Plasma-enhanced Chemical Vapor Deposition Technology Research Articles

Localized corrosion of nitrogen-doped diamond-like carbon films on the surface of 304 stainless steel

Nitrogen-doped diamond-like carbon (N-DLC) films with different nitrogen content were prepared on the surface of 304 stainless steel (SS) using plasma-enhanced chemical vapour deposition technology. Localized failure mechanisms of the N-DLC films under long-term exposure to sodium chloride solutions have been investigated. The results demonstrated that nitrogen doping significantly affected the failure behavior of the N-DLC films. When undoped, the number of pore defects in the film is high, providing a channel for the corrosive medium to attack the substrate metal. Meanwhile, due to the high internal stress within the undoped film, extensive exfoliation of the film occurred under the effect of the growth of oxides at the film-substrate interface. The DLC film on 304 SS is subject to stress corrosion cracking failure during long-term service in sodium chloride solution. However, when nitrogen doping is 10 sccm, the pH of the micro-zone solution was highly variable due to the dissolution of nitrogen in the film and the processes of formation and hydrolysis of NH4+. A large number of residual metal cations dissolved from the substrate combine with oxygen at the corrosion pits mouth to form oxides. This can aggravate the occlusion effect of the pits and severe pitting corrosion of 304 SS occurs under autocatalytic effects. The N-DLC film with 5 sccm nitrogen addition showed the excellent durability properties. The evolution mechanism of oxidation and dissolution behaviors in the presence of variations in local hydrochemistry is also discussed.

Unsymmetric design of self-supported sheet electrode: Breaking the tradeoff between electrical conduction and surface wetting for fast energy storage and excellent cycling stability

Biomass-derived porous carbon materials are suitable candidates for energy storage due to their rich pore structure, high specific area, and tunable surface functionality. Carbon electrodes are often required to have both excellent conductivity and wettability, while one needs to be compromised for optimized outcomes. Herein, we constructed a self-supported Carbonized Wood@Graphene Nanosheets (CW@GNs) composite electrode by growing GNs on one side of the CW surface with a plasma-enhanced chemical vapor deposition technology. Both electrical conductivity and interfacial wettability can be obtained simultaneously in CW@GNs electrodes. The CW@GNs-1h showed a satisfactory specific capacitance of 210.2F g−1, while the value of pure CW was 177.2F g−1. Furthermore, a symmetrical supercapacitor assembled with two CW@GNs-1h monoliths performed an excellent energy density of 7.8 Wh kg−1 at 250.8 W kg−1, retaining attractive cycling stability (99.02%) after 50,000 cycles. These results demonstrated the effectiveness of the unsymmetric design in a double-sided sheet electrode that breakthrough the tradeoff of electrical conductivity and surface wettability, and thus enhanced energy storage capacity and cycling stability were achieved.

Failure mechanisms of nitrogen-doped diamond-like carbon films: Exfoliation or localized attack behaviour of films under hydrochemistry evolution

Nitrogen-doped diamond-like carbon (N-DLC) films with different nitrogen content were prepared on the surface of 2024 aluminium alloy using plasma-enhanced chemical vapour deposition technology. The failure mechanisms of the N-DLC films during seawater exposure have been investigated. The results demonstrated that nitrogen doping significantly affected the failure behaviour of the DLC films in seawater. Extensive exfoliation of the DLC film was found without the addition of nitrogen. However, when the nitrogen flow rate is 10 sccm and 15 sccm, significant localized corrosion of the DLC film and the aluminium alloy substrate occurred. The difference in the thermodynamic process of corrosion of the N-DLC films was mainly due to the changes in pH value on the local solution caused by the formation and hydrolysis of NH4+. In the DLC film without nitrogen additive, large oxide particles were formed at the film-substrate interface due to the acidification of the solution. Meanwhile, the internal stress of the DLC film was high under this condition. The film was easily exfoliated and ultimately lost its protective effect on the substrate. The corrosion products could not grow sustainably due to the variable pH value when excess nitrogen was added to the DLC film. No extensive exfoliation of the DLC films with 10 sccm and 15 sccm nitrogen addition has occurred, but obvious corrosion channels were formed in the substrate because of the localized corrosion. The evolution mechanism of oxidation behaviour in the presence of variations in local hydrochemistry is also discussed.

Application of dual-layer polysilicon deposited by PECVD in n-type TOPCon solar cells

Plasma-enhanced chemical vapor deposition (PECVD) has attracted much attention in the current mass-production of n-type tunnel oxide passivated contact (TOPCon) crystalline silicon (c-Si) solar cells because of the advantages of fast film forming rate and compatibility with in-situ doping. However, the PECVD technology is limited by the effect of ion bombardment on the ultra-thin SiO2 layer during gas ionization, together with the inevitable front wrap-around poly-Si. Here, the dual-layer poly-Si stack made up of the intrinsic poly-Si(i) and in-situ P-doped poly-Si(n+) has been achieved by adjusting the deposition power, pulse voltage duty cycle, and flow rate of the PH3, which effectively protects the tunneling SiO2 layer through the weakened ion bombardment to improve the interface passivation and contact resistivity. We have demonstrated that the pinhole density is an important reason for the thinner SiO2 layer optimized less than 1.0 nm. More importantly, the conversion efficiency of n-type TOPCon c-Si solar cells can be improved by more than 0.10% and 0.15%, respectively, by the combination of the dual-layer poly-Si stack and wrap-around poly-Si removal compared with the single-layer poly-Si counterpart with the same thickness.

24.7% industrial tunnel oxide passivated contact solar cells prepared through tube PECVD integrating with plasma-assisted oxygen oxidation and in-situ doped polysilicon

Tunnel oxide passivated contact (TOPCon) solar cells have gradually dominated the industrial silicon solar cells. In this paper, we have adopted the tube plasma-enhanced chemical vapor deposition (PECVD) technology integrating with nano SiOx (Tox) and in-situ phosphorus-doped polysilicon (n + poly-Si), in which Tox is prepared by plasma-assisted oxygen (O2) oxidation. Passivation and contact performance of TOPCon solar cells have been investigated under different thicknesses of Tox, and the following simulation has confirmed the optimal electrical properties, i.e., the implied open-circuit voltage (iVOC) of the hydrogenated lifetime sample is promoted to more than 736.1 mV on the textured wafer, corresponding to a lowest single-sided saturation current density (J0) of 4.6 fA/cm2, and the contact resistivity of 1.55 mΩ cm2 extracted from the transmission line method. Characterizations are carried out to conform the rear stack passivation layers satisfy the requirement of the high-efficiency TOPCon solar cells. Finally, we have fabricated the large-sized TOPCon solar cells with an average efficiency of 24.5% and a maximum efficiency of 24.7%, respectively. The above work has demonstrated the tube PECVD technology integrating with plasma-assisted O2 oxidation and in-situ doped poly-Si has the potential for the mass-production TOPCon in industry.

24.4% industrial tunnel oxide passivated contact solar cells with ozone-gas oxidation Nano SiOx and tube PECVD prepared in-situ doped polysilicon

Ozone-gas oxidation (OGO) technology, capable of integrating into tube plasma-enhanced chemical vapor deposition (PECVD) technology, is developed to prepare the Nano SiO x layer for tunnel oxide passivated contact (TOPCon) solar cells in this work. The effects of gas flow, oxidation temperature, and annealing temperature on passivation quality are investigated. The X-ray photoelectron spectroscopy (XPS) indicates that OGO SiO x possesses a Si 4+ proportion of about 20%, higher than the nitric acid oxidized (NAOS) SiO x and plasma-assisted N 2 O oxidation (PANO) SiO x . The implied open-circuit voltage ( iV oc ) of the hydrogenated lifetime sample is promoted to more than 740 mV with the highest value of 748 mV, corresponding to a lowest single-sided saturation current density ( J 0,s ) of 3.1 fA/cm 2 . The contact resistivity extracted from the Cox-Strack method is < 9 mΩ cm 2 as the annealing temperature is more than 840 °C. Finally, we prepared the large-sized TOPCon solar cells with an average efficiency of 24.37% and a maximum efficiency of 24.41%, respectively. The above work shows that the tube PECVD technology integrated with ozone gas oxidation has the potential for the mass-production TOPCon industry. • Ozone-gas oxidation (OGO) technology is integrated into tube PECVD technology. • OGO SiO x and P-doped a-Si:H can be prepared by the same graphite-boat carrier. • OGO SiO x shows a high proportion of Si 4+ without ion bombardment. • The highest iV oc of 748 mV corresponding to the lowest J 0,s of 3.1 fA/cm 2 . • Average efficiency of 158.75 mm TOPCon cells reaches ∼24.4%.

Highly improved passivation of PECVD p-type TOPCon by suppressing plasma-oxidation ion-bombardment-induced damages

Tunnel oxide passivated contact (TOPCon) integrated with a plasma-enhanced chemical vapor deposition (PECVD) boron-doped polysilicon has the potential to achieve high-efficiency and low-cost solar cells. In this contribution, we explore the feasibility of using PECVD technology to prepare high-performance p-type TOPCon (p-TOPCon) by growing two-step oxidation (TSO), i.e., a nitric acid oxidation (NAOS) SiOx without ion-bombardment followed by a plasma-assist N2O oxidation (PANO) SiOx layer. The experimental results reveal that for p-TOPCon structures on polished wafers with the conventional plasma oxidation SiOx, raising plasma oxidation powers to increase the thickness and oxidation degree of SiOx cannot ensure high-quality passivation due to the appearance of high-density defects caused by plasma ion-bombardment. In the presence of an additional NAOS SiOx layer, ion-bombardment-induced defects can be effectively suppressed, leading to a remarkable improvement in passivation properties. In detail, the optimal p-TOPCon with TSO SiOx achieves a maximum implied open-circuit voltage (iVoc) of ∼712 mV and a minimum single-sided saturation current density (J0,s) of ∼10 fA/cm2, manifesting an increment of iVoc by ∼10 mV, and a reduction of J0,s by ∼5 fA/cm2. Finally, the numerical simulations reveal that n-type Si solar cells featuring p-TOPCon rear junction and Al electrode could receive an efficiency of 24.6% based on the state-of-the-art device fabrication technology. In general, this work provides a new way to boost the passivation quality of PECVD p-TOPCon devices.

High-Sensitivity Focus-Induced Photoresponse in Amorphous Silicon Photodiodes for Enhanced Three-Dimensional Imaging Sensors

In this work, we report on the bias-tunable and highly sensitive irradiance-dependent focus-induced photoresponse (FIP) in amorphous silicon p-i-n diodes for enhanced three-dimensional imaging applications. We identify a nonlinear current breakdown at irradiance down to at least $0.6\phantom{\rule{0.25em}{0ex}}\ensuremath{\mu}\mathrm{W}/\mathrm{m}{\mathrm{m}}^{2}$ due to defect-induced electrical field screening, surpassing state-of-the-art device sensitivities by at least a factor of 16 in the visible range. We further demonstrate the tunability of FIP by systematic device and field engineering to enable both precise and long-range high-resolution distance measurements in just one device architecture. We evaluate distance measurements up to at least 15 m and achieve a depth resolution of 2.1 mm at 3.3 m. The reproducible low-temperature (300 \ifmmode^\circ\else\textdegree\fi{}C or lower) plasma-enhanced chemical vapor-deposition technology enables systematic tailoring of the FIP for three-dimensional imaging applications and allows for back-end sensor integration on top of silicon or flexible electronics with fill factors up to 100%.

Innovative modification of the surface of screen-printed carbon electrodes by nanofilms directly deposited in cold acrylonitrile plasma

This work describes a pioneering example of the application of plasma-enhanced chemical vapor deposition (PECVD) for the direct modification of commercially available screen-printed carbon electrodes (SPCEs) with plasma-deposited (polymerized) acrylonitrile (pp-AN) nanofilms. The developed method enables fast and simple deposition of the films directly on the surface of the working electrode with excellent reproducibility and repeatability. The films were deposited at various plasma power levels (P = 10–80 W) and deposition times (2–4 min), with thicknesses in the range 50–500 nm. The films were characterized in terms of surface morphology (SEM and AFM analysis) and DC electrical conductivity. The cyclic voltammetry measurements performed in the presence of [Fe(CN)6]4−\\3− indicated that, depending on the type of deposited film, the sensors have radically different electrochemical properties. An electrode covered with pp-AN film deposited at P = 10 W with a thickness of approx. 60 nm exhibits the highest sensitivity of the materials studied, and has a favorable peak current ratio, an improved peak separation value, and a well-developed surface area. In general, sensors with pp-AN films deposited at P ≥ 40 W show the microelectrode effect (characterized by the sigmoidal shape of cyclic voltammograms). The excellent homogeneity and mechanical durability of the resulting nanofilms, as well as their outstanding long-term stability (up to six months), demonstrate that PECVD technology offers a real opportunity for the mass production of sensors that can be almost freely functionalized to provide properties such as selectivity and sensitivity.

Improvement of electrochemical performances of ultrathin Ti-coated Si-based multilayer nanofibers as anode materials for lithium-ion batteries

Fullerene-like carbon core/silicon shell (FLC/Si) nanofibers are prepared via an electrospinning method followed by plasma-enhanced chemical vapor deposition technology. Then, a thin metal Ti layer is coated by electron beam physical vapor deposition. The multilayer FLC/Si/Ti electrode exhibits remarkably improved electrochemical properties as a lithium-ion battery anode compared to the uncoated anode, i.e., a higher initial Coulombic efficiency, more stable cycle performance, higher capacity and excellent rate capability (capacity over 1000 mA h g−1 at 3200 mA g−1). These improved electrochemical performances of the multilayer FLC/Si/Ti electrode can be attributed to the presence of a Ti layer on the surface of the electrode.

Construction of high performance N-doped Na3V2(PO4)2F3/C cathode assisting by plasma enhanced chemical vapor deposition for sodium-ion batteries

One N-doped carbon coated Na3V2(PO4)2F3/C cathode for sodium-ion batteries was successfully prepared by a Plasma enhanced chemical vapor deposition (PECVD) method. N2 gas is used as the nitrogen source and it is ionized to form chemically active nitrogen ion. It can easily react with the carbon atoms in sample Na3V2(PO4)2F3/C. Research results show that the introduction of N does not affect the crystal structure of the material. The N-doped carbon layer in sample Na3V2(PO4)2F3/C becomes more and more homogeneous. The formation of the pyridinic nitrogen, pyrrolic nitrogen and graphitic nitrogen in the carbon layer can generate additional active sites to shorten the transmission distance of sodium ions, which can improve the electrochemical performance of Na3V2(PO4)2F3/C cathode. The NVPF@N-3 cathode treated by PECVD for 30 min displays excellent rate performance (109.8 mAh•g−1 at 5 C) and cyclic performance, in which the capacity retention after 1000 cycles at 10 C is 91.4% and the crystal structure of NVPF@N-3 is well maintained. This research demonstrates that the pyrolytic carbon in Na3V2(PO4)2F3/C cathode for sodium-ion batteries can be effectively doped by Nitrogen through a novel PECVD technology.

Effect of nitrogen flow on the properties of carbon nitride films deposited by electron cyclotron resonance plasma-enhanced chemical vapor deposition

Amorphous hydrogenated carbon nitride (a-CNx:H) films were fabricated via electron cyclotron resonance microwave plasma-enhanced chemical vapor deposition technology using N2 and C2H2 as nitrogen and carbon sources, respectively. The effects of the N2/C2H2 gas flow ratio on the composition, bond structure, scratch resistance, and optical properties of the a-CNx:H films were investigated. X-ray photoluminescence spectroscopy and Raman spectroscopy results indicated that the N/C atomic ratio, carbon 1s sp3/sp2 ratio, and nitrogen 1s sp3/sp2 ratio increased with increasing N2/C2H2 gas ratio. Pin-on-disk wear tests conducted with a pin made of ultrahigh-molecular weight polyethylene indicated that all the a-CNx:H films exhibited good scratch resistance; however, rubbing with a stainless-steel ball weakened the wear resistance of the a-CNx:H films as the N2/C2H2 gas ratio changed from 5/30 to 30/30. The measured transmittance spectra showed that nitrogen incorporation into the carbon films increased their transmittance in the visible to near-infrared regions. The optical bandgap of the a-CNx:H films was obtained by the Tauc method, which demonstrated that when the N2/C2H2 gas flow ratio changed from 0/30 to 30/30, the optical bandgap increased from 1.18 to 1.86 eV. Our results suggest that a-CNx:H films can be used as optical and protective coatings.

Influence of DLC Coatings Deposited by PECVD Technology on the Wear Resistance of Carbide End Mills and Surface Roughness of AlCuMg2 and 41Cr4 Workpieces

The primary purpose of this work was to study the effectiveness of using diamond-like coatings (DLC) to increase the wear resistance of carbide end mills and improve the surface quality of the processed part when milling aluminum alloy and low-carbon steel. The functional role of forming an adhesive sublayer based on (CrAlSi)N immediately before the application of the external DLC film by plasma-enhanced chemical vapor deposition (PECVD) technology in the composition of a multicomponent gas mixture containing tetramethylsilane was established in the article. The article shows the degree of influence of the adhesive sublayer on important physical, mechanical, and structural characteristics of DLCs (hardness, modulus of elasticity, index of plasticity, and others). A quantitative assessment of the effect of single-layer DLCs and double-layer (CrAlSi)N/DLCs on the wear rate of end mills during operation and the surface roughness of machined parts made of aluminum alloy AlCuMg2 and low-carbon steel 41Cr4 was performed.

The influence of NH3 flow rate on the microstructure and oxidation properties of a-Si-C-N:H films prepared by PECVD technology

Hydrogenated amorphous silicon carbon nitride (a-Si-C-N:H) films embedded with carbon nanoclusters were deposited by plasma enhanced chemical vapour deposition (PECVD) method. The microstructure and oxidation properties of the films were mainly analysed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectroscopy (XPS), Raman and high-resolution transmission electron microscopy (HRTEM). The influence of the NH3 flow rate on the film oxidation properties in air at room temperature has been investigated. The results showed that the carbon atoms tend to bond with each other during the film deposition and then form carbon nanoclusters. In addition, with increasing NH3 flow rate, the results also indicated that more N and C atoms bonded with Si atoms would be replaced by O atoms, and the N atoms mainly bonded with C atoms and the O atoms mainly bonded with Si atoms. Furthermore, the films became more and more dense, but the film oxidation was more and more serious. The oxidation of the film was mainly attributed to the production of the related silicon dangling bonds and the formation of the smaller carbon nanoclusters.

Low Temperature Synthesis of WS2 Using PECVD for Hydrogen Evolution Catalysis

Hydrogen holds tremendous promise as one of many alternatives for clean energy generation with high energy density and zeroes environmental impact. Hydrogen can be easily produced by using Platinum-based catalyst to efficiently lowers the large potential of electrolysis, but confined due to scarce and expensiveness. Transition metal dichalcogenides (TMDCs) such as MX2 (M stands for Mo or W, Nb, Ta etc. and X= S, Se etc.) is essential materials which show promising catalytic activity. The bond between the metal and the chalcogen is a covalent bond, and the three layers themselves are held together by a weak van der Waals force. Tungsten Disulfide (WS2) is a representative transition metal dichalcogenide (TMDC), has been freshly pursued as one of the promising alternatives for hydrogen evolution reaction (HER). Tungsten Disulfide is one of the promising TMDC materials due to its various application in electronics, catalysis, optical and other fields. The WS2 elements were previously synthesized by different processes such as mechanical exfoliation, chemical exfoliation, chemical vapor deposition etc. In this work, we report a strategy for synthesis few layers of WS2 at relatively low temperature (300 °C) using plasma enhanced chemical vapor deposition (PECVD) technique. The PECVD technology utilized to grow WS2 thin film directly on the 4-inch Si-SiO2 wafer. The quality of a synthesized WS2 was characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), High-resolution transmission electron microscopy (HR-TEM), and energy dispersive spectrometry (EDS) mapping. The thickness of the synthesized WS2 film was found to be around a few nanometers and showed multilayered structure (~5-6 layers). The PECVD shows the advantage for the large area synthesis of WS2 thin film with high uniformity, purity, and reproducibility for the mass production. The PECVD technology utilized to directly grown on glassy carbon electrode (GCE) for analysis of HER performance without any transfer process. The catalysis shows overpotential (η) of 0.50 V and Tafel slope 122.0 mV/decade. The HER performance of synthesized films was similar or higher when compared with drop casting technique. Figure 1

Film materials based on a-SiNx:H with high refractive index obtained by plasma enhanced chemical vapour deposition technology

In this work, the investigation results of amorphous hydrogenated silicon nitride layers (a-SiNx:H) obtained by plasma-enhanced chemical vapour deposition technology have been presented. Chemical compositions, surface morphology and surface topography studies were performed on the layers using Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectrometry and atomic force microscopy methods. By using optical methods: spectroscopic ellipsometry and thermal spectroscopic ellipsometry; the optical parameters (refractive index, extinction coefficients), optical band gap of a-SiNx:H layers and film thickness in the spectral range of 190–1700 nm have been determined. Additionally, we carried out thermo-optical studies to determine the temperature hysteresis of optical parameters. a-SiNx:H layers exhibit similar properties as non-stoichiometric Si-rich silicon nitride layers. They exhibited amorphous structure and their main components were silicon. After heating and cooling processes values of refractive index n and extinction coefficient k return to the baseline. In our paper we present thermal dependence of a-SiNx:H films refractive index. Presented layers showed similar optical constants to silicon substrate but they exhibiting much better dielectric properties than Si. a-SiNx:H layers exhibited very high refractive indices (about 3.8). The layers, presented in this work may potentially have broad applications in optoelectronics, photovoltaics and photonics.

Enhancement for Potential-Induced Degradation Resistance of Crystalline Silicon Solar Cells via Anti-Reflection Coating by Industrial PECVD Methods

The issue of potential-induced degradation (PID) has gained more concerns due to causing the catastrophic failures in photovoltaic (PV) modules. One of the approaches to diminish PID is to modify the anti-reflection coating (ARC) layer upon the front surface of crystalline silicon solar cells. Here, we focus on the modification of ARC films to realize PID-free step-by-step through three delicate experiments. Firstly, the ARC films deposited by direct plasma enhanced chemical vapor deposition (PECVD) and by indirect PECVD were investigated. The results showed that the efficiency degradation of solar cells by indirect PECVD method is up to −33.82%, which is out of the IEC 62804 standard and is significantly more severe than by the direct PECVD method (−0.82%). Next, the performance of PID-resist for the solar cell via indirect PECVD was improved significantly (PID reduced from −31.82% to −2.79%) by a pre-oxidation step, which not only meets the standard but also has higher throughput than direct PECVD. Lastly, we applied a novel PECVD technology, called the pulsed-plasma (PP) PECVD method, to deal with the PID issue. The results of the HF-etching rate test and FTIR measurement indicated the films deposited by PP PECVD have higher potential against PID in consideration of less oxygen content in this film. That demonstrated the film properties were changed by applied a new control of freedom, i.e., PP method. In addition, the 96 h PID result of the integrated PP method was only −2.07%, which was comparable to that of the integrated traditional CP method. In summary, we proposed three effective or potential approaches to eliminate the PID issue, and all approaches satisfied the IEC 62804 standard of less than 5% power loss in PV modules.

PECVD-induced growing of diverse nanomaterials on carbon nanofibers under various conditions

Plasma enhanced chemical vapor deposition (PECVD) has been employed as a key technique to grow carbon nanomaterials on certain substrates. In this letter, diverse carbon nanomaterials have been grown successfully on the surface of carbon nanofibers fabricated by PECVD technology. PECVD power showed dramatic effects on the morphologies and structures of nanomaterials on the carbon nanofiber surface. With the increase of power, the nanomaterials were seemed to be gradually changed from carbon nanowires to the graphene sheets and the specific surface areas of the films were improved significantly.

Direct growth of nanographene at low temperature from carbon black for highly sensitive temperature detectors

Graphene has attracted tremendous research interest owing to its widespread potential applications. However, these applications are partially hampered by the lack of a general method to produce high-quality graphene at low cost. Here, to the best of our knowledge, we use low-cost solid carbon allotropes as the precursor in plasma-enhanced chemical vapor deposition (PECVD) for the first time, and find that the hydrogen plasma and reaction temperature play a crucial role in the process. Hydrogen plasma etches carbon black, and produces graphene crystals in a high-temperature zone. Based on this finding, a modified PECVD technology is developed, which produces transparent conductive nanographene films directly on various substrates at a temperature as low as 600 °C. For application, the closely packed structure of the nanographene film enables a remarkable temperature-dependent behavior of the resistance with a ratio higher than that previously reported, indicating its great potential for usage in highly sensitive temperature detectors.

Highly efficient shrinkage of inverted-pyramid silicon nanopores by plasma-enhanced chemical vapor deposition technology

Solid-state nanopore-based analysis systems are currently one of the most attractive and promising platforms in sensing fields. This work presents a highly efficient method to shrink inverted-pyramid silicon nanopores using plasma-enhanced chemical vapor deposition (PECVD) technology by the deposition of SiNx onto the surface of the nanopore. The contraction of the inverted-pyramid silicon nanopores when subjected to the PECVD process has been modeled and carefully analyzed, and the modeling data are in good agreement with the experimental results within a specific PECVD shrinkage period (∼0–600 s). Silicon nanopores within a 50–400 nm size range contract to sub-10 nm dimensions. Additionally, the inner structure of the nanopores after the PECVD process has been analyzed by focused ion beam cutting process. The results show an inner structure morphology change from inverted-pyramid to hourglass, which may enhance the spatial resolution of sensing devices.