MgAl/PbPc/Cu Organic Thin-Film Diode Preparation and Gas-Sensing Characteristics Analysis

Thin-film diode structure is MgAl/PbPc/Cu if lead phthalocyanine is taken as organic semiconductor gas-sensing material with methods such as vacuum thermal evaporation or magnetron sputtering. Use Keithley 4200 semiconductor instrument and Gas-sensing measurement system to analyze gas-sensing characteristic of Schottky diode device, the sensitive degree of NO2 with different density can be compared through theoretical analysis of measured current and voltage data. The measurement result shows: when the device is placed in 10ppm NO2 environment, after 74 minutes, forward current is decreased by 65 times, the corresponding MgAl/PbPc Schottky barrier height rises about 20meV. Reversed current of the device is 4 times larger because the increase of minority carrier electron number in PbPc thin-film is being absorbed by NO2.

Ringing Effect and Reversed Current Analysis of RC-Pulse Generator in Electrical Discharge Machining

RC-pulse generator has a simple structure and it is easy to be made and repaired. Especially RC-pulse generator can provide high frequency and low energy discharges. Therefore RC-pulse generators are used in micro-EDM field. But its high tool wear ratio and low efficiency restrict its applications. Ringing effect is considered to have effect on the defects. This research was done to study the ringing effect in electrical discharge. Taguchi method was used and discharge curves of voltage and current were recorded and analyzed. Ringing effect plays a key role in discharges and reversed current. A waveform model established with ringing effect theory is almost the same as the waveforms recorded in the experiment. Reversed current exists in almost a half time of discharge period which is the representation of ringing effect. Suitable process parameters can reduce reversed current and proper improvements could eliminate reversed current which will reduce the tool wear ratio and increase the efficiency in RC-pulse generator.