Fabrication of a highly controllable Si-MOS quantum dot device

Integrating a micro-magnet (MM) to a quantum dot (QD) is a promising route to realize highly coherent control of single electron spins on a chip [1]. In order to apply this spinmanipulation technique to Si QDs, miniaturizing the QD while maintaining the controllability is essential to lift the valley degeneracy [2]. Here we fabricated a MOS-QD under a thin gate oxide integrated with Al gates to accumulate and define a QD. At 4.2 K, we observed Coulomb diamonds indicating the formation of a QD with a charging energy E_C of 15 meV. This relatively large E_C for gate defined QDs encouragingly suggests that this device structure enables to reduce the size of fully-tunable QDs. We also claim that this structure with thinly oxidized Al gates is compatible with electron-spin-resonance (ESR) experiments with MMs.