5 research outputs found
Combining Anisotropic Etching and PDMS Casting for Three-Dimensional Analysis of Laser Ablation Processes
State-of-the-art
laser ablation (LA) depth-profiling techniques
(e.g. LA-ICP-MS, LIBS, and LIMS) allow for chemical composition analysis
of solid materials with high spatial resolution at micro- and nanometer
levels. Accurate determination of LA-volume is essential to correlate
the recorded chemical information to the specific location inside
the sample. In this contribution, we demonstrate two novel approaches
towards a better quantitative analysis of LA craters with dimensions
at micrometer level formed by femtosecond-LA processes on single-crystalline
SiÂ(100) and polycrystalline Cu model substrates. For our parametric
crater evolution studies, both the number of applied laser shots and
the pulse energy were systematically varied, thus yielding 2D matrices
of LA craters which vary in depth, diameter, and crater volume. To
access the 3D structure of LA craters formed on Si(100), we applied
a combination of standard lithographic and deep reactive-ion etching
(DRIE) techniques followed by a HR-SEM inspection of the previously
formed crater cross sections. As DRIE is not applicable for other
material classes such as metals, an alternative and more versatile
preparation technique was developed and applied to the LA craters
formed on the Cu substrate. After the initial LA treatment, the Cu
surface was subjected to a polydimethylsiloxane (PDMS) casting process
yielding a mold being a full 3D replica of the LA craters, which was
then analyzed by HR-SEM. Both approaches revealed cone-like shaped
craters with depths ranging between 1 and 70 ÎŒm and showed a
larger ablation depth of Cu that exceed the one of Si by a factor
of about 3
Depth Profiling and Cross-Sectional Laser Ablation Ionization Mass Spectrometry Studies of Through-Silicon-Vias
Through-silicon-via (TSV) technology
enables 3D integration of
multiple 2D components in advanced microchip architectures. Key in
the TSV fabrication is an additive-assisted Cu electroplating process
in which the additives employed may get embedded in the TSV body.
This incorporation negatively influences the reliability and durability
of the Cu interconnects. Here, we present a novel approach toward
the chemical analysis of TSVs which is based on femtosecond laser
ablation ionization mass spectrometry (fs-LIMS). The conditions for
LIMS depth profiling were identified by a systematic variation of
the laser pulse energy and the number of laser shots applied. In this
contribution, new aspects are addressed related to the analysis of
highly heterogeneous specimens having dimensions in the range of the
probing beam itself. Particularly challenging were the different chemical
and physical properties of which the target specimens were composed.
Depth profiling of the TSVs along their main axis (approach 1) revealed
a gradient in the carbon (C) content. These differences in the C concentration
inside the TSVs could be confirmed and quantified by LIMS analyses
of cross-sectionally sliced TSVs (approach 2). Our quantitative analysis
revealed a C content that is âŒ1.5 times higher at the TSV top
surface compared to its bottom. Complementary Scanning Auger Microscopy
(SAM) data confirmed a preferential embedment of suppressor additives
at the side walls of the TSV. These results demonstrate that the TSV
filling concept significantly deviates from common Damascene electroplating
processes and will therefore contribute to a more comprehensive, mechanistic
understanding of the underlying mechanisms
Toward Three-Dimensional Chemical Imaging of Ternary CuâSnâPb Alloys Using Femtosecond Laser Ablation/Ionization Mass Spectrometry
Femtosecond laser
ablation/ionization mass spectrometry (LIMS)
has been applied to probe the spatial element composition of three
ternary CuâSnâPb model bronze alloys (lead bronzes:
CuSn10Pb10, CuSn7Pb15, and CuSn5Pb20), which were recently identified
as high-performance cathode materials in the context of electro-organic
synthesis (dehalogenation, deoxygenation) of pharmaceutically relevant
building blocks. The quantitative and spatially resolved element analysis
of such cathode materials will help in understanding the observed
profound differences in their electrochemical reactivity and stability.
For that purpose, we developed a measurement procedure using the LIMS
technique which allows analyzing the element composition of these
ternary alloys in all three spatial dimensions. Their chemical composition
was determined spotwise, by ablating material from various surface
locations on a 4 Ă 4 raster array (50 ÎŒm pitch distance,
ablation crater diameter of âŒ20 ÎŒm). The element analyses
show significant chemical inhomogeneities in all three ternary bronze
alloys with profound local deviations from their nominal bulk compositions
and indicate further differences in the nature and origin of these
compositional inhomogeneities. In addition, the element analyses showed
specific compositional correlations among the major elements (Cu,
Sn, and Pb) in these alloys. On selected sample positions minor (Ni,
Zn, Ag, and Sb) and trace elements (C, P, Fe, and As) were quantified.
These results are in agreement with inductively coupled plasma collision/reaction
interface mass spectrometry (ICPâCRI-MS) and laser ablation
inductively coupled plasma mass spectrometry (LA-ICPMS) reference
measurements, thus proving the LIMS depth profiling technique as a
powerful alternative methodology to conventional quantification techniques
with the advantage, however, of a highly localized measurement capability
Table1.docx
<p>Growth in sodium chloride (NaCl) is known to induce stress in non-halophilic microorganisms leading to effects on the microbial metabolism and cell structure. Microorganisms have evolved a number of adaptations, both structural and metabolic, to counteract osmotic stress. These strategies are well-understood for organisms in NaCl-rich brines such as the accumulation of certain organic solutes (known as either compatible solutes or osmolytes). Less well studied are responses to ionic environments such as sulfate-rich brines which are prevalent on Earth but can also be found on Mars. In this paper, we investigated the global metabolic response of the anaerobic bacterium Yersinia intermedia MASE-LG-1 to osmotic salt stress induced by either magnesium sulfate (MgSO<sub>4</sub>) or NaCl at the same water activity (0.975). Using a non-targeted mass spectrometry approach, the intensity of hundreds of metabolites was measured. The compatible solutes L-asparagine and sucrose were found to be increased in both MgSO<sub>4</sub> and NaCl compared to the control sample, suggesting a similar osmotic response to different ionic environments. We were able to demonstrate that Yersinia intermedia MASE-LG-1 accumulated a range of other compatible solutes. However, we also found the global metabolic responses, especially with regard to amino acid metabolism and carbohydrate metabolism, to be salt-specific, thus, suggesting ion-specific regulation of specific metabolic pathways.</p
Image1.PDF
<p>Growth in sodium chloride (NaCl) is known to induce stress in non-halophilic microorganisms leading to effects on the microbial metabolism and cell structure. Microorganisms have evolved a number of adaptations, both structural and metabolic, to counteract osmotic stress. These strategies are well-understood for organisms in NaCl-rich brines such as the accumulation of certain organic solutes (known as either compatible solutes or osmolytes). Less well studied are responses to ionic environments such as sulfate-rich brines which are prevalent on Earth but can also be found on Mars. In this paper, we investigated the global metabolic response of the anaerobic bacterium Yersinia intermedia MASE-LG-1 to osmotic salt stress induced by either magnesium sulfate (MgSO<sub>4</sub>) or NaCl at the same water activity (0.975). Using a non-targeted mass spectrometry approach, the intensity of hundreds of metabolites was measured. The compatible solutes L-asparagine and sucrose were found to be increased in both MgSO<sub>4</sub> and NaCl compared to the control sample, suggesting a similar osmotic response to different ionic environments. We were able to demonstrate that Yersinia intermedia MASE-LG-1 accumulated a range of other compatible solutes. However, we also found the global metabolic responses, especially with regard to amino acid metabolism and carbohydrate metabolism, to be salt-specific, thus, suggesting ion-specific regulation of specific metabolic pathways.</p