Th. Ganetsos

Investigation and optimization of the emission parameters of alloy liquid metal ion sources

Abstract Liquid metal ion sources (LMIS) are one of the key elements in focused ion beam (FIB) technology. For special tasks, alloy LMIS are needed which have to be operated in the most cases at elevated temperatures. For the adjustment of an optimal beam performance in a FIB system, the source parameters, temperature of the ion emitter and the energy spread of the different ion species used are of fundamental importance. Emitters wetted with Au73Ge27, Au77Ge14Si9 and Co36Nd64 alloys were investigated with respect to the influence of the source temperature on the emission current–extraction voltage characteristics, the mass distribution, as well as the energy spread of the different emitted ions using an equipment containing an ExB mass filter and a retarding field energy analyser. The energy spread significantly determines the available FIB spot size and depends also on the emission current, the charge state, and the mass of ions or clusters. The axial angular intensity and the resulting target current of the FIB were measured as a function of the source parameters. Two operating regimes were found. Either one works in a high stable target current mode with lower resolution (emission current ∼10 μA), or in the high resolution, high chromatic angular intensity mode (emission current a few μA), with a reduced target current and less current stability, both at source temperatures some 10 K above the melting point.

Temperature dependence of the electric characteristics of liquid metal alloy ion sources

In spite of the fact that a great deal of research has been carried out on liquid metal ion sources, surprisingly few results exist on the temperature dependence of their electric characteristics. In this article we study two liquid metal alloy ion sources (LMAISs), namely Co36 Nd64 and Au77 Ge14 Si9 . While the results of the former alloy were as expected, the latter displayed an entirely different dependence of its electric characteristics on temperature. The unusual results of the Au77 Ge14 Si9 LMAIS are explained in terms of the abnormal behaviour of its surface tension coefficient with temperature.

Morphology and oxidation kinetics of SiO2 layers on silicon

The morphology, density and thickness of SiO2 layers grown on silicon are determined by neutron reflectivity. The validity of different oxidation models is examined using the neutron reflectivity determined thickness for different growth times and temperatures in conjunction with those available in the literature on ellipsometry data. Two of the oxidation models fit all the data sets very well without the incorporation of a fast initial growth. All the data sets give energy of diffusion of 2.1 ± 0.1 eV and the chemical reaction activation energy of 1.86 ± 0.08 eV.

Electrohydrodynamic instabilities on a liquid anode displaying an anomalous surface tension coefficient

In the search for a deeper understanding of the factors governing the stability of liquid metal field-ion emitters, the behaviour of a liquid anode with an anomalous surface tension coefficient is studied. The main parameter in this experimental study is the emitter temperature. At the conclusion of the work an important result emerged: apart from the surface tension coefficient, space-charge effects constitute a major factor influencing emitter stability.

Temperature dependence of emission frequency spectra of a liquid metal anode

In an attempt to understand the instabilities that develop on an ion-emitting molten metal anode, we study current oscillograms and emission frequency spectra, as a function of emission current and emitter temperature. It is concluded that increasing the temperature affects adversely the stability of the emitter, thus enhancing the emission of droplets. However, a droplet emission mode, as well as an understanding thereof, is useful for deposition purposes.

Fundamental properties of erbium-ions-producing liquid metal alloy ion sources

Abstract We describe the electric characteristics and mass spectra of two liquid metal alloy ion sources; namely Er 70 Fe 22 Cr 3 Ni 5 and Er 69 Ni 31 . Erbium ions are of great interest for optoelectronic applications. For the first time in the literature the energy spread of triply charged ions (Er 3+ ) is reported.

Doubly-charged ions from liquid metal alloy ion sources: direct field-evaporation or post-ionization?

We investigate the temperature dependence of the mass spectrum of the ion beam emitted by an Au77Ge14Si9 liquid metal alloy ion source. Our results strongly point towards the co-existence of two mechanisms for the emission of doubly-charged monomer ions: direct field evaporation and post-ionization.

On the temperature dependence of the mass spectra of AuGe and AuGeSi liquid metal alloy ion sources

This reports on an extensive study of the characteristics of AuGe and AuGeSi liquid metal alloy ion sources as a model system for new semiconductor compatible FIB sources. Such characteristics include ion beam mass spectra. A careful investigation has been undertaken where the emitter temperature is the main variable parameter.This work concerns the temperature dependence of the mass spectra of two needle-type liquid metal alloy ion sources (LMAISs), namely Au77Ge14Si9 (Tm=364 o C) and Au73Ge27 (Tm=365 o C). The sources are important for producing SiGe implanted layers. The experimental results, in conjunction with existing theories, strongly points towards the co-existence of two mechanisms for the emission of doubly-charged monomer ions: direct filed-evaporation and post-ionisation.

Effect of temperature on the emission characteristics of liquid metal alloy ion sources

In spite of the fact that a great deal of research has been carried out on liquid metal ion sources, surprisingly few results exist on the temperature dependence of their emission characteristics. In this article we study two liquid metal alloy ion sources (LMAISs), namely Co36Nd64 and Au77Ge14Si9. While the results of the former source were as expected, the latter displayed an entirely different dependence of its emission characteristics on temperature. The unusual results of the Au77Ge14Si9 LMAIS are explained in terms of the abnormal behavior of the surface tension of the alloy with temperature.

On the dynamics of liquid metal ion sources

The mechanisms governing the formation of the liquid metal cone that constitutes the basis of a liquid metal ion source (LMIS) are investigated. Cone formation times ranging from <20 ns up to several hundreds of ms have been reported in the literature. This paper attempts to explain these differences by devising a theoretical model that encompasses inertial and flow effects.