Cross beam lithography (FIB+EBL) and dip pen nanolithography for nanoparticle conductivity measurements

Focused ion beam lithography is a very powerful technique for directly writing patterns on many substrates, it is a maskless and resistless technique that allows a very wide range of applications, providing a resolution down to 10nm. Using a system composed by a 30keV gallium ion beam column plus a 30keV electron beam, nanogaps for electrical measurements of nanoparticle were fabricated with a resolution down to the nanometer scale, by exploiting FIB milling (FIBM) and electron beam lithography (EBL). Starting from prepatterned samples a square pattern reduces the width of the gold wire and a narrow line pattern opens a gap of less than 7nm. Electrical measurements and AFM tapping mode imaging were performed on the gaps. We patterned the ends of the gold leads with dip pen nanolithography using mercapto-undecanol (MUD) to form a bond between the nanoparticle and the alcohol group attached to the gold surface. After this assembly, devices showed an increase in conductivity (10–100-fold increase). Measuring the device again one week later, we saw almost no change in conductivity, showing that we deposit a multiparticle cluster and measure its conductivity.