scholarly journals Numerical Investigation of Graphene and STO Based Tunable Terahertz Absorber with Switchable Bifunctionality of Broadband and Narrowband Absorption

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 2044
Author(s):  
Yan Liu ◽  
Rui Huang ◽  
Zhengbiao Ouyang
Keyword(s):  
Energy Level ◽  
Fermi Energy ◽  
High Performance ◽  
Thermal Control ◽  
Rate Of Change ◽  
Center Frequency ◽  
Fermi Energy Level ◽  
Broadband Absorption ◽  
Terahertz Absorber ◽  
The Cross

A graphene metamaterial and strontium titanate (STO)-based terahertz absorber with tunable and switchable bifunctionality has been numerically investigated in this work. Through electrically tuning the Fermi energy level of the cross-shaped graphene, the bandwidth of the proposed absorber varies continuously from 0.12 THz to 0.38 THz with the absorptance exceeding 90%, which indicates the functionality of broadband absorption. When the Fermi energy level of the cross-shaped graphene is 0 eV, the proposed absorber exhibits the other functionality of narrowband absorption owing to the thermal control of the relative permittivity of STO, and the rate of change of the center frequency is 50% ranging from 0.56 THz to 0.84 THz. The peak intensity of the narrowband absorption approximates to nearly 100% through adjusting the Fermi energy level of the graphene strips. The calculated results indicate that it is not sensitive to the polarization for wide incidence angles. The proposed absorber can realize tunable bifunctionality of broadband absorption with a tunable bandwidth and narrowband absorption with a tunable center frequency, which provides an alternative design opinion of the tunable terahertz devices with high performance for high-density integrated systems.

scholarly journals A Broadband Tunable Terahertz Metamaterial Absorber Based on Single-Layer Complementary Gammadion-Shaped Graphene

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 860 ◽  
Author(s):  
Fu Chen ◽  
Yongzhi Cheng ◽  
Hui Luo
Keyword(s):  
Energy Level ◽  
Graphene Sheet ◽  
Fermi Energy ◽  
Single Layer ◽  
Dielectric Substrate ◽  
Transverse Magnetic ◽  
Metamaterial Absorber ◽  
Absorption Capacity ◽  
Fermi Energy Level ◽  
Broadband Absorption

We present a simple design of a broadband tunable metamaterial absorber (MMA) in the terahertz (THz) region, which consists of a single layer complementary gammadion-shaped (CGS) graphene sheet and a polydimethylsiloxane (PDMS) dielectric substrate placed on a continuous metal film. The Fermi energy level (Ef) of the graphene can be modulated dynamically by the applied DC bias voltage, which enables us to electrically control the absorption performance of the proposed MMA flexibly. When Ef = 0.8 eV, the relative bandwidth of the proposed MMA, which represents the frequency region of absorption beyond 90%, can reaches its maximal value of 72.1%. Simulated electric field distributions reveal that the broadband absorption mainly originates from the excitation of surface plasmon polaritons (SPPs) on the CGS graphene sheet. Furthermore, the proposed MMA is polarization-insensitive and has wide angles for both transverse-electric (TE) and transverse-magnetic (TM) waves in the broadband frequency range. The broadband absorption capacity of the designed MMA can be effectively adjusted by varying the Fermi energy level of graphene. Lastly, the absorbance of the MMA can be adjusted from 42% to 99.1% by changing the Ef from 0 eV to 0.8 eV, which is in agreement with the theoretical calculation by using the interference 41theory. Due to its simple structure and flexible tunability, the proposed MMA has potential application prospects in tunable filtering, modulators, sensing, and other multispectral devices.

Intersubband Transitions in In0.07Ga0.93As/Al0.4Ga0.6As Multiple Quantum Wells

1994 ◽  
Vol 299 ◽  
Author(s):  
F. Szmulowicz ◽  
M. O. Manasreh ◽  
C. Kutsche ◽  
C. E. Stutz
Keyword(s):  
Energy Level ◽  
Quantum Well ◽  
Quantum Wells ◽  
Excited States ◽  
Fermi Energy ◽  
Multiple Quantum Well ◽  
Energy Separation ◽  
Multiple Quantum ◽  
Fermi Energy Level ◽  
Intersubband Transitions

AbstractIntersubband transitions in a series of well-doped ([Si] = 2.0×1018cm−3) In0.07Ga0.93As/Al0.4Ga0.6As multiple quantum well samples were studied as a function of the well width by using the optical absorption technique. A single intersubband transition is observed in samples in which the Fermi energy level is between the ground and the first excited states in the quantum well. On the other hand, two intersubband transitions were recorded in samples where the Fermi energy level lies between the first and the second excited states. These two intersubband transitions were attributed to ground-to-first excited states and first-to-second excited states transitions. The energy separation between the latter two intersubband transitions was found to increase as the well width is increased. The fact that two intersubband transitions were observed in certain samples may suggest that specially designed quantum wells can be used for two color long wavelength infrared detectors.

Graphene-based dual-band independently tunable infrared absorber

Nanoscale ◽  
2018 ◽  
Vol 10 (33) ◽  
pp. 15564-15570 ◽  
Author(s):  
Peng Sun ◽  
Chenglong You ◽  
Amirreza Mahigir ◽  
Tongtong Liu ◽  
Feng Xia ◽  
...  
Keyword(s):  
Energy Level ◽  
Resonant Frequency ◽  
Fermi Energy ◽  
Dual Band ◽  
Fermi Energy Level ◽  
P Absorption

Absorption peaks can independently tune each resonant frequency by only changing the Fermi energy level of one.

scholarly journals Investigation of dopant centres dominating the conduction process in the bulk of un-doped GaSb

2019 ◽  
Vol 13 (4) ◽  
pp. 315-327
Author(s):  
Megersa Wodajo Shura
Keyword(s):  
Energy Level ◽  
Hall Effect ◽  
Fermi Energy ◽  
Activation Energies ◽  
Acceptor Level ◽  
Level System ◽  
Fermi Energy Level ◽  
Majority Carrier ◽  
Temperature Regimes ◽  
Hall Effect Measurements

Abstract In this paper, first, the theoretical description of the effects of the dopant densities and the activation energies on the ionization densities, the chemical potentials corresponding to each dopant levels, the majority carrier densities and the Fermi-energy levels in one-acceptor-level system, highly compensated system and two-acceptor-level system are described in detail. Upon fitting the theoretical to the experimental results obtained by the temperature-dependent Hall effect measurements for three samples of un-doped GaSb, the dopant densities and the activation energies for a system with different dopants are investigated. The obtained results revealed that the dopant activation energy has less (no) effect on the Fermi-energy level and the majority carrier density in the highest temperature regimes. The doping density has also less (no) effect on the Fermi-energy level in the lowest temperature regimes. Finally, fitting of the theoretical to the experimental Hall effect measurements results confirmed the presence of three acceptor and one donor levels dominating the majority carrier densities at different temperature regions in all the samples of un-doped GaSb semiconductor.

scholarly journals Switchable and Dual-Tunable Multilayered Terahertz Absorber Based on Patterned Graphene and Vanadium Dioxide

Micromachines ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 619
Author(s):  
Hongyao Liu ◽  
Panpan Wang ◽  
Jiali Wu ◽  
Xin Yan ◽  
Xueguang Yuan ◽  
...  
Keyword(s):  
Fermi Level ◽  
Vanadium Dioxide ◽  
High Performance ◽  
Incidence Angle ◽  
Multilayered Structure ◽  
Dual Band ◽  
Broadband Absorption ◽  
Terahertz Absorber ◽  
Polarization Insensitive ◽  
Absorption Performance

In this paper, a switchable and dual-tunable terahertz absorber based on patterned graphene and vanadium dioxide is proposed and analyzed. By controlling the Fermi level of graphene and the temperature of vanadium dioxide, the device’s function can be switched and its absorbing properties can be tuned. When the vanadium dioxide is in an insulator state, the device can be switched from near-total reflection (>97%) to ultra-broadband absorption (4.5–10.61 THz) as the Fermi level of graphene changes from 0 to 0.8 eV. When the vanadium dioxide is changed to a metal state, the device can act as a single-band absorber (when the Fermi level of graphene is 0 eV) and a dual-band absorber with peaks of 4.16 THz and 7.3 THz (when the Fermi level of graphene is 0.8 eV). Additionally, the absorber is polarization-insensitive and can maintain a stable high-absorption performance within a 55° incidence angle. The multilayered structure shows great potential for switchable and tunable high-performance terahertz devices.

scholarly journals The effect of elastic strains on the adsorption energy of H, O, and OH in transition metals

2021 ◽  
Vol 23 (37) ◽  
pp. 21295-21306
Author(s):  
Carmen Martínez-Alonso ◽  
José Manuel Guevara-Vela ◽  
Javier LLorca
Keyword(s):  
Transition Metals ◽  
Energy Level ◽  
Adsorption Energy ◽  
Fermi Energy ◽  
Fermi Energy Level ◽  
General Law ◽  
Adsorption Energies ◽  
Elastic Strains

The adsorption energies of H, O, and OH on 11 transition metals were calculated as a function of strain. They were related to the Fermi energy level which only depended on the change of the area of the hole due to strain following a general law.

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