Engineering thermal transport within Si thin films: The impact of nanoslot alignment and ion implantation

In recent years, nanoporous Si films have been intensively studied for their poten-tial applications in thermoelectrics and the thermal management of devices. To minimize the thermal conductivity, ultrafine nanoporous patterns are required but the smallest structure size is largely limited by the spatial resolution of the employed nanofabrication techniques. Along this line, an effectively smaller char-acteristic length of a nanoporous film can be achieved with offset nanoslot pat-terns. Compared with periodic circular pores, the nanoslot pattern can achieve an even lower thermal conductivity, where a much smaller porosity is required using ultra-narrow nanoslots. The obtained low thermal conductivity can be understood from the thermally dead volume revealed by phonon Monte Carlo simulations. To further minimize the contribution from short-wavelength pho-nons, an additional 25% thermal conductivity reduction can be achieved with Ga ions implanted using a focused ion beam.

Automated summary

Nanoporous Si films have potential applications in thermoelectrics and thermal management of devices. Offset nanoslot patterns achieve smaller characteristic lengths and lower thermal conductivity compared to periodic circular pores. Additional reduction in thermal conductivity can be achieved by implanting Ga ions.