Semiconductor Nanotubes Research Articles

Manifestation of the Aharonov–Bohm effect in hydrodynamic instability of an electron beam moving along a semiconductor nanotube

Manifestation of the Aharonov–Bohm effect in hydrodynamic instability of an electron beam moving along a semiconductor nanotube

System of metastable volume-localized electronic states in positively charged semiconductor single-wall carbon nanotubes

The volume-localized electronic states (SAMOs) with a maximum of their electron wave functions located in the cavity of nanomaterials have been experimentally and theoretically demonstrated in a fullerene. The existence of SAMOs in single-wall carbon nanotubes (SWCNTs) was also predicted theoretically. In the present paper, these volume states in semiconductor SWCNTs were theoretically investigated using numerical quantum modeling based on density functional theory (DFT). It is shown that the well appears in the center of the tube, whose depth increases with increasing positive charge, since the total potential of a positively charged structure can be represented as the sum of the Coulomb potential and the potential of the atoms of the tube wall. In this context, in addition to the well-studied surface-localized states, states localized in the volume of the cylinder also occur. Using the components of the electric transition dipole moment, the lifetime of the volume states was preliminarily estimated in comparison to the lifetime of the ordinary surface states.

Review of: "Meanwhile, vertical nanotubes grow more in the proliferation of 2D ballistic nanotransistors. If it is assumed that semiconductor and metal nanotubes can be grown and oriented on the surface with desired precision, they will provide the possibility of compression and increasing the speed of the integrated electronics as much as possible"

Review of: "Meanwhile, vertical nanotubes grow more in the proliferation of 2D ballistic nanotransistors. If it is assumed that semiconductor and metal nanotubes can be grown and oriented on the surface with desired precision, they will provide the possibility of compression and increasing the speed of the integrated electronics as much as possible"

Investigation of adsorption properties of SF6 decomposed gases (SO2 and SO2F2) on pristine and Ti-decorated SWCNT surfaces: A DFT study

DFT calculations were employed to investigate the adsorption of gases produced from SF6 decomposition (SO2 and SO2F2) on pristine and Ti- -decorated single-walled carbon nanotubes (Ti-(8,0) SWCNT). All structures were relaxed and their structural and electronic properties were investigated before and after gas adsorption on the surface of the nanotubes. (Ti-(8,0) SWCNT) was found to have high chemisorption sensitivity to Ti, SO2F2 and SO2 adsorptions on its surface. The electronic properties of (8,0) SWCNT were altered from semiconductor to metallic upon decoration with Ti, as demonstrated by the calculated band structures and the density of states (DOS). SO2F2 and SO2 adsorption on the surface of (Ti-(8,0) SWCNT) from different sides transformed the conductor (Ti-(8,0) SWCNT) into a semiconductor nanotube. To more carefully study the nature of adsorption, partial density of states (PDOS) calculations were also made. Additionally, Ti decoration induced a magnetization of approximately 2.61 ?B in (8,0) SWCNT, which disappeared after gas adsorption.

Strain-induced Aharonov-Bohm effect at nanoscale and ground state of a carbon nanotube with zigzag edges

Magnetic flux piercing a carbon nanotube induce periodic gap oscillations which represent the Aharonov-Bohm effect at nanoscale. Here we point out, by analyzing numerically the anisotropic Hubbard model on a honeycomb lattice, that similar oscillations should be observable when uniaxial strain is applied to a nanotube. In both cases, a vector potential (magnetic- or strain-induced) may affect the measurable quantities at zero field. The analysis, carried out within the Gutzwiller Approximation, shows that for small semiconducting nanotube with zigzag edges and realistic value of the Hubbard repulsion (U/t0=1.6, with t0≈2.5eV being the equilibrium hopping integral) energy gap can be reduced by a factor of more than 100 due to the strain.

Manifestation of the Aharonov-Bohm effect in the interaction of moving charges with a semiconductor nanotube with dielectric filling

Manifestation of the Aharonov-Bohm effect in the interaction of moving charges with a semiconductor nanotube with dielectric filling

Measuring the Diameter of Single-Wall Carbon Nanotubes Using AFM.

In this work, we identify two issues that can significantly affect the accuracy of AFM measurements of the diameter of single-wall carbon nanotubes (SWCNTs) and propose a protocol that reduces errors associated with these issues. Measurements of the nanotube height under different applied forces demonstrate that even moderate forces significantly compress several different types of SWCNTs, leading to errors in measured diameters that must be minimized and/or corrected. Substrate and nanotube roughness also make major contributions to the uncertainty associated with the extraction of diameters from measured images. An analysis method has been developed that reduces the uncertainties associated with this extraction to <0.1 nm. This method is then applied to measure the diameter distribution of individual highly semiconducting enriched nanotubes in networks prepared from polyfluorene/SWCNT dispersions. Good agreement is obtained between diameter distributions for the same sample measured with two different commercial AFM instruments, indicating the reproducibility of the method. The reduced uncertainty in diameter measurements based on this method facilitates: (1) determination of the thickness of the polymer layer wrapping the nanotubes and (2) measurement of nanotube compression at tube-tube junctions within the network.

Quantum dispersion properties of eigenmodes in semiconductor nanotubes with dielectric filling in dc magnetic field

Dispersion properties of electromagnetic eigenmodes in a semiconductor nanotube (with quadratic electron dispersion law) filled by a nonmagnetic dielectric and placed in a coaxial dc magnetic field are studied theoretically. A new quantum electrodynamical phenomenon is predicted. Namely, it is shown that increase in the electron density n02D in the nanotube results in the appearance of new branches in the eigenmodes spectrum. These branches arise in a bifurcation manner at some critical values of n02D, when a new electron energy subzone starts to fill in. The number of branches monotonously increases with growth n02D and oscillates with increase in the number of magnetic flux quanta through the nanotube (i.e., a peculiar Aharonov–Bohm effect takes place). We also found that the dispersion curves have parts with anomalous dispersion. The analytical expression for electron energy loss due to the excitation of eigenmodes under the Cherenkov resonance condition is derived and numerically analyzed.

Enhanced inactivation of bacteria on capacitive semiconductor nanotubes by Self-Discharging triggered photoelectrocatalysis

Hospital-acquired infections and antibiotic-resistant pathogens are major threats to human health. We develop an antibacterial film that maintains the long-term stability of titania (TiO2) while minimizing the disadvantages, the low photocatalytic efficiency of TiO2, especially in visible light, that limits the application of TiO2. Here, TiO2 nanotubes are modified with capacitive materials as a visible-light-triggered antimicrobial surface; its mechanism is based on substantially increased content of reactive oxygen species produced from the photocatalytic reaction during the electrochemical capacitive process. The system is functionalized with MIL-125(Ti) nanosheets and monodispersed Fe2O3 nanoparticles, enabling a large capacitance (149.0 mF cm−2) in a neutral aqueous electrolyte and high visible-light absorption. Importantly, the photocatalytic activities of the resulting capacitive semiconductor are proportional to the bias provided by the capacitive sample in its self-discharging (SD) process. As a proof-of-concept of the SD-triggered photoelectrocatalysis, the capacitive semiconductor exhibits ≥ 99.9 % reduction in Escherichia coli and Staphylococcus aureus by only 30 min treatment and remarkably has a bacteria-free surface for recycling bacterial applications. Furthermore, the assembled asymmetric supercapacitor cell also exhibits excellent performance in bacteria inactivation, suggesting an efficient sterilization device for environmental applications.

Compensation points in the lattice of semiconductor nanotubes

In the present work, we investigated the thermodynamic properties of the lattice formed by noninteracting nanotubes using a single-walled nanotube model in a longitudinal magnetic field. We show that the specific heat of nondegenerate electron gas in semiconductor nanotubes changes from kB/2 to kB as temperature increases. Magnetization has a “saw-tooth” form as a function of the magnetic field. For the lattice of nanotubes with two different radii, we found ordinary compensation points, points at which the magnetization vanishes at fixed values of the magnetic field strength.

Heat capacity and magnetization of identical and non-identical semiconductor nanotubes

In the present work, we investigated the thermodynamic properties of the lattice formed by non-interacting nanotubes using a single-walled nanotube model in a longitudinal magnetic field. Using the energy spectrum, we derived the exact analytic expression for the single-particle partition function and used it to determine the magnetic moment and specific heat. Magnetization has a “saw-tooth” form as a function of the magnetic field. For the lattice of nanotubes with two different radii, we found ordinary compensation points, points at which the magnetization vanishes at fixed values of the magnetic field strength.

Aluminum oxide nanotubes fabricated via laser ablation process: Application as superhydrophobic surfaces

Laser-induced surface structuring is a promising technique for the novel formation of nanostructures that can effectively be used to modify the surface and synthesis of nanostructures. Metallic and semiconductor oxide nanotubes presently have been attracted in an extensive domain of materials that range from optoelectronic, gas sensor, catalyst, and superhydrophobic surface applications. In this work, aluminum oxide nanotubes were successfully fabricated by laser ablation processes of a 40-nm gold nanolayer coated on an aluminum surface plate inside the ethanol. A continuous-wave fiber laser with a power of 40 W was used to create Al2O3 nanotubes. The electron diffraction pattern analysis of these nanotubes demonstrated that the Al2O3 nanotubes had a single crystal and hexagonal crystal structure with the lattice parameter of a = 0.432 nm as well as zone axis of z=12¯13¯. These nanotubes had a highly-crystalline structure with about 50–200 nm diameters, 10–50 nm wall thicknesses, and 5–20 µm length as well as open-ended. In addition, aluminum oxide nanotubes structures indicated a near superhydrophobic behavior with about 155° ± 2° as a contact angle using experimental and simulation approaches. Meanwhile, molecular dynamics simulation was applied to investigate the wetting property of the aluminum surface and the aluminum surface containing Al2O3 nanoparticles and Al2O3 nanotubes. The effect of the Al2O3 nanotubes on wetting properties was considerable compared to the Al2O3 nanoparticles. The growth mechanism of Al2O3 nanotubes was proposed and illustrated in detail. Also, the obtained findings of this work can be applied to superhydrophobic surfaces in industrial production.

A Comparison for Saturable Absorbers: Carbon Nanotube Versus Graphene

Saturable absorbers (SAs) have been regarded as a low‐cost yet robust and compact solution to pulse generation in different fiber and solid‐state ultrafast lasers. Following the development of different artificial SAs and semiconductor SA mirrors, carbon nanotube (CNT) and graphene are discovered and employed as SAs for solid‐state as well as fiber lasers. In the past decade, a growing number of SAs based on new materials like MXenes and metal halide perovskites have emerged, while CNT and graphene are still irreplaceable by new materials due to their fascinating saturable absorption properties. Instead of searching for new SAs, the investigation of transient dynamics for mode‐locked pulse generation still relies on the use of CNT and graphene SAs in the fiber laser system due to their reproducible performance and facile fabrication. In this review, a comparison between CNT and graphene will be thoroughly studied in terms of optical nonlinearity, relaxation and recovery time, saturation intensity or fluence, modulation depth, non‐saturable loss, and damage threshold dynamics. In the end, this review will address the challenges in the selection of SAs and provides recommendations for CNT and graphene SAs used in different mode‐locked fiber lasers.

Carbon Nanotubes Film Integrated With Silicon Microfluidic Channel for a Novel Composite THz Metasurface

Owing to the unique electromagnetic response ability, artificial electromagnetic metasurfaces have potential applications in medical, imaging, sensing, and other fields. In this paper, a novel composite THz metasurface integrated by carbon nanotubes (CNTs) resonant metasurface and silicon microfluidic channel has been proposed, which combines the advantages of semiconductor and carbon nanotubes film materials. The absorption characteristics and the refractive index sensing capabilities are investigated comprehensively. Calculation results show that two obvious resonant absorption peaks located at 1.20 THz and 1.85 THz and the absorption is nearly 99.6% and 89.8%, respectively; the device performs a good linear relationship between the position of resonant absorption peaks and the refractive index, and the frequency sensitivity can achieve 492 GHz/RIU. The influence of structural parameters and the offset of the center of the CNTs metasurface on the absorption spectrum demonstrate that the novel composite metasurface has a good reliability and stability and can be used for sensing various materials in other frequency regions range from radio frequency through THz and to the infrared regime. This novel composite metasurface has good biocompatibility and low cost, which widens the application range of terahertz functional devices.

Ordinary Compensation Points in the Lattice of Semiconductor Nanotube

Ordinary Compensation Points in the Lattice of Semiconductor Nanotube

Room temperature dilute magnetic semiconductor response in (Gd, Co) co-doped ZnO for efficient spintronics applications.

The co-precipitation approach was utilized to experimentally synthesize ZnO, Zn0.96Gd0.04O and Zn0.96-x Gd0.04Co x O (Co = 0, 0.01, 0.03, 0.04) diluted magnetic semiconductor nanotubes. The influence of gadolinium and cobalt doping on the microstructure, morphology, and optical characteristics of ZnO was investigated, and the Gd doping and Co co-doping of the host ZnO was verified by XRD and EDX. The structural investigation revealed that the addition of gadolinium and cobalt to ZnO reduced crystallinity while maintaining the preferred orientation. The SEM study uncovered that the gadolinium and cobalt dopants did not affect the morphology of the produced nanotubes, which is further confirmed through TEM. In the UV-vis spectra, no defect-related absorption peaks were found. By raising the co-doping content, the crystalline phase of the doped samples was enhanced. It was discovered that the dielectric response and the a.c. electrical conductivity display a significant dependent relationship. With the decreasing frequency and increasing Co co-dopant concentration, the ε r and ε'' values decreased. It was also discovered that the ε r, ε'', and a.c. electrical conductivity increased when doping was present. Above room temperature, co-doped ZnO nanotubes exhibited ferromagnetic properties. The ferromagnetic behaviour increased as Gd (0.03) doping increased. Increasing the Co content decreased the ferromagnetic behaviour. It was observed that Zn0.96-x Gd0.04Co x O (x = 0.03) nanotubes exhibit superior electrical conductivity, magnetic and dielectric characteristics compared to pure ZnO. This high ferromagnetism is typically a result of a magnetic semiconductor that has been diluted. In addition, these nanoparticles are utilized to design spintronic-based applications in the form of thin-films.

Semiconductor nanotube eigenmodes and the Aharonov–Bohm effect

In the present work, the spectra of electromagnetic eigenmodes of a structure consisting of a semiconductor nanotube filled with a nonmagnetic dielectric are theoretically investigated. This structure is placed in a constant magnetic field parallel to the nanotube axis. The walls of the nanotube are assumed to be infinitely thin. The dispersion equation for eigenmodes in such a structure is derived taking into account the retardation effect. From the dispersion equation it follows that in the general case the bulk-surface and surface eigenmodes can exist in such a structure. These eigenmodes with a nonzero azimuthal mode index are hybrids ones and can experience Aharonov-Bohm oscillations with the magnetic field changes.

Semiconductor nanochannels in metallic carbon nanotubes by thermomechanical chirality alteration.

Carbon nanotubes have a helical structure wherein the chirality determines whether they are metallic or semiconducting. Using in situ transmission electron microscopy, we applied heating and mechanical strain to alter the local chirality and thereby control the electronic properties of individual single-wall carbon nanotubes. A transition trend toward a larger chiral angle region was observed and explained in terms of orientation-dependent dislocation formation energy. A controlled metal-to-semiconductor transition was realized to create nanotube transistors with a semiconducting nanotube channel covalently bonded between a metallic nanotube source and drain. Additionally, quantum transport at room temperature was demonstrated for the fabricated nanotube transistors with a channel length as short as 2.8 nanometers.

Ultrafast Interface Charge Separation in Carbon Nanodot-Nanotube Hybrids.

Carbon dots are an emerging family of zero-dimensional nanocarbons behaving as tunable light harvesters and photoactivated charge donors. Coupling them to carbon nanotubes, which are well-known electron acceptors with excellent charge transport capabilities, is very promising for several applications. Here, we first devised a route to achieve the stable electrostatic binding of carbon dots to multi- or single-walled carbon nanotubes, as confirmed by several experimental observations. The photoluminescence of carbon dots is strongly quenched when they contact either semiconductive or conductive nanotubes, indicating a strong electronic coupling to both. Theoretical simulations predict a favorable energy level alignment within these complexes, suggesting a photoinduced electron transfer from dots to nanotubes, which is a process of high functional interest. Femtosecond transient absorption confirms indeed an ultrafast (<100 fs) electron transfer independent of nanotubes being conductive or semiconductive in nature, followed by a much slower back electron transfer (≈60 ps) from the nanotube to the carbon dots. The high degree of charge separation and delocalization achieved in these nanohybrids entails significant photocatalytic properties, as we demonstrate by the reduction of silver ions in solution. The results are very promising in view of using these “all-carbon” nanohybrids as efficient light harvesters for applications in artificial photocatalysis and photosynthesis.

Recognition of metallic and semiconductor single-wall carbon nanotubes using the photoelectric method

an innovative application of deep barrier silicon structures for sensory devices with photoelectrical transformation has been suggested. The principal possibility of the photovoltaic transducer implementation for identification of metallic and semiconductor single-wall carbon nanotubes covered with surfactant in water solution was analyzed in detail. The obtained results are qualitatively explained by local electrostatic influence on the parameters of recombination centers at the silicon surface. This influence can be associated with the dipole moment of molecules absorbed at the surface of the nanotube from surfactant sodium dodecylbenzene sulfonate (SDBS). Moreover, the spatial configuration of charged fragments near the defects at the silicon surface can occur. Another possible reason for carbon nanotubes identification is due to the different polarizability of metallic and semiconductor nanotubes. These results are explained in the frame of Stevenson-Keyes's theory. The reported effect can be further applied as the basis for the control and selection of carbon nanotubes with different conductivity types.