Polycrystalline deposits

Various investigations into the epitaxial deposition of CdS onto different singlecrystal substrates have been carried out by Lincot et al. On InP, which is closely lattice matched to CdS (<0.1% difference), epitaxial deposition (c-axis of hexagonal CdS perpendicular to the substrate) occurs on the (111) P polar face of the InP but polycrystalline deposition on the (111) In face [49,56]. This difference was clearly due to differing chemical or electrostatic interaction between the InP faces... 

Barnes et al. (Section 7.15, Ref. 10) observed similar results on copper singlecrystal surfaces near the (100) face below 10 mV ridges, 40-70-mV platelets, 70-100 mV blocks, and fine platelets and above 100 mV, polycrystalline deposit. The four basic structural forms are shown in Figure 7.19. 

There has been much controversy over the precise crystallochemical nature of inner-ear deposits. Otoliths appear to be polycrystalline deposits (53). Otoconia, in contrast, show an evolutionary trend toward small (10 jLtm), discrete, elongated structures with pseudo three-fold symmetry characteristic of single crystals of calcite extended along the crystallographic c axis (Fig. 11) (.54). 

Fig. 9 Winand diagram showing different possible types of polycrystalline deposits as a function of r/r lim and inhibition intensity [8],...

Layered nanostructures can be deposited from the electrochemical environment by applying a time dependent voltage program to the working electrode (5) or by using a sequential deposition scheme such as electrochemical atomic layer epitaxy (EC-ALE) (6-10). In EC-ALE, a surface-limited electrochemical reaction, such as underpotential deposition (upd), is used to synthesize a binary compound by successive deposition of each element from its respective solution precursor. EC-ALE is an attractive electrosynthetic alternative to conventional deposition methods that is inexpensive, operates at ambient temperature and pressure and provides precise film thickness control. This technique promises to overcome many problems associated with other electrosynthetic approaches, such as the formation of highly polycrystalline deposits and interfacial interdiffusion. For example, we have recently used EC-ALE to fabricate stable semiconductor heterojunctions with extremely abrupt interfaces (11). 

Physical vapor deposition (PVD) is a technique for making thin films at low temperatures and is widely used in planar technology in electronics. It consists of evaporating or sputtering a solid, such as a metal, an alloy, or a mixture of solids, in a vacuum and condensing the compound on the substrate to be covered. In certain variations the vapor is reacted with gases introduced in the vacuum. That variation is reactive evaporation or reactive sputtering. The product can be a polycrystalline deposit or a powder. 

It can be seen from Fig. 4.9 that the structure of the deposit obtained by the RC in the second range is more similar to the one obtained in the DC than in the PC regime. However, the surface coarseness of this deposit is considerably lower than in the DC regime, and it is close to the surface coarseness obtained in the PC deposition. This is because in the RC deposition, there is a considerable concentration polarization, producing polycrystalline deposit. 

A cartoon of E-ALD suggests that at the UPD potential, a ML deposits on the surface and there is no more deposition until the formal potential (E ) for bulk deposition is reached. The truth is that different pairs of elements result in different coverages at different potentials. Polycrystalline substrates result in polycrystalline deposits. Each substrate crystallographic... 

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