Thermal process of a silicon wafer under a CW laser and 100-10000 Hz pulsed laser irradiation.

The thermal process of a (001) silicon wafer subjected to a continuous-wave (CW) laser and 100-10000 Hz pulsed laser irradiation is investigated experimentally and numerically. The temperature evolution of the spot center is measured using an infrared radiation pyrometer. The waveforms of the temperature evolution curves provide valuable information about melting, solidification, vaporization, and fracture. To gain a better understanding of the thermal process, a three-dimensional finite element model is established, and numerical simulations are conducted to analyze the temperature, stress, and dislocation field. The results show that the 10 kHz laser exhibits the highest heating efficiency before vaporization, but the lowest ablation efficiency after vaporization due to the shielding effect of vapor. The diffusion time of vapor is found to be more than 50 µs. Fracture occurs during 1 kHz laser irradiation. The motion of liquid may play a significant role, but it cannot be evidenced by a simulation due to complex dependence of material parameters on dislocation. This issue should be addressed as a priority in future studies.

Tunneling transport of 2D anisotropic XC (X = P, As, Sb, Bi) with a direct band gap and high mobility: a DFT coupled with NEGF study.

Direct bandgap and significant anisotropic properties are crucial and beneficial for nanoelectronic applications. In this work, through first-principles calculations, we investigate novel two-dimensional (2D) α-XC (X = P, As, Sb, Bi) materials, which possess a direct bandgap of 0.73 to 1.40 eV with remarkable anisotropic electronic properties. Intriguingly, 2D α-XC presents the highest electron mobility near 8 × 103 cm2 V-1 s-1 along the Γ-X direction. Moreover, the transfer characteristics of the 2D α-XC TFETs are thoroughly assessed through NEGF methods. AsC TFETs demonstrate an on-state current larger than 2.2 × 103 µA µm-1, which can satisfy the International Technology Roadmap for Semiconductors (ITRS) for high-performance requirements. In particular, the minimum value of subthreshold swing of devices is as low as 15 mV dec-1, indicating excellent device switching characteristics. The relevant calculation results show that 2D α-XC monolayers could be a promising candidate in next-generation high-performance device applications.

Synergistic effect of reduced graphene oxide/carbon nanotube hybrid papers on cross-plane thermal and mechanical properties.

Graphene paper has attracted great attention as a heat dissipation material due to its excellent thermal conductivity and mechanical properties. However, the thermal conductivity of graphene paper in the normal direction is relatively poor. In this work, the cross-plane thermal conductivities (K ⊥) and mechanical properties of the reduced graphene oxide/carbon nanotube papers with different CNT loadings were studied systematically. It was found that the K ⊥ decreased from 0.0393 W m-1 K-1 for 0 wt% paper to 0.0250 W m-1 K-1 for 3 wt% paper, and then increased to 0.1199 W m-1 K-1 for 20 wt% paper. The papers demonstrated a maximum elastic modulus of 6.1 GPa with 10 wt% CNT loading. The CNTs acted as scaffolds to restrain the graphene sheets from corrugating and to reinforce the mechanical properties of the hybrid papers. The more CNTs that filled the gaps between graphene sheets, the greater the number of channels of the transmission of phonons and the looser the structure in the cross-plane direction. Further mechanism analysis revealed the synergistic effects of CNT loadings and graphene sheets on enhancing the thermal and mechanical performance of the papers.