Nanomembranes Research Articles

Strain Engineered Semiconductor Nanomembranes for Photonic and Optoelectronic Applications

AbstractWhen semiconductor crystals are made into the form of thin sheets, i.e., nanomembranes, their properties and behaviors may be remarkably different from their bulk counterparts. A plethora of fascinating science and important applications arise consequently, some of which are investigated in recent years, and there are still a lot more to be discovered in the future. Nanomembranes (NMs) provide a good platform for strain engineering and offer tremendous research opportunities in photonics and optoelectronics applications. Strain alters energy band line up of a material furthermore influencing its carrier mobility which impacts a wide range of applications. In this article, the strain‐engineered NMs are reviewed using semiconductor materials as a model system for photonics and optoelectronics applications. While many fundamental aspects of NMs are discussed and outlined different methods for strain engineering of NM, the use of semiconductor NMs for photonics and optoelectronics applications is the locus of the present review article.

Non-enzymatic cholesterol biosensor: Electrochemical sensing based on peptide-polylactic acid thin film

Cholesterol is a fundamental lipid prevalent in eukaryotic cell membranes and circulating in the bloodstream bound to lipoproteins. It serves as a precursor to steroid hormones and is regarded as a biomarker for cardiovascular disease and other metabolic disorders. Numerous cholesterol detection methods predominantly rely on enzymes, which suffer from instability, leading to non-cost-effective biosensors with low sensitivity and poor reusability. Therefore, monitoring cholesterol levels with a feasible, rapid, and stable biosensor is critical for diagnosing and treating various disorders. This study aimed to develop a non-enzymatic cholesterol biosensor based on a selected cholesterol recognition peptide as the detection element. Screen-printed carbon electrodes (SPEs) modified with biocompatible poly-L-lactic acid (PLLA) porous nanomembranes (NMs) were utilized as support for the covalent immobilization of the peptide. Data obtained from electrochemical impedance spectroscopy (EIS) demonstrated the peptide's effective binding affinity towards cholesterol, paving the way for its implementation. The determination of cholesterol with the proposed biosensor exhibited a low limit of detection of 6.31 μM with linear responses ranging from 2–15 μM and 20–40 μM. These findings present an alternative method for cholesterol sensing by integrating novel peptides as biorecognition motifs with biocompatible polymeric materials, potentially useful as biocompatible and future point-of-care sensors.

Nucleation-Limited Kinetics of GaAs Nanostructures Grown by Selective Area Epitaxy: Implications for Shape Engineering in Optoelectronics Devices.

The growth kinetics of vertical III-V nanowires (NWs) were clarified long ago. The increasing aspect ratio of NWs results in an increase in the surface area, which, in turn, enhances the material collection. The group III adatom diffusion from the NW sidewalls to the top sustains a superlinear growth regime. In this work, we report on the growth of different GaAs nanostructures by selective area MOVPE on GaAs (111)B substrates. We show that the opening dimensions and geometry qualitatively alter the morphology and height evolution of the structures. We compare the time evolution of vertical GaAs NWs stemming from circular holes and horizontal GaAs nanomembranes (NMs) growing from one-dimensional (1D) rectangular slits on the same substrate. While NW heights grow exponentially with time, NMs surprisingly exhibit sublinear kinetics. The absence of visible atomic steps on the top facets of both NWs and NMs suggests layer-by-layer growth in the mononuclear mode. We interpret these observations within a self-consistent growth model, which links the diffusion flux of Ga adatoms to the position- and shape-dependent nucleation rate on top of NWs and NMs. Specifically, the island nucleation rate is lower on top of the NMs than that on the NWs, resulting in the total diffusion flux being directed from the top facet to the sidewalls. This gives a sublinear height evolution for the NMs. These results open innovative perspectives for shape engineering of III-V nanostructures and new avenues for the design of optoelectronics and photonic devices.

A study on preparation of low-cost environment-friendly self-assembled nanocellulose membrane from waste paper

In the context of green development, different types of waste paper were used in this study to prepare environment-friendly nanocellulose membrane by using different pretreatment processes. The results showed that all nanocellulose membranes had a novel microscopic composite morphology: nanocellulose fibers in the middle were tightly arranged and had a certain direction, while nanocellulose fibers at the edge were arranged randomly. Moreover, the type of waste paper affected the formation and property of nanocellulose membranes deeply compared with the pretreatment process. Nanocellulose membrane prepared from office waste paper had a high transmittance (50.8 %) and low oxygen transmission rate (1.548·10−3/cm3mm/(m2·d·KPa)) while that prepared from waste corrugated paper had a high yield (50.63 %), high folding number (81 times), and low water vapor transmission rate (1550.24 g·m−2·day−1). Meanwhile, nanocellulose membrane prepared without any deinking treatment had a significant performance advantage in terms of water vapor barrier and folding resistance. Therefore, in actual application, deinking treatment can be selectivity omitted, which will simplify the preparation process flow and reduce the production cost of nanocellulose membrane. Furthermore, in order to satisfy different application requirements, the appropriate raw materials and treatment processes can be chosen to prepare nanocellulose membranes with different properties. This study provides a simple and low-cost way to prepare high-performance environment-friendly self-assembled nano membrane material, and also achieves the high value utilization of waste paper, which has a certain ecological, economic, and social benefits.

P-GaAs/n-Ga2O3 heterojunction diode with breakdown voltage of ∼800 V

As an attractive next generation ultrawide bandgap material, Ga2O3 has been demonstrated to be capable of high voltage operation. However, the lack of shallow p-type dopant in Ga2O3 leads to difficulties in developing Ga2O3 based bipolar devices. The semiconductor grafting technology, by bonding a single crystalline p-type semiconductor nanomembrane (NM) to n-Ga2O3 to from abrupt heterojunction, offers a way to expand the application of Ga2O3 in bipolar areas. In this Letter, we report a p-GaAs/(001)-Ga2O3 heterojunction diode fabricated using semiconductor grafting technology. The single crystalline GaAs NM was prepared and transferred onto a Ga2O3 substrate, showing good integrity. Diodes of a mesa diameter of 25 μm were fabricated, showing a high breakdown voltage of ∼800 V, a power figure of merit of 126.5 MW/cm2, and a calculated 1D peak electric field of 1.60 MV/cm. The turn on voltage of the diode was determined to be around 1.91 V with an on–off ratio to be 6 × 106 at −4/4 V and the specific on resistance to be 5.06 mΩ cm2. The ideality factor was extracted to be approximately 1.34, indicating reasonable interface quality. The interfacial defects and the self-passivation effects of Ga2O3 are discussed, and the theoretical band diagram was analyzed for the p-GaAs/n-Ga2O3 heterojunction. By managing the peak electric field with suitable edge termination techniques, higher breakdown voltage can be expected. In addition, by taking advantage of the InGaAsP alloy system, a wide variety of GaAs-Ga2O3 based high voltage HBT can be further developed.

Strain modulation in crumpled Si nanomembranes: Light detection beyond the Si absorption limit.

Although Si is extensively used in micro-nano electronics, its inherent optical absorption cutoff at 1100-nm limits its photonic and optoelectronic applications in visible to partly near infrared (NIR) spectral range. Recently, strain engineering has emerged as a promising approach for extending device functionality via tuning the material properties, including change in optical bandgap. In this study, the reduction in bandgap with applied strain was used for extending the absorption limit of crystalline Si up to 1310 nm beyond its intrinsic bandgap, which was achieved by creating the crumpled structures in Si nanomembranes (NMs). The concept was used to develop a prototype NIR image sensor by organizing metal-semiconductor-metal-configured crumpled Si NM photosensing pixels in 6 × 6 array. The geometry-controlled, self-sustained strain induction in Si NMs provided an exclusive photon management with shortening of optical bandgap and enhanced photoresponse beyond the conventional Si absorption limit.

Sequential fabrication of multiple Ge nanomembranes from a single wafer: Towards sustainable recycling of Ge substrates

Germanium (Ge) substrates are employed for III-V multijunction solar cells (MJSCs). However, due to limited availability and environmental impact, Ge is a critical raw material. Detachable Ge nanomembranes (NMs) are gaining attention to reduce Ge consumption through substrate reuse. The Porous germanium Efficient Epitaxial LayEr Release (PEELER) process enables Ge NM detachment and substrate reuse, reducing costs and Ge material consumption. In this work, we demonstrate the sequential production of three NMs from one parent substrate using the PEELER process, yielding monocrystalline NMs, with a surface suitable for further epitaxial growth of III-V layers (RMS < 3.2 nm). By avoiding the costly Chemical Mechanical Polishing (CMP), our approach enables a more economical and sustainable production of high-efficiency Ge-based solar cells, compared to the conventional production process.

Experimental research on enhancing heat and mass transfer of porous ceramic membrane with acoustic field

Transport membrane condenser is a water heat recovery technology based on condensation mechanism. Limited by the price of ceramic membrane, it focuses on enhancing the heat and mass transfer technology of ceramic membrane. Acoustic enhancement of heat and mass transfer is an efficient enhancement method. In order to explore the heat and mass transfer characteristics of ceramic membrane enhanced by audible sound field under different condensation mechanisms, the corresponding experimental platform was built. The results show that due to the condensation characteristics of capillary condensation, the heat and mass transfer performance of the nano membrane under the action of sound field is greatly improved, with a maximum increase of 53.44% and 53.22%, respectively; This article presents an analysis of the economic advantages of utilizing acoustic waves in conjunction with ceramic membranes. It is found that the recovery period can be shortened by 3.2 years when acoustic waves are employed. The findings of this study offer a valuable foundation for improving heat and mass transfer in flue gas moisture recovery systems utilizing ceramic membranes.

Development of high performance thin-film (nano) composite membranes for forward osmosis desalination applications- a review

The impact of different additives on the achievement of FO membranes was designed, reviewed, and highlighted the performances of nanocomposite over traditional membranes with evidenced literature support. This review found that the surface hydrophilicity, roughness, porosity, FO water permeation, solute retention, reverse solute permeates (RSP), and specific reverse salt permeate (SRSP) has been greatly affected by the alteration of a skin layered structure of FO membrane. The review revealed that the TFN-FO membranes showed very high surface hydrophilic properties than the TFC-FO membranes. For example, the graphene quantum dots (GODs) based UiO66-NH2 crystals (GQDs@UiO66-NH2, 250 ppm, TFN-0.25%) membrane had a goniometer (contact angle) reading of 12° which indicated a super-hydrophilic property of nanocomposite membrane over traditional TFC membranes. In addition, the TFN-FO membrane showed the highest FO permeation rate of 84.7 L m-2h−1 for the ZnO-based TFN membrane (TFN-ZnO-0.5) and a very lower RSP value of 0.005 g/L for nylon-6 (N6) substrate containing silica dioxide (SiO2) nano particle (NP) support membrane with polyamide (PA) layer nano membrane (E. Spun N6/SiO2-PA/SiO2 TFN) suggested an excellent FO performance than TFC membranes. This review also suggested that the TFN membranes provided enhanced salt rejection and FO water flux with superior fouling resistant properties which are important parameters to enhance FO performances. Hence, TFN-FO membranes can utilize as a suitable candidate for desalination applications compared to TFC membranes.

Identifying the features of surface roughness and H2 bubble production on the super-hydrophobic properties of Al2O3 and Mg membranes

This research investigates Alumina (Al2O3) and Magnesium nano membrane layers using hybrid technology. Hybrid is a concept of combining two or more materials/elements to achieve something better. Hybrid technology was developed because of the possibility of combining materials/elements which, if used simultaneously, has more advantages than if used independently. The problem to be solved is to find the best composition of Alumina and Magnesium hybrid membranes. Superhydrophobic properties of the membrane are achieved at a percentage of Mg: 50 %, Al2O3:50 %. At a composition below 50 % Mg, the small surface roughness has a low surface tension, while the H2 production reaction by Mg is also low, so the surface tension carrying capacity of the gas and the roughness of the droplets is not strong, which causes the hydrophobicity to be low. In compositions above 50 % Mg, H2 production by high Mg makes bubbles cover the roughness peaks so that the surface tension is lower and changes the superhydrophobic to hydrophobic properties. At a high Mg percentage, H2 production is very large, while surface roughness decreases due to minimal Al2O3. As a result, the roughness grooves are unable to accommodate H2 gas bubbles, the bubbles completely cover the roughness peaks which are the source of surface tension so that the hydrophobic properties become hydrophilic. The results of this best hybrid composition can be used as a guide in making superhydrophobic membranes on Alumina (Al2O3) and Magnesium alloys. This membrane application is used as a filtration membrane in the water purification process. Superhydrophobic membranes are widely applied in membrane distillation, membrane gas absorption and pervaporation

Advances in Functionalization of Bioresorbable Nanomembranes and Nanoparticles for Their Use in Biomedicine.

Bioresorbable nanomembranes (NMs) and nanoparticles (NPs) are powerful polymeric materials playing an important role in biomedicine, as they can effectively reduce infections and inflammatory clinical patient conditions due to their high biocompatibility, ability to physically interact with biomolecules, large surface area, and low toxicity. In this review, the most common bioabsorbable materials such as those belonging to natural polymers and proteins for the manufacture of NMs and NPs are reviewed. In addition to biocompatibility and bioresorption, current methodology on surface functionalization is also revisited and the most recent applications are highlighted. Considering the most recent use in the field of biosensors, tethered lipid bilayers, drug delivery, wound dressing, skin regeneration, targeted chemotherapy and imaging/diagnostics, functionalized NMs and NPs have become one of the main pillars of modern biomedical applications.

Preparation and Characterization of Nano Membrane for Fuel Cell

The preparation of apolymeric membrane by a chemical method was introduced for a Polymer Electrolyte Membrane (PEM) fuel cell. Cobalt oxide (Co3O5) was used in the coexistent of two polymers to speed up the reaction process and to obtain the best results. Different tests were implemented along the research to evaluate the new membrane such as X-ray, Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared Spectroscopy (FTIR). The new membrane shown an increment both in the current (I) and the volume of Hydrogen (H2) at a constant voltage (V).

Pushing On-Chip Photosensitivity Forward Using Edge-Driven Vertical Organic Phototransistors

Developing high-performance photosensors using prototype device architectures is essential to pushing forward developing and advancing next-generation optoelectronic applications. This work reports an organic phototransistor (OPT) with an ultra-short conducting channel (tens of nanometers) and outstanding photoelectric conversion efficiency. The OPT is based on a vertical organic field-effect transistor (VOFET) architecture, which utilizes a rolled-up metallic nanomembrane (NM) as the drain electrode and a photolithographically patterned (rectangular-shaped) perforated source electrode. These features expand the concept of conventional VOFETs as the former enables the incorporation of ultra-thin active layers and allows reliable control over gate-induced modulation of channel current. Using the engineering as abovementioned strategies, we focused on obtaining an improved device performance, studying their fundamental operating principle, and further investigating their application as photosensors. The optimized devices exhibited low operating voltages (<5 V) and enhanced on/off current ratio (∼105). The VOFET photoresponse was characterized by measuring the electrical characteristics in the dark and under illumination using three different monochromatic light colors. Under blue light, our devices demonstrated impressive photosensitivity (Pmax ≈ 105) and fast photoelectric conversion (steep light-induced threshold voltage shift), demonstrating that the rolled-up NM OPT shows excellent potential as a highly sensitive photodetector with low power consumption.

Synthesis and Characteristics of Transferrable Single‐Crystalline AlN Nanomembranes

AbstractSingle‐crystalline inorganic semiconductor nanomembranes (NMs) have attracted great attention over the last decade, which poses great advantages to complex device integration. Applications in heterogeneous electronics and flexible electronics have been demonstrated with various semiconductor nanomembranes. Single‐crystalline aluminum nitride (AlN), as an ultrawide‐bandgap semiconductor with great potential in applications such as high‐power electronics has not been demonstrated in its NM forms. This very first report demonstrates the creation, transfer‐printing, and characteristics of the high‐quality single‐crystalline AlN NMs. This work successfully transfers the AlN NMs onto various foreign substrates. The crystalline quality of the NMs has been characterized by a broad range of techniques before and after the transfer‐printing and no degradation in crystal quality has been observed. Interestingly, a partial relaxation of the tensile stress has been observed when comparing the original as‐grown AlN epi and the transferred AlN NMs. In addition, the transferred AlN NMs exhibits the presence of piezoelectricity at the nanoscale, as confirmed by piezoelectric force microscopy. This work also comments on the advantages and the challenges of the approach. Potentially, the novel approach opens a viable path for the development of the AlN‐based heterogeneous integration and future novel electronics and optoelectronics.

Integration of Conductive Nanocomposites and Nanomembranes for High‐Performance Stretchable Conductors

Stretchable metallic nanocomposites are viable material candidates for high‐performance soft biointerfacing electrodes. However, it is still challenging to fabricate a stretchable metallic nanocomposite that features outstanding charge transfer capability and low impedance as well as high conductivity and mechanical stability. Herein, a material strategy for a stretchable conductor that meets such requirements by integrating stretchable conductive nanocomposites with stretchable conductive nanomembranes (NMs) is presented. The silver nanowire (Ag NW) NM fabricated by the float assembly method is integrated with the Ag NW nanocomposite prepared by the drop‐casting method. The compactly assembled NWs in the NM maximize conductivity by reinforcing the percolation networks of the nanocomposite. Moreover, the NM lowers impedance by allowing efficient charge transfer to the target tissue through the exposed NWs. After their integration, a high conductivity of ≈35 700 S cm−1 is obtained, and the impedance is decreased by ≈88.9% (at 1000 Hz) in comparison with the original Ag NW‐based nanocomposite (i.e., without integration of the NM). The soft bioelectrode using the stretchable conductor successfully records electrograms from the rat heart, recognizes various arrhythmic events, and applies feedback pacing.

Theory of diffusion-induced selective area growth of III-V nanostructures

Selective area growth of nanomembranes (NMs), nanofins, and planar nanowires (NWs) can pave the way for monolithic integration of III-V photonics with Si electronics and enable fabrication of scalable NW networks required for fundamental studies in low-temperature transport physics. Herein, we present an attempt to develop the kinetic growth theory of III-V NMs and related nanostructures in selective area epitaxy. The growth process is assumed to be driven by surface diffusion of group III adatoms. The populations of adatoms diffusing on the mask surface, NM sidewalls, and the top are described by three diffusion equations linked by six boundary conditions. The resulting growth equation provides the NM height as a function of time, slit width and pitch, and deposition conditions. The width and pitch dependences of the NM growth rate are found to be qualitatively different for different directions of the adatom diffusion fluxes (from the mask surface onto the NM or in the opposite direction). A good correlation of the model with the data on the growth kinetics of GaAs NMs by selective area molecular beam epitaxy is demonstrated.

Strong Plasmon-Mie Resonance in Si@Pd Core-Ω Shell Nanocavity.

The surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR) can be used to enhance the generation of the hot electrons in plasmon metal nanocavity. In this paper, Pd nanomembrane (NMB) is sputtered on the surface of Si nanosphere (NS) on glass substrate to form the Si@Pd core-Ω shell nanocavity. A plasmon-Mie resonance is induced in the nanocavity by coupling the plasmon resonance with the Mie resonance to control the optical property of Si NS. When this nanocavity is excited by near-infrared-1 (NIR-1, 650 nm-900 nm) femtosecond (fs) laser, the luminescence intensity of Si NS is dramatically enhanced due to the synergistic interaction of plasmon and Mie resonance. The generation of resonance coupling regulates resonant mode of the nanocavity to realize multi-dimensional nonlinear optical response, which can be utilized in the fields of biological imaging and nanoscale light source.

Resonance Coupling in Si@WS2Core-Ω Shell Nanostructure.

Realizing strong laser-matter interaction in a heterostructure consisting of two-dimensional transition metal dichalcogenides (TMDCs) and an optical nanocavity is a potential strategy for novel photonic devices. In this paper, two core-Ω shell nanostructures, Si@WS2 core-Ω shell nanostructure on glass/Si substrates, are briefly introduced. A strong laser-matter interaction occurred in the Si@WS2 core-Ω shell nanostructure when it was excited by femtosecond (fs) laser in the near-infrared-1 region (NIR-1, 650 nm-950 nm), resulting in a resonance coupling between the electric dipole resonance (EDR) of the Si nanosphere (NS) and the exciton resonance of the WS2 nanomembrane (NMB). The generation of resonance coupling regulates the resonant mode of the nanostructure to realize the multi-dimensional nonlinear optical response, which can be utilized in the fields of biological imaging and nanoscale light source.

Wafer-scale detachable monocrystalline germanium nanomembranes for the growth of III-V materials and substrate reuse.

Germanium (Ge) is increasingly used as a substrate for high-performance optoelectronics, photovoltaics, and electronic devices. These devices are usually grown on thick and rigid Ge substrates manufactured by classical wafering techniques. Nanomembranes (NMs) provide an alternative to this approach while offering wafer-scale lateral dimensions, weight reduction, waste limitation, and cost effectiveness. Herein, we introduce the Porous germanium Efficient Epitaxial LayEr Release (PEELER) process, which consists of the fabrication of wafer-scale detachable Ge NMs on porous Ge (PGe) and substrate reuse. We demonstrate the growth of Ge NMs with monocrystalline quality as revealed by high-resolution transmission electron microscopy (HRTEM) characterization. Together with the surface roughness below 1 nm, it makes the Ge NMs suitable for growth of III-V materials. Additionally, the embedded nanoengineered weak layer enables the detachment of the Ge NMs. Finally, we demonstrate the wet-etch-reconditioning process of the Ge substrate, allowing its reuse, to produce multiple free-standing NMs from a single parent wafer. The PEELER process significantly reduces the consumption of Ge in the fabrication process, paving the way for a new generation of low-cost flexible optoelectronic devices.

Improved Tunneling Property of p+Si Nanomembrane/n+GaAs Heterostructures through Ultraviolet/Ozone Interface Treatment

Here, heterostructures composed of p+Si nanomembranes (NM)/n+GaAs were fabricated by ultraviolet/ozone (UV/O3, UVO) treatment, and their tunneling properties were investigated. The hydrogen (H)-terminated Si NM was bonded to the oxygen (O)-terminated GaAs substrate, leading to Si/GaAs tunnel junctions (TJs). The atomic-scale features of the H-O-terminated Si/GaAs TJ were analyzed and compared to those of Si/GaAs heterojunctions with no UVO treatment. The electrical characteristics demonstrated the emergence of negative differential resistance, with an average peak-to-valley current ratio of 3.49, which was examined based on the band-to-band tunneling and thermionic emission theories.