Prof. Roberto Hiroki Miwa

Federal University of Uberlandia, Brazil
Full professor in the department of physics at the Federal University of Uberlândia-MG, Brazil, since 1995. I am currently working on computational simulations applied to material science, in particular solid interfaces (metal/semiconductor), surfaces (molecular self-assembly), and searching for exotic electronic properties on 2D systems.

Talk title: PtSe2/metal interfaces: electronic and eletronic transport properties, and the access to the topological gap in PtSe2[VSe] monolayer
Among the two-dimensional materials, platinum diselenide (PtSe2) has been the subject of several studies addressing applications in different areas, for instance, the development of electronic devices like 2D transistors and sensors. One important feature to take advantage of in nanoelectronics is (i) the tickness dependency of the bandgap of the few-layer systems of PtSe2. Meanwhile, (ii) recent theoretical study predicted the emergence of (topological) Quantum Spin-Hall phase in PtSe2-ML mediated by the presence of selenium vacancies, PtSe2[VSe]-ML [Nano Letters 21, 9398 (2021)]. Here, based on the density functional theory, in (i) we performed first-principles calculations of the structural, electronic, and electronic transport properties of the monolayer (ML), bilayer (BL) and trilayer (TL) of PtSe2 lying on the Au(111) surface, PtSe2-X/Au (X = ML, BL, and TL). We found the emergence of chemical interaction between the PtSe2 adlayer and the Au(111) surface, resulting in an ohmic contact, and the hole doping of PtSe2. The semiconductor PtSe2-ML becomes metallic in PtSe2-ML/Au, whereas, in PtSe2-BL/Au, the topmost PtSe2 layer, which is not in contact with the Au(111) surface, remains semi conductor. Further electronic transport calculations unveiled the tickness dependence of the electronic transmittance and the Schottky barriers along the PtSe2-X channels in contact with PtSe2-X/Au(111) leads. Based on the (present) atomistic understanding of the electronic properties of PtSe2-X/Au, we propose a heterostructure composed of PtSe2-TL intercalated by metallic contacts Au(111), Au/PtSe2-TL/Au, in which the metal-to-semiconductor transition can be carried out through mechanical strain. In (ii), we show that through a suitable choice of the metal contact, it is possible to control the access of the non-trivial gap in PtSe2[VSe]-ML. We believe that these findings are timely, bringing important contributions to the applicability of few-layer PtSe2 for developing 2D electronic devices.