Significant Increase In Surface Roughness Research Articles

Fundamental Studies of Electrochemically Controlled Surface Oxidation and Hydrophobicity of Natural Enargite

The surface oxidation and hydrophobicity of natural enargite (Cu(3)AsS(4)) and the formation of oxidation species at the mineral surface have been examined by a novel experimental approach that combines electrochemical techniques and atomic force microscopy (AFM). This approach allows for in-situ, synchronized electrochemical control and examination of the oxidative surface morphology of enargite. Combined with ex-situ cryo X-ray photoelectron spectroscopy surface analysis, the surface speciation of enargite surface oxidation has been obtained, comparing the newly fractured natural enargite surface with those that have been electrochemically oxidized at pHs 4 and 10. At pH 4, surface layer formations consisting of metal-deficient sulfide and elemental sulfur were identified, associated with a limited increase in root-mean-square (rms) roughness (1.228 to 3.143 nm) and apparent heterogeneous distribution of surface products as demonstrated by AFM imaging. A mechanism of initial rapid dissolution of Cu followed by diffusion-limited surface layer deposition was identified. At pH 10, a similar mechanism was identified although the differences between the initial and diffusion-limited phases were less definitive. Surface species were identified as copper sulfate and copper hydroxide. A significant increase in surface roughness was found as rms roughness increased from 0.795 to 9.723 nm. Dynamic (receding) contact angle measurements were obtained by a droplet evaporation method. No significant difference in the contact angle on a surface oxidized at pH 10 and the freshly polished surface was found. A significant difference was found between the polished surface and that oxidized at pH 4, with an increase in contact angle of about 13° (46° to 59°) after oxidation. Competing effects of hydrophilic (copper oxides and hydroxides) and hydrophobic (elemental sulfur) species on the mineral surface under oxidizing conditions at pH 4 and the change in surface roughness at pH 10 may contribute to the observed effects of electrochemically controlled oxidation on enargite hydrophobicity.

Stick-slip friction and wear of articular joints

Stick-slip friction was observed in articular cartilage under certain loading and sliding conditions and systematically studied. Using the Surface Forces Apparatus, we show that stick-slip friction can induce permanent morphological changes (a change in the roughness indicative of wear/damage) in cartilage surfaces, even under mild loading and sliding conditions. The different load and speed regimes can be represented by friction maps--separating regimes of smooth and stick-slip sliding; damage generally occurs within the stick-slip regimes. Prolonged exposure of cartilage surfaces to stick-slip sliding resulted in a significant increase of surface roughness, indicative of severe morphological changes of the cartilage superficial zone. To further investigate the factors that are conducive to stick-slip and wear, we selectively digested essential components of cartilage: type II collagen, hyaluronic acid (HA), and glycosaminoglycans (GAGs). Compared with the normal cartilage, HA and GAG digestions modified the stick-slip behavior and increased surface roughness (wear) during sliding, whereas collagen digestion decreased the surface roughness. Importantly, friction forces increased up to 2, 10, and 5 times after HA, GAGs, and collagen digestion, respectively. Also, each digestion altered the friction map in different ways. Our results show that (i) wear is not directly related to the friction coefficient but (ii) more directly related to stick-slip sliding, even when present at small amplitudes, and that (iii) the different molecular components of joints work synergistically to prevent wear. Our results also suggest potential noninvasive diagnostic tools for sensing stick-slip in joints.

Surface Roughness of Polyvinyl Siloxane Impression Materials Following Chemical Disinfection, Autoclave and Microwave Sterilization

Autoclave sterilization and microwave sterilization has been suggested as the effective methods for the disinfection of elastomeric impressions, but subjecting elastomeric impressions to extreme temperature may have adverse effects on critical properties of the elastomers. To evaluate the effect of chemical disinfection as well as autoclave and microwave sterilization on the surface roughness of elastomeric impression materials. The surface roughness of five commercially available polyvinyl siloxane impression materials (Coltene President, Affinis Perfect impression, Aquasil, 3M ESPE Express and GC Exafast) were evaluated after subjecting them to chemical disinfection, autoclaving and microwave sterilization using a Talysurf Intra 50 instrument. Twenty specimens from each material were fabricated and divided into four equal groups, three experimental and one control (n=25). The differences in the mean surface roughness between the treatment groups were recorded and statistically analyzed. No statistically significant increase in the surface roughness was observed when the specimens were subjected to chemical disinfection and autoclave sterilization, increase in roughness and discoloration was observed in all the materials when specimens were subjected to microwave sterilization. Chemical disinfection did not have a significant effect but, since it is less effective, autoclave sterilization can be considered effective and autoclaving did not show any specimen discoloration as in microwave sterilization. Microwave sterilization may be considered when impressions are used to make diagnostic casts. A significant increase in surface roughness may produce rougher casts, resulting in rougher tissue surfaces for denture and cast restorations. Autoclave sterilization of vinyl polysiloxane elastomeric impressions for 5 minutes at 134°C at 20 psi may be considered an effective method over chemical disinfection and microwave sterilization, because chemical disinfection does not eliminate all disease-causing microorganisms and microwave sterilization leads to a rougher impression surface.

Electromechanical reliability of flexible transparent electrodes during and after exposure to acrylic acid

The effect of deposition temperature on pulsed laser deposition (PLD) fabricated flexible transparent electrodes subjected to mechanical loading, after exposure to acrylic acid, and the combined effect of fatigue and corrosion on sputter-deposited polyester-based indium tin oxide (ITO) films are both investigated in this study. Acrylic acid containing pressure sensitive adhesives, which are commonly used in various flexible device stacks, can corrode the ITO film. In addition, fatigue due to cyclic loading can lead to film cracking. The combined effect of fatigue and corrosion can lead to catastrophic failure of the system. We found that PLD-produced ITO on polyethylene naphthalate samples deposited at 150°C performs better than samples deposited at 50°C under uniaxial mechanical loading. They were found to exhibit higher crack onset strain than their 50°C counterparts. However, they were observed to be more sensitive to increasing acid concentrations. Scanning electron microscopy images show a larger number of adhesive cracks on the surfaces of the 150°C-deposited samples than the 50°C-deposited samples. Atomic force microscopy results reveal that the increased temperature causes a significant increase in surface roughness which may affect the corrosion behavior of the ITO film.Furthermore, in situ electrical resistance measurements and crack density analysis suggest that the combination of fatigue and corrosion can cause film failure at low strains, less than those needed for failure with no corrosion. For example, at 0.9% applied strain and 500,000cycles, the crack density under fatigue–corrosion is 1.7 times that of the fatigue-only case.

Changes in the surface roughness and friction coefficient of orthodontic bracket slots before and after treatment

In this study, we tested the surface roughness of bracket slots and the friction coefficient between the bracket and the stainless steel archwire before and after orthodontic treatment. There were four experimental groups: groups 1 and 2 were 3M new and retrieved brackets, respectively, and groups 3 and 4 were BioQuick new and retrieved brackets, respectively. All retrieved brackets were taken from patients with the first premolar extraction and using sliding mechanics to close the extraction space. The surface roughness of specimens was evaluated using an optical interferometry profilometer, which is faster and nondestructive compared with a stylus profilometer, and provided a larger field, needing no sample preparation, compared with atomic force microscopy. Orthodontic treatment resulted in significant increases in surface roughness and coefficient of friction for both brands of brackets. However, there was no significant difference by brand for new or retrieved brackets. These retrieval analysis results highlight the necessity of reevaluating the properties and clinical behavior of brackets during treatment to make appropriate treatment decisions.

Influence of surface properties of resin‐based composites on in vitro Streptococcus mutans biofilm development

The aim of this in vitro study was to evaluate the influence of physicochemical surface properties of resin-based composites on Streptococcus mutans biofilm formation. Specimens were prepared from each of four resin-based composites by polymerization against Mylar strips. Half of the number of specimens received no further surface treatment, whereas the other half were subjected to a polishing treatment. Surface roughness (SR) and topography were assessed using profilometry and atomic force microscopy. Surface free-energy (SFE) was determined, and the chemical surface composition was analysed by X-ray photoelectron spectroscopy (XPS). S. mutans biofilms were formed on the surface of the resin-based composite specimens for either 48 or 96 h using an artificial mouth system (AMS). Polishing caused a significant decrease in SFE, and XPS analysis indicated an increase of surface silicon and a decrease of surface carbon. Only for Grandio was a significant increase in SR identified after polishing, which was probably related to the higher concentration of filler particles on its surface. Significantly less S. mutans biofilm formation was observed on polished resin-based composites than on unpolished resin-based composites. These results indicate that the proportions of resin matrix and filler particles on the surface of resin-based composites strongly influence S. mutans biofilm formation in vitro, suggesting that minimization of resin matrix exposure might be useful to reduce biofilm formation on the surface of resin-based composites.

The effect of surface treatments on the microroughness of laser‐sintered and vacuum‐cast base metal alloys for dental prosthetic frameworks

This study aimed to evaluate the effect of four chemomechanical surface treatments on the surface average microroughness and profile of laser-sintered and vacuum-cast dental prosthetic structures. Square-shaped blocks (10 mm × 10 mm × 1.5 mm) were prepared as follows: (1) laser-sintered CoCr (L) (ST2724G); (2) cast Co-Cr (C) (Gemium-cn); and (3) cast Ni-Cr-Ti (T) (Tilite). Specimens of each alloy group were randomly divided into five subgroups (n = 10 each), depending on the conditioning method used: (1) no treatment (control); (2) sandblasting (125 μm Al₂O₃-particles); (3) silica coating (50 μm silica-modified Al₂O₃-particles); (4) oxidation; and (5) oxidation plus opacification. Subgroups 2 and 3 represent "inner" pretreatments proposed for ceramometal restorations to improve the metal surface area available for luting cements. Subgroups 4 and 5 are the "outer" pretreatments required for bonding the aesthetic veneering ceramics to the underlying metal frameworks. Average surface roughness (Ra/μm) was determined using a surface profilometer. Data were analyzed by two-way ANOVA and Student-Newman-Keuls tests (α = 0.05). Metal surface topography was SEM-analyzed. Despite the inner pretreatment applied, L samples resulted in the highest microroughness (P < 0.001), whereas sandblasting produced a surface-smoothing effect in cast specimens. After oxidation, a significant increase in surface roughness occurred in all groups compared with controls, L specimens being the roughest (P < 0.001). Opacification caused a flattening effect of all oxidized structures; all opacified groups resulting in similar microroughness. Laser sintering of Co-Cr enhances the roughness of metal structures, which may improve the frameworks' microretention of the cements, and of the opaquer before the copings are veneered with the aesthetic ceramics.

Changes in intraocular lens surface roughness during cataract surgery assessed by atomic force microscopy

To analyze the changes in optic surface roughness before and after injection of various intraocular lens (IOL) models using atomic force microscopy (AFM). Departments of Ophthalmology, Medical University of Graz, General Hospital Linz and University Hospital Basel; Upper Austria University, School of Applied Health and Social Sciences, Linz, Austria. Experimental study. The morphology and surface roughness of 3 hydrophobic acrylic IOLs from different manufacturers were analyzed by AFM in liquid using the tapping mode. First, AFM was performed on IOLs taken from the original package without further manipulation. In a second step, under sterile conditions, an experienced cataract surgeon loaded the IOLs into the appropriate injection system and pushed them through a system resembling an IOL implantation in cataract surgery; this was followed by AFM evaluation. Finally, 3 samples of a preloaded hydrophilic acrylic IOL taken from the original cartridge were compared with 3 samples that were pushed through the implantation system. Comparison of the arithmetic mean, standard deviation, root mean square, and surface skewness of the IOLs before and after injection showed a significant increase in surface roughness (P<.05). Standard application procedures of IOLs may alter the IOL surface. Increases in the surface roughness of IOLs may influence postoperative posterior capsule opacification. Further studies are necessary to evaluate the interfacial properties of IOLs.

The effect of helium ion implantation on the relaxation of strained InGaAs thin films

Previous work on pseudomorphic SiGe on Si has shown that a significant reduction in the threading dislocation density can be achieved through appropriate ion beam processing. Helium ion implantation was used in an analogous study to induce strain relaxation within strained pseudomorphic InGaAs layers on GaAs through the intentional introduction of subsurface damage without the introduction of surface nucleated dislocations and their associated threading segments. Wafers of fully-strained 28 nm thick films of In 0.24Ga 0.76As were separately implanted with helium doses of 5 × 10 14, 2 × 10 15, and 1 × 10 16 cm −2 at 25 keV. These wafers became substrates for additional InGaAs film growth. The final InGaAs films always exhibited lower residual strain as compared to films grown directly on a control substrate of non-implanted GaAs. The broadening of the X-ray peaks indicates an increase in dislocation density within the InGaAs films and the strain relaxation was found to occur with a significant increase in surface roughness. This result stands in contrast to related work on SiGe films on Si where a reduction of the threading dislocation density within a SiGe film was observed. The reaction of the InGaAs/GaAs structure and materials to ion irradiation, with local disturbance to the stoichiometry, could preclude the use of ion beam techniques for realizing a reduction in threading dislocation density during strain relaxation.

Effect of separating layer thickness on W/Si multilayer replication

The direct replication of W/Si multilayers and the effect of separating layer thickness on the performance of the multilayer before and after replication are investigated systematically. Platinum separating layers with different layer thicknesses were first deposited onto different supersmooth mandrels and then W/Si multilayers with the similar structure were deposited onto these Pt-coated mandrels by using a high vacuum DC magnetron sputtering system. After the deposition, these multilayers were replicated onto the commercially available float glass substrates by epoxy replication technique. These multilayers before and after replication are characterized by grazing-incident X-ray reflectance measurement and atomic force microscope. The measured results show that before and after replication, the reflectivity curves are much similar to those calculated and the surface roughness of each sample is close to that of the mandrel, when the separating layer thickness is larger than 1.5 nm. These results reveal that the W/Si multilayer with the separating layer thickness larger than 1.5 nm can be successfully replicated onto a substrate without modification of the structure, significant increase of surface roughness or apparent change of reflectivity.

Investigation of direct replication techniques on periodic multilayers

The direct replication of a periodic W/Si multilayer was investigated systematically. The W/Si multilayer was deposited by a high vacuum dc magnetron sputtering system. After deposition, the multilayer was transferred from the supersmooth mandrel onto a commercially available float glass substrate by the epoxy replication technique. The multilayer was characterized by the grazing incident x-ray reflectance (GIXR) measurement, atomic force microscope (AFM), and Zygo GPI interferometer before and after replication. The measured results showed that the multilayer structure and reflectivity were almost the same, and the surface roughness was 0.22 and 0.23 nm before and after replication, respectively. It was demonstrated that the W/Si multilayer was successfully replicated without modification of the structure, a significant increase of surface roughness, or apparent change of reflectivity. The optical figure of the substrate after replication experienced significant changes of many waves but was actually improved for this specific test. Future studies will focus on learning how to control the resulting optical figure of our replication process on a thin substrate.

Surface roughness of etched composite resin in light of composite repair

ObjectivesIn search for clinically effective composite repair protocols, the effect of various etching protocols on the surface roughness of composite resins with different filler composition were investigated. MethodsOf two composite resins (hybrid-filled Clearfil AP-X; nano-filled Filtek Supreme XT) specimens of 3mm thick with a diameter of 7mm were prepared (n=24). The top surface was polished with 4000-grit SiC-abrasive paper and subjected to one of eight surface treatments: (n=3): negative control (NC), 37% phosphoric acid for 20s (37PA-20s), 3% hydrofluoric acid for 20s (3HF-20s), for 120s (3HF-120s), 9.6% hydrofluoric acid for 20s (9.6HF-20s), for 120s (9.6%HF-120s), 37PA-20s followed by 9.6%HF for 120s (37PA-20s/9.6HF-120s) and 9.6%HF for 120s followed by 37PA-20s (9.6HF-120s/37PA-20s). Roughness (Sa) was measured using a 3D noncontact optical interferometer (WYKO) and surface topography imaged by SEM. Multilevel models were used to estimate the variances within a sample and between samples in each group. Using the resulting overall variances and the means for each group, the eight groups were compared consecutively using t-tests (p<0.05). ResultsThe hybrid-filled composite resin demonstrated a significantly rougher surface than the nano-filled (p<0.05). For both composites 9.6%HF-120s, 37PA-20s/9.6HF-120s and 9.6%HF-120s/37PA-20s resulted in a large increase in roughness compared to the other groups (p<0.05). For the hybrid-filled, the succeeding groups (37PA-20s, 3HF-20s, 3HF-120s and 9.6HF-20s) resulted in a statistically significant increase in surface roughness (p<0.02). For the nano-filled only a statistically significant increase in roughness was found between 3HF-20s and 3HF-120s (p<0.001) and between 9.6HF-20s and 9.6HF-120s (p<0.001). SEM surface characterization revealed that the hybrid-filled composite resin was much more affected by etching than the nano-filled. SignificanceComposite resins should not be seen as a group of materials having identical properties when it comes to repair. The effect of etching will depend on the composition of the filler particles.

Disinfection procedures: Their efficacy and effect on dimensional accuracy and surface quality of an irreversible hydrocolloid impression material

Objectives This study investigated the antibacterial efficacy and effect of 0.55% ortho-phthalaldehyde (Cidex OPA ®) and 0.5% sodium hypochlorite (NaOCl) on the dimensional accuracy and surface quality of gypsum casts retrieved from an irreversible hydrocolloid impression material. Methods A simulated clinical cast and technique was developed to compare the dimensional accuracy and surface quality changes of the test gypsum casts with controls. Dimensional accuracy measurements were completed between fixed points using a travelling microscope under low angle illumination at a magnification of ×3. Surface quality changes of “smooth” and “rough” areas on the cast were evaluated by means of optical profilometry. The efficacy of the disinfection procedures against Pseudomonas aeruginosa was evaluated by determining the number of colony forming units (cfu) recovered after disinfection of alginate discs inoculated with 1 × 10 6 cfu for defined intervals. Results The dimensional accuracy of the gypsum casts was not significantly affected by the disinfection protocols. Neither disinfectant solution nor immersion time had an effect on the surface roughness of the “smooth” area on the cast, however, a significant increase in surface roughness was observed with increasing immersion time for the “rough” surface. Complete elimination of viable Pseudomonas aeruginosa cells from alginate discs was obtained after 30 and 120 s immersion in Cidex OPA ® and NaOCl, respectively. Conclusions Immersion of irreversible hydrocolloid impressions in Cidex OPA ® for 30 s was proved to be the most effective disinfection procedure.

Characterization of the alumina scale formed on a commercial MCrAlYHfSi coating

A commercial NiCoCrAlYHfSi coating deposited on a Ni-base superalloy substrate was characterized before and after high temperature oxidation. The combination of Y, Hf and Si additions is reported to improve coating performance. Advanced characterization techniques including scanning-transmission electron microscopy were used to study the segregation behavior of Y and Hf ions to the alumina grain boundaries after 200 h at 1050 °C and 100 and 200 h exposures at 1100 °C. After both exposure times, two distinct oxide layers were observed. The outer transient layer included many Y- and Hf-rich oxide particles. The inner layer consisted of columnar α-Al 2O 3 grains normal to the surface of the coating. Segregation of Y and Hf ions was found on the alumina grain boundaries as has been observed in model alloys with similar compositions. Isothermal exposures for up to 200 h at 1050° and 1100 °C caused a minimal increase in surface roughness. However, 200 1-h cycles at 1100 °C resulted in a more significant increase in surface roughness.

A quantitative AFM analysis of nano-scale surface roughness in various orthodontic brackets

In orthodontics, the surface roughnesses of orthodontic archwire and brackets affect the effectiveness of arch-guided tooth movement, corrosion behavior, and the aesthetics of orthodontic components. Atomic force microscopy (AFM) measurements were used to provide quantitative information on the surface roughness of the orthodontic material. In this study, the changes in surface roughness of various orthodontic bracket slots before and after sliding movement of archwire in vitro and in vivo were observed through the utilization of AFM. Firstly, we characterized the surface of four types of brackets slots as follows: conventional stainless steel (Succes ®), conventional ceramic (Perfect ®), self-ligating stainless steel (Damon ®) and self-ligating ceramic (Clippy-C ®) brackets. Succes ® and Damon ® brackets showed relatively smooth surfaces, while Perfect ® had the roughest surface among the four types of brackets used. Secondly, after in vitro sliding test with beta titanium wire in two conventional brackets (Succes ® and Perfect ®), there were significant increases in only stainless steel bracket, Succes ®. Thirdly, after clinical orthodontic treatment for a maximum of 2 years, the self-ligating stainless steel bracket, Damon ®, showed a significant increase in surface roughness. But self-ligating ceramic brackets, Clippy-C ®, represented less significant changes in roughness parameters than self-ligating stainless steel ones. Based on the results of the AFM measurements, it is suggested that the self-ligating ceramic bracket has great possibility to exhibit less friction and better biocompatibility than the other tested brackets. This implies that these bracket slots will aid in the effectiveness of arch-guided tooth movement.

Role of membrane sialic acid and glycophorin protein in thorium induced aggregation and hemolysis of human erythrocytes

Thorium-232 ( 232Th), a natural radionuclide from the actinide family, is abundantly present in monazite and other ores. It is used as one of the prime fuel materials in nuclear industry and may pose an exposure risk to nuclear workers and members of the public. Human erythrocytes, as a classical cellular membrane model, were coincubated with 232Th in order to elucidate whether this naturally occurring important radionuclide produced perturbations to cell membrane. Present study revealed that erythrocytes underwent aggregation or lysis depending on the ratio of 232Th to cell. Scanning electron micrographs showed that erythrocytes transformed into equinocytes and/or spherocytes after 232Th treatment. Further examination of erythrocyte by atomic force microscopy suggested significant increase in surface roughness after 232Th treatment. Experiments on neuraminidase treated and/or anti-GpA antibody blocked erythrocytes suggested significant role of membrane sialic acid and glycophorin A (GpA) protein in aggregation or hemolytic effects of 232Th. Further results showed that 232Th caused hemolysis by colloid osmotic mechanism, as evidenced by potassium efflux, osmotic protection and osmotic fragility studies. Osmoprotection experiments indicated that hemolysis get elicited through the formation of membrane pores of ∼2.0 nm in size. Hemolysis studies in presence of inhibitors (TEA, bumetanide, DIDS and amiloride) revealed the role of K + channel, Na +/K +/2Cl − channel, Cl −/HCO 3 − anion exchanger and Na +/H + antiporter in 232Th induced erythrolysis. Presence of non-diffusible cation (N-methyl d-glucasamine) or anion (gluconate) in erythrocyte suspending medium further confirm the role of Na + and Cl − influx in hemolytic effect of 232Th. These findings provide significant insight in structural, biochemical and osmotic toxic effects of 232Th on human erythrocytes.

Effects of 20% demineralization on surface physical properties of compact bone scaffold and bone remodeling response at interface after orthotopic implantation

To enhance osteointegration with preservation of mechanical strength, a surface modification technique using 20% surface demineralization in a controlled manner was applied to custom-built cylindrical bio-derived compact bones (20% surface-demineralized cylindrical compact bio-derived bone scaffold: SDCBS); an undemineralized version was the control. The micro-surface topography of the two types of bone scaffolds was characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). 20% demineralization led to significant increases in surface roughness (38.19%, P=0.001) and surface area (15.1%, P=0.030), compared with the control group's, while the decrease in mechanical properties was not statistically significant. Results of orthotopic implantation for 9 months demonstrated that 20% surface demineralization caused significantly rapid and homogeneous bone remodeling at the interface compared to control and led to a significantly rapid osteointegration of SDCBS with the host bone at the early and intermediate stages of osteointegration. The study indicates the potential of SDCBS in repairing clinical bone defects, and would help direct the use of various processes of biomaterials to support defect repairs within osseous sites.

Physio‐Chemical Modifications of Polystyrene and Poly(propylene) Surfaces by Electron Beam‐Generated Plasmas Produced in Argon

AbstractPulsed, electron beam generated plasmas produced in argon were used to modify the surfaces of polystyrene and poly(propylene). The influence of plasma parameters including duty factor, plasma period and exposure time on the surface chemistry, energy and morphology was investigated. In these plasmas, the energy of ions striking the surfaces was modest (≤ 5 eV) and comparable to the bond strength of most polymers. Despite the lack of reactive species in the background, a substantial modification in the chemical composition of the polymer surface occurred, leading to a significant increase in surface energy. These changes occurred without a significant increase in surface roughness, or loss of material due to etching. Indeed, the surface morphology of polystyrene was practically unchanged, whereas the surface of poly(propylene) became smoother with plasma exposure. Based on theoretical estimations, the ions play major role in the modification of polymers.magnified image

Microstructure evolution of the Ir-inserted Ni silicides with additional annealing

Thermally-evaporated 10 nm-Ni/1 nm-Ir/(poly)Si structures were fabricated in order to investigate the thermal stability of Ir-inserted nickel silicide after additional annealing. The silicide samples underwent rapid thermal annealing at 300 ° C to 1200 ° C for 40 s, followed by 30 min annealing at the given RTA temperatures. Silicides suitable for the salicide process were formed on the top of the single crystal and polycrystalline silicon substrates, mimicking actives and gates. The sheet resistance was measured using a four-point probe. High resolution x-ray diffraction and Auger depth profiling were used for phase and chemical composition analysis, respectively. Transmission electron microscope and scanning probe microscope were used to determine the cross-section structure and surface roughness. The silicide, which formed on single crystal silicon substrate with surface agglomeration after additional annealing, could defer the transformation of Ni(Ir)Si to Ni(Ir)Si2 and was stable at temperatures up to 1200 °C. Moreover, the silicide thickness doubled. There were no outstanding changes in the silicide thickness on polycrystalline silicon. However, after additional annealing, the silicon-silicide mixing became serious and showed high resistance at temperatures >700 °C. Auger depth profiling confirmed the increased thickness of the silicide layers after additional annealing without a change in composition. For a single crystal silicon substrate, the sheet resistance increased slightly due to the significant increases in surface roughness caused by surface agglomeration after additional annealing. Otherwise, there were almost no changes in surface roughness on the polycrystalline silicon substrate. The Ir-inserted nickel monosilicide was able to maintain a low resistance in a wide temperature range and is considered suitable for the nano-thick silicide process.

Surface Roughness of Auto Polymerized Acrylic Resin According to Different Manipulation and Polishing Methods

To test the hypothesis that no differences exists in the in situ level of surface roughness of an auto polymerized acrylic resin irrespective of the method of manipulation and polishing. Forty volunteers received the test specimens. Surface roughness was evaluated using a rugosimeter. Samples of auto polymerized acrylic resin were submitted to two methods of manipulation--mass and addition--as well as to two types of polishing--mechanical and chemical. Four test groups were designated according to manipulation and polishing techniques: mass-mechanical, mass-chemical, addition-mechanical, and addition-chemical. Five measures of surface roughness were taken from each sample and average surface roughness (Ra) was determined before and 20 days after the samples were worn by the volunteers. The data obtained were analyzed by the Student's t-test for paired samples as well as by analysis of variance. Significant differences in Ra were found between mechanical and chemical polishing. Surface roughness was not influenced by manipulation techniques. Mechanical polishing presented the lowest values of Ra. There was a significant increase in surface roughness after volunteers wore the specimens for 20 days. The hypothesis is rejected. There were differences on the surface roughness according to the different methods of manipulation and polishing used, but high values of surface roughness were found for all groups. Mechanical polishing showed the lowest values of surface roughness and thus should be preferred.