Fabrication of the vertically aligned SiNW arrays for the nanosecond thermoreflectance measurements. (a,e) SiNW arrays are formed using the top-down etching. (b,f) Parylene is conformally deposited in between NWs and acts as a mechanical scaffold for the top metal transducer layer. (c,g) The SiNW tips are exposed by chemical mechanical polishing to ensure good thermal contact between the SiNWs and the metal film, and (d,h) a metal film is deposited over the SiNW array. The scale bars on the SEM images are 5 μm.