Moth Eyes

Kim Y.-C. and Do Y.R., Nanohole-templated organic light-emitting diodes fabricated using laser-interfering lithography moth-eye lighting. Opt Exp. 13 (2005) 1598... 

Ideally, the surface of the transparent cover should have a gradient of the index of refraction ranging from 1.0 for air to the index of refraction of the cover material. For the required very small indices of refraction no materials exist in nature. Such small indices of refraction can only be made by effective media in which the cover material is mixed with air on a subwavelength scale as described in Sect. 1. Subwavelength surface-relief structures with a continuous profile as shown in Fig. 2 form an effective refractive index gradient and are therefore well suited for broadband AR surfaces. This type of AR surface-relief grating is called a moth-eye structure according to the example found in nature on the cornea of... 

Fig. 2 SEM picture of an artificial moth-eye structure originated in photoresist...

However, the arrangements of the natural world have been utilizing its optical behaviours with skills far beyond human intelligence. One T)f them is known as Moth Eye Principle and the eyes of a moth, flying in the air toward evening, have characteristic concave and convex structure. 

Until now, fabrication of moth eye inspired nanostructures was quite costly and it was hard to make a large area sample, fri this point of view, phase shift lithography is a very promising method to fabricate it. The required pattern size is well matched with critical dimensicm of phase shift lithography and continuous fahricaticHi on... 

Phase-Shift Lithography, Fig. 8 SEM images of moth eye (a) and moth eye inspired nanostructures (b). (a) from dartmouth college and (b) from Nanotechweb.org... 

Figure 18.19 Schematic of the WLP setup, showing two moth-eye textures A and B, the stmctured Ti getter area C and the poly-Si distance frame D, metallized with AuSn for eutectic bonding.

The Moth-Eye Efifect — From Fundamentals to Commercial Exploitation... 

Fig. 1. SEM picture of natural moth-eye structures (flour moth, Ephestia kuehniella). Fraunhofer ISE.

Fig. 2. SEM picture of an artificial moth-eye structure made at Fraunhofer ISE and illustration of the graded refractive index. The periods of the crossed grating are 250 nm each. Fraunhofer ISE.

Fig. 3. Image of a flat-panel display with standard anti-glare surface (left side) and combined moth-eye anti-reflective and anti-glare (MARAG ) surface (right side). On the flat-panel display, the head of a flour moth (SEM image) is shown. MacDermid Autotype.

For applications in which an AR solution is required only for visible wavelengths, moth-eye sttuctures compete with intetference coatings. In most existing application cases, the lower cost of moth-eye structures is the reason to use them although they... 

Fig. 13. SEM pictures of an MARAG structure in photoresist at two different magnifications. The smooth undulation necessary for a good anti-glare effea can he seen in the left picture in which the white rectangle indicates the location of the right piaure. At the 22 times larger magnification of the right picture, the moth-eye structures can he made visible. Fraunhofer ISE.

Clapham PB, HutleyMC. (1973) Reduaionof lens reflection by the moth eye principle. Nature (London) 244 281-282. 

---