Effects of Annealing Temperature and Ambient on Metal/PtSe₂ Contact Alloy Formation

Forming gas annealing is a common process step used to improve the performance of devices based on transition-metal dichalcogenides (TMDs). Here, the impact of forming gas anneal is investigated for PtSe₂-based devices. A range of annealing temperatures (150, 250, and 350 °C) were used both in inert (0/100% H₂/N₂) and forming gas (5/95% H₂/N₂) environments to separate the contribution of temperature and ambient. The samples are electrically characterized by circular transfer length method structures, from which contact resistance and sheet resistance are analyzed. Ti and Ni are used as metal contacts. Ti does not react with PtSe₂ at any given annealing step. In contrast to this, Ni reacts with PtSe₂, resulting in a contact alloy formation. The results are supported by a combination of X-ray photoelectron spectroscopy, Raman spectroscopy, energy-dispersive X-ray spectroscopy, and cross-sectional transmission electron microscopy. The work sheds light on the impact of forming gas annealing on TMD-metal interfaces, and on the TMD film itself, which could be of great interest to improve the contact resistance of TMD-based devices.