Optics: measuring and testing – By shade or color – With color transmitting filter
Patent
1992-09-04
1994-11-29
McGraw, Vincent P.
Optics: measuring and testing
By shade or color
With color transmitting filter
324 715, 356237, G01N 2125, G01N 2189
Patent
active
053694953
ABSTRACT:
Contamination of a fluid medium is measured using a thin-wafer sensor having a front surface and a back surface. The thin-wafer sensor is made of relatively pure p-type silicon and has a thickness less than the bulk diffusion length of the material. The back surface is placed in physical contact with the fluid being monitored either by building the sensor into a fluid testing chamber in line with the system using the fluid, or by immersing an encapsulated version of the sensor into the fluid medium. A photovoltaic generating and sensing system generates and measures e.g., the surface photovoltage (SPV), at the front surface. A series of SPVs are measured and used to derive the minority carrier diffusion length L of the sensor. The carrier diffusion length value is used to calculate the surface recombination velocity at the back surface. The surface recombination velocity value is used to determine the surface concentration of contaminants at the back surface, which may be used to calculate the concentration of contaminants in the fluid medium.
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Hantis K. P.
McGraw Vincent P.
University of South Florida
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