Logic gates constructed on CdS nanobelt field-effect transistors with high-κ HfO2 top-gate dielectrics

A high-performance NOT logic gate (inverter) was constructed by combining two identical metal-insulator-semiconductor field-effect transistors (MISFETs) made on an individual CdS nanobelt (NB). The MISFETs, which used high-kappa HfO2 dielectrics as the top-gate insulator layer, show excellent performance, such as low threshold voltage (similar to-0.1 V), a high on/off ratio (similar to 10(8)), small subthreshold swing (similar to 65 mV dec(-1)) and threshold voltage hysteresis (similar to 30 mV). The supply voltage for the inverter can be as low as 1 V with a voltage gain as high as 14. When the supply voltage is 7 V, the voltage gain is 72, which is the best reported value, as far as we know, for the inverters based on NB/NW n-channel MISFETs. Besides, the inverter can work in a larger input range with highly stable output voltages. Their high output voltages can make full use of the supply voltages, and their low output voltages can be close to zero. NAND and NOR logic gates have been constructed by assembling three such CdS NB MISFETs, which show high performances as well. The operating principle of the inverter is discussed in detail.