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Graphene nanobubbles (GNBs) have attracted much attention due to the ability to generate large pseudo-magnetic fields unattainable by ordinary laboratory magnets. However, GNBs are always randomly produced by the reported protocols, therefore, their size and location are difficult to manipulate, which restricts their potential applications. Here, using the functional atomic force microscopy (AFM), we demonstrate the ability to form programmable GNBs. The precision of AFM facilitates the location definition of GNBs, and their size and shape are tuned by the stimulus bias of AFM tip. With tuning the tip voltage, the bubble contour can gradually transit from parabolic to Gaussian profile. Moreover, the unique three-fold symmetric pseudo-magnetic field pattern with monotonous regularity, which is only theoretically predicted previously, is directly observed in the GNB with an approximately parabolic profile. Our study may provide an opportunity to study high magnetic field regimes with the designed periodicity in two dimensional materials. Presence of nano-bubbles within an atomically thin material generates potentially large pseudo-magnetic fields. Here, the authors report an innovative technique to induce nano-bubbles in graphene with desirable features and high precision through energized AFM tips, and experimentally measure three-fold symmetric pseudo-magnetic fields up to 120 T.

Metal–semiconductor junctions are essential components in electronic and optoelectronic devices. With two-dimensional semiconductors, conventional metal deposition via ion bombardment results in chemical disorder and Fermi-level pinning. Transfer printing techniques—in which metal electrodes are predeposited and transferred to create van der Waals junctions—have thus been developed, but the predeposition of metal electrodes creates chemical bonds on the substrate, which makes subsequent transfer difficult. Here we report a graphene-assisted metal transfer printing process that can be used to form van der Waals contacts between two-dimensional materials and three-dimensional metal electrodes. We show that arrays of metal electrodes with both weak (copper, silver and gold) and strong (platinum, titanium and nickel) adhesion strengths can be delaminated from a four-inch graphene wafer due to its weak van der Waals force and absence of dangling bonds, and transfer printed onto different substrates (graphene, molybdenum disulfide and silicon dioxide). We use this approach to create molybdenum disulfide field-effect transistors with different printed metal electrodes, allowing the Schottky barrier height to be tuned and ohmic and Schottky contacts to be formed. We also demonstrate the batch production of molybdenum disulfide transistor arrays with uniform electrical characteristics. A variety of metal electrodes can be deposited on a graphene substrate, delaminated and transferred onto two-dimensional semiconductors to form high-quality metal–semiconductor interfaces.

The integration of complex oxides with a wide spectrum of functionalities on Si, Ge and flexible substrates is highly demanded for functional devices in information technology. We demonstrate the remote epitaxy of BaTiO 3 (BTO) on Ge using a graphene intermediate layer, which forms a prototype of highly heterogeneous epitaxial systems. The Ge surface orientation dictates the outcome of remote epitaxy. Single crystalline epitaxial BTO 3-δ films were grown on graphene/Ge (011), whereas graphene/Ge (001) led to textured films. The graphene plays an important role in surface passivation. The remote epitaxial deposition of BTO 3-δ follows the Volmer-Weber growth mode, with the strain being partially relaxed at the very beginning of the growth. Such BTO 3-δ films can be easily exfoliated and transferred to arbitrary substrates like Si and flexible polyimide. The transferred BTO 3-δ films possess enhanced flexoelectric properties with a gauge factor of as high as 1127. These results not only expand the understanding of heteroepitaxy, but also open a pathway for the applications of devices based on complex oxides. The integration of epitaxial complex oxides on semiconductor and flexible substrates is required but challenging. Here, the authors report the highly heterogeneous epitaxy of transferrable BaTiO 3-δ membrane with enhanced flexoelectricity on Ge (011).

Bioresorbable electronic devices and/or systems are of great appeal in the field of biomedical engineering due to their unique characteristics that can be dissolved and resorbed after a predefined period, thus eliminating the costs and risks associated with the secondary surgery for retrieval. Among them, passive electronic components or systems are attractive for the clear structure design, simple fabrication process, and ease of data extraction. This work reviews the recent progress on bioresorbable passive electronic devices and systems, with an emphasis on their applications in biomedical engineering. Materials strategies, device architectures, integration approaches, and applications of bioresorbable passive devices are discussed. Furthermore, this work also overviews wireless passive systems fabricated with the combination of various passive components for vital sign monitoring, drug delivering, and nerve regeneration. Finally, we conclude with some perspectives on future fundamental studies, application opportunities, and remaining challenges of bioresorbable passive electronics.

Realising ubiquitous environmental monitoring and smart sensing devices compatible with Internet of Things (IoT) and 6 G networks requires transistors with terahertz (THz) cutoff frequencies ( f T ) for efficient signal processing. However, the carrier transit time intrinsically limits conventional devices. Vertical two-dimensional (2D) base transistors offer a way to exceed this limit, yet interface losses typically suppress current gain, degrade high-frequency performance, and hinder THz operation. Here, we report a silicon–graphene–germanium barristor that overcomes these obstacles. Wafer-scale single-crystal graphene was epitaxially grown on germanium and integrated with silicon membranes, forming asymmetric Schottky barriers at the graphene–silicon and graphene–germanium interfaces. Using graphene’s quantum capacitance, the asymmetric barriers enable distinct hot-carrier emission at both terminals and greatly increase the current gain, while graphene’s atomic thickness minimises the perpendicular transit time. As a result, the device achieves a current gain up to 1.8 × 10 7 and an intrinsic f T up to 132 GHz, with modelling and simulation indicating scalability into the THz regime. These findings establish a promising high-frequency transistor paradigm for IoT sensors and systems. Vertical 2D base transistors hold potential for the realization of high-frequency electronics for Internet of Things and 6 G networks. Here, the authors report the realization of silicon-graphene-germanium barristors with current gain up to 1.8 × 10 7 and intrinsic cutoff frequencies up to 132 GHz.

Two magnetic-field-induced quantum critical behaviors were recently discovered in two dimensional electron gas (2DEG) at LaTiO 3 /SrTiO 3 interface and interpreted by disordered superconducting puddles coupled through 2DEG. In this scenario, the 2DEG is proposed to undergo a spontaneous phase separation and breaks up into locally superconducting puddles in a metallic matrix. However, as the inhomogeneous superconducting 2DEG is only illative, this proposal still lacks the direct experimental demonstration. Here, we artificially construct superconducting puddles-2DEG hybrid system by depositing tin nanoislands array on single crystalline monolayer graphene, where the two quantum critical behaviors are reproduced. Through the finite-size scaling analysis on magnetoresistivity, we show that the two quantum critical behaviors result from the intra-island and inter-island phase coherence, respectively, which are further illustrated by the phase diagram. This work provides a platform to study superconducting quantum phase transitions in a 2D system and helps to integrate superconducting devices into semiconductor technology. Two quantum critical behaviors appear in a two dimensional electron gas (2DEG) but its origin remains to be attested. Here, Sun et al. construct superconducting puddles-2DEG hybrid system by depositing tin nano-islands array on monolayer graphene where the two quantum critical behaviors are reproduced, suggesting the formation of inhomogeneous superconducting 2DEG.

MoO X (X < 3) has shown its promising potential as an efficient hole-selective passivating contact in crystalline Si solar cells. The device performance highly depends on the film properties of MoO X film, which is significantly affected by different synthesis methods. In this work, Si solar cells with c -Si( p )/MoO X rear contacts were demonstrated, where the MoO X films were realized by thermal evaporation (TE), atomic layer deposition (ALD), and UV-assisted ALD (UV-ALD) methods. A pronounced efficiency drop was disclosed with the order of TE, ALD, and UV-ALD MoO X . Subsequently, the contact propertieis, crystallinity, chemical states, roughness, density, and refractive indices of MoO X films were systematically characterized by a series of microscopic and spectroscopic analyses. It is found that the TE film is composed of nanocrystals, while ALD methods yield amorphous feature with a smaller density and refractive indices. A mild UV illumination (3.5 mW/cm 2 ) slightly reduces the film roughness, while a stronger (35 mW/cm 2 ) one increases the film density, roughness, and growth rate significantly.

Transient electronics that can disappear or degrade via physical disintegration or chemical reaction over a pre-defined operational period provide essential for their applications in implantable bioelectronics due to the complete elimination of the second surgical extraction. However, the dissolution of commonly utilized bioresorbable materials often accompanies hydrogen production, which may cause potential or irreparable harm to the human body. This paper introduces germanium nanomembrane-based bioresorbable electronic sensors, where the chemical dissolution of all utilized materials in biofluidic theoretically have no gaseous products. In particular, the superior electronic transport of germanium enables the demonstrated bioresorbable electronic sensors to successfully distinguish the crosstalk of different physiological signals, such as temperature and strain, suggesting the significant prospect for the construction of dual or multi-parameter biosensors. Systematical studies reveal the gauge factor and temperature coefficient of resistance comparable to otherwise similar devices with gaseous products during their dissolution.

The successful synthesis of wafer‐scale single crystalline graphene on semiconducting Ge substrate has been considered a significant breakthrough toward the manufacturing of graphene‐based electronic and photonic devices; however, the assumed extremely high electrical mobility has not been found yet due to the lack of an adequate characterization method. Herein, state‐of‐the‐art transfer methods are developed to encapsulate the single crystalline graphene, which is grown on semiconducting Ge(110), in two hexagonal boron nitride (hBN) flakes, then acquire its inherent electrical mobility precisely via edge‐contact technique. It is found that single crystalline graphene grown on Ge(110) possesses a maximum carrier mobility of over 100 000 cm2 V−1 s−1 at low temperatures (2.3 K), which is superior to that obtained from graphene grown on other nonmetal substrates. Due to the extremely high mobility, well‐defined quantum Hall effect and Shubnikov‐de Haas oscillations can be observed at low temperatures as well. The study suggests that the excellent carrier mobility of graphene grown on Ge(110) may open an avenue to develop the practical graphene‐based nanodevices with high performance. The graphene grown on 4 in. Ge(110) substrate is directly peeled from the substrate directly using the hexagonal boron nitride (hBN)‐assisted dry transfer method. In electrical transport measurements using the edge‐contact Hall device, hBN‐encapsulated graphene shows extremely high carrier mobility, resulting in the observation of quantum Hall effects and Shubnikov‐de Haas oscillations.

Near-infrared perfect wave harvesting of graphene is theoretically and numerically obtained in a hybrid dielectric configuration without assistance of a reflecting mirror. The absorption is increased 43-fold compared to a suspended graphene layer at normal incidence. The mechanism of perfect absorption is based on critical coupling with a guided resonance introduced by a silicon bar array and Fabry–Perot (FP) effect of a silicon oxide layer. This lossless design is expected to find applications to allow the active area with effective generation and fast transport of photocarriers, paving a new way for on-chip small-footprint ultrahigh responsivity and ultrahigh-speed photodetection in silicon photonics.