Methods and structures for monolithically integrating monocrystalline silicon and monocrystalline non-silicon materials and devices are provided. All word lines of one or more memory cell blocks that have not been selected in a self refresh mode are controlled to have a floating potential substantially at ground level. The number of transducers and their positional relationship limits the generation of interference signals, is conservative in power consumption, and provides a tool having enhanced negotiability through the pipeline. Automatic focus adjustment is achieved by sensing output of the reflected light as well as changes in focal position due to contamination of the machining lens 62.