ACCURATE MEASUREMENTS OF MEAN INNER POTENTIAL OF CRYSTAL WEDGES USINGDIGITAL ELECTRON HOLOGRAMS

The mean inner potential of a solid is a fundamental property of the m aterial and depends on both composition and structure. By using cleave d crystal wedges of known angle, combined with digital recording of of f-axis electron holograms and with theoretical calculations of dynamic al effects, the mean inner potential of Si (9.26+/-0.08 V), MgO (13.01 +/-0.08 V), GaAs (14.53+/-0.17 V) and PbS (17.19+/-0.12 V) is measured with high accuracy of about 1%. Dynamical contributions to the phase of the transmitted beam are found by Bloch wave calculations to be les s than 5% when the crystal wedges are tilted away from zone-axis orien tations and from major Kikuchi bands. The accuracy of the present meth od is a factor of 3 better than previously achieved by reflection high -energy electron diffraction and electron interferometry. The major ca uses of uncertainty were specimen imperfections and errors in phase me asurement and magnification calibration.