scholarly journals Electron Microscopy Studies of Undoped and Phosphorus Doped Si:H and Si,C:H Films

1993 ◽  
Vol 297 ◽  
Author(s):  
Y.L. Chen ◽  
J. Bentley ◽  
C. Wang ◽  
G. Lucovsky ◽  
D.M. Maher
Keyword(s):  
Volume Fraction ◽  
Chemical Vapor ◽  
Dark Field ◽  
Degree Of Crystallinity ◽  
Phosphorus Doping ◽  
Two Phase ◽  
Dark Field Imaging ◽  
Electron Microscopes ◽  
Average Size ◽  
Phosphorus Doped

The microstructure of undoped and phosphorus doped Si:H and Si,C:H films was analyzed by selected-area diffraction, conical dark-field imaging, energy-dispersive x-ray spectroscopy and electron energy-loss spectroscopy in transmission electron microscopes. Thin films were synthesized by remote plasma-enhanced chemical vapor deposition and characterized in terms of degree of crystallinity. The distribution of phosphorus in the Si:H and Si,C:H films, and carbon in the Si,C:H films was evaluated. The results indicate that i) the microstructure of a film may be two phase, consisting of silicon microcrystallites in an amorphous matrix, ii) phosphorus doping as well as the presence of carbon influences the degree of crystallinity by reducing the average size and volume fraction of microcrystallites, iii) the presence of carbon and phosphorus doping completely suppresses the crystalline phase, iv) phosphorus is distributed at approximately the same concentration in both the crystalline and amorphous phases of diphasic films, and v) carbon is detected in the amorphous phase of the Si,C:H films.

Growth of hematite on (0001) and {1102} sapphire substrates

1990 ◽  
Vol 48 (4) ◽  
pp. 376-377
Author(s):  
Lisa A. Tietz ◽  
Scott R. Summerfelt ◽  
C. Barry Carter
Keyword(s):  
Imaging Techniques ◽  
Chemical Vapor ◽  
Interface Energy ◽  
Dark Field ◽  
Cation Sublattice ◽  
Sapphire Substrates ◽  
Dark Field Imaging ◽  
Weak Beam ◽  
Pressure Chemical ◽  
Interface Structures

Defects in thin films are often introduced at the substrate-film interface during the early stages of growth. The interface structures of semiconductor heterojunctions have been extensively studied because of the electrical activity of defects in these materials. Much less attention has been paid to the structure of oxide-oxide heterojunctions. In this study, the structures of the interfaces formed between hematite (α-Fe2O3) and two orientations of sapphire (α-Al2O3) are examined in relationship to the defects introduced into the hematite film. In such heterojunctions, the oxygen sublattice is expected to have a strong influence on the epitaxy; however, defects which involve only the cation sublattice may be introduced at the interface with little increase in interface energy.Oxide heterojunctions were produced by depositing small quantities of hematite directly onto electrontransparent sapphire substrates using low-pressure chemical vapor deposition. Prior to deposition, the ionthinned substrates were chemically cleaned and annealed at 1400°C to give “clean”, crystalline surfaces. Hematite was formed by the reaction of FeCl3 vapor with water vapor at 1150°C and 1-2 Torr. The growth of the hematite and the interface structures formed on (0001) and {102} substrates have been studied by bright-field, strong- and weak-beam dark-field imaging techniques.

scholarly journals Effects of Polydispersity on the Phase Behavior of Additive Hard Spheres in Solution

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1543
Author(s):  
Luka Sturtewagen ◽  
Erik van der Linden
Keyword(s):  
Phase Behavior ◽  
Critical Point ◽  
Volume Fraction ◽  
Hard Spheres ◽  
Second Virial Coefficient ◽  
Two Phase ◽  
Different Types ◽  
Asymmetric Partitioning ◽  
Average Size ◽  
Liquid Liquid Phase Separation

The ability to separate enzymes, nucleic acids, cells, and viruses is an important asset in life sciences. This can be realised by using their spontaneous asymmetric partitioning over two macromolecular aqueous phases in equilibrium with one another. Such phases can already form while mixing two different types of macromolecules in water. We investigate the effect of polydispersity of the macromolecules on the two-phase formation. We study theoretically the phase behavior of a model polydisperse system: an asymmetric binary mixture of hard spheres, of which the smaller component is monodisperse and the larger component is polydisperse. The interactions are modelled in terms of the second virial coefficient and are assumed to be additive hard sphere interactions. The polydisperse component is subdivided into sub-components and has an average size ten times the size of the monodisperse component. We calculate the theoretical liquid–liquid phase separation boundary (the binodal), the critical point, and the spinodal. We vary the distribution of the polydisperse component in terms of skewness, modality, polydispersity, and number of sub-components. We compare the phase behavior of the polydisperse mixtures with their concomittant monodisperse mixtures. We find that the largest species in the larger (polydisperse) component causes the largest shift in the position of the phase boundary, critical point, and spinodal compared to the binary monodisperse binary mixtures. The polydisperse component also shows fractionation. The smaller species of the polydisperse component favor the phase enriched in the smaller component. This phase also has a higher-volume fraction compared to the monodisperse mixture.

The ORNL Aberration-Corrected STEM/TEM Project

2001 ◽  
Vol 7 (S2) ◽  
pp. 906-907
Author(s):  
L. F. Allard ◽  
E. Voelkl ◽  
D. A. Blom ◽  
T. A. Nolan ◽  
F. Kahl ◽  
...  
Keyword(s):  
Spherical Aberration ◽  
National Laboratory ◽  
Dark Field ◽  
Electron Gun ◽  
Objective Lens ◽  
Resolution Limit ◽  
Oak Ridge ◽  
Transfer Characteristics ◽  
Dark Field Imaging ◽  
Electron Microscopes

Field emission electron microscopes operating at 200kV or 300kV and incorporating aberration correctors for either the incident electron probe or for the primary aberrations of the objective lens (OL) are currently under development for several laboratories in the world. OL-corrected instruments require monochromators for the electron beam, built into the electron gun prior to the accelerating stages, in order to optimize the contrast transfer characteristics of the objective lens to push the instrumental resolution limit to well beyond 0.1nm. This will allow the point resolution limit as controlled by the correction of spherical aberration Cs to potentially extend to the instrumental limit of better than 0.1nm. Figure 1 shows the contrast transfer characteristics of a Cs-corrected 200kV TEM, both without and with a beam monochromator.Dedicated STEM instruments such as the 300kV VG-603 and lOOkV VG-501 at Oak Ridge National Laboratory, and other VG instruments at Cornell University and IBM Co. are also being adapted (by Nion Co., Kirkland, WA) to incorporate aberration correctors for the incident probe. The aim is to improve the resolution of the VG-603 instrument in dark-field imaging mode, for example, from 0.13nm to 0.05nm. in another ORNL project, the High Temperature Materials Laboratory has contracted JEOL Ltd. to construct a STEM-TEM instrument with a probe corrector designed and built by CEOS GmbH (Heidelberg, Germany).

Phosphorus Doping of Boron Carbon Alloys

1996 ◽  
Vol 452 ◽  
Author(s):  
Seong-Don Hwang ◽  
P. A. Dowben ◽  
A. Cheeseman ◽  
J. T. Spencer ◽  
D. N. Mcilroy
Keyword(s):  
Chemical Vapor Deposition ◽  
Band Gap ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Single Source ◽  
Phosphorus Doping ◽  
Alloy Films ◽  
Phosphorus Doped ◽  
Boron Carbon

AbstractPhosphorus doped boron carbon alloy films were made by chemical vapor deposition from a single source compound, dimeric chloro-phospha(III) carburane ((C2B10H10)2(PCl)2). Phosphorus doped B5C materials exhibit increases in the band gap from 0.9 eV to 2.6 eV.

Experimental Investigation of Microstructure and Piezoresistive Properties of Phosphorus-Doped Hydrogenated Nanocrystalline Silicon Thin Films Prepared by PECVD

2014 ◽  
Vol 609-610 ◽  
pp. 208-217 ◽  
Author(s):  
Hai Bin Pan ◽  
Jian Ning Ding ◽  
Guang Gui Cheng ◽  
Bao Guo Cao
Keyword(s):  
Thin Films ◽  
Experimental Investigation ◽  
Evaluation System ◽  
Room Temperature ◽  
Chemical Vapor ◽  
Nanocrystalline Silicon ◽  
Two Phase ◽  
Good Thermal Stability ◽  
Silicon Thin Films ◽  
Phosphorus Doped

This paper presents an experimental investigation of microstructure and piezoresistive properties of phosphorus-doped hydrogenated nanocrystalline silicon (nc-Si:H) thin films. The phosphorus-doped nc-Si:H thin films (5% doping ratio of PH3 to SiH4) were deposited by plasma enhanced chemical vapor deposition (PECVD) technique. The microstructure and surface morphology of the deposited thin films was characterized and analyzed with Raman spectroscopy and atomic force microscopy (AFM), respectively. The piezoresistive properties of the deposited thin films were investigated with a designed four-point bending-based evaluation system. In addition, the influence of temperature on the piezoresistive properties of these thin films was evaluated with the temperature coefficient of resistance (TCR) measurements from room temperature up to 80°C. The experimental results show that phosphorus-doped nc-Si:H thin films prepared by PECVD technique are a two-phase material that constitutes of nanocrystalline silicon and amorphous silicon, and they present a granular structure composed of homogeneously scattered nanoclusters formed by nanocrystalline silicon grains (6nm). Moreover, phosphorus-doped nc-Si:H thin films exhibit negative GF at room temperature and show good thermal stability from room temperature up to 80°C, and the value of GF and TCR is about-31 and-509ppm/°C, respectively. These features could make phosphorus-doped nc-Si:H thin films act as a promising material for piezoresistive-based MEMS sensor.

Single-Crystal Structural Study of La2Cu0.95Li0.05O4.

1987 ◽  
Vol 99 ◽  
Author(s):  
J. M. Delgado ◽  
J. S. Speck ◽  
R. K. McMullan ◽  
G. Diaz de Delgado ◽  
B. J. Wuensch
Keyword(s):  
Single Crystal ◽  
Volume Fraction ◽  
Site Occupancy ◽  
Structure Type ◽  
Dark Field ◽  
Space Group ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Bulk Chemical ◽  
Vibration Parameters

ABSTRACTA large crystal of flux-grown La2CuO4, examined through single-crystal neutron diffraction, was found to have an orthorhombic superstructure derived from the K2NiF4 structure type with a=5.359(1), b=5.363(1), c=13.127(2) Å. The pattern of systematically absent intensities indicated space group Pccn but meaningful refinement of thermal vibration parameters could not be obtained in this symmetry. Systematic examination of all possible orthorhombic subgroups of Fmmm yielded satisfactory refinement to R(F2)=2.57% only in space group Bmab. Incorporation in the crystal of Li derived from the flux results in an orthorhombic distortion smaller than found for pure La2CuO4. Refinement of the Cu site occupancy provided Cu0.95Li0.050(3), in excellent accord with a bulk chemical analysis. Reflections which violate the systematic absences of Bmab are attributed to a smaller volume fraction of domains in orientation twinned by 90° rotation about c. This interpretation is supported by transmission electron microscopy which revealed intergrown lamellae. Dark field imaging with a forbidden reflection illuminated only the twin lamellae.

Polycrystalline β-SiC Film Growth on Si by ECR-CVD at 178 - 500°C

1995 ◽  
Vol 403 ◽  
Author(s):  
Kuan-Lun Cheng ◽  
Chih-Chien Liu ◽  
Chung-Min Fu ◽  
Huang-Chung Cheng ◽  
Chiapyng Lee ◽  
...  
Keyword(s):  
Electron Cyclotron Resonance ◽  
Film Growth ◽  
Film Surface ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Dark Field ◽  
Cross Sectional ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Field Imaging

AbstractPolycrystalline β-SiC, with grain size up to 0.2 μm, was grown on silicon substrate by electron cyclotron resonance chemical vapor deposition (ECR-CVD) from SiH4/CH4/H2 at 178–500 °C. The nucleation process and surface structure of polycrystalline SiC were investigated via observing the film surface by atomic force microscopy (AFM). Reaction species which promote polycrystalline SiC was in-situ monitored by quadruple mass spectrum analysers during deposition process, which is crucial for the control of polycrystalline SiC growth. The microstructure of SiC films were inspected by bright-field imaging, dark-field imaging, and electron diffraction in cross-sectional transmission electron microscopy. This paper will also discuss the key parameters for the nucleation and growth of polycrystalline β-SiC at very low temperature in ECR-CVD system.

A Study On High Coercivity And Lio Ordered Phase In Copt And Fept Thin Films

1999 ◽  
Vol 562 ◽  
Author(s):  
R. A. Ristau ◽  
K. Barmak ◽  
L. H. Lewis ◽  
K. R. Coffey ◽  
J. K. Howard
Keyword(s):  
Quantum Interference ◽  
Volume Fraction ◽  
Magnetic Domain ◽  
Dark Field ◽  
High Coercivity ◽  
Face Centered Cubic ◽  
Two Phase ◽  
Transmission Electron ◽  
Face Centered ◽  
The Relationship

ABSTRACTThis study relates the microstructure of equiatomic binary alloys of CoPt and FePt with their room-temperature hysteretic magnetic properties, particularly their high coercivity. A transformation from an atomically disordered, face-centered-cubic structure to the Li0 ordered structure occurred during post-deposition annealing and was characterized using digital analysis of dark-field transmission electron microscopy (TEM) images. The transformation was observed to follow first-order nucleation and growth kinetics, and the ordered volume fraction transformed was quantified at numerous points during the transformation. The ordered volume fraction was then compared to the magnetic coercivity data obtained from a superconducting quantum interference device (SQUID) magnetometer. Although the relationship most commonly described in the literature is that the highest coercivity corresponds to a two phase ordered/disordered mixture, the maximum value for coercivity in this study was found to correspond to the fully ordered state. Furthermore, in samples that were less than fully ordered, a direct relationship between ordered volume fraction and coercivity was observed. The proposed mechanism for the high coercivity in these films is an increasing density of magnetic domain wall pinning sites concurrent with an increasing fraction of ordered phase.

Computer Simulation of the Imaging of Atomic Defects in Metals

1977 ◽  
Vol 35 ◽  
pp. 14-16 ◽  
Author(s):  
P. M. Fields ◽  
J. M. Cowley
Keyword(s):  
Local Strain ◽  
Dark Field ◽  
Objective Lens ◽  
Heavy Atoms ◽  
Dark Field Imaging ◽  
Resolution Electron ◽  
Localized Defects ◽  
Computer Calculations ◽  
Electron Microscopes ◽  
Diffraction Patterns

Localized defects in metals, such as vacancies and interstitials, should have scattering powers for electrons comparable with those of the single heavy atoms which have been imaged in recent years by use of high resolution electron microscopes. It should therefore be possible to obtain appreciable contrast from such defects with current lOOkV electron microscopes. However in order to distinguish the intensity variations due to these defects from those due to specimen surface structure, contamination or other causes, it may be necessary to use the improved resolution of high voltage microscopes so that the characteristic shapes of the defects and their local strain fields can be recognized.In order to test these speculations, we have made computer calculations of the images and diffraction patterns to be expected from split interstitials in thin crystals of gold and aluminum for bright-field and dark-field imaging with a lOOkV microscope with an objective lens having Cs = 1.8mm and for a l000kV microscope, Cs = 1.8mm.

Inversion Domain Boundaries in Ain and GaN Thin Films

1998 ◽  
Vol 4 (S2) ◽  
pp. 636-637
Author(s):  
K. Dovidenko ◽  
S. Oktyabrsky ◽  
J. Narayan
Keyword(s):  
Thin Films ◽  
Imaging Techniques ◽  
Chemical Vapor ◽  
Dark Field ◽  
Organic Chemical ◽  
Extended Defects ◽  
Cross Sectional ◽  
Dark Field Imaging ◽  
Aln Film ◽  
Domain Boundaries

High-resolution transmission electron microscopy (HRTEM), multislice image simulation and multiple dark field TEM imaging techniques have been used to investigate the structure of extended defects in AlN and GaN thin films grown on (0001) α-Al2O3 by metal-organic chemical vapor deposition (MOCVD). AlN layers were grown directly on the (0001) sapphire. In the case of GaN thin films, 300-500 Å AlN buffer was deposited first.Cross-sectional TEM revealed the presence of domain boundaries in these Ill-nitride films. In this study we investigated these defects by multiple dark field imaging technique and proved some of them to be IDBs lying in planes. The multiple dark field images of several adjacent domains of AlN film are shown in Fig. 1 (a, b). The images were obtained exactly in [110] zone of AlN using (0002) and (000) reflections.

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