Semiconductor Films Made On Water

Materials scientists have demonstrated a simple, inexpensive technique for growing ultrathin semiconductor sheets on the surface of water (ACS Nano, DOI: 10.1021/nn2050906). Current methods for making thin films, or nanomembranes, involve growing the materials on a solid substrate such as silicon and then etching away the substrate to release the membrane. This expensive, time-consuming method limits the types of materials that scientists can make because the membrane’s crystal structure ends up matching that of the substrate. In the new method, Xudong Wang and colleagues at the University of Wisconsin, Madison, ditched the usual solid substrate and instead simply mixed two zinc oxide precursors in water and then added a high concentration of the surfactant sodium dodecyl sulfate. In a few hours, the water was covered with a zinc hydroxy dodecyl sulfate membrane a few hundred nanometers thick. The researchers then scooped up the film using a silicon or carbon substrate and heated it to produce a final zinc oxide film. Wang thinks the method holds promise for producing flexible electronics, light-emitting diodes, and medical sensors.