Silicon nanogaps for integrating molecular devices
Conference poster, 2003
We are presenting a silicon structure constituting a vertical nanogap. Nanogaps are needed for connecting molecules and for measuring their transport properties. The main advantage of our structure is the CMOS compatible processing, showing excellent reproducibility. Gaps in the range of 3-15 nm have been fabricated. The structure is made from a silicon wafer covered with a thin layer of silicon dioxide (determining the gap size) and a top polysilicon layer. A trench is etched so the stack is reached from the side, and then the insulating silicon dioxide layer is partially removed by selective etching. Towards integration of molecular devices into CMOS technology, the challenges we face include attachment of different types of nano components such as molecules, clusters and nano crystals to the silicon/silicon dioxide surface, control of the surface leakage and control of the tunneling through the oxide.
Study on solvents confirmed no predominant surface leakage induced by the presence of solvents like Toluene and Chloroform. From the experiments performed by insertion of conjugate molecules (derivative of terthiophene in this case) in gaps revealed significant increment of the current at low bias but at high bias, the tunneling current through the oxide smears out the effect. The surface leakage was in this case found to be high with respect to the virgin sample. Measurements on CdSe nanocrystals showed a strong impact on the current at the first voltage sweep but this effect is not stable for the subsequent sweeps. Functionalization of the surface prior to insertion of molecules or clusters is preferable.