Substrates Used with Photoelectron Spectroscopy

university wafer substrates

Wafers Used for X-ray Photoelectron Spectroscopy

A mechanical engineering PhD student requested a quote for the following.

I would like to purchase some silicon wafers from you.
I don"t have special request because of the application of these silicon wafers. They will be used as sample substrates for Scanning electron microscope and X-ray photoelectron spectroscopy. I think your inexpensive silicon wafers may fit my requirement: ULTRA-PURE AND ULTRA-CLEAN. But the diameter should be 1" silicon wafer. Can you send me a quote? And please let me know if you have any suggestion.

Reference #198208 for specs and pricing.

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How are Substrates used with Photoelectron?

Substrates play an important role in experiments and applications involving photoelectrons, especially in photoelectron spectroscopy techniques like X-ray Photoelectron Spectroscopy (XPS) and Ultraviolet Photoelectron Spectroscopy (UPS). Here’s how substrates are used with photoelectrons:

  1. Supporting Thin Films or Coatings: Substrates serve as a stable base for thin films or coatings under study. These films may be the actual material generating photoelectrons when exposed to photons. For example, thin metallic or semiconductor films are often deposited on substrates like silicon or glass, allowing the properties of the film to be studied without interference from the substrate material.

  2. Minimizing Background Interference: In photoelectron spectroscopy, substrates are chosen to minimize interference in the photoelectron signal. For example, insulating or low-electron-yield substrates may be selected to reduce background noise and ensure a cleaner signal from the material of interest. Conductive substrates, like gold or silicon wafers, are also used to prevent charge buildup when studying non-conductive samples, which can distort measurements.

  3. Providing Mechanical and Thermal Stability: Substrates support samples and help maintain them in a stable position during measurements, especially in high-vacuum environments required for techniques like XPS. They also offer thermal stability, as photoelectron spectroscopy may involve thermal processes that could otherwise deform or damage sensitive samples.

  4. Enhancing Contrast and Signal Quality: Thick oxide layers on substrates, for example, can create high-contrast conditions under an optical microscope, which is helpful for positioning samples and assessing uniformity before and after analysis. In the case of using substrates with well-defined surface characteristics (like flatness or oxide thickness), they can aid in aligning and focusing the photoelectron source precisely.

  5. Enabling Specialized Studies with Surface-Sensitive Layers: For certain advanced experiments, substrates are chosen with specific properties that interact with the material under study, like specific crystal orientations or work functions. By carefully choosing a substrate’s material and properties, researchers can study interactions at interfaces, work functions, or catalytic behaviors in ways that wouldn’t be possible with a less controlled surface.

In short, substrates provide the necessary physical, chemical, and electronic foundation to enable precise and reproducible measurements of materials’ photoelectron properties.

 

What Is A Photoelectron?

A photoelectron is an electron that is ejected from an atom, molecule, or solid material when it absorbs energy from light (or more generally, electromagnetic radiation). This process is known as the photoelectric effect. When photons of sufficient energy hit a material, they can transfer their energy to electrons, which may then overcome the binding forces holding them in place and be emitted from the material.

The key points about photoelectrons include:

  1. Origin: Photoelectrons originate from the surface of a material, typically metals, although they can also come from non-metallic materials when exposed to high-energy photons (e.g., X-rays or ultraviolet light).

  2. Energy Dependence: The energy of a photoelectron depends on the energy of the incoming photon and the binding energy of the electron in the material. According to Einstein's photoelectric equation:

  3. Ephoton = Ebinding + Ekinetic of electron

  4. where is the energy needed to free the electron, and is the kinetic energy of the ejected photoelectron.

  5. Applications: Photoelectrons are fundamental to photoelectron spectroscopy (e.g., XPS, UPS), where they help reveal information about the electronic structure and chemical composition of materials. This is used in physics, chemistry, and material science.

  6. Dependence on Photon Energy: Only photons with energy equal to or greater than the material's work function (the minimum energy needed to eject an electron from a material) can produce photoelectrons.

Photoelectrons are a key concept in understanding quantum mechanics and solid-state physics, a

What Is Angle-Resolved Photoelectron Spectroscopy (ARPES)?

Angle-Resolved Photoelectron Spectroscopy (ARPES) is an advanced experimental technique used to investigate the electronic structure of materials. By measuring the energy and momentum of electrons ejected from a material when it is exposed to a beam of light (often ultraviolet or x-ray photons), ARPES provides detailed information about the energy levels and distribution of electrons within the material. This makes it particularly valuable for studying the electronic properties of complex materials like superconductors, topological insulators, and semiconductors.

Here's a breakdown of how ARPES works and what it reveals:

  1. Photon Excitation: A photon beam with known energy strikes the surface of the material, causing electrons within the material to be excited and ejected.

  2. Measurement of Ejected Electrons: These ejected electrons are collected by a detector that measures both their kinetic energy and the angle at which they leave the surface.

  3. Energy and Momentum Information: By analyzing the energy and angle, researchers can back-calculate the binding energy and momentum of electrons within the material. This gives insight into the material's band structure (the range of allowed energies for electrons in the material).

  4. Electronic Structure Mapping: The resulting data helps researchers create a "map" of the electronic structure, showing details like energy bands, Fermi surfaces, and other electronic states. This information is critical for understanding electrical conductivity, electron mobility, and other electronic properties.

ARPES is highly surface-sensitive, meaning it mainly provides information about the outermost atomic layers. Its insights are crucial in fields like condensed matter physics, where understanding surface and near-surface electronic states is key.

Silicon Wafers Used For Electronic Band Structure Studies

A postdoct requested a quote for the following.

We need a quote for 25 Silicon Wafer item #1318. Please offer size and weight for calculate freight cost:

76.2mm P B <100> 0.001-0.005 ohm-cm 380um SSP Prime

The subtrates will be used as conductive substrates for molybdenum or tungsten disulfide nanopatterned thin-films for the electronic band structure studies using Angle-Resolved Photoelectron Spectroscopy (ARPES)

Reference #316645 for specs and pricing.