The Effect of the Degree of Fluorination on the MOCVD Growth of Cobalt Oxide Thin Films using Co(II) Acetylacetonate Complexes
Christian Stienen, Detlef Rogalla, Oleg Prymak, Georg Bendt
Abstract
Abstract The structurally related cobalt β‐diketonate complexes Co(acac) 2 , Co(acac) 2 ⋅ TMEDA, Co(tfac) 2 ⋅ TMEDA, and Co(hfac) 2 ⋅ TMEDA (acac=2,4‐pentanedionate, tfac=1,1,1‐trifluoro‐2,4‐pentane‐dionate, hfac=1,1,1,5,5,5‐hexafluoro‐2,4‐pentane‐dionate, TMEDA= N , N , N ′, N ′‐tetramethylethylenediamine) were thermochemically (thermogravimetric analysis, differential scanning calorimetry) and spectroscopically (infrared, UV‐VIS and electron resonance spectroscopy) characterised and used as precursor for the MOCVD growth of cobalt monoxide (CoO) thin films. The influence of the degree of fluorination of the cobalt precursors on the morphology (scanning electron microscopy) and phase composition (X‐ray diffraction) of the CoO films is demonstrated. Carbon, nitrogen and fluorine impurities as a result of the thermal decomposition of the 2,4‐pentanedionate and tetraamine ligands in the films were identified by X‐ray photoelectron spectroscopy, time‐of‐flight secondary ion mass spectrometry, Rutherford backscattering spectrometry and nuclear reaction analysis. In addition, the influence of these contaminants on the electrocatalytically activity for the oxygen evolution reaction (OER) in alkaline media of the MOCVD grown CoO films is shown.