Effects of dielectric stoichiometry on the photoluminescence properties of encapsulated WSe2 monolayers

Martín-Sánchez, Javier and Mariscal, Antonio and De Luca, Marta and Tarazaga Martín-Luengo, Aitana and Gramse, Georg and Halilovic, Alma and Serna, Rosalia and Bonanni, Alberta and Zardo, Ilaria and Trotta, Rinaldo and Rastelli, Armando. (2017) Effects of dielectric stoichiometry on the photoluminescence properties of encapsulated WSe2 monolayers. Nano Research, 11 (3). pp. 1399-1414.

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Official URL: https://edoc.unibas.ch/59663/

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Two-dimensional transition metal dichalcogenide semiconductors have emerged as promising candidates for optoelectronic devices with unprecedented properties and ultra-compact footprints. However, the high sensitivity of atomically thin materials to the surrounding dielectric media imposes severe limitations on their practical applicability. Hence, to enable the effective integration of these materials in devices, the development of reliable encapsulation procedures that preserve their physical properties is required. Here, the excitonic photoluminescence (at room temperature and 10 K) is assessed on mechanically exfoliated WSe 2 monolayer flakes encapsulated with SiO   and Al x O y  layers by means of chemical and physical deposition techniques. Conformal coating on untreated and nonfunctionalized flakes is successfully achieved by all the techniques examined, with the exception of atomic layer deposition, for which a cluster-like oxide coating is formed. No significant compositional or strain state changes in the flakes are detected upon encapsulation, independently of the technique adopted. Remarkably, our results show that the optical emission of the flakes is strongly influenced by the stoichiometry quality of the encapsulating oxide. When the encapsulation is carried out with slightly sub-stoichiometric oxides, two remarkable phenomena are observed. First, dominant trion (charged exciton) photoluminescence is detected at room temperature, revealing a clear electrical doping of the monolayers. Second, a strong decrease in the optical emission of the monolayers is observed, and attributed to non-radiative recombination processes and/or carrier transfer from the flake to the oxide. Power- and temperature-dependent photoluminescence measurements further confirm that stoichiometric oxides obtained by physical deposition lead to a successful encapsulation, opening a promising route for the development of integrated two-dimensional devices.
Faculties and Departments:05 Faculty of Science > Departement Physik > Physik > Experimental Material Physics (Zardo)
UniBasel Contributors:Zardo, Ilaria and De Luca, Marta
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:Springer ; Tsinghua University Press
Note:Publication type according to Uni Basel Research Database: Journal article
Identification Number:
Last Modified:28 Feb 2018 12:25
Deposited On:28 Feb 2018 12:25

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