Surface Crystal Orientation Research Articles

Effect of pre-deposition RF plasma etching on wafer surface morphology and crystal orientation of piezoelectric AlN thin films.

In this work, we describe the design and operation of a planarized capacitively coupled RF plasma module and investigate the effects of non-reactive RF plasma etching on Si (100) wafer surface morphology and crystal orientation of Al bottom electrodes and subsequently deposited AlN films. To ensure formation of highly (111) textured Al electrode, a thin 25-nm AlN seed layer was grown before the Al deposition. The seed layer's orientation efficiency improved with increasing the RF power from 70 to 300 W and resulted in narrowing the Al (111) rocking curves. AFM and XRD data have shown that crystal orientations of both the electrode and reactively sputtered AlN film are considerably improved when the substrate micro roughness is reduced from an ordinary level of a few nanometers to atomic level corresponding to root mean square roughness as low as about 0.2 to 0.3 nm. The most perfectly crystallized film stacks of 100-nm Al and 500-nm AlN were obtained in this work using etching in Ar plasma optimized to create an atomically smooth, epi-ready Si surface morphology that enables superior AlN seed layer nucleation conditions. X-ray rocking curves around the Al (111) and AlN (0002) diffraction peaks exhibited extremely low FWHM values of 0.68° and 1.05°, respectively.

Physical matching of metals: grain orientation association at fracture edge.

The objective of this study was to examine whether surface crystal orientation can be used to associate or differentiate metal fracture fragments. The orientations of individual crystals and crystals across the fracture plane were measured on polished steel and iron alloy surfaces using Electron Backscattered Diffraction/ Orientation Imaging Microscopy (EBSD/OIM). This investigation examined crystallographic characteristics within a metal. This study showed that for transgranular fracture, it is feasible that pieces of grains could be associated across the fracture surface with the difference in orientation between grains (misorientation) along a length sequence of grain orientations on one side of the fracture surface to associate the other side of a fracture surface. Regarding pair comparisons of crystals on fracture surfaces, it was estimated that the probability for an ordered sequence of six distinct oriented grains along a fracture surface to occur again is about 1 in 4.82 (10)(30) or 2.07 (10)(-31).

Electrochemical Characterization of a Cu(II)-Glutamate Alkaline Solution for Copper Electrodeposition

In this study, a cyanide-free electrolyte containing glutamate as a complexing agent is investigated as a more environmentally friendly alternative for alkaline copper plating. The solution was prepared using copper sulfate, sodium glutamate and potassium hydroxide. The pH of the electrolyte (pH = 8) and the ratio ligand:copper (R = 3), were chosen from equilibrium diagrams in order to avoid the formation of insoluble complexes and oxides. The electrochemical response of the system was determined by means of cyclic voltammetry. The results showed that copper electroreduction occurs in a two steps pathway with a cuprous-glutamate complex as an intermediate. Galvanostatic deposits obtained from the bath under study had proper brightness and roughness at the selected current density conditions. Scanning electron microscopy and X-Ray diffraction were carried out in order to characterize deposits surface morphology and crystal orientation. Chronoamperometric experiments together with atomic force microscopy proved that copper deposits grow through an instantaneous nucleation mechanism in which nuclei are not exactly spherical. These preliminary studies suggest that the Cu+2-glutamate electrolyte may be suitable for the replacement of cyanide baths in copper electrodeposition at high pH without the need of additives as this electrolyte acts as a self-levelling system. Also, the use of this electrolyte could eliminate the need of performing strike deposits on less noble substrates, allowing a one step plating process.

Comparative simulation study of the structure of the plastic zone produced by nanoindentation

Using molecular-dynamics simulation, we study nanoindentation in fcc (Cu and Al) and bcc (Fe and Ta) metals by a spherical indenter and investigate the size of the plastic zone generated. We find that while it does not strongly depend on crystal structure, surface orientation, and indentation parameters, the extent of the plastic zone is substantially larger before the retraction of the indenter. After retraction, the results are in good agreement with available published data. Plasticity develops by the generation, propagation and reaction of dislocations; they fall into two groups, those that adhere to the indentation pit, and those that have been emitted either into the substrate interior or glide along the surface. The total length of the dislocation network generated roughly follows available geometrical estimates; results for individual surface orientations may, however, differ quite strongly. The radial distribution of the dislocations attached to the indentation pit is computed; as a rule it shows a maximum at some depth below the indentation pit.

Influence of silver/silicon dioxide on infrared absorption spectroscopy of sodium nitrate

Quickly detecting of ocean nutrient was one important task in marine pollution monitoring. We discovered the application of surface-enhanced infrared absorption spectroscopy in the detection of ocean nutrient through researching the evaporation of sodium nitrate solution. The silicon dioxide (SiO2) with highly dispersion was prepared by Stober method, The silver/silica (Ag/SiO2) composite materials were prepared by mixing ammonia solution and silicon dioxide aqueous solution. Three kinds of composite materials with different surface morphology were fabricated through optimizing the experimental parameter and changing the experimental process. The surface morphology, crystal orientation and surface plasmon resonance were investigated by means of the scanning electronic microscope (SEM), X-ray diffraction (XRD), UV-Visible absorption spectrum and infrared ab- sorption spectroscopy. The SEM images showed that the sample A was purified SiO2, sample B and sample C were mixture of silver nanoparticle and silicon dioxide, while sample D was completed nanoshell structure. The absorption spectroscopy showed that there was surface plasmon resonance in the UV-visible region, while there was possibility of surface plasmon resonance in the Infrared absorption region. The effect of Ag/SiO2 composite material on the infrared absorption spectra of sodium nitrite solution was investigated through systematically analyzing the infrared absorption spectroscopy of sodium nitrate solution during its evaporation, i. e. the peak integration area of nitrate and the peak integration area of water molecule. The experimental results show that the integration area of nitrate was enhanced greatly during the evaporation process while the integration area of water molecule decreased continuously. The integration area of nitrate comes from the anti-symmetric stretch vibration and the enhancement of the vibration is attributed to the interface effect of Ag/SiO2 which is consistent with Jensen T.R's result.

Surface Controlled Growth of Thin-Film Strontium Titanate Nanotube Arrays on Silicon

We demonstrate the vertical self-organized growth of thin-film SrTiO3 (STO) nanotube arrays (NTAs) on SiO2 substrate. The surface morphology and crystal orientation of the grains at the exterior wall of the backbone TiO2 nanotube arrays were found to play an important role in the growth rate as well as the final morphology of the STO NTAs. A formation mechanism is proposed that involves nucleation of SrTiO3 nanocubes through a semitopochemical route followed by a self-assembly process resulting from the Ostwald-ripening-assisted oriented attachment of SrTiO3 nanocubes. It was shown that under appropriate reaction kinetics the nanotube architecture of the overall template can be maintained to form STO NTAs. The application of this novel platform enables a controlled and efficient mass fabrication of STO NTAs on widely used inexpensive silicon substrates, which can potentially lead to full integration with electronics in the near future.

Stress-induced phase transformation and optical coupling of silver nanoparticle superlattices into mechanically stable nanowires.

One-dimensional silver materials display unique optical and electrical properties with promise as functional blocks for a new generation of nanoelectronics. To date, synthetic approaches and property engineering of silver nanowires have primarily focused on chemical methods. Here we report a simple physical method of metal nanowire synthesis, based on stress-induced phase transformation and sintering of spherical Ag nanoparticle superlattices. Two phase transformations of nanoparticles under stress have been observed at distinct length scales. First, the lattice dimensions of silver nanoparticle superlattices may be reversibly manipulated between 0-8 GPa compressive stresses to enable systematic and reversible changes in mesoscale optical coupling between silver nanoparticles. Second, stresses greater than 8 GPa induced an atomic lattice phase transformation, which induced sintering of silver nanoparticles into micron-length scale nanowires. The nanowire synthesis mechanism displays a dependence on both nanoparticle crystal surface orientation and presence of particular grain boundaries to enable nanoparticle consolidation into nanowires.

Pulse electrodeposition and corrosion properties of Ni–Si3N4 nanocomposite coatings

The development of modern technology requires metallic materials with better surface properties. In the present investigation; Si3N4-reinforced nickel nanocomposite coatings were deposited on a mild steel substrate using pulse current electrodeposition process employing a nickel acetate bath. Surface morphology, composition, microstructure and crystal orientation of Ni and Ni–Si3N4 nanocomposite coatings were investigated by scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffraction analysis, respectively. The effect of incorporation of Si3N4 particles in the Ni nanocomposite coating on the micro hardness, corrosion behaviour has been evaluated. Smooth composite deposits containing well-distributed silicon nitride particles were obtained and the crystal grains on the surface of Ni–Si3N4 composite coating are compact. The crystallite structure was face centred cubic (fcc) for electrodeposited nickel and Ni–Si3N4 nanocomposite coatings. The micro hardness of the composite coatings (720 HV) was higher than that of pure nickel (310 HV) due to dispersion-strengthening and matrix grain refining and increased with the increase of incorporated Si3N4 particle content. The corrosion potential (E corr) in the case of Ni–Si3N4 nanocomposite had shown a negative shift, confirming the cathodic protective nature of the coating.

Modulated optical properties of nonpolar gallium nitride via surface in-situ functionalization with cysteamine assisted phosphoric acid

In-situ functionalization of nonpolar a-plane gallium nitride (GaN) surface was achieved by adding cysteamine to phosphoric acid, aiming to modulate its optical properties. The emission properties and oxide formation were explored through surface characterization with atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and water contact angle. Nonpolar a-plane bulk GaN sample sliced from a GaN boule and nonpolar a-plane GaN thin layer heteroepitaxially grown on r-plane sapphire were used to elucidate the effects of in-situ functionalization of identical surface orientation of GaN crystals with different defect ensembles. The addition of cysteamine to the phosphoric acid solution was found to result in: (i) increased surface roughness, (ii) no change to hydrophobicity, (iii) decreased oxygen content at high solution temperatures and increased gallium and nitrogen content versus phosphoric acid solutions at similar temperatures without cysteamine. The in-situ functionalization resulted in enhanced PL intensity from the nonpolar bulk GaN, while the PL intensity from the nonpolar heteroepitaxially grown GaN layer on sapphire was significantly reduced. The opposite PL modulation was explained by the effects of different defects present in the two samples on the nonradiative recombination.

Crystallization-Driven Surface Segregation and Surface Structures in Poly(l-lactide)-block-Poly(ethylene glycol) Copolymer Thick Films

In this work, we used poly(L-lactide)-block-poly(ethylene glycol) (PLLA-b-PEG) copolymer thick films to investigate the effect of crystallization on surface segregation, surface crystal orientation, and morphology by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), reflection optical microscopy (ROM), and two-dimensional grazing incident wide-angle X-ray scattering (2D GIWAXS) methods. ATR-FTIR results indicated that the surface fraction of PLLA block increased from 0.48 to 0.79 when T(c,PLLA) increased from 70 to 110 °C. Polarized ATR-FTIR and 2D GIWAXS results indicated that PLLA crystal lamellae preferentially oriented parallel to the film surface with increasing T(c,PLLA). The surface crystallinity of PLLA was almost independent of T(c,PLLA), while the surface crystallinity of PEG decreased with increasing T(c,PLLA). On the basis of surface crystal orientation and crystallization kinetics, we suggested that the excess of PLLA component at the surface was mainly dominated by a coupling effect of crystallization behavior and surface segregation.

Direct Observations of the Dissolution of Fluorite Surfaces with Different Orientations

Atomic force microscopy has been used to observe the surface dynamics during dissolution of polished fluorite surfaces with different orientations. These surfaces, with an initially high density of atomic scale defects, showed fast changes during the first seconds in contact with a solution. Different types of structures developed on each surface, depending on its initial orientation and solution composition. These structures dissolved slower than the main surface persisting for at least 67.5 days of continuous dissolution. A new interpretation of traditional kinetic and thermodynamic models of dissolution applied to surfaces with a high density of steps is proposed to explain the observations. The new model includes the following: (a) fast initial dissolution at defect sites, (b) formation of a fluid boundary layer at the mineral–solution interface enriched in the dissolving ions, and (c) precipitation of more stable fluorite structures nucleated at surface defects. This model highlights the importance of considering surface defects and crystal orientation for advancing our understanding of processes happening at the mineral–solution interface and for developing more accurate kinetic dissolution and crystal growth models essential in Earth and material sciences.

Macro-to-Nano Scale Modeling the Effect of Surface Energies on Surface Melting Phenomena in Metallic NanoTubes/Wires

Among nonomaterial with different geometric shapes, nanotubes and nanowires received special attentions with increasing applications in electronic industry and nanorobotic due to their unique properties. Therefore, in order to study the fundamental properties of nanotubes/wires, in this paper we will focus on modeling the melting of different crystal surface of metallic materials. Although there are different models in literature based on change of cohesion energy or coordination number at nanoscale, here we present a generalized thermodynamics model which considers layer by layer melting of nanotubes/wires. This model considered the surface energy of solid-gas, liquid-gas and solid-liquid along with the effect of fcc, bcc and hcp crystallography of different metals and their different surface crystal plane orientations. During the analytical simulation of surface melting, different run have been performed for variable size of tubes/wires in order to involve the size effect at nanoscale. Calculation results of model will be presented for some metallic systems such as: Ni, Pb, Fe and Zn. Results of our calculations show good agreement with experimental results and other theoretical predictions in literatures. Our model provides a powerful tool to analysis melting phenomena of metallic nanotubes/wires at different crystal structures and surface plane orientations for various sizes at nanoscale.

Effects of crystal orientation on the dissolution of calcite by chemical and microscopic analysis

The purpose of this work was to examine the effects of polished crystal-surface orientation and degree of solution undersaturation on the dissolution kinetics of calcite. Crystallographic surface orientations utilized in this study included natural calcite specimens polished approximately parallel to the (104) plane, giving rise to surfaces with flat terraces with few steps, as well as fully kinked surfaces created by sectioning approximately parallel to the (001) plane. Results from inductively coupled plasma optical emission spectroscopy (ICP-OES) and vertical scanning interferometry (VSI) investigations revealed how crystallographic orientations of calcite with initially higher energy surface morphologies were associated with greater extent of reaction, greater surface retreat, and therefore, greater initial transient dissolution rates than those with lower energy initial surface morphologies. However, both the ICP-OES and atomic force microscopy (AFM) results confirm that the effects of crystal orientation become minimal under long-term conditions because (1) variously oriented calcite surfaces exhibited similar “long-term” rates and (2) orientations with high initial reactive site densities developed lower energy morphologies. Estimating a step rate coefficient from the experimental data from a miscut sample suggest that these coefficients may be highly morphology dependent. Results from this study are significant for predicting long term calcite dissolution rates because they suggest that the “long-term” dissolution rate of calcite will be governed by the rates of the rhombohedral faces and microfacets and the time-scale for approaching such conditions is of the order of days at room temperature and slightly alkaline solution conditions.

Effect of nicotinamide on electrodeposition of Al from aluminium chloride (AlCl3)-1-butyl-3-methylimidazolium chloride ([Bmim]Cl) ionic liquids

The effect of nicotinamide on the electrodeposition of Al was first investigated in the ionic liquid [Bmim]Cl/AlCl3 (40.0/60.0, mol%) by means of cyclic voltammetry and chronopotentiometry. Cyclic voltammograms indicated that nicotinamide produced an inhibiting effect on Al deposition, which can be attributed to the adsorption of nicotinamide on the electrode surface. Galvanostatic deposition experiments revealed that nicotinamide served as a very effective leveling agent, resulting in highly uniform and smooth Al deposits. The effects of temperature and current density on the surface morphologies and crystal orientations of Al deposits were also studied. As the temperature was increased from 30 to 70 A degrees C, the grain size of Al deposits increased but the intensity of the preferred (200) crystallographic plane weakened. By contrast, the opposite applied just with increasing current density from 3.4 to 9.4 mA cm(-2).

Modification to an Auger Electron Spectroscopy system for measuring segregation in a bi-crystal

It is reported that different crystal surface orientations yield different segregation fluxes. Although there were a few attempts to confirm these predictions experimentally, it is very difficult to compare data without making a few assumptions. Parameters like temperature measurement, crystal history and spectrometer variables are all adding to the complexity of directly comparing the segregation behaviour from one crystal to another. This investigation makes use of a Cu bi-crystal, modifications to the scanning control unit of the AES electron beam to eliminate the difference in experimental parameters and specialized written software to automate the data acquisition process. This makes direct comparison of segregation parameters on two different orientations possible. The paper describes the electron beam modifications, experimental setup and procedures, as well as the software developed to control the electron beam and automate data acquisition.

Facile synthesis and catalytic oxidation property of palygorskite/mesocrystalline Ce1−xMnxO2 nanocomposites

We have developed a one-pot chemical approach to prepare palygorskite (PG) supported mesocrystalline Ce1−xMnxO2 oxides with controllable surface coverage, crystal orientation and dopant fraction. Transmission electron microscopy reveals that the surface is composed of a single phase based on the face-centered cubic CeO2 and the crystals are highly oriented with the axis [100] parallel to the longitudinal direction of PG as if the Mn3+ molar fraction x is 0.2 or less. However, when the Mn3+ molar fraction is larger than 0.2, a mixture of face-centered cubic (fcc) CeO2 and body-centered cubic (bcc) α-Mn2O3 forms and the preferential crystal orientation disappears as revealed by XRD and Raman measurements. The acetate group and PG support are believed to play significant role in the mesoscally oriented attachment. The effects of the molar fraction of Mn3+ on the degradation rate of methyl orange are investigated. Results show that PG/Ce1−xMnxO2 composite has remarkably enhanced catalytic activity as compared with pure PG and PG/CeO2, and the maximum degradation rate of methyl orange reaches 98% when the molar fraction x is 0.2, due to the unique mesocrystalline structure with adequate oxygen vacancies as well as predominant exposure of highly active {200} planes.

Nano-Machining Polishing Method on Metal Materials

Ice desk can realize the polishing on the metal material. Ice desk polishing can decrease the surface. Ice desk polishing can get ideal polishing result on LY12 aluminum alloy, which is nonferrous metal and unsuitable for traditional grinding and polishing. Under micro-loading or zero-loading, when the two faces are in sliding friction and the interval of boundary interface decreases to the degree that molecular force can make its function, the main reason removing the metal surface materials is lattice relaxing, structure splitting, surface energy and adherence energy in the interface. Crystal structure, surface crystal orientation, surface bias-gathering effect, adsorbs effect etc. is all have influences on the surface roughness of the metal material.

Physical and electrochemical characterizations of Ni-SiO2 nanocomposite coatings

Advances in materials performance often require the development of composite system. In the present investigation, SiO2-reinforced nickel composite coatings were deposited on a mild steel substrate using direct current electrodeposition process employing a nickel acetate bath. Surface morphology, composition, microstructure and crystal orientation of the Ni and Ni-SiO2 nanocomposite coatings were investigated by scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffraction analysis, respectively. The effect of incorporation of SiO2 particles in the Ni nanocomposite coating on the microhardness and corrosion behaviour has been evaluated. Smooth composite deposits containing well-distributed silicon oxide particles were obtained. The preferred growth process of the nickel matrix in crystallographic directions , and is strongly influenced by SiO2 nanoparticles. The average crystallite size was calculated by using X-ray diffraction analysis and it was ~23 nm for electrodeposited nickel and ~21 nm for Ni-SiO2 nanocomposite coatings. The crystallite structure was fcc for electrodeposited nickel and Ni-SiO2 nanocomposite coatings. The incorporation of SiO2 particles into the Ni matrices was found to improve corrosion resistance of pure Ni coatings. The corrosion potential (Ecorr) in the case of Ni-SiO2 nanocomposite coatings had shown a negative shift, confirming the cathodic protective nature of the coating. The Ni-SiO2 composite coatings have exhibited significantly improved microhardness (615 HV) compared to pure nickel coatings (265 HV)

Electrodeposition of purified aluminum coatings from dimethylsulfone–AlCl3 electrolytes with trimethylamine hydrochloride

Aluminum (Al) coatings have been electrodeposited from dimethylsulfone (DMSO2)–AlCl3 electrolytes, but the coatings usually contained trace amounts of chlorine (Cl) and sulfur (S) as impurities. Since these impurities make the coatings hard and brittle, and moreover may adversely affect the corrosion- and oxidation-resistances of the Al coatings, it would be desirable to decrease their contents in the Al coatings. Examination of the Al coatings electrodeposited from the electrolytes with the addition of various amounts of trimethylamine hydrochloride (TMA) revealed that the Cl and S contents of the Al coatings decreased with increasing concentration of TMA in the electrolyte. The addition of TMA also brought about changes in the surface morphology and crystal orientation of the Al coatings. Preferential adsorption of TMA on the surface of the Al deposit was inferred to be a cause of the exclusion of Cl and S from the Al coating. As a result of the decrease in Cl and S contents, the Al coatings were softened.

Surface modification of yttria-stabilized-zirconia thin films under various oxygen partial pressures

This report discusses the structural and spectroscopic analysis of yttria-stabilized-zirconia (YSZ) thin films grown on Al2O3(0001) substrates. It is found that the changes of oxygen partial pressure during the growth are closely related to the surface chemical compositions and the surface crystal orientations of the thin films. The presence of oxygen partial pressure produces a polycrystalline structure on the thin film while a preferred orientation of crystal structures is formed under no oxygen partial pressure. Difficulty arises in identifying the structure of the thin films due to the broad characteristics of the x-ray diffraction (XRD) peaks; however, the XRD rocking scan suggests the existence of two lateral domain sizes. The chemical analysis of the thin films from x-ray photoelectron spectroscopy measurements indicates the enrichment of surface yttrium-oxide as the oxygen partial pressure increases. The detailed analysis of valence band spectra also suggests that the thin films undergo a surface structural phase transition, i.e., transforming from a single tetragonal structure to a mixed (cubic+monoclinic) structure. Furthermore, the optical data display the small increments of the band gap as the oxygen partial pressure increases, which reflects the presence of the structural phase transition of the thin films.