The measurement and control of ionization of the depositing flux during thin film growth

Optical emission spectroscopy (OES) has been used for detailed characterization of the magnetron discharge during magnetron sputter deposition. In particular, we have studied the ionization of the sputtered flux as it travels from the target, and have observed the influence of the deposition parameters upon the ionization level. The addition of a secondary, radio frequency plasma between target and substrate during film growth leads to a significant increase in ionization of the depositing flux at the substrate. Using this technique we have assessed the influence of ionization of the depositing flux upon film growth through the measurement of film structure and properties, observing large variations as a function of total ion flux, ion energy and ionization fraction (the proportion of the depositing flux which is ionized). This illustrates the increase in control of film growth which is possible through ionization of the depositing flux, and leads to further understanding of the mechanisms involved. We have also used OES for the study of the laser plume during pulsed laser deposition of complex oxides, and have illustrated the formation of molecular oxide species as ablated material travels from target to substrate. (C) 2002 Elsevier Science Ltd. All rights reserved.