Wide Band Gap Of Ain Thin Films Of Semiconductor Materials-ion Beam Synthesis And Characterization,

Aluminum Nltride (AlN) is a promising material for a variety of technologicalapplications because it has many exceptional properties, such as wide band gap(WBG) and negative electron affinity (NEA)AlN thin films were prepared by Reactive Ion Beam Coating and Reactive DirectCurrent Magnetron Sputtering We used non-Rutherford backscattering (non-RBS),X-ray Photoelectron spectroscopy (XPS) and Auger Electron SpeCtroscopy (AES) toanalyze the composition of the AlN thin films Atomic Force Microscopy (AFM) wasapplied to study the morphology of the films The X-ray Diffraction was applied toinvestigate the crystal characterization of the films The resistivity was measured bythe four-point-resistivity-probe The optical bandgap of AlN thin films weredetermined by the UV-Vis transmittance spectra In addition, we studied the fieldemission properties of films With different morphology The infrared reflectancespectra can be used to study the optical properties of the AlN thin filmsWe found that in the Reactive Ion Beam Coating (RIBC), the composition andthe morphology of the films were dramatically influenced by the preparationconditions, such as the beam energy, the nitrogen partial pressure, the totalargon/nitrogen pressure, etc Among them, the beam energy is the most importantfactor, which determines the Al/N ratios and the morphology of the films The higherbeam energy will cause the increase of sputtering rate of Al Thus, the Al content willexceed the N content In addition, we find that smooth surfaces are formed when theAl/N ratio is near l l, if Al is richer than N, the surface grows much rougher It isproposed that Al condensation may due to the low temperature and low energydeposition process If the films are composed of surplus Al, and the temperature andbeam energy is not high enough to give the Al adatoms enough surface migrationenergy, the Al partlcles may condense, and then grow up to form protrudlng tlPs Thelncrease of depos1tlon beam energy wlll also cause an lncrease of the deposltlon rateThe reIatlvely hlgher deposltlon rate will also contnbute to the condensatlon of AlConsequently, we conslder both the dePoslt1on enefgy and the deposltlon rate as thelmportant factors of the formatlon of the tlps Electron field em1sslon propertles werealso studled to find the relatlonshlp between the comPosltlonal, morphologlcal andelectron field emlss1on propert1es of the AlN th1n films The protrudlng t1ps of AlNthln films, whlch have surplus Al, may contrlbute to the electron field emlss1on atvery low electrlc field The electron emlsslon charaCtenstlcs agree wlth Fowler-Nordhelm formu1a In add1t1on, a modlfied ultra-h1gh vacuum scannlng tunnellngmlcroscope (U'VH-STM) was used to study the local electron field em1sslonpropertles of AlN thln films Nanoscale topograPhy/ apparent local barrler heIght(LBH) / field emlss1on (FE) current maps were acqu1red 1n the same area The LBHlmage lndlcates dlfferent chem1cal comPosltlons of those dlstlnCt areas as observed lnthe topograPhlc lmage The correspondlng FE current maPs show a good agreementwlth the LBH imagesThe areC method has dlfficultles 1n preparlng th1n films wlth good crystalllneSo AlN thln films were also prepared by Reactlve Dlrect Current MagnetronSputtenng In thls deposltlon system, we can ralse the substrate temperature to about800'C, and the deposltlon rate 1s relat1vely slower All these can be beneficlal for theonental growth of the thln films We studled the relatlonshIp between the deposlt1onparameters and the crystal structure We succeeded ln find1ng a set of aPpropnateparameters to prePare AlN thln films wlth prefered crystalllne or1entatlon Moreover,we wlsh all these work can contrbute to the appllcatlon of AlN thln films ln field ofmlcroelectronlcs ln futllre...