I. A. Palani

Influence of ZnO buffer layer on ZnO nanowire growth by nanoparticle-assisted pulsed laser deposition

We have succeeded in growing various ZnO nanocrystals, such as nanowires, nanorods, and nanowalls, by a nanoparticle-assisted pulsed-laser deposition (NAPLD). In this study, low-density ZnO nanowires were synthesized by introduction of a ZnO buffer layer. Low-density hexagonal cone-shape ZnO cores are formed on the buffer layer, and vertically-aligned ZnO nanowires are grown on the cores. The density of the nanowires was clearly decreased with increasing the thickness of the Buffer layer. The buffer layer can be used as one of the effective additives to control the growth density of the ZnO nano-crystals synthesized by NAPLD.

Investigation on production of highly textured Sb doped polycrystalline silicon using solid state Nd:YAG laser for photovoltaic application

Efficient doping of amorphous silicon(a-Si) is a key issue in the field of photovoltaic applications. In this paper an attempt has been made to produce a highly highly textured Sb doped a-Si. The a-Si were coated with Sb to a thickness of 200nm using vacuum evaporation method and treated with an Nd:YAG laser of 355nm with a threshold fluence of 460mJ/cm2 by overlapping the laser spots to 90% of its size. The samples are retretaed with a low laser fluence of 230mJ/cm2 respectively so as to crytsallize and diffuse the Sb on to the surface and to activate the dopant. The laser doped and subequently laser textured samples were analysed through Scanning Electron microscope (SEM), X-ray diffraction (XRD) & Atomic Force Microscope(AFM).The traces of SiSb in the XRD peak with improved surface roughness were observed on the laser doped samples. This represents that the dopants are highly diffused on the a-Si.

Lasing Characteristics of an Optically-Pumped Single ZnO Nanocrystal and Nanomachining for Controlling Oscillation Wavelength

Lasing characteristics from a single ZnO nanocrystal excited by third harmonic of a Q-switched Nd:YAG laser beam (355 nm, 5 ns) were investigated for the application to ultraviolet (UV) laser diode (LD) by using ZnO nanocrystals as building blocks. Those ZnO nanocrystals were synthesized on a silicon substrate with a catalyst of gold by a carbothermal chemical vapor deposition (CVD) method. ZnO nanowires and ZnO nanosheets were synthesized by changing the synthesis conditions and the dependence of lasing characteristics on the different forms were investigated. The emission spectra observed from a single ZnO nanowire and ZnO nanosheet showed the obvious lasing characteristics having mode structure and a threshold for lasing on the input–output characteristics. The threshold power density of a ZnO nanowire and a ZnO nanosheet was measured to be about 150 and 50 kW/cm2, respectively. Then, the oscillation mechanisms were discussed on those ZnO nanocrystals, and it was concluded that each lasing mechanism was attributed to the microcavity effect due to the strong UV light confinement caused by the high refractive index of ZnO (≈2.4) for UV light. ZnO can be a superior UV laser medium and an UV nano-laser source also can be expected. However, the observed lasing spectra from both ZnO nanocrystals had mode structure, and a single longitudinal mode lasing would be required for the stabilization of the output power and the prevention of light dispersion. Therefore, we considered the possibilities of the single longitudinal mode lasing from a single ZnO nanowire using distributed Bragg reflector lasing machined by focused ion beam with Ga ions focused up to 7 nm and a single ZnO nanosheet using subwavelength machining by Fresnel diffraction for 2D photonic crystal. We also observed the laser-induced motions (LIM) of ZnO nanocrystals dispersed on a substrate in the air when they were excited by the UV laser beam at high excitation power over several MW/cm2 which could be attributed to the electromotive force due to piezo effects of ZnO nanocrystals, and a simple alignment method of ZnO nanocrystals was considered by the use of the LIM and voltage-applied electrodes on a substrate.

Synthesis and characterization of well-aligned ZnO:Sb nanowires

Vertically-aligned ZnO nanowires on a sapphire substrate have been synthesized by a nanoparticle-assisted pulsed-laser deposition using a Sb2O3 doped ZnO target. Uniform cone-shape core was formed at the bottom of each vertically-aligned ZnO nanowire. The nanowires consist of single-crystalline wurzite ZnO crystal with a growth direction along [0001]. The room-temperature photo luminescence spectrum exhibited a strong ultraviolet emission at around 380 nm.

Characterization of Sb-Al co-doped ZnO nanowires synthesized using nanoparticle-assisted pulsed-laser deposition

Sb-Al co-doped ZnO nanowires have been successfully synthesized using nanoparticles-assisted pulsed-laser deposition. These nanowires possess wurzite crystal structures with a sharp UV emission, highly suitable for optoelectronics applications.

Annealing and texturing of a-Si film using Nd 3+ :YAG laser with Gaussian and flat-top beam profiles

An application of a pulsed, solid-state laser with a Gaussian and flat-top beam profiles is considered for annealing and nano-texturing of amorphous-silicon (a-Si) films. Investigations are performed with the third harmonics (355 nm) Nd3+:YAG laser. To crystallize and subsequently induce texture, a-Si films are treated by spatial-overlapping of the laser spots on the surface by 90% of its size. The generation of texturization mechanism in laser assisted annealing and texturing is theoretically investigated and experimentally analyzed.

Investigation on laser cleaning of thin films deposited on sapphire

The selective and large area laser cleaning of thin films deposited on sapphire substarte was experimentally investigated. The parameters are optimized for efficient cleaning and the samples were analyzed through SEM and AFM.