Decoupled flux control for molecular beam epitaxy

摘要

Improvement of the manufacturing capability for the molecular beam epitaxy (MBE) process is demonstrated with respect to the consistent achievement of effusion cell flux stability of 1% of setpoint values. This performance was obtained by decoupling the principal sources of flux variability from each cell temperature control system including: cell shutter opening flux disturbances with implementation of a feedforward compensator that precisely cancels evaporant mass enthalpy transients; electric power frequency-correlation flux disturbances with substitution of heater DC drivers for the standard AC triac drivers; and flux process disorder resulting from coupled temperature controller proportional-integral-derivative (PID) tuning values with identification of decoupled trapezoidal PID tuning values.