Determine the Three-Dimensional Crystallographic Misorientation in Heterostructures by Selected Area Diffraction (SAD) i
- PDF / 929,995 Bytes
- 6 Pages / 415.8 x 637.2 pts Page_size
- 114 Downloads / 178 Views
X. J. Guo"', C.-Y. Wen", J. H. Huangb'd, H. C. Shihd ')ept. of Chemistry, National Taiwan University, Taipei, Taiwan bCenter of Materials Sciences, National Tsing-Hua University, Hsinchu, Taiwan VCenter for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan d[Dept. of Materials Science and Engineering, National Tsing-Hua University, Hsinchu, Taiwan. Abstract We proposed a concise and novel scheme to determine the crystallographic misorientation of heteroepitaxial structures. In addition to subtle high-resolution transmission electron microscope images, the information revealed from selected-area diffraction patterns at the interfaces offers another path to determine the angles of misorientations. The principle is to extract the basically three-dimensional misorientation information from a two-dimensional selected-area diffraction pattern through the employment of the Laue circle. Introduction Heteroepitaxy is a very important technology in determining the successfulness in many branches of the modern industry, especially in the semiconductor device fabrications. However, it is found that the deposited heteroepitaxial structures generally exhibit crystallographic misorientations with respect to the corresponding substrates [1-5]. These misorientation phenomena, usually detected and measured by x-ray diffractions (XRD), have been known since the early beginning of the semiconductor heteroepitaxy, but the mechanism of the formation is not fully understood [6]. Studying misorientation phenomena of the heteroepitaxial interfaces in the atomic scale is necessary and will greatly contribute to our understanding of the mechanisms of the heteroepitaxial growth. Transmission electron microscopy (TEM), especially high-resolution transmission electron microscopy (HRTEM) is one of the most powerful and popular tools to probe and characterize the details of the microstructures. In order to reveal the morphological features of the interface and to investigate the basic crystallographic relationships between the two materials of the heteroepitaxial structure, HRTEM combining with selected area diffraction (SAD) are usually performed in cross-sectional views. While attempts are made to align a zone axis of one crystal in the misoriented heteroepitaxial structure exactly parallel to the electron beam, the other crystal will be observed in a non-ideal imaging condition, that is, misoriented by a small angle from the exact zone axis. Unless it is a pure tilt misorientation [7] and the tilt axis is parallel to the electron beam, a heteroepitaxial misorientation cannot be seen and measured via the cross-sectional transmission electron micrographs and will adversely make it difficult to obtain clear information of the crystals both side simultaneously. 271 Mat. Res. Soc. Symp. Proc. Vol. 618 ©2000 Materials Research Society
In order to determine the misorientation between the two crystals that meet at an interface, several accurate and precise electron diffraction techniques can be employed [8, 9]. But these techniqu
Data Loading...
