Scientists use Powerful Magnets to Simulate Reduced Gravity During Crystal Growth

June 19, 1996
Scientists from the Space Sciences Laboratory at NASA's Marshall Space Flight Center are using magnetic fields up to 100,000 times the strength of the Earth's magnetic field to study the effects of gravity on the growth of silicon and germanium crystals in the laboratory. Magnetic fields are a useful means of simulating reduced gravity during crystal growth.

Crystals are grown by melting a rod of silicon or germanium, both important materials in the manufacturing of computer components, and then cooling the rod under carefully controlled conditions. The diagram at right (click on it for a bigger view) illustrates the industrial method. Traditionally even the most strict controls on laboratory environments could not prevent imperfections and impurities from being generated in the final crystal. One option is to grow these crystals in the near-zero-g environment of space, for example aboard the space shuttle. This resulted in a significant improvement in the quality of crystals that could be grown. However, spaceflight is an expensive option, and growing time is limited.

Using magnetic fields in the laboratory, crystals have been grown under desirable conditions that could only otherwise be obtained in space. Magnetic fields, however, are limited in many ways as a simulator of reduced gravity one of which being the size of crystals that can be grown. The combination of a low-gravity environment in addition to the use of magnetic fields would help to overcome this size limitation. Scientists at MSFC are working on a furnace (at left) to be flown aboard the International Space Station that will combine the benefits of a low-gravity environment and a strong magnetic field.