We report fabrication and characterization of metal-semiconductor-metal photoconductive detectors based on Al-doped ZnO thin films fabricated by radio frequency magnetron sputtering.Optical and structural properties of the thin films were characterized using various techniques.At 6 V bias,a responsivity higher than 4 A/W in the wavelength shorter than 350 nm was obtained,and this responsibility dropped quickly and reached the noise floor in the visible region.Transient response measurement revealed that the detector had a fast photoresponse with a rise time of 9 ns and a fall time of 1.2 μs.
SUN JianDAI QianLIU FengJuanHUANG HaiQinLI ZhenJunZHANG XiQingWANG YongSheng
Ag/ZnO/Pt structure resistive switching devices are fabricated by radio frequency （RF） magnetron sputtering at room temperature. The memory devices exhibit stable and reversible resistive switching behavior. The ratio of high resistance state to low resistance state can reach as high as 102. The retention mea- surement indicates that the memory property of these devices can be maintained for a long time （over 104 s under 0.1-V durable stress）. Moreover, the operation voltages are very low, -0.4 V （OFF state） and 0.8 V （ON state）. A high-voltage forming process is not required in the initial state, and multi-step reset process is demonstrated. Resistive switching device with the Ag/ZnO/ITO structure is constructed for comparison with the Ag/ZnO/Pt device.
Ag/ZnO/Zn/Pt structure resistive switching devices are prepared by radio frequency magnetron sputtering.The ZnO thin films are grown at room temperature and 400 C substrate temperature,respectively.By comparing the data,we find that the latter device displayed better stability in the repetitive switching cycle test,and the resistance ratio between a high resistance state and a low resistance state is correspondingly increased.After 104-s storage time measurement,this device exhibits a good retention property.Moreover,the operation voltages are very low:-0.3 V/-0.7 V(OFF state) and 0.3 V(ON state).A high-voltage forming process in the initial state is not required,and a multistep reset process is demonstrated.
A high performance heterojunction organic ultraviolet photodetector based on NPB and Bphen has been fabricated. A trans- parent conducting polymer PEDOT：PSS coated quartz substrate instead of ITO coated glass substrate as anode is propitious to detect shorter wavelength ultraviolet light. As a result, the device shows a low dark current density, a high responsivity of 502 mA/W and a detectivity of 2.67x1012 cm Hz1/Zfw which is illuminated by a 220 nm ultraviolet light with an intensity of 1.6 mW/cm2. Moreover, the performance of the PEDOT：PSS transparent electrode device is better than the semi-transparent A1 electrode device electrode because of the higher transmittance and electrode properties.
We fabricate an ultraviolet photodetector based on a blend of poly （N-vinylcarbazole） （PVK） and 2- tert-butylphenyl-5-biphenyl-1, 3, 4-oxadiazole （PBD） using spin coating. The device exhibites a low dark current density of 2.2×10 3 μA/cm 2 at zero bias. The spectral response of the device shows a narrow bandpass characteristic from 300 to 355 nm, and the peak response is 18.6 mA/W located at 334 nm with a bias of –1 V. We also study the performances of photodetectors with different blend layer thicknesses. The largest photocurrent density is obtained with a blend of 90 nm at the same voltage.
Ag/ZnO/Zn/Pt structure resistive switching devices are prepared by radio frequency magnetron sputtering. The ZnO thin films are grown at room temperature and 400 ℃ substrate temperature, respectively. By comparing the data, we find that the latter device displayed better stability in the repetitive switching cycle test, and the resistance ratio between a high resistance state and a low resistance state is correspondingly increased. After 104-s storage time measurement, this device exhibits a good retention property. Moreover, the operation voltages are very low： -0.3 V/-0.7 V （OFF state） and 0.3 V （ON state）. A high-voltage forming process in the initial state is not required, and a multistep reset process is demonstrated.
