F. Solis-Pomar

Growth of vertically aligned ZnO nanorods using textured ZnO films

A hydrothermal method to grow vertical-aligned ZnO nanorod arrays on ZnO films obtained by atomic layer deposition (ALD) is presented. The growth of ZnO nanorods is studied as function of the crystallographic orientation of the ZnO films deposited on silicon (100) substrates. Different thicknesses of ZnO films around 40 to 180 nm were obtained and characterized before carrying out the growth process by hydrothermal methods. A textured ZnO layer with preferential direction in the normal c-axes is formed on substrates by the decomposition of diethylzinc to provide nucleation sites for vertical nanorod growth. Crystallographic orientation of the ZnO nanorods and ZnO-ALD films was determined by X-ray diffraction analysis. Composition, morphologies, length, size, and diameter of the nanorods were studied using a scanning electron microscope and energy dispersed x-ray spectroscopy analyses. In this work, it is demonstrated that crystallinity of the ZnO-ALD films plays an important role in the vertical-aligned ZnO nanorod growth. The nanorod arrays synthesized in solution had a diameter, length, density, and orientation desirable for a potential application as photosensitive materials in the manufacture of semiconductor-polymer solar cells.PACS61.46.Hk, Nanocrystals; 61.46.Km, Structure of nanowires and nanorods; 81.07.Gf, Nanowires; 81.15.Gh, Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Growth of ZnO Nanowires Using Au/Pd Nanoparticles as Catalyst

. Zinc Oxide nanowires (ZnO-NWs) were grown by vapor-liquid-solid (VLS) through chemical vapor deposition (CVD) with Au/Pd nanoparticles (Au/Pd-NPs) as catalyst. (Au/Pd)-NPs of 5 nm were synthesized by inert gas condensation technique (IGC), deposited on silicon substrates and characterized by atomic force microscopy (AFM). The substrate with the catalytic seeds was introduced in the reaction system where the ZnO-NWs were grown under different conditions such as: system pressure, position of the substrates with respect to the precursor material source, growth time and temperature. The nanostructures obtained were characterized by scanning electron microscopy (SEM), energy dispersed x-ray spectroscopy (EDX), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The growth parameters and the effect of catalyst nanoparticles coalescence on the ZnO-NWs dimensions is also discussed in this work.

Optical and structural characterization of oleic acid-stabilized CdTe nanocrystals for solution thin film processing

Summary This work presents results of the optical and structural characterization of oleic acid-stabilized cadmium telluride nanocrystals (CdTe-NC) synthesized by an organometallic route. After being cleaned, the CdTe-NC were dispersed in toluene to obtain an ink-like dispersion, which was drop-cast on glass substrate to deposit a thin film. The CdTe-NC colloidal dispersion as well as the CdTe drop-cast thin films were characterized with regard to the optical and structural properties. TEM analysis indicates that the CdTe-NC have a nearly spherical shape (3.5 nm as mean size). Electron diffraction and XRD diffraction analyses indicated the bulk-CdTe face-centered cubic structure for CdTe-NC. An additional diffraction line corresponding to the octahedral Cd3P2 was also detected as a secondary phase, which probably originates by reacting free cadmium ions with trioctylphosphine (the tellurium reducing agent). The Raman spectrum exhibits two broad bands centered at 141.6 and 162.3 cm−1, which could be associated to the TO and LO modes of cubic CdTe nanocrystals, respectively. Additional peaks located in the 222 to 324 cm−1 range, agree fairly well with the wavenumbers reported for TO modes of octahedral Cd3P2.

Pb(core)/ZnO(shell) nanowires obtained by microwave-assisted method

In this study, Pb-filled ZnO nanowires [Pb(core)/ZnO(shell)] were synthesized by a simple and novel one-step vapor transport and condensation method by microwave-assisted decomposition of zinc ferrite. The synthesis was performed using a conventional oven at 1000 W and 5 min of treatment. After synthesis, a spongy white cotton-like material was obtained in the condensation zone of the reaction system. HRTEM analysis revealed that product consists of a Pb-(core) with (fcc) cubic structure that preferentially grows in the [111] direction and a hexagonal wurtzite ZnO-(Shell) that grows in the [001] direction. Nanowire length was more than 5 μm and a statistical analysis determined that the shell and core diameters were 21.00 ± 3.00 and 4.00 ± 1.00 nm, respectively. Experimental, structural details, and synthesis mechanism are discussed in this study.

Synthesis of fe nanoparticles functionalized with oleic acid synthesized by inert gas condensation

In this work, we study the synthesis of monodispersed Fe nanoparticles (Fe-NPs) in situ functionalized with oleic acid. The nanoparticles were self-assembled by inert gas condensation (IGC) technique by using magnetron-sputtering process. Structural characterization of Fe-NPs was performed by transmission electron microscopy (TEM). Particle size control was carried out through the following parameters: (i) condensation zone length, (ii) magnetron power, and (iii) gas flow (Ar and He). Typically the nanoparticles generated by IGC showed diameters which ranged from ∼0.7 to 20 nm. Mass spectroscopy of Fe-NPs in the deposition system allowed the study of in situ nanoparticle formation, through a quadrupole mass filter (QMF) that one can use together with a mass filter. When the deposition system works without quadrupole mass filter, the particle diameter distribution is around +/-20%. When the quadrupole is in line, then the distribution can be reduced to around +/-2%.

Design and Simulation of an Antenna-Coupled Microbolometer at 30 THz

We propose a model of antenna-coupled microbolometer to be included in an array for receiving and detecting long wave infrared (LWIR) electromagnetic radiation. The antenna is joined to microstrip bandpass filters thus forming a single metal structure to define the operation frequency band. The antenna and microstrip filters are modeled in aluminum thin film. The microbolometer is modeled with superconducting niobium, all together on a silicon nitride membrane. The squared pixel structure is designed on a support frame of 20 m in size. Simulation results for this antenna exhibit a frequency range of operation from 27 to 35 THz and is configured for two arrays, one of and the other one of elements. The device has been simulated by means of the commercial electromagnetic software (HFSS), which is based on the finite elements method. The predicted values for the figures of merit of this microbolometer are as follows: ns, V/W, and = , respectively.

A simple method for the deposition of nanostructured tellurium synthesized in ammonia solution

In this work, we report a highly adherent, and uniform deposition of nanostructured tellurium. The deposition of the nanostructured tellurium was realized by the dripping of a modified solution of NaHTe based on the dissolution of NaBH4 and tellurium powder in an aqueous solution of NH4OH. This method allowed the relatively simple manipulation of tellurium nanostructures under laboratory ambient, without requiring the use of organic stabilizers. Transmission electron microscopy (TEM) was realized on a powder sample obtained by the reaction between H2Te and aqueous solution of NH4OH. TEM analysis indicated that tellurium nanorods and Y-type nanostructures are grown from tellurium nanoparticles, such as in a hydrothermal system. Then, the nanoparticles serve as seeds for the growth of more extended tellurium nanostructures. Electron diffraction and X-ray diffraction analysis showed that depositions have the hexagonal structure of tellurium highly oriented on (101) direction.