C3Al: A tunable bandgap semiconductor with high electron mobility and negative Poisson's ratio

Two-dimensional materials with suitable band gaps and high carrier mobility are considered to be ideal for fabricating next-generation microelectronics devices. In this paper, the C3Al crystal structure, electronic and mechanical properties are systematically investigated based on a first-principles method. We find that C3Al is an auxetic semiconductor material with wide band gap and high carrier mobility. Electrons have good transport properties but holes are almost completely scattered in the zigzag direction. C3Al is one of the few materials with negative Poisson's ratio effect. In addition, the electronic properties of C3Al can transform from semiconductor to metal by tuning straining and stacking. The bare-edge and H-terminated C3Al nanoribbons shows an enriched set of electronic properties of semiconductors, half-semiconductor, bipolar magnetic semiconductors, non-magnetic metals, magnetic metals, and half-metals. These results not only provide a theoretically novel and promising crystal configuration, but also further explore the potential of the material for applications in biosensing, strain sensors, transistors, and various nano-optical devices.