Coating antireflection

CH2—CI2—) —(—CF2— CFH—) (39). Ceramic crystals have a higher piezoelectric efficiency. Their high acoustic impedance compared to body tissues necessitates impedance matching layers between the piezoelectric and the tissue. These layers are similar in function to the antireflective coatings on a lens. Polymer piezoelectric materials possess a more favorable impedance relative to body tissues but have poorer performance characteristics. Newer transducer materials are piezoelectric composites containing ceramic crystals embedded in a polymer matrix (see Composite materials, polymer-MATRIX Piezoelectrics). 

Antireflection coatings are used over the silicon surface which, without the coating, reflects ca 35% of incident sunlight. A typical coating consists of a single layer of a transparent dielectric material with a refractive index of ca 2, which is between the index of siUcon and ait or cover material. Materials such as titanium dioxide, tantalum pentoxide, Ta20, or siUcon nitride, Si N, ca 0.08-p.m thick are common. The coating and a physically textured... 

Antireflective (AR) coatings are required on optics to reduce the reflective surface losses. Vitreous siHca coatings in the form of porous or multilayer films are used extensively in this appHcation. Antireflective coatings have been developed which employ coUoidal fused siHca sol—gel particles made from organometaUic materials (253). 

Optical Coatings. Thin surface coatings are appHed to optical components to improve performance. Wideband antireflection coatings for the visible and ir regions need materials with a refractive iadex of for the best efficieacy. Cerium fluoride, a stable material resistant to humidity damage, has a suitable iadex, 1.63 ia the visible, 1.59 ia the iafrared, and is transparent over the range 0.5 p.m to 5 p.m. It is one of the compounds used to build up the multilayers deposited on lenses, sensors, and the like. 

Fig. 4.50. IBSCA spectra of an antireflective coating on soda-lime glass (Si02-Ti02-Si02/Ti02-substrate) conditions 5 keVAr" bombardment.

CVD titanium nitride (TiN) is the most important interstitial-nitride coating from an application standpoint. It is used extensively to provide wear resistance and as a diffusion barrier and antireflection coating in semiconductor devices. 1 °]... 

Antireflection coatings, optical waveguides and photoelectrochemical cells. 

Nitrides by plasma CVD as antireflection coatings for photovoltaic cells. 

The transparent top contact is deposited last of all, which imposes restrictions on the process temperature. Thermally evaporated ITO and ZnO deposited by metal-organic CVD (MOCVD) are most suitable. At a typical thickness of 70 nm the ITO serves as a good antireflection coating as well. Due to the somewhat high sheet resistance, a metal (Ag) grid is necessary to reduce the series resistance [11]. 

Despite such limitations, plasma-deposited a-C(N) H films were found to be used in a number of applications. The stress reduction induced by nitrogen incorporation [12] and consequent adhesion improvement, allowed the development of a-C(N) H antireflective coatings for Ge-based infrared detectors [13]. It was also found that N can electronically dope a-C H films, and can strongly decrease the defect density, which gives prospects on its use as a semiconductor material [14]. Nitrogen incorporation was also found to decrease the threshold electric field in electron-field emission process [15], making possible the use of a-C(N) H films as an overcoat on emission tips in flat-panel display devices [16]. 

Both xerogels and aerogels are characteristically high surface area materials (surface areas normally exceed 500 m2/g). Unlike wet gels, many uses exist for dried gels due to their high surface areas and small pore sizes (typically, < 20 nm diameters). Examples include catalyst supports (12.). ultrafiltration media (18), antireflective coatings (19-20), and ultra-low dielectric constant films. (Lenahan, P. M. and Brinker, C. J., unpublished results.)... 

There are also several proposals to use anodic aluminum oxides in producing optoelectronic devices. Porous oxides may find use as antireflecting coatings for optical pathways. Anodic alumina films doped by Eu and Tb are promising for application in electroluminescent cells for TEELs.28... 

Development of multifunctional sol—gel coatings antireflection coatings with enhanced self-cleaning capacity. Solar Energy Materials and Solar Cells, 94, 1081-1088. 

Floch H.G., Belleville P.F., Scratch-resistant single-layer antireflective coating by a low-temperature sol-gel route, SPIE Proc. 1758, 135-150, (1992). 

Gangopadhyay et al.48 used a CBD ZnS antireflection coating on large-area commercial monocrystalline silicon solar cells, resulting in a 13.8% efficiency. Ennaoui et al.49 deposited CBD Zn(Se,OH)x films on Cu(In,Ga)(S,Se)2. They reported an active-area efficiency of up to 15.7% and a total-area efficiency of up to 13.26% for such devices. 

Gangopadhyay, U. Kim, K. Mangalaraj, D. Junsin, Y. 2004. Low cost CBD ZnS antireflection coating on large area commercial mono-crystalline silicon solar cells. Appl. Surf. Sci. 230 364-370. 

In the present experiment, the optical fiber is aligned to the sensor chip using a separate micropositioner, and no antireflection coatings are used on the chip facets. As a result, the observed noise floor is limited by vibrations and interference effects of the present experimental setup. With the adoption of well-established packaging... 

Porous Si02 nanoparticles deposited by a common wet-coating sol-gel technique, for instance, form a single-layer, low-refractive-index and cost-efficient antireflective coating on glass as an alternative to common multilayer compositions (Figure 4.3).4 The coating thereby obtained exhibits porosity of up to 50% and a refractive index between 1.25 and 1.3, which corresponds to a transmission maximum up to 99% and an... 

K. R. Armstrong and F. J. Low. Far-Infrared Filters Utilizing Small Particle Scattering and Antireflection Coatings , Applied Optics, Vol. 13, No. 2, pp. 425-430, February 1974. 

Since both aerogels and xerogels have high surface areas and small pore diameters they are used as ultrafiltration media, antireflective coatings, and catalysts supports. Final densi-fication is carried out by viscous sintering. 

The wafers are processed into solar cells, the majority of which have a diode structure, as sketched in Figure 11.4, characterized by a thin, diffused, doped emitter, screen-printed front and back contacts and a front-surface antireflective coating. Prior to the effective cell manufacturing step, a chemical treatment of the silicon wafers removes... 

TiN film of approximately 300 A is typically used in the back-end interconnect process, as both the cap layer for the aluminum metal deposition sequence and an antireflective coating for the subsequent photolithography step. Since this TiN cannot be a substrate for oxide thickness measurement in ILD, the aluminum beneath the TiN must be used as the substrate. In other words, the TiN is a component of the film to be measured. Thus, its refractive index or thickness must be known to determine the unknown oxide thickness. However, the refractive index of TiN is not constant, but varies with thickness. As a result, the TiN thickness must be precisely controlled to enable the validity of the substrate modeling. 

Yoldas BE, Partlow PW (1985) Eormation of broad band antireflective coatings on fused silica for high power laser applications. Thin Solid Eilms 129 1-14... 

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