Key Takeaways & Executive Findings
- •• • FeIn2Se4 photodetector exhibits broadband photoresponse from 405 to 638 nm excitation wavelengths, with strong absorption spanning 510–1028 nm, enabling versatile visible-to-NIR detection. • • Angle-resolved polarized Raman spectroscopy reveals 60° periodic intensity variation in four characteristic Raman modes, confirming pronounced in-plane anisotropy for polarization-sensitive detection. • • XPS analysis after two weeks of air exposure at 84.8% RH and 32°C shows only partial surface oxidation (In2O3 and SeO2 peaks), whereas binary chalcogenides like In2Se3 and FeSe degrade rapidly, demonstrating superior environmental stability. • • Device maintained a pronounced temporal response after two weeks and a weak but measurable photoresponse after two months, indicating long-term operational durability under ambient conditions.
Abstract
Layered chalcogenide compounds have attracted considerable attention for optoelectronic applications due to their rich structural diversity and unique physical properties, including high carrier mobility, ferromagnetism, ferroelectricity, and outstanding optoelectronic and thermoelectric performance. Their tunable bandgaps and strong light absorption render them highly suitable for next-generation photodetectors. However, the environmental instability of many 2D chalcogenides poses a critical challenge for practical applications. In this work, we report a high-performance, polarization-sensitive photodetector based on an air-stable ternary chalcogenide FeIn2Se4. Angle-resolved polarized Raman spectroscopy reveals that the four characteristic Raman modes exhibit a 60° periodic variation in intensity, highlighting the material's pronounced in-plane anisotropy. Benefiting from its strong absorption over a broad spectral range (510–1028 nm), the FeIn2Se4-based device demonstrates reliable photoresponse under multiple excitation wavelengths (405, 473, 515, and 638 nm), showcasing its wideband detection capabilities. Furthermore, XPS measurements after prolonged air exposure confirm the enhanced chemical stability of FeIn2Se4 compared to binary chalcogenides. These findings demonstrate that 2D ternary FeIn2Se4 is an excellent candidate for advanced anisotropic optoelectronic devices, offering broadband photodetection, robust polarization sensitivity, and excellent environmental resilience.
1. Introduction
Conventional 2D photodetectors based on binary chalcogenides such as MoS2, WSe2, and black phosphorus suffer from inherent environmental instability, which severely limits their practical deployment. Exposure to ambient oxygen and moisture leads to rapid oxidation and degradation of device performance, necessitating encapsulation or inert-atmosphere operation. This bottleneck has hindered the commercialization of high-performance 2D optoelectronics, particularly for applications requiring long-term reliability.
Ternary layered chalcogenides, such as FeIn2Se4, offer a promising solution by integrating multiple elements to enhance chemical stability while preserving desirable optoelectronic properties. This work demonstrates that FeIn2Se4 not only exhibits strong broadband absorption and anisotropic optical characteristics but also maintains structural integrity under prolonged air exposure, addressing the critical stability challenge. The material's ability to sustain photoresponse over two months in ambient conditions marks a significant advancement toward practical, air-stable photodetectors.
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Haoge Cheng, Jianyu Zhu, Hua Zhang, Shuangmei Xue, Andrew T.S. Wee, Dingguan Wang (2026). Polarization-Sensitive Air-Stable Photodetector Based on Ternary Layered Compound FeIn2Se4. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3760-y
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Frequently Asked Questions
What is the operational spectral range of the FeIn2Se4 photodetector, and how does it compare to existing binary chalcogenide devices?
The FeIn2Se4 photodetector operates across a broad spectral range from 405 to 638 nm excitation wavelengths, with strong absorption spanning 510–1028 nm. This wideband capability is comparable to or exceeds that of many binary chalcogenides, which often have narrower absorption windows. The device's response under multiple wavelengths demonstrates its versatility for visible-to-NIR detection.
How does the environmental stability of FeIn2Se4 compare to binary chalcogenides under accelerated aging conditions?
Under accelerated aging at 84.8% RH and 32°C for two weeks, FeIn2Se4 exhibits only partial surface oxidation, as evidenced by low-intensity In2O3 and SeO2 peaks in XPS spectra. In contrast, binary compounds such as In2Se3 and FeSe rapidly form oxides (In2O3, Fe2O3, SeO2), leading to significant degradation. FeIn2Se4 maintains a pronounced photoresponse after two weeks and a weak but measurable response after two months, indicating superior long-term stability.
What is the origin of the polarization sensitivity in FeIn2Se4, and how is it quantified?
Polarization sensitivity arises from the material's in-plane anisotropic crystal structure. Angle-resolved polarized Raman spectroscopy reveals that the four characteristic Raman modes exhibit a 60° periodic variation in intensity, confirming pronounced anisotropy. This structural anisotropy translates into polarization-dependent photoresponse, enabling the device to discriminate light polarization.
What are the key material synthesis and device fabrication challenges for scaling FeIn2Se4 photodetectors?
The paper does not detail synthesis and fabrication specifics, but typical challenges for ternary layered compounds include achieving phase-pure crystals, controlling thickness during exfoliation, and ensuring uniform contact electrodes. The demonstrated air stability simplifies packaging, but large-area growth and integration with existing semiconductor processes remain open questions.
How does the photoresponse of FeIn2Se4 under different wavelengths compare in terms of responsivity and speed?
The paper reports reliable photoresponse at 405, 473, 515, and 638 nm, but does not provide specific responsivity or response time values. Further characterization is needed to quantify performance metrics relative to established materials.
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