Label-free and real-time immunodetection of the avian influenza a hemagglutinin peptide using a silicon field-effect transistor fabricated by a nickel self-aligned silicide process

Electrical immunodetection of the avian influenza A (H5N1) hemagglutinin (HA) peptide, the IN peptide, with anti-HA antibody was demonstrated using a field-effect transistor (FET) with an n-type silicon (Si) channel and a nickel (Ni) self-aligned silicide source/drain that was fabricated by a conventional top-down process. The specific binding of the IN peptide with anti-HA antibody in phosphate buffered saline (PBS) occurs on the patterned SiO ₂ surface through covalent linkage. Positive ions in the buffer create majority carriers in the n-type Si channel, leading to a rapid increase in current across that channel. However, specific binding of the negatively charged antigens on the SiO ₂ surface overlaying the Si channel results in the reduction of electrons induced in the Si channel by the positive ions, causing a significant decrease in the channel current. The settling time for obtaining a stable signal change, driven by the negatively charged antigens bound to antibody, extrapolates to approximately 32 s.