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This paper reports on the ohmic contact formed by the conductive glass layer found at the interface of Ag/Si contacts on lowly doped emitter silicon solar cells due to the presence of semimetal nanoparticles. The scanning electron microscopy and scanning transmission electron microscope analyses revealed an interface glass layer (IGL) thickness of greater than 380 nm, which was enriched with micro-sized alloys composed of semimetal nanoparticles. This IGL was conductive as confirmed by conductive atomic force microscopy (C-AFM). The presence of these semimetal nanoparticles, identified as Ag 2 Te and PbTe, was both endowed with low bandgap energies as confirmed by Raman spectroscopy and energy dispersive x-ray spectroscopy. These semimetal nanoparticles were found only in the IGL and formed a "bridge" to connect the Ag gridline and Si emitter for carrier transport. Based on the modified Fowler–Nordheim tunneling process, the modeled C-AFM I–V characteristic curve showed a barrier height of 0.1 eV corresponding to an IGL thickness of only 18 nm. Thus, the carrier transport mechanism "through the conductive bridge" was formed by the semimetal nanoparticles embedded in the IGL. Therefore, the high conductivity of the interface glass led to the specific contact resistance to be independent of the emitter peak doping concentration. [ABSTRACT FROM AUTHOR]

Manganese doped tin oxide nanoparticles with manganese content varying from 0 to 15 mol % were synthesized using sol-gel method. The structural and compositional analysis was carried out using x-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive x-ray analysis (EDAX). Dielectric and impedance spectroscopy was carried out at room temperature to explore the electrical properties of Mn doped SnO2. XRD analysis indicated the formation of single phase rutile type tetragonal structure of all the samples. The crystallite size was observed to vary from 16.2 to 7.1 nm as the Mn content was increased. The XRD, SEM, and EDAX results corroborated the successful doping of Mn in the SnO2 matrix. Complex impedance analysis was used to distinguish the grain and grain boundary contributions to the system, suggesting the dominance of grain boundary resistance in the doped samples. The dielectric constant [variant_greek_epsilon]′, dielectric loss tan δ and ac conductivity σac were studied as a function of frequency and composition and the behavior has been explained on the basis of Maxwell-Wagner interfacial model. All the dielectric parameters were found to decrease with the increase in doping concentration. Moreover, it has been observed that the dielectric loss approaches to zero in case of high dopant concentration (9%, 15%) at high frequencies. [ABSTRACT FROM AUTHOR]

We have studied the effect of annealing (at temperatures 300, 400, and 500 °C) on nanoparticulate CdS film on silicon substrate deposited by hybrid Langmuir–Blodgett chemical bath deposition technique. Width, intensity, and the line shape of the longitudinal optical phonon in Raman spectra and photoluminescence (PL) spectra suggest that the annealing brings about coalescence of nanoparticles at 300 °C, increasing the size of the nanoparticles and also increases the red region PL related to surface states. Annealing at 400 °C leads to two different coexistent states, showing larger nanoparticles and bulklike film. On further annealing at 500 °C, PL shows a drastic redshift to PL of bulklike CdS. This is well brought out by resonance Raman measurements and later confirmed by scanning electron microscope data. Most interesting observation is that PL and Raman results together are indicative of phase transformation of nanoparticulate hexagonal CdS film to bulklike cubic CdS film on annealing at 500 °C, unlike cubic to hexagonal structural phase transition observed in bulk CdS films. [ABSTRACT FROM AUTHOR]

CoSb3 nanocomposites with different contents of CoSb3 nanoparticles were prepared by mixing nanosized CoSb3 particles obtained via polyol method and micron-sized particles obtained via solid state reaction. X-ray diffractometer and field emission scanning electron microscope were used to characterize the prepared products. The thermoelectric properties of the nanocomposites with different amounts of nanoparticles as dispersants were measured from room temperature to around 500 °C. Due to the grain boundaries scattering, the lattice thermal conductivity was observed to decrease as the amount of nanoparticles increased. The electrical properties were also improved by the addition of nanoparticles. The ZT value of the nanocomposites with 10 wt % of nanoparticles was nearly doubled that of the sample without any nanoparticles. [ABSTRACT FROM AUTHOR]

The aligned CdS nanorods are obtained by dispersing CdS in the conducting polyaniline matrix. The rods are about 50 nm in diameter and 400 nm in length. The significant changes of electronic absorption spectra of CdS nanorods and conducting polyaniline indicate the strong interaction between them. CdS—Polyaniline nanocomposites exhibit a three-dimensional Mott’s hopping process in the electrical conduction. Temperature variation of frequency dependent conductivity implies the correlated barrier hopping. The barrier height increases with the content of CdS. [ABSTRACT FROM AUTHOR]

We present low-temperature studies of the optical properties of single CdS nanorods in relation to their morphology. Keeping track of the same nanorods in the photoluminescence (PL) study and during scanning electron microscope imaging, we were able to distinguish intrinsic spectral features of the nanorods from those of nanocluster aggregates. We observed strong PL polarization in the direction perpendicular to the nanorod axis. The sharp peaks in the “blue” region of the PL spectra are redshifted relative to those of bulk CdS and of CdS microparticles in a glass matrix. Finally, we observe a very interesting “spectral diffusion” of the main emission peaks with the following characteristics: (a) Energy–energy correlation of the two main peaks, and (b) correlation and anticorrelation between energy and intensity for the two peaks. Possible mechanisms behind this phenomenon are discussed. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report a technique to characterize adhesion of monolayered/multilayered graphene sheets on silicon wafer. Nanoparticles trapped at graphene-silicon interface act as point wedges to support axisymmetric blisters. Local adhesion strength is found by measuring the particle height and blister radius using a scanning electron microscope. Adhesion energy of the typical graphene-silicon interface is measured to be 151±28 mJ/m2. The proposed method and our measurements provide insights in fabrication and reliability of microelectromechanical/nanoelectromechanical systems. [ABSTRACT FROM AUTHOR]

Understanding biomaterial is very important for superior material development. Here, we report structural and nanophotonic properties of crab shell. The fibrous shell is composed of nanocrystalline calcite, which gives the structure very high strength. Scanning electron microscope cross section and energy dispersive x-ray shows top surface (reddish) is fibrous with metal nanoparticle segregation, while the bottom layer is composed of layered nanohole array similar to air-dielectric photonic lattice structure. The air-dielectric nanohole arrays are disordered but correlated with fractal dimension >1 and able to block infrared. Nanocrystalline calcite and metal nanoparticles can also block extreme level of UV. [ABSTRACT FROM AUTHOR]

Nano-graphene particles (NGPs) were deposited by a pulsed discharge (PD) to ethanol in Ar gas atmosphere of about 600 Torr. The frequency (f) of the PD was changed from 1 to 5 kHz at constant duty ratio of 20%. Evaluations of the NGPs were performed with scanning electron microscope, high resolution transmission electron microscope, and Raman spectra. When f was changed from 1 to 5 kHz, domain size of the NGPs was decreased from 34 to 19 nm. The number of the graphene layers (GLs) was decreased from about 20 to 4, though the number of GLs was scattered from 24 to 2. These results show that the domain size and the number of the GLs can be controlled with f of the PD. [ABSTRACT FROM AUTHOR]

The vertically aligned ZnO nanorod arrays were achieved from aqueous chemical route on soda lime and transparent conducting oxide coated glass substrates. The length of nanorods was varied from 1.6 μm to 4.5 μm by varying deposition time. The aspect ratio of ZnO nanorod was increased with increasing deposition time. Cadmium sulfide (CdS) nanoparticles have been subjected to self-assemble onto ZnO nanorods (ZNRs) using chemical bath deposition method. The synthesized CdS/ZnO nanorod arrays were characterized for their optical, structural, and morphological properties with UV-visible absorption spectroscopy (UV-Vis), x-ray diffraction, energy-dispersive x-ray analysis, x-ray photoelectron spectroscopy, contact angle measurement, and scanning electron microscopy. The cross-section images of the samples clearly depict different lengths of ZnO nanorods. UV-vis absorption spectrum shows the significant red shifting after covering of the CdS nanoparticles over the ZnO nanorods. The lengths of ZnO nanorod arrays are an effective parameter to improve the photoelectrochemical performance of CdS nanoparticles sensitized ZnO solar cells. We obtain a highest total light-to-electricity power conversion efficiency of 1.2% for relatively larger area (1 cm2) solar cells. [ABSTRACT FROM AUTHOR]

Hollow BiFeO3 nanoparticles were synthesized by an electrospray route for the first time. The phase purity and structure have been investigated by x-ray diffraction and Raman spectroscopy. Transmission and scanning electron microscope investigations revealed that the as-obtained BiFeO3 hollow spheres were polycrystalline, with a shell thickness of 35 nm. The formation mechanism can be possibly explained by Ostwald ripening. Raman spectra have verified decreased vibrational frequencies in BiFeO3 nanoparticles. These hollow and core-shell multiferroic nanoparticles exhibit significantly enhanced ferromagnetism from 5 to 600 K due to a broken spiral spin structure. The ferroelectricity of hollow BiFeO3 particles exhibits a lower switching electric field, which is confirmed by Kelvin probe force microscopy. [ABSTRACT FROM AUTHOR]