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• The adsorption behavior of C 60 molecules on Ag 5 Se 2 surface was studied. • The nucleation and growth processes of C 60 islands were studied. • The adsorption orientation of C 60 on the Ag 5 Se 2 surface was identified. Extensive research has been conducted on the use of surface nanotemplates, whether artificially or naturally patterned, to regulate the self-assembly processes on surfaces. It has become clear that in order to gain a better understanding and control over the formation of well-ordered two-dimensional nanostructure arrays, detailed investigations into the nucleation and growth of adsorbates (molecules, atoms, or clusters) on the surface nanotemplates are essential. The present study focuses on the self-assembly structure, nucleation, and growth process of C 60 molecules on the patterned Ag 5 Se 2 /Ag(111) surface, utilizing low-temperature scanning tunneling microscopy. The findings reveal that C 60 molecules exhibit a preference for appearing at the triangular domain boundaries on the Ag 5 Se 2 /Ag(111) surface. As coverage increases, the molecules continue to grow across regions, ultimately forming a densely packed island self-assembled structure. Owing to the weak interaction between C 60 molecules and Ag 5 Se 2 /Ag(111), the molecules adopt various orientation configurations. This research contributes valuable insights into the fabrication of carbon nanodevices on patterned substrates. [ABSTRACT FROM AUTHOR]

The electrochemical nucleation and growth of bismuth (Bi) crystallites on copper substrates were investigated using cyclic voltammetry and chronoamperometry measurements, and scanning electron microscopy (SEM). The experimental current transients were analyzed according to the Scharifker and Hills and Mirkin-Nilov and Heerman-Tarallo models. At relatively low overpotentials and low Bi concentration, Bi deposition can be described by a model involving progressive nucleation on active sites and 3D diffusion-controlled growth. At higher Bi concentration, the growth mechanism shifts to the instantaneous nucleation mode. These results were also confirmed by SEM analysis. The values of some kinetic parameters such as the nucleation rate, the number density of active sites and the diffusion coefficient of Bi3+ ions were also calculated using different theoretical approaches. X-ray diffraction measurements revealed that the Bi crystallites grow in the rhombohedral crystal structure along the [012] direction. The optical properties of the dispersed Bi nanoparticles on the Cu surface were discussed in the ultraviolet-visible (UV–Vis) wavelength range. It was found that the UV–Vis spectrum exhibit a strong resonant optical absorption on the surface with the smallest Bi crystallite size (200 nm). • Electrodeposition of highly oriented Bi crystallites on Cu substrates • Electrochemical nucleation and growth mechanism of bismuth crystallites was studied. • Different sizes of Bi nanopaticles (BiNPs) were synthesized. • Correlations between the morphology of Bi/Cu surface and their optical properties [ABSTRACT FROM AUTHOR]

Cadmium sulfide is the main choice among n-type semiconductors for several solar cell technologies due to its excellent optical, structural and electronic characteristics. Even when it has been widely studied, there are still unsolved aspects related with the understanding of nucleation and growth mechanisms. For that, the initial growth stages of CdS deposited by chemical bath deposition (CBD) were carefully studied by in-situ X-ray photoelectron spectroscopy (XPS) by connecting a glove box with the CBD setup to the XPS introduction chamber. The CdS thin films were synthesized by CBD method onto glass substrates using CdCl 2 as the cadmium precursor, sodium citrate as the complexing agent and thiourea as the sulfur source. XPS analysis revealed the presence of Cd(OH) 2 and Cd-Citrate species, which facilitates nucleation to later promote the formation of CdS. During the deposition time (0–10 min) the pH changes from 12.1 to 10.8. Considering this, the following combination of mechanisms during the deposition: the hydroxide (above pH 11) and complex-decomposition (below pH 11) was proposed by using a distribution species diagram. The resulting films are close to the ideal stoichiometric CdS after 10 min of deposition. Furthermore, the film thicknesses determined by XPS ultra-thin film analysis, were about 2.37 and 13.7 nm, for 6 and 10 min, respectively, in good agreement with ellipsometry measurements. • CdS films deposited by chemical bath deposition were studied by in situ XPS. • XPS revealed the presence of Cd(OH) 2 and Cd-Citrate species at the initial stages. • The hydroxide (pH > 11) and complex-decomposition (pH < 11) mechanisms were proposed. • The thicknesses obtained by XPS were validated by spectroscopic ellipsometry. • The stoichiometry ratio [S/Cd] after 10 min was 0.92. [ABSTRACT FROM AUTHOR]

Abstract Band gap grading of Cu 2 ZnSn(S,Se) 4 (CZTSSe) solar cells can be achieved by varying the S r = [S]/([S] + [Se]) ratio in the absorber layer with depth. One approach is a two-step annealing process where the absorber is first sulfurized to Cu 2 ZnSnS 4 (CZTS) followed by selenization to form CZTSSe. However, once nucleation of CZTSSe initiates, the rapid interchange of S and Se limits the control over the S r ratio with depth. Here, we have studied incorporation of Se into CZTS and observed the behavior of Se below and up to the nucleation temperature of CZTSSe. Se diffusion at 337 and 360 °C is dominated by grain boundary diffusion while some increase of Se is also seen in the region from 100 to 800 nm from the surface. After selenization at 409 °C, recrystallization is observed and CZTSSe grains are formed. The recrystallization is more rapid for a smaller average grain size and is facilitated by diffusion of Na from the back contact. The grain boundary diffusion is identified with secondary ion mass spectrometry measurements by measuring the accumulation in the CZTS/Mo interface for three samples with different average grain size. Highlights • Three sulfide Cu 2 ZnSnS 4 samples with different average grain sizes are fabricated. • Se is incorporated in sulfide Cu 2 ZnSnS 4 by selenization at 337, 360 and 409 °C. • Grain boundary diffusion of Se is observed at 337 and 360 °C. • Nucleation and recrystallization of a Cu 2 ZnSn(S x ,Se 1-x) 4 phase is seen at 409 °C. • Sodium diffuses from the Cu 2 ZnSnS 4 /Mo interface to support recrystallization. [ABSTRACT FROM AUTHOR]

This paper discusses the nucleation and growth mechanisms of ZnO nanorod thin-films and larger sized crystallites that form within the solution and on surfaces during an ultra-fast microwave heating growth process. In particular, the work focusses on the elimination of crystallites as this is necessary to improve thin-film uniformity and to prevent electrical short circuits between electrodes in device applications. High microwave power during the early stages of ZnO deposition was found to be a key factor in the formation of unwanted crystallites on substrate surfaces. Once formed, the crystallites, grow at a much faster rate than the nanorods and quickly dominate the thin-film structure. A new two-step microwave heating method was developed that eliminates the onset of crystallite formation, allowing the deposition of large-area nanorod thin-films that are free from crystallites. A dissolution-recrystallization mechanism is proposed to explain why this procedure is successful and we demonstrate the importance of the work in the fabrication of low-cost memristor devices. [ABSTRACT FROM AUTHOR]

A unique structure of a thin layer consisting of cesium iodine, manifested by a “ladder-like” fractal structure formed by spin-coating is reported herein. The ladder-like structure is made of mm-size domains, each comprising of a highly correlated, perpendicularly interconnected, network of CsI lines. Each line served as the growth origin of 2–3 levels of short, perpendicularly-oriented CsI crystals, yielding a fractal dimension of 1.53. The observed structure differs from common Diffusion Limited Aggregation (DLA) shapes by the absence of any morphological indicators that may point on the origin of growth. Furthermore, the perfect orthogonal alignment of all junctions in the CsI structure is very rare in DLA type of growth. A formation mechanism is presented, based on studying the evolution of this structure at different spinning rates and on a variety of substrates. It is proposed that this unique structure originates from a rare combination of conditions: strong anisotropy in surface energy between different facets arising from the primitive ionic crystal of CsI, the strong water-breaking property of cesium ions and an unusual effect of mesoporous substrates in preventing premature nucleation. [ABSTRACT FROM AUTHOR]

Assembly of metal-organic framework (MOF) thin-films with well-ordered growth directions enables many practical applications and is likely part of the future of functional nanomaterials. Insights into the formation pathway of the MOF thin films would allow better control over the growth directions and possibly the amount of guest molecules absorbed into the MOF pores. Here, we investigate the nucleation and growth of oriented Cu 3 (BTC) 2 ∙xH 2 O MOF (HKUST-1, BTC = benzene-1,3,5-tricarboxylic acid) thin films on the thermal SiO 2 surface using a room temperature stepwise layer-by-layer (LBL) method. Initial stages of LBL growth were characterized with X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy analysis in order to understand nucleation and growth kinetics. HKUST-1 thin films with preferred growth along the [111] direction on the thermal SiO 2 surface were obtained in the absence of not only a gold substrate, but also organic-based self-assembled monolayers (SAMs). It is found that the formation of HKUST-1 is initiated by deposition of copper acetate on the thermal SiO 2 surface followed by ligand exchange between coordinated acetate from the copper precursor and the BTC ligands. As the LBL growth cycle is increased, HKUST-1 crystals on the thermal SiO 2 surfaces are continuously forming and growing and finally the crystallites coalesce into a continuous film. Highly oriented HKUST-1 thin films on thermal SiO 2 surface with complete surface coverage and ~90 nm thickness were obtained at ~80 cycles of LBL growth under the conditions used in this study. [ABSTRACT FROM AUTHOR]

The initial reaction between Pt and molten Sn has been studied by dipping tests of 1 and 2 s. It was found that both PtSn and PtSn 4 formed in the first second of contact. PtSn formed 7 nm (1 s) and 20 nm (2 s) thick layers on top of the Pt substrate but PtSn 4 formed scattered particles in the liquid Sn. No orientation relationship was found between Pt and PtSn. PtSn nucleates heterogeneously on Pt by its larger energy of formation than PtSn 4 and PtSn 4 nucleates in liquid Sn by the very low solubility of Pt in molten Sn. [ABSTRACT FROM AUTHOR]

• Kesterite Cu 2 ZnSnS 4 thin film is synthesized by electrodeposition. • Cu-Zn-Sn-S growth revealed progressive nucleation and diffusion-limited growth. • The applied potential does not influence the nucleation. • The CZTS physicochemical properties depend on the electrodeposition time. In this paper, earth-abundant and environmentally friendly kesterite Cu 2 ZnSnS 4 (CZTS) thin films are successfully synthesized by electrodeposition on Indium Tin Oxide (ITO) coated glass for photovoltaic application. For the first time, the electrochemical nucleation and growth mechanisms of the kesterite electrodeposition are investigated. Here, the electrochemical growth mechanism is studied and the diffusion coefficient D is calculated for different applied potentials. Our findings show that kesterite deposition occurs through progressive nucleation followed by the limited growth of diffusion of 3D hemispheric islands. Furthermore, it has been proven that the type of nucleation and growth is not influenced by the applied potential. Scanning electron microscopy, X-ray diffraction and UV–vis are used to characterize the physicochemical properties of the prepared samples. The morphological and crystallographic investigations reveal a different morphology and structure of the CZTS film deposited at different potentials for different times. Among the samples studied, the CZTS thin film prepared at −1.1 V for 60 min offers the best properties with 2.4 µm thickness after annealing at 450 °C. [ABSTRACT FROM AUTHOR]

In this study, GaAs crystals were grown by chemical beam epitaxy on nominal (001) Si substrate over Ge nano-seeds placed within nano-holes opened through a 0.6 nm silica layer. GaAs crystal morphology and atomic organization at the interface between Ge and GaAs were studied by using complementary Scanning Transmission Electron Microscopy, energy dispersive X-ray spectrometry and dark-field electron holography. Fourfold symmetry GaAs crystals were obtained and found to be completely relaxed and twin free. Thus, the use of Ge nano-seeds to initiate the growth of GaAs results in the suppression of twins previously observed for direct GaAs growth on nominal (001) Si. Nevertheless, anti-phase domains were detected. A simple atomistic model is proposed which explains how Anti-Phase Boundaries develop at the junctions between Ge {113} facets, and {113} and {111} facets for As-stabilized GaAs growth. [ABSTRACT FROM AUTHOR]

Cadmium sulfide (CdS) ceramic thin films were successfully synthesized via the microwave-assisted chemical bath deposition process in a short reaction period of 5 min at 65 °C. As long as the molar ratios of thiourea to cadmium sulfide ([TU]/[CdSO 4 ] molar ratios) were below 50, dense CdS films formed on Cu(In,Ga)Se 2 absorbers. Upon elevating the [TU]/[CdSO 4 ] molar ratios, a large number of CdS particles precipitated in the bulk solutions, leading to the formation of holes on CdS films and a reduction in the film thickness. These phenomena imply that elevating the concentration of thiourea facilitates homogeneous nucleation and suppresses the growth of CdS films. The photovoltaic properties of Cu(In, Ga)Se 2 solar cells were influenced by the different [TU]/[CdSO 4 ] molar ratios. When the [TU]/[CdSO 4 ] molar ratio was 30, a relatively high efficiency of 10.83% was achieved. According to diode analysis, increasing the [TU]/[CdSO 4 ] molar ratios raised the diode factor (A) values. The microwave-assisted chemical bath deposition process was demonstrated to be a potential process for the fast deposition of CdS ceramic thin films. [ABSTRACT FROM AUTHOR]

We study heteroepitaxial thin films grown on patterned substrates using a two-dimensional ball and spring model. Island size and its uniformity as a function of patterned substrate parameters and growth conditions are investigated in an early stage of growth using fast kinetic Monte Carlo simulations. In contrast to the flat substrate, patterned substrates provide preferred sites for island formation at the beginning of growth and promote island size uniformity. A patterned substrate parameter enables us to modify island size in a considerable range. Island size uniformity is further enhanced by stress suppression at the island edges when lattice mismatch is increased. Island size, however, decreases as the growth temperature is increased due to the constraint of periodicity of patterned substrates imposed. An upper bound of a patterned substrate parameter before island size becomes less uniform seems to closely connect to island period and island edge spacing of the flat substrate. [ABSTRACT FROM AUTHOR]

The buckling structures of rigid films on soft substrates exhibit a “mexican hat” shape characterized by a nanometer scale depression at both edges. Based on finite elements simulations, a mathematical formulation is proposed to extract the elastic modulus mismatch between the film and its substrate, from the fine characterization of the buckle morphology. [ABSTRACT FROM AUTHOR]

The effect of varying the thickness of Pt top electrodes made by the electron beam induced deposition technique on the domain nucleation characteristics of Pb(Zr,Ti)O 3 films has been investigated by piezoresponse force microscopy. The advantage of this experimental setup is that the nucleation position can be precisely controlled allowing comparison between two capacitor structures with different top electrode thicknesses and negating the role of defect-induced polarization switching scenarios. In the ultrathin limit (< 5 nm), the coercive biases of polarization switching change substantially relative to thicker electrodes, from − 4.6 to − 2.6 V and from + 3.5 to 5.5 V respectively, which we link to a work function size effect. The evolution of the piezoresponse and coercive biases as a function of hysteresis loop cycling is presented and contrasted with that obtained on the bare film surface with no top electrode. To provide a counterpoint to the observed effects with top electrodes, we have demonstrated the variation in switching due to a top silicon oxide insulating layer. This work has revealed a method which could be used to control nucleation bias in ferroelectric thin film systems. [ABSTRACT FROM AUTHOR]

This paper reports on the structural evolution of the silicon–rich SiC/c–Si interface upon 1100 °C, 30 min thermal treatment, which is typically used when fabricating c–Si based devices that incorporate Si–nanocrystals in an SiC matrix. The onset of local interfacial epitaxy is revealed and analyzed. The inhibitory effect of a thin SiC interfacial buffer layer is reported. The investigation is based on Transmission Electron Microscopy and UV–Visible Reflectance spectroscopy. We show that a minimum thickness is required for the SiC buffer layer to preserve the presence and quality of the interface. The investigation also indicates that the epitaxial regrowth occurs in competition with random nucleation, which turns out to be the dominant crystallization mechanism in silicon rich SiC. A value 3 ÷ 10 nm is given for the diffusion distance of carbon in silicon upon 1100 °C, 30 min thermal treatment, which confirms previously reported results. The investigation shows that qualitative as well as quantitative structural information can be rapidly and routinely obtained by careful analysis of UV–Visible Reflectance spectral data. [ABSTRACT FROM AUTHOR]

Metal-induced layer exchange (MILE) has attracted increasing attention as a way to lower the crystallization temperature of amorphous semiconductor thin films on insulating substrates. This paper demonstrates that the quality of the catalytic Al layer strongly influences the growth properties in the MILE of amorphous Ge. The growth velocity of the MILE significantly decreases with increasing the deposition temperature of Al ( T Al : RT–200 °C), while the grain size of crystallized Ge becomes maximum (28 μm) at T Al = 100 °C. This behavior is attributed to the Al grain size depending on T Al , which influences both the nucleation frequency and the lateral growth velocity of Ge in Al. These findings give new insight into MILE for fabricating high-quality semiconductor thin films at low temperatures on inexpensive substrates. [ABSTRACT FROM AUTHOR]

The Ni(V)/Al multilayers, known as NanoFoil® (bilayer thickness of λ ~ 50 nm, total thickness of 80 μm), were used for in-situ transmission electron microscopy heating experiments carried out in order to establish the nucleation sites and growth modes of the intermetallic phases formed during their reaction. The performed observations showed that while the intermediate Al 3 Ni and Al 3 Ni 2 phases nucleate at Ni(V)/Al and Ni(V)/Al 3 Ni interfaces, respectively, the final NiAl nucleates throughout the intermixed Al 3 Ni and Al 3 Ni 2 (original Al) layer. The growth of the Al 3 Ni crystallites proceeds by a moving planar front along the Al layer changing the Ni(V)/Al into Ni(V)/Al 3 Ni multilayers. The growth of Al 3 Ni 2 crystallites resembles the standard coarsening of rounded precipitates. The growth of final NiAl phase is much faster than Al 3 Ni 2 and results in formation of a string of cubical crystallites separated by a discontinuous layer of fine Al 8 V 5 crystallites. The described series of phase transformations might be considered as a model for solid state diffusion controlled reaction of Ni/Al multilayers. [ABSTRACT FROM AUTHOR]

Effects of Ge growth rate and growth temperature were investigated on C-mediated formation of Ge quantum dots (QDs) on Si (100) substrate. The samples were prepared by a solid-source molecular beam epitaxy. Ge dots were scaled down and dot density increased with increasing Ge growth rate up to about 2 nm/min, and dot size and density were saturated beyond that. The effect of Ge growth temperature was strong at slow Ge growth rate, while it was insensitive at fast Ge growth rate. Consequently, minimum mean dot diameter of about 25 nm and maximum dot density of about 1.1 × 10 11 cm − 2 were obtained at growth temperature of 450 °C. These results suggest that the Ge growth condition of fast growth rate or low growth temperature acts effectively to increase the nucleation probability of Ge adatoms and consequently enables to form Ge QDs by maximizing the effects of C-mediated surface reconstruction. [ABSTRACT FROM AUTHOR]

The joint impact of the Si/Al layer thickness on the growth kinetics, the crystalline orientation and the size of the poly-Si grains resulting from aluminum-induced crystallization process is analyzed. It is shown that the surface coverage of resulting poly-Si layers rapidly decreases together with annealing temperature and the Si/Al ratio. The surplus of a-Si over the Al needed to ensure continuity of the poly-Si thin film is in the range of 35%–50% for Al layers thicker than 225 nm, but rapidly goes up to 200% as the thickness of the Al layer decreases below 50 nm. It is demonstrated that the angular distribution of grain orientations is discrete and shifts towards the {111} direction as the Si/Al increases. It is reported that during an isothermal annealing, the nucleation of Si grains occurs in two steps. Finally, a simple model of the aluminum-induced crystallization process explaining the two-step nucleation is proposed. [ABSTRACT FROM AUTHOR]

Ag nanoparticles were formed in PbZr 0.52 Ti 0.48 O 3 (PZT) thin films by the sol–gel technique through two stage processes. In the first stage, Ag-Pb alloy particles formed in all film heat treated for different time from 1 min to 10 min. The average size of the particles increased from 0.16 μm to 0.43 μm while the mole ratio of Pb/(Pb + Ag) in the alloy particles increased from 0.7% to 27%. After that in the second stage with the heat treatment time above 10 min, the lead rich Ag-Pb alloy particles started to decompose gradually. The silver nanoparticles formed in the thin film to form nano-Ag/PZT composite. The number of the silver nanoparticles of about 6 nm in size increased with increasing the heat treatment time from 20 min to 180 min. The permittivity and tunability of the nano-Ag/PZT composite thin film were 120% and 46% higher than those of the PZT thin film without Ag nanoparticles, respectively. [ABSTRACT FROM AUTHOR]

Low-temperature (≤ 300 °C) formation of orientation-controlled large-grain (≥ 10 μm) Ge-rich (≥ 50%) SiGe crystals on insulator are realized by the gold-induced layer-exchange technique. Stacked structures of a-Si 1 − x Ge x (0 ≤ x ≤ 1)/Au/SiO 2 are employed as starting materials. Here, thin-Al 2 O 3 layers are introduced as diffusion barrier at a-SiGe/Au interfaces to suppress random bulk-nucleation and make (111)-oriented interface-nucleation on SiO 2 dominant. For samples with Ge fraction of 80%–100%, (111)-oriented large-grains (≥ 10 μm) are obtained through layer-exchange during annealing at 250 °C. On the other hand, layer-exchange for Ge fraction of 50% does not proceed at 250 °C. This phenomenon is attributed to retardation of lateral growth by introduction of Si. To enhance lateral growth, increase of annealing temperature is examined. As a result, (111)-oriented large-grains (≥ 10 μm) are realized for SiGe with Ge fraction of 50%–100%, having uniform composition profiles, by annealing at 300 °C. This technique is very useful to realize high-performance flexible electronics, employing plastic substrates (softening temperature: ~ 350 °C). [ABSTRACT FROM AUTHOR]

A rapid melting growth of Ge on insulating substrate was developed using amorphous Si seed. Spontaneous nucleation process and lateral growth process occurred at different annealing temperature. Single-crystal Ge stripes on the insulator substrate were obtained as the Ge stripe was dominated by the lateral growth process along the stripes. Different single-crystal Ge stripe has different orientation. No preferential orientation was observed. Spatial gradient of solidification temperature along the Ge stripes induced by Si–Ge mixing in seeding region is the key to cause lateral growth of Ge stripes. Saturation of Si concentration along the Ge stripes at higher annealing temperature was observed, which was explained by limited Si volume in the seeding region. [ABSTRACT FROM AUTHOR]

Twelve inch wafer-to-wafer bumpless direct Cu bonding was achieved at room temperature for 60 h, and followed by annealing at 300 °C for 30 min. Interconnections with different pad pitches from 6 μm to 25 μm were obtained. Low electrical resistances of 27.73 mΩ indicated the bonding was completed. High shear strength of 35.9 MPa suggested the potential application of this process in wafer thinning. Observations of interface morphology presented continuous and tight bonding interface. Grain orientation inspections indicated that two kinds of preferred orientations were found at the bonding interface, one of which was near (100) and the other was near (110). This difference for preferred orientations may be related with yielding process. Furthermore, grain boundaries were found to be respectively zigzag and straight at the bonding interface. Based on these observations, bonding mechanism is proposed by the driven force of energy minimization theory. In bonded Cu pads, strain-favorable grain (with lower free energy) growth happened at the expense of other less strain-favorable grains (with higher free energy). Besides initial grain nucleation was formed by small grain connection with the same orientation at the bonding interface and grain growth happened after further annealing. [ABSTRACT FROM AUTHOR]

ZnO and ZnS nanodots deposited by simple, non-vacuum ultrasonic spray methods, spray pyrolysis and ion layer gas reaction, are used to control the nucleation and thereby the morphology of electrochemically grown ZnO nanorod arrays. The ZnO nanodot density and subsequently the density of electrochemically deposited ZnO nanorods is increased by increasing the aerosol flow and decreasing the substrate temperature during ZnO nanodot deposition. By increasing the substrate temperature during ZnO nanodot deposition, moreover, the nanorod tilt with respect to the substrate (normal) can be decreased. To tune the density of electrochemically deposited ZnO nanorods to lower values compared to growth on the bare substrate, ZnS nanodots are used to block energetically favorable nucleation sites for electrochemical ZnO nanorod growth and thereby reduce the ZnO nanorod density. [ABSTRACT FROM AUTHOR]

The orientation relationships and interfaces between ζ′-Au 5 Sn and Au have been studied by transmission electron microscopy. Epitaxial Au thin films were grown on the single-crystal NaCl surfaces and Sn was evaporated to form ζ′-Au 5 Sn. Results showed that on both the ( 1 ¯ 11 ) Au and (001) Au surfaces the (0001) ζ′ plane is the common interface surface with a common orientation relationship of ( 1 ¯ 100 ) ζ′ //(110) Au , which has a small misfit of 1.9%. The Au atoms have good matches across both interfaces. That δ-AuSn forms before ζ′-Au 5 Sn in the solid-state Au/Sn interfacial reactions was discussed by heterogeneous nucleation theory. Both phases have good orientation relationships to Au and therefore low interfacial energies. Analysis of the interfaces indicated that the ζ′-Au 5 Sn/Au interfacial energies should be less than δ-AuSn/Au, which favors the nucleation of ζ′-Au 5 Sn. However, the energy of formation of δ-AuSn is much larger, about 2.3 times, than that of ζ′-Au 5 Sn by data from references. Therefore δ-AuSn forms before ζ′-Au 5 Sn. [ABSTRACT FROM AUTHOR]

The orientation relationships and interfacial planes of the ε-Ag 3 Sn/Ag and ζ-Ag 4 Sn/Ag interfaces have been studied by transmission electron microscopy. Epitaxial Ag thin films were grown on the NaCl (001) and (111) surfaces and Sn was evaporated at various temperatures or by further annealing to form ε-Ag 3 Sn and ζ-Ag 4 Sn. Results showed that both phases have good orientation relationships with Ag on the (111) Ag surface but none on the (001) Ag surface. The energy of formation of ε-Ag 3 Sn is 1.62 times that of ζ-Ag 4 Sn. According to the heterogeneous nucleation theory, the critical nucleus size can be significantly reduced by coherent interfaces. The above interfaces results indicate that the interfacial energies of the ζ-Ag 4 Sn/Ag and ε-Ag 3 Sn/Ag interfaces are similar. Therefore ε-Ag 3 Sn should have a smaller critical nucleus size. Consequently ε-Ag 3 Sn nucleates first and forms before ζ-Ag 4 Sn in the Ag/Sn interfacial reaction. [ABSTRACT FROM AUTHOR]

Al–Si nano-porous templates were prepared using filtered cathodic vacuum arc deposition and investigated as surface-enhanced Raman scattering (SERS) active substrates. Al–Si thin films were deposited onto silicon substrates followed by immersion in ammonia solution to remove the aluminium columns to form a nano-porous structure. The pore size and density were controlled mainly by the deposition bias voltage applied to the substrate. Gold particles were deposited onto the nano-porous Al–Si templates by displacement deposition in a solution containing HAuCl 4 (0.1 mM). The size and dispersion of the deposited Au particles were controlled by the concentration of Au ions, the immersion time and morphology of the Al–Si template. The SERS-activity was measured with Cresyl Violet (C 25 N 3 H 30 Cl) dye as the target molecule, and the enhancement was influenced by the morphology of the nano-porous Al–Si templates. As the pore size decreased a higher density of nucleation sites for the growth of Au nanoparticles was formed resulting in a shorter inter-particle spacing of Au particles, and an enhancement of the Raman signal. [ABSTRACT FROM AUTHOR]

A way to prepare metallic precursors for CuIn 1 − x ,Ga x Se 2 (CIGS) solar cells has been recently introduced leading to efficiencies above 12.4%. It consists in the electrodeposition of Cu–In–Ga mixed oxides in an acidic nitrate aqueous solution followed by thermal reduction and selenization. This paper investigates, in a first part, the nucleation and growth mechanisms taking place during the co-electrodeposition of Cu–In–Ga oxide/hydroxide film. Scanning Electron Microscope observations coupled to Energy Dispersive X-ray spectrometry point out that the deposition is initiated by the formation of metallic copper nuclei. These nuclei enable the growth of Cu–In–Ga oxide film. This observation confirms that freshly deposited copper catalyzes nitrate reduction leading to an increase in the surface pH enabling the precipitation of the Cu–In–Ga hydroxides. In a second part, precursor films were elaborated with increasing Ga(NO 3 ) 3 concentration. After reduction of the films in hydrogen and selenization heat treatments, X-ray diffraction analysis shows the incorporation of Ga into the CIGS phase with increasing Ga content in the optimal composition range for photovoltaic applications (x = 0.25–0.34). Gallium composition profiles are evidenced in the films with a tendency to higher concentration near the Mo surface. Increasing annealing temperature allows a better homogenization of Ga in the film. The consequences are correlated to optoelectronic measurements (Eg and cell efficiency) with bandgap measurement and cell efficiencies (10 to 12%). [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) nanorod arrays with controllable packing density have been prepared on transparent conductive oxide substrates using a short, simple galvanic nucleation step. The packing density of the ZnO nanorods (NR) was increased by ~ 200% from 8.5 × 10 8 cm − 2 to 1.7 × 10 9 cm − 2 by increasing the initial galvanic nucleation (IGN) current density from − 0.2 mA/cm 2 to − 1.4 mA/cm 2 . Coinciding with the increase in NR density, a decrease in average NR diameter and length is observed. A strong influence of the IGN step on the optical properties can be correlated, despite otherwise identical deposition conditions. Photoluminescence measurements show decreasing Vis:UV emission, indicating a relative decrease of deep-level defects, and thus an improvement in crystal quality of the ZnO NR induced by the IGN step. The light scattering strongly decreases with increasing IGN current density, while simultaneously an increase in total and specular transmittance and a decrease in absorbance and reflectance are observed. Angular-resolved transmission and reflection measurements demonstrate non-Lambertian scattering with the angular distribution depending on wavelength and NR morphology. Thus, the variation of the IGN allows tuning the optical properties to optimize solar cell performance. [ABSTRACT FROM AUTHOR]

We report the growth of SnS thin films on mica substrates by molecular beam epitaxy. Excellent 2D layered structure and strong (001) texture were observed with a record low rocking curve full width at half maximum of ~0.101° for the SnS(004) diffraction. An interface model is used to investigate the nucleation of SnS on mica which indicates the co-existence of six pairs of lateral growth orientations and is in excellent agreement with the experimental Φ-scan measurements indicating 12 peaks separated by 30° from each other. To control the lateral growth of the SnS epilayers we investigate the utilization of a thin SnSe buffer layer deposited on the mica substrate prior to the growth of the SnS thin film. The excellent lattice match between SnSe and mica enhances the alignment of the nucleation of SnS and suppresses the minor lateral orientations along the mica[110] direction and its orthogonal axis. Detailed low-frequency noise measurement was performed to characterize the trap density in the films and our results clearly demonstrate substantial reduction in the density of the localized states in the SnS epilayer with the use of an SnSe buffer layer. [ABSTRACT FROM AUTHOR]

We report here on the atomic migration and associated nucleation mechanisms of Si nanocrystals on LaAlO3(001) surface, a high-κ crystalline oxide. Chemical and structural properties were investigated using X-ray photoelectron spectroscopy, X-ray photoelectron diffraction (XPD), reflection high-energy electron diffraction (RHEED), and ex situ with atomic force microscopy. The Si deposition was achieved by molecular beam epitaxy at room temperature. The morphological and chemical properties were followed as a function of isochronal post-growth annealing at increasing temperatures up to 800°C by 100°C steps. Up to 500°C the Si layer remains amorphous without any interdiffusion and interfacial alloy formation. Above 500°C Si nanocrystals nucleate on the surface by transformation of the amorphous Si layer into Si crystalline islands. Two kinds of annealing treatments were performed (direct current and electronic bombardment), leading to a better crystal quality (without stacking faults or twins) for a direct current heating process. Finally, a preferential epitaxial relationship between LaAlO3 and the Si islands was deduced by RHEED and confirmed by XPD: Si(001) planes are parallel to the LaAlO3(001) surface and rotated by 45° around the [001] growth axis. [ABSTRACT FROM AUTHOR]

Abstract: The orientation relationships and interfaces between ε-Cu3Sn and Cu have been studied by transmission electron microscopy. Epitaxial Cu thin films were grown on the NaCl (001) and (111) surfaces and then Sn was evaporated onto the Cu films at 200 or 150°C to form ε-Cu3Sn directly. On the (111)Cu surface the interface is (001)ε and (100)ε is parallel to Cu with a low misfit in the direction. However, no orientation relationship was found on the (001)Cu surface. Experimentally Cu3Sn forms after Cu6Sn5 in the reaction of Cu and Sn-containing solder. Analysis showed that the interfacial energies of the Cu6Sn5/Cu interfaces should be lower than those of the Cu3Sn/Cu interfaces due to better interfacial coherency. That is the main reason that Cu6Sn5 nucleates before Cu3Sn, even though Cu3Sn has a larger energy of formation. [Copyright &y& Elsevier]

Abstract: We use classical molecular dynamics and the modified embedded atom method to determine residence times and descent pathways of Ti and N adatoms on square, single-atom-high, TiN islands on TiN(001). Simulations are carried out at 1000K, which is within the optimal range for TiN(001) epitaxial growth. Results show that the frequency of descent events, and overall adatom residence times, depend strongly on both the TiN(001) diffusion barrier for each species as well as the adatom island-edge location immediately prior to descent. Ti adatoms, with a low diffusion barrier, rapidly move toward the island periphery, via funneling, where they diffuse along upper island edges. The primary descent mechanism for Ti adatoms is via push-out/exchange with Ti island-edge atoms, a process in which the adatom replaces an island edge atom by moving down while pushing the edge atom out onto the terrace to occupy an epitaxial position along the island edge. Double push-out events are also observed for Ti adatoms descending at N corner positions. N adatoms, with a considerably higher diffusion barrier on TiN(001), require much longer times to reach island edges and, consequently, have significantly longer residence times. N adatoms are found to descend onto the terrace by direct hopping over island edges and corner atoms, as well as by concerted push-out/exchange with N atoms adjacent to Ti corners. For both adspecies, we also observe several complex adatom/island interactions, before and after descent onto the terrace, including two instances of Ti island-atom ascent onto the island surface. [Copyright &y& Elsevier]

Abstract: Li2O–Nb2O5 ternary compound thin films were deposited by dual sputtering from LiNbO3 and Li2O targets to cover a wide range of Li/Nb molar ratios. When all parts of the films were crystallized during sputtering at elevated temperatures, pyrochlore phase crystallites of Li3NbO4, LiNbO3, and LiNb3O8 were preferentially oriented toward their respective (222), (006), and ( ) directions. These closely packed crystallographic planes having the lowest surface free energies were initially created under exposure to the plasma and the crystallization that followed proceeded exclusively on these seed planes. The volume fraction of each crystalline component as a function of the Li/Nb molar ratio obeyed the established phase diagram. In contrast, solid-phase crystallization of pre-deposited amorphous films through post annealing exhibited a non-equilibrium nature, and the volume fraction of each crystalline component depended on the crystallization rate rather than the Li/Nb molar ratio. Solid-phase crystallization decelerated when excess Li2O was contained in the film. Specifically, LiNbO3 crystallites with near-stoichiometric compositions were randomly oriented without the operating mechanism of preferential orientation toward c-planes. In certain situations, crystalline domains were spatially of inhomogeneous composition, resulting in the simultaneous coexistence of Li3NbO4, LiNbO3, and LiNb3O8. [Copyright &y& Elsevier]

TiO2/ZnO:Al (AZO) bilayers were grown by DC reactive sputtering at temperature below 200°C. The AZO structure was tuned in such a way that (0002) and (11-20) preferentially oriented and fiber textured domains were formed. The TiO2 layers grown at 150°C on those two kinds of substrates are partially crystalline (and not amorphous as expected) in a composition which is substrate-dependent. Anatase was selectively formed on (0002) oriented AZO substrates after deposition, and maintained for annealing temperatures up to 650°C. A mixture of anatase and rutile has instead nucleated and grown on the (11-20) oriented AZO substrate, with their relative amount changing by increasing the annealing temperature. Anatase selectivity and also its nucleation at low temperature are promising issues to realise flexible dye sensitised solar cells. [ABSTRACT FROM AUTHOR]

Abstract: Deposition of functional ceramic films on different substrates by using soft aqueous solution processing can represent a cheap, low- energy and environmental friendly alternative to other film technologies. In this study β-Ni(OH)2 polycrystalline films were grown on polytetrafluoroethylene, NiO, glass, copper, and Y:ZrO2 substrates from Ni2+–NH4OH aqueous solutions. A careful control of solution supersaturation was essential to induce heterogeneous nucleation on the substrate and film growth. This was realized through the gradual decomposition of the nickel amino complexes Ni(NH3)n 2+ using two different methods. Thermodynamic modeling of the Ni–NH4OH–H2O system was used to provide some general indications for defining the experimental conditions most suitable for film deposition and understanding the role of solution chemistry on film formation. Film microstructure and texture can be controlled by varying the substrate, the ammonia concentration, the ammonia evaporation rate, the soaking time and by adding a surfactant like sodium dodecylbenzensulphonate. As a result, films with different morphologies and orientations, as well as a uniform decoration of the substrate surface with Ni(OH)2 crystals, were obtained. The proposed method can be extended to the preparation of oxide and hydroxide films of other transition metals forming moderately stable amino complexes. [Copyright &y& Elsevier]

Ruthenium (Ru) thin films were grown on thermally-grown SiO2 substrates using atomic layer deposition (ALD) by a sequential supply of (ethylbenzene)(1,3-cyclohexadiene)Ru(0) (EBCHDRu, C14H18Ru), and molecular oxygen (O2) at deposition temperatures ranging from 140 to 350°C. A self-limiting film growth was confirmed at the deposition temperature of 225°C and the growth rate was 0.1nm/cycle on the SiO2 substrate with a negligible number of incubation cycles (approximately 2cycles). Plan-view transmission electron microscopy analysis showed that nucleation was started after only 3 ALD cycles and the maximum nuclei density of 1.43×1012/cm2 was obtained after 5 ALD cycles. A continuous Ru film with a thickness of ~4nm was formed after 40 ALD cycles. The film resistivity was decreased with increasing deposition temperature, which was closely related to its crystallinity, microstructure, and density, and the minimum resistivity of ~14 μΩ-cm was obtained at the deposition temperature of 310°C. The step coverage was approximately 100% at trench (aspect ratio: 4.5) with the top opening size of ~25nm. Finally, the ALD-Ru film was evaluated in terms of its performance as a seed layer for Cu electroplating. [ABSTRACT FROM AUTHOR]

Abstract: An ionic nucleation was proposed to deposit crystallized silicon film fast at 130°C. Initially, ionic argon was introduced into the deposition of amorphous silicon film for a short time. The energetic argon particles bombarded the grown surface slightly and reduced the nucleation. Then the argon flow was turned off and the film deposition remained proceeding. The low temperature deposited film was crystallized well. When this processed silicon film acted as a channel of bottom-gate thin-film transistor, it possessed current drivability superior to that of thin-film transistor using hydrogen diluted crystallized silicon channel. [Copyright &y& Elsevier]

Abstract: Tin-doped indium oxide (ITO) films were deposited on Si(100) and glass substrates at different deposition time by direct current pulse magnetron sputtering. The step profiler, four-point probe measurements and atomic force microscopy were used to study the thickness, sheet resistance, as well as the nucleation and growth behavior of ITO films, respectively. The dynamic scaling of roughness evolution could be divided into three stages, which are the growth of islands, the coalescence of islands, and the homogeneous growth, respectively. Compared with the glass substrate, it needs long time to nucleate on Si(100) substrate for fewer defects on the surface. Base on the result above, the mechanisms of defect nucleation and islands coalescence could be given. [Copyright &y& Elsevier]

Abstract: In this study we investigated the influence of cobalt thickness (from 50nm to 10nm) on the kinetics and texture of CoSi2 layers. In-situ X-ray diffraction measurements were performed during isothermal annealing to determine CoSi2 kinetics as explained in a previous publication. Decreasing the initial cobalt thickness (50nm, 30nm, and 10nm) induces a slowdown of the formation rate, especially for the 10nm Co layer. A model based on CoSi2 nucleation is used to explain this phenomenon. [Copyright &y& Elsevier]