Brighton Staff Mpofu

A key challenge facing fabrication of nanomaterials is the ability to precisely control the surface morphology of the nanostructures through exploitation of process parameters. In this study, palladium thin films with carefully controlled surface morphologies are obtained through the careful choice of the reducing agent used during the pre‐plating activation step in the three‐step autocatalytic electroless plating consisting of 1) surface functionalization; 2) surface activation; and 3) deposition of the film onto alumina substrates. It is important to note that the reducing agents that influenced the surface morphology of the palladium thin films are employed in the pre‐plating activation step instead of the widely utilized electroless deposition step. It is revealed in the high‐resolution scanning electron microscope results that the hydrogen reducing agent yields a dense film with 3D spheroidal morphologies with an average cluster size of ≈415 nm while the hydrazine reducing agent produces a very smooth uniform surface morphology consisting of extremely small grains. The obtained results can be exploited in controlling and tailoring the surface‐dependent properties of the palladium thin film for applications in gas sensors, detectors, or palladium‐based membranes.

Understanding the effects of thin film electroless deposition parameters at nanoscale is crucial for complete understanding and control of the thin film deposition process. In this study, we investigated and optimized the effect of PdCl 2 precursor concentration on the nanoscale surface morphology of electroless deposited Pd thin film. The FESEM characterization of plain substrates showed that the dominant features of plain alumina substrates were terraces, steps and bumpy microstructures and the final surface morphologies of the deposited Pd thin film was strongly dependant on the surface morphologies of the substrate. FESEM characterization results of seeding technique displayed a thin film of Pd nanoparticles on the surface of the alumina substrate. The number of times that the seeding process was carried out was optimized at five seeding times using hydrazine as a reducing agent. FESEM characterization revealed that the nanoscale surface morphology of the Pd thin film was strongly dependent on PdCl 2 precursor concentration. Three types of secondary nanoscale surface morphologies formed were nanorods, nanoflakes and flower-like Pd nanostructures at various concentrations. The nanoflake surface density was strongly dependent on PdCl 2 precursor concentration. Results of this research provided a foundation and method to tailor the nanoscale surface morphology to the specific requirement of surface dependent processes or reactions.