P. V. Minakov

Study of polycrystalline boron-doped diamond films by Raman spectroscopy and optical absorption spectroscopy

The effect of the degree of doping polycrystalline diamond films by boron on their Raman and absorption spectra has been studied in the visible region (from 200 to 1000 nm). As the boron concentration increases in a polycrystalline diamond film, its Raman spectrum exhibits a number of new specific features caused by the effect of boron atoms on the diamond lattice. The dependences that relate these features to the boron concentration in the films are given. Moreover, the absorption spectra of the films have revealed a peak whose maximum corresponds to photons with an energy near 2 eV.

Electron flow enhancement with a diamond membrane

Secondary electron emission from 2.5-to 5.0-µm thick diamond films (membranes) is considered. The process is studied in the reflection regime, where secondary electrons leave the front surface of the membrane exposed to primary electrons, and in the transmission regime, where primary electrons cause secondary emission from the opposite surface. The secondary emission coefficient is determined based on the behavior of 0.1-to 30-keV electrons in the solid. In the reflection regime, the secondary emission coefficient may be higher than 100 for electron energies of about 3 keV; in the transmission regime, it is no more than 5 even for 30-keV electrons. The emissivity of the membranes in the transmission regime can be improved, specifically, by using porous membranes, which allow one to obtain characteristics similar to those in the reflection regime. Experimental data obtained agree with calculations. The production of diamond films, including porous membranes, is described.

High-current electron gun with a field-emission cathode and diamond grid

Control grids used in high-current devices with field emission cathodes should be made of an appropriate, “grid-grade” material. Such a material must offer a high mechanical strength, thermal conductivity, and electric conductivity. In addition, grids as thin as several microns must be available. As a grid material, boron-doped diamond is tested.

Multi beam X-ray tube with the field emitter on the base of nanocrystalline graphite for computer tomography

A multiple-beam X-ray tube on the basis of field emitters has been designed and developed. The X-ray tube is powered by 140 kV anode supply. Each beam is driven by 1 kV cathode to grid supply. Electron trajectories calculation and experimental measurement of I–V characteristics are presented.

Electron flux amplifier on diamond-coated silicon grating

Diamond membranes are capable of amplifying electron flux, but membranes with dimensions exceeding 10 mm2 are subject to deformation and sagging. In order to avoid this, it is suggested to build electron flux amplifier on a silicon grating coated with a diamond film. The possibility of using these gratings instead of microchannel plates is discussed, in particular, in cases where this grating directly plays the role of X-ray, UV, or proton detector.

Correlation between Plasma OES and Properties of B-doped Diamond Films Grown by MW PE CVD

Boron doped polycrystalline diamond films were grown using MW PE CVD technique. Optical emission spectra (OES) of MWplasma in the region from 200 nm to 800 nm during boron doped polycrystalline diamond films growth were in situ investigated. Raman spectroscopy method was used for structural investigation of grown polycrystalline diamond films. Also, absorption spectroscopy method was used for optical properties investigation of all grown films.

Triode generators on the basis of FE emitters

Electron phase trajectories for high frequency Ku-band in a diode with a nanocrystalline graphite (NCG) field emitter are compared with one with a thermo-cathode. It is shown that the field electron (FE) cathode differs from the thermo-cathode and forms short electron bunches, which can be efficiently decelerated in an output cavity. The scheme and advantages of a triode generator with a FE cathode are described. 1-D analytical evaluation of output power for the triode generator is carried out. The conclusion is drawn that maximum output power strongly depends on current density, and rises up to 80 W for 15 A/cm2.

Controlling Plasma Composition during Carbon Film Deposition in Microwave Discharges by Means of Optical-Emission Spectroscopy

Optical emission spectra from the microwave discharge plasma that is used to activate gas-phase deposition of carbon films are systematically investigated under various deposition conditions. The line emission intensities from CH and C2 radicals, which are responsible for the growth of the diamond and graphite phases, respectively, are studied as functions of the main macroparameters of the process. To find the relation between the features of the emission spectra and the composition of the films obtained, the films were examined using Raman spectroscopy and electron microscopy. It is shown that monitoring the relative intensities of the spectral lines can be used to obtain the desired type of film, in which case the state of the substrate surface and the presence of a catalyst on it also play an important role. Experiments on the deposition of carbon films in the pulsed regime of plasma excitation show the possibility of changing the phase composition of the film by varying both the pulse repetition rate and the off-duty factor. At the same average microwave power, the rate of film deposition in the pulsed regime of plasma excitation is lower than that in a continuous discharge; however, the growth rate of the graphite phase decreases insignificantly.