Resolving surface potential variation in Ge/MoS2 heterostructures with Kelvin probe force microscopy

Abstract

In this work, we employ an atomic force microscopy-based technique, Kelvin probe force microscopy, to analyze heterogeneities of four different 2D/3D Ge/MoS2 heterostructures with Ge chemical vapor deposition (CVD) time. High-contrast spatially resolved contact potential difference (CPD) maps reveal the evolution of the samples by Ge deposition. The CPD map in an as-prepared sample does not display any heterogeneity, but CPD contrasts along the grain boundaries are obviously noticed as Ge is deposited on MoS2. With a sufficiently long Ge CVD deposition time, strong grain-to-grain CPD variations over the 2D/3D heterostructures are observed. The results show the variations of the work function from grain to grain that are attributed to the strain induced by the Ge island formation on the cracked MoS2 initiated by sulfur vacancies.

Microwave Facilitated Covalent Organic Framework/Transition Metal Dichalcogenide Heterostructures

“…At extremely short microwave reaction times, initial attachment of COF-5 was observed to occur at both the edge sites and basal plane of the monolayer MoS 2 , despite the high reactivity of the edge sites relative to the basal plane surface (further details in the Supporting Information, Figures S2−S5). 36,42 The fewlayer COF particles were shown to selectively attach to the monolayer TMDC and exhibit uniform coverage on the surface with minimal deposition on the silicon substrate, as depicted in the atomic force microscopy image in Figure 1d. Height profiles shown in Figure 1e depict a few-layer COF film with a thickness between 1 and 1.5 nm, which was verified by the cross-section TEM image in Figure 1f (additional images in the Supporting Information, S19).…”