Chemical ionization source, the reagent gas is present in large excess compared to the analyte. Electrons entering the source with energy around 200-500 eV will preferentially ionize the reagent gas. Then, the ion/molecule reactions produces more stable reagent ions and the resultant collisions with other reagent gas molecules will create an ionization plasma. Positive and negative ions of the analyte are formed by reactions with this plasma. The following reactions are possible with methane as the reagent gas. If ammonia is the reagent gas, For isobutane as the reagent gas, Self chemical ionization is possible if the reagent ion is an ionized
Depletion region the bulk semiconductor, then a spontaneous depletion region forms if the gate is electrically shorted to the substrate, in much the same manner as described for the p–n junction above. The principle of charge neutrality says the sum of positive charges must equal the sum of negative charges: where "n" and "p" are the number of free electrons and holes, and formula_28 and formula_29 are the number of ionized donors and acceptors "per unit of length", respectively. In this way, both formula_28 and formula_29 can be viewed as doping spacial densities. If we assume full ionization and that formula_32, then: