[14a-D62-1~12] 9.2 Nanowires and Nanoparticles

▲ [14a-D62-11] Field-Effect Transistors of Lead Chalcogenides Quantum Dot Nanocubes and Core@Shell Nanocrystals Assemblies

〇Satria Zulkarnaen Bisri¹, Daiki Shin², Maria Ibanez^3,4, Maksym Kovalenko^3,4, Yoshihiro Iwasa^1,2 (1.RIKEN-CEMS, 2.Univ. Tokyo, 3.ETH Zurich, 4.EMPA)

Keywords:colloidal quantum dots, colloidal nanocrystals, field effect transistors

Colloidal quantum dots (CQD) assemblies emerge as a new type of hybrid solid thin films that exploit the size-dependent quantum confinement properties of the individual QDs: energy bandgap variations and formation of discrete energy sub-bands. , The materials choices for colloidal QD electronic devices are still limited. Currently, for solar cells and photodetector applications, mostly are exploiting the well-known quasi-spherical PbS QDs. Efforts to study charge transports of PbS QDs using field effect transistors have made significant progress. Meanwhile, the properties of many other QDs, including the other lead chalcogenides, have yet to be investigated. Here we demonstrate FETs of colloidal QDs using various form factors of lead chalcogenide nanocrystals in order to clarify the influence of the shapes, couplings, and assembly conformations towards the charge carrier transport properties. Electron transport characteristics of quasi-spherical QDs and nanocubes of PbS and PbTe are compared using both conventional approach to fabricate solid gate FETs as well as FET using ionic liquid gate. The surface stoichiometry difference as well as the variations of assemblies induced by the usage of crosslinking ligands make variations of intrinsic carrier density and transport behavior. Some of them behaves as ambipolar transport, while the others shows quasi-metallic behavior that weakly modulated by gate voltage. In addition, we also show the first demonstration of FETs using core@shell QDs, in which PbTe is alloyed inside PbS shell. the utilization of ionic liquid gating also unravel peculiar properties of core@shell QDs that is different from single compound QDs. These findings will broaden the material choices for developments of various electronic devices based on QD assemblies. Furthermore, some of them are also prospective to investigate the physics at nanoscale assemblies, e.g. thermoelectricity, emerging magnetism or superconductivity.