Laser-assisted deposition

Vacuum deposition techniques, such as sputtering, electron beam evaporation, and plasma deposition are common. Photopolymerization and laser-assisted depositions are used for preparation of specialized layers, particularly in the fabrication of sensing arrays. Most commercial instruments have thickness monitors (Chapter 4) that allow precise control of the deposition process. 

M.J. Santos, A.J. Silvestre, and O. Conde, Laser-assisted deposition of r-B4C coatings using ethylene as carbon precursor. Surface and Coatings Technology, 151 -152, 160-164(2002). 

Chemical Vapor Deposition. In chemical vapor deposition (CVD), often referred to as vapor transport, the desired constituent(s) to be deposited are ia the form of a compound existing as a vapor at an appropriate temperature. This vapor decomposes with or without a reducing or oxidizing agent at the substrate— vapor interface for film growth. CVD has been used successfully for preparing garnet and ortho ferrite films (24,25). Laser-assisted CVD is also practiced. 

Plasma-jet diamond techniques yield growth rates of about 980 p.m/h (163,164). However, the rate of diamond deposition is still one to two orders of magnitude lower than the HP—HT technology, which is about 10,000 p.m/h (165). Diamond deposition rates of ca 1 p.m/s have been reported usiag laser-assisted techniques (166). This rate is comparable to the HP—HT synthesis. 

The most widely deposition technique is the ion assisted deposition (lAD). A material in a melting-pot is vaporized by heating either with an electron beam, or by Joule effect, or with a laser beam, or with microwaves, or whatever else. The vapor flow condensates on the substrate. In the same time, an ion... 

Shinn, G. B. Gillespie, P. M. Wilson, W. L., Jr. Duncan, W. M. 1989. Laser-assisted metalorganic chemical vapor deposition of zinc selenide epitaxial films. Appl. Phys. Lett. 54 2440-2442. 

There are numerous materials, both metallic and ceramic, that are produced via CVD processes, including some exciting new applications such as CVD diamond, but they all involve deposition on some substrate, making them fundamentally composite materials. There are equally numerous modifications to the basic CVD processes, leading to such exotic-sounding processes as vapor-phase epitaxy (VPE), atomic-layer epitaxy (ALE), chemical-beam epitaxy (CBE), plasma-enhanced CVD (PECVD), laser-assisted CVD (LACVD), and metal-organic compound CVD (MOCVD). We will discuss the specifics of CVD processing equipment and more CVD materials in Chapter 7. 

Donor adducts of aluminum and gallium trihydride were the subject of considerable interest in the late 1960s and early 1970s.1 Thin-film deposition and microelectronic device fabrication has been the driving force for the recent resurgence of synthetic and theoretical interest in these adducts of alane and gallane.24 This is directly attributable to their utility as low-temperature, relatively stable precursors for both conventional and laser-assisted CVD,59 and has resulted in the commercial availability of at least one adduct of alane. The absence of direct metal-carbon bonds in adducts of metal hydrides can minimize the formation of deleterious carbonaceous material during applications of CVD techniques, in contrast to some metal alkyl species.10, 11... 

Pyrolytic-laser-assisted CVD is analogous to thermally driven CVD, but instead of a diffuse heating source, a focused laser beam is used to define deposition areas spatially (32, 38, 39) or to heat the gas phase selectively (228). The use of laser has the added advantages of increased energy flux and rapid heating. To avoid photochemistry, the gas phase must be transparent to the radiation. 

Figure 16. Examples of deposition shapes in pyrolytic-laser-assisted CVD (a) first-order surface reaction, no mass-transfer effects (b) first-order surface reaction, depletion effects and (c) Langmuir-Hinshelwood surface kinetics, no mass transfer effects. The ratio r/w is the radial position relative to the beam...

In laser-assisted thermal CVD by gas-phase heating, the laser is used to vibrationally excite the gas (e.g., SiH4) and active film precursors (e.g., SiH2). The modeling of these processes revolves around the transport phenomena that control the access of the film precursors to the surface, as exemplified by the finite-element analysis by Patnaik and Brown of amorphous silicon deposition (228). 

The methods mostly used for nano-cBN deposition are ion-beam-assisted deposition (IBAD) [199] mass selected ion beam deposition (IBD) [200] ion plating [201] RF- or magnetron sputtering [202] and laser deposition [203] (Fig. 13). 

Bondi, S. N., et al. (2006), Laser assisted chemical vapor deposition synthesis of carbon nanotubes and their characterization, Carbon, 44,1393-1403. 

Boyd IW, Zhang J-Y, Bergonzo P (1995) New excimer ultraviolet sources for photo-assisted deposition of thin films an alternative to excimer laser-induced deposition, Proc. SPIE-Int. Soc. Opt. Eng. 2403 290-301. 

Laser-assisted chemical vapor deposition a CVD in which the excitation is delivered from photons delivered from a laser Metal-organic chemical vapor deposition (MOCVD) the same as CVD, except that the precursor is a volatile organometallic or coordination compound with carbon-containing ligands... 

There are many physical deposition (PD) processes which can be used to deposit lubricating films on surfaces, and several of them have been used, either separately or in combination, for depositing molybdenum disulphide. They include Ion Beam Enhanced (or Assisted) Deposition (IBED or IBAD), and Pulsed Laser Deposition (PLD), but the most important so far is sputtering, or more precisely sputter-coating. 

Laser-induced chemical hquid deposition of copper fihns on qnartz and glass from Cn(acac)2 (7a) as precnrsor was reported by Onchi and collaborators 2. The process is realized throngh the interaction of copper coUoids with the appropriate snrfaces. It was fonnd that, depending on whether the laser irradiation is discontinnons (ArF laser) or continnons (KrF laser), closed copper fihns or nano-islands were formed. This method differs from the laser-assisted liqnid-phase metallization of polymers, wherein a laser beam was nsed to enhance chemical rednction of copper(II) salts. ... 

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