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Cu-Ni alloys are promising catalysts for precisely controlling the number of graphene layers grown by chemical vapor deposition (CVD). However, the theoretical understanding of the effect of the Ni atomic fraction on the active species, which helps determine the mechanism of graphene growth, is still limited. Here, we examine the energetics, electronic properties, and populations of potential carbon source species (CH

Hydrogels are three-dimensional (3D) polymer networks that are water-absorbent, insoluble, flexible, and biocompatible. The freeze-thaw technique is a physical cross-linking method for hydrogel synthesis, which can form a stable structure and non-toxic materials. Biopolymer hydrogel is a solution to environmental pollution due to synthetic polymers, which have been widely used as hydrogel base materials. This paper uses starch composite as precursor solutions for the preparation of hydrogels. The precursor solution ratios (potato starch/gelatin) of 20:0, 20:1, 20:2, 20:3, and 0:20 were labeled as SCG1, SCG2, SCG3, SCG4, and SCG5, respectively. Morphological results showed a cross-linking between polymer chains (solid area) and porosity (liquid area). During the freeze-thaw process, gelatin interfered with a cross-linking process of the hydroxyl group so that the solid phase decreased and the pore size was irregular and enlarged. The swelling degree increased with the gelatin composition, while the weight loss showed the opposite result. SCG1 showed the highest swelling degree value of around 319.39 ± 35.05a % and lower weight loss of about 19.26 ± 9.91a %, which showed a higher degradability. SCG1 has good mechanical properties with Young Modulus, onset strain, and onset stress of about 1.4 ± 0.33a KPa, 145.11 ± 47.28b %, and 1.62 ± 0.08c KPa, although the highest compressive strength was shown by SCG5 of 25.63 ± 2.75a KPa. In general, we found that the physical properties of starch hydrogels showed a potential to be used as a functional food matrix: higher swelling degree, modulus elasticity, and degradability. For gelatin hydrogels, it is necessary to modify the process to become a potential matrix as a media delivery.

Chemical solution deposition (CSD) is a technique for making a film by keeping synthetic arrangements on the outer layer of the substrate. The outcomes show that the band gap energy of the LiTaO3 film is 1 eV. Electrons are more effectively invigorated to the valence band than to the conduction band on the grounds that the energy required is not excessively huge. Niobium-doped LiTaO3 film has a band gap energy of 1.15 eV. A large amount of energy is needed for electrons to be energized from the valence band to the conduction band. The rubidium-doped LiTaO3 film has a band gap energy of 1.30 eV.

This study investigated the structural and electronic properties of bulk, bilayer, and monolayer SnSe using the density functional theory (DFT) method. We succeeded in calculating the bandgap and identifying accurately the transformation of the band structure from bulk to monolayer systems using generalized gradient approximation. An increase in the lattice parameter a and a decrease in the lattice parameter b were observed when the bulk dimensions were reduced to a monolayer. The reduction of van der Waals interactions when the dimensions of a system are reduced is the main factor that causes changes in lattice parameters. The indirect bandgap of bulk SnSe (0.56 eV, 0.3∆→0.7Σ) becomes wider in the monolayer system (0.94 eV, 0.2∆→0.8Σ). Bandgap widening is predicted due to the emergence of the quantum confinement effect in low-dimensional systems. Furthermore, we found the formation of a quasi-degenerate minimum conduction band in the monolayer SnSe. With the formation of these bands, we predict the monolayer SnSe will have better thermoelectric properties than the bulk or bilayer system. This study provides an in-depth understanding of the electronic structure of SnSe and its correlation to thermoelectric properties.

In this paper, we optimize Ag catalysts for CNT growth by analyzing the relationship between the growth parameters of the Ag catalyst and the structure of the island. The structure of the islands i...

Doping with nitrogen atom is an effective way to modify the electronic and magnetic properties of graphene. In this paper, we studied the effect of the number of dopant atoms on the electronic and magnetic properties of the two most common nitrogen bond configurations in N-doped graphene, that is, graphitic and pyridinic, using density functional theory (DFT). We found that the formation of graphitic and pyridinic configurations can initiate the transition of the electronic properties of graphene from semimetal to metal with n-type conductivity for the graphitic configuration and p-type conductivity for the pyridinic configuration. The formation of a bandgap-like structure was observed in both configurations. The bandgap increased with the increase in the number of dopant atoms. We also observed that the formation of graphitic configuration did not cause a transition to the magnetic properties of graphene even though the number of dopant atoms was increased. In the pyridinic configuration, the increase in the number of dopant atoms caused graphene to be paramagnetic, with the remarkable total magnetic moment of 0.400 μB per cell in the pyridinic-N3 model. This study provides a deeper understanding of the modification of electronic and magnetic properties of N-doped graphene by controlling the bond configuration and the number of nitrogen dopants.

Nickel thin film, aimed at catalyst layer for HWC-in plasma-PECVD-growth of graphene, has been deposited on SiO2 glass of microscope slide by thermal evaporation method. The thickness of the as-deposited Ni films was not uniform ranging from 200 nm to 700 nm as revealed from cross sectional SEM image. To reduce the film thickness and improve the crystal quality of the films, the samples were annealed in the furnace with three different temperatures, T = 400 °C, 500 °C, and 600 °C, for three hours. SEM images of the post-treatment indicated that the film thickness decreased to about 100–200 nm after annealed at 500 °C for 3 h. Increasing the annealing temperature to 600 °C leads the nickel atoms out of the substrate so that it leaves the substrate without nickel thin film anymore. The disappearing of the Nickel film after annealing at temperature 600 °C was confirmed by EDS spectrum examination which showed that there was no nickel element in the sample. Due to the loss of nickel thin film after annealing at 600 °C, we set the annealing temperature at 500 °C and optimized duration of annealing. It was found that after annealing for 4 h the obtained thickness of thin film was averagely 44 ± 6 nm with some spread piles on the film. Increasing annealing duration to 5 h lead to increasing the thickness of thin film nickel to be 66 ± 14 nm which seems contradict with our expectation. However, the tens order magnitude of thin film thickness obtained is the expected result for graphene growth.

In this report, we study nonlinear electrical behaviors found in vertical-architecture transistors based on wrap-around-gated gallium nitride (GaN) nanowires (NWs) by extending a one-dimensional case of the Landauer-Buttiker formula. Here, the GaN NWs are considered “almost” one-dimensional ideal wires connecting the drain and source terminals, with the gate terminal serving to control the flowing current. Unlike previous models, which require several parameters and complex calculations, our proposed model only needs three parameters and simple calculations to match the experimental data. With this model, we confirm that the maximum current before saturation is a consequence of quasi-ballistic drain current. Thus, electron mobility has no effect in this device. Using a simple formulation, we discuss gating hysteresis in the device that is mediated by the selected oxide layer interface. We show that the memory effect of the device is attributed to time-delay current. The shorter gate length increases the transmission coefficient. As a result, the model can be employed to predict the next-generation NW transistor performance.

In this paper, an analytical expression of the electron spin-dependent tunneling current through a potential barrier by applying a bias voltage was investigated. An Airy wavefunction was applied to derive the transmittance through the barrier by considering a zinc-blende material, which depends on the spin states indicated as ‘up’ and ‘down’. The obtained transmittance was employed to compute the polarization and spin-dependent tunneling current. The spin-dependent tunneling current was then observed at various bias voltages and temperatures. It was shown that the spin-polarized current increases as the bias voltage increases. It was also shown that the increase of temperature enhances the spin-dependent tunneling current.

The structural properties and optical responses of ZnO0.94 and Zn0.94O systems as the possible models of ZnO system containing elemental defect states were studied using the plane-wave method within the generalized gradient approximation. The pristine ZnO system was used as the reference. The simulated XRD patterns showed the three highest intensity for (100), (002), and (101) orientations for all the systems. Compared to O vacancy, Zn vacancy mostly provided higher structure factor shifts of ZnO system. Moreover, the strongest local-symmetry distortion at ZnO4 tetrahedra was implied in Zn0.94O system. The optical responses showed that all the systems exhibited the optical dichroism based on the extinction coefficient spectra. Interestingly, Zn0.94O system showed the lowest energy levels of absorption and high-reflectance edges. Additionally, the highest saturation threshold energy of the effective number of valence electrons was obtained for this system. The result emphasizes the importance of Zn vacancy in providing the significant effect on the optical responses of ZnO system. Keywords: Structural properties, Optical responses, Optical dichroism, ZnO

Silver (Ag) nanocatalyst has been deposited on SiO2 glass substrate by the thermal evaporation method. The layer thickness was about 2.42 mm. The Ag nanocatalyst was then annealed at a temperature of 400 °C with the variation of annealing time for 1, 2, 3, and 4 h. Several spectroscopy methods were carried out to characterize the samples. From the scanning electron microscope (SEM) images showed that the diameter size of the nanoparticles were mostly 0.252 μ m, 0.236 μ m, 0.193 μ m, and 0.108 μ m, respectively. Energy Dispersive X-ray (EDX) spectroscopy revealed that composition of Ag for each sample are 0.26%, 0.14%, 0.48% and 0.04% respectively. Based on the SEM, the smallest diameter of particles was obtained after annealing for 4 h, and EDX results, the most Ag composition was obtained after annealing for 3 h. The results from Fourier transform infrared (FTIR) spectroscopy do not indicate the presence of Si O Ag bonds at SiO2/Ag, where based on literature, their peaks are at 827 cm−1 and 1749 cm−1.

In this paper, we have calculated an electron transmittance through Fe/GaAs/Fe in a magnetic tunnel junction (MTJ). The transmittance was computed by using the Airy wavefunction approach by considering the Dresselhaus effect. The calculated result shows that the electron transmittance for each spin state is different. The incident angle affects electron transmittance and electron polarization. It was also shown that electron polarization is also affected by the energy of the electron and the barrier width. Besides, the electron transmittance is quasisymmetric to the incident angle.

One promising method for growing carbon-based materials, especially for electronics and optoelectronics application, is PECVD (Plasma Enhanced Chemical Vapor Deposition). In addition to the large-area thin film obtained, this method also requires relatively lower growth temperature. By modifying the PECVD reactor through the application of Hot-Wire Cell (HWC) placed between two electrodes (called In Plasma, IP), and plasma generator frequency of 70 MHz which is categorized as Very High Frequency (VHF), graphene flakes have been successfully grown by using methane (CH4) gas as precursor at pressure 300 mTorr and substrate temperature of 275°C on corning glass substrate. This result indicates that this method is potentially to grow graphene at lower temperature by adjusting several growth parameters, especially temperature of hot wire cell that plays important role in the deposition process. It should be noted that important factor that greatly determined the successful of graphene flakes growth was the use of metal catalyst in the form of very thin film. In this research, silver was used as metal catalyst which was prepared by evaporation method and then annealed at 600°C for 30-60 minutes.

The optical response of spherical nanoparticles was studied based on the quasi-static approximation of classical electrodynamics. The simple Drude model was used to calculate the complex dielectric function of the metal. We investigated the behavior of the absorption cross-section spectra of metallic spherical core–shell (including dielectric-metal and metal-dielectric) nanoparticles numerically. We found that the number of resonance peaks in the absorption cross-section spectra depends on the number of metal-dielectric interfaces of the nanostructure, as predicted by plasmonic hybridization theory. Furthermore, the absorption cross-section spectra can be precisely controlled by changing the thickness of the shell and the dielectric constant of the medium.

A polyvinyl alcohol (PVA) hydrogel loaded with guava leaf extract (GLE) has potential applications as a wound dressing with good antibacterial activity. This study succeeded in fabricating a PVA hydrogel containing GLE using the freeze–thaw (FT) method. By varying the GLE concentration, we can adjust the physical properties of the hydrogel. The addition of GLE results in a decrease in cross-linking during gelation and an increase in the pore size of the hydrogels. The increase of the pore size made the swelling increase and the mechanical strength decrease. The weight loss of the hydrogel also increases because the phosphate buffer saline (PBS) dissolves the GLE. Increasing the GLE concentration caused the Fourier-transform infrared (FTIR) absorbance peaks to widen due to hydrogen bonds formed during the FT process. The crystalline phase was transformed into an amorphous phase in the PVA/GLE hydrogel based on the X-ray diffraction (XRD) spectra. The differential scanning calorimetry (DSC) characterization showed a significant decrease in the hydrogel weight over temperatures of 30–150 °C due to the evaporation of water from the hydrogel matrix. The zone of inhibition of the PVA/GLE hydrogel increased with antibacterial activity against Staphylococcus aureus of 17.93% per gram and 15.79% per gram against Pseudomonas aeruginosa.

In this work, we present the bond order redefinition needed to reduce the inherent noise in order to enhance the accuracy of molecular dynamics simulations. We propose defining the bond order as a fraction of energy distribution. It happens due to the character of the material in nature, which tries to maintain its environment. To show the necessity, we developed a factory empirical interatomic potential (FEIP) for carbon that implements the redefinition with a short-range interaction approach. FEIP has been shown to enhance the accuracy of the calculation of lattice constants, cohesive energy, elastic properties, and phonons compared to experimental data, and can even be compared to other potentials with the long-range interaction approach. The enhancements due to FEIP can reduce the inherent noise, then provide a better prediction of the energy based on the behaviour of the atomic environment. FEIP can also transform simple two-body interactions into many-body interactions, which is useful for enhancing accuracy. Due to implementing the bond order redefinition, FEIP offers faster calculations than other complex interatomic potentials.

The present mindset has changed and evolved noticeably from its conventional practice to an inventive method wherein the objective of Waqf can be achieved easily and effectively. This innovation of ongoing charitable deed appears in the form of cash Waqf which has been progressively popular due to its effectiveness and flexibility in terms of the collection, investment, and distribution. Importantly, in many countries, the model of cash Waqf has evolved and flourished as a tool for financial sources and wealth distribution. Singapore and Malaysia are among the countries in which this model is considerably matured to achieve its effectiveness and valuable purpose (Abdullah Nadwi and Kroessin 2013; Saifuddin et al. 2014). Despite the significant role of cash waqf in socio-economic development, there has been a substantial gap in the literature discussing the potential roles of cash waqf in supporting SDGs. Thus, the main purpose of this study is to explore the potential role of cash to support SDGs. This study is qualitative, in which it uses the library research skill as a method of research. In this regard, the secondary data were used to analyse some existing models of cash waqf and its possible role to support SDGs. Since the SDGs consists of 17 goals, this study, however, focuses on analysing two goals of SDGs that could possibly for practical in the context of cash waqf.

Dye-sensitised solar cells (DSSCs) have attracted immense attention in photovoltaics research and development due to the low cost of fabrication, sustainability and use of abundant natural resources. Natural dyes were adapted to DSSCs as a sensitiser but unfortunately proved to have poor efficiency. Herein, we manufactured two organic dyes from yellow and red gambier fruits and treated both dyes with methanol and isopropyl alcohol. The photoanode and photocathode were prepared from TiO2, sensitiser and indium thin dioxide (ITO); and carbon and indium thin dioxide, respectively. An electrolyte was made by mixing potassium iodide and iodine. The doctor blade method was used to add the semiconductor to the surface of the conducting ITO. UV-Vis and FTIR spectroscopic measurements have been performed to determine the absorbance and functional groups in the gambier extracts. From the analysis of UV-Vis and FTIR spectra, and photovoltaic measurements made under solar irradiation, we found that the gambier extracts are dominated by tannin and flavonoids and that dyes using isopropyl alcohol as the solvent have higher efficiency than using methanol, respectively. This indicates that the gambier extracts and solvents might influence the performance of DSSCs., Indonesia Ministry of Research and Technology/National Agency for Research and Innovation; Riset Desentralisasi PDUPT Research Grant

There has been a lack of studies that highlight the potential roles of corporate waqf in supporting Sustainable Development Goals (SDGs) even though both concepts share the same objective to improve the socio-economic development of all human beings. For instance, it is the central role of waqf generally and corporate waqf mainly to provide continuous benefit for the poor and the needy such the aspects of education, health and providing financial assistance. These aspects genuinely reflect some of the goals in the SDGs. Thus, it is the aim of the study to explore the potential role of corporate waqf in supporting SDGs by examining the experiences of selected corporate waqf institutions in Malaysia and Singapore. Analysing the potential role of corporate waqf could perhaps bridge the gaps between the objective of corporate waqf and SDGs so that the impact on the policy made not only incongruent with the Shariah principles but also the SDGs. It is hoped that this alignment could expand the current role of corporate waqf to achieve more holistic socio-economic development goal at the national and global level. This study is organized into five sections, and they are introduction, literature review, research methodology, the experience of selected corporate waqf institutions in Malaysia and Singapore and conclusion.

The insulator layer and the substrate material play an important role in determining the performance of metal-insulator-semiconductor type solar cells. Here, the effects of insulator layer ...

Modifying the bandgap and magnetic properties of graphene is one of the keys to realizing graphene-based nanodevices. Here, we investigate the effect of nitrogen concentration in the pyrrolic bond configuration on the magnetic properties of graphene using the spin-polarized Density Functional Theory (DFT) method. For a better understanding, we also calculated the electronic and structural properties of the pyrrolic N-doped graphene. This study used three models, i.e., pristine graphene and pyrrolic N-doped graphene with two nitrogen concentrations (N x G1 − x , x=2.000% and 3.125%). We observed that the higher the dopant concentration, the more the deformation of the planar structure in pyrrolic N-doped graphene. This is indicated by the more wrinkled structure that forms. Semi-metal to metal transitions were also observed in both models of pyrrolic N-doped graphene. Asymmetry behavior in the spin-polarized density of states (SPDOS) was also observed in both pyrrolic N-doped graphene models. The total magnetic moment increases with increasing dopant concentration. At a concentration of 2.000%, the resulting total magnetic moment is 1.68 µB/cell, and at a concentration of 3.125%, it is 1.74 µB/cell. We suggest that defects and nitrogen impurities play a crucial role in the transition of the magnetic properties of graphene. Our result shows that nitrogen-doped graphene with pyrrolic configuration is a promising candidate for nanomagnetic devices.

A sharp electrode model was employed to study tunneling phenomena in split-gate memory cell which has a sharp floating gate structure. This kind of structure are said to give significant tunnel current increase due to electric field enhancement. In this study we evaluate this claim by studying electron transmittance through potential barrier formed by a general triangular shaped electrode. It is shown that, sharp electrode give rise to a nonlinear potential barrier that are thinner than barrier from planar electrode. Using transfer matrix method, we show that electron transmittance from sharp electrode are higher than those of planar one, and has an ever increasing difference as the applied voltage increased. We also show that for a sharp-planar electrode pair, the most probable path of electron tunneling is the one that perpendicular to the tip-edge, due to the horizontal potential barrier has its lowest value at this direction.

In this study, the spin-polarized currents in a magnetic tunnel junction (MTJ) with a Fe/GaAs/Fe structure were calculated by considering the Dresselhaus effect. The spin-polarized current was calculated using the Airy wavefunction approach and then compared to the transfer matrix method (TMM) to check the accuracy. It was shown that the total spin-polarized current density evaluated via the Airy-wavefunction approach matches that obtained with the TMM. It was also shown that the current density increases as the barrier width decreases. In addition, the temperature and the incident angle of the electrons affect the current density, where the maximum current density is obtained when the electrons come in a direction perpendicular to the barrier. We herein determined analytically that a high device performance of the MTJ could be achieved by simply controlling the device parameters of barrier width, temperature and incident angle of the electron.

Natural dyes still have low efficiency, although there are good opportunities to apply them in dye-sensitised solar cells (DSSCs). In this research, the working-electrode was prepared from indium tin oxide (ITO) and titanium oxide (TiO2), using the doctor blade method for doping TiO2 on ITO glass. Then, the working-electrode was soaked in gambier extract for 24 hours. The counter-electrode and electrolyte were made from burning a candle and mixing KI + I2, respectively. UV-vis and FTIR spectra have been made to investigate the effect of the concentration of red and yellow gambier prepared by maceration and evaporation from methanol. They were used to analyse absorbances and compounds in gambier, respectively. From UV-vis and FTIR spectra results, we obtained that the organic dyes from the red and yellow gambier fruits could have a high potential to be used as a sensitiser to absorb photons in DSSCs. From the I–V measurement, we found that the efficiency tends to increase as the concentration increases. It indicates that the concentration of natural dyes could increase the performance of DSSC. Furthermore, an efficiency of 3.248% was found to be achievable for DSSCs from a 70% concentration of yellow gambier fruit dye.

The organic dyes used in dye-sensitised solar cells (DSSCs) possess a low efficiency, leading to problems in the development of more efficient and cheaper DSSCs. In this work, we analysed the effect of the concentrations of organic dye from yellow and red gambier (Uncaria) fruits. The concentrations were prepared with isopropyl alcohol at concentrations of 30, 50 and 70%, respectively. Titanium oxide (TiO2) is a semiconductor which was used in this work by utilising the method of the doctor blade, and indium tin oxide (ITO) was used as the conductive glass. The counter electrode and electrolyte were fabricated by burning candle and mixing KI + I2, respectively. The characteristic spectra of UV-Vis and FTIR were used to analyse the gambier fruit. We obtained that the tannins from red and yellow gambier fruit extract are highly potential to apply as a sensitiser in DSSCs. Furthermore, the measurement of current and voltage was employed under sun irradiation. We obtained that the highest efficiencies were 0.819924 % and 1.747999 % for red and yellow extract, respectively. It indicates that the concentration of the organic dye could improve the performance of DSSCs.

A simple spray pyrolysis method has successfully used to synthesize carbon nanotubes (CNTs). Their structural characteristics were characterized by employing field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) analysis, and X-ray diffraction (XRD) methods. FE-SEM images confirmed that the diameters of CNTs were in the range of 20 to 80 nm. The average diameter of CNTs increased considerably as the growth temperature increased (above 700 oC). The changes in growth time and ferrocene mass altered the average diameter of CNTs slightly. EDX analysis and XRD patterns indicated that Fe2O3 and Fe3O4, which originate from the oxidation of ferrocene catalyst, are the main impurities of the CNTs. The concentrations of Fe2O3 and Fe3O4 became lower and higher, respectively, for the growth temperatures higher than 700°C because Fe2O3 is the most stable at high temperatures.

Analytical expressions of electron transmittance and tunneling current in a metal-oxide-semiconductor (MOS) capacitor with a high dielectric constant (high-K) oxide stack of HfO2 and SiO2 and a negative bias applied to the metal gate were derived. Exponential- and Airy-wavefunction approaches were employed in deriving analytically the electron transmittance and tunneling current. A numerical approach based on a transfer matrix method was used as a standard to evaluate the analytical approaches. It was found that the transmittances obtained under the exponential- and Airy-wavefunction approaches and the TMM are matching for low electron energies, while for higher energies only the transmittances calculated by employing the Airy- wavefunction approach is the same as those computed by using the TMM. It was also found that the tunneling currents calculated by using the exponential- and the Airy-wavefunction approaches and the TMM are equal for low oxide voltages (lower than 0.5 V), while for higher oxide voltages only the tunneling currents computed under the Airy-wavefunction approach fit those obtained under the TMM. Therefore, the Airy-wavefunction approach provides a better analytical model to tunneling processes in the MOS capacitor.

An analytical expression of electron direct transmittance and tunneling time through a nanometer-thick trapezoidal potential barrier have been derived by using a phase-time method with Airy wavefunction solution. The expression is applied to Si(100)/HfO2/Si(100) (isotropic) and Si(110)/HfO2/Si(110) (anisotropic) structures calculated under the consideration of barrier width, incident energy, incident angle, and bias voltage. The calculated results are discussed and comparisons between the isotropic and anisotropic heterostructures are discussed.

In this paper, we present a model of gate tunneling current in cylindrical surrounding-gate MOSFETs through dual layer high-k dielectric/SiO2 stacks. The model was derived under a quantum perturbation theory by taking into account both structural and electrical confinement effects. The influences of high-k materials and SiO2 thickness on the gate tunneling current have been studied. The calculated results show that the HfO2 is the most effective high-k material to decrease the gate tunneling current. It is also shown that the gate tunneling current is reduced with the SiO2 thickness. In addition, the obtained tunneling currents are fitted well with those obtained under the self-consistent calculation.

A theoretical model of electron tunneling current in a p-n junction based on strained armchair graphenenanoribbons (AGNRs) is developed. The effects of strain to the energy dispersion relation and the band gap of AGNR are formulated under the extended tight binding method. The electron transmittance was derived by utilizing the transfer matrix method. The calculated transmittance was then used to obtain the tunneling current by employing the Landauer formula with Gauss Quadrature computation method. The effects of strain to the energy band gap, AGNR width, and tunneling current are studied thoroughly.

We have developed a model of the tunneling current in n-p-n bipolar transistor based on armchair graphene nanoribbon (AGNR). Airy-wavefunction approach is employed to obtain electron transmittance, and the obtained transmittance is then used to obtain the tunneling current. The tunneling current is calculated for various variables such as base-emitter voltage, base-current voltage, and AGNR width. It is found that the tunneling current increases with increasing the base-emitter voltage or the base-collector voltage. This result is due to the lowered barrier height of the base region caused by the increase in the base-emitter voltage or the base-collector voltage. In addition, the tunneling current density increases with the width for narrow AGNR and, on the other hand, it decreases for wide AGNR. This finding might be due to the contributions of the band gap energy and the electron effective mass of AGNR which are inversely proportional to the AGNR width.

We simulate quantum mechanical tunneling current in armchair graphene nanoribbon tunnel field-effect transistors (AGNR-TFETs). The relativistic Dirac equation is used to determine electron wave functions in the AGNRs, while the potential profile is solved by the Poisson equation. We use a transfer matrix method (TMM) to calculate the electron transmittance and the Dirac electron tunneling current in the AGNR-TFETs. The results show that the Dirac electron tunneling current increases with increasing the drain and gate voltages. Moreover, the AGNR width and the thickness of insulator affect the characteristics of the Dirac electron tunneling currents.