Preparation And Doping Of Ultrathin Wall Zinc Oxide Single Crystal Microtubes

ZnO is one of the representatives of the third generation semiconductor materials.It has gained wide attention because its excellent performance.ZnO has a wide range of applications in the formation of efficient and stable UV/blue LED?UV laser output?photodetector?transparent conductive oxide electrode?solar cells?gas sensors and field effect transistors.In recent years,ZnO microrod/tube has attracted wide attention because its regular hexagonal cross-sectional geometry.It can provide a new multifunctional platform for ZnO micro/nanophotonic research.For example,micron-sized ZnO rods/tubes can be used as an optical microcavity that combines UV photoluminescence and UV lasers with multiple resonance modes.The optical whispering gallery mode?WGM?can be enhanced through the total internal reflection in hexagonal tubular microtubes.The Q value of the ZnO-based microcavity can be increased and a low threshold UV laser output can be realized.Firstly,the ultra-thin-wall ZnO single-crystal microtubes with<0001>orientation have been successfully grown by optical vapor supersaturation position?OVSP?.The diameter of the zinc oxide single crystal microtubes is 75-250um.The wall thickness of it is<500 nm.The mechanism for growth of ultra-thin-wall microtubes by optical vapor supersaturation position is initially revealed.We found that the ceramic rods are sintered in the temperature range of 600°C to 800°C can grow the zinc oxide single crystal microtubes with a complete hexagonal cross sectional structure.Then,we used an optical floating zone furnace?10000H-HR-I VPO-PC,Crystal Systems?.Its full power was 6000W we used 60%of the power?ie60%@6000W?to grow for 9 hours.The ultrathin-wall zinc oxide single-crystal microtubes with complete morphology have a wall thickness of only 450 nm and can realize low-threshold UV laser output.At present,there have been no reports of such thin-walled zinc oxide materials.In addition,a method for rapid growth of zinc oxide microtubes is proposed in this paper—in situ optical vapor supersaturation position?IOVSP?in order to improve the efficiency of the preparation and save energy.First,the light power of the optical Float Furnace is set at 30%for 6 hours for optical preheating.Then,the lamp power increases directly to 60%for the growth of microtubules.The microtube has smooth surface,complete structure and complete hexagon end face with a wall thickness of about 500 nm.This fast-growing zinc oxide microtube process is nearly three times more efficient than optical gas-phase supersaturation?OVSP?,providing a time saving and easy way to grow high-quality ultra-thin-wall ZnO.The single crystal microtube not only achieves energy conservation and utilization but also creates favorable conditions for realizing its industrial production.Finally,the doping of Al was also performed on the basis of the growth of ultrathin-wall ZnO single-crystal microtubes.We proposed a new solid-phase method to realize Al-doped ZnO microtubes.Through doping,the conductivity of microtubes has been successfully improved by nearly ten times(the resistivity of undoped ultrathin-wall zinc oxide microtubes is¹0^-2?·cm).The morphology and microtubule structure of the Al-doped ZnO single crystal microtubules are similar to those of the undoped microtubes.Al-doped does not destroy the optical microcavity structure of the special regular hexagonal cross section of the microtubes.The EDS,XRD,Raman,and temperature-dependent photoluminescence analysis confirm that Al³⁺replaces the Zn²⁺sites and Zn?0/-1?vacancies in the ZnO lattice.The Al doping as the donor level provides a large amount of free electrons to increase the carrier concentration,so that the resistivity of Al-doped ZnO microtubules is reduced to¹0^-3?·cm.The work in this paper provides a new method for the doping of tubular ZnO elements,improves the optoelectronic performance of ZnO microtubes.It reveals that the doped microtubes have great potential in the application of optoelectronic devices.