Smoothest surface ever is a mirror for atoms

Metal materials reflect helium atoms much better but are harder to bend precisely into the right shape. Now materials scientists from the Autonomous University of Madrid led by Amadeo Vázquez de Parga have combined silicon and metal to make what they say is the smoothest surface ever made.

They made the near-perfect mirror by coating a thin layer of lead onto a silicon surface. This is not straightforward, because when a very thin metal layer is deposited onto a flat silicon surface it usually forms an uneven coating of differently sized bumps that perform badly as a mirror for helium atoms.