|M.Sc Student||Zvulun Eran|
|Subject||Shockwave Generation by Electrical Explosion of a|
Semiconductor Thin Film Sub-Millimeter Bridge
|Department||Department of Physics||Supervisor||Professor Yakov Krasik|
|Full Thesis text|
Semiconductor bridge is a device used in various miniaturized systems for ignition of different energetic materials. This device originated in the late 60's and was improved during the 80's. It is comprised of a highly doped, polycrystalline, silicon element, and manufactured using microelectronic fabrication methods. By means of a current pulse, the bridge is rapidly heated and during a time scale of less than a microsecond, reaches melting, then vaporization and finally ionization, forming a plasma spark. There are two mechanisms by which the plasma ignites or detonates the energetic material placed above the bridge. The first mechanism is the plasma temperature which ignites the materials by heat transfer. The second mechanism is the rapid pressure buildup during the microsecond expansion of the bridge.
There are several studies which were carried out, investigating the plasma properties of the bridge, including plasma density and temperature by means of both probes and spectroscopic measurements. Much research was done on the electrical characteristics of the device. On the other hand, very little research can be found regarding the pressure generated by the semiconductor bridge explosion. Such a research is important for the investigation of the pressure ignition mechanism.
In the present research, we have studied the semiconductor bridge device immersed in an incompressible, transparent media, namely water, and investigated the properties of the shock waves emanating from the device shortly after the explosion. Electrical measurements were performed and compared to previous studies, and the explosion was imaged using a direct camera imaging. The SW was imaged both using shadow imaging and reference beam interferometry methods; both optical methods used a laser backlight. The results of these measurements were agreed between each other and were used as input parameters to a self-similar water flow model which allows one to obtain pressure and density distributions between the SW front and the expanding boundary of the plasma which is formed as a result of the bridge explosion. It was shown that pressure up to 8?108 Pa is generated at the front of the expanding plasma.
The experimental and numerical model results showed that the energy of the generated water flow exceeds significantly the energy deposited into the exploded device. It is supposed that the source of the additional energy could be the combustion of aluminum and silicon atoms released in gas-form during their oxidation in contact with the water, which acts as an oxidizing media.