Influence of nanocrystal size on optical properties of Si nanocrystals embedded in SiO2 synthesized by Si ion implantation

Liu, Ding; Chen, T. P.; Liu, Y.; Yang, Ming; Wong, Jen It; Liu, Y. C.; Trigg, A. D.; Zhu, Furong; Tan, Ming Yan; Fung, S.

doi:10.1063/1.2730560

Cited by 42 publications

(31 citation statements)

References 32 publications

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“…confinement, which corresponds 12 to a population of excited Si-nc with an average size of 4 -5 nm, in accordance with EFTEM. Other studies 3 attribute a 0.6 eV gap expansion to smaller Si-nc ͑ϳ2 nm͒.…”

Section: 1011mentioning

confidence: 74%

Direct modulation of electroluminescence from silicon nanocrystals beyond radiative recombination rates

Carreras

Arbiol

Garrido

et al. 2008

Applied Physics Letters

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We propose a light emitting transistor based on silicon nanocrystals provided with 200 Mbits/ s built-in modulation. Suppression of electroluminescence from silicon nanocrystals embedded into the gate oxide of a field effect transistor is achieved by fast Auger quenching. In this process, a modulating drain signal causes heating of carriers in the channel and facilitates the charge injection into the nanocrystals. This excess of charge enables fast nonradiative processes that are used to obtain 100% modulation depths at modulating voltages of ϳ1 V. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2889499͔Silicon-based light emitting diodes 1-4 ͑LEDs͒ and electro-optical modulators [5][6][7] have recently shown potential for a monolithic integration of photonics and mainstream electronics. The majority of current silicon electro-optical modulators are based on plasma dispersion effects.7 Some reports conclude that they suffer from high power consumption ͑theoretical lower limit of current density of 10 4 A / cm 2 ͒ 6 and thus poor scalability. A metal-oxidesemiconductor field effect transistor ͑MOSFET͒-based electroluminescent device would operate at lower power, merging the functionalities of an all-silicon LED and a high-speed modulator in a single transistor which can be readily integrated into silicon technology.The devices studied in this work are MOSFETs with 100-nm-thick optically transparent polycrystalline silicon ͑polysilicon͒ gate electrodes and embedded silicon nanocrystals ͑Si-nc͒ in the gate oxide. The nanocrystals were obtained after 6.5 keV Si + ion implantation into thermally grown SiO 2 15-nm-thick layers and resulted in atomic Si peak excess of 20% at a projected range of ϳ12 nm, as simulated by SRIM ͑Ref. 8͒ code. The samples subsequently underwent an annealing in N 2 at 1100°C for 4 h. A phosphorous implantation was used to define source and drain zones. A polysilicon layer was deposited by low-pressure chemical vapor deposition and degenerately doped with POCl 3 to form a semitransparent gate electrode. Standard microelectronic processes of photolithography and etching were used to form the transistor structure.The atomic silicon peak excess inside the matrix was confirmed to be 20% by x-ray photoelectron spectroscopy. The presence of Si-nc in the oxide was further verified by energy filtered transmission electron microscopy ͑EFTEM͒ at a silicon plasmon energy of ϳ17 eV. Silicon nanocrystals were imaged at an average distance of 10.5 nm from the gate. The diameter of the observed nanoparticles was 4-5 nm.Time-resolved electroluminescence ͑EL͒ was obtained with a detector ͑H7422P͒ and a photon counter ͑SR430͒. Electroluminescence spectra were obtained via a cryogenically cooled PI Spec-10-100B/LN charge-coupled device and an Acton 2300i grating spectrometer. Data were corrected with the overall optical transfer function.The transistor structure resembles that of a Si-nc memory, 9 having a floating gate embedded in the oxide made up of Si-nc. As schematically shown in Fig. 1͑a͒, when a po...

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Section: 1011mentioning

confidence: 74%

Direct modulation of electroluminescence from silicon nanocrystals beyond radiative recombination rates

Carreras

Arbiol

Garrido

et al. 2008

Applied Physics Letters

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“…Comparison with recent measurements of the linear dielectric function of Si NCs [11,12] is also instructive. For 4.5 to 6 nm diameter Si NCs, these measurements show a slight blue shift of the E 1 critical point energy, qualititatively consistent with our SHG spectrum of 3 nm Si NCs.…”

Section: Nc At Entrance Scanmentioning

confidence: 94%

“…Moreover, Ref. [11] reports a strong size-dependent red shift of the E 2 resonance, which begins to merge with E 1 for 4.5 nm NCs. This strong size-dependence of the E 2 energy may explain the broad plateau in this region in our sample with 30% size fluctuations.…”

Section: Nc At Entrance Scanmentioning

confidence: 95%

Second‐harmonic spectroscopy of Si nanocrystals embedded in silica

Wirth

Wei

Gielis

et al. 2008

Phys. Status Solidi (c)

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Extending previous second‐harmonic generation (SHG) single‐wavelength studies [1] of Si nanocrystals (NCs) embedded in fused silica, we implement spectroscopic cross‐polarized two‐beam SHG (XP2‐SHG) by employing an optical parametric amplifier as a source of widely tunable (1.6 ≤ Eph ≤ 2.4 eV) femtosecond pulses. Subsequent isolation of the SH signal produced by the NCs yields the oscillator strength and phase of their nonlinear response. We obtain a broad resonance between bulk Si E1 and E2 critical points. Possible explanations for the spectroscopic result are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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“…The spectrum is centred at ∼725 nm and has a full-width at half-maximum of ∼220 nm. Compared to bulk silicon, this represents a ∼0.6 eV of gap expansion as a consequence of quantum confinement, which corresponds [18] to a population of excited Si-nc with an average size of 4-5 nm. This observation is in agreement with particle sizes measured by EFTEM.…”

Section: Methodsmentioning

confidence: 99%

Auger quenching-based modulation of electroluminescence from ion-implanted silicon nanocrystals

et al. 2008

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Abstract. We describe high-speed control of light from silicon nanocrystals under electrical excitation. The nanocrystals are fabricated by ion implantation of Si + in the 15-nm-thick gate oxide of a field effect transistor at 6.5 keV. A characteristic readpeaked electroluminescence is obtained either by DC or AC gate excitation. However, AC gate excitation it is found to have a frequency response that is limited by the radiative lifetimes of silicon nanocrystals, which make impossible the direct modulation of light beyond 100 Kb/s rates. As a solution, we demonstrate that combined DC gate excitation along with an AC channel hot electron injection of electrons into the nanocrystals may be used to obtain a 100%-deep modulation at rates of 200 Mb/s and low modulating voltages. This approach, may find applications in biological sensing integrated into CMOS, single-photon emitters, or direct encoding of information into light from Si-nc doped with Erbium systems, which exhibit net optical gain. In this respect, the main advantage compared to conventional electro-optical modulators based on plasma dispersion effects is the low power consumption (10 5 times smaller) and thus the inherent large scale of integration. A detailed electrical characterization is also given. A Si/SiO 2 barrier change from Φ b =3.2 eV to 4.2 eV is found while the injection mechanism is changed from Fowler-Nordheim to Channel Hot Electron, which is a clear signature of nanocrystal charging and subsequent electroluminescence quenching.

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Influence of nanocrystal size on optical properties of Si nanocrystals embedded in SiO2 synthesized by Si ion implantation

Cited by 42 publications

References 32 publications

Direct modulation of electroluminescence from silicon nanocrystals beyond radiative recombination rates

Direct modulation of electroluminescence from silicon nanocrystals beyond radiative recombination rates

Second‐harmonic spectroscopy of Si nanocrystals embedded in silica

Auger quenching-based modulation of electroluminescence from ion-implanted silicon nanocrystals

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