Ultraviolet detection with ultrathin ZnO epitaxial films treated with oxygen plasma

Abstract

We have investigated the effects of oxygen plasma treatment on the UV detection properties of ultrathin (∼20-nm-thick) ZnO epitaxial films. Highly epitaxial ZnO films grown on sapphire were exposed to oxygen-radical-rich, inductively coupled plasma, and then their UV detection properties were characterized at 325 nm wavelength using a photoconductor structure. The oxygen plasma treatment is found to dramatically enhance the UV detection properties of ZnO, reducing the decay time constant (to below 50 μs) and increasing the on/off ratio of photocurrent (to over 1000) with high UV responsivity (1–10 A/W). This result, in conjunction with the microstructural and electrical characterization results, indicates that the plasma treatment efficiently suppresses the chemisorption sites (primarily the oxygen deficiency sites) on surface and also the oxygen vacancies in ZnO, therefore results in major reduction of the chemisorption effects and the dark current, respectively.

Microscopic origins of the surface exciton photoluminescence in ZnO nanostructures

“…18,20,[37][38][39][40][41][42] However, as reported in sections 3.2 and 3.3 above, the absence of any significant or consistent changes in the SX peak either following both O and Ar plasma treatments or after illuminating with UV light in high vacuum lead us to conclude that the SX is not due to adsorbed O/O 2 on the nanostructure surfaces.…”

New detection systems for UV solar reference scanning spectroradiometers

“…Moreover, ZnO-based photoconductors have already shown dark currents as low as 400 pA and responsivity in the range of 1-10 A/W [8].…”

Ultraviolet detectors based on ZnO films by thermal oxidation of Zn metallic films

“…As a wide bandgap semiconductor, ZnO is a promising material for potential applications such as ultraviolet (UV) light emitting diodes, laser diodes, and photodetectors [1][2][3][4][5][6]. UV detection has many applications, such as air quality monitoring, gas sensing, missile plume detection, etc.…”