Where Doping is Legal
MU Research Reactor scientist John Farmer is shaping silicon’s role in electronics.
Silicon, the 14th element on the periodic table, is about as common as dirt. Or sand, to be precise. It makes up about a quarter of the Earth’s crust and, depending on how it’s handled, appears in products from caulk to computer chips.
John Farmer, senior research scientist at the MU Research Reactor (MURR), has helped shape silicon’s rapidly growing role in electronics during the past three decades. Silicon circuits handle the shock-absorber role that rows of vacuum tubes formerly played, he says. They decrease wear and tear by absorbing the power spikes that come every time an electronic device turns on or off.
And silicon chips are compact. “If a smartphone were built using vacuum tube technology, it would be the size of a football field, one meter thick,” he says. “It would consume more power than the cities of St. Louis and Kansas City combined.”
Farmer and others at MURR have greatly refined silicon through doping, or irradiation. When bombarded with neutrons, silicon partly transmutes into phosphorus, which makes it a first-rate electrical conductor. Doped silicon is the material to handle megawatts of power — 4,000 volts, 1,000 amps — in applications such as the bullet trains in planning stages in California.
Neutron-doped silicon is already making automobiles greener, Farmer says. Specialized electronic devices in hybrid cars require two wafer-thin slices of doped silicon 5 inches in diameter.
And doped silicon will make next-generation power grids efficient by vastly reducing power loss during long-distance transport of electricity. The high-grade silicon will all but obliterate the current 30 percent energy loss.