Undoped and Mn doped ZnO samples with different percentage of Mn content (1 mol%, 2 mol% and 3mol%) were synthesized by a simple solvo-thermal method. We have studied the structural, chemical and optical properties of the samples by using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray (EDX) analysis, Fourier transform infrared (FTIR) spectroscopy and UV-VIS spectroscopy. The XRD spectra show that all the samples are hexagonal wurtzite structures. The lattice parameters calculated for the Mn doped ZnO from the XRD pattern were found to be slightly larger than those of the undoped ZnO, which indicates substitution of Mn in ZnO lattice. SEM photograph shows the grain size of undoped ZnO is bigger than the Mn doped ZnO's indicating hindrance of grain growth upon Mn doping. As the Mn doping increases the optical band gap decreases for the range of Mn doping reported here.

We report the spatial maps of the localized surface plasmon resonances associated photon emission in a truncated tetrahedral gold nanoparticle on a silicon substrate. Site-specific cathodoluminescence spectroscopy and imaging in a scanning electron microscope shows stronger photon emission in the visible range near the tips of the particle in contact with the substrate compared to the edges of the particle. Strong local field variations on a length scale as short as 19 nm are resolved. We also perform FDTD simulations of both the spectra and, for the first time, the full cathodoluminescence images. Excellent agreement is obtained with the experimental results, and the detailed information available from the simulated results makes it possible to identify the signature of out-of-plane higher order modes in the truncated tetrahedral gold particle.

Employing cathodoluminescence (CL) spectroscopy and imaging in a field emission gun (FEG) scanning electron microscope (SEM), we study localized surface plasmon (LSP) modes on individual tilted gold nanodecahedron sitting on a silicon substrate. We experimentally resolve three distinct LSP modes in the far-field radiation acquired via CL. The experimental spectra and intensity maps of plasmon modes are in excellent agreement with the spectra and 2D-CL image obtained from finite difference time domain (FDTD) simulations. Detail analysis reveals the signature of a quadrupolar surface plasmon mode in addition to the two dipolar modes along azimuthal and polar direction of the decahedron. The experimental method and the theoretical formalism presented here provide useful insight into the plasmonic behavior of complex shaped metal nanoparticle supported by a high index substrate.

Using cross-section transmission electron microscopy ͑XTEM͒ we have studied the surface and subsurface structure of individual ripples having submicron scale wavelength and nanometer scale amplitude, generated by obliquely incident ͑50-120 keV͒ Ar ion bombardment of Si. The XTEM results reveal that the front slopes of ion-induced ripples have amorphous layers containing bubbles with sizes ranging from about 3 to 15 nm facing the ion beam direction. A thinner amorphous layer without bubbles, on the other hand, persists on the rear slope of ripples. We also observe an irregular interface between a-Si and c-Si, which is due to the direct impact amorphization mechanism prevalent near the end-of-range during heavy ion irradiation.

We performed cathodoluminescence (CL) spectroscopy and imaging in a high-resolution scanning electron microscope to locally and selectively excite and investigate the plasmonic properties of a multi-branched gold nanostar on a silicon substrate. This method allows us to map the local density of optical states from the nanostar with a spatial resolution down to a few nanometers. We resolve, both in the spatial and spectral domain, different plasmon modes associated with the nanostar. Finite-difference time-domain (FDTD) numerical simulations are performed to support the experimental observations. We investigate the effect of the substrate on the plasmonic properties of these complex-shaped nanostars. The powerful CL-FDTD combination helps us to understand the effect of the substrate on the plasmonic response of branched nanoparticles.