There is no single, direct method to measure the Density of States (DOS) of double perovskite alloys experimentally. However, DOS can be inferred or calculated using a combination of experimental techniques and theoretical simulations. The density of states is a key property in understanding the electronic structure, and it requires sophisticated methods to probe. Here’s how it is typically done:

1. Experimental Techniques:

a) Photoemission Spectroscopy (PES):

• X-ray Photoelectron Spectroscopy (XPS): Measures the electronic structure by analyzing the kinetic energy of electrons emitted from a sample upon exposure to X-rays. XPS can give insights into the occupied electronic states, particularly the valence band structure.
• Ultraviolet Photoelectron Spectroscopy (UPS): Similar to XPS but uses UV light and is more sensitive to valence states.

These techniques provide information about the occupied states in the material, allowing an indirect measurement of the DOS near the Fermi level.

b) Inverse Photoemission Spectroscopy (IPES):

• This technique complements PES by providing information about the unoccupied states above the Fermi level. Together with PES, a complete DOS profile (both occupied and unoccupied states) can be constructed.

c) Scanning Tunneling Spectroscopy (STS):

• STS measures the local density of states (LDOS) by probing the tunneling current between a metallic tip and the sample surface. It is highly sensitive to surface states and can give spatially resolved information about DOS at the atomic scale. However, it mainly focuses on the surface electronic states, which may differ from bulk DOS.

d) Electron Energy Loss Spectroscopy (EELS):

• EELS, used in conjunction with transmission electron microscopy (TEM), can probe the unoccupied electronic states by analyzing the energy loss of electrons as they pass through the sample. This technique provides information about the conduction band and gives insight into the unoccupied states.

e) Optical Absorption and Reflectivity Measurements:

• These techniques can provide indirect information about the DOS, especially near the band edges, by studying how the material interacts with light. Absorption spectroscopy can reveal the nature of band gaps and excitonic states.

2. Theoretical Simulations:

In practice, experimental methods are often supplemented with Density Functional Theory (DFT) calculations to predict and calculate the DOS. DFT can be used to model the electronic structure of double perovskite alloys and generate theoretical DOS curves that can be compared with experimental data.

• DFT is particularly effective for complex materials like double perovskites, which may have multiple atoms per unit cell, different atomic occupancies, and varying orbital contributions (e.g., transition metals and oxygen anions). Theoretical DOS from DFT calculations provides the complete profile (both occupied and unoccupied states) and can be compared with PES, IPES, and STS data to validate the results.