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Modern society, revolutionized by the Internet of Things (IoTs), is witnessing exponential growth in the number of connected devices and the volume of data being generated and shared, raising significant concerns about safeguarding classified information against various cyber threats. Here, we introduce a lightweight, robust hardware security primitive based on the electromagnetic physical unclonable function (PUF) for cryptographic identification and authentication of wireless devices. Unlike traditional digital-based PUFs, the proposed electromagnetic PUF keys are generated using graphene-based harmonic transponders, of which the inherent variations in electronic properties of ambipolar graphene field-effect transistors (GFETs) result in highly stochastic, mixed modulations of radio frequency (RF) signals (i.e., unique electromagnetic fingerprints). Our experimental results demonstrate that this electromagnetic PUF exhibits excellent PUF performance metrics in terms of randomness, uniqueness, reliability, and resistance to machine learning-based modeling attacks. Moreover, the PUF keys can be reconfigured by altering the RF excitation frequency or through the electrostatic gating effect, further strengthening the security and resilience against modeling attacks. The proposed electromagnetic PUF may be well-suited for a variety of wireless authentication, encryption, and anticounterfeiting applications, and supports cryptographic key generation. 

Two-dimensional (2D) semiconductors are promising candidates for next-generation flexible electronics, but their performance is often limited by low electron mobility and substantial Schottky barriers (SBs) at metal contacts. Here, we demonstrate that PdSe2/WSe2 nanosheet-based van der Waals heterostructures outperform PdSe2 or WSe2 nanosheets alone as channel materials for n-type field-effect transistors. Here, the WSe2 nanosheet serves as a buffer layer, mitigating Fermi-level pinning and reducing SBs between Ti metal and PdSe2 nanosheets. These heterostructures achieve two-terminal effective mobility exceeding 200 cm2 V–1 s–1 at room temperature and nearing 680 cm2 V–1 s–1 at 77 K. Additionally, the increased bandgap in thinner PdSe2 nanosheets enables high on/off ratios (∼107) in PdSe2/WSe2. These results underscore the potential of PdSe2/WSe2 nanosheet-based heterostructures and the importance of interfacial engineering in advancing 2D electronic devices. 

We propose zero-bias, wavelength-scalable, and polarization-selective mid-infrared photodetectors based on metal–insulator–metal (MIM) metasurfaces. Specifically, these photodetectors leverage the second-order quantum conductivity sourced from photon-assisted tunneling and strong electric field localization in the MIM nanojunction to achieve efficient optical rectification. We show that by tailoring metasurface geometry, the incident infrared radiation can be efficiently coupled into the MIM heterojunction, with certain wavelength and polarization selectivity, and the optical rectification effect can be achieved with a photoresponsivity as high as tens of mA/W. Such results may pave a promising route toward the next-generation mid-infrared photodetection and energy harvesting.