Figure . An illustration of one ALD cycle for AlN from TMA and NH3 showing gaseous TMA reacting with the -NH2 groups on the surface, depositing a sub monolayer of Al atoms terminated by -CH3 groups followed by NH3 which reacts with the -CH3 groups converting the surface layer into AlN and recuperating an -NH2 terminated surface. Gas phase CH4 is released in both the TMA and the NH3 pulses (with more CH4 signals detected during the second half cycle, rendering the TMA adsorption and its subsequent reaction with NH2 groups in the first half cycle the rate-determining steps) as a reaction byproduct that is removed from the reactor by pumping and/or purging before the next ALD half-cycle.