Suresh C. Kuiry

Synthesis of Nanocrystalline Ceria Particles for High Temperature Oxidation Resistant Coating

Cerium oxide has been investigated to be an effective coating material for high temperature applications for various alumina- and chromia-forming alloys. The present study investigates the use of microemulsion method to obtain monodispersed, non-agglomerated nanocrystalline ceria particles in the range of 5 nm using sodium bis(2-ethylhexyl) sulphosuccinate (AOT) as a surfactant. Furthermore, the use of non-agglomerated nanocrystalline ceria particles to develop improved high temperature oxidation resistant coatings on AISI 304-grade stainless steel was investigated. It was found that non-agglomerated nanocrystalline ceria particles were more effective in improving the oxidation resistance than the agglomerated nanocrystalline particles.

Chemical Mechanical Planarization of Copper: Role of Oxidants and Inhibitors

Investigations were carried out to understand the effect of hydrogen peroxide as an oxidant and benzotriazole (BTA) as an inhibitor on the chemical mechanical planarization (CMP) of copper. Cu-CMP was studied using electrochemistry and removal rate measurements in solutions containing the oxidizer and the inhibitor. In the presence of 0.1 M glycine, the copper removal rate was high in the solution containing 5% H 2 O 2 at pH 2 because of a Cu-glycine complexation reaction. The dissolution rate of Cu increased due to the formation of the highly soluble Cu-glycine complex in the presence of hydrogen peroxide. Addition of 0.01 M BTA in the solution containing 0.1 M glycine and 5% H 2 O 2 at pH 2 exhibited a reduction in the Cu removal rate by the formation of a Cu-BTA complex on the surface of copper that inhibits the dissolution. X-ray photoelectron spectroscopy and secondary-ion mass spectroscopy investigations revealed the formation of a Cu-glycine complex, which aided the understanding of the mechanism of Cu-oxidant-inhibitor interaction during polishing.

In situ synthesis of carbon nanotubes decorated with palladium nanoparticles using arc-discharge in solution method

A unique, simple, inexpensive, and one-step synthesis route to produce carbon nanotubes (CNTs) decorated with palladium nanoparticles using a simplified dc arc-discharge in solution is reported. Zero-loss energy filtered transmission electron microscopy and scanning transmission electron microscopy confirm the presence of 3nm palladium nanoparticles. Such palladium nanoparticles form during the reduction of palladium tetra-chloro-square-planar complex. The deconvoluted x-ray photoelectron spectroscopy envelope shows the presence of palladium on the decorated CNTs. The energy dispersive spectroscopy suggests no functionalization of atomic chlorine to the sidewall of the CNTs. The presence of dislodged graphene sheets with wavy morphology supports the formation of CNTs through the “scroll mechanism.”

Effect of pH and H 2 O 2 on Ta Chemical Mechanical Planarization Electrochemistry and X-Ray Photoelectron Spectroscopy Studies

Tantalum is used as a diffusion barrier and adhesion promoter layer between the dielectric material and copper interconnects. The present study was intended to investigate the effect of oxidizer and solution pH on chemical mechanical planarization of tantalum. High purity Ta disks were used to study the dissolution and oxidation kinetics under static and dynamic conditions using various solutions in acidic and alkaline pH regimes. The electrochemical measurements during dynamic polishing of a Ta disk were carried out using slurries containing silica and alumina particles with hydrogen peroxide at various pH levels. The affected surface layers of the statically etched Ta disk were investigated using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and secondary ion mass spectrometry (SIMS). Ta metal was observed to oxidize in aqueous solutions at pH 2, 4, and 12 in absence of HO. The oxidation process follows the parabolic kinetic law and oxidation rate was observed to be higher in an alkaline region than in an acidic region. In the presence of HO, however, Ta dissolved in the alkaline region. The dissolution was found to be greater at pH 12 mainly because of enhanced dissociation of HO in alkaline region. At pH 2, on the contrary, mass gain was observed probably due to an increase in OH content on the top of Ta oxide formed on the surface as confirmed by XPS and SIMS depth profile studies. XPS study revealed that the oxidation of tantalum takes place at a rapid rate and forms soluble oxotantalate and hydroxotantalate in solution at pH 12 in the presence of hydrogen peroxide. AFM study validates both the XPS and the SIMS results, indicating formation of a thin impervious oxide layer on Ta in a solution at pH 2 with 5% HO, and a porous layer was formed on Ta in solution with 5% HO at pH 12. Consequently, the dissolution rate in alkaline region was enhanced which was confirmed by dynamic removal rate measurements, electrochemistry, and XPS studies.

Palladium nanoparticle arrays using template-assisted electrodeposition

Palladium nanoparticles are being increasingly considered as room-temperature hydrogen sensors and storage materials. Pd nanoparticle arrays have been synthesized using template-assisted electrodeposition. The template based on Al film on a polymeric substrate was characterized by scanning electron microscopy and energy dispersive spectroscopy. X-ray photoelectron spectroscopy study confirmed that the deposited nanoparticles were of metallic Pd. High-resolution transmission electron microscopy investigation revealed that Pd nanoparticles consisted of a large number of nanocrystallites in the size range of 5–10 nm.

Template-Assisted Deposition of Palladium Nanoarrays Preparation, Microscopic, and Spectroscopic Studies

An in situ, easy, and versatile method to decorate a polymer substrate with uniformly spaced centimeter-long arrays of 5-10 nm palladium nanoparticles is reported. The electrochemical deposition of palladium nanoarrays isdescribed as well as results from various microscopic and spectroscopic characterizations, such as transmission electron microscopy, scanning electron microscopy, optical microscopy, and electron spectroscopy for chemical analysis for their size, morphology, chemical constituent, and chemical state, respectively. The Pd nanoarrays were synthesized using a special kind of active template from an electrolyte solution of ionic strength 0.10626 mol g - 1 . The effect of curvature on the active template is discussed briefly. Understanding of the preferentially deposited Pd nanoparticles to form nanoarrays longitudinally under controlled conditions can lead to the preparation of low-cost, lightweight, reliable hydrogen sensors for safety monitoring applications.

Optoelectronically automated system for carbon nanotubes synthesis via arc-discharge in solution

The method of arc discharge in the solution is unique and inexpensive route for synthesis of the carbon nanotubes (CNTs), carbon onions, and other carbon nanostructures. Such a method can be used for in situ synthesis of CNTs decorated with nanoparticles. Herein, we report a simple and inexpensive optoelectronically automated system for arc discharge in solution synthesis of CNTs. The optoelectronic system maintains a constant gap between the two electrodes allowing a continuous synthesis of the carbon nanostructures. The system operates in a feedback loop consisting of an electrode-gap detector and an analog electronic unit, as controller. This computerized feeding system of the anode was used for in situ nanoparticles incorporated CNTs. For example, we have successfully decorated CNTs with ceria, silica, and palladium nanoparticles. Characterizations of nanostructures are performed using high-resolution transmission electron microscopy, scanning transmission electron microscopy, energy dispersive spectr...

Oxidation kinetics and surface chemistry of an Fe-Cr-Al-Y alloy medium made of 12-μm diameter fibers at elevated temperatures in dry air

Fiber media composed of Fe–Cr–Al–Y alloy are being used increasingly as materials for high-temperature applications for their excellent oxidation resistance. The oxidation kinetics of Fe–Cr–Al–Y alloy fiber medium as a heat-resistant material for high-temperature applications was studied in dry air at 1073, 1188, 1255, and 1318 K. The oxidation process followed the parabolic kinetic law. The alumina-scale growth was found to be influenced by short-circuit diffusion and the presence of stresses related to oxide-scale growth. The surface of the oxide scale formed on the fiber medium was analyzed using X-ray photoelectron spectroscopy, which revealed that the outer surface of the oxide scale formed on the fiber medium composed of 12-μm diameter Fe–Cr–Al–Y alloy fibers, consisted of θ-Al2O3, α-Al2O3, and Cr-oxide. The metastable θ-Al2O3 subsequently partially transformed into the more stable α-phase following a time-temperature-transformation relationship. The surface morphology and the cross section of the oxide scale formed on the fiber medium in the temperature range 1073–1318 K in dry air, have been studied by scanning-electron spectroscopy (SEM) and focused-ion beam, respectively.

Impact of CMP consumables on copper metallization reliability

Over the past few years, the chemical mechanical planarization (CMP) community has systematically characterized the device reliability issues associated with the introduction of copper metallization into integrated circuit fabrication. To gain further understanding of the impact of CMP processing on device performance, this paper reports in detail the interactions of simulated copper slurries and pristine segmented polyurethanes. These studies clearly show that polyurethane is fundamentally incompatible with some of the chemicals used in copper CMP, such as hydrogen peroxide. Experimental copper polishing data on both polyurethane and polyolefin-based pads are compared. The pad performance differences between the polyurethane and polyolefin-based pads are explained based on the chemistry of the base polymers used in the pad fabrication. These results are incorporated into the design and fabrication of a new class of polyolefins-based application specific pads.