Conformal Deposition Research Articles

Addressing fabrication challenges in perovskite-silicon tandem solar cells with advanced simulation techniques

Abstract In the pursuit of higher conversion efficiency, the PV industry has turned its focus towards perovskite-silicon tandem solar cells, which currently represent the peak of innovation. To surpass the efficiency limits of traditional single-junction cells, researchers are exploring the potential of these tandem solar cells by integrating the merits of perovskite and silicon. However, integrating these cells brings different challenges, such as deposition methods and material misalignments. Thus, in this work, we are using advanced simulation techniques, including Silvaco ATLAS’s Victory Process and Device Simulator to imitate the actual manufacturing processes. Primarily this research work focuses on three scenarios: shunting, planarization and conformal deposition to emulate the experimental conditions. The obtained results show the potential and effectiveness of process simulations in accurately predicting and improving the PV performance of the tandem solar cell. Two different perovskite-silicon tandem solar cells are designed using process simulations which showed a conversion efficiency of 27.51% and 29.08% respectively. This work highlights the importance of using simulation tools for the further development of tandem solar cell technology. Detailed process and device simulations reported in this work may pave the way in the fabrication of optimised perovskite/silicon tandem solar cell.

Single-step, conformal, and efficient assembly of ligand-exchanged quantum dots for optoelectronic devices via an electric field.

Quantum dots (QDs) are promising materials for optoelectronic applications, but their widespread adoption requires controllable, selective, and scalable deposition methods. While traditional methods like spin coating and drop casting are suitable for small-scale deposition onto flat substrates, and ink-jet printing offers precision for small areas, these methods struggle with conformal deposition onto non-planar, large area substrates or selective deposition onto large area chips. Electrophoretic deposition (EPD) is an efficient and versatile technique capable of achieving conformal and selective area deposition over large areas, but its application to QD films has been limited. Previous EPD studies on QD films used QDs with native ligands, which hinder charge transport in optoelectronic devices. Here, we combined in-solution ligand exchange with EPD to deposit dense PbSe QD films. Through solvent engineering, we controlled the growth rate of PbSe QD films and used an in situ quartz crystal microbalance to measure the growth rate as a function of applied potential. We demonstrated the efficacy of this methodology by conformally depositing PbSe QD films onto textured silicon substrates via EPD and fabricating infrared photodetectors. The responsivity of the as-fabricated IR PDs at 1200 nm was ∼0.01 A W-1 and response times were 4.6 ms (on) and 4.7 ms (off).

Fabrication of nonplanar tapered fibers to integrate optical and electrical signals for neural interfaces in vivo.

Implantable multifunctional probes have transformed neuroscience research, offering access to multifaceted brain activity that was previously unattainable. Typically, simultaneous access to both optical and electrical signals requires separate probes, while their integration into a single device can result in the emergence of photogenerated electrical artifacts, affecting the quality of high-frequency neural recordings. Among the nontrivial strategies aimed at the realization of an implantable multifunctional interface, the integration of optical and electrical capabilities on a single, minimally invasive, tapered optical fiber probe has been recently demonstrated using fibertrodes. Fibertrodes require the application of a set of planar microfabrication techniques to a nonplanar system with low and nonconstant curvature radius. Here we develop a process based on multiple conformal depositions, nonplanar two-photon lithography and chemical wet etching steps to obtain metallic patterns on the highly curved surface of the fiber taper. We detail the manufacturing, encapsulation and back end of the fibertrodes. The design of the probe can be adapted for different experimental requirements. Using the optical setup design, it is possible to perform angle selective light coupling with the fibertrodes and their implantation and use in vivo. The fabrication of fibertrodes is estimated to require 5-9 d. Nonetheless, due to the high scalability of a large part of the protocol, the manufacture of multiple fibertrodes simultaneously substantially reduces the required time for each probe. The procedure is suitable for users with expertise in microfabrication of electronics and neural recordings.

Incorporating thermal co-evaporation in current-matched all-perovskite triple-junction solar cells.

Thermal co-evaporation of halide perovskites is a solution-free, conformal, scalable, and controllable deposition technique with great potential for commercial applications, particularly in multi-junction solar cells. Monolithic triple-junction perovskite solar cells have garnered significant attention because they can achieve very high efficiencies. Nevertheless, challenges arise in fabricating these devices, as they require multiple layers and precise current matching across complex absorber stacks. Here we demonstrate a current-matched monolithic all-perovskite p-i-n triple-junction solar cell enabled by controlled thermal co-evaporation of various absorber layers in the stack. The top and middle subcells were fabricated by developing optimized thermally co-evaporated Cs0.3FA0.7Pb(I0.56Br0.44)3 (1.80 eV bandgap) and FAPbI3 (1.53 eV) perovskites, respectively, while the bottom subcell employed a solution-processed Cs0.25FA0.75Pb0.5Sn0.5I3 (1.25 eV) perovskite. By optimising absorber thicknesses and compositions through optical modelling, we achieve excellent current matching between the top (9.6 mA cm-2), middle (9.3 mA cm-2), and bottom subcells (9.0 mA cm-2), achieving an overall efficiency of 15.8%. Optical modelling simulations suggest that current matching and efficiency up to 11.4 mA cm-2 and 37.6% respectively could be attainable using the latest interlayer materials. This work highlights the potential of scalable vapour-based deposition techniques for advancing multi-junction perovskite-based solar cells, paving the way for future developments in this field.

Pinning the Surface Layered Oxide Structure in High Temperature Calcination Using Conformal Atomic Layer Deposition Coating for Fast Charging Cathode

AbstractIn the solid‐state synthesis of layered oxides, achieving cathode powder with precise morphology, crystal structure, and surface properties demands a delicate balance between thermodynamics and kinetics. Elevated temperatures are indispensable for driving the reaction toward completion, facilitating the formation of ordered layered structures essential for efficient lithium‐ion transportation in Li‐ion batteries. However, high temperatures risk inducing Li/Ni mixing and rock‐salt formation, particularly pronounced in layered oxides rich in Ni content, detrimentally impacting their performance. To address this challenge, the approach involves a precisely designed conformal coating with a high affinity for oxygen atoms, strategically employed to pin the surface layered oxide structure even under elevated temperatures. By preventing undesired surface decomposition during the high‐temperature lithiation process, this innovation fosters the formation of well‐ordered layered structures on the surface. Consequently, this pioneering strategy substantially mitigated phase separation during high‐rate cycling, thereby unlocking exceptional rate capability and cycle stability in layered oxide cathodes. The strategy establishes a new pathway for synthesizing next‐generation, high‐power density battery materials.

Layer-by-Layer Growth of Two-Dimensional Tellurium Thin Films via Ultrahigh-Pressure Atomic Layer Deposition for p-Type Semiconductors.

Tellurium (Te) has emerged as a prominent candidate among two-dimensional materials due to its impressive properties, such as high mobility, stability, and compatibility with low-temperature processing. However, achieving consistent uniformity over large areas for ultrathin Te films deposited at low temperatures has remained a substantial challenge. Atomic layer deposition (ALD) has been proposed as a promising solution, offering precise thickness control and highly conformal thin film deposition even at low temperatures. This study introduces a successful method for the layer-by-layer growth of Te thin films using high-pressure ALD (HP-ALD) with a multiple-dosing (MD) strategy. The resulting films exhibit a promising Hall mobility of 51.2 cm2 V-1 s-1, alongside high stability and excellent surface coverage. The integration of HP-ALD with MD represents a significant advancement in Te thin film fabrication, overcoming previous limitations and paving the way for the broader utilization of Te in next-generation technologies.

Conformal Conductive Polymer Deposition on Carbon Nanotube Forests

Carbon nanotube (CNT) forests are highly conductive and possess a large surface area, making them promising as electrode support materials for electrochemical applications including energy storage and water desalination. However, these forests often suffer from mechanical collapse when exposed to liquids, limiting their effectiveness in wet environments. In this study, we explore the use of vapor-phase oxidative molecular layer deposition (oMLD) to deposit thin, redox-active polymer films onto CNT forests to enhance their mechanical and electrochemical properties. We evaluate the mechanical behavior of the polymer-coated CNT forests using nanoindentation compression tests and solvent evaporation tests. The modulus and buckling stress of the forests increase with the thickness of the polymer coating, indicating enhanced mechanical strength conferred by the oMLD process. Furthermore, solvent evaporation tests demonstrate that the morphology of the polymer-coated CNT forests remains undisturbed by surface tension forces, in contrast to uncoated CNT forests which collapse and densify. This preservation of morphology underscores the effectiveness of the polymer coating in protecting the CNT forests from structural degradation in liquid environments. To gain deeper insights, finite element simulations analyze the mechanical properties of both coated and uncoated CNT forests. The simulations reveal that the increase in buckling load scales with the bending stiffness of individual CNTs and their coatings, highlighting the synergistic effect of the polymer coating on the overall forest structure. Finally, electrochemical characterization in aqueous electrolyte indicates an increase in charge capacity with polymer thickness for thin films, and a decrease in charge capacity at high film thicknesses arising from restricted pore volume. This work indicates that oMLD polymer coatings enhance the mechanical strength and electrochemical activity of CNT-based substrates. The findings from this study contribute to the development of more efficient and durable CNT-based electrodes for water desalination and energy storage applications.

(Invited) Application of Electroless Plating to 3D Interconnection Technology of LSIs

In the interconnection of LSIs and 3D integration technologies, high aspect ratio structures (HRS) such as via holes and trenches with very small dimensions were used. In these HRSs, deposition of metals has been studied using CVD or ALD which are based on a surface reaction dominated deposition process. On the other hand, electroless plating is also based on the surface reaction mechanism, therefore a conformal deposition profile is possible. Furthermore, with use of additives, control of deposition profile such as bottom-up fill is enabled by the electroless plating. Production cost would be significantly reduced by the use of electroless plating as compared to CVDs which use high vacuum chambers. Cu electroless bottom-up fill (superfill) is possible for sub-micrometer diameter holes with addition of inhibitors. Conformal deposition profile of electroless Co-alloy barrier metals is achieved for a high aspect ratio TSVs. In the high aspect TSV structures, a combination of electroless barrier metal and Cu electroplated bottom-up fill would be the most important technology. Furthermore, I would like to introduce electroplating of Ru using hydrazine as a reducing agent. This technology enables to deposit a Ru film which shows significant reduction of resistivity after annealing in the forming gas ambient.

Controlled Engineering of Defects and Interfaces in Thermoelectric Materials With Atomic Layer Deposition

AbstractEnhancing the performance of thermoelectric materials remains critical for practical applications. Increasing the power factor and reducing the thermal conductivity are key strategies for improving the thermoelectric performance. Doping, incorporating secondary phases, and generating dislocations can be used to introduce defects and grain boundaries to improve the thermoelectric performance. The application of an ultrathin film as a coating on thermoelectric materials via atomic layer deposition (ALD) has recently attracted attention as a novel approach to enhance the performance. The excellent conformality of ALD enables the conformal deposition of ultrathin films on powder to enable the interfacial properties to be meticulously controlled even after sintering. Using ALD to deposit an ultrathin layer on the thermoelectric powder matrix induces various defects through the interactions of the coating material with the thermoelectric matrix, which provide exquisite control over the material properties. This review discusses the phenomena induced by applying ultrathin coatings to thermoelectric materials through ALD, elucidates the underlying mechanisms, and examines the effects on the thermoelectric performance. Based on these insights, innovative pathways for applying ALD to thermoelectric materials are proposed, and robust strategies for enhancing these properties through the precise modulation of diverse defects and interfaces are discussed.

Conformal Sodium Deposition Facilitated by Ion Adsorption‐Intercalation Process within Hetero‐Interface for Stable Sodium Metal Batteries

AbstractSodium (Na) metal battery is regarded as one of the most promising candidates for large‐scale energy storage devices, benefiting from the abundant sodium reserves and low cost. However, its practical application is hindered by the dendrite growth and unstable electrode‐electrolyte interface. Herein, a 3D sodiophilic structure composed of a carbon matrix overlaid with g‐C3N4 coating layers (g‐C3N4/3D‐C) is designed to stabilize the Na plating/stripping behavior. The sodiophilicity is endowed by a highly reversible adsorption‐intercalation process at the hetero‐interface, which can guide conformal Na deposition and induce the formation of inorganic‐rich solid‐electrolyte interphases with high structural stability and fast Na‐ion transport. Meanwhile, the 3D scaffold can effectively accommodate Na deposition during Na plating/stripping and depress the dendrite formation. As a result, the half cell assembled with g‐C3N4/3D‐C electrode delivers long‐term cycling performance at 1.0 mA cm−2 with a high Coulombic efficiency of 99.92% for over 2000 cycles and of 99.94% even at 5 mA cm−2, 10 mAh cm−2. The practical feasibility of the g‐C3N4/3D‐C is verified with full cells, which shows favorable rate capability and long‐cycle performance. The sodiophilic hetero‐interface construction strategy proposed in this work sparks new insights for designing high‐performance Na metal anodes.

Strain-Controlled Galvanic Synthesis of Platinum Icosahedral Nanoframes and Their Enhanced Catalytic Activity toward Oxygen Reduction.

The unique strain distribution on the surface of a Pd icosahedral nanocrystal is leveraged to control the sites for oxidation and reduction involved in the galvanic replacement reaction. Specifically, Pd is oxidized and dissolved from the center of each {111} facet due to its tensile strain, while the Pt(II) precursor adsorbs onto the vertices and edges featuring a compressive strain, followed by surface reduction and conformal deposition of the Pt atoms. Once the galvanic reaction is initiated, the {111} facets become more vulnerable to oxidation and dissolution, as the vertices and edges are protected by the deposited Pt atoms. The site-selected galvanic reaction naturally results in the formation of Pt icosahedral nanoframes covered by compressively strained {111} facets, which show enhanced catalytic activity and durability toward oxygen reduction relative to commercial Pt/C.

Conformal SnO2 and NiOx charge transport layers for pragmatic air-processed perovskite solar cells

The industrialization of perovskite (PVK) solar cells (PSCs) necessitates simple manufacturing, cheapness, nontoxicity, high efficiency, and stability. We report an air-processed lead halide PSCs with cheap, nontoxic, stable NiOx and SnO2 as the hole and electron transport layers separately, to meet all the above commercial requests. By preparing the NiOx (water-dispersible) and SnO2 (oil-dispersible) quantum dots (QDs) with good conductivity and energy band matched well with that of PVK, we fabricate inverted PSCs (ITO/NiOx/PVK/SnO2/Ag) with efficiency up to 20.1/14.6% for active areas of 0.0707/1 cm2, under 1 sun simulated illumination with enhanced UV light ratio. The UV-light resistant PSCs reported here will impel their application in the high altitude areas with strong UV light. Importantly, the monodisperse size and dominant (110) plane of SnO2 QDs achieved by controlling the solvothermal parameters, realize the conformal deposition and defect prevention of SnO2, respectively, thus improving the PSC efficiency and stability.

Interplay of physical and textural properties in porous, nanostructured hard‑carbons as electrode materials for non-Faradic energy storage devices

This work presents a systematic investigation on the non-Faradic energy storage ability of non-graphitizable, porosity engineered hard‑carbon nanostructures as electrode materials. The persistent challenge of inducing and tuning porosity in hard‑carbon nanostructures is overcome here, by utilizing dendritic fibrous nano silica (DFNS) as a sacrificial template for uniform and conformal deposition of carbon through thermal chemical vapor deposition, leading to the formation of porosity tuned, nanostructured hard‑carbon florets (NCF). This strategy enables precisely crafted six varieties of NCF with varying yet monodisperse dimensions (NCF 90, NCF 350, NCF 366, NCF 430, NCF 540 and NCF 600), SSA (494–719 m2/g) and textural features such as pore volume (0.67–1.24 cm3/g) and pore diameter (3.83–5.65 nm). In contrast to current understanding, NCF 366 with defect length of 16 nm, defect density of 2.65 × 1011 cm−2, micro- to mesoscale pore ratio of 0.16 and specific surface area of 535 m2/g achieves the highest energy density of 14.6 Wh/kg and power density 10.0 kW/kg, when compared to NCF 90 with higher SSA (719 m2/g) and pore volume (1.24 cm3/g). Thus, this work manifests the critical contributions of tuning the pore structures and optimizing the relative contributions from multi-scale pore structures to achieve high-performing energy storage devices.

Validation of dual-energy CT-based composition analysis using fresh animal tissues and composition-optimized tissue equivalent samples

Objective. Proton therapy allows for highly conformal dose deposition, but is sensitive to range uncertainties. Several approaches currently under development measure composition-dependent secondary radiation to monitor the delivered proton range in-vivo. To fully utilize these methods, an estimate of the elemental composition of the patient’s tissue is often needed. Approach. A published dual-energy computed tomography (DECT)-based composition-extraction algorithm was validated against reference compositions obtained with two independent methods. For this purpose, a set of phantoms containing either fresh porcine tissue or tissue-mimicking samples with known, realistic compositions were imaged with a CT scanner at two different energies. Then, the prompt gamma-ray (PG) signal during proton irradiation was measured with a PG detector prototype. The PG workflow used pre-calculated Monte Carlo simulations to obtain an optimized estimate of the sample’s carbon and oxygen contents. The compositions were also assessed with chemical combustion analysis (CCA), and the stopping-power ratio (SPR) was measured with a multi-layer ionization chamber. The DECT images were used to calculate SPR-, density- and elemental composition maps, and to assign voxel-wise compositions from a selection of human tissues. For a more comprehensive set of reference compositions, the original selection was extended by 135 additional tissues, corresponding to spongiosa, high-density bones and low-density tissues. Results. The root-mean-square error for the soft tissue carbon and oxygen content was 8.5 wt% and 9.5 wt% relative to the CCA result and 2.1 wt% and 10.3 wt% relative to the PG result. The phosphorous and calcium content were predicted within 0.4 wt% and 1.1 wt% of the CCA results, respectively. The largest discrepancies were encountered in samples whose composition deviated the most from tabulated compositions or that were more inhomogeneous. Significance. Overall, DECT-based composition estimations of relevant elements were in equal or better agreement with the ground truth than the established SECT-approach and could contribute to in-vivo dose verification measurements.

Laser Deposition of Metal Halide Perovskites.

Vacuum-based or vapor-phase deposition is the most mature and widely used method for thin-film growth in the semiconductor industry. Yet, the vapor-phase growth of halide perovskites remains relatively underexplored compared to solution process deposition. The intrinsically largely distinct volatilities of organic and inorganic components in halide perovskites challenge the standard physical vapor deposition techniques. Thermal coevaporation tackles this with independent thermally controlled sources per precursor. Alternatively, pulsed laser deposition uses the energy of a laser to eject material from a target via thermal and nonthermal processes. This provides high versatility in the target composition, enabling the deposition of complex (including hybrid) thin films from a single-source target. This Perspective presents an overview of recent advances in laser-based deposition of halide perovskites, discusses advantages and challenges, and motivates the development of physical vapor deposition methods for hybrid materials, especially for applications requiring dry, conformal, and multilayer deposition.

Localized surface roughening to improve adhesion of electroless seed layer in through-glass vias

This article reports the improvement of the adhesion of the electroless seed layer deposited on glass substrates used in creating through-glass vias (TGV) by localized surface roughening. Four glass substrates having varying roughness characteristics were prepared by electrochemical discharge machining (ECDM) and ultrasonic machining (USM). The electroless nickel seed layer was deposited directly on glass without any adhesion layer, followed by electrodeposited copper layers. In-depth surface topography and morphology analysis reveal the mechanism behind the improved adhesion during standard peel and cross-hatch adhesion tests, which were used to determine the interlayer adhesion.Localized roughening techniques generated specific microfeatures, i.e., microgrooves (in USM) or ridges (in ECDM), increasing the surface area. These features acted as interlocking/nucleation sites to hold the electroless nickel atoms, resulting in higher interfacial adhesion. USM-roughened samples exhibited stronger interfacial adhesion than their ECDM-roughened counterparts, which indicated that the interlayer adhesion depends on topography and the roughened surface's morphology. The surface with negative skewness and positive excess kurtosis promotes mechanical interlocking, offering a promising strategy for enhancing interlayer adhesion. Finally, conformal deposition in a 6 × 6 array of through-holes having an aspect ratio of ∼4 was also demonstrated.

Rapid, microwave-assisted deposition of anisotropic silver nanostructures on various substrates.

A facile, rapid, and scalable in situ microwave-assisted solvothermal technique (MAST) has been developed to deposit anisotropic silver nanoparticles (AgNP) on various substrates in a solution medium. SEM-EDS and XRD were used to characterize the morphology and structure of the deposits. Deposition on non-patterned aluminium led to near-spherical AgNP agglomerates all across the surface. Deposition on the glass at optimum solution concentration led to mirror-like coatings comprising spherical ∼50 nm particles, whereas no coating occurred at lower concentrations. AgNPs decorated the hexagonal pattern formed on a nano-patterned aluminium (NPA) substrate. Among various precursor concentrations used for deposition on NPA, the 10 μM concentration resulted in conformal deposition, with nanoparticles decorating the hexagons in NPA. In contrast, AgNP density was lower in the concave dimples on NPA. Our work demonstrates a quick and easy approach for the AgNPs' deposition, with control over size, and morphology. It can be used for deposition on large substrates, potentially making it suitable for surface-enhanced spectroscopic applications.

Haze factor of silver nanowires in variable refractive index environment: experimental and simulation approaches

While silver nanowires (Ag NWs) have been demonstrated as a highly efficient transparent conducting material, they suffer from strong light scattering, which is quantified by a large haze factor (HF) in the optical spectrum. Here we investigate the influence of the dielectric environment on the light scattering of Ag NWs by comparing experimental measurements and simulations. In air, two peaks on the HF spectra are observed experimentally at the wavelength of λ I = 350 nm and λ II = 380 nm and are attributed by simulations to the influence of the Ag NWs pentagonal shape on the localized surface plasmon resonance. The relative intensity between the two peaks is found to be dependent on whether the Ag NWs are in contact with the glass substrate or not. The HF behaviour in the near IR region seems to be dominated by Rayleigh scattering following simulations results. Dielectric environments of Ag NWs with various refractive indexes were obtained experimentally by the conformal deposition of different metal oxide coatings using atomic layer deposition, including Al-doped zinc oxide, Al2O3 and SiO2 coatings. The HF is found to be correlated with the refractive index environment in terms of HF peaks position, intensity and broadening. This trend of HF peaks is supported by a theoretical model to understand the optical mechanism behind this phenomenon.

Direct Electrodeposition of Electrically Conducting Ni3(HITP)2 MOF Nanostructures for Micro-Supercapacitor Integration.

Micro-supercapacitors emerge as an important electrical energy storage technology expected to play a critical role in the large-scale deployment of autonomous microdevices for health, sensing, monitoring, and other IoT applications. Electrochemical double-layer capacitive storage requires a combination of high surface area and high electronic conductivity, with these being attained only in porous or nanostructured carbons, and recently found also in conducting metal-organic frameworks (MOFs). However, techniques for conformal deposition at micro- and nanoscale of these materials are complex, costly, and hard to upscale. Herein, the study reports direct, one step non-sacrificial anodic electrochemical deposition of Ni3(2,3,6,7,10,11-hexaiminotriphenylene)2 - Ni3(HITP)2, a porous and electrically conducting MOF. Employing this strategy enables the growth of Ni3(HITP)2 films on a variety of 2D substrates as well as on 3D nanostructured substrates to form Ni3(HITP)2 nanotubes and Pt@ Ni3(HITP)2 core-shell nanowires. Based on the optimal electrodeposition protocols, Ni3(HITP)2 films interdigitated micro-supercapacitors are fabricated and tested as a proof of concept.

Effect of TiO2 nanoparticle load on photoelectric properties of TiO2/VGs heterojunction

Preparation of Titanium dioxides loaded vertical graphene nanosheets (TiO2/VGs) composite films with heterojunctions by a multi-plasma combination method. Highly vertically oriented VGs were prepared by helicon wave plasma chemical vapor deposition (HWP-CVD), and TiO2 nanoparticles were deposited on VGs templates by ultra-high vacuum magnetron sputtering (UH-MS). By controlling the sputtering time of TiO2 nanoparticles to modulate the nanoparticle loading content. The morphology, structure, and photocatalytic performance of heterojunction TiO2/VGs composite films were investigated. The characterization results of morphology and structure show that the structure of VGs nanosheets is not altered by the increase of the deposited particle content, indicating that VGs have excellent mechanical properties as a template for TiO2 loading. As the deposition time of the TiO2 nanoparticles increases, the loading type progresses from epitaxial growth at the beginning to conformal deposition and eventually to gap-filling growth. Photoelectric performance tests showed that the heterojunctions were formed at the interface between TiO2 and VGs. The photovoltage test results show that the photogenerated carriers are effectively separated at the interface, and the nanosheets can promote the migration of separated electrons to the external circuit. The variation in photocurrent density shows a positive correlation with the number of TiO2 attachment sites and loading content on the surface of the VGs nanosheets.