Electronic band structure of calcium oxide

We have measured the bulk energy-momentum resolved valence band structure of calcium oxide by the means of electron momentum spectroscopy (EMS). We have extracted the band dispersions, bandwidths and inter-valance gap, electron momentum density (EMD) and density of occupied states (DOS) from the measured data. The experimental results are compared with theoretical band structure calculations performed within the full potential linear muffin-tin orbital (FP-LMTO) approximation. The valence band dispersions are in good general agreement with the theory, although small discrepancies exist. We have obtained 0.63 ± 0.15 and 1.2 ± 0.1 eV for the widths of the s-and p-subbands correspondingly. While the last number agrees well to the theoretical value of 2.6 eV after accounting for the experimental conditions, the former one suggests a slightly higher value compared to the theory. The measured intervalence gap of 14.69 ± 0.05 eV is at odds with the theoretical prediction being larger as much as about 1.7 eV. However, the measured s-p subband splitting of 16 eV agrees well to the measurement of other researches. The experiment also reveals a significantly higher intensity of the p-subband compared to the s-subband than follows from the theory. We have also made measurements of the Ca 3s and 3p core levels. Their splitting of 18.7 eV is in excellent agreement with the literature data and their § Permanent address: Physics Dept., Shahid Bahonar University, Kerman, Iran. * Corresponding author. E-mail address: [email protected]