Disclosed are computers and methods of operating those computers. According to the method of the invention, a mosaic single-crystal diamond having a large area and good quality can be produced relatively easily. The facets are formed in a single ion beam etching step. By adjusting the amount of current supplied to the emitter in a state in which the driving voltage is sustained higher than the minimum voltage, a stable amount of emission current can be sustained and electron emission without fluctuations can be realized, even when the performance of the field emission device in emitting electrons deteriorates due to driving time elapsing. The first hydraulic coupling is electronically-controlled. A second film is then bonded to the other side of the piezoelectric material.