Memory chips were made from transistors with carbon nanotubes. These nanotubes retained their electrical properties and memories even after they were bombarded with high levels of radiation. Credit: Adapted from ACS Nano 2021, DOI: 10.1021/acsnano.1c04194
NASA's Orion space mission will send astronauts to Mars. It is pushing the boundaries of human exploration. Spacecrafts are subject to a constant stream of harmful cosmic radiation that can damage or even destroy electronics. Researchers reporting in ACS Nano have shown that transistors and circuits made with carbon nanotubes can be set up to preserve their memory and electrical properties after exposure to high levels of radiation.
Current technology's energy efficiency and robustness limit the life span and distance of deep-space missions. Space radiation can cause damage to electronics, data glitches and even complete computer failure, for example. One option is to use carbon nanotubes in commonly used electronic components such as field-effect transistors. These tubes with a single atom thickness are expected to make transistors less energy-intensive than those made from more conventional silicon-based components. The ultra-small size and shape of these nanotubes could help to reduce radiation effects on memory chips that contain them. The radiation tolerance of carbon nanotube field effect transistors has not yet been extensively studied. Pritpal Kanhaiya and Max Shulaker, along with their colleagues, wanted to find out if it was possible to engineer a field-effect transistor that can withstand high radiation levels and to build memory chips based upon these transistors.
The researchers used carbon nanotubes to create the semiconducting layer for field-effect transistors. They then tested various configurations of transistors with different levels of shielding. This included thin layers of titanium, hafnium oxide, and platinum metal around the semiconducting material. The team discovered that shields placed above and below carbon nanotubes could protect the transistor's electrical properties from incoming radiation, which is much higher than the radiation tolerance of most silicon-based electronics. The shields were only placed below the carbon nanotubes and protected them up to 2Mrad. This is comparable to commercially-available silicon-based radiation-tolerant electronics. The team also built static random-access memories (SRAM) chips using the bottom shield version field-effect transistors to balance fabrication complexity and radiation resistance. These memory chips were similar to the silicon-based SRAM devices in that they had an identical X-ray radiation threshold.
Researchers say these results suggest that carbon nanotube field effect transistors, particularly double-shielded, could be a promising addition for next-generation electronics to space exploration.
For durable electronics, explore Radiation-immune chips and repairable chips