Development of Induced Crystallization as a Pattern Transfer Mechanism for Nanofabrication

A novel pattern transfer technique, based upon direct contact between nanofabricated printheads and amorphous films/substrates is being developed. Transfer of features from printhead to substrate is via an induced crystallization mechanism, with a goal of controlling crystal nucleation at dimensions comparable to the printhead features. To realize such a printing mechanism, appropriate mediums/materials that can be crystallized through contact with the printhead elements must be identified. From a range of candidate materials we focus on Ge and Indium Tin Oxide (ITO) films grown by molecular beam epitaxy or sputtering. The crystallization may be induced directly by heating (thermally), pressure (mechanically), or electrical conduction through the contact points. Crystallization of many amorphous materials is known to be self sustaining (so called “explosive crystallization”), raising the need to identify mechanisms for abruptly stopping crystallization if feature dimensions are to be constrained. A set of amorphous or nanocrystalline samples have been studied during crystallization by a heated printhead fabricated with a Focused Ion Beam (FIB). A simplified continuum model suggests the feasibility of achieving lateral confinement of the induced crystallization. In order to characterize fully the transitional and final substrate states, real-time observation of nanoscale crystallization in the transmission electron microscope (TEM) is in progress. A special TEM goniometer is being developed which incorporates a piezoelectrically driven tip and a heating capability to enable observation of tip-substrate contact at elevated temperatures that should give invaluable insight into crystallization mechanisms.