Research on real-time optical flux monitoring technology in molecular beam epitaxy based on LED light source

In this study, an LED with a spectral width between narrow and wide spectrum light sources was employed as the meso-spectral light source solution. Based on atomic absorption, non-invasive real-time multi-element flux intensity measurement and monitoring were achieved during molecular beam epitaxy growth. This approach features self-calibration capabilities, effectively suppressing fluctuations and drifts in the light source and optical path without requiring an additional calibration path, thereby demonstrating strong robustness. By integrating precise calculations of the epitaxial growth rate of the calibration plate, the light absorption of the proposed method was calibrated to the flux intensity of the cells. Under experimental conditions where flux intensity was adjusted by the temperature gradient of the cell, the characteristic spectral light absorbance signal exhibited a significant linear correlation with the plasma gauge current signal (Spearman's τ=1.0, p<0.01). Through the analysis of the Ga flux monitoring data, the coefficient of variation of its light absorption signal was 5.85%, confirming the reliability of the beam monitoring scheme. This paper also explores the advantages of using an LED light source in molecular beam epitaxy flux monitoring systems, provides a detailed analysis of signal errors and drift caused by atomic deposition, and proposes optimization methods for instrument structure in practical applications. A key feature of this study is the replacement of traditional hollow cathode lamp or inefficient thermal light sources with a high-efficiency, long-life, and low-cost LED light source. The monitoring process is simplified through the nearby point reference method, enabling simultaneous monitoring of multiple elements. This approach offers a cost-effective and practical solution for flux monitoring, with significant application potential in MBE growth rate monitoring and stability closed-loop control.