SCREENING EFFECT ON (110) HIGH-RESOLUTION ELECTRON-MICROSCOPY IMAGE OF COMPOUND SEMICONDUCTORS

Structural images of <110>-oriented compound semiconductors (GaAs, ZnSe and CdTe crystals) have been taken by high-resolution electron microscopy using the through-focus technique. Two white spots which look like the corresponding nearest atomic columns appear in the images with different intensities accompanying its elongation along the <001> direction. These experimental images are discussed in comparison with the images simulated by using two different crystal potentials: screened and neutral. As a result the following information can be obtained. (1) The difference between intensities of two nearest white spots of ZnSe and CdTe observed may occur by an interference of 000 and 002 beams and coincides closely with that of the spots calculated by using screened potential. (2) The specimen thickness estimated by image matching of the experimental image with the calculated image is thinner for that using the screened potential than for that using the neutral potential.