Order from disorder: guiding nanoscale crystallization of amorphous solids

Interfaces, stress, and precrystalline order have important roles in the nanoscale crystallization of amorphous solids. Crystallization processes at this scale impact fields including electronic materials, biomineralization, and atmospheric science. Similar fundamental nucleation and growth phenomena occur in a range of systems from complex oxide electronic materials to water and ice. In each case, crystallization is influenced at crystalline/amorphous interfaces by structural templating leading to the nucleation of crystals and to the selection of specific crystalline polymorphs. In addition to interface effects, the structural similarity between individual polymorphs and the amorphous form can lead to preferential nucleation of these polymorphs away from interfaces. A common feature among crystallizing amorphous materials is that the timescale that characterizes crystallization are longer than the Maxwell stress relaxation time. The nanoscale distribution of stress resulting from the density difference between amorphous and crystalline induces defect formation phenomena that are similar in multiple systems. Similarly, the timescale for relaxing chemical inhomogeneity can be sufficiently long that chemical profiles established within nanoscale amorphous layers are incorporated into the crystallized solids. Finally, there are indications that it is possible to design forms of amorphous materials to include structural chemical or structural features that influence subsequent crystallization phenomena. Further directions in influencing crystallization at the nanoscale can include the development of amorphous materials with these specific forms of chemical or structural order in the amorphous material, the design of nanoscale environments controlling the stress distribution, and extending similar concepts to a wider range of compounds.