The concept of transient electronics emerged to minimize E-waste. Ideal transient electronics operate equivalent to conventional electronics, and the entire device disintegrates after a stable operation period. The discovery of graphene opened a new realm of two-dimensional(2D) material science. 2D materials appealed to the attention of the scientific community on account of their combinations of electronic, optical, robust mechanical, and chemical properties that are characteristically distinct from their parental 3D materials. Furthermore, the diverse inclusion of different electronic/optical properties of 2D material makes them advantageous entrants towards novel electronics/ optoelectronics applications. Near atomic thick two-dimensional (2D) molybdenum disulfide (MoS2) terminated with sulfide anions poises minimal toxicity. However, 2D TMDs integrated optoelectronic transient devices and their intrinsic transient characteristics are not extensively explored. A green approach, such as water-assisted integration of 2D MoS2, only requires water and paves the way for integrating 2D MoS2 into any arbitrary substrate, i.e., biodegradable cellulose and Ca-alginate for potential transient electronics. Our studies outlined the feasibility of integrating 2D MoS2 and biodegradable and biocompatible metals/substrates in transient electronics. We drafted a water-assisted green integration of 2D MoS2 on biodegradable cellulose and curved/ tubular natural rubber substrate. We also edged the integration of calcium alginate on 2D MoS2 as an active device component. We demonstrated proof-of-concept 2D MoS2 integrated transient electronics, i.e., pressure sensor, photodetector, biodegradable electrolyte gated 2D MoS2 field effect transistor (FET). In this study, we outlined the dissolution characteristics of 2D MoS2 using food ingredient baking soda buffer solution; furthermore, we studied a novel approach of ultraviolet, UV-triggered degradation of 2D MoS2 on calcium alginate incorporated with riboflavin polymer matrix. Overall, our study sketched the likelihood of integrating 2D MoS2 towards transient electronic devices, and transient characteristics of 2D MoS2 enabled on biodegradable polymers.

2D semiconductors are one of the most promising materials for next-generation electronics. Realizing continuous 2D monolayer semiconductors with single-crystalline structure at the wafer scale is still a challenge. We developed an epitaxial phase conversion (EPC) process to meet these requirements. The EPC process is a two-step process, where the sulfurization process was carried out on pre-deposited Mo-containing films. Traditionally, two-step processes for 2D MoS2 and other chalcogenides have suffered low-quality film and non-discontinuity at monolayer thickness. The reason was regarded as the low lattice quality of precursor film. The EPC process solves these problems by carefully preparing the precursor film and carefully controlling the sulfurization process. The precursor film in the EPC process is epitaxial MoO2 grown on 2″ diameter sapphire substrate by pulsed laser deposition. This epitaxial precursor contains significantly fewer defects compared to amorphous precursor films. Thus fewer defects are inherited by the EPC MoS2 film. Therefore, EPC MoS2 film quality is much better. The EPC prepared monolayer MoS2 devices to show field-effect mobility between 10 ~ 30 cm2·V-1s-1, which is the best among the two-step process. We also developed a CLAP method further to reduce the defects in the precursor oxide film; thus, in-plane texture in the thicker MoS2 film was eliminated, and a single-crystalline structure was obtained in the wafer-scale MoS2 films. The potentially feasible technique to further improve the 2D film quality is pointed out for our next research plan. Meanwhile, the epitaxial phase conversion process was proposed to be as a universal growth method. Last but not least, we demonstrate several potential applications of the wafer-scale single-crystalline MoS2 film we developed, such as logic circuits, flexible electronics, and seeding layer of van der Waal or remote epitaxial growth.

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