Role of Surface Adsorbates on the Photoresponse of (MO)CVD-Grown Graphene–MoS₂ Heterostructure Photodetectors

Abstract

A promising strategy toward ultrathin, sensitive photodetectors is the combination of a photoactive semiconducting transition-metal dichalcogenide (TMDC) monolayer like MoS2 with highly conductive graphene. Such devices often exhibit a complex and contradictory photoresponse as incident light can trigger both photoconductivity and photoinduced desorption of molecules from the surface. Here, we use metal–organic chemical vapor deposition (MOCVD) to directly grow MoS2 on top of graphene that is deposited on a sapphire wafer via chemical vapor deposition (CVD) for realizing graphene–MoS2 photodetectors. Two-color optical pump–electrical probe experiments allow for separation of light-induced carrier transfer across the graphene–MoS2 heterointerface from adsorbate-induced effects. We demonstrate that adsorbates strongly modify both magnitude and sign of the photoconductivity. This is attributed to a change of the graphene doping from p- to n-type in case adsorbates are being desorbed, while in either case, photogenerated electrons are transferred from MoS2 to graphene. This nondestructive probing method sheds light on the charge carrier transfer mechanisms and the role of adsorbates in two-dimensional (2D) heterostructure photodetectors.

Synergistic Effects of Plasmonic Au Nanoislands on a MoSe2 Nanoflake/ZnO Nanorod Heterostructure for an Enhanced Broadband Photoresponse

“…From the enlarged version of one switching cycle presented in Figure S7, SI, the rise time and fall (recovery) time of the plasmonic device are found to be ∼1.8 and ∼2.8 s, respectively, while those of the nonplasmonic device are ∼1.4 and ∼5 s, respectively. The relatively slower response of the devices to light irradiation is attributed to various defect states in ZnO and MoSe 2 nanostructures as both the semiconductors are very much sensitive to the ambient atmosphere. ,, …”

DoE‐Assisted Development of a 2H−MoS2‐Catalyzed Approach for the Production of Indole Derivatives

“…In the wake of the reported ability of TMDCs to interact with molecular species present in the environment, [39,40] we hypothesized that subjecting the 2H−MoS 2 to a “cleaning treatment” would render the Lewis acid sites more accessible to the carbonylic carbon of 2 a , resulting in boosted catalytic ability. In fact, it is known that the adsorption of molecules alter some of the physical properties of the pristine material [41,42] . Hence, we treated 2H−MoS 2 under vacuum at 50 °C (labelled as MoS 2 ‐50 °C‐vac) to remove adsorbates and boost activity.…”

“…In fact, it is known that the adsorption of molecules alter some of the physical properties of the pristine material. [41,42] Hence, we treated 2HÀ MoS 2 under vacuum at 50 °C (labelled as MoS 2 -50 °C-vac) to remove adsorbates and boost activity. The hypothesis was corroborated by the increment in activity of MoS 2 -50 °C-vac as compared to the pristine 2HÀ MoS 2 (Entries 1-2, Table 1), and with a production rate reaching a value of 5.93 mmol 3a g Cat.…”

Towards large scale integration of MoS2/graphene heterostructure with ALD-grown MoS2

“…However, a key drawback of these methods is that they are not scalable. Recently promising results were obtained thanks to direct (Metal Organic) chemical vapour deposition (MO) CVD [24,25] or atomic layer deposition growth (ALD) of MoS 2 on graphene on large scale [26]. But controlling the direct growth of 2D heterostructures is extremely tricky.…”