscale are very challenging and some of the current thermal methods have spatial resolution issues, which makes the evaluation even more difficult in the case of these nanostructured materials [4]. Here, we describe the calibration work and the considerations needed to extract information of the SThM images of Cu2Se (fig.1). The contact potential difference obtained by kelvin probe force microscopy (KPFM) and the SThM measures of Ag2Se (fig. 2) are also discussed in this work.