Nanopyramid Arrays Research Articles

Surface-passivated plasmonic nano-pyramids for bulk heterojunction solar cell photocurrent enhancement

We report that self-assembled gold (Au) nanopyramid arrays can greatly enhance the photocurrent of narrow bandgap organic solar cells using their plasmonic near-field effect. The plasmonic enhanced power conversion efficiency exhibited up to 200% increase under the AM 1.5 solar illumination.

Fabrication and Optical Properties of Green emission semipolar {101̅1} InGaN/GaN MQWs Selective Grown on GaN Nanopyramid Arrays

AbstractWe report that the high crystalline and high efficiency green emission semipolar {101̅1} InGaN/GaN multiple quantum wells (MQWs) grown on the {101̅1} facets of GaN nanopyramid arrays by selective area epitaxy. Clear and sharp interfaces of the semipolar {101̅1} InGaN/GaN MQWs was observed by transmission electron microscopy images. As comparing with (0001) MQWs, the internal electric field of {101̅1} MQWs was remarkably reduced from 1.7 MV/cm to 0.5 MV/cm, and the room temperature (RT) internal quantum efficiency (IQE) at green emission was enhanced by about 80%. This greatly enhancement of IQE is due to suppress the polarization effect in the {101̅1} MQWs which shorten the radiative recombination to compete with nonradiative recombination at RT. These results evince that the {101̅1} planes are promising for solving the efficiency green gap of III-nitride light emitters.

High-Density Periodic Arrays of Self-Aligned Subwavelength Nanopyramids for Surface-Enhanced Raman Spectroscopy

Novel nanotextured surfaces are presented with periodically self-aligned subwavelength nanogroove and nanopyramid structures with precisely defined pitch lambda(g) that are closely packed with 2 nm separation gaps over large areas and form high-density arrays of hot-spot scattering sites ideally suited for surface-enhanced Raman scattering (SERS) and Raman spectroscopy. The simple self-aligning fabrication technique requires only a single lithography step and wet anisotropic etching. Measured average Raman enhancement factors of G approximate to 10(6) from rhodamine 60 (R6G) on patterned Au surfaces with lambda(g) = 200 nm are consistent with numerical calculations. The nanostructured surfaces can be scaled to smaller dimensions, which results in increased enhancement as well as increased hot-spot spatial density.

Nanopyramid surface plasmon resonance sensors

We report the achievement of sensitive chemical and biological sensing using periodic gold nanopyramids with nanoscale sharp tips created by a simple and scalable colloidal templating approach. The sharp tips and the long-range periodic structure of the nanopyramid arrays enable the excitement of both localized and propagating surface plasmons. The optical reflection and the detection sensitivity of the templated nanopyramid surface plasmon resonance sensors agree reasonably well with the theoretical predictions using a finite-difference time-domain model. We have also demonstrated that specific antigen-antibody binding can be detected by using nanopyramid arrays in a real-time and label-free manner.

Plasmonic Crystals: A Platform to Catalog Resonances from Ultraviolet to Near‐Infrared Wavelengths in a Plasmonic Library

AbstractSurface plasmons are responsible for a variety of phenomena, including nanoscale optical focusing, negative refraction, and surface‐enhanced Raman scattering. Their characteristic evanescent electromagnetic fields offer opportunities for sub‐diffraction imaging, optical cloaking, and label‐free molecular sensing. The selection of materials for such applications, however, has been traditionally limited to the noble metals Au and Ag because there has been no side‐by‐side comparison of other materials. This feature article describes recent progress on manipulating surface plasmons from ultraviolet to near‐infrared wavelengths using plasmonic crystals made from 2D nanopyramidal arrays. A library of plasmon resonances is constructed in the form of dispersion diagrams for a series of unconventional and new composite plasmonic materials. These resonances are tuned by controlling both intrinsic factors (unit cell shape, materials type) and extrinsic factors (excitation conditions, dielectric environment). Finally, plasmonic crystals with reduced lattice symmetries are fabricated as another means to tailor resonances for broadband coupling.

Enhanced light extraction in nitride light-emitting diodes by epitaxially grown photonic-crystal nanopyramid arrays

A photonic crystal has been created on the p-layer of an InGaN light-emitting diode wafer by selective area growth, thus avoiding the etch processes that are detrimental to the active region. Nanopyramid arrays with either hexagonal or Archimedian lattices were grown in apertures defined by nanoimprint lithography. Electroluminescence measurements show that the pyramids improve the on-axis light output by up to 1.9–2.0 times. This technique could be extended to higher aspect ratio nanostructures that will have stronger coupling between the guided modes and the photonic crystal.

Surface-enhanced Raman scattering on periodic metal nanotips with tunablesharpness

This paper reports on a scalable bottom-up technology for producing periodic goldnanotips with tunable sharpness as surface-enhanced Raman scattering (SERS)substrates. Inverted silicon pyramidal pits, which are templated from non-close-packedcolloidal crystals prepared by a spin-coating technology, are used as structuraltemplates to replicate arrays of polymer nanopyramids with nanoscale sharp tips.The deposition of a thin layer of gold on the polymer nanopyramids leads tothe formation of SERS-active substrates with a high enhancement factor (up to108). The thickness of the deposited metal determines the sharpness of the nanotips and theresulting Raman enhancement factor. Finite-element electromagnetic modeling shows thatthe nanotips can significantly enhance the local electromagnetic field and the sharpness ofnanotips greatly affects the SERS enhancement.

Electrochemical SERS at Periodic Metallic Nanopyramid Arrays

This paper reports a simple and scalable colloidal templating nanofabrication technology for generating periodic metallic nanopyramid arrays as electrodes for electrochemical surface-enhanced Raman spectroscopy (SERS). These periodic arrays of nanopyramids with nanoscale sharp tips and high tip density can enhance the local electromagnetic field in the vicinity of the nanotips, resulting in high SERS enhancement (on the order of 106). The effect of the applied electrode potential and the electrode redox reactions on the SERS enhancement has been investigated. Finite element electromagnetic modeling has also been developed to simulate the electric field amplitude distribution and the corresponding Raman enhancement factors surrounding arrays of nanopyramids.

Fabrication of large area nanoprism arrays and their application for surface enhancedRaman spectroscopy

This work demonstrates the fabrication of metallic nanoprism (triangular nanostructure)arrays using a low-cost and high-throughput process. In the method, the triangularstructure is defined by the shadow of a pyramid during angle evaporation of ametal etching mask. The pyramids were created by nanoimprint lithography inpolymethylmethacrylate (PMMA) using a mould having an inverse-pyramid-shaped holearray formed by KOH wet etching of silicon. Silver and gold nanoprism arrays with aperiod of 200 nm and an edge length of 100 nm have been fabricated and used aseffective substrates for surface enhanced Raman spectroscopy (SERS) detectionof rhodamine 6G (R6G) molecules. Numerical calculations confirmed the greatenhancement of electric field near the sharp nanoprism corners, as well as the detrimentaleffect of the chromium adhesion layer on localized surface plasmon resonance.The current method can also be used to fabricate non-equilateral nanoprism andthree-dimensional (3D) nanopyramid arrays, and it can be readily extended to othermetals.

Templated Fabrication of Periodic Metallic Nanopyramid Arrays

This paper reports a simple self-assembly-based templating approach for fabricating wafer-scale, periodic metallic nanopyramid arrays with nanoscale tips and high tip density (6 × 108 tips cm-2). Spin-coated, non-close-packed monolayer colloidal crystals are used as templates to create chromium nanohole arrays, which are utilized as etching masks to fabricate inverted silicon pyramidal pits by anisotropic KOH etching. Wafer-scale metallic pyramid arrays with sharp nanotips can then be replicated from silicon templates by a simple adhesive peeling process. This nonlithographic technique combines the simplicity and cost benefits of bottom-up self-assembly with the scalability and compatibility of standard top-down microfabrication in creating periodic metallic nanostructures that are not easily available by conventional nanofabrication. The resulting nanopyramid arrays show stable surface enhancements for Raman scattering from benzenethiol molecules adsorbed at the metal surfaces, even though these sputtered films are not rough.

Controlled growth and field emission properties of zinc oxide nanopyramid arrays

Single-crystalline, pyramidal zinc oxide nanorods have been synthesized in a large quantity on p-Si substrate via catalyst-free thermal chemical vapor deposition at low temperature. SEM investigations showed that the nanorods were vertically aligned on the substrate, with diameters ranging from 60 to 80 nm and lengths about 1.5 μm. A self-catalysis VLS growth mechanism was proposed for the formation of the ZnO nanorods. The field emission properties of the ZnO nanopyramid arrays were investigated. A turn-on field about 3.8 V/μm was obtained at a current density of 10 μA/cm 2, and the field emission data was analyzed by applying the Fowler–Nordheim theory. The stability of emission current density under a high voltage was also tested, indicating that the ZnO nanostructures are promising for an application such as field emission sources.

Self-organized tantalum oxide nanopyramidal arrays for antireflective structure

A self-organized tantalum oxide nanopyramidal structure without tedious semiconductor processing is proposed in this letter. Construction of pyramid arrays with a close-packed periodicity of 200nm and a height of 200nm was achieved by the anodic alumina template method directly on the substrate. The tantalum oxide nanopyramidal structure was formed as the underlying tantalum film oxidized and localized precisely by the pore of alumina. The reflectance from the spectroscopic measurement suggests that the nanopyramidal array structures have more broadband antireflection (<2%) than the nanodot arrays and thin film structures.

Selective growth of carbon nanostructures on nickel implanted nanopyramid array

Carbon nanostructures (CN) have been selectively grown directly onto the top of nickel ion implanted nanopyramid array (Ni NPA) by the plasma enhanced chemical vapor deposition (p-CVD) technique. Firstly, NPA were fabricated by taking advantage of the anisotropic etching characteristics of silicon in hydrazine (N 2H 4H 2O); where the ion implanted area acted as a mask for hydrazine etching. Secondly, carbon nanostructures were grown on Ni NPA by feeding methane/hydrogen (CH 4/H 2) mixtures into p-CVD reactor. The change of concentration ratio of methane to hydrogen dramatically affected the growth selectivity of CN. Methane concentrations lower than 20%, promoted the selective growth of CN on the top of Ni NPA. Morphology and chemical nature of grown species were studied by employing scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy, respectively.

FABRICATION OF ULTRAHIGH-DENSITY NANO-PYRAMID ARRAYS (NPAs) ON (100) SILICON WAFER USING SCANNING PROBE LITHOGRAPHY AND ANISOTROPIC WET ETCHING

International Journal of Computational Engineering ScienceVol. 04, No. 03, pp. 695-698 (2003) Poster PapersNo AccessFABRICATION OF ULTRAHIGH-DENSITY NANO-PYRAMID ARRAYS (NPAs) ON (100) SILICON WAFER USING SCANNING PROBE LITHOGRAPHY AND ANISOTROPIC WET ETCHINGJENG T. SHEU, CHENG C. CHEN, SUN P. YEH, and HSEIH T. CHOUJENG T. SHEUDepartment of Electrical Engineering, National Chi Nan University, No. 1, University Rd., Puli, Nantou 545, Taiwan, R.O.C. Search for more papers by this author , CHENG C. CHENDepartment of Electrical Engineering, National Chi Nan University, No. 1, University Rd., Puli, Nantou 545, Taiwan, R.O.C. Search for more papers by this author , SUN P. YEHDepartment of Electrical Engineering, National Chi Nan University, No. 1, University Rd., Puli, Nantou 545, Taiwan, R.O.C. Search for more papers by this author , and HSEIH T. CHOUDepartment of Electronic Engineering, National Yunlin University of Science and Technology, 123, University Rd., Section 3, Touliu , Yunlin 640, Taiwan, R.O.C. Search for more papers by this author https://doi.org/10.1142/S1465876303002076Cited by:0 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail AbstractConvex and concave nano-pyramid Arrays (NPAs) with an areal bit density of 258 Gbits/in2 has been demonstrated by means of scanning probe lithography (SPL) and wet ecthing on the (100) silicon wafer. We investigated the use of a contact-mode atomic force microscope (AFM) in the generation of oxide patterns on silicon (100) surfaces. Subsequently, utilizing oxide patterns as Si etching masks, the Si substrate was dipped in aqueous KOH solution, where un-oxidized regions are selectively etched by aqueous KOH orientation-dependent etching (ODE). Using this simple process, 20nm convex NPAs with 100nm pitch can be fabricated successfully. Similarly, about 2nm concave NPAs with 100nm were obtained after the oxidized samples were dipped in acqueous HF solution, the oxide regions were selectively etched away. To demonstarte the capability of this technology, the ascii codes were written on silicon and the data storage density more than 10 times of current optical recording has been achieved. We also demonstrated that the minimum size of the pyramids and the minimum pitch could be easily controlled by the apex size of the pyramid, that is, the size of the oxidized region by AFM-based field-induced oxidation. The results indicated that this technique has potentials to provide a pathway to the higher densities that will be needed in the decades ahead.Keywords:Nano-pyramid Arraysscanning probe lithographyatomic force microscopeorientation-dependent etching References J. Itoh, Appl. Surf. Sci. 111, 194 (1997). Crossref, Google ScholarS. Y. Chouet al., J. Vac. Sci&Technolo. B 15, 2897 (1997). Crossref, Google ScholarM. Kohet al., Jpn. J. Appl. Phys. 39, 2168 (2000). Google ScholarJ. A. Dagataet al., Appl. Phys. Lett. 56, 2001 (1990). Crossref, Google ScholarE. S. Snow and P. M. Campbell, Appl. Phys. Lett. 64, 1932 (1994). Crossref, Google ScholarJ. A. Dagataet al., J. Appl. Phys. 84, 6891 (1998). Crossref, Google Scholar K. E. Bean , IEEE Trans. Electron Devices ED-25 1185 . Google ScholarS. M. Sze, Semiconductor Device: Physics and Technology (Wiley, New York, 1981) p. 66. Google ScholarPh. Avouriset al., Appl. Phys. A 66, 659 (1998). Crossref, Google Scholar FiguresReferencesRelatedDetails Recommended Vol. 04, No. 03 Metrics History KeywordsNano-pyramid Arraysscanning probe lithographyatomic force microscopeorientation-dependent etchingPDF download

Novel Process for High-Density Buried Nanopyramid Array Fabrication by Means of Dopant Ion Implantation and Wet Etching

A simple and high-throughput process to fabricate a high-density buried nanopyramid array (BNPA) on a Si surface has been developed by means of dopant ion implantation and wet etching. In this process, the combination of two interesting etching phenomena was utilized to form the BNPA. One is the enhanced etching of ion-exposed SiO2 in HF. The other is the newly found retarded etching of ion-exposed Si in hydrazine (N2H4). A p-type Si(100) substrate with 27-nm-thick SiO2 was exposed to 50-keV phosphorus ions with a dotted pattern. Then, the ion-exposed SiO2 was selectively etched away by dipping in HF. Finally, the BNPA was formed under the patterned SiO2 layer by dipping in hydrazine. By using this simple process, the BNPA with 250 nm pitch was successfully fabricated. The electrical property of the fabricated nanopyramid was also investigated using scanning Maxwell-stress microscopy (SMM).

Simple nanostructuring on silicon surface by means of focused beam patterning and wet etching

Two simple and easy processes have been demonstrated to fabricate two-dimensional (2-D) nanostructure array on Si surfaces by using only focused beam patterning and wet etching. First, we took advantage of the enhanced etch rate (ER) of electron-beam-exposed SiO 2 in HF based solution. A 30-nm thick oxide layer was shot with 30-keV focused-electron beam with spot doses ranging from 20 to 140 pC/dot. After development of SiO 2 layer in 1% HF solution, the Si substrate was etched by hydrazine (N 2H 4H 2O) to form pyramidal etch-pits. By using this process, 50-nm concave nanopyramid array (NPA) with 100-nm period can be fabricated successfully. Second, we utilized the newly found retarded ER of ion-beam-exposed Si in hydrazine. 2-D arrays of dots were written directly on the Si substrate with 60-keV Si focused-ion beam (FIB) with a dose of 5×10 14 ions/cm 2. The Si substrate was then dipped in hydrazine solution, where the unexposed region was selectively etched by hydrazine. By using this process, 100-nm convex NPA with 200-nm period can be fabricated easily. The performance of the proposed processes is compared in terms of pattern size, throughput and process diversity.

Simple fabrication of high density concave nanopyramid array (NPA)on Si surface

A simple process to fabricate two-dimensional (2-D) concave nanopyramid array (NPA) with nanometer period on Si surface has been developed by using electron beam (EB) irradiation and wet etching. The enhanced etch rate (ER) of EB-exposed SiO 2 in HF-based solution has been utilized. Mask oxide layers with the thicknesses of 11–30 nm were shot with 30-keV focused EB at spot doses ranging from 20 to 140 pC/dot. EB-exposed SiO 2 layers were selectively etched by dipping in 1% HF or buffered HF (BHF). The Si substrates were then dipped in anisotropic etchant hydrazine (N 2H 4·H 2O) to form concave NPAs, where patterned SiO 2 layers were used as etch mask. By using this simple process, 50-nm period concave NPA with the size of 20 nm was fabricated successfully.

New Process for Si Nanopyramid Array (NPA) Fabrication by Ion-Beam Irradiation and Wet Etching

It has been found that the rate of Si etching by hydrazine (N2H4H2O) is drastically retarded by ion-beam exposure. By utilizing this new phenomenon, a simple process of fabricating nanopyramid arrays (NPAs) on a Si surface is proposed. Two-dimensional arrays of dots and lines are written directly on a Si substrate with 60 keV Si, P and BF2 ion beams at doses of 1013–1015 cm-2. Subsequently, the Si substrate is dipped in hydrazine solution, where unexposed regions are selectively etched by hydrazine. Using this simple process, 130 nm convex NPAs with 200 nm pitch and 40 nm concave NPAs with 150 nm pitch can be fabricated easily. It is shown that the electrical property of the apex of the pyramid can be controlled by dopant ion irradiation. The cause of the retarded etch rate of ion-beam-exposed Si by hydrazine is comprehensively discussed.