M.Sc Student | Irad Leiser |
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Subject | Investigation of the Plasma Parameters During the Explosion of a Semiconductor Bridge(SCB) |

Department | Department of Physics |

Supervisor | Full Professor Krasik Yakov |

Full Thesis text |

The SCB is a miniaturized ignition component made of a thin-film, polycrystalline, silicon resistor. It ignites through rapid heating of the bridge by a current pulse. The heat dissipated by the bridge melts, vaporizes and then ionizes the silicon atoms to form a plasma burst.

The primary aim of this research was to estimate the energy stored in a SCB plasma versus the bridge dimensions and the amplitude of the ignition current. A secondary aim was to estimate the electrical input (power, current, action integral) necessary to create a SCB plasma burst as a function of bridge dimensions.

It is known that the energy stored in the plasma (assuming ideal plasma, i.e., the plasma thermal energy significantly larger than the potential, Coulomb energy of the plasma charged particles) can be calculated from its temperature and density. It should be noted that the plasma temperature can be determined assuming a valid quasi-static state, where at least each ionized species is at local thermal equilibrium (LTE). Therefore the primary objective of this research was to study the parameters of the SCB plasma, mainly the density and temperature, for various bridge dimensions and input currents.

Measurements of the plasma parameters were carried out using several experimental techniques:

-Electrical measurements of the current and voltage on the SCB during the different stages of the burst. These measurements were analyzed using the Spitzer conductivity model to estimate the plasma temperature, and the electrical drift model to estimate the plasma density.

-Optical photography of the plasma burst at known delays from the initiation. The analysis of the optical photography included estimation of the plasma temperature through the measurement of the plasma front propagation velocity.

-Spectroscopic measurements of the radiating species in the plasma burst. The lines measured were Si II-III lines of the bridge, and Ar II lines from Argon gas injected into the plasma. To calculate the plasma density and temperature, both collisional radiative models and the Boltzmann approximation were used.

The plasma properties of the SCB are an electron temperature of ~2.2 eV and an electron density in the range of and Ne=5·1015-1017cm-3, which means the SCB plasma properties are similar to those typical for high pressure arcs. The energy stored in the plasma investigated is ~3.1·1015eV= 0.5mJ, which indicates an ionization efficiency of ~40%.

These properties indicate that the SCB can be used as a micro-plasma generator with a reasonable efficiency.