Electron paramagnet resonance of electron states in two-dimensional quantum dot arrays

Abstract

Electron paramagnetic resonance and spin echo methods are used to probe the spin dynamics in two-dimensional quantum dot (QD) arrays with different shape of nanoclusters. Two types of QD structures were investigated: 1) with single shaped QDs (hut-clusters having the ratio of height h to lateral size l, h/l = 0.1), and 2) with two groups of QDs, hut- and dome-clusters (h/l = 0.2). Both types of structures demonstrate the EPR signals from electrons localized in QD layers. The orientation dependence of EPR line width for first type structures is well described by the model of spin relaxation through precession in the effective magnetic field, arising during tunneling between QDs due to structure-inversion-asymmetry. In the experiments on structures with dome-clusters the additional peculiarity, which cannot be explained within the framework of precession model, is observed. The different orientation dependencies can be explained by different localization degree of electrons in the investigated structures. Spin echo measurements provide the longest spin decoherence time for structures with single shaped QDs.