Bridge-Enhanced Nanoscale Impedance Microscopy on Organic Light-Emitting Diodes,Public Deposited
The use of a variable resistor-capacitor (RC) bridge circuit was previously reported to be a viable solution to the spurious contribution of fringe capacitance during nanoscale impedance microscopy (NIM). In this paper, a refinement of this technique combined with standard NIM is presented as an impedance characterization tool for organic light-emitting diodes (OLEDs). In this technique, a sinusoidal bias is split into two equal branches, which are subsequently sent to the tunable RC circuit and the sample. By balancing the phase and magnitude of the two branches, the contribution to the current through the sample/tip junction can be directly monitored. To demonstrate the improved detection limit offered by this technique over more conventional NIM, conductive AFM measurements were performed on 8 µm by 8 µm OLED devices, demonstrating significant improvement in resolution in the current and phase maps. This paper also suggests possible future research that is necessary to fully enable impedance spectroscopy at the nanoscale.