Sahu et al. Nanoscale Research Letters 2011, 6:178 http://www.nanoscalereslett.com/content/6/1/178 N A N O E X P R E S S Open Access Effect of annealing treatments on photoluminescence and charge storage mechanism in silicon-rich SiN :H films x Bhabani Shankar Sahu*, Florian Delachat, Abdelilah Slaoui, Marzia Carrada, Gerald Ferblantier, Dominique Muller Abstract In this study, a wide range of a-SiNx:H films with an excess of silicon (20 to 50%) were prepared with an electron- cyclotron resonance plasma-enhanced chemical vapor deposition system under the flows of NH3 and SiH4. The silicon-rich a-SiNx:H films (SRSN) were sandwiched between a bottom thermal SiO2 and a top Si3N4 layer, and subsequently annealed within the temperature range of 500-1100°C in N2 to study the effect of annealing temperature on light-emitting and charge storage properties. A strong visible photoluminescence (PL) at room temperature has been observed for the as-deposited SRSN films as well as for films annealed up to 1100°C. The possible origins of the PL are briefly discussed. The authors have succeeded in the formation of amorphous Si quantum dots with an average size of about 3 to 3.6 nm by varying excess amount of Si and annealing temperature. Electrical properties have been investigated on Al/Si3N4/SRSN/SiO2/Si structures by capacitance- voltage and conductance-voltage analysis techniques. A significant memory window of 4.45 V was obtained at a low operating voltage of ± 8 V for the sample containing 25% excess silicon and annealed at 1000°C, indicating its utility in low-power memory devices. Introduction Silicon nitride-based dielectrics are drawing considerable attention because of their utility in a wide variety of electronic and optoelectronic applications due to their compatibility with the existing mainstream CMOS tech- nology and tunable emission in visible range, which can be applied for developing non-volatile memories and Si- based light-emitting diodes [1-6]. The field strength is needed for electroluminescence in SiOx close to the breakdown strength of silicon oxide (6-10 MV/cm) [7,8]. In this regard, SiNx can be a better choice, as the field needed to inject electrons and holes (2-4 MV/cm) is weaker than that of SiO2, and is much lower than the breakdown strength of Si3N4 (9 MV/cm) [9,10]. Even if the band gap of Si3N4 is approximately 5.3 eV (8.2 eV for SiO2), it should be sufficient to confine charge car- riers into SiNx matrix [11]. In addition, SRSN also con- tains a high density of deep level electron and hole traps, which can give rise to a strong trapping of elec- trons and holes, indicating its utility for light-emitting * Correspondence: sahu.bhabani@iness.c-strasbourg.fr InESS-UdS-CNRS, 23 Rue du Loess, 67037 Strasbourg, France as well as charge storage devices. Another major interest for using silicon nitride rather than silicon oxide is the possibility of obtaining efficient emission at relatively shorter wavelength. Several authors have reported intense luminescence in blue-green region, which is very rare in silicon oxide-based materials [12,13] and there- fore provides the possibility for fabricating full-color devices based on silicon technology. Previous studies revealed that the PL from silicon nitride films can be significantly enhanced with the introduction of a ther- mal SiO2 buffer interlayer and subsequent high-tem- perature annealing in N2 ambient [14]. However, it is still unclear at which annealing temperatures the PL is the strongest, and how does this annealing temperature depend on excess of Si in the silicon-rich silicon nitride (SRSN) films, and what physical mechanisms are responsible for the PL enhancement. In addition, SiN/SiO2 stack structures have wide applications in non-volatile charge memories (NVMs). Their use started since early 1970s as metal-nitride- oxide-silicon (MNOS) structures [15], and their various derivatives, such as metal-oxide-nitride-oxide- silicon (MONOS), silicon-nitride-oxide-silicon (SNOS), © 2011 Sahu et al; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.