STUDY ON BAND STRUCTURE OF NANOPOROUS SILICON THIN FILM

2018 ◽  
Vol 25 (01) ◽  
pp. 1850045
Author(s):  
XUEKE WU ◽  
YANLIN TANG
Keyword(s):  
Thin Film ◽  
Band Structure ◽  
Density Functional ◽  
First Principles Calculation ◽  
Generalized Gradient ◽  
Silicon Thin Film ◽  
Functional Theory ◽  
Nanoporous Silicon ◽  
Matrix Layer ◽  
Calculation Results

We investigate the energy band structure of nanoporous silicon thin film using first principles calculation based on density functional theory (DFT) with the generalized gradient approximation (GGA). The calculation results show that the band gaps of nanoporous silicon increase with increasing porosity, increase with decreasing the thickness of matrix layer, and almost independent of the thickness of pore layer. Moreover, the band structure of nanoporous silicon can be transformed from indirect to direct gap on thin films of (111) and (110) faces. It will be the guidance and reference for the fabrication of porous silicon optoelectronic devices.

scholarly journals Effect of Yb Concentration on the Structural, Magnetic and Optoelectronic Properties of Yb Doped ZnO: First Principles Calculation

2021 ◽  
Author(s):  
Mohamed Achehboune ◽  
Mohammed Khenfouch ◽  
Issam Boukhoubza ◽  
Issam Derkaoui ◽  
Bakang Moses Mothudi ◽  
...  
Keyword(s):  
Band Gap ◽  
Conduction Band ◽  
Density Functional ◽  
Blue Shift ◽  
First Principles Calculation ◽  
Theoretical Research ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Doped Zno ◽  
Good Agreement

Abstract Density functional theory-based investigation of the electronic, magnetic, and optical characteristics in pure and ytterbium (Yb) doped ZnO has been carried out by the plane-wave pseudopotential technique with generalized gradient approximation. The calculated lattice parameters and band gap of pure ZnO are in good agreement with the experimental results. The energy band-gap increases with the increase of Yb concentration. The Fermi level moves upward into the conduction band after doping with Yb, which shows the properties of an n-type se miconductor. New defects were created in the band-gap near the conduction band attributed to the Yb-4f states. The magnetic properties of ZnO were found to be affected by Yb doping; ferromagnetic property was observed for 4.17% Yb due to spin polarization of Yb-4f electrons. The calculated optical properties imply that Yb doped causes a blue shift of the absorption peaks, significantly enhances the absorption of the visible light, and the blue shift of the reflectivity spectrum was observed. Besides, a better transmittance of approximately 88% was observed for 4.17% Yb doped ZnO system. The refractive index and the extinction coefficient were observed to decrease as the Yb dopant concentration increased. As a result, we believe that our findings will be useful in understanding the doping impact in ZnO and will motivate further theoretical research.

First-principles study on the band structure, magnetic and elastic properties of half-metallic Cr2MnAl

2015 ◽  
Vol 29 (24) ◽  
pp. 1550139 ◽  
Author(s):  
Santao Qi ◽  
Chuan-Hui Zhang ◽  
Bao Chen ◽  
Jiang Shen
Keyword(s):  
Band Structure ◽  
Band Gap ◽  
Elastic Properties ◽  
Density Functional ◽  
Stable State ◽  
Generalized Gradient ◽  
Half Metallic ◽  
Text Type ◽  
Calculation Results ◽  
Indirect Band Gap

In this study, we have investigated the structural, electronic, magnetic and elastic properties of the full-Heusler [Formula: see text] alloy in the framework of density functional theory with generalized gradient approximation (GGA). The calculated results showed that [Formula: see text] was stable in ferrimagnetic configuration and crystallized in the [Formula: see text]-type structure. From the band structure and density of states calculation results, we concluded that [Formula: see text] belongs to a kind of half-metallic compound with an indirect band gap of 0.37 eV. Immediately thereafter, we have analyzed the origin of half-metallic band gap. The total magnetic moment of [Formula: see text] at the stable state is [Formula: see text] per formula unit, obeying the Slater–Pauling rule [Formula: see text]. In addition, various mechanical properties have been obtained and discussed based on the three principle elastic tensor elements [Formula: see text] and [Formula: see text] for the first time in the present work. We expect that our calculated results may trigger the application of [Formula: see text] in future spintronics field.

scholarly journals First-Principles Calculation of Transition Metal Hyperfine Coupling Constants with the Strongly Constrained and Appropriately Normed (SCAN) Density Functional and its Hybrid Variants

2019 ◽  
Vol 5 (4) ◽  
pp. 69 ◽  
Author(s):  
Dimitrios A. Pantazis
Keyword(s):  
Transition Metal ◽  
First Principles ◽  
Density Functional ◽  
Hyperfine Coupling ◽  
Coupling Constants ◽  
First Principles Calculation ◽  
Chemical System ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Hyperfine Coupling Constants

Density functional theory (DFT) is used extensively for the first-principles calculation of hyperfine coupling constants in both main-group and transition metal systems. As with many other properties, the performance of DFT for hyperfine coupling constants is of variable quality, particularly for transition metal complexes, because it strongly depends on the nature of the chemical system and the type of approximation to the exchange-correlation functional. Recently, a meta-generalized-gradient approximation (mGGA) functional was proposed that obeys all known exact constraints for such a method, known as the Strongly Constrained and Appropriately Normed (SCAN) functional. In view of its theoretically superior formulation a benchmark set of complexes is used to assess the performance of SCAN for the challenging case of transition metal hyperfine coupling constants. In addition, two global hybrid versions of the functional, SCANh and SCAN0, are described and tested. The values computed with the new functionals are compared with experiment and with those of other DFT approximations. Although the original SCAN and the SCAN-based hybrids may offer improved hyperfine coupling constants for specific systems, no uniform improvement is observed. On the contrary, there are specific cases where the new functionals fail badly due to a flawed description of the underlying electronic structure. Therefore, despite these methodological advances, systematically accurate and system-independent prediction of transition metal hyperfine coupling constants with DFT remains an unmet challenge.

First Principles Calculation on Adsorption of S on Fe(100) with Different Pressure

2012 ◽  
Vol 217-219 ◽  
pp. 1811-1814
Author(s):  
Xue Tao Hu ◽  
Qiang Luo ◽  
Zeng Ling Ran
Keyword(s):  
Hydrostatic Pressure ◽  
Adsorption Energy ◽  
First Principles ◽  
Density Functional ◽  
First Principles Calculation ◽  
Hollow Site ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Generalized Gradient Approximation ◽  
Adsorption Energies

Using periodic density functional theory within the generalized-gradient approximation to electron exchange and correlation, we have studied S adsorption four-fold hollow site on Fe(100) in different hydrostatic pressure. We find that the adsorption height decreases with hydrostatic pressure increasing is non-monotonic. The adsorption energy decreases with an increase with pressure is monotonic and we have obtained density of states is almost unchanged, the adsorption energy change is mainly caused by lattice deformation in the hydrostatic pressure, and the adsorption energies increase linearly with pressure.

Half-Metallic and Optical Properties of Cu and Cr Codoped AlN

2013 ◽  
Vol 842 ◽  
pp. 205-209
Author(s):  
Yu Qin Fan ◽  
Xue Yao
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Hole Concentration ◽  
First Principles Calculation ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Metallic Material ◽  
Half Metallic ◽  
Type Semiconductor ◽  
P Type

The Half-metallic and optical properties of wurtzite Cu and Cr codoped AlN were investigated by first-principles calculation based on density functional theory (DFT) using the generalized gradient approximation (GGA) for the exchange-correlation potential. It is shown that the Cu and Cr codoped AlN is a typical half-metallic material at the equilibrium lattice constant. As a p-type semiconductor, there exhibits higher hole concentration in Cu and Cr codoped AlN comparing with Cu doped AlN or Cr doped AlN, which indicates a significant increase in TC. This result suggests that it is possible to achieve high TC materials by Cu and Cr codoped AlN. In addition, the band gap of Cu and Cr codoped AlN is reduced and the absorption ability to ultraviolet light is expanded obviously, a noticeable red-shift of the absorption spectra edge is observed in the Cu and Cr codoped system and two new absorption peaks appear at around 28 nm and 225 nm.

Hydrogen Atom Adsorption on α-Al2O3(0001) Surface from First Principles

2011 ◽  
Vol 399-401 ◽  
pp. 2261-2265 ◽  
Author(s):  
Jian Gong Hu ◽  
Yi Sheng Zhang ◽  
Li Chao Jia ◽  
Bin Zhu ◽  
Hong Guang Yang ◽  
...  
Keyword(s):  
Adsorption Energy ◽  
First Principles ◽  
Density Functional ◽  
First Principles Calculation ◽  
Large Decrease ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Generalized Gradient Approximation ◽  
The Density Functional Theory ◽  
Low Coverage

First-principles calculation based on the density functional theory in the generalized gradient approximation was adopted to systematically investigate the α-Al2O3(0001) surface structure and the adsorption of H atom on the α-Al2O3(0001) surface. The calculations show that the O atop site is the energetically most favorable adsorption site at low coverage: at the H coverage of 1/6 ML (monolayer), the adsorption energy reaches up to7.61eV; in the regime of higher H coverages, the H atoms prefer to form atom cluster on the α-Al2O3(0001) surface, and the adsorption energy on the α-Al2O3(0001) with a pre-adsorbed H atom gets smaller, which illustrates that α-Al2O3that can prevent the penetration of hydrogen. With the increase of H coverage, the dipole moment reduces, which leads to a large decrease in the work function.

Density Functional Theory Analysis on Behavior of Metal Impurities in Ge (100) / Si (100)

2012 ◽  
Vol 725 ◽  
pp. 243-246
Author(s):  
Takahiro Maeta ◽  
Koji Sueoka
Keyword(s):  
Thin Film ◽  
Density Functional ◽  
First Principles Calculation ◽  
Theory Analysis ◽  
Strained Si ◽  
Functional Theory ◽  
Actual Structure ◽  
Metal Impurities ◽  
New Material ◽  
The Stability

Ge (100) thin film on Si (100) substrate is one of the new material technologies in the post scaling. In this study, we analyzed the stability of metal impurities of 4th row element around the interface of Ge (100) / Si (100) structure by using first-principles calculation. Considering the actual structure of the Ge thin film on Si (100) substrate, six calculation models were prepared. The calculated results showed that (1) Sc and Zn atoms are most stable at Ge surface, (2) Ti - Cr atoms are most stable in tensile plane-strained Si layer, (3) Mn - Cu atoms are most stable in compressive plane-strained Ge layer. These results indicate that the metal impurities concentrate on the strained region around the interface and/or Ge surface.

scholarly journals Insight into Physical and Thermodynamic Properties of X3Ir (X = Ti, V, Cr, Nb and Mo) Compounds Influenced by Refractory Elements: A First-Principles Calculation

Crystals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 104 ◽  
Author(s):  
Dong Chen ◽  
Jiwei Geng ◽  
Yi Wu ◽  
Mingliang Wang ◽  
Cunjuan Xia
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
Local Density ◽  
First Principles Calculation ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Debye Temperatures ◽  
Experimental Parameters ◽  
Experimental Values

The effects of refractory metals on physical and thermodynamic properties of X3Ir (X = Ti, V, Cr, Nb and Mo) compounds were investigated using local density approximation (LDA) and generalized gradient approximation (GGA) methods within the first-principles calculations based on density functional theory. The optimized lattice parameters were both in good compliance with the experimental parameters. The GGA method could achieve an improved structural optimization compared to the LDA method, and thus was utilized to predict the elastic, thermodynamic and electronic properties of X3Ir (X = Ti, V, Cr, Nb and Mo) compounds. The calculated mechanical properties (i.e., elastic constants, elastic moduli and elastic anisotropic behaviors) were rationalized and discussed in these intermetallics. For instance, the derived bulk moduli exhibited the sequence of Ti3Ir < Nb3Ir < V3Ir < Cr3Ir < Mo3Ir. This behavior was discussed in terms of the volume of unit cell and electron density. Furthermore, Debye temperatures were derived and were found to show good consistency with the experimental values, indicating the precision of our calculations. Finally, the electronic structures were analyzed to explain the ductile essences in the iridium compounds.

scholarly journals Spin Polarization Properties of Two Dimensional GaP3 Induced by 3d Transition-Metal Doping

Micromachines ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 743
Author(s):  
Huihui Wei ◽  
Jiatian Guo ◽  
Xiaobo Yuan ◽  
Junfeng Ren
Keyword(s):  
Transition Metal ◽  
Spin Polarization ◽  
Density Functional ◽  
Polarization Property ◽  
First Principles Calculation ◽  
Transition Metal Doping ◽  
Functional Theory ◽  
Density Distributions ◽  
Calculation Results ◽  
Spin Electronic

The electronic structure and spin polarization properties of monolayer GaP3 induced by transition metal (TM) doping were investigated through a first-principles calculation based on density functional theory. The calculation results show that all the doped systems perform spin polarization properties, and the Fe–doped system shows the greatest spin polarization property with the biggest magnetic moment. Based on the analysis from the projected density of states, it was found that the new spin electronic states originated from the p–d orbital couplings between TM atoms and GaP3 lead to spin polarization. The spin polarization results were verified by calculating the spin density distributions and the charge transfer. It is effective to introduce the spin polarization in monolayer GaP3 by doping TM atoms, and our work provides theoretical calculation supports for the applications of triphosphide in spintronics.

Electronic structure, elastic and thermal properties of semiconductor GaX (X = N, P, As, Sb) with zinc blende from first-principles calculation

2014 ◽  
Vol 28 (27) ◽  
pp. 1450183 ◽  
Author(s):  
Bingcheng Luo ◽  
Xiaowen Wu ◽  
Guowu Li
Keyword(s):  
Thermal Properties ◽  
Band Structure ◽  
Density Of States ◽  
Density Functional ◽  
First Principles Calculation ◽  
Functional Theory ◽  
Zinc Blende ◽  
Direct Band ◽  
Structure Density ◽  
Potential Methods

The band structure, density of states, elastic properties and thermal properties of semiconductor GaX (X = N , P , As , Sb ) with zinc blende were calculated by using the first principle plane-wave pseudo-potential methods based on density functional theory (DFT). The band structure and density of states for GaN , GaP , GaAs and GaSb show that GaX compounds are semiconductors with a direct band gap of 1.542, 1.445, 0.34 and 0.257 eV, respectively. The elastic constants and modulus are calculated showing that GaX are mechanically stable and GaN has the largest modulus. The anisotropy factor, internal-strain parameter, shear to bulk modulus and Poisson's ratio are also calculated indicating that GaX exhibit a brittle, anisotropic and plastic character. The dependencies of the Debye temperature, heat capacity, enthalpy, the entropy and free energy on temperature are also investigated. Comparisons with the available experiment and other theoretical calculation show reasonable agreement.

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