Focused ion beam direct deposition has been developed as a new technique for making patterned metal film directly on substrates. The 20 keV Au+ ion beam is focused, deflected, and finally decelerated to 30–200 eV between the objective lens and substrate. The decelerated beam is deposited on the substrate at room temperature. The beam diameter can be tuned between 0.5 and 8 μm and the beam current varies from 40 pA to 10 nA, corresponding to the beam diameter. Current density was about 20 mA/cm2, so that the deposition rate in the beam spot was estimated about 0.02 μm/s. The purity of gold film was measured with Auger electron spectroscopy and contents of carbon and oxygen, undesirable impurities, were below detection limits. The resistivity was constant at 3.7±0.1 μΩ cm for deposition over the ion energy range of 34–194 eV.
Angular distribution of scattered ions at glancing angle incidence of 3 keV He ions on a (001) surface of GaAs is studied during its molecular beam epitaxial growth. We report observation of intensity oscillations of the scattered ions from the growing surface. The period of the oscillations corresponds to the growth time of one monomolecular layer. The oscillations of the intensity is due to the oscillatory change in surface step density during layer-by-layer growth of the surface. This observation is in agreement with the intensity oscillations of reflection high-energy electron diffraction (RHEED) from epitaxially growing surface of GaAs.
Focused ion beam direct deposition of niobium has been developed as a technique for fabricating superconductive thin films. A Nb2+ ion beam extracted from a Nb10–Au50–Cu40 liquid metal ion source was accelerated to 40 keV, focused, deflected and finally decelerated to 50–1000 eV. The beam current density was 0.4–2 mA/cm2 and the minimum deposited linewidth was about 0.5 μm. The sticking probability of the Nb2+ ion beam and the critical temperature of deposited niobium films were measured. The deposition at different deposition rates and different residual gas pressure were performed. A clear relation was obtained between the critical temperature and the concentration of contaminations. This relation is consistent with the published relation for bulk niobium if it is assumed that the sticking probability of residual gas is 0.2. However, dependence of the critical temperature on ion energy was not observed.
It has been found that the exposure of a Si (100) surface to an As ionized cluster beam (ICB) is effective in the preparation of the surface prior to epitaxial growth of GaAs under conventional high vacuum conditions of 2×10−5 Pa. This process is achieved at a temperature as low as 600 °C. A clear 1×2 or 2×2 reflection high energy electron diffraction pattern observed after the procedure indicates good ordering of the sample surface. The cleaning process is attributed to chemical and physical sputtering by As ICB in the first stage and to the subsequent As termination of Si dangling bonds. It has been found that the optimum preparation conditions are an accelerating voltage of the As ionized cluster beam of 1.3 kV and a substrate temperature of 600 °C. GaAs films deposited on As ICB treated Si (100) substrates show good crystal quality with single domain structure.
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