It is well known that any 4-dimensional hyperkähler metric with two commuting Killing fields may be obtained explicitly, via the Gibbons-Hawking Ansatz, from a harmonic function invariant under a Killing field on R 3 . In this paper, we find all selfdual Einstein metrics of nonzero scalar curvature with two commuting Killing fields. They are given explicitly in terms of a local eigenfunction of the Laplacian on the hyperbolic plane. We discuss the relation of this construction to a class of selfdual spaces found by Joyce, and some Einstein-Weyl spaces found by Ward, and then show that certain 'multipole' hyperbolic eigenfunctions yield explicit formulae for the quaternion-kähler quotients of HP m−1 by an (m − 2)-torus first studied by Galicki and Lawson. As a consequence we are able to place the well-known cohomogeneity one metrics, the quaternion-kähler quotients of HP 2 (and noncompact analogues), and the more recently studied selfdual Einstein Hermitian metrics in a unified framework, and give new complete examples.

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Epitaxial growth of sp 2 -hybridized boron nitride (sp 2 BN) films on sapphire substrates is demonstrated in a hot wall chemical vapor deposition reactor at the temperature of 1500 °C, using triethyl boron and ammonia as precursors. The influence of the main important process parameters, temperature, N/B ratio, B/H 2 ratio, and carrier gas composition on the quality of the grown layers is investigated in detail. X-ray diffraction shows that epitaxial rhombohedral BN (r-BN) film can be deposited only in a narrow process parameter window; outside this window either turbostratic-BN or amorphous BN is favored if BN is formed. In addition, a thin strained AlN buffer layer is needed to support epitaxial growth of r-BN film on sapphire since only turbostratic BN is formed on sapphire substrate. The quality of the grown film is also affected by the B/H 2 ratio as seen from a change of the spacing between the basal planes as revealed by X-ray diffraction. Time-of-flight elastic recoil detection analysis shows an enhancement of the C and O impurities incorporation at lower growth temperatures. The gas phase chemistry for the deposition is discussed as well as the impact of the growth rate on the quality of the BN film.

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