Insulator-protected mechanically controlled break junctions for measuring single-molecule conductance in aqueous environments
N. Muthusubramanian (TU Delft - Applied Sciences)
E. Galan
C. Maity (TU Delft - Applied Sciences)
R. Eelkema (TU Delft - Applied Sciences)
F. C. Grozema (TU Delft - Applied Sciences)
H. S J Van Der Zant (TU Delft - Applied Sciences)
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Abstract
We present a method to fabricate insulated gold mechanically controlled break junctions (MCBJ) by coating the metal with a thin layer of aluminum oxide using plasma enhanced atomic layer deposition. The Al2O3 thickness deposited on the MCBJ devices was varied from 2 to 15 nm to test the suppression of leakage currents in deionized water and phosphate buffered saline. Junctions coated with a 15 nm thick oxide layer yielded atomically sharp electrodes and negligible conductance counts in the range of 1 to 10-4 G0 (1 G0 = 77 μS), where single-molecule conductances are commonly observed. The insulated devices were used to measure the conductance of an amphiphilic oligophenylene ethynylene derivative in deionized water.