Au Nanogap Research Articles

Molecular sensing with the tunnel junction of an Au nanogap in solution

The tunnel junction of a gold nanogap was fabricated electrochemically for a molecularsensing device in solution. The tunnel junction was sensitive enough to detect the variationof a potential barrier within the nanogap, such as the chemical adsorption ofmolecules. By monitoring the variation of the tunneling current, which represents thechange of a potential barrier due to molecular adsorption, the molecules could bedetected.

Fabrication of Nano-Gap Electrode Pairs Using Atomic-Layer-Deposited Sacrificial Layer and Shadow Deposition

We propose a new fabrication process of nano-gap electrode pairs using an atomic-layer-deposited (ALD) sacrificial layer and the shadow deposition technique. In this process, gap width can be precisely controlled by the number of deposition cycles of the ALD process, whereas junction area is defined by the deposition angle of the second electrode material through an overhanging shadow mask on top of the first electrode. In comparison with our previous method, process reliability has been highly improved because the unintentional deposition of the second electrode material on the sidewall of the first electrode is completely prevented. We have fabricated 10 ×10 arrays of n-type polycrystalline silicon (n-poly-Si)/Au nano-gap electrode pairs with gap widths of 6 and 9 nm, which show good insulating properties at room temperature.

Fabrication of single electron transistors with molecular tunnel barriers using ac dielectrophoresis technique

We demonstrate the fabrication and characterization of single electron transistors composed of Au nanoparticles and insulating molecular tunnel barriers. We fabricated these devices by forming a 1,8-octanedithiol self-assembled monolayer on Au nanogap electrode pairs and by bridging them with colloidal Au nanoparticles using ac dielectrophoresis. We observed the typical characteristics of these single electron transistors at the temperature from 4.2 to 300 K. The measured data were consistent with the orthodox theory of Coulomb blockade.

Electrical conduction of thiol modified 60bp Poly(dG)-poly DNA molecules through Au nanoparticles

A novel transport measurement scheme of 60 base pairs of poly (dG) -poly (dC) DNA molecules using Au nanoparticles is devised and implemented. Thiol (-SH) terminations are synthesized at both 5’ and 3’ ends of the double stranded DNA molecules and they can be chemisorbed on the Au surface through sulfur atoms by covalent bonding. These thiol-modified ends make chemical bindings with Au nanoparticles and Au nano-gap electrodes, forming a stable electrode-DNA-nanoparticle-DNA-electrode conduction channel. This transport channel is self-formed and is stable due to robust bonding of thiol and Au. The current-voltage characteristic measured from our device shows a nonlinear behavior and the voltage gap is comparable to the result of previous experiment using the same molecules. This self-trapping method by thiol modified DNA molecules would also be a promising technique for efficient nanoparticle trapping.

A Self-Assembled Nano Optical Switch and Transistor Based on a Rigid Conjugated Polymer, Thioacetyl-End-Functionalized Poly(para-phenylene ethynylene)

A nanometer-scale optical switch and transistor were fabricated with thioacetyl-end-functionalized poly(para-phenylene ethynylene)s and Au nanogap electrodes by self-assembly. With photoirradiation, the switch can be switched on/off quickly with a switching ratio as high as 1000. Moreover, the device works well as a p-type transistor. With an increase in gate bias, strong conductance oscillation was observed in this self-assembled transistor (under low temperature 147 K), which is very likely due to single-electron charging oscillations arising from electron tunneling through the nanometer-scale transistor.