Research Interests
Transition Metal Silicides
Due to their low resistivity, transition metal silicides play a crucial role as contact layers and diffusion barriers between semiconductor devices and interconnects in integrated circuits. The continued miniaturization of CMOS devices and the resulting decrease in silicide layer thickness necessitate methods with high sensitivity to the outermost atomic layers to study phase transitions in ultrathin films. This is where the Time-of-Flight Low-Energy Ion Scattering (ToF-LEIS) method proves valuable, offering the ability to investigate the formation and structure of transition metal silicides in-situ and in a non-destructive manner.
An example of my research in this field is our study of ultra-thin nickel silicide films (3.6 nm deposited Ni). By combining multiple ex-situ and in-situ experiments, we demonstrated that the phase transition in ultrathin films differs from that observed in thicker films (>4 nm deposited Ni). While thick films follow the transition sequence of Ni-on-Si to orthorhombic Ni2Si to orthorhombic NiSi and finally to cubic NiSi2, our results revealed that in ultrathin films on Si(100) substrates, the NiSi phase is absent, with a direct transition from Ni2Si to NiSi2 occurring.
Titanium-Based Films
Ti-based thin films are widely used as wear-resistant coatings for mechanical tools, corrosion-resistant coatings for medical implants, diffusion barriers in thin film electronics, and in many other applications, making them ideal candidates for in-situ ToF-LEIS experiments.
In our study, we conducted in-situ investigations on the effects of low oxygen exposure and high temperatures on four coatings: in-situ grown Ti and ex-situ grown Ti, TiN, and (Ti,Al)N. We found that the ex-situ samples retained a persistent surface oxide layer that could not be removed by ion sputtering, thereby limiting the effects of additional oxygen exposure compared to the in-situ sample. The nitride samples demonstrated high stability against further oxidation, even at elevated temperatures. Furthermore, we observed the formation of an Al-rich surface layer on (Ti,Al)N at temperatures exceeding 600 °C.
Interaction Between Slow Ions and Matter
My research also focuses on the fundamental interactions between slow ions and matter, such as electronic energy loss and the interatomic potential. These properties are critical for applications like ion beam analysis, material modification using ion beams, and studies of radiation damage. For instance, measurements of electronic energy loss for light ions in titanium enhance the accuracy of quantitative ToF-LEIS analysis. Additionally, experimental determinations of the interatomic potential for nuclear fusion-relevant atom combinations will aid in predicting the behavior of plasma-facing walls in future fusion reactors.