Laser ablation and deposition of wide bandgap semiconductors: plasma and nanostructure of deposits diagnosis

Abstract

Nanostructured CdS and ZnS films on Si (100) substrates were obtained by nanosecond pulsed laser deposition at the wavelengths of 266 and 532 nm. The effect of laser irradiation wavelength on the surface structure and crystallinity of deposits was characterized, together with the composition, expansion dynamics and thermodynamic parameters of the ablation plume. Deposits were analyzed by environmental scanning electron microscopy, atomic force microscopy and X-ray diffraction, while in situ monitoring of the plume was carried out with spectral, temporal and spatial resolution by optical emission spectroscopy. The deposits consist of nanoparticle assembled films but ablation in the visible results in larger aggregates overimposed on the film surface.The aggregate free films grown at 266 nm on heated substrates are thicker than those grown at room temperature and in the former case they reveal a crystalline structure congruent with that of the initial target material. The observed trends are discussed in reference to the light absorption step, the plasma composition and the nucleation processes occurring on the substrate.

Harmonic generation by atomic and nanoparticle precursors in a ZnS laser ablation plasma

“…Thin films and nanostructures of this compound are becoming of interest for the fabrication of electrodes for solar energy conversion, nonlinear optical devices, light emitting diodes, lasers, and others [27]. PLD has been advantageously applied as a synthesis procedure for ZnS thin films and nanostructures, as it provides control routes of their crystallinity and crystal lattice (cubic or hexagonal) and morphology at nanometer scale, based on the choice of laser and deposition parameters [26][27][28][29][30].…”

Pulsed laser ablation and deposition of ZnS:Cr

“…All films had a smooth surface, and no particulates or droplets were observed by optical microscope or SEM, which can be due to the small laser wavelength used for the ablation process, i.e. 248 nm [24]. From EDS line scans (not shown) we found that Cr is randomly distributed, and there are no Cr clusters in the films.…”

Micrometric rods grown by nanosecond pulsed laser deposition of boron carbide

“…The laser wavelength is known to exert a crucial effect on the composition and dynamics of the ablation plume [34] and thus on the properties of material grown on a substrate by PLD. Boron carbide is considered a p-type semiconductor with a bandgap of 2.09 eV and a number of intermediate gap states [4,35].…”