DOI: 10.18150/1fendc
title: Experimental and theoretical band alignment study of MPS3 (M = Mn, Fe, Co, Ni) for designing tailored 2D heterostructures

description: Files include the data presented in the manuscript entitled: "Experimental and theoretical band alignment study of MPS3 (M = Mn, Fe, Co, Ni) for designing tailored 2D heterostructures" by D. Majchrzak et al. (https://doi.org/10.1038/s41699-025-00578-w)Figure 1. a Mounting of NiPS3 sample on a molybdenum plate using silver paste. b The sample is exfoliated under ultra-high vacuum conditions. Adhesive tape is affixed to the side of the preparation chamber, and the forward motion of the transfer arm allows for the exfoliation process. c Wide XPS spectrum and d high-resolution XPS spectra of S-2p, Ni-2p, and P-2p core level lines for exfoliated NiPS3 relative to the valence band maximum.Figure 2. a UPS spectra relative to the vacuum level, measured using He I photons (hν = 21.2 eV) for all studied and exfoliated MPS3. Gray dashed lines represent experimentally determined values of ionization potential. b Room temperature optical absorption spectra. c The excitation scheme of d–d and charge transfer (CT) transitions for all employed systems. d Schematic band alignment diagram for all studied MPS3 constructed based on a UPS and b absorption results.Figure 3. a Calculation of the vacuum level for all employed systems based on the macroscopic planar average of the Hartree potential for 7-layer slab of MPX3 crystals in the direction normal to the surface. At the top, additional visualization of the geometric structure of the slab. Ionization potential (b–d). Position of the valence band peak relative to vacuum level for b different antiferromagnetic ordering of MnPS3, c as a function of the Hubbard parameter U for MnPS3, d for all employed bulk crystals and monolayers. VB denotes the energy of the valence band maximum.Figure 4. a Visualization of the nearest environment of the transition metal ion (MS6 cluster) with a description of the splittings associated with the crystal field of this cluster. b Density of states with projection onto the transition metal (M), sulfur (S), and phosphorus (P) states. VBM is set to 0. c Calculated band alignments and band offsets for MPX3 bulk crystals, referenced to the vacuum level. The dotted line separates occupied (below) and unoccupied levels (above). Green color represents ligand region (1), while red denotes d states localized and unoccupied above the dotted line (2), and red-green shaded region – d states hybridized with p states below the dotted line (3). d Green and violet lines indicate the energy of d–d transitions (peak maxima, with green areas representing peak widths) and the absorption edge from absorption measurements (see Fig. 2b), respectively. Charge transfer excitation involves electron transfer from ligand states to ion d states, resulting in a ligand-to-metal transition. These transitions are typically more intense than d–d transitions and contribute to a strong absorption onset.Figure 5. a The band alignments with the indicated hydrogen reduction potential and oxidation potential in all pH range (blue areas). b Illustrative band diagram for MnPS3/NiPS3 heterostructure serving as a potential water-splitting system. The numbers (1–3) indicate the initial stages of the process that lead to the water-splitting reaction. (1) The semiconductors MnPS3 and NiPS3 absorb the light and create photogenerated carriers (electrons and holes). (2) Non-radiative interlayer recombination of the electron and hole at the interface (charge transfer – electron located at CBM in NiPS3 is transferred to VBM in MnPS3). (3) Photoexcited electrons in MnPS3 (photocathode) participate in the reduction of protons (H+) to hydrogen gas (H2) (HER), whereas photoholes at the NiPS3 (photoanode) oxidize water molecules, generating oxygen gas (O2).Data was calculated using OriginLab software and in case of XPS/UPS spectra using CasaXPS software.