Nanocrystallite formation in Pd capped PrH3−δ films

Restricting the palladium cap layer thickness to ≤9 nm on top of 170 nm Pr films during in situ hydrogen loading has been shown to result in nanocrystallite size PrH_3−δ films even though the deposited Pr films are of large crystallite size. The effect is attributed to hydrogen-induced stresses in the PrH_3−δ films, which trigger structural rearrangement. These nanocrystalline films show a blue shift of the transmittance edge with respect to PrH_3−δ films of large crystallite size. The approximate size of the nanocrystallites calculated from the blue shift using an effective mass approximation (EMA) theory is supported by XRD, TEM and AFM measurements.