Modulation electron beam

In color picture tubes, the final color is formed by additive mixing of red, green, and blue light. Each of the three phosphors (Table 58) is excited by its own modulated electron beam and emits light of intensity corresponding to the particular degree of excitation. The phosphors for color picture tubes have an average particle size of 8-10 pm. 

Instead of measuring the transmission of electrons one can measure the transmission of the target particles in a crossed-beam experiment, where a beam of electrons intersects a beam of target particles (Bederson, 1968). The recoil imparted to the target atom or molecule deflects it out of the original beam and the decreased beam intensity is a measure of the total cross section. Usually one uses a d.c. molecular beam and a modulated electron beam and associated phase-sensitive detection of the transmitted molecular beam. If the two beams are rectangular with a common dimension h, then (Bederson, 1968)... 

The SEM/SFM hybrid system [6] gives the advantage of using two microprobes of acoustic waves simultaneously. In this work a locally modulated electron beam is used to generate acoustic waves in a ferroelectric sample. The resulting surface acoustic waves are detected with an SFM tip in contact to the sample surface. As a sample a room temperature ferroelectric BaTiO3 is used. Due to different mechanical properties with respect to domain orientation, ferroelectric domain structures can be detected in the acoustic image. 

If the speed of electrons in a focused electron beam is velocity modulated, as seen in Eq. (6.44), then the electron flow is no longer uniform and smooth. Some electrons in the beam are faster or slower than others, and as a result electrons tend to bunch together as they travel from the electron gun in the beginning to the electron collector at the end. The traveling electron charge density in the velocity modulated electron beam is expressed by... 

The thermodynamic properties of UC2 have been studied by several scientists. Coninck et al. (1976) conducted experiments on UC2 and provided correlations for the calculation of the thermal diffusivity, thermal conductivity, and emissivity of UC2 as functions of temperature. Coninck et al. (1976) used the modulated electron beam technique in order to determine the thermal diffusivity of UC2 samples. In this technique, an electron gun is used to bombard a material in the form of a thin solid plate from one face. The electron gun is modulated to vary sinusoidally as a function of time. The phase difference between the temperature fluctuations of the two faces of the plate is measured, which is used to determine the thermal diffusivity of the material (Wheeler, 1965). Then, thermal conductivity is calculated as the multiplication of thermal diffusivity, density, and speciflc heat as shown in Eq. [18.3]. 

Wheeler, M.J., 1965. Thermal diffusivity at incandescent temperatures by a modulated electron beam technique. British Journal of Applied Physics 16, 365—376. 

An electron gun produces and accelerates the electron beam, which is reduced in diameter (demagnified) by one or more electromagnetic electron lenses. Electromagnetic scanning coils move this small electron probe (i.e., the beam) across the specimen in a raster. Electron detectors beyond the specimen collect a signal that is used to modulate the intensity on a cathode-ray tube that is scanned in synchronism with the beam on the specimen. A schematic of the essential components in a dedicated STEM system is shown in Figure 2. 

Commercial versions of PR are available. Other contactless methods of electro-modulation are Electron-Beam Electro-reflectance (EBER) and Contacdess Electroreflectance (CER). In EBER the pump beam of Figure 2 is replaced by a modulated low-energy electron beam (- 200 eV) chopped at about 1 kHz. However, the sample and electron gun must be placed in an ultrahigh vacuum chamber. Contactless electroreflectance uses a capacitor-like arrangement. 

These complicated systems are controlled by means of a computer, which in real time monitors the various operating parameters of the column and stage position and which in addition, transfers primary pattern data directly to the electron deflection system. The rate at which the data can be transmitted to the electron optical column ultimately governs the modulation rate of the electron beam machine, i.e., flash time. Modulation rates in excess of 100 MHz have been achieved, and it is conceivable that much higher modulation rates will be attained in the future. 

We have recently described another spectroscopic rnethod for observing IM reactions at atmospheric pressure that utilizes the photodetachment-modulated electron capture detector (PDM-ECD) as a means of monitoring the negative ions either consumed or produced in an IM reaction. The reaction of interest is made to occiu in a steady-state flow-through reactor in which ionization of the buffer gas is continuously caused by a Ni-on-Pt foil beta emitter. A chopped light beam of... 

Another relatively recent development is electron generators that are essentially sealed vacuum tubes with a 2.5 pm-thick silica ceramic window or a 5-10 pm titanium window as the beam exit. Such electron beam tubes or bulbs are capable of operating at 50 to 150 kV,64-67 71 and can be stacked into modules to cure wide webs. It is conceivable that a miniature electron beam could provide an efficient low-cost means to cure thin coatings, adhesives (clear and filled) and inks. Examples of such miniature electron beam equipment are shown in Figures 3.21 and 3.22. 

Clearly, the sensitivity of a resist should be commensurate with machine design parameters to allow optimized throughput. For example, an electron beam exposure system writing at a modulation rate of 20 MHz (dwell time of 50 nsec), a beam current of 5 x 10-8 amps at 10 kV, and an address structure (spot size) of 0.25 2 would require a resist with a sensitivity of 10 6 C/cm2 (1 / 2) or better in order to write the maximum number of wafers per hour of which it is capable. The same argument also applies to other exposure tools. 

Figure 88. Oscilloscope tube a) Cathode b) Modulator c) Electron lens d)Y-plates e) X-plates f) Electron beam g) Phosphor screen...

Periodic microstructures can be corroborated by observations of wavevectors /3 in transmission electron microscope (TEM) images, particularly if the sample is oriented with the modulation waves directed perpendicular to the electron-beam direction (e.g., with the beam along [001] for a crystal with (100) modulations). 

Most of the high precision spectroscopy of He Rydberg states has been done by microwave resonance, which is probably the best way of obtaining the zero field energies. Wing et a/.8-12 used a 30-1000pA/cm2 electron beam to bombard He gas at 10-5-10-2 Torr. As electron bombardment favors the production of low states, it is possible to detect A transitions driven by microwaves. The microwave power was square wave modulated at 40 Hz, and the optical emission from a specific Rydberg state was monitored. When microwave transitions occurred to or... 

Figure 26.2 N KLL peak-shape in some nitrides 8 recorded with a primary electron beam of 5 keV, 0.5 pA and peak-to-peak modulation of 3 V.

In the experiments we have used two approaches. First, we have simulated the kinetics of a bistable optical system in the Debye relaxation appoximation for different forms of potential by means of electronic analog simulation. Secondly, we have investigated the kinetics of a double-cavity membrane system (DCMS) driven by two modulated laser beams at different wavelengths. This system is known to display optical bistability [111]. 

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