Fabrication of silicon nanoporous humidity sensors and their electrical and spectroscopic characterizations

This thesis is concerned with fabrication of nanometer to micrometer sized porous silicon structures utilized as a relative humidity sensor by electrochemical anodization method, and Raman spectrometry, image processing, SEM, photoluminescence, AFM, current-voltage and capacitance-voltage experimental methods were used to investigate both structural and electrical properties of porous silicon structures formed in sensors. Electrochemical anodization conditions affecting the porous structure have been investigated with regard to the fabrication process steps and its effect on the sensitivity of the relative humidity sensors made from porous silicon material. Nanometer sized structure is analysed by different methods to determine optimized pore diameters for the best sensitive relative humidity sensor; A new analysis method was realised, quantified and reported based on Raman spectroscopy together with the assisting techniques such as SEM, image processing, photoluminescence and AFM in this thesis. This experimental method was then applied to porous silicon samples fabricated in this thesis work and a new application of this experiment was realised. This work shows that using Raman spectroscopy measurements it is possible to determine that the structure contains nanometer-sized porous silicon structures within a sample. It is also possible to state that long-term stability of the sensor in other words its mechanical degradation and relative humidity sensitivity were determined by Raman spectroscopy technique in place of capacitance measuremets. The ability to tailor the porous structure and pore size of the material is investigated, and the parameters effecting the structure and size for a material containing nanometer-sized porous structure are defined and reported.