A compact unified sample stage for 2D materials ultra-thin film growth and in situ optoelectronic measurements in UHV

The investigation of optoelectronic devices based on atomically thin two-dimensional layered materials is often hindered by ambient contamination and low efficiency of material growth and device fabrication. We propose a versatile ultra-high vacuum apparatus with a compact unified sample stage designed for the fast optimization of ultra-thin 2D material film preparation and in situ optoelectronic transport measurements. The stage unifies the functions of (ultra-high vacuum) UHV evaporation, film resistance monitoring, and optoelectronic transport measurement. Unique mini-evaporators have been developed for the co-deposition of source materials in a compact space. Radiation heating and temperature measurement have been integrated in the stage for sample treatment. Insulating substrates with pre-deposited electrodes can be mounted on a specially designed flag-type sample holder with multiple contact pins for resistance monitoring during materials growth, as well as electrical transport measurement under varying heating temperatures. External light source illumination can be conducted through an optical entrance window in the chamber, which enables the in situ optoelectronic transport measurements. The performance of the apparatus has been validated by the successful metallic (Au, Cr, Pd) and semiconductor (SnSe) film resistance monitoring, the excellent photoresponse of SnSe films in UHV, and the temperature-dependent resistance evolution of the 2H-MoTe2 film with heating-induced Te vacancies. This UHV system based on the compact unified sample stage provides a new method and apparatus that could facilitate the investigation of various sensitive 2D layered materials for optoelectronic devices.