Scanning probe microscopy: C-AFM (Conductive Atomic Force Microscopy)

Service description

The service can perform analysis of conductive properties while acquiring topographic imaging. The mode of operation is contact, using a conductive tip and applying a potential difference between tip and sample. The equipment is capable of measuring the current flowing through the circuit. As a result, different conductive areas of the sample will be reflected in the corresponding current map. Therefore, the analysis will obtain images of topography, friction, current and resistance map simultaneously. To measure the current we use Resiscope V2, a device capable of measuring the current from pA to mA, as consisting of a logarithmic amplifier with a module for dynamic range of operation. The module applies a voltage of -10V to +10 Volts in the sample, while tip remains grounded. The module is able to limit the current flowing to avoid burning sample/tip. To limit the current, the device adds a known resistance in series to the sample. The equipment is capable of doing spectroscopy, reading different inputs, deflection, topography, current or resistance and as we change the loading force and voltage. You can perform a combination of these spectroscopies, to visualize the variation of various inputs simultaneously. Spectroscopies may be used in "cycles" so that studying hysteresis effects in the sample. Service has a wide range of conductivity tips available, from doped diamond, platinum coating to solid platinum tips. We can perform tests in low relative humidity, less than 3%, and nitrogen gas. The maximum achievable image size is 90 x 90 um2, with a maximum resolution of 8192 x 8192 points. The service can also perform "Photo Current Force Microscopy" mode in which an external accessory is used to illuminate the sample while its conductivity is measured. The illumination of the sample is performed by a 5 mm RGB LED that emits a light output 1.2 mW at the following wavelengths: Red - 625-630 nm, Green - 517-520 nm and Blue - 465-470 nm. For the realization of images in conductivity, we have the following equipment: Agilent 5500LS, scanner 90x90 um2 in X / Y and 15 microns in the Z axis equipped with accessory Resiscope V2. Closed Loop mode is included in the equipment which significantly improves the positioning in X and Y. The system has also a motorized stage, with ~3 micron accuracy, and ~15 cm range in X / Y and 3 cm in Z, so that samples can be as large as 25 x 25 cm2 and 3 cm thick. It is implemented a device for measuring humidity and temperature, and sample heater module. Equipment noise is about 0.05 nm. The system has a device for illuminating samples from the bottom, compatible with the conductivity mode.

Service description

Current sensing AFM allows detailed analysis of the conductivity of samples along with normal topography analysis from AFM. To do CSAFM, you need a specially coated cantilever and a modified scanner.