Low-Dimensional Material Devices For Atomic Defect Engineering, Ionic And Molecular Transport

With the advancement of nanofabrication techniques and the growth and synthesis of novel low-dimensional materials, such graphene and transition metal dichalcogenides, it is possible to probe the fundamental principles of ion and molecule transport down to the single-atom scale. Understanding these ionic and atomic interactions during molecular transport at an atomic level play a pivotal role in developing solid-state aquaporins or bio- mimicking artificial membrane proteins channels. Apart from biological processes in living cells, ionic transport plays a vital role in membrane-based technologies such as water purification, desalination, separation techniques and energy harvesting. This thesis focuses on developing low-dimensional devices and creating sub-nanometer pores or point defects for exploring molecular and ionic transport phenomena at an atomic scale. Additionally, defect engineering of such point defects also has potential quantum applications, including quantum sensing and computation. First, I discuss the fabrication process of these low-dimensional devices, including 2D materials growth, transfer with the help of nanofabrication techniques and various characterization modes. Further, in this regime of angstrom-scale confinements, I investigate ionic transport phenomenon in monolayer 2D materials with single sub-nanometer pore and an ensemble of sub-nanometer pores and report experimental results showing strong deviation from continuum physics. Macroscopic quantities such as bulk ion concentration for these angstrom-size systems become insufficient to explain features of the measured ion conductance and its scaling with experimental parameters such as ion concentration and surface charge of the pore (edge atoms).