RHEED Pole Figure Measurements of Biaxial Thin Film Growth Front Evolution

2011 ◽  
Vol 1308 ◽  
Author(s):  
Gwo-Ching Wang ◽  
Yu Liu ◽  
Churamani Gaire ◽  
Wen Yuan ◽  
Toh-Ming Lu
Keyword(s):  
Pole Figure ◽  
Film Growth ◽  
Texture Evolution ◽  
Growth Front ◽  
High Energy ◽  
Film Deposition ◽  
Oblique Angle Deposition ◽  
X Rays ◽  
Biaxial Texture ◽  
Figure Technique

ABSTRACTThe most frequently used characterization technique for biaxial texture formation in thin films is x-ray pole figure analysis. However, x-rays interact weakly with matter and can penetrate a few microns deep into the film. The texture obtained by x-rays is therefore an average texture from the entire thickness of the film. As the texture of a film often changes during growth, information on the basic mechanisms that control the final texture is often lost. In contrast electrons interact strongly with matter and they have very limited penetration and escape depths of a few nm. In this paper we will show how we can use our newly developed reflection high energy electron diffraction (RHEED) surface pole figure technique to probe the surface texture evolution of the growth front from the initial stage (nm thick) to the later stage. The RHEED pole figure technique is a surface-sensitive technique that allows us to obtain information on the dynamic behavior of texture evolution of the growth front during film deposition. We shall explain the principle, measurement, and construction of such RHEED surface pole figures. An example of the biaxial texture evolution of CaF2 due to the atomic shadowing effect during oblique angle deposition is described.

Reflection High-energy Electron Diffraction Study of Nanostructures: From Diffraction Patterns to Surface Pole Figure

2009 ◽  
Vol 1184 ◽  
Author(s):  
Fu Tang ◽  
Toh-Ming Lu ◽  
Gwo Ching Wang
Keyword(s):  
Pole Figure ◽  
Electron Diffraction Study ◽  
High Energy ◽  
Oblique Angle Deposition ◽  
High Energy Electron ◽  
Oblique Angle ◽  
Biaxial Texture ◽  
Out Of Plane ◽  
Diffraction Patterns ◽  
Angle Deposition

AbstractIn this report we present a brief overview of the growth of nanostructures by the oblique angle deposition where the nanostructures possess both out-of-plane and in-plane preferred orientations or a biaxial texture. The degree of preferred crystal orientations can be quantitatively determined from a method called “RHEED surface pole figure analysis” that we developed recently.

Spectroscopic and Ion Probe Characterization of the Transport Process Following Laser Ablation of Yba2Cu3Ox

1990 ◽  
Vol 191 ◽  
Author(s):  
David B. Geohegan ◽  
Douglas N. Mashburn
Keyword(s):  
Laser Ablation ◽  
Ground State ◽  
Film Growth ◽  
Laser Energy ◽  
High Energy ◽  
Film Deposition ◽  
Oxygen Absorption ◽  
Total Charge ◽  
Laser Plume ◽  
Ion Probe

ABSTRACTSpatial and temporal measurements of the optical absorption, optical emission and ion probe response in the ablation plume formed following pulsed 248 nm irradiation of Y1Ba2Cu3Ox are reported over laser energy densities from near threshold into the film growth regime. Time of flight absorbance-velocity profiles in vacuum indicate the formation and acceleration of a plasma front, with ions leading neutrals on the edge of the expanding plume. Ion probe screening measurements show that the laser plume is a well-shielded plasma with Debye lengths <10 μm at film deposition distances. Velocity distributions and estimates of ground state Ba+, Ba, Y+, and Y densities indicate that the populations of the ions outnumber those of the neutrals at high energy densities in vacuum. Measurements of the slowing of the plasma front and attenuation of the total charge reaching the substrate are reported for laser ablation in background pressures of oxygen. Absorption by ground state YO and BaO in the region close to the pellet indicates oxide densities ˜5 × 1013 cm−3 close to the pellet.

Quasi-single Crystal Semiconductors on Glass Substrates Through Biaxially Oriented Buffer Layers

2010 ◽  
Vol 1268 ◽  
Author(s):  
Toh-Ming Lu ◽  
Huafang Li ◽  
Churamani Gaire ◽  
Nicholas LiCausi ◽  
Tzu Liang Chan ◽  
...  
Keyword(s):  
Single Crystal ◽  
Pole Figure ◽  
High Efficiency ◽  
High Energy ◽  
Buffer Layers ◽  
Oblique Angle Deposition ◽  
Semiconductor Films ◽  
Single Crystalline ◽  
Glass Substrates ◽  
Volume Production

AbstractHigh efficiency photovoltaic devices are normally fabricated on single crystalline substrates. These single crystalline substrates are expensive and volume production for widespread usage has not been realistic. To date, large volume production of solar cells is on less expensive non-crystalline substrates such as glass. Typically the films grown on glass are polycrystalline with less than ideal efficiency. It was proposed that a dramatic gain in the efficiency may be achieved if one uses a biaxially oriented buffer layer on glass to grow biaxial semiconductor films to fabricate solar devices compared to that of films grown directly on glass. Biaxial films are not exactly single crystal but have strongly preferred crystallographic orientations in both the out-of-plane and in-plane directions. Typically the misorientation between grains can be small (within a few degrees) and may possess low carrier recombination rate. In this paper we shall discuss growth techniques that would allow one to produce biaxial buffer layers on glass. A specific strategy using an atomic shadowing mechanism in an oblique angle deposition configuration that allows one to grow biaxial buffer layers such as CaF2on glass substrate will be discussed in detail. Results of heteroepitaxy of semiconductor materials such as CdTe and Ge on these biaxial buffer/glass substrates characterized by x-ray pole figure, reflection high energy electron diffraction (RHEED) pole figure and transmission electron microscopy (TEM) will be presented.

Texture evolution of vertically aligned biaxial tungsten nanorods using RHEED surface pole figure technique

2010 ◽  
Vol 21 (32) ◽  
pp. 325704 ◽  
Author(s):  
R Krishnan ◽  
Y Liu ◽  
C Gaire ◽  
L Chen ◽  
G-C Wang ◽  
...  
Keyword(s):  
Pole Figure ◽  
Texture Evolution ◽  
Vertically Aligned ◽  
Figure Technique

Hydrogenated Amorphous Silicon Thin-Film Deposition by Direct Photo-Enhanced Decomposition of Silane Using an Internal Hydrogen Discharge Lamp.

1986 ◽  
Vol 70 ◽  
Author(s):  
P. A. Robertson ◽  
W. I. Milne
Keyword(s):  
Thin Film ◽  
Amorphous Silicon ◽  
Film Growth ◽  
Hydrogenated Amorphous Silicon ◽  
Thin Film Deposition ◽  
High Energy ◽  
Film Deposition ◽  
Discharge Lamp ◽  
Hydrogen Discharge ◽  
Hydrogenated Amorphous

ABSTRACTHydrogenated amorphous silicon (a-Si:H) thin films have been deposited from silane using a novel photo-enhanced decomposition technique. The system comprises a hydrogen discharge lamp contained within the reaction vessel; this unified approach allows high energy photon excitation of the silane molecules without absorption by window materials or the need for mercury sensitisation. The film growth rates (exceeding 4 Å/s) and material properties obtained are comparable to those of films produced by plasma-enhanced CVD techniques. The reduction of energetic charged particles in the film growth region should enable the fabrication of cleaner semiconductor/insulator interfaces in thin-film transistors.

The Basic Physical Principles of Ion, Electron, and X-Ray Detectors and Their Application to Microanalysis

1985 ◽  
Vol 43 ◽  
pp. 154-157
Author(s):  
A.J. Tousimis
Keyword(s):  
Ion Beam ◽  
Depth Resolution ◽  
Sample Surface ◽  
High Energy ◽  
X Rays ◽  
X Ray ◽  
Electrons And Ions ◽  
Spatial Depth ◽  
Minimum Surface Area ◽  
Physical Principles

An integral and of prime importance of any microtopography and microanalysis instrument system is its electron, x-ray and ion detector(s). The resolution and sensitivity of the electron microscope (TEM, SEM, STEM) and microanalyzers (SIMS and electron probe x-ray microanalyzers) are closely related to those of the sensing and recording devices incorporated with them.Table I lists characteristic sensitivities, minimum surface area and depth analyzed by various methods. Smaller ion, electron and x-ray beam diameters than those listed, are possible with currently available electromagnetic or electrostatic columns. Therefore, improvements in sensitivity and spatial/depth resolution of microanalysis will follow that of the detectors. In most of these methods, the sample surface is subjected to a stationary, line or raster scanning photon, electron or ion beam. The resultant radiation: photons (low energy) or high energy (x-rays), electrons and ions are detected and analyzed.

Modifications of a JEOL 2000EX TEM for insSitu surface studies

1993 ◽  
Vol 51 ◽  
pp. 640-641
Author(s):  
Michael T. Marshall ◽  
Xianghong Tong ◽  
J. Murray Gibson
Keyword(s):  
Electron Diffraction ◽  
Surface Science ◽  
Film Growth ◽  
High Vacuum ◽  
High Energy ◽  
Energy Electron ◽  
Ultra High Vacuum ◽  
Transmission Electron ◽  
Fundamental Insight

We have modified a JEOL 2000EX Transmission Electron Microscope (TEM) to allow in-situ ultra-high vacuum (UHV) surface science experiments as well as transmission electron diffraction and imaging. Our goal is to support research in the areas of in-situ film growth, oxidation, and etching on semiconducter surfaces and, hence, gain fundamental insight of the structural components involved with these processes. The large volume chamber needed for such experiments limits the resolution to about 30 Å, primarily due to electron optics. Figure 1 shows the standard JEOL 2000EX TEM. The UHV chamber in figure 2 replaces the specimen area of the TEM, as shown in figure 3. The chamber is outfitted with Low Energy Electron Diffraction (LEED), Auger Electron Spectroscopy (AES), Residual Gas Analyzer (RGA), gas dosing, and evaporation sources. Reflection Electron Microscopy (REM) is also possible. This instrument is referred to as SHEBA (Surface High-energy Electron Beam Apparatus).The UHV chamber measures 800 mm in diameter and 400 mm in height. JEOL provided adapter flanges for the column.

“Cartography” in 7-Dimensions at CHESS: Mapping of Structure in Real Space, Reciprocal Space, and Time Using High-Energy X-rays

2020 ◽  
Vol 33 (6) ◽  
pp. 11-16
Author(s):  
K. E. Nygren, ◽  
D. C. Pagan, ◽  
J. P. C. Ruff ◽  
E. Arenholz ◽  
J. D. Brock
Keyword(s):  
High Energy ◽  
Real Space ◽  
Reciprocal Space ◽  
X Rays ◽  
Space And Time

scholarly journals The interstellar medium in young supernova remnants: key to the production of cosmic X-rays and $\gamma $-rays

2021 ◽  
Vol 366 (6) ◽  
Author(s):  
Hidetoshi Sano ◽  
Yasuo Fukui
Keyword(s):  
Interstellar Medium ◽  
Supernova Remnants ◽  
Cosmic Ray ◽  
High Energy ◽  
X Rays ◽  
Interstellar Gas ◽  
High Energy Radiation ◽  
Dense Cores ◽  
The Relationship ◽  
Turbulent Velocity Field

AbstractWe review recent progress in elucidating the relationship between high-energy radiation and the interstellar medium (ISM) in young supernova remnants (SNRs) with ages of ∼2000 yr, focusing in particular on RX J1713.7−3946 and RCW 86. Both SNRs emit strong nonthermal X-rays and TeV $\gamma $ γ -rays, and they contain clumpy distributions of interstellar gas that includes both atomic and molecular hydrogen. We find that shock–cloud interactions provide a viable explanation for the spatial correlation between the X-rays and ISM. In these interactions, the supernova shocks hit the typically pc-scale dense cores, generating a highly turbulent velocity field that amplifies the magnetic field up to 0.1–1 mG. This amplification leads to enhanced nonthermal synchrotron emission around the clumps, whereas the cosmic-ray electrons do not penetrate the clumps. Accordingly, the nonthermal X-rays exhibit a spatial distribution similar to that of the ISM on the pc scale, while they are anticorrelated at sub-pc scales. These results predict that hadronic $\gamma $ γ -rays can be emitted from the dense cores, resulting in a spatial correspondence between the $\gamma $ γ -rays and the ISM. The current pc-scale resolution of $\gamma $ γ -ray observations is too low to resolve this correspondence. Future $\gamma $ γ -ray observations with the Cherenkov Telescope Array will be able to resolve the sub-pc-scale $\gamma $ γ -ray distribution and provide clues to the origin of these cosmic $\gamma $ γ -rays.

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