Effect of the preparation method on the gas sensing properties of nanostructured CoAl2O4

We report the effects of varying the oxygen partial pressure (OPP) on the structural and electronic properties of SiO x/Si heterolayers grown by RF reactive sputtering. The produced samples present silicon poly-crystalline characteristics for low values of OPP. The crystallinity decreases as the OPP increases due to oxygen interdiffusion until the silicon crystal structure becomes amorphous. The results of infrared and Raman spectroscopies show higher deviation from stoichiometry and an increment of structural disorder for samples grown with higher values of OPP. Room temperature photoluminescence (PL) is present in all as-grown samples. The PL spectra show two bands, around 1.87 and 2.16 eV, for all the samples, while a third broad band at lower energy shows up and shifts to the red as OPP increases. Our results indicate that silicon-related room temperature PL emission is correlated with the stoichiometry of the SiO x and to the formation of silicon crystals embedded in a silicon dioxide matrix. " 2009 IOP Publishing Ltd.",,,,,,"10.1088/0268-1242/24/10/105028",,,"http://hdl.handle.net/20.500.12104/41032","http://www.scopus.com/inward/record.url?eid=2-s2.0-70350625073&partnerID=40&md5=9a5e700b2cf44a959912dd1afffd8eeb",,,,,,"10",,"Semiconductor Science and Technology",,,,"24",,"Scopu

Synthesis and characterization of hydroxyapatite nanoparticles and their application in protein adsorption

Hydroxyapatite (HAp) is a bioceramic material used to decrease the operatory time for bone trauma fixing, protein purification, prosthetic covering, and complementing the consolidation and substitution in bone solutions since this material works in favor of the bone neoformation when it is in touch with the physiological tissue. In this work the hydrothermal method, by using a starting solution containing hydrate dipotassium hydrogen phosphate, K 2HPO4�3H2O, and cetyltrimethylammonium bromide, CTAB, dissolved in deionized water was employed to synthesize HAp nanoparticles with sizes between 15 and 60 nm, high policrystallinity and Ca/P and Ca/O ratios close to the theoretical. The synthesized HAp particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS). Pellets with a diameter of 5 mm and weight of 150 mg were used to support the fibrinogen (FGN) and bovine serum albumin (BSA) adsorption (0.15, 0.7, and 1.5 mg/ml) studies. The protein adsorption studies were carried out via atomic force microscopy (AFM). � 2010 Elsevier B.V. All rights reserved

Photoluminescence of as-grown and thermal annealed SiOx/Si- nanocrystals heterolayers grown by reactive rf sputtering

SiOx/Si -nanocrystals (Si NCs) heterolayers were fabricated employing a rf magnetron sputtering system. The synthesis process, through modification of the oxygen partial pressure of the plasma, promotes the synthesis of stoichiometric SiO2 layers and affect the Si NCs layer giving place to SiOx /Si NCs (1.64<x<2) interfaces. All as-grown samples showed strong photoluminescence (PL) bands in the visible and near-infrared regions; transmission electron microscopy measurements confirmed the presence of Si NCs. Thermal annealing at 1100 �C promoted the SiO 2 stoichiometry in the interface and the crystallization of more Si NCs. The results allow us to clearly identify the origin of the PL bands; indicating that the near-infrared emission is related to the nonstoichiometric oxide while the red and green bands are originated in Si NCs. � 2010 American Institute of Physics

Aluminum doped ZnO by reactive sputtering of coaxial Zn and Al metallic targets

Transparent films of aluminum doped zinc oxide were obtained by reactive sputtering employing metallic zinc and aluminum targets. The targets were coaxially superposed in a single magnetron, by using a center hollow aluminum plate. Two different hole radii in the aluminum target were employed trying to modify the aluminum content. Sputtering power was kept constant at 50 W and temperature was set to 300, 400 and 500 °C. Oxygen partial pressure was 20 and 40% in argon. Film transparencies up to 85% were obtained using this method. X-ray diffraction and Raman spectroscopy measurements were performed to monitor the crystalline structure of the films. Sample resistance was determined by current voltage measurements. Zapotitlán Springer Science+Business Media, LLC 2007

Stemming the tide? Assessing the deterrent effects of the immigration reform and control act

Transparent conducting SnO 2:Cd thin films were prepared by RF reactive magnetron co-sputtering on glass slides at a substrate temperature of 500 °C using CdO as cadmium source. The films were deposited under a mixed argon/oxygen atmosphere. The structural, optical and electrical properties were analyzed as a function of the Cd amount in the target. The X-ray diffraction shows that polycrystalline films were grown with both the tetragonal and orthorhombic phases of SnO 2. The obtained films have high transmittance and conductivity. The figure of merit of SnO 2:Cd films are in the order of 10 -3 ? -1, which suggests that these films can be considered as candidates for transparent electrodes. " 2011 Elsevier B.V. All rights reserved.",,,,,,"10.1016/j.apsusc.2011.10.072",,,"http://hdl.handle.net/20.500.12104/44797","http://www.scopus.com/inward/record.url?eid=2-s2.0-84855523682&partnerID=40&md5=2776217c42f70b8ef71efeeda2a8975a",,,,,,"7",,"Applied Surface Science",,"245

Structural, optical and electrical properties of Cd-doped SnO 2 thin films grown by RF reactive magnetron co-sputtering

Transparent conducting SnO 2:Cd thin films were prepared by RF reactive magnetron co-sputtering on glass slides at a substrate temperature of 500 °C using CdO as cadmium source. The films were deposited under a mixed argon/oxygen atmosphere. The structural, optical and electrical properties were analyzed as a function of the Cd amount in the target. The X-ray diffraction shows that polycrystalline films were grown with both the tetragonal and orthorhombic phases of SnO 2. The obtained films have high transmittance and conductivity. The figure of merit of SnO 2:Cd films are in the order of 10 -3 Ω -1, which suggests that these films can be considered as candidates for transparent electrodes. © 2011 Elsevier B.V. All rights reserved

Synthesis of CdS Nanocrystals by Employing the By-Products of the Anaerobic Respiratory Process of Desulfovibrio alaskensis 6SR Bacteria

A novel methodology for the direct synthesis of CdS nanoparticles, using a biological agent that avoids the extracellular processing, and the results of the characterization of CdS nanocrystals are presented. The by-products of the anaerobic respiratory process of Desulfovibrio alaskensis 6SR along with aqueous solutions of Cd salts were successfully employed to produce CdS nanocrystals with mixed cubic and hexagonal phases. Nanocrystal size has a narrow size distribution with little dependence on the Cd concentration. Both the presence of the crystallographic cubic phase and the crystalline order decrease as Cd concentration increases. The band gap values obtained from optical transmission measurements are lower than those of the bulk crystal. Raman spectroscopy characterization agrees with electron transmission microscopy images and X-ray diffraction results indicating that the method promotes the formation of high structural quality nanocrystals when low concentrations of the Cd salt are used