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

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

Emission characteristics of liquid metal alloy ion sources (LMAIS) were investigated with respect to temperature. The behaviour of LMAIS were found to be normal with respect to temperature dependence. The LMAIS investigated were Co36Nd64 and Au77Ge14Si9 and results were explained in terms of abnormal behaviour of the surface tension of alloys

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 Co36Nd64 and Au77Ge14Si9. 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 Au77Ge14Si9 LMAIS are explained in terms of the abnormal behaviour of its surface tension coefficient with temperature

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

The mechanisms of ion beams emitted by an Au77Ge14Si9 liquid metal alloy ion source (LMAIS) were examined. The abundance of the monomer ions produced by this source was also examined as a function of emitter temperature. The ion beam was analyzed using an E×B filter. Results strongly point towards the co-existence of two mechanisms - direct field evaporation and post-ionization

The mass spectrum of a tin liquid metal ion source

Tin is an important metal with new potential applications regarding the fabrication of novel devices. In this work the mass spectrum of a tin liquid metal ion source (LMIS) is studied in detail. Sn++ was found to dominate in the beam both over Sn+ and over cluster ions. By studying the behaviour of the relative intensities of Sn+ and Sn ++, as a function of emission current, the conclusion is reached that both Sn+ and Sn++ are emitted as a result of direct field-evaporation from the liquid surface. Cluster ions form by ion impact-aided droplet disintegration. © 2004 Published by Elsevier B.V

Investigation of emission instabilities of liquid metal ion sources

Ion emission instabilities have been investigated using simultaneously taken current oscillograms and frequency spectra, for Ga, AuGe and AuGeSi liquid metal ion sources (LMISs). The current fluctuation intensity depends nonlinearly on emission current: it displays an S-like shape and tends towards saturation at currents of 70-80 μA in the case of Ga. The saturation value of the mean fluctuation amplitude (rms) is ∼5 μA about the d.c. level for this source. For alloy sources the emitter temperature was varied between 400 and 1060 °C; the onset for the appearance of current fluctuations - indicative of electrohydrodynamic instabilities at the liquid anode - varied with temperature. Moreover, it was found that with increasing temperature a LMIS becomes increasingly unstable. The experimental results are supported by existing theory. © 2004 Elsevier B.V. All rights reserved

Study of a liquid metal field ion emitter for the production of Si ions

The study of AuSi liquid metal alloy ion sources (LMAIs) for the production of Si ions is not new. However, the present work encompasses in a concise form almost all fundamental aspects of source behaviour, in particular of a Au 82Si18 source. A key finding, manifested in the behaviour of the ion extraction voltage with temperature, is the abnormal behaviour of the surface tension coefficient of the alloy with temperature. An important deduction, however, concerns the mechanisms responsible for the creation of doubly charged ions: reasons of self-consistency suggest that while Si ++ is directly field-evaporated, Au++ must form by the post-ionization of Au+. © 2004 Elsevier B.V. All rights reserved

Can direct field-evaporation of doubly charged ions and post-ionisation from the singly charged state co-exist?

A tin liquid metal ion source (LMIS) containing ∼14% Pb has been studied. From a careful examination of the mass spectra of the source, it is concluded that post-ionisation (PI) is the most probable mechanism for the formation of Pb2+ ions. In the case of tin, however, both Sn + and Sn2+ appear to form by direct field-evaporation. This view is supported by energy deficit measurements on the Sn+ and Sn2+ beams. Our results for Pb2+/Pb+ agree with those of Komuro with a pure Pb source. The reason for this is understandable and is related to the similarity between the evaporation fields of Sn and Pb. For the sake of completeness, we also present measurements of the energy spread of the Sn2+ and Sn+ beams. Copyright © 2007 John Wiley & Sons, Ltd

The effect of electrode geometry on the stability of a liquid metal ion emitter

The effect on source stability of removing the extractor electrode from a liquid metal ion source system has been investigated. The noise of the current and the corresponding frequency spectra were carefully studied. The findings in the two cases, i.e. with and without an extractor electrode, were found to be very different. The explanation for this is given in terms of different droplet emission mechanisms being operative in the two cases. The liquid emitter used was a AuGeSi alloy. Focused Ge and Si ion beams are important for microelectronics applications. Thus, an understanding of the mechanisms that lead to source instability is essential. © 2003 Elsevier B.V. All rights reserved

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