Writing with catalytic ink shapes ZnO thin films
Writing with catalytic ink shapes ZnO thin films lead image
Unique properties, including high exciton binding energy and a strong piezoelectric effect, make zinc oxide (ZnO) nanostructures ideal for a variety of applications in optoelectronics, sensors, transducers and more. The geometry of a ZnO thin film controls its properties but controlling that geometry can be challenging. The authors have developed a new way to make ZnO thin films that allows more control of the final shape.
The two-step process, mask-free direct-write fabrication, combines direct-write patterning and chemical vapor deposition. First, the authors used AFM-style cantilever tips coated with iron, the catalytic ink, to draw their desired shape for ZnO on a silicon surface. Then during deposition, ZnO vapors crystallized only where the catalytic ink was drawn.
Prior to this research, making ZnO thin films with controlled geometries required either a master template called a mask, or carving ZnO into the desired shape after synthesis. The new method does not require a mask; the catalytic ink is the template. Author Irma Kuljanishvili said that this process allows for more fine-tuning to ZnO geometry, while maintaining desired film thickness and width.
The authors also showed that ZnO is compatible with other materials by using their process to synthesize ZnO on graphene and boron nitride, creating multilayered thin films with nearly 2-D thickness. Each layer plays a specific role: Graphene, for example, can provide a pool of fast-moving charges to the ZnO layer, while boron nitride is insulating. The layered architecture could improve device photosensitivity and generate more power as well. They plan to add to the library of materials that can be layered with ZnO, and would like to examine if the catalyst ink could contribute new functionality.
Source: “Mask-free fabrication and chemical vapor deposition synthesis of ultra-thin zinc oxide microribbons on Si/SiO2 and 2D substrates,” by Dheyaa Alameri, Leonidas E. Ocola, and Irma Kuljanishvili, Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films (2018). The article can be accessed at https://doi.org/10.1116/1.5036533 .
