Title: Electric Field-Induced Non-Volatile Doping in 2D Field Effect Transistors (FETs) for Secure Polymorphic Circuits

Abstract: Hardware security comes at a high price in the U.S. at $200 billion annually. Polymorphic electronics provide a potential solution to hardware security threats by preventing unauthorized parties from accessing circuitry information through, for example, reverse engineering. The goal of this work is to obscure a device’s function by taking advantage of electric double layer (EDL) gating to reconfigure NAND gates to and from NOR gates on-demand. The key innovation is a custom-synthesized polymer electrolyte that reacts under an electric field (~V/nm) created by the EDL, retaining charges in the channel by crosslinking the solid polymer electrolyte (SPE). The first EF-sensitive reaction explored in this work is the Menshutkin reaction within a polyethylene oxide-based copolymer. Chemical and thermal characterization will be presented. 

Aim 1 of this proposal is to demonstrate non-volatile doping of graphene field effect transistors (GFETs). The first results indicate that positive voltages induce non-volatile n-type doping (~10¹² cm^-2).  When followed by a negative programming voltage, the shift becomes less n-type. Within Aim 1, additional crosslinking mechanisms are proposed including Diels-Alder and azide-alkyne cycloadditions. In Aim 2, temperature modulation of a dual-gated FET is used to isolate the impact of trapped ions doping the surface from free ions in the bulk. Preliminary results are consistent with those from the single-gate in Aim 1. The proposed work of Aim 2 includes quantifying sheet carrier densities using Hall measurements, measuring doping retention, exploring the effect of salt concentration on doping and retention, and demonstrating non-volatile doping on 2D semiconductors. Aim 3 is to demonstrate application in logic inverters and create polymorphic circuits where the same hardware can dynamically reconfigure to perform multiple logical functions. Aim 4 focuses on crosslinking the ions themselves (as opposed to the polymer matrix in which they are solvated) via doubly polymerization ionic liquid (DPIL). While the DPILs have already been shown to lock EDLs thermally and by ultraviolet light, preliminary evidence suggests they are also electric-field sensitive. The proposed work for Aim 4 consists of quantifying the ion-locking effect using an electric field, quantifying sheet carrier densities, and measuring doping retention.

Committee Chair:

Dr. Susan Fullerton

Department of Chemical and Petroleum Engineering

Department of Electrical and Computer Engineering

University of Pittsburgh

Committee Members:

Dr. James McKone

Department of Chemical and Petroleum Engineering

University of Pittsburgh

Dr. Lei Li

Department of Chemical and Petroleum Engineering

University of Pittsburgh

Dr. Nathan Youngblood

Department of Electrical and Computer Engineering

University of Pittsburgh