Physical characteristics of Cu2Te are poorly investigated due to limited Te sources available and unclear atomic positions of crystal structure. Herein, hexagonal Cu2Te microdisks are successfully prepared via chemical vapor deposition procedure using GaTe as Te source. The epitaxial growth mechanism of the Cu2Te hexagonal structures with the orthorhombic phase is rationalized by proposed layer‐over‐layer growth model. The photoluminescence (PL) spectrum of Cu2Te microdisks shows a new red emission band in addition to usual infrared light emission due to Cu deficiency. Single Cu2Te microdisk operates as an optical microcavity supporting whispering gallery modes for red lasing around 627.5 nm. This Cu2Te microdisk microcavity exhibits a high quality factor of 1568 and a low lasing threshold of 125 kW cm−2 at room temperature. Meanwhile, Cu2Te microdisks have been exhibited as an ideal platform for surface enhanced Raman scattering (SERS) eliminating drawbacks of noble metal substrates with detection limitation to nanomolar level and an enhancement factor of ≈1.95 × 105. Hexagonal Cu2Te microdisks turn out to be an efficient microcavity for red lasing and low‐cost nonmetallic SERS substrates, opening potential applications in photonics and biological detection of aromatic molecules.

Introducing the density of states or defects within the band gap in two-dimensional nanomaterials by rare-earth (RE) element substitution would make them potential candidates for application in next-generation optoelectronic devices. Furthermore, doping with RE elements possessing fine-structured spectral emission and absorption can improve the fundamental research and technological applications of two-dimensional nanomaterial-based photoelectrochemical (PEC) activity due to abundant active sites and low interfacial contact resistance with the electrolyte. Herein, an Er-doping strategy is utilized for the synthesis of Er-doped WS 2 nanosheets to simultaneously achieve both upconversion and downconversion emissions, which can efficiently absorb more solar light for PEC activity. We first report a two-step method combining magnetic sputtering and sulfurization to synthesize Er-doped WS 2 nanosheet-based electrodes. The effect of Er doping into a single-phase hexagonal-structured WS 2 (p-type semiconductor)based electrode on PEC activity is investigated and compared with pristine WS 2 counterparts under one standard sun condition. Results indicate that a photocurrent density of −20 μA•cm −2 at −0.21 V versus RHE (reversible hydrogen electrode) with an enhancement factor of ∼200-fold due to a wider absorbance range (400−808 nm) and a decreased overpotential for hydrogen reduction are achieved. Moreover, the resistance of the Er-doped WS 2 electrode is found to be decreased from 500 to 28 kΩ, with nearly a 20-fold decrease compared with that of the pristine WS 2 counterparts, contributing to the higher efficiency in electron transfer into the electrolyte. The mechanism is confirmed by Monte Carlo simulations and first-principles calculations. The Er-doped WS 2 nanosheets are therefore a promising substitute for noble metals in PEC applications.

The integration of 2D nanomaterials with silicon is expected to enrich the applications of 2D functional nanomaterials and pave the way for next‐generation, nanoscale optoelectronics with enhanced performances. Herein, a strategy for rare earth element doping is utilized for the synthesis of 2D WS2:Er nanosheets to achieve up‐conversion and down‐conversion emissions ranging from visible to near‐infrared regions. Moreover, the potential integration of the synthesized 2D nanosheets in silicon platforms is demonstrated by the realization of an infrared photodetector based on a WS2:Er/Si heterojunction. These devices operate at room temperature and show a high photoresponsivity of ≈39.8 mA W−1 (at 980 nm) and a detectivity of 2.79 × 1010 cm Hz1/2 W−1. Moreover, the dark current and noise power density are suppressed effectively by van der Waals‐assisted p–n heterojunction. This work fundamentally contributes to establishing infrared detection by rare element doping of 2D materials in heterojunctions with Si, at the forefront of infrared 2DMs‐based photonics.