8. Summary and conclusions

An innovative single-atom transistor configuration is suggested, which can be simplified and simulated by a simple model. The model consists of a narrow conducting wire, a single-point defect, and an electric field. This device's configuration does not require fine atomic-size gate contact and atomic-size accuracy for positioning the single atom. The device's mechanism is not based on resonant tunneling, and therefore, high accuracy is less essential. The gate is a capacitor that can be considerably larger than the point defect. Moreover, it was shown that this device can be extremely fast with a time response much shorter than any cuttingedge transistor.

The temporal analysis reveals a clear advantage of this configuration over resonant-tunneling ones (like [10, 14]). In resonant-tunneling devices, the signal's extinction ratio depends on the resonance state's lifetime. That is, there is no "zerocurrent" in resonant-tunneling devices. The minimum current ("zero") is actually a tunneling current, which is inversely proportional to the resonance state's lifetime. Therefore, in resonant-tunneling devices, "fast device" and "low minimum

current" are competing demands. When seeking the former, one has to compromise on the latter, and vice versa.

No such compromise is required in the proposed transistor configuration since it has been shown that this configuration always keeps (at least theoretically) extinction ratio of 100%.
