Palladium films with nominal thicknesses varying between 0.5 and 40 nm have been grown by electron beam evaporation on polished MgO(OO1) wafers, kept at substrate temperatures, T_s, of 100, 300 and 600 °C. Microstructure, strain and orientation of the Pd films were studied using a combination of x-ray diffraction (XRD) and transmission electron microscopy (TEM).

Two types of TEM samples were prepared: MgO substrates chemically thinned to electron transparency prior to growth, using phosphoric acid (H₃P0₄), and carbon lift-off samples, where a thin conductive amorphous carbon coating containing the palladium particles, was stripped off the MgO wafer substrates and collected on microscope grids. The lift-off samples proved to be the most suited ones for nucleation and growth studies.

The method of grazing incidence XRD (GIXRD) using a standard laboratory x-ray source was explored in the case of very thin films. By GIXRD, epitaxial Pd was detected for films with a nominal thickness 0.5 nm for films grown at 600 °C, ≥ 1 nm for films grown at 300 °C and ≥ 2.5 nm for films grown at 100 °C. In a few cases, also four 111-oriented Pd domains rotated 90 degrees with respect to each other were detected using GIXRD.

The growth morphology, observed in TEM, showed nucleation and initial three­ dimensional particle growth, for all T_s values. The Pd particles started to coalesce at a nominal film thickness ≤ 1 nm. For T_s = 300 and 600 °C, the coalescence was liquid-like, and secondary nucleation was observed from nominal film thicknesses of 2.5 nm. Increasing growth temperature resulted in a decreased substrate coverage. Continuous film formation was obtained at thickness 10 nm and 20 nm for T_s = 100 and 300 °C, respectively.

The average Pd particle sizes, calculated from the GIXRD 2θ peak broadening, were comparable to the particle sizes seen in TEM. For T_s = 600 °C, the lateral Pd d₀₂₀ plane distance was expanded ~0.8 % for nominal film thicknesses < 2.5 nm, whereas thicker films showed bulk Pd lattice spacing. T_s = 300 °C, an average lattice expansion for nominal thicknesses ≤ 2.5 nm, and for T_s = 100 °C for film thicknesses ≤ 10 nm