Physical, generally vapor deposition

In general, vapor deposition methods refer to any process in which materials in a vapor state are condensed on a surface to form a solid-phase. These processes are normally used to form coatings to alter the mechanical, electrical, thermal, optical, corrosion resistance and wear resistance properties of various substrates. Recently, vapor deposition methods have been widely explored to fabricate various nanomaterials such as NS-T102. Vapor deposition processes usually take place in a vacuum chamber. If no chemical reaction occurs, this process is called physical vapor deposition (PVD) otherwise, it is called chemical vapor deposition (CVD). In CVD processes, thermal energy heats the gases in the coating chamber and drives the deposition reaction. 

Metallization layers are generally deposited either by CVD or by physical vapor deposition methods such as evaporation (qv) or sputtering. In recent years sputter deposition has become the predominant technique for aluminum metallization. Energetic ions are used to bombard a target such as soHd aluminum to release atoms that subsequentiy condense on the desired substrate surface. The quaUty of the deposited layers depends on the cleanliness and efficiency of the vacuum systems used in the process. The mass deposited per unit area can be calculated using the cosine law of deposition ... 

The most intensive development of the nanoparticle area concerns the synthesis of metal particles for applications in physics or in micro/nano-electronics generally. Besides the use of physical techniques such as atom evaporation, synthetic techniques based on salt reduction or compound precipitation (oxides, sulfides, selenides, etc.) have been developed, and associated, in general, to a kinetic control of the reaction using high temperatures, slow addition of reactants, or use of micelles as nanoreactors [15-20]. Organometallic compounds have also previously been used as material precursors in high temperature decomposition processes, for example in chemical vapor deposition [21]. Metal carbonyls have been widely used as precursors of metals either in the gas phase (OMCVD for the deposition of films or nanoparticles) or in solution for the synthesis after thermal treatment [22], UV irradiation or sonolysis [23,24] of fine powders or metal nanoparticles. 

CVD [Chemical Vapor Deposition] A general term for any process for depositing a solid on a solid surface by a chemical reaction from reactants in the gas phase. To be distinguished from Physical Vapor Deposition (PVD), in which no chemical reaction takes place. (For the ten international conferences held on this between 1967 and 1987 see the reference by Stinton et al. below.)... 

It becomes clear from the above discussion that metal catalyst films suitable for ATR spectroscopy must be very thin. Such films are generally not homogeneous. In many cases physical vapor deposition leads to films composed of metal islands. The morphology depends on the substrate (IRE), the metal, and preparation conditions such as evaporation rate, substrate temperature, and background gas. 

Chemical and physical vapor deposition technique has been widely applied for the preparation of such photocatalytic thin films. Since these vapor methods need an instrumental setup which enables control of temperature and pressure, their initial and running costs are generally high and the size of substrate is limited. Spray method, in which titanium alkoxide and water is sprayed on a substrate heated at a desired temperature, affords Ti02 thin films.69) However, like the sol-gel route, the physical properties and photocatalytic activity of Ti02 strongly depend on many factors such as temperature of substrate, flow rate of carrier gas, and partial pressure of starting material in the system. 

Physical vapor deposition and chemical vapor deposition are both techniques for producing thin films. Both rely on the transfer of mass from the vapor phase to a solid surface. A third technique, related to chemical vapor deposition but generally considered distinct from it, is molecular beam epitaxy (MBE) (Joyce and Joyce, 2004), in which a neutral beam of atoms is used to deposit a layer of adsorbed atoms. To deposit a compound, two molecular beams are used, depositing the constituent elements in the compound sequentially. Although this appears to make the deposition of any size film of any composition a simple matter (shown schematically below in Figure 3.26), the technical requirements for achieving this deposition are severe. 

Recently, many methods in the synthesis of c-BN films were studied, which include physical vapor deposition [1,5-7] (PVD) and chemical vapor deposition [1,8,9] (CVD, such as PECVD, HFCVD, MW-ECR-CVD). Most experiments have indicated that the commercial application of c-BN films depends on enhancement and improvement in the stability and repeatability of preparation process. Generally, ion energy flow density or ion bombardment was attributed to the essential factor with the influence in the c-BN formation [1,10-13]. However, it is noted that the discrepancy between PVD and CVD maybe result from the difference in the substrate temperature (Ts , ). Unfortunately, the role which Tjub plays on the growth of cubic phase in PVD was seldom investigated systemically. 

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