Gold Nanoparticles Monolayer Based Field-Effect Molecular Sensors

The rapid and efficient sensing mechanism of molecules and bimolecular species is crucial for healthcare, biomedical, and safety applications. Such sensors need to be robust and able to measure low concentrations of molecular species. Utilizing the intriguing effect of the enhanced electric field from charged gold nanoparticles (Au-NPs), due to their extremely small size, on the Schottky barrier narrowing and the energy band bending at the interface with Si substrates, a novel sensitive molecular sensor is developed, and presented herein. This is achieved by forming a strip of Au-NPs monolayer between two metal electrodes on a thin native oxide layer (≈2nm), covering the surface of an n-type silicon substrate. The high electric field on the negatively charged monolayer of Au-NPs leads to the depression of the conduction band, thus a tunneling channel of electrons is formed under the monolayer of NPs and beneath the silicon oxide layer. The depth of this tunneling channel can be regulated by modulating the net charge, hence the electric field, on the NPs when they are exposed to various polar or charged molecules. This effective nano-sensing platform can be explored for the detection and analysis of various molecules of interest.