We have investigated how ion irradiation can selectively promote the formation of dense sp3-bonded cubic boron nitride (cBN) over the graphite-like sp2-bonded phases. We have conducted a series of experiments using ion-assisted pulsed laser deposition in which either the ion mass (mion) or ion energy (E) was varied in conjunction with the ratio of ion flux to depositing atom flux (J/a). For a fixed ion energy and mass, there is a critical J/a above which cBN formation is initiated, a window of J/a values in which large cBN percentages are obtained, and a point at which J/a is so large that the resputter and deposition rates balance and there is no net film deposition, in agreement with Kester and Messier. As do Kester and Messier, we find that cBN formation is controlled by a combination of experimental parameters that scale with the momentum of the ions. However, unlike Kester and Messier, we do not find that cBN formation scales with the maximum momentum that can be transferred in a single binary collision, as either incorrectly formulated by Targove and Macleod and used by Kester and Messier, or as correctly formulated. Instead we observe that cBN formation best scales with the total momentum of the incident ions, (mionE)1/2. We also consider the mechanistic origins of this (mionE)1/2 dependence. Computer simulations of the interaction of ions with BN show that cBN formation cannot be simply scaled to parameters such as the number of atomic displacements or the number of vacancies produced by the ion irradiation. A critical examination of the literature shows that none of the proposed models satisfactorily accounts for the observed (mionE)1/2 dependence. We present a quantitative model that describes the generation of stress during ion-assisted film growth. The model invokes a kinetic approach to defect production and loss. We apply a simplified version of the model to cBN synthesis, and find that it predicts an approximate (mionE)1/2 dependence for cBN formation.

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Radiation damage in metals at elevated temperatures produces small dislocation loops and voids. The growth of these sinks is determined by the steady−state diffusion of point defects migrating in the stress field of these sinks. To obtain the steady−state current of point defects to these spherical sinks a perturbation method is developed to deal with the drift term of the diffusion equation. It is shown that the contribution of the drift term to the current can be expressed by a bias factor which differs from unity if the point defects interact with the spherical sink. Explicit expressions of the bias factors for voids and infinitesimal dislocation loops are given. If the metal is subject to external loads the bias factors of voids depend on the elastic dilatation, whereas the bias factors for dislocation loops depend on the deviatoric elastic strain. These results then provide the basis for stress−induced swelling and irradiation creep of metals. Both of these phenomena are briefly discussed.