A blog on the repair, operation and calibration of surface analysis systems and components including electron spectrometers, sputter ion guns and vacuum related hardware.
Print PDFUsing Ta2O5 or SiO2 works well for aligning an ion beam to the focal point of an X-ray photoelectron or scanning Auger electron spectrometer. Because the current measured into the Faraday cup is in the low nA range, a picoammeter (such as the RBD Instruments Inc. Another benefit of using a Faraday cup is that you can also determine the electric current density using a multiplication factor.
While observing the picoammeter, adjust the focus (objective) and condenser on the ion gun control and the mechanical offsets (thumbscrews) on the ion gun for maximum current into the Faraday cup. This entry was posted in Ion Sources and tagged faraday cup, ion beam alignment, picoammeter by Randy.
Faraday cup, and check out Faraday cup on Wikipedia, Youtube, Google News, Google Books, and Twitter on Digplanet. When a beam or packet of ions hits the metal it gains a small net charge while the ions are neutralized. Similarly, a Faraday cup can act as a collector for electrons in a vacuum (for instance from an electron beam).
The conventional Faraday cup is applied for measurements of ion (or electron) flows from plasma boundaries and comprises a metallic cylindrical receiver-cap a€“ 1 (Fig. The counting of charges collected per unit time is impacted by two error sources: 1) the emission of low-energy secondary electrons from the surface struck by the incident charge and 2) backscattering (~180 degree scattering) of the incident particle, which causes it to leave the collecting surface, at least temporarily.
A device to measure the properties of charged elementary particle, atomic or simple molecular beams during or after acceleration, or the properties of neutral particle beams produced in an intermediate stage of charged particle acceleration. A description of the device, its operating principle, and its performance should have been published in a journal or in the proceedings of a conference or workshop that is in the public domain.
Nominations are open to candidates of any nationality for work done at any geographical location. The Award Committee may release the names of entrants and a list of publications related to an entry if requested by a third party. Show transcribed image text Assume that the Faraday Cup and Grounding Cage act like coaxial conducting cylinders (ignore that there is a bottom to the Faraday Cup, and allow the height of the Grounding Cage to be equal to the height of the Faraday Cup). But, in order to optimize the ion beam focus at larger beam sizes, a Faraday cup is required. For Auger electron spectrometers, acquire an elastic peak just to the side of the Faraday cup hole and then move the Faraday cup hole to the center of the TV image. This will ground the target and apply +90V to the ion lead on the specimen stage (which in turn makes the electrical contact to the Faraday cup).
By optimizing a few ranges of current and using those parameters to acquire depth profiles on a standard such as SiO2 or TaO5 (both available from RBD) you can create a matrix of reproducible sputter rates.


The resulting current can be measured and used to determine the number of ions or electrons hitting the cup.[1] The Faraday cup is named after Michael Faraday who first theorized ions around 1830. The metal can then be discharged to measure a small current equivalent to the number of impinging ions.
Thus, a measured current of one nanoamp (10a?’9 A) corresponds to about 6 billion ions striking the faraday cup each second. 1) closed with, and insulated from, a washer-type metallic electron-suppressor lid - 2 provided with the round axial through enter-hollow of an aperture with a surface area . All of the Faraday cup elements and their assembly that interact with plasma are fabricated usually of temperature-resistant materials (often these are stainless steel and teflon or ceramic for insulators).
Especially with electrons, it is fundamentally impossible to distinguish between a fresh new incident electron and one that has been backscattered or even a fast secondary electron.
The device may operate by detecting secondary beams of charged, neutral, massive or mass less particles. Laboratory design notes, internal technical notes, etc., do not qualify but may be submitted to support other publications. There are no restrictions for candidates, with the only exception that they cannot be members in charge of the BIW Program Committee.
Unpublished supporting material will not be disclosed nor will the names of persons supporting a nomination. The inside cylinder is isolated from the outside cylinder with the outside cylinder attached to ground.
When the bias box is set to the ion input, the target is grounded and the output of the bias box is routed from the ion lead (Faraday cup) on the specimen stage to the input of the picoammeter. For X-ray photoelectron spectroscopy systems, move the Faraday cup hole to the center of the system microscope’s image at the highest possible magnification setting. Once the mechanical offsets on the ion gun have been adjusted to where no further increase in current is noted, lock them down securely and also make sure that the ion gun housing is tight.
Essentially the Faraday cup is part of a circuit where ions are the charge carriers in vacuum and the faraday cup is the interface to the solid metal where electrons act as the charge carriers (as in most circuits). Faraday cups are not as sensitive as electron multiplier detectors, but are highly regarded for accuracy because of the direct relation between the measured current and number of ions.This device is considered a universal charge detector because of its independence from the energy, mass, chemistry, etc. Both the receiver cup and the electron-suppressor lid are enveloped in, and insulated from, a grounded cylindrical shield - 3 having an axial round hole coinciding with the hole in the electron-suppressor lid - 2.
For processing of the Faraday cup I-V characteristic, we are going to assume that the Faraday cup is installed far enough away from an investigated plasma source where the flow of ions could be considered as the flow of particles with parallel velocities directed exactly along the Faraday cup axis. Full and open disclosure is necessary to the extent that a potential user could design a similar device. In the event of deciding between works of similar quality, preference will be given to candidates in an early stage of their beam instrumentation career.


When an ion beam is larger than the 250um Faraday cup aperture, only the portion of the beam that is 250um or smaller is measured. Do not adjust the mechanical offsets for subsequent focus adjustments at different condenser (COND) or beam voltage settings. By measuring the electric current (the number of electrons flowing through the circuit per second) in the metal part of the circuit the number of charges being carried by the ions in the vacuum part of the circuit can be determined.
The mass of primary beam particles shall be no greater than the order of 1000 atomic mass units. More than one article may be submitted (together) to satisfy this requirement; for example, an article describing the principle plus another article describing the performance. Determine the following, showing all work: Use values measured for charging the Faraday Cup with the PVC disk. By adjusting the ion beam focus and position for maximum current into the Faraday cup, the ion beam can be aligned and the current density can be optimized for any ion beam condition. In those cases, short out the target and and connect the picoammeter to the ion lead on the specimen stage. Instead, you can optimize the position of the ion beam into the Faraday cup by using the offset adjustments on the ion gun control if necessary.
Once accepted by the Award Committee a nomination shall remain eligible for two successive competitions unless withdrawn by a candidate.
Typically, though, the 04-303 ion source is operated at 3-to-4kV with 15MPa of argon pressure. Electric capacity is formed of the capacity of the receiver-cup - 1 to the grounded shield - 3 and the capacity of the RF cable. Therefore, the maximum ion current passing into a Faraday cup under those conditions is more in the range of 150 to 200nA. The signal from enables an observer to acquire an I-V characteristic of the Faraday cup by oscilloscope. The solid line represents the Faraday Cup, while the dashed line represents the Grounding Cage. Proper operating conditions: (due to possible potential sag) and , where is the ion free path.



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