In recent years, transition metal dichalcogenide (TMD)-based electronics have experienced a prosperous stage of development, and some considerable applications include field-effect transistors, photodetectors, and light-emitting diodes. Chemical vapor deposition (CVD), a typical bottom-up approach for preparing 2D materials, is widely used to synthesize large-area 2D TMD films and is a promising method for mass production to implement them for practical applications. In this review, we investigate recent progress in controlled CVD growth of 2D TMDs, aiming for controlled nucleation and orientation, using various CVD strategies such as choice of precursors or substrates, process optimization, and system engineering. We then survey different patterning methods, such as surface patterning, metal precursor patterning, and postgrowth sulfurization/selenization/tellurization, to mass produce heterostructures for device applications. With these strategies, various well-designed architectures, such as wafer-scale single crystals, vertical and lateral heterostructures, patterned structures, and arrays, are achieved. In addition, we further discuss various electronics made from CVD-grown TMDs to demonstrate the diverse application scenarios. Finally, perspectives regarding the current challenges of controlled CVD growth of 2D TMDs are also suggested.

As global population growth continues, the rapidly increasing demand for food and the environmental impact of this demand is a growing concern. Most food in Hong Kong is imported, which has implications for the associated environmental footprint. The carbon and water footprints (CF and WF) of the average Hong Kong diet were estimated from available sources and compared to well-accepted sustainable diets to characterize environmental sustainability. The total CF was 5701.90 g CO2-eq per capita/day, and the WF was 4782.31 L per capita/day. While meat products contributed only 22% to the weight, they were responsible for 57% and 53% of the total CF and WF, respectively. The impacts of the Hong Kong diet were greater than those of well-accepted sustainable diets, possibly due to the heavy consumption of meat and the import of foods. This confirms an urgency to increase environmental awareness among Hong Kong’s consumers and make interventions toward the adoption of sustainable, plant-based diets.

and optical properties, such as direct-toindirect band gap transition with thickness decreasing, [1] orbit-spin coupling, [2] and spin-valley locking [3] heralding the great potential of TMDs in optical and optoelectronic applications. [4][5][6] The band alignment semiconducting heterojunction is divided into three categories according to the relative positions of their energy bands, that is, type I (straddling), type II (staggered), and type III (broken). Type II structure can efficiently separate electrons and holes on two sides of the heterojunction, extending the photoexcited carrier lifetime, [7] therefore are preferable for field-effect-transistor-based photodetector, solar cell, photocatalyst, etc. In a type I heterostructure, both electrons and holes tend to transfer from wide to narrow bandgap side, largely increasing the chance of recombination of electrons and holes and facilitating photon generation and luminescent efficiency, therefore are suitable for devices like light-emitting diodes . [8] Heterojunctions composed of two monolayer TMDs are usually type II structures, while type I structures are rarely observed [9] and only reported on MoTe 2 /WSe 2 , [10] ReS 2 /MoS 2 , [11] etc. The limitations to obtaining vertical type I TMD heterostructures mainly originate from Atomically thin monolayer semiconducting transition metal dichalcogenides (TMDs), exhibiting direct band gap and strong light-matter interaction, are promising for optoelectronic devices. However, an efficient band alignment engineering method is required to further broaden their practical applications as versatile optoelectronics. In this work, the band alignment of two vertically stacked monolayer TMDs using the chemical vapor deposition (CVD) method is effectively tuned by two strategies: 1) formulating the compositions of MoS 2(1-x) Se 2x alloys, and 2) varying the twist angles of the stacked heterobilayer structures. Photoluminescence (PL) results combined with density functional theory (DFT) calculation show that by changing the alloy composition, a continuously tunable band alignment and a transition of type II-type I-type II band alignment of TMD heterobilayer is achieved. Moreover, only at moderate (10°-50°) twist angles, a PL enhancement of 28%-110% caused by the type I alignment is observed, indicating that the twist angle is coupled with the global band structure of heterobilayer. A heterojunction device made with MoS 0.76 Se 1.24 /WS 2 of 14° displays a significantly high photoresponsivity (55.9 A W -1 ), large detectivity (1.07 × 10 10 Jones), and high external quantum efficiency (135%). These findings provide engineering tools for heterostructure design for their application in optoelectronic devices.