Surface-enhanced Raman scattering (SERS) has been widely established as a powerful analytical technique in molecular fingerprint recognition. Although conventional noble metal-based SERS substrates show admirable enhancement of the Raman signals, challenges on reproducibility, biocompatibility, and costs limit their implementations as the preferred analysis platforms. Recently, researches on SERS substrates have found that some innovatively prepared metal oxides/chalcogenides could produce noble metal comparable SERS enhancement, which profoundly expanded the material selection. Nevertheless, to tune the SERS enhancement of these materials, careful experimental designs and sophisticated processes were needed. Here, an electrically tunable SERS substrate based on tungsten oxides (WO3–x ) is demonstrated. An electric field is used to introduce the defects in the oxide on an individual substrate, readily invoking the SERS detection capability, and further tuning the enhancement factor is achieved through electrical programming of the oxide leakage level. Additionally, by virtue of in situ tuning the defect density and enhancement factor, the substrate can adapt to different molecular concentrations, potentially improving the detection range. These results not only help build a better understanding of the chemical mechanism but also open an avenue for engaging non-noble metal materials as multifunctional SERS substrates.

Ultrasensitive SERS-based immunoassay induced by SiO2@Au nanoprobe and hydrophilic–hydrophobic assembly substrate.

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Current understanding of the bias temperature instability degradation usually comprises two parts: (1) shallow-level component that can recover within a short time and (2) deep level traps that the emission time of the trapped carrier is extremely long. Prevenient studies of the positive bias temperature instability degradation in the high-κ n-MOSFET indicate that oxygen vacancy (V O ) is the dominant defect type that responds for the shallow electron trapping. However, recent experimental results reveal that the V O defect density required to accommodate the experimental measured recoverable threshold voltage degradation (ΔV th ) is much higher than that of the reasonable atomic structure in the amorphous HfO 2 . On the other hand, investigations on the disordered Hf-O-Hf network in the amorphous HfO 2 reveal their capabilities as charge trapping centers; therefore, in this work, atomic simulation work is performed, and our results show that the disordered Hf-O-Hf networks can act as effective electron capture centers with shallow levels near the Si conduction band. Moreover, the high density of the stretched Hf-O-Hf networks in the amorphous HfO 2 also significantly enriches the shallow electron traps in the oxide.