The PASiNP arrays show excellent antireflection property and give a low reflection loss of 2.84% within the wavelength range of 200 1,000 nm.
At the thickness of 2.2 mm, a relative low reflection loss (−17 GHz) corresponding to the frequency of 13.6 GHz was obtained.
For the other ARCs, the Si3N4/MgF2 DLARC shows the low reflection loss ~10% for the long wavelengths 700 nm and high reflection loss > 20% for shorter wavelengths 400 nm, lower than that of individual Si3N4 or MgF2 SLARC [27].
The typical sub-wavelength structure of PASiNP arrays had excellent antireflection property with a low reflection loss of 2.84% for incident light within the wavelength range of 200 1,000 nm.
SiNWs arrays also show comparatively low reflection losses than planner semiconductor [14] which definitely leads to higher absorption also.
Silicon nanowire arrays also show comparatively low reflection losses than planner semiconductor [14] which definitely leads to higher absorption also.
The PASiNP structure remarkably reduces the reflection of Si surface and demonstrates a low average reflection loss of ~2.84% (solid line in Fig. 3) within the same wavelength range, which is far lower than that of pristine Si wafer and previously developed Si micro-/nanostructures, as well as other ARCs [7, 8, 20, 24 27].
At the optimum thickness of the composite layers, a low value of reflection loss (less than −10 dB) has been predicted for wide incidence angles up to 60° for both TE and TM polarization, which is well consistent with the reflected power measured by free-space arch test.
Relative high filling ratio and poor reflection loss performance in low frequency are two major challenges in promoting microwave response of current carbon material which could be overcome by rational structure engineering.
As an example of the 2.96 mm thickness sample, the rock-bottom on the reflection loss curve was low to −58.1 dB at 12.4 GHz and the bandwidth below −10.0 dB could be as wide as 6.2 GHz, which was remarkable superior to those of the pure graphite oxide as well as other hybrids of graphene oxide that had ever been reported.
