We present a study on InAs/InGaAs QDs nanostructures grown by molecular beam epitaxy on InGaAs metamorphic buffers, that are designed so as to determine the strain of QD and, then, to shift the luminescence emission t...We present a study on InAs/InGaAs QDs nanostructures grown by molecular beam epitaxy on InGaAs metamorphic buffers, that are designed so as to determine the strain of QD and, then, to shift the luminescence emission towards the 1.5 μm region （QD strain engineering）. Moreover, we embed the QDs in InAIAs or GaAs barriers in addition to the InGaAs confining layers, in order to increase the activation energy for confined carrier thermal escape; thus, we reduce the thermal quenching of the photoluminescence, which prevents room temperature emission in the long wavelength range. We study the dependence of QD properties, such as emission energy and activation energy, on barrier thickness and height and we discuss how it is possible to compensate for the barrier-induced QD emission blue-shift taking advantage of QD strain engineering. Furthermore, the combination of enhanced barriers and QD strain engineering in such metamorphic QD nanostmctures allowed us to obtain room temperature emission up to 1.46μm, thus proving how this is a valuable approach in the auest for 1.55 um room temperature emission from ODs grown on GaAs substrates.展开更多
We experimentally demonstrate an efficient enhancement of luminescence from two-dimensional(2D) hexagonal photonic crystal(PC) airbridge double-heterostructure microcavity with Er-doped silicon(Si) as light emitters o...We experimentally demonstrate an efficient enhancement of luminescence from two-dimensional(2D) hexagonal photonic crystal(PC) airbridge double-heterostructure microcavity with Er-doped silicon(Si) as light emitters on siliconon-insulator(SOI) wafer at room temperature.A single sharp resonant peak at 1 529.6 nm dominates the photoluminescence(PL) spectrum with the pumping power of 12.5 m W.The obvious red shift and the degraded quality factor(Q-factor) of resonant peak appear with the pumping power increasing,and the maximum measured Q-factor of 4 905 is achieved at the pumping power of 1.5 m W.The resonant peak is observed to shift depending on the structural parameters of PC,which indicates a possible method to control the wavelength of enhanced luminescence for Si-based light emitters based on PC microcavity.展开更多
This work deals with the study of optical and morphological properties of InGaAs/AlGaAs quantum dot(QD) structures grown by molecular beam epitaxy(MBE) . Photoluminescence(PL) emission energies,activation energies of ...This work deals with the study of optical and morphological properties of InGaAs/AlGaAs quantum dot(QD) structures grown by molecular beam epitaxy(MBE) . Photoluminescence(PL) emission energies,activation energies of PL quenching and QD sizes are studied as functions of the Al content in the AlyGa1-yAs confining layers(CL) . We show that the PL emission energy of In(Ga) As/AlyGa1-yAs QD structures increases with increasing y and that the sizes of InAs/AlyGa1-yAs QDs decrease with increasing y. By the comparison of the experimental results with those of an effective-mass model developed to calculate the QD fundamental transition energies,we show that the blueshift of emission energy has to be ascribed not only to the increase in barrier discontinuities that confine the carriers into QDs but even to effects related to changes of the QD morphology dependent on CL composition. Moreover,we show that the Al content in the barriers determines also the activation energy of thermal quenching of PL,which depends on the thermal escape of carriers from QD levels. These studies resulted in the preparation of structures with efficient light-emission in the 980 nm spectral window of interest for lightwave communications.展开更多
Well-dispersed CdS quantum dots (QDs) with narrow size-distribution were prepared using generation 4.5 ester-terminated PAMAM dendrimers as inner-templates. The average diameter of CdS QDs was 1.5 nm and the photolumi...Well-dispersed CdS quantum dots (QDs) with narrow size-distribution were prepared using generation 4.5 ester-terminated PAMAM dendrimers as inner-templates. The average diameter of CdS QDs was 1.5 nm and the photoluminescence was purple. The room temperature photoluminescence quantum yield (RT-PQY) was 0.015. The diameter of CdS QDs increased with the increase of n / nPAMAM, also the color of photoluminescence was tunable and could be changed from purple to blue.展开更多
ZnO/diamond-like carbon (DLC) thin films are deposited by pulsed laser deposition (PLD) on Si (111) wafer. Visible room-temperature photoluminescence (PL) is observed from ZnO/DLC thin films by fluorescence spectropho...ZnO/diamond-like carbon (DLC) thin films are deposited by pulsed laser deposition (PLD) on Si (111) wafer. Visible room-temperature photoluminescence (PL) is observed from ZnO/DLC thin films by fluorescence spectrophotometer. The Gaussian curve fitting of PL spectra reveals that the broadband visible emission contains three components with λ=508 nm, 554 nm and 698 nm. The origin and possible mechanism of the visible PL are discussed, and they can be attributed to the PL recombination of ZnO and DLC thin films.展开更多
A series of Co-doped ZnO thin films have been prepared by direct current reactive magnetron sputtering on glass substrates.The structural characterization by means of X-ray diffraction (XRD) and scanning electron micr...A series of Co-doped ZnO thin films have been prepared by direct current reactive magnetron sputtering on glass substrates.The structural characterization by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) gave no evidence of second phase formation.The qualitative composition and chemical state were characterized by energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectronic spectrometry (XPS),respectively.The results confirmed that Co was incorporated as Co3+,occupying the Zn2+ sites in ZnO's wurtzite structure.The luminescence properties of the films were investigated by room temperature photoluminescence,and the optical properties were studied by optical transmittance.The magnetic analysis was carried out at room temperature and at 50 K by Quantum Design MPMS (SQUID) XL.The results showed that all the Co-doped ZnO thin films prepared by direct current magnetron sputtering were not ferromagnetic above 50 K.展开更多
基金The work has been partially supported by the "SANDiE" Networkof Excellence of EU(contract no. NMP4-CT-2004-500101).
文摘We present a study on InAs/InGaAs QDs nanostructures grown by molecular beam epitaxy on InGaAs metamorphic buffers, that are designed so as to determine the strain of QD and, then, to shift the luminescence emission towards the 1.5 μm region （QD strain engineering）. Moreover, we embed the QDs in InAIAs or GaAs barriers in addition to the InGaAs confining layers, in order to increase the activation energy for confined carrier thermal escape; thus, we reduce the thermal quenching of the photoluminescence, which prevents room temperature emission in the long wavelength range. We study the dependence of QD properties, such as emission energy and activation energy, on barrier thickness and height and we discuss how it is possible to compensate for the barrier-induced QD emission blue-shift taking advantage of QD strain engineering. Furthermore, the combination of enhanced barriers and QD strain engineering in such metamorphic QD nanostmctures allowed us to obtain room temperature emission up to 1.46μm, thus proving how this is a valuable approach in the auest for 1.55 um room temperature emission from ODs grown on GaAs substrates.
基金supported by the National Natural Science Foundation of China(No.61205044)
文摘We experimentally demonstrate an efficient enhancement of luminescence from two-dimensional(2D) hexagonal photonic crystal(PC) airbridge double-heterostructure microcavity with Er-doped silicon(Si) as light emitters on siliconon-insulator(SOI) wafer at room temperature.A single sharp resonant peak at 1 529.6 nm dominates the photoluminescence(PL) spectrum with the pumping power of 12.5 m W.The obvious red shift and the degraded quality factor(Q-factor) of resonant peak appear with the pumping power increasing,and the maximum measured Q-factor of 4 905 is achieved at the pumping power of 1.5 m W.The resonant peak is observed to shift depending on the structural parameters of PC,which indicates a possible method to control the wavelength of enhanced luminescence for Si-based light emitters based on PC microcavity.
基金The work has been partially supported by the "SANDiE" Networkof Excellence of EU (contract No. NMP4-CT-2004-500101).
文摘This work deals with the study of optical and morphological properties of InGaAs/AlGaAs quantum dot(QD) structures grown by molecular beam epitaxy(MBE) . Photoluminescence(PL) emission energies,activation energies of PL quenching and QD sizes are studied as functions of the Al content in the AlyGa1-yAs confining layers(CL) . We show that the PL emission energy of In(Ga) As/AlyGa1-yAs QD structures increases with increasing y and that the sizes of InAs/AlyGa1-yAs QDs decrease with increasing y. By the comparison of the experimental results with those of an effective-mass model developed to calculate the QD fundamental transition energies,we show that the blueshift of emission energy has to be ascribed not only to the increase in barrier discontinuities that confine the carriers into QDs but even to effects related to changes of the QD morphology dependent on CL composition. Moreover,we show that the Al content in the barriers determines also the activation energy of thermal quenching of PL,which depends on the thermal escape of carriers from QD levels. These studies resulted in the preparation of structures with efficient light-emission in the 980 nm spectral window of interest for lightwave communications.
文摘Well-dispersed CdS quantum dots (QDs) with narrow size-distribution were prepared using generation 4.5 ester-terminated PAMAM dendrimers as inner-templates. The average diameter of CdS QDs was 1.5 nm and the photoluminescence was purple. The room temperature photoluminescence quantum yield (RT-PQY) was 0.015. The diameter of CdS QDs increased with the increase of n / nPAMAM, also the color of photoluminescence was tunable and could be changed from purple to blue.
基金supported by the National Natural Science Foundation of China (No.10974077)the Project of Shandong Province Higher Educational Science and Technology Program (No.J08LI04)
文摘ZnO/diamond-like carbon (DLC) thin films are deposited by pulsed laser deposition (PLD) on Si (111) wafer. Visible room-temperature photoluminescence (PL) is observed from ZnO/DLC thin films by fluorescence spectrophotometer. The Gaussian curve fitting of PL spectra reveals that the broadband visible emission contains three components with λ=508 nm, 554 nm and 698 nm. The origin and possible mechanism of the visible PL are discussed, and they can be attributed to the PL recombination of ZnO and DLC thin films.
基金supported by the National Natural Science Foundation of China (Grant Nos.60576016,10774013,10804006)National High-Tech Research and Development Program of China (Grant No.2006AA03Z0412)+5 种基金111 project (Grant No.B08002)Fund for the Doctoral Program of Higher Education in China (RFDP) (Grant Nos.20070004024,20070004031)Beijing Natural Science Foundation of China (BNSFC) (Grant No.1102028)National Basic Research Program of China (Grant No.2010CB327705)National Natural Science Funds for Distinguished Young Scholar (Grant No.60825407)DIF Beijing Jiaotong University (Grant Nos.141028522,141036522)
文摘A series of Co-doped ZnO thin films have been prepared by direct current reactive magnetron sputtering on glass substrates.The structural characterization by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) gave no evidence of second phase formation.The qualitative composition and chemical state were characterized by energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectronic spectrometry (XPS),respectively.The results confirmed that Co was incorporated as Co3+,occupying the Zn2+ sites in ZnO's wurtzite structure.The luminescence properties of the films were investigated by room temperature photoluminescence,and the optical properties were studied by optical transmittance.The magnetic analysis was carried out at room temperature and at 50 K by Quantum Design MPMS (SQUID) XL.The results showed that all the Co-doped ZnO thin films prepared by direct current magnetron sputtering were not ferromagnetic above 50 K.
