scholarly journals Modelling of Graphene Nanoribbon Fermi Energy

2010 ◽  
Vol 2010 ◽  
pp. 1-6 ◽  
Author(s):  
Zaharah Johari ◽  
Mohammad Taghi Ahmadi ◽  
Desmond Chang Yih Chek ◽  
N. Aziziah Amin ◽  
Razali Ismail
Keyword(s):  
Band Structure ◽  
Carrier Concentration ◽  
Fermi Energy ◽  
Minimum Energy ◽  
Graphene Nanoribbon ◽  
Promising Alternative ◽  
Band Energy ◽  
One Dimensional ◽  
Statistic Study ◽  
Degenerate Regime

Graphene nanoribbon (GNR) is a promising alternative to carbon nanotube (CNT) to overcome the chirality challenge as a nanoscale device channel. Due to the one-dimensional behavior of plane GNR, the carrier statistic study is attractive. Research works have been done on carrier statistic study of GNR especially in the parabolic part of the band structure using Boltzmann approximation (nondegenerate regime). Based on the quantum confinement effect, we have improved the fundamental study in degenerate regime for both the parabolic and nonparabolic parts of GNR band energy. Our results demonstrate that the band energy of GNR near to the minimum band energy is parabolic. In this part of the band structure, the Fermi-Dirac integrals are sufficient for the carrier concentration study. The Fermi energy showed the temperature-dependent behavior similar to any other one-dimensional device in nondegenerate regime. However in the degenerate regime, the normalized Fermi energy with respect to the band edge is a function of carrier concentration. The numerical solution of Fermi-Dirac integrals for nonparabolic region, which is away from the minimum energy band structure of GNR, is also presented.

Numerical Analysis Of Carrier Statistics In Lowdimensional Nanostructure Devices

2012 ◽  
Author(s):  
Ismail Saad ◽  
M. Taghi Ahmadi ◽  
Munawar A. Riyadi ◽  
Razali Ismail ◽  
Vijay K. Arora
Keyword(s):  
Numerical Analysis ◽  
Key Words ◽  
Carrier Concentration ◽  
Fermi Energy ◽  
Density Of State ◽  
One Dimensional ◽  
Low Dimensional ◽  
De Broglie Wavelength ◽  
Strongly Degenerate ◽  
Degenerate Regime

Statistik pembawa bagi dimensi–bawah strukturnano adalah diperjelaskan. Ketumpatan kawasan (DOS) adalah bersamaan dengan λDd, di mana d ialah dimensi bagi strukturnano dan λD ialah gelombang De–Broglie bersamaan dengan kamiran Fermi–Dirac yang merangkumi statistik pembawa bagi semua tahap kemerosotan. Pada regim tak–merosot, hasil kajian menunjukkan pengreplikanan apa yang ditafsirkan dari statistic Boltzman. Akan tetapi, pada regim merosot hasilan adalah berubah–ubah. Hasilan bagi semua dimensi telah dianalisis secara berangka dan dibandingkan bagi kesemua tiga arah Cartesian. Dengan menggunakan DOS yang sepadan, kepekatan pembawa pada semua dimensi telah didapati berdasarkan statistik Fermi – Dirac. Tenaga Fermi yang berlandaskan hujung jalur adalah berfungsi kepada suhu yang tidak bergantung pada kepekatan pembawa pada regim tak–merosot. Di regim merosot yang tinggi, tenaga Fermi adalah berfungsi kepada kepekatan pembawa bersesuaian dengan dimensi tersebut tetapi tidak bergantung pada suhu. Kata kunci: Statistik pembawa; kepekatan pembawa; peranti satu–dimensi; pembawa merosot dan tak merosot The carrier statistics for low–dimensional nanostructure is elaborated. The density of state (DOS) is proportional to λDd where d is the dimensionality of the nanostructure and λD is the De–Broglie wavelength proportion of Fermi–Dirac (FD) integral that covers the carrier statistics to all degeneracy level. In the non-degenerate regime the results replicate what is expected from the Boltzmann statistics. However, the results vary in degenerate regime. The results for all dimensions are numerically analyzed and compared for all three Cartesian directions. With appropriate DOS, the carrier concentration in all dimensions is obtained based on the FD statistic. Fermi energy with respect to band edge is a function of temperature that is independent of the carrier concentration in the non–degenerate regime. In the strongly degenerate regime, the Fermi energy is a function of carrier concentration appropriate for given dimensionality, but is independent of temperature. Key words: Carrier statistics; carrier concentration; one dimensional devices; degenerate and nondegenerate carrier

EFFECTIVE MOBILITY MODEL OF GRAPHENE NANORIBBON IN PARABOLIC BAND ENERGY

2011 ◽  
Vol 25 (10) ◽  
pp. 739-745 ◽  
Author(s):  
N. A. AMIN ◽  
M. T. AHMADI ◽  
Z. JOHARI ◽  
S. M. MOUSAVI ◽  
R. ISMAIL
Keyword(s):  
Experimental Data ◽  
Band Structure ◽  
Transport Properties ◽  
Conventional Method ◽  
Dirac Point ◽  
Graphene Nanoribbons ◽  
Mobility Model ◽  
Band Energy ◽  
One Dimensional ◽  
Effective Mobility

In this letter, we investigate the transport properties of one-dimensional semiconducting Graphene nanoribbons (GNRs) with parabolic band structure near the Dirac point. The analytical model of effective mobility is developed by using the conductance approach, which differs from the conventional method of extracting the effective mobility using the well-known Matthiessen rule. Graphene nanoribbons conductance model developed was applied in the Drude model to obtain the effective mobility, which then gives nearly close comparison with the experimental data.

The Shubnikov – de Haas effect in dilute lead-in-bismuth alloys

1968 ◽  
Vol 46 (21) ◽  
pp. 2413-2423 ◽  
Author(s):  
On-Ting Woo ◽  
R. J. Balcombe
Keyword(s):  
Band Structure ◽  
Fermi Surface ◽  
Carrier Concentration ◽  
Fermi Energy ◽  
Dilute Alloys ◽  
Haas Effect ◽  
Effect Of Alloying

The differential Shubnikov – de Haas effect has been studied in samples of bismuth containing up to 50 parts per million of lead. The results indicate that the only effect of alloying on the band structure of bismuth is to shift the Fermi energy; the sizes of the various pieces of the Fermi surface are changed, but their shapes are not distorted. The ratio of the change in net carrier concentration to the concentration of lead atoms is found to be only 0.4, which is anomalously low, compared with values of about 1.0 found for dilute alloys of other metals in bismuth.

LOW-FIELD MOBILITY MODEL ON PARABOLIC BAND ENERGY OF GRAPHENE NANORIBBON

2011 ◽  
Vol 25 (04) ◽  
pp. 281-290 ◽  
Author(s):  
N. AZIZIAH AMIN ◽  
ZAHARAH JOHARI ◽  
MOHAMMAD TAGHI AHMADI ◽  
RAZALI ISMAIL
Keyword(s):  
Carrier Mobility ◽  
Carrier Transport ◽  
Mobility Model ◽  
Graphene Nanoribbon ◽  
Band Energy ◽  
Low Field ◽  
Field Mobility ◽  
Increasing Temperature ◽  
Degenerate Regime ◽  
Low Field Mobility

The carrier mobility in low-field specifically in parabolic energy region of one-dimensional graphene nanoribbon (GNR) band energy is presented in this work. Low-field mobility model describe the carrier transport and its dependency factors when dealing with degenerate and non-degenerate principals. The result shows that the low-field mobility strongly depends on the temperature in the non-degenerate regime in which it sharply decreases with increasing temperature in the range of 10–250 K but the mobility is less affected by the temperature above 250 K. The effect of varying the GNR width to the mobility is also demonstrated in this work. In addition, it is also shown that the mobility depends on the carrier concentration in degenerate domain in which it increases at higher carrier concentrations.

scholarly journals Band structure, phase transitions, and semiconductor analogs in one-dimensional solid light systems

2009 ◽  
Vol 80 (6) ◽  
Author(s):  
James Quach ◽  
Melissa I. Makin ◽  
Chun-Hsu Su ◽  
Andrew D. Greentree ◽  
Lloyd C. L. Hollenberg
Keyword(s):  
Phase Transitions ◽  
Band Structure ◽  
One Dimensional ◽  
Structure Phase

Robust One-Dimensional Metallic Band Structure of Silicide Nanowires

2005 ◽  
Vol 95 (20) ◽  
Author(s):  
H. W. Yeom ◽  
Y. K. Kim ◽  
E. Y. Lee ◽  
K.-D. Ryang ◽  
P. G. Kang
Keyword(s):  
Band Structure ◽  
One Dimensional

Peculiarities of band structure of one-dimensional photonic crystals

Optik ◽  
2019 ◽  
Vol 180 ◽  
pp. 745-753 ◽  
Author(s):  
A.H. Gevorgyan ◽  
H. Gharagulyan ◽  
S.A. Mkhitaryan
Keyword(s):  
Photonic Crystals ◽  
Band Structure ◽  
One Dimensional

scholarly journals A NOVEL FRACTAL GEOMETRY DOPING FOR GRAPHENE NANORIBBON AND THE OPTIMIZATION OF CRYSTAL: A DENSITY FUNCTIONAL THEORY (DFT) STUDY

2020 ◽  
Vol 17 (35) ◽  
pp. 1148-1158
Author(s):  
Mohammed L. JABBAR ◽  
Kadhum J. AL-SHEJAIRY
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Energy Gap ◽  
Minimum Energy ◽  
Graphene Nanoribbon ◽  
Chemical Doping ◽  
Functional Theory ◽  
Lower Reactivity ◽  
The Density Functional Theory ◽  
Semiconductor Behavior

Chemical doping is a promising route to engineering and controlling the electronic properties of the zigzag graphene nanoribbon (ZGNR). By using the first-principles of the density functional theory (DFT) calculations at the B3LYP/ 6-31G, which implemented in the Gaussian 09 software, various properties, such as the geometrical structure, DOS, HOMO, LUMO infrared spectra, and energy gap of the ZGNR, were investigated with various sites and concentrations of the phosphorus (P). It was observed that the ZGNR could be converted from linear to fractal dimension by using phosphorus (P) impurities. Also, the fractal binary tree of the ZGNR and P-ZGNR structures is a highlight. The results demonstrated that the energy gap has different values, which located at this range from 0.51eV to 1.158 eV for pristine ZGNR and P-ZGNR structures. This range of energy gap is variable according to the use of GNRs in any apparatus. Then, the P-ZGNR has semiconductor behavior. Moreover, there are no imaginary wavenumbers on the evaluated vibrational spectrum confirms that the model corresponds to minimum energy. Then, these results make P-ZGNR can be utilized in various applications due to this structure became more stable and lower reactivity.

Built-in Potential and Open Circuit Voltage of Heterojunction CuIn1-xGaxSe2 Solar Cells

2005 ◽  
Vol 865 ◽  
Author(s):  
Akimasa Yamada ◽  
Koji Matsubara ◽  
Keiichiro Sakurai ◽  
Shogo Ishizuka ◽  
Hitoshi Tampo Hajime ◽  
...  
Keyword(s):  
Solar Cells ◽  
Conduction Band ◽  
Fermi Energy ◽  
Open Circuit Voltage ◽  
Material Selection ◽  
Open Circuit ◽  
Flat Band ◽  
Band Energy ◽  
Low X ◽  
P Type

AbstractThe reasons why the open circuit voltage (Voc) of high-x CuIn1-xGaxSe2 (CIGS)/ZnO solar cells remain low are discussed. Here it is shown that the Voc ceiling can be interpreted simply on the basis of a model that the valence-band energy (Ev) of CIGS is almost immovable irrespective of x. When the conduction-band energy (Ec) of ZnO is lower than that of high-x CIGS (DEc<0), the built-in potential (Vbi) of a CIGS/ZnO junction is equivalent to the flat-band potential (Vbi) that arises from the separation between the Fermi energies of the two materials. If the Ev (and therefore the Fermi energy) of p-type CIGS is constant with increasing x, the Vbi and Voc that follows the Vbi remain unchanged since the Fermi energy of ZnO is constant. This unchangeable Voc reduces the conversion efficiency of high-x CIGS cells in cooperation with reduced photocurrents due to a larger bandgap. A positive offset, ΔEc>o gives rise to a photoelectrons barrier in the conduction-band that partially cancels Voc, thus the Voc of a low-x CIGS cell is governed by the Ec of CIGS. Based upon this concept, a material selection guideline is given for the windows and transparent electrodes appropriate for high-x CIGS absorbers-based solar cells.

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