Annealing of ion-implanted defects in diamond by MeV ion-beam irradiation

Defects and amorphous C layers or clusters in a type-Ib diamond formed by C - or P-ion implantation under certain doses are clearly annealed or epitaxi ally crystallized during thermal annealing at 750 degrees C or during mega- electron-volt (MeV) ion-beam irradiation at 750 degrees C. Implanted P atom s are incorporated into substitutional sites after complete crystallization by using MeV-ion-beam irradiation. This is confirmed by using the Rutherfo rd-backscattering-spectroscopy channeling method. A considerable amount of defects or amorphous clusters are formed by C-ion implantation at a 50-keV energy for a 1x10(15)/cm(2) dose. However, they are crystallized epitaxiall y to the crystalline diamond by using only thermal annealing at 750 degrees C or by using MeV-ion-beam irradiation at 750 degrees C. Above 2x10(15)/cm (2) C doses, continuous amorphous layers are formed internally in the subst rate and epitaxial crystallizations proceed from both the crystalline subst rate and the crystalline-surface region. Moreover, the rate of crystallizat ion is higher for annealing with MeV-ion-beam irradiation than for thermal annealing at the same temperature. Epitaxial crystallization of the interna l amorphous layer, however, stops in both thermal annealing and MeV-ion-bea m irradiation, even if annealing time or irradiation dose increases. This i s probably due to amorphous C changing into the graphite layers that occurs during thermal annealing or MeV-ion-beam irradiation. Graphite formation i s also observed for the as implanted sample before annealing. Direct eviden ce of graphite formation is given from the channeling yield difference betw een samples for a 2x10(15)/cm(2) dose and for a 3x10(15)/cm(2) dose, showin g clearly the stopping power difference between sp(2) (graphite) and sp(3) (diamond) bonding. Amorphous layers in diamond can be formed by C-ion impla ntation at a more than one order of magnitude smaller amount of doses, comp ared with those needed for the amorphization of the Si substrates. A calcul ated number of vacancies created per incident C ion in Si is larger than in diamond. Nevertheless, diamond is amorphized faster than Si. A mechanism i s proposed for forming the amorphous layer in diamond. This consists of a b ond-breaking process due to inelastic electronic scattering and the movemen t process of C atoms after bond breaking with the assistance of elastic nuc lear scattering without recoil, induced by ion implantation. Atomistic mode ls for ion-beam-induced epitaxial crystallization (IBIEC) and for low-tempe rature crystallization of implantation-amorphized epitaxial Si layer formed by ultrahigh vacuum chemical-vapor deposition are proposed and discussed, putting particular emphasis on the role of both nuclear and electronic scat tering of incident MeV-ion beam. A similar atomistic model for the inclusio n of implanted P atoms into substitutional sites is also proposed, based on this atomistic IBIEC model. [S0163-1829(99)10227-3].