Low-temperature growth of two-dimensional InP nanosheets for optoelectronic applications

Abstract

Two-dimensional (2D) III–V semiconductors hold exceptional promise for next-generation electronic and optoelectronic devices; however, their scalable synthesis remains a long-standing challenge owing to the strong, directional covalent bonding in non-layered crystal structures—which inherently suppresses natural cleavage and lateral growth. Here, we report a controllable, low-temperature (<450 °C) chemical vapor deposition (CVD) strategy enabling the direct synthesis of ultrathin, single- to few-layer InP nanosheets on commercially available mica substrates—without requiring costly lattice-matched buffers or catalytic templates. The as-grown InP nanosheets exhibit atomic-level thickness uniformity, large lateral dimensions (>10 μm), and high crystallinity, as confirmed by atomic-resolution imaging and electron diffraction. Cross-sectional scanning transmission electron microscopy (STEM) unambiguously reveals the absence of an interfacial van der Waals gap at the InP/mica interface, demonstrating that growth proceeds via interfacial chemical interaction rather than weak physisorption—thus representing a departure from conventional van der Waals epitaxy. Critically, nanosheet formation is exclusively observed on mica, whereas only isotropic nanoparticles nucleate on SiO2 and sapphire under identical conditions—highlighting mica's unique role as an atomically smooth, chemically inert, and defect-poor substrate that kinetically favors anisotropic lateral extension over 3D islanding. Polarization-resolved second-harmonic generation (SHG) measurements further confirm the non-centrosymmetric structure of the nanosheets and reveal exceptional optical homogeneity across micrometer-scale domains. Field-effect transistors fabricated from individual InP nanosheets show excellent bias stability, while photodetectors exhibit reproducible photoresponse with a maximum responsivity of 510 mA W−1 and a peak detectivity of 3.2 × 109 Jones under low-intensity illumination (0.1 mW cm−2). Collectively, this work establishes a generalizable, template-free route toward the 2D integration of non-layered III–V semiconductors and underscores the viability of 2D InP as a high-performance platform for ultrathin optoelectronics and quantum-confined devices.