Ultrafast and low temperature synthesis of highly crystalline and patternable few-layers tungsten diselenide by laser irradiation assisted selenization process

Abstract

Recently, a few attempts to synthesize monolayers of transition metal dichalcogenides (TMDs) using the chemical vapor deposition (CVD) process had been demonstrated. However, the development of alternative processes to synthesize TMDs is an important step because of the time-consuming, required transfer and low thermal efficiency of the CVD process. Here, we demonstrate a method to achieve few-layers WSe 2 on an insulator via laser irradiation assisted selenization (LIAS) process directly, for which the amorphous WO 3 film undergoes a reduction process in the presence of selenium gaseous vapors to form WSe 2, utilizing laser annealing as a heating source. Detailed growth parameters such as laser power and laser irradiation time were investigated. In addition, microstructures, optical and electrical properties were investigated. Furthermore, a patternable WSe 2 concept was demonstrated by patterning the WO 3 film followed by the laser irradiation. By combining the patternable process, the transfer-free WSe 2 back gate field effect transistor (FET) devices are realized on 300 nm-thick SiO 2 /P + Si substrate with extracted field effect mobility of -0.2 cm 2 V -1 s -1. Similarly, the reduction process by the laser irradiation can be also applied for the synthesis of other TMDs such as MoSe 2 from other metal oxides such as MO 3 film, suggesting that the process can be further extended to other TMDs. The method ensures one-step process to fabricate patternable TMDs, highlighting the uniqueness of the laser irradiation for the synthesis of different TMDs.