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Surface doping of nano/mesostructured materials to promote and optimize chemi-transistor sensing performance represents the most advanced research trend in the field of solid-state chemical sensing.
In spite of the promising results emerging from metal-doping of a number of nanostructured semiconductors, its applicability to silicon-based chemi-transistor sensors has been hindered so far by the difficulties in integrating the composite metal-silicon nanostructures using the complementary metal-oxide-semi-conductor (CMOS) technology.
Moreover the possibility to control the morphology of the final sensing materials at the nano-scale, providing a route to outperform standard chemi-transistor sensors based on bulk materials, and perform sensing nano-materials with higher sensitivity towards chemical changes upon surface adsorption of molecules, which stems from affinity of their electronic structure with interacting molecules.
The ordered cocrystallization of nanoparticles into binary superlattices (NBSL) enables close contact of nanocrystals with distinct physical properties, providing a route to ’metamaterials’ design, where the final electrical properties depends on the morphology and the packaging of the final structure.
The development of novel nanostructured materials for gas-sensing applications based on the composite porous silicon/gold nanostructures (cSiAuNs) and binary nanocrystal superlattices of this thesis, as well as the integration of such new materials into transistor structures, well complies with the latest research trends in the sensor fields, and push research on gas sensors towards novel materials with advanced features. Engineering of morphology and metal-doping of the porous matrix and the binary nanocrystal superlattices, in terms of both composition elements and stoichiometry, would furthermore offer the possibility of achieving advanced sens- ing materials with self-tuning/self-repairing features.
Here we propose a facile and effective top-down method for the high-yield fabrication of chemi-transistor sensors making use of composite porous silicon/gold nanostructures (cSiAuNs) and semiconductor nanocrystals superlattices (SL) structure, acting as sensing gate. In par- ticular, we investigate the integration of those materials synthesized by metal-assisted etch- ing (MAE) and colloidal synthesis, respectively, in solid-state junction-field-effect transistors (JFETs).
The final chemi-transistor sensors are CMOS compatible, operate at room temperature, and are reliable, sensitive, and fully recoverable for the detection of NO2 at concentrations between 100 and 500 ppb, up to 48 h of continuous operation.