Group IV Quantum Dots and Nanoparticles

AbstractThe narrow gap semiconductor alloys SnxGe1−x, and SnxSi1−x offer the possibility for engineering tunable direct energy gap Group IV semiconductor materials. For pseudomorphic SnxGe1−x, alloys grown on Ge (001) by molecular beam epitaxy, an indirect-to-direct bandgap transition with increasing Sn composition is observed, and the effects of misfit on the bandgap analyzed in terms of a deformation potential model. Key results are that pseudomorphic strain has only a very slight effect on the energy gap of SnxGe1−x, alloys grown on Ge (001) but for SnxGe1−x alloys grown on Ge (111) no indirect-to-direct gap transition is expected. In the SnxSi1−x system, ultrathin pseudomorphic epitaxially-stabilized α-SnxSi1−x alloys are grown on Si (001) substrates by conventional molecular beam epitaxy. Coherently strained oa-Sn quantum dots are formed within a defect-free Si (001) crystal by phase separation of the thin SnxSi1−x layers embedded in Si (001). Phase separation of the thin alloy film, and subsequent evolution occurs via growth and coarsening of regularly-shaped α-Sn quantum dots that appear as 4–6 nm diameter tetrakaidecahedra with facets oriented along elastically soft [100] directions. Attenuated total reflectance infrared absorption measurements indicate an absorption feature due to the α-Sn quantum dot array with onset at ˜0.3 eV and absorption strength of 8 × 103 cm−1, which are consistent with direct interband transitions.

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Exploiting the biological windows: current perspectives on fluorescent bioprobes emitting above 1000 nm

Nanoscale Horizons ◽

10.1039/c5nh00073d ◽

2016 ◽

Vol 1 (3) ◽

pp. 168-184 ◽

Cited By ~ 251

Author(s):

Eva Hemmer ◽

Antonio Benayas ◽

François Légaré ◽

Fiorenzo Vetrone

Keyword(s):

Quantum Dots ◽

Rare Earth ◽

Near Infrared ◽

Group Iv ◽

Current Trends ◽

Fluorescent Bioprobes ◽

Biological Windows

Rare-earth based nanoparticles, Group-IV nanostructures, and novel quantum dots in the near-infrared (NIR) spotlight: current trends, material merits, and latest developments in NIR-to-NIR bioimaging.

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Electrophoretic Deposition of Quantum Dots and Characterisation of Composites

Materials ◽

10.3390/ma12244089 ◽

2019 ◽

Vol 12 (24) ◽

pp. 4089 ◽

Cited By ~ 3

Author(s):

Finn Purcell-Milton ◽

Antton Curutchet ◽

Yurii Gun’ko

Keyword(s):

Quantum Dots ◽

Dielectric Constant ◽

Electrophoretic Deposition ◽

Fold Increase ◽

Group Iv ◽

Device Fabrication ◽

Colloidal Quantum Dots ◽

Cdse Qds ◽

Depth Study ◽

First Time

Electrophoretic deposition (EPD) is an emerging technique in nanomaterial-based device fabrication. Here, we report an in-depth study of this approach as a means to deposit colloidal quantum dots (CQDs), in a range of solvents. For the first time, we report the significant improvement of EPD performance via the use of dichloromethane (DCM) for deposition of CQDs, producing a corresponding CQD-TiO2 composite with a near 10-fold increase in quantum dot loading relative to more commonly used solvents such as chloroform or toluene. We propose this effect is due to the higher dielectric constant of the solvent relative to more commonly used and therefore the stronger effect of EPD in this medium, though there remains the possibility that changes in zeta potential may also play an important role. In addition, this solvent choice enables the true universality of QD EPD to be demonstrated, via the sensitization of porous TiO2 electrodes with a range of ligand capped CdSe QDs and a range of group II-VI CQDs including CdS, CdSe/CdS, CdS/CdSe and CdTe/CdSe, and group IV-VI PbS QDs.

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Physical mechanism for photon emissions from group-IV-semiconductor quantum-dots in quartz-glass and thermal-oxide layers

Japanese Journal of Applied Physics ◽

10.35848/1347-4065/ac3dc9 ◽

2021 ◽

Author(s):

Tomohisa Mizuno ◽

Kohki Murakawa ◽

Kazuma Yoshimizu ◽

Takashi Aoki ◽

Toshiyuki SAMESHIMA

Keyword(s):

Quantum Dots ◽

Quartz Glass ◽

Group Iv ◽

Semiconductor Quantum Dots ◽

Implantation Technique ◽

Dangling Bond ◽

Impurity Density ◽

Bond Density ◽

Thermal Oxide ◽

Group Iv Semiconductor

Abstract We experimentally studied the influence of both impurity density and dangling-bond density on PL emissions from group-IV-semiconductor quantum-dots (IV-QDs) of Si and SiC fabricated by hot-ion implantation technique, to improve the PL intensity (IPL) from IV-QDs embedded in two types of insulators of quartz glass (QZ) with low impurity density and thermal-oxide (OX) layers. First, we verified the IPL reduction in the IV-QDs in QZ. However, we demonstrated the IPL enhancement of IV-QDs in doped QZ, which is attributable to multiple-level emission owing to acceptor and donor ion implantations into QZ. Secondly, we confirmed the large IPL enhancement of IV-QDs in QZ and OX, owing to forming gas annealing with H2/N2 mixed gas, which are attributable to the reduction of the dangling-bond density in IV-QDs. Consequently, it is possible to improve the IPL of IV-QDs by increasing impurity density and reducing dangling-bond density.

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Investigation of GaSb/GaAs Quantum Dots Formation on Ge (001) Substrate and Effect of Anti-Phase Domains

MRS Advances ◽

10.1557/adv.2016.172 ◽

2016 ◽

Vol 1 (23) ◽

pp. 1729-1734 ◽

Cited By ~ 1

Author(s):

Zon ◽

Thanavorn Poempool ◽

Suwit Kiravittaya ◽

Suwat Sopitpan ◽

Supachok Thainoi ◽

...

Keyword(s):

Quantum Dots ◽

Buffer Layer ◽

Growth Temperature ◽

Molecular Beam ◽

Sample Surface ◽

Layer Growth ◽

Group Iv ◽

Optimum Conditions ◽

Molecular Beam Epitaxial ◽

Molecular Beam Epitaxial Growth

ABSTRACTThe effects of GaAs anti-phase domains (APDs) on the growth of GaSb quantum dots (QDs) are investigated by molecular beam epitaxial growth of GaAs on Ge (001) substrate. Ge is a group-IV element and GaAs is a polar III-V compound semiconductor. Due to polar/non polar interface, GaAs APDs are formed. Initial formation of APD relates to a non-uniform growth of high index GaAs surfaces. However, due to high sticking coefficient of Sb atoms at low substrate growth temperature, GaSb QDs can be formed on the whole surface of the sample without any effects from APD boundary. The buffer layer growth temperature is one of the key roles to control the APDs formation. Therefore we tried to adjust the optimum conditions such as buffer layer thickness and growth temperature to get nearly flat sample surface with large APDs for high QDs density (∼ 8×109 dots/cm2). Low-temperature photoluminescence is conducted and GaSb QDs peak is observed at the energy range of 1.0 eV-1.3 eV.

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