In today's digital ecosystem, telecommunications have become the basis for businesses, governments, communities, and families to seamlessly connect and share information. Over time, telecommunications are expected to further expand. Therefore, there has been a great demand for light sources and photodetectors that work in the telecommunication band (1.3-1.5 µm) for signal transmission through silica optical fibers. Two-dimensional (2D) materials -i.e. single layers of a crystal, with atomic thickness- can nowadays be obtained from layered materials, thanks to the fact that the different layers are bound by the weak van der Waals force. Besides their atomic thickness, 2D materials are highly flexible and can withstand three to five times more strain (i.e., elastic deformation) than traditional three-dimensional semiconductors. As a two-dimensional material, MoTe2 has all these characteristics. MoTe2 has a band gap of 1.1 eV (i.e., ~1.13 µm) for a single layer and 0.98 eV (i.e., ~1.27 µm) for a bulk, making it a potentially suitable source material for the telecom band. However, the tuning of light emission is still the bottleneck for exploring the entire telecom span. As demonstrated by the host group, a process based on hydrogen irradiation on 2D multilayers (MoS2, WS2, WSe2, MoTe2) is able to induce the creation of strained nanometric or micrometric domes of monolayer thickness. The process can be exploited to achieve strains ~10%, which have not been demonstrated by other strain techniques used for 2D materials. The technique further allows us to gain control over the shape and size of the dome. While the effect of strain in domes formed in MoS2, WS2, and WSe2 has been widely studied by the host group, the effect on MoTe2 has not been characterized, yet. This project aims to explore the possibility to tune the luminescence properties of MoTe2 through strain in order to make it a controllable light source in the telecommunication wavelength range.
Since, the first exfoliation of graphene in 2004, 2D materials have drawn a great attention for their unmatched optical, electrical and physical properties, which makes them appealing for electronic and optoelectronic devices. However, compared to other TMDs, MoTe2 has unstable structure both under uni-directional strain and temperature. This becomes more complicated under uncontrolled strain. Therefore even though it has the potential to become a telecom wavelength source, it has been rarely explored. "TWIST-MoTe2" aims to resolve this limitation by presenting a precise controlled strain in MoTe2 bubbles. Here, we propose to create MoTe2 bubbles of different size comparably in the micron range, see Fig 2 (b). This would allow us to gain control over the excitonic emission and widen the state-of-the-art knowledge in this field.
QEs capable of operating in O-C telecommunication bands (1.31 and 1.55 µm) have not been demonstrated in TMDCs at room temperature, which is very important for future quantum device applications. Here, we propose to generate periodic potentials via the realization of ordered arrays of domes, such as in Fig. 4. In previous studies, the group of the proposer have demonstrate that the formation of domes subject locally the 2D membrane to strains that seamlessly increase while going from the edge towards the centre of the dome [Blu,20,prr]. Strain leads to a reduction of the bandgap [Cha,13]. Therefore, whenever arrays of domes are created, we achieve local seamless bandgap reductions that are expected to act as a periodic potential, which would trap excitons at the potential minima on top of the domes. Therefore in ordered nano-bubble, the localized exciton can behave as quantum emitters, which are expected to emit single photon even at room temperature.
We envision our early demonstration of MoTe2 for infrared optoelectronics will instigate further study of van der Waals heterostructure of MoTe2 and other TMDs to explore the broader emission spectrum.