Photoluminescence (PL)¶
Photoluminescence spectroscopy measures light emission from materials upon optical excitation. PL is essential for characterizing optical and electronic properties of semiconductors, quantum dots, and luminescent materials.
Overview¶
This schema package defines:
- DTUPLMeasurement - PL measurements with excitation conditions, emission spectra, and optical properties
PL measurements extend BaseMeasurement, providing:
- Links to measured samples and instrument
- Excitation source parameters (wavelength, power, spot size)
- Detection configuration (spectrometer, detector, filters)
- Emission spectra and peak analysis
- Temperature-dependent measurements
Typical Usage¶
- Select samples: Reference samples to characterize
- Set excitation: Laser wavelength, power, spot size, beam profile
- Configure detection: Spectrometer grating, detector, integration time
- Measure spectrum: Collect emission intensity vs. wavelength
- Analysis: Identify peaks, calculate bandgap, extract quantum efficiency
- Temperature dependence (optional): PL at multiple temperatures
Position-Based Mapping
PL measurements are inherently position-aware, mapping optical properties to specific coordinates. Each measured position corresponds to a sample position entry on combinatorial libraries, enabling composition-property correlations across gradient libraries. Multiple positions can be measured and their data aggregated to create property maps.
What PL Tells You¶
- Bandgap energy: Emission peak position relates to bandgap
- Optical quality: Intensity indicates radiative efficiency
- Defect states: Sub-bandgap peaks show trap states
- Strain: Peak shifts indicate strain state
- Composition: For alloys, bandgap tracks composition
- Quantum efficiency: Relative emission intensity
Common PL Features¶
- Band edge emission: Main peak near bandgap energy
- Exciton peaks: Sharp features at low temperature
- Defect emission: Broad, lower-energy peaks
- Donor-acceptor pairs: Characteristic peak shapes and shifts
- Temperature dependence: Peak shifts and intensity changes
Key Parameters¶
- Excitation wavelength: Must be above bandgap (shorter wavelength than emission)
- Excitation power: Linear regime vs. high-injection effects
- Spot size: Spatial resolution vs. signal
- Temperature: Room temp, cryogenic for high-resolution
- Time resolution: Steady-state vs. time-resolved PL
PL for Materials Screening¶
- Spatially-resolved PL: Map emission across composition gradient
- Quick screening: Fast, non-destructive, identifies promising compositions
- Composition-bandgap trends: Guide further investigation
- Compare to targets: Verify expected optical properties
Related Schemas¶
- Measured samples: Samples from Sputtering, RTP
- Instrument: DTUInstrument (PL system with laser and spectrometer)
- Complementary: XRD for structure, Ellipsometry for optical constants
- Analysis: Jupyter Analysis for peak fitting, bandgap extraction
Schema Documentation¶
PLMappingResult¶
inherits from: nomad_measurements.mapping.schema.MappingResult, nomad.datamodel.metainfo.plot.PlotSection
properties:
| name | type | |
|---|---|---|
| position | str |
The position of the PL spectrum |
| peak_lambda | float64 |
Peak wavelength of the PL spectrum unit= meter |
| peak_intensity | float64 |
Peak intensity of the PL spectrum unit= volt |
| signal_intensity | float64 |
Signal intensity of the PL spectrum |
| peak_fwhm | float64 |
Peak full width at half maximum of the PL spectrum unit= meter |
normalization:
The normalizer for the PLMappingResult class.
Args: archive (EntryArchive): The archive containing the section that is being normalized. logger (BoundLogger): A structlog logger.
PLMetadata¶
inherits from: nomad.datamodel.data.ArchiveSection
properties:
| name | type | |
|---|---|---|
| thickness | float64 |
The thickness the machine assumes for the sample unit= meter |
| wafer_diameter | float64 |
The diameter of the wafer unit= meter |
| scan_diameter | float64 |
The diameter of the scan unit= meter |
| resolution | float64 |
The resolution of the scan unit= meter |
| scan_rate | float64 |
The rate of the scan. The unit is points per second (pts/s) and therefore only right as long as the resolution is 1mm unit= meter / second |
| used_laser | float64 |
The wavelength of the laser used unit= meter |
| used_power | float64 |
The power of the laser used unit= watt |
| used_filter | str |
The filter used for the measurement |
| gain_factor | float64 |
The gain factor used for the measurement, it is unitless and scales the signal intensity |
| temperature | float64 |
The temperature during the measurement unit= kelvin |
| center_wafelength | float64 |
The center wavelength of the measurement unit= meter |
| wavelength_range | float64 |
The range of the wavelength shape= [2], unit=meter |
| slit_width | float64 |
The slit width used for the measurement unit= meter |
| gratings | float64 |
The gratings used for the measurement unit= gram / meter |
| detector | str |
The detector used for the measurement |
normalization:
The normalizer for the PLMetadata class.
Args: archive (EntryArchive): The archive containing the section that is being normalized. logger (BoundLogger): A structlog logger.
DTUPLMeasurement¶
inherits from: nomad_dtu_nanolab_plugin.schema_packages.basesections.DtuNanolabMeasurement, nomad.datamodel.metainfo.plot.PlotSection, nomad.datamodel.data.EntryData
properties:
| name | type | |
|---|---|---|
| pl_data_file | str |
|
| pl_overview_file | str |
|
| metadata | PLMetadata |
The metadata of the PL measurement sub-section |
| results | PLMappingResult |
The PL results. sub-section, repeats |
normalization:
The normalize function of the DTUXRDMeasurement section.
Args: archive (EntryArchive): The archive containing the section that is being normalized. logger (BoundLogger): A structlog logger.