Robust Thermal Transport across the Surface-Active Bonding SiC-on-SiC.

Surface-active bonding (SAB) is a promising technique for semiconductors directly bonding. However, the interlayer of the bonding interface and the reduced layer thickness may affect thermal transport. In this study, the temperature-dependent cross-plane thermal conductivity of 4H-SiC thin films and the effective thermal boundary resistance (TBReff) of the bonding SiC-on-SiC are measured by the multiple-probe wavelength nanosecond transient thermoreflectance (MW-TTR). The measured temperature-dependent cross-plane thermal conductivity of the 4H-SiC thin film exhibits good quantitative agreement with calculation by density functional theory (DFT) including higher-order four-phonon (4ph) scattering, especially at high temperatures (>400 K). The theoretical calculations indicate the non-negligible importance of 4ph scattering in 4H-SiC high-temperature applications, due to the significantly increasing 4ph scattering rate at increasing temperature and strong temperature dependence of 4ph scattering. The measured nonzero but small TBReff (2.33 + 0.43/-1.15 m2 K/GW) at the SiC-SiC interface is analyzed with molecular dynamics (MD) simulation, indicating that a strong bonding interface with an extremely thin interlayer is formed by the SAB process. Two-dimensional finite element simulations of the experimental equivalent structures are further investigated, and the significant effects (at least 19 °C) of TBReff on the maximum temperature (Tmax) are confirmed. This study provides insight into the fundamental phonon transport and interface thermal transport mechanism in SAB SiC-on-SiC and paves the way for improved 4H-SiC efficient device manufacturing and thermal management.

Controlled synthesis of sodium alginate electrospun nanofiber membranes for multi-occasion adsorption and separation of methylene blue.

Herein, the three kinds of water-insoluble alginate-based nanofiber membranes were prepared by electrospinning and followed with crosslinking by calcium chloride (CaCl2), glutaraldehyde vapor (GA), and trifluoroacetic acid (TFA) crosslinking, respectively. All the sodium alginate(SA) nanofiber membranes present excellent integrated adsorption performance toward methylene blue (MB). Among these, CaCl2 crosslinked SA membranes exhibit the maximum actual adsorption capacity of 2230 mg/g and shortest adsorption equilibrium time of 50 min to date. On the basis of the selective adsorption of SA, the nanofiber membranes can separate MB/ methyl orange (MO) mixture solution and maintain high separation efficiency even after five cycles. In addition, respective applicable condition for differentially crosslinked SA nanofiber membranes was evaluated. The TFA crosslinked membranes have the least reduction in the adsorption capacity in acidic environment and GA crosslinked membranes adsorb better in alkaline environment. For seawater environment, GA crosslinked membranes show obvious adsorption performance than other crosslinked membranes.