| Summary: | Off-axis electron holography promises to fulfill the requirements of the semiconductor industry for a technique that can be used to provide quantitative information about dopant potentials in semiconductors with nanometer spatial resolution. The technique involves using an electron biprism in a transmission electron microscope (TEM) to interfere a coherent electron wave that has passed through a specimen with a reference wave that has passed only through vacuum. The focused-ion-beam (FIB) miller is the preferred method of sample preparation for semiconductor TEM analysis. In the FIB, a 30kV Ga ion beam is used to thin the specimen in the region of interest. It is increasingly recognised that this method of TEM specimen preparation and subsequent treatments have a profound influence on the phase shifts measured from doped semiconductors. In addition to the effect on the phase shift of surface depletion resulting from the presence of the specimen surfaces, the electrostatic potential in the specimen may be affected by the combined effects of oxidation, physical damage and the implantation of ions such as Ar and Ga during preparation of the sample for electron microscopy, as well as by the effects of irradiation by high-energy electrons during examination in the TEM. Semiconductor specimens have been prepared for examination using electron holography by combining advanced sample preparation techniques such as annealing and Ar ion milling in order to assess the effect of these treatments on the measured phase shifts across the junctions.
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