| 1. |
- Bovin, J O, et al.
(författare)
-
TEM-tomography of FAU-zeolite crystals containing Pt-clusters
- 1996
-
Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991. ; 62:4, s. 81-277
-
Tidskriftsartikel (refereegranskat)abstract
- A method for preparing ultrathin sections (- 20 nm) of inorganic solids has been developed using ultramicrotomy of resin-embedded crystal fragments. Undamaged crystals, oriented along a crystallographic direction, could be imaged with transmission electron microscopy (TEM) at a resolution better than 0.5 nm. The true internal structure of the crystals could be investigated by imaging the second in a series of at least three consecutive ultrathin sections. Such TEM-tomography proved that Pt-ion exchanged FAU zeolite crystals, after reduction and oxidation, are occupied internally and randomly of large platinum clusters mainly in the {111-twin planes. TEM-tomography could be useful in man made nanostructures like semiconductors, epitaxial thin films, hard metal coatings, ceramics, catalysts, and biomaterials.
|
|
| 2. |
|
|
| 3. |
- Henning, P, et al.
(författare)
-
Compositional information from amorphous Si-Ge multilayers using high-resolution electron microscopy imaging and direct digital recording
- 1996
-
Ingår i: Ultramicroscopy. - 0304-3991. ; 66:3-4, s. 221-235
-
Tidskriftsartikel (refereegranskat)abstract
- A simple method for extracting compositional information from high-resolution electron microscopy images of an amorphous two-element system using a slow-scan CCD camera has been developed. The method has been evaluated on amorphous Si/Ge multilayers. The characterisation of the multilayers provided information about thickness of the layers, maximum concentrations within the layers and elemental profiles across the boundaries. It was shown that the intensity profiles could be corrected for the wedge shape of the specimen and that the derived compositional profile was independent of average sample thickness variation within the range of the cross-section sample thickness.The results have been compared to analysis performed by Auger electron spectroscopy depth profiling on as-prepared multilayers as well as by energy-dispersive X-ray analysis and electron energy filtered images of cross-sections. The proposed HREM image contrast evaluation method gave spatial resolution in chemical analysis across the thin layers comparable in accuracy to the other methods, whereas the oscillation amplitude for the concentration is slightly less due to specimen preparation artifacts.
|
|
| 4. |
- Hertz, H.M, et al.
(författare)
-
Optically trapped non-linear particles as probes for scanning near-field optical microscopy
- 1995
-
Ingår i: Ultramicroscopy. - 0304-3991. ; 57:2-3, s. 309-312
-
Tidskriftsartikel (refereegranskat)abstract
- We use the frequency doubled light from an optically trapped lithium niobate particle for non-intrusive scanning near-field optical microscopy. The detected power from this 50-100 nm diameter probe is currently tens of pW and is expected to approach nW with an improved detection system. The current experimental resolution is approximately 0.5 [mu]m, while the ultimate theoretical resolution is 70-90 nm. An acoustic trap which potentially allows higher resolution imaging is briefly described.
|
|
| 5. |
- Wallenberg, LR, et al.
(författare)
-
Atomic-resolution study of structural rearrangements in small platinum crystals
- 1986
-
Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991. ; 20:1-2, s. 71-75
-
Tidskriftsartikel (refereegranskat)abstract
- Structural rearrangements in small Pt crystals, which were initiated by the incident electron beam, have been studied in real time with a 400 kV high-resolution electron microscope equipped with TV image viewing and videorecording facilities. The phenomena of crystal growth, particle coalescence and atomic clouds above particular surfaces were recorded at the atomic level and have been analysed using frame-by-frame playback facilities.
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Wallenberg, Reine, et al.
(författare)
-
Vanadium Oxide on TiO2(B) - a HREM Study of Catalysis by Support Interaction
- 1990
-
Ingår i: Ultramicroscopy. - 0304-3991. ; 34:1-2, s. 33-40
-
Tidskriftsartikel (refereegranskat)abstract
- A model catalyst system with a loading range between 1/4 to 10 theoretical layers of vanadium oxide on TiO2(B ) support was tried for selective ammoxidation and oxidation of toluene. In the case of ammoxidation, a peak in conversion rate per unit surface area was found for a catalyst with a coverage of about 2 theoretical layers, indicating a strong interaction between the catalyst and the otherwise inactive support. The presence and amount of vanadium oxide on the support surface was verified by diffuse reflectance infrared spectroscopy, energy-dispersive elemental X-ray mapping and chemical analysis. By high resolution electron microscopy, the 32~ volume loss of the K2Ti409 support precursor on calcination was shown to be achieved by formation of microscopic, facetted voids ("negative crystals") in the bulk of the material. Initially, surfaces appeared dean and without any anomalous surface features. This can be explained by similar scattering power of V and Ti, and similar structure types. However, the active phase could be "developed" to visibility by prolonged exposure to the electron beam, which produced 1-2 am particles of reduced vanadium oxides on the surface.
|
|
| 9. |
- Czigany, Zs., et al.
(författare)
-
Imaging of fullerene-like structures in CNx thin films by electron microscopy, Sample preparation artefacts due to ion-beam milling
- 2003
-
Ingår i: Ultramicroscopy. - 0304-3991 .- 1879-2723. ; 94:3-4, s. 163-173
-
Tidskriftsartikel (refereegranskat)abstract
- The microstructure of CNx thin films, deposited by reactive magnetron sputtering, was investigated by transmission electron microscopy (TEM) at 200kV in plan-view and cross-sectional samples. Imaging artefacts arise in high-resolution TEM due to overlap of nm-sized fullerene-like features for specimen thickness above 5nm. The thinnest and apparently artefact-free areas were obtained at the fracture edges of plan-view specimens floated-off from NaCl substrates. Cross-sectional samples were prepared by ion-beam milling at low energy to minimize sample preparation artefacts. The depth of the ion-bombardment-induced surface amorphization was determined by TEM cross sections of ion-milled fullerene-like CNx surfaces. The thickness of the damaged surface layer at 5° grazing incidence was 13 and 10nm at 3 and 0.8keV, respectively, which is approximately three times larger than that observed on Si prepared under the same conditions. The shallowest damage depth, observed for 0.25keV, was less than 1nm. Chemical changes due to N loss and graphitization were also observed by X-ray photoelectron spectroscopy. As a consequence of chemical effects, sputtering rates of CNx films were similar to that of Si, which enables relatively fast ion-milling procedure compared to carbon compounds. No electron beam damage of fullerene-like CNx was observed at 200kV. © 2002 Elsevier Science B.V. All rights reserved.
|
|
| 10. |
|
|
