Silicon nanopillars were fabricated by using deep UV lithography, highly anisotropic silicon reactive ion etching based on fluorine chemistry, and high-temperature thermal oxidation for further thinning. Pillars with a diameter below 10 nm and a height in the 0.4–0.6 μm range were obtained while lying on a very smooth bottom silicon surface. An isolating transparent polymer was then used to fill in the etched area containing the pillars and, therefore, planarize and isolate the pillars. Oxygen plasma was used in order to remove the resistance from the top of the pillars. They were then contacted by a thin contact layer (gold or indium tin oxide), evaporated on the top of them. An Ohmic contact was also formed on the back side of the wafer. The obtained device showed rectifying behavior and forward voltages exceeding 10–12 V electroluminescence was observed, visible with the naked eye.

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Visible luminescence from silicon nanostructures fabricated by using conventional lithographic and reactive ion etching techniques and final thinning by high temperature thermal oxidation was obtained at room temperature under 488 nm argon laser excitation. Highly anisotropic vertical silicon pillars with aspect ratios as high as 25:1 and diameter below 0.1 μm, as well as silicon walls of the same sizes were first produced, which were further thinned by several cycles of thermal oxidation and oxide removal by HF dip. Sub-10 nm diameter silicon pillars and same thickness silicon walls with height in the μm range were thus produced. The fabrication process involved high resolution deep-UV lithography, highly anisotropic silicon etching, and final thinning of the silicon structures by oxidation and oxide removal. The initial pattern of dots and lines was defined by optical lithography using the well known silylation process. The resolution of the process in dot and line size definition was equal to 0.22 μm but lower dimensions down to less than 0.1 μm were obtained in overexposed regions during dry development in a plasma reactor. Three different masks were used for the silicon etching: Cr or Al metal masks or silylated photoresist, all being resistant to the silicon etchants. Highly anisotropic reactive ion etching was achieved by a process using a mixture of SF6 and CHF3 gases at room temperature.

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