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Topography acquisition. ZnSSe/GaAs laser structure.
Preparation steps for topography study of the heterostructure on the cleavages
a) A 50 mm scanner, an optical viewing system, and x-y translation stage may be necessary to have comfortable conditions of measurements.
b) The samples with freshly prepared cleavages may be griped in a miniature vice or fixed by a super glue on the vertical side of the small block. A double-side scotch can be used instead of glue, but when the linear sizes of the sample are less than 1 mm, the scotch is often not effective means for good fixation.
c) The cantilever beam should be parallel or perpendicular to the cleavage edges to facilitate the search of the edge in the scan area.
d) Before approach, the tip should be placed in the center of the scanning area, and approximately 15-20 mm away of the edge of the cleavage (for the reference, when using the optical viewing system, the width of the cantilever NSG11 is about 50 mm).
e) When the edge has been found, first we move the tip several microns away of the edge, then withdraw the tip from the sample (switch out a feedback loop), close a microscope by the protective cover, suspend the whole system, and finally switch on a feedback loop again.
No specific recommendations for the cantilever type can be given. Any new and good contact or resonant cantilever permits to get good topography data on usually atomically flat cleavages. The only demand is not to ruin the cantilever in search of the sample edge.
Specific parameters of the scan can be found in f1.opt and f1.mdt
AFM images are obtained by commercial SPM P4 with NSG11 cantilevers.
Additional information about laser structures were received with usage of Contact EFM, Kelvin mode.
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