Unveil thermoelectric properties of 2D α-In2Se3

Recently bidimensional (2D) van der Waals (vdW) III−VI semiconductors have drawn intense attention due to their unique electronic properties [1]. Among these materials, In₂Se₃ in its most studied a and b phases, shows a great potential for a wide variety of applications in electronics, photonics and even thermoelectricity, due to its good mobility, excellent photoresponsivity, exotic ferroelectricity, and unique band structure [2-4]. In₂Se₃ possess an in- and out-of-plane ferroelectricity, which remains robust down to the monolayer limit. Moreover, very recently, 2H α-In₂Se₃ single crystals have also shown the occurrence of a 2D electron gas (2DEG) at their surface [5] (see Fig.), with high electron density (~10¹³ elec/cm²) even at room temperature, comparable to what achieved in AlGaN/GaN material systems. First-principles calculations based on the density functional theory and Boltzmann transport theory show that monolayered α-In2Se3 is also a great candidate for high-performance thermoelectric materials with the power factor PF and the figure of merit ZT as high as 0.02W/mK2 and 2.18 at room temperature [4].

In this context, the main goal of the internship is to go a step forward in the investigation of the thermoelectric properties of α-In2Se3 and the influence of the 2DEG formed at its surface on the electric and thermoelectric response. The student will fabricate α-In₂Se₃ based devices in a 4 contact configuration with a local gate for electric and thermoelectric investigation.  The activity will cover sample fabrication in clean room (dry transfer of the 2D material, e-beam lithography, etching, metal deposition …) and electrical measurements in a multi-probe station as a function of the temperature. The team has a strong expertise in the investigation of charge and spin transport in 2D materials and in clean room micro and nano fabrication techniques. This expertise will be exploited in the project.