Hyperthermal ion beam system optimized for studying the effects of kinetic energy on thin-film growth

A hyperthermal and low-energy ion beam (10-1000 eV) optimized for studying morphological trends in epitaxial metal thin films as a function of atomic kinetic energy has been built and characterized. The ion beam line produces metal and inert gas ions and is specially designed to produce up to 2.9 muA of highly collimated ions with single amu mass resolution while precisely controlling the ion's energy, achieving a DeltaE/Esimilar to0.1. Energy resolution can be enhanced further at the expense of flux. Varying the focal length of the final electrostatic lens allows the flux density to be adjusted from 10 to 500 nA/mm2. The beam line has been coupled to an ultra-high-vacuum deposition chamber with a versatile sample manipulator, an electron beam deposition source, residual gas analysis, and real-time reflection high-energy electron diffraction (RHEED). Once prepared, the sample can be moved in situ to perform Auger electron spectroscopy (AES), and scanning tunneling microscopy (STM). The high fluxes with narrow energy distributions this apparatus produces allows the poorly understood hyperthermal energy regime to be probed with RHEED, AES, and STM. The atomic kinetic energy can be varied to measure effects on nuclei densities, growth mode, and surface morphology. STM images of copper films deposited under a variety of conditions illustrate the diverse range of possible results. (C) 2002 American Institute of Physics.