Occasionally a dust particle will settle on the polished surface of the crystal prior to mounting in the experimental setup. To remove it, dry nitrogen should be used and should be sufficient to blow such particulates off the surface. In a few remote cases, the particle will still stick to the surface and cannot be removed. In that case, acetone p.A. can be used to clear the surface. Drop a single droplet of acetone p.A. on the polished surface, and blow it off the polished surface under an angle using dry nitrogen before it has a chance to dry and form stains. Do not use ethanol, since it has the tendency to leave a hazy, organic residue on the surface that will then need to be removed through extensive sputtering and annealing.