ICMCTF2016 Session FP: Symposium F Poster Session

Cupric oxide (CuO) with a monoclinic struture and cuprous oxide (Cu₂O) with a cubric structure, stable phases of the well-established copper-oxide compounds, exhibit naturally p-type conduction derived from copper vacancies (V_Cu). The band gap energies of CuO and Cu₂O have been reported to be ~1.35 and ~2.1eV, respectively [1]. On the other hand, zinc oxide (ZnO) with a hexagonal wurtzite structure has the band gap energy of 3.37 eV, which is transparent to the visible light. It is also known that ZnO films doped with the group III elements (B, Al, Ga and In) or the VII element (F) exhibit low resistivity n-type conduction. Therefore, much attention has been paid to the fabrication of ZnO/Cu₂O or ZnO/CuO heterojunction solar cells. Recently we have reported the successful growth of the cone-shape ZnO nanorods (NRs)/CuO/ heterojunctions by chemical bath depostion (CBD) [2,3]. In this paper, we will describe a new and simple CBD based technique to prepare Cu₂O films.

The mixed aqueous solution of Cu(NO₃)₂3H₂O and hexamethylenetetramine (HMT) poured into a Pyrex glass beaker was placed into the water bath and stirred by the rotator. The Au/SiO₂/Si wafer with a piece of iron (Fe) plate on its rear was immersed in the mixed aqueous solution. The concentration of the mixed aqueous solution was varied in the range from 0.012 to 0.075 M. The molar ratio of HMT to Cu(NO₃)₂3H₂O in the mixed solutions was kept at 1:1. The growth time was chnaged in the range from 5 to 180 min. The bath temperature was maintained at 88 °C.

No film was formed on the Au/SiO₂/Si substrate wihout the assistance of the Fe plate. The use of the Fe plate led to the formation of the reddish brown films. The films exhibited (110), (111), (200),(220) and (311) peaks of cubic Cu₂O except for the (400) peak of Si and the (111) peak of Au. Regardless of the growth time, the films grown from the aqueous solution of 0.05 M were composed of angular-shaped grains. With the growth time, however, both the average grain size and the film thickness increased continuously. When the growth time increased from 15 to 180 min, the growth rate decreased from 70 to 34 nm/min. The surface morphology was found to be strongly dependent on the concentration of the mixed aqueous solution. Especially, the film grown using the mixed aqueous solution of 0.012 M was composed of rounded particles and nanowires.

<<References>> [1]B. K. Meyer et al., Phys. Status Solidi B 249 (2012) 1487. [2] T. Terasako et al. , Sol. Energ. Mater. Sol. Cells 132 (2015) 74. [3] T. Terasako et al. Thin Solid Films (to be published).

Aluminum-doped zinc oxide films (AZO) were deposited on glass substrates by magnetron sputtering. The effect of power and deposition temperature on wettability and optical properties of AZO films are studied in detail. The increase of RF power from 60W to 180W leads to evolution of (100), (002) and (101) textures of zinc oxide. The XRD results shows increased preferred orientation of (002) plane along c-axis for deposited AZO films and its grain size increases with increase in deposition temperature from 200ºC to 600ºC. The static and dynamic contact angle formed by water and ethylene glycol varies as a function of RF power and deposition temperature. The optical properties like transmission, refractive index and band gap were measured in the wavelength range of 350-800 nm.

NiTi alloys exhibit good properties like shape memory behavior, high corrosion resistant, having the closest elasticity modulus of a human bone, superior biocompatibility properties e.i. However, the surface problems that arise during the use of this alloy limits the usage in the industry and health sector. in recent years, micro-arc oxidation (MAO) method is used to improve the surface properties and increase the usage of these alloys. In this study, the TiO2 coatings were deposited on yhe NiTİ substrates. The surface topography, morphology, crystallographic structure and thickness of the coatings were determined using Scanning Electron Microscopy (SEM), XRD. The hardness was measured using a microhardness tester. Corrosion properties were investigated by using potentiostat test unit in two different media as NaCl solution and simulated body fluid (SBF). The results show that the coated samples have higher corrosion resistance than uncoated samples in the two different media.

Key Words: MAO, Corrosion resistant, NiTi alloy

Bismuth oxide (Bi₂O₃), nitrogen doped bismuth oxide (Bi₂O₃:N) and tantalum doped bismuth oxide (Bi₂O₃:Ta) thin films were deposited by magnetron sputtering technique. The results indicated that it was possible to obtain Bi₂O₃ films in pure cubic delta phase, even though we have introduced other elements in the original crystalline structure. X-ray diffraction, profilometry, scanning electron microscopy, and optical transmission were used to characterize the films. The photocatalytic activity for each one of the Bi₂O₃ films was evaluated testing the degradation of indigo carmine dye (C₁₆H₈N₂Na₂O₈S₂) solution under UV light, and white light. The dye degradation and the kinetic of the reaction were estimated measuring the variation of the dye absorption band as a function of the irradiation time. After calculating and comparing the reaction kinetic constants, it was concluded that using UV light, there is not an appreciable difference of the photocatalytic activity between Bi₂O₃ andBi₂O₃:N films, meanwhile we could notice a negative effect in the photocatalytic performance of Bi₂O₃:Ta films. On the other hand, we observed that when visible light (white light) was used; Bi₂O₃:N films had a better performance than Bi₂O₃ films . These results suggest that doping Bi₂O₃ films might improve the visible-light photocatalytic activity of the material for water treatment applications.

Acknowledgement: The research leading to these results has received funding from the European Community Seven Framework Programme (FP7-NMP-2010-EU-MEXICO) and CONACYT under grant agreements nº 263878 and 125141, respectively. Phocscleen 318977.

In this study an optoelectronic design is reported and characterized. The device is made of p-type MgO solved in sodium silicate binder and n-type GaSe0.5S0.5 heterojunction. It is described by means of X-ray diffraction, optical absorption and reflection in the incident light wavelength range of 190–1100 nm and by means of dark and 406 nm laser excited current (I)–voltage (V) characteristics. The optical reflectance was also measured as a function of angle of incidence of light in the range of 35–801. The structural analysis revealed no change in the existing phases of the device composers. In addition, it was observed that for pure sodium silicate and for a 67% content of MgO solved in sodium silicate binder (33%), the heterojunction exhibits a valence band shift of 0.40 and 0.70 eV, respectively. The painting of MgO improved the light absorbability significantly. On the other hand, the angle-dependent reflectance measurements on the crystal displayed a Brewster condition at 70o The MgO/ GaSe0.5S0.5 heterojunction exhibited no Brewster condition when irradiated from the MgO side. Moreover, for the crystal and the MgO/ GaSe0.5S0.5 heterojunction, the dielectric spectral analysis revealed a pronounced increase in the quality factor of the device. The I–V characteristics of the device revealed typical optoelectronic properties with high photo-response that could amplify the dark current times when irradiated with 5 mW power laser light. The structural, optical, dielectric and electrical features of the MgO/GaSe0.5S0.5 heterojunction nominate it for use in visible light communication technology.