ABSTRACT
Epitaxial growth stands as a key method for integrating semiconductors into heterostructures, offering a potent avenue to explore the electronic and optoelectronic characteristics of cutting-edge materials, such as transition metal dichalcogenide (TMD) and perovskites. Nevertheless, the layer-by-layer growth atop TMD materials confronts a substantial energy barrier, impeding the adsorption and nucleation of perovskite atoms on the 2D surface. Here, we epitaxially grown an inorganic lead-free perovskite on TMD and formed van der Waals (vdW) heterojunctions. Our work employs a monomolecular membrane-assisted growth strategy that reduces the contact angle and simultaneously diminishing the energy barrier for Cs3Sb2Br9 surface nucleation. By controlling the nucleation temperature, we achieved a reduction in the thickness of the Cs3Sb2Br9 epitaxial layer from 30 to approximately 4 nm. In the realm of inorganic lead-free perovskite and TMD heterojunctions, we observed long-lived interlayer exciton of 9.9 ns, approximately 36 times longer than the intralayer exciton lifetime, which benefited from the excellent interlayer coupling brought by direct epitaxial growth. Our research introduces a monomolecular membrane-assisted growth strategy that expands the diversity of materials attainable through vdW epitaxial growth, potentially contributing to future applications in optoelectronics involving heterojunctions.
ABSTRACT
The objective of this research was to develop highly effective conductive polymer composite (CPC) materials for flexible piezoresistive sensors, utilizing hollow three-dimensional graphitic shells as a highly conductive particulate component. Polystyrene (PS), a cost-effective and robust polymer widely used in various applications such as household appliances, electronics, automotive parts, packaging, and thermal insulation materials, was chosen as the polymer matrix. The hollow spherical three-dimensional graphitic shells (GS) were synthesized through chemical vapor deposition (CVD) with magnesium oxide (MgO) nanoparticles serving as a support, which was removed post-synthesis and employed as the conductive filler. Commercial multi-walled carbon nanotubes (CNTs) were used as a reference one-dimensional graphene material. The main focus of this study was to investigate the impact of the GS on the piezoresistive response of carbon/polymer composite thin films. The distribution and arrangement of GS and CNTs in the polymer matrix were analyzed using techniques such as X-ray diffraction and scanning electron microscopy, while the electrical, thermal, and mechanical properties of the composites were also evaluated. The results revealed that the PS composite films filled with GS exhibited a more pronounced piezoresistive response as compared to the CNT-based composites, despite their lower mechanical and thermal performance.