Silicon Nanosheets: A Promising 2D Material with Strong Ultrafast Nonlinear Optical Response

The ultrafast third-order nonlinear optical (NLO) response of hydride-terminated silicon nanosheets (SiNS-H), the so-called silicane, along with a silicane derivative, namely, 1-dodecene-functionalized silicon nanosheets (SiNS-C12H25 or SiNS-dodecene), is investigated under 50 fs, 800 nm laser pulses. Silicane, the freestanding H-terminated form of silicene, gains more stability through functionalization. The chemical modification of H-terminated silicon nanosheets with 1-dodecene resulted in substantial enhancement of the NLO response, while it gave rise to a very strong enhancement of the nonlinear absorption of silicane, the latter exhibiting negligible nonlinear absorption prior to its functionalization. Finally, the NLO response of the investigated SiNSs is compared to that of single- (SLG) and few-layered (FLG) graphene nanosheets, all measured under the same experimental conditions. Furthermore, the NLO response of these SiNSs is compared to some other recently synthesized two-dimensional (2D) materials, such as some molybdenum dichalcogenides, MoX2(X = S, Se, Te), a layered transition-metal dichalcogenide (e.g., NbS2), and titanium carbideTi3C2Tx monolayers. The present results demonstrate the great potential of these silicon-based 2D materials, for several photonic and optoelectronic applications.