简介:Alargediamondcrystalupto500μmindiameterwithasmooth(100)facetatitstophasbeensynthesizedonMosubstratethroughmicrowaveplasmachemicalvapordeposition(MPCVD).Itsmorphologyandqualitywerecharacterizedbyscanningelectronmicroscopy(SEM),andthegrowthmechanismwasroughlyillustratedfrombothmacroscopicandmicroscopicviewpoints.Itwasfoundthatmorphologicalinstabilitiesareamajorfactorresultinginsynthesisoflargediamondcrystals,moreover,highmicrowavepowerdensity(MPD),highCH4concentrations,highpressure,highsubstratesurfacetemperatureandtheadditionofasmallamountofO2werealsonecessaryforthesynthesisoflargediamondcrystals.
简介:BasedonthesinglebiasingelectrodeexperimentstooptimizetheconfinementofplasmainthedeviceofKT-5Ctokamak,dual-biasingelectrodeswereinsertedintotheKT5Cplasmaforthefirsttimetoexploretheenhancingeffectsofbiasingandthemechanismsofthebiasing.Bymeansofapplyingdifferentcombinationsofbiasingvoltagesontothedualelectrodes,thechangesofE_r,whicharethekeyfactorforboostinguptheE_r×Bflowshear,wereobserved.Thetimeevolutionshowedthattheinnerelectrodeplayedamajorroleindual-biasing,whichdrewlargercurrentthantheouterone.Theouterelectrodeproducedlittleinfluence.Itturnedoutthatthedual-biasingelectrodeswereaseffectiveasasingleoneinimprovingtheplasmaconfinement,forthemechanismofbiasingwasessentiallyanedgeeffect.