Using the Green’s function method, we study the modulation of the conductance in zigzag graphene nanoribbon (ZGNR) junctions by the gate voltages. As long as the difference between the gate voltages applied on the left and right ZGNRs (ΔV) remains unchanged, the conductance profiles for different cases are exactly the same, except to a displacement along EF-axis. It is found that the transmission of electrons from the upper/lower edge state of the left ZGNR to the lower/upper edge state of the right ZGNR is forbidden, therefore, the width of the conductance gap increases first and then decreases as |ΔV| increases. The upper/lower edge states and conduction/valence subbands of ZGNR under higher/lower gate voltage (VH/VL) determine step positions of the conductance when EF >VH/EF < VL. But when VL ≤ EF ≤ VH, the conductance profile is mainly determined by the upper and lower edge states, a few lowest conduction subbands/topmost valence subbands of ZGNR under lower/higher gate voltage. These results are helpful to the exploration and application of a new kind of field effect transistor based on ZGNR junctions.
{"title":"Gate Voltage-Modulated Conductance in Zigzag Graphene Nanoribbon Junctions","authors":"Ming Li, Zhikang Feng, Zheng-Yin Zhao","doi":"10.1155/2023/6463744","DOIUrl":"https://doi.org/10.1155/2023/6463744","url":null,"abstract":"Using the Green’s function method, we study the modulation of the conductance in zigzag graphene nanoribbon (ZGNR) junctions by the gate voltages. As long as the difference between the gate voltages applied on the left and right ZGNRs (ΔV) remains unchanged, the conductance profiles for different cases are exactly the same, except to a displacement along EF-axis. It is found that the transmission of electrons from the upper/lower edge state of the left ZGNR to the lower/upper edge state of the right ZGNR is forbidden, therefore, the width of the conductance gap increases first and then decreases as |ΔV| increases. The upper/lower edge states and conduction/valence subbands of ZGNR under higher/lower gate voltage (VH/VL) determine step positions of the conductance when EF >VH/EF < VL. But when VL ≤ EF ≤ VH, the conductance profile is mainly determined by the upper and lower edge states, a few lowest conduction subbands/topmost valence subbands of ZGNR under lower/higher gate voltage. These results are helpful to the exploration and application of a new kind of field effect transistor based on ZGNR junctions.","PeriodicalId":7382,"journal":{"name":"Advances in Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2023-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73562243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We investigated the transport properties of diluted magnetic semiconductors (DMSs) theoretically by using the Heisenberg and Ruderman–Kittel–Kasuya–Yosida (RKKY) exchange interaction models by considering both spin and charge disorder. The formalism is applied to the specific case of Ga 1 − x Mn x As . Using the Heisenberg model and the Green function formalism the total thermal excitation of the magnon is calculated. The magnetization and Curie temperature of Mn -doped GaAs is calculated. The theoretical calculation of T C of Ga 1 − x Mn x As at x = 0.08 has a good agreement with the experimental calculation at x = 0.08 (i.e., 162 k). The exchange interaction constant and spin-dependent relaxation time is calculated by using RKKY interaction. The electrical conductivity and hole mobility are calculated by using the Boltzmann transport equation and the spin-dependent relaxation time. The electrical conductivity of Mn -doped III–V DMS is exponentially increased with temperature and magnetic impurity concentration. Hole mobility of Mn -doped III–V diluted magnetic semiconductor is increased with the magnetic impurity concentration.
利用Heisenberg和Ruderman-Kittel-Kasuya-Yosida (RKKY)交换相互作用模型，在考虑自旋和电荷无序的情况下，从理论上研究了稀释磁性半导体(dms)的输运性质。该公式适用于Ga 1−x Mn x As的特殊情况。利用海森堡模型和格林函数形式，计算了磁振子的总热激发。计算了掺杂锰的砷化镓的磁化强度和居里温度。Ga 1−x Mn x As在x = 0.08时的理论计算结果与x = 0.08(即162 k)时的实验计算结果吻合较好。利用RKKY相互作用计算了交换相互作用常数和自旋相关的弛豫时间。利用玻尔兹曼输运方程和自旋相关弛豫时间计算了电导率和空穴迁移率。Mn掺杂的III-V DMS的电导率随温度和磁性杂质浓度呈指数增长。Mn掺杂的III-V稀释磁性半导体的空穴迁移率随磁性杂质浓度的增加而增加。
{"title":"The Study of Transport Properties of (III−Mn) V Diluted Magnetic Semiconductors","authors":"Edosa Tasisa Jira, H. Berry","doi":"10.1155/2023/8860586","DOIUrl":"https://doi.org/10.1155/2023/8860586","url":null,"abstract":"We investigated the transport properties of diluted magnetic semiconductors (DMSs) theoretically by using the Heisenberg and Ruderman–Kittel–Kasuya–Yosida (RKKY) exchange interaction models by considering both spin and charge disorder. The formalism is applied to the specific case of \u0000 \u0000 \u0000 Ga\u0000 \u0000 1\u0000 −\u0000 x\u0000 \u0000 \u0000 \u0000 Mn\u0000 \u0000 x\u0000 \u0000 \u0000 As\u0000 \u0000 . Using the Heisenberg model and the Green function formalism the total thermal excitation of the magnon is calculated. The magnetization and Curie temperature of \u0000 \u0000 Mn\u0000 \u0000 -doped \u0000 \u0000 GaAs\u0000 \u0000 is calculated. The theoretical calculation of \u0000 \u0000 \u0000 T\u0000 \u0000 C\u0000 \u0000 \u0000 \u0000 of \u0000 \u0000 \u0000 Ga\u0000 \u0000 1\u0000 −\u0000 x\u0000 \u0000 \u0000 \u0000 Mn\u0000 \u0000 x\u0000 \u0000 \u0000 As\u0000 \u0000 at x = 0.08 has a good agreement with the experimental calculation at x = 0.08 (i.e., 162 k). The exchange interaction constant and spin-dependent relaxation time is calculated by using RKKY interaction. The electrical conductivity and hole mobility are calculated by using the Boltzmann transport equation and the spin-dependent relaxation time. The electrical conductivity of \u0000 \u0000 Mn\u0000 \u0000 -doped III–V DMS is exponentially increased with temperature and magnetic impurity concentration. Hole mobility of \u0000 \u0000 Mn\u0000 \u0000 -doped III–V diluted magnetic semiconductor is increased with the magnetic impurity concentration.","PeriodicalId":7382,"journal":{"name":"Advances in Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2023-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88989315","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recent experimental results suggest that higher mobility of perovskite-type ligand passivated PbS quantum dots (QDs) could be useful for efficient solar cell applications. However, theoretical understanding of the mechanism through first principal modeling is still lacking. In this study, electronic-, optical-, and temperature-dependent carrier mobility for perovskite ligand passivated PbS QD array is calculated by using the first-principles density functional theory (DFT) combined with the nonequilibrium Green’s function (NEGF) technique and a molecular dynamics (MD)-Landauer approach. It is found that formamidinium (FA)-liganded QDs have higher mobility and enhanced optical absorption comparing to that of Cl-liganded QDs. The difference could be understood through the intermediate band featured electronic structure.
{"title":"Electronic-, Optical-, and Temperature-Dependent Carrier Mobility Simulations of Perovskite-Type Liganded PbS Quantum Dot Array","authors":"Kenta Kumakura, Chih-Chieh Chen, T. Sogabe","doi":"10.1155/2023/9580055","DOIUrl":"https://doi.org/10.1155/2023/9580055","url":null,"abstract":"Recent experimental results suggest that higher mobility of perovskite-type ligand passivated PbS quantum dots (QDs) could be useful for efficient solar cell applications. However, theoretical understanding of the mechanism through first principal modeling is still lacking. In this study, electronic-, optical-, and temperature-dependent carrier mobility for perovskite ligand passivated PbS QD array is calculated by using the first-principles density functional theory (DFT) combined with the nonequilibrium Green’s function (NEGF) technique and a molecular dynamics (MD)-Landauer approach. It is found that formamidinium (FA)-liganded QDs have higher mobility and enhanced optical absorption comparing to that of Cl-liganded QDs. The difference could be understood through the intermediate band featured electronic structure.","PeriodicalId":7382,"journal":{"name":"Advances in Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2023-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87700700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Masuma Bagum, S. Islam, E. A. Khan, J. Khandaker, Fannana Ahmed
ZnO, ZnO (calcined at 400°C), nitrogen-doped ZnO nanoparticles, and activated carbon (AC) impregnated with ZnO (ZnO/AC) nanocomposites were synthesized by the hydrothermal method. The structural, morphological, and optical properties of the synthesized complexes were studied by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformation infrared analysis (FTIR), Brunauer−Emmett−Teller (BET) analysis, and UV-visible spectroscopy analysis. The degradation of the antibiotic metronidazole (MNZ) from aqueous solutions was examined by the photocatalytic process of those synthesized complexes. Among the four complexes, ZnO/AC was confirmed to be a capable prospective both as an efficient photocatalyst and as an adsorbent. The optimal photodegradation condition obtained was 0.9 g/L and pH = 9. After 300 minutes, 99% of MNZ was removed by ZnO/AC. Finally, gas chromatography-mass spectroscopy was conducted to identify the degradation intermediates.
{"title":"Degradation of Metronidazole from Aqueous Environment Using Hydrothermally Synthesized ZnO, N-Doped ZnO, and ZnO/AC Nanoparticles","authors":"Masuma Bagum, S. Islam, E. A. Khan, J. Khandaker, Fannana Ahmed","doi":"10.1155/2023/8706698","DOIUrl":"https://doi.org/10.1155/2023/8706698","url":null,"abstract":"ZnO, ZnO (calcined at 400°C), nitrogen-doped ZnO nanoparticles, and activated carbon (AC) impregnated with ZnO (ZnO/AC) nanocomposites were synthesized by the hydrothermal method. The structural, morphological, and optical properties of the synthesized complexes were studied by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformation infrared analysis (FTIR), Brunauer−Emmett−Teller (BET) analysis, and UV-visible spectroscopy analysis. The degradation of the antibiotic metronidazole (MNZ) from aqueous solutions was examined by the photocatalytic process of those synthesized complexes. Among the four complexes, ZnO/AC was confirmed to be a capable prospective both as an efficient photocatalyst and as an adsorbent. The optimal photodegradation condition obtained was 0.9 g/L and pH = 9. After 300 minutes, 99% of MNZ was removed by ZnO/AC. Finally, gas chromatography-mass spectroscopy was conducted to identify the degradation intermediates.","PeriodicalId":7382,"journal":{"name":"Advances in Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2023-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90574658","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mohammad Jahidul Islam, Md. Sabbir Hasan Sohag, Unesco Chakma, A. Kumer, M. Alam, Mohammed Nazrul Islam Khan
The stannite structured ZnAg2SnS4 was developed from its parent composition ZnAg2GeS4, which is considered to be an excellent photocatalytic material, as the demands for photocatalytic effect on organic and waste water treatment have been increasing around the globe. First and foremost, the geometry optimization was performed by density functional theory (DFT) of the generalized gradient approximation (GGA) with Perdew–Burke–Ernzerhof (PBE)-ballpark figured as the successful candidate for computational screening containing heavy metal complexes. The structural geometry parameters were determined along with the electronic band structure, density of state (DOS), partial density of state (PDOS), Mulliken charge population, elastic constant, and optical characteristics. When the Ge (ZnAg2GeS4) atom has been swapped out by a Sn (ZnAg2SnS4) atom, the changes in band gap is noticeable, which rises from 0.94 eV to 1.15 eV with the same geometry and surface area. But, after 7% Fe doping, it has decreased to 0.32 eV. The PDOS demonstrates that the production of hydrogen for photocatalytic influence on wastewater treatment is dependent on the Fe atom's ability to induce and boost the electron density in both the conduction band and the valence band. The study of the elastic constant and mechanical constant revealed that these crystals are extremely stable in any environment. The dielectric constant and optical absorptions illustrate the superior evidence for photocatalytic activity. To sum up, it could be said that after doping of Fe, the elastic constant and mechanical constant show all universal anisotropic index crystals and ZnAg2Sn0.93Fe0.07S4 can absorb a variety of UV radiation, which raises the possibility that it could function as a photocatalyst.
{"title":"Structural, Electronic, Elastic, Mechanical, and Opto-Electronic Properties for ZnAg2SnS4 and ZnAg2Sn0.93Fe0.07S4 Photocatalyst Effort on Wastewater Treatment through the First Principle Study","authors":"Mohammad Jahidul Islam, Md. Sabbir Hasan Sohag, Unesco Chakma, A. Kumer, M. Alam, Mohammed Nazrul Islam Khan","doi":"10.1155/2023/8717656","DOIUrl":"https://doi.org/10.1155/2023/8717656","url":null,"abstract":"The stannite structured ZnAg2SnS4 was developed from its parent composition ZnAg2GeS4, which is considered to be an excellent photocatalytic material, as the demands for photocatalytic effect on organic and waste water treatment have been increasing around the globe. First and foremost, the geometry optimization was performed by density functional theory (DFT) of the generalized gradient approximation (GGA) with Perdew–Burke–Ernzerhof (PBE)-ballpark figured as the successful candidate for computational screening containing heavy metal complexes. The structural geometry parameters were determined along with the electronic band structure, density of state (DOS), partial density of state (PDOS), Mulliken charge population, elastic constant, and optical characteristics. When the Ge (ZnAg2GeS4) atom has been swapped out by a Sn (ZnAg2SnS4) atom, the changes in band gap is noticeable, which rises from 0.94 eV to 1.15 eV with the same geometry and surface area. But, after 7% Fe doping, it has decreased to 0.32 eV. The PDOS demonstrates that the production of hydrogen for photocatalytic influence on wastewater treatment is dependent on the Fe atom's ability to induce and boost the electron density in both the conduction band and the valence band. The study of the elastic constant and mechanical constant revealed that these crystals are extremely stable in any environment. The dielectric constant and optical absorptions illustrate the superior evidence for photocatalytic activity. To sum up, it could be said that after doping of Fe, the elastic constant and mechanical constant show all universal anisotropic index crystals and ZnAg2Sn0.93Fe0.07S4 can absorb a variety of UV radiation, which raises the possibility that it could function as a photocatalyst.","PeriodicalId":7382,"journal":{"name":"Advances in Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2023-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86226489","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To examine the effects of the nonlocal thermoelastic parameters in a nanoscale semiconductor material, a novel nonlocal model with variable thermal conductivity is provided in this study. The photothermal diffusion (PTD) processes in a chemical action are utilized in the framework of the governing equations. When elastic, thermal, and plasma waves interact, the nonlocal continuum theory is used to create this model. For the main formulations to get the analytical solutions of the thermal stress, displacement, carrier density, and temperature during the nanoscale thermo-photo-electric medium, the Laplace transformation approach in one dimension (1D) of a thin circular plate is utilized. To create the physical fields, mechanical forces and thermal loads are applied to the semiconductor’s free surface. To acquire the full solutions of the research areas in the time-space domains, the inverse of the Laplace transform is applied with several numerical approximation techniques. Under the impact of nonlocal factors, the principal physical fields are visually depicted and theoretically explained.
{"title":"Photo Thermal Diffusion of Excited Nonlocal Semiconductor Circular Plate Medium with Variable Thermal Conductivity","authors":"Shreen El-Sapa, K. Lotfy, A. El-Bary, M. H. Ahmed","doi":"10.1155/2023/1106568","DOIUrl":"https://doi.org/10.1155/2023/1106568","url":null,"abstract":"To examine the effects of the nonlocal thermoelastic parameters in a nanoscale semiconductor material, a novel nonlocal model with variable thermal conductivity is provided in this study. The photothermal diffusion (PTD) processes in a chemical action are utilized in the framework of the governing equations. When elastic, thermal, and plasma waves interact, the nonlocal continuum theory is used to create this model. For the main formulations to get the analytical solutions of the thermal stress, displacement, carrier density, and temperature during the nanoscale thermo-photo-electric medium, the Laplace transformation approach in one dimension (1D) of a thin circular plate is utilized. To create the physical fields, mechanical forces and thermal loads are applied to the semiconductor’s free surface. To acquire the full solutions of the research areas in the time-space domains, the inverse of the Laplace transform is applied with several numerical approximation techniques. Under the impact of nonlocal factors, the principal physical fields are visually depicted and theoretically explained.","PeriodicalId":7382,"journal":{"name":"Advances in Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2023-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78584456","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The manuscript substantiates the structural and electronic properties of covalent triazine frameworks (CTF)/As van der Waals heterostructures (vdWh) employing the standard first-principles calculation method. The numerical results designate that the CTF/As vdWh has robust crystal structures, a type-II band alignment (BA), and an indirect bandgap of 1.44 eV. The calculated results demonstrate that the strain could lead to interesting indirect-direct semiconductor transitions, while the external electric field could give rise to type-II to type-I BA and semiconductor-metal transitions. The underlined outcomes present the workability of CTF/As vdWhs in unprecedented high-performance optoelectronic equipment.
{"title":"Theoretical Study on the Electronic Properties of Two-Dimensional Covalent Triazine Frameworks/As van der Waals Heterostructures","authors":"Jianhua Zhu, Li Hao, Jing Pan, X. Tan","doi":"10.1155/2023/7601146","DOIUrl":"https://doi.org/10.1155/2023/7601146","url":null,"abstract":"The manuscript substantiates the structural and electronic properties of covalent triazine frameworks (CTF)/As van der Waals heterostructures (vdWh) employing the standard first-principles calculation method. The numerical results designate that the CTF/As vdWh has robust crystal structures, a type-II band alignment (BA), and an indirect bandgap of 1.44 eV. The calculated results demonstrate that the strain could lead to interesting indirect-direct semiconductor transitions, while the external electric field could give rise to type-II to type-I BA and semiconductor-metal transitions. The underlined outcomes present the workability of CTF/As vdWhs in unprecedented high-performance optoelectronic equipment.","PeriodicalId":7382,"journal":{"name":"Advances in Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2023-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73719218","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, the structural, electronic, elastic, phonon vibration, thermodynamic features, and optical properties of the orthorhombic phase of (space group Pnma) C a H f S 3 were examined by first-principles calculations utilizing the plane wave ultrasoft pseudopotentials in generalized gradient approximations (GGAs) and with Hubbard on-site correction (DFT + U). To improve the value of the band gap, the exchange correlation potential is also approximated with Hubbard correction (GGA + U). The equilibrium state properties such as lattice parameters, unit cell volume, bulk modulus, and its derivative were calculated and are in good agreement with the existing data. The mechanical properties such as bulk modulus, shear modulus, Young’s modulus, and elastic anisotropy were determined from the obtained elastic constants. The ratio of bulk modulus to shear modulus confirms that the orthorhombic phase of C a H f S 3 is a ductile material. In addition, the longitudinal sound velocity, transverse sound velocity, and Debye temperature for C a H f S 3 have been computed. The absence of negative frequencies in the phonon dispersion curve and the phonon density of states confirm that C a H f S 3 in the orthorhombic phase is dynamically stable. The thermodynamic parameters such as free energy, entropy, and heat capacity were examined with variations in temperature. Finally, the absorption coefficient, dielectric constant, energy loss function, reflectivity, and refractive index are discussed in detail in the spectral range 0–1.6 Ry (21.77 eV). The polarizations along (100), (010), and (001) directions significantly show different optical responses.
本研究利用平面波超软赝势在广义梯度近似(GGAs)和Hubbard现场校正(DFT + U)下的第一性原理计算，研究了(空间群)Pnma C a H f S 3正交相的结构、电子、弹性、声子振动、热力学特征和光学性质。为了提高带隙值，交换相关电位也用Hubbard校正(GGA + U)逼近。计算了晶格参数、单体胞体积、体积模量及其导数等平衡态性质，与已有数据吻合较好。根据得到的弹性常数确定了材料的体模量、剪切模量、杨氏模量和弹性各向异性等力学性能。体积模量与剪切模量的比值证实了C a H f S 3的正交相是一种延性材料。此外，还计算了C a H f S 3的纵向声速、横向声速和德拜温度。声子色散曲线中不存在负频率和态的声子密度，证实了正交相中的C a H f S 3是动态稳定的。热力学参数如自由能、熵和热容随温度的变化而变化。最后，详细讨论了0 ~ 1.6 Ry (21.77 eV)光谱范围内的吸收系数、介电常数、能量损失函数、反射率和折射率。沿(100)、(010)和(001)方向的偏振表现出明显不同的光学响应。
{"title":"The First-Principles Investigation of Structural Stability, Mechanical, Vibrational, Thermodynamic, and Optical Properties of CaHfS3 for Optoelectronic Application","authors":"Mulugetta Kassa, N. Debelo, M. Woldemariam","doi":"10.1155/2023/9332399","DOIUrl":"https://doi.org/10.1155/2023/9332399","url":null,"abstract":"In this study, the structural, electronic, elastic, phonon vibration, thermodynamic features, and optical properties of the orthorhombic phase of (space group Pnma) \u0000 \u0000 C\u0000 a\u0000 H\u0000 f\u0000 \u0000 \u0000 S\u0000 \u0000 \u0000 3\u0000 \u0000 \u0000 \u0000 were examined by first-principles calculations utilizing the plane wave ultrasoft pseudopotentials in generalized gradient approximations (GGAs) and with Hubbard on-site correction (DFT + U). To improve the value of the band gap, the exchange correlation potential is also approximated with Hubbard correction (GGA + U). The equilibrium state properties such as lattice parameters, unit cell volume, bulk modulus, and its derivative were calculated and are in good agreement with the existing data. The mechanical properties such as bulk modulus, shear modulus, Young’s modulus, and elastic anisotropy were determined from the obtained elastic constants. The ratio of bulk modulus to shear modulus confirms that the orthorhombic phase of \u0000 \u0000 \u0000 \u0000 C\u0000 a\u0000 H\u0000 f\u0000 S\u0000 \u0000 \u0000 3\u0000 \u0000 \u0000 \u0000 is a ductile material. In addition, the longitudinal sound velocity, transverse sound velocity, and Debye temperature for \u0000 \u0000 C\u0000 a\u0000 H\u0000 f\u0000 \u0000 \u0000 S\u0000 \u0000 \u0000 3\u0000 \u0000 \u0000 \u0000 have been computed. The absence of negative frequencies in the phonon dispersion curve and the phonon density of states confirm that \u0000 \u0000 \u0000 \u0000 C\u0000 a\u0000 H\u0000 f\u0000 S\u0000 \u0000 \u0000 3\u0000 \u0000 \u0000 \u0000 in the orthorhombic phase is dynamically stable. The thermodynamic parameters such as free energy, entropy, and heat capacity were examined with variations in temperature. Finally, the absorption coefficient, dielectric constant, energy loss function, reflectivity, and refractive index are discussed in detail in the spectral range 0–1.6 Ry (21.77 eV). The polarizations along (100), (010), and (001) directions significantly show different optical responses.","PeriodicalId":7382,"journal":{"name":"Advances in Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2023-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86170751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Genene Shiferaw Aga, Pooran Singh, Chernet Amente Geffe
Ternary boron-carbon-nitride compounds are the hardest, chemically stable, and most applicable semiconductors in optoelectronic devices. We investigate the quasi-particle and excitonic properties of type II o-BC2N using many-body perturbation theory (MBPT). The state-of-the-art GW and BSE methods were used to determine the accurate band gap and excited-state characteristics of this material. We simulate the convergence test and structural optimization in DFT, which is the starting point for the GW calculation. We also compute the convergence test of the parameters in GW and BSE. As a result, the bandgap of our system is found to be 2.31 eV and 1.95 eV using the GW approximation and DFT-PBE, respectively. Since the valence and conduction band edges are located at different Brillouin zones, we decide that o-BC2N is an indirect bandgap semiconductor. In addition, by applying the scissor operator, we corrected the quasi-particle bandgap, which shows almost the same result as the GW approximation. Furthermore, using the BSE algorithm, we calculate the optical bandgap of type II o-BC2N to be 4.0 eV with the excitonic effect and 4.4 eV without the excitonic effect. The highest peaks of the imaginary dielectric function with the excitonic effect shift to a lower energy level at 11 eV than without the excitonic effect at 13.5 eV. The electron charge distribution is computed by fixing the hole position. Finally, we suggest that type II o-BC2N is promising for the application of optoelectronic semiconductors.
{"title":"First-Principles Study of the Quasi-Particle and Excitonic Effect in o-BC2N: The GW + BSE Study","authors":"Genene Shiferaw Aga, Pooran Singh, Chernet Amente Geffe","doi":"10.1155/2023/7808434","DOIUrl":"https://doi.org/10.1155/2023/7808434","url":null,"abstract":"Ternary boron-carbon-nitride compounds are the hardest, chemically stable, and most applicable semiconductors in optoelectronic devices. We investigate the quasi-particle and excitonic properties of type II o-BC2N using many-body perturbation theory (MBPT). The state-of-the-art GW and BSE methods were used to determine the accurate band gap and excited-state characteristics of this material. We simulate the convergence test and structural optimization in DFT, which is the starting point for the GW calculation. We also compute the convergence test of the parameters in GW and BSE. As a result, the bandgap of our system is found to be 2.31 eV and 1.95 eV using the GW approximation and DFT-PBE, respectively. Since the valence and conduction band edges are located at different Brillouin zones, we decide that o-BC2N is an indirect bandgap semiconductor. In addition, by applying the scissor operator, we corrected the quasi-particle bandgap, which shows almost the same result as the GW approximation. Furthermore, using the BSE algorithm, we calculate the optical bandgap of type II o-BC2N to be 4.0 eV with the excitonic effect and 4.4 eV without the excitonic effect. The highest peaks of the imaginary dielectric function with the excitonic effect shift to a lower energy level at 11 eV than without the excitonic effect at 13.5 eV. The electron charge distribution is computed by fixing the hole position. Finally, we suggest that type II o-BC2N is promising for the application of optoelectronic semiconductors.","PeriodicalId":7382,"journal":{"name":"Advances in Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2023-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82186747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-01DOI: 10.12677/cmp.2023.122003
梦瑶 张
An ultra-sensitive H 2 S gas sensor based on Cu 2 O/CNF (carbon nanofibers) heterostructures is reported in this paper. Cu 2 O/CNF heterostructures were prepared by two-dimensional electrochemical in - situ deposition. Through the characterization of the sensor, it is found that the heterostructure has a large specific surface area and a clear heterogeneous interface
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