Limits...
Effect of annealing treatments on photoluminescence and charge storage mechanism in silicon-rich SiNx:H films.

Sahu BS, Delachat F, Slaoui A, Carrada M, Ferblantier G, Muller D - Nanoscale Res Lett (2011)

Bottom Line: 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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: InESS-UdS-CNRS, 23 Rue du Loess, 67037 Strasbourg, France. sahu.bhabani@iness.c-strasbourg.fr.

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.

No MeSH data available.


Room temperature PL spectra. (a) (Color online) Room temperature PL spectra of the sample S3 (29 at.% of silicon excess) subjected to thermal annealing within the temperature range of 500-1100°C, evolution of PL intensities (b), and energies (c) as a function of annealing temperature, (d) evolution of PL intensity of the sample S2, which has been subjected to annealing at 1100°C in N2, and subsequently in forming gas (10% H2 + 90% N2
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211231&req=5

Figure 5: Room temperature PL spectra. (a) (Color online) Room temperature PL spectra of the sample S3 (29 at.% of silicon excess) subjected to thermal annealing within the temperature range of 500-1100°C, evolution of PL intensities (b), and energies (c) as a function of annealing temperature, (d) evolution of PL intensity of the sample S2, which has been subjected to annealing at 1100°C in N2, and subsequently in forming gas (10% H2 + 90% N2

Mentions: Figure 5a shows the evolution of PL of sample S3 containing 29 at.% of excess Si with thermal annealing treatment of up to 1100°C. This evolution is similar for all other samples and is depicted in Figure 5b,c. As evident from Figure 5b, PL intensity increases and reaches a maximum at an annealing temperature of 700°C. A further increase in annealing temperature leads to a significant reduction of the PL intensity. The PL intensity drops to approximately 24% and approximately 10% of its peak value at 900 and 1100°C, respectively. The decrease in PL peak can be attributed to introduction of considerable amount of non-radiative defects after high-temperature annealing. It is reseaonable to expect more disordered structure, which is caused by the breaking of hydrogen bonds and subsequent effusion of hydrogen during high temperature thermal treatment. This phenomenon induces an increase in the number of dangling bonds, giving rise to an enhanced number of non-radiative recombination centers. Thus, the PL observed in the as-deposited sample quenches after high-temperature annealing above 700°C. In addition, a phase separation generally occurs when silicon-rich silicon nitride samples are annealed at high temperature (≥ 950°C), resulting in the formation of Si-nps embedded in a nearly stoichiometric silicon nitride matrix. Although, Si3N4 matrix itself could passivate some dangling bonds, causing non-radiative quenching, there are still a large number of dangling bonds existing in the film, especially at the interface region between Si-nps and Si3N4 matrix. Previously, it has been shown that one dangling bond is sufficient to quench the luminescence of a Si-np [42]. In this respect, the passivation of silicon- and nitrogen-dangling bonds acting as non-radiative recombination centers is an essential requirement for increasing the radiative yield without affecting the emission mechanism. In this regard, some previously annealed samples are subjected to an additional rapid thermal annealing in forming gas at 900°C for 1 min. Figure 5d shows the PL spectra of the sample S2, which has been subjected to annealing at 1100°C in N2, and subsequently in forming gas (10% H2 + 90% N2). The PL peak intensity increases about 28% due to this additional forming gas annealing step, indicating passivation of some non-radiative recombination centers. It is noteworthy that the overall behavior of the PL band remains unchanged, indicating no change in the emission mechanism. Optimization of this hydrogen passivation process is currently under investigation.


Effect of annealing treatments on photoluminescence and charge storage mechanism in silicon-rich SiNx:H films.

Sahu BS, Delachat F, Slaoui A, Carrada M, Ferblantier G, Muller D - Nanoscale Res Lett (2011)

Room temperature PL spectra. (a) (Color online) Room temperature PL spectra of the sample S3 (29 at.% of silicon excess) subjected to thermal annealing within the temperature range of 500-1100°C, evolution of PL intensities (b), and energies (c) as a function of annealing temperature, (d) evolution of PL intensity of the sample S2, which has been subjected to annealing at 1100°C in N2, and subsequently in forming gas (10% H2 + 90% N2
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211231&req=5

Figure 5: Room temperature PL spectra. (a) (Color online) Room temperature PL spectra of the sample S3 (29 at.% of silicon excess) subjected to thermal annealing within the temperature range of 500-1100°C, evolution of PL intensities (b), and energies (c) as a function of annealing temperature, (d) evolution of PL intensity of the sample S2, which has been subjected to annealing at 1100°C in N2, and subsequently in forming gas (10% H2 + 90% N2
Mentions: Figure 5a shows the evolution of PL of sample S3 containing 29 at.% of excess Si with thermal annealing treatment of up to 1100°C. This evolution is similar for all other samples and is depicted in Figure 5b,c. As evident from Figure 5b, PL intensity increases and reaches a maximum at an annealing temperature of 700°C. A further increase in annealing temperature leads to a significant reduction of the PL intensity. The PL intensity drops to approximately 24% and approximately 10% of its peak value at 900 and 1100°C, respectively. The decrease in PL peak can be attributed to introduction of considerable amount of non-radiative defects after high-temperature annealing. It is reseaonable to expect more disordered structure, which is caused by the breaking of hydrogen bonds and subsequent effusion of hydrogen during high temperature thermal treatment. This phenomenon induces an increase in the number of dangling bonds, giving rise to an enhanced number of non-radiative recombination centers. Thus, the PL observed in the as-deposited sample quenches after high-temperature annealing above 700°C. In addition, a phase separation generally occurs when silicon-rich silicon nitride samples are annealed at high temperature (≥ 950°C), resulting in the formation of Si-nps embedded in a nearly stoichiometric silicon nitride matrix. Although, Si3N4 matrix itself could passivate some dangling bonds, causing non-radiative quenching, there are still a large number of dangling bonds existing in the film, especially at the interface region between Si-nps and Si3N4 matrix. Previously, it has been shown that one dangling bond is sufficient to quench the luminescence of a Si-np [42]. In this respect, the passivation of silicon- and nitrogen-dangling bonds acting as non-radiative recombination centers is an essential requirement for increasing the radiative yield without affecting the emission mechanism. In this regard, some previously annealed samples are subjected to an additional rapid thermal annealing in forming gas at 900°C for 1 min. Figure 5d shows the PL spectra of the sample S2, which has been subjected to annealing at 1100°C in N2, and subsequently in forming gas (10% H2 + 90% N2). The PL peak intensity increases about 28% due to this additional forming gas annealing step, indicating passivation of some non-radiative recombination centers. It is noteworthy that the overall behavior of the PL band remains unchanged, indicating no change in the emission mechanism. Optimization of this hydrogen passivation process is currently under investigation.

Bottom Line: 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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: InESS-UdS-CNRS, 23 Rue du Loess, 67037 Strasbourg, France. sahu.bhabani@iness.c-strasbourg.fr.

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.

No MeSH data available.