LOW-ENERGY (5-LESS-THAN-E(I)LESS-THAN-100 EV), HIGH-BRIGHTNESS, ULTRAHIGH-VACUUM ION-SOURCE FOR PRIMARY ION-BEAM DEPOSITION - APPLICATIONS FOR AL AND GE

The design, operation, and use of a double-grid, electron-impact, ultrahigh-vacuum compatible, low-energy ion source capable of operating with relatively low-vapor-pressure solid source materials such as Al and Ge are described. The source can run at cell temperatures up to 1450 degrees C and deliver ion current densities J(i) > 30 mA cm(-2) (corresponding to 1.9 x 10(17) cm(-2) s(-1) at source-to-substrate separations d of 2 cm, and J(i) > 100 mu A cm(-2) (6.3 x 10(15) cm(-2) s(-1)) at d = 40 cm with beam energies which can be varied from 5 to 100 eV. The uniformity in the ion current density from a 2.6-cm-diam source over 6-cm-diam substrates is better than 97%. A postextraction magnetic filter was used to separate the ion and neutral components and provide a purr ion beam. Initial nucleation and growth experiments on amorphous carbon substrates at 30 degrees C using thermal and accelerated (E(Al)+ = 35 and 75 eV) Al+ beams show that the average island size in layers with thicknesses between 2 and 6 nm increases by factors ranging from 3 to 14 with increasing ion energy. Layers deposited with thermal Al have an island size distribution which is near-Gaussian while Al islands formed from ion beams exhibit a bimodal size distribution. (C) 1995 American Vacuum Society.