Tunable coupling capacitance of double-quantum-dot single-electron transistor with multiple gates

Double quantum dot (DQD) devices can be usable for a single electron pump or a qubit, in which capacitive coupling between the dots plays an important role. In these applications, at the same time, dot sizes and the number of electrons in the QDs should be also controlled. Here, we fabricated multi-gate Si DQDs surrounded by the almost hard-wall potential by the use of pattern-dependent oxidation, and succeeded to control the coupling capacitance by changing the voltages applied to the gates. In other words, the potential barrier height and width between DQDs can be tuned by changing gate voltages.