Magnetically Guided Nano–Micro Shaping and Slicing of Silicon

Abstract

Silicon is one of the most important materials for modern electronics, telecom, and photovoltaic (PV) solar cells. With the rapidly expanding use of Si in the global economy, it would be highly desirable to reduce the overall use of Si material, especially to make the PVs more affordable and widely used as a renewable energy source. Here we report the first successful direction-guided, nano/microshaping of silicon, the intended direction of which is dictated by an applied magnetic field. Micrometer thin, massively parallel silicon sheets, very tall Si microneedles, zigzag bent Si nanowires, and tunnel drilling into Si substrates have all been demonstrated. The technique, utilizing narrow array of Au/Fe/Au trilayer etch lines, is particularly effective in producing only micrometer-thick Si sheets by rapid and inexpensive means with only 5 μm level slicing loss of Si material, thus practically eliminating the waste (and also the use) of Si material compared to the ~200 μm kerf loss per slicing and ~200 μm thick wafer in the typical saw-cut Si solar cell preparation. We expect that such nano/microshaping will enable a whole new family of novel Si geometries and exciting applications, including flexible Si circuits and highly antireflective zigzag nanowire coatings.

Direct Imprinting of Porous Silicon via Metal‐Assisted Chemical Etching

“…On the one hand, thin-fi lm based MACE still relies on 2D templating techniques to pattern the catalyst-such as photolithography, [ 33 ] e-beam lithography, [ 22 ] interference lithography, [ 35 ] thin-fi lm dewetting, [ 25 ] nanosphere lithography, [ 36 ] and block-copolymer lithography. While there has been reported success in the control the catalyst etch direction to achieve 3D features via magnetic-assisted MACE [ 38,39 ] and engineering the catalyst motion, [ 22,[40][41][42] these approaches have limited control over the span of 3D features it can produce and have not been demonstrated to have high repeatability. This characteristic adds to the processing complexity, generates waste, and makes MACE's cost and scalability a function of other processes.…”

Tailored Assembly of Molecular Water Oxidation Catalysts on Photoelectrodes for Artificial Photosynthesis

“…[32][33][34] For bias-free watersplitting PEC cells, any combination of n-and p-type semiconductors can be utilized as a photoanode (e.g., Fe 2 O 3 , [35,36] BiVO 4 , [37,38] WO 3 , [39][40][41] etc.) and a photocathode (e.g., Si, [42,43] Cu 2 O, [44,45] CuBi 2 O 4 , [46,47] etc. ), respectively, if a combined band gap is larger than 1.23 eV and the VB edge of a photoanode and the CB edge of a photocathode straddle the redox poten- tials for OER and HER.…”

Effect of isopropanol on gold assisted chemical etching of silicon microstructures

“…Moreover, charge carriers are injected into Si and charge distribution affects the catalyst movement [21], so that parallel and elongated structures [16] are more difficult to etch than spaced cavities [22]. Electron-hole concentration balancing structures were used to achieve a vertical etch profile [16], negative carbon mask [23,24], electrical bias [24,25], magnetic catalyst [26] to improve the control of the catalyst movement [27][28][29]. The holes diffuse from the Si under the metal to either the off-metal areas or to the walls of the pore if the rate of the holes consumption at the Au-Si interface is smaller than the rate of holes injection.…”