Experimental bulk energy bands for diamond usinghν-dependent photoemission

Using photon-energy-dependent photoemission techniques with a diamond (111)-(1 × 1) crystal surface, we have determined critical points of energy bands at $\Gamma$ and $L$ (${\Gamma }_1=-21\mathrm{}$ eV, $L_1=-12.8\mathrm{}$ eV, $L_2^{\prime }=-15.2\mathrm{}$ eV, ${\Gamma }_{15}=+6.0\mathrm{}$ eV, ${\Gamma }_2^{\prime }=+15.3\mathrm{}$ eV, $L_2^{\prime }=+20\mathrm{}$ eV, $\Gamma =+24\mathrm{}$ eV with respect to the top of the valence band ${\Gamma }_{25}^{\prime }$). Recent ab initio calculations agree with our results within 0.6 eV for the valence bands and show qualitative agreement for the empty conduction bands. The final bands are observed to be non-free-electron-like up to at least + 30 eV.