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Papers by Ali JAFFAL

Research paper thumbnail of Optical Polarization Properties of Wurtzite InP and InAs/InP Nanowires Grown on Silicon(111)

Research paper thumbnail of Bright single InAs quantum dots at telecom wavelengths in conical tapered InP nanowires monolithically grown on Si

Research paper thumbnail of Highly linearly polarized emission at telecom bands from single InAs/InP quantum dot-nanowires by geometry tailoring

Research paper thumbnail of Highly linear polarized emission at telecom bands in InAs/InP quantum dot-nanowires by geometry tailoring

Nanoscale, Oct 21, 2021

Nanowire (NW)-based opto-electronic devices require certain engineering in the NW geometry to rea... more Nanowire (NW)-based opto-electronic devices require certain engineering in the NW geometry to realize polarized-dependent light sources and photodetectors. We present a growth procedure to produce InAs/InP quantum dot-nanowires (QD-NWs) with an elongated top-view crosssection relying on the vapor-liquid-solid method using molecular beam epitaxy. By interrupting the rotation of the sample during the radial growth sequence of the InP shell, hexagonal asymmetric (HA) NWs with long/short cross-section axes were obtained instead of the usual symmetrical shape. Polarization-resolved photoluminescence measurements have revealed a significant influence of the asymmetric shaped NWs on the InAs QD emission polarization with the photons being mainly polarized parallel to the NW long cross-section axis. A degree of linear polarization (DLP) up to 91% is obtained, being at the state of the art for the reported DLP values from QD-NWs. More importantly, the growth protocol herein is fully compatible with the current applications of HA NWs covering a wide range of devices such as polarized light emitting diodes and photodetectors.

Research paper thumbnail of A nanowire-based telecom band single photon source monolithically grown on silicon

Research paper thumbnail of Single photon emission with a Gaussian far-field at telecom wavelength from single InAs/InP quantum dot-nanowires monolithically grown on Si

Research paper thumbnail of Optimizing the shape of InAs/InP quantum dot-nanowires grown by MBE on silicon for efficient light sources emitting in the telecom band

Research paper thumbnail of InAs/InP quantum dot-nanowire single photon sources in the telecom band grown monolithically on silicon substrates

Research paper thumbnail of Towards controlling the optical properties of InAs/InP quantum dot- nanowires using a hybrid amorphous silicon/III-V semiconductor photonic structure

Research paper thumbnail of Highly linear polarized emission at telecom bands in InAs/InP quantum dot-nanowires by geometry tailoring

Nanoscale, 2021

Nanowire (NW)-based opto-electronic devices require certain engineering in the NW geometry to rea... more Nanowire (NW)-based opto-electronic devices require certain engineering in the NW geometry to realize polarized-dependent light sources and photodetectors. We present a growth procedure to produce InAs/InP quantum dot-nanowires (QD-NWs) with...

Research paper thumbnail of Density-controlled growth of vertical InP nanowires on Si(111) substrates

Nanotechnology, 2020

A procedure to achieve the density-controlled growth of gold-catalyzed InP nanowires (NWs) on (11... more A procedure to achieve the density-controlled growth of gold-catalyzed InP nanowires (NWs) on (111) silicon substrates using the vapor-liquid-solid method by molecular beam epitaxy is reported. We develop an effective and mask-free method based on controlling the number and the size of the Au-In catalyst droplets in addition to the conditions for the NW nucleation. We show that the NW density can be tuned with values in the range of 18 µm-2 to < 0.1 µm-2 by the suitable choice of the In/Au catalyst beam equivalent pressure (BEP) ratio, by the phosphorous BEP and the growth temperature. The same degree of control is transferred to InAs/InP quantum dot-nanowires, taking advantage of the ultra-low density to study by micro-photoluminescence the optical properties of a single quantum dot-nanowires emitting in the telecom band monolithically grown on silicon. Optical spectroscopy at cryogenic temperature successfully confirmed the relevance of our method to excite single InAs quantum dots on the as-grown sample, which opens the path for large-scale applications based on single quantum dot-nanowire devices integrated on silicon.

Research paper thumbnail of Controlling the shape of a tapered nanowire: lessons from the Burton-Cabrera-Frank model

Nanotechnology, 2020

The propagation of sidewall steps during the growth of nanowires is calculated in the frame of th... more The propagation of sidewall steps during the growth of nanowires is calculated in the frame of the Burton-Cabrera-Frank model. The stable shape of the nanowire comprises a cylinder section on top of a cone section: their characteristics are obtained as a function of the radius of the catalystnanowire area, the desorption-limited diffusion length of adatoms on the terraces, and the sticking of adatoms at step edges. The comparison with experimental data allows us to evaluate these last two parameters for InP and ZnTe nanowires; it reveals a different behavior for the two materials, related to a difference by an order of magnitude of the desorption-limited diffusion length.

Research paper thumbnail of InAs quantum dot in a needlelike tapered InP nanowire: a telecom band single photon source monolithically grown on silicon

Nanoscale, 2019

Fabrication of a NW-based single photon source on silicon emitting in the telecom band with a Gau... more Fabrication of a NW-based single photon source on silicon emitting in the telecom band with a Gaussian far-field emission profile.

Research paper thumbnail of Shape-selective purification of gold nanorods with low aspect ratio using a simple centrifugation method

Gold Bulletin, 2017

This work presents a new and simple procedure for the shape selective purification of gold nanoro... more This work presents a new and simple procedure for the shape selective purification of gold nanorods from a mixture of rods and spheres. Previously reported methods were time-consuming and revealed several drawbacks such as low yields and difficulty to recover the purified nanoparticles. Additionally, they were mostly applied to high aspect ratio (AR) nanorods. Our process is based on only simple and short centrifugation steps in order to precipitate specifically gold nanospheres. Samples containing low AR nanorods (AR < 6) were selected to perform the purification process. The supernatant content was followed by UV-Visible absorption spectroscopy after each centrifugation step. Then, transmission electron microscopy (TEM) allowed extract the purification efficiency thanks to shape analyses performed on more than 1000 nanoparticles. These results showed that our centrifugation process was applied successfully to three sizes of nanorods (2.4, 3.7, and 5.3). High purification yields of 72 and 78% were attained for AR = 3.7 and AR = 5.3 nanorods, respectively.

Research paper thumbnail of Folate-modified silicon carbide nanoparticles as multiphoton imaging nanoprobes for cancer-cell-specific labeling

RSC Advances, 2017

SHG-active SiC nanoparticles were modified with folic acid for cancer-cell-specific labelling.

Research paper thumbnail of Optical Polarization Properties of Wurtzite InP and InAs/InP Nanowires Grown on Silicon(111)

Research paper thumbnail of Bright single InAs quantum dots at telecom wavelengths in conical tapered InP nanowires monolithically grown on Si

Research paper thumbnail of Highly linearly polarized emission at telecom bands from single InAs/InP quantum dot-nanowires by geometry tailoring

Research paper thumbnail of Highly linear polarized emission at telecom bands in InAs/InP quantum dot-nanowires by geometry tailoring

Nanoscale, Oct 21, 2021

Nanowire (NW)-based opto-electronic devices require certain engineering in the NW geometry to rea... more Nanowire (NW)-based opto-electronic devices require certain engineering in the NW geometry to realize polarized-dependent light sources and photodetectors. We present a growth procedure to produce InAs/InP quantum dot-nanowires (QD-NWs) with an elongated top-view crosssection relying on the vapor-liquid-solid method using molecular beam epitaxy. By interrupting the rotation of the sample during the radial growth sequence of the InP shell, hexagonal asymmetric (HA) NWs with long/short cross-section axes were obtained instead of the usual symmetrical shape. Polarization-resolved photoluminescence measurements have revealed a significant influence of the asymmetric shaped NWs on the InAs QD emission polarization with the photons being mainly polarized parallel to the NW long cross-section axis. A degree of linear polarization (DLP) up to 91% is obtained, being at the state of the art for the reported DLP values from QD-NWs. More importantly, the growth protocol herein is fully compatible with the current applications of HA NWs covering a wide range of devices such as polarized light emitting diodes and photodetectors.

Research paper thumbnail of A nanowire-based telecom band single photon source monolithically grown on silicon

Research paper thumbnail of Single photon emission with a Gaussian far-field at telecom wavelength from single InAs/InP quantum dot-nanowires monolithically grown on Si

Research paper thumbnail of Optimizing the shape of InAs/InP quantum dot-nanowires grown by MBE on silicon for efficient light sources emitting in the telecom band

Research paper thumbnail of InAs/InP quantum dot-nanowire single photon sources in the telecom band grown monolithically on silicon substrates

Research paper thumbnail of Towards controlling the optical properties of InAs/InP quantum dot- nanowires using a hybrid amorphous silicon/III-V semiconductor photonic structure

Research paper thumbnail of Highly linear polarized emission at telecom bands in InAs/InP quantum dot-nanowires by geometry tailoring

Nanoscale, 2021

Nanowire (NW)-based opto-electronic devices require certain engineering in the NW geometry to rea... more Nanowire (NW)-based opto-electronic devices require certain engineering in the NW geometry to realize polarized-dependent light sources and photodetectors. We present a growth procedure to produce InAs/InP quantum dot-nanowires (QD-NWs) with...

Research paper thumbnail of Density-controlled growth of vertical InP nanowires on Si(111) substrates

Nanotechnology, 2020

A procedure to achieve the density-controlled growth of gold-catalyzed InP nanowires (NWs) on (11... more A procedure to achieve the density-controlled growth of gold-catalyzed InP nanowires (NWs) on (111) silicon substrates using the vapor-liquid-solid method by molecular beam epitaxy is reported. We develop an effective and mask-free method based on controlling the number and the size of the Au-In catalyst droplets in addition to the conditions for the NW nucleation. We show that the NW density can be tuned with values in the range of 18 µm-2 to < 0.1 µm-2 by the suitable choice of the In/Au catalyst beam equivalent pressure (BEP) ratio, by the phosphorous BEP and the growth temperature. The same degree of control is transferred to InAs/InP quantum dot-nanowires, taking advantage of the ultra-low density to study by micro-photoluminescence the optical properties of a single quantum dot-nanowires emitting in the telecom band monolithically grown on silicon. Optical spectroscopy at cryogenic temperature successfully confirmed the relevance of our method to excite single InAs quantum dots on the as-grown sample, which opens the path for large-scale applications based on single quantum dot-nanowire devices integrated on silicon.

Research paper thumbnail of Controlling the shape of a tapered nanowire: lessons from the Burton-Cabrera-Frank model

Nanotechnology, 2020

The propagation of sidewall steps during the growth of nanowires is calculated in the frame of th... more The propagation of sidewall steps during the growth of nanowires is calculated in the frame of the Burton-Cabrera-Frank model. The stable shape of the nanowire comprises a cylinder section on top of a cone section: their characteristics are obtained as a function of the radius of the catalystnanowire area, the desorption-limited diffusion length of adatoms on the terraces, and the sticking of adatoms at step edges. The comparison with experimental data allows us to evaluate these last two parameters for InP and ZnTe nanowires; it reveals a different behavior for the two materials, related to a difference by an order of magnitude of the desorption-limited diffusion length.

Research paper thumbnail of InAs quantum dot in a needlelike tapered InP nanowire: a telecom band single photon source monolithically grown on silicon

Nanoscale, 2019

Fabrication of a NW-based single photon source on silicon emitting in the telecom band with a Gau... more Fabrication of a NW-based single photon source on silicon emitting in the telecom band with a Gaussian far-field emission profile.

Research paper thumbnail of Shape-selective purification of gold nanorods with low aspect ratio using a simple centrifugation method

Gold Bulletin, 2017

This work presents a new and simple procedure for the shape selective purification of gold nanoro... more This work presents a new and simple procedure for the shape selective purification of gold nanorods from a mixture of rods and spheres. Previously reported methods were time-consuming and revealed several drawbacks such as low yields and difficulty to recover the purified nanoparticles. Additionally, they were mostly applied to high aspect ratio (AR) nanorods. Our process is based on only simple and short centrifugation steps in order to precipitate specifically gold nanospheres. Samples containing low AR nanorods (AR < 6) were selected to perform the purification process. The supernatant content was followed by UV-Visible absorption spectroscopy after each centrifugation step. Then, transmission electron microscopy (TEM) allowed extract the purification efficiency thanks to shape analyses performed on more than 1000 nanoparticles. These results showed that our centrifugation process was applied successfully to three sizes of nanorods (2.4, 3.7, and 5.3). High purification yields of 72 and 78% were attained for AR = 3.7 and AR = 5.3 nanorods, respectively.

Research paper thumbnail of Folate-modified silicon carbide nanoparticles as multiphoton imaging nanoprobes for cancer-cell-specific labeling

RSC Advances, 2017

SHG-active SiC nanoparticles were modified with folic acid for cancer-cell-specific labelling.

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