Combinatorial Hardware and Software for Accelerated Discovery of Multianion Optoelectronic Thin Films
Eugène Bertin
National Centre for Nano Fabrication and Characterization - DTU Orbit, Lyngby, Denmark
Résumé
Multi-anion semiconductors, compounds combining two or more anion species such as S, P, N or Se, offer a remarkable degree of chemical and structural diversity for optoelectronics, yet thin-film synthesis studies remain scarce. We address this with a glove-box-integrated combinatorial platform: a reactive sputtering chamber (PH3, H2S, NH3, N2 and a S cracking source), a rapid thermal annealing furnace sharing the same reactive gases, and an evaporator for volatile metals. Two-dimensional compositional gradients on a single substrate enable rapid mapping of unexplored composition space, while an IA-ready data infrastructure built on NOMAD captures the structural, optoelectronic property data of the entire sample libraries. Across more than 20,000 samples in exotic ternary systems including, Zr-S-N, Ba-Cd-P, Cu-P-S, Ag-P-S, Sn-P-S, Sb-P-S, Ba-P-S, Ba-Zr-S and Ba-P-Te, we highlight the defect-tolerant Zintl phase BaCd2P2 realized for the first time as a thin film, BaP4Te2 with unusual P-Te bonds and novel SnPS3 and Cu3PS4, two vacuum-process phosphosulfides with photoluminescence.
We also report the first sulfonitride Zr2SN2 thin film, a member of the unexplored (Hf,Zr)2(S,Se)N2 chalconitride family that resist the usual trade-off between refractive index, transparency and free-carrier conductivity. Hybrid density functional theory predicts light effective masses, UV absorption edges and sub-bandgap refractive indices up to 2.84, exceeding TiO2 and SiC, but no thin-film synthesis route existed. Reactive sputtering followed by rapid thermal annealing yields the first chalconitride thin film, Zr2SN2, which confirms the predictions: refractive index n > 2.7, absorption edge at 2.9 eV, and degenerate n-type conductivity (carrier concentration >1020 cm-3, in-grain mobility > 8 cm2V-1s-1). Theory traces this unusual combination to a decoupled band structure with forbidden optical transitions at the direct band, very large join density of states in the UV, and low effective masses at the indirect one. A transparent conductor that is also a high-index dielectric could serve as anti-reflection, index-matching and charge-extraction layer at once in thin-film photovoltaics and opens a new design space for photonics more broadly. Zr2SN2 exemplifies what combinatorial exploration of multi-anion chemistry can deliver.
Contact : Léo Choubrac (MIOPS)
