Degenerately doped semiconductor nanocrystals (NCs) exhibit a localized surface plasmon resonance (LSPR) in the infrared range of the electromagnetic spectrum. Unlike metals, semiconductor NCs offer tunable LSPR characteristics enabled by doping, or via electrochemical or photochemical charging. Tuning plasmonic properties through carrier density modulation suggests potential applications in smart optoelectronics, catalysis and sensing. Here, we elucidate fundamental aspects of LSPR modulation through dynamic carrier density tuning in Sn-doped InO (Sn:InO) NCs. Monodisperse Sn:InO NCs with various doping levels and sizes were synthesized and assembled in uniform films. NC films were then charged in an in situ electrochemical cell and the LSPR modulation spectra were monitored. Based on spectral shifts and intensity modulation of the LSPR, combined with optical modelling, it was found that often-neglected semiconductor properties, specifically band structure modification due to doping and surface states, strongly affect LSPR modulation. Fermi level pinning by surface defect states creates a surface depletion layer that alters the LSPR properties; it determines the extent of LSPR frequency modulation, diminishes the expected near-field enhancement, and strongly reduces sensitivity of the LSPR to the surroundings.

Area-selective atomic layer deposition (ALD) is an approach to self-aligned, bottom-up nanofabrication with the potential to overcome many of the challenges facing the semiconductor industry around continued device downscaling. Currently, the most common method for achieving area-selective ALD uses self-assembled monolayers (SAMs) as a means of surface deactivation. Alternative routes are also being pursued that may better meet the demands of high-volume device manufacturing and overcome some disadvantages of the SAM method. One promising alternative is the use of small molecule inhibitors (SMIs). This Perspective provides an overview of the current developments in the use of SMIs for selective deposition by describing systems from the literature and providing insight into SMI selection. Although little is yet known about the mechanistic behavior of SMIs, this Perspective aims to lay the framework for both a better understanding of their inhibitive performance and strategies to innovate their design. It establishes two key interfaces—between the ALD precursor and the inhibitor, and between the inhibitor and the substrate—and discusses the role of each in selective deposition. Building upon the established understanding of SAMs together with current knowledge of SMIs, this Perspective aims to define guiding principles and key considerations for improving SMI design.

In the version of this Letter originally published, the isotopic enrichments in the caption of Fig. 1a were incorrectly given as "red-10 B 98.7%, purple-natural abundant, brown-10 B 51%, cyan-11 B 83% and blue-11 B 99.2%"; they should have read "red-11 B 99.2%, purple-natural abundant, brown-10 B 51%, cyan-10 B 83% and blue-10 B 98.7%".