Nanofabrication Technology Research Articles

Quantum error correction with silicon spin qubits

Future large-scale quantum computers will rely on quantum error correction (QEC) to protect the fragile quantum information during computation1,2. Among the possible candidate platforms for realizing quantum computing devices, the compatibility with mature nanofabrication technologies of silicon-based spin qubits offers promise to overcome the challenges in scaling up device sizes from the prototypes of today to large-scale computers3–5. Recent advances in silicon-based qubits have enabled the implementations of high-quality one-qubit and two-qubit systems6–8. However, the demonstration of QEC, which requires three or more coupled qubits1, and involves a three-qubit gate9–11 or measurement-based feedback, remains an open challenge. Here we demonstrate a three-qubit phase-correcting code in silicon, in which an encoded three-qubit state is protected against any phase-flip error on one of the three qubits. The correction to this encoded state is performed by a three-qubit conditional rotation, which we implement by an efficient single-step resonantly driven iToffoli gate. As expected, the error correction mitigates the errors owing to one-qubit phase-flip, as well as the intrinsic dephasing mainly owing to quasi-static phase noise. These results show successful implementation of QEC and the potential of a silicon-based platform for large-scale quantum computing.

Visualizing Dynamic Environmental Processes in Liquid at Nanoscale via Liquid-Phase Electron Microscopy.

Visualizing the structure and processes in liquids at the nanoscale is essential for understanding the fundamental mechanisms and underlying processes of environmental research. Cutting-edge progress of in situ liquid-phase (scanning) transmission electron microscopy (LP-S/TEM) and inferred possible applications are highlighted as a more and more indispensable tool for visualization of dynamic environmental processes in this Perspective. Advancements in nanofabrication technology, high-speed imaging, comprehensive detectors, and spectroscopy analysis have made it increasingly convenient to use LP S/TEM, thus providing an approach for visualization of direct and insightful scientific information with the exciting possibility of solving an increasing number of tricky environmental problems. This includes evaluating the transformation fate and path of contamination, assessing toxicology of nanomaterials, simulating solid surface corrosion processes in the environment, and observing water pollution control processes. Distinct nanoscale or even atomic understanding of the reaction would provide dependable and precise identification and quantification of contaminants in dynamic processes, thus facilitating trouble-tracing of environmental problems with amplifying complexity.

Recent Developments and Current Applications of Organic Nanomaterials in Cartilage Repair

Regeneration of cartilage is difficult due to the unique microstructure, unique multizone organization, and avascular nature of cartilage tissue. The development of nanomaterials and nanofabrication technologies holds great promise for the repair and regeneration of injured or degenerated cartilage tissue. Nanomaterials have structural components smaller than 100 nm in at least one dimension and exhibit unique properties due to their nanoscale structure and high specific surface area. The unique properties of nanomaterials include, but are not limited to, increased chemical reactivity, mechanical strength, degradability, and biocompatibility. As an emerging nanomaterial, organic nanocomposites can mimic natural cartilage in terms of microstructure, physicochemical, mechanical, and biological properties. The integration of organic nanomaterials is expected to develop scaffolds that better mimic the extracellular matrix (ECM) environment of cartilage to enhance scaffold-cell interactions and improve the functionality of engineered tissue constructs. Next-generation hydrogel technology and bioprinting can be used not only for healing cartilage injury areas but also for extensive osteoarthritic degenerative changes within the joint. Although more challenges need to be solved before they can be translated into full-fledged commercial products, nano-organic composites remain very promising candidates for the future development of cartilage tissue engineering.

Integrated Polarization-Splitting Grating Coupler for Chip-Scale Atomic Magnetometer.

Atomic magnetometers (AMs) are widely acknowledged as one of the most sensitive kind of instruments for bio-magnetic field measurement. Recently, there has been growing interest in developing chip-scale AMs through nanophotonics and current CMOS-compatible nanofabrication technology, in pursuit of substantial reduction in volume and cost. In this study, an integrated polarization-splitting grating coupler is demonstrated to achieve both efficient coupling and polarization splitting at the D1 transition wavelength of rubidium (795 nm). With this device, linearly polarized probe light that experienced optical rotation due to magnetically induced circular birefringence (of alkali medium) can be coupled and split into individual output ports. This is especially advantageous for emerging chip-scale AMs in that differential detection of ultra-weak magnetic field can be achieved through compact planar optical components. In addition, the device is designed with silicon nitride material on silicon dioxide that is deposited on a silicon substrate, being compatible with the current CMOS nanofabrication industry. Our study paves the way for the development of on-chip AMs that are the foundation for future multi-channel high-spatial resolution bio-magnetic imaging instruments.

Zeeman and hyperfine interactions of a single Er3+167 ion in Si

Er-doped Si is a promising candidate for quantum information applications due to its telecom wavelength optical transition and its compatibility with Si nanofabrication technologies. Recent spectroscopic studies based on photoluminescence excitation have shown multiple well-defined lattice sites that Er occupies in Si. Here we report a measurement of the Zeeman and hyperfine tensors of a single $^{167}\mathrm{Er}^{3+}$ ion in Si. All the obtained tensors are highly anisotropic with the largest value principal axes aligning in nearly the same direction, and the trace of the lowest crystal field level $\mathbf{g}$-tensor is $17.78\ifmmode\pm\else\textpm\fi{}0.40$. The results indicate that this specific Er site is likely to be a distorted cubic site that exhibits monoclinic (${\mathrm{C}}_{1}$) symmetry. Finally, zero first-order-Zeeman fields are identified for this site and could be used to reduce decoherence of hyperfine spin states in future experiments.

The Transformation from Surface Wave into Radiation Wave Using Composite Subwavelength Holes Array

Smith–Purcell radiation (SPR) is a phenomenon in that free electrons moving above a periodic structure deliver a part of their kinetic energies to electromagnetic waves. It plays an important role in the development of radiation sources and beam diagnosis. With the development of nanofabrication technology, various complex micro-nano-metallic periodic or aperiodic structures have been adopted to improve the efficiency and coherence of SPR. In general, when free electrons move above the metallic periodic structure, the localized surface wave and Smith–Purcell radiation wave are excited simultaneously. As the frequency of the surface wave is always lower than the threshold of Smith–Purcell radiation, the surface wave cannot be radiated. Here, the surface wave is transformed into SPR by using a novel composite subwavelength hole array, thus the SPR is enhanced and it becomes coherent and easy to tune. This work provides a competitive approach to achieve a coherent and high-efficiency THz radiation source.

Applications of Titanium Dioxide Nanostructure in Stomatology

Breakthroughs in the field of nanotechnology, especially in nanochemistry and nanofabrication technologies, have been attracting much attention, and various nanomaterials have recently been developed for biomedical applications. Among these nanomaterials, nanoscale titanium dioxide (nano-TiO2) has been widely valued in stomatology due to the fact of its excellent biocompatibility, antibacterial activity, and photocatalytic activity as well as its potential use for applications such as dental implant surface modification, tissue engineering and regenerative medicine, drug delivery carrier, dental material additives, and oral tumor diagnosis and treatment. However, the biosafety of nano-TiO2 is controversial and has become a key constraint in the development of nano-TiO2 applications in stomatology. Therefore, in this review, we summarize recent research regarding the applications of nano-TiO2 in stomatology, with an emphasis on its performance characteristics in different fields, and evaluations of the biological security of nano-TiO2 applications. In addition, we discuss the challenges, prospects, and future research directions regarding applications of nano-TiO2 in stomatology that are significant and worthy of further exploration.

Deep-ultraviolet localized surface plasmon resonance using Ga nanoparticles

Localized surface plasmon resonance (LSPR) with Ga nanoparticles (NPs) was achieved and tuned over the entire deep-ultraviolet (DUV) wavelength range. Ga NPs with nano hemisphere structures were fabricated by combining vapor deposition and thermal annealing without top-down nanofabrication technology. We successfully fabricated Ga2O3 NPs by thermally annealing Ga NPs at high temperatures. The coating of Ga NPs with Al2O3 thin films prevented oxidation and improved the robustness of Ga NPs, which have a low melting point and are unstable at room temperature, enabling device applications. Furthermore, we fabricated a new NP structure with Ga or Ga2O3 located on Al mirror substrates, which can be applied to LSPR-enhanced light-emitting materials and devices.

Synthesis and Characterization of Boron Thin Films Using Chemical and Physical Vapor Depositions

Boron as thin film material is of relevance for use in modern micro- and nano-fabrication technology. In this research boron thin films are realized by a number of physical and chemical deposition methods, including magnetron sputtering, electron-beam evaporation, plasma enhanced chemical vapor deposition (CVD), thermal/non-plasma CVD, remote plasma CVD and atmospheric pressure CVD. Various physical, mechanical and chemical characteristics of these boron thin films are investigated, i.e., deposition rate, uniformity, roughness, stress, composition, defectivity and chemical resistance. Boron films realized by plasma enhanced chemical vapor deposition (PECVD) are found to be inert for conventional wet chemical etchants and have the lowest amount of defects, which makes this the best candidate to be integrated into the micro-fabrication processes. By varying the deposition parameters in the PECVD process, the influences of plasma power, pressure and precursor inflow on the deposition rate and intrinsic stress are further explored. Utilization of PECVD boron films as hard mask for wet etching is demonstrated by means of patterning followed by selective structuring of the silicon substrate, which shows that PECVD boron thin films can be successfully applied for micro-fabrication.

Enhanced Terahertz Generation From the Lithium Niobate Metasurface

The lithium niobate (LiNbO3) metasurface is an attractive platform for nonlinear frequency conversion due to its excellent nonlinearity, high damage threshold, and strong enhancement of the driving field. Here, we demonstrated the nonlinear metasurface for terahertz (THz) generation from LiNbO3on an insulator. The THz electric field from the LiNbO3metasurface of 300 nm thickness is enhanced by more than one order of magnitude compared to the unstructured sample. The enhanced terahertz electric field is very selective in the excitation wavelength due to its resonant feature and is highly anisotropic with respect to the excitation polarization. The polarization direction of the THz electric field can be controlled by rotating the optical axis of the LiNbO3metasurface. By combining the nanofabrication technology of the LiNbO3metasurface and ultrafast nonlinear optics, our work paves the way for the design of new compact terahertz photonic devices that integrate THz emitters into LiNbO3-based chips with multifaceted capabilities.

Multiple plasmonic hot spots platform: Nanogap coupled gold nanoparticles

Au-polymer-Au nanogap (Au-P-Au)-coupled gold nanoparticle (Au NP) platforms are fabricated via a combination of nanoskiving and polymer-assisted assembly. The structure consists of multiple types of nanogaps, specified as nanogaps within Au-P-Au, narrow nanogaps between assembled Au NPs, and nanogaps between Au NPs and the edge of the nanogap. The electric field is strongly enhanced in the nanogaps due to the confinement of incident light, generating multiple “hot spots”. The Au-P-Au-coupled Au NP platform promotes a significant surface-enhanced Raman scattering (SERS) performance, achieving a maximum enhancement factor of 1.36 × 108 and a sensitive detection of glucose. The united nanofabrication technology for Au-P-Au-coupled Au NP platforms with a considerable SERS enhancement would facilitate the applications of nonlinear optics, nano-photonics, and surface-enhanced spectroscopy.

Modeling of High-Performance SPR Refractive Index Sensor Employing Novel 2D Materials for Detection of Malaria Pathogens.

The present work exhibits a novel design of surface plasmon resonance (SPR) biosensor, which comprises CaF2 prism, TiO2, metal (Ag/Au), PtSe2, 2D materials (graphene/transition metal dichalcogenides (MoS2/WS2)) and sensing medium, for point-of-care detection of various stages of malaria diseases. The transfer matrix method (TMM) is employed to examine the angular reflectivity of the proposed structure after judiciously optimizing the layer thicknesses and layer numbers. Phase interrogation technique is utilised to validate the position of occurrence of resonance angles. Additionally, the proposed SPR structure is designed using COMSOL Multiphysics, to assay the electric field intensity and electric field enhancement factor near the edge of 2D material-sensing layer interface. Simulation upshots revealed that the use of new class of 2D materials catapult the sensor performance to a new height compared to the traditional SPR configuration. A maximum sensitivity of 240.10°/RIU, quality factor of 78.46 RIU-1 and detection accuracy of 1.99 is attained for Ag-based SPR configuration with bilayer of WS2. Sensing parameters are compared with previously reported works to prove the superiority of the present research. Moreover, the real-time and label-free detection of malaria diseases makes the suggested sensor worth to fabricate as a SPR chip with the recent nanofabrication technologies.

Manipulation and readout of spin states of a single-molecule magnet by a spin-polarized current

Single-molecule memory device based on a single-molecule magnet (SMM) is one of the ultimate goals of semiconductor nanofabrication technologies. Here, we study how to manipulate and readout the SMM's two spin-state of stored information that characterized by the maximum and minimum average value of the $Z$-component of the total spin of the SMM and the conduction-electron, which are recognized as the information bits "$1$" and "$0$". We demonstrate that the switching time depends on both the sequential tunneling gap $\varepsilon_{se}$ and the spin-selection-rule allowed transition-energy $\varepsilon_{trans}$, which can be tuned by the gate voltage. In particular, when the external bias voltage is turned off, in the cases of the unoccupied and doubly-occupied ground eigenstates, the time derivative of the transport current can be used to read out the SMM's two spin-state of stored information. Moreover, the tunneling strength of and the asymmetry of the SMM-electrode coupling have a strong influence on the switching time, but that have a slight influence on the readout time that being on the order of nanoseconds. Our results suggest a SMM-based memory device, and provide fundamental insight into the electrical controllable manipulation and readout of the SMM's two spin-state of stored information.

Detecting nonlocality by second-harmonic generation from a graphene-wrapped nanoparticle.

With the rapid development of nanofabrication technology and nonlinear optics, the nonlinear detection by nanostructures is highly appreciated. In this paper, we study the second-harmonic generation by a spherical nonlocal plasmonic nanoparticle wrapped with graphene. We develop a simple method for calculating the electric field at second-harmonic frequency and analyze the influence of the nonlocal response of the metal on the second-harmonic. We find that this nanostructure can probe the material's properties by detecting the radiation intensity of the second-harmonic generation. In addition, the nonlocal response of the plasmonic core can promote the absorption efficiency of second-harmonic generation. Our study may offer a new way for studying the plasmonic quantum effects and nonlinear probing technology and improving the nonlinear conversion efficiency of photonic devices.

Gaptronics: multilevel photonics applications spanning zero-nanometer limits

Abstract With recent advances in nanofabrication technology, various metallic gap structures with gap widths reaching a few to sub-nanometer, and even ‘zero-nanometer’, have been realized. At such regime, metallic gaps not only exhibit strong electromagnetic field confinement and enhancement, but also incorporate various quantum phenomena in a macroscopic scale, finding applications in ultrasensitive detection using nanosystems, enhancement of light–matter interactions in low-dimensional materials, and ultralow-power manipulation of electromagnetic waves, etc. Therefore, moving beyond nanometer to ‘zero-nanometer’ can greatly diversify applications of metallic gaps and may open the field of dynamic ‘gaptronics.’ In this paper, an overview is given on wafer-scale metallic gap structures down to zero-nanometer gap width limit. Theoretical description of metallic gaps from sub-10 to zero-nanometer limit, various wafer-scale fabrication methods and their applications are presented. With such versatility and broadband applicability spanning visible to terahertz and even microwaves, the field of ‘gaptronics’ can be a central building block for photochemistry, quantum optical devices, and 5/6G communications.

Single-layer metalens for achromatic focusing with wide field of view in the visible range

Metalenses have attracted extensive attention due to their capability of flexible wavefront manipulation by subwavelength nanostructures. However, the development of metalenses has been deeply limited by the field of view (FOV) and spectral bandwidth. Existing wide FOV and achromatic metalenses usually adopt cascaded metasurfaces to correct aberrations, resulting in inevitable challenges for nano-fabrication technologies. In this paper, we design a wide FOV metalens with a numerical aperture of 0.24 which can provide a diffraction-limited FOV for over 40° at three discrete wavelengths of 473 nm (blue), 532 nm (green), and 632.8 nm (red). The metalens involves only a single layer of metasurface integrated on a flat substrate to correct aberration. This method considerably simplifies the architectures compared with the cascaded metalenses and conventional bulky optical systems. In addition, an achromatic wide FOV metalens with an operating wavelength range from 492 to 592 nm is further designed to demonstrate the generality of the proposed method. The simulated results indicate that metalenses have a great achromatic and diffraction-limited focusing performance within a large incident angle region, which is expected to have promising applications in imaging, holography, machine vision, and other fields.

Correlative AFM and Scanning Microlens Microscopy for Time-Efficient Multiscale Imaging.

With the rapid evolution of microelectronics and nanofabrication technologies, the feature sizes of large‐scale integrated circuits continue to move toward the nanoscale. There is a strong need to improve the quality and efficiency of integrated circuit inspection, but it remains a great challenge to provide both rapid imaging and circuit node‐level high‐resolution images simultaneously using a conventional microscope. This paper proposes a nondestructive, high‐throughput, multiscale correlation imaging method that combines atomic force microscopy (AFM) with microlens‐based scanning optical microscopy. In this method, a microlens is coupled to the end of the AFM cantilever and the sample‐facing side of the microlens contains a focused ion beam deposited tip which serves as the AFM scanning probe. The introduction of a microlens improves the imaging resolution of the AFM optical system, providing a 3–4× increase in optical imaging magnification while the scanning imaging throughput is improved ≈8×. The proposed method bridges the resolution gap between traditional optical imaging and AFM, achieves cross‐scale rapid imaging with micrometer to nanometer resolution, and improves the efficiency of AFM‐based large‐scale imaging and detection. Simultaneously, nanoscale‐level correlation between the acquired optical image and structure information is enabled by the method, providing a powerful tool for semiconductor device inspection.

3‐D Nanofabrication of Silicon and Nanostructure Fine‐Tuning via Helium Ion Implantation

AbstractDespite the continued scaling down of semiconductor manufacturing, traditional lithography‐based nanofabrication only produces thin film structures, not 3‐D shapes. 3‐D nanofabrication remains a major challenge, especially for semiconductor materials. Most 3‐D nanofabrication techniques, such as two‐photon printing and stereolithography, mostly work for polymer materials, not solid‐state semiconductor materials. Here, a method capable of fabricating sophisticated 3‐D nanostructures of silicon based on the subsurface swelling phenomenon using focused helium ion swelling is reported. Silicon nanosphere arrays, hierarchical nanospheres mimicking compound lenses, nano‐Taichi symbols, three‐layer nanotowers, and nanopumpkins have been demonstrated, which are challenging for existing nanofabrication technology. The produced silicon nanostructures exhibit super small surface roughness as small as 0.1 nm, two orders of magnitude better than existing 3‐D nanofabrication technologies normally above 10 nm. The super small surface roughness opens doors for many exciting applications in photonics, indicating small photon losses. Moreover, it is demonstrated ultraprecise fine‐tuning of critical dimensions of ready‐made nanostructures or nanodevices, such as tuning the tilting angle of the tip on the atomic force microscopy probe and reducing the nanogap between two metal electrodes from 200 to 4 nm, which is promising for improving nanodevice performances by tuning the critical dimensions to desired ranges.

Cellular nanointerface of vertical nanostructure arrays and its applications.

Vertically standing nanostructures with various morphologies have been developed with the emergence of the micro-/nanofabrication technology. When cells are cultured on them, various bio–nano interfaces between cells and vertical nanostructures would impact the cellular activities, depending on the shape, density, and height of nanostructures. Many cellular pathway activation processes involving a series of intracellular molecules (proteins, RNA, DNA, enzymes, etc.) would be triggered by the cell morphological changes induced by nanostructures, affecting the cell proliferation, apoptosis, differentiation, immune activation, cell adhesion, cell migration, and other behaviors. In addition, the highly localized cellular nanointerface enhances coupled stimulation on cells. Therefore, understanding the mechanism of the cellular nanointerface can not only provide innovative tools for regulating specific cell functions but also offers new aspects to understand the fundamental cellular activities that could facilitate the precise monitoring and treatment of diseases in the future. This review mainly describes the fabrication technology of vertical nanostructures, analyzing the formation of cellular nanointerfaces and the effects of cellular nanointerfaces on cells' fates and functions. At last, the applications of cellular nanointerfaces based on various nanostructures are summarized.

DNA Nanotechnology-Enabled Fabrication of Metal Nanomorphology.

In recent decades, DNA nanotechnology has grown into a highly innovative and widely established field. DNA nanostructures have extraordinary structural programmability and can accurately organize nanoscale materials, especially in guiding the synthesis of metal nanomaterials, which have unique advantages in controlling the growth morphology of metal nanomaterials. This review started with the evolution in DNA nanotechnology and the types of DNA nanostructures. Next, a DNA-based nanofabrication technology, DNA metallization, was introduced. In this section, we systematically summarized the DNA-oriented synthesis of metal nanostructures with different morphologies and structures. Furthermore, the applications of metal nanostructures constructed from DNA templates in various fields including electronics, catalysis, sensing, and bioimaging were figured out. Finally, the development prospects and challenges of metal nanostructures formed under the morphology control by DNA nanotechnology were discussed.