Measurement of AC Ion Current from Ionizer by Using Faraday Cage
AC ionizer with high frequency became more common in semiconductor industries. Neutralization mechanism of such equipment is, however, not well understood because the measurement of extremely small ion current is interfered by AC induction. Our attempt is to use the Faraday cage that is directly connected to an AC ionizer. At frequencies of 1 Hz and 10 Hz, clear pulse shape ion currents were measured. The amounts of transported charges increase with both applied voltage and pressure. The effect of pressure is more significant than voltage. At higher frequency, the measured current changes from pulse to sinusoidal shape. From the delay time of 1 kHz, the average air velocity between the needle and Faraday cage was calculated. From DC corona measurement inside the nozzle, it became clear that the portion of transported charge to the Faraday cage is quite small.
A Low-Voltage Microwave Plasma Ionizer With Reduced Electric Overstress Due to Displacement Current Coupling From a High-AC Voltage Source
A low-voltage microwave plasma ionizer was proposed as an ac-type ionizer. A structure to improve the ionizing performance and stability of the plasma ionizer was proposed. A dedicated source module was also designed to generate microwave power for the ionizer. The ionizing performance of the proposed ionizer was experimentally investigated using a charged plate monitor, and the factors required to achieve good performance were found. The risk of electric overstress due to displacement current coupling from the ac voltage source in the ionizer was then investigated. It was experimentally confirmed that the proposed microwave plasma ionizer has a much lower risk of electric overstress at a close distance than a conventional ac-type corona ionizer.
Selective etching of InP in NaF solution
Abstract The crossing porous structure of InP has been obtained by electrochemical etching in NaF solutions. The behavior of the periodic oscillation occurs at different potential ranges for the different concentrations of solutions, and it will disappear with the concentration of the solution decreased. The scanning electron microscope (SEM) image shows that the pores have two directions on the surface and are perpendicular to each other. The two directions are assigned to [0 1 1] and [ 0 1 ¯ 1 ], respectively. The SEM image of the cross-section also shows that the two directions are assigned to [1 1 1]B and [ 1 1 ¯ 1 ¯ ]B. Both are due to the selective etching of F− ions. The crossing porous structure of InP is a very promising feature for the three-dimensional structure of III–V compound semiconductors for photonic band gap materials.