Antireflective coating properties

Optical Properties. The addition of lanthanum oxide to PZT has a rather remarkable effect on the optical transparency, especially when the amount of lanthanum exceeds seven atom percent. Thin polished plates characteristically transmit about 67% of the incident light. When broadband antireflection coatings are applied to the major surfaces, this transmission is increased to greater than 98%. Surface reflection losses are a function of the index of refraction (n = 2.5) of the PLZT. 

In Chapter 9 properties of antireflection coatings were examined. At that time the simplified case of a single film separating air and a substrate was considered. Here the discussion is on how such a film might be produced. Acmal films, such as the anti-reflective coatings on the lenses found in eyeglasses, contain multiple layers plus a protective coating. 

In general, polyimides exhibit a high refractive index typically between 1.6 and 1.7 and hence can be of definite practical interest particularly as antireflection coatings. Also, similar to parylene thin films, polyimides exhibit anisotropic optical properties. The reported values of refractive index of polyimides were n = 1.653 and n = 1.624 before curing and... 

LB coatings may be modified, for example, when an LB-coated substrate is soaked in a suitable solvent such as acetone, alcohol or benzene, and the multilayer is skeletonized due to the dissolving out of the free fatty acid, reducing its actual thickness slightly, but decreasing the refractive index appreciably. This property is used to control the refractive index to produce antireflection coatings for glass. The holes in these skeletonized films can also be filled with other materials in vapor or liquid form. 

There are basically two ways to achieve high visual transmittance simultaneously with high infrared reflectance. One is the use of the interference effect in all-dielectric multilayers, the other is the use of intrinsic optical properties of electrically conducting films such as Au, Ag, and others which have high infrared reflection with relatively low visual absorption. Their suitability as transparent heat mirror can be improved by antireflection coating for the visible. Figure 25 shows an example for such types of heat mirrors, according to Fan et al. [102]. 

The performance metrics used to judge the quality of a given antireflection coating include optical parameters (n and k), plasma etch rate, coating properties (whether highly planarizing or somewhat conformal), reflectivity, thickness, and compatibility with the given resist to which it is paired. 

Figure 9.17 Reflectance of TE, TM, and average TE-TM polarization states obtained on optimized multilayer BARC at NA 1.2 and under (a) normal incidence and (b) full angular incidence 0-45 deg. (c) Thickness and optical properties (n and k) values of film stack used in the simulation of (b). The thickness and n and k values of the antireflection coating used in (a) are 35 nm, 1.70, and 0.20, respectively. (Courtesy of B.W. Smith.)...

The general approach used to make a dielectric mirror is to lay down a stack of thin films that have alternately higher and lower refractive indices. Manipulation of the thickness and the refractive index of each layer in the stack allows the optical properties to be modified at will to produce virtually perfect mirrors and virtually perfect antireflection coatings - both of which can be mned to respond to very specific wavelengths - as well as a variety of optical filters. The fabrication of such devices falls... 

For the development of cheap solar cells, layers of a heavily doped semicon-dnctor like ITO, which may act as a barrier-forming semiconductor, a wide band gap window, and an antireflection coating in the heterostructure [1, 24], attract particular interest. It was shown [25] that the application of vacuumless technologies such as pyrolysis in air for the production of the above-mentioned layers can substantially influence the properties of interfacial layers. The IR spectra of 10283-SiOj -Si heterostructures in solar cells were studied. The 10383 films were produced by thermal decomposition of a complex of the general form L3ln (where L is a ligand). Thermal decomposition of this compound on a heated Si substrate (T = 230-270°C) produces a film of indium sulfide with good adhesion... 

Vinod PN (2009) Specific contact resistance and carrier tuimeling properties of the silver metal/ porous silicon/p-Si ohmic contact structure. J Alloys Compd 470 393-396 Vinod PN (2013) The fire-through processed screen-printed Ag thick film metal contacts formed on an electrochemically etched porous silicon antireflection coating of silicon solar cells. RSC Adv 3 3618-3622... 

Ben Rabna M, Salem M, El Khakani MA, Bessais B, Gaadi M (2013) Monocrystalline silicon surface passivation by Al203/porous silicon combined treatment. Mat Sci Eng B 178 695-697 Bilyalov R, Stabnans L, Schirone L, Levy-Clement C (1999) Use of porous silicon antireflection coating in multicrystalline silicon solar cell processing. IEEE Trans Electron Dev 46 2035-2040 Canham L (ed) (1997) Properties of porous silicon. lEE-Inspec, London... 

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