Effect of sputtering pressure on pulsed-DC sputtered iridium oxide films

This paper reports the influence of the sputtering pressure, ranging from 5 to 50 mTorr using a mixture of Ar and O2 (1:1), on the properties of the IrOx films deposited by pulsed-DC reactive sputtering. The sputtered IrOx films were characterized by surface analysis methods (scanning electron microscopy, atomic force microscopy, energy dispersive X-ray spectrometry, X-ray diffraction), four-point probe method, and electrochemical techniques (cyclic voltammetry and electrochemical impedance spectroscopy). The optimal sputtering pressure was identified to be 5 mTorr at which the activated IrOx film showed highest charge storage capacity of 28.3 mC/cm2, which was almost three times higher than that of samples deposited at 50 mTorr. The IrOx films deposited at low pressure showed excellent mechanical electrical and electrochemical characteristics and hence can be recommended as an ideal stimulation electrode material for neuroprosthetic applications.