Dielectric properties of ultrathin AlO (1.1-4.4 nm) in metal-insulator-metal (M-I-M) Al/AlO/Al trilayers fabricated in situ using an integrated sputtering and atomic layer deposition (ALD) system were investigated. An M-I interfacial layer (IL) formed during the pre-ALD sample transfer even under high vacuum has a profound effect on the dielectric properties of the AlO with a significantly reduced dielectric constant (ε) of 0.5-3.3 as compared to the bulk ε ∼ 9.2. Moreover, the observed soft-type electric breakdown suggests defects in both the M-I interface and the AlO film. By controlling the pre-ALD exposure to reduce the IL to a negligible level, a high ε up to 8.9 was obtained on the ALD AlO films with thicknesses from 3.3 to 4.4 nm, corresponding to an effective oxide thickness (EOT) of ∼1.4-1.9 nm, respectively, which are comparable to the EOTs found in high-K dielectrics like HfO at 3-4 nm in thickness and further suggest that the ultrathin ALD AlO produced in optimal conditions may provide a low-cost alternative gate dielectric for CMOS. While ε decreases at a smaller AlO thickness, the hard-type dielectric breakdown at 32 MV/cm and in situ scanning tunneling spectroscopy revealed band gap ∼2.63 eV comparable to that of an epitaxial AlO film. This suggests that the IL is unlikely a dominant reason for the reduced ε at the AlO thickness of 1.1-2.2 nm but rather a consequence of the electron tunneling as confirmed in the transport measurement. This result demonstrates the critical importance in controlling the IL to achieving high-performance ultrathin dielectric in MIM structures.

Plasmonic metal nanostructures provide a promising strategy for light trapping and therefore can dramatically enhance photocurrent in optoelectronics only if the trapped light can be coupled effectively from plasmons to excitons, whereas the reverse transfer of energy, charge, and heat from excitons to plasmons can be suppressed. Motivated by this, this work develops a scheme to implement a metafilm with Ag nanoparticles (NPs) embedded in 10 nm thick silica (Ag NPs–silica metafilm) to the active device channel of a hybrid perovskite film/graphene photodetector. Remarkably, an enhancement factor of 7.45 in photoresponsivity, the highest so far among all the reports adopting plasmonic metal NPs in perovskite photodetectors, has been achieved on the photodetectors with the Ag NPs–silica metafilms. Considering that the synthesis of the Ag NPs–silica metafilms can be readily scaled up to coat both rigid and flexible substrates, this result provides a low-cost metaplatform for a variety of high-performance optoelectronic device applications.

Coupling plasmons and excitons provide a promising approach to enhance the performance of photodetectors based on two-dimensional (2D) atomic layer heterostructures. Herein, we report a nanohybrid photodetector achieved by transferring a nonmetallic plasmonic WS2 nanodisk/graphene van der Waal (vdW) heterostructure grown using chemical vapor deposition, on metallic plasmonic Ag nanoparticles embedded in 20 nm thick silica (AgNP-metafilm) fabricated using in situ Ag and Si evaporation through a shadow mask. This nanohybrid photodetector enables not only superposition of the plasmonic effects from the two plasmonic nanostructures, but also the effective coupling of the plasmons and excitons in WS2 nanodisks upon illumination. This leads to a high responsivity of 11.7 A/W on the graphene/WS2 nanodisks/AgNP-metafilm under an incident illumination power of 5.5 × 10–8 W at 450 nm, which represents a 500% enhancement over that of the counterpart without the AgNP-metafilm. The finite element time-domain simulation of the local light field distribution indicates that the enhancement can be attributed to enhancement of exciton (electron–hole pair) excitation and exciton–plasmon coupling in the graphene/WS2 nanodisks/AgNP-metafilm photodetectors. In addition, the approach for fabrication of the graphene/WS2 nanodisks/AgNP-metafilm heterostructures is scalable and cost efficient and hence promising for commercial applications.

A nanohybrid architecture composed of single-wall carbon nanotube films and graphene heterostructures (SWCNT/ graphene) was developed as a three-dimensional (3D) electrode. Atomic layer deposition (ALD) was used for conformal coating of catalytic Pt nanoparticles on the 3D ALD-Pt@SWCNT/graphene nanohybrid architecture for further enhancement of H 2 sensing, taking advantage of the large sensing area and conformally coated nanostructures of the catalytic Pt. Remarkably, the H 2 response was found to be improved by 50% in the SWCNT/graphene nanohybrid, indicating that graphene provides a more efficient charge transport. The ALD-Pt further enhances the H 2 responsivity of the 3D ALD-Pt @SWCNT/graphene nanohybrids. By coating 10 cycles of ALD-Pt on the SWCNT/graphene nanohybrid, the H 2 response (2.77%) is approximately twice that (1.4%) of its counterpart without the ALD-Pt. By further optimizing the 3D ALD-Pt@ SWCNT/graphene nanohybrids with respect to the ALD-Pt cycle numbers and SWCNT film thickness, a H 2 responsivity as high as 7.5% was achieved on the SWCNT/graphene nanohybrid sample with a 560 nm thick SWCNT film and 50 cycles of ALD-Pt.

Colloidal quantum dot (QD)/graphene nanohybrid heterostructures provide a promising scheme for quantum sensors as they take advantage of the strong quantum confinement in QDs with enhanced light−matter interaction, spectral tunability, suppressed phonon scattering, and extraordinary charge mobility in graphene at room temperature. Herein, we report development of a flexible, nine-channel PbS QD/graphene nanohybrid imaging array on polyethylene terephthalate using a facile process for device fabrication, signal acquisition, and processing. The PbS QD/graphene imaging array exhibited high and uniform photoresponse. At a 1.0 V bias, the highest responsivity was 9.56 × 10 3 −3.24 × 10 3 A/W for 400−1000 nm incident light [ultraviolet−visible−near-infrared (UV−vis−NIR)] with a power of 900 pW. In addition, the array has a consistent spectral response with bending down to a radius of curvature of a few millimeters. The demonstration of imaging at broadband wavelengths in the UV−vis− NIR range indicates that QD/graphene nanohybrids provide a viable approach for flexible photodetectors and imagers.