Characteristics and surface analysis of ion beam deposition from binary boron platinum (Pt58B42) liquid-metal ion source

Abstract

Characteristics of a eutectic boron platinum (Pt58B42) liquid-metal ion source (LMIS) were analyzed and investigated with a quadrupole mass spectrometer (QMS), Auger electron spectroscopy (AES), and Rutherford backscattering spectroscopy (RBS). The source characteristics can be explained by the hydrodynamic model, particularly for needle geometry LMIS. Surface analysis with RBS and AES indicated that more boron is produced in the ion beam than left in the liquid alloy reservoir and more droplets are produced with a 10-μm emitter tip radius, which reduced boron current in the beam. The source instability was associated with droplet formation. AES results show that substantial neutral ions were produced which was not detected by QMS. RBS results on the depleted residual alloy remaining on the carbon ribbon heater indicated that the cause of the alloy system’s short lifetime (33 h) is due to a change in alloy stoichiometry to a higher platinum content. Three different emitter tip radii (2.5, 5, and 10 μm) made of graphite were used in the present investigation. Higher boron current and high stability during ion emission was recorded with 2.5-μm graphite emitter tip radius than with the 5- or 10-μm tip radii.