Rapid Thermal Research Articles

Silver Nanoparticles SERS Sensors Using Rapid Thermal CVD Nanoscale Graphene Islands as Templates

Surface enhanced Raman scattering (SERS) sensors have been fabricated by rapid thermal chemical vapor deposition of high-density nanoscale discrete graphene islands on copper foils followed by electroless chemical plating of discrete, closely spaced, and irregularly shaped silver nanoparticles on the copper surface where it is not covered by graphene islands. By fine tuning of the size and distribution of graphene islands and adjusting the deposition time for silver nanoparticles, nanoscale gaps between silver particles are fabricated. SERS sensors exhibiting Raman scattering signal enhancement factors as high as 1014 in reference to a bare copper have been demonstrated. Raman scattering signal has been measured from as low as 10−16 M of R6G molecules in water. This article reports effects and optimization process of size and distribution of graphene islands on desirable morphology of chemically plated silver nanoparticles. The density of nanoscale gaps of a few nanometers in distance between neighboring silver nanoparticles is optimized, resulting in the demonstration of SERS sensors with very low detection limits for R6G molecules.

Damage Evaluation of TBC by Rapid Thermal Cycling Test Utilizing a Laser Irradiation

Thermal barrier coating (TBC) is deposited onto the gas turbine blade surface in order to protect the substrate from high-temperature combustion gas. Cracks and delamination of the ceramic coating which come from high heat flux loading are serious problem in TBC. In this study, the rapid thermal cycling device utilizing laser irradiation was developed. It was then investigated how the damage progresses in the ceramic coating exposed to cyclic rapid thermal loading. As a result, a sintering layer was formed in the surface of the ceramic coating, although such phenomenon was not recognized in TBC sample tested by the conventional thermal cycling test using an electric furnace. It was also revealed from the cross-sectional observation that the vertical crack was initiated at the surface of TBC and propagated into sintering layer. Finally, mechanical factors of those damages from finite element analysis using the TBC model including sintering progress was discussed

Estimation of Residual Stresses by Nanoindentation in an Experimental High Strength Microalloyed Steel Subjected to Rapid Thermal Cycles

The effect of welding thermal cycles on the microstructure and residual stresses was studied in the welding zone of an experimental high strength microalloyed steel with an acicular ferrite and quasi-polygonal ferrite microstructure. Autogenous gas tungsten arc welding was performed on a plate of microalloyed steel to produce a weld bead neglecting the weld joint design and the selection of filler material. To obtain a high welding quality, the welding speed and distance between the electrode and plate was controlled with a small vehicle. To determine the residual stresses, nanoindentation tests were performed in each one of the welding zones and subzones of the heat-affected zone (HAZ). These results showed that all of the nanoindentations presented pile-up and sink-in, and thus, a modification was proposed to calculate the actual contact area and determine the residual stresses. Tensile residual stresses were presented in the coarse-grained HAZ (grain boundary ferrite, acicular ferrite, and bainite); fine-grained HAZ (polygonal ferrite); subcritical HAZ (acicular ferrite and quasi-polygonal ferrite); and base material (acicular ferrite and quasi-polygonal ferrite). The fusion zone (acicular ferrite and bainite) and intercritical HAZ (quasi-polygonal ferrite) had compressive residual stresses.

Thermally Driven Order-Disorder Transition in Two-Dimensional Soft Cellular Systems.

Many systems, including biological tissues and foams, are made of highly packed units having high deformability but low compressibility. At two dimensions, these systems offer natural tesselations of a plane with fixed density, in which transitions from ordered to disordered patterns are often observed, in both directions. Using a modified cellular Potts model algorithm that allows rapid thermalization of extensive systems, we numerically explore the order-disorder transition of monodisperse, two-dimensional cellular systems driven by thermal agitation. We show that the transition follows most of the predictions of Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) theory developed for melting of 2D solids, extending the validity of this theory to systems with many-body interactions. In particular, we show the existence of an intermediate hexatic phase, which preserves the orientational order of the regular hexagonal tiling but loses its positional order. In addition to shedding light on the structural changes observed in experimental systems, our study shows that soft cellular systems offer macroscopic systems in which the KTHNY melting scenario can be explored, in the continuation of Bragg's experiments on bubble rafts.

Rapid Thermal Characterization of Graphene Oxide—Nanocalorimetry as a Pathway for Novel Insights in Tribology

The use of solid lubricants such as graphene, graphene oxide, and other nanoparticles have gained notable attention in the tribological community to reduce friction and wear thus aiming at improved energy efficiency and sustainability. Tribological experiments unify rather extreme conditions such as high contact pressures, small contact areas, relative sliding motion, and rapid heating. This combination leads to mechanically- and/or thermally induced chemical, structural and microstructural modifications of the lubricating nanoparticles during rubbing thus altering their material’s properties. Due to the high sensitivity, we propose nanocalorimetry as the method of choice to shed more light on the thermally-induced processes and changes. As a model material for solid lubricants, we explore the transitions of graphene oxide under heating with 1000 °C/s up to 600 °C using quasi-adiabatic nanocalorimetry. We identify a strong exothermic runaway reaction at 317 °C. This runaway is preceded by exothermic reactions between 75–125 °C, which are correlated with the release of intercalated species and the formation of CO and CO2.

Growth of Cu2ZnSnS4 Thin Films Using Moderate Annealing Temperature and Short Dwell Time

In this study CZTS thin films were fabricated by a two-stage process that sputter deposition of metallic Cu, Zn, and Sn on Mo coated glass substrates and annealing process at 500 °C using various short dwell times (4, 8, and 12 min) using Rapid Thermal Processing (RTP) approach. The X-ray diffraction (XRD), Raman spectroscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), and photoluminescence were employed to characterize the CZTS samples synthesized employing different sulfurization times. It was observed that all CZTS thin films showed Cu-poor and Zn-rich composition according to EDX results. XRD patterns displayed formation of kesterite CZTS and CuS secondary phases. Raman spectra of the films justified formation of kesterite CZTS phase for all CZTS thin films and formation of CTS phase, which is difficult to distinguish by XRD pattern of the films for CZTS-8 and CZTS-12 samples. SEM images of the films displayed dense, void-free, and inhomogeneous surface structure regardless of the sulfurization time. The optical band gap of the films as determined by photoluminescence was found to be about 1.36-1.37 eV.

Hydrogenated amorphous silicon films deposited by electron cyclotron resonance chemical vapor deposition at room temperature with different radio frequency chuck powers

In this work, we present the morphological and electrical characterization of hydrogenated amorphous siliconfilms, which were deposited at room temperature on a n+-type silicon substrate using the electron cyclotron resonance chemical vapor deposition (ECR-CVD) technique. To study the hydrogen incorporation into the films, radio-frequency (RF) chuck powers of 1 W, 3 W and 5 W in the silicon substrates were applied during the ECR-CVD depositions. The deposited films were p+ doped using boron ion implantation (B+ I/I) and annealed at 1273 K, using a Rapid Thermal Annealing (RTA) process for dopant activation. The hydrogen concentration, the crystalline level, the surface roughness were obtained by, respectively, Fourier-transform infrared spectroscopy of the as-deposited films; Raman spectroscopy and atomic force microscopy of the films, after the B+ I/I and RTA. The Fourier-transform infrared and Raman spectra were deconvoluted as gaussian curves to extract the molecular bond concentration between silicon and hydrogen and their vibrational modes, respectively. These analyses indicated that: the H concentration is reduced with the increase of RF chuck powers, and, the films changed from totally amorphous to partially crystalline, respectively, when are compared the structures, before and after the B+ I/I and RTA. Diodes with three p+ a-Si/n++c-Si structures were fabricated with aluminun electrodes and current-voltage curves were extracted, indicating that the devices, with films deposited with 5 W, presented the best results, with ideality factor of 1.1.

Photoelectrochemical Applications of SrNbO2n Thin Films Synthesized Via a Two-Step Process at Reduced Temperatures

Oxynitride materials often exhibit a perovskite structure in which the oxygen and nitrogen occupy the same lattice sites. Such oxynitride perovskites, for example SrNbO2N with a favorable bandgap of 1.8 eV for tandems, are studied as photoanodes for photoelectrochemical (PEC) water splitting applications. These photoanodes are an essential component to the OER side of the water splitting cell. In literature, SrNbO2N PEC electrodes are often prepared using ammonolysis of deposited Sr2Nb2O7 oxide at high temperatures. To transform Sr2Nb2O7 into SrNbO2N, the ammonolysis temperature has to reach over 900 °C for the time period of minutes to hours. This often leads to intermixing and reactions between the layers in the thin film device stack. In this presentation, PEC measurements of photocurrent are presented for SrNbO2N on n-Si in ferro/ferricyanide, at varying thicknesses and Sr:Nb ratios. For the deposition of these films, we show a two-step low-temperature synthesis approach to SrNbO2N on Si for tandem PEC applications. In the first step, combinatorial RF sputtering (sometimes with a nitrogen plasma cracker) is used to deposit Sr1+yNb1-yO2-xN1+x at ambient temperature with varying Sr:Nb and O:N ratios. In the second step, these films are annealed in a nitrogen atmosphere using Rapid Thermal Annealing (RTA). We surveyed a series of temperatures and times to determine the minimum temperatures needed to obtain highly crystalline SrNbO2N for PEC applications without reaction with the Si substrate. The resulting film morphology, crystalline structure, and other characterization across the combinatorial spread was characterized. Photocurrent was observed in these materials over a range of varying thicknesses and compositions using a solar simulator and a standard 3-electrode setup.

Effects of Rapid Thermal Annealing on the Structural, Optical, and Electrical Properties of ZnO/Ag/SnO2 Tri-Layer Films

ZnO 50 nm/Ag 10 nm/SnO2 50 nm (ZAS) tri-layer films were deposited on a glass substrate by RF and DC magnetron sputtering and then underwent rapid thermal annealing in a low vacuum of 1×10-3 Torr to investigate the effects of post-deposition annealing on the optical and electrical properties of the films. The peak intensity of the XRD pattern related to the ZnO (002) peak of the annealed films was higher than that of the as-deposited film and the full width at half-maximum of the ZnO (002) diffraction peak of the annealed films was smaller than that of the as-deposited film. Therefore, the crystallinity of ZnO was improved by rapid annealing. However, crystallization of the Ag interlayer and SnO2 surface layer were not significantly affected by the annealing temperature, compared with the ZnO bottom layer. From the observed electrical properties and optical band gap, it was concluded that the blue shift in the optical band gap is related to the carrier density of the films. The band gap increased from 4.19 eV to 4.24 eV, with the carrier density increasing from 7.09 × 1021 cm-3 to 7.77 × 1021 cm-3. However, the film annealed at 450 °C showed a decreased band gap energy of 4.17 eV due to the decreased carrier density of 6.80 × 1021 cm-3. The as-deposited ZAS films showed a sheet resistance of 11.0 Ω/□ and a visible transmittance of 80.8%, whereas the films annealed at 450 °C had a higher visible transmittance of 82.3% and a lower sheet resistance of 6.55 Ω/□. The results indicate that ZAS thin films may be possible substitutes for conventional Sn-doped In2O3 transparent electrodes in various optoelectronic devices. Key words: ZnO/Ag/SnO2, magnetron sputtering, annealing, AFM, XRD

Near‐Surface Defect Control by Vacancy Injecting/Out‐Diffusing Rapid Thermal Annealing

Rapid thermal annealing (RTA) can be applied to dissolve small defects such as voids or small‐sized oxygen precipitates and to manipulate vacancies in a specific depth from the surface. This can be achieved at elevated temperatures around 1300 °C and via NH3 dissociation at the surface at temperatures >1150 °C. In an earlier study (Araki et al., 2013), it had been demonstrated already that even under oxidizing ambient, enhanced bulk micro defects formation around 1300–1350 °C can occur. The near‐surface region is monitored via its homogeneity of precipitation and in‐depth vacancy profiling by Pt‐diffusion. Simulations of defect dissolution during RTA processes are performed up to 1290 °C under different ambient. The size‐dependent defect dissolution behavior is predicted and verified by measurement of the gate oxide integrity.

Fast Synthesis of Graphene with a Desired Structure via Ni-Catalyzed Transformation of Amorphous Carbon during Rapid Thermal Processing: Insights from Molecular Dynamics and Experimental Study

Fast transfer-free synthesis of graphene on a given dielectric substrate is achieved by Ni-catalyzed solid-state transformation of amorphous carbon (a-C) through rapid thermal processing (RTP). Nev...

Mixed morphology in low molar mass fluorinated block copolymers

New low molar mass (Mn ~ 20 kg mol−1) polystyrene-b-poly(methyl methacrylate-co-perfluorohexylethyl acrylate) (PS-b-P(MMA-co-FA)) block copolymers were synthesized all consisting of ~70 mol% PS block and ~30 mol% P(MMA-co-FA) block. The amount of FA counits in the latter block was increased (0.5, 1, 3 and 4 mol%) in order to enhance the incompatibility between the two blocks and to form different self-assembled nanostructures. The block copolymers were thermally annealed by Rapid Thermal Processing (RTP) over wide ranges of temperatures and times. Complementary SEM and AFM analyses evidenced that the introduction of FA counits above a critical content (~2 mol%) drove a self-assembly process through mixed morphologies. These were formed at a distance from the polymer–air interface and consisted of perpendicular cylinders of P(MMA-co-FA) in a PS matrix laying at the substrate– polymer interface, and surmounted PS stripes and PS dots. Modification by low amounts of FA produced block copolymer samples that self-assembled in new, mixed nanostructures, even though they possessed much lower molar masses than those of analogous well established PS-b-PMMA block copolymers.

Multizone Rapid Thermal Processing to Overcome Challenges in Carbon Nanotube Manufacturing by Chemical Vapor Deposition

For the scalable production of commercial products based on vertically aligned carbon nanotubes (VACNTs), referred to as CNT forests, key manufacturing challenges must be overcome. In this work, we describe some of the main challenges currently facing CNT forest manufacturing, along with how we address these challenges with our custom-built rapid thermal processing chemical vapor deposition (CVD) reactor. First, the complexity of the multistep processes and reaction pathways involved in CNT growth by CVD limits the control on CNT population growth dynamics. Importantly, gas-phase decomposition of hydrocarbons, formation of catalyst nanoparticles, and catalytic growth of CNTs are typically coupled. Here, we demonstrated a decoupled recipe with independent control of each step. Second, significant run-to-run variations plague CNT growth by CVD. To improve growth consistency, we designed various measures to remove oxygen-containing molecules from the reactor, including air baking between runs, dynamic pumping down cycles, and low-pressure baking before growth. Third, real-time measurements during growth are needed for process monitoring. We implement in situ height kinetics via videography. The combination of approaches presented here has the potential to transform lab-scale CNT synthesis to robust manufacturing processes.

Ultrafast excited state dynamics and femtosecond nonlinear optical properties of laser fabricated Au and Ag50Au50 nanoparticles

The localized surface plasmon dynamics of laser ablated gold and gold-silver alloy nanoparticles (NPs) near interband and intraband excitation wavelengths were investigated using femtosecond (fs) transient absorption spectroscopy. Interband excitation with 70 fs laser pulses at a wavelength of 400 nm demonstrated plasmon photo-bleach and a transient absorption in the wings of the bleach spectrum. With intraband excitation, Ag50Au50 alloy NPs depicted a fast electron thermalization time of ~180 fs. A slower decay of positive absorption from alloy NPs was observed when compared to pure Au NPs. These NPs demonstrated a rapid initial electron thermalization and exhibited similar electron-phonon relaxation times. The third-order nonlinear optical (NLO) properties were measured using the Z-scan technique with 1 kHz repetition rate fs pulses at 800 nm. It is observed that the alloy NPs possessed large value of the NLO susceptibility χ(3) (~10−13 esu) compared to pure gold NPs at 800 nm finding applications in different areas of photonics.

Thermalization in the quantum Ising model—approximations, limits, and beyond

We present quantitative predictions for quantum simulator experiments on Ising models from trapped ions to Rydberg chains and show how the thermalization, and thus decoherence times, can be controlled by considering common, independent, and end-cap couplings to the bath. We find (i) independent baths enable more rapid thermalization in comparison to a common one; (ii) the thermalization timescale depends strongly on the position in the Ising phase diagram; (iii) for a common bath larger system sizes show a significant slow down in the thermalization process; and (iv) finite-size scaling indicates a subradiance effect slowing thermalization rates toward the infinite spin chain limit. We find it is necessary to treat the full multi-channel Lindblad master equation rather than the commonly used single-channel local Lindblad approximation to make accurate predictions on a classical computer. This method reduces the number of qubits one can practically classical simulate by at least a factor of 4, in turn showing a quantum advantage for such thermalization problems at a factor of 4 smaller qubit number for open quantum systems as opposed to closed ones. Thus, our results encourage open quantum system exploration in noisy intermediate-scale quantum technologies.

Bi-Related Below Band Gap Optical Absorption Band Produced in GaSbBi After Rapid Thermal Anneal at High Temperatures

A detailed study on annealing-induced below band gap absorption in GaSbBi layers, grown by liquid phase epitaxy, is presented. It is shown that, other than the already reported below band gap absorption in GaSb and GaSbBi, due to free carrier absorption and light hole to heavy hole transitions, an additional absorption band near the band edge appears after a rapid thermal anneal of the layers. The magnitude of absorption and the band spread is found to increase with that of Bi in the material. It is supposed that this additional absorption band is due to electronic transitions from the band edge to the Bi-related defect complexes in GaSbBi which are formed during annealing.

Inovasi Penyisipan Karbon dari Pektin pada Pembuatan Membran Interlayer-free Silika-pektin

Water scarcity is the main issues in Indonesia especially for coastal areas. As a consequence, the water has high salinity of >50.000 ppm salt concentration where an appropriate treatment is necessary before consumed. In this case, desalination process could be carried out using inorganic silica membranes. However, during the process the pore of silica membranes were collapsed due to the directly contact of pores to water molecules for a long term performance. Thereby, in this work the innovation of membrane fabrication using carbon templated in silica matrices has been successfully fabricated. Literally, the carbon templates could be improving the membrane hydro-stability. The interlayer-free silica-pectin membrane was fabricated using TEOS as silica precursor and carbon templated from pectin apple. All membranes waere calcined in variance temperature of 300 and 400°C via Rapid Thermal Processing (RTP). The FTIR results show some functionalization of siloxane, silanol and a new bond of silica-carbon. Whereas, the SEM images show the membrane morphology that the membrane not dense and crack-free with thin film's thickness of ~ 1 μm. An excellent condition of interlayer-free silica-pectin membrane was obtained at pectin concentration of 2.5 %wt. (300°C) and 0.5 %wt. (400°C) with highest functionalization of siloxane and silica-carbon bonds. The existence of silica-carbon bonds were capable to enhancing the membrane hydro-stability. In addition, the carbon chains were contributed to form a smaller pores but also robust pore structures. Those fabricated membranes were shown a good promising due to fast and low cost fabrication with high quality to applicate in seawater desalination.

A Rapid Thermal Nanoimprint Apparatus through Induction Heating of Nickel Mold.

Thermal nanoimprint lithography is playing a vital role in fabricating micro/nanostructures on polymer materials by the advantages of low cost, high throughput, and high resolution. However, a typical thermal nanoimprint process usually takes tens of minutes due to the relatively low heating and cooling rate in the thermal imprint cycle. In this study, we developed an induction heating apparatus for the thermal imprint with a mold made of ferromagnetic material, nickel. By applying an external high-frequency alternating magnetic field, heat was generated by the eddy currents and magnetic hysteresis losses of the ferromagnetic nickel mold at high speed. Once the external alternating magnetic field was cut off, the system would cool down fast owe to the small thermal capacity of the nickel mold; thus, providing a high heating and cooling rate for the thermal nanoimprint process. In this paper, nanostructures were successfully replicated onto polymer sheets with the scale of 4-inch diameter within 5 min.

Effect of Inert Annealing Gases on Morphology of Gold Nanoparticles Produced by Using Rapid Thermal Annealing

Metallic nanoparticles have various potential applications. Recent studies have showed that their morphology had a strong influence on their optical and electrical properties. In this work, rapid thermal annealing was used to produce gold nanoparticles on silicon substrates. Morphology control of the gold nanoparticles was made by changing inert annealing gases. Spherical gold nanoparticles were obtained with nitrogen while hemispherical gold nanoparticles were formed with argon.

Morphological and electrical properties of Nickel based Ohmic contacts formed by laser annealing process on n-type 4H-SiC

This work reports on the morphological and electrical properties of Ni-based back-side Ohmic contacts formed by laser annealing process for SiC power diodes. Nickel films, 100 nm thick, have been sputtered on the back-side of heavily doped 110 µm 4H-SiC thinned substrates after mechanical grinding. Then, to achieve Ohmic behavior, the metal films have been irradiated with an UV excimer laser with a wavelength of 310 nm, an energy density of 4.7 J/cm2 and pulse duration of 160 ns. The morphological and structural properties of the samples were analyzed by means of different techniques. Nanoscale electrical analyses by conductive Atomic Force Microscopy (C-AFM) allowed correlating the morphology of the annealed metal films with their local electrical properties. Ohmic behavior of the contacts fabricated by laser annealing have been investigated and compared with the standard Rapid Thermal Annealing (RTA) process. Finally, it was integrated in the fabrication of 650V SiC Schottky diodes.