1. Hybrid Molecular-Semiconductor Chemical Sensor 12.11.02 - Group Members: Robert Anderson, Fesaha Gebrehiwot, Stephanie Padilla, and Ari Vogel - Project Advisor: Dr. Trevor Thornton Hybrid Molecular MOSFET Chemical Sensor

2. Hybrid Molecular-Semiconductor Chemical Sensor Abstract This project aims to develop a Hybrid Molecular MOSFET chemical sensor that is highly integrated, inexpensive, and versatile. The sensor consists of a polarizable molecular monolayer that adheres to an underlying CMOS-compatible integrated circuit. The molecular monolayers are designed in such a way that their physical structure changes after exposure to the chemical of interest. The change in physical structure leads to a change in their electrical polarization, which is detected by a sensitive transistor immediately below the monolayer. A simple pH sensor was realized in order to demonstrate the working principles of the HM-FET.

3. Hybrid Molecular-Semiconductor Chemical Sensor Theory The HM-FET chemical sensor is based on a fully depleted Silicon-on-Insulator (SOI) MOSFET. Due to the buried oxide in an SOI structure, the substrate voltage can be used in place of a conventional gate voltage. This allows the active surface to be free of any metal contacts. The channel is 150nm thick, and therefore the threshold voltage of the device can easily be controlled by the charge accumulated on the surface of the device. As the charge increases at the surface, additional carriers are available to allow greater current flow. Also, the native oxide of the silicon channel can be used as a bonding film for attaching the monolayer to the device.

4. Hybrid Molecular-Semiconductor Chemical Sensor

5. Sensor Applications The HM-FET has a wide range of envisioned applications.  DNA decoder  Crime scene investigation  Medical applications  Chemical sensor  Planetary exploration  Detection of harmful natural gases  Detection of biological or chemical agents  pH sensor

6. Hybrid Molecular-Semiconductor Chemical Sensor Conclusion From the experimental and simulated results, a working pH sensor was constructed. The pH sensor demonstrates the working principles of an HM-FET by observing shifts in the threshold voltage when a charge is present at the surface of the device. The diverse applications of the HM-FET along with their benefits are evident, and therefore the team recommends that this design project be further pursued. The HM-FET can be used to make the world a safer and more educated place, and the technology is very close to being available to the public.

7. Hybrid Molecular-Semiconductor Chemical Sensor

8. Atlas Device Model

9. Hybrid Molecular-Semiconductor Chemical Sensor Matched Simulated vs. Experimental

10. Hybrid Molecular-Semiconductor Chemical Sensor Linear Relationship V th

11. Hybrid Molecular-Semiconductor Chemical Sensor Experimental (From B. Reddy)