Diamond discs

A few ATR probes are commercially available. In the near-IR ATR probes are mostly used as easy-to-use sticking probes for liquids and solids. As the aim is primarily to identify a material, not to measure low concentrations, probes with typically one or two reflections (Figure 5-d) are used. In the mid-IR, similar layouts can be found, using e.g. zinc selenide, germanium or silicon crystals as sensing elements. More sensitive and generally better suited for industrial process control DiComp -type probes (Figure 5-e). The actual ATR element is in this case a thin diamond disc supported by a suitably shaped ZnSe crystal. ATR probes of that type are available off the shelf with between one and nine reflections. If more... 

The samples were cut perpendicular to the surface and embedded in coldsetting resin. Then they were ground with 125 qm and 20 qm diamond discs. After ultrasonic cleaning, further polishing was applied with 3 qm and occasionally 1 qm diamond paste for about 2-5 h. For optimum phase... 

Considering more complex samples or samples that demand a more laborious pretreatment, a more laborious contamination control should be adopted. Slavin and coworkers [104], in order to determine aluminum in bone, wore powderless gloves and used tantalum knives and scrapers (made from ultra-pure tantalum, relatively free from aluminum) to remove adhering tissue from bone. They also used a diamond-disc saw to cut small segments of the sample for analysis, besides using only plasticware and sub-boiling distilled HN03. 

Figure 10.16 ATR three reflection device and examples of spectra. The small diamond disc (diameter 0.75 mm) enables the isolation of the sample examined from the ZnSe crystal. Chemically inert and resistant, diamond is appropriate for examination of aU sorts of hard samples which are pressed against its surface or contain water. Above right, are reproduced two spectra obtained with such a device. Spectra obtained from a drop of sulfuric acid (H2SO41M) deposited as a sample (reproduced courtesy of SensIR). Below, spectrum of water at 25 °C and of heated water vapour (250 °C) Inti Lab 32,(2), 2002).

The separation of dentin and enamel is usually carried out mechanically by chipping the enamel in a mortar made of an inert material (Helsby, 1974 Retief et al, 1974) or by grinding with a diamond disc (Steinnes et al, 1974 Stack et al, 1977). A carbide steel... 

Resin-bonded diamond discs placed on a flat table-top function quite well for rapid hand grinding of a saw-cut surface of epoxy-encapsulated clinkers preparatory to polishing (Hoodmaker, personal communication, 1985). Afew drops of propylene glycol are used as the grinding and polishing liquid. The diamond discs are cleaned with soap and water. 

FIG. 21. Optical images of several free-standing, boron-doped diamond disc OTEs. Diamond discs fabricated and provided for the research by Dr. James E. Butler at NRL. 

Figure 23B presents IR transmission spectra for (5) an optically pure and mechanically polished white diamond disc, (6) an undoped and polished (both sides) Si substrate, and (7 and 8) moderately and heavily boron-doped microcrystalline diamond thin films deposited on the undoped Si. The white diamond is relatively free of structural defects and chemical impurities. There is reduced transparency between 2500 and 1500 cm due to the two-phonon absorption. Diamond films with more... 

FIG. 23. Transmission spectra for different materials in the (A) UV/Vis and (B) IR regions of the electromagnetic spectrum. The electrodes in (A) are (1) a thin film of ITO on quartz, (2) a thin film of boron-doped nanocrystalline diamond on quartz, (3) a thin film of mechanically polished and boron-doped diamond on an optically pure, white diamond substrate, and (4) a free-standing, boron-doped, and mechanically polished diamond disc. The electrodes in (B) are (5) an optically pure and mechanically polished white diamond disc, (6) an undoped and polished (both sides) Si substrate, and (7 and 8) moderately and heavily boron-doped microcrystalline diamond thin films deposited on the undoped Si. (Reprinted with permission from Interface 2003, 12, 33. Copyright (2003) The Electrochemical Society, Inc.) (From Ref. 158.)... 

Diamond disc pad conditioning in chemical mechanical polishing... 

The governing principle of pad conditioning is to introduce friction between the polishing pad and the diamond disc, which characterizes a two-body abrasive wear mechanism. As illustrated in Figure 13.3, the diamond abrasives embedded on the disc create microscopic cuts or furrows on the pad surface to continually regenerate new pad surface and asperities. At the same time, they remove the glazed or accumulated particles on the polishing pad surface. 

Figure 13.2 Diamond disc conditioners employed in CMP. Photo courtesy of Abrasive Technology Inc.

Figure 13.3 Diamond disc conditioner and interaction between the conditioner and the pad in CMP.

Figure 13.5 is adapted from previous published reports. It shows and summarizes the effect of diamond disc pad conditioning on pad surface asperity, surface profile, and process control parameters. From Figure 13.5, it can be seen that diamond disc conditioning plays a key role in maintaming removal rates [15], within-wafer... 

Figure 13.4 Diamond disc pad conditioning unit assembly (after Ref. [13,14]).

In the past two decades, the geometry, material, and manufacture of diamond disc conditioners have evolved significantly. Notable stages of this transition are presented in Figure 13.6. Brievogel et al. [20] invented an initial pad conditioning device in... 

Adapted from Sung et al. (after Ref. [24]) Adapted from Tsai et al. (after Ref. [25]) Figure 13.6 Diamond disc conditioner evolution. 

To overcome the initial shortcomings, another device was proposed to employ a larger diameter metal disc on which diamond abrasives are uniformly arranged and coated [13]. In this case, pressure applied to the diamond disc controls the depth of cut (or penetration) in the pad. 

Many different ways to manufacture diamond disc conditioners have been reported [13,22,44—45]. In one description by Wielonski and Peterman [45], diamond disc fabrication typically begins with forming a disc-shaped metallic substrate of material such as stainless steel. The stainless steel disc is then coated with a monolayer of abrasive particles. 

Typically natural diamond particles or synthetic diamonds such as cubic boron nitride particles are preferred. These particles are distributed in a random or structured pattern using conventional techniques. A bonding metal such as nickel is often deposited on the diamonds to secure them to the substrate. A typical diamond disc conditioner stmcture is illustrated in Figure 13.7. 

Figure 13.7 Diamond disc conditioner structure (after Ref. [45]).

Pressure Conditioning pressure is related to the down force applied to the conditioner disc. Pad wear rate increases with the conditioning contact pressure between the diamond disc and the polishing pad. 

Similarly, rotational speed of the diamond disc may be varied at each section with its highest speed at an edge part of the polishing pad, the lowest rotational speed at an intermediate part, and a medium rotational speed at a center part [52]. Such methods of variation have been adapted to uniformly condition the polishing pad and reduce costs associated with managing, maintaining, and replacing the diamond disc [51]. 

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