Disc-shaped nanocrystal model for simulating the diffraction peak profile from a one-dimensional superlattice and its application to Pt/AlN superlattice films

On the basis of the film structure of a Pt/AlN multilayer film which exhibits a superlattice peak after annealing, a disc-shaped nanocrystal model is proposed for simulating the diffraction line profile from a one-dimensional superlattice. The proposed model demonstrates that a superlattice peak can arise even from just two disc-shaped nanocrystals and even with a large misorientation (a few degrees), provided both the thickness and the in-plane crystal size of the nanocrystals are of the order of nanometres. Using the model, the superlattice peaks from Pt/AlN superlattices are analysed quantitatively and the effect of annealing on the film is discussed.

Towards 3D image-based nanocrystallography by means of transmission electron goniometry

ABSTRACTIt is well known that the crystallographic phase and morphology of many materials changes with the crystal size in the tens of nanometer range and that many nanocrystals possess structural defects in excess of their equilibrium levels. A need to determine the ideal and real structure of individual nanoparticles, therefore, arises. High-resolution phase-contrast transmission electron microscopy (TEM) and atomic resolution Z-contrast scanning TEM (STEM) when combined with transmission electron goniometry offer the opportunity of develop dedicated methods for the crystallographic characterization of nanoparticles in three dimensions. This paper describes tilt strategies for taking data from individual nanocrystals “as found”, so as to provide information on their lattice structure and orientation, as well as on the structure and orientation of their surfaces and structural defects. Internet based java applets that facilitate the application of this technique for cubic crystals with calibrated tilt-rotation and double-tilt holders are mentioned briefly. The enhanced viability of image-based nanocrystallography in future aberration-corrected TEMs and STEMs is illustrated on a nanocrystal model system.