Molybdenum Oxides Deposited by Modulated Pulse Power Magnetron Sputtering: Stoichiometry as a Function of Process Parameters

Abstract

Molybdenum oxide films were deposited using modulated pulse power magnetron sputtering (MPPMS) from a molybdenum target in a reactive environment where the flow rate of oxygen was varied from 0 sccm to 2.00 sccm. By varying the amount of reactive oxygen available during deposition, the composition of the films ranged from metallic Mo to fully stoichiometric MoO 3 , when the molybdenum target became poisoned, due to the formation of a dielectric surface oxide coating. Film compositions were verified using high energy resolution x-ray photoelectron spectroscopy. Target poisoning occurred at an oxygen flow rate of 1.25 sccm and reversed when the flow rate decreased to about 1.00 sccm. MoO 3 films deposited via MPPMS had densities of 3.8 g cm À3 , 81% of the density of crystalline a-MoO 3 as determined by x-ray reflectivity (XRR). In addition, XRR and atomic force microscopy data showed sub-nanometer surface roughness values. From spectroscopic ellipsometry, the measured refractive index of the MoO 3 films at 589 nm was 1.97 with extinction coefficient values <0.02 at wavelengths above the measured absorption edge of 506 nm (2.45 eV).

Molybdenum Oxide Thin Films Grown on Flexible ITO-Coated PET Substrates

“…The Mo 5+ and Mo 6+ oxidation states had Mo 3d 5/2 and Mo 3d 3/2 peak positions at 231.17 eV and 234.30 eV, and 232.17 eV and 235.30 eV ( Figure 3 a) and at 231.53 eV and 234.66 eV and 232.60 eV and 235.73 eV ( Figure 3 b), correspondingly. All these values were in agreement with the literature [ 42 , 43 , 44 , 45 , 46 ].…”

“…For the Mo 0 state, the Mo 3d 5/2 and Mo 3d 3/2 positions were found at 227.37 eV and 230.50 eV ( Figure 3a (Figure 3b), correspondingly. All these values were in agreement with the literature [42][43][44][45][46]. Figure 3c shows the core level XPS spectrum for representative thin films deposited at a flow rate ratio of O 2 /Ar of 0.32.…”

Hybrid co-deposition of molybdenum doped niobium pentoxide (NbxMoyOz) thin films

“…The relatively small magnitude of the enthalpy of formation for MoO3 results in a low driving force for compound formation, rendering it easily reducible to the optically absorbing cation Mo 5+ , corresponding to the surface phase Mo2O5 [34][35][36]. The facile reduction of MoO3 to Mo2O5 during reactive magnetron co-sputtering, associated with optical gap and extinction coefficient tailorability, has been reported previously by our research group [17,37]. This work utilizes reactive magnetron co-sputtering to deposit mixed-valent NbxMoyOz films through manipulation of the oxygen content by using the Mo deposition flux as both a getter and an essential component within the films.…”