Tailoring ultra-fast charge transfer in MoS₂

Abstract

Charge transfer dynamics are of importance in functional materials used in devices. This property is morphology dependent in MoS2. Compared to a single crystal it is faster in a nanoparticle sample and even faster for a MoS2 graphene oxide composite.

Understanding ultrafast charge transfer processes in SnS and SnS2: using the core hole clock method to measure attosecond orbital-dependent electron delocalisation in semiconducting layered materials

“…Although, exceptions to this trend can be found to the delocalisation of electrons from adsorbates, 22 it is the common trend observed so far for all semiconducting materials analysed by CHC. [23][24][25]31,33,37 In this manuscript, we will use the delocalisation time measured at energies 0.4 eV above the absorption maximum as a characteristic and comparable value for each molecular orbital contribution to the conduction band.…”

“…21,22 In the last decade, the CHC method has been applied to study semiconducting materials, starting with the pioneering work of Rocco and Garcia-Basabe on a series of thiophene containing semiconducting polymers, [23][24][25][26] and with a couple of other groups following with incremental work on polymers and other complex conjugated systems. [27][28][29] These studies provide maps of delocalisation times across the conduction band of these semiconductor materials that have been related to the molecular composition, 30 structure, 23,24 morphology 31 and material interactions at different substrates and heterojunctions. 27 However, as recognised in a recent 2020 publication, CHC studies of complex organic semiconductor materials are still scarce.…”

“…Despite the unique charge transfer dynamics information that this method can provide, only seven CHC publications have appeared so far on such systems. These publications have focused on the study of three different metal chalcogenides: MoS2, [31][32][33][34] TaS2 35 and SnS2. 36,37 and shown the sensitivity of the technique to measure changes in the charge transfer dynamics depending on material phase, 32,34 additives 34 and substrate interactions.…”

“…36,37 and shown the sensitivity of the technique to measure changes in the charge transfer dynamics depending on material phase, 32,34 additives 34 and substrate interactions. 31 For the three studied materials, CHC data has also been used to try to distinguish between in plane and out of plane delocalisation processes in these layered materials in order to try to measure differences between inter-and intra-layer charge transfer processes. [34][35][36][37] In this sense, SnS2 has been studied in two publications, using different absorption edges and analysis approaches, that have provided somehow contradictory results.…”

Hard x-ray photoelectron spectroscopy: a snapshot of the state-of-the-art in 2020

“…In MoS 2 charge transfer dynamics have been shown to vary depending on the morphology of the sample, including a single crystal, nanoparticles, and a composite of MoS 2 sandwiching a graphene backbone, using CHCS. [171] Whilst they are similar for the crystal and nanoparticle cases, owing to the local character of the probe, the composite exhibits a bi-modal charge transfer time distribution as a function of excitation energy. The switch between to regimes of charge transfer times is attributed to the core excited electron having sufficient energy to overcome the Schottky barrier created in the MoS 2 /graphene interface.…”