Studies of Molecular Precursors Used in FEBID Fabrication of Nanostructures

The adoption of nanotechnology is increasingly important in many aspects of our daily life influencing the clothes we wear and most of the electronic devices we use while also underpinning the development of drugs and medical techniques that we will need at some point in our lives. The methods by which nanoscale devices are fabricated is changing from a 'top down' etching based procedure to a 'bottom up' molecule by molecule deposition and assembly. The focus of the present research is the development, design, and analysis of new precursors for focused electron beam induced deposition (FEBID) and extreme ultraviolet nanolithography (EUVL) through a large pool of experimental and computational resources. The research is divided into two areas: gas - phase analysis of precursors (largely used for fragment and radicals' analysis, and molecular design) and surface and deposition science (physical deposition of precursors, simulation analysis of surface - molecule interactions and characterization of deposition processes to obtain optimal process parameters for molecular structures). It is necessary to collect data such as cross sections of electron - molecule interactions e.g., dissociative ionization (DI) and dissociative electron attachment (DEA) to provide accurate simulations that can be used to improve the FEBID and EUVL while understanding surface processes such as molecular absorption and diffusion to determine the structure and purity of the nanostructures formed by these methods. The objective of this thesis is to provide a gas - phase and deposition analysis of potential and widely used precursors for FEBID and EUVL at the nanoscale. To achieve this the experimental technique of velocity sliced map imaging (VsMI) was used in conjunction with theoretical tools such as density functional theory (DFT) simulations using Gaussian 16 software and evaluation of cross-section data for molecular dissociation at low electron energies of 0 - 20 eV using Quantemol-N. Results of the gas - phase analysis of negative ionic fragments formed by DEA and DI with their appearance, dissociation and ionization energies, angular distributions and kinetic energies, cross-sections for DEA fragmentation at low energy and excited states calculations at values up to 10 eV are presented. These results are used as the inputs to the models of the FEBID processes. The electronic, structural, and kinetic properties of several FEBID precursors are explored, and FEBID method used to create nanostructures using a Zeiss MeRiT SEM with GEMINI column operated at 20 kV. Analysis of the deposits was performed using EDX and atomic force microscopy (AFM) analysis as well as electron stimulated desorption (ESD) and temperature programmed desorption (TPD). Complementary simulations of the dynamics of processes at the surface were studied using MBN Explorer and surface - molecule interactions with great results in simulating the deposition process of islands and structures (results presented in Chapter 8).