It is now possible to create atomically thin regions of dopant atoms in silicon patterned with lateral dimensions ranging from the atomic scale (angstroms) to micrometers. These structures are building blocks of quantum devices for physics research and they are likely also to serve as key components of devices for next-generation classical and quantum information processing. Until now, the characteristics of buried dopant nanostructures could only be inferred from destructive techniques and/or the performance of the final electronic device; this severely limits engineering and manufacture of real-world devices based on atomic-scale lithography. Here, we use scanning microwave microscopy (SMM) to image and electronically characterize three-dimensional phosphorus nanostructures fabricated via scanning tunneling microscope–based lithography. The SMM measurements, which are completely nondestructive and sensitive to as few as 1900 to 4200 densely packed P atoms 4 to 15 nm below a silicon surface, yield electrical and geometric properties in agreement with those obtained from electrical transport and secondary ion mass spectroscopy for unpatterned phosphorus δ layers containing ~10¹³ P atoms. The imaging resolution was 37 ± 1 nm in lateral and 4 ± 1 nm in vertical directions, both values depending on SMM tip size and depth of dopant layers. In addition, finite element modeling indicates that resolution can be substantially improved using further optimized tips and microwave gradient detection. Our results on three-dimensional dopant structures reveal reduced carrier mobility for shallow dopant layers and suggest that SMM could aid the development of fabrication processes for surface code quantum computers.

Nanoscale investigations by scanning probe microscopy have provided major contributions to the rapid development of organic-inorganic halide perovskites (OIHP) as optoelectronic devices. Further improvement of device level properties requires a deeper understanding of the performance-limiting mechanisms such as ion migration, phase segregation and their effects on charge extraction both at the nano- and macroscale. Here, we have studied the dynamic electrical response of Cs0.05(FA0.83MA0.17)0.95PbI3-xBrx perovskite structures by employing conventional and microsecond time-resolved open-loop Kelvin probe force microscopy (KPFM). Our results indicate strong negative charge carrier trapping upon illumination and very slow (>1s) relaxation of charges at the grain boundaries. The fast electronic recombination and transport dynamics on the microsecond scale probed by time-resolved open-loop KPFM show diffusion of charge carriers towards grain boundaries and indicate locally higher recombination rates due to intrinsic compositional heterogeneity. The nanoscale electrostatic effects revealed are summarized in a collective model for mixed-halide CsFAMA. Results on multilayer solar cell structures draw direct relations between nanoscale ionic transport, charge accumulation, recombination properties and the final device performance. Our findings extend the current understanding of complex charge carrier dynamics in stable multi-cation OIHP structures.

The electrochemical performance of carbon-based supercapacitors containing ionic liquid electrolytes was investigated through calibrated impedance spectroscopy and finite element modeling (FEM). To ensure precisely calibrated complex impedance measurements over a wide frequency range the measured pouch cells were mounted in a pressure fixture with stable terminal contacts, and a two-term impedance calibration workflow was applied. For the physical interpretation of the measurement results, FEM was used. Experimental findings demonstrated a clear dependency of the capacitive behavior on the electrode material, where cells with activated carbon electrodes showed lower impedance compared to cells with graphene electrodes. For FEM, we used a volume-averaged approach to study the effect of the electrode structure on the EIS response of the cells. The simulated impedance results showed a good agreement with experimental data in the middle- to high-frequency regions, ranging from 10 Hz to 10 kHz. Deviations from the ideal Warburg impedance were observed at lower frequencies, suggesting nonlinearity effects of the porous structure on ion transport mechanisms. FEM analysis was performed for both graphene and activated carbon electrodes showing a steeper transition region for activated carbon electrodes, indicating a reduced diffusion resistance for electrolyte ions.

Electrochemical microscopy techniques have extended the understanding of surface chemistry to the micrometer and even sub‐micrometer level. However, fundamental questions related to charge transport at the solid‐electrolyte interface, such as catalytic reactions or operation of individual ion channels, require improved spatial resolutions down to the nanoscale. A prerequisite for single‐molecule electrochemical sensitivity is the reliable detection of a few electrons per second, that is, currents in the atto‐Ampere (10⁻¹⁸ A) range, 1000 times below today's electrochemical microscopes. This work reports local cyclic voltammetry (CV) measurements at the solid‐liquid interface on ferrocene self‐assembled monolayer (SAM) with sub‐atto‐Ampere sensitivity and simultaneous spatial resolution < 80 nm. Such sensitivity is obtained through measurements of the charging of the local faradaic interface capacitance at GHz frequencies. Nanometer‐scale details of different molecular organizations with a 19% packing density difference are resolved, with an extremely small dispersion of the molecular electrical properties. This is predicted previously based on weak electrostatic interactions between neighboring redox molecules in a SAM configuration. These results open new perspectives for nano‐electrochemistry like the study of quantum mechanical resonance in complex molecules and a wide range of applications from electrochemical catalysis to biophysics.