Cadmium selenide (CdSe) thin films were deposited on indium tin oxide (ITO) coated glass substrates using pulsed laser deposition (PLD) technique under different growth temperatures. Samples were investigated for their structural, morphological, and optical properties through X-ray diffraction (XRD), atomic force microscopy (AFM), and UV-Vis-NIR spectroscopy. AFM analysis revealed that the surface roughness of the as-grown CdSe thin films increased with the increase in deposition temperature. The optical constants and film thickness were obtained from spectroscopic ellipsometry analysis and are discussed in detail. The optical band gap of the as-grown CdSe thin films, calculated from the Tauc plot analysis, matched with the ellipsometry measurements, with a band gap of ~1.71 eV for a growth temperature range of 150 °C to 400 °C. The CdSe thin films were found to have a refractive index of ~3.0 and extinction coefficient of ~1.0, making it a suitable candidate for photovoltaics.

Various types of 2D/2D prototype devices based on graphene (G) and boron nitride nanosheets (BNNS) were fabricated to study the charge tunneling phenomenon pertinent to vertical transistors for digital and high frequency electronics. Specifically, G/BNNS/metal, G/SiO₂, and G/BNNS/SiO₂ heterostructures were investigated under direct current (DC-bias) conditions at room temperature. Bilayer graphene and BNNS were grown separately and transferred subsequently onto the substrates to fabricate 2D device architectures. High-resolution transmission electron microscopy confirmed the bilayer graphene structure and few layer BNNS sheets having a hexagonal B₃-N₃ lattice. The current vs voltage I(V) data for the G/BNNS/Metal devices show Schottky barrier characteristics with very low forward voltage drop, Fowler-Nordheim behavior, and 10⁻⁴ Ω/sq. sheet resistance. This result is ascribed to the combination of fast electron transport within graphene grains and out-of-plane tunneling in BNNS that circumvents grain boundary resistance. A theoretical model based on electron tunneling is used to qualitatively describe the behavior of the 2D G/BNNS/metal devices.

Nitrogen-doped graphene quantum dots (NGQDs) have gained significant attention due to their various physical and chemical properties; however, there is a gap in the study of NGQDs’ magnetic properties. This work adds to the efforts of bridging the gap by demonstrating the room temperature paramagnetism in GQDs doped with Nitrogen up to 3.26 at.%. The focus of this experimental work was to confirm the paramagnetic behavior of metal free NGQDs resulting from the pyridinic N configuration in the GQDs host. Metal-free nitrogen-doped NGQDs were synthesized using glucose and liquid ammonia as precursors by microwave-assisted synthesis. This was followed by dialysis filtration. The morphology, optical, and magnetic properties of the synthesized NGQDs were characterized carefully through atomic force microscopy (AFM), transmission electron microscopy (TEM)), UV-VIS spectroscopy, fluorescence, X-ray photon spectroscopy (XPS), and vibrating sample magnetometer (VSM). The high-resolution TEM analysis of NGQDs showed that the NGQDs have a hexagonal crystalline structure with a lattice fringe of ~0.24 nm of (1120) graphene plane. The N1s peak using XPS was assigned to pyridinic, pyrrolic, graphitic, and oxygenated NGQDs. The magnetic study showed the room-temperature paramagnetic behavior of NGQDs with pyridinic N configuration, which was found to have a magnetization of 20.8 emu/g.

In this study, we experimentally demonstrate that the magnetic properties of nitrogen-doped graphene (NG) are influenced by the configuration of nitrogen dopants, namely graphitic, pyridinic, and pyrrolic, along with the overall nitrogen concentration. The NG materials were prepared via a two-step thermal treatment process. The first step involved heating in ammonia at 400 °C, followed by a second post-annealing step at 600 °C. Scanning Electron Microscopy–Energy Dispersive X-ray Spectroscopy (SEM–EDS) analysis performed at 25 μm resolution confirmed uniform elemental distribution across the samples. X-ray photoelectron spectroscopy (XPS) revealed that while the total nitrogen content decreased from 11.9 at.% in NG to 5.5 at.% in the post-annealed sample, the ratio of graphitic to pyrrolic nitrogen increased from 0.4% to 3.8% and the ratio of graphitic to pyridinic nitrogen increased from 0.8% to 2.5%. Raman spectroscopy confirmed the presence of prominent D and G bands at ~1352 cm⁻¹ and ~1589 cm⁻¹, respectively, along with a 2D band at ~2692 cm⁻¹, indicating the presence of few-layered graphene and defect-related features. The ${\displaystyle \frac{{\mathrm{I}}_{\mathrm{D}}}{{\mathrm{I}}_{\mathrm{G}}}}$ ratio increased from 1.12 to 1.27 in the post-annealed sample, indicating increased disorder after annealing. Magnetic characterization showed a marked enhancement in the magnetic properties with increased graphitic nitrogen content. The saturation magnetization (M_s) reached 0.13 emu g⁻¹, ~42% higher than that of the material heated in ammonia, with the coercivity increasing from 40 Oe to 750 Oe. These results emphasize the pivotal role of nitrogen configuration in the graphene host, specifically the promotion of graphitic nitrogen species, in tailoring the ferromagnetic response of NG.