高质量三方硒纳米线、带、网格结构的可控生长与机理研究毕业论

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1、中国科学技术大学博士学位论文摘要AbstractInthisdissertation，basedonthelowmeltingpoint，thehighevaporationvaporpressureandthecrystalstructurecomposedofinfinitehelicalchainsparalleltoCaxis，wehavesuccessfullypreparedhigh—qualitytrigonalselenium(f-Se)nanowires，nanoribbons，andnanowirenetworksvia

2、physicalvapordepositionroutesaswellasquasiquantum—sizedseleniumtelluriumalloyrodsandspindlesthroughawetchemicalsynthesis．1．High—qualit／t-Senanowiresandnanoribbonswerepreparedinalargescalebyavaporphasemethod，andthedetailedinvestigationsonthemechanismsrevealthevapor-solution

3、—solidgrowthmodeintheirformation．Duetothetemperatureofdepositionzonehigherthanthemeltingpointofselenium，gaseousseleniumwillcondenseintodropletsfirstly．Asthecontinuoustransportationofselenium，dropletswillgrowintolargerspeciesuntiltocontacteachother,whichthendevelopedintoser

4、ies-woundbeadsconfinedanddirectedbythehighlyanisotropiccrystalstructureoft-Se．Ahighertemperaturegradientalongthetubeaxisfavorstotheformationofseries—woundbeadshavingdefiniteboundariesthatevolveintonanoribbons，whileunderthecontrolofalowertemperaturegradienttheboundariesbetw

5、eenthebeadssarefaintandtheseries—woundbeadsdevelopintonanowireseventually．2．Avapor-solidgrowthmodewillproducetwokindsofnanowirenetworks．Duetothetemperatureofdepositionzonelowerthanthemeltingpointofselenium，gaseousseleniumwillcondenseintothree-dimensionallypackedmicrosphere

6、sunderthecontrolofkineticalgrowthrate．Crystallizationwillinducethemtotransformintolayer-structures，whichdevelopintonanowirenetworkswiththeincludedangleof900．IfthecondensationprocessWascontrolledbythermodynamicsequilibrium，thegaseousseleniuminclinestoformtrianglenanocrystal

7、s，whichdevelopintonanowirenetworkswiththeincludedangleof600(1200)．3．Quasiquantum-sizedandmonodispersedlow-dimensionalseleniumtelluriumalloysweresynthesizedthroughtheCO—reductionofthemixedaqueoussolutionofSe02andTe02undertheprotectionandstabilizationofPVP．Thedramaticallyred

8、ucedsizeofalloyrodslcadstothedecreaseoftheirmeltingpoint,andintheexperimentweobserveaphen