Exciton Emission in Molybdenum Telluride Homobilayers with Fine-Tuned Twist-Angles

Layered 2H-molybdenum ditelluride (MoTe2) is a promising near-infrared material with optical activity, which enables hybrid-integrated with silicon photonics for communication purposes. The use of various artificial hetero-stacking or twist-stacking techniques can further expand the emission bandwidth and offer more choices of optical-active materials used as building blocks in on-chip optoelectronic devices. However, while the twisting technique is an effective tool for adjusting interlayer interaction in van der Waals materials, a systematic experimental study of twisted MoTe2 homobilayers is currently lacking. Here, a series of MoTe2 homobilayers were prepared with precisely controlled twist-angles from 0 degrees to 60 degrees, with a particular focus on the small-twist region. Conducting photoluminescence measurements at low temperatures enabled observation of the evolution of exciton emission as the twist angle increases. Neutral and charged excitons were also identified in a dual-gated 1.4 degrees twisted MoTe2 through gate-dependent and field-dependent photoluminescence measurements. Furthermore, spatially-resolved photoluminescence measurements revealed the critical role of the interface conditions, including interlayer spacing and strain, in addition to the twist-angle, in determining the excitonic behavior of the material. This study provides compelling experimental evidence for understanding the twist-angle-dependent excitonic behaviors in atomically thin semiconductors.