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A new structure is proposed to improve the external quantum efficiency of porous silicon (PS) light emitting diodes (LED). It is based on a heterojunction between n-type doped silicon and PS. The heterojunction is formed due to the doping selectivity of the etching process used to form PS. The improvement of the proposed LED structure with respect to usual metal/PS LED is demonstrated. This is thought to be due to a different injection mechanism for which carriers are injected directly into conduction band states. Anodic oxidation experiments show further improvements in the LED efficiency.

Time‐of‐flight mass spectrometry and covariance mapping technique were used to investigate the formation of charged species in the laser ablation of a Pb(Ti0.48Zr0.52)O3 target. Mass spectra were taken both in high vacuum and in an oxygen environment in order to clarify the effect of oxygen on the plume composition. The analysis of charged species in the plume has been carried out as a function of the distance between the target and spectrometer axis. The relative abundance of atomic, monoxide, and heavy ions has been measured and discussed. The velocities of atomic ions in the laser plume have been evaluated. Pb transport from target to substrate has been found to be mainly due to Pb‐containing heavy species, whose abundance is greater in an oxygen environment with respect to a high vacuum condition. Ionic yield and covariance mapping analysis indicate that oxidation of ablated material starts at a distance very close to the plume range. The data show that, close to the deposition distance, a significant fraction of the plume is composed of heavy species containing Pb and oxides. These are appropriate precursors for the stoichiometric growth of ferroelectric films. The oxides are important carriers of oxygen atoms, and the Pb‐containing heavy species preserve the metal stoichiometry with respect to Pb, which is the most volatile element in the composition.

The time‐of‐flight mass spectrometry has been used to investigate the formation of charged species in the laser ablation of YBa2Cu3O7−δ (YBCO) target. Mass spectra were taken both in high vacuum and in oxygen environment for two values of the laser energy density (0.74 and 2.5 J cm−2). The analysis of the charged species in the plume has been carried out as a function of the distance between the target and the spectrometer axis and the relative abundance of Cu, Y, Ba, CuO, YO, and BaO ions has been measured and discussed. In this paper the formation of heavy species and YBCO clusters is also discussed. The plume range has been evaluated as a function of the absorbed energy at a distance from the target plane close to that one at which good quality high Tc superconducting films are obtained, the plume composition has been found to be characterized by the presence of a series of oxide clusters originating from the interaction between the ablated material and the environmental oxygen. This confirms that the interaction between the plume and the environmental oxygen plays an important role both in the formation of heavy charged species and in the capture of the oxygen required to obtain the correct stoichiometric composition of the deposited film.

Near-field optical spectroscopy has been used to investigate photoluminescence features of porous silicon microcavity samples with a subwavelength space resolution. The emission is found to be markedly dependent on the lateral position, with the presence of relatively narrow spectral features peaked at different wavelengths in the range 610–690 nm. Furthermore, the spectrum obtained by summing up spectra taken at different sampling points (relative displacement ∼100 nm) recovers the standard (macroscopic) photoluminescence spectrum of porous silicon, except for the presence of a dip around the resonance wavelength of the microcavity resonator.

Pb(Ti0.48Zr0.52)O3 films produced by pulsed laser ablation deposition have been locally examined for their homogeneity and thickness through a comparative use of Raman and infrared spectroscopy. Raman scattering intensity appears to be an oscillating function of the position of the point under measurements. The observed oscillations were explained by light interference effects in the film and used to obtain the thickness profile and the refractive index dispersion of the film. The intensity distribution in Raman spectra across the film differs from that of the target. This difference is larger at the center than near the edge of the film.