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We introduce a phase diagram for boron nitride film growth. It is based on studies of the influence of the ion energy and substrate temperature on the phase formation using mass-selected ion-beam deposition of B ϩ and N ϩ ions. For the formation of the cubic phase we find threshold values of 125 eV for the ion energy and 150°C for the substrate temperature. Furthermore, we find a characteristic ion energy and substrate temperature dependence of the compressive stress, yielding low stress values for high energies and/or temperatures. c-BN nucleation and growth is attributed to a subsurface process qualitatively described by the subplantation model. ͓S0163-1829͑97͒05519-7͔Regarding mechanical and electronic applications, cubic boron nitride ͑c-BN͒ may leave diamond far behind, because it is chemically inert against iron and oxygen at high temperatures, 1 and because it can be p and n type doped. 2 So far, low pressure synthesis of c-BN thin films is only possible with a variety of ion-assisted physical and chemical vapor deposition techniques. 3 These films are usually nanocrystalline, with a textured h-BN interface layer. Attempts to grow c-BN by chemical processes alone have failed so far. 4 It is therefore generally accepted that ion bombardment is necessary for c-BN nucleation and growth; however, a satisfactory understanding of the underlying mechanisms is still lacking. An unwanted side effect is the ion-induced high compressive film stress, which limits the achievable film thickness to only a few hundred nm, insufficient for most tribological applications. The growth of low-stress c-BN films is therefore highly desirable.The c-BN growth conditions for ion-beam-assisted deposition ͑IBAD͒ were investigated in systematic studies. 3,5 With IBAD, films are usually grown using evaporated boron atoms and additional ion bombardment, typically with a mixture of N 2 ϩ , N ϩ , and Ar ϩ ions. In addition, the ion angle of incidence may vary for different deposition systems. IBAD growth is therefore rather complex, and a variety of different processes such as condensation and thermal desorption, implantation of ions, recoil implantation of atoms deposited on the surface, and sputtering have to be considered. The c-BN growth regime is thus a complex function of three parameters: substrate temperature, ion energy, and the flux ratio of ions to neutral ͑boron͒ atoms. 3,5 Furthermore, c-BN growth takes place at conditions close to the resputter limit due to the intense heavy ion bombardment. Kester et al. introduced the average momentum transferred to the boron atoms deposited on the surface as a more universal parameter to characterize c-BN growth. 5 Sputter yield and nuclear stopping are quantities which depend on the square root of the ion energy ͑or the ion momentum͒ to a first approximation. On the other hand, nuclear stopping itself determines the range of low-energy ions in matter, the energy transfer to recoil atoms, and the deposited energy density. As a consequence, several models for c-BN nucleation and growth wer...

We have studied the growth and the properties of (t)a-C:F films prepared by the deposition of mass separated 12C+ and 19F+ ions as a function of the F concentration. The films are always strongly F deficient due to the formation of volatile F2 and CFx molecules during the deposition process. A maximum F content of about 25 at. % is obtained for an ion charge ratio of C+:F+=1:1. The observed mechanical, optical, electrical, and structural properties as well as the thermal stability of the films are strongly influenced by the F content. A three step progression of the film structure is evident for increasing F concentration: the amorphous three-dimensional network of tetrahedrally bonded carbon atoms of pure carbon films (ta-C) with diamondlike properties is doped for very low F concentrations (ta-C:F). A further increase of the F content results first in transformation to a graphitelike amorphous structure (a-C:F) before the deposited films become porous and to a polymerlike one for the highest F content.

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