Characterization of atomic layer deposited semiconducting Co3O4

Abstract

The authors report on the optical and electrical properties of atomic layer deposited (ALD) Co3O4 on Si, SiO2/Si, and Co/Si substrates using Co(Cp)2 and ozone. Within the ALD temperature window of 175 and 275 °C, the growth per cycle (GPC) on Si is approximately 0.050 nm/cycle. GPC is slightly lower on SiO2 (0.043 nm/cycle) and much higher on Co substrates (0.21 nm/cycle) due to rapid ozone oxidation of Co during ALD. Grazing incidence x-ray diffraction (GIXRD) indicates a randomly oriented polycrystalline Co3O4 phase. The refractive index, measured using variable angle spectroscopic ellipsometry, is found to be ∼2.8 within the ALD window. Optical transitions of 0.76, 1.50, and 2.22 eV are found from absorption analysis. Four-point probe measurements indicate resistivity in the range of 4.1–10.9 Ω cm. GIXRD, refractive index, optical transitions, and resistivity are all consistent with p-type semiconducting Co3O4.