I am interested in your quartz wafers, specifically those with 0.35mm thickness, for Raman spectroscopy applications. Do you have Raman spectra available for these wafers? If so I would appreciate it if you would send those to me.
What Substrates are Used for Raman Spectroscopy?
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What is Raman Spectra?
Raman spectra are graphs that show the intensity of Raman scattering as a function of the energy or wavelength of the scattered light. They provide information about the vibrational and rotational modes of molecules in a sample, which can be used to identify and characterize chemical compounds. Raman spectra are typically obtained by illuminating a sample with a laser and measuring the inelastic scattering of photons using a spectrometer. The resulting spectrum contains peaks at specific energies or wavelengths, corresponding to the vibrational modes of the molecules in the sample. Each peak in the spectrum is associated with a specific vibrational mode, which can be used to identify the molecular structure of the sample. Raman spectra are a powerful tool for chemical analysis and are used in a wide range of applications in fields such as materials science, chemistry, biology, and medicine.
What is Raman Spectroscopy Wavelength Range?
The wavelength range used for Raman spectroscopy typically involves visible light. It spans approximately 200 to 800 nm, though this can vary depending on the specific system being examined and the laser source used.
However, the wavelength range of the observed Raman shift (which is different from the incident light wavelength) usually falls within the wavenumber range of 10 to 4000 cm-1. This range corresponds to energies associated with molecular vibrational transitions, which Raman spectroscopy is often used to study.
What is Raman Spectroscopy?
The Raman effect is a form of inelastic light scattering, resulting from vibrational excitations of a molecule
(see the figure below). When a sample is illuminated with a monochromatic laser light, some of the molecular vibrations will be scattered at frequencies different from the incident frequency, or color. These frequencies are unique to the type of molecules and types of bonds they contain, which is why a Raman spectrum can identify the molecules present in a sample.
Raman spectroscopy uses a laser to excite the vibrational modes of a sample, and a photomultiplier to detect these frequencies as light is scattered from the sample. Usually, the laser beam is focused on a specific layer of interest to avoid unwanted interference from other layers. Typical Raman spectra are recorded at a fixed wavelength, such as visible or near-infrared, although FT-Raman can use lasers with longer wavelengths for greater sensitivity.
Raman spectroscopy has numerous applications in (bio)chemistry and solid-state physics, for example analyzing crystallinity or the diameter of single or multi-walled carbon nanotubes. The technique is non-destructive and can be applied to gaseous, liquid, or solid-state samples. Raman spectroscopy is also an important tool in forensic science, for example identifying trace evidence from a crime scene. The technique can also provide useful information about the structure of a metal compound by investigating the metal-ligand bond, and it can help identify organic molecules by analyzing functional groups and their fingerprints.
How Does Raman Spectroscopy Work?
When light interacts with materials, the vast majority of photons disperse at their original frequency (called
elastic scattering). However a very small fraction of photons are scattered with a different frequency, which is called inelastic scattering or Raman scattering. C V Raman discovered this effect and won the 1930 physics Nobel Prize for it.
Inelastic Scattering of Light
The chemistry of Raman spectroscopy is based upon inelastic scattering of monochromatic light, typically from lasers in the visible, near infrared and near ultraviolet range, by vibrations and phonons in molecules. This causes a change in the energy of photons of the laser radiation that is detected by the instrument, which can be measured as a shift in wavelength. The change in energy gives information about the vibrational modes of the molecules that are detected, much like IR spectroscopy.
Unlike elastic (Rayleigh) scattering, the vibrations that cause Raman scattering are largely localized within the molecule. Consequently, the resulting scattered photons have less overall energy and are thus more sensitive to molecular vibrations. This gives a molecular fingerprint, or chemical profile, of the sample that can be used to determine its composition and structure.
A sample's Raman spectrum is often very broad with many peaks due to the fact that the vibrational modes of most molecules involve many different bonds and vibrational energies. This sensitivity makes the method ideal for analyzing samples containing many different chemicals. It also allows identification of a sample's molecular structure even when the sample is a gas.
In contrast to infrared spectroscopy, which requires molecular vibrations that are excited at lower energy levels, Raman spectroscopy can detect vibrations at higher levels. As a result, it is often possible to identify organic molecules using Raman spectroscopy, which are very difficult to identify with IR spectroscopy.
Molecular Vibrations
When a molecule absorbs light it can vibrate at a frequency that's unique to the molecule and type of bond. If this happens then some of the absorbed energy will be scattered outward at a different frequency and color from the original beam. This is called inelastic scattering or Raman effect and it was discovered by Sir C.V. Raman in 1930. The frequencies of the scattered light can tell us which molecules are present in the sample and about their structure.
To perform Raman spectroscopy the sample is illuminated with monochromatic visible radiation. The absorbed energy creates a virtual state in the electron cloud of a molecule that has the same momentum as its ground electronic state. A portion of this energy is used to excite a vibrational or rotational mode in the molecule and the remainder is emitted as a photon with reduced energy. This emitted photon is known as a Raman photon.
The vibrational modes that are detected by Raman spectroscopy are related to the changing polarizability of a molecule. For a molecule to be Raman active there must be a change in the polarizability when the molecule absorbs the radiation. A simple example is carbon dioxide. The symmetric stretch vibration is Raman active but the asymmetric bend (infrared) is not.
Photons
Raman spectroscopy is a non-destructive analytical technique based on the inelastic scattering of photons from vibrational modes (although rotational and other low frequency modes may be observed). The energy of the scattered photons is shifted, providing valuable information about molecular structure. Raman spectroscopy is named after Indian physicist C V Raman who first described the scattering phenomenon in 1928. It is commonly used in chemistry to provide a structural fingerprint by which molecules can be identified.
In a typical Raman experiment, a monochromatic laser in the visible, near infrared or even ultraviolet wavelengths is used as the excitation source. This interacts with atomic and molecular vibrations, or phonons, which cause the photons’ energy to be shifted up or down. The resulting Raman spectrum can be analyzed to give valuable information about the vibrational modes of the molecules involved, as well as other physical properties such as molecular bond lengths and vibrational frequencies.
The intensity of the Raman signal is related to the polarizability of the molecule. Molecules with a small permanent dipole moment tend to be Raman active, while those with large dipole moments do not. Hence, for a given chemical system, the vibrational features accessible by Raman spectroscopy are typically different from those accessed by IR spectroscopy.
Because of this, the sensitivity of Raman spectra is often greater than that of IR spectra. This allows for detection of vibrational features in liquids and gases that would be impossible or at least extremely difficult to observe with IR instruments.
Detectors
When light strikes a molecule, some of it is scattered away with a loss or gain of energy, resulting in vibrations that can be detected. The frequencies of the scattering light are unique to the molecule and type of bonds it contains, so the Raman spectrum provides valuable information about the chemical structure of a sample.
To collect a Raman spectrum, a monochromatic laser at a specific wavelength is used to illuminate the sample. The majority of the photons are scattered without any change in energy (Rayleigh scattering), but a small proportion lose or gain energy to molecular vibrations. These vibrations can then be detected by sensitive detectors to produce a detailed, information-rich spectral fingerprint of the sample.
Raman spectroscopy works well for samples in solid, liquid or gaseous form and can be used to answer qualitative and quantitative analytical questions. It is a powerful tool for characterizing materials and can be applied to a broad range of industrial applications.
One of the most popular applications of Raman spectroscopy is in forensics and archaeology. For example, a Raman spectrum can help identify the paints and pigments in paintings and other cultural artifacts. IRUG's comprehensive, rigorously peer-reviewed online database of spectra is available for use by researchers and conservators worldwide. In addition to its ability to determine the chemical composition of a sample, Raman spectroscopy can also detect polymorphic forms of a material, such as sintering and solidification.
How are Silicon Substrates Used With Raman Spectroscopy?
Silicon is a common substrate material in Raman spectroscopy because it is optically transparent and has a low Raman scattering cross-section, which minimizes background noise in the Raman spectra. Additionally, silicon substrates are often coated with a thin layer of silicon dioxide (SiO2), which provides a smooth and flat surface for the sample to be analyzed. The SiO2 layer also enhances the Raman signal by creating a surface-enhanced Raman scattering (SERS) effect.
What other Substrates Work Well with Raman Spectroscopy?
The choice of substrate material for Raman spectroscopy depends on the nature of the sample and the experimental conditions. Silicon is a commonly used substrate for Raman spectroscopy due to its low Raman scattering cross-section and high optical transparency. Other materials such as glass, quartz, and sapphire can also be used as substrates, depending on the specific application. The thickness and roughness of the substrate can also affect the Raman signal intensity, so it is important to choose a substrate with a suitable thickness and surface quality. In some cases, special substrates, such as those with nanostructured surfaces, can be used to enhance the Raman signal through surface-enhanced Raman scattering (SERS). Ultimately, the choice of substrate material and specifications should be optimized for the specific sample and experimental conditions to obtain the best results.
What are Raman Spectrometer Certified Reference Standard?
Raman spectrometer certified reference standards are high-quality samples that have been extensively characterized and certified for use in calibrating and validating Raman spectrometers. These standards are typically used to ensure that Raman instruments are working accurately and producing consistent results over time.
Certified reference standards for Raman spectroscopy can include a range of materials, such as inorganic compounds, organic compounds, and polymers. They are typically characterized using multiple analytical techniques, such as X-ray diffraction, infrared spectroscopy, and thermal analysis, to ensure their purity and structural integrity. The standards are then analyzed using a Raman spectrometer under controlled conditions to establish their Raman spectra and validate the performance of the instrument.
Raman spectrometer certified reference standards are important for ensuring the accuracy and reliability of Raman spectroscopy measurements, and are used in a wide range of applications, including pharmaceuticals, biomedical research, forensics, and materials science.
Raman Spectrometer Certified Reference Standard
A government researcher asked for the following:
I am looking for a raman spectrometer certified reference standard. I prefer a Si wafer. Do you have any that would suffice and are certified for QA purposes?
Refrence #225404 for specs and pricing.
What is a Raman Spectrometer?
A Raman spectrometer is an instrument that uses Raman spectroscopy to analyze the vibrational and rotational modes of molecules in a sample. It works by illuminating a sample with a laser and measuring the inelastic scattering of photons as the laser light interacts with the sample. The scattered photons are then collected and analyzed using a spectrometer to generate a Raman spectrum, which provides information about the chemical composition and molecular structure of the sample.
A Raman spectrometer typically consists of several components, including a laser source, a sample holder, a microscope or other optics for focusing the laser light onto the sample, and a spectrometer for collecting and analyzing the scattered photons. Raman spectrometers can be configured in a variety of ways, depending on the specific application and sample requirements.
Raman spectrometers are widely used in a range of fields, including materials science, chemistry, biology, and medicine, for applications such as chemical analysis, quality control, and characterization of materials. They are a powerful analytical tool that can provide detailed information about the chemical and structural properties of a wide range of materials.