An IR Study on the Stability of Y(DPM)3, Ba(DPM)2 and Cu(CPM)2 for UV Irradiation

Ultraviolet-irradiation effects at 3∼8 eV (400∼150 nm) have been studied for Y(DPM)3, Ba(DPM)2 and Cu (DPM)2 (DPM: dipivaloylmethane) metalorganic chelates which are commonly used for YBa2Cu3O7-x superconducting-film formation by metalorganic chemical vapor deposition (MOCVD). An IR spectral analysis shows that the chelate ring of Ba(DPM)2 is most sensitively affected when irradiated in a 200∼300 nm region through a π-π* transition of the ligand orbital, and Y(DPM)3 shows a similar, but much more modest reaction. On the contrary, Cu(DPM)2 is very stable for all the light sources used. Such a difference of stability is deeply related to the metal-oxygen bonding nature of these chelates.