  The prospect of building a quantum information processor underlies many
recent advances ion trap fabrication techniques. Potentially, a quantum
computer could be constructed from a large array of interconnected ion traps.
We report on a micrometer-scale ion trap, fabricated from bulk silicon using
micro-electromechanical systems (MEMS) techniques. The trap geometry is
relatively simple in that the electrodes lie in a single plane beneath the
ions. In such a trap we confine laser-cooled 24Mg+ ions approximately 40
microns above the surface. The fabrication technique and planar electrode
geometry together make this approach amenable to scaling up to large trap
arrays. In addition we observe that little laser cooling light is scattered by
the electrodes.
