Tuning of channel conductance of au nanowires using ultrafast electromigration controlled by a field-programmable gate array

Feedback-controlled electromigration (FCE) has been employed to control metal nanowires with quantized conductance and to create nanogaps. However, the formation of nanostructures by conventional FCE procedure using a microprocessor-based controller with a general purpose operating system (GPOS) is considerably slow process. Therefore, we proposed an ultrafast FCE method using a field-programmable gate array (FPGA) to immediately and precisely control the channel conductance of Au nanowires. In this report, we study the tuning of quantized conductance of Au nanowires by ultrafast FCE using FPGA-based control system with a constant-voltage (CV) method. First, in the FCE procedure, preset values of quantized conductance of Au nanowires were defined as 25 G₀, 15 G₀, and 5 G₀ (G₀ = 2e²/h). The conductance of the Au nanowires during FCE procedure decreased until the conductance reached the preset values within an order of a millisecond. Furthermore, the quantized conductance plateaus of the Au nanowires were precisely controlled by the CV procedure with the preset values of 15 G₀ and 5 G₀. These results imply that the combination of FCE and CV procedures with FPGA-based control system can precisely and stably tune the channel conductance of Au nanowires with millisecond-scale resolution.