Electrical characterization and modeling of SiC IC test structures

Ohmic contacts and resistor structures have been evaluated for a 4HSiC ECL technology. Sheet resistance, contact resistance, transfer length and specific contact resistivity have been measured with the linear transfer length method. Values for such parameters are reported for each layer of npn bipolar junction transistors in the temperature range from 27 to 300 C. Sheet resistance exhibits a 60% decrease with increasing temperature in the p-type layer, while a non-monotonous dependence is found for the ntype layers, with values spreading in a range which is wide about 10% the room temperature value. Strip and serpentine integrated resistors have also been tested. Simulations of sheet resistance for n- and p-type layers are compared to experimental data. Different sources for incomplete ionization and mobility are considered. A good agreement is finally found for the ptype layer, while the need to model the metal-non-metal transition arises in the n-type layer

A Monte Carlo ray-tracing simulation of coherent X-ray diffractive imaging

Coherent diffractive imaging (CDI) experiments are adequately simulated assuming the thin sample approximation and using a Fresnel or Fraunhofer wavefront propagator to obtain the diffraction pattern. Although this method is used in wave-based or hybrid X-ray simulators, here the applicability and effectiveness of an alternative approach that is based solely on ray tracing of Huygens wavelets are investigated. It is shown that diffraction fringes of a grating-like source are accurately predicted and that diffraction patterns of a ptychography dataset from an experiment with realistic parameters can be sampled well enough to be retrieved by a standard phase-retrieval algorithm. Potentials and limits of this approach are highlighted. It is suggested that it could be applied to study imperfect or non-standard CDI configurations lacking a satisfactory theoretical formulation. The considerable computational effort required by this method is justified by the great flexibility provided for easy simulation of a large-parameter space

Image Registration in Multi-Modal Scanning Microscopy: A Solar Cell Case Study

Scanning probe measurements are an indispensable tool of solar cell research today, and the compatibility with simultaneous acquisition of complementary measurement modes is a particular strength. However, multi-modal data acquisition is often limited by different scan-parameter requirements. As a consequence, the modalities may be assessed subsequently rather than simultaneously. In this instance, image registration serves as a tool to align two-dimensional datasets at nanoscale. Here, we showcase an example of two subsequent scanning Xray microscopy measurements of solar cells with a Cu(In,Ga)Se2 absorber, the first measurement being optimized for X-ray beam induced current and the second for X-ray fluorescence. We discuss different approaches and pitfalls of image registration and its potential combination with Gaussian filtering. This finally allows us to proceed with the investigation of point-by-point correlations

Comparison between Gibson–Cooke and Macroduct Methods in the Cystic Fibrosis Neonatal Screening Program and in Subjects Who Are Cystic Fibrosis Screen-Positive with an Inconclusive Diagnosis

The sweat test (ST) is the current diagnostic gold standard for cystic fibrosis (CF). Many CF centres have switched from the Gibson–Cooke method to the Macroduct system-based method. We used these methods simultaneously to compare CF screening outcomes. STs using both methods were performed simultaneously between March and December 2022 at CF Centre in Florence. We included newborns who underwent newborn bloodspot screening (NBS), newborns undergoing transfusion immediately after birth, and children with CF screen-positive, inconclusive diagnosis (CFSPID). We assessed 72 subjects (median age 4.4 months; range 0–76.7): 30 (41.7%) NBS-positive, 18 (25.0%) newborns who underwent transfusion, and 24 (33.3%) children with CFSPID. No significant differences were found between valid sample numbers, by patient ages and groups (p = 0.10) and between chloride concentrations (p = 0.13), except for sweat chloride (SC) measured by the Gibson–Cooke and Macroduct methods in CFSPID group (29.0, IQR: 20.0–48.0 and 22.5, IQR: 15.5–30.8, respectively; p = 0.01). The Macroduct and Gibson–Cooke methods showed substantial agreement with the SC values, except for CFSPID, whose result may depend on the method of sweat collection. In case of invalid values with Macroduct, the test should be repeated with Gibson–Cooke method