טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentTeitz Liora
SubjectTheoretical Investigation of Two-Dimensional Dielectric
Materials for MoS2-Based Field-Effect Transistors
DepartmentDepartment of Materials Science and Engineering
Supervisor Professor Maytal Caspary-Toroker


Abstract

The size of the Field Effect Transistor (FET) has been decreasing exponentially each year to keep up with the demands of the microelectronic industry. However, this scaling is now reaching its limits due to the performance of the materials currently used in the FET. In this aspect, attention has recently been turning towards twodimensional (2D) materials. Two-dimensional dielectric materials that can inhibit electronic leakage are vital for developing next-generation all-2D electronic devices. However, few comprehensive studies of the atomistic nature of 2D insulating dielectrics currently exist. In this work, computational design strategies based on Density Functional Theory and quantum dynamics simulations are used to assess the charge permeability through dielectric materials. A useful protocol for discovering promising dielectrics is described. The protocol is demonstrated on promising candidates including hBN, which is the common choice as a 2D dielectric material, and 2D SiC and BeO, which are materials that have not yet been used as gate dielectrics. The interfaces of these materials with MoS2, currently the most common channel material in all-2D transistors, are studied. The atomic structures of the interfaces are determined and their stabilities are evaluated by studying the interface formation energies and the presence of stress/strain at the interfaces. The interface electronic structures are characterized by studying the band structures, band offsets, and charge transfer at the interface. These important quantities reveal that all three materials chosen are good dielectric materials, but SiC is the poorest among them, BeO has the best insulting properties as a monolayer and hBN prevents the most charge leakage at the interface. It is shown how this protocol can also consider the effects of external potentials and temperatures.