A planar excimer-halogen radiation source pumped by transverse RF discharge

We present the characteristics of a planar source of wideband shortwave radiation pumped by transverse RF (f=1.76 MHz) discharge in a Kr/Xe/Cl₂ mixture (P≤500 Pa). The spectral characteristics of the plasma emission were studied in the wavelength interval of 130–600 nm. The oscillograms of the voltage, current, and output radiation intensity and the diagrams of the output power depending on the gas pressure, partial composition of the working gas mixture, and discharge power are presented. It is established that the source produces emission predominantly in the spectral interval of 170–330 nm, representing a system of the molecular emission bands XeCl(D, B-X), KrCl(B-X), Cl₂(D′-A′), and Cl₂**. For a maximum output power in the UV-VUV range, the optimum working gas mixture is Kr/Xe/Cl₂ with the partial pressures P(Kr)/P(Xe)/P(Cl₂)=150–200/150–200/20–40 Pa. The maximum power irradiated within a solid angle of 4π via two output holes with a total area of S≤ 100 cm² reaches 30–40 W. In the region of a threshold with respect to the transverse discharge initiation, there are narrow peaks of plasma emission that are probably related to the jumps in the density of electrons and the positive and negative ions at the boundary between the plasma and the RF discharge layer.     

Characteristics and plasma parameters of a short-wavelength low-pressure discharge lamp

We have studied the working optical characteristics and electron kinetic coefficients of a short-wavelength, electric discharge exciplex-halogen UV-VUV lamp employing a mixture of argon and chlorine with a total pressure of P = 0.5–10 kPa. The lamp operates on a system of broadened electron-vibrational bands of ArCl (175 nm) and chlorine (200, 258 nm) molecules, which overlap to form a continuum in the spectral range of 160–260 nm. It is established that the optimum mixtures are those with p(Ar) − p(Cl₂) = (2–4)−(0.15–0.30) kPa. The average output power of the short-wavelength radiation is 1–2 W at an efficiency of ∼5%. The electron energy distribution functions (EDFs) and the discharge plasma parameters have been calculated by solving the Boltzmann equation for a gas mixture with the experimentally determined optimum composition in the range of E/P values from 1 to 200 V/(cm Torr), where E is the electric field strength and P is the total gas pressure. Using the obtained EDFs, the electron transport characteristics, specific discharge power losses for the main elementary processes, and rate constants of electron processes are determined.     

The characteristics of a confined discharge in a helium-chlorine gas mixture

The electrical and optical characteristics of a confined (cage) discharge in a He-Cl₂ mixture at pressures within 0.1–1.5 kPa were studied. It was established that the negative glow plasma in this discharge is a source of wideband radiation in a wavelength range from 170 to 270 nm with the emission peaks at λ_max=195 nm [Cl₂(¹Σ?¹Π₄)], 200 nm [C1₂**, and 258 nm [Cl₂(D′-A′)]. Optimum conditions ensuring the maximum intensity of emission in the UV-VUV range due to transitions in the chlorine molecule have been established. The results are of interest from the standpoint of the development of a stationary shortwave low-pressure lamp filled with a He-Cl₂ gas mixture.     

Shortwave krypton-bromine excimer low-pressure lamp

The emission characteristics are reported for a small short-wavelength (UV) lamp filled with a krypton-bromine mixture and pumped by longitudinal glow discharge at a 100-mm distance between electrodes in a quartz tube with an internal diameter of 14 mm. The emission spectrum is formed by the resonance atomic lines of bromine (163.3 and 157.6 nm) and the molecular lines of bromine (Br₂) and krypton bromide (KrBr). An increase in the partial pressure of bromine in the working mixture from 50 to 270 Pa is accompanied by a decrease in the intensity of emission lines due to atomic bromine and leads to the formation of VUV-UV continuum based on the molecular bands due to Br₂ and KrBr. The operation regime was optimized with respect to the glow discharge current and the gas mixture pressure and composition. The optimum partial pressure of krypton is within 500–800 Pa, and that of bromine vapor is within 100–250 Pa. The average total VUV-UV output radiation power reached 5 W at an efficiency of 8–10%.     

The optimum characteristics of a halogen lamp pumped by transverse RF discharge

We report on the optimized characteristics of a small-size bactericidal lamp pumped by transverse RF (f=1.76 MHz) discharge, operating on a system of the molecular emission bands of chlorine in a wavelength range of 195–310 nm. The spectral characteristics of the plasma emission were measured and the intensity of chlorine emission bands were studied as functions of the total pressure and partial composition of a helium-chlorine mixture. Oscillograms of the pumping current and output radiation intensity were measured and the total output radiation power was determined. It is established that the lamp radiates predominantly in a bactericidal wavelength interval on an electron-vibrational transition at 200 nm in Cl₂** molecules. The optimum partial pressures of helium and chlorine are 100–300 and 90–120 Pa, respectively. The maximum output power of UV emission from the side cylindrical surface of the lamp reached 10 W. The lamp can be used in photochemistry, ecology, genetics, and medicine.     

Excited nitrogen molecule formation in a DC-glow-discharge-pumped excimer lamp

The plasma in an excimer lamp operating in the λ=258 nm [Cl₂(D′-A′)] and 175 nm [ArCl(B-X)] modes using an Ar-Cl₂ gas mixture excited with a longitudinal dc glow discharge was studied by the method of spectroscopic diagnostics. In the presence of small air admixtures (P≤30 Pa) in the working medium, the plasma exhibits the formation of excited nitrogen molecules decaying with the emission of molecular bands in the 193–271 nm wavelength range. The emission intensities of both molecular and excimer bands were measured and the conditions were determined under which the excited nitrogen molecules most significantly affect the optical characteristics of the discharge.     

A high-power low-pressure iodine lamp pumped by glow discharge

We present the working characteristics of a high-power UV-VUV electric-discharge lamp filled with a working mixture of helium and iodine vapor (He-I₂) at a low pressure (0.1–1.5 kPa) and pumped by a dc glow discharge at a power of 15–200 W. The power of the total output UV radiation and the main emission peak at λ = 206.2 nm were studied as dependent on the electric power supplied to the glow discharge and on the partial pressure of helium in the He-I₂ mixture. The emission characteristics of the glow discharge plasma were studied in the spectral range from 200 to 350 nm. In this range, the lamp is operating predominantly on a resonance emission line of excited iodine atoms (λ = 206.2 nm, FWHM = 0.10–0.12 nm) and on a system of electronic-vibrational bands of excited iodine molecules with the main peak at λ = 342 nm. The contribution of the resonance emission due to excited iodine atoms to the total UV emission from the glow discharge plasma does not exceed 50%. The optimum partial pressure of helium is within 400–800 Pa. The total UV radiation power of the lamp operating in the optimum regime reaches 25 W at an efficiency of η ≤15%.     

UV emission from capacitive discharge in inert gas-iodine vapor mixture

We have studied the optical characteristics of capacitive discharge in binary mixtures of helium, neon, argon, and krypton with iodine vapor in a spectral range of 180–300 nm. It is established that the main power of UV radiation from the discharge plasma is concentrated in the emission lines at 183.0 and 206.2 nm. The intensity of emission due the spectral lines of iodine atom was optimized with respect to the inert gas type and partial pressure. The optimum results were obtained using He-I₂ mixture with partial pressures of helium within 0.8–2.0 kPa and iodine vapor below 50–60 Pa. Being excited with a trains of nanosecond current pulses at a repetition rate of 10–100 Hz, the capacitive discharge emitted pulses with duration not exceeding 400–500 ns.     

The formation of excited chlorine atoms in a low-pressure transverse volume discharge

The characteristics of a transverse volume discharge (TVD) in chlorine at low pressures (P(Cl₂)=0.1–1.5 kPa) were studied. The excited chlorine atoms were formed in a 18×2.2× (0.5–1.0) cm volume using relatively low values of the capacitor bank charging voltage (U _ch ≤ 10 kV) in the pulsed discharge voltage source. The optical emission from plasma was studied in a spectral range from 500 to 900 nm. Homogeneous TVD pulses of short duration (τ; ≤ 100 ns) obtained under these conditions are of interest for use in UV-VUV lamps employed in pulsed plasmachemical reactors for dry etching of thin films. The density of excited atomic chlorine radicals can be monitored on medium-resolution spectrometers using the ClI emission lines with λ=725, 754, and 821 (2) nm.     

Short-wavelength XeBr-Br gas discharge lamp

The output characteristics of a small-size gas-discharge lamp emitting in the 160–300 nm wavelength range are reported. The working medium—a mixture of xenon and bromine vapor—was excited in a longitudinal glow discharge in a quartz tube with an interelectrode distance of 100 mm. The emission spectrum is formed by the molecular lines of xenon bromide at 282 nm [XeBr(B-X)] and 220 nm [XeBr(D-X)] and the atomic resonance lines of bromine at 163.3 and 157.6 nm. An increase in the partial pressure of xenon in the working mixture from 130 to 800 Pa is accompanied by a decrease in the intensity of emission lines due to atomic bromine and an increase in the intensity of emission from xenon bromide molecules. The operation regime was optimized with respect to the energy supplied to the glow discharge and the working gas mixture pressure and composition. The optimum partial pressure of xenon is within 600–800 Pa, and that of bromine vapor, within 50–100 Pa. The average total VUV-UV output radiation power reached 7 W.     

Bromine-iodine excimer electric-discharge lamp with continuous UV radiation spectrum

The optical characteristics of a small-size UV lamp filled with a working mixture of xenon and krypton with bromine and iodine vapor and pumped by longitudinal electric discharge have been studied. The lamp emits a resonance atomic line of iodine I* at 206.2 nm (with a full width at half maximum of 0.10 nm) and a continuum in the range 220–390 nm, which is formed by the emission bands of diatomic molecules [XeI(B-X), XeBr(B,D-X), Br₂(B-X), I₂(B-X), and IBr(B-X)]. The optimum partial pressure of iodine vapor is 100–200 Pa, that of bromine vapor ranges from 130 to 400 Pa, and that of heavy inert gases, from 400 to 800 Pa. The average total UV output radiation power was 10–12 W at an efficiency of 10–12%.     

Low-pressure ultraviolet emitter utilizing chlorine and krypton chloride molecules

Results are given of an investigation of the electrical and optical characteristics of the plasma of a longitudinal high-frequency discharge in a krypton/chlorine mixture (P 1000 Pa). The high-frequency discharge is ignited in a cylindrical quartz tube with an inside diameter of 14 mm and a distance between the anode and cathode of 30 mm. The dynamics of current and radiation of the high-frequency discharge utilizing krypton/chlorine mixtures of different compositions and pressures are investigated. It is found that a longitudinal high-frequency in a krypton/chlorine mixture is a broadband excimer-halogen emitter in the 200–260 nm spectral range. The ultraviolet spectrum of the lamp is formed as a result of overlapping of broadened radiation bands of chlorine and krypton chloride molecules (200 nm ₂ ^** , 222 nm KrCl, and 257 nm Cl ₂ ^* ). The optimal composition of a Kr/Cl₂ mixture is determined, which is necessary to obtain the maximal power of ultraviolet radiation.Translated from Teplofizika Vysokikh Temperatur, Vol. 42, No. 6, 2004, pp. 865–868.Original Russian Text Copyright © 2004 by A. K. Shuaibov, I. V. Shevera, and A. A. General.     

The parameters of plasma and the kinetics of generation and loss of active particles under conditions of discharge in chlorine

The parameters of plasma and the kinetics of generation and loss of active particles are investigated under conditions of a dc glow discharge in chlorine (P = 40–280 Pa, i _p = 5–15 mA). It is found that the generation of atoms in chlorine plasma is supported by the dissociation of Cl₂ molecules under electron impact, and the contribution by dissociative attachment does not exceed 10%. Calculation data are obtained on the mass composition of neutral and charged particles of plasma. It is demonstrated that the assumption of the first kinetic order of heterogeneous loss of atoms provides for adequate agreement of the experimentally obtained and calculated values of E/N, of the concentration of chlorine atoms, and of the density of positive ion flux to the surface of discharge tube.     

An Inductively Coupled Plasma Source for the Gaseous Electronics Conference RF Reference Cell

In order to extend the operating range of the GEC RF Reference Cell, we developed an inductively coupled plasma source that replaced the standard parallel-plate upper-electrode assembly. Voltage and current probes, Langmuir probes, and an 80 GHz interferometer provided information on plasmas formed in argon, chlorine, and nitrogen at pressures from 0.1 Pa to 3 Pa. For powers deposited in the plasma from 20 W to 300 W, the source produced peak electron densities between 10¹⁰/cm³ and 10¹²/cm³ and electron temperatures near 4 eV. The electron density peaked on axis with typical full-width at half maximum of 7 cm to 9 cm. Discharges in chlorine and nitrogen had bimodal operation that was clearly evident from optical emission intensity. A dim mode occurred at low power and a bright mode at high power. The transition between modes had hysteresis. After many hours of high-power operation, films formed on electrodes and walls of one Cell. These deposits affected the dim-to-bright mode transition, and also apparently caused generation of hot electrons and increased the plasma potential.     

Influence of the annealing temperature on a crystal phase of W/WC bilayers grown by pulsed arc discharge

The X-ray diffraction technique was used to study the influence of the temperature on a crystal phase of W/WC bilayer produced by the plasma-assisted pulsed arc discharge. In order to grow the films, a target of W with 99.9999% purity and stainless-steel 304 substrate were used. For the production of W layer, the reaction chamber was filled up with argon gas until reaching a 300 Pa and the discharge was performed at 270 V with 3 pulses. The WC layer was grown in a methane atmosphere at 300 Pa and 275 V discharge voltage with 4 pulses. The active and passive times of the pulsed discharge were 1 and 0.5 s, respectively. The influence of post-annealing temperature of their crystal phases was studied at the post-annealing temperatures up to 600 °C. As-grown layer comprised of mixed phases WC, W₂C and W. The post-annealed layer also comprised of the mixed phases of WC, W₂C and W at annealing temperatures below 600 °C. At the annealing temperature above 600 °C, XRD diffractograms showed only substrate and W peaks, and tungsten carbide peaks were not observed, but the presence of WO phases were detected for an annealing temperature of 600 °C. XPS analyses showed the presence of WC before the annealing process and the existence of C-C bond that is considered responsible for the high polycrystallinity of the material was also detected. The XPS showed the formation of WO₂ and WO₃ without the presence of WC for post-annealing at 600 °C.     

Preparation and properties of nickel silicide layers by the diffusion and CVD processes using Si2Cl6 as a source of silicon

Nickel plate was siliconized with a gas mixture of Si₂Cl₆, H₂ and argon in the temperature range 400 to 900° C, and the siliconizing conditions and some of its properties were examined, Appreciable weight increase of the nickel plate was observed above 450° C, which is 200 to 300° C lower than that obtained using SiCl₄ as a source of silicon. Siliconizing of the surface and the resistance to high-temperature oxidation and hot corrosion were improved, Nickel silicide layers were also obtained by the CVD process using a gas mixture of Si₂Cl₆, H₂ and argon.     

Pulsed microwave radiator for the band system λ=175 nm ArCl(B-X)/236 nm XeCl(D−X)/258 nm Cl2*/308 nm XeCl(B-X)

Parameters of a multiwave radiator pumped with transverse volume discharge in an Ar-Xe-Cl₂ mixture at a pressure of P=5–30 kPa were optimized. It is shown that, at a partial xenon pressure in the mixture below 0.4 kPa, the discharge may serve a multiwave radiation source operating on the electron-vibrational transitions with λ=175 nm ArCl(B-X), 236 nm XeCl(D-X), 258 nm Cl₂(D′-A′), and 308 nm XeCl(B-X). The emission line intensities have comparable values, which may be of interest for applications in the short-wave pulsed photometry, microelectronics, and photochemistry.     

Spectral measurements of the probability of recombination of active particles of plasma on solid surfaces in chlorine and its mixtures with inert and molecular gases

Systematic investigations are performed of the spectral characteristics of plasma of chlorine and its mixtures with oxygen, nitrogen, hydrogen, and argon in a dc glow discharge under conditions of continuous modulation of discharge current with rectangular pulses which provide for 100% modulation of discharge current (P _total = 100 Pa, i _d = 11 mA). The possibility is demonstrated of using the relaxation (pulse) procedure for determining the absolute values of the probability of loss of chlorine atoms in plasma of variable-composition chlorine mixtures by atomic chlorine radiation. The absolute values are determined of the probabilities of loss of chlorine atoms on the reactor wall in plasma of mixtures of chlorine with the gases identified above, and it is demonstrated that the prevailing mechanism of the loss of atoms is the wall recombination by the first kinetic order.     

A xenon-iodine electric discharge bactericidal lamp

We present the working characteristics of a continuous UV lamp emitting at λ=206 nm, pumped by a longitudinal glow discharge. The pressure of the working Xe-I₂ gas-vapor mixture was within 0.1–10 kPa. The power deposited in the discharge was varied within 10–130 W. The current-voltage characteristics, the emission spectra in a 200–600 nm wavelength range, the line emission intensity as a function of the power deposited in the discharge plasma, and the partial pressure of xenon in the lamp were studied. It is established that the lamp operates in the range of 206–342 nm on a resonance line of iodine at 206 nm and on the bands at 253 nm [XeI(B-X)] and 342 nm [I₂(B-X)]. Not less than half of the output UV emission power is concentrated in the bactericidal spectral interval (around λ=206 nm). The total UV emission power of the lamp reaches 6–7 W at an efficiency of ≤5%.     

The parameters of plasma and the kinetics of generation and loss of active particles in chlorine-nitrogen mixtures

An investigation is performed of the effect of the initial composition of Cl₂/N₂ mixture on the electrophysical and kinetic parameters of plasma of a dc glow discharge. It is found that the dilution of chlorine with nitrogen causes a variation of the electron energy distribution function (EEDF), which is accompanied by an increase in the average electron energy and in the rate constants of threshold elementary processes. It is demonstrated that the principal mechanism of generation of chlorine atoms is the dissociation of Cl₂ molecules under electron impact; in so doing, the contributions by stepwise processes involving metastable molecules N ₂ ^* (A ³Σ _u ⁺ ) and vibrationally excited molecules N ₂ ^* (v > 7) are negligible. The assumption of the first kinetic order of heterogeneous recombination of chlorine atoms with a probability of (4–5) × 10^?4 provides for adequate agreement between the calculation and experimental data on reduced field intensity, rate constant of recombination, and concentration of atoms.