Principal Investigator: Meyya Meyyappan
Radiation exposure is a serious issue in manned space exploration. The impact of radiation on electronic equipment and other payloads is also a major concern. The knowledge base in these areas is typically developed on ground-based testing and modeling efforts. As a rule, there is no in situ monitoring of various radiations and their energy levels as the equipment needed for measurement is bulky, expensive, and requires special training for operation.
The goal of this project is to develop a postage-stamp sized chip to detect radiation sources (alpha, gamma, X-ray, protons, etc.) and their energy levels, like a radiation nose (r-nose). This system will use a conventional silicon complementary metal oxide semiconductor (CMOS) chip, except that the silicon dioxide dielectric will be replaced with a liquid dielectric.
Some liquids react to radiation exposure with a change in molecular structure, leading to a change in properties such as dielectric constant and polarization. Inspired by such responsivity of liquids, we propose to construct a transistor with a radiation-responsive liquid as a gate dielectric replacing the conventional oxide gate layer. The current voltage characteristics of the liquid gate dielectric transistor would change upon exposure to any type of radiation. Different types of liquids that specifically interact with various target radiations can be used in an array of transistors serving as a radiation nose to discriminate different radiation sources. Moreover, the fluidity of the liquid facilitates the exchange of the damaged liquid with fresh liquid after some time, allowing a reusable sensor.
Selection of liquid-state gate dielectric is important for an acceptable device performance, and the choice should satisfy the following requirements: insulating properties, proper dielectric constant, dielectric strength, thermal stability, high purity, low moisture absorption, low viscosity, and responsive to radiation. The product of this project is a radiation sensor chip and test results for gamma radiation.
Availability of on-site or in-situ monitoring of various radiations in real time would enable safer long duration manned flights. Currently such monitoring is not possible due to lack of technology.