Project Summary: Among the high-mobility two-dimensional transition metal dichalcogenides, PtSe2 is of particular interest due to its record high carrier mobility of 210 cm2/Vs, sizeable band gap and air stability to address the current need for low-power, high-performance and ultra-thin body electronics. A scalable fabrication process with highly precise thickness control on ultra-smooth insulating gate oxides however has not been achieved to date. This work is addressing this gap by presenting ultra-thin growth of PtSe2 layers on insulating Al2O3. Due to the chosen growth technique, the approach is scalable and offers precise control over the PtSe2 layer thickness. We engineered deposition parameters to fabricate smooth, single crystal PtSe2 films of varying thickness. (0001)-oriented films were obtained at growth temperatures of 200 °C to 300 °C and a necessary Se oversupply of 10 to 15 times the Pt flux. The in-plane crystallographic orientation however was found to be random and nominal 3-layer thick PtSe2 films presented as disconnected islands in TEM as shown on the right with no discernable 2-dimensional structure. Only after a post-growth anneal in Se to slightly higher temperatures than the growth temperature, the typical expected 2-dimensional layered structure was observed with a preferred in-plane epitaxial orientation in the PtSe2 film as shown on the right. Published in 2D Materials 9, 025029 (2022).
2DCC Role: The 2DCC MBE2 facility was used for growth of the films and 2DCC personnel examined the films using Raman, XRD, AFM, and TEM characterization.
What Has Been Achieved: We used MBE to synthesize the TMD PtSe2.
Importance of the Achievement: This work demonstrates a scalable growth process for a high mobility 2D semiconductor in the ultrathin limit.
Unique Feature(s) of the MIP that Enabled this Achievement: The MBE2 of 2DCC, equipped with Se and Pt in an electron beam evaporator that enabled the co-deposition of Pt and Se.
Maria Hilse, Ke Wang, and Roman Engel-Herbert, “Molecular Beam Epitaxy of PtSe2 Using a Co-deposition Approach,” 2D Materials 9, 025029 (2022).
Acknowledgements: Work of the presented paper has been facilitated by The Pennsylvania State University Two-Dimensional Crystal Consortium—Materials Innovation Platform (2DCC-MIP), which is supported by NSF cooperative Agreements Nos. DMR-1539916 and DMR-2039351.