Microstructural Analysis of Copper Foil Etched and Annealed in ECR Plasma Reactor

Microstructural analysis of commercially available cold-rolled polycrystalline copper foil, etched and annealed in an in-house developed Electron Cyclotron Resonance (ECR) Plasma Enhanced Chemical Vapour Deposition (PE-CVD) reactor, have been carried out using x-ray diffraction (XRD) studies. The annealing experiments were carried out under a vacuum environment, keeping the working pressure of the reactor at 50×10-3 mbar, for three different time spans of 30 mins, 45 mins and 1 hour at 823 K (550 °C) and 923 K (650 °C) respectively in presence of hydrogen plasma. The XRD studies reveal the significance of annealing time at two different temperatures for the determination of physical and microstructural parameters such as the average grain size and micro-strain in copper lattice by Williamson-Hall (W-H) method.

Direct measurement of electron Bernstein waves in Low Aspect ratio Torus Experiment

By using a newly developed five-pin probe antenna and two-dimensional mechanical probe driving system, the 2-D wave pattern of phase and amplitude has been directly measured in Low Aspect ratio Torus Experiment (LATE), for an overdense ECR plasma with microwave obliquely injected. In the case of O-mode injection, an EBW-like wave pattern has been detected for the first time, in a localized region near the upper hybrid resonance layer. The pattern has a short wavelength of about 2 mm and is also electrostatic and backward. In the case of X-mode injection, the 2-D wave pattern is quite different and no EBW signal can be observed. By adjusting the toroidal magnetic field in O-mode injection, it is found that both the position and size of the EBW region have changed, which suggest the localized condition of efficient O-X-B conversion and high collisional damping rate of EBWs in these experiments.

Thermal annealing ambiance effect on phosphorus passivation and reactivation mechanisms in silicon-based Schottky diodes hydrogenated by MW-ECR plasma

The main objective of this work is to investigate the effect of thermal annealing in forming gas atmosphere on the mechanism of deactivation and reactivation of phosphorus in silicon-based Schottky diodes. Firstly, the microwave plasma power, initial phosphorus concentration in the samples and hydrogen flux were fixed as 650 W, 1015 cm–3, and 30 sccm, respectively, to investigate the behavior of different working parameters of diodes, specifically the duration and temperature of hydrogenation. Secondly, few samples hydrogenated at 400 °C for 1 h were annealed under the forming gas (10% H2 + 90% N2) within the temperature range from 100 to 700 °C for 1 h. The profiles of active phosphorus concentration were monitored by evaluating the change in concentration of phosphorus after hydrogenation or thermal annealing in a forming gas environment through capacitance-voltage measurements. The obtained results depict the temperature and duration of hydrogenation, which ultimately reveals the complex behavior of phosphorous and hydrogen in silicon. However, the phosphorus passivation rate is homogeneous over all the depths measured at 400 °C. The thermal annealing in a forming gas indicates the increase in passivation rate of phosphorus as a function of annealing temperature, till the passivation rate attains saturation in the sample annealed at 400 °C. At higher temperatures, a decrease in the concentration of phosphorous-hydrogen complexes is observed due to the dissociation of these complexes and reactivation of phosphorus under thermal effect.

Comparative Study of High Temperature Anti-oxidation Property of Sputtering Deposited Stoichiometric and Si-rich SiC Films

Stoichiometric and silicon-rich (Si-rich) SiC films were deposited by Microwave Electron Cyclotron Resonance (MW-ECR) plasma enhanced RF magnetron sputtering method. As-deposited films were oxidized at 800, 900 and 1000 ℃ in air for 60 min. The chemical composition and structure of the films were analyzed by X-ray Photoelectron Spectroscopy (XPS), Raman spectroscopy and Fourier Transform Infrared spectroscopy (FT-IR). The surface morphology of the films before and after high temperature oxidation was measured by atomic force microscopy. The mechanical property of the films was measured by a Nano-indenter. The anti-oxidation temperature of the Si-rich SiC film is 100 ℃ higher than that of the stoichiometric SiC film. The oxidation layer thickness of the Si-rich SiC film is thinner than that of the stoichiometric SiC film in depth direction. The large amount of extra silicon in the Si-rich SiC film plays an important role in the improvement of its high temperature anti-oxidation property.

Probing Electron Properties in ECR Plasmas Using X-ray Bremsstrahlung and Fluorescence Emission

A quantitative analysis of X-ray emission from an electron cyclotron resonance (ECR) plasma was performed to probe the spatial properties of electrons having energy for effective ionisation. A series of measurements were taken by INFN-LNS and ATOMKI, capturing spatially and spectrally resolved X-ray maps as well as volumetric emissions from argon plasma. Comparing the former with model generated maps (involving space-resolved phenomenological electron energy distribution function and geometrical efficiency calculated using ray-tracing Monte Carlo (MC) routine) furnished information on structural aspects of the plasma. Similarly, fitting a model composed of bremsstrahlung and fluorescence to the volumetric X-ray spectrum provided valuable insight into the density and temperature of confined and lost electrons. The latter can be fed back to existing electron kinetics models for simulating more relevant energies, consequently improving theoretical X-ray maps and establishing the method as an excellent indirect diagnostic tool for warm electrons, required for both fundamental and applied research in ECR plasmas.

Effects of gas adsorbed on solid surface during gas breakdown in electron cyclotron resonance discharge

The microwave breakdown power (Pwb) in an ECR plasma source was not merely determined by pressure (gas flow rate), but found to vary with the time interval between two successive breakdowns. The measured Pwb dropped rapidly from a high value at a short time interval to a low level at a long time interval. The obtained dependence of Pwb on pressure (gas flow rate) exhibited distinct features: the normal monotonicity and abnormal non-monotonicity at the short and long time intervals, respectively. The effective zone in the antenna’s surface bombarded by hot electrons heated in the ECR layer was validated by (1) masking the antenna with a film having a variable radius; (2) calculating the distribution of the vertical component of the microwave electric field with respect to the static magnetic field; (3) imaging glows of transient breakdown discharges with a fast camera. The reduction in Pwb was mainly attributed to the enhanced emission of δ-electrons from the gas-adsorbed antenna under the bombardment of energetic electrons coming from the ECR layer.. The correlation between the dynamic gas coverage and the coefficient emission of δ-electrons was established to understand the abnormal ECR breakdown features.

PECVD SiNx Thin Films for Protecting Highly Reflective Silver Mirrors: Are They Better Than ALD AlOx Films?

Protection of silver surface from corrosion is an important topic, as this metal is highly susceptible to damage by atomic oxygen, halogenated, acidic and sulfur-containing molecules. Protective coatings need to be efficient at relatively small thicknesses, transparent and must not affect the surface in any detrimental way, during the deposition or over its lifetime. We compare PECVD-deposited SiNx films to efficiency of ALD-deposited AlOx films as protectors of front surface silver mirrors against damage by oxygen plasma. Films of different thickness were deposited at room temperature and exposed to O2 ECR-plasma for various durations. Results were analyzed with optical and SEM microscopy, pulsed GD-OES, spectroscopic ellipsometry and spectrophotometry on reflection. Studies indicate that both films provide protection after certain minimal thickness. While this critical thickness seems to be smaller for SiNx films during short plasma exposures, longer plasma treatment reveals that the local defects in PECVD-deposited films (most likely due to erosion of some regions of the film and pinholes) steadily multiply with time of treatment and lead to slow drop of reflectance of SiNx-protected mirrors, whereas we showed before that ALD-deposited AlOx films reliably protect silver surface during long plasma exposures.