Journal of Nano Research Vol. 60

Abstract: In this research, we detailed how the following factors affect the scattering of light by nanofluids: (1) nanoparticle sizes, (2) volume fraction of nanoparticles, and (3) nanoparticle materials. Mie theory was used to calculate the radiative properties of the nanofluids. The radiative properties were then applied into the Radiative Transfer Equation (RTE) to solve for the transmittance and reflectance of light through the nanofluids. The RTE was solved using the Monte Carlo method. Results showed that when the size of nanoparticles and the volume fraction increase, absorption and scattering coefficients increase as well. For silver nanofluids, absorption and scattering coefficients decrease beyond nanoparticle size of about 50 nm. Transmittance of light decreased when nanoparticle sizes increased. When comparing between TiO₂, Ag, and SiO₂ nanofluids, Ag nanofluids exhibit the highest light absorption followed by TiO₂ and SiO₂.

Abstract: A nonlinear spring model is proposed to investigate the oscillation behavior of oscillators based on double-walled carbon nanotubes (DWCNTs) with open end by using the finite element (FE) method, where non-linear spring elements are used to represent the van der Waals (vdW) interaction between tubes. Compared to the linear spring FE model, the proposed non-linear springs can more accurately describe the interaction between nanotubes because the vdW interaction is a kind of strongly non-linear force. The influence of boundary conditions, geometric parameters of the DWCNTs, and the layer spacing of tubes on the natural frequencies is especially studied. Various oscillation modes and the corresponding natural frequencies are obtained. Compared to the results obtained by using the linear spring model, the natural frequencies of oscillators based on DWCNTs are in qualitatively better agreement with those obtained from the analytical method and the molecular dynamics (MD) method. From the FE results, it also can be seen that, DWCNTs is expected to be a nanoscale oscillatory device, and its oscillation mode and natural frequency can be adjusted by changing the geometric parameters and boundary condition of the tubes. The proposed nonlinear spring model is helpful for the design of the nano-oscillators under various conditions.

Abstract: This paper starts from the leakage currents through the gates of the last MOSFET generations and propose a related structure, which can be inherently included as parasitic device in any future MOSFET sub-22nm or can be deliberated fabricated to induce its own behavior. This structure is abbreviated in this paper by p-NOI (planar-Nothing On Insulator) and it can be simply produced by the planar Si-technology. Its concept is derived from the NOI (Nothing On Insulator) concept, but replaces the vacuum with oxide. The conduction mechanism is based on a thin oxide tunneling, under the Fowler-Nordheim's law. The current flow occurs from a source to a lateral drain, without an inversion channel and without a lateral pn junction, as in the MOSFET case. A similar investigated device by other authors is a fabricated MIM (Metal-Insulator-Metal) structure, which is compared with the actual p-NOI simulation. Finally, a dual gate p-NOI device is investigated. The depletion-accumulation transition is captured by the static I-V static characteristics. Using two steps of oxide, of 2nm and 10nm, a second planar-NOI structure with three terminals was studied. The (G) terminal is associated to a Gate and the (S) terminal is associated to a Source of a Field Effect Transistor. Some particular applications as diode or transistor are emphasized versus the gate biasing regime.

Abstract: The micro-nanostructures were prepared on the surface of 304 stainless steel by one-step anodizing with perchloric acid-ethylene glycol electrolyte. The morphologys, phase behaviour and microstructures of the prepared micro-nanostructures were characterized by SEM, XRD and metallographic examinations. The corrosion resistance and hydrophobic properties of 304 stainless steel after anodizing at different times were studied by Tafel test and contact angle test. The results show that when the anodization voltage is 30V, the electrolyte is 5vol% perchloric acid-ethylene glycol, the reaction temperature is 0 ± 5 ° C，and the anodization time is 15min, a honeycomb micro-nanostructure having an average pore diameter of 143 nm, an average pore spacing of 124 nm and a uniform distribution can be prepared on the surface of 304 stainless steel. The prepared nanostructure has a contact angle with water of 128° and a hydrophobicity of 86.3%, which corrosion resistance is 21 times higher than that of ordinary 304 stainless steel in 3.5 wt% NaCl solution. Metallographic microscopic observation and XRD indicate that the anodic oxidation begins along the grain boundary of the austenite, and then the micro-nano holes grow on the austenite and fill the entire austenite phase. Finally, Fe₂O₃ structure with uniformly distributed micro-nano pores is formed on the surface of the stainless steel.

Abstract: Here, the adsorption behavior of the CO₂ molecules on electronic properties of zigzag and armchair ZnO nanotubes (ZnONTs) has been studied at M06-2X/6-31G(d) level of theory. It is found that CO₂ molecules can be physically adsorbed on the nanotubes. Two minima structures A (monodentate) and B (bidentate) were found on the potential energy surface. Inspection of the results shows that in zigzag and armchair nanotubes, the monodentate complex is more stable than bidentate complex. Also, the stability of complexes increases by increasing the number of CO₂ molecules. Comparison of adsorption energies shows that adsorption of CO₂ molecules over zigzag (6, 0) model is stronger than armchair (4,4) model. In this work, the various parameters such as electronic chemical potential (m), hardness (ƞ), softness (S), the maximum amount of electronic charge (DN_max), electrophilicity index (ω), dipole moment and work function were investigated to evaluate the reactivity of structures. It is predicted that the conductivity and reactivity of nanotubes increase upon complexation. Based on the natural bond orbital (NBO) analysis, in all complexes charge transfer occurs from CO₂ molecules to the nanotube. Theory of atoms in molecules (AIM) was also applied to characterize O_CO2… Zn interaction in nanotubes. In addition, the interaction strength is studied through the reduced density gradient (RDG) function. It is predicted that the ZnONTs can be introduced as a favorable candidate in the design and construction of sensors for detecting CO₂ molecules.

Abstract: Transparent conducting Cobalt-fluorine co-doped tin oxide (SnO₂: (Co, F)) thin filmswere deposited onto preheated glass substrates using the chemical spray pyrolysis method. The ([Co²⁺]/[Sn⁴⁺]) atomic concentration ratio (y)in the spray solution was varied between 0 and 5 at. %. The structural, electrical, optical and photoluminescence properties of these films were studied. It is found that the thin films are polycrystalline with a tetragonal crystal structure corresponding to SnO₂ phase having a preferred orientation along the (200) plane. Transmission and reflection spectra reveal the presence of interference fringes indicating thickness uniformity and surface homogeneity of the deposited thin films. The electrical resistivity (ρ), volume carrier concentration density (N_v), surface carrier concentration density (N_s) and Hall mobility (μ) of the synthesized thin films were determined from the Hall Effect measurements in the Van der Paw-configuration and the following results were obtained: n-type conductivity in all deposited films, a low resistivity of 1.16×10^-2 Ω.cm, and a high Hall mobility of 15.13×10² cm².V^-1.s^-1with Co concentration equals to 3 at. %. These results show that the electrical properties of these thin films where greatly improved making them suitable as ohmic contact in photovoltaic application devices.

Abstract: In recent years, the tunable plasmon modes in the terahertz region of a multilayer graphene structure interacting with a metallic film substrate have attracted significant interest motivated by the graphene´s unique optical and electronic properties and the possibility to enhance light-matter interaction. In this work, the plasmon waves in graphene layered systems on a conducting thin film are investigated, the hybrid graphene-metal metamaterialis surrounded by two semi-infinite materials with different dielectric constants ε₁andε₂, respectively. The dispersion relations of electronic collective excitations are calculated by the zeros of an effective dielectric constant obtained from a recursive relation for the amplitudes associated with the electric field between graphene layers in the metamaterial. Long-range Coulomb interactions based on the hybrid layered graphene-metal structure lead new set spectra of collective excitations. At long wavelength (q®0) the optical modes (w~q^1/2)depend on the two-dimensional carrier density, the metallic thickness, the metallic substrate plasmon frequency, the number of the graphene layers and the dielectric constants in which the hybrid graphene-metal structure is embedded. This latter plays an important role in a wide range of applications such as a surface plasmon resonance biological sensors and terahertz surface plasmons in optically pumped graphene metamaterials.

Abstract: High UV-light sensitivity, fast response, and low power consumption are the most important features of nanowire-based devices for new applications in photodetectors, optical switches, and image sensors. Single AlN nanowire deep ultraviolet (UV) photodetector has been fabricated utilizing very high-quality AlN nanowires through a very practical dielectrophoretic assembly scheme. The low-voltage (≤ 3 V) operating UV photodetector has selectively shown a high photocurrent response to the 254 nm UV light. Furthermore, the photocurrent transients have been modelled to determine the rise and decay time constants as 7.7 s and 11.5 s, respectively. In consequence, combination of deep UV light selectivity and low voltage operation make AlN nanowires great candidates for the development of compact deep UV photodetectors.

Abstract: The last 19 years have seen intense research made on zinc oxide (ZnO) material mainly due to the ability of converting the natural n-type material into p-type. For a long time, the p-type state was impossible to attain and maintain. The review focuses on ways of improving the doped ZnO material which acts as a channel for nanowire field effect transistor (NWFET) and biosensor. The biosensor has specific binding which is called functionalisation achieved by attaching a variety of compounds on the designated sensing area. Reference electrodes and buffers are used as controllers. Top-down fabrication processes are preferred over bottom-up because they pave way for mass production. Different growth techniques are reviewed and discussed. Strengths and weaknesses of the FET and sensor are also reviewed.

Abstract: In this work, we have analyzed the digital and analog performance for InGaAs/InP heterojunction Gate all around MOS structure. A detailed study on the impact of Barrier thickness on different analog and digital performance for an InGaAs/InP hetero structure GAA MOSFET is carried out by using TCAD device simulation. The electrical parameters such as surface potential, electric field, transfer characteristics, output characteristics, transconductance and output conductance is carried out and analyzed by varying the barrier thickness from 1 nm to 4 nm. Based on the simulation results it is investigated that the effect of the all electrical parameters in the nanoscale devices. It has been seen from the presented results that the influence of barrier thickness variation gives the notable improvement in drain current. The impact of InGaAs/InP hetero structure and barrier thickness variation claims GAA MOSFET as a promising candidate for VLSI applications. Keywords: Heterojunction, InGaAs/InP, TCAD, Analog parameters.