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2.10 Summary

Electrons follow the energy landscape of the circuit, which is formed by the network of interconnected quantum dots. With the voltage sources one deforms the energy landscape and thus controls the transfer of electrons. Depending on the material and size of the quantum dots, different components of the energy are dominating. Metal quantum dots larger than 3 nm in diameter and semiconductor quantum dots larger than 10 nm in diameter can be described sufficiently with the classical electrostatic charging energy. For smaller quantum dots the quantum confinement energy has to be taken into account.

Electrons move preferably to lower points in the energy landscape. The probability or rate of a transition from one location to another depends exponentially on the energy difference the electron experiences. The Coulomb blockade can be viewed as an electron trapped in a local minimum of the energy landscape. Co-tunneling events transport electrons from one local minimum to another lower lying minimum. Therefore, co-tunneling makes stable states instable and introduces errors in device behavior.

Christoph Wasshuber