Secondary electron imaging of titania thin film for surface potential analysis

The thickness and the local thickness variation of thin film specimens are critical parameters for many types of AEM analysis. The local thickness variation of the thin film specimen can be estimated from the surface roughness of the specimen. TEM specimens of most materials, especially multi-phase materials, have rough surfaces as observed by secondary electron imaging. However, there is little quantitative assessment of the surface roughness because of the difficulty of specimen thickness measurement. In this study, surface roughness of TEM specimens prepared using chemical etching, electropolishing, and ion beam thinning was measured using a direct phase detecting optical interferometer. This interferometer gives a quantitative three dimensional map of the surface topography with a depth resolution of ∼0.7 nm by converting digitized light intensity at each point of a 1024×1024 array into the optical path difference using the three-measurement algorithm. The horizontal resolution of the interferometer (∼340 nm) is limited by optical diffraction and is poor by the TEM standard. The quantitative information obtained by the interferometer is complimentary to the secondary electron imaging in STEM or PEG SEM for characterizing TEM specimen surfaces.

Download Full-text

Secondary electron imaging of YBa2Cu3O7-x high-Tc superconductors in Scanning Transmission Electron Microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100155396 ◽

1989 ◽

Vol 47 ◽

pp. 684-685

Author(s):

D. R. Liu ◽

D. B. Williams

Keyword(s):

Electron Microscope ◽

Secondary Electron ◽

Scanning Transmission Electron Microscope ◽

Superconducting Phase ◽

Contrast Imaging ◽

High Tc ◽

Bright Contrast ◽

Transmission Electron ◽

Scanning Transmission ◽

Electron Imaging

The secondary electron imaging technique in a scanning electron microscope (SEM) has been used first by Millman et al. in 1987 to distinguish between the superconducting phase and the non-superconducting phase of the YBa2Cu3O7-x superconductors. They observed that, if the sample was cooled down below the transition temperature Tc and imaged with secondary electrons, some regions in the image would show dark contrast whereas others show bright contrast. In general, the contrast variation of a SEM image is the variation of the secondary electron yield over a specimen, which in turn results from the change of topography and conductivity over the specimen. Nevertheless, Millman et al. were able to demonstrate with their experimental results that the dominant contrast mechanism should be the conductivity variation and that the regions of dark contrast were the superconducting phase whereas the regions of bright contrast were the non-superconducting phase, because the latter was a poor conductor and consequently, the charge building-up resulted in high secondary electron emission. This observation has since aroused much interest amoung the people in electron microscopy and high Tc superconductivity. The present paper is the preliminary report of our attempt to carry out the secondary electron imaging of this material in a scanning transmission electron microscope (STEM) rather than in a SEM. The advantage of performing secondary electron imaging in a TEM is obvious that, in a TEM, the spatial resolution is higher and many more complementary techniques, e.g, diffraction contrast imaging, phase contrast imaging, electron diffraction and various microanalysis techniques, are available.

Download Full-text

Studies of Ge/Si(100) and Observation of Atomic Steps on Si(100) using Biassed Secondary Electron Imaging in a UHV STEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010018029x ◽

1990 ◽

Vol 48 (1) ◽

pp. 308-309

Author(s):

Mohan Krishnamurthy ◽

Jeff S. Drucker ◽

John A. Venablest

Keyword(s):

Secondary Electron ◽

Critical Thickness ◽

Surface Defects ◽

Film Growth ◽

Growth Parameters ◽

High Vacuum ◽

Ultra High Vacuum ◽

Surface Steps ◽

Epitaxial Crystal Growth ◽

Electron Imaging

Secondary Electron Imaging (SEI) has become a useful mode of studying surfaces in SEM[1] and STEM[2,3] instruments. Samples have been biassed (b-SEI) to provide increased sensitivity to topographic and thin film deposits in ultra high vacuum (UHV)-SEM[1,4]; but this has not generally been done in previous STEM studies. The recently developed UHV-STEM ( codenamed MIDAS) at ASU has efficient collection of secondary electrons using a 'parallelizer' and full sample preparation system[5]. Here we report in-situ deposition and annealing studies on the Ge/Si(100) epitaxial system, and the observation of surface steps on vicinal Si(100) using b-SEI under UHV conditions in MIDAS.Epitaxial crystal growth has previously been studied using SEM and SAM based experiments [4]. The influence of surface defects such as steps on epitaxial growth requires study with high spatial resolution, which we report for the Ge/Si(100) system. Ge grows on Si(100) in the Stranski-Krastonov growth mode wherein it forms pseudomorphic layers for the first 3-4 ML (critical thickness) and beyond which it clusters into islands[6]. In the present experiment, Ge was deposited onto clean Si(100) substrates misoriented 1° and 5° toward <110>. This was done using a mini MBE Knudsen cell at base pressure ~ 5×10-11 mbar and at typical rates of 0.1ML/min (1ML =0.14nm). Depositions just above the critical thickness were done for substrates kept at room temperature, 375°C and 525°C. The R T deposits were annealed at 375°C and 525°C for various times. Detailed studies were done of the initial stages of clustering into very fine (∼1nm) Ge islands and their subsequent coarsening and facetting with longer anneals. From the particle size distributions as a function of time and temperature, useful film growth parameters have been obtained. Fig. 1 shows a b-SE image of Ge island size distribution for a R T deposit and anneal at 525°C. Fig.2(a) shows the distribution for a deposition at 375°C and Fig.2(b) shows at a higher magnification a large facetted island of Ge. Fig.3 shows a distribution of very fine islands from a 525°C deposition. A strong contrast is obtained from these islands which are at most a few ML thick and mottled structure can be seen in the background between the islands, especially in Fig.2(a) and Fig.3.

Download Full-text

Impact of chosen force fields and applied load on thin film lubrication

Friction ◽

10.1007/s40544-020-0464-2 ◽

2021 ◽

Author(s):

Thi D. Ta ◽

Hien D. Ta ◽

Kiet A. Tieu ◽

Bach H. Tran

Keyword(s):

Thin Film ◽

Shear Stress ◽

Surface Structure ◽

Rheological Properties ◽

Surface Potential ◽

Applied Load ◽

Velocity Slip ◽

Thin Film Lubrication ◽

Lubrication Performance ◽

Film Lubrication

AbstractThe rapid development of molecular dynamics (MD) simulations, as well as classical and reactive atomic potentials, has enabled tribologists to gain new insights into lubrication performance at the fundamental level. However, the impact of adopted potentials on the rheological properties and tribological performance of hydrocarbons has not been researched adequately. This extensive study analyzed the effects of surface structure, applied load, and force field (FF) on the thin film lubrication of hexadecane. The lubricant film became more solid-like as the applied load increased. In particular, with increasing applied load, there was an increase in the velocity slip, shear viscosity, and friction. The degree of ordering structure also changed with the applied load but rather insignificantly. It was also significantly dependent on the surface structure. The chosen FFs significantly influenced the lubrication performance, rheological properties, and molecular structure. The adaptive intermolecular reactive empirical bond order (AIREBO) potential resulted in more significant liquid-like behaviors, and the smallest velocity slip, degree of ordering structure, and shear stress were compared using the optimized potential for liquid simulations of united atoms (OPLS-UAs), condensed-phase optimized molecular potential for atomic simulation studies (COMPASS), and ReaxFF. Generally, classical potentials, such as OPLS-UA and COMPASS, exhibit more solid-like behavior than reactive potentials do. Furthermore, owing to the solid-like behavior, the lubricant temperatures obtained from OPLS-UA and COMPASS were much lower than those obtained from AIREBO and ReaxFF. The increase in shear stress, as well as the decrease in velocity slip with an increase in the surface potential parameter ζ, remained conserved for all chosen FFs, thus indicating that the proposed surface potential parameter ζ for the COMPASS FF can be verified for a wide range of atomic models.

Download Full-text

Synthesis of a mesoporous titania thin film with a pseudo-single-crystal framework by liquid-phase epitaxial growth, and enhancement of photocatalytic activity

RSC Advances ◽

10.1039/d0ra08019e ◽

2020 ◽

Vol 10 (67) ◽

pp. 40658-40662

Author(s):

Norihiro Suzuki ◽

Chiaki Terashima ◽

Kazuya Nakata ◽

Ken-ichi Katsumata ◽

Akira Fujishima

Keyword(s):

Thin Film ◽

Photocatalytic Activity ◽

Liquid Phase ◽

Single Crystal ◽

Chemical Process ◽

Anatase Phase ◽

Mesoporous Titania ◽

Titania Thin Film ◽

Liquid Phase Epitaxial Growth ◽

Pseudo Single Crystal

An anatase-phase mesoporous titania thin film with a pseudo-single-crystal framework was facilely synthesized by an inexpensive chemical process.

Download Full-text

Studies of Supported Metal Catalysts Using Low Voltage Biased Secondary Electron Imaging in a JSM-6320f Fe-SEM

Microscopy and Microanalysis ◽

10.1017/s1431927600013003 ◽

1997 ◽

Vol 3 (S2) ◽

pp. 1223-1224

Author(s):

J. Liu ◽

R. L. Ornberg ◽

J. R. Ebner

Keyword(s):

Secondary Electron ◽

Low Voltage ◽

Supported Catalysts ◽

High Surface ◽

High Surface Area ◽

Incident Beam ◽

Active Species ◽

Supported Metal Catalysts ◽

Active Components ◽

Electron Imaging

Many industrial catalysts have a complex geometric structure to enable reacting gases or fluids to reach as much of the active surface of the catalyst as possible. The catalyzing surface frequently consists of a complex chemical mixture of different phases produced by an evolved chemical process. The active components are often very small particles dispersed on high-surface-area supports. The catalytic properties of this type of catalyst depend on the structure, composition, and morphology of the active species as well as the supports. TEM/STEM and associated techniques have been used extensively to characterize the structure and composition of supported catalysts. Surface morphology of supported catalysts is generally examined by secondary electron imaging, especially at low incident beam energies. It is, however, frequently found that small metal particles are not usually seen in SE images because of the complication of support topography

Download Full-text

“Wien–type” Filtered Secondary Electron Imaging of Immunocytochemically Labeled Methacrylate Sections of Tissues in a Field Emission Scanning Electron Microscope (FESEM)

Microscopy and Microanalysis ◽

10.1017/s1431927605501338 ◽

2005 ◽

Vol 11 (S02) ◽

Cited By ~ 1

Author(s):

C A Ackerley ◽

A Tilups ◽

C Nielsen

Keyword(s):

Electron Microscope ◽

Scanning Electron Microscope ◽

Field Emission ◽

Secondary Electron ◽

Electron Imaging ◽

Scanning Electron

Download Full-text

Numerical studies of surface potential, mobility and Seebeck coefficient of organic thin film transistor based on 2,3 benzanthracene: Light effect

Synthetic Metals ◽

10.1016/j.synthmet.2017.10.006 ◽

2017 ◽

Vol 233 ◽

pp. 119-126 ◽

Cited By ~ 3

Author(s):

A. Jouili ◽

S. Mansouri ◽

Abdullah G. Al-Sehemi ◽

Ahmed A. Al-Ghamdi ◽

L. El Mir ◽

...

Keyword(s):

Thin Film ◽

Seebeck Coefficient ◽

Surface Potential ◽

Thin Film Transistor ◽

Organic Thin Film ◽

Organic Thin Film Transistor ◽

Light Effect ◽

Numerical Studies ◽

Potential Mobility

Download Full-text

Some Comparisons of Ag Deposits on Ge and Si(111)

MRS Proceedings ◽

10.1557/proc-280-55 ◽

1992 ◽

Vol 280 ◽

Cited By ~ 3

Author(s):

F. L. Metcalfe ◽

J. A. Venables

Keyword(s):

Crystal Growth ◽

Surface Diffusion ◽

Secondary Electron ◽

Diffusion Length ◽

Effective Diffusion ◽

Rate Equations ◽

Kinetic Rate ◽

Annealing Conditions ◽

Electron Imaging

ABSTRACTCrystal growth and surface diffusion have been studied in the Ag/Ge(lll) system using UHV-SEM based techniques, biassed secondary electron imaging (b-SEI), micro-AES and RHEED. Ag was deposited through and past a mask of holes held close to the substrate at 300<Td< 775K. Under certain conditions, the Ag patches were observed to split into two regions corresponding to the √3×√3R30° (hereafter √3) and a lower coverage 4×4 structure, each of which were easily observable using b-SEI. These patch widths were measured as a function of Td, and of annealing times at temperatures Ta, and effective diffusion coefficents extracted. The diffusion length of adatoms over the 4×4 structure is larger than that over the √3 structure. These observations are modelled using kinetic rate equations, and the results are compared with previous studies of Ag/Si(111). We find that energies characterising processes on top of the √3 layers of both systems are very similar, but that processes involved in the formation of the layers are quite different. The coverage of the √3 Ag/Ge(111) layer is close to 1 ML for all Td studied, unlike √3 Ag/Si(111). where it depends on deposition and annealing conditions.

Download Full-text