Yao-Lun Chen

Synthesis and characterization of fluorinated β-ketoiminate and imino-alcoholate Pd complexes: precursors for palladium chemical vapor deposition

The design and synthesis of Pd complexes with two β-ketoiminate or with two imino-alcoholate chelate ligands is reported. In order to establish their structures in the solid-state, methoxyethyl substituted complexes 1c and 2c were characterized by single crystal X-ray diffraction, showing a square-planar local coordination for the Pd atom, but the β-ketoiminate ligands of 1c gave a bent basal plane involving two chelating hexagons, which was in sharp contrast to the boat configuration of the imino-alcoholate ligands observed in the second complex 2c. Chemical vapor deposition (CVD) experiments were conducted at deposition temperatures of 250–350 °C. Scanning electron micrographs (SEM) were taken to reveal the surface morphologies and grain sizes of the Pd metal thin films. The resulting thin films were found to contain a low level of carbon and oxygen impurities using O2 as the carrier gas, as measured by X-ray photoelectron spectroscopy (XPS).

Deposition of Ru and RuO2 thin films employing dicarbonyl bis-diketonate ruthenium complexes as CVD source reagents

Reaction of Ru3(CO)12 with 6 eq. of β-diketone ligands (hfac)H, (tmhd)H, (acac)H and (tfac)H at 160–170 °C in a hydrocarbon solvent (pentane or hexane) affords the diketonate complexes [Ru(CO)2(hfac)2] (1), [Ru(CO)2(tmhd)2] (2), [Ru(CO)2(acac)2] (3) and [Ru(CO)2(tfac)2] (4) in high yields. These ruthenium complexes were characterized by spectroscopic methods; a single crystal X-ray diffraction study was carried out on one isomer of the tfac complex (4a), revealing an octahedral coordination geometry with two CO ligands located at cis-positions and with the CF3 groups of the β-diketonate ligands trans to the CO ligands. Thermogravimetric analysis of complex (1) showed an enhanced volatility compared to the parent acac complex (3), attributed to the CF3 group reducing intermolecular attraction. Employing complexes (1) and (2) as CVD source reagents, ruthenium thin films can be deposited at temperatures of 350 °C–450 °C under an H2 atmosphere or at temperatures of 275 °C–400 °C using a 2% mixture of O2 in argon as carrier gas. For deposition carried out using complex (1) and under 100% O2 atmosphere, RuO2 thin films with a preferred (200) orientation were obtained. The as-deposited thin films were characterized by surface and physical analytical techniques, such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction analysis (XRD) and four-point probe measurement.

Deposition of osmium thin films using pyrazolate complexes as CVD source reagents

The reaction of Os3(CO)12 with 1.2 eq. of pyrazole (3,5-(CF3)2-pz)H at 190 °C affords triosmium complex Os3(CO)10(3,5-(CF3)2-pz)(μ-H) (1) as the isolable product. Upon further treatment with excess pyrazole (3,5-(CF3)2-pz)H under more forcing conditions, complex 1 converts to a diosmium pyrazolate complex [Os(CO)3(3,5-(CF3)2-pz)]2 (2) in high yield. These osmium complexes are characterized by spectroscopic methods and single crystal X-ray diffraction study, showing the expected triangular and linear Os–Os backbone and with one and two bridging pyrazolate ligands for complexes 1 and 2, respectively. The thermal properties are studied by TG analysis and the deposition experiments are carried out using a cold-wall CVD apparatus. The as-deposited thin films are characterized using XPS, XRD and SEM and electrical resistivity measurement. It seems that the Os metal thin films are best deposited at an optimal temperature of 450–500 °C and using complex 2 as the source reagent.

Preparation and characterization of RuO2 thin films from Ru(CO)2(tmhd)2 by metalorganic chemical vapor deposition

Abstract A new metalorganic ruthenium compound which contained two β-diketonate and two CO ligands arranged in cis-disposition was used in preparation of high quality ruthenium dioxide (RuO2) thin films by cold-wall metalorganic chemical vapor deposition. A detailed characterization of the films including scanning electron microscopy (SEM), electrical resistivity, Raman scattering and X-ray diffraction measurements were carried out. The surface morphology of the films was investigated by SEM, from which a columnar growth pattern was observed using a cross-sectional scanning electron micrograph analysis. The resistivity measurement shows a metallic conducting characteristic, while Raman study indicates the formation of a high quality, nearly stress-free RuO2 film. In addition, changes of structural and electrical properties after thermal annealing are discussed.

The crystalline properties of carbon nitride nanotubes synthesized by electron cyclotron resonance plasma

Abstract Carbon nitride nanotubes (CN-NT) have been synthesized by an electron cyclotron resonance chemical vapor deposition (ECR–CVD) system with a mixture of C 2 H 2 and N 2 as precursors without using any catalyst. The carbon nitride nanotubes were synthesized in an anodic alumina membrane as template in which a packed array of parallel, straight and uniform channels with a diameter of approximately 50-nm and 30-μm thick exists. Samples were analyzed by field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Preliminary results showed that the properties of the deposited carbon nitride nanostructures depend on process parameters, such as deposited temperature, ratio of the precursors and microwave power. The aligned nanostructures have been verified by FESEM and HRTEM. The FTIR spectra reveal that some of the carbon atoms may have possibly been substituted by oxygen atom in the carbon nitride nanotubes. From the XPS results, N is either bonded to two C atoms (sp 2 pyridine-like type) or to three (sp 3 urotropine-like type) in the hexagonal sheets. The Raman spectrum showed that carbon nitride nanotubes have a high degree of graphitization.