First-principles investigation of the conductive filament configuration in rutile TiO2-x ReRAM

2012 ◽  
Vol 1430 ◽  
Author(s):  
Liang Zhao ◽  
Seong-Geon Park ◽  
Blanka Magyari-Köpe ◽  
Yoshio Nishi
Keyword(s):  
High Resistance ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Conductive Filament ◽  
Low Resistance ◽  
Vacancy Ordering ◽  
Calculation Results ◽  
Resistance State

ABSTRACTThe interactions and ordering of oxygen vacancies in rutile TiO2 were thoroughly investigated by density functional calculations to search for atomic configurations of the conductive filament. As random isolated vacancies could not support the low-resistance state conduction in TiO2 ReRAM, vacancy ordering was introduced in [110] and [001] directions of the lattice to study the electronic structures. The calculation results revealed that a di-vacancy chain in [001] direction makes the electrons delocalized in that direction, which is identified as a possible configuration of the conductive filament. This low-resistance state can be effectively disrupted by moving oxygen vacancies out of the filament to reach high-resistance states.

ELECTRONIC STRUCTURES AND THE STABILITY OF MgO SURFACE: DENSITY FUNCTIONAL STUDY

2015 ◽  
Vol 22 (03) ◽  
pp. 1550037 ◽  
Author(s):  
DIAN-NA ZHANG ◽  
LI ZHAO ◽  
JIA-FU WANG ◽  
YAN-LI LI
Keyword(s):  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Chemical Potential ◽  
Surface States ◽  
Functional Study ◽  
Functional Theory ◽  
Calculation Results ◽  
The Stability ◽  
Mgo Surface

The electronic structures and the stability of the low-index surface (001), (011) and (111) for MgO were investigated by first-principles method based on density functional theory (DFT). We analyzed the stability of the MgO slab in equilibrium with an arbitrary oxygen environment. The density of states (DOS) and the band structures of MgO slabs were calculated and compared with those of the bulk MgO . Our calculation results reveal that the stabilities of the surface vary with the change of O chemical potential. In addition, the (001) and (011) surfaces are semiconductors, which are similar to that of the bulk MgO . However, the MgO (111) surface exhibits metallic property due to the effect of the surface states, which is different from that of the bulk MgO .

Phase Structures and Properties of Au-Pd-M (M=Zr, Mo, Y) System

2015 ◽  
Vol 816 ◽  
pp. 722-725
Author(s):  
Ming Xie ◽  
You Cai Yang ◽  
Ji Ming Zhang ◽  
Yong Tai Chen ◽  
Sai Bei Wang ◽  
...  
Keyword(s):  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Solidification Rate ◽  
Potential Method ◽  
Functional Theory ◽  
Structures And Properties ◽  
The Density Functional Theory ◽  
Calculation Results ◽  
Pseudo Potential

A series of new alloys including Au-Pd-M (M=Zr, Mo, Y) were developed in this study. The physical properties, electrical properties parameters and thermodynamics database of the alloys were established. The phase structure and composition were analyzed. The calculation results were verified by experiments. The influence of solidification rate to microstructures, morphology and grain size of Au-Pd-M alloys were analyzed. A first-principles plane-wave pseudo-potential method based on the density functional theory was used to investigate the electronic structures, bonding characters and energetic stability of Au-Pd-M alloys, the calculating results indicated that Au-Pd-Mo formed more easily than Au-Pd-Zr and Au-Pd-Y, and the formed Au-Pd-Mo is more stable than Au-Pd-Zr and Au-Pd-Y.

Electronic Structure and Optical Properties of La or In Doped SnO2: First-Principles Calculations

2011 ◽  
Vol 393-395 ◽  
pp. 80-83
Author(s):  
Chang Peng Chen ◽  
Mei Lan Qi
Keyword(s):  
Optical Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Density Functional Method ◽  
Functional Method ◽  
First Principles Calculations ◽  
Effective Reduction ◽  
Calculation Results ◽  
Impurity Elements

Based on the density functional method, the electronic structures and the optical properties for pure and La or In doped SnO2 are comparatively investigated in detail. The calculation results indicate that both the doping of La and the doping of In induce effective reduction of the band gap of SnO2, the impurity elements form new highly localized impurity energy level at the top of the valence band near the Fermi level. The interaction between electrons changed after doping which leads to the change of electrical properties .Meanwhile, red shifts are revealed in both the imaginary part of dielectric function and the absorption spectra corresponding to the change of band gaps

scholarly journals Comparative Study on Electronic Structure and Optical Properties of α-Fe2O3, Ag/α-Fe2O3 and S/α-Fe2O3

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 424
Author(s):  
Cuihua Zhao ◽  
Baishi Li ◽  
Xi Zhou ◽  
Jianhua Chen ◽  
Hongqun Tang
Keyword(s):  
Optical Properties ◽  
Optical Absorption ◽  
Electronic Structures ◽  
Density Functional ◽  
Peak Strength ◽  
Visible Range ◽  
High Symmetry ◽  
Functional Theory ◽  
Optical Absorption Peak ◽  
Calculation Results

The electronic structures and optical properties of pure, Ag-doped and S-doped α-Fe2O3 were studied using density functional theory (DFT). The calculation results show that the structure of α-Fe2O3 crystal changes after Ag and S doping, which leads to the different points of the high symmetry of Ag-doped and S-doped α-Fe2O3 with that of pure α-Fe2O3 in the energy band, as well as different Brillouin paths. In addition, the band gap of α-Fe2O3 becomes smaller after Ag and S doping, and the optical absorption peak shifts slightly toward the short wavelength, with the increased peak strength of S/α-Fe2O3 and the decreased peak strength of Ag/α-Fe2O3. However, the optical absorption in the visible range is enhanced after Ag and S doping compared with that of pure α-Fe2O3 when the wavelength is greater than 380 nm, and the optical absorption of S-doped α-Fe2O3 is stronger than that of Ag-doped α-Fe2O3.

The Quantum Length Dependence of Conductance in Molecular Device: An Ab Initio Study

2010 ◽  
Vol 663-665 ◽  
pp. 519-522
Author(s):  
Cai Juan Xia ◽  
Han Chen Liu ◽  
Ying Tang Zhang
Keyword(s):  
Electronic Transport ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Molecular Device ◽  
Functional Theory ◽  
Length Dependence ◽  
Molecular Conductance ◽  
Homo Lumo ◽  
Molecular Compounds

By Applying Nonequilibrium Green’s Function Formalism Combined First-Principles Density Functional Theory, we Investigate the Electronic Transport Properties of Thiophene and Furan Molecules with Different Quantum Length. the Influence of HOMO-LUMO Gaps and the Spatial Distributions of Molecular Orbitals on the Electronic Transport through the Molecular Device Are Discussed in Detail. the Results Show that the Transport Behaviors Are Determined by the Distinct Electronic Structures of the Molecular Compounds. the Length Dependence of Molecular Conductance Exhibits its Diversity for Different Molecules.

Electronic structure of the thermoelectric materials PbTe and AgPb18SbTe20 from first-principles calculations

2010 ◽  
Vol 25 (6) ◽  
pp. 1030-1036 ◽  
Author(s):  
Pengxian Lu ◽  
Zigang Shen ◽  
Xing Hu
Keyword(s):  
Band Structure ◽  
Thermoelectric Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Partial Density ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Scanning Transmission ◽  
Linearized Augmented Plane Wave

To investigate the effects of substituting Ag and Sb for Pb on the thermoelectric properties of PbTe, the electronic structures of PbTe and AgPb18SbTe20 were calculated by using the linearized augmented plane wave based on the density-functional theory of the first principles. By comparing the differences in the band structure, the partial density of states (PDOS), the scanning transmission microscope, and the electron density difference for PbTe and AgPb18SbTe20, we explained the reason from the aspect of electronic structures why the thermoelectric properties of AgPb18SbTe20 could be improved significantly. Our results suggest that the excellent thermoelectric properties of AgPb18SbTe20 should be attributed in part to the narrowing of its band gap, band structure anisotropy, the much extrema and large DOS near Fermi energy, as well as the large effective mass of electrons. Moreover, the complex bonding behaviors for which the strong bonds and the weak bonds are coexisted, and the electrovalence and covalence of Pb–Te bond are mixed should also play an important role in the enhancement of the thermoelectric properties of the AgPb18SbTe20.

Mechanisms of Nitrogen Incorporation at 4H-SiC/SiO2 Interface during Nitric Oxide Passivation – A First Principles Study

2016 ◽  
Vol 858 ◽  
pp. 465-468 ◽  
Author(s):  
D.P. Ettisserry ◽  
Neil Goldsman ◽  
Akin Akturk ◽  
Aivars J. Lelis
Keyword(s):  
Nitric Oxide ◽  
Silicon Dioxide ◽  
First Principles ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Functional Theory ◽  
Power Mosfets ◽  
Voltage Instability ◽  
Nitrogen Incorporation ◽  
Effective Mobility

In this work, we investigate the behavior of Nitrogen atoms at 4H-Silicon Carbide (4H-SiC)/Silicon dioxide (SiO2) interface during nitric oxide passivation using ab-initio Density Functional Theory. Our calculations suggest different possible energetically favorable and competing mechanisms by which nitrogen atoms could a) incorporate themselves into the oxide, just above the 4H-SiC substrate, and b) substitute for carbon atoms at the 4H-SiC surface. We attribute the former process to cause increased threshold voltage instability (hole traps), and the latter to result in improved effective mobility through channel counter-doping, apart from removing interface traps in 4H-SiC power MOSFETs. These results support recent electrical and XPS measurements. Additionally, Nitric Oxide passivation is shown to energetically favor re-oxidation of the 4H-SiC surface accompanied by the generation of oxygen vacancies under the conditions considered in this work.

Probing the electronic structures of Con (n = 1–5) clusters on γ-Al2O3 surfaces using first-principles calculations

2017 ◽  
Vol 19 (5) ◽  
pp. 3679-3687 ◽  
Author(s):  
Tao Yang ◽  
Masahiro Ehara
Keyword(s):  
Density Functional Theory ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
First Principles Calculations ◽  
Functional Theory

Using density functional theory calculations, we discussed the geometric and electronic structures and nucleation of small Co clusters on γ-Al2O3(100) and γ-Al2O3(110) surfaces.

The tuning effect of the electric field on the physical properties of some typical wurtzite semiconductors

2017 ◽  
Vol 31 (33) ◽  
pp. 1750310 ◽  
Author(s):  
Jia-Ning Li ◽  
San-Lue Hu ◽  
Hao-Yu Dong ◽  
Xiao-Ying Xu ◽  
Jia-Fu Wang ◽  
...  
Keyword(s):  
Electric Field ◽  
Physical Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Great Influence ◽  
Semiconductor Materials ◽  
Functional Theory ◽  
The Stability ◽  
Wurtzite Semiconductors

Under the tuning of an external electric field, the variation of the geometric structures and the band gaps of the wurtzite semiconductors ZnS, ZnO, BeO, AlN, SiC and GaN have been investigated by the first-principles method based on density functional theory. The stability, density of states, band structures and the charge distribution have been analyzed under the electric field along (001) and (00[Formula: see text]) directions. Furthermore, the corresponding results have been compared without the electric field. According to our calculation, we find that the magnitude and the direction of the electric field have a great influence on the electronic structures of the wurtzite materials we mentioned above, which induce a phase transition from semiconductor to metal under a certain electric field. Therefore, we can regulate their physical properties of this type of semiconductor materials by tuning the magnitude and the direction of the electric field.

Enhanced Resistance Switching of Ga2O3 Thin Films by Ultraviolet Radiation

2020 ◽  
Vol 20 (5) ◽  
pp. 3283-3286 ◽  
Author(s):  
Yuehua An ◽  
Xia Shen ◽  
Yuying Hao ◽  
Pengfei Guo ◽  
Weihua Tang
Keyword(s):  
Ultraviolet Radiation ◽  
High Resistance ◽  
High Resistance State ◽  
High Ratio ◽  
Resistance Switching ◽  
Resistive State ◽  
Oxide Systems ◽  
Low Resistance ◽  
Resistance State

Conductive filament mechanism can explain major resistance switching behaviors. The forming/deforming of the filaments define the high/low resistance states. The ratio of high/low resistance depends on the characterization of the filaments. In many oxide systems, the oxygen vacancies are important to forming the conductive filaments for the resistance switching behaviors. As ultrawide band gap semiconductor, Ga2O3 has very high resistance for its high resistance state, while its low resistive state has relative high resistance, which normally results in low ratio of high/low resistance. In this letter, we report a high ratio of high/low resistance by ultraviolet radiation. The I–V characteristics of Au/Ti/β-Ga2O3/W sandwich structure device shows that the HRS to LRS ratio of 5 orders is achieved.

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