| Summary: | 碩士 === 南台科技大學 === 光電工程系 === 98 === Abstract
Owing to its high sensitivity of electric, chemical and physical properties to outer environments, porous silicon (PS) is also an important material for development of chemical sensors. And in the part of multi-layered porous-Si (MLPS) structures such as Bragg reflectors and porous silicon optical micro-cavity due to it have the special optical properties. So the porous silicon (PS) becomes a major way and has been applied in design and fabrication a new type of optically chemical sensors.
In this work, we demonstrated the etching current density was periodically switched between large and little during the anodic process on low resistivity of silicon substrate, which for fabrication multi-layered porous-Si (MLPS) structures on Bragg reflectors and design the particular MLPS structure on porous silicon optical micro-cavity. Then take Measure the Reflectivity and Photo-response spectra of the two structures that responding to different chemistry of organic compounds (such as methanol, acetone, ethanol and dimethyl enter).
Experimental results showed that the better periodical variation of MLPS Bragg reflectors had the lower reflectivity and higher photo-responsivity of absorbed chemistry of organic compounds. The reflectivity of devices decreased while their photo-responsivity peak increased, when responding to chemical species with higher refractive index. Therefore, make use of the cross-reference for special optical sensing properties of such reflectivity, photo-responsivity, and refractive index to promote the sensitivity on sensing devices for chemical species.
Porous silicon optical micro-cavity has quite special optical properties on the reflectivity spectra for organic compounds. It showed the variation in single peak value of reflectivity spectra. Moreover, the important point that we discovered the peak displacement changed on the reflectivity spectra was linear relationship for absorbed the different refractive index of chemistry of organic compounds. The peak value changed on reflectivity spectra of orange and red (during 600 nm~750 nm) in visible light wavelength. But use of the special optical properties of such structures in measurement and analysis has the very high sensitivity for different chemical species. And it has the quite high potential and application value about measurement and analysis in chemistry.
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