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Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.
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Metal electrode materials are being extensively evaluated as potential replacements for polysilicon in order to eliminate gate depletion, reduce gate resistance, overcome equivalent oxide thickness (EOT) scaling limitations and Fermi... more
Metal electrode materials are being extensively evaluated as potential replacements for polysilicon in order to eliminate gate depletion, reduce gate resistance, overcome equivalent oxide thickness (EOT) scaling limitations and Fermi level pinning effects associated with the reaction between Hf-based dielectric films and the polysilicon electrode. High-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) using X-ray spectra and electron energy
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Extended defects are of considerable importance in determining the electronic properties of semiconductors, especially in photovoltaics (PVs), due to their effects on electron-hole recombination. We employ model systems to study the... more
Extended defects are of considerable importance in determining the electronic properties of semiconductors, especially in photovoltaics (PVs), due to their effects on electron-hole recombination. We employ model systems to study the effects of dislocations in CdTe by constructing grain boundaries using wafer bonding. Atomic-resolution scanning transmission electron microscopy (STEM) of a [1-10]/(110) 4.8° tilt grain boundary reveals that the interface is composed of three distinct types of Lomer dislocations. Geometrical phase analysis is used to map strain fields, while STEM and density functional theory (DFT) modeling determine the atomic structure at the interface. The electronic structure of the dislocation cores calculated using DFT shows significant mid-gap states and different charge-channeling tendencies. Cl-doping is shown to reduce the midgap states, while maintaining the charge separation effects. This report offers novel avenues for exploring grain boundary effects in Cd...
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Synthesis of good quality graphite on Ni using IC-PECVD at a low temperature of 380 °C in a hydrogen free environment.
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ABSTRACTSolute segregation to grain boundaries is a fundamental phenomenon in polycrystalline metal-oxide electroceramics that has enormous implications for the macroscopic dielectric behavior of the materials. This paper presents a... more
ABSTRACTSolute segregation to grain boundaries is a fundamental phenomenon in polycrystalline metal-oxide electroceramics that has enormous implications for the macroscopic dielectric behavior of the materials. This paper presents a systematic study of solute segregation in a model dielectric, titanium dioxide. We investigate the relative role of the electrostatic versus strain energy driving forces for segregation by studying yttrium-doped specimens. Through analytical transmission electron microscopy studies, we quantitatively determine the segregation behavior of the material. The measured Gibbsian interfacial excesses are compared to thermodynamic predictions.
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ABSTRACTMultiple silicon nanowires were synthesized using large gallium pools and microwave plasma. Results showed that nanowires growing out of different sized large gallium drops show little variation in diameters, suggesting that our... more
ABSTRACTMultiple silicon nanowires were synthesized using large gallium pools and microwave plasma. Results showed that nanowires growing out of different sized large gallium drops show little variation in diameters, suggesting that our non-traditional technique can be used to synthesize bulk amounts of monodispersed nanowires out of thin films of molten gallium.
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ABSTRACTWe present a novel synthesis technique to grow bulk quantities of semiconductor nanowires at temperatures less than 500 °C. Gallium is used as the liquid medium in a mechanism similar to vapor-liquid-solid (VLS). We demonstrated... more
ABSTRACTWe present a novel synthesis technique to grow bulk quantities of semiconductor nanowires at temperatures less than 500 °C. Gallium is used as the liquid medium in a mechanism similar to vapor-liquid-solid (VLS). We demonstrated this low temperature technique with silicon and carbon nanowires. Gallium exhibits extremely low solubility for several elemental semiconductors. This property enables nucleation and growth of nanometer scale wires from large sized gallium droplets (>1 μm) eliminating the need for creation of quantum sized metal droplets.
Research Interests: Materials Science, Materials, Silicon, Nanowire, Nanotechnology, and 5 moreSemiconductor, Nucleation, MRS, Nanometre, and Gallium
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Research Interests: Engineering, Materials Science, Technology, Crystallography, Semiconductors, and 15 moreRaman Spectroscopy, Transmission Electron Microscopy, Nanowire, Nanotechnology, Medicine, Nanoscience, Nanotubes, CHEMICAL SCIENCES, Phonon, Scanning Electron Microscope, Molecular Conformation, Gallium, Raman Scattering, Electric Conductivity, and Nanoscience and nanotechnology
Research Interests: Engineering, Materials Science, Applied Physics, Transmission Electron Microscopy, Scanning Transmission Electron Microscopy, and 15 moreMathematical Sciences, High Resolution Transmission Electron Microscopy, Applied, DIELECTRIC, Physical sciences, Experimental Evaluation, Thermal Stability, Cross Section, Phase Separation, Reaction Mechanism, Electrode, Gamma Ray, Electron Energy Loss Spectroscopy, High Angle Annular Dark Field, and Ruthenium(Mathematical Sciences, High Resolution Transmission Electron Microscopy, Applied, DIELECTRIC, Physical sciences, Experimental Evaluation, Thermal Stability, Cross Section, Phase Separation, Reaction Mechanism, Electrode, Gamma Ray, Electron Energy Loss Spectroscopy, High Angle Annular Dark Field, and Ruthenium)
(Mathematical Sciences, High Resolution Transmission Electron Microscopy, Applied, DIELECTRIC, Physical sciences, Experimental Evaluation, Thermal Stability, Cross Section, Phase Separation, Reaction Mechanism, Electrode, Gamma Ray, Electron Energy Loss Spectroscopy, High Angle Annular Dark Field, and Ruthenium)
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ABSTRACT Control of the particle size and composition are important for realizing scientifically and technologically useful nanocrystalline materials. Growth of semiconductor particles in glass produces composite materials that are... more
ABSTRACT Control of the particle size and composition are important for realizing scientifically and technologically useful nanocrystalline materials. Growth of semiconductor particles in glass produces composite materials that are mechanically, thermally, and chemically robust and that can exhibit significant quantum confinement effects. Measurement of particle composition is difficult for dilute nanoparticle composites. We have been able to deduce size, strain, and composition of nanometer-sized (ZnS)_x(CdS)_1-x particles precipitated in glass by the coordinated analysis of Raman scattering, optical absorption, and x-ray absorption spectroscopies. We have found that the Zn/Cd concentration ratio in particles can be quantitatively related to the average particle size using nucleation and ripening theories.
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Research Interests: Condensed Matter Physics, Quantum Physics, Electron Microscopy, Surface Science, Epitaxial Growth, and 10 moreSurface Roughness, High Resolution Transmission Electron Microscopy, Thin Film, Titanium dioxide, Energy Dispersive X-Ray Analysis, X ray diffraction, Room Temperature, Single Crystal, Titanium oxide, and X Ray Photoelectron Spectroscopy
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ABSTRACT We have studied ferromagnetism of Mn-implanted epitaxial Ge films on silicon. The Ge films were grown by ultrahigh vacuum chemical vapor deposition using a mixture of germane (GeH4) and methylgermane (CH3GeH3) gases with a carbon... more
ABSTRACT We have studied ferromagnetism of Mn-implanted epitaxial Ge films on silicon. The Ge films were grown by ultrahigh vacuum chemical vapor deposition using a mixture of germane (GeH4) and methylgermane (CH3GeH3) gases with a carbon concentration of less than 1 at. %, and observed surface rms roughness of ∼0.5 nm, as measured by atomic force microscopy. Manganese ions were implanted in epitaxial Ge films grown on Si (100) wafers to an effective concentration of ∼16, 12, 6, and 2 at. %. Superconducting quantum interference device measurements showed that only the three highest Mn concentration samples are ferromagnetic, while the fourth sample, with [Mn] = 2 at. %, is paramagnetic. X-ray absorption spectroscopy and x-ray magnetic circular dichroism measurements indicate that localized Mn moments are ferromagnetically coupled below the Curie temperature. Isothermal annealing of Mn-implanted Ge films with [Mn] = 16 at. % at 300 °C for up to 1200 s decreases the magnetization but does not change the Curie temperature, suggesting that the amount of the magnetic phase slowly decreases with time at this anneal temperature. Furthermore, transmission electron microscopy and synchrotron grazing incidence x-ray diffraction experiments show that the Mn-implanted region is amorphous, and we believe that it is this phase that is responsible for the ferromagnetism. This is supported by our observation that high-temperature annealing leads to recrystallization and transformation of the material into a paramagnetic phase.
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InGaAs/GaAs quantum wires (QWRs) show promise for the next generation opto-electronic devices. High-index GaAs substrates provide a new opportunity for the growth of uniform arrays of InGaAs quantum wires (QWRs). Previous scanning... more
InGaAs/GaAs quantum wires (QWRs) show promise for the next generation opto-electronic devices. High-index GaAs substrates provide a new opportunity for the growth of uniform arrays of InGaAs quantum wires (QWRs). Previous scanning tunneling microscopy (STM) ...
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... style="font-size: 11px; padding: 0px 0px 10px 0px; font-weight:bold; color: #045989;">Si Nano-Meshes Investigated Using Transmission Electron Microscopy</div><div... more
... style="font-size: 11px; padding: 0px 0px 10px 0px; font-weight:bold; color: #045989;">Si Nano-Meshes Investigated Using Transmission Electron Microscopy</div><div style="font-size: 11px;"><b>GD Lian,ME Curtis,PR Larson,KL Hobbs,JC Keay,MB Johnson,DA Blom and LF ...
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... Go to Previous Abstract in TOC; Blog this Article close. Copy and paste this code to insert a reference to this article in your blog or online ... by Shallow-Trench Isolation Strain Relaxation In Embedded... more
... Go to Previous Abstract in TOC; Blog this Article close. Copy and paste this code to insert a reference to this article in your blog or online ... by Shallow-Trench Isolation Strain Relaxation In Embedded SiGe</div><br><div style="font-size: 10px;"><b>C Vartuli,G Lian,YS Choi and J ...
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ABSTRACT Instrumentation and Techniques SymposiaDirect Comparison of Convergent Beam Electron Diffraction and Geometric Phase Analysis for Local Strain MeasurementArticle author querydiercks d [PubMed] [Google Scholar]lian g [PubMed]... more
ABSTRACT Instrumentation and Techniques SymposiaDirect Comparison of Convergent Beam Electron Diffraction and Geometric Phase Analysis for Local Strain MeasurementArticle author querydiercks d [PubMed] [Google Scholar]lian g [PubMed] [Google Scholar]chung j [PubMed] [Google Scholar]kaufman m [PubMed] [Google Scholar]D Diercksa1, G Liana2, J Chunga2 and M Kaufmana3a1 University of North Texas
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Local Lattice Strain Measurement using Geometric Phase Analysis of Annular Dark Field Images from Scanning Transmission Electron Microscopy Jayhoon Chung,* Guoda Lian,* and Lew Rabenberg ** ... References [1] J. Huang, MJ Kim, PR... more
Local Lattice Strain Measurement using Geometric Phase Analysis of Annular Dark Field Images from Scanning Transmission Electron Microscopy Jayhoon Chung,* Guoda Lian,* and Lew Rabenberg ** ... References [1] J. Huang, MJ Kim, PR Chidambaram et al., Appl. Phys. ...
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Effects of side reactions during the formation of high quality colloidal nanocrystals were studied using ZnO as a model system. In this case, an irreversible side reaction, formation of esters, was identified to accompany formation of ZnO... more
Effects of side reactions during the formation of high quality colloidal nanocrystals were studied using ZnO as a model system. In this case, an irreversible side reaction, formation of esters, was identified to accompany formation of ZnO nanocrystals through the chemical reaction between zinc stearate and an excess amount of alcohols in hydrocarbon solvents at elevated temperatures. This irreversible side reaction made the resulting nanocrystals stable and with nearly unity yield regardless of their size, shape, and size/shape distribution. Ostwald ripening and intraparticle ripening were stopped due to the extremely low solubility/stability of the possible monomers because all free ligands in the solution were consumed by the side reaction. However, focusing on size distribution and 1D growth that are needed for the growth of high quality nanocrystals could still occur for high yield reactions. Upon the addition of a small amount of stearic acid or phosphonic acid, immediate partial dissolution of ZnO nanocrystals took place. Although the excess alcohol could not react with the resulting zinc phosphonic acid salt, it could force the newly formed zinc stearate gradually but completely back onto the existing nanocrystals. The results in this report indicate that side reactions are extremely important for the formation of high quality nanocrystals by affecting their quality, yield, and stability under growth conditions. Due to their lack of information in the literature and obvious practical advantages, studies of side reactions accompanying formation of nanocrystals are important for both fundamental science related to crystallization and industrial production of high quality nanocrystals.
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Convergent beam electron diffraction and geometric phase analysis were used to measure strain in the gate channel of a p-type strained silicon metal-oxide-semiconductor field-effect transistor. These measurements were made on exactly the... more
Convergent beam electron diffraction and geometric phase analysis were used to measure strain in the gate channel of a p-type strained silicon metal-oxide-semiconductor field-effect transistor. These measurements were made on exactly the same transmission electron microscopy specimen allowing for direct comparison of the relative advantages of each technique. The trends in the strain values show good agreement in both the [110] and [001] directions, but the absolute strain values are offset from each other. This difference in the absolute strain measured using the two techniques is attributed to the way the reference strain is defined for each.
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This letter reports that geometric phase analysis of high-resolution images acquired in the high-angle annular darkfield scanning transmission electron microscopy can map strains at levels of accuracy and reproducibility needed for... more
This letter reports that geometric phase analysis of high-resolution images acquired in the high-angle annular darkfield scanning transmission electron microscopy can map strains at levels of accuracy and reproducibility needed for strained-silicon-device development. Two-dimensional strain maps were reconstructed for a p-type metal-oxide-semiconductor device which was strain-engineered using a recessed source and drain. This metrology provides sufficiently practical and reproducible local-strain tensors which can be measured on a routine basis. The techniques demonstrated here are informative for process development and failure analysis in the semiconductor industry.
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Research Interests: Biomaterials, Biomechanics, Nanoparticles, Transmission Electron Microscopy, Multidisciplinary, and 21 moreMagnetic field, Endocytosis, Silica, Female, Animals, Male, Nanotubes, Electromagnetic Fields, Sterilization, Electromagnetic Field, Mechanical Stress, Epithelial cells, Particle Size, Size Distribution, Rare Earth, Guinea Pig, Micromanipulation, Materials Testing, Energy Dispersive Spectroscopy, Biocompatible Materials, and Tympanic Membrane(Magnetic field, Endocytosis, Silica, Female, Animals, Male, Nanotubes, Electromagnetic Fields, Sterilization, Electromagnetic Field, Mechanical Stress, Epithelial cells, Particle Size, Size Distribution, Rare Earth, Guinea Pig, Micromanipulation, Materials Testing, Energy Dispersive Spectroscopy, Biocompatible Materials, and Tympanic Membrane)
(Magnetic field, Endocytosis, Silica, Female, Animals, Male, Nanotubes, Electromagnetic Fields, Sterilization, Electromagnetic Field, Mechanical Stress, Epithelial cells, Particle Size, Size Distribution, Rare Earth, Guinea Pig, Micromanipulation, Materials Testing, Energy Dispersive Spectroscopy, Biocompatible Materials, and Tympanic Membrane)
... Jayhoon Chung, Guoda Lian, Lew Rabenberg. ... J.Huang, MJKim, PRChidambaram, RBIrwin, PJJones, JWWeijtmans, EMKoontz, YGWang, S.Tang, and R.Wise, Probing nanoscale local lattice strains in advanced Si complementary... more
... Jayhoon Chung, Guoda Lian, Lew Rabenberg. ... J.Huang, MJKim, PRChidambaram, RBIrwin, PJJones, JWWeijtmans, EMKoontz, YGWang, S.Tang, and R.Wise, Probing nanoscale local lattice strains in advanced Si complementary metal-oxide-semiconductor devices, Appl. ...