Quantitative Untersuchungen �ber die papierchromatographische Wanderung der Schilddr�senhormone

Müller, Klaus Robert; Skrube, H.; Spitzy, H.

doi:10.1007/bf01234696

Cited by 3 publications

(1 citation statement)

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“…In the so -called direct bombardment mode ( DBM ) [12] , a negative target potential U DBM is applied with respect to the reference electrode, which is usually grounded. The difference between the plasma potential Φ Pl , some 10 eV positive with respect to the reference electrode, and the sample potential determined by U DBM (see Figure 9.6 ) accelerates the Ar -ions arriving at the plasma boundary towards the sample, and allows for sputtering with ion current densities of about 1 mA cm − 2 , even at low bombarding energies of about 100 eV.…”

Section: Plasma Snmsmentioning

confidence: 99%

Electron‐Impact (EI) Secondary Neutral Mass Spectrometry (SNMS)

Kopnarski¹,

Jenett²

2011

Surface and Thin Film Analysis

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IntroductionSince the early days of sputtering it has been known that, for most cases, the fl ux of particles ejected from a solid under ion bombardment consists predominantly of sputtered neutral s ( SN )s [1] . Thus, in order to enhance sensitivity the pioneers of surface investigation by mass spectrometry applied the process of postionization [2] . Very shortly afterwards, however, due to the rather limited postionization effi ciency when using electron beam methods, and also because of diffi culties with parasitic ion and residual gas suppression, the direct detection of secondary ions provided an advantage over using the neutral component of the sputtered particle fl ux. As a consequence, sophisticated SIMS instruments were developed with, prior to SNMS, SIMS being introduced into the fi eld of surfaceand thin -fi lm analysis.In contrast, a serious limitation of SIMS -the so -called matrix effect -emerged whereby, for a certain concentration of an element X, the secondary ion yield could vary by orders of magnitude as a function of the surface contamination and matrix composition (see e.g., Ref.[3] ). Indeed, in many cases -and especially with unknown or technical samples that had changing matrices -this would hamper quantifi cation, or even make it impossible. Subsequently, during the early 1970s, H. Oechsner [4] developed a strategy to improve quantifi cation by using the effective postionization of the neutral particle fl ux via the electron component of a low -pressure noble gas plasma. In addition to the high postionization effi ciency, this special postionization arrangement provided two further advantages: (i) an almost perfect suppression of the secondary ions; and (ii) the possibility of a lowenergy primary bombardment which featured excellent depth resolution for sputter depth profi ling.In the meantime, electron beam and laser SNMS had also been developed for postionization purposes, and had expanded into the fi eld of applied surface -and thin -fi lm analysis. The latter technique is described fully in Chapter 10 of this

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Section: Plasma Snmsmentioning

confidence: 99%