We investigated the high absolute photoluminescence quantum yields (PL QYs) from tunable luminescent amorphous silicon oxynitride (a-SiN_xO_y) films. The PL QY of 8.38 percent has been achieved at PL peak energy of 2.55 eV in a-SiN_xO_y systems, which is higher than those of reported nanocrystal-Si embedded silicon nitride films. The existence of N-Si-O bonding states was confirmed by performing FTIR, XPS and EPR measurements. The PL QY is proportional to the concentration of N_x defects, indicating the dominant contribution of luminescent N-Si-O bonding states in radiative recombination processes. Particularly, we precisely monitored the ns-PL lifetimes evolution profile versus detected emission wavelengths, and further verified that the N-Si-O bonding states are responsible for highly efficient PL.

We reported the study on the photoluminescence internal quantum efficiency (PL IQE) and external quantum efficiency (PL EQE) from the amorphous silicon oxynitride (a-SiNO) films, which were fabricated by plasma-enhanced chemical vapor deposition followed by in situ plasma oxidation. We employed the direct measurement of absolute quantum efficiency within a calibrated integration sphere to obtain the PL EQE. Then, we calculated the PL IQE by combing the measured EQE and optical parameters of light extraction factor, reflectivity, and transmittance of the a-SiNO thin films. We also derived the PL QE through investigating the characteristic of the temperature dependent PL. These results show that the PL IQE as high as 60% has been achieved at peak wavelength of about 470 nm, which is much higher than that of Si nanocrystal embedded thin films.

Si nanocrystals are formed by using KrF pulsed laser crystallization of an amorphous SiC/ultrathin amorphous Si/amorphous SiC sandwiched structure. Electrons and holes are injected into Si nanocrystals via a biased conductive AFM tip and the carrier decay and transportation behaviours at the nanoscale are studied by joint characterization techniques of Kelvin probe force microscopy (KPFM) and conductive atomic force microscopy (CAFM). Quantification of the surface charge density is realized by solving the Poisson equation based on KPFM measurements. Besides, the asymmetric barrier height for electrons and holes is considered to play a dominant role in controlling the charge retention and transportation characteristics. The methodology developed in this work is promising for studying the charge injection and transportation process in other materials and structures at the nanoscale.

We have reported high internal quantum efficiency (IQE) (∼60%) of photoluminescence (PL) at 470 nm wavelength from oxygenated amorphous silicon nitride (a-SiN_x:O) films. In this work, we explored the dynamics of high PL IQE from luminescent N-Si-O bonding states in a-SiN_x:O films by using a combination of time resolved PL (TRPL) and temperature dependent PL (TDPL) measurements. The TRPL measurements include time integrated PL, microsecond range PL, and nanosecond range PL measurement modes. The a-SiN_x:O films exhibit ns PL decay dynamics that is independent of pumping fluence (W_PF) and uniform across the PL spectrum, which is different from the PL decay behavior in a-SiN_x films. Particularly, we precisely monitored the temporal evolution of the PL spectra profile to verify that the luminescent N-Si-O bonding states are responsible for the observed blue PL with a radiative recombination rate of ∼10⁸ s⁻¹. Such very fast radiative recombination rate can be compared with that in direct band gap CdSe nanocrystals and can also help us to understand the high PL IQE in a-SiN_x:O films. Moreover, by combining the TD-PL lifetimes with the PL IQE values, the temperature dependence of radiative and nonradiative lifetime can be determined.

Last year, we have reported that the internal quantum efficiency of photoluminescence (PL) from amorphous silicon oxynitride (a-SiN_xO_y) films has been achieved as high as 60%. The present work intensively investigated the mechanisms for tunable PL in the 2.05–2.95 eV range from our a-SiN_x:O films, by using a combination of optical characterizations, X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) measurements. The results of XPS, EPR, and photoluminescence excited measurements indicated that the incorporation of oxygen atoms into silicon nitride (a-SiN_x) networks not only reduced the band tail structure disorder (Urbach tail width E_U) but also created N-Si-O (N_x) defect states in the band gap. We have discovered the distinctive PL characteristics from a-SiN_x:O films with various NH_3/SiH₄ ratios. The PL peak energy (E_PL) is independent of the excitation energy (E_exc) and the PL intensity (I_PL) is regardless of the optical band gap (E_opt) but is proportional to the N_x defects concentration, both of which are completely different from the PL characteristics by band tail states recombination mechanism, in which the E_PL is proportional to E_exc (when E_exc ≤ E_opt) and the I_PL is dependent on the relative position of E_exc and E_opt. Based on the N-Si-O bonding configurations and the distinctive PL characteristics, the radiative recombination mechanism through the N-Si-O defect states has been proposed, by which the performance of stimulated emission may be realized in this kind of a-SiN_x:O films.