Alane Precursors Research Articles

Synthesis of Intramolecular P/Al-Based Frustrated Lewis Pairs via Aluminum-Tin-Exchange and their Reactivity toward CO2.

Frustrated Lewis pairs (FLPs) composed of acidic alane and basic phosphane functions, separated by a xanthene linker, can be prepared through the corresponding Me3Sn derivative and methyl aluminum compounds with elimination of Me4Sn. This way MeClAl‐, Cl2Al‐ and (C6F5)2Al‐ moieties could be introduced and the resulting FLPs are stabilized by a further equivalent of the alane precursors. In contact with the FLPs CO2 is bound via the C atom at the phosphane functions and the two O atoms at the Al centers. The residues at the latter determine the binding strength. Hence, in case of MeClAl CO2 capture occurs at higher pressure and under ambient conditions CO2 is released again, while for Cl2Al and (C6F5)2Al CO2 binding becomes irreversible. The results of DFT calculations rationalize these findings by the high thermodynamic stabilization in case of more electronegative residues, which concomitantly lead to higher barriers, and in case of (C6F5)2Al further stabilization is achieved through a low reorganization energy.

Creation of Quaternary Stereogenic Centers via Copper-Catalyzed Asymmetric Conjugate Addition of Alkenyl Alanes to α,β-Unsaturated Cyclic Ketones

SimplePhos ligands proved to be very powerful ligands in the generation of quaternary stereogenic centers by Michael addition of alkenyl-aluminum reagents to cyclic enones. Using commercially available and easily accessible alkenylbromides as alane precursors the present procedure offers a facile access to β-alkenyl-substituted cyclohexanones with high enantioselectivities up to 96%.

Templated Synthesis of Aluminum Nanoparticles - A New Route to Stable Energetic Materials

Nanoscale structural cavities in ionomer membrane films were used as templates for the facile synthesis of small aluminum nanoparticles via catalytic decomposition of an alane precursor. The loading of reactive aluminum in the composite film could be varied, up to more than half of the film weight. While the embedded nanoparticles were protected by the membrane structure from any significant oxidation for the composite films to exhibit surprising stability in ambient air, they could be fully accessed in base water for the hydrogen production quantitatively. The templated synthesis may represent a new route for stable aluminum nanoparticles and related energetic nanomaterials.

CVD of conformal alumina thin films via hydrolysis of AlH3(NMe2Et)

Deposition of highly conformal alumina thin films has been carried out by hydrolysis of the liquid alane precursor, AlH3(NMe2Et). Depositions onto Si wafers, quartz and carbon fibres were all carried out utilizing a hot-wall atmospheric pressure chemical vapour deposition (APCVD) system. Optimum growth conditions were found to be at 165°C and with an AlH3(NMe2Et):H2O ratio of less than 1:25. Films were characterized by SEM, microprobe and electrical conductivity measurements. Growth rates were of the order of 40–80 Å min−1 at 165°C. The conformality of the films was illustrated using silicon wafers that were etched prior to deposition. Deposition onto ZnS EL-phosphor particles was accomplished in a simple fluidized-bed APCVD reactor. The deposited films were conformal and continuous. No significant reduction in the initial brightness or change in the colour balance of the phosphor was observed from the coating process. Copyright © 2000 John Wiley & Sons, Ltd.

Fabrication of aluminium nitride/diamond and gallium nitride/diamond SAW devices

Abstract Surface acoustic wave (SAW) devices have been fabricated from thin films of gallium nitride and aluminium nitride deposited on a range of chemical vapour deposition (CVD) diamond substrates. The growth of aluminium nitride and gallium nitride layers on diamond by chemical beam epitaxy (CBE) is reported for the first time. Triethyl gallium and ethyldimethylamine alane precursors were used in conjunction with nitrogen from an RF atom source to deposit the gallium nitride and aluminium nitride layers at substrate temperatures in the range 540 to 575 °C. These layers have been characterised by Raman spectroscopy and atomic force microscopy. The SAW structures were completed by the deposition of gold or aluminium interdigitated electrode structures on the as-deposited nitride surfaces. Preliminary testing indicates that these devices operate as bandpass filters with characteristics consistent with the propagation of acoustic waves at very high phase velocities within the nitride–diamond multi-layer substrate.

Chemical Vapor Deposition of Conformal Alumina Thin Films

AbstractDeposition of highly conformal alumina thin films has been carried out by hydrolysis of the liquid alane precursor, AlH3(NMe2Et). Deposition onto Si wafers, quartz and carbon fibers were all carried out utilizing a hot-wall atmospheric pressure chemical vapor deposition (APCVD) system, while deposition onto ceramic particles was accomplished in a simple fluidized-bed APCVD reactor. Films were characterized by SEM, microprobe and electrical conductivity measurements. Growth rates were on the order of 40 - 80 Å.min−1at 165 °C. The conformality of the films was illustrated using silicon wafers that were etched prior to deposition.

Growth of AlN by metalorganic molecular beam epitaxy

Thin film AlN has been grown on Al2O3 and GaAs substrates by metalorganic molecular beam epitaxy using amine bonded alane precursors and either tertiarybutylamine or nitrogen from a compact electron cyclotron resonance (ECR) plasma source operating at 2.45 GHz. Typical growth pressures were in the 0.5–1×10−4 Torr range. The growth rates, impurity backgrounds, and surface morphologies were examined for both nitrogen sources and both the solid and liquid alanes. In general, growth efficiencies were good for both alane precursors, allowing for deposition of the low temperature, ∼400 °C, AlN buffers needed for subsequent growth of GaN and InGaAlN alloys. Low growth temperatures could not be obtained using tertiarybutylamine, presumably due to poor decomposition efficiency of the source at low temperatures. The structural quality of material grown at high temperatures from the ECR plasma was measured by atomic force microscopy, high resolution x-ray diffraction, and transmission electron microscopy, indicating single crystal material with a surface roughness of ∼8 Å and an x-ray full width half-maximum of 430 arcsec. This ECR plasma-derived material was of sufficient quality to allow for the growth of multiple quantum well InGaAlN structures.

A comparison of alane precursors for growth of AlAs and AlGaAs by metalorganic molecular beam epitaxy

A comparison of alane precursors for growth of AlAs and AlGaAs by metalorganic molecular beam epitaxy

AlN Grown by Metalorganic Molecular Beam Epitaxy

AbstractThin film AlN has been grown on Al2O3 and GaAs substrates by metalorganic molecular beam epitaxy (MOMBE) using amine bonded alane precursors, tertiarybutylamine, and nitrogen from a compact electron cyclotron resonance (ECR) plasma source operating at 2.45 GHz. Typical growth pressures were in the 0.5 − 1 × 10−4 Torr range. The growth rates, impurity backgrounds and surface morphologies were examined for both nitrogen sources and both the solid and liquid alanes. In general, growth efficiencies were good for both alane precursors, allowing for deposition of the low temperature, ∼ 400°C, AlN buffers needed for subsequent growth of GaN and InGaAlN alloys. Low growth temperatures could not be obtained using tertiarybutylamine, presumably due to poor decomposition efficiency of the source at low temperatures. The structural quality of material grown at high temperatures from the ECR plasma was measured by atomic force microscopy (AFM) and high resolution x-ray diffraction (HRXRD), indicating a surface roughness of ∼ 8 Å and an x-ray width half maximum (FWHM) of 430 arcsec.

Argon-ion laser direct-write Al deposition from trialkylamine alane precursors

Laser direct writing of aluminum lines on Si, GaAs and Al2O3 substrates using the trialkylamine alane precursors, (C2H5)3N · AlH3 (TEAA) and (CH3)3N · AlH3 (TMAA), is reported. Deposition, carried out with a continuous wave Ar+ laser working at 514 nm, results from the thermal decomposition of the precursor via laser-induced surface heating at temperatures in excess of 360 K. It proceeds in two steps: surface nucleation, which occurs typically in 0.01 to 0.1 s depending on the laser power and the substrate nature; and the successive Al growth. Uniform lines are produced at scanning speeds up to 300 μm/s. Higher deposited heights are obtained with TMAA due to its higher vapor pressure when compared to TEAA. 7 μm wide, 0.7 μm thick Al lines are generated by a single surface scan at a scanning speed of 100 μm/s and a high power density (1.55 MW/cm2). Passing N2 or He gas through a TEAA bubbler increases the deposited height by a factor 1.6 in comparison to deposition without the bubbler. Al lines deposited from TEAA and TMAA are polycrystalline. The rate of crystallite growth is greater than the rate of nucleation, leading to an increase of the surface roughness with the line thickness. Adhesion of the deposit to the substrates is good and Al lines with resistivities down to 4.5 μΩ cm, i.e. twice the bulk value are obtained.

Photoluminescence on high-quality AlxGa1−xAs grown by metalorganic vapor-phase epitaxy using alane bis(dimethylethylamine)

Photoluminescence (PL) spectra are reported of initial results of AlxGa1−xAs grown by metalorganic vapor-phase epitaxy (MOVPE), using a new precursor, alane bis(dimethylethylamine), as the aluminum source. The advantage of this new precursor over other alane precursors used previously is that it is liquid at room temperature. Using this new precursor instead of trimethylaluminum (TMAl), we found a reduction by a factor 6 in carbon incorporation when it was used together with trimethylgallium (TMGa), whereas a reduction by a factor 50 was found when it was used in combination with triethylgallium (TEGa). At low excitation density the linewidth of the separate donor bound exciton (D0,X) was 2.6 meV at an Al fraction of 0.31. This is comparable with the smallest values ever reported in literature for MOVPE-grown AlxGa1−xAs with an Al fraction higher than 20%. This narrow linewidth indicates a very uniform aluminum composition.

Laser Assisted CVD of Aluminum from a Novel Liquid Alane Precursor

ABSTRACTWe describe pyrolytic laser assisted chemical vapor deposition of Al from dimethylethylamine-alane with 514 nm radiation from an Ar+ laser. Results from deposition on different substrates, including Pt, Au, W, and Si, provide insight into to thermal and nucleation effects in the laser writing process. High purity Al lines with resistivity close to bulk Al are reported for a range of operating conditions. The relationship between operating parameters and the resulting properties of the deposited lines is investigated. We also demonstrate a two-step fast writing process based on fast laser nucleation of lines followed by selective chemical vapor deposition of Al on the nucleated pattern.