Low power silicon evaporation source—Construction, performances, and applications

Abstract

The construction of a low power silicon evaporation source for thin film deposition applications is proposed in this article. A few differently shaped tungsten filaments were mounted inside a quartz glass crucible, which assured an effective heating of silicon wafer pieces. The sublimation process was monitored at filament powers in the range of 8–22 W, which corresponds to temperatures far below the melting point of Si. The operation of the evaporation source requires only the use of a low voltage power supply. All considered models of evaporation sources are characterized by an easy construction. The measurements carried out with the use of a quartz crystal microbalance sensor enabled to determine the deposition rate at different filament powers for all constructed Si sources and confirm the long-term stability of the silicon flux. The experimental data exhibit the Polany–Wigner dependence of the deposition rate as a function of inverse of power at higher filament powers. Auger electron spectroscopy was used to monitor the deposition of Si on Ag(100) under constant silicon flux. The Auger signal recorded from Si and Ag reflects the growth of subsequent silicon layers. This enabled the determination of the Frank–van der Merwe growth mode of Si on Ag(100) at early stages of growth, the formation time of one Si monolayer, and, thus, the deposition rate. The presented designs of the Si source exhibit long time stable evaporation fully controlled by the applied filament power, which is crucial in the precise adsorption of ultrathin Si layers.