Doped Armchair Graphene Nanoribbons Research Articles

Optical absorption rate in doped armchair graphene nanoribbon due to impurity atoms effects

Optical absorption rate in doped armchair graphene nanoribbon due to impurity atoms effects

A First Principles Investigation of the Bulk and Electronic Properties of Doped Armchair Graphene Nanoribbon for Sensing Dimethyl Disulphide

Studies have revealed that sulphur compounds from dimethyl disulphide, an essential semiochemical, support a number of crucial plant growth processes, including protein synthesis, nitrogen metabolism, and enzyme activity. Dimethyl disulphide is a crucial fertiliser that aids in the growth and promotion of diverse plant species, according to numerous research. Sensing the presence or level of sulphur can fundamentally help in managing the inputs that are delivered in the field, leading to the success of environmentally friendly agricultural practises. The availability of this crucial voc affects the vigour and longevity of plant species. In this article, we use the density functional theory approach to analyse the adsorption behaviour of a dimethyl disulphide molecule on a graphene nanoribbon doped with boron. The analysis of the nanoribbon's bulk, electrical, and transport properties demonstrates its potential for the detection of this crucial volatile organic molecule.

Adsorption of Li/Na atom on pristine and boron doped armchair graphene nanoribbons: A DFT study

Adsorption of Li/Na atom on pristine and boron doped armchair graphene nanoribbons: A DFT study

A DFT modulated analysis of manganese doped graphene nanoribbons as a potential material for sensing of highly toxic gases CO, PH3 and SbH3

A theoretical Density-functional theory (DFT) study has been carried out to explore the interaction of highly toxic gases carbon monoxide (CO), phosphine (PH3) and stibine (SbH3) with pristine (AGNR) and manganese (Mn) doped armchair graphene nanoribbon (AGNR-Mn). The adsorption behaviour of these gases has been analyzed by calculating the binding distance, adsorption energy (Eads), band structure, density of state spectrum, and current-voltage characteristics. In the case of AGNR, the highest Eads = −0.19 eV has been observed for the CO gas. The Mn doping leads to the high stability and substantial improvement in adsorption performance due to covalent interaction with gas molecules. The enhancement in adsorption energy by 19, 26 and 23 times for CO, PH3 and SbH3 respectively has been observed using AGNR-Mn instead of AGNR. The adsorption of these gases shows a considerable enhancement in the DOS around Fermi level. Furthermore, using I-V characteristics, the response of all these gases is observed and it has been found that the response of PH3 and SbH3 gas to AGNR-Mn are 48% and 45% respectively. These findings indicate that the AGNR-Mn system can be explored as a highly sensitive material for potential gas sensing of PH3 and SbH3.

First-principles calculations of electrical conductivities of edge-modified graphene nanoribbons: Strain effect

We investigate the influence of strain on the electrical properties of graphene nanoribbons that have potential applications in making sensors and other optoelectronic devices. In particular, we chose pristine armchair graphene nanoribbons with 7 zigzag edges (7aGNRsH), boron doped armchair graphene nanoribbons with 7 zigzag edges (7aGNRsH-B) and armchair graphene nanoribbons with 7 zigzag edges that have one carbon atom vacancy (7aGNRsH-V). Based on first-principles calculations, results show that pristine unstrained 7aGNRsH is electrically nonconductive but turns to be electrically conductive in a wide range of energy spectrum , e.g., from IR to visible to UV, due to the application of strain engineering. In metallic unstrained and strained 7aGNRsH-B and 7aGNRsH-V, non-vanishing electrical conductivity in the IR, visible and UV energy spectrum regimes are observed. We also investigate the influence of strain on the Berry curvature of 7aGNRsH, 7aGNRsH-B and 7aGNRsH-V nanoribbons. The results show that fermions are spread through out the Brillouin zone in the reciprocal space for semiconducting unstrained 7aGNRsH but localized near the Γ -point for strained 7aGNRsH that have out-of-plane deformations due to strain engineering. For metallics 7aGNRsH-B and 7aGNRsH-V, Berry curvature plots show that fermions are localized far away from the Γ -point. In two atom boron doped p-type armchair graphene nanoribbons with 7 zigzag edges (7aGNRsH-2B), large peaks in electrical conductivity at IR energy spectrum regimes can be observed. These peaks of electrical conductivities in 7aGNRSH-2B may be detectable in experimentally synthesized structure in Cloke et al. (2015) [1] . • In Figs. 2 , 3 , 4 , we have provided results for band structures calculations obtained from pw.x and maximally localized wannier 90 method that are in excellent agreement. This provides foundation for investigation of influence of strain on the Berry curvature and electrical conductivity. Note that 7 boron doped armchair graphene nanoribbons in Fig. 3 and one carbon vacancy in 7 armchair graphene nanoribbons in Fig. 4 are metallic in nature. • When we apply strain, we have a relaxed shape armchair graphene nanoribbon and thus we expect localization of fermions near Gamma-point which can be clearly seen in Fig. 8 . • Since Fermi energy stays below the top of the valence band in metallic boron doped and vacancy of one carbon atom in graphene nanoribbon, we see the cut-off point in Berry curvature in Fig. 5 . • Most importantly in Figs. 6 , 11 and 12 , we see that intrinsic 7 armchair graphene nanoribbon is not conductive but metallic boron doped and vacancy created nanoribbon are conductive in the wide range of energy spectrum regimes, e.g., from IR to visible to UV.

Spin-thermoelectric properties and giant tunneling magnetoresistance of boron-substituted graphene nanoribbon: a first principle study

In this study we have designed a spin caloritronic device based on boron doped armchair graphene nanoribbons (B2-7AGNR). In presence of ferromagnetic (FM) graphitic-carbon nitride (g-C4N3) electrodes the spin-thermoelectric features of the device, both for FM and antiferromagnetic (AFM) states, are studied using first principle calculations. The spin polarized transmission peaks and the presence of density of states near the Fermi level indicate that the system have large spin-thermoelectric figure of merit. In addition, it is observed that the system has a large tunneling magnetoresistance due to the difference in total current between FM and AFM configurations. Further studies reveal that the spin component of the Seebeck coefficient of the device is much higher than the other zigzag and armchair nanoribbons. When the spin magnetic moments of the electrodes are aligned in parallel manner, spin-thermoelectric figure of merit of the system becomes significantly high. It has also been found that on decreasing temperature the efficiency of the device increases. As a whole, the numerical results show that g-C4N3-B2-7AGNR-g-C4N3 system in FM configuration is an efficient low temperature thermoelectric device.

π -magnetism and spin-dependent transport in boron pair doped armchair graphene nanoribbons

Carbon-based magnetic nanostructures have long spin coherent length and are promising for spintronics applications in data storage and information processing. Recent experiments demonstrate that a pair of substitutional boron atoms (B2) doped 7-atom-wide armchair graphene nanoribbons (B2-7AGNRs) have intrinsic magnetism, providing a quasi-1D magnetic material platform for spintronics. In this work, we demonstrate that the magnetism in B2-7AGNRs is contributed by π-electrons, originating from the imbalance of electrons in two spin channels in response to boron dopants. The spin-dependent transport across single and double boron pair doped 7AGNRs (B2-7AGNRs and 2B2-7AGNRs) by constructing lateral graphene nanoribbon heterojunctions has been investigated by using first-principles calculations. We show that for B2-7AGNRs with spin splitting π-electronic states near the Fermi level, by applying a bias voltage, one can obtain a current spin polarization over 90% and a negative differential resistance effect. For 2B2-7AGNRs, two spin centers have been found to be antiferromagnetically coupled. We demonstrate a magnetoresistance effect over 15 000% by setting those two spin centers to be ferromagnetic and antiferromagnetic alignments. Based on the above spin-polarized transport properties, we reveal that GNR heterojunctions based on B2-7AGNRs could be potentially applied in quasi-1D spintronic devices.

Density Functional Theory Study of Manganese doped Armchair Graphene Nanoribbon for Effective Carbon Dioxide Gas Sensing

Density Functional Theory Study of Manganese doped Armchair Graphene Nanoribbon for Effective Carbon Dioxide Gas Sensing

Density functional theory study of carbon monoxide adsorption on transition metal doped armchair graphene nanoribbon

Density Functional Theory calculations are used to study adsorption of carbon monoxide gas on transition metal doped armchair graphene nanoribbon. Sensing behaviour of pristine armchair graphene nanoribbon (Pr-AGNR) and different geometries of osmium doped AGNR such as one-edge doped AGNR, center doped AGNR and both-edge doped AGNR have been investigated. Most stable adsorption geometry, adsorption energy, binding distance, band structure and density of states of different geometries using in our work have been discussed. Electronic properties of different sensing materials can be interpreted in terms of band structure and density of states. It was studied that a weak type of physical adsorption process took place when CO molecule interacts with pristine AGNR with a very small amount of adsorption energy of amount −0.22 eV. This suggests that pristine graphene is not a good adsorber for CO adsorption. In contrast, doping of graphene with osmium atom enhances the adsorption energy of Pr-AGNR to greater extent. Computational results concluded that osmium doping in graphene nanoribbon at one-edge and both-edge position increases the adsorption energies with values −6.77 eV and −9.53 eV respectively which is 30 times and 43 times greater than in comparison to Pr-AGNR. Energy gap calculations proves that large band gap variations are observed for both-edge doped graphene nanoribbon. Sharp and intense peaks at various energy levels from density of states analysis of both-edge doped geometry confirms adsorption of CO. Our results predicts that both-edge osmium doped sensing material can be considered as promising sensing material for CO adsorption.

Bandgap engineering in Ga and P doped armchair graphene nanoribbons: DFT analysis

The paper reports a study, on calculations performed through plane wave Density functional theory (DFT) combined with non-equilibrium Green's function (NEGF) formalism, to analyze the electronic and structural properties of armchair graphene nanoribbons (AGNR) doped with Phosphorous (P) (N type), and Gallium (Ga) (P type), with two different doping concentration viz 6.25% and 12.5%. It has been observed that (3, 0) Pristine AGNR exhibit a band gap of 1.06 eV. While, on doping with P, and Ga induce metallicity in AGNR, where with increasing doping concentration current increases linearly in Ga doped AGNR whereas, with increasing concentration of P, current decreases in P doped AGNR but AGNR remains Metallic. AGNRs with 6.25% doping concentration can be used as interconnect application due to linear rise in current and other counterparts can be used in electrode of transistor.

Phosphorus doped armchair graphene nanoribbon as a sensing platform of NH3 detection: A DFT investigation

The variation in geometrical and electronic properties of armchair graphene nanoribbon (AGNR) along with pristine and phosphorus (P-AGNR) doped configuration in the presence of ammonia gas (NH3) have been identified in this work. The density functional theory based calculations have been performed in order to detect and equate the sensitivity of modified armchair graphene nanoribbon towards NH3 sensing. Further, the variation in geometrical and electronic properties of AGNR and P-AGNR have been analyzed by considering the cohesive energy, band structure, density of states, and conductance. Hence, our findings shows that P doped AGNR can upsurge its sensitivity towards NH3 gas by the order of 106 times owing to the enhancement in the conductance. Overall, results shows the great potential in the area of designing the graphene nanoribbon based sensors.

Quantum transport properties of gas molecules adsorbed on Fe doped armchair graphene nanoribbons: A first principle study

Graphene, when doped with transition metals, is considered, both experimentally and theoretically, as a good candidate for the detection of gas molecules as CO, CO2, NO or NO2. This opens new perspectives for gas sensor set-ups considering that devices based on 2 dimensional graphene are more sensitive to detect molecules than solid-state gas sensors. The state of the arts on gas adsorption on Fe doped armchair graphene nanoribbons (Fe-AGNR) is still in its starting phase and thorough investigations of the mechanism of the adsorption on graphene need to be done. In the present work, the electronic and transport properties of molecules adsorbed on Fe-AGNR are scrutinized using ab-initio calculations. We observe that the adsorption of gas molecules on Fe-AGNR changes significantly the electronic properties of both the valence and the conduction band. Besides, The adsorbed molecules change the local electron density of states of the graphene nanoribbons, modifying thus the conductivity, being one of the main output quantity of the gas sensors. We also observe that the adsorbed molecules induce specific impurity bands which play a role in the transport properties. Finally, considering the observed variations of electrical conductance induced by the molecules, we propose several strategies to set-up gas sensors for CO, CO2, NO and NO2 molecules. These strategies are either based on the measurement of the conductance in the valence or the conduction band (using either p or n-doped Fe-AGNR) or to the spin polarization induced by the NO and NO2 molecules.

Arsenic sensing using Al/Fe doped armchair graphene nanoribbons: Theoretical investigations

Comparative computational analysis of electrical sensing capabilities of AGNR, Al-doped AGNR and Fe-doped AGNR towards arsenic species in +3 and + 5 oxidation states is presented. For this adsorption studies of arsenous and arsenic acid in different orientations on pristine and metal-doped AGNR are carried out. The adsorption energy (Eads) of arsenous acid on doped-AGNRs is nearly same (~-1.70 eV in orientation B1), however for arsenic acid adsorbed on Al-AGNR, Eads is quite high (−10.69 eV) vis-à-vis that for Fe-AGNR (−2.87 eV). The sensitivity trend based on change in current upon adsorption follows order Fe-AGNR > Al- AGNR > P-AGNR.

First-Principles Investigation of Pd-Doped Armchair Graphene Nanoribbons as a Potential Rectifier

A first-principles investigation is carried out on palladium (Pd)-doped armchair graphene nanoribbons (AGNRs) to investigate their structural, electronic and transport properties. The structural analysis of the considered Pd-doped nanoribbons reveals that single Pd doping at the edges of AGNRs results in the most stable configuration. The present findings reveal that the electronic transport properties are strongly dependent on the number of dopant atoms and their positions. Furthermore, it is noted that the proposed two-probe devices exhibit peculiar nonlinear I–V characteristics indicating potential for rectification behavior. Excellent high rectification ratio (RR) and reverse rectification ratio (RRR) are on the order of $$1.8\times 10^{5}$$ and $$9.7\times 10^{4}$$ , respectively, are found for center-Pd-doped 7-AGNRs. The interesting rectifying I–V behavior can be explained by the localization/delocalization effect of frontier orbitals along with the variation of the transmission spectra with the applied bias voltage. These findings indicate that Pd-doped armchair GNRs are a potential candidate for use in next-generation ultralow-power nanoscale switching devices.

Quantum electrical transport of n-type and p-type AGNRs junctions

Abstract By first-principles calculations, we study quantum electrical transport properties of four nanojunctions based on armchair graphene nanoribbons (AGNRs) in the presence of nitrogen (N) and boron (B) atoms. The theoretical calculations perform within the non-equilibrium Green’s function (NEGF) method combined with density functional theory (DFT). The numerical results show distinct properties, such as converting the system into n-type and p-type semiconductors with several energy gaps due to mid-gap states. These characteristics may be useful in near-infrared photodetectors. By referring to the band structures spectra, we perceive that the effective mass of carriers increases in the doped AGNR systems. Moreover, we calculate the current–voltage characteristic and quantum capacitance of four AGNR nanodevices, theoretically. According to our results, a rectifying effect is observed at low bias voltage, while the threshold voltages depend on the type of doping.

Large rectification ratio induced by nitrogen and boron doping in adjacent armchair graphene nanoribbons

The rectification behavior of two and three separated armchair graphene nanoribbons (AGNRs) which one of them plays the role of channel and others play the role of side gates is investigated. The tight-binding density functional approach (DFTB) and non-equilibrium Green function method (NEGF) are employed for calculations. The nitrogen (N) and boron (B) atoms are used to dope the side gates. The results show that these devices have low threshold voltage and their rectification ratios are higher than one doped AGNR device, with the maximum value of 3.18 × 108. Also, without doping the channel, it can become to n-type or p-type semiconductor, only by doping the side gates. The current-voltage characteristics of these devices are similar and have little dependence on side gates width.

Carrier statistics of highly doped armchair graphene nanoribbons with edge disorder

Graphene has been observed to have a superior electronic property that can potentially revolutionise microelectronic circuits. In this study, highly doped armchair graphene nanoribbons (AGNRs) with randomly generated edge disorders are explored in terms of the band structure, density of state (DOS), Fermi energy, and carrier concentration. An AGNR model was generated based on the nearest-neighbour tight-binding (TB) approach, and computations of the electronic properties in a GNR were conducted using a recursive non-equilibrium Green's function (NEGF) formalism. This study focuses on 10-AGNRs of three varying ribbon lengths of 5, 15, and 30 unit cells. In addition, we also investigate two other varying ribbon widths, namely, 11-AGNRs and 12-AGNRs, with a length of 5-unit cells. The size of the Hamiltonian operator matrix is dependent on the varying dimensions. Nitrogen and boron dopants are used for n- and p-type doping, respectively. The electronic properties and carrier statistics are then compared and discussed for non-pristine AGNRs. In addition, the carrier concentration is also presented and computed based on the Fermi-Dirac probability function. It was found that a varying width causes non-pristine AGNRs to alternate between two semiconducting states, followed by a metallic state. The carrier concentration increases with width owing to a higher intrinsic carrier density. Van-Hove singularities of the DOS of non-pristine AGNRs increase with the dimensions of the crystalline solid. The Fermi level moves inside the conduction and valence bands for highly concentrated n- and p-type doping.

Effect of H and F termination on the electronic and transport properties of the BN doped armchair graphene nanoribbons: From first principles calculations

Using the density functional theory (DFT) and quantum transport calculations based on the nonequilibrium Green's functions (NEGF), we investigate the electronic and transport properties of hybrid AGNRs with symmetrically double-lines-doped BN pairs along the length direction of the nanoribbons, which are terminated by H and F atoms. We present that AGNRs with BN doping at edge positions are the most stable states among same width's ones, regardless of the edge passivation. The results show that they are semiconductor materials, which have different narrow direct band gaps according to edge passivation and ribbon width. Interestingly, F atoms play the role of increasing the band gap than H atoms. The calculated I–V curves reveal that the currents increase with over threshold bias voltage equal to their band gaps, especially, the current of F/F-terminated 9-h-BN-AGNR increases more rapidly than the others.

The effects of electron–phonon interaction on anisotropic RKKY interaction in graphene nanoribbon

We study the Ruderman–Kittle–Kasuya–Yosida (RKKY) interaction in doped armchair graphene nanoribbon. The effects of both external magnetic field and electron-Holstein phonon on RKKY interaction have been addressed. RKKY interaction as a function of distance between localized moments has been analyzed. It has been shown that a magnetic field along the z-axis mediates an anisotropic interaction which corresponds to a XXZ model interaction between two magnetic moments. In order to calculate the exchange interaction along arbitrary direction between two magnetic moments, we should obtain both transverse and longitudinal static spin susceptibilities of armchair graphene nanoribbon in the presence of electron-phonon coupling and magnetic field. The spin susceptibility components are calculated using the spin dependent Green’s function approach for Holstein model Hamiltonian. The effects of spin polarization on the dependence of exchange interaction on distance between moments are investigated via calculating correlation function of spin density operators. Our results show the influences of magnetic field on the spatial behavior of in-plane and longitudinal RKKY interactions are different in the presence of magnetic field.

Transverse spin susceptibilities of doped armchair graphene nanoribbon due to electron-phonon interaction

We present the behaviors of both dynamical and static charge susceptibilities of undoped armchair graphene nanoribbon using the Green's function approach in the context of Holstein model Hamiltonian. Specially, the effects of magnetic field and electron-phonon coupling strength on the plasmon modes of armchair graphene nanoribbon are investigated via calculating correlation function of charge density operators. Random phase approximation has been implemented to find the interacting dynamical charge susceptibility. The electrons in this systems interacts with each other by mediation of dispersionless Holstein phonons. Our results show the increase of electron phonon coupling strength leads to decrease intensity of charge collective mode Also the frequency position of the collective mode tends to higher frequencies with electron phonon coupling. We also show that the frequency positions of plasmon mode of armchair nanoribbon are not affected by increase of magnetic field. Furthermore the number of collective excitation mode increases with ribbon width in the presence of electron-phonon interaction. Finally the temperature dependence of static charge structure factor of armchair graphene nanoribbon is studied. The effects of both magnetic field, ribbon width and electron-phonon interaction on the static structure factor are addressed in details.