RESUMO
On-going prediction and synthesis of two-dimensional materials attract remarkable attention to engineer high performance intended devices. Through this, comprehensive and detailed uncovering of the material properties could be accelerated to achieve this goal. Hexagonal boron arsenide (h-BAs), a graphene counterpart, is among the most attractive 2D semiconductors. In this work, our objective is to explore the mechanical, electronic, and thermal properties of h-BAs. We found that this novel 2D material can show a high elastic modulus of 260 GPa, which is independent of the loading direction. We also observed that this system shows a direct and narrow band-gap of 1.0 eV, which is highly desirable for electronic applications. The focus of our investigation is to gain an in-depth understanding of the thermal transport along the monolayer h-BAs and further tune the thermal conductivity by strain engineering. In this regard, the thermal conductivity of a stress-free and pristine monolayer was predicted to be 180.2 W m-1 K-1, which can be substantially enhanced to 375.0 W m-1 K-1 and 406.2 W m-1 K-1, with only 3% straining along the armchair and zigzag directions, respectively. The underlying mechanism for such a remarkable boosting of thermal conductivity in h-BAs was correlated to the fact that stretching makes the flexural out-of-plane mode the dominant heat carrier. Our results not only improve the understanding concerning the heat transfer in h-BAs nanosheets but also offer possible new routes to drastically improve the thermal conductivity, which can play critical roles in thermal management systems.
RESUMO
Regarding the spin field effect transistor (spin FET) challenges such as mismatch effect in spin injection and insufficient spin life time, we propose a silicene based device which can be a promising candidate to overcome some of those problems. Using non-equilibrium Green's function method, we investigate the spin-dependent conductance in a zigzag silicene nanoribbon connected to two magnetized leads which are supposed to be either in parallel or anti-parallel configurations. For both configurations, a controllable spin current can be obtained when the Rashba effect is present; thus, we can have a spin filter device. In addition, for anti-parallel configuration, in the absence of Rashba effect, there is an intrinsic energy gap in the system (OFF-state); while, in the presence of Rashba effect, electrons with flipped spin can pass through the channel and make the ON-state. The current voltage (I-V) characteristics which can be tuned by changing the gate voltage or Rashba strength, are studied. More importantly, reducing the mismatch conductivity as well as energy consumption make the silicene based spin FET more efficient relative to the spin FET based on two-dimensional electron gas proposed by Datta and Das. Also, we show that, at the same conditions, the current and [Formula: see text] ratio of silicene based spin FET are significantly greater than that of the graphene based one.
