The discovery of ferromagnetism in van der Waals (vdW) materials has enriched the understanding of two-dimensional (2D) magnetic orders and opened new avenues for fundamental physics research and next generation spintronics. However, achieving ferromagnetic order at room temperature, along with strong perpendicular magnetic anisotropy, remains a significant challenge. In this work, we report wafer-scale growth of vdW ferromagnet Fe₃GaTe₂ using molecular beam epitaxy. The epitaxial Fe₃GaTe₂ films exhibit robust ferromagnetism, exemplified by high Curie temperature (T_C = 420 K) and large perpendicular magnetic anisotropy (PMA) constant K_U = 6.7 × 10⁵J/m³ at 300 K for nine-unit-cell film. Notably, the ferromagnetic order is preserved even in the one-unit-cell film with T_C reaching 345 K, benefiting from the strong PMA (K_U = 1.8×10⁵J/m³ at 300 K). In comparison to exfoliated Fe₃GaTe₂ flakes, our epitaxial films with the same thickness show the significant enhancement of T_C, which could be ascribed to the tensile strain effect from the substrate. The successful realization of wafer-scale ferromagnetic Fe₃GaTe₂ films with T_C far above room temperature represents a substantial advancement (in some aspects or some fields, e.g. material science), paving the way for the development of 2D magnet-based spintronic devices.

Time resolved photoluminescence (TRPL) and transient absorption (TA) spectroscopy reveal an ultrafast charge transfer (CT) process, with an electron localization time constant $39\pm 9\text{ps}$ , between the ZnO host and the Cu dopants in Cu-doped ZnO nanowires. This CT process effectively competes with the ZnO band edge emission, resulting in the quenching of the ZnO UV emission. TRPL measurements show that the UV decay dynamics coincides with the buildup of the Cu-related green emission. TA measurements probing the state-filling of the band edge and defect states provide further support to the CT model where the bleaching dynamics concur with the TRPL lifetimes.

We carried out the phase selective preparations of hollow spheres of ccp- and hcp-Co, Co₃O₄, α-Fe, Fe₃O₄ and α-Fe₂O₃ with a diameter of ca. 600 nm and a shell thickness of 40 nm, using polystyrene (PS)-bead templates. The 600 nm PS beads were uniformly coated with cobalt or iron hydroxides by means of a homogeneous precipitation method. These cobalt-salt/PS hybrid particles were calcined in air at 400 °C and were transformed into Co₃O₄ hollow spheres. The hcp-Co hollow spheres were obtained by a reduction reaction of the Co₃O₄ particles under a stream of a 1 ∶ 1 mixed gas of H₂ and N₂ at 400 °C; in contrast, the ccp-Co hollow spheres were obtained by the calcination of the parent cobalt-salt/PS particles under H₂–N₂ at 400 °C. Hollow spheres of Fe₃O₄ and α-Fe₂O₃ were selectively prepared by calcination of iron-salt/PS particles at 400–500 °C in two different atmospheres, namely under H₂–N₂ and in air, respectively. Furthermore, the α-Fe₂O₃ particles were reduced into α-Fe under H₂–N₂ at 350 °C without any changes in morphology. These spheres were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) analyses. Magnetic measurements revealed a significant temperature dependence of the coercive field for the Fe₃O₄ (magnetite) particles, whereas the magnetic properties of the other particles were generally similar to those of the corresponding bulk samples. Surface chemical modifications were carried out on the Fe₃O₄ hollow spheres; the surfaces were grafted with poly(4-N-methylvinylpyridinium) brushes. This treatment was found to induce good dispersibility in water.

We investigate the optical property of bent ZnO nanowires (NWs) obtained by low energy argon ion milling. At room temperature, the bent NWs demonstrates an enhanced near band edge ultraviolet emission, while the deep level green emission is totally suppressed. Temperature dependent photoluminescence measurements were carried out between 10 and 300 K for both the as-grown and the bent ZnO NWs. It is found that the emission peak energy of the bent NWs systematically shifts to lower energy compared to the as-grown NWs in the whole measured temperature range. Our results indicate that the redshift in the emission peak is related to the uniaxial tensile strain and the enhanced exciton–phonon coupling strength in the bent ZnO NWs.