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Contact and non-contact based atomic force microscopy (AFM) approaches have been extensively utilized to explore various nanoscale surface properties. In most AFM-based measurements, a concurrent electrostatic effect between the AFM tip/cantilever and sample surface can occur. This electrostatic effect often hinders accurate measurements. Thus, it is very important to quantify as well as remove the impact of the electrostatic effect on AFM-based measurements. In this study, we examine the impact of the electrostatic effect on the electromechanical (EM) response in piezoresponse force microscopy as a model AFM mode. We quantitatively studied the effects of increasing the external electric field and reducing the spring constant of a cantilever. Further, we explored ways to minimize the electrostatic effect. The results provide broad guidelines for quantitatively analyzing the EM response as well as, eventually, for obtaining the electrostatic-free EM response. The conclusions can be applied to other AFM-based measurements that are subject to a strong electrostatic effect between the AFM tip/cantilever and sample surface, regardless of contact and non-contact modes.

Extreme UV made easier The properties of coherent EUV (extreme ultraviolet) light make it a prime candidate for exciting technological applications. At present though, the equipment needed to generate the short wavelength light is costly and bulky. A new system described in this issue could reduce both cost and bulk. It uses the conventional principle of high-harmonic generation via the interaction of a femtosecond laser pulse with a gas, but adopts a novel concept of amplifying light via local plasmon field enhancement. The beam from a modest femtosecond laser is focused onto a nanostructure consisting of bow-tie-shaped gold elements on a sapphire substrate. This may enable the construction of a laptop-sized EUV light source at a reasonable cost. A paper demonstrating high harmonic generation that requires no extra amplifier cavities. This is achieved by exploiting the local field enhancement induced by resonant plasmons within a metallic nanostructure consisting of bow-tie-shaped gold elements on a sapphire substrate. High-harmonic generation by focusing a femtosecond laser onto a gas is a well-known method of producing coherent extreme-ultraviolet (EUV) light 1 , 2 , 3 . This nonlinear conversion process requires high pulse intensities, greater than 10 13  W cm -2 , which are not directly attainable using only the output power of a femtosecond oscillator. Chirped-pulse amplification enables the pulse intensity to exceed this threshold by incorporating several regenerative and/or multi-pass amplifier cavities in tandem 4 , 5 . Intracavity pulse amplification (designed not to reduce the pulse repetition rate) also requires a long cavity 6 , 7 . Here we demonstrate a method of high-harmonic generation that requires no extra cavities. This is achieved by exploiting the local field enhancement induced by resonant plasmons within a metallic nanostructure consisting of bow-tie-shaped gold elements on a sapphire substrate. In our experiment, the output beam emitted from a modest femtosecond oscillator (100-kW peak power, 1.3-nJ pulse energy and 10-fs pulse duration) is directly focused onto the nanostructure with a pulse intensity of only 10 11  W cm -2 . The enhancement factor exceeds 20 dB, which is sufficient to produce EUV wavelengths down to 47 nm by injection with an argon gas jet. The method could form the basis for constructing laptop-sized EUV light sources for advanced lithography and high-resolution imaging applications.

Piezoelectric and ferroelectric materials have garnered significant interest owing to their excellent physical properties and multiple potential applications. Accordingly, the need for evaluating piezoelectric and ferroelectric properties has also increased. The piezoelectric and ferroelectric properties are evaluated macroscopically using laser interferometers and polarization–electric field loop measurements. However, as the research focus is shifted from bulk to nanosized materials, scanning probe microscopy (SPM) techniques have been suggested as an alternative approach for evaluating piezoelectric and ferroelectric properties. In this Progress Report, the recent progress on the nanoscale evaluation of piezoelectric and ferroelectric properties of diverse materials using SPM‐based methods is summarized. Among the SPM techniques, the focus is on recent studies that are related to piezoresponse force microscopy and conductive atomic force microscopy; further, the utilization of these two modes to understand piezoelectric and ferroelectric properties at the nanoscale level is discussed. This work can provide guidelines for evaluating the piezoelectric and ferroelectric properties of materials based on SPM techniques. Piezoelectric and ferroelectric materials have been of significant interest owing to their remarkable physical properties. This Progress Report summarizes the recent advances in the nanoscale evaluation of piezoelectric and ferroelectric properties of diverse materials using approaches based on scanning probe microscopy.

Unraveling local dynamic charge processes is vital for progress in diverse fields, from microelectronics to energy storage. This relies on the ability to map charge carrier motion across multiple length- and timescales and understanding how these processes interact with the inherent material heterogeneities. Towards addressing this challenge, we introduce high-speed sparse scanning Kelvin probe force microscopy, which combines sparse scanning and image reconstruction. This approach is shown to enable sub-second imaging (>3 frames per second) of nanoscale charge dynamics, representing several orders of magnitude improvement over traditional Kelvin probe force microscopy imaging rates. Bridging this improved spatiotemporal resolution with macroscale device measurements, we successfully visualize electrochemically mediated diffusion of mobile surface ions on a LaAlO 3 /SrTiO 3 planar device. Such processes are known to impact band-alignment and charge-transfer dynamics at these heterointerfaces. Furthermore, we monitor the diffusion of oxygen vacancies at the single grain level in polycrystalline TiO 2 . Through temperature-dependent measurements, we identify a charge diffusion activation energy of 0.18 eV, in good agreement with previously reported values and confirmed by DFT calculations. Together, these findings highlight the effectiveness and versatility of our method in understanding ionic charge carrier motion in microelectronics or nanoscale material systems. Dynamic mapping of charge motion across multiple length- and timescales is essential for understanding a variety of phenomena. Here, the authors introduce sparse scanning KPFM, which enables fast nanoscale charge mapping at 3 frames per second to track ion migration.

To address the demands of emerging data‐centric computing applications, ferroelectric field‐effect transistors (Fe‐FETs) are considered the forefront of semiconductor electronics owing to their energy and area efficiency and merged logic–memory functionalities. Herein, the fabrication and application of an Fe‐FET, which is integrated with a van der Waals ferroelectrics heterostructure (CuInP2S6/α‐In2Se3), is reported. Leveraging enhanced polarization originating from the dipole coupling of CIPS and α‐In2Se3, the fabricated Fe‐FET exhibits a large memory window of 14.5 V at VGS = ±10 V, reaching a memory window to sweep range of ≈72%. Piezoelectric force microscopy measurements confirm the enhanced polarization‐induced wider hysteresis loop of the double‐stacked ferroelectrics compared to single ferroelectric layers. The Landau–Khalatnikov theory is extended to analyze the ferroelectric characteristics of a ferroelectric heterostructure, providing detailed explanations of the hysteresis behaviors and enhanced memory window formation. The fabricated Fe‐FET shows nonvolatile memory characteristics, with a high on/off current ratio of over 106, long retention time (>104 s), and stable cyclic endurance (>104 cycles). Furthermore, the applicability of the ferroelectrics heterostructure is investigated for artificial synapses and for hardware neural networks through training and inference simulation. These results provide a promising pathway for exploring low‐dimensional ferroelectronics. The authors report on the fabrication and application of a ferroelectric transistor integrated with a van der Waals ferroelectrics heterostructure (CuInP2S6/α‐In2Se3). Leveraging enhanced polarization originating from the dipole coupling, the fabricated device exhibits a large memory window and nonvolatile memory characteristics with long retention time and stable cyclic endurance, providing a promising pathway for exploring low‐dimensional ferroelectronics.

Herein, the direct growth of polar orthorhombic phase in Hf 0.5 Zr 0.5 O 2 (HZO) thin films is reported using Pulsed Laser Deposition (PLD). The growth of HZO onto a preheated (700 °C) silicon substrate mimics the rapid thermal annealing, which allows the formation of smaller crystallites (~9.7 nm) with large surface energy leading to the stabilization of metastable orthorhombic phase. Unlike atomic layer deposition (ALD) of HZO, PLD is more advantageous for depositing highly crystalline thin films through optimized parameters, such as laser fluence and background gas pressure. Further, the PLD -HZO is integrated with HfO 2 dielectric and the resulting gate stacks have been used in the bottom gate FET architecture-‘Si// PLD -HZO/HfO 2 /MoS 2 //Ti/Au’. The NCFETs have yielded a sub-thermionic subthreshold swing (SS for  = 33.03 ± 8.7 mV/dec. and SS rev  = 36.4 ± 7.7 mV/dec.) and a negligible hysteresis (~28 mV), which is capable in realizing low power integrated digital/analog circuits.

The unique properties of ferroelectric materials enable a plethora of applications, which are hindered by the phenomenon known as ferroelectric fatigue that leads to the degradation of ferroelectric properties with polarization cycling. Multiple microscopic models explaining fatigue have been suggested; however, the chemical origins remain poorly understood. Here, we utilize multimodal chemical imaging that combines atomic force microscopy with time-of-flight secondary mass spectrometry to explore the chemical phenomena associated with fatigue in PbZr 0.2 Ti 0.8 O 3 (PZT) thin films. Investigations reveal that the degradation of ferroelectric properties is correlated with a local chemical change and migration of electrode ions into the PZT structure. Density functional theory simulations support the experimental results and demonstrate stable doping of the thin surface PZT layer with copper ions, leading to a decrease in the spontaneous polarization. Overall, the performed research allows for the observation and understanding of the chemical phenomena associated with polarization cycling and their effects on ferroelectric functionality. Ferroelectric fatigue degrades ferroelectric properties upon polarization cycling, but its underlying chemistry is poorly understood. Here, the authors show by multimodal chemical imaging that fatigue in PbZr0.2Ti0.8O3 thin films is associated with Cu + ions migration from the electrode into the film structure.

Selective thin-film removal is needed in many microfabrication processes such as 3-D patterning of optoelectronic devices and localized repairing of integrated circuits. Various wet or dry etching methods are available, but laser machining is a tool of green manufacturing as it can remove thin films by ablation without use of toxic chemicals. However, laser ablation causes thermal damage on neighboring patterns and underneath substrates, hindering its extensive use with high precision and integrity. Here, using ultrashort laser pulses of sub-picosecond duration, we demonstrate an ultrafast mechanism of laser ablation that leads to selective removal of a thin metal film with minimal damage on the substrate. The ultrafast laser ablation is accomplished with the insertion of a transition metal interlayer that offers high electron–phonon coupling to trigger vaporization in a picosecond timescale. This contained form of heat transfer permits lifting off the metal thin-film layer while blocking heat conduction to the substrate. Our ultrafast scheme of selective thin film removal is analytically validated using a two-temperature model of heat transfer between electrons and phonons in material. Further, experimental verification is made using 0.2 ps laser pulses by micropatterning metal films for various applications.

Negative differential capacitance in ferroelectrics, which can be stabilized using a dielectric, could be used to overcome the limitations of capacitive coupling in electronic devices. However, the use of negative differential capacitance in scaled silicon-based structures—such as those used in advanced low-power logic devices—remains challenging. Here we report the electrical performance enhancement due to negative differential capacitance in metal–oxide–semiconductor capacitors based on ferroelectric zirconium-doped hafnia (Hf 0.5 Zr 0.5 O 2 ) with a thickness down to 1 nm. The devices exhibit superior performance to physically thinner control devices without the ferroelectric zirconium-doped hafnia. An S-shaped polarization–electric field relation verifies the negative differential capacitance effect. The effect is also achieved in field-effect transistors in which high- κ hafnia is replaced with the ferroelectric zirconium-doped hafnia, leading to an increase in on current and decrease in off current along with negative drain-induced barrier lowering. The negative differential capacitance exhibits endurance over more than 10 15  cycles and can be tuned using doping that controls the interface charges. Ferroelectric zirconium-doped hafnia (Hf 0.5 Zr 0.5 O 2 ) can be used to create negative differential capacitance behaviour in capacitors and transistor gate stacks, providing reliable enhancements in switching performance.

Comparison between single- and the poly-crystalline structures provides essential information on the role of long-range translational symmetry and grain boundaries. In particular, by comparing single- and poly-crystalline transition metal oxides (TMOs), one can study intriguing physical phenomena such as electronic and ionic conduction at the grain boundaries, phonon propagation and various domain properties. In order to make an accurate comparison, however, both single- and poly-crystalline samples should have the same quality, e.g., stoichiometry, crystallinity, thickness, etc. Here, by studying the surface properties of atomically flat poly-crystalline SrTiO 3 (STO), we propose an approach to simultaneously fabricate both single- and poly-crystalline epitaxial TMO thin films on STO substrates. In order to grow TMOs epitaxially with atomic precision, an atomically flat, single-terminated surface of the substrate is a prerequisite. We first examined (100), (110) and (111) oriented single-crystalline STO surfaces, which required different annealing conditions to achieve atomically flat surfaces, depending on the surface energy. A poly-crystalline STO surface was then prepared at the optimum condition for which all the domains with different crystallographic orientations could be successfully flattened. Based on our atomically flat poly-crystalline STO substrates, we envision expansion of the studies regarding the TMO domains and grain boundaries.