Klaus van Benthem
Oak Ridge National Laboratory
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Publication
Featured researches published by Klaus van Benthem.
Applied Physics Letters | 2005
Klaus van Benthem; Andrew R. Lupini; Miyoung Kim; Hion Suck Baik; Seok-Joo Doh; Jong-Ho Lee; Mark P. Oxley; Scott D. Findlay; Leslie J. Allen; Julia T. Luck; Stephen J. Pennycook
The aberration-corrected scanning transmission electron microscope allows probes to be formed with less than 1-A diameter, providing sufficient sensitivity to observe individual Hf atoms within the SiO2 passivating layer of a HfO2∕SiO2∕Si alternative gate dielectric stack. Furthermore, the depth resolution is sufficient to localize the atom positions to half-nanometer precision in the third dimension. From a through-focal series of images, we demonstrate a three-dimensional reconstruction of the Hf atom sites, representing a three-dimensional map of potential breakdown sites within the gate dielectric.
Applied Physics Letters | 2012
Cecile S. Bonifacio; Jorgen F. Rufner; Troy B. Holland; Klaus van Benthem
The removal of ultra-thin oxide surface layers on nanometric nickel particles is investigated in the framework of electric field-induced dielectric breakdown. In situ transmission electron microscopy was used to directly apply electrical biasing to agglomerates of nanoparticles during simultaneous imaging of the contact area between two adjacent particles. The applied electrical field initiated dielectric breakdown of the surface layers through percolation of oxygen vacancies and the migration of oxygen away from the particle contact, which leads to the formation of metallic necks and their subsequent growth. The experimental results represent direct evidence for surface cleaning effects during electric field-assisted sintering.
Applied Physics Letters | 2008
Klaus van Benthem; Gayle S. Painter; Frank W. Averill; Stephen J. Pennycook; Paul F. Becher
Electron beam irradiation during scanning transmission electron microscopy has been used to probe the relative abundance and stabilities of gadolinium adsorption sites in polycrystalline silicon nitride ceramics. Site-specific binding strengths in the interface plane between β-Si3N4 grains and the adjacent amorphous triple pockets were found to be consistent with theoretical predictions. Decreasing stability was found for Gd within partially ordered planes further from the interface. Atomic level characterization such as that reported here provides detailed insights that will allow one to tailor new functional ceramic microstructures with improved macroscopic mechanical properties.
Journal of Spacecraft and Rockets | 2006
Maja Kisa; Long Li; Judith C. Yang; Timothy K. Minton; William G. Stratton; Paul M. Voyles; Xidong Chen; Klaus van Benthem; S. J. Pennycook
We review and summarize all of our microstructural comparisons of the silica and Si/SiO x interface created by the oxidation of Si(100) in atomic oxygen and molecular oxygen, using primarily electron microscopy techniques. A laser detonation source was used to produce atomic oxygen with kinetic energy 5.1 eV, whereas a conventional furnace was used to expose Si single crystal to thermal molecular oxygen. The silica formed on Si(100) by atomic oxygen is thicker, more homogeneous, and less amorphous (similar to alpha-quartz), as compared to the oxide layer created by molecular oxygen. High-angle annular dark field imaging and high-spatial-resolution electron energy loss spectroscopy confirmed that the Si/SiO x interface created by atomic oxygen is abrupt, containing no suboxides, as opposed to the broad interface with transitional states formed by molecular oxygen. Preliminary fluctuation electron microscopy results confirmed increased medium-range ordering in SiO x formed by atomic oxygen compared to the nonregular arrangement present in the amorphous oxide formed by the oxidation of Si(100) in molecular oxygen. Differences in the oxide films grown by exposure to atomic and molecular oxygen are discussed in the context of the thermionic emission model of silicon oxidation.
Microscopy and Microanalysis | 2016
Xi Cen; Andrew M. Thron; Xinming Zhang; Klaus van Benthem
Thin films deposited at low temperatures are often kinetically constrained and will dewet the underlying substrate when heat-treated. Dewetting can be a serious concern in microelectronics reliability [1], while it can also be utilized for engineering of nanostructures with potentials in storage [2], catalysis [3], or optical/magnetic applications [4]. Mechanisms for dewetting of single layer films have been studied extensively. However little work has been reported on the cross-sectional characterization of dewetting processes for multilayer or alloyed thin films.
Microscopy and Microanalysis | 2005
Andrew R. Lupini; Matthew F. Chisholm; Klaus van Benthem; L. J. Allen; Mark P. Oxley; Scott D. Findlay; M. Varela; Stephen J. Pennycook
In an article published in Microscopy and Microanalysis recently ( Jia et al., 2004 ), it was claimed that aberration-corrected high resolution transmission electron microscopy (HRTEM) allows the quantitative measurement of oxygen concentrations in ceramic materials with atomic resolution. Similar claims have recently appeared elsewhere, based on images obtained through aberration correction ( Jia et al., 2003 ; Jia & Urban, 2004 ) or very high voltages ( Zhang et al., 2003 ). Seeing oxygen columns is a significant achievement of great importance ( Spence, 2003 ) that will doubtlessly allow some exciting new science; however, other models could provide a better explanation for some of the experimental data than variations in the oxygen concentration. Quantification of the oxygen concentrations was attempted by comparing experimental images with simulations in which the fractional occupancy in individual oxygen columns was reduced. The results were interpreted as representing nonstoichiometry within the bulk and at grain boundaries. This is plausible because previous studies have shown that grain boundaries can be nonstoichiometric ( Kim et al., 2001 ), and it is indeed possible that oxygen vacancies are present at boundaries or in the bulk. However, is this the only possible interpretation? We show that for the thicknesses considered a better match to the images is obtained using a simple model of surface damage in which atoms are removed from the surface, which would usually be interpreted as surface damage or local thickness variation (from ion milling, for example).
Microscopy and Microanalysis | 2015
Hasti Majidi; Klaus van Benthem
Electric field-assisted sintering (EFAS) techniques, which include spark plasma sintering and “flash sintering”, have demonstrated the potential for enhanced densification at lower temperatures compared to conventional methods of sintering.[1-2] However, the fundamental mechanisms governing the enhancements of the densification processes are debated in the literature. The separate effects of the applied field and/or the resulting current remain unknown.[3] Studying the mechanisms of EFAS therefore requires separating the effects of the electric field from those of the electric current. Here, we report, for the first time, in situ scanning transmission electron microscopy (STEM) observations and quantitative shrinkage analysis of 3 mol% yttria-stablized zirconia (3YSZ) powder agglomerates during consolidation in the presence of a non-contacting externally applied electric field.
Microscopy and Microanalysis | 2017
Cecile Bonifacio Fittz; Hasti Majidi; Klaus van Benthem
The properties of nanoscale materials can be significantly different from that of their bulk counterparts, which is attributed to increasing surface to volume ratios for continuously decreasing dimensions, and potentially culminating in quantum confinement [1]. For instance, Navrotsky and co-workers suggest considerable errors in oxygen fugacity of 100-200K when using thermodynamic data for bulk phases to calculate reduction-oxidation phase equilibria for various metal oxides at the nanoscale [2].
212th ECS Meeting | 2007
Klaus van Benthem; Stephen J. Pennycook
Aberration correction in the scanning transmission electron microscope brings sub- ngstr m electron probe sizes and single atom sensitivity which enable the characterization of semiconductor devices and their defects with unprecedented detail. Further benefits include simultaneous bright field and dark field image acquisition and a new three-dimensional imaging technique. Here, we will review some major results obtained by aberration corrected scanning transmission electron microscopy and highlight some future research directions.
Microscopy and Microanalysis | 2014
Jorgen F. Rufner; Thomas LaGrange; Ricardo H. R. Castro; Klaus van Benthem
Appling a contact or non-contact electric field during sintering, i.e., electric field assisted sintering (EFAS), can improve consolidation behavior and is commonly used in many sintering techniques, e.g., Spark Plasma Sintering (SPS)[1], Flash Sintering[2], and Pulsed Electric Current Activated Sintering (PECAS)[3][4]. Electric fields have been shown to densify ceramic powders within seconds as well as, depending on the experimental conditions, retarding or enhancing grain growth, however, the mechanisms which affect sample densification and grain growth remain unclear [1] [2][4]. To control and tailor microstructural aspects of sintered materials, better correlation is required of the applied non-contact electrical fields and current to the resultant microstructure. Due to the complexities of the sintering processes, we have chosen to isolate our investigation to the influence of noncontact electric fields on microstructural evolution.