Visible light emission spectra of individual microstructures of porous Si

Abstract

We have measured the spectra of visible light emitted from the individual structures of porous Si (PS) below the probe tip of the scanning tunneling microscope (STM), and found that the peak energy of the emission spectrum shifts with the size of nanometer-scale structures on the PS surface. Samples with a PS layer ∼50 nm thick were formed by anodic etching of p+Si(100) substrates (∼0.005 Ω cm). The STM images show that protrusions whose dimensions are 3–10 nm in diameter are distributed on the PS surface. The peak energy of the STM light emission spectrum shifts from ∼1.7 to ∼2.1 eV as the diameter of the structure below the STM tip decreases from ∼9 to ∼3 nm. The measured peak shift with the size of the structure is consistent with the shift of the energy gap predicted on the basis of a quantum confinement model.

Positron irradiation: A technique for modifying the photoluminescent structures of porous silicon

“…17 crystallites decreased in size from 9 to 3 nm. 18 Thus, our most straightforward hypothesis to explain the two-peak PL is to relate it to the nano-Si crystallites and the presence of positrons.…”

Origin of photoluminescence in nanocrystalline Si:H films

“…The PL peak energy in H-terminated nc-Si is very sensitive to the nanocrystal size [33,34], compared with surface-oxidized nc-Si [5,34]. Luminescence properties of H-terminated nc-Si are considered to be different from those of surface-oxidized nc-Si [35].…”

Functional properties of luminescent porous silicon as a component of optoelectronic integration

“…In the visible-light emission mechanism of PS, quantum-sized silicon crystallites play an important role. Much experimental data supporting band-gap widening in PS have been reported by means of optical absorption [3,4], vacuum ultraviolet photoelectron spectroscopy [5,6] and direct observation of silicon nanocrystallites [7,8]. Visible luminescence was also observed from a Si/SiO 2 superlattice [9].…”