Research on Alkali Metal Evaporation Source Based on Glass Tube Sealing Technology

Alkali metal doping plays an important role in molecular beam epitaxy of semiconductor materials. The existing alkali metal evaporation source uses alkali metal release agent as raw material, and the amount of alkali metal obtained by evaporation is small. Therefore, an evaporation source for obtaining a large amount of alkali metal by sealing alkali metal elements with glass tubes was independently developed, the amount of alkali metal evaperation can reach 2 g, much higher alkali content than existing evaporation sources(5 mg). In the glove box, the alkali metal element is placed in the glass tube with a ball valve at the opening. After take out, it is connected to the vacuum pump group for pumping treatment, and then the glass tube is rotated and heated to complete the drawing seal. The packaged glass tube is placed inside the evaporation source, and when used, the rotating baffle breaks the glass tube orifice for evaporation coating. The alkali metal evaporation source is mainly composed of raw material placement component, filament heating component, rotating baffle component and power supply temperature control component. The nonlinear tuning PID control of the heating power supply circuit achieves the goal of controlling the temperature error of the evaporation source within ± 0.1 K within 5 minutes.Stable temperature can improve the stability of molecular beam current, and thus improve the uniformity of the film. Experiments show that the alkali metal evaporation source can evaporate alkali metal, nonlinear tuning PID regulator can meet the requirements of molecular beam epitaxy growth on evaporation source temperature control accuracy.