Application of the CBED method for the determination of lattice parameters of cubic Sic films on 6H SiC substrates

Many-beam Bloch wave CBED pattern simulation is used to determine the lattice parameter of thin cubic SiC films on 6H SiC substrates from experimental on-axis CBED patterns at zones showing lattice parameter change sensitive HOLZ line shifts. Experiments are carried out at [320] and [331] zone axes. The agreement of three ratios between defined HOLZ lines in each zone axis pattern ensures a lattice parameter determination with high accuracy. For two SiC layers the lattice parameters are determined with an accuracy of 0.0001 nm to be 0.4374 nm and 0.4369 nm. Their significant differences are addressed to the different growth parameters resulting in differently strained layers. The values determined are up to 0.4% higher than X-ray data of bulk material. The strain in the thin film may be one main reason for the difference. From experiments at both liquid nitrogen and room temperature the linear thermal expansion of the layers has been determined to be (6.7±0.2)×10”6/K.