| The focus of this dissertation is to explore novel effects in metal nanofilms, particularly, the quantum size effect (QSE) and strain effect, through the methodology of first-principles density functional theory (DFT) calculations. The QSE has already been shown to affect many properties of metal nanofilms, such as surface energy, work function, and even superconducting transition temperature. Based on the extensive DFT calculations that I carried out in the last five years, we further demonstrate that several new properties of metal nanofilms, including edge/surface stress, elastic constants, and adatom-adatom binding energy can also be modulated by QSE to exhibit strong thickness dependence. Specifically, this dissertation includes the following five chapters of topics: (1) interplay between strain effect and quantum size effect in metal nanofilm; (2) quantum manifestation of elastic constants in nanostructures; (3) QSE on adatom-adatom binding energy and island nucleation; (4) quantum manifestations of graphene edge stress and edge instability; (5) bistability of nanoscale islands induced by anisotropic stress. Overall, my dissertation research not only has explained a number of puzzling experimental observations and resolved some existing controversies, but also made some interesting theoretical predictions in novel quantum aspects of thin film growth and nanomechanics. It is my hope that these studies will further our fundamental understanding of QSE and strain effect in metal nanofilms, with broader implications in other low-dimensional nanostructures as well as in potential technological applications of nanostructures. |
