1. Introduction

Diffusion on the nano/atomic scales in multilayers, thin films has many challenging features even if the role of structural defects can be neglected and 'only' the effects related to the nano/atomic scale raise. Different examples for diffusional nanoscale effects, we have discovered in the last ten years, are summarized in this document.

• We show that interface shift kinetics may differ form the ones predicted by continuum approximations (anomalous diffusion kinetics) even in such cases in which nobody thought before, e.g. in completely miscible systems.

• We show that in solid state reaction, reaction layers form and start to grow highly off-stoichiometricaly and an initially existing stoichiometric compound layer may dissolve then re-form off-stoichiometricly. Our findings are of primary importance for nanotechnologies where early stages of SSR are utilized.

• We also show that an initially diffused interface may sharpen even in completely miscible systems. This phenomenon could provide a useful tool for the improvement of interfaces and offer a way to fabricate of e.g. better X-ray or neutron mirrors, microelectronic devices or multilayers with giant magnetic resistance.

The strength of this work is that the experimental results are supported by intensive theoretical/computer simulation activity. Usually first we discovered a new effect, then we tried to find its experimental evidence. Sometimes, however, it happened that the interpretation of the experimental results demanded theoretical/computational supports.