In Situ Patterning of Ultrasharp Dopant Profiles in Silicon

We develop a method for patterning a buried two-dimensional electron gas (2DEG) in silicon using low kinetic energy electron stimulated desorption (LEESD) of a monohydride resist mask. A buried 2DEG forms as a result of placing a dense and narrow profile of phosphorus dopants beneath the silicon surface; a so-called δ -layer. Such 2D dopant profiles have previously been studied theoretically, and by angle-resolved photoemission spectroscopy, and have been shown to host a 2DEG with properties desirable for atomic-scale devices and quantum computation applications. Here we outline a patterning method based on low kinetic energy electron beam lithography, combined with in situ characterization, and demonstrate the formation of patterned features with dopant concentrations sufficient to create localized 2DEG states

Activation of 2D cobalt hydroxide with 0D cobalt oxide decoration for microplastics degradation and hydrogen evolution

Abstract The 2D semiconductors are important players in environmental and energy fields due to their unique catalytic and physical properties defined by their dimensionality. Versatile functionalities on one 2D matrix will enlarge its application scopes but require dedicated engineering paths. In this work, we present a cross-dimensional strategy by decorating 0D Co₃O₄ onto 2D Co(OH)₂ to form a multifunctional photocatalyst. The one-pot hydrothermally synthesized Co₃O₄@Co(OH)₂ composite is capable of degrading polystyrene microplastics with an efficiency of 40% under 0.495 W white LED illumination. In a separated experiment, H₂ evolution reaction from water splitting was evaluated in absence of sacrificial agents leading to 43 μmolg⁻¹ and to an apparent quantum efficiency of 3.48% at 420 nm. The study of the energy band diagrams by UV–Visible and ambient photoemission spectroscopy and the analysis of the radicals involved in the reaction of photocatalytic degradation allow to unveil the mechanisms for both the processes herein studied. Finally, we could confirm that the heterostructure benefits the redox potentials of 2D and 0D counterparts and facile electron transfers when crossing two different dimensions. These results provide guidelines and inspiration for cross-dimensional activations of low-dimensional materials for versatile functionalities

Unraveling compensation between electron transfer and strain in Ni-Ag-MoS₂ photocatalyst

Abstract Despite the boom in catalytic response via constructing interfaces, understanding interfaces’ interaction in heterostructures is still a paradox. In this work, the interaction of Ni with MoS₂ in Ni-Ag-MoS₂ heterostructure are unveiled through synchrotron X-PEEM and what’s more, the missing interaction mechanism at the Ag-MoS₂ interface is probed via Raman mapping. The observed competition between the downshift of the E2g¹ and A1g modes due to charge carrier injection and the upshift of the E2g¹ and A1g modes due to compressive strain during reverse laser power experiment is assigned to the non-uniform growth of Ag nanoparticles, their intimate contact with MoS₂, and Ag intercalated layered MoS₂. The substantial improvement of the H₂ yield of the Ni-Ag-MoS₂ (∼55 μmol h−1 g−1) over the pristine MoS₂ and the binary Ag-MoS₂ evidence successful bonding of Ni, Ag and MoS₂. This study highlights the importance of considering both electronic coupling and strain to optically tune electromechanical properties of MoS₂