Control of Silicon Nanocrystallite Luminescence Behavior Through Surface Treatments

MRS Proceedings ◽

10.1557/proc-405-277 ◽

1995 ◽

Vol 405 ◽

Cited By ~ 1

Author(s):

A. A. Seraphin ◽

S.-T. Ngiam ◽

K. D. Kolenbrander

Keyword(s):

Photoelectron Spectroscopy ◽

Surface Passivation ◽

Particle Surface ◽

Nanocrystallite Size ◽

Carrier Recombination ◽

Simple Quantum ◽

Acid Etch ◽

Emission Behavior ◽

Silicon Nanocrystallites

AbstractThe visible photoluminescence from thin films of silicon nanocrystallites produced by a pulsed laser ablation supersonic expansion source has been studied to determine the role of particle surface and size in the emission behavior. Variation of nanocrystallite size and surface through a variety of chemical treatments and processing steps has shown that the visible emission can be explained using only a simple quantum confinement model. Particle size has been reduced through a series of acid etch and reoxidation cycles and compared to sample emission wavelength. The role of surface species in determining emission behavior has been studied by chemically altering the surfaces and comparing their surface properties as determined by x-ray photoelectron spectroscopy to their photoluminescence behavior. Nanocrystallite size controls the emission energy, while surface passivation only determines emission intensity, through control of excited carrier recombination pathways.

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The Enabling Role of Surface Passivation in Visible Photoluminescence from Si Nanoparticles

MRS Proceedings ◽

10.1557/proc-318-433 ◽

1993 ◽

Vol 318 ◽

Author(s):

A.A. Seraphin ◽

E. Werwa ◽

L.A. Chiu ◽

K.D. Kolenbrander

Keyword(s):

Room Temperature ◽

Surface Passivation ◽

Light Emission ◽

Supersonic Expansion ◽

Expansion Technique ◽

Si Nanoparticles ◽

Silicon Nanocrystallites ◽

Pl Emission ◽

Si Nanocrystallites

ABSTRACTSilicon nanocrystallites have been studied in a variety of passivating environments to study the role of surface passivation in visible light emission from the particles. Thin films of Si nanocrystallites have been deposited by a laser ablation supersonic expansion technique. The films show significant room temperature photoluminescence (PL) behavior only after processing to achieve surface passivation. Passivation effects on light emission are studied through PL emission spectroscopy on clusters in the gas phase, as well as films in a variety of passivating media. The intensity of PL emission seems to scale with the extent of surface passivation, but the specific nature of the passivating species is not critical in defining the wavelength of emitted light.

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Design of Grating Al2O3 Passivation Structure Optimized for High-Efficiency Cu(In,Ga)Se2 Solar Cells

Sensors ◽

10.3390/s21144849 ◽

2021 ◽

Vol 21 (14) ◽

pp. 4849

Author(s):

Chan Hyeon Park ◽

Jun Yong Kim ◽

Shi-Joon Sung ◽

Dae-Hwan Kim ◽

Yun Seon Do

Keyword(s):

Solar Cells ◽

High Efficiency ◽

Surface Passivation ◽

Rear Surface ◽

Maximum Efficiency ◽

Structural Factors ◽

Carrier Recombination ◽

Cigs Solar Cells ◽

Effective Carrier ◽

Opening Width

In this paper, we propose an optimized structure of thin Cu(In,Ga)Se2 (CIGS) solar cells with a grating aluminum oxide (Al2O3) passivation layer (GAPL) providing nano-sized contact openings in order to improve power conversion efficiency using optoelectrical simulations. Al2O3 is used as a rear surface passivation material to reduce carrier recombination and improve reflectivity at a rear surface for high efficiency in thin CIGS solar cells. To realize high efficiency for thin CIGS solar cells, the optimized structure was designed by manipulating two structural factors: the contact opening width (COW) and the pitch of the GAPL. Compared with an unpassivated thin CIGS solar cell, the efficiency was improved up to 20.38% when the pitch of the GAPL was 7.5–12.5 μm. Furthermore, the efficiency was improved as the COW of the GAPL was decreased. The maximum efficiency value occurred when the COW was 100 nm because of the effective carrier recombination inhibition and high reflectivity of the Al2O3 insulator passivation with local contacts. These results indicate that the designed structure has optimized structural points for high-efficiency thin CIGS solar cells. Therefore, the photovoltaic (PV) generator and sensor designers can achieve the higher performance of photosensitive thin CIGS solar cells by considering these results.

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Removal of hexavalent chromium from wastewater by Cu/Fe bimetallic nanoparticles

Scientific Reports ◽

10.1038/s41598-021-90414-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jien Ye ◽

Yi Wang ◽

Qiao Xu ◽

Hanxin Wu ◽

Jianhao Tong ◽

...

Keyword(s):

Hexavalent Chromium ◽

Removal Efficiency ◽

Photoelectron Spectroscopy ◽

Bimetallic Nanoparticles ◽

Chemical Reduction ◽

Particle Surface ◽

Zerovalent Iron ◽

Order Model ◽

X Ray ◽

Nanoscale Zerovalent Iron

AbstractPassivation of nanoscale zerovalent iron hinders its efficiency in water treatment, and loading another catalytic metal has been found to improve the efficiency significantly. In this study, Cu/Fe bimetallic nanoparticles were prepared by liquid-phase chemical reduction for removal of hexavalent chromium (Cr(VI)) from wastewater. Synthesized bimetallic nanoparticles were characterized by transmission electron microscopy, Brunauer–Emmet–Teller isotherm, and X-ray diffraction. The results showed that Cu loading can significantly enhance the removal efficiency of Cr(VI) by 29.3% to 84.0%, and the optimal Cu loading rate was 3% (wt%). The removal efficiency decreased with increasing initial pH and Cr(VI) concentration. The removal of Cr(VI) was better fitted by pseudo-second-order model than pseudo-first-order model. Thermodynamic analysis revealed that the Cr(VI) removal was spontaneous and endothermic, and the increase of reaction temperature facilitated the process. X-ray photoelectron spectroscopy (XPS) analysis indicated that Cr(VI) was completely reduced to Cr(III) and precipitated on the particle surface as hydroxylated Cr(OH)3 and CrxFe1−x(OH)3 coprecipitation. Our work could be beneficial for the application of iron-based nanomaterials in remediation of wastewater.

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Role of ALD Al2O3 Surface Passivation on the Performance of p-Type Cu2O Thin Film Transistors

ACS Applied Materials & Interfaces ◽

10.1021/acsami.0c18915 ◽

2021 ◽

Vol 13 (3) ◽

pp. 4156-4164

Author(s):

Mari Napari ◽

Tahmida N. Huq ◽

David J. Meeth ◽

Mikko J. Heikkilä ◽

Kham M. Niang ◽

...

Keyword(s):

Thin Film ◽

Thin Film Transistors ◽

Surface Passivation ◽

Cu2o Thin Film ◽

P Type

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Influence of TOPO and TOPO-CdSe/ZnS Quantum Dots on Luminescence Photodynamics of InP/InAsP/InPHeterostructure Nanowires

Nanomaterials ◽

10.3390/nano11030640 ◽

2021 ◽

Vol 11 (3) ◽

pp. 640

Author(s):

Artem I. Khrebtov ◽

Vladimir V. Danilov ◽

Anastasia S. Kulagina ◽

Rodion R. Reznik ◽

Ivan D. Skurlov ◽

...

Keyword(s):

Quantum Dots ◽

Excited States ◽

Molecular Beam ◽

Surface Passivation ◽

Low Energy ◽

Trioctylphosphine Oxide ◽

Reverse Transfer ◽

Semiconductor Heterostructure ◽

Ligand Type

The passivation influence by ligands coverage with trioctylphosphine oxide (TOPO) and TOPO including colloidal CdSe/ZnS quantum dots (QDs) on optical properties of the semiconductor heterostructure, namely an array of InP nanowires (NWs) with InAsP nanoinsertion grown by Au-assisted molecular beam epitaxy on Si (111) substrates, was investigated. A significant dependence of the photoluminescence (PL) dynamics of the InAsP insertions on the ligand type was shown, which was associated with the changes in the excitation translation channels in the heterostructure. This change was caused by a different interaction of the ligand shells with the surface of InP NWs, which led to the formation of different interfacial low-energy states at the NW-ligand boundary, such as surface-localized antibonding orbitals and hybridized states that were energetically close to the radiating state and participate in the transfer of excitation. It was shown that the quenching of excited states associated with the capture of excitation to interfacial low-energy traps was compensated by the increasing role of the “reverse transfer” mechanism. As a result, the effectiveness of TOPO-CdSe/ZnS QDs as a novel surface passivation coating was demonstrated.

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Yttrium doped phosphate-based glasses: structural and degradation analyses

Biomedical glasses ◽

10.1515/bglass-2020-0004 ◽

2020 ◽

Vol 6 (1) ◽

pp. 34-49

Author(s):

Abul Arafat ◽

Sabrin A. Samad ◽

Jeremy J. Titman ◽

Andrew L. Lewis ◽

Emma R. Barney ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Structural Changes ◽

Xrd Analysis ◽

Calcium Pyrophosphate ◽

Ion Release ◽

Subsequent Increase ◽

Structural Characterisation ◽

Release Studies ◽

Degradation Properties

AbstractThis study investigates the role of yttrium in phosphate-based glasses in the system 45(P2O5)–25(CaO)– (30-x)(Na2O)–x(Y2O3) (0≤x≤5) prepared via melt quenching and focuses on their structural characterisation and degradation properties. The structural analyses were performed using a combination of solid-state nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). 31P NMR analysis showed that depolymerisation of the phosphate network occurred which increased with Y2O3 content as metaphosphate units (Q2) decreased with subsequent increase in pyrophosphate species (Q1). The NMR results correlated well with structural changes observed via FTIR and XPS analyses. XRD analysis of crystallised glass samples revealed the presence of calcium pyrophosphate (Ca2P2O7) and sodium metaphosphate (NaPO3) phases for all the glass formulations explored. Yttrium-containing phases were found for the formulations containing 3 and 5 mol% Y2O3. Degradation analyses performed in Phosphate buffer saline (PBS) and Milli-Q water revealed significantly reduced rates with addition of Y2O3 content. This decrease was attributed to the formation of Y-O-P bonds where the octahedral structure of yttrium (YO6) cross-linked phosphate chains, subsequently leading to an increase in chemical durability of the glasses. The ion release studies also showed good correlation with the degradation profiles.

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Microcharacterization of Interfaces

MRS Proceedings ◽

10.1557/proc-18-7 ◽

1982 ◽

Vol 18 ◽

Author(s):

P. M. PETROFF

Keyword(s):

Phase Contrast ◽

Molecular Beam ◽

Minority Carrier ◽

Carrier Recombination ◽

Roughening Transition ◽

Semiconductor Heterostructure ◽

Transmission Electron ◽

Quantum Well Wire ◽

Interfacial Strain

The atomic structure of semiconductor heterostructure interfaces and metalsemiconductor interfaces are best characterized by transmission electron microscopy (TEM). Both phase contrast TEM and structure factor contrast TEM are able to distinguish very small structural (two monolayers) or compositional (less than 0.2%) fluctuations at interfaces. Applications of these techniques to the study of the roughening transition temperature at the Gal−xAlxAs–GaAs and Ga1−xAlxAs–Ge interfaces grown by molecular beam epitaxy are presented. Minority carrier recombination at interfaces is characterized on a microscopic scale by low temperature cathodoluminescence. This technique is used to demonstrate the role of interfaces in gettering defects in Gal1−xAlxAs/GaAs heterostructures. Finally, the effects of interfacial strain in producing a localization of the luminescence in GaAs quantum well wire structures will be discussed.

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Incorporation and Role of Nitrogen During Oxynitridation of Silicon Studied by Photoelectron Spectroscopy

MRS Proceedings ◽

10.1557/proc-567-51 ◽

1999 ◽

Vol 567 ◽

Cited By ~ 1

Author(s):

Masayuki Suzuki ◽

Yoji Saito

Keyword(s):

Photoelectron Spectroscopy ◽

High Vacuum ◽

Oxide Films ◽

Silicon Surfaces ◽

Gaseous Mixtures ◽

X Ray ◽

Initial Stage ◽

Thermal Stability Of

ABSTRACTWe tried direct oxynitridation of silicon surfaces by remote-plasma-exited nitrogen and oxygen gaseous mixtures at 700°C in a high vacuum. The oxynitrided surfaces were investigated with in-situ X-ray photoelectron spectroscopy. With increase of the oxynitridation time, the surface density of nitrogen gradually increases, but that of oxygen shows nearly saturation behavior after the rapid increase in the initial stage. We also annealed the grown oxynitride and oxide films to investigate the role of the contained nitrogen. The desorption rate of oxygen from the oxynitride films is much less than that from oxide films. We confirmed that nitrogen stabilizes the thermal stability of these oxynitride films.

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