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Simple, fast, and cost-effective fabrication of wafer-scale nanohole arrays on silicon for antireflection

A simple, fast, and cost-effective method was developed in this paper for the high-throughput fabrication of nanohole arrays on silicon (Si), which is utilized for antireflection. Wafer-scale polystyrene (PS) monolayer colloidal crystal was developed as templates by spin-coating method. Metallic shadow mask was prepared by lifting off the oxygen etched PS beads from the deposited chromium film. Nanohole arrays were fabricated by Si dry etching. A series of nanohole arrays were fabricated with the similar diameter but with different depth. It is found that the maximum depth of the Si-hole was determined by the diameter of the Cr-mask. The antireflection ability of these Si-hole arrays was investigated. The results show that the reflection decreases with the depth of the Si-hole. The deepest Si-hole arrays show the best antireflection ability (reflection 600 nm), which was about 28 percent of the nonpatterned silicon wafers reflection. The proposed method has the potential for high-throughput fabrication of patterned Si wafer, and the low reflectivity allows the application of these wafers in crystalline silicon solar cells.

Antireflection characteristics of inverted nanopyramid arrays fabricated by low-cost nanosphere lithography technology

A simple and effective process based on nanosphere lithography for the fabrication of periodic inverted nanopyramid structure is presented in this article. The prepared nanostructure has almost a drop of 40% in the average reflectance at normal incidence, when compared with its corresponding bare silicon surface. Moreover, we obtained the reflection spectra for bare silicon substrate and prepared nanostructure through experiments and numerical calculations, and the results agreed well with each other, respectively. Therefore, we can combine the simulation method and fabrication method together to optimize the nanostructured antireflection coatings for better antireflection characteristics, and this methodology is robust and promising for the development of crystalline silicon solar cells. We further discussed the influences of pyramid size and the lattice constant of the nanopyramid array on the antireflection effect by numerical calculation, and we got a conclusion that the antireflection effect is positively correlated with the area-ratio defined as the ratio of the sum of the area of the nanopyramid holes in a unit cell to the area of a unit cell. Finally, we provide some direction and help for other researchers about the antireflection application of inverted nanopyramid arrays.

A Novel Fabrication Process of Large Area Triangular Nanocavity Arrays by Bilayer Nanosphere Lithography

A simple and novel self-assembly based process is presented in this paper for the fabrication of gold triangular nanocavity arrays. This process combines nanosphere lithography (NSL) with some standard MEMS technologies. A carboxylated polystyrene (PS) nanosphere bilayer with a relatively large area is fabricated on silicon wafer as the starting template by spin-coating. Oxygen plasma etching, metal deposition and lifting-off of the PS upper layer are then orderly carried out for the formation of triangular space, which is made up of Cr film and the remaining PS nanoparticles. Then silicon etching is used to transfer the triangle pattern onto the silicon wafer. Finally, a 50 nm thick gold layer is deposited on the pattern to fabricate gold triangular nanocavity arrays. With this strategy, both the period and the cavity size can be adjusted independently. This will allow the tuning of the optical properties for desired application.

Inexpensive and fast fabrication of ordered gold nanocone arrays

Metallic nanocones are particularly interesting recently for the electromagnetic field concentration occur near sharp tips, but the fabrication is still a problem for their application. In this paper, a simple self-assembly based templating approach was presented for the fabrication of ordered gold nanocone arrays. The double-layered silica colloidal crystal was utilized as etching masks to develop inverted tapered silicon nanopits onto silicon substrates. Gold nanocone arrays can then be replicated from silicon templates simply by sacrificial layer removing and adhesive peeling process. The resulting gold nanocone array was characterized by field emission scanning electron microscopy (SEM).

MEMS Assisted Fabrication of Cr Nanobowls

Various bowl-shape nanostructures have attracted widely attention for their potential applications in novel optical, electronic and biomedical fields. With the assistance of MEMS standard process, we present an inexpensive and fast approach in this paper for the fabrication of 2-D interconnected networks of Cr nanobowls. Spin-coated monolayer silica-polymer hexagonal ordered colloidal crystal was used as starting templates to create polymer nanowells. Then metal deposition and calcination process helped to develop Cr nanobowls with polymer nanowells as templates. The 2-D nanostructures were characterized by field emission scanning electron microscopy (SEM). Our fabrication approach of nanobowls can be extended to a wide range of metal materials and substrates with controlled size and wall thickness.