- What is difference between Conductive atomic force microscopy (CAFM) i-v measurement and Scanning tunneling spectroscopy (STS) i-v measurement mechanism ?
In STM the tip is kept at a distance of usually several Angstrøm above the surface. The feedback system uses tunneling current to correct for height and material properties. In STM material properties are dominated by the local density of states (LDOS). Measuring dI/dV curves, you are probing the LDOS.
In AFM you are at direct contact to the surface or in intermittent contact to the surface (such as in PeakForce Tuna). Here dI/dV diagrams are measured in direct material contact and therefore you gain information about the resistance between your coated cantilever and conductive surface (and by imaging also about the lateral resistivity of your sample). Measuring the LDOS using C-AFM ist quite a challenge and can be achieved for example by placing a non-conductive molecule in between the tip and surface avoiding direct contact with the surface. Such an experiment was performed in the reference below.
Article Exploring the Electronic and Mechanical Properties of Protei...
The major difference between STM and CAFM is feedback system. CAFM has force beek back system which gives you better control on tip-sample interaction. This method is suitable to characterize the materials with low conductivity, where as STM feedback relies on the magnitude of current measured by the tip, so it is more suitable for the materials with high conductivity. I-V curves measured with both the methods give more or less the same information about the material.
In STM the tip is kept at a distance of usually several Angstrøm above the surface. The feedback system uses tunneling current to correct for height and material properties. In STM material properties are dominated by the local density of states (LDOS). Measuring dI/dV curves, you are probing the LDOS.
In AFM you are at direct contact to the surface or in intermittent contact to the surface (such as in PeakForce Tuna). Here dI/dV diagrams are measured in direct material contact and therefore you gain information about the resistance between your coated cantilever and conductive surface (and by imaging also about the lateral resistivity of your sample). Measuring the LDOS using C-AFM ist quite a challenge and can be achieved for example by placing a non-conductive molecule in between the tip and surface avoiding direct contact with the surface. Such an experiment was performed in the reference below.
Article Exploring the Electronic and Mechanical Properties of Protei...
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