Preparation Of Tellurium Micro-nano Material And Its Application In Sensors

This paper studies the synthesis and the characterization of semiconductor tellurium micro-nano material, the preparation and measurement of some sensor. The main contents are as follows:(1) Using the hydrothermal process, we synthetized the tellurium nanorods, and other morphology of tellurium nanomaterials by controlling the different surfactants, and their structure were characterized;(2) Tellurium nanorods were filtrated onto the flexible nylon membrane, the flexible photoconductor sensor was prepared. We proposed a simple physical model to analyze its performances. Aditionally, a photoconductor sensor based on a single nanorod was prepared and investigated.(3) Flexible strain sensors have been prepared by placing a single ultralong tellurium micrometer wire on a flexible polystyrene substrate and bonded with silver paste. We explained the mechanism about the strain sensor.(4) The chemical sensor based on a single ultralong tellurium micrometer wire was successfully prepared, which had response to humidity and alcohol, respectively. We got the following main results:1.1. In the hydrothermal process, different morphologies of tellurium nanomaterials were synthetized by controlling the surfactants. When SDS and NaCl were added, tellurium nanorods show very uniform sizes with lengths ranging from300to600nm. their widths varied from30to50nm. The electron diffraction pattern was obtained on a single tellurium nanorod, which indicates that the nanorod is single-crystal. The ultralong tellurium microwires were prepared by hydrothermal process, the biggest length is10mm, which we have never seen in other reported work.2. The tellurium nanorods were filtrated onto the flexible nylon porous membrane and packed with PMMA(polymethyl methacrylate). Then the flexible photoconductive sensors were prepared, which can be applied in photo detection on the curved surfaces and other non-plannar faces. Because of its narrow Energy band gap, Te has response to different waves of lights. In this paper, we used the white light as the power source, the optical film had an obvious photoconductive response, the switch ratio was related to the thickness of the photosensing materials. Meanwhile, we used a simple physical model to explain the relation of the switch ratio and the film thickness. Like the improper fractional function, the switch ratio decreases as the thickness of films increases, and there is a theoretical maximum value and lower limit value of1. For the photoconductor sensor based on a single Te nanorod, which was fast response to light, the photoswitch was remarkable.3. Two types of flexible strain sensor devices based on a single ultralong Te micrometer wire have been demonstrated. Te micrometer wire was placed on the PS substrate and bonded with silver paste. The current increased as the compressive strain increased and decreased as the strain decreases in our two sensors. The stretch or compressive strain produces symmetric effects on the sensor of back to back Schottky barrier contacts. The Schottky barrier heights change as stretch strain and compressive strain. For strain sensor with single Schottky barrier, the current increased more significantly with the compression strain at the negative voltage. For the first sensor in our work, The GF is approximately107using the formula of (ΔR/R)/ε. But for the second strain sensor with single-end Schottky barrier in our work, The GF is approximately1000. So, the sensor with single Schottky barrier is more suitable for detecting the strains. And this device showed remarkable. The piezoelectric current and voltage were detected. Flexible Te/PDMS composites pressure sensor showed significant response to pressure. The resistance of the composites decreased three orders of magnitude with10N.4. Chemical sensors based on the single ultralong Te micrometer wire have been demonstrated, which can be used to detect humidity, alcohol. Like other reported works about p-type semiconductor alcohol sensor devices, the current decreased when the sensor touched alcohol. This sensor showed various Ⅰ-Ⅴ behaviors in water, ethanol, methanol, and isopropanol due to their different abilities for providing free electric electrons, which can be applied in detecting different solutions. The response time was rapid in methanol and the current decreased by three orders of magnitude, and the changes of resistance were remarkable. The sensor also presented different shapes of I-V behaviors in different concentrations of alcohol aqueous solutions. Te is a p-type semiconductor with holes as the majority carriers, the p-type semiconductor materials become low conductive due to the concentration of holes decrease in alcohol solutions. The chemical sensor can be used in humidity detector. The current decreased as the humidity increased. When the sensor was applied with strains, the sensitivity and resolution ratio increased.