Multimode scanning near-field photoluminescence spectroscopy and its application for studies of InGaN epitaxial layers and quantum wells

The paper reviews our recent achievements in developing a multimode scanning near-field optical microscopy (SNOM) technique. The multimode SNOM apparatus allows us to simultaneously measure spatial variations of photoluminescence spectra in the illumination and illumination-collection modes, their transients and sample surface morphology. The potential of this technique has been demonstrated on a polar InGaN epitaxial layer and nonpolar InGaN/GaN quantum wells. SNOM measurements have allowed revealing a number of phenomena, such as the band potential fluctuations and their correlation to the surface morphology, spatial nonuniformity of the radiative and nonradiative lifetimes, as well as the extended band nature of localized states. The combination of different modes enabled measurements of the ambipolar carrier diffusion and its anisotropy.

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Development of a Combined Scanning Ion-Conductance and Nearfield Optical Microscope to Image Living Cells

Microscopy and Microanalysis ◽

10.1017/s1431927600018201 ◽

1999 ◽

Vol 5 (S2) ◽

pp. 976-977

Author(s):

M. Raval ◽

D. Klenerman ◽

T. Rayment ◽

Y. Korchev ◽

M. Lab

Keyword(s):

Optical Microscopy ◽

Biological Samples ◽

Near Field ◽

Sample Surface ◽

Optical Microscope ◽

Ion Conductance ◽

Simultaneous Generation ◽

Simple Arrangement ◽

Wavelength Resolution ◽

Sub Wavelength

It is important to be able to image biological samples in a manner that is non-invasive and allows the sample to retain its functionality during imaging.A member of the SPM (scanning probe microscopy) family, SNOM (scanning near-field optical microscopy), has emerged as a technique that allows optical and topographic imaging of biological samples whilst satisfying the above stated criteria. The basic operating principle of SNOM is as follows. Light is coupled down a fibre-optic probe with an output aperture of sub-wavelength dimensions. The probe is then scanned over the sample surface from a distance that is approximately equal to the size of its aperture. By this apparently simple arrangement, the diffraction limit posed by conventional optical microscopy is overcome and simultaneous generation of optical and topographic images of sub-wavelength resolution is made possible. Spatial resolution values of lOOnm in air and 60nm in liquid[1,2] are achievable with SNOM.

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Characterization of the self-assembled InP structure grown on the GaInP epitaxial layer mismatched to GaAs substrate by near-field scanning optical microscopy (NSOM)

10.1117/12.532752 ◽

2004 ◽

Author(s):

Hao Wang ◽

Changjun Liao ◽

Guanghan Fan ◽

Song-Hao Liu ◽

Yangzhe Wu ◽

...

Keyword(s):

Optical Microscopy ◽

Epitaxial Layer ◽

Gaas Substrate ◽

Near Field ◽

The Self ◽

Self Assembled ◽

Scanning Optical Microscopy ◽

Near Field Scanning

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Nanoscale Characterization of Surface Plasmon-Coupled Photoluminescence Enhancement in Pseudo Micro Blue LEDs Using Near-Field Scanning Optical Microscopy

Nanomaterials ◽

10.3390/nano10040751 ◽

2020 ◽

Vol 10 (4) ◽

pp. 751

Author(s):

Yufeng Li ◽

Aixing Li ◽

Ye Zhang ◽

Peng Hu ◽

Wei Du ◽

...

Keyword(s):

Quantum Wells ◽

Optical Microscopy ◽

Surface Plasmon ◽

Plasmon Resonance ◽

Near Field ◽

Excitation Power ◽

Localized Surface Plasmon ◽

Excitation Density ◽

Multiple Quantum ◽

Excitation Power Density

The microcave array with extreme large aspect ratio was fabricated on the p-GaN capping layer followed by Ag nanoparticles preparation. The coupling distance between the dual-wavelength InGaN/GaN multiple quantum wells and the localized surface plasmon resonance was carefully characterized in nanometer scale by scanning near-field optical microscopy. The effects of coupling distance and excitation power on the enhancement of photoluminescence were investigated. The penetration depth was measured in the range of 39–55 nm depending on the excitation density. At low excitation power density, the maximum enhancement of 103 was achieved at the optimum coupling distance of 25 nm. Time-resolved photoluminescence shows that the recombination life time was shortened from 5.86 to 1.47 ns by the introduction of Ag nanoparticle plasmon resonance.

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Tapping Mode Near-Field Scanning Optical Microscopy of Molecular Crystals and Thin Films

Microscopy and Microanalysis ◽

10.1017/s1431927600018298 ◽

1999 ◽

Vol 5 (S2) ◽

pp. 994-995

Author(s):

C. Daniel Frisbie ◽

Andrey Kosterin ◽

Helena Stadniychuk

Keyword(s):

Optical Microscopy ◽

Spatial Resolution ◽

Laser Light ◽

Near Field ◽

Sample Surface ◽

Reflected Light ◽

Surface Laser ◽

Scanning Optical Microscopy ◽

Diffraction Effects ◽

Near Field Scanning

The diffraction of visible light limits the spatial resolution in conventional optical microscopy to about 200-300 nm. In near-field scanning optical microscopy (NSOM), resolution is improved by bringing the light source, such as the end of an optical fiber, very close to the sample surface. Laser light coupled into the opposite end of the fiber propagates down the fiber core and is emitted from the aperture of the tip. When the sample is in the near-field(roughly within one tip diameter of the end of the tip), the spatial resolution is essentially equal to the diameter of the aperture at the end of the tip and is not determined by diffraction effects. Two-dimensional imaging is accomplished by raster-scanning the sample underneath the fiber tip and collecting transmitted or reflected light at a photodetector.

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Nanoscale Characterization of V-defect in InGaN/GaN QWs LEDs using Near-Field Scanning Optical Microscopy

Nanomaterials ◽

10.3390/nano9040633 ◽

2019 ◽

Vol 9 (4) ◽

pp. 633 ◽

Cited By ~ 3

Author(s):

Li ◽

Tang ◽

Zhang ◽

Guo ◽

Li ◽

...

Keyword(s):

Quantum Wells ◽

Optical Microscopy ◽

Quantum Efficiency ◽

External Quantum Efficiency ◽

Near Field ◽

Light Output ◽

Current Injection ◽

Light Output Power ◽

Scanning Optical Microscopy ◽

Near Field Scanning

The size of the V-defects in the GaN/InGaN-based quantum wells blue light-emitting diode (LED) was intentionally modified from 50 nm to 300 nm. High resolution photoluminescence and electroluminescence of a single large V-defect were investigated by near-field scanning optical microscopy. The current distribution along the {10-11} facets of the large defect was measured by conductive atomic force microscopy. Nearly 20 times the current injection and dominant emission from bottom quantum wells were found in the V-defect compared to its vicinity. Such enhanced current injection into the bottom part of quantum wells through V-defect results in higher light output power. Reduced external quantum efficiency droops were achieved due to more uniform carrier distribution. The un-encapsulated fabricated chip shows light output power of 172.5 mW and 201.7 mW at 400 mA, and external quantum efficiency drop of 22.3% and 15.4% for the sample without and with large V-defects, respectively. Modified V-defects provide a simple and eﬀective approach to suppress the efficiency droop problem that occurs at high current injection, while improving overall quantum efficiency.

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