Some proposed improvements in the scanning ion microprobe

Three improvements, which we have investigated, promise to lead to a scanning ion microprobe with a space resolution of about 15 nm. The improvements are: (1) use of a field-evaporation (EHD) ion source with liquid gallium to give a brightness exceeding 10(10) A m-2 sr-1 at 21 KeV, (2) a high efficiency (10%) collecting system for secondary ions, and (3) enhancement of the secondary-ion yield by cesium deposition. With this instrument, tracing with stable isotopes would offer a number of advantages over autoradiography.