High Energy Electron Reflection Essay

Superior Essays
Reflection High-Energy Electron Refraction Intensity Oscillations

Reflection high-energy electron refraction (RHEED) has been used as a surface probe for in situ observation of monolayer growth using molecular beam epitaxy (MBE) because of its high surface sensitivity and a near grazing incidence. It utilizes diffraction of electrons by surface atoms[1] and the RHEED intensity oscillation can convey morphological information of the growth surface if the intensity oscillation pattern is properly interpreted[2].

The wave properties of electrons make techniques like RHEED feasible. Low-energy electron diffraction (LEED) has also been used to determine the surface structure as well. But RHEED is more preferable to LEED because of its forward
…show more content…
4. Schematic diagram of the correlation of surface coverage of 2-D clusters with idealized RHEED oscillations. (Adapted from J.R. Arthur, Surface science 500 (2002) 189-217)

There are similar in situ surface studies techniques used by means of optics, such as reflectance difference spectroscopy (RDS), which also known as reflectance anisotropy (RAS). This technique measures the difference in reflectance between two orthogonal polarization states of light falling at near-normal incidence on the sample surface[8]. The typical setup of RAS spectrometer is shown in Fig. 5. The details of how RAS works are given somewhere else[8]. Fig. 5. Typical setup of RAS spectrometer. (Adapted from Z. Sobiesierski et al, Journal of Physics: Condensed Matter 10 (1998)
…show more content…
Besides, the overall intensity decreases as the mole fraction of Ge increases. K. Sakamoto et al[9] also did a comparison experiment to find a more favorable condition for Ge growth on Si, the result is shown in Fig. 7. More than 10 periods of oscillations can be seen at room temperature, so K. Sakamoto et al[9] concluded that lower temperature is more preferable because the surface migration would be suppressed. Fig. 7. RHEED intensity oscillations during the Ge growth on Si(001) (a) at 450°C and (b) at room temperature. The RHEED patterns during growth at 450°C are also shown. (Adapted from K. Sakamoto et al, Japanese journal of applied physics 26 (1987) 666)

By interpreting the RHEED intensity oscillation patterns, the surface structure can be approximated. In this paper, they did an approximation of what the structure looks like at different stages. Fig. 8 shows the Schematic illustration of Ge growth on Si(001) at 450°C, derived from the RHEED intensity oscillation shown in Fig. 7 (a). Fig. 8. Schematic illustration of Ge growth on Si(001) at 450°C, derived from the RHEED intensity oscillation shown in Fig. 7 (a). (Adapted from K. Sakamoto et al, Japanese journal

Related Documents

  • Great Essays

    Therefore, the electrons may be described as occupying an atomic orbital, or by a wave function  which is a solution to the Schrodinger wave equation. The atomic orbitals must satisfy the following conditions to interact to form molecular orbitals. Atomic orbitals must (i) have roughly the same energy (ii) overlap one another as much as possible (iii) have the same symmetry with respect to bonding molecular axis. 4. Ligand Field Theory (LFT): LFT is a more comprehensive and sophisticated theory is now evolved from the combination of CFT and MOT.…

    • 1014 Words
    • 5 Pages
    Great Essays
  • Great Essays

    Congo Red Lab Report

    • 1045 Words
    • 5 Pages

    Scanning electron microscopy/Energy-dispersive X-ray spectroscopy employed to analyze the size, morphology and structures of the ZnO and ZnO/CR nanoparticles. The elemental analysis of both ZnO and ZnO/CR were determined by SEM-EDS using ZAF method standardless quantitative analysis [14]. The crystal structure of ZnO and ZnO/CR was investigated by X-ray diffraction (XRD)using = 0.1542 nm and 2 values started from 10 to 80. In addition the structural properties of ZnO and ZnO/CR were analyzed by Shimadzu FTIR spectrometer (from400 to 4000 cm-1) at room temperature. pH values measured by pH meter (HANNA).…

    • 1045 Words
    • 5 Pages
    Great Essays
  • Superior Essays

    Hot Tin Essay

    • 1256 Words
    • 6 Pages

    The above graph shows temperature of Sn0.3Ag0.7Cux In alloy as a function of indi-um weight percentage. Initially with no traces of Indium, the solidus temperature & liquidus temperature are 219.40̊C and 241.70̊C. It clearly shows that the temperature range goes wider as the concentration of indium is increased [6]. This is not a cost effective solution as indium is very costly. Titanium oxide nano particles addition led to temperature changing from 217 to 217.64 degree Celsius [7].…

    • 1256 Words
    • 6 Pages
    Superior Essays
  • Great Essays

    Spectroscopy Essay

    • 1635 Words
    • 7 Pages

    Spectroscopy is used in physical and analytical chemistry because atoms and molecules have unique spectra (Anon., n.d.). As a result, these spectra can be used to detect, identify and quantify…

    • 1635 Words
    • 7 Pages
    Great Essays
  • Superior Essays

    Gating Pulse Synthesis

    • 1722 Words
    • 7 Pages

    The ratio of the number of attosecond-gated electrons respect to the total number of electrons of the original electron pulse represent the attosecond optical gating efficiency which depends on the original electron pulse duration. It is calculated by dividing the integration of the coupling part of the spectrum by the integration of all spectrum. This relation is illustrated in Fig. 4D. Thus, the attosecond optical gating of short (few tens femtosecond) electron pulse will allow the generation of the attosecond electron pulses with the sufficient strength to capture the electron motion in the act, which opens the way for attaining the attosecond resolution in electron microscopy and establishing the…

    • 1722 Words
    • 7 Pages
    Superior Essays
  • Improved Essays

    2.2. Instrumentation The residual concentration of metal ion in the filtrate were analyzed by GBC, Sensaa Series Atomic Absorption Spectrometry (computerized AAS) with air-acetylene flame under the optimum instrumental conditions as shown in (Table 1). The solution pH was measured using digital pH meter (Hanna instrument model HI 8519, Italy). Fourier transform infrared (FT-IR) spectra were measured on Nicolet is 10 FTIR spectrometer in the range of (4000 to 400 cm-1). Scanning electron microscope (SEM, Quanta 250 FEG, FEI Company, USA) at an accelerating voltage of 30 kV was used for evaluation of surface morphology and particle size determination.…

    • 1649 Words
    • 7 Pages
    Improved Essays
  • Decent Essays

    Two diagnostics commonly applied in combustion are the Rayleigh and Mie scattering. When the incident light interacts with molecules and particulate-matter much smaller than the wavelength, Rayleigh scattering is produced. Mie scattering is also an elastic light scattering in case the particles are larger than the incident wavelength of light. Elastic light scattering (ELS) is a powerful technique to characterize nanoparticles. The particle morphology, such as aggregate size, gyration radius, and fractal dimension can be estimated by ELS \cite{Sorensen}.…

    • 794 Words
    • 4 Pages
    Decent Essays
  • Superior Essays

    For the plots of simulated IR and Raman spectra, pure Lorentzian band shapes were used with a band width (FWHM) of 10 cm−1. The vibrational modes were assigned by means of visual inspection using the GAUSS VIEW program [11]. The analysis for the vibrational modes of 2NAP is presented in some detail in order to better describe the basis for the assignments. From the basic theory of Raman scattering, Raman activities (si) calculated by GAUSSIAN 09W program has been converted to relative Raman intensities (Ii) using the following…

    • 2780 Words
    • 12 Pages
    Superior Essays
  • Improved Essays

    These values are comparable to those published in other literature [47]. Although the temperature dependence of the temperature of NiO nanoparticles exhibits typical semiconductor feature like the other oxides under study, the -T data don't fit well with Eq.9 where the accurate analyses confirm that the data are better represented by the following…

    • 861 Words
    • 4 Pages
    Improved Essays
  • Improved Essays

    The porosity of the samples was calculated using the relation, P(%)=(ρ_x-ρ_B)/ρ_x ×100. The dielectric and magnetic properties were carried out using WAYNE KERR 6500B Impedance Analyzer. To measure dielectric properties the samples were painted by conducting silver paste on both sides. The dielectric constant (ε′) was calculated from the capacitance using the formula: ε^'=Ct/(ε_0 A), where C is the capacitance of the pellet, A is the cross-sectional area of the electrode and ε_0 ( = 8.85×10-12 F/m) is the permittivity in free space. The relation: σ_ac=ω〖ε^'…

    • 896 Words
    • 4 Pages
    Improved Essays