Trends in sputtering

Smentkowski, Vincent S.

doi:10.1016/s0079-6816(99)00021-0

Cited by 200 publications

(139 citation statements)

References 178 publications

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“…This phenomenon is in agreement with the general trend of surface roughening upon keV ion impact [62]. As for the observed discoloration from gold-like color for unexposed TiN to a purple-like color for exposed TiN, the measured roughness increase might play a role.…”

Section: Surface Characterizationsupporting

confidence: 90%

IonCCD Detector for Miniature Sector-Field Mass Spectrometer: Investigation of Peak Shape and Detector Surface Artifacts Induced by keV Ion Detection

Hadjar

Schlathölter

Davila

et al. 2011

J. Am. Soc. Mass Spectrom.

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A recently described ion charge coupled device detector IonCCD (Sinha and Wadsworth, Rev. Sci. Instrum. 76(2), 2005; Hadjar, J. Am. Soc. Mass Spectrom. 22(4), [612][613][614][615][616][617][618][619][620][621][622][623][624] 2011) is implemented in a miniature mass spectrometer of sector-field instrument type and MattauchHerzog (MH)-geometry (Rev. Sci. Instrum. 62(11), 2618-2620, 1991; Burgoyne, Hieftje and Hites J. Am. Soc. Mass Spectrom. 8(4), 307-318, 1997; Nishiguchi, Eur. J. Mass Spectrom. 14 (1), 7-15, 2008) for simultaneous ion detection. In this article, we present first experimental evidence for the signature of energy loss the detected ion experiences in the detector material. The two energy loss processes involved at keV ion kinetic energies are electronic and nuclear stopping. Nuclear stopping is related to surface modification and thus damage of the IonCCD detector material. By application of the surface characterization techniques atomic force microscopy (AFM) and X-ray photoelectrons spectroscopy (XPS), we could show that the detector performance remains unaffected by ion impact for the parameter range observed in this study. Secondary electron emission from the (detector) surface is a feature typically related to electronic stopping. We show experimentally that the properties of the MH-mass spectrometer used in the experiments, in combination with the IonCCD, are ideally suited for observation of these stopping related secondary electrons, which manifest in reproducible artifacts in the mass spectra. The magnitude of the artifacts is found to increase linearly as a function of detected ion velocity. The experimental findings are in agreement with detailed modeling of the ion trajectories in the mass spectrometer. By comparison of experiment and simulation, we show that a detector bias retarding the ions or an increase of the B-field of the IonCCD can efficiently suppress the artifact, which is necessary for quantitative mass spectrometry.

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Section: Surface Characterizationsupporting

confidence: 90%

IonCCD Detector for Miniature Sector-Field Mass Spectrometer: Investigation of Peak Shape and Detector Surface Artifacts Induced by keV Ion Detection

Hadjar

Schlathölter

Davila

et al. 2011

J. Am. Soc. Mass Spectrom.

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“…A measure of the removal rate of surface atoms is the sputter yield Y, defined as the ratio between the number of sputter ejected atoms and the number of incident projectiles. Excellent review articles on sputtering are available in the literature [3][4][5][6][7][8][9], and only the essential features are discussed here. Based on the large amount of experimental (see e.g.…”

Section: What Is Sputtering ?mentioning

confidence: 99%

“…However, since many review articles are available [3][4][5][6][7][8][9], only the essential points are discussed here. Then, a basic system design is described.…”

Section: Introduction: How Popular Is Sputter Deposition ?mentioning

confidence: 99%

Sputter Deposition Processes

Depla

Mahieu

Greene

2010

Handbook of Deposition Technologies for Films and Coatings

123

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Sputter deposition is a widely used technique to deposit thin films on substrates. The technique is based upon ion bombardment of a source material, the target. Ion bombardment results in a vapor due to a purely physical process, i.e. the sputtering of the target material. Hence, this technique is part of the class of physical vapor deposition techniques, which includes, for example, thermal evaporation and pulsed laser deposition. The most common approach for growing thin films by sputter deposition is the use of a magnetron source in which positive ions present in the plasma of a magnetically enhanced glow discharge bombard the target. This popular technique forms the focus of this chapter. The target can be powered in different ways, ranging from dc for conductive targets, to rf for nonconductive targets, to a variety of different ways of applying current and/or voltage pulses to the target. Since sputtering is a purely physical process, adding chemistry to, for example, deposit a compound layer must be done ad hoc through the addition of a reactive gas to the plasma, i.e. reactive sputtering. The undesirable reaction of the reactive gas with the target material results in a non-linear behavior of the deposition parameters as a function of the reactive gas flow. To model this behavior, the fluxes of the various species towards the target must be determined. However, equally important are the fluxes of species incident at the substrate because they not only influence the reactive sputter deposition process, but also control the growth of the desired film. Indeed, the microstructure of magnetron sputter deposited films is defined by the identity of the particles arriving at the substrate, their fluxes and the energy per particle.

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“…Mass spectra were dead time corrected and mass calibrated using the IONTOF software, exported as ASCII files, and integrated using a custom FORTRAN code using empirically derived integration limits (hereafter referred to as raw data). Visual inspections of the spectra were performed, and the following elemental peaks were chosen for further analyses based on their appearance in one or more of the cultures analyzed and on minimal isobaric interferences: 7 Li, 11 B, Na, 24 Mg, Al, 28 Figure 2 shows selected regions corresponding to these elements of a representative spectrum of the B. subtilis spores grown in the G medium. TOF-SIMS analyses of the graphite substrate, under similar conditions to those used for spore analyses, showed only minor elemental ion counts of Na, Al, 28 Si, 39 K, 40 Ca, and 51 V. 28 Si and 51 V were excluded from further analyses, based on detection at the same order of magnitude in the graphite planchette as in samples containing spores.…”

Section: Methodsmentioning

confidence: 99%

Differentiation of Spores of Bacillus subtilis Grown in Different Media by Elemental Characterization Using Time-of-Flight Secondary Ion Mass Spectrometry

Cliff

Jarman

Valentine

et al. 2005

Appl Environ Microbiol

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We demonstrate the use of time-of-flight secondary ion mass spectrometry (TOF-SIMS) in a forensics application to distinguish Bacillus subtilis spores grown in various media based on the elemental signatures of the spores. Triplicate cultures grown in each of four different media were analyzed to obtain TOF-SIMS signatures comprised of 16 elemental intensities. Analysis of variance was unable to distinguish growth medium types based on 40 Ca-normalized signatures of any single normalized element. Principal component analysis proved successful in separating the spores into groups consistent with the media in which they were prepared. Confusion matrices constructed using nearest-neighbor classification of the PCA scores confirmed the predictive utility of TOF-SIMS elemental signatures in identifying sporulation medium. Theoretical calculations based on the number and density of spores in an analysis area indicate an analytical sample size of about 1 ng, making this technique an attractive method for bioforensics applications.The 2001 anthrax attacks in the United States have increased interest in developing analytical methods for determining the source of biological materials. In this regard, there is clear evidence that the chemistry of bacterial spores reflects their growth history. Whiteaker et al. (34) were able to distinguish spores grown on blood agar by detecting heme groups on the spore surfaces by matrix-assisted laser desorption ionization mass spectrometry. Horita and Vass (13) and KreuzerMartin et al. (16,17) have shown that the stable isotope signatures of bacteria reflect those of the medium in which they grew. Here we explore a method capable of distinguishing the growth media in which spores of the Bacillus anthracis surrogate Bacillus subtilis were prepared based on the elemental signature of the dried spores.Metals associate with bacteria in several fundamental ways. Major constituents of the culture medium can be incorporated into cells to maintain osmotic and ionic balance, and trace metals can be assimilated as part of enzymatic cofactors. Metals may also be adsorbed to surfaces of cells during any part of an organism's growth history (3, 6) or be precipitated as a consequence of bacterial metabolism (4). In addition, B. anthracis and other spore-forming bacteria accumulate metals in the spore core, complexed to dipicolinic acid, during the sporulation process (21,29,30). This process is apparently correlated to heat resistance (10,15,26), and this phenomenon has led to interest in the metal content of bacterial spores related to food safety, general survivability in the environment, and astrobiology (1,15,18,(20)(21)(22)(23).The first report directly indicating that Bacillus spore metal content could be altered by the metal content of the growth medium dates back to 1959 (27). Under normal conditions, Ca is by far the most abundant metal found associated with the spore, potentially making up more than 3% of the spore weight (21). It is localized primarily in the spore core and to a lesser ext...

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Trends in sputtering

Cited by 200 publications

References 178 publications

IonCCD Detector for Miniature Sector-Field Mass Spectrometer: Investigation of Peak Shape and Detector Surface Artifacts Induced by keV Ion Detection

IonCCD Detector for Miniature Sector-Field Mass Spectrometer: Investigation of Peak Shape and Detector Surface Artifacts Induced by keV Ion Detection

Sputter Deposition Processes

Differentiation of Spores of Bacillus subtilis Grown in Different Media by Elemental Characterization Using Time-of-Flight Secondary Ion Mass Spectrometry

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