Low temperature insertion of energy levels into the ZnO nanorod's bandgap by nanotube conversion

• Large arrays of highly oriented ZnO nanotubes have been fabricated and characterized.
• Very high intentional level of defects was introduced to the nanorods.
• The conversion of nanorods to nanotubes must be monitored all the way to the end.
• Long conversion decreased the number of surface levels in the ZnO's bandgap.

Finding a material for complete absorption and emission of the visible range of the electromagnetic spectrum has been always a challenge for optoelectronic research groups. One dimensional zinc oxide (ZnO) nanostructures with wide bandgaps have been proposed as candidates to solve this problem. We have developed, characterized and optimized an approach to create a very high level of intentional defects or surface states to fill ZnO nanorods bandgap energy diagram. This process was performed systematically at a low temperature with high throughput on the hexagonal ZnO nanorods. These nanorods were 2.5 μm in length and grown with chemical bath deposition. The best conversion process occurred in a 2 M KCl solution at 90 °C for 5 h. ZnO nanotubes have presented a reasonably high performance photon collection and emission.