A calibration algorithm based on one-port vector network analyzer (VNA) calibration for scanning microwave microscopes (SMMs) is presented and used to extract quantitative carrier densities from a semiconducting n-doped GaAs multilayer sample. This robust and versatile algorithm is instrument and frequency independent, as we demonstrate by analyzing experimental data from two different, cantilever- and tuning fork-based, microscope setups operating in a wide frequency range up to 27.5 GHz. To benchmark the SMM results, comparison with secondary ion mass spectrometry is undertaken. Furthermore, we show SMM data on a GaAs p-n junction distinguishing p- and n-doped layers.

Scattering parameters are fundamental quantities in radio frequency and microwave metrology. Traceability to SI units for these measurements is established with the help of calculable standards. Progress has been made over recent years in characterizing these standards. Major steps forward have been achieved with advanced modelling of the entire standard, including connector interface and with the use of multivariate uncertainty evaluation, taking correlations fully into account. The improvements have led to more consistent, more accurate measurements.

Measuring the material parameters with a vector network analyzer (VNA) usually requires time-domain gating and complicated free-space calibrations. At terahertz frequencies, classic calibrations become more problematic and uncertainty calculation for time gating is not clearly defined. The here investigated method skips these steps and is based on normalization to a “Thru” connection and analyzing error terms and multiple-reflection phenomena (ripples). It is shown that at specific frequencies, the ripples are very small. Based on this, the “standard load” method is introduced, which simplifies the error correction for transmission and reflection measurements for the whole frequency range. Results are presented in 75-110- and 500-750-GHz bands with a quasi-TEM free-space setup. Various material slabs (thin, thick, lossy, and low-loss) have been tested to show the reliability and general usefulness of the method. This method that is initially based on a “Thru” connection only provides a simple and low-cost alternative to the conventional standards (Line, Match, Short, and so on) and calibration techniques.

The evaluation of measurement uncertainties in vector network analysis is a demanding task. The metrology guide EURAMET cg-12 (formerly EA 10/12) is dedicated to this topic and serves as a guideline for calibration laboratories and national metrology institutes. The guide has been revised, acknowledging the technical progress in the field. The new method is in agreement with relevant standards on uncertainty evaluation.

Scanning microwave microscopy (SMM) is a combination of an atomic force microscope with a vector network analyzer (VNA) to measure locally resolved impedances. The technique finds application in the realms of semiconductor industries, material sciences, or biology. To determine quantitative material properties from the measured impedances, the system must be calibrated. Transferring the calibration from the calibration substrate onto the material under test is strongly limited when using unshielded probes, as the electromagnetic coupling to the surroundings can reach several centimeters. This work reports the fabrication of coaxially shielded probes for a scanning microwave microscope and their integration into such an instrument. We discuss a calibration method with dielectric references, using a simulation-assisted 1-port VNA calibration algorithm. Uncertainty considerations of the measurement process are included and propagation throughout the algorithm is performed. The calibration is verified with an additional dielectric reference. As an application example, the results for a static-random-access memory sample are presented. We identified system-related drift and trace noise as the dominant contributors to the uncertainties of the calibrated results. The here presented shielded tips can broaden the application scope of SMM, as they are door-openers for measurements in liquids.