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• Capture zone distributions (CZD) were plotted for 2D Ge islands nucleated on Si(111)-(7 × 7) terraces at 550–650 °C. • Obtained CZDs were described by generalized Wigner distribution. • Critical nucleus size of 2D Ge island was found to consist of 3–5 particles. • CZD analyses indicates on AL kinetics of 2D Ge nucleation at elevated. T Recently we have studied the concentration N 2 D of 2D Ge island nucleated on large-scale Si(111)-(7 × 7) terraces at 550 − 650 °C as function of the substrate temperature T and Ge deposition rate R [J. Cryst. Growth. 531 (2020) 125347], where we have shown that N 2 D (R) dependence is characterized by a power law with scaling exponent χ = 1 ± 0.1. However, in the frames of classical Venables rate-equation approach, the obtained range of χ values do not allow one to unambiguously determine the critical nucleus size i , since χ = 1 ± 0.1 can be attributed to both diffusion limited (DL) and attachment limited (AL) growth regimes. In order to determine an exact i size and growth kinetics, in this work, we have investigated the scaled capture-zone distribution (CZD) of nucleated 2D Ge islands on the same Ge/Si(111)-(7 × 7) samples and described it by the generalized Wigner distribution P β = a β A β exp - b β A 2 , where P β is the probability density of getting into some region of capture zone values, A is normalized Voronoi cell area for 2D island, β = i χ is scaling parameter directly related to the critical nucleus size i. It has been shown that the kinetics of 2D Ge island nucleation on the wide Si(111)-(7 × 7) terraces at elevated temperatures should procced under AL growth kinetics with i = 3–5 particles. [ABSTRACT FROM AUTHOR]

• Al 0.9 Ga 0.1 N alloys grown by PA-MBE show clear evidence of phase segregation in XRD. • XRD peak shows splitting: Peak separation changes with varying growth parameters. • Weighted averages of XRD peaks remain the same: Overall composition is unchanged. • Long-range atomic ordering is observed in alloys with minimal phase segregation. • Route to efficient deep-UV emitters through carrier localization at bandgap minima. AlGaN alloys with very high AlN mole fraction (∼90 %) were grown by plasma-assisted molecular beam epitaxy (PA-MBE) and their alloy properties were investigated by high-resolution X-ray diffraction (HR-XRD) measurements. Growth was carried out employing a series of group III/V ratios and for samples grown under a high group-III regime, phase-segregation in the alloy was evident from a characteristic splitting of the AlGaN (0002) peak in the HR-XRD pattern. With decreasing excess group-III conditions the separation of peak positions continuously reduced, till a single peak was observed. However, for samples where such splitting was absent, spontaneous superlattice peaks were seen at lower incident angles of the XRD patterns indicating the presence of long-range atomic ordering (LRAO). Thus, for AlGaN alloys with extremely high Al content, effects of phase-segregation, or of LRAO were observed, depending on the kinetics of growth. These results on phase-segregation effects are expected to promote the development of high-efficiency deep ultraviolet emitters for skin-safe germicidal action by mitigating the detrimental effect of dislocations and related non-radiative recombination centers through carrier localization processes at potential minima. [ABSTRACT FROM AUTHOR]

• Amorphous SnSe 2 layer was crystallized by heating to 250 °C to initiate vdW epitaxy. • SnSe 2 film screw dislocations density is ∼18 and ∼2 μm−2 for Si and Bi 2 Se 3 substrates. • SnSe 2 film has a hexagonal lattice structure (space group P 3 ¯ m 1 (no. 164)) • Decrease in Se:Sn flux ratio switches SnSe 2 epitaxy to nucleation of SnSe 3D islands. We have studied the structural and morphological features of SnSe 2 films grown on Si(111) and Bi 2 Se 3 (0001) surfaces in an in situ reflection electron microscope. On both substrates, the SnSe 2 growth started at 100 °C as an amorphous layer, and when thickness reached 1 nm, crystallized by raising the growth temperature to 250 °C without interruption of Sn and Se fluxes. The introduction of this growth-initiating stage has decreased the concentration of screw dislocations on films' surfaces to ∼18 and ∼2 μm−2 for the Si(111) and Bi 2 Se 3 (0001) substrates, respectively. High-resolution transmission electron microscopy investigation has shown that the layered SnSe 2 film has a hexagonal lattice structure corresponding to the space group P 3 ¯ m 1 (no. 164) with lattice parameters a = 0.38 nm and c = 0.62 nm. Raman spectroscopy has shown vibrational modes corresponding to the 1T-SnSe 2 phase. We have shown that the decrease in Se:Sn flux ratio switches growth mode from Frank—van der Merwe type SnSe 2 epitaxy to Volmer—Weber type nucleation of SnSe 3D islands. [ABSTRACT FROM AUTHOR]

• Impurity-induced 2D phase forms on Bi 2 Se 3 surface during submonolayer In deposition. • Islands of indium-induced surface phase have a height of 0.4 nm. • During indium deposition, area of the surface phase increases until complete coverage. • The phase locally suppresses sublimation, which creates multilayer star-shaped islands. Using in situ reflection electron microscopy, transformations of Bi 2 Se 3 (0001) surface during In deposition have been studied. We first report the formation of an In-induced surface phase that precedes nucleation and growth of a layered In 2 Se 3 at substrate temperatures around 400 °C. The surface phase nucleates on Bi 2 Se 3 (0001) terraces as islands having high In content and a height of 0.4 nm. During continuous In deposition, the area of these islands increases and suppresses Bi 2 Se 3 sublimation from the regions covered by the In-induced surface phase. This locally suppressed sublimation and sublimation-induced ascending motion of Bi 2 Se 3 atomic steps create multilayer triangular star-shaped islands. [ABSTRACT FROM AUTHOR]