Integrating Two-Dimensional Nanomaterials and Molecular Dielectrics for Radiation-Hard Non-Volatile Memory

The coupling of hybrid organic-inorganic gate dielectrics with emergent unconventional semiconductors has yielded transistor devices exhibiting record-setting transport properties. However, extensive electronic transport measurements on these high-capacitance systems are often convoluted with the electronic response of the semiconducting silicon substrate. In my first publication, we demonstrate the growth of solution-processed zirconia self-assembled nanodielectrics (Zr-SAND) on template-stripped aluminum substrates. The resulting Zr-SAND on Al structures leverage the ultrasmooth (r.m.s. roughness < 4 Å), chemically uniform nature of template-stripped metal substrates to demonstrate the same exceptional electronic uniformity (capacitance ~ 700 nF cm-2, leakage current < 1 A cm-2 at -2 MV cm-1) and multilayer growth of Zr-SAND on Si, while exhibiting superior temperature and voltage capacitance responses. These results are important to conduct detailed transport measurements in emergent transistor technologies featuring SAND as well as for future applications in integrated circuits or flexible electronics. Atomically thin MoS2 has generated tremendous interest as a nanomaterial for emerging electronic applications. Its low-dimensional nature and potential for low-power electronics are particularly appealing for space-bound electronics, motivating the need to develop a fundamental understanding of the response of MoS2-based electronic devices to the space radiation environment. In my second publication, we gauge the response of MoS2 field-effect transistors (FETs) to vacuum ultraviolet (VUV) total ionizing dose (TID) radiation. Single-layer (SL) and multilayer (ML) MoS2 FETs are compared to identify differences that arise from thickness and band structure variations. Computations from the evolution of the FET transport properties are leveraged to identify the nature of the VUV-induced trapped charge, isolating the effects of interface and bulk oxide trapped charge. In both the SL and ML cases, oxide trapped holes compete with interface trapped electrons, exhibiting an overall shift toward negative gate bias. Raman spectroscopy identifies no variation as a result of VUV exposure, eliminating crystalline damage or oxidation as a possible mechanism that contributes to the MoS2 FET evolution. Overall, because the charge trapping behavior in this MoS2 electronic system is consistent with that observed in conventional electronic systems, this work presents avenues for achieving radiation hardness in future MoS2-based electronic devices. With the growing adoption of interconnected electronic devices in consumer and industrial applications, there is increasing demand for robust security protocols in connected devices to securely transmit and receive sensitive data. Hardware true random number generators (TRNGs), commonly used to create encryption keys, offer significant advantages over software pseudo-random number generators. However, future portable networked devices will require small, low cost, flexible TRNGs with low computational complexity. These rigorous constraints position single-walled carbon nanotubes (SWCNTs) as the ideal candidates for the semiconducting components in next-generation security devices. In my third publication, we demonstrate the first solution-processed TRNG using SWCNT static random access memory (SRAM) cells that digitize thermal noise to generate random bits. We design a bit generation strategy that can be readily implemented in hardware with minimal transistor and computational overhead, and the quality of our generated output is confirmed using standardized statistical tests. By using solution-processed semiconducting SWCNT networks as the semiconducting channel and CMOS compatible fabrication, we demonstrate a promising approach to low-cost, ultra-thin, and flexible security devices. These increasingly complex demonstrations of single-walled carbon nanotube-based (SWCNT) integrated circuit elements mark the maturation of the technology for use in next-generation electronics devices. In addition to the SRAM work described above, organic materials have been leveraged as dopant and encapsulation layers to enable stable SWCNT-based rail-to-rail, low power complementary metal-oxide-semiconductor (CMOS) circuit elements. As SWCNT-CMOS is adopted in emerging technologies, its suitability for use in next-generation space applications must be assessed. In my fourth publication, we study total ionizing dose (TID) effects in enhancement-mode SWCNT-CMOS inverters having the same organic doping and encapsulation layers utilized in the TRNG work. Details of the evolution of the device transport properties are revealed by in situ and in operando measurements, identifying the n-type device as the more TID-sensitive component of the CMOS system by revealing over an order of magnitude larger degradation of the static power dissipation. Radiation-hardening approaches are explored, and the SWNCT-CMOS technology is found to be TID-hard under dynamic bias operation. The incorporation of organic materials as dopants presents a unique system for the study of space radiation effects while the CMOS integration allows the study of system-level effects previously unobservable in SWCNT devices.