Computer-aided design of nanoscale devices and sensors is a cost effective way to infuse emerging nanoelectronics technologies in on-board information processing.
Benefit Nanoscale devices and sensors have the potential to enable revolutionary advances in onboard data processing, communication and sensing capability which are central to the exploration mission. Modeling and simulation are crucial in designing and choosing appropriate technologies for NASA missions. Applications include autonomy, science, and self-monitoring exploration space missions. Mission applications include:
Research Overview We work in close association with experimentalists, in house, as well as in academia and industry. Our core capabilities consist of high-fidelity model development and large-scale simulation of nanoelectronics and sensors and exploration of their capabilities for mission applications. Topics with current focus are:
Semiconductor and Molecular Device Modeling : We have developed and continue to develop theory, algorithm and simulation tools for nanodevices based on physics and engineering approaches to explore capability. Our physical models, algorithms and software are applicable to charge transport in a wide range of nanoscale devices and molecules. A hierarchy of methods that include drift-diffusion, Boltzmann and Non-equilibrium Green's Function equations form the basis for the modeling tools. The simulations use inputs from tight-binding, effective mass, ab initio and molecular dynamics approaches, depending on the degree of accuracy desired. The output from these simulations are current-voltage (I-V) characteristics of devices and their dependence on design parameters. Nanotransistors based on silicon, carbon nanotubes, and nanowires are our current focus.Right: Chemical and electromecanical sensors based on carbon nanotubes and nanowires.
Molecular Electronics : Our capabilities are based on rigorous computational quantum chemistry approaches to determine factors that affect the electronic characteristics of molecules for potential application in computing and sensing. Factors that affect the I-V curves of molecules such as changing molecule-metal contact interaction and molecule-metal contact orientation are explored. Considering the difficulties and cost of experiments at the molecular scale, our approach is an effective way to explore phenomena at the molecular scale and exploit them for application.
Carbon nanotube and atomic-scale devices : In addition to detailed theory and models, we have also developed phenomenological models based on traditional semiconductor device physics that can be applied to a wide variety of nanodevices. These models have proved to be useful to understand the device operation mechanisms in the context of design, leading to the invention of novel devices or optimizing existing devices.
Sensors : The primary focus here is to develop carbon nanotube and nanowire based chemical and electromechanical sensors. Our very accurate quantum chemistry modeling and simulation capabilities are used to evaluate the sensitivity and specificity of the interaction of nanotubes and nanowires with various adsorbates. We also model the role of adsorbates on the electronic functioning of the sensor. With similar capability, we have explored the electromechanical properties of carbon nanotubes for actuation and sensing.
Background NASA missions in the future require increased onboard data processing, communication, and sensing capability. New devices based on nanotechnology offer increased processing and sensing capability at reduced volume, weight and power levels, which are critical to mission goals and success. The advantages of nanodevices include: (i) greatly increased spacecraft information processing capabilities operating in harsh-limited resource environments, (ii) improved computational and sensing capabilities in spacecraft for increased autonomy, (iii) improved monitoring capabilities in manned long term space missions, (iv) wiring with increased strength, long life and ultra high current carrying capacities, (v) sensor arrays with orders of magnitude increase in sensitivity and resolution and (vi) new generation of photovoltaics. In contrast to operation on earth, electronics and sensors in missions operate in harsh radiation, temperature and not fully characterized environmental conditions. Modeling and simulation are central to NASA in performance evaluation and down selection of the most relevant technologies because of large costs associated with reproducible fabrication of nanodevices.Right: A molecule between gold contacts. The chemistry of moleculecontact is acurately modeled.
Our interdisciplinary effort consisting of engineers, chemists and applied physicists, plays a leading role in the discovery, identification of potential nanoelectronics and sensor technologies, and exploration of capabilities through the use of high-fidelity modeling and large-scale simulation.