The starting material is a slice of monocrystalline, semiconductor grade silicon which is about 3 inches in diameter and 20 to 40 mils thick; only a very small part 30 of the silicon slice is seen in the FIGURES. The slice is first oxidized in dry Oz or steam at a temperature in the nature of 900??? to 1100??? C. to create a thin layer 31 of silicon oxide of about 1000 A. The oxide layer 31 preven