A method for studying pico to microsecond time-resolved core-level spectroscopy used to investigate electron dynamics in quantum dots

AbstractTime-resolved photoelectron spectroscopy can give insights into carrier dynamics and offers the possibility of element and site-specific information through the measurements of core levels. In this paper, we demonstrate that this method can access electrons dynamics in PbS quantum dots over a wide time window spanning from pico- to microseconds in a single experiment carried out at the synchrotron facility BESSY II. The method is sensitive to small changes in core level positions. Fast measurements at low pump fluences are enabled by the use of a pump laser at a lower repetition frequency than the repetition frequency of the X-ray pulses used to probe the core level electrons: Through the use of a time-resolved spectrometer, time-dependent analysis of data from all synchrotron pulses is possible. Furthermore, by picosecond control of the pump laser arrival at the sample relative to the X-ray pulses, a time-resolution limited only by the length of the X-ray pulses is achieved. Using this method, we studied the charge dynamics in thin film samples of PbS quantum dots on n-type MgZnO substrates through time-resolved measurements of the Pb 5d core level. We found a time-resolved core level shift, which we could assign to electron injection and charge accumulation at the MgZnO/PbS quantum dots interface. This assignment was confirmed through the measurement of PbS films with different thicknesses. Our results therefore give insight into the magnitude of the photovoltage generated specifically at the MgZnO/PbS interface and into the timescale of charge transport and electron injection, as well as into the timescale of charge recombination at this interface. It is a unique feature of our method that the timescale of both these processes can be accessed in a single experiment and investigated for a specific interface.

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Photoinduced Charge Carrier Dynamics and Electron Injection Efficiencies in Au Nanoparticle-Sensitized TiO2 Determined with Picosecond Time-Resolved X-ray Photoelectron Spectroscopy

The Journal of Physical Chemistry Letters ◽

10.1021/acs.jpclett.0c00825 ◽

2020 ◽

Vol 11 (14) ◽

pp. 5476-5481

Author(s):

Mario Borgwardt ◽

Johannes Mahl ◽

Friedrich Roth ◽

Lukas Wenthaus ◽

Felix Brauße ◽

...

Keyword(s):

Charge Carrier ◽

Photoelectron Spectroscopy ◽

Electron Injection ◽

Carrier Dynamics ◽

Au Nanoparticle ◽

Time Resolved ◽

X Ray ◽

Charge Carrier Dynamics ◽

Photoinduced Charge

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Self-Organized Lead(II) Sulfide Quantum Dots Superlattice

MRS Advances ◽

10.1557/adv.2017.246 ◽

2017 ◽

Vol 2 (15) ◽

pp. 841-846 ◽

Cited By ~ 3

Author(s):

José Maria C. da Silva Filho ◽

Victor A. Ermakov ◽

Luiz G. Bonato ◽

Ana F. Nogueira ◽

Francisco C. Marques

Keyword(s):

Quantum Dots ◽

Interplanar Spacing ◽

Face Centered Cubic ◽

X Ray ◽

Self Organized ◽

Transmission Electron ◽

The Mean ◽

Face Centered ◽

Pbs Quantum Dots ◽

Deposited Films

ABSTRACTWe show that superlattice (SL) of PbS quantum dots (QD) can be easily prepared by drop casting of colloidal QD solution onto glass substrate and the ordering level can be controlled by the substrate temperature. A QD solution was dropped on glass and dried at 25, 40, 70 and 100°C resulting in formation of different SL structures. X-ray diffractograms (XRD) of deposited films show a set of sharp and intense peaks that are higher order satellites of a unique peak at 1.8 degrees (two theta), which corresponds, using the Bragg’s Law, to an interplanar spacing of 5.3 nm. The mean particles diameter, calculated through the broadening of the (111) peak of PbS using the Scherrer’s formula, were in agreement with the interplanar spacing. Transmission electron microscopy (TEM) measurements were also used to study the SL structure, which showed mainly a face centered cubic (FCC) arrangement of the QD. The photoluminescence (PL) spectrum of QD in the SL showed a shift toward lower energy compared to one in solution. It can be attributed to the fluorescence resonant energy transfer (FRET) between neighbors QD´s. Moreover, we observed greater redshift of PL peak for film with lower drying temperature, suggesting that it has a more organized structure.

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Chemical Structure of MEH-PPV/LiF/Al Interface

MRS Proceedings ◽

10.1557/proc-734-b7.4 ◽

2002 ◽

Vol 734 ◽

Cited By ~ 1

Author(s):

X. D. Feng ◽

D. Grozea ◽

Z. H. Lu

Keyword(s):

Oxygen Concentration ◽

Chemical Structure ◽

Electron Injection ◽

Core Level ◽

Photoemission Spectroscopy ◽

X Ray ◽

Electron Injection Layer

ABSTRACTWe studied the poly [2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV)/LiF/Al interface by angle-dependent X-ray photoemission spectroscopy (XPS). The changes in the C1s, O 1s, Al 2p core level spectra, and the evolution of O to C and Li to F atomic ratios at different photoelectron take-off angles were carefully analyzed. A reduced oxygen concentration with a LiF layer at the interface suggests that LiF can help reduce the oxidation of Al. The interface was found rich in Li+ ions, some of which might be attached to MEH-PPV to form “N type” doping. The electron injection layer consists of Li+doped MEH-PPV, LiF, Al oxides, and metallic Al.

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Time-resolved soft X-ray core-level photoemission spectroscopy at 880 °C using the pulsed laser and synchrotron radiation and the pulse heating current

Surface Science ◽

10.1016/j.susc.2016.09.006 ◽

2017 ◽

Vol 656 ◽

pp. 43-47 ◽

Cited By ~ 1

Author(s):

T. Abukawa ◽

S. Yamamoto ◽

R. Yukawa ◽

S. Kanzaki ◽

K. Mukojima ◽

...

Keyword(s):

Synchrotron Radiation ◽

Pulse Heating ◽

Pulsed Laser ◽

Core Level ◽

Photoemission Spectroscopy ◽

Time Resolved ◽

X Ray ◽

Heating Current

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Synthesis and Growth Mechanism of Stable Prenucleated (≈0.8 nm Diameter) PbS Quantum Dots by Medium Energy Ion Scattering Spectroscopy

Materials ◽

10.3390/ma12071109 ◽

2019 ◽

Vol 12 (7) ◽

pp. 1109

Author(s):

Young Park ◽

Seung Park ◽

Kang-Won Jung ◽

Yunju Hwang ◽

Saurav Sorcar ◽

...

Keyword(s):

Quantum Dots ◽

Growth Mechanism ◽

Nucleation Theory ◽

Classical Nucleation Theory ◽

Medium Energy ◽

Ion Scattering ◽

X Ray ◽

Vis Spectroscopy ◽

Medium Energy Ion Scattering ◽

Pbs Quantum Dots

In the current work, stable prenucleated PbS quantum dots (QDs) with a sub-nanometer (0.8 nm) size have been successfully synthesized via a systematically designed experiment. A detailed analysis of critical nucleation, growth, and stability for such ultrasmall prenucleated clusters is done. The experimental strategy is based on controlled concentration, temperature and injection of respective precursors, thus enabling us to control nucleation rate and separation of stable sub-nanometer PbS QDs with size 0.8 nm. Significantly, by providing additional thermal energy to sub-nanometer PbS QDs, we achieved the fully nucleated cubic crystalline structure of PbS with size of around 1.5 nm. The size and composition of the prenucleated QDs are investigated by sophisticated tools like X-ray photoelectron spectroscopy (XPS) and medium energy ion scattering (MEIS) spectroscopy which confirms the synthesis of PbS with Pb2+ rich surface while the UV-Vis spectroscopy and X-ray diffraction (XRD) data suggests an alternative crystallization path. Non-classical nucleation theory is employed to substantiate the growth mechanism of prenucleated PbS QDs.

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Fiber-based cryogenic and time-resolved spectroscopy of PbS quantum dots

Optics Express ◽

10.1364/oe.19.001786 ◽

2011 ◽

Vol 19 (3) ◽

pp. 1786 ◽

Cited By ~ 12

Author(s):

Matthew T. Rakher ◽

Ranojoy Bose ◽

Chee Wei Wong ◽

Kartik Srinivasan

Keyword(s):

Quantum Dots ◽

Time Resolved ◽

Time Resolved Spectroscopy ◽

Pbs Quantum Dots

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Electron Injection from Colloidal PbS Quantum Dots into Titanium Dioxide Nanoparticles

ACS Nano ◽

10.1021/nn800336b ◽

2008 ◽

Vol 2 (11) ◽

pp. 2206-2212 ◽

Cited By ~ 469

Author(s):

Byung-Ryool Hyun ◽

Yu-Wu. Zhong ◽

Adam C. Bartnik ◽

Liangfeng Sun ◽

Hector D. Abruña ◽

...

Keyword(s):

Quantum Dots ◽

Titanium Dioxide ◽

Titanium Dioxide Nanoparticles ◽

Electron Injection ◽

Pbs Quantum Dots

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FACILE SYNTHESIS OF COLLOIDAL PbS QUANTUM DOTS

International Journal of Nanoscience ◽

10.1142/s0219581x12400418 ◽

2012 ◽

Vol 11 (06) ◽

pp. 1240041

Author(s):

CHAO LIU ◽

YANG JIANG ◽

JIAN HUANG ◽

HONGYAN DUAN

Keyword(s):

Quantum Dots ◽

Heating Temperature ◽

Growth Time ◽

Photovoltaic Devices ◽

X Ray Diffraction ◽

Facile Synthesis ◽

X Ray ◽

Transmission Electron ◽

20 Nm ◽

Pbs Quantum Dots

Lead sulfide ( PbS ) quantum dots (QDs) capped with oleic acid and oleic amine were synthesized by using safe and innocuous sulfur powder as S source instead of the bis (trimethylsilyl) sulfide ((TMS)2S). QDs with size distribution from 20 nm to 3 nm were gained by controlling the experiment parameters such as heating temperature, capping agents and the growth time. The morphology and crystal structure of the as-prepared PbS QDs were characterized by (high-resolution) transmission electron microscopy (HR-TEM) images and powder X-ray diffraction (XRD). This method may offer a new route to synthesize PbS QDs for photovoltaic devices.

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Re-Entry Jet and Shock Induced Cavity Shedding in Cloud Cavitating Flow Around an Axisymmetric Projectile

Volume 2: Development and Applications in Computational Fluid Dynamics; Industrial and Environmental Applications of Fluid Mechanics; Fluid Measurement and Instrumentation; Cavitation and Phase Change ◽

10.1115/fedsm2018-83200 ◽

2018 ◽

Cited By ~ 1

Author(s):

Yiwei Wang ◽

Bingsheng Ye ◽

Jingzhu Wang ◽

Chenguang Huang

Keyword(s):

Source Code ◽

Axisymmetric Body ◽

Cavitating Flow ◽

Shock Propagation ◽

Single Experiment ◽

Time Resolved ◽

X Ray ◽

Cavity Shedding ◽

Cavity Closure ◽

Inducing Factors

Shedding is one of the most important expressions of the instability of cavitating flow. Most previous research works were focused on the shedding mechanism induced by the re-entry jet. Shock induced shedding on a wedge is identified recently by using time resolved X-ray densitometry which attracted lots of attention. In the present paper, cavitation dynamics around an axisymmetric body are investigated. Both shock propagation and re-entry jet as inducing factors of shedding are observed in different cycles in a single experiment. Relevant numerical simulations are carried out based on a fully compressible approach under the framework of the open-source code OpenFOAM. Numerical and experimental results agree well with each other. Results indicate shedding is induced by the re-entry jet in the first cycle. Re-entry jet occurs and cut the cavity off on the should which induces the shedding of cloud cavity in the first cycle. However in the second and subsequent cycles, shocks are generated by the collapse of shedding cavities and propagate to the cavity closure and induces stronger re-entry jet. Its effect on cavity instability is indirect which still needs a strong re-entry jet as the medium media.

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