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Photodoping as a nonvolatile and reversible method can be used to modify the carrier distribution at the heterojunction interface. Herein, we explore the 2D/3D van der Waals (vdW) graphene/silicon (G/Si) heterostructure in real time by terahertz (THz) emission spectroscopy. Photoinduced doping is introduced by a continuous wave laser, which leads to a screening effect to the built-in electric field at the interface. The resulting decrease in transient photocurrent reduces the THz emission amplitude from the G/Si heterostructure. The photoinduced doping effect suggests a 40% THz intrinsic modulation depth at external reverse bias. This work provides an effective way to actively control the THz emission process from the G/Si interface and paves the way for analyzing the interfacial process under photoinduced doping in vdW heterostructures. [ABSTRACT FROM AUTHOR]

Abstract: This work focuses on the optimization of the rheological properties of silicon suspensions by changing the concentration of a dispersant and the pH value of the dispersing medium. The zeta potential and rheological properties of silicon suspensions as a function of tetramethyl ammonium hydroxide (TMAH) concentration were carried out. The results show that the isoelectric point of the silicon particles was at pH 1.6. A silicon suspension with 46 vol.% particles displayed a minimum viscosity at pH 9.6. The results also show that TMAH is an efficient dispersant by enhancing the absolute value of the zeta potential of silicon particles. The optimum dosage of the dispersant was 0.4 wt.% of silicon particles. [Copyright &y& Elsevier]

Abstract: Pure aluminum matrix composite reinforced with a high volume fraction of silicon particles (Al/Sip) was fabricated by gas-pressured infiltration. The results of four point flexural strength tests show that Al/Sip has low flexural strength. The analysis of the fractograph reveals the fracture mechanism of Al/Sip. The fracture of Al/Sip is primarily dominated by the fracture of brittle silicon particles and the subsequent link up of damage through the matrix. The pre-existent microcracks in silicon particles that were made during the process of compacting will also lower the flexural strength of Al/Sip composite. The hybrid particle reinforced pure aluminum matrix composite (Al/Sip+SiCp) was fabricated in the same way. Results show the flexural strength can be improved by 11.3% compared with Al/Sip when 6 vol.% silicon particles are replaced by silicon carbide particles with the same volume fraction and size. The reason is that SiCp with higher fracture stress and higher elastic modulus can prevent the rapid expansion of cracks through the composite and lower the stress in silicon particles. [Copyright &y& Elsevier]