Design and fabrication of a dual-resistive evaporation system controlled using labview
Keng’werere, Joshua Mose
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ABSTRACT Vacuum evaporation is one of the mostly commonly used method for depositing thin films of metals, semiconductors or dielectrics on various substrates. Either molecular beam epitaxy (MBE), electron-beam (e-beam) or resistance heating is employed for heating the evaporant source material in vacuum. Resistive evaporation is the oldest method of depositing thin films in magnetron sputtering systems. As a problem common to deposition of films using resistive evaporation, the source materials are subjected to the same temperature and pressure condition which means that only materials of the same element can be evaporated to form a thin film. Therefore, two or more elements in different evaporation boats in the same vacuum cannot be evaporated at the same time to form a uniform thin film of an alloy or compound. This forces a researcher to use alternative methods such as molecular beam epitaxy or e-beam evaporation to deposit thin films of compounds or alloys. These methods are not economical for small laboratory research work. This is because the equipment involved is complex and costly partly because of the complexity of achieving Ultra-high and clean, vacuum conditions. The parameters involved in molecular beam epitaxy are many and therefore difficult to control. This leaves resistive evaporation as the only economical option for small laboratory and research work for thin film applications. To solve the problem of deposition of films of alloys or compounds using resistive evaporation, a dual-resistive evaporation system was designed. It involved the use of two evaporation boats inclined to each other in the vacuum chamber at an angle of 45o to allow maximum mixing of evaporants before deposition to form a uniform thin film. The system had a designed and fabricated power supply (to run the electronic circuitry) with a margin of error of ± 1 %. The temperature measurement range of the system range from -200oC to +1350oC. Its response time was 0.10 seconds. The system measured temperatures within accuracy of ±2.0oC.The system was controlled using LabVIEW application software.