Mechanically-controlled break junction MCBJ

An alternative method to position two electrodes at nanometer distances apart is the mechanically-controlled, break junction (MCBJ) technique. An ultra-thin, notched Au wire on a flexible substrate can be broken reliably by pushing on the Au with a piezoelectric piston, cracking the Au (Fig. 4). This produces a gap between the Au shards whose size can be finely varied to 1 A by a piston or control rod [46, 47]. When UE molecules with thiol groups on both ends are present in a surrounding solution, the gap can be adjusted until the molecules can span it. A dilute solution means the number of spanning molecules will be small, and the least-common-multiple of current flow among many junctions indicates those spanned by a single molecule [47]. 

Fig. 4 Design of the Mechanically-Controlled Break Junction (MCBJ) technique...

Fig. 2 (a) Schematic representation of a mechanically controlled break junction (MCBJ). The inset shows the SEM image of a nanofabricated gold bridge [40]. (b) Principle of an STM-based break junction experiment (STM-BJ)... 

Charge transport in Au alkanedithiol Au junctions was measured with a variety of techniques. These include mechanically controlled break junctions (MCBJ [213], STM [205,208,270-275] and conducting AFM break... 

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