A new approach for functionalising oxidised MWCNTs using hydroxylated imidazolium bromide via esterification reaction is reported. The bromide anion of a functionalised MWCNTs was exchanged with bis(trifluoromethanesulfonyl) imide (TFSI) through a metathesis reaction to improve its solubility in the IL medium. Composite was characterized with IR, XPS, EDX and TGA analysis, which clearly confirmed that the MWCNTs were functionalized with IL. For potential application as lubricant, the tribological properties of the IL-functionalised MWCNTs (MWCNT-IL) were also evaluated. It was confirmed that even low concentrations of MWCNT-IL composite in ILs causes a significant improvement in the anti-wear and friction properties.

Catalyst-free vapor phase transport was applied for the growth of ZnO nanoemitters. A single-crystalline ZnO:Al seed layer was deposited and used as a pseudo-catalyst. The desired morphology of nanostructures can be achieved by means of modifying the growth rates of crystal planes via adjustment in the growth conditions. The field emission characteristics of ZnO nanoemitters satisfied the Fowler-Nordheim relationship. The high aspect ratio of nanoemitters had a low turn-on electric field of 0.18 MV/m at emission current density of 0.1 μA/cm2. A stable electron emission with a variation of less than 14% was measured.

Elongated micro- and nanostructures of Sn doped or Sn and Cr co-doped monoclinic gallium oxide have been grown by a thermal method. The presence of Sn during growth has been shown to strongly influence the morphology of the resulting structures, including Sn doped branched wires, whips, and needles. Subsequent co-doping with Cr is achieved through thermal diffusion for photonic purposes. The formation mechanism of the branched structures has been studied by transmission electron microscopy (TEM). Epitaxial growth has been demonstrated in some cases, revealed by a very high quality interface between the central rod and the branches of the structures, while in other cases, formation of extended defects such as twins has been observed in the interface region. Cathodoluminescence (CL) measurements show a Sn-related complex band in the Sn-doped structures. In the Sn−Cr co-doped samples, the characteristic, very intense Cr3+ red luminescence emission quenches the bands observed in the Sn doped samples. Branched, Sn−Cr co-doped structures were studied with microphotoluminescence imaging and spectroscopy, and waveguiding behavior was observed along the trunks and branches of these structures.

In this work we present new results on the morphological and microstructural properties of GaAs-AlxGa1-xAs (x≈0.24) core-shell nanowires (NWs) epitaxially grown on (111)B-GaAs substrates by Au-catalyst assisted metalorganic vapor phase epitaxy (MOVPE). Optimized growth conditions allowed us to fabricate highly-dense arrays of vertically-aligned (i.e., along the <111> crystallographic orientation) NWs. The NW arrays were investigated by Helium Ion microscopy (HeIM) and X-ray double- and triple-axis measurements and reciprocal space mapping (RSM). We demonstrate that these techniques can be employed in order to correlate some intrinsically local morphological information with statistically relevant (i.e. averaged over millions-to-billions of NWs) data on the NW structural properties.

Axial heterostructure nanowires with Si and SiGe segments have been grown using Au metal seed as catalyst by chemical vapor deposition (CVD) via vapor-liquid-solid process (VLS). We report on the effect of growth intervention on the droplet stability which in turn modifies NW morphology and interfacial abruptness. Growth stop of 2 minutes on transition from one material to another have been demonstrated to suppress reservoir effect by Au catalyst. The two SiGe/Si and Si/SiGe heterointerfaces are found to be assymetric. The former being diffused while the latter one is sharp. Furthermore, geometric phase analysis reports elastic deformation at the heterointerface. Nanowire undergoes rotation in both clock and anticlockwise direction at their sidewalls with an angle of 2.5° in order to accommodate this strain.

We report the growth of ZnO horizontal (NRs) on p-Si substrate at low temperature without any assisting mechanism. The NRs were grown at 90°C on a ZnO film previously deposited using metal-organic chemical vapor deposition. The horizontal nanowires have diameters in the range of 200 – 500nm and lengths between 1 – 7 µm, depending upon the duration of the growth and the ratio of the precursors. The density of the NRs was controlled by varying the concentration of zinc nitrate (Zn(NO3)2) while keeping hexamethylenetetramine (HMTA) constant. Density of horizontal NRs increased with lower zinc nitrate concentration (from 11.35 to 3.29 mMol) for a growth duration of 18hrs. Increased zinc nitrate concentration of 3.29mMol resulted in an asymmetric growth along the vertical axis due to oxygen termination giving rise to slower growth rates.

We present a computational analysis of thermal transport in Silicon-Germanium alloy nanowires (SiGeNWs), particularly focusing on the relative roles of alloy scattering and boundary scattering to the significant reduction of thermal conductivity (κ). Our nonequilibrium molecular dynamics (NEMD) simulations confirm the strong dependence of κ on Si:Ge ratio, as observed in previous experimental studies. Interestingly, as the amount of impurity increases, the difference in κ between SiGe bulk and SiGeNW becomes smaller. Especially, κSiGeNW and κSiGe have similar κ values when the Ge content is 20-80 %. From a nonequilibrium Green’s function (NEGF)-density functional theory (DFT) analysis, it is suggested that the most reduction in transmission channels is attributed to the strong alloy scattering effect for both Si0.8Ge0.2 bulk and Si0.8Ge0.2 NW. The boundary scattering effect in the SiGe alloy system seems to be unimportant as alloy scattering is dominant. The improved understanding provides fundamental insight into how to modify Si-based materials to enhance their thermoelectric (TE) properties through nanostructuring and alloying.

Nanowire arrays have been proposed to enhance light trapping, increase efficiencies, and reduced material cost in photovoltaic solar cells. In this work we present a new crystalline silicon nanowire array structure, inspired by fractal geometry. The array structure is assumed to be an infinite 2D array in the x and y directions, and composed of vertically aligned SiNW suspended in air. Hexagonal fractal-like geometry is adapted in arranging cylindrical SiNW in these arrays. Full-wave finite element method 3D simulation is used to compute reflectance, transmittance and absorptance of the array for a normal incidence plane wave. The proposed fractal-like distribution of SiNW arrays yield broad absorption spectrum and enhanced efficiency while using less material. The efficiency of the proposed fractal-like SiNW arrays achieve ∼100% enhancement over that of the equivalent thickness flat c-Si film, and ∼18% enhancement over an equivalent height hexagonal array. The proposed optimized structures achieved a filling ratio ∼25%, which is ∼33% less than the corresponding hexagonal array.

In this study, the formation of Ni-(GeSn)x on strained and relaxed Ge1−xSnx (0.01≤x≤ 0.03) nanowires in contact areas has been investigated. The epi-layers were grown at different temperatures (290 to 380°C) by RPCVD technique. The strain in GeSn layers tailored through carefully chosen of growth parameters and virtual substrate. The nanowires were fabricated through both I-line and dry-etching. 15 nm Ni was deposited either on the contact areas or whole length of nanowires. The wires went through rapid thermal annealing at intervals of 360 to 550°C for 30s in N2 ambient. The results show the thermal stability and amount of particular phases were strain-dependent. The formation of Ni-GeSn was eased when GeSn layers were strain-free. When the Sn content is high the epi-layers suffer from Sn segregation. The Sn-rich surface impedes remarkably the Ni diffusion. The electrical conductivity measurement of nanowires shows low resistivity and Ohmic contact are obtained for Ni-GeSn.

Advanced electrochemical technique was elaborated to fabricate self-organized CdSe nanowire structures from aqueous electrolytes on ITO coated glass substrates. We have recently been demonstrated successful electrochemical formation of free-assistent CdSe nanowire structures with diameter around 30 nm. This work has extended our previous research of electrodeposition of Cd chalcogenide (CdSe, CdS) nanowires to formation of core-shell CdSe/CdTe photosensitive nanowire structures. CdSe nanowire structures were synthesized potentiostatically from an acidic solution of H2SeO3 and CdCl2 at room temperature. Then the CdSe (core) nanowires were further passivated with CdTe (shell) thin film by method of electrochemical deposition from acidic solution of H2TeO3 and CdCl2. The effect of interfacial passivation with CdTe layer on the performance of the prepared photovoltaic structures was investigated and special account was paid to the morphology, composition and photovoltaic properties of obtained CdSe/CdTe nano-layers. It should be noted, that electrically conductive polymer photoabsorbers (poly (3-octylthiophene) etc.) were applied successfully for preparation of high work-function ohmic contact-sensitizer layer to CdTe shells. The electrodeposition and spin-casting techniques were applied step-by-step to prepare complete hybrid photovoltaic structures.

Optical properties of ZnO-CdTe electrochemically prepared on a core-shell nanostructure (NS) were studied. Numerical simulations based on effective medium approximation give higher absorption than ZnO-CdS samples and a sensitive dependence on CdTe content. The absorption edges for deep black samples found by transmittance (T(λ)) and diffuse reflectance (Rdiff(λ)) measurements were at 1.33eV and 1.55eV, respectively. A split-off band edge was also found by Rdiff(λ) at ∼2.5eV. The red shift observed in T(λ), previously observed in ZnO-CdS, and may confirm the enhancement of sub-bandgap absorption due to the NS nature of samples.