Deterministic Epitaxial Growth of van der Waals Monolayer Lattices

Abstract

Deterministic epitaxial growth of atomically thin two-dimensional (2D) materials, especially three-atom-thick monolayer (ML) transition metal dichalcogenides (TMDCs), plays an important role in the realization of ultra-scaled electronic circuits. Nondeterministic growth can induce unexpected grain boundaries (GBs) as well as desired inherent lattices. The GB, which forms where two adjoining crystals merge with different orientations from each other, can possess new physical properties that differ from intrinsic properties of the crystal. Thus, suppressing such GBs to realize the intrinsic properties of the material or controlling GBs in a desired form is essential for the development of next-generation semiconductor platforms. This dissertation focuses on the deterministic epitaxial growth of 2D lattices, especially mirror twin boundary (MTB) lattices and single crystal lattices. First of all, ML TMDCs and their representative growth methods will be summarized in Chapter I. Then, in Chapter II, the epitaxial relationship between the growing material and the substrate will be briefed. Next, the lattice of 2D materials, including inherent lattices and MTB lattices, will be introduced in Chapter III. Based on these, deterministic one-dimensional (1D) metallic MTB lattices are realized on c- plane sapphire substrates by van der Waals epitaxy (in Chapter IV). Such MTBs have been applied as the ultra-scaled gate. In addition, inherent single crystal lattices are achieved on vicinal c-plane sapphire substrates by vicinal epitaxy (in Chapter V). Such uniform and high-quality single crystals have enabled the growth of single crystalline textures even on amorphous substrates.