Search

Soon after realizing superbly important properties of few layer graphene and its derivatives, other layered materials have also received a great deal of interest in recent times, owing to their finite band gaps and layer-dependent optoelectronic responses. In this review, we discuss a variety of two-dimensional (2D) materials, highlighting fabrication routes already in practice and their technological relevance in a particular field, including photocatalysis, hydrogen evolution, sensing, actuation, and biomedical applications. Basically, layered materials processed via two widely accepted bottom-up and top-down approaches have been revisited. Because of large surface area, active reactive sites, tunable band gap etc., 2D systems are believed to deliberate their key performance in smart devices, from excellent electrodes to energy efficient candidates and from color switchable elements to high-precision biosensors. Given the importance of quality, reliability, and product cost realized in any commercial product, there exists ample scope to expand this frontier field of research for the benefit of society at large.

We report on the highly symmetric excitonic emission, manifested Raman active modes, and electrical properties of WSe2 and WS2 nanoflakes subjected to energetic β-particles. Raman spectra have revealed numerous mixed modes and a declining trend of the E12g-to-A1g intensity ratio with radiation dose (0–4.8 kGy). The nanoscale WSe2 exhibits a remarkable luminescence peak, located at ~ 675 nm and characterized by a combinatorial effect of both 2s and 2p excitons, whereas the nanoflakes of WS2 offered a testimony to charged excitons (trions) in the range ~ 624–630 nm. Moreover, a moderate (from ~ 2.29 to ~ 2.88 ns) and a nearly sevenfold enhancement in the slow life-time decay parameters have been observed for the irradiated WSe2 and WS2 nanoflakes, respectively. Furthermore, the rectifying nature of the I–V trends suggests formation of metal–semiconductor nanojunctions with transport characteristics described by parameters such as ideality factor (η) and barrier height (φb), both of which gave a declining trend with increasing β-dose. As substantiated by transport characteristics and first principle calculations, a semi-metallic behavior of WSe2 was also realized due to the introduction of excessive chalcogen defects at the highest radiation dose. The results would strengthen our insights prior to their deployment in next-generation nanodevices integrating nano-electronics and nano-photonics at large.

The effect of 80 keV Xe+ ion irradiation on the Raman spectra and electrical conductivity of 10B pencil-lead graphitic systems is being reported. The creation of localized nanoscale defects and a nearly five-fold improvement in the root mean square (RMS) roughness have been ascertained through atomic force microscopy (AFM) imaging studies. The introduction of defects is also substantiated by the appearance of the ∼1360 cm−1 peak (D-mode) along with the fundamental G-band (∼1600 cm−1) in the Raman spectra. With increasing fluence, the D-to-G band intensity ratio offered an increasing trend up to ∼0.44. Moreover, I–V characteristics indicated a significant drop in the conductivity of the irradiated graphitic systems. We ascribe it to substantial lowering of the mobility of the electrons owing to enhanced carrier-defect scattering events occurring in the irradiated systems. Mediated by defects introduced, a clear connection between the Raman characteristics and carrier transport phenomena is established.