Kelvin force microscopy

Wang, S.J., Cheng, G., Jiang, X.H., Li, Y.C., Huang, Y.B., and Du, Z.L. (2006) Direct observation of photoinduced charge redistribution of WCfi—Ti02 double layer nanocomposite films by photoassisted Kelvin force microscopy. Applied Physics Letters, 88 (21), 212108. 

Kelvin Force Microscopy (KFM) is closely related to EFM in that it can also provide surface potential maps, but in the form of work-function variations. This is derived by measuring the Contact Potential Difference (CPD) between the surface and the tip. This can be done to a spatial resolution of a couple of nanometers. 

Fujihira, M. 1999. Kelvin probe force microscopy of molecular surfaces. Ann. Rev. Mater. Sci. 29 353-380. 

Piezoresponse force microscopy (pfm) [11] and Kelvin probe force microscopy (kpfm) [9] were applied to deduce the polarization and local electric potential distribution over the whole cross section of the pzt sample (see Figure 12.3 and Figure 12.4) under static conditions as well as after switching. The details of our setup are described elsewhere [9,11],... 

The variation of the work function in the vertical direction of multilayers was investigated by Kelvin probe force microscopy (KPFM) on a fracture cross-section of a film deposited on a silicon substrate, shown in Fig. 2.18. This method is described in detail in [184]. A variation of the work function of about 60-100 meV is clearly seen from the bright-dark contrast as well... 

Fig. 2.18. Kelvin probe force microscopy (KPFM) picture of the cross-section of a modulation doped Zni- Mg CtAl/ZnO film on a silicon substrate. The contact potential is given relative to pyrolytic graphite ( = 4.07 eV). The local variation of the contact potential is shown on the left side, while the chemical composition, determined by SIMS is displayed on the right side. Deposition parameters p = 0.2Pa, P = 75Wrf, Tsub = 300°C, single layer thickness dZno = dZni xMgxO Ai = 160 nm...

The detection and compensation of the a.c. current is the classical Kelvin method however, the resulting electrostatic forces, i.e. the corresponding cantilever bending, can also be used to establish a potential sensitive feedback. If an a.c. voltage is applied between the tip and the back electrode of the sample instead of using the dither piezo, the Maxwell stress microscopy (MSM) [379-381] or the electrostatic force microscopy (EFM) [317, 382-393] can be performed. 

Many-pass techniques Electric Force Microscopy (EFM) Scanning Capacitance Microscopy (SCaM) Kelvin Probe Microscopy (SKM) DC Magnetic Force Microscopy (DC MFM) AC Magnetic Force Microscopy (AC MFM) Dissipation Force Microscopy-Scanning Surface Potential Microscopy (SSPM) Scanning Maxwell Stress Microscpy (SMMM) Magnetic Force Microscopy (MFM) Van der Waals Force Microscopy (VDWFM)... 

As could already be inferred from the cross-sectional SEM images, the fullerene clusters are in fact surroimded by a polymer-rich skin layer [55,60]. Using Kelvin probe force microscopy Hoppe et al. were able to confirm this by the detection of a considerably increased work function on top of the polymer... 

Hoppe H, Glatzel T, Niggemann M, Hinsch A, Lux-Steiner MC, Sariciftci NS (2005) Kelvin probe force microscopy study on conjugated polymer/fullerene bulk heterojunction organic solar cells. Nano Lett 5 269... 

A further spatially resolved method, also based on work function contrast, is scanning Kelvin probe microscopy (SKPM). As an extended version of atomic force microscopy (AFM), additional information on the local surface potential is revealed by a second feedback circuit. The method delivers information depending on the value (p (p(x) + A x). Here, A(zS(x) is the difference in work function between the sample and the AFM tip and cp(x) is the local electric potential [12]. (p x) itself gives information on additional surface charges due to... 

For all nc-AFM measurements, a Kelvin probe force microscopy (KPFM) feedback controller was additionally activated for simultaneous topographic imaging [19]. In order to compensate for electrically or electronically induced artefacts, an ac voltage was applied between tip and sample and used in combination with lock-in techniques and a feedback controller to compensate for the contact potential difference (CPD) between tip and sample. With this method, nc-AFM is assiued to image the sample topography without any artefacts originating from different local surface potentials [20]. 

Puntambekar, K.P., Pesavento, PV. and Frisbie, C.D., Surface potential profiling and contact resistance measurements on operating pentacene thin-fikn transistors by Kelvin probe force microscopy, Appl. Phys. Lett, 83, 5539-5541, 2003. 

Second, channel potential measurements by Kelvin probe force microscopy and the four-probe method, which are described later in this chapter, indicate that the contact resistances and temperature dependences associated with the individual source and drain electrodes are nearly identical. From a thermionic emission... 

While the previously described techniques both require extrapolation of measured data in order to calculate the contact resistance, Kelvin probe force microscopy (KFM, also known as scanning surface potential microscopy or scanning potenti-ometry) can be used to determine the source and drain contributions to the contact resistance directly. In KFM, a conductive atomic force microscope (AFM) tip is scanned over the operational OFET channel twice. On the first pass, the topography... 

Characterizing these many aspects of microstructure is necessary to establish relationships between primary chemical structure, processing, and performance. Currently, the most commonly used methods are scanning probe microscopy techniques such as atomic force microscopy (AFM) or kelvin probe force microscopy... 

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