Growth Of Ceramic Films Research Articles

Nucleation and Growth of Ceramic Films on Metallic Surfaces

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Mosaic, Single-Crystal CaCO3 Thin Films Fabricated on Modified Polymer Templates

Mosaic, single-crystal CaCO3 thin films have been prepared on modified poly(ethylene terephthalate) (PET) templates. Surface modification of PET through the introduction of carboxylic acid groups (COOH-PET), and the subsequent physical and chemical adsorption of poly(allylamine hydrochloride) (PAH) at pH 8 (PAH8-PET) and pH 11 (PAH11-PET), afford template surfaces that influenced the phase transition of an amorphous CaCO3 (ACC) films during crystallization in air. Macroscopic ACC thin films are prepared on modified PET films in the presence of poly(acrylic acid). Polycrystalline, spherulitic vaterite (CaCO3) films are observed to form on native PET and PAH11-PET, while mosaic, single-crystal calcitic (CaCO3) films form on COOH-PET and PAH8-PET templates. These results confirm that single-crystal CaCO3 growth patterns are dependent on the surface characteristics of the PET template. We infer therefore, that the nucleation and growth of ceramic films on polymeric templates can be controlled by chemical modification of the polymeric template surface, and by the subsequent attachment of ionic polyelectrolytes.

Formation of Patterned Continuous Calcium Carbonate Films on Self-Assembled Monolayers via Nanoparticle-Directed Crystallization

The controlled growth of ceramic films on a solid substrate can be accomplished by using monolayer-protected gold nanoparticles as nucleation directors (see Figure). The combination of biomimetics and nanoscience/nanotechnologies such as that employed here should open up new possibilities to hitherto unknown smart composite materials having enhanced mechanical, physical, and chemical properties.

Reactions of laser-ablated aluminum atoms with nitrogen during condensation at 10 K. Infrared spectra and density functional calculations for AlxNy molecular species

Laser-ablated aluminum atoms react with dinitrogen on condensation at 10 K to form N3 radicals and the subject molecules, which are identified by nitrogen isotopic substitution, further reactions on annealing, and comparison with isotopic frequencies computed by density functional theory. The major AlN3 product is identified from three fundamentals and a statistically mixed nitrogen isotopic octet pattern. The aluminum-rich Al2N and Al3N species are major products produced on annealing to allow diffusion and further reaction of trapped species. This work provides the first experimental evidence for molecular AlxNy species that may be involved in ceramic film growth.

Reactions of Laser-Ablated Aluminum Atoms with Nitrogen Atoms and Molecules. Infrared Spectra and Density Functional Calculations for the AlN2, Al2N, Al2N2, AlN3, and Al3N Molecules

Laser-ablated aluminum atoms react with dinitrogen on condensation at 10 K to form N3 radical and the subject molecules, which are identified by nitrogen isotopic substitution, further reactions on annealing, and comparison with isotopic frequencies computed by density functional theory. The major AlN3 product is identified from three fundamentals and a statistically mixed nitrogen isotopic octet pattern. The aluminum rich Al2N and Al3N species are major products on annealing to allow diffusion and further reaction of trapped species. This work provides the first experimental evidence for molecular AlxNy species that may be involved in ceramic film growth.

Evidence of transition metal diffusion during hydrothermal ceramic film growth: Ba(Ti,Zr)O3on layered Ti–Zr alloy

Ti–Zr alloy thin films of 20–60 nm in thickness were evaporated on Pt-coated silicon wafers. The films exhibited a layered Ti–Zr depth distribution. The films were then treated hydrothermally in 0.25 M Ba(OH)2at 150 and 200 °C for 4–8 h. Films treated at 150 °C did not exhibit reflections from the Ba(TixZr1−x)O3perovskite structure by x-ray diffraction, although a slight barium content was detected by x-ray photoelectron spectrometry. On the other hand, the films treated hydrothermally at 200 °C revealed reflections corresponding to perovskite Ba(TixZr1−x)O3. These films exhibited a homogeneous titanium and zirconium depth distribution, as shown by x-ray photoelectron spectroscopy and Auger depth profiles, proving that either titanium or zirconium ions diffuse during the hydrothemal treatment. The initial Ti–Zr film was completely consumed during the hydrothermal process, leading to a film of homogeneous composition (Ba, Ti, and Zr) up to the interface with the platinum layer.

Tailored Ceramic Film Growth at Low Temperature by Reactive Sputter Deposition

Reactive sputter deposition of ceramic films with tailored structure is addressed in this article. We begin with a brief overview of reactive sputter deposition specifically related to oxide and nitride films, including techniques for in situ plasma diagnostics. We identify two flux components in the plasma that have a controlling influence on film structure and stoichiometry: (1) the flux bearing sputtered target species, which consists of atoms (M) or reacted molecules (MOx or MNx), and (2) the reactive gas flux-containing species in various states of activation. Nonelectronic plasma reactions in which one partner is an excited rare gas species are described, and their role in modifying the sputtered flux, as well as in creating activated reactive gas species, is discussed. We then illustrate the general concepts presented in the overview using four examples of technologically interesting materials grown by rf diode sputter deposition at temperature below 300°C, including: (1) fifth period metal (Zr, Y, Nb) oxides, (2) zirconia-alumina and zirconia-yttria nano-laminates, (3) nanocrystalline aluminum nitride, and (4) vitreous sp2 and sp3-bonded boron nitride. Together, these diverse examples form a complementary set that demonstrates the ability to tailor film properties once the chemical and energetic parameters of the deposition process are understood.

In situ sputter deposition discharge diagnostics for tailoring ceramic film growth

Reactive sputter deposition is widely used for growing technologically important ceramic films, including high melting point phases near room temperature, metastable phases, and nanoscale layered structures with controlled interfaces. Film properties are governed by kinetic processes at each electrode and in the gas phase. A knowledge of the reacting species and reaction paths is essential for reproducible growth of desired ceramic phases and structures. Obtaining this knowledge is the first critical step in developing transferrable processes. In this article, we briefly describe reactive sputter deposition of oxides and nitrides from metal and ceramic targets, and identify important chemical features of the process. Production of activated gas species by plasma volume collisions between ground state reactive gas molecules and rare gas atoms in low-lying metastable energy states is discussed. We then review mass and optical spectrometric methods for real-time monitoring of nonelectronic species in the discharge, and using many examples, show how the information obtained from in situ diagnostics gives insight into the chemistry of ceramic film growth.

Nucleation and Growth of Oriented Ceramic Films onto Organic Interfaces

New materials synthetic methods are being investigated involving heterogeneous nucleation and growth of ceramic films from aqueous solutions onto surfaces modified with organic functional groups. Dense, nanocrystalline, iron hydroxide films were deposited onto sulfonated polystyrene and sulfonated self-assembling monolayers on oxidized silicon. (020) oriented goethite films were formed resulting in chains of edge-shared octahedra in the [001] direction lying parallel to the surface. Deposition amounts varied with pH primarily due to changes in solution supersaturation. The best films were formed when deposition occurred heterogeneously at supersaturations just below the critical supersaturation. Induction times decreased with increasing sulfonate site density due to a reduction in interfacial energy. Nucleation was initiated by binding of cationic species to sulfonate sites and hydrolysis and condensation reactions resulted in the growth and coalescence of crystallites.

Laser MBE for Atomically Defined Ceramic Film Growth

ABSTRACTLaser MBE is a process especially useful for epitaxial layer-by-layer growth of ceramic thin films directly from sintered ceramic targets. By employing high vacuum MBE conditions, the process has a restriction in the controllability of chemical composition, e.g. nonstoi chiometry in oxides and nitrides, as compared with conventional pulsed laser deposition, but instead gains the possibility of in situ monitoring of surface reaction on an atomic scale by RHEED. Ever since our first success in observing RHEED intensity oscillation for CeO2 film growth on Si(l11), we have verified the molecular layer epitaxy by laser MBE for perovskite oxides (SrTiO3, BaTiO3, SrVO3 ,etc) and infinite-layer cuprates MCuO2 (M= Sr, Ba, Ca) on SrTiO3 substrates as well as for oxide and nitride films on Si substrates. Key factors to design the laser MBE system, operation parameters, and recent experimental results are presented and discussed.

In situ growth of epitaxial yttrium aluminum oxide (YAlO3) thin films by metalorganic chemical vapor deposition

The successful integration of high-temperature superconducting (HTS) materials into active and passive microelectronics technologies depends crucially upon advances in the fundamental science of thin film formation and performance. To this end, considerable progress has recently been made in the growth of HTS films by both physical vapor deposition (PVD) and metal-organic chemical vapor deposition (MOCVD) techniques. Equally important for multilayer device fabrication is the quest for lattice-matched, chemically compatible, low dielectric constant/low dielectric loss materials for use as substrates, buffers, dielectrics, insulators, and overlayers. As in HTS film formation, MOCVD offers the attraction for insulating ceramic film growth of the ability to coat complex shapes, simplified apparatus, adaptability to large scale-area depositions, and depositions at low temperatures. YAlO[sub 3] is an example of a promising insulating material for HTS device applications, having a good lattice and thermal expansion match with YBCO, BSCCO, and TBCCO as well as excellent dielectric properties [epsilon] [approx] 16 at 77 K, 10 GHz; tan [delta] = 1 [times] 10[sup [minus]5] at 77 K, 10 GHz. Furthermore, YA1O exhibits no phase transitions between 25 and 1300[degrees]C, which in other materials results in twinning and degradation of film properties. The authors report here the first in situmore » (not requiring a postanneal) deposition of phase-pure epitaxial thin films of YA1O by MOCVD. 12 refs., 4 figs.« less

Rapid Growth of Ceramic Films by Particle-Vapor Codeposition

AbstractParticle-enhanced chemical vapor deposition (PECVD) is capable of producing ceramic films at high deposition rates. A mathematical model of the particle-vapor codeposition process has been developed and has been applied to PECVD processes to predict deposition rate enhancements and deposit properties.

Application of Plasma to Processing for Ceramics

The thermal plasma processing for ceramics was surveyed with a stress on plasma spraying, plasma CVD and plasma sintering. The development of the low pressure plasma process and RF plasma process in plasma spraying is worth of special mention. These processes will be applied to ceramics coating in near future. Researches on thermal CVD are being carried out very actively for synthesis of high purity ultra fine ceramic powders such as silicon nitride and silicon carbide. This process has a very high potential as a means for rapid growth of ceramic films on various substrates. Low pressure RF inductive plasma and high power microwave plasma have characteristics quite different from RF glow discharge plasma. It is very interesting that these plasmas are applied to synthesize diamond and cubic boron nitride films. Rapid sintering of ceramic powders in plasma atmosphere is one of the most important applications of plasma to materials processing, but many problems remain to be solved in the sintering process.

Application of plasma to processing for ceramics

The thermal plasma processing for ceramics was surveyed with a stress on plasma spraying, plasma CVD and plasma sintering. The development of the low pressure plasma process and RF plasma process in plasma spraying is worth of special mention. These processes will be applied to ceramics coating in near future. Researches on thermal CVD are being carried out very actively for synthesis of high purity ultra fine ceramic powders such as silicon nitride and silicon carbide. This process has a very high potential as a means for rapid growth of ceramic films on various substrates. Low pressure RF inductive plasma and high power microwave plasma have characteristics quite different from RF glow discharge plasma. It is very interesting that these plasmas are applied to synthesize diamond and cubic boron nitride films. Rapid sintering of ceramic powders in plasma atmosphere is one of the most important applications of plasma to materials processing, but many problems remain to be solved in the sintering process.