Length scale discontinuities between non-crystalline and nano-crystalline thin films: Chemical bonding self-organization, broken constraints and reductions of macroscopic strain

Abstract

This paper identifies different length scales, λs, for strain-reducing chemical bonding self-organizations in non-crystalline and nano-crystalline thin films. Length scales have been identified through spectroscopic studies, thermal heat flow measurements, and are analyzed by semi-empirical bond-constraint theory (SE-BCT) and symmetry adapted linear combinations (SALC) of atomic states. In both instances, strain-reducing self-organizations result in reduced defect densities that are minimized and enabling for device applications. The length scale for non-crystalline solids extends to at most 1nm, and more generally to 0.5–0.8nm; however, there are two different length scales for nano-crystalline films: one is <2.5nm and is characterized by suppression of longer range ordering required for complex unit cells based on more than one primitive unit cell and the second is >3–3.5nm and defines a regime where complex unit cells, comprised of two or more primitive unit cells are stabilized and the electronic structure is changed.