EAGER: Self Assembled Monolayer Doping for Advanced 3D Nano & Flexible Semiconductor Structures

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Non-technical:Electrical conductivity is a property that defines the ability to pass electric current through a material. The conductivity of semiconductors can be charged by orders of magnitudes by introducing dopants, trace impurities at the levels of parts per million. Doping makes possible the integrated circuits at the heart of a wide range of devices. Through clever innovations in engineering semiconductor conductivity, patterning, and deposition of conductors and insulators, the semiconductor industry has steadily made circuitry smaller, faster, and more powerful. Applications span computers, communications, healthcare and energy, leading to the emergence of the Internet of Things (IoT). Most current doping techniques rely on planar rigid substrates. To reach the next frontier, there is need to devise new atomic scale chemical means to deposit ultrathin layers of dopant molecules in precise locations in three dimensions. Molecular monolayer doping (MLD) is a doping method with the capability to produce ultra-shallow junctions for planar and non-planar structures. A low-cost reaction chamber for MLD uses materials that are commonly found in chemistry stockrooms and local home goods stores. MLD is presently at a stage where atomic layer deposition was in the early 70s and ion implantation was in the early 60s. Both are now high volume manufacturing techniques. The PIs will optimize self-assembling of dopant atoms into the silicon surface with topography at nanoscales to create futuristic computing, IoT and energy devices. It will provide an excellent research and education bridge between chemistry and electronics.Technical:The objective of the proposed work is to demonstrate the operation of low voltage, 2D material-based phase change switches at radio-frequency (RF) frequencies. Switches are required for reconfigurable RF front-end circuits in wireless systems with multi-band transmit/receive capabilities. Compared to solid-state or electro-mechanical, phase change switches promise low loss, high cut-off frequencies, high isolation and rapid switching. Two-dimensional (2D) molybdenum telluride (MoTe2) has been shown to demonstrate phase change properties, with theoretically projected voltage requirements significantly lower than traditional thin film phase change materials. Low voltage switching, coupled with flexibility and transparency make 2D phase change switches attractive candidates for next-generation, mobile nanosystems. The proposed work will experimentally validate and characterize large area, 2D MoTe2 RF switches. This will involve fabrication of the devices, as well as experimental exploration of the low-voltage and frequency response performance limits. These results will be key to the future development of phase change devices, the establishment of predictive models and the demonstration of reconfigurable nano-circuits. The intellectual merit of this EAGER proposal comprises of the following: (1) exploring and establishing a fundamental understanding of trade-offs between phase control techniques, such as heat and voltage, applied to 2D MoTe2 and related allows in order to establish behavioral models and achieve low-energy switching devices; (2) unlocking large-area chemical vapor deposition (CVD) of 2D phase change films, paying particular attention to thickness control for low-energy phase transitions, as well as increased mobility for high-frequency operation; and (3) establishing basic design procedures for the first RF switches using 2D phase change materials, which will be validated through fabrication and characterization. This results of proposed work stand to have immense implications for low-power wireless circuits and accelerate the advent of wireless sensor nodes within the Internet of Things and beyond.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.