Typical Surface Morphology Research Articles

Electroless Ni–P coating of different magnesium alloys

Abstract Coating of AZ31B, AE 42 and ZRE1 wrought magnesium alloys was carried out using electroless Ni plating technique in a solution of nickel sulphate, sodium hypophosphite, ammonium hydrogen fluoride and glycine with a zinc immersion pre-treatment. The results of SEM/EDX investigations and X-ray diffraction indicate that the coat exhibit a typical surface morphology with compact nodules with good adherence to the substrate. The coat was composed of amorphous structure, which transformed to a mixture of crystalline Ni and Ni 3 P precipitates after heat treatment at 673°K for 1 h. The phosphorous (P) content increased gradually from the substrate towards the surface reaching a maximum of 10 wt.% to 18 wt.% on the surface depending on the substrate alloy and the thickness of deposit. The hardness of the coat was found to increase with the P content and also after heat treatment. The electrochemical corrosion test in NaCl solution indicated a great improvement in the corrosion resistance of the Mg substrates and that a noble behaviour of Ni–P was obtained regardless of the heat treatment process. The forming ability test indicates that hot rolling of the coated substrate does not succeed to keep a continuous coat due to cracking of the coat in both as-coated and heat treated specimens.

Scanning electron microscopy and resistive transition of in-situ grown YBCO films by pulsed laser deposition

In this paper we summarize the deposition parameters, the crystalline structure and the critical temperature of the in-situ grown YBa2Cu3O7-δ (YBCO) films obtained by pulsed laser deposition (PLD) using our kinetic cool-down regime, described in previous papers. We analyze the resistive transition curves and the corresponding scanning electron microscopy (SEM) pictures of the best in-situ grown YBCO films, in order to better characterize the films and refine the deposition process. SEM pictures reveal the typical surface morphology of both in-situ grown and post-deposition, oxygen atmosphere annealed YBCO films. A significant smoother surface of the in-situ grown films is obtained.

EFFECTS OF RAPID THERMAL ANNEALING ON MICROSTRUCTURES AND PROPERTIES OF PZT-PT/TI STACKS FOR MEMS APPLICATION

ABSTRACT The effects of rapid thermal annealing (RTA) on microstructures, properties, and residual stress of Pt/Ti electrodes and sol-gel derived lead zirconate titanate (PZT) films were investigated. It was found that when heating rate was 3.5°C/s, the Pt/Ti electrode conglomerated to form a typical hillock surface morphology, companied by remarkable degradations in both surface roughness and electric conductivity. When using 10.5°C/s as the heating rate, the Pt/Ti conglomeration and degradation can be effectively retarded. Accordingly, the PZT film exhibited different properties at various RTA conditions. Furthermore, Ti diffusion was found mainly happened in a short period after heat-treatment started.

Characterization of the Microstructure of Phase Segregated Amylopectin and β-Lactoglobulin Dry Mixtures

The microstructure of phase-segregated amylopectin (AP) and β-lactoglobulin (βlg) mixtures formed during drying from solutions with different concentrations and different polysaccharide and protein ratios have been studied using atomic force microscopy (AFM) and transmission electron microscopy (TEM). AFM was used as the main technique and TEM was used to confirm the results. Systems with only one of the components, AP or βlg, displayed even structures. When the polysaccharide and the protein were in the same system they phase segregated with a sharp boundary between the phases. According to the type of surface morphology of the phase-segregated samples, they were grouped into: domains wetting the air-water surface and domains appearing to be immersed in the solid film. The size range of the domains varied widely from about some nanometers to about a few micrometers which was determined by kinetic reasons or by restrictions given by the film structure of the sample. The two phase systems were AP-continuous phase at AP to βlg ratios above about 1:3 and βlg-continuous phase at ratios below about 1:6. Between these ratios, the systems appeared more or less bicontinuous. The morphology as well as its position in the phase diagram suggested a spinodal phase separation. Phase separation was also observed in the metastable region (AP to βlg ratio 3:1), although the domains were smaller and less developed and it was interpreted as binodal phase separation.

Modelling the impact of high‐rise buildings in urban areas on precipitation initiation

AbstractThe impact of urban areas upon precipitation distribution has been studied for many years. However, the relative importance of the distribution and type of surface morphology and urban heating remains unclear.A simple model of the surface sensible heat flux is used to explore the impact of urban heterogeneity. Sensitivity experiments are carried out to test the validity of the model, and experiments with a schematic urban morphology are used to investigate the impact of different types of building arrays. It is found that high‐rise buildings over relatively small areas may have just as much impact as somewhat lower buildings covering a much larger area. The urban area produces considerable spatial variation in surface sensible heat flux. Data from a C‐band radar located to the north of Greater Manchester provides evidence that convective cells may be initiated by the sensible heat flux input generated by the high‐rise buildings in the city centre when the atmospheric boundary layer is unstable. Copyright © 2007 Royal Meteorological Society

SiC Coatings Deposited by RF Magnetron Sputtering

Amorphous SiC coatings were deposited by RF magnetron sputtering from a sintered SiC target onto Si(100) substrate at room temperature. The influence of RF power on the surface morphology and the RMS surface roughness of the resulting SiC coatings was studied by using atomic force microscopy. Two types of surface morphologies were obtained. The corresponding forming mechanisms were also discussed.

Microstructure characterization of InAs 0.93Sb 0.07 films grown by ramp-cooled liquid phase epitaxy

InAs 0.93Sb 0.07 alloy thin films were grown by ramp-cooled liquid phase epitaxy on (100) InAs substrate using horizontally sliding multi-wells graphite boats. The systematic microstructural characterizations of the epi-grown films were analyzed by X-ray diffraction, scanning electronic microscopy and energy dispersive spectra. Four typical surface morphologies of the films were observed, which depend sensitively on growth parameters such as the growth temperature, the substrate etching time, the flux of the hydrogen, and the cooling range and rate. The film shows high crystal perfection with (100) orientation, as evidenced by X-ray measurement. The crystal quality of the epilayer was evaluated by the X-ray double axes diffraction, and the dislocation density was estimated through fitting the (200) and (400) rocking curves by Gaussian lineshape.

PLLA Morphology Controlled by Dry-cast Process

Abstract The influence of solvent evaporation rate, in the dry-casting process, on crystallinity and morphology of crystallizable polymeric membrane was studied. Poly-l-lactic acid (PLLA) was taken as an example. The membranes were characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). By controlling the solvent evaporation rate, samples with various crystallinities were prepared. From higher to lower crystallinity the membranes exhibit three types of surface morphology in sequence: granule, stripe and smooth.

Effects of mechanical stimuli and microfiber-based substrate on neurite outgrowth and guidance

We introduced mechanical stimuli and micropatterned substrate with microfibers to investigate their effects on neurite outgrowth along with nerve growth factor in vitro. Two types of surface morphology were used: a surface that was coated by laminin alone and a surface where in microfibers was added on the laminin surface. PC-12 cells were seeded on both surface types and cultured for 2 d. The magnitudes of shear stresses ranged from 0.10 to 1.50 Pa. Two days after stimulation by shear stress, neurite outgrowth and its direction were measured by F-actin staining and digital image processing. When a shear stress of 0.50 Pa was applied, neurons were most highly aligned with microfibers. The average length of neurite outgrowth with microfibers was largest at a shear stress of 0.25 Pa. The results suggest that micropatterned fibers and fluid-induced shear stress are promising for stimulating neurite outgrowth in a desired direction.

Comparison of Gas and Liquid Propylene Polymerization Technique - Hydrogen Effect on Thermal, Rheological, and Morphological Properties of PP

A comparison of PP qualities, which are produced with two different polymerization techniques-gas phase(GP) and liquid pool (LP)-under precise control of the polymerization temperature (70 °C) and pressure (GP = 25 bar, LP < 60 bar) using identical Ziegler-Natta catalyst (TiCl4/phthalate/MgCl2 + TEA/silane), is presented. A series of homopolymer PP in a wide MW range from 100 000 to 1 600 000 g · mol-1 was polymerized. During polymerization all samples were characterized exactly by their Rp-profil. The effect of hydrogen on the initial reaction rate and on MW and MWD was analyzed on the basis of this so-called kinetic fingerprint. The results showed that the polymerization rate reached a maximum for LP, of about 150 kg · gcat-1 · h-1, in contrast to GP with a maximum of Rp,0 = 45 kg · gcat-1 · h-1. Analysis was carried out by means of GPC, SEM, DSC, platte-platte rheometer, and WAXS. The results first showed that the MWD of LP PP is narrower (PD ~ 6.8) than for the GP PP (PD ~ 8), polymerized in two steps. An SEM study of the powder particle shows the typical dent surface morphology of polymers using Ziegler-Natta catalysts for polymerization. WAXS and DSC analysis demonstrated that almost only the α-modification of crystalline structure exists and that the crystallinity becomes considerably higher after solidification from melt. Furthermore, it was found that the crystallite size distribution depends on the polymerization technique. Rheological studies indicate that GP PP behaves more elastically. To summarize, it is shown that PP produced with the LP polymerization technique is more homogenous and of high quality.

CMP surface characteristics of twinned copper subgrains

Copper wafers are polished with an experimental slurry prepared to contain strong oxidizing components for revealing grain structures. Two types of surface morphologies, twinned and equiaxed grains, are observed on two groups of wafers, following chemical mechanical planarization (CMP). An atomic force microscope surface analysis indicates that the equiaxed grain structure provides better overall surface quality than the twinned structure. A polishing model is proposed to explain the surface relief among the twinned subgrains. The results suggest that Cu electroplating and the subsequent annealing processes should be optimized to promote uniform equiaxed grains for better integration with CMP and other chip manufacturing processes.

In situ spectroscopic ellipsometry of hydrogen-argon plasma cleaned silicon surfaces

A low energy hydrogen-argon plasma was applied to clean silicon (100) surface. In situ spectroscopic ellipsometry in the UV–Vis range was used to characterise the morphology and etching damage in dependence on the substrate temperature. Ex situ atomic force microscopy and in situ reflection high-energy electron diffraction was used to characterise complementary the surface morphology and surface structure. In dependence of the substrate temperature two types of surface morphologies could be classified. Using spectroscopic ellipsometry the optimum conditions for the silicon surface cleaning were determined.

Study of surface defects on 3C–SiC films grown on Si(1 1 1) by CVD

Monocrystalline 3C–SiC layers were synthesized by atmospheric pressure chemical vapor deposition on Si(1 1 1) substrates using SiH 4 and C 3H 8 gases at temperatures between 1350°C and 1400°C. Both atomic force microscopy and X-ray diffraction spectroscopy measurements reveal a notable dependence of surface morphology and layer quality on the C/Si ratio in the gas phase during experiment. In particular, three types of surface morphologies have been observed: (i) rough, (ii) mirror-like and (iii) pyramidal defect covered, attributed to lack of C, C limited growth and stacking faults generation, respectively. From Raman spectral peak shifts, a tensile strain state of the SiC films, lower for the 1400°C grown series, was found.

Atomic force microscopy studies on surface morphologies of CdHg(SCN)4 crystals grown in solutions containing excessive amount of Cd(II) cations

AbstractSurface morphologies of CdHg(SCN)4 (CMTC) crystals grown from solutions with excessive amount of Cd(II) cations (5%, 20% and 50% in molar ratio) have been investigated by atomic force microscopy (AFM). [Cd(SCN)n]2‐n (n ≤ 4) complex anions formed by addition of excessive Cd(II) cations in the solutions have been found to act either as growth units or impurities during CMTC crystal growth. On the prismatic faces, incorporation of [Cd(SCN)n]2‐n (n ≤ 4) complex anions as growth units leads to the formation of well‐oriented protuberance trains at the step fronts, named as “locally anisotropic crystal growth”. These protuberances become fewer, less distinct and nearly disappeared with the increase of excessive Cd(II) cations in the solutions. The pyramidal face, however, varies from regular 2D nucleation growth at a low concentration of Cd(II) to much rougher growth surfaces at high concentrations, exhibiting typical surface morphologies where crystal growth is completely inhibited by impurities. Observations in this experiment provide a new picture of crystal growth.

AFM observation of as-grown ( [formula omitted]) Bi-2223 and ( [formula omitted]) Y-123 thin films by MOCVD

In high temperature superconductors (HTS) the coherence length along non- c-axis directions is longer. This feature can be useful when designing electronics devices based on HTS. Therefore, growth and characterization of non- c-axis oriented thin HTS films is of great interest. In this paper we present our comparative results on preparation by MOCVD and characterization by atomic force microscopy, X-ray diffraction and transport measurements of as-grown (1 1 9) Bi-2223 and (1 0 3) Y-123 thin films on (1 1 0) SrTiO 3. The films have shown the same type of surface morphology (grains with mountain-range shape, aligned in parallel chains to the [0 0 1] substrate’s azimuth). This morphology is the result of the orientation relationship between the (1 1 9) Bi-2223 or (1 0 3) Y-123 and (1 1 0) SrTiO 3. The transport measurements with temperature revealed strong anisotropy of the films in the normal state region when the measuring current has been applied in-plane, parallel and perpendicular to the edges (from the basal plane) of the mountain-range grains. Higher values for T c0 have been obtained for the Y-123 films (42 K) than for the Bi-2223 ones (31 K). The both films are as-grown and non-oxygenated ones.

Microstructure, electrochemical surface and electrocatalytic properties of IrO2+Ta2O5 oxide electrodes

X-ray diffraction (XRD) and scanning electron microscopy (SEM) have been used to characterize physical structure of IrO2+Ta2O5 films over the whole composition range by thermodecomposition of chloride solutions heated at 450°C. Solid solubilization between Ta component and IrO2 rutile in the mixed films was measured, and three typical surface morphologies of the oxide coatings were observed. The surface electrochemical properties of Ti/IrO2-Ta2O5 electrodes were studied by cyclic voltammetry at varying potential scan rate, and a ‘double-layer’ electrochemical structure containing the ‘inner’ and ‘outer’ layers has been distinguished. The voltammetric charge appears to decline with the decrease of grain size of oxide coatings as a result of the effect of surface tension. However, the coatings of 70% IrO2+30% Ta2O5 with the finest grains still exhibit the highest apparent activity for oxygen evolution evaluated by the anodic current at a constant potential. This result is interpreted by the measurements of open-circuit potential (Eoc) and double-layer capacitance (Cdl) using electrochemical impedance spectroscopy (EIS). Thereby, the reliability of voltammetric charge obtained in ‘double-layer’ potential region in determining the real electrocatalytic activity for O2 evolution has been discussed.

Si(0 0 1) surface oxidation by N2O

Ultra-thin homogeneous oxynitride films are prepared on Si(001). The Si surface is cleaned in UHV by heating (flashing) and is exposed to different pressures of N2O at altered temperatures. Thus oxynitride layers of different thickness and different properties are grown depending on the N2O pressure and the Si temperature. This is illustrated by a schematic diagram. The properties of the different oxynitride layers were studied by a combined photoemission electron microscopy (PEEM) and photoelectron spectroscopy (PES) investigation using highly monochromatic synchrotron radiation. The amount of oxygen and nitrogen incorporated in the oxynitride layers is determined from the PES measurements. The typical surface morphology for different preparation conditions is shown in PEEM images.

Formation and characterization of metal-polymer nanostructured composites

Nanostructured metal (Pd, Sn, Cu)-polymer (poly- para-xylylene) and metal-oxide-polymer composites reveal synergism of properties of the initial components, which gives rise to specific electrical, mechanical, and optical properties related to an ordered distribution of nanoparticles over the matrix volume. Methods where polymerisation and formation of the nanoparticles are performed simultaneously are very promising. This paper reports on the experimental set-up for the production of nanocomposites by vacuum co-condensation of the metal and a monomer (paracyclophane) vapours. AFM studies reveal the metal nanoparticles to have a size of 7 to 10 nm. Depending on the metal concentration in as-prepared composites, three different types of surface morphology are distinguished. The percolation threshold of these systems is evaluated by measuring the temperature dependence of the electrical resistance. The type of Absorbance versus Wavelength dependency for the samples beyond the percolation threshold differs from that of the sample with a nano-metal content below the threshold.

Substrate dependent growth of highly conductive RuO2 films

We have prepared thin RuO 2 films by thermal evaporation metal organic chemical vapour deposition on r-plane Al 2 O 3 , MgO, LaAlO 3 and SrTiO 3 single crystal substrates. The films were grown at deposition temperature TD = 500 C, X-ray diffraction analysis show different type of preferred growth, depending on a substrate. Atomic force microscopy revealed typical surface morphology for each type of substrate. Room temperature resistivity of the films on various substrates varied between 30 and 40 μΩcm The best parameters were obtained for epitaxialy grown RuO 2 film on the r-plane cut Al 2 O 3 substrate with a room temperature resistivity about 30 μΩcm and residual resistivity ratio (resistivity ratio between room temperature and 4.2 K) close to30.

MOBILITY KEY TO SILICON ETCHING

BUCKING CONVENTIONAL wisdom, researchers at the University of North Carolina, Chapel Hill, report that surface diffusion plays a key role in silicon etching. The finding contradicts current models that describe halogen etching of semiconductors as a purely kinetic process. Etching silicon with chlorine or bromine is a standard procedure for preparing the semiconductor for applications in micro-electronics. The process has been well studied, and molecular mechanisms have been developed to describe the reaction's elemental steps. Although successful in some regards, today's models fall short when it comes to providing a detailed account of certain common etching scenarios. For example, bromine etching of the (100) crystal face of silicon is known to result in two types of surface morphologies, depending on reaction temperature. Typically, scientists have invoked separate mechanisms to rationalize each type of morphology. Now, based on real-time scanning tunneling microscopy analysis of etching, chemistry pr...