Impact of CVD Growth Promoters in the Band Alignment of Single Phase 2D MoS₂ and MoTe₂ Layers on SiO₂/Si

In view of an integration of 2-dimensional (2D) transition metal dichalcogenides (TMDs) in microelectronics processes and devices, growth methodologies and strategies for a direct integration on top of Si wafers are highly demanding and needed. Among the growth methods, chemical vapor deposition (CVD) based approaches are considered the most promising way to satisfy the requirement for the controlled, uniform growth of 2D TMDs over large areas at the wafer scale. To target such conditions, the use of organic or inorganic molecules, known as growth promoters, has been successfully implemented in several CVD growth processes; the use of perylenes, such as PTAS, or inorganic salts, such as KCl or NaOH, spread in solid form or mixed and delivered in liquid solutions inside the CVD reactor together with the Mo and S precursors has been attained and reported [1, 2, 3, 4].<br/>Despite the wide consideration for the integration of TMDs in microelectronics platforms, minimal consideration has been given to address the band alignment of such 2D layers on SiO₂/Si substrates, the natural choice to be considered for the direct integration of 2D TMDs in CMOS fabrication process. Motivated by this gap, in this study, we studied the band alignment of two TMDs, namely, MoS₂, probably the TMD at the best maturity stage in terms of growth control over large areas, and 1T’ or 2H-phase MoTe₂, possibly the most promising for resistive switching, neuromorphic and optoelectronics applications [5]. In particular, our study focuses on the impact of the growth promoters on the band alignment at the interface between the TMDs layers and the substrate.<br/>Here, we make use of internal photoemission (IPE) and x-ray photoelectron (XPS) spectroscopies to measure and calculate the band alignment. For MoS₂, we found values spanning from 4.2 eV, when using PTAS or NaOH, down to 3.9 eV for KCl to compare with 3.6 eV in MoS₂ with no promoters [6]; for CVD-grown MoTe₂, we extracted a 3.9 eV value for 1T’-phase moving to 4.2 eV for 2H-MoTe₂, with a shift of 0.4 eV consistent with the value observed in single phase exfoliated layers.<br/><br/>[1] Z. Ye et al., Emerging MoS₂ Wafer Scale Technique for Integrated Circuits, Nano-Micro Lett. 2023, 15:38<br/>[2] T. Kang et al., Strategies for Controlled Growth of Transition Metal Dichalcogenides by Chemical Vapor Deposition for Integrated Electronics, ACS Mater. Au 2022, 2, 665−685<br/>[3] A. Cataldo et al., Effects of inorganic seed promoters on MoS₂ few-layers grown via chemical vapor deposition, J. Cryst. Grow. 2024, 627, 127530<br/>[4] P.P. Tummala et al., Large Area Growth and Phase Selectivity of MoTe₂ Nanosheets through Simulation-Guided CVD Tellurization, Adv. Mater. Interf. 2023, 10, 2200971<br/>[5] I.M. Datye et al., Localized Heating and Switching in MoTe₂-Based Resistive Memory Devices, Nano Lett. 2020, 20, 1461–1467<br/>[6] P.P. Tummala et al., Impact of CVD chemistry on band alignment at the MoS₂/SiO₂ interface, Solid-State Electronics 2023, 209, 108782