Electroluminescence microspectroscopy of silicon nanocrystals obtained by Si⁺ion implantation in SiO₂

Abstract

Room-temperature electroluminescence (EL) has been measured at both macroscopic and microscopic levels from metal-oxide-semiconductor devices containing silicon nanocrystals (Si-nc) embedded in silicon dioxide (SiO(2)) obtained by high-temperature annealing (1050 and 1100 °C) after Si(+) ion implantation. It is found that spatially integrated (macroscopic) EL is dominated by a near-infrared band centered where the photoluminescence (PL) band of Si-nc (from 700 to 1000 nm) is located. However, on a microscopic scale, EL emission is inhomogeneous, the sample surface exhibiting many visible spots of micron-order diameter. EL spectra from a microscopic surface of ∼1 µm(2)(μEL) on visible spots have revealed dominant contributions between ∼550 and ∼650 nm, attributed to oxide defects. These spectral features rapidly decrease with distance from a bright spot, while lower-intensity near-infrared contributions (750-950 nm) remain unaffected up to relatively large distances before eventually becoming extinct. The macroscopic EL measurements can be explained as a superposition of the μEL and PL spectra. A luminescent mechanism is proposed in which charge carriers mostly tunnel through high-defect-density channels in the oxide, yielding bright visible spots, while Si-nc in these channels and their surroundings contribute to the luminescence by hosting electron-hole recombinations (EL) and/or exhibiting PL due to optical excitation from the nearby visible EL spot.

Effects of an Applied Electric Field on Silicon Nanocrystals Photoluminescence

“…The implantation profiles, according to SRIM simulations and previously published for similar samples [6], indicate a maximal excess Si concentration of 9 x 10 21 cm -3 (28%) with a majority of implanted ions lying in the lower half of the oxide, near the Si/SiO 2 interface. The sample has been annealed at 1050ºC for 1 hour under N 2 ambient, and then passivated in a forming gas of H 2 (5%) and N 2 (95%) at 500ºC for 30 min.…”

Visible electroluminescence on FTO/thin SRO/n-Si structures

“…SRO films can be obtained by Si-implantation into thermal SiO 2 layers, laser ablation, electrochemistry, low-energy cluster beam deposition, reactive Si deposition, sputtering, plasma enhanced chemical vapour deposition (PECVD) or low pressure chemical vapour deposition (LPCVD) [9][10][11][12][13][14][15][16][17]. There are few works using SiO x (x ≤ 2) films as active layer to obtain electroluminescent devices and they usually require high voltages to obtain narrow bands of electroluminescence (EL) and even the exact nature of the transitions have not been conclusively established probably due to the difficulty of carrier injection in a semi-insulating material [18][19][20]. Also, there are other reports of EL from Si based materials, but in these reports, the used material like contact electrode can be expensive, not easily obtained, without the best optical or electrical properties and then, the EL devices produce low efficiency.…”