scholarly journals DFT-Based Studies on Carbon Adsorption on the wz-GaN Surfaces and the Influence of Point Defects on the Stability of the Diamond–GaN Interfaces

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6532
Author(s):  
Malgorzata Sznajder ◽  
Roman Hrytsak
Keyword(s):  
Density Functional ◽  
High Electron Mobility Transistors ◽  
Growth Direction ◽  
First Principles Calculation ◽  
High Electron ◽  
Interfacial Layers ◽  
Adsorption Sites ◽  
Carbon Adsorption ◽  
The Stability ◽  
Reliability Performance

Integration of diamond with GaN-based high-electron-mobility transistors improves thermal management, influencing the reliability, performance, and lifetime of GaN-based devices. The current GaN-on-diamond integration technology requires precise interface engineering and appropriate interfacial layers. In this respect, we performed first principles calculation on the stability of diamond–GaN interfaces in the framework of density functional theory. Initially, some stable adsorption sites of C atoms were found on the Ga- and N-terminated surfaces that enabled the creation of a flat carbon monolayer. Following this, a model of diamond–GaN heterojunction with the growth direction [111] was constructed based on carbon adsorption results on GaN{0001} surfaces. Finally, we demonstrate the ways of improving the energetic stability of diamond–GaN interfaces by means of certain reconstructions induced by substitutional dopants present in the topmost GaN substrate’s layer.

scholarly journals Numerical Investigation of the Stability and Spintronic Properties of Selected Quaternary Alloys

2021 ◽  
Vol 3 (4) ◽  
pp. 6-12
Author(s):  
Adewumi I. Popoola ◽  
S. Babatunde Akinpelu
Keyword(s):  
Data Storage ◽  
Density Functional ◽  
First Principles Calculation ◽  
Electronic Charge ◽  
Quaternary Alloys ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Ferromagnetic Character ◽  
The Stability ◽  
Full Heusler

The use of electronic charge and spins (spintronics) has been proposed for much better data storage. This class of material is believed to have excellent capability for data integrity, low dynamic power consumption and high-density storage that showcases excellent protection against data loss. The spintronic and related properties have been investigated on four newly proposed quaternary alloys (NbRhGeCo, NbRhGeCr, NbRhGeFe and NbRhGeNi) through the first-principles calculation method of the Density Functional Theory (DFT). Specifically, the phonon frequencies, elastic stabilities, and the electronic structure were systematically studied in the full Heusler structure. The results predict that NbRhGeFe and NbRhGeCr are elastically and structurally stable. Both NbRhGeFe and NbRhGeCo are half-metals with ferromagnetic character, but NbRhGeCo is unfortunately elastically unstable. NbRhGeCr and NbRhGeNi are non-magnetic metallic alloys in their spin channels.  All the results predict NbRhGeFe to be the only suitable among all the four alloys for spintronic application.

scholarly journals Effects of Doped Elements (Si, Cr, W and Nb) on the Stability, Mechanical Properties and Electronic Structures of MoAlB Phase by the First-Principles Calculation

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4221
Author(s):  
Yongxin Jian ◽  
Zhifu Huang ◽  
Yu Wang ◽  
Jiandong Xing
Keyword(s):  
Mechanical Properties ◽  
Chemical Bonding ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Formation Enthalpy ◽  
First Principles Calculation ◽  
Elemental Doping ◽  
The Stability ◽  
W Doping

First-principles calculations based on density functional theory (DFT) have been performed to explore the effects of Si, Cr, W, and Nb elements on the stability, mechanical properties, and electronic structures of MoAlB ternary boride. The five crystals, with the formulas of Mo4Al4B4, Mo4Al3SiB4, Mo3CrAl4B4, Mo3WAl4B4, and Mo3NbAl4B4, have been respectively established. All the calculated crystals are thermodynamically stable, according to the negative cohesive energy and formation enthalpy. By the calculation of elastic constants, the mechanical moduli and ductility evolutions of MoAlB with elemental doping can be further estimated, with the aid of B/G and Poisson’s ratios. Si and W doping cannot only enhance the Young’s modulus of MoAlB, but also improve the ductility to some degree. Simultaneously, the elastic moduli of MoAlB are supposed to become more isotropic after Si and W addition. However, Cr and Nb doping plays a negative role in ameliorating the mechanical properties. Through the analysis of electronic structures and chemical bonding, the evolutions of chemical bondings can be disclosed with the addition of dopant. The enhancement of B-B, Al/Si-B, and Al/Si-Mo bondings takes place after Si substitution, and W addition apparently intensifies the bonding with B and Al. In this case, the strengthening of chemical bonding after Si and W doping exactly accounts for the improvement of mechanical properties of MoAlB. Additionally, Si doping can also improve the Debye temperature and melting point of the MoAlB crystal. Overall, Si element is predicted to be the optimized dopant to ameliorate the mechanical properties of MoAlB.

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 The Study on Structural and Photoelectric Properties of Zincblende InGaN via First Principles Calculation

Crystals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1159
Author(s):  
Juan Song ◽  
Zijiang Luo ◽  
Xuefei Liu ◽  
Ershi Li ◽  
Chong Jiang ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
Dielectric Function ◽  
Density Functional ◽  
High Electron Mobility Transistor ◽  
First Principles Calculation ◽  
High Electron ◽  
Lattice Constants ◽  
Photoelectric Properties ◽  
Alternative Material ◽  
Calculation Results

In this paper, the structure and photoelectric characteristics of zincblende InxGa1−xN alloys are systematically calculated and analyzed based on the density functional theory, including the lattice constant, band structure, distribution of electronic states, dielectric function, and absorption coefficient. The calculation results show that with the increase in x, the lattice constants and the supercell volume increase, whereas the bandgap tends to decrease, and InxGa1−xN alloys are direct band gap semiconductor materials. In addition, the imaginary part of the dielectric function and the absorption coefficient are found to redshift with the increase in indium composition, expanding the absorption range of visible light. By analyzing the lattice constants, polarization characteristics, and photoelectric properties of the InxGa1−xN systems, it is observed that zincblende InxGa1−xN can be used as an alternative material to replace the channel layer of wurtzite InxGa1−xN heterojunction high electron mobility transistor (HEMT) devices to achieve the manufacture of HEMT devices with higher power and higher frequency. In addition, it also provides a theoretical reference for the practical application of InxGa1−xN systems in optoelectronic devices.

Effect of Cu, S Co-Doping on Properties of AgSnO2 Contact Material

2020 ◽  
Vol 12 (8) ◽  
pp. 1242-1251
Author(s):  
Wang Jingqin ◽  
Liu Zhou ◽  
Chen Ling ◽  
Yu Shuangmiao ◽  
Zhu Yancai
Keyword(s):  
Density Functional ◽  
Electrical Contact ◽  
Sol Gel ◽  
Hole Mobility ◽  
First Principles Calculation ◽  
Powder Metallurgy Method ◽  
Co Doping ◽  
The Stability ◽  
Conductive Properties ◽  
Co Doped

The stability, elastic properties and conductive properties of Cu-doped SnO2, S-doped SnO2 and Cu, S-codoped SnO 2were studied by using the first-principles calculation method based on the density functional theory. The corresponding doped SnO2 powders were prepared by sol–gel method, while AgSnO2–Cu and AgSnO2–Cu–S contacts were obtained by powder metallurgy method for experimental verification. No diffraction peaks were associated with Cu and S in the XRD patterns of the doped SnO2 powders, indicating that the doped SnO2 retained the tetragonal crystal structure. The doping formation energy of Cu, S co-doped system was found to be lower than that of Cu single doping system and S single doping system. The bulk modulus, shear modulus and Young's modulus of the co-doped system became lower, the ability to resist compression deformation and shear deformation was also weakened, while its toughness was greatly improved. The hardness of the AgSnO2–Cu–S contact was 103.55 HV, which is less than the hardness of the AgSnO2–Cu contact (112.86 HV). The calculations indicated that Cu, S co-doping could narrow the band gap, reduce the hole effective mass and the acceptor ionization energy, improve the hole mobility, and enhance the conductivity of the material. The electrical contact simulation experiments showed that the conductive properties, arc corrosion resistance and welding resistance of AgSnO2–Cu–S contact were better than those of the AgSnO2–Cu contact. The conductivity of AgSnO2–Cu–S contact was 29.948 mS · m–1, the contact resistance was 1.109 Ωm ; the average arc duration and average arc energy were 1.480 ms and 171.65 mJ, respectively.

First Principle Study of Hydrazine and OH- Co-Adsorption on Ni(111) in High Coverage System

2014 ◽  
Vol 893 ◽  
pp. 35-38 ◽  
Author(s):  
Andam Deatama Refino ◽  
Mohammad Kemal Agusta ◽  
Hermawan Kresno Dipojono ◽  
Nugraha
Keyword(s):  
Density Functional ◽  
Co Adsorption ◽  
Stable Configuration ◽  
Nickel Surface ◽  
Gauche Conformation ◽  
High Coverage ◽  
Adsorption Mechanisms ◽  
Adsorption Sites ◽  
The Stability ◽  
In Cis

Theoretical investigation of co-adsorption process between hydrazine (N2H4) and OH- on Ni(111) is performed using density functional theory. OH- adsorption mechanisms at various adsorption sites as well as its interaction with hydrazine in various conformations (anti, cis, and gauche) are studied. The stability of OH- adsorption on nickel surface is significantly influenced by the presence of hydrazine molecule. Among the three conformations of hydrazine, OH- adsorption on nickel surface doesn't occur in cis conformation. Otherwise, co-adsorption occurs in system with gauche and anti conformation. In anti system, hydrazine conformation is transformed during relaxation process and forms gauche conformation as the most stable configuration of the system.

Preparation of Self-Assembly Monolayer by Scratching Si(100) Surface in the Presence of Aryl Diazonium Salts

2009 ◽  
Vol 60-61 ◽  
pp. 406-409
Author(s):  
Li Qiu Shi ◽  
Tao Sun ◽  
Feng Yu ◽  
Shen Dong ◽  
Fu Long Yuan
Keyword(s):  
Self Assembly ◽  
Density Functional ◽  
Active Species ◽  
First Principles Calculation ◽  
Silicon Sample ◽  
Covalent Bonds ◽  
Self Assembling ◽  
Aryldiazonium Salt ◽  
Before And After ◽  
The Stability

Mechanical scratching and chemical self-assembling can be combined to fabricate nano- or micro-scale functional structures on the oxide-coated silicon. The chemo-active species, such as NO2C6H4 groups, can be produce from aryldiazonium salt due to the breaking of chemical bond of silicon substrate when the diamond tool scratches the silicon sample in the presence of 4-benzoic nitryl diazonium tetrafluoroborate (NO2C6H4N2BF4). They may then induce grafting of an organic monolayer on the substrate via Si-C connection. The surface morphologies before and after chemomechanical reaction are characterized with Atomic Force Microscopy (AFM). We propose that chemomechanical reaction, which occurred during scratching the silicon surface, produce NO2C6H4 groups from aryldiazonium salt. The NO2C6H4 groups further bond with surface Si atoms via Si-C covalent bonds as confirmed from Infrared Spectroscopy (IR) results. To better understand the framework of the self-assembly monolayers (SAMs) on Si (100) surface, the first principles calculation at density functional theory levels has been employed to investigate the binding energy, bonds length and bonds angle. The reduced energy of system illuminates that the SAMs can be fabricated easily between aryldiazonium salt and Si (100) surface. The stability of system can be improved and SAMs can firmly stay on Si (100) surface.

First-Principles Study of the Self-Assembly Monolayer on Silicon (100) Surface

2012 ◽  
Vol 430-432 ◽  
pp. 28-31
Author(s):  
Li Qiu Shi ◽  
Feng Yu ◽  
Xiao Ping Hu ◽  
Xiao Wen Li ◽  
Tao Sun ◽  
...  
Keyword(s):  
Binding Energy ◽  
First Principles ◽  
Self Assembly ◽  
Density Functional ◽  
Covalent Bond ◽  
First Principles Calculation ◽  
Functional Theory ◽  
Aryldiazonium Salt ◽  
Before And After ◽  
The Stability

The first principles calculation based density functional theory has been employed to investigate the changes of energy, bonds length and bonds angle of aryldiazonium salt Self-assembly monolayer (SAMs) on silicon (100) surface. The steady structure and binding energy can be determined. It is shown that the partial bonds length and bonds angle have been changed obviously before and after self-assembly. The reduced energy of system is-101.95eV, i.e. binding energy, which is emitted energy of Si-C covalent bond coming into being, illuminates that the SAMs can be fabricated easily between aryldiazonium salt and Si (100) surface. The stability of system can be improved and SAMs can firmly stay on Si (100) surface.

HVPE-GROWN AlGaN/GaN HEMTs

2003 ◽  
Vol 764 ◽  
Author(s):  
B. Luo ◽  
F. Ren ◽  
M. A. Mastro ◽  
D. Tsvetkov ◽  
A. Pechnikov ◽  
...  
Keyword(s):  
High Electron Mobility Transistors ◽  
Hydride Vapor Phase Epitaxy ◽  
Root Mean Square Roughness ◽  
High Electron ◽  
Electron Mobility Transistors ◽  
Current Collapse ◽  
Collapse Characteristics ◽  
Capacitance Voltage ◽  
Source Current ◽  
Measurement Area

AbstractHigh quality undoped AlGaN/GaN high electron mobility transistors(HEMTs) structures have been gorwn by Hydride Vapor Phase Epitaxy (HVPE). The morphology of the films grown on Al2O3 substrates is excellent with root-mean-square roughness of ∼0.2nm over 10×10μm2 measurement area. Capacitance-voltage measurements show formation of dense sheet of charge at the AlGaN/GaN interface. HEMTs with 1μm gate length fabricated on these structures show transconductances in excess of 110 mS/mm and drain-source current above 0.6A/mm. Gate lag measurements show similar current collapse characteristics to HEMTs fabricated in MBE- or MOCVD grown material.

Tuning Transition Metal Carbides Activity by Surface Metal Alloying: Case Study on CO2 Capture and Activation

2018 ◽  
Author(s):  
Marti Lopez ◽  
Luke Broderick ◽  
John J Carey ◽  
Francesc Vines ◽  
Michael Nolan ◽  
...  
Keyword(s):  
Transition Metal ◽  
Co2 Capture ◽  
Density Functional ◽  
Deep Understanding ◽  
Metal Carbides ◽  
Transition Metal Carbides ◽  
Adsorption Sites ◽  
Surface Metal ◽  
A Minor

<div>CO2 is one of the main actors in the greenhouse effect and its removal from the atmosphere is becoming an urgent need. Thus, CO2 capture and storage (CCS) and CO2 capture and usage (CCU) technologies are intensively investigated as technologies to decrease the concentration</div><div>of atmospheric CO2. Both CCS and CCU require appropriate materials to adsorb/release and adsorb/activate CO2, respectively. Recently, it has been theoretically and experimentally shown that transition metal carbides (TMC) are able to capture, store, and activate CO2. To further improve the adsorption capacity of these materials, a deep understanding of the atomic level processes involved is essential. In the present work, we theoretically investigate the possible effects of surface metal doping of these TMCs by taking TiC as a textbook case and Cr, Hf, Mo, Nb, Ta, V, W, and Zr as dopants. Using periodic slab models with large</div><div>supercells and state-of-the-art density functional theory based calculations we show that CO2 adsorption is enhanced by doping with metals down a group but worsened along the d series. Adsorption sites, dispersion and coverage appear to play a minor, secondary constant effect. The dopant-induced adsorption enhancement is highly biased by the charge rearrangement at the surface. In all cases, CO2 activation is found but doping can shift the desorption temperature by up to 135 K.</div>

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