Photoluminescence and optically detected magnetic resonance investigations on porous silicon

Meyer, B. K.; Hofmann, Detlev M.; Stadler, Wolfgang; Petrova‐Koch, V.; Koch, F.; Emanuelsson, P.; Omling, P.

doi:10.1016/0022-2313(93)90121-3

Cited by 20 publications

(15 citation statements)

References 11 publications

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“…Several authors have already identified the P,-defect (a silicon dangling bond at the Si/SiOz interface) as the major defect in porous Si [4,5]. Fig.…”

Section: Resultsmentioning

confidence: 99%

Radiative and Nonradiative Recombination in Porous Silicon. What Can We Learn from Spin Resonance?

Stutzmann

Brandt

1995

Physica Status Solidi (b)

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Recent results of spin-resonance investigations of porous silicon are presented. Special attention is given to nonradiative and radiative recombination processes as detected by spin-dependent recombination (spin-dependent photoconductivity, SDPC, and optically detected magnetic resonance, ODMR). P,-like defects are identified as the main recombination centers which quench both photoconductivity and visible photoluminescence in porous Si. Strongly localized triplet excitons are found as the initial states of visible luminescence. IntroductionIn many cases, electron spin resonance (ESR) and related techniques have been instrumental in clarifying details of recombination processes in semiconductors and insulators. Particularly informative are combinations of spin resonance with photoconductivity (spindependent photoconductivity, SDPC) and luminescence (optically detected magnetic resonance, ODMR) which make use of spin-selection rules for radiative and nonradiative transitions involving paramagnetic states with electronic spin S =I= 0. In a simple picture, the final state of recombination is a doubly occupied, diamagnetic (S = 0) state according to the Pauli principle. The excited state prior to the recombination can be a parallel (S = 1, triplet state) or antiparallel (S = 0, singlet) combination of the electron and hole spins, respectively. Thus, if we neglect changes in the orbital momentum L for the sake of simplicity, nonradiative recombination can only occur out of the singlet state, since phonons have no spin, whereas radiative recombination occurs out of the triplet state to account for the orbital momentum J = 1 carried away by the emitted photon. In spin resonance the induced spin-flips of either the electron or hole state effectively change singlet into triplet combinations and vice versa, thereby also modulating the lifetime of the excited state. This modulation is finally detected as a small, resonant decrease or increase of the photoconductivity and the luminescence, which constitutes the measured signal.

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“…Several authors have already identified the P,-defect (a silicon dangling bond at the Si/SiOz interface) as the major defect in porous Si [4,5]. Fig.…”

Section: Resultsmentioning

confidence: 99%

Radiative and Nonradiative Recombination in Porous Silicon. What Can We Learn from Spin Resonance?

Stutzmann

Brandt

1995

Physica Status Solidi (b)

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“…The 0.9 eV peak is generally assigned to the recombination of photoexcited carriers via Si dangling bonds at the interfaces between nc-Si and SiO 2 matrices ͑Si P b centers͒. [15][16][17][18] The intensity of this peak shows the same Ge concentration dependence as that of the main band. The integrated PL intensities of the 0.9 and 1.4 eV peaks at 10 K are shown in Fig.…”

Section: Methodsmentioning

confidence: 94%

Electron spin resonance study of defects in Si1−xGex alloy nanocrystals embedded in SiO2 matrices: Mechanism of luminescence quenching

Toshikiyo

Tokunaga

Takeoka

et al. 2001

Journal of Applied Physics

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Dangling bond defects in Si1−xGex alloy nanocrystals (nc-Si1−xGex) as small as 4 nm in diameter embedded in SiO2 thin films were studied by electron spin resonance (ESR), and the effects of the defects on photoluminescence (PL) properties were discussed. It was found that the ESR spectrum is a superposition of signals from Si and Ge dangling bonds at the interfaces between nc-Si1−xGex and SiO2 matrices (Si and Ge Pb centers). As the Ge concentration increased, the signal from the Ge Pb centers increased, while that from the Si Pb centers was nearly independent of Ge concentration. The increase in the number of Ge Pb centers was accompanied by strong quenching of the PL. The observed correlation between the two measurements suggests that the Ge Pb centers act as efficient nonradiative recombination centers for photogenerated carriers, resulting in the quenching of the main PL.

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“…Similar to the main peak, the lowenergy peak exhibits a size-dependent shift. However, the amount of the shift is about half that of the main peak [3,[51][52][53][54]. The size-dependent shift of the low-energy peak is considered to reflect that of the conduction band edge.…”

Section: Fundamental Propertiesmentioning

confidence: 99%

Optical Properties of Intrinsic and Shallow Impurity‐Doped Silicon Nanocrystals

Fujii

2010

Silicon Nanocrystals

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The electronic band structure of silicon (Si) crystals is significantly modified when the size is reduced to below the exciton Bohr radius ($4.9 nm) of bulk Si crystals due to the quantum size effect. The quantum size effect manifests itself as a high-energy shift of the luminescence band and an enhancement of the spontaneous emission rate. Furthermore, enlargement of the singlet-triplet splitting energy of exciton states with decreasing size has been demonstrated [1-4]. The modified band structure opens up new application of Si nanocrystals in the fields where bulk Si crystal has not been involved. Besides well-known high-efficiency visible photoluminescence (PL), one of the most exotic new feature of Si nanocrystals is their ability to generate a kind of active oxygen species called singlet oxygen by energy transfer from excitons to oxygen molecules (O 2 ) adsorbed onto the surface of Si nanocrystals [5]. This feature is due to the molecule-like energy structure of Si nanocrystals and is a direct consequence of the quantum size effects. Similarly, efficient photosensitization of rare earth ions by Si nanocrystals has been reported and this phenomenon is expected to lead to the development of an efficient planar waveguide-type optical amplifier operating at the optical telecommunication wavelength. Since almost all new features of Si nanocrystals arise from the modified electronic band structure, its deep understanding is indispensable to explore new nano-Si-based research fields and devices. Fortunately, the energy structure of Si nanocrystals is almost clarified, at least qualitatively, by detailed optical spectroscopy. In Section 3.2, we briefly summarize fundamental optical properties of intrinsic Si nanocrystals [1][2][3][4][5][6][7][8].The properties of Si nanocrystals can be controlled by the size, shape, surface termination, and so on. An additional freedom of material design can be introduced by impurity doping. The introduction of shallow impurities in a semiconductor significantly modifies its optical and electrical transport properties. Actually, a precise control of an impurity profile is key to achieve desirable functions in almost all kinds Silicon Nanocrystals: Fundamentals, Synthesis and Applications. Edited by Lorenzo Pavesi and Rasit Turan

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Photoluminescence and optically detected magnetic resonance investigations on porous silicon

Cited by 20 publications

References 11 publications

Radiative and Nonradiative Recombination in Porous Silicon. What Can We Learn from Spin Resonance?

Radiative and Nonradiative Recombination in Porous Silicon. What Can We Learn from Spin Resonance?

Electron spin resonance study of defects in Si1−xGex alloy nanocrystals embedded in SiO2 matrices: Mechanism of luminescence quenching

Optical Properties of Intrinsic and Shallow Impurity‐Doped Silicon Nanocrystals

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