Enhanced photothermal conversion in vertically oriented gallium arsenide nanowire arrays

Area of Science:

• Materials Science
• Nanotechnology
• Optics

Background:

• Vertically etched gallium arsenide (GaAs) nanowire arrays are investigated for their photothermal properties.
• Understanding these properties is crucial for applications requiring localized heating and light absorption.

Purpose of the Study:

• To examine the photothermal behavior of GaAs nanowire arrays with varying diameters.
• To determine the influence of nanowire diameter and photonic lattice structure on light absorption and temperature distribution.
• To explore the potential for optimizing photothermal conversion efficiency through structural and wavelength tuning.

Main Methods:

• Utilized Raman spectroscopy to measure nanowire temperatures.
• Analyzed spectral red-shift of TO and LO phonons to determine temperature.
• Employed a 532 nm laser with a specific energy density for illumination.
• Conducted computer simulations to validate experimental findings and explore wavelength dependence.

Main Results:

• Nanowire temperature showed a strong dependence on diameter, peaking at 95 nm.
• Temperatures reached up to 600 K (top facets) and 440 K (sidewalls) for 95 nm nanowires.
• Heating decreased for diameters smaller or larger than 95 nm.
• Resonant coupling of laser light into optical modes explained the diameter-dependent heating and increased absorption.

Conclusions:

• Photonic lattice structures significantly enhance and tune the photothermal properties of GaAs nanowires.
• Smaller nanowire diameters do not necessarily yield more efficient photothermal conversion.
• Optimized photothermal conversion can be achieved through careful selection of nanowire diameter and laser wavelength.
• The diameter and wavelength dependence allows for the creation of localized temperature gradients using arrays with varying diameters.