Quasi-fivefold symmetric electron diffraction patterns due to multiple twinning in silicon thin films grown from hexamethyldisiloxane

2016 ◽  
Vol 49 (6) ◽  
pp. 2226-2234 ◽  
Author(s):  
Farah Haddad ◽  
Prabal Goyal ◽  
Erik V. Johnson ◽  
Junegie Hong ◽  
Pere Roca i Cabarrocas ◽  
...  
Keyword(s):  
Thin Films ◽  
Electron Diffraction ◽  
Chemical Vapour ◽  
Growth Conditions ◽  
Growth Direction ◽  
Fivefold Symmetry ◽  
Silicon Thin Films ◽  
Carbon Impurities ◽  
Diffraction Patterns ◽  
Multiple Twinning

Unusual quasi-fivefold symmetric electron diffraction patterns are observed for silicon thin films grown by plasma-enhanced chemical vapour deposition and containing oxygen and carbon impurities in the range of 0.3–5.5%. These films were grown on crystalline (100) silicon wafers using a liquid precursor, hexamethyldisiloxane (HMDSO), mixed with silane, hydrogen and diborane diluted in argon. The occurrence of this quasi-fivefold symmetry is explained by multiple twinning and imperfect epitaxy. A quantitative method performed on the diffraction patterns is developed to evaluate the number of twin operations. This method is also used to discriminate twin positions from random microcrystalline ones in the diffraction patterns and thus to estimate their respective ratios for different growth conditions. Quite remarkably, the random microcrystalline part remains in the range of a few per cent and the diffracted intensities are the sum of two main contributions: multiple (micro-) twinned and amorphous. Increasing the amount of HMDSO decreases the microtwinned part directly to the benefit of the amorphous part with no significant microcrystalline phase. The causes of twinning are presented and discussed by comparing the observations with the literature; dynamical considerations where the system tends to align {111} planes with the growth direction would explain multiple twinning and, in turn, the fivefold symmetry.

scholarly journals Odd electron diffraction patterns in silicon nanowires and silicon thin films explained by microtwins and nanotwins

2009 ◽  
Vol 42 (2) ◽  
pp. 242-252 ◽  
Author(s):  
Cyril Cayron ◽  
Martien Den Hertog ◽  
Laurence Latu-Romain ◽  
Céline Mouchet ◽  
Christopher Secouard ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Silicon Nanowires ◽  
Si Nanowires ◽  
Silicon Thin Films ◽  
Transmission Electron ◽  
Diffraction Patterns

Odd electron diffraction patterns (EDPs) have been obtained by transmission electron microscopy (TEM) on silicon nanowires grownviathe vapour–liquid–solid method and on silicon thin films deposited by electron beam evaporation. Many explanations have been given in the past, without consensus among the scientific community: size artifacts, twinning artifacts or, more widely accepted, the existence of new hexagonal Si phases. In order to resolve this issue, the microstructures of Si nanowires and Si thin films have been characterized by TEM, high-resolution transmission electron microscopy (HRTEM) and high-resolution scanning transmission electron microscopy. Despite the differences in the geometries and elaboration processes, the EDPs of the materials show great similarities. The different hypotheses reported in the literature have been investigated. It was found that the positions of the diffraction spots in the EDPs could be reproduced by simulating a hexagonal structure withc/a= 12(2/3)1/2, but the intensities in many EDPs remained unexplained. Finally, it was established that all the experimental data,i.e.EDPs and HRTEM images, agree with a classical cubic silicon structure containing two microstructural defects: (i) overlapping Σ3 microtwins which induce extra spots by double diffraction, and (ii) nanotwins which induce extra spots as a result of streaking effects. It is concluded that there is no hexagonal phase in the Si nanowires and the Si thin films presented in this work.

Planar defects in ordered (Ga,In)P

1988 ◽  
Vol 46 ◽  
pp. 902-903
Author(s):  
S. McKernan ◽  
C. B. Carter ◽  
D. Bour ◽  
J. R. Shealy
Keyword(s):  
Electron Diffraction ◽  
Vapor Phase ◽  
Growth Direction ◽  
High Density ◽  
Ordered Structure ◽  
Planar Defects ◽  
Diffraction Patterns ◽  
Ternary Semiconductors ◽  
Anion Species ◽  
Metallic Vapor

The growth of ternary III-V semiconductors by organo-metallic vapor phase epitaxy (OMVPE) is widely practiced. It has been generally assumed that the resulting structure is the same as that of the corresponding binary semiconductors, but with the two different cation or anion species randomly distributed on their appropriate sublattice sites. Recently several different ternary semiconductors including AlxGa1-xAs, Gaxln-1-xAs and Gaxln1-xP1-6 have been observed in ordered states. A common feature of these ordered compounds is that they contain a relatively high density of defects. This is evident in electron diffraction patterns from these materials where streaks, which are typically parallel to the growth direction, are associated with the extra reflections arising from the ordering. However, where the (Ga,ln)P epilayer is reasonably well ordered the streaking is extremely faint, and the intensity of the ordered spot at 1/2(111) is much greater than that at 1/2(111). In these cases it is possible to image relatively clearly many of the defects found in the ordered structure.

Electron diffraction studies of amorphous and polycrystalline thin films

1990 ◽  
Vol 48 (4) ◽  
pp. 118-119
Author(s):  
D J H Cockayne ◽  
D R McKenzie
Keyword(s):  
Thin Films ◽  
Electron Diffraction ◽  
Polycrystalline Materials ◽  
Good Resolution ◽  
Scattered Intensity ◽  
Radial Density ◽  
X Ray ◽  
Polycrystalline Thin Films ◽  
Nitrogen Ion ◽  
Diffraction Patterns

The study of amorphous and polycrystalline materials by obtaining radial density functions G(r) from X-ray or neutron diffraction patterns is a well-developed technique. We have developed a method for carrying out the same technique using electron diffraction in a standard TEM. It has the advantage that studies can be made of thin films, and on regions of specimen too small for X-ray and neutron studies. As well, it can be used to obtain nearest neighbour distances and coordination numbers from the same region of specimen from which HREM, EDS and EELS data is obtained.The reduction of the scattered intensity I(s) (s = 2sinθ/λ ) to the radial density function, G(r), assumes single and elastic scattering. For good resolution in r, data must be collected to high s. Previous work in this field includes pioneering experiments by Grigson and by Graczyk and Moss. In our work, the electron diffraction pattern from an amorphous or polycrystalline thin film is scanned across the entrance aperture to a PEELS fitted to a conventional TEM, using a ramp applied to the post specimen scan coils. The elastically scattered intensity I(s) is obtained by selecting the elastically scattered electrons with the PEELS, and collecting directly into the MCA. Figure 1 shows examples of I(s) collected from two thin ZrN films, one polycrystalline and one amorphous, prepared by evaporation while under nitrogen ion bombardment.

STEM and ELS Observation of Early Oxide Formation on the Surface of Cr Thin Films

1980 ◽  
Vol 38 ◽  
pp. 412-413
Author(s):  
Fumio Watari ◽  
J. M. Cowley
Keyword(s):  
Thin Films ◽  
Optical System ◽  
Room Temperature ◽  
Oxide Formation ◽  
Initial Nucleation ◽  
Diffraction Patterns ◽  
Relationship Of ◽  
Multiple Twinning ◽  
Moderately High Temperature

STEM coupled with the optical system was used for the investigation of the early oxidation on the surface of Cr. Cr thin films (30 – 1000Å) were prepared by evaporation onto the polished or air-cleaved NaCl substrates at room temperature and 45°C in a vacuum of 10−6 Torr with an evaporation speed 0.3Å/sec. Rather thick specimens (200 – 1000Å) with various preferred orientations were used for the investigation of the oxidation at moderately high temperature (600 − 1100°C). Selected area diffraction patterns in these specimens are usually very much complicated by the existence of the different kinds of oxides and their multiple twinning. The determination of the epitaxial orientation relationship of the oxides formed on the Cr surface was made possible by intensive use of the optical system and microdiffraction techniques. Prior to the formation of the known rhombohedral Cr2O3, a thin spinel oxide, probably analogous to γ -Al203 or γ -Fe203, was formed. Fig. 1a shows the distinct epitaxial growth of the spinel (001) as well as the rhombohedral (125) on the well-oriented Cr(001) surface. In the case of the Cr specimen with the (001) preferred orientation (Fig. 1b), the rings explainable by spinel structure appeared as well as the well defined epitaxial spots of the spinel (001). The microdif fraction from 20A areas (Fig. 2a) clearly shows the same pattern as Fig. Ia with the weaker oxide spots among the more intense Cr spots, indicating that the thickness of the oxide is much less than that of Cr. The rhombohedral Cr2O3 was nucleated preferably at the Cr(011) sites provided by the polycrystalline nature of the present specimens with the relation Cr2O3 (001)//Cr(011), and by further oxidation it grew into full coverage of the rest of the Cr surface with the orientation determined by the initial nucleation.

Computer Analysis of Electron Diffraction From thin Films

1998 ◽  
Vol 4 (S2) ◽  
pp. 344-345
Author(s):  
Warren MoberlyChan ◽  
R. Kilaas ◽  
L-H. Chan ◽  
T. Nolan ◽  
P. Dorsey ◽  
...  
Keyword(s):  
Thin Films ◽  
Electron Diffraction ◽  
Computer Processing ◽  
Information Storage ◽  
Engineering Properties ◽  
Digital Recording ◽  
Longitudinal Recording ◽  
Diffraction Patterns ◽  
User Friendly ◽  
Co Alloys

As engineering properties are miniaturized by mo thinner films, crystallographic analyses become more appropriate by electron diffraction than XRD. Without synchrotron sources, XRD scans of such films often expose one peak at best. However, these thinner films become more suited for TEM, with less artifacts from sample preparation. XRD scans with peaks in the noise are quantitatively accepted, while vast differences in electron diffraction patterns remain unquantified. Digital recording of TEM information removes the uncertain hand waving of the darkroom; and fast, user-friendly computer processing especially removes the nonstatistical art in image analysis. This work inputs 16-bit (>65,000 gray levels) images of ring diffraction patterns into Digital Micrograph and utilizes a Rotation Average subroutine (1) to plot peak intensities.Information storage in a hard drive utilizes sputtered thin films of HCP-Co-alloys with magnetic bits tied to the crystallographic orientation of each grain. Longitudinal-recording density and signal-to-noise can be enhanced for thin films with c-axes of all grains in plane.

Far infrared spectra of amorphous-Si:H thin films on polyethylene

1983 ◽  
Vol 61 (2) ◽  
pp. 305-308
Author(s):  
M. S. Mathur ◽  
H. C. Card ◽  
K. C. Kao ◽  
S. R. Mejia ◽  
G. C. Tabisz
Keyword(s):  
Thin Films ◽  
Microwave Plasma ◽  
Chemical Vapour ◽  
Far Infrared ◽  
Substrate Material ◽  
Absorption Bands ◽  
Silicon Thin Films ◽  
Infrared Measurements ◽  
Hydrogenated Amorphous

Hydrogenated amorphous-silicon thin films (a-Si:H) were deposited by microwave plasma chemical-vapour decomposition of SiH4, on thin polyethylene sheets. The high-resolution, far infrared measurements were performed on these films in the 700–50 cm−1 region on a Nicolet far infrared interferometer. The use of polyethylene as the substrate material permitted the determination of the absorption bands at 656.4, 652, 639.4, and 543 cm−1 with a shoulder at 539 cm−1 and a broad feature at 70.8 cm−1. These features provided evidence for SiH, SiH2 (as predicted by Lucovsky et al.), and SiH3 combinations in the film, as well as far more complex systems.

Amorphous and nc-Si:H Intrinsic Thin Films for Solar Cells Applications

2010 ◽  
Vol 657 ◽  
pp. 191-207
Author(s):  
Sylvain Halindintwali ◽  
Dirk Knoesen ◽  
Basil A. Julies ◽  
Theo Muller ◽  
Christopher J. Arendse
Keyword(s):  
Thin Films ◽  
Solar Cells ◽  
Thermal Activation ◽  
Chemical Vapour ◽  
Deposition Process ◽  
Silicon Thin Films ◽  
Chemical Vapour Deposition Technique ◽  
Structural And Electrical Properties ◽  
Uv Visible

This contribution discusses the deposition process and properties of intrinsic silicon thin films processed by the hot wire chemical vapour deposition technique. We review some fundamental characterization techniques that are used to probe into the quality of the material and thus decide its susceptibility to be used as the intrinsic layer in solar cells industry. This paper covers the optical, structural and electrical properties of the material. Results from UV-visible and IR spectroscopy, XRD and Raman scattering, X-section TEM as well as dark and photo-currents are given. It is shown that the thermal activation energy is a good measure of the quality of the sample.

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