Research On Temperature/Bias Voltage Regulation Of Spectral Selective Response And Memory Characteristics Of Single CdS Nanoribbon-based Photodetectors

As one of the most studied metal chalcogenides,cadmium sulfide?CdS?has excellent physical and chemical properties and it can be fabricated into a high-performance photodetector.Due to the limitation of the bandgap width of CdS,however,the current research on the photoelectric properties of CdS is mainly focused on the ultraviolet?UV?-visible?VIS?light range,which will greatly limit the application of CdS.In order to solve this problem,the M-S-M structure device was fabricated by using one-dimensional?1D?CdS micro/nano-belts prepared by a high temperature thermal evaporation method,and the photoelectric properties of the device were investigated under different work states.Based on this,a high performance self-powered photodetector was produced as well.The main research results are as follows:?1?Although the work function of silver electrode?Ag?is smaller than that of CdS,the Schottky-like junction is formed between semiconductor and metal because the abundant surface states of nanostructure CdS make it impossible to form a desired ohmic contact.The 1D micro/nanostructure CdS-based photodetectors have good photoelectric response characteristics.Their responsivity is about 10⁷ AW^-1,the photo-to-dark current ratio is 10⁴,and the photoconductive gain is 10⁷.At 20 V high voltage,moreover,the I-V curves show a saturation tendency,which indicates that the conduction mechanism originates from a thermionic emission.?2?The spectral response range of the device can show tunable selectivity to above-and below-bandgap at different temperatures,and can be controlled by temperature and bias.More importantly,the modulated spectral response characteristics can show a good memory behavior of reversible writing and erasing by the temperature and bias voltage,which fully proves temperature/bias control of materials defects and surface states.?3?This paper further discusses the improvement and regulation of nanomaterial defects and surface/interface states by a thermal treatment.It is found that the I-V curve of the whole thermal-treated device exhibits an ohmic contact-like linear relationship,and the diode-like rectification characteristic and the reverse current increase do not occur with the application of bias voltage and illumination.The devices with thermal treatment at one end have different barrier heights at both ends,and therefore the device will exhibit solar photovoltaic effect.Under zero bias voltage,self-powered detection can be realized by adjusting the barrier height at both ends of the device through thermal treatment.The detector produces high photovoltage of 50 mV and photocurrent of 0.5 nA under illumination.It can also detect the range of UV-VIS light,which provides a new idea for the application of CdS nanomaterials.