Young's modulus and hardness of Pd thin films

Abstract Young's modulus E f and hardness H f of Pd thin films were measured by the nano-indentation technique. Pd films were made under various conditions with the film thickness t f varied from 20 to 280 nm and deposition temperature T s from 25 to 360 °C in vacuum. As an independent check, the Young's modulus 〈 E f 〉 of some selected Pd films was measured again by the X-ray diffraction plus stress measurement. The values of E f and 〈 E f 〉 in general agree with each other for the same Pd film. The surface morphology of each film was examined by an atomic force microscope, and the surface roughness parameters, such as S q and S a , were calculated. From X-ray diffraction studies we estimated the grain size D and the ratio I 111 / I 200 , where I 111 and I 200 are the peak amplitudes of the (111) and (200) diffraction lines, of the Pd films. We also find that both E f and H f are dependent on t f . In short, E f increases when 20 nm t f t f = 196 nm, and decreases afterwards, while H f decreases monotonically with increasing t f . The E f data are analyzed based on the structural properties, such as the ratio I 111 / I 200 and the density δ , of each Pd film. The H f data are discussed based on the t f dependence of grain size D . Finally, the conditions required to make a good nano-indentation measurement on a thin-film sample are summarized.