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Identifying Clusters and/or Small-Size Quantum Dots in Colloidal CdSe Ensembles with Optical Spectroscopy
摘要： It is well-known that optical absorption and photoluminescence (PL) provide information that is sensitive to the size and size distribution of colloidal binary semiconductor quantum dots (QDs). To explore the nature of reaction products, clusters, and/or small-size QDs, we show that it is important to perform as well photoluminescence excitation (PLE) spectroscopy. For two non-hot-injection reactions of cadmium oleate (Cd(OA)2) and selenium (Se) in 1-octadecene (ODE), we show that sequentially extracted products displayed a similar apparent red shift in both absorption and PL with a full width at half-maximum (fwhm) of ～30 nm. We demonstrate that one reaction (with the presence of diphenyl phosphine (HPPh2)) produced multiple types of clusters (with slightly different optical properties) in one ensemble, while the other reaction (without HPPh2) yielded primarily small-size QDs. Our findings provide evidence for the probable existence of clusters within small-size CdSe QD products, the existence of which complicates the size determination of small-size CdSe QDs.
关键词： optical absorption,photoluminescence,photoluminescence excitation spectroscopy,clusters,CdSe quantum dots
更新于2025-09-16 10:30:52
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Er-doped antimonite Sb2O3?PbO?ZnO/ZnS glasses studied by low-temperature photoluminescence spectroscopy
摘要： Antimonite glasses Sb2O3?PbO?ZnO/ZnS doped with ErCl3 within the range of 0.25-1.0% were prepared and investigated by means of transmission, photoluminescence excitation and photoluminescence (PL) spectroscopy. In the studied glasses, the wavelength of 522 nm was found to be the most suitable for PL excitation of Er3+ ions doped in both the NIR and VIS spectral ranges. The PL spectra excited by wavelengths at 522 and/or 514.5 nm were measured at room and low temperatures (4 K) in the wavelength range of 400–1700 nm. Low-temperature PL spectroscopy allowed us to observe both the broad luminescence of the host glass centered at around 1050 nm and the narrow emissions caused by Er3+ ions. Special attention was given to the wavelengths where the broad-band luminescence of the host overlaps with 4f–4f transitions within Er3+ ions. A broad PL band of the host glass was observed together with a superimposed narrow emission band at 985 nm (4I11/2? 4I15/2) and a narrow absorption dip at about 970 nm (4I15/2? 4I11/2). This absorption dip is a direct experimental evidence of energy transfer from the electronic structure of the host glass to 4f states of doped-in Er3+ ions. The strongest PL band at 1530 nm, representing transition from the lowest excited manifold 4I13/2 to the ground state manifold 4I15/2 was measured at 300 K and 4 K. The broadening at elevated temperature occurs primarily in the high energy part of the spectrum due to thermal excitation of electrons within the 4I13/2 manifold.
关键词： photoluminescence excitation spectroscopy,broad-band luminescence,low-temperature photoluminescence spectroscopy,erbium,antimonite glasses
更新于2025-09-09 09:28:46
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Identification of the shallow donor state in Sb doped ZnO by photoluminescence excitation spectroscopy
摘要： Photoluminescence excitation (PLE) spectroscopy was used to investigate the optical properties of the recently discovered 3364.3 meV antimony-related donor bound exciton (D0X) in zinc oxide. By suitable control of the growth conditions, we achieved samples in which the Sb-related donor emission was the dominant near-bandgap luminescence feature. Resonant excitation using a tunable UV source enabled the observation of the two electron transitions of the donor bound exciton, enabling the direct determination of the binding energy of the Sb donor at 42:2 + 0:5 meV, the lowest value yet reported for a donor in this material. The two electron transitions exhibit an unusual blue shift with increasing temperature, which is explained in terms of thermalization of excited states of the D0X initial state. The D0X excited states were probed by PLE and follow the trends of conventional shallow group III donors such as Al, Ga, and In.
关键词： binding energy,two electron transitions,shallow donor state,Photoluminescence excitation spectroscopy,Sb doped ZnO
更新于2025-09-09 09:28:46