Scanning probe microscopy (SPM) is a valuable technique by which one can investigate the physical characteristics of the surfaces of materials. However, its throughput is hampered by the time-consuming nature of running an experiment and the significant domain knowledge required. Recent studies have shown the value of multiple forms of automation in improving this, but their use is limited due to the difficulty of integrating them with SPMs other than the one it was developed for. We have built a framework that allows for tasks written with it to be run on multiple SPM systems. Our framework defines generic commands and data structures that are passed among separate software processes, with the final SPM commands sent to the microscope after passing through an SPM-specific translator. The use of configuration files allows automation logic to be further decoupled from experiment specifics. A mediation layer permits background tasks to intermittently control the microscope, fixing detected experiment problems. Our framework has been tested on various SPM controllers, validating that it can integrate with all existing scripting interfaces types. An automated experiment was run to ensure overall running beyond integration testing.

Kagome lattices provide an exciting space for the exploration of graphene-like π-conjugated molecular systems with flat bands. Using heterotriangulene-derived precursors, along with an on-surface Ullmann coupling process, makes growing polymers with Kagome lattices accessible and straightforward. Here, we use scanning tunneling microscopy alongside high-resolution atomic force microscopy to examine the evolution of tribromotrioxaazatriangulene on Au(111) into ordered, covalent films. Using density functional theory and scanning probe methods, we find previously unreported organometallic intermediate states involving Au adatoms incorporated within the growing polymer lattice. We also find that a majority of polymer edges remain brominated up to 250 ^∘C and a large number of edges bonded to Au adatoms coordinated to an adjacent bromine atom. These observations suggest that residual bromine could play a role in stabilizing the polymer edges to Au adatoms and thereby influence the growth pathways that lead to ordered Kagome polymer lattices.

Understanding O2 bubble nucleation and growth during the oxygen evolution reaction (OER) is crucial to comprehend their influence on the location and distribution of catalytically active sites in the process. To achieve this goal, mapping the spatial variation of nanoscale dynamic individual steps at the electrocatalytic interfaces is vital, as it further enables a detailed understanding of the mechanism of the process. Here, we combine tapping mode AFM imaging with a Pt ultramicroelectrode to investigate oxygen bubble nucleation, growth, and detachment. Our AFM feedback error signal and topography data reveal that O2 gas bubbles nucleate at step-edge sites and interact with catalytically active sites. This interaction between primary catalytic sites and bubble nucleation sites is the main reason for a decrease in the current density at a given high overpotential of the OER. Our findings advance the understanding of the complexity of phenomena involved in electrolytic gas evolution reactions on catalytic surfaces.

As silicon-based devices continue to shrink to the nanoscale, traps at the Si-SiO_2 interface pose increasing challenges to device performance. These traps reduce channel carrier mobility and shift threshold voltages in integrated circuits, and introduce charge noise in quantum systems, reducing their coherence times. Knowledge of the precise location of such traps aids in understanding their influence on device performance. In this work, we demonstrate that frequency-modulated atomic force microscopy (fm-AFM) allows the detection of individual traps. We use this to study how sample preparation, specifically the introduction of a buried hydrogen termination layer, and post-processing annealing in forming gas (N_2+H_2), affects the density of donor-like traps in Si(100)-SiO_2 systems. We spatially map and quantify traps in both conventionally prepared ("pristine") silicon samples and those processed under ultra-high vacuum for hydrogen resist lithography (HRL). We confirm previous studies demonstrating hydrogen passivation of traps and find that hydrogen termination further reduces the donor-like trap density. We also observe a significant reduction in two-level donor-like traps in the hydrogen-terminated samples compared to pristine silicon samples. These findings suggest that HRL-prepared silicon may offer advantages for high-performance nanoscale and atomic-scale devices due to reduced trap densities.

Electrocatalytic processes occurring at heterogeneous interfaces are complex and understanding molecular-level details remains challenging. Atomic force microscope (AFM) can detect force interactions down to the atomic level, but so far it has been mainly used to study in-situ surface reconstructions of electrocatalysts. We employ AFM for the first time to investigate the gas-evolving platinum (Pt) ultramicroelectrode (UME) using the force noise method under in-situ electrochemical conditions. We detect excess force noise when the individual H 2 gas bubble nucleation, growth, and detachment events are observed at the Pt microelectrode. The excess noise varies linearly with the applied potential on a semi-log plot. Electrochemical measurements yield the size of the H 2 gas bubble ∼1-10 μm. However, from the deflection signal, the H 2 bubble radius with a mean value of 321 μm is obtained indicating that the force noise detected at the AFM tip is mainly due to the coalescence of small bubbles generated at the Pt UME interface. Our report shows an alternative method to probe the gas-bubble dynamics at the catalytic interface with high sensitivity. The present method could potentially be useful in mapping the bubble nucleation sites at heterogeneous electrocatalytic interfaces.

Electrocatalytic processes occurring at a heterogeneous interface are complex, and their understanding at the molecular level remains challenging. Atomic force microscopy (AFM) can detect force interactions down to the atomic level, but so far it has been mainly used to obtain in situ images of electrocatalysts. Here, for the first time, we employ AFM to investigate gas evolution at a platinum ultramicroelectrode (Pt UME) under electrochemical conditions using force noise measurements. We detect excess force noise when individual H2 gas bubble nucleation, growth, and detachment events occur at the Pt UME. Based on our in situ AFM, electrochemical, and optical microscopy analyses, we conclude that larger size H2 gas bubbles remain pinned to the UME surface while smaller H2 gas bubbles are released until an overpotential of -0.8 V vs RHE. This study demonstrates the viability of in situ AFM in studying gas evolution under electrocatalytic conditions and contributes to a mechanistic understanding of the H2 gas bubble detachments during the hydrogen evolution reaction (HER).

Solid-state nanopores exhibit dynamically variable sizes influenced by buffer conditions and applied electric field. While dynamical pore behavior can complicate biomolecular sensing, it also offers opportunities for controlled, in situ modification of pore size post-fabrication. In order to optimally harness solid-state pore dynamics for controlled growth, there is a need to systematically quantify pore growth dynamics and ideally develop quantitative models to describe pore growth. Using high-voltage pulse conditioning, we investigate the expansion of nanopores and track their growth over time. Our findings reveal that pore growth follows a two-regime model: an initial transient regime characterized by an exponential rise, followed by a steady-state regime with linear growth. The pore growth rate increases with voltage, while the duration of the transition regime decreases with voltage. We propose a simple electrochemical etching model based on hydrolysis and solute removal to quantify time-dynamics of growing pores and rationalize the mechanism of electric-field driven pore growth, with numerical solutions aligning closely with experimental data. These insights enhance the understanding of nanopore conditioning, providing a theoretical framework for controlled pore size modification.

We use electrostatic force microscopy to spatially resolve random telegraph noise at the Si/SiO$_2$ interface. Our measurements demonstrate that two-state fluctuations are localized at interfacial traps, with bias-dependent rates and amplitudes. These two-level systems lead to correlated carrier number and mobility fluctuations with a range of characteristic timescales; taken together as an ensemble, they give rise to a $1/f$ power spectral trend. Such individual defect fluctuations at the Si/SiO$_2$ interface impair the performance and reliability of nanoscale semiconductor devices, and will be a significant source of noise in semiconductor-based quantum sensors and computers. The fluctuations measured here are associated with a four-fold competition of rates, including slow two-state switching on the order of seconds and, in one state, fast switching on the order of nanoseconds which is associated with energy loss.

The ongoing development of single electron, nano-, and atomic scale semiconductor devices would greatly benefit from a characterization tool capable of detecting single electron charging events with high spatial resolution at low temperatures. In this work, we introduce a novel Atomic Force Microscope (AFM) instrument capable of measuring critical device dimensions, surface roughness, electrical surface potential, and ultimately the energy levels of quantum dots and single electron transistors in ultra miniaturized semiconductor devices. The characterization of nanofabricated devices with this type of instrument presents a challenge: finding the device. We, therefore, also present a process to efficiently find a nanometer sized quantum dot buried in a 10 × 10 mm2 silicon sample using a combination of optical positioning, capacitive sensors, and AFM topography in a vacuum.

The Si/SiO$_2$ interface is populated by isolated trap states which modify its electronic properties. These traps are of critical interest for the development of semiconductor-based quantum sensors and computers, as well as nanoelectronic devices. Here, we study the electric susceptibility of the Si/SiO$_2$ interface with nm spatial resolution using frequency-modulated atomic force microscopy to measure a patterned dopant delta-layer buried 2 nm beneath the silicon native oxide interface. We show that surface charge organization timescales, which range from 1-150 ns, increase significantly around interfacial states. We conclude that dielectric loss under time-varying gate biases at MHz and sub-MHz frequencies in metal-insulator-semiconductor capacitor device architectures is highly spatially heterogeneous over nm length scales. Supplemental GIFs can be found at https://doi.org/10.6084/m9.figshare.25546687

Controlling the morphology and composition of semiconductor nano- and micro-structures is crucial for fundamental studies and applications. Here, Si-Ge semiconductor nanostructures were fabricated using photolithographically defined micro-crucibles on Si substrates. Interestingly, the nanostructure morphology and composition of these structures are strongly dependent on the size of the liquid–vapour interface (i.e., the opening of the micro-crucible) in the CVD deposition step of Ge. In particular, Ge crystallites nucleate in micro-crucibles with larger opening sizes (3.74–4.73 μm2), while no such crystallites are found in micro-crucibles with smaller openings of 1.15 μm2. This interface area tuning also results in the formation of unique semiconductor nanostructures: lateral nano-trees (for smaller openings) and nano-rods (for larger openings). Further TEM imaging reveals that these nanostructures have an epitaxial relationship with the underlying Si substrate. This geometrical dependence on the micro-scale vapour–liquid–solid (VLS) nucleation and growth is explained within a dedicated model, where the incubation time for the VLS Ge nucleation is inversely proportional to the opening size. The geometric effect on the VLS nucleation can be used for the fine tuning of the morphology and composition of different lateral nano- and micro-structures by simply changing the area of the liquid–vapour interface.

In this work, we experimentally demonstrate two-state fluctuations in a metal-insulatorsemiconductor (MIS) device formed out of a metallic atomic force microscopy tip, vacuum gap, and multilayer MoSe2 sample. We show that noise in this device is intrinsically bias-dependent due to the bias-dependent surface potential, and does not require that the frequency or magnitude of individual dopant fluctuations are themselves bias-dependent. Finally, we measure spatial nonhomogeneities in band bending (charge reorganization) timescales.

Long-term stable cell culture is a critical tool to better understand cell function. Most adherent cell culture models require a polymer substrate coating of poly-lysine or poly-ornithine for the cells to adhere and survive. However, polypeptide-based substrates are degraded by proteolysis and it remains a challenge to maintain healthy cell cultures for extended periods of time. Here, we report the development of an enhanced cell culture substrate based on a coating of dendritic polyglycerol amine (dPGA), a non-protein macromolecular biomimetic of poly-lysine, to promote the adhesion and survival of neurons in cell culture. We show that this new polymer coating provides enhanced survival, differentiation and long-term stability for cultures of primary neurons or neurons derived from human induced pluripotent stem cells (hiPSCs). Atomic force microscopy analysis provides evidence that greater nanoscale roughness contributes to the enhanced capacity of dPGA-coated surfaces to support cells in culture. We conclude that dPGA is a cytocompatible, functionally superior, easy to use, low cost and highly stable alternative to poly-cationic polymer cell culture substrate coatings such as poly-lysine and poly-ornithine. Summary statementHere, we describe a novel dendritic polyglycerol amine-based substrate coating, demonstrating superior performance compared to current polymer coatings for long-term culture of primary neurons and neurons derived from induced pluripotent stem cells.

Transition metal dichalcogenides (TMDCs) have attracted significant attention for optoelectronic, photovoltaic and photoelectrochemical applications. The properties of TMDCs are highly dependent on the number of stacked atomic layers, which is usually counted post-fabrication, using a combination of optical methods and atomic force microscopy (AFM) height measurements. Here, we use photoluminescence spectroscopy and three different AFM methods to demonstrate significant discrepancies in height measurements of exfoliated MoSe$_2$ flakes on SiO$_2$ depending on the method used. We highlight that overlooking effects from electrostatic forces, contaminants and surface binding can be misleading when measuring the height of a MoSe$_2$ flake. These factors must be taken into account as a part of the protocol for counting TMDC layers.

Transition metal dichalcogenides (TMDCs) have attracted significant attention for optoelectronic, photovoltaic and photoelectrochemical applications. The properties of TMDCs are highly dependent on the number of stacked atomic layers, which is usually counted post-fabrication, using a combination of optical methods and atomic force microscopy height measurements. Here, we use photoluminescence spectroscopy, Raman spectroscopy, and three different AFM methods to demonstrate significant discrepancies in height measurements of exfoliated MoSe2flakes on SiO2depending on the method used. We also highlight the often overlooked effect that electrostatic forces can be misleading when measuring the height of a MoSe2flake using AFM.

Metal-oxide semiconductors (MOS) are widely utilized for catalytic and photocatalytic applications in which the dynamics of charged carriers (e.g., electrons, holes) play important roles. Under operation conditions, photoinduced surface oxygen vacancies (PI-SOV) can greatly impact the dynamics of charge carriers. However, current knowledge regarding the effect of PI-SOV on the dynamics of hole migration in MOS films, such as titanium dioxide, is solely based upon volume-averaged measurements and/or vacuum conditions. This limits the basic understanding of hole-vacancy interactions, as they are not capable of revealing time-resolved variations during operation. Here, we measured the effect of PI-SOV on the dynamics of hole migration using time-resolved atomic force microscopy. Our findings demonstrate that the time constant associated with hole migration is strongly affected by PI-SOV, in a reversible manner. These results will nucleate an insightful understanding of the physics of hole dynamics and thus enable emerging technologies, facilitated by engineering hole-vacancy interactions.

Inducing an inversion layer in organic semiconductors is a highly nontrivial, but critical, achievement for producing organic field-effect transistor (OFET) devices, which rely on the generation of inversion, accumulation, and depletion regimes for successful operation. Here, we develop a pulsed bias technique to characterize the dopant type of any organic material system, without prior knowledge or characterization of the material in question. We use this technique on a pentacene/PTCDI heterostructure and thus deduce that pentacene is exhibiting n-doped like response. The source of the additional charges in the pentacene island can be identified by charging rings in the dissipation channel of the noncontact atomic force microscopy (AFM) signal, a typical signature for localized charge transfer from the AFM tip to the sample. Additionally, through tip-induced band-bending, we generate inversion, depletion, and accumulation regimes over a 20 nm radius, three monolayer thick n-doped pentacene island. Our findings demonstrate that nanometer-scale lateral extent and thickness are sufficient for an OFET device to operate in the inversion regime.

The ground and excited electronic level structure of quantum systems is of fundamental importance for their optical, electronic and chemical properties. Single-electron sensitive electrostatic force measurement with AFM has been demonstrated to be capable of quantitative energy level spectroscopy of individual and coupled semiconductor quantum dots (QD). In our experiments the oscillation of a dc biased AFM tip modulates the charge state of a QD. The QD is separated from a back gate via a tunnelling barrier. The resulting charge dynamics leads to measurable changes in cantilever resonance frequency and dissipation. The tip of our AFM can thus be described as a movable gate to address a QD of choice and is at the same time a charge detector with single electron sensitivity. Key to the experimental implementation is that the QD-back electrode tunnelling barrier is engineered to have a QD-back electrode tunnelling rate similar to the AFM cantilever mechanical resonance frequency.

Reliable operation of frequency modulation mode atomic force microscopy (FM-AFM) depends on a clean resonance of an AFM cantilever. It is recognized that the spurious mechanical resonances which originate from various mechanical components in the microscope body are excited by a piezoelectric elemen that is intended for exciting the AFM cantilever oscillation and these spurious resonance modes cause the serious undesirable signal artifacts in both frequency shift and dissipation signals. We present an experimental setup to excite only the oscillation of the AFM cantilever in a fiber-optic interferometer system using optical excitation force. While the optical excitation force is provided by a separate laser light source with a different wavelength (excitation laser : λ=1310 nm), the excitation laser light is still guided through the same single-mode optical fiber that guides the laser light (detection laser : λ=1550 nm) used for the interferometric detection of the cantilever deflection. We present the details of the instrumentation and its performance. This setup allows us to eliminate the problems associated with the spurious mechanical resonances such as the apparent dissipation signal and the inaccuracy in the resonance frequency measurement.

A method to measure the dimensions of objects below the optical diffraction limit using diffraction analysis of out-of-focus bright-field images is presented. The method relies on the comparison of the diffraction patterns of an object of unknown size to those of calibration objects of known size. Correlative scanning electron microscope measurements are used to demonstrate the applicability of this method to measure 100 nm microbeads as well as objects with a geometry different from the calibration objects. This technique is important in the context of tethered particle experiments, in which bio-filaments are bound between a substrate and a microbead. This procedure is applied to obtain the diameters of axonal extensions or neurites that are mechanically created in samples of rat hippocampal neurons. The dependence of neurite geometry on mechanical pull speed is investigated, and the diameter is found to be rate independent.