The defects into the hexagonal network of a sp²-hybridized carbon atom have been demonstrated to have a significant influence on intrinsic properties of graphene systems. In this paper, we presented a study of temperature-dependent Raman spectra of G peak and D’ band at low temperatures from 78 to 318 K in defective monolayer to few-layer graphene induced by ion C+ bombardment under the determination of vacancy uniformity. Defects lead to the increase of the negative temperature coefficient of G peak, with a value almost identical to that of D’ band. However, the variation of frequency and linewidth of G peak with layer number is contrary to D’ band. It derives from the related electron-phonon interaction in G and D’ phonon in the disorder-induced Raman scattering process. Our results are helpful to understand the mechanism of temperature-dependent phonons in graphene-based materials and provide valuable information on thermal properties of defects for the application of graphene-based devices.

Application of 3D self-supported FeCoS ₂ @N-HCNF nanocomposites as potassium ion battery anodes.

Sb₂Se₃ has recently emerged as a promising material for optic-electronic applications. In this work, trapped carrier recombination in Sb₂Se₃ was investigated by joint use of time-resolved microwave conductivity (TRMC) and photoluminescence (PL) spectroscopy. trapped carrier thermal excitation into the continuous band was observed in TRMC kinetics. Based on the exponential band tail model, the depth of the trap state, where trapped carriers are released into a continuous band, was estimated to range from 33.0 meV to 110.0 meV at room temperature. Temperature-varying TRMC and PL were further employed to study the influence of temperature on the trapped carrier recombination. Negative thermal quenchings of PL intensity and quantity of thermal emission carriers were observed and can be well explained by the thermal excitation of deep trapped carriers into shallow trap states and the continuous band. Two thermal activation energies of 12.5 meV and 304.0 meV were also revealed. This work is helpful for understanding the trapped carrier recombination process in polycrystalline Sb₂Se₃ film.

MoS₂ and ReS₂ are typical transition metal chalcogenides with many excellent electrical and optical properties. Due to different lattice symmetries, ReS₂ offers one more dimension than MoS₂ to tune its physical properties. In this paper, we studied the polarized reflection spectra in single-layer MoS₂ and ReS₂. The explicit difference identifies strong angle-dependent properties in single-layer ReS₂ distinct from single-layer MoS₂. The results of samples on both SiO₂/Si substrate and quartz substrate show single-layer ReS₂ is in-plane anisotropic and the change period of reflection intensity is estimated with the polarization angles.