As a part of producing MOSFET transistors, a p-type silicon (Si) wafer containing boron (B) dopants at a concentration of 1x1019 atoms/cm3 is being processed to create a PN junction by doping the wafer with phosphorous (P) atoms using a P-producing gas. Assume that the wafer does not contain P prior to the diffusion process. The solubility of P in Si at 1000°C is 1x1020 atoms/cm3. It is determined that the PN junction depth of 1 um was produced after 60 minutes at 1000°C. The activation energy for estimating the diffusion coefficient of P in Si is 2.5x105 J/mole. Based on this result, estimate the pre-exponential constant for the diffusion coefficient of P in Si at 1000°C in cm2/s.

An  atom  (ours, not carroll's) consists of a positively charged  nucleus, surrounded by one or more negatively charged particles called  electrons. the positive charges equal the negative charges, so the atom has no overall charge; it is electrically neutral. most of an atom's mass is in its nucleus; the mass of an electron is only 1/1836 the mass of the lightest nucleus, that of hydrogen. although the nucleus is heavy, it is quite small compared with the overall size of an atom. the radius of a typical atom is around 0.1 to 0.25 nanometres (nm), whereas the radius of a nucleus is about 10-6  nm.  *  if an atom were enlarged to the size of the earth, its nucleus would be only 200 feet in diameter and could easily rest inside a small football stadium.read more on -

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