Jan 20, 2009
Annihilation of conductive paths and single electron trapping in SRO films
Silicon nanoparticles (Si-nps) embedded in a dielectric matrix has become a photonic material with a large variety of promising applications. On the one hand these nanometric-sized silicon particles embedded in a dielectric matrix show a strong and stable luminescence seeming as an excellent alternative for light emitting devices (LED’s) fabrication. On the other hand, Si-nps have also shown light detection properties, especially in the UV region. Our research is focused mainly on these novel properties using Si-nps from annealed silicon rich oxide (SRO) films. Nevertheless, in order to get such functional and novel devices based on Si-nps, a complete understanding of their electrical properties is necessary.
In our recent work published in Nanotechnology, we studied the electrical properties of SRO films containing Si-nps. Current versus Voltage (I–V) and Capacitance versus voltage (C–V) characteristics of these Si-nps were measured using MOS-like structures. High current was observed at low negative and positive voltages, and then at a certain voltage (Vdrop), the current dropped to a low conduction state until a high electric field again activated a high conduction state. C–V measurements demonstrated a capacitance reduction parallel to the current dropping, but without appreciable flat-band voltage (VFB) shift. As known, if charge gets trapped in a SiO2 matrix with embedded Si-nps, it should produce a VFB shifting in the C–V curves. In our experiment, a VFB shift was observed only when the devices were biased just after the current has dropped. These effects were related to the presence and annihilation of conduction paths established among Si-nps and Si-nanoclusters (Si-ncls) within the silica matrix through the formation of neutral defects (E’ centres).
I–V curves measured after the current dropping exhibited a clear staircase behaviour – a quantum phenomenon – due to Coulomb blockade (CB) effects which result of single electron trapping in the Si-nps. Such quantum effects are usually observed at very low temperatures, but in our research we have been able to observe them at room temperature. These effects are another interesting application for Si-nps in order to get single electron devices (SEDs), where the Coulomb blockade (CB) has been considered as the mechanism to ensure the manipulation of a single electron.
About the author
The work was performed in the Instituto de Microelectrónica de Barcelona (IMB-CNM, CSIC) and INAOE. A Morales Sánchez, Ph.D. is currently a Researcher in the Electronics Department of the National Institute of Astrophysics, Optics and Electronics (INAOE) in Puebla, México. He works on the compositional, structural, optical and electrical properties of materials with silicon nanoparticles for applications in optoelectronic devices. J Barreto is a Ph.D. candidate and C Domínguez Horna is a Research Professor. Both are based at the Instituto de Microelectrónica de Barcelona (IMB-CNM, CSIC). M Aceves Mijares is currently a Professor in the Electronics Department of INAOE. J A Luna López is postdoctoral researcher in the Centro de Investigación en Dispositivos Semiconductores (CIDS) of the Benemérita Universidad Autónoma de Puebla (BUAP).