Mar 30, 2010
Multi-segment electrodeposited nanowires sense light
Electrodeposition can be a simple and successful tool for fabricating complex, functional nanostructures as highlighted by a group of researchers from Romania and Germany. The team has developed a template-based approach for preparing nanowire CdTe homojunction photodiodes and has recently published its results in the journal Nanotechnology.
The scientists start with polycarbonate foils (30 µm thick), which are irradiated with swift heavy ions (specific energy=11.4 MeV/nucleon) at GSI Darmstadt's UNILAC facility. The ion tracks are then etched to obtain cylindrical parallel pores. These nanoporous ion track membranes can now be used as templates for electrodepositing the diode nanowires.
When depositing CdTe, due to the characteristics of the electrochemical process, the operator is able to tune the composition just by choosing the electrode potential. Thus, the composition can be either stoichiometric on a certain potential range or present an excess of Cd or Te. A slight excess of Cd will lead to n-type conduction while a slight excess of Te will lead to p-type conduction.
By applying a predefined sequence of potentials, the researchers are able to deposit multisegment nanowires with the structure Cd – CdTe p – CdTe n –Cd. The electrical response of the material shows that these multi-segment nanowires exhibit rectifying IV characteristics and are sensitive to light.
A major advantage of the technique is that it can lead to ultra-high densities of photosensing devices in excess of 109 per centimetre square. The devices are functional as grown, no further manipulation being required.
Full details can be found in the journal Nanotechnology.
About the author
The preparation of the nanosized devices was performed at the National Institute for Materials Physics (NIMP), Romania, while the characterization was performed in the Faculty of Physics, Bucharest University, Romania. Elena Matei is a PhD student working at NIMP, in the Laboratory of Multifunctional Materials and Structures since 2006. Dr Lucian Ion is a reader in condensed matter physics and Prof. Stefan Antohe is Pro-dean of the Faculty of Physics. Prof. Reinhard Neumann is head of the Materials Research Department at GSI Darmstadt, Germany. Dr Ionut Enculescu is head of the Laboratory of Multifunctional Materials and Structures at NIMP.