Thin film synthesis of SrZn2P2 with SrI2 post-annealing for enhanced crystallinity and optoelectronic quality

Sita Dugu; Shaham Quadir; Christopher P. Muzzillo; Zhenkun Yuan; Smitakshi Goswami; Xiaojing Hao; Jialiang Huang; Guillermo Esparza; Baptiste Julien; David Fenning; Jifeng Liu; Geoffroy Hautier; Andriy Zakutayev; Sage R. Bauers

arXiv · 2604.26995

Thin film synthesis of SrZn2P2 with SrI2 post-annealing for enhanced crystallinity and optoelectronic quality

Sita Dugu·Shaham Quadir·Christopher P. Muzzillo·Zhenkun Yuan·Smitakshi Goswami·Xiaojing Hao·Jialiang Huang·Guillermo Esparza·Baptiste Julien·David Fenning·Jifeng Liu·Geoffroy Hautier·Andriy Zakutayev·Sage R. Bauers

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Abstract

Ternary Zintl phosphides are promising light-absorbing semiconductors for thin-film optoelectronic applications, but strategies for controlling their microstructure and optoelectronic quality remain underexplored. Here, we report the synthesis of phase-pure SrZn2P2 thin films using radio-frequency co-sputtering in a PH3 + Ar atmosphere and investigate the impact of post-growth processing on their structural and optical properties. Grazing-incidence X-ray scattering and Raman spectroscopy confirm the formation of crystalline SrZn2P2 films over a finite compositional window. Optical measurements reveal strong absorption near the direct-band-gap energy (~1.8 eV) and near-band-edge photoluminescence. Further, we have studied the effects of chemically compatible halide-assisted annealing. It is found that SrI2 treatments lead to pronounced grain growth and reduced diffraction peak broadening while preserving phase purity, in contrast to rapid thermal or forming-gas annealing. Notably, annealing with SrI2 at 450 °C significantly enhances both the intensity and spatial uniformity of the photoluminescence, thus connecting the observed microstructural consolidation with improved radiative recombination. Our study demonstrates that halide-assisted annealing provides an effective pathway for microstructural control in SrZn2P2 thin films and highlights a generalizable processing strategy for advancing Zintl phosphide semiconductors toward optoelectronic applications.

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Sita Dugu, Shaham Quadir, Christopher P. Muzzillo, Zhenkun Yuan, Smitakshi Goswami, Xiaojing Hao, Jialiang Huang, Guillermo Esparza, Baptiste Julien, David Fenning, Jifeng Liu, Geoffroy Hautier, Andriy Zakutayev, Sage R. Bauers. 2026-04-29. Thin film synthesis of SrZn2P2 with SrI2 post-annealing for enhanced crystallinity and optoelectronic quality. https://arxiv.org/abs/2604.26995

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