A method of forming a dielectric layer on a further layer of a semiconductor device is disclosed. Each of the first and second shims including projecting portions arranged to aid with loosening of the shims from each other. A path from the host system is connected to each unit and all units are inventoried through the connected storage processor. Preferred embodiments include diffractive beam expanders for virtual displays. A secondary stone is then placed within the cavity and a bonding agent is applied to the planar surface of one of the first and second portions.