Cadmium chalcogenides nanowires obtained in ion track templates

Metal chalcogenide semiconductor nanowires are of particular interest for several reasons. First, II-VI semiconductors present a broad range of band gaps (from 0.15 eV in HgTe to 3.68 eV in ZnS). Second, most of them have direct energy gaps making them particularly important for electro-luminescence devices. Third, these kinds of semiconductors can be electrochemically deposited from aqueous solutions. The deposition process on macroscopic electrodes has been extensively studied in the last decades, driven by the large amount of applications that II-VI and IV-VI semiconductor devices have nowadays. Examples are the use of CdTe in a broad range of optoelectronic devices such as infrared, X-ray, and gamma ray detectors, the investigations of CdTe/CdS systems as a good alternative to silicon solar cells, and the use of ZnSe to prepare light emitting or laser diodes in the blue band. Moreover, these semiconductor compounds form solid solutions over a considerable range of compositions, and even better control over various properties and structural changes may be achieved in ternary semiconductors. This paper presents some of our results in preparing CdS and CdTe nanowires by the template method. We used ion track-etched nanoporous polycarbonate membranes which were filled by electrochemical deposition, a method extensively used for preparing metallic nanostructures [1,2]. The bath used for deposition of CdS nanowires contains 200 mM CdCl2⋅2H2O and 10 mM Na2S2O3⋅5H2O at pH 2-3, the following reaction taking place at the working electrode: Cd+S2O3 +2e→CdS+SO3 Figure 1 displays a scanning electron microscopy (SEM) image of a CdS nanowire array with rectangular cross-section which was deposited at -750 mV at 90 °C.