Ultralow reflectance induced by nanowire array on polycrystalline diamond

Nanostructured blackbodies have a wide application in the fields of light control, energy harvesting and desalination, benefiting from their efficient absorption and radiation on rays with specific wavelength. However, present blackbody materials often suffer deficiencies in stability and mechanical strength. Diamond is an ideal material for blackbody application owing to its excellent stability and corrosion resistance. In this paper, a highdensity nanowire array was fabricated on polycrystalline diamond substrate by two-step etching, including hydrogen/oxygen plasma etching and inductively coupled plasma etching. The diamond nanowires have a length of several micrometers and a diameter of about 52 nm. The reflectance spectra verified that the diamond nanowire array has an ultralow average reflectance of 0.7 % within the 500-2000 nm range, demonstrating a reflection reduction by 2530 % compared to the original polycrystalline diamond. The lowest reflectance of 0.5 % was achieved at a wavelength of 1796 nm.