130,510 research outputs found
A new spectrometer for grazing incidence X-ray fluorescence for the characterization of Arsenic implants and Hf based high-k layers
No full textGrazing Incidence X-ray Fluorescence Analysis (GIXRF) takes advantage of the total external reflection of X-rays on a smooth, polished surface. Due to the penetration depth of only a few nanometers at very small incidence angles, GIXRF is able to probe the elemental composition in the near surface region of the sample. Furthermore by adjusting the angle of incidence and measuring the angle-dependent X-ray fluorescence signals, the technique is able to provide information on the total dose and depth distribution of the elements. The depth profile information is ambigous, thus the evaluation process, which consists of fitting the measured data to simulations, needs additional input from another technique. In the present work a GIXRF measuring chamber is presented, which was designed, constructed and tested within the context of the EC funded European Integrated Activity of Excellence and Networking for Nano and Micro-Electronics Analysis (ANNA) . Moreover an acquisition and control software and a measurement protocol were developed and tested. GIXRF measurements for the characterization of Ultra Shallow Junctions (USJ) were used to ascertain the performance of the new instrument. Secondary Ion Mass Spectrometry (SIMS) was used as a complementary technique for the depth profile evaluation. The dose quantification of the implanted Arsenic was compared with Instrumental Neutron Activation Analysis (INAA) and SIMS. Furthermore Hafnium based high k layers on Silicon were analyzed and the results compared to other techniques of the ANNA partners. Part of this work has been published in the following publications: 1. D. Ingerle, F. Meirer, N. Zoeger, G. Pepponi, D. Giubertoni, G. Steinhauser, P. Wobrauschek, C. Streli, A new spectrometer for grazing incidence X-ray fluorescence for the characterization of Arsenic implants and Hf based high-k layers, Spectrochimica Acta Part B: Atomic Spectroscopy 65 (6) (2010) 429-433. doi:10.1016/j.sab.2004.04.014 2. G. Pepponi, D. Giubertoni, M. Bersani, F. Meirer, D. Ingerle, G. Steinhauser, C. Streli, P. Hoenicke, B. Beckhoff, Grazing incidence x-ray fluorescence and secondary ion mass spectrometry combined approach for the characterization of ultrashallow arsenic distribution in silicon, Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures 28 (1) (2010) C1C59. doi:10.1116/1.3292647 3. D. Giubertoni, G. Pepponi, B. Beckhoff, P. Hoenicke, F. Gennaro, F. Meirer, 4 D. Ingerle, G. Steinhauser, M. Fried, P. Petrik, A. Parisini, M. A. Reading, C. Streli, J. van den Berg, M. Bersani, Multi-technique characterization of arsenic ultra shallow junctions in silicon within the ANNA consortium, AIP Conference Proceedings 1173 (2009) (2009) 45-49. doi:10.1063/1.325125
Implementing light elements detection and quantification in aluminosilicate materials using a Low-Z total-reflection X-ray fluorescence spectrometer
No full textTotal-reflection X-ray fluorescence (TXRF) is a well-established atomic spectroscopy technique used for the elemental characterization of different kinds of matrixes in several fields. Previous works demonstrated its applicability for the elemental quantification of aluminosilicates and, in particular, clays. However, one of the limits of the previously developed methods was the detection and quantification of light elements, in particular for those elements with an atomic number (Z) below 13 (Al). In the present work a new TXRF-based analytical method for the quantification of light elements in aluminosilicate materials is described, using an in-house built Low-Z TXRF spectrometer equipped with a Cr source, a multilayer monochromator, an SDD detector equipped with an ultrathin Si3N4 window and a vacuum chamber. Samples were prepared as simple slurries (dispersing 50 mg of powder into 2.5 mL of 1%-Triton X-100 water solution and adding Ag as internal standard) and 10 μL were deposited onto a quartz carrier and dried before the analysis. Light elements such as F, Na and Mg were quantified with a limit of detection of 682, 260 and 133 mg/kg, respectively. Carbon and oxygen could also be detected. The new method allowed a complete analysis of major elements in aluminosilicates from F to Fe. The method showed a good accuracy in the range of 80–120% and the results agreed with the data obtained with a commercial TXRF spectrometer (for elements >13) and WDXRF, employed as reference methods. Despite a lower precision in respect to WDXRF, in some samples the quantification of F was possible only by using the Low-Z TXRF spectrometer. Finally, the method demonstrated to be suitable for the analysis of aluminosilicates, in particular when low amounts of sample (few milligrams) are available
Low-Z TXRF spectrometer: a new strategy for the quantification of light elements in clays
No full textClay minerals are a very important constituent of soils which influence several bulk properties such
as water retention and cation exchange capacity. Moreover, they are used in many environmental
fields (i.e. landfill isolation, water depuration, soil remediation, etc) due to their properties and
capability to adsorb potentially toxic elements and pollutant. Both in soil science and environmental
studies the full characterization of the clay fraction should be performed for the whole comprehension
of the soil behavior and/or for the assessment of remediation strategies. Together with mineralogical
and physical investigations, chemical analysis of clays is a crucial step in their study and
characterization. Elemental analysis is usually performed by ICP-AES, ICP-MS, after complete
mineralization of the sample, or by EDXRF and WDXRF, using 1 - 5 g of material. However, in
some soils the clay fraction is not very abundant and the procurement of the suitable quantity of
sample can led to very high time-consuming sedimentation procedure. Also in sorption studies, where
a very few amount of sample is usually tested, the procurement of the suitable amount of clay sample
can be a problem. Total-reflection X-ray fluorescence spectroscopy proved to be a valuable method
for the analysis of these very small samples. A method for the elemental analysis of clays using TXRF
was already developed [1] but light elements like Na and Mg could not be quantified due to the
limitations of commercially available spectrometers for the analysis of light elements. However, the
quantification of these two elements is very important for an exhaustive chemical characterization of
aluminosilicates.
For this reason, in the present work, a new strategy for the analysis of light elements in clays is
presented. The study was carried out using a Low-Z TXRF spectrometer [2] equipped with a Cr
source (30 kV, 10 mA), an Atominstitut TXRF Vacuum Chamber (1 mbar), a W/C multilayer
monochromator and a SDD with an ultrathin Si3N4 window [3]. A set of six different aluminosilicaterock reference materials was used for calibration and other three reference materials were used for
validation. Samples were prepared as suspension using Ag as internal standard. In this way, all the
elements from F to Ti were detected and quantified with good accuracy (80 - 120%). Moreover, Fe
was also quantified using Lα lines. The obtained results will be discussed on both the analytical and
applicative point of view, with the aim of identifying the best equipment and condition for a full
elemental characterization of aluminosilicate
A new strategy for the quantification of light elements (F-Fe) in aluminosilicates via a Low-Z TXRF spectrometer
No full textAluminosilicates are the most abundant minerals on the earth and are widely studied and exploited for both research and industrial purposes. The interest of scientists and companies is also focused on the development of new synthetic materials with an aluminosilicate matrix (geopolymers, zeolites, concretes, ceramics, composites, etc.) which can be used in several fields from food processing to space exploration. Together with mineralogical and physical investigations, chemical analysis of aluminosilicates is a crucial step in their study and characterization. Due to their abundance, sample procurement is not a problem and elemental analysis is usually performed by ICP-AES, ICP-MS, after complete mineralization of the sample, or by EDXRF and WDXRF, using 1-5 g of material. However, in some fields of research (i.e. ceramic archaeometry, material synthesis, catalysis, sorption studies, clays extraction from sediments and soils, etc.) only a very few amount of sample is usually available, and a method which could allow a reliable chemical analysis and preserve the sample as much as possible is required. A method for the elemental analysis of clays using TXRF was already developed[1] but light elements like Na and Mg could not be quantified due to the limitations of commercially available spectrometers for the analysis of light elements. However, the quantification of these two elements is very important for an exhaustive chemical characterization of aluminosilicates.
For this reason, in the present work, a new strategy for the analysis of light elements in aluminosilicates is presented. The study was carried out using a Low-Z TXRF spectrometer[2] equipped with a Cr source (30 kV, 10 mA), an Atominstitut TXRF Vacuum Chamber (1 mbar), a W/C multilayer monochromator and a SDD with an ultrathin Si3N4 window[3]. A set of six different aluminosilicate-rock reference materials was used for calibration and other three reference materials were used for validation. Samples were prepared as suspension using Ag as internal standard. In this way, all the elements from F to Ti were detected and quantified with good accuracy (80-120%). Moreover, Fe was also quantified using Lα lines. The same samples were also analyzed with a commercial TXRF (Mo source) and a WDXRF spectrometers. After the comparison of the results obtained with the three techniques, it can be concluded that the elemental concentrations determined with the Low-Z spectrometer are statistically similar to the ones obtained with the other two instruments (for the elements each of them can quantify) demonstrating the suitability of the method for the quantification of light and most important elements in samples with an aluminosilicate matrix
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
JGIXA — A software package for the calculation and fitting of grazing incidence X-ray fluorescence and X-ray reflectivity data for the characterization of nanometer-layers and ultra-shallow-implants
No full textAbstractGrazing incidence XRF (GIXRF) is a very surface sensitive, nondestructive analytical tool making use of the phenomenon of total external reflection of X-rays on smooth polished surfaces. In recent years the method experienced a revival, being a powerful tool for process analysis and control in the fabrication of semiconductor based devices. Due to the downscaling of the process size for semiconductor devices, junction depths as well as layer thicknesses are reduced to a few nanometers, i.e. the length scale where GIXRF is highly sensitive. GIXRF measures the X-ray fluorescence induced by an X-ray beam incident under varying grazing angles and results in angle dependent intensity curves. These curves are correlated to the layer thickness, depth distribution and mass density of the elements in the sample. But the evaluation of these measurements is ambiguous with regard to the exact distribution function for the implants as well as for the thickness and density of nanometer-thin layers. In order to overcome this ambiguity, GIXRF can be combined with X-ray reflectometry (XRR). This is straightforward, as both techniques use similar measurement procedures and the same fundamental physical principles can be used for a combined data evaluation strategy. Such a combined analysis removes ambiguities in the determined physical properties of the studied sample and, being a correlative spectroscopic method, also significantly reduces experimental uncertainties of the individual techniques.In this paper we report our approach to a correlative data analysis, based on a concurrent calculation and fitting of simultaneously recorded GIXRF and XRR data. Based on this approach we developed JGIXA (Java Grazing Incidence X-ray Analysis), a multi-platform software package equipped with a user-friendly graphic user interface (GUI) and offering various optimization algorithms. Software and data evaluation approach were benchmarked by characterizing metal and metal oxide layers on Silicon as well as Arsenic implants in Silicon. The results of the different optimization algorithms have been compared to test the convergence of the algorithms. Finally, simulations for Iron nanoparticles on bulk Silicon and on a W/C multilayer are presented, using the assumption of an unaltered X-ray Standing Wave above the surface
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Characterization of As Implants and Hf Layer with a new Spectrometer for Grazing Incidence XRF
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