Rare earths (Europium, cerium)-doped CdS nanofilms are prepared using the growth technique chemical bath deposition (CBD) at the reservoir temperature of 70±2°C varying the synthesis time in a wide range. For the rare earths doped CdS nanofilms the synthesis time was ranged from 80 to 135 min. The rare earths molar concentration was in the range 0.0≤x≤3.47, which was determined by energy dispersive X-ray spectroscopy (EDS). The X-ray diffraction (XRD) analysis reveals that CdS nanofilms showed the zinc blende (ZB) crystalline phase. The nanocrystal size was ranged from 2.67 to 2.35 nm for the CdS and 1.84-2.33 nm for rare earth-doped CdS that were determined by the Debye-Scherrer equation from ZB (111) direction and it was confirmed by transmission electron microscopy (TEM). The doped CdS exhibits a direct band gap that diminishes with the increase of the synthesis time, from 2.50 to 2.42 eV, which was obtained by transmittance. The room-temperature photoluminescence of CdS presents the band-to-band transition at 431 nm, which is associated with quantum confinement because the grain size is less than its Bohr exciton radius and a dominant band at 523 nm, which is called the optical signature of interstitial oxygen. Eu3+-doped CdS photoluminescence shows the dominant radiative peak at 576 nm that is associated to the intra-4f radiative transition of Eu3+ ions, which corresponds to the magnetic dipole transition, (5D0→7F1). For the Ce3+-doped CdS the dominant radiative transitions are clearly redshifted. Additionally, other radiative peaks associated at structural defects are observed. The passivation of the CdS by rare earths was approximately of two orders of magnitude obtaining better results with cerium.

This work presents the characterization of ZnTe nanolayers grown on GaAs and GaSb (100) substrates by the Atomic Layer Deposition (ALD) regime. Under certain conditions, the alternating exposition of a substrate surface to the element vapours makes possible the growth of atomic layers in a reactor where the atmosphere is high-purity hydrogen. ZnTe was grown simultaneously on GaAs and GaSb at the same run, allowing, a comparison between the effects produced by the superficial processes due to the different used substrates, thereby eliminating possible unintended changes of growth parameters. Nanolayers on GaSb maintained their shiny appearance even at temperatures near 420°C. It was found that for exposure times below 2.5 s there was not growth on GaAs, while for GaSb the shortest time was 1.5 s at 385°C. By HRXRD the peak corresponding to (004) diffraction plane of ZnTe was identified and investigated, the FWHM resulted very wide (600-800 arcsec) indicating a highly distorted lattice mainly due to mosaicity. Raman scattering shows the peak corresponding to LO-ZnTe, which is weak and slightly shifted in comparison with the reported for the bulk ZnTe at 210 cm-1. Additionally, the measurements suggest that the crystalline quality have a dependence with the growth temperature.

In this work reports results related to growth and characterization of AlxGa1-xAs epilayers, which were grown in a metallic-arsenic-based-MOCVD system. The gallium and aluminium used precursors were trimethylgallium (TMGa) and trimethylaluminium (TMAl), respectively. By photoluminescence measurements observed, that only samples grown at temperatures above 800°C display photoluminescence. Hall measurements on the samples showed highly compensated material. Samples grown at temperatures lower than 750°C were highly resistive. Independently of the V/III ratio; the samples grown at higher temperatures were n-type. As the temperature is increased the layer compensation decreases. The AlxGa1-xAs epilayers resulted n-type with an electron concentration of 1×1017 cm-3 and a corresponding carrier mobility of ~2200 cm2/V×s. Raman spectra show vibrational bands associated to TO-GaAs-like (262 cm−1), LO-GaAs-like (275 cm-1), TO-AlAs-like (369 cm-1) and LO-AlAs-like (377 cm-1). The Raman spectra show the epilayers become more defective as the growth temperature is increased. The chemical composition was studied by SIMS exhibit the presence of silicon, carbon and oxygen as main residual impurities. The silicon concentration of ~1.0×1017 cm-3 is very close to the carrier concentration determined by the van der Pauw measurements. The residual oxygen detected on the samples maybe responsible of the weak photoluminescence signal of the AlxGa1-xAs layers.