The discovery of Dirac semimetal has stimulated bourgeoning interests for exploring exotic quantum-transport phenomena, holding great promise for manipulating the performance of photoelectric devices that are related to nontrivial band topology. Nevertheless, it still remains elusive on both the device implementation and immediate results, with some enhanced or technically applicable electronic properties signified by the Dirac fermiology. By means of Pt doping, a type-II Dirac semimetal Ir1–xPtxTe2 with protected crystal structure and tunable Fermi level has been achieved in this work. It has been envisioned that the metal–semimetal–metal device exhibits an order of magnitude performance improvement at terahertz frequency when the Fermi level is aligned with the Dirac node (i.e., x ∼ 0.3) and a room-temperature photoresponsivity of 0.52 A·W–1 at 0.12 THz and 0.45 A·W–1 at 0.3 THz, which benefited from the excitation of type-II Dirac fermions. Furthermore, van der Waals integration with Dirac semimetals exhibits superb performance with noise equivalent power less than 24 pW·Hz–0.5, rivaling the state-of-the-art detectors. Our work provides a route to explore the nontrivial topology of Dirac semimetal for addressing targeted applications in imaging and biomedical sensing across a terahertz gap.
In this thesis, we studied the characteristics and applications of a metamaterials resonator based on ohm-ring. In the range of 0.2–1.4 THz, the resonator exhibited two significant resonant peaks, which were shifted with different surface permittivity. We applied this feature to terahertz (THz) sensing. Under a same THz-TDS transmission system, the terahertz spectra of chlorpheniramine maleate could not reflect the content information at all when the concentration was <1%. But this information could be obtained with the aid of the resonator. Our work demonstrates that metamaterials is a sensitive tool for THz sensing, and have the promising potential for the detection for of small quantities of drug, which was hard to detect by direct THz sensing.
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