Construction And Properties Of New-type UV Photodetectors Based On Graphene/TiO₂ Schottky Juntion

Titanium oxide?TiO₂?has received special research interest at home and abroad in the field of photoelectric detection because it is a wide band-gap semiconductor material which can strongly absorb light illumination in UV region and has stable physical and chemical,excellent photoelectric properties,as well as no pollution to the environment.In this thesis,we conducted a systematic study on two kinds of high-performance photodetectors based on TiO₂ and graphene.The main research results are as follows:1)The TiO₂ nanotube?TiO₂NT?arrays were prepared via a potentiostatic anodization method.The fabrication of a single-layer graphene?SLG?-TiO₂ NT array heterostructures ultraviolet photodetector?UVPD?was finished by transferring chemical vapor deposition derived SLG on the surface of TiO₂ NT array.The subsequent investigations are focused on the morphology,electrical properties and photoelectric properties of the PDs.The PD based on TiO₂ NT array annealed in air showed a better rectifying behavior and was highly sensitive to UV light irradiation.The PD based on a medium tube length of 9.6 ?m exhibited the highest device performance with responsivity?R?of 0.126 A/W,detectivity?D*?of 3.3×1011 cm·Hz1/2·W-1 and on-off ratio of 1868.2)The dissertation proposed a simple Schottky junction UVA and UV PD by transferring SLG film onto the surface of commercial single-crystal TiO₂ wafer for UV light detection.The PD excellent stability,reproducibility and spectral selectivity with peak sensitivity at 410 nm while virtually blind to illumination with wavelength less than 330 nm,or wavelength more than 490 nm.The on-off ratio is as high as 6.8×104.In addition,the device was able to probe fast-switching optical signal with frequency as high as 400 Hz with very good reproducibility.The rise/fall times were estimated to be 0.74 and 1.18 ms,which are far faster than most other TiO₂ based devices.The totality of the above results signifies that the SLG-TiO₂ Schottky junction photodetectors may have promising application in future high-speed,high-sensitivity optoelectronic nanodevices and systems.