Polysilicon has great benefit in application of pH sensor due to the unique properties and easiness to use top-down approach. In this paper, we present fabrication and characterization of undoped polysilicon nanowire (NW) for pH sensor application. The fabrication processes steps involve were photolithography, etching, deposition and oxidation. 3-aminopropyltriethoxysilane or APTES were used to enhance the sensitivity of polysilicon layer as well as able to provide surface modification by undergoing protonation and deprotonation process. Surface analysis using SEM were used for surface morphology analysis. Different types of pH solution provide different resistivity and conductivity towards polysilicon surface. In addition, voltage, current, conductance against pH level are characterized and compared. Alkaline solution has the higher current as compared to acidic. This was due to the polysilicon layer contains more holes which are easily being attracted bySiO¯ to the surface and hence, forming a strong channel from source to drain. Results obtain reveal a linearity of pH measurement with a corresponding sensitivity of 4.65 nS/pH.
The Young’s two-slits experiment is arguably one of the most famous and beautiful experiments in physics. In introductory physics labs the experiment is almost exclusively carried out using a laser, and it is introduced this way in some introductory physics textbooks. In the case of laser illumination, light passes directly through the slits and spreads out by diffraction so that interference fringes can be viewed on a distant screen. Most students, in our experience, are unaware that the experiment can be carried out in any other way. But the laser approach depends on the remarkable light emitted by the laser: it is spatially coherent, meaning that the phase relationship between the light emitted from the slits is constant, and it is extremely bright, meaning that real interference fringes can be seen on the screen. When carried out with classical, incoherent light, a quasi-monochromatic source such a sodium lamp must first be rendered spatially coherent by focusing the light through a pinhole and then using this light to illuminate the two slits. Fringe patterns will certainly be formed, but they need to be observed by either viewing with an eyepiece or allowing them to fall directly on the photosensor of a camera. It is implied in other physics texts that the fringe pattern can be cast onto a screen and viewed, but this is not feasible because the fringes are just not bright enough. Here we report an arrangement where an extended incoherent source can be used and fringes made bright enough to be observed on a screen.
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