In recent years, the phenomenon of optical second harmonic generation (SHG) has attracted significant attention as a pivotal nonlinear optical effect in research. Notably, in low-dimensional materials (LDMs), SHG detection has become an instrumental tool for elucidating nonlinear optical properties due to their pronounced second-order susceptibility and distinct electronic structure. This review offers an exhaustive overview of the generation process and experimental configurations for SHG in such materials. It underscores the latest advancements in harnessing SHG as a sensitive probe for investigating the nonlinear optical attributes of these materials, with a particular focus on its pivotal role in unveiling electronic structures, bandgap characteristics, and crystal symmetry. By analyzing SHG signals, researchers can glean invaluable insights into the microscopic properties of these materials. Furthermore, this paper delves into the applications of optical SHG in imaging and time-resolved experiments. Finally, future directions and challenges toward the improvement in the NLO in LDMs are discussed to provide an outlook in this rapidly developing field, offering crucial perspectives for the design and optimization of pertinent devices.

The performance and reliability of silicon carbide (SiC) MOS devices are critically influenced by the quality of the SiC/SiO ₂ interface. Defects such as interface state density (Dit), near interface traps (NITs), and effective fixed charges (N _eff ) degrade electrical performance by limiting carrier mobility and causing instability. This study investigates post-deposition annealing (PDA) in N2, O ₂ , Ar and vacuum atmospheres using electrical characterization (C-V measurements) and physical-chemical analysis (SIMS, XPS). Results reveal a graded interfacial transition region with two co-existing defect domains: a carbon-dominated zone (containing SiO _x C _y and C clusters) and a silicon-rich zone (with Si interstitials and suboxides). Reactive anneals (N ₂ , O ₂ ) effects chemical passivation of carbon-related defects, thereby leading to a reduction in the Dit and NITs, among which N ₂ exhibits the highest efficacy. Inert Ar annealing induces thermal restructuring of the silicon-rich region, reducing in a decrease in both its thickness and Si concentration, thereby lowering Neff. Vacuum annealing, by contrast, yields only marginal improvement. N ₂ PDA emerges as the optimal strategy, synergistically combining chemical passivation and thermal restructuring to simultaneously minimize Dit, NITs, and N _eff . This work establishes a spatially targeted framework for interface reconstruction, providing critical insights for developing high-performance SiC power devices.