Synthesis and characterisation of carbon nanotubes and zinc oxide composites: sub-millisecond UV response

In this study, various morphological configurations of zinc oxide (ZnO) were fabricated onto the carbon nanotube (CNT) network by influencing the pH levels of the growth solution (specifically, pH values of 5, 7, and 9). The CNT network was fabricated using the thermal chemical vapour deposition method, while the ZnO nanostructure was synthesised using the chemical bath deposition technique. The growth of the multi-walled CNT network was confirmed by utilising field emission gun transmission electron microscopy and Raman spectroscopy. On the other hand, the investigation of the distinct morphology of pH-dependent ZnO on the CNT network was confirmed by employing field emission scanning electron microscopy. Three specific types of UV photo-sensing devices were manufactured utilising the synthesised samples, and a comprehensive investigation was conducted to analyse their UV-responsive characteristics. The analysis of the UV-responsive behaviour involved subjecting the devices to an array of UV LEDs. The intensity of the 365 nm UV LED array varied between 18.7 and 95.22 μW/cm 2 . For a device fabricated with ZnO grown at pH 5, the maximum photocurrent was recorded to be 40.7 ± 0.26 μA, and the external quantum efficiency was 5359 ± 73%. The device also showed remarkable responsivity to UV radiation with a pulsing frequency of 500 Hz. Exceptional response time and recovery time of 316 μs and 364 μs have been measured for the device.