The relationship between bonding, structure and optical properties in reactive sputter deposited chrome oxycarbonitride
The latest attenuated phase-shift photomask technology requires the precise control of macroscopic properties such as optical transmission, reflectance, and chemical reactivity. This requires a fundamental understanding of the relationship between atomic bonding and property variation. Thin films of reactive sputter deposited Cr-O-C-N are compositionally graded to produce specific attenuation and phase shift of optical radiation. The above mentioned relationship was determined for these films. Compositions resolved on a sub-nm scale were measured in 120–150 nm thick CrOCN films by sputtered neutral mass spectroscopy. Near edge structure in electron energy loss from transmission electron microscopy and Cr core level shift in X-ray photoemission spectroscopy further support this conclusion. Extended X-ray analysis of fine structure was determined the nearest neighbor distances consistent with proposed bonding configurations and to confirm the lack of long range order in the system. Four point resistivity measurements characterized the transport properties of CrOCN. Variable angle spectroscopic ellipsometry gave film optical properties. The existence of a ternary continuous random network in CrOCN was demonstrated. The ternary network was based on the substitution of nitrogen for oxygen in the octahedral Cr2O3 bonding configuration. The ternary network lacked order beyond fourth chrome nearest neighbors. The limits of N substitution for O in the ternary were determined for eight compositions of CrOCN. It was also shown that the composition of this network at high [O] is very close to the stoichiometry of Cr2O3. At low [O], N substitution becomes substantial. The relationship between the stoichiometry of the ternary network and film properties was determined. A trend major optical absorption at lower energies in CrOCN films with increasing nitrogen substitution in this compound was shown in compositions greater than 40% oxygen. The mechanism of optical tunability of the CrOCN system is explained in terms of the electronic structure. In particular, N substitution for O in a CrON ternary compound in the system decreases the width of a gap in the density of electronic states in the material. This gap is responsible for the major optical absorption in CrOCN. Tailoring the gap directly tailors the transmission and phase shift properties of CrOCN.
Smith, Jackson Robert, "The relationship between bonding, structure and optical properties in reactive sputter deposited chrome oxycarbonitride" (2001). Dissertations available from ProQuest. AAI3003694.