Atomic Resolution on MgO (100) at T=5K using qPlus Non-Contact AFM mode
(Result of the month 12/2007)

MgO is a commonly available substrate for epitaxial thin film deposition. The MgO(100) surface also plays an important role as substrate for deposition of metal nano clusters. The morphologic analysis of such clusters helps understanding catalytic processes.


Such clustered nanostructures have to be investigated using (NC-)AFM due to their insulating nature. However, the in-situ cleaving process typically creates large surface charges which render it nearly impossible to image the surface without further thermal treatment. Compensation voltages for the surface potential can climb up to 30V for a freshly cleaved MgO sample. The typically small amplitude of the qPlus sensor combined with its stiffness helps, if used as an NC-AFM probe, to be much more sensitive to the short-ranged forces which exclusively create the topographical contrast. The topographical images 1 and 2 have been taken during a customer demonstration at low temperature (T=5K) with an Omicron LT STM/AFM equipped with a qPlus sensor. For the present experiment the freshly cleaved MgO sample was not thermally treated and immediatlely cooled to liquid Helium temperature. Almost immmediately after cooling down atomic resolution could be achieved.

Such clustered nanostructures have to be investigated using (NC-)AFM due to their insulating nature. However, the in-situ cleaving process typically creates large surface charges which render it nearly impossible to image the surface without further thermal treatment. Compensation voltages for the surface potential can climb up to 30V for a freshly cleaved MgO sample. The typically small amplitude of the qPlus sensor combined with its stiffness helps, if used as an NC-AFM probe, to be much more sensitive to the short-ranged forces which exclusively create the topographical contrast. The topographical images 1 and 2 have been taken during a customer demonstration at low temperature (T=5K) with an Omicron LT STM/AFM equipped with a qPlus sensor. For the present experiment the freshly cleaved MgO sample was not thermally treated and immediatlely cooled to liquid Helium temperature. Almost immmediately after cooling down atomic resolution could be achieved.
Atomic resolution AFM on MgO(100) using QPlus force detection at T=5 K. Measurements in were taken at constant frequency shift. Typical corrugation less than 10 pm. The change of contrast is due to tip changes. The row-wise appearance of the atoms in some parts of the images is due to an asymmetric tip shape.


Data Courtesy of: C. Barth, CRMCN-CNRS, 13288 Marseille Cedex 09, France
Measurements performed by: C. Barth, Marseille and Omicron Nanotechnology GmbH

 
This result has been obtained with :
LT STM
MATRIX SPM Control System

download as pdf

 
 
RoM Archive