Control parameters on the fabrication of ZnO hollow nanocolumns

[EN] The present work reports on the fabrication of hollow ZnO nanocolumns by a sequential combination of electrochemical deposition, chemical attack and regeneration. Initially, ZnO nanocolumns were deposited in two different substrates, namely Fluor Tin Oxide and Indium Tin Oxide. In a further step, a statistical analysis on the most influencing control parameters in the dissolution stage to produce the hollow ZnO nanowires on the FTO substrates was carried out. The control variables considered were electrolyte concentration, dissolution time and temperature, whereas the output variable was the percentage of the hollow nanocolumns obtained. The statistical analysis consisted of a two-level factorial design of experiments on three variables, therefore involving a series of 8 experiments. An analysis of variance (ANOVA) on the results was also carried out. The results showed that all the control variables were significant, the most important being the dissolution time.This work was supported by the Spanish Government through MCINN Grant MAT2009-14625-C03-03, Generalitat Valenciana programme PROMETEO/2009/063 and European Commission through NanoCIS project FP7-PEOPLE-2010-IRSES (ref. 269279). Technical support given to the authors by the Servei de Microscopia at the Universitat Politecnica de Valencia (Spain) is greatly acknowledged.Cembrero Cil, J.; Busquets Mataix, DJ.; Rayón Encinas, E.; Pascual Guillamón, M.; Pérez Puig, MA.; Marí Soucase, B. (2013). Control parameters on the fabrication of ZnO hollow nanocolumns. Materials Science in Semiconductor Processing. 16:211-216. https://doi.org/10.1016/j.mssp.2012.04.014S2112161

Photoluminescent properties of electrochemically synthetized ZnO nanotubes

ZnO nanotubes were prepared by a sequential combination of electrochemical deposition, chemical attack and regeneration. ZnO nanocolumns were initially electrodeposited on conductive substrates and then converted into nanotubes by a process involving chemical etching and subsequent regrowth. The morphology of these ZnO nanocolumns and derived nanotubes was monitored by Scanning Electron Microscopy and their optical properties was studied by photoluminescence spectroscopy. Photoluminescence were measured as a function of temperature, from 6 to 300 K, for both nanocolumns and nanotubes. In order to study the behaviour of induced intrinsic defect all ZnO films were annealed in air at 400 °C and their photoluminescent properties were also registered before and after annealing. The behaviour of photoluminescence is explained taking into account the contribution of different point defects. A band energy diagram related to intrinsic defects was proposed to describe the behaviour of photoluminescence spectraThis work was supported by Ministerio de Economia y Competitividad (ENE2013-46624-C4-4-R) and Generalitat Valenciana (Prometeus 2014/044).Gracia Jimenez, JM.; Cembrero Cil, J.; Mollar García, MA.; Marí Soucase, B. (2016). Photoluminescent properties of electrochemically synthetized ZnO nanotubes. Materials Characterization. 119:152-158. https://doi.org/10.1016/j.matchar.2016.07.022S15215811

Obtención de columnas de ZnO. Variables a controlar (I)

In the present paper, the electroplating process to obtain columns of zinc oxide (ZnO) on a glass substrate covered with a conductive oxide layer of tin and fluorine (FTO or SnO2; F), has been described. The electrolyte used is a solution of ZnCl2 (5 x 10-3 M) and 0,1 M of KCl in desminerized water. The following parameters have been controlled: current density, time of substrate exposure to the electrolyte and the process temperature. The measured parameter was the average height of the columns evaluated by Atomic Force Microscopy (AFM). In order to investigate the influence of the principal factors and its interactions that have taken place in the electroplating process, a factorial design at two levels (high + and low -) has been used.The results show that the current density and time exposure help the formation of column growth, but the elevate temperature (80 – 90ºC) has a negative influence.<br><br>En el presente trabajo se describe el proceso de electrodeposición utilizado por los autores para la obtención de columnas de óxido de zinc (ZnO) sobre un sustrato de vidrio recubierto de una capa conductora de óxido de estaño y flúor (FTO). Como electrolito se empleó una solución de concentración 5⋅10-3 M de ZnCl2 y 0,1 M de KCl en agua desmineralizada y las variables o factores a controlar fueron la densidad de corriente, el tiempo de exposición del sustrato al electrolito y la temperatura del proceso. La variable respuesta fue la altura promedio de las columnas de ZnO medidas con el microscopio de fuerza atómica (AFM). Para investigar la influencia de los principales factores e interacciones que intervienen en el proceso de crecimiento, se ha utilizado un diseño factorial combinando tres parámetros de crecimiento con dos niveles diferentes (alto + y bajo - ). Esto supone realizar un total de 8 experiencias de parámetros de crecimiento diferentes. Los resultados muestran que la densidad de corriente y el tiempo de exposición favorecen la formación y el crecimiento de las columnas, mientras que la temperatura considerada alta (85 – 90 ºC) influye en sentido negativo

Solution growth of ZnO sub-micro rods enhanced by electric field

Recently the one-dimensional ZnO nanostructures have attracted much attention in gas sensor applications owing to their increased role of the surface. The authors have obtained ZnO rods of sub-micron size using the solution growth method with the growth temperature below 100.C. Investigations indicate that the rods have a well-defined hexagonal morphology and a wurtzite structure. The best uniformity and alignment of the sub-micron crystals was however obtained when electrodeposition from aqueous solution was developed. Sizes of these rods depend on the growth parameters. Moreover electrodeposition leads to a faster growth rate of ZnO sub-micron rods (2 hrs) as compared to the growth from solution (8 hrs). After electrodeposition the rods can be easily reoriented in external electric fields by using substrates with electrodes of appropriate geometry and configuration (dielectrophoretic effect). This enables the preparation of samples which can be used in gas sensor technology