Enabling High‐Temperature Atomic‐Scale Investigations with Combinatorial Processing Platforms Using Improved Thermal SiO2 Diffusion and Reaction Barriers

Interactions at high temperatures between thin films and the Si substrate limit materials discovery using combinatorial processing platforms (CPPs). To overcome this, a diffusion and reaction barrier, SiO2, by thermal oxidation of Si tips is developed. The application of this diffusion barrier in CPPs for atomic‐scale investigations of new materials in atom probe tomography is reported. Thermal SiO2 layers (20 and 50 nm thick) are examined as barriers to separate coatings from Si tips. Pt is chosen as it easily forms silicides. CPPs are sequentially annealed in vacuum at 400 °C for 10 h, 600 °C for 2 h, and 800 °C for 2 h. The thermal SiO2 diffusion barrier remains stable and prevents intermixing at least up to 800 °C. Moreover, it provides improved film adhesion as dewetting of Pt on the oxide surface occurred at 800 °C instead of 600 °C without a thermal diffusion barrier. A comprehensive structural and chemical analysis of the Pt film, the thermal SiO2 layer, and their interfaces is performed using scanning and transmission electron microscopy, and atom probe tomography. As a result, the thermal SiO2 forms a stable barrier, even at the lowest thickness of 20 nm, avoiding the formation of Pt silicides, even at 800 °C. A thermal SiO2 diffusion barrier on a pre‐sharpened Si tip array is developed for the combinatorial processing platform approach, allowing direct atom probe tomography experiments without additional sample preparation. Two distinct oxide thicknesses covered by a sputtered Pt film are tested. Sequential annealing procedures in vacuum up to 800 °C and TEM/APT investigations are conducted and the thermal SiO2 effectively inhibited intermixing and interdiffusion between Pt and Si, preventing silicide formation, even at elevated temperatures.