Rhenium-based 2D transition metal dichalcogenides such as ReSe2 are suitable candidates as photoactive materials for optoelectronic devices. Here, photodetectors based on mechanically exfoliated ReSe2 crystals were fabricated using chemical vapor deposited (CVD) graphene single-crystal (GSC) as lateral contacts. A “pick & place” method was adopted to transfer the desired crystals to the intended position, easing the device fabrication while reducing potential contaminations. A similar device with Au was fabricated to compare contacts’ performance. Lastly, a CVD hexagonal boron nitride (hBN) substrate passivation layer was designed and introduced in the device architecture. Raman spectroscopy was carried out to evaluate the device materials’ structural and electronic properties. Kelvin probe force measurements were done to calculate the materials’ work function, measuring a minimal Schottky barrier height for the GSC/ReSe2 contact (0.06 eV). Regarding the electrical performance, I-V curves showed sizable currents in the GSC/ReSe2 devices in the dark and under illumination. The devices presented high photocurrent and responsivity, along with an external quantum efficiency greatly exceeding 100%, confirming the non-blocking nature of the GSC contacts at high bias voltage (above 2 V). When introducing the hBN passivation layer, the device under white light reached a photo-to-dark current ratio up to 106.

Hexagonal boron nitride, h-BN, is a critical 2D insulator used as a substrate, gate dielectric, or encapsulation layer for graphene and other 2D materials and their van der Waals heterostructures.It is also promising as an active layer in single-photon emitters and other photonic devices. With chemical formula H 3 N-BH 3 , ammonia borane is the most attractive precursor for up-scalable growth of large-area h-BN, using chemical vapor deposition given its stoichiometric B:N ratio, high stability under ambient conditions, non-toxicity, and high solubility in common solvents.Here, the synthesis of large-area (100 mm × 150 mm) crystalline hexagonal boron nitride layers by thermal activation and decomposition of the precursor ammonia borane is presented. We describe two different reaction pathways for h-BN synthesis, providing evidence for dis-similarities in the sublimation kinetics of ammonia borane and how these differences critically influence the growth of h-BN. This understanding helps us accelerate h-BN production, re-use precursors, and reduce machine runtime, paving the way for upscalability. Moreover, our work provides a consistent unified view explaining the diverse deposition conditions reported in the literature for h-BN grown by CVD using ammonia borane as a precursor.

Hexagonal boron nitride (h-BN) has potential applications in protective coatings, single photon emitters and as substrate for graphene electronics. In this paper, we report on the growth of h-BN by chemical vapor deposition (CVD) using ammonia borane as the precursor. Use of CVD allows controlled synthesis over large areas defined by process parameters, e.g. temperature, time, process chamber pressure and gas partial pressures. Furthermore, independently grown graphene and h-BN layers are put together to realize enhancement in electronic properties of graphene.