Optimization of the in situ cleavage process for Ⅲ-Ⅴ/Si(001) investigations by cross-sectional scanning tunneling microscopy

摘要

Interfaces between epitaxial layers forming electronic devices have long been recognized to have an important impact on their functionality. Cross-sectional measurements have, therefore, attained an important role in the characterization of these layers to acquire a deep understanding of their structural and electronic properties. For cross-sectional measurements relying on in situ cleavage, achieving control over the cleavage process is crucial. Particularly, cross-sectional scanning tunneling microscopy relies on atomically flat cleavage surfaces for the investigation of a multitude of material systems with the greatest possible detail. For the investigation of Ⅲ-Ⅴ semiconductors grown on Si(001), samples are normally cleaved by applying a force in the [001] direction in order to generate and analyze {110} cleavage surfaces. These surfaces are best suited for cross-sectional investigations as they are perpendicular to the growth surface as well as to each other. In this work, we show that for cleaving Si (001) in such a way, sawing rather than notching samples to create a predetermined breaking point results in significantly improved cleavage surfaces. For this purpose, a statistical investigation of the cleavage of Si(001) wafers is presented. We further demonstrate the proficiency of sawing as the sample-preparation method for cross-sectional scanning tunneling microscopy by investigating the interfacial region of high-quality GaP/Si(001) samples as well as a state-of-the-art GaSb/Si(001) sample.