Abstract
A large variety of two-dimensional (2D) materials exhibit unique physical and chemical properties. Detailed knowledge of the structure and dynamical properties of these intriguing modern materials is essential for developing a fundamental understanding of their properties. In this thesis, investigations of the structure, morphology, and dynamics of 2D materials on metal substrates have been carried using low energy electron microscopy (LEEM) and diffraction (LEED). The interplay of complementary anisotropic strain relief by nano-wrinkles and substrate-induced corrugation in graphene on a vicinal copper surface is found to induce one dimensional nano-wrinkle morphology perpendicular to facets/steps on the underlying substrate. The residual compressive strain is determined using high spatially-resolved μLEED measurements to be 0.7% and 0.3% perpendicular to nano-wrinkles and facets, respectively. The substrate facets that induce corrugation in graphene are identified using LEED facet spot analysis to be (110), (531), (351) and (665). This behavior contrasts with random wrinkle network that was observed in the absence of substrate-induced corrugation on a flat copper surface. We also observed the formation of a new oxygen-deficient 2D copper oxide structure at the Cu(111) surface that exhibits intriguing domain pattern formation and dynamical behavior. This structure may be attributed to a honeycomb-like Cu2O(111) surface oxide layer with a periodic array of Stone–Wales defects. Depletion of oxygen by thermal desorption is accommodated by the formation of oxygen-free regions that coexist with the oxide structure in a sequence of island, stripe and inverse island patterns with decreasing oxygen content. Several sequential evolution mechanisms of the characteristic length scale are identified by rescaling analysis of the structure function that is measured from observations of phase separation during cooling. Further development of LEEM image formation theory was also performed to support extension of the work described in this thesis in the future. The extended Fourier Optics (FO) approach for modeling image formation in aberration-corrected LEEM is presented. This work broadens our capabilities to understand the origins of LEEM image contrast and to perform quantitative evaluation of contrast.