The emerging field of flexible electronics is bursting with significant findings that have great potential for wearable sensors, e-skins, flexible displays, and energy conversions. One of the inexorable trends is development of large-scale flexible electronics with high density and good performance so as to satisfy the multitudinous precise and advanced specialized purposes. Among efforts of various materials, such as organic semiconductor, carbon nanotubes, and zinc oxide (ZnO) thin-films, considerable attentions have been paid to the rising two-dimensional (2D) materials, such as MoS2. This extremely thin material has strong mechanical robustness and low-cost wafer-scale synthesis technology, making it more suitable for building large-scale flexible devices.
Recently, we design and fabricate flexible electronics based on 4-inch monolayer MoS2 wafers. Those MoS2 wafers were achieved by epitaxy techniques in a multisource chemical vapor deposition (CVD) system. During the growth, substrates were vertically placed in the growth chamber to guarantee source concentration homogeneity along the horizontal direction. Benefiting from the new multisource design and the optimization of the growth process, we successfully realized a high material uniformity across the entire 4-inch wafer and a domain size greater than 20 μm on average.
We build large-scale flexible field-effect transistors (FETs) arrays and various logic circuits. These devices are of high quality and reproducibility. The transistors are highly integrated with a device density of 1,518 transistors per cm2 and a yield of 97 %, exhibiting high on/off ratios of1010, current densities of around 35 μA μm-1, mobilities of around 55 cm2V-1s-1, and a moderate flexibility of 1%. We further demonstrate the diversity of such MoS2 transistors for integrated logic circuits application, such as inverters, NOR gates, NAND gates, SRAMs, AND gates and 5-stage ring oscillators by integrating 2, 2, 3, 4, 5 and 12 transistors, respectively. Notably, we achieved a high voltage gain of 43/107 at a bias voltage of Vdd=2V/4V for an inverter, and a stable oscillation frequency of 13.12 MHz at Vdd=15V for a 5-stage ring oscillator. These values are comparable to the current state-of-the-art flexible devices made of various semiconductor materials.
If you are interested in our work, please refer to the paper published in Nature electronics: “Large-scale flexible and transparent electronics based on molybdenum disulfide field-effect transistors” following the link:https://doi.org/10.1038/s41928-020-00475-8