SIMULATION OF NANOSCALE ETCHING FOR NANOTUBE AND GRAPHENE DEVICES

2012 ◽  
Vol 1451 ◽  
pp. 21-24
Author(s):  
Koichi Kusakabe
Keyword(s):  
Hydrogen Atom ◽  
Density Functional ◽  
Carbon Materials ◽  
Tube Wall ◽  
Hydrogen Atoms ◽  
Functional Theory ◽  
Wales Defect ◽  
The Density Functional Theory ◽  
Graphene Devices ◽  
Tungsten Tip

ABSTRACTIn order to find an efficient method to etch nano-carbon materials by hydrogenation in a controlled manner, we have studied hydrogen-atom adsorption on various deformed nanotubes using computer simulations based on the density-functional theory. The nanotube with an atomic lack is compared to a deformed tube with the Stone-Wales defect and a twisted tube wall. Similar to the known experimental etching condition for graphene, an atomic lack is effective to accumulate hydrogen atoms around the defect. Compared to the flat graphene, however, nanotube walls with curvature allow on-top adsorption of a hydrogen atom and selectivity in the hydrogenated site becomes worse. To achieve a controlled etching process, usage of a tungsten tip which realizes focused hydrogenation is proposed for natotubes and curved graphene.

Anisotropically Nanostructured Silicon: A First-Principle Approach.

2004 ◽  
Vol 832 ◽  
Author(s):  
Yuri Bonder ◽  
Chumin Wang
Keyword(s):  
Experimental Data ◽  
Density Functional ◽  
First Principle ◽  
Hydrogen Atoms ◽  
Functional Theory ◽  
Nanostructured Silicon ◽  
Plane Anisotropy ◽  
The Density Functional Theory ◽  
The Difference ◽  
Good Agreement

ABSTRACTOptical properties of birefringent porous-silicon layers are studied within the density functional theory. Starting from a (110)-oriented supercell of 32 silicon atoms, columns of atoms in directions [100] and [010] are removed and the dangling bonds are saturated with hydrogen atoms. The results show an in-plane anisotropy in the dielectric function and in the refractive index (n). The difference Δn defined as n[110] -n[001] is compared with experimental data and a good agreement is observed. Also, the possibility in determining the morphology of pores by using polarized lights is analyzed.

DECOMPOSITION OF SiH4 ON THE SA TYPE STEPPED Si(100) SURFACE

2002 ◽  
Vol 09 (03n04) ◽  
pp. 1401-1407 ◽  
Author(s):  
ŞENAY KATIRCIOĞlu ◽  
ŞAKIR ERKOÇ
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Atom ◽  
Density Functional ◽  
Reaction Path ◽  
Density Functional Theory Method ◽  
Dissociative Adsorption ◽  
Theory Method ◽  
Functional Theory ◽  
Initial Stage ◽  
The Density Functional Theory

The density functional theory method is used to explore the mechanism of dissociative adsorption of silane (SiH4) on the SA type stepped Si(100) surface. Two reaction paths are described that produce silyl (SiH3) and hydrogen atom fragments adsorbed on the dimer bonds present on each terrace. It has been found that the initial stage of the dissociation of SiH4 on the SA type stepped Si(100) surface shows similarity to the dissociation of SiH4 on the flat Si(100) surface; SiH3 and hydrogen fragments bond to the Si dimer atoms by following the first reaction path.

scholarly journals SIMULASI PERUBAHAN DENSITAS MUATAN ADSORPSI ATOM HIDROGEN-GRAFENA DENGAN TEORI FUNGSI KERAPATAN

2018 ◽  
Vol 3 (2) ◽  
pp. 179-184
Author(s):  
Albert Zicko Johannes
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Atom ◽  
Charge Density ◽  
Density Functional ◽  
Structural Changes ◽  
Density Functional Theory Method ◽  
Hexagonal Structure ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Center Position

Abstrak Peristiwa adsorpsi atom Hidrogen pada Grafena menyebabkan terjadinya perubahan struktur Grafena. Perubahan ini mempengaruhi keadaan densitas muatan Grafena. Pada simulasi ini posisi atom Hidrogen pada permukaan lembaran Grafena divariasikan, yaitu pada posisi tepat di atas atom Karbon (Top), posisi di tengah antara dua atom Karbon (Bridge), dan posisi pusat struktur heksagonal (Hollow). Simulasi dilakukan dengan metode Teori Fungsi Kerapatan dengan model Grafena ukuran 2x2. Hasil yang diperoleh menunjukkan adsorpsi atom Hidrogen memilih posisi Top sebagai yang paling stabil dibandingkan dengan posisi Bridge dan Hollow. Hasil dari posisi Top menunjukkan elektron dari atom Hidrogen digunakan mengikat Grafena dengan energi ikat sebesar -1.7 eV. Perubahan densitas muatan menunjukkan terjadinya perpindahan elektron menuju Grafena disertai transformasi isosurface yang unik untuk setiap posisi atom Hidrogen dengan perubahan terbesar terjadi pada posisi Top.  Kata kunci: Densitas muatan, Grafena, Adsorpsi, Teori Fungsi Kerapatan  Abstract [Title: The Simulation of Charge Density Diffrential for Hydrogen Atom - Graphene Adsorption with Density Functional Theory] Hydrogen atom adsorption on Graphene cause structural changes. This change affect Graphene charge density. In this simulation the position of Hydrogen atom on the surface of Graphene sheet are varied out, which is on the position directly above the Carbon atom (Top), the position on the middle between two Carbon atoms (Bridge), and the center position of the hexagonal structure (Hollow). The simulation is done by the Density Functional Theory method with a 2x2 size Graphene model. The results obtained showed that Hydrogen atom adsorption chose the Top position as the most balanced compared with the position of Bridge and Hollow. The results from the Top position indicate that electrons from Hydrogen atom are used to bind the Graphene with binding energy of -1.7 eV. The charge density differential indicate the occurrence of electron transfer towards Graphene accompanied by a transformation of the isosurface that are unique for each Hydrogen atom positions with the biggest change is shown in the Top position.  Keywords: Charge Density, Graphene, Adsorption, Density Functional Theory

scholarly journals Атомная и электронная структура реконструкций поверхности (111) в кристаллах ZnSe и CdSe

2018 ◽  
Vol 60 (1) ◽  
pp. 187
Author(s):  
В.Л. Бекенев ◽  
С.М. Зубкова
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Hydrogen Atoms ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
A Charge ◽  
Quantum Espresso ◽  
First Time ◽  
Vacuum Gap ◽  
The Ideal

AbstractThe atomic and electron structure of four variants of polar (111)-(2 × 2) surfaces in ZnSe and CdSe terminated by a cation, namely, the ideal, relaxed, reconstructed, and relaxed after reconstruction surfaces, are calculated for the first time from the first principles. The surface is simulated by a film with a thickness of 12 atomic layers and a vacuum gap of ~16 Å in the layered superlattice approximation. Four fictitious hydrogen atoms with a charge of 0.5 electrons each are added for closing dangling Se bonds on the opposite side of the film. Ab initio calculations are performed using the QUANTUM ESPRESSO software based on the density functional theory. It is shown that relaxation results in splitting of atomic layers. We calculate and analyze the band structures and total and layer-wise densities of electron states for four variants of the surface.

scholarly journals The influence hydrogen atom addition has on charge switching during motion of the metal atom in endohedral Ca@C 60 H 4 isomers

2016 ◽  
Vol 374 (2076) ◽  
pp. 20150319
Author(s):  
G. Raggi ◽  
E. Besley ◽  
A. J. Stace
Keyword(s):  
Hydrogen Atom ◽  
Density Functional ◽  
Fullerene Cage ◽  
Hydrogen Atoms ◽  
Endohedral Fullerene ◽  
Calcium Atom ◽  
Carbon Cage ◽  
Functional Theory ◽  
Buckminster Fullerene ◽  
Selection Of

Density functional theory has been applied in a study of charge transfer between an endohedral calcium atom and the fullerene cage in Ca@C 60 H 4 and [Ca@C 60 H 4 ] + isomers. Previous calculations on Ca@C 60 have shown that the motion of calcium within a fullerene is accompanied by large changes in electron density on the carbon cage. Based on this observation, it has been proposed that a tethered endohedral fullerene might form the bases of a nanoswitch. Through the addition of hydrogen atoms to one hemisphere of the cage it is shown that, when compared with Ca @C 60 , asymmetric and significantly reduced energy barriers can be generated with respect to motion of the calcium atom. It is proposed that hydrogen atom addition to a fullerene might offer a route for creating a bi-stable nanoswitch that can be fine-tuned through the selection of an appropriate isomer and number of atoms attached to the cage of an endohedral fullerene. This article is part of the themed issue ‘Fullerenes: past, present and future, celebrating the 30th anniversary of Buckminster Fullerene’.

scholarly journals Vibrational Study of the Hydrogen Adsorption on the Missing Row Platinum (110) Surface

2020 ◽  
Vol 30 (1) ◽  
pp. 27
Author(s):  
Tran Thi Thu Hanh ◽  
Nguyen Van Hoa
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Atom ◽  
Density Functional ◽  
Hydrogen Adsorption ◽  
Ultrahigh Vacuum ◽  
Adsorption Model ◽  
Platinum Surface ◽  
Functional Theory ◽  
Vibrational Study ◽  
The Density Functional Theory

The hydrogen vibration was investigated to analyze its affect on the hydrogen adsorption on the missing row platinum surface (H/Pt(110)-(1\(\times\)2) model) in the ultrahigh vacuum (UHV). The density functional theory (DFT) combined with the approximation oscillation of the hydrogen atom on the surface was used. When the hydrogen coverage ΘH on the surface is 100% (\(\Theta\) = 1 ML), and taking into account the vibrational effect, the bond formed at the edge of the first layer (short bridge) is the most stable site. The vibrational effect on the adsorption model H/Pt(110)-(1\(\times\)2) is significant.

First Principles Study of Thermal Conductance Across Cu/Graphene/Cu Nanocomposition and the Effect of Hydrogenation

2016 ◽  
Author(s):  
Yi Tao ◽  
Chenhan Liu ◽  
Juekuan Yang ◽  
Kedong Bi ◽  
Weiyu Chen ◽  
...  
Keyword(s):  
Thermal Transport ◽  
Density Functional ◽  
Thermal Conductance ◽  
Hydrogen Atoms ◽  
Functional Theory ◽  
Hydrogenated Graphene ◽  
Interfacial Thermal Conductance ◽  
The Density Functional Theory ◽  
Equilibrium Separation ◽  
Transport Channels

In this work, the interfacial thermal conductance across Cu/graphene/Cu interfaces is investigated using the density functional theory (DFT) and the nonequilibrium Green’s function (NEGF) method. In order to study how hydrogenation of graphene affects thermal transport behaviors at the interfaces of Cu/graphene/Cu, we also analyze the interfacial thermal conductance across Cu/hydrogenated-graphene/Cu (Cu/H-graphene/Cu) with both double-sided and single-sided hydrogenated graphene. Our results show that, the interfacial thermal conductance across Cu/H-graphene/Cu interfaces is almost twice of the value across Cu/graphene/Cu interfaces. For Cu/H-graphene/Cu with double-sided hydrogenated graphene (Cu/DH-graphene/Cu), the hydrogen atoms between graphene and Cu layers provide additional thermal transport channels. While for Cu/H-graphene/Cu with single-sided hydrogenated graphene (Cu/SH-graphene/Cu), the hydrogen atoms not only provide additional thermal transport channels at the hydrogenated side of graphene, but also reduce the equilibrium separation between graphene and Cu layers at the non-hydrogenated side of graphene due to the transfer of massive electrons, which enhances the interface coupling between graphene and Cu layers. The phonon transmission shows that both double-sided and single-sided hydrogenation of graphene can increase the heat transport across the interface. Our calculation indicates that the interfacial thermal conductance of Cu/graphene/Cu nanocomposition can be improved by hydrogenation.

Density Functional Theory Calculations of Atomic Hydrogen Adsorption on (3, 3) Single-Wall Carbon Nanotubes with Vacancy Defects

2014 ◽  
Vol 687-691 ◽  
pp. 4315-4318
Author(s):  
Zong Sheng Li
Keyword(s):  
Carbon Nanotubes ◽  
Density Functional Theory ◽  
Hydrogen Atom ◽  
Density Functional ◽  
Single Wall Carbon Nanotubes ◽  
Adsorbed Hydrogen ◽  
Hydrogen Atoms ◽  
Functional Theory ◽  
Vacancy Defects ◽  
Single Wall Carbon

In this paper, we have employed density functional theory (DFT) to investigate the adsorption mechanisms of atomic hydrogens on the sidewalls of (3, 3) single-wall carbon nanotubes (CNTs) which have vacancy defects. All the calculations were performed using the generalized gradient approximation (GGA) with the Perdew, Burke and Ernzerhof (PBE) correlation functional.Our results show that hydrogen atoms can chemically adsorb on the defective nanotube. Bonding energy of per hydrogen atom decreases with the number of adsorbed hydrogen atoms. The hydrogen atoms will enhance the electrical conductivity of the (3, 3) nanotube. Besides one hydrogen atom adsorbing on the nanotube with a vacancy defect (MVD), hydrogen atoms move towards the MVD of the nanotube.

scholarly journals SIMULASI PERUBAHAN DENSITAS MUATAN ADSORPSI ATOM HIDROGEN-GRAFENA DENGAN TEORI FUNGSI KERAPATAN

2018 ◽  
Vol 3 (3) ◽  
pp. 179-184
Author(s):  
Albert Zicko Johannes
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Atom ◽  
Charge Density ◽  
Density Functional ◽  
Structural Changes ◽  
Density Functional Theory Method ◽  
Hexagonal Structure ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Center Position

Abstrak Peristiwa adsorpsi atom Hidrogen pada Grafena menyebabkan terjadinya perubahan struktur Grafena. Perubahan ini mempengaruhi keadaan densitas muatan Grafena. Pada simulasi ini posisi atom Hidrogen pada permukaan lembaran Grafena divariasikan, yaitu pada posisi tepat di atas atom Karbon (Top), posisi di tengah antara dua atom Karbon (Bridge), dan posisi pusat struktur heksagonal (Hollow). Simulasi dilakukan dengan metode Teori Fungsi Kerapatan dengan model Grafena ukuran 2x2. Hasil yang diperoleh menunjukkan adsorpsi atom Hidrogen memilih posisi Top sebagai yang paling stabil dibandingkan dengan posisi Bridge dan Hollow. Hasil dari posisi Top menunjukkan elektron dari atom Hidrogen digunakan mengikat Grafena dengan energi ikat sebesar -1.7 eV. Perubahan densitas muatan menunjukkan terjadinya perpindahan elektron menuju Grafena disertai transformasi isosurface yang unik untuk setiap posisi atom Hidrogen dengan perubahan terbesar terjadi pada posisi Top.  Kata kunci: Densitas muatan, Grafena, Adsorpsi, Teori Fungsi Kerapatan  Abstract [Title: The Simulation of Charge Density Diffrential for Hydrogen Atom - Graphene Adsorption with Density Functional Theory] Hydrogen atom adsorption on Graphene cause structural changes. This change affect Graphene charge density. In this simulation the position of Hydrogen atom on the surface of Graphene sheet are varied out, which is on the position directly above the Carbon atom (Top), the position on the middle between two Carbon atoms (Bridge), and the center position of the hexagonal structure (Hollow). The simulation is done by the Density Functional Theory method with a 2x2 size Graphene model. The results obtained showed that Hydrogen atom adsorption chose the Top position as the most balanced compared with the position of Bridge and Hollow. The results from the Top position indicate that electrons from Hydrogen atom are used to bind the Graphene with binding energy of -1.7 eV. The charge density differential indicate the occurrence of electron transfer towards Graphene accompanied by a transformation of the isosurface that are unique for each Hydrogen atom positions with the biggest change is shown in the Top position.  Keywords: Charge Density, Graphene, Adsorption, Density Functional Theory

HYDROGEN ADSORPTION ON β-TiAl (001) AND Ni/TiAl (001) SURFACES

2014 ◽  
Vol 21 (03) ◽  
pp. 1450034 ◽  
Author(s):  
A. A. KARIM MUBARAK ◽  
MAHMOUD ALELAIMI
Keyword(s):  
Density Functional ◽  
Hydrogen Adsorption ◽  
Correlation Energy ◽  
Full Potential ◽  
Generalized Gradient ◽  
Hydrogen Atoms ◽  
Functional Theory ◽  
Plane Wave Method ◽  
The Density Functional Theory ◽  
Linearized Augmented Plane Wave

In this paper, we present first principles calculations of the energetic, electronic and magnetic properties of the variant termination of TiAl (001) and Ni / TiAl (001) surfaces with and without hydrogen atoms. The calculations have been performed within the density functional theory using full-potential linearized augmented plane wave method. The generalized gradient approximation (GGA) is utilized as the exchange-correlation energy. The octahedral site is the stable absorption site of H atom in the β- TiAl system. This absorption reduces the cohesive energy of β- TiAl system due to increase in the lattice constant. The surface energy for both TiAl (001) terminations is calculated. The stable adsorption site of H atoms on the variant termination of TiAl (001) surface is performed. The adsorption energy of hydrogen on Ti is more energetic than that on Al . The adsorption of H atom on both terminations of H / Ni / TiAl (001) is more preferable at the bridge site. The adsorption energies are enhanced on Ni atom due to the contraction between d- Ni bands and TiAl substrate band.

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