"A 500×500 µm photoluminescence image of “Ancient of Days” was created in porous silicon using focused helium beam writing and subsequent electrochemical etching in hydrofluoric acid. Due to quantum confinement effect, visible light emission is observed from the nanosized silicon skeleton left behind after etching. It is found that pre-irradiation with a helium beam is able to change the local resistivity of the silicon and the emission wavelength of the porous silicon formed. The higher the dose of the beam, the redder the photoluminescence wavelength becomes." Credit: Ee Jin Teo, National University of Singapore
essentialsaltes) wrote, 