Precision Ion Polishing System -A New Instrument for TEM Specimen Preparation of Materials

Abstract

AbstractThe article describes the design, construction and performance of a new bench top instrument for high speed ion beam thinning and polishing of materials. In this system, the combination of very low angle ion milling and powerful ion guns has led to the rapid production of high quality TEM specimens. The main subassemblies are (1) a work chamber (2) gas control system (3) vacuum system and (4) electrical system. The work chamber consists of a pair of newly designed Penning type ion guns and Faraday cups to measure ion currents. The Whisperlok™ mechanism provides specimen rotation, pneumatically driven airlock for very fast specimen exchange and transmission/reflection illumination for specimen viewing. The ion guns are mounted to deliver a nominal, 4° milling angle on the specimen surface with precision alignment of ±2° about horizontal and vertical axes. The actual thinning is undertaken from one side using a single, post-type specimen holder which minimizes the specimen heating and contamination. The ion beam current of each gun can be individually optimized by varying the flow rate of the ionizing gas. The main chamber is evacuated by diaphragm and molecular drag pumps to produce a clean, dry vacuum in the 10−6Torr range. The discharge and accelerating voltages required for the operation of each gun are provided by a dual high voltage power supply capable of delivering ion energies in the range; 1 keV to 6keV. TEM micrographs of typical ion polished specimens of semiconductors, metals, ceramics and composites are included to illustrate the performance of the instrument.