Abstract
In this paper, we show the broadband antireflection property of radio frequency sputter-grown zinc tin oxide (ZTO) thin films grown on ion-beam fabricated self-organized nanoscale rippled- (R-Si) and faceted-Si (F-Si) substrates. For the sake of comparison, ZTO film has been deposited simultaneously on pristine-Si (P-Si) substrate as well. X-ray diffraction studies show the amorphous nature of the films. Atomic force microscopic studies reveal the conformal growth of ZTO thin films (granular in nature) on both R- and F-Si substrates (up to 60 nm). Surface reflectance measurements show a large reduction in the average broadband (300–800 nm) surface reflectance (at 550 nm) from 43.9% for P-Si substrate to 42% and 32% for R-Si and F-Si substrate, respectively. In addition, we show a further reduction in the surface reflectance following the growth of ZTO overlayers (in the range of 15–60 nm) on P-Si, R-Si, and F-Si substrates. As a matter of fact, there is a continuous reduction in surface reflectance up to a thickness of 60 nm, beyond which the reflectance minimum starts increasing. The large reduction in the surface reflectance of ZTO coated P-, R-, and F-Si substrates are attributed to the graded refractive index of the heterostructures driven by the surface morphology of the substrates and the different average surface heights of the films. This study will be very useful for efficient ZTO-based optoelectronic devices and heterojunction solar cell applications.
Published Version
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