Nanoscale three-dimensional structural and chemical relationships using FIB tomography.

摘要

The Ga+ Focused Ion Beam (FIB) has become an important tool in materials science for studying and modifying materials systems at the micro and nanometer level. The technique, due to its ability to perform precision in-situ milling, has been extended to studying three-dimensional structural and chemical relationships. With the help of computer algorithms for processing data and graphics packages for display, three-dimensional systems can easily be reconstructed and the structure interrogated to obtain both qualitative and quantitative information. It is possible to study features at spatial resolutions at the tens of nanometers level and volumes with dimensions of up to tens of microns. This allows the reconstruction of many systems in the size range important to nanotechnology.;Three-dimensional reconstructions can provide a better understanding of the fundamental mechanisms in a range of complex systems. We have studied the self-assembly in epitaxial semiconductor quantum dot systems. Multi-layered structures, known as superlattices, are known to organize so that the Quantum Dots (QDs) on successive layers nucleate and grow above the buried QDs. The self-assembly occurs such that the QDs in the later layers deviate from being centered on the lower QDs to positions that more evenly space the quantum dots. Using the three-dimensional reconstructions, we have compared the actual structures with theoretical models and shown where the models agree and deviate from the actual structures.