Coating anti-reflection

Diffusion barriers and anti-reflection coatings in integrated circuits. 

Optical coatings, anti-reflection coatings, and coatings for hot mirrors. 

Get the light into the detector. This may sound trivial, but unless a good anti-reflection coating is used, a significant fraction of the light will be reflected at the surface of the photosensitive material. 

Getting light into the detector anti-reflection coatings... 

In comparison to infrared detectors, it is much more difficult for silicon-based optical detectors to achieve high QE over a wide bandpass. The main challenge is the tremendous variation of absorption depth shown in Fig. 8. In addition, the index of refraction varies significantly for A = 0.32-1.1 m, as shown in Fig. 10, making it difficult to optimize anti-reflection coatings for broad bandpass. 

Figure 18. Transmission of crystalline quartz in the range beyond 20 microns. The A and C curves were obtained for anti-reflection coated samples and the B curve for...

In conclusion, it has been demonstrated that the manufacture of waveguides, Bragg reflectors, Fabry-Perot filters and anti-reflective coatings can be based on PS thin films. Such filters are applied for example in gas sensors, as described in the preceding section. 

Methods have been developed for fabrication of the highly-ordered titania nanotuhe arrays from titanium thin films atop a substrate compatible with photolithographic processing, notably silicon or FTO coated glass [104]. The resulting transparent nanotuhe array structure, illustrated in Fig. 5.16, is promising for applications such as anti-reflection coatings and dye sensitized solar cells (DSSCs). Fig. 5.17 shows the typical anodization behavior of a 400 nm Ti thin film anodized at 10 V in an HE based electrolyte. Eor a fixed HE concentration, the dimensions of the tube vary with respect to... 

The solid residue of ammonium chloride left after evaporation of the solvent water decomposes to gaseous HC1 and NH3 during the baking. Anti-reflective coatings (e.g., of alumina or titania) may also be applied by sol-gel methodology. 

Optics Issues relative to hygroscopic optics and the need to pay attention to mirror mounts relative to vibration and/or thermal effects have already been addressed. Zinc selenide is an important alternative material, especially when anti-reflection coated. If potassium bromide absolutely has to be used for its lower transmission range (down to 400 cm-1) then a protective coating must be used. Most process analyzers use protective windows between the spectrometer and the sample interface. If used, back reflections from the window surfaces into the interferometer must be avoided because these will cause photometric errors. 

A substrate 10 of HgCdTe is provided with an upper surface region 11 formed by an annealing procedure, or as an epitaxial layer or evaporated film. A layer of insulating material 12 is formed in which windows are provided. The windows are partially filled with a thin layer of metal 13 which is deposited therein to form a metal-semiconductor diode with the upper surface region. The metal layer is deposited to a thickness on the order of 10-50 nm thick and is sufficiently thin to be semi-transparent to infrared radiation. A thick layer of metal 14 is deposited to form an expanded contact and an anti-reflection coating 15 is provided. External conductors in the form of jumper wires 16 are ball bonded to the contact 14. 

The substrate 52 is removed and a grid 34 is deposited followed by an anti-reflection coating. Due to the increased resilience of the support relative to the chip, any differential expansion or contraction of the support relative to the chip due to changes in temperature can occur without the development of excessive stress and strain in the contacts. Furthermore, the structure eliminates a significant amount of cross-talk between signals of neighboring detectors. 

Fig. 16 Photocurrent-voltage curve of a solar cell based on complex 26. The cell was equipped with an anti-reflective coating. The conversion efficiency in full AM 1.5 sunlight illumination (100 mW cm-2) is 11.18%. The cell is masked with black plastic to avoid the diffusive light leaving an active cell area of 0.158 cm2...

Ip is degassed and then distilled into a previously evacuated 23 cm long quartz cell with wedged (1.5°) anti-reflection coated windows epoxied on the ends. The cell is mounted in the laser cavity on X-Y-Z translation stages, and the I2 is frozen into the sidearm by dipping it in+a cold bath. The dye lasing threshold is measured, and the Ar laser is then set to the desired power. For one set of experiments, threshold pump power is near ( 11%) 550 mW, while for a second set the threshold is near 790 mW. 

In addition to the use of specialized filter sets for mFISH protocols, other features of the filters which have improved image quality are broad band AR(anti-reflection) coatings and polished substrates. 

Johnson, B. 2006. Anti-Reflection Coatings. Omega Optical Application Note. 

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