Stranski-Krastanov growth mechanism

Au(lll) substrate is modified at low A by a commensurate 2D Cuads overlayer (cf. Section 3.4). The deposition of 3D Cu bulk phase follows a Stranski-Krastanov growth mechanism, l.e., formation of 3D islands on top of an internally strained 2D Cuads overlayer [4.44, 4.80, 4.81]. 

The results obtained in the system k x hkl)/Cv , where 2D Me UPD phenomena occur followed by a Stranski-Krastanov growth mechanism in the OPD range, show that electrochemical 3D Me phase formation processes can be used for structuring and modification of metal single crystal surfaces in the nanometer range. Local electrochemical processes are initiated by in situ local probe methods using appropriate polarization routines. 

Stranski-Krastanov growth has been documented for copper on Au(lll) [101, 102], Pt(100) and Pt(lll) [103], for silver on Au(lll) [104, 105], for cadmium on Cu(lll) [106] and for lead on Ag(100) and Ag(lll) [107-109]. In all of these examples, an active metal is deposited onto a low-index plane of a more noble metal. Since the substrate does not undergo electrochemical transformations at the deposition potential, a reproducible surface can be presented to the solution. At the same time, the substrate metal must be carefully prepared and characterized so that the nucleation and growth mechanisms can be clearly identified, and information can be obtained by variation of the density of surface features, including steps, defects and dislocations. 

If fls Am, misfit is present, positive or negative, and growth proceeds by the Stranski-Krastanov mechanism, which is composed of two steps. In the first step a 2D overlayer of M ij on S is formed, and in the second step 3D crystallites grow on top of this predeposited overlayer (Fig. 7.20). 

Figure 5.1. Scheme of the different mechanisms of growth (a) Frank-van der Merwe, (b) Voimer-Weber and (c) Stranski-Krastanov. The substrate and overlayers are represented by dark grey and light grey shading, respectively. 

Ikemiya et al. [445] have investigated both the atomic structure and growth of electrodeposited Te films on Au(lOO) and Au(lll) with large lattice misfits. Deposition was performed in sulfuric acid solutions using in situ AFM. On both substrates, bulk-deposited Te films were formed according to the Stranski-Krastanov mechanism. Their atomic structures changed with the increasing film thickness. 

This indicates that the UPD-OPD transition obviously proceeds via the Stranski-Krastanov mechanism (cf. Fig. Ic) involving the formation and growth of 3D Pb crystallites on top of the 2D internally strained Pb UPD adlayers which act as precursors for the nucleation and growth process in the OPD range. The unstrained 2D hep surface structure of a 3D Pb(lll) crystal face is reached after deposition of about 10 Pb monolayers as shown in Fig. 4.18. The interatomic distance corresponds to [Pg.194]

In the case of strong Meads-S interaction, expanded commensurate Meads overlayers as well as one or two close-packed commensurate or incommensurate Meads monolayers can be formed in the UPD range depending on AE (Fig. 6.13). Then, metal deposition in the OPD range follows either the Frank-van der Merwe (Fig. 6.13a) or the Stranski-Krastanov (Fig. 6.13b) growth mechanisms in the absence or presence of significant crystallographic Me-S misfit, respectively. In the first case, a... 

Figure 2.23. Growth of metal overlayers can occur in three different modes. Shown here is the behavior of the ratio of substrate and adsorbate Auger signals as a function of the deposition time for films that grow by the Volmer-Weber, Frank-van der Merwe, and Stranski-Krastanov types of mechanisms.

Stranski—Krastanov Often, growth of thin films occurs in the regime between the Volmer—Weber and Frank—van der Merwe mechanisms, in which an initial layer is formed on the substrate, but then 3D island structures form. 

The model predicts that the critical thickness for island formation depends inversely on the square of the misfit. For the growth of strained InGaAs layers on a GaAs substrate Wessels estimates that the transition to the Stranski-Krastanov mechanism occurs when hcrit x/ > 1.8 x 10 [cm]. 

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