Prorerties of Nanostructured Porous Semiconductors Studied Via Noise Spectroscopy
- PDF / 411,971 Bytes
- 11 Pages / 595 x 842 pts (A4) Page_size
- 21 Downloads / 187 Views
PRORERTIES OF NANOSTRUCTURED POROUS SEMICONDUCTORS STUDIED VIA NOISE SPECTROSCOPY Vitali Parkhutik Department of Materials Science, Technical University of Valencia, Spain . Tel: 34-96-652-84-29, E-mail [email protected]
Summary Formation of porous layers via localized corrosion of semiconductors is a reliable method to produce nano-structured semiconducting materials. The formation process is assisted by strong fluctuations (noise) of the anodic potential or current applied to the corroding material. Electrical and optical characteristics of nanoparticles are also quit noisy. The noise is a result of heterogeneity of the electrochemical reactions involved into the formation of pores and pits, transient phenomena in the formed porous layers, their exchange by energy with environment, etc. Therefore, analyzing the noise would be useful to understand the nature of the formation processes and properties of nanoparticles. Here we present the results of studying the formation of porous silicon and electrical properties of the formed porous layers with the help of so-called Flicker-Noise Spectroscopy (FNS), method allowing to quantify and analyze the information contained in noisy signals. The method is different from existing approaches in that it allows not only to represent the noisy signals but estract physically meaning information from them. It is shown that using the FNS approach one can extract useful information on the kinetics of the electrochemical and electrical processes.
1. Fundamentals of the electrical noise in complex physical and chemical systems 1.1. Noise as an indicator of the processes assisting the corrosion of materials and properties of the porous films Electrochemical etching of silicon in acid and alkaline solutions has found wide applications in Si micromachining, wafer cleaning prior fabrication of integrated circuits, fabrication of porous silicon layers which are further used in chemical and biological sensors [1,2]. Other semiconductors have also been etched to produce porous layers with non-linear optical and electrical characteristics determined by quantum-confinement effects in remnant crystalline clusters of semiconducting material incorporated into the pore walls [2]. Electrical signals registered during etching of silicon are very noisy similar to any electrochemical corrosion reaction [3]. The noise is due to heterogeneous nature of the corrosion reaction where many factors are contributing such as locally enhanced electric field, gas bubbles evolution, generation of defects of the crystalline structure, etc. The intensity of noise is the function of electrolyte composition and temperature, applied electric current (or potential), etc. The noise is a kind of information produced by the corroding material and it might be very important source of knowledge about the nature of the corrosion processes. Generally, any time series V(t) acquired from complex physical, chemical, biological or sociological system would contain a pronounced stochastic component (noise). The same will be
Data Loading...
