ELECTRONIC STRUCTURE OF BORON NITRIDE BASED SOLID SOLUTIONS

T.P.Zhdanova,V.V.Ilyasov

Don state technical university Rostov-on-Don.

The physical properties of solid solutions are strongly affected by crystalline network irregularities (defects). In practice,the sinthesized cubic boron nitride (c-BN) usually contains s,p-elements admixtures (Li,C,O,Mg,Al) and vacancies of the base elements as well. Experimental data[1,2] characterize c-BN to be of high nitrogen deficiency that leads to high density of nitrogen vacancies and causes C and O intrusions in nitrides. Nevertheless, today no theory has been created to describe satisfactorily the interactions between different components in BN-C, BN-O. That is why we tried to perform the electronic structure simulations for BN_xC_1-x and B_xCN_1-x, BN_xO_1-x and B_xCO_1-x (x=0.25) in cluster version of local coherent potential approach of the quantum multiple scattering theory [3]. To describe crystal potential a muffin-tin approximation has been chosen.

It occured that the appearance of nitrogen and boron vacancies as well as O admixtures significantly affects the behaviour of the distribution density of elektronic states.

It was demonstrated, that the top of the valence band shifted towards the higher energy values in comparison to pure binar sample. The shift values obtained were: 0.18R_y - for BN_0.75C_0.25, 0.09R_y - for BN_0.75C_0.25, 0.22R_y - for B_0.75NC_0.25 and negliable value - for B_0.75NO_0.25.

The forbidden band width dependence on the type of defects was also studied. It increased if nitrogen was substituted and decreased in the case of boron substitutions.

1. V.B.Shipilo, A.M.Zaitsev and E.M.Shishinok. J.Appl.Spectroscopy 45.601 (1986).
2. V.G.Aleshin, A.N.Sokolov, A.A.Shulzhenko. Superhard Matter 38,12 (1985).
3. V.V.Ilyasov, N.Ya.Safontseva, I.Ya.Nikiforov. Sov. Phys. Solid State. 36 (1994) 451-459.