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Relationship Between Current Transport and Electroluminescence in Si+-Implanted SiO2 Thin Films Liang Ding, T. P. Chen, Ming Yang, Student Member, IEEE, Jen It Wong, Graduate Student Member, IEEE, Zhanhong Cen, Yang Liu, Furong Zhu, and Ampere A. Tseng
Abstract—Relationship between current transport and electroluminescence (EL) in the system of excess Si distributed in SiO2 thin films synthesized with low-energy ion implantation has been examined. A linear relationship is found, and both of them follow a power law and are determined by the concentration and distribution of the excess Si in the oxide films. With the knowledge of the dependence of the transport on the concentration and distribution of the excess Si, one can predict the effect of the implantation recipe on the EL intensity. Index Terms—Current transport, electroluminescence, photoluminescence, Si LED, silicon nanocrystal.
I. I NTRODUCTION
O
VER the past decade, intensive research has been carried out on the development of light-emitting devices (LEDs) that are compatible with the mainstream silicon technology [1]– [3]. Si nanocrystals (nc-Si) embedded in SiO2 thin films have been shown to be promising for the application in silicon-based LEDs [1]–[7]. The nc-Si can be synthesized with the technique of Si ion implantation into SiO2 thin films. Strong photoluminescence (PL) in the wavelength range from red to blue and visible electroluminescence (EL) from the Si+ -implanted SiO2 films have been frequently reported [4]–[10]. Previous studies (for example, those reported in [4]–[10]) were usually focused on the luminescence properties and light emission behaviors. There is still a lack of detailed study on the effect of the current transport in the Si+ -implanted SiO2 films on the EL. In this paper, visible EL has been observed from the Si+ -implanted SiO2 film synthesized with low-energy ion implantation, and the relationship between the EL and the current transport in Manuscript received December 5, 2008; revised June 22, 2009. First published September 29, 2009; current version published October 21, 2009. This work was supported by the National Research Foundation of Singapore under Project NRF-G-CRP 2007-01. The review of this paper was arranged by Editor H. S. Momose. L. Ding was with the School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798. He is now with the Institute of Microelectronics, Singapore 117685. T. P. Chen, M. Yang, J. I. Wong, and Z. Cen are with the School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (e-mail:
[email protected]). Y. Liu was with the School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798. He is now with the University of Electronic Science and Technology, Chengdu 610054, China. F. Zhu is with the Institute of Materials Research and Engineering, Singapore 117602. A. A. Tseng is with the Department of Mechanical and Aerospace Engineering, Arizona State University, Tempe, AZ 85287 USA. Digital Object Identifier 10.1109/TED.2009.2031017
the material system has been studied. The effect of the current transport on the EL has been examined by varying the ion implantation recipe (i.e., the Si ion implantation dose and implantation energy). It is shown that the EL could be greatly enhanced by using a suitable ion implantation recipe. II. E XPERIMENTAL S ETUP Thirty-nanometer SiO2 thin films were thermally grown on p-type Si wafers with (100) orientation at 950 ◦ C in dry oxygen. Si ions were then implanted into SiO2 films with various implantation doses at different implantation energies. Table I summarizes the fabrication conditions of the samples under investigation in this paper. For the study of the influence of implantation dose, three samples (denoted as samples 5a, 5b, and 5c, see Table I) were fabricated with the implantation doses of 1 × 1016 , 2 × 1015 , and 3 × 1014 cm−2 , respectively, at the fixed implantation energy of 5 keV. For the study of the influence of the distribution of excess Si, also three samples (denoted as samples 2a, 5a, and 8a, see Table I) were fabricated at the implantation energies of 2, 5, and 8 keV, respectively, with the fixed implantation dose of 1 × 1016 cm−2 . After the ion implantation, thermal annealing was carried out at either 1000 ◦ C or 1100 ◦ C in N2 ambient for 60 min to induce the nanocrystallization of excess Si atoms in the SiO2 . It has been frequently reported that the annealing above 900 ◦ C can lead to phase separation and crystallization of excess Si in the Si suboxide [11]–[13]. However, the fully crystallization of excess Si only occurs when the annealing temperature is at or above 1100 ◦ C [14], [15]. For the electrical and EL measurements, the backside of the wafer was coated with a layer of aluminum with the thickness of about 1 μm as the back ohmic contact, and a 130-nm indium tin oxide (ITO) layer was deposited onto the surface of the Si+ -implanted SiO2 thin film with a pad radius of 1.2 mm. The ITO layer has a sheet resistance of 25 Ω/sq and an average transmittance of 85% over the visible wavelength range. Fig. 1 shows the schematic cross section of the MOS-like light-emitting structure with the Si+ -implanted SiO2 as the gate oxide. The current–voltage (I–V ) measurements were conducted with an HP4156A semiconductor characterization system. The PL measurements were conducted using the 325-nm line of a He–Cd laser as the excitation source. The EL measurements were carried out with a PDS-1 photomultiplier tube detector together with a monochromator. All the measurements were performed at room temperature.
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TABLE I S UMMARY OF THE I MPLANTATION R ECIPES AND OXIDE T HICKNESSES FOR A LL THE S AMPLES U SED IN T HIS PAPER
Fig. 2. EL spectra for sample 5a under different gate voltages. The sample was annealed at 1000 ◦ C for 60 min.
Fig. 1. Schematic illustration of the device structure.
III. R ESULTS AND D ISCUSSION Visible EL can be observed when a negative voltage is applied to the ITO gate. All the samples exhibit similar EL spectra. As examples, Fig. 2 shows the EL spectra corrected to both the transparency of ITO film and the EL measurement system for sample 5a under different gate voltages (Vg ). As shown in this figure, the EL spectra extend over the visible range from ∼400 to ∼800 nm with the main EL peak located at ∼600 nm. The EL intensity increases with the applied gate voltage as a result of the increase in the current across the oxide. It should be pointed out that no EL was detected under a positive gate voltage due to the lack of sufficient hole injection from the ITO gate. In addition, although it has been reported that annealing at 1100 ◦ C leads to a strong PL emission related to the formation of nc-Si [9], [10], no strong PL was observed from samples 5a, 5b, 5c, 8a, and 2a (see Table I) which were annealed at either 1000 ◦ C or 1100 ◦ C (note that these samples are used in the study of EL and current transport). The following factors may be responsible for the absence of strong PL: 1) there is a PL quenching by the nonradiative defects which are formed in the SiO2 matrix due to the ion implantation but could not be fully recovered by the annealing at the slightly lower temperature (i.e., 1000 ◦ C) [9], [16]; 2) the implantation dose is too low to induce a PL signal detectable by our PL measurement system; and 3) the film (∼30 nm) is too thin (i.e., the excess-Si-distributed region is too narrow) to produce a strong PL signal. Indeed, as elaborated below, PL emission is observed from sample 10d with a higher implantation dose
Fig. 3. PL spectra of sample 100e. The sample was annealed at either 1000 ◦ C or 1100 ◦ C for 30 min.
(4 × 1016 cm−2 ) for the annealing at 1100 ◦ C, but no PL is observed for the annealing at 1000 ◦ C. Moreover, a thicker oxide thickness (∼1000 nm) with a wide excess-Si-distributed region and synthesized with a Si ion implantation dose of 1 × 1017 cm−2 (denoted as sample 100e, see Table I) exhibits PL emission for both the annealing at 1000 ◦ C and 1100 ◦ C, as shown in Fig. 3. Light emission (either PL or EL) at ∼600 nm from the ionimplanted SiO2 thin films has been frequently reported [9], [10]. As previously mentioned, our samples used for the current transport and EL studies do not exhibit strong PL that is related to the nc-Si, indicating that the EL band peaked at ∼600 nm observed in this paper could not originate from the Si nanocrystals. It has been reported that luminescence at around 600 nm is caused by some radiative defects formed in Si-implanted SiO2 [10]. It was also reported that the SiO2 films implanted with Ge ions exhibit an EL band at ∼600 nm [17]. Therefore, one can suggest that the ∼600-nm EL band observed in this paper is due to the radiative defects in the SiO2 matrix introduced by the ion implantation. In order to further clarify the mechanism of light emission, some samples have been fabricated with a thicker oxide (∼1000 nm) and implanted with a higher dose (1 × 1017 cm−2 ) of Si ions at 100 keV (i.e., sample 100e, see
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Fig. 4. EL spectra of sample 5a annealed at either 1000 ◦ C or 1100 ◦ C for 60 min. The EL spectra were taken under the gate voltage of −15 V.
Table I). PL can be detected from sample 100e for annealings at both 1000 ◦ C and 1100 ◦ C, but no EL is observed due to the extremely low current injection with such a large film thickness. The annealing at 1100 ◦ C yields a much stronger PL peak. As shown in Fig. 3, the PL intensity for the annealing at 1000 ◦ C is almost 30 times lower than that for the annealing at 1100 ◦ C. The Gaussian-shaped PL spectrum located at ∼750 nm for the annealing at 1100 ◦ C has been proved to be due to the Si nanocrystals. For the annealing at 1000 ◦ C, the PL spectrum has two clear luminescence bands located at ∼600 and ∼750 nm, respectively, although their intensities are much lower than that of the ∼750-nm band of the annealing at 1100 ◦ C. The existence of the weak ∼750-nm PL band for the annealing at 1000 ◦ C suggests that the 1000-◦ C annealing can also lead to the formation of Si nanocrystals. However, the nonradiative defects that could not be fully recovered by the annealing at 1000 ◦ C quench the PL emission, resulting in the ∼750-nm band much weaker than that for the annealing at 1100 ◦ C. As regards to the dominance of ∼600-nm luminescence band in the EL spectra, it is probably due to the fact that the energy distribution of injected carriers can easily satisfy the requirement of excitation energy for the related luminescent defects while the excitation of nc-Si as an active medium by injected carriers is relatively difficult [18]. In contrast to the large impact of annealing temperature on the PL shown in Fig. 3, there is no much difference in the EL between the annealing at 1000 ◦ C and 1100 ◦ C, as shown in Fig. 4. On the other hand, to make a comparison between EL and PL, sample 10d with 30-nm-thick SiO2 was fabricated with the implantation dose of 4 × 1016 cm−2 at the implantation energy of 10 keV. Both PL and EL can be detected for the annealing at 1100 ◦ C, but no PL is observed for the annealing at 1000 ◦ C. Fig. 5 shows the comparison between the PL and EL for the annealing at 1100 ◦ C. As shown in the figure, the PL and EL spectra present remarkably different traits. Being similar to the situation shown in Fig. 2 for sample 5a, the EL shown in Fig. 5 also presents the main peak at ∼600 nm which has been attributed to the radiative defects introduced by Si ion implantation. However, the PL shown in Fig. 5 exhibits a redshift as compared with the PL shown in Fig. 3. This can be explained in terms of the quantum size effect on the nc-Si
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Fig. 5. PL and EL spectra of sample 10d. The sample was annealed at 1100 ◦ C for 60 min. The EL spectrum was taken under the gate voltage of −15 V.
bandgap [19]. The stopping and range of ions in matter SRIM simulation [20] shows that the concentration of the excess Si in the oxide of sample 10d used in the measurements of Fig. 5 is higher than that of the sample 100e used in the measurements of Fig. 3. Therefore, for sample 10d, the nc-Si size is expected to be bigger and thus its bandgap is believed to be smaller. In conclusion, the results discussed above support the argument that the EL is due to the radiative defects formed in the Siimplanted SiO2 while the strong PL peak is related to the nc-Si. As there is no significant difference in the EL between the annealing at 1000 ◦ C and 1100 ◦ C, the relationship between the current transport and the EL is studied only for the annealing at 1000 ◦ C. The concentrations and the distribution profiles of the three samples (i.e., samples 5a, 5b, and 5c, see Table I) with different implantation doses, which are obtained from the SRIM simulations, are shown in the inset of Fig. 6. The peak concentrations of excess Si in the SiO2 thin film for the three samples are 1 × 1022 , 2 × 1021 , and 3 × 1020 cm−3 , respectively. As these samples have the same implantation energy (i.e., 5 keV), they have the same distribution range of excess Si, namely, the excess Si is distributed from the SiO2 surface to a depth of ∼22 nm in the SiO2 thin film. This means that there is no excess Si in the oxide in the region from the depth of ∼22 nm to the SiO2 –substrate interface. In other words, there is a tunnel oxide (i.e., the pure SiO2 region without the excess Si) with the thickness of ∼8 nm for all the three samples. The I–V characteristics for the three samples are also shown in Fig. 6. Under a negative gate bias, electrons are injected from the ITO gate while holes are injected from the p-Si substrate. The injected carriers can be transported through tunneling or other mechanisms via the defects, nc-Si, and Si nanoclusters which have been confirmed to coexist in the Si+ -implanted SiO2 films after the annealing at 1000 ◦ C [9], [11]–[16]. Conductive percolation paths are thus formed, and the situation is somewhat similar to that of the neutral oxide traps in SiO2 thin films [21]. With the formation of many conductive percolation paths in the excess-Si-distributed region, the conduction of the system is enhanced. This explains why the current conduction increases with the concentration of excess Si, as shown in Fig. 6. As a result of the increase in the current conduction, more electrons
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Fig. 6. Dependence of the current and the integrated EL intensity on the voltage as a function of the implantation dose (samples 5a, 5b, and 5c). The implantation energy is fixed at 5 keV. The inset shows the concentrations and distributions of the excess Si in the oxide thin film obtained from the SRIM simulations.
Fig. 8. α0 and ζ as functions of (a) implantation dose or (b) implantation energy.
Fig. 7. Dependence of the current and the integrated EL intensity on the voltage as a function of the implantation energy (samples 2a, 5a, and 8a). The implantation dose is fixed at 1 × 1016 cm−2 . The inset shows the concentrations and distributions of the excess Si in the oxide thin film obtained from the SRIM simulations.
injected from the ITO gate and more holes injected from the p-type Si substrate are transported in the Si-implanted region, leading to an increase in the radiative recombination of the injected electrons and holes and thus an increase in the EL intensity. Indeed, as shown in Fig. 6, the integrated EL intensity increases with the concentration of excess Si following the same trend of the current conduction. On the other hand, to study the influence of the distribution of excess Si, various distributions are achieved by varying the implantation energy. The inset of Fig. 7 shows the concentrations of excess Si and distribution profiles for samples 2a, 5a, and 8a which were fabricated at the implantation energies of 2, 5 and 8 keV, respectively, with the fixed implantation dose of 1 × 1016 cm−2 . For sample 2a, the excess Si is distributed from the SiO2 surface to a depth of ∼14 nm in the SiO2 thin film, forming a tunnel oxide of ∼16 nm. For sample 5a, the excess Si is distributed from the SiO2 surface to a depth of ∼22 nm, forming a tunnel oxide of ∼8 nm; and for sample 8a, the excess Si is distributed from the SiO2 surface until the SiO2 –substrate
interface leading to no tunnel oxide formed. As a constant implantation dose is used, the peak concentration of excess Si decreases with the extension of the Si+ -implanted region. With higher implantation energy, the excess-Si-distributed region extends wider while the pure oxide becomes thinner, thus the voltage drop in the excess-Si-distributed region increases for a given applied voltage. Therefore, for a given applied voltage the current will be higher. On the other hand, when the excess Si is distributed throughout the entire SiO2 thin film (i.e., the situation of sample 8a), conductive percolation paths connecting the substrate to the gate will be formed, leading to a large increase in the current conduction. As a result of the two scenarios, the current conduction increases with the implantation energy, as shown in Fig. 7. As the EL intensity reflects the transport of the injected carriers, the increase of the current conduction is translated to an increase in the EL intensity with the implantation energy, as shown in Fig. 7 also. It is shown in Figs. 6 and 7 that the I–V characteristics for all the samples follow a power law: J = α0 V ζ
(1)
where J is the current density, V is the absolute value of the applied gate voltage, α0 is a coefficient, and ζ is the scaling exponent. The power-law behavior could be explained by a model similar to the one of the collective charge transport in arrays of normal-metal quantum dots [22]. The values of the two parameters α0 and ζ obtained from the power-law fittings
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the samples. Obviously, the dependence of both the α0 and ζ on the concentration and distribution of the excess Si is similar to that of the α0 and ζ. Therefore, with the knowledge of the influence of the implantation recipe on the α0 and ζ obtained from the transport study, one can predict the effect of the implantation recipe on the EL intensity, which should be useful in designing nc-Si LEDs synthesized with the ion implantation technique. As an example, the influence of the implantation recipe on the integrated EL intensity, which is obtained from the calculation based on the aforementioned power law, is shown in Fig. 9. The corresponding experimental result is also included in the figure for comparison. As shown in the figure, the calculation is in good agreement with the experiment. It is also shown in the figure that the EL intensity increases with the implantation dose and/or the implantation energy. IV. C ONCLUSION
Fig. 9. Integrated EL intensity under the gate voltage of −15 V as a function of (a) implantation dose or (b) implantation energy. The calculated EL intensity is based on the power law shown in (2).
shown in Figs. 6 and 7 are shown in Fig. 8. As shown in Fig. 8, α0 increases with both the implantation dose [Fig. 8(a)] and the implantation energy [Fig. 8(b)]. As α0 reflects the conductance of the material system, it increases when more conduction paths are formed with a higher concentration of excess Si or when the Si+ -implanted region extends with higher implantation energy. On the other hand, ζ is found to be in the range of ∼2.4–∼3 for different samples. This is much larger than the values obtained from simulations and experiments of 2-D transport, where ζ ranges from 1.67 to 2.26 [22], [23]. This could suggest that the current conduction in the system of Si+ -implanted SiO2 thin film is a quasi-3-D transport. As shown in Fig. 8(a), ζ slightly increases with the implantation dose; however, as shown in Fig. 8(b), ζ decreases with the implantation energy, indicating that the increase in the implantation energy would lead to the evolution toward the 2-D transport due to the increase in the lateral spacing between the adjacent defects, Si nanoclusters, or nc-Si. As the EL intensity is proportional to the current, the dependence of the integrated EL intensity on the voltage also follows a power law given by: IEL = α0 V ζ
(2)
where IEL is the integrated EL intensity, ζ = ζ within the experimental and fitting errors, and α0 /α0 is a constant for all
In summary, capacitorlike light-emitting structures based on the Si+ -implanted SiO2 films have been fabricated by lowenergy ion implantation. The current transport in the material system follows a power law, and it is affected by the implantation recipe. A linear relationship between the EL and the current transport is observed. The current transport changes with both the concentration and distribution of implanted Si ions. In addition, it has been found that the EL intensity evolves with both the concentration and distribution of the implanted Si ions in a trend similar to that of the current transport. The EL intensity increases with the implantation dose and the implantation energy, which is due to the influence of the concentration and distribution of excess Si on the current transport. R EFERENCES [1] P. M. Fauchet, “Progress toward nanoscale silicon light emitters,” IEEE J. Sel. Topics Quantum Electron., vol. 4, no. 6, pp. 1020–1028, Nov./Dec. 1998. [2] L.-Y. Chen, W.-H. Chen, and F. C.-N. Hong, “Visible electroluminescence from silicon nanocrystals embedded in amorphous silicon nitride matrix,” Appl. Phys. Lett., vol. 86, no. 19, pp. 193 506-1–193 506-3, May 2005. [3] J. Valenta, N. Lalic, and J. Linnros, “Electroluminescence of single silicon nanocrystals,” Appl. Phys. Lett., vol. 84, no. 9, pp. 1459–1461, Mar. 2004. [4] L. Rebohle, J. von Borany, R. A. Yankov, W. Skorupa, I. E. Tyschenko, H. Frob, and K. Leo, “Strong blue and violet photoluminescence and electroluminescence from germanium-implanted and silicon-implanted silicon-dioxide layers,” Appl. Phys. Lett., vol. 71, no. 19, pp. 2809–2811, Nov. 1997. [5] T. Matsuda, K. Nishihara, M. Kawabe, H. Iwata, S. Iwatsubo, and T. Ohzone, “Blue electroluminescence from MOS capacitors with Siimplanted SiO2 ,” Solid State Electron., vol. 48, no. 10, pp. 1933–1941, Jul. 2004. [6] C.-J. Lin and G.-R. Lin, “Defect-enhanced visible electroluminescence of multi-energy silicon implanted silicon dioxide film,” IEEE J. Quantum Electron., vol. 41, no. 3, pp. 441–447, Mar. 2005. [7] M. Kulakci, U. Serincan, and R. Turan, “Electroluminescence generated by a metal oxide semiconductor light emitting diode (MOS-LED) with Si nanocrystals embedded in SiO2 layers by ion implantation,” Semicond. Sci. Technol., vol. 21, no. 12, pp. 1527–1532, Sep. 2006. [8] G.-R. Lin and C.-J. Lin, “Improved blue-green electroluminescence of metal–oxide–semiconductor diode fabricated on multirecipe Si-implanted and annealed SiO2 /Si substrate,” J. Appl. Phys., vol. 95, no. 12, pp. 8484– 8486, Jun. 2004. [9] B. Garrido, M. López, A. Pérez-Rodríguez, C. García, P. Pellegrino, R. Ferré, J. A. Moreno, J. R. Morante, C. Bonafos, M. Carrada, A. Claverie, J. de la Torre, and A. Souifi, “Optical and electrical properties of Si-nanocrystals ion beam synthesized in SiO2 ,” Nucl. Instrum. Methods Phys. Res. B, Beam Interact. Mater. At., vol. 216, pp. 213–221, Dec. 2003.
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[10] J. Y. Jeong, S. Im, M. S. Oh, H. B. Kim, K. H. Chae, C. N. Whang, and J. H. Song, “Defect versus nanocrystal luminescence emitted from room temperature and hot-implanted SiO2 layers,” J. Lumin., vol. 80, no. 1, pp. 285–289, Mar. 1999. [11] K. S. Min, K. V. Shcheglov, C. M. Yang, H. A. Atwater, M. L. Brongersma, and A. Polman, “Defect-related versus excitonic visible light emission from ion beam synthesized Si nanocrystals in SiO2 ,” Appl. Phys. Lett., vol. 69, no. 14, pp. 2033–2035, Sep. 1996. [12] L. X. Yi, J. Heitmann, R. Scholz, and M. Zacharias, “Si rings, Si clusters, and Si nanocrystals—Different states of ultrathin SiO2 layers,” Appl. Phys. Lett., vol. 81, no. 22, pp. 4248–4250, Nov. 2002. [13] L. X. Yi, J. Heitmann, R. Scholz, and M. Zacharias, “Phase separation of thin SiO layers in amorphous SiO/SiO2 superlattices during annealing,” J. Phys., Condens. Matter, vol. 15, no. 39, pp. S2 887–S2 895, Sep. 2003. [14] B. Fazio, M. Vulpio, C. Gerardi, Y. Liao, I. Crupi, S. Lombardo, S. Trusso, and F. Neri, “Residual crystalline silicon phase in silicon-rich-oxide films subjected to high temperature annealing,” J. Electrochem. Soc., vol. 149, no. 7, pp. G376–G378, May 2002. [15] X. Y. Chen, Y. F. Lu, Y. H. Wu, B. J. Cho, L. J. Tang, D. Lu, and J. R. Dong, “Correlation between optical properties and Si nanocrystal formation of Si-rich Si oxide films prepared by plasma-enhanced chemical vapor deposition,” Appl. Surf. Sci., vol. 253, no. 5, pp. 2718–2726, Jul. 2006. [16] S. Cheylan, N. Langford, and R. G. Elliman, “The effect of ion-irradiation and annealing on the luminescence of Si nanocrystals in SiO2 ,” Nucl. Instrum. Methods Phys. Res. B, Beam Interact. Mater. At., vol. 166/167, pp. 851–856, May 2000. [17] J.-Y. Zhang, Y.-H. Ye, X.-L. Tan, and X.-M. Bao, “Voltage-controlled electroluminescence from SiO2 films containing Ge nanocrystals and its mechanism,” Appl. Phys. A, Solids Surf., vol. 71, no. 3, pp. 299–303, Mar. 2000. [18] H.-Z. Song, X.-M. Bao, N.-S. Li, and J.-Y. Zhang, “Relation between electroluminescence and photoluminescence of Si+ -implanted SiO2 ,” J. Appl. Phys., vol. 82, no. 8, pp. 4028–4032, Oct. 1997. [19] L. Ding, T. P. Chen, Y. Liu, C. Y. Ng, M. Yang, J. I. Wong, F. R. Zhu, M. C. Tan, S. Fung, X. D. Chen, and Y. Huang, “Evolution of photoluminescence mechanisms of Si+ -implanted SiO2 films with thermal annealing,” J. Nanosci. Nanotechnol., vol. 8, no. 7, pp. 3555–3560, Aug. 2008. [20] J. F. Ziegler and J. P. Biersac. [Online]. Available: http://www.srim.org [21] T. P. Chen, M. S. Tse, and X. Zeng, “Snapback behavior of the postbreakdown I– V characteristics in ultrathin SiO2 films,” Appl. Phys. Lett., vol. 78, no. 4, pp. 492–494, Jan. 2001. [22] A. A. Middleton and N. S. Wingreen, “Collective transport in arrays of small metallic dots,” Phys. Rev. Lett., vol. 71, no. 19, pp. 3198–3201, Nov. 1993. [23] R. Parthasarathy, X.-M. Lin, and H. M. Jaeger, “Electronic transport in metal nanocrystal array on scaling behavior,” Phys. Rev. Lett., vol. 87, no. 18, pp. 186 807-1–186 807-4, Oct. 2001.
Liang Ding was born in China, in 1982. He received the B.Sc. degree in physics (optical and optoelectronic physics) from Huazhong University of Science and Technology, Wuhan, China, in 2004 and the Ph.D. degree from the Division of Microelectronics, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, in 2009. Since October 2008, he has been with the Institute of Microelectronics, Agency for Science, Technology and Research, Singapore, as a Senior Research Engineer. His current research interests involve Si photonic devices based on SOI platform, and optoelectronic properties of semiconductor nanocrystal materials and the device applications. Dr. Ding was awarded the prestigious Singapore Millennium Foundation Ph.D. Fellowship in 2007. In 2008, he received the Chinese Government Award for Outstanding Self-financed Student Abroad.
T. P. Chen received the Ph.D. degree from The University of Hong Kong, Hong Kong, in 1994. From February 1990 to October 1991, he was a Visiting Scientist with Fritz-Haber Institute of Max-Planck Society, Berlin, Germany. From 1994 to 1997, he was a Postdoctoral Fellow with The University of Hong Kong, and the National University of Singapore, Singapore. From June to December 1996, he was with Chartered Semiconductor Manufacturing, Ltd., Singapore. He was with PSB Singapore for two-and-a-half years, as a Senior Scientist, before he joined Nanyang Technological University, Singapore, in February 2000, where he is currently an Associate Professor with the Division of Microelectronics, School of Electrical and Electronic Engineering. He is the author or coauthor of 170 peer-reviewed journal papers, more than 80 conference proceeding papers, and one book chapter. He is the holder of two granted and one pending U.S. patents. His current research interests include nanoscale CMOS devices and reliability physics, semiconductor and metal nanocrystals/ nanoparticles and their applications in nanoelectronic devices (memories and single/few-electron devices) and photonic/optoelectronic devices (light emitters, Plasmon waveguides, optical interconnects), Si optoelectronic integrated circuits for chip-to-chip and system-to-system communication, and flexible/ printing electronics.
Ming Yang (S’06) was born in Xiamen, China, in 1982. He received the B.Eng. degree (first-class honors) in microelectronics from Nanyang Technological University, Singapore, in 2005, where he is currently working toward the Ph.D. degree, in which his research interest involves the electrical and optoelectronic properties of nanoscale materials and their device applications.
Jen It Wong (S’03) was born in Johor Bahru, Malaysia, in 1982. He received the B.Eng. degree in microelectronics from the School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, in 2005, where he is currently working toward the Ph.D. degree. His research focuses on studies of semiconductor nanocrystals with particular interest on their application for optoelectronic device and memory device.
Zhanhong Cen received the B.Sc. degree in physics and the M.Sc. degree in physics (microelectronics) from Nanjing University, Nanjing, China, in 2003 and 2006, respectively. He is currently working toward the Ph.D. degree at the Nanyang Technological University, Singapore. His current research interests include optoelectronic properties and the applications of semiconductor nanocrystals.
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Yang Liu received the B.Sc. degree in microelectronics from Jilin University, Changchun, China, in 1998 and the Ph.D. degree from Nanyang Technological University, Singapore, in 2005. From May 2005 to July 2006, he was a Research Fellow with Nanyang Technological University. In 2008, he joined the University of Electronic Science and Technology, Chengdu, China, as a Full Professor, where he is currently a Professor with the School of Microelectronics. His current research focus on nanocrystals/nanoparticles and their applications in electronic devices (Flash memory device, resistive memory device, power device, etc.) and optoelectronic devices (Si-based light emission devices, optoelectronic memory) and Si-based optical ICs. Since 2002, he has been authoring/coauthoring more than 60 peer-reviewed journal papers and 20 conference papers. Dr. Liu was awarded the prestigious two-year Singapore Millennium Foundation Fellowship in 2006.
Furong Zhu received the Ph.D. degree from Charles Darwin University, Australia, in 1993. From 1993 to 1995, he did his postdoctorate with the Department of EEE, Kyoto University, Kyoto, Japan, and from 1995 to 1997, he was a Research Fellow with Murdoch University, Perth, Australia. In 1997, he joined the Institute of Materials Research and Engineering, Singapore, where he is currently a Program Manager. His current research includes OLEDs, organic photovoltaics, and thin-film materials-oriented research.
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Ampere A. Tseng received the Ph.D. degree in mechanical engineering from Georgia Institute of Technology, Atlanta, in 1978. He is a Professor of engineering with Arizona State University (ASU), Tempe. He has published more than 250 referred papers with nine U.S. patents under his credentials. He has edited more than ten technical monographs and has been an editor for more than ten different technical journals. Dr. Tseng was a recipient of the Superior Performance Award of Martin Marietta Laboratories, RCA Service Award, Alcoa Foundation Research Award, and ASU 1999–2000 Faculty Award. He chaired the ASME Materials Division in 1991–1992 and was selected as an ASME Fellow in 1995. In addition, he chaired the 2000 NSF Workshop on Manufacturing of MEMS and the 1st International Workshop on Tip-Based Nanofabrication in 2008, as well as cochaired the 1992 International Conference on Transport Phenomena in Processing and the 1999 NSF U.S.–China Workshop on Advanced Machine Tool Research. He has received more than three million dollars in research funding directly from government agencies and industries. In 1990, he managed to secure 12 million dollars from U.S. Department of Energy to establish the Center for Automation Technology and became its first Center Director at Drexel University. From 1996 to 2001, he was the founding Director of the Manufacturing Institute, ASU, and the nine million dollars’ donation from Motorola to Manufacturing Institute in 1997, which was the largest single gift in ASU history.
