eXSpy Metadata Structure#

eXSpy extends the HyperSpy metadata structure with conventions for metadata specific to its signal types. Refer to the HyperSpy metadata documentation for general metadata fields.

The metadata of any signal objects is stored in the metadata attribute, which has a tree structure. By convention, the node labels are capitalized and the ones for leaves are not capitalized. When a leaf contains a quantity that is not dimensionless, the units can be given in an extra leaf with the same label followed by the _units suffix.

Besides directly accessing the metadata tree structure, e.g. s.metadata.Signal.signal_type, the HyperSpy methods hyperspy.misc.utils.DictionaryTreeBrowser.set_item(), hyperspy.misc.utils.DictionaryTreeBrowser.has_item() and hyperspy.misc.utils.DictionaryTreeBrowser.get_item() can be used to add to, search for and read from items in the metadata tree, respectively.

The EELS of EDS specific metadata structure is represented in the following tree diagram. The default units are given in parentheses. Details about the leaves can be found in the following sections of this chapter. Note that not all types of leaves will apply to every type of measurement.

metadata
├── General
│   └── # see HyperSpy
├── Sample
│   ├── # see HyperSpy
│   ├── elements
│   └── xray_lines
├── Signal
│   ├── signal_type
│   └── # otherwise see HyperSpy
└── Acquisition_instrument
    ├── SEM
    │   ├── Detector
    │   │   ├── detector_type
    │   │   └── EDS
    │   │       ├── azimuth_angle (º)
    │   │       ├── elevation_angle (º)
    │   │       ├── energy_resolution_MnKa (eV)
    │   │       ├── live_time (s)
    │   │       └── real_time (s)
    │   ├── beam_current (nA)
    │   ├── beam_energy (keV)
    │   ├── probe_area (nm²)
    │   ├── convergence_angle (mrad)
    │   ├── magnification
    │   ├── microscope
    │   ├── Stage
    │   │   ├── rotation (º)
    │   │   ├── tilt_alpha (º)
    │   │   ├── tilt_beta (º)
    │   │   ├── x (mm)
    │   │   ├── y (mm)
    │   │   └── z (mm)
    │   └── working_distance (mm)
    └── TEM
        ├── Detector
        │   ├── EDS
        │   │   ├── azimuth_angle (º)
        │   │   ├── elevation_angle (º)
        │   │   ├── energy_resolution_MnKa (eV)
        │   │   ├── live_time (s)
        │   │   └── real_time (s)
        │   └── EELS
        │       ├── aperture (mm)
        │       ├── collection_angle (mrad)
        │       ├── dwell_time (s)
        │       ├── exposure (s)
        │       ├── frame_number
        │       └── spectrometer
        ├── acquisition_mode
        ├── beam_current (nA)
        ├── beam_energy (keV)
        ├── probe_area (nm²)
        ├── camera_length (mm)
        ├── convergence_angle (mrad)
        ├── magnification
        ├── microscope
        └── Stage
            ├── rotation (º)
            ├── tilt_alpha (º)
            ├── tilt_beta (º)
            ├── x (mm)
            ├── y (mm)
            └── z (mm)

General#

See HyperSpy-Metadata-General.

Sample#

elements

type: list

A list of the symbols of the elements composing the sample, e.g. [‘B’, ‘N’] for a sample composed of Boron and Nitrogen.

xray_lines

type: list

A list of the symbols of the X-ray lines to be used for processing, e.g. [‘Al_Ka’, ‘Ni_Lb’] for the K alpha line of Aluminum and the L beta line of Nickel.

Signal#

signal_type

type: string

String that describes the type of signal. Currently, the only eXSpy specific signal class is EELS, EDS, EDS_SEM or EDS_TEM.

Acquisition_instrument#

TEM#

Contain information relevant to transmission electron microscope signals.

microscope

type: Str

The microscope model, e.g. VG 501

acquisition_mode

type: Str

Either ‘TEM’ or ‘STEM’

camera_length

type: Float

The camera length in mm.

convergence_angle

type: Float

The beam convergence semi-angle in mrad.

beam_energy

type: Float

The energy of the electron beam in keV

beam_current

type: Float

The beam current in nA.

probe_area

type: Float

The illumination area of the electron beam in nm².

dwell_time

type: Float

The dwell time in seconds. This is relevant for STEM acquisition

exposure

type: Float

The exposure time in seconds. This is relevant for TEM acquisition.

magnification

type: Float

The magnification.

SEM#

Contain information relevant to scanning electron microscope signals.

microscope

type: Str

The microscope model, e.g. VG 501

convergence_angle

type: Float

The beam convergence semi-angle in mrad.

beam_energy

type: Float

The energy of the electron beam in keV

beam_current

type: Float

The beam current in nA.

probe_area

type: Float

The illumination area of the electron beam in nm².

magnification

type: Float

The magnification.

working_distance

type: Float

The working distance in mm.

Stage#

tilt_alpha

type: Float

A tilt of the stage in degree.

tilt_beta

type: Float

Another tilt of the stage in degree.

rotation

type: Float

The rotation of the stage in degree.

x

type: Float

The position of the stage in mm along the x axis.

y

type: Float

The position of the stage in mm along the y axis.

z

type: Float

The position of the stage in mm along the z axis.

Detector#

All instruments can contain a “Detector” node with information about the detector used to acquire the signal. EDX and EELS detectors should follow the following structure:

detector_type

type: Str

The type of the detector, e.g. SE for SEM

EELS#

This node stores parameters relevant to electron energy loss spectroscopy signals.

aperture_size

type: Float

The entrance aperture size of the spectrometer in mm.

collection_angle

type: Float

The collection semi-angle in mrad.

dwell_time

type: Float

The dwell time in seconds. This is relevant for STEM acquisition

exposure

type: Float

The exposure time in seconds. This is relevant for TEM acquisition.

frame_number

type: int

The number of frames/spectra integrated during the acquisition.

spectrometer

type: Str

The spectrometer model, e.g. Gatan Enfinium ER (Model 977).

EDS#

This node stores parameters relevant to electron X-ray energy dispersive spectroscopy data.

azimuth_angle

type: Float

The azimuth angle of the detector in degree. If the azimuth is zero, the detector is perpendicular to the tilt axis.

elevation_angle

type: Float

The elevation angle of the detector in degree. The detector is perpendicular to the surface with an angle of 90.

energy_resolution_MnKa

type: Float

The full width at half maximum (FWHM) of the manganese K alpha (Mn Ka) peak in eV. This value is used as a first approximation of the energy resolution of the detector.

real_time

type: Float

The time spent to record the spectrum in second.

live_time

type: Float

The time spent to record the spectrum in second, compensated for the dead time of the detector.