Porous Silicon for Chemical Sensing

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Rihab Ahmed M. A., Nimir
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The aim of this thesis is to synthesize porous silicon (P-Si) with the electrochemical small size sensors for physiological analyte, i.e. a human body, health and dealing with drug treatment. By functionalizing the porous silicon (P-Si) surface sensitive, selective cheap sensors can easily be engineered. The method adopted in this thesis was the electrochemical etching method. The experiment set up have been built which composed of an electrochemical cell and used current-voltage source to provide the electrical signal of enhancing the etching. Three different types of substrates were used. These were high and low doping: P-type Si (001), having a resistivity of .001T86;cm/P-type Si (001) having a resistivity of .0.01T86;cm/n-type Si (001) with a resistivity of 0.001T86;cm. The chemicals have been obtained as follows: The HF(48%) , ethanol(98%) and the de-ionized water. The container which accommodates the mixture (electrolyte) was Teflon. The sample (P-type or n- type) Si was partially immersed in the electrolyte solution and the voltage-current were applied. Of the synthesized porous silicon in this thesis was performed by employing the scanning electron microscopy (SEM). It is known as the most crucial instrument in basic and advanced science and technology. The parameters which were varied were the etching current, applied voltage, the composition of the aqueous etching solution (contains three different solutions), the time of the etching process and finally the substrate used which was n- or P-type Si with the possibility of high and low doping. In this thesis, the fabricated porous silicon structures contain a variety of different structures. For examples: *The sample P-type Si(low resistivity) ,the SEM images were: 1. P-Si branched particles 2. A collection of micro P-Si wires 3. A network of P-Si lines *The sample n-types (low resistivity), the SEM image was: A star like P-Si particles.
Porous Silicon for Chemical Sensing