Rhenium disulfide (ReS2), which possessed a unique direct band gap from the bulk to monolayer, played a very important role in establishing optoelectronic devices, while the rapid recombination of electron-hole pairs might hinder its further applications. Therefore, to improve its photocurrent performance, a bimetallic co-chamber feeding atomic layer deposition (ALD) with a precise dose regulation strategy was used to fabricate MoS2-ReS2 heterojunctions with a controllable Mo-to-Re ratio in this work. Furthermore, because of the controlled addition of Mo atoms, the electron-transfer capacity, carrier mobility, and photocurrent response of these heterojunctions were significantly improved among which the sample obtained under 100 supercycles (one supercycle for this sample consists of the following in turn: one ReCl5 pulse, one H2S pulse, one ReCl5 pulse, one MoCl5 pulse, and one H2S pulse; the real Mo-to-Re ratio Rr = 57.9%) exhibited the best photocurrent response. Due to the significant improvement in optoelectronic performance, a photoelectrochemical (PEC) biosensor with the basis of the above optimized sample could achieve the ultrasensitive detection of cancer-related miRNA-21 ranging from 10 aM to 1 nM with a low detection limit of 2.8 aM.
Keywords: ALD; MoS2; ReS2; heterojunctions; miRNA-21.