| 1. |
- Cubillas, Pablo, et al.
(author)
-
Spiral Growth on Nanoporous Silicoaluminophosphate STA-7 as Observed by Atomic Force Microscopy
- 2009
-
In: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 9:9, s. 4041-4050
-
Journal article (peer-reviewed)abstract
- Atomic force microscopy was used to study the surface of STA-7 crystals. STA-7 is a silicoaluminophosphate, nanoporous solid formed by interlinked double six ring units (D6R). Observations showed the formation of three distinct types of spirals at tow supersaturation conditions. The {001} face shows spirals with isotropic shapes and a Burgers vector of 0.9 nm, which corresponds to one D6R or one unit cell along the < 001 > direction. The {100} face contains two distinct types of spirals. The first has a Burgers vector of 0.9 rim, or half a unit cell along < 100 >. This dislocation produces a change in the ""stacking"" sequence of the D6Rs generating all overgrowth with the AEI structure. The second type is an interlaced spiral and is generated by a dislocation with a Burgers vector of 1.8 nm or one unit cell, leading to the formation of two substeps each with a different growth anisotropy. This anisotropy is directed by the shape of the substep and the energetics of template attachment. The preponderance of a surface coating of a secondary phase will have significant consequences on applications reliant on intracrystalline diffusion, such as catalysis, where, owing to diffusion limitations, the outermost structure dominates the functional properties.
|
|
| 2. |
|
|
| 3. |
- Stevens, Sam M, et al.
(author)
-
Nanoscale Electron Beam Damage Studied by Atomic Force Microscopy
- 2009
-
In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:43, s. 18441-18443
-
Journal article (peer-reviewed)abstract
- High-resoln. SEM (HRSEM) has recently been added to the arsenal of characterization tools for material scientists to observe nanoscale surface features on both conducting and insulating materials. It is now therefore crucial to understand whether the intense electron beam will damage the features of interest. The authors were able, for the 1st time, to measure and quantify this damage using a combination of HRSEM and at. force microscopy (AFM), and as a consequence, the bulk of the damage, expressed as a depression on the crystal surface, is confined primarily to a subsurface vol. Simulations demonstrate that the depth of the depression is proportional to the interaction vol. of impact electrons below the crystal surface. More importantly, the nanometer surface features are conserved, and there is negligible assocd. loss of the crit. information in nanoscopic surface topog. These results confirm the usefulness of HRSEM as a tool for surface anal. not only for scientists studying crystal growth but also for materials scientists analyzing any surface at the nanoscale.
|
|
