Papers by Manh Cuong Nguyen
New spin excitations in metals
Bulletin of the American Physical Society, 2019
Physical Review B, 2018
Measurements of temperature-dependent resistance and magnetization under hydrostatic pressures up... more Measurements of temperature-dependent resistance and magnetization under hydrostatic pressures up to 2.13 GPa are reported for single-crystalline, superconducting BaBi3. A temperaturepressure phase diagram is determined and the results suggest three different superconducting phases α, β, and γ in the studied pressure range. We further show that occurrence of the three superconducting phases is intuitively linked to phase transitions at higher temperature which are likely first order and structural in nature. With the α phase being the ambient-pressure tetragonal structure (P 4/mmm), our first-principle calculations suggest the β phase to be cubic structure (P m − 3m) and the γ phase to be a distorted tetragonal structure where the Bi atoms are moved out of the face-centered position. Finally, an analysis of the evolution of the superconducting upper critical field with pressure further confirms these transitions in the superconducting state and suggests a possible change of band structure or a Lifshitz transition near 1.54 GPa in γ phase. Given the large atomic numbers of both Ba and Bi, our results establish BaBi3 as a good candidate for the study of the interplay of structure with superconductivity in the presence of strong spin-orbit coupling.
Electrical characterization of gate stack charge traps in floating body gate-all-around field-effect-transistors
Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena
Individual charge traps in the gate stack of gate-all-around field-effect-transistors have been i... more Individual charge traps in the gate stack of gate-all-around field-effect-transistors have been identified from their random telegraph noise (RTN) characteristics in the time and frequency domains. The energy level and depth location of the corresponding charge traps were extracted from capture/emission time constant and corner frequency. The charge traps were determined to be the excited states of oxygen vacancies in the dielectric located 3 nm away from the interface. Both the time domain and frequency domain RTN measurements lead to an identical result.
Nano Convergence
The effects of the grain size of Pt bottom electrodes on the ferroelectricity of hafnium zirconiu... more The effects of the grain size of Pt bottom electrodes on the ferroelectricity of hafnium zirconium oxide (HZO) were studied in terms of the orthorhombic phase transformation. HZO thin films were deposited by chemical solution deposition on the Pt bottom electrodes with various grain sizes which had been deposited by direct current sputtering. All the samples were crystallized by rapid thermal annealing at 700 °C to allow a phase transformation. The crystallographic phases were determined by grazing incidence X-ray diffraction, which showed that the bottom electrode with smaller Pt grains resulted in a larger orthorhombic phase composition in the HZO film. As a result, capacitors with smaller Pt grains for the bottom electrode showed greater ferroelectric polarization. The smaller grains produced larger in-plane stress which led to more orthorhombic phase transformation and higher ferroelectric polarization.
Journal of the Korean Physical Society, 2018
This paper reports the deposition of a metal line using a multilayer stack and laser-induced forw... more This paper reports the deposition of a metal line using a multilayer stack and laser-induced forward transfer (LIFT) using a low cost continuous wave blue laser with a wavelength of 450 nm. The donor structure was composed of a light-to-heat (LTH) layer, a release layer, and a transfer layer in series. Amorphous silicon as the LTH layer absorbs photon energy and converts it to heat. A release layer was melted so that a silver transfer layer would be transferred to the receiver substrate. The transferred silver layer showed reasonable physical and electrical characteristics. A low cost fine linewidth metal layer could be achieved using this modified LIFT technique and blue laser.
Scientific Reports, 2017
We studied the impact of H2 pressure during post-metallization annealing on the chemical composit... more We studied the impact of H2 pressure during post-metallization annealing on the chemical composition of a HfO2/Al2O3 gate stack on a HCl wet-cleaned In0.53Ga0.47As substrate by comparing the forming gas annealing (at atmospheric pressure with a H2 partial pressure of 0.04 bar) and H2 high-pressure annealing (H2-HPA at 30 bar) methods. In addition, the effectiveness of H2-HPA on the passivation of the interface states was compared for both p- and n-type In0.53Ga0.47As substrates. The decomposition of the interface oxide and the subsequent out-diffusion of In and Ga atoms toward the high-k film became more significant with increasing H2 pressure. Moreover, the increase in the H2 pressure significantly improved the capacitance‒voltage characteristics, and its effect was more pronounced on the p-type In0.53Ga0.47As substrate. However, the H2-HPA induced an increase in the leakage current, probably because of the out-diffusion and incorporation of In/Ga atoms within the high-k stack.
International Journal of Social Network Mining, 2015
In this work, we propose a new efficient agglomerative algorithm for hierarchical clustering anal... more In this work, we propose a new efficient agglomerative algorithm for hierarchical clustering analysis (HCA) of large networks. This algorithm, called Mod-Müllner, is an adaptation of an existing algorithm proposed by Müllner in 2011 and initially dedicated to HCA of pairwise dissimilarities. Mod-Müllner performs a greedy optimisation of the modularity, a widely used measure for network partitioning. We show that thanks to adapted data structures, Mod-Müllner achieves lower running times than other agglomerative algorithms, while producing comparable solutions. Finally, Mod-Müllner is compared to the Louvain method on simulated and real-world datasets. For both methods, the improved solutions obtained through single-level and multilevel refinements are studied.
Bulletin of the American Physical Society, Mar 3, 2014
Bulletin of the American Physical Society, Mar 5, 2015
fluctuations and increases in price and the issues in supply recently of rare earth metals reheat... more fluctuations and increases in price and the issues in supply recently of rare earth metals reheated the sought for non-rare earth permanent magnets. Alnico permanent magnets have been considered as promising replacements for rare earth-based permanent magnets due to the superiors in the magnetic performance at high temperature and the abundances of the constituent elements. Using lattice Monte Carlo simulation in combination with cluster expansion method we study the atomic structure of alnico 5-7 permanent magnets. We observed the phase separation into FeCo-rich and NiAl-rich phases in alnico 5-7 at low temperature, which is consistent with experiment. The phase boundary between these two phases is quite sharp. Both FeCo-rich and NiAl-rich phases are in B2 ordering with Fe and Al sitting on ?-site and Ni and Co sitting on ?-site. The degree of order of NiAl-rich phase is quite higher than that of FeCo-rich phase and it decreases with temperature slower than that of FeCo-rich phase. We also observed a small and increasing with annealing temperature magnetic moment in NiAl-rich phase, implying that the magnetic properties of alnico 5-7 could be improved by lowering annealing temperature to diminish the magnetism in NiAl-rich phase.
The binding energy of exciton in semiconductor carbon nanotubes
Communications in Physics
ABSTRACT
Effects of La Incorporation in Hf Based Dielectric on Leakage Conduction and Carrier Scattering Mechanisms
Journal of Nanoscience and Nanotechnology, 2015
Metal-oxide-semiconductor field effect transistors (MOSFETs) with various doses of La-incorporate... more Metal-oxide-semiconductor field effect transistors (MOSFETs) with various doses of La-incorporated in Hafnium-based dielectrics were characterized to evaluate the effect of La on dielectric and device properties. It is found that the Poole-Frenkel emission model could explain our experimental leakage current conduction mechanism reasonably and barrier heights of localized Poole-Frenkel trap sites increase gradually with increasing La incorporation. Cryogenic measurement (from 100 K to 300 K) of MOSFETs reveals that, as the content of La incorporation in the dielectric increases, the more increase of maximum effective mobility has been found at low temperature. It is mainly attributed to the more reduction of phonon scattering due to higher content of La atoms at the interface of dielectric and channel. Though it is relatively small, the existence of La in dielectric reduces coulomb scattering rate as well.
A motif-network search scheme is proposed to study the crystal structures of the dilithium/disodi... more A motif-network search scheme is proposed to study the crystal structures of the dilithium/disodium transition metal orthosilicates A2MSiO4. Using this fast and efficient method, the structures of all six combinations with A = Li or Na and M = Mn, Fe or Co were extensively explored. In addition to finding all previously reported structures, we discovered many other different crystal structures which are highly degenerate in energy. These tetrahedral-network-based structures can be classified into 1D, 2D and 3D types based on M-Si-O frames. A clear trend of the structural preference in different systems was revealed and possible indicators that affect the structure stabilities were introduced. For the case of Na systems which have been much less investigated in the literature relative to the Li systems, we predicted their ground state structures and found evidence for the existence of new structural motifs.
Solid-State Electronics, 2015
The trap distribution of a polysilicon (poly-Si) channel in a metal-oxide-semiconductor field eff... more The trap distribution of a polysilicon (poly-Si) channel in a metal-oxide-semiconductor field effect transistor (MOSFET) was extracted successfully using a variable amplitude charge pumping method (VACP) and an energy band bending model. Compared to single crystal Si channels, the poly-Si channels exhibited a high density of bulk channel traps due to the presence of grain boundaries. The densities of the trap states existing in the poly-silicon channel with various grain sizes and channel thicknesses were extracted and compared. The grain size of poly-Si was found to have a stronger impact on the trap distribution than the channel thickness. After hot carrier stress, the trap density in the poly-silicon channel increases and the generated traps are located both at mid gap energy level and near the conduction band energy level.
Journal of Theoretical Chemistry, 2013
The stability orders of a number of alkaline earth oxide cluster isomers (MO)n, M = Mg, Ca, Sr, B... more The stability orders of a number of alkaline earth oxide cluster isomers (MO)n, M = Mg, Ca, Sr, Ba and 1≤n≥6 have been determined by means of density functional theory studies using the LDA-PWC functional. Among the candidate structures, the hexagonal-ring-based isomers and the slab shapes are found to display similar stabilities. Stacks of hexagonal (MO)3 rings are found to be the slightly preferred growth strategy among the (MgO)6, isomers. In contrast, the slab structures are slightly preferred for the other alkaline metal oxide (MO)6 clusters. An explanation based on packing and aromaticity arguments has been proposed. This study may have important implications for modeling and understanding the initial growth patterns of small nanostructures of alkaline earth metals.
RSC Adv., 2014
New ground state structure of BeB2 with Z = 4. B atoms form hexagonal layers intercalated by Be a... more New ground state structure of BeB2 with Z = 4. B atoms form hexagonal layers intercalated by Be atoms.
A DC Programming Approach for Finding Communities in Networks
Neural Computation, 2014
Automatic discovery of community structures in complex networks is a fundamental task in many dis... more Automatic discovery of community structures in complex networks is a fundamental task in many disciplines, including physics, biology, and the social sciences. The most used criterion for characterizing the existence of a community structure in a network is modularity, a quantitative measure proposed by Newman and Girvan ( 2004 ). The discovery community can be formulated as the so-called modularity maximization problem that consists of finding a partition of nodes of a network with the highest modularity. In this letter, we propose a fast and scalable algorithm called DCAM, based on DC (difference of convex function) programming and DCA (DC algorithms), an innovative approach in nonconvex programming framework for solving the modularity maximization problem. The special structure of the problem considered here has been well exploited to get an inexpensive DCA scheme that requires only a matrix-vector product at each iteration. Starting with a very large number of communities, DCAM ...
Network Intrusion Detection Based on Multi-Class Support Vector Machine
Computational Collective Intelligence. Technologies and Applications, 2012
The application of multi-class support vector machine (SVM) for network intrusion detection was r... more The application of multi-class support vector machine (SVM) for network intrusion detection was researched, and the key technique problems and solutions were discussed. Our designed SVM classifier was evaluated with a benchmark dataset used in the third ...
Neurocomputing, 2015
This paper studies the problem of feature selection in the context of Semi-Supervised Support Vec... more This paper studies the problem of feature selection in the context of Semi-Supervised Support Vector Machine (S3VM). The zero norm, a natural concept dealing with sparsity, is used for feature selection purpose. Due to two nonconvex terms (the loss function of unlabeled data and the ℓ 0 term), we are faced with a NP hard optimization problem. Two continuous approaches based on DC (Difference of Convex functions) programming and DCA (DC Algorithms) are developed. The first is DC approximation approach that approximates the ℓ 0-norm by a DC function. The second is an exact reformulation approach based on exact penalty techniques in DC programming. All the resulting optimization problems are DC programs for which DCA are investigated. Several usual sparse inducing functions are considered, and six versions of DCA are developed. Empirical numerical experiments on several Benchmark datasets show the efficiency of the proposed algorithms, in both feature selection and classification.
Interface Structure Prediction from First-Principles
The Journal of Physical Chemistry C, 2014
Information about the atomic structures at solid–solid interfaces is crucial for understanding an... more Information about the atomic structures at solid–solid interfaces is crucial for understanding and predicting the performance of materials. Due to the complexity of the interfaces, it is very challenging to resolve their atomic structures using either experimental techniques or computer simulations. In this paper, we present an efficient first-principles computational method for interface structure prediction based on an adaptive genetic algorithm. This approach significantly reduces the computational cost, while retaining the accuracy of first-principles prediction. The method is applied to the investigation of both stoichiometric and nonstoichiometric SrTiO3 Σ3(112)[110] grain boundaries with unit cell containing up to 200 atoms. Several novel low-energy structures are discovered, which provide fresh insights into the structure and stability of the grain boundaries.
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Papers by Manh Cuong Nguyen