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Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 18, Iss. 5 — Mar. 1, 2010
  • pp: 4449–4456
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Plasma power controlled deposition of SiOx with manipulated Si Quantum Dot size for photoluminescent wavelength tailoring

Bo-Han Lai, Chih-Hsien Cheng, Yi-Hao Pai, and Gong-Ru Lin  »View Author Affiliations


Optics Express, Vol. 18, Issue 5, pp. 4449-4456 (2010)
http://dx.doi.org/10.1364/OE.18.004449


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Abstract

Plasma power controlled PECVD of SiOx under SiH4/N2O gas mixture with manipulated Si quantum dot (Si-QD) size for tailoring photoluminescent (PL) wavelength is demonstrated. The incomplete decomposition of N2O at high plasma power facilitates Si-rich SiOx deposition to enlarge O/Si composition ratio and to shrink Si-QD size. As RF plasma power increases from 20 to 70 W, the O/Si ratio is increased from 1 to 1.6 and the average Si-QD size is reduced from 4.5 to 1.7, which increases Si-QD density from 3.2 × 1017 to 3.02 × 1018 cm−3 and blue-shifts PL wavelength from 780 to 380 nm.

© 2010 OSA

1. Introduction

Since 1990, the room-temperature red photoluminescence (PL) from nanocrystallite Si prepared by chemical dissolution of anodized porous Si was preliminarily demonstrated [1

1. L. T. Canham, “Si quantum wire array fabrication by electrochemical and chemical dissolution of wafers,” Appl. Phys. Lett. 57(10), 1046–1048 (1990). [CrossRef]

]. The blue shift phenomenon of PL peak was also observed as the Si porosity increases by lengthening the immersion time in 40% aqueous HF [1

1. L. T. Canham, “Si quantum wire array fabrication by electrochemical and chemical dissolution of wafers,” Appl. Phys. Lett. 57(10), 1046–1048 (1990). [CrossRef]

]. The PL peak of the embedded Si-QD can be detuned by altering different fabrication methods and recipes with reactive pulsed laser deposition at modified the laser power, and then the Si nanostructures yields the red to infrared PL spectra from 620 to 830 nm [2

2. G. Ledoux, J. Gong, F. Huisken, O. Guillois, and C. Reynaud, “Photoluminescence of size-separated silicon nanocrystals: Confirmation of quantum confinement,” Appl. Phys. Lett. 80(25), 4834–4836 (2002). [CrossRef]

]. By using Si-ion-implantation with post-annealing and changing the dosage and energy of Si+ ions, the PL peak around blue-green (470-550 nm) and near-infrared (710-800 nm) region can be obtained [3

3. P. Mutti, G. Ghislotti, S. Bertoni, L. Bonoldi, G. F. Cerofolini, L. Meda, E. Grilli, and M. Guzzi, “Room-temperature visible luminescence from Si nanocrystals in Si implanted SiO2 layers,” Appl. Phys. Lett. 66(7), 851–853 (1995). [CrossRef]

]. By employing the magnetron sputtering deposition and concurrently varying the temperature and ratio of the sputtering targets, the larger Si-QDs with near-infrared PL spectra between 830 and 1030 nm are usually observed [4

4. Y. Osaka, K. Tsunetomo, F. Toyomura, H. Myoren, and K. Kohno, “Visible photoluminescence from Si microcrystals embedded in SiO2 glass films,” Jpn. J. Appl. Phys. 31(Part 2, No. 3B), L365–L366 (1992). [CrossRef]

]. For PECVD fabrication, both near-infrared and blue PL (780-800 and 410 nm) were concurrently observed by altering the fluence ratio of reactant gases and substrate temperature [5

5. C. J. Lin, C. K. Lin, C. W. Chang, Y. L. Chueh, H. C. Kuo, W. G. Diau, L. J. Chou, and G. R. Lin, “Photoluminescence of Plasma Enhanced Chemical Vapor Deposition Amorphous Silicon Oxide with Silicon Nanocrystals Grown at Different Fluence Ratios and Substrate Temperatures,” Jpn. J. Appl. Phys. 45(No. 2A), 1040–1043 (2006). [CrossRef]

]. Therefore, it is an important issue to fine-tune the process parameter for controlling the PL at different colors. In addition, it is relatively easy to deposit lots of excessive silicon by changing the deposition recipes in PECVD system, which provides a Si-rich environment for precipitation of dense Si-QDs in the SiOx film after high temperature annealing. In this work, we demonstrated by changing the radio frequency (RF) plasma power during the PECVD system, the wavelength tunable PL spectra can be obtained from the Si-rich SiOx film and correlated with different Si-QD size, which corresponds to different O/Si composition ratio of the PECVD grown SiOx sample.

2. Experiment setup

3. Results and Discussion

Figure 1
Fig. 1 The PL patterns and HRTEM micrographs of Si-QDs buried in post-annealed Si-rich SiOx grown at RF plasma power of 20, 30, 50, 60, and 70 W, respectively. (From left to right).
shows the PL patterns of Si-rich SiOx with emitting color changing at different RF plasma powers. The color of PL patterns are blue-shifted (red, orange, white, green, blue) with Si-QD average size revealing a decreasing trend (4.5 ± 0.2, 3.5 ± 0.2, 2.5 ± 0.1, 2.1 ± 0.1 and 1.7 ± 0.1 nm obtained from HRTEM image) when increasing RF plasma power (20, 30, 50, 60, and 70 W). Figure 2 (a)
Fig. 2 (a) The PL peak wavelength and intensity (normalized to film thickness) of the post-annealed Si-rich SiOx film versus RF plasma power during PECVD growth. (b) The PL peak wavelength versus Si-QD size
reveals the PL with their intensities normalized to the SiOx film thickness when growing the SiOx film at different RF plasma powers. With RF plasma power increasing from 20 to 70 W, the peak wavelength of PL decreases from 780 to 380 nm and the normalized intensity of PL increases from 0.81 to 5.02 count/nm. For Si-QD size below 3 nm, the HRTEM analyzed average size of Si-QD correlates well with its PL wavelength predicted with a theoretical formula of λ = 1.24/(1.12 + 3.73/d1.39) reported by Delerue et al. [6

6. C. Delerue, G. Allan, and M. Lannoo, “Theoretical aspects of the luminescence of porous silicon,” Phys. Rev. B 48(15), 11024–11036 (1993). [CrossRef]

], where λ is the peak wavelength and d is the Si-QD diameter. It is expected that the Si-H bonds are reduced in the SiOx film grown at high plasma powers, such that the Si-QD are surrounded by fewer hydrogen atoms, which somewhat violates the Delerue’s assumption that all the dangling bonds at Si-QD surface are passivated with hydrogen atoms [6

6. C. Delerue, G. Allan, and M. Lannoo, “Theoretical aspects of the luminescence of porous silicon,” Phys. Rev. B 48(15), 11024–11036 (1993). [CrossRef]

]. Therefore, such a disparity about average Si-QD size obtained from experimental data and theoretical simulation can be well elucidated. Recently, Pi et al. attributed the blue emission to defect states but not to the quantum confinement effect of Si-QDs [7

7. X. D. Pi, R. W. Liptak, J. D. Nowak, N. P. Wells, C. B. Carter, S. A. Campbell, and U. Kortshagen, “Air-stable full-visible-spectrum emission from silicon nanocrystals synthesized by an all-gas-phase plasma approach,” Nanotech. 19(24), 245603 (2008). [CrossRef]

]. The blue PL emission is correlated with the oxidation-induced defects at the surface of Si-NCs. Moreover, the Si-QD surrounding also plays a role on the PL spectrum since the oxidation of the QD surface induces a strong red-shifted PL signal, which has been shown and modeled by Wolkin et al. [8

8. M. V. Wolkin, J. Jorne, P. M. Fauchet, G. Allan, and C. Delerue, “Electronic states and luminescence in porous silicon quantum dots: The role of oxygen,” Phys. Rev. Lett. 82(1), 197–200 (1999). [CrossRef]

]. The recombination mechanism in the oxidized Si-QD is different from that of the original Si-QD under hydrogen passivation. The red-shift of PL obtained from the porous Si sample after oxidation is mainly related to recombination involving a trapped electron or exciton within Si-O bonds. As stated by Wolkin et al. [8

8. M. V. Wolkin, J. Jorne, P. M. Fauchet, G. Allan, and C. Delerue, “Electronic states and luminescence in porous silicon quantum dots: The role of oxygen,” Phys. Rev. Lett. 82(1), 197–200 (1999). [CrossRef]

], the originally oxygen-free porous Si sample kept in Ar atmosphere shows blue PL at wavelength around 400 nm. After exposure by oxygen, the PL is significantly shifted to 600 nm with a 3-dB spectral linewidth greatly broadening from 100 to 200 nm. The FTIR analysis clearly indicates that the absorption at 1070 cm−1 and 850 cm−1 related to Si-O-Si and Si-O-H bonds exist in the oxidized porous Si sample with their intensities enlarging and gradually saturating by lengthening the exposing duration in oxygen environment up to 24 hrs. The PL is dominated by carriers trapped in Si = O bonds after oxidation. However, such a red-shifted PL phenomenon becomes less distinct in the oxygen invasive porous Si sample with Si-QD size larger than 2 nm (for the sample with green PL), while the wavelength shift greatly reduces to 100 nm or less. If the Si-QD size further enlarges to 2.42 nm (for the sample with yellow PL), such a PL wavelength shift completely diminishes no matter the porous Si sample is exposed in oxygen atmosphere or not.

The thickness of Si-rich SiOx film as a function of the RF plasma power during PECVD growth is shown in Fig. 3
Fig. 3 (a) Thickness of the post-annealed Si-rich SiOx film synthesized under different RF plasma powers. Inset: the normalized PL of Si-QDs within Si-rich SiOx film.
. When increasing RF plasma power from 20 to 70 W, the thickness of the Si-rich SiOx film exponentially increases from 80 to 160 nm. As the RF plasma power increases in the PECVD system, the SiH4 and N2O molecules obtain more kinetic energy to decompose themselves in PECVD chamber, thus accelerating the surface reaction and increasing the deposition rate to increase SiOx film thickness at higher RF plasma powers. The inset of Fig. 3 shows the PL spectra of Si-rich SiOx film grown at RF plasma powers from 20 to 70W with their intensities normalized to the SiOx film thickness (in the unit of count/nm). All of the as-grown samples exhibit PL spectra around 400 to 500 nm due to E’δ and weak oxygen bond (WOB) defects [3

3. P. Mutti, G. Ghislotti, S. Bertoni, L. Bonoldi, G. F. Cerofolini, L. Meda, E. Grilli, and M. Guzzi, “Room-temperature visible luminescence from Si nanocrystals in Si implanted SiO2 layers,” Appl. Phys. Lett. 66(7), 851–853 (1995). [CrossRef]

,9

9. J. C. Cheang-Wong, A. Oliver, J. Roiz, J. M. Hernandez, L. Rodrigues-Fernandez, J. G. Morales, and A. Crespo-Sosa, “Optical properties of Ir2+-implanted silica glass,” Nucl. Instrum. Methods Phys. Res. B 175, 490–494 (2001). [CrossRef]

]. After annealing at 1100°C, the PL intensities at visible and near-infrared bands can be greatly enhanced, which is due to the precipitation of Si-QDs in the SiO2 host matrix by heat treatment. The PL blue-shifts its peak from 780 to 380 nm by raising RF plasma power, indicating that the Si-QD in SiOx film greatly shrinks its size. Note that the PL peak centered at 760 nm for the SiOx sample grown at 70 W appears as an artificial signal due to the second order harmonics of the blue PL peak wavelength at 380 nm, which is caused by the grating of the monochromator. From the normalized PL analyses of the SiOx samples prepared at different RF plasma powers shown as below, it is clearly seen that the PL spectral linewidth elucidates a less confined size distribution of Si-QDs within the SiOx grown at lower RF plasma power. When the SiOx is in an extremely Si-rich condition with high density of excessive Si atoms, the Si-QDs with versatile size can be precipitated as a lot of Si atoms are distributed within the diffusion range at a specific annealing temperature. Except the sample grown at RF plasma power of 70 W with a left-side cut blue PL spectrum due to the 325-nm laser line filter, we also observe that enlarging the RF plasma power from 20 to 60 W during SiOx growth apparently shrinks the PL spectral linewidth from 280 to 210 nm. Such a narrowing PL linewidth directly corresponds to a varied standard deviation of Si-QD size from 22% to 16% with shrinking Si-QD size. We did not take into account the sample with blue PL as the observed spectrum is somewhat distorted due to the high-pass laser line filter in front of the monochromator, which induces a sharp cut around the wavelength of 350 nm.

Figure 4 (a)
Fig. 4 (a) TEM-XEDS measured O/Si composition ratios of as-grown and 10-min post-annealed SiOx film versus RF plasma power. (b) The RF plasma power dependent size and volume density of Si-QDs in post-annealed SiOx samples.
shows the O/Si composition ratios of the as-grown and annealed SiOx samples obtained from TEM-XEDS. In more detail, there are distinct deviation on the density of Si and O atoms dissociated from SiH4 and N2O at low RF plasma powers, since the dissociation energy of SiH4 (75.6 kcal/mol) is much smaller than that of N2O (112 kcal/mol), yielding more Si than O to facilitate the synthesis of Si-rich SiOx. Thus, a higher concentration of the excessive Si atoms can easier be obtained with lower RF plasma power during PECVD growth. Because the oxygen is unable to be decomposed from the N2O molecule under a low-plasma power deposition, and therefore the largest concentration of the excessive Si atom can be expected in the SiOx grown under RF plasma power of 20 W, in which more excess Si atoms can contribute to the formation of Si-QD. With the XEDS analysis built-in with the TEM system, the O/Si composition ratio can be quantitatively calculated by using the Cliff-Lorimer equation [12

12. D. B. Williams, and C. B. Carter, Transmission Electron Microscopy, New York: Plenum, pp. 599–619 (1996).

]. The weight percentages of elements (CA and CB) in a binary system and their XEDS measured signal intensities can be correlated with CA/CB = kAB × (IA/IB), where the term kAB is the Cliff-Lorimer factor, IA and IB are the TEM/XEDS measured signal intensities [12

12. D. B. Williams, and C. B. Carter, Transmission Electron Microscopy, New York: Plenum, pp. 599–619 (1996).

]. The absolute values of CA and CB are obtained at a specific kAB factor while assuming A and B atoms constitute 100% of the specimen (i.e. CA + CB = 100%). After subtracting the background noise and integrating the peak intensity, the individual compositions in terms of atomic% or weight fraction can be obtained [12

12. D. B. Williams, and C. B. Carter, Transmission Electron Microscopy, New York: Plenum, pp. 599–619 (1996).

]. Such a calculation procedure is similar with those used in XPS or RBS analyses. The O/Si ratio of the as-grown SiOx is linearly increased from 1 to 1.6 as RF plasma power enlarges from 20 to 70 W. Similar increasing trend stands for the SiOx sample after annealing. Apparently, the SiOx film also enlarges its O/Si composition ratio by at least Δ(O/Si) = 0.08 after 10-min annealing. A larger deviation up to Δ(O/Si) = 0.15 between the as-grown and annealed SiOx grown at lower RF plasma powers is mainly attributed to the enhanced Si-QD precipitation procedure in these cases. There is still a partial pressure of oxygen existed in the furnace even though the SiOx samples were annealed under flowing N2 ambient. The excess Si atom density for the SiOx grown at RF plasma power of 20 W is the highest one among all samples, such that the residual oxygen atoms can easily invade into SiOx films with lower O/Si composition ratios during furnace annealing. With increasing RF plasma power, the N2O can be dissociated more completely to promote more free radicals of O atoms during the reaction on Si substrate surface, which involves the replacement of Si-H bonds by Si-O bonds to increase O/Si composition ratio. When annealing at higher temperatures, the excessive interstitial Si atoms obtain larger kinetic energy to accumulate and to form bigger Si-QDs. Since there are numerous Si and insufficient O atoms, the Si atoms can simply move and accumulate without restrain by Si-O bonds. That is, it could be easier to synthesize Si-rich SiOx film embedded with larger Si-QDs if the PECVD-grown SiOx film has lower O/Si composition ratio to preserve dense excessive Si atoms congenitally. In contrast, only small Si-QDs can be precipitated by the aggregation of fewer Si atoms in PECVD-grown SiOx film with high O/Si composition ratios. These few Si atoms must travel a long distance within SiOx matrix and restrain from more Si-O bonds. The inset of Fig. 3 also shows that the size of Si-QD is concurrently decreased from 4.5 ± 0.2 nm to 1.7 ± 0.1 nm as the RF plasma power increases from 20 to 70 W. Moreover, the TEM-estimated volume density of Si-QDs within the SiOx grown at RF plasma power from 20 to 70 W is increased from 3.2 × 1017 to 3 × 1018 cm−3 in Fig. 4 (b). Finite at a specific annealing temperature constrain the moving range of interstitial Si atoms, thus providing the precipitated Si-QD with smaller size and higher density in the high-O/Si-ratio SiOx grown with larger RF plasma power.

To realize the correlation between Si atom diffusion and nucleation, the effective diffusion characteristics of interstitial Si atom in sub-stoichiometric SiOx is simulated. The Si-QDs can eventually be found by moving the Si atom directly from one interstitial site to other interstitial sites following the diffusion equation of J = -D[∂C/∂r] + <v>FC under a driving force F, where J is the diffusion flux (mol cm−2sec), D is the diffusion coefficient (cm2 sec−1) of the Si atom in SiOx, and C is the concentration of the interstitial Si atoms, as based the Si diffusion species (mol cm−3), ∂C/∂r is the concentration gradient along the diffusion axis, and <v>F is the atomic velocity of the excess Si atom under a certain driving forces. The definition of driving forces, the diffusion equation can be rewritten as a function of Gibbs free energy by J = -D[∂C/∂r] + [CDΔGm/akT] under a driving force of F = ΔGm/a, where T and k are the temperature and Boltzmann constant, respectively, ΔGm is the change of Gibbs free energy, a is the distance between neighboring lattice planes, and the F is the driving force of atomic diffusion. In our case, the negative diffusion flux caused by Si atom nucleation from low-concentration to a high-concentration region, occurs by ΔH<0 and ΔS>0 at a given annealing temperature, which can produce the ΔGm<0 condition and favor the interstitial Si atom diffusion and nucleation. It is observed that the Si-QD diameter enlarges with increased Si atomic content, and when annealed at the given annealing temperature and time. The growth velocity of Si-QD with a radius (r) in SiOx host matrix is expressed as [dr/dt]ro = [D/(Cb-Ca)](∂C/∂r)ro, where ro is the initial Si-QD radius, D is the Si atomic diffusion coefficient in SiOx host matrix, Ca is the composition ratio of SiO2, Cb is the composition ratio of Si-QD, and C is the composition ratio of the oxide matrix near the Si-QD. By combining above equations, the D* can be rewritten as D* = {[(r2 2-r1 2)/2t]⋅[(Cb-Ca)/(Cm-Ca)]⋅exp(-Q/kT)}. Note that the equation not only expresses the proportionality of Si-QD radius to SiOx composition ratio, but also correlates the composition ratio with the activation energy of the SiOx host matrix at a given annealing temperature and time. According to Fick's first and second Laws, the diffusion length of (4Dt)0.5 is proportional to the square root of the time and diffusion coefficient. Therefore, the diffusion length is larger than the matrix size, finite Si atoms can thus self-aggregate to form the Si-QDs.

4. Conclusion

Acknowledgement

This work is partially supported by the National Science Council of Republic of China and National Taiwan University Center for Information and Electronics Technologies under grants NSC98-2221-E-002-023-MY3, NSC 98-2623-E-002-002-ET, NSC 98-2622-E-002-023-CC3 and 98R0062-07.

References and links

1.

L. T. Canham, “Si quantum wire array fabrication by electrochemical and chemical dissolution of wafers,” Appl. Phys. Lett. 57(10), 1046–1048 (1990). [CrossRef]

2.

G. Ledoux, J. Gong, F. Huisken, O. Guillois, and C. Reynaud, “Photoluminescence of size-separated silicon nanocrystals: Confirmation of quantum confinement,” Appl. Phys. Lett. 80(25), 4834–4836 (2002). [CrossRef]

3.

P. Mutti, G. Ghislotti, S. Bertoni, L. Bonoldi, G. F. Cerofolini, L. Meda, E. Grilli, and M. Guzzi, “Room-temperature visible luminescence from Si nanocrystals in Si implanted SiO2 layers,” Appl. Phys. Lett. 66(7), 851–853 (1995). [CrossRef]

4.

Y. Osaka, K. Tsunetomo, F. Toyomura, H. Myoren, and K. Kohno, “Visible photoluminescence from Si microcrystals embedded in SiO2 glass films,” Jpn. J. Appl. Phys. 31(Part 2, No. 3B), L365–L366 (1992). [CrossRef]

5.

C. J. Lin, C. K. Lin, C. W. Chang, Y. L. Chueh, H. C. Kuo, W. G. Diau, L. J. Chou, and G. R. Lin, “Photoluminescence of Plasma Enhanced Chemical Vapor Deposition Amorphous Silicon Oxide with Silicon Nanocrystals Grown at Different Fluence Ratios and Substrate Temperatures,” Jpn. J. Appl. Phys. 45(No. 2A), 1040–1043 (2006). [CrossRef]

6.

C. Delerue, G. Allan, and M. Lannoo, “Theoretical aspects of the luminescence of porous silicon,” Phys. Rev. B 48(15), 11024–11036 (1993). [CrossRef]

7.

X. D. Pi, R. W. Liptak, J. D. Nowak, N. P. Wells, C. B. Carter, S. A. Campbell, and U. Kortshagen, “Air-stable full-visible-spectrum emission from silicon nanocrystals synthesized by an all-gas-phase plasma approach,” Nanotech. 19(24), 245603 (2008). [CrossRef]

8.

M. V. Wolkin, J. Jorne, P. M. Fauchet, G. Allan, and C. Delerue, “Electronic states and luminescence in porous silicon quantum dots: The role of oxygen,” Phys. Rev. Lett. 82(1), 197–200 (1999). [CrossRef]

9.

J. C. Cheang-Wong, A. Oliver, J. Roiz, J. M. Hernandez, L. Rodrigues-Fernandez, J. G. Morales, and A. Crespo-Sosa, “Optical properties of Ir2+-implanted silica glass,” Nucl. Instrum. Methods Phys. Res. B 175, 490–494 (2001). [CrossRef]

10.

H. S. Bae, T. G. Kim, C. N. Whang, S. Im, J. S. Yun, and J. H. Song, “Electroluminescence mechanism in SiOx layers containing radiative centers,” J. Appl. Phys. 91(7), 4078 (2002). [CrossRef]

11.

J. B. Khurgin, E. W. Forsythe, G. S. Tompa, and B. A. Khan, “Influence of the size dispersion on the emission spectra of the Si nanostructures,” Appl. Phys. Lett. 69(9), 1241–1243 (1996). [CrossRef]

12.

D. B. Williams, and C. B. Carter, Transmission Electron Microscopy, New York: Plenum, pp. 599–619 (1996).

13.

D. V. Tsu, G. Lucovsky, and B. N. Davidson, “Effect of the neighbors and alloy matrix on SiH stretching vibrations in the amorphous SiOr:H (0<r<2) alloy system,” Phys. Rev. B 40(3), 1795–1805 (1989). [CrossRef]

14.

W. B. Pollard and G. Lucovsky, “Phonons in polysilane alloys,” Phys. Rev. B 26(6), 3172–3180 (1982). [CrossRef]

15.

G. Lucovsky, “A structural interpretation of the infrared-absorption spectra of A-Si-H-O alloys,” Sol. Energy Mater. 8(1-3), 165–175 (1982). [CrossRef]

OCIS Codes
(250.5230) Optoelectronics : Photoluminescence
(310.1860) Thin films : Deposition and fabrication
(160.4236) Materials : Nanomaterials

ToC Category:
Materials

History
Original Manuscript: June 4, 2009
Revised Manuscript: November 25, 2009
Manuscript Accepted: November 29, 2009
Published: February 19, 2010

Citation
Bo-Han Lai, Chih-Hsien Cheng, Yi-Hao Pai, and Gong-Ru Lin, "Plasma power controlled deposition of SiOx with manipulated Si Quantum Dot size for photoluminescent wavelength tailoring," Opt. Express 18, 4449-4456 (2010)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-5-4449


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References

  1. L. T. Canham, “Si quantum wire array fabrication by electrochemical and chemical dissolution of wafers,” Appl. Phys. Lett. 57(10), 1046–1048 (1990). [CrossRef]
  2. G. Ledoux, J. Gong, F. Huisken, O. Guillois, and C. Reynaud, “Photoluminescence of size-separated silicon nanocrystals: Confirmation of quantum confinement,” Appl. Phys. Lett. 80(25), 4834–4836 (2002). [CrossRef]
  3. P. Mutti, G. Ghislotti, S. Bertoni, L. Bonoldi, G. F. Cerofolini, L. Meda, E. Grilli, and M. Guzzi, “Room-temperature visible luminescence from Si nanocrystals in Si implanted SiO2 layers,” Appl. Phys. Lett. 66(7), 851–853 (1995). [CrossRef]
  4. Y. Osaka, K. Tsunetomo, F. Toyomura, H. Myoren, and K. Kohno, “Visible photoluminescence from Si microcrystals embedded in SiO2 glass films,” Jpn. J. Appl. Phys. 31(Part 2, No. 3B), L365–L366 (1992). [CrossRef]
  5. C. J. Lin, C. K. Lin, C. W. Chang, Y. L. Chueh, H. C. Kuo, W. G. Diau, L. J. Chou, and G. R. Lin, “Photoluminescence of Plasma Enhanced Chemical Vapor Deposition Amorphous Silicon Oxide with Silicon Nanocrystals Grown at Different Fluence Ratios and Substrate Temperatures,” Jpn. J. Appl. Phys. 45(No. 2A), 1040–1043 (2006). [CrossRef]
  6. C. Delerue, G. Allan, and M. Lannoo, “Theoretical aspects of the luminescence of porous silicon,” Phys. Rev. B 48(15), 11024–11036 (1993). [CrossRef]
  7. X. D. Pi, R. W. Liptak, J. D. Nowak, N. P. Wells, C. B. Carter, S. A. Campbell, and U. Kortshagen, “Air-stable full-visible-spectrum emission from silicon nanocrystals synthesized by an all-gas-phase plasma approach,” Nanotech. 19(24), 245603 (2008). [CrossRef]
  8. M. V. Wolkin, J. Jorne, P. M. Fauchet, G. Allan, and C. Delerue, “Electronic states and luminescence in porous silicon quantum dots: The role of oxygen,” Phys. Rev. Lett. 82(1), 197–200 (1999). [CrossRef]
  9. J. C. Cheang-Wong, A. Oliver, J. Roiz, J. M. Hernandez, L. Rodrigues-Fernandez, J. G. Morales, and A. Crespo-Sosa, “Optical properties of Ir2+-implanted silica glass,” Nucl. Instrum. Methods Phys. Res. B 175, 490–494 (2001). [CrossRef]
  10. H. S. Bae, T. G. Kim, C. N. Whang, S. Im, J. S. Yun, and J. H. Song, “Electroluminescence mechanism in SiOx layers containing radiative centers,” J. Appl. Phys. 91(7), 4078 (2002). [CrossRef]
  11. J. B. Khurgin, E. W. Forsythe, G. S. Tompa, and B. A. Khan, “Influence of the size dispersion on the emission spectra of the Si nanostructures,” Appl. Phys. Lett. 69(9), 1241–1243 (1996). [CrossRef]
  12. D. B. Williams, and C. B. Carter, Transmission Electron Microscopy, New York: Plenum, pp. 599–619 (1996).
  13. D. V. Tsu, G. Lucovsky, and B. N. Davidson, “Effect of the neighbors and alloy matrix on SiH stretching vibrations in the amorphous SiOr:H (0<r<2) alloy system,” Phys. Rev. B 40(3), 1795–1805 (1989). [CrossRef]
  14. W. B. Pollard and G. Lucovsky, “Phonons in polysilane alloys,” Phys. Rev. B 26(6), 3172–3180 (1982). [CrossRef]
  15. G. Lucovsky, “A structural interpretation of the infrared-absorption spectra of A-Si-H-O alloys,” Sol. Energy Mater. 8(1-3), 165–175 (1982). [CrossRef]

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