A cooler way to protect silicon surfaces

Silicon, the material of high-tech devices from computer chips to solar cells, requires a surface coating before they can be used in these applications. The coating ''passivates'' the material, tying up loose atomic bonds to prevent oxidation that would ruin its electrical properties.

But this passivation process consumes a lot of heat and energy, making it costly and limiting the kinds of materials that can be added to the devices.

Now a team of MIT researchers has found a way to passivate silicon at room temperature, which could be a significant boon to solar-cell production and other silicon-based technologies.

The research, by graduate student Rong Yang and engineering professors Karen Gleason and Tonio Buonassisi, was recently published online in the journal Advanced Materials.

Typically, silicon surfaces are passivated with a coating of silicon nitride, which requires heating a device to 400 degrees Celsius, explains Gleason, the Alexander and I. Michael Kasser Professor of Chemical Engineering.

By contrast, the process Gleason's team uses decomposes organic vapours over wires heated to 300 C, but the silicon itself never goes above 20 C - room temperature. Heating those wires requires much less power than illuminating an ordinary light bulb, so the energy costs of the process are quite low.