Synthesis And Negative Photoconductivity Of Hexagonal Tellurium One-dimensional Nanostructures

Tellurium,as a direct narrow bandgap semiconductor,has a band gap of 0.34 eV.It possesses excellent physical and chemical properties.Because of large surface-to-volume ratio and well carrier transport channels,tellurium nanomaterial is a very important semiconductor optoelectronic material,thereby there are broad prospects of application in the field of semiconductor nano-optoelectronic devices.Te nanowires have been successfully synthesized by a simple hydrothermal method.The individual Te nanowire devices with the structure of Au-Te nanowire-Au has been fabricated by standard photolithography technique and lift-off pro-cess.We studied the Te nanowire optoelectronic devices under laser irradiation with difference wave length and intensity.The research results are listed as follows:(1)Tellurium nanowires with the characteristics of high purity,well monodis-persity and good crystallinity were synthesized by hydrothermal method.Au/Te nanowire/Au nano-devices were fabricated by standard photolithography tech-nique and lift-off process.By analyzing the output characteristic and transfer characteristic of the nano-device field effect transistor(FET),it is found that tel-lurium nanowire is a typical P-type semiconductor with the mobility of hole is 387.777 cm2v-1s-1 at room temperature and under air condition.The Ids-Vds curves show a straight line through the origin at different gate voltages,indicating good ohmic contact between the electrodes and the nanowires.(2)The effects of different wavelengths on the photoconductivity of Te nanowires were studied.In the air and vacuum environment,the photoconductivity of tel-lurium nanowire(with diameter of 612 nm)irradiated by red light(A=650 nm)is negative.When irradiated by green light(A=532 nm)and blue light(A=450 nm),the tellurium nanodevices exhibit positive photoconductivity.The results show that the Te nanowire negative photoconductivity depends on the wavelength of the light,and have no concern with atmosphere.(3)The effect of diameter on the photoconductivity of Te nanowires was investigated.When the diameter of the tellurium nanowires is 467 nm,the pho-toconductivity of the devices is negative at three different wavelengths(450 nm,532 nm and 650 nm),which is very different from that of the tellurium nanowires with a diameter of 612 nm.Therefore,we find that the photoconductive behavior of the nanowires is related to its size.(4)The effects of different laser intensities on the photoconductivity of Te nanowires were compared.When irradiated by blue light(A=450 nm)with differ-ent luminous intensity in the air,the samples exhibit positive photoconductivity.Therefore we can see that the negative photoconductivity of the samples does not depend on the light intensity.In summary,the photoconductivity of Te nanowire depends on the wavelength of light and the diameter of nanowires,rather than gas adsorption or light inten-sity.Whether the negative photoconductivity is caused by the interaction between surface plasmon and electrons needs further study.