研究目的
To create and characterize highly efficient photosensors using nanostructured silicon on reduced graphene oxide with high photoresponsivity at room temperature.
研究成果
The research successfully demonstrates the fabrication of rGO-Si photosensors with high photoresponsivity (3.55 A/W) at room temperature using a non-equilibrium PLA technique. Key findings include the formation of direct band gap Si nanostructures, high-quality rGO with minimal defects, Ohmic junctions enabling non-rectifying behavior, and efficient ballistic charge transport. The devices show potential for applications in optoelectronics and opto-spintronics due to their negative magnetoresistance. Future work should focus on improving response times and exploring integration into multifunctional devices.
研究不足
The response and decay times (1.65 s and 2.07 s) are slower than some Schottky-based devices due to the Ohmic nature requiring external bias for carrier separation. The process relies on specific laser parameters and substrate thermal conductivity, limiting scalability or application on other substrates like Si wafers. The study is conducted at room temperature and specific light intensities, and further optimization may be needed for broader operational conditions.
1：Experimental Design and Method Selection:
The study uses a non-equilibrium processing route involving pulsed laser annealing (PLA) with nanosecond excimer laser pulses to melt alternating layers of Si and amorphous carbon, forming Si micropillars and nanoreceptors on rGO layers. This method is chosen for its ability to create direct band gap Si and high-quality rGO without chemical reducing agents.
2：Sample Selection and Data Sources:
Alternating layers of Si and amorphous carbon (total thickness 500 nm) are deposited on c-sapphire substrates using pulsed laser deposition (PLD). The samples are characterized before and after PLA.
3：List of Experimental Equipment and Materials:
Equipment includes KrF excimer laser for PLD (wavelength 248 nm, pulse duration 25 ns, energy density 3.0-3.5 J/cm2), ArF excimer laser for PLA (wavelength 193 nm, pulse duration 20 ns, energy density 0.6 J/cm2), Alpha300 R confocal Raman imaging instrument with 532 nm laser, FEI Verios 460L SEM for high-resolution SEM and EDX, TOF-SIMS, XPS with PHOIBOS 150 analyzer, EBSD HKL Nordlys detector in FEI Quanta 3D FEG microscope, PPMS for temperature and magnetic field-dependent resistance measurements, Keithley 2000 digital multimeter and 2400 sourcemeter for photosensing, and halogen bulb light source. Materials include amorphous carbon, silicon, c-sapphire substrates.
4：0-5 J/cm2), ArF excimer laser for PLA (wavelength 193 nm, pulse duration 20 ns, energy density 6 J/cm2), Alpha300 R confocal Raman imaging instrument with 532 nm laser, FEI Verios 460L SEM for high-resolution SEM and EDX, TOF-SIMS, XPS with PHOIBOS 150 analyzer, EBSD HKL Nordlys detector in FEI Quanta 3D FEG microscope, PPMS for temperature and magnetic field-dependent resistance measurements, Keithley 2000 digital multimeter and 2400 sourcemeter for photosensing, and halogen bulb light source. Materials include amorphous carbon, silicon, c-sapphire substrates. Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The procedure involves depositing Si and amorphous carbon layers on c-sapphire via PLD, irradiating with a single ArF laser pulse in air for PLA to form rGO-Si structures, followed by characterization using Raman spectroscopy, XPS, PL spectroscopy, SEM, EDX, EBSD, resistance vs. time measurements under white light illumination, and temperature-dependent resistance and magnetoresistance measurements.
5：Data Analysis Methods:
Data analysis includes Raman peak fitting for sp2 carbon percentage and stress calculation, XPS deconvolution for bonding states and C/O ratio, PL analysis for band gap determination, exponential fitting for response and decay times, ES-VRH and Arrhenius models for electrical conduction analysis, and magnetoresistance calculation.
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FEI Verios 460L SEM
Verios 460L
FEI
Used for high-resolution SEM and EDX measurements.
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Keithley 2000 digital multimeter
2000
Keithley
Used for electrical measurements in photosensing.
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Keithley 2400 sourcemeter
2400
Keithley
Used as a source meter for electrical measurements.
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KrF excimer laser
Used for pulsed laser deposition of Si and amorphous carbon layers.
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ArF excimer laser
Used for pulsed laser annealing to form rGO-Si structures.
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Alpha300 R confocal Raman imaging instrument
Alpha300 R
Used for Raman spectroscopy measurements.
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TOF-SIMS
Used for depth profiling of elements.
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XPS analyzer
PHOIBOS 150
Used for X-ray photoelectron spectroscopy.
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EBSD HKL Nordlys detector
HKL Nordlys
Used for electron backscatter diffraction in FEI Quanta 3D FEG microscope.
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PPMS
Used for temperature and magnetic field-dependent resistance measurements.
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Halogen bulb
Used as a white light source for photosensing measurements.
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