We present an algorithm for reconstructing a sample surface potential from its Kelvin probe force microscopy (KPFM) image. The measured KPFM image is a weighted average of the surface potential underneath the tip apex due to the long-range electrostatic forces. We model the KPFM measurement by a linear shift-invariant system where the impulse response is the point spread function (PSF). By calculating the PSF of the KPFM probe (tip+cantilever) and using the measured noise statistics, we deconvolve the measured KPFM image to obtain the surface potential of the sample.The reconstruction algorithm is applied to measurements of CdS-PbS nanorods measured in amplitude modulation KPFM (AM-KPFM) and to graphene layers measured in frequency modulation KPFM (FM-KPFM). We show that in the AM-KPFM measurements the averaging effect is substantial, whereas in the FM-KPFM measurements the averaging effect is negligible.

InAs nanowires are candidates for future high-speed electronic and optoelectronic applications due to their high electron mobility and large coherence length. However, InAs surfaces are known to possess a high concentration of donor-type surface states, which results in an electron accumulation layer and, consequently, Fermi level pinning. Since the surface to volume ratio in nanowires is very large, the effect of surface states is greatly enhanced. We present a method for directly determining the density and energy distribution of single nanowire surface states using Kelvin probe force microscopy measured on a nanowire field-effect transistor and interpreted by electrostatic modeling. Here, the method is applied to individual InAs nanowires, which similarly to bulk InAs exhibit a prominent accumulation layer consisting of a large concentration of donor-type surface states. Nevertheless, due to the small diameter of the nanowires, the electron accumulation and Fermi level pinning take place within the entire nanowire. V C 2012 American Institute of Physics.

No abstract

In order to understand the mechanism of biosensing of field-effect-based biosensors and optimize their performance, the effect of each of its molecular building blocks must be understood. In this work the effect of the self-assembled linker molecules on the top of a biofield-effect transistor was studied in detail. We have combined Kelvin probe force microscopy, current-voltage measurements, and device simulations in order to trace the mechanism of silicon-on-insulator biological field-effect transistors. The measurements were conducted on the widely used linker molecules (3-aminopropyl)trimethoxysilane (APTMS) and (11-aminoundecyl)triethoxysilane (AUTES), which were self-assembled on an ozone-activated silicon oxide surface covering the transistor channel. The work function of the modified silicon oxide decreased by more then 1.5 eV, while the transistor threshold voltage increased by about 30 V following the self-assembly. A detailed analysis indicates that these changes are due to negative-induced charges on the top dielectric layer, and an effective dipole due to the polar monolayer. The results were compared with metal gated transistors fabricated on the same die, and a factor converting the molecular charge to the metal gate voltage was extracted.