Minor structural changes in transition metal dichalcogenides can have dramatic effects on their electronic properties. This makes the quest for key parameters that enable a selective choice between the competing metallic and semiconducting phases in the 2D MoTe 2 system compelling. Herein, we report the optimal conditions at which the choice of the initial seed layer dictates the type of crystal structure of atomically-thin MoTe 2 films grown by chemical vapour deposition (CVD). When Mo metal is used as a seed layer, semiconducting 2H-MoTe 2 is the only product. Conversely, MoO 3 leads to the preferential growth of metallic 1T′-MoTe 2. The control over phase growth allows for simultaneous deposition of both 2H-MoTe 2 and 1T′-MoTe 2 phases on a single substrate during one CVD reaction. Furthermore, Rhodamine 6G dye can be detected using few-layered 1T′-MoTe 2 films down to 5 nM concentration, demonstrating surface enhanced Raman spectroscopy (SERS) with sensitivity several orders of magnitude higher than for bulk 1T′-MoTe 2 .

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A key benefit of photonic crystal surface emitting lasers (PCSELs) is the abillity to increase output power through scaling the emission area while mainting high quality single mode emission, allowing them to close the brightness gap which exists between semiconductor lasers and gas and fibre lasers. However, there are practical limits to the size, and hence power, of an individual PCSEL device and there are trade-offs between single-mode stability and parasitic in-plane losses with increasing device size. In this paper we discuss 2D coherent arrays as an approach to area and coherent power scaling of PCSELs. We demonstrate in two and three element PCSEL arrays an increase in the differential efficiency of the system due to a reduction in in-plane loss.

We report the engineering of air voids embedded in GaAs-based photonic crystal surface-emitting lasers realized by metalorganic vapor-phase epitaxy regrowth. Two distinct void geometries are obtained by modifying the photonic crystal grating profile within the reactor prior to regrowth. The mechanism of void formation is inferred from scanning transmission electron microscopy analysis, with the evolution of the growth front illustrated though the use of an AlAs/GaAs superlattice structure. Competition between rapid lateral growth of the (100) surface and slow diffusion across higher index planes is exploited in order to increase the void volume, leading to an order of magnitude reduction in threshold current and an increase in output power through an increase in the associated grating coupling strength.

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Minor structural changes in transition metal dichalcogenides can have dramatic effects on their electronic properties. This makes the quest for key parameters that can enable a selective choice between the competing metallic and semiconducting phases in the 2D MoTe₂ system compelling. Herein, we report the optimal conditions at which the choice of the initial seed layer dictates the type of crystal structure of atomically-thin MoTe₂ films grown by chemical vapour deposition (CVD). When Mo metal is used as a seed layer, phase-pure semiconducting 2H-MoTe₂ is the only product. Conversely, MoO₃ leads to the preferential growth of phase-pure metallic 1Tꞌ-MoTe₂. The control over phase growth allows for simultaneous deposition of both 2H-MoTe₂ and 1Tꞌ-MoTe₂ phases on a single substrate during one CVD reaction. Furthermore, Rhodamine 6G dye can be detected using few-layered 1Tꞌ-MoTe₂ films down to 5 nM concentration which is several orders of magnitude higher than the value observed for bulk 1Tꞌ-MoTe₂.

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This paper analyzes 2D photonic crystal surface-emitting laser diodes with void-containing and all-semiconductor structures by comparing their simulated mode distribution, band structure, and coupling coefficients. A photonic crystal design with a square lattice and circle atoms is considered.