![]() ![]() Some incident electrons undergo a single, elastic scattering event at the crystal surface, a process termed kinematic scattering. Two types of diffraction contribute to RHEED patterns. Users characterize the crystallography of the sample surface through analysis of the diffraction patterns. Some of the electron waves created by constructive interference collide with the detector, creating specific diffraction patterns according to the surface features of the sample. The diffracted electrons interfere constructively at specific angles according to the crystal structure and spacing of the atoms at the sample surface and the wavelength of the incident electrons. Atoms at the sample surface atoms diffract (scatter) the incident electrons due to the wavelike properties of electrons. The glancing angle of incident electrons prevents them from escaping the bulk of the sample and reaching the detector. In the RHEED setup, only atoms at the sample surface contribute to the RHEED pattern. Figure 1 shows the most basic setup of a RHEED system. The electrons interfere according to the position of atoms on the sample surface, so the diffraction pattern at the detector is a function of the sample surface. Incident electrons diffract from atoms at the surface of the sample, and a small fraction of the diffracted electrons interfere constructively at specific angles and form regular patterns on the detector. The electron gun generates a beam of electrons which strike the sample at a very small angle relative to the sample surface. Low energy electron diffraction (LEED) is also surface sensitive, but LEED achieves surface sensitivity through the use of low energy electrons.Ī RHEED system requires an electron source (gun), photoluminescent detector screen and a sample with a clean surface, although modern RHEED systems have additional parts to optimize the technique. Transmission electron microscopy, another common electron diffraction method samples the bulk of the sample due to the geometry of the system. RHEED systems gather information only from the surface layer of the sample, which distinguishes RHEED from other materials characterization methods that rely on diffraction of high-energy electrons. Read more about how to correctly acknowledge RSC content.Reflection high-energy electron diffraction (RHEED) is a technique used to characterize the surface of crystalline materials. Permission is not required) please go to the Copyright If you want to reproduce the wholeĪrticle in a third-party commercial publication (excluding your thesis/dissertation for which If you are the author of this article, you do not need to request permission to reproduce figuresĪnd diagrams provided correct acknowledgement is given. Provided correct acknowledgement is given. If you are an author contributing to an RSC publication, you do not need to request permission Please go to the Copyright Clearance Center request page. To request permission to reproduce material from this article in a commercial publication, Provided that the correct acknowledgement is given and it is not used for commercial purposes. This article in other publications, without requesting further permission from the RSC, Baumbach,Ĭreative Commons Attribution-NonCommercial 3.0 Unported Licence. Furthermore, we demonstrate, how careful analysis of in situ RHEED if supported by ex situ XRD and scanning electron microscopy (SEM), all usually available at conventional MBE laboratories, can also provide highly quantitative feedback on polytypism during growth allowing validation of current vapour–liquid–solid (VLS) growth models.Ĭorrelating in situ RHEED and XRD to study growth dynamics of polytypism in nanowires In particular, the combination of RHEED and XRD allows for translating quantitatively the time-resolved information into a height-resolved information on the crystalline structure without a priori assumptions on the growth model. Exploiting the complementarity by a correlative data analysis presently offers the most comprehensive experimental access to the growth dynamics of statistical NW ensembles under standard MBE growth conditions. Simultaneously recorded in situ RHEED and in situ XRD intensities show strongly differing temporal behaviour and provide evidence of the highly complementary information value of both diffraction techniques. We analyse and compare the methodical potential of reflection high-energy electron diffraction (RHEED) and X-ray diffraction reciprocal space imaging (XRD) for in situ growth characterization during molecular-beam epitaxy (MBE). Therefore, quantitative feedback over the structure evolution of the NW ensemble during growth is highly desirable. Design of novel nanowire (NW) based semiconductor devices requires deep understanding and technological control of NW growth. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |