Deborah A. Neumayer

Second‐harmonic generation of poled BaTiO3 thin films

Second‐harmonic generation of 1.064 μm incident light was measured on BaTiO3 thin films prepared by metalorganic chemical vapor deposition. Upon corona poling of the film, the second‐harmonic signal was significantly enhanced. The second‐order nonlinear optical susceptibility, d, of the poled film reaches ∼7.5 times that of the quartz. The enhanced second‐harmonic generation shows a very slow decay at room temperature.

NONLINEAR OPTICAL PROPERTIES OF TEXTURED STRONTIUM BARIUM NIOBATE THIN FILMS PREPARED BY METALORGANIC CHEMICAL VAPOR DEPOSITION

Highly textured strontium barium niobate thin films were deposited in situ by low pressure metalorganic chemical vapor deposition. [001]‐oriented strontium barium niobate films on single crystal (100) magnesium oxide substrates were obtained at a growth temperature of 800 °C. Second‐harmonic generation of 1.064 μm incident light was measured on the thin films. The nonlinear optical susceptibility of the films was as high as 8.7 times that of quartz (∼3.0 pm/V), which is comparable to the bulk value.

Synthesis, characterization and crystal structure of a new thermally stable and volatile precursor [bis(1,1,1,2,2,3,3,7,7,8,8,9,9,9-tetradecafluorononane-4,6-dionato)2–tetraglyme]barium(II) for MOCVD application

The new tetraglyme adduct of barium bis(1,1,1,2,2,3,3,7,7,8,8,9,9,9-tetradecafluorononane-4,6-dionate) complex has been prepared and characterized by X-ray crystallography, 1H and 13C NMR, IR, mass spectrometry and thermogravimetric–differential scanning calorimetric (TG–DSC) analyses. The complex can be easily and cleanly vaporized at 90 °C (10–2mmHg) from the liquid phase. It is thermally stable, volatile and non-hygroscopic. The thermal stability can be attributed to the saturation of coordination sites due to the tetraglyme ligand which appears wrapped around the barium centre. The adduct has been used as an MOCVD precursor for the synthesis of BaPbO3 films by a combined approach of MOCVD and lead vapour diffusion. PbCO3 has been used as lead source.

Metal‐organic chemical vapor deposition/open flow thallium annealing route to epitaxial Tl2Ba2Ca2Cu3O10 thin films

Phase‐pure epitaxial Tl2Ba2Ca2Cu3O10 thin films have been grown on single crystal (110) LaAlO3 substrates using an improved metal‐organic chemical vapor deposition process. First, Ba‐Ca‐Cu‐Ox precursor films are grown on LaAlO3 (110) substrates using Ba(hfa)2⋅tet, Ca(hfa)2⋅tet, and Cu(hfa)2 (hfa=hexafluoroacetylacetonate; tet=tetraglyme) as volatile metalorganic precursors. Thallium is then incorporated into the films during a post‐anneal in the presence of a Tl2O3, BaO, CaO, CuO powder mixture at 820 °C for 12 h in a flowing 10% O2/Ar atmosphere. The films have a transport‐measured Tc=115 K and Jc=1.5×105 A/cm2 (80 K), while magnetic hysteresis measurements yield Jc=6×105 A/cm2 (77 K). Preliminary surface resistance measurements give Rs=0.35 mΩ at 5 K, 10 GHz.

Metalorganic chemical vapor deposition route to epitaxial neodymium gallate thin films

Phase‐pure epitaxial thin films of the YBa2Cu3O7−δ lattice‐matched, low dielectric loss perovskite insulator NdGaO3 have been grown on (110) LaAlO3 substrates by a metalorganic chemical vapor deposition (MOCVD)/post‐annealing process. Amorphous Nd‐Ga‐O films are first prepared by MOCVD using the volatile metalorganic β‐diketonate precursors Nd(dpm)3 and Ga(dpm)3 (dpm=dipivaloylmethanate). Subsequent postannealing affords phase pure, highly oriented [(001) and/or (110) orientations perpendicular to the substrate surface] and epitaxial NdGaO3 films as assessed by x‐ray diffraction θ‐2θ, ω, and φ scans. Cross‐sectional high‐resolution electron microscopic images show that the epitaxial growth occurs with atomically abrupt film‐substrate interfaces and with coexisting NdGaO3 (001) and (110) orientation domains.

Heteroepitaxy of high-Tc superconducting TlBaCaCuO films on metal-coated substrates

Abstract Superconducting TlBaCaCuO thin films have been successfully grown on gold-coated oxide substrates (yttria-stabilized zirconia (YSZ)) using a combination of metal-to-organic chemical vapor deposition (MOCVD) and Tl vapor diffusion. BaCaCuO films are first prepared by MOCVD using “second-generation” precursors with improved thermal stability and volatility. Thallium is then incorporated into these films by annealing in the presence of a mixture of oxides (Tl 2 O 3 , BaO, CaO and CuO) of a specific composition. The resultant films consists predominantly of single-phase Tl 2 Ba 2 CaCu 2 O x superconductor with preferential orientation of the crystallite c -axes perpendicular to the substrate surface. A magnetically determined T c value of about 95 K for Tl 2 Ba 2 CaCu 2 O x on Au/YSZ compares well with a transport T c value of 94 K. Attempts to form superconductors on platinum-coated oxide substrates (MgO) led to the formation of a PtTlO phase.

Initial evaluation and comparison of plasma damage to atomic layer carbon materials using conventional and low Te plasma sources

The ability to achieve atomic layer precision is the utmost goal in the implementation of atomic layer etch technology. Carbon-based materials such as carbon nanotubes (CNTs) and graphene are single atomic layers of carbon with unique properties and, as such, represent the ultimate candidates to study the ability to process with atomic layer precision and assess impact of plasma damage to atomic layer materials. In this work, the authors use these materials to evaluate the atomic layer processing capabilities of electron beam generated plasmas. First, the authors evaluate damage to semiconducting CNTs when exposed to beam-generated plasmas and compare these results against the results using typical plasma used in semiconductor processing. The authors find that the beam generated plasma resulted in significantly lower current degradation in comparison to typical plasmas. Next, the authors evaluated the use of electron beam generated plasmas to process graphene-based devices by functionalizing graphene with...

AZIDO AND AMIDO DERIVATIVES OF ALUMINIUM(III)

Abstract The piperidinyl-substituted aluminium azide, [(pip)2AlN3]2 (5) (pip = piperidinyl, has been synthesised via the reaction between [(pip)2AlCl]2 and one equivalent of NaN3. A related pyrrolyl derivative, [(Me2N(H))Al(pyr)3] (7) (pyr = pyrrolyl, was prepared via the dimethylamine elimination reaction between [Al2(NMe2)6] and six equivalents of pyrrole. A third aluminium amido complex, [Li(Al(NHtBu)4)]2 (9), has been isolated from the salt elimination reaction between AlCl3 and an excess of LiNHtBu. all three compounds have been characterised by X-ray crystallography; compounds 5 and 9 are dimeric in the solid state, whereas 7 is monomeric.

Metal-organic chemical vapor deposition-derived lead- and bismuth-doped high-Tc superconducting TlBaCaCuO films

Abstract Superconducting Pb- and Bi-doped TlBaCaCuO films can be prepared on a variety of substrates by a two-step process, based on metal-organic chemical vapor deposition (MOCVD). MBaCaCuO films (M  Pb or Bi) are first prepared by MOCVD using precursors exhibiting improved thermal stability and volatility over previously used complexes. These characteristics allow better control over the stoichiometry of the deposited films. In the second step, thallium is incorporated into these films by a vapor diffusion process using mixtures of Tl2O3, BaO, CaO and CuO of specific composition as the source of volatile thallium oxides. The resultant films consist predominantly of single-phase TlMBaCaCuO exhibiting preferential orientation of the CuO planes parallel to the substrate surface. The superconducting properties of these films have been examined by resistivity and magnetization measurements.

MOCVD precursor design issues. Recent advances in the chemistry and vapor pressure characteristics of Ba(hexafluoroacetylacetonate)2·polyether complexes

Abstract This contribution presents synthetic, structural and volatility results for a series of new Ba(hfa) 2 polyether (hfa=1,1,1,5,5,5-hexafluoropentane-2,4-dionate) MOCVD precursors. The major emphasis of this study is on the synthesis and characterization of new Ba(hexafluoroacetylacetonate) 2 ·polyether complexes as on well as elucidating relationships between volatility, melting point and molecular architecture using a variety of techniques, including reduced pressure thermogravimetric analysis (TGA). The results provide insights into tuning Ba precursor volatility characteristics based on straightforward modifications of the polyether structure.