Reduction Of Film Thickness Research Articles

Magnetic and magneto-optical characteristics of spin coated Co0.6Zn0.4Fe1.7Mn0.3O4 thin films on Pt (111) coated Si substrate

Abstract This paper reports magnetic and magneto-optical properties of Co0.6Zn0.4Fe1.7Mn0.3O4 nanocrystalline thin films (thickness ∼140–200 nm) deposited on Pt (1 1 1)/Ti/SiO2/Si substrates by spin coating technique. Deposited films are then annealed at 600 °C and 700 °C for 60 min (significant reduction in film thickness from 200 nm to 140 nm was noted with the increase in post deposition annealing temperature). The X ray diffraction patterns confirmed the spinel cubic structure of Co0.6Zn0.4Fe1.7Mn0.3O4 films with polycrystalline phase and also indicated a partial texture orientation. Deposited films showed magnetic anisotropy as evidenced from magnetic and magneto-optical measurements. Higher in plane remnant magnetization and low coercivity values as compared to out of plane ones were observed for both samples, indicating in plane alignment of easy axis of magnetization.

Extraction of elastic modulus of porous ultra-thin low-k films by two-dimensional finite-element simulations of nanoindentation

Continuous scaling of integrated circuits has led to the introduction of highly porous low dielectric constant (low-k) materials, whose inferior mechanical properties raise concerns regarding the reliability of integrated circuits. Nanoindentation is proven to be a straightforward method to study mechanical properties of films. However, in the case of low-k, the measurement and analysis are complex due to the porous nature of the films and reduced film thicknesses which give rise to substrate effects. A methodology that combines nanoindentation experiments with finite-element simulations is proposed and validated in this study to extract the substrate-free elastic modulus of porous ultra-thin low-k films. Furthermore, it is shown that imperfections of the nanoindentation probe significantly affect the finite-element results. An effective analytical method that captures the actual nanoindenter behavior upon indentation is proposed by taking both tip radius and conical imperfections into account. Using this method combined with finite element modeling, the elastic modulus of sub-100 nm thick low-k films is successfully extracted. Standard indentation tests clearly overestimated the actual modulus for such thin films, which emphasizes the importance of the proposed methodology.

Tuning thermoelectricity in a Bi2Se3 topological insulator via varied film thickness

We report thermoelectric transport studies on Bi2Se3 topological insulator thin films with varied thickness grown by molecular beam epitaxy. We find that the Seebeck coefficient and thermoelectric power factor decrease systematically with the reduction of film thickness. These experimental observations can be explained quantitatively by theoretical calculations based on realistic electronic band structure of the Bi2Se3 thin films. This work illustrates the crucial role played by the topological surface states on the thermoelectric transport of topological insulators, and sheds new light on further improvement of their thermoelectric performance.

Comparative study on the tensile bond strength and marginal fit of complete veneer cast metal crowns using various luting agents: An in vitro study.

Introduction:Several commercially available luting agents are used to cement the dental restorations such as intra-coronal, extra-coronal, and fixed partial dentures. Tensile bond strength (TBS) and accurate marginal fit are the essential factors to determine the good clinical results in fixed prosthesis. The retentivity of the luting cements is assessed by their adhesive capacity over the tooth surface and metal surface. Generally, the adhesive ability has been evaluated with in vitro testing, with tensile bond tests. The failure of fixed prosthesis may be happened as a result of incomplete seating during cementation. Most research on cementation of crowns relates seating failure to the thickness of the cement film.Materials and Methods:The study is divided into four groups with 10 samples for each of the luting cement taken up for testing TBS and four groups with 5 samples for each luting agent chosen for assessing marginal fit. The results were tabulated and statistically analyzed.Results:In this in vitro study, the TBS of luting cements, and marginal fit in relation to luting cements were tested by using appropriate testing devices. The TBS of cement is measured using universal testing machine, and the results are tabulated. The marginal gap that exists between the margin of the cast metal crown, and the finish line is measured using travelling microscope before and after cementation. The difference between these two values gives the discrepancy that is due to the film thickness of cement used for luting the restoration.Summary and Conclusion:The TBS value of zinc phosphate cement and glass ionomer cement were found to be almost same. The chemical adhesiveness of the glass ionomer with calcium ions of enamel and dentin may be the attributed reason (ionic bonding). In this study, the polycarboxylate is the one that showed low TBS, and it may be attributed to the weakness of the cement due to reduced film thickness, though this cement has a chemical bonding nature. The observation of results of marginal fit in this study is the increased gap found in zinc phosphate cement followed by resin cement, zinc polycarboxylate, and glass ionomer cement. It is agreeable to estimate the marginal fit of the restoration, which could be affected by the film thickness of the luting cement along with other factors.

Self-Assembled Monolayers Generated from Unsymmetrical Partially Fluorinated Spiroalkanedithiols.

Self-assembled monolayers (SAMs) were prepared on gold substrates from an unsymmetrical partially fluorinated spiroalkanedithiol adsorbate with the specific structure of [CH3(CH2)7][CF3(CF2)7(CH2)8]C[CH2SH]2 (SADT) and compared to SAMs formed from the semifluorinated monothiol F8H10SH [CF3(CF2)7(CH2)10SH] of analogous chain length and n-octadecanethiol. The adsorbate with two alkyl chains, one terminally fluorinated and the other nonfluorinated, was designed to form monolayers in which the bulky helical fluorocarbon segments assemble on top of an underlying layer of well-packed trans-extended alkyl chains. Different combinations of deposition solvents and temperatures were used to produce the bidentate SAMs. Characterization of the resulting monolayers revealed that SAMs formed in DMF at room temperature allow complete binding of the sulfur headgroups to the surface and exhibit higher conformational order than those produced using alternative solvent/temperature combinations. The reduced film thicknesses and enhanced wettability of the SADT SAMs, as compared to the SAMs generated from F8H10SH, suggest loose packing and an increase in the tilt of the terminal fluorocarbon chain segments. Nevertheless, the density of the underlying hydrocarbon chains of the SADT SAMs was higher than that of the F8H10SH SAMs, owing to the double-chained structure of the new adsorbate. The conformational orders of the SAM systems were observed to decrease as follows: C18SH > F8H10SH > SADT. However, the SAMs formed from this new double-chained bidentate adsorbate in DMF expose a fluorinated interface with a relatively low surface roughness, as determined by contact-angle hysteresis.

Effects of inclination angle during Al-doped ZnO film deposition and number of bending cycles on electrical, piezoelectric, optical, and mechanical properties and fatigue life

A flat plate with an adjustable inclination angle between the ion beam and the direction normal to a polyethylene terephthalate (PET) substrate is designed for a deposition stage. Five inclination angles are used to prepare PET/aluminum-doped zinc oxide specimens in order to examine the effects of inclination angle and number of bending cycles on several parameters. The O2 peak intensity ratio (IRO2), obtained from x-ray photoelectron spectroscopy, is identified as one of the controlling factors of the electrical, optical, piezoelectric, and mechanical properties. The effect of inclination angle on IRO2 and the effects of IRO2 on the peak intensity ratios, IRZnO (002) and IRZnO (103), obtained from x-ray diffraction analyses, the composite grain size, and the residual stress in the thin film are investigated systematically. An increase in the inclination angle increases the peak intensity ratios of IRO2 and IRAl2O3, and reduces that of IRZnO. An increase in IRO2 decreases the volume fraction of IRZnO (002) but increases the residual stress of the thin film, and is favorable for the reduction of the composite grain size. The carrier mobility and electrical resistance decrease and carrier concentration increases when IRO2 and IRAl2O3 increase or IRZnO decreases. An increase in the residual stress reduces the fatigue life and piezoelectric coefficient of specimens. The application of a nonzero inclination angle increases the transmittance integration (TI) over the wavelengths of visible light and the intensities of the three peaks in the photoluminescence spectrum. A reduction in film thickness leads to increases in the energy gap and electrical resistance and a decrease in TI.

Elucidating the Sole Contribution from Electromagnetic Near‐Fields in Plasmon‐Enhanced Cu2O Photocathodes

Despite many promising reports of plasmon‐enhanced photocatalysis, the inability to identify the individual contributions from multiple enhancement mechanisms has delayed the development of general design rules for engineering efficient plasmonic photocatalysts. Herein, a plasmonic photocathode comprised of Au@SiO2 (core@shell) nanoparticles embedded within a Cu2O nanowire network is constructed to exclusively examine the contribution from one such mechanism: electromagnetic near‐field enhancement. The influence of the local electromagnetic field intensity is correlated with the overall light‐harvesting efficiency of the device through variation of the SiO2 shell thickness (5–22 nm) to systematically tailor the distance between the plasmonic Au nanoparticles and the Cu2O nanowires. A threefold increase in device photocurrent is achieved upon integrating the Au@SiO2 nanoparticles into the Cu2O nanowire network, further enabling a 40% reduction in semiconductor film thickness while maintaining photocathode performance. Photoelectrochemical results are further correlated with photoluminescence studies and optical simulations to confirm that the near‐field enhancement is the sole mechanism responsible for increased light absorption in the plasmonic photocathode.

Influence of the electrolyte film thickness and NaCl concentration on the oxygen reduction current on platinum

Measurements of oxygen reduction current are performed on a platinum electrode submerged under NaCl electrolyte films of different thickness. The chloride concentration is kept constant or increases due to evaporation. Measurements are supported by the numerical Multi-Ion Transport and Reaction Model (MITReM). In case of constant salt concentration, oxygen reduction current is proportional to the reciprocal of the electrolyte film thicknesses down to 50–75μm; for lower thicknesses deviation from the Fick's law takes place. For evaporating films, oxygen current is the result of two counteracting phenomena: reducing film thickness and increasing salt concentration leading to decrease of oxygen solubility.

Effects of rapid thermal annealing on LPCVD silicon nitride

The effects of rapid thermal anneal (RTA) on film thickness, refractive index and residual stress of low pressure chemical vapor deposited (LPCVD) silicon nitride films are experimentally investigated. With the increase of RTA time, film thickness decreases in an exponential way and refractive index increases. Both film thickness and refractive index reach a relatively stable value after 10min RTA process and higher RTA temperature leads to larger reduction in film thickness. Residual stress of Si–Si3N4 system monotonically increases with RTA time. Based on Maxwell viscoelastic model, a model which considers film densification and viscous flow simultaneously is obtained to quantitatively calculate the effect of RTA on residual stress. In the 900°C and 1000°C RTA process, film densification is dominated in the 60min RTA process and both the mechanisms are more active with the increase of annealing temperature.

Comparison of B2O3 and BN deposited by atomic layer deposition for forming ultrashallow dopant regions by solid state diffusion

In this study, the authors investigated atomic layer deposition (ALD) of B2O3 and BN for conformal, ultrashallow B doping applications and compared the effect of dopant-containing overlayers on sheet resistance (Rs) and B profiles for both types of films subjected to a drive-in thermal anneal. For the deposition of B2O3, tris(dimethylamido)borane and O3 were used as coreactants and for the deposition of BN, BCl3 and NH3 were used as coreactants. Due to the extreme air instability of B2O3 films, physical analysis was performed on B2O3 films, which were capped in-situ with ∼30 Å ALD grown Al2O3 layers. For the BN films, in-situ ALD grown Si3N4 capping layers (∼30 Å) were used for comparison. From spectroscopic ellipsometry, a thickness decrease was observed after 1000 °C, 30 s anneal for the B2O3 containing stack with 60 ALD cycles of B2O3, whereas the BN containing stacks showed negligible thickness decrease after the annealing step, regardless of the number of BN cycles tested. The postanneal reduction in film thickness as well as decrease in Rs for the B2O3 containing stack suggests that the solid state diffusion dopant mechanism is effective, whereas for the BN containing stacks this phenomenon seems to be suppressed. Further clarification of the effectiveness of the B2O3 containing layer compared to the film stacks with BN was evidenced in backside secondary ion mass spectrometry profiling of B atoms. Thus, B2O3 formed by an ALD process and subsequently capped in-situ followed by a drive-in anneal offers promise as a dopant source for ultrashallow doping, whereas the same method using BN seems ineffective. An integrated approach for B2O3 deposition and annealing on a clustered tool also demonstrated controllable Rs reduction without the use of a capping layer.

Depth-Resolved Structural and Compositional Characterization of Ion-Implanted Polystyrene that Enables Direct Covalent Immobilization of Biomolecules

A polystyrene film spun onto polished silicon substrates was implanted with argon ions using plasma immersion ion implantation (PIII) to activate its surface for single-step immobilization of biological molecules. The film was subsequently investigated by X-ray and neutron reflectometry, ultraviolet (UV)–visible (vis) and Fourier transform infrared (FTIR) ellipsometry, FTIR and Raman spectroscopy, as well as nuclear reaction analysis to determine the structural and compositional transformations associated with the surface activation. The ion irradiation resulted in a significant densification of the carbon structure, which was accompanied by hydrogen loss. The density and hydrogen profiles in the modified surface layers were found to agree with the expected depths of ion implantation as calculated by the Stopping and Range of Ions in Matter (SRIM) software. The data demonstrate that the reduction in film thickness is due to ion-induced densification rather than the removal of material by etching. Characte...

Correlation of Polysiloxane Molecular Structure to Shear-Thinning Power-Law Exponent Using Elastohydrodynamic Film Thickness Measurements

Siloxane-based polymers (polysiloxanes) are susceptible to temporary shear-thinning that manifests as a reduction of elastohydrodynamic film thickness with increasing entrainment speed or effective shear rate. The departure from Newtonian film thickness can be predicted with the power-law exponent ns, an indicator of the severity of shear-thinning in a polymeric fluid that is influenced by the macromolecular structure. In this paper, a combination of extant rheological and tribological models is applied to determine the power-law exponent of several polysiloxanes using film thickness measurements. Film thickness data at several temperatures and slide-to-roll ratios are used to validate the methodology for several siloxane-based polymers with alkyl and aryl branches.

Irradiation effects of graphene and thin layer graphite induced by swift heavy ions**Project supported by the National Natural Science Foundation of China (Grant Nos. 11179003, 10975164, 10805062, 11005134, and 11275237).

Graphene and thin graphite films deposited on SiO2/Si are irradiated by swift heavy ions (209Bi, 9.5 MeV/u) with the fluences in a range of 1011 ions/cm2–1012 ions/cm2 at room temperature. Both pristine and irradiated samples are investigated by Raman spectroscopy. For pristine graphite films, the “blue shift” of 2D bond and the “red shift” of G bond with the decrease of thickness are found in the Raman spectra. For both irradiated graphene and thin graphite films, the disorder-induced D peak and D′ peak are detected at the fluence above a threshold Φth. The thinner the film, the lower the Φth is. In this work, the graphite films thicker than 60 nm reveal defect free via the absence of a D bond signal under the swift heavy ion irradiation till the fluence of 2.6 × 1012 ions/cm2. For graphite films thinner than 6 nm, the area ratios between D peak and G peak increase sharply with reducing film thickness. It concludes that it is much easier to induce defects in thinner films than in thicker ones by swift heavy ions. The intensities of the D peak and D′ peak increase with increasing ion fluence, which predicts the continuous impacting of swift heavy ions can lead to the increasing of defects in samples. Different defect types are detected in graphite films of different thickness values. The main defect types are discussed via the various intensity ratios between the D peak and D′ peak (HD/HD′).

High performance carbon nanotube based composite film from layer-by-layer deposition

So far, preparation of strong carbon nanotube (CNT)/polymer composites still faces big challenges mainly due to the limited controls of CNT dispersion and alignment in polymers. Here, a new “layer-by-layer deposition” method is put forward to prepare CNT/polyvinyl alcohol (PVA) composite films. This is based on intermittent deposition of aligned CNT and PVA layers on a paper tape substrate. The in situ deposition allows PVA to infiltrate into the CNT film efficiently, and, as a result, the mechanical property of CNT/PVA composite film has been improved remarkably. For example, the composite film possesses a tensile strength of 1.7GPa, which is almost one order of magnitude and 20 times higher than those of the pure CNT and PVA films, respectively. The high performance of the composite film could be ascribed to the role of PVA infiltration, which leads to not only the formation of strong interfacial bonding between CNTs and PVA matrix but also the reduction of film thickness. The novel process offers a new research direction for preparing CNT-based composites and future performance maximization.

Influence of Semiconductor Thickness and Molecular Weight on the Charge Transport of a Naphthalenediimide-Based Copolymer in Thin-Film Transistors.

The N-type semiconducting polymer, P(NDI2OD-T2), with different molecular weights (MW=23, 72, and 250 kg/mol) was used for the fabrication of field-effect transistors (FETs) with different semiconductor layer thicknesses. FETs with semiconductor layer thicknesses from ∼15 to 50 nm exhibit similar electron mobilities (μ's) of 0.2-0.45 cm2 V(-1) s(-1). Reduction of the active film thickness led to decreased μ values; however, FETs with ∼2 and ∼5 nm thick P(NDI2OD-T2) films still exhibit substantial μ's of 0.01-0.02 and ∼10(-4) cm2 V(-1) s(-1), respectively. Interestingly, the lowest molecular weight sample (P-23, MW≈23 kg/mol, polydispersity index (PDI)=1.9) exhibited higher μ than the highest molecular weight sample (P-250, MW≈250 kg/mol, PDI=2.3) measured for thicker devices (15-50 nm). This is rather unusual behavior because typically charge carrier mobility increases with MW where improved grain-to-grain connectivity usually enhances transport events. We attribute this result to the high crystallinity of the lowest MW sample, as confirmed by differential scanning calorimetry and X-ray diffraction studies, which may (over)compensate for other effects.

Photothermally reprogrammable buckling of nanocomposite gel sheets.

Patterning deformation within the plane of thin elastic sheets represents a powerful tool for the definition of complex and stimuli-responsive 3D buckled shapes. Previous experimental methods, however, have focused on sheets that access a limited number of shapes pre-programmed into the sheet, restricting the degree of dynamic control. Here, we demonstrate on-demand reconfigurable buckling of poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAM) hydrogel network films containing gold nanoparticles (AuNPs) by patterned photothermal deswelling. Predictable, easily controllable, and reversible transformations from a single flat gel sheet to numerous different three-dimensional forms are shown. Importantly, the response time is limited by poroelastic mass transport, rather than photochemical switching kinetics, enabling reconfiguration of shape on timescales of several seconds, with further increases in speed possible by reducing film thickness.

Photothermally Reprogrammable Buckling of Nanocomposite Gel Sheets

AbstractPatterning deformation within the plane of thin elastic sheets represents a powerful tool for the definition of complex and stimuli‐responsive 3D buckled shapes. Previous experimental methods, however, have focused on sheets that access a limited number of shapes pre‐programmed into the sheet, restricting the degree of dynamic control. Here, we demonstrate on‐demand reconfigurable buckling of poly(N‐isopropylacrylamide‐co‐acrylic acid) (PNIPAM) hydrogel network films containing gold nanoparticles (AuNPs) by patterned photothermal deswelling. Predictable, easily controllable, and reversible transformations from a single flat gel sheet to numerous different three‐dimensional forms are shown. Importantly, the response time is limited by poroelastic mass transport, rather than photochemical switching kinetics, enabling reconfiguration of shape on timescales of several seconds, with further increases in speed possible by reducing film thickness.

EXPERIMENTAL INVESTIGATION ON BEHAVIORS AND HEAT TRANSFER IN SHEAR-DRIVEN LIQUID FILM FLOW

Experimental investigation on heat transfer characteristics of shear-driven liquid film in co-current gas flow is presented at different heat fluxes up to 300 kW/m2, gas Reynolds numbers up to 3175, liquid film Reynolds numbers of 27.6 − 75.7 and inlet liquid temperatures of 25, 40, and 80° C. Water and nitrogen are used as test liquid and gas, respectively. The heated section is a rectangular duct with 30 mm in width and 5 mm in height. The heated length is 100 mm divided into 10 segments in the flow direction by the structure of thermally insulated, which makes possible the evaluation of local heat transfer coefficients. The unexpected initiation of liquid film rupture at the upstream edge of heated section is observed under some combinations of heat fluxes and inlet liquid temperatures. In addition, the decrease in the width of dry area towards the downstream is observed with increasing interfacial temperature. The local heat transfer coefficient is increased towards the downstream because of the reduction of liquid film thickness by the enhanced interfacial shear stress exerted by the increased gas flow rate due to the evaporation, while it is decreased by the extension of dry area with increasing gas Reynolds number. A simple analysis for the interfacial force balance of the shear stresses in liquid and gas phases and the thermocapillary stress is performed to confirm the importance of thermocapillary force on the behaviors of liquid film. The variation of surface tension with temperature plays an important role in the liquid film behaviors and the corresponding heat transfer.

Effects of Ethanol Contamination on Friction and Elastohydrodynamic Film Thickness of Engine Oils

The use of ethanol as engine fuel has increased for environmental reasons, both in flex-fuel engines and as increasing amounts of ethanol blended with gasoline in conventional engines. This article describes an investigation into the effects of ethanol contamination of lubricants during engine use with ethanol fuel. To facilitate this, a new technique was developed to measure small amounts of ethanol in lubricants. Elastohydrodynamic film thickness measurements and Stribeck curves were obtained for Group I base and formulated oils containing small added amounts of ethanol. The effect of the water present in hydrated ethanol was evaluated by carrying out tests using both hydrated and anhydrous ethanol. Measurements were also carried out using a Group II base oil with added ethanol. These measurements showed that in the low entrainment speed region, where the elastohydrodynamic film is very thin so that boundary lubrication prevails, the addition of ethanol produced a boundary film, which was not present for the base oils. By contrast, the addition of ethanol to formulated oil reduced film thickness in all lubrication regimes. The friction tests showed friction reduction due to addition of ethanol to the base oil, in particular at low speeds. For the formulated oil, ethanol reduced friction at high speeds, which was associated with a reduction in the viscosity of the lubricant, but at low speeds, ethanol reduced the formation of a boundary layer, increasing friction. The presence of water in hydrated ethanol did not significantly change the film thickness and friction when compared with anhydrous ethanol.

Low-threshold stimulated emission of surface plasmons polaritons

The stimulated emission threshold of surface plasmon polaritons (SPPs) propagating at the interface of silver and dye-doped polymer can be reduced by an order of magnitude if the operation range is changed from visible to near-infrared. The stimulated emission is observed at the polymer thickness, which is much below the cut-off for a regular photonic waveguide, proving SPP origin of the stimulated emission mode. With reduction of the polymer film thickness, the intensity of the stimulated emission decreases, its threshold increases, and the emission line experiences a blue shift—all in agreement with the laser theory. The dependence of the stimulated emission threshold on the polymer film thickness suggests quenching of dye molecule emission in vicinity of the silver surface.