铬掺杂氧化锌薄膜的超声喷雾法制备及其光学与磁学性质

用注射超声喷雾法将前驱体由针管直接送入超声喷头内,在石英基板上制备Zn_(1-x)Cr_xO(x=0.0,0.01,0.03,0.05)薄膜。采用X射线衍射仪、扫描电子显微镜、荧光光谱仪、紫外-可见分光光度计、振动样品磁强计(VSM)等对薄膜的结构、光学和磁学性质进行测量。实验结果表明,未掺杂的ZnO薄膜为六角纤锌矿结构,沿着c轴(002)择优取向,而Cr掺杂抑制了薄膜的c轴择优取向性;掺杂后的薄膜平均晶粒尺寸均增大,且当x=3%时,晶粒尺寸最大,达31.4nm。扫描电镜(SEM)下薄膜呈球形颗粒状,并且在x=5%下,薄膜出现了长条状的微观形貌。Cr掺杂使样品的光致发光谱(PL)发生了很大的变化:未掺杂的样品的PL谱在378nm处存在一个紫外发射峰,对应于550nm附近还存在一个由于缺陷态引起的绿光发射峰;掺Cr样品只有在350~550nm的很宽的范围内存在一个发射峰,对其进行高斯拟合后,发现掺Cr量为x=1%,3%,5%下样品均存在V_(Zn)(锌空位)、Zn_i(Zn间隙位)、V_(Zn)~-(带一个电子的锌空位)内部缺陷态,且当x=3%时,V_(Zn)最多。Cr的掺杂使得薄膜的带隙增大,并且x=3%时,禁带宽度最大,达到3.374eV。掺Cr的三个样品均具有室温铁磁性,且x=3%样品的磁化强度最大,其与V_(Zn)(锌空位)最大相对应,验证了Cr~(3+)和V_(Zn)的缺陷复合体是ZnO∶Cr样品具有稳定的铁磁有序的最有利条件的理论预测。

The Optics and Magnetic Properties of Cr Doped ZnO Thin Films Synthesized by Ultrasonic Spraying Technology

The precursor solution is sent to the ultrasonic nozzle directly through a needle tube to prepare Zn1-x CrxO(x=0, 0.01,0.03 and 0.05)films on quartz substratesby ultrasonic spray method.The structures,optical and magnetic properties of the films were measured by X-ray diffracmeter(XRD),scanning electron microscope(SEM),fluorescence spectrometer,ultravi-olet-visible light detector,vibrating sample magnetometer (VSM)and so on.The experimental results indicate that,the undope-dZnO thin films exhibit the hexagonal wurtzite crystalline structure with a preferential orientation of (002);the Cr doping re-strains the preferred orientation of C axis;the average grain sizes of the samples increase withCr doping,and thesize attains the maximum(31.4 nm)when x=3%.The SEMimages show that the Zn1-xCrxO (x=0,0.01,0.03 and 0.05)films are grain-like particles.And it exhibits a long strip shape when x=5%.Moreover,the doping of Cr makes the photoluminescence (PL)spec-tra of Zn1-xCrxO films change evidently.The undoped sample shows an ultraviolet emission peak at 378 nm as well as a defect related green peak at around 550 nm.However,for the doping samples,there is only a wide range of emission peak from 350 to 550 nm.By gaussian fitting,it is found thatVZn,Zni andV-Zn defects exist in the Cr doping films,andVZn is largest when x=3%.The band gap increases with the doping of Cr,and reaches the maximum when x=3%.The doping of Cr hasthe band gap of the samples increase,and the band gapreachs themaximum(3.37 eV)when x=3%.Magnetic measured results show that threedoping samples Zn1-x Crx O(x=1%,3% and 5%)are ferromagnetic at room temperature,and the magnetization of Zn1-x CrxO (x=3%)is the largest,which is corresponding to the mostVZn defect.The experimental results also prove the the oretical prediction that the substitutive Cr in the oxidation state of +3 and the neutral Zn vacancy in the ZnO∶Cr sample are the most favorable defect complex to maintain a high stability of ferromagnetic order.