A certain silicon wafer has been uniformly doped with boron to a level of 1.2x1015 atoms/cm3 . The wafer is ion implanted with relatively low energy arsenic atoms at an energy of 100 keV and a dose of 1013 atoms/cm2 . The wafer is then annealed for 5 hours at 1100 C. (a) Is the uppermost portion of the wafer n-type or p-type? Justify your