The refractive index data was fitted using parameters

from [24, 25] for a-Si, from [26] for AZO, and from [27] for GZO, see Table 1. Only the latter one has a significant free charge carrier concentration according to the parameters used here, which leads to a pronounced plasmon resonance; the dielectric function of a-Si and AZO is simply characterized by the band gap and the constant refractive index at longer wavelengths, see also Figure 1b,c,d. Figure 5 compares the scattering efficiencies for spherical nanoparticles (in air) from the three semiconductors which are characterized by a band gap around 800 nm (for a-Si) and 400 nm (for AZO and GZO). NU7441 clinical trial For wavelengths below the band gap (i.e., in terms of energy above), the absorption is dominant, and thus scattering can only be exploited for wavelengths well beyond the band gap. Since LY294002 this is the case above 1,000 nm only for the a-Si nanoparticles, they cannot be expected to perform well in a device operating in the visible wavelength range. The band gap has to be chosen as low (in wavelengths, but high in energy) as possible. For AZO, the scattering efficiency is 1 for wavelengths larger than the band gap at around 400 nm making it comparable to a dielectric. This is not surprising since low-doped

semiconducting materials far away from a specific resonance will show dielectric-like behavior. Comparing a dielectric nanoparticle to one made of a low-doped semiconductor, the latter loses in terms of scattering efficiency since it shows parasitic absorption below the band gap. Figure 5 Maps of scattering efficiency for semiconductor nanoparticles. Spherical particle made from (a) a-Si, (b) AZO, and (c) GZO with refractive indices fitted with parameters from [24, 25], [26], and [27], respectively (note the different wavelength range

in (c)). For the highly doped semiconductor, the situation is slightly different. Also here, parasitic absorption dominates for wavelengths below the band gap. But additionally, the free charge carriers of the highly doped semiconductor lead to CUDC-907 further parasitic absorption new in the wavelength range where they become dominant, compare Figure 5c (and also see the Additional file 3: Figure S3 for the individual absorption and scattering cross sections). Yet, they also give rise to a plasmonic resonance since the according requirements for the refractive index (∈ 1 = −2) can be fulfilled. For GZO, the conditions are met at λ approximately 2,000 nm so that a further resonance occurs here. This peak can be attributed to the dipole electric mode as shown in Figure 6 where the sum of the scattering cross section for an r = 170 nm GZO nanoparticle is depicted together with the different order electric and magnetic modes.