Nanotechnology最新文献

In recent years, flexible pressure sensors have been seen widespread adoption in various fields such as electronic skin, smart wearables, and human-computer interaction systems. Owing to the electrical conductivity and adaptability to flexible substrates, vertical graphene nanowalls (VGNs) have recently been recognized as promising materials for pressure-sensing applications. Our study presented the synthesis of high-quality VGNs via plasma enhanced chemical vapor deposition and the incorporation of a metal layer by electron beam evaporation, forming a stacked structure of VGNs/Metal/VGNs. Metal nanoparticles attached to the edges and surfaces of graphene nanosheets can alter the charge transport paths within the material to enhance the responsiveness of the sensor. This layered structure effectively fulfilled the requirements of flexible pressure sensors, exhibiting high sensitivity (40.15 kPa^-1), low response time (88 ms), and short recovery time (97 ms). The pressure sensitivity remained intact even after 1000 bending cycles. Additionally, the factors contributing to the impressive pressure-sensing performance of this composite were found and its capability to detect human pulse and finger flexion signals was demonstrated, making it a promising candidate for applications of wearable electronics devices.

In this study, intrinsic ZnO powder was sintered and intercalated with particles. The resulting powder, along with a commercial p-type product, was consolidated into bulk materials, and their thermal conductivity was measured across a temperature range of 350 K-700 K. The thermal conductivity of the commercial p-type ZnO was found to be lower than that of intrinsic ZnO, attributed to controlled doping. Notably, our demonstration illustrated that the thermal conductivity can be reduced by a factor of 5-10 in the presence of AlZn₂O₄and ZnP₂precipitates. This methodology presents a feasible approach for the future design of ZnO-based thermoelectric materials, particularly for thermal heat scavenging applications.

Nanowire (NW) optoelectronic and electrical devices offer unique advantages over bulk materials but are generally made by contacting entire NW arrays in parallel. In contrast, ultra-high-resolution displays and photodetectors require electrical connections to individual NWs inside an array. Here, we demonstrate a scheme for fabricating such single NW vertical devices by contacting individual NWs within a dense NW array. We contrast benzocyclobutene and SiO2 planarization methods for these devices and find that the latter leads to dramatically improved processing yield as well as higher-quality diodes. Further, we find that replacing the metal top contact with transparent indium tin oxide does not decrease electrical performance, allowing for transparent top contacts. We improve the ideality factor of the devices from a previous n = 14 to n = 1.8, with the best devices as low as n = 1.5. The devices are characterized as both photodetectors with detectivities up to 2.45 AW^-1and photocurrent densities of up to 185 mAcm^-2under 0.76 suns illumination. Despite poor performance as light emitting diodes, the devices show great resilience to current densities up to 4×108 mAcm^-2. In combination with growth optimization, the flexibility of the processing allows for use of these devices as ultra-high-resolution photodetectors and displays.

Magnetic domain walls and skyrmions in thin film micro- and nanostructures have been of interest to a growing number of researchers since the turn of the millennium, motivated by the rich interplay of materials, interface and spin physics as well as by the potential for applications in data storage, sensing and computing. This review focuses on the manipulation of magnetic domain walls and skyrmions by piezoelectric strain, which has received increasing attention recently. Static strain profiles generated, for example, by voltage applied to a piezoelectric-ferromagnetic heterostructure, and dynamic strain profiles produced by surface acoustic waves, are reviewed here. As demonstrated by the success of magnetic random access memory, thin magnetic films have been successfully incorporated into CMOS back-end of line device fabrication. The purpose of this review is therefore not only to highlight promising piezoelectric and magnetic materials and their properties when combined, but also to galvanise interest in the spin textures in these heterostructures for a variety of spin- and straintronic devices.

Theoretical analysis of the electrostatic force between a metallic tip and semiconductor surface in Kelvin probe force microscopy (KPFM) measurements has been challenging due to the complexity introduced by tip-induced band bending (TIBB). In this study, we present a method for numerically computing the electrostatic forces in a fully three-dimensional (3D) configuration. Our calculations on a system composed of a metallic tip and GaAs(110) surface revealed deviations from parabolic behavior in the bias dependence of the electrostatic force, which is consistent with previously reported experimental results. In addition, we show that the tip radii estimated from curve fitting of the theory to experimental data provide reasonable values, consistent with the shapes of tip apex observed using scanning electron microscopy. The 3D simulation, which accounted for the influence of TIBB, enables a detailed analysis of the physics involved in KPFM measurements of semiconductor samples, thereby contributing to the development of more accurate measurement and analytical methods. .

In this paper, we propose a doping- and capacitor-less 1T-DRAM cell, which achieved virtual doping by leveraging charge plasma and bias-induced electrostatic doping (bias-ED) techniques in a 5 nm-thick intrinsic silicon body, thereby eliminating doping processes. Platinum was in contact with the drain, while aluminum was in contact with the source, enabling virtual doping of the silicon body into ap*-i-n* configuration via the charge-plasma technique. Two coupled polarity gates and one control gate are positioned above the intrinsic channel region. The intrinsic channel region is virtually doped through the bias-ED by applying voltages to the gates, forming potential wells inside the channel. The voltage applied to the two coupled polarity gates determines whether the device operates in thep- orn-channel mode, whereas the control gate governs the flow of charge carriers. Charge carriers are stored and released in the potential wells inside the channel by adjusting the gate, effectively replacing the capacitor. In this device, the placement of polarity gates on either side of the control gate enables the observation of the reconfigurable characteristics. Moreover, the proposed device utilizes a feedback mechanism, enabling excellent memory characteristics such as a high on/off current ratio of ∼10⁹, steep switching behavior of ∼0.2µV dec^-1, short write time of 10 ns, long hold retention of over 100 s, and long read retention of over 600 s.

Recently, all-oxide ferroelectric tunnel junctions, with single or composite potential barriers based on SrRuO₃/BaTiO₃/SrTiO₃(SRO/BTO/STO) perovskites, have drawn a particular interest for high density low power applications, due to their highly tunable transport properties and device scaling down possibility to atomic size. Here, using first principles calculations and the NEGFs formalism, we explore the electronic structure and tunneling transport properties in magnetoelectric SRO/BTO/mSTO/SRO interfaces, (m= 0, 2, or 4 unit cells), considering both the RuO₆octahedra tilts and magnetic SRO electrodes. Our main results may be summarized as follows: i) The band alignment schemes predict that polarization direction may determine both Schottky barrier or Ohmic contacts form(STO)=0, but only Schottky contacts form(STO)=2 and 4 junctions; ii) The tunnel electroresistance and tunnel magnetoresistance ratios are evaluated at 0 and 300 K; iii) The most magnetoelectric responsive interfaces are obtained for them(STO)=2 heterostructure, this system also showing co-existent giant tunnel electroresistance and tunnel magnetoresistance effects; iv) The interfacial magnetoelectric coupling is not strong enough to control the tunnel magnetoresistance by polarization switching, in spite of significant SRO ferromagnetism.

The irritation and adhesion of wound healing biomaterials to wet wounds should be addressed for achieving effective wound healing. In this study, a stable multifunctional hydrogels (BGs/HA suspension gels) were prepared using superfine powder of bioactive glasses (BGs), the biocompatible materials hyaluronic acid (HA) and carbomer940, which had good adhesion and low irritation properties for use in moist complex wounds. The average particle size of BGs/HA suspension gels was 13.11 ± 0.29 μm, and the bioactive glass content was 15.8 ± 0.2% (m/m). The results of cell proliferation, cell migration, and immunofluorescence staining experiments showed that in the initial stage of wound healing, the ionic extract of BGs formulations promoted the proliferation and migration of L929 cells and induced the secretion of α-SMA and collagen I. In the final stage of repair, the ionic extract of the BGs formulation regulated the differentiation of fibroblast, which contributed to the reduction of pathological scar formation. In vivo experiments showed that the wound healing rate of BGs/HA suspension gels group exceeded higher than that of the conventional BGs superfine powder group. Although BGs/HA suspension gels were comparable to its commercially available counterpart (Dermlin paste) in promoting wound healing, it addressed the problem of localized irritation caused by the high pH and low adhesion of BGs products. This study confirmed the specific regulatory effect of BGs/HA suspension gels on L929 cells, which provided a reference for the clinical application of BGs in wound dressing.

Magic-angle twisted bilayer graphene (TBG) is a tunable material with remarkably flat energy bands near the Fermi level, leading to fascinating transport properties and correlated states at low temperatures. However, grown pristine samples of this material tend to break up into landscapes of twist-angle domains, strongly influencing the physical properties of each individual sample. This poses a significant problem to the interpretation and comparison between measurements obtained from different samples. In this work, we study numerically the effects of twist-angle disorder on quantum electron transport in mesoscopic samples of magic-angle TBG. We find a significant property of twist-angle disorder that distinguishes it from onsite-energy disorder: it leads to an asymmetric broadening of the energy-resolved conductance. The magnitude of the twist-angle variation has a strong effect on conductance, while the number of twist-angle domains is of much lesser significance. We further establish a relationship between the asymmetric broadening and the asymmetric density of states of TBG at angles smaller than the first magic angle. Our results show that the qualitative differences between the types of disorder in the energy-resolved conductance of TBG samples can be used to characterize them at temperatures above the critical temperatures of the correlated phases, enabling systematic experimental studies of the effects of the different types of disorders also on the other properties such as the competition of the different types of correlated states appearing at lower temperatures.