Chemically Amplified Dehydration of Thin Oxide Films

The hydrous material Al(PO4)(0.6)O-0.6-zH(2)O (AlPO) is studied in thin-film form to determine whether bulk diffusion or near-surface densification controls thermal dehydration. From X-ray reflectivity measurements, a dense surface crust is found to form on heating AlPO films. Capacitance-voltage measurements reveal the presence of mobile protons associated with trapped -OH and H2O in the films. Deposition of a thin solutionprocessed HfO2 top coat on the AlPO film lowers the dehydration temperature by 250 degrees C. Characterization of the AlPO/HfO2 interface by medium energy ion scattering and transmission electron microscopy reveals little interdiffusion between the layers. The top coat affects densification of the near-surface region of the AlPO film, thereby amplifying water loss at low temperatures.