The surface analysis of insulators by SIMS: Charge neutralization and stabilization of the surface potential

Abstract

As part of an ongoing programme of reference work for surface analysis at the NPL, the problem of surface charging when analysing insulators by static SIMS is discussed. Meaningful analysis requires stabilization of the surface potential to a defined reference point, here taken as the potential that would exist if the insulator was a conductor. In SIMS spectra it is shown that both the absolute and relative intensities of peaks depend on the surface potential. It is also shown that, only by the correct design of an electron flood source, can the surface be stabilized to a given constant reference potential. The relevant design principles are illustrated by measurements on isolated targets which define the characteristics of the flood source. Stabilization is effected to within the f0.5 eV required for static SIMS.

Dependence of high density polyethylene XPS spectrum on electron flood gun parameters

“…Ispitivan je uticaj parametara elektronskog topa (emisiona struja i ubrzavajući napon) na položaj i širinu Si2s pika u XPS spektru HDPE-a. Kod neprovodnih uzoraka, uticaj viška naelektrisanja se obično koriguje postavljanjem pika C1s na referentnu vrednost energije u XPS spektru [8,9]. Korekcija se vrši na ugljeniku zbog toga što njegov pik nije širok i uvek je adsorbovan iz vazduha na površini uzorka, zbog čega je uvek prisutan u XPS spektru.…”

Charge Neutralization in Nickel Coated Simulated High Level Waste Glass Analyzed by Secondary Ion Mass Spectrometry

“…The effective charge build up on the analysis region depends on the intensity of incoming primary charged ions and sputtered secondary electrons and ions [7,8]. Such charging affects primary as well as secondary ion trajectories which ultimately leads to instability, reduction, or even complete suppression of the secondary ion currents [7,8,15,16]. Charging effects also promote field enhanced migration of the mobile ions in the solid insulator samples, thereby leading to erroneous depth profiles [7].…”

Recent advances in dual mode charge compensation for XPS analysis

“…3 To overcome such topographical difficulties, some XPS instruments are configured with "dual-beam flood sources," which use a combination of low energy electrons and argon ions, where the energy of the ions is expected to be below that required for bond breaking. 4 The use of argon as a neutralising agent has been used previously in both SIMS and AES communities 5,6 and is employed to eliminate charges on the sample surface in unilluminated area surrounding the X-ray footprint, aiding the neutralisation of the illuminated region with the low energy electrons. Indeed, even for an XPS system configured with an electron-only flood source, one of the present authors has often used back-filling of the analysis chamber with a low pressure of argon to aid charge neutralisation for particularly rough samples.…”