RMMF XPS Online Quiz

1. What possible methods could be used to improve the signal/noise ratio of your XPS spectrum?

Take more scans

Increase scan dwell time

Increase the pass energy

Increase the spot size

All of the above

To improve the signal/noise ratio of the XPS spectrum, multiple methods can be used. Taking more scans increases the amount of data collected, which can help to enhance the signal and reduce the noise. Increasing the scan dwell time allows for a longer integration time, resulting in a stronger signal. Increasing the pass energy can improve the resolution of the spectrum, making it easier to distinguish between the signal and noise. Lastly, increasing the spot size can provide a larger area for data collection, increasing the overall signal strength. Therefore, all of the mentioned methods can be used to improve the signal/noise ratio of the XPS spectrum.

Explanation

To improve the signal/noise ratio of the XPS spectrum, multiple methods can be used. Taking more scans increases the amount of data collected, which can help to enhance the signal and reduce the noise. Increasing the scan dwell time allows for a longer integration time, resulting in a stronger signal. Increasing the pass energy can improve the resolution of the spectrum, making it easier to distinguish between the signal and noise. Lastly, increasing the spot size can provide a larger area for data collection, increasing the overall signal strength. Therefore, all of the mentioned methods can be used to improve the signal/noise ratio of the XPS spectrum.

2. XPS is achieved by firing an X-ray beam at a sample, and then measuring the kinetic energy of the emitted electrons. How deep are these measured electrons coming from?

1 - 20 nm

1 - 20 microns

1 - 20 angstroms

1 - 20 mm

Though the X-rays penetrate quite deep, it is the near surface electrons which have enough kinetic energy to get to the detector which are analysed in XPS.

Explanation

Though the X-rays penetrate quite deep, it is the near surface electrons which have enough kinetic energy to get to the detector which are analysed in XPS.

3. After excitation from the x-rays, photoemission occurs, ejecting electrons from the sample with a variety of energies (forming an XPS spectrum). What energy of the electrons is being directly measured by the spectrometer?

Kinetic energy

Binding energy

Thermal energy

The spectrometer directly measures the kinetic energy of the electrons that are ejected from the sample after being excited by x-rays. This is because the kinetic energy of the electrons is directly related to their velocity and can be measured by analyzing their motion in the spectrometer. Binding energy refers to the energy required to remove an electron from an atom, while thermal energy is the energy associated with the random motion of particles in a sample.

Explanation

The spectrometer directly measures the kinetic energy of the electrons that are ejected from the sample after being excited by x-rays. This is because the kinetic energy of the electrons is directly related to their velocity and can be measured by analyzing their motion in the spectrometer. Binding energy refers to the energy required to remove an electron from an atom, while thermal energy is the energy associated with the random motion of particles in a sample.

4. Most samples that have been exposed to the atmosphere will have a detectable quantity of adventitious carbon contamination. (Typically with a layer thickness of 1-2 nm). What is the binding energy of the C1s peak for this adventitious carbon?

284.8 eV

285 keV

292 eV

1220 eV

Visit https://xpssimplified.com/ for binding energies of subshell electrons.

Explanation

Visit https://xpssimplified.com/ for binding energies of subshell electrons.

5. A well resolved Si2p spectrum of pure silicon has two peaks. Why is this?

Each peak represents a chemical state, and it has two chemical states

Each peak represents an electron with a different angular momentum from the 2p subshell.

There is overlap with the adventitious carbon peak which is present with ALL samples.

The sample drifted during analysis

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Explanation

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6. XPS is a good technique for measuring the atomic concentration of a bulk sample

True

False

XPS, or X-ray photoelectron spectroscopy, is not a suitable technique for measuring the atomic concentration of a bulk sample. XPS is primarily used to analyze the surface composition and chemical state of materials. It provides information about the elements present on the surface and their chemical bonding, but it does not provide quantitative measurements of atomic concentration throughout the bulk of a sample. Other techniques, such as Auger electron spectroscopy or energy-dispersive X-ray spectroscopy, are better suited for determining atomic concentration in bulk samples.

Explanation

XPS, or X-ray photoelectron spectroscopy, is not a suitable technique for measuring the atomic concentration of a bulk sample. XPS is primarily used to analyze the surface composition and chemical state of materials. It provides information about the elements present on the surface and their chemical bonding, but it does not provide quantitative measurements of atomic concentration throughout the bulk of a sample. Other techniques, such as Auger electron spectroscopy or energy-dispersive X-ray spectroscopy, are better suited for determining atomic concentration in bulk samples.

7. What is the energy (in eV) of the aluminium K-alpha x-rays used for analysis in the Thermo K-Alpha XPS system used in the RMMF?

The energy of the aluminium K-alpha x-rays used for analysis in the Thermo K-Alpha XPS system used in the RMMF is 1486.7 eV.

Explanation

The energy of the aluminium K-alpha x-rays used for analysis in the Thermo K-Alpha XPS system used in the RMMF is 1486.7 eV.

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8. EDS is a technique where an electron beam is focused onto a sample and used to probe the resulting x-rays. XRF is a technique performed by shining an x-ray beam onto a sample at atmospheric conditions, and measuring the resulting x-rays from it. XPS is a technique performed by shining an x-ray beam onto a sample at ultra-high vacuum and measuring the low energy electrons emitted from the surface of the sample. Using this information, please match the technique to the sample.

The scientist wants to collect the atomic concentration of a bulk mineral sample

The scientist has a sample with nano/micro scaled features and wishes to map the composition of the sample

The scientist wishes to determine the concentration of the surface of their sample

It is important to know:

What scale the analysis technique is analysing.

The depth (interaction volume) of analysis

Explanation

It is important to know:

What scale the analysis technique is analysing.

The depth (interaction volume) of analysis

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9. A typical XPS system operates in ultra high vacuum conditions ((UHV; P < 10⁻⁹ millibar)) Which of these samples are NOT suitable for XPS analysis at UHV?

A piece of rock with many pores

A thin continuous metal film

A sample which contains water

A sample which outgasses in UHV

A solid polymer which is stable under x-rays in UHV

A monomer sample

Nanoparticles on a conductive substrate

A non-conductive sample

XPS analysis requires ultra high vacuum conditions, which means that any sample that can release gas or contain moisture is not suitable for analysis. A piece of rock with many pores can release gas, a sample containing water can introduce moisture, a sample that outgasses in UHV can release gas, and a monomer sample can also release gas. Therefore, these samples are not suitable for XPS analysis at UHV.

Explanation

XPS analysis requires ultra high vacuum conditions, which means that any sample that can release gas or contain moisture is not suitable for analysis. A piece of rock with many pores can release gas, a sample containing water can introduce moisture, a sample that outgasses in UHV can release gas, and a monomer sample can also release gas. Therefore, these samples are not suitable for XPS analysis at UHV.

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10. Which of the following peaks would represent Auger electron emission?

O KLL

Ba MNN

Ba 3d

O1s

Auger electron emission occurs when an electron from a higher energy level fills the hole left by an ejected core electron, resulting in the emission of an Auger electron. In this case, both O KLL and Ba MNN represent core-level electron transitions, where an electron from a higher energy level fills a core-level hole. Therefore, both O KLL and Ba MNN peaks could potentially represent Auger electron emission. The other options, Ba 3d and O1s, do not involve core-level electron transitions and are not relevant to Auger electron emission.

Explanation

Auger electron emission occurs when an electron from a higher energy level fills the hole left by an ejected core electron, resulting in the emission of an Auger electron. In this case, both O KLL and Ba MNN represent core-level electron transitions, where an electron from a higher energy level fills a core-level hole. Therefore, both O KLL and Ba MNN peaks could potentially represent Auger electron emission. The other options, Ba 3d and O1s, do not involve core-level electron transitions and are not relevant to Auger electron emission.

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Rmmf XPS Online Quiz